1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
3 @c 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 @c 2010, 2011 Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 978-0-9831592-3-0 @*
107 @node Top, Summary, (dir), (dir)
109 @top Debugging with @value{GDBN}
111 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
113 This is the @value{EDITION} Edition, for @value{GDBN}
114 @ifset VERSION_PACKAGE
115 @value{VERSION_PACKAGE}
117 Version @value{GDBVN}.
119 Copyright (C) 1988-2010 Free Software Foundation, Inc.
121 This edition of the GDB manual is dedicated to the memory of Fred
122 Fish. Fred was a long-standing contributor to GDB and to Free
123 software in general. We will miss him.
126 * Summary:: Summary of @value{GDBN}
127 * Sample Session:: A sample @value{GDBN} session
129 * Invocation:: Getting in and out of @value{GDBN}
130 * Commands:: @value{GDBN} commands
131 * Running:: Running programs under @value{GDBN}
132 * Stopping:: Stopping and continuing
133 * Reverse Execution:: Running programs backward
134 * Process Record and Replay:: Recording inferior's execution and replaying it
135 * Stack:: Examining the stack
136 * Source:: Examining source files
137 * Data:: Examining data
138 * Optimized Code:: Debugging optimized code
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Extending GDB:: Extending @value{GDBN}
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
158 * JIT Interface:: Using the JIT debugging interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 @ifset SYSTEM_READLINE
163 * Command Line Editing: (rluserman). Command Line Editing
164 * Using History Interactively: (history). Using History Interactively
166 @ifclear SYSTEM_READLINE
167 * Command Line Editing:: Command Line Editing
168 * Using History Interactively:: Using History Interactively
170 * In Memoriam:: In Memoriam
171 * Formatting Documentation:: How to format and print @value{GDBN} documentation
172 * Installing GDB:: Installing GDB
173 * Maintenance Commands:: Maintenance Commands
174 * Remote Protocol:: GDB Remote Serial Protocol
175 * Agent Expressions:: The GDB Agent Expression Mechanism
176 * Target Descriptions:: How targets can describe themselves to
178 * Operating System Information:: Getting additional information from
180 * Trace File Format:: GDB trace file format
181 * Index Section Format:: .gdb_index section format
182 * Copying:: GNU General Public License says
183 how you can copy and share GDB
184 * GNU Free Documentation License:: The license for this documentation
193 @unnumbered Summary of @value{GDBN}
195 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
196 going on ``inside'' another program while it executes---or what another
197 program was doing at the moment it crashed.
199 @value{GDBN} can do four main kinds of things (plus other things in support of
200 these) to help you catch bugs in the act:
204 Start your program, specifying anything that might affect its behavior.
207 Make your program stop on specified conditions.
210 Examine what has happened, when your program has stopped.
213 Change things in your program, so you can experiment with correcting the
214 effects of one bug and go on to learn about another.
217 You can use @value{GDBN} to debug programs written in C and C@t{++}.
218 For more information, see @ref{Supported Languages,,Supported Languages}.
219 For more information, see @ref{C,,C and C++}.
221 Support for D is partial. For information on D, see
225 Support for Modula-2 is partial. For information on Modula-2, see
226 @ref{Modula-2,,Modula-2}.
228 Support for OpenCL C is partial. For information on OpenCL C, see
229 @ref{OpenCL C,,OpenCL C}.
232 Debugging Pascal programs which use sets, subranges, file variables, or
233 nested functions does not currently work. @value{GDBN} does not support
234 entering expressions, printing values, or similar features using Pascal
238 @value{GDBN} can be used to debug programs written in Fortran, although
239 it may be necessary to refer to some variables with a trailing
242 @value{GDBN} can be used to debug programs written in Objective-C,
243 using either the Apple/NeXT or the GNU Objective-C runtime.
246 * Free Software:: Freely redistributable software
247 * Contributors:: Contributors to GDB
251 @unnumberedsec Free Software
253 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
254 General Public License
255 (GPL). The GPL gives you the freedom to copy or adapt a licensed
256 program---but every person getting a copy also gets with it the
257 freedom to modify that copy (which means that they must get access to
258 the source code), and the freedom to distribute further copies.
259 Typical software companies use copyrights to limit your freedoms; the
260 Free Software Foundation uses the GPL to preserve these freedoms.
262 Fundamentally, the General Public License is a license which says that
263 you have these freedoms and that you cannot take these freedoms away
266 @unnumberedsec Free Software Needs Free Documentation
268 The biggest deficiency in the free software community today is not in
269 the software---it is the lack of good free documentation that we can
270 include with the free software. Many of our most important
271 programs do not come with free reference manuals and free introductory
272 texts. Documentation is an essential part of any software package;
273 when an important free software package does not come with a free
274 manual and a free tutorial, that is a major gap. We have many such
277 Consider Perl, for instance. The tutorial manuals that people
278 normally use are non-free. How did this come about? Because the
279 authors of those manuals published them with restrictive terms---no
280 copying, no modification, source files not available---which exclude
281 them from the free software world.
283 That wasn't the first time this sort of thing happened, and it was far
284 from the last. Many times we have heard a GNU user eagerly describe a
285 manual that he is writing, his intended contribution to the community,
286 only to learn that he had ruined everything by signing a publication
287 contract to make it non-free.
289 Free documentation, like free software, is a matter of freedom, not
290 price. The problem with the non-free manual is not that publishers
291 charge a price for printed copies---that in itself is fine. (The Free
292 Software Foundation sells printed copies of manuals, too.) The
293 problem is the restrictions on the use of the manual. Free manuals
294 are available in source code form, and give you permission to copy and
295 modify. Non-free manuals do not allow this.
297 The criteria of freedom for a free manual are roughly the same as for
298 free software. Redistribution (including the normal kinds of
299 commercial redistribution) must be permitted, so that the manual can
300 accompany every copy of the program, both on-line and on paper.
302 Permission for modification of the technical content is crucial too.
303 When people modify the software, adding or changing features, if they
304 are conscientious they will change the manual too---so they can
305 provide accurate and clear documentation for the modified program. A
306 manual that leaves you no choice but to write a new manual to document
307 a changed version of the program is not really available to our
310 Some kinds of limits on the way modification is handled are
311 acceptable. For example, requirements to preserve the original
312 author's copyright notice, the distribution terms, or the list of
313 authors, are ok. It is also no problem to require modified versions
314 to include notice that they were modified. Even entire sections that
315 may not be deleted or changed are acceptable, as long as they deal
316 with nontechnical topics (like this one). These kinds of restrictions
317 are acceptable because they don't obstruct the community's normal use
320 However, it must be possible to modify all the @emph{technical}
321 content of the manual, and then distribute the result in all the usual
322 media, through all the usual channels. Otherwise, the restrictions
323 obstruct the use of the manual, it is not free, and we need another
324 manual to replace it.
326 Please spread the word about this issue. Our community continues to
327 lose manuals to proprietary publishing. If we spread the word that
328 free software needs free reference manuals and free tutorials, perhaps
329 the next person who wants to contribute by writing documentation will
330 realize, before it is too late, that only free manuals contribute to
331 the free software community.
333 If you are writing documentation, please insist on publishing it under
334 the GNU Free Documentation License or another free documentation
335 license. Remember that this decision requires your approval---you
336 don't have to let the publisher decide. Some commercial publishers
337 will use a free license if you insist, but they will not propose the
338 option; it is up to you to raise the issue and say firmly that this is
339 what you want. If the publisher you are dealing with refuses, please
340 try other publishers. If you're not sure whether a proposed license
341 is free, write to @email{licensing@@gnu.org}.
343 You can encourage commercial publishers to sell more free, copylefted
344 manuals and tutorials by buying them, and particularly by buying
345 copies from the publishers that paid for their writing or for major
346 improvements. Meanwhile, try to avoid buying non-free documentation
347 at all. Check the distribution terms of a manual before you buy it,
348 and insist that whoever seeks your business must respect your freedom.
349 Check the history of the book, and try to reward the publishers that
350 have paid or pay the authors to work on it.
352 The Free Software Foundation maintains a list of free documentation
353 published by other publishers, at
354 @url{http://www.fsf.org/doc/other-free-books.html}.
357 @unnumberedsec Contributors to @value{GDBN}
359 Richard Stallman was the original author of @value{GDBN}, and of many
360 other @sc{gnu} programs. Many others have contributed to its
361 development. This section attempts to credit major contributors. One
362 of the virtues of free software is that everyone is free to contribute
363 to it; with regret, we cannot actually acknowledge everyone here. The
364 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
365 blow-by-blow account.
367 Changes much prior to version 2.0 are lost in the mists of time.
370 @emph{Plea:} Additions to this section are particularly welcome. If you
371 or your friends (or enemies, to be evenhanded) have been unfairly
372 omitted from this list, we would like to add your names!
375 So that they may not regard their many labors as thankless, we
376 particularly thank those who shepherded @value{GDBN} through major
378 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
379 Jim Blandy (release 4.18);
380 Jason Molenda (release 4.17);
381 Stan Shebs (release 4.14);
382 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
383 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
384 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
385 Jim Kingdon (releases 3.5, 3.4, and 3.3);
386 and Randy Smith (releases 3.2, 3.1, and 3.0).
388 Richard Stallman, assisted at various times by Peter TerMaat, Chris
389 Hanson, and Richard Mlynarik, handled releases through 2.8.
391 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
392 in @value{GDBN}, with significant additional contributions from Per
393 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
394 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
395 much general update work leading to release 3.0).
397 @value{GDBN} uses the BFD subroutine library to examine multiple
398 object-file formats; BFD was a joint project of David V.
399 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
401 David Johnson wrote the original COFF support; Pace Willison did
402 the original support for encapsulated COFF.
404 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
406 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
407 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
409 Jean-Daniel Fekete contributed Sun 386i support.
410 Chris Hanson improved the HP9000 support.
411 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
412 David Johnson contributed Encore Umax support.
413 Jyrki Kuoppala contributed Altos 3068 support.
414 Jeff Law contributed HP PA and SOM support.
415 Keith Packard contributed NS32K support.
416 Doug Rabson contributed Acorn Risc Machine support.
417 Bob Rusk contributed Harris Nighthawk CX-UX support.
418 Chris Smith contributed Convex support (and Fortran debugging).
419 Jonathan Stone contributed Pyramid support.
420 Michael Tiemann contributed SPARC support.
421 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
422 Pace Willison contributed Intel 386 support.
423 Jay Vosburgh contributed Symmetry support.
424 Marko Mlinar contributed OpenRISC 1000 support.
426 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
428 Rich Schaefer and Peter Schauer helped with support of SunOS shared
431 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
432 about several machine instruction sets.
434 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
435 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
436 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
437 and RDI targets, respectively.
439 Brian Fox is the author of the readline libraries providing
440 command-line editing and command history.
442 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
443 Modula-2 support, and contributed the Languages chapter of this manual.
445 Fred Fish wrote most of the support for Unix System Vr4.
446 He also enhanced the command-completion support to cover C@t{++} overloaded
449 Hitachi America (now Renesas America), Ltd. sponsored the support for
450 H8/300, H8/500, and Super-H processors.
452 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
454 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
457 Toshiba sponsored the support for the TX39 Mips processor.
459 Matsushita sponsored the support for the MN10200 and MN10300 processors.
461 Fujitsu sponsored the support for SPARClite and FR30 processors.
463 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
466 Michael Snyder added support for tracepoints.
468 Stu Grossman wrote gdbserver.
470 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
471 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
473 The following people at the Hewlett-Packard Company contributed
474 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
475 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
476 compiler, and the Text User Interface (nee Terminal User Interface):
477 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
478 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
479 provided HP-specific information in this manual.
481 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
482 Robert Hoehne made significant contributions to the DJGPP port.
484 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
485 development since 1991. Cygnus engineers who have worked on @value{GDBN}
486 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
487 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
488 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
489 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
490 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
491 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
492 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
493 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
494 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
495 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
496 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
497 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
498 Zuhn have made contributions both large and small.
500 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
501 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
503 Jim Blandy added support for preprocessor macros, while working for Red
506 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
507 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
508 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
509 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
510 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
511 with the migration of old architectures to this new framework.
513 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
514 unwinder framework, this consisting of a fresh new design featuring
515 frame IDs, independent frame sniffers, and the sentinel frame. Mark
516 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
517 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
518 trad unwinders. The architecture-specific changes, each involving a
519 complete rewrite of the architecture's frame code, were carried out by
520 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
521 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
522 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
523 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
526 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
527 Tensilica, Inc.@: contributed support for Xtensa processors. Others
528 who have worked on the Xtensa port of @value{GDBN} in the past include
529 Steve Tjiang, John Newlin, and Scott Foehner.
531 Michael Eager and staff of Xilinx, Inc., contributed support for the
532 Xilinx MicroBlaze architecture.
535 @chapter A Sample @value{GDBN} Session
537 You can use this manual at your leisure to read all about @value{GDBN}.
538 However, a handful of commands are enough to get started using the
539 debugger. This chapter illustrates those commands.
542 In this sample session, we emphasize user input like this: @b{input},
543 to make it easier to pick out from the surrounding output.
546 @c FIXME: this example may not be appropriate for some configs, where
547 @c FIXME...primary interest is in remote use.
549 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
550 processor) exhibits the following bug: sometimes, when we change its
551 quote strings from the default, the commands used to capture one macro
552 definition within another stop working. In the following short @code{m4}
553 session, we define a macro @code{foo} which expands to @code{0000}; we
554 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
555 same thing. However, when we change the open quote string to
556 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
557 procedure fails to define a new synonym @code{baz}:
566 @b{define(bar,defn(`foo'))}
570 @b{changequote(<QUOTE>,<UNQUOTE>)}
572 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
575 m4: End of input: 0: fatal error: EOF in string
579 Let us use @value{GDBN} to try to see what is going on.
582 $ @b{@value{GDBP} m4}
583 @c FIXME: this falsifies the exact text played out, to permit smallbook
584 @c FIXME... format to come out better.
585 @value{GDBN} is free software and you are welcome to distribute copies
586 of it under certain conditions; type "show copying" to see
588 There is absolutely no warranty for @value{GDBN}; type "show warranty"
591 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
596 @value{GDBN} reads only enough symbol data to know where to find the
597 rest when needed; as a result, the first prompt comes up very quickly.
598 We now tell @value{GDBN} to use a narrower display width than usual, so
599 that examples fit in this manual.
602 (@value{GDBP}) @b{set width 70}
606 We need to see how the @code{m4} built-in @code{changequote} works.
607 Having looked at the source, we know the relevant subroutine is
608 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
609 @code{break} command.
612 (@value{GDBP}) @b{break m4_changequote}
613 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
617 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
618 control; as long as control does not reach the @code{m4_changequote}
619 subroutine, the program runs as usual:
622 (@value{GDBP}) @b{run}
623 Starting program: /work/Editorial/gdb/gnu/m4/m4
631 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
632 suspends execution of @code{m4}, displaying information about the
633 context where it stops.
636 @b{changequote(<QUOTE>,<UNQUOTE>)}
638 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
640 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
644 Now we use the command @code{n} (@code{next}) to advance execution to
645 the next line of the current function.
649 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
654 @code{set_quotes} looks like a promising subroutine. We can go into it
655 by using the command @code{s} (@code{step}) instead of @code{next}.
656 @code{step} goes to the next line to be executed in @emph{any}
657 subroutine, so it steps into @code{set_quotes}.
661 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
663 530 if (lquote != def_lquote)
667 The display that shows the subroutine where @code{m4} is now
668 suspended (and its arguments) is called a stack frame display. It
669 shows a summary of the stack. We can use the @code{backtrace}
670 command (which can also be spelled @code{bt}), to see where we are
671 in the stack as a whole: the @code{backtrace} command displays a
672 stack frame for each active subroutine.
675 (@value{GDBP}) @b{bt}
676 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
680 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
681 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
683 #4 0x79dc in expand_input () at macro.c:40
684 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
688 We step through a few more lines to see what happens. The first two
689 times, we can use @samp{s}; the next two times we use @code{n} to avoid
690 falling into the @code{xstrdup} subroutine.
694 0x3b5c 532 if (rquote != def_rquote)
696 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
697 def_lquote : xstrdup(lq);
699 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
702 538 len_lquote = strlen(rquote);
706 The last line displayed looks a little odd; we can examine the variables
707 @code{lquote} and @code{rquote} to see if they are in fact the new left
708 and right quotes we specified. We use the command @code{p}
709 (@code{print}) to see their values.
712 (@value{GDBP}) @b{p lquote}
713 $1 = 0x35d40 "<QUOTE>"
714 (@value{GDBP}) @b{p rquote}
715 $2 = 0x35d50 "<UNQUOTE>"
719 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
720 To look at some context, we can display ten lines of source
721 surrounding the current line with the @code{l} (@code{list}) command.
727 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
729 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
732 538 len_lquote = strlen(rquote);
733 539 len_rquote = strlen(lquote);
740 Let us step past the two lines that set @code{len_lquote} and
741 @code{len_rquote}, and then examine the values of those variables.
745 539 len_rquote = strlen(lquote);
748 (@value{GDBP}) @b{p len_lquote}
750 (@value{GDBP}) @b{p len_rquote}
755 That certainly looks wrong, assuming @code{len_lquote} and
756 @code{len_rquote} are meant to be the lengths of @code{lquote} and
757 @code{rquote} respectively. We can set them to better values using
758 the @code{p} command, since it can print the value of
759 any expression---and that expression can include subroutine calls and
763 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
765 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
770 Is that enough to fix the problem of using the new quotes with the
771 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
772 executing with the @code{c} (@code{continue}) command, and then try the
773 example that caused trouble initially:
779 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
786 Success! The new quotes now work just as well as the default ones. The
787 problem seems to have been just the two typos defining the wrong
788 lengths. We allow @code{m4} exit by giving it an EOF as input:
792 Program exited normally.
796 The message @samp{Program exited normally.} is from @value{GDBN}; it
797 indicates @code{m4} has finished executing. We can end our @value{GDBN}
798 session with the @value{GDBN} @code{quit} command.
801 (@value{GDBP}) @b{quit}
805 @chapter Getting In and Out of @value{GDBN}
807 This chapter discusses how to start @value{GDBN}, and how to get out of it.
811 type @samp{@value{GDBP}} to start @value{GDBN}.
813 type @kbd{quit} or @kbd{Ctrl-d} to exit.
817 * Invoking GDB:: How to start @value{GDBN}
818 * Quitting GDB:: How to quit @value{GDBN}
819 * Shell Commands:: How to use shell commands inside @value{GDBN}
820 * Logging Output:: How to log @value{GDBN}'s output to a file
824 @section Invoking @value{GDBN}
826 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
827 @value{GDBN} reads commands from the terminal until you tell it to exit.
829 You can also run @code{@value{GDBP}} with a variety of arguments and options,
830 to specify more of your debugging environment at the outset.
832 The command-line options described here are designed
833 to cover a variety of situations; in some environments, some of these
834 options may effectively be unavailable.
836 The most usual way to start @value{GDBN} is with one argument,
837 specifying an executable program:
840 @value{GDBP} @var{program}
844 You can also start with both an executable program and a core file
848 @value{GDBP} @var{program} @var{core}
851 You can, instead, specify a process ID as a second argument, if you want
852 to debug a running process:
855 @value{GDBP} @var{program} 1234
859 would attach @value{GDBN} to process @code{1234} (unless you also have a file
860 named @file{1234}; @value{GDBN} does check for a core file first).
862 Taking advantage of the second command-line argument requires a fairly
863 complete operating system; when you use @value{GDBN} as a remote
864 debugger attached to a bare board, there may not be any notion of
865 ``process'', and there is often no way to get a core dump. @value{GDBN}
866 will warn you if it is unable to attach or to read core dumps.
868 You can optionally have @code{@value{GDBP}} pass any arguments after the
869 executable file to the inferior using @code{--args}. This option stops
872 @value{GDBP} --args gcc -O2 -c foo.c
874 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
875 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
877 You can run @code{@value{GDBP}} without printing the front material, which describes
878 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
885 You can further control how @value{GDBN} starts up by using command-line
886 options. @value{GDBN} itself can remind you of the options available.
896 to display all available options and briefly describe their use
897 (@samp{@value{GDBP} -h} is a shorter equivalent).
899 All options and command line arguments you give are processed
900 in sequential order. The order makes a difference when the
901 @samp{-x} option is used.
905 * File Options:: Choosing files
906 * Mode Options:: Choosing modes
907 * Startup:: What @value{GDBN} does during startup
911 @subsection Choosing Files
913 When @value{GDBN} starts, it reads any arguments other than options as
914 specifying an executable file and core file (or process ID). This is
915 the same as if the arguments were specified by the @samp{-se} and
916 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
917 first argument that does not have an associated option flag as
918 equivalent to the @samp{-se} option followed by that argument; and the
919 second argument that does not have an associated option flag, if any, as
920 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
921 If the second argument begins with a decimal digit, @value{GDBN} will
922 first attempt to attach to it as a process, and if that fails, attempt
923 to open it as a corefile. If you have a corefile whose name begins with
924 a digit, you can prevent @value{GDBN} from treating it as a pid by
925 prefixing it with @file{./}, e.g.@: @file{./12345}.
927 If @value{GDBN} has not been configured to included core file support,
928 such as for most embedded targets, then it will complain about a second
929 argument and ignore it.
931 Many options have both long and short forms; both are shown in the
932 following list. @value{GDBN} also recognizes the long forms if you truncate
933 them, so long as enough of the option is present to be unambiguous.
934 (If you prefer, you can flag option arguments with @samp{--} rather
935 than @samp{-}, though we illustrate the more usual convention.)
937 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
938 @c way, both those who look for -foo and --foo in the index, will find
942 @item -symbols @var{file}
944 @cindex @code{--symbols}
946 Read symbol table from file @var{file}.
948 @item -exec @var{file}
950 @cindex @code{--exec}
952 Use file @var{file} as the executable file to execute when appropriate,
953 and for examining pure data in conjunction with a core dump.
957 Read symbol table from file @var{file} and use it as the executable
960 @item -core @var{file}
962 @cindex @code{--core}
964 Use file @var{file} as a core dump to examine.
966 @item -pid @var{number}
967 @itemx -p @var{number}
970 Connect to process ID @var{number}, as with the @code{attach} command.
972 @item -command @var{file}
974 @cindex @code{--command}
976 Execute commands from file @var{file}. The contents of this file is
977 evaluated exactly as the @code{source} command would.
978 @xref{Command Files,, Command files}.
980 @item -eval-command @var{command}
981 @itemx -ex @var{command}
982 @cindex @code{--eval-command}
984 Execute a single @value{GDBN} command.
986 This option may be used multiple times to call multiple commands. It may
987 also be interleaved with @samp{-command} as required.
990 @value{GDBP} -ex 'target sim' -ex 'load' \
991 -x setbreakpoints -ex 'run' a.out
994 @item -directory @var{directory}
995 @itemx -d @var{directory}
996 @cindex @code{--directory}
998 Add @var{directory} to the path to search for source and script files.
1002 @cindex @code{--readnow}
1004 Read each symbol file's entire symbol table immediately, rather than
1005 the default, which is to read it incrementally as it is needed.
1006 This makes startup slower, but makes future operations faster.
1011 @subsection Choosing Modes
1013 You can run @value{GDBN} in various alternative modes---for example, in
1014 batch mode or quiet mode.
1021 Do not execute commands found in any initialization files. Normally,
1022 @value{GDBN} executes the commands in these files after all the command
1023 options and arguments have been processed. @xref{Command Files,,Command
1029 @cindex @code{--quiet}
1030 @cindex @code{--silent}
1032 ``Quiet''. Do not print the introductory and copyright messages. These
1033 messages are also suppressed in batch mode.
1036 @cindex @code{--batch}
1037 Run in batch mode. Exit with status @code{0} after processing all the
1038 command files specified with @samp{-x} (and all commands from
1039 initialization files, if not inhibited with @samp{-n}). Exit with
1040 nonzero status if an error occurs in executing the @value{GDBN} commands
1041 in the command files. Batch mode also disables pagination, sets unlimited
1042 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1043 off} were in effect (@pxref{Messages/Warnings}).
1045 Batch mode may be useful for running @value{GDBN} as a filter, for
1046 example to download and run a program on another computer; in order to
1047 make this more useful, the message
1050 Program exited normally.
1054 (which is ordinarily issued whenever a program running under
1055 @value{GDBN} control terminates) is not issued when running in batch
1059 @cindex @code{--batch-silent}
1060 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1061 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1062 unaffected). This is much quieter than @samp{-silent} and would be useless
1063 for an interactive session.
1065 This is particularly useful when using targets that give @samp{Loading section}
1066 messages, for example.
1068 Note that targets that give their output via @value{GDBN}, as opposed to
1069 writing directly to @code{stdout}, will also be made silent.
1071 @item -return-child-result
1072 @cindex @code{--return-child-result}
1073 The return code from @value{GDBN} will be the return code from the child
1074 process (the process being debugged), with the following exceptions:
1078 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1079 internal error. In this case the exit code is the same as it would have been
1080 without @samp{-return-child-result}.
1082 The user quits with an explicit value. E.g., @samp{quit 1}.
1084 The child process never runs, or is not allowed to terminate, in which case
1085 the exit code will be -1.
1088 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1089 when @value{GDBN} is being used as a remote program loader or simulator
1094 @cindex @code{--nowindows}
1096 ``No windows''. If @value{GDBN} comes with a graphical user interface
1097 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1098 interface. If no GUI is available, this option has no effect.
1102 @cindex @code{--windows}
1104 If @value{GDBN} includes a GUI, then this option requires it to be
1107 @item -cd @var{directory}
1109 Run @value{GDBN} using @var{directory} as its working directory,
1110 instead of the current directory.
1112 @item -data-directory @var{directory}
1113 @cindex @code{--data-directory}
1114 Run @value{GDBN} using @var{directory} as its data directory.
1115 The data directory is where @value{GDBN} searches for its
1116 auxiliary files. @xref{Data Files}.
1120 @cindex @code{--fullname}
1122 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1123 subprocess. It tells @value{GDBN} to output the full file name and line
1124 number in a standard, recognizable fashion each time a stack frame is
1125 displayed (which includes each time your program stops). This
1126 recognizable format looks like two @samp{\032} characters, followed by
1127 the file name, line number and character position separated by colons,
1128 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1129 @samp{\032} characters as a signal to display the source code for the
1133 @cindex @code{--epoch}
1134 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1135 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1136 routines so as to allow Epoch to display values of expressions in a
1139 @item -annotate @var{level}
1140 @cindex @code{--annotate}
1141 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1142 effect is identical to using @samp{set annotate @var{level}}
1143 (@pxref{Annotations}). The annotation @var{level} controls how much
1144 information @value{GDBN} prints together with its prompt, values of
1145 expressions, source lines, and other types of output. Level 0 is the
1146 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1147 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1148 that control @value{GDBN}, and level 2 has been deprecated.
1150 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1154 @cindex @code{--args}
1155 Change interpretation of command line so that arguments following the
1156 executable file are passed as command line arguments to the inferior.
1157 This option stops option processing.
1159 @item -baud @var{bps}
1161 @cindex @code{--baud}
1163 Set the line speed (baud rate or bits per second) of any serial
1164 interface used by @value{GDBN} for remote debugging.
1166 @item -l @var{timeout}
1168 Set the timeout (in seconds) of any communication used by @value{GDBN}
1169 for remote debugging.
1171 @item -tty @var{device}
1172 @itemx -t @var{device}
1173 @cindex @code{--tty}
1175 Run using @var{device} for your program's standard input and output.
1176 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1178 @c resolve the situation of these eventually
1180 @cindex @code{--tui}
1181 Activate the @dfn{Text User Interface} when starting. The Text User
1182 Interface manages several text windows on the terminal, showing
1183 source, assembly, registers and @value{GDBN} command outputs
1184 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1185 Text User Interface can be enabled by invoking the program
1186 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1187 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1190 @c @cindex @code{--xdb}
1191 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1192 @c For information, see the file @file{xdb_trans.html}, which is usually
1193 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1196 @item -interpreter @var{interp}
1197 @cindex @code{--interpreter}
1198 Use the interpreter @var{interp} for interface with the controlling
1199 program or device. This option is meant to be set by programs which
1200 communicate with @value{GDBN} using it as a back end.
1201 @xref{Interpreters, , Command Interpreters}.
1203 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1204 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1205 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1206 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1207 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1208 @sc{gdb/mi} interfaces are no longer supported.
1211 @cindex @code{--write}
1212 Open the executable and core files for both reading and writing. This
1213 is equivalent to the @samp{set write on} command inside @value{GDBN}
1217 @cindex @code{--statistics}
1218 This option causes @value{GDBN} to print statistics about time and
1219 memory usage after it completes each command and returns to the prompt.
1222 @cindex @code{--version}
1223 This option causes @value{GDBN} to print its version number and
1224 no-warranty blurb, and exit.
1229 @subsection What @value{GDBN} Does During Startup
1230 @cindex @value{GDBN} startup
1232 Here's the description of what @value{GDBN} does during session startup:
1236 Sets up the command interpreter as specified by the command line
1237 (@pxref{Mode Options, interpreter}).
1241 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1242 used when building @value{GDBN}; @pxref{System-wide configuration,
1243 ,System-wide configuration and settings}) and executes all the commands in
1247 Reads the init file (if any) in your home directory@footnote{On
1248 DOS/Windows systems, the home directory is the one pointed to by the
1249 @code{HOME} environment variable.} and executes all the commands in
1253 Processes command line options and operands.
1256 Reads and executes the commands from init file (if any) in the current
1257 working directory. This is only done if the current directory is
1258 different from your home directory. Thus, you can have more than one
1259 init file, one generic in your home directory, and another, specific
1260 to the program you are debugging, in the directory where you invoke
1264 If the command line specified a program to debug, or a process to
1265 attach to, or a core file, @value{GDBN} loads any auto-loaded
1266 scripts provided for the program or for its loaded shared libraries.
1267 @xref{Auto-loading}.
1269 If you wish to disable the auto-loading during startup,
1270 you must do something like the following:
1273 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1276 The following does not work because the auto-loading is turned off too late:
1279 $ gdb -ex "set auto-load-scripts off" myprogram
1283 Reads command files specified by the @samp{-x} option. @xref{Command
1284 Files}, for more details about @value{GDBN} command files.
1287 Reads the command history recorded in the @dfn{history file}.
1288 @xref{Command History}, for more details about the command history and the
1289 files where @value{GDBN} records it.
1292 Init files use the same syntax as @dfn{command files} (@pxref{Command
1293 Files}) and are processed by @value{GDBN} in the same way. The init
1294 file in your home directory can set options (such as @samp{set
1295 complaints}) that affect subsequent processing of command line options
1296 and operands. Init files are not executed if you use the @samp{-nx}
1297 option (@pxref{Mode Options, ,Choosing Modes}).
1299 To display the list of init files loaded by gdb at startup, you
1300 can use @kbd{gdb --help}.
1302 @cindex init file name
1303 @cindex @file{.gdbinit}
1304 @cindex @file{gdb.ini}
1305 The @value{GDBN} init files are normally called @file{.gdbinit}.
1306 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1307 the limitations of file names imposed by DOS filesystems. The Windows
1308 ports of @value{GDBN} use the standard name, but if they find a
1309 @file{gdb.ini} file, they warn you about that and suggest to rename
1310 the file to the standard name.
1314 @section Quitting @value{GDBN}
1315 @cindex exiting @value{GDBN}
1316 @cindex leaving @value{GDBN}
1319 @kindex quit @r{[}@var{expression}@r{]}
1320 @kindex q @r{(@code{quit})}
1321 @item quit @r{[}@var{expression}@r{]}
1323 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1324 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1325 do not supply @var{expression}, @value{GDBN} will terminate normally;
1326 otherwise it will terminate using the result of @var{expression} as the
1331 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1332 terminates the action of any @value{GDBN} command that is in progress and
1333 returns to @value{GDBN} command level. It is safe to type the interrupt
1334 character at any time because @value{GDBN} does not allow it to take effect
1335 until a time when it is safe.
1337 If you have been using @value{GDBN} to control an attached process or
1338 device, you can release it with the @code{detach} command
1339 (@pxref{Attach, ,Debugging an Already-running Process}).
1341 @node Shell Commands
1342 @section Shell Commands
1344 If you need to execute occasional shell commands during your
1345 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1346 just use the @code{shell} command.
1350 @cindex shell escape
1351 @item shell @var{command string}
1352 Invoke a standard shell to execute @var{command string}.
1353 If it exists, the environment variable @code{SHELL} determines which
1354 shell to run. Otherwise @value{GDBN} uses the default shell
1355 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1358 The utility @code{make} is often needed in development environments.
1359 You do not have to use the @code{shell} command for this purpose in
1364 @cindex calling make
1365 @item make @var{make-args}
1366 Execute the @code{make} program with the specified
1367 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1370 @node Logging Output
1371 @section Logging Output
1372 @cindex logging @value{GDBN} output
1373 @cindex save @value{GDBN} output to a file
1375 You may want to save the output of @value{GDBN} commands to a file.
1376 There are several commands to control @value{GDBN}'s logging.
1380 @item set logging on
1382 @item set logging off
1384 @cindex logging file name
1385 @item set logging file @var{file}
1386 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1387 @item set logging overwrite [on|off]
1388 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1389 you want @code{set logging on} to overwrite the logfile instead.
1390 @item set logging redirect [on|off]
1391 By default, @value{GDBN} output will go to both the terminal and the logfile.
1392 Set @code{redirect} if you want output to go only to the log file.
1393 @kindex show logging
1395 Show the current values of the logging settings.
1399 @chapter @value{GDBN} Commands
1401 You can abbreviate a @value{GDBN} command to the first few letters of the command
1402 name, if that abbreviation is unambiguous; and you can repeat certain
1403 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1404 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1405 show you the alternatives available, if there is more than one possibility).
1408 * Command Syntax:: How to give commands to @value{GDBN}
1409 * Completion:: Command completion
1410 * Help:: How to ask @value{GDBN} for help
1413 @node Command Syntax
1414 @section Command Syntax
1416 A @value{GDBN} command is a single line of input. There is no limit on
1417 how long it can be. It starts with a command name, which is followed by
1418 arguments whose meaning depends on the command name. For example, the
1419 command @code{step} accepts an argument which is the number of times to
1420 step, as in @samp{step 5}. You can also use the @code{step} command
1421 with no arguments. Some commands do not allow any arguments.
1423 @cindex abbreviation
1424 @value{GDBN} command names may always be truncated if that abbreviation is
1425 unambiguous. Other possible command abbreviations are listed in the
1426 documentation for individual commands. In some cases, even ambiguous
1427 abbreviations are allowed; for example, @code{s} is specially defined as
1428 equivalent to @code{step} even though there are other commands whose
1429 names start with @code{s}. You can test abbreviations by using them as
1430 arguments to the @code{help} command.
1432 @cindex repeating commands
1433 @kindex RET @r{(repeat last command)}
1434 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1435 repeat the previous command. Certain commands (for example, @code{run})
1436 will not repeat this way; these are commands whose unintentional
1437 repetition might cause trouble and which you are unlikely to want to
1438 repeat. User-defined commands can disable this feature; see
1439 @ref{Define, dont-repeat}.
1441 The @code{list} and @code{x} commands, when you repeat them with
1442 @key{RET}, construct new arguments rather than repeating
1443 exactly as typed. This permits easy scanning of source or memory.
1445 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1446 output, in a way similar to the common utility @code{more}
1447 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1448 @key{RET} too many in this situation, @value{GDBN} disables command
1449 repetition after any command that generates this sort of display.
1451 @kindex # @r{(a comment)}
1453 Any text from a @kbd{#} to the end of the line is a comment; it does
1454 nothing. This is useful mainly in command files (@pxref{Command
1455 Files,,Command Files}).
1457 @cindex repeating command sequences
1458 @kindex Ctrl-o @r{(operate-and-get-next)}
1459 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1460 commands. This command accepts the current line, like @key{RET}, and
1461 then fetches the next line relative to the current line from the history
1465 @section Command Completion
1468 @cindex word completion
1469 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1470 only one possibility; it can also show you what the valid possibilities
1471 are for the next word in a command, at any time. This works for @value{GDBN}
1472 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1474 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1475 of a word. If there is only one possibility, @value{GDBN} fills in the
1476 word, and waits for you to finish the command (or press @key{RET} to
1477 enter it). For example, if you type
1479 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1480 @c complete accuracy in these examples; space introduced for clarity.
1481 @c If texinfo enhancements make it unnecessary, it would be nice to
1482 @c replace " @key" by "@key" in the following...
1484 (@value{GDBP}) info bre @key{TAB}
1488 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1489 the only @code{info} subcommand beginning with @samp{bre}:
1492 (@value{GDBP}) info breakpoints
1496 You can either press @key{RET} at this point, to run the @code{info
1497 breakpoints} command, or backspace and enter something else, if
1498 @samp{breakpoints} does not look like the command you expected. (If you
1499 were sure you wanted @code{info breakpoints} in the first place, you
1500 might as well just type @key{RET} immediately after @samp{info bre},
1501 to exploit command abbreviations rather than command completion).
1503 If there is more than one possibility for the next word when you press
1504 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1505 characters and try again, or just press @key{TAB} a second time;
1506 @value{GDBN} displays all the possible completions for that word. For
1507 example, you might want to set a breakpoint on a subroutine whose name
1508 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1509 just sounds the bell. Typing @key{TAB} again displays all the
1510 function names in your program that begin with those characters, for
1514 (@value{GDBP}) b make_ @key{TAB}
1515 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1516 make_a_section_from_file make_environ
1517 make_abs_section make_function_type
1518 make_blockvector make_pointer_type
1519 make_cleanup make_reference_type
1520 make_command make_symbol_completion_list
1521 (@value{GDBP}) b make_
1525 After displaying the available possibilities, @value{GDBN} copies your
1526 partial input (@samp{b make_} in the example) so you can finish the
1529 If you just want to see the list of alternatives in the first place, you
1530 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1531 means @kbd{@key{META} ?}. You can type this either by holding down a
1532 key designated as the @key{META} shift on your keyboard (if there is
1533 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1535 @cindex quotes in commands
1536 @cindex completion of quoted strings
1537 Sometimes the string you need, while logically a ``word'', may contain
1538 parentheses or other characters that @value{GDBN} normally excludes from
1539 its notion of a word. To permit word completion to work in this
1540 situation, you may enclose words in @code{'} (single quote marks) in
1541 @value{GDBN} commands.
1543 The most likely situation where you might need this is in typing the
1544 name of a C@t{++} function. This is because C@t{++} allows function
1545 overloading (multiple definitions of the same function, distinguished
1546 by argument type). For example, when you want to set a breakpoint you
1547 may need to distinguish whether you mean the version of @code{name}
1548 that takes an @code{int} parameter, @code{name(int)}, or the version
1549 that takes a @code{float} parameter, @code{name(float)}. To use the
1550 word-completion facilities in this situation, type a single quote
1551 @code{'} at the beginning of the function name. This alerts
1552 @value{GDBN} that it may need to consider more information than usual
1553 when you press @key{TAB} or @kbd{M-?} to request word completion:
1556 (@value{GDBP}) b 'bubble( @kbd{M-?}
1557 bubble(double,double) bubble(int,int)
1558 (@value{GDBP}) b 'bubble(
1561 In some cases, @value{GDBN} can tell that completing a name requires using
1562 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1563 completing as much as it can) if you do not type the quote in the first
1567 (@value{GDBP}) b bub @key{TAB}
1568 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1569 (@value{GDBP}) b 'bubble(
1573 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1574 you have not yet started typing the argument list when you ask for
1575 completion on an overloaded symbol.
1577 For more information about overloaded functions, see @ref{C Plus Plus
1578 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1579 overload-resolution off} to disable overload resolution;
1580 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1582 @cindex completion of structure field names
1583 @cindex structure field name completion
1584 @cindex completion of union field names
1585 @cindex union field name completion
1586 When completing in an expression which looks up a field in a
1587 structure, @value{GDBN} also tries@footnote{The completer can be
1588 confused by certain kinds of invalid expressions. Also, it only
1589 examines the static type of the expression, not the dynamic type.} to
1590 limit completions to the field names available in the type of the
1594 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1595 magic to_fputs to_rewind
1596 to_data to_isatty to_write
1597 to_delete to_put to_write_async_safe
1602 This is because the @code{gdb_stdout} is a variable of the type
1603 @code{struct ui_file} that is defined in @value{GDBN} sources as
1610 ui_file_flush_ftype *to_flush;
1611 ui_file_write_ftype *to_write;
1612 ui_file_write_async_safe_ftype *to_write_async_safe;
1613 ui_file_fputs_ftype *to_fputs;
1614 ui_file_read_ftype *to_read;
1615 ui_file_delete_ftype *to_delete;
1616 ui_file_isatty_ftype *to_isatty;
1617 ui_file_rewind_ftype *to_rewind;
1618 ui_file_put_ftype *to_put;
1625 @section Getting Help
1626 @cindex online documentation
1629 You can always ask @value{GDBN} itself for information on its commands,
1630 using the command @code{help}.
1633 @kindex h @r{(@code{help})}
1636 You can use @code{help} (abbreviated @code{h}) with no arguments to
1637 display a short list of named classes of commands:
1641 List of classes of commands:
1643 aliases -- Aliases of other commands
1644 breakpoints -- Making program stop at certain points
1645 data -- Examining data
1646 files -- Specifying and examining files
1647 internals -- Maintenance commands
1648 obscure -- Obscure features
1649 running -- Running the program
1650 stack -- Examining the stack
1651 status -- Status inquiries
1652 support -- Support facilities
1653 tracepoints -- Tracing of program execution without
1654 stopping the program
1655 user-defined -- User-defined commands
1657 Type "help" followed by a class name for a list of
1658 commands in that class.
1659 Type "help" followed by command name for full
1661 Command name abbreviations are allowed if unambiguous.
1664 @c the above line break eliminates huge line overfull...
1666 @item help @var{class}
1667 Using one of the general help classes as an argument, you can get a
1668 list of the individual commands in that class. For example, here is the
1669 help display for the class @code{status}:
1672 (@value{GDBP}) help status
1677 @c Line break in "show" line falsifies real output, but needed
1678 @c to fit in smallbook page size.
1679 info -- Generic command for showing things
1680 about the program being debugged
1681 show -- Generic command for showing things
1684 Type "help" followed by command name for full
1686 Command name abbreviations are allowed if unambiguous.
1690 @item help @var{command}
1691 With a command name as @code{help} argument, @value{GDBN} displays a
1692 short paragraph on how to use that command.
1695 @item apropos @var{args}
1696 The @code{apropos} command searches through all of the @value{GDBN}
1697 commands, and their documentation, for the regular expression specified in
1698 @var{args}. It prints out all matches found. For example:
1709 set symbol-reloading -- Set dynamic symbol table reloading
1710 multiple times in one run
1711 show symbol-reloading -- Show dynamic symbol table reloading
1712 multiple times in one run
1717 @item complete @var{args}
1718 The @code{complete @var{args}} command lists all the possible completions
1719 for the beginning of a command. Use @var{args} to specify the beginning of the
1720 command you want completed. For example:
1726 @noindent results in:
1737 @noindent This is intended for use by @sc{gnu} Emacs.
1740 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1741 and @code{show} to inquire about the state of your program, or the state
1742 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1743 manual introduces each of them in the appropriate context. The listings
1744 under @code{info} and under @code{show} in the Index point to
1745 all the sub-commands. @xref{Index}.
1750 @kindex i @r{(@code{info})}
1752 This command (abbreviated @code{i}) is for describing the state of your
1753 program. For example, you can show the arguments passed to a function
1754 with @code{info args}, list the registers currently in use with @code{info
1755 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1756 You can get a complete list of the @code{info} sub-commands with
1757 @w{@code{help info}}.
1761 You can assign the result of an expression to an environment variable with
1762 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1763 @code{set prompt $}.
1767 In contrast to @code{info}, @code{show} is for describing the state of
1768 @value{GDBN} itself.
1769 You can change most of the things you can @code{show}, by using the
1770 related command @code{set}; for example, you can control what number
1771 system is used for displays with @code{set radix}, or simply inquire
1772 which is currently in use with @code{show radix}.
1775 To display all the settable parameters and their current
1776 values, you can use @code{show} with no arguments; you may also use
1777 @code{info set}. Both commands produce the same display.
1778 @c FIXME: "info set" violates the rule that "info" is for state of
1779 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1780 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1784 Here are three miscellaneous @code{show} subcommands, all of which are
1785 exceptional in lacking corresponding @code{set} commands:
1788 @kindex show version
1789 @cindex @value{GDBN} version number
1791 Show what version of @value{GDBN} is running. You should include this
1792 information in @value{GDBN} bug-reports. If multiple versions of
1793 @value{GDBN} are in use at your site, you may need to determine which
1794 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1795 commands are introduced, and old ones may wither away. Also, many
1796 system vendors ship variant versions of @value{GDBN}, and there are
1797 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1798 The version number is the same as the one announced when you start
1801 @kindex show copying
1802 @kindex info copying
1803 @cindex display @value{GDBN} copyright
1806 Display information about permission for copying @value{GDBN}.
1808 @kindex show warranty
1809 @kindex info warranty
1811 @itemx info warranty
1812 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1813 if your version of @value{GDBN} comes with one.
1818 @chapter Running Programs Under @value{GDBN}
1820 When you run a program under @value{GDBN}, you must first generate
1821 debugging information when you compile it.
1823 You may start @value{GDBN} with its arguments, if any, in an environment
1824 of your choice. If you are doing native debugging, you may redirect
1825 your program's input and output, debug an already running process, or
1826 kill a child process.
1829 * Compilation:: Compiling for debugging
1830 * Starting:: Starting your program
1831 * Arguments:: Your program's arguments
1832 * Environment:: Your program's environment
1834 * Working Directory:: Your program's working directory
1835 * Input/Output:: Your program's input and output
1836 * Attach:: Debugging an already-running process
1837 * Kill Process:: Killing the child process
1839 * Inferiors and Programs:: Debugging multiple inferiors and programs
1840 * Threads:: Debugging programs with multiple threads
1841 * Forks:: Debugging forks
1842 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1846 @section Compiling for Debugging
1848 In order to debug a program effectively, you need to generate
1849 debugging information when you compile it. This debugging information
1850 is stored in the object file; it describes the data type of each
1851 variable or function and the correspondence between source line numbers
1852 and addresses in the executable code.
1854 To request debugging information, specify the @samp{-g} option when you run
1857 Programs that are to be shipped to your customers are compiled with
1858 optimizations, using the @samp{-O} compiler option. However, some
1859 compilers are unable to handle the @samp{-g} and @samp{-O} options
1860 together. Using those compilers, you cannot generate optimized
1861 executables containing debugging information.
1863 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1864 without @samp{-O}, making it possible to debug optimized code. We
1865 recommend that you @emph{always} use @samp{-g} whenever you compile a
1866 program. You may think your program is correct, but there is no sense
1867 in pushing your luck. For more information, see @ref{Optimized Code}.
1869 Older versions of the @sc{gnu} C compiler permitted a variant option
1870 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1871 format; if your @sc{gnu} C compiler has this option, do not use it.
1873 @value{GDBN} knows about preprocessor macros and can show you their
1874 expansion (@pxref{Macros}). Most compilers do not include information
1875 about preprocessor macros in the debugging information if you specify
1876 the @option{-g} flag alone, because this information is rather large.
1877 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1878 provides macro information if you specify the options
1879 @option{-gdwarf-2} and @option{-g3}; the former option requests
1880 debugging information in the Dwarf 2 format, and the latter requests
1881 ``extra information''. In the future, we hope to find more compact
1882 ways to represent macro information, so that it can be included with
1887 @section Starting your Program
1893 @kindex r @r{(@code{run})}
1896 Use the @code{run} command to start your program under @value{GDBN}.
1897 You must first specify the program name (except on VxWorks) with an
1898 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1899 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1900 (@pxref{Files, ,Commands to Specify Files}).
1904 If you are running your program in an execution environment that
1905 supports processes, @code{run} creates an inferior process and makes
1906 that process run your program. In some environments without processes,
1907 @code{run} jumps to the start of your program. Other targets,
1908 like @samp{remote}, are always running. If you get an error
1909 message like this one:
1912 The "remote" target does not support "run".
1913 Try "help target" or "continue".
1917 then use @code{continue} to run your program. You may need @code{load}
1918 first (@pxref{load}).
1920 The execution of a program is affected by certain information it
1921 receives from its superior. @value{GDBN} provides ways to specify this
1922 information, which you must do @emph{before} starting your program. (You
1923 can change it after starting your program, but such changes only affect
1924 your program the next time you start it.) This information may be
1925 divided into four categories:
1928 @item The @emph{arguments.}
1929 Specify the arguments to give your program as the arguments of the
1930 @code{run} command. If a shell is available on your target, the shell
1931 is used to pass the arguments, so that you may use normal conventions
1932 (such as wildcard expansion or variable substitution) in describing
1934 In Unix systems, you can control which shell is used with the
1935 @code{SHELL} environment variable.
1936 @xref{Arguments, ,Your Program's Arguments}.
1938 @item The @emph{environment.}
1939 Your program normally inherits its environment from @value{GDBN}, but you can
1940 use the @value{GDBN} commands @code{set environment} and @code{unset
1941 environment} to change parts of the environment that affect
1942 your program. @xref{Environment, ,Your Program's Environment}.
1944 @item The @emph{working directory.}
1945 Your program inherits its working directory from @value{GDBN}. You can set
1946 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1947 @xref{Working Directory, ,Your Program's Working Directory}.
1949 @item The @emph{standard input and output.}
1950 Your program normally uses the same device for standard input and
1951 standard output as @value{GDBN} is using. You can redirect input and output
1952 in the @code{run} command line, or you can use the @code{tty} command to
1953 set a different device for your program.
1954 @xref{Input/Output, ,Your Program's Input and Output}.
1957 @emph{Warning:} While input and output redirection work, you cannot use
1958 pipes to pass the output of the program you are debugging to another
1959 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1963 When you issue the @code{run} command, your program begins to execute
1964 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1965 of how to arrange for your program to stop. Once your program has
1966 stopped, you may call functions in your program, using the @code{print}
1967 or @code{call} commands. @xref{Data, ,Examining Data}.
1969 If the modification time of your symbol file has changed since the last
1970 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1971 table, and reads it again. When it does this, @value{GDBN} tries to retain
1972 your current breakpoints.
1977 @cindex run to main procedure
1978 The name of the main procedure can vary from language to language.
1979 With C or C@t{++}, the main procedure name is always @code{main}, but
1980 other languages such as Ada do not require a specific name for their
1981 main procedure. The debugger provides a convenient way to start the
1982 execution of the program and to stop at the beginning of the main
1983 procedure, depending on the language used.
1985 The @samp{start} command does the equivalent of setting a temporary
1986 breakpoint at the beginning of the main procedure and then invoking
1987 the @samp{run} command.
1989 @cindex elaboration phase
1990 Some programs contain an @dfn{elaboration} phase where some startup code is
1991 executed before the main procedure is called. This depends on the
1992 languages used to write your program. In C@t{++}, for instance,
1993 constructors for static and global objects are executed before
1994 @code{main} is called. It is therefore possible that the debugger stops
1995 before reaching the main procedure. However, the temporary breakpoint
1996 will remain to halt execution.
1998 Specify the arguments to give to your program as arguments to the
1999 @samp{start} command. These arguments will be given verbatim to the
2000 underlying @samp{run} command. Note that the same arguments will be
2001 reused if no argument is provided during subsequent calls to
2002 @samp{start} or @samp{run}.
2004 It is sometimes necessary to debug the program during elaboration. In
2005 these cases, using the @code{start} command would stop the execution of
2006 your program too late, as the program would have already completed the
2007 elaboration phase. Under these circumstances, insert breakpoints in your
2008 elaboration code before running your program.
2010 @kindex set exec-wrapper
2011 @item set exec-wrapper @var{wrapper}
2012 @itemx show exec-wrapper
2013 @itemx unset exec-wrapper
2014 When @samp{exec-wrapper} is set, the specified wrapper is used to
2015 launch programs for debugging. @value{GDBN} starts your program
2016 with a shell command of the form @kbd{exec @var{wrapper}
2017 @var{program}}. Quoting is added to @var{program} and its
2018 arguments, but not to @var{wrapper}, so you should add quotes if
2019 appropriate for your shell. The wrapper runs until it executes
2020 your program, and then @value{GDBN} takes control.
2022 You can use any program that eventually calls @code{execve} with
2023 its arguments as a wrapper. Several standard Unix utilities do
2024 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2025 with @code{exec "$@@"} will also work.
2027 For example, you can use @code{env} to pass an environment variable to
2028 the debugged program, without setting the variable in your shell's
2032 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2036 This command is available when debugging locally on most targets, excluding
2037 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2039 @kindex set disable-randomization
2040 @item set disable-randomization
2041 @itemx set disable-randomization on
2042 This option (enabled by default in @value{GDBN}) will turn off the native
2043 randomization of the virtual address space of the started program. This option
2044 is useful for multiple debugging sessions to make the execution better
2045 reproducible and memory addresses reusable across debugging sessions.
2047 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2048 On @sc{gnu}/Linux you can get the same behavior using
2051 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2054 @item set disable-randomization off
2055 Leave the behavior of the started executable unchanged. Some bugs rear their
2056 ugly heads only when the program is loaded at certain addresses. If your bug
2057 disappears when you run the program under @value{GDBN}, that might be because
2058 @value{GDBN} by default disables the address randomization on platforms, such
2059 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2060 disable-randomization off} to try to reproduce such elusive bugs.
2062 On targets where it is available, virtual address space randomization
2063 protects the programs against certain kinds of security attacks. In these
2064 cases the attacker needs to know the exact location of a concrete executable
2065 code. Randomizing its location makes it impossible to inject jumps misusing
2066 a code at its expected addresses.
2068 Prelinking shared libraries provides a startup performance advantage but it
2069 makes addresses in these libraries predictable for privileged processes by
2070 having just unprivileged access at the target system. Reading the shared
2071 library binary gives enough information for assembling the malicious code
2072 misusing it. Still even a prelinked shared library can get loaded at a new
2073 random address just requiring the regular relocation process during the
2074 startup. Shared libraries not already prelinked are always loaded at
2075 a randomly chosen address.
2077 Position independent executables (PIE) contain position independent code
2078 similar to the shared libraries and therefore such executables get loaded at
2079 a randomly chosen address upon startup. PIE executables always load even
2080 already prelinked shared libraries at a random address. You can build such
2081 executable using @command{gcc -fPIE -pie}.
2083 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2084 (as long as the randomization is enabled).
2086 @item show disable-randomization
2087 Show the current setting of the explicit disable of the native randomization of
2088 the virtual address space of the started program.
2093 @section Your Program's Arguments
2095 @cindex arguments (to your program)
2096 The arguments to your program can be specified by the arguments of the
2098 They are passed to a shell, which expands wildcard characters and
2099 performs redirection of I/O, and thence to your program. Your
2100 @code{SHELL} environment variable (if it exists) specifies what shell
2101 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2102 the default shell (@file{/bin/sh} on Unix).
2104 On non-Unix systems, the program is usually invoked directly by
2105 @value{GDBN}, which emulates I/O redirection via the appropriate system
2106 calls, and the wildcard characters are expanded by the startup code of
2107 the program, not by the shell.
2109 @code{run} with no arguments uses the same arguments used by the previous
2110 @code{run}, or those set by the @code{set args} command.
2115 Specify the arguments to be used the next time your program is run. If
2116 @code{set args} has no arguments, @code{run} executes your program
2117 with no arguments. Once you have run your program with arguments,
2118 using @code{set args} before the next @code{run} is the only way to run
2119 it again without arguments.
2123 Show the arguments to give your program when it is started.
2127 @section Your Program's Environment
2129 @cindex environment (of your program)
2130 The @dfn{environment} consists of a set of environment variables and
2131 their values. Environment variables conventionally record such things as
2132 your user name, your home directory, your terminal type, and your search
2133 path for programs to run. Usually you set up environment variables with
2134 the shell and they are inherited by all the other programs you run. When
2135 debugging, it can be useful to try running your program with a modified
2136 environment without having to start @value{GDBN} over again.
2140 @item path @var{directory}
2141 Add @var{directory} to the front of the @code{PATH} environment variable
2142 (the search path for executables) that will be passed to your program.
2143 The value of @code{PATH} used by @value{GDBN} does not change.
2144 You may specify several directory names, separated by whitespace or by a
2145 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2146 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2147 is moved to the front, so it is searched sooner.
2149 You can use the string @samp{$cwd} to refer to whatever is the current
2150 working directory at the time @value{GDBN} searches the path. If you
2151 use @samp{.} instead, it refers to the directory where you executed the
2152 @code{path} command. @value{GDBN} replaces @samp{.} in the
2153 @var{directory} argument (with the current path) before adding
2154 @var{directory} to the search path.
2155 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2156 @c document that, since repeating it would be a no-op.
2160 Display the list of search paths for executables (the @code{PATH}
2161 environment variable).
2163 @kindex show environment
2164 @item show environment @r{[}@var{varname}@r{]}
2165 Print the value of environment variable @var{varname} to be given to
2166 your program when it starts. If you do not supply @var{varname},
2167 print the names and values of all environment variables to be given to
2168 your program. You can abbreviate @code{environment} as @code{env}.
2170 @kindex set environment
2171 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2172 Set environment variable @var{varname} to @var{value}. The value
2173 changes for your program only, not for @value{GDBN} itself. @var{value} may
2174 be any string; the values of environment variables are just strings, and
2175 any interpretation is supplied by your program itself. The @var{value}
2176 parameter is optional; if it is eliminated, the variable is set to a
2178 @c "any string" here does not include leading, trailing
2179 @c blanks. Gnu asks: does anyone care?
2181 For example, this command:
2188 tells the debugged program, when subsequently run, that its user is named
2189 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2190 are not actually required.)
2192 @kindex unset environment
2193 @item unset environment @var{varname}
2194 Remove variable @var{varname} from the environment to be passed to your
2195 program. This is different from @samp{set env @var{varname} =};
2196 @code{unset environment} removes the variable from the environment,
2197 rather than assigning it an empty value.
2200 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2202 by your @code{SHELL} environment variable if it exists (or
2203 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2204 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2205 @file{.bashrc} for BASH---any variables you set in that file affect
2206 your program. You may wish to move setting of environment variables to
2207 files that are only run when you sign on, such as @file{.login} or
2210 @node Working Directory
2211 @section Your Program's Working Directory
2213 @cindex working directory (of your program)
2214 Each time you start your program with @code{run}, it inherits its
2215 working directory from the current working directory of @value{GDBN}.
2216 The @value{GDBN} working directory is initially whatever it inherited
2217 from its parent process (typically the shell), but you can specify a new
2218 working directory in @value{GDBN} with the @code{cd} command.
2220 The @value{GDBN} working directory also serves as a default for the commands
2221 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2226 @cindex change working directory
2227 @item cd @var{directory}
2228 Set the @value{GDBN} working directory to @var{directory}.
2232 Print the @value{GDBN} working directory.
2235 It is generally impossible to find the current working directory of
2236 the process being debugged (since a program can change its directory
2237 during its run). If you work on a system where @value{GDBN} is
2238 configured with the @file{/proc} support, you can use the @code{info
2239 proc} command (@pxref{SVR4 Process Information}) to find out the
2240 current working directory of the debuggee.
2243 @section Your Program's Input and Output
2248 By default, the program you run under @value{GDBN} does input and output to
2249 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2250 to its own terminal modes to interact with you, but it records the terminal
2251 modes your program was using and switches back to them when you continue
2252 running your program.
2255 @kindex info terminal
2257 Displays information recorded by @value{GDBN} about the terminal modes your
2261 You can redirect your program's input and/or output using shell
2262 redirection with the @code{run} command. For example,
2269 starts your program, diverting its output to the file @file{outfile}.
2272 @cindex controlling terminal
2273 Another way to specify where your program should do input and output is
2274 with the @code{tty} command. This command accepts a file name as
2275 argument, and causes this file to be the default for future @code{run}
2276 commands. It also resets the controlling terminal for the child
2277 process, for future @code{run} commands. For example,
2284 directs that processes started with subsequent @code{run} commands
2285 default to do input and output on the terminal @file{/dev/ttyb} and have
2286 that as their controlling terminal.
2288 An explicit redirection in @code{run} overrides the @code{tty} command's
2289 effect on the input/output device, but not its effect on the controlling
2292 When you use the @code{tty} command or redirect input in the @code{run}
2293 command, only the input @emph{for your program} is affected. The input
2294 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2295 for @code{set inferior-tty}.
2297 @cindex inferior tty
2298 @cindex set inferior controlling terminal
2299 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2300 display the name of the terminal that will be used for future runs of your
2304 @item set inferior-tty /dev/ttyb
2305 @kindex set inferior-tty
2306 Set the tty for the program being debugged to /dev/ttyb.
2308 @item show inferior-tty
2309 @kindex show inferior-tty
2310 Show the current tty for the program being debugged.
2314 @section Debugging an Already-running Process
2319 @item attach @var{process-id}
2320 This command attaches to a running process---one that was started
2321 outside @value{GDBN}. (@code{info files} shows your active
2322 targets.) The command takes as argument a process ID. The usual way to
2323 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2324 or with the @samp{jobs -l} shell command.
2326 @code{attach} does not repeat if you press @key{RET} a second time after
2327 executing the command.
2330 To use @code{attach}, your program must be running in an environment
2331 which supports processes; for example, @code{attach} does not work for
2332 programs on bare-board targets that lack an operating system. You must
2333 also have permission to send the process a signal.
2335 When you use @code{attach}, the debugger finds the program running in
2336 the process first by looking in the current working directory, then (if
2337 the program is not found) by using the source file search path
2338 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2339 the @code{file} command to load the program. @xref{Files, ,Commands to
2342 The first thing @value{GDBN} does after arranging to debug the specified
2343 process is to stop it. You can examine and modify an attached process
2344 with all the @value{GDBN} commands that are ordinarily available when
2345 you start processes with @code{run}. You can insert breakpoints; you
2346 can step and continue; you can modify storage. If you would rather the
2347 process continue running, you may use the @code{continue} command after
2348 attaching @value{GDBN} to the process.
2353 When you have finished debugging the attached process, you can use the
2354 @code{detach} command to release it from @value{GDBN} control. Detaching
2355 the process continues its execution. After the @code{detach} command,
2356 that process and @value{GDBN} become completely independent once more, and you
2357 are ready to @code{attach} another process or start one with @code{run}.
2358 @code{detach} does not repeat if you press @key{RET} again after
2359 executing the command.
2362 If you exit @value{GDBN} while you have an attached process, you detach
2363 that process. If you use the @code{run} command, you kill that process.
2364 By default, @value{GDBN} asks for confirmation if you try to do either of these
2365 things; you can control whether or not you need to confirm by using the
2366 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2370 @section Killing the Child Process
2375 Kill the child process in which your program is running under @value{GDBN}.
2378 This command is useful if you wish to debug a core dump instead of a
2379 running process. @value{GDBN} ignores any core dump file while your program
2382 On some operating systems, a program cannot be executed outside @value{GDBN}
2383 while you have breakpoints set on it inside @value{GDBN}. You can use the
2384 @code{kill} command in this situation to permit running your program
2385 outside the debugger.
2387 The @code{kill} command is also useful if you wish to recompile and
2388 relink your program, since on many systems it is impossible to modify an
2389 executable file while it is running in a process. In this case, when you
2390 next type @code{run}, @value{GDBN} notices that the file has changed, and
2391 reads the symbol table again (while trying to preserve your current
2392 breakpoint settings).
2394 @node Inferiors and Programs
2395 @section Debugging Multiple Inferiors and Programs
2397 @value{GDBN} lets you run and debug multiple programs in a single
2398 session. In addition, @value{GDBN} on some systems may let you run
2399 several programs simultaneously (otherwise you have to exit from one
2400 before starting another). In the most general case, you can have
2401 multiple threads of execution in each of multiple processes, launched
2402 from multiple executables.
2405 @value{GDBN} represents the state of each program execution with an
2406 object called an @dfn{inferior}. An inferior typically corresponds to
2407 a process, but is more general and applies also to targets that do not
2408 have processes. Inferiors may be created before a process runs, and
2409 may be retained after a process exits. Inferiors have unique
2410 identifiers that are different from process ids. Usually each
2411 inferior will also have its own distinct address space, although some
2412 embedded targets may have several inferiors running in different parts
2413 of a single address space. Each inferior may in turn have multiple
2414 threads running in it.
2416 To find out what inferiors exist at any moment, use @w{@code{info
2420 @kindex info inferiors
2421 @item info inferiors
2422 Print a list of all inferiors currently being managed by @value{GDBN}.
2424 @value{GDBN} displays for each inferior (in this order):
2428 the inferior number assigned by @value{GDBN}
2431 the target system's inferior identifier
2434 the name of the executable the inferior is running.
2439 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2440 indicates the current inferior.
2444 @c end table here to get a little more width for example
2447 (@value{GDBP}) info inferiors
2448 Num Description Executable
2449 2 process 2307 hello
2450 * 1 process 3401 goodbye
2453 To switch focus between inferiors, use the @code{inferior} command:
2456 @kindex inferior @var{infno}
2457 @item inferior @var{infno}
2458 Make inferior number @var{infno} the current inferior. The argument
2459 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2460 in the first field of the @samp{info inferiors} display.
2464 You can get multiple executables into a debugging session via the
2465 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2466 systems @value{GDBN} can add inferiors to the debug session
2467 automatically by following calls to @code{fork} and @code{exec}. To
2468 remove inferiors from the debugging session use the
2469 @w{@code{remove-inferiors}} command.
2472 @kindex add-inferior
2473 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2474 Adds @var{n} inferiors to be run using @var{executable} as the
2475 executable. @var{n} defaults to 1. If no executable is specified,
2476 the inferiors begins empty, with no program. You can still assign or
2477 change the program assigned to the inferior at any time by using the
2478 @code{file} command with the executable name as its argument.
2480 @kindex clone-inferior
2481 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2482 Adds @var{n} inferiors ready to execute the same program as inferior
2483 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2484 number of the current inferior. This is a convenient command when you
2485 want to run another instance of the inferior you are debugging.
2488 (@value{GDBP}) info inferiors
2489 Num Description Executable
2490 * 1 process 29964 helloworld
2491 (@value{GDBP}) clone-inferior
2494 (@value{GDBP}) info inferiors
2495 Num Description Executable
2497 * 1 process 29964 helloworld
2500 You can now simply switch focus to inferior 2 and run it.
2502 @kindex remove-inferiors
2503 @item remove-inferiors @var{infno}@dots{}
2504 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2505 possible to remove an inferior that is running with this command. For
2506 those, use the @code{kill} or @code{detach} command first.
2510 To quit debugging one of the running inferiors that is not the current
2511 inferior, you can either detach from it by using the @w{@code{detach
2512 inferior}} command (allowing it to run independently), or kill it
2513 using the @w{@code{kill inferiors}} command:
2516 @kindex detach inferiors @var{infno}@dots{}
2517 @item detach inferior @var{infno}@dots{}
2518 Detach from the inferior or inferiors identified by @value{GDBN}
2519 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2520 still stays on the list of inferiors shown by @code{info inferiors},
2521 but its Description will show @samp{<null>}.
2523 @kindex kill inferiors @var{infno}@dots{}
2524 @item kill inferiors @var{infno}@dots{}
2525 Kill the inferior or inferiors identified by @value{GDBN} inferior
2526 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2527 stays on the list of inferiors shown by @code{info inferiors}, but its
2528 Description will show @samp{<null>}.
2531 After the successful completion of a command such as @code{detach},
2532 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2533 a normal process exit, the inferior is still valid and listed with
2534 @code{info inferiors}, ready to be restarted.
2537 To be notified when inferiors are started or exit under @value{GDBN}'s
2538 control use @w{@code{set print inferior-events}}:
2541 @kindex set print inferior-events
2542 @cindex print messages on inferior start and exit
2543 @item set print inferior-events
2544 @itemx set print inferior-events on
2545 @itemx set print inferior-events off
2546 The @code{set print inferior-events} command allows you to enable or
2547 disable printing of messages when @value{GDBN} notices that new
2548 inferiors have started or that inferiors have exited or have been
2549 detached. By default, these messages will not be printed.
2551 @kindex show print inferior-events
2552 @item show print inferior-events
2553 Show whether messages will be printed when @value{GDBN} detects that
2554 inferiors have started, exited or have been detached.
2557 Many commands will work the same with multiple programs as with a
2558 single program: e.g., @code{print myglobal} will simply display the
2559 value of @code{myglobal} in the current inferior.
2562 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2563 get more info about the relationship of inferiors, programs, address
2564 spaces in a debug session. You can do that with the @w{@code{maint
2565 info program-spaces}} command.
2568 @kindex maint info program-spaces
2569 @item maint info program-spaces
2570 Print a list of all program spaces currently being managed by
2573 @value{GDBN} displays for each program space (in this order):
2577 the program space number assigned by @value{GDBN}
2580 the name of the executable loaded into the program space, with e.g.,
2581 the @code{file} command.
2586 An asterisk @samp{*} preceding the @value{GDBN} program space number
2587 indicates the current program space.
2589 In addition, below each program space line, @value{GDBN} prints extra
2590 information that isn't suitable to display in tabular form. For
2591 example, the list of inferiors bound to the program space.
2594 (@value{GDBP}) maint info program-spaces
2597 Bound inferiors: ID 1 (process 21561)
2601 Here we can see that no inferior is running the program @code{hello},
2602 while @code{process 21561} is running the program @code{goodbye}. On
2603 some targets, it is possible that multiple inferiors are bound to the
2604 same program space. The most common example is that of debugging both
2605 the parent and child processes of a @code{vfork} call. For example,
2608 (@value{GDBP}) maint info program-spaces
2611 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2614 Here, both inferior 2 and inferior 1 are running in the same program
2615 space as a result of inferior 1 having executed a @code{vfork} call.
2619 @section Debugging Programs with Multiple Threads
2621 @cindex threads of execution
2622 @cindex multiple threads
2623 @cindex switching threads
2624 In some operating systems, such as HP-UX and Solaris, a single program
2625 may have more than one @dfn{thread} of execution. The precise semantics
2626 of threads differ from one operating system to another, but in general
2627 the threads of a single program are akin to multiple processes---except
2628 that they share one address space (that is, they can all examine and
2629 modify the same variables). On the other hand, each thread has its own
2630 registers and execution stack, and perhaps private memory.
2632 @value{GDBN} provides these facilities for debugging multi-thread
2636 @item automatic notification of new threads
2637 @item @samp{thread @var{threadno}}, a command to switch among threads
2638 @item @samp{info threads}, a command to inquire about existing threads
2639 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2640 a command to apply a command to a list of threads
2641 @item thread-specific breakpoints
2642 @item @samp{set print thread-events}, which controls printing of
2643 messages on thread start and exit.
2644 @item @samp{set libthread-db-search-path @var{path}}, which lets
2645 the user specify which @code{libthread_db} to use if the default choice
2646 isn't compatible with the program.
2650 @emph{Warning:} These facilities are not yet available on every
2651 @value{GDBN} configuration where the operating system supports threads.
2652 If your @value{GDBN} does not support threads, these commands have no
2653 effect. For example, a system without thread support shows no output
2654 from @samp{info threads}, and always rejects the @code{thread} command,
2658 (@value{GDBP}) info threads
2659 (@value{GDBP}) thread 1
2660 Thread ID 1 not known. Use the "info threads" command to
2661 see the IDs of currently known threads.
2663 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2664 @c doesn't support threads"?
2667 @cindex focus of debugging
2668 @cindex current thread
2669 The @value{GDBN} thread debugging facility allows you to observe all
2670 threads while your program runs---but whenever @value{GDBN} takes
2671 control, one thread in particular is always the focus of debugging.
2672 This thread is called the @dfn{current thread}. Debugging commands show
2673 program information from the perspective of the current thread.
2675 @cindex @code{New} @var{systag} message
2676 @cindex thread identifier (system)
2677 @c FIXME-implementors!! It would be more helpful if the [New...] message
2678 @c included GDB's numeric thread handle, so you could just go to that
2679 @c thread without first checking `info threads'.
2680 Whenever @value{GDBN} detects a new thread in your program, it displays
2681 the target system's identification for the thread with a message in the
2682 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2683 whose form varies depending on the particular system. For example, on
2684 @sc{gnu}/Linux, you might see
2687 [New Thread 0x41e02940 (LWP 25582)]
2691 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2692 the @var{systag} is simply something like @samp{process 368}, with no
2695 @c FIXME!! (1) Does the [New...] message appear even for the very first
2696 @c thread of a program, or does it only appear for the
2697 @c second---i.e.@: when it becomes obvious we have a multithread
2699 @c (2) *Is* there necessarily a first thread always? Or do some
2700 @c multithread systems permit starting a program with multiple
2701 @c threads ab initio?
2703 @cindex thread number
2704 @cindex thread identifier (GDB)
2705 For debugging purposes, @value{GDBN} associates its own thread
2706 number---always a single integer---with each thread in your program.
2709 @kindex info threads
2710 @item info threads @r{[}@var{id}@dots{}@r{]}
2711 Display a summary of all threads currently in your program. Optional
2712 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2713 means to print information only about the specified thread or threads.
2714 @value{GDBN} displays for each thread (in this order):
2718 the thread number assigned by @value{GDBN}
2721 the target system's thread identifier (@var{systag})
2724 the thread's name, if one is known. A thread can either be named by
2725 the user (see @code{thread name}, below), or, in some cases, by the
2729 the current stack frame summary for that thread
2733 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2734 indicates the current thread.
2738 @c end table here to get a little more width for example
2741 (@value{GDBP}) info threads
2743 3 process 35 thread 27 0x34e5 in sigpause ()
2744 2 process 35 thread 23 0x34e5 in sigpause ()
2745 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2749 On Solaris, you can display more information about user threads with a
2750 Solaris-specific command:
2753 @item maint info sol-threads
2754 @kindex maint info sol-threads
2755 @cindex thread info (Solaris)
2756 Display info on Solaris user threads.
2760 @kindex thread @var{threadno}
2761 @item thread @var{threadno}
2762 Make thread number @var{threadno} the current thread. The command
2763 argument @var{threadno} is the internal @value{GDBN} thread number, as
2764 shown in the first field of the @samp{info threads} display.
2765 @value{GDBN} responds by displaying the system identifier of the thread
2766 you selected, and its current stack frame summary:
2769 (@value{GDBP}) thread 2
2770 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2771 #0 some_function (ignore=0x0) at example.c:8
2772 8 printf ("hello\n");
2776 As with the @samp{[New @dots{}]} message, the form of the text after
2777 @samp{Switching to} depends on your system's conventions for identifying
2780 @vindex $_thread@r{, convenience variable}
2781 The debugger convenience variable @samp{$_thread} contains the number
2782 of the current thread. You may find this useful in writing breakpoint
2783 conditional expressions, command scripts, and so forth. See
2784 @xref{Convenience Vars,, Convenience Variables}, for general
2785 information on convenience variables.
2787 @kindex thread apply
2788 @cindex apply command to several threads
2789 @item thread apply [@var{threadno} | all] @var{command}
2790 The @code{thread apply} command allows you to apply the named
2791 @var{command} to one or more threads. Specify the numbers of the
2792 threads that you want affected with the command argument
2793 @var{threadno}. It can be a single thread number, one of the numbers
2794 shown in the first field of the @samp{info threads} display; or it
2795 could be a range of thread numbers, as in @code{2-4}. To apply a
2796 command to all threads, type @kbd{thread apply all @var{command}}.
2799 @cindex name a thread
2800 @item thread name [@var{name}]
2801 This command assigns a name to the current thread. If no argument is
2802 given, any existing user-specified name is removed. The thread name
2803 appears in the @samp{info threads} display.
2805 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2806 determine the name of the thread as given by the OS. On these
2807 systems, a name specified with @samp{thread name} will override the
2808 system-give name, and removing the user-specified name will cause
2809 @value{GDBN} to once again display the system-specified name.
2812 @cindex search for a thread
2813 @item thread find [@var{regexp}]
2814 Search for and display thread ids whose name or @var{systag}
2815 matches the supplied regular expression.
2817 As well as being the complement to the @samp{thread name} command,
2818 this command also allows you to identify a thread by its target
2819 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2823 (@value{GDBN}) thread find 26688
2824 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2825 (@value{GDBN}) info thread 4
2827 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2830 @kindex set print thread-events
2831 @cindex print messages on thread start and exit
2832 @item set print thread-events
2833 @itemx set print thread-events on
2834 @itemx set print thread-events off
2835 The @code{set print thread-events} command allows you to enable or
2836 disable printing of messages when @value{GDBN} notices that new threads have
2837 started or that threads have exited. By default, these messages will
2838 be printed if detection of these events is supported by the target.
2839 Note that these messages cannot be disabled on all targets.
2841 @kindex show print thread-events
2842 @item show print thread-events
2843 Show whether messages will be printed when @value{GDBN} detects that threads
2844 have started and exited.
2847 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2848 more information about how @value{GDBN} behaves when you stop and start
2849 programs with multiple threads.
2851 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2852 watchpoints in programs with multiple threads.
2855 @kindex set libthread-db-search-path
2856 @cindex search path for @code{libthread_db}
2857 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2858 If this variable is set, @var{path} is a colon-separated list of
2859 directories @value{GDBN} will use to search for @code{libthread_db}.
2860 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2861 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2862 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2865 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2866 @code{libthread_db} library to obtain information about threads in the
2867 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2868 to find @code{libthread_db}.
2870 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2871 refers to the default system directories that are
2872 normally searched for loading shared libraries.
2874 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2875 refers to the directory from which @code{libpthread}
2876 was loaded in the inferior process.
2878 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2879 @value{GDBN} attempts to initialize it with the current inferior process.
2880 If this initialization fails (which could happen because of a version
2881 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2882 will unload @code{libthread_db}, and continue with the next directory.
2883 If none of @code{libthread_db} libraries initialize successfully,
2884 @value{GDBN} will issue a warning and thread debugging will be disabled.
2886 Setting @code{libthread-db-search-path} is currently implemented
2887 only on some platforms.
2889 @kindex show libthread-db-search-path
2890 @item show libthread-db-search-path
2891 Display current libthread_db search path.
2893 @kindex set debug libthread-db
2894 @kindex show debug libthread-db
2895 @cindex debugging @code{libthread_db}
2896 @item set debug libthread-db
2897 @itemx show debug libthread-db
2898 Turns on or off display of @code{libthread_db}-related events.
2899 Use @code{1} to enable, @code{0} to disable.
2903 @section Debugging Forks
2905 @cindex fork, debugging programs which call
2906 @cindex multiple processes
2907 @cindex processes, multiple
2908 On most systems, @value{GDBN} has no special support for debugging
2909 programs which create additional processes using the @code{fork}
2910 function. When a program forks, @value{GDBN} will continue to debug the
2911 parent process and the child process will run unimpeded. If you have
2912 set a breakpoint in any code which the child then executes, the child
2913 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2914 will cause it to terminate.
2916 However, if you want to debug the child process there is a workaround
2917 which isn't too painful. Put a call to @code{sleep} in the code which
2918 the child process executes after the fork. It may be useful to sleep
2919 only if a certain environment variable is set, or a certain file exists,
2920 so that the delay need not occur when you don't want to run @value{GDBN}
2921 on the child. While the child is sleeping, use the @code{ps} program to
2922 get its process ID. Then tell @value{GDBN} (a new invocation of
2923 @value{GDBN} if you are also debugging the parent process) to attach to
2924 the child process (@pxref{Attach}). From that point on you can debug
2925 the child process just like any other process which you attached to.
2927 On some systems, @value{GDBN} provides support for debugging programs that
2928 create additional processes using the @code{fork} or @code{vfork} functions.
2929 Currently, the only platforms with this feature are HP-UX (11.x and later
2930 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2932 By default, when a program forks, @value{GDBN} will continue to debug
2933 the parent process and the child process will run unimpeded.
2935 If you want to follow the child process instead of the parent process,
2936 use the command @w{@code{set follow-fork-mode}}.
2939 @kindex set follow-fork-mode
2940 @item set follow-fork-mode @var{mode}
2941 Set the debugger response to a program call of @code{fork} or
2942 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2943 process. The @var{mode} argument can be:
2947 The original process is debugged after a fork. The child process runs
2948 unimpeded. This is the default.
2951 The new process is debugged after a fork. The parent process runs
2956 @kindex show follow-fork-mode
2957 @item show follow-fork-mode
2958 Display the current debugger response to a @code{fork} or @code{vfork} call.
2961 @cindex debugging multiple processes
2962 On Linux, if you want to debug both the parent and child processes, use the
2963 command @w{@code{set detach-on-fork}}.
2966 @kindex set detach-on-fork
2967 @item set detach-on-fork @var{mode}
2968 Tells gdb whether to detach one of the processes after a fork, or
2969 retain debugger control over them both.
2973 The child process (or parent process, depending on the value of
2974 @code{follow-fork-mode}) will be detached and allowed to run
2975 independently. This is the default.
2978 Both processes will be held under the control of @value{GDBN}.
2979 One process (child or parent, depending on the value of
2980 @code{follow-fork-mode}) is debugged as usual, while the other
2985 @kindex show detach-on-fork
2986 @item show detach-on-fork
2987 Show whether detach-on-fork mode is on/off.
2990 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2991 will retain control of all forked processes (including nested forks).
2992 You can list the forked processes under the control of @value{GDBN} by
2993 using the @w{@code{info inferiors}} command, and switch from one fork
2994 to another by using the @code{inferior} command (@pxref{Inferiors and
2995 Programs, ,Debugging Multiple Inferiors and Programs}).
2997 To quit debugging one of the forked processes, you can either detach
2998 from it by using the @w{@code{detach inferiors}} command (allowing it
2999 to run independently), or kill it using the @w{@code{kill inferiors}}
3000 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3003 If you ask to debug a child process and a @code{vfork} is followed by an
3004 @code{exec}, @value{GDBN} executes the new target up to the first
3005 breakpoint in the new target. If you have a breakpoint set on
3006 @code{main} in your original program, the breakpoint will also be set on
3007 the child process's @code{main}.
3009 On some systems, when a child process is spawned by @code{vfork}, you
3010 cannot debug the child or parent until an @code{exec} call completes.
3012 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3013 call executes, the new target restarts. To restart the parent
3014 process, use the @code{file} command with the parent executable name
3015 as its argument. By default, after an @code{exec} call executes,
3016 @value{GDBN} discards the symbols of the previous executable image.
3017 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3021 @kindex set follow-exec-mode
3022 @item set follow-exec-mode @var{mode}
3024 Set debugger response to a program call of @code{exec}. An
3025 @code{exec} call replaces the program image of a process.
3027 @code{follow-exec-mode} can be:
3031 @value{GDBN} creates a new inferior and rebinds the process to this
3032 new inferior. The program the process was running before the
3033 @code{exec} call can be restarted afterwards by restarting the
3039 (@value{GDBP}) info inferiors
3041 Id Description Executable
3044 process 12020 is executing new program: prog2
3045 Program exited normally.
3046 (@value{GDBP}) info inferiors
3047 Id Description Executable
3053 @value{GDBN} keeps the process bound to the same inferior. The new
3054 executable image replaces the previous executable loaded in the
3055 inferior. Restarting the inferior after the @code{exec} call, with
3056 e.g., the @code{run} command, restarts the executable the process was
3057 running after the @code{exec} call. This is the default mode.
3062 (@value{GDBP}) info inferiors
3063 Id Description Executable
3066 process 12020 is executing new program: prog2
3067 Program exited normally.
3068 (@value{GDBP}) info inferiors
3069 Id Description Executable
3076 You can use the @code{catch} command to make @value{GDBN} stop whenever
3077 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3078 Catchpoints, ,Setting Catchpoints}.
3080 @node Checkpoint/Restart
3081 @section Setting a @emph{Bookmark} to Return to Later
3086 @cindex snapshot of a process
3087 @cindex rewind program state
3089 On certain operating systems@footnote{Currently, only
3090 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3091 program's state, called a @dfn{checkpoint}, and come back to it
3094 Returning to a checkpoint effectively undoes everything that has
3095 happened in the program since the @code{checkpoint} was saved. This
3096 includes changes in memory, registers, and even (within some limits)
3097 system state. Effectively, it is like going back in time to the
3098 moment when the checkpoint was saved.
3100 Thus, if you're stepping thru a program and you think you're
3101 getting close to the point where things go wrong, you can save
3102 a checkpoint. Then, if you accidentally go too far and miss
3103 the critical statement, instead of having to restart your program
3104 from the beginning, you can just go back to the checkpoint and
3105 start again from there.
3107 This can be especially useful if it takes a lot of time or
3108 steps to reach the point where you think the bug occurs.
3110 To use the @code{checkpoint}/@code{restart} method of debugging:
3115 Save a snapshot of the debugged program's current execution state.
3116 The @code{checkpoint} command takes no arguments, but each checkpoint
3117 is assigned a small integer id, similar to a breakpoint id.
3119 @kindex info checkpoints
3120 @item info checkpoints
3121 List the checkpoints that have been saved in the current debugging
3122 session. For each checkpoint, the following information will be
3129 @item Source line, or label
3132 @kindex restart @var{checkpoint-id}
3133 @item restart @var{checkpoint-id}
3134 Restore the program state that was saved as checkpoint number
3135 @var{checkpoint-id}. All program variables, registers, stack frames
3136 etc.@: will be returned to the values that they had when the checkpoint
3137 was saved. In essence, gdb will ``wind back the clock'' to the point
3138 in time when the checkpoint was saved.
3140 Note that breakpoints, @value{GDBN} variables, command history etc.
3141 are not affected by restoring a checkpoint. In general, a checkpoint
3142 only restores things that reside in the program being debugged, not in
3145 @kindex delete checkpoint @var{checkpoint-id}
3146 @item delete checkpoint @var{checkpoint-id}
3147 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3151 Returning to a previously saved checkpoint will restore the user state
3152 of the program being debugged, plus a significant subset of the system
3153 (OS) state, including file pointers. It won't ``un-write'' data from
3154 a file, but it will rewind the file pointer to the previous location,
3155 so that the previously written data can be overwritten. For files
3156 opened in read mode, the pointer will also be restored so that the
3157 previously read data can be read again.
3159 Of course, characters that have been sent to a printer (or other
3160 external device) cannot be ``snatched back'', and characters received
3161 from eg.@: a serial device can be removed from internal program buffers,
3162 but they cannot be ``pushed back'' into the serial pipeline, ready to
3163 be received again. Similarly, the actual contents of files that have
3164 been changed cannot be restored (at this time).
3166 However, within those constraints, you actually can ``rewind'' your
3167 program to a previously saved point in time, and begin debugging it
3168 again --- and you can change the course of events so as to debug a
3169 different execution path this time.
3171 @cindex checkpoints and process id
3172 Finally, there is one bit of internal program state that will be
3173 different when you return to a checkpoint --- the program's process
3174 id. Each checkpoint will have a unique process id (or @var{pid}),
3175 and each will be different from the program's original @var{pid}.
3176 If your program has saved a local copy of its process id, this could
3177 potentially pose a problem.
3179 @subsection A Non-obvious Benefit of Using Checkpoints
3181 On some systems such as @sc{gnu}/Linux, address space randomization
3182 is performed on new processes for security reasons. This makes it
3183 difficult or impossible to set a breakpoint, or watchpoint, on an
3184 absolute address if you have to restart the program, since the
3185 absolute location of a symbol will change from one execution to the
3188 A checkpoint, however, is an @emph{identical} copy of a process.
3189 Therefore if you create a checkpoint at (eg.@:) the start of main,
3190 and simply return to that checkpoint instead of restarting the
3191 process, you can avoid the effects of address randomization and
3192 your symbols will all stay in the same place.
3195 @chapter Stopping and Continuing
3197 The principal purposes of using a debugger are so that you can stop your
3198 program before it terminates; or so that, if your program runs into
3199 trouble, you can investigate and find out why.
3201 Inside @value{GDBN}, your program may stop for any of several reasons,
3202 such as a signal, a breakpoint, or reaching a new line after a
3203 @value{GDBN} command such as @code{step}. You may then examine and
3204 change variables, set new breakpoints or remove old ones, and then
3205 continue execution. Usually, the messages shown by @value{GDBN} provide
3206 ample explanation of the status of your program---but you can also
3207 explicitly request this information at any time.
3210 @kindex info program
3212 Display information about the status of your program: whether it is
3213 running or not, what process it is, and why it stopped.
3217 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3218 * Continuing and Stepping:: Resuming execution
3220 * Thread Stops:: Stopping and starting multi-thread programs
3224 @section Breakpoints, Watchpoints, and Catchpoints
3227 A @dfn{breakpoint} makes your program stop whenever a certain point in
3228 the program is reached. For each breakpoint, you can add conditions to
3229 control in finer detail whether your program stops. You can set
3230 breakpoints with the @code{break} command and its variants (@pxref{Set
3231 Breaks, ,Setting Breakpoints}), to specify the place where your program
3232 should stop by line number, function name or exact address in the
3235 On some systems, you can set breakpoints in shared libraries before
3236 the executable is run. There is a minor limitation on HP-UX systems:
3237 you must wait until the executable is run in order to set breakpoints
3238 in shared library routines that are not called directly by the program
3239 (for example, routines that are arguments in a @code{pthread_create}
3243 @cindex data breakpoints
3244 @cindex memory tracing
3245 @cindex breakpoint on memory address
3246 @cindex breakpoint on variable modification
3247 A @dfn{watchpoint} is a special breakpoint that stops your program
3248 when the value of an expression changes. The expression may be a value
3249 of a variable, or it could involve values of one or more variables
3250 combined by operators, such as @samp{a + b}. This is sometimes called
3251 @dfn{data breakpoints}. You must use a different command to set
3252 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3253 from that, you can manage a watchpoint like any other breakpoint: you
3254 enable, disable, and delete both breakpoints and watchpoints using the
3257 You can arrange to have values from your program displayed automatically
3258 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3262 @cindex breakpoint on events
3263 A @dfn{catchpoint} is another special breakpoint that stops your program
3264 when a certain kind of event occurs, such as the throwing of a C@t{++}
3265 exception or the loading of a library. As with watchpoints, you use a
3266 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3267 Catchpoints}), but aside from that, you can manage a catchpoint like any
3268 other breakpoint. (To stop when your program receives a signal, use the
3269 @code{handle} command; see @ref{Signals, ,Signals}.)
3271 @cindex breakpoint numbers
3272 @cindex numbers for breakpoints
3273 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3274 catchpoint when you create it; these numbers are successive integers
3275 starting with one. In many of the commands for controlling various
3276 features of breakpoints you use the breakpoint number to say which
3277 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3278 @dfn{disabled}; if disabled, it has no effect on your program until you
3281 @cindex breakpoint ranges
3282 @cindex ranges of breakpoints
3283 Some @value{GDBN} commands accept a range of breakpoints on which to
3284 operate. A breakpoint range is either a single breakpoint number, like
3285 @samp{5}, or two such numbers, in increasing order, separated by a
3286 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3287 all breakpoints in that range are operated on.
3290 * Set Breaks:: Setting breakpoints
3291 * Set Watchpoints:: Setting watchpoints
3292 * Set Catchpoints:: Setting catchpoints
3293 * Delete Breaks:: Deleting breakpoints
3294 * Disabling:: Disabling breakpoints
3295 * Conditions:: Break conditions
3296 * Break Commands:: Breakpoint command lists
3297 * Save Breakpoints:: How to save breakpoints in a file
3298 * Error in Breakpoints:: ``Cannot insert breakpoints''
3299 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3303 @subsection Setting Breakpoints
3305 @c FIXME LMB what does GDB do if no code on line of breakpt?
3306 @c consider in particular declaration with/without initialization.
3308 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3311 @kindex b @r{(@code{break})}
3312 @vindex $bpnum@r{, convenience variable}
3313 @cindex latest breakpoint
3314 Breakpoints are set with the @code{break} command (abbreviated
3315 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3316 number of the breakpoint you've set most recently; see @ref{Convenience
3317 Vars,, Convenience Variables}, for a discussion of what you can do with
3318 convenience variables.
3321 @item break @var{location}
3322 Set a breakpoint at the given @var{location}, which can specify a
3323 function name, a line number, or an address of an instruction.
3324 (@xref{Specify Location}, for a list of all the possible ways to
3325 specify a @var{location}.) The breakpoint will stop your program just
3326 before it executes any of the code in the specified @var{location}.
3328 When using source languages that permit overloading of symbols, such as
3329 C@t{++}, a function name may refer to more than one possible place to break.
3330 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3333 It is also possible to insert a breakpoint that will stop the program
3334 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3335 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3338 When called without any arguments, @code{break} sets a breakpoint at
3339 the next instruction to be executed in the selected stack frame
3340 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3341 innermost, this makes your program stop as soon as control
3342 returns to that frame. This is similar to the effect of a
3343 @code{finish} command in the frame inside the selected frame---except
3344 that @code{finish} does not leave an active breakpoint. If you use
3345 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3346 the next time it reaches the current location; this may be useful
3349 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3350 least one instruction has been executed. If it did not do this, you
3351 would be unable to proceed past a breakpoint without first disabling the
3352 breakpoint. This rule applies whether or not the breakpoint already
3353 existed when your program stopped.
3355 @item break @dots{} if @var{cond}
3356 Set a breakpoint with condition @var{cond}; evaluate the expression
3357 @var{cond} each time the breakpoint is reached, and stop only if the
3358 value is nonzero---that is, if @var{cond} evaluates as true.
3359 @samp{@dots{}} stands for one of the possible arguments described
3360 above (or no argument) specifying where to break. @xref{Conditions,
3361 ,Break Conditions}, for more information on breakpoint conditions.
3364 @item tbreak @var{args}
3365 Set a breakpoint enabled only for one stop. @var{args} are the
3366 same as for the @code{break} command, and the breakpoint is set in the same
3367 way, but the breakpoint is automatically deleted after the first time your
3368 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3371 @cindex hardware breakpoints
3372 @item hbreak @var{args}
3373 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3374 @code{break} command and the breakpoint is set in the same way, but the
3375 breakpoint requires hardware support and some target hardware may not
3376 have this support. The main purpose of this is EPROM/ROM code
3377 debugging, so you can set a breakpoint at an instruction without
3378 changing the instruction. This can be used with the new trap-generation
3379 provided by SPARClite DSU and most x86-based targets. These targets
3380 will generate traps when a program accesses some data or instruction
3381 address that is assigned to the debug registers. However the hardware
3382 breakpoint registers can take a limited number of breakpoints. For
3383 example, on the DSU, only two data breakpoints can be set at a time, and
3384 @value{GDBN} will reject this command if more than two are used. Delete
3385 or disable unused hardware breakpoints before setting new ones
3386 (@pxref{Disabling, ,Disabling Breakpoints}).
3387 @xref{Conditions, ,Break Conditions}.
3388 For remote targets, you can restrict the number of hardware
3389 breakpoints @value{GDBN} will use, see @ref{set remote
3390 hardware-breakpoint-limit}.
3393 @item thbreak @var{args}
3394 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3395 are the same as for the @code{hbreak} command and the breakpoint is set in
3396 the same way. However, like the @code{tbreak} command,
3397 the breakpoint is automatically deleted after the
3398 first time your program stops there. Also, like the @code{hbreak}
3399 command, the breakpoint requires hardware support and some target hardware
3400 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3401 See also @ref{Conditions, ,Break Conditions}.
3404 @cindex regular expression
3405 @cindex breakpoints at functions matching a regexp
3406 @cindex set breakpoints in many functions
3407 @item rbreak @var{regex}
3408 Set breakpoints on all functions matching the regular expression
3409 @var{regex}. This command sets an unconditional breakpoint on all
3410 matches, printing a list of all breakpoints it set. Once these
3411 breakpoints are set, they are treated just like the breakpoints set with
3412 the @code{break} command. You can delete them, disable them, or make
3413 them conditional the same way as any other breakpoint.
3415 The syntax of the regular expression is the standard one used with tools
3416 like @file{grep}. Note that this is different from the syntax used by
3417 shells, so for instance @code{foo*} matches all functions that include
3418 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3419 @code{.*} leading and trailing the regular expression you supply, so to
3420 match only functions that begin with @code{foo}, use @code{^foo}.
3422 @cindex non-member C@t{++} functions, set breakpoint in
3423 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3424 breakpoints on overloaded functions that are not members of any special
3427 @cindex set breakpoints on all functions
3428 The @code{rbreak} command can be used to set breakpoints in
3429 @strong{all} the functions in a program, like this:
3432 (@value{GDBP}) rbreak .
3435 @item rbreak @var{file}:@var{regex}
3436 If @code{rbreak} is called with a filename qualification, it limits
3437 the search for functions matching the given regular expression to the
3438 specified @var{file}. This can be used, for example, to set breakpoints on
3439 every function in a given file:
3442 (@value{GDBP}) rbreak file.c:.
3445 The colon separating the filename qualifier from the regex may
3446 optionally be surrounded by spaces.
3448 @kindex info breakpoints
3449 @cindex @code{$_} and @code{info breakpoints}
3450 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3451 @itemx info break @r{[}@var{n}@dots{}@r{]}
3452 Print a table of all breakpoints, watchpoints, and catchpoints set and
3453 not deleted. Optional argument @var{n} means print information only
3454 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3455 For each breakpoint, following columns are printed:
3458 @item Breakpoint Numbers
3460 Breakpoint, watchpoint, or catchpoint.
3462 Whether the breakpoint is marked to be disabled or deleted when hit.
3463 @item Enabled or Disabled
3464 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3465 that are not enabled.
3467 Where the breakpoint is in your program, as a memory address. For a
3468 pending breakpoint whose address is not yet known, this field will
3469 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3470 library that has the symbol or line referred by breakpoint is loaded.
3471 See below for details. A breakpoint with several locations will
3472 have @samp{<MULTIPLE>} in this field---see below for details.
3474 Where the breakpoint is in the source for your program, as a file and
3475 line number. For a pending breakpoint, the original string passed to
3476 the breakpoint command will be listed as it cannot be resolved until
3477 the appropriate shared library is loaded in the future.
3481 If a breakpoint is conditional, @code{info break} shows the condition on
3482 the line following the affected breakpoint; breakpoint commands, if any,
3483 are listed after that. A pending breakpoint is allowed to have a condition
3484 specified for it. The condition is not parsed for validity until a shared
3485 library is loaded that allows the pending breakpoint to resolve to a
3489 @code{info break} with a breakpoint
3490 number @var{n} as argument lists only that breakpoint. The
3491 convenience variable @code{$_} and the default examining-address for
3492 the @code{x} command are set to the address of the last breakpoint
3493 listed (@pxref{Memory, ,Examining Memory}).
3496 @code{info break} displays a count of the number of times the breakpoint
3497 has been hit. This is especially useful in conjunction with the
3498 @code{ignore} command. You can ignore a large number of breakpoint
3499 hits, look at the breakpoint info to see how many times the breakpoint
3500 was hit, and then run again, ignoring one less than that number. This
3501 will get you quickly to the last hit of that breakpoint.
3504 @value{GDBN} allows you to set any number of breakpoints at the same place in
3505 your program. There is nothing silly or meaningless about this. When
3506 the breakpoints are conditional, this is even useful
3507 (@pxref{Conditions, ,Break Conditions}).
3509 @cindex multiple locations, breakpoints
3510 @cindex breakpoints, multiple locations
3511 It is possible that a breakpoint corresponds to several locations
3512 in your program. Examples of this situation are:
3516 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3517 instances of the function body, used in different cases.
3520 For a C@t{++} template function, a given line in the function can
3521 correspond to any number of instantiations.
3524 For an inlined function, a given source line can correspond to
3525 several places where that function is inlined.
3528 In all those cases, @value{GDBN} will insert a breakpoint at all
3529 the relevant locations@footnote{
3530 As of this writing, multiple-location breakpoints work only if there's
3531 line number information for all the locations. This means that they
3532 will generally not work in system libraries, unless you have debug
3533 info with line numbers for them.}.
3535 A breakpoint with multiple locations is displayed in the breakpoint
3536 table using several rows---one header row, followed by one row for
3537 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3538 address column. The rows for individual locations contain the actual
3539 addresses for locations, and show the functions to which those
3540 locations belong. The number column for a location is of the form
3541 @var{breakpoint-number}.@var{location-number}.
3546 Num Type Disp Enb Address What
3547 1 breakpoint keep y <MULTIPLE>
3549 breakpoint already hit 1 time
3550 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3551 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3554 Each location can be individually enabled or disabled by passing
3555 @var{breakpoint-number}.@var{location-number} as argument to the
3556 @code{enable} and @code{disable} commands. Note that you cannot
3557 delete the individual locations from the list, you can only delete the
3558 entire list of locations that belong to their parent breakpoint (with
3559 the @kbd{delete @var{num}} command, where @var{num} is the number of
3560 the parent breakpoint, 1 in the above example). Disabling or enabling
3561 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3562 that belong to that breakpoint.
3564 @cindex pending breakpoints
3565 It's quite common to have a breakpoint inside a shared library.
3566 Shared libraries can be loaded and unloaded explicitly,
3567 and possibly repeatedly, as the program is executed. To support
3568 this use case, @value{GDBN} updates breakpoint locations whenever
3569 any shared library is loaded or unloaded. Typically, you would
3570 set a breakpoint in a shared library at the beginning of your
3571 debugging session, when the library is not loaded, and when the
3572 symbols from the library are not available. When you try to set
3573 breakpoint, @value{GDBN} will ask you if you want to set
3574 a so called @dfn{pending breakpoint}---breakpoint whose address
3575 is not yet resolved.
3577 After the program is run, whenever a new shared library is loaded,
3578 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3579 shared library contains the symbol or line referred to by some
3580 pending breakpoint, that breakpoint is resolved and becomes an
3581 ordinary breakpoint. When a library is unloaded, all breakpoints
3582 that refer to its symbols or source lines become pending again.
3584 This logic works for breakpoints with multiple locations, too. For
3585 example, if you have a breakpoint in a C@t{++} template function, and
3586 a newly loaded shared library has an instantiation of that template,
3587 a new location is added to the list of locations for the breakpoint.
3589 Except for having unresolved address, pending breakpoints do not
3590 differ from regular breakpoints. You can set conditions or commands,
3591 enable and disable them and perform other breakpoint operations.
3593 @value{GDBN} provides some additional commands for controlling what
3594 happens when the @samp{break} command cannot resolve breakpoint
3595 address specification to an address:
3597 @kindex set breakpoint pending
3598 @kindex show breakpoint pending
3600 @item set breakpoint pending auto
3601 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3602 location, it queries you whether a pending breakpoint should be created.
3604 @item set breakpoint pending on
3605 This indicates that an unrecognized breakpoint location should automatically
3606 result in a pending breakpoint being created.
3608 @item set breakpoint pending off
3609 This indicates that pending breakpoints are not to be created. Any
3610 unrecognized breakpoint location results in an error. This setting does
3611 not affect any pending breakpoints previously created.
3613 @item show breakpoint pending
3614 Show the current behavior setting for creating pending breakpoints.
3617 The settings above only affect the @code{break} command and its
3618 variants. Once breakpoint is set, it will be automatically updated
3619 as shared libraries are loaded and unloaded.
3621 @cindex automatic hardware breakpoints
3622 For some targets, @value{GDBN} can automatically decide if hardware or
3623 software breakpoints should be used, depending on whether the
3624 breakpoint address is read-only or read-write. This applies to
3625 breakpoints set with the @code{break} command as well as to internal
3626 breakpoints set by commands like @code{next} and @code{finish}. For
3627 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3630 You can control this automatic behaviour with the following commands::
3632 @kindex set breakpoint auto-hw
3633 @kindex show breakpoint auto-hw
3635 @item set breakpoint auto-hw on
3636 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3637 will try to use the target memory map to decide if software or hardware
3638 breakpoint must be used.
3640 @item set breakpoint auto-hw off
3641 This indicates @value{GDBN} should not automatically select breakpoint
3642 type. If the target provides a memory map, @value{GDBN} will warn when
3643 trying to set software breakpoint at a read-only address.
3646 @value{GDBN} normally implements breakpoints by replacing the program code
3647 at the breakpoint address with a special instruction, which, when
3648 executed, given control to the debugger. By default, the program
3649 code is so modified only when the program is resumed. As soon as
3650 the program stops, @value{GDBN} restores the original instructions. This
3651 behaviour guards against leaving breakpoints inserted in the
3652 target should gdb abrubptly disconnect. However, with slow remote
3653 targets, inserting and removing breakpoint can reduce the performance.
3654 This behavior can be controlled with the following commands::
3656 @kindex set breakpoint always-inserted
3657 @kindex show breakpoint always-inserted
3659 @item set breakpoint always-inserted off
3660 All breakpoints, including newly added by the user, are inserted in
3661 the target only when the target is resumed. All breakpoints are
3662 removed from the target when it stops.
3664 @item set breakpoint always-inserted on
3665 Causes all breakpoints to be inserted in the target at all times. If
3666 the user adds a new breakpoint, or changes an existing breakpoint, the
3667 breakpoints in the target are updated immediately. A breakpoint is
3668 removed from the target only when breakpoint itself is removed.
3670 @cindex non-stop mode, and @code{breakpoint always-inserted}
3671 @item set breakpoint always-inserted auto
3672 This is the default mode. If @value{GDBN} is controlling the inferior
3673 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3674 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3675 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3676 @code{breakpoint always-inserted} mode is off.
3679 @cindex negative breakpoint numbers
3680 @cindex internal @value{GDBN} breakpoints
3681 @value{GDBN} itself sometimes sets breakpoints in your program for
3682 special purposes, such as proper handling of @code{longjmp} (in C
3683 programs). These internal breakpoints are assigned negative numbers,
3684 starting with @code{-1}; @samp{info breakpoints} does not display them.
3685 You can see these breakpoints with the @value{GDBN} maintenance command
3686 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3689 @node Set Watchpoints
3690 @subsection Setting Watchpoints
3692 @cindex setting watchpoints
3693 You can use a watchpoint to stop execution whenever the value of an
3694 expression changes, without having to predict a particular place where
3695 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3696 The expression may be as simple as the value of a single variable, or
3697 as complex as many variables combined by operators. Examples include:
3701 A reference to the value of a single variable.
3704 An address cast to an appropriate data type. For example,
3705 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3706 address (assuming an @code{int} occupies 4 bytes).
3709 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3710 expression can use any operators valid in the program's native
3711 language (@pxref{Languages}).
3714 You can set a watchpoint on an expression even if the expression can
3715 not be evaluated yet. For instance, you can set a watchpoint on
3716 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3717 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3718 the expression produces a valid value. If the expression becomes
3719 valid in some other way than changing a variable (e.g.@: if the memory
3720 pointed to by @samp{*global_ptr} becomes readable as the result of a
3721 @code{malloc} call), @value{GDBN} may not stop until the next time
3722 the expression changes.
3724 @cindex software watchpoints
3725 @cindex hardware watchpoints
3726 Depending on your system, watchpoints may be implemented in software or
3727 hardware. @value{GDBN} does software watchpointing by single-stepping your
3728 program and testing the variable's value each time, which is hundreds of
3729 times slower than normal execution. (But this may still be worth it, to
3730 catch errors where you have no clue what part of your program is the
3733 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3734 x86-based targets, @value{GDBN} includes support for hardware
3735 watchpoints, which do not slow down the running of your program.
3739 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3740 Set a watchpoint for an expression. @value{GDBN} will break when the
3741 expression @var{expr} is written into by the program and its value
3742 changes. The simplest (and the most popular) use of this command is
3743 to watch the value of a single variable:
3746 (@value{GDBP}) watch foo
3749 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3750 argument, @value{GDBN} breaks only when the thread identified by
3751 @var{threadnum} changes the value of @var{expr}. If any other threads
3752 change the value of @var{expr}, @value{GDBN} will not break. Note
3753 that watchpoints restricted to a single thread in this way only work
3754 with Hardware Watchpoints.
3756 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3757 (see below). The @code{-location} argument tells @value{GDBN} to
3758 instead watch the memory referred to by @var{expr}. In this case,
3759 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3760 and watch the memory at that address. The type of the result is used
3761 to determine the size of the watched memory. If the expression's
3762 result does not have an address, then @value{GDBN} will print an
3765 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3766 of masked watchpoints, if the current architecture supports this
3767 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3768 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3769 to an address to watch. The mask specifies that some bits of an address
3770 (the bits which are reset in the mask) should be ignored when matching
3771 the address accessed by the inferior against the watchpoint address.
3772 Thus, a masked watchpoint watches many addresses simultaneously---those
3773 addresses whose unmasked bits are identical to the unmasked bits in the
3774 watchpoint address. The @code{mask} argument implies @code{-location}.
3778 (@value{GDBP}) watch foo mask 0xffff00ff
3779 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3783 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3784 Set a watchpoint that will break when the value of @var{expr} is read
3788 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3789 Set a watchpoint that will break when @var{expr} is either read from
3790 or written into by the program.
3792 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3793 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3794 This command prints a list of watchpoints, using the same format as
3795 @code{info break} (@pxref{Set Breaks}).
3798 If you watch for a change in a numerically entered address you need to
3799 dereference it, as the address itself is just a constant number which will
3800 never change. @value{GDBN} refuses to create a watchpoint that watches
3801 a never-changing value:
3804 (@value{GDBP}) watch 0x600850
3805 Cannot watch constant value 0x600850.
3806 (@value{GDBP}) watch *(int *) 0x600850
3807 Watchpoint 1: *(int *) 6293584
3810 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3811 watchpoints execute very quickly, and the debugger reports a change in
3812 value at the exact instruction where the change occurs. If @value{GDBN}
3813 cannot set a hardware watchpoint, it sets a software watchpoint, which
3814 executes more slowly and reports the change in value at the next
3815 @emph{statement}, not the instruction, after the change occurs.
3817 @cindex use only software watchpoints
3818 You can force @value{GDBN} to use only software watchpoints with the
3819 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3820 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3821 the underlying system supports them. (Note that hardware-assisted
3822 watchpoints that were set @emph{before} setting
3823 @code{can-use-hw-watchpoints} to zero will still use the hardware
3824 mechanism of watching expression values.)
3827 @item set can-use-hw-watchpoints
3828 @kindex set can-use-hw-watchpoints
3829 Set whether or not to use hardware watchpoints.
3831 @item show can-use-hw-watchpoints
3832 @kindex show can-use-hw-watchpoints
3833 Show the current mode of using hardware watchpoints.
3836 For remote targets, you can restrict the number of hardware
3837 watchpoints @value{GDBN} will use, see @ref{set remote
3838 hardware-breakpoint-limit}.
3840 When you issue the @code{watch} command, @value{GDBN} reports
3843 Hardware watchpoint @var{num}: @var{expr}
3847 if it was able to set a hardware watchpoint.
3849 Currently, the @code{awatch} and @code{rwatch} commands can only set
3850 hardware watchpoints, because accesses to data that don't change the
3851 value of the watched expression cannot be detected without examining
3852 every instruction as it is being executed, and @value{GDBN} does not do
3853 that currently. If @value{GDBN} finds that it is unable to set a
3854 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3855 will print a message like this:
3858 Expression cannot be implemented with read/access watchpoint.
3861 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3862 data type of the watched expression is wider than what a hardware
3863 watchpoint on the target machine can handle. For example, some systems
3864 can only watch regions that are up to 4 bytes wide; on such systems you
3865 cannot set hardware watchpoints for an expression that yields a
3866 double-precision floating-point number (which is typically 8 bytes
3867 wide). As a work-around, it might be possible to break the large region
3868 into a series of smaller ones and watch them with separate watchpoints.
3870 If you set too many hardware watchpoints, @value{GDBN} might be unable
3871 to insert all of them when you resume the execution of your program.
3872 Since the precise number of active watchpoints is unknown until such
3873 time as the program is about to be resumed, @value{GDBN} might not be
3874 able to warn you about this when you set the watchpoints, and the
3875 warning will be printed only when the program is resumed:
3878 Hardware watchpoint @var{num}: Could not insert watchpoint
3882 If this happens, delete or disable some of the watchpoints.
3884 Watching complex expressions that reference many variables can also
3885 exhaust the resources available for hardware-assisted watchpoints.
3886 That's because @value{GDBN} needs to watch every variable in the
3887 expression with separately allocated resources.
3889 If you call a function interactively using @code{print} or @code{call},
3890 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3891 kind of breakpoint or the call completes.
3893 @value{GDBN} automatically deletes watchpoints that watch local
3894 (automatic) variables, or expressions that involve such variables, when
3895 they go out of scope, that is, when the execution leaves the block in
3896 which these variables were defined. In particular, when the program
3897 being debugged terminates, @emph{all} local variables go out of scope,
3898 and so only watchpoints that watch global variables remain set. If you
3899 rerun the program, you will need to set all such watchpoints again. One
3900 way of doing that would be to set a code breakpoint at the entry to the
3901 @code{main} function and when it breaks, set all the watchpoints.
3903 @cindex watchpoints and threads
3904 @cindex threads and watchpoints
3905 In multi-threaded programs, watchpoints will detect changes to the
3906 watched expression from every thread.
3909 @emph{Warning:} In multi-threaded programs, software watchpoints
3910 have only limited usefulness. If @value{GDBN} creates a software
3911 watchpoint, it can only watch the value of an expression @emph{in a
3912 single thread}. If you are confident that the expression can only
3913 change due to the current thread's activity (and if you are also
3914 confident that no other thread can become current), then you can use
3915 software watchpoints as usual. However, @value{GDBN} may not notice
3916 when a non-current thread's activity changes the expression. (Hardware
3917 watchpoints, in contrast, watch an expression in all threads.)
3920 @xref{set remote hardware-watchpoint-limit}.
3922 @node Set Catchpoints
3923 @subsection Setting Catchpoints
3924 @cindex catchpoints, setting
3925 @cindex exception handlers
3926 @cindex event handling
3928 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3929 kinds of program events, such as C@t{++} exceptions or the loading of a
3930 shared library. Use the @code{catch} command to set a catchpoint.
3934 @item catch @var{event}
3935 Stop when @var{event} occurs. @var{event} can be any of the following:
3938 @cindex stop on C@t{++} exceptions
3939 The throwing of a C@t{++} exception.
3942 The catching of a C@t{++} exception.
3945 @cindex Ada exception catching
3946 @cindex catch Ada exceptions
3947 An Ada exception being raised. If an exception name is specified
3948 at the end of the command (eg @code{catch exception Program_Error}),
3949 the debugger will stop only when this specific exception is raised.
3950 Otherwise, the debugger stops execution when any Ada exception is raised.
3952 When inserting an exception catchpoint on a user-defined exception whose
3953 name is identical to one of the exceptions defined by the language, the
3954 fully qualified name must be used as the exception name. Otherwise,
3955 @value{GDBN} will assume that it should stop on the pre-defined exception
3956 rather than the user-defined one. For instance, assuming an exception
3957 called @code{Constraint_Error} is defined in package @code{Pck}, then
3958 the command to use to catch such exceptions is @kbd{catch exception
3959 Pck.Constraint_Error}.
3961 @item exception unhandled
3962 An exception that was raised but is not handled by the program.
3965 A failed Ada assertion.
3968 @cindex break on fork/exec
3969 A call to @code{exec}. This is currently only available for HP-UX
3973 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3974 @cindex break on a system call.
3975 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3976 syscall is a mechanism for application programs to request a service
3977 from the operating system (OS) or one of the OS system services.
3978 @value{GDBN} can catch some or all of the syscalls issued by the
3979 debuggee, and show the related information for each syscall. If no
3980 argument is specified, calls to and returns from all system calls
3983 @var{name} can be any system call name that is valid for the
3984 underlying OS. Just what syscalls are valid depends on the OS. On
3985 GNU and Unix systems, you can find the full list of valid syscall
3986 names on @file{/usr/include/asm/unistd.h}.
3988 @c For MS-Windows, the syscall names and the corresponding numbers
3989 @c can be found, e.g., on this URL:
3990 @c http://www.metasploit.com/users/opcode/syscalls.html
3991 @c but we don't support Windows syscalls yet.
3993 Normally, @value{GDBN} knows in advance which syscalls are valid for
3994 each OS, so you can use the @value{GDBN} command-line completion
3995 facilities (@pxref{Completion,, command completion}) to list the
3998 You may also specify the system call numerically. A syscall's
3999 number is the value passed to the OS's syscall dispatcher to
4000 identify the requested service. When you specify the syscall by its
4001 name, @value{GDBN} uses its database of syscalls to convert the name
4002 into the corresponding numeric code, but using the number directly
4003 may be useful if @value{GDBN}'s database does not have the complete
4004 list of syscalls on your system (e.g., because @value{GDBN} lags
4005 behind the OS upgrades).
4007 The example below illustrates how this command works if you don't provide
4011 (@value{GDBP}) catch syscall
4012 Catchpoint 1 (syscall)
4014 Starting program: /tmp/catch-syscall
4016 Catchpoint 1 (call to syscall 'close'), \
4017 0xffffe424 in __kernel_vsyscall ()
4021 Catchpoint 1 (returned from syscall 'close'), \
4022 0xffffe424 in __kernel_vsyscall ()
4026 Here is an example of catching a system call by name:
4029 (@value{GDBP}) catch syscall chroot
4030 Catchpoint 1 (syscall 'chroot' [61])
4032 Starting program: /tmp/catch-syscall
4034 Catchpoint 1 (call to syscall 'chroot'), \
4035 0xffffe424 in __kernel_vsyscall ()
4039 Catchpoint 1 (returned from syscall 'chroot'), \
4040 0xffffe424 in __kernel_vsyscall ()
4044 An example of specifying a system call numerically. In the case
4045 below, the syscall number has a corresponding entry in the XML
4046 file, so @value{GDBN} finds its name and prints it:
4049 (@value{GDBP}) catch syscall 252
4050 Catchpoint 1 (syscall(s) 'exit_group')
4052 Starting program: /tmp/catch-syscall
4054 Catchpoint 1 (call to syscall 'exit_group'), \
4055 0xffffe424 in __kernel_vsyscall ()
4059 Program exited normally.
4063 However, there can be situations when there is no corresponding name
4064 in XML file for that syscall number. In this case, @value{GDBN} prints
4065 a warning message saying that it was not able to find the syscall name,
4066 but the catchpoint will be set anyway. See the example below:
4069 (@value{GDBP}) catch syscall 764
4070 warning: The number '764' does not represent a known syscall.
4071 Catchpoint 2 (syscall 764)
4075 If you configure @value{GDBN} using the @samp{--without-expat} option,
4076 it will not be able to display syscall names. Also, if your
4077 architecture does not have an XML file describing its system calls,
4078 you will not be able to see the syscall names. It is important to
4079 notice that these two features are used for accessing the syscall
4080 name database. In either case, you will see a warning like this:
4083 (@value{GDBP}) catch syscall
4084 warning: Could not open "syscalls/i386-linux.xml"
4085 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4086 GDB will not be able to display syscall names.
4087 Catchpoint 1 (syscall)
4091 Of course, the file name will change depending on your architecture and system.
4093 Still using the example above, you can also try to catch a syscall by its
4094 number. In this case, you would see something like:
4097 (@value{GDBP}) catch syscall 252
4098 Catchpoint 1 (syscall(s) 252)
4101 Again, in this case @value{GDBN} would not be able to display syscall's names.
4104 A call to @code{fork}. This is currently only available for HP-UX
4108 A call to @code{vfork}. This is currently only available for HP-UX
4113 @item tcatch @var{event}
4114 Set a catchpoint that is enabled only for one stop. The catchpoint is
4115 automatically deleted after the first time the event is caught.
4119 Use the @code{info break} command to list the current catchpoints.
4121 There are currently some limitations to C@t{++} exception handling
4122 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4126 If you call a function interactively, @value{GDBN} normally returns
4127 control to you when the function has finished executing. If the call
4128 raises an exception, however, the call may bypass the mechanism that
4129 returns control to you and cause your program either to abort or to
4130 simply continue running until it hits a breakpoint, catches a signal
4131 that @value{GDBN} is listening for, or exits. This is the case even if
4132 you set a catchpoint for the exception; catchpoints on exceptions are
4133 disabled within interactive calls.
4136 You cannot raise an exception interactively.
4139 You cannot install an exception handler interactively.
4142 @cindex raise exceptions
4143 Sometimes @code{catch} is not the best way to debug exception handling:
4144 if you need to know exactly where an exception is raised, it is better to
4145 stop @emph{before} the exception handler is called, since that way you
4146 can see the stack before any unwinding takes place. If you set a
4147 breakpoint in an exception handler instead, it may not be easy to find
4148 out where the exception was raised.
4150 To stop just before an exception handler is called, you need some
4151 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4152 raised by calling a library function named @code{__raise_exception}
4153 which has the following ANSI C interface:
4156 /* @var{addr} is where the exception identifier is stored.
4157 @var{id} is the exception identifier. */
4158 void __raise_exception (void **addr, void *id);
4162 To make the debugger catch all exceptions before any stack
4163 unwinding takes place, set a breakpoint on @code{__raise_exception}
4164 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4166 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4167 that depends on the value of @var{id}, you can stop your program when
4168 a specific exception is raised. You can use multiple conditional
4169 breakpoints to stop your program when any of a number of exceptions are
4174 @subsection Deleting Breakpoints
4176 @cindex clearing breakpoints, watchpoints, catchpoints
4177 @cindex deleting breakpoints, watchpoints, catchpoints
4178 It is often necessary to eliminate a breakpoint, watchpoint, or
4179 catchpoint once it has done its job and you no longer want your program
4180 to stop there. This is called @dfn{deleting} the breakpoint. A
4181 breakpoint that has been deleted no longer exists; it is forgotten.
4183 With the @code{clear} command you can delete breakpoints according to
4184 where they are in your program. With the @code{delete} command you can
4185 delete individual breakpoints, watchpoints, or catchpoints by specifying
4186 their breakpoint numbers.
4188 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4189 automatically ignores breakpoints on the first instruction to be executed
4190 when you continue execution without changing the execution address.
4195 Delete any breakpoints at the next instruction to be executed in the
4196 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4197 the innermost frame is selected, this is a good way to delete a
4198 breakpoint where your program just stopped.
4200 @item clear @var{location}
4201 Delete any breakpoints set at the specified @var{location}.
4202 @xref{Specify Location}, for the various forms of @var{location}; the
4203 most useful ones are listed below:
4206 @item clear @var{function}
4207 @itemx clear @var{filename}:@var{function}
4208 Delete any breakpoints set at entry to the named @var{function}.
4210 @item clear @var{linenum}
4211 @itemx clear @var{filename}:@var{linenum}
4212 Delete any breakpoints set at or within the code of the specified
4213 @var{linenum} of the specified @var{filename}.
4216 @cindex delete breakpoints
4218 @kindex d @r{(@code{delete})}
4219 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4220 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4221 ranges specified as arguments. If no argument is specified, delete all
4222 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4223 confirm off}). You can abbreviate this command as @code{d}.
4227 @subsection Disabling Breakpoints
4229 @cindex enable/disable a breakpoint
4230 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4231 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4232 it had been deleted, but remembers the information on the breakpoint so
4233 that you can @dfn{enable} it again later.
4235 You disable and enable breakpoints, watchpoints, and catchpoints with
4236 the @code{enable} and @code{disable} commands, optionally specifying
4237 one or more breakpoint numbers as arguments. Use @code{info break} to
4238 print a list of all breakpoints, watchpoints, and catchpoints if you
4239 do not know which numbers to use.
4241 Disabling and enabling a breakpoint that has multiple locations
4242 affects all of its locations.
4244 A breakpoint, watchpoint, or catchpoint can have any of four different
4245 states of enablement:
4249 Enabled. The breakpoint stops your program. A breakpoint set
4250 with the @code{break} command starts out in this state.
4252 Disabled. The breakpoint has no effect on your program.
4254 Enabled once. The breakpoint stops your program, but then becomes
4257 Enabled for deletion. The breakpoint stops your program, but
4258 immediately after it does so it is deleted permanently. A breakpoint
4259 set with the @code{tbreak} command starts out in this state.
4262 You can use the following commands to enable or disable breakpoints,
4263 watchpoints, and catchpoints:
4267 @kindex dis @r{(@code{disable})}
4268 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4269 Disable the specified breakpoints---or all breakpoints, if none are
4270 listed. A disabled breakpoint has no effect but is not forgotten. All
4271 options such as ignore-counts, conditions and commands are remembered in
4272 case the breakpoint is enabled again later. You may abbreviate
4273 @code{disable} as @code{dis}.
4276 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4277 Enable the specified breakpoints (or all defined breakpoints). They
4278 become effective once again in stopping your program.
4280 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4281 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4282 of these breakpoints immediately after stopping your program.
4284 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4285 Enable the specified breakpoints to work once, then die. @value{GDBN}
4286 deletes any of these breakpoints as soon as your program stops there.
4287 Breakpoints set by the @code{tbreak} command start out in this state.
4290 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4291 @c confusing: tbreak is also initially enabled.
4292 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4293 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4294 subsequently, they become disabled or enabled only when you use one of
4295 the commands above. (The command @code{until} can set and delete a
4296 breakpoint of its own, but it does not change the state of your other
4297 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4301 @subsection Break Conditions
4302 @cindex conditional breakpoints
4303 @cindex breakpoint conditions
4305 @c FIXME what is scope of break condition expr? Context where wanted?
4306 @c in particular for a watchpoint?
4307 The simplest sort of breakpoint breaks every time your program reaches a
4308 specified place. You can also specify a @dfn{condition} for a
4309 breakpoint. A condition is just a Boolean expression in your
4310 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4311 a condition evaluates the expression each time your program reaches it,
4312 and your program stops only if the condition is @emph{true}.
4314 This is the converse of using assertions for program validation; in that
4315 situation, you want to stop when the assertion is violated---that is,
4316 when the condition is false. In C, if you want to test an assertion expressed
4317 by the condition @var{assert}, you should set the condition
4318 @samp{! @var{assert}} on the appropriate breakpoint.
4320 Conditions are also accepted for watchpoints; you may not need them,
4321 since a watchpoint is inspecting the value of an expression anyhow---but
4322 it might be simpler, say, to just set a watchpoint on a variable name,
4323 and specify a condition that tests whether the new value is an interesting
4326 Break conditions can have side effects, and may even call functions in
4327 your program. This can be useful, for example, to activate functions
4328 that log program progress, or to use your own print functions to
4329 format special data structures. The effects are completely predictable
4330 unless there is another enabled breakpoint at the same address. (In
4331 that case, @value{GDBN} might see the other breakpoint first and stop your
4332 program without checking the condition of this one.) Note that
4333 breakpoint commands are usually more convenient and flexible than break
4335 purpose of performing side effects when a breakpoint is reached
4336 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4338 Break conditions can be specified when a breakpoint is set, by using
4339 @samp{if} in the arguments to the @code{break} command. @xref{Set
4340 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4341 with the @code{condition} command.
4343 You can also use the @code{if} keyword with the @code{watch} command.
4344 The @code{catch} command does not recognize the @code{if} keyword;
4345 @code{condition} is the only way to impose a further condition on a
4350 @item condition @var{bnum} @var{expression}
4351 Specify @var{expression} as the break condition for breakpoint,
4352 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4353 breakpoint @var{bnum} stops your program only if the value of
4354 @var{expression} is true (nonzero, in C). When you use
4355 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4356 syntactic correctness, and to determine whether symbols in it have
4357 referents in the context of your breakpoint. If @var{expression} uses
4358 symbols not referenced in the context of the breakpoint, @value{GDBN}
4359 prints an error message:
4362 No symbol "foo" in current context.
4367 not actually evaluate @var{expression} at the time the @code{condition}
4368 command (or a command that sets a breakpoint with a condition, like
4369 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4371 @item condition @var{bnum}
4372 Remove the condition from breakpoint number @var{bnum}. It becomes
4373 an ordinary unconditional breakpoint.
4376 @cindex ignore count (of breakpoint)
4377 A special case of a breakpoint condition is to stop only when the
4378 breakpoint has been reached a certain number of times. This is so
4379 useful that there is a special way to do it, using the @dfn{ignore
4380 count} of the breakpoint. Every breakpoint has an ignore count, which
4381 is an integer. Most of the time, the ignore count is zero, and
4382 therefore has no effect. But if your program reaches a breakpoint whose
4383 ignore count is positive, then instead of stopping, it just decrements
4384 the ignore count by one and continues. As a result, if the ignore count
4385 value is @var{n}, the breakpoint does not stop the next @var{n} times
4386 your program reaches it.
4390 @item ignore @var{bnum} @var{count}
4391 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4392 The next @var{count} times the breakpoint is reached, your program's
4393 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4396 To make the breakpoint stop the next time it is reached, specify
4399 When you use @code{continue} to resume execution of your program from a
4400 breakpoint, you can specify an ignore count directly as an argument to
4401 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4402 Stepping,,Continuing and Stepping}.
4404 If a breakpoint has a positive ignore count and a condition, the
4405 condition is not checked. Once the ignore count reaches zero,
4406 @value{GDBN} resumes checking the condition.
4408 You could achieve the effect of the ignore count with a condition such
4409 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4410 is decremented each time. @xref{Convenience Vars, ,Convenience
4414 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4417 @node Break Commands
4418 @subsection Breakpoint Command Lists
4420 @cindex breakpoint commands
4421 You can give any breakpoint (or watchpoint or catchpoint) a series of
4422 commands to execute when your program stops due to that breakpoint. For
4423 example, you might want to print the values of certain expressions, or
4424 enable other breakpoints.
4428 @kindex end@r{ (breakpoint commands)}
4429 @item commands @r{[}@var{range}@dots{}@r{]}
4430 @itemx @dots{} @var{command-list} @dots{}
4432 Specify a list of commands for the given breakpoints. The commands
4433 themselves appear on the following lines. Type a line containing just
4434 @code{end} to terminate the commands.
4436 To remove all commands from a breakpoint, type @code{commands} and
4437 follow it immediately with @code{end}; that is, give no commands.
4439 With no argument, @code{commands} refers to the last breakpoint,
4440 watchpoint, or catchpoint set (not to the breakpoint most recently
4441 encountered). If the most recent breakpoints were set with a single
4442 command, then the @code{commands} will apply to all the breakpoints
4443 set by that command. This applies to breakpoints set by
4444 @code{rbreak}, and also applies when a single @code{break} command
4445 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4449 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4450 disabled within a @var{command-list}.
4452 You can use breakpoint commands to start your program up again. Simply
4453 use the @code{continue} command, or @code{step}, or any other command
4454 that resumes execution.
4456 Any other commands in the command list, after a command that resumes
4457 execution, are ignored. This is because any time you resume execution
4458 (even with a simple @code{next} or @code{step}), you may encounter
4459 another breakpoint---which could have its own command list, leading to
4460 ambiguities about which list to execute.
4463 If the first command you specify in a command list is @code{silent}, the
4464 usual message about stopping at a breakpoint is not printed. This may
4465 be desirable for breakpoints that are to print a specific message and
4466 then continue. If none of the remaining commands print anything, you
4467 see no sign that the breakpoint was reached. @code{silent} is
4468 meaningful only at the beginning of a breakpoint command list.
4470 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4471 print precisely controlled output, and are often useful in silent
4472 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4474 For example, here is how you could use breakpoint commands to print the
4475 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4481 printf "x is %d\n",x
4486 One application for breakpoint commands is to compensate for one bug so
4487 you can test for another. Put a breakpoint just after the erroneous line
4488 of code, give it a condition to detect the case in which something
4489 erroneous has been done, and give it commands to assign correct values
4490 to any variables that need them. End with the @code{continue} command
4491 so that your program does not stop, and start with the @code{silent}
4492 command so that no output is produced. Here is an example:
4503 @node Save Breakpoints
4504 @subsection How to save breakpoints to a file
4506 To save breakpoint definitions to a file use the @w{@code{save
4507 breakpoints}} command.
4510 @kindex save breakpoints
4511 @cindex save breakpoints to a file for future sessions
4512 @item save breakpoints [@var{filename}]
4513 This command saves all current breakpoint definitions together with
4514 their commands and ignore counts, into a file @file{@var{filename}}
4515 suitable for use in a later debugging session. This includes all
4516 types of breakpoints (breakpoints, watchpoints, catchpoints,
4517 tracepoints). To read the saved breakpoint definitions, use the
4518 @code{source} command (@pxref{Command Files}). Note that watchpoints
4519 with expressions involving local variables may fail to be recreated
4520 because it may not be possible to access the context where the
4521 watchpoint is valid anymore. Because the saved breakpoint definitions
4522 are simply a sequence of @value{GDBN} commands that recreate the
4523 breakpoints, you can edit the file in your favorite editing program,
4524 and remove the breakpoint definitions you're not interested in, or
4525 that can no longer be recreated.
4528 @c @ifclear BARETARGET
4529 @node Error in Breakpoints
4530 @subsection ``Cannot insert breakpoints''
4532 If you request too many active hardware-assisted breakpoints and
4533 watchpoints, you will see this error message:
4535 @c FIXME: the precise wording of this message may change; the relevant
4536 @c source change is not committed yet (Sep 3, 1999).
4538 Stopped; cannot insert breakpoints.
4539 You may have requested too many hardware breakpoints and watchpoints.
4543 This message is printed when you attempt to resume the program, since
4544 only then @value{GDBN} knows exactly how many hardware breakpoints and
4545 watchpoints it needs to insert.
4547 When this message is printed, you need to disable or remove some of the
4548 hardware-assisted breakpoints and watchpoints, and then continue.
4550 @node Breakpoint-related Warnings
4551 @subsection ``Breakpoint address adjusted...''
4552 @cindex breakpoint address adjusted
4554 Some processor architectures place constraints on the addresses at
4555 which breakpoints may be placed. For architectures thus constrained,
4556 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4557 with the constraints dictated by the architecture.
4559 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4560 a VLIW architecture in which a number of RISC-like instructions may be
4561 bundled together for parallel execution. The FR-V architecture
4562 constrains the location of a breakpoint instruction within such a
4563 bundle to the instruction with the lowest address. @value{GDBN}
4564 honors this constraint by adjusting a breakpoint's address to the
4565 first in the bundle.
4567 It is not uncommon for optimized code to have bundles which contain
4568 instructions from different source statements, thus it may happen that
4569 a breakpoint's address will be adjusted from one source statement to
4570 another. Since this adjustment may significantly alter @value{GDBN}'s
4571 breakpoint related behavior from what the user expects, a warning is
4572 printed when the breakpoint is first set and also when the breakpoint
4575 A warning like the one below is printed when setting a breakpoint
4576 that's been subject to address adjustment:
4579 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4582 Such warnings are printed both for user settable and @value{GDBN}'s
4583 internal breakpoints. If you see one of these warnings, you should
4584 verify that a breakpoint set at the adjusted address will have the
4585 desired affect. If not, the breakpoint in question may be removed and
4586 other breakpoints may be set which will have the desired behavior.
4587 E.g., it may be sufficient to place the breakpoint at a later
4588 instruction. A conditional breakpoint may also be useful in some
4589 cases to prevent the breakpoint from triggering too often.
4591 @value{GDBN} will also issue a warning when stopping at one of these
4592 adjusted breakpoints:
4595 warning: Breakpoint 1 address previously adjusted from 0x00010414
4599 When this warning is encountered, it may be too late to take remedial
4600 action except in cases where the breakpoint is hit earlier or more
4601 frequently than expected.
4603 @node Continuing and Stepping
4604 @section Continuing and Stepping
4608 @cindex resuming execution
4609 @dfn{Continuing} means resuming program execution until your program
4610 completes normally. In contrast, @dfn{stepping} means executing just
4611 one more ``step'' of your program, where ``step'' may mean either one
4612 line of source code, or one machine instruction (depending on what
4613 particular command you use). Either when continuing or when stepping,
4614 your program may stop even sooner, due to a breakpoint or a signal. (If
4615 it stops due to a signal, you may want to use @code{handle}, or use
4616 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4620 @kindex c @r{(@code{continue})}
4621 @kindex fg @r{(resume foreground execution)}
4622 @item continue @r{[}@var{ignore-count}@r{]}
4623 @itemx c @r{[}@var{ignore-count}@r{]}
4624 @itemx fg @r{[}@var{ignore-count}@r{]}
4625 Resume program execution, at the address where your program last stopped;
4626 any breakpoints set at that address are bypassed. The optional argument
4627 @var{ignore-count} allows you to specify a further number of times to
4628 ignore a breakpoint at this location; its effect is like that of
4629 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4631 The argument @var{ignore-count} is meaningful only when your program
4632 stopped due to a breakpoint. At other times, the argument to
4633 @code{continue} is ignored.
4635 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4636 debugged program is deemed to be the foreground program) are provided
4637 purely for convenience, and have exactly the same behavior as
4641 To resume execution at a different place, you can use @code{return}
4642 (@pxref{Returning, ,Returning from a Function}) to go back to the
4643 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4644 Different Address}) to go to an arbitrary location in your program.
4646 A typical technique for using stepping is to set a breakpoint
4647 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4648 beginning of the function or the section of your program where a problem
4649 is believed to lie, run your program until it stops at that breakpoint,
4650 and then step through the suspect area, examining the variables that are
4651 interesting, until you see the problem happen.
4655 @kindex s @r{(@code{step})}
4657 Continue running your program until control reaches a different source
4658 line, then stop it and return control to @value{GDBN}. This command is
4659 abbreviated @code{s}.
4662 @c "without debugging information" is imprecise; actually "without line
4663 @c numbers in the debugging information". (gcc -g1 has debugging info but
4664 @c not line numbers). But it seems complex to try to make that
4665 @c distinction here.
4666 @emph{Warning:} If you use the @code{step} command while control is
4667 within a function that was compiled without debugging information,
4668 execution proceeds until control reaches a function that does have
4669 debugging information. Likewise, it will not step into a function which
4670 is compiled without debugging information. To step through functions
4671 without debugging information, use the @code{stepi} command, described
4675 The @code{step} command only stops at the first instruction of a source
4676 line. This prevents the multiple stops that could otherwise occur in
4677 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4678 to stop if a function that has debugging information is called within
4679 the line. In other words, @code{step} @emph{steps inside} any functions
4680 called within the line.
4682 Also, the @code{step} command only enters a function if there is line
4683 number information for the function. Otherwise it acts like the
4684 @code{next} command. This avoids problems when using @code{cc -gl}
4685 on MIPS machines. Previously, @code{step} entered subroutines if there
4686 was any debugging information about the routine.
4688 @item step @var{count}
4689 Continue running as in @code{step}, but do so @var{count} times. If a
4690 breakpoint is reached, or a signal not related to stepping occurs before
4691 @var{count} steps, stepping stops right away.
4694 @kindex n @r{(@code{next})}
4695 @item next @r{[}@var{count}@r{]}
4696 Continue to the next source line in the current (innermost) stack frame.
4697 This is similar to @code{step}, but function calls that appear within
4698 the line of code are executed without stopping. Execution stops when
4699 control reaches a different line of code at the original stack level
4700 that was executing when you gave the @code{next} command. This command
4701 is abbreviated @code{n}.
4703 An argument @var{count} is a repeat count, as for @code{step}.
4706 @c FIX ME!! Do we delete this, or is there a way it fits in with
4707 @c the following paragraph? --- Vctoria
4709 @c @code{next} within a function that lacks debugging information acts like
4710 @c @code{step}, but any function calls appearing within the code of the
4711 @c function are executed without stopping.
4713 The @code{next} command only stops at the first instruction of a
4714 source line. This prevents multiple stops that could otherwise occur in
4715 @code{switch} statements, @code{for} loops, etc.
4717 @kindex set step-mode
4719 @cindex functions without line info, and stepping
4720 @cindex stepping into functions with no line info
4721 @itemx set step-mode on
4722 The @code{set step-mode on} command causes the @code{step} command to
4723 stop at the first instruction of a function which contains no debug line
4724 information rather than stepping over it.
4726 This is useful in cases where you may be interested in inspecting the
4727 machine instructions of a function which has no symbolic info and do not
4728 want @value{GDBN} to automatically skip over this function.
4730 @item set step-mode off
4731 Causes the @code{step} command to step over any functions which contains no
4732 debug information. This is the default.
4734 @item show step-mode
4735 Show whether @value{GDBN} will stop in or step over functions without
4736 source line debug information.
4739 @kindex fin @r{(@code{finish})}
4741 Continue running until just after function in the selected stack frame
4742 returns. Print the returned value (if any). This command can be
4743 abbreviated as @code{fin}.
4745 Contrast this with the @code{return} command (@pxref{Returning,
4746 ,Returning from a Function}).
4749 @kindex u @r{(@code{until})}
4750 @cindex run until specified location
4753 Continue running until a source line past the current line, in the
4754 current stack frame, is reached. This command is used to avoid single
4755 stepping through a loop more than once. It is like the @code{next}
4756 command, except that when @code{until} encounters a jump, it
4757 automatically continues execution until the program counter is greater
4758 than the address of the jump.
4760 This means that when you reach the end of a loop after single stepping
4761 though it, @code{until} makes your program continue execution until it
4762 exits the loop. In contrast, a @code{next} command at the end of a loop
4763 simply steps back to the beginning of the loop, which forces you to step
4764 through the next iteration.
4766 @code{until} always stops your program if it attempts to exit the current
4769 @code{until} may produce somewhat counterintuitive results if the order
4770 of machine code does not match the order of the source lines. For
4771 example, in the following excerpt from a debugging session, the @code{f}
4772 (@code{frame}) command shows that execution is stopped at line
4773 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4777 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4779 (@value{GDBP}) until
4780 195 for ( ; argc > 0; NEXTARG) @{
4783 This happened because, for execution efficiency, the compiler had
4784 generated code for the loop closure test at the end, rather than the
4785 start, of the loop---even though the test in a C @code{for}-loop is
4786 written before the body of the loop. The @code{until} command appeared
4787 to step back to the beginning of the loop when it advanced to this
4788 expression; however, it has not really gone to an earlier
4789 statement---not in terms of the actual machine code.
4791 @code{until} with no argument works by means of single
4792 instruction stepping, and hence is slower than @code{until} with an
4795 @item until @var{location}
4796 @itemx u @var{location}
4797 Continue running your program until either the specified location is
4798 reached, or the current stack frame returns. @var{location} is any of
4799 the forms described in @ref{Specify Location}.
4800 This form of the command uses temporary breakpoints, and
4801 hence is quicker than @code{until} without an argument. The specified
4802 location is actually reached only if it is in the current frame. This
4803 implies that @code{until} can be used to skip over recursive function
4804 invocations. For instance in the code below, if the current location is
4805 line @code{96}, issuing @code{until 99} will execute the program up to
4806 line @code{99} in the same invocation of factorial, i.e., after the inner
4807 invocations have returned.
4810 94 int factorial (int value)
4812 96 if (value > 1) @{
4813 97 value *= factorial (value - 1);
4820 @kindex advance @var{location}
4821 @itemx advance @var{location}
4822 Continue running the program up to the given @var{location}. An argument is
4823 required, which should be of one of the forms described in
4824 @ref{Specify Location}.
4825 Execution will also stop upon exit from the current stack
4826 frame. This command is similar to @code{until}, but @code{advance} will
4827 not skip over recursive function calls, and the target location doesn't
4828 have to be in the same frame as the current one.
4832 @kindex si @r{(@code{stepi})}
4834 @itemx stepi @var{arg}
4836 Execute one machine instruction, then stop and return to the debugger.
4838 It is often useful to do @samp{display/i $pc} when stepping by machine
4839 instructions. This makes @value{GDBN} automatically display the next
4840 instruction to be executed, each time your program stops. @xref{Auto
4841 Display,, Automatic Display}.
4843 An argument is a repeat count, as in @code{step}.
4847 @kindex ni @r{(@code{nexti})}
4849 @itemx nexti @var{arg}
4851 Execute one machine instruction, but if it is a function call,
4852 proceed until the function returns.
4854 An argument is a repeat count, as in @code{next}.
4861 A signal is an asynchronous event that can happen in a program. The
4862 operating system defines the possible kinds of signals, and gives each
4863 kind a name and a number. For example, in Unix @code{SIGINT} is the
4864 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4865 @code{SIGSEGV} is the signal a program gets from referencing a place in
4866 memory far away from all the areas in use; @code{SIGALRM} occurs when
4867 the alarm clock timer goes off (which happens only if your program has
4868 requested an alarm).
4870 @cindex fatal signals
4871 Some signals, including @code{SIGALRM}, are a normal part of the
4872 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4873 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4874 program has not specified in advance some other way to handle the signal.
4875 @code{SIGINT} does not indicate an error in your program, but it is normally
4876 fatal so it can carry out the purpose of the interrupt: to kill the program.
4878 @value{GDBN} has the ability to detect any occurrence of a signal in your
4879 program. You can tell @value{GDBN} in advance what to do for each kind of
4882 @cindex handling signals
4883 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4884 @code{SIGALRM} be silently passed to your program
4885 (so as not to interfere with their role in the program's functioning)
4886 but to stop your program immediately whenever an error signal happens.
4887 You can change these settings with the @code{handle} command.
4890 @kindex info signals
4894 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4895 handle each one. You can use this to see the signal numbers of all
4896 the defined types of signals.
4898 @item info signals @var{sig}
4899 Similar, but print information only about the specified signal number.
4901 @code{info handle} is an alias for @code{info signals}.
4904 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4905 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4906 can be the number of a signal or its name (with or without the
4907 @samp{SIG} at the beginning); a list of signal numbers of the form
4908 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4909 known signals. Optional arguments @var{keywords}, described below,
4910 say what change to make.
4914 The keywords allowed by the @code{handle} command can be abbreviated.
4915 Their full names are:
4919 @value{GDBN} should not stop your program when this signal happens. It may
4920 still print a message telling you that the signal has come in.
4923 @value{GDBN} should stop your program when this signal happens. This implies
4924 the @code{print} keyword as well.
4927 @value{GDBN} should print a message when this signal happens.
4930 @value{GDBN} should not mention the occurrence of the signal at all. This
4931 implies the @code{nostop} keyword as well.
4935 @value{GDBN} should allow your program to see this signal; your program
4936 can handle the signal, or else it may terminate if the signal is fatal
4937 and not handled. @code{pass} and @code{noignore} are synonyms.
4941 @value{GDBN} should not allow your program to see this signal.
4942 @code{nopass} and @code{ignore} are synonyms.
4946 When a signal stops your program, the signal is not visible to the
4948 continue. Your program sees the signal then, if @code{pass} is in
4949 effect for the signal in question @emph{at that time}. In other words,
4950 after @value{GDBN} reports a signal, you can use the @code{handle}
4951 command with @code{pass} or @code{nopass} to control whether your
4952 program sees that signal when you continue.
4954 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4955 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4956 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4959 You can also use the @code{signal} command to prevent your program from
4960 seeing a signal, or cause it to see a signal it normally would not see,
4961 or to give it any signal at any time. For example, if your program stopped
4962 due to some sort of memory reference error, you might store correct
4963 values into the erroneous variables and continue, hoping to see more
4964 execution; but your program would probably terminate immediately as
4965 a result of the fatal signal once it saw the signal. To prevent this,
4966 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4969 @cindex extra signal information
4970 @anchor{extra signal information}
4972 On some targets, @value{GDBN} can inspect extra signal information
4973 associated with the intercepted signal, before it is actually
4974 delivered to the program being debugged. This information is exported
4975 by the convenience variable @code{$_siginfo}, and consists of data
4976 that is passed by the kernel to the signal handler at the time of the
4977 receipt of a signal. The data type of the information itself is
4978 target dependent. You can see the data type using the @code{ptype
4979 $_siginfo} command. On Unix systems, it typically corresponds to the
4980 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4983 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4984 referenced address that raised a segmentation fault.
4988 (@value{GDBP}) continue
4989 Program received signal SIGSEGV, Segmentation fault.
4990 0x0000000000400766 in main ()
4992 (@value{GDBP}) ptype $_siginfo
4999 struct @{...@} _kill;
5000 struct @{...@} _timer;
5002 struct @{...@} _sigchld;
5003 struct @{...@} _sigfault;
5004 struct @{...@} _sigpoll;
5007 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5011 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5012 $1 = (void *) 0x7ffff7ff7000
5016 Depending on target support, @code{$_siginfo} may also be writable.
5019 @section Stopping and Starting Multi-thread Programs
5021 @cindex stopped threads
5022 @cindex threads, stopped
5024 @cindex continuing threads
5025 @cindex threads, continuing
5027 @value{GDBN} supports debugging programs with multiple threads
5028 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5029 are two modes of controlling execution of your program within the
5030 debugger. In the default mode, referred to as @dfn{all-stop mode},
5031 when any thread in your program stops (for example, at a breakpoint
5032 or while being stepped), all other threads in the program are also stopped by
5033 @value{GDBN}. On some targets, @value{GDBN} also supports
5034 @dfn{non-stop mode}, in which other threads can continue to run freely while
5035 you examine the stopped thread in the debugger.
5038 * All-Stop Mode:: All threads stop when GDB takes control
5039 * Non-Stop Mode:: Other threads continue to execute
5040 * Background Execution:: Running your program asynchronously
5041 * Thread-Specific Breakpoints:: Controlling breakpoints
5042 * Interrupted System Calls:: GDB may interfere with system calls
5043 * Observer Mode:: GDB does not alter program behavior
5047 @subsection All-Stop Mode
5049 @cindex all-stop mode
5051 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5052 @emph{all} threads of execution stop, not just the current thread. This
5053 allows you to examine the overall state of the program, including
5054 switching between threads, without worrying that things may change
5057 Conversely, whenever you restart the program, @emph{all} threads start
5058 executing. @emph{This is true even when single-stepping} with commands
5059 like @code{step} or @code{next}.
5061 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5062 Since thread scheduling is up to your debugging target's operating
5063 system (not controlled by @value{GDBN}), other threads may
5064 execute more than one statement while the current thread completes a
5065 single step. Moreover, in general other threads stop in the middle of a
5066 statement, rather than at a clean statement boundary, when the program
5069 You might even find your program stopped in another thread after
5070 continuing or even single-stepping. This happens whenever some other
5071 thread runs into a breakpoint, a signal, or an exception before the
5072 first thread completes whatever you requested.
5074 @cindex automatic thread selection
5075 @cindex switching threads automatically
5076 @cindex threads, automatic switching
5077 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5078 signal, it automatically selects the thread where that breakpoint or
5079 signal happened. @value{GDBN} alerts you to the context switch with a
5080 message such as @samp{[Switching to Thread @var{n}]} to identify the
5083 On some OSes, you can modify @value{GDBN}'s default behavior by
5084 locking the OS scheduler to allow only a single thread to run.
5087 @item set scheduler-locking @var{mode}
5088 @cindex scheduler locking mode
5089 @cindex lock scheduler
5090 Set the scheduler locking mode. If it is @code{off}, then there is no
5091 locking and any thread may run at any time. If @code{on}, then only the
5092 current thread may run when the inferior is resumed. The @code{step}
5093 mode optimizes for single-stepping; it prevents other threads
5094 from preempting the current thread while you are stepping, so that
5095 the focus of debugging does not change unexpectedly.
5096 Other threads only rarely (or never) get a chance to run
5097 when you step. They are more likely to run when you @samp{next} over a
5098 function call, and they are completely free to run when you use commands
5099 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5100 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5101 the current thread away from the thread that you are debugging.
5103 @item show scheduler-locking
5104 Display the current scheduler locking mode.
5107 @cindex resume threads of multiple processes simultaneously
5108 By default, when you issue one of the execution commands such as
5109 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5110 threads of the current inferior to run. For example, if @value{GDBN}
5111 is attached to two inferiors, each with two threads, the
5112 @code{continue} command resumes only the two threads of the current
5113 inferior. This is useful, for example, when you debug a program that
5114 forks and you want to hold the parent stopped (so that, for instance,
5115 it doesn't run to exit), while you debug the child. In other
5116 situations, you may not be interested in inspecting the current state
5117 of any of the processes @value{GDBN} is attached to, and you may want
5118 to resume them all until some breakpoint is hit. In the latter case,
5119 you can instruct @value{GDBN} to allow all threads of all the
5120 inferiors to run with the @w{@code{set schedule-multiple}} command.
5123 @kindex set schedule-multiple
5124 @item set schedule-multiple
5125 Set the mode for allowing threads of multiple processes to be resumed
5126 when an execution command is issued. When @code{on}, all threads of
5127 all processes are allowed to run. When @code{off}, only the threads
5128 of the current process are resumed. The default is @code{off}. The
5129 @code{scheduler-locking} mode takes precedence when set to @code{on},
5130 or while you are stepping and set to @code{step}.
5132 @item show schedule-multiple
5133 Display the current mode for resuming the execution of threads of
5138 @subsection Non-Stop Mode
5140 @cindex non-stop mode
5142 @c This section is really only a place-holder, and needs to be expanded
5143 @c with more details.
5145 For some multi-threaded targets, @value{GDBN} supports an optional
5146 mode of operation in which you can examine stopped program threads in
5147 the debugger while other threads continue to execute freely. This
5148 minimizes intrusion when debugging live systems, such as programs
5149 where some threads have real-time constraints or must continue to
5150 respond to external events. This is referred to as @dfn{non-stop} mode.
5152 In non-stop mode, when a thread stops to report a debugging event,
5153 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5154 threads as well, in contrast to the all-stop mode behavior. Additionally,
5155 execution commands such as @code{continue} and @code{step} apply by default
5156 only to the current thread in non-stop mode, rather than all threads as
5157 in all-stop mode. This allows you to control threads explicitly in
5158 ways that are not possible in all-stop mode --- for example, stepping
5159 one thread while allowing others to run freely, stepping
5160 one thread while holding all others stopped, or stepping several threads
5161 independently and simultaneously.
5163 To enter non-stop mode, use this sequence of commands before you run
5164 or attach to your program:
5167 # Enable the async interface.
5170 # If using the CLI, pagination breaks non-stop.
5173 # Finally, turn it on!
5177 You can use these commands to manipulate the non-stop mode setting:
5180 @kindex set non-stop
5181 @item set non-stop on
5182 Enable selection of non-stop mode.
5183 @item set non-stop off
5184 Disable selection of non-stop mode.
5185 @kindex show non-stop
5187 Show the current non-stop enablement setting.
5190 Note these commands only reflect whether non-stop mode is enabled,
5191 not whether the currently-executing program is being run in non-stop mode.
5192 In particular, the @code{set non-stop} preference is only consulted when
5193 @value{GDBN} starts or connects to the target program, and it is generally
5194 not possible to switch modes once debugging has started. Furthermore,
5195 since not all targets support non-stop mode, even when you have enabled
5196 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5199 In non-stop mode, all execution commands apply only to the current thread
5200 by default. That is, @code{continue} only continues one thread.
5201 To continue all threads, issue @code{continue -a} or @code{c -a}.
5203 You can use @value{GDBN}'s background execution commands
5204 (@pxref{Background Execution}) to run some threads in the background
5205 while you continue to examine or step others from @value{GDBN}.
5206 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5207 always executed asynchronously in non-stop mode.
5209 Suspending execution is done with the @code{interrupt} command when
5210 running in the background, or @kbd{Ctrl-c} during foreground execution.
5211 In all-stop mode, this stops the whole process;
5212 but in non-stop mode the interrupt applies only to the current thread.
5213 To stop the whole program, use @code{interrupt -a}.
5215 Other execution commands do not currently support the @code{-a} option.
5217 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5218 that thread current, as it does in all-stop mode. This is because the
5219 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5220 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5221 changed to a different thread just as you entered a command to operate on the
5222 previously current thread.
5224 @node Background Execution
5225 @subsection Background Execution
5227 @cindex foreground execution
5228 @cindex background execution
5229 @cindex asynchronous execution
5230 @cindex execution, foreground, background and asynchronous
5232 @value{GDBN}'s execution commands have two variants: the normal
5233 foreground (synchronous) behavior, and a background
5234 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5235 the program to report that some thread has stopped before prompting for
5236 another command. In background execution, @value{GDBN} immediately gives
5237 a command prompt so that you can issue other commands while your program runs.
5239 You need to explicitly enable asynchronous mode before you can use
5240 background execution commands. You can use these commands to
5241 manipulate the asynchronous mode setting:
5244 @kindex set target-async
5245 @item set target-async on
5246 Enable asynchronous mode.
5247 @item set target-async off
5248 Disable asynchronous mode.
5249 @kindex show target-async
5250 @item show target-async
5251 Show the current target-async setting.
5254 If the target doesn't support async mode, @value{GDBN} issues an error
5255 message if you attempt to use the background execution commands.
5257 To specify background execution, add a @code{&} to the command. For example,
5258 the background form of the @code{continue} command is @code{continue&}, or
5259 just @code{c&}. The execution commands that accept background execution
5265 @xref{Starting, , Starting your Program}.
5269 @xref{Attach, , Debugging an Already-running Process}.
5273 @xref{Continuing and Stepping, step}.
5277 @xref{Continuing and Stepping, stepi}.
5281 @xref{Continuing and Stepping, next}.
5285 @xref{Continuing and Stepping, nexti}.
5289 @xref{Continuing and Stepping, continue}.
5293 @xref{Continuing and Stepping, finish}.
5297 @xref{Continuing and Stepping, until}.
5301 Background execution is especially useful in conjunction with non-stop
5302 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5303 However, you can also use these commands in the normal all-stop mode with
5304 the restriction that you cannot issue another execution command until the
5305 previous one finishes. Examples of commands that are valid in all-stop
5306 mode while the program is running include @code{help} and @code{info break}.
5308 You can interrupt your program while it is running in the background by
5309 using the @code{interrupt} command.
5316 Suspend execution of the running program. In all-stop mode,
5317 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5318 only the current thread. To stop the whole program in non-stop mode,
5319 use @code{interrupt -a}.
5322 @node Thread-Specific Breakpoints
5323 @subsection Thread-Specific Breakpoints
5325 When your program has multiple threads (@pxref{Threads,, Debugging
5326 Programs with Multiple Threads}), you can choose whether to set
5327 breakpoints on all threads, or on a particular thread.
5330 @cindex breakpoints and threads
5331 @cindex thread breakpoints
5332 @kindex break @dots{} thread @var{threadno}
5333 @item break @var{linespec} thread @var{threadno}
5334 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5335 @var{linespec} specifies source lines; there are several ways of
5336 writing them (@pxref{Specify Location}), but the effect is always to
5337 specify some source line.
5339 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5340 to specify that you only want @value{GDBN} to stop the program when a
5341 particular thread reaches this breakpoint. @var{threadno} is one of the
5342 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5343 column of the @samp{info threads} display.
5345 If you do not specify @samp{thread @var{threadno}} when you set a
5346 breakpoint, the breakpoint applies to @emph{all} threads of your
5349 You can use the @code{thread} qualifier on conditional breakpoints as
5350 well; in this case, place @samp{thread @var{threadno}} before or
5351 after the breakpoint condition, like this:
5354 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5359 @node Interrupted System Calls
5360 @subsection Interrupted System Calls
5362 @cindex thread breakpoints and system calls
5363 @cindex system calls and thread breakpoints
5364 @cindex premature return from system calls
5365 There is an unfortunate side effect when using @value{GDBN} to debug
5366 multi-threaded programs. If one thread stops for a
5367 breakpoint, or for some other reason, and another thread is blocked in a
5368 system call, then the system call may return prematurely. This is a
5369 consequence of the interaction between multiple threads and the signals
5370 that @value{GDBN} uses to implement breakpoints and other events that
5373 To handle this problem, your program should check the return value of
5374 each system call and react appropriately. This is good programming
5377 For example, do not write code like this:
5383 The call to @code{sleep} will return early if a different thread stops
5384 at a breakpoint or for some other reason.
5386 Instead, write this:
5391 unslept = sleep (unslept);
5394 A system call is allowed to return early, so the system is still
5395 conforming to its specification. But @value{GDBN} does cause your
5396 multi-threaded program to behave differently than it would without
5399 Also, @value{GDBN} uses internal breakpoints in the thread library to
5400 monitor certain events such as thread creation and thread destruction.
5401 When such an event happens, a system call in another thread may return
5402 prematurely, even though your program does not appear to stop.
5405 @subsection Observer Mode
5407 If you want to build on non-stop mode and observe program behavior
5408 without any chance of disruption by @value{GDBN}, you can set
5409 variables to disable all of the debugger's attempts to modify state,
5410 whether by writing memory, inserting breakpoints, etc. These operate
5411 at a low level, intercepting operations from all commands.
5413 When all of these are set to @code{off}, then @value{GDBN} is said to
5414 be @dfn{observer mode}. As a convenience, the variable
5415 @code{observer} can be set to disable these, plus enable non-stop
5418 Note that @value{GDBN} will not prevent you from making nonsensical
5419 combinations of these settings. For instance, if you have enabled
5420 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5421 then breakpoints that work by writing trap instructions into the code
5422 stream will still not be able to be placed.
5427 @item set observer on
5428 @itemx set observer off
5429 When set to @code{on}, this disables all the permission variables
5430 below (except for @code{insert-fast-tracepoints}), plus enables
5431 non-stop debugging. Setting this to @code{off} switches back to
5432 normal debugging, though remaining in non-stop mode.
5435 Show whether observer mode is on or off.
5437 @kindex may-write-registers
5438 @item set may-write-registers on
5439 @itemx set may-write-registers off
5440 This controls whether @value{GDBN} will attempt to alter the values of
5441 registers, such as with assignment expressions in @code{print}, or the
5442 @code{jump} command. It defaults to @code{on}.
5444 @item show may-write-registers
5445 Show the current permission to write registers.
5447 @kindex may-write-memory
5448 @item set may-write-memory on
5449 @itemx set may-write-memory off
5450 This controls whether @value{GDBN} will attempt to alter the contents
5451 of memory, such as with assignment expressions in @code{print}. It
5452 defaults to @code{on}.
5454 @item show may-write-memory
5455 Show the current permission to write memory.
5457 @kindex may-insert-breakpoints
5458 @item set may-insert-breakpoints on
5459 @itemx set may-insert-breakpoints off
5460 This controls whether @value{GDBN} will attempt to insert breakpoints.
5461 This affects all breakpoints, including internal breakpoints defined
5462 by @value{GDBN}. It defaults to @code{on}.
5464 @item show may-insert-breakpoints
5465 Show the current permission to insert breakpoints.
5467 @kindex may-insert-tracepoints
5468 @item set may-insert-tracepoints on
5469 @itemx set may-insert-tracepoints off
5470 This controls whether @value{GDBN} will attempt to insert (regular)
5471 tracepoints at the beginning of a tracing experiment. It affects only
5472 non-fast tracepoints, fast tracepoints being under the control of
5473 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5475 @item show may-insert-tracepoints
5476 Show the current permission to insert tracepoints.
5478 @kindex may-insert-fast-tracepoints
5479 @item set may-insert-fast-tracepoints on
5480 @itemx set may-insert-fast-tracepoints off
5481 This controls whether @value{GDBN} will attempt to insert fast
5482 tracepoints at the beginning of a tracing experiment. It affects only
5483 fast tracepoints, regular (non-fast) tracepoints being under the
5484 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5486 @item show may-insert-fast-tracepoints
5487 Show the current permission to insert fast tracepoints.
5489 @kindex may-interrupt
5490 @item set may-interrupt on
5491 @itemx set may-interrupt off
5492 This controls whether @value{GDBN} will attempt to interrupt or stop
5493 program execution. When this variable is @code{off}, the
5494 @code{interrupt} command will have no effect, nor will
5495 @kbd{Ctrl-c}. It defaults to @code{on}.
5497 @item show may-interrupt
5498 Show the current permission to interrupt or stop the program.
5502 @node Reverse Execution
5503 @chapter Running programs backward
5504 @cindex reverse execution
5505 @cindex running programs backward
5507 When you are debugging a program, it is not unusual to realize that
5508 you have gone too far, and some event of interest has already happened.
5509 If the target environment supports it, @value{GDBN} can allow you to
5510 ``rewind'' the program by running it backward.
5512 A target environment that supports reverse execution should be able
5513 to ``undo'' the changes in machine state that have taken place as the
5514 program was executing normally. Variables, registers etc.@: should
5515 revert to their previous values. Obviously this requires a great
5516 deal of sophistication on the part of the target environment; not
5517 all target environments can support reverse execution.
5519 When a program is executed in reverse, the instructions that
5520 have most recently been executed are ``un-executed'', in reverse
5521 order. The program counter runs backward, following the previous
5522 thread of execution in reverse. As each instruction is ``un-executed'',
5523 the values of memory and/or registers that were changed by that
5524 instruction are reverted to their previous states. After executing
5525 a piece of source code in reverse, all side effects of that code
5526 should be ``undone'', and all variables should be returned to their
5527 prior values@footnote{
5528 Note that some side effects are easier to undo than others. For instance,
5529 memory and registers are relatively easy, but device I/O is hard. Some
5530 targets may be able undo things like device I/O, and some may not.
5532 The contract between @value{GDBN} and the reverse executing target
5533 requires only that the target do something reasonable when
5534 @value{GDBN} tells it to execute backwards, and then report the
5535 results back to @value{GDBN}. Whatever the target reports back to
5536 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5537 assumes that the memory and registers that the target reports are in a
5538 consistant state, but @value{GDBN} accepts whatever it is given.
5541 If you are debugging in a target environment that supports
5542 reverse execution, @value{GDBN} provides the following commands.
5545 @kindex reverse-continue
5546 @kindex rc @r{(@code{reverse-continue})}
5547 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5548 @itemx rc @r{[}@var{ignore-count}@r{]}
5549 Beginning at the point where your program last stopped, start executing
5550 in reverse. Reverse execution will stop for breakpoints and synchronous
5551 exceptions (signals), just like normal execution. Behavior of
5552 asynchronous signals depends on the target environment.
5554 @kindex reverse-step
5555 @kindex rs @r{(@code{step})}
5556 @item reverse-step @r{[}@var{count}@r{]}
5557 Run the program backward until control reaches the start of a
5558 different source line; then stop it, and return control to @value{GDBN}.
5560 Like the @code{step} command, @code{reverse-step} will only stop
5561 at the beginning of a source line. It ``un-executes'' the previously
5562 executed source line. If the previous source line included calls to
5563 debuggable functions, @code{reverse-step} will step (backward) into
5564 the called function, stopping at the beginning of the @emph{last}
5565 statement in the called function (typically a return statement).
5567 Also, as with the @code{step} command, if non-debuggable functions are
5568 called, @code{reverse-step} will run thru them backward without stopping.
5570 @kindex reverse-stepi
5571 @kindex rsi @r{(@code{reverse-stepi})}
5572 @item reverse-stepi @r{[}@var{count}@r{]}
5573 Reverse-execute one machine instruction. Note that the instruction
5574 to be reverse-executed is @emph{not} the one pointed to by the program
5575 counter, but the instruction executed prior to that one. For instance,
5576 if the last instruction was a jump, @code{reverse-stepi} will take you
5577 back from the destination of the jump to the jump instruction itself.
5579 @kindex reverse-next
5580 @kindex rn @r{(@code{reverse-next})}
5581 @item reverse-next @r{[}@var{count}@r{]}
5582 Run backward to the beginning of the previous line executed in
5583 the current (innermost) stack frame. If the line contains function
5584 calls, they will be ``un-executed'' without stopping. Starting from
5585 the first line of a function, @code{reverse-next} will take you back
5586 to the caller of that function, @emph{before} the function was called,
5587 just as the normal @code{next} command would take you from the last
5588 line of a function back to its return to its caller
5589 @footnote{Unless the code is too heavily optimized.}.
5591 @kindex reverse-nexti
5592 @kindex rni @r{(@code{reverse-nexti})}
5593 @item reverse-nexti @r{[}@var{count}@r{]}
5594 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5595 in reverse, except that called functions are ``un-executed'' atomically.
5596 That is, if the previously executed instruction was a return from
5597 another function, @code{reverse-nexti} will continue to execute
5598 in reverse until the call to that function (from the current stack
5601 @kindex reverse-finish
5602 @item reverse-finish
5603 Just as the @code{finish} command takes you to the point where the
5604 current function returns, @code{reverse-finish} takes you to the point
5605 where it was called. Instead of ending up at the end of the current
5606 function invocation, you end up at the beginning.
5608 @kindex set exec-direction
5609 @item set exec-direction
5610 Set the direction of target execution.
5611 @itemx set exec-direction reverse
5612 @cindex execute forward or backward in time
5613 @value{GDBN} will perform all execution commands in reverse, until the
5614 exec-direction mode is changed to ``forward''. Affected commands include
5615 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5616 command cannot be used in reverse mode.
5617 @item set exec-direction forward
5618 @value{GDBN} will perform all execution commands in the normal fashion.
5619 This is the default.
5623 @node Process Record and Replay
5624 @chapter Recording Inferior's Execution and Replaying It
5625 @cindex process record and replay
5626 @cindex recording inferior's execution and replaying it
5628 On some platforms, @value{GDBN} provides a special @dfn{process record
5629 and replay} target that can record a log of the process execution, and
5630 replay it later with both forward and reverse execution commands.
5633 When this target is in use, if the execution log includes the record
5634 for the next instruction, @value{GDBN} will debug in @dfn{replay
5635 mode}. In the replay mode, the inferior does not really execute code
5636 instructions. Instead, all the events that normally happen during
5637 code execution are taken from the execution log. While code is not
5638 really executed in replay mode, the values of registers (including the
5639 program counter register) and the memory of the inferior are still
5640 changed as they normally would. Their contents are taken from the
5644 If the record for the next instruction is not in the execution log,
5645 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5646 inferior executes normally, and @value{GDBN} records the execution log
5649 The process record and replay target supports reverse execution
5650 (@pxref{Reverse Execution}), even if the platform on which the
5651 inferior runs does not. However, the reverse execution is limited in
5652 this case by the range of the instructions recorded in the execution
5653 log. In other words, reverse execution on platforms that don't
5654 support it directly can only be done in the replay mode.
5656 When debugging in the reverse direction, @value{GDBN} will work in
5657 replay mode as long as the execution log includes the record for the
5658 previous instruction; otherwise, it will work in record mode, if the
5659 platform supports reverse execution, or stop if not.
5661 For architecture environments that support process record and replay,
5662 @value{GDBN} provides the following commands:
5665 @kindex target record
5669 This command starts the process record and replay target. The process
5670 record and replay target can only debug a process that is already
5671 running. Therefore, you need first to start the process with the
5672 @kbd{run} or @kbd{start} commands, and then start the recording with
5673 the @kbd{target record} command.
5675 Both @code{record} and @code{rec} are aliases of @code{target record}.
5677 @cindex displaced stepping, and process record and replay
5678 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5679 will be automatically disabled when process record and replay target
5680 is started. That's because the process record and replay target
5681 doesn't support displaced stepping.
5683 @cindex non-stop mode, and process record and replay
5684 @cindex asynchronous execution, and process record and replay
5685 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5686 the asynchronous execution mode (@pxref{Background Execution}), the
5687 process record and replay target cannot be started because it doesn't
5688 support these two modes.
5693 Stop the process record and replay target. When process record and
5694 replay target stops, the entire execution log will be deleted and the
5695 inferior will either be terminated, or will remain in its final state.
5697 When you stop the process record and replay target in record mode (at
5698 the end of the execution log), the inferior will be stopped at the
5699 next instruction that would have been recorded. In other words, if
5700 you record for a while and then stop recording, the inferior process
5701 will be left in the same state as if the recording never happened.
5703 On the other hand, if the process record and replay target is stopped
5704 while in replay mode (that is, not at the end of the execution log,
5705 but at some earlier point), the inferior process will become ``live''
5706 at that earlier state, and it will then be possible to continue the
5707 usual ``live'' debugging of the process from that state.
5709 When the inferior process exits, or @value{GDBN} detaches from it,
5710 process record and replay target will automatically stop itself.
5713 @item record save @var{filename}
5714 Save the execution log to a file @file{@var{filename}}.
5715 Default filename is @file{gdb_record.@var{process_id}}, where
5716 @var{process_id} is the process ID of the inferior.
5718 @kindex record restore
5719 @item record restore @var{filename}
5720 Restore the execution log from a file @file{@var{filename}}.
5721 File must have been created with @code{record save}.
5723 @kindex set record insn-number-max
5724 @item set record insn-number-max @var{limit}
5725 Set the limit of instructions to be recorded. Default value is 200000.
5727 If @var{limit} is a positive number, then @value{GDBN} will start
5728 deleting instructions from the log once the number of the record
5729 instructions becomes greater than @var{limit}. For every new recorded
5730 instruction, @value{GDBN} will delete the earliest recorded
5731 instruction to keep the number of recorded instructions at the limit.
5732 (Since deleting recorded instructions loses information, @value{GDBN}
5733 lets you control what happens when the limit is reached, by means of
5734 the @code{stop-at-limit} option, described below.)
5736 If @var{limit} is zero, @value{GDBN} will never delete recorded
5737 instructions from the execution log. The number of recorded
5738 instructions is unlimited in this case.
5740 @kindex show record insn-number-max
5741 @item show record insn-number-max
5742 Show the limit of instructions to be recorded.
5744 @kindex set record stop-at-limit
5745 @item set record stop-at-limit
5746 Control the behavior when the number of recorded instructions reaches
5747 the limit. If ON (the default), @value{GDBN} will stop when the limit
5748 is reached for the first time and ask you whether you want to stop the
5749 inferior or continue running it and recording the execution log. If
5750 you decide to continue recording, each new recorded instruction will
5751 cause the oldest one to be deleted.
5753 If this option is OFF, @value{GDBN} will automatically delete the
5754 oldest record to make room for each new one, without asking.
5756 @kindex show record stop-at-limit
5757 @item show record stop-at-limit
5758 Show the current setting of @code{stop-at-limit}.
5760 @kindex set record memory-query
5761 @item set record memory-query
5762 Control the behavior when @value{GDBN} is unable to record memory
5763 changes caused by an instruction. If ON, @value{GDBN} will query
5764 whether to stop the inferior in that case.
5766 If this option is OFF (the default), @value{GDBN} will automatically
5767 ignore the effect of such instructions on memory. Later, when
5768 @value{GDBN} replays this execution log, it will mark the log of this
5769 instruction as not accessible, and it will not affect the replay
5772 @kindex show record memory-query
5773 @item show record memory-query
5774 Show the current setting of @code{memory-query}.
5778 Show various statistics about the state of process record and its
5779 in-memory execution log buffer, including:
5783 Whether in record mode or replay mode.
5785 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5787 Highest recorded instruction number.
5789 Current instruction about to be replayed (if in replay mode).
5791 Number of instructions contained in the execution log.
5793 Maximum number of instructions that may be contained in the execution log.
5796 @kindex record delete
5799 When record target runs in replay mode (``in the past''), delete the
5800 subsequent execution log and begin to record a new execution log starting
5801 from the current address. This means you will abandon the previously
5802 recorded ``future'' and begin recording a new ``future''.
5807 @chapter Examining the Stack
5809 When your program has stopped, the first thing you need to know is where it
5810 stopped and how it got there.
5813 Each time your program performs a function call, information about the call
5815 That information includes the location of the call in your program,
5816 the arguments of the call,
5817 and the local variables of the function being called.
5818 The information is saved in a block of data called a @dfn{stack frame}.
5819 The stack frames are allocated in a region of memory called the @dfn{call
5822 When your program stops, the @value{GDBN} commands for examining the
5823 stack allow you to see all of this information.
5825 @cindex selected frame
5826 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5827 @value{GDBN} commands refer implicitly to the selected frame. In
5828 particular, whenever you ask @value{GDBN} for the value of a variable in
5829 your program, the value is found in the selected frame. There are
5830 special @value{GDBN} commands to select whichever frame you are
5831 interested in. @xref{Selection, ,Selecting a Frame}.
5833 When your program stops, @value{GDBN} automatically selects the
5834 currently executing frame and describes it briefly, similar to the
5835 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5838 * Frames:: Stack frames
5839 * Backtrace:: Backtraces
5840 * Selection:: Selecting a frame
5841 * Frame Info:: Information on a frame
5846 @section Stack Frames
5848 @cindex frame, definition
5850 The call stack is divided up into contiguous pieces called @dfn{stack
5851 frames}, or @dfn{frames} for short; each frame is the data associated
5852 with one call to one function. The frame contains the arguments given
5853 to the function, the function's local variables, and the address at
5854 which the function is executing.
5856 @cindex initial frame
5857 @cindex outermost frame
5858 @cindex innermost frame
5859 When your program is started, the stack has only one frame, that of the
5860 function @code{main}. This is called the @dfn{initial} frame or the
5861 @dfn{outermost} frame. Each time a function is called, a new frame is
5862 made. Each time a function returns, the frame for that function invocation
5863 is eliminated. If a function is recursive, there can be many frames for
5864 the same function. The frame for the function in which execution is
5865 actually occurring is called the @dfn{innermost} frame. This is the most
5866 recently created of all the stack frames that still exist.
5868 @cindex frame pointer
5869 Inside your program, stack frames are identified by their addresses. A
5870 stack frame consists of many bytes, each of which has its own address; each
5871 kind of computer has a convention for choosing one byte whose
5872 address serves as the address of the frame. Usually this address is kept
5873 in a register called the @dfn{frame pointer register}
5874 (@pxref{Registers, $fp}) while execution is going on in that frame.
5876 @cindex frame number
5877 @value{GDBN} assigns numbers to all existing stack frames, starting with
5878 zero for the innermost frame, one for the frame that called it,
5879 and so on upward. These numbers do not really exist in your program;
5880 they are assigned by @value{GDBN} to give you a way of designating stack
5881 frames in @value{GDBN} commands.
5883 @c The -fomit-frame-pointer below perennially causes hbox overflow
5884 @c underflow problems.
5885 @cindex frameless execution
5886 Some compilers provide a way to compile functions so that they operate
5887 without stack frames. (For example, the @value{NGCC} option
5889 @samp{-fomit-frame-pointer}
5891 generates functions without a frame.)
5892 This is occasionally done with heavily used library functions to save
5893 the frame setup time. @value{GDBN} has limited facilities for dealing
5894 with these function invocations. If the innermost function invocation
5895 has no stack frame, @value{GDBN} nevertheless regards it as though
5896 it had a separate frame, which is numbered zero as usual, allowing
5897 correct tracing of the function call chain. However, @value{GDBN} has
5898 no provision for frameless functions elsewhere in the stack.
5901 @kindex frame@r{, command}
5902 @cindex current stack frame
5903 @item frame @var{args}
5904 The @code{frame} command allows you to move from one stack frame to another,
5905 and to print the stack frame you select. @var{args} may be either the
5906 address of the frame or the stack frame number. Without an argument,
5907 @code{frame} prints the current stack frame.
5909 @kindex select-frame
5910 @cindex selecting frame silently
5912 The @code{select-frame} command allows you to move from one stack frame
5913 to another without printing the frame. This is the silent version of
5921 @cindex call stack traces
5922 A backtrace is a summary of how your program got where it is. It shows one
5923 line per frame, for many frames, starting with the currently executing
5924 frame (frame zero), followed by its caller (frame one), and on up the
5929 @kindex bt @r{(@code{backtrace})}
5932 Print a backtrace of the entire stack: one line per frame for all
5933 frames in the stack.
5935 You can stop the backtrace at any time by typing the system interrupt
5936 character, normally @kbd{Ctrl-c}.
5938 @item backtrace @var{n}
5940 Similar, but print only the innermost @var{n} frames.
5942 @item backtrace -@var{n}
5944 Similar, but print only the outermost @var{n} frames.
5946 @item backtrace full
5948 @itemx bt full @var{n}
5949 @itemx bt full -@var{n}
5950 Print the values of the local variables also. @var{n} specifies the
5951 number of frames to print, as described above.
5956 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5957 are additional aliases for @code{backtrace}.
5959 @cindex multiple threads, backtrace
5960 In a multi-threaded program, @value{GDBN} by default shows the
5961 backtrace only for the current thread. To display the backtrace for
5962 several or all of the threads, use the command @code{thread apply}
5963 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5964 apply all backtrace}, @value{GDBN} will display the backtrace for all
5965 the threads; this is handy when you debug a core dump of a
5966 multi-threaded program.
5968 Each line in the backtrace shows the frame number and the function name.
5969 The program counter value is also shown---unless you use @code{set
5970 print address off}. The backtrace also shows the source file name and
5971 line number, as well as the arguments to the function. The program
5972 counter value is omitted if it is at the beginning of the code for that
5975 Here is an example of a backtrace. It was made with the command
5976 @samp{bt 3}, so it shows the innermost three frames.
5980 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5982 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5983 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5985 (More stack frames follow...)
5990 The display for frame zero does not begin with a program counter
5991 value, indicating that your program has stopped at the beginning of the
5992 code for line @code{993} of @code{builtin.c}.
5995 The value of parameter @code{data} in frame 1 has been replaced by
5996 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5997 only if it is a scalar (integer, pointer, enumeration, etc). See command
5998 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5999 on how to configure the way function parameter values are printed.
6001 @cindex optimized out, in backtrace
6002 @cindex function call arguments, optimized out
6003 If your program was compiled with optimizations, some compilers will
6004 optimize away arguments passed to functions if those arguments are
6005 never used after the call. Such optimizations generate code that
6006 passes arguments through registers, but doesn't store those arguments
6007 in the stack frame. @value{GDBN} has no way of displaying such
6008 arguments in stack frames other than the innermost one. Here's what
6009 such a backtrace might look like:
6013 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6015 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6016 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6018 (More stack frames follow...)
6023 The values of arguments that were not saved in their stack frames are
6024 shown as @samp{<optimized out>}.
6026 If you need to display the values of such optimized-out arguments,
6027 either deduce that from other variables whose values depend on the one
6028 you are interested in, or recompile without optimizations.
6030 @cindex backtrace beyond @code{main} function
6031 @cindex program entry point
6032 @cindex startup code, and backtrace
6033 Most programs have a standard user entry point---a place where system
6034 libraries and startup code transition into user code. For C this is
6035 @code{main}@footnote{
6036 Note that embedded programs (the so-called ``free-standing''
6037 environment) are not required to have a @code{main} function as the
6038 entry point. They could even have multiple entry points.}.
6039 When @value{GDBN} finds the entry function in a backtrace
6040 it will terminate the backtrace, to avoid tracing into highly
6041 system-specific (and generally uninteresting) code.
6043 If you need to examine the startup code, or limit the number of levels
6044 in a backtrace, you can change this behavior:
6047 @item set backtrace past-main
6048 @itemx set backtrace past-main on
6049 @kindex set backtrace
6050 Backtraces will continue past the user entry point.
6052 @item set backtrace past-main off
6053 Backtraces will stop when they encounter the user entry point. This is the
6056 @item show backtrace past-main
6057 @kindex show backtrace
6058 Display the current user entry point backtrace policy.
6060 @item set backtrace past-entry
6061 @itemx set backtrace past-entry on
6062 Backtraces will continue past the internal entry point of an application.
6063 This entry point is encoded by the linker when the application is built,
6064 and is likely before the user entry point @code{main} (or equivalent) is called.
6066 @item set backtrace past-entry off
6067 Backtraces will stop when they encounter the internal entry point of an
6068 application. This is the default.
6070 @item show backtrace past-entry
6071 Display the current internal entry point backtrace policy.
6073 @item set backtrace limit @var{n}
6074 @itemx set backtrace limit 0
6075 @cindex backtrace limit
6076 Limit the backtrace to @var{n} levels. A value of zero means
6079 @item show backtrace limit
6080 Display the current limit on backtrace levels.
6084 @section Selecting a Frame
6086 Most commands for examining the stack and other data in your program work on
6087 whichever stack frame is selected at the moment. Here are the commands for
6088 selecting a stack frame; all of them finish by printing a brief description
6089 of the stack frame just selected.
6092 @kindex frame@r{, selecting}
6093 @kindex f @r{(@code{frame})}
6096 Select frame number @var{n}. Recall that frame zero is the innermost
6097 (currently executing) frame, frame one is the frame that called the
6098 innermost one, and so on. The highest-numbered frame is the one for
6101 @item frame @var{addr}
6103 Select the frame at address @var{addr}. This is useful mainly if the
6104 chaining of stack frames has been damaged by a bug, making it
6105 impossible for @value{GDBN} to assign numbers properly to all frames. In
6106 addition, this can be useful when your program has multiple stacks and
6107 switches between them.
6109 On the SPARC architecture, @code{frame} needs two addresses to
6110 select an arbitrary frame: a frame pointer and a stack pointer.
6112 On the MIPS and Alpha architecture, it needs two addresses: a stack
6113 pointer and a program counter.
6115 On the 29k architecture, it needs three addresses: a register stack
6116 pointer, a program counter, and a memory stack pointer.
6120 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6121 advances toward the outermost frame, to higher frame numbers, to frames
6122 that have existed longer. @var{n} defaults to one.
6125 @kindex do @r{(@code{down})}
6127 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6128 advances toward the innermost frame, to lower frame numbers, to frames
6129 that were created more recently. @var{n} defaults to one. You may
6130 abbreviate @code{down} as @code{do}.
6133 All of these commands end by printing two lines of output describing the
6134 frame. The first line shows the frame number, the function name, the
6135 arguments, and the source file and line number of execution in that
6136 frame. The second line shows the text of that source line.
6144 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6146 10 read_input_file (argv[i]);
6150 After such a printout, the @code{list} command with no arguments
6151 prints ten lines centered on the point of execution in the frame.
6152 You can also edit the program at the point of execution with your favorite
6153 editing program by typing @code{edit}.
6154 @xref{List, ,Printing Source Lines},
6158 @kindex down-silently
6160 @item up-silently @var{n}
6161 @itemx down-silently @var{n}
6162 These two commands are variants of @code{up} and @code{down},
6163 respectively; they differ in that they do their work silently, without
6164 causing display of the new frame. They are intended primarily for use
6165 in @value{GDBN} command scripts, where the output might be unnecessary and
6170 @section Information About a Frame
6172 There are several other commands to print information about the selected
6178 When used without any argument, this command does not change which
6179 frame is selected, but prints a brief description of the currently
6180 selected stack frame. It can be abbreviated @code{f}. With an
6181 argument, this command is used to select a stack frame.
6182 @xref{Selection, ,Selecting a Frame}.
6185 @kindex info f @r{(@code{info frame})}
6188 This command prints a verbose description of the selected stack frame,
6193 the address of the frame
6195 the address of the next frame down (called by this frame)
6197 the address of the next frame up (caller of this frame)
6199 the language in which the source code corresponding to this frame is written
6201 the address of the frame's arguments
6203 the address of the frame's local variables
6205 the program counter saved in it (the address of execution in the caller frame)
6207 which registers were saved in the frame
6210 @noindent The verbose description is useful when
6211 something has gone wrong that has made the stack format fail to fit
6212 the usual conventions.
6214 @item info frame @var{addr}
6215 @itemx info f @var{addr}
6216 Print a verbose description of the frame at address @var{addr}, without
6217 selecting that frame. The selected frame remains unchanged by this
6218 command. This requires the same kind of address (more than one for some
6219 architectures) that you specify in the @code{frame} command.
6220 @xref{Selection, ,Selecting a Frame}.
6224 Print the arguments of the selected frame, each on a separate line.
6228 Print the local variables of the selected frame, each on a separate
6229 line. These are all variables (declared either static or automatic)
6230 accessible at the point of execution of the selected frame.
6233 @cindex catch exceptions, list active handlers
6234 @cindex exception handlers, how to list
6236 Print a list of all the exception handlers that are active in the
6237 current stack frame at the current point of execution. To see other
6238 exception handlers, visit the associated frame (using the @code{up},
6239 @code{down}, or @code{frame} commands); then type @code{info catch}.
6240 @xref{Set Catchpoints, , Setting Catchpoints}.
6246 @chapter Examining Source Files
6248 @value{GDBN} can print parts of your program's source, since the debugging
6249 information recorded in the program tells @value{GDBN} what source files were
6250 used to build it. When your program stops, @value{GDBN} spontaneously prints
6251 the line where it stopped. Likewise, when you select a stack frame
6252 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6253 execution in that frame has stopped. You can print other portions of
6254 source files by explicit command.
6256 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6257 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6258 @value{GDBN} under @sc{gnu} Emacs}.
6261 * List:: Printing source lines
6262 * Specify Location:: How to specify code locations
6263 * Edit:: Editing source files
6264 * Search:: Searching source files
6265 * Source Path:: Specifying source directories
6266 * Machine Code:: Source and machine code
6270 @section Printing Source Lines
6273 @kindex l @r{(@code{list})}
6274 To print lines from a source file, use the @code{list} command
6275 (abbreviated @code{l}). By default, ten lines are printed.
6276 There are several ways to specify what part of the file you want to
6277 print; see @ref{Specify Location}, for the full list.
6279 Here are the forms of the @code{list} command most commonly used:
6282 @item list @var{linenum}
6283 Print lines centered around line number @var{linenum} in the
6284 current source file.
6286 @item list @var{function}
6287 Print lines centered around the beginning of function
6291 Print more lines. If the last lines printed were printed with a
6292 @code{list} command, this prints lines following the last lines
6293 printed; however, if the last line printed was a solitary line printed
6294 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6295 Stack}), this prints lines centered around that line.
6298 Print lines just before the lines last printed.
6301 @cindex @code{list}, how many lines to display
6302 By default, @value{GDBN} prints ten source lines with any of these forms of
6303 the @code{list} command. You can change this using @code{set listsize}:
6306 @kindex set listsize
6307 @item set listsize @var{count}
6308 Make the @code{list} command display @var{count} source lines (unless
6309 the @code{list} argument explicitly specifies some other number).
6311 @kindex show listsize
6313 Display the number of lines that @code{list} prints.
6316 Repeating a @code{list} command with @key{RET} discards the argument,
6317 so it is equivalent to typing just @code{list}. This is more useful
6318 than listing the same lines again. An exception is made for an
6319 argument of @samp{-}; that argument is preserved in repetition so that
6320 each repetition moves up in the source file.
6322 In general, the @code{list} command expects you to supply zero, one or two
6323 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6324 of writing them (@pxref{Specify Location}), but the effect is always
6325 to specify some source line.
6327 Here is a complete description of the possible arguments for @code{list}:
6330 @item list @var{linespec}
6331 Print lines centered around the line specified by @var{linespec}.
6333 @item list @var{first},@var{last}
6334 Print lines from @var{first} to @var{last}. Both arguments are
6335 linespecs. When a @code{list} command has two linespecs, and the
6336 source file of the second linespec is omitted, this refers to
6337 the same source file as the first linespec.
6339 @item list ,@var{last}
6340 Print lines ending with @var{last}.
6342 @item list @var{first},
6343 Print lines starting with @var{first}.
6346 Print lines just after the lines last printed.
6349 Print lines just before the lines last printed.
6352 As described in the preceding table.
6355 @node Specify Location
6356 @section Specifying a Location
6357 @cindex specifying location
6360 Several @value{GDBN} commands accept arguments that specify a location
6361 of your program's code. Since @value{GDBN} is a source-level
6362 debugger, a location usually specifies some line in the source code;
6363 for that reason, locations are also known as @dfn{linespecs}.
6365 Here are all the different ways of specifying a code location that
6366 @value{GDBN} understands:
6370 Specifies the line number @var{linenum} of the current source file.
6373 @itemx +@var{offset}
6374 Specifies the line @var{offset} lines before or after the @dfn{current
6375 line}. For the @code{list} command, the current line is the last one
6376 printed; for the breakpoint commands, this is the line at which
6377 execution stopped in the currently selected @dfn{stack frame}
6378 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6379 used as the second of the two linespecs in a @code{list} command,
6380 this specifies the line @var{offset} lines up or down from the first
6383 @item @var{filename}:@var{linenum}
6384 Specifies the line @var{linenum} in the source file @var{filename}.
6386 @item @var{function}
6387 Specifies the line that begins the body of the function @var{function}.
6388 For example, in C, this is the line with the open brace.
6390 @item @var{function}:@var{label}
6391 Specifies the line where @var{label} appears in @var{function}.
6393 @item @var{filename}:@var{function}
6394 Specifies the line that begins the body of the function @var{function}
6395 in the file @var{filename}. You only need the file name with a
6396 function name to avoid ambiguity when there are identically named
6397 functions in different source files.
6400 Specifies the line at which the label named @var{label} appears.
6401 @value{GDBN} searches for the label in the function corresponding to
6402 the currently selected stack frame. If there is no current selected
6403 stack frame (for instance, if the inferior is not running), then
6404 @value{GDBN} will not search for a label.
6406 @item *@var{address}
6407 Specifies the program address @var{address}. For line-oriented
6408 commands, such as @code{list} and @code{edit}, this specifies a source
6409 line that contains @var{address}. For @code{break} and other
6410 breakpoint oriented commands, this can be used to set breakpoints in
6411 parts of your program which do not have debugging information or
6414 Here @var{address} may be any expression valid in the current working
6415 language (@pxref{Languages, working language}) that specifies a code
6416 address. In addition, as a convenience, @value{GDBN} extends the
6417 semantics of expressions used in locations to cover the situations
6418 that frequently happen during debugging. Here are the various forms
6422 @item @var{expression}
6423 Any expression valid in the current working language.
6425 @item @var{funcaddr}
6426 An address of a function or procedure derived from its name. In C,
6427 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6428 simply the function's name @var{function} (and actually a special case
6429 of a valid expression). In Pascal and Modula-2, this is
6430 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6431 (although the Pascal form also works).
6433 This form specifies the address of the function's first instruction,
6434 before the stack frame and arguments have been set up.
6436 @item '@var{filename}'::@var{funcaddr}
6437 Like @var{funcaddr} above, but also specifies the name of the source
6438 file explicitly. This is useful if the name of the function does not
6439 specify the function unambiguously, e.g., if there are several
6440 functions with identical names in different source files.
6447 @section Editing Source Files
6448 @cindex editing source files
6451 @kindex e @r{(@code{edit})}
6452 To edit the lines in a source file, use the @code{edit} command.
6453 The editing program of your choice
6454 is invoked with the current line set to
6455 the active line in the program.
6456 Alternatively, there are several ways to specify what part of the file you
6457 want to print if you want to see other parts of the program:
6460 @item edit @var{location}
6461 Edit the source file specified by @code{location}. Editing starts at
6462 that @var{location}, e.g., at the specified source line of the
6463 specified file. @xref{Specify Location}, for all the possible forms
6464 of the @var{location} argument; here are the forms of the @code{edit}
6465 command most commonly used:
6468 @item edit @var{number}
6469 Edit the current source file with @var{number} as the active line number.
6471 @item edit @var{function}
6472 Edit the file containing @var{function} at the beginning of its definition.
6477 @subsection Choosing your Editor
6478 You can customize @value{GDBN} to use any editor you want
6480 The only restriction is that your editor (say @code{ex}), recognizes the
6481 following command-line syntax:
6483 ex +@var{number} file
6485 The optional numeric value +@var{number} specifies the number of the line in
6486 the file where to start editing.}.
6487 By default, it is @file{@value{EDITOR}}, but you can change this
6488 by setting the environment variable @code{EDITOR} before using
6489 @value{GDBN}. For example, to configure @value{GDBN} to use the
6490 @code{vi} editor, you could use these commands with the @code{sh} shell:
6496 or in the @code{csh} shell,
6498 setenv EDITOR /usr/bin/vi
6503 @section Searching Source Files
6504 @cindex searching source files
6506 There are two commands for searching through the current source file for a
6511 @kindex forward-search
6512 @item forward-search @var{regexp}
6513 @itemx search @var{regexp}
6514 The command @samp{forward-search @var{regexp}} checks each line,
6515 starting with the one following the last line listed, for a match for
6516 @var{regexp}. It lists the line that is found. You can use the
6517 synonym @samp{search @var{regexp}} or abbreviate the command name as
6520 @kindex reverse-search
6521 @item reverse-search @var{regexp}
6522 The command @samp{reverse-search @var{regexp}} checks each line, starting
6523 with the one before the last line listed and going backward, for a match
6524 for @var{regexp}. It lists the line that is found. You can abbreviate
6525 this command as @code{rev}.
6529 @section Specifying Source Directories
6532 @cindex directories for source files
6533 Executable programs sometimes do not record the directories of the source
6534 files from which they were compiled, just the names. Even when they do,
6535 the directories could be moved between the compilation and your debugging
6536 session. @value{GDBN} has a list of directories to search for source files;
6537 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6538 it tries all the directories in the list, in the order they are present
6539 in the list, until it finds a file with the desired name.
6541 For example, suppose an executable references the file
6542 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6543 @file{/mnt/cross}. The file is first looked up literally; if this
6544 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6545 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6546 message is printed. @value{GDBN} does not look up the parts of the
6547 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6548 Likewise, the subdirectories of the source path are not searched: if
6549 the source path is @file{/mnt/cross}, and the binary refers to
6550 @file{foo.c}, @value{GDBN} would not find it under
6551 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6553 Plain file names, relative file names with leading directories, file
6554 names containing dots, etc.@: are all treated as described above; for
6555 instance, if the source path is @file{/mnt/cross}, and the source file
6556 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6557 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6558 that---@file{/mnt/cross/foo.c}.
6560 Note that the executable search path is @emph{not} used to locate the
6563 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6564 any information it has cached about where source files are found and where
6565 each line is in the file.
6569 When you start @value{GDBN}, its source path includes only @samp{cdir}
6570 and @samp{cwd}, in that order.
6571 To add other directories, use the @code{directory} command.
6573 The search path is used to find both program source files and @value{GDBN}
6574 script files (read using the @samp{-command} option and @samp{source} command).
6576 In addition to the source path, @value{GDBN} provides a set of commands
6577 that manage a list of source path substitution rules. A @dfn{substitution
6578 rule} specifies how to rewrite source directories stored in the program's
6579 debug information in case the sources were moved to a different
6580 directory between compilation and debugging. A rule is made of
6581 two strings, the first specifying what needs to be rewritten in
6582 the path, and the second specifying how it should be rewritten.
6583 In @ref{set substitute-path}, we name these two parts @var{from} and
6584 @var{to} respectively. @value{GDBN} does a simple string replacement
6585 of @var{from} with @var{to} at the start of the directory part of the
6586 source file name, and uses that result instead of the original file
6587 name to look up the sources.
6589 Using the previous example, suppose the @file{foo-1.0} tree has been
6590 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6591 @value{GDBN} to replace @file{/usr/src} in all source path names with
6592 @file{/mnt/cross}. The first lookup will then be
6593 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6594 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6595 substitution rule, use the @code{set substitute-path} command
6596 (@pxref{set substitute-path}).
6598 To avoid unexpected substitution results, a rule is applied only if the
6599 @var{from} part of the directory name ends at a directory separator.
6600 For instance, a rule substituting @file{/usr/source} into
6601 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6602 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6603 is applied only at the beginning of the directory name, this rule will
6604 not be applied to @file{/root/usr/source/baz.c} either.
6606 In many cases, you can achieve the same result using the @code{directory}
6607 command. However, @code{set substitute-path} can be more efficient in
6608 the case where the sources are organized in a complex tree with multiple
6609 subdirectories. With the @code{directory} command, you need to add each
6610 subdirectory of your project. If you moved the entire tree while
6611 preserving its internal organization, then @code{set substitute-path}
6612 allows you to direct the debugger to all the sources with one single
6615 @code{set substitute-path} is also more than just a shortcut command.
6616 The source path is only used if the file at the original location no
6617 longer exists. On the other hand, @code{set substitute-path} modifies
6618 the debugger behavior to look at the rewritten location instead. So, if
6619 for any reason a source file that is not relevant to your executable is
6620 located at the original location, a substitution rule is the only
6621 method available to point @value{GDBN} at the new location.
6623 @cindex @samp{--with-relocated-sources}
6624 @cindex default source path substitution
6625 You can configure a default source path substitution rule by
6626 configuring @value{GDBN} with the
6627 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6628 should be the name of a directory under @value{GDBN}'s configured
6629 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6630 directory names in debug information under @var{dir} will be adjusted
6631 automatically if the installed @value{GDBN} is moved to a new
6632 location. This is useful if @value{GDBN}, libraries or executables
6633 with debug information and corresponding source code are being moved
6637 @item directory @var{dirname} @dots{}
6638 @item dir @var{dirname} @dots{}
6639 Add directory @var{dirname} to the front of the source path. Several
6640 directory names may be given to this command, separated by @samp{:}
6641 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6642 part of absolute file names) or
6643 whitespace. You may specify a directory that is already in the source
6644 path; this moves it forward, so @value{GDBN} searches it sooner.
6648 @vindex $cdir@r{, convenience variable}
6649 @vindex $cwd@r{, convenience variable}
6650 @cindex compilation directory
6651 @cindex current directory
6652 @cindex working directory
6653 @cindex directory, current
6654 @cindex directory, compilation
6655 You can use the string @samp{$cdir} to refer to the compilation
6656 directory (if one is recorded), and @samp{$cwd} to refer to the current
6657 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6658 tracks the current working directory as it changes during your @value{GDBN}
6659 session, while the latter is immediately expanded to the current
6660 directory at the time you add an entry to the source path.
6663 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6665 @c RET-repeat for @code{directory} is explicitly disabled, but since
6666 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6668 @item set directories @var{path-list}
6669 @kindex set directories
6670 Set the source path to @var{path-list}.
6671 @samp{$cdir:$cwd} are added if missing.
6673 @item show directories
6674 @kindex show directories
6675 Print the source path: show which directories it contains.
6677 @anchor{set substitute-path}
6678 @item set substitute-path @var{from} @var{to}
6679 @kindex set substitute-path
6680 Define a source path substitution rule, and add it at the end of the
6681 current list of existing substitution rules. If a rule with the same
6682 @var{from} was already defined, then the old rule is also deleted.
6684 For example, if the file @file{/foo/bar/baz.c} was moved to
6685 @file{/mnt/cross/baz.c}, then the command
6688 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6692 will tell @value{GDBN} to replace @samp{/usr/src} with
6693 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6694 @file{baz.c} even though it was moved.
6696 In the case when more than one substitution rule have been defined,
6697 the rules are evaluated one by one in the order where they have been
6698 defined. The first one matching, if any, is selected to perform
6701 For instance, if we had entered the following commands:
6704 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6705 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6709 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6710 @file{/mnt/include/defs.h} by using the first rule. However, it would
6711 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6712 @file{/mnt/src/lib/foo.c}.
6715 @item unset substitute-path [path]
6716 @kindex unset substitute-path
6717 If a path is specified, search the current list of substitution rules
6718 for a rule that would rewrite that path. Delete that rule if found.
6719 A warning is emitted by the debugger if no rule could be found.
6721 If no path is specified, then all substitution rules are deleted.
6723 @item show substitute-path [path]
6724 @kindex show substitute-path
6725 If a path is specified, then print the source path substitution rule
6726 which would rewrite that path, if any.
6728 If no path is specified, then print all existing source path substitution
6733 If your source path is cluttered with directories that are no longer of
6734 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6735 versions of source. You can correct the situation as follows:
6739 Use @code{directory} with no argument to reset the source path to its default value.
6742 Use @code{directory} with suitable arguments to reinstall the
6743 directories you want in the source path. You can add all the
6744 directories in one command.
6748 @section Source and Machine Code
6749 @cindex source line and its code address
6751 You can use the command @code{info line} to map source lines to program
6752 addresses (and vice versa), and the command @code{disassemble} to display
6753 a range of addresses as machine instructions. You can use the command
6754 @code{set disassemble-next-line} to set whether to disassemble next
6755 source line when execution stops. When run under @sc{gnu} Emacs
6756 mode, the @code{info line} command causes the arrow to point to the
6757 line specified. Also, @code{info line} prints addresses in symbolic form as
6762 @item info line @var{linespec}
6763 Print the starting and ending addresses of the compiled code for
6764 source line @var{linespec}. You can specify source lines in any of
6765 the ways documented in @ref{Specify Location}.
6768 For example, we can use @code{info line} to discover the location of
6769 the object code for the first line of function
6770 @code{m4_changequote}:
6772 @c FIXME: I think this example should also show the addresses in
6773 @c symbolic form, as they usually would be displayed.
6775 (@value{GDBP}) info line m4_changequote
6776 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6780 @cindex code address and its source line
6781 We can also inquire (using @code{*@var{addr}} as the form for
6782 @var{linespec}) what source line covers a particular address:
6784 (@value{GDBP}) info line *0x63ff
6785 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6788 @cindex @code{$_} and @code{info line}
6789 @cindex @code{x} command, default address
6790 @kindex x@r{(examine), and} info line
6791 After @code{info line}, the default address for the @code{x} command
6792 is changed to the starting address of the line, so that @samp{x/i} is
6793 sufficient to begin examining the machine code (@pxref{Memory,
6794 ,Examining Memory}). Also, this address is saved as the value of the
6795 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6800 @cindex assembly instructions
6801 @cindex instructions, assembly
6802 @cindex machine instructions
6803 @cindex listing machine instructions
6805 @itemx disassemble /m
6806 @itemx disassemble /r
6807 This specialized command dumps a range of memory as machine
6808 instructions. It can also print mixed source+disassembly by specifying
6809 the @code{/m} modifier and print the raw instructions in hex as well as
6810 in symbolic form by specifying the @code{/r}.
6811 The default memory range is the function surrounding the
6812 program counter of the selected frame. A single argument to this
6813 command is a program counter value; @value{GDBN} dumps the function
6814 surrounding this value. When two arguments are given, they should
6815 be separated by a comma, possibly surrounded by whitespace. The
6816 arguments specify a range of addresses to dump, in one of two forms:
6819 @item @var{start},@var{end}
6820 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6821 @item @var{start},+@var{length}
6822 the addresses from @var{start} (inclusive) to
6823 @code{@var{start}+@var{length}} (exclusive).
6827 When 2 arguments are specified, the name of the function is also
6828 printed (since there could be several functions in the given range).
6830 The argument(s) can be any expression yielding a numeric value, such as
6831 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6833 If the range of memory being disassembled contains current program counter,
6834 the instruction at that location is shown with a @code{=>} marker.
6837 The following example shows the disassembly of a range of addresses of
6838 HP PA-RISC 2.0 code:
6841 (@value{GDBP}) disas 0x32c4, 0x32e4
6842 Dump of assembler code from 0x32c4 to 0x32e4:
6843 0x32c4 <main+204>: addil 0,dp
6844 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6845 0x32cc <main+212>: ldil 0x3000,r31
6846 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6847 0x32d4 <main+220>: ldo 0(r31),rp
6848 0x32d8 <main+224>: addil -0x800,dp
6849 0x32dc <main+228>: ldo 0x588(r1),r26
6850 0x32e0 <main+232>: ldil 0x3000,r31
6851 End of assembler dump.
6854 Here is an example showing mixed source+assembly for Intel x86, when the
6855 program is stopped just after function prologue:
6858 (@value{GDBP}) disas /m main
6859 Dump of assembler code for function main:
6861 0x08048330 <+0>: push %ebp
6862 0x08048331 <+1>: mov %esp,%ebp
6863 0x08048333 <+3>: sub $0x8,%esp
6864 0x08048336 <+6>: and $0xfffffff0,%esp
6865 0x08048339 <+9>: sub $0x10,%esp
6867 6 printf ("Hello.\n");
6868 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6869 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6873 0x08048348 <+24>: mov $0x0,%eax
6874 0x0804834d <+29>: leave
6875 0x0804834e <+30>: ret
6877 End of assembler dump.
6880 Here is another example showing raw instructions in hex for AMD x86-64,
6883 (gdb) disas /r 0x400281,+10
6884 Dump of assembler code from 0x400281 to 0x40028b:
6885 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6886 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6887 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6888 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6889 End of assembler dump.
6892 Some architectures have more than one commonly-used set of instruction
6893 mnemonics or other syntax.
6895 For programs that were dynamically linked and use shared libraries,
6896 instructions that call functions or branch to locations in the shared
6897 libraries might show a seemingly bogus location---it's actually a
6898 location of the relocation table. On some architectures, @value{GDBN}
6899 might be able to resolve these to actual function names.
6902 @kindex set disassembly-flavor
6903 @cindex Intel disassembly flavor
6904 @cindex AT&T disassembly flavor
6905 @item set disassembly-flavor @var{instruction-set}
6906 Select the instruction set to use when disassembling the
6907 program via the @code{disassemble} or @code{x/i} commands.
6909 Currently this command is only defined for the Intel x86 family. You
6910 can set @var{instruction-set} to either @code{intel} or @code{att}.
6911 The default is @code{att}, the AT&T flavor used by default by Unix
6912 assemblers for x86-based targets.
6914 @kindex show disassembly-flavor
6915 @item show disassembly-flavor
6916 Show the current setting of the disassembly flavor.
6920 @kindex set disassemble-next-line
6921 @kindex show disassemble-next-line
6922 @item set disassemble-next-line
6923 @itemx show disassemble-next-line
6924 Control whether or not @value{GDBN} will disassemble the next source
6925 line or instruction when execution stops. If ON, @value{GDBN} will
6926 display disassembly of the next source line when execution of the
6927 program being debugged stops. This is @emph{in addition} to
6928 displaying the source line itself, which @value{GDBN} always does if
6929 possible. If the next source line cannot be displayed for some reason
6930 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6931 info in the debug info), @value{GDBN} will display disassembly of the
6932 next @emph{instruction} instead of showing the next source line. If
6933 AUTO, @value{GDBN} will display disassembly of next instruction only
6934 if the source line cannot be displayed. This setting causes
6935 @value{GDBN} to display some feedback when you step through a function
6936 with no line info or whose source file is unavailable. The default is
6937 OFF, which means never display the disassembly of the next line or
6943 @chapter Examining Data
6945 @cindex printing data
6946 @cindex examining data
6949 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6950 @c document because it is nonstandard... Under Epoch it displays in a
6951 @c different window or something like that.
6952 The usual way to examine data in your program is with the @code{print}
6953 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6954 evaluates and prints the value of an expression of the language your
6955 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6956 Different Languages}). It may also print the expression using a
6957 Python-based pretty-printer (@pxref{Pretty Printing}).
6960 @item print @var{expr}
6961 @itemx print /@var{f} @var{expr}
6962 @var{expr} is an expression (in the source language). By default the
6963 value of @var{expr} is printed in a format appropriate to its data type;
6964 you can choose a different format by specifying @samp{/@var{f}}, where
6965 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6969 @itemx print /@var{f}
6970 @cindex reprint the last value
6971 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6972 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6973 conveniently inspect the same value in an alternative format.
6976 A more low-level way of examining data is with the @code{x} command.
6977 It examines data in memory at a specified address and prints it in a
6978 specified format. @xref{Memory, ,Examining Memory}.
6980 If you are interested in information about types, or about how the
6981 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6982 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6986 * Expressions:: Expressions
6987 * Ambiguous Expressions:: Ambiguous Expressions
6988 * Variables:: Program variables
6989 * Arrays:: Artificial arrays
6990 * Output Formats:: Output formats
6991 * Memory:: Examining memory
6992 * Auto Display:: Automatic display
6993 * Print Settings:: Print settings
6994 * Pretty Printing:: Python pretty printing
6995 * Value History:: Value history
6996 * Convenience Vars:: Convenience variables
6997 * Registers:: Registers
6998 * Floating Point Hardware:: Floating point hardware
6999 * Vector Unit:: Vector Unit
7000 * OS Information:: Auxiliary data provided by operating system
7001 * Memory Region Attributes:: Memory region attributes
7002 * Dump/Restore Files:: Copy between memory and a file
7003 * Core File Generation:: Cause a program dump its core
7004 * Character Sets:: Debugging programs that use a different
7005 character set than GDB does
7006 * Caching Remote Data:: Data caching for remote targets
7007 * Searching Memory:: Searching memory for a sequence of bytes
7011 @section Expressions
7014 @code{print} and many other @value{GDBN} commands accept an expression and
7015 compute its value. Any kind of constant, variable or operator defined
7016 by the programming language you are using is valid in an expression in
7017 @value{GDBN}. This includes conditional expressions, function calls,
7018 casts, and string constants. It also includes preprocessor macros, if
7019 you compiled your program to include this information; see
7022 @cindex arrays in expressions
7023 @value{GDBN} supports array constants in expressions input by
7024 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7025 you can use the command @code{print @{1, 2, 3@}} to create an array
7026 of three integers. If you pass an array to a function or assign it
7027 to a program variable, @value{GDBN} copies the array to memory that
7028 is @code{malloc}ed in the target program.
7030 Because C is so widespread, most of the expressions shown in examples in
7031 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7032 Languages}, for information on how to use expressions in other
7035 In this section, we discuss operators that you can use in @value{GDBN}
7036 expressions regardless of your programming language.
7038 @cindex casts, in expressions
7039 Casts are supported in all languages, not just in C, because it is so
7040 useful to cast a number into a pointer in order to examine a structure
7041 at that address in memory.
7042 @c FIXME: casts supported---Mod2 true?
7044 @value{GDBN} supports these operators, in addition to those common
7045 to programming languages:
7049 @samp{@@} is a binary operator for treating parts of memory as arrays.
7050 @xref{Arrays, ,Artificial Arrays}, for more information.
7053 @samp{::} allows you to specify a variable in terms of the file or
7054 function where it is defined. @xref{Variables, ,Program Variables}.
7056 @cindex @{@var{type}@}
7057 @cindex type casting memory
7058 @cindex memory, viewing as typed object
7059 @cindex casts, to view memory
7060 @item @{@var{type}@} @var{addr}
7061 Refers to an object of type @var{type} stored at address @var{addr} in
7062 memory. @var{addr} may be any expression whose value is an integer or
7063 pointer (but parentheses are required around binary operators, just as in
7064 a cast). This construct is allowed regardless of what kind of data is
7065 normally supposed to reside at @var{addr}.
7068 @node Ambiguous Expressions
7069 @section Ambiguous Expressions
7070 @cindex ambiguous expressions
7072 Expressions can sometimes contain some ambiguous elements. For instance,
7073 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7074 a single function name to be defined several times, for application in
7075 different contexts. This is called @dfn{overloading}. Another example
7076 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7077 templates and is typically instantiated several times, resulting in
7078 the same function name being defined in different contexts.
7080 In some cases and depending on the language, it is possible to adjust
7081 the expression to remove the ambiguity. For instance in C@t{++}, you
7082 can specify the signature of the function you want to break on, as in
7083 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7084 qualified name of your function often makes the expression unambiguous
7087 When an ambiguity that needs to be resolved is detected, the debugger
7088 has the capability to display a menu of numbered choices for each
7089 possibility, and then waits for the selection with the prompt @samp{>}.
7090 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7091 aborts the current command. If the command in which the expression was
7092 used allows more than one choice to be selected, the next option in the
7093 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7096 For example, the following session excerpt shows an attempt to set a
7097 breakpoint at the overloaded symbol @code{String::after}.
7098 We choose three particular definitions of that function name:
7100 @c FIXME! This is likely to change to show arg type lists, at least
7103 (@value{GDBP}) b String::after
7106 [2] file:String.cc; line number:867
7107 [3] file:String.cc; line number:860
7108 [4] file:String.cc; line number:875
7109 [5] file:String.cc; line number:853
7110 [6] file:String.cc; line number:846
7111 [7] file:String.cc; line number:735
7113 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7114 Breakpoint 2 at 0xb344: file String.cc, line 875.
7115 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7116 Multiple breakpoints were set.
7117 Use the "delete" command to delete unwanted
7124 @kindex set multiple-symbols
7125 @item set multiple-symbols @var{mode}
7126 @cindex multiple-symbols menu
7128 This option allows you to adjust the debugger behavior when an expression
7131 By default, @var{mode} is set to @code{all}. If the command with which
7132 the expression is used allows more than one choice, then @value{GDBN}
7133 automatically selects all possible choices. For instance, inserting
7134 a breakpoint on a function using an ambiguous name results in a breakpoint
7135 inserted on each possible match. However, if a unique choice must be made,
7136 then @value{GDBN} uses the menu to help you disambiguate the expression.
7137 For instance, printing the address of an overloaded function will result
7138 in the use of the menu.
7140 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7141 when an ambiguity is detected.
7143 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7144 an error due to the ambiguity and the command is aborted.
7146 @kindex show multiple-symbols
7147 @item show multiple-symbols
7148 Show the current value of the @code{multiple-symbols} setting.
7152 @section Program Variables
7154 The most common kind of expression to use is the name of a variable
7157 Variables in expressions are understood in the selected stack frame
7158 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7162 global (or file-static)
7169 visible according to the scope rules of the
7170 programming language from the point of execution in that frame
7173 @noindent This means that in the function
7188 you can examine and use the variable @code{a} whenever your program is
7189 executing within the function @code{foo}, but you can only use or
7190 examine the variable @code{b} while your program is executing inside
7191 the block where @code{b} is declared.
7193 @cindex variable name conflict
7194 There is an exception: you can refer to a variable or function whose
7195 scope is a single source file even if the current execution point is not
7196 in this file. But it is possible to have more than one such variable or
7197 function with the same name (in different source files). If that
7198 happens, referring to that name has unpredictable effects. If you wish,
7199 you can specify a static variable in a particular function or file,
7200 using the colon-colon (@code{::}) notation:
7202 @cindex colon-colon, context for variables/functions
7204 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7205 @cindex @code{::}, context for variables/functions
7208 @var{file}::@var{variable}
7209 @var{function}::@var{variable}
7213 Here @var{file} or @var{function} is the name of the context for the
7214 static @var{variable}. In the case of file names, you can use quotes to
7215 make sure @value{GDBN} parses the file name as a single word---for example,
7216 to print a global value of @code{x} defined in @file{f2.c}:
7219 (@value{GDBP}) p 'f2.c'::x
7222 @cindex C@t{++} scope resolution
7223 This use of @samp{::} is very rarely in conflict with the very similar
7224 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7225 scope resolution operator in @value{GDBN} expressions.
7226 @c FIXME: Um, so what happens in one of those rare cases where it's in
7229 @cindex wrong values
7230 @cindex variable values, wrong
7231 @cindex function entry/exit, wrong values of variables
7232 @cindex optimized code, wrong values of variables
7234 @emph{Warning:} Occasionally, a local variable may appear to have the
7235 wrong value at certain points in a function---just after entry to a new
7236 scope, and just before exit.
7238 You may see this problem when you are stepping by machine instructions.
7239 This is because, on most machines, it takes more than one instruction to
7240 set up a stack frame (including local variable definitions); if you are
7241 stepping by machine instructions, variables may appear to have the wrong
7242 values until the stack frame is completely built. On exit, it usually
7243 also takes more than one machine instruction to destroy a stack frame;
7244 after you begin stepping through that group of instructions, local
7245 variable definitions may be gone.
7247 This may also happen when the compiler does significant optimizations.
7248 To be sure of always seeing accurate values, turn off all optimization
7251 @cindex ``No symbol "foo" in current context''
7252 Another possible effect of compiler optimizations is to optimize
7253 unused variables out of existence, or assign variables to registers (as
7254 opposed to memory addresses). Depending on the support for such cases
7255 offered by the debug info format used by the compiler, @value{GDBN}
7256 might not be able to display values for such local variables. If that
7257 happens, @value{GDBN} will print a message like this:
7260 No symbol "foo" in current context.
7263 To solve such problems, either recompile without optimizations, or use a
7264 different debug info format, if the compiler supports several such
7265 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7266 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7267 produces debug info in a format that is superior to formats such as
7268 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7269 an effective form for debug info. @xref{Debugging Options,,Options
7270 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7271 Compiler Collection (GCC)}.
7272 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7273 that are best suited to C@t{++} programs.
7275 If you ask to print an object whose contents are unknown to
7276 @value{GDBN}, e.g., because its data type is not completely specified
7277 by the debug information, @value{GDBN} will say @samp{<incomplete
7278 type>}. @xref{Symbols, incomplete type}, for more about this.
7280 If you append @kbd{@@entry} string to a function parameter name you get its
7281 value at the time the function got called. If the value is not available an
7282 error message is printed. Entry values are available only with some compilers.
7283 Entry values are normally also printed at the function parameter list according
7284 to @ref{set print entry-values}.
7287 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7293 (gdb) print i@@entry
7297 Strings are identified as arrays of @code{char} values without specified
7298 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7299 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7300 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7301 defines literal string type @code{"char"} as @code{char} without a sign.
7306 signed char var1[] = "A";
7309 You get during debugging
7314 $2 = @{65 'A', 0 '\0'@}
7318 @section Artificial Arrays
7320 @cindex artificial array
7322 @kindex @@@r{, referencing memory as an array}
7323 It is often useful to print out several successive objects of the
7324 same type in memory; a section of an array, or an array of
7325 dynamically determined size for which only a pointer exists in the
7328 You can do this by referring to a contiguous span of memory as an
7329 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7330 operand of @samp{@@} should be the first element of the desired array
7331 and be an individual object. The right operand should be the desired length
7332 of the array. The result is an array value whose elements are all of
7333 the type of the left argument. The first element is actually the left
7334 argument; the second element comes from bytes of memory immediately
7335 following those that hold the first element, and so on. Here is an
7336 example. If a program says
7339 int *array = (int *) malloc (len * sizeof (int));
7343 you can print the contents of @code{array} with
7349 The left operand of @samp{@@} must reside in memory. Array values made
7350 with @samp{@@} in this way behave just like other arrays in terms of
7351 subscripting, and are coerced to pointers when used in expressions.
7352 Artificial arrays most often appear in expressions via the value history
7353 (@pxref{Value History, ,Value History}), after printing one out.
7355 Another way to create an artificial array is to use a cast.
7356 This re-interprets a value as if it were an array.
7357 The value need not be in memory:
7359 (@value{GDBP}) p/x (short[2])0x12345678
7360 $1 = @{0x1234, 0x5678@}
7363 As a convenience, if you leave the array length out (as in
7364 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7365 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7367 (@value{GDBP}) p/x (short[])0x12345678
7368 $2 = @{0x1234, 0x5678@}
7371 Sometimes the artificial array mechanism is not quite enough; in
7372 moderately complex data structures, the elements of interest may not
7373 actually be adjacent---for example, if you are interested in the values
7374 of pointers in an array. One useful work-around in this situation is
7375 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7376 Variables}) as a counter in an expression that prints the first
7377 interesting value, and then repeat that expression via @key{RET}. For
7378 instance, suppose you have an array @code{dtab} of pointers to
7379 structures, and you are interested in the values of a field @code{fv}
7380 in each structure. Here is an example of what you might type:
7390 @node Output Formats
7391 @section Output Formats
7393 @cindex formatted output
7394 @cindex output formats
7395 By default, @value{GDBN} prints a value according to its data type. Sometimes
7396 this is not what you want. For example, you might want to print a number
7397 in hex, or a pointer in decimal. Or you might want to view data in memory
7398 at a certain address as a character string or as an instruction. To do
7399 these things, specify an @dfn{output format} when you print a value.
7401 The simplest use of output formats is to say how to print a value
7402 already computed. This is done by starting the arguments of the
7403 @code{print} command with a slash and a format letter. The format
7404 letters supported are:
7408 Regard the bits of the value as an integer, and print the integer in
7412 Print as integer in signed decimal.
7415 Print as integer in unsigned decimal.
7418 Print as integer in octal.
7421 Print as integer in binary. The letter @samp{t} stands for ``two''.
7422 @footnote{@samp{b} cannot be used because these format letters are also
7423 used with the @code{x} command, where @samp{b} stands for ``byte'';
7424 see @ref{Memory,,Examining Memory}.}
7427 @cindex unknown address, locating
7428 @cindex locate address
7429 Print as an address, both absolute in hexadecimal and as an offset from
7430 the nearest preceding symbol. You can use this format used to discover
7431 where (in what function) an unknown address is located:
7434 (@value{GDBP}) p/a 0x54320
7435 $3 = 0x54320 <_initialize_vx+396>
7439 The command @code{info symbol 0x54320} yields similar results.
7440 @xref{Symbols, info symbol}.
7443 Regard as an integer and print it as a character constant. This
7444 prints both the numerical value and its character representation. The
7445 character representation is replaced with the octal escape @samp{\nnn}
7446 for characters outside the 7-bit @sc{ascii} range.
7448 Without this format, @value{GDBN} displays @code{char},
7449 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7450 constants. Single-byte members of vectors are displayed as integer
7454 Regard the bits of the value as a floating point number and print
7455 using typical floating point syntax.
7458 @cindex printing strings
7459 @cindex printing byte arrays
7460 Regard as a string, if possible. With this format, pointers to single-byte
7461 data are displayed as null-terminated strings and arrays of single-byte data
7462 are displayed as fixed-length strings. Other values are displayed in their
7465 Without this format, @value{GDBN} displays pointers to and arrays of
7466 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7467 strings. Single-byte members of a vector are displayed as an integer
7471 @cindex raw printing
7472 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7473 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7474 Printing}). This typically results in a higher-level display of the
7475 value's contents. The @samp{r} format bypasses any Python
7476 pretty-printer which might exist.
7479 For example, to print the program counter in hex (@pxref{Registers}), type
7486 Note that no space is required before the slash; this is because command
7487 names in @value{GDBN} cannot contain a slash.
7489 To reprint the last value in the value history with a different format,
7490 you can use the @code{print} command with just a format and no
7491 expression. For example, @samp{p/x} reprints the last value in hex.
7494 @section Examining Memory
7496 You can use the command @code{x} (for ``examine'') to examine memory in
7497 any of several formats, independently of your program's data types.
7499 @cindex examining memory
7501 @kindex x @r{(examine memory)}
7502 @item x/@var{nfu} @var{addr}
7505 Use the @code{x} command to examine memory.
7508 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7509 much memory to display and how to format it; @var{addr} is an
7510 expression giving the address where you want to start displaying memory.
7511 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7512 Several commands set convenient defaults for @var{addr}.
7515 @item @var{n}, the repeat count
7516 The repeat count is a decimal integer; the default is 1. It specifies
7517 how much memory (counting by units @var{u}) to display.
7518 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7521 @item @var{f}, the display format
7522 The display format is one of the formats used by @code{print}
7523 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7524 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7525 The default is @samp{x} (hexadecimal) initially. The default changes
7526 each time you use either @code{x} or @code{print}.
7528 @item @var{u}, the unit size
7529 The unit size is any of
7535 Halfwords (two bytes).
7537 Words (four bytes). This is the initial default.
7539 Giant words (eight bytes).
7542 Each time you specify a unit size with @code{x}, that size becomes the
7543 default unit the next time you use @code{x}. For the @samp{i} format,
7544 the unit size is ignored and is normally not written. For the @samp{s} format,
7545 the unit size defaults to @samp{b}, unless it is explicitly given.
7546 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7547 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7548 Note that the results depend on the programming language of the
7549 current compilation unit. If the language is C, the @samp{s}
7550 modifier will use the UTF-16 encoding while @samp{w} will use
7551 UTF-32. The encoding is set by the programming language and cannot
7554 @item @var{addr}, starting display address
7555 @var{addr} is the address where you want @value{GDBN} to begin displaying
7556 memory. The expression need not have a pointer value (though it may);
7557 it is always interpreted as an integer address of a byte of memory.
7558 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7559 @var{addr} is usually just after the last address examined---but several
7560 other commands also set the default address: @code{info breakpoints} (to
7561 the address of the last breakpoint listed), @code{info line} (to the
7562 starting address of a line), and @code{print} (if you use it to display
7563 a value from memory).
7566 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7567 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7568 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7569 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7570 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7572 Since the letters indicating unit sizes are all distinct from the
7573 letters specifying output formats, you do not have to remember whether
7574 unit size or format comes first; either order works. The output
7575 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7576 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7578 Even though the unit size @var{u} is ignored for the formats @samp{s}
7579 and @samp{i}, you might still want to use a count @var{n}; for example,
7580 @samp{3i} specifies that you want to see three machine instructions,
7581 including any operands. For convenience, especially when used with
7582 the @code{display} command, the @samp{i} format also prints branch delay
7583 slot instructions, if any, beyond the count specified, which immediately
7584 follow the last instruction that is within the count. The command
7585 @code{disassemble} gives an alternative way of inspecting machine
7586 instructions; see @ref{Machine Code,,Source and Machine Code}.
7588 All the defaults for the arguments to @code{x} are designed to make it
7589 easy to continue scanning memory with minimal specifications each time
7590 you use @code{x}. For example, after you have inspected three machine
7591 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7592 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7593 the repeat count @var{n} is used again; the other arguments default as
7594 for successive uses of @code{x}.
7596 When examining machine instructions, the instruction at current program
7597 counter is shown with a @code{=>} marker. For example:
7600 (@value{GDBP}) x/5i $pc-6
7601 0x804837f <main+11>: mov %esp,%ebp
7602 0x8048381 <main+13>: push %ecx
7603 0x8048382 <main+14>: sub $0x4,%esp
7604 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7605 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7608 @cindex @code{$_}, @code{$__}, and value history
7609 The addresses and contents printed by the @code{x} command are not saved
7610 in the value history because there is often too much of them and they
7611 would get in the way. Instead, @value{GDBN} makes these values available for
7612 subsequent use in expressions as values of the convenience variables
7613 @code{$_} and @code{$__}. After an @code{x} command, the last address
7614 examined is available for use in expressions in the convenience variable
7615 @code{$_}. The contents of that address, as examined, are available in
7616 the convenience variable @code{$__}.
7618 If the @code{x} command has a repeat count, the address and contents saved
7619 are from the last memory unit printed; this is not the same as the last
7620 address printed if several units were printed on the last line of output.
7622 @cindex remote memory comparison
7623 @cindex verify remote memory image
7624 When you are debugging a program running on a remote target machine
7625 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7626 remote machine's memory against the executable file you downloaded to
7627 the target. The @code{compare-sections} command is provided for such
7631 @kindex compare-sections
7632 @item compare-sections @r{[}@var{section-name}@r{]}
7633 Compare the data of a loadable section @var{section-name} in the
7634 executable file of the program being debugged with the same section in
7635 the remote machine's memory, and report any mismatches. With no
7636 arguments, compares all loadable sections. This command's
7637 availability depends on the target's support for the @code{"qCRC"}
7642 @section Automatic Display
7643 @cindex automatic display
7644 @cindex display of expressions
7646 If you find that you want to print the value of an expression frequently
7647 (to see how it changes), you might want to add it to the @dfn{automatic
7648 display list} so that @value{GDBN} prints its value each time your program stops.
7649 Each expression added to the list is given a number to identify it;
7650 to remove an expression from the list, you specify that number.
7651 The automatic display looks like this:
7655 3: bar[5] = (struct hack *) 0x3804
7659 This display shows item numbers, expressions and their current values. As with
7660 displays you request manually using @code{x} or @code{print}, you can
7661 specify the output format you prefer; in fact, @code{display} decides
7662 whether to use @code{print} or @code{x} depending your format
7663 specification---it uses @code{x} if you specify either the @samp{i}
7664 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7668 @item display @var{expr}
7669 Add the expression @var{expr} to the list of expressions to display
7670 each time your program stops. @xref{Expressions, ,Expressions}.
7672 @code{display} does not repeat if you press @key{RET} again after using it.
7674 @item display/@var{fmt} @var{expr}
7675 For @var{fmt} specifying only a display format and not a size or
7676 count, add the expression @var{expr} to the auto-display list but
7677 arrange to display it each time in the specified format @var{fmt}.
7678 @xref{Output Formats,,Output Formats}.
7680 @item display/@var{fmt} @var{addr}
7681 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7682 number of units, add the expression @var{addr} as a memory address to
7683 be examined each time your program stops. Examining means in effect
7684 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7687 For example, @samp{display/i $pc} can be helpful, to see the machine
7688 instruction about to be executed each time execution stops (@samp{$pc}
7689 is a common name for the program counter; @pxref{Registers, ,Registers}).
7692 @kindex delete display
7694 @item undisplay @var{dnums}@dots{}
7695 @itemx delete display @var{dnums}@dots{}
7696 Remove items from the list of expressions to display. Specify the
7697 numbers of the displays that you want affected with the command
7698 argument @var{dnums}. It can be a single display number, one of the
7699 numbers shown in the first field of the @samp{info display} display;
7700 or it could be a range of display numbers, as in @code{2-4}.
7702 @code{undisplay} does not repeat if you press @key{RET} after using it.
7703 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7705 @kindex disable display
7706 @item disable display @var{dnums}@dots{}
7707 Disable the display of item numbers @var{dnums}. A disabled display
7708 item is not printed automatically, but is not forgotten. It may be
7709 enabled again later. Specify the numbers of the displays that you
7710 want affected with the command argument @var{dnums}. It can be a
7711 single display number, one of the numbers shown in the first field of
7712 the @samp{info display} display; or it could be a range of display
7713 numbers, as in @code{2-4}.
7715 @kindex enable display
7716 @item enable display @var{dnums}@dots{}
7717 Enable display of item numbers @var{dnums}. It becomes effective once
7718 again in auto display of its expression, until you specify otherwise.
7719 Specify the numbers of the displays that you want affected with the
7720 command argument @var{dnums}. It can be a single display number, one
7721 of the numbers shown in the first field of the @samp{info display}
7722 display; or it could be a range of display numbers, as in @code{2-4}.
7725 Display the current values of the expressions on the list, just as is
7726 done when your program stops.
7728 @kindex info display
7730 Print the list of expressions previously set up to display
7731 automatically, each one with its item number, but without showing the
7732 values. This includes disabled expressions, which are marked as such.
7733 It also includes expressions which would not be displayed right now
7734 because they refer to automatic variables not currently available.
7737 @cindex display disabled out of scope
7738 If a display expression refers to local variables, then it does not make
7739 sense outside the lexical context for which it was set up. Such an
7740 expression is disabled when execution enters a context where one of its
7741 variables is not defined. For example, if you give the command
7742 @code{display last_char} while inside a function with an argument
7743 @code{last_char}, @value{GDBN} displays this argument while your program
7744 continues to stop inside that function. When it stops elsewhere---where
7745 there is no variable @code{last_char}---the display is disabled
7746 automatically. The next time your program stops where @code{last_char}
7747 is meaningful, you can enable the display expression once again.
7749 @node Print Settings
7750 @section Print Settings
7752 @cindex format options
7753 @cindex print settings
7754 @value{GDBN} provides the following ways to control how arrays, structures,
7755 and symbols are printed.
7758 These settings are useful for debugging programs in any language:
7762 @item set print address
7763 @itemx set print address on
7764 @cindex print/don't print memory addresses
7765 @value{GDBN} prints memory addresses showing the location of stack
7766 traces, structure values, pointer values, breakpoints, and so forth,
7767 even when it also displays the contents of those addresses. The default
7768 is @code{on}. For example, this is what a stack frame display looks like with
7769 @code{set print address on}:
7774 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7776 530 if (lquote != def_lquote)
7780 @item set print address off
7781 Do not print addresses when displaying their contents. For example,
7782 this is the same stack frame displayed with @code{set print address off}:
7786 (@value{GDBP}) set print addr off
7788 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7789 530 if (lquote != def_lquote)
7793 You can use @samp{set print address off} to eliminate all machine
7794 dependent displays from the @value{GDBN} interface. For example, with
7795 @code{print address off}, you should get the same text for backtraces on
7796 all machines---whether or not they involve pointer arguments.
7799 @item show print address
7800 Show whether or not addresses are to be printed.
7803 When @value{GDBN} prints a symbolic address, it normally prints the
7804 closest earlier symbol plus an offset. If that symbol does not uniquely
7805 identify the address (for example, it is a name whose scope is a single
7806 source file), you may need to clarify. One way to do this is with
7807 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7808 you can set @value{GDBN} to print the source file and line number when
7809 it prints a symbolic address:
7812 @item set print symbol-filename on
7813 @cindex source file and line of a symbol
7814 @cindex symbol, source file and line
7815 Tell @value{GDBN} to print the source file name and line number of a
7816 symbol in the symbolic form of an address.
7818 @item set print symbol-filename off
7819 Do not print source file name and line number of a symbol. This is the
7822 @item show print symbol-filename
7823 Show whether or not @value{GDBN} will print the source file name and
7824 line number of a symbol in the symbolic form of an address.
7827 Another situation where it is helpful to show symbol filenames and line
7828 numbers is when disassembling code; @value{GDBN} shows you the line
7829 number and source file that corresponds to each instruction.
7831 Also, you may wish to see the symbolic form only if the address being
7832 printed is reasonably close to the closest earlier symbol:
7835 @item set print max-symbolic-offset @var{max-offset}
7836 @cindex maximum value for offset of closest symbol
7837 Tell @value{GDBN} to only display the symbolic form of an address if the
7838 offset between the closest earlier symbol and the address is less than
7839 @var{max-offset}. The default is 0, which tells @value{GDBN}
7840 to always print the symbolic form of an address if any symbol precedes it.
7842 @item show print max-symbolic-offset
7843 Ask how large the maximum offset is that @value{GDBN} prints in a
7847 @cindex wild pointer, interpreting
7848 @cindex pointer, finding referent
7849 If you have a pointer and you are not sure where it points, try
7850 @samp{set print symbol-filename on}. Then you can determine the name
7851 and source file location of the variable where it points, using
7852 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7853 For example, here @value{GDBN} shows that a variable @code{ptt} points
7854 at another variable @code{t}, defined in @file{hi2.c}:
7857 (@value{GDBP}) set print symbol-filename on
7858 (@value{GDBP}) p/a ptt
7859 $4 = 0xe008 <t in hi2.c>
7863 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7864 does not show the symbol name and filename of the referent, even with
7865 the appropriate @code{set print} options turned on.
7868 Other settings control how different kinds of objects are printed:
7871 @item set print array
7872 @itemx set print array on
7873 @cindex pretty print arrays
7874 Pretty print arrays. This format is more convenient to read,
7875 but uses more space. The default is off.
7877 @item set print array off
7878 Return to compressed format for arrays.
7880 @item show print array
7881 Show whether compressed or pretty format is selected for displaying
7884 @cindex print array indexes
7885 @item set print array-indexes
7886 @itemx set print array-indexes on
7887 Print the index of each element when displaying arrays. May be more
7888 convenient to locate a given element in the array or quickly find the
7889 index of a given element in that printed array. The default is off.
7891 @item set print array-indexes off
7892 Stop printing element indexes when displaying arrays.
7894 @item show print array-indexes
7895 Show whether the index of each element is printed when displaying
7898 @item set print elements @var{number-of-elements}
7899 @cindex number of array elements to print
7900 @cindex limit on number of printed array elements
7901 Set a limit on how many elements of an array @value{GDBN} will print.
7902 If @value{GDBN} is printing a large array, it stops printing after it has
7903 printed the number of elements set by the @code{set print elements} command.
7904 This limit also applies to the display of strings.
7905 When @value{GDBN} starts, this limit is set to 200.
7906 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7908 @item show print elements
7909 Display the number of elements of a large array that @value{GDBN} will print.
7910 If the number is 0, then the printing is unlimited.
7912 @item set print frame-arguments @var{value}
7913 @kindex set print frame-arguments
7914 @cindex printing frame argument values
7915 @cindex print all frame argument values
7916 @cindex print frame argument values for scalars only
7917 @cindex do not print frame argument values
7918 This command allows to control how the values of arguments are printed
7919 when the debugger prints a frame (@pxref{Frames}). The possible
7924 The values of all arguments are printed.
7927 Print the value of an argument only if it is a scalar. The value of more
7928 complex arguments such as arrays, structures, unions, etc, is replaced
7929 by @code{@dots{}}. This is the default. Here is an example where
7930 only scalar arguments are shown:
7933 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7938 None of the argument values are printed. Instead, the value of each argument
7939 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7942 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7947 By default, only scalar arguments are printed. This command can be used
7948 to configure the debugger to print the value of all arguments, regardless
7949 of their type. However, it is often advantageous to not print the value
7950 of more complex parameters. For instance, it reduces the amount of
7951 information printed in each frame, making the backtrace more readable.
7952 Also, it improves performance when displaying Ada frames, because
7953 the computation of large arguments can sometimes be CPU-intensive,
7954 especially in large applications. Setting @code{print frame-arguments}
7955 to @code{scalars} (the default) or @code{none} avoids this computation,
7956 thus speeding up the display of each Ada frame.
7958 @item show print frame-arguments
7959 Show how the value of arguments should be displayed when printing a frame.
7961 @anchor{set print entry-values}
7962 @item set print entry-values @var{value}
7963 @kindex set print entry-values
7964 Set printing of frame argument values at function entry. In some cases
7965 @value{GDBN} can determine the value of function argument which was passed by
7966 the function caller, even if the value was modified inside the called function
7967 and therefore is different. With optimized code, the current value could be
7968 unavailable, but the entry value may still be known.
7970 The default value is @code{default} (see below for its description). Older
7971 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
7972 this feature will behave in the @code{default} setting the same way as with the
7975 This functionality is currently supported only by DWARF 2 debugging format and
7976 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
7977 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
7980 The @var{value} parameter can be one of the following:
7984 Print only actual parameter values, never print values from function entry
7988 #0 different (val=6)
7989 #0 lost (val=<optimized out>)
7991 #0 invalid (val=<optimized out>)
7995 Print only parameter values from function entry point. The actual parameter
7996 values are never printed.
7998 #0 equal (val@@entry=5)
7999 #0 different (val@@entry=5)
8000 #0 lost (val@@entry=5)
8001 #0 born (val@@entry=<optimized out>)
8002 #0 invalid (val@@entry=<optimized out>)
8006 Print only parameter values from function entry point. If value from function
8007 entry point is not known while the actual value is known, print the actual
8008 value for such parameter.
8010 #0 equal (val@@entry=5)
8011 #0 different (val@@entry=5)
8012 #0 lost (val@@entry=5)
8014 #0 invalid (val@@entry=<optimized out>)
8018 Print actual parameter values. If actual parameter value is not known while
8019 value from function entry point is known, print the entry point value for such
8023 #0 different (val=6)
8024 #0 lost (val@@entry=5)
8026 #0 invalid (val=<optimized out>)
8030 Always print both the actual parameter value and its value from function entry
8031 point, even if values of one or both are not available due to compiler
8034 #0 equal (val=5, val@@entry=5)
8035 #0 different (val=6, val@@entry=5)
8036 #0 lost (val=<optimized out>, val@@entry=5)
8037 #0 born (val=10, val@@entry=<optimized out>)
8038 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8042 Print the actual parameter value if it is known and also its value from
8043 function entry point if it is known. If neither is known, print for the actual
8044 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8045 values are known and identical, print the shortened
8046 @code{param=param@@entry=VALUE} notation.
8048 #0 equal (val=val@@entry=5)
8049 #0 different (val=6, val@@entry=5)
8050 #0 lost (val@@entry=5)
8052 #0 invalid (val=<optimized out>)
8056 Always print the actual parameter value. Print also its value from function
8057 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8058 if both values are known and identical, print the shortened
8059 @code{param=param@@entry=VALUE} notation.
8061 #0 equal (val=val@@entry=5)
8062 #0 different (val=6, val@@entry=5)
8063 #0 lost (val=<optimized out>, val@@entry=5)
8065 #0 invalid (val=<optimized out>)
8069 For analysis messages on possible failures of frame argument values at function
8070 entry resolution see @ref{set debug entry-values}.
8072 @item show print entry-values
8073 Show the method being used for printing of frame argument values at function
8076 @item set print repeats
8077 @cindex repeated array elements
8078 Set the threshold for suppressing display of repeated array
8079 elements. When the number of consecutive identical elements of an
8080 array exceeds the threshold, @value{GDBN} prints the string
8081 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8082 identical repetitions, instead of displaying the identical elements
8083 themselves. Setting the threshold to zero will cause all elements to
8084 be individually printed. The default threshold is 10.
8086 @item show print repeats
8087 Display the current threshold for printing repeated identical
8090 @item set print null-stop
8091 @cindex @sc{null} elements in arrays
8092 Cause @value{GDBN} to stop printing the characters of an array when the first
8093 @sc{null} is encountered. This is useful when large arrays actually
8094 contain only short strings.
8097 @item show print null-stop
8098 Show whether @value{GDBN} stops printing an array on the first
8099 @sc{null} character.
8101 @item set print pretty on
8102 @cindex print structures in indented form
8103 @cindex indentation in structure display
8104 Cause @value{GDBN} to print structures in an indented format with one member
8105 per line, like this:
8120 @item set print pretty off
8121 Cause @value{GDBN} to print structures in a compact format, like this:
8125 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8126 meat = 0x54 "Pork"@}
8131 This is the default format.
8133 @item show print pretty
8134 Show which format @value{GDBN} is using to print structures.
8136 @item set print sevenbit-strings on
8137 @cindex eight-bit characters in strings
8138 @cindex octal escapes in strings
8139 Print using only seven-bit characters; if this option is set,
8140 @value{GDBN} displays any eight-bit characters (in strings or
8141 character values) using the notation @code{\}@var{nnn}. This setting is
8142 best if you are working in English (@sc{ascii}) and you use the
8143 high-order bit of characters as a marker or ``meta'' bit.
8145 @item set print sevenbit-strings off
8146 Print full eight-bit characters. This allows the use of more
8147 international character sets, and is the default.
8149 @item show print sevenbit-strings
8150 Show whether or not @value{GDBN} is printing only seven-bit characters.
8152 @item set print union on
8153 @cindex unions in structures, printing
8154 Tell @value{GDBN} to print unions which are contained in structures
8155 and other unions. This is the default setting.
8157 @item set print union off
8158 Tell @value{GDBN} not to print unions which are contained in
8159 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8162 @item show print union
8163 Ask @value{GDBN} whether or not it will print unions which are contained in
8164 structures and other unions.
8166 For example, given the declarations
8169 typedef enum @{Tree, Bug@} Species;
8170 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8171 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8182 struct thing foo = @{Tree, @{Acorn@}@};
8186 with @code{set print union on} in effect @samp{p foo} would print
8189 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8193 and with @code{set print union off} in effect it would print
8196 $1 = @{it = Tree, form = @{...@}@}
8200 @code{set print union} affects programs written in C-like languages
8206 These settings are of interest when debugging C@t{++} programs:
8209 @cindex demangling C@t{++} names
8210 @item set print demangle
8211 @itemx set print demangle on
8212 Print C@t{++} names in their source form rather than in the encoded
8213 (``mangled'') form passed to the assembler and linker for type-safe
8214 linkage. The default is on.
8216 @item show print demangle
8217 Show whether C@t{++} names are printed in mangled or demangled form.
8219 @item set print asm-demangle
8220 @itemx set print asm-demangle on
8221 Print C@t{++} names in their source form rather than their mangled form, even
8222 in assembler code printouts such as instruction disassemblies.
8225 @item show print asm-demangle
8226 Show whether C@t{++} names in assembly listings are printed in mangled
8229 @cindex C@t{++} symbol decoding style
8230 @cindex symbol decoding style, C@t{++}
8231 @kindex set demangle-style
8232 @item set demangle-style @var{style}
8233 Choose among several encoding schemes used by different compilers to
8234 represent C@t{++} names. The choices for @var{style} are currently:
8238 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8241 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8242 This is the default.
8245 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8248 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8251 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8252 @strong{Warning:} this setting alone is not sufficient to allow
8253 debugging @code{cfront}-generated executables. @value{GDBN} would
8254 require further enhancement to permit that.
8257 If you omit @var{style}, you will see a list of possible formats.
8259 @item show demangle-style
8260 Display the encoding style currently in use for decoding C@t{++} symbols.
8262 @item set print object
8263 @itemx set print object on
8264 @cindex derived type of an object, printing
8265 @cindex display derived types
8266 When displaying a pointer to an object, identify the @emph{actual}
8267 (derived) type of the object rather than the @emph{declared} type, using
8268 the virtual function table.
8270 @item set print object off
8271 Display only the declared type of objects, without reference to the
8272 virtual function table. This is the default setting.
8274 @item show print object
8275 Show whether actual, or declared, object types are displayed.
8277 @item set print static-members
8278 @itemx set print static-members on
8279 @cindex static members of C@t{++} objects
8280 Print static members when displaying a C@t{++} object. The default is on.
8282 @item set print static-members off
8283 Do not print static members when displaying a C@t{++} object.
8285 @item show print static-members
8286 Show whether C@t{++} static members are printed or not.
8288 @item set print pascal_static-members
8289 @itemx set print pascal_static-members on
8290 @cindex static members of Pascal objects
8291 @cindex Pascal objects, static members display
8292 Print static members when displaying a Pascal object. The default is on.
8294 @item set print pascal_static-members off
8295 Do not print static members when displaying a Pascal object.
8297 @item show print pascal_static-members
8298 Show whether Pascal static members are printed or not.
8300 @c These don't work with HP ANSI C++ yet.
8301 @item set print vtbl
8302 @itemx set print vtbl on
8303 @cindex pretty print C@t{++} virtual function tables
8304 @cindex virtual functions (C@t{++}) display
8305 @cindex VTBL display
8306 Pretty print C@t{++} virtual function tables. The default is off.
8307 (The @code{vtbl} commands do not work on programs compiled with the HP
8308 ANSI C@t{++} compiler (@code{aCC}).)
8310 @item set print vtbl off
8311 Do not pretty print C@t{++} virtual function tables.
8313 @item show print vtbl
8314 Show whether C@t{++} virtual function tables are pretty printed, or not.
8317 @node Pretty Printing
8318 @section Pretty Printing
8320 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8321 Python code. It greatly simplifies the display of complex objects. This
8322 mechanism works for both MI and the CLI.
8325 * Pretty-Printer Introduction:: Introduction to pretty-printers
8326 * Pretty-Printer Example:: An example pretty-printer
8327 * Pretty-Printer Commands:: Pretty-printer commands
8330 @node Pretty-Printer Introduction
8331 @subsection Pretty-Printer Introduction
8333 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8334 registered for the value. If there is then @value{GDBN} invokes the
8335 pretty-printer to print the value. Otherwise the value is printed normally.
8337 Pretty-printers are normally named. This makes them easy to manage.
8338 The @samp{info pretty-printer} command will list all the installed
8339 pretty-printers with their names.
8340 If a pretty-printer can handle multiple data types, then its
8341 @dfn{subprinters} are the printers for the individual data types.
8342 Each such subprinter has its own name.
8343 The format of the name is @var{printer-name};@var{subprinter-name}.
8345 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8346 Typically they are automatically loaded and registered when the corresponding
8347 debug information is loaded, thus making them available without having to
8348 do anything special.
8350 There are three places where a pretty-printer can be registered.
8354 Pretty-printers registered globally are available when debugging
8358 Pretty-printers registered with a program space are available only
8359 when debugging that program.
8360 @xref{Progspaces In Python}, for more details on program spaces in Python.
8363 Pretty-printers registered with an objfile are loaded and unloaded
8364 with the corresponding objfile (e.g., shared library).
8365 @xref{Objfiles In Python}, for more details on objfiles in Python.
8368 @xref{Selecting Pretty-Printers}, for further information on how
8369 pretty-printers are selected,
8371 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8374 @node Pretty-Printer Example
8375 @subsection Pretty-Printer Example
8377 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8380 (@value{GDBP}) print s
8382 static npos = 4294967295,
8384 <std::allocator<char>> = @{
8385 <__gnu_cxx::new_allocator<char>> = @{
8386 <No data fields>@}, <No data fields>
8388 members of std::basic_string<char, std::char_traits<char>,
8389 std::allocator<char> >::_Alloc_hider:
8390 _M_p = 0x804a014 "abcd"
8395 With a pretty-printer for @code{std::string} only the contents are printed:
8398 (@value{GDBP}) print s
8402 @node Pretty-Printer Commands
8403 @subsection Pretty-Printer Commands
8404 @cindex pretty-printer commands
8407 @kindex info pretty-printer
8408 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8409 Print the list of installed pretty-printers.
8410 This includes disabled pretty-printers, which are marked as such.
8412 @var{object-regexp} is a regular expression matching the objects
8413 whose pretty-printers to list.
8414 Objects can be @code{global}, the program space's file
8415 (@pxref{Progspaces In Python}),
8416 and the object files within that program space (@pxref{Objfiles In Python}).
8417 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8418 looks up a printer from these three objects.
8420 @var{name-regexp} is a regular expression matching the name of the printers
8423 @kindex disable pretty-printer
8424 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8425 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8426 A disabled pretty-printer is not forgotten, it may be enabled again later.
8428 @kindex enable pretty-printer
8429 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8430 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8435 Suppose we have three pretty-printers installed: one from library1.so
8436 named @code{foo} that prints objects of type @code{foo}, and
8437 another from library2.so named @code{bar} that prints two types of objects,
8438 @code{bar1} and @code{bar2}.
8441 (gdb) info pretty-printer
8448 (gdb) info pretty-printer library2
8453 (gdb) disable pretty-printer library1
8455 2 of 3 printers enabled
8456 (gdb) info pretty-printer
8463 (gdb) disable pretty-printer library2 bar:bar1
8465 1 of 3 printers enabled
8466 (gdb) info pretty-printer library2
8473 (gdb) disable pretty-printer library2 bar
8475 0 of 3 printers enabled
8476 (gdb) info pretty-printer library2
8485 Note that for @code{bar} the entire printer can be disabled,
8486 as can each individual subprinter.
8489 @section Value History
8491 @cindex value history
8492 @cindex history of values printed by @value{GDBN}
8493 Values printed by the @code{print} command are saved in the @value{GDBN}
8494 @dfn{value history}. This allows you to refer to them in other expressions.
8495 Values are kept until the symbol table is re-read or discarded
8496 (for example with the @code{file} or @code{symbol-file} commands).
8497 When the symbol table changes, the value history is discarded,
8498 since the values may contain pointers back to the types defined in the
8503 @cindex history number
8504 The values printed are given @dfn{history numbers} by which you can
8505 refer to them. These are successive integers starting with one.
8506 @code{print} shows you the history number assigned to a value by
8507 printing @samp{$@var{num} = } before the value; here @var{num} is the
8510 To refer to any previous value, use @samp{$} followed by the value's
8511 history number. The way @code{print} labels its output is designed to
8512 remind you of this. Just @code{$} refers to the most recent value in
8513 the history, and @code{$$} refers to the value before that.
8514 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8515 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8516 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8518 For example, suppose you have just printed a pointer to a structure and
8519 want to see the contents of the structure. It suffices to type
8525 If you have a chain of structures where the component @code{next} points
8526 to the next one, you can print the contents of the next one with this:
8533 You can print successive links in the chain by repeating this
8534 command---which you can do by just typing @key{RET}.
8536 Note that the history records values, not expressions. If the value of
8537 @code{x} is 4 and you type these commands:
8545 then the value recorded in the value history by the @code{print} command
8546 remains 4 even though the value of @code{x} has changed.
8551 Print the last ten values in the value history, with their item numbers.
8552 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8553 values} does not change the history.
8555 @item show values @var{n}
8556 Print ten history values centered on history item number @var{n}.
8559 Print ten history values just after the values last printed. If no more
8560 values are available, @code{show values +} produces no display.
8563 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8564 same effect as @samp{show values +}.
8566 @node Convenience Vars
8567 @section Convenience Variables
8569 @cindex convenience variables
8570 @cindex user-defined variables
8571 @value{GDBN} provides @dfn{convenience variables} that you can use within
8572 @value{GDBN} to hold on to a value and refer to it later. These variables
8573 exist entirely within @value{GDBN}; they are not part of your program, and
8574 setting a convenience variable has no direct effect on further execution
8575 of your program. That is why you can use them freely.
8577 Convenience variables are prefixed with @samp{$}. Any name preceded by
8578 @samp{$} can be used for a convenience variable, unless it is one of
8579 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8580 (Value history references, in contrast, are @emph{numbers} preceded
8581 by @samp{$}. @xref{Value History, ,Value History}.)
8583 You can save a value in a convenience variable with an assignment
8584 expression, just as you would set a variable in your program.
8588 set $foo = *object_ptr
8592 would save in @code{$foo} the value contained in the object pointed to by
8595 Using a convenience variable for the first time creates it, but its
8596 value is @code{void} until you assign a new value. You can alter the
8597 value with another assignment at any time.
8599 Convenience variables have no fixed types. You can assign a convenience
8600 variable any type of value, including structures and arrays, even if
8601 that variable already has a value of a different type. The convenience
8602 variable, when used as an expression, has the type of its current value.
8605 @kindex show convenience
8606 @cindex show all user variables
8607 @item show convenience
8608 Print a list of convenience variables used so far, and their values.
8609 Abbreviated @code{show conv}.
8611 @kindex init-if-undefined
8612 @cindex convenience variables, initializing
8613 @item init-if-undefined $@var{variable} = @var{expression}
8614 Set a convenience variable if it has not already been set. This is useful
8615 for user-defined commands that keep some state. It is similar, in concept,
8616 to using local static variables with initializers in C (except that
8617 convenience variables are global). It can also be used to allow users to
8618 override default values used in a command script.
8620 If the variable is already defined then the expression is not evaluated so
8621 any side-effects do not occur.
8624 One of the ways to use a convenience variable is as a counter to be
8625 incremented or a pointer to be advanced. For example, to print
8626 a field from successive elements of an array of structures:
8630 print bar[$i++]->contents
8634 Repeat that command by typing @key{RET}.
8636 Some convenience variables are created automatically by @value{GDBN} and given
8637 values likely to be useful.
8640 @vindex $_@r{, convenience variable}
8642 The variable @code{$_} is automatically set by the @code{x} command to
8643 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8644 commands which provide a default address for @code{x} to examine also
8645 set @code{$_} to that address; these commands include @code{info line}
8646 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8647 except when set by the @code{x} command, in which case it is a pointer
8648 to the type of @code{$__}.
8650 @vindex $__@r{, convenience variable}
8652 The variable @code{$__} is automatically set by the @code{x} command
8653 to the value found in the last address examined. Its type is chosen
8654 to match the format in which the data was printed.
8657 @vindex $_exitcode@r{, convenience variable}
8658 The variable @code{$_exitcode} is automatically set to the exit code when
8659 the program being debugged terminates.
8662 @vindex $_sdata@r{, inspect, convenience variable}
8663 The variable @code{$_sdata} contains extra collected static tracepoint
8664 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8665 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8666 if extra static tracepoint data has not been collected.
8669 @vindex $_siginfo@r{, convenience variable}
8670 The variable @code{$_siginfo} contains extra signal information
8671 (@pxref{extra signal information}). Note that @code{$_siginfo}
8672 could be empty, if the application has not yet received any signals.
8673 For example, it will be empty before you execute the @code{run} command.
8676 @vindex $_tlb@r{, convenience variable}
8677 The variable @code{$_tlb} is automatically set when debugging
8678 applications running on MS-Windows in native mode or connected to
8679 gdbserver that supports the @code{qGetTIBAddr} request.
8680 @xref{General Query Packets}.
8681 This variable contains the address of the thread information block.
8685 On HP-UX systems, if you refer to a function or variable name that
8686 begins with a dollar sign, @value{GDBN} searches for a user or system
8687 name first, before it searches for a convenience variable.
8689 @cindex convenience functions
8690 @value{GDBN} also supplies some @dfn{convenience functions}. These
8691 have a syntax similar to convenience variables. A convenience
8692 function can be used in an expression just like an ordinary function;
8693 however, a convenience function is implemented internally to
8698 @kindex help function
8699 @cindex show all convenience functions
8700 Print a list of all convenience functions.
8707 You can refer to machine register contents, in expressions, as variables
8708 with names starting with @samp{$}. The names of registers are different
8709 for each machine; use @code{info registers} to see the names used on
8713 @kindex info registers
8714 @item info registers
8715 Print the names and values of all registers except floating-point
8716 and vector registers (in the selected stack frame).
8718 @kindex info all-registers
8719 @cindex floating point registers
8720 @item info all-registers
8721 Print the names and values of all registers, including floating-point
8722 and vector registers (in the selected stack frame).
8724 @item info registers @var{regname} @dots{}
8725 Print the @dfn{relativized} value of each specified register @var{regname}.
8726 As discussed in detail below, register values are normally relative to
8727 the selected stack frame. @var{regname} may be any register name valid on
8728 the machine you are using, with or without the initial @samp{$}.
8731 @cindex stack pointer register
8732 @cindex program counter register
8733 @cindex process status register
8734 @cindex frame pointer register
8735 @cindex standard registers
8736 @value{GDBN} has four ``standard'' register names that are available (in
8737 expressions) on most machines---whenever they do not conflict with an
8738 architecture's canonical mnemonics for registers. The register names
8739 @code{$pc} and @code{$sp} are used for the program counter register and
8740 the stack pointer. @code{$fp} is used for a register that contains a
8741 pointer to the current stack frame, and @code{$ps} is used for a
8742 register that contains the processor status. For example,
8743 you could print the program counter in hex with
8750 or print the instruction to be executed next with
8757 or add four to the stack pointer@footnote{This is a way of removing
8758 one word from the stack, on machines where stacks grow downward in
8759 memory (most machines, nowadays). This assumes that the innermost
8760 stack frame is selected; setting @code{$sp} is not allowed when other
8761 stack frames are selected. To pop entire frames off the stack,
8762 regardless of machine architecture, use @code{return};
8763 see @ref{Returning, ,Returning from a Function}.} with
8769 Whenever possible, these four standard register names are available on
8770 your machine even though the machine has different canonical mnemonics,
8771 so long as there is no conflict. The @code{info registers} command
8772 shows the canonical names. For example, on the SPARC, @code{info
8773 registers} displays the processor status register as @code{$psr} but you
8774 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8775 is an alias for the @sc{eflags} register.
8777 @value{GDBN} always considers the contents of an ordinary register as an
8778 integer when the register is examined in this way. Some machines have
8779 special registers which can hold nothing but floating point; these
8780 registers are considered to have floating point values. There is no way
8781 to refer to the contents of an ordinary register as floating point value
8782 (although you can @emph{print} it as a floating point value with
8783 @samp{print/f $@var{regname}}).
8785 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8786 means that the data format in which the register contents are saved by
8787 the operating system is not the same one that your program normally
8788 sees. For example, the registers of the 68881 floating point
8789 coprocessor are always saved in ``extended'' (raw) format, but all C
8790 programs expect to work with ``double'' (virtual) format. In such
8791 cases, @value{GDBN} normally works with the virtual format only (the format
8792 that makes sense for your program), but the @code{info registers} command
8793 prints the data in both formats.
8795 @cindex SSE registers (x86)
8796 @cindex MMX registers (x86)
8797 Some machines have special registers whose contents can be interpreted
8798 in several different ways. For example, modern x86-based machines
8799 have SSE and MMX registers that can hold several values packed
8800 together in several different formats. @value{GDBN} refers to such
8801 registers in @code{struct} notation:
8804 (@value{GDBP}) print $xmm1
8806 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8807 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8808 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8809 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8810 v4_int32 = @{0, 20657912, 11, 13@},
8811 v2_int64 = @{88725056443645952, 55834574859@},
8812 uint128 = 0x0000000d0000000b013b36f800000000
8817 To set values of such registers, you need to tell @value{GDBN} which
8818 view of the register you wish to change, as if you were assigning
8819 value to a @code{struct} member:
8822 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8825 Normally, register values are relative to the selected stack frame
8826 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8827 value that the register would contain if all stack frames farther in
8828 were exited and their saved registers restored. In order to see the
8829 true contents of hardware registers, you must select the innermost
8830 frame (with @samp{frame 0}).
8832 However, @value{GDBN} must deduce where registers are saved, from the machine
8833 code generated by your compiler. If some registers are not saved, or if
8834 @value{GDBN} is unable to locate the saved registers, the selected stack
8835 frame makes no difference.
8837 @node Floating Point Hardware
8838 @section Floating Point Hardware
8839 @cindex floating point
8841 Depending on the configuration, @value{GDBN} may be able to give
8842 you more information about the status of the floating point hardware.
8847 Display hardware-dependent information about the floating
8848 point unit. The exact contents and layout vary depending on the
8849 floating point chip. Currently, @samp{info float} is supported on
8850 the ARM and x86 machines.
8854 @section Vector Unit
8857 Depending on the configuration, @value{GDBN} may be able to give you
8858 more information about the status of the vector unit.
8863 Display information about the vector unit. The exact contents and
8864 layout vary depending on the hardware.
8867 @node OS Information
8868 @section Operating System Auxiliary Information
8869 @cindex OS information
8871 @value{GDBN} provides interfaces to useful OS facilities that can help
8872 you debug your program.
8874 @cindex @code{ptrace} system call
8875 @cindex @code{struct user} contents
8876 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8877 machines), it interfaces with the inferior via the @code{ptrace}
8878 system call. The operating system creates a special sata structure,
8879 called @code{struct user}, for this interface. You can use the
8880 command @code{info udot} to display the contents of this data
8886 Display the contents of the @code{struct user} maintained by the OS
8887 kernel for the program being debugged. @value{GDBN} displays the
8888 contents of @code{struct user} as a list of hex numbers, similar to
8889 the @code{examine} command.
8892 @cindex auxiliary vector
8893 @cindex vector, auxiliary
8894 Some operating systems supply an @dfn{auxiliary vector} to programs at
8895 startup. This is akin to the arguments and environment that you
8896 specify for a program, but contains a system-dependent variety of
8897 binary values that tell system libraries important details about the
8898 hardware, operating system, and process. Each value's purpose is
8899 identified by an integer tag; the meanings are well-known but system-specific.
8900 Depending on the configuration and operating system facilities,
8901 @value{GDBN} may be able to show you this information. For remote
8902 targets, this functionality may further depend on the remote stub's
8903 support of the @samp{qXfer:auxv:read} packet, see
8904 @ref{qXfer auxiliary vector read}.
8909 Display the auxiliary vector of the inferior, which can be either a
8910 live process or a core dump file. @value{GDBN} prints each tag value
8911 numerically, and also shows names and text descriptions for recognized
8912 tags. Some values in the vector are numbers, some bit masks, and some
8913 pointers to strings or other data. @value{GDBN} displays each value in the
8914 most appropriate form for a recognized tag, and in hexadecimal for
8915 an unrecognized tag.
8918 On some targets, @value{GDBN} can access operating-system-specific information
8919 and display it to user, without interpretation. For remote targets,
8920 this functionality depends on the remote stub's support of the
8921 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8926 List the types of OS information available for the target. If the
8927 target does not return a list of possible types, this command will
8930 @kindex info os processes
8931 @item info os processes
8932 Display the list of processes on the target. For each process,
8933 @value{GDBN} prints the process identifier, the name of the user, and
8934 the command corresponding to the process.
8937 @node Memory Region Attributes
8938 @section Memory Region Attributes
8939 @cindex memory region attributes
8941 @dfn{Memory region attributes} allow you to describe special handling
8942 required by regions of your target's memory. @value{GDBN} uses
8943 attributes to determine whether to allow certain types of memory
8944 accesses; whether to use specific width accesses; and whether to cache
8945 target memory. By default the description of memory regions is
8946 fetched from the target (if the current target supports this), but the
8947 user can override the fetched regions.
8949 Defined memory regions can be individually enabled and disabled. When a
8950 memory region is disabled, @value{GDBN} uses the default attributes when
8951 accessing memory in that region. Similarly, if no memory regions have
8952 been defined, @value{GDBN} uses the default attributes when accessing
8955 When a memory region is defined, it is given a number to identify it;
8956 to enable, disable, or remove a memory region, you specify that number.
8960 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8961 Define a memory region bounded by @var{lower} and @var{upper} with
8962 attributes @var{attributes}@dots{}, and add it to the list of regions
8963 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8964 case: it is treated as the target's maximum memory address.
8965 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8968 Discard any user changes to the memory regions and use target-supplied
8969 regions, if available, or no regions if the target does not support.
8972 @item delete mem @var{nums}@dots{}
8973 Remove memory regions @var{nums}@dots{} from the list of regions
8974 monitored by @value{GDBN}.
8977 @item disable mem @var{nums}@dots{}
8978 Disable monitoring of memory regions @var{nums}@dots{}.
8979 A disabled memory region is not forgotten.
8980 It may be enabled again later.
8983 @item enable mem @var{nums}@dots{}
8984 Enable monitoring of memory regions @var{nums}@dots{}.
8988 Print a table of all defined memory regions, with the following columns
8992 @item Memory Region Number
8993 @item Enabled or Disabled.
8994 Enabled memory regions are marked with @samp{y}.
8995 Disabled memory regions are marked with @samp{n}.
8998 The address defining the inclusive lower bound of the memory region.
9001 The address defining the exclusive upper bound of the memory region.
9004 The list of attributes set for this memory region.
9009 @subsection Attributes
9011 @subsubsection Memory Access Mode
9012 The access mode attributes set whether @value{GDBN} may make read or
9013 write accesses to a memory region.
9015 While these attributes prevent @value{GDBN} from performing invalid
9016 memory accesses, they do nothing to prevent the target system, I/O DMA,
9017 etc.@: from accessing memory.
9021 Memory is read only.
9023 Memory is write only.
9025 Memory is read/write. This is the default.
9028 @subsubsection Memory Access Size
9029 The access size attribute tells @value{GDBN} to use specific sized
9030 accesses in the memory region. Often memory mapped device registers
9031 require specific sized accesses. If no access size attribute is
9032 specified, @value{GDBN} may use accesses of any size.
9036 Use 8 bit memory accesses.
9038 Use 16 bit memory accesses.
9040 Use 32 bit memory accesses.
9042 Use 64 bit memory accesses.
9045 @c @subsubsection Hardware/Software Breakpoints
9046 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9047 @c will use hardware or software breakpoints for the internal breakpoints
9048 @c used by the step, next, finish, until, etc. commands.
9052 @c Always use hardware breakpoints
9053 @c @item swbreak (default)
9056 @subsubsection Data Cache
9057 The data cache attributes set whether @value{GDBN} will cache target
9058 memory. While this generally improves performance by reducing debug
9059 protocol overhead, it can lead to incorrect results because @value{GDBN}
9060 does not know about volatile variables or memory mapped device
9065 Enable @value{GDBN} to cache target memory.
9067 Disable @value{GDBN} from caching target memory. This is the default.
9070 @subsection Memory Access Checking
9071 @value{GDBN} can be instructed to refuse accesses to memory that is
9072 not explicitly described. This can be useful if accessing such
9073 regions has undesired effects for a specific target, or to provide
9074 better error checking. The following commands control this behaviour.
9077 @kindex set mem inaccessible-by-default
9078 @item set mem inaccessible-by-default [on|off]
9079 If @code{on} is specified, make @value{GDBN} treat memory not
9080 explicitly described by the memory ranges as non-existent and refuse accesses
9081 to such memory. The checks are only performed if there's at least one
9082 memory range defined. If @code{off} is specified, make @value{GDBN}
9083 treat the memory not explicitly described by the memory ranges as RAM.
9084 The default value is @code{on}.
9085 @kindex show mem inaccessible-by-default
9086 @item show mem inaccessible-by-default
9087 Show the current handling of accesses to unknown memory.
9091 @c @subsubsection Memory Write Verification
9092 @c The memory write verification attributes set whether @value{GDBN}
9093 @c will re-reads data after each write to verify the write was successful.
9097 @c @item noverify (default)
9100 @node Dump/Restore Files
9101 @section Copy Between Memory and a File
9102 @cindex dump/restore files
9103 @cindex append data to a file
9104 @cindex dump data to a file
9105 @cindex restore data from a file
9107 You can use the commands @code{dump}, @code{append}, and
9108 @code{restore} to copy data between target memory and a file. The
9109 @code{dump} and @code{append} commands write data to a file, and the
9110 @code{restore} command reads data from a file back into the inferior's
9111 memory. Files may be in binary, Motorola S-record, Intel hex, or
9112 Tektronix Hex format; however, @value{GDBN} can only append to binary
9118 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9119 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9120 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9121 or the value of @var{expr}, to @var{filename} in the given format.
9123 The @var{format} parameter may be any one of:
9130 Motorola S-record format.
9132 Tektronix Hex format.
9135 @value{GDBN} uses the same definitions of these formats as the
9136 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9137 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9141 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9142 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9143 Append the contents of memory from @var{start_addr} to @var{end_addr},
9144 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9145 (@value{GDBN} can only append data to files in raw binary form.)
9148 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9149 Restore the contents of file @var{filename} into memory. The
9150 @code{restore} command can automatically recognize any known @sc{bfd}
9151 file format, except for raw binary. To restore a raw binary file you
9152 must specify the optional keyword @code{binary} after the filename.
9154 If @var{bias} is non-zero, its value will be added to the addresses
9155 contained in the file. Binary files always start at address zero, so
9156 they will be restored at address @var{bias}. Other bfd files have
9157 a built-in location; they will be restored at offset @var{bias}
9160 If @var{start} and/or @var{end} are non-zero, then only data between
9161 file offset @var{start} and file offset @var{end} will be restored.
9162 These offsets are relative to the addresses in the file, before
9163 the @var{bias} argument is applied.
9167 @node Core File Generation
9168 @section How to Produce a Core File from Your Program
9169 @cindex dump core from inferior
9171 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9172 image of a running process and its process status (register values
9173 etc.). Its primary use is post-mortem debugging of a program that
9174 crashed while it ran outside a debugger. A program that crashes
9175 automatically produces a core file, unless this feature is disabled by
9176 the user. @xref{Files}, for information on invoking @value{GDBN} in
9177 the post-mortem debugging mode.
9179 Occasionally, you may wish to produce a core file of the program you
9180 are debugging in order to preserve a snapshot of its state.
9181 @value{GDBN} has a special command for that.
9185 @kindex generate-core-file
9186 @item generate-core-file [@var{file}]
9187 @itemx gcore [@var{file}]
9188 Produce a core dump of the inferior process. The optional argument
9189 @var{file} specifies the file name where to put the core dump. If not
9190 specified, the file name defaults to @file{core.@var{pid}}, where
9191 @var{pid} is the inferior process ID.
9193 Note that this command is implemented only for some systems (as of
9194 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9197 @node Character Sets
9198 @section Character Sets
9199 @cindex character sets
9201 @cindex translating between character sets
9202 @cindex host character set
9203 @cindex target character set
9205 If the program you are debugging uses a different character set to
9206 represent characters and strings than the one @value{GDBN} uses itself,
9207 @value{GDBN} can automatically translate between the character sets for
9208 you. The character set @value{GDBN} uses we call the @dfn{host
9209 character set}; the one the inferior program uses we call the
9210 @dfn{target character set}.
9212 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9213 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9214 remote protocol (@pxref{Remote Debugging}) to debug a program
9215 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9216 then the host character set is Latin-1, and the target character set is
9217 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9218 target-charset EBCDIC-US}, then @value{GDBN} translates between
9219 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9220 character and string literals in expressions.
9222 @value{GDBN} has no way to automatically recognize which character set
9223 the inferior program uses; you must tell it, using the @code{set
9224 target-charset} command, described below.
9226 Here are the commands for controlling @value{GDBN}'s character set
9230 @item set target-charset @var{charset}
9231 @kindex set target-charset
9232 Set the current target character set to @var{charset}. To display the
9233 list of supported target character sets, type
9234 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9236 @item set host-charset @var{charset}
9237 @kindex set host-charset
9238 Set the current host character set to @var{charset}.
9240 By default, @value{GDBN} uses a host character set appropriate to the
9241 system it is running on; you can override that default using the
9242 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9243 automatically determine the appropriate host character set. In this
9244 case, @value{GDBN} uses @samp{UTF-8}.
9246 @value{GDBN} can only use certain character sets as its host character
9247 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9248 @value{GDBN} will list the host character sets it supports.
9250 @item set charset @var{charset}
9252 Set the current host and target character sets to @var{charset}. As
9253 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9254 @value{GDBN} will list the names of the character sets that can be used
9255 for both host and target.
9258 @kindex show charset
9259 Show the names of the current host and target character sets.
9261 @item show host-charset
9262 @kindex show host-charset
9263 Show the name of the current host character set.
9265 @item show target-charset
9266 @kindex show target-charset
9267 Show the name of the current target character set.
9269 @item set target-wide-charset @var{charset}
9270 @kindex set target-wide-charset
9271 Set the current target's wide character set to @var{charset}. This is
9272 the character set used by the target's @code{wchar_t} type. To
9273 display the list of supported wide character sets, type
9274 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9276 @item show target-wide-charset
9277 @kindex show target-wide-charset
9278 Show the name of the current target's wide character set.
9281 Here is an example of @value{GDBN}'s character set support in action.
9282 Assume that the following source code has been placed in the file
9283 @file{charset-test.c}:
9289 = @{72, 101, 108, 108, 111, 44, 32, 119,
9290 111, 114, 108, 100, 33, 10, 0@};
9291 char ibm1047_hello[]
9292 = @{200, 133, 147, 147, 150, 107, 64, 166,
9293 150, 153, 147, 132, 90, 37, 0@};
9297 printf ("Hello, world!\n");
9301 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9302 containing the string @samp{Hello, world!} followed by a newline,
9303 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9305 We compile the program, and invoke the debugger on it:
9308 $ gcc -g charset-test.c -o charset-test
9309 $ gdb -nw charset-test
9310 GNU gdb 2001-12-19-cvs
9311 Copyright 2001 Free Software Foundation, Inc.
9316 We can use the @code{show charset} command to see what character sets
9317 @value{GDBN} is currently using to interpret and display characters and
9321 (@value{GDBP}) show charset
9322 The current host and target character set is `ISO-8859-1'.
9326 For the sake of printing this manual, let's use @sc{ascii} as our
9327 initial character set:
9329 (@value{GDBP}) set charset ASCII
9330 (@value{GDBP}) show charset
9331 The current host and target character set is `ASCII'.
9335 Let's assume that @sc{ascii} is indeed the correct character set for our
9336 host system --- in other words, let's assume that if @value{GDBN} prints
9337 characters using the @sc{ascii} character set, our terminal will display
9338 them properly. Since our current target character set is also
9339 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9342 (@value{GDBP}) print ascii_hello
9343 $1 = 0x401698 "Hello, world!\n"
9344 (@value{GDBP}) print ascii_hello[0]
9349 @value{GDBN} uses the target character set for character and string
9350 literals you use in expressions:
9353 (@value{GDBP}) print '+'
9358 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9361 @value{GDBN} relies on the user to tell it which character set the
9362 target program uses. If we print @code{ibm1047_hello} while our target
9363 character set is still @sc{ascii}, we get jibberish:
9366 (@value{GDBP}) print ibm1047_hello
9367 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9368 (@value{GDBP}) print ibm1047_hello[0]
9373 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9374 @value{GDBN} tells us the character sets it supports:
9377 (@value{GDBP}) set target-charset
9378 ASCII EBCDIC-US IBM1047 ISO-8859-1
9379 (@value{GDBP}) set target-charset
9382 We can select @sc{ibm1047} as our target character set, and examine the
9383 program's strings again. Now the @sc{ascii} string is wrong, but
9384 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9385 target character set, @sc{ibm1047}, to the host character set,
9386 @sc{ascii}, and they display correctly:
9389 (@value{GDBP}) set target-charset IBM1047
9390 (@value{GDBP}) show charset
9391 The current host character set is `ASCII'.
9392 The current target character set is `IBM1047'.
9393 (@value{GDBP}) print ascii_hello
9394 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9395 (@value{GDBP}) print ascii_hello[0]
9397 (@value{GDBP}) print ibm1047_hello
9398 $8 = 0x4016a8 "Hello, world!\n"
9399 (@value{GDBP}) print ibm1047_hello[0]
9404 As above, @value{GDBN} uses the target character set for character and
9405 string literals you use in expressions:
9408 (@value{GDBP}) print '+'
9413 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9416 @node Caching Remote Data
9417 @section Caching Data of Remote Targets
9418 @cindex caching data of remote targets
9420 @value{GDBN} caches data exchanged between the debugger and a
9421 remote target (@pxref{Remote Debugging}). Such caching generally improves
9422 performance, because it reduces the overhead of the remote protocol by
9423 bundling memory reads and writes into large chunks. Unfortunately, simply
9424 caching everything would lead to incorrect results, since @value{GDBN}
9425 does not necessarily know anything about volatile values, memory-mapped I/O
9426 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9427 memory can be changed @emph{while} a gdb command is executing.
9428 Therefore, by default, @value{GDBN} only caches data
9429 known to be on the stack@footnote{In non-stop mode, it is moderately
9430 rare for a running thread to modify the stack of a stopped thread
9431 in a way that would interfere with a backtrace, and caching of
9432 stack reads provides a significant speed up of remote backtraces.}.
9433 Other regions of memory can be explicitly marked as
9434 cacheable; see @pxref{Memory Region Attributes}.
9437 @kindex set remotecache
9438 @item set remotecache on
9439 @itemx set remotecache off
9440 This option no longer does anything; it exists for compatibility
9443 @kindex show remotecache
9444 @item show remotecache
9445 Show the current state of the obsolete remotecache flag.
9447 @kindex set stack-cache
9448 @item set stack-cache on
9449 @itemx set stack-cache off
9450 Enable or disable caching of stack accesses. When @code{ON}, use
9451 caching. By default, this option is @code{ON}.
9453 @kindex show stack-cache
9454 @item show stack-cache
9455 Show the current state of data caching for memory accesses.
9458 @item info dcache @r{[}line@r{]}
9459 Print the information about the data cache performance. The
9460 information displayed includes the dcache width and depth, and for
9461 each cache line, its number, address, and how many times it was
9462 referenced. This command is useful for debugging the data cache
9465 If a line number is specified, the contents of that line will be
9468 @item set dcache size @var{size}
9470 @kindex set dcache size
9471 Set maximum number of entries in dcache (dcache depth above).
9473 @item set dcache line-size @var{line-size}
9474 @cindex dcache line-size
9475 @kindex set dcache line-size
9476 Set number of bytes each dcache entry caches (dcache width above).
9477 Must be a power of 2.
9479 @item show dcache size
9480 @kindex show dcache size
9481 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9483 @item show dcache line-size
9484 @kindex show dcache line-size
9485 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9489 @node Searching Memory
9490 @section Search Memory
9491 @cindex searching memory
9493 Memory can be searched for a particular sequence of bytes with the
9494 @code{find} command.
9498 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9499 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9500 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9501 etc. The search begins at address @var{start_addr} and continues for either
9502 @var{len} bytes or through to @var{end_addr} inclusive.
9505 @var{s} and @var{n} are optional parameters.
9506 They may be specified in either order, apart or together.
9509 @item @var{s}, search query size
9510 The size of each search query value.
9516 halfwords (two bytes)
9520 giant words (eight bytes)
9523 All values are interpreted in the current language.
9524 This means, for example, that if the current source language is C/C@t{++}
9525 then searching for the string ``hello'' includes the trailing '\0'.
9527 If the value size is not specified, it is taken from the
9528 value's type in the current language.
9529 This is useful when one wants to specify the search
9530 pattern as a mixture of types.
9531 Note that this means, for example, that in the case of C-like languages
9532 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9533 which is typically four bytes.
9535 @item @var{n}, maximum number of finds
9536 The maximum number of matches to print. The default is to print all finds.
9539 You can use strings as search values. Quote them with double-quotes
9541 The string value is copied into the search pattern byte by byte,
9542 regardless of the endianness of the target and the size specification.
9544 The address of each match found is printed as well as a count of the
9545 number of matches found.
9547 The address of the last value found is stored in convenience variable
9549 A count of the number of matches is stored in @samp{$numfound}.
9551 For example, if stopped at the @code{printf} in this function:
9557 static char hello[] = "hello-hello";
9558 static struct @{ char c; short s; int i; @}
9559 __attribute__ ((packed)) mixed
9560 = @{ 'c', 0x1234, 0x87654321 @};
9561 printf ("%s\n", hello);
9566 you get during debugging:
9569 (gdb) find &hello[0], +sizeof(hello), "hello"
9570 0x804956d <hello.1620+6>
9572 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9573 0x8049567 <hello.1620>
9574 0x804956d <hello.1620+6>
9576 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9577 0x8049567 <hello.1620>
9579 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9580 0x8049560 <mixed.1625>
9582 (gdb) print $numfound
9585 $2 = (void *) 0x8049560
9588 @node Optimized Code
9589 @chapter Debugging Optimized Code
9590 @cindex optimized code, debugging
9591 @cindex debugging optimized code
9593 Almost all compilers support optimization. With optimization
9594 disabled, the compiler generates assembly code that corresponds
9595 directly to your source code, in a simplistic way. As the compiler
9596 applies more powerful optimizations, the generated assembly code
9597 diverges from your original source code. With help from debugging
9598 information generated by the compiler, @value{GDBN} can map from
9599 the running program back to constructs from your original source.
9601 @value{GDBN} is more accurate with optimization disabled. If you
9602 can recompile without optimization, it is easier to follow the
9603 progress of your program during debugging. But, there are many cases
9604 where you may need to debug an optimized version.
9606 When you debug a program compiled with @samp{-g -O}, remember that the
9607 optimizer has rearranged your code; the debugger shows you what is
9608 really there. Do not be too surprised when the execution path does not
9609 exactly match your source file! An extreme example: if you define a
9610 variable, but never use it, @value{GDBN} never sees that
9611 variable---because the compiler optimizes it out of existence.
9613 Some things do not work as well with @samp{-g -O} as with just
9614 @samp{-g}, particularly on machines with instruction scheduling. If in
9615 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9616 please report it to us as a bug (including a test case!).
9617 @xref{Variables}, for more information about debugging optimized code.
9620 * Inline Functions:: How @value{GDBN} presents inlining
9621 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9624 @node Inline Functions
9625 @section Inline Functions
9626 @cindex inline functions, debugging
9628 @dfn{Inlining} is an optimization that inserts a copy of the function
9629 body directly at each call site, instead of jumping to a shared
9630 routine. @value{GDBN} displays inlined functions just like
9631 non-inlined functions. They appear in backtraces. You can view their
9632 arguments and local variables, step into them with @code{step}, skip
9633 them with @code{next}, and escape from them with @code{finish}.
9634 You can check whether a function was inlined by using the
9635 @code{info frame} command.
9637 For @value{GDBN} to support inlined functions, the compiler must
9638 record information about inlining in the debug information ---
9639 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9640 other compilers do also. @value{GDBN} only supports inlined functions
9641 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9642 do not emit two required attributes (@samp{DW_AT_call_file} and
9643 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9644 function calls with earlier versions of @value{NGCC}. It instead
9645 displays the arguments and local variables of inlined functions as
9646 local variables in the caller.
9648 The body of an inlined function is directly included at its call site;
9649 unlike a non-inlined function, there are no instructions devoted to
9650 the call. @value{GDBN} still pretends that the call site and the
9651 start of the inlined function are different instructions. Stepping to
9652 the call site shows the call site, and then stepping again shows
9653 the first line of the inlined function, even though no additional
9654 instructions are executed.
9656 This makes source-level debugging much clearer; you can see both the
9657 context of the call and then the effect of the call. Only stepping by
9658 a single instruction using @code{stepi} or @code{nexti} does not do
9659 this; single instruction steps always show the inlined body.
9661 There are some ways that @value{GDBN} does not pretend that inlined
9662 function calls are the same as normal calls:
9666 You cannot set breakpoints on inlined functions. @value{GDBN}
9667 either reports that there is no symbol with that name, or else sets the
9668 breakpoint only on non-inlined copies of the function. This limitation
9669 will be removed in a future version of @value{GDBN}; until then,
9670 set a breakpoint by line number on the first line of the inlined
9674 Setting breakpoints at the call site of an inlined function may not
9675 work, because the call site does not contain any code. @value{GDBN}
9676 may incorrectly move the breakpoint to the next line of the enclosing
9677 function, after the call. This limitation will be removed in a future
9678 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9679 or inside the inlined function instead.
9682 @value{GDBN} cannot locate the return value of inlined calls after
9683 using the @code{finish} command. This is a limitation of compiler-generated
9684 debugging information; after @code{finish}, you can step to the next line
9685 and print a variable where your program stored the return value.
9689 @node Tail Call Frames
9690 @section Tail Call Frames
9691 @cindex tail call frames, debugging
9693 Function @code{B} can call function @code{C} in its very last statement. In
9694 unoptimized compilation the call of @code{C} is immediately followed by return
9695 instruction at the end of @code{B} code. Optimizing compiler may replace the
9696 call and return in function @code{B} into one jump to function @code{C}
9697 instead. Such use of a jump instruction is called @dfn{tail call}.
9699 During execution of function @code{C}, there will be no indication in the
9700 function call stack frames that it was tail-called from @code{B}. If function
9701 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9702 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9703 some cases @value{GDBN} can determine that @code{C} was tail-called from
9704 @code{B}, and it will then create fictitious call frame for that, with the
9705 return address set up as if @code{B} called @code{C} normally.
9707 This functionality is currently supported only by DWARF 2 debugging format and
9708 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9709 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9712 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9713 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9717 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9719 Stack level 1, frame at 0x7fffffffda30:
9720 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9721 tail call frame, caller of frame at 0x7fffffffda30
9722 source language c++.
9723 Arglist at unknown address.
9724 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9727 The detection of all the possible code path executions can find them ambiguous.
9728 There is no execution history stored (possible @ref{Reverse Execution} is never
9729 used for this purpose) and the last known caller could have reached the known
9730 callee by multiple different jump sequences. In such case @value{GDBN} still
9731 tries to show at least all the unambiguous top tail callers and all the
9732 unambiguous bottom tail calees, if any.
9735 @anchor{set debug entry-values}
9736 @item set debug entry-values
9737 @kindex set debug entry-values
9738 When set to on, enables printing of analysis messages for both frame argument
9739 values at function entry and tail calls. It will show all the possible valid
9740 tail calls code paths it has considered. It will also print the intersection
9741 of them with the final unambiguous (possibly partial or even empty) code path
9744 @item show debug entry-values
9745 @kindex show debug entry-values
9746 Show the current state of analysis messages printing for both frame argument
9747 values at function entry and tail calls.
9750 The analysis messages for tail calls can for example show why the virtual tail
9751 call frame for function @code{c} has not been recognized (due to the indirect
9752 reference by variable @code{x}):
9755 static void __attribute__((noinline, noclone)) c (void);
9756 void (*x) (void) = c;
9757 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9758 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9759 int main (void) @{ x (); return 0; @}
9761 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9762 DW_TAG_GNU_call_site 0x40039a in main
9764 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9767 #1 0x000000000040039a in main () at t.c:5
9770 Another possibility is an ambiguous virtual tail call frames resolution:
9774 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9775 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9776 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9777 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9778 static void __attribute__((noinline, noclone)) b (void)
9779 @{ if (i) c (); else e (); @}
9780 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9781 int main (void) @{ a (); return 0; @}
9783 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9784 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9785 tailcall: reduced: 0x4004d2(a) |
9788 #1 0x00000000004004d2 in a () at t.c:8
9789 #2 0x0000000000400395 in main () at t.c:9
9792 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9793 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9795 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9796 @ifset HAVE_MAKEINFO_CLICK
9798 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9799 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9801 @ifclear HAVE_MAKEINFO_CLICK
9803 @set CALLSEQ1B @value{CALLSEQ1A}
9804 @set CALLSEQ2B @value{CALLSEQ2A}
9807 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9808 The code can have possible execution paths @value{CALLSEQ1B} or
9809 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9811 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9812 has found. It then finds another possible calling sequcen - that one is
9813 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9814 printed as the @code{reduced:} calling sequence. That one could have many
9815 futher @code{compare:} and @code{reduced:} statements as long as there remain
9816 any non-ambiguous sequence entries.
9818 For the frame of function @code{b} in both cases there are different possible
9819 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9820 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9821 therefore this one is displayed to the user while the ambiguous frames are
9824 There can be also reasons why printing of frame argument values at function
9829 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9830 static void __attribute__((noinline, noclone)) a (int i);
9831 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9832 static void __attribute__((noinline, noclone)) a (int i)
9833 @{ if (i) b (i - 1); else c (0); @}
9834 int main (void) @{ a (5); return 0; @}
9837 #0 c (i=i@@entry=0) at t.c:2
9838 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9839 function "a" at 0x400420 can call itself via tail calls
9840 i=<optimized out>) at t.c:6
9841 #2 0x000000000040036e in main () at t.c:7
9844 @value{GDBN} cannot find out from the inferior state if and how many times did
9845 function @code{a} call itself (via function @code{b}) as these calls would be
9846 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9847 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9848 prints @code{<optimized out>} instead.
9851 @chapter C Preprocessor Macros
9853 Some languages, such as C and C@t{++}, provide a way to define and invoke
9854 ``preprocessor macros'' which expand into strings of tokens.
9855 @value{GDBN} can evaluate expressions containing macro invocations, show
9856 the result of macro expansion, and show a macro's definition, including
9857 where it was defined.
9859 You may need to compile your program specially to provide @value{GDBN}
9860 with information about preprocessor macros. Most compilers do not
9861 include macros in their debugging information, even when you compile
9862 with the @option{-g} flag. @xref{Compilation}.
9864 A program may define a macro at one point, remove that definition later,
9865 and then provide a different definition after that. Thus, at different
9866 points in the program, a macro may have different definitions, or have
9867 no definition at all. If there is a current stack frame, @value{GDBN}
9868 uses the macros in scope at that frame's source code line. Otherwise,
9869 @value{GDBN} uses the macros in scope at the current listing location;
9872 Whenever @value{GDBN} evaluates an expression, it always expands any
9873 macro invocations present in the expression. @value{GDBN} also provides
9874 the following commands for working with macros explicitly.
9878 @kindex macro expand
9879 @cindex macro expansion, showing the results of preprocessor
9880 @cindex preprocessor macro expansion, showing the results of
9881 @cindex expanding preprocessor macros
9882 @item macro expand @var{expression}
9883 @itemx macro exp @var{expression}
9884 Show the results of expanding all preprocessor macro invocations in
9885 @var{expression}. Since @value{GDBN} simply expands macros, but does
9886 not parse the result, @var{expression} need not be a valid expression;
9887 it can be any string of tokens.
9890 @item macro expand-once @var{expression}
9891 @itemx macro exp1 @var{expression}
9892 @cindex expand macro once
9893 @i{(This command is not yet implemented.)} Show the results of
9894 expanding those preprocessor macro invocations that appear explicitly in
9895 @var{expression}. Macro invocations appearing in that expansion are
9896 left unchanged. This command allows you to see the effect of a
9897 particular macro more clearly, without being confused by further
9898 expansions. Since @value{GDBN} simply expands macros, but does not
9899 parse the result, @var{expression} need not be a valid expression; it
9900 can be any string of tokens.
9903 @cindex macro definition, showing
9904 @cindex definition of a macro, showing
9905 @cindex macros, from debug info
9906 @item info macro @var{macro}
9907 Show the current definition of the named @var{macro}, and describe the
9908 source location or compiler command-line where that definition was established.
9911 @item info macros @var{linespec}
9912 Show all macro definitions that are in effect at the location specified
9913 by @var{linespec}, and describe the source location or compiler
9914 command-line where those definitions were established.
9916 @kindex info definitions
9917 @item info definitions @var{macro}
9918 Show all definitions of the named @var{macro} that are defined in the current
9919 compilation unit, and describe the source location or compiler command-line
9920 where those definitions were established.
9922 @kindex macro define
9923 @cindex user-defined macros
9924 @cindex defining macros interactively
9925 @cindex macros, user-defined
9926 @item macro define @var{macro} @var{replacement-list}
9927 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9928 Introduce a definition for a preprocessor macro named @var{macro},
9929 invocations of which are replaced by the tokens given in
9930 @var{replacement-list}. The first form of this command defines an
9931 ``object-like'' macro, which takes no arguments; the second form
9932 defines a ``function-like'' macro, which takes the arguments given in
9935 A definition introduced by this command is in scope in every
9936 expression evaluated in @value{GDBN}, until it is removed with the
9937 @code{macro undef} command, described below. The definition overrides
9938 all definitions for @var{macro} present in the program being debugged,
9939 as well as any previous user-supplied definition.
9942 @item macro undef @var{macro}
9943 Remove any user-supplied definition for the macro named @var{macro}.
9944 This command only affects definitions provided with the @code{macro
9945 define} command, described above; it cannot remove definitions present
9946 in the program being debugged.
9950 List all the macros defined using the @code{macro define} command.
9953 @cindex macros, example of debugging with
9954 Here is a transcript showing the above commands in action. First, we
9955 show our source files:
9963 #define ADD(x) (M + x)
9968 printf ("Hello, world!\n");
9970 printf ("We're so creative.\n");
9972 printf ("Goodbye, world!\n");
9979 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9980 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9981 compiler includes information about preprocessor macros in the debugging
9985 $ gcc -gdwarf-2 -g3 sample.c -o sample
9989 Now, we start @value{GDBN} on our sample program:
9993 GNU gdb 2002-05-06-cvs
9994 Copyright 2002 Free Software Foundation, Inc.
9995 GDB is free software, @dots{}
9999 We can expand macros and examine their definitions, even when the
10000 program is not running. @value{GDBN} uses the current listing position
10001 to decide which macro definitions are in scope:
10004 (@value{GDBP}) list main
10007 5 #define ADD(x) (M + x)
10012 10 printf ("Hello, world!\n");
10014 12 printf ("We're so creative.\n");
10015 (@value{GDBP}) info macro ADD
10016 Defined at /home/jimb/gdb/macros/play/sample.c:5
10017 #define ADD(x) (M + x)
10018 (@value{GDBP}) info macro Q
10019 Defined at /home/jimb/gdb/macros/play/sample.h:1
10020 included at /home/jimb/gdb/macros/play/sample.c:2
10022 (@value{GDBP}) macro expand ADD(1)
10023 expands to: (42 + 1)
10024 (@value{GDBP}) macro expand-once ADD(1)
10025 expands to: once (M + 1)
10029 In the example above, note that @code{macro expand-once} expands only
10030 the macro invocation explicit in the original text --- the invocation of
10031 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10032 which was introduced by @code{ADD}.
10034 Once the program is running, @value{GDBN} uses the macro definitions in
10035 force at the source line of the current stack frame:
10038 (@value{GDBP}) break main
10039 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10041 Starting program: /home/jimb/gdb/macros/play/sample
10043 Breakpoint 1, main () at sample.c:10
10044 10 printf ("Hello, world!\n");
10048 At line 10, the definition of the macro @code{N} at line 9 is in force:
10051 (@value{GDBP}) info macro N
10052 Defined at /home/jimb/gdb/macros/play/sample.c:9
10054 (@value{GDBP}) macro expand N Q M
10055 expands to: 28 < 42
10056 (@value{GDBP}) print N Q M
10061 As we step over directives that remove @code{N}'s definition, and then
10062 give it a new definition, @value{GDBN} finds the definition (or lack
10063 thereof) in force at each point:
10066 (@value{GDBP}) next
10068 12 printf ("We're so creative.\n");
10069 (@value{GDBP}) info macro N
10070 The symbol `N' has no definition as a C/C++ preprocessor macro
10071 at /home/jimb/gdb/macros/play/sample.c:12
10072 (@value{GDBP}) next
10074 14 printf ("Goodbye, world!\n");
10075 (@value{GDBP}) info macro N
10076 Defined at /home/jimb/gdb/macros/play/sample.c:13
10078 (@value{GDBP}) macro expand N Q M
10079 expands to: 1729 < 42
10080 (@value{GDBP}) print N Q M
10085 In addition to source files, macros can be defined on the compilation command
10086 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10087 such a way, @value{GDBN} displays the location of their definition as line zero
10088 of the source file submitted to the compiler.
10091 (@value{GDBP}) info macro __STDC__
10092 Defined at /home/jimb/gdb/macros/play/sample.c:0
10099 @chapter Tracepoints
10100 @c This chapter is based on the documentation written by Michael
10101 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10103 @cindex tracepoints
10104 In some applications, it is not feasible for the debugger to interrupt
10105 the program's execution long enough for the developer to learn
10106 anything helpful about its behavior. If the program's correctness
10107 depends on its real-time behavior, delays introduced by a debugger
10108 might cause the program to change its behavior drastically, or perhaps
10109 fail, even when the code itself is correct. It is useful to be able
10110 to observe the program's behavior without interrupting it.
10112 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10113 specify locations in the program, called @dfn{tracepoints}, and
10114 arbitrary expressions to evaluate when those tracepoints are reached.
10115 Later, using the @code{tfind} command, you can examine the values
10116 those expressions had when the program hit the tracepoints. The
10117 expressions may also denote objects in memory---structures or arrays,
10118 for example---whose values @value{GDBN} should record; while visiting
10119 a particular tracepoint, you may inspect those objects as if they were
10120 in memory at that moment. However, because @value{GDBN} records these
10121 values without interacting with you, it can do so quickly and
10122 unobtrusively, hopefully not disturbing the program's behavior.
10124 The tracepoint facility is currently available only for remote
10125 targets. @xref{Targets}. In addition, your remote target must know
10126 how to collect trace data. This functionality is implemented in the
10127 remote stub; however, none of the stubs distributed with @value{GDBN}
10128 support tracepoints as of this writing. The format of the remote
10129 packets used to implement tracepoints are described in @ref{Tracepoint
10132 It is also possible to get trace data from a file, in a manner reminiscent
10133 of corefiles; you specify the filename, and use @code{tfind} to search
10134 through the file. @xref{Trace Files}, for more details.
10136 This chapter describes the tracepoint commands and features.
10139 * Set Tracepoints::
10140 * Analyze Collected Data::
10141 * Tracepoint Variables::
10145 @node Set Tracepoints
10146 @section Commands to Set Tracepoints
10148 Before running such a @dfn{trace experiment}, an arbitrary number of
10149 tracepoints can be set. A tracepoint is actually a special type of
10150 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10151 standard breakpoint commands. For instance, as with breakpoints,
10152 tracepoint numbers are successive integers starting from one, and many
10153 of the commands associated with tracepoints take the tracepoint number
10154 as their argument, to identify which tracepoint to work on.
10156 For each tracepoint, you can specify, in advance, some arbitrary set
10157 of data that you want the target to collect in the trace buffer when
10158 it hits that tracepoint. The collected data can include registers,
10159 local variables, or global data. Later, you can use @value{GDBN}
10160 commands to examine the values these data had at the time the
10161 tracepoint was hit.
10163 Tracepoints do not support every breakpoint feature. Ignore counts on
10164 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10165 commands when they are hit. Tracepoints may not be thread-specific
10168 @cindex fast tracepoints
10169 Some targets may support @dfn{fast tracepoints}, which are inserted in
10170 a different way (such as with a jump instead of a trap), that is
10171 faster but possibly restricted in where they may be installed.
10173 @cindex static tracepoints
10174 @cindex markers, static tracepoints
10175 @cindex probing markers, static tracepoints
10176 Regular and fast tracepoints are dynamic tracing facilities, meaning
10177 that they can be used to insert tracepoints at (almost) any location
10178 in the target. Some targets may also support controlling @dfn{static
10179 tracepoints} from @value{GDBN}. With static tracing, a set of
10180 instrumentation points, also known as @dfn{markers}, are embedded in
10181 the target program, and can be activated or deactivated by name or
10182 address. These are usually placed at locations which facilitate
10183 investigating what the target is actually doing. @value{GDBN}'s
10184 support for static tracing includes being able to list instrumentation
10185 points, and attach them with @value{GDBN} defined high level
10186 tracepoints that expose the whole range of convenience of
10187 @value{GDBN}'s tracepoints support. Namely, support for collecting
10188 registers values and values of global or local (to the instrumentation
10189 point) variables; tracepoint conditions and trace state variables.
10190 The act of installing a @value{GDBN} static tracepoint on an
10191 instrumentation point, or marker, is referred to as @dfn{probing} a
10192 static tracepoint marker.
10194 @code{gdbserver} supports tracepoints on some target systems.
10195 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10197 This section describes commands to set tracepoints and associated
10198 conditions and actions.
10201 * Create and Delete Tracepoints::
10202 * Enable and Disable Tracepoints::
10203 * Tracepoint Passcounts::
10204 * Tracepoint Conditions::
10205 * Trace State Variables::
10206 * Tracepoint Actions::
10207 * Listing Tracepoints::
10208 * Listing Static Tracepoint Markers::
10209 * Starting and Stopping Trace Experiments::
10210 * Tracepoint Restrictions::
10213 @node Create and Delete Tracepoints
10214 @subsection Create and Delete Tracepoints
10217 @cindex set tracepoint
10219 @item trace @var{location}
10220 The @code{trace} command is very similar to the @code{break} command.
10221 Its argument @var{location} can be a source line, a function name, or
10222 an address in the target program. @xref{Specify Location}. The
10223 @code{trace} command defines a tracepoint, which is a point in the
10224 target program where the debugger will briefly stop, collect some
10225 data, and then allow the program to continue. Setting a tracepoint or
10226 changing its actions doesn't take effect until the next @code{tstart}
10227 command, and once a trace experiment is running, further changes will
10228 not have any effect until the next trace experiment starts.
10230 Here are some examples of using the @code{trace} command:
10233 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10235 (@value{GDBP}) @b{trace +2} // 2 lines forward
10237 (@value{GDBP}) @b{trace my_function} // first source line of function
10239 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10241 (@value{GDBP}) @b{trace *0x2117c4} // an address
10245 You can abbreviate @code{trace} as @code{tr}.
10247 @item trace @var{location} if @var{cond}
10248 Set a tracepoint with condition @var{cond}; evaluate the expression
10249 @var{cond} each time the tracepoint is reached, and collect data only
10250 if the value is nonzero---that is, if @var{cond} evaluates as true.
10251 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10252 information on tracepoint conditions.
10254 @item ftrace @var{location} [ if @var{cond} ]
10255 @cindex set fast tracepoint
10256 @cindex fast tracepoints, setting
10258 The @code{ftrace} command sets a fast tracepoint. For targets that
10259 support them, fast tracepoints will use a more efficient but possibly
10260 less general technique to trigger data collection, such as a jump
10261 instruction instead of a trap, or some sort of hardware support. It
10262 may not be possible to create a fast tracepoint at the desired
10263 location, in which case the command will exit with an explanatory
10266 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10269 @item strace @var{location} [ if @var{cond} ]
10270 @cindex set static tracepoint
10271 @cindex static tracepoints, setting
10272 @cindex probe static tracepoint marker
10274 The @code{strace} command sets a static tracepoint. For targets that
10275 support it, setting a static tracepoint probes a static
10276 instrumentation point, or marker, found at @var{location}. It may not
10277 be possible to set a static tracepoint at the desired location, in
10278 which case the command will exit with an explanatory message.
10280 @value{GDBN} handles arguments to @code{strace} exactly as for
10281 @code{trace}, with the addition that the user can also specify
10282 @code{-m @var{marker}} as @var{location}. This probes the marker
10283 identified by the @var{marker} string identifier. This identifier
10284 depends on the static tracepoint backend library your program is
10285 using. You can find all the marker identifiers in the @samp{ID} field
10286 of the @code{info static-tracepoint-markers} command output.
10287 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10288 Markers}. For example, in the following small program using the UST
10294 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10299 the marker id is composed of joining the first two arguments to the
10300 @code{trace_mark} call with a slash, which translates to:
10303 (@value{GDBP}) info static-tracepoint-markers
10304 Cnt Enb ID Address What
10305 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10311 so you may probe the marker above with:
10314 (@value{GDBP}) strace -m ust/bar33
10317 Static tracepoints accept an extra collect action --- @code{collect
10318 $_sdata}. This collects arbitrary user data passed in the probe point
10319 call to the tracing library. In the UST example above, you'll see
10320 that the third argument to @code{trace_mark} is a printf-like format
10321 string. The user data is then the result of running that formating
10322 string against the following arguments. Note that @code{info
10323 static-tracepoint-markers} command output lists that format string in
10324 the @samp{Data:} field.
10326 You can inspect this data when analyzing the trace buffer, by printing
10327 the $_sdata variable like any other variable available to
10328 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10331 @cindex last tracepoint number
10332 @cindex recent tracepoint number
10333 @cindex tracepoint number
10334 The convenience variable @code{$tpnum} records the tracepoint number
10335 of the most recently set tracepoint.
10337 @kindex delete tracepoint
10338 @cindex tracepoint deletion
10339 @item delete tracepoint @r{[}@var{num}@r{]}
10340 Permanently delete one or more tracepoints. With no argument, the
10341 default is to delete all tracepoints. Note that the regular
10342 @code{delete} command can remove tracepoints also.
10347 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10349 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10353 You can abbreviate this command as @code{del tr}.
10356 @node Enable and Disable Tracepoints
10357 @subsection Enable and Disable Tracepoints
10359 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10362 @kindex disable tracepoint
10363 @item disable tracepoint @r{[}@var{num}@r{]}
10364 Disable tracepoint @var{num}, or all tracepoints if no argument
10365 @var{num} is given. A disabled tracepoint will have no effect during
10366 a trace experiment, but it is not forgotten. You can re-enable
10367 a disabled tracepoint using the @code{enable tracepoint} command.
10368 If the command is issued during a trace experiment and the debug target
10369 has support for disabling tracepoints during a trace experiment, then the
10370 change will be effective immediately. Otherwise, it will be applied to the
10371 next trace experiment.
10373 @kindex enable tracepoint
10374 @item enable tracepoint @r{[}@var{num}@r{]}
10375 Enable tracepoint @var{num}, or all tracepoints. If this command is
10376 issued during a trace experiment and the debug target supports enabling
10377 tracepoints during a trace experiment, then the enabled tracepoints will
10378 become effective immediately. Otherwise, they will become effective the
10379 next time a trace experiment is run.
10382 @node Tracepoint Passcounts
10383 @subsection Tracepoint Passcounts
10387 @cindex tracepoint pass count
10388 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10389 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10390 automatically stop a trace experiment. If a tracepoint's passcount is
10391 @var{n}, then the trace experiment will be automatically stopped on
10392 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10393 @var{num} is not specified, the @code{passcount} command sets the
10394 passcount of the most recently defined tracepoint. If no passcount is
10395 given, the trace experiment will run until stopped explicitly by the
10401 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10402 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10404 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10405 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10406 (@value{GDBP}) @b{trace foo}
10407 (@value{GDBP}) @b{pass 3}
10408 (@value{GDBP}) @b{trace bar}
10409 (@value{GDBP}) @b{pass 2}
10410 (@value{GDBP}) @b{trace baz}
10411 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10412 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10413 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10414 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10418 @node Tracepoint Conditions
10419 @subsection Tracepoint Conditions
10420 @cindex conditional tracepoints
10421 @cindex tracepoint conditions
10423 The simplest sort of tracepoint collects data every time your program
10424 reaches a specified place. You can also specify a @dfn{condition} for
10425 a tracepoint. A condition is just a Boolean expression in your
10426 programming language (@pxref{Expressions, ,Expressions}). A
10427 tracepoint with a condition evaluates the expression each time your
10428 program reaches it, and data collection happens only if the condition
10431 Tracepoint conditions can be specified when a tracepoint is set, by
10432 using @samp{if} in the arguments to the @code{trace} command.
10433 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10434 also be set or changed at any time with the @code{condition} command,
10435 just as with breakpoints.
10437 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10438 the conditional expression itself. Instead, @value{GDBN} encodes the
10439 expression into an agent expression (@pxref{Agent Expressions})
10440 suitable for execution on the target, independently of @value{GDBN}.
10441 Global variables become raw memory locations, locals become stack
10442 accesses, and so forth.
10444 For instance, suppose you have a function that is usually called
10445 frequently, but should not be called after an error has occurred. You
10446 could use the following tracepoint command to collect data about calls
10447 of that function that happen while the error code is propagating
10448 through the program; an unconditional tracepoint could end up
10449 collecting thousands of useless trace frames that you would have to
10453 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10456 @node Trace State Variables
10457 @subsection Trace State Variables
10458 @cindex trace state variables
10460 A @dfn{trace state variable} is a special type of variable that is
10461 created and managed by target-side code. The syntax is the same as
10462 that for GDB's convenience variables (a string prefixed with ``$''),
10463 but they are stored on the target. They must be created explicitly,
10464 using a @code{tvariable} command. They are always 64-bit signed
10467 Trace state variables are remembered by @value{GDBN}, and downloaded
10468 to the target along with tracepoint information when the trace
10469 experiment starts. There are no intrinsic limits on the number of
10470 trace state variables, beyond memory limitations of the target.
10472 @cindex convenience variables, and trace state variables
10473 Although trace state variables are managed by the target, you can use
10474 them in print commands and expressions as if they were convenience
10475 variables; @value{GDBN} will get the current value from the target
10476 while the trace experiment is running. Trace state variables share
10477 the same namespace as other ``$'' variables, which means that you
10478 cannot have trace state variables with names like @code{$23} or
10479 @code{$pc}, nor can you have a trace state variable and a convenience
10480 variable with the same name.
10484 @item tvariable $@var{name} [ = @var{expression} ]
10486 The @code{tvariable} command creates a new trace state variable named
10487 @code{$@var{name}}, and optionally gives it an initial value of
10488 @var{expression}. @var{expression} is evaluated when this command is
10489 entered; the result will be converted to an integer if possible,
10490 otherwise @value{GDBN} will report an error. A subsequent
10491 @code{tvariable} command specifying the same name does not create a
10492 variable, but instead assigns the supplied initial value to the
10493 existing variable of that name, overwriting any previous initial
10494 value. The default initial value is 0.
10496 @item info tvariables
10497 @kindex info tvariables
10498 List all the trace state variables along with their initial values.
10499 Their current values may also be displayed, if the trace experiment is
10502 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10503 @kindex delete tvariable
10504 Delete the given trace state variables, or all of them if no arguments
10509 @node Tracepoint Actions
10510 @subsection Tracepoint Action Lists
10514 @cindex tracepoint actions
10515 @item actions @r{[}@var{num}@r{]}
10516 This command will prompt for a list of actions to be taken when the
10517 tracepoint is hit. If the tracepoint number @var{num} is not
10518 specified, this command sets the actions for the one that was most
10519 recently defined (so that you can define a tracepoint and then say
10520 @code{actions} without bothering about its number). You specify the
10521 actions themselves on the following lines, one action at a time, and
10522 terminate the actions list with a line containing just @code{end}. So
10523 far, the only defined actions are @code{collect}, @code{teval}, and
10524 @code{while-stepping}.
10526 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10527 Commands, ,Breakpoint Command Lists}), except that only the defined
10528 actions are allowed; any other @value{GDBN} command is rejected.
10530 @cindex remove actions from a tracepoint
10531 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10532 and follow it immediately with @samp{end}.
10535 (@value{GDBP}) @b{collect @var{data}} // collect some data
10537 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10539 (@value{GDBP}) @b{end} // signals the end of actions.
10542 In the following example, the action list begins with @code{collect}
10543 commands indicating the things to be collected when the tracepoint is
10544 hit. Then, in order to single-step and collect additional data
10545 following the tracepoint, a @code{while-stepping} command is used,
10546 followed by the list of things to be collected after each step in a
10547 sequence of single steps. The @code{while-stepping} command is
10548 terminated by its own separate @code{end} command. Lastly, the action
10549 list is terminated by an @code{end} command.
10552 (@value{GDBP}) @b{trace foo}
10553 (@value{GDBP}) @b{actions}
10554 Enter actions for tracepoint 1, one per line:
10557 > while-stepping 12
10558 > collect $pc, arr[i]
10563 @kindex collect @r{(tracepoints)}
10564 @item collect @var{expr1}, @var{expr2}, @dots{}
10565 Collect values of the given expressions when the tracepoint is hit.
10566 This command accepts a comma-separated list of any valid expressions.
10567 In addition to global, static, or local variables, the following
10568 special arguments are supported:
10572 Collect all registers.
10575 Collect all function arguments.
10578 Collect all local variables.
10581 Collect the return address. This is helpful if you want to see more
10585 @vindex $_sdata@r{, collect}
10586 Collect static tracepoint marker specific data. Only available for
10587 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10588 Lists}. On the UST static tracepoints library backend, an
10589 instrumentation point resembles a @code{printf} function call. The
10590 tracing library is able to collect user specified data formatted to a
10591 character string using the format provided by the programmer that
10592 instrumented the program. Other backends have similar mechanisms.
10593 Here's an example of a UST marker call:
10596 const char master_name[] = "$your_name";
10597 trace_mark(channel1, marker1, "hello %s", master_name)
10600 In this case, collecting @code{$_sdata} collects the string
10601 @samp{hello $yourname}. When analyzing the trace buffer, you can
10602 inspect @samp{$_sdata} like any other variable available to
10606 You can give several consecutive @code{collect} commands, each one
10607 with a single argument, or one @code{collect} command with several
10608 arguments separated by commas; the effect is the same.
10610 The command @code{info scope} (@pxref{Symbols, info scope}) is
10611 particularly useful for figuring out what data to collect.
10613 @kindex teval @r{(tracepoints)}
10614 @item teval @var{expr1}, @var{expr2}, @dots{}
10615 Evaluate the given expressions when the tracepoint is hit. This
10616 command accepts a comma-separated list of expressions. The results
10617 are discarded, so this is mainly useful for assigning values to trace
10618 state variables (@pxref{Trace State Variables}) without adding those
10619 values to the trace buffer, as would be the case if the @code{collect}
10622 @kindex while-stepping @r{(tracepoints)}
10623 @item while-stepping @var{n}
10624 Perform @var{n} single-step instruction traces after the tracepoint,
10625 collecting new data after each step. The @code{while-stepping}
10626 command is followed by the list of what to collect while stepping
10627 (followed by its own @code{end} command):
10630 > while-stepping 12
10631 > collect $regs, myglobal
10637 Note that @code{$pc} is not automatically collected by
10638 @code{while-stepping}; you need to explicitly collect that register if
10639 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10642 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10643 @kindex set default-collect
10644 @cindex default collection action
10645 This variable is a list of expressions to collect at each tracepoint
10646 hit. It is effectively an additional @code{collect} action prepended
10647 to every tracepoint action list. The expressions are parsed
10648 individually for each tracepoint, so for instance a variable named
10649 @code{xyz} may be interpreted as a global for one tracepoint, and a
10650 local for another, as appropriate to the tracepoint's location.
10652 @item show default-collect
10653 @kindex show default-collect
10654 Show the list of expressions that are collected by default at each
10659 @node Listing Tracepoints
10660 @subsection Listing Tracepoints
10663 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10664 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10665 @cindex information about tracepoints
10666 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10667 Display information about the tracepoint @var{num}. If you don't
10668 specify a tracepoint number, displays information about all the
10669 tracepoints defined so far. The format is similar to that used for
10670 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10671 command, simply restricting itself to tracepoints.
10673 A tracepoint's listing may include additional information specific to
10678 its passcount as given by the @code{passcount @var{n}} command
10682 (@value{GDBP}) @b{info trace}
10683 Num Type Disp Enb Address What
10684 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10686 collect globfoo, $regs
10695 This command can be abbreviated @code{info tp}.
10698 @node Listing Static Tracepoint Markers
10699 @subsection Listing Static Tracepoint Markers
10702 @kindex info static-tracepoint-markers
10703 @cindex information about static tracepoint markers
10704 @item info static-tracepoint-markers
10705 Display information about all static tracepoint markers defined in the
10708 For each marker, the following columns are printed:
10712 An incrementing counter, output to help readability. This is not a
10715 The marker ID, as reported by the target.
10716 @item Enabled or Disabled
10717 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10718 that are not enabled.
10720 Where the marker is in your program, as a memory address.
10722 Where the marker is in the source for your program, as a file and line
10723 number. If the debug information included in the program does not
10724 allow @value{GDBN} to locate the source of the marker, this column
10725 will be left blank.
10729 In addition, the following information may be printed for each marker:
10733 User data passed to the tracing library by the marker call. In the
10734 UST backend, this is the format string passed as argument to the
10736 @item Static tracepoints probing the marker
10737 The list of static tracepoints attached to the marker.
10741 (@value{GDBP}) info static-tracepoint-markers
10742 Cnt ID Enb Address What
10743 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10744 Data: number1 %d number2 %d
10745 Probed by static tracepoints: #2
10746 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10752 @node Starting and Stopping Trace Experiments
10753 @subsection Starting and Stopping Trace Experiments
10757 @cindex start a new trace experiment
10758 @cindex collected data discarded
10760 This command takes no arguments. It starts the trace experiment, and
10761 begins collecting data. This has the side effect of discarding all
10762 the data collected in the trace buffer during the previous trace
10766 @cindex stop a running trace experiment
10768 This command takes no arguments. It ends the trace experiment, and
10769 stops collecting data.
10771 @strong{Note}: a trace experiment and data collection may stop
10772 automatically if any tracepoint's passcount is reached
10773 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10776 @cindex status of trace data collection
10777 @cindex trace experiment, status of
10779 This command displays the status of the current trace data
10783 Here is an example of the commands we described so far:
10786 (@value{GDBP}) @b{trace gdb_c_test}
10787 (@value{GDBP}) @b{actions}
10788 Enter actions for tracepoint #1, one per line.
10789 > collect $regs,$locals,$args
10790 > while-stepping 11
10794 (@value{GDBP}) @b{tstart}
10795 [time passes @dots{}]
10796 (@value{GDBP}) @b{tstop}
10799 @anchor{disconnected tracing}
10800 @cindex disconnected tracing
10801 You can choose to continue running the trace experiment even if
10802 @value{GDBN} disconnects from the target, voluntarily or
10803 involuntarily. For commands such as @code{detach}, the debugger will
10804 ask what you want to do with the trace. But for unexpected
10805 terminations (@value{GDBN} crash, network outage), it would be
10806 unfortunate to lose hard-won trace data, so the variable
10807 @code{disconnected-tracing} lets you decide whether the trace should
10808 continue running without @value{GDBN}.
10811 @item set disconnected-tracing on
10812 @itemx set disconnected-tracing off
10813 @kindex set disconnected-tracing
10814 Choose whether a tracing run should continue to run if @value{GDBN}
10815 has disconnected from the target. Note that @code{detach} or
10816 @code{quit} will ask you directly what to do about a running trace no
10817 matter what this variable's setting, so the variable is mainly useful
10818 for handling unexpected situations, such as loss of the network.
10820 @item show disconnected-tracing
10821 @kindex show disconnected-tracing
10822 Show the current choice for disconnected tracing.
10826 When you reconnect to the target, the trace experiment may or may not
10827 still be running; it might have filled the trace buffer in the
10828 meantime, or stopped for one of the other reasons. If it is running,
10829 it will continue after reconnection.
10831 Upon reconnection, the target will upload information about the
10832 tracepoints in effect. @value{GDBN} will then compare that
10833 information to the set of tracepoints currently defined, and attempt
10834 to match them up, allowing for the possibility that the numbers may
10835 have changed due to creation and deletion in the meantime. If one of
10836 the target's tracepoints does not match any in @value{GDBN}, the
10837 debugger will create a new tracepoint, so that you have a number with
10838 which to specify that tracepoint. This matching-up process is
10839 necessarily heuristic, and it may result in useless tracepoints being
10840 created; you may simply delete them if they are of no use.
10842 @cindex circular trace buffer
10843 If your target agent supports a @dfn{circular trace buffer}, then you
10844 can run a trace experiment indefinitely without filling the trace
10845 buffer; when space runs out, the agent deletes already-collected trace
10846 frames, oldest first, until there is enough room to continue
10847 collecting. This is especially useful if your tracepoints are being
10848 hit too often, and your trace gets terminated prematurely because the
10849 buffer is full. To ask for a circular trace buffer, simply set
10850 @samp{circular-trace-buffer} to on. You can set this at any time,
10851 including during tracing; if the agent can do it, it will change
10852 buffer handling on the fly, otherwise it will not take effect until
10856 @item set circular-trace-buffer on
10857 @itemx set circular-trace-buffer off
10858 @kindex set circular-trace-buffer
10859 Choose whether a tracing run should use a linear or circular buffer
10860 for trace data. A linear buffer will not lose any trace data, but may
10861 fill up prematurely, while a circular buffer will discard old trace
10862 data, but it will have always room for the latest tracepoint hits.
10864 @item show circular-trace-buffer
10865 @kindex show circular-trace-buffer
10866 Show the current choice for the trace buffer. Note that this may not
10867 match the agent's current buffer handling, nor is it guaranteed to
10868 match the setting that might have been in effect during a past run,
10869 for instance if you are looking at frames from a trace file.
10873 @node Tracepoint Restrictions
10874 @subsection Tracepoint Restrictions
10876 @cindex tracepoint restrictions
10877 There are a number of restrictions on the use of tracepoints. As
10878 described above, tracepoint data gathering occurs on the target
10879 without interaction from @value{GDBN}. Thus the full capabilities of
10880 the debugger are not available during data gathering, and then at data
10881 examination time, you will be limited by only having what was
10882 collected. The following items describe some common problems, but it
10883 is not exhaustive, and you may run into additional difficulties not
10889 Tracepoint expressions are intended to gather objects (lvalues). Thus
10890 the full flexibility of GDB's expression evaluator is not available.
10891 You cannot call functions, cast objects to aggregate types, access
10892 convenience variables or modify values (except by assignment to trace
10893 state variables). Some language features may implicitly call
10894 functions (for instance Objective-C fields with accessors), and therefore
10895 cannot be collected either.
10898 Collection of local variables, either individually or in bulk with
10899 @code{$locals} or @code{$args}, during @code{while-stepping} may
10900 behave erratically. The stepping action may enter a new scope (for
10901 instance by stepping into a function), or the location of the variable
10902 may change (for instance it is loaded into a register). The
10903 tracepoint data recorded uses the location information for the
10904 variables that is correct for the tracepoint location. When the
10905 tracepoint is created, it is not possible, in general, to determine
10906 where the steps of a @code{while-stepping} sequence will advance the
10907 program---particularly if a conditional branch is stepped.
10910 Collection of an incompletely-initialized or partially-destroyed object
10911 may result in something that @value{GDBN} cannot display, or displays
10912 in a misleading way.
10915 When @value{GDBN} displays a pointer to character it automatically
10916 dereferences the pointer to also display characters of the string
10917 being pointed to. However, collecting the pointer during tracing does
10918 not automatically collect the string. You need to explicitly
10919 dereference the pointer and provide size information if you want to
10920 collect not only the pointer, but the memory pointed to. For example,
10921 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10925 It is not possible to collect a complete stack backtrace at a
10926 tracepoint. Instead, you may collect the registers and a few hundred
10927 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
10928 (adjust to use the name of the actual stack pointer register on your
10929 target architecture, and the amount of stack you wish to capture).
10930 Then the @code{backtrace} command will show a partial backtrace when
10931 using a trace frame. The number of stack frames that can be examined
10932 depends on the sizes of the frames in the collected stack. Note that
10933 if you ask for a block so large that it goes past the bottom of the
10934 stack, the target agent may report an error trying to read from an
10938 If you do not collect registers at a tracepoint, @value{GDBN} can
10939 infer that the value of @code{$pc} must be the same as the address of
10940 the tracepoint and use that when you are looking at a trace frame
10941 for that tracepoint. However, this cannot work if the tracepoint has
10942 multiple locations (for instance if it was set in a function that was
10943 inlined), or if it has a @code{while-stepping} loop. In those cases
10944 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10949 @node Analyze Collected Data
10950 @section Using the Collected Data
10952 After the tracepoint experiment ends, you use @value{GDBN} commands
10953 for examining the trace data. The basic idea is that each tracepoint
10954 collects a trace @dfn{snapshot} every time it is hit and another
10955 snapshot every time it single-steps. All these snapshots are
10956 consecutively numbered from zero and go into a buffer, and you can
10957 examine them later. The way you examine them is to @dfn{focus} on a
10958 specific trace snapshot. When the remote stub is focused on a trace
10959 snapshot, it will respond to all @value{GDBN} requests for memory and
10960 registers by reading from the buffer which belongs to that snapshot,
10961 rather than from @emph{real} memory or registers of the program being
10962 debugged. This means that @strong{all} @value{GDBN} commands
10963 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10964 behave as if we were currently debugging the program state as it was
10965 when the tracepoint occurred. Any requests for data that are not in
10966 the buffer will fail.
10969 * tfind:: How to select a trace snapshot
10970 * tdump:: How to display all data for a snapshot
10971 * save tracepoints:: How to save tracepoints for a future run
10975 @subsection @code{tfind @var{n}}
10978 @cindex select trace snapshot
10979 @cindex find trace snapshot
10980 The basic command for selecting a trace snapshot from the buffer is
10981 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10982 counting from zero. If no argument @var{n} is given, the next
10983 snapshot is selected.
10985 Here are the various forms of using the @code{tfind} command.
10989 Find the first snapshot in the buffer. This is a synonym for
10990 @code{tfind 0} (since 0 is the number of the first snapshot).
10993 Stop debugging trace snapshots, resume @emph{live} debugging.
10996 Same as @samp{tfind none}.
10999 No argument means find the next trace snapshot.
11002 Find the previous trace snapshot before the current one. This permits
11003 retracing earlier steps.
11005 @item tfind tracepoint @var{num}
11006 Find the next snapshot associated with tracepoint @var{num}. Search
11007 proceeds forward from the last examined trace snapshot. If no
11008 argument @var{num} is given, it means find the next snapshot collected
11009 for the same tracepoint as the current snapshot.
11011 @item tfind pc @var{addr}
11012 Find the next snapshot associated with the value @var{addr} of the
11013 program counter. Search proceeds forward from the last examined trace
11014 snapshot. If no argument @var{addr} is given, it means find the next
11015 snapshot with the same value of PC as the current snapshot.
11017 @item tfind outside @var{addr1}, @var{addr2}
11018 Find the next snapshot whose PC is outside the given range of
11019 addresses (exclusive).
11021 @item tfind range @var{addr1}, @var{addr2}
11022 Find the next snapshot whose PC is between @var{addr1} and
11023 @var{addr2} (inclusive).
11025 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11026 Find the next snapshot associated with the source line @var{n}. If
11027 the optional argument @var{file} is given, refer to line @var{n} in
11028 that source file. Search proceeds forward from the last examined
11029 trace snapshot. If no argument @var{n} is given, it means find the
11030 next line other than the one currently being examined; thus saying
11031 @code{tfind line} repeatedly can appear to have the same effect as
11032 stepping from line to line in a @emph{live} debugging session.
11035 The default arguments for the @code{tfind} commands are specifically
11036 designed to make it easy to scan through the trace buffer. For
11037 instance, @code{tfind} with no argument selects the next trace
11038 snapshot, and @code{tfind -} with no argument selects the previous
11039 trace snapshot. So, by giving one @code{tfind} command, and then
11040 simply hitting @key{RET} repeatedly you can examine all the trace
11041 snapshots in order. Or, by saying @code{tfind -} and then hitting
11042 @key{RET} repeatedly you can examine the snapshots in reverse order.
11043 The @code{tfind line} command with no argument selects the snapshot
11044 for the next source line executed. The @code{tfind pc} command with
11045 no argument selects the next snapshot with the same program counter
11046 (PC) as the current frame. The @code{tfind tracepoint} command with
11047 no argument selects the next trace snapshot collected by the same
11048 tracepoint as the current one.
11050 In addition to letting you scan through the trace buffer manually,
11051 these commands make it easy to construct @value{GDBN} scripts that
11052 scan through the trace buffer and print out whatever collected data
11053 you are interested in. Thus, if we want to examine the PC, FP, and SP
11054 registers from each trace frame in the buffer, we can say this:
11057 (@value{GDBP}) @b{tfind start}
11058 (@value{GDBP}) @b{while ($trace_frame != -1)}
11059 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11060 $trace_frame, $pc, $sp, $fp
11064 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11065 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11066 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11067 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11068 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11069 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11070 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11071 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11072 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11073 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11074 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11077 Or, if we want to examine the variable @code{X} at each source line in
11081 (@value{GDBP}) @b{tfind start}
11082 (@value{GDBP}) @b{while ($trace_frame != -1)}
11083 > printf "Frame %d, X == %d\n", $trace_frame, X
11093 @subsection @code{tdump}
11095 @cindex dump all data collected at tracepoint
11096 @cindex tracepoint data, display
11098 This command takes no arguments. It prints all the data collected at
11099 the current trace snapshot.
11102 (@value{GDBP}) @b{trace 444}
11103 (@value{GDBP}) @b{actions}
11104 Enter actions for tracepoint #2, one per line:
11105 > collect $regs, $locals, $args, gdb_long_test
11108 (@value{GDBP}) @b{tstart}
11110 (@value{GDBP}) @b{tfind line 444}
11111 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11113 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11115 (@value{GDBP}) @b{tdump}
11116 Data collected at tracepoint 2, trace frame 1:
11117 d0 0xc4aa0085 -995491707
11121 d4 0x71aea3d 119204413
11124 d7 0x380035 3670069
11125 a0 0x19e24a 1696330
11126 a1 0x3000668 50333288
11128 a3 0x322000 3284992
11129 a4 0x3000698 50333336
11130 a5 0x1ad3cc 1758156
11131 fp 0x30bf3c 0x30bf3c
11132 sp 0x30bf34 0x30bf34
11134 pc 0x20b2c8 0x20b2c8
11138 p = 0x20e5b4 "gdb-test"
11145 gdb_long_test = 17 '\021'
11150 @code{tdump} works by scanning the tracepoint's current collection
11151 actions and printing the value of each expression listed. So
11152 @code{tdump} can fail, if after a run, you change the tracepoint's
11153 actions to mention variables that were not collected during the run.
11155 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11156 uses the collected value of @code{$pc} to distinguish between trace
11157 frames that were collected at the tracepoint hit, and frames that were
11158 collected while stepping. This allows it to correctly choose whether
11159 to display the basic list of collections, or the collections from the
11160 body of the while-stepping loop. However, if @code{$pc} was not collected,
11161 then @code{tdump} will always attempt to dump using the basic collection
11162 list, and may fail if a while-stepping frame does not include all the
11163 same data that is collected at the tracepoint hit.
11164 @c This is getting pretty arcane, example would be good.
11166 @node save tracepoints
11167 @subsection @code{save tracepoints @var{filename}}
11168 @kindex save tracepoints
11169 @kindex save-tracepoints
11170 @cindex save tracepoints for future sessions
11172 This command saves all current tracepoint definitions together with
11173 their actions and passcounts, into a file @file{@var{filename}}
11174 suitable for use in a later debugging session. To read the saved
11175 tracepoint definitions, use the @code{source} command (@pxref{Command
11176 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11177 alias for @w{@code{save tracepoints}}
11179 @node Tracepoint Variables
11180 @section Convenience Variables for Tracepoints
11181 @cindex tracepoint variables
11182 @cindex convenience variables for tracepoints
11185 @vindex $trace_frame
11186 @item (int) $trace_frame
11187 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11188 snapshot is selected.
11190 @vindex $tracepoint
11191 @item (int) $tracepoint
11192 The tracepoint for the current trace snapshot.
11194 @vindex $trace_line
11195 @item (int) $trace_line
11196 The line number for the current trace snapshot.
11198 @vindex $trace_file
11199 @item (char []) $trace_file
11200 The source file for the current trace snapshot.
11202 @vindex $trace_func
11203 @item (char []) $trace_func
11204 The name of the function containing @code{$tracepoint}.
11207 Note: @code{$trace_file} is not suitable for use in @code{printf},
11208 use @code{output} instead.
11210 Here's a simple example of using these convenience variables for
11211 stepping through all the trace snapshots and printing some of their
11212 data. Note that these are not the same as trace state variables,
11213 which are managed by the target.
11216 (@value{GDBP}) @b{tfind start}
11218 (@value{GDBP}) @b{while $trace_frame != -1}
11219 > output $trace_file
11220 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11226 @section Using Trace Files
11227 @cindex trace files
11229 In some situations, the target running a trace experiment may no
11230 longer be available; perhaps it crashed, or the hardware was needed
11231 for a different activity. To handle these cases, you can arrange to
11232 dump the trace data into a file, and later use that file as a source
11233 of trace data, via the @code{target tfile} command.
11238 @item tsave [ -r ] @var{filename}
11239 Save the trace data to @var{filename}. By default, this command
11240 assumes that @var{filename} refers to the host filesystem, so if
11241 necessary @value{GDBN} will copy raw trace data up from the target and
11242 then save it. If the target supports it, you can also supply the
11243 optional argument @code{-r} (``remote'') to direct the target to save
11244 the data directly into @var{filename} in its own filesystem, which may be
11245 more efficient if the trace buffer is very large. (Note, however, that
11246 @code{target tfile} can only read from files accessible to the host.)
11248 @kindex target tfile
11250 @item target tfile @var{filename}
11251 Use the file named @var{filename} as a source of trace data. Commands
11252 that examine data work as they do with a live target, but it is not
11253 possible to run any new trace experiments. @code{tstatus} will report
11254 the state of the trace run at the moment the data was saved, as well
11255 as the current trace frame you are examining. @var{filename} must be
11256 on a filesystem accessible to the host.
11261 @chapter Debugging Programs That Use Overlays
11264 If your program is too large to fit completely in your target system's
11265 memory, you can sometimes use @dfn{overlays} to work around this
11266 problem. @value{GDBN} provides some support for debugging programs that
11270 * How Overlays Work:: A general explanation of overlays.
11271 * Overlay Commands:: Managing overlays in @value{GDBN}.
11272 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11273 mapped by asking the inferior.
11274 * Overlay Sample Program:: A sample program using overlays.
11277 @node How Overlays Work
11278 @section How Overlays Work
11279 @cindex mapped overlays
11280 @cindex unmapped overlays
11281 @cindex load address, overlay's
11282 @cindex mapped address
11283 @cindex overlay area
11285 Suppose you have a computer whose instruction address space is only 64
11286 kilobytes long, but which has much more memory which can be accessed by
11287 other means: special instructions, segment registers, or memory
11288 management hardware, for example. Suppose further that you want to
11289 adapt a program which is larger than 64 kilobytes to run on this system.
11291 One solution is to identify modules of your program which are relatively
11292 independent, and need not call each other directly; call these modules
11293 @dfn{overlays}. Separate the overlays from the main program, and place
11294 their machine code in the larger memory. Place your main program in
11295 instruction memory, but leave at least enough space there to hold the
11296 largest overlay as well.
11298 Now, to call a function located in an overlay, you must first copy that
11299 overlay's machine code from the large memory into the space set aside
11300 for it in the instruction memory, and then jump to its entry point
11303 @c NB: In the below the mapped area's size is greater or equal to the
11304 @c size of all overlays. This is intentional to remind the developer
11305 @c that overlays don't necessarily need to be the same size.
11309 Data Instruction Larger
11310 Address Space Address Space Address Space
11311 +-----------+ +-----------+ +-----------+
11313 +-----------+ +-----------+ +-----------+<-- overlay 1
11314 | program | | main | .----| overlay 1 | load address
11315 | variables | | program | | +-----------+
11316 | and heap | | | | | |
11317 +-----------+ | | | +-----------+<-- overlay 2
11318 | | +-----------+ | | | load address
11319 +-----------+ | | | .-| overlay 2 |
11321 mapped --->+-----------+ | | +-----------+
11322 address | | | | | |
11323 | overlay | <-' | | |
11324 | area | <---' +-----------+<-- overlay 3
11325 | | <---. | | load address
11326 +-----------+ `--| overlay 3 |
11333 @anchor{A code overlay}A code overlay
11337 The diagram (@pxref{A code overlay}) shows a system with separate data
11338 and instruction address spaces. To map an overlay, the program copies
11339 its code from the larger address space to the instruction address space.
11340 Since the overlays shown here all use the same mapped address, only one
11341 may be mapped at a time. For a system with a single address space for
11342 data and instructions, the diagram would be similar, except that the
11343 program variables and heap would share an address space with the main
11344 program and the overlay area.
11346 An overlay loaded into instruction memory and ready for use is called a
11347 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11348 instruction memory. An overlay not present (or only partially present)
11349 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11350 is its address in the larger memory. The mapped address is also called
11351 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11352 called the @dfn{load memory address}, or @dfn{LMA}.
11354 Unfortunately, overlays are not a completely transparent way to adapt a
11355 program to limited instruction memory. They introduce a new set of
11356 global constraints you must keep in mind as you design your program:
11361 Before calling or returning to a function in an overlay, your program
11362 must make sure that overlay is actually mapped. Otherwise, the call or
11363 return will transfer control to the right address, but in the wrong
11364 overlay, and your program will probably crash.
11367 If the process of mapping an overlay is expensive on your system, you
11368 will need to choose your overlays carefully to minimize their effect on
11369 your program's performance.
11372 The executable file you load onto your system must contain each
11373 overlay's instructions, appearing at the overlay's load address, not its
11374 mapped address. However, each overlay's instructions must be relocated
11375 and its symbols defined as if the overlay were at its mapped address.
11376 You can use GNU linker scripts to specify different load and relocation
11377 addresses for pieces of your program; see @ref{Overlay Description,,,
11378 ld.info, Using ld: the GNU linker}.
11381 The procedure for loading executable files onto your system must be able
11382 to load their contents into the larger address space as well as the
11383 instruction and data spaces.
11387 The overlay system described above is rather simple, and could be
11388 improved in many ways:
11393 If your system has suitable bank switch registers or memory management
11394 hardware, you could use those facilities to make an overlay's load area
11395 contents simply appear at their mapped address in instruction space.
11396 This would probably be faster than copying the overlay to its mapped
11397 area in the usual way.
11400 If your overlays are small enough, you could set aside more than one
11401 overlay area, and have more than one overlay mapped at a time.
11404 You can use overlays to manage data, as well as instructions. In
11405 general, data overlays are even less transparent to your design than
11406 code overlays: whereas code overlays only require care when you call or
11407 return to functions, data overlays require care every time you access
11408 the data. Also, if you change the contents of a data overlay, you
11409 must copy its contents back out to its load address before you can copy a
11410 different data overlay into the same mapped area.
11415 @node Overlay Commands
11416 @section Overlay Commands
11418 To use @value{GDBN}'s overlay support, each overlay in your program must
11419 correspond to a separate section of the executable file. The section's
11420 virtual memory address and load memory address must be the overlay's
11421 mapped and load addresses. Identifying overlays with sections allows
11422 @value{GDBN} to determine the appropriate address of a function or
11423 variable, depending on whether the overlay is mapped or not.
11425 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11426 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11431 Disable @value{GDBN}'s overlay support. When overlay support is
11432 disabled, @value{GDBN} assumes that all functions and variables are
11433 always present at their mapped addresses. By default, @value{GDBN}'s
11434 overlay support is disabled.
11436 @item overlay manual
11437 @cindex manual overlay debugging
11438 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11439 relies on you to tell it which overlays are mapped, and which are not,
11440 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11441 commands described below.
11443 @item overlay map-overlay @var{overlay}
11444 @itemx overlay map @var{overlay}
11445 @cindex map an overlay
11446 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11447 be the name of the object file section containing the overlay. When an
11448 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11449 functions and variables at their mapped addresses. @value{GDBN} assumes
11450 that any other overlays whose mapped ranges overlap that of
11451 @var{overlay} are now unmapped.
11453 @item overlay unmap-overlay @var{overlay}
11454 @itemx overlay unmap @var{overlay}
11455 @cindex unmap an overlay
11456 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11457 must be the name of the object file section containing the overlay.
11458 When an overlay is unmapped, @value{GDBN} assumes it can find the
11459 overlay's functions and variables at their load addresses.
11462 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11463 consults a data structure the overlay manager maintains in the inferior
11464 to see which overlays are mapped. For details, see @ref{Automatic
11465 Overlay Debugging}.
11467 @item overlay load-target
11468 @itemx overlay load
11469 @cindex reloading the overlay table
11470 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11471 re-reads the table @value{GDBN} automatically each time the inferior
11472 stops, so this command should only be necessary if you have changed the
11473 overlay mapping yourself using @value{GDBN}. This command is only
11474 useful when using automatic overlay debugging.
11476 @item overlay list-overlays
11477 @itemx overlay list
11478 @cindex listing mapped overlays
11479 Display a list of the overlays currently mapped, along with their mapped
11480 addresses, load addresses, and sizes.
11484 Normally, when @value{GDBN} prints a code address, it includes the name
11485 of the function the address falls in:
11488 (@value{GDBP}) print main
11489 $3 = @{int ()@} 0x11a0 <main>
11492 When overlay debugging is enabled, @value{GDBN} recognizes code in
11493 unmapped overlays, and prints the names of unmapped functions with
11494 asterisks around them. For example, if @code{foo} is a function in an
11495 unmapped overlay, @value{GDBN} prints it this way:
11498 (@value{GDBP}) overlay list
11499 No sections are mapped.
11500 (@value{GDBP}) print foo
11501 $5 = @{int (int)@} 0x100000 <*foo*>
11504 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11508 (@value{GDBP}) overlay list
11509 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11510 mapped at 0x1016 - 0x104a
11511 (@value{GDBP}) print foo
11512 $6 = @{int (int)@} 0x1016 <foo>
11515 When overlay debugging is enabled, @value{GDBN} can find the correct
11516 address for functions and variables in an overlay, whether or not the
11517 overlay is mapped. This allows most @value{GDBN} commands, like
11518 @code{break} and @code{disassemble}, to work normally, even on unmapped
11519 code. However, @value{GDBN}'s breakpoint support has some limitations:
11523 @cindex breakpoints in overlays
11524 @cindex overlays, setting breakpoints in
11525 You can set breakpoints in functions in unmapped overlays, as long as
11526 @value{GDBN} can write to the overlay at its load address.
11528 @value{GDBN} can not set hardware or simulator-based breakpoints in
11529 unmapped overlays. However, if you set a breakpoint at the end of your
11530 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11531 you are using manual overlay management), @value{GDBN} will re-set its
11532 breakpoints properly.
11536 @node Automatic Overlay Debugging
11537 @section Automatic Overlay Debugging
11538 @cindex automatic overlay debugging
11540 @value{GDBN} can automatically track which overlays are mapped and which
11541 are not, given some simple co-operation from the overlay manager in the
11542 inferior. If you enable automatic overlay debugging with the
11543 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11544 looks in the inferior's memory for certain variables describing the
11545 current state of the overlays.
11547 Here are the variables your overlay manager must define to support
11548 @value{GDBN}'s automatic overlay debugging:
11552 @item @code{_ovly_table}:
11553 This variable must be an array of the following structures:
11558 /* The overlay's mapped address. */
11561 /* The size of the overlay, in bytes. */
11562 unsigned long size;
11564 /* The overlay's load address. */
11567 /* Non-zero if the overlay is currently mapped;
11569 unsigned long mapped;
11573 @item @code{_novlys}:
11574 This variable must be a four-byte signed integer, holding the total
11575 number of elements in @code{_ovly_table}.
11579 To decide whether a particular overlay is mapped or not, @value{GDBN}
11580 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11581 @code{lma} members equal the VMA and LMA of the overlay's section in the
11582 executable file. When @value{GDBN} finds a matching entry, it consults
11583 the entry's @code{mapped} member to determine whether the overlay is
11586 In addition, your overlay manager may define a function called
11587 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11588 will silently set a breakpoint there. If the overlay manager then
11589 calls this function whenever it has changed the overlay table, this
11590 will enable @value{GDBN} to accurately keep track of which overlays
11591 are in program memory, and update any breakpoints that may be set
11592 in overlays. This will allow breakpoints to work even if the
11593 overlays are kept in ROM or other non-writable memory while they
11594 are not being executed.
11596 @node Overlay Sample Program
11597 @section Overlay Sample Program
11598 @cindex overlay example program
11600 When linking a program which uses overlays, you must place the overlays
11601 at their load addresses, while relocating them to run at their mapped
11602 addresses. To do this, you must write a linker script (@pxref{Overlay
11603 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11604 since linker scripts are specific to a particular host system, target
11605 architecture, and target memory layout, this manual cannot provide
11606 portable sample code demonstrating @value{GDBN}'s overlay support.
11608 However, the @value{GDBN} source distribution does contain an overlaid
11609 program, with linker scripts for a few systems, as part of its test
11610 suite. The program consists of the following files from
11611 @file{gdb/testsuite/gdb.base}:
11615 The main program file.
11617 A simple overlay manager, used by @file{overlays.c}.
11622 Overlay modules, loaded and used by @file{overlays.c}.
11625 Linker scripts for linking the test program on the @code{d10v-elf}
11626 and @code{m32r-elf} targets.
11629 You can build the test program using the @code{d10v-elf} GCC
11630 cross-compiler like this:
11633 $ d10v-elf-gcc -g -c overlays.c
11634 $ d10v-elf-gcc -g -c ovlymgr.c
11635 $ d10v-elf-gcc -g -c foo.c
11636 $ d10v-elf-gcc -g -c bar.c
11637 $ d10v-elf-gcc -g -c baz.c
11638 $ d10v-elf-gcc -g -c grbx.c
11639 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11640 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11643 The build process is identical for any other architecture, except that
11644 you must substitute the appropriate compiler and linker script for the
11645 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11649 @chapter Using @value{GDBN} with Different Languages
11652 Although programming languages generally have common aspects, they are
11653 rarely expressed in the same manner. For instance, in ANSI C,
11654 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11655 Modula-2, it is accomplished by @code{p^}. Values can also be
11656 represented (and displayed) differently. Hex numbers in C appear as
11657 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11659 @cindex working language
11660 Language-specific information is built into @value{GDBN} for some languages,
11661 allowing you to express operations like the above in your program's
11662 native language, and allowing @value{GDBN} to output values in a manner
11663 consistent with the syntax of your program's native language. The
11664 language you use to build expressions is called the @dfn{working
11668 * Setting:: Switching between source languages
11669 * Show:: Displaying the language
11670 * Checks:: Type and range checks
11671 * Supported Languages:: Supported languages
11672 * Unsupported Languages:: Unsupported languages
11676 @section Switching Between Source Languages
11678 There are two ways to control the working language---either have @value{GDBN}
11679 set it automatically, or select it manually yourself. You can use the
11680 @code{set language} command for either purpose. On startup, @value{GDBN}
11681 defaults to setting the language automatically. The working language is
11682 used to determine how expressions you type are interpreted, how values
11685 In addition to the working language, every source file that
11686 @value{GDBN} knows about has its own working language. For some object
11687 file formats, the compiler might indicate which language a particular
11688 source file is in. However, most of the time @value{GDBN} infers the
11689 language from the name of the file. The language of a source file
11690 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11691 show each frame appropriately for its own language. There is no way to
11692 set the language of a source file from within @value{GDBN}, but you can
11693 set the language associated with a filename extension. @xref{Show, ,
11694 Displaying the Language}.
11696 This is most commonly a problem when you use a program, such
11697 as @code{cfront} or @code{f2c}, that generates C but is written in
11698 another language. In that case, make the
11699 program use @code{#line} directives in its C output; that way
11700 @value{GDBN} will know the correct language of the source code of the original
11701 program, and will display that source code, not the generated C code.
11704 * Filenames:: Filename extensions and languages.
11705 * Manually:: Setting the working language manually
11706 * Automatically:: Having @value{GDBN} infer the source language
11710 @subsection List of Filename Extensions and Languages
11712 If a source file name ends in one of the following extensions, then
11713 @value{GDBN} infers that its language is the one indicated.
11731 C@t{++} source file
11737 Objective-C source file
11741 Fortran source file
11744 Modula-2 source file
11748 Assembler source file. This actually behaves almost like C, but
11749 @value{GDBN} does not skip over function prologues when stepping.
11752 In addition, you may set the language associated with a filename
11753 extension. @xref{Show, , Displaying the Language}.
11756 @subsection Setting the Working Language
11758 If you allow @value{GDBN} to set the language automatically,
11759 expressions are interpreted the same way in your debugging session and
11762 @kindex set language
11763 If you wish, you may set the language manually. To do this, issue the
11764 command @samp{set language @var{lang}}, where @var{lang} is the name of
11765 a language, such as
11766 @code{c} or @code{modula-2}.
11767 For a list of the supported languages, type @samp{set language}.
11769 Setting the language manually prevents @value{GDBN} from updating the working
11770 language automatically. This can lead to confusion if you try
11771 to debug a program when the working language is not the same as the
11772 source language, when an expression is acceptable to both
11773 languages---but means different things. For instance, if the current
11774 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11782 might not have the effect you intended. In C, this means to add
11783 @code{b} and @code{c} and place the result in @code{a}. The result
11784 printed would be the value of @code{a}. In Modula-2, this means to compare
11785 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11787 @node Automatically
11788 @subsection Having @value{GDBN} Infer the Source Language
11790 To have @value{GDBN} set the working language automatically, use
11791 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11792 then infers the working language. That is, when your program stops in a
11793 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11794 working language to the language recorded for the function in that
11795 frame. If the language for a frame is unknown (that is, if the function
11796 or block corresponding to the frame was defined in a source file that
11797 does not have a recognized extension), the current working language is
11798 not changed, and @value{GDBN} issues a warning.
11800 This may not seem necessary for most programs, which are written
11801 entirely in one source language. However, program modules and libraries
11802 written in one source language can be used by a main program written in
11803 a different source language. Using @samp{set language auto} in this
11804 case frees you from having to set the working language manually.
11807 @section Displaying the Language
11809 The following commands help you find out which language is the
11810 working language, and also what language source files were written in.
11813 @item show language
11814 @kindex show language
11815 Display the current working language. This is the
11816 language you can use with commands such as @code{print} to
11817 build and compute expressions that may involve variables in your program.
11820 @kindex info frame@r{, show the source language}
11821 Display the source language for this frame. This language becomes the
11822 working language if you use an identifier from this frame.
11823 @xref{Frame Info, ,Information about a Frame}, to identify the other
11824 information listed here.
11827 @kindex info source@r{, show the source language}
11828 Display the source language of this source file.
11829 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11830 information listed here.
11833 In unusual circumstances, you may have source files with extensions
11834 not in the standard list. You can then set the extension associated
11835 with a language explicitly:
11838 @item set extension-language @var{ext} @var{language}
11839 @kindex set extension-language
11840 Tell @value{GDBN} that source files with extension @var{ext} are to be
11841 assumed as written in the source language @var{language}.
11843 @item info extensions
11844 @kindex info extensions
11845 List all the filename extensions and the associated languages.
11849 @section Type and Range Checking
11852 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11853 checking are included, but they do not yet have any effect. This
11854 section documents the intended facilities.
11856 @c FIXME remove warning when type/range code added
11858 Some languages are designed to guard you against making seemingly common
11859 errors through a series of compile- and run-time checks. These include
11860 checking the type of arguments to functions and operators, and making
11861 sure mathematical overflows are caught at run time. Checks such as
11862 these help to ensure a program's correctness once it has been compiled
11863 by eliminating type mismatches, and providing active checks for range
11864 errors when your program is running.
11866 @value{GDBN} can check for conditions like the above if you wish.
11867 Although @value{GDBN} does not check the statements in your program,
11868 it can check expressions entered directly into @value{GDBN} for
11869 evaluation via the @code{print} command, for example. As with the
11870 working language, @value{GDBN} can also decide whether or not to check
11871 automatically based on your program's source language.
11872 @xref{Supported Languages, ,Supported Languages}, for the default
11873 settings of supported languages.
11876 * Type Checking:: An overview of type checking
11877 * Range Checking:: An overview of range checking
11880 @cindex type checking
11881 @cindex checks, type
11882 @node Type Checking
11883 @subsection An Overview of Type Checking
11885 Some languages, such as Modula-2, are strongly typed, meaning that the
11886 arguments to operators and functions have to be of the correct type,
11887 otherwise an error occurs. These checks prevent type mismatch
11888 errors from ever causing any run-time problems. For example,
11896 The second example fails because the @code{CARDINAL} 1 is not
11897 type-compatible with the @code{REAL} 2.3.
11899 For the expressions you use in @value{GDBN} commands, you can tell the
11900 @value{GDBN} type checker to skip checking;
11901 to treat any mismatches as errors and abandon the expression;
11902 or to only issue warnings when type mismatches occur,
11903 but evaluate the expression anyway. When you choose the last of
11904 these, @value{GDBN} evaluates expressions like the second example above, but
11905 also issues a warning.
11907 Even if you turn type checking off, there may be other reasons
11908 related to type that prevent @value{GDBN} from evaluating an expression.
11909 For instance, @value{GDBN} does not know how to add an @code{int} and
11910 a @code{struct foo}. These particular type errors have nothing to do
11911 with the language in use, and usually arise from expressions, such as
11912 the one described above, which make little sense to evaluate anyway.
11914 Each language defines to what degree it is strict about type. For
11915 instance, both Modula-2 and C require the arguments to arithmetical
11916 operators to be numbers. In C, enumerated types and pointers can be
11917 represented as numbers, so that they are valid arguments to mathematical
11918 operators. @xref{Supported Languages, ,Supported Languages}, for further
11919 details on specific languages.
11921 @value{GDBN} provides some additional commands for controlling the type checker:
11923 @kindex set check type
11924 @kindex show check type
11926 @item set check type auto
11927 Set type checking on or off based on the current working language.
11928 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11931 @item set check type on
11932 @itemx set check type off
11933 Set type checking on or off, overriding the default setting for the
11934 current working language. Issue a warning if the setting does not
11935 match the language default. If any type mismatches occur in
11936 evaluating an expression while type checking is on, @value{GDBN} prints a
11937 message and aborts evaluation of the expression.
11939 @item set check type warn
11940 Cause the type checker to issue warnings, but to always attempt to
11941 evaluate the expression. Evaluating the expression may still
11942 be impossible for other reasons. For example, @value{GDBN} cannot add
11943 numbers and structures.
11946 Show the current setting of the type checker, and whether or not @value{GDBN}
11947 is setting it automatically.
11950 @cindex range checking
11951 @cindex checks, range
11952 @node Range Checking
11953 @subsection An Overview of Range Checking
11955 In some languages (such as Modula-2), it is an error to exceed the
11956 bounds of a type; this is enforced with run-time checks. Such range
11957 checking is meant to ensure program correctness by making sure
11958 computations do not overflow, or indices on an array element access do
11959 not exceed the bounds of the array.
11961 For expressions you use in @value{GDBN} commands, you can tell
11962 @value{GDBN} to treat range errors in one of three ways: ignore them,
11963 always treat them as errors and abandon the expression, or issue
11964 warnings but evaluate the expression anyway.
11966 A range error can result from numerical overflow, from exceeding an
11967 array index bound, or when you type a constant that is not a member
11968 of any type. Some languages, however, do not treat overflows as an
11969 error. In many implementations of C, mathematical overflow causes the
11970 result to ``wrap around'' to lower values---for example, if @var{m} is
11971 the largest integer value, and @var{s} is the smallest, then
11974 @var{m} + 1 @result{} @var{s}
11977 This, too, is specific to individual languages, and in some cases
11978 specific to individual compilers or machines. @xref{Supported Languages, ,
11979 Supported Languages}, for further details on specific languages.
11981 @value{GDBN} provides some additional commands for controlling the range checker:
11983 @kindex set check range
11984 @kindex show check range
11986 @item set check range auto
11987 Set range checking on or off based on the current working language.
11988 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11991 @item set check range on
11992 @itemx set check range off
11993 Set range checking on or off, overriding the default setting for the
11994 current working language. A warning is issued if the setting does not
11995 match the language default. If a range error occurs and range checking is on,
11996 then a message is printed and evaluation of the expression is aborted.
11998 @item set check range warn
11999 Output messages when the @value{GDBN} range checker detects a range error,
12000 but attempt to evaluate the expression anyway. Evaluating the
12001 expression may still be impossible for other reasons, such as accessing
12002 memory that the process does not own (a typical example from many Unix
12006 Show the current setting of the range checker, and whether or not it is
12007 being set automatically by @value{GDBN}.
12010 @node Supported Languages
12011 @section Supported Languages
12013 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12014 assembly, Modula-2, and Ada.
12015 @c This is false ...
12016 Some @value{GDBN} features may be used in expressions regardless of the
12017 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12018 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12019 ,Expressions}) can be used with the constructs of any supported
12022 The following sections detail to what degree each source language is
12023 supported by @value{GDBN}. These sections are not meant to be language
12024 tutorials or references, but serve only as a reference guide to what the
12025 @value{GDBN} expression parser accepts, and what input and output
12026 formats should look like for different languages. There are many good
12027 books written on each of these languages; please look to these for a
12028 language reference or tutorial.
12031 * C:: C and C@t{++}
12033 * Objective-C:: Objective-C
12034 * OpenCL C:: OpenCL C
12035 * Fortran:: Fortran
12037 * Modula-2:: Modula-2
12042 @subsection C and C@t{++}
12044 @cindex C and C@t{++}
12045 @cindex expressions in C or C@t{++}
12047 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12048 to both languages. Whenever this is the case, we discuss those languages
12052 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12053 @cindex @sc{gnu} C@t{++}
12054 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12055 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12056 effectively, you must compile your C@t{++} programs with a supported
12057 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12058 compiler (@code{aCC}).
12060 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
12061 format; if it doesn't work on your system, try the stabs+ debugging
12062 format. You can select those formats explicitly with the @code{g++}
12063 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
12064 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
12065 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
12068 * C Operators:: C and C@t{++} operators
12069 * C Constants:: C and C@t{++} constants
12070 * C Plus Plus Expressions:: C@t{++} expressions
12071 * C Defaults:: Default settings for C and C@t{++}
12072 * C Checks:: C and C@t{++} type and range checks
12073 * Debugging C:: @value{GDBN} and C
12074 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12075 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12079 @subsubsection C and C@t{++} Operators
12081 @cindex C and C@t{++} operators
12083 Operators must be defined on values of specific types. For instance,
12084 @code{+} is defined on numbers, but not on structures. Operators are
12085 often defined on groups of types.
12087 For the purposes of C and C@t{++}, the following definitions hold:
12092 @emph{Integral types} include @code{int} with any of its storage-class
12093 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12096 @emph{Floating-point types} include @code{float}, @code{double}, and
12097 @code{long double} (if supported by the target platform).
12100 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12103 @emph{Scalar types} include all of the above.
12108 The following operators are supported. They are listed here
12109 in order of increasing precedence:
12113 The comma or sequencing operator. Expressions in a comma-separated list
12114 are evaluated from left to right, with the result of the entire
12115 expression being the last expression evaluated.
12118 Assignment. The value of an assignment expression is the value
12119 assigned. Defined on scalar types.
12122 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12123 and translated to @w{@code{@var{a} = @var{a op b}}}.
12124 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12125 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12126 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12129 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12130 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12134 Logical @sc{or}. Defined on integral types.
12137 Logical @sc{and}. Defined on integral types.
12140 Bitwise @sc{or}. Defined on integral types.
12143 Bitwise exclusive-@sc{or}. Defined on integral types.
12146 Bitwise @sc{and}. Defined on integral types.
12149 Equality and inequality. Defined on scalar types. The value of these
12150 expressions is 0 for false and non-zero for true.
12152 @item <@r{, }>@r{, }<=@r{, }>=
12153 Less than, greater than, less than or equal, greater than or equal.
12154 Defined on scalar types. The value of these expressions is 0 for false
12155 and non-zero for true.
12158 left shift, and right shift. Defined on integral types.
12161 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12164 Addition and subtraction. Defined on integral types, floating-point types and
12167 @item *@r{, }/@r{, }%
12168 Multiplication, division, and modulus. Multiplication and division are
12169 defined on integral and floating-point types. Modulus is defined on
12173 Increment and decrement. When appearing before a variable, the
12174 operation is performed before the variable is used in an expression;
12175 when appearing after it, the variable's value is used before the
12176 operation takes place.
12179 Pointer dereferencing. Defined on pointer types. Same precedence as
12183 Address operator. Defined on variables. Same precedence as @code{++}.
12185 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12186 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12187 to examine the address
12188 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12192 Negative. Defined on integral and floating-point types. Same
12193 precedence as @code{++}.
12196 Logical negation. Defined on integral types. Same precedence as
12200 Bitwise complement operator. Defined on integral types. Same precedence as
12205 Structure member, and pointer-to-structure member. For convenience,
12206 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12207 pointer based on the stored type information.
12208 Defined on @code{struct} and @code{union} data.
12211 Dereferences of pointers to members.
12214 Array indexing. @code{@var{a}[@var{i}]} is defined as
12215 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12218 Function parameter list. Same precedence as @code{->}.
12221 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12222 and @code{class} types.
12225 Doubled colons also represent the @value{GDBN} scope operator
12226 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12230 If an operator is redefined in the user code, @value{GDBN} usually
12231 attempts to invoke the redefined version instead of using the operator's
12232 predefined meaning.
12235 @subsubsection C and C@t{++} Constants
12237 @cindex C and C@t{++} constants
12239 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12244 Integer constants are a sequence of digits. Octal constants are
12245 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12246 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12247 @samp{l}, specifying that the constant should be treated as a
12251 Floating point constants are a sequence of digits, followed by a decimal
12252 point, followed by a sequence of digits, and optionally followed by an
12253 exponent. An exponent is of the form:
12254 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12255 sequence of digits. The @samp{+} is optional for positive exponents.
12256 A floating-point constant may also end with a letter @samp{f} or
12257 @samp{F}, specifying that the constant should be treated as being of
12258 the @code{float} (as opposed to the default @code{double}) type; or with
12259 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12263 Enumerated constants consist of enumerated identifiers, or their
12264 integral equivalents.
12267 Character constants are a single character surrounded by single quotes
12268 (@code{'}), or a number---the ordinal value of the corresponding character
12269 (usually its @sc{ascii} value). Within quotes, the single character may
12270 be represented by a letter or by @dfn{escape sequences}, which are of
12271 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12272 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12273 @samp{@var{x}} is a predefined special character---for example,
12274 @samp{\n} for newline.
12277 String constants are a sequence of character constants surrounded by
12278 double quotes (@code{"}). Any valid character constant (as described
12279 above) may appear. Double quotes within the string must be preceded by
12280 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12284 Pointer constants are an integral value. You can also write pointers
12285 to constants using the C operator @samp{&}.
12288 Array constants are comma-separated lists surrounded by braces @samp{@{}
12289 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12290 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12291 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12294 @node C Plus Plus Expressions
12295 @subsubsection C@t{++} Expressions
12297 @cindex expressions in C@t{++}
12298 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12300 @cindex debugging C@t{++} programs
12301 @cindex C@t{++} compilers
12302 @cindex debug formats and C@t{++}
12303 @cindex @value{NGCC} and C@t{++}
12305 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
12306 proper compiler and the proper debug format. Currently, @value{GDBN}
12307 works best when debugging C@t{++} code that is compiled with
12308 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
12309 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
12310 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
12311 stabs+ as their default debug format, so you usually don't need to
12312 specify a debug format explicitly. Other compilers and/or debug formats
12313 are likely to work badly or not at all when using @value{GDBN} to debug
12319 @cindex member functions
12321 Member function calls are allowed; you can use expressions like
12324 count = aml->GetOriginal(x, y)
12327 @vindex this@r{, inside C@t{++} member functions}
12328 @cindex namespace in C@t{++}
12330 While a member function is active (in the selected stack frame), your
12331 expressions have the same namespace available as the member function;
12332 that is, @value{GDBN} allows implicit references to the class instance
12333 pointer @code{this} following the same rules as C@t{++}.
12335 @cindex call overloaded functions
12336 @cindex overloaded functions, calling
12337 @cindex type conversions in C@t{++}
12339 You can call overloaded functions; @value{GDBN} resolves the function
12340 call to the right definition, with some restrictions. @value{GDBN} does not
12341 perform overload resolution involving user-defined type conversions,
12342 calls to constructors, or instantiations of templates that do not exist
12343 in the program. It also cannot handle ellipsis argument lists or
12346 It does perform integral conversions and promotions, floating-point
12347 promotions, arithmetic conversions, pointer conversions, conversions of
12348 class objects to base classes, and standard conversions such as those of
12349 functions or arrays to pointers; it requires an exact match on the
12350 number of function arguments.
12352 Overload resolution is always performed, unless you have specified
12353 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12354 ,@value{GDBN} Features for C@t{++}}.
12356 You must specify @code{set overload-resolution off} in order to use an
12357 explicit function signature to call an overloaded function, as in
12359 p 'foo(char,int)'('x', 13)
12362 The @value{GDBN} command-completion facility can simplify this;
12363 see @ref{Completion, ,Command Completion}.
12365 @cindex reference declarations
12367 @value{GDBN} understands variables declared as C@t{++} references; you can use
12368 them in expressions just as you do in C@t{++} source---they are automatically
12371 In the parameter list shown when @value{GDBN} displays a frame, the values of
12372 reference variables are not displayed (unlike other variables); this
12373 avoids clutter, since references are often used for large structures.
12374 The @emph{address} of a reference variable is always shown, unless
12375 you have specified @samp{set print address off}.
12378 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12379 expressions can use it just as expressions in your program do. Since
12380 one scope may be defined in another, you can use @code{::} repeatedly if
12381 necessary, for example in an expression like
12382 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12383 resolving name scope by reference to source files, in both C and C@t{++}
12384 debugging (@pxref{Variables, ,Program Variables}).
12387 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12388 calling virtual functions correctly, printing out virtual bases of
12389 objects, calling functions in a base subobject, casting objects, and
12390 invoking user-defined operators.
12393 @subsubsection C and C@t{++} Defaults
12395 @cindex C and C@t{++} defaults
12397 If you allow @value{GDBN} to set type and range checking automatically, they
12398 both default to @code{off} whenever the working language changes to
12399 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12400 selects the working language.
12402 If you allow @value{GDBN} to set the language automatically, it
12403 recognizes source files whose names end with @file{.c}, @file{.C}, or
12404 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12405 these files, it sets the working language to C or C@t{++}.
12406 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12407 for further details.
12409 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12410 @c unimplemented. If (b) changes, it might make sense to let this node
12411 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12414 @subsubsection C and C@t{++} Type and Range Checks
12416 @cindex C and C@t{++} checks
12418 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12419 is not used. However, if you turn type checking on, @value{GDBN}
12420 considers two variables type equivalent if:
12424 The two variables are structured and have the same structure, union, or
12428 The two variables have the same type name, or types that have been
12429 declared equivalent through @code{typedef}.
12432 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12435 The two @code{struct}, @code{union}, or @code{enum} variables are
12436 declared in the same declaration. (Note: this may not be true for all C
12441 Range checking, if turned on, is done on mathematical operations. Array
12442 indices are not checked, since they are often used to index a pointer
12443 that is not itself an array.
12446 @subsubsection @value{GDBN} and C
12448 The @code{set print union} and @code{show print union} commands apply to
12449 the @code{union} type. When set to @samp{on}, any @code{union} that is
12450 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12451 appears as @samp{@{...@}}.
12453 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12454 with pointers and a memory allocation function. @xref{Expressions,
12457 @node Debugging C Plus Plus
12458 @subsubsection @value{GDBN} Features for C@t{++}
12460 @cindex commands for C@t{++}
12462 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12463 designed specifically for use with C@t{++}. Here is a summary:
12466 @cindex break in overloaded functions
12467 @item @r{breakpoint menus}
12468 When you want a breakpoint in a function whose name is overloaded,
12469 @value{GDBN} has the capability to display a menu of possible breakpoint
12470 locations to help you specify which function definition you want.
12471 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12473 @cindex overloading in C@t{++}
12474 @item rbreak @var{regex}
12475 Setting breakpoints using regular expressions is helpful for setting
12476 breakpoints on overloaded functions that are not members of any special
12478 @xref{Set Breaks, ,Setting Breakpoints}.
12480 @cindex C@t{++} exception handling
12483 Debug C@t{++} exception handling using these commands. @xref{Set
12484 Catchpoints, , Setting Catchpoints}.
12486 @cindex inheritance
12487 @item ptype @var{typename}
12488 Print inheritance relationships as well as other information for type
12490 @xref{Symbols, ,Examining the Symbol Table}.
12492 @cindex C@t{++} symbol display
12493 @item set print demangle
12494 @itemx show print demangle
12495 @itemx set print asm-demangle
12496 @itemx show print asm-demangle
12497 Control whether C@t{++} symbols display in their source form, both when
12498 displaying code as C@t{++} source and when displaying disassemblies.
12499 @xref{Print Settings, ,Print Settings}.
12501 @item set print object
12502 @itemx show print object
12503 Choose whether to print derived (actual) or declared types of objects.
12504 @xref{Print Settings, ,Print Settings}.
12506 @item set print vtbl
12507 @itemx show print vtbl
12508 Control the format for printing virtual function tables.
12509 @xref{Print Settings, ,Print Settings}.
12510 (The @code{vtbl} commands do not work on programs compiled with the HP
12511 ANSI C@t{++} compiler (@code{aCC}).)
12513 @kindex set overload-resolution
12514 @cindex overloaded functions, overload resolution
12515 @item set overload-resolution on
12516 Enable overload resolution for C@t{++} expression evaluation. The default
12517 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12518 and searches for a function whose signature matches the argument types,
12519 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12520 Expressions, ,C@t{++} Expressions}, for details).
12521 If it cannot find a match, it emits a message.
12523 @item set overload-resolution off
12524 Disable overload resolution for C@t{++} expression evaluation. For
12525 overloaded functions that are not class member functions, @value{GDBN}
12526 chooses the first function of the specified name that it finds in the
12527 symbol table, whether or not its arguments are of the correct type. For
12528 overloaded functions that are class member functions, @value{GDBN}
12529 searches for a function whose signature @emph{exactly} matches the
12532 @kindex show overload-resolution
12533 @item show overload-resolution
12534 Show the current setting of overload resolution.
12536 @item @r{Overloaded symbol names}
12537 You can specify a particular definition of an overloaded symbol, using
12538 the same notation that is used to declare such symbols in C@t{++}: type
12539 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12540 also use the @value{GDBN} command-line word completion facilities to list the
12541 available choices, or to finish the type list for you.
12542 @xref{Completion,, Command Completion}, for details on how to do this.
12545 @node Decimal Floating Point
12546 @subsubsection Decimal Floating Point format
12547 @cindex decimal floating point format
12549 @value{GDBN} can examine, set and perform computations with numbers in
12550 decimal floating point format, which in the C language correspond to the
12551 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12552 specified by the extension to support decimal floating-point arithmetic.
12554 There are two encodings in use, depending on the architecture: BID (Binary
12555 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12556 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12559 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12560 to manipulate decimal floating point numbers, it is not possible to convert
12561 (using a cast, for example) integers wider than 32-bit to decimal float.
12563 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12564 point computations, error checking in decimal float operations ignores
12565 underflow, overflow and divide by zero exceptions.
12567 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12568 to inspect @code{_Decimal128} values stored in floating point registers.
12569 See @ref{PowerPC,,PowerPC} for more details.
12575 @value{GDBN} can be used to debug programs written in D and compiled with
12576 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12577 specific feature --- dynamic arrays.
12580 @subsection Objective-C
12582 @cindex Objective-C
12583 This section provides information about some commands and command
12584 options that are useful for debugging Objective-C code. See also
12585 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12586 few more commands specific to Objective-C support.
12589 * Method Names in Commands::
12590 * The Print Command with Objective-C::
12593 @node Method Names in Commands
12594 @subsubsection Method Names in Commands
12596 The following commands have been extended to accept Objective-C method
12597 names as line specifications:
12599 @kindex clear@r{, and Objective-C}
12600 @kindex break@r{, and Objective-C}
12601 @kindex info line@r{, and Objective-C}
12602 @kindex jump@r{, and Objective-C}
12603 @kindex list@r{, and Objective-C}
12607 @item @code{info line}
12612 A fully qualified Objective-C method name is specified as
12615 -[@var{Class} @var{methodName}]
12618 where the minus sign is used to indicate an instance method and a
12619 plus sign (not shown) is used to indicate a class method. The class
12620 name @var{Class} and method name @var{methodName} are enclosed in
12621 brackets, similar to the way messages are specified in Objective-C
12622 source code. For example, to set a breakpoint at the @code{create}
12623 instance method of class @code{Fruit} in the program currently being
12627 break -[Fruit create]
12630 To list ten program lines around the @code{initialize} class method,
12634 list +[NSText initialize]
12637 In the current version of @value{GDBN}, the plus or minus sign is
12638 required. In future versions of @value{GDBN}, the plus or minus
12639 sign will be optional, but you can use it to narrow the search. It
12640 is also possible to specify just a method name:
12646 You must specify the complete method name, including any colons. If
12647 your program's source files contain more than one @code{create} method,
12648 you'll be presented with a numbered list of classes that implement that
12649 method. Indicate your choice by number, or type @samp{0} to exit if
12652 As another example, to clear a breakpoint established at the
12653 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12656 clear -[NSWindow makeKeyAndOrderFront:]
12659 @node The Print Command with Objective-C
12660 @subsubsection The Print Command With Objective-C
12661 @cindex Objective-C, print objects
12662 @kindex print-object
12663 @kindex po @r{(@code{print-object})}
12665 The print command has also been extended to accept methods. For example:
12668 print -[@var{object} hash]
12671 @cindex print an Objective-C object description
12672 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12674 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12675 and print the result. Also, an additional command has been added,
12676 @code{print-object} or @code{po} for short, which is meant to print
12677 the description of an object. However, this command may only work
12678 with certain Objective-C libraries that have a particular hook
12679 function, @code{_NSPrintForDebugger}, defined.
12682 @subsection OpenCL C
12685 This section provides information about @value{GDBN}s OpenCL C support.
12688 * OpenCL C Datatypes::
12689 * OpenCL C Expressions::
12690 * OpenCL C Operators::
12693 @node OpenCL C Datatypes
12694 @subsubsection OpenCL C Datatypes
12696 @cindex OpenCL C Datatypes
12697 @value{GDBN} supports the builtin scalar and vector datatypes specified
12698 by OpenCL 1.1. In addition the half- and double-precision floating point
12699 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12700 extensions are also known to @value{GDBN}.
12702 @node OpenCL C Expressions
12703 @subsubsection OpenCL C Expressions
12705 @cindex OpenCL C Expressions
12706 @value{GDBN} supports accesses to vector components including the access as
12707 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12708 supported by @value{GDBN} can be used as well.
12710 @node OpenCL C Operators
12711 @subsubsection OpenCL C Operators
12713 @cindex OpenCL C Operators
12714 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12718 @subsection Fortran
12719 @cindex Fortran-specific support in @value{GDBN}
12721 @value{GDBN} can be used to debug programs written in Fortran, but it
12722 currently supports only the features of Fortran 77 language.
12724 @cindex trailing underscore, in Fortran symbols
12725 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12726 among them) append an underscore to the names of variables and
12727 functions. When you debug programs compiled by those compilers, you
12728 will need to refer to variables and functions with a trailing
12732 * Fortran Operators:: Fortran operators and expressions
12733 * Fortran Defaults:: Default settings for Fortran
12734 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12737 @node Fortran Operators
12738 @subsubsection Fortran Operators and Expressions
12740 @cindex Fortran operators and expressions
12742 Operators must be defined on values of specific types. For instance,
12743 @code{+} is defined on numbers, but not on characters or other non-
12744 arithmetic types. Operators are often defined on groups of types.
12748 The exponentiation operator. It raises the first operand to the power
12752 The range operator. Normally used in the form of array(low:high) to
12753 represent a section of array.
12756 The access component operator. Normally used to access elements in derived
12757 types. Also suitable for unions. As unions aren't part of regular Fortran,
12758 this can only happen when accessing a register that uses a gdbarch-defined
12762 @node Fortran Defaults
12763 @subsubsection Fortran Defaults
12765 @cindex Fortran Defaults
12767 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12768 default uses case-insensitive matches for Fortran symbols. You can
12769 change that with the @samp{set case-insensitive} command, see
12770 @ref{Symbols}, for the details.
12772 @node Special Fortran Commands
12773 @subsubsection Special Fortran Commands
12775 @cindex Special Fortran commands
12777 @value{GDBN} has some commands to support Fortran-specific features,
12778 such as displaying common blocks.
12781 @cindex @code{COMMON} blocks, Fortran
12782 @kindex info common
12783 @item info common @r{[}@var{common-name}@r{]}
12784 This command prints the values contained in the Fortran @code{COMMON}
12785 block whose name is @var{common-name}. With no argument, the names of
12786 all @code{COMMON} blocks visible at the current program location are
12793 @cindex Pascal support in @value{GDBN}, limitations
12794 Debugging Pascal programs which use sets, subranges, file variables, or
12795 nested functions does not currently work. @value{GDBN} does not support
12796 entering expressions, printing values, or similar features using Pascal
12799 The Pascal-specific command @code{set print pascal_static-members}
12800 controls whether static members of Pascal objects are displayed.
12801 @xref{Print Settings, pascal_static-members}.
12804 @subsection Modula-2
12806 @cindex Modula-2, @value{GDBN} support
12808 The extensions made to @value{GDBN} to support Modula-2 only support
12809 output from the @sc{gnu} Modula-2 compiler (which is currently being
12810 developed). Other Modula-2 compilers are not currently supported, and
12811 attempting to debug executables produced by them is most likely
12812 to give an error as @value{GDBN} reads in the executable's symbol
12815 @cindex expressions in Modula-2
12817 * M2 Operators:: Built-in operators
12818 * Built-In Func/Proc:: Built-in functions and procedures
12819 * M2 Constants:: Modula-2 constants
12820 * M2 Types:: Modula-2 types
12821 * M2 Defaults:: Default settings for Modula-2
12822 * Deviations:: Deviations from standard Modula-2
12823 * M2 Checks:: Modula-2 type and range checks
12824 * M2 Scope:: The scope operators @code{::} and @code{.}
12825 * GDB/M2:: @value{GDBN} and Modula-2
12829 @subsubsection Operators
12830 @cindex Modula-2 operators
12832 Operators must be defined on values of specific types. For instance,
12833 @code{+} is defined on numbers, but not on structures. Operators are
12834 often defined on groups of types. For the purposes of Modula-2, the
12835 following definitions hold:
12840 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12844 @emph{Character types} consist of @code{CHAR} and its subranges.
12847 @emph{Floating-point types} consist of @code{REAL}.
12850 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12854 @emph{Scalar types} consist of all of the above.
12857 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12860 @emph{Boolean types} consist of @code{BOOLEAN}.
12864 The following operators are supported, and appear in order of
12865 increasing precedence:
12869 Function argument or array index separator.
12872 Assignment. The value of @var{var} @code{:=} @var{value} is
12876 Less than, greater than on integral, floating-point, or enumerated
12880 Less than or equal to, greater than or equal to
12881 on integral, floating-point and enumerated types, or set inclusion on
12882 set types. Same precedence as @code{<}.
12884 @item =@r{, }<>@r{, }#
12885 Equality and two ways of expressing inequality, valid on scalar types.
12886 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12887 available for inequality, since @code{#} conflicts with the script
12891 Set membership. Defined on set types and the types of their members.
12892 Same precedence as @code{<}.
12895 Boolean disjunction. Defined on boolean types.
12898 Boolean conjunction. Defined on boolean types.
12901 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12904 Addition and subtraction on integral and floating-point types, or union
12905 and difference on set types.
12908 Multiplication on integral and floating-point types, or set intersection
12912 Division on floating-point types, or symmetric set difference on set
12913 types. Same precedence as @code{*}.
12916 Integer division and remainder. Defined on integral types. Same
12917 precedence as @code{*}.
12920 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12923 Pointer dereferencing. Defined on pointer types.
12926 Boolean negation. Defined on boolean types. Same precedence as
12930 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12931 precedence as @code{^}.
12934 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12937 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12941 @value{GDBN} and Modula-2 scope operators.
12945 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12946 treats the use of the operator @code{IN}, or the use of operators
12947 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12948 @code{<=}, and @code{>=} on sets as an error.
12952 @node Built-In Func/Proc
12953 @subsubsection Built-in Functions and Procedures
12954 @cindex Modula-2 built-ins
12956 Modula-2 also makes available several built-in procedures and functions.
12957 In describing these, the following metavariables are used:
12962 represents an @code{ARRAY} variable.
12965 represents a @code{CHAR} constant or variable.
12968 represents a variable or constant of integral type.
12971 represents an identifier that belongs to a set. Generally used in the
12972 same function with the metavariable @var{s}. The type of @var{s} should
12973 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12976 represents a variable or constant of integral or floating-point type.
12979 represents a variable or constant of floating-point type.
12985 represents a variable.
12988 represents a variable or constant of one of many types. See the
12989 explanation of the function for details.
12992 All Modula-2 built-in procedures also return a result, described below.
12996 Returns the absolute value of @var{n}.
12999 If @var{c} is a lower case letter, it returns its upper case
13000 equivalent, otherwise it returns its argument.
13003 Returns the character whose ordinal value is @var{i}.
13006 Decrements the value in the variable @var{v} by one. Returns the new value.
13008 @item DEC(@var{v},@var{i})
13009 Decrements the value in the variable @var{v} by @var{i}. Returns the
13012 @item EXCL(@var{m},@var{s})
13013 Removes the element @var{m} from the set @var{s}. Returns the new
13016 @item FLOAT(@var{i})
13017 Returns the floating point equivalent of the integer @var{i}.
13019 @item HIGH(@var{a})
13020 Returns the index of the last member of @var{a}.
13023 Increments the value in the variable @var{v} by one. Returns the new value.
13025 @item INC(@var{v},@var{i})
13026 Increments the value in the variable @var{v} by @var{i}. Returns the
13029 @item INCL(@var{m},@var{s})
13030 Adds the element @var{m} to the set @var{s} if it is not already
13031 there. Returns the new set.
13034 Returns the maximum value of the type @var{t}.
13037 Returns the minimum value of the type @var{t}.
13040 Returns boolean TRUE if @var{i} is an odd number.
13043 Returns the ordinal value of its argument. For example, the ordinal
13044 value of a character is its @sc{ascii} value (on machines supporting the
13045 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13046 integral, character and enumerated types.
13048 @item SIZE(@var{x})
13049 Returns the size of its argument. @var{x} can be a variable or a type.
13051 @item TRUNC(@var{r})
13052 Returns the integral part of @var{r}.
13054 @item TSIZE(@var{x})
13055 Returns the size of its argument. @var{x} can be a variable or a type.
13057 @item VAL(@var{t},@var{i})
13058 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13062 @emph{Warning:} Sets and their operations are not yet supported, so
13063 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13067 @cindex Modula-2 constants
13069 @subsubsection Constants
13071 @value{GDBN} allows you to express the constants of Modula-2 in the following
13077 Integer constants are simply a sequence of digits. When used in an
13078 expression, a constant is interpreted to be type-compatible with the
13079 rest of the expression. Hexadecimal integers are specified by a
13080 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13083 Floating point constants appear as a sequence of digits, followed by a
13084 decimal point and another sequence of digits. An optional exponent can
13085 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13086 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13087 digits of the floating point constant must be valid decimal (base 10)
13091 Character constants consist of a single character enclosed by a pair of
13092 like quotes, either single (@code{'}) or double (@code{"}). They may
13093 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13094 followed by a @samp{C}.
13097 String constants consist of a sequence of characters enclosed by a
13098 pair of like quotes, either single (@code{'}) or double (@code{"}).
13099 Escape sequences in the style of C are also allowed. @xref{C
13100 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13104 Enumerated constants consist of an enumerated identifier.
13107 Boolean constants consist of the identifiers @code{TRUE} and
13111 Pointer constants consist of integral values only.
13114 Set constants are not yet supported.
13118 @subsubsection Modula-2 Types
13119 @cindex Modula-2 types
13121 Currently @value{GDBN} can print the following data types in Modula-2
13122 syntax: array types, record types, set types, pointer types, procedure
13123 types, enumerated types, subrange types and base types. You can also
13124 print the contents of variables declared using these type.
13125 This section gives a number of simple source code examples together with
13126 sample @value{GDBN} sessions.
13128 The first example contains the following section of code:
13137 and you can request @value{GDBN} to interrogate the type and value of
13138 @code{r} and @code{s}.
13141 (@value{GDBP}) print s
13143 (@value{GDBP}) ptype s
13145 (@value{GDBP}) print r
13147 (@value{GDBP}) ptype r
13152 Likewise if your source code declares @code{s} as:
13156 s: SET ['A'..'Z'] ;
13160 then you may query the type of @code{s} by:
13163 (@value{GDBP}) ptype s
13164 type = SET ['A'..'Z']
13168 Note that at present you cannot interactively manipulate set
13169 expressions using the debugger.
13171 The following example shows how you might declare an array in Modula-2
13172 and how you can interact with @value{GDBN} to print its type and contents:
13176 s: ARRAY [-10..10] OF CHAR ;
13180 (@value{GDBP}) ptype s
13181 ARRAY [-10..10] OF CHAR
13184 Note that the array handling is not yet complete and although the type
13185 is printed correctly, expression handling still assumes that all
13186 arrays have a lower bound of zero and not @code{-10} as in the example
13189 Here are some more type related Modula-2 examples:
13193 colour = (blue, red, yellow, green) ;
13194 t = [blue..yellow] ;
13202 The @value{GDBN} interaction shows how you can query the data type
13203 and value of a variable.
13206 (@value{GDBP}) print s
13208 (@value{GDBP}) ptype t
13209 type = [blue..yellow]
13213 In this example a Modula-2 array is declared and its contents
13214 displayed. Observe that the contents are written in the same way as
13215 their @code{C} counterparts.
13219 s: ARRAY [1..5] OF CARDINAL ;
13225 (@value{GDBP}) print s
13226 $1 = @{1, 0, 0, 0, 0@}
13227 (@value{GDBP}) ptype s
13228 type = ARRAY [1..5] OF CARDINAL
13231 The Modula-2 language interface to @value{GDBN} also understands
13232 pointer types as shown in this example:
13236 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13243 and you can request that @value{GDBN} describes the type of @code{s}.
13246 (@value{GDBP}) ptype s
13247 type = POINTER TO ARRAY [1..5] OF CARDINAL
13250 @value{GDBN} handles compound types as we can see in this example.
13251 Here we combine array types, record types, pointer types and subrange
13262 myarray = ARRAY myrange OF CARDINAL ;
13263 myrange = [-2..2] ;
13265 s: POINTER TO ARRAY myrange OF foo ;
13269 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13273 (@value{GDBP}) ptype s
13274 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13277 f3 : ARRAY [-2..2] OF CARDINAL;
13282 @subsubsection Modula-2 Defaults
13283 @cindex Modula-2 defaults
13285 If type and range checking are set automatically by @value{GDBN}, they
13286 both default to @code{on} whenever the working language changes to
13287 Modula-2. This happens regardless of whether you or @value{GDBN}
13288 selected the working language.
13290 If you allow @value{GDBN} to set the language automatically, then entering
13291 code compiled from a file whose name ends with @file{.mod} sets the
13292 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13293 Infer the Source Language}, for further details.
13296 @subsubsection Deviations from Standard Modula-2
13297 @cindex Modula-2, deviations from
13299 A few changes have been made to make Modula-2 programs easier to debug.
13300 This is done primarily via loosening its type strictness:
13304 Unlike in standard Modula-2, pointer constants can be formed by
13305 integers. This allows you to modify pointer variables during
13306 debugging. (In standard Modula-2, the actual address contained in a
13307 pointer variable is hidden from you; it can only be modified
13308 through direct assignment to another pointer variable or expression that
13309 returned a pointer.)
13312 C escape sequences can be used in strings and characters to represent
13313 non-printable characters. @value{GDBN} prints out strings with these
13314 escape sequences embedded. Single non-printable characters are
13315 printed using the @samp{CHR(@var{nnn})} format.
13318 The assignment operator (@code{:=}) returns the value of its right-hand
13322 All built-in procedures both modify @emph{and} return their argument.
13326 @subsubsection Modula-2 Type and Range Checks
13327 @cindex Modula-2 checks
13330 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13333 @c FIXME remove warning when type/range checks added
13335 @value{GDBN} considers two Modula-2 variables type equivalent if:
13339 They are of types that have been declared equivalent via a @code{TYPE
13340 @var{t1} = @var{t2}} statement
13343 They have been declared on the same line. (Note: This is true of the
13344 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13347 As long as type checking is enabled, any attempt to combine variables
13348 whose types are not equivalent is an error.
13350 Range checking is done on all mathematical operations, assignment, array
13351 index bounds, and all built-in functions and procedures.
13354 @subsubsection The Scope Operators @code{::} and @code{.}
13356 @cindex @code{.}, Modula-2 scope operator
13357 @cindex colon, doubled as scope operator
13359 @vindex colon-colon@r{, in Modula-2}
13360 @c Info cannot handle :: but TeX can.
13363 @vindex ::@r{, in Modula-2}
13366 There are a few subtle differences between the Modula-2 scope operator
13367 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13372 @var{module} . @var{id}
13373 @var{scope} :: @var{id}
13377 where @var{scope} is the name of a module or a procedure,
13378 @var{module} the name of a module, and @var{id} is any declared
13379 identifier within your program, except another module.
13381 Using the @code{::} operator makes @value{GDBN} search the scope
13382 specified by @var{scope} for the identifier @var{id}. If it is not
13383 found in the specified scope, then @value{GDBN} searches all scopes
13384 enclosing the one specified by @var{scope}.
13386 Using the @code{.} operator makes @value{GDBN} search the current scope for
13387 the identifier specified by @var{id} that was imported from the
13388 definition module specified by @var{module}. With this operator, it is
13389 an error if the identifier @var{id} was not imported from definition
13390 module @var{module}, or if @var{id} is not an identifier in
13394 @subsubsection @value{GDBN} and Modula-2
13396 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13397 Five subcommands of @code{set print} and @code{show print} apply
13398 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13399 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13400 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13401 analogue in Modula-2.
13403 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13404 with any language, is not useful with Modula-2. Its
13405 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13406 created in Modula-2 as they can in C or C@t{++}. However, because an
13407 address can be specified by an integral constant, the construct
13408 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13410 @cindex @code{#} in Modula-2
13411 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13412 interpreted as the beginning of a comment. Use @code{<>} instead.
13418 The extensions made to @value{GDBN} for Ada only support
13419 output from the @sc{gnu} Ada (GNAT) compiler.
13420 Other Ada compilers are not currently supported, and
13421 attempting to debug executables produced by them is most likely
13425 @cindex expressions in Ada
13427 * Ada Mode Intro:: General remarks on the Ada syntax
13428 and semantics supported by Ada mode
13430 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13431 * Additions to Ada:: Extensions of the Ada expression syntax.
13432 * Stopping Before Main Program:: Debugging the program during elaboration.
13433 * Ada Tasks:: Listing and setting breakpoints in tasks.
13434 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13435 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13437 * Ada Glitches:: Known peculiarities of Ada mode.
13440 @node Ada Mode Intro
13441 @subsubsection Introduction
13442 @cindex Ada mode, general
13444 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13445 syntax, with some extensions.
13446 The philosophy behind the design of this subset is
13450 That @value{GDBN} should provide basic literals and access to operations for
13451 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13452 leaving more sophisticated computations to subprograms written into the
13453 program (which therefore may be called from @value{GDBN}).
13456 That type safety and strict adherence to Ada language restrictions
13457 are not particularly important to the @value{GDBN} user.
13460 That brevity is important to the @value{GDBN} user.
13463 Thus, for brevity, the debugger acts as if all names declared in
13464 user-written packages are directly visible, even if they are not visible
13465 according to Ada rules, thus making it unnecessary to fully qualify most
13466 names with their packages, regardless of context. Where this causes
13467 ambiguity, @value{GDBN} asks the user's intent.
13469 The debugger will start in Ada mode if it detects an Ada main program.
13470 As for other languages, it will enter Ada mode when stopped in a program that
13471 was translated from an Ada source file.
13473 While in Ada mode, you may use `@t{--}' for comments. This is useful
13474 mostly for documenting command files. The standard @value{GDBN} comment
13475 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13476 middle (to allow based literals).
13478 The debugger supports limited overloading. Given a subprogram call in which
13479 the function symbol has multiple definitions, it will use the number of
13480 actual parameters and some information about their types to attempt to narrow
13481 the set of definitions. It also makes very limited use of context, preferring
13482 procedures to functions in the context of the @code{call} command, and
13483 functions to procedures elsewhere.
13485 @node Omissions from Ada
13486 @subsubsection Omissions from Ada
13487 @cindex Ada, omissions from
13489 Here are the notable omissions from the subset:
13493 Only a subset of the attributes are supported:
13497 @t{'First}, @t{'Last}, and @t{'Length}
13498 on array objects (not on types and subtypes).
13501 @t{'Min} and @t{'Max}.
13504 @t{'Pos} and @t{'Val}.
13510 @t{'Range} on array objects (not subtypes), but only as the right
13511 operand of the membership (@code{in}) operator.
13514 @t{'Access}, @t{'Unchecked_Access}, and
13515 @t{'Unrestricted_Access} (a GNAT extension).
13523 @code{Characters.Latin_1} are not available and
13524 concatenation is not implemented. Thus, escape characters in strings are
13525 not currently available.
13528 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13529 equality of representations. They will generally work correctly
13530 for strings and arrays whose elements have integer or enumeration types.
13531 They may not work correctly for arrays whose element
13532 types have user-defined equality, for arrays of real values
13533 (in particular, IEEE-conformant floating point, because of negative
13534 zeroes and NaNs), and for arrays whose elements contain unused bits with
13535 indeterminate values.
13538 The other component-by-component array operations (@code{and}, @code{or},
13539 @code{xor}, @code{not}, and relational tests other than equality)
13540 are not implemented.
13543 @cindex array aggregates (Ada)
13544 @cindex record aggregates (Ada)
13545 @cindex aggregates (Ada)
13546 There is limited support for array and record aggregates. They are
13547 permitted only on the right sides of assignments, as in these examples:
13550 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13551 (@value{GDBP}) set An_Array := (1, others => 0)
13552 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13553 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13554 (@value{GDBP}) set A_Record := (1, "Peter", True);
13555 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13559 discriminant's value by assigning an aggregate has an
13560 undefined effect if that discriminant is used within the record.
13561 However, you can first modify discriminants by directly assigning to
13562 them (which normally would not be allowed in Ada), and then performing an
13563 aggregate assignment. For example, given a variable @code{A_Rec}
13564 declared to have a type such as:
13567 type Rec (Len : Small_Integer := 0) is record
13569 Vals : IntArray (1 .. Len);
13573 you can assign a value with a different size of @code{Vals} with two
13577 (@value{GDBP}) set A_Rec.Len := 4
13578 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13581 As this example also illustrates, @value{GDBN} is very loose about the usual
13582 rules concerning aggregates. You may leave out some of the
13583 components of an array or record aggregate (such as the @code{Len}
13584 component in the assignment to @code{A_Rec} above); they will retain their
13585 original values upon assignment. You may freely use dynamic values as
13586 indices in component associations. You may even use overlapping or
13587 redundant component associations, although which component values are
13588 assigned in such cases is not defined.
13591 Calls to dispatching subprograms are not implemented.
13594 The overloading algorithm is much more limited (i.e., less selective)
13595 than that of real Ada. It makes only limited use of the context in
13596 which a subexpression appears to resolve its meaning, and it is much
13597 looser in its rules for allowing type matches. As a result, some
13598 function calls will be ambiguous, and the user will be asked to choose
13599 the proper resolution.
13602 The @code{new} operator is not implemented.
13605 Entry calls are not implemented.
13608 Aside from printing, arithmetic operations on the native VAX floating-point
13609 formats are not supported.
13612 It is not possible to slice a packed array.
13615 The names @code{True} and @code{False}, when not part of a qualified name,
13616 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13618 Should your program
13619 redefine these names in a package or procedure (at best a dubious practice),
13620 you will have to use fully qualified names to access their new definitions.
13623 @node Additions to Ada
13624 @subsubsection Additions to Ada
13625 @cindex Ada, deviations from
13627 As it does for other languages, @value{GDBN} makes certain generic
13628 extensions to Ada (@pxref{Expressions}):
13632 If the expression @var{E} is a variable residing in memory (typically
13633 a local variable or array element) and @var{N} is a positive integer,
13634 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13635 @var{N}-1 adjacent variables following it in memory as an array. In
13636 Ada, this operator is generally not necessary, since its prime use is
13637 in displaying parts of an array, and slicing will usually do this in
13638 Ada. However, there are occasional uses when debugging programs in
13639 which certain debugging information has been optimized away.
13642 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13643 appears in function or file @var{B}.'' When @var{B} is a file name,
13644 you must typically surround it in single quotes.
13647 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13648 @var{type} that appears at address @var{addr}.''
13651 A name starting with @samp{$} is a convenience variable
13652 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13655 In addition, @value{GDBN} provides a few other shortcuts and outright
13656 additions specific to Ada:
13660 The assignment statement is allowed as an expression, returning
13661 its right-hand operand as its value. Thus, you may enter
13664 (@value{GDBP}) set x := y + 3
13665 (@value{GDBP}) print A(tmp := y + 1)
13669 The semicolon is allowed as an ``operator,'' returning as its value
13670 the value of its right-hand operand.
13671 This allows, for example,
13672 complex conditional breaks:
13675 (@value{GDBP}) break f
13676 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13680 Rather than use catenation and symbolic character names to introduce special
13681 characters into strings, one may instead use a special bracket notation,
13682 which is also used to print strings. A sequence of characters of the form
13683 @samp{["@var{XX}"]} within a string or character literal denotes the
13684 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13685 sequence of characters @samp{["""]} also denotes a single quotation mark
13686 in strings. For example,
13688 "One line.["0a"]Next line.["0a"]"
13691 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13695 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13696 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13700 (@value{GDBP}) print 'max(x, y)
13704 When printing arrays, @value{GDBN} uses positional notation when the
13705 array has a lower bound of 1, and uses a modified named notation otherwise.
13706 For example, a one-dimensional array of three integers with a lower bound
13707 of 3 might print as
13714 That is, in contrast to valid Ada, only the first component has a @code{=>}
13718 You may abbreviate attributes in expressions with any unique,
13719 multi-character subsequence of
13720 their names (an exact match gets preference).
13721 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13722 in place of @t{a'length}.
13725 @cindex quoting Ada internal identifiers
13726 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13727 to lower case. The GNAT compiler uses upper-case characters for
13728 some of its internal identifiers, which are normally of no interest to users.
13729 For the rare occasions when you actually have to look at them,
13730 enclose them in angle brackets to avoid the lower-case mapping.
13733 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13737 Printing an object of class-wide type or dereferencing an
13738 access-to-class-wide value will display all the components of the object's
13739 specific type (as indicated by its run-time tag). Likewise, component
13740 selection on such a value will operate on the specific type of the
13745 @node Stopping Before Main Program
13746 @subsubsection Stopping at the Very Beginning
13748 @cindex breakpointing Ada elaboration code
13749 It is sometimes necessary to debug the program during elaboration, and
13750 before reaching the main procedure.
13751 As defined in the Ada Reference
13752 Manual, the elaboration code is invoked from a procedure called
13753 @code{adainit}. To run your program up to the beginning of
13754 elaboration, simply use the following two commands:
13755 @code{tbreak adainit} and @code{run}.
13758 @subsubsection Extensions for Ada Tasks
13759 @cindex Ada, tasking
13761 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13762 @value{GDBN} provides the following task-related commands:
13767 This command shows a list of current Ada tasks, as in the following example:
13774 (@value{GDBP}) info tasks
13775 ID TID P-ID Pri State Name
13776 1 8088000 0 15 Child Activation Wait main_task
13777 2 80a4000 1 15 Accept Statement b
13778 3 809a800 1 15 Child Activation Wait a
13779 * 4 80ae800 3 15 Runnable c
13784 In this listing, the asterisk before the last task indicates it to be the
13785 task currently being inspected.
13789 Represents @value{GDBN}'s internal task number.
13795 The parent's task ID (@value{GDBN}'s internal task number).
13798 The base priority of the task.
13801 Current state of the task.
13805 The task has been created but has not been activated. It cannot be
13809 The task is not blocked for any reason known to Ada. (It may be waiting
13810 for a mutex, though.) It is conceptually "executing" in normal mode.
13813 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13814 that were waiting on terminate alternatives have been awakened and have
13815 terminated themselves.
13817 @item Child Activation Wait
13818 The task is waiting for created tasks to complete activation.
13820 @item Accept Statement
13821 The task is waiting on an accept or selective wait statement.
13823 @item Waiting on entry call
13824 The task is waiting on an entry call.
13826 @item Async Select Wait
13827 The task is waiting to start the abortable part of an asynchronous
13831 The task is waiting on a select statement with only a delay
13834 @item Child Termination Wait
13835 The task is sleeping having completed a master within itself, and is
13836 waiting for the tasks dependent on that master to become terminated or
13837 waiting on a terminate Phase.
13839 @item Wait Child in Term Alt
13840 The task is sleeping waiting for tasks on terminate alternatives to
13841 finish terminating.
13843 @item Accepting RV with @var{taskno}
13844 The task is accepting a rendez-vous with the task @var{taskno}.
13848 Name of the task in the program.
13852 @kindex info task @var{taskno}
13853 @item info task @var{taskno}
13854 This command shows detailled informations on the specified task, as in
13855 the following example:
13860 (@value{GDBP}) info tasks
13861 ID TID P-ID Pri State Name
13862 1 8077880 0 15 Child Activation Wait main_task
13863 * 2 807c468 1 15 Runnable task_1
13864 (@value{GDBP}) info task 2
13865 Ada Task: 0x807c468
13868 Parent: 1 (main_task)
13874 @kindex task@r{ (Ada)}
13875 @cindex current Ada task ID
13876 This command prints the ID of the current task.
13882 (@value{GDBP}) info tasks
13883 ID TID P-ID Pri State Name
13884 1 8077870 0 15 Child Activation Wait main_task
13885 * 2 807c458 1 15 Runnable t
13886 (@value{GDBP}) task
13887 [Current task is 2]
13890 @item task @var{taskno}
13891 @cindex Ada task switching
13892 This command is like the @code{thread @var{threadno}}
13893 command (@pxref{Threads}). It switches the context of debugging
13894 from the current task to the given task.
13900 (@value{GDBP}) info tasks
13901 ID TID P-ID Pri State Name
13902 1 8077870 0 15 Child Activation Wait main_task
13903 * 2 807c458 1 15 Runnable t
13904 (@value{GDBP}) task 1
13905 [Switching to task 1]
13906 #0 0x8067726 in pthread_cond_wait ()
13908 #0 0x8067726 in pthread_cond_wait ()
13909 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13910 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13911 #3 0x806153e in system.tasking.stages.activate_tasks ()
13912 #4 0x804aacc in un () at un.adb:5
13915 @item break @var{linespec} task @var{taskno}
13916 @itemx break @var{linespec} task @var{taskno} if @dots{}
13917 @cindex breakpoints and tasks, in Ada
13918 @cindex task breakpoints, in Ada
13919 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13920 These commands are like the @code{break @dots{} thread @dots{}}
13921 command (@pxref{Thread Stops}).
13922 @var{linespec} specifies source lines, as described
13923 in @ref{Specify Location}.
13925 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13926 to specify that you only want @value{GDBN} to stop the program when a
13927 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13928 numeric task identifiers assigned by @value{GDBN}, shown in the first
13929 column of the @samp{info tasks} display.
13931 If you do not specify @samp{task @var{taskno}} when you set a
13932 breakpoint, the breakpoint applies to @emph{all} tasks of your
13935 You can use the @code{task} qualifier on conditional breakpoints as
13936 well; in this case, place @samp{task @var{taskno}} before the
13937 breakpoint condition (before the @code{if}).
13945 (@value{GDBP}) info tasks
13946 ID TID P-ID Pri State Name
13947 1 140022020 0 15 Child Activation Wait main_task
13948 2 140045060 1 15 Accept/Select Wait t2
13949 3 140044840 1 15 Runnable t1
13950 * 4 140056040 1 15 Runnable t3
13951 (@value{GDBP}) b 15 task 2
13952 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13953 (@value{GDBP}) cont
13958 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13960 (@value{GDBP}) info tasks
13961 ID TID P-ID Pri State Name
13962 1 140022020 0 15 Child Activation Wait main_task
13963 * 2 140045060 1 15 Runnable t2
13964 3 140044840 1 15 Runnable t1
13965 4 140056040 1 15 Delay Sleep t3
13969 @node Ada Tasks and Core Files
13970 @subsubsection Tasking Support when Debugging Core Files
13971 @cindex Ada tasking and core file debugging
13973 When inspecting a core file, as opposed to debugging a live program,
13974 tasking support may be limited or even unavailable, depending on
13975 the platform being used.
13976 For instance, on x86-linux, the list of tasks is available, but task
13977 switching is not supported. On Tru64, however, task switching will work
13980 On certain platforms, including Tru64, the debugger needs to perform some
13981 memory writes in order to provide Ada tasking support. When inspecting
13982 a core file, this means that the core file must be opened with read-write
13983 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13984 Under these circumstances, you should make a backup copy of the core
13985 file before inspecting it with @value{GDBN}.
13987 @node Ravenscar Profile
13988 @subsubsection Tasking Support when using the Ravenscar Profile
13989 @cindex Ravenscar Profile
13991 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13992 specifically designed for systems with safety-critical real-time
13996 @kindex set ravenscar task-switching on
13997 @cindex task switching with program using Ravenscar Profile
13998 @item set ravenscar task-switching on
13999 Allows task switching when debugging a program that uses the Ravenscar
14000 Profile. This is the default.
14002 @kindex set ravenscar task-switching off
14003 @item set ravenscar task-switching off
14004 Turn off task switching when debugging a program that uses the Ravenscar
14005 Profile. This is mostly intended to disable the code that adds support
14006 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14007 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14008 To be effective, this command should be run before the program is started.
14010 @kindex show ravenscar task-switching
14011 @item show ravenscar task-switching
14012 Show whether it is possible to switch from task to task in a program
14013 using the Ravenscar Profile.
14018 @subsubsection Known Peculiarities of Ada Mode
14019 @cindex Ada, problems
14021 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14022 we know of several problems with and limitations of Ada mode in
14024 some of which will be fixed with planned future releases of the debugger
14025 and the GNU Ada compiler.
14029 Static constants that the compiler chooses not to materialize as objects in
14030 storage are invisible to the debugger.
14033 Named parameter associations in function argument lists are ignored (the
14034 argument lists are treated as positional).
14037 Many useful library packages are currently invisible to the debugger.
14040 Fixed-point arithmetic, conversions, input, and output is carried out using
14041 floating-point arithmetic, and may give results that only approximate those on
14045 The GNAT compiler never generates the prefix @code{Standard} for any of
14046 the standard symbols defined by the Ada language. @value{GDBN} knows about
14047 this: it will strip the prefix from names when you use it, and will never
14048 look for a name you have so qualified among local symbols, nor match against
14049 symbols in other packages or subprograms. If you have
14050 defined entities anywhere in your program other than parameters and
14051 local variables whose simple names match names in @code{Standard},
14052 GNAT's lack of qualification here can cause confusion. When this happens,
14053 you can usually resolve the confusion
14054 by qualifying the problematic names with package
14055 @code{Standard} explicitly.
14058 Older versions of the compiler sometimes generate erroneous debugging
14059 information, resulting in the debugger incorrectly printing the value
14060 of affected entities. In some cases, the debugger is able to work
14061 around an issue automatically. In other cases, the debugger is able
14062 to work around the issue, but the work-around has to be specifically
14065 @kindex set ada trust-PAD-over-XVS
14066 @kindex show ada trust-PAD-over-XVS
14069 @item set ada trust-PAD-over-XVS on
14070 Configure GDB to strictly follow the GNAT encoding when computing the
14071 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14072 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14073 a complete description of the encoding used by the GNAT compiler).
14074 This is the default.
14076 @item set ada trust-PAD-over-XVS off
14077 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14078 sometimes prints the wrong value for certain entities, changing @code{ada
14079 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14080 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14081 @code{off}, but this incurs a slight performance penalty, so it is
14082 recommended to leave this setting to @code{on} unless necessary.
14086 @node Unsupported Languages
14087 @section Unsupported Languages
14089 @cindex unsupported languages
14090 @cindex minimal language
14091 In addition to the other fully-supported programming languages,
14092 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14093 It does not represent a real programming language, but provides a set
14094 of capabilities close to what the C or assembly languages provide.
14095 This should allow most simple operations to be performed while debugging
14096 an application that uses a language currently not supported by @value{GDBN}.
14098 If the language is set to @code{auto}, @value{GDBN} will automatically
14099 select this language if the current frame corresponds to an unsupported
14103 @chapter Examining the Symbol Table
14105 The commands described in this chapter allow you to inquire about the
14106 symbols (names of variables, functions and types) defined in your
14107 program. This information is inherent in the text of your program and
14108 does not change as your program executes. @value{GDBN} finds it in your
14109 program's symbol table, in the file indicated when you started @value{GDBN}
14110 (@pxref{File Options, ,Choosing Files}), or by one of the
14111 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14113 @cindex symbol names
14114 @cindex names of symbols
14115 @cindex quoting names
14116 Occasionally, you may need to refer to symbols that contain unusual
14117 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14118 most frequent case is in referring to static variables in other
14119 source files (@pxref{Variables,,Program Variables}). File names
14120 are recorded in object files as debugging symbols, but @value{GDBN} would
14121 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14122 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14123 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14130 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14133 @cindex case-insensitive symbol names
14134 @cindex case sensitivity in symbol names
14135 @kindex set case-sensitive
14136 @item set case-sensitive on
14137 @itemx set case-sensitive off
14138 @itemx set case-sensitive auto
14139 Normally, when @value{GDBN} looks up symbols, it matches their names
14140 with case sensitivity determined by the current source language.
14141 Occasionally, you may wish to control that. The command @code{set
14142 case-sensitive} lets you do that by specifying @code{on} for
14143 case-sensitive matches or @code{off} for case-insensitive ones. If
14144 you specify @code{auto}, case sensitivity is reset to the default
14145 suitable for the source language. The default is case-sensitive
14146 matches for all languages except for Fortran, for which the default is
14147 case-insensitive matches.
14149 @kindex show case-sensitive
14150 @item show case-sensitive
14151 This command shows the current setting of case sensitivity for symbols
14154 @kindex info address
14155 @cindex address of a symbol
14156 @item info address @var{symbol}
14157 Describe where the data for @var{symbol} is stored. For a register
14158 variable, this says which register it is kept in. For a non-register
14159 local variable, this prints the stack-frame offset at which the variable
14162 Note the contrast with @samp{print &@var{symbol}}, which does not work
14163 at all for a register variable, and for a stack local variable prints
14164 the exact address of the current instantiation of the variable.
14166 @kindex info symbol
14167 @cindex symbol from address
14168 @cindex closest symbol and offset for an address
14169 @item info symbol @var{addr}
14170 Print the name of a symbol which is stored at the address @var{addr}.
14171 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14172 nearest symbol and an offset from it:
14175 (@value{GDBP}) info symbol 0x54320
14176 _initialize_vx + 396 in section .text
14180 This is the opposite of the @code{info address} command. You can use
14181 it to find out the name of a variable or a function given its address.
14183 For dynamically linked executables, the name of executable or shared
14184 library containing the symbol is also printed:
14187 (@value{GDBP}) info symbol 0x400225
14188 _start + 5 in section .text of /tmp/a.out
14189 (@value{GDBP}) info symbol 0x2aaaac2811cf
14190 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14194 @item whatis [@var{arg}]
14195 Print the data type of @var{arg}, which can be either an expression
14196 or a name of a data type. With no argument, print the data type of
14197 @code{$}, the last value in the value history.
14199 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14200 is not actually evaluated, and any side-effecting operations (such as
14201 assignments or function calls) inside it do not take place.
14203 If @var{arg} is a variable or an expression, @code{whatis} prints its
14204 literal type as it is used in the source code. If the type was
14205 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14206 the data type underlying the @code{typedef}. If the type of the
14207 variable or the expression is a compound data type, such as
14208 @code{struct} or @code{class}, @code{whatis} never prints their
14209 fields or methods. It just prints the @code{struct}/@code{class}
14210 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14211 such a compound data type, use @code{ptype}.
14213 If @var{arg} is a type name that was defined using @code{typedef},
14214 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14215 Unrolling means that @code{whatis} will show the underlying type used
14216 in the @code{typedef} declaration of @var{arg}. However, if that
14217 underlying type is also a @code{typedef}, @code{whatis} will not
14220 For C code, the type names may also have the form @samp{class
14221 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14222 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14225 @item ptype [@var{arg}]
14226 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14227 detailed description of the type, instead of just the name of the type.
14228 @xref{Expressions, ,Expressions}.
14230 Contrary to @code{whatis}, @code{ptype} always unrolls any
14231 @code{typedef}s in its argument declaration, whether the argument is
14232 a variable, expression, or a data type. This means that @code{ptype}
14233 of a variable or an expression will not print literally its type as
14234 present in the source code---use @code{whatis} for that. @code{typedef}s at
14235 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14236 fields, methods and inner @code{class typedef}s of @code{struct}s,
14237 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14239 For example, for this variable declaration:
14242 typedef double real_t;
14243 struct complex @{ real_t real; double imag; @};
14244 typedef struct complex complex_t;
14246 real_t *real_pointer_var;
14250 the two commands give this output:
14254 (@value{GDBP}) whatis var
14256 (@value{GDBP}) ptype var
14257 type = struct complex @{
14261 (@value{GDBP}) whatis complex_t
14262 type = struct complex
14263 (@value{GDBP}) whatis struct complex
14264 type = struct complex
14265 (@value{GDBP}) ptype struct complex
14266 type = struct complex @{
14270 (@value{GDBP}) whatis real_pointer_var
14272 (@value{GDBP}) ptype real_pointer_var
14278 As with @code{whatis}, using @code{ptype} without an argument refers to
14279 the type of @code{$}, the last value in the value history.
14281 @cindex incomplete type
14282 Sometimes, programs use opaque data types or incomplete specifications
14283 of complex data structure. If the debug information included in the
14284 program does not allow @value{GDBN} to display a full declaration of
14285 the data type, it will say @samp{<incomplete type>}. For example,
14286 given these declarations:
14290 struct foo *fooptr;
14294 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14297 (@value{GDBP}) ptype foo
14298 $1 = <incomplete type>
14302 ``Incomplete type'' is C terminology for data types that are not
14303 completely specified.
14306 @item info types @var{regexp}
14308 Print a brief description of all types whose names match the regular
14309 expression @var{regexp} (or all types in your program, if you supply
14310 no argument). Each complete typename is matched as though it were a
14311 complete line; thus, @samp{i type value} gives information on all
14312 types in your program whose names include the string @code{value}, but
14313 @samp{i type ^value$} gives information only on types whose complete
14314 name is @code{value}.
14316 This command differs from @code{ptype} in two ways: first, like
14317 @code{whatis}, it does not print a detailed description; second, it
14318 lists all source files where a type is defined.
14321 @cindex local variables
14322 @item info scope @var{location}
14323 List all the variables local to a particular scope. This command
14324 accepts a @var{location} argument---a function name, a source line, or
14325 an address preceded by a @samp{*}, and prints all the variables local
14326 to the scope defined by that location. (@xref{Specify Location}, for
14327 details about supported forms of @var{location}.) For example:
14330 (@value{GDBP}) @b{info scope command_line_handler}
14331 Scope for command_line_handler:
14332 Symbol rl is an argument at stack/frame offset 8, length 4.
14333 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14334 Symbol linelength is in static storage at address 0x150a1c, length 4.
14335 Symbol p is a local variable in register $esi, length 4.
14336 Symbol p1 is a local variable in register $ebx, length 4.
14337 Symbol nline is a local variable in register $edx, length 4.
14338 Symbol repeat is a local variable at frame offset -8, length 4.
14342 This command is especially useful for determining what data to collect
14343 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14346 @kindex info source
14348 Show information about the current source file---that is, the source file for
14349 the function containing the current point of execution:
14352 the name of the source file, and the directory containing it,
14354 the directory it was compiled in,
14356 its length, in lines,
14358 which programming language it is written in,
14360 whether the executable includes debugging information for that file, and
14361 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14363 whether the debugging information includes information about
14364 preprocessor macros.
14368 @kindex info sources
14370 Print the names of all source files in your program for which there is
14371 debugging information, organized into two lists: files whose symbols
14372 have already been read, and files whose symbols will be read when needed.
14374 @kindex info functions
14375 @item info functions
14376 Print the names and data types of all defined functions.
14378 @item info functions @var{regexp}
14379 Print the names and data types of all defined functions
14380 whose names contain a match for regular expression @var{regexp}.
14381 Thus, @samp{info fun step} finds all functions whose names
14382 include @code{step}; @samp{info fun ^step} finds those whose names
14383 start with @code{step}. If a function name contains characters
14384 that conflict with the regular expression language (e.g.@:
14385 @samp{operator*()}), they may be quoted with a backslash.
14387 @kindex info variables
14388 @item info variables
14389 Print the names and data types of all variables that are defined
14390 outside of functions (i.e.@: excluding local variables).
14392 @item info variables @var{regexp}
14393 Print the names and data types of all variables (except for local
14394 variables) whose names contain a match for regular expression
14397 @kindex info classes
14398 @cindex Objective-C, classes and selectors
14400 @itemx info classes @var{regexp}
14401 Display all Objective-C classes in your program, or
14402 (with the @var{regexp} argument) all those matching a particular regular
14405 @kindex info selectors
14406 @item info selectors
14407 @itemx info selectors @var{regexp}
14408 Display all Objective-C selectors in your program, or
14409 (with the @var{regexp} argument) all those matching a particular regular
14413 This was never implemented.
14414 @kindex info methods
14416 @itemx info methods @var{regexp}
14417 The @code{info methods} command permits the user to examine all defined
14418 methods within C@t{++} program, or (with the @var{regexp} argument) a
14419 specific set of methods found in the various C@t{++} classes. Many
14420 C@t{++} classes provide a large number of methods. Thus, the output
14421 from the @code{ptype} command can be overwhelming and hard to use. The
14422 @code{info-methods} command filters the methods, printing only those
14423 which match the regular-expression @var{regexp}.
14426 @cindex reloading symbols
14427 Some systems allow individual object files that make up your program to
14428 be replaced without stopping and restarting your program. For example,
14429 in VxWorks you can simply recompile a defective object file and keep on
14430 running. If you are running on one of these systems, you can allow
14431 @value{GDBN} to reload the symbols for automatically relinked modules:
14434 @kindex set symbol-reloading
14435 @item set symbol-reloading on
14436 Replace symbol definitions for the corresponding source file when an
14437 object file with a particular name is seen again.
14439 @item set symbol-reloading off
14440 Do not replace symbol definitions when encountering object files of the
14441 same name more than once. This is the default state; if you are not
14442 running on a system that permits automatic relinking of modules, you
14443 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14444 may discard symbols when linking large programs, that may contain
14445 several modules (from different directories or libraries) with the same
14448 @kindex show symbol-reloading
14449 @item show symbol-reloading
14450 Show the current @code{on} or @code{off} setting.
14453 @cindex opaque data types
14454 @kindex set opaque-type-resolution
14455 @item set opaque-type-resolution on
14456 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14457 declared as a pointer to a @code{struct}, @code{class}, or
14458 @code{union}---for example, @code{struct MyType *}---that is used in one
14459 source file although the full declaration of @code{struct MyType} is in
14460 another source file. The default is on.
14462 A change in the setting of this subcommand will not take effect until
14463 the next time symbols for a file are loaded.
14465 @item set opaque-type-resolution off
14466 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14467 is printed as follows:
14469 @{<no data fields>@}
14472 @kindex show opaque-type-resolution
14473 @item show opaque-type-resolution
14474 Show whether opaque types are resolved or not.
14476 @kindex maint print symbols
14477 @cindex symbol dump
14478 @kindex maint print psymbols
14479 @cindex partial symbol dump
14480 @item maint print symbols @var{filename}
14481 @itemx maint print psymbols @var{filename}
14482 @itemx maint print msymbols @var{filename}
14483 Write a dump of debugging symbol data into the file @var{filename}.
14484 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14485 symbols with debugging data are included. If you use @samp{maint print
14486 symbols}, @value{GDBN} includes all the symbols for which it has already
14487 collected full details: that is, @var{filename} reflects symbols for
14488 only those files whose symbols @value{GDBN} has read. You can use the
14489 command @code{info sources} to find out which files these are. If you
14490 use @samp{maint print psymbols} instead, the dump shows information about
14491 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14492 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14493 @samp{maint print msymbols} dumps just the minimal symbol information
14494 required for each object file from which @value{GDBN} has read some symbols.
14495 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14496 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14498 @kindex maint info symtabs
14499 @kindex maint info psymtabs
14500 @cindex listing @value{GDBN}'s internal symbol tables
14501 @cindex symbol tables, listing @value{GDBN}'s internal
14502 @cindex full symbol tables, listing @value{GDBN}'s internal
14503 @cindex partial symbol tables, listing @value{GDBN}'s internal
14504 @item maint info symtabs @r{[} @var{regexp} @r{]}
14505 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14507 List the @code{struct symtab} or @code{struct partial_symtab}
14508 structures whose names match @var{regexp}. If @var{regexp} is not
14509 given, list them all. The output includes expressions which you can
14510 copy into a @value{GDBN} debugging this one to examine a particular
14511 structure in more detail. For example:
14514 (@value{GDBP}) maint info psymtabs dwarf2read
14515 @{ objfile /home/gnu/build/gdb/gdb
14516 ((struct objfile *) 0x82e69d0)
14517 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14518 ((struct partial_symtab *) 0x8474b10)
14521 text addresses 0x814d3c8 -- 0x8158074
14522 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14523 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14524 dependencies (none)
14527 (@value{GDBP}) maint info symtabs
14531 We see that there is one partial symbol table whose filename contains
14532 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14533 and we see that @value{GDBN} has not read in any symtabs yet at all.
14534 If we set a breakpoint on a function, that will cause @value{GDBN} to
14535 read the symtab for the compilation unit containing that function:
14538 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14539 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14541 (@value{GDBP}) maint info symtabs
14542 @{ objfile /home/gnu/build/gdb/gdb
14543 ((struct objfile *) 0x82e69d0)
14544 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14545 ((struct symtab *) 0x86c1f38)
14548 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14549 linetable ((struct linetable *) 0x8370fa0)
14550 debugformat DWARF 2
14559 @chapter Altering Execution
14561 Once you think you have found an error in your program, you might want to
14562 find out for certain whether correcting the apparent error would lead to
14563 correct results in the rest of the run. You can find the answer by
14564 experiment, using the @value{GDBN} features for altering execution of the
14567 For example, you can store new values into variables or memory
14568 locations, give your program a signal, restart it at a different
14569 address, or even return prematurely from a function.
14572 * Assignment:: Assignment to variables
14573 * Jumping:: Continuing at a different address
14574 * Signaling:: Giving your program a signal
14575 * Returning:: Returning from a function
14576 * Calling:: Calling your program's functions
14577 * Patching:: Patching your program
14581 @section Assignment to Variables
14584 @cindex setting variables
14585 To alter the value of a variable, evaluate an assignment expression.
14586 @xref{Expressions, ,Expressions}. For example,
14593 stores the value 4 into the variable @code{x}, and then prints the
14594 value of the assignment expression (which is 4).
14595 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14596 information on operators in supported languages.
14598 @kindex set variable
14599 @cindex variables, setting
14600 If you are not interested in seeing the value of the assignment, use the
14601 @code{set} command instead of the @code{print} command. @code{set} is
14602 really the same as @code{print} except that the expression's value is
14603 not printed and is not put in the value history (@pxref{Value History,
14604 ,Value History}). The expression is evaluated only for its effects.
14606 If the beginning of the argument string of the @code{set} command
14607 appears identical to a @code{set} subcommand, use the @code{set
14608 variable} command instead of just @code{set}. This command is identical
14609 to @code{set} except for its lack of subcommands. For example, if your
14610 program has a variable @code{width}, you get an error if you try to set
14611 a new value with just @samp{set width=13}, because @value{GDBN} has the
14612 command @code{set width}:
14615 (@value{GDBP}) whatis width
14617 (@value{GDBP}) p width
14619 (@value{GDBP}) set width=47
14620 Invalid syntax in expression.
14624 The invalid expression, of course, is @samp{=47}. In
14625 order to actually set the program's variable @code{width}, use
14628 (@value{GDBP}) set var width=47
14631 Because the @code{set} command has many subcommands that can conflict
14632 with the names of program variables, it is a good idea to use the
14633 @code{set variable} command instead of just @code{set}. For example, if
14634 your program has a variable @code{g}, you run into problems if you try
14635 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14636 the command @code{set gnutarget}, abbreviated @code{set g}:
14640 (@value{GDBP}) whatis g
14644 (@value{GDBP}) set g=4
14648 The program being debugged has been started already.
14649 Start it from the beginning? (y or n) y
14650 Starting program: /home/smith/cc_progs/a.out
14651 "/home/smith/cc_progs/a.out": can't open to read symbols:
14652 Invalid bfd target.
14653 (@value{GDBP}) show g
14654 The current BFD target is "=4".
14659 The program variable @code{g} did not change, and you silently set the
14660 @code{gnutarget} to an invalid value. In order to set the variable
14664 (@value{GDBP}) set var g=4
14667 @value{GDBN} allows more implicit conversions in assignments than C; you can
14668 freely store an integer value into a pointer variable or vice versa,
14669 and you can convert any structure to any other structure that is the
14670 same length or shorter.
14671 @comment FIXME: how do structs align/pad in these conversions?
14672 @comment /doc@cygnus.com 18dec1990
14674 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14675 construct to generate a value of specified type at a specified address
14676 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14677 to memory location @code{0x83040} as an integer (which implies a certain size
14678 and representation in memory), and
14681 set @{int@}0x83040 = 4
14685 stores the value 4 into that memory location.
14688 @section Continuing at a Different Address
14690 Ordinarily, when you continue your program, you do so at the place where
14691 it stopped, with the @code{continue} command. You can instead continue at
14692 an address of your own choosing, with the following commands:
14696 @item jump @var{linespec}
14697 @itemx jump @var{location}
14698 Resume execution at line @var{linespec} or at address given by
14699 @var{location}. Execution stops again immediately if there is a
14700 breakpoint there. @xref{Specify Location}, for a description of the
14701 different forms of @var{linespec} and @var{location}. It is common
14702 practice to use the @code{tbreak} command in conjunction with
14703 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14705 The @code{jump} command does not change the current stack frame, or
14706 the stack pointer, or the contents of any memory location or any
14707 register other than the program counter. If line @var{linespec} is in
14708 a different function from the one currently executing, the results may
14709 be bizarre if the two functions expect different patterns of arguments or
14710 of local variables. For this reason, the @code{jump} command requests
14711 confirmation if the specified line is not in the function currently
14712 executing. However, even bizarre results are predictable if you are
14713 well acquainted with the machine-language code of your program.
14716 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14717 On many systems, you can get much the same effect as the @code{jump}
14718 command by storing a new value into the register @code{$pc}. The
14719 difference is that this does not start your program running; it only
14720 changes the address of where it @emph{will} run when you continue. For
14728 makes the next @code{continue} command or stepping command execute at
14729 address @code{0x485}, rather than at the address where your program stopped.
14730 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14732 The most common occasion to use the @code{jump} command is to back
14733 up---perhaps with more breakpoints set---over a portion of a program
14734 that has already executed, in order to examine its execution in more
14739 @section Giving your Program a Signal
14740 @cindex deliver a signal to a program
14744 @item signal @var{signal}
14745 Resume execution where your program stopped, but immediately give it the
14746 signal @var{signal}. @var{signal} can be the name or the number of a
14747 signal. For example, on many systems @code{signal 2} and @code{signal
14748 SIGINT} are both ways of sending an interrupt signal.
14750 Alternatively, if @var{signal} is zero, continue execution without
14751 giving a signal. This is useful when your program stopped on account of
14752 a signal and would ordinary see the signal when resumed with the
14753 @code{continue} command; @samp{signal 0} causes it to resume without a
14756 @code{signal} does not repeat when you press @key{RET} a second time
14757 after executing the command.
14761 Invoking the @code{signal} command is not the same as invoking the
14762 @code{kill} utility from the shell. Sending a signal with @code{kill}
14763 causes @value{GDBN} to decide what to do with the signal depending on
14764 the signal handling tables (@pxref{Signals}). The @code{signal} command
14765 passes the signal directly to your program.
14769 @section Returning from a Function
14772 @cindex returning from a function
14775 @itemx return @var{expression}
14776 You can cancel execution of a function call with the @code{return}
14777 command. If you give an
14778 @var{expression} argument, its value is used as the function's return
14782 When you use @code{return}, @value{GDBN} discards the selected stack frame
14783 (and all frames within it). You can think of this as making the
14784 discarded frame return prematurely. If you wish to specify a value to
14785 be returned, give that value as the argument to @code{return}.
14787 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14788 Frame}), and any other frames inside of it, leaving its caller as the
14789 innermost remaining frame. That frame becomes selected. The
14790 specified value is stored in the registers used for returning values
14793 The @code{return} command does not resume execution; it leaves the
14794 program stopped in the state that would exist if the function had just
14795 returned. In contrast, the @code{finish} command (@pxref{Continuing
14796 and Stepping, ,Continuing and Stepping}) resumes execution until the
14797 selected stack frame returns naturally.
14799 @value{GDBN} needs to know how the @var{expression} argument should be set for
14800 the inferior. The concrete registers assignment depends on the OS ABI and the
14801 type being returned by the selected stack frame. For example it is common for
14802 OS ABI to return floating point values in FPU registers while integer values in
14803 CPU registers. Still some ABIs return even floating point values in CPU
14804 registers. Larger integer widths (such as @code{long long int}) also have
14805 specific placement rules. @value{GDBN} already knows the OS ABI from its
14806 current target so it needs to find out also the type being returned to make the
14807 assignment into the right register(s).
14809 Normally, the selected stack frame has debug info. @value{GDBN} will always
14810 use the debug info instead of the implicit type of @var{expression} when the
14811 debug info is available. For example, if you type @kbd{return -1}, and the
14812 function in the current stack frame is declared to return a @code{long long
14813 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14814 into a @code{long long int}:
14817 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14819 (@value{GDBP}) return -1
14820 Make func return now? (y or n) y
14821 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14822 43 printf ("result=%lld\n", func ());
14826 However, if the selected stack frame does not have a debug info, e.g., if the
14827 function was compiled without debug info, @value{GDBN} has to find out the type
14828 to return from user. Specifying a different type by mistake may set the value
14829 in different inferior registers than the caller code expects. For example,
14830 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14831 of a @code{long long int} result for a debug info less function (on 32-bit
14832 architectures). Therefore the user is required to specify the return type by
14833 an appropriate cast explicitly:
14836 Breakpoint 2, 0x0040050b in func ()
14837 (@value{GDBP}) return -1
14838 Return value type not available for selected stack frame.
14839 Please use an explicit cast of the value to return.
14840 (@value{GDBP}) return (long long int) -1
14841 Make selected stack frame return now? (y or n) y
14842 #0 0x00400526 in main ()
14847 @section Calling Program Functions
14850 @cindex calling functions
14851 @cindex inferior functions, calling
14852 @item print @var{expr}
14853 Evaluate the expression @var{expr} and display the resulting value.
14854 @var{expr} may include calls to functions in the program being
14858 @item call @var{expr}
14859 Evaluate the expression @var{expr} without displaying @code{void}
14862 You can use this variant of the @code{print} command if you want to
14863 execute a function from your program that does not return anything
14864 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14865 with @code{void} returned values that @value{GDBN} will otherwise
14866 print. If the result is not void, it is printed and saved in the
14870 It is possible for the function you call via the @code{print} or
14871 @code{call} command to generate a signal (e.g., if there's a bug in
14872 the function, or if you passed it incorrect arguments). What happens
14873 in that case is controlled by the @code{set unwindonsignal} command.
14875 Similarly, with a C@t{++} program it is possible for the function you
14876 call via the @code{print} or @code{call} command to generate an
14877 exception that is not handled due to the constraints of the dummy
14878 frame. In this case, any exception that is raised in the frame, but has
14879 an out-of-frame exception handler will not be found. GDB builds a
14880 dummy-frame for the inferior function call, and the unwinder cannot
14881 seek for exception handlers outside of this dummy-frame. What happens
14882 in that case is controlled by the
14883 @code{set unwind-on-terminating-exception} command.
14886 @item set unwindonsignal
14887 @kindex set unwindonsignal
14888 @cindex unwind stack in called functions
14889 @cindex call dummy stack unwinding
14890 Set unwinding of the stack if a signal is received while in a function
14891 that @value{GDBN} called in the program being debugged. If set to on,
14892 @value{GDBN} unwinds the stack it created for the call and restores
14893 the context to what it was before the call. If set to off (the
14894 default), @value{GDBN} stops in the frame where the signal was
14897 @item show unwindonsignal
14898 @kindex show unwindonsignal
14899 Show the current setting of stack unwinding in the functions called by
14902 @item set unwind-on-terminating-exception
14903 @kindex set unwind-on-terminating-exception
14904 @cindex unwind stack in called functions with unhandled exceptions
14905 @cindex call dummy stack unwinding on unhandled exception.
14906 Set unwinding of the stack if a C@t{++} exception is raised, but left
14907 unhandled while in a function that @value{GDBN} called in the program being
14908 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14909 it created for the call and restores the context to what it was before
14910 the call. If set to off, @value{GDBN} the exception is delivered to
14911 the default C@t{++} exception handler and the inferior terminated.
14913 @item show unwind-on-terminating-exception
14914 @kindex show unwind-on-terminating-exception
14915 Show the current setting of stack unwinding in the functions called by
14920 @cindex weak alias functions
14921 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14922 for another function. In such case, @value{GDBN} might not pick up
14923 the type information, including the types of the function arguments,
14924 which causes @value{GDBN} to call the inferior function incorrectly.
14925 As a result, the called function will function erroneously and may
14926 even crash. A solution to that is to use the name of the aliased
14930 @section Patching Programs
14932 @cindex patching binaries
14933 @cindex writing into executables
14934 @cindex writing into corefiles
14936 By default, @value{GDBN} opens the file containing your program's
14937 executable code (or the corefile) read-only. This prevents accidental
14938 alterations to machine code; but it also prevents you from intentionally
14939 patching your program's binary.
14941 If you'd like to be able to patch the binary, you can specify that
14942 explicitly with the @code{set write} command. For example, you might
14943 want to turn on internal debugging flags, or even to make emergency
14949 @itemx set write off
14950 If you specify @samp{set write on}, @value{GDBN} opens executable and
14951 core files for both reading and writing; if you specify @kbd{set write
14952 off} (the default), @value{GDBN} opens them read-only.
14954 If you have already loaded a file, you must load it again (using the
14955 @code{exec-file} or @code{core-file} command) after changing @code{set
14956 write}, for your new setting to take effect.
14960 Display whether executable files and core files are opened for writing
14961 as well as reading.
14965 @chapter @value{GDBN} Files
14967 @value{GDBN} needs to know the file name of the program to be debugged,
14968 both in order to read its symbol table and in order to start your
14969 program. To debug a core dump of a previous run, you must also tell
14970 @value{GDBN} the name of the core dump file.
14973 * Files:: Commands to specify files
14974 * Separate Debug Files:: Debugging information in separate files
14975 * Index Files:: Index files speed up GDB
14976 * Symbol Errors:: Errors reading symbol files
14977 * Data Files:: GDB data files
14981 @section Commands to Specify Files
14983 @cindex symbol table
14984 @cindex core dump file
14986 You may want to specify executable and core dump file names. The usual
14987 way to do this is at start-up time, using the arguments to
14988 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14989 Out of @value{GDBN}}).
14991 Occasionally it is necessary to change to a different file during a
14992 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14993 specify a file you want to use. Or you are debugging a remote target
14994 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14995 Program}). In these situations the @value{GDBN} commands to specify
14996 new files are useful.
14999 @cindex executable file
15001 @item file @var{filename}
15002 Use @var{filename} as the program to be debugged. It is read for its
15003 symbols and for the contents of pure memory. It is also the program
15004 executed when you use the @code{run} command. If you do not specify a
15005 directory and the file is not found in the @value{GDBN} working directory,
15006 @value{GDBN} uses the environment variable @code{PATH} as a list of
15007 directories to search, just as the shell does when looking for a program
15008 to run. You can change the value of this variable, for both @value{GDBN}
15009 and your program, using the @code{path} command.
15011 @cindex unlinked object files
15012 @cindex patching object files
15013 You can load unlinked object @file{.o} files into @value{GDBN} using
15014 the @code{file} command. You will not be able to ``run'' an object
15015 file, but you can disassemble functions and inspect variables. Also,
15016 if the underlying BFD functionality supports it, you could use
15017 @kbd{gdb -write} to patch object files using this technique. Note
15018 that @value{GDBN} can neither interpret nor modify relocations in this
15019 case, so branches and some initialized variables will appear to go to
15020 the wrong place. But this feature is still handy from time to time.
15023 @code{file} with no argument makes @value{GDBN} discard any information it
15024 has on both executable file and the symbol table.
15027 @item exec-file @r{[} @var{filename} @r{]}
15028 Specify that the program to be run (but not the symbol table) is found
15029 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15030 if necessary to locate your program. Omitting @var{filename} means to
15031 discard information on the executable file.
15033 @kindex symbol-file
15034 @item symbol-file @r{[} @var{filename} @r{]}
15035 Read symbol table information from file @var{filename}. @code{PATH} is
15036 searched when necessary. Use the @code{file} command to get both symbol
15037 table and program to run from the same file.
15039 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15040 program's symbol table.
15042 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15043 some breakpoints and auto-display expressions. This is because they may
15044 contain pointers to the internal data recording symbols and data types,
15045 which are part of the old symbol table data being discarded inside
15048 @code{symbol-file} does not repeat if you press @key{RET} again after
15051 When @value{GDBN} is configured for a particular environment, it
15052 understands debugging information in whatever format is the standard
15053 generated for that environment; you may use either a @sc{gnu} compiler, or
15054 other compilers that adhere to the local conventions.
15055 Best results are usually obtained from @sc{gnu} compilers; for example,
15056 using @code{@value{NGCC}} you can generate debugging information for
15059 For most kinds of object files, with the exception of old SVR3 systems
15060 using COFF, the @code{symbol-file} command does not normally read the
15061 symbol table in full right away. Instead, it scans the symbol table
15062 quickly to find which source files and which symbols are present. The
15063 details are read later, one source file at a time, as they are needed.
15065 The purpose of this two-stage reading strategy is to make @value{GDBN}
15066 start up faster. For the most part, it is invisible except for
15067 occasional pauses while the symbol table details for a particular source
15068 file are being read. (The @code{set verbose} command can turn these
15069 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15070 Warnings and Messages}.)
15072 We have not implemented the two-stage strategy for COFF yet. When the
15073 symbol table is stored in COFF format, @code{symbol-file} reads the
15074 symbol table data in full right away. Note that ``stabs-in-COFF''
15075 still does the two-stage strategy, since the debug info is actually
15079 @cindex reading symbols immediately
15080 @cindex symbols, reading immediately
15081 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15082 @itemx file @r{[} -readnow @r{]} @var{filename}
15083 You can override the @value{GDBN} two-stage strategy for reading symbol
15084 tables by using the @samp{-readnow} option with any of the commands that
15085 load symbol table information, if you want to be sure @value{GDBN} has the
15086 entire symbol table available.
15088 @c FIXME: for now no mention of directories, since this seems to be in
15089 @c flux. 13mar1992 status is that in theory GDB would look either in
15090 @c current dir or in same dir as myprog; but issues like competing
15091 @c GDB's, or clutter in system dirs, mean that in practice right now
15092 @c only current dir is used. FFish says maybe a special GDB hierarchy
15093 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15097 @item core-file @r{[}@var{filename}@r{]}
15099 Specify the whereabouts of a core dump file to be used as the ``contents
15100 of memory''. Traditionally, core files contain only some parts of the
15101 address space of the process that generated them; @value{GDBN} can access the
15102 executable file itself for other parts.
15104 @code{core-file} with no argument specifies that no core file is
15107 Note that the core file is ignored when your program is actually running
15108 under @value{GDBN}. So, if you have been running your program and you
15109 wish to debug a core file instead, you must kill the subprocess in which
15110 the program is running. To do this, use the @code{kill} command
15111 (@pxref{Kill Process, ,Killing the Child Process}).
15113 @kindex add-symbol-file
15114 @cindex dynamic linking
15115 @item add-symbol-file @var{filename} @var{address}
15116 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15117 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15118 The @code{add-symbol-file} command reads additional symbol table
15119 information from the file @var{filename}. You would use this command
15120 when @var{filename} has been dynamically loaded (by some other means)
15121 into the program that is running. @var{address} should be the memory
15122 address at which the file has been loaded; @value{GDBN} cannot figure
15123 this out for itself. You can additionally specify an arbitrary number
15124 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15125 section name and base address for that section. You can specify any
15126 @var{address} as an expression.
15128 The symbol table of the file @var{filename} is added to the symbol table
15129 originally read with the @code{symbol-file} command. You can use the
15130 @code{add-symbol-file} command any number of times; the new symbol data
15131 thus read keeps adding to the old. To discard all old symbol data
15132 instead, use the @code{symbol-file} command without any arguments.
15134 @cindex relocatable object files, reading symbols from
15135 @cindex object files, relocatable, reading symbols from
15136 @cindex reading symbols from relocatable object files
15137 @cindex symbols, reading from relocatable object files
15138 @cindex @file{.o} files, reading symbols from
15139 Although @var{filename} is typically a shared library file, an
15140 executable file, or some other object file which has been fully
15141 relocated for loading into a process, you can also load symbolic
15142 information from relocatable @file{.o} files, as long as:
15146 the file's symbolic information refers only to linker symbols defined in
15147 that file, not to symbols defined by other object files,
15149 every section the file's symbolic information refers to has actually
15150 been loaded into the inferior, as it appears in the file, and
15152 you can determine the address at which every section was loaded, and
15153 provide these to the @code{add-symbol-file} command.
15157 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15158 relocatable files into an already running program; such systems
15159 typically make the requirements above easy to meet. However, it's
15160 important to recognize that many native systems use complex link
15161 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15162 assembly, for example) that make the requirements difficult to meet. In
15163 general, one cannot assume that using @code{add-symbol-file} to read a
15164 relocatable object file's symbolic information will have the same effect
15165 as linking the relocatable object file into the program in the normal
15168 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15170 @kindex add-symbol-file-from-memory
15171 @cindex @code{syscall DSO}
15172 @cindex load symbols from memory
15173 @item add-symbol-file-from-memory @var{address}
15174 Load symbols from the given @var{address} in a dynamically loaded
15175 object file whose image is mapped directly into the inferior's memory.
15176 For example, the Linux kernel maps a @code{syscall DSO} into each
15177 process's address space; this DSO provides kernel-specific code for
15178 some system calls. The argument can be any expression whose
15179 evaluation yields the address of the file's shared object file header.
15180 For this command to work, you must have used @code{symbol-file} or
15181 @code{exec-file} commands in advance.
15183 @kindex add-shared-symbol-files
15185 @item add-shared-symbol-files @var{library-file}
15186 @itemx assf @var{library-file}
15187 The @code{add-shared-symbol-files} command can currently be used only
15188 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15189 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15190 @value{GDBN} automatically looks for shared libraries, however if
15191 @value{GDBN} does not find yours, you can invoke
15192 @code{add-shared-symbol-files}. It takes one argument: the shared
15193 library's file name. @code{assf} is a shorthand alias for
15194 @code{add-shared-symbol-files}.
15197 @item section @var{section} @var{addr}
15198 The @code{section} command changes the base address of the named
15199 @var{section} of the exec file to @var{addr}. This can be used if the
15200 exec file does not contain section addresses, (such as in the
15201 @code{a.out} format), or when the addresses specified in the file
15202 itself are wrong. Each section must be changed separately. The
15203 @code{info files} command, described below, lists all the sections and
15207 @kindex info target
15210 @code{info files} and @code{info target} are synonymous; both print the
15211 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15212 including the names of the executable and core dump files currently in
15213 use by @value{GDBN}, and the files from which symbols were loaded. The
15214 command @code{help target} lists all possible targets rather than
15217 @kindex maint info sections
15218 @item maint info sections
15219 Another command that can give you extra information about program sections
15220 is @code{maint info sections}. In addition to the section information
15221 displayed by @code{info files}, this command displays the flags and file
15222 offset of each section in the executable and core dump files. In addition,
15223 @code{maint info sections} provides the following command options (which
15224 may be arbitrarily combined):
15228 Display sections for all loaded object files, including shared libraries.
15229 @item @var{sections}
15230 Display info only for named @var{sections}.
15231 @item @var{section-flags}
15232 Display info only for sections for which @var{section-flags} are true.
15233 The section flags that @value{GDBN} currently knows about are:
15236 Section will have space allocated in the process when loaded.
15237 Set for all sections except those containing debug information.
15239 Section will be loaded from the file into the child process memory.
15240 Set for pre-initialized code and data, clear for @code{.bss} sections.
15242 Section needs to be relocated before loading.
15244 Section cannot be modified by the child process.
15246 Section contains executable code only.
15248 Section contains data only (no executable code).
15250 Section will reside in ROM.
15252 Section contains data for constructor/destructor lists.
15254 Section is not empty.
15256 An instruction to the linker to not output the section.
15257 @item COFF_SHARED_LIBRARY
15258 A notification to the linker that the section contains
15259 COFF shared library information.
15261 Section contains common symbols.
15264 @kindex set trust-readonly-sections
15265 @cindex read-only sections
15266 @item set trust-readonly-sections on
15267 Tell @value{GDBN} that readonly sections in your object file
15268 really are read-only (i.e.@: that their contents will not change).
15269 In that case, @value{GDBN} can fetch values from these sections
15270 out of the object file, rather than from the target program.
15271 For some targets (notably embedded ones), this can be a significant
15272 enhancement to debugging performance.
15274 The default is off.
15276 @item set trust-readonly-sections off
15277 Tell @value{GDBN} not to trust readonly sections. This means that
15278 the contents of the section might change while the program is running,
15279 and must therefore be fetched from the target when needed.
15281 @item show trust-readonly-sections
15282 Show the current setting of trusting readonly sections.
15285 All file-specifying commands allow both absolute and relative file names
15286 as arguments. @value{GDBN} always converts the file name to an absolute file
15287 name and remembers it that way.
15289 @cindex shared libraries
15290 @anchor{Shared Libraries}
15291 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15292 and IBM RS/6000 AIX shared libraries.
15294 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15295 shared libraries. @xref{Expat}.
15297 @value{GDBN} automatically loads symbol definitions from shared libraries
15298 when you use the @code{run} command, or when you examine a core file.
15299 (Before you issue the @code{run} command, @value{GDBN} does not understand
15300 references to a function in a shared library, however---unless you are
15301 debugging a core file).
15303 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15304 automatically loads the symbols at the time of the @code{shl_load} call.
15306 @c FIXME: some @value{GDBN} release may permit some refs to undef
15307 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15308 @c FIXME...lib; check this from time to time when updating manual
15310 There are times, however, when you may wish to not automatically load
15311 symbol definitions from shared libraries, such as when they are
15312 particularly large or there are many of them.
15314 To control the automatic loading of shared library symbols, use the
15318 @kindex set auto-solib-add
15319 @item set auto-solib-add @var{mode}
15320 If @var{mode} is @code{on}, symbols from all shared object libraries
15321 will be loaded automatically when the inferior begins execution, you
15322 attach to an independently started inferior, or when the dynamic linker
15323 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15324 is @code{off}, symbols must be loaded manually, using the
15325 @code{sharedlibrary} command. The default value is @code{on}.
15327 @cindex memory used for symbol tables
15328 If your program uses lots of shared libraries with debug info that
15329 takes large amounts of memory, you can decrease the @value{GDBN}
15330 memory footprint by preventing it from automatically loading the
15331 symbols from shared libraries. To that end, type @kbd{set
15332 auto-solib-add off} before running the inferior, then load each
15333 library whose debug symbols you do need with @kbd{sharedlibrary
15334 @var{regexp}}, where @var{regexp} is a regular expression that matches
15335 the libraries whose symbols you want to be loaded.
15337 @kindex show auto-solib-add
15338 @item show auto-solib-add
15339 Display the current autoloading mode.
15342 @cindex load shared library
15343 To explicitly load shared library symbols, use the @code{sharedlibrary}
15347 @kindex info sharedlibrary
15349 @item info share @var{regex}
15350 @itemx info sharedlibrary @var{regex}
15351 Print the names of the shared libraries which are currently loaded
15352 that match @var{regex}. If @var{regex} is omitted then print
15353 all shared libraries that are loaded.
15355 @kindex sharedlibrary
15357 @item sharedlibrary @var{regex}
15358 @itemx share @var{regex}
15359 Load shared object library symbols for files matching a
15360 Unix regular expression.
15361 As with files loaded automatically, it only loads shared libraries
15362 required by your program for a core file or after typing @code{run}. If
15363 @var{regex} is omitted all shared libraries required by your program are
15366 @item nosharedlibrary
15367 @kindex nosharedlibrary
15368 @cindex unload symbols from shared libraries
15369 Unload all shared object library symbols. This discards all symbols
15370 that have been loaded from all shared libraries. Symbols from shared
15371 libraries that were loaded by explicit user requests are not
15375 Sometimes you may wish that @value{GDBN} stops and gives you control
15376 when any of shared library events happen. Use the @code{set
15377 stop-on-solib-events} command for this:
15380 @item set stop-on-solib-events
15381 @kindex set stop-on-solib-events
15382 This command controls whether @value{GDBN} should give you control
15383 when the dynamic linker notifies it about some shared library event.
15384 The most common event of interest is loading or unloading of a new
15387 @item show stop-on-solib-events
15388 @kindex show stop-on-solib-events
15389 Show whether @value{GDBN} stops and gives you control when shared
15390 library events happen.
15393 Shared libraries are also supported in many cross or remote debugging
15394 configurations. @value{GDBN} needs to have access to the target's libraries;
15395 this can be accomplished either by providing copies of the libraries
15396 on the host system, or by asking @value{GDBN} to automatically retrieve the
15397 libraries from the target. If copies of the target libraries are
15398 provided, they need to be the same as the target libraries, although the
15399 copies on the target can be stripped as long as the copies on the host are
15402 @cindex where to look for shared libraries
15403 For remote debugging, you need to tell @value{GDBN} where the target
15404 libraries are, so that it can load the correct copies---otherwise, it
15405 may try to load the host's libraries. @value{GDBN} has two variables
15406 to specify the search directories for target libraries.
15409 @cindex prefix for shared library file names
15410 @cindex system root, alternate
15411 @kindex set solib-absolute-prefix
15412 @kindex set sysroot
15413 @item set sysroot @var{path}
15414 Use @var{path} as the system root for the program being debugged. Any
15415 absolute shared library paths will be prefixed with @var{path}; many
15416 runtime loaders store the absolute paths to the shared library in the
15417 target program's memory. If you use @code{set sysroot} to find shared
15418 libraries, they need to be laid out in the same way that they are on
15419 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15422 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15423 retrieve the target libraries from the remote system. This is only
15424 supported when using a remote target that supports the @code{remote get}
15425 command (@pxref{File Transfer,,Sending files to a remote system}).
15426 The part of @var{path} following the initial @file{remote:}
15427 (if present) is used as system root prefix on the remote file system.
15428 @footnote{If you want to specify a local system root using a directory
15429 that happens to be named @file{remote:}, you need to use some equivalent
15430 variant of the name like @file{./remote:}.}
15432 For targets with an MS-DOS based filesystem, such as MS-Windows and
15433 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15434 absolute file name with @var{path}. But first, on Unix hosts,
15435 @value{GDBN} converts all backslash directory separators into forward
15436 slashes, because the backslash is not a directory separator on Unix:
15439 c:\foo\bar.dll @result{} c:/foo/bar.dll
15442 Then, @value{GDBN} attempts prefixing the target file name with
15443 @var{path}, and looks for the resulting file name in the host file
15447 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15450 If that does not find the shared library, @value{GDBN} tries removing
15451 the @samp{:} character from the drive spec, both for convenience, and,
15452 for the case of the host file system not supporting file names with
15456 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15459 This makes it possible to have a system root that mirrors a target
15460 with more than one drive. E.g., you may want to setup your local
15461 copies of the target system shared libraries like so (note @samp{c} vs
15465 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15466 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15467 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15471 and point the system root at @file{/path/to/sysroot}, so that
15472 @value{GDBN} can find the correct copies of both
15473 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15475 If that still does not find the shared library, @value{GDBN} tries
15476 removing the whole drive spec from the target file name:
15479 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15482 This last lookup makes it possible to not care about the drive name,
15483 if you don't want or need to.
15485 The @code{set solib-absolute-prefix} command is an alias for @code{set
15488 @cindex default system root
15489 @cindex @samp{--with-sysroot}
15490 You can set the default system root by using the configure-time
15491 @samp{--with-sysroot} option. If the system root is inside
15492 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15493 @samp{--exec-prefix}), then the default system root will be updated
15494 automatically if the installed @value{GDBN} is moved to a new
15497 @kindex show sysroot
15499 Display the current shared library prefix.
15501 @kindex set solib-search-path
15502 @item set solib-search-path @var{path}
15503 If this variable is set, @var{path} is a colon-separated list of
15504 directories to search for shared libraries. @samp{solib-search-path}
15505 is used after @samp{sysroot} fails to locate the library, or if the
15506 path to the library is relative instead of absolute. If you want to
15507 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15508 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15509 finding your host's libraries. @samp{sysroot} is preferred; setting
15510 it to a nonexistent directory may interfere with automatic loading
15511 of shared library symbols.
15513 @kindex show solib-search-path
15514 @item show solib-search-path
15515 Display the current shared library search path.
15517 @cindex DOS file-name semantics of file names.
15518 @kindex set target-file-system-kind (unix|dos-based|auto)
15519 @kindex show target-file-system-kind
15520 @item set target-file-system-kind @var{kind}
15521 Set assumed file system kind for target reported file names.
15523 Shared library file names as reported by the target system may not
15524 make sense as is on the system @value{GDBN} is running on. For
15525 example, when remote debugging a target that has MS-DOS based file
15526 system semantics, from a Unix host, the target may be reporting to
15527 @value{GDBN} a list of loaded shared libraries with file names such as
15528 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15529 drive letters, so the @samp{c:\} prefix is not normally understood as
15530 indicating an absolute file name, and neither is the backslash
15531 normally considered a directory separator character. In that case,
15532 the native file system would interpret this whole absolute file name
15533 as a relative file name with no directory components. This would make
15534 it impossible to point @value{GDBN} at a copy of the remote target's
15535 shared libraries on the host using @code{set sysroot}, and impractical
15536 with @code{set solib-search-path}. Setting
15537 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15538 to interpret such file names similarly to how the target would, and to
15539 map them to file names valid on @value{GDBN}'s native file system
15540 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15541 to one of the supported file system kinds. In that case, @value{GDBN}
15542 tries to determine the appropriate file system variant based on the
15543 current target's operating system (@pxref{ABI, ,Configuring the
15544 Current ABI}). The supported file system settings are:
15548 Instruct @value{GDBN} to assume the target file system is of Unix
15549 kind. Only file names starting the forward slash (@samp{/}) character
15550 are considered absolute, and the directory separator character is also
15554 Instruct @value{GDBN} to assume the target file system is DOS based.
15555 File names starting with either a forward slash, or a drive letter
15556 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15557 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15558 considered directory separators.
15561 Instruct @value{GDBN} to use the file system kind associated with the
15562 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15563 This is the default.
15568 @node Separate Debug Files
15569 @section Debugging Information in Separate Files
15570 @cindex separate debugging information files
15571 @cindex debugging information in separate files
15572 @cindex @file{.debug} subdirectories
15573 @cindex debugging information directory, global
15574 @cindex global debugging information directory
15575 @cindex build ID, and separate debugging files
15576 @cindex @file{.build-id} directory
15578 @value{GDBN} allows you to put a program's debugging information in a
15579 file separate from the executable itself, in a way that allows
15580 @value{GDBN} to find and load the debugging information automatically.
15581 Since debugging information can be very large---sometimes larger
15582 than the executable code itself---some systems distribute debugging
15583 information for their executables in separate files, which users can
15584 install only when they need to debug a problem.
15586 @value{GDBN} supports two ways of specifying the separate debug info
15591 The executable contains a @dfn{debug link} that specifies the name of
15592 the separate debug info file. The separate debug file's name is
15593 usually @file{@var{executable}.debug}, where @var{executable} is the
15594 name of the corresponding executable file without leading directories
15595 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15596 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15597 checksum for the debug file, which @value{GDBN} uses to validate that
15598 the executable and the debug file came from the same build.
15601 The executable contains a @dfn{build ID}, a unique bit string that is
15602 also present in the corresponding debug info file. (This is supported
15603 only on some operating systems, notably those which use the ELF format
15604 for binary files and the @sc{gnu} Binutils.) For more details about
15605 this feature, see the description of the @option{--build-id}
15606 command-line option in @ref{Options, , Command Line Options, ld.info,
15607 The GNU Linker}. The debug info file's name is not specified
15608 explicitly by the build ID, but can be computed from the build ID, see
15612 Depending on the way the debug info file is specified, @value{GDBN}
15613 uses two different methods of looking for the debug file:
15617 For the ``debug link'' method, @value{GDBN} looks up the named file in
15618 the directory of the executable file, then in a subdirectory of that
15619 directory named @file{.debug}, and finally under the global debug
15620 directory, in a subdirectory whose name is identical to the leading
15621 directories of the executable's absolute file name.
15624 For the ``build ID'' method, @value{GDBN} looks in the
15625 @file{.build-id} subdirectory of the global debug directory for a file
15626 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15627 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15628 are the rest of the bit string. (Real build ID strings are 32 or more
15629 hex characters, not 10.)
15632 So, for example, suppose you ask @value{GDBN} to debug
15633 @file{/usr/bin/ls}, which has a debug link that specifies the
15634 file @file{ls.debug}, and a build ID whose value in hex is
15635 @code{abcdef1234}. If the global debug directory is
15636 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15637 debug information files, in the indicated order:
15641 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15643 @file{/usr/bin/ls.debug}
15645 @file{/usr/bin/.debug/ls.debug}
15647 @file{/usr/lib/debug/usr/bin/ls.debug}.
15650 You can set the global debugging info directory's name, and view the
15651 name @value{GDBN} is currently using.
15655 @kindex set debug-file-directory
15656 @item set debug-file-directory @var{directories}
15657 Set the directories which @value{GDBN} searches for separate debugging
15658 information files to @var{directory}. Multiple directory components can be set
15659 concatenating them by a directory separator.
15661 @kindex show debug-file-directory
15662 @item show debug-file-directory
15663 Show the directories @value{GDBN} searches for separate debugging
15668 @cindex @code{.gnu_debuglink} sections
15669 @cindex debug link sections
15670 A debug link is a special section of the executable file named
15671 @code{.gnu_debuglink}. The section must contain:
15675 A filename, with any leading directory components removed, followed by
15678 zero to three bytes of padding, as needed to reach the next four-byte
15679 boundary within the section, and
15681 a four-byte CRC checksum, stored in the same endianness used for the
15682 executable file itself. The checksum is computed on the debugging
15683 information file's full contents by the function given below, passing
15684 zero as the @var{crc} argument.
15687 Any executable file format can carry a debug link, as long as it can
15688 contain a section named @code{.gnu_debuglink} with the contents
15691 @cindex @code{.note.gnu.build-id} sections
15692 @cindex build ID sections
15693 The build ID is a special section in the executable file (and in other
15694 ELF binary files that @value{GDBN} may consider). This section is
15695 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15696 It contains unique identification for the built files---the ID remains
15697 the same across multiple builds of the same build tree. The default
15698 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15699 content for the build ID string. The same section with an identical
15700 value is present in the original built binary with symbols, in its
15701 stripped variant, and in the separate debugging information file.
15703 The debugging information file itself should be an ordinary
15704 executable, containing a full set of linker symbols, sections, and
15705 debugging information. The sections of the debugging information file
15706 should have the same names, addresses, and sizes as the original file,
15707 but they need not contain any data---much like a @code{.bss} section
15708 in an ordinary executable.
15710 The @sc{gnu} binary utilities (Binutils) package includes the
15711 @samp{objcopy} utility that can produce
15712 the separated executable / debugging information file pairs using the
15713 following commands:
15716 @kbd{objcopy --only-keep-debug foo foo.debug}
15721 These commands remove the debugging
15722 information from the executable file @file{foo} and place it in the file
15723 @file{foo.debug}. You can use the first, second or both methods to link the
15728 The debug link method needs the following additional command to also leave
15729 behind a debug link in @file{foo}:
15732 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15735 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15736 a version of the @code{strip} command such that the command @kbd{strip foo -f
15737 foo.debug} has the same functionality as the two @code{objcopy} commands and
15738 the @code{ln -s} command above, together.
15741 Build ID gets embedded into the main executable using @code{ld --build-id} or
15742 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15743 compatibility fixes for debug files separation are present in @sc{gnu} binary
15744 utilities (Binutils) package since version 2.18.
15749 @cindex CRC algorithm definition
15750 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15751 IEEE 802.3 using the polynomial:
15753 @c TexInfo requires naked braces for multi-digit exponents for Tex
15754 @c output, but this causes HTML output to barf. HTML has to be set using
15755 @c raw commands. So we end up having to specify this equation in 2
15760 <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>
15761 + <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
15767 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15768 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15772 The function is computed byte at a time, taking the least
15773 significant bit of each byte first. The initial pattern
15774 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15775 the final result is inverted to ensure trailing zeros also affect the
15778 @emph{Note:} This is the same CRC polynomial as used in handling the
15779 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15780 , @value{GDBN} Remote Serial Protocol}). However in the
15781 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15782 significant bit first, and the result is not inverted, so trailing
15783 zeros have no effect on the CRC value.
15785 To complete the description, we show below the code of the function
15786 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15787 initially supplied @code{crc} argument means that an initial call to
15788 this function passing in zero will start computing the CRC using
15791 @kindex gnu_debuglink_crc32
15794 gnu_debuglink_crc32 (unsigned long crc,
15795 unsigned char *buf, size_t len)
15797 static const unsigned long crc32_table[256] =
15799 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15800 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15801 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15802 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15803 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15804 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15805 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15806 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15807 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15808 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15809 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15810 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15811 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15812 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15813 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15814 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15815 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15816 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15817 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15818 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15819 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15820 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15821 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15822 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15823 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15824 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15825 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15826 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15827 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15828 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15829 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15830 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15831 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15832 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15833 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15834 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15835 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15836 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15837 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15838 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15839 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15840 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15841 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15842 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15843 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15844 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15845 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15846 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15847 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15848 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15849 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15852 unsigned char *end;
15854 crc = ~crc & 0xffffffff;
15855 for (end = buf + len; buf < end; ++buf)
15856 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15857 return ~crc & 0xffffffff;
15862 This computation does not apply to the ``build ID'' method.
15866 @section Index Files Speed Up @value{GDBN}
15867 @cindex index files
15868 @cindex @samp{.gdb_index} section
15870 When @value{GDBN} finds a symbol file, it scans the symbols in the
15871 file in order to construct an internal symbol table. This lets most
15872 @value{GDBN} operations work quickly---at the cost of a delay early
15873 on. For large programs, this delay can be quite lengthy, so
15874 @value{GDBN} provides a way to build an index, which speeds up
15877 The index is stored as a section in the symbol file. @value{GDBN} can
15878 write the index to a file, then you can put it into the symbol file
15879 using @command{objcopy}.
15881 To create an index file, use the @code{save gdb-index} command:
15884 @item save gdb-index @var{directory}
15885 @kindex save gdb-index
15886 Create an index file for each symbol file currently known by
15887 @value{GDBN}. Each file is named after its corresponding symbol file,
15888 with @samp{.gdb-index} appended, and is written into the given
15892 Once you have created an index file you can merge it into your symbol
15893 file, here named @file{symfile}, using @command{objcopy}:
15896 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15897 --set-section-flags .gdb_index=readonly symfile symfile
15900 There are currently some limitation on indices. They only work when
15901 for DWARF debugging information, not stabs. And, they do not
15902 currently work for programs using Ada.
15904 @node Symbol Errors
15905 @section Errors Reading Symbol Files
15907 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15908 such as symbol types it does not recognize, or known bugs in compiler
15909 output. By default, @value{GDBN} does not notify you of such problems, since
15910 they are relatively common and primarily of interest to people
15911 debugging compilers. If you are interested in seeing information
15912 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15913 only one message about each such type of problem, no matter how many
15914 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15915 to see how many times the problems occur, with the @code{set
15916 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15919 The messages currently printed, and their meanings, include:
15922 @item inner block not inside outer block in @var{symbol}
15924 The symbol information shows where symbol scopes begin and end
15925 (such as at the start of a function or a block of statements). This
15926 error indicates that an inner scope block is not fully contained
15927 in its outer scope blocks.
15929 @value{GDBN} circumvents the problem by treating the inner block as if it had
15930 the same scope as the outer block. In the error message, @var{symbol}
15931 may be shown as ``@code{(don't know)}'' if the outer block is not a
15934 @item block at @var{address} out of order
15936 The symbol information for symbol scope blocks should occur in
15937 order of increasing addresses. This error indicates that it does not
15940 @value{GDBN} does not circumvent this problem, and has trouble
15941 locating symbols in the source file whose symbols it is reading. (You
15942 can often determine what source file is affected by specifying
15943 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15946 @item bad block start address patched
15948 The symbol information for a symbol scope block has a start address
15949 smaller than the address of the preceding source line. This is known
15950 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15952 @value{GDBN} circumvents the problem by treating the symbol scope block as
15953 starting on the previous source line.
15955 @item bad string table offset in symbol @var{n}
15958 Symbol number @var{n} contains a pointer into the string table which is
15959 larger than the size of the string table.
15961 @value{GDBN} circumvents the problem by considering the symbol to have the
15962 name @code{foo}, which may cause other problems if many symbols end up
15965 @item unknown symbol type @code{0x@var{nn}}
15967 The symbol information contains new data types that @value{GDBN} does
15968 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15969 uncomprehended information, in hexadecimal.
15971 @value{GDBN} circumvents the error by ignoring this symbol information.
15972 This usually allows you to debug your program, though certain symbols
15973 are not accessible. If you encounter such a problem and feel like
15974 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15975 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15976 and examine @code{*bufp} to see the symbol.
15978 @item stub type has NULL name
15980 @value{GDBN} could not find the full definition for a struct or class.
15982 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15983 The symbol information for a C@t{++} member function is missing some
15984 information that recent versions of the compiler should have output for
15987 @item info mismatch between compiler and debugger
15989 @value{GDBN} could not parse a type specification output by the compiler.
15994 @section GDB Data Files
15996 @cindex prefix for data files
15997 @value{GDBN} will sometimes read an auxiliary data file. These files
15998 are kept in a directory known as the @dfn{data directory}.
16000 You can set the data directory's name, and view the name @value{GDBN}
16001 is currently using.
16004 @kindex set data-directory
16005 @item set data-directory @var{directory}
16006 Set the directory which @value{GDBN} searches for auxiliary data files
16007 to @var{directory}.
16009 @kindex show data-directory
16010 @item show data-directory
16011 Show the directory @value{GDBN} searches for auxiliary data files.
16014 @cindex default data directory
16015 @cindex @samp{--with-gdb-datadir}
16016 You can set the default data directory by using the configure-time
16017 @samp{--with-gdb-datadir} option. If the data directory is inside
16018 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16019 @samp{--exec-prefix}), then the default data directory will be updated
16020 automatically if the installed @value{GDBN} is moved to a new
16023 The data directory may also be specified with the
16024 @code{--data-directory} command line option.
16025 @xref{Mode Options}.
16028 @chapter Specifying a Debugging Target
16030 @cindex debugging target
16031 A @dfn{target} is the execution environment occupied by your program.
16033 Often, @value{GDBN} runs in the same host environment as your program;
16034 in that case, the debugging target is specified as a side effect when
16035 you use the @code{file} or @code{core} commands. When you need more
16036 flexibility---for example, running @value{GDBN} on a physically separate
16037 host, or controlling a standalone system over a serial port or a
16038 realtime system over a TCP/IP connection---you can use the @code{target}
16039 command to specify one of the target types configured for @value{GDBN}
16040 (@pxref{Target Commands, ,Commands for Managing Targets}).
16042 @cindex target architecture
16043 It is possible to build @value{GDBN} for several different @dfn{target
16044 architectures}. When @value{GDBN} is built like that, you can choose
16045 one of the available architectures with the @kbd{set architecture}
16049 @kindex set architecture
16050 @kindex show architecture
16051 @item set architecture @var{arch}
16052 This command sets the current target architecture to @var{arch}. The
16053 value of @var{arch} can be @code{"auto"}, in addition to one of the
16054 supported architectures.
16056 @item show architecture
16057 Show the current target architecture.
16059 @item set processor
16061 @kindex set processor
16062 @kindex show processor
16063 These are alias commands for, respectively, @code{set architecture}
16064 and @code{show architecture}.
16068 * Active Targets:: Active targets
16069 * Target Commands:: Commands for managing targets
16070 * Byte Order:: Choosing target byte order
16073 @node Active Targets
16074 @section Active Targets
16076 @cindex stacking targets
16077 @cindex active targets
16078 @cindex multiple targets
16080 There are multiple classes of targets such as: processes, executable files or
16081 recording sessions. Core files belong to the process class, making core file
16082 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16083 on multiple active targets, one in each class. This allows you to (for
16084 example) start a process and inspect its activity, while still having access to
16085 the executable file after the process finishes. Or if you start process
16086 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16087 presented a virtual layer of the recording target, while the process target
16088 remains stopped at the chronologically last point of the process execution.
16090 Use the @code{core-file} and @code{exec-file} commands to select a new core
16091 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16092 specify as a target a process that is already running, use the @code{attach}
16093 command (@pxref{Attach, ,Debugging an Already-running Process}).
16095 @node Target Commands
16096 @section Commands for Managing Targets
16099 @item target @var{type} @var{parameters}
16100 Connects the @value{GDBN} host environment to a target machine or
16101 process. A target is typically a protocol for talking to debugging
16102 facilities. You use the argument @var{type} to specify the type or
16103 protocol of the target machine.
16105 Further @var{parameters} are interpreted by the target protocol, but
16106 typically include things like device names or host names to connect
16107 with, process numbers, and baud rates.
16109 The @code{target} command does not repeat if you press @key{RET} again
16110 after executing the command.
16112 @kindex help target
16114 Displays the names of all targets available. To display targets
16115 currently selected, use either @code{info target} or @code{info files}
16116 (@pxref{Files, ,Commands to Specify Files}).
16118 @item help target @var{name}
16119 Describe a particular target, including any parameters necessary to
16122 @kindex set gnutarget
16123 @item set gnutarget @var{args}
16124 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16125 knows whether it is reading an @dfn{executable},
16126 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16127 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16128 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16131 @emph{Warning:} To specify a file format with @code{set gnutarget},
16132 you must know the actual BFD name.
16136 @xref{Files, , Commands to Specify Files}.
16138 @kindex show gnutarget
16139 @item show gnutarget
16140 Use the @code{show gnutarget} command to display what file format
16141 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16142 @value{GDBN} will determine the file format for each file automatically,
16143 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16146 @cindex common targets
16147 Here are some common targets (available, or not, depending on the GDB
16152 @item target exec @var{program}
16153 @cindex executable file target
16154 An executable file. @samp{target exec @var{program}} is the same as
16155 @samp{exec-file @var{program}}.
16157 @item target core @var{filename}
16158 @cindex core dump file target
16159 A core dump file. @samp{target core @var{filename}} is the same as
16160 @samp{core-file @var{filename}}.
16162 @item target remote @var{medium}
16163 @cindex remote target
16164 A remote system connected to @value{GDBN} via a serial line or network
16165 connection. This command tells @value{GDBN} to use its own remote
16166 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16168 For example, if you have a board connected to @file{/dev/ttya} on the
16169 machine running @value{GDBN}, you could say:
16172 target remote /dev/ttya
16175 @code{target remote} supports the @code{load} command. This is only
16176 useful if you have some other way of getting the stub to the target
16177 system, and you can put it somewhere in memory where it won't get
16178 clobbered by the download.
16180 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16181 @cindex built-in simulator target
16182 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16190 works; however, you cannot assume that a specific memory map, device
16191 drivers, or even basic I/O is available, although some simulators do
16192 provide these. For info about any processor-specific simulator details,
16193 see the appropriate section in @ref{Embedded Processors, ,Embedded
16198 Some configurations may include these targets as well:
16202 @item target nrom @var{dev}
16203 @cindex NetROM ROM emulator target
16204 NetROM ROM emulator. This target only supports downloading.
16208 Different targets are available on different configurations of @value{GDBN};
16209 your configuration may have more or fewer targets.
16211 Many remote targets require you to download the executable's code once
16212 you've successfully established a connection. You may wish to control
16213 various aspects of this process.
16218 @kindex set hash@r{, for remote monitors}
16219 @cindex hash mark while downloading
16220 This command controls whether a hash mark @samp{#} is displayed while
16221 downloading a file to the remote monitor. If on, a hash mark is
16222 displayed after each S-record is successfully downloaded to the
16226 @kindex show hash@r{, for remote monitors}
16227 Show the current status of displaying the hash mark.
16229 @item set debug monitor
16230 @kindex set debug monitor
16231 @cindex display remote monitor communications
16232 Enable or disable display of communications messages between
16233 @value{GDBN} and the remote monitor.
16235 @item show debug monitor
16236 @kindex show debug monitor
16237 Show the current status of displaying communications between
16238 @value{GDBN} and the remote monitor.
16243 @kindex load @var{filename}
16244 @item load @var{filename}
16246 Depending on what remote debugging facilities are configured into
16247 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16248 is meant to make @var{filename} (an executable) available for debugging
16249 on the remote system---by downloading, or dynamic linking, for example.
16250 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16251 the @code{add-symbol-file} command.
16253 If your @value{GDBN} does not have a @code{load} command, attempting to
16254 execute it gets the error message ``@code{You can't do that when your
16255 target is @dots{}}''
16257 The file is loaded at whatever address is specified in the executable.
16258 For some object file formats, you can specify the load address when you
16259 link the program; for other formats, like a.out, the object file format
16260 specifies a fixed address.
16261 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16263 Depending on the remote side capabilities, @value{GDBN} may be able to
16264 load programs into flash memory.
16266 @code{load} does not repeat if you press @key{RET} again after using it.
16270 @section Choosing Target Byte Order
16272 @cindex choosing target byte order
16273 @cindex target byte order
16275 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16276 offer the ability to run either big-endian or little-endian byte
16277 orders. Usually the executable or symbol will include a bit to
16278 designate the endian-ness, and you will not need to worry about
16279 which to use. However, you may still find it useful to adjust
16280 @value{GDBN}'s idea of processor endian-ness manually.
16284 @item set endian big
16285 Instruct @value{GDBN} to assume the target is big-endian.
16287 @item set endian little
16288 Instruct @value{GDBN} to assume the target is little-endian.
16290 @item set endian auto
16291 Instruct @value{GDBN} to use the byte order associated with the
16295 Display @value{GDBN}'s current idea of the target byte order.
16299 Note that these commands merely adjust interpretation of symbolic
16300 data on the host, and that they have absolutely no effect on the
16304 @node Remote Debugging
16305 @chapter Debugging Remote Programs
16306 @cindex remote debugging
16308 If you are trying to debug a program running on a machine that cannot run
16309 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16310 For example, you might use remote debugging on an operating system kernel,
16311 or on a small system which does not have a general purpose operating system
16312 powerful enough to run a full-featured debugger.
16314 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16315 to make this work with particular debugging targets. In addition,
16316 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16317 but not specific to any particular target system) which you can use if you
16318 write the remote stubs---the code that runs on the remote system to
16319 communicate with @value{GDBN}.
16321 Other remote targets may be available in your
16322 configuration of @value{GDBN}; use @code{help target} to list them.
16325 * Connecting:: Connecting to a remote target
16326 * File Transfer:: Sending files to a remote system
16327 * Server:: Using the gdbserver program
16328 * Remote Configuration:: Remote configuration
16329 * Remote Stub:: Implementing a remote stub
16333 @section Connecting to a Remote Target
16335 On the @value{GDBN} host machine, you will need an unstripped copy of
16336 your program, since @value{GDBN} needs symbol and debugging information.
16337 Start up @value{GDBN} as usual, using the name of the local copy of your
16338 program as the first argument.
16340 @cindex @code{target remote}
16341 @value{GDBN} can communicate with the target over a serial line, or
16342 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16343 each case, @value{GDBN} uses the same protocol for debugging your
16344 program; only the medium carrying the debugging packets varies. The
16345 @code{target remote} command establishes a connection to the target.
16346 Its arguments indicate which medium to use:
16350 @item target remote @var{serial-device}
16351 @cindex serial line, @code{target remote}
16352 Use @var{serial-device} to communicate with the target. For example,
16353 to use a serial line connected to the device named @file{/dev/ttyb}:
16356 target remote /dev/ttyb
16359 If you're using a serial line, you may want to give @value{GDBN} the
16360 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16361 (@pxref{Remote Configuration, set remotebaud}) before the
16362 @code{target} command.
16364 @item target remote @code{@var{host}:@var{port}}
16365 @itemx target remote @code{tcp:@var{host}:@var{port}}
16366 @cindex @acronym{TCP} port, @code{target remote}
16367 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16368 The @var{host} may be either a host name or a numeric @acronym{IP}
16369 address; @var{port} must be a decimal number. The @var{host} could be
16370 the target machine itself, if it is directly connected to the net, or
16371 it might be a terminal server which in turn has a serial line to the
16374 For example, to connect to port 2828 on a terminal server named
16378 target remote manyfarms:2828
16381 If your remote target is actually running on the same machine as your
16382 debugger session (e.g.@: a simulator for your target running on the
16383 same host), you can omit the hostname. For example, to connect to
16384 port 1234 on your local machine:
16387 target remote :1234
16391 Note that the colon is still required here.
16393 @item target remote @code{udp:@var{host}:@var{port}}
16394 @cindex @acronym{UDP} port, @code{target remote}
16395 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16396 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16399 target remote udp:manyfarms:2828
16402 When using a @acronym{UDP} connection for remote debugging, you should
16403 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16404 can silently drop packets on busy or unreliable networks, which will
16405 cause havoc with your debugging session.
16407 @item target remote | @var{command}
16408 @cindex pipe, @code{target remote} to
16409 Run @var{command} in the background and communicate with it using a
16410 pipe. The @var{command} is a shell command, to be parsed and expanded
16411 by the system's command shell, @code{/bin/sh}; it should expect remote
16412 protocol packets on its standard input, and send replies on its
16413 standard output. You could use this to run a stand-alone simulator
16414 that speaks the remote debugging protocol, to make net connections
16415 using programs like @code{ssh}, or for other similar tricks.
16417 If @var{command} closes its standard output (perhaps by exiting),
16418 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16419 program has already exited, this will have no effect.)
16423 Once the connection has been established, you can use all the usual
16424 commands to examine and change data. The remote program is already
16425 running; you can use @kbd{step} and @kbd{continue}, and you do not
16426 need to use @kbd{run}.
16428 @cindex interrupting remote programs
16429 @cindex remote programs, interrupting
16430 Whenever @value{GDBN} is waiting for the remote program, if you type the
16431 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16432 program. This may or may not succeed, depending in part on the hardware
16433 and the serial drivers the remote system uses. If you type the
16434 interrupt character once again, @value{GDBN} displays this prompt:
16437 Interrupted while waiting for the program.
16438 Give up (and stop debugging it)? (y or n)
16441 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16442 (If you decide you want to try again later, you can use @samp{target
16443 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16444 goes back to waiting.
16447 @kindex detach (remote)
16449 When you have finished debugging the remote program, you can use the
16450 @code{detach} command to release it from @value{GDBN} control.
16451 Detaching from the target normally resumes its execution, but the results
16452 will depend on your particular remote stub. After the @code{detach}
16453 command, @value{GDBN} is free to connect to another target.
16457 The @code{disconnect} command behaves like @code{detach}, except that
16458 the target is generally not resumed. It will wait for @value{GDBN}
16459 (this instance or another one) to connect and continue debugging. After
16460 the @code{disconnect} command, @value{GDBN} is again free to connect to
16463 @cindex send command to remote monitor
16464 @cindex extend @value{GDBN} for remote targets
16465 @cindex add new commands for external monitor
16467 @item monitor @var{cmd}
16468 This command allows you to send arbitrary commands directly to the
16469 remote monitor. Since @value{GDBN} doesn't care about the commands it
16470 sends like this, this command is the way to extend @value{GDBN}---you
16471 can add new commands that only the external monitor will understand
16475 @node File Transfer
16476 @section Sending files to a remote system
16477 @cindex remote target, file transfer
16478 @cindex file transfer
16479 @cindex sending files to remote systems
16481 Some remote targets offer the ability to transfer files over the same
16482 connection used to communicate with @value{GDBN}. This is convenient
16483 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16484 running @code{gdbserver} over a network interface. For other targets,
16485 e.g.@: embedded devices with only a single serial port, this may be
16486 the only way to upload or download files.
16488 Not all remote targets support these commands.
16492 @item remote put @var{hostfile} @var{targetfile}
16493 Copy file @var{hostfile} from the host system (the machine running
16494 @value{GDBN}) to @var{targetfile} on the target system.
16497 @item remote get @var{targetfile} @var{hostfile}
16498 Copy file @var{targetfile} from the target system to @var{hostfile}
16499 on the host system.
16501 @kindex remote delete
16502 @item remote delete @var{targetfile}
16503 Delete @var{targetfile} from the target system.
16508 @section Using the @code{gdbserver} Program
16511 @cindex remote connection without stubs
16512 @code{gdbserver} is a control program for Unix-like systems, which
16513 allows you to connect your program with a remote @value{GDBN} via
16514 @code{target remote}---but without linking in the usual debugging stub.
16516 @code{gdbserver} is not a complete replacement for the debugging stubs,
16517 because it requires essentially the same operating-system facilities
16518 that @value{GDBN} itself does. In fact, a system that can run
16519 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16520 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16521 because it is a much smaller program than @value{GDBN} itself. It is
16522 also easier to port than all of @value{GDBN}, so you may be able to get
16523 started more quickly on a new system by using @code{gdbserver}.
16524 Finally, if you develop code for real-time systems, you may find that
16525 the tradeoffs involved in real-time operation make it more convenient to
16526 do as much development work as possible on another system, for example
16527 by cross-compiling. You can use @code{gdbserver} to make a similar
16528 choice for debugging.
16530 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16531 or a TCP connection, using the standard @value{GDBN} remote serial
16535 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16536 Do not run @code{gdbserver} connected to any public network; a
16537 @value{GDBN} connection to @code{gdbserver} provides access to the
16538 target system with the same privileges as the user running
16542 @subsection Running @code{gdbserver}
16543 @cindex arguments, to @code{gdbserver}
16544 @cindex @code{gdbserver}, command-line arguments
16546 Run @code{gdbserver} on the target system. You need a copy of the
16547 program you want to debug, including any libraries it requires.
16548 @code{gdbserver} does not need your program's symbol table, so you can
16549 strip the program if necessary to save space. @value{GDBN} on the host
16550 system does all the symbol handling.
16552 To use the server, you must tell it how to communicate with @value{GDBN};
16553 the name of your program; and the arguments for your program. The usual
16557 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16560 @var{comm} is either a device name (to use a serial line) or a TCP
16561 hostname and portnumber. For example, to debug Emacs with the argument
16562 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16566 target> gdbserver /dev/com1 emacs foo.txt
16569 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16572 To use a TCP connection instead of a serial line:
16575 target> gdbserver host:2345 emacs foo.txt
16578 The only difference from the previous example is the first argument,
16579 specifying that you are communicating with the host @value{GDBN} via
16580 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16581 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16582 (Currently, the @samp{host} part is ignored.) You can choose any number
16583 you want for the port number as long as it does not conflict with any
16584 TCP ports already in use on the target system (for example, @code{23} is
16585 reserved for @code{telnet}).@footnote{If you choose a port number that
16586 conflicts with another service, @code{gdbserver} prints an error message
16587 and exits.} You must use the same port number with the host @value{GDBN}
16588 @code{target remote} command.
16590 @subsubsection Attaching to a Running Program
16591 @cindex attach to a program, @code{gdbserver}
16592 @cindex @option{--attach}, @code{gdbserver} option
16594 On some targets, @code{gdbserver} can also attach to running programs.
16595 This is accomplished via the @code{--attach} argument. The syntax is:
16598 target> gdbserver --attach @var{comm} @var{pid}
16601 @var{pid} is the process ID of a currently running process. It isn't necessary
16602 to point @code{gdbserver} at a binary for the running process.
16605 You can debug processes by name instead of process ID if your target has the
16606 @code{pidof} utility:
16609 target> gdbserver --attach @var{comm} `pidof @var{program}`
16612 In case more than one copy of @var{program} is running, or @var{program}
16613 has multiple threads, most versions of @code{pidof} support the
16614 @code{-s} option to only return the first process ID.
16616 @subsubsection Multi-Process Mode for @code{gdbserver}
16617 @cindex @code{gdbserver}, multiple processes
16618 @cindex multiple processes with @code{gdbserver}
16620 When you connect to @code{gdbserver} using @code{target remote},
16621 @code{gdbserver} debugs the specified program only once. When the
16622 program exits, or you detach from it, @value{GDBN} closes the connection
16623 and @code{gdbserver} exits.
16625 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16626 enters multi-process mode. When the debugged program exits, or you
16627 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16628 though no program is running. The @code{run} and @code{attach}
16629 commands instruct @code{gdbserver} to run or attach to a new program.
16630 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16631 remote exec-file}) to select the program to run. Command line
16632 arguments are supported, except for wildcard expansion and I/O
16633 redirection (@pxref{Arguments}).
16635 @cindex @option{--multi}, @code{gdbserver} option
16636 To start @code{gdbserver} without supplying an initial command to run
16637 or process ID to attach, use the @option{--multi} command line option.
16638 Then you can connect using @kbd{target extended-remote} and start
16639 the program you want to debug.
16641 In multi-process mode @code{gdbserver} does not automatically exit unless you
16642 use the option @option{--once}. You can terminate it by using
16643 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16644 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16645 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16646 @option{--multi} option to @code{gdbserver} has no influence on that.
16648 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16650 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16652 @code{gdbserver} normally terminates after all of its debugged processes have
16653 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16654 extended-remote}, @code{gdbserver} stays running even with no processes left.
16655 @value{GDBN} normally terminates the spawned debugged process on its exit,
16656 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16657 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16658 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16659 stays running even in the @kbd{target remote} mode.
16661 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16662 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16663 completeness, at most one @value{GDBN} can be connected at a time.
16665 @cindex @option{--once}, @code{gdbserver} option
16666 By default, @code{gdbserver} keeps the listening TCP port open, so that
16667 additional connections are possible. However, if you start @code{gdbserver}
16668 with the @option{--once} option, it will stop listening for any further
16669 connection attempts after connecting to the first @value{GDBN} session. This
16670 means no further connections to @code{gdbserver} will be possible after the
16671 first one. It also means @code{gdbserver} will terminate after the first
16672 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16673 connections and even in the @kbd{target extended-remote} mode. The
16674 @option{--once} option allows reusing the same port number for connecting to
16675 multiple instances of @code{gdbserver} running on the same host, since each
16676 instance closes its port after the first connection.
16678 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16680 @cindex @option{--debug}, @code{gdbserver} option
16681 The @option{--debug} option tells @code{gdbserver} to display extra
16682 status information about the debugging process.
16683 @cindex @option{--remote-debug}, @code{gdbserver} option
16684 The @option{--remote-debug} option tells @code{gdbserver} to display
16685 remote protocol debug output. These options are intended for
16686 @code{gdbserver} development and for bug reports to the developers.
16688 @cindex @option{--wrapper}, @code{gdbserver} option
16689 The @option{--wrapper} option specifies a wrapper to launch programs
16690 for debugging. The option should be followed by the name of the
16691 wrapper, then any command-line arguments to pass to the wrapper, then
16692 @kbd{--} indicating the end of the wrapper arguments.
16694 @code{gdbserver} runs the specified wrapper program with a combined
16695 command line including the wrapper arguments, then the name of the
16696 program to debug, then any arguments to the program. The wrapper
16697 runs until it executes your program, and then @value{GDBN} gains control.
16699 You can use any program that eventually calls @code{execve} with
16700 its arguments as a wrapper. Several standard Unix utilities do
16701 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16702 with @code{exec "$@@"} will also work.
16704 For example, you can use @code{env} to pass an environment variable to
16705 the debugged program, without setting the variable in @code{gdbserver}'s
16709 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16712 @subsection Connecting to @code{gdbserver}
16714 Run @value{GDBN} on the host system.
16716 First make sure you have the necessary symbol files. Load symbols for
16717 your application using the @code{file} command before you connect. Use
16718 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16719 was compiled with the correct sysroot using @code{--with-sysroot}).
16721 The symbol file and target libraries must exactly match the executable
16722 and libraries on the target, with one exception: the files on the host
16723 system should not be stripped, even if the files on the target system
16724 are. Mismatched or missing files will lead to confusing results
16725 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16726 files may also prevent @code{gdbserver} from debugging multi-threaded
16729 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16730 For TCP connections, you must start up @code{gdbserver} prior to using
16731 the @code{target remote} command. Otherwise you may get an error whose
16732 text depends on the host system, but which usually looks something like
16733 @samp{Connection refused}. Don't use the @code{load}
16734 command in @value{GDBN} when using @code{gdbserver}, since the program is
16735 already on the target.
16737 @subsection Monitor Commands for @code{gdbserver}
16738 @cindex monitor commands, for @code{gdbserver}
16739 @anchor{Monitor Commands for gdbserver}
16741 During a @value{GDBN} session using @code{gdbserver}, you can use the
16742 @code{monitor} command to send special requests to @code{gdbserver}.
16743 Here are the available commands.
16747 List the available monitor commands.
16749 @item monitor set debug 0
16750 @itemx monitor set debug 1
16751 Disable or enable general debugging messages.
16753 @item monitor set remote-debug 0
16754 @itemx monitor set remote-debug 1
16755 Disable or enable specific debugging messages associated with the remote
16756 protocol (@pxref{Remote Protocol}).
16758 @item monitor set libthread-db-search-path [PATH]
16759 @cindex gdbserver, search path for @code{libthread_db}
16760 When this command is issued, @var{path} is a colon-separated list of
16761 directories to search for @code{libthread_db} (@pxref{Threads,,set
16762 libthread-db-search-path}). If you omit @var{path},
16763 @samp{libthread-db-search-path} will be reset to its default value.
16765 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16766 not supported in @code{gdbserver}.
16769 Tell gdbserver to exit immediately. This command should be followed by
16770 @code{disconnect} to close the debugging session. @code{gdbserver} will
16771 detach from any attached processes and kill any processes it created.
16772 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16773 of a multi-process mode debug session.
16777 @subsection Tracepoints support in @code{gdbserver}
16778 @cindex tracepoints support in @code{gdbserver}
16780 On some targets, @code{gdbserver} supports tracepoints, fast
16781 tracepoints and static tracepoints.
16783 For fast or static tracepoints to work, a special library called the
16784 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16785 This library is built and distributed as an integral part of
16786 @code{gdbserver}. In addition, support for static tracepoints
16787 requires building the in-process agent library with static tracepoints
16788 support. At present, the UST (LTTng Userspace Tracer,
16789 @url{http://lttng.org/ust}) tracing engine is supported. This support
16790 is automatically available if UST development headers are found in the
16791 standard include path when @code{gdbserver} is built, or if
16792 @code{gdbserver} was explicitly configured using @option{--with-ust}
16793 to point at such headers. You can explicitly disable the support
16794 using @option{--with-ust=no}.
16796 There are several ways to load the in-process agent in your program:
16799 @item Specifying it as dependency at link time
16801 You can link your program dynamically with the in-process agent
16802 library. On most systems, this is accomplished by adding
16803 @code{-linproctrace} to the link command.
16805 @item Using the system's preloading mechanisms
16807 You can force loading the in-process agent at startup time by using
16808 your system's support for preloading shared libraries. Many Unixes
16809 support the concept of preloading user defined libraries. In most
16810 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16811 in the environment. See also the description of @code{gdbserver}'s
16812 @option{--wrapper} command line option.
16814 @item Using @value{GDBN} to force loading the agent at run time
16816 On some systems, you can force the inferior to load a shared library,
16817 by calling a dynamic loader function in the inferior that takes care
16818 of dynamically looking up and loading a shared library. On most Unix
16819 systems, the function is @code{dlopen}. You'll use the @code{call}
16820 command for that. For example:
16823 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16826 Note that on most Unix systems, for the @code{dlopen} function to be
16827 available, the program needs to be linked with @code{-ldl}.
16830 On systems that have a userspace dynamic loader, like most Unix
16831 systems, when you connect to @code{gdbserver} using @code{target
16832 remote}, you'll find that the program is stopped at the dynamic
16833 loader's entry point, and no shared library has been loaded in the
16834 program's address space yet, including the in-process agent. In that
16835 case, before being able to use any of the fast or static tracepoints
16836 features, you need to let the loader run and load the shared
16837 libraries. The simplest way to do that is to run the program to the
16838 main procedure. E.g., if debugging a C or C@t{++} program, start
16839 @code{gdbserver} like so:
16842 $ gdbserver :9999 myprogram
16845 Start GDB and connect to @code{gdbserver} like so, and run to main:
16849 (@value{GDBP}) target remote myhost:9999
16850 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16851 (@value{GDBP}) b main
16852 (@value{GDBP}) continue
16855 The in-process tracing agent library should now be loaded into the
16856 process; you can confirm it with the @code{info sharedlibrary}
16857 command, which will list @file{libinproctrace.so} as loaded in the
16858 process. You are now ready to install fast tracepoints, list static
16859 tracepoint markers, probe static tracepoints markers, and start
16862 @node Remote Configuration
16863 @section Remote Configuration
16866 @kindex show remote
16867 This section documents the configuration options available when
16868 debugging remote programs. For the options related to the File I/O
16869 extensions of the remote protocol, see @ref{system,
16870 system-call-allowed}.
16873 @item set remoteaddresssize @var{bits}
16874 @cindex address size for remote targets
16875 @cindex bits in remote address
16876 Set the maximum size of address in a memory packet to the specified
16877 number of bits. @value{GDBN} will mask off the address bits above
16878 that number, when it passes addresses to the remote target. The
16879 default value is the number of bits in the target's address.
16881 @item show remoteaddresssize
16882 Show the current value of remote address size in bits.
16884 @item set remotebaud @var{n}
16885 @cindex baud rate for remote targets
16886 Set the baud rate for the remote serial I/O to @var{n} baud. The
16887 value is used to set the speed of the serial port used for debugging
16890 @item show remotebaud
16891 Show the current speed of the remote connection.
16893 @item set remotebreak
16894 @cindex interrupt remote programs
16895 @cindex BREAK signal instead of Ctrl-C
16896 @anchor{set remotebreak}
16897 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16898 when you type @kbd{Ctrl-c} to interrupt the program running
16899 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16900 character instead. The default is off, since most remote systems
16901 expect to see @samp{Ctrl-C} as the interrupt signal.
16903 @item show remotebreak
16904 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16905 interrupt the remote program.
16907 @item set remoteflow on
16908 @itemx set remoteflow off
16909 @kindex set remoteflow
16910 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16911 on the serial port used to communicate to the remote target.
16913 @item show remoteflow
16914 @kindex show remoteflow
16915 Show the current setting of hardware flow control.
16917 @item set remotelogbase @var{base}
16918 Set the base (a.k.a.@: radix) of logging serial protocol
16919 communications to @var{base}. Supported values of @var{base} are:
16920 @code{ascii}, @code{octal}, and @code{hex}. The default is
16923 @item show remotelogbase
16924 Show the current setting of the radix for logging remote serial
16927 @item set remotelogfile @var{file}
16928 @cindex record serial communications on file
16929 Record remote serial communications on the named @var{file}. The
16930 default is not to record at all.
16932 @item show remotelogfile.
16933 Show the current setting of the file name on which to record the
16934 serial communications.
16936 @item set remotetimeout @var{num}
16937 @cindex timeout for serial communications
16938 @cindex remote timeout
16939 Set the timeout limit to wait for the remote target to respond to
16940 @var{num} seconds. The default is 2 seconds.
16942 @item show remotetimeout
16943 Show the current number of seconds to wait for the remote target
16946 @cindex limit hardware breakpoints and watchpoints
16947 @cindex remote target, limit break- and watchpoints
16948 @anchor{set remote hardware-watchpoint-limit}
16949 @anchor{set remote hardware-breakpoint-limit}
16950 @item set remote hardware-watchpoint-limit @var{limit}
16951 @itemx set remote hardware-breakpoint-limit @var{limit}
16952 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16953 watchpoints. A limit of -1, the default, is treated as unlimited.
16955 @cindex limit hardware watchpoints length
16956 @cindex remote target, limit watchpoints length
16957 @anchor{set remote hardware-watchpoint-length-limit}
16958 @item set remote hardware-watchpoint-length-limit @var{limit}
16959 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
16960 a remote hardware watchpoint. A limit of -1, the default, is treated
16963 @item show remote hardware-watchpoint-length-limit
16964 Show the current limit (in bytes) of the maximum length of
16965 a remote hardware watchpoint.
16967 @item set remote exec-file @var{filename}
16968 @itemx show remote exec-file
16969 @anchor{set remote exec-file}
16970 @cindex executable file, for remote target
16971 Select the file used for @code{run} with @code{target
16972 extended-remote}. This should be set to a filename valid on the
16973 target system. If it is not set, the target will use a default
16974 filename (e.g.@: the last program run).
16976 @item set remote interrupt-sequence
16977 @cindex interrupt remote programs
16978 @cindex select Ctrl-C, BREAK or BREAK-g
16979 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16980 @samp{BREAK-g} as the
16981 sequence to the remote target in order to interrupt the execution.
16982 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16983 is high level of serial line for some certain time.
16984 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16985 It is @code{BREAK} signal followed by character @code{g}.
16987 @item show interrupt-sequence
16988 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16989 is sent by @value{GDBN} to interrupt the remote program.
16990 @code{BREAK-g} is BREAK signal followed by @code{g} and
16991 also known as Magic SysRq g.
16993 @item set remote interrupt-on-connect
16994 @cindex send interrupt-sequence on start
16995 Specify whether interrupt-sequence is sent to remote target when
16996 @value{GDBN} connects to it. This is mostly needed when you debug
16997 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16998 which is known as Magic SysRq g in order to connect @value{GDBN}.
17000 @item show interrupt-on-connect
17001 Show whether interrupt-sequence is sent
17002 to remote target when @value{GDBN} connects to it.
17006 @item set tcp auto-retry on
17007 @cindex auto-retry, for remote TCP target
17008 Enable auto-retry for remote TCP connections. This is useful if the remote
17009 debugging agent is launched in parallel with @value{GDBN}; there is a race
17010 condition because the agent may not become ready to accept the connection
17011 before @value{GDBN} attempts to connect. When auto-retry is
17012 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17013 to establish the connection using the timeout specified by
17014 @code{set tcp connect-timeout}.
17016 @item set tcp auto-retry off
17017 Do not auto-retry failed TCP connections.
17019 @item show tcp auto-retry
17020 Show the current auto-retry setting.
17022 @item set tcp connect-timeout @var{seconds}
17023 @cindex connection timeout, for remote TCP target
17024 @cindex timeout, for remote target connection
17025 Set the timeout for establishing a TCP connection to the remote target to
17026 @var{seconds}. The timeout affects both polling to retry failed connections
17027 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17028 that are merely slow to complete, and represents an approximate cumulative
17031 @item show tcp connect-timeout
17032 Show the current connection timeout setting.
17035 @cindex remote packets, enabling and disabling
17036 The @value{GDBN} remote protocol autodetects the packets supported by
17037 your debugging stub. If you need to override the autodetection, you
17038 can use these commands to enable or disable individual packets. Each
17039 packet can be set to @samp{on} (the remote target supports this
17040 packet), @samp{off} (the remote target does not support this packet),
17041 or @samp{auto} (detect remote target support for this packet). They
17042 all default to @samp{auto}. For more information about each packet,
17043 see @ref{Remote Protocol}.
17045 During normal use, you should not have to use any of these commands.
17046 If you do, that may be a bug in your remote debugging stub, or a bug
17047 in @value{GDBN}. You may want to report the problem to the
17048 @value{GDBN} developers.
17050 For each packet @var{name}, the command to enable or disable the
17051 packet is @code{set remote @var{name}-packet}. The available settings
17054 @multitable @columnfractions 0.28 0.32 0.25
17057 @tab Related Features
17059 @item @code{fetch-register}
17061 @tab @code{info registers}
17063 @item @code{set-register}
17067 @item @code{binary-download}
17069 @tab @code{load}, @code{set}
17071 @item @code{read-aux-vector}
17072 @tab @code{qXfer:auxv:read}
17073 @tab @code{info auxv}
17075 @item @code{symbol-lookup}
17076 @tab @code{qSymbol}
17077 @tab Detecting multiple threads
17079 @item @code{attach}
17080 @tab @code{vAttach}
17083 @item @code{verbose-resume}
17085 @tab Stepping or resuming multiple threads
17091 @item @code{software-breakpoint}
17095 @item @code{hardware-breakpoint}
17099 @item @code{write-watchpoint}
17103 @item @code{read-watchpoint}
17107 @item @code{access-watchpoint}
17111 @item @code{target-features}
17112 @tab @code{qXfer:features:read}
17113 @tab @code{set architecture}
17115 @item @code{library-info}
17116 @tab @code{qXfer:libraries:read}
17117 @tab @code{info sharedlibrary}
17119 @item @code{memory-map}
17120 @tab @code{qXfer:memory-map:read}
17121 @tab @code{info mem}
17123 @item @code{read-sdata-object}
17124 @tab @code{qXfer:sdata:read}
17125 @tab @code{print $_sdata}
17127 @item @code{read-spu-object}
17128 @tab @code{qXfer:spu:read}
17129 @tab @code{info spu}
17131 @item @code{write-spu-object}
17132 @tab @code{qXfer:spu:write}
17133 @tab @code{info spu}
17135 @item @code{read-siginfo-object}
17136 @tab @code{qXfer:siginfo:read}
17137 @tab @code{print $_siginfo}
17139 @item @code{write-siginfo-object}
17140 @tab @code{qXfer:siginfo:write}
17141 @tab @code{set $_siginfo}
17143 @item @code{threads}
17144 @tab @code{qXfer:threads:read}
17145 @tab @code{info threads}
17147 @item @code{get-thread-local-@*storage-address}
17148 @tab @code{qGetTLSAddr}
17149 @tab Displaying @code{__thread} variables
17151 @item @code{get-thread-information-block-address}
17152 @tab @code{qGetTIBAddr}
17153 @tab Display MS-Windows Thread Information Block.
17155 @item @code{search-memory}
17156 @tab @code{qSearch:memory}
17159 @item @code{supported-packets}
17160 @tab @code{qSupported}
17161 @tab Remote communications parameters
17163 @item @code{pass-signals}
17164 @tab @code{QPassSignals}
17165 @tab @code{handle @var{signal}}
17167 @item @code{hostio-close-packet}
17168 @tab @code{vFile:close}
17169 @tab @code{remote get}, @code{remote put}
17171 @item @code{hostio-open-packet}
17172 @tab @code{vFile:open}
17173 @tab @code{remote get}, @code{remote put}
17175 @item @code{hostio-pread-packet}
17176 @tab @code{vFile:pread}
17177 @tab @code{remote get}, @code{remote put}
17179 @item @code{hostio-pwrite-packet}
17180 @tab @code{vFile:pwrite}
17181 @tab @code{remote get}, @code{remote put}
17183 @item @code{hostio-unlink-packet}
17184 @tab @code{vFile:unlink}
17185 @tab @code{remote delete}
17187 @item @code{noack-packet}
17188 @tab @code{QStartNoAckMode}
17189 @tab Packet acknowledgment
17191 @item @code{osdata}
17192 @tab @code{qXfer:osdata:read}
17193 @tab @code{info os}
17195 @item @code{query-attached}
17196 @tab @code{qAttached}
17197 @tab Querying remote process attach state.
17199 @item @code{traceframe-info}
17200 @tab @code{qXfer:traceframe-info:read}
17201 @tab Traceframe info
17203 @item @code{disable-randomization}
17204 @tab @code{QDisableRandomization}
17205 @tab @code{set disable-randomization}
17209 @section Implementing a Remote Stub
17211 @cindex debugging stub, example
17212 @cindex remote stub, example
17213 @cindex stub example, remote debugging
17214 The stub files provided with @value{GDBN} implement the target side of the
17215 communication protocol, and the @value{GDBN} side is implemented in the
17216 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17217 these subroutines to communicate, and ignore the details. (If you're
17218 implementing your own stub file, you can still ignore the details: start
17219 with one of the existing stub files. @file{sparc-stub.c} is the best
17220 organized, and therefore the easiest to read.)
17222 @cindex remote serial debugging, overview
17223 To debug a program running on another machine (the debugging
17224 @dfn{target} machine), you must first arrange for all the usual
17225 prerequisites for the program to run by itself. For example, for a C
17230 A startup routine to set up the C runtime environment; these usually
17231 have a name like @file{crt0}. The startup routine may be supplied by
17232 your hardware supplier, or you may have to write your own.
17235 A C subroutine library to support your program's
17236 subroutine calls, notably managing input and output.
17239 A way of getting your program to the other machine---for example, a
17240 download program. These are often supplied by the hardware
17241 manufacturer, but you may have to write your own from hardware
17245 The next step is to arrange for your program to use a serial port to
17246 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17247 machine). In general terms, the scheme looks like this:
17251 @value{GDBN} already understands how to use this protocol; when everything
17252 else is set up, you can simply use the @samp{target remote} command
17253 (@pxref{Targets,,Specifying a Debugging Target}).
17255 @item On the target,
17256 you must link with your program a few special-purpose subroutines that
17257 implement the @value{GDBN} remote serial protocol. The file containing these
17258 subroutines is called a @dfn{debugging stub}.
17260 On certain remote targets, you can use an auxiliary program
17261 @code{gdbserver} instead of linking a stub into your program.
17262 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17265 The debugging stub is specific to the architecture of the remote
17266 machine; for example, use @file{sparc-stub.c} to debug programs on
17269 @cindex remote serial stub list
17270 These working remote stubs are distributed with @value{GDBN}:
17275 @cindex @file{i386-stub.c}
17278 For Intel 386 and compatible architectures.
17281 @cindex @file{m68k-stub.c}
17282 @cindex Motorola 680x0
17284 For Motorola 680x0 architectures.
17287 @cindex @file{sh-stub.c}
17290 For Renesas SH architectures.
17293 @cindex @file{sparc-stub.c}
17295 For @sc{sparc} architectures.
17297 @item sparcl-stub.c
17298 @cindex @file{sparcl-stub.c}
17301 For Fujitsu @sc{sparclite} architectures.
17305 The @file{README} file in the @value{GDBN} distribution may list other
17306 recently added stubs.
17309 * Stub Contents:: What the stub can do for you
17310 * Bootstrapping:: What you must do for the stub
17311 * Debug Session:: Putting it all together
17314 @node Stub Contents
17315 @subsection What the Stub Can Do for You
17317 @cindex remote serial stub
17318 The debugging stub for your architecture supplies these three
17322 @item set_debug_traps
17323 @findex set_debug_traps
17324 @cindex remote serial stub, initialization
17325 This routine arranges for @code{handle_exception} to run when your
17326 program stops. You must call this subroutine explicitly near the
17327 beginning of your program.
17329 @item handle_exception
17330 @findex handle_exception
17331 @cindex remote serial stub, main routine
17332 This is the central workhorse, but your program never calls it
17333 explicitly---the setup code arranges for @code{handle_exception} to
17334 run when a trap is triggered.
17336 @code{handle_exception} takes control when your program stops during
17337 execution (for example, on a breakpoint), and mediates communications
17338 with @value{GDBN} on the host machine. This is where the communications
17339 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17340 representative on the target machine. It begins by sending summary
17341 information on the state of your program, then continues to execute,
17342 retrieving and transmitting any information @value{GDBN} needs, until you
17343 execute a @value{GDBN} command that makes your program resume; at that point,
17344 @code{handle_exception} returns control to your own code on the target
17348 @cindex @code{breakpoint} subroutine, remote
17349 Use this auxiliary subroutine to make your program contain a
17350 breakpoint. Depending on the particular situation, this may be the only
17351 way for @value{GDBN} to get control. For instance, if your target
17352 machine has some sort of interrupt button, you won't need to call this;
17353 pressing the interrupt button transfers control to
17354 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17355 simply receiving characters on the serial port may also trigger a trap;
17356 again, in that situation, you don't need to call @code{breakpoint} from
17357 your own program---simply running @samp{target remote} from the host
17358 @value{GDBN} session gets control.
17360 Call @code{breakpoint} if none of these is true, or if you simply want
17361 to make certain your program stops at a predetermined point for the
17362 start of your debugging session.
17365 @node Bootstrapping
17366 @subsection What You Must Do for the Stub
17368 @cindex remote stub, support routines
17369 The debugging stubs that come with @value{GDBN} are set up for a particular
17370 chip architecture, but they have no information about the rest of your
17371 debugging target machine.
17373 First of all you need to tell the stub how to communicate with the
17377 @item int getDebugChar()
17378 @findex getDebugChar
17379 Write this subroutine to read a single character from the serial port.
17380 It may be identical to @code{getchar} for your target system; a
17381 different name is used to allow you to distinguish the two if you wish.
17383 @item void putDebugChar(int)
17384 @findex putDebugChar
17385 Write this subroutine to write a single character to the serial port.
17386 It may be identical to @code{putchar} for your target system; a
17387 different name is used to allow you to distinguish the two if you wish.
17390 @cindex control C, and remote debugging
17391 @cindex interrupting remote targets
17392 If you want @value{GDBN} to be able to stop your program while it is
17393 running, you need to use an interrupt-driven serial driver, and arrange
17394 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17395 character). That is the character which @value{GDBN} uses to tell the
17396 remote system to stop.
17398 Getting the debugging target to return the proper status to @value{GDBN}
17399 probably requires changes to the standard stub; one quick and dirty way
17400 is to just execute a breakpoint instruction (the ``dirty'' part is that
17401 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17403 Other routines you need to supply are:
17406 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17407 @findex exceptionHandler
17408 Write this function to install @var{exception_address} in the exception
17409 handling tables. You need to do this because the stub does not have any
17410 way of knowing what the exception handling tables on your target system
17411 are like (for example, the processor's table might be in @sc{rom},
17412 containing entries which point to a table in @sc{ram}).
17413 @var{exception_number} is the exception number which should be changed;
17414 its meaning is architecture-dependent (for example, different numbers
17415 might represent divide by zero, misaligned access, etc). When this
17416 exception occurs, control should be transferred directly to
17417 @var{exception_address}, and the processor state (stack, registers,
17418 and so on) should be just as it is when a processor exception occurs. So if
17419 you want to use a jump instruction to reach @var{exception_address}, it
17420 should be a simple jump, not a jump to subroutine.
17422 For the 386, @var{exception_address} should be installed as an interrupt
17423 gate so that interrupts are masked while the handler runs. The gate
17424 should be at privilege level 0 (the most privileged level). The
17425 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17426 help from @code{exceptionHandler}.
17428 @item void flush_i_cache()
17429 @findex flush_i_cache
17430 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17431 instruction cache, if any, on your target machine. If there is no
17432 instruction cache, this subroutine may be a no-op.
17434 On target machines that have instruction caches, @value{GDBN} requires this
17435 function to make certain that the state of your program is stable.
17439 You must also make sure this library routine is available:
17442 @item void *memset(void *, int, int)
17444 This is the standard library function @code{memset} that sets an area of
17445 memory to a known value. If you have one of the free versions of
17446 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17447 either obtain it from your hardware manufacturer, or write your own.
17450 If you do not use the GNU C compiler, you may need other standard
17451 library subroutines as well; this varies from one stub to another,
17452 but in general the stubs are likely to use any of the common library
17453 subroutines which @code{@value{NGCC}} generates as inline code.
17456 @node Debug Session
17457 @subsection Putting it All Together
17459 @cindex remote serial debugging summary
17460 In summary, when your program is ready to debug, you must follow these
17465 Make sure you have defined the supporting low-level routines
17466 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17468 @code{getDebugChar}, @code{putDebugChar},
17469 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17473 Insert these lines near the top of your program:
17481 For the 680x0 stub only, you need to provide a variable called
17482 @code{exceptionHook}. Normally you just use:
17485 void (*exceptionHook)() = 0;
17489 but if before calling @code{set_debug_traps}, you set it to point to a
17490 function in your program, that function is called when
17491 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17492 error). The function indicated by @code{exceptionHook} is called with
17493 one parameter: an @code{int} which is the exception number.
17496 Compile and link together: your program, the @value{GDBN} debugging stub for
17497 your target architecture, and the supporting subroutines.
17500 Make sure you have a serial connection between your target machine and
17501 the @value{GDBN} host, and identify the serial port on the host.
17504 @c The "remote" target now provides a `load' command, so we should
17505 @c document that. FIXME.
17506 Download your program to your target machine (or get it there by
17507 whatever means the manufacturer provides), and start it.
17510 Start @value{GDBN} on the host, and connect to the target
17511 (@pxref{Connecting,,Connecting to a Remote Target}).
17515 @node Configurations
17516 @chapter Configuration-Specific Information
17518 While nearly all @value{GDBN} commands are available for all native and
17519 cross versions of the debugger, there are some exceptions. This chapter
17520 describes things that are only available in certain configurations.
17522 There are three major categories of configurations: native
17523 configurations, where the host and target are the same, embedded
17524 operating system configurations, which are usually the same for several
17525 different processor architectures, and bare embedded processors, which
17526 are quite different from each other.
17531 * Embedded Processors::
17538 This section describes details specific to particular native
17543 * BSD libkvm Interface:: Debugging BSD kernel memory images
17544 * SVR4 Process Information:: SVR4 process information
17545 * DJGPP Native:: Features specific to the DJGPP port
17546 * Cygwin Native:: Features specific to the Cygwin port
17547 * Hurd Native:: Features specific to @sc{gnu} Hurd
17548 * Neutrino:: Features specific to QNX Neutrino
17549 * Darwin:: Features specific to Darwin
17555 On HP-UX systems, if you refer to a function or variable name that
17556 begins with a dollar sign, @value{GDBN} searches for a user or system
17557 name first, before it searches for a convenience variable.
17560 @node BSD libkvm Interface
17561 @subsection BSD libkvm Interface
17564 @cindex kernel memory image
17565 @cindex kernel crash dump
17567 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17568 interface that provides a uniform interface for accessing kernel virtual
17569 memory images, including live systems and crash dumps. @value{GDBN}
17570 uses this interface to allow you to debug live kernels and kernel crash
17571 dumps on many native BSD configurations. This is implemented as a
17572 special @code{kvm} debugging target. For debugging a live system, load
17573 the currently running kernel into @value{GDBN} and connect to the
17577 (@value{GDBP}) @b{target kvm}
17580 For debugging crash dumps, provide the file name of the crash dump as an
17584 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17587 Once connected to the @code{kvm} target, the following commands are
17593 Set current context from the @dfn{Process Control Block} (PCB) address.
17596 Set current context from proc address. This command isn't available on
17597 modern FreeBSD systems.
17600 @node SVR4 Process Information
17601 @subsection SVR4 Process Information
17603 @cindex examine process image
17604 @cindex process info via @file{/proc}
17606 Many versions of SVR4 and compatible systems provide a facility called
17607 @samp{/proc} that can be used to examine the image of a running
17608 process using file-system subroutines. If @value{GDBN} is configured
17609 for an operating system with this facility, the command @code{info
17610 proc} is available to report information about the process running
17611 your program, or about any process running on your system. @code{info
17612 proc} works only on SVR4 systems that include the @code{procfs} code.
17613 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17614 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17620 @itemx info proc @var{process-id}
17621 Summarize available information about any running process. If a
17622 process ID is specified by @var{process-id}, display information about
17623 that process; otherwise display information about the program being
17624 debugged. The summary includes the debugged process ID, the command
17625 line used to invoke it, its current working directory, and its
17626 executable file's absolute file name.
17628 On some systems, @var{process-id} can be of the form
17629 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17630 within a process. If the optional @var{pid} part is missing, it means
17631 a thread from the process being debugged (the leading @samp{/} still
17632 needs to be present, or else @value{GDBN} will interpret the number as
17633 a process ID rather than a thread ID).
17635 @item info proc mappings
17636 @cindex memory address space mappings
17637 Report the memory address space ranges accessible in the program, with
17638 information on whether the process has read, write, or execute access
17639 rights to each range. On @sc{gnu}/Linux systems, each memory range
17640 includes the object file which is mapped to that range, instead of the
17641 memory access rights to that range.
17643 @item info proc stat
17644 @itemx info proc status
17645 @cindex process detailed status information
17646 These subcommands are specific to @sc{gnu}/Linux systems. They show
17647 the process-related information, including the user ID and group ID;
17648 how many threads are there in the process; its virtual memory usage;
17649 the signals that are pending, blocked, and ignored; its TTY; its
17650 consumption of system and user time; its stack size; its @samp{nice}
17651 value; etc. For more information, see the @samp{proc} man page
17652 (type @kbd{man 5 proc} from your shell prompt).
17654 @item info proc all
17655 Show all the information about the process described under all of the
17656 above @code{info proc} subcommands.
17659 @comment These sub-options of 'info proc' were not included when
17660 @comment procfs.c was re-written. Keep their descriptions around
17661 @comment against the day when someone finds the time to put them back in.
17662 @kindex info proc times
17663 @item info proc times
17664 Starting time, user CPU time, and system CPU time for your program and
17667 @kindex info proc id
17669 Report on the process IDs related to your program: its own process ID,
17670 the ID of its parent, the process group ID, and the session ID.
17673 @item set procfs-trace
17674 @kindex set procfs-trace
17675 @cindex @code{procfs} API calls
17676 This command enables and disables tracing of @code{procfs} API calls.
17678 @item show procfs-trace
17679 @kindex show procfs-trace
17680 Show the current state of @code{procfs} API call tracing.
17682 @item set procfs-file @var{file}
17683 @kindex set procfs-file
17684 Tell @value{GDBN} to write @code{procfs} API trace to the named
17685 @var{file}. @value{GDBN} appends the trace info to the previous
17686 contents of the file. The default is to display the trace on the
17689 @item show procfs-file
17690 @kindex show procfs-file
17691 Show the file to which @code{procfs} API trace is written.
17693 @item proc-trace-entry
17694 @itemx proc-trace-exit
17695 @itemx proc-untrace-entry
17696 @itemx proc-untrace-exit
17697 @kindex proc-trace-entry
17698 @kindex proc-trace-exit
17699 @kindex proc-untrace-entry
17700 @kindex proc-untrace-exit
17701 These commands enable and disable tracing of entries into and exits
17702 from the @code{syscall} interface.
17705 @kindex info pidlist
17706 @cindex process list, QNX Neutrino
17707 For QNX Neutrino only, this command displays the list of all the
17708 processes and all the threads within each process.
17711 @kindex info meminfo
17712 @cindex mapinfo list, QNX Neutrino
17713 For QNX Neutrino only, this command displays the list of all mapinfos.
17717 @subsection Features for Debugging @sc{djgpp} Programs
17718 @cindex @sc{djgpp} debugging
17719 @cindex native @sc{djgpp} debugging
17720 @cindex MS-DOS-specific commands
17723 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17724 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17725 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17726 top of real-mode DOS systems and their emulations.
17728 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17729 defines a few commands specific to the @sc{djgpp} port. This
17730 subsection describes those commands.
17735 This is a prefix of @sc{djgpp}-specific commands which print
17736 information about the target system and important OS structures.
17739 @cindex MS-DOS system info
17740 @cindex free memory information (MS-DOS)
17741 @item info dos sysinfo
17742 This command displays assorted information about the underlying
17743 platform: the CPU type and features, the OS version and flavor, the
17744 DPMI version, and the available conventional and DPMI memory.
17749 @cindex segment descriptor tables
17750 @cindex descriptor tables display
17752 @itemx info dos ldt
17753 @itemx info dos idt
17754 These 3 commands display entries from, respectively, Global, Local,
17755 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17756 tables are data structures which store a descriptor for each segment
17757 that is currently in use. The segment's selector is an index into a
17758 descriptor table; the table entry for that index holds the
17759 descriptor's base address and limit, and its attributes and access
17762 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17763 segment (used for both data and the stack), and a DOS segment (which
17764 allows access to DOS/BIOS data structures and absolute addresses in
17765 conventional memory). However, the DPMI host will usually define
17766 additional segments in order to support the DPMI environment.
17768 @cindex garbled pointers
17769 These commands allow to display entries from the descriptor tables.
17770 Without an argument, all entries from the specified table are
17771 displayed. An argument, which should be an integer expression, means
17772 display a single entry whose index is given by the argument. For
17773 example, here's a convenient way to display information about the
17774 debugged program's data segment:
17777 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17778 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17782 This comes in handy when you want to see whether a pointer is outside
17783 the data segment's limit (i.e.@: @dfn{garbled}).
17785 @cindex page tables display (MS-DOS)
17787 @itemx info dos pte
17788 These two commands display entries from, respectively, the Page
17789 Directory and the Page Tables. Page Directories and Page Tables are
17790 data structures which control how virtual memory addresses are mapped
17791 into physical addresses. A Page Table includes an entry for every
17792 page of memory that is mapped into the program's address space; there
17793 may be several Page Tables, each one holding up to 4096 entries. A
17794 Page Directory has up to 4096 entries, one each for every Page Table
17795 that is currently in use.
17797 Without an argument, @kbd{info dos pde} displays the entire Page
17798 Directory, and @kbd{info dos pte} displays all the entries in all of
17799 the Page Tables. An argument, an integer expression, given to the
17800 @kbd{info dos pde} command means display only that entry from the Page
17801 Directory table. An argument given to the @kbd{info dos pte} command
17802 means display entries from a single Page Table, the one pointed to by
17803 the specified entry in the Page Directory.
17805 @cindex direct memory access (DMA) on MS-DOS
17806 These commands are useful when your program uses @dfn{DMA} (Direct
17807 Memory Access), which needs physical addresses to program the DMA
17810 These commands are supported only with some DPMI servers.
17812 @cindex physical address from linear address
17813 @item info dos address-pte @var{addr}
17814 This command displays the Page Table entry for a specified linear
17815 address. The argument @var{addr} is a linear address which should
17816 already have the appropriate segment's base address added to it,
17817 because this command accepts addresses which may belong to @emph{any}
17818 segment. For example, here's how to display the Page Table entry for
17819 the page where a variable @code{i} is stored:
17822 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17823 @exdent @code{Page Table entry for address 0x11a00d30:}
17824 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17828 This says that @code{i} is stored at offset @code{0xd30} from the page
17829 whose physical base address is @code{0x02698000}, and shows all the
17830 attributes of that page.
17832 Note that you must cast the addresses of variables to a @code{char *},
17833 since otherwise the value of @code{__djgpp_base_address}, the base
17834 address of all variables and functions in a @sc{djgpp} program, will
17835 be added using the rules of C pointer arithmetics: if @code{i} is
17836 declared an @code{int}, @value{GDBN} will add 4 times the value of
17837 @code{__djgpp_base_address} to the address of @code{i}.
17839 Here's another example, it displays the Page Table entry for the
17843 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17844 @exdent @code{Page Table entry for address 0x29110:}
17845 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17849 (The @code{+ 3} offset is because the transfer buffer's address is the
17850 3rd member of the @code{_go32_info_block} structure.) The output
17851 clearly shows that this DPMI server maps the addresses in conventional
17852 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17853 linear (@code{0x29110}) addresses are identical.
17855 This command is supported only with some DPMI servers.
17858 @cindex DOS serial data link, remote debugging
17859 In addition to native debugging, the DJGPP port supports remote
17860 debugging via a serial data link. The following commands are specific
17861 to remote serial debugging in the DJGPP port of @value{GDBN}.
17864 @kindex set com1base
17865 @kindex set com1irq
17866 @kindex set com2base
17867 @kindex set com2irq
17868 @kindex set com3base
17869 @kindex set com3irq
17870 @kindex set com4base
17871 @kindex set com4irq
17872 @item set com1base @var{addr}
17873 This command sets the base I/O port address of the @file{COM1} serial
17876 @item set com1irq @var{irq}
17877 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17878 for the @file{COM1} serial port.
17880 There are similar commands @samp{set com2base}, @samp{set com3irq},
17881 etc.@: for setting the port address and the @code{IRQ} lines for the
17884 @kindex show com1base
17885 @kindex show com1irq
17886 @kindex show com2base
17887 @kindex show com2irq
17888 @kindex show com3base
17889 @kindex show com3irq
17890 @kindex show com4base
17891 @kindex show com4irq
17892 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17893 display the current settings of the base address and the @code{IRQ}
17894 lines used by the COM ports.
17897 @kindex info serial
17898 @cindex DOS serial port status
17899 This command prints the status of the 4 DOS serial ports. For each
17900 port, it prints whether it's active or not, its I/O base address and
17901 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17902 counts of various errors encountered so far.
17906 @node Cygwin Native
17907 @subsection Features for Debugging MS Windows PE Executables
17908 @cindex MS Windows debugging
17909 @cindex native Cygwin debugging
17910 @cindex Cygwin-specific commands
17912 @value{GDBN} supports native debugging of MS Windows programs, including
17913 DLLs with and without symbolic debugging information.
17915 @cindex Ctrl-BREAK, MS-Windows
17916 @cindex interrupt debuggee on MS-Windows
17917 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17918 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17919 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17920 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17921 sequence, which can be used to interrupt the debuggee even if it
17924 There are various additional Cygwin-specific commands, described in
17925 this section. Working with DLLs that have no debugging symbols is
17926 described in @ref{Non-debug DLL Symbols}.
17931 This is a prefix of MS Windows-specific commands which print
17932 information about the target system and important OS structures.
17934 @item info w32 selector
17935 This command displays information returned by
17936 the Win32 API @code{GetThreadSelectorEntry} function.
17937 It takes an optional argument that is evaluated to
17938 a long value to give the information about this given selector.
17939 Without argument, this command displays information
17940 about the six segment registers.
17942 @item info w32 thread-information-block
17943 This command displays thread specific information stored in the
17944 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17945 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17949 This is a Cygwin-specific alias of @code{info shared}.
17951 @kindex dll-symbols
17953 This command loads symbols from a dll similarly to
17954 add-sym command but without the need to specify a base address.
17956 @kindex set cygwin-exceptions
17957 @cindex debugging the Cygwin DLL
17958 @cindex Cygwin DLL, debugging
17959 @item set cygwin-exceptions @var{mode}
17960 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17961 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17962 @value{GDBN} will delay recognition of exceptions, and may ignore some
17963 exceptions which seem to be caused by internal Cygwin DLL
17964 ``bookkeeping''. This option is meant primarily for debugging the
17965 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17966 @value{GDBN} users with false @code{SIGSEGV} signals.
17968 @kindex show cygwin-exceptions
17969 @item show cygwin-exceptions
17970 Displays whether @value{GDBN} will break on exceptions that happen
17971 inside the Cygwin DLL itself.
17973 @kindex set new-console
17974 @item set new-console @var{mode}
17975 If @var{mode} is @code{on} the debuggee will
17976 be started in a new console on next start.
17977 If @var{mode} is @code{off}, the debuggee will
17978 be started in the same console as the debugger.
17980 @kindex show new-console
17981 @item show new-console
17982 Displays whether a new console is used
17983 when the debuggee is started.
17985 @kindex set new-group
17986 @item set new-group @var{mode}
17987 This boolean value controls whether the debuggee should
17988 start a new group or stay in the same group as the debugger.
17989 This affects the way the Windows OS handles
17992 @kindex show new-group
17993 @item show new-group
17994 Displays current value of new-group boolean.
17996 @kindex set debugevents
17997 @item set debugevents
17998 This boolean value adds debug output concerning kernel events related
17999 to the debuggee seen by the debugger. This includes events that
18000 signal thread and process creation and exit, DLL loading and
18001 unloading, console interrupts, and debugging messages produced by the
18002 Windows @code{OutputDebugString} API call.
18004 @kindex set debugexec
18005 @item set debugexec
18006 This boolean value adds debug output concerning execute events
18007 (such as resume thread) seen by the debugger.
18009 @kindex set debugexceptions
18010 @item set debugexceptions
18011 This boolean value adds debug output concerning exceptions in the
18012 debuggee seen by the debugger.
18014 @kindex set debugmemory
18015 @item set debugmemory
18016 This boolean value adds debug output concerning debuggee memory reads
18017 and writes by the debugger.
18021 This boolean values specifies whether the debuggee is called
18022 via a shell or directly (default value is on).
18026 Displays if the debuggee will be started with a shell.
18031 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18034 @node Non-debug DLL Symbols
18035 @subsubsection Support for DLLs without Debugging Symbols
18036 @cindex DLLs with no debugging symbols
18037 @cindex Minimal symbols and DLLs
18039 Very often on windows, some of the DLLs that your program relies on do
18040 not include symbolic debugging information (for example,
18041 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18042 symbols in a DLL, it relies on the minimal amount of symbolic
18043 information contained in the DLL's export table. This section
18044 describes working with such symbols, known internally to @value{GDBN} as
18045 ``minimal symbols''.
18047 Note that before the debugged program has started execution, no DLLs
18048 will have been loaded. The easiest way around this problem is simply to
18049 start the program --- either by setting a breakpoint or letting the
18050 program run once to completion. It is also possible to force
18051 @value{GDBN} to load a particular DLL before starting the executable ---
18052 see the shared library information in @ref{Files}, or the
18053 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18054 explicitly loading symbols from a DLL with no debugging information will
18055 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18056 which may adversely affect symbol lookup performance.
18058 @subsubsection DLL Name Prefixes
18060 In keeping with the naming conventions used by the Microsoft debugging
18061 tools, DLL export symbols are made available with a prefix based on the
18062 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18063 also entered into the symbol table, so @code{CreateFileA} is often
18064 sufficient. In some cases there will be name clashes within a program
18065 (particularly if the executable itself includes full debugging symbols)
18066 necessitating the use of the fully qualified name when referring to the
18067 contents of the DLL. Use single-quotes around the name to avoid the
18068 exclamation mark (``!'') being interpreted as a language operator.
18070 Note that the internal name of the DLL may be all upper-case, even
18071 though the file name of the DLL is lower-case, or vice-versa. Since
18072 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18073 some confusion. If in doubt, try the @code{info functions} and
18074 @code{info variables} commands or even @code{maint print msymbols}
18075 (@pxref{Symbols}). Here's an example:
18078 (@value{GDBP}) info function CreateFileA
18079 All functions matching regular expression "CreateFileA":
18081 Non-debugging symbols:
18082 0x77e885f4 CreateFileA
18083 0x77e885f4 KERNEL32!CreateFileA
18087 (@value{GDBP}) info function !
18088 All functions matching regular expression "!":
18090 Non-debugging symbols:
18091 0x6100114c cygwin1!__assert
18092 0x61004034 cygwin1!_dll_crt0@@0
18093 0x61004240 cygwin1!dll_crt0(per_process *)
18097 @subsubsection Working with Minimal Symbols
18099 Symbols extracted from a DLL's export table do not contain very much
18100 type information. All that @value{GDBN} can do is guess whether a symbol
18101 refers to a function or variable depending on the linker section that
18102 contains the symbol. Also note that the actual contents of the memory
18103 contained in a DLL are not available unless the program is running. This
18104 means that you cannot examine the contents of a variable or disassemble
18105 a function within a DLL without a running program.
18107 Variables are generally treated as pointers and dereferenced
18108 automatically. For this reason, it is often necessary to prefix a
18109 variable name with the address-of operator (``&'') and provide explicit
18110 type information in the command. Here's an example of the type of
18114 (@value{GDBP}) print 'cygwin1!__argv'
18119 (@value{GDBP}) x 'cygwin1!__argv'
18120 0x10021610: "\230y\""
18123 And two possible solutions:
18126 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18127 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18131 (@value{GDBP}) x/2x &'cygwin1!__argv'
18132 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18133 (@value{GDBP}) x/x 0x10021608
18134 0x10021608: 0x0022fd98
18135 (@value{GDBP}) x/s 0x0022fd98
18136 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18139 Setting a break point within a DLL is possible even before the program
18140 starts execution. However, under these circumstances, @value{GDBN} can't
18141 examine the initial instructions of the function in order to skip the
18142 function's frame set-up code. You can work around this by using ``*&''
18143 to set the breakpoint at a raw memory address:
18146 (@value{GDBP}) break *&'python22!PyOS_Readline'
18147 Breakpoint 1 at 0x1e04eff0
18150 The author of these extensions is not entirely convinced that setting a
18151 break point within a shared DLL like @file{kernel32.dll} is completely
18155 @subsection Commands Specific to @sc{gnu} Hurd Systems
18156 @cindex @sc{gnu} Hurd debugging
18158 This subsection describes @value{GDBN} commands specific to the
18159 @sc{gnu} Hurd native debugging.
18164 @kindex set signals@r{, Hurd command}
18165 @kindex set sigs@r{, Hurd command}
18166 This command toggles the state of inferior signal interception by
18167 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18168 affected by this command. @code{sigs} is a shorthand alias for
18173 @kindex show signals@r{, Hurd command}
18174 @kindex show sigs@r{, Hurd command}
18175 Show the current state of intercepting inferior's signals.
18177 @item set signal-thread
18178 @itemx set sigthread
18179 @kindex set signal-thread
18180 @kindex set sigthread
18181 This command tells @value{GDBN} which thread is the @code{libc} signal
18182 thread. That thread is run when a signal is delivered to a running
18183 process. @code{set sigthread} is the shorthand alias of @code{set
18186 @item show signal-thread
18187 @itemx show sigthread
18188 @kindex show signal-thread
18189 @kindex show sigthread
18190 These two commands show which thread will run when the inferior is
18191 delivered a signal.
18194 @kindex set stopped@r{, Hurd command}
18195 This commands tells @value{GDBN} that the inferior process is stopped,
18196 as with the @code{SIGSTOP} signal. The stopped process can be
18197 continued by delivering a signal to it.
18200 @kindex show stopped@r{, Hurd command}
18201 This command shows whether @value{GDBN} thinks the debuggee is
18204 @item set exceptions
18205 @kindex set exceptions@r{, Hurd command}
18206 Use this command to turn off trapping of exceptions in the inferior.
18207 When exception trapping is off, neither breakpoints nor
18208 single-stepping will work. To restore the default, set exception
18211 @item show exceptions
18212 @kindex show exceptions@r{, Hurd command}
18213 Show the current state of trapping exceptions in the inferior.
18215 @item set task pause
18216 @kindex set task@r{, Hurd commands}
18217 @cindex task attributes (@sc{gnu} Hurd)
18218 @cindex pause current task (@sc{gnu} Hurd)
18219 This command toggles task suspension when @value{GDBN} has control.
18220 Setting it to on takes effect immediately, and the task is suspended
18221 whenever @value{GDBN} gets control. Setting it to off will take
18222 effect the next time the inferior is continued. If this option is set
18223 to off, you can use @code{set thread default pause on} or @code{set
18224 thread pause on} (see below) to pause individual threads.
18226 @item show task pause
18227 @kindex show task@r{, Hurd commands}
18228 Show the current state of task suspension.
18230 @item set task detach-suspend-count
18231 @cindex task suspend count
18232 @cindex detach from task, @sc{gnu} Hurd
18233 This command sets the suspend count the task will be left with when
18234 @value{GDBN} detaches from it.
18236 @item show task detach-suspend-count
18237 Show the suspend count the task will be left with when detaching.
18239 @item set task exception-port
18240 @itemx set task excp
18241 @cindex task exception port, @sc{gnu} Hurd
18242 This command sets the task exception port to which @value{GDBN} will
18243 forward exceptions. The argument should be the value of the @dfn{send
18244 rights} of the task. @code{set task excp} is a shorthand alias.
18246 @item set noninvasive
18247 @cindex noninvasive task options
18248 This command switches @value{GDBN} to a mode that is the least
18249 invasive as far as interfering with the inferior is concerned. This
18250 is the same as using @code{set task pause}, @code{set exceptions}, and
18251 @code{set signals} to values opposite to the defaults.
18253 @item info send-rights
18254 @itemx info receive-rights
18255 @itemx info port-rights
18256 @itemx info port-sets
18257 @itemx info dead-names
18260 @cindex send rights, @sc{gnu} Hurd
18261 @cindex receive rights, @sc{gnu} Hurd
18262 @cindex port rights, @sc{gnu} Hurd
18263 @cindex port sets, @sc{gnu} Hurd
18264 @cindex dead names, @sc{gnu} Hurd
18265 These commands display information about, respectively, send rights,
18266 receive rights, port rights, port sets, and dead names of a task.
18267 There are also shorthand aliases: @code{info ports} for @code{info
18268 port-rights} and @code{info psets} for @code{info port-sets}.
18270 @item set thread pause
18271 @kindex set thread@r{, Hurd command}
18272 @cindex thread properties, @sc{gnu} Hurd
18273 @cindex pause current thread (@sc{gnu} Hurd)
18274 This command toggles current thread suspension when @value{GDBN} has
18275 control. Setting it to on takes effect immediately, and the current
18276 thread is suspended whenever @value{GDBN} gets control. Setting it to
18277 off will take effect the next time the inferior is continued.
18278 Normally, this command has no effect, since when @value{GDBN} has
18279 control, the whole task is suspended. However, if you used @code{set
18280 task pause off} (see above), this command comes in handy to suspend
18281 only the current thread.
18283 @item show thread pause
18284 @kindex show thread@r{, Hurd command}
18285 This command shows the state of current thread suspension.
18287 @item set thread run
18288 This command sets whether the current thread is allowed to run.
18290 @item show thread run
18291 Show whether the current thread is allowed to run.
18293 @item set thread detach-suspend-count
18294 @cindex thread suspend count, @sc{gnu} Hurd
18295 @cindex detach from thread, @sc{gnu} Hurd
18296 This command sets the suspend count @value{GDBN} will leave on a
18297 thread when detaching. This number is relative to the suspend count
18298 found by @value{GDBN} when it notices the thread; use @code{set thread
18299 takeover-suspend-count} to force it to an absolute value.
18301 @item show thread detach-suspend-count
18302 Show the suspend count @value{GDBN} will leave on the thread when
18305 @item set thread exception-port
18306 @itemx set thread excp
18307 Set the thread exception port to which to forward exceptions. This
18308 overrides the port set by @code{set task exception-port} (see above).
18309 @code{set thread excp} is the shorthand alias.
18311 @item set thread takeover-suspend-count
18312 Normally, @value{GDBN}'s thread suspend counts are relative to the
18313 value @value{GDBN} finds when it notices each thread. This command
18314 changes the suspend counts to be absolute instead.
18316 @item set thread default
18317 @itemx show thread default
18318 @cindex thread default settings, @sc{gnu} Hurd
18319 Each of the above @code{set thread} commands has a @code{set thread
18320 default} counterpart (e.g., @code{set thread default pause}, @code{set
18321 thread default exception-port}, etc.). The @code{thread default}
18322 variety of commands sets the default thread properties for all
18323 threads; you can then change the properties of individual threads with
18324 the non-default commands.
18329 @subsection QNX Neutrino
18330 @cindex QNX Neutrino
18332 @value{GDBN} provides the following commands specific to the QNX
18336 @item set debug nto-debug
18337 @kindex set debug nto-debug
18338 When set to on, enables debugging messages specific to the QNX
18341 @item show debug nto-debug
18342 @kindex show debug nto-debug
18343 Show the current state of QNX Neutrino messages.
18350 @value{GDBN} provides the following commands specific to the Darwin target:
18353 @item set debug darwin @var{num}
18354 @kindex set debug darwin
18355 When set to a non zero value, enables debugging messages specific to
18356 the Darwin support. Higher values produce more verbose output.
18358 @item show debug darwin
18359 @kindex show debug darwin
18360 Show the current state of Darwin messages.
18362 @item set debug mach-o @var{num}
18363 @kindex set debug mach-o
18364 When set to a non zero value, enables debugging messages while
18365 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18366 file format used on Darwin for object and executable files.) Higher
18367 values produce more verbose output. This is a command to diagnose
18368 problems internal to @value{GDBN} and should not be needed in normal
18371 @item show debug mach-o
18372 @kindex show debug mach-o
18373 Show the current state of Mach-O file messages.
18375 @item set mach-exceptions on
18376 @itemx set mach-exceptions off
18377 @kindex set mach-exceptions
18378 On Darwin, faults are first reported as a Mach exception and are then
18379 mapped to a Posix signal. Use this command to turn on trapping of
18380 Mach exceptions in the inferior. This might be sometimes useful to
18381 better understand the cause of a fault. The default is off.
18383 @item show mach-exceptions
18384 @kindex show mach-exceptions
18385 Show the current state of exceptions trapping.
18390 @section Embedded Operating Systems
18392 This section describes configurations involving the debugging of
18393 embedded operating systems that are available for several different
18397 * VxWorks:: Using @value{GDBN} with VxWorks
18400 @value{GDBN} includes the ability to debug programs running on
18401 various real-time operating systems.
18404 @subsection Using @value{GDBN} with VxWorks
18410 @kindex target vxworks
18411 @item target vxworks @var{machinename}
18412 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18413 is the target system's machine name or IP address.
18417 On VxWorks, @code{load} links @var{filename} dynamically on the
18418 current target system as well as adding its symbols in @value{GDBN}.
18420 @value{GDBN} enables developers to spawn and debug tasks running on networked
18421 VxWorks targets from a Unix host. Already-running tasks spawned from
18422 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18423 both the Unix host and on the VxWorks target. The program
18424 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18425 installed with the name @code{vxgdb}, to distinguish it from a
18426 @value{GDBN} for debugging programs on the host itself.)
18429 @item VxWorks-timeout @var{args}
18430 @kindex vxworks-timeout
18431 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18432 This option is set by the user, and @var{args} represents the number of
18433 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18434 your VxWorks target is a slow software simulator or is on the far side
18435 of a thin network line.
18438 The following information on connecting to VxWorks was current when
18439 this manual was produced; newer releases of VxWorks may use revised
18442 @findex INCLUDE_RDB
18443 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18444 to include the remote debugging interface routines in the VxWorks
18445 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18446 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18447 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18448 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18449 information on configuring and remaking VxWorks, see the manufacturer's
18451 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18453 Once you have included @file{rdb.a} in your VxWorks system image and set
18454 your Unix execution search path to find @value{GDBN}, you are ready to
18455 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18456 @code{vxgdb}, depending on your installation).
18458 @value{GDBN} comes up showing the prompt:
18465 * VxWorks Connection:: Connecting to VxWorks
18466 * VxWorks Download:: VxWorks download
18467 * VxWorks Attach:: Running tasks
18470 @node VxWorks Connection
18471 @subsubsection Connecting to VxWorks
18473 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18474 network. To connect to a target whose host name is ``@code{tt}'', type:
18477 (vxgdb) target vxworks tt
18481 @value{GDBN} displays messages like these:
18484 Attaching remote machine across net...
18489 @value{GDBN} then attempts to read the symbol tables of any object modules
18490 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18491 these files by searching the directories listed in the command search
18492 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18493 to find an object file, it displays a message such as:
18496 prog.o: No such file or directory.
18499 When this happens, add the appropriate directory to the search path with
18500 the @value{GDBN} command @code{path}, and execute the @code{target}
18503 @node VxWorks Download
18504 @subsubsection VxWorks Download
18506 @cindex download to VxWorks
18507 If you have connected to the VxWorks target and you want to debug an
18508 object that has not yet been loaded, you can use the @value{GDBN}
18509 @code{load} command to download a file from Unix to VxWorks
18510 incrementally. The object file given as an argument to the @code{load}
18511 command is actually opened twice: first by the VxWorks target in order
18512 to download the code, then by @value{GDBN} in order to read the symbol
18513 table. This can lead to problems if the current working directories on
18514 the two systems differ. If both systems have NFS mounted the same
18515 filesystems, you can avoid these problems by using absolute paths.
18516 Otherwise, it is simplest to set the working directory on both systems
18517 to the directory in which the object file resides, and then to reference
18518 the file by its name, without any path. For instance, a program
18519 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18520 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18521 program, type this on VxWorks:
18524 -> cd "@var{vxpath}/vw/demo/rdb"
18528 Then, in @value{GDBN}, type:
18531 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18532 (vxgdb) load prog.o
18535 @value{GDBN} displays a response similar to this:
18538 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18541 You can also use the @code{load} command to reload an object module
18542 after editing and recompiling the corresponding source file. Note that
18543 this makes @value{GDBN} delete all currently-defined breakpoints,
18544 auto-displays, and convenience variables, and to clear the value
18545 history. (This is necessary in order to preserve the integrity of
18546 debugger's data structures that reference the target system's symbol
18549 @node VxWorks Attach
18550 @subsubsection Running Tasks
18552 @cindex running VxWorks tasks
18553 You can also attach to an existing task using the @code{attach} command as
18557 (vxgdb) attach @var{task}
18561 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18562 or suspended when you attach to it. Running tasks are suspended at
18563 the time of attachment.
18565 @node Embedded Processors
18566 @section Embedded Processors
18568 This section goes into details specific to particular embedded
18571 @cindex send command to simulator
18572 Whenever a specific embedded processor has a simulator, @value{GDBN}
18573 allows to send an arbitrary command to the simulator.
18576 @item sim @var{command}
18577 @kindex sim@r{, a command}
18578 Send an arbitrary @var{command} string to the simulator. Consult the
18579 documentation for the specific simulator in use for information about
18580 acceptable commands.
18586 * M32R/D:: Renesas M32R/D
18587 * M68K:: Motorola M68K
18588 * MicroBlaze:: Xilinx MicroBlaze
18589 * MIPS Embedded:: MIPS Embedded
18590 * OpenRISC 1000:: OpenRisc 1000
18591 * PA:: HP PA Embedded
18592 * PowerPC Embedded:: PowerPC Embedded
18593 * Sparclet:: Tsqware Sparclet
18594 * Sparclite:: Fujitsu Sparclite
18595 * Z8000:: Zilog Z8000
18598 * Super-H:: Renesas Super-H
18607 @item target rdi @var{dev}
18608 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18609 use this target to communicate with both boards running the Angel
18610 monitor, or with the EmbeddedICE JTAG debug device.
18613 @item target rdp @var{dev}
18618 @value{GDBN} provides the following ARM-specific commands:
18621 @item set arm disassembler
18623 This commands selects from a list of disassembly styles. The
18624 @code{"std"} style is the standard style.
18626 @item show arm disassembler
18628 Show the current disassembly style.
18630 @item set arm apcs32
18631 @cindex ARM 32-bit mode
18632 This command toggles ARM operation mode between 32-bit and 26-bit.
18634 @item show arm apcs32
18635 Display the current usage of the ARM 32-bit mode.
18637 @item set arm fpu @var{fputype}
18638 This command sets the ARM floating-point unit (FPU) type. The
18639 argument @var{fputype} can be one of these:
18643 Determine the FPU type by querying the OS ABI.
18645 Software FPU, with mixed-endian doubles on little-endian ARM
18648 GCC-compiled FPA co-processor.
18650 Software FPU with pure-endian doubles.
18656 Show the current type of the FPU.
18659 This command forces @value{GDBN} to use the specified ABI.
18662 Show the currently used ABI.
18664 @item set arm fallback-mode (arm|thumb|auto)
18665 @value{GDBN} uses the symbol table, when available, to determine
18666 whether instructions are ARM or Thumb. This command controls
18667 @value{GDBN}'s default behavior when the symbol table is not
18668 available. The default is @samp{auto}, which causes @value{GDBN} to
18669 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18672 @item show arm fallback-mode
18673 Show the current fallback instruction mode.
18675 @item set arm force-mode (arm|thumb|auto)
18676 This command overrides use of the symbol table to determine whether
18677 instructions are ARM or Thumb. The default is @samp{auto}, which
18678 causes @value{GDBN} to use the symbol table and then the setting
18679 of @samp{set arm fallback-mode}.
18681 @item show arm force-mode
18682 Show the current forced instruction mode.
18684 @item set debug arm
18685 Toggle whether to display ARM-specific debugging messages from the ARM
18686 target support subsystem.
18688 @item show debug arm
18689 Show whether ARM-specific debugging messages are enabled.
18692 The following commands are available when an ARM target is debugged
18693 using the RDI interface:
18696 @item rdilogfile @r{[}@var{file}@r{]}
18698 @cindex ADP (Angel Debugger Protocol) logging
18699 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18700 With an argument, sets the log file to the specified @var{file}. With
18701 no argument, show the current log file name. The default log file is
18704 @item rdilogenable @r{[}@var{arg}@r{]}
18705 @kindex rdilogenable
18706 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18707 enables logging, with an argument 0 or @code{"no"} disables it. With
18708 no arguments displays the current setting. When logging is enabled,
18709 ADP packets exchanged between @value{GDBN} and the RDI target device
18710 are logged to a file.
18712 @item set rdiromatzero
18713 @kindex set rdiromatzero
18714 @cindex ROM at zero address, RDI
18715 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18716 vector catching is disabled, so that zero address can be used. If off
18717 (the default), vector catching is enabled. For this command to take
18718 effect, it needs to be invoked prior to the @code{target rdi} command.
18720 @item show rdiromatzero
18721 @kindex show rdiromatzero
18722 Show the current setting of ROM at zero address.
18724 @item set rdiheartbeat
18725 @kindex set rdiheartbeat
18726 @cindex RDI heartbeat
18727 Enable or disable RDI heartbeat packets. It is not recommended to
18728 turn on this option, since it confuses ARM and EPI JTAG interface, as
18729 well as the Angel monitor.
18731 @item show rdiheartbeat
18732 @kindex show rdiheartbeat
18733 Show the setting of RDI heartbeat packets.
18737 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18738 The @value{GDBN} ARM simulator accepts the following optional arguments.
18741 @item --swi-support=@var{type}
18742 Tell the simulator which SWI interfaces to support.
18743 @var{type} may be a comma separated list of the following values.
18744 The default value is @code{all}.
18757 @subsection Renesas M32R/D and M32R/SDI
18760 @kindex target m32r
18761 @item target m32r @var{dev}
18762 Renesas M32R/D ROM monitor.
18764 @kindex target m32rsdi
18765 @item target m32rsdi @var{dev}
18766 Renesas M32R SDI server, connected via parallel port to the board.
18769 The following @value{GDBN} commands are specific to the M32R monitor:
18772 @item set download-path @var{path}
18773 @kindex set download-path
18774 @cindex find downloadable @sc{srec} files (M32R)
18775 Set the default path for finding downloadable @sc{srec} files.
18777 @item show download-path
18778 @kindex show download-path
18779 Show the default path for downloadable @sc{srec} files.
18781 @item set board-address @var{addr}
18782 @kindex set board-address
18783 @cindex M32-EVA target board address
18784 Set the IP address for the M32R-EVA target board.
18786 @item show board-address
18787 @kindex show board-address
18788 Show the current IP address of the target board.
18790 @item set server-address @var{addr}
18791 @kindex set server-address
18792 @cindex download server address (M32R)
18793 Set the IP address for the download server, which is the @value{GDBN}'s
18796 @item show server-address
18797 @kindex show server-address
18798 Display the IP address of the download server.
18800 @item upload @r{[}@var{file}@r{]}
18801 @kindex upload@r{, M32R}
18802 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18803 upload capability. If no @var{file} argument is given, the current
18804 executable file is uploaded.
18806 @item tload @r{[}@var{file}@r{]}
18807 @kindex tload@r{, M32R}
18808 Test the @code{upload} command.
18811 The following commands are available for M32R/SDI:
18816 @cindex reset SDI connection, M32R
18817 This command resets the SDI connection.
18821 This command shows the SDI connection status.
18824 @kindex debug_chaos
18825 @cindex M32R/Chaos debugging
18826 Instructs the remote that M32R/Chaos debugging is to be used.
18828 @item use_debug_dma
18829 @kindex use_debug_dma
18830 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18833 @kindex use_mon_code
18834 Instructs the remote to use the MON_CODE method of accessing memory.
18837 @kindex use_ib_break
18838 Instructs the remote to set breakpoints by IB break.
18840 @item use_dbt_break
18841 @kindex use_dbt_break
18842 Instructs the remote to set breakpoints by DBT.
18848 The Motorola m68k configuration includes ColdFire support, and a
18849 target command for the following ROM monitor.
18853 @kindex target dbug
18854 @item target dbug @var{dev}
18855 dBUG ROM monitor for Motorola ColdFire.
18860 @subsection MicroBlaze
18861 @cindex Xilinx MicroBlaze
18862 @cindex XMD, Xilinx Microprocessor Debugger
18864 The MicroBlaze is a soft-core processor supported on various Xilinx
18865 FPGAs, such as Spartan or Virtex series. Boards with these processors
18866 usually have JTAG ports which connect to a host system running the Xilinx
18867 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18868 This host system is used to download the configuration bitstream to
18869 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18870 communicates with the target board using the JTAG interface and
18871 presents a @code{gdbserver} interface to the board. By default
18872 @code{xmd} uses port @code{1234}. (While it is possible to change
18873 this default port, it requires the use of undocumented @code{xmd}
18874 commands. Contact Xilinx support if you need to do this.)
18876 Use these GDB commands to connect to the MicroBlaze target processor.
18879 @item target remote :1234
18880 Use this command to connect to the target if you are running @value{GDBN}
18881 on the same system as @code{xmd}.
18883 @item target remote @var{xmd-host}:1234
18884 Use this command to connect to the target if it is connected to @code{xmd}
18885 running on a different system named @var{xmd-host}.
18888 Use this command to download a program to the MicroBlaze target.
18890 @item set debug microblaze @var{n}
18891 Enable MicroBlaze-specific debugging messages if non-zero.
18893 @item show debug microblaze @var{n}
18894 Show MicroBlaze-specific debugging level.
18897 @node MIPS Embedded
18898 @subsection MIPS Embedded
18900 @cindex MIPS boards
18901 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18902 MIPS board attached to a serial line. This is available when
18903 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18906 Use these @value{GDBN} commands to specify the connection to your target board:
18909 @item target mips @var{port}
18910 @kindex target mips @var{port}
18911 To run a program on the board, start up @code{@value{GDBP}} with the
18912 name of your program as the argument. To connect to the board, use the
18913 command @samp{target mips @var{port}}, where @var{port} is the name of
18914 the serial port connected to the board. If the program has not already
18915 been downloaded to the board, you may use the @code{load} command to
18916 download it. You can then use all the usual @value{GDBN} commands.
18918 For example, this sequence connects to the target board through a serial
18919 port, and loads and runs a program called @var{prog} through the
18923 host$ @value{GDBP} @var{prog}
18924 @value{GDBN} is free software and @dots{}
18925 (@value{GDBP}) target mips /dev/ttyb
18926 (@value{GDBP}) load @var{prog}
18930 @item target mips @var{hostname}:@var{portnumber}
18931 On some @value{GDBN} host configurations, you can specify a TCP
18932 connection (for instance, to a serial line managed by a terminal
18933 concentrator) instead of a serial port, using the syntax
18934 @samp{@var{hostname}:@var{portnumber}}.
18936 @item target pmon @var{port}
18937 @kindex target pmon @var{port}
18940 @item target ddb @var{port}
18941 @kindex target ddb @var{port}
18942 NEC's DDB variant of PMON for Vr4300.
18944 @item target lsi @var{port}
18945 @kindex target lsi @var{port}
18946 LSI variant of PMON.
18948 @kindex target r3900
18949 @item target r3900 @var{dev}
18950 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18952 @kindex target array
18953 @item target array @var{dev}
18954 Array Tech LSI33K RAID controller board.
18960 @value{GDBN} also supports these special commands for MIPS targets:
18963 @item set mipsfpu double
18964 @itemx set mipsfpu single
18965 @itemx set mipsfpu none
18966 @itemx set mipsfpu auto
18967 @itemx show mipsfpu
18968 @kindex set mipsfpu
18969 @kindex show mipsfpu
18970 @cindex MIPS remote floating point
18971 @cindex floating point, MIPS remote
18972 If your target board does not support the MIPS floating point
18973 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18974 need this, you may wish to put the command in your @value{GDBN} init
18975 file). This tells @value{GDBN} how to find the return value of
18976 functions which return floating point values. It also allows
18977 @value{GDBN} to avoid saving the floating point registers when calling
18978 functions on the board. If you are using a floating point coprocessor
18979 with only single precision floating point support, as on the @sc{r4650}
18980 processor, use the command @samp{set mipsfpu single}. The default
18981 double precision floating point coprocessor may be selected using
18982 @samp{set mipsfpu double}.
18984 In previous versions the only choices were double precision or no
18985 floating point, so @samp{set mipsfpu on} will select double precision
18986 and @samp{set mipsfpu off} will select no floating point.
18988 As usual, you can inquire about the @code{mipsfpu} variable with
18989 @samp{show mipsfpu}.
18991 @item set timeout @var{seconds}
18992 @itemx set retransmit-timeout @var{seconds}
18993 @itemx show timeout
18994 @itemx show retransmit-timeout
18995 @cindex @code{timeout}, MIPS protocol
18996 @cindex @code{retransmit-timeout}, MIPS protocol
18997 @kindex set timeout
18998 @kindex show timeout
18999 @kindex set retransmit-timeout
19000 @kindex show retransmit-timeout
19001 You can control the timeout used while waiting for a packet, in the MIPS
19002 remote protocol, with the @code{set timeout @var{seconds}} command. The
19003 default is 5 seconds. Similarly, you can control the timeout used while
19004 waiting for an acknowledgment of a packet with the @code{set
19005 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19006 You can inspect both values with @code{show timeout} and @code{show
19007 retransmit-timeout}. (These commands are @emph{only} available when
19008 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19010 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19011 is waiting for your program to stop. In that case, @value{GDBN} waits
19012 forever because it has no way of knowing how long the program is going
19013 to run before stopping.
19015 @item set syn-garbage-limit @var{num}
19016 @kindex set syn-garbage-limit@r{, MIPS remote}
19017 @cindex synchronize with remote MIPS target
19018 Limit the maximum number of characters @value{GDBN} should ignore when
19019 it tries to synchronize with the remote target. The default is 10
19020 characters. Setting the limit to -1 means there's no limit.
19022 @item show syn-garbage-limit
19023 @kindex show syn-garbage-limit@r{, MIPS remote}
19024 Show the current limit on the number of characters to ignore when
19025 trying to synchronize with the remote system.
19027 @item set monitor-prompt @var{prompt}
19028 @kindex set monitor-prompt@r{, MIPS remote}
19029 @cindex remote monitor prompt
19030 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19031 remote monitor. The default depends on the target:
19041 @item show monitor-prompt
19042 @kindex show monitor-prompt@r{, MIPS remote}
19043 Show the current strings @value{GDBN} expects as the prompt from the
19046 @item set monitor-warnings
19047 @kindex set monitor-warnings@r{, MIPS remote}
19048 Enable or disable monitor warnings about hardware breakpoints. This
19049 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19050 display warning messages whose codes are returned by the @code{lsi}
19051 PMON monitor for breakpoint commands.
19053 @item show monitor-warnings
19054 @kindex show monitor-warnings@r{, MIPS remote}
19055 Show the current setting of printing monitor warnings.
19057 @item pmon @var{command}
19058 @kindex pmon@r{, MIPS remote}
19059 @cindex send PMON command
19060 This command allows sending an arbitrary @var{command} string to the
19061 monitor. The monitor must be in debug mode for this to work.
19064 @node OpenRISC 1000
19065 @subsection OpenRISC 1000
19066 @cindex OpenRISC 1000
19068 @cindex or1k boards
19069 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19070 about platform and commands.
19074 @kindex target jtag
19075 @item target jtag jtag://@var{host}:@var{port}
19077 Connects to remote JTAG server.
19078 JTAG remote server can be either an or1ksim or JTAG server,
19079 connected via parallel port to the board.
19081 Example: @code{target jtag jtag://localhost:9999}
19084 @item or1ksim @var{command}
19085 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19086 Simulator, proprietary commands can be executed.
19088 @kindex info or1k spr
19089 @item info or1k spr
19090 Displays spr groups.
19092 @item info or1k spr @var{group}
19093 @itemx info or1k spr @var{groupno}
19094 Displays register names in selected group.
19096 @item info or1k spr @var{group} @var{register}
19097 @itemx info or1k spr @var{register}
19098 @itemx info or1k spr @var{groupno} @var{registerno}
19099 @itemx info or1k spr @var{registerno}
19100 Shows information about specified spr register.
19103 @item spr @var{group} @var{register} @var{value}
19104 @itemx spr @var{register @var{value}}
19105 @itemx spr @var{groupno} @var{registerno @var{value}}
19106 @itemx spr @var{registerno @var{value}}
19107 Writes @var{value} to specified spr register.
19110 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19111 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19112 program execution and is thus much faster. Hardware breakpoints/watchpoint
19113 triggers can be set using:
19116 Load effective address/data
19118 Store effective address/data
19120 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19125 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19126 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19128 @code{htrace} commands:
19129 @cindex OpenRISC 1000 htrace
19132 @item hwatch @var{conditional}
19133 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19134 or Data. For example:
19136 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19138 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19142 Display information about current HW trace configuration.
19144 @item htrace trigger @var{conditional}
19145 Set starting criteria for HW trace.
19147 @item htrace qualifier @var{conditional}
19148 Set acquisition qualifier for HW trace.
19150 @item htrace stop @var{conditional}
19151 Set HW trace stopping criteria.
19153 @item htrace record [@var{data}]*
19154 Selects the data to be recorded, when qualifier is met and HW trace was
19157 @item htrace enable
19158 @itemx htrace disable
19159 Enables/disables the HW trace.
19161 @item htrace rewind [@var{filename}]
19162 Clears currently recorded trace data.
19164 If filename is specified, new trace file is made and any newly collected data
19165 will be written there.
19167 @item htrace print [@var{start} [@var{len}]]
19168 Prints trace buffer, using current record configuration.
19170 @item htrace mode continuous
19171 Set continuous trace mode.
19173 @item htrace mode suspend
19174 Set suspend trace mode.
19178 @node PowerPC Embedded
19179 @subsection PowerPC Embedded
19181 @cindex DVC register
19182 @value{GDBN} supports using the DVC (Data Value Compare) register to
19183 implement in hardware simple hardware watchpoint conditions of the form:
19186 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19187 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19190 The DVC register will be automatically used when @value{GDBN} detects
19191 such pattern in a condition expression, and the created watchpoint uses one
19192 debug register (either the @code{exact-watchpoints} option is on and the
19193 variable is scalar, or the variable has a length of one byte). This feature
19194 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19197 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19198 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19199 in which case watchpoints using only one debug register are created when
19200 watching variables of scalar types.
19202 You can create an artificial array to watch an arbitrary memory
19203 region using one of the following commands (@pxref{Expressions}):
19206 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19207 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19210 PowerPC embedded processors support masked watchpoints. See the discussion
19211 about the @code{mask} argument in @ref{Set Watchpoints}.
19213 @cindex ranged breakpoint
19214 PowerPC embedded processors support hardware accelerated
19215 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19216 the inferior whenever it executes an instruction at any address within
19217 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19218 use the @code{break-range} command.
19220 @value{GDBN} provides the following PowerPC-specific commands:
19223 @kindex break-range
19224 @item break-range @var{start-location}, @var{end-location}
19225 Set a breakpoint for an address range.
19226 @var{start-location} and @var{end-location} can specify a function name,
19227 a line number, an offset of lines from the current line or from the start
19228 location, or an address of an instruction (see @ref{Specify Location},
19229 for a list of all the possible ways to specify a @var{location}.)
19230 The breakpoint will stop execution of the inferior whenever it
19231 executes an instruction at any address within the specified range,
19232 (including @var{start-location} and @var{end-location}.)
19234 @kindex set powerpc
19235 @item set powerpc soft-float
19236 @itemx show powerpc soft-float
19237 Force @value{GDBN} to use (or not use) a software floating point calling
19238 convention. By default, @value{GDBN} selects the calling convention based
19239 on the selected architecture and the provided executable file.
19241 @item set powerpc vector-abi
19242 @itemx show powerpc vector-abi
19243 Force @value{GDBN} to use the specified calling convention for vector
19244 arguments and return values. The valid options are @samp{auto};
19245 @samp{generic}, to avoid vector registers even if they are present;
19246 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19247 registers. By default, @value{GDBN} selects the calling convention
19248 based on the selected architecture and the provided executable file.
19250 @item set powerpc exact-watchpoints
19251 @itemx show powerpc exact-watchpoints
19252 Allow @value{GDBN} to use only one debug register when watching a variable
19253 of scalar type, thus assuming that the variable is accessed through the
19254 address of its first byte.
19256 @kindex target dink32
19257 @item target dink32 @var{dev}
19258 DINK32 ROM monitor.
19260 @kindex target ppcbug
19261 @item target ppcbug @var{dev}
19262 @kindex target ppcbug1
19263 @item target ppcbug1 @var{dev}
19264 PPCBUG ROM monitor for PowerPC.
19267 @item target sds @var{dev}
19268 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19271 @cindex SDS protocol
19272 The following commands specific to the SDS protocol are supported
19276 @item set sdstimeout @var{nsec}
19277 @kindex set sdstimeout
19278 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19279 default is 2 seconds.
19281 @item show sdstimeout
19282 @kindex show sdstimeout
19283 Show the current value of the SDS timeout.
19285 @item sds @var{command}
19286 @kindex sds@r{, a command}
19287 Send the specified @var{command} string to the SDS monitor.
19292 @subsection HP PA Embedded
19296 @kindex target op50n
19297 @item target op50n @var{dev}
19298 OP50N monitor, running on an OKI HPPA board.
19300 @kindex target w89k
19301 @item target w89k @var{dev}
19302 W89K monitor, running on a Winbond HPPA board.
19307 @subsection Tsqware Sparclet
19311 @value{GDBN} enables developers to debug tasks running on
19312 Sparclet targets from a Unix host.
19313 @value{GDBN} uses code that runs on
19314 both the Unix host and on the Sparclet target. The program
19315 @code{@value{GDBP}} is installed and executed on the Unix host.
19318 @item remotetimeout @var{args}
19319 @kindex remotetimeout
19320 @value{GDBN} supports the option @code{remotetimeout}.
19321 This option is set by the user, and @var{args} represents the number of
19322 seconds @value{GDBN} waits for responses.
19325 @cindex compiling, on Sparclet
19326 When compiling for debugging, include the options @samp{-g} to get debug
19327 information and @samp{-Ttext} to relocate the program to where you wish to
19328 load it on the target. You may also want to add the options @samp{-n} or
19329 @samp{-N} in order to reduce the size of the sections. Example:
19332 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19335 You can use @code{objdump} to verify that the addresses are what you intended:
19338 sparclet-aout-objdump --headers --syms prog
19341 @cindex running, on Sparclet
19343 your Unix execution search path to find @value{GDBN}, you are ready to
19344 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19345 (or @code{sparclet-aout-gdb}, depending on your installation).
19347 @value{GDBN} comes up showing the prompt:
19354 * Sparclet File:: Setting the file to debug
19355 * Sparclet Connection:: Connecting to Sparclet
19356 * Sparclet Download:: Sparclet download
19357 * Sparclet Execution:: Running and debugging
19360 @node Sparclet File
19361 @subsubsection Setting File to Debug
19363 The @value{GDBN} command @code{file} lets you choose with program to debug.
19366 (gdbslet) file prog
19370 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19371 @value{GDBN} locates
19372 the file by searching the directories listed in the command search
19374 If the file was compiled with debug information (option @samp{-g}), source
19375 files will be searched as well.
19376 @value{GDBN} locates
19377 the source files by searching the directories listed in the directory search
19378 path (@pxref{Environment, ,Your Program's Environment}).
19380 to find a file, it displays a message such as:
19383 prog: No such file or directory.
19386 When this happens, add the appropriate directories to the search paths with
19387 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19388 @code{target} command again.
19390 @node Sparclet Connection
19391 @subsubsection Connecting to Sparclet
19393 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19394 To connect to a target on serial port ``@code{ttya}'', type:
19397 (gdbslet) target sparclet /dev/ttya
19398 Remote target sparclet connected to /dev/ttya
19399 main () at ../prog.c:3
19403 @value{GDBN} displays messages like these:
19409 @node Sparclet Download
19410 @subsubsection Sparclet Download
19412 @cindex download to Sparclet
19413 Once connected to the Sparclet target,
19414 you can use the @value{GDBN}
19415 @code{load} command to download the file from the host to the target.
19416 The file name and load offset should be given as arguments to the @code{load}
19418 Since the file format is aout, the program must be loaded to the starting
19419 address. You can use @code{objdump} to find out what this value is. The load
19420 offset is an offset which is added to the VMA (virtual memory address)
19421 of each of the file's sections.
19422 For instance, if the program
19423 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19424 and bss at 0x12010170, in @value{GDBN}, type:
19427 (gdbslet) load prog 0x12010000
19428 Loading section .text, size 0xdb0 vma 0x12010000
19431 If the code is loaded at a different address then what the program was linked
19432 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19433 to tell @value{GDBN} where to map the symbol table.
19435 @node Sparclet Execution
19436 @subsubsection Running and Debugging
19438 @cindex running and debugging Sparclet programs
19439 You can now begin debugging the task using @value{GDBN}'s execution control
19440 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19441 manual for the list of commands.
19445 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19447 Starting program: prog
19448 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19449 3 char *symarg = 0;
19451 4 char *execarg = "hello!";
19456 @subsection Fujitsu Sparclite
19460 @kindex target sparclite
19461 @item target sparclite @var{dev}
19462 Fujitsu sparclite boards, used only for the purpose of loading.
19463 You must use an additional command to debug the program.
19464 For example: target remote @var{dev} using @value{GDBN} standard
19470 @subsection Zilog Z8000
19473 @cindex simulator, Z8000
19474 @cindex Zilog Z8000 simulator
19476 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19479 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19480 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19481 segmented variant). The simulator recognizes which architecture is
19482 appropriate by inspecting the object code.
19485 @item target sim @var{args}
19487 @kindex target sim@r{, with Z8000}
19488 Debug programs on a simulated CPU. If the simulator supports setup
19489 options, specify them via @var{args}.
19493 After specifying this target, you can debug programs for the simulated
19494 CPU in the same style as programs for your host computer; use the
19495 @code{file} command to load a new program image, the @code{run} command
19496 to run your program, and so on.
19498 As well as making available all the usual machine registers
19499 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19500 additional items of information as specially named registers:
19505 Counts clock-ticks in the simulator.
19508 Counts instructions run in the simulator.
19511 Execution time in 60ths of a second.
19515 You can refer to these values in @value{GDBN} expressions with the usual
19516 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19517 conditional breakpoint that suspends only after at least 5000
19518 simulated clock ticks.
19521 @subsection Atmel AVR
19524 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19525 following AVR-specific commands:
19528 @item info io_registers
19529 @kindex info io_registers@r{, AVR}
19530 @cindex I/O registers (Atmel AVR)
19531 This command displays information about the AVR I/O registers. For
19532 each register, @value{GDBN} prints its number and value.
19539 When configured for debugging CRIS, @value{GDBN} provides the
19540 following CRIS-specific commands:
19543 @item set cris-version @var{ver}
19544 @cindex CRIS version
19545 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19546 The CRIS version affects register names and sizes. This command is useful in
19547 case autodetection of the CRIS version fails.
19549 @item show cris-version
19550 Show the current CRIS version.
19552 @item set cris-dwarf2-cfi
19553 @cindex DWARF-2 CFI and CRIS
19554 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19555 Change to @samp{off} when using @code{gcc-cris} whose version is below
19558 @item show cris-dwarf2-cfi
19559 Show the current state of using DWARF-2 CFI.
19561 @item set cris-mode @var{mode}
19563 Set the current CRIS mode to @var{mode}. It should only be changed when
19564 debugging in guru mode, in which case it should be set to
19565 @samp{guru} (the default is @samp{normal}).
19567 @item show cris-mode
19568 Show the current CRIS mode.
19572 @subsection Renesas Super-H
19575 For the Renesas Super-H processor, @value{GDBN} provides these
19580 @kindex regs@r{, Super-H}
19581 Show the values of all Super-H registers.
19583 @item set sh calling-convention @var{convention}
19584 @kindex set sh calling-convention
19585 Set the calling-convention used when calling functions from @value{GDBN}.
19586 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19587 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19588 convention. If the DWARF-2 information of the called function specifies
19589 that the function follows the Renesas calling convention, the function
19590 is called using the Renesas calling convention. If the calling convention
19591 is set to @samp{renesas}, the Renesas calling convention is always used,
19592 regardless of the DWARF-2 information. This can be used to override the
19593 default of @samp{gcc} if debug information is missing, or the compiler
19594 does not emit the DWARF-2 calling convention entry for a function.
19596 @item show sh calling-convention
19597 @kindex show sh calling-convention
19598 Show the current calling convention setting.
19603 @node Architectures
19604 @section Architectures
19606 This section describes characteristics of architectures that affect
19607 all uses of @value{GDBN} with the architecture, both native and cross.
19614 * HPPA:: HP PA architecture
19615 * SPU:: Cell Broadband Engine SPU architecture
19620 @subsection x86 Architecture-specific Issues
19623 @item set struct-convention @var{mode}
19624 @kindex set struct-convention
19625 @cindex struct return convention
19626 @cindex struct/union returned in registers
19627 Set the convention used by the inferior to return @code{struct}s and
19628 @code{union}s from functions to @var{mode}. Possible values of
19629 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19630 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19631 are returned on the stack, while @code{"reg"} means that a
19632 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19633 be returned in a register.
19635 @item show struct-convention
19636 @kindex show struct-convention
19637 Show the current setting of the convention to return @code{struct}s
19646 @kindex set rstack_high_address
19647 @cindex AMD 29K register stack
19648 @cindex register stack, AMD29K
19649 @item set rstack_high_address @var{address}
19650 On AMD 29000 family processors, registers are saved in a separate
19651 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19652 extent of this stack. Normally, @value{GDBN} just assumes that the
19653 stack is ``large enough''. This may result in @value{GDBN} referencing
19654 memory locations that do not exist. If necessary, you can get around
19655 this problem by specifying the ending address of the register stack with
19656 the @code{set rstack_high_address} command. The argument should be an
19657 address, which you probably want to precede with @samp{0x} to specify in
19660 @kindex show rstack_high_address
19661 @item show rstack_high_address
19662 Display the current limit of the register stack, on AMD 29000 family
19670 See the following section.
19675 @cindex stack on Alpha
19676 @cindex stack on MIPS
19677 @cindex Alpha stack
19679 Alpha- and MIPS-based computers use an unusual stack frame, which
19680 sometimes requires @value{GDBN} to search backward in the object code to
19681 find the beginning of a function.
19683 @cindex response time, MIPS debugging
19684 To improve response time (especially for embedded applications, where
19685 @value{GDBN} may be restricted to a slow serial line for this search)
19686 you may want to limit the size of this search, using one of these
19690 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19691 @item set heuristic-fence-post @var{limit}
19692 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19693 search for the beginning of a function. A value of @var{0} (the
19694 default) means there is no limit. However, except for @var{0}, the
19695 larger the limit the more bytes @code{heuristic-fence-post} must search
19696 and therefore the longer it takes to run. You should only need to use
19697 this command when debugging a stripped executable.
19699 @item show heuristic-fence-post
19700 Display the current limit.
19704 These commands are available @emph{only} when @value{GDBN} is configured
19705 for debugging programs on Alpha or MIPS processors.
19707 Several MIPS-specific commands are available when debugging MIPS
19711 @item set mips abi @var{arg}
19712 @kindex set mips abi
19713 @cindex set ABI for MIPS
19714 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19715 values of @var{arg} are:
19719 The default ABI associated with the current binary (this is the
19730 @item show mips abi
19731 @kindex show mips abi
19732 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19735 @itemx show mipsfpu
19736 @xref{MIPS Embedded, set mipsfpu}.
19738 @item set mips mask-address @var{arg}
19739 @kindex set mips mask-address
19740 @cindex MIPS addresses, masking
19741 This command determines whether the most-significant 32 bits of 64-bit
19742 MIPS addresses are masked off. The argument @var{arg} can be
19743 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19744 setting, which lets @value{GDBN} determine the correct value.
19746 @item show mips mask-address
19747 @kindex show mips mask-address
19748 Show whether the upper 32 bits of MIPS addresses are masked off or
19751 @item set remote-mips64-transfers-32bit-regs
19752 @kindex set remote-mips64-transfers-32bit-regs
19753 This command controls compatibility with 64-bit MIPS targets that
19754 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19755 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19756 and 64 bits for other registers, set this option to @samp{on}.
19758 @item show remote-mips64-transfers-32bit-regs
19759 @kindex show remote-mips64-transfers-32bit-regs
19760 Show the current setting of compatibility with older MIPS 64 targets.
19762 @item set debug mips
19763 @kindex set debug mips
19764 This command turns on and off debugging messages for the MIPS-specific
19765 target code in @value{GDBN}.
19767 @item show debug mips
19768 @kindex show debug mips
19769 Show the current setting of MIPS debugging messages.
19775 @cindex HPPA support
19777 When @value{GDBN} is debugging the HP PA architecture, it provides the
19778 following special commands:
19781 @item set debug hppa
19782 @kindex set debug hppa
19783 This command determines whether HPPA architecture-specific debugging
19784 messages are to be displayed.
19786 @item show debug hppa
19787 Show whether HPPA debugging messages are displayed.
19789 @item maint print unwind @var{address}
19790 @kindex maint print unwind@r{, HPPA}
19791 This command displays the contents of the unwind table entry at the
19792 given @var{address}.
19798 @subsection Cell Broadband Engine SPU architecture
19799 @cindex Cell Broadband Engine
19802 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19803 it provides the following special commands:
19806 @item info spu event
19808 Display SPU event facility status. Shows current event mask
19809 and pending event status.
19811 @item info spu signal
19812 Display SPU signal notification facility status. Shows pending
19813 signal-control word and signal notification mode of both signal
19814 notification channels.
19816 @item info spu mailbox
19817 Display SPU mailbox facility status. Shows all pending entries,
19818 in order of processing, in each of the SPU Write Outbound,
19819 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19822 Display MFC DMA status. Shows all pending commands in the MFC
19823 DMA queue. For each entry, opcode, tag, class IDs, effective
19824 and local store addresses and transfer size are shown.
19826 @item info spu proxydma
19827 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19828 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19829 and local store addresses and transfer size are shown.
19833 When @value{GDBN} is debugging a combined PowerPC/SPU application
19834 on the Cell Broadband Engine, it provides in addition the following
19838 @item set spu stop-on-load @var{arg}
19840 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19841 will give control to the user when a new SPE thread enters its @code{main}
19842 function. The default is @code{off}.
19844 @item show spu stop-on-load
19846 Show whether to stop for new SPE threads.
19848 @item set spu auto-flush-cache @var{arg}
19849 Set whether to automatically flush the software-managed cache. When set to
19850 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19851 cache to be flushed whenever SPE execution stops. This provides a consistent
19852 view of PowerPC memory that is accessed via the cache. If an application
19853 does not use the software-managed cache, this option has no effect.
19855 @item show spu auto-flush-cache
19856 Show whether to automatically flush the software-managed cache.
19861 @subsection PowerPC
19862 @cindex PowerPC architecture
19864 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19865 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19866 numbers stored in the floating point registers. These values must be stored
19867 in two consecutive registers, always starting at an even register like
19868 @code{f0} or @code{f2}.
19870 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19871 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19872 @code{f2} and @code{f3} for @code{$dl1} and so on.
19874 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19875 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19878 @node Controlling GDB
19879 @chapter Controlling @value{GDBN}
19881 You can alter the way @value{GDBN} interacts with you by using the
19882 @code{set} command. For commands controlling how @value{GDBN} displays
19883 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19888 * Editing:: Command editing
19889 * Command History:: Command history
19890 * Screen Size:: Screen size
19891 * Numbers:: Numbers
19892 * ABI:: Configuring the current ABI
19893 * Messages/Warnings:: Optional warnings and messages
19894 * Debugging Output:: Optional messages about internal happenings
19895 * Other Misc Settings:: Other Miscellaneous Settings
19903 @value{GDBN} indicates its readiness to read a command by printing a string
19904 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19905 can change the prompt string with the @code{set prompt} command. For
19906 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19907 the prompt in one of the @value{GDBN} sessions so that you can always tell
19908 which one you are talking to.
19910 @emph{Note:} @code{set prompt} does not add a space for you after the
19911 prompt you set. This allows you to set a prompt which ends in a space
19912 or a prompt that does not.
19916 @item set prompt @var{newprompt}
19917 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19919 @kindex show prompt
19921 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19924 Versions of @value{GDBN} that ship with Python scripting enabled have
19925 prompt extensions. The commands for interacting with these extensions
19929 @kindex set extended-prompt
19930 @item set extended-prompt @var{prompt}
19931 Set an extended prompt that allows for substitutions.
19932 @xref{gdb.prompt}, for a list of escape sequences that can be used for
19933 substitution. Any escape sequences specified as part of the prompt
19934 string are replaced with the corresponding strings each time the prompt
19940 set extended-prompt Current working directory: \w (gdb)
19943 Note that when an extended-prompt is set, it takes control of the
19944 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
19946 @kindex show extended-prompt
19947 @item show extended-prompt
19948 Prints the extended prompt. Any escape sequences specified as part of
19949 the prompt string with @code{set extended-prompt}, are replaced with the
19950 corresponding strings each time the prompt is displayed.
19954 @section Command Editing
19956 @cindex command line editing
19958 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19959 @sc{gnu} library provides consistent behavior for programs which provide a
19960 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19961 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19962 substitution, and a storage and recall of command history across
19963 debugging sessions.
19965 You may control the behavior of command line editing in @value{GDBN} with the
19966 command @code{set}.
19969 @kindex set editing
19972 @itemx set editing on
19973 Enable command line editing (enabled by default).
19975 @item set editing off
19976 Disable command line editing.
19978 @kindex show editing
19980 Show whether command line editing is enabled.
19983 @ifset SYSTEM_READLINE
19984 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19986 @ifclear SYSTEM_READLINE
19987 @xref{Command Line Editing},
19989 for more details about the Readline
19990 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19991 encouraged to read that chapter.
19993 @node Command History
19994 @section Command History
19995 @cindex command history
19997 @value{GDBN} can keep track of the commands you type during your
19998 debugging sessions, so that you can be certain of precisely what
19999 happened. Use these commands to manage the @value{GDBN} command
20002 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20003 package, to provide the history facility.
20004 @ifset SYSTEM_READLINE
20005 @xref{Using History Interactively, , , history, GNU History Library},
20007 @ifclear SYSTEM_READLINE
20008 @xref{Using History Interactively},
20010 for the detailed description of the History library.
20012 To issue a command to @value{GDBN} without affecting certain aspects of
20013 the state which is seen by users, prefix it with @samp{server }
20014 (@pxref{Server Prefix}). This
20015 means that this command will not affect the command history, nor will it
20016 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20017 pressed on a line by itself.
20019 @cindex @code{server}, command prefix
20020 The server prefix does not affect the recording of values into the value
20021 history; to print a value without recording it into the value history,
20022 use the @code{output} command instead of the @code{print} command.
20024 Here is the description of @value{GDBN} commands related to command
20028 @cindex history substitution
20029 @cindex history file
20030 @kindex set history filename
20031 @cindex @env{GDBHISTFILE}, environment variable
20032 @item set history filename @var{fname}
20033 Set the name of the @value{GDBN} command history file to @var{fname}.
20034 This is the file where @value{GDBN} reads an initial command history
20035 list, and where it writes the command history from this session when it
20036 exits. You can access this list through history expansion or through
20037 the history command editing characters listed below. This file defaults
20038 to the value of the environment variable @code{GDBHISTFILE}, or to
20039 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20042 @cindex save command history
20043 @kindex set history save
20044 @item set history save
20045 @itemx set history save on
20046 Record command history in a file, whose name may be specified with the
20047 @code{set history filename} command. By default, this option is disabled.
20049 @item set history save off
20050 Stop recording command history in a file.
20052 @cindex history size
20053 @kindex set history size
20054 @cindex @env{HISTSIZE}, environment variable
20055 @item set history size @var{size}
20056 Set the number of commands which @value{GDBN} keeps in its history list.
20057 This defaults to the value of the environment variable
20058 @code{HISTSIZE}, or to 256 if this variable is not set.
20061 History expansion assigns special meaning to the character @kbd{!}.
20062 @ifset SYSTEM_READLINE
20063 @xref{Event Designators, , , history, GNU History Library},
20065 @ifclear SYSTEM_READLINE
20066 @xref{Event Designators},
20070 @cindex history expansion, turn on/off
20071 Since @kbd{!} is also the logical not operator in C, history expansion
20072 is off by default. If you decide to enable history expansion with the
20073 @code{set history expansion on} command, you may sometimes need to
20074 follow @kbd{!} (when it is used as logical not, in an expression) with
20075 a space or a tab to prevent it from being expanded. The readline
20076 history facilities do not attempt substitution on the strings
20077 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20079 The commands to control history expansion are:
20082 @item set history expansion on
20083 @itemx set history expansion
20084 @kindex set history expansion
20085 Enable history expansion. History expansion is off by default.
20087 @item set history expansion off
20088 Disable history expansion.
20091 @kindex show history
20093 @itemx show history filename
20094 @itemx show history save
20095 @itemx show history size
20096 @itemx show history expansion
20097 These commands display the state of the @value{GDBN} history parameters.
20098 @code{show history} by itself displays all four states.
20103 @kindex show commands
20104 @cindex show last commands
20105 @cindex display command history
20106 @item show commands
20107 Display the last ten commands in the command history.
20109 @item show commands @var{n}
20110 Print ten commands centered on command number @var{n}.
20112 @item show commands +
20113 Print ten commands just after the commands last printed.
20117 @section Screen Size
20118 @cindex size of screen
20119 @cindex pauses in output
20121 Certain commands to @value{GDBN} may produce large amounts of
20122 information output to the screen. To help you read all of it,
20123 @value{GDBN} pauses and asks you for input at the end of each page of
20124 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20125 to discard the remaining output. Also, the screen width setting
20126 determines when to wrap lines of output. Depending on what is being
20127 printed, @value{GDBN} tries to break the line at a readable place,
20128 rather than simply letting it overflow onto the following line.
20130 Normally @value{GDBN} knows the size of the screen from the terminal
20131 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20132 together with the value of the @code{TERM} environment variable and the
20133 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20134 you can override it with the @code{set height} and @code{set
20141 @kindex show height
20142 @item set height @var{lpp}
20144 @itemx set width @var{cpl}
20146 These @code{set} commands specify a screen height of @var{lpp} lines and
20147 a screen width of @var{cpl} characters. The associated @code{show}
20148 commands display the current settings.
20150 If you specify a height of zero lines, @value{GDBN} does not pause during
20151 output no matter how long the output is. This is useful if output is to a
20152 file or to an editor buffer.
20154 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20155 from wrapping its output.
20157 @item set pagination on
20158 @itemx set pagination off
20159 @kindex set pagination
20160 Turn the output pagination on or off; the default is on. Turning
20161 pagination off is the alternative to @code{set height 0}. Note that
20162 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20163 Options, -batch}) also automatically disables pagination.
20165 @item show pagination
20166 @kindex show pagination
20167 Show the current pagination mode.
20172 @cindex number representation
20173 @cindex entering numbers
20175 You can always enter numbers in octal, decimal, or hexadecimal in
20176 @value{GDBN} by the usual conventions: octal numbers begin with
20177 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20178 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20179 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20180 10; likewise, the default display for numbers---when no particular
20181 format is specified---is base 10. You can change the default base for
20182 both input and output with the commands described below.
20185 @kindex set input-radix
20186 @item set input-radix @var{base}
20187 Set the default base for numeric input. Supported choices
20188 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20189 specified either unambiguously or using the current input radix; for
20193 set input-radix 012
20194 set input-radix 10.
20195 set input-radix 0xa
20199 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20200 leaves the input radix unchanged, no matter what it was, since
20201 @samp{10}, being without any leading or trailing signs of its base, is
20202 interpreted in the current radix. Thus, if the current radix is 16,
20203 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20206 @kindex set output-radix
20207 @item set output-radix @var{base}
20208 Set the default base for numeric display. Supported choices
20209 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20210 specified either unambiguously or using the current input radix.
20212 @kindex show input-radix
20213 @item show input-radix
20214 Display the current default base for numeric input.
20216 @kindex show output-radix
20217 @item show output-radix
20218 Display the current default base for numeric display.
20220 @item set radix @r{[}@var{base}@r{]}
20224 These commands set and show the default base for both input and output
20225 of numbers. @code{set radix} sets the radix of input and output to
20226 the same base; without an argument, it resets the radix back to its
20227 default value of 10.
20232 @section Configuring the Current ABI
20234 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20235 application automatically. However, sometimes you need to override its
20236 conclusions. Use these commands to manage @value{GDBN}'s view of the
20243 One @value{GDBN} configuration can debug binaries for multiple operating
20244 system targets, either via remote debugging or native emulation.
20245 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20246 but you can override its conclusion using the @code{set osabi} command.
20247 One example where this is useful is in debugging of binaries which use
20248 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20249 not have the same identifying marks that the standard C library for your
20254 Show the OS ABI currently in use.
20257 With no argument, show the list of registered available OS ABI's.
20259 @item set osabi @var{abi}
20260 Set the current OS ABI to @var{abi}.
20263 @cindex float promotion
20265 Generally, the way that an argument of type @code{float} is passed to a
20266 function depends on whether the function is prototyped. For a prototyped
20267 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20268 according to the architecture's convention for @code{float}. For unprototyped
20269 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20270 @code{double} and then passed.
20272 Unfortunately, some forms of debug information do not reliably indicate whether
20273 a function is prototyped. If @value{GDBN} calls a function that is not marked
20274 as prototyped, it consults @kbd{set coerce-float-to-double}.
20277 @kindex set coerce-float-to-double
20278 @item set coerce-float-to-double
20279 @itemx set coerce-float-to-double on
20280 Arguments of type @code{float} will be promoted to @code{double} when passed
20281 to an unprototyped function. This is the default setting.
20283 @item set coerce-float-to-double off
20284 Arguments of type @code{float} will be passed directly to unprototyped
20287 @kindex show coerce-float-to-double
20288 @item show coerce-float-to-double
20289 Show the current setting of promoting @code{float} to @code{double}.
20293 @kindex show cp-abi
20294 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20295 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20296 used to build your application. @value{GDBN} only fully supports
20297 programs with a single C@t{++} ABI; if your program contains code using
20298 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20299 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20300 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20301 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20302 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20303 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20308 Show the C@t{++} ABI currently in use.
20311 With no argument, show the list of supported C@t{++} ABI's.
20313 @item set cp-abi @var{abi}
20314 @itemx set cp-abi auto
20315 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20318 @node Messages/Warnings
20319 @section Optional Warnings and Messages
20321 @cindex verbose operation
20322 @cindex optional warnings
20323 By default, @value{GDBN} is silent about its inner workings. If you are
20324 running on a slow machine, you may want to use the @code{set verbose}
20325 command. This makes @value{GDBN} tell you when it does a lengthy
20326 internal operation, so you will not think it has crashed.
20328 Currently, the messages controlled by @code{set verbose} are those
20329 which announce that the symbol table for a source file is being read;
20330 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20333 @kindex set verbose
20334 @item set verbose on
20335 Enables @value{GDBN} output of certain informational messages.
20337 @item set verbose off
20338 Disables @value{GDBN} output of certain informational messages.
20340 @kindex show verbose
20342 Displays whether @code{set verbose} is on or off.
20345 By default, if @value{GDBN} encounters bugs in the symbol table of an
20346 object file, it is silent; but if you are debugging a compiler, you may
20347 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20352 @kindex set complaints
20353 @item set complaints @var{limit}
20354 Permits @value{GDBN} to output @var{limit} complaints about each type of
20355 unusual symbols before becoming silent about the problem. Set
20356 @var{limit} to zero to suppress all complaints; set it to a large number
20357 to prevent complaints from being suppressed.
20359 @kindex show complaints
20360 @item show complaints
20361 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20365 @anchor{confirmation requests}
20366 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20367 lot of stupid questions to confirm certain commands. For example, if
20368 you try to run a program which is already running:
20372 The program being debugged has been started already.
20373 Start it from the beginning? (y or n)
20376 If you are willing to unflinchingly face the consequences of your own
20377 commands, you can disable this ``feature'':
20381 @kindex set confirm
20383 @cindex confirmation
20384 @cindex stupid questions
20385 @item set confirm off
20386 Disables confirmation requests. Note that running @value{GDBN} with
20387 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20388 automatically disables confirmation requests.
20390 @item set confirm on
20391 Enables confirmation requests (the default).
20393 @kindex show confirm
20395 Displays state of confirmation requests.
20399 @cindex command tracing
20400 If you need to debug user-defined commands or sourced files you may find it
20401 useful to enable @dfn{command tracing}. In this mode each command will be
20402 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20403 quantity denoting the call depth of each command.
20406 @kindex set trace-commands
20407 @cindex command scripts, debugging
20408 @item set trace-commands on
20409 Enable command tracing.
20410 @item set trace-commands off
20411 Disable command tracing.
20412 @item show trace-commands
20413 Display the current state of command tracing.
20416 @node Debugging Output
20417 @section Optional Messages about Internal Happenings
20418 @cindex optional debugging messages
20420 @value{GDBN} has commands that enable optional debugging messages from
20421 various @value{GDBN} subsystems; normally these commands are of
20422 interest to @value{GDBN} maintainers, or when reporting a bug. This
20423 section documents those commands.
20426 @kindex set exec-done-display
20427 @item set exec-done-display
20428 Turns on or off the notification of asynchronous commands'
20429 completion. When on, @value{GDBN} will print a message when an
20430 asynchronous command finishes its execution. The default is off.
20431 @kindex show exec-done-display
20432 @item show exec-done-display
20433 Displays the current setting of asynchronous command completion
20436 @cindex gdbarch debugging info
20437 @cindex architecture debugging info
20438 @item set debug arch
20439 Turns on or off display of gdbarch debugging info. The default is off
20441 @item show debug arch
20442 Displays the current state of displaying gdbarch debugging info.
20443 @item set debug aix-thread
20444 @cindex AIX threads
20445 Display debugging messages about inner workings of the AIX thread
20447 @item show debug aix-thread
20448 Show the current state of AIX thread debugging info display.
20449 @item set debug check-physname
20451 Check the results of the ``physname'' computation. When reading DWARF
20452 debugging information for C@t{++}, @value{GDBN} attempts to compute
20453 each entity's name. @value{GDBN} can do this computation in two
20454 different ways, depending on exactly what information is present.
20455 When enabled, this setting causes @value{GDBN} to compute the names
20456 both ways and display any discrepancies.
20457 @item show debug check-physname
20458 Show the current state of ``physname'' checking.
20459 @item set debug dwarf2-die
20460 @cindex DWARF2 DIEs
20461 Dump DWARF2 DIEs after they are read in.
20462 The value is the number of nesting levels to print.
20463 A value of zero turns off the display.
20464 @item show debug dwarf2-die
20465 Show the current state of DWARF2 DIE debugging.
20466 @item set debug displaced
20467 @cindex displaced stepping debugging info
20468 Turns on or off display of @value{GDBN} debugging info for the
20469 displaced stepping support. The default is off.
20470 @item show debug displaced
20471 Displays the current state of displaying @value{GDBN} debugging info
20472 related to displaced stepping.
20473 @item set debug event
20474 @cindex event debugging info
20475 Turns on or off display of @value{GDBN} event debugging info. The
20477 @item show debug event
20478 Displays the current state of displaying @value{GDBN} event debugging
20480 @item set debug expression
20481 @cindex expression debugging info
20482 Turns on or off display of debugging info about @value{GDBN}
20483 expression parsing. The default is off.
20484 @item show debug expression
20485 Displays the current state of displaying debugging info about
20486 @value{GDBN} expression parsing.
20487 @item set debug frame
20488 @cindex frame debugging info
20489 Turns on or off display of @value{GDBN} frame debugging info. The
20491 @item show debug frame
20492 Displays the current state of displaying @value{GDBN} frame debugging
20494 @item set debug gnu-nat
20495 @cindex @sc{gnu}/Hurd debug messages
20496 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20497 @item show debug gnu-nat
20498 Show the current state of @sc{gnu}/Hurd debugging messages.
20499 @item set debug infrun
20500 @cindex inferior debugging info
20501 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20502 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20503 for implementing operations such as single-stepping the inferior.
20504 @item show debug infrun
20505 Displays the current state of @value{GDBN} inferior debugging.
20506 @item set debug jit
20507 @cindex just-in-time compilation, debugging messages
20508 Turns on or off debugging messages from JIT debug support.
20509 @item show debug jit
20510 Displays the current state of @value{GDBN} JIT debugging.
20511 @item set debug lin-lwp
20512 @cindex @sc{gnu}/Linux LWP debug messages
20513 @cindex Linux lightweight processes
20514 Turns on or off debugging messages from the Linux LWP debug support.
20515 @item show debug lin-lwp
20516 Show the current state of Linux LWP debugging messages.
20517 @item set debug observer
20518 @cindex observer debugging info
20519 Turns on or off display of @value{GDBN} observer debugging. This
20520 includes info such as the notification of observable events.
20521 @item show debug observer
20522 Displays the current state of observer debugging.
20523 @item set debug overload
20524 @cindex C@t{++} overload debugging info
20525 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20526 info. This includes info such as ranking of functions, etc. The default
20528 @item show debug overload
20529 Displays the current state of displaying @value{GDBN} C@t{++} overload
20531 @cindex expression parser, debugging info
20532 @cindex debug expression parser
20533 @item set debug parser
20534 Turns on or off the display of expression parser debugging output.
20535 Internally, this sets the @code{yydebug} variable in the expression
20536 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20537 details. The default is off.
20538 @item show debug parser
20539 Show the current state of expression parser debugging.
20540 @cindex packets, reporting on stdout
20541 @cindex serial connections, debugging
20542 @cindex debug remote protocol
20543 @cindex remote protocol debugging
20544 @cindex display remote packets
20545 @item set debug remote
20546 Turns on or off display of reports on all packets sent back and forth across
20547 the serial line to the remote machine. The info is printed on the
20548 @value{GDBN} standard output stream. The default is off.
20549 @item show debug remote
20550 Displays the state of display of remote packets.
20551 @item set debug serial
20552 Turns on or off display of @value{GDBN} serial debugging info. The
20554 @item show debug serial
20555 Displays the current state of displaying @value{GDBN} serial debugging
20557 @item set debug solib-frv
20558 @cindex FR-V shared-library debugging
20559 Turns on or off debugging messages for FR-V shared-library code.
20560 @item show debug solib-frv
20561 Display the current state of FR-V shared-library code debugging
20563 @item set debug target
20564 @cindex target debugging info
20565 Turns on or off display of @value{GDBN} target debugging info. This info
20566 includes what is going on at the target level of GDB, as it happens. The
20567 default is 0. Set it to 1 to track events, and to 2 to also track the
20568 value of large memory transfers. Changes to this flag do not take effect
20569 until the next time you connect to a target or use the @code{run} command.
20570 @item show debug target
20571 Displays the current state of displaying @value{GDBN} target debugging
20573 @item set debug timestamp
20574 @cindex timestampping debugging info
20575 Turns on or off display of timestamps with @value{GDBN} debugging info.
20576 When enabled, seconds and microseconds are displayed before each debugging
20578 @item show debug timestamp
20579 Displays the current state of displaying timestamps with @value{GDBN}
20581 @item set debugvarobj
20582 @cindex variable object debugging info
20583 Turns on or off display of @value{GDBN} variable object debugging
20584 info. The default is off.
20585 @item show debugvarobj
20586 Displays the current state of displaying @value{GDBN} variable object
20588 @item set debug xml
20589 @cindex XML parser debugging
20590 Turns on or off debugging messages for built-in XML parsers.
20591 @item show debug xml
20592 Displays the current state of XML debugging messages.
20595 @node Other Misc Settings
20596 @section Other Miscellaneous Settings
20597 @cindex miscellaneous settings
20600 @kindex set interactive-mode
20601 @item set interactive-mode
20602 If @code{on}, forces @value{GDBN} to assume that GDB was started
20603 in a terminal. In practice, this means that @value{GDBN} should wait
20604 for the user to answer queries generated by commands entered at
20605 the command prompt. If @code{off}, forces @value{GDBN} to operate
20606 in the opposite mode, and it uses the default answers to all queries.
20607 If @code{auto} (the default), @value{GDBN} tries to determine whether
20608 its standard input is a terminal, and works in interactive-mode if it
20609 is, non-interactively otherwise.
20611 In the vast majority of cases, the debugger should be able to guess
20612 correctly which mode should be used. But this setting can be useful
20613 in certain specific cases, such as running a MinGW @value{GDBN}
20614 inside a cygwin window.
20616 @kindex show interactive-mode
20617 @item show interactive-mode
20618 Displays whether the debugger is operating in interactive mode or not.
20621 @node Extending GDB
20622 @chapter Extending @value{GDBN}
20623 @cindex extending GDB
20625 @value{GDBN} provides three mechanisms for extension. The first is based
20626 on composition of @value{GDBN} commands, the second is based on the
20627 Python scripting language, and the third is for defining new aliases of
20630 To facilitate the use of the first two extensions, @value{GDBN} is capable
20631 of evaluating the contents of a file. When doing so, @value{GDBN}
20632 can recognize which scripting language is being used by looking at
20633 the filename extension. Files with an unrecognized filename extension
20634 are always treated as a @value{GDBN} Command Files.
20635 @xref{Command Files,, Command files}.
20637 You can control how @value{GDBN} evaluates these files with the following
20641 @kindex set script-extension
20642 @kindex show script-extension
20643 @item set script-extension off
20644 All scripts are always evaluated as @value{GDBN} Command Files.
20646 @item set script-extension soft
20647 The debugger determines the scripting language based on filename
20648 extension. If this scripting language is supported, @value{GDBN}
20649 evaluates the script using that language. Otherwise, it evaluates
20650 the file as a @value{GDBN} Command File.
20652 @item set script-extension strict
20653 The debugger determines the scripting language based on filename
20654 extension, and evaluates the script using that language. If the
20655 language is not supported, then the evaluation fails.
20657 @item show script-extension
20658 Display the current value of the @code{script-extension} option.
20663 * Sequences:: Canned Sequences of Commands
20664 * Python:: Scripting @value{GDBN} using Python
20665 * Aliases:: Creating new spellings of existing commands
20669 @section Canned Sequences of Commands
20671 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20672 Command Lists}), @value{GDBN} provides two ways to store sequences of
20673 commands for execution as a unit: user-defined commands and command
20677 * Define:: How to define your own commands
20678 * Hooks:: Hooks for user-defined commands
20679 * Command Files:: How to write scripts of commands to be stored in a file
20680 * Output:: Commands for controlled output
20684 @subsection User-defined Commands
20686 @cindex user-defined command
20687 @cindex arguments, to user-defined commands
20688 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20689 which you assign a new name as a command. This is done with the
20690 @code{define} command. User commands may accept up to 10 arguments
20691 separated by whitespace. Arguments are accessed within the user command
20692 via @code{$arg0@dots{}$arg9}. A trivial example:
20696 print $arg0 + $arg1 + $arg2
20701 To execute the command use:
20708 This defines the command @code{adder}, which prints the sum of
20709 its three arguments. Note the arguments are text substitutions, so they may
20710 reference variables, use complex expressions, or even perform inferior
20713 @cindex argument count in user-defined commands
20714 @cindex how many arguments (user-defined commands)
20715 In addition, @code{$argc} may be used to find out how many arguments have
20716 been passed. This expands to a number in the range 0@dots{}10.
20721 print $arg0 + $arg1
20724 print $arg0 + $arg1 + $arg2
20732 @item define @var{commandname}
20733 Define a command named @var{commandname}. If there is already a command
20734 by that name, you are asked to confirm that you want to redefine it.
20735 @var{commandname} may be a bare command name consisting of letters,
20736 numbers, dashes, and underscores. It may also start with any predefined
20737 prefix command. For example, @samp{define target my-target} creates
20738 a user-defined @samp{target my-target} command.
20740 The definition of the command is made up of other @value{GDBN} command lines,
20741 which are given following the @code{define} command. The end of these
20742 commands is marked by a line containing @code{end}.
20745 @kindex end@r{ (user-defined commands)}
20746 @item document @var{commandname}
20747 Document the user-defined command @var{commandname}, so that it can be
20748 accessed by @code{help}. The command @var{commandname} must already be
20749 defined. This command reads lines of documentation just as @code{define}
20750 reads the lines of the command definition, ending with @code{end}.
20751 After the @code{document} command is finished, @code{help} on command
20752 @var{commandname} displays the documentation you have written.
20754 You may use the @code{document} command again to change the
20755 documentation of a command. Redefining the command with @code{define}
20756 does not change the documentation.
20758 @kindex dont-repeat
20759 @cindex don't repeat command
20761 Used inside a user-defined command, this tells @value{GDBN} that this
20762 command should not be repeated when the user hits @key{RET}
20763 (@pxref{Command Syntax, repeat last command}).
20765 @kindex help user-defined
20766 @item help user-defined
20767 List all user-defined commands, with the first line of the documentation
20772 @itemx show user @var{commandname}
20773 Display the @value{GDBN} commands used to define @var{commandname} (but
20774 not its documentation). If no @var{commandname} is given, display the
20775 definitions for all user-defined commands.
20777 @cindex infinite recursion in user-defined commands
20778 @kindex show max-user-call-depth
20779 @kindex set max-user-call-depth
20780 @item show max-user-call-depth
20781 @itemx set max-user-call-depth
20782 The value of @code{max-user-call-depth} controls how many recursion
20783 levels are allowed in user-defined commands before @value{GDBN} suspects an
20784 infinite recursion and aborts the command.
20787 In addition to the above commands, user-defined commands frequently
20788 use control flow commands, described in @ref{Command Files}.
20790 When user-defined commands are executed, the
20791 commands of the definition are not printed. An error in any command
20792 stops execution of the user-defined command.
20794 If used interactively, commands that would ask for confirmation proceed
20795 without asking when used inside a user-defined command. Many @value{GDBN}
20796 commands that normally print messages to say what they are doing omit the
20797 messages when used in a user-defined command.
20800 @subsection User-defined Command Hooks
20801 @cindex command hooks
20802 @cindex hooks, for commands
20803 @cindex hooks, pre-command
20806 You may define @dfn{hooks}, which are a special kind of user-defined
20807 command. Whenever you run the command @samp{foo}, if the user-defined
20808 command @samp{hook-foo} exists, it is executed (with no arguments)
20809 before that command.
20811 @cindex hooks, post-command
20813 A hook may also be defined which is run after the command you executed.
20814 Whenever you run the command @samp{foo}, if the user-defined command
20815 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20816 that command. Post-execution hooks may exist simultaneously with
20817 pre-execution hooks, for the same command.
20819 It is valid for a hook to call the command which it hooks. If this
20820 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20822 @c It would be nice if hookpost could be passed a parameter indicating
20823 @c if the command it hooks executed properly or not. FIXME!
20825 @kindex stop@r{, a pseudo-command}
20826 In addition, a pseudo-command, @samp{stop} exists. Defining
20827 (@samp{hook-stop}) makes the associated commands execute every time
20828 execution stops in your program: before breakpoint commands are run,
20829 displays are printed, or the stack frame is printed.
20831 For example, to ignore @code{SIGALRM} signals while
20832 single-stepping, but treat them normally during normal execution,
20837 handle SIGALRM nopass
20841 handle SIGALRM pass
20844 define hook-continue
20845 handle SIGALRM pass
20849 As a further example, to hook at the beginning and end of the @code{echo}
20850 command, and to add extra text to the beginning and end of the message,
20858 define hookpost-echo
20862 (@value{GDBP}) echo Hello World
20863 <<<---Hello World--->>>
20868 You can define a hook for any single-word command in @value{GDBN}, but
20869 not for command aliases; you should define a hook for the basic command
20870 name, e.g.@: @code{backtrace} rather than @code{bt}.
20871 @c FIXME! So how does Joe User discover whether a command is an alias
20873 You can hook a multi-word command by adding @code{hook-} or
20874 @code{hookpost-} to the last word of the command, e.g.@:
20875 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20877 If an error occurs during the execution of your hook, execution of
20878 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20879 (before the command that you actually typed had a chance to run).
20881 If you try to define a hook which does not match any known command, you
20882 get a warning from the @code{define} command.
20884 @node Command Files
20885 @subsection Command Files
20887 @cindex command files
20888 @cindex scripting commands
20889 A command file for @value{GDBN} is a text file made of lines that are
20890 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20891 also be included. An empty line in a command file does nothing; it
20892 does not mean to repeat the last command, as it would from the
20895 You can request the execution of a command file with the @code{source}
20896 command. Note that the @code{source} command is also used to evaluate
20897 scripts that are not Command Files. The exact behavior can be configured
20898 using the @code{script-extension} setting.
20899 @xref{Extending GDB,, Extending GDB}.
20903 @cindex execute commands from a file
20904 @item source [-s] [-v] @var{filename}
20905 Execute the command file @var{filename}.
20908 The lines in a command file are generally executed sequentially,
20909 unless the order of execution is changed by one of the
20910 @emph{flow-control commands} described below. The commands are not
20911 printed as they are executed. An error in any command terminates
20912 execution of the command file and control is returned to the console.
20914 @value{GDBN} first searches for @var{filename} in the current directory.
20915 If the file is not found there, and @var{filename} does not specify a
20916 directory, then @value{GDBN} also looks for the file on the source search path
20917 (specified with the @samp{directory} command);
20918 except that @file{$cdir} is not searched because the compilation directory
20919 is not relevant to scripts.
20921 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20922 on the search path even if @var{filename} specifies a directory.
20923 The search is done by appending @var{filename} to each element of the
20924 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20925 and the search path contains @file{/home/user} then @value{GDBN} will
20926 look for the script @file{/home/user/mylib/myscript}.
20927 The search is also done if @var{filename} is an absolute path.
20928 For example, if @var{filename} is @file{/tmp/myscript} and
20929 the search path contains @file{/home/user} then @value{GDBN} will
20930 look for the script @file{/home/user/tmp/myscript}.
20931 For DOS-like systems, if @var{filename} contains a drive specification,
20932 it is stripped before concatenation. For example, if @var{filename} is
20933 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20934 will look for the script @file{c:/tmp/myscript}.
20936 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20937 each command as it is executed. The option must be given before
20938 @var{filename}, and is interpreted as part of the filename anywhere else.
20940 Commands that would ask for confirmation if used interactively proceed
20941 without asking when used in a command file. Many @value{GDBN} commands that
20942 normally print messages to say what they are doing omit the messages
20943 when called from command files.
20945 @value{GDBN} also accepts command input from standard input. In this
20946 mode, normal output goes to standard output and error output goes to
20947 standard error. Errors in a command file supplied on standard input do
20948 not terminate execution of the command file---execution continues with
20952 gdb < cmds > log 2>&1
20955 (The syntax above will vary depending on the shell used.) This example
20956 will execute commands from the file @file{cmds}. All output and errors
20957 would be directed to @file{log}.
20959 Since commands stored on command files tend to be more general than
20960 commands typed interactively, they frequently need to deal with
20961 complicated situations, such as different or unexpected values of
20962 variables and symbols, changes in how the program being debugged is
20963 built, etc. @value{GDBN} provides a set of flow-control commands to
20964 deal with these complexities. Using these commands, you can write
20965 complex scripts that loop over data structures, execute commands
20966 conditionally, etc.
20973 This command allows to include in your script conditionally executed
20974 commands. The @code{if} command takes a single argument, which is an
20975 expression to evaluate. It is followed by a series of commands that
20976 are executed only if the expression is true (its value is nonzero).
20977 There can then optionally be an @code{else} line, followed by a series
20978 of commands that are only executed if the expression was false. The
20979 end of the list is marked by a line containing @code{end}.
20983 This command allows to write loops. Its syntax is similar to
20984 @code{if}: the command takes a single argument, which is an expression
20985 to evaluate, and must be followed by the commands to execute, one per
20986 line, terminated by an @code{end}. These commands are called the
20987 @dfn{body} of the loop. The commands in the body of @code{while} are
20988 executed repeatedly as long as the expression evaluates to true.
20992 This command exits the @code{while} loop in whose body it is included.
20993 Execution of the script continues after that @code{while}s @code{end}
20996 @kindex loop_continue
20997 @item loop_continue
20998 This command skips the execution of the rest of the body of commands
20999 in the @code{while} loop in whose body it is included. Execution
21000 branches to the beginning of the @code{while} loop, where it evaluates
21001 the controlling expression.
21003 @kindex end@r{ (if/else/while commands)}
21005 Terminate the block of commands that are the body of @code{if},
21006 @code{else}, or @code{while} flow-control commands.
21011 @subsection Commands for Controlled Output
21013 During the execution of a command file or a user-defined command, normal
21014 @value{GDBN} output is suppressed; the only output that appears is what is
21015 explicitly printed by the commands in the definition. This section
21016 describes three commands useful for generating exactly the output you
21021 @item echo @var{text}
21022 @c I do not consider backslash-space a standard C escape sequence
21023 @c because it is not in ANSI.
21024 Print @var{text}. Nonprinting characters can be included in
21025 @var{text} using C escape sequences, such as @samp{\n} to print a
21026 newline. @strong{No newline is printed unless you specify one.}
21027 In addition to the standard C escape sequences, a backslash followed
21028 by a space stands for a space. This is useful for displaying a
21029 string with spaces at the beginning or the end, since leading and
21030 trailing spaces are otherwise trimmed from all arguments.
21031 To print @samp{@w{ }and foo =@w{ }}, use the command
21032 @samp{echo \@w{ }and foo = \@w{ }}.
21034 A backslash at the end of @var{text} can be used, as in C, to continue
21035 the command onto subsequent lines. For example,
21038 echo This is some text\n\
21039 which is continued\n\
21040 onto several lines.\n
21043 produces the same output as
21046 echo This is some text\n
21047 echo which is continued\n
21048 echo onto several lines.\n
21052 @item output @var{expression}
21053 Print the value of @var{expression} and nothing but that value: no
21054 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21055 value history either. @xref{Expressions, ,Expressions}, for more information
21058 @item output/@var{fmt} @var{expression}
21059 Print the value of @var{expression} in format @var{fmt}. You can use
21060 the same formats as for @code{print}. @xref{Output Formats,,Output
21061 Formats}, for more information.
21064 @item printf @var{template}, @var{expressions}@dots{}
21065 Print the values of one or more @var{expressions} under the control of
21066 the string @var{template}. To print several values, make
21067 @var{expressions} be a comma-separated list of individual expressions,
21068 which may be either numbers or pointers. Their values are printed as
21069 specified by @var{template}, exactly as a C program would do by
21070 executing the code below:
21073 printf (@var{template}, @var{expressions}@dots{});
21076 As in @code{C} @code{printf}, ordinary characters in @var{template}
21077 are printed verbatim, while @dfn{conversion specification} introduced
21078 by the @samp{%} character cause subsequent @var{expressions} to be
21079 evaluated, their values converted and formatted according to type and
21080 style information encoded in the conversion specifications, and then
21083 For example, you can print two values in hex like this:
21086 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21089 @code{printf} supports all the standard @code{C} conversion
21090 specifications, including the flags and modifiers between the @samp{%}
21091 character and the conversion letter, with the following exceptions:
21095 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21098 The modifier @samp{*} is not supported for specifying precision or
21102 The @samp{'} flag (for separation of digits into groups according to
21103 @code{LC_NUMERIC'}) is not supported.
21106 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21110 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21113 The conversion letters @samp{a} and @samp{A} are not supported.
21117 Note that the @samp{ll} type modifier is supported only if the
21118 underlying @code{C} implementation used to build @value{GDBN} supports
21119 the @code{long long int} type, and the @samp{L} type modifier is
21120 supported only if @code{long double} type is available.
21122 As in @code{C}, @code{printf} supports simple backslash-escape
21123 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21124 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21125 single character. Octal and hexadecimal escape sequences are not
21128 Additionally, @code{printf} supports conversion specifications for DFP
21129 (@dfn{Decimal Floating Point}) types using the following length modifiers
21130 together with a floating point specifier.
21135 @samp{H} for printing @code{Decimal32} types.
21138 @samp{D} for printing @code{Decimal64} types.
21141 @samp{DD} for printing @code{Decimal128} types.
21144 If the underlying @code{C} implementation used to build @value{GDBN} has
21145 support for the three length modifiers for DFP types, other modifiers
21146 such as width and precision will also be available for @value{GDBN} to use.
21148 In case there is no such @code{C} support, no additional modifiers will be
21149 available and the value will be printed in the standard way.
21151 Here's an example of printing DFP types using the above conversion letters:
21153 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21157 @item eval @var{template}, @var{expressions}@dots{}
21158 Convert the values of one or more @var{expressions} under the control of
21159 the string @var{template} to a command line, and call it.
21164 @section Scripting @value{GDBN} using Python
21165 @cindex python scripting
21166 @cindex scripting with python
21168 You can script @value{GDBN} using the @uref{http://www.python.org/,
21169 Python programming language}. This feature is available only if
21170 @value{GDBN} was configured using @option{--with-python}.
21172 @cindex python directory
21173 Python scripts used by @value{GDBN} should be installed in
21174 @file{@var{data-directory}/python}, where @var{data-directory} is
21175 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21176 This directory, known as the @dfn{python directory},
21177 is automatically added to the Python Search Path in order to allow
21178 the Python interpreter to locate all scripts installed at this location.
21180 Additionally, @value{GDBN} commands and convenience functions which
21181 are written in Python and are located in the
21182 @file{@var{data-directory}/python/gdb/command} or
21183 @file{@var{data-directory}/python/gdb/function} directories are
21184 automatically imported when @value{GDBN} starts.
21187 * Python Commands:: Accessing Python from @value{GDBN}.
21188 * Python API:: Accessing @value{GDBN} from Python.
21189 * Auto-loading:: Automatically loading Python code.
21190 * Python modules:: Python modules provided by @value{GDBN}.
21193 @node Python Commands
21194 @subsection Python Commands
21195 @cindex python commands
21196 @cindex commands to access python
21198 @value{GDBN} provides one command for accessing the Python interpreter,
21199 and one related setting:
21203 @item python @r{[}@var{code}@r{]}
21204 The @code{python} command can be used to evaluate Python code.
21206 If given an argument, the @code{python} command will evaluate the
21207 argument as a Python command. For example:
21210 (@value{GDBP}) python print 23
21214 If you do not provide an argument to @code{python}, it will act as a
21215 multi-line command, like @code{define}. In this case, the Python
21216 script is made up of subsequent command lines, given after the
21217 @code{python} command. This command list is terminated using a line
21218 containing @code{end}. For example:
21221 (@value{GDBP}) python
21223 End with a line saying just "end".
21229 @kindex maint set python print-stack
21230 @item maint set python print-stack
21231 This command is now deprecated. Instead use @code{set python
21234 @kindex set python print-stack
21235 @item set python print-stack
21236 By default, @value{GDBN} will not print a stack trace when an error
21237 occurs in a Python script. This can be controlled using @code{set
21238 python print-stack}: if @code{on}, then Python stack printing is
21239 enabled; if @code{off}, the default, then Python stack printing is
21243 It is also possible to execute a Python script from the @value{GDBN}
21247 @item source @file{script-name}
21248 The script name must end with @samp{.py} and @value{GDBN} must be configured
21249 to recognize the script language based on filename extension using
21250 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21252 @item python execfile ("script-name")
21253 This method is based on the @code{execfile} Python built-in function,
21254 and thus is always available.
21258 @subsection Python API
21260 @cindex programming in python
21262 @cindex python stdout
21263 @cindex python pagination
21264 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21265 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21266 A Python program which outputs to one of these streams may have its
21267 output interrupted by the user (@pxref{Screen Size}). In this
21268 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21271 * Basic Python:: Basic Python Functions.
21272 * Exception Handling:: How Python exceptions are translated.
21273 * Values From Inferior:: Python representation of values.
21274 * Types In Python:: Python representation of types.
21275 * Pretty Printing API:: Pretty-printing values.
21276 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21277 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21278 * Inferiors In Python:: Python representation of inferiors (processes)
21279 * Events In Python:: Listening for events from @value{GDBN}.
21280 * Threads In Python:: Accessing inferior threads from Python.
21281 * Commands In Python:: Implementing new commands in Python.
21282 * Parameters In Python:: Adding new @value{GDBN} parameters.
21283 * Functions In Python:: Writing new convenience functions.
21284 * Progspaces In Python:: Program spaces.
21285 * Objfiles In Python:: Object files.
21286 * Frames In Python:: Accessing inferior stack frames from Python.
21287 * Blocks In Python:: Accessing frame blocks from Python.
21288 * Symbols In Python:: Python representation of symbols.
21289 * Symbol Tables In Python:: Python representation of symbol tables.
21290 * Lazy Strings In Python:: Python representation of lazy strings.
21291 * Breakpoints In Python:: Manipulating breakpoints using Python.
21295 @subsubsection Basic Python
21297 @cindex python functions
21298 @cindex python module
21300 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21301 methods and classes added by @value{GDBN} are placed in this module.
21302 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21303 use in all scripts evaluated by the @code{python} command.
21305 @findex gdb.PYTHONDIR
21306 @defvar gdb.PYTHONDIR
21307 A string containing the python directory (@pxref{Python}).
21310 @findex gdb.execute
21311 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21312 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21313 If a GDB exception happens while @var{command} runs, it is
21314 translated as described in @ref{Exception Handling,,Exception Handling}.
21316 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21317 command as having originated from the user invoking it interactively.
21318 It must be a boolean value. If omitted, it defaults to @code{False}.
21320 By default, any output produced by @var{command} is sent to
21321 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21322 @code{True}, then output will be collected by @code{gdb.execute} and
21323 returned as a string. The default is @code{False}, in which case the
21324 return value is @code{None}. If @var{to_string} is @code{True}, the
21325 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21326 and height, and its pagination will be disabled; @pxref{Screen Size}.
21329 @findex gdb.breakpoints
21330 @defun gdb.breakpoints ()
21331 Return a sequence holding all of @value{GDBN}'s breakpoints.
21332 @xref{Breakpoints In Python}, for more information.
21335 @findex gdb.parameter
21336 @defun gdb.parameter (parameter)
21337 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21338 string naming the parameter to look up; @var{parameter} may contain
21339 spaces if the parameter has a multi-part name. For example,
21340 @samp{print object} is a valid parameter name.
21342 If the named parameter does not exist, this function throws a
21343 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21344 parameter's value is converted to a Python value of the appropriate
21345 type, and returned.
21348 @findex gdb.history
21349 @defun gdb.history (number)
21350 Return a value from @value{GDBN}'s value history (@pxref{Value
21351 History}). @var{number} indicates which history element to return.
21352 If @var{number} is negative, then @value{GDBN} will take its absolute value
21353 and count backward from the last element (i.e., the most recent element) to
21354 find the value to return. If @var{number} is zero, then @value{GDBN} will
21355 return the most recent element. If the element specified by @var{number}
21356 doesn't exist in the value history, a @code{gdb.error} exception will be
21359 If no exception is raised, the return value is always an instance of
21360 @code{gdb.Value} (@pxref{Values From Inferior}).
21363 @findex gdb.parse_and_eval
21364 @defun gdb.parse_and_eval (expression)
21365 Parse @var{expression} as an expression in the current language,
21366 evaluate it, and return the result as a @code{gdb.Value}.
21367 @var{expression} must be a string.
21369 This function can be useful when implementing a new command
21370 (@pxref{Commands In Python}), as it provides a way to parse the
21371 command's argument as an expression. It is also useful simply to
21372 compute values, for example, it is the only way to get the value of a
21373 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21376 @findex gdb.post_event
21377 @defun gdb.post_event (event)
21378 Put @var{event}, a callable object taking no arguments, into
21379 @value{GDBN}'s internal event queue. This callable will be invoked at
21380 some later point, during @value{GDBN}'s event processing. Events
21381 posted using @code{post_event} will be run in the order in which they
21382 were posted; however, there is no way to know when they will be
21383 processed relative to other events inside @value{GDBN}.
21385 @value{GDBN} is not thread-safe. If your Python program uses multiple
21386 threads, you must be careful to only call @value{GDBN}-specific
21387 functions in the main @value{GDBN} thread. @code{post_event} ensures
21391 (@value{GDBP}) python
21395 > def __init__(self, message):
21396 > self.message = message;
21397 > def __call__(self):
21398 > gdb.write(self.message)
21400 >class MyThread1 (threading.Thread):
21402 > gdb.post_event(Writer("Hello "))
21404 >class MyThread2 (threading.Thread):
21406 > gdb.post_event(Writer("World\n"))
21408 >MyThread1().start()
21409 >MyThread2().start()
21411 (@value{GDBP}) Hello World
21416 @defun gdb.write (string @r{[}, stream{]})
21417 Print a string to @value{GDBN}'s paginated output stream. The
21418 optional @var{stream} determines the stream to print to. The default
21419 stream is @value{GDBN}'s standard output stream. Possible stream
21426 @value{GDBN}'s standard output stream.
21431 @value{GDBN}'s standard error stream.
21436 @value{GDBN}'s log stream (@pxref{Logging Output}).
21439 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21440 call this function and will automatically direct the output to the
21445 @defun gdb.flush ()
21446 Flush the buffer of a @value{GDBN} paginated stream so that the
21447 contents are displayed immediately. @value{GDBN} will flush the
21448 contents of a stream automatically when it encounters a newline in the
21449 buffer. The optional @var{stream} determines the stream to flush. The
21450 default stream is @value{GDBN}'s standard output stream. Possible
21457 @value{GDBN}'s standard output stream.
21462 @value{GDBN}'s standard error stream.
21467 @value{GDBN}'s log stream (@pxref{Logging Output}).
21471 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21472 call this function for the relevant stream.
21475 @findex gdb.target_charset
21476 @defun gdb.target_charset ()
21477 Return the name of the current target character set (@pxref{Character
21478 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21479 that @samp{auto} is never returned.
21482 @findex gdb.target_wide_charset
21483 @defun gdb.target_wide_charset ()
21484 Return the name of the current target wide character set
21485 (@pxref{Character Sets}). This differs from
21486 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21490 @findex gdb.solib_name
21491 @defun gdb.solib_name (address)
21492 Return the name of the shared library holding the given @var{address}
21493 as a string, or @code{None}.
21496 @findex gdb.decode_line
21497 @defun gdb.decode_line @r{[}expression@r{]}
21498 Return locations of the line specified by @var{expression}, or of the
21499 current line if no argument was given. This function returns a Python
21500 tuple containing two elements. The first element contains a string
21501 holding any unparsed section of @var{expression} (or @code{None} if
21502 the expression has been fully parsed). The second element contains
21503 either @code{None} or another tuple that contains all the locations
21504 that match the expression represented as @code{gdb.Symtab_and_line}
21505 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21506 provided, it is decoded the way that @value{GDBN}'s inbuilt
21507 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21510 @defun gdb.prompt_hook (current_prompt)
21511 @anchor{prompt_hook}
21513 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21514 assigned to this operation before a prompt is displayed by
21517 The parameter @code{current_prompt} contains the current @value{GDBN}
21518 prompt. This method must return a Python string, or @code{None}. If
21519 a string is returned, the @value{GDBN} prompt will be set to that
21520 string. If @code{None} is returned, @value{GDBN} will continue to use
21521 the current prompt.
21523 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21524 such as those used by readline for command input, and annotation
21525 related prompts are prohibited from being changed.
21528 @node Exception Handling
21529 @subsubsection Exception Handling
21530 @cindex python exceptions
21531 @cindex exceptions, python
21533 When executing the @code{python} command, Python exceptions
21534 uncaught within the Python code are translated to calls to
21535 @value{GDBN} error-reporting mechanism. If the command that called
21536 @code{python} does not handle the error, @value{GDBN} will
21537 terminate it and print an error message containing the Python
21538 exception name, the associated value, and the Python call stack
21539 backtrace at the point where the exception was raised. Example:
21542 (@value{GDBP}) python print foo
21543 Traceback (most recent call last):
21544 File "<string>", line 1, in <module>
21545 NameError: name 'foo' is not defined
21548 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21549 Python code are converted to Python exceptions. The type of the
21550 Python exception depends on the error.
21554 This is the base class for most exceptions generated by @value{GDBN}.
21555 It is derived from @code{RuntimeError}, for compatibility with earlier
21556 versions of @value{GDBN}.
21558 If an error occurring in @value{GDBN} does not fit into some more
21559 specific category, then the generated exception will have this type.
21561 @item gdb.MemoryError
21562 This is a subclass of @code{gdb.error} which is thrown when an
21563 operation tried to access invalid memory in the inferior.
21565 @item KeyboardInterrupt
21566 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21567 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21570 In all cases, your exception handler will see the @value{GDBN} error
21571 message as its value and the Python call stack backtrace at the Python
21572 statement closest to where the @value{GDBN} error occured as the
21575 @findex gdb.GdbError
21576 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21577 it is useful to be able to throw an exception that doesn't cause a
21578 traceback to be printed. For example, the user may have invoked the
21579 command incorrectly. Use the @code{gdb.GdbError} exception
21580 to handle this case. Example:
21584 >class HelloWorld (gdb.Command):
21585 > """Greet the whole world."""
21586 > def __init__ (self):
21587 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21588 > def invoke (self, args, from_tty):
21589 > argv = gdb.string_to_argv (args)
21590 > if len (argv) != 0:
21591 > raise gdb.GdbError ("hello-world takes no arguments")
21592 > print "Hello, World!"
21595 (gdb) hello-world 42
21596 hello-world takes no arguments
21599 @node Values From Inferior
21600 @subsubsection Values From Inferior
21601 @cindex values from inferior, with Python
21602 @cindex python, working with values from inferior
21604 @cindex @code{gdb.Value}
21605 @value{GDBN} provides values it obtains from the inferior program in
21606 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21607 for its internal bookkeeping of the inferior's values, and for
21608 fetching values when necessary.
21610 Inferior values that are simple scalars can be used directly in
21611 Python expressions that are valid for the value's data type. Here's
21612 an example for an integer or floating-point value @code{some_val}:
21619 As result of this, @code{bar} will also be a @code{gdb.Value} object
21620 whose values are of the same type as those of @code{some_val}.
21622 Inferior values that are structures or instances of some class can
21623 be accessed using the Python @dfn{dictionary syntax}. For example, if
21624 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21625 can access its @code{foo} element with:
21628 bar = some_val['foo']
21631 Again, @code{bar} will also be a @code{gdb.Value} object.
21633 A @code{gdb.Value} that represents a function can be executed via
21634 inferior function call. Any arguments provided to the call must match
21635 the function's prototype, and must be provided in the order specified
21638 For example, @code{some_val} is a @code{gdb.Value} instance
21639 representing a function that takes two integers as arguments. To
21640 execute this function, call it like so:
21643 result = some_val (10,20)
21646 Any values returned from a function call will be stored as a
21649 The following attributes are provided:
21652 @defvar Value.address
21653 If this object is addressable, this read-only attribute holds a
21654 @code{gdb.Value} object representing the address. Otherwise,
21655 this attribute holds @code{None}.
21658 @cindex optimized out value in Python
21659 @defvar Value.is_optimized_out
21660 This read-only boolean attribute is true if the compiler optimized out
21661 this value, thus it is not available for fetching from the inferior.
21665 The type of this @code{gdb.Value}. The value of this attribute is a
21666 @code{gdb.Type} object (@pxref{Types In Python}).
21669 @defvar Value.dynamic_type
21670 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21671 type information (@acronym{RTTI}) to determine the dynamic type of the
21672 value. If this value is of class type, it will return the class in
21673 which the value is embedded, if any. If this value is of pointer or
21674 reference to a class type, it will compute the dynamic type of the
21675 referenced object, and return a pointer or reference to that type,
21676 respectively. In all other cases, it will return the value's static
21679 Note that this feature will only work when debugging a C@t{++} program
21680 that includes @acronym{RTTI} for the object in question. Otherwise,
21681 it will just return the static type of the value as in @kbd{ptype foo}
21682 (@pxref{Symbols, ptype}).
21685 @defvar Value.is_lazy
21686 The value of this read-only boolean attribute is @code{True} if this
21687 @code{gdb.Value} has not yet been fetched from the inferior.
21688 @value{GDBN} does not fetch values until necessary, for efficiency.
21692 myval = gdb.parse_and_eval ('somevar')
21695 The value of @code{somevar} is not fetched at this time. It will be
21696 fetched when the value is needed, or when the @code{fetch_lazy}
21701 The following methods are provided:
21704 @defun Value.__init__ (@var{val})
21705 Many Python values can be converted directly to a @code{gdb.Value} via
21706 this object initializer. Specifically:
21709 @item Python boolean
21710 A Python boolean is converted to the boolean type from the current
21713 @item Python integer
21714 A Python integer is converted to the C @code{long} type for the
21715 current architecture.
21718 A Python long is converted to the C @code{long long} type for the
21719 current architecture.
21722 A Python float is converted to the C @code{double} type for the
21723 current architecture.
21725 @item Python string
21726 A Python string is converted to a target string, using the current
21729 @item @code{gdb.Value}
21730 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21732 @item @code{gdb.LazyString}
21733 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21734 Python}), then the lazy string's @code{value} method is called, and
21735 its result is used.
21739 @defun Value.cast (type)
21740 Return a new instance of @code{gdb.Value} that is the result of
21741 casting this instance to the type described by @var{type}, which must
21742 be a @code{gdb.Type} object. If the cast cannot be performed for some
21743 reason, this method throws an exception.
21746 @defun Value.dereference ()
21747 For pointer data types, this method returns a new @code{gdb.Value} object
21748 whose contents is the object pointed to by the pointer. For example, if
21749 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21756 then you can use the corresponding @code{gdb.Value} to access what
21757 @code{foo} points to like this:
21760 bar = foo.dereference ()
21763 The result @code{bar} will be a @code{gdb.Value} object holding the
21764 value pointed to by @code{foo}.
21767 @defun Value.dynamic_cast (type)
21768 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21769 operator were used. Consult a C@t{++} reference for details.
21772 @defun Value.reinterpret_cast (type)
21773 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21774 operator were used. Consult a C@t{++} reference for details.
21777 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
21778 If this @code{gdb.Value} represents a string, then this method
21779 converts the contents to a Python string. Otherwise, this method will
21780 throw an exception.
21782 Strings are recognized in a language-specific way; whether a given
21783 @code{gdb.Value} represents a string is determined by the current
21786 For C-like languages, a value is a string if it is a pointer to or an
21787 array of characters or ints. The string is assumed to be terminated
21788 by a zero of the appropriate width. However if the optional length
21789 argument is given, the string will be converted to that given length,
21790 ignoring any embedded zeros that the string may contain.
21792 If the optional @var{encoding} argument is given, it must be a string
21793 naming the encoding of the string in the @code{gdb.Value}, such as
21794 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21795 the same encodings as the corresponding argument to Python's
21796 @code{string.decode} method, and the Python codec machinery will be used
21797 to convert the string. If @var{encoding} is not given, or if
21798 @var{encoding} is the empty string, then either the @code{target-charset}
21799 (@pxref{Character Sets}) will be used, or a language-specific encoding
21800 will be used, if the current language is able to supply one.
21802 The optional @var{errors} argument is the same as the corresponding
21803 argument to Python's @code{string.decode} method.
21805 If the optional @var{length} argument is given, the string will be
21806 fetched and converted to the given length.
21809 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
21810 If this @code{gdb.Value} represents a string, then this method
21811 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21812 In Python}). Otherwise, this method will throw an exception.
21814 If the optional @var{encoding} argument is given, it must be a string
21815 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21816 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21817 @var{encoding} argument is an encoding that @value{GDBN} does
21818 recognize, @value{GDBN} will raise an error.
21820 When a lazy string is printed, the @value{GDBN} encoding machinery is
21821 used to convert the string during printing. If the optional
21822 @var{encoding} argument is not provided, or is an empty string,
21823 @value{GDBN} will automatically select the encoding most suitable for
21824 the string type. For further information on encoding in @value{GDBN}
21825 please see @ref{Character Sets}.
21827 If the optional @var{length} argument is given, the string will be
21828 fetched and encoded to the length of characters specified. If
21829 the @var{length} argument is not provided, the string will be fetched
21830 and encoded until a null of appropriate width is found.
21833 @defun Value.fetch_lazy ()
21834 If the @code{gdb.Value} object is currently a lazy value
21835 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
21836 fetched from the inferior. Any errors that occur in the process
21837 will produce a Python exception.
21839 If the @code{gdb.Value} object is not a lazy value, this method
21842 This method does not return a value.
21847 @node Types In Python
21848 @subsubsection Types In Python
21849 @cindex types in Python
21850 @cindex Python, working with types
21853 @value{GDBN} represents types from the inferior using the class
21856 The following type-related functions are available in the @code{gdb}
21859 @findex gdb.lookup_type
21860 @defun gdb.lookup_type (name @r{[}, block@r{]})
21861 This function looks up a type by name. @var{name} is the name of the
21862 type to look up. It must be a string.
21864 If @var{block} is given, then @var{name} is looked up in that scope.
21865 Otherwise, it is searched for globally.
21867 Ordinarily, this function will return an instance of @code{gdb.Type}.
21868 If the named type cannot be found, it will throw an exception.
21871 If the type is a structure or class type, or an enum type, the fields
21872 of that type can be accessed using the Python @dfn{dictionary syntax}.
21873 For example, if @code{some_type} is a @code{gdb.Type} instance holding
21874 a structure type, you can access its @code{foo} field with:
21877 bar = some_type['foo']
21880 @code{bar} will be a @code{gdb.Field} object; see below under the
21881 description of the @code{Type.fields} method for a description of the
21882 @code{gdb.Field} class.
21884 An instance of @code{Type} has the following attributes:
21888 The type code for this type. The type code will be one of the
21889 @code{TYPE_CODE_} constants defined below.
21892 @defvar Type.sizeof
21893 The size of this type, in target @code{char} units. Usually, a
21894 target's @code{char} type will be an 8-bit byte. However, on some
21895 unusual platforms, this type may have a different size.
21899 The tag name for this type. The tag name is the name after
21900 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21901 languages have this concept. If this type has no tag name, then
21902 @code{None} is returned.
21906 The following methods are provided:
21909 @defun Type.fields ()
21910 For structure and union types, this method returns the fields. Range
21911 types have two fields, the minimum and maximum values. Enum types
21912 have one field per enum constant. Function and method types have one
21913 field per parameter. The base types of C@t{++} classes are also
21914 represented as fields. If the type has no fields, or does not fit
21915 into one of these categories, an empty sequence will be returned.
21917 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
21920 This attribute is not available for @code{static} fields (as in
21921 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21922 position of the field. For @code{enum} fields, the value is the
21923 enumeration member's integer representation.
21926 The name of the field, or @code{None} for anonymous fields.
21929 This is @code{True} if the field is artificial, usually meaning that
21930 it was provided by the compiler and not the user. This attribute is
21931 always provided, and is @code{False} if the field is not artificial.
21933 @item is_base_class
21934 This is @code{True} if the field represents a base class of a C@t{++}
21935 structure. This attribute is always provided, and is @code{False}
21936 if the field is not a base class of the type that is the argument of
21937 @code{fields}, or if that type was not a C@t{++} class.
21940 If the field is packed, or is a bitfield, then this will have a
21941 non-zero value, which is the size of the field in bits. Otherwise,
21942 this will be zero; in this case the field's size is given by its type.
21945 The type of the field. This is usually an instance of @code{Type},
21946 but it can be @code{None} in some situations.
21950 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
21951 Return a new @code{gdb.Type} object which represents an array of this
21952 type. If one argument is given, it is the inclusive upper bound of
21953 the array; in this case the lower bound is zero. If two arguments are
21954 given, the first argument is the lower bound of the array, and the
21955 second argument is the upper bound of the array. An array's length
21956 must not be negative, but the bounds can be.
21959 @defun Type.const ()
21960 Return a new @code{gdb.Type} object which represents a
21961 @code{const}-qualified variant of this type.
21964 @defun Type.volatile ()
21965 Return a new @code{gdb.Type} object which represents a
21966 @code{volatile}-qualified variant of this type.
21969 @defun Type.unqualified ()
21970 Return a new @code{gdb.Type} object which represents an unqualified
21971 variant of this type. That is, the result is neither @code{const} nor
21975 @defun Type.range ()
21976 Return a Python @code{Tuple} object that contains two elements: the
21977 low bound of the argument type and the high bound of that type. If
21978 the type does not have a range, @value{GDBN} will raise a
21979 @code{gdb.error} exception (@pxref{Exception Handling}).
21982 @defun Type.reference ()
21983 Return a new @code{gdb.Type} object which represents a reference to this
21987 @defun Type.pointer ()
21988 Return a new @code{gdb.Type} object which represents a pointer to this
21992 @defun Type.strip_typedefs ()
21993 Return a new @code{gdb.Type} that represents the real type,
21994 after removing all layers of typedefs.
21997 @defun Type.target ()
21998 Return a new @code{gdb.Type} object which represents the target type
22001 For a pointer type, the target type is the type of the pointed-to
22002 object. For an array type (meaning C-like arrays), the target type is
22003 the type of the elements of the array. For a function or method type,
22004 the target type is the type of the return value. For a complex type,
22005 the target type is the type of the elements. For a typedef, the
22006 target type is the aliased type.
22008 If the type does not have a target, this method will throw an
22012 @defun Type.template_argument (n @r{[}, block@r{]})
22013 If this @code{gdb.Type} is an instantiation of a template, this will
22014 return a new @code{gdb.Type} which represents the type of the
22015 @var{n}th template argument.
22017 If this @code{gdb.Type} is not a template type, this will throw an
22018 exception. Ordinarily, only C@t{++} code will have template types.
22020 If @var{block} is given, then @var{name} is looked up in that scope.
22021 Otherwise, it is searched for globally.
22026 Each type has a code, which indicates what category this type falls
22027 into. The available type categories are represented by constants
22028 defined in the @code{gdb} module:
22031 @findex TYPE_CODE_PTR
22032 @findex gdb.TYPE_CODE_PTR
22033 @item gdb.TYPE_CODE_PTR
22034 The type is a pointer.
22036 @findex TYPE_CODE_ARRAY
22037 @findex gdb.TYPE_CODE_ARRAY
22038 @item gdb.TYPE_CODE_ARRAY
22039 The type is an array.
22041 @findex TYPE_CODE_STRUCT
22042 @findex gdb.TYPE_CODE_STRUCT
22043 @item gdb.TYPE_CODE_STRUCT
22044 The type is a structure.
22046 @findex TYPE_CODE_UNION
22047 @findex gdb.TYPE_CODE_UNION
22048 @item gdb.TYPE_CODE_UNION
22049 The type is a union.
22051 @findex TYPE_CODE_ENUM
22052 @findex gdb.TYPE_CODE_ENUM
22053 @item gdb.TYPE_CODE_ENUM
22054 The type is an enum.
22056 @findex TYPE_CODE_FLAGS
22057 @findex gdb.TYPE_CODE_FLAGS
22058 @item gdb.TYPE_CODE_FLAGS
22059 A bit flags type, used for things such as status registers.
22061 @findex TYPE_CODE_FUNC
22062 @findex gdb.TYPE_CODE_FUNC
22063 @item gdb.TYPE_CODE_FUNC
22064 The type is a function.
22066 @findex TYPE_CODE_INT
22067 @findex gdb.TYPE_CODE_INT
22068 @item gdb.TYPE_CODE_INT
22069 The type is an integer type.
22071 @findex TYPE_CODE_FLT
22072 @findex gdb.TYPE_CODE_FLT
22073 @item gdb.TYPE_CODE_FLT
22074 A floating point type.
22076 @findex TYPE_CODE_VOID
22077 @findex gdb.TYPE_CODE_VOID
22078 @item gdb.TYPE_CODE_VOID
22079 The special type @code{void}.
22081 @findex TYPE_CODE_SET
22082 @findex gdb.TYPE_CODE_SET
22083 @item gdb.TYPE_CODE_SET
22086 @findex TYPE_CODE_RANGE
22087 @findex gdb.TYPE_CODE_RANGE
22088 @item gdb.TYPE_CODE_RANGE
22089 A range type, that is, an integer type with bounds.
22091 @findex TYPE_CODE_STRING
22092 @findex gdb.TYPE_CODE_STRING
22093 @item gdb.TYPE_CODE_STRING
22094 A string type. Note that this is only used for certain languages with
22095 language-defined string types; C strings are not represented this way.
22097 @findex TYPE_CODE_BITSTRING
22098 @findex gdb.TYPE_CODE_BITSTRING
22099 @item gdb.TYPE_CODE_BITSTRING
22102 @findex TYPE_CODE_ERROR
22103 @findex gdb.TYPE_CODE_ERROR
22104 @item gdb.TYPE_CODE_ERROR
22105 An unknown or erroneous type.
22107 @findex TYPE_CODE_METHOD
22108 @findex gdb.TYPE_CODE_METHOD
22109 @item gdb.TYPE_CODE_METHOD
22110 A method type, as found in C@t{++} or Java.
22112 @findex TYPE_CODE_METHODPTR
22113 @findex gdb.TYPE_CODE_METHODPTR
22114 @item gdb.TYPE_CODE_METHODPTR
22115 A pointer-to-member-function.
22117 @findex TYPE_CODE_MEMBERPTR
22118 @findex gdb.TYPE_CODE_MEMBERPTR
22119 @item gdb.TYPE_CODE_MEMBERPTR
22120 A pointer-to-member.
22122 @findex TYPE_CODE_REF
22123 @findex gdb.TYPE_CODE_REF
22124 @item gdb.TYPE_CODE_REF
22127 @findex TYPE_CODE_CHAR
22128 @findex gdb.TYPE_CODE_CHAR
22129 @item gdb.TYPE_CODE_CHAR
22132 @findex TYPE_CODE_BOOL
22133 @findex gdb.TYPE_CODE_BOOL
22134 @item gdb.TYPE_CODE_BOOL
22137 @findex TYPE_CODE_COMPLEX
22138 @findex gdb.TYPE_CODE_COMPLEX
22139 @item gdb.TYPE_CODE_COMPLEX
22140 A complex float type.
22142 @findex TYPE_CODE_TYPEDEF
22143 @findex gdb.TYPE_CODE_TYPEDEF
22144 @item gdb.TYPE_CODE_TYPEDEF
22145 A typedef to some other type.
22147 @findex TYPE_CODE_NAMESPACE
22148 @findex gdb.TYPE_CODE_NAMESPACE
22149 @item gdb.TYPE_CODE_NAMESPACE
22150 A C@t{++} namespace.
22152 @findex TYPE_CODE_DECFLOAT
22153 @findex gdb.TYPE_CODE_DECFLOAT
22154 @item gdb.TYPE_CODE_DECFLOAT
22155 A decimal floating point type.
22157 @findex TYPE_CODE_INTERNAL_FUNCTION
22158 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22159 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22160 A function internal to @value{GDBN}. This is the type used to represent
22161 convenience functions.
22164 Further support for types is provided in the @code{gdb.types}
22165 Python module (@pxref{gdb.types}).
22167 @node Pretty Printing API
22168 @subsubsection Pretty Printing API
22170 An example output is provided (@pxref{Pretty Printing}).
22172 A pretty-printer is just an object that holds a value and implements a
22173 specific interface, defined here.
22175 @defun pretty_printer.children (self)
22176 @value{GDBN} will call this method on a pretty-printer to compute the
22177 children of the pretty-printer's value.
22179 This method must return an object conforming to the Python iterator
22180 protocol. Each item returned by the iterator must be a tuple holding
22181 two elements. The first element is the ``name'' of the child; the
22182 second element is the child's value. The value can be any Python
22183 object which is convertible to a @value{GDBN} value.
22185 This method is optional. If it does not exist, @value{GDBN} will act
22186 as though the value has no children.
22189 @defun pretty_printer.display_hint (self)
22190 The CLI may call this method and use its result to change the
22191 formatting of a value. The result will also be supplied to an MI
22192 consumer as a @samp{displayhint} attribute of the variable being
22195 This method is optional. If it does exist, this method must return a
22198 Some display hints are predefined by @value{GDBN}:
22202 Indicate that the object being printed is ``array-like''. The CLI
22203 uses this to respect parameters such as @code{set print elements} and
22204 @code{set print array}.
22207 Indicate that the object being printed is ``map-like'', and that the
22208 children of this value can be assumed to alternate between keys and
22212 Indicate that the object being printed is ``string-like''. If the
22213 printer's @code{to_string} method returns a Python string of some
22214 kind, then @value{GDBN} will call its internal language-specific
22215 string-printing function to format the string. For the CLI this means
22216 adding quotation marks, possibly escaping some characters, respecting
22217 @code{set print elements}, and the like.
22221 @defun pretty_printer.to_string (self)
22222 @value{GDBN} will call this method to display the string
22223 representation of the value passed to the object's constructor.
22225 When printing from the CLI, if the @code{to_string} method exists,
22226 then @value{GDBN} will prepend its result to the values returned by
22227 @code{children}. Exactly how this formatting is done is dependent on
22228 the display hint, and may change as more hints are added. Also,
22229 depending on the print settings (@pxref{Print Settings}), the CLI may
22230 print just the result of @code{to_string} in a stack trace, omitting
22231 the result of @code{children}.
22233 If this method returns a string, it is printed verbatim.
22235 Otherwise, if this method returns an instance of @code{gdb.Value},
22236 then @value{GDBN} prints this value. This may result in a call to
22237 another pretty-printer.
22239 If instead the method returns a Python value which is convertible to a
22240 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22241 the resulting value. Again, this may result in a call to another
22242 pretty-printer. Python scalars (integers, floats, and booleans) and
22243 strings are convertible to @code{gdb.Value}; other types are not.
22245 Finally, if this method returns @code{None} then no further operations
22246 are peformed in this method and nothing is printed.
22248 If the result is not one of these types, an exception is raised.
22251 @value{GDBN} provides a function which can be used to look up the
22252 default pretty-printer for a @code{gdb.Value}:
22254 @findex gdb.default_visualizer
22255 @defun gdb.default_visualizer (value)
22256 This function takes a @code{gdb.Value} object as an argument. If a
22257 pretty-printer for this value exists, then it is returned. If no such
22258 printer exists, then this returns @code{None}.
22261 @node Selecting Pretty-Printers
22262 @subsubsection Selecting Pretty-Printers
22264 The Python list @code{gdb.pretty_printers} contains an array of
22265 functions or callable objects that have been registered via addition
22266 as a pretty-printer. Printers in this list are called @code{global}
22267 printers, they're available when debugging all inferiors.
22268 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22269 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22272 Each function on these lists is passed a single @code{gdb.Value}
22273 argument and should return a pretty-printer object conforming to the
22274 interface definition above (@pxref{Pretty Printing API}). If a function
22275 cannot create a pretty-printer for the value, it should return
22278 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22279 @code{gdb.Objfile} in the current program space and iteratively calls
22280 each enabled lookup routine in the list for that @code{gdb.Objfile}
22281 until it receives a pretty-printer object.
22282 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22283 searches the pretty-printer list of the current program space,
22284 calling each enabled function until an object is returned.
22285 After these lists have been exhausted, it tries the global
22286 @code{gdb.pretty_printers} list, again calling each enabled function until an
22287 object is returned.
22289 The order in which the objfiles are searched is not specified. For a
22290 given list, functions are always invoked from the head of the list,
22291 and iterated over sequentially until the end of the list, or a printer
22292 object is returned.
22294 For various reasons a pretty-printer may not work.
22295 For example, the underlying data structure may have changed and
22296 the pretty-printer is out of date.
22298 The consequences of a broken pretty-printer are severe enough that
22299 @value{GDBN} provides support for enabling and disabling individual
22300 printers. For example, if @code{print frame-arguments} is on,
22301 a backtrace can become highly illegible if any argument is printed
22302 with a broken printer.
22304 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22305 attribute to the registered function or callable object. If this attribute
22306 is present and its value is @code{False}, the printer is disabled, otherwise
22307 the printer is enabled.
22309 @node Writing a Pretty-Printer
22310 @subsubsection Writing a Pretty-Printer
22311 @cindex writing a pretty-printer
22313 A pretty-printer consists of two parts: a lookup function to detect
22314 if the type is supported, and the printer itself.
22316 Here is an example showing how a @code{std::string} printer might be
22317 written. @xref{Pretty Printing API}, for details on the API this class
22321 class StdStringPrinter(object):
22322 "Print a std::string"
22324 def __init__(self, val):
22327 def to_string(self):
22328 return self.val['_M_dataplus']['_M_p']
22330 def display_hint(self):
22334 And here is an example showing how a lookup function for the printer
22335 example above might be written.
22338 def str_lookup_function(val):
22339 lookup_tag = val.type.tag
22340 if lookup_tag == None:
22342 regex = re.compile("^std::basic_string<char,.*>$")
22343 if regex.match(lookup_tag):
22344 return StdStringPrinter(val)
22348 The example lookup function extracts the value's type, and attempts to
22349 match it to a type that it can pretty-print. If it is a type the
22350 printer can pretty-print, it will return a printer object. If not, it
22351 returns @code{None}.
22353 We recommend that you put your core pretty-printers into a Python
22354 package. If your pretty-printers are for use with a library, we
22355 further recommend embedding a version number into the package name.
22356 This practice will enable @value{GDBN} to load multiple versions of
22357 your pretty-printers at the same time, because they will have
22360 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22361 can be evaluated multiple times without changing its meaning. An
22362 ideal auto-load file will consist solely of @code{import}s of your
22363 printer modules, followed by a call to a register pretty-printers with
22364 the current objfile.
22366 Taken as a whole, this approach will scale nicely to multiple
22367 inferiors, each potentially using a different library version.
22368 Embedding a version number in the Python package name will ensure that
22369 @value{GDBN} is able to load both sets of printers simultaneously.
22370 Then, because the search for pretty-printers is done by objfile, and
22371 because your auto-loaded code took care to register your library's
22372 printers with a specific objfile, @value{GDBN} will find the correct
22373 printers for the specific version of the library used by each
22376 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22377 this code might appear in @code{gdb.libstdcxx.v6}:
22380 def register_printers(objfile):
22381 objfile.pretty_printers.add(str_lookup_function)
22385 And then the corresponding contents of the auto-load file would be:
22388 import gdb.libstdcxx.v6
22389 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22392 The previous example illustrates a basic pretty-printer.
22393 There are a few things that can be improved on.
22394 The printer doesn't have a name, making it hard to identify in a
22395 list of installed printers. The lookup function has a name, but
22396 lookup functions can have arbitrary, even identical, names.
22398 Second, the printer only handles one type, whereas a library typically has
22399 several types. One could install a lookup function for each desired type
22400 in the library, but one could also have a single lookup function recognize
22401 several types. The latter is the conventional way this is handled.
22402 If a pretty-printer can handle multiple data types, then its
22403 @dfn{subprinters} are the printers for the individual data types.
22405 The @code{gdb.printing} module provides a formal way of solving these
22406 problems (@pxref{gdb.printing}).
22407 Here is another example that handles multiple types.
22409 These are the types we are going to pretty-print:
22412 struct foo @{ int a, b; @};
22413 struct bar @{ struct foo x, y; @};
22416 Here are the printers:
22420 """Print a foo object."""
22422 def __init__(self, val):
22425 def to_string(self):
22426 return ("a=<" + str(self.val["a"]) +
22427 "> b=<" + str(self.val["b"]) + ">")
22430 """Print a bar object."""
22432 def __init__(self, val):
22435 def to_string(self):
22436 return ("x=<" + str(self.val["x"]) +
22437 "> y=<" + str(self.val["y"]) + ">")
22440 This example doesn't need a lookup function, that is handled by the
22441 @code{gdb.printing} module. Instead a function is provided to build up
22442 the object that handles the lookup.
22445 import gdb.printing
22447 def build_pretty_printer():
22448 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22450 pp.add_printer('foo', '^foo$', fooPrinter)
22451 pp.add_printer('bar', '^bar$', barPrinter)
22455 And here is the autoload support:
22458 import gdb.printing
22460 gdb.printing.register_pretty_printer(
22461 gdb.current_objfile(),
22462 my_library.build_pretty_printer())
22465 Finally, when this printer is loaded into @value{GDBN}, here is the
22466 corresponding output of @samp{info pretty-printer}:
22469 (gdb) info pretty-printer
22476 @node Inferiors In Python
22477 @subsubsection Inferiors In Python
22478 @cindex inferiors in Python
22480 @findex gdb.Inferior
22481 Programs which are being run under @value{GDBN} are called inferiors
22482 (@pxref{Inferiors and Programs}). Python scripts can access
22483 information about and manipulate inferiors controlled by @value{GDBN}
22484 via objects of the @code{gdb.Inferior} class.
22486 The following inferior-related functions are available in the @code{gdb}
22489 @defun gdb.inferiors ()
22490 Return a tuple containing all inferior objects.
22493 @defun gdb.selected_inferior ()
22494 Return an object representing the current inferior.
22497 A @code{gdb.Inferior} object has the following attributes:
22500 @defvar Inferior.num
22501 ID of inferior, as assigned by GDB.
22504 @defvar Inferior.pid
22505 Process ID of the inferior, as assigned by the underlying operating
22509 @defvar Inferior.was_attached
22510 Boolean signaling whether the inferior was created using `attach', or
22511 started by @value{GDBN} itself.
22515 A @code{gdb.Inferior} object has the following methods:
22518 @defun Inferior.is_valid ()
22519 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22520 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22521 if the inferior no longer exists within @value{GDBN}. All other
22522 @code{gdb.Inferior} methods will throw an exception if it is invalid
22523 at the time the method is called.
22526 @defun Inferior.threads ()
22527 This method returns a tuple holding all the threads which are valid
22528 when it is called. If there are no valid threads, the method will
22529 return an empty tuple.
22532 @findex gdb.read_memory
22533 @defun Inferior.read_memory (address, length)
22534 Read @var{length} bytes of memory from the inferior, starting at
22535 @var{address}. Returns a buffer object, which behaves much like an array
22536 or a string. It can be modified and given to the @code{gdb.write_memory}
22540 @findex gdb.write_memory
22541 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22542 Write the contents of @var{buffer} to the inferior, starting at
22543 @var{address}. The @var{buffer} parameter must be a Python object
22544 which supports the buffer protocol, i.e., a string, an array or the
22545 object returned from @code{gdb.read_memory}. If given, @var{length}
22546 determines the number of bytes from @var{buffer} to be written.
22549 @findex gdb.search_memory
22550 @defun Inferior.search_memory (address, length, pattern)
22551 Search a region of the inferior memory starting at @var{address} with
22552 the given @var{length} using the search pattern supplied in
22553 @var{pattern}. The @var{pattern} parameter must be a Python object
22554 which supports the buffer protocol, i.e., a string, an array or the
22555 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22556 containing the address where the pattern was found, or @code{None} if
22557 the pattern could not be found.
22561 @node Events In Python
22562 @subsubsection Events In Python
22563 @cindex inferior events in Python
22565 @value{GDBN} provides a general event facility so that Python code can be
22566 notified of various state changes, particularly changes that occur in
22569 An @dfn{event} is just an object that describes some state change. The
22570 type of the object and its attributes will vary depending on the details
22571 of the change. All the existing events are described below.
22573 In order to be notified of an event, you must register an event handler
22574 with an @dfn{event registry}. An event registry is an object in the
22575 @code{gdb.events} module which dispatches particular events. A registry
22576 provides methods to register and unregister event handlers:
22579 @defun EventRegistry.connect (object)
22580 Add the given callable @var{object} to the registry. This object will be
22581 called when an event corresponding to this registry occurs.
22584 @defun EventRegistry.disconnect (object)
22585 Remove the given @var{object} from the registry. Once removed, the object
22586 will no longer receive notifications of events.
22590 Here is an example:
22593 def exit_handler (event):
22594 print "event type: exit"
22595 print "exit code: %d" % (event.exit_code)
22597 gdb.events.exited.connect (exit_handler)
22600 In the above example we connect our handler @code{exit_handler} to the
22601 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22602 called when the inferior exits. The argument @dfn{event} in this example is
22603 of type @code{gdb.ExitedEvent}. As you can see in the example the
22604 @code{ExitedEvent} object has an attribute which indicates the exit code of
22607 The following is a listing of the event registries that are available and
22608 details of the events they emit:
22613 Emits @code{gdb.ThreadEvent}.
22615 Some events can be thread specific when @value{GDBN} is running in non-stop
22616 mode. When represented in Python, these events all extend
22617 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22618 events which are emitted by this or other modules might extend this event.
22619 Examples of these events are @code{gdb.BreakpointEvent} and
22620 @code{gdb.ContinueEvent}.
22623 @defvar ThreadEvent.inferior_thread
22624 In non-stop mode this attribute will be set to the specific thread which was
22625 involved in the emitted event. Otherwise, it will be set to @code{None}.
22629 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22631 This event indicates that the inferior has been continued after a stop. For
22632 inherited attribute refer to @code{gdb.ThreadEvent} above.
22634 @item events.exited
22635 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22636 @code{events.ExitedEvent} has two attributes:
22638 @defvar ExitedEvent.exit_code
22639 An integer representing the exit code, if available, which the inferior
22640 has returned. (The exit code could be unavailable if, for example,
22641 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22642 the attribute does not exist.
22644 @defvar ExitedEvent inferior
22645 A reference to the inferior which triggered the @code{exited} event.
22650 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22652 Indicates that the inferior has stopped. All events emitted by this registry
22653 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22654 will indicate the stopped thread when @value{GDBN} is running in non-stop
22655 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22657 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22659 This event indicates that the inferior or one of its threads has received as
22660 signal. @code{gdb.SignalEvent} has the following attributes:
22663 @defvar SignalEvent.stop_signal
22664 A string representing the signal received by the inferior. A list of possible
22665 signal values can be obtained by running the command @code{info signals} in
22666 the @value{GDBN} command prompt.
22670 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22672 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22673 been hit, and has the following attributes:
22676 @defvar BreakpointEvent.breakpoints
22677 A sequence containing references to all the breakpoints (type
22678 @code{gdb.Breakpoint}) that were hit.
22679 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22681 @defvar BreakpointEvent.breakpoint
22682 A reference to the first breakpoint that was hit.
22683 This function is maintained for backward compatibility and is now deprecated
22684 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22688 @item events.new_objfile
22689 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22690 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22693 @defvar NewObjFileEvent.new_objfile
22694 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22695 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22701 @node Threads In Python
22702 @subsubsection Threads In Python
22703 @cindex threads in python
22705 @findex gdb.InferiorThread
22706 Python scripts can access information about, and manipulate inferior threads
22707 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22709 The following thread-related functions are available in the @code{gdb}
22712 @findex gdb.selected_thread
22713 @defun gdb.selected_thread ()
22714 This function returns the thread object for the selected thread. If there
22715 is no selected thread, this will return @code{None}.
22718 A @code{gdb.InferiorThread} object has the following attributes:
22721 @defvar InferiorThread.name
22722 The name of the thread. If the user specified a name using
22723 @code{thread name}, then this returns that name. Otherwise, if an
22724 OS-supplied name is available, then it is returned. Otherwise, this
22725 returns @code{None}.
22727 This attribute can be assigned to. The new value must be a string
22728 object, which sets the new name, or @code{None}, which removes any
22729 user-specified thread name.
22732 @defvar InferiorThread.num
22733 ID of the thread, as assigned by GDB.
22736 @defvar InferiorThread.ptid
22737 ID of the thread, as assigned by the operating system. This attribute is a
22738 tuple containing three integers. The first is the Process ID (PID); the second
22739 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22740 Either the LWPID or TID may be 0, which indicates that the operating system
22741 does not use that identifier.
22745 A @code{gdb.InferiorThread} object has the following methods:
22748 @defun InferiorThread.is_valid ()
22749 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22750 @code{False} if not. A @code{gdb.InferiorThread} object will become
22751 invalid if the thread exits, or the inferior that the thread belongs
22752 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22753 exception if it is invalid at the time the method is called.
22756 @defun InferiorThread.switch ()
22757 This changes @value{GDBN}'s currently selected thread to the one represented
22761 @defun InferiorThread.is_stopped ()
22762 Return a Boolean indicating whether the thread is stopped.
22765 @defun InferiorThread.is_running ()
22766 Return a Boolean indicating whether the thread is running.
22769 @defun InferiorThread.is_exited ()
22770 Return a Boolean indicating whether the thread is exited.
22774 @node Commands In Python
22775 @subsubsection Commands In Python
22777 @cindex commands in python
22778 @cindex python commands
22779 You can implement new @value{GDBN} CLI commands in Python. A CLI
22780 command is implemented using an instance of the @code{gdb.Command}
22781 class, most commonly using a subclass.
22783 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
22784 The object initializer for @code{Command} registers the new command
22785 with @value{GDBN}. This initializer is normally invoked from the
22786 subclass' own @code{__init__} method.
22788 @var{name} is the name of the command. If @var{name} consists of
22789 multiple words, then the initial words are looked for as prefix
22790 commands. In this case, if one of the prefix commands does not exist,
22791 an exception is raised.
22793 There is no support for multi-line commands.
22795 @var{command_class} should be one of the @samp{COMMAND_} constants
22796 defined below. This argument tells @value{GDBN} how to categorize the
22797 new command in the help system.
22799 @var{completer_class} is an optional argument. If given, it should be
22800 one of the @samp{COMPLETE_} constants defined below. This argument
22801 tells @value{GDBN} how to perform completion for this command. If not
22802 given, @value{GDBN} will attempt to complete using the object's
22803 @code{complete} method (see below); if no such method is found, an
22804 error will occur when completion is attempted.
22806 @var{prefix} is an optional argument. If @code{True}, then the new
22807 command is a prefix command; sub-commands of this command may be
22810 The help text for the new command is taken from the Python
22811 documentation string for the command's class, if there is one. If no
22812 documentation string is provided, the default value ``This command is
22813 not documented.'' is used.
22816 @cindex don't repeat Python command
22817 @defun Command.dont_repeat ()
22818 By default, a @value{GDBN} command is repeated when the user enters a
22819 blank line at the command prompt. A command can suppress this
22820 behavior by invoking the @code{dont_repeat} method. This is similar
22821 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22824 @defun Command.invoke (argument, from_tty)
22825 This method is called by @value{GDBN} when this command is invoked.
22827 @var{argument} is a string. It is the argument to the command, after
22828 leading and trailing whitespace has been stripped.
22830 @var{from_tty} is a boolean argument. When true, this means that the
22831 command was entered by the user at the terminal; when false it means
22832 that the command came from elsewhere.
22834 If this method throws an exception, it is turned into a @value{GDBN}
22835 @code{error} call. Otherwise, the return value is ignored.
22837 @findex gdb.string_to_argv
22838 To break @var{argument} up into an argv-like string use
22839 @code{gdb.string_to_argv}. This function behaves identically to
22840 @value{GDBN}'s internal argument lexer @code{buildargv}.
22841 It is recommended to use this for consistency.
22842 Arguments are separated by spaces and may be quoted.
22846 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22847 ['1', '2 "3', '4 "5', "6 '7"]
22852 @cindex completion of Python commands
22853 @defun Command.complete (text, word)
22854 This method is called by @value{GDBN} when the user attempts
22855 completion on this command. All forms of completion are handled by
22856 this method, that is, the @key{TAB} and @key{M-?} key bindings
22857 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22860 The arguments @var{text} and @var{word} are both strings. @var{text}
22861 holds the complete command line up to the cursor's location.
22862 @var{word} holds the last word of the command line; this is computed
22863 using a word-breaking heuristic.
22865 The @code{complete} method can return several values:
22868 If the return value is a sequence, the contents of the sequence are
22869 used as the completions. It is up to @code{complete} to ensure that the
22870 contents actually do complete the word. A zero-length sequence is
22871 allowed, it means that there were no completions available. Only
22872 string elements of the sequence are used; other elements in the
22873 sequence are ignored.
22876 If the return value is one of the @samp{COMPLETE_} constants defined
22877 below, then the corresponding @value{GDBN}-internal completion
22878 function is invoked, and its result is used.
22881 All other results are treated as though there were no available
22886 When a new command is registered, it must be declared as a member of
22887 some general class of commands. This is used to classify top-level
22888 commands in the on-line help system; note that prefix commands are not
22889 listed under their own category but rather that of their top-level
22890 command. The available classifications are represented by constants
22891 defined in the @code{gdb} module:
22894 @findex COMMAND_NONE
22895 @findex gdb.COMMAND_NONE
22896 @item gdb.COMMAND_NONE
22897 The command does not belong to any particular class. A command in
22898 this category will not be displayed in any of the help categories.
22900 @findex COMMAND_RUNNING
22901 @findex gdb.COMMAND_RUNNING
22902 @item gdb.COMMAND_RUNNING
22903 The command is related to running the inferior. For example,
22904 @code{start}, @code{step}, and @code{continue} are in this category.
22905 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22906 commands in this category.
22908 @findex COMMAND_DATA
22909 @findex gdb.COMMAND_DATA
22910 @item gdb.COMMAND_DATA
22911 The command is related to data or variables. For example,
22912 @code{call}, @code{find}, and @code{print} are in this category. Type
22913 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22916 @findex COMMAND_STACK
22917 @findex gdb.COMMAND_STACK
22918 @item gdb.COMMAND_STACK
22919 The command has to do with manipulation of the stack. For example,
22920 @code{backtrace}, @code{frame}, and @code{return} are in this
22921 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22922 list of commands in this category.
22924 @findex COMMAND_FILES
22925 @findex gdb.COMMAND_FILES
22926 @item gdb.COMMAND_FILES
22927 This class is used for file-related commands. For example,
22928 @code{file}, @code{list} and @code{section} are in this category.
22929 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22930 commands in this category.
22932 @findex COMMAND_SUPPORT
22933 @findex gdb.COMMAND_SUPPORT
22934 @item gdb.COMMAND_SUPPORT
22935 This should be used for ``support facilities'', generally meaning
22936 things that are useful to the user when interacting with @value{GDBN},
22937 but not related to the state of the inferior. For example,
22938 @code{help}, @code{make}, and @code{shell} are in this category. Type
22939 @kbd{help support} at the @value{GDBN} prompt to see a list of
22940 commands in this category.
22942 @findex COMMAND_STATUS
22943 @findex gdb.COMMAND_STATUS
22944 @item gdb.COMMAND_STATUS
22945 The command is an @samp{info}-related command, that is, related to the
22946 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22947 and @code{show} are in this category. Type @kbd{help status} at the
22948 @value{GDBN} prompt to see a list of commands in this category.
22950 @findex COMMAND_BREAKPOINTS
22951 @findex gdb.COMMAND_BREAKPOINTS
22952 @item gdb.COMMAND_BREAKPOINTS
22953 The command has to do with breakpoints. For example, @code{break},
22954 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22955 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22958 @findex COMMAND_TRACEPOINTS
22959 @findex gdb.COMMAND_TRACEPOINTS
22960 @item gdb.COMMAND_TRACEPOINTS
22961 The command has to do with tracepoints. For example, @code{trace},
22962 @code{actions}, and @code{tfind} are in this category. Type
22963 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22964 commands in this category.
22966 @findex COMMAND_OBSCURE
22967 @findex gdb.COMMAND_OBSCURE
22968 @item gdb.COMMAND_OBSCURE
22969 The command is only used in unusual circumstances, or is not of
22970 general interest to users. For example, @code{checkpoint},
22971 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22972 obscure} at the @value{GDBN} prompt to see a list of commands in this
22975 @findex COMMAND_MAINTENANCE
22976 @findex gdb.COMMAND_MAINTENANCE
22977 @item gdb.COMMAND_MAINTENANCE
22978 The command is only useful to @value{GDBN} maintainers. The
22979 @code{maintenance} and @code{flushregs} commands are in this category.
22980 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22981 commands in this category.
22984 A new command can use a predefined completion function, either by
22985 specifying it via an argument at initialization, or by returning it
22986 from the @code{complete} method. These predefined completion
22987 constants are all defined in the @code{gdb} module:
22990 @findex COMPLETE_NONE
22991 @findex gdb.COMPLETE_NONE
22992 @item gdb.COMPLETE_NONE
22993 This constant means that no completion should be done.
22995 @findex COMPLETE_FILENAME
22996 @findex gdb.COMPLETE_FILENAME
22997 @item gdb.COMPLETE_FILENAME
22998 This constant means that filename completion should be performed.
23000 @findex COMPLETE_LOCATION
23001 @findex gdb.COMPLETE_LOCATION
23002 @item gdb.COMPLETE_LOCATION
23003 This constant means that location completion should be done.
23004 @xref{Specify Location}.
23006 @findex COMPLETE_COMMAND
23007 @findex gdb.COMPLETE_COMMAND
23008 @item gdb.COMPLETE_COMMAND
23009 This constant means that completion should examine @value{GDBN}
23012 @findex COMPLETE_SYMBOL
23013 @findex gdb.COMPLETE_SYMBOL
23014 @item gdb.COMPLETE_SYMBOL
23015 This constant means that completion should be done using symbol names
23019 The following code snippet shows how a trivial CLI command can be
23020 implemented in Python:
23023 class HelloWorld (gdb.Command):
23024 """Greet the whole world."""
23026 def __init__ (self):
23027 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23029 def invoke (self, arg, from_tty):
23030 print "Hello, World!"
23035 The last line instantiates the class, and is necessary to trigger the
23036 registration of the command with @value{GDBN}. Depending on how the
23037 Python code is read into @value{GDBN}, you may need to import the
23038 @code{gdb} module explicitly.
23040 @node Parameters In Python
23041 @subsubsection Parameters In Python
23043 @cindex parameters in python
23044 @cindex python parameters
23045 @tindex gdb.Parameter
23047 You can implement new @value{GDBN} parameters using Python. A new
23048 parameter is implemented as an instance of the @code{gdb.Parameter}
23051 Parameters are exposed to the user via the @code{set} and
23052 @code{show} commands. @xref{Help}.
23054 There are many parameters that already exist and can be set in
23055 @value{GDBN}. Two examples are: @code{set follow fork} and
23056 @code{set charset}. Setting these parameters influences certain
23057 behavior in @value{GDBN}. Similarly, you can define parameters that
23058 can be used to influence behavior in custom Python scripts and commands.
23060 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23061 The object initializer for @code{Parameter} registers the new
23062 parameter with @value{GDBN}. This initializer is normally invoked
23063 from the subclass' own @code{__init__} method.
23065 @var{name} is the name of the new parameter. If @var{name} consists
23066 of multiple words, then the initial words are looked for as prefix
23067 parameters. An example of this can be illustrated with the
23068 @code{set print} set of parameters. If @var{name} is
23069 @code{print foo}, then @code{print} will be searched as the prefix
23070 parameter. In this case the parameter can subsequently be accessed in
23071 @value{GDBN} as @code{set print foo}.
23073 If @var{name} consists of multiple words, and no prefix parameter group
23074 can be found, an exception is raised.
23076 @var{command-class} should be one of the @samp{COMMAND_} constants
23077 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23078 categorize the new parameter in the help system.
23080 @var{parameter-class} should be one of the @samp{PARAM_} constants
23081 defined below. This argument tells @value{GDBN} the type of the new
23082 parameter; this information is used for input validation and
23085 If @var{parameter-class} is @code{PARAM_ENUM}, then
23086 @var{enum-sequence} must be a sequence of strings. These strings
23087 represent the possible values for the parameter.
23089 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23090 of a fourth argument will cause an exception to be thrown.
23092 The help text for the new parameter is taken from the Python
23093 documentation string for the parameter's class, if there is one. If
23094 there is no documentation string, a default value is used.
23097 @defvar Parameter.set_doc
23098 If this attribute exists, and is a string, then its value is used as
23099 the help text for this parameter's @code{set} command. The value is
23100 examined when @code{Parameter.__init__} is invoked; subsequent changes
23104 @defvar Parameter.show_doc
23105 If this attribute exists, and is a string, then its value is used as
23106 the help text for this parameter's @code{show} command. The value is
23107 examined when @code{Parameter.__init__} is invoked; subsequent changes
23111 @defvar Parameter.value
23112 The @code{value} attribute holds the underlying value of the
23113 parameter. It can be read and assigned to just as any other
23114 attribute. @value{GDBN} does validation when assignments are made.
23117 There are two methods that should be implemented in any
23118 @code{Parameter} class. These are:
23120 @defun Parameter.get_set_string (self)
23121 @value{GDBN} will call this method when a @var{parameter}'s value has
23122 been changed via the @code{set} API (for example, @kbd{set foo off}).
23123 The @code{value} attribute has already been populated with the new
23124 value and may be used in output. This method must return a string.
23127 @defun Parameter.get_show_string (self, svalue)
23128 @value{GDBN} will call this method when a @var{parameter}'s
23129 @code{show} API has been invoked (for example, @kbd{show foo}). The
23130 argument @code{svalue} receives the string representation of the
23131 current value. This method must return a string.
23134 When a new parameter is defined, its type must be specified. The
23135 available types are represented by constants defined in the @code{gdb}
23139 @findex PARAM_BOOLEAN
23140 @findex gdb.PARAM_BOOLEAN
23141 @item gdb.PARAM_BOOLEAN
23142 The value is a plain boolean. The Python boolean values, @code{True}
23143 and @code{False} are the only valid values.
23145 @findex PARAM_AUTO_BOOLEAN
23146 @findex gdb.PARAM_AUTO_BOOLEAN
23147 @item gdb.PARAM_AUTO_BOOLEAN
23148 The value has three possible states: true, false, and @samp{auto}. In
23149 Python, true and false are represented using boolean constants, and
23150 @samp{auto} is represented using @code{None}.
23152 @findex PARAM_UINTEGER
23153 @findex gdb.PARAM_UINTEGER
23154 @item gdb.PARAM_UINTEGER
23155 The value is an unsigned integer. The value of 0 should be
23156 interpreted to mean ``unlimited''.
23158 @findex PARAM_INTEGER
23159 @findex gdb.PARAM_INTEGER
23160 @item gdb.PARAM_INTEGER
23161 The value is a signed integer. The value of 0 should be interpreted
23162 to mean ``unlimited''.
23164 @findex PARAM_STRING
23165 @findex gdb.PARAM_STRING
23166 @item gdb.PARAM_STRING
23167 The value is a string. When the user modifies the string, any escape
23168 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23169 translated into corresponding characters and encoded into the current
23172 @findex PARAM_STRING_NOESCAPE
23173 @findex gdb.PARAM_STRING_NOESCAPE
23174 @item gdb.PARAM_STRING_NOESCAPE
23175 The value is a string. When the user modifies the string, escapes are
23176 passed through untranslated.
23178 @findex PARAM_OPTIONAL_FILENAME
23179 @findex gdb.PARAM_OPTIONAL_FILENAME
23180 @item gdb.PARAM_OPTIONAL_FILENAME
23181 The value is a either a filename (a string), or @code{None}.
23183 @findex PARAM_FILENAME
23184 @findex gdb.PARAM_FILENAME
23185 @item gdb.PARAM_FILENAME
23186 The value is a filename. This is just like
23187 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23189 @findex PARAM_ZINTEGER
23190 @findex gdb.PARAM_ZINTEGER
23191 @item gdb.PARAM_ZINTEGER
23192 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23193 is interpreted as itself.
23196 @findex gdb.PARAM_ENUM
23197 @item gdb.PARAM_ENUM
23198 The value is a string, which must be one of a collection string
23199 constants provided when the parameter is created.
23202 @node Functions In Python
23203 @subsubsection Writing new convenience functions
23205 @cindex writing convenience functions
23206 @cindex convenience functions in python
23207 @cindex python convenience functions
23208 @tindex gdb.Function
23210 You can implement new convenience functions (@pxref{Convenience Vars})
23211 in Python. A convenience function is an instance of a subclass of the
23212 class @code{gdb.Function}.
23214 @defun Function.__init__ (name)
23215 The initializer for @code{Function} registers the new function with
23216 @value{GDBN}. The argument @var{name} is the name of the function,
23217 a string. The function will be visible to the user as a convenience
23218 variable of type @code{internal function}, whose name is the same as
23219 the given @var{name}.
23221 The documentation for the new function is taken from the documentation
23222 string for the new class.
23225 @defun Function.invoke (@var{*args})
23226 When a convenience function is evaluated, its arguments are converted
23227 to instances of @code{gdb.Value}, and then the function's
23228 @code{invoke} method is called. Note that @value{GDBN} does not
23229 predetermine the arity of convenience functions. Instead, all
23230 available arguments are passed to @code{invoke}, following the
23231 standard Python calling convention. In particular, a convenience
23232 function can have default values for parameters without ill effect.
23234 The return value of this method is used as its value in the enclosing
23235 expression. If an ordinary Python value is returned, it is converted
23236 to a @code{gdb.Value} following the usual rules.
23239 The following code snippet shows how a trivial convenience function can
23240 be implemented in Python:
23243 class Greet (gdb.Function):
23244 """Return string to greet someone.
23245 Takes a name as argument."""
23247 def __init__ (self):
23248 super (Greet, self).__init__ ("greet")
23250 def invoke (self, name):
23251 return "Hello, %s!" % name.string ()
23256 The last line instantiates the class, and is necessary to trigger the
23257 registration of the function with @value{GDBN}. Depending on how the
23258 Python code is read into @value{GDBN}, you may need to import the
23259 @code{gdb} module explicitly.
23261 @node Progspaces In Python
23262 @subsubsection Program Spaces In Python
23264 @cindex progspaces in python
23265 @tindex gdb.Progspace
23267 A program space, or @dfn{progspace}, represents a symbolic view
23268 of an address space.
23269 It consists of all of the objfiles of the program.
23270 @xref{Objfiles In Python}.
23271 @xref{Inferiors and Programs, program spaces}, for more details
23272 about program spaces.
23274 The following progspace-related functions are available in the
23277 @findex gdb.current_progspace
23278 @defun gdb.current_progspace ()
23279 This function returns the program space of the currently selected inferior.
23280 @xref{Inferiors and Programs}.
23283 @findex gdb.progspaces
23284 @defun gdb.progspaces ()
23285 Return a sequence of all the progspaces currently known to @value{GDBN}.
23288 Each progspace is represented by an instance of the @code{gdb.Progspace}
23291 @defvar Progspace.filename
23292 The file name of the progspace as a string.
23295 @defvar Progspace.pretty_printers
23296 The @code{pretty_printers} attribute is a list of functions. It is
23297 used to look up pretty-printers. A @code{Value} is passed to each
23298 function in order; if the function returns @code{None}, then the
23299 search continues. Otherwise, the return value should be an object
23300 which is used to format the value. @xref{Pretty Printing API}, for more
23304 @node Objfiles In Python
23305 @subsubsection Objfiles In Python
23307 @cindex objfiles in python
23308 @tindex gdb.Objfile
23310 @value{GDBN} loads symbols for an inferior from various
23311 symbol-containing files (@pxref{Files}). These include the primary
23312 executable file, any shared libraries used by the inferior, and any
23313 separate debug info files (@pxref{Separate Debug Files}).
23314 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23316 The following objfile-related functions are available in the
23319 @findex gdb.current_objfile
23320 @defun gdb.current_objfile ()
23321 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23322 sets the ``current objfile'' to the corresponding objfile. This
23323 function returns the current objfile. If there is no current objfile,
23324 this function returns @code{None}.
23327 @findex gdb.objfiles
23328 @defun gdb.objfiles ()
23329 Return a sequence of all the objfiles current known to @value{GDBN}.
23330 @xref{Objfiles In Python}.
23333 Each objfile is represented by an instance of the @code{gdb.Objfile}
23336 @defvar Objfile.filename
23337 The file name of the objfile as a string.
23340 @defvar Objfile.pretty_printers
23341 The @code{pretty_printers} attribute is a list of functions. It is
23342 used to look up pretty-printers. A @code{Value} is passed to each
23343 function in order; if the function returns @code{None}, then the
23344 search continues. Otherwise, the return value should be an object
23345 which is used to format the value. @xref{Pretty Printing API}, for more
23349 A @code{gdb.Objfile} object has the following methods:
23351 @defun Objfile.is_valid ()
23352 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23353 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23354 if the object file it refers to is not loaded in @value{GDBN} any
23355 longer. All other @code{gdb.Objfile} methods will throw an exception
23356 if it is invalid at the time the method is called.
23359 @node Frames In Python
23360 @subsubsection Accessing inferior stack frames from Python.
23362 @cindex frames in python
23363 When the debugged program stops, @value{GDBN} is able to analyze its call
23364 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23365 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23366 while its corresponding frame exists in the inferior's stack. If you try
23367 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23368 exception (@pxref{Exception Handling}).
23370 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23374 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23378 The following frame-related functions are available in the @code{gdb} module:
23380 @findex gdb.selected_frame
23381 @defun gdb.selected_frame ()
23382 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23385 @findex gdb.newest_frame
23386 @defun gdb.newest_frame ()
23387 Return the newest frame object for the selected thread.
23390 @defun gdb.frame_stop_reason_string (reason)
23391 Return a string explaining the reason why @value{GDBN} stopped unwinding
23392 frames, as expressed by the given @var{reason} code (an integer, see the
23393 @code{unwind_stop_reason} method further down in this section).
23396 A @code{gdb.Frame} object has the following methods:
23399 @defun Frame.is_valid ()
23400 Returns true if the @code{gdb.Frame} object is valid, false if not.
23401 A frame object can become invalid if the frame it refers to doesn't
23402 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23403 an exception if it is invalid at the time the method is called.
23406 @defun Frame.name ()
23407 Returns the function name of the frame, or @code{None} if it can't be
23411 @defun Frame.type ()
23412 Returns the type of the frame. The value can be one of:
23414 @item gdb.NORMAL_FRAME
23415 An ordinary stack frame.
23417 @item gdb.DUMMY_FRAME
23418 A fake stack frame that was created by @value{GDBN} when performing an
23419 inferior function call.
23421 @item gdb.INLINE_FRAME
23422 A frame representing an inlined function. The function was inlined
23423 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23425 @item gdb.TAILCALL_FRAME
23426 A frame representing a tail call. @xref{Tail Call Frames}.
23428 @item gdb.SIGTRAMP_FRAME
23429 A signal trampoline frame. This is the frame created by the OS when
23430 it calls into a signal handler.
23432 @item gdb.ARCH_FRAME
23433 A fake stack frame representing a cross-architecture call.
23435 @item gdb.SENTINEL_FRAME
23436 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23441 @defun Frame.unwind_stop_reason ()
23442 Return an integer representing the reason why it's not possible to find
23443 more frames toward the outermost frame. Use
23444 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23445 function to a string. The value can be one of:
23448 @item gdb.FRAME_UNWIND_NO_REASON
23449 No particular reason (older frames should be available).
23451 @item gdb.FRAME_UNWIND_NULL_ID
23452 The previous frame's analyzer returns an invalid result.
23454 @item gdb.FRAME_UNWIND_OUTERMOST
23455 This frame is the outermost.
23457 @item gdb.FRAME_UNWIND_UNAVAILABLE
23458 Cannot unwind further, because that would require knowing the
23459 values of registers or memory that have not been collected.
23461 @item gdb.FRAME_UNWIND_INNER_ID
23462 This frame ID looks like it ought to belong to a NEXT frame,
23463 but we got it for a PREV frame. Normally, this is a sign of
23464 unwinder failure. It could also indicate stack corruption.
23466 @item gdb.FRAME_UNWIND_SAME_ID
23467 This frame has the same ID as the previous one. That means
23468 that unwinding further would almost certainly give us another
23469 frame with exactly the same ID, so break the chain. Normally,
23470 this is a sign of unwinder failure. It could also indicate
23473 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23474 The frame unwinder did not find any saved PC, but we needed
23475 one to unwind further.
23481 Returns the frame's resume address.
23484 @defun Frame.block ()
23485 Return the frame's code block. @xref{Blocks In Python}.
23488 @defun Frame.function ()
23489 Return the symbol for the function corresponding to this frame.
23490 @xref{Symbols In Python}.
23493 @defun Frame.older ()
23494 Return the frame that called this frame.
23497 @defun Frame.newer ()
23498 Return the frame called by this frame.
23501 @defun Frame.find_sal ()
23502 Return the frame's symtab and line object.
23503 @xref{Symbol Tables In Python}.
23506 @defun Frame.read_var (variable @r{[}, block@r{]})
23507 Return the value of @var{variable} in this frame. If the optional
23508 argument @var{block} is provided, search for the variable from that
23509 block; otherwise start at the frame's current block (which is
23510 determined by the frame's current program counter). @var{variable}
23511 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23512 @code{gdb.Block} object.
23515 @defun Frame.select ()
23516 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23521 @node Blocks In Python
23522 @subsubsection Accessing frame blocks from Python.
23524 @cindex blocks in python
23527 Within each frame, @value{GDBN} maintains information on each block
23528 stored in that frame. These blocks are organized hierarchically, and
23529 are represented individually in Python as a @code{gdb.Block}.
23530 Please see @ref{Frames In Python}, for a more in-depth discussion on
23531 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23532 detailed technical information on @value{GDBN}'s book-keeping of the
23535 The following block-related functions are available in the @code{gdb}
23538 @findex gdb.block_for_pc
23539 @defun gdb.block_for_pc (pc)
23540 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23541 block cannot be found for the @var{pc} value specified, the function
23542 will return @code{None}.
23545 A @code{gdb.Block} object has the following methods:
23548 @defun Block.is_valid ()
23549 Returns @code{True} if the @code{gdb.Block} object is valid,
23550 @code{False} if not. A block object can become invalid if the block it
23551 refers to doesn't exist anymore in the inferior. All other
23552 @code{gdb.Block} methods will throw an exception if it is invalid at
23553 the time the method is called. This method is also made available to
23554 the Python iterator object that @code{gdb.Block} provides in an iteration
23555 context and via the Python @code{iter} built-in function.
23559 A @code{gdb.Block} object has the following attributes:
23562 @defvar Block.start
23563 The start address of the block. This attribute is not writable.
23567 The end address of the block. This attribute is not writable.
23570 @defvar Block.function
23571 The name of the block represented as a @code{gdb.Symbol}. If the
23572 block is not named, then this attribute holds @code{None}. This
23573 attribute is not writable.
23576 @defvar Block.superblock
23577 The block containing this block. If this parent block does not exist,
23578 this attribute holds @code{None}. This attribute is not writable.
23581 @defvar Block.global_block
23582 The global block associated with this block. This attribute is not
23586 @defvar Block.static_block
23587 The static block associated with this block. This attribute is not
23591 @defvar Block.is_global
23592 @code{True} if the @code{gdb.Block} object is a global block,
23593 @code{False} if not. This attribute is not
23597 @defvar Block.is_static
23598 @code{True} if the @code{gdb.Block} object is a static block,
23599 @code{False} if not. This attribute is not writable.
23603 @node Symbols In Python
23604 @subsubsection Python representation of Symbols.
23606 @cindex symbols in python
23609 @value{GDBN} represents every variable, function and type as an
23610 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23611 Similarly, Python represents these symbols in @value{GDBN} with the
23612 @code{gdb.Symbol} object.
23614 The following symbol-related functions are available in the @code{gdb}
23617 @findex gdb.lookup_symbol
23618 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23619 This function searches for a symbol by name. The search scope can be
23620 restricted to the parameters defined in the optional domain and block
23623 @var{name} is the name of the symbol. It must be a string. The
23624 optional @var{block} argument restricts the search to symbols visible
23625 in that @var{block}. The @var{block} argument must be a
23626 @code{gdb.Block} object. If omitted, the block for the current frame
23627 is used. The optional @var{domain} argument restricts
23628 the search to the domain type. The @var{domain} argument must be a
23629 domain constant defined in the @code{gdb} module and described later
23632 The result is a tuple of two elements.
23633 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23635 If the symbol is found, the second element is @code{True} if the symbol
23636 is a field of a method's object (e.g., @code{this} in C@t{++}),
23637 otherwise it is @code{False}.
23638 If the symbol is not found, the second element is @code{False}.
23641 @findex gdb.lookup_global_symbol
23642 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23643 This function searches for a global symbol by name.
23644 The search scope can be restricted to by the domain argument.
23646 @var{name} is the name of the symbol. It must be a string.
23647 The optional @var{domain} argument restricts the search to the domain type.
23648 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23649 module and described later in this chapter.
23651 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23655 A @code{gdb.Symbol} object has the following attributes:
23658 @defvar Symbol.type
23659 The type of the symbol or @code{None} if no type is recorded.
23660 This attribute is represented as a @code{gdb.Type} object.
23661 @xref{Types In Python}. This attribute is not writable.
23664 @defvar Symbol.symtab
23665 The symbol table in which the symbol appears. This attribute is
23666 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23667 Python}. This attribute is not writable.
23670 @defvar Symbol.name
23671 The name of the symbol as a string. This attribute is not writable.
23674 @defvar Symbol.linkage_name
23675 The name of the symbol, as used by the linker (i.e., may be mangled).
23676 This attribute is not writable.
23679 @defvar Symbol.print_name
23680 The name of the symbol in a form suitable for output. This is either
23681 @code{name} or @code{linkage_name}, depending on whether the user
23682 asked @value{GDBN} to display demangled or mangled names.
23685 @defvar Symbol.addr_class
23686 The address class of the symbol. This classifies how to find the value
23687 of a symbol. Each address class is a constant defined in the
23688 @code{gdb} module and described later in this chapter.
23691 @defvar Symbol.is_argument
23692 @code{True} if the symbol is an argument of a function.
23695 @defvar Symbol.is_constant
23696 @code{True} if the symbol is a constant.
23699 @defvar Symbol.is_function
23700 @code{True} if the symbol is a function or a method.
23703 @defvar Symbol.is_variable
23704 @code{True} if the symbol is a variable.
23708 A @code{gdb.Symbol} object has the following methods:
23711 @defun Symbol.is_valid ()
23712 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23713 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23714 the symbol it refers to does not exist in @value{GDBN} any longer.
23715 All other @code{gdb.Symbol} methods will throw an exception if it is
23716 invalid at the time the method is called.
23720 The available domain categories in @code{gdb.Symbol} are represented
23721 as constants in the @code{gdb} module:
23724 @findex SYMBOL_UNDEF_DOMAIN
23725 @findex gdb.SYMBOL_UNDEF_DOMAIN
23726 @item gdb.SYMBOL_UNDEF_DOMAIN
23727 This is used when a domain has not been discovered or none of the
23728 following domains apply. This usually indicates an error either
23729 in the symbol information or in @value{GDBN}'s handling of symbols.
23730 @findex SYMBOL_VAR_DOMAIN
23731 @findex gdb.SYMBOL_VAR_DOMAIN
23732 @item gdb.SYMBOL_VAR_DOMAIN
23733 This domain contains variables, function names, typedef names and enum
23735 @findex SYMBOL_STRUCT_DOMAIN
23736 @findex gdb.SYMBOL_STRUCT_DOMAIN
23737 @item gdb.SYMBOL_STRUCT_DOMAIN
23738 This domain holds struct, union and enum type names.
23739 @findex SYMBOL_LABEL_DOMAIN
23740 @findex gdb.SYMBOL_LABEL_DOMAIN
23741 @item gdb.SYMBOL_LABEL_DOMAIN
23742 This domain contains names of labels (for gotos).
23743 @findex SYMBOL_VARIABLES_DOMAIN
23744 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23745 @item gdb.SYMBOL_VARIABLES_DOMAIN
23746 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23747 contains everything minus functions and types.
23748 @findex SYMBOL_FUNCTIONS_DOMAIN
23749 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23750 @item gdb.SYMBOL_FUNCTION_DOMAIN
23751 This domain contains all functions.
23752 @findex SYMBOL_TYPES_DOMAIN
23753 @findex gdb.SYMBOL_TYPES_DOMAIN
23754 @item gdb.SYMBOL_TYPES_DOMAIN
23755 This domain contains all types.
23758 The available address class categories in @code{gdb.Symbol} are represented
23759 as constants in the @code{gdb} module:
23762 @findex SYMBOL_LOC_UNDEF
23763 @findex gdb.SYMBOL_LOC_UNDEF
23764 @item gdb.SYMBOL_LOC_UNDEF
23765 If this is returned by address class, it indicates an error either in
23766 the symbol information or in @value{GDBN}'s handling of symbols.
23767 @findex SYMBOL_LOC_CONST
23768 @findex gdb.SYMBOL_LOC_CONST
23769 @item gdb.SYMBOL_LOC_CONST
23770 Value is constant int.
23771 @findex SYMBOL_LOC_STATIC
23772 @findex gdb.SYMBOL_LOC_STATIC
23773 @item gdb.SYMBOL_LOC_STATIC
23774 Value is at a fixed address.
23775 @findex SYMBOL_LOC_REGISTER
23776 @findex gdb.SYMBOL_LOC_REGISTER
23777 @item gdb.SYMBOL_LOC_REGISTER
23778 Value is in a register.
23779 @findex SYMBOL_LOC_ARG
23780 @findex gdb.SYMBOL_LOC_ARG
23781 @item gdb.SYMBOL_LOC_ARG
23782 Value is an argument. This value is at the offset stored within the
23783 symbol inside the frame's argument list.
23784 @findex SYMBOL_LOC_REF_ARG
23785 @findex gdb.SYMBOL_LOC_REF_ARG
23786 @item gdb.SYMBOL_LOC_REF_ARG
23787 Value address is stored in the frame's argument list. Just like
23788 @code{LOC_ARG} except that the value's address is stored at the
23789 offset, not the value itself.
23790 @findex SYMBOL_LOC_REGPARM_ADDR
23791 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23792 @item gdb.SYMBOL_LOC_REGPARM_ADDR
23793 Value is a specified register. Just like @code{LOC_REGISTER} except
23794 the register holds the address of the argument instead of the argument
23796 @findex SYMBOL_LOC_LOCAL
23797 @findex gdb.SYMBOL_LOC_LOCAL
23798 @item gdb.SYMBOL_LOC_LOCAL
23799 Value is a local variable.
23800 @findex SYMBOL_LOC_TYPEDEF
23801 @findex gdb.SYMBOL_LOC_TYPEDEF
23802 @item gdb.SYMBOL_LOC_TYPEDEF
23803 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23805 @findex SYMBOL_LOC_BLOCK
23806 @findex gdb.SYMBOL_LOC_BLOCK
23807 @item gdb.SYMBOL_LOC_BLOCK
23809 @findex SYMBOL_LOC_CONST_BYTES
23810 @findex gdb.SYMBOL_LOC_CONST_BYTES
23811 @item gdb.SYMBOL_LOC_CONST_BYTES
23812 Value is a byte-sequence.
23813 @findex SYMBOL_LOC_UNRESOLVED
23814 @findex gdb.SYMBOL_LOC_UNRESOLVED
23815 @item gdb.SYMBOL_LOC_UNRESOLVED
23816 Value is at a fixed address, but the address of the variable has to be
23817 determined from the minimal symbol table whenever the variable is
23819 @findex SYMBOL_LOC_OPTIMIZED_OUT
23820 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23821 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
23822 The value does not actually exist in the program.
23823 @findex SYMBOL_LOC_COMPUTED
23824 @findex gdb.SYMBOL_LOC_COMPUTED
23825 @item gdb.SYMBOL_LOC_COMPUTED
23826 The value's address is a computed location.
23829 @node Symbol Tables In Python
23830 @subsubsection Symbol table representation in Python.
23832 @cindex symbol tables in python
23834 @tindex gdb.Symtab_and_line
23836 Access to symbol table data maintained by @value{GDBN} on the inferior
23837 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23838 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23839 from the @code{find_sal} method in @code{gdb.Frame} object.
23840 @xref{Frames In Python}.
23842 For more information on @value{GDBN}'s symbol table management, see
23843 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23845 A @code{gdb.Symtab_and_line} object has the following attributes:
23848 @defvar Symtab_and_line.symtab
23849 The symbol table object (@code{gdb.Symtab}) for this frame.
23850 This attribute is not writable.
23853 @defvar Symtab_and_line.pc
23854 Indicates the current program counter address. This attribute is not
23858 @defvar Symtab_and_line.line
23859 Indicates the current line number for this object. This
23860 attribute is not writable.
23864 A @code{gdb.Symtab_and_line} object has the following methods:
23867 @defun Symtab_and_line.is_valid ()
23868 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23869 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23870 invalid if the Symbol table and line object it refers to does not
23871 exist in @value{GDBN} any longer. All other
23872 @code{gdb.Symtab_and_line} methods will throw an exception if it is
23873 invalid at the time the method is called.
23877 A @code{gdb.Symtab} object has the following attributes:
23880 @defvar Symtab.filename
23881 The symbol table's source filename. This attribute is not writable.
23884 @defvar Symtab.objfile
23885 The symbol table's backing object file. @xref{Objfiles In Python}.
23886 This attribute is not writable.
23890 A @code{gdb.Symtab} object has the following methods:
23893 @defun Symtab.is_valid ()
23894 Returns @code{True} if the @code{gdb.Symtab} object is valid,
23895 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
23896 the symbol table it refers to does not exist in @value{GDBN} any
23897 longer. All other @code{gdb.Symtab} methods will throw an exception
23898 if it is invalid at the time the method is called.
23901 @defun Symtab.fullname ()
23902 Return the symbol table's source absolute file name.
23906 @node Breakpoints In Python
23907 @subsubsection Manipulating breakpoints using Python
23909 @cindex breakpoints in python
23910 @tindex gdb.Breakpoint
23912 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
23915 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
23916 Create a new breakpoint. @var{spec} is a string naming the
23917 location of the breakpoint, or an expression that defines a
23918 watchpoint. The contents can be any location recognized by the
23919 @code{break} command, or in the case of a watchpoint, by the @code{watch}
23920 command. The optional @var{type} denotes the breakpoint to create
23921 from the types defined later in this chapter. This argument can be
23922 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
23923 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
23924 allows the breakpoint to become invisible to the user. The breakpoint
23925 will neither be reported when created, nor will it be listed in the
23926 output from @code{info breakpoints} (but will be listed with the
23927 @code{maint info breakpoints} command). The optional @var{wp_class}
23928 argument defines the class of watchpoint to create, if @var{type} is
23929 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
23930 assumed to be a @code{gdb.WP_WRITE} class.
23933 @defun Breakpoint.stop (self)
23934 The @code{gdb.Breakpoint} class can be sub-classed and, in
23935 particular, you may choose to implement the @code{stop} method.
23936 If this method is defined as a sub-class of @code{gdb.Breakpoint},
23937 it will be called when the inferior reaches any location of a
23938 breakpoint which instantiates that sub-class. If the method returns
23939 @code{True}, the inferior will be stopped at the location of the
23940 breakpoint, otherwise the inferior will continue.
23942 If there are multiple breakpoints at the same location with a
23943 @code{stop} method, each one will be called regardless of the
23944 return status of the previous. This ensures that all @code{stop}
23945 methods have a chance to execute at that location. In this scenario
23946 if one of the methods returns @code{True} but the others return
23947 @code{False}, the inferior will still be stopped.
23949 You should not alter the execution state of the inferior (i.e.@:, step,
23950 next, etc.), alter the current frame context (i.e.@:, change the current
23951 active frame), or alter, add or delete any breakpoint. As a general
23952 rule, you should not alter any data within @value{GDBN} or the inferior
23955 Example @code{stop} implementation:
23958 class MyBreakpoint (gdb.Breakpoint):
23960 inf_val = gdb.parse_and_eval("foo")
23967 The available watchpoint types represented by constants are defined in the
23972 @findex gdb.WP_READ
23974 Read only watchpoint.
23977 @findex gdb.WP_WRITE
23979 Write only watchpoint.
23982 @findex gdb.WP_ACCESS
23983 @item gdb.WP_ACCESS
23984 Read/Write watchpoint.
23987 @defun Breakpoint.is_valid ()
23988 Return @code{True} if this @code{Breakpoint} object is valid,
23989 @code{False} otherwise. A @code{Breakpoint} object can become invalid
23990 if the user deletes the breakpoint. In this case, the object still
23991 exists, but the underlying breakpoint does not. In the cases of
23992 watchpoint scope, the watchpoint remains valid even if execution of the
23993 inferior leaves the scope of that watchpoint.
23996 @defun Breakpoint.delete
23997 Permanently deletes the @value{GDBN} breakpoint. This also
23998 invalidates the Python @code{Breakpoint} object. Any further access
23999 to this object's attributes or methods will raise an error.
24002 @defvar Breakpoint.enabled
24003 This attribute is @code{True} if the breakpoint is enabled, and
24004 @code{False} otherwise. This attribute is writable.
24007 @defvar Breakpoint.silent
24008 This attribute is @code{True} if the breakpoint is silent, and
24009 @code{False} otherwise. This attribute is writable.
24011 Note that a breakpoint can also be silent if it has commands and the
24012 first command is @code{silent}. This is not reported by the
24013 @code{silent} attribute.
24016 @defvar Breakpoint.thread
24017 If the breakpoint is thread-specific, this attribute holds the thread
24018 id. If the breakpoint is not thread-specific, this attribute is
24019 @code{None}. This attribute is writable.
24022 @defvar Breakpoint.task
24023 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24024 id. If the breakpoint is not task-specific (or the underlying
24025 language is not Ada), this attribute is @code{None}. This attribute
24029 @defvar Breakpoint.ignore_count
24030 This attribute holds the ignore count for the breakpoint, an integer.
24031 This attribute is writable.
24034 @defvar Breakpoint.number
24035 This attribute holds the breakpoint's number --- the identifier used by
24036 the user to manipulate the breakpoint. This attribute is not writable.
24039 @defvar Breakpoint.type
24040 This attribute holds the breakpoint's type --- the identifier used to
24041 determine the actual breakpoint type or use-case. This attribute is not
24045 @defvar Breakpoint.visible
24046 This attribute tells whether the breakpoint is visible to the user
24047 when set, or when the @samp{info breakpoints} command is run. This
24048 attribute is not writable.
24051 The available types are represented by constants defined in the @code{gdb}
24055 @findex BP_BREAKPOINT
24056 @findex gdb.BP_BREAKPOINT
24057 @item gdb.BP_BREAKPOINT
24058 Normal code breakpoint.
24060 @findex BP_WATCHPOINT
24061 @findex gdb.BP_WATCHPOINT
24062 @item gdb.BP_WATCHPOINT
24063 Watchpoint breakpoint.
24065 @findex BP_HARDWARE_WATCHPOINT
24066 @findex gdb.BP_HARDWARE_WATCHPOINT
24067 @item gdb.BP_HARDWARE_WATCHPOINT
24068 Hardware assisted watchpoint.
24070 @findex BP_READ_WATCHPOINT
24071 @findex gdb.BP_READ_WATCHPOINT
24072 @item gdb.BP_READ_WATCHPOINT
24073 Hardware assisted read watchpoint.
24075 @findex BP_ACCESS_WATCHPOINT
24076 @findex gdb.BP_ACCESS_WATCHPOINT
24077 @item gdb.BP_ACCESS_WATCHPOINT
24078 Hardware assisted access watchpoint.
24081 @defvar Breakpoint.hit_count
24082 This attribute holds the hit count for the breakpoint, an integer.
24083 This attribute is writable, but currently it can only be set to zero.
24086 @defvar Breakpoint.location
24087 This attribute holds the location of the breakpoint, as specified by
24088 the user. It is a string. If the breakpoint does not have a location
24089 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24090 attribute is not writable.
24093 @defvar Breakpoint.expression
24094 This attribute holds a breakpoint expression, as specified by
24095 the user. It is a string. If the breakpoint does not have an
24096 expression (the breakpoint is not a watchpoint) the attribute's value
24097 is @code{None}. This attribute is not writable.
24100 @defvar Breakpoint.condition
24101 This attribute holds the condition of the breakpoint, as specified by
24102 the user. It is a string. If there is no condition, this attribute's
24103 value is @code{None}. This attribute is writable.
24106 @defvar Breakpoint.commands
24107 This attribute holds the commands attached to the breakpoint. If
24108 there are commands, this attribute's value is a string holding all the
24109 commands, separated by newlines. If there are no commands, this
24110 attribute is @code{None}. This attribute is not writable.
24113 @node Lazy Strings In Python
24114 @subsubsection Python representation of lazy strings.
24116 @cindex lazy strings in python
24117 @tindex gdb.LazyString
24119 A @dfn{lazy string} is a string whose contents is not retrieved or
24120 encoded until it is needed.
24122 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24123 @code{address} that points to a region of memory, an @code{encoding}
24124 that will be used to encode that region of memory, and a @code{length}
24125 to delimit the region of memory that represents the string. The
24126 difference between a @code{gdb.LazyString} and a string wrapped within
24127 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24128 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24129 retrieved and encoded during printing, while a @code{gdb.Value}
24130 wrapping a string is immediately retrieved and encoded on creation.
24132 A @code{gdb.LazyString} object has the following functions:
24134 @defun LazyString.value ()
24135 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24136 will point to the string in memory, but will lose all the delayed
24137 retrieval, encoding and handling that @value{GDBN} applies to a
24138 @code{gdb.LazyString}.
24141 @defvar LazyString.address
24142 This attribute holds the address of the string. This attribute is not
24146 @defvar LazyString.length
24147 This attribute holds the length of the string in characters. If the
24148 length is -1, then the string will be fetched and encoded up to the
24149 first null of appropriate width. This attribute is not writable.
24152 @defvar LazyString.encoding
24153 This attribute holds the encoding that will be applied to the string
24154 when the string is printed by @value{GDBN}. If the encoding is not
24155 set, or contains an empty string, then @value{GDBN} will select the
24156 most appropriate encoding when the string is printed. This attribute
24160 @defvar LazyString.type
24161 This attribute holds the type that is represented by the lazy string's
24162 type. For a lazy string this will always be a pointer type. To
24163 resolve this to the lazy string's character type, use the type's
24164 @code{target} method. @xref{Types In Python}. This attribute is not
24169 @subsection Auto-loading
24170 @cindex auto-loading, Python
24172 When a new object file is read (for example, due to the @code{file}
24173 command, or because the inferior has loaded a shared library),
24174 @value{GDBN} will look for Python support scripts in several ways:
24175 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24178 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24179 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24180 * Which flavor to choose?::
24183 The auto-loading feature is useful for supplying application-specific
24184 debugging commands and scripts.
24186 Auto-loading can be enabled or disabled,
24187 and the list of auto-loaded scripts can be printed.
24190 @kindex set auto-load-scripts
24191 @item set auto-load-scripts [yes|no]
24192 Enable or disable the auto-loading of Python scripts.
24194 @kindex show auto-load-scripts
24195 @item show auto-load-scripts
24196 Show whether auto-loading of Python scripts is enabled or disabled.
24198 @kindex info auto-load-scripts
24199 @cindex print list of auto-loaded scripts
24200 @item info auto-load-scripts [@var{regexp}]
24201 Print the list of all scripts that @value{GDBN} auto-loaded.
24203 Also printed is the list of scripts that were mentioned in
24204 the @code{.debug_gdb_scripts} section and were not found
24205 (@pxref{.debug_gdb_scripts section}).
24206 This is useful because their names are not printed when @value{GDBN}
24207 tries to load them and fails. There may be many of them, and printing
24208 an error message for each one is problematic.
24210 If @var{regexp} is supplied only scripts with matching names are printed.
24215 (gdb) info auto-load-scripts
24217 Yes py-section-script.py
24218 full name: /tmp/py-section-script.py
24219 Missing my-foo-pretty-printers.py
24223 When reading an auto-loaded file, @value{GDBN} sets the
24224 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24225 function (@pxref{Objfiles In Python}). This can be useful for
24226 registering objfile-specific pretty-printers.
24228 @node objfile-gdb.py file
24229 @subsubsection The @file{@var{objfile}-gdb.py} file
24230 @cindex @file{@var{objfile}-gdb.py}
24232 When a new object file is read, @value{GDBN} looks for
24233 a file named @file{@var{objfile}-gdb.py},
24234 where @var{objfile} is the object file's real name, formed by ensuring
24235 that the file name is absolute, following all symlinks, and resolving
24236 @code{.} and @code{..} components. If this file exists and is
24237 readable, @value{GDBN} will evaluate it as a Python script.
24239 If this file does not exist, and if the parameter
24240 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24241 then @value{GDBN} will look for @var{real-name} in all of the
24242 directories mentioned in the value of @code{debug-file-directory}.
24244 Finally, if this file does not exist, then @value{GDBN} will look for
24245 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24246 @var{data-directory} is @value{GDBN}'s data directory (available via
24247 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24248 is the object file's real name, as described above.
24250 @value{GDBN} does not track which files it has already auto-loaded this way.
24251 @value{GDBN} will load the associated script every time the corresponding
24252 @var{objfile} is opened.
24253 So your @file{-gdb.py} file should be careful to avoid errors if it
24254 is evaluated more than once.
24256 @node .debug_gdb_scripts section
24257 @subsubsection The @code{.debug_gdb_scripts} section
24258 @cindex @code{.debug_gdb_scripts} section
24260 For systems using file formats like ELF and COFF,
24261 when @value{GDBN} loads a new object file
24262 it will look for a special section named @samp{.debug_gdb_scripts}.
24263 If this section exists, its contents is a list of names of scripts to load.
24265 @value{GDBN} will look for each specified script file first in the
24266 current directory and then along the source search path
24267 (@pxref{Source Path, ,Specifying Source Directories}),
24268 except that @file{$cdir} is not searched, since the compilation
24269 directory is not relevant to scripts.
24271 Entries can be placed in section @code{.debug_gdb_scripts} with,
24272 for example, this GCC macro:
24275 /* Note: The "MS" section flags are to remove duplicates. */
24276 #define DEFINE_GDB_SCRIPT(script_name) \
24278 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24280 .asciz \"" script_name "\"\n\
24286 Then one can reference the macro in a header or source file like this:
24289 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24292 The script name may include directories if desired.
24294 If the macro is put in a header, any application or library
24295 using this header will get a reference to the specified script.
24297 @node Which flavor to choose?
24298 @subsubsection Which flavor to choose?
24300 Given the multiple ways of auto-loading Python scripts, it might not always
24301 be clear which one to choose. This section provides some guidance.
24303 Benefits of the @file{-gdb.py} way:
24307 Can be used with file formats that don't support multiple sections.
24310 Ease of finding scripts for public libraries.
24312 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24313 in the source search path.
24314 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24315 isn't a source directory in which to find the script.
24318 Doesn't require source code additions.
24321 Benefits of the @code{.debug_gdb_scripts} way:
24325 Works with static linking.
24327 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24328 trigger their loading. When an application is statically linked the only
24329 objfile available is the executable, and it is cumbersome to attach all the
24330 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24333 Works with classes that are entirely inlined.
24335 Some classes can be entirely inlined, and thus there may not be an associated
24336 shared library to attach a @file{-gdb.py} script to.
24339 Scripts needn't be copied out of the source tree.
24341 In some circumstances, apps can be built out of large collections of internal
24342 libraries, and the build infrastructure necessary to install the
24343 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24344 cumbersome. It may be easier to specify the scripts in the
24345 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24346 top of the source tree to the source search path.
24349 @node Python modules
24350 @subsection Python modules
24351 @cindex python modules
24353 @value{GDBN} comes with several modules to assist writing Python code.
24356 * gdb.printing:: Building and registering pretty-printers.
24357 * gdb.types:: Utilities for working with types.
24358 * gdb.prompt:: Utilities for prompt value substitution.
24362 @subsubsection gdb.printing
24363 @cindex gdb.printing
24365 This module provides a collection of utilities for working with
24369 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24370 This class specifies the API that makes @samp{info pretty-printer},
24371 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24372 Pretty-printers should generally inherit from this class.
24374 @item SubPrettyPrinter (@var{name})
24375 For printers that handle multiple types, this class specifies the
24376 corresponding API for the subprinters.
24378 @item RegexpCollectionPrettyPrinter (@var{name})
24379 Utility class for handling multiple printers, all recognized via
24380 regular expressions.
24381 @xref{Writing a Pretty-Printer}, for an example.
24383 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24384 Register @var{printer} with the pretty-printer list of @var{obj}.
24385 If @var{replace} is @code{True} then any existing copy of the printer
24386 is replaced. Otherwise a @code{RuntimeError} exception is raised
24387 if a printer with the same name already exists.
24391 @subsubsection gdb.types
24394 This module provides a collection of utilities for working with
24395 @code{gdb.Types} objects.
24398 @item get_basic_type (@var{type})
24399 Return @var{type} with const and volatile qualifiers stripped,
24400 and with typedefs and C@t{++} references converted to the underlying type.
24405 typedef const int const_int;
24407 const_int& foo_ref (foo);
24408 int main () @{ return 0; @}
24415 (gdb) python import gdb.types
24416 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24417 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24421 @item has_field (@var{type}, @var{field})
24422 Return @code{True} if @var{type}, assumed to be a type with fields
24423 (e.g., a structure or union), has field @var{field}.
24425 @item make_enum_dict (@var{enum_type})
24426 Return a Python @code{dictionary} type produced from @var{enum_type}.
24430 @subsubsection gdb.prompt
24433 This module provides a method for prompt value-substitution.
24436 @item substitute_prompt (@var{string})
24437 Return @var{string} with escape sequences substituted by values. Some
24438 escape sequences take arguments. You can specify arguments inside
24439 ``@{@}'' immediately following the escape sequence.
24441 The escape sequences you can pass to this function are:
24445 Substitute a backslash.
24447 Substitute an ESC character.
24449 Substitute the selected frame; an argument names a frame parameter.
24451 Substitute a newline.
24453 Substitute a parameter's value; the argument names the parameter.
24455 Substitute a carriage return.
24457 Substitute the selected thread; an argument names a thread parameter.
24459 Substitute the version of GDB.
24461 Substitute the current working directory.
24463 Begin a sequence of non-printing characters. These sequences are
24464 typically used with the ESC character, and are not counted in the string
24465 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24466 blue-colored ``(gdb)'' prompt where the length is five.
24468 End a sequence of non-printing characters.
24474 substitute_prompt (``frame: \f,
24475 print arguments: \p@{print frame-arguments@}'')
24478 @exdent will return the string:
24481 "frame: main, print arguments: scalars"
24486 @section Creating new spellings of existing commands
24487 @cindex aliases for commands
24489 It is often useful to define alternate spellings of existing commands.
24490 For example, if a new @value{GDBN} command defined in Python has
24491 a long name to type, it is handy to have an abbreviated version of it
24492 that involves less typing.
24494 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24495 of the @samp{step} command even though it is otherwise an ambiguous
24496 abbreviation of other commands like @samp{set} and @samp{show}.
24498 Aliases are also used to provide shortened or more common versions
24499 of multi-word commands. For example, @value{GDBN} provides the
24500 @samp{tty} alias of the @samp{set inferior-tty} command.
24502 You can define a new alias with the @samp{alias} command.
24507 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24511 @var{ALIAS} specifies the name of the new alias.
24512 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24515 @var{COMMAND} specifies the name of an existing command
24516 that is being aliased.
24518 The @samp{-a} option specifies that the new alias is an abbreviation
24519 of the command. Abbreviations are not shown in command
24520 lists displayed by the @samp{help} command.
24522 The @samp{--} option specifies the end of options,
24523 and is useful when @var{ALIAS} begins with a dash.
24525 Here is a simple example showing how to make an abbreviation
24526 of a command so that there is less to type.
24527 Suppose you were tired of typing @samp{disas}, the current
24528 shortest unambiguous abbreviation of the @samp{disassemble} command
24529 and you wanted an even shorter version named @samp{di}.
24530 The following will accomplish this.
24533 (gdb) alias -a di = disas
24536 Note that aliases are different from user-defined commands.
24537 With a user-defined command, you also need to write documentation
24538 for it with the @samp{document} command.
24539 An alias automatically picks up the documentation of the existing command.
24541 Here is an example where we make @samp{elms} an abbreviation of
24542 @samp{elements} in the @samp{set print elements} command.
24543 This is to show that you can make an abbreviation of any part
24547 (gdb) alias -a set print elms = set print elements
24548 (gdb) alias -a show print elms = show print elements
24549 (gdb) set p elms 20
24551 Limit on string chars or array elements to print is 200.
24554 Note that if you are defining an alias of a @samp{set} command,
24555 and you want to have an alias for the corresponding @samp{show}
24556 command, then you need to define the latter separately.
24558 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24559 @var{ALIAS}, just as they are normally.
24562 (gdb) alias -a set pr elms = set p ele
24565 Finally, here is an example showing the creation of a one word
24566 alias for a more complex command.
24567 This creates alias @samp{spe} of the command @samp{set print elements}.
24570 (gdb) alias spe = set print elements
24575 @chapter Command Interpreters
24576 @cindex command interpreters
24578 @value{GDBN} supports multiple command interpreters, and some command
24579 infrastructure to allow users or user interface writers to switch
24580 between interpreters or run commands in other interpreters.
24582 @value{GDBN} currently supports two command interpreters, the console
24583 interpreter (sometimes called the command-line interpreter or @sc{cli})
24584 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24585 describes both of these interfaces in great detail.
24587 By default, @value{GDBN} will start with the console interpreter.
24588 However, the user may choose to start @value{GDBN} with another
24589 interpreter by specifying the @option{-i} or @option{--interpreter}
24590 startup options. Defined interpreters include:
24594 @cindex console interpreter
24595 The traditional console or command-line interpreter. This is the most often
24596 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24597 @value{GDBN} will use this interpreter.
24600 @cindex mi interpreter
24601 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24602 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24603 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24607 @cindex mi2 interpreter
24608 The current @sc{gdb/mi} interface.
24611 @cindex mi1 interpreter
24612 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24616 @cindex invoke another interpreter
24617 The interpreter being used by @value{GDBN} may not be dynamically
24618 switched at runtime. Although possible, this could lead to a very
24619 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24620 enters the command "interpreter-set console" in a console view,
24621 @value{GDBN} would switch to using the console interpreter, rendering
24622 the IDE inoperable!
24624 @kindex interpreter-exec
24625 Although you may only choose a single interpreter at startup, you may execute
24626 commands in any interpreter from the current interpreter using the appropriate
24627 command. If you are running the console interpreter, simply use the
24628 @code{interpreter-exec} command:
24631 interpreter-exec mi "-data-list-register-names"
24634 @sc{gdb/mi} has a similar command, although it is only available in versions of
24635 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24638 @chapter @value{GDBN} Text User Interface
24640 @cindex Text User Interface
24643 * TUI Overview:: TUI overview
24644 * TUI Keys:: TUI key bindings
24645 * TUI Single Key Mode:: TUI single key mode
24646 * TUI Commands:: TUI-specific commands
24647 * TUI Configuration:: TUI configuration variables
24650 The @value{GDBN} Text User Interface (TUI) is a terminal
24651 interface which uses the @code{curses} library to show the source
24652 file, the assembly output, the program registers and @value{GDBN}
24653 commands in separate text windows. The TUI mode is supported only
24654 on platforms where a suitable version of the @code{curses} library
24657 @pindex @value{GDBTUI}
24658 The TUI mode is enabled by default when you invoke @value{GDBN} as
24659 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
24660 You can also switch in and out of TUI mode while @value{GDBN} runs by
24661 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24662 @xref{TUI Keys, ,TUI Key Bindings}.
24665 @section TUI Overview
24667 In TUI mode, @value{GDBN} can display several text windows:
24671 This window is the @value{GDBN} command window with the @value{GDBN}
24672 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24673 managed using readline.
24676 The source window shows the source file of the program. The current
24677 line and active breakpoints are displayed in this window.
24680 The assembly window shows the disassembly output of the program.
24683 This window shows the processor registers. Registers are highlighted
24684 when their values change.
24687 The source and assembly windows show the current program position
24688 by highlighting the current line and marking it with a @samp{>} marker.
24689 Breakpoints are indicated with two markers. The first marker
24690 indicates the breakpoint type:
24694 Breakpoint which was hit at least once.
24697 Breakpoint which was never hit.
24700 Hardware breakpoint which was hit at least once.
24703 Hardware breakpoint which was never hit.
24706 The second marker indicates whether the breakpoint is enabled or not:
24710 Breakpoint is enabled.
24713 Breakpoint is disabled.
24716 The source, assembly and register windows are updated when the current
24717 thread changes, when the frame changes, or when the program counter
24720 These windows are not all visible at the same time. The command
24721 window is always visible. The others can be arranged in several
24732 source and assembly,
24735 source and registers, or
24738 assembly and registers.
24741 A status line above the command window shows the following information:
24745 Indicates the current @value{GDBN} target.
24746 (@pxref{Targets, ,Specifying a Debugging Target}).
24749 Gives the current process or thread number.
24750 When no process is being debugged, this field is set to @code{No process}.
24753 Gives the current function name for the selected frame.
24754 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24755 When there is no symbol corresponding to the current program counter,
24756 the string @code{??} is displayed.
24759 Indicates the current line number for the selected frame.
24760 When the current line number is not known, the string @code{??} is displayed.
24763 Indicates the current program counter address.
24767 @section TUI Key Bindings
24768 @cindex TUI key bindings
24770 The TUI installs several key bindings in the readline keymaps
24771 @ifset SYSTEM_READLINE
24772 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24774 @ifclear SYSTEM_READLINE
24775 (@pxref{Command Line Editing}).
24777 The following key bindings are installed for both TUI mode and the
24778 @value{GDBN} standard mode.
24787 Enter or leave the TUI mode. When leaving the TUI mode,
24788 the curses window management stops and @value{GDBN} operates using
24789 its standard mode, writing on the terminal directly. When reentering
24790 the TUI mode, control is given back to the curses windows.
24791 The screen is then refreshed.
24795 Use a TUI layout with only one window. The layout will
24796 either be @samp{source} or @samp{assembly}. When the TUI mode
24797 is not active, it will switch to the TUI mode.
24799 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24803 Use a TUI layout with at least two windows. When the current
24804 layout already has two windows, the next layout with two windows is used.
24805 When a new layout is chosen, one window will always be common to the
24806 previous layout and the new one.
24808 Think of it as the Emacs @kbd{C-x 2} binding.
24812 Change the active window. The TUI associates several key bindings
24813 (like scrolling and arrow keys) with the active window. This command
24814 gives the focus to the next TUI window.
24816 Think of it as the Emacs @kbd{C-x o} binding.
24820 Switch in and out of the TUI SingleKey mode that binds single
24821 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24824 The following key bindings only work in the TUI mode:
24829 Scroll the active window one page up.
24833 Scroll the active window one page down.
24837 Scroll the active window one line up.
24841 Scroll the active window one line down.
24845 Scroll the active window one column left.
24849 Scroll the active window one column right.
24853 Refresh the screen.
24856 Because the arrow keys scroll the active window in the TUI mode, they
24857 are not available for their normal use by readline unless the command
24858 window has the focus. When another window is active, you must use
24859 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24860 and @kbd{C-f} to control the command window.
24862 @node TUI Single Key Mode
24863 @section TUI Single Key Mode
24864 @cindex TUI single key mode
24866 The TUI also provides a @dfn{SingleKey} mode, which binds several
24867 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24868 switch into this mode, where the following key bindings are used:
24871 @kindex c @r{(SingleKey TUI key)}
24875 @kindex d @r{(SingleKey TUI key)}
24879 @kindex f @r{(SingleKey TUI key)}
24883 @kindex n @r{(SingleKey TUI key)}
24887 @kindex q @r{(SingleKey TUI key)}
24889 exit the SingleKey mode.
24891 @kindex r @r{(SingleKey TUI key)}
24895 @kindex s @r{(SingleKey TUI key)}
24899 @kindex u @r{(SingleKey TUI key)}
24903 @kindex v @r{(SingleKey TUI key)}
24907 @kindex w @r{(SingleKey TUI key)}
24912 Other keys temporarily switch to the @value{GDBN} command prompt.
24913 The key that was pressed is inserted in the editing buffer so that
24914 it is possible to type most @value{GDBN} commands without interaction
24915 with the TUI SingleKey mode. Once the command is entered the TUI
24916 SingleKey mode is restored. The only way to permanently leave
24917 this mode is by typing @kbd{q} or @kbd{C-x s}.
24921 @section TUI-specific Commands
24922 @cindex TUI commands
24924 The TUI has specific commands to control the text windows.
24925 These commands are always available, even when @value{GDBN} is not in
24926 the TUI mode. When @value{GDBN} is in the standard mode, most
24927 of these commands will automatically switch to the TUI mode.
24929 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24930 terminal, or @value{GDBN} has been started with the machine interface
24931 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24932 these commands will fail with an error, because it would not be
24933 possible or desirable to enable curses window management.
24938 List and give the size of all displayed windows.
24942 Display the next layout.
24945 Display the previous layout.
24948 Display the source window only.
24951 Display the assembly window only.
24954 Display the source and assembly window.
24957 Display the register window together with the source or assembly window.
24961 Make the next window active for scrolling.
24964 Make the previous window active for scrolling.
24967 Make the source window active for scrolling.
24970 Make the assembly window active for scrolling.
24973 Make the register window active for scrolling.
24976 Make the command window active for scrolling.
24980 Refresh the screen. This is similar to typing @kbd{C-L}.
24982 @item tui reg float
24984 Show the floating point registers in the register window.
24986 @item tui reg general
24987 Show the general registers in the register window.
24990 Show the next register group. The list of register groups as well as
24991 their order is target specific. The predefined register groups are the
24992 following: @code{general}, @code{float}, @code{system}, @code{vector},
24993 @code{all}, @code{save}, @code{restore}.
24995 @item tui reg system
24996 Show the system registers in the register window.
25000 Update the source window and the current execution point.
25002 @item winheight @var{name} +@var{count}
25003 @itemx winheight @var{name} -@var{count}
25005 Change the height of the window @var{name} by @var{count}
25006 lines. Positive counts increase the height, while negative counts
25009 @item tabset @var{nchars}
25011 Set the width of tab stops to be @var{nchars} characters.
25014 @node TUI Configuration
25015 @section TUI Configuration Variables
25016 @cindex TUI configuration variables
25018 Several configuration variables control the appearance of TUI windows.
25021 @item set tui border-kind @var{kind}
25022 @kindex set tui border-kind
25023 Select the border appearance for the source, assembly and register windows.
25024 The possible values are the following:
25027 Use a space character to draw the border.
25030 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25033 Use the Alternate Character Set to draw the border. The border is
25034 drawn using character line graphics if the terminal supports them.
25037 @item set tui border-mode @var{mode}
25038 @kindex set tui border-mode
25039 @itemx set tui active-border-mode @var{mode}
25040 @kindex set tui active-border-mode
25041 Select the display attributes for the borders of the inactive windows
25042 or the active window. The @var{mode} can be one of the following:
25045 Use normal attributes to display the border.
25051 Use reverse video mode.
25054 Use half bright mode.
25056 @item half-standout
25057 Use half bright and standout mode.
25060 Use extra bright or bold mode.
25062 @item bold-standout
25063 Use extra bright or bold and standout mode.
25068 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25071 @cindex @sc{gnu} Emacs
25072 A special interface allows you to use @sc{gnu} Emacs to view (and
25073 edit) the source files for the program you are debugging with
25076 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25077 executable file you want to debug as an argument. This command starts
25078 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25079 created Emacs buffer.
25080 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25082 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25087 All ``terminal'' input and output goes through an Emacs buffer, called
25090 This applies both to @value{GDBN} commands and their output, and to the input
25091 and output done by the program you are debugging.
25093 This is useful because it means that you can copy the text of previous
25094 commands and input them again; you can even use parts of the output
25097 All the facilities of Emacs' Shell mode are available for interacting
25098 with your program. In particular, you can send signals the usual
25099 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25103 @value{GDBN} displays source code through Emacs.
25105 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25106 source file for that frame and puts an arrow (@samp{=>}) at the
25107 left margin of the current line. Emacs uses a separate buffer for
25108 source display, and splits the screen to show both your @value{GDBN} session
25111 Explicit @value{GDBN} @code{list} or search commands still produce output as
25112 usual, but you probably have no reason to use them from Emacs.
25115 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25116 a graphical mode, enabled by default, which provides further buffers
25117 that can control the execution and describe the state of your program.
25118 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25120 If you specify an absolute file name when prompted for the @kbd{M-x
25121 gdb} argument, then Emacs sets your current working directory to where
25122 your program resides. If you only specify the file name, then Emacs
25123 sets your current working directory to the directory associated
25124 with the previous buffer. In this case, @value{GDBN} may find your
25125 program by searching your environment's @code{PATH} variable, but on
25126 some operating systems it might not find the source. So, although the
25127 @value{GDBN} input and output session proceeds normally, the auxiliary
25128 buffer does not display the current source and line of execution.
25130 The initial working directory of @value{GDBN} is printed on the top
25131 line of the GUD buffer and this serves as a default for the commands
25132 that specify files for @value{GDBN} to operate on. @xref{Files,
25133 ,Commands to Specify Files}.
25135 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25136 need to call @value{GDBN} by a different name (for example, if you
25137 keep several configurations around, with different names) you can
25138 customize the Emacs variable @code{gud-gdb-command-name} to run the
25141 In the GUD buffer, you can use these special Emacs commands in
25142 addition to the standard Shell mode commands:
25146 Describe the features of Emacs' GUD Mode.
25149 Execute to another source line, like the @value{GDBN} @code{step} command; also
25150 update the display window to show the current file and location.
25153 Execute to next source line in this function, skipping all function
25154 calls, like the @value{GDBN} @code{next} command. Then update the display window
25155 to show the current file and location.
25158 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25159 display window accordingly.
25162 Execute until exit from the selected stack frame, like the @value{GDBN}
25163 @code{finish} command.
25166 Continue execution of your program, like the @value{GDBN} @code{continue}
25170 Go up the number of frames indicated by the numeric argument
25171 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25172 like the @value{GDBN} @code{up} command.
25175 Go down the number of frames indicated by the numeric argument, like the
25176 @value{GDBN} @code{down} command.
25179 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25180 tells @value{GDBN} to set a breakpoint on the source line point is on.
25182 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25183 separate frame which shows a backtrace when the GUD buffer is current.
25184 Move point to any frame in the stack and type @key{RET} to make it
25185 become the current frame and display the associated source in the
25186 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25187 selected frame become the current one. In graphical mode, the
25188 speedbar displays watch expressions.
25190 If you accidentally delete the source-display buffer, an easy way to get
25191 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25192 request a frame display; when you run under Emacs, this recreates
25193 the source buffer if necessary to show you the context of the current
25196 The source files displayed in Emacs are in ordinary Emacs buffers
25197 which are visiting the source files in the usual way. You can edit
25198 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25199 communicates with Emacs in terms of line numbers. If you add or
25200 delete lines from the text, the line numbers that @value{GDBN} knows cease
25201 to correspond properly with the code.
25203 A more detailed description of Emacs' interaction with @value{GDBN} is
25204 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25207 @c The following dropped because Epoch is nonstandard. Reactivate
25208 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25210 @kindex Emacs Epoch environment
25214 Version 18 of @sc{gnu} Emacs has a built-in window system
25215 called the @code{epoch}
25216 environment. Users of this environment can use a new command,
25217 @code{inspect} which performs identically to @code{print} except that
25218 each value is printed in its own window.
25223 @chapter The @sc{gdb/mi} Interface
25225 @unnumberedsec Function and Purpose
25227 @cindex @sc{gdb/mi}, its purpose
25228 @sc{gdb/mi} is a line based machine oriented text interface to
25229 @value{GDBN} and is activated by specifying using the
25230 @option{--interpreter} command line option (@pxref{Mode Options}). It
25231 is specifically intended to support the development of systems which
25232 use the debugger as just one small component of a larger system.
25234 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25235 in the form of a reference manual.
25237 Note that @sc{gdb/mi} is still under construction, so some of the
25238 features described below are incomplete and subject to change
25239 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25241 @unnumberedsec Notation and Terminology
25243 @cindex notational conventions, for @sc{gdb/mi}
25244 This chapter uses the following notation:
25248 @code{|} separates two alternatives.
25251 @code{[ @var{something} ]} indicates that @var{something} is optional:
25252 it may or may not be given.
25255 @code{( @var{group} )*} means that @var{group} inside the parentheses
25256 may repeat zero or more times.
25259 @code{( @var{group} )+} means that @var{group} inside the parentheses
25260 may repeat one or more times.
25263 @code{"@var{string}"} means a literal @var{string}.
25267 @heading Dependencies
25271 * GDB/MI General Design::
25272 * GDB/MI Command Syntax::
25273 * GDB/MI Compatibility with CLI::
25274 * GDB/MI Development and Front Ends::
25275 * GDB/MI Output Records::
25276 * GDB/MI Simple Examples::
25277 * GDB/MI Command Description Format::
25278 * GDB/MI Breakpoint Commands::
25279 * GDB/MI Program Context::
25280 * GDB/MI Thread Commands::
25281 * GDB/MI Ada Tasking Commands::
25282 * GDB/MI Program Execution::
25283 * GDB/MI Stack Manipulation::
25284 * GDB/MI Variable Objects::
25285 * GDB/MI Data Manipulation::
25286 * GDB/MI Tracepoint Commands::
25287 * GDB/MI Symbol Query::
25288 * GDB/MI File Commands::
25290 * GDB/MI Kod Commands::
25291 * GDB/MI Memory Overlay Commands::
25292 * GDB/MI Signal Handling Commands::
25294 * GDB/MI Target Manipulation::
25295 * GDB/MI File Transfer Commands::
25296 * GDB/MI Miscellaneous Commands::
25299 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25300 @node GDB/MI General Design
25301 @section @sc{gdb/mi} General Design
25302 @cindex GDB/MI General Design
25304 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25305 parts---commands sent to @value{GDBN}, responses to those commands
25306 and notifications. Each command results in exactly one response,
25307 indicating either successful completion of the command, or an error.
25308 For the commands that do not resume the target, the response contains the
25309 requested information. For the commands that resume the target, the
25310 response only indicates whether the target was successfully resumed.
25311 Notifications is the mechanism for reporting changes in the state of the
25312 target, or in @value{GDBN} state, that cannot conveniently be associated with
25313 a command and reported as part of that command response.
25315 The important examples of notifications are:
25319 Exec notifications. These are used to report changes in
25320 target state---when a target is resumed, or stopped. It would not
25321 be feasible to include this information in response of resuming
25322 commands, because one resume commands can result in multiple events in
25323 different threads. Also, quite some time may pass before any event
25324 happens in the target, while a frontend needs to know whether the resuming
25325 command itself was successfully executed.
25328 Console output, and status notifications. Console output
25329 notifications are used to report output of CLI commands, as well as
25330 diagnostics for other commands. Status notifications are used to
25331 report the progress of a long-running operation. Naturally, including
25332 this information in command response would mean no output is produced
25333 until the command is finished, which is undesirable.
25336 General notifications. Commands may have various side effects on
25337 the @value{GDBN} or target state beyond their official purpose. For example,
25338 a command may change the selected thread. Although such changes can
25339 be included in command response, using notification allows for more
25340 orthogonal frontend design.
25344 There's no guarantee that whenever an MI command reports an error,
25345 @value{GDBN} or the target are in any specific state, and especially,
25346 the state is not reverted to the state before the MI command was
25347 processed. Therefore, whenever an MI command results in an error,
25348 we recommend that the frontend refreshes all the information shown in
25349 the user interface.
25353 * Context management::
25354 * Asynchronous and non-stop modes::
25358 @node Context management
25359 @subsection Context management
25361 In most cases when @value{GDBN} accesses the target, this access is
25362 done in context of a specific thread and frame (@pxref{Frames}).
25363 Often, even when accessing global data, the target requires that a thread
25364 be specified. The CLI interface maintains the selected thread and frame,
25365 and supplies them to target on each command. This is convenient,
25366 because a command line user would not want to specify that information
25367 explicitly on each command, and because user interacts with
25368 @value{GDBN} via a single terminal, so no confusion is possible as
25369 to what thread and frame are the current ones.
25371 In the case of MI, the concept of selected thread and frame is less
25372 useful. First, a frontend can easily remember this information
25373 itself. Second, a graphical frontend can have more than one window,
25374 each one used for debugging a different thread, and the frontend might
25375 want to access additional threads for internal purposes. This
25376 increases the risk that by relying on implicitly selected thread, the
25377 frontend may be operating on a wrong one. Therefore, each MI command
25378 should explicitly specify which thread and frame to operate on. To
25379 make it possible, each MI command accepts the @samp{--thread} and
25380 @samp{--frame} options, the value to each is @value{GDBN} identifier
25381 for thread and frame to operate on.
25383 Usually, each top-level window in a frontend allows the user to select
25384 a thread and a frame, and remembers the user selection for further
25385 operations. However, in some cases @value{GDBN} may suggest that the
25386 current thread be changed. For example, when stopping on a breakpoint
25387 it is reasonable to switch to the thread where breakpoint is hit. For
25388 another example, if the user issues the CLI @samp{thread} command via
25389 the frontend, it is desirable to change the frontend's selected thread to the
25390 one specified by user. @value{GDBN} communicates the suggestion to
25391 change current thread using the @samp{=thread-selected} notification.
25392 No such notification is available for the selected frame at the moment.
25394 Note that historically, MI shares the selected thread with CLI, so
25395 frontends used the @code{-thread-select} to execute commands in the
25396 right context. However, getting this to work right is cumbersome. The
25397 simplest way is for frontend to emit @code{-thread-select} command
25398 before every command. This doubles the number of commands that need
25399 to be sent. The alternative approach is to suppress @code{-thread-select}
25400 if the selected thread in @value{GDBN} is supposed to be identical to the
25401 thread the frontend wants to operate on. However, getting this
25402 optimization right can be tricky. In particular, if the frontend
25403 sends several commands to @value{GDBN}, and one of the commands changes the
25404 selected thread, then the behaviour of subsequent commands will
25405 change. So, a frontend should either wait for response from such
25406 problematic commands, or explicitly add @code{-thread-select} for
25407 all subsequent commands. No frontend is known to do this exactly
25408 right, so it is suggested to just always pass the @samp{--thread} and
25409 @samp{--frame} options.
25411 @node Asynchronous and non-stop modes
25412 @subsection Asynchronous command execution and non-stop mode
25414 On some targets, @value{GDBN} is capable of processing MI commands
25415 even while the target is running. This is called @dfn{asynchronous
25416 command execution} (@pxref{Background Execution}). The frontend may
25417 specify a preferrence for asynchronous execution using the
25418 @code{-gdb-set target-async 1} command, which should be emitted before
25419 either running the executable or attaching to the target. After the
25420 frontend has started the executable or attached to the target, it can
25421 find if asynchronous execution is enabled using the
25422 @code{-list-target-features} command.
25424 Even if @value{GDBN} can accept a command while target is running,
25425 many commands that access the target do not work when the target is
25426 running. Therefore, asynchronous command execution is most useful
25427 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25428 it is possible to examine the state of one thread, while other threads
25431 When a given thread is running, MI commands that try to access the
25432 target in the context of that thread may not work, or may work only on
25433 some targets. In particular, commands that try to operate on thread's
25434 stack will not work, on any target. Commands that read memory, or
25435 modify breakpoints, may work or not work, depending on the target. Note
25436 that even commands that operate on global state, such as @code{print},
25437 @code{set}, and breakpoint commands, still access the target in the
25438 context of a specific thread, so frontend should try to find a
25439 stopped thread and perform the operation on that thread (using the
25440 @samp{--thread} option).
25442 Which commands will work in the context of a running thread is
25443 highly target dependent. However, the two commands
25444 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25445 to find the state of a thread, will always work.
25447 @node Thread groups
25448 @subsection Thread groups
25449 @value{GDBN} may be used to debug several processes at the same time.
25450 On some platfroms, @value{GDBN} may support debugging of several
25451 hardware systems, each one having several cores with several different
25452 processes running on each core. This section describes the MI
25453 mechanism to support such debugging scenarios.
25455 The key observation is that regardless of the structure of the
25456 target, MI can have a global list of threads, because most commands that
25457 accept the @samp{--thread} option do not need to know what process that
25458 thread belongs to. Therefore, it is not necessary to introduce
25459 neither additional @samp{--process} option, nor an notion of the
25460 current process in the MI interface. The only strictly new feature
25461 that is required is the ability to find how the threads are grouped
25464 To allow the user to discover such grouping, and to support arbitrary
25465 hierarchy of machines/cores/processes, MI introduces the concept of a
25466 @dfn{thread group}. Thread group is a collection of threads and other
25467 thread groups. A thread group always has a string identifier, a type,
25468 and may have additional attributes specific to the type. A new
25469 command, @code{-list-thread-groups}, returns the list of top-level
25470 thread groups, which correspond to processes that @value{GDBN} is
25471 debugging at the moment. By passing an identifier of a thread group
25472 to the @code{-list-thread-groups} command, it is possible to obtain
25473 the members of specific thread group.
25475 To allow the user to easily discover processes, and other objects, he
25476 wishes to debug, a concept of @dfn{available thread group} is
25477 introduced. Available thread group is an thread group that
25478 @value{GDBN} is not debugging, but that can be attached to, using the
25479 @code{-target-attach} command. The list of available top-level thread
25480 groups can be obtained using @samp{-list-thread-groups --available}.
25481 In general, the content of a thread group may be only retrieved only
25482 after attaching to that thread group.
25484 Thread groups are related to inferiors (@pxref{Inferiors and
25485 Programs}). Each inferior corresponds to a thread group of a special
25486 type @samp{process}, and some additional operations are permitted on
25487 such thread groups.
25489 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25490 @node GDB/MI Command Syntax
25491 @section @sc{gdb/mi} Command Syntax
25494 * GDB/MI Input Syntax::
25495 * GDB/MI Output Syntax::
25498 @node GDB/MI Input Syntax
25499 @subsection @sc{gdb/mi} Input Syntax
25501 @cindex input syntax for @sc{gdb/mi}
25502 @cindex @sc{gdb/mi}, input syntax
25504 @item @var{command} @expansion{}
25505 @code{@var{cli-command} | @var{mi-command}}
25507 @item @var{cli-command} @expansion{}
25508 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25509 @var{cli-command} is any existing @value{GDBN} CLI command.
25511 @item @var{mi-command} @expansion{}
25512 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25513 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25515 @item @var{token} @expansion{}
25516 "any sequence of digits"
25518 @item @var{option} @expansion{}
25519 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25521 @item @var{parameter} @expansion{}
25522 @code{@var{non-blank-sequence} | @var{c-string}}
25524 @item @var{operation} @expansion{}
25525 @emph{any of the operations described in this chapter}
25527 @item @var{non-blank-sequence} @expansion{}
25528 @emph{anything, provided it doesn't contain special characters such as
25529 "-", @var{nl}, """ and of course " "}
25531 @item @var{c-string} @expansion{}
25532 @code{""" @var{seven-bit-iso-c-string-content} """}
25534 @item @var{nl} @expansion{}
25543 The CLI commands are still handled by the @sc{mi} interpreter; their
25544 output is described below.
25547 The @code{@var{token}}, when present, is passed back when the command
25551 Some @sc{mi} commands accept optional arguments as part of the parameter
25552 list. Each option is identified by a leading @samp{-} (dash) and may be
25553 followed by an optional argument parameter. Options occur first in the
25554 parameter list and can be delimited from normal parameters using
25555 @samp{--} (this is useful when some parameters begin with a dash).
25562 We want easy access to the existing CLI syntax (for debugging).
25565 We want it to be easy to spot a @sc{mi} operation.
25568 @node GDB/MI Output Syntax
25569 @subsection @sc{gdb/mi} Output Syntax
25571 @cindex output syntax of @sc{gdb/mi}
25572 @cindex @sc{gdb/mi}, output syntax
25573 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25574 followed, optionally, by a single result record. This result record
25575 is for the most recent command. The sequence of output records is
25576 terminated by @samp{(gdb)}.
25578 If an input command was prefixed with a @code{@var{token}} then the
25579 corresponding output for that command will also be prefixed by that same
25583 @item @var{output} @expansion{}
25584 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25586 @item @var{result-record} @expansion{}
25587 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25589 @item @var{out-of-band-record} @expansion{}
25590 @code{@var{async-record} | @var{stream-record}}
25592 @item @var{async-record} @expansion{}
25593 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25595 @item @var{exec-async-output} @expansion{}
25596 @code{[ @var{token} ] "*" @var{async-output}}
25598 @item @var{status-async-output} @expansion{}
25599 @code{[ @var{token} ] "+" @var{async-output}}
25601 @item @var{notify-async-output} @expansion{}
25602 @code{[ @var{token} ] "=" @var{async-output}}
25604 @item @var{async-output} @expansion{}
25605 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25607 @item @var{result-class} @expansion{}
25608 @code{"done" | "running" | "connected" | "error" | "exit"}
25610 @item @var{async-class} @expansion{}
25611 @code{"stopped" | @var{others}} (where @var{others} will be added
25612 depending on the needs---this is still in development).
25614 @item @var{result} @expansion{}
25615 @code{ @var{variable} "=" @var{value}}
25617 @item @var{variable} @expansion{}
25618 @code{ @var{string} }
25620 @item @var{value} @expansion{}
25621 @code{ @var{const} | @var{tuple} | @var{list} }
25623 @item @var{const} @expansion{}
25624 @code{@var{c-string}}
25626 @item @var{tuple} @expansion{}
25627 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25629 @item @var{list} @expansion{}
25630 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25631 @var{result} ( "," @var{result} )* "]" }
25633 @item @var{stream-record} @expansion{}
25634 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25636 @item @var{console-stream-output} @expansion{}
25637 @code{"~" @var{c-string}}
25639 @item @var{target-stream-output} @expansion{}
25640 @code{"@@" @var{c-string}}
25642 @item @var{log-stream-output} @expansion{}
25643 @code{"&" @var{c-string}}
25645 @item @var{nl} @expansion{}
25648 @item @var{token} @expansion{}
25649 @emph{any sequence of digits}.
25657 All output sequences end in a single line containing a period.
25660 The @code{@var{token}} is from the corresponding request. Note that
25661 for all async output, while the token is allowed by the grammar and
25662 may be output by future versions of @value{GDBN} for select async
25663 output messages, it is generally omitted. Frontends should treat
25664 all async output as reporting general changes in the state of the
25665 target and there should be no need to associate async output to any
25669 @cindex status output in @sc{gdb/mi}
25670 @var{status-async-output} contains on-going status information about the
25671 progress of a slow operation. It can be discarded. All status output is
25672 prefixed by @samp{+}.
25675 @cindex async output in @sc{gdb/mi}
25676 @var{exec-async-output} contains asynchronous state change on the target
25677 (stopped, started, disappeared). All async output is prefixed by
25681 @cindex notify output in @sc{gdb/mi}
25682 @var{notify-async-output} contains supplementary information that the
25683 client should handle (e.g., a new breakpoint information). All notify
25684 output is prefixed by @samp{=}.
25687 @cindex console output in @sc{gdb/mi}
25688 @var{console-stream-output} is output that should be displayed as is in the
25689 console. It is the textual response to a CLI command. All the console
25690 output is prefixed by @samp{~}.
25693 @cindex target output in @sc{gdb/mi}
25694 @var{target-stream-output} is the output produced by the target program.
25695 All the target output is prefixed by @samp{@@}.
25698 @cindex log output in @sc{gdb/mi}
25699 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25700 instance messages that should be displayed as part of an error log. All
25701 the log output is prefixed by @samp{&}.
25704 @cindex list output in @sc{gdb/mi}
25705 New @sc{gdb/mi} commands should only output @var{lists} containing
25711 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25712 details about the various output records.
25714 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25715 @node GDB/MI Compatibility with CLI
25716 @section @sc{gdb/mi} Compatibility with CLI
25718 @cindex compatibility, @sc{gdb/mi} and CLI
25719 @cindex @sc{gdb/mi}, compatibility with CLI
25721 For the developers convenience CLI commands can be entered directly,
25722 but there may be some unexpected behaviour. For example, commands
25723 that query the user will behave as if the user replied yes, breakpoint
25724 command lists are not executed and some CLI commands, such as
25725 @code{if}, @code{when} and @code{define}, prompt for further input with
25726 @samp{>}, which is not valid MI output.
25728 This feature may be removed at some stage in the future and it is
25729 recommended that front ends use the @code{-interpreter-exec} command
25730 (@pxref{-interpreter-exec}).
25732 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25733 @node GDB/MI Development and Front Ends
25734 @section @sc{gdb/mi} Development and Front Ends
25735 @cindex @sc{gdb/mi} development
25737 The application which takes the MI output and presents the state of the
25738 program being debugged to the user is called a @dfn{front end}.
25740 Although @sc{gdb/mi} is still incomplete, it is currently being used
25741 by a variety of front ends to @value{GDBN}. This makes it difficult
25742 to introduce new functionality without breaking existing usage. This
25743 section tries to minimize the problems by describing how the protocol
25746 Some changes in MI need not break a carefully designed front end, and
25747 for these the MI version will remain unchanged. The following is a
25748 list of changes that may occur within one level, so front ends should
25749 parse MI output in a way that can handle them:
25753 New MI commands may be added.
25756 New fields may be added to the output of any MI command.
25759 The range of values for fields with specified values, e.g.,
25760 @code{in_scope} (@pxref{-var-update}) may be extended.
25762 @c The format of field's content e.g type prefix, may change so parse it
25763 @c at your own risk. Yes, in general?
25765 @c The order of fields may change? Shouldn't really matter but it might
25766 @c resolve inconsistencies.
25769 If the changes are likely to break front ends, the MI version level
25770 will be increased by one. This will allow the front end to parse the
25771 output according to the MI version. Apart from mi0, new versions of
25772 @value{GDBN} will not support old versions of MI and it will be the
25773 responsibility of the front end to work with the new one.
25775 @c Starting with mi3, add a new command -mi-version that prints the MI
25778 The best way to avoid unexpected changes in MI that might break your front
25779 end is to make your project known to @value{GDBN} developers and
25780 follow development on @email{gdb@@sourceware.org} and
25781 @email{gdb-patches@@sourceware.org}.
25782 @cindex mailing lists
25784 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25785 @node GDB/MI Output Records
25786 @section @sc{gdb/mi} Output Records
25789 * GDB/MI Result Records::
25790 * GDB/MI Stream Records::
25791 * GDB/MI Async Records::
25792 * GDB/MI Frame Information::
25793 * GDB/MI Thread Information::
25794 * GDB/MI Ada Exception Information::
25797 @node GDB/MI Result Records
25798 @subsection @sc{gdb/mi} Result Records
25800 @cindex result records in @sc{gdb/mi}
25801 @cindex @sc{gdb/mi}, result records
25802 In addition to a number of out-of-band notifications, the response to a
25803 @sc{gdb/mi} command includes one of the following result indications:
25807 @item "^done" [ "," @var{results} ]
25808 The synchronous operation was successful, @code{@var{results}} are the return
25813 This result record is equivalent to @samp{^done}. Historically, it
25814 was output instead of @samp{^done} if the command has resumed the
25815 target. This behaviour is maintained for backward compatibility, but
25816 all frontends should treat @samp{^done} and @samp{^running}
25817 identically and rely on the @samp{*running} output record to determine
25818 which threads are resumed.
25822 @value{GDBN} has connected to a remote target.
25824 @item "^error" "," @var{c-string}
25826 The operation failed. The @code{@var{c-string}} contains the corresponding
25831 @value{GDBN} has terminated.
25835 @node GDB/MI Stream Records
25836 @subsection @sc{gdb/mi} Stream Records
25838 @cindex @sc{gdb/mi}, stream records
25839 @cindex stream records in @sc{gdb/mi}
25840 @value{GDBN} internally maintains a number of output streams: the console, the
25841 target, and the log. The output intended for each of these streams is
25842 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25844 Each stream record begins with a unique @dfn{prefix character} which
25845 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25846 Syntax}). In addition to the prefix, each stream record contains a
25847 @code{@var{string-output}}. This is either raw text (with an implicit new
25848 line) or a quoted C string (which does not contain an implicit newline).
25851 @item "~" @var{string-output}
25852 The console output stream contains text that should be displayed in the
25853 CLI console window. It contains the textual responses to CLI commands.
25855 @item "@@" @var{string-output}
25856 The target output stream contains any textual output from the running
25857 target. This is only present when GDB's event loop is truly
25858 asynchronous, which is currently only the case for remote targets.
25860 @item "&" @var{string-output}
25861 The log stream contains debugging messages being produced by @value{GDBN}'s
25865 @node GDB/MI Async Records
25866 @subsection @sc{gdb/mi} Async Records
25868 @cindex async records in @sc{gdb/mi}
25869 @cindex @sc{gdb/mi}, async records
25870 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25871 additional changes that have occurred. Those changes can either be a
25872 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25873 target activity (e.g., target stopped).
25875 The following is the list of possible async records:
25879 @item *running,thread-id="@var{thread}"
25880 The target is now running. The @var{thread} field tells which
25881 specific thread is now running, and can be @samp{all} if all threads
25882 are running. The frontend should assume that no interaction with a
25883 running thread is possible after this notification is produced.
25884 The frontend should not assume that this notification is output
25885 only once for any command. @value{GDBN} may emit this notification
25886 several times, either for different threads, because it cannot resume
25887 all threads together, or even for a single thread, if the thread must
25888 be stepped though some code before letting it run freely.
25890 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25891 The target has stopped. The @var{reason} field can have one of the
25895 @item breakpoint-hit
25896 A breakpoint was reached.
25897 @item watchpoint-trigger
25898 A watchpoint was triggered.
25899 @item read-watchpoint-trigger
25900 A read watchpoint was triggered.
25901 @item access-watchpoint-trigger
25902 An access watchpoint was triggered.
25903 @item function-finished
25904 An -exec-finish or similar CLI command was accomplished.
25905 @item location-reached
25906 An -exec-until or similar CLI command was accomplished.
25907 @item watchpoint-scope
25908 A watchpoint has gone out of scope.
25909 @item end-stepping-range
25910 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25911 similar CLI command was accomplished.
25912 @item exited-signalled
25913 The inferior exited because of a signal.
25915 The inferior exited.
25916 @item exited-normally
25917 The inferior exited normally.
25918 @item signal-received
25919 A signal was received by the inferior.
25922 The @var{id} field identifies the thread that directly caused the stop
25923 -- for example by hitting a breakpoint. Depending on whether all-stop
25924 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25925 stop all threads, or only the thread that directly triggered the stop.
25926 If all threads are stopped, the @var{stopped} field will have the
25927 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25928 field will be a list of thread identifiers. Presently, this list will
25929 always include a single thread, but frontend should be prepared to see
25930 several threads in the list. The @var{core} field reports the
25931 processor core on which the stop event has happened. This field may be absent
25932 if such information is not available.
25934 @item =thread-group-added,id="@var{id}"
25935 @itemx =thread-group-removed,id="@var{id}"
25936 A thread group was either added or removed. The @var{id} field
25937 contains the @value{GDBN} identifier of the thread group. When a thread
25938 group is added, it generally might not be associated with a running
25939 process. When a thread group is removed, its id becomes invalid and
25940 cannot be used in any way.
25942 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25943 A thread group became associated with a running program,
25944 either because the program was just started or the thread group
25945 was attached to a program. The @var{id} field contains the
25946 @value{GDBN} identifier of the thread group. The @var{pid} field
25947 contains process identifier, specific to the operating system.
25949 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25950 A thread group is no longer associated with a running program,
25951 either because the program has exited, or because it was detached
25952 from. The @var{id} field contains the @value{GDBN} identifier of the
25953 thread group. @var{code} is the exit code of the inferior; it exists
25954 only when the inferior exited with some code.
25956 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25957 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25958 A thread either was created, or has exited. The @var{id} field
25959 contains the @value{GDBN} identifier of the thread. The @var{gid}
25960 field identifies the thread group this thread belongs to.
25962 @item =thread-selected,id="@var{id}"
25963 Informs that the selected thread was changed as result of the last
25964 command. This notification is not emitted as result of @code{-thread-select}
25965 command but is emitted whenever an MI command that is not documented
25966 to change the selected thread actually changes it. In particular,
25967 invoking, directly or indirectly (via user-defined command), the CLI
25968 @code{thread} command, will generate this notification.
25970 We suggest that in response to this notification, front ends
25971 highlight the selected thread and cause subsequent commands to apply to
25974 @item =library-loaded,...
25975 Reports that a new library file was loaded by the program. This
25976 notification has 4 fields---@var{id}, @var{target-name},
25977 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25978 opaque identifier of the library. For remote debugging case,
25979 @var{target-name} and @var{host-name} fields give the name of the
25980 library file on the target, and on the host respectively. For native
25981 debugging, both those fields have the same value. The
25982 @var{symbols-loaded} field is emitted only for backward compatibility
25983 and should not be relied on to convey any useful information. The
25984 @var{thread-group} field, if present, specifies the id of the thread
25985 group in whose context the library was loaded. If the field is
25986 absent, it means the library was loaded in the context of all present
25989 @item =library-unloaded,...
25990 Reports that a library was unloaded by the program. This notification
25991 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25992 the same meaning as for the @code{=library-loaded} notification.
25993 The @var{thread-group} field, if present, specifies the id of the
25994 thread group in whose context the library was unloaded. If the field is
25995 absent, it means the library was unloaded in the context of all present
25998 @item =breakpoint-created,bkpt=@{...@}
25999 @itemx =breakpoint-modified,bkpt=@{...@}
26000 @itemx =breakpoint-deleted,bkpt=@{...@}
26001 Reports that a breakpoint was created, modified, or deleted,
26002 respectively. Only user-visible breakpoints are reported to the MI
26005 The @var{bkpt} argument is of the same form as returned by the various
26006 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26008 Note that if a breakpoint is emitted in the result record of a
26009 command, then it will not also be emitted in an async record.
26013 @node GDB/MI Frame Information
26014 @subsection @sc{gdb/mi} Frame Information
26016 Response from many MI commands includes an information about stack
26017 frame. This information is a tuple that may have the following
26022 The level of the stack frame. The innermost frame has the level of
26023 zero. This field is always present.
26026 The name of the function corresponding to the frame. This field may
26027 be absent if @value{GDBN} is unable to determine the function name.
26030 The code address for the frame. This field is always present.
26033 The name of the source files that correspond to the frame's code
26034 address. This field may be absent.
26037 The source line corresponding to the frames' code address. This field
26041 The name of the binary file (either executable or shared library) the
26042 corresponds to the frame's code address. This field may be absent.
26046 @node GDB/MI Thread Information
26047 @subsection @sc{gdb/mi} Thread Information
26049 Whenever @value{GDBN} has to report an information about a thread, it
26050 uses a tuple with the following fields:
26054 The numeric id assigned to the thread by @value{GDBN}. This field is
26058 Target-specific string identifying the thread. This field is always present.
26061 Additional information about the thread provided by the target.
26062 It is supposed to be human-readable and not interpreted by the
26063 frontend. This field is optional.
26066 Either @samp{stopped} or @samp{running}, depending on whether the
26067 thread is presently running. This field is always present.
26070 The value of this field is an integer number of the processor core the
26071 thread was last seen on. This field is optional.
26074 @node GDB/MI Ada Exception Information
26075 @subsection @sc{gdb/mi} Ada Exception Information
26077 Whenever a @code{*stopped} record is emitted because the program
26078 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26079 @value{GDBN} provides the name of the exception that was raised via
26080 the @code{exception-name} field.
26082 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26083 @node GDB/MI Simple Examples
26084 @section Simple Examples of @sc{gdb/mi} Interaction
26085 @cindex @sc{gdb/mi}, simple examples
26087 This subsection presents several simple examples of interaction using
26088 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26089 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26090 the output received from @sc{gdb/mi}.
26092 Note the line breaks shown in the examples are here only for
26093 readability, they don't appear in the real output.
26095 @subheading Setting a Breakpoint
26097 Setting a breakpoint generates synchronous output which contains detailed
26098 information of the breakpoint.
26101 -> -break-insert main
26102 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26103 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26104 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26108 @subheading Program Execution
26110 Program execution generates asynchronous records and MI gives the
26111 reason that execution stopped.
26117 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26118 frame=@{addr="0x08048564",func="main",
26119 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26120 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26125 <- *stopped,reason="exited-normally"
26129 @subheading Quitting @value{GDBN}
26131 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26139 Please note that @samp{^exit} is printed immediately, but it might
26140 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26141 performs necessary cleanups, including killing programs being debugged
26142 or disconnecting from debug hardware, so the frontend should wait till
26143 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26144 fails to exit in reasonable time.
26146 @subheading A Bad Command
26148 Here's what happens if you pass a non-existent command:
26152 <- ^error,msg="Undefined MI command: rubbish"
26157 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26158 @node GDB/MI Command Description Format
26159 @section @sc{gdb/mi} Command Description Format
26161 The remaining sections describe blocks of commands. Each block of
26162 commands is laid out in a fashion similar to this section.
26164 @subheading Motivation
26166 The motivation for this collection of commands.
26168 @subheading Introduction
26170 A brief introduction to this collection of commands as a whole.
26172 @subheading Commands
26174 For each command in the block, the following is described:
26176 @subsubheading Synopsis
26179 -command @var{args}@dots{}
26182 @subsubheading Result
26184 @subsubheading @value{GDBN} Command
26186 The corresponding @value{GDBN} CLI command(s), if any.
26188 @subsubheading Example
26190 Example(s) formatted for readability. Some of the described commands have
26191 not been implemented yet and these are labeled N.A.@: (not available).
26194 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26195 @node GDB/MI Breakpoint Commands
26196 @section @sc{gdb/mi} Breakpoint Commands
26198 @cindex breakpoint commands for @sc{gdb/mi}
26199 @cindex @sc{gdb/mi}, breakpoint commands
26200 This section documents @sc{gdb/mi} commands for manipulating
26203 @subheading The @code{-break-after} Command
26204 @findex -break-after
26206 @subsubheading Synopsis
26209 -break-after @var{number} @var{count}
26212 The breakpoint number @var{number} is not in effect until it has been
26213 hit @var{count} times. To see how this is reflected in the output of
26214 the @samp{-break-list} command, see the description of the
26215 @samp{-break-list} command below.
26217 @subsubheading @value{GDBN} Command
26219 The corresponding @value{GDBN} command is @samp{ignore}.
26221 @subsubheading Example
26226 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26227 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26228 fullname="/home/foo/hello.c",line="5",times="0"@}
26235 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26236 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26237 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26238 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26239 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26240 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26241 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26242 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26243 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26244 line="5",times="0",ignore="3"@}]@}
26249 @subheading The @code{-break-catch} Command
26250 @findex -break-catch
26253 @subheading The @code{-break-commands} Command
26254 @findex -break-commands
26256 @subsubheading Synopsis
26259 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26262 Specifies the CLI commands that should be executed when breakpoint
26263 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26264 are the commands. If no command is specified, any previously-set
26265 commands are cleared. @xref{Break Commands}. Typical use of this
26266 functionality is tracing a program, that is, printing of values of
26267 some variables whenever breakpoint is hit and then continuing.
26269 @subsubheading @value{GDBN} Command
26271 The corresponding @value{GDBN} command is @samp{commands}.
26273 @subsubheading Example
26278 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26279 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26280 fullname="/home/foo/hello.c",line="5",times="0"@}
26282 -break-commands 1 "print v" "continue"
26287 @subheading The @code{-break-condition} Command
26288 @findex -break-condition
26290 @subsubheading Synopsis
26293 -break-condition @var{number} @var{expr}
26296 Breakpoint @var{number} will stop the program only if the condition in
26297 @var{expr} is true. The condition becomes part of the
26298 @samp{-break-list} output (see the description of the @samp{-break-list}
26301 @subsubheading @value{GDBN} Command
26303 The corresponding @value{GDBN} command is @samp{condition}.
26305 @subsubheading Example
26309 -break-condition 1 1
26313 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26314 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26315 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26316 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26317 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26318 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26319 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26320 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26321 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26322 line="5",cond="1",times="0",ignore="3"@}]@}
26326 @subheading The @code{-break-delete} Command
26327 @findex -break-delete
26329 @subsubheading Synopsis
26332 -break-delete ( @var{breakpoint} )+
26335 Delete the breakpoint(s) whose number(s) are specified in the argument
26336 list. This is obviously reflected in the breakpoint list.
26338 @subsubheading @value{GDBN} Command
26340 The corresponding @value{GDBN} command is @samp{delete}.
26342 @subsubheading Example
26350 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26351 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26352 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26353 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26354 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26355 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26356 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26361 @subheading The @code{-break-disable} Command
26362 @findex -break-disable
26364 @subsubheading Synopsis
26367 -break-disable ( @var{breakpoint} )+
26370 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26371 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26373 @subsubheading @value{GDBN} Command
26375 The corresponding @value{GDBN} command is @samp{disable}.
26377 @subsubheading Example
26385 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26386 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26387 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26388 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26389 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26390 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26391 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26392 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26393 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26394 line="5",times="0"@}]@}
26398 @subheading The @code{-break-enable} Command
26399 @findex -break-enable
26401 @subsubheading Synopsis
26404 -break-enable ( @var{breakpoint} )+
26407 Enable (previously disabled) @var{breakpoint}(s).
26409 @subsubheading @value{GDBN} Command
26411 The corresponding @value{GDBN} command is @samp{enable}.
26413 @subsubheading Example
26421 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26422 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26423 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26424 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26425 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26426 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26427 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26428 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26429 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26430 line="5",times="0"@}]@}
26434 @subheading The @code{-break-info} Command
26435 @findex -break-info
26437 @subsubheading Synopsis
26440 -break-info @var{breakpoint}
26444 Get information about a single breakpoint.
26446 @subsubheading @value{GDBN} Command
26448 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26450 @subsubheading Example
26453 @subheading The @code{-break-insert} Command
26454 @findex -break-insert
26456 @subsubheading Synopsis
26459 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26460 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26461 [ -p @var{thread} ] [ @var{location} ]
26465 If specified, @var{location}, can be one of:
26472 @item filename:linenum
26473 @item filename:function
26477 The possible optional parameters of this command are:
26481 Insert a temporary breakpoint.
26483 Insert a hardware breakpoint.
26484 @item -c @var{condition}
26485 Make the breakpoint conditional on @var{condition}.
26486 @item -i @var{ignore-count}
26487 Initialize the @var{ignore-count}.
26489 If @var{location} cannot be parsed (for example if it
26490 refers to unknown files or functions), create a pending
26491 breakpoint. Without this flag, @value{GDBN} will report
26492 an error, and won't create a breakpoint, if @var{location}
26495 Create a disabled breakpoint.
26497 Create a tracepoint. @xref{Tracepoints}. When this parameter
26498 is used together with @samp{-h}, a fast tracepoint is created.
26501 @subsubheading Result
26503 The result is in the form:
26506 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26507 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26508 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26509 times="@var{times}"@}
26513 where @var{number} is the @value{GDBN} number for this breakpoint,
26514 @var{funcname} is the name of the function where the breakpoint was
26515 inserted, @var{filename} is the name of the source file which contains
26516 this function, @var{lineno} is the source line number within that file
26517 and @var{times} the number of times that the breakpoint has been hit
26518 (always 0 for -break-insert but may be greater for -break-info or -break-list
26519 which use the same output).
26521 Note: this format is open to change.
26522 @c An out-of-band breakpoint instead of part of the result?
26524 @subsubheading @value{GDBN} Command
26526 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26527 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26529 @subsubheading Example
26534 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26535 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26537 -break-insert -t foo
26538 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26539 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26542 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26543 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26544 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26545 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26546 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26547 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26548 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26549 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26550 addr="0x0001072c", func="main",file="recursive2.c",
26551 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26552 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26553 addr="0x00010774",func="foo",file="recursive2.c",
26554 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26556 -break-insert -r foo.*
26557 ~int foo(int, int);
26558 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26559 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26563 @subheading The @code{-break-list} Command
26564 @findex -break-list
26566 @subsubheading Synopsis
26572 Displays the list of inserted breakpoints, showing the following fields:
26576 number of the breakpoint
26578 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26580 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26583 is the breakpoint enabled or no: @samp{y} or @samp{n}
26585 memory location at which the breakpoint is set
26587 logical location of the breakpoint, expressed by function name, file
26590 number of times the breakpoint has been hit
26593 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26594 @code{body} field is an empty list.
26596 @subsubheading @value{GDBN} Command
26598 The corresponding @value{GDBN} command is @samp{info break}.
26600 @subsubheading Example
26605 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26606 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26607 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26608 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26609 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26610 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26611 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26612 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26613 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26614 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26615 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26616 line="13",times="0"@}]@}
26620 Here's an example of the result when there are no breakpoints:
26625 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26626 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26627 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26628 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26629 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26630 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26631 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26636 @subheading The @code{-break-passcount} Command
26637 @findex -break-passcount
26639 @subsubheading Synopsis
26642 -break-passcount @var{tracepoint-number} @var{passcount}
26645 Set the passcount for tracepoint @var{tracepoint-number} to
26646 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26647 is not a tracepoint, error is emitted. This corresponds to CLI
26648 command @samp{passcount}.
26650 @subheading The @code{-break-watch} Command
26651 @findex -break-watch
26653 @subsubheading Synopsis
26656 -break-watch [ -a | -r ]
26659 Create a watchpoint. With the @samp{-a} option it will create an
26660 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26661 read from or on a write to the memory location. With the @samp{-r}
26662 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26663 trigger only when the memory location is accessed for reading. Without
26664 either of the options, the watchpoint created is a regular watchpoint,
26665 i.e., it will trigger when the memory location is accessed for writing.
26666 @xref{Set Watchpoints, , Setting Watchpoints}.
26668 Note that @samp{-break-list} will report a single list of watchpoints and
26669 breakpoints inserted.
26671 @subsubheading @value{GDBN} Command
26673 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26676 @subsubheading Example
26678 Setting a watchpoint on a variable in the @code{main} function:
26683 ^done,wpt=@{number="2",exp="x"@}
26688 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26689 value=@{old="-268439212",new="55"@},
26690 frame=@{func="main",args=[],file="recursive2.c",
26691 fullname="/home/foo/bar/recursive2.c",line="5"@}
26695 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26696 the program execution twice: first for the variable changing value, then
26697 for the watchpoint going out of scope.
26702 ^done,wpt=@{number="5",exp="C"@}
26707 *stopped,reason="watchpoint-trigger",
26708 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26709 frame=@{func="callee4",args=[],
26710 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26711 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26716 *stopped,reason="watchpoint-scope",wpnum="5",
26717 frame=@{func="callee3",args=[@{name="strarg",
26718 value="0x11940 \"A string argument.\""@}],
26719 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26720 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26724 Listing breakpoints and watchpoints, at different points in the program
26725 execution. Note that once the watchpoint goes out of scope, it is
26731 ^done,wpt=@{number="2",exp="C"@}
26734 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26735 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26736 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26737 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26738 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26739 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26740 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26741 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26742 addr="0x00010734",func="callee4",
26743 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26744 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
26745 bkpt=@{number="2",type="watchpoint",disp="keep",
26746 enabled="y",addr="",what="C",times="0"@}]@}
26751 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26752 value=@{old="-276895068",new="3"@},
26753 frame=@{func="callee4",args=[],
26754 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26755 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26758 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26759 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26760 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26761 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26762 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26763 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26764 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26765 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26766 addr="0x00010734",func="callee4",
26767 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26768 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
26769 bkpt=@{number="2",type="watchpoint",disp="keep",
26770 enabled="y",addr="",what="C",times="-5"@}]@}
26774 ^done,reason="watchpoint-scope",wpnum="2",
26775 frame=@{func="callee3",args=[@{name="strarg",
26776 value="0x11940 \"A string argument.\""@}],
26777 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26778 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26781 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26782 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26783 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26784 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26785 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26786 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26787 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26788 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26789 addr="0x00010734",func="callee4",
26790 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26791 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26796 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26797 @node GDB/MI Program Context
26798 @section @sc{gdb/mi} Program Context
26800 @subheading The @code{-exec-arguments} Command
26801 @findex -exec-arguments
26804 @subsubheading Synopsis
26807 -exec-arguments @var{args}
26810 Set the inferior program arguments, to be used in the next
26813 @subsubheading @value{GDBN} Command
26815 The corresponding @value{GDBN} command is @samp{set args}.
26817 @subsubheading Example
26821 -exec-arguments -v word
26828 @subheading The @code{-exec-show-arguments} Command
26829 @findex -exec-show-arguments
26831 @subsubheading Synopsis
26834 -exec-show-arguments
26837 Print the arguments of the program.
26839 @subsubheading @value{GDBN} Command
26841 The corresponding @value{GDBN} command is @samp{show args}.
26843 @subsubheading Example
26848 @subheading The @code{-environment-cd} Command
26849 @findex -environment-cd
26851 @subsubheading Synopsis
26854 -environment-cd @var{pathdir}
26857 Set @value{GDBN}'s working directory.
26859 @subsubheading @value{GDBN} Command
26861 The corresponding @value{GDBN} command is @samp{cd}.
26863 @subsubheading Example
26867 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26873 @subheading The @code{-environment-directory} Command
26874 @findex -environment-directory
26876 @subsubheading Synopsis
26879 -environment-directory [ -r ] [ @var{pathdir} ]+
26882 Add directories @var{pathdir} to beginning of search path for source files.
26883 If the @samp{-r} option is used, the search path is reset to the default
26884 search path. If directories @var{pathdir} are supplied in addition to the
26885 @samp{-r} option, the search path is first reset and then addition
26887 Multiple directories may be specified, separated by blanks. Specifying
26888 multiple directories in a single command
26889 results in the directories added to the beginning of the
26890 search path in the same order they were presented in the command.
26891 If blanks are needed as
26892 part of a directory name, double-quotes should be used around
26893 the name. In the command output, the path will show up separated
26894 by the system directory-separator character. The directory-separator
26895 character must not be used
26896 in any directory name.
26897 If no directories are specified, the current search path is displayed.
26899 @subsubheading @value{GDBN} Command
26901 The corresponding @value{GDBN} command is @samp{dir}.
26903 @subsubheading Example
26907 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26908 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26910 -environment-directory ""
26911 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26913 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26914 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26916 -environment-directory -r
26917 ^done,source-path="$cdir:$cwd"
26922 @subheading The @code{-environment-path} Command
26923 @findex -environment-path
26925 @subsubheading Synopsis
26928 -environment-path [ -r ] [ @var{pathdir} ]+
26931 Add directories @var{pathdir} to beginning of search path for object files.
26932 If the @samp{-r} option is used, the search path is reset to the original
26933 search path that existed at gdb start-up. If directories @var{pathdir} are
26934 supplied in addition to the
26935 @samp{-r} option, the search path is first reset and then addition
26937 Multiple directories may be specified, separated by blanks. Specifying
26938 multiple directories in a single command
26939 results in the directories added to the beginning of the
26940 search path in the same order they were presented in the command.
26941 If blanks are needed as
26942 part of a directory name, double-quotes should be used around
26943 the name. In the command output, the path will show up separated
26944 by the system directory-separator character. The directory-separator
26945 character must not be used
26946 in any directory name.
26947 If no directories are specified, the current path is displayed.
26950 @subsubheading @value{GDBN} Command
26952 The corresponding @value{GDBN} command is @samp{path}.
26954 @subsubheading Example
26959 ^done,path="/usr/bin"
26961 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26962 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26964 -environment-path -r /usr/local/bin
26965 ^done,path="/usr/local/bin:/usr/bin"
26970 @subheading The @code{-environment-pwd} Command
26971 @findex -environment-pwd
26973 @subsubheading Synopsis
26979 Show the current working directory.
26981 @subsubheading @value{GDBN} Command
26983 The corresponding @value{GDBN} command is @samp{pwd}.
26985 @subsubheading Example
26990 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26994 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26995 @node GDB/MI Thread Commands
26996 @section @sc{gdb/mi} Thread Commands
26999 @subheading The @code{-thread-info} Command
27000 @findex -thread-info
27002 @subsubheading Synopsis
27005 -thread-info [ @var{thread-id} ]
27008 Reports information about either a specific thread, if
27009 the @var{thread-id} parameter is present, or about all
27010 threads. When printing information about all threads,
27011 also reports the current thread.
27013 @subsubheading @value{GDBN} Command
27015 The @samp{info thread} command prints the same information
27018 @subsubheading Result
27020 The result is a list of threads. The following attributes are
27021 defined for a given thread:
27025 This field exists only for the current thread. It has the value @samp{*}.
27028 The identifier that @value{GDBN} uses to refer to the thread.
27031 The identifier that the target uses to refer to the thread.
27034 Extra information about the thread, in a target-specific format. This
27038 The name of the thread. If the user specified a name using the
27039 @code{thread name} command, then this name is given. Otherwise, if
27040 @value{GDBN} can extract the thread name from the target, then that
27041 name is given. If @value{GDBN} cannot find the thread name, then this
27045 The stack frame currently executing in the thread.
27048 The thread's state. The @samp{state} field may have the following
27053 The thread is stopped. Frame information is available for stopped
27057 The thread is running. There's no frame information for running
27063 If @value{GDBN} can find the CPU core on which this thread is running,
27064 then this field is the core identifier. This field is optional.
27068 @subsubheading Example
27073 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27074 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27075 args=[]@},state="running"@},
27076 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27077 frame=@{level="0",addr="0x0804891f",func="foo",
27078 args=[@{name="i",value="10"@}],
27079 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27080 state="running"@}],
27081 current-thread-id="1"
27085 @subheading The @code{-thread-list-ids} Command
27086 @findex -thread-list-ids
27088 @subsubheading Synopsis
27094 Produces a list of the currently known @value{GDBN} thread ids. At the
27095 end of the list it also prints the total number of such threads.
27097 This command is retained for historical reasons, the
27098 @code{-thread-info} command should be used instead.
27100 @subsubheading @value{GDBN} Command
27102 Part of @samp{info threads} supplies the same information.
27104 @subsubheading Example
27109 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27110 current-thread-id="1",number-of-threads="3"
27115 @subheading The @code{-thread-select} Command
27116 @findex -thread-select
27118 @subsubheading Synopsis
27121 -thread-select @var{threadnum}
27124 Make @var{threadnum} the current thread. It prints the number of the new
27125 current thread, and the topmost frame for that thread.
27127 This command is deprecated in favor of explicitly using the
27128 @samp{--thread} option to each command.
27130 @subsubheading @value{GDBN} Command
27132 The corresponding @value{GDBN} command is @samp{thread}.
27134 @subsubheading Example
27141 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27142 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27146 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27147 number-of-threads="3"
27150 ^done,new-thread-id="3",
27151 frame=@{level="0",func="vprintf",
27152 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27153 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27157 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27158 @node GDB/MI Ada Tasking Commands
27159 @section @sc{gdb/mi} Ada Tasking Commands
27161 @subheading The @code{-ada-task-info} Command
27162 @findex -ada-task-info
27164 @subsubheading Synopsis
27167 -ada-task-info [ @var{task-id} ]
27170 Reports information about either a specific Ada task, if the
27171 @var{task-id} parameter is present, or about all Ada tasks.
27173 @subsubheading @value{GDBN} Command
27175 The @samp{info tasks} command prints the same information
27176 about all Ada tasks (@pxref{Ada Tasks}).
27178 @subsubheading Result
27180 The result is a table of Ada tasks. The following columns are
27181 defined for each Ada task:
27185 This field exists only for the current thread. It has the value @samp{*}.
27188 The identifier that @value{GDBN} uses to refer to the Ada task.
27191 The identifier that the target uses to refer to the Ada task.
27194 The identifier of the thread corresponding to the Ada task.
27196 This field should always exist, as Ada tasks are always implemented
27197 on top of a thread. But if @value{GDBN} cannot find this corresponding
27198 thread for any reason, the field is omitted.
27201 This field exists only when the task was created by another task.
27202 In this case, it provides the ID of the parent task.
27205 The base priority of the task.
27208 The current state of the task. For a detailed description of the
27209 possible states, see @ref{Ada Tasks}.
27212 The name of the task.
27216 @subsubheading Example
27220 ^done,tasks=@{nr_rows="3",nr_cols="8",
27221 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27222 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27223 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27224 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27225 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27226 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27227 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27228 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27229 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27230 state="Child Termination Wait",name="main_task"@}]@}
27234 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27235 @node GDB/MI Program Execution
27236 @section @sc{gdb/mi} Program Execution
27238 These are the asynchronous commands which generate the out-of-band
27239 record @samp{*stopped}. Currently @value{GDBN} only really executes
27240 asynchronously with remote targets and this interaction is mimicked in
27243 @subheading The @code{-exec-continue} Command
27244 @findex -exec-continue
27246 @subsubheading Synopsis
27249 -exec-continue [--reverse] [--all|--thread-group N]
27252 Resumes the execution of the inferior program, which will continue
27253 to execute until it reaches a debugger stop event. If the
27254 @samp{--reverse} option is specified, execution resumes in reverse until
27255 it reaches a stop event. Stop events may include
27258 breakpoints or watchpoints
27260 signals or exceptions
27262 the end of the process (or its beginning under @samp{--reverse})
27264 the end or beginning of a replay log if one is being used.
27266 In all-stop mode (@pxref{All-Stop
27267 Mode}), may resume only one thread, or all threads, depending on the
27268 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27269 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27270 ignored in all-stop mode. If the @samp{--thread-group} options is
27271 specified, then all threads in that thread group are resumed.
27273 @subsubheading @value{GDBN} Command
27275 The corresponding @value{GDBN} corresponding is @samp{continue}.
27277 @subsubheading Example
27284 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27285 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27291 @subheading The @code{-exec-finish} Command
27292 @findex -exec-finish
27294 @subsubheading Synopsis
27297 -exec-finish [--reverse]
27300 Resumes the execution of the inferior program until the current
27301 function is exited. Displays the results returned by the function.
27302 If the @samp{--reverse} option is specified, resumes the reverse
27303 execution of the inferior program until the point where current
27304 function was called.
27306 @subsubheading @value{GDBN} Command
27308 The corresponding @value{GDBN} command is @samp{finish}.
27310 @subsubheading Example
27312 Function returning @code{void}.
27319 *stopped,reason="function-finished",frame=@{func="main",args=[],
27320 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27324 Function returning other than @code{void}. The name of the internal
27325 @value{GDBN} variable storing the result is printed, together with the
27332 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27333 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27334 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27335 gdb-result-var="$1",return-value="0"
27340 @subheading The @code{-exec-interrupt} Command
27341 @findex -exec-interrupt
27343 @subsubheading Synopsis
27346 -exec-interrupt [--all|--thread-group N]
27349 Interrupts the background execution of the target. Note how the token
27350 associated with the stop message is the one for the execution command
27351 that has been interrupted. The token for the interrupt itself only
27352 appears in the @samp{^done} output. If the user is trying to
27353 interrupt a non-running program, an error message will be printed.
27355 Note that when asynchronous execution is enabled, this command is
27356 asynchronous just like other execution commands. That is, first the
27357 @samp{^done} response will be printed, and the target stop will be
27358 reported after that using the @samp{*stopped} notification.
27360 In non-stop mode, only the context thread is interrupted by default.
27361 All threads (in all inferiors) will be interrupted if the
27362 @samp{--all} option is specified. If the @samp{--thread-group}
27363 option is specified, all threads in that group will be interrupted.
27365 @subsubheading @value{GDBN} Command
27367 The corresponding @value{GDBN} command is @samp{interrupt}.
27369 @subsubheading Example
27380 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27381 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27382 fullname="/home/foo/bar/try.c",line="13"@}
27387 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27391 @subheading The @code{-exec-jump} Command
27394 @subsubheading Synopsis
27397 -exec-jump @var{location}
27400 Resumes execution of the inferior program at the location specified by
27401 parameter. @xref{Specify Location}, for a description of the
27402 different forms of @var{location}.
27404 @subsubheading @value{GDBN} Command
27406 The corresponding @value{GDBN} command is @samp{jump}.
27408 @subsubheading Example
27411 -exec-jump foo.c:10
27412 *running,thread-id="all"
27417 @subheading The @code{-exec-next} Command
27420 @subsubheading Synopsis
27423 -exec-next [--reverse]
27426 Resumes execution of the inferior program, stopping when the beginning
27427 of the next source line is reached.
27429 If the @samp{--reverse} option is specified, resumes reverse execution
27430 of the inferior program, stopping at the beginning of the previous
27431 source line. If you issue this command on the first line of a
27432 function, it will take you back to the caller of that function, to the
27433 source line where the function was called.
27436 @subsubheading @value{GDBN} Command
27438 The corresponding @value{GDBN} command is @samp{next}.
27440 @subsubheading Example
27446 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27451 @subheading The @code{-exec-next-instruction} Command
27452 @findex -exec-next-instruction
27454 @subsubheading Synopsis
27457 -exec-next-instruction [--reverse]
27460 Executes one machine instruction. If the instruction is a function
27461 call, continues until the function returns. If the program stops at an
27462 instruction in the middle of a source line, the address will be
27465 If the @samp{--reverse} option is specified, resumes reverse execution
27466 of the inferior program, stopping at the previous instruction. If the
27467 previously executed instruction was a return from another function,
27468 it will continue to execute in reverse until the call to that function
27469 (from the current stack frame) is reached.
27471 @subsubheading @value{GDBN} Command
27473 The corresponding @value{GDBN} command is @samp{nexti}.
27475 @subsubheading Example
27479 -exec-next-instruction
27483 *stopped,reason="end-stepping-range",
27484 addr="0x000100d4",line="5",file="hello.c"
27489 @subheading The @code{-exec-return} Command
27490 @findex -exec-return
27492 @subsubheading Synopsis
27498 Makes current function return immediately. Doesn't execute the inferior.
27499 Displays the new current frame.
27501 @subsubheading @value{GDBN} Command
27503 The corresponding @value{GDBN} command is @samp{return}.
27505 @subsubheading Example
27509 200-break-insert callee4
27510 200^done,bkpt=@{number="1",addr="0x00010734",
27511 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27516 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27517 frame=@{func="callee4",args=[],
27518 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27519 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27525 111^done,frame=@{level="0",func="callee3",
27526 args=[@{name="strarg",
27527 value="0x11940 \"A string argument.\""@}],
27528 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27529 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27534 @subheading The @code{-exec-run} Command
27537 @subsubheading Synopsis
27540 -exec-run [--all | --thread-group N]
27543 Starts execution of the inferior from the beginning. The inferior
27544 executes until either a breakpoint is encountered or the program
27545 exits. In the latter case the output will include an exit code, if
27546 the program has exited exceptionally.
27548 When no option is specified, the current inferior is started. If the
27549 @samp{--thread-group} option is specified, it should refer to a thread
27550 group of type @samp{process}, and that thread group will be started.
27551 If the @samp{--all} option is specified, then all inferiors will be started.
27553 @subsubheading @value{GDBN} Command
27555 The corresponding @value{GDBN} command is @samp{run}.
27557 @subsubheading Examples
27562 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27567 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27568 frame=@{func="main",args=[],file="recursive2.c",
27569 fullname="/home/foo/bar/recursive2.c",line="4"@}
27574 Program exited normally:
27582 *stopped,reason="exited-normally"
27587 Program exited exceptionally:
27595 *stopped,reason="exited",exit-code="01"
27599 Another way the program can terminate is if it receives a signal such as
27600 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27604 *stopped,reason="exited-signalled",signal-name="SIGINT",
27605 signal-meaning="Interrupt"
27609 @c @subheading -exec-signal
27612 @subheading The @code{-exec-step} Command
27615 @subsubheading Synopsis
27618 -exec-step [--reverse]
27621 Resumes execution of the inferior program, stopping when the beginning
27622 of the next source line is reached, if the next source line is not a
27623 function call. If it is, stop at the first instruction of the called
27624 function. If the @samp{--reverse} option is specified, resumes reverse
27625 execution of the inferior program, stopping at the beginning of the
27626 previously executed source line.
27628 @subsubheading @value{GDBN} Command
27630 The corresponding @value{GDBN} command is @samp{step}.
27632 @subsubheading Example
27634 Stepping into a function:
27640 *stopped,reason="end-stepping-range",
27641 frame=@{func="foo",args=[@{name="a",value="10"@},
27642 @{name="b",value="0"@}],file="recursive2.c",
27643 fullname="/home/foo/bar/recursive2.c",line="11"@}
27653 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27658 @subheading The @code{-exec-step-instruction} Command
27659 @findex -exec-step-instruction
27661 @subsubheading Synopsis
27664 -exec-step-instruction [--reverse]
27667 Resumes the inferior which executes one machine instruction. If the
27668 @samp{--reverse} option is specified, resumes reverse execution of the
27669 inferior program, stopping at the previously executed instruction.
27670 The output, once @value{GDBN} has stopped, will vary depending on
27671 whether we have stopped in the middle of a source line or not. In the
27672 former case, the address at which the program stopped will be printed
27675 @subsubheading @value{GDBN} Command
27677 The corresponding @value{GDBN} command is @samp{stepi}.
27679 @subsubheading Example
27683 -exec-step-instruction
27687 *stopped,reason="end-stepping-range",
27688 frame=@{func="foo",args=[],file="try.c",
27689 fullname="/home/foo/bar/try.c",line="10"@}
27691 -exec-step-instruction
27695 *stopped,reason="end-stepping-range",
27696 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27697 fullname="/home/foo/bar/try.c",line="10"@}
27702 @subheading The @code{-exec-until} Command
27703 @findex -exec-until
27705 @subsubheading Synopsis
27708 -exec-until [ @var{location} ]
27711 Executes the inferior until the @var{location} specified in the
27712 argument is reached. If there is no argument, the inferior executes
27713 until a source line greater than the current one is reached. The
27714 reason for stopping in this case will be @samp{location-reached}.
27716 @subsubheading @value{GDBN} Command
27718 The corresponding @value{GDBN} command is @samp{until}.
27720 @subsubheading Example
27724 -exec-until recursive2.c:6
27728 *stopped,reason="location-reached",frame=@{func="main",args=[],
27729 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27734 @subheading -file-clear
27735 Is this going away????
27738 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27739 @node GDB/MI Stack Manipulation
27740 @section @sc{gdb/mi} Stack Manipulation Commands
27743 @subheading The @code{-stack-info-frame} Command
27744 @findex -stack-info-frame
27746 @subsubheading Synopsis
27752 Get info on the selected frame.
27754 @subsubheading @value{GDBN} Command
27756 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27757 (without arguments).
27759 @subsubheading Example
27764 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27765 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27766 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27770 @subheading The @code{-stack-info-depth} Command
27771 @findex -stack-info-depth
27773 @subsubheading Synopsis
27776 -stack-info-depth [ @var{max-depth} ]
27779 Return the depth of the stack. If the integer argument @var{max-depth}
27780 is specified, do not count beyond @var{max-depth} frames.
27782 @subsubheading @value{GDBN} Command
27784 There's no equivalent @value{GDBN} command.
27786 @subsubheading Example
27788 For a stack with frame levels 0 through 11:
27795 -stack-info-depth 4
27798 -stack-info-depth 12
27801 -stack-info-depth 11
27804 -stack-info-depth 13
27809 @subheading The @code{-stack-list-arguments} Command
27810 @findex -stack-list-arguments
27812 @subsubheading Synopsis
27815 -stack-list-arguments @var{print-values}
27816 [ @var{low-frame} @var{high-frame} ]
27819 Display a list of the arguments for the frames between @var{low-frame}
27820 and @var{high-frame} (inclusive). If @var{low-frame} and
27821 @var{high-frame} are not provided, list the arguments for the whole
27822 call stack. If the two arguments are equal, show the single frame
27823 at the corresponding level. It is an error if @var{low-frame} is
27824 larger than the actual number of frames. On the other hand,
27825 @var{high-frame} may be larger than the actual number of frames, in
27826 which case only existing frames will be returned.
27828 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27829 the variables; if it is 1 or @code{--all-values}, print also their
27830 values; and if it is 2 or @code{--simple-values}, print the name,
27831 type and value for simple data types, and the name and type for arrays,
27832 structures and unions.
27834 Use of this command to obtain arguments in a single frame is
27835 deprecated in favor of the @samp{-stack-list-variables} command.
27837 @subsubheading @value{GDBN} Command
27839 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27840 @samp{gdb_get_args} command which partially overlaps with the
27841 functionality of @samp{-stack-list-arguments}.
27843 @subsubheading Example
27850 frame=@{level="0",addr="0x00010734",func="callee4",
27851 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27852 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27853 frame=@{level="1",addr="0x0001076c",func="callee3",
27854 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27855 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27856 frame=@{level="2",addr="0x0001078c",func="callee2",
27857 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27858 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27859 frame=@{level="3",addr="0x000107b4",func="callee1",
27860 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27861 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27862 frame=@{level="4",addr="0x000107e0",func="main",
27863 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27864 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27866 -stack-list-arguments 0
27869 frame=@{level="0",args=[]@},
27870 frame=@{level="1",args=[name="strarg"]@},
27871 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27872 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27873 frame=@{level="4",args=[]@}]
27875 -stack-list-arguments 1
27878 frame=@{level="0",args=[]@},
27880 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27881 frame=@{level="2",args=[
27882 @{name="intarg",value="2"@},
27883 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27884 @{frame=@{level="3",args=[
27885 @{name="intarg",value="2"@},
27886 @{name="strarg",value="0x11940 \"A string argument.\""@},
27887 @{name="fltarg",value="3.5"@}]@},
27888 frame=@{level="4",args=[]@}]
27890 -stack-list-arguments 0 2 2
27891 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27893 -stack-list-arguments 1 2 2
27894 ^done,stack-args=[frame=@{level="2",
27895 args=[@{name="intarg",value="2"@},
27896 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27900 @c @subheading -stack-list-exception-handlers
27903 @subheading The @code{-stack-list-frames} Command
27904 @findex -stack-list-frames
27906 @subsubheading Synopsis
27909 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
27912 List the frames currently on the stack. For each frame it displays the
27917 The frame number, 0 being the topmost frame, i.e., the innermost function.
27919 The @code{$pc} value for that frame.
27923 File name of the source file where the function lives.
27924 @item @var{fullname}
27925 The full file name of the source file where the function lives.
27927 Line number corresponding to the @code{$pc}.
27929 The shared library where this function is defined. This is only given
27930 if the frame's function is not known.
27933 If invoked without arguments, this command prints a backtrace for the
27934 whole stack. If given two integer arguments, it shows the frames whose
27935 levels are between the two arguments (inclusive). If the two arguments
27936 are equal, it shows the single frame at the corresponding level. It is
27937 an error if @var{low-frame} is larger than the actual number of
27938 frames. On the other hand, @var{high-frame} may be larger than the
27939 actual number of frames, in which case only existing frames will be returned.
27941 @subsubheading @value{GDBN} Command
27943 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27945 @subsubheading Example
27947 Full stack backtrace:
27953 [frame=@{level="0",addr="0x0001076c",func="foo",
27954 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27955 frame=@{level="1",addr="0x000107a4",func="foo",
27956 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27957 frame=@{level="2",addr="0x000107a4",func="foo",
27958 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27959 frame=@{level="3",addr="0x000107a4",func="foo",
27960 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27961 frame=@{level="4",addr="0x000107a4",func="foo",
27962 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27963 frame=@{level="5",addr="0x000107a4",func="foo",
27964 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27965 frame=@{level="6",addr="0x000107a4",func="foo",
27966 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27967 frame=@{level="7",addr="0x000107a4",func="foo",
27968 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27969 frame=@{level="8",addr="0x000107a4",func="foo",
27970 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27971 frame=@{level="9",addr="0x000107a4",func="foo",
27972 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27973 frame=@{level="10",addr="0x000107a4",func="foo",
27974 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27975 frame=@{level="11",addr="0x00010738",func="main",
27976 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27980 Show frames between @var{low_frame} and @var{high_frame}:
27984 -stack-list-frames 3 5
27986 [frame=@{level="3",addr="0x000107a4",func="foo",
27987 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27988 frame=@{level="4",addr="0x000107a4",func="foo",
27989 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27990 frame=@{level="5",addr="0x000107a4",func="foo",
27991 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27995 Show a single frame:
27999 -stack-list-frames 3 3
28001 [frame=@{level="3",addr="0x000107a4",func="foo",
28002 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28007 @subheading The @code{-stack-list-locals} Command
28008 @findex -stack-list-locals
28010 @subsubheading Synopsis
28013 -stack-list-locals @var{print-values}
28016 Display the local variable names for the selected frame. If
28017 @var{print-values} is 0 or @code{--no-values}, print only the names of
28018 the variables; if it is 1 or @code{--all-values}, print also their
28019 values; and if it is 2 or @code{--simple-values}, print the name,
28020 type and value for simple data types, and the name and type for arrays,
28021 structures and unions. In this last case, a frontend can immediately
28022 display the value of simple data types and create variable objects for
28023 other data types when the user wishes to explore their values in
28026 This command is deprecated in favor of the
28027 @samp{-stack-list-variables} command.
28029 @subsubheading @value{GDBN} Command
28031 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28033 @subsubheading Example
28037 -stack-list-locals 0
28038 ^done,locals=[name="A",name="B",name="C"]
28040 -stack-list-locals --all-values
28041 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28042 @{name="C",value="@{1, 2, 3@}"@}]
28043 -stack-list-locals --simple-values
28044 ^done,locals=[@{name="A",type="int",value="1"@},
28045 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28049 @subheading The @code{-stack-list-variables} Command
28050 @findex -stack-list-variables
28052 @subsubheading Synopsis
28055 -stack-list-variables @var{print-values}
28058 Display the names of local variables and function arguments for the selected frame. If
28059 @var{print-values} is 0 or @code{--no-values}, print only the names of
28060 the variables; if it is 1 or @code{--all-values}, print also their
28061 values; and if it is 2 or @code{--simple-values}, print the name,
28062 type and value for simple data types, and the name and type for arrays,
28063 structures and unions.
28065 @subsubheading Example
28069 -stack-list-variables --thread 1 --frame 0 --all-values
28070 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28075 @subheading The @code{-stack-select-frame} Command
28076 @findex -stack-select-frame
28078 @subsubheading Synopsis
28081 -stack-select-frame @var{framenum}
28084 Change the selected frame. Select a different frame @var{framenum} on
28087 This command in deprecated in favor of passing the @samp{--frame}
28088 option to every command.
28090 @subsubheading @value{GDBN} Command
28092 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28093 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28095 @subsubheading Example
28099 -stack-select-frame 2
28104 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28105 @node GDB/MI Variable Objects
28106 @section @sc{gdb/mi} Variable Objects
28110 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28112 For the implementation of a variable debugger window (locals, watched
28113 expressions, etc.), we are proposing the adaptation of the existing code
28114 used by @code{Insight}.
28116 The two main reasons for that are:
28120 It has been proven in practice (it is already on its second generation).
28123 It will shorten development time (needless to say how important it is
28127 The original interface was designed to be used by Tcl code, so it was
28128 slightly changed so it could be used through @sc{gdb/mi}. This section
28129 describes the @sc{gdb/mi} operations that will be available and gives some
28130 hints about their use.
28132 @emph{Note}: In addition to the set of operations described here, we
28133 expect the @sc{gui} implementation of a variable window to require, at
28134 least, the following operations:
28137 @item @code{-gdb-show} @code{output-radix}
28138 @item @code{-stack-list-arguments}
28139 @item @code{-stack-list-locals}
28140 @item @code{-stack-select-frame}
28145 @subheading Introduction to Variable Objects
28147 @cindex variable objects in @sc{gdb/mi}
28149 Variable objects are "object-oriented" MI interface for examining and
28150 changing values of expressions. Unlike some other MI interfaces that
28151 work with expressions, variable objects are specifically designed for
28152 simple and efficient presentation in the frontend. A variable object
28153 is identified by string name. When a variable object is created, the
28154 frontend specifies the expression for that variable object. The
28155 expression can be a simple variable, or it can be an arbitrary complex
28156 expression, and can even involve CPU registers. After creating a
28157 variable object, the frontend can invoke other variable object
28158 operations---for example to obtain or change the value of a variable
28159 object, or to change display format.
28161 Variable objects have hierarchical tree structure. Any variable object
28162 that corresponds to a composite type, such as structure in C, has
28163 a number of child variable objects, for example corresponding to each
28164 element of a structure. A child variable object can itself have
28165 children, recursively. Recursion ends when we reach
28166 leaf variable objects, which always have built-in types. Child variable
28167 objects are created only by explicit request, so if a frontend
28168 is not interested in the children of a particular variable object, no
28169 child will be created.
28171 For a leaf variable object it is possible to obtain its value as a
28172 string, or set the value from a string. String value can be also
28173 obtained for a non-leaf variable object, but it's generally a string
28174 that only indicates the type of the object, and does not list its
28175 contents. Assignment to a non-leaf variable object is not allowed.
28177 A frontend does not need to read the values of all variable objects each time
28178 the program stops. Instead, MI provides an update command that lists all
28179 variable objects whose values has changed since the last update
28180 operation. This considerably reduces the amount of data that must
28181 be transferred to the frontend. As noted above, children variable
28182 objects are created on demand, and only leaf variable objects have a
28183 real value. As result, gdb will read target memory only for leaf
28184 variables that frontend has created.
28186 The automatic update is not always desirable. For example, a frontend
28187 might want to keep a value of some expression for future reference,
28188 and never update it. For another example, fetching memory is
28189 relatively slow for embedded targets, so a frontend might want
28190 to disable automatic update for the variables that are either not
28191 visible on the screen, or ``closed''. This is possible using so
28192 called ``frozen variable objects''. Such variable objects are never
28193 implicitly updated.
28195 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28196 fixed variable object, the expression is parsed when the variable
28197 object is created, including associating identifiers to specific
28198 variables. The meaning of expression never changes. For a floating
28199 variable object the values of variables whose names appear in the
28200 expressions are re-evaluated every time in the context of the current
28201 frame. Consider this example:
28206 struct work_state state;
28213 If a fixed variable object for the @code{state} variable is created in
28214 this function, and we enter the recursive call, the variable
28215 object will report the value of @code{state} in the top-level
28216 @code{do_work} invocation. On the other hand, a floating variable
28217 object will report the value of @code{state} in the current frame.
28219 If an expression specified when creating a fixed variable object
28220 refers to a local variable, the variable object becomes bound to the
28221 thread and frame in which the variable object is created. When such
28222 variable object is updated, @value{GDBN} makes sure that the
28223 thread/frame combination the variable object is bound to still exists,
28224 and re-evaluates the variable object in context of that thread/frame.
28226 The following is the complete set of @sc{gdb/mi} operations defined to
28227 access this functionality:
28229 @multitable @columnfractions .4 .6
28230 @item @strong{Operation}
28231 @tab @strong{Description}
28233 @item @code{-enable-pretty-printing}
28234 @tab enable Python-based pretty-printing
28235 @item @code{-var-create}
28236 @tab create a variable object
28237 @item @code{-var-delete}
28238 @tab delete the variable object and/or its children
28239 @item @code{-var-set-format}
28240 @tab set the display format of this variable
28241 @item @code{-var-show-format}
28242 @tab show the display format of this variable
28243 @item @code{-var-info-num-children}
28244 @tab tells how many children this object has
28245 @item @code{-var-list-children}
28246 @tab return a list of the object's children
28247 @item @code{-var-info-type}
28248 @tab show the type of this variable object
28249 @item @code{-var-info-expression}
28250 @tab print parent-relative expression that this variable object represents
28251 @item @code{-var-info-path-expression}
28252 @tab print full expression that this variable object represents
28253 @item @code{-var-show-attributes}
28254 @tab is this variable editable? does it exist here?
28255 @item @code{-var-evaluate-expression}
28256 @tab get the value of this variable
28257 @item @code{-var-assign}
28258 @tab set the value of this variable
28259 @item @code{-var-update}
28260 @tab update the variable and its children
28261 @item @code{-var-set-frozen}
28262 @tab set frozeness attribute
28263 @item @code{-var-set-update-range}
28264 @tab set range of children to display on update
28267 In the next subsection we describe each operation in detail and suggest
28268 how it can be used.
28270 @subheading Description And Use of Operations on Variable Objects
28272 @subheading The @code{-enable-pretty-printing} Command
28273 @findex -enable-pretty-printing
28276 -enable-pretty-printing
28279 @value{GDBN} allows Python-based visualizers to affect the output of the
28280 MI variable object commands. However, because there was no way to
28281 implement this in a fully backward-compatible way, a front end must
28282 request that this functionality be enabled.
28284 Once enabled, this feature cannot be disabled.
28286 Note that if Python support has not been compiled into @value{GDBN},
28287 this command will still succeed (and do nothing).
28289 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28290 may work differently in future versions of @value{GDBN}.
28292 @subheading The @code{-var-create} Command
28293 @findex -var-create
28295 @subsubheading Synopsis
28298 -var-create @{@var{name} | "-"@}
28299 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28302 This operation creates a variable object, which allows the monitoring of
28303 a variable, the result of an expression, a memory cell or a CPU
28306 The @var{name} parameter is the string by which the object can be
28307 referenced. It must be unique. If @samp{-} is specified, the varobj
28308 system will generate a string ``varNNNNNN'' automatically. It will be
28309 unique provided that one does not specify @var{name} of that format.
28310 The command fails if a duplicate name is found.
28312 The frame under which the expression should be evaluated can be
28313 specified by @var{frame-addr}. A @samp{*} indicates that the current
28314 frame should be used. A @samp{@@} indicates that a floating variable
28315 object must be created.
28317 @var{expression} is any expression valid on the current language set (must not
28318 begin with a @samp{*}), or one of the following:
28322 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28325 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28328 @samp{$@var{regname}} --- a CPU register name
28331 @cindex dynamic varobj
28332 A varobj's contents may be provided by a Python-based pretty-printer. In this
28333 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28334 have slightly different semantics in some cases. If the
28335 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28336 will never create a dynamic varobj. This ensures backward
28337 compatibility for existing clients.
28339 @subsubheading Result
28341 This operation returns attributes of the newly-created varobj. These
28346 The name of the varobj.
28349 The number of children of the varobj. This number is not necessarily
28350 reliable for a dynamic varobj. Instead, you must examine the
28351 @samp{has_more} attribute.
28354 The varobj's scalar value. For a varobj whose type is some sort of
28355 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28356 will not be interesting.
28359 The varobj's type. This is a string representation of the type, as
28360 would be printed by the @value{GDBN} CLI.
28363 If a variable object is bound to a specific thread, then this is the
28364 thread's identifier.
28367 For a dynamic varobj, this indicates whether there appear to be any
28368 children available. For a non-dynamic varobj, this will be 0.
28371 This attribute will be present and have the value @samp{1} if the
28372 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28373 then this attribute will not be present.
28376 A dynamic varobj can supply a display hint to the front end. The
28377 value comes directly from the Python pretty-printer object's
28378 @code{display_hint} method. @xref{Pretty Printing API}.
28381 Typical output will look like this:
28384 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28385 has_more="@var{has_more}"
28389 @subheading The @code{-var-delete} Command
28390 @findex -var-delete
28392 @subsubheading Synopsis
28395 -var-delete [ -c ] @var{name}
28398 Deletes a previously created variable object and all of its children.
28399 With the @samp{-c} option, just deletes the children.
28401 Returns an error if the object @var{name} is not found.
28404 @subheading The @code{-var-set-format} Command
28405 @findex -var-set-format
28407 @subsubheading Synopsis
28410 -var-set-format @var{name} @var{format-spec}
28413 Sets the output format for the value of the object @var{name} to be
28416 @anchor{-var-set-format}
28417 The syntax for the @var{format-spec} is as follows:
28420 @var{format-spec} @expansion{}
28421 @{binary | decimal | hexadecimal | octal | natural@}
28424 The natural format is the default format choosen automatically
28425 based on the variable type (like decimal for an @code{int}, hex
28426 for pointers, etc.).
28428 For a variable with children, the format is set only on the
28429 variable itself, and the children are not affected.
28431 @subheading The @code{-var-show-format} Command
28432 @findex -var-show-format
28434 @subsubheading Synopsis
28437 -var-show-format @var{name}
28440 Returns the format used to display the value of the object @var{name}.
28443 @var{format} @expansion{}
28448 @subheading The @code{-var-info-num-children} Command
28449 @findex -var-info-num-children
28451 @subsubheading Synopsis
28454 -var-info-num-children @var{name}
28457 Returns the number of children of a variable object @var{name}:
28463 Note that this number is not completely reliable for a dynamic varobj.
28464 It will return the current number of children, but more children may
28468 @subheading The @code{-var-list-children} Command
28469 @findex -var-list-children
28471 @subsubheading Synopsis
28474 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28476 @anchor{-var-list-children}
28478 Return a list of the children of the specified variable object and
28479 create variable objects for them, if they do not already exist. With
28480 a single argument or if @var{print-values} has a value of 0 or
28481 @code{--no-values}, print only the names of the variables; if
28482 @var{print-values} is 1 or @code{--all-values}, also print their
28483 values; and if it is 2 or @code{--simple-values} print the name and
28484 value for simple data types and just the name for arrays, structures
28487 @var{from} and @var{to}, if specified, indicate the range of children
28488 to report. If @var{from} or @var{to} is less than zero, the range is
28489 reset and all children will be reported. Otherwise, children starting
28490 at @var{from} (zero-based) and up to and excluding @var{to} will be
28493 If a child range is requested, it will only affect the current call to
28494 @code{-var-list-children}, but not future calls to @code{-var-update}.
28495 For this, you must instead use @code{-var-set-update-range}. The
28496 intent of this approach is to enable a front end to implement any
28497 update approach it likes; for example, scrolling a view may cause the
28498 front end to request more children with @code{-var-list-children}, and
28499 then the front end could call @code{-var-set-update-range} with a
28500 different range to ensure that future updates are restricted to just
28503 For each child the following results are returned:
28508 Name of the variable object created for this child.
28511 The expression to be shown to the user by the front end to designate this child.
28512 For example this may be the name of a structure member.
28514 For a dynamic varobj, this value cannot be used to form an
28515 expression. There is no way to do this at all with a dynamic varobj.
28517 For C/C@t{++} structures there are several pseudo children returned to
28518 designate access qualifiers. For these pseudo children @var{exp} is
28519 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28520 type and value are not present.
28522 A dynamic varobj will not report the access qualifying
28523 pseudo-children, regardless of the language. This information is not
28524 available at all with a dynamic varobj.
28527 Number of children this child has. For a dynamic varobj, this will be
28531 The type of the child.
28534 If values were requested, this is the value.
28537 If this variable object is associated with a thread, this is the thread id.
28538 Otherwise this result is not present.
28541 If the variable object is frozen, this variable will be present with a value of 1.
28544 The result may have its own attributes:
28548 A dynamic varobj can supply a display hint to the front end. The
28549 value comes directly from the Python pretty-printer object's
28550 @code{display_hint} method. @xref{Pretty Printing API}.
28553 This is an integer attribute which is nonzero if there are children
28554 remaining after the end of the selected range.
28557 @subsubheading Example
28561 -var-list-children n
28562 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28563 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28565 -var-list-children --all-values n
28566 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28567 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28571 @subheading The @code{-var-info-type} Command
28572 @findex -var-info-type
28574 @subsubheading Synopsis
28577 -var-info-type @var{name}
28580 Returns the type of the specified variable @var{name}. The type is
28581 returned as a string in the same format as it is output by the
28585 type=@var{typename}
28589 @subheading The @code{-var-info-expression} Command
28590 @findex -var-info-expression
28592 @subsubheading Synopsis
28595 -var-info-expression @var{name}
28598 Returns a string that is suitable for presenting this
28599 variable object in user interface. The string is generally
28600 not valid expression in the current language, and cannot be evaluated.
28602 For example, if @code{a} is an array, and variable object
28603 @code{A} was created for @code{a}, then we'll get this output:
28606 (gdb) -var-info-expression A.1
28607 ^done,lang="C",exp="1"
28611 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28613 Note that the output of the @code{-var-list-children} command also
28614 includes those expressions, so the @code{-var-info-expression} command
28617 @subheading The @code{-var-info-path-expression} Command
28618 @findex -var-info-path-expression
28620 @subsubheading Synopsis
28623 -var-info-path-expression @var{name}
28626 Returns an expression that can be evaluated in the current
28627 context and will yield the same value that a variable object has.
28628 Compare this with the @code{-var-info-expression} command, which
28629 result can be used only for UI presentation. Typical use of
28630 the @code{-var-info-path-expression} command is creating a
28631 watchpoint from a variable object.
28633 This command is currently not valid for children of a dynamic varobj,
28634 and will give an error when invoked on one.
28636 For example, suppose @code{C} is a C@t{++} class, derived from class
28637 @code{Base}, and that the @code{Base} class has a member called
28638 @code{m_size}. Assume a variable @code{c} is has the type of
28639 @code{C} and a variable object @code{C} was created for variable
28640 @code{c}. Then, we'll get this output:
28642 (gdb) -var-info-path-expression C.Base.public.m_size
28643 ^done,path_expr=((Base)c).m_size)
28646 @subheading The @code{-var-show-attributes} Command
28647 @findex -var-show-attributes
28649 @subsubheading Synopsis
28652 -var-show-attributes @var{name}
28655 List attributes of the specified variable object @var{name}:
28658 status=@var{attr} [ ( ,@var{attr} )* ]
28662 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28664 @subheading The @code{-var-evaluate-expression} Command
28665 @findex -var-evaluate-expression
28667 @subsubheading Synopsis
28670 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28673 Evaluates the expression that is represented by the specified variable
28674 object and returns its value as a string. The format of the string
28675 can be specified with the @samp{-f} option. The possible values of
28676 this option are the same as for @code{-var-set-format}
28677 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28678 the current display format will be used. The current display format
28679 can be changed using the @code{-var-set-format} command.
28685 Note that one must invoke @code{-var-list-children} for a variable
28686 before the value of a child variable can be evaluated.
28688 @subheading The @code{-var-assign} Command
28689 @findex -var-assign
28691 @subsubheading Synopsis
28694 -var-assign @var{name} @var{expression}
28697 Assigns the value of @var{expression} to the variable object specified
28698 by @var{name}. The object must be @samp{editable}. If the variable's
28699 value is altered by the assign, the variable will show up in any
28700 subsequent @code{-var-update} list.
28702 @subsubheading Example
28710 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28714 @subheading The @code{-var-update} Command
28715 @findex -var-update
28717 @subsubheading Synopsis
28720 -var-update [@var{print-values}] @{@var{name} | "*"@}
28723 Reevaluate the expressions corresponding to the variable object
28724 @var{name} and all its direct and indirect children, and return the
28725 list of variable objects whose values have changed; @var{name} must
28726 be a root variable object. Here, ``changed'' means that the result of
28727 @code{-var-evaluate-expression} before and after the
28728 @code{-var-update} is different. If @samp{*} is used as the variable
28729 object names, all existing variable objects are updated, except
28730 for frozen ones (@pxref{-var-set-frozen}). The option
28731 @var{print-values} determines whether both names and values, or just
28732 names are printed. The possible values of this option are the same
28733 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28734 recommended to use the @samp{--all-values} option, to reduce the
28735 number of MI commands needed on each program stop.
28737 With the @samp{*} parameter, if a variable object is bound to a
28738 currently running thread, it will not be updated, without any
28741 If @code{-var-set-update-range} was previously used on a varobj, then
28742 only the selected range of children will be reported.
28744 @code{-var-update} reports all the changed varobjs in a tuple named
28747 Each item in the change list is itself a tuple holding:
28751 The name of the varobj.
28754 If values were requested for this update, then this field will be
28755 present and will hold the value of the varobj.
28758 @anchor{-var-update}
28759 This field is a string which may take one of three values:
28763 The variable object's current value is valid.
28766 The variable object does not currently hold a valid value but it may
28767 hold one in the future if its associated expression comes back into
28771 The variable object no longer holds a valid value.
28772 This can occur when the executable file being debugged has changed,
28773 either through recompilation or by using the @value{GDBN} @code{file}
28774 command. The front end should normally choose to delete these variable
28778 In the future new values may be added to this list so the front should
28779 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28782 This is only present if the varobj is still valid. If the type
28783 changed, then this will be the string @samp{true}; otherwise it will
28787 If the varobj's type changed, then this field will be present and will
28790 @item new_num_children
28791 For a dynamic varobj, if the number of children changed, or if the
28792 type changed, this will be the new number of children.
28794 The @samp{numchild} field in other varobj responses is generally not
28795 valid for a dynamic varobj -- it will show the number of children that
28796 @value{GDBN} knows about, but because dynamic varobjs lazily
28797 instantiate their children, this will not reflect the number of
28798 children which may be available.
28800 The @samp{new_num_children} attribute only reports changes to the
28801 number of children known by @value{GDBN}. This is the only way to
28802 detect whether an update has removed children (which necessarily can
28803 only happen at the end of the update range).
28806 The display hint, if any.
28809 This is an integer value, which will be 1 if there are more children
28810 available outside the varobj's update range.
28813 This attribute will be present and have the value @samp{1} if the
28814 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28815 then this attribute will not be present.
28818 If new children were added to a dynamic varobj within the selected
28819 update range (as set by @code{-var-set-update-range}), then they will
28820 be listed in this attribute.
28823 @subsubheading Example
28830 -var-update --all-values var1
28831 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28832 type_changed="false"@}]
28836 @subheading The @code{-var-set-frozen} Command
28837 @findex -var-set-frozen
28838 @anchor{-var-set-frozen}
28840 @subsubheading Synopsis
28843 -var-set-frozen @var{name} @var{flag}
28846 Set the frozenness flag on the variable object @var{name}. The
28847 @var{flag} parameter should be either @samp{1} to make the variable
28848 frozen or @samp{0} to make it unfrozen. If a variable object is
28849 frozen, then neither itself, nor any of its children, are
28850 implicitly updated by @code{-var-update} of
28851 a parent variable or by @code{-var-update *}. Only
28852 @code{-var-update} of the variable itself will update its value and
28853 values of its children. After a variable object is unfrozen, it is
28854 implicitly updated by all subsequent @code{-var-update} operations.
28855 Unfreezing a variable does not update it, only subsequent
28856 @code{-var-update} does.
28858 @subsubheading Example
28862 -var-set-frozen V 1
28867 @subheading The @code{-var-set-update-range} command
28868 @findex -var-set-update-range
28869 @anchor{-var-set-update-range}
28871 @subsubheading Synopsis
28874 -var-set-update-range @var{name} @var{from} @var{to}
28877 Set the range of children to be returned by future invocations of
28878 @code{-var-update}.
28880 @var{from} and @var{to} indicate the range of children to report. If
28881 @var{from} or @var{to} is less than zero, the range is reset and all
28882 children will be reported. Otherwise, children starting at @var{from}
28883 (zero-based) and up to and excluding @var{to} will be reported.
28885 @subsubheading Example
28889 -var-set-update-range V 1 2
28893 @subheading The @code{-var-set-visualizer} command
28894 @findex -var-set-visualizer
28895 @anchor{-var-set-visualizer}
28897 @subsubheading Synopsis
28900 -var-set-visualizer @var{name} @var{visualizer}
28903 Set a visualizer for the variable object @var{name}.
28905 @var{visualizer} is the visualizer to use. The special value
28906 @samp{None} means to disable any visualizer in use.
28908 If not @samp{None}, @var{visualizer} must be a Python expression.
28909 This expression must evaluate to a callable object which accepts a
28910 single argument. @value{GDBN} will call this object with the value of
28911 the varobj @var{name} as an argument (this is done so that the same
28912 Python pretty-printing code can be used for both the CLI and MI).
28913 When called, this object must return an object which conforms to the
28914 pretty-printing interface (@pxref{Pretty Printing API}).
28916 The pre-defined function @code{gdb.default_visualizer} may be used to
28917 select a visualizer by following the built-in process
28918 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28919 a varobj is created, and so ordinarily is not needed.
28921 This feature is only available if Python support is enabled. The MI
28922 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
28923 can be used to check this.
28925 @subsubheading Example
28927 Resetting the visualizer:
28931 -var-set-visualizer V None
28935 Reselecting the default (type-based) visualizer:
28939 -var-set-visualizer V gdb.default_visualizer
28943 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28944 can be used to instantiate this class for a varobj:
28948 -var-set-visualizer V "lambda val: SomeClass()"
28952 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28953 @node GDB/MI Data Manipulation
28954 @section @sc{gdb/mi} Data Manipulation
28956 @cindex data manipulation, in @sc{gdb/mi}
28957 @cindex @sc{gdb/mi}, data manipulation
28958 This section describes the @sc{gdb/mi} commands that manipulate data:
28959 examine memory and registers, evaluate expressions, etc.
28961 @c REMOVED FROM THE INTERFACE.
28962 @c @subheading -data-assign
28963 @c Change the value of a program variable. Plenty of side effects.
28964 @c @subsubheading GDB Command
28966 @c @subsubheading Example
28969 @subheading The @code{-data-disassemble} Command
28970 @findex -data-disassemble
28972 @subsubheading Synopsis
28976 [ -s @var{start-addr} -e @var{end-addr} ]
28977 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28985 @item @var{start-addr}
28986 is the beginning address (or @code{$pc})
28987 @item @var{end-addr}
28989 @item @var{filename}
28990 is the name of the file to disassemble
28991 @item @var{linenum}
28992 is the line number to disassemble around
28994 is the number of disassembly lines to be produced. If it is -1,
28995 the whole function will be disassembled, in case no @var{end-addr} is
28996 specified. If @var{end-addr} is specified as a non-zero value, and
28997 @var{lines} is lower than the number of disassembly lines between
28998 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28999 displayed; if @var{lines} is higher than the number of lines between
29000 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29003 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29004 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29005 mixed source and disassembly with raw opcodes).
29008 @subsubheading Result
29010 The output for each instruction is composed of four fields:
29019 Note that whatever included in the instruction field, is not manipulated
29020 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29022 @subsubheading @value{GDBN} Command
29024 There's no direct mapping from this command to the CLI.
29026 @subsubheading Example
29028 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29032 -data-disassemble -s $pc -e "$pc + 20" -- 0
29035 @{address="0x000107c0",func-name="main",offset="4",
29036 inst="mov 2, %o0"@},
29037 @{address="0x000107c4",func-name="main",offset="8",
29038 inst="sethi %hi(0x11800), %o2"@},
29039 @{address="0x000107c8",func-name="main",offset="12",
29040 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29041 @{address="0x000107cc",func-name="main",offset="16",
29042 inst="sethi %hi(0x11800), %o2"@},
29043 @{address="0x000107d0",func-name="main",offset="20",
29044 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29048 Disassemble the whole @code{main} function. Line 32 is part of
29052 -data-disassemble -f basics.c -l 32 -- 0
29054 @{address="0x000107bc",func-name="main",offset="0",
29055 inst="save %sp, -112, %sp"@},
29056 @{address="0x000107c0",func-name="main",offset="4",
29057 inst="mov 2, %o0"@},
29058 @{address="0x000107c4",func-name="main",offset="8",
29059 inst="sethi %hi(0x11800), %o2"@},
29061 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29062 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29066 Disassemble 3 instructions from the start of @code{main}:
29070 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29072 @{address="0x000107bc",func-name="main",offset="0",
29073 inst="save %sp, -112, %sp"@},
29074 @{address="0x000107c0",func-name="main",offset="4",
29075 inst="mov 2, %o0"@},
29076 @{address="0x000107c4",func-name="main",offset="8",
29077 inst="sethi %hi(0x11800), %o2"@}]
29081 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29085 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29087 src_and_asm_line=@{line="31",
29088 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29089 testsuite/gdb.mi/basics.c",line_asm_insn=[
29090 @{address="0x000107bc",func-name="main",offset="0",
29091 inst="save %sp, -112, %sp"@}]@},
29092 src_and_asm_line=@{line="32",
29093 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29094 testsuite/gdb.mi/basics.c",line_asm_insn=[
29095 @{address="0x000107c0",func-name="main",offset="4",
29096 inst="mov 2, %o0"@},
29097 @{address="0x000107c4",func-name="main",offset="8",
29098 inst="sethi %hi(0x11800), %o2"@}]@}]
29103 @subheading The @code{-data-evaluate-expression} Command
29104 @findex -data-evaluate-expression
29106 @subsubheading Synopsis
29109 -data-evaluate-expression @var{expr}
29112 Evaluate @var{expr} as an expression. The expression could contain an
29113 inferior function call. The function call will execute synchronously.
29114 If the expression contains spaces, it must be enclosed in double quotes.
29116 @subsubheading @value{GDBN} Command
29118 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29119 @samp{call}. In @code{gdbtk} only, there's a corresponding
29120 @samp{gdb_eval} command.
29122 @subsubheading Example
29124 In the following example, the numbers that precede the commands are the
29125 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29126 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29130 211-data-evaluate-expression A
29133 311-data-evaluate-expression &A
29134 311^done,value="0xefffeb7c"
29136 411-data-evaluate-expression A+3
29139 511-data-evaluate-expression "A + 3"
29145 @subheading The @code{-data-list-changed-registers} Command
29146 @findex -data-list-changed-registers
29148 @subsubheading Synopsis
29151 -data-list-changed-registers
29154 Display a list of the registers that have changed.
29156 @subsubheading @value{GDBN} Command
29158 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29159 has the corresponding command @samp{gdb_changed_register_list}.
29161 @subsubheading Example
29163 On a PPC MBX board:
29171 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29172 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29175 -data-list-changed-registers
29176 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29177 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29178 "24","25","26","27","28","30","31","64","65","66","67","69"]
29183 @subheading The @code{-data-list-register-names} Command
29184 @findex -data-list-register-names
29186 @subsubheading Synopsis
29189 -data-list-register-names [ ( @var{regno} )+ ]
29192 Show a list of register names for the current target. If no arguments
29193 are given, it shows a list of the names of all the registers. If
29194 integer numbers are given as arguments, it will print a list of the
29195 names of the registers corresponding to the arguments. To ensure
29196 consistency between a register name and its number, the output list may
29197 include empty register names.
29199 @subsubheading @value{GDBN} Command
29201 @value{GDBN} does not have a command which corresponds to
29202 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29203 corresponding command @samp{gdb_regnames}.
29205 @subsubheading Example
29207 For the PPC MBX board:
29210 -data-list-register-names
29211 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29212 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29213 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29214 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29215 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29216 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29217 "", "pc","ps","cr","lr","ctr","xer"]
29219 -data-list-register-names 1 2 3
29220 ^done,register-names=["r1","r2","r3"]
29224 @subheading The @code{-data-list-register-values} Command
29225 @findex -data-list-register-values
29227 @subsubheading Synopsis
29230 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29233 Display the registers' contents. @var{fmt} is the format according to
29234 which the registers' contents are to be returned, followed by an optional
29235 list of numbers specifying the registers to display. A missing list of
29236 numbers indicates that the contents of all the registers must be returned.
29238 Allowed formats for @var{fmt} are:
29255 @subsubheading @value{GDBN} Command
29257 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29258 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29260 @subsubheading Example
29262 For a PPC MBX board (note: line breaks are for readability only, they
29263 don't appear in the actual output):
29267 -data-list-register-values r 64 65
29268 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29269 @{number="65",value="0x00029002"@}]
29271 -data-list-register-values x
29272 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29273 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29274 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29275 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29276 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29277 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29278 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29279 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29280 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29281 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29282 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29283 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29284 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29285 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29286 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29287 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29288 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29289 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29290 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29291 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29292 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29293 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29294 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29295 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29296 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29297 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29298 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29299 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29300 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29301 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29302 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29303 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29304 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29305 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29306 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29307 @{number="69",value="0x20002b03"@}]
29312 @subheading The @code{-data-read-memory} Command
29313 @findex -data-read-memory
29315 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29317 @subsubheading Synopsis
29320 -data-read-memory [ -o @var{byte-offset} ]
29321 @var{address} @var{word-format} @var{word-size}
29322 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29329 @item @var{address}
29330 An expression specifying the address of the first memory word to be
29331 read. Complex expressions containing embedded white space should be
29332 quoted using the C convention.
29334 @item @var{word-format}
29335 The format to be used to print the memory words. The notation is the
29336 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29339 @item @var{word-size}
29340 The size of each memory word in bytes.
29342 @item @var{nr-rows}
29343 The number of rows in the output table.
29345 @item @var{nr-cols}
29346 The number of columns in the output table.
29349 If present, indicates that each row should include an @sc{ascii} dump. The
29350 value of @var{aschar} is used as a padding character when a byte is not a
29351 member of the printable @sc{ascii} character set (printable @sc{ascii}
29352 characters are those whose code is between 32 and 126, inclusively).
29354 @item @var{byte-offset}
29355 An offset to add to the @var{address} before fetching memory.
29358 This command displays memory contents as a table of @var{nr-rows} by
29359 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29360 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29361 (returned as @samp{total-bytes}). Should less than the requested number
29362 of bytes be returned by the target, the missing words are identified
29363 using @samp{N/A}. The number of bytes read from the target is returned
29364 in @samp{nr-bytes} and the starting address used to read memory in
29367 The address of the next/previous row or page is available in
29368 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29371 @subsubheading @value{GDBN} Command
29373 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29374 @samp{gdb_get_mem} memory read command.
29376 @subsubheading Example
29378 Read six bytes of memory starting at @code{bytes+6} but then offset by
29379 @code{-6} bytes. Format as three rows of two columns. One byte per
29380 word. Display each word in hex.
29384 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29385 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29386 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29387 prev-page="0x0000138a",memory=[
29388 @{addr="0x00001390",data=["0x00","0x01"]@},
29389 @{addr="0x00001392",data=["0x02","0x03"]@},
29390 @{addr="0x00001394",data=["0x04","0x05"]@}]
29394 Read two bytes of memory starting at address @code{shorts + 64} and
29395 display as a single word formatted in decimal.
29399 5-data-read-memory shorts+64 d 2 1 1
29400 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29401 next-row="0x00001512",prev-row="0x0000150e",
29402 next-page="0x00001512",prev-page="0x0000150e",memory=[
29403 @{addr="0x00001510",data=["128"]@}]
29407 Read thirty two bytes of memory starting at @code{bytes+16} and format
29408 as eight rows of four columns. Include a string encoding with @samp{x}
29409 used as the non-printable character.
29413 4-data-read-memory bytes+16 x 1 8 4 x
29414 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29415 next-row="0x000013c0",prev-row="0x0000139c",
29416 next-page="0x000013c0",prev-page="0x00001380",memory=[
29417 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29418 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29419 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29420 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29421 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29422 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29423 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29424 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29428 @subheading The @code{-data-read-memory-bytes} Command
29429 @findex -data-read-memory-bytes
29431 @subsubheading Synopsis
29434 -data-read-memory-bytes [ -o @var{byte-offset} ]
29435 @var{address} @var{count}
29442 @item @var{address}
29443 An expression specifying the address of the first memory word to be
29444 read. Complex expressions containing embedded white space should be
29445 quoted using the C convention.
29448 The number of bytes to read. This should be an integer literal.
29450 @item @var{byte-offset}
29451 The offsets in bytes relative to @var{address} at which to start
29452 reading. This should be an integer literal. This option is provided
29453 so that a frontend is not required to first evaluate address and then
29454 perform address arithmetics itself.
29458 This command attempts to read all accessible memory regions in the
29459 specified range. First, all regions marked as unreadable in the memory
29460 map (if one is defined) will be skipped. @xref{Memory Region
29461 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29462 regions. For each one, if reading full region results in an errors,
29463 @value{GDBN} will try to read a subset of the region.
29465 In general, every single byte in the region may be readable or not,
29466 and the only way to read every readable byte is to try a read at
29467 every address, which is not practical. Therefore, @value{GDBN} will
29468 attempt to read all accessible bytes at either beginning or the end
29469 of the region, using a binary division scheme. This heuristic works
29470 well for reading accross a memory map boundary. Note that if a region
29471 has a readable range that is neither at the beginning or the end,
29472 @value{GDBN} will not read it.
29474 The result record (@pxref{GDB/MI Result Records}) that is output of
29475 the command includes a field named @samp{memory} whose content is a
29476 list of tuples. Each tuple represent a successfully read memory block
29477 and has the following fields:
29481 The start address of the memory block, as hexadecimal literal.
29484 The end address of the memory block, as hexadecimal literal.
29487 The offset of the memory block, as hexadecimal literal, relative to
29488 the start address passed to @code{-data-read-memory-bytes}.
29491 The contents of the memory block, in hex.
29497 @subsubheading @value{GDBN} Command
29499 The corresponding @value{GDBN} command is @samp{x}.
29501 @subsubheading Example
29505 -data-read-memory-bytes &a 10
29506 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29508 contents="01000000020000000300"@}]
29513 @subheading The @code{-data-write-memory-bytes} Command
29514 @findex -data-write-memory-bytes
29516 @subsubheading Synopsis
29519 -data-write-memory-bytes @var{address} @var{contents}
29526 @item @var{address}
29527 An expression specifying the address of the first memory word to be
29528 read. Complex expressions containing embedded white space should be
29529 quoted using the C convention.
29531 @item @var{contents}
29532 The hex-encoded bytes to write.
29536 @subsubheading @value{GDBN} Command
29538 There's no corresponding @value{GDBN} command.
29540 @subsubheading Example
29544 -data-write-memory-bytes &a "aabbccdd"
29550 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29551 @node GDB/MI Tracepoint Commands
29552 @section @sc{gdb/mi} Tracepoint Commands
29554 The commands defined in this section implement MI support for
29555 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29557 @subheading The @code{-trace-find} Command
29558 @findex -trace-find
29560 @subsubheading Synopsis
29563 -trace-find @var{mode} [@var{parameters}@dots{}]
29566 Find a trace frame using criteria defined by @var{mode} and
29567 @var{parameters}. The following table lists permissible
29568 modes and their parameters. For details of operation, see @ref{tfind}.
29573 No parameters are required. Stops examining trace frames.
29576 An integer is required as parameter. Selects tracepoint frame with
29579 @item tracepoint-number
29580 An integer is required as parameter. Finds next
29581 trace frame that corresponds to tracepoint with the specified number.
29584 An address is required as parameter. Finds
29585 next trace frame that corresponds to any tracepoint at the specified
29588 @item pc-inside-range
29589 Two addresses are required as parameters. Finds next trace
29590 frame that corresponds to a tracepoint at an address inside the
29591 specified range. Both bounds are considered to be inside the range.
29593 @item pc-outside-range
29594 Two addresses are required as parameters. Finds
29595 next trace frame that corresponds to a tracepoint at an address outside
29596 the specified range. Both bounds are considered to be inside the range.
29599 Line specification is required as parameter. @xref{Specify Location}.
29600 Finds next trace frame that corresponds to a tracepoint at
29601 the specified location.
29605 If @samp{none} was passed as @var{mode}, the response does not
29606 have fields. Otherwise, the response may have the following fields:
29610 This field has either @samp{0} or @samp{1} as the value, depending
29611 on whether a matching tracepoint was found.
29614 The index of the found traceframe. This field is present iff
29615 the @samp{found} field has value of @samp{1}.
29618 The index of the found tracepoint. This field is present iff
29619 the @samp{found} field has value of @samp{1}.
29622 The information about the frame corresponding to the found trace
29623 frame. This field is present only if a trace frame was found.
29624 @xref{GDB/MI Frame Information}, for description of this field.
29628 @subsubheading @value{GDBN} Command
29630 The corresponding @value{GDBN} command is @samp{tfind}.
29632 @subheading -trace-define-variable
29633 @findex -trace-define-variable
29635 @subsubheading Synopsis
29638 -trace-define-variable @var{name} [ @var{value} ]
29641 Create trace variable @var{name} if it does not exist. If
29642 @var{value} is specified, sets the initial value of the specified
29643 trace variable to that value. Note that the @var{name} should start
29644 with the @samp{$} character.
29646 @subsubheading @value{GDBN} Command
29648 The corresponding @value{GDBN} command is @samp{tvariable}.
29650 @subheading -trace-list-variables
29651 @findex -trace-list-variables
29653 @subsubheading Synopsis
29656 -trace-list-variables
29659 Return a table of all defined trace variables. Each element of the
29660 table has the following fields:
29664 The name of the trace variable. This field is always present.
29667 The initial value. This is a 64-bit signed integer. This
29668 field is always present.
29671 The value the trace variable has at the moment. This is a 64-bit
29672 signed integer. This field is absent iff current value is
29673 not defined, for example if the trace was never run, or is
29678 @subsubheading @value{GDBN} Command
29680 The corresponding @value{GDBN} command is @samp{tvariables}.
29682 @subsubheading Example
29686 -trace-list-variables
29687 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29688 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29689 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29690 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29691 body=[variable=@{name="$trace_timestamp",initial="0"@}
29692 variable=@{name="$foo",initial="10",current="15"@}]@}
29696 @subheading -trace-save
29697 @findex -trace-save
29699 @subsubheading Synopsis
29702 -trace-save [-r ] @var{filename}
29705 Saves the collected trace data to @var{filename}. Without the
29706 @samp{-r} option, the data is downloaded from the target and saved
29707 in a local file. With the @samp{-r} option the target is asked
29708 to perform the save.
29710 @subsubheading @value{GDBN} Command
29712 The corresponding @value{GDBN} command is @samp{tsave}.
29715 @subheading -trace-start
29716 @findex -trace-start
29718 @subsubheading Synopsis
29724 Starts a tracing experiments. The result of this command does not
29727 @subsubheading @value{GDBN} Command
29729 The corresponding @value{GDBN} command is @samp{tstart}.
29731 @subheading -trace-status
29732 @findex -trace-status
29734 @subsubheading Synopsis
29740 Obtains the status of a tracing experiment. The result may include
29741 the following fields:
29746 May have a value of either @samp{0}, when no tracing operations are
29747 supported, @samp{1}, when all tracing operations are supported, or
29748 @samp{file} when examining trace file. In the latter case, examining
29749 of trace frame is possible but new tracing experiement cannot be
29750 started. This field is always present.
29753 May have a value of either @samp{0} or @samp{1} depending on whether
29754 tracing experiement is in progress on target. This field is present
29755 if @samp{supported} field is not @samp{0}.
29758 Report the reason why the tracing was stopped last time. This field
29759 may be absent iff tracing was never stopped on target yet. The
29760 value of @samp{request} means the tracing was stopped as result of
29761 the @code{-trace-stop} command. The value of @samp{overflow} means
29762 the tracing buffer is full. The value of @samp{disconnection} means
29763 tracing was automatically stopped when @value{GDBN} has disconnected.
29764 The value of @samp{passcount} means tracing was stopped when a
29765 tracepoint was passed a maximal number of times for that tracepoint.
29766 This field is present if @samp{supported} field is not @samp{0}.
29768 @item stopping-tracepoint
29769 The number of tracepoint whose passcount as exceeded. This field is
29770 present iff the @samp{stop-reason} field has the value of
29774 @itemx frames-created
29775 The @samp{frames} field is a count of the total number of trace frames
29776 in the trace buffer, while @samp{frames-created} is the total created
29777 during the run, including ones that were discarded, such as when a
29778 circular trace buffer filled up. Both fields are optional.
29782 These fields tell the current size of the tracing buffer and the
29783 remaining space. These fields are optional.
29786 The value of the circular trace buffer flag. @code{1} means that the
29787 trace buffer is circular and old trace frames will be discarded if
29788 necessary to make room, @code{0} means that the trace buffer is linear
29792 The value of the disconnected tracing flag. @code{1} means that
29793 tracing will continue after @value{GDBN} disconnects, @code{0} means
29794 that the trace run will stop.
29798 @subsubheading @value{GDBN} Command
29800 The corresponding @value{GDBN} command is @samp{tstatus}.
29802 @subheading -trace-stop
29803 @findex -trace-stop
29805 @subsubheading Synopsis
29811 Stops a tracing experiment. The result of this command has the same
29812 fields as @code{-trace-status}, except that the @samp{supported} and
29813 @samp{running} fields are not output.
29815 @subsubheading @value{GDBN} Command
29817 The corresponding @value{GDBN} command is @samp{tstop}.
29820 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29821 @node GDB/MI Symbol Query
29822 @section @sc{gdb/mi} Symbol Query Commands
29826 @subheading The @code{-symbol-info-address} Command
29827 @findex -symbol-info-address
29829 @subsubheading Synopsis
29832 -symbol-info-address @var{symbol}
29835 Describe where @var{symbol} is stored.
29837 @subsubheading @value{GDBN} Command
29839 The corresponding @value{GDBN} command is @samp{info address}.
29841 @subsubheading Example
29845 @subheading The @code{-symbol-info-file} Command
29846 @findex -symbol-info-file
29848 @subsubheading Synopsis
29854 Show the file for the symbol.
29856 @subsubheading @value{GDBN} Command
29858 There's no equivalent @value{GDBN} command. @code{gdbtk} has
29859 @samp{gdb_find_file}.
29861 @subsubheading Example
29865 @subheading The @code{-symbol-info-function} Command
29866 @findex -symbol-info-function
29868 @subsubheading Synopsis
29871 -symbol-info-function
29874 Show which function the symbol lives in.
29876 @subsubheading @value{GDBN} Command
29878 @samp{gdb_get_function} in @code{gdbtk}.
29880 @subsubheading Example
29884 @subheading The @code{-symbol-info-line} Command
29885 @findex -symbol-info-line
29887 @subsubheading Synopsis
29893 Show the core addresses of the code for a source line.
29895 @subsubheading @value{GDBN} Command
29897 The corresponding @value{GDBN} command is @samp{info line}.
29898 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
29900 @subsubheading Example
29904 @subheading The @code{-symbol-info-symbol} Command
29905 @findex -symbol-info-symbol
29907 @subsubheading Synopsis
29910 -symbol-info-symbol @var{addr}
29913 Describe what symbol is at location @var{addr}.
29915 @subsubheading @value{GDBN} Command
29917 The corresponding @value{GDBN} command is @samp{info symbol}.
29919 @subsubheading Example
29923 @subheading The @code{-symbol-list-functions} Command
29924 @findex -symbol-list-functions
29926 @subsubheading Synopsis
29929 -symbol-list-functions
29932 List the functions in the executable.
29934 @subsubheading @value{GDBN} Command
29936 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
29937 @samp{gdb_search} in @code{gdbtk}.
29939 @subsubheading Example
29944 @subheading The @code{-symbol-list-lines} Command
29945 @findex -symbol-list-lines
29947 @subsubheading Synopsis
29950 -symbol-list-lines @var{filename}
29953 Print the list of lines that contain code and their associated program
29954 addresses for the given source filename. The entries are sorted in
29955 ascending PC order.
29957 @subsubheading @value{GDBN} Command
29959 There is no corresponding @value{GDBN} command.
29961 @subsubheading Example
29964 -symbol-list-lines basics.c
29965 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
29971 @subheading The @code{-symbol-list-types} Command
29972 @findex -symbol-list-types
29974 @subsubheading Synopsis
29980 List all the type names.
29982 @subsubheading @value{GDBN} Command
29984 The corresponding commands are @samp{info types} in @value{GDBN},
29985 @samp{gdb_search} in @code{gdbtk}.
29987 @subsubheading Example
29991 @subheading The @code{-symbol-list-variables} Command
29992 @findex -symbol-list-variables
29994 @subsubheading Synopsis
29997 -symbol-list-variables
30000 List all the global and static variable names.
30002 @subsubheading @value{GDBN} Command
30004 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30006 @subsubheading Example
30010 @subheading The @code{-symbol-locate} Command
30011 @findex -symbol-locate
30013 @subsubheading Synopsis
30019 @subsubheading @value{GDBN} Command
30021 @samp{gdb_loc} in @code{gdbtk}.
30023 @subsubheading Example
30027 @subheading The @code{-symbol-type} Command
30028 @findex -symbol-type
30030 @subsubheading Synopsis
30033 -symbol-type @var{variable}
30036 Show type of @var{variable}.
30038 @subsubheading @value{GDBN} Command
30040 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30041 @samp{gdb_obj_variable}.
30043 @subsubheading Example
30048 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30049 @node GDB/MI File Commands
30050 @section @sc{gdb/mi} File Commands
30052 This section describes the GDB/MI commands to specify executable file names
30053 and to read in and obtain symbol table information.
30055 @subheading The @code{-file-exec-and-symbols} Command
30056 @findex -file-exec-and-symbols
30058 @subsubheading Synopsis
30061 -file-exec-and-symbols @var{file}
30064 Specify the executable file to be debugged. This file is the one from
30065 which the symbol table is also read. If no file is specified, the
30066 command clears the executable and symbol information. If breakpoints
30067 are set when using this command with no arguments, @value{GDBN} will produce
30068 error messages. Otherwise, no output is produced, except a completion
30071 @subsubheading @value{GDBN} Command
30073 The corresponding @value{GDBN} command is @samp{file}.
30075 @subsubheading Example
30079 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30085 @subheading The @code{-file-exec-file} Command
30086 @findex -file-exec-file
30088 @subsubheading Synopsis
30091 -file-exec-file @var{file}
30094 Specify the executable file to be debugged. Unlike
30095 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30096 from this file. If used without argument, @value{GDBN} clears the information
30097 about the executable file. No output is produced, except a completion
30100 @subsubheading @value{GDBN} Command
30102 The corresponding @value{GDBN} command is @samp{exec-file}.
30104 @subsubheading Example
30108 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30115 @subheading The @code{-file-list-exec-sections} Command
30116 @findex -file-list-exec-sections
30118 @subsubheading Synopsis
30121 -file-list-exec-sections
30124 List the sections of the current executable file.
30126 @subsubheading @value{GDBN} Command
30128 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30129 information as this command. @code{gdbtk} has a corresponding command
30130 @samp{gdb_load_info}.
30132 @subsubheading Example
30137 @subheading The @code{-file-list-exec-source-file} Command
30138 @findex -file-list-exec-source-file
30140 @subsubheading Synopsis
30143 -file-list-exec-source-file
30146 List the line number, the current source file, and the absolute path
30147 to the current source file for the current executable. The macro
30148 information field has a value of @samp{1} or @samp{0} depending on
30149 whether or not the file includes preprocessor macro information.
30151 @subsubheading @value{GDBN} Command
30153 The @value{GDBN} equivalent is @samp{info source}
30155 @subsubheading Example
30159 123-file-list-exec-source-file
30160 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30165 @subheading The @code{-file-list-exec-source-files} Command
30166 @findex -file-list-exec-source-files
30168 @subsubheading Synopsis
30171 -file-list-exec-source-files
30174 List the source files for the current executable.
30176 It will always output the filename, but only when @value{GDBN} can find
30177 the absolute file name of a source file, will it output the fullname.
30179 @subsubheading @value{GDBN} Command
30181 The @value{GDBN} equivalent is @samp{info sources}.
30182 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30184 @subsubheading Example
30187 -file-list-exec-source-files
30189 @{file=foo.c,fullname=/home/foo.c@},
30190 @{file=/home/bar.c,fullname=/home/bar.c@},
30191 @{file=gdb_could_not_find_fullpath.c@}]
30196 @subheading The @code{-file-list-shared-libraries} Command
30197 @findex -file-list-shared-libraries
30199 @subsubheading Synopsis
30202 -file-list-shared-libraries
30205 List the shared libraries in the program.
30207 @subsubheading @value{GDBN} Command
30209 The corresponding @value{GDBN} command is @samp{info shared}.
30211 @subsubheading Example
30215 @subheading The @code{-file-list-symbol-files} Command
30216 @findex -file-list-symbol-files
30218 @subsubheading Synopsis
30221 -file-list-symbol-files
30226 @subsubheading @value{GDBN} Command
30228 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30230 @subsubheading Example
30235 @subheading The @code{-file-symbol-file} Command
30236 @findex -file-symbol-file
30238 @subsubheading Synopsis
30241 -file-symbol-file @var{file}
30244 Read symbol table info from the specified @var{file} argument. When
30245 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30246 produced, except for a completion notification.
30248 @subsubheading @value{GDBN} Command
30250 The corresponding @value{GDBN} command is @samp{symbol-file}.
30252 @subsubheading Example
30256 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30263 @node GDB/MI Memory Overlay Commands
30264 @section @sc{gdb/mi} Memory Overlay Commands
30266 The memory overlay commands are not implemented.
30268 @c @subheading -overlay-auto
30270 @c @subheading -overlay-list-mapping-state
30272 @c @subheading -overlay-list-overlays
30274 @c @subheading -overlay-map
30276 @c @subheading -overlay-off
30278 @c @subheading -overlay-on
30280 @c @subheading -overlay-unmap
30282 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30283 @node GDB/MI Signal Handling Commands
30284 @section @sc{gdb/mi} Signal Handling Commands
30286 Signal handling commands are not implemented.
30288 @c @subheading -signal-handle
30290 @c @subheading -signal-list-handle-actions
30292 @c @subheading -signal-list-signal-types
30296 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30297 @node GDB/MI Target Manipulation
30298 @section @sc{gdb/mi} Target Manipulation Commands
30301 @subheading The @code{-target-attach} Command
30302 @findex -target-attach
30304 @subsubheading Synopsis
30307 -target-attach @var{pid} | @var{gid} | @var{file}
30310 Attach to a process @var{pid} or a file @var{file} outside of
30311 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30312 group, the id previously returned by
30313 @samp{-list-thread-groups --available} must be used.
30315 @subsubheading @value{GDBN} Command
30317 The corresponding @value{GDBN} command is @samp{attach}.
30319 @subsubheading Example
30323 =thread-created,id="1"
30324 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30330 @subheading The @code{-target-compare-sections} Command
30331 @findex -target-compare-sections
30333 @subsubheading Synopsis
30336 -target-compare-sections [ @var{section} ]
30339 Compare data of section @var{section} on target to the exec file.
30340 Without the argument, all sections are compared.
30342 @subsubheading @value{GDBN} Command
30344 The @value{GDBN} equivalent is @samp{compare-sections}.
30346 @subsubheading Example
30351 @subheading The @code{-target-detach} Command
30352 @findex -target-detach
30354 @subsubheading Synopsis
30357 -target-detach [ @var{pid} | @var{gid} ]
30360 Detach from the remote target which normally resumes its execution.
30361 If either @var{pid} or @var{gid} is specified, detaches from either
30362 the specified process, or specified thread group. There's no output.
30364 @subsubheading @value{GDBN} Command
30366 The corresponding @value{GDBN} command is @samp{detach}.
30368 @subsubheading Example
30378 @subheading The @code{-target-disconnect} Command
30379 @findex -target-disconnect
30381 @subsubheading Synopsis
30387 Disconnect from the remote target. There's no output and the target is
30388 generally not resumed.
30390 @subsubheading @value{GDBN} Command
30392 The corresponding @value{GDBN} command is @samp{disconnect}.
30394 @subsubheading Example
30404 @subheading The @code{-target-download} Command
30405 @findex -target-download
30407 @subsubheading Synopsis
30413 Loads the executable onto the remote target.
30414 It prints out an update message every half second, which includes the fields:
30418 The name of the section.
30420 The size of what has been sent so far for that section.
30422 The size of the section.
30424 The total size of what was sent so far (the current and the previous sections).
30426 The size of the overall executable to download.
30430 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30431 @sc{gdb/mi} Output Syntax}).
30433 In addition, it prints the name and size of the sections, as they are
30434 downloaded. These messages include the following fields:
30438 The name of the section.
30440 The size of the section.
30442 The size of the overall executable to download.
30446 At the end, a summary is printed.
30448 @subsubheading @value{GDBN} Command
30450 The corresponding @value{GDBN} command is @samp{load}.
30452 @subsubheading Example
30454 Note: each status message appears on a single line. Here the messages
30455 have been broken down so that they can fit onto a page.
30460 +download,@{section=".text",section-size="6668",total-size="9880"@}
30461 +download,@{section=".text",section-sent="512",section-size="6668",
30462 total-sent="512",total-size="9880"@}
30463 +download,@{section=".text",section-sent="1024",section-size="6668",
30464 total-sent="1024",total-size="9880"@}
30465 +download,@{section=".text",section-sent="1536",section-size="6668",
30466 total-sent="1536",total-size="9880"@}
30467 +download,@{section=".text",section-sent="2048",section-size="6668",
30468 total-sent="2048",total-size="9880"@}
30469 +download,@{section=".text",section-sent="2560",section-size="6668",
30470 total-sent="2560",total-size="9880"@}
30471 +download,@{section=".text",section-sent="3072",section-size="6668",
30472 total-sent="3072",total-size="9880"@}
30473 +download,@{section=".text",section-sent="3584",section-size="6668",
30474 total-sent="3584",total-size="9880"@}
30475 +download,@{section=".text",section-sent="4096",section-size="6668",
30476 total-sent="4096",total-size="9880"@}
30477 +download,@{section=".text",section-sent="4608",section-size="6668",
30478 total-sent="4608",total-size="9880"@}
30479 +download,@{section=".text",section-sent="5120",section-size="6668",
30480 total-sent="5120",total-size="9880"@}
30481 +download,@{section=".text",section-sent="5632",section-size="6668",
30482 total-sent="5632",total-size="9880"@}
30483 +download,@{section=".text",section-sent="6144",section-size="6668",
30484 total-sent="6144",total-size="9880"@}
30485 +download,@{section=".text",section-sent="6656",section-size="6668",
30486 total-sent="6656",total-size="9880"@}
30487 +download,@{section=".init",section-size="28",total-size="9880"@}
30488 +download,@{section=".fini",section-size="28",total-size="9880"@}
30489 +download,@{section=".data",section-size="3156",total-size="9880"@}
30490 +download,@{section=".data",section-sent="512",section-size="3156",
30491 total-sent="7236",total-size="9880"@}
30492 +download,@{section=".data",section-sent="1024",section-size="3156",
30493 total-sent="7748",total-size="9880"@}
30494 +download,@{section=".data",section-sent="1536",section-size="3156",
30495 total-sent="8260",total-size="9880"@}
30496 +download,@{section=".data",section-sent="2048",section-size="3156",
30497 total-sent="8772",total-size="9880"@}
30498 +download,@{section=".data",section-sent="2560",section-size="3156",
30499 total-sent="9284",total-size="9880"@}
30500 +download,@{section=".data",section-sent="3072",section-size="3156",
30501 total-sent="9796",total-size="9880"@}
30502 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30509 @subheading The @code{-target-exec-status} Command
30510 @findex -target-exec-status
30512 @subsubheading Synopsis
30515 -target-exec-status
30518 Provide information on the state of the target (whether it is running or
30519 not, for instance).
30521 @subsubheading @value{GDBN} Command
30523 There's no equivalent @value{GDBN} command.
30525 @subsubheading Example
30529 @subheading The @code{-target-list-available-targets} Command
30530 @findex -target-list-available-targets
30532 @subsubheading Synopsis
30535 -target-list-available-targets
30538 List the possible targets to connect to.
30540 @subsubheading @value{GDBN} Command
30542 The corresponding @value{GDBN} command is @samp{help target}.
30544 @subsubheading Example
30548 @subheading The @code{-target-list-current-targets} Command
30549 @findex -target-list-current-targets
30551 @subsubheading Synopsis
30554 -target-list-current-targets
30557 Describe the current target.
30559 @subsubheading @value{GDBN} Command
30561 The corresponding information is printed by @samp{info file} (among
30564 @subsubheading Example
30568 @subheading The @code{-target-list-parameters} Command
30569 @findex -target-list-parameters
30571 @subsubheading Synopsis
30574 -target-list-parameters
30580 @subsubheading @value{GDBN} Command
30584 @subsubheading Example
30588 @subheading The @code{-target-select} Command
30589 @findex -target-select
30591 @subsubheading Synopsis
30594 -target-select @var{type} @var{parameters @dots{}}
30597 Connect @value{GDBN} to the remote target. This command takes two args:
30601 The type of target, for instance @samp{remote}, etc.
30602 @item @var{parameters}
30603 Device names, host names and the like. @xref{Target Commands, ,
30604 Commands for Managing Targets}, for more details.
30607 The output is a connection notification, followed by the address at
30608 which the target program is, in the following form:
30611 ^connected,addr="@var{address}",func="@var{function name}",
30612 args=[@var{arg list}]
30615 @subsubheading @value{GDBN} Command
30617 The corresponding @value{GDBN} command is @samp{target}.
30619 @subsubheading Example
30623 -target-select remote /dev/ttya
30624 ^connected,addr="0xfe00a300",func="??",args=[]
30628 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30629 @node GDB/MI File Transfer Commands
30630 @section @sc{gdb/mi} File Transfer Commands
30633 @subheading The @code{-target-file-put} Command
30634 @findex -target-file-put
30636 @subsubheading Synopsis
30639 -target-file-put @var{hostfile} @var{targetfile}
30642 Copy file @var{hostfile} from the host system (the machine running
30643 @value{GDBN}) to @var{targetfile} on the target system.
30645 @subsubheading @value{GDBN} Command
30647 The corresponding @value{GDBN} command is @samp{remote put}.
30649 @subsubheading Example
30653 -target-file-put localfile remotefile
30659 @subheading The @code{-target-file-get} Command
30660 @findex -target-file-get
30662 @subsubheading Synopsis
30665 -target-file-get @var{targetfile} @var{hostfile}
30668 Copy file @var{targetfile} from the target system to @var{hostfile}
30669 on the host system.
30671 @subsubheading @value{GDBN} Command
30673 The corresponding @value{GDBN} command is @samp{remote get}.
30675 @subsubheading Example
30679 -target-file-get remotefile localfile
30685 @subheading The @code{-target-file-delete} Command
30686 @findex -target-file-delete
30688 @subsubheading Synopsis
30691 -target-file-delete @var{targetfile}
30694 Delete @var{targetfile} from the target system.
30696 @subsubheading @value{GDBN} Command
30698 The corresponding @value{GDBN} command is @samp{remote delete}.
30700 @subsubheading Example
30704 -target-file-delete remotefile
30710 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30711 @node GDB/MI Miscellaneous Commands
30712 @section Miscellaneous @sc{gdb/mi} Commands
30714 @c @subheading -gdb-complete
30716 @subheading The @code{-gdb-exit} Command
30719 @subsubheading Synopsis
30725 Exit @value{GDBN} immediately.
30727 @subsubheading @value{GDBN} Command
30729 Approximately corresponds to @samp{quit}.
30731 @subsubheading Example
30741 @subheading The @code{-exec-abort} Command
30742 @findex -exec-abort
30744 @subsubheading Synopsis
30750 Kill the inferior running program.
30752 @subsubheading @value{GDBN} Command
30754 The corresponding @value{GDBN} command is @samp{kill}.
30756 @subsubheading Example
30761 @subheading The @code{-gdb-set} Command
30764 @subsubheading Synopsis
30770 Set an internal @value{GDBN} variable.
30771 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
30773 @subsubheading @value{GDBN} Command
30775 The corresponding @value{GDBN} command is @samp{set}.
30777 @subsubheading Example
30787 @subheading The @code{-gdb-show} Command
30790 @subsubheading Synopsis
30796 Show the current value of a @value{GDBN} variable.
30798 @subsubheading @value{GDBN} Command
30800 The corresponding @value{GDBN} command is @samp{show}.
30802 @subsubheading Example
30811 @c @subheading -gdb-source
30814 @subheading The @code{-gdb-version} Command
30815 @findex -gdb-version
30817 @subsubheading Synopsis
30823 Show version information for @value{GDBN}. Used mostly in testing.
30825 @subsubheading @value{GDBN} Command
30827 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
30828 default shows this information when you start an interactive session.
30830 @subsubheading Example
30832 @c This example modifies the actual output from GDB to avoid overfull
30838 ~Copyright 2000 Free Software Foundation, Inc.
30839 ~GDB is free software, covered by the GNU General Public License, and
30840 ~you are welcome to change it and/or distribute copies of it under
30841 ~ certain conditions.
30842 ~Type "show copying" to see the conditions.
30843 ~There is absolutely no warranty for GDB. Type "show warranty" for
30845 ~This GDB was configured as
30846 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
30851 @subheading The @code{-list-features} Command
30852 @findex -list-features
30854 Returns a list of particular features of the MI protocol that
30855 this version of gdb implements. A feature can be a command,
30856 or a new field in an output of some command, or even an
30857 important bugfix. While a frontend can sometimes detect presence
30858 of a feature at runtime, it is easier to perform detection at debugger
30861 The command returns a list of strings, with each string naming an
30862 available feature. Each returned string is just a name, it does not
30863 have any internal structure. The list of possible feature names
30869 (gdb) -list-features
30870 ^done,result=["feature1","feature2"]
30873 The current list of features is:
30876 @item frozen-varobjs
30877 Indicates support for the @code{-var-set-frozen} command, as well
30878 as possible presense of the @code{frozen} field in the output
30879 of @code{-varobj-create}.
30880 @item pending-breakpoints
30881 Indicates support for the @option{-f} option to the @code{-break-insert}
30884 Indicates Python scripting support, Python-based
30885 pretty-printing commands, and possible presence of the
30886 @samp{display_hint} field in the output of @code{-var-list-children}
30888 Indicates support for the @code{-thread-info} command.
30889 @item data-read-memory-bytes
30890 Indicates support for the @code{-data-read-memory-bytes} and the
30891 @code{-data-write-memory-bytes} commands.
30892 @item breakpoint-notifications
30893 Indicates that changes to breakpoints and breakpoints created via the
30894 CLI will be announced via async records.
30895 @item ada-task-info
30896 Indicates support for the @code{-ada-task-info} command.
30899 @subheading The @code{-list-target-features} Command
30900 @findex -list-target-features
30902 Returns a list of particular features that are supported by the
30903 target. Those features affect the permitted MI commands, but
30904 unlike the features reported by the @code{-list-features} command, the
30905 features depend on which target GDB is using at the moment. Whenever
30906 a target can change, due to commands such as @code{-target-select},
30907 @code{-target-attach} or @code{-exec-run}, the list of target features
30908 may change, and the frontend should obtain it again.
30912 (gdb) -list-features
30913 ^done,result=["async"]
30916 The current list of features is:
30920 Indicates that the target is capable of asynchronous command
30921 execution, which means that @value{GDBN} will accept further commands
30922 while the target is running.
30925 Indicates that the target is capable of reverse execution.
30926 @xref{Reverse Execution}, for more information.
30930 @subheading The @code{-list-thread-groups} Command
30931 @findex -list-thread-groups
30933 @subheading Synopsis
30936 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
30939 Lists thread groups (@pxref{Thread groups}). When a single thread
30940 group is passed as the argument, lists the children of that group.
30941 When several thread group are passed, lists information about those
30942 thread groups. Without any parameters, lists information about all
30943 top-level thread groups.
30945 Normally, thread groups that are being debugged are reported.
30946 With the @samp{--available} option, @value{GDBN} reports thread groups
30947 available on the target.
30949 The output of this command may have either a @samp{threads} result or
30950 a @samp{groups} result. The @samp{thread} result has a list of tuples
30951 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
30952 Information}). The @samp{groups} result has a list of tuples as value,
30953 each tuple describing a thread group. If top-level groups are
30954 requested (that is, no parameter is passed), or when several groups
30955 are passed, the output always has a @samp{groups} result. The format
30956 of the @samp{group} result is described below.
30958 To reduce the number of roundtrips it's possible to list thread groups
30959 together with their children, by passing the @samp{--recurse} option
30960 and the recursion depth. Presently, only recursion depth of 1 is
30961 permitted. If this option is present, then every reported thread group
30962 will also include its children, either as @samp{group} or
30963 @samp{threads} field.
30965 In general, any combination of option and parameters is permitted, with
30966 the following caveats:
30970 When a single thread group is passed, the output will typically
30971 be the @samp{threads} result. Because threads may not contain
30972 anything, the @samp{recurse} option will be ignored.
30975 When the @samp{--available} option is passed, limited information may
30976 be available. In particular, the list of threads of a process might
30977 be inaccessible. Further, specifying specific thread groups might
30978 not give any performance advantage over listing all thread groups.
30979 The frontend should assume that @samp{-list-thread-groups --available}
30980 is always an expensive operation and cache the results.
30984 The @samp{groups} result is a list of tuples, where each tuple may
30985 have the following fields:
30989 Identifier of the thread group. This field is always present.
30990 The identifier is an opaque string; frontends should not try to
30991 convert it to an integer, even though it might look like one.
30994 The type of the thread group. At present, only @samp{process} is a
30998 The target-specific process identifier. This field is only present
30999 for thread groups of type @samp{process} and only if the process exists.
31002 The number of children this thread group has. This field may be
31003 absent for an available thread group.
31006 This field has a list of tuples as value, each tuple describing a
31007 thread. It may be present if the @samp{--recurse} option is
31008 specified, and it's actually possible to obtain the threads.
31011 This field is a list of integers, each identifying a core that one
31012 thread of the group is running on. This field may be absent if
31013 such information is not available.
31016 The name of the executable file that corresponds to this thread group.
31017 The field is only present for thread groups of type @samp{process},
31018 and only if there is a corresponding executable file.
31022 @subheading Example
31026 -list-thread-groups
31027 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31028 -list-thread-groups 17
31029 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31030 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31031 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31032 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31033 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31034 -list-thread-groups --available
31035 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31036 -list-thread-groups --available --recurse 1
31037 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31038 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31039 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31040 -list-thread-groups --available --recurse 1 17 18
31041 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31042 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31043 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31047 @subheading The @code{-add-inferior} Command
31048 @findex -add-inferior
31050 @subheading Synopsis
31056 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31057 inferior is not associated with any executable. Such association may
31058 be established with the @samp{-file-exec-and-symbols} command
31059 (@pxref{GDB/MI File Commands}). The command response has a single
31060 field, @samp{thread-group}, whose value is the identifier of the
31061 thread group corresponding to the new inferior.
31063 @subheading Example
31068 ^done,thread-group="i3"
31071 @subheading The @code{-interpreter-exec} Command
31072 @findex -interpreter-exec
31074 @subheading Synopsis
31077 -interpreter-exec @var{interpreter} @var{command}
31079 @anchor{-interpreter-exec}
31081 Execute the specified @var{command} in the given @var{interpreter}.
31083 @subheading @value{GDBN} Command
31085 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31087 @subheading Example
31091 -interpreter-exec console "break main"
31092 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31093 &"During symbol reading, bad structure-type format.\n"
31094 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31099 @subheading The @code{-inferior-tty-set} Command
31100 @findex -inferior-tty-set
31102 @subheading Synopsis
31105 -inferior-tty-set /dev/pts/1
31108 Set terminal for future runs of the program being debugged.
31110 @subheading @value{GDBN} Command
31112 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31114 @subheading Example
31118 -inferior-tty-set /dev/pts/1
31123 @subheading The @code{-inferior-tty-show} Command
31124 @findex -inferior-tty-show
31126 @subheading Synopsis
31132 Show terminal for future runs of program being debugged.
31134 @subheading @value{GDBN} Command
31136 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31138 @subheading Example
31142 -inferior-tty-set /dev/pts/1
31146 ^done,inferior_tty_terminal="/dev/pts/1"
31150 @subheading The @code{-enable-timings} Command
31151 @findex -enable-timings
31153 @subheading Synopsis
31156 -enable-timings [yes | no]
31159 Toggle the printing of the wallclock, user and system times for an MI
31160 command as a field in its output. This command is to help frontend
31161 developers optimize the performance of their code. No argument is
31162 equivalent to @samp{yes}.
31164 @subheading @value{GDBN} Command
31168 @subheading Example
31176 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31177 addr="0x080484ed",func="main",file="myprog.c",
31178 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31179 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31187 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31188 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31189 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31190 fullname="/home/nickrob/myprog.c",line="73"@}
31195 @chapter @value{GDBN} Annotations
31197 This chapter describes annotations in @value{GDBN}. Annotations were
31198 designed to interface @value{GDBN} to graphical user interfaces or other
31199 similar programs which want to interact with @value{GDBN} at a
31200 relatively high level.
31202 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31206 This is Edition @value{EDITION}, @value{DATE}.
31210 * Annotations Overview:: What annotations are; the general syntax.
31211 * Server Prefix:: Issuing a command without affecting user state.
31212 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31213 * Errors:: Annotations for error messages.
31214 * Invalidation:: Some annotations describe things now invalid.
31215 * Annotations for Running::
31216 Whether the program is running, how it stopped, etc.
31217 * Source Annotations:: Annotations describing source code.
31220 @node Annotations Overview
31221 @section What is an Annotation?
31222 @cindex annotations
31224 Annotations start with a newline character, two @samp{control-z}
31225 characters, and the name of the annotation. If there is no additional
31226 information associated with this annotation, the name of the annotation
31227 is followed immediately by a newline. If there is additional
31228 information, the name of the annotation is followed by a space, the
31229 additional information, and a newline. The additional information
31230 cannot contain newline characters.
31232 Any output not beginning with a newline and two @samp{control-z}
31233 characters denotes literal output from @value{GDBN}. Currently there is
31234 no need for @value{GDBN} to output a newline followed by two
31235 @samp{control-z} characters, but if there was such a need, the
31236 annotations could be extended with an @samp{escape} annotation which
31237 means those three characters as output.
31239 The annotation @var{level}, which is specified using the
31240 @option{--annotate} command line option (@pxref{Mode Options}), controls
31241 how much information @value{GDBN} prints together with its prompt,
31242 values of expressions, source lines, and other types of output. Level 0
31243 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31244 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31245 for programs that control @value{GDBN}, and level 2 annotations have
31246 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31247 Interface, annotate, GDB's Obsolete Annotations}).
31250 @kindex set annotate
31251 @item set annotate @var{level}
31252 The @value{GDBN} command @code{set annotate} sets the level of
31253 annotations to the specified @var{level}.
31255 @item show annotate
31256 @kindex show annotate
31257 Show the current annotation level.
31260 This chapter describes level 3 annotations.
31262 A simple example of starting up @value{GDBN} with annotations is:
31265 $ @kbd{gdb --annotate=3}
31267 Copyright 2003 Free Software Foundation, Inc.
31268 GDB is free software, covered by the GNU General Public License,
31269 and you are welcome to change it and/or distribute copies of it
31270 under certain conditions.
31271 Type "show copying" to see the conditions.
31272 There is absolutely no warranty for GDB. Type "show warranty"
31274 This GDB was configured as "i386-pc-linux-gnu"
31285 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31286 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31287 denotes a @samp{control-z} character) are annotations; the rest is
31288 output from @value{GDBN}.
31290 @node Server Prefix
31291 @section The Server Prefix
31292 @cindex server prefix
31294 If you prefix a command with @samp{server } then it will not affect
31295 the command history, nor will it affect @value{GDBN}'s notion of which
31296 command to repeat if @key{RET} is pressed on a line by itself. This
31297 means that commands can be run behind a user's back by a front-end in
31298 a transparent manner.
31300 The @code{server } prefix does not affect the recording of values into
31301 the value history; to print a value without recording it into the
31302 value history, use the @code{output} command instead of the
31303 @code{print} command.
31305 Using this prefix also disables confirmation requests
31306 (@pxref{confirmation requests}).
31309 @section Annotation for @value{GDBN} Input
31311 @cindex annotations for prompts
31312 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31313 to know when to send output, when the output from a given command is
31316 Different kinds of input each have a different @dfn{input type}. Each
31317 input type has three annotations: a @code{pre-} annotation, which
31318 denotes the beginning of any prompt which is being output, a plain
31319 annotation, which denotes the end of the prompt, and then a @code{post-}
31320 annotation which denotes the end of any echo which may (or may not) be
31321 associated with the input. For example, the @code{prompt} input type
31322 features the following annotations:
31330 The input types are
31333 @findex pre-prompt annotation
31334 @findex prompt annotation
31335 @findex post-prompt annotation
31337 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31339 @findex pre-commands annotation
31340 @findex commands annotation
31341 @findex post-commands annotation
31343 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31344 command. The annotations are repeated for each command which is input.
31346 @findex pre-overload-choice annotation
31347 @findex overload-choice annotation
31348 @findex post-overload-choice annotation
31349 @item overload-choice
31350 When @value{GDBN} wants the user to select between various overloaded functions.
31352 @findex pre-query annotation
31353 @findex query annotation
31354 @findex post-query annotation
31356 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31358 @findex pre-prompt-for-continue annotation
31359 @findex prompt-for-continue annotation
31360 @findex post-prompt-for-continue annotation
31361 @item prompt-for-continue
31362 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31363 expect this to work well; instead use @code{set height 0} to disable
31364 prompting. This is because the counting of lines is buggy in the
31365 presence of annotations.
31370 @cindex annotations for errors, warnings and interrupts
31372 @findex quit annotation
31377 This annotation occurs right before @value{GDBN} responds to an interrupt.
31379 @findex error annotation
31384 This annotation occurs right before @value{GDBN} responds to an error.
31386 Quit and error annotations indicate that any annotations which @value{GDBN} was
31387 in the middle of may end abruptly. For example, if a
31388 @code{value-history-begin} annotation is followed by a @code{error}, one
31389 cannot expect to receive the matching @code{value-history-end}. One
31390 cannot expect not to receive it either, however; an error annotation
31391 does not necessarily mean that @value{GDBN} is immediately returning all the way
31394 @findex error-begin annotation
31395 A quit or error annotation may be preceded by
31401 Any output between that and the quit or error annotation is the error
31404 Warning messages are not yet annotated.
31405 @c If we want to change that, need to fix warning(), type_error(),
31406 @c range_error(), and possibly other places.
31409 @section Invalidation Notices
31411 @cindex annotations for invalidation messages
31412 The following annotations say that certain pieces of state may have
31416 @findex frames-invalid annotation
31417 @item ^Z^Zframes-invalid
31419 The frames (for example, output from the @code{backtrace} command) may
31422 @findex breakpoints-invalid annotation
31423 @item ^Z^Zbreakpoints-invalid
31425 The breakpoints may have changed. For example, the user just added or
31426 deleted a breakpoint.
31429 @node Annotations for Running
31430 @section Running the Program
31431 @cindex annotations for running programs
31433 @findex starting annotation
31434 @findex stopping annotation
31435 When the program starts executing due to a @value{GDBN} command such as
31436 @code{step} or @code{continue},
31442 is output. When the program stops,
31448 is output. Before the @code{stopped} annotation, a variety of
31449 annotations describe how the program stopped.
31452 @findex exited annotation
31453 @item ^Z^Zexited @var{exit-status}
31454 The program exited, and @var{exit-status} is the exit status (zero for
31455 successful exit, otherwise nonzero).
31457 @findex signalled annotation
31458 @findex signal-name annotation
31459 @findex signal-name-end annotation
31460 @findex signal-string annotation
31461 @findex signal-string-end annotation
31462 @item ^Z^Zsignalled
31463 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31464 annotation continues:
31470 ^Z^Zsignal-name-end
31474 ^Z^Zsignal-string-end
31479 where @var{name} is the name of the signal, such as @code{SIGILL} or
31480 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31481 as @code{Illegal Instruction} or @code{Segmentation fault}.
31482 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31483 user's benefit and have no particular format.
31485 @findex signal annotation
31487 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31488 just saying that the program received the signal, not that it was
31489 terminated with it.
31491 @findex breakpoint annotation
31492 @item ^Z^Zbreakpoint @var{number}
31493 The program hit breakpoint number @var{number}.
31495 @findex watchpoint annotation
31496 @item ^Z^Zwatchpoint @var{number}
31497 The program hit watchpoint number @var{number}.
31500 @node Source Annotations
31501 @section Displaying Source
31502 @cindex annotations for source display
31504 @findex source annotation
31505 The following annotation is used instead of displaying source code:
31508 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31511 where @var{filename} is an absolute file name indicating which source
31512 file, @var{line} is the line number within that file (where 1 is the
31513 first line in the file), @var{character} is the character position
31514 within the file (where 0 is the first character in the file) (for most
31515 debug formats this will necessarily point to the beginning of a line),
31516 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31517 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31518 @var{addr} is the address in the target program associated with the
31519 source which is being displayed. @var{addr} is in the form @samp{0x}
31520 followed by one or more lowercase hex digits (note that this does not
31521 depend on the language).
31523 @node JIT Interface
31524 @chapter JIT Compilation Interface
31525 @cindex just-in-time compilation
31526 @cindex JIT compilation interface
31528 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31529 interface. A JIT compiler is a program or library that generates native
31530 executable code at runtime and executes it, usually in order to achieve good
31531 performance while maintaining platform independence.
31533 Programs that use JIT compilation are normally difficult to debug because
31534 portions of their code are generated at runtime, instead of being loaded from
31535 object files, which is where @value{GDBN} normally finds the program's symbols
31536 and debug information. In order to debug programs that use JIT compilation,
31537 @value{GDBN} has an interface that allows the program to register in-memory
31538 symbol files with @value{GDBN} at runtime.
31540 If you are using @value{GDBN} to debug a program that uses this interface, then
31541 it should work transparently so long as you have not stripped the binary. If
31542 you are developing a JIT compiler, then the interface is documented in the rest
31543 of this chapter. At this time, the only known client of this interface is the
31546 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31547 JIT compiler communicates with @value{GDBN} by writing data into a global
31548 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31549 attaches, it reads a linked list of symbol files from the global variable to
31550 find existing code, and puts a breakpoint in the function so that it can find
31551 out about additional code.
31554 * Declarations:: Relevant C struct declarations
31555 * Registering Code:: Steps to register code
31556 * Unregistering Code:: Steps to unregister code
31560 @section JIT Declarations
31562 These are the relevant struct declarations that a C program should include to
31563 implement the interface:
31573 struct jit_code_entry
31575 struct jit_code_entry *next_entry;
31576 struct jit_code_entry *prev_entry;
31577 const char *symfile_addr;
31578 uint64_t symfile_size;
31581 struct jit_descriptor
31584 /* This type should be jit_actions_t, but we use uint32_t
31585 to be explicit about the bitwidth. */
31586 uint32_t action_flag;
31587 struct jit_code_entry *relevant_entry;
31588 struct jit_code_entry *first_entry;
31591 /* GDB puts a breakpoint in this function. */
31592 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31594 /* Make sure to specify the version statically, because the
31595 debugger may check the version before we can set it. */
31596 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31599 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31600 modifications to this global data properly, which can easily be done by putting
31601 a global mutex around modifications to these structures.
31603 @node Registering Code
31604 @section Registering Code
31606 To register code with @value{GDBN}, the JIT should follow this protocol:
31610 Generate an object file in memory with symbols and other desired debug
31611 information. The file must include the virtual addresses of the sections.
31614 Create a code entry for the file, which gives the start and size of the symbol
31618 Add it to the linked list in the JIT descriptor.
31621 Point the relevant_entry field of the descriptor at the entry.
31624 Set @code{action_flag} to @code{JIT_REGISTER} and call
31625 @code{__jit_debug_register_code}.
31628 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31629 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31630 new code. However, the linked list must still be maintained in order to allow
31631 @value{GDBN} to attach to a running process and still find the symbol files.
31633 @node Unregistering Code
31634 @section Unregistering Code
31636 If code is freed, then the JIT should use the following protocol:
31640 Remove the code entry corresponding to the code from the linked list.
31643 Point the @code{relevant_entry} field of the descriptor at the code entry.
31646 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31647 @code{__jit_debug_register_code}.
31650 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31651 and the JIT will leak the memory used for the associated symbol files.
31654 @chapter Reporting Bugs in @value{GDBN}
31655 @cindex bugs in @value{GDBN}
31656 @cindex reporting bugs in @value{GDBN}
31658 Your bug reports play an essential role in making @value{GDBN} reliable.
31660 Reporting a bug may help you by bringing a solution to your problem, or it
31661 may not. But in any case the principal function of a bug report is to help
31662 the entire community by making the next version of @value{GDBN} work better. Bug
31663 reports are your contribution to the maintenance of @value{GDBN}.
31665 In order for a bug report to serve its purpose, you must include the
31666 information that enables us to fix the bug.
31669 * Bug Criteria:: Have you found a bug?
31670 * Bug Reporting:: How to report bugs
31674 @section Have You Found a Bug?
31675 @cindex bug criteria
31677 If you are not sure whether you have found a bug, here are some guidelines:
31680 @cindex fatal signal
31681 @cindex debugger crash
31682 @cindex crash of debugger
31684 If the debugger gets a fatal signal, for any input whatever, that is a
31685 @value{GDBN} bug. Reliable debuggers never crash.
31687 @cindex error on valid input
31689 If @value{GDBN} produces an error message for valid input, that is a
31690 bug. (Note that if you're cross debugging, the problem may also be
31691 somewhere in the connection to the target.)
31693 @cindex invalid input
31695 If @value{GDBN} does not produce an error message for invalid input,
31696 that is a bug. However, you should note that your idea of
31697 ``invalid input'' might be our idea of ``an extension'' or ``support
31698 for traditional practice''.
31701 If you are an experienced user of debugging tools, your suggestions
31702 for improvement of @value{GDBN} are welcome in any case.
31705 @node Bug Reporting
31706 @section How to Report Bugs
31707 @cindex bug reports
31708 @cindex @value{GDBN} bugs, reporting
31710 A number of companies and individuals offer support for @sc{gnu} products.
31711 If you obtained @value{GDBN} from a support organization, we recommend you
31712 contact that organization first.
31714 You can find contact information for many support companies and
31715 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
31717 @c should add a web page ref...
31720 @ifset BUGURL_DEFAULT
31721 In any event, we also recommend that you submit bug reports for
31722 @value{GDBN}. The preferred method is to submit them directly using
31723 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
31724 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
31727 @strong{Do not send bug reports to @samp{info-gdb}, or to
31728 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
31729 not want to receive bug reports. Those that do have arranged to receive
31732 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
31733 serves as a repeater. The mailing list and the newsgroup carry exactly
31734 the same messages. Often people think of posting bug reports to the
31735 newsgroup instead of mailing them. This appears to work, but it has one
31736 problem which can be crucial: a newsgroup posting often lacks a mail
31737 path back to the sender. Thus, if we need to ask for more information,
31738 we may be unable to reach you. For this reason, it is better to send
31739 bug reports to the mailing list.
31741 @ifclear BUGURL_DEFAULT
31742 In any event, we also recommend that you submit bug reports for
31743 @value{GDBN} to @value{BUGURL}.
31747 The fundamental principle of reporting bugs usefully is this:
31748 @strong{report all the facts}. If you are not sure whether to state a
31749 fact or leave it out, state it!
31751 Often people omit facts because they think they know what causes the
31752 problem and assume that some details do not matter. Thus, you might
31753 assume that the name of the variable you use in an example does not matter.
31754 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
31755 stray memory reference which happens to fetch from the location where that
31756 name is stored in memory; perhaps, if the name were different, the contents
31757 of that location would fool the debugger into doing the right thing despite
31758 the bug. Play it safe and give a specific, complete example. That is the
31759 easiest thing for you to do, and the most helpful.
31761 Keep in mind that the purpose of a bug report is to enable us to fix the
31762 bug. It may be that the bug has been reported previously, but neither
31763 you nor we can know that unless your bug report is complete and
31766 Sometimes people give a few sketchy facts and ask, ``Does this ring a
31767 bell?'' Those bug reports are useless, and we urge everyone to
31768 @emph{refuse to respond to them} except to chide the sender to report
31771 To enable us to fix the bug, you should include all these things:
31775 The version of @value{GDBN}. @value{GDBN} announces it if you start
31776 with no arguments; you can also print it at any time using @code{show
31779 Without this, we will not know whether there is any point in looking for
31780 the bug in the current version of @value{GDBN}.
31783 The type of machine you are using, and the operating system name and
31787 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
31788 ``@value{GCC}--2.8.1''.
31791 What compiler (and its version) was used to compile the program you are
31792 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
31793 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
31794 to get this information; for other compilers, see the documentation for
31798 The command arguments you gave the compiler to compile your example and
31799 observe the bug. For example, did you use @samp{-O}? To guarantee
31800 you will not omit something important, list them all. A copy of the
31801 Makefile (or the output from make) is sufficient.
31803 If we were to try to guess the arguments, we would probably guess wrong
31804 and then we might not encounter the bug.
31807 A complete input script, and all necessary source files, that will
31811 A description of what behavior you observe that you believe is
31812 incorrect. For example, ``It gets a fatal signal.''
31814 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
31815 will certainly notice it. But if the bug is incorrect output, we might
31816 not notice unless it is glaringly wrong. You might as well not give us
31817 a chance to make a mistake.
31819 Even if the problem you experience is a fatal signal, you should still
31820 say so explicitly. Suppose something strange is going on, such as, your
31821 copy of @value{GDBN} is out of synch, or you have encountered a bug in
31822 the C library on your system. (This has happened!) Your copy might
31823 crash and ours would not. If you told us to expect a crash, then when
31824 ours fails to crash, we would know that the bug was not happening for
31825 us. If you had not told us to expect a crash, then we would not be able
31826 to draw any conclusion from our observations.
31829 @cindex recording a session script
31830 To collect all this information, you can use a session recording program
31831 such as @command{script}, which is available on many Unix systems.
31832 Just run your @value{GDBN} session inside @command{script} and then
31833 include the @file{typescript} file with your bug report.
31835 Another way to record a @value{GDBN} session is to run @value{GDBN}
31836 inside Emacs and then save the entire buffer to a file.
31839 If you wish to suggest changes to the @value{GDBN} source, send us context
31840 diffs. If you even discuss something in the @value{GDBN} source, refer to
31841 it by context, not by line number.
31843 The line numbers in our development sources will not match those in your
31844 sources. Your line numbers would convey no useful information to us.
31848 Here are some things that are not necessary:
31852 A description of the envelope of the bug.
31854 Often people who encounter a bug spend a lot of time investigating
31855 which changes to the input file will make the bug go away and which
31856 changes will not affect it.
31858 This is often time consuming and not very useful, because the way we
31859 will find the bug is by running a single example under the debugger
31860 with breakpoints, not by pure deduction from a series of examples.
31861 We recommend that you save your time for something else.
31863 Of course, if you can find a simpler example to report @emph{instead}
31864 of the original one, that is a convenience for us. Errors in the
31865 output will be easier to spot, running under the debugger will take
31866 less time, and so on.
31868 However, simplification is not vital; if you do not want to do this,
31869 report the bug anyway and send us the entire test case you used.
31872 A patch for the bug.
31874 A patch for the bug does help us if it is a good one. But do not omit
31875 the necessary information, such as the test case, on the assumption that
31876 a patch is all we need. We might see problems with your patch and decide
31877 to fix the problem another way, or we might not understand it at all.
31879 Sometimes with a program as complicated as @value{GDBN} it is very hard to
31880 construct an example that will make the program follow a certain path
31881 through the code. If you do not send us the example, we will not be able
31882 to construct one, so we will not be able to verify that the bug is fixed.
31884 And if we cannot understand what bug you are trying to fix, or why your
31885 patch should be an improvement, we will not install it. A test case will
31886 help us to understand.
31889 A guess about what the bug is or what it depends on.
31891 Such guesses are usually wrong. Even we cannot guess right about such
31892 things without first using the debugger to find the facts.
31895 @c The readline documentation is distributed with the readline code
31896 @c and consists of the two following files:
31899 @c Use -I with makeinfo to point to the appropriate directory,
31900 @c environment var TEXINPUTS with TeX.
31901 @ifclear SYSTEM_READLINE
31902 @include rluser.texi
31903 @include hsuser.texi
31907 @appendix In Memoriam
31909 The @value{GDBN} project mourns the loss of the following long-time
31914 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
31915 to Free Software in general. Outside of @value{GDBN}, he was known in
31916 the Amiga world for his series of Fish Disks, and the GeekGadget project.
31918 @item Michael Snyder
31919 Michael was one of the Global Maintainers of the @value{GDBN} project,
31920 with contributions recorded as early as 1996, until 2011. In addition
31921 to his day to day participation, he was a large driving force behind
31922 adding Reverse Debugging to @value{GDBN}.
31925 Beyond their technical contributions to the project, they were also
31926 enjoyable members of the Free Software Community. We will miss them.
31928 @node Formatting Documentation
31929 @appendix Formatting Documentation
31931 @cindex @value{GDBN} reference card
31932 @cindex reference card
31933 The @value{GDBN} 4 release includes an already-formatted reference card, ready
31934 for printing with PostScript or Ghostscript, in the @file{gdb}
31935 subdirectory of the main source directory@footnote{In
31936 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
31937 release.}. If you can use PostScript or Ghostscript with your printer,
31938 you can print the reference card immediately with @file{refcard.ps}.
31940 The release also includes the source for the reference card. You
31941 can format it, using @TeX{}, by typing:
31947 The @value{GDBN} reference card is designed to print in @dfn{landscape}
31948 mode on US ``letter'' size paper;
31949 that is, on a sheet 11 inches wide by 8.5 inches
31950 high. You will need to specify this form of printing as an option to
31951 your @sc{dvi} output program.
31953 @cindex documentation
31955 All the documentation for @value{GDBN} comes as part of the machine-readable
31956 distribution. The documentation is written in Texinfo format, which is
31957 a documentation system that uses a single source file to produce both
31958 on-line information and a printed manual. You can use one of the Info
31959 formatting commands to create the on-line version of the documentation
31960 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
31962 @value{GDBN} includes an already formatted copy of the on-line Info
31963 version of this manual in the @file{gdb} subdirectory. The main Info
31964 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
31965 subordinate files matching @samp{gdb.info*} in the same directory. If
31966 necessary, you can print out these files, or read them with any editor;
31967 but they are easier to read using the @code{info} subsystem in @sc{gnu}
31968 Emacs or the standalone @code{info} program, available as part of the
31969 @sc{gnu} Texinfo distribution.
31971 If you want to format these Info files yourself, you need one of the
31972 Info formatting programs, such as @code{texinfo-format-buffer} or
31975 If you have @code{makeinfo} installed, and are in the top level
31976 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
31977 version @value{GDBVN}), you can make the Info file by typing:
31984 If you want to typeset and print copies of this manual, you need @TeX{},
31985 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
31986 Texinfo definitions file.
31988 @TeX{} is a typesetting program; it does not print files directly, but
31989 produces output files called @sc{dvi} files. To print a typeset
31990 document, you need a program to print @sc{dvi} files. If your system
31991 has @TeX{} installed, chances are it has such a program. The precise
31992 command to use depends on your system; @kbd{lpr -d} is common; another
31993 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
31994 require a file name without any extension or a @samp{.dvi} extension.
31996 @TeX{} also requires a macro definitions file called
31997 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
31998 written in Texinfo format. On its own, @TeX{} cannot either read or
31999 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32000 and is located in the @file{gdb-@var{version-number}/texinfo}
32003 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32004 typeset and print this manual. First switch to the @file{gdb}
32005 subdirectory of the main source directory (for example, to
32006 @file{gdb-@value{GDBVN}/gdb}) and type:
32012 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32014 @node Installing GDB
32015 @appendix Installing @value{GDBN}
32016 @cindex installation
32019 * Requirements:: Requirements for building @value{GDBN}
32020 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32021 * Separate Objdir:: Compiling @value{GDBN} in another directory
32022 * Config Names:: Specifying names for hosts and targets
32023 * Configure Options:: Summary of options for configure
32024 * System-wide configuration:: Having a system-wide init file
32028 @section Requirements for Building @value{GDBN}
32029 @cindex building @value{GDBN}, requirements for
32031 Building @value{GDBN} requires various tools and packages to be available.
32032 Other packages will be used only if they are found.
32034 @heading Tools/Packages Necessary for Building @value{GDBN}
32036 @item ISO C90 compiler
32037 @value{GDBN} is written in ISO C90. It should be buildable with any
32038 working C90 compiler, e.g.@: GCC.
32042 @heading Tools/Packages Optional for Building @value{GDBN}
32046 @value{GDBN} can use the Expat XML parsing library. This library may be
32047 included with your operating system distribution; if it is not, you
32048 can get the latest version from @url{http://expat.sourceforge.net}.
32049 The @file{configure} script will search for this library in several
32050 standard locations; if it is installed in an unusual path, you can
32051 use the @option{--with-libexpat-prefix} option to specify its location.
32057 Remote protocol memory maps (@pxref{Memory Map Format})
32059 Target descriptions (@pxref{Target Descriptions})
32061 Remote shared library lists (@pxref{Library List Format})
32063 MS-Windows shared libraries (@pxref{Shared Libraries})
32065 Traceframe info (@pxref{Traceframe Info Format})
32069 @cindex compressed debug sections
32070 @value{GDBN} will use the @samp{zlib} library, if available, to read
32071 compressed debug sections. Some linkers, such as GNU gold, are capable
32072 of producing binaries with compressed debug sections. If @value{GDBN}
32073 is compiled with @samp{zlib}, it will be able to read the debug
32074 information in such binaries.
32076 The @samp{zlib} library is likely included with your operating system
32077 distribution; if it is not, you can get the latest version from
32078 @url{http://zlib.net}.
32081 @value{GDBN}'s features related to character sets (@pxref{Character
32082 Sets}) require a functioning @code{iconv} implementation. If you are
32083 on a GNU system, then this is provided by the GNU C Library. Some
32084 other systems also provide a working @code{iconv}.
32086 If @value{GDBN} is using the @code{iconv} program which is installed
32087 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32088 This is done with @option{--with-iconv-bin} which specifies the
32089 directory that contains the @code{iconv} program.
32091 On systems without @code{iconv}, you can install GNU Libiconv. If you
32092 have previously installed Libiconv, you can use the
32093 @option{--with-libiconv-prefix} option to configure.
32095 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32096 arrange to build Libiconv if a directory named @file{libiconv} appears
32097 in the top-most source directory. If Libiconv is built this way, and
32098 if the operating system does not provide a suitable @code{iconv}
32099 implementation, then the just-built library will automatically be used
32100 by @value{GDBN}. One easy way to set this up is to download GNU
32101 Libiconv, unpack it, and then rename the directory holding the
32102 Libiconv source code to @samp{libiconv}.
32105 @node Running Configure
32106 @section Invoking the @value{GDBN} @file{configure} Script
32107 @cindex configuring @value{GDBN}
32108 @value{GDBN} comes with a @file{configure} script that automates the process
32109 of preparing @value{GDBN} for installation; you can then use @code{make} to
32110 build the @code{gdb} program.
32112 @c irrelevant in info file; it's as current as the code it lives with.
32113 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32114 look at the @file{README} file in the sources; we may have improved the
32115 installation procedures since publishing this manual.}
32118 The @value{GDBN} distribution includes all the source code you need for
32119 @value{GDBN} in a single directory, whose name is usually composed by
32120 appending the version number to @samp{gdb}.
32122 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32123 @file{gdb-@value{GDBVN}} directory. That directory contains:
32126 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32127 script for configuring @value{GDBN} and all its supporting libraries
32129 @item gdb-@value{GDBVN}/gdb
32130 the source specific to @value{GDBN} itself
32132 @item gdb-@value{GDBVN}/bfd
32133 source for the Binary File Descriptor library
32135 @item gdb-@value{GDBVN}/include
32136 @sc{gnu} include files
32138 @item gdb-@value{GDBVN}/libiberty
32139 source for the @samp{-liberty} free software library
32141 @item gdb-@value{GDBVN}/opcodes
32142 source for the library of opcode tables and disassemblers
32144 @item gdb-@value{GDBVN}/readline
32145 source for the @sc{gnu} command-line interface
32147 @item gdb-@value{GDBVN}/glob
32148 source for the @sc{gnu} filename pattern-matching subroutine
32150 @item gdb-@value{GDBVN}/mmalloc
32151 source for the @sc{gnu} memory-mapped malloc package
32154 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32155 from the @file{gdb-@var{version-number}} source directory, which in
32156 this example is the @file{gdb-@value{GDBVN}} directory.
32158 First switch to the @file{gdb-@var{version-number}} source directory
32159 if you are not already in it; then run @file{configure}. Pass the
32160 identifier for the platform on which @value{GDBN} will run as an
32166 cd gdb-@value{GDBVN}
32167 ./configure @var{host}
32172 where @var{host} is an identifier such as @samp{sun4} or
32173 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32174 (You can often leave off @var{host}; @file{configure} tries to guess the
32175 correct value by examining your system.)
32177 Running @samp{configure @var{host}} and then running @code{make} builds the
32178 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32179 libraries, then @code{gdb} itself. The configured source files, and the
32180 binaries, are left in the corresponding source directories.
32183 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32184 system does not recognize this automatically when you run a different
32185 shell, you may need to run @code{sh} on it explicitly:
32188 sh configure @var{host}
32191 If you run @file{configure} from a directory that contains source
32192 directories for multiple libraries or programs, such as the
32193 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32195 creates configuration files for every directory level underneath (unless
32196 you tell it not to, with the @samp{--norecursion} option).
32198 You should run the @file{configure} script from the top directory in the
32199 source tree, the @file{gdb-@var{version-number}} directory. If you run
32200 @file{configure} from one of the subdirectories, you will configure only
32201 that subdirectory. That is usually not what you want. In particular,
32202 if you run the first @file{configure} from the @file{gdb} subdirectory
32203 of the @file{gdb-@var{version-number}} directory, you will omit the
32204 configuration of @file{bfd}, @file{readline}, and other sibling
32205 directories of the @file{gdb} subdirectory. This leads to build errors
32206 about missing include files such as @file{bfd/bfd.h}.
32208 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32209 However, you should make sure that the shell on your path (named by
32210 the @samp{SHELL} environment variable) is publicly readable. Remember
32211 that @value{GDBN} uses the shell to start your program---some systems refuse to
32212 let @value{GDBN} debug child processes whose programs are not readable.
32214 @node Separate Objdir
32215 @section Compiling @value{GDBN} in Another Directory
32217 If you want to run @value{GDBN} versions for several host or target machines,
32218 you need a different @code{gdb} compiled for each combination of
32219 host and target. @file{configure} is designed to make this easy by
32220 allowing you to generate each configuration in a separate subdirectory,
32221 rather than in the source directory. If your @code{make} program
32222 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32223 @code{make} in each of these directories builds the @code{gdb}
32224 program specified there.
32226 To build @code{gdb} in a separate directory, run @file{configure}
32227 with the @samp{--srcdir} option to specify where to find the source.
32228 (You also need to specify a path to find @file{configure}
32229 itself from your working directory. If the path to @file{configure}
32230 would be the same as the argument to @samp{--srcdir}, you can leave out
32231 the @samp{--srcdir} option; it is assumed.)
32233 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32234 separate directory for a Sun 4 like this:
32238 cd gdb-@value{GDBVN}
32241 ../gdb-@value{GDBVN}/configure sun4
32246 When @file{configure} builds a configuration using a remote source
32247 directory, it creates a tree for the binaries with the same structure
32248 (and using the same names) as the tree under the source directory. In
32249 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32250 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32251 @file{gdb-sun4/gdb}.
32253 Make sure that your path to the @file{configure} script has just one
32254 instance of @file{gdb} in it. If your path to @file{configure} looks
32255 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32256 one subdirectory of @value{GDBN}, not the whole package. This leads to
32257 build errors about missing include files such as @file{bfd/bfd.h}.
32259 One popular reason to build several @value{GDBN} configurations in separate
32260 directories is to configure @value{GDBN} for cross-compiling (where
32261 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32262 programs that run on another machine---the @dfn{target}).
32263 You specify a cross-debugging target by
32264 giving the @samp{--target=@var{target}} option to @file{configure}.
32266 When you run @code{make} to build a program or library, you must run
32267 it in a configured directory---whatever directory you were in when you
32268 called @file{configure} (or one of its subdirectories).
32270 The @code{Makefile} that @file{configure} generates in each source
32271 directory also runs recursively. If you type @code{make} in a source
32272 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32273 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32274 will build all the required libraries, and then build GDB.
32276 When you have multiple hosts or targets configured in separate
32277 directories, you can run @code{make} on them in parallel (for example,
32278 if they are NFS-mounted on each of the hosts); they will not interfere
32282 @section Specifying Names for Hosts and Targets
32284 The specifications used for hosts and targets in the @file{configure}
32285 script are based on a three-part naming scheme, but some short predefined
32286 aliases are also supported. The full naming scheme encodes three pieces
32287 of information in the following pattern:
32290 @var{architecture}-@var{vendor}-@var{os}
32293 For example, you can use the alias @code{sun4} as a @var{host} argument,
32294 or as the value for @var{target} in a @code{--target=@var{target}}
32295 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32297 The @file{configure} script accompanying @value{GDBN} does not provide
32298 any query facility to list all supported host and target names or
32299 aliases. @file{configure} calls the Bourne shell script
32300 @code{config.sub} to map abbreviations to full names; you can read the
32301 script, if you wish, or you can use it to test your guesses on
32302 abbreviations---for example:
32305 % sh config.sub i386-linux
32307 % sh config.sub alpha-linux
32308 alpha-unknown-linux-gnu
32309 % sh config.sub hp9k700
32311 % sh config.sub sun4
32312 sparc-sun-sunos4.1.1
32313 % sh config.sub sun3
32314 m68k-sun-sunos4.1.1
32315 % sh config.sub i986v
32316 Invalid configuration `i986v': machine `i986v' not recognized
32320 @code{config.sub} is also distributed in the @value{GDBN} source
32321 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32323 @node Configure Options
32324 @section @file{configure} Options
32326 Here is a summary of the @file{configure} options and arguments that
32327 are most often useful for building @value{GDBN}. @file{configure} also has
32328 several other options not listed here. @inforef{What Configure
32329 Does,,configure.info}, for a full explanation of @file{configure}.
32332 configure @r{[}--help@r{]}
32333 @r{[}--prefix=@var{dir}@r{]}
32334 @r{[}--exec-prefix=@var{dir}@r{]}
32335 @r{[}--srcdir=@var{dirname}@r{]}
32336 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32337 @r{[}--target=@var{target}@r{]}
32342 You may introduce options with a single @samp{-} rather than
32343 @samp{--} if you prefer; but you may abbreviate option names if you use
32348 Display a quick summary of how to invoke @file{configure}.
32350 @item --prefix=@var{dir}
32351 Configure the source to install programs and files under directory
32354 @item --exec-prefix=@var{dir}
32355 Configure the source to install programs under directory
32358 @c avoid splitting the warning from the explanation:
32360 @item --srcdir=@var{dirname}
32361 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32362 @code{make} that implements the @code{VPATH} feature.}@*
32363 Use this option to make configurations in directories separate from the
32364 @value{GDBN} source directories. Among other things, you can use this to
32365 build (or maintain) several configurations simultaneously, in separate
32366 directories. @file{configure} writes configuration-specific files in
32367 the current directory, but arranges for them to use the source in the
32368 directory @var{dirname}. @file{configure} creates directories under
32369 the working directory in parallel to the source directories below
32372 @item --norecursion
32373 Configure only the directory level where @file{configure} is executed; do not
32374 propagate configuration to subdirectories.
32376 @item --target=@var{target}
32377 Configure @value{GDBN} for cross-debugging programs running on the specified
32378 @var{target}. Without this option, @value{GDBN} is configured to debug
32379 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32381 There is no convenient way to generate a list of all available targets.
32383 @item @var{host} @dots{}
32384 Configure @value{GDBN} to run on the specified @var{host}.
32386 There is no convenient way to generate a list of all available hosts.
32389 There are many other options available as well, but they are generally
32390 needed for special purposes only.
32392 @node System-wide configuration
32393 @section System-wide configuration and settings
32394 @cindex system-wide init file
32396 @value{GDBN} can be configured to have a system-wide init file;
32397 this file will be read and executed at startup (@pxref{Startup, , What
32398 @value{GDBN} does during startup}).
32400 Here is the corresponding configure option:
32403 @item --with-system-gdbinit=@var{file}
32404 Specify that the default location of the system-wide init file is
32408 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32409 it may be subject to relocation. Two possible cases:
32413 If the default location of this init file contains @file{$prefix},
32414 it will be subject to relocation. Suppose that the configure options
32415 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32416 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32417 init file is looked for as @file{$install/etc/gdbinit} instead of
32418 @file{$prefix/etc/gdbinit}.
32421 By contrast, if the default location does not contain the prefix,
32422 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32423 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32424 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32425 wherever @value{GDBN} is installed.
32428 @node Maintenance Commands
32429 @appendix Maintenance Commands
32430 @cindex maintenance commands
32431 @cindex internal commands
32433 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32434 includes a number of commands intended for @value{GDBN} developers,
32435 that are not documented elsewhere in this manual. These commands are
32436 provided here for reference. (For commands that turn on debugging
32437 messages, see @ref{Debugging Output}.)
32440 @kindex maint agent
32441 @kindex maint agent-eval
32442 @item maint agent @var{expression}
32443 @itemx maint agent-eval @var{expression}
32444 Translate the given @var{expression} into remote agent bytecodes.
32445 This command is useful for debugging the Agent Expression mechanism
32446 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32447 expression useful for data collection, such as by tracepoints, while
32448 @samp{maint agent-eval} produces an expression that evaluates directly
32449 to a result. For instance, a collection expression for @code{globa +
32450 globb} will include bytecodes to record four bytes of memory at each
32451 of the addresses of @code{globa} and @code{globb}, while discarding
32452 the result of the addition, while an evaluation expression will do the
32453 addition and return the sum.
32455 @kindex maint info breakpoints
32456 @item @anchor{maint info breakpoints}maint info breakpoints
32457 Using the same format as @samp{info breakpoints}, display both the
32458 breakpoints you've set explicitly, and those @value{GDBN} is using for
32459 internal purposes. Internal breakpoints are shown with negative
32460 breakpoint numbers. The type column identifies what kind of breakpoint
32465 Normal, explicitly set breakpoint.
32468 Normal, explicitly set watchpoint.
32471 Internal breakpoint, used to handle correctly stepping through
32472 @code{longjmp} calls.
32474 @item longjmp resume
32475 Internal breakpoint at the target of a @code{longjmp}.
32478 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32481 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32484 Shared library events.
32488 @kindex set displaced-stepping
32489 @kindex show displaced-stepping
32490 @cindex displaced stepping support
32491 @cindex out-of-line single-stepping
32492 @item set displaced-stepping
32493 @itemx show displaced-stepping
32494 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32495 if the target supports it. Displaced stepping is a way to single-step
32496 over breakpoints without removing them from the inferior, by executing
32497 an out-of-line copy of the instruction that was originally at the
32498 breakpoint location. It is also known as out-of-line single-stepping.
32501 @item set displaced-stepping on
32502 If the target architecture supports it, @value{GDBN} will use
32503 displaced stepping to step over breakpoints.
32505 @item set displaced-stepping off
32506 @value{GDBN} will not use displaced stepping to step over breakpoints,
32507 even if such is supported by the target architecture.
32509 @cindex non-stop mode, and @samp{set displaced-stepping}
32510 @item set displaced-stepping auto
32511 This is the default mode. @value{GDBN} will use displaced stepping
32512 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32513 architecture supports displaced stepping.
32516 @kindex maint check-symtabs
32517 @item maint check-symtabs
32518 Check the consistency of psymtabs and symtabs.
32520 @kindex maint cplus first_component
32521 @item maint cplus first_component @var{name}
32522 Print the first C@t{++} class/namespace component of @var{name}.
32524 @kindex maint cplus namespace
32525 @item maint cplus namespace
32526 Print the list of possible C@t{++} namespaces.
32528 @kindex maint demangle
32529 @item maint demangle @var{name}
32530 Demangle a C@t{++} or Objective-C mangled @var{name}.
32532 @kindex maint deprecate
32533 @kindex maint undeprecate
32534 @cindex deprecated commands
32535 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
32536 @itemx maint undeprecate @var{command}
32537 Deprecate or undeprecate the named @var{command}. Deprecated commands
32538 cause @value{GDBN} to issue a warning when you use them. The optional
32539 argument @var{replacement} says which newer command should be used in
32540 favor of the deprecated one; if it is given, @value{GDBN} will mention
32541 the replacement as part of the warning.
32543 @kindex maint dump-me
32544 @item maint dump-me
32545 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
32546 Cause a fatal signal in the debugger and force it to dump its core.
32547 This is supported only on systems which support aborting a program
32548 with the @code{SIGQUIT} signal.
32550 @kindex maint internal-error
32551 @kindex maint internal-warning
32552 @item maint internal-error @r{[}@var{message-text}@r{]}
32553 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
32554 Cause @value{GDBN} to call the internal function @code{internal_error}
32555 or @code{internal_warning} and hence behave as though an internal error
32556 or internal warning has been detected. In addition to reporting the
32557 internal problem, these functions give the user the opportunity to
32558 either quit @value{GDBN} or create a core file of the current
32559 @value{GDBN} session.
32561 These commands take an optional parameter @var{message-text} that is
32562 used as the text of the error or warning message.
32564 Here's an example of using @code{internal-error}:
32567 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
32568 @dots{}/maint.c:121: internal-error: testing, 1, 2
32569 A problem internal to GDB has been detected. Further
32570 debugging may prove unreliable.
32571 Quit this debugging session? (y or n) @kbd{n}
32572 Create a core file? (y or n) @kbd{n}
32576 @cindex @value{GDBN} internal error
32577 @cindex internal errors, control of @value{GDBN} behavior
32579 @kindex maint set internal-error
32580 @kindex maint show internal-error
32581 @kindex maint set internal-warning
32582 @kindex maint show internal-warning
32583 @item maint set internal-error @var{action} [ask|yes|no]
32584 @itemx maint show internal-error @var{action}
32585 @itemx maint set internal-warning @var{action} [ask|yes|no]
32586 @itemx maint show internal-warning @var{action}
32587 When @value{GDBN} reports an internal problem (error or warning) it
32588 gives the user the opportunity to both quit @value{GDBN} and create a
32589 core file of the current @value{GDBN} session. These commands let you
32590 override the default behaviour for each particular @var{action},
32591 described in the table below.
32595 You can specify that @value{GDBN} should always (yes) or never (no)
32596 quit. The default is to ask the user what to do.
32599 You can specify that @value{GDBN} should always (yes) or never (no)
32600 create a core file. The default is to ask the user what to do.
32603 @kindex maint packet
32604 @item maint packet @var{text}
32605 If @value{GDBN} is talking to an inferior via the serial protocol,
32606 then this command sends the string @var{text} to the inferior, and
32607 displays the response packet. @value{GDBN} supplies the initial
32608 @samp{$} character, the terminating @samp{#} character, and the
32611 @kindex maint print architecture
32612 @item maint print architecture @r{[}@var{file}@r{]}
32613 Print the entire architecture configuration. The optional argument
32614 @var{file} names the file where the output goes.
32616 @kindex maint print c-tdesc
32617 @item maint print c-tdesc
32618 Print the current target description (@pxref{Target Descriptions}) as
32619 a C source file. The created source file can be used in @value{GDBN}
32620 when an XML parser is not available to parse the description.
32622 @kindex maint print dummy-frames
32623 @item maint print dummy-frames
32624 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
32627 (@value{GDBP}) @kbd{b add}
32629 (@value{GDBP}) @kbd{print add(2,3)}
32630 Breakpoint 2, add (a=2, b=3) at @dots{}
32632 The program being debugged stopped while in a function called from GDB.
32634 (@value{GDBP}) @kbd{maint print dummy-frames}
32635 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
32636 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
32637 call_lo=0x01014000 call_hi=0x01014001
32641 Takes an optional file parameter.
32643 @kindex maint print registers
32644 @kindex maint print raw-registers
32645 @kindex maint print cooked-registers
32646 @kindex maint print register-groups
32647 @kindex maint print remote-registers
32648 @item maint print registers @r{[}@var{file}@r{]}
32649 @itemx maint print raw-registers @r{[}@var{file}@r{]}
32650 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
32651 @itemx maint print register-groups @r{[}@var{file}@r{]}
32652 @itemx maint print remote-registers @r{[}@var{file}@r{]}
32653 Print @value{GDBN}'s internal register data structures.
32655 The command @code{maint print raw-registers} includes the contents of
32656 the raw register cache; the command @code{maint print
32657 cooked-registers} includes the (cooked) value of all registers,
32658 including registers which aren't available on the target nor visible
32659 to user; the command @code{maint print register-groups} includes the
32660 groups that each register is a member of; and the command @code{maint
32661 print remote-registers} includes the remote target's register numbers
32662 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
32663 @value{GDBN} Internals}.
32665 These commands take an optional parameter, a file name to which to
32666 write the information.
32668 @kindex maint print reggroups
32669 @item maint print reggroups @r{[}@var{file}@r{]}
32670 Print @value{GDBN}'s internal register group data structures. The
32671 optional argument @var{file} tells to what file to write the
32674 The register groups info looks like this:
32677 (@value{GDBP}) @kbd{maint print reggroups}
32690 This command forces @value{GDBN} to flush its internal register cache.
32692 @kindex maint print objfiles
32693 @cindex info for known object files
32694 @item maint print objfiles
32695 Print a dump of all known object files. For each object file, this
32696 command prints its name, address in memory, and all of its psymtabs
32699 @kindex maint print section-scripts
32700 @cindex info for known .debug_gdb_scripts-loaded scripts
32701 @item maint print section-scripts [@var{regexp}]
32702 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
32703 If @var{regexp} is specified, only print scripts loaded by object files
32704 matching @var{regexp}.
32705 For each script, this command prints its name as specified in the objfile,
32706 and the full path if known.
32707 @xref{.debug_gdb_scripts section}.
32709 @kindex maint print statistics
32710 @cindex bcache statistics
32711 @item maint print statistics
32712 This command prints, for each object file in the program, various data
32713 about that object file followed by the byte cache (@dfn{bcache})
32714 statistics for the object file. The objfile data includes the number
32715 of minimal, partial, full, and stabs symbols, the number of types
32716 defined by the objfile, the number of as yet unexpanded psym tables,
32717 the number of line tables and string tables, and the amount of memory
32718 used by the various tables. The bcache statistics include the counts,
32719 sizes, and counts of duplicates of all and unique objects, max,
32720 average, and median entry size, total memory used and its overhead and
32721 savings, and various measures of the hash table size and chain
32724 @kindex maint print target-stack
32725 @cindex target stack description
32726 @item maint print target-stack
32727 A @dfn{target} is an interface between the debugger and a particular
32728 kind of file or process. Targets can be stacked in @dfn{strata},
32729 so that more than one target can potentially respond to a request.
32730 In particular, memory accesses will walk down the stack of targets
32731 until they find a target that is interested in handling that particular
32734 This command prints a short description of each layer that was pushed on
32735 the @dfn{target stack}, starting from the top layer down to the bottom one.
32737 @kindex maint print type
32738 @cindex type chain of a data type
32739 @item maint print type @var{expr}
32740 Print the type chain for a type specified by @var{expr}. The argument
32741 can be either a type name or a symbol. If it is a symbol, the type of
32742 that symbol is described. The type chain produced by this command is
32743 a recursive definition of the data type as stored in @value{GDBN}'s
32744 data structures, including its flags and contained types.
32746 @kindex maint set dwarf2 always-disassemble
32747 @kindex maint show dwarf2 always-disassemble
32748 @item maint set dwarf2 always-disassemble
32749 @item maint show dwarf2 always-disassemble
32750 Control the behavior of @code{info address} when using DWARF debugging
32753 The default is @code{off}, which means that @value{GDBN} should try to
32754 describe a variable's location in an easily readable format. When
32755 @code{on}, @value{GDBN} will instead display the DWARF location
32756 expression in an assembly-like format. Note that some locations are
32757 too complex for @value{GDBN} to describe simply; in this case you will
32758 always see the disassembly form.
32760 Here is an example of the resulting disassembly:
32763 (gdb) info addr argc
32764 Symbol "argc" is a complex DWARF expression:
32768 For more information on these expressions, see
32769 @uref{http://www.dwarfstd.org/, the DWARF standard}.
32771 @kindex maint set dwarf2 max-cache-age
32772 @kindex maint show dwarf2 max-cache-age
32773 @item maint set dwarf2 max-cache-age
32774 @itemx maint show dwarf2 max-cache-age
32775 Control the DWARF 2 compilation unit cache.
32777 @cindex DWARF 2 compilation units cache
32778 In object files with inter-compilation-unit references, such as those
32779 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
32780 reader needs to frequently refer to previously read compilation units.
32781 This setting controls how long a compilation unit will remain in the
32782 cache if it is not referenced. A higher limit means that cached
32783 compilation units will be stored in memory longer, and more total
32784 memory will be used. Setting it to zero disables caching, which will
32785 slow down @value{GDBN} startup, but reduce memory consumption.
32787 @kindex maint set profile
32788 @kindex maint show profile
32789 @cindex profiling GDB
32790 @item maint set profile
32791 @itemx maint show profile
32792 Control profiling of @value{GDBN}.
32794 Profiling will be disabled until you use the @samp{maint set profile}
32795 command to enable it. When you enable profiling, the system will begin
32796 collecting timing and execution count data; when you disable profiling or
32797 exit @value{GDBN}, the results will be written to a log file. Remember that
32798 if you use profiling, @value{GDBN} will overwrite the profiling log file
32799 (often called @file{gmon.out}). If you have a record of important profiling
32800 data in a @file{gmon.out} file, be sure to move it to a safe location.
32802 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
32803 compiled with the @samp{-pg} compiler option.
32805 @kindex maint set show-debug-regs
32806 @kindex maint show show-debug-regs
32807 @cindex hardware debug registers
32808 @item maint set show-debug-regs
32809 @itemx maint show show-debug-regs
32810 Control whether to show variables that mirror the hardware debug
32811 registers. Use @code{ON} to enable, @code{OFF} to disable. If
32812 enabled, the debug registers values are shown when @value{GDBN} inserts or
32813 removes a hardware breakpoint or watchpoint, and when the inferior
32814 triggers a hardware-assisted breakpoint or watchpoint.
32816 @kindex maint set show-all-tib
32817 @kindex maint show show-all-tib
32818 @item maint set show-all-tib
32819 @itemx maint show show-all-tib
32820 Control whether to show all non zero areas within a 1k block starting
32821 at thread local base, when using the @samp{info w32 thread-information-block}
32824 @kindex maint space
32825 @cindex memory used by commands
32827 Control whether to display memory usage for each command. If set to a
32828 nonzero value, @value{GDBN} will display how much memory each command
32829 took, following the command's own output. This can also be requested
32830 by invoking @value{GDBN} with the @option{--statistics} command-line
32831 switch (@pxref{Mode Options}).
32834 @cindex time of command execution
32836 Control whether to display the execution time for each command. If
32837 set to a nonzero value, @value{GDBN} will display how much time it
32838 took to execute each command, following the command's own output.
32839 The time is not printed for the commands that run the target, since
32840 there's no mechanism currently to compute how much time was spend
32841 by @value{GDBN} and how much time was spend by the program been debugged.
32842 it's not possibly currently
32843 This can also be requested by invoking @value{GDBN} with the
32844 @option{--statistics} command-line switch (@pxref{Mode Options}).
32846 @kindex maint translate-address
32847 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
32848 Find the symbol stored at the location specified by the address
32849 @var{addr} and an optional section name @var{section}. If found,
32850 @value{GDBN} prints the name of the closest symbol and an offset from
32851 the symbol's location to the specified address. This is similar to
32852 the @code{info address} command (@pxref{Symbols}), except that this
32853 command also allows to find symbols in other sections.
32855 If section was not specified, the section in which the symbol was found
32856 is also printed. For dynamically linked executables, the name of
32857 executable or shared library containing the symbol is printed as well.
32861 The following command is useful for non-interactive invocations of
32862 @value{GDBN}, such as in the test suite.
32865 @item set watchdog @var{nsec}
32866 @kindex set watchdog
32867 @cindex watchdog timer
32868 @cindex timeout for commands
32869 Set the maximum number of seconds @value{GDBN} will wait for the
32870 target operation to finish. If this time expires, @value{GDBN}
32871 reports and error and the command is aborted.
32873 @item show watchdog
32874 Show the current setting of the target wait timeout.
32877 @node Remote Protocol
32878 @appendix @value{GDBN} Remote Serial Protocol
32883 * Stop Reply Packets::
32884 * General Query Packets::
32885 * Architecture-Specific Protocol Details::
32886 * Tracepoint Packets::
32887 * Host I/O Packets::
32889 * Notification Packets::
32890 * Remote Non-Stop::
32891 * Packet Acknowledgment::
32893 * File-I/O Remote Protocol Extension::
32894 * Library List Format::
32895 * Memory Map Format::
32896 * Thread List Format::
32897 * Traceframe Info Format::
32903 There may be occasions when you need to know something about the
32904 protocol---for example, if there is only one serial port to your target
32905 machine, you might want your program to do something special if it
32906 recognizes a packet meant for @value{GDBN}.
32908 In the examples below, @samp{->} and @samp{<-} are used to indicate
32909 transmitted and received data, respectively.
32911 @cindex protocol, @value{GDBN} remote serial
32912 @cindex serial protocol, @value{GDBN} remote
32913 @cindex remote serial protocol
32914 All @value{GDBN} commands and responses (other than acknowledgments
32915 and notifications, see @ref{Notification Packets}) are sent as a
32916 @var{packet}. A @var{packet} is introduced with the character
32917 @samp{$}, the actual @var{packet-data}, and the terminating character
32918 @samp{#} followed by a two-digit @var{checksum}:
32921 @code{$}@var{packet-data}@code{#}@var{checksum}
32925 @cindex checksum, for @value{GDBN} remote
32927 The two-digit @var{checksum} is computed as the modulo 256 sum of all
32928 characters between the leading @samp{$} and the trailing @samp{#} (an
32929 eight bit unsigned checksum).
32931 Implementors should note that prior to @value{GDBN} 5.0 the protocol
32932 specification also included an optional two-digit @var{sequence-id}:
32935 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
32938 @cindex sequence-id, for @value{GDBN} remote
32940 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
32941 has never output @var{sequence-id}s. Stubs that handle packets added
32942 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
32944 When either the host or the target machine receives a packet, the first
32945 response expected is an acknowledgment: either @samp{+} (to indicate
32946 the package was received correctly) or @samp{-} (to request
32950 -> @code{$}@var{packet-data}@code{#}@var{checksum}
32955 The @samp{+}/@samp{-} acknowledgments can be disabled
32956 once a connection is established.
32957 @xref{Packet Acknowledgment}, for details.
32959 The host (@value{GDBN}) sends @var{command}s, and the target (the
32960 debugging stub incorporated in your program) sends a @var{response}. In
32961 the case of step and continue @var{command}s, the response is only sent
32962 when the operation has completed, and the target has again stopped all
32963 threads in all attached processes. This is the default all-stop mode
32964 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
32965 execution mode; see @ref{Remote Non-Stop}, for details.
32967 @var{packet-data} consists of a sequence of characters with the
32968 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
32971 @cindex remote protocol, field separator
32972 Fields within the packet should be separated using @samp{,} @samp{;} or
32973 @samp{:}. Except where otherwise noted all numbers are represented in
32974 @sc{hex} with leading zeros suppressed.
32976 Implementors should note that prior to @value{GDBN} 5.0, the character
32977 @samp{:} could not appear as the third character in a packet (as it
32978 would potentially conflict with the @var{sequence-id}).
32980 @cindex remote protocol, binary data
32981 @anchor{Binary Data}
32982 Binary data in most packets is encoded either as two hexadecimal
32983 digits per byte of binary data. This allowed the traditional remote
32984 protocol to work over connections which were only seven-bit clean.
32985 Some packets designed more recently assume an eight-bit clean
32986 connection, and use a more efficient encoding to send and receive
32989 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
32990 as an escape character. Any escaped byte is transmitted as the escape
32991 character followed by the original character XORed with @code{0x20}.
32992 For example, the byte @code{0x7d} would be transmitted as the two
32993 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
32994 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
32995 @samp{@}}) must always be escaped. Responses sent by the stub
32996 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
32997 is not interpreted as the start of a run-length encoded sequence
33000 Response @var{data} can be run-length encoded to save space.
33001 Run-length encoding replaces runs of identical characters with one
33002 instance of the repeated character, followed by a @samp{*} and a
33003 repeat count. The repeat count is itself sent encoded, to avoid
33004 binary characters in @var{data}: a value of @var{n} is sent as
33005 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33006 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33007 code 32) for a repeat count of 3. (This is because run-length
33008 encoding starts to win for counts 3 or more.) Thus, for example,
33009 @samp{0* } is a run-length encoding of ``0000'': the space character
33010 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33013 The printable characters @samp{#} and @samp{$} or with a numeric value
33014 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33015 seven repeats (@samp{$}) can be expanded using a repeat count of only
33016 five (@samp{"}). For example, @samp{00000000} can be encoded as
33019 The error response returned for some packets includes a two character
33020 error number. That number is not well defined.
33022 @cindex empty response, for unsupported packets
33023 For any @var{command} not supported by the stub, an empty response
33024 (@samp{$#00}) should be returned. That way it is possible to extend the
33025 protocol. A newer @value{GDBN} can tell if a packet is supported based
33028 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33029 commands for register access, and the @samp{m} and @samp{M} commands
33030 for memory access. Stubs that only control single-threaded targets
33031 can implement run control with the @samp{c} (continue), and @samp{s}
33032 (step) commands. Stubs that support multi-threading targets should
33033 support the @samp{vCont} command. All other commands are optional.
33038 The following table provides a complete list of all currently defined
33039 @var{command}s and their corresponding response @var{data}.
33040 @xref{File-I/O Remote Protocol Extension}, for details about the File
33041 I/O extension of the remote protocol.
33043 Each packet's description has a template showing the packet's overall
33044 syntax, followed by an explanation of the packet's meaning. We
33045 include spaces in some of the templates for clarity; these are not
33046 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33047 separate its components. For example, a template like @samp{foo
33048 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33049 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33050 @var{baz}. @value{GDBN} does not transmit a space character between the
33051 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33054 @cindex @var{thread-id}, in remote protocol
33055 @anchor{thread-id syntax}
33056 Several packets and replies include a @var{thread-id} field to identify
33057 a thread. Normally these are positive numbers with a target-specific
33058 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33059 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33062 In addition, the remote protocol supports a multiprocess feature in
33063 which the @var{thread-id} syntax is extended to optionally include both
33064 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33065 The @var{pid} (process) and @var{tid} (thread) components each have the
33066 format described above: a positive number with target-specific
33067 interpretation formatted as a big-endian hex string, literal @samp{-1}
33068 to indicate all processes or threads (respectively), or @samp{0} to
33069 indicate an arbitrary process or thread. Specifying just a process, as
33070 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33071 error to specify all processes but a specific thread, such as
33072 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33073 for those packets and replies explicitly documented to include a process
33074 ID, rather than a @var{thread-id}.
33076 The multiprocess @var{thread-id} syntax extensions are only used if both
33077 @value{GDBN} and the stub report support for the @samp{multiprocess}
33078 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33081 Note that all packet forms beginning with an upper- or lower-case
33082 letter, other than those described here, are reserved for future use.
33084 Here are the packet descriptions.
33089 @cindex @samp{!} packet
33090 @anchor{extended mode}
33091 Enable extended mode. In extended mode, the remote server is made
33092 persistent. The @samp{R} packet is used to restart the program being
33098 The remote target both supports and has enabled extended mode.
33102 @cindex @samp{?} packet
33103 Indicate the reason the target halted. The reply is the same as for
33104 step and continue. This packet has a special interpretation when the
33105 target is in non-stop mode; see @ref{Remote Non-Stop}.
33108 @xref{Stop Reply Packets}, for the reply specifications.
33110 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33111 @cindex @samp{A} packet
33112 Initialized @code{argv[]} array passed into program. @var{arglen}
33113 specifies the number of bytes in the hex encoded byte stream
33114 @var{arg}. See @code{gdbserver} for more details.
33119 The arguments were set.
33125 @cindex @samp{b} packet
33126 (Don't use this packet; its behavior is not well-defined.)
33127 Change the serial line speed to @var{baud}.
33129 JTC: @emph{When does the transport layer state change? When it's
33130 received, or after the ACK is transmitted. In either case, there are
33131 problems if the command or the acknowledgment packet is dropped.}
33133 Stan: @emph{If people really wanted to add something like this, and get
33134 it working for the first time, they ought to modify ser-unix.c to send
33135 some kind of out-of-band message to a specially-setup stub and have the
33136 switch happen "in between" packets, so that from remote protocol's point
33137 of view, nothing actually happened.}
33139 @item B @var{addr},@var{mode}
33140 @cindex @samp{B} packet
33141 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33142 breakpoint at @var{addr}.
33144 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33145 (@pxref{insert breakpoint or watchpoint packet}).
33147 @cindex @samp{bc} packet
33150 Backward continue. Execute the target system in reverse. No parameter.
33151 @xref{Reverse Execution}, for more information.
33154 @xref{Stop Reply Packets}, for the reply specifications.
33156 @cindex @samp{bs} packet
33159 Backward single step. Execute one instruction in reverse. No parameter.
33160 @xref{Reverse Execution}, for more information.
33163 @xref{Stop Reply Packets}, for the reply specifications.
33165 @item c @r{[}@var{addr}@r{]}
33166 @cindex @samp{c} packet
33167 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33168 resume at current address.
33170 This packet is deprecated for multi-threading support. @xref{vCont
33174 @xref{Stop Reply Packets}, for the reply specifications.
33176 @item C @var{sig}@r{[};@var{addr}@r{]}
33177 @cindex @samp{C} packet
33178 Continue with signal @var{sig} (hex signal number). If
33179 @samp{;@var{addr}} is omitted, resume at same address.
33181 This packet is deprecated for multi-threading support. @xref{vCont
33185 @xref{Stop Reply Packets}, for the reply specifications.
33188 @cindex @samp{d} packet
33191 Don't use this packet; instead, define a general set packet
33192 (@pxref{General Query Packets}).
33196 @cindex @samp{D} packet
33197 The first form of the packet is used to detach @value{GDBN} from the
33198 remote system. It is sent to the remote target
33199 before @value{GDBN} disconnects via the @code{detach} command.
33201 The second form, including a process ID, is used when multiprocess
33202 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33203 detach only a specific process. The @var{pid} is specified as a
33204 big-endian hex string.
33214 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33215 @cindex @samp{F} packet
33216 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33217 This is part of the File-I/O protocol extension. @xref{File-I/O
33218 Remote Protocol Extension}, for the specification.
33221 @anchor{read registers packet}
33222 @cindex @samp{g} packet
33223 Read general registers.
33227 @item @var{XX@dots{}}
33228 Each byte of register data is described by two hex digits. The bytes
33229 with the register are transmitted in target byte order. The size of
33230 each register and their position within the @samp{g} packet are
33231 determined by the @value{GDBN} internal gdbarch functions
33232 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33233 specification of several standard @samp{g} packets is specified below.
33235 When reading registers from a trace frame (@pxref{Analyze Collected
33236 Data,,Using the Collected Data}), the stub may also return a string of
33237 literal @samp{x}'s in place of the register data digits, to indicate
33238 that the corresponding register has not been collected, thus its value
33239 is unavailable. For example, for an architecture with 4 registers of
33240 4 bytes each, the following reply indicates to @value{GDBN} that
33241 registers 0 and 2 have not been collected, while registers 1 and 3
33242 have been collected, and both have zero value:
33246 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33253 @item G @var{XX@dots{}}
33254 @cindex @samp{G} packet
33255 Write general registers. @xref{read registers packet}, for a
33256 description of the @var{XX@dots{}} data.
33266 @item H @var{op} @var{thread-id}
33267 @cindex @samp{H} packet
33268 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33269 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33270 it should be @samp{c} for step and continue operations (note that this
33271 is deprecated, supporting the @samp{vCont} command is a better
33272 option), @samp{g} for other operations. The thread designator
33273 @var{thread-id} has the format and interpretation described in
33274 @ref{thread-id syntax}.
33285 @c 'H': How restrictive (or permissive) is the thread model. If a
33286 @c thread is selected and stopped, are other threads allowed
33287 @c to continue to execute? As I mentioned above, I think the
33288 @c semantics of each command when a thread is selected must be
33289 @c described. For example:
33291 @c 'g': If the stub supports threads and a specific thread is
33292 @c selected, returns the register block from that thread;
33293 @c otherwise returns current registers.
33295 @c 'G' If the stub supports threads and a specific thread is
33296 @c selected, sets the registers of the register block of
33297 @c that thread; otherwise sets current registers.
33299 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33300 @anchor{cycle step packet}
33301 @cindex @samp{i} packet
33302 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33303 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33304 step starting at that address.
33307 @cindex @samp{I} packet
33308 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33312 @cindex @samp{k} packet
33315 FIXME: @emph{There is no description of how to operate when a specific
33316 thread context has been selected (i.e.@: does 'k' kill only that
33319 @item m @var{addr},@var{length}
33320 @cindex @samp{m} packet
33321 Read @var{length} bytes of memory starting at address @var{addr}.
33322 Note that @var{addr} may not be aligned to any particular boundary.
33324 The stub need not use any particular size or alignment when gathering
33325 data from memory for the response; even if @var{addr} is word-aligned
33326 and @var{length} is a multiple of the word size, the stub is free to
33327 use byte accesses, or not. For this reason, this packet may not be
33328 suitable for accessing memory-mapped I/O devices.
33329 @cindex alignment of remote memory accesses
33330 @cindex size of remote memory accesses
33331 @cindex memory, alignment and size of remote accesses
33335 @item @var{XX@dots{}}
33336 Memory contents; each byte is transmitted as a two-digit hexadecimal
33337 number. The reply may contain fewer bytes than requested if the
33338 server was able to read only part of the region of memory.
33343 @item M @var{addr},@var{length}:@var{XX@dots{}}
33344 @cindex @samp{M} packet
33345 Write @var{length} bytes of memory starting at address @var{addr}.
33346 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33347 hexadecimal number.
33354 for an error (this includes the case where only part of the data was
33359 @cindex @samp{p} packet
33360 Read the value of register @var{n}; @var{n} is in hex.
33361 @xref{read registers packet}, for a description of how the returned
33362 register value is encoded.
33366 @item @var{XX@dots{}}
33367 the register's value
33371 Indicating an unrecognized @var{query}.
33374 @item P @var{n@dots{}}=@var{r@dots{}}
33375 @anchor{write register packet}
33376 @cindex @samp{P} packet
33377 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33378 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33379 digits for each byte in the register (target byte order).
33389 @item q @var{name} @var{params}@dots{}
33390 @itemx Q @var{name} @var{params}@dots{}
33391 @cindex @samp{q} packet
33392 @cindex @samp{Q} packet
33393 General query (@samp{q}) and set (@samp{Q}). These packets are
33394 described fully in @ref{General Query Packets}.
33397 @cindex @samp{r} packet
33398 Reset the entire system.
33400 Don't use this packet; use the @samp{R} packet instead.
33403 @cindex @samp{R} packet
33404 Restart the program being debugged. @var{XX}, while needed, is ignored.
33405 This packet is only available in extended mode (@pxref{extended mode}).
33407 The @samp{R} packet has no reply.
33409 @item s @r{[}@var{addr}@r{]}
33410 @cindex @samp{s} packet
33411 Single step. @var{addr} is the address at which to resume. If
33412 @var{addr} is omitted, resume at same address.
33414 This packet is deprecated for multi-threading support. @xref{vCont
33418 @xref{Stop Reply Packets}, for the reply specifications.
33420 @item S @var{sig}@r{[};@var{addr}@r{]}
33421 @anchor{step with signal packet}
33422 @cindex @samp{S} packet
33423 Step with signal. This is analogous to the @samp{C} packet, but
33424 requests a single-step, rather than a normal resumption of execution.
33426 This packet is deprecated for multi-threading support. @xref{vCont
33430 @xref{Stop Reply Packets}, for the reply specifications.
33432 @item t @var{addr}:@var{PP},@var{MM}
33433 @cindex @samp{t} packet
33434 Search backwards starting at address @var{addr} for a match with pattern
33435 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33436 @var{addr} must be at least 3 digits.
33438 @item T @var{thread-id}
33439 @cindex @samp{T} packet
33440 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33445 thread is still alive
33451 Packets starting with @samp{v} are identified by a multi-letter name,
33452 up to the first @samp{;} or @samp{?} (or the end of the packet).
33454 @item vAttach;@var{pid}
33455 @cindex @samp{vAttach} packet
33456 Attach to a new process with the specified process ID @var{pid}.
33457 The process ID is a
33458 hexadecimal integer identifying the process. In all-stop mode, all
33459 threads in the attached process are stopped; in non-stop mode, it may be
33460 attached without being stopped if that is supported by the target.
33462 @c In non-stop mode, on a successful vAttach, the stub should set the
33463 @c current thread to a thread of the newly-attached process. After
33464 @c attaching, GDB queries for the attached process's thread ID with qC.
33465 @c Also note that, from a user perspective, whether or not the
33466 @c target is stopped on attach in non-stop mode depends on whether you
33467 @c use the foreground or background version of the attach command, not
33468 @c on what vAttach does; GDB does the right thing with respect to either
33469 @c stopping or restarting threads.
33471 This packet is only available in extended mode (@pxref{extended mode}).
33477 @item @r{Any stop packet}
33478 for success in all-stop mode (@pxref{Stop Reply Packets})
33480 for success in non-stop mode (@pxref{Remote Non-Stop})
33483 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33484 @cindex @samp{vCont} packet
33485 @anchor{vCont packet}
33486 Resume the inferior, specifying different actions for each thread.
33487 If an action is specified with no @var{thread-id}, then it is applied to any
33488 threads that don't have a specific action specified; if no default action is
33489 specified then other threads should remain stopped in all-stop mode and
33490 in their current state in non-stop mode.
33491 Specifying multiple
33492 default actions is an error; specifying no actions is also an error.
33493 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33495 Currently supported actions are:
33501 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33505 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33510 The optional argument @var{addr} normally associated with the
33511 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33512 not supported in @samp{vCont}.
33514 The @samp{t} action is only relevant in non-stop mode
33515 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33516 A stop reply should be generated for any affected thread not already stopped.
33517 When a thread is stopped by means of a @samp{t} action,
33518 the corresponding stop reply should indicate that the thread has stopped with
33519 signal @samp{0}, regardless of whether the target uses some other signal
33520 as an implementation detail.
33523 @xref{Stop Reply Packets}, for the reply specifications.
33526 @cindex @samp{vCont?} packet
33527 Request a list of actions supported by the @samp{vCont} packet.
33531 @item vCont@r{[};@var{action}@dots{}@r{]}
33532 The @samp{vCont} packet is supported. Each @var{action} is a supported
33533 command in the @samp{vCont} packet.
33535 The @samp{vCont} packet is not supported.
33538 @item vFile:@var{operation}:@var{parameter}@dots{}
33539 @cindex @samp{vFile} packet
33540 Perform a file operation on the target system. For details,
33541 see @ref{Host I/O Packets}.
33543 @item vFlashErase:@var{addr},@var{length}
33544 @cindex @samp{vFlashErase} packet
33545 Direct the stub to erase @var{length} bytes of flash starting at
33546 @var{addr}. The region may enclose any number of flash blocks, but
33547 its start and end must fall on block boundaries, as indicated by the
33548 flash block size appearing in the memory map (@pxref{Memory Map
33549 Format}). @value{GDBN} groups flash memory programming operations
33550 together, and sends a @samp{vFlashDone} request after each group; the
33551 stub is allowed to delay erase operation until the @samp{vFlashDone}
33552 packet is received.
33554 The stub must support @samp{vCont} if it reports support for
33555 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
33556 this case @samp{vCont} actions can be specified to apply to all threads
33557 in a process by using the @samp{p@var{pid}.-1} form of the
33568 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
33569 @cindex @samp{vFlashWrite} packet
33570 Direct the stub to write data to flash address @var{addr}. The data
33571 is passed in binary form using the same encoding as for the @samp{X}
33572 packet (@pxref{Binary Data}). The memory ranges specified by
33573 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
33574 not overlap, and must appear in order of increasing addresses
33575 (although @samp{vFlashErase} packets for higher addresses may already
33576 have been received; the ordering is guaranteed only between
33577 @samp{vFlashWrite} packets). If a packet writes to an address that was
33578 neither erased by a preceding @samp{vFlashErase} packet nor by some other
33579 target-specific method, the results are unpredictable.
33587 for vFlashWrite addressing non-flash memory
33593 @cindex @samp{vFlashDone} packet
33594 Indicate to the stub that flash programming operation is finished.
33595 The stub is permitted to delay or batch the effects of a group of
33596 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
33597 @samp{vFlashDone} packet is received. The contents of the affected
33598 regions of flash memory are unpredictable until the @samp{vFlashDone}
33599 request is completed.
33601 @item vKill;@var{pid}
33602 @cindex @samp{vKill} packet
33603 Kill the process with the specified process ID. @var{pid} is a
33604 hexadecimal integer identifying the process. This packet is used in
33605 preference to @samp{k} when multiprocess protocol extensions are
33606 supported; see @ref{multiprocess extensions}.
33616 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
33617 @cindex @samp{vRun} packet
33618 Run the program @var{filename}, passing it each @var{argument} on its
33619 command line. The file and arguments are hex-encoded strings. If
33620 @var{filename} is an empty string, the stub may use a default program
33621 (e.g.@: the last program run). The program is created in the stopped
33624 @c FIXME: What about non-stop mode?
33626 This packet is only available in extended mode (@pxref{extended mode}).
33632 @item @r{Any stop packet}
33633 for success (@pxref{Stop Reply Packets})
33637 @anchor{vStopped packet}
33638 @cindex @samp{vStopped} packet
33640 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
33641 reply and prompt for the stub to report another one.
33645 @item @r{Any stop packet}
33646 if there is another unreported stop event (@pxref{Stop Reply Packets})
33648 if there are no unreported stop events
33651 @item X @var{addr},@var{length}:@var{XX@dots{}}
33653 @cindex @samp{X} packet
33654 Write data to memory, where the data is transmitted in binary.
33655 @var{addr} is address, @var{length} is number of bytes,
33656 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
33666 @item z @var{type},@var{addr},@var{kind}
33667 @itemx Z @var{type},@var{addr},@var{kind}
33668 @anchor{insert breakpoint or watchpoint packet}
33669 @cindex @samp{z} packet
33670 @cindex @samp{Z} packets
33671 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
33672 watchpoint starting at address @var{address} of kind @var{kind}.
33674 Each breakpoint and watchpoint packet @var{type} is documented
33677 @emph{Implementation notes: A remote target shall return an empty string
33678 for an unrecognized breakpoint or watchpoint packet @var{type}. A
33679 remote target shall support either both or neither of a given
33680 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
33681 avoid potential problems with duplicate packets, the operations should
33682 be implemented in an idempotent way.}
33684 @item z0,@var{addr},@var{kind}
33685 @itemx Z0,@var{addr},@var{kind}
33686 @cindex @samp{z0} packet
33687 @cindex @samp{Z0} packet
33688 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
33689 @var{addr} of type @var{kind}.
33691 A memory breakpoint is implemented by replacing the instruction at
33692 @var{addr} with a software breakpoint or trap instruction. The
33693 @var{kind} is target-specific and typically indicates the size of
33694 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
33695 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
33696 architectures have additional meanings for @var{kind};
33697 see @ref{Architecture-Specific Protocol Details}.
33699 @emph{Implementation note: It is possible for a target to copy or move
33700 code that contains memory breakpoints (e.g., when implementing
33701 overlays). The behavior of this packet, in the presence of such a
33702 target, is not defined.}
33714 @item z1,@var{addr},@var{kind}
33715 @itemx Z1,@var{addr},@var{kind}
33716 @cindex @samp{z1} packet
33717 @cindex @samp{Z1} packet
33718 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
33719 address @var{addr}.
33721 A hardware breakpoint is implemented using a mechanism that is not
33722 dependant on being able to modify the target's memory. @var{kind}
33723 has the same meaning as in @samp{Z0} packets.
33725 @emph{Implementation note: A hardware breakpoint is not affected by code
33738 @item z2,@var{addr},@var{kind}
33739 @itemx Z2,@var{addr},@var{kind}
33740 @cindex @samp{z2} packet
33741 @cindex @samp{Z2} packet
33742 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
33743 @var{kind} is interpreted as the number of bytes to watch.
33755 @item z3,@var{addr},@var{kind}
33756 @itemx Z3,@var{addr},@var{kind}
33757 @cindex @samp{z3} packet
33758 @cindex @samp{Z3} packet
33759 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
33760 @var{kind} is interpreted as the number of bytes to watch.
33772 @item z4,@var{addr},@var{kind}
33773 @itemx Z4,@var{addr},@var{kind}
33774 @cindex @samp{z4} packet
33775 @cindex @samp{Z4} packet
33776 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
33777 @var{kind} is interpreted as the number of bytes to watch.
33791 @node Stop Reply Packets
33792 @section Stop Reply Packets
33793 @cindex stop reply packets
33795 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
33796 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
33797 receive any of the below as a reply. Except for @samp{?}
33798 and @samp{vStopped}, that reply is only returned
33799 when the target halts. In the below the exact meaning of @dfn{signal
33800 number} is defined by the header @file{include/gdb/signals.h} in the
33801 @value{GDBN} source code.
33803 As in the description of request packets, we include spaces in the
33804 reply templates for clarity; these are not part of the reply packet's
33805 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
33811 The program received signal number @var{AA} (a two-digit hexadecimal
33812 number). This is equivalent to a @samp{T} response with no
33813 @var{n}:@var{r} pairs.
33815 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
33816 @cindex @samp{T} packet reply
33817 The program received signal number @var{AA} (a two-digit hexadecimal
33818 number). This is equivalent to an @samp{S} response, except that the
33819 @samp{@var{n}:@var{r}} pairs can carry values of important registers
33820 and other information directly in the stop reply packet, reducing
33821 round-trip latency. Single-step and breakpoint traps are reported
33822 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
33826 If @var{n} is a hexadecimal number, it is a register number, and the
33827 corresponding @var{r} gives that register's value. @var{r} is a
33828 series of bytes in target byte order, with each byte given by a
33829 two-digit hex number.
33832 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
33833 the stopped thread, as specified in @ref{thread-id syntax}.
33836 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
33837 the core on which the stop event was detected.
33840 If @var{n} is a recognized @dfn{stop reason}, it describes a more
33841 specific event that stopped the target. The currently defined stop
33842 reasons are listed below. @var{aa} should be @samp{05}, the trap
33843 signal. At most one stop reason should be present.
33846 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
33847 and go on to the next; this allows us to extend the protocol in the
33851 The currently defined stop reasons are:
33857 The packet indicates a watchpoint hit, and @var{r} is the data address, in
33860 @cindex shared library events, remote reply
33862 The packet indicates that the loaded libraries have changed.
33863 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
33864 list of loaded libraries. @var{r} is ignored.
33866 @cindex replay log events, remote reply
33868 The packet indicates that the target cannot continue replaying
33869 logged execution events, because it has reached the end (or the
33870 beginning when executing backward) of the log. The value of @var{r}
33871 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
33872 for more information.
33876 @itemx W @var{AA} ; process:@var{pid}
33877 The process exited, and @var{AA} is the exit status. This is only
33878 applicable to certain targets.
33880 The second form of the response, including the process ID of the exited
33881 process, can be used only when @value{GDBN} has reported support for
33882 multiprocess protocol extensions; see @ref{multiprocess extensions}.
33883 The @var{pid} is formatted as a big-endian hex string.
33886 @itemx X @var{AA} ; process:@var{pid}
33887 The process terminated with signal @var{AA}.
33889 The second form of the response, including the process ID of the
33890 terminated process, can be used only when @value{GDBN} has reported
33891 support for multiprocess protocol extensions; see @ref{multiprocess
33892 extensions}. The @var{pid} is formatted as a big-endian hex string.
33894 @item O @var{XX}@dots{}
33895 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
33896 written as the program's console output. This can happen at any time
33897 while the program is running and the debugger should continue to wait
33898 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
33900 @item F @var{call-id},@var{parameter}@dots{}
33901 @var{call-id} is the identifier which says which host system call should
33902 be called. This is just the name of the function. Translation into the
33903 correct system call is only applicable as it's defined in @value{GDBN}.
33904 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
33907 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
33908 this very system call.
33910 The target replies with this packet when it expects @value{GDBN} to
33911 call a host system call on behalf of the target. @value{GDBN} replies
33912 with an appropriate @samp{F} packet and keeps up waiting for the next
33913 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
33914 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
33915 Protocol Extension}, for more details.
33919 @node General Query Packets
33920 @section General Query Packets
33921 @cindex remote query requests
33923 Packets starting with @samp{q} are @dfn{general query packets};
33924 packets starting with @samp{Q} are @dfn{general set packets}. General
33925 query and set packets are a semi-unified form for retrieving and
33926 sending information to and from the stub.
33928 The initial letter of a query or set packet is followed by a name
33929 indicating what sort of thing the packet applies to. For example,
33930 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
33931 definitions with the stub. These packet names follow some
33936 The name must not contain commas, colons or semicolons.
33938 Most @value{GDBN} query and set packets have a leading upper case
33941 The names of custom vendor packets should use a company prefix, in
33942 lower case, followed by a period. For example, packets designed at
33943 the Acme Corporation might begin with @samp{qacme.foo} (for querying
33944 foos) or @samp{Qacme.bar} (for setting bars).
33947 The name of a query or set packet should be separated from any
33948 parameters by a @samp{:}; the parameters themselves should be
33949 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
33950 full packet name, and check for a separator or the end of the packet,
33951 in case two packet names share a common prefix. New packets should not begin
33952 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
33953 packets predate these conventions, and have arguments without any terminator
33954 for the packet name; we suspect they are in widespread use in places that
33955 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
33956 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
33959 Like the descriptions of the other packets, each description here
33960 has a template showing the packet's overall syntax, followed by an
33961 explanation of the packet's meaning. We include spaces in some of the
33962 templates for clarity; these are not part of the packet's syntax. No
33963 @value{GDBN} packet uses spaces to separate its components.
33965 Here are the currently defined query and set packets:
33969 @item QAllow:@var{op}:@var{val}@dots{}
33970 @cindex @samp{QAllow} packet
33971 Specify which operations @value{GDBN} expects to request of the
33972 target, as a semicolon-separated list of operation name and value
33973 pairs. Possible values for @var{op} include @samp{WriteReg},
33974 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
33975 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
33976 indicating that @value{GDBN} will not request the operation, or 1,
33977 indicating that it may. (The target can then use this to set up its
33978 own internals optimally, for instance if the debugger never expects to
33979 insert breakpoints, it may not need to install its own trap handler.)
33982 @cindex current thread, remote request
33983 @cindex @samp{qC} packet
33984 Return the current thread ID.
33988 @item QC @var{thread-id}
33989 Where @var{thread-id} is a thread ID as documented in
33990 @ref{thread-id syntax}.
33991 @item @r{(anything else)}
33992 Any other reply implies the old thread ID.
33995 @item qCRC:@var{addr},@var{length}
33996 @cindex CRC of memory block, remote request
33997 @cindex @samp{qCRC} packet
33998 Compute the CRC checksum of a block of memory using CRC-32 defined in
33999 IEEE 802.3. The CRC is computed byte at a time, taking the most
34000 significant bit of each byte first. The initial pattern code
34001 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34003 @emph{Note:} This is the same CRC used in validating separate debug
34004 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34005 Files}). However the algorithm is slightly different. When validating
34006 separate debug files, the CRC is computed taking the @emph{least}
34007 significant bit of each byte first, and the final result is inverted to
34008 detect trailing zeros.
34013 An error (such as memory fault)
34014 @item C @var{crc32}
34015 The specified memory region's checksum is @var{crc32}.
34018 @item QDisableRandomization:@var{value}
34019 @cindex disable address space randomization, remote request
34020 @cindex @samp{QDisableRandomization} packet
34021 Some target operating systems will randomize the virtual address space
34022 of the inferior process as a security feature, but provide a feature
34023 to disable such randomization, e.g.@: to allow for a more deterministic
34024 debugging experience. On such systems, this packet with a @var{value}
34025 of 1 directs the target to disable address space randomization for
34026 processes subsequently started via @samp{vRun} packets, while a packet
34027 with a @var{value} of 0 tells the target to enable address space
34030 This packet is only available in extended mode (@pxref{extended mode}).
34035 The request succeeded.
34038 An error occurred. @var{nn} are hex digits.
34041 An empty reply indicates that @samp{QDisableRandomization} is not supported
34045 This packet is not probed by default; the remote stub must request it,
34046 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34047 This should only be done on targets that actually support disabling
34048 address space randomization.
34051 @itemx qsThreadInfo
34052 @cindex list active threads, remote request
34053 @cindex @samp{qfThreadInfo} packet
34054 @cindex @samp{qsThreadInfo} packet
34055 Obtain a list of all active thread IDs from the target (OS). Since there
34056 may be too many active threads to fit into one reply packet, this query
34057 works iteratively: it may require more than one query/reply sequence to
34058 obtain the entire list of threads. The first query of the sequence will
34059 be the @samp{qfThreadInfo} query; subsequent queries in the
34060 sequence will be the @samp{qsThreadInfo} query.
34062 NOTE: This packet replaces the @samp{qL} query (see below).
34066 @item m @var{thread-id}
34068 @item m @var{thread-id},@var{thread-id}@dots{}
34069 a comma-separated list of thread IDs
34071 (lower case letter @samp{L}) denotes end of list.
34074 In response to each query, the target will reply with a list of one or
34075 more thread IDs, separated by commas.
34076 @value{GDBN} will respond to each reply with a request for more thread
34077 ids (using the @samp{qs} form of the query), until the target responds
34078 with @samp{l} (lower-case ell, for @dfn{last}).
34079 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34082 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34083 @cindex get thread-local storage address, remote request
34084 @cindex @samp{qGetTLSAddr} packet
34085 Fetch the address associated with thread local storage specified
34086 by @var{thread-id}, @var{offset}, and @var{lm}.
34088 @var{thread-id} is the thread ID associated with the
34089 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34091 @var{offset} is the (big endian, hex encoded) offset associated with the
34092 thread local variable. (This offset is obtained from the debug
34093 information associated with the variable.)
34095 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34096 load module associated with the thread local storage. For example,
34097 a @sc{gnu}/Linux system will pass the link map address of the shared
34098 object associated with the thread local storage under consideration.
34099 Other operating environments may choose to represent the load module
34100 differently, so the precise meaning of this parameter will vary.
34104 @item @var{XX}@dots{}
34105 Hex encoded (big endian) bytes representing the address of the thread
34106 local storage requested.
34109 An error occurred. @var{nn} are hex digits.
34112 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34115 @item qGetTIBAddr:@var{thread-id}
34116 @cindex get thread information block address
34117 @cindex @samp{qGetTIBAddr} packet
34118 Fetch address of the Windows OS specific Thread Information Block.
34120 @var{thread-id} is the thread ID associated with the thread.
34124 @item @var{XX}@dots{}
34125 Hex encoded (big endian) bytes representing the linear address of the
34126 thread information block.
34129 An error occured. This means that either the thread was not found, or the
34130 address could not be retrieved.
34133 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34136 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34137 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34138 digit) is one to indicate the first query and zero to indicate a
34139 subsequent query; @var{threadcount} (two hex digits) is the maximum
34140 number of threads the response packet can contain; and @var{nextthread}
34141 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34142 returned in the response as @var{argthread}.
34144 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34148 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34149 Where: @var{count} (two hex digits) is the number of threads being
34150 returned; @var{done} (one hex digit) is zero to indicate more threads
34151 and one indicates no further threads; @var{argthreadid} (eight hex
34152 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34153 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34154 digits). See @code{remote.c:parse_threadlist_response()}.
34158 @cindex section offsets, remote request
34159 @cindex @samp{qOffsets} packet
34160 Get section offsets that the target used when relocating the downloaded
34165 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34166 Relocate the @code{Text} section by @var{xxx} from its original address.
34167 Relocate the @code{Data} section by @var{yyy} from its original address.
34168 If the object file format provides segment information (e.g.@: @sc{elf}
34169 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34170 segments by the supplied offsets.
34172 @emph{Note: while a @code{Bss} offset may be included in the response,
34173 @value{GDBN} ignores this and instead applies the @code{Data} offset
34174 to the @code{Bss} section.}
34176 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34177 Relocate the first segment of the object file, which conventionally
34178 contains program code, to a starting address of @var{xxx}. If
34179 @samp{DataSeg} is specified, relocate the second segment, which
34180 conventionally contains modifiable data, to a starting address of
34181 @var{yyy}. @value{GDBN} will report an error if the object file
34182 does not contain segment information, or does not contain at least
34183 as many segments as mentioned in the reply. Extra segments are
34184 kept at fixed offsets relative to the last relocated segment.
34187 @item qP @var{mode} @var{thread-id}
34188 @cindex thread information, remote request
34189 @cindex @samp{qP} packet
34190 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34191 encoded 32 bit mode; @var{thread-id} is a thread ID
34192 (@pxref{thread-id syntax}).
34194 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34197 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34201 @cindex non-stop mode, remote request
34202 @cindex @samp{QNonStop} packet
34204 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34205 @xref{Remote Non-Stop}, for more information.
34210 The request succeeded.
34213 An error occurred. @var{nn} are hex digits.
34216 An empty reply indicates that @samp{QNonStop} is not supported by
34220 This packet is not probed by default; the remote stub must request it,
34221 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34222 Use of this packet is controlled by the @code{set non-stop} command;
34223 @pxref{Non-Stop Mode}.
34225 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34226 @cindex pass signals to inferior, remote request
34227 @cindex @samp{QPassSignals} packet
34228 @anchor{QPassSignals}
34229 Each listed @var{signal} should be passed directly to the inferior process.
34230 Signals are numbered identically to continue packets and stop replies
34231 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34232 strictly greater than the previous item. These signals do not need to stop
34233 the inferior, or be reported to @value{GDBN}. All other signals should be
34234 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34235 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34236 new list. This packet improves performance when using @samp{handle
34237 @var{signal} nostop noprint pass}.
34242 The request succeeded.
34245 An error occurred. @var{nn} are hex digits.
34248 An empty reply indicates that @samp{QPassSignals} is not supported by
34252 Use of this packet is controlled by the @code{set remote pass-signals}
34253 command (@pxref{Remote Configuration, set remote pass-signals}).
34254 This packet is not probed by default; the remote stub must request it,
34255 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34257 @item qRcmd,@var{command}
34258 @cindex execute remote command, remote request
34259 @cindex @samp{qRcmd} packet
34260 @var{command} (hex encoded) is passed to the local interpreter for
34261 execution. Invalid commands should be reported using the output
34262 string. Before the final result packet, the target may also respond
34263 with a number of intermediate @samp{O@var{output}} console output
34264 packets. @emph{Implementors should note that providing access to a
34265 stubs's interpreter may have security implications}.
34270 A command response with no output.
34272 A command response with the hex encoded output string @var{OUTPUT}.
34274 Indicate a badly formed request.
34276 An empty reply indicates that @samp{qRcmd} is not recognized.
34279 (Note that the @code{qRcmd} packet's name is separated from the
34280 command by a @samp{,}, not a @samp{:}, contrary to the naming
34281 conventions above. Please don't use this packet as a model for new
34284 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34285 @cindex searching memory, in remote debugging
34286 @cindex @samp{qSearch:memory} packet
34287 @anchor{qSearch memory}
34288 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34289 @var{address} and @var{length} are encoded in hex.
34290 @var{search-pattern} is a sequence of bytes, hex encoded.
34295 The pattern was not found.
34297 The pattern was found at @var{address}.
34299 A badly formed request or an error was encountered while searching memory.
34301 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34304 @item QStartNoAckMode
34305 @cindex @samp{QStartNoAckMode} packet
34306 @anchor{QStartNoAckMode}
34307 Request that the remote stub disable the normal @samp{+}/@samp{-}
34308 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34313 The stub has switched to no-acknowledgment mode.
34314 @value{GDBN} acknowledges this reponse,
34315 but neither the stub nor @value{GDBN} shall send or expect further
34316 @samp{+}/@samp{-} acknowledgments in the current connection.
34318 An empty reply indicates that the stub does not support no-acknowledgment mode.
34321 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34322 @cindex supported packets, remote query
34323 @cindex features of the remote protocol
34324 @cindex @samp{qSupported} packet
34325 @anchor{qSupported}
34326 Tell the remote stub about features supported by @value{GDBN}, and
34327 query the stub for features it supports. This packet allows
34328 @value{GDBN} and the remote stub to take advantage of each others'
34329 features. @samp{qSupported} also consolidates multiple feature probes
34330 at startup, to improve @value{GDBN} performance---a single larger
34331 packet performs better than multiple smaller probe packets on
34332 high-latency links. Some features may enable behavior which must not
34333 be on by default, e.g.@: because it would confuse older clients or
34334 stubs. Other features may describe packets which could be
34335 automatically probed for, but are not. These features must be
34336 reported before @value{GDBN} will use them. This ``default
34337 unsupported'' behavior is not appropriate for all packets, but it
34338 helps to keep the initial connection time under control with new
34339 versions of @value{GDBN} which support increasing numbers of packets.
34343 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34344 The stub supports or does not support each returned @var{stubfeature},
34345 depending on the form of each @var{stubfeature} (see below for the
34348 An empty reply indicates that @samp{qSupported} is not recognized,
34349 or that no features needed to be reported to @value{GDBN}.
34352 The allowed forms for each feature (either a @var{gdbfeature} in the
34353 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34357 @item @var{name}=@var{value}
34358 The remote protocol feature @var{name} is supported, and associated
34359 with the specified @var{value}. The format of @var{value} depends
34360 on the feature, but it must not include a semicolon.
34362 The remote protocol feature @var{name} is supported, and does not
34363 need an associated value.
34365 The remote protocol feature @var{name} is not supported.
34367 The remote protocol feature @var{name} may be supported, and
34368 @value{GDBN} should auto-detect support in some other way when it is
34369 needed. This form will not be used for @var{gdbfeature} notifications,
34370 but may be used for @var{stubfeature} responses.
34373 Whenever the stub receives a @samp{qSupported} request, the
34374 supplied set of @value{GDBN} features should override any previous
34375 request. This allows @value{GDBN} to put the stub in a known
34376 state, even if the stub had previously been communicating with
34377 a different version of @value{GDBN}.
34379 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34384 This feature indicates whether @value{GDBN} supports multiprocess
34385 extensions to the remote protocol. @value{GDBN} does not use such
34386 extensions unless the stub also reports that it supports them by
34387 including @samp{multiprocess+} in its @samp{qSupported} reply.
34388 @xref{multiprocess extensions}, for details.
34391 This feature indicates that @value{GDBN} supports the XML target
34392 description. If the stub sees @samp{xmlRegisters=} with target
34393 specific strings separated by a comma, it will report register
34397 This feature indicates whether @value{GDBN} supports the
34398 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34399 instruction reply packet}).
34402 Stubs should ignore any unknown values for
34403 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34404 packet supports receiving packets of unlimited length (earlier
34405 versions of @value{GDBN} may reject overly long responses). Additional values
34406 for @var{gdbfeature} may be defined in the future to let the stub take
34407 advantage of new features in @value{GDBN}, e.g.@: incompatible
34408 improvements in the remote protocol---the @samp{multiprocess} feature is
34409 an example of such a feature. The stub's reply should be independent
34410 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34411 describes all the features it supports, and then the stub replies with
34412 all the features it supports.
34414 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34415 responses, as long as each response uses one of the standard forms.
34417 Some features are flags. A stub which supports a flag feature
34418 should respond with a @samp{+} form response. Other features
34419 require values, and the stub should respond with an @samp{=}
34422 Each feature has a default value, which @value{GDBN} will use if
34423 @samp{qSupported} is not available or if the feature is not mentioned
34424 in the @samp{qSupported} response. The default values are fixed; a
34425 stub is free to omit any feature responses that match the defaults.
34427 Not all features can be probed, but for those which can, the probing
34428 mechanism is useful: in some cases, a stub's internal
34429 architecture may not allow the protocol layer to know some information
34430 about the underlying target in advance. This is especially common in
34431 stubs which may be configured for multiple targets.
34433 These are the currently defined stub features and their properties:
34435 @multitable @columnfractions 0.35 0.2 0.12 0.2
34436 @c NOTE: The first row should be @headitem, but we do not yet require
34437 @c a new enough version of Texinfo (4.7) to use @headitem.
34439 @tab Value Required
34443 @item @samp{PacketSize}
34448 @item @samp{qXfer:auxv:read}
34453 @item @samp{qXfer:features:read}
34458 @item @samp{qXfer:libraries:read}
34463 @item @samp{qXfer:memory-map:read}
34468 @item @samp{qXfer:sdata:read}
34473 @item @samp{qXfer:spu:read}
34478 @item @samp{qXfer:spu:write}
34483 @item @samp{qXfer:siginfo:read}
34488 @item @samp{qXfer:siginfo:write}
34493 @item @samp{qXfer:threads:read}
34498 @item @samp{qXfer:traceframe-info:read}
34503 @item @samp{qXfer:fdpic:read}
34508 @item @samp{QNonStop}
34513 @item @samp{QPassSignals}
34518 @item @samp{QStartNoAckMode}
34523 @item @samp{multiprocess}
34528 @item @samp{ConditionalTracepoints}
34533 @item @samp{ReverseContinue}
34538 @item @samp{ReverseStep}
34543 @item @samp{TracepointSource}
34548 @item @samp{QAllow}
34553 @item @samp{QDisableRandomization}
34558 @item @samp{EnableDisableTracepoints}
34565 These are the currently defined stub features, in more detail:
34568 @cindex packet size, remote protocol
34569 @item PacketSize=@var{bytes}
34570 The remote stub can accept packets up to at least @var{bytes} in
34571 length. @value{GDBN} will send packets up to this size for bulk
34572 transfers, and will never send larger packets. This is a limit on the
34573 data characters in the packet, including the frame and checksum.
34574 There is no trailing NUL byte in a remote protocol packet; if the stub
34575 stores packets in a NUL-terminated format, it should allow an extra
34576 byte in its buffer for the NUL. If this stub feature is not supported,
34577 @value{GDBN} guesses based on the size of the @samp{g} packet response.
34579 @item qXfer:auxv:read
34580 The remote stub understands the @samp{qXfer:auxv:read} packet
34581 (@pxref{qXfer auxiliary vector read}).
34583 @item qXfer:features:read
34584 The remote stub understands the @samp{qXfer:features:read} packet
34585 (@pxref{qXfer target description read}).
34587 @item qXfer:libraries:read
34588 The remote stub understands the @samp{qXfer:libraries:read} packet
34589 (@pxref{qXfer library list read}).
34591 @item qXfer:memory-map:read
34592 The remote stub understands the @samp{qXfer:memory-map:read} packet
34593 (@pxref{qXfer memory map read}).
34595 @item qXfer:sdata:read
34596 The remote stub understands the @samp{qXfer:sdata:read} packet
34597 (@pxref{qXfer sdata read}).
34599 @item qXfer:spu:read
34600 The remote stub understands the @samp{qXfer:spu:read} packet
34601 (@pxref{qXfer spu read}).
34603 @item qXfer:spu:write
34604 The remote stub understands the @samp{qXfer:spu:write} packet
34605 (@pxref{qXfer spu write}).
34607 @item qXfer:siginfo:read
34608 The remote stub understands the @samp{qXfer:siginfo:read} packet
34609 (@pxref{qXfer siginfo read}).
34611 @item qXfer:siginfo:write
34612 The remote stub understands the @samp{qXfer:siginfo:write} packet
34613 (@pxref{qXfer siginfo write}).
34615 @item qXfer:threads:read
34616 The remote stub understands the @samp{qXfer:threads:read} packet
34617 (@pxref{qXfer threads read}).
34619 @item qXfer:traceframe-info:read
34620 The remote stub understands the @samp{qXfer:traceframe-info:read}
34621 packet (@pxref{qXfer traceframe info read}).
34623 @item qXfer:fdpic:read
34624 The remote stub understands the @samp{qXfer:fdpic:read}
34625 packet (@pxref{qXfer fdpic loadmap read}).
34628 The remote stub understands the @samp{QNonStop} packet
34629 (@pxref{QNonStop}).
34632 The remote stub understands the @samp{QPassSignals} packet
34633 (@pxref{QPassSignals}).
34635 @item QStartNoAckMode
34636 The remote stub understands the @samp{QStartNoAckMode} packet and
34637 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
34640 @anchor{multiprocess extensions}
34641 @cindex multiprocess extensions, in remote protocol
34642 The remote stub understands the multiprocess extensions to the remote
34643 protocol syntax. The multiprocess extensions affect the syntax of
34644 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
34645 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
34646 replies. Note that reporting this feature indicates support for the
34647 syntactic extensions only, not that the stub necessarily supports
34648 debugging of more than one process at a time. The stub must not use
34649 multiprocess extensions in packet replies unless @value{GDBN} has also
34650 indicated it supports them in its @samp{qSupported} request.
34652 @item qXfer:osdata:read
34653 The remote stub understands the @samp{qXfer:osdata:read} packet
34654 ((@pxref{qXfer osdata read}).
34656 @item ConditionalTracepoints
34657 The remote stub accepts and implements conditional expressions defined
34658 for tracepoints (@pxref{Tracepoint Conditions}).
34660 @item ReverseContinue
34661 The remote stub accepts and implements the reverse continue packet
34665 The remote stub accepts and implements the reverse step packet
34668 @item TracepointSource
34669 The remote stub understands the @samp{QTDPsrc} packet that supplies
34670 the source form of tracepoint definitions.
34673 The remote stub understands the @samp{QAllow} packet.
34675 @item QDisableRandomization
34676 The remote stub understands the @samp{QDisableRandomization} packet.
34678 @item StaticTracepoint
34679 @cindex static tracepoints, in remote protocol
34680 The remote stub supports static tracepoints.
34682 @item EnableDisableTracepoints
34683 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
34684 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
34685 to be enabled and disabled while a trace experiment is running.
34690 @cindex symbol lookup, remote request
34691 @cindex @samp{qSymbol} packet
34692 Notify the target that @value{GDBN} is prepared to serve symbol lookup
34693 requests. Accept requests from the target for the values of symbols.
34698 The target does not need to look up any (more) symbols.
34699 @item qSymbol:@var{sym_name}
34700 The target requests the value of symbol @var{sym_name} (hex encoded).
34701 @value{GDBN} may provide the value by using the
34702 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
34706 @item qSymbol:@var{sym_value}:@var{sym_name}
34707 Set the value of @var{sym_name} to @var{sym_value}.
34709 @var{sym_name} (hex encoded) is the name of a symbol whose value the
34710 target has previously requested.
34712 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
34713 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
34719 The target does not need to look up any (more) symbols.
34720 @item qSymbol:@var{sym_name}
34721 The target requests the value of a new symbol @var{sym_name} (hex
34722 encoded). @value{GDBN} will continue to supply the values of symbols
34723 (if available), until the target ceases to request them.
34728 @item QTDisconnected
34735 @xref{Tracepoint Packets}.
34737 @item qThreadExtraInfo,@var{thread-id}
34738 @cindex thread attributes info, remote request
34739 @cindex @samp{qThreadExtraInfo} packet
34740 Obtain a printable string description of a thread's attributes from
34741 the target OS. @var{thread-id} is a thread ID;
34742 see @ref{thread-id syntax}. This
34743 string may contain anything that the target OS thinks is interesting
34744 for @value{GDBN} to tell the user about the thread. The string is
34745 displayed in @value{GDBN}'s @code{info threads} display. Some
34746 examples of possible thread extra info strings are @samp{Runnable}, or
34747 @samp{Blocked on Mutex}.
34751 @item @var{XX}@dots{}
34752 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
34753 comprising the printable string containing the extra information about
34754 the thread's attributes.
34757 (Note that the @code{qThreadExtraInfo} packet's name is separated from
34758 the command by a @samp{,}, not a @samp{:}, contrary to the naming
34759 conventions above. Please don't use this packet as a model for new
34776 @xref{Tracepoint Packets}.
34778 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
34779 @cindex read special object, remote request
34780 @cindex @samp{qXfer} packet
34781 @anchor{qXfer read}
34782 Read uninterpreted bytes from the target's special data area
34783 identified by the keyword @var{object}. Request @var{length} bytes
34784 starting at @var{offset} bytes into the data. The content and
34785 encoding of @var{annex} is specific to @var{object}; it can supply
34786 additional details about what data to access.
34788 Here are the specific requests of this form defined so far. All
34789 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
34790 formats, listed below.
34793 @item qXfer:auxv:read::@var{offset},@var{length}
34794 @anchor{qXfer auxiliary vector read}
34795 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
34796 auxiliary vector}. Note @var{annex} must be empty.
34798 This packet is not probed by default; the remote stub must request it,
34799 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34801 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
34802 @anchor{qXfer target description read}
34803 Access the @dfn{target description}. @xref{Target Descriptions}. The
34804 annex specifies which XML document to access. The main description is
34805 always loaded from the @samp{target.xml} annex.
34807 This packet is not probed by default; the remote stub must request it,
34808 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34810 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
34811 @anchor{qXfer library list read}
34812 Access the target's list of loaded libraries. @xref{Library List Format}.
34813 The annex part of the generic @samp{qXfer} packet must be empty
34814 (@pxref{qXfer read}).
34816 Targets which maintain a list of libraries in the program's memory do
34817 not need to implement this packet; it is designed for platforms where
34818 the operating system manages the list of loaded libraries.
34820 This packet is not probed by default; the remote stub must request it,
34821 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34823 @item qXfer:memory-map:read::@var{offset},@var{length}
34824 @anchor{qXfer memory map read}
34825 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
34826 annex part of the generic @samp{qXfer} packet must be empty
34827 (@pxref{qXfer read}).
34829 This packet is not probed by default; the remote stub must request it,
34830 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34832 @item qXfer:sdata:read::@var{offset},@var{length}
34833 @anchor{qXfer sdata read}
34835 Read contents of the extra collected static tracepoint marker
34836 information. The annex part of the generic @samp{qXfer} packet must
34837 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
34840 This packet is not probed by default; the remote stub must request it,
34841 by supplying an appropriate @samp{qSupported} response
34842 (@pxref{qSupported}).
34844 @item qXfer:siginfo:read::@var{offset},@var{length}
34845 @anchor{qXfer siginfo read}
34846 Read contents of the extra signal information on the target
34847 system. The annex part of the generic @samp{qXfer} packet must be
34848 empty (@pxref{qXfer read}).
34850 This packet is not probed by default; the remote stub must request it,
34851 by supplying an appropriate @samp{qSupported} response
34852 (@pxref{qSupported}).
34854 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
34855 @anchor{qXfer spu read}
34856 Read contents of an @code{spufs} file on the target system. The
34857 annex specifies which file to read; it must be of the form
34858 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
34859 in the target process, and @var{name} identifes the @code{spufs} file
34860 in that context to be accessed.
34862 This packet is not probed by default; the remote stub must request it,
34863 by supplying an appropriate @samp{qSupported} response
34864 (@pxref{qSupported}).
34866 @item qXfer:threads:read::@var{offset},@var{length}
34867 @anchor{qXfer threads read}
34868 Access the list of threads on target. @xref{Thread List Format}. The
34869 annex part of the generic @samp{qXfer} packet must be empty
34870 (@pxref{qXfer read}).
34872 This packet is not probed by default; the remote stub must request it,
34873 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34875 @item qXfer:traceframe-info:read::@var{offset},@var{length}
34876 @anchor{qXfer traceframe info read}
34878 Return a description of the current traceframe's contents.
34879 @xref{Traceframe Info Format}. The annex part of the generic
34880 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
34882 This packet is not probed by default; the remote stub must request it,
34883 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34885 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
34886 @anchor{qXfer fdpic loadmap read}
34887 Read contents of @code{loadmap}s on the target system. The
34888 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
34889 executable @code{loadmap} or interpreter @code{loadmap} to read.
34891 This packet is not probed by default; the remote stub must request it,
34892 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34894 @item qXfer:osdata:read::@var{offset},@var{length}
34895 @anchor{qXfer osdata read}
34896 Access the target's @dfn{operating system information}.
34897 @xref{Operating System Information}.
34904 Data @var{data} (@pxref{Binary Data}) has been read from the
34905 target. There may be more data at a higher address (although
34906 it is permitted to return @samp{m} even for the last valid
34907 block of data, as long as at least one byte of data was read).
34908 @var{data} may have fewer bytes than the @var{length} in the
34912 Data @var{data} (@pxref{Binary Data}) has been read from the target.
34913 There is no more data to be read. @var{data} may have fewer bytes
34914 than the @var{length} in the request.
34917 The @var{offset} in the request is at the end of the data.
34918 There is no more data to be read.
34921 The request was malformed, or @var{annex} was invalid.
34924 The offset was invalid, or there was an error encountered reading the data.
34925 @var{nn} is a hex-encoded @code{errno} value.
34928 An empty reply indicates the @var{object} string was not recognized by
34929 the stub, or that the object does not support reading.
34932 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
34933 @cindex write data into object, remote request
34934 @anchor{qXfer write}
34935 Write uninterpreted bytes into the target's special data area
34936 identified by the keyword @var{object}, starting at @var{offset} bytes
34937 into the data. @var{data}@dots{} is the binary-encoded data
34938 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
34939 is specific to @var{object}; it can supply additional details about what data
34942 Here are the specific requests of this form defined so far. All
34943 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
34944 formats, listed below.
34947 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
34948 @anchor{qXfer siginfo write}
34949 Write @var{data} to the extra signal information on the target system.
34950 The annex part of the generic @samp{qXfer} packet must be
34951 empty (@pxref{qXfer write}).
34953 This packet is not probed by default; the remote stub must request it,
34954 by supplying an appropriate @samp{qSupported} response
34955 (@pxref{qSupported}).
34957 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
34958 @anchor{qXfer spu write}
34959 Write @var{data} to an @code{spufs} file on the target system. The
34960 annex specifies which file to write; it must be of the form
34961 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
34962 in the target process, and @var{name} identifes the @code{spufs} file
34963 in that context to be accessed.
34965 This packet is not probed by default; the remote stub must request it,
34966 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34972 @var{nn} (hex encoded) is the number of bytes written.
34973 This may be fewer bytes than supplied in the request.
34976 The request was malformed, or @var{annex} was invalid.
34979 The offset was invalid, or there was an error encountered writing the data.
34980 @var{nn} is a hex-encoded @code{errno} value.
34983 An empty reply indicates the @var{object} string was not
34984 recognized by the stub, or that the object does not support writing.
34987 @item qXfer:@var{object}:@var{operation}:@dots{}
34988 Requests of this form may be added in the future. When a stub does
34989 not recognize the @var{object} keyword, or its support for
34990 @var{object} does not recognize the @var{operation} keyword, the stub
34991 must respond with an empty packet.
34993 @item qAttached:@var{pid}
34994 @cindex query attached, remote request
34995 @cindex @samp{qAttached} packet
34996 Return an indication of whether the remote server attached to an
34997 existing process or created a new process. When the multiprocess
34998 protocol extensions are supported (@pxref{multiprocess extensions}),
34999 @var{pid} is an integer in hexadecimal format identifying the target
35000 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35001 the query packet will be simplified as @samp{qAttached}.
35003 This query is used, for example, to know whether the remote process
35004 should be detached or killed when a @value{GDBN} session is ended with
35005 the @code{quit} command.
35010 The remote server attached to an existing process.
35012 The remote server created a new process.
35014 A badly formed request or an error was encountered.
35019 @node Architecture-Specific Protocol Details
35020 @section Architecture-Specific Protocol Details
35022 This section describes how the remote protocol is applied to specific
35023 target architectures. Also see @ref{Standard Target Features}, for
35024 details of XML target descriptions for each architecture.
35028 @subsubsection Breakpoint Kinds
35030 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35035 16-bit Thumb mode breakpoint.
35038 32-bit Thumb mode (Thumb-2) breakpoint.
35041 32-bit ARM mode breakpoint.
35047 @subsubsection Register Packet Format
35049 The following @code{g}/@code{G} packets have previously been defined.
35050 In the below, some thirty-two bit registers are transferred as
35051 sixty-four bits. Those registers should be zero/sign extended (which?)
35052 to fill the space allocated. Register bytes are transferred in target
35053 byte order. The two nibbles within a register byte are transferred
35054 most-significant - least-significant.
35060 All registers are transferred as thirty-two bit quantities in the order:
35061 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35062 registers; fsr; fir; fp.
35066 All registers are transferred as sixty-four bit quantities (including
35067 thirty-two bit registers such as @code{sr}). The ordering is the same
35072 @node Tracepoint Packets
35073 @section Tracepoint Packets
35074 @cindex tracepoint packets
35075 @cindex packets, tracepoint
35077 Here we describe the packets @value{GDBN} uses to implement
35078 tracepoints (@pxref{Tracepoints}).
35082 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35083 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35084 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35085 the tracepoint is disabled. @var{step} is the tracepoint's step
35086 count, and @var{pass} is its pass count. If an @samp{F} is present,
35087 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35088 the number of bytes that the target should copy elsewhere to make room
35089 for the tracepoint. If an @samp{X} is present, it introduces a
35090 tracepoint condition, which consists of a hexadecimal length, followed
35091 by a comma and hex-encoded bytes, in a manner similar to action
35092 encodings as described below. If the trailing @samp{-} is present,
35093 further @samp{QTDP} packets will follow to specify this tracepoint's
35099 The packet was understood and carried out.
35101 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35103 The packet was not recognized.
35106 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35107 Define actions to be taken when a tracepoint is hit. @var{n} and
35108 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35109 this tracepoint. This packet may only be sent immediately after
35110 another @samp{QTDP} packet that ended with a @samp{-}. If the
35111 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35112 specifying more actions for this tracepoint.
35114 In the series of action packets for a given tracepoint, at most one
35115 can have an @samp{S} before its first @var{action}. If such a packet
35116 is sent, it and the following packets define ``while-stepping''
35117 actions. Any prior packets define ordinary actions --- that is, those
35118 taken when the tracepoint is first hit. If no action packet has an
35119 @samp{S}, then all the packets in the series specify ordinary
35120 tracepoint actions.
35122 The @samp{@var{action}@dots{}} portion of the packet is a series of
35123 actions, concatenated without separators. Each action has one of the
35129 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35130 a hexadecimal number whose @var{i}'th bit is set if register number
35131 @var{i} should be collected. (The least significant bit is numbered
35132 zero.) Note that @var{mask} may be any number of digits long; it may
35133 not fit in a 32-bit word.
35135 @item M @var{basereg},@var{offset},@var{len}
35136 Collect @var{len} bytes of memory starting at the address in register
35137 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35138 @samp{-1}, then the range has a fixed address: @var{offset} is the
35139 address of the lowest byte to collect. The @var{basereg},
35140 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35141 values (the @samp{-1} value for @var{basereg} is a special case).
35143 @item X @var{len},@var{expr}
35144 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35145 it directs. @var{expr} is an agent expression, as described in
35146 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35147 two-digit hex number in the packet; @var{len} is the number of bytes
35148 in the expression (and thus one-half the number of hex digits in the
35153 Any number of actions may be packed together in a single @samp{QTDP}
35154 packet, as long as the packet does not exceed the maximum packet
35155 length (400 bytes, for many stubs). There may be only one @samp{R}
35156 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35157 actions. Any registers referred to by @samp{M} and @samp{X} actions
35158 must be collected by a preceding @samp{R} action. (The
35159 ``while-stepping'' actions are treated as if they were attached to a
35160 separate tracepoint, as far as these restrictions are concerned.)
35165 The packet was understood and carried out.
35167 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35169 The packet was not recognized.
35172 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35173 @cindex @samp{QTDPsrc} packet
35174 Specify a source string of tracepoint @var{n} at address @var{addr}.
35175 This is useful to get accurate reproduction of the tracepoints
35176 originally downloaded at the beginning of the trace run. @var{type}
35177 is the name of the tracepoint part, such as @samp{cond} for the
35178 tracepoint's conditional expression (see below for a list of types), while
35179 @var{bytes} is the string, encoded in hexadecimal.
35181 @var{start} is the offset of the @var{bytes} within the overall source
35182 string, while @var{slen} is the total length of the source string.
35183 This is intended for handling source strings that are longer than will
35184 fit in a single packet.
35185 @c Add detailed example when this info is moved into a dedicated
35186 @c tracepoint descriptions section.
35188 The available string types are @samp{at} for the location,
35189 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35190 @value{GDBN} sends a separate packet for each command in the action
35191 list, in the same order in which the commands are stored in the list.
35193 The target does not need to do anything with source strings except
35194 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35197 Although this packet is optional, and @value{GDBN} will only send it
35198 if the target replies with @samp{TracepointSource} @xref{General
35199 Query Packets}, it makes both disconnected tracing and trace files
35200 much easier to use. Otherwise the user must be careful that the
35201 tracepoints in effect while looking at trace frames are identical to
35202 the ones in effect during the trace run; even a small discrepancy
35203 could cause @samp{tdump} not to work, or a particular trace frame not
35206 @item QTDV:@var{n}:@var{value}
35207 @cindex define trace state variable, remote request
35208 @cindex @samp{QTDV} packet
35209 Create a new trace state variable, number @var{n}, with an initial
35210 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35211 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35212 the option of not using this packet for initial values of zero; the
35213 target should simply create the trace state variables as they are
35214 mentioned in expressions.
35216 @item QTFrame:@var{n}
35217 Select the @var{n}'th tracepoint frame from the buffer, and use the
35218 register and memory contents recorded there to answer subsequent
35219 request packets from @value{GDBN}.
35221 A successful reply from the stub indicates that the stub has found the
35222 requested frame. The response is a series of parts, concatenated
35223 without separators, describing the frame we selected. Each part has
35224 one of the following forms:
35228 The selected frame is number @var{n} in the trace frame buffer;
35229 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35230 was no frame matching the criteria in the request packet.
35233 The selected trace frame records a hit of tracepoint number @var{t};
35234 @var{t} is a hexadecimal number.
35238 @item QTFrame:pc:@var{addr}
35239 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35240 currently selected frame whose PC is @var{addr};
35241 @var{addr} is a hexadecimal number.
35243 @item QTFrame:tdp:@var{t}
35244 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35245 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35246 is a hexadecimal number.
35248 @item QTFrame:range:@var{start}:@var{end}
35249 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35250 currently selected frame whose PC is between @var{start} (inclusive)
35251 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35254 @item QTFrame:outside:@var{start}:@var{end}
35255 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35256 frame @emph{outside} the given range of addresses (exclusive).
35259 Begin the tracepoint experiment. Begin collecting data from
35260 tracepoint hits in the trace frame buffer. This packet supports the
35261 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35262 instruction reply packet}).
35265 End the tracepoint experiment. Stop collecting trace frames.
35267 @item QTEnable:@var{n}:@var{addr}
35269 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35270 experiment. If the tracepoint was previously disabled, then collection
35271 of data from it will resume.
35273 @item QTDisable:@var{n}:@var{addr}
35275 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35276 experiment. No more data will be collected from the tracepoint unless
35277 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35280 Clear the table of tracepoints, and empty the trace frame buffer.
35282 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35283 Establish the given ranges of memory as ``transparent''. The stub
35284 will answer requests for these ranges from memory's current contents,
35285 if they were not collected as part of the tracepoint hit.
35287 @value{GDBN} uses this to mark read-only regions of memory, like those
35288 containing program code. Since these areas never change, they should
35289 still have the same contents they did when the tracepoint was hit, so
35290 there's no reason for the stub to refuse to provide their contents.
35292 @item QTDisconnected:@var{value}
35293 Set the choice to what to do with the tracing run when @value{GDBN}
35294 disconnects from the target. A @var{value} of 1 directs the target to
35295 continue the tracing run, while 0 tells the target to stop tracing if
35296 @value{GDBN} is no longer in the picture.
35299 Ask the stub if there is a trace experiment running right now.
35301 The reply has the form:
35305 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35306 @var{running} is a single digit @code{1} if the trace is presently
35307 running, or @code{0} if not. It is followed by semicolon-separated
35308 optional fields that an agent may use to report additional status.
35312 If the trace is not running, the agent may report any of several
35313 explanations as one of the optional fields:
35318 No trace has been run yet.
35321 The trace was stopped by a user-originated stop command.
35324 The trace stopped because the trace buffer filled up.
35326 @item tdisconnected:0
35327 The trace stopped because @value{GDBN} disconnected from the target.
35329 @item tpasscount:@var{tpnum}
35330 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35332 @item terror:@var{text}:@var{tpnum}
35333 The trace stopped because tracepoint @var{tpnum} had an error. The
35334 string @var{text} is available to describe the nature of the error
35335 (for instance, a divide by zero in the condition expression).
35336 @var{text} is hex encoded.
35339 The trace stopped for some other reason.
35343 Additional optional fields supply statistical and other information.
35344 Although not required, they are extremely useful for users monitoring
35345 the progress of a trace run. If a trace has stopped, and these
35346 numbers are reported, they must reflect the state of the just-stopped
35351 @item tframes:@var{n}
35352 The number of trace frames in the buffer.
35354 @item tcreated:@var{n}
35355 The total number of trace frames created during the run. This may
35356 be larger than the trace frame count, if the buffer is circular.
35358 @item tsize:@var{n}
35359 The total size of the trace buffer, in bytes.
35361 @item tfree:@var{n}
35362 The number of bytes still unused in the buffer.
35364 @item circular:@var{n}
35365 The value of the circular trace buffer flag. @code{1} means that the
35366 trace buffer is circular and old trace frames will be discarded if
35367 necessary to make room, @code{0} means that the trace buffer is linear
35370 @item disconn:@var{n}
35371 The value of the disconnected tracing flag. @code{1} means that
35372 tracing will continue after @value{GDBN} disconnects, @code{0} means
35373 that the trace run will stop.
35377 @item qTV:@var{var}
35378 @cindex trace state variable value, remote request
35379 @cindex @samp{qTV} packet
35380 Ask the stub for the value of the trace state variable number @var{var}.
35385 The value of the variable is @var{value}. This will be the current
35386 value of the variable if the user is examining a running target, or a
35387 saved value if the variable was collected in the trace frame that the
35388 user is looking at. Note that multiple requests may result in
35389 different reply values, such as when requesting values while the
35390 program is running.
35393 The value of the variable is unknown. This would occur, for example,
35394 if the user is examining a trace frame in which the requested variable
35400 These packets request data about tracepoints that are being used by
35401 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35402 of data, and multiple @code{qTsP} to get additional pieces. Replies
35403 to these packets generally take the form of the @code{QTDP} packets
35404 that define tracepoints. (FIXME add detailed syntax)
35408 These packets request data about trace state variables that are on the
35409 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35410 and multiple @code{qTsV} to get additional variables. Replies to
35411 these packets follow the syntax of the @code{QTDV} packets that define
35412 trace state variables.
35416 These packets request data about static tracepoint markers that exist
35417 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35418 first piece of data, and multiple @code{qTsSTM} to get additional
35419 pieces. Replies to these packets take the following form:
35423 @item m @var{address}:@var{id}:@var{extra}
35425 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35426 a comma-separated list of markers
35428 (lower case letter @samp{L}) denotes end of list.
35430 An error occurred. @var{nn} are hex digits.
35432 An empty reply indicates that the request is not supported by the
35436 @var{address} is encoded in hex.
35437 @var{id} and @var{extra} are strings encoded in hex.
35439 In response to each query, the target will reply with a list of one or
35440 more markers, separated by commas. @value{GDBN} will respond to each
35441 reply with a request for more markers (using the @samp{qs} form of the
35442 query), until the target responds with @samp{l} (lower-case ell, for
35445 @item qTSTMat:@var{address}
35446 This packets requests data about static tracepoint markers in the
35447 target program at @var{address}. Replies to this packet follow the
35448 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35449 tracepoint markers.
35451 @item QTSave:@var{filename}
35452 This packet directs the target to save trace data to the file name
35453 @var{filename} in the target's filesystem. @var{filename} is encoded
35454 as a hex string; the interpretation of the file name (relative vs
35455 absolute, wild cards, etc) is up to the target.
35457 @item qTBuffer:@var{offset},@var{len}
35458 Return up to @var{len} bytes of the current contents of trace buffer,
35459 starting at @var{offset}. The trace buffer is treated as if it were
35460 a contiguous collection of traceframes, as per the trace file format.
35461 The reply consists as many hex-encoded bytes as the target can deliver
35462 in a packet; it is not an error to return fewer than were asked for.
35463 A reply consisting of just @code{l} indicates that no bytes are
35466 @item QTBuffer:circular:@var{value}
35467 This packet directs the target to use a circular trace buffer if
35468 @var{value} is 1, or a linear buffer if the value is 0.
35472 @subsection Relocate instruction reply packet
35473 When installing fast tracepoints in memory, the target may need to
35474 relocate the instruction currently at the tracepoint address to a
35475 different address in memory. For most instructions, a simple copy is
35476 enough, but, for example, call instructions that implicitly push the
35477 return address on the stack, and relative branches or other
35478 PC-relative instructions require offset adjustment, so that the effect
35479 of executing the instruction at a different address is the same as if
35480 it had executed in the original location.
35482 In response to several of the tracepoint packets, the target may also
35483 respond with a number of intermediate @samp{qRelocInsn} request
35484 packets before the final result packet, to have @value{GDBN} handle
35485 this relocation operation. If a packet supports this mechanism, its
35486 documentation will explicitly say so. See for example the above
35487 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
35488 format of the request is:
35491 @item qRelocInsn:@var{from};@var{to}
35493 This requests @value{GDBN} to copy instruction at address @var{from}
35494 to address @var{to}, possibly adjusted so that executing the
35495 instruction at @var{to} has the same effect as executing it at
35496 @var{from}. @value{GDBN} writes the adjusted instruction to target
35497 memory starting at @var{to}.
35502 @item qRelocInsn:@var{adjusted_size}
35503 Informs the stub the relocation is complete. @var{adjusted_size} is
35504 the length in bytes of resulting relocated instruction sequence.
35506 A badly formed request was detected, or an error was encountered while
35507 relocating the instruction.
35510 @node Host I/O Packets
35511 @section Host I/O Packets
35512 @cindex Host I/O, remote protocol
35513 @cindex file transfer, remote protocol
35515 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
35516 operations on the far side of a remote link. For example, Host I/O is
35517 used to upload and download files to a remote target with its own
35518 filesystem. Host I/O uses the same constant values and data structure
35519 layout as the target-initiated File-I/O protocol. However, the
35520 Host I/O packets are structured differently. The target-initiated
35521 protocol relies on target memory to store parameters and buffers.
35522 Host I/O requests are initiated by @value{GDBN}, and the
35523 target's memory is not involved. @xref{File-I/O Remote Protocol
35524 Extension}, for more details on the target-initiated protocol.
35526 The Host I/O request packets all encode a single operation along with
35527 its arguments. They have this format:
35531 @item vFile:@var{operation}: @var{parameter}@dots{}
35532 @var{operation} is the name of the particular request; the target
35533 should compare the entire packet name up to the second colon when checking
35534 for a supported operation. The format of @var{parameter} depends on
35535 the operation. Numbers are always passed in hexadecimal. Negative
35536 numbers have an explicit minus sign (i.e.@: two's complement is not
35537 used). Strings (e.g.@: filenames) are encoded as a series of
35538 hexadecimal bytes. The last argument to a system call may be a
35539 buffer of escaped binary data (@pxref{Binary Data}).
35543 The valid responses to Host I/O packets are:
35547 @item F @var{result} [, @var{errno}] [; @var{attachment}]
35548 @var{result} is the integer value returned by this operation, usually
35549 non-negative for success and -1 for errors. If an error has occured,
35550 @var{errno} will be included in the result. @var{errno} will have a
35551 value defined by the File-I/O protocol (@pxref{Errno Values}). For
35552 operations which return data, @var{attachment} supplies the data as a
35553 binary buffer. Binary buffers in response packets are escaped in the
35554 normal way (@pxref{Binary Data}). See the individual packet
35555 documentation for the interpretation of @var{result} and
35559 An empty response indicates that this operation is not recognized.
35563 These are the supported Host I/O operations:
35566 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
35567 Open a file at @var{pathname} and return a file descriptor for it, or
35568 return -1 if an error occurs. @var{pathname} is a string,
35569 @var{flags} is an integer indicating a mask of open flags
35570 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
35571 of mode bits to use if the file is created (@pxref{mode_t Values}).
35572 @xref{open}, for details of the open flags and mode values.
35574 @item vFile:close: @var{fd}
35575 Close the open file corresponding to @var{fd} and return 0, or
35576 -1 if an error occurs.
35578 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
35579 Read data from the open file corresponding to @var{fd}. Up to
35580 @var{count} bytes will be read from the file, starting at @var{offset}
35581 relative to the start of the file. The target may read fewer bytes;
35582 common reasons include packet size limits and an end-of-file
35583 condition. The number of bytes read is returned. Zero should only be
35584 returned for a successful read at the end of the file, or if
35585 @var{count} was zero.
35587 The data read should be returned as a binary attachment on success.
35588 If zero bytes were read, the response should include an empty binary
35589 attachment (i.e.@: a trailing semicolon). The return value is the
35590 number of target bytes read; the binary attachment may be longer if
35591 some characters were escaped.
35593 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
35594 Write @var{data} (a binary buffer) to the open file corresponding
35595 to @var{fd}. Start the write at @var{offset} from the start of the
35596 file. Unlike many @code{write} system calls, there is no
35597 separate @var{count} argument; the length of @var{data} in the
35598 packet is used. @samp{vFile:write} returns the number of bytes written,
35599 which may be shorter than the length of @var{data}, or -1 if an
35602 @item vFile:unlink: @var{pathname}
35603 Delete the file at @var{pathname} on the target. Return 0,
35604 or -1 if an error occurs. @var{pathname} is a string.
35609 @section Interrupts
35610 @cindex interrupts (remote protocol)
35612 When a program on the remote target is running, @value{GDBN} may
35613 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
35614 a @code{BREAK} followed by @code{g},
35615 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
35617 The precise meaning of @code{BREAK} is defined by the transport
35618 mechanism and may, in fact, be undefined. @value{GDBN} does not
35619 currently define a @code{BREAK} mechanism for any of the network
35620 interfaces except for TCP, in which case @value{GDBN} sends the
35621 @code{telnet} BREAK sequence.
35623 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
35624 transport mechanisms. It is represented by sending the single byte
35625 @code{0x03} without any of the usual packet overhead described in
35626 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
35627 transmitted as part of a packet, it is considered to be packet data
35628 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
35629 (@pxref{X packet}), used for binary downloads, may include an unescaped
35630 @code{0x03} as part of its packet.
35632 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
35633 When Linux kernel receives this sequence from serial port,
35634 it stops execution and connects to gdb.
35636 Stubs are not required to recognize these interrupt mechanisms and the
35637 precise meaning associated with receipt of the interrupt is
35638 implementation defined. If the target supports debugging of multiple
35639 threads and/or processes, it should attempt to interrupt all
35640 currently-executing threads and processes.
35641 If the stub is successful at interrupting the
35642 running program, it should send one of the stop
35643 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
35644 of successfully stopping the program in all-stop mode, and a stop reply
35645 for each stopped thread in non-stop mode.
35646 Interrupts received while the
35647 program is stopped are discarded.
35649 @node Notification Packets
35650 @section Notification Packets
35651 @cindex notification packets
35652 @cindex packets, notification
35654 The @value{GDBN} remote serial protocol includes @dfn{notifications},
35655 packets that require no acknowledgment. Both the GDB and the stub
35656 may send notifications (although the only notifications defined at
35657 present are sent by the stub). Notifications carry information
35658 without incurring the round-trip latency of an acknowledgment, and so
35659 are useful for low-impact communications where occasional packet loss
35662 A notification packet has the form @samp{% @var{data} #
35663 @var{checksum}}, where @var{data} is the content of the notification,
35664 and @var{checksum} is a checksum of @var{data}, computed and formatted
35665 as for ordinary @value{GDBN} packets. A notification's @var{data}
35666 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
35667 receiving a notification, the recipient sends no @samp{+} or @samp{-}
35668 to acknowledge the notification's receipt or to report its corruption.
35670 Every notification's @var{data} begins with a name, which contains no
35671 colon characters, followed by a colon character.
35673 Recipients should silently ignore corrupted notifications and
35674 notifications they do not understand. Recipients should restart
35675 timeout periods on receipt of a well-formed notification, whether or
35676 not they understand it.
35678 Senders should only send the notifications described here when this
35679 protocol description specifies that they are permitted. In the
35680 future, we may extend the protocol to permit existing notifications in
35681 new contexts; this rule helps older senders avoid confusing newer
35684 (Older versions of @value{GDBN} ignore bytes received until they see
35685 the @samp{$} byte that begins an ordinary packet, so new stubs may
35686 transmit notifications without fear of confusing older clients. There
35687 are no notifications defined for @value{GDBN} to send at the moment, but we
35688 assume that most older stubs would ignore them, as well.)
35690 The following notification packets from the stub to @value{GDBN} are
35694 @item Stop: @var{reply}
35695 Report an asynchronous stop event in non-stop mode.
35696 The @var{reply} has the form of a stop reply, as
35697 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
35698 for information on how these notifications are acknowledged by
35702 @node Remote Non-Stop
35703 @section Remote Protocol Support for Non-Stop Mode
35705 @value{GDBN}'s remote protocol supports non-stop debugging of
35706 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
35707 supports non-stop mode, it should report that to @value{GDBN} by including
35708 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
35710 @value{GDBN} typically sends a @samp{QNonStop} packet only when
35711 establishing a new connection with the stub. Entering non-stop mode
35712 does not alter the state of any currently-running threads, but targets
35713 must stop all threads in any already-attached processes when entering
35714 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
35715 probe the target state after a mode change.
35717 In non-stop mode, when an attached process encounters an event that
35718 would otherwise be reported with a stop reply, it uses the
35719 asynchronous notification mechanism (@pxref{Notification Packets}) to
35720 inform @value{GDBN}. In contrast to all-stop mode, where all threads
35721 in all processes are stopped when a stop reply is sent, in non-stop
35722 mode only the thread reporting the stop event is stopped. That is,
35723 when reporting a @samp{S} or @samp{T} response to indicate completion
35724 of a step operation, hitting a breakpoint, or a fault, only the
35725 affected thread is stopped; any other still-running threads continue
35726 to run. When reporting a @samp{W} or @samp{X} response, all running
35727 threads belonging to other attached processes continue to run.
35729 Only one stop reply notification at a time may be pending; if
35730 additional stop events occur before @value{GDBN} has acknowledged the
35731 previous notification, they must be queued by the stub for later
35732 synchronous transmission in response to @samp{vStopped} packets from
35733 @value{GDBN}. Because the notification mechanism is unreliable,
35734 the stub is permitted to resend a stop reply notification
35735 if it believes @value{GDBN} may not have received it. @value{GDBN}
35736 ignores additional stop reply notifications received before it has
35737 finished processing a previous notification and the stub has completed
35738 sending any queued stop events.
35740 Otherwise, @value{GDBN} must be prepared to receive a stop reply
35741 notification at any time. Specifically, they may appear when
35742 @value{GDBN} is not otherwise reading input from the stub, or when
35743 @value{GDBN} is expecting to read a normal synchronous response or a
35744 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
35745 Notification packets are distinct from any other communication from
35746 the stub so there is no ambiguity.
35748 After receiving a stop reply notification, @value{GDBN} shall
35749 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
35750 as a regular, synchronous request to the stub. Such acknowledgment
35751 is not required to happen immediately, as @value{GDBN} is permitted to
35752 send other, unrelated packets to the stub first, which the stub should
35755 Upon receiving a @samp{vStopped} packet, if the stub has other queued
35756 stop events to report to @value{GDBN}, it shall respond by sending a
35757 normal stop reply response. @value{GDBN} shall then send another
35758 @samp{vStopped} packet to solicit further responses; again, it is
35759 permitted to send other, unrelated packets as well which the stub
35760 should process normally.
35762 If the stub receives a @samp{vStopped} packet and there are no
35763 additional stop events to report, the stub shall return an @samp{OK}
35764 response. At this point, if further stop events occur, the stub shall
35765 send a new stop reply notification, @value{GDBN} shall accept the
35766 notification, and the process shall be repeated.
35768 In non-stop mode, the target shall respond to the @samp{?} packet as
35769 follows. First, any incomplete stop reply notification/@samp{vStopped}
35770 sequence in progress is abandoned. The target must begin a new
35771 sequence reporting stop events for all stopped threads, whether or not
35772 it has previously reported those events to @value{GDBN}. The first
35773 stop reply is sent as a synchronous reply to the @samp{?} packet, and
35774 subsequent stop replies are sent as responses to @samp{vStopped} packets
35775 using the mechanism described above. The target must not send
35776 asynchronous stop reply notifications until the sequence is complete.
35777 If all threads are running when the target receives the @samp{?} packet,
35778 or if the target is not attached to any process, it shall respond
35781 @node Packet Acknowledgment
35782 @section Packet Acknowledgment
35784 @cindex acknowledgment, for @value{GDBN} remote
35785 @cindex packet acknowledgment, for @value{GDBN} remote
35786 By default, when either the host or the target machine receives a packet,
35787 the first response expected is an acknowledgment: either @samp{+} (to indicate
35788 the package was received correctly) or @samp{-} (to request retransmission).
35789 This mechanism allows the @value{GDBN} remote protocol to operate over
35790 unreliable transport mechanisms, such as a serial line.
35792 In cases where the transport mechanism is itself reliable (such as a pipe or
35793 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
35794 It may be desirable to disable them in that case to reduce communication
35795 overhead, or for other reasons. This can be accomplished by means of the
35796 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
35798 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
35799 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
35800 and response format still includes the normal checksum, as described in
35801 @ref{Overview}, but the checksum may be ignored by the receiver.
35803 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
35804 no-acknowledgment mode, it should report that to @value{GDBN}
35805 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
35806 @pxref{qSupported}.
35807 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
35808 disabled via the @code{set remote noack-packet off} command
35809 (@pxref{Remote Configuration}),
35810 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
35811 Only then may the stub actually turn off packet acknowledgments.
35812 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
35813 response, which can be safely ignored by the stub.
35815 Note that @code{set remote noack-packet} command only affects negotiation
35816 between @value{GDBN} and the stub when subsequent connections are made;
35817 it does not affect the protocol acknowledgment state for any current
35819 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
35820 new connection is established,
35821 there is also no protocol request to re-enable the acknowledgments
35822 for the current connection, once disabled.
35827 Example sequence of a target being re-started. Notice how the restart
35828 does not get any direct output:
35833 @emph{target restarts}
35836 <- @code{T001:1234123412341234}
35840 Example sequence of a target being stepped by a single instruction:
35843 -> @code{G1445@dots{}}
35848 <- @code{T001:1234123412341234}
35852 <- @code{1455@dots{}}
35856 @node File-I/O Remote Protocol Extension
35857 @section File-I/O Remote Protocol Extension
35858 @cindex File-I/O remote protocol extension
35861 * File-I/O Overview::
35862 * Protocol Basics::
35863 * The F Request Packet::
35864 * The F Reply Packet::
35865 * The Ctrl-C Message::
35867 * List of Supported Calls::
35868 * Protocol-specific Representation of Datatypes::
35870 * File-I/O Examples::
35873 @node File-I/O Overview
35874 @subsection File-I/O Overview
35875 @cindex file-i/o overview
35877 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
35878 target to use the host's file system and console I/O to perform various
35879 system calls. System calls on the target system are translated into a
35880 remote protocol packet to the host system, which then performs the needed
35881 actions and returns a response packet to the target system.
35882 This simulates file system operations even on targets that lack file systems.
35884 The protocol is defined to be independent of both the host and target systems.
35885 It uses its own internal representation of datatypes and values. Both
35886 @value{GDBN} and the target's @value{GDBN} stub are responsible for
35887 translating the system-dependent value representations into the internal
35888 protocol representations when data is transmitted.
35890 The communication is synchronous. A system call is possible only when
35891 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
35892 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
35893 the target is stopped to allow deterministic access to the target's
35894 memory. Therefore File-I/O is not interruptible by target signals. On
35895 the other hand, it is possible to interrupt File-I/O by a user interrupt
35896 (@samp{Ctrl-C}) within @value{GDBN}.
35898 The target's request to perform a host system call does not finish
35899 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
35900 after finishing the system call, the target returns to continuing the
35901 previous activity (continue, step). No additional continue or step
35902 request from @value{GDBN} is required.
35905 (@value{GDBP}) continue
35906 <- target requests 'system call X'
35907 target is stopped, @value{GDBN} executes system call
35908 -> @value{GDBN} returns result
35909 ... target continues, @value{GDBN} returns to wait for the target
35910 <- target hits breakpoint and sends a Txx packet
35913 The protocol only supports I/O on the console and to regular files on
35914 the host file system. Character or block special devices, pipes,
35915 named pipes, sockets or any other communication method on the host
35916 system are not supported by this protocol.
35918 File I/O is not supported in non-stop mode.
35920 @node Protocol Basics
35921 @subsection Protocol Basics
35922 @cindex protocol basics, file-i/o
35924 The File-I/O protocol uses the @code{F} packet as the request as well
35925 as reply packet. Since a File-I/O system call can only occur when
35926 @value{GDBN} is waiting for a response from the continuing or stepping target,
35927 the File-I/O request is a reply that @value{GDBN} has to expect as a result
35928 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
35929 This @code{F} packet contains all information needed to allow @value{GDBN}
35930 to call the appropriate host system call:
35934 A unique identifier for the requested system call.
35937 All parameters to the system call. Pointers are given as addresses
35938 in the target memory address space. Pointers to strings are given as
35939 pointer/length pair. Numerical values are given as they are.
35940 Numerical control flags are given in a protocol-specific representation.
35944 At this point, @value{GDBN} has to perform the following actions.
35948 If the parameters include pointer values to data needed as input to a
35949 system call, @value{GDBN} requests this data from the target with a
35950 standard @code{m} packet request. This additional communication has to be
35951 expected by the target implementation and is handled as any other @code{m}
35955 @value{GDBN} translates all value from protocol representation to host
35956 representation as needed. Datatypes are coerced into the host types.
35959 @value{GDBN} calls the system call.
35962 It then coerces datatypes back to protocol representation.
35965 If the system call is expected to return data in buffer space specified
35966 by pointer parameters to the call, the data is transmitted to the
35967 target using a @code{M} or @code{X} packet. This packet has to be expected
35968 by the target implementation and is handled as any other @code{M} or @code{X}
35973 Eventually @value{GDBN} replies with another @code{F} packet which contains all
35974 necessary information for the target to continue. This at least contains
35981 @code{errno}, if has been changed by the system call.
35988 After having done the needed type and value coercion, the target continues
35989 the latest continue or step action.
35991 @node The F Request Packet
35992 @subsection The @code{F} Request Packet
35993 @cindex file-i/o request packet
35994 @cindex @code{F} request packet
35996 The @code{F} request packet has the following format:
35999 @item F@var{call-id},@var{parameter@dots{}}
36001 @var{call-id} is the identifier to indicate the host system call to be called.
36002 This is just the name of the function.
36004 @var{parameter@dots{}} are the parameters to the system call.
36005 Parameters are hexadecimal integer values, either the actual values in case
36006 of scalar datatypes, pointers to target buffer space in case of compound
36007 datatypes and unspecified memory areas, or pointer/length pairs in case
36008 of string parameters. These are appended to the @var{call-id} as a
36009 comma-delimited list. All values are transmitted in ASCII
36010 string representation, pointer/length pairs separated by a slash.
36016 @node The F Reply Packet
36017 @subsection The @code{F} Reply Packet
36018 @cindex file-i/o reply packet
36019 @cindex @code{F} reply packet
36021 The @code{F} reply packet has the following format:
36025 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36027 @var{retcode} is the return code of the system call as hexadecimal value.
36029 @var{errno} is the @code{errno} set by the call, in protocol-specific
36031 This parameter can be omitted if the call was successful.
36033 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36034 case, @var{errno} must be sent as well, even if the call was successful.
36035 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36042 or, if the call was interrupted before the host call has been performed:
36049 assuming 4 is the protocol-specific representation of @code{EINTR}.
36054 @node The Ctrl-C Message
36055 @subsection The @samp{Ctrl-C} Message
36056 @cindex ctrl-c message, in file-i/o protocol
36058 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36059 reply packet (@pxref{The F Reply Packet}),
36060 the target should behave as if it had
36061 gotten a break message. The meaning for the target is ``system call
36062 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36063 (as with a break message) and return to @value{GDBN} with a @code{T02}
36066 It's important for the target to know in which
36067 state the system call was interrupted. There are two possible cases:
36071 The system call hasn't been performed on the host yet.
36074 The system call on the host has been finished.
36078 These two states can be distinguished by the target by the value of the
36079 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36080 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36081 on POSIX systems. In any other case, the target may presume that the
36082 system call has been finished --- successfully or not --- and should behave
36083 as if the break message arrived right after the system call.
36085 @value{GDBN} must behave reliably. If the system call has not been called
36086 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36087 @code{errno} in the packet. If the system call on the host has been finished
36088 before the user requests a break, the full action must be finished by
36089 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36090 The @code{F} packet may only be sent when either nothing has happened
36091 or the full action has been completed.
36094 @subsection Console I/O
36095 @cindex console i/o as part of file-i/o
36097 By default and if not explicitly closed by the target system, the file
36098 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36099 on the @value{GDBN} console is handled as any other file output operation
36100 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36101 by @value{GDBN} so that after the target read request from file descriptor
36102 0 all following typing is buffered until either one of the following
36107 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36109 system call is treated as finished.
36112 The user presses @key{RET}. This is treated as end of input with a trailing
36116 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36117 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36121 If the user has typed more characters than fit in the buffer given to
36122 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36123 either another @code{read(0, @dots{})} is requested by the target, or debugging
36124 is stopped at the user's request.
36127 @node List of Supported Calls
36128 @subsection List of Supported Calls
36129 @cindex list of supported file-i/o calls
36146 @unnumberedsubsubsec open
36147 @cindex open, file-i/o system call
36152 int open(const char *pathname, int flags);
36153 int open(const char *pathname, int flags, mode_t mode);
36157 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36160 @var{flags} is the bitwise @code{OR} of the following values:
36164 If the file does not exist it will be created. The host
36165 rules apply as far as file ownership and time stamps
36169 When used with @code{O_CREAT}, if the file already exists it is
36170 an error and open() fails.
36173 If the file already exists and the open mode allows
36174 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36175 truncated to zero length.
36178 The file is opened in append mode.
36181 The file is opened for reading only.
36184 The file is opened for writing only.
36187 The file is opened for reading and writing.
36191 Other bits are silently ignored.
36195 @var{mode} is the bitwise @code{OR} of the following values:
36199 User has read permission.
36202 User has write permission.
36205 Group has read permission.
36208 Group has write permission.
36211 Others have read permission.
36214 Others have write permission.
36218 Other bits are silently ignored.
36221 @item Return value:
36222 @code{open} returns the new file descriptor or -1 if an error
36229 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36232 @var{pathname} refers to a directory.
36235 The requested access is not allowed.
36238 @var{pathname} was too long.
36241 A directory component in @var{pathname} does not exist.
36244 @var{pathname} refers to a device, pipe, named pipe or socket.
36247 @var{pathname} refers to a file on a read-only filesystem and
36248 write access was requested.
36251 @var{pathname} is an invalid pointer value.
36254 No space on device to create the file.
36257 The process already has the maximum number of files open.
36260 The limit on the total number of files open on the system
36264 The call was interrupted by the user.
36270 @unnumberedsubsubsec close
36271 @cindex close, file-i/o system call
36280 @samp{Fclose,@var{fd}}
36282 @item Return value:
36283 @code{close} returns zero on success, or -1 if an error occurred.
36289 @var{fd} isn't a valid open file descriptor.
36292 The call was interrupted by the user.
36298 @unnumberedsubsubsec read
36299 @cindex read, file-i/o system call
36304 int read(int fd, void *buf, unsigned int count);
36308 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36310 @item Return value:
36311 On success, the number of bytes read is returned.
36312 Zero indicates end of file. If count is zero, read
36313 returns zero as well. On error, -1 is returned.
36319 @var{fd} is not a valid file descriptor or is not open for
36323 @var{bufptr} is an invalid pointer value.
36326 The call was interrupted by the user.
36332 @unnumberedsubsubsec write
36333 @cindex write, file-i/o system call
36338 int write(int fd, const void *buf, unsigned int count);
36342 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36344 @item Return value:
36345 On success, the number of bytes written are returned.
36346 Zero indicates nothing was written. On error, -1
36353 @var{fd} is not a valid file descriptor or is not open for
36357 @var{bufptr} is an invalid pointer value.
36360 An attempt was made to write a file that exceeds the
36361 host-specific maximum file size allowed.
36364 No space on device to write the data.
36367 The call was interrupted by the user.
36373 @unnumberedsubsubsec lseek
36374 @cindex lseek, file-i/o system call
36379 long lseek (int fd, long offset, int flag);
36383 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36385 @var{flag} is one of:
36389 The offset is set to @var{offset} bytes.
36392 The offset is set to its current location plus @var{offset}
36396 The offset is set to the size of the file plus @var{offset}
36400 @item Return value:
36401 On success, the resulting unsigned offset in bytes from
36402 the beginning of the file is returned. Otherwise, a
36403 value of -1 is returned.
36409 @var{fd} is not a valid open file descriptor.
36412 @var{fd} is associated with the @value{GDBN} console.
36415 @var{flag} is not a proper value.
36418 The call was interrupted by the user.
36424 @unnumberedsubsubsec rename
36425 @cindex rename, file-i/o system call
36430 int rename(const char *oldpath, const char *newpath);
36434 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36436 @item Return value:
36437 On success, zero is returned. On error, -1 is returned.
36443 @var{newpath} is an existing directory, but @var{oldpath} is not a
36447 @var{newpath} is a non-empty directory.
36450 @var{oldpath} or @var{newpath} is a directory that is in use by some
36454 An attempt was made to make a directory a subdirectory
36458 A component used as a directory in @var{oldpath} or new
36459 path is not a directory. Or @var{oldpath} is a directory
36460 and @var{newpath} exists but is not a directory.
36463 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
36466 No access to the file or the path of the file.
36470 @var{oldpath} or @var{newpath} was too long.
36473 A directory component in @var{oldpath} or @var{newpath} does not exist.
36476 The file is on a read-only filesystem.
36479 The device containing the file has no room for the new
36483 The call was interrupted by the user.
36489 @unnumberedsubsubsec unlink
36490 @cindex unlink, file-i/o system call
36495 int unlink(const char *pathname);
36499 @samp{Funlink,@var{pathnameptr}/@var{len}}
36501 @item Return value:
36502 On success, zero is returned. On error, -1 is returned.
36508 No access to the file or the path of the file.
36511 The system does not allow unlinking of directories.
36514 The file @var{pathname} cannot be unlinked because it's
36515 being used by another process.
36518 @var{pathnameptr} is an invalid pointer value.
36521 @var{pathname} was too long.
36524 A directory component in @var{pathname} does not exist.
36527 A component of the path is not a directory.
36530 The file is on a read-only filesystem.
36533 The call was interrupted by the user.
36539 @unnumberedsubsubsec stat/fstat
36540 @cindex fstat, file-i/o system call
36541 @cindex stat, file-i/o system call
36546 int stat(const char *pathname, struct stat *buf);
36547 int fstat(int fd, struct stat *buf);
36551 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
36552 @samp{Ffstat,@var{fd},@var{bufptr}}
36554 @item Return value:
36555 On success, zero is returned. On error, -1 is returned.
36561 @var{fd} is not a valid open file.
36564 A directory component in @var{pathname} does not exist or the
36565 path is an empty string.
36568 A component of the path is not a directory.
36571 @var{pathnameptr} is an invalid pointer value.
36574 No access to the file or the path of the file.
36577 @var{pathname} was too long.
36580 The call was interrupted by the user.
36586 @unnumberedsubsubsec gettimeofday
36587 @cindex gettimeofday, file-i/o system call
36592 int gettimeofday(struct timeval *tv, void *tz);
36596 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
36598 @item Return value:
36599 On success, 0 is returned, -1 otherwise.
36605 @var{tz} is a non-NULL pointer.
36608 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
36614 @unnumberedsubsubsec isatty
36615 @cindex isatty, file-i/o system call
36620 int isatty(int fd);
36624 @samp{Fisatty,@var{fd}}
36626 @item Return value:
36627 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
36633 The call was interrupted by the user.
36638 Note that the @code{isatty} call is treated as a special case: it returns
36639 1 to the target if the file descriptor is attached
36640 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
36641 would require implementing @code{ioctl} and would be more complex than
36646 @unnumberedsubsubsec system
36647 @cindex system, file-i/o system call
36652 int system(const char *command);
36656 @samp{Fsystem,@var{commandptr}/@var{len}}
36658 @item Return value:
36659 If @var{len} is zero, the return value indicates whether a shell is
36660 available. A zero return value indicates a shell is not available.
36661 For non-zero @var{len}, the value returned is -1 on error and the
36662 return status of the command otherwise. Only the exit status of the
36663 command is returned, which is extracted from the host's @code{system}
36664 return value by calling @code{WEXITSTATUS(retval)}. In case
36665 @file{/bin/sh} could not be executed, 127 is returned.
36671 The call was interrupted by the user.
36676 @value{GDBN} takes over the full task of calling the necessary host calls
36677 to perform the @code{system} call. The return value of @code{system} on
36678 the host is simplified before it's returned
36679 to the target. Any termination signal information from the child process
36680 is discarded, and the return value consists
36681 entirely of the exit status of the called command.
36683 Due to security concerns, the @code{system} call is by default refused
36684 by @value{GDBN}. The user has to allow this call explicitly with the
36685 @code{set remote system-call-allowed 1} command.
36688 @item set remote system-call-allowed
36689 @kindex set remote system-call-allowed
36690 Control whether to allow the @code{system} calls in the File I/O
36691 protocol for the remote target. The default is zero (disabled).
36693 @item show remote system-call-allowed
36694 @kindex show remote system-call-allowed
36695 Show whether the @code{system} calls are allowed in the File I/O
36699 @node Protocol-specific Representation of Datatypes
36700 @subsection Protocol-specific Representation of Datatypes
36701 @cindex protocol-specific representation of datatypes, in file-i/o protocol
36704 * Integral Datatypes::
36706 * Memory Transfer::
36711 @node Integral Datatypes
36712 @unnumberedsubsubsec Integral Datatypes
36713 @cindex integral datatypes, in file-i/o protocol
36715 The integral datatypes used in the system calls are @code{int},
36716 @code{unsigned int}, @code{long}, @code{unsigned long},
36717 @code{mode_t}, and @code{time_t}.
36719 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
36720 implemented as 32 bit values in this protocol.
36722 @code{long} and @code{unsigned long} are implemented as 64 bit types.
36724 @xref{Limits}, for corresponding MIN and MAX values (similar to those
36725 in @file{limits.h}) to allow range checking on host and target.
36727 @code{time_t} datatypes are defined as seconds since the Epoch.
36729 All integral datatypes transferred as part of a memory read or write of a
36730 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
36733 @node Pointer Values
36734 @unnumberedsubsubsec Pointer Values
36735 @cindex pointer values, in file-i/o protocol
36737 Pointers to target data are transmitted as they are. An exception
36738 is made for pointers to buffers for which the length isn't
36739 transmitted as part of the function call, namely strings. Strings
36740 are transmitted as a pointer/length pair, both as hex values, e.g.@:
36747 which is a pointer to data of length 18 bytes at position 0x1aaf.
36748 The length is defined as the full string length in bytes, including
36749 the trailing null byte. For example, the string @code{"hello world"}
36750 at address 0x123456 is transmitted as
36756 @node Memory Transfer
36757 @unnumberedsubsubsec Memory Transfer
36758 @cindex memory transfer, in file-i/o protocol
36760 Structured data which is transferred using a memory read or write (for
36761 example, a @code{struct stat}) is expected to be in a protocol-specific format
36762 with all scalar multibyte datatypes being big endian. Translation to
36763 this representation needs to be done both by the target before the @code{F}
36764 packet is sent, and by @value{GDBN} before
36765 it transfers memory to the target. Transferred pointers to structured
36766 data should point to the already-coerced data at any time.
36770 @unnumberedsubsubsec struct stat
36771 @cindex struct stat, in file-i/o protocol
36773 The buffer of type @code{struct stat} used by the target and @value{GDBN}
36774 is defined as follows:
36778 unsigned int st_dev; /* device */
36779 unsigned int st_ino; /* inode */
36780 mode_t st_mode; /* protection */
36781 unsigned int st_nlink; /* number of hard links */
36782 unsigned int st_uid; /* user ID of owner */
36783 unsigned int st_gid; /* group ID of owner */
36784 unsigned int st_rdev; /* device type (if inode device) */
36785 unsigned long st_size; /* total size, in bytes */
36786 unsigned long st_blksize; /* blocksize for filesystem I/O */
36787 unsigned long st_blocks; /* number of blocks allocated */
36788 time_t st_atime; /* time of last access */
36789 time_t st_mtime; /* time of last modification */
36790 time_t st_ctime; /* time of last change */
36794 The integral datatypes conform to the definitions given in the
36795 appropriate section (see @ref{Integral Datatypes}, for details) so this
36796 structure is of size 64 bytes.
36798 The values of several fields have a restricted meaning and/or
36804 A value of 0 represents a file, 1 the console.
36807 No valid meaning for the target. Transmitted unchanged.
36810 Valid mode bits are described in @ref{Constants}. Any other
36811 bits have currently no meaning for the target.
36816 No valid meaning for the target. Transmitted unchanged.
36821 These values have a host and file system dependent
36822 accuracy. Especially on Windows hosts, the file system may not
36823 support exact timing values.
36826 The target gets a @code{struct stat} of the above representation and is
36827 responsible for coercing it to the target representation before
36830 Note that due to size differences between the host, target, and protocol
36831 representations of @code{struct stat} members, these members could eventually
36832 get truncated on the target.
36834 @node struct timeval
36835 @unnumberedsubsubsec struct timeval
36836 @cindex struct timeval, in file-i/o protocol
36838 The buffer of type @code{struct timeval} used by the File-I/O protocol
36839 is defined as follows:
36843 time_t tv_sec; /* second */
36844 long tv_usec; /* microsecond */
36848 The integral datatypes conform to the definitions given in the
36849 appropriate section (see @ref{Integral Datatypes}, for details) so this
36850 structure is of size 8 bytes.
36853 @subsection Constants
36854 @cindex constants, in file-i/o protocol
36856 The following values are used for the constants inside of the
36857 protocol. @value{GDBN} and target are responsible for translating these
36858 values before and after the call as needed.
36869 @unnumberedsubsubsec Open Flags
36870 @cindex open flags, in file-i/o protocol
36872 All values are given in hexadecimal representation.
36884 @node mode_t Values
36885 @unnumberedsubsubsec mode_t Values
36886 @cindex mode_t values, in file-i/o protocol
36888 All values are given in octal representation.
36905 @unnumberedsubsubsec Errno Values
36906 @cindex errno values, in file-i/o protocol
36908 All values are given in decimal representation.
36933 @code{EUNKNOWN} is used as a fallback error value if a host system returns
36934 any error value not in the list of supported error numbers.
36937 @unnumberedsubsubsec Lseek Flags
36938 @cindex lseek flags, in file-i/o protocol
36947 @unnumberedsubsubsec Limits
36948 @cindex limits, in file-i/o protocol
36950 All values are given in decimal representation.
36953 INT_MIN -2147483648
36955 UINT_MAX 4294967295
36956 LONG_MIN -9223372036854775808
36957 LONG_MAX 9223372036854775807
36958 ULONG_MAX 18446744073709551615
36961 @node File-I/O Examples
36962 @subsection File-I/O Examples
36963 @cindex file-i/o examples
36965 Example sequence of a write call, file descriptor 3, buffer is at target
36966 address 0x1234, 6 bytes should be written:
36969 <- @code{Fwrite,3,1234,6}
36970 @emph{request memory read from target}
36973 @emph{return "6 bytes written"}
36977 Example sequence of a read call, file descriptor 3, buffer is at target
36978 address 0x1234, 6 bytes should be read:
36981 <- @code{Fread,3,1234,6}
36982 @emph{request memory write to target}
36983 -> @code{X1234,6:XXXXXX}
36984 @emph{return "6 bytes read"}
36988 Example sequence of a read call, call fails on the host due to invalid
36989 file descriptor (@code{EBADF}):
36992 <- @code{Fread,3,1234,6}
36996 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37000 <- @code{Fread,3,1234,6}
37005 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37009 <- @code{Fread,3,1234,6}
37010 -> @code{X1234,6:XXXXXX}
37014 @node Library List Format
37015 @section Library List Format
37016 @cindex library list format, remote protocol
37018 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37019 same process as your application to manage libraries. In this case,
37020 @value{GDBN} can use the loader's symbol table and normal memory
37021 operations to maintain a list of shared libraries. On other
37022 platforms, the operating system manages loaded libraries.
37023 @value{GDBN} can not retrieve the list of currently loaded libraries
37024 through memory operations, so it uses the @samp{qXfer:libraries:read}
37025 packet (@pxref{qXfer library list read}) instead. The remote stub
37026 queries the target's operating system and reports which libraries
37029 The @samp{qXfer:libraries:read} packet returns an XML document which
37030 lists loaded libraries and their offsets. Each library has an
37031 associated name and one or more segment or section base addresses,
37032 which report where the library was loaded in memory.
37034 For the common case of libraries that are fully linked binaries, the
37035 library should have a list of segments. If the target supports
37036 dynamic linking of a relocatable object file, its library XML element
37037 should instead include a list of allocated sections. The segment or
37038 section bases are start addresses, not relocation offsets; they do not
37039 depend on the library's link-time base addresses.
37041 @value{GDBN} must be linked with the Expat library to support XML
37042 library lists. @xref{Expat}.
37044 A simple memory map, with one loaded library relocated by a single
37045 offset, looks like this:
37049 <library name="/lib/libc.so.6">
37050 <segment address="0x10000000"/>
37055 Another simple memory map, with one loaded library with three
37056 allocated sections (.text, .data, .bss), looks like this:
37060 <library name="sharedlib.o">
37061 <section address="0x10000000"/>
37062 <section address="0x20000000"/>
37063 <section address="0x30000000"/>
37068 The format of a library list is described by this DTD:
37071 <!-- library-list: Root element with versioning -->
37072 <!ELEMENT library-list (library)*>
37073 <!ATTLIST library-list version CDATA #FIXED "1.0">
37074 <!ELEMENT library (segment*, section*)>
37075 <!ATTLIST library name CDATA #REQUIRED>
37076 <!ELEMENT segment EMPTY>
37077 <!ATTLIST segment address CDATA #REQUIRED>
37078 <!ELEMENT section EMPTY>
37079 <!ATTLIST section address CDATA #REQUIRED>
37082 In addition, segments and section descriptors cannot be mixed within a
37083 single library element, and you must supply at least one segment or
37084 section for each library.
37086 @node Memory Map Format
37087 @section Memory Map Format
37088 @cindex memory map format
37090 To be able to write into flash memory, @value{GDBN} needs to obtain a
37091 memory map from the target. This section describes the format of the
37094 The memory map is obtained using the @samp{qXfer:memory-map:read}
37095 (@pxref{qXfer memory map read}) packet and is an XML document that
37096 lists memory regions.
37098 @value{GDBN} must be linked with the Expat library to support XML
37099 memory maps. @xref{Expat}.
37101 The top-level structure of the document is shown below:
37104 <?xml version="1.0"?>
37105 <!DOCTYPE memory-map
37106 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37107 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37113 Each region can be either:
37118 A region of RAM starting at @var{addr} and extending for @var{length}
37122 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37127 A region of read-only memory:
37130 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37135 A region of flash memory, with erasure blocks @var{blocksize}
37139 <memory type="flash" start="@var{addr}" length="@var{length}">
37140 <property name="blocksize">@var{blocksize}</property>
37146 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37147 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37148 packets to write to addresses in such ranges.
37150 The formal DTD for memory map format is given below:
37153 <!-- ................................................... -->
37154 <!-- Memory Map XML DTD ................................ -->
37155 <!-- File: memory-map.dtd .............................. -->
37156 <!-- .................................... .............. -->
37157 <!-- memory-map.dtd -->
37158 <!-- memory-map: Root element with versioning -->
37159 <!ELEMENT memory-map (memory | property)>
37160 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37161 <!ELEMENT memory (property)>
37162 <!-- memory: Specifies a memory region,
37163 and its type, or device. -->
37164 <!ATTLIST memory type CDATA #REQUIRED
37165 start CDATA #REQUIRED
37166 length CDATA #REQUIRED
37167 device CDATA #IMPLIED>
37168 <!-- property: Generic attribute tag -->
37169 <!ELEMENT property (#PCDATA | property)*>
37170 <!ATTLIST property name CDATA #REQUIRED>
37173 @node Thread List Format
37174 @section Thread List Format
37175 @cindex thread list format
37177 To efficiently update the list of threads and their attributes,
37178 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37179 (@pxref{qXfer threads read}) and obtains the XML document with
37180 the following structure:
37183 <?xml version="1.0"?>
37185 <thread id="id" core="0">
37186 ... description ...
37191 Each @samp{thread} element must have the @samp{id} attribute that
37192 identifies the thread (@pxref{thread-id syntax}). The
37193 @samp{core} attribute, if present, specifies which processor core
37194 the thread was last executing on. The content of the of @samp{thread}
37195 element is interpreted as human-readable auxilliary information.
37197 @node Traceframe Info Format
37198 @section Traceframe Info Format
37199 @cindex traceframe info format
37201 To be able to know which objects in the inferior can be examined when
37202 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37203 memory ranges, registers and trace state variables that have been
37204 collected in a traceframe.
37206 This list is obtained using the @samp{qXfer:traceframe-info:read}
37207 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37209 @value{GDBN} must be linked with the Expat library to support XML
37210 traceframe info discovery. @xref{Expat}.
37212 The top-level structure of the document is shown below:
37215 <?xml version="1.0"?>
37216 <!DOCTYPE traceframe-info
37217 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37218 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37224 Each traceframe block can be either:
37229 A region of collected memory starting at @var{addr} and extending for
37230 @var{length} bytes from there:
37233 <memory start="@var{addr}" length="@var{length}"/>
37238 The formal DTD for the traceframe info format is given below:
37241 <!ELEMENT traceframe-info (memory)* >
37242 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37244 <!ELEMENT memory EMPTY>
37245 <!ATTLIST memory start CDATA #REQUIRED
37246 length CDATA #REQUIRED>
37249 @include agentexpr.texi
37251 @node Target Descriptions
37252 @appendix Target Descriptions
37253 @cindex target descriptions
37255 One of the challenges of using @value{GDBN} to debug embedded systems
37256 is that there are so many minor variants of each processor
37257 architecture in use. It is common practice for vendors to start with
37258 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37259 and then make changes to adapt it to a particular market niche. Some
37260 architectures have hundreds of variants, available from dozens of
37261 vendors. This leads to a number of problems:
37265 With so many different customized processors, it is difficult for
37266 the @value{GDBN} maintainers to keep up with the changes.
37268 Since individual variants may have short lifetimes or limited
37269 audiences, it may not be worthwhile to carry information about every
37270 variant in the @value{GDBN} source tree.
37272 When @value{GDBN} does support the architecture of the embedded system
37273 at hand, the task of finding the correct architecture name to give the
37274 @command{set architecture} command can be error-prone.
37277 To address these problems, the @value{GDBN} remote protocol allows a
37278 target system to not only identify itself to @value{GDBN}, but to
37279 actually describe its own features. This lets @value{GDBN} support
37280 processor variants it has never seen before --- to the extent that the
37281 descriptions are accurate, and that @value{GDBN} understands them.
37283 @value{GDBN} must be linked with the Expat library to support XML
37284 target descriptions. @xref{Expat}.
37287 * Retrieving Descriptions:: How descriptions are fetched from a target.
37288 * Target Description Format:: The contents of a target description.
37289 * Predefined Target Types:: Standard types available for target
37291 * Standard Target Features:: Features @value{GDBN} knows about.
37294 @node Retrieving Descriptions
37295 @section Retrieving Descriptions
37297 Target descriptions can be read from the target automatically, or
37298 specified by the user manually. The default behavior is to read the
37299 description from the target. @value{GDBN} retrieves it via the remote
37300 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37301 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37302 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37303 XML document, of the form described in @ref{Target Description
37306 Alternatively, you can specify a file to read for the target description.
37307 If a file is set, the target will not be queried. The commands to
37308 specify a file are:
37311 @cindex set tdesc filename
37312 @item set tdesc filename @var{path}
37313 Read the target description from @var{path}.
37315 @cindex unset tdesc filename
37316 @item unset tdesc filename
37317 Do not read the XML target description from a file. @value{GDBN}
37318 will use the description supplied by the current target.
37320 @cindex show tdesc filename
37321 @item show tdesc filename
37322 Show the filename to read for a target description, if any.
37326 @node Target Description Format
37327 @section Target Description Format
37328 @cindex target descriptions, XML format
37330 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37331 document which complies with the Document Type Definition provided in
37332 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37333 means you can use generally available tools like @command{xmllint} to
37334 check that your feature descriptions are well-formed and valid.
37335 However, to help people unfamiliar with XML write descriptions for
37336 their targets, we also describe the grammar here.
37338 Target descriptions can identify the architecture of the remote target
37339 and (for some architectures) provide information about custom register
37340 sets. They can also identify the OS ABI of the remote target.
37341 @value{GDBN} can use this information to autoconfigure for your
37342 target, or to warn you if you connect to an unsupported target.
37344 Here is a simple target description:
37347 <target version="1.0">
37348 <architecture>i386:x86-64</architecture>
37353 This minimal description only says that the target uses
37354 the x86-64 architecture.
37356 A target description has the following overall form, with [ ] marking
37357 optional elements and @dots{} marking repeatable elements. The elements
37358 are explained further below.
37361 <?xml version="1.0"?>
37362 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37363 <target version="1.0">
37364 @r{[}@var{architecture}@r{]}
37365 @r{[}@var{osabi}@r{]}
37366 @r{[}@var{compatible}@r{]}
37367 @r{[}@var{feature}@dots{}@r{]}
37372 The description is generally insensitive to whitespace and line
37373 breaks, under the usual common-sense rules. The XML version
37374 declaration and document type declaration can generally be omitted
37375 (@value{GDBN} does not require them), but specifying them may be
37376 useful for XML validation tools. The @samp{version} attribute for
37377 @samp{<target>} may also be omitted, but we recommend
37378 including it; if future versions of @value{GDBN} use an incompatible
37379 revision of @file{gdb-target.dtd}, they will detect and report
37380 the version mismatch.
37382 @subsection Inclusion
37383 @cindex target descriptions, inclusion
37386 @cindex <xi:include>
37389 It can sometimes be valuable to split a target description up into
37390 several different annexes, either for organizational purposes, or to
37391 share files between different possible target descriptions. You can
37392 divide a description into multiple files by replacing any element of
37393 the target description with an inclusion directive of the form:
37396 <xi:include href="@var{document}"/>
37400 When @value{GDBN} encounters an element of this form, it will retrieve
37401 the named XML @var{document}, and replace the inclusion directive with
37402 the contents of that document. If the current description was read
37403 using @samp{qXfer}, then so will be the included document;
37404 @var{document} will be interpreted as the name of an annex. If the
37405 current description was read from a file, @value{GDBN} will look for
37406 @var{document} as a file in the same directory where it found the
37407 original description.
37409 @subsection Architecture
37410 @cindex <architecture>
37412 An @samp{<architecture>} element has this form:
37415 <architecture>@var{arch}</architecture>
37418 @var{arch} is one of the architectures from the set accepted by
37419 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37422 @cindex @code{<osabi>}
37424 This optional field was introduced in @value{GDBN} version 7.0.
37425 Previous versions of @value{GDBN} ignore it.
37427 An @samp{<osabi>} element has this form:
37430 <osabi>@var{abi-name}</osabi>
37433 @var{abi-name} is an OS ABI name from the same selection accepted by
37434 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
37436 @subsection Compatible Architecture
37437 @cindex @code{<compatible>}
37439 This optional field was introduced in @value{GDBN} version 7.0.
37440 Previous versions of @value{GDBN} ignore it.
37442 A @samp{<compatible>} element has this form:
37445 <compatible>@var{arch}</compatible>
37448 @var{arch} is one of the architectures from the set accepted by
37449 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37451 A @samp{<compatible>} element is used to specify that the target
37452 is able to run binaries in some other than the main target architecture
37453 given by the @samp{<architecture>} element. For example, on the
37454 Cell Broadband Engine, the main architecture is @code{powerpc:common}
37455 or @code{powerpc:common64}, but the system is able to run binaries
37456 in the @code{spu} architecture as well. The way to describe this
37457 capability with @samp{<compatible>} is as follows:
37460 <architecture>powerpc:common</architecture>
37461 <compatible>spu</compatible>
37464 @subsection Features
37467 Each @samp{<feature>} describes some logical portion of the target
37468 system. Features are currently used to describe available CPU
37469 registers and the types of their contents. A @samp{<feature>} element
37473 <feature name="@var{name}">
37474 @r{[}@var{type}@dots{}@r{]}
37480 Each feature's name should be unique within the description. The name
37481 of a feature does not matter unless @value{GDBN} has some special
37482 knowledge of the contents of that feature; if it does, the feature
37483 should have its standard name. @xref{Standard Target Features}.
37487 Any register's value is a collection of bits which @value{GDBN} must
37488 interpret. The default interpretation is a two's complement integer,
37489 but other types can be requested by name in the register description.
37490 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
37491 Target Types}), and the description can define additional composite types.
37493 Each type element must have an @samp{id} attribute, which gives
37494 a unique (within the containing @samp{<feature>}) name to the type.
37495 Types must be defined before they are used.
37498 Some targets offer vector registers, which can be treated as arrays
37499 of scalar elements. These types are written as @samp{<vector>} elements,
37500 specifying the array element type, @var{type}, and the number of elements,
37504 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
37508 If a register's value is usefully viewed in multiple ways, define it
37509 with a union type containing the useful representations. The
37510 @samp{<union>} element contains one or more @samp{<field>} elements,
37511 each of which has a @var{name} and a @var{type}:
37514 <union id="@var{id}">
37515 <field name="@var{name}" type="@var{type}"/>
37521 If a register's value is composed from several separate values, define
37522 it with a structure type. There are two forms of the @samp{<struct>}
37523 element; a @samp{<struct>} element must either contain only bitfields
37524 or contain no bitfields. If the structure contains only bitfields,
37525 its total size in bytes must be specified, each bitfield must have an
37526 explicit start and end, and bitfields are automatically assigned an
37527 integer type. The field's @var{start} should be less than or
37528 equal to its @var{end}, and zero represents the least significant bit.
37531 <struct id="@var{id}" size="@var{size}">
37532 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37537 If the structure contains no bitfields, then each field has an
37538 explicit type, and no implicit padding is added.
37541 <struct id="@var{id}">
37542 <field name="@var{name}" type="@var{type}"/>
37548 If a register's value is a series of single-bit flags, define it with
37549 a flags type. The @samp{<flags>} element has an explicit @var{size}
37550 and contains one or more @samp{<field>} elements. Each field has a
37551 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
37555 <flags id="@var{id}" size="@var{size}">
37556 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37561 @subsection Registers
37564 Each register is represented as an element with this form:
37567 <reg name="@var{name}"
37568 bitsize="@var{size}"
37569 @r{[}regnum="@var{num}"@r{]}
37570 @r{[}save-restore="@var{save-restore}"@r{]}
37571 @r{[}type="@var{type}"@r{]}
37572 @r{[}group="@var{group}"@r{]}/>
37576 The components are as follows:
37581 The register's name; it must be unique within the target description.
37584 The register's size, in bits.
37587 The register's number. If omitted, a register's number is one greater
37588 than that of the previous register (either in the current feature or in
37589 a preceding feature); the first register in the target description
37590 defaults to zero. This register number is used to read or write
37591 the register; e.g.@: it is used in the remote @code{p} and @code{P}
37592 packets, and registers appear in the @code{g} and @code{G} packets
37593 in order of increasing register number.
37596 Whether the register should be preserved across inferior function
37597 calls; this must be either @code{yes} or @code{no}. The default is
37598 @code{yes}, which is appropriate for most registers except for
37599 some system control registers; this is not related to the target's
37603 The type of the register. @var{type} may be a predefined type, a type
37604 defined in the current feature, or one of the special types @code{int}
37605 and @code{float}. @code{int} is an integer type of the correct size
37606 for @var{bitsize}, and @code{float} is a floating point type (in the
37607 architecture's normal floating point format) of the correct size for
37608 @var{bitsize}. The default is @code{int}.
37611 The register group to which this register belongs. @var{group} must
37612 be either @code{general}, @code{float}, or @code{vector}. If no
37613 @var{group} is specified, @value{GDBN} will not display the register
37614 in @code{info registers}.
37618 @node Predefined Target Types
37619 @section Predefined Target Types
37620 @cindex target descriptions, predefined types
37622 Type definitions in the self-description can build up composite types
37623 from basic building blocks, but can not define fundamental types. Instead,
37624 standard identifiers are provided by @value{GDBN} for the fundamental
37625 types. The currently supported types are:
37634 Signed integer types holding the specified number of bits.
37641 Unsigned integer types holding the specified number of bits.
37645 Pointers to unspecified code and data. The program counter and
37646 any dedicated return address register may be marked as code
37647 pointers; printing a code pointer converts it into a symbolic
37648 address. The stack pointer and any dedicated address registers
37649 may be marked as data pointers.
37652 Single precision IEEE floating point.
37655 Double precision IEEE floating point.
37658 The 12-byte extended precision format used by ARM FPA registers.
37661 The 10-byte extended precision format used by x87 registers.
37664 32bit @sc{eflags} register used by x86.
37667 32bit @sc{mxcsr} register used by x86.
37671 @node Standard Target Features
37672 @section Standard Target Features
37673 @cindex target descriptions, standard features
37675 A target description must contain either no registers or all the
37676 target's registers. If the description contains no registers, then
37677 @value{GDBN} will assume a default register layout, selected based on
37678 the architecture. If the description contains any registers, the
37679 default layout will not be used; the standard registers must be
37680 described in the target description, in such a way that @value{GDBN}
37681 can recognize them.
37683 This is accomplished by giving specific names to feature elements
37684 which contain standard registers. @value{GDBN} will look for features
37685 with those names and verify that they contain the expected registers;
37686 if any known feature is missing required registers, or if any required
37687 feature is missing, @value{GDBN} will reject the target
37688 description. You can add additional registers to any of the
37689 standard features --- @value{GDBN} will display them just as if
37690 they were added to an unrecognized feature.
37692 This section lists the known features and their expected contents.
37693 Sample XML documents for these features are included in the
37694 @value{GDBN} source tree, in the directory @file{gdb/features}.
37696 Names recognized by @value{GDBN} should include the name of the
37697 company or organization which selected the name, and the overall
37698 architecture to which the feature applies; so e.g.@: the feature
37699 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
37701 The names of registers are not case sensitive for the purpose
37702 of recognizing standard features, but @value{GDBN} will only display
37703 registers using the capitalization used in the description.
37710 * PowerPC Features::
37716 @subsection ARM Features
37717 @cindex target descriptions, ARM features
37719 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
37721 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
37722 @samp{lr}, @samp{pc}, and @samp{cpsr}.
37724 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
37725 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
37726 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
37729 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
37730 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
37732 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
37733 it should contain at least registers @samp{wR0} through @samp{wR15} and
37734 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
37735 @samp{wCSSF}, and @samp{wCASF} registers are optional.
37737 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
37738 should contain at least registers @samp{d0} through @samp{d15}. If
37739 they are present, @samp{d16} through @samp{d31} should also be included.
37740 @value{GDBN} will synthesize the single-precision registers from
37741 halves of the double-precision registers.
37743 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
37744 need to contain registers; it instructs @value{GDBN} to display the
37745 VFP double-precision registers as vectors and to synthesize the
37746 quad-precision registers from pairs of double-precision registers.
37747 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
37748 be present and include 32 double-precision registers.
37750 @node i386 Features
37751 @subsection i386 Features
37752 @cindex target descriptions, i386 features
37754 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
37755 targets. It should describe the following registers:
37759 @samp{eax} through @samp{edi} plus @samp{eip} for i386
37761 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
37763 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
37764 @samp{fs}, @samp{gs}
37766 @samp{st0} through @samp{st7}
37768 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
37769 @samp{foseg}, @samp{fooff} and @samp{fop}
37772 The register sets may be different, depending on the target.
37774 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
37775 describe registers:
37779 @samp{xmm0} through @samp{xmm7} for i386
37781 @samp{xmm0} through @samp{xmm15} for amd64
37786 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
37787 @samp{org.gnu.gdb.i386.sse} feature. It should
37788 describe the upper 128 bits of @sc{ymm} registers:
37792 @samp{ymm0h} through @samp{ymm7h} for i386
37794 @samp{ymm0h} through @samp{ymm15h} for amd64
37797 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
37798 describe a single register, @samp{orig_eax}.
37800 @node MIPS Features
37801 @subsection MIPS Features
37802 @cindex target descriptions, MIPS features
37804 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
37805 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
37806 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
37809 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
37810 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
37811 registers. They may be 32-bit or 64-bit depending on the target.
37813 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
37814 it may be optional in a future version of @value{GDBN}. It should
37815 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
37816 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
37818 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
37819 contain a single register, @samp{restart}, which is used by the
37820 Linux kernel to control restartable syscalls.
37822 @node M68K Features
37823 @subsection M68K Features
37824 @cindex target descriptions, M68K features
37827 @item @samp{org.gnu.gdb.m68k.core}
37828 @itemx @samp{org.gnu.gdb.coldfire.core}
37829 @itemx @samp{org.gnu.gdb.fido.core}
37830 One of those features must be always present.
37831 The feature that is present determines which flavor of m68k is
37832 used. The feature that is present should contain registers
37833 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
37834 @samp{sp}, @samp{ps} and @samp{pc}.
37836 @item @samp{org.gnu.gdb.coldfire.fp}
37837 This feature is optional. If present, it should contain registers
37838 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
37842 @node PowerPC Features
37843 @subsection PowerPC Features
37844 @cindex target descriptions, PowerPC features
37846 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
37847 targets. It should contain registers @samp{r0} through @samp{r31},
37848 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
37849 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
37851 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
37852 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
37854 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
37855 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
37858 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
37859 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
37860 will combine these registers with the floating point registers
37861 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
37862 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
37863 through @samp{vs63}, the set of vector registers for POWER7.
37865 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
37866 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
37867 @samp{spefscr}. SPE targets should provide 32-bit registers in
37868 @samp{org.gnu.gdb.power.core} and provide the upper halves in
37869 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
37870 these to present registers @samp{ev0} through @samp{ev31} to the
37873 @node TIC6x Features
37874 @subsection TMS320C6x Features
37875 @cindex target descriptions, TIC6x features
37876 @cindex target descriptions, TMS320C6x features
37877 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
37878 targets. It should contain registers @samp{A0} through @samp{A15},
37879 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
37881 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
37882 contain registers @samp{A16} through @samp{A31} and @samp{B16}
37883 through @samp{B31}.
37885 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
37886 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
37888 @node Operating System Information
37889 @appendix Operating System Information
37890 @cindex operating system information
37896 Users of @value{GDBN} often wish to obtain information about the state of
37897 the operating system running on the target---for example the list of
37898 processes, or the list of open files. This section describes the
37899 mechanism that makes it possible. This mechanism is similar to the
37900 target features mechanism (@pxref{Target Descriptions}), but focuses
37901 on a different aspect of target.
37903 Operating system information is retrived from the target via the
37904 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
37905 read}). The object name in the request should be @samp{osdata}, and
37906 the @var{annex} identifies the data to be fetched.
37909 @appendixsection Process list
37910 @cindex operating system information, process list
37912 When requesting the process list, the @var{annex} field in the
37913 @samp{qXfer} request should be @samp{processes}. The returned data is
37914 an XML document. The formal syntax of this document is defined in
37915 @file{gdb/features/osdata.dtd}.
37917 An example document is:
37920 <?xml version="1.0"?>
37921 <!DOCTYPE target SYSTEM "osdata.dtd">
37922 <osdata type="processes">
37924 <column name="pid">1</column>
37925 <column name="user">root</column>
37926 <column name="command">/sbin/init</column>
37927 <column name="cores">1,2,3</column>
37932 Each item should include a column whose name is @samp{pid}. The value
37933 of that column should identify the process on the target. The
37934 @samp{user} and @samp{command} columns are optional, and will be
37935 displayed by @value{GDBN}. The @samp{cores} column, if present,
37936 should contain a comma-separated list of cores that this process
37937 is running on. Target may provide additional columns,
37938 which @value{GDBN} currently ignores.
37940 @node Trace File Format
37941 @appendix Trace File Format
37942 @cindex trace file format
37944 The trace file comes in three parts: a header, a textual description
37945 section, and a trace frame section with binary data.
37947 The header has the form @code{\x7fTRACE0\n}. The first byte is
37948 @code{0x7f} so as to indicate that the file contains binary data,
37949 while the @code{0} is a version number that may have different values
37952 The description section consists of multiple lines of @sc{ascii} text
37953 separated by newline characters (@code{0xa}). The lines may include a
37954 variety of optional descriptive or context-setting information, such
37955 as tracepoint definitions or register set size. @value{GDBN} will
37956 ignore any line that it does not recognize. An empty line marks the end
37959 @c FIXME add some specific types of data
37961 The trace frame section consists of a number of consecutive frames.
37962 Each frame begins with a two-byte tracepoint number, followed by a
37963 four-byte size giving the amount of data in the frame. The data in
37964 the frame consists of a number of blocks, each introduced by a
37965 character indicating its type (at least register, memory, and trace
37966 state variable). The data in this section is raw binary, not a
37967 hexadecimal or other encoding; its endianness matches the target's
37970 @c FIXME bi-arch may require endianness/arch info in description section
37973 @item R @var{bytes}
37974 Register block. The number and ordering of bytes matches that of a
37975 @code{g} packet in the remote protocol. Note that these are the
37976 actual bytes, in target order and @value{GDBN} register order, not a
37977 hexadecimal encoding.
37979 @item M @var{address} @var{length} @var{bytes}...
37980 Memory block. This is a contiguous block of memory, at the 8-byte
37981 address @var{address}, with a 2-byte length @var{length}, followed by
37982 @var{length} bytes.
37984 @item V @var{number} @var{value}
37985 Trace state variable block. This records the 8-byte signed value
37986 @var{value} of trace state variable numbered @var{number}.
37990 Future enhancements of the trace file format may include additional types
37993 @node Index Section Format
37994 @appendix @code{.gdb_index} section format
37995 @cindex .gdb_index section format
37996 @cindex index section format
37998 This section documents the index section that is created by @code{save
37999 gdb-index} (@pxref{Index Files}). The index section is
38000 DWARF-specific; some knowledge of DWARF is assumed in this
38003 The mapped index file format is designed to be directly
38004 @code{mmap}able on any architecture. In most cases, a datum is
38005 represented using a little-endian 32-bit integer value, called an
38006 @code{offset_type}. Big endian machines must byte-swap the values
38007 before using them. Exceptions to this rule are noted. The data is
38008 laid out such that alignment is always respected.
38010 A mapped index consists of several areas, laid out in order.
38014 The file header. This is a sequence of values, of @code{offset_type}
38015 unless otherwise noted:
38019 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38020 Version 4 differs by its hashing function.
38023 The offset, from the start of the file, of the CU list.
38026 The offset, from the start of the file, of the types CU list. Note
38027 that this area can be empty, in which case this offset will be equal
38028 to the next offset.
38031 The offset, from the start of the file, of the address area.
38034 The offset, from the start of the file, of the symbol table.
38037 The offset, from the start of the file, of the constant pool.
38041 The CU list. This is a sequence of pairs of 64-bit little-endian
38042 values, sorted by the CU offset. The first element in each pair is
38043 the offset of a CU in the @code{.debug_info} section. The second
38044 element in each pair is the length of that CU. References to a CU
38045 elsewhere in the map are done using a CU index, which is just the
38046 0-based index into this table. Note that if there are type CUs, then
38047 conceptually CUs and type CUs form a single list for the purposes of
38051 The types CU list. This is a sequence of triplets of 64-bit
38052 little-endian values. In a triplet, the first value is the CU offset,
38053 the second value is the type offset in the CU, and the third value is
38054 the type signature. The types CU list is not sorted.
38057 The address area. The address area consists of a sequence of address
38058 entries. Each address entry has three elements:
38062 The low address. This is a 64-bit little-endian value.
38065 The high address. This is a 64-bit little-endian value. Like
38066 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38069 The CU index. This is an @code{offset_type} value.
38073 The symbol table. This is an open-addressed hash table. The size of
38074 the hash table is always a power of 2.
38076 Each slot in the hash table consists of a pair of @code{offset_type}
38077 values. The first value is the offset of the symbol's name in the
38078 constant pool. The second value is the offset of the CU vector in the
38081 If both values are 0, then this slot in the hash table is empty. This
38082 is ok because while 0 is a valid constant pool index, it cannot be a
38083 valid index for both a string and a CU vector.
38085 The hash value for a table entry is computed by applying an
38086 iterative hash function to the symbol's name. Starting with an
38087 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38088 the string is incorporated into the hash using the formula depending on the
38093 The formula is @code{r = r * 67 + c - 113}.
38096 The formula is @code{r = r * 67 + tolower (c) - 113}.
38099 The terminating @samp{\0} is not incorporated into the hash.
38101 The step size used in the hash table is computed via
38102 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38103 value, and @samp{size} is the size of the hash table. The step size
38104 is used to find the next candidate slot when handling a hash
38107 The names of C@t{++} symbols in the hash table are canonicalized. We
38108 don't currently have a simple description of the canonicalization
38109 algorithm; if you intend to create new index sections, you must read
38113 The constant pool. This is simply a bunch of bytes. It is organized
38114 so that alignment is correct: CU vectors are stored first, followed by
38117 A CU vector in the constant pool is a sequence of @code{offset_type}
38118 values. The first value is the number of CU indices in the vector.
38119 Each subsequent value is the index of a CU in the CU list. This
38120 element in the hash table is used to indicate which CUs define the
38123 A string in the constant pool is zero-terminated.
38128 @node GNU Free Documentation License
38129 @appendix GNU Free Documentation License
38138 % I think something like @colophon should be in texinfo. In the
38140 \long\def\colophon{\hbox to0pt{}\vfill
38141 \centerline{The body of this manual is set in}
38142 \centerline{\fontname\tenrm,}
38143 \centerline{with headings in {\bf\fontname\tenbf}}
38144 \centerline{and examples in {\tt\fontname\tentt}.}
38145 \centerline{{\it\fontname\tenit\/},}
38146 \centerline{{\bf\fontname\tenbf}, and}
38147 \centerline{{\sl\fontname\tensl\/}}
38148 \centerline{are used for emphasis.}\vfill}
38150 % Blame: doc@cygnus.com, 1991.