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. Version 3.1 and later of @value{NGCC},
1877 the @sc{gnu} C compiler, provides macro information if you are using
1878 the DWARF debugging format, and specify the option @option{-g3}.
1880 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1881 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1882 information on @value{NGCC} options affecting debug information.
1884 You will have the best debugging experience if you use the latest
1885 version of the DWARF debugging format that your compiler supports.
1886 DWARF is currently the most expressive and best supported debugging
1887 format in @value{GDBN}.
1891 @section Starting your Program
1897 @kindex r @r{(@code{run})}
1900 Use the @code{run} command to start your program under @value{GDBN}.
1901 You must first specify the program name (except on VxWorks) with an
1902 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1903 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1904 (@pxref{Files, ,Commands to Specify Files}).
1908 If you are running your program in an execution environment that
1909 supports processes, @code{run} creates an inferior process and makes
1910 that process run your program. In some environments without processes,
1911 @code{run} jumps to the start of your program. Other targets,
1912 like @samp{remote}, are always running. If you get an error
1913 message like this one:
1916 The "remote" target does not support "run".
1917 Try "help target" or "continue".
1921 then use @code{continue} to run your program. You may need @code{load}
1922 first (@pxref{load}).
1924 The execution of a program is affected by certain information it
1925 receives from its superior. @value{GDBN} provides ways to specify this
1926 information, which you must do @emph{before} starting your program. (You
1927 can change it after starting your program, but such changes only affect
1928 your program the next time you start it.) This information may be
1929 divided into four categories:
1932 @item The @emph{arguments.}
1933 Specify the arguments to give your program as the arguments of the
1934 @code{run} command. If a shell is available on your target, the shell
1935 is used to pass the arguments, so that you may use normal conventions
1936 (such as wildcard expansion or variable substitution) in describing
1938 In Unix systems, you can control which shell is used with the
1939 @code{SHELL} environment variable.
1940 @xref{Arguments, ,Your Program's Arguments}.
1942 @item The @emph{environment.}
1943 Your program normally inherits its environment from @value{GDBN}, but you can
1944 use the @value{GDBN} commands @code{set environment} and @code{unset
1945 environment} to change parts of the environment that affect
1946 your program. @xref{Environment, ,Your Program's Environment}.
1948 @item The @emph{working directory.}
1949 Your program inherits its working directory from @value{GDBN}. You can set
1950 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1951 @xref{Working Directory, ,Your Program's Working Directory}.
1953 @item The @emph{standard input and output.}
1954 Your program normally uses the same device for standard input and
1955 standard output as @value{GDBN} is using. You can redirect input and output
1956 in the @code{run} command line, or you can use the @code{tty} command to
1957 set a different device for your program.
1958 @xref{Input/Output, ,Your Program's Input and Output}.
1961 @emph{Warning:} While input and output redirection work, you cannot use
1962 pipes to pass the output of the program you are debugging to another
1963 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1967 When you issue the @code{run} command, your program begins to execute
1968 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1969 of how to arrange for your program to stop. Once your program has
1970 stopped, you may call functions in your program, using the @code{print}
1971 or @code{call} commands. @xref{Data, ,Examining Data}.
1973 If the modification time of your symbol file has changed since the last
1974 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1975 table, and reads it again. When it does this, @value{GDBN} tries to retain
1976 your current breakpoints.
1981 @cindex run to main procedure
1982 The name of the main procedure can vary from language to language.
1983 With C or C@t{++}, the main procedure name is always @code{main}, but
1984 other languages such as Ada do not require a specific name for their
1985 main procedure. The debugger provides a convenient way to start the
1986 execution of the program and to stop at the beginning of the main
1987 procedure, depending on the language used.
1989 The @samp{start} command does the equivalent of setting a temporary
1990 breakpoint at the beginning of the main procedure and then invoking
1991 the @samp{run} command.
1993 @cindex elaboration phase
1994 Some programs contain an @dfn{elaboration} phase where some startup code is
1995 executed before the main procedure is called. This depends on the
1996 languages used to write your program. In C@t{++}, for instance,
1997 constructors for static and global objects are executed before
1998 @code{main} is called. It is therefore possible that the debugger stops
1999 before reaching the main procedure. However, the temporary breakpoint
2000 will remain to halt execution.
2002 Specify the arguments to give to your program as arguments to the
2003 @samp{start} command. These arguments will be given verbatim to the
2004 underlying @samp{run} command. Note that the same arguments will be
2005 reused if no argument is provided during subsequent calls to
2006 @samp{start} or @samp{run}.
2008 It is sometimes necessary to debug the program during elaboration. In
2009 these cases, using the @code{start} command would stop the execution of
2010 your program too late, as the program would have already completed the
2011 elaboration phase. Under these circumstances, insert breakpoints in your
2012 elaboration code before running your program.
2014 @kindex set exec-wrapper
2015 @item set exec-wrapper @var{wrapper}
2016 @itemx show exec-wrapper
2017 @itemx unset exec-wrapper
2018 When @samp{exec-wrapper} is set, the specified wrapper is used to
2019 launch programs for debugging. @value{GDBN} starts your program
2020 with a shell command of the form @kbd{exec @var{wrapper}
2021 @var{program}}. Quoting is added to @var{program} and its
2022 arguments, but not to @var{wrapper}, so you should add quotes if
2023 appropriate for your shell. The wrapper runs until it executes
2024 your program, and then @value{GDBN} takes control.
2026 You can use any program that eventually calls @code{execve} with
2027 its arguments as a wrapper. Several standard Unix utilities do
2028 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2029 with @code{exec "$@@"} will also work.
2031 For example, you can use @code{env} to pass an environment variable to
2032 the debugged program, without setting the variable in your shell's
2036 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2040 This command is available when debugging locally on most targets, excluding
2041 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2043 @kindex set disable-randomization
2044 @item set disable-randomization
2045 @itemx set disable-randomization on
2046 This option (enabled by default in @value{GDBN}) will turn off the native
2047 randomization of the virtual address space of the started program. This option
2048 is useful for multiple debugging sessions to make the execution better
2049 reproducible and memory addresses reusable across debugging sessions.
2051 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2052 On @sc{gnu}/Linux you can get the same behavior using
2055 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2058 @item set disable-randomization off
2059 Leave the behavior of the started executable unchanged. Some bugs rear their
2060 ugly heads only when the program is loaded at certain addresses. If your bug
2061 disappears when you run the program under @value{GDBN}, that might be because
2062 @value{GDBN} by default disables the address randomization on platforms, such
2063 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2064 disable-randomization off} to try to reproduce such elusive bugs.
2066 On targets where it is available, virtual address space randomization
2067 protects the programs against certain kinds of security attacks. In these
2068 cases the attacker needs to know the exact location of a concrete executable
2069 code. Randomizing its location makes it impossible to inject jumps misusing
2070 a code at its expected addresses.
2072 Prelinking shared libraries provides a startup performance advantage but it
2073 makes addresses in these libraries predictable for privileged processes by
2074 having just unprivileged access at the target system. Reading the shared
2075 library binary gives enough information for assembling the malicious code
2076 misusing it. Still even a prelinked shared library can get loaded at a new
2077 random address just requiring the regular relocation process during the
2078 startup. Shared libraries not already prelinked are always loaded at
2079 a randomly chosen address.
2081 Position independent executables (PIE) contain position independent code
2082 similar to the shared libraries and therefore such executables get loaded at
2083 a randomly chosen address upon startup. PIE executables always load even
2084 already prelinked shared libraries at a random address. You can build such
2085 executable using @command{gcc -fPIE -pie}.
2087 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2088 (as long as the randomization is enabled).
2090 @item show disable-randomization
2091 Show the current setting of the explicit disable of the native randomization of
2092 the virtual address space of the started program.
2097 @section Your Program's Arguments
2099 @cindex arguments (to your program)
2100 The arguments to your program can be specified by the arguments of the
2102 They are passed to a shell, which expands wildcard characters and
2103 performs redirection of I/O, and thence to your program. Your
2104 @code{SHELL} environment variable (if it exists) specifies what shell
2105 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2106 the default shell (@file{/bin/sh} on Unix).
2108 On non-Unix systems, the program is usually invoked directly by
2109 @value{GDBN}, which emulates I/O redirection via the appropriate system
2110 calls, and the wildcard characters are expanded by the startup code of
2111 the program, not by the shell.
2113 @code{run} with no arguments uses the same arguments used by the previous
2114 @code{run}, or those set by the @code{set args} command.
2119 Specify the arguments to be used the next time your program is run. If
2120 @code{set args} has no arguments, @code{run} executes your program
2121 with no arguments. Once you have run your program with arguments,
2122 using @code{set args} before the next @code{run} is the only way to run
2123 it again without arguments.
2127 Show the arguments to give your program when it is started.
2131 @section Your Program's Environment
2133 @cindex environment (of your program)
2134 The @dfn{environment} consists of a set of environment variables and
2135 their values. Environment variables conventionally record such things as
2136 your user name, your home directory, your terminal type, and your search
2137 path for programs to run. Usually you set up environment variables with
2138 the shell and they are inherited by all the other programs you run. When
2139 debugging, it can be useful to try running your program with a modified
2140 environment without having to start @value{GDBN} over again.
2144 @item path @var{directory}
2145 Add @var{directory} to the front of the @code{PATH} environment variable
2146 (the search path for executables) that will be passed to your program.
2147 The value of @code{PATH} used by @value{GDBN} does not change.
2148 You may specify several directory names, separated by whitespace or by a
2149 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2150 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2151 is moved to the front, so it is searched sooner.
2153 You can use the string @samp{$cwd} to refer to whatever is the current
2154 working directory at the time @value{GDBN} searches the path. If you
2155 use @samp{.} instead, it refers to the directory where you executed the
2156 @code{path} command. @value{GDBN} replaces @samp{.} in the
2157 @var{directory} argument (with the current path) before adding
2158 @var{directory} to the search path.
2159 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2160 @c document that, since repeating it would be a no-op.
2164 Display the list of search paths for executables (the @code{PATH}
2165 environment variable).
2167 @kindex show environment
2168 @item show environment @r{[}@var{varname}@r{]}
2169 Print the value of environment variable @var{varname} to be given to
2170 your program when it starts. If you do not supply @var{varname},
2171 print the names and values of all environment variables to be given to
2172 your program. You can abbreviate @code{environment} as @code{env}.
2174 @kindex set environment
2175 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2176 Set environment variable @var{varname} to @var{value}. The value
2177 changes for your program only, not for @value{GDBN} itself. @var{value} may
2178 be any string; the values of environment variables are just strings, and
2179 any interpretation is supplied by your program itself. The @var{value}
2180 parameter is optional; if it is eliminated, the variable is set to a
2182 @c "any string" here does not include leading, trailing
2183 @c blanks. Gnu asks: does anyone care?
2185 For example, this command:
2192 tells the debugged program, when subsequently run, that its user is named
2193 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2194 are not actually required.)
2196 @kindex unset environment
2197 @item unset environment @var{varname}
2198 Remove variable @var{varname} from the environment to be passed to your
2199 program. This is different from @samp{set env @var{varname} =};
2200 @code{unset environment} removes the variable from the environment,
2201 rather than assigning it an empty value.
2204 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2206 by your @code{SHELL} environment variable if it exists (or
2207 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2208 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2209 @file{.bashrc} for BASH---any variables you set in that file affect
2210 your program. You may wish to move setting of environment variables to
2211 files that are only run when you sign on, such as @file{.login} or
2214 @node Working Directory
2215 @section Your Program's Working Directory
2217 @cindex working directory (of your program)
2218 Each time you start your program with @code{run}, it inherits its
2219 working directory from the current working directory of @value{GDBN}.
2220 The @value{GDBN} working directory is initially whatever it inherited
2221 from its parent process (typically the shell), but you can specify a new
2222 working directory in @value{GDBN} with the @code{cd} command.
2224 The @value{GDBN} working directory also serves as a default for the commands
2225 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2230 @cindex change working directory
2231 @item cd @var{directory}
2232 Set the @value{GDBN} working directory to @var{directory}.
2236 Print the @value{GDBN} working directory.
2239 It is generally impossible to find the current working directory of
2240 the process being debugged (since a program can change its directory
2241 during its run). If you work on a system where @value{GDBN} is
2242 configured with the @file{/proc} support, you can use the @code{info
2243 proc} command (@pxref{SVR4 Process Information}) to find out the
2244 current working directory of the debuggee.
2247 @section Your Program's Input and Output
2252 By default, the program you run under @value{GDBN} does input and output to
2253 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2254 to its own terminal modes to interact with you, but it records the terminal
2255 modes your program was using and switches back to them when you continue
2256 running your program.
2259 @kindex info terminal
2261 Displays information recorded by @value{GDBN} about the terminal modes your
2265 You can redirect your program's input and/or output using shell
2266 redirection with the @code{run} command. For example,
2273 starts your program, diverting its output to the file @file{outfile}.
2276 @cindex controlling terminal
2277 Another way to specify where your program should do input and output is
2278 with the @code{tty} command. This command accepts a file name as
2279 argument, and causes this file to be the default for future @code{run}
2280 commands. It also resets the controlling terminal for the child
2281 process, for future @code{run} commands. For example,
2288 directs that processes started with subsequent @code{run} commands
2289 default to do input and output on the terminal @file{/dev/ttyb} and have
2290 that as their controlling terminal.
2292 An explicit redirection in @code{run} overrides the @code{tty} command's
2293 effect on the input/output device, but not its effect on the controlling
2296 When you use the @code{tty} command or redirect input in the @code{run}
2297 command, only the input @emph{for your program} is affected. The input
2298 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2299 for @code{set inferior-tty}.
2301 @cindex inferior tty
2302 @cindex set inferior controlling terminal
2303 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2304 display the name of the terminal that will be used for future runs of your
2308 @item set inferior-tty /dev/ttyb
2309 @kindex set inferior-tty
2310 Set the tty for the program being debugged to /dev/ttyb.
2312 @item show inferior-tty
2313 @kindex show inferior-tty
2314 Show the current tty for the program being debugged.
2318 @section Debugging an Already-running Process
2323 @item attach @var{process-id}
2324 This command attaches to a running process---one that was started
2325 outside @value{GDBN}. (@code{info files} shows your active
2326 targets.) The command takes as argument a process ID. The usual way to
2327 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2328 or with the @samp{jobs -l} shell command.
2330 @code{attach} does not repeat if you press @key{RET} a second time after
2331 executing the command.
2334 To use @code{attach}, your program must be running in an environment
2335 which supports processes; for example, @code{attach} does not work for
2336 programs on bare-board targets that lack an operating system. You must
2337 also have permission to send the process a signal.
2339 When you use @code{attach}, the debugger finds the program running in
2340 the process first by looking in the current working directory, then (if
2341 the program is not found) by using the source file search path
2342 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2343 the @code{file} command to load the program. @xref{Files, ,Commands to
2346 The first thing @value{GDBN} does after arranging to debug the specified
2347 process is to stop it. You can examine and modify an attached process
2348 with all the @value{GDBN} commands that are ordinarily available when
2349 you start processes with @code{run}. You can insert breakpoints; you
2350 can step and continue; you can modify storage. If you would rather the
2351 process continue running, you may use the @code{continue} command after
2352 attaching @value{GDBN} to the process.
2357 When you have finished debugging the attached process, you can use the
2358 @code{detach} command to release it from @value{GDBN} control. Detaching
2359 the process continues its execution. After the @code{detach} command,
2360 that process and @value{GDBN} become completely independent once more, and you
2361 are ready to @code{attach} another process or start one with @code{run}.
2362 @code{detach} does not repeat if you press @key{RET} again after
2363 executing the command.
2366 If you exit @value{GDBN} while you have an attached process, you detach
2367 that process. If you use the @code{run} command, you kill that process.
2368 By default, @value{GDBN} asks for confirmation if you try to do either of these
2369 things; you can control whether or not you need to confirm by using the
2370 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2374 @section Killing the Child Process
2379 Kill the child process in which your program is running under @value{GDBN}.
2382 This command is useful if you wish to debug a core dump instead of a
2383 running process. @value{GDBN} ignores any core dump file while your program
2386 On some operating systems, a program cannot be executed outside @value{GDBN}
2387 while you have breakpoints set on it inside @value{GDBN}. You can use the
2388 @code{kill} command in this situation to permit running your program
2389 outside the debugger.
2391 The @code{kill} command is also useful if you wish to recompile and
2392 relink your program, since on many systems it is impossible to modify an
2393 executable file while it is running in a process. In this case, when you
2394 next type @code{run}, @value{GDBN} notices that the file has changed, and
2395 reads the symbol table again (while trying to preserve your current
2396 breakpoint settings).
2398 @node Inferiors and Programs
2399 @section Debugging Multiple Inferiors and Programs
2401 @value{GDBN} lets you run and debug multiple programs in a single
2402 session. In addition, @value{GDBN} on some systems may let you run
2403 several programs simultaneously (otherwise you have to exit from one
2404 before starting another). In the most general case, you can have
2405 multiple threads of execution in each of multiple processes, launched
2406 from multiple executables.
2409 @value{GDBN} represents the state of each program execution with an
2410 object called an @dfn{inferior}. An inferior typically corresponds to
2411 a process, but is more general and applies also to targets that do not
2412 have processes. Inferiors may be created before a process runs, and
2413 may be retained after a process exits. Inferiors have unique
2414 identifiers that are different from process ids. Usually each
2415 inferior will also have its own distinct address space, although some
2416 embedded targets may have several inferiors running in different parts
2417 of a single address space. Each inferior may in turn have multiple
2418 threads running in it.
2420 To find out what inferiors exist at any moment, use @w{@code{info
2424 @kindex info inferiors
2425 @item info inferiors
2426 Print a list of all inferiors currently being managed by @value{GDBN}.
2428 @value{GDBN} displays for each inferior (in this order):
2432 the inferior number assigned by @value{GDBN}
2435 the target system's inferior identifier
2438 the name of the executable the inferior is running.
2443 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2444 indicates the current inferior.
2448 @c end table here to get a little more width for example
2451 (@value{GDBP}) info inferiors
2452 Num Description Executable
2453 2 process 2307 hello
2454 * 1 process 3401 goodbye
2457 To switch focus between inferiors, use the @code{inferior} command:
2460 @kindex inferior @var{infno}
2461 @item inferior @var{infno}
2462 Make inferior number @var{infno} the current inferior. The argument
2463 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2464 in the first field of the @samp{info inferiors} display.
2468 You can get multiple executables into a debugging session via the
2469 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2470 systems @value{GDBN} can add inferiors to the debug session
2471 automatically by following calls to @code{fork} and @code{exec}. To
2472 remove inferiors from the debugging session use the
2473 @w{@code{remove-inferiors}} command.
2476 @kindex add-inferior
2477 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2478 Adds @var{n} inferiors to be run using @var{executable} as the
2479 executable. @var{n} defaults to 1. If no executable is specified,
2480 the inferiors begins empty, with no program. You can still assign or
2481 change the program assigned to the inferior at any time by using the
2482 @code{file} command with the executable name as its argument.
2484 @kindex clone-inferior
2485 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2486 Adds @var{n} inferiors ready to execute the same program as inferior
2487 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2488 number of the current inferior. This is a convenient command when you
2489 want to run another instance of the inferior you are debugging.
2492 (@value{GDBP}) info inferiors
2493 Num Description Executable
2494 * 1 process 29964 helloworld
2495 (@value{GDBP}) clone-inferior
2498 (@value{GDBP}) info inferiors
2499 Num Description Executable
2501 * 1 process 29964 helloworld
2504 You can now simply switch focus to inferior 2 and run it.
2506 @kindex remove-inferiors
2507 @item remove-inferiors @var{infno}@dots{}
2508 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2509 possible to remove an inferior that is running with this command. For
2510 those, use the @code{kill} or @code{detach} command first.
2514 To quit debugging one of the running inferiors that is not the current
2515 inferior, you can either detach from it by using the @w{@code{detach
2516 inferior}} command (allowing it to run independently), or kill it
2517 using the @w{@code{kill inferiors}} command:
2520 @kindex detach inferiors @var{infno}@dots{}
2521 @item detach inferior @var{infno}@dots{}
2522 Detach from the inferior or inferiors identified by @value{GDBN}
2523 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2524 still stays on the list of inferiors shown by @code{info inferiors},
2525 but its Description will show @samp{<null>}.
2527 @kindex kill inferiors @var{infno}@dots{}
2528 @item kill inferiors @var{infno}@dots{}
2529 Kill the inferior or inferiors identified by @value{GDBN} inferior
2530 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2531 stays on the list of inferiors shown by @code{info inferiors}, but its
2532 Description will show @samp{<null>}.
2535 After the successful completion of a command such as @code{detach},
2536 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2537 a normal process exit, the inferior is still valid and listed with
2538 @code{info inferiors}, ready to be restarted.
2541 To be notified when inferiors are started or exit under @value{GDBN}'s
2542 control use @w{@code{set print inferior-events}}:
2545 @kindex set print inferior-events
2546 @cindex print messages on inferior start and exit
2547 @item set print inferior-events
2548 @itemx set print inferior-events on
2549 @itemx set print inferior-events off
2550 The @code{set print inferior-events} command allows you to enable or
2551 disable printing of messages when @value{GDBN} notices that new
2552 inferiors have started or that inferiors have exited or have been
2553 detached. By default, these messages will not be printed.
2555 @kindex show print inferior-events
2556 @item show print inferior-events
2557 Show whether messages will be printed when @value{GDBN} detects that
2558 inferiors have started, exited or have been detached.
2561 Many commands will work the same with multiple programs as with a
2562 single program: e.g., @code{print myglobal} will simply display the
2563 value of @code{myglobal} in the current inferior.
2566 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2567 get more info about the relationship of inferiors, programs, address
2568 spaces in a debug session. You can do that with the @w{@code{maint
2569 info program-spaces}} command.
2572 @kindex maint info program-spaces
2573 @item maint info program-spaces
2574 Print a list of all program spaces currently being managed by
2577 @value{GDBN} displays for each program space (in this order):
2581 the program space number assigned by @value{GDBN}
2584 the name of the executable loaded into the program space, with e.g.,
2585 the @code{file} command.
2590 An asterisk @samp{*} preceding the @value{GDBN} program space number
2591 indicates the current program space.
2593 In addition, below each program space line, @value{GDBN} prints extra
2594 information that isn't suitable to display in tabular form. For
2595 example, the list of inferiors bound to the program space.
2598 (@value{GDBP}) maint info program-spaces
2601 Bound inferiors: ID 1 (process 21561)
2605 Here we can see that no inferior is running the program @code{hello},
2606 while @code{process 21561} is running the program @code{goodbye}. On
2607 some targets, it is possible that multiple inferiors are bound to the
2608 same program space. The most common example is that of debugging both
2609 the parent and child processes of a @code{vfork} call. For example,
2612 (@value{GDBP}) maint info program-spaces
2615 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2618 Here, both inferior 2 and inferior 1 are running in the same program
2619 space as a result of inferior 1 having executed a @code{vfork} call.
2623 @section Debugging Programs with Multiple Threads
2625 @cindex threads of execution
2626 @cindex multiple threads
2627 @cindex switching threads
2628 In some operating systems, such as HP-UX and Solaris, a single program
2629 may have more than one @dfn{thread} of execution. The precise semantics
2630 of threads differ from one operating system to another, but in general
2631 the threads of a single program are akin to multiple processes---except
2632 that they share one address space (that is, they can all examine and
2633 modify the same variables). On the other hand, each thread has its own
2634 registers and execution stack, and perhaps private memory.
2636 @value{GDBN} provides these facilities for debugging multi-thread
2640 @item automatic notification of new threads
2641 @item @samp{thread @var{threadno}}, a command to switch among threads
2642 @item @samp{info threads}, a command to inquire about existing threads
2643 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2644 a command to apply a command to a list of threads
2645 @item thread-specific breakpoints
2646 @item @samp{set print thread-events}, which controls printing of
2647 messages on thread start and exit.
2648 @item @samp{set libthread-db-search-path @var{path}}, which lets
2649 the user specify which @code{libthread_db} to use if the default choice
2650 isn't compatible with the program.
2654 @emph{Warning:} These facilities are not yet available on every
2655 @value{GDBN} configuration where the operating system supports threads.
2656 If your @value{GDBN} does not support threads, these commands have no
2657 effect. For example, a system without thread support shows no output
2658 from @samp{info threads}, and always rejects the @code{thread} command,
2662 (@value{GDBP}) info threads
2663 (@value{GDBP}) thread 1
2664 Thread ID 1 not known. Use the "info threads" command to
2665 see the IDs of currently known threads.
2667 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2668 @c doesn't support threads"?
2671 @cindex focus of debugging
2672 @cindex current thread
2673 The @value{GDBN} thread debugging facility allows you to observe all
2674 threads while your program runs---but whenever @value{GDBN} takes
2675 control, one thread in particular is always the focus of debugging.
2676 This thread is called the @dfn{current thread}. Debugging commands show
2677 program information from the perspective of the current thread.
2679 @cindex @code{New} @var{systag} message
2680 @cindex thread identifier (system)
2681 @c FIXME-implementors!! It would be more helpful if the [New...] message
2682 @c included GDB's numeric thread handle, so you could just go to that
2683 @c thread without first checking `info threads'.
2684 Whenever @value{GDBN} detects a new thread in your program, it displays
2685 the target system's identification for the thread with a message in the
2686 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2687 whose form varies depending on the particular system. For example, on
2688 @sc{gnu}/Linux, you might see
2691 [New Thread 0x41e02940 (LWP 25582)]
2695 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2696 the @var{systag} is simply something like @samp{process 368}, with no
2699 @c FIXME!! (1) Does the [New...] message appear even for the very first
2700 @c thread of a program, or does it only appear for the
2701 @c second---i.e.@: when it becomes obvious we have a multithread
2703 @c (2) *Is* there necessarily a first thread always? Or do some
2704 @c multithread systems permit starting a program with multiple
2705 @c threads ab initio?
2707 @cindex thread number
2708 @cindex thread identifier (GDB)
2709 For debugging purposes, @value{GDBN} associates its own thread
2710 number---always a single integer---with each thread in your program.
2713 @kindex info threads
2714 @item info threads @r{[}@var{id}@dots{}@r{]}
2715 Display a summary of all threads currently in your program. Optional
2716 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2717 means to print information only about the specified thread or threads.
2718 @value{GDBN} displays for each thread (in this order):
2722 the thread number assigned by @value{GDBN}
2725 the target system's thread identifier (@var{systag})
2728 the thread's name, if one is known. A thread can either be named by
2729 the user (see @code{thread name}, below), or, in some cases, by the
2733 the current stack frame summary for that thread
2737 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2738 indicates the current thread.
2742 @c end table here to get a little more width for example
2745 (@value{GDBP}) info threads
2747 3 process 35 thread 27 0x34e5 in sigpause ()
2748 2 process 35 thread 23 0x34e5 in sigpause ()
2749 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2753 On Solaris, you can display more information about user threads with a
2754 Solaris-specific command:
2757 @item maint info sol-threads
2758 @kindex maint info sol-threads
2759 @cindex thread info (Solaris)
2760 Display info on Solaris user threads.
2764 @kindex thread @var{threadno}
2765 @item thread @var{threadno}
2766 Make thread number @var{threadno} the current thread. The command
2767 argument @var{threadno} is the internal @value{GDBN} thread number, as
2768 shown in the first field of the @samp{info threads} display.
2769 @value{GDBN} responds by displaying the system identifier of the thread
2770 you selected, and its current stack frame summary:
2773 (@value{GDBP}) thread 2
2774 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2775 #0 some_function (ignore=0x0) at example.c:8
2776 8 printf ("hello\n");
2780 As with the @samp{[New @dots{}]} message, the form of the text after
2781 @samp{Switching to} depends on your system's conventions for identifying
2784 @vindex $_thread@r{, convenience variable}
2785 The debugger convenience variable @samp{$_thread} contains the number
2786 of the current thread. You may find this useful in writing breakpoint
2787 conditional expressions, command scripts, and so forth. See
2788 @xref{Convenience Vars,, Convenience Variables}, for general
2789 information on convenience variables.
2791 @kindex thread apply
2792 @cindex apply command to several threads
2793 @item thread apply [@var{threadno} | all] @var{command}
2794 The @code{thread apply} command allows you to apply the named
2795 @var{command} to one or more threads. Specify the numbers of the
2796 threads that you want affected with the command argument
2797 @var{threadno}. It can be a single thread number, one of the numbers
2798 shown in the first field of the @samp{info threads} display; or it
2799 could be a range of thread numbers, as in @code{2-4}. To apply a
2800 command to all threads, type @kbd{thread apply all @var{command}}.
2803 @cindex name a thread
2804 @item thread name [@var{name}]
2805 This command assigns a name to the current thread. If no argument is
2806 given, any existing user-specified name is removed. The thread name
2807 appears in the @samp{info threads} display.
2809 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2810 determine the name of the thread as given by the OS. On these
2811 systems, a name specified with @samp{thread name} will override the
2812 system-give name, and removing the user-specified name will cause
2813 @value{GDBN} to once again display the system-specified name.
2816 @cindex search for a thread
2817 @item thread find [@var{regexp}]
2818 Search for and display thread ids whose name or @var{systag}
2819 matches the supplied regular expression.
2821 As well as being the complement to the @samp{thread name} command,
2822 this command also allows you to identify a thread by its target
2823 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2827 (@value{GDBN}) thread find 26688
2828 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2829 (@value{GDBN}) info thread 4
2831 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2834 @kindex set print thread-events
2835 @cindex print messages on thread start and exit
2836 @item set print thread-events
2837 @itemx set print thread-events on
2838 @itemx set print thread-events off
2839 The @code{set print thread-events} command allows you to enable or
2840 disable printing of messages when @value{GDBN} notices that new threads have
2841 started or that threads have exited. By default, these messages will
2842 be printed if detection of these events is supported by the target.
2843 Note that these messages cannot be disabled on all targets.
2845 @kindex show print thread-events
2846 @item show print thread-events
2847 Show whether messages will be printed when @value{GDBN} detects that threads
2848 have started and exited.
2851 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2852 more information about how @value{GDBN} behaves when you stop and start
2853 programs with multiple threads.
2855 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2856 watchpoints in programs with multiple threads.
2859 @kindex set libthread-db-search-path
2860 @cindex search path for @code{libthread_db}
2861 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2862 If this variable is set, @var{path} is a colon-separated list of
2863 directories @value{GDBN} will use to search for @code{libthread_db}.
2864 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2865 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2866 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2869 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2870 @code{libthread_db} library to obtain information about threads in the
2871 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2872 to find @code{libthread_db}.
2874 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2875 refers to the default system directories that are
2876 normally searched for loading shared libraries.
2878 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2879 refers to the directory from which @code{libpthread}
2880 was loaded in the inferior process.
2882 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2883 @value{GDBN} attempts to initialize it with the current inferior process.
2884 If this initialization fails (which could happen because of a version
2885 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2886 will unload @code{libthread_db}, and continue with the next directory.
2887 If none of @code{libthread_db} libraries initialize successfully,
2888 @value{GDBN} will issue a warning and thread debugging will be disabled.
2890 Setting @code{libthread-db-search-path} is currently implemented
2891 only on some platforms.
2893 @kindex show libthread-db-search-path
2894 @item show libthread-db-search-path
2895 Display current libthread_db search path.
2897 @kindex set debug libthread-db
2898 @kindex show debug libthread-db
2899 @cindex debugging @code{libthread_db}
2900 @item set debug libthread-db
2901 @itemx show debug libthread-db
2902 Turns on or off display of @code{libthread_db}-related events.
2903 Use @code{1} to enable, @code{0} to disable.
2907 @section Debugging Forks
2909 @cindex fork, debugging programs which call
2910 @cindex multiple processes
2911 @cindex processes, multiple
2912 On most systems, @value{GDBN} has no special support for debugging
2913 programs which create additional processes using the @code{fork}
2914 function. When a program forks, @value{GDBN} will continue to debug the
2915 parent process and the child process will run unimpeded. If you have
2916 set a breakpoint in any code which the child then executes, the child
2917 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2918 will cause it to terminate.
2920 However, if you want to debug the child process there is a workaround
2921 which isn't too painful. Put a call to @code{sleep} in the code which
2922 the child process executes after the fork. It may be useful to sleep
2923 only if a certain environment variable is set, or a certain file exists,
2924 so that the delay need not occur when you don't want to run @value{GDBN}
2925 on the child. While the child is sleeping, use the @code{ps} program to
2926 get its process ID. Then tell @value{GDBN} (a new invocation of
2927 @value{GDBN} if you are also debugging the parent process) to attach to
2928 the child process (@pxref{Attach}). From that point on you can debug
2929 the child process just like any other process which you attached to.
2931 On some systems, @value{GDBN} provides support for debugging programs that
2932 create additional processes using the @code{fork} or @code{vfork} functions.
2933 Currently, the only platforms with this feature are HP-UX (11.x and later
2934 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2936 By default, when a program forks, @value{GDBN} will continue to debug
2937 the parent process and the child process will run unimpeded.
2939 If you want to follow the child process instead of the parent process,
2940 use the command @w{@code{set follow-fork-mode}}.
2943 @kindex set follow-fork-mode
2944 @item set follow-fork-mode @var{mode}
2945 Set the debugger response to a program call of @code{fork} or
2946 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2947 process. The @var{mode} argument can be:
2951 The original process is debugged after a fork. The child process runs
2952 unimpeded. This is the default.
2955 The new process is debugged after a fork. The parent process runs
2960 @kindex show follow-fork-mode
2961 @item show follow-fork-mode
2962 Display the current debugger response to a @code{fork} or @code{vfork} call.
2965 @cindex debugging multiple processes
2966 On Linux, if you want to debug both the parent and child processes, use the
2967 command @w{@code{set detach-on-fork}}.
2970 @kindex set detach-on-fork
2971 @item set detach-on-fork @var{mode}
2972 Tells gdb whether to detach one of the processes after a fork, or
2973 retain debugger control over them both.
2977 The child process (or parent process, depending on the value of
2978 @code{follow-fork-mode}) will be detached and allowed to run
2979 independently. This is the default.
2982 Both processes will be held under the control of @value{GDBN}.
2983 One process (child or parent, depending on the value of
2984 @code{follow-fork-mode}) is debugged as usual, while the other
2989 @kindex show detach-on-fork
2990 @item show detach-on-fork
2991 Show whether detach-on-fork mode is on/off.
2994 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2995 will retain control of all forked processes (including nested forks).
2996 You can list the forked processes under the control of @value{GDBN} by
2997 using the @w{@code{info inferiors}} command, and switch from one fork
2998 to another by using the @code{inferior} command (@pxref{Inferiors and
2999 Programs, ,Debugging Multiple Inferiors and Programs}).
3001 To quit debugging one of the forked processes, you can either detach
3002 from it by using the @w{@code{detach inferiors}} command (allowing it
3003 to run independently), or kill it using the @w{@code{kill inferiors}}
3004 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3007 If you ask to debug a child process and a @code{vfork} is followed by an
3008 @code{exec}, @value{GDBN} executes the new target up to the first
3009 breakpoint in the new target. If you have a breakpoint set on
3010 @code{main} in your original program, the breakpoint will also be set on
3011 the child process's @code{main}.
3013 On some systems, when a child process is spawned by @code{vfork}, you
3014 cannot debug the child or parent until an @code{exec} call completes.
3016 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3017 call executes, the new target restarts. To restart the parent
3018 process, use the @code{file} command with the parent executable name
3019 as its argument. By default, after an @code{exec} call executes,
3020 @value{GDBN} discards the symbols of the previous executable image.
3021 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3025 @kindex set follow-exec-mode
3026 @item set follow-exec-mode @var{mode}
3028 Set debugger response to a program call of @code{exec}. An
3029 @code{exec} call replaces the program image of a process.
3031 @code{follow-exec-mode} can be:
3035 @value{GDBN} creates a new inferior and rebinds the process to this
3036 new inferior. The program the process was running before the
3037 @code{exec} call can be restarted afterwards by restarting the
3043 (@value{GDBP}) info inferiors
3045 Id Description Executable
3048 process 12020 is executing new program: prog2
3049 Program exited normally.
3050 (@value{GDBP}) info inferiors
3051 Id Description Executable
3057 @value{GDBN} keeps the process bound to the same inferior. The new
3058 executable image replaces the previous executable loaded in the
3059 inferior. Restarting the inferior after the @code{exec} call, with
3060 e.g., the @code{run} command, restarts the executable the process was
3061 running after the @code{exec} call. This is the default mode.
3066 (@value{GDBP}) info inferiors
3067 Id Description Executable
3070 process 12020 is executing new program: prog2
3071 Program exited normally.
3072 (@value{GDBP}) info inferiors
3073 Id Description Executable
3080 You can use the @code{catch} command to make @value{GDBN} stop whenever
3081 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3082 Catchpoints, ,Setting Catchpoints}.
3084 @node Checkpoint/Restart
3085 @section Setting a @emph{Bookmark} to Return to Later
3090 @cindex snapshot of a process
3091 @cindex rewind program state
3093 On certain operating systems@footnote{Currently, only
3094 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3095 program's state, called a @dfn{checkpoint}, and come back to it
3098 Returning to a checkpoint effectively undoes everything that has
3099 happened in the program since the @code{checkpoint} was saved. This
3100 includes changes in memory, registers, and even (within some limits)
3101 system state. Effectively, it is like going back in time to the
3102 moment when the checkpoint was saved.
3104 Thus, if you're stepping thru a program and you think you're
3105 getting close to the point where things go wrong, you can save
3106 a checkpoint. Then, if you accidentally go too far and miss
3107 the critical statement, instead of having to restart your program
3108 from the beginning, you can just go back to the checkpoint and
3109 start again from there.
3111 This can be especially useful if it takes a lot of time or
3112 steps to reach the point where you think the bug occurs.
3114 To use the @code{checkpoint}/@code{restart} method of debugging:
3119 Save a snapshot of the debugged program's current execution state.
3120 The @code{checkpoint} command takes no arguments, but each checkpoint
3121 is assigned a small integer id, similar to a breakpoint id.
3123 @kindex info checkpoints
3124 @item info checkpoints
3125 List the checkpoints that have been saved in the current debugging
3126 session. For each checkpoint, the following information will be
3133 @item Source line, or label
3136 @kindex restart @var{checkpoint-id}
3137 @item restart @var{checkpoint-id}
3138 Restore the program state that was saved as checkpoint number
3139 @var{checkpoint-id}. All program variables, registers, stack frames
3140 etc.@: will be returned to the values that they had when the checkpoint
3141 was saved. In essence, gdb will ``wind back the clock'' to the point
3142 in time when the checkpoint was saved.
3144 Note that breakpoints, @value{GDBN} variables, command history etc.
3145 are not affected by restoring a checkpoint. In general, a checkpoint
3146 only restores things that reside in the program being debugged, not in
3149 @kindex delete checkpoint @var{checkpoint-id}
3150 @item delete checkpoint @var{checkpoint-id}
3151 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3155 Returning to a previously saved checkpoint will restore the user state
3156 of the program being debugged, plus a significant subset of the system
3157 (OS) state, including file pointers. It won't ``un-write'' data from
3158 a file, but it will rewind the file pointer to the previous location,
3159 so that the previously written data can be overwritten. For files
3160 opened in read mode, the pointer will also be restored so that the
3161 previously read data can be read again.
3163 Of course, characters that have been sent to a printer (or other
3164 external device) cannot be ``snatched back'', and characters received
3165 from eg.@: a serial device can be removed from internal program buffers,
3166 but they cannot be ``pushed back'' into the serial pipeline, ready to
3167 be received again. Similarly, the actual contents of files that have
3168 been changed cannot be restored (at this time).
3170 However, within those constraints, you actually can ``rewind'' your
3171 program to a previously saved point in time, and begin debugging it
3172 again --- and you can change the course of events so as to debug a
3173 different execution path this time.
3175 @cindex checkpoints and process id
3176 Finally, there is one bit of internal program state that will be
3177 different when you return to a checkpoint --- the program's process
3178 id. Each checkpoint will have a unique process id (or @var{pid}),
3179 and each will be different from the program's original @var{pid}.
3180 If your program has saved a local copy of its process id, this could
3181 potentially pose a problem.
3183 @subsection A Non-obvious Benefit of Using Checkpoints
3185 On some systems such as @sc{gnu}/Linux, address space randomization
3186 is performed on new processes for security reasons. This makes it
3187 difficult or impossible to set a breakpoint, or watchpoint, on an
3188 absolute address if you have to restart the program, since the
3189 absolute location of a symbol will change from one execution to the
3192 A checkpoint, however, is an @emph{identical} copy of a process.
3193 Therefore if you create a checkpoint at (eg.@:) the start of main,
3194 and simply return to that checkpoint instead of restarting the
3195 process, you can avoid the effects of address randomization and
3196 your symbols will all stay in the same place.
3199 @chapter Stopping and Continuing
3201 The principal purposes of using a debugger are so that you can stop your
3202 program before it terminates; or so that, if your program runs into
3203 trouble, you can investigate and find out why.
3205 Inside @value{GDBN}, your program may stop for any of several reasons,
3206 such as a signal, a breakpoint, or reaching a new line after a
3207 @value{GDBN} command such as @code{step}. You may then examine and
3208 change variables, set new breakpoints or remove old ones, and then
3209 continue execution. Usually, the messages shown by @value{GDBN} provide
3210 ample explanation of the status of your program---but you can also
3211 explicitly request this information at any time.
3214 @kindex info program
3216 Display information about the status of your program: whether it is
3217 running or not, what process it is, and why it stopped.
3221 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3222 * Continuing and Stepping:: Resuming execution
3223 * Skipping Over Functions and Files::
3224 Skipping over functions and files
3226 * Thread Stops:: Stopping and starting multi-thread programs
3230 @section Breakpoints, Watchpoints, and Catchpoints
3233 A @dfn{breakpoint} makes your program stop whenever a certain point in
3234 the program is reached. For each breakpoint, you can add conditions to
3235 control in finer detail whether your program stops. You can set
3236 breakpoints with the @code{break} command and its variants (@pxref{Set
3237 Breaks, ,Setting Breakpoints}), to specify the place where your program
3238 should stop by line number, function name or exact address in the
3241 On some systems, you can set breakpoints in shared libraries before
3242 the executable is run. There is a minor limitation on HP-UX systems:
3243 you must wait until the executable is run in order to set breakpoints
3244 in shared library routines that are not called directly by the program
3245 (for example, routines that are arguments in a @code{pthread_create}
3249 @cindex data breakpoints
3250 @cindex memory tracing
3251 @cindex breakpoint on memory address
3252 @cindex breakpoint on variable modification
3253 A @dfn{watchpoint} is a special breakpoint that stops your program
3254 when the value of an expression changes. The expression may be a value
3255 of a variable, or it could involve values of one or more variables
3256 combined by operators, such as @samp{a + b}. This is sometimes called
3257 @dfn{data breakpoints}. You must use a different command to set
3258 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3259 from that, you can manage a watchpoint like any other breakpoint: you
3260 enable, disable, and delete both breakpoints and watchpoints using the
3263 You can arrange to have values from your program displayed automatically
3264 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3268 @cindex breakpoint on events
3269 A @dfn{catchpoint} is another special breakpoint that stops your program
3270 when a certain kind of event occurs, such as the throwing of a C@t{++}
3271 exception or the loading of a library. As with watchpoints, you use a
3272 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3273 Catchpoints}), but aside from that, you can manage a catchpoint like any
3274 other breakpoint. (To stop when your program receives a signal, use the
3275 @code{handle} command; see @ref{Signals, ,Signals}.)
3277 @cindex breakpoint numbers
3278 @cindex numbers for breakpoints
3279 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3280 catchpoint when you create it; these numbers are successive integers
3281 starting with one. In many of the commands for controlling various
3282 features of breakpoints you use the breakpoint number to say which
3283 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3284 @dfn{disabled}; if disabled, it has no effect on your program until you
3287 @cindex breakpoint ranges
3288 @cindex ranges of breakpoints
3289 Some @value{GDBN} commands accept a range of breakpoints on which to
3290 operate. A breakpoint range is either a single breakpoint number, like
3291 @samp{5}, or two such numbers, in increasing order, separated by a
3292 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3293 all breakpoints in that range are operated on.
3296 * Set Breaks:: Setting breakpoints
3297 * Set Watchpoints:: Setting watchpoints
3298 * Set Catchpoints:: Setting catchpoints
3299 * Delete Breaks:: Deleting breakpoints
3300 * Disabling:: Disabling breakpoints
3301 * Conditions:: Break conditions
3302 * Break Commands:: Breakpoint command lists
3303 * Save Breakpoints:: How to save breakpoints in a file
3304 * Error in Breakpoints:: ``Cannot insert breakpoints''
3305 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3309 @subsection Setting Breakpoints
3311 @c FIXME LMB what does GDB do if no code on line of breakpt?
3312 @c consider in particular declaration with/without initialization.
3314 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3317 @kindex b @r{(@code{break})}
3318 @vindex $bpnum@r{, convenience variable}
3319 @cindex latest breakpoint
3320 Breakpoints are set with the @code{break} command (abbreviated
3321 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3322 number of the breakpoint you've set most recently; see @ref{Convenience
3323 Vars,, Convenience Variables}, for a discussion of what you can do with
3324 convenience variables.
3327 @item break @var{location}
3328 Set a breakpoint at the given @var{location}, which can specify a
3329 function name, a line number, or an address of an instruction.
3330 (@xref{Specify Location}, for a list of all the possible ways to
3331 specify a @var{location}.) The breakpoint will stop your program just
3332 before it executes any of the code in the specified @var{location}.
3334 When using source languages that permit overloading of symbols, such as
3335 C@t{++}, a function name may refer to more than one possible place to break.
3336 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3339 It is also possible to insert a breakpoint that will stop the program
3340 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3341 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3344 When called without any arguments, @code{break} sets a breakpoint at
3345 the next instruction to be executed in the selected stack frame
3346 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3347 innermost, this makes your program stop as soon as control
3348 returns to that frame. This is similar to the effect of a
3349 @code{finish} command in the frame inside the selected frame---except
3350 that @code{finish} does not leave an active breakpoint. If you use
3351 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3352 the next time it reaches the current location; this may be useful
3355 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3356 least one instruction has been executed. If it did not do this, you
3357 would be unable to proceed past a breakpoint without first disabling the
3358 breakpoint. This rule applies whether or not the breakpoint already
3359 existed when your program stopped.
3361 @item break @dots{} if @var{cond}
3362 Set a breakpoint with condition @var{cond}; evaluate the expression
3363 @var{cond} each time the breakpoint is reached, and stop only if the
3364 value is nonzero---that is, if @var{cond} evaluates as true.
3365 @samp{@dots{}} stands for one of the possible arguments described
3366 above (or no argument) specifying where to break. @xref{Conditions,
3367 ,Break Conditions}, for more information on breakpoint conditions.
3370 @item tbreak @var{args}
3371 Set a breakpoint enabled only for one stop. @var{args} are the
3372 same as for the @code{break} command, and the breakpoint is set in the same
3373 way, but the breakpoint is automatically deleted after the first time your
3374 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3377 @cindex hardware breakpoints
3378 @item hbreak @var{args}
3379 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3380 @code{break} command and the breakpoint is set in the same way, but the
3381 breakpoint requires hardware support and some target hardware may not
3382 have this support. The main purpose of this is EPROM/ROM code
3383 debugging, so you can set a breakpoint at an instruction without
3384 changing the instruction. This can be used with the new trap-generation
3385 provided by SPARClite DSU and most x86-based targets. These targets
3386 will generate traps when a program accesses some data or instruction
3387 address that is assigned to the debug registers. However the hardware
3388 breakpoint registers can take a limited number of breakpoints. For
3389 example, on the DSU, only two data breakpoints can be set at a time, and
3390 @value{GDBN} will reject this command if more than two are used. Delete
3391 or disable unused hardware breakpoints before setting new ones
3392 (@pxref{Disabling, ,Disabling Breakpoints}).
3393 @xref{Conditions, ,Break Conditions}.
3394 For remote targets, you can restrict the number of hardware
3395 breakpoints @value{GDBN} will use, see @ref{set remote
3396 hardware-breakpoint-limit}.
3399 @item thbreak @var{args}
3400 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3401 are the same as for the @code{hbreak} command and the breakpoint is set in
3402 the same way. However, like the @code{tbreak} command,
3403 the breakpoint is automatically deleted after the
3404 first time your program stops there. Also, like the @code{hbreak}
3405 command, the breakpoint requires hardware support and some target hardware
3406 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3407 See also @ref{Conditions, ,Break Conditions}.
3410 @cindex regular expression
3411 @cindex breakpoints at functions matching a regexp
3412 @cindex set breakpoints in many functions
3413 @item rbreak @var{regex}
3414 Set breakpoints on all functions matching the regular expression
3415 @var{regex}. This command sets an unconditional breakpoint on all
3416 matches, printing a list of all breakpoints it set. Once these
3417 breakpoints are set, they are treated just like the breakpoints set with
3418 the @code{break} command. You can delete them, disable them, or make
3419 them conditional the same way as any other breakpoint.
3421 The syntax of the regular expression is the standard one used with tools
3422 like @file{grep}. Note that this is different from the syntax used by
3423 shells, so for instance @code{foo*} matches all functions that include
3424 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3425 @code{.*} leading and trailing the regular expression you supply, so to
3426 match only functions that begin with @code{foo}, use @code{^foo}.
3428 @cindex non-member C@t{++} functions, set breakpoint in
3429 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3430 breakpoints on overloaded functions that are not members of any special
3433 @cindex set breakpoints on all functions
3434 The @code{rbreak} command can be used to set breakpoints in
3435 @strong{all} the functions in a program, like this:
3438 (@value{GDBP}) rbreak .
3441 @item rbreak @var{file}:@var{regex}
3442 If @code{rbreak} is called with a filename qualification, it limits
3443 the search for functions matching the given regular expression to the
3444 specified @var{file}. This can be used, for example, to set breakpoints on
3445 every function in a given file:
3448 (@value{GDBP}) rbreak file.c:.
3451 The colon separating the filename qualifier from the regex may
3452 optionally be surrounded by spaces.
3454 @kindex info breakpoints
3455 @cindex @code{$_} and @code{info breakpoints}
3456 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3457 @itemx info break @r{[}@var{n}@dots{}@r{]}
3458 Print a table of all breakpoints, watchpoints, and catchpoints set and
3459 not deleted. Optional argument @var{n} means print information only
3460 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3461 For each breakpoint, following columns are printed:
3464 @item Breakpoint Numbers
3466 Breakpoint, watchpoint, or catchpoint.
3468 Whether the breakpoint is marked to be disabled or deleted when hit.
3469 @item Enabled or Disabled
3470 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3471 that are not enabled.
3473 Where the breakpoint is in your program, as a memory address. For a
3474 pending breakpoint whose address is not yet known, this field will
3475 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3476 library that has the symbol or line referred by breakpoint is loaded.
3477 See below for details. A breakpoint with several locations will
3478 have @samp{<MULTIPLE>} in this field---see below for details.
3480 Where the breakpoint is in the source for your program, as a file and
3481 line number. For a pending breakpoint, the original string passed to
3482 the breakpoint command will be listed as it cannot be resolved until
3483 the appropriate shared library is loaded in the future.
3487 If a breakpoint is conditional, @code{info break} shows the condition on
3488 the line following the affected breakpoint; breakpoint commands, if any,
3489 are listed after that. A pending breakpoint is allowed to have a condition
3490 specified for it. The condition is not parsed for validity until a shared
3491 library is loaded that allows the pending breakpoint to resolve to a
3495 @code{info break} with a breakpoint
3496 number @var{n} as argument lists only that breakpoint. The
3497 convenience variable @code{$_} and the default examining-address for
3498 the @code{x} command are set to the address of the last breakpoint
3499 listed (@pxref{Memory, ,Examining Memory}).
3502 @code{info break} displays a count of the number of times the breakpoint
3503 has been hit. This is especially useful in conjunction with the
3504 @code{ignore} command. You can ignore a large number of breakpoint
3505 hits, look at the breakpoint info to see how many times the breakpoint
3506 was hit, and then run again, ignoring one less than that number. This
3507 will get you quickly to the last hit of that breakpoint.
3510 @value{GDBN} allows you to set any number of breakpoints at the same place in
3511 your program. There is nothing silly or meaningless about this. When
3512 the breakpoints are conditional, this is even useful
3513 (@pxref{Conditions, ,Break Conditions}).
3515 @cindex multiple locations, breakpoints
3516 @cindex breakpoints, multiple locations
3517 It is possible that a breakpoint corresponds to several locations
3518 in your program. Examples of this situation are:
3522 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3523 instances of the function body, used in different cases.
3526 For a C@t{++} template function, a given line in the function can
3527 correspond to any number of instantiations.
3530 For an inlined function, a given source line can correspond to
3531 several places where that function is inlined.
3534 In all those cases, @value{GDBN} will insert a breakpoint at all
3535 the relevant locations@footnote{
3536 As of this writing, multiple-location breakpoints work only if there's
3537 line number information for all the locations. This means that they
3538 will generally not work in system libraries, unless you have debug
3539 info with line numbers for them.}.
3541 A breakpoint with multiple locations is displayed in the breakpoint
3542 table using several rows---one header row, followed by one row for
3543 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3544 address column. The rows for individual locations contain the actual
3545 addresses for locations, and show the functions to which those
3546 locations belong. The number column for a location is of the form
3547 @var{breakpoint-number}.@var{location-number}.
3552 Num Type Disp Enb Address What
3553 1 breakpoint keep y <MULTIPLE>
3555 breakpoint already hit 1 time
3556 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3557 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3560 Each location can be individually enabled or disabled by passing
3561 @var{breakpoint-number}.@var{location-number} as argument to the
3562 @code{enable} and @code{disable} commands. Note that you cannot
3563 delete the individual locations from the list, you can only delete the
3564 entire list of locations that belong to their parent breakpoint (with
3565 the @kbd{delete @var{num}} command, where @var{num} is the number of
3566 the parent breakpoint, 1 in the above example). Disabling or enabling
3567 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3568 that belong to that breakpoint.
3570 @cindex pending breakpoints
3571 It's quite common to have a breakpoint inside a shared library.
3572 Shared libraries can be loaded and unloaded explicitly,
3573 and possibly repeatedly, as the program is executed. To support
3574 this use case, @value{GDBN} updates breakpoint locations whenever
3575 any shared library is loaded or unloaded. Typically, you would
3576 set a breakpoint in a shared library at the beginning of your
3577 debugging session, when the library is not loaded, and when the
3578 symbols from the library are not available. When you try to set
3579 breakpoint, @value{GDBN} will ask you if you want to set
3580 a so called @dfn{pending breakpoint}---breakpoint whose address
3581 is not yet resolved.
3583 After the program is run, whenever a new shared library is loaded,
3584 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3585 shared library contains the symbol or line referred to by some
3586 pending breakpoint, that breakpoint is resolved and becomes an
3587 ordinary breakpoint. When a library is unloaded, all breakpoints
3588 that refer to its symbols or source lines become pending again.
3590 This logic works for breakpoints with multiple locations, too. For
3591 example, if you have a breakpoint in a C@t{++} template function, and
3592 a newly loaded shared library has an instantiation of that template,
3593 a new location is added to the list of locations for the breakpoint.
3595 Except for having unresolved address, pending breakpoints do not
3596 differ from regular breakpoints. You can set conditions or commands,
3597 enable and disable them and perform other breakpoint operations.
3599 @value{GDBN} provides some additional commands for controlling what
3600 happens when the @samp{break} command cannot resolve breakpoint
3601 address specification to an address:
3603 @kindex set breakpoint pending
3604 @kindex show breakpoint pending
3606 @item set breakpoint pending auto
3607 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3608 location, it queries you whether a pending breakpoint should be created.
3610 @item set breakpoint pending on
3611 This indicates that an unrecognized breakpoint location should automatically
3612 result in a pending breakpoint being created.
3614 @item set breakpoint pending off
3615 This indicates that pending breakpoints are not to be created. Any
3616 unrecognized breakpoint location results in an error. This setting does
3617 not affect any pending breakpoints previously created.
3619 @item show breakpoint pending
3620 Show the current behavior setting for creating pending breakpoints.
3623 The settings above only affect the @code{break} command and its
3624 variants. Once breakpoint is set, it will be automatically updated
3625 as shared libraries are loaded and unloaded.
3627 @cindex automatic hardware breakpoints
3628 For some targets, @value{GDBN} can automatically decide if hardware or
3629 software breakpoints should be used, depending on whether the
3630 breakpoint address is read-only or read-write. This applies to
3631 breakpoints set with the @code{break} command as well as to internal
3632 breakpoints set by commands like @code{next} and @code{finish}. For
3633 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3636 You can control this automatic behaviour with the following commands::
3638 @kindex set breakpoint auto-hw
3639 @kindex show breakpoint auto-hw
3641 @item set breakpoint auto-hw on
3642 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3643 will try to use the target memory map to decide if software or hardware
3644 breakpoint must be used.
3646 @item set breakpoint auto-hw off
3647 This indicates @value{GDBN} should not automatically select breakpoint
3648 type. If the target provides a memory map, @value{GDBN} will warn when
3649 trying to set software breakpoint at a read-only address.
3652 @value{GDBN} normally implements breakpoints by replacing the program code
3653 at the breakpoint address with a special instruction, which, when
3654 executed, given control to the debugger. By default, the program
3655 code is so modified only when the program is resumed. As soon as
3656 the program stops, @value{GDBN} restores the original instructions. This
3657 behaviour guards against leaving breakpoints inserted in the
3658 target should gdb abrubptly disconnect. However, with slow remote
3659 targets, inserting and removing breakpoint can reduce the performance.
3660 This behavior can be controlled with the following commands::
3662 @kindex set breakpoint always-inserted
3663 @kindex show breakpoint always-inserted
3665 @item set breakpoint always-inserted off
3666 All breakpoints, including newly added by the user, are inserted in
3667 the target only when the target is resumed. All breakpoints are
3668 removed from the target when it stops.
3670 @item set breakpoint always-inserted on
3671 Causes all breakpoints to be inserted in the target at all times. If
3672 the user adds a new breakpoint, or changes an existing breakpoint, the
3673 breakpoints in the target are updated immediately. A breakpoint is
3674 removed from the target only when breakpoint itself is removed.
3676 @cindex non-stop mode, and @code{breakpoint always-inserted}
3677 @item set breakpoint always-inserted auto
3678 This is the default mode. If @value{GDBN} is controlling the inferior
3679 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3680 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3681 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3682 @code{breakpoint always-inserted} mode is off.
3685 @cindex negative breakpoint numbers
3686 @cindex internal @value{GDBN} breakpoints
3687 @value{GDBN} itself sometimes sets breakpoints in your program for
3688 special purposes, such as proper handling of @code{longjmp} (in C
3689 programs). These internal breakpoints are assigned negative numbers,
3690 starting with @code{-1}; @samp{info breakpoints} does not display them.
3691 You can see these breakpoints with the @value{GDBN} maintenance command
3692 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3695 @node Set Watchpoints
3696 @subsection Setting Watchpoints
3698 @cindex setting watchpoints
3699 You can use a watchpoint to stop execution whenever the value of an
3700 expression changes, without having to predict a particular place where
3701 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3702 The expression may be as simple as the value of a single variable, or
3703 as complex as many variables combined by operators. Examples include:
3707 A reference to the value of a single variable.
3710 An address cast to an appropriate data type. For example,
3711 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3712 address (assuming an @code{int} occupies 4 bytes).
3715 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3716 expression can use any operators valid in the program's native
3717 language (@pxref{Languages}).
3720 You can set a watchpoint on an expression even if the expression can
3721 not be evaluated yet. For instance, you can set a watchpoint on
3722 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3723 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3724 the expression produces a valid value. If the expression becomes
3725 valid in some other way than changing a variable (e.g.@: if the memory
3726 pointed to by @samp{*global_ptr} becomes readable as the result of a
3727 @code{malloc} call), @value{GDBN} may not stop until the next time
3728 the expression changes.
3730 @cindex software watchpoints
3731 @cindex hardware watchpoints
3732 Depending on your system, watchpoints may be implemented in software or
3733 hardware. @value{GDBN} does software watchpointing by single-stepping your
3734 program and testing the variable's value each time, which is hundreds of
3735 times slower than normal execution. (But this may still be worth it, to
3736 catch errors where you have no clue what part of your program is the
3739 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3740 x86-based targets, @value{GDBN} includes support for hardware
3741 watchpoints, which do not slow down the running of your program.
3745 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3746 Set a watchpoint for an expression. @value{GDBN} will break when the
3747 expression @var{expr} is written into by the program and its value
3748 changes. The simplest (and the most popular) use of this command is
3749 to watch the value of a single variable:
3752 (@value{GDBP}) watch foo
3755 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3756 argument, @value{GDBN} breaks only when the thread identified by
3757 @var{threadnum} changes the value of @var{expr}. If any other threads
3758 change the value of @var{expr}, @value{GDBN} will not break. Note
3759 that watchpoints restricted to a single thread in this way only work
3760 with Hardware Watchpoints.
3762 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3763 (see below). The @code{-location} argument tells @value{GDBN} to
3764 instead watch the memory referred to by @var{expr}. In this case,
3765 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3766 and watch the memory at that address. The type of the result is used
3767 to determine the size of the watched memory. If the expression's
3768 result does not have an address, then @value{GDBN} will print an
3771 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3772 of masked watchpoints, if the current architecture supports this
3773 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3774 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3775 to an address to watch. The mask specifies that some bits of an address
3776 (the bits which are reset in the mask) should be ignored when matching
3777 the address accessed by the inferior against the watchpoint address.
3778 Thus, a masked watchpoint watches many addresses simultaneously---those
3779 addresses whose unmasked bits are identical to the unmasked bits in the
3780 watchpoint address. The @code{mask} argument implies @code{-location}.
3784 (@value{GDBP}) watch foo mask 0xffff00ff
3785 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3789 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3790 Set a watchpoint that will break when the value of @var{expr} is read
3794 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3795 Set a watchpoint that will break when @var{expr} is either read from
3796 or written into by the program.
3798 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3799 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3800 This command prints a list of watchpoints, using the same format as
3801 @code{info break} (@pxref{Set Breaks}).
3804 If you watch for a change in a numerically entered address you need to
3805 dereference it, as the address itself is just a constant number which will
3806 never change. @value{GDBN} refuses to create a watchpoint that watches
3807 a never-changing value:
3810 (@value{GDBP}) watch 0x600850
3811 Cannot watch constant value 0x600850.
3812 (@value{GDBP}) watch *(int *) 0x600850
3813 Watchpoint 1: *(int *) 6293584
3816 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3817 watchpoints execute very quickly, and the debugger reports a change in
3818 value at the exact instruction where the change occurs. If @value{GDBN}
3819 cannot set a hardware watchpoint, it sets a software watchpoint, which
3820 executes more slowly and reports the change in value at the next
3821 @emph{statement}, not the instruction, after the change occurs.
3823 @cindex use only software watchpoints
3824 You can force @value{GDBN} to use only software watchpoints with the
3825 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3826 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3827 the underlying system supports them. (Note that hardware-assisted
3828 watchpoints that were set @emph{before} setting
3829 @code{can-use-hw-watchpoints} to zero will still use the hardware
3830 mechanism of watching expression values.)
3833 @item set can-use-hw-watchpoints
3834 @kindex set can-use-hw-watchpoints
3835 Set whether or not to use hardware watchpoints.
3837 @item show can-use-hw-watchpoints
3838 @kindex show can-use-hw-watchpoints
3839 Show the current mode of using hardware watchpoints.
3842 For remote targets, you can restrict the number of hardware
3843 watchpoints @value{GDBN} will use, see @ref{set remote
3844 hardware-breakpoint-limit}.
3846 When you issue the @code{watch} command, @value{GDBN} reports
3849 Hardware watchpoint @var{num}: @var{expr}
3853 if it was able to set a hardware watchpoint.
3855 Currently, the @code{awatch} and @code{rwatch} commands can only set
3856 hardware watchpoints, because accesses to data that don't change the
3857 value of the watched expression cannot be detected without examining
3858 every instruction as it is being executed, and @value{GDBN} does not do
3859 that currently. If @value{GDBN} finds that it is unable to set a
3860 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3861 will print a message like this:
3864 Expression cannot be implemented with read/access watchpoint.
3867 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3868 data type of the watched expression is wider than what a hardware
3869 watchpoint on the target machine can handle. For example, some systems
3870 can only watch regions that are up to 4 bytes wide; on such systems you
3871 cannot set hardware watchpoints for an expression that yields a
3872 double-precision floating-point number (which is typically 8 bytes
3873 wide). As a work-around, it might be possible to break the large region
3874 into a series of smaller ones and watch them with separate watchpoints.
3876 If you set too many hardware watchpoints, @value{GDBN} might be unable
3877 to insert all of them when you resume the execution of your program.
3878 Since the precise number of active watchpoints is unknown until such
3879 time as the program is about to be resumed, @value{GDBN} might not be
3880 able to warn you about this when you set the watchpoints, and the
3881 warning will be printed only when the program is resumed:
3884 Hardware watchpoint @var{num}: Could not insert watchpoint
3888 If this happens, delete or disable some of the watchpoints.
3890 Watching complex expressions that reference many variables can also
3891 exhaust the resources available for hardware-assisted watchpoints.
3892 That's because @value{GDBN} needs to watch every variable in the
3893 expression with separately allocated resources.
3895 If you call a function interactively using @code{print} or @code{call},
3896 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3897 kind of breakpoint or the call completes.
3899 @value{GDBN} automatically deletes watchpoints that watch local
3900 (automatic) variables, or expressions that involve such variables, when
3901 they go out of scope, that is, when the execution leaves the block in
3902 which these variables were defined. In particular, when the program
3903 being debugged terminates, @emph{all} local variables go out of scope,
3904 and so only watchpoints that watch global variables remain set. If you
3905 rerun the program, you will need to set all such watchpoints again. One
3906 way of doing that would be to set a code breakpoint at the entry to the
3907 @code{main} function and when it breaks, set all the watchpoints.
3909 @cindex watchpoints and threads
3910 @cindex threads and watchpoints
3911 In multi-threaded programs, watchpoints will detect changes to the
3912 watched expression from every thread.
3915 @emph{Warning:} In multi-threaded programs, software watchpoints
3916 have only limited usefulness. If @value{GDBN} creates a software
3917 watchpoint, it can only watch the value of an expression @emph{in a
3918 single thread}. If you are confident that the expression can only
3919 change due to the current thread's activity (and if you are also
3920 confident that no other thread can become current), then you can use
3921 software watchpoints as usual. However, @value{GDBN} may not notice
3922 when a non-current thread's activity changes the expression. (Hardware
3923 watchpoints, in contrast, watch an expression in all threads.)
3926 @xref{set remote hardware-watchpoint-limit}.
3928 @node Set Catchpoints
3929 @subsection Setting Catchpoints
3930 @cindex catchpoints, setting
3931 @cindex exception handlers
3932 @cindex event handling
3934 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3935 kinds of program events, such as C@t{++} exceptions or the loading of a
3936 shared library. Use the @code{catch} command to set a catchpoint.
3940 @item catch @var{event}
3941 Stop when @var{event} occurs. @var{event} can be any of the following:
3944 @cindex stop on C@t{++} exceptions
3945 The throwing of a C@t{++} exception.
3948 The catching of a C@t{++} exception.
3951 @cindex Ada exception catching
3952 @cindex catch Ada exceptions
3953 An Ada exception being raised. If an exception name is specified
3954 at the end of the command (eg @code{catch exception Program_Error}),
3955 the debugger will stop only when this specific exception is raised.
3956 Otherwise, the debugger stops execution when any Ada exception is raised.
3958 When inserting an exception catchpoint on a user-defined exception whose
3959 name is identical to one of the exceptions defined by the language, the
3960 fully qualified name must be used as the exception name. Otherwise,
3961 @value{GDBN} will assume that it should stop on the pre-defined exception
3962 rather than the user-defined one. For instance, assuming an exception
3963 called @code{Constraint_Error} is defined in package @code{Pck}, then
3964 the command to use to catch such exceptions is @kbd{catch exception
3965 Pck.Constraint_Error}.
3967 @item exception unhandled
3968 An exception that was raised but is not handled by the program.
3971 A failed Ada assertion.
3974 @cindex break on fork/exec
3975 A call to @code{exec}. This is currently only available for HP-UX
3979 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3980 @cindex break on a system call.
3981 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3982 syscall is a mechanism for application programs to request a service
3983 from the operating system (OS) or one of the OS system services.
3984 @value{GDBN} can catch some or all of the syscalls issued by the
3985 debuggee, and show the related information for each syscall. If no
3986 argument is specified, calls to and returns from all system calls
3989 @var{name} can be any system call name that is valid for the
3990 underlying OS. Just what syscalls are valid depends on the OS. On
3991 GNU and Unix systems, you can find the full list of valid syscall
3992 names on @file{/usr/include/asm/unistd.h}.
3994 @c For MS-Windows, the syscall names and the corresponding numbers
3995 @c can be found, e.g., on this URL:
3996 @c http://www.metasploit.com/users/opcode/syscalls.html
3997 @c but we don't support Windows syscalls yet.
3999 Normally, @value{GDBN} knows in advance which syscalls are valid for
4000 each OS, so you can use the @value{GDBN} command-line completion
4001 facilities (@pxref{Completion,, command completion}) to list the
4004 You may also specify the system call numerically. A syscall's
4005 number is the value passed to the OS's syscall dispatcher to
4006 identify the requested service. When you specify the syscall by its
4007 name, @value{GDBN} uses its database of syscalls to convert the name
4008 into the corresponding numeric code, but using the number directly
4009 may be useful if @value{GDBN}'s database does not have the complete
4010 list of syscalls on your system (e.g., because @value{GDBN} lags
4011 behind the OS upgrades).
4013 The example below illustrates how this command works if you don't provide
4017 (@value{GDBP}) catch syscall
4018 Catchpoint 1 (syscall)
4020 Starting program: /tmp/catch-syscall
4022 Catchpoint 1 (call to syscall 'close'), \
4023 0xffffe424 in __kernel_vsyscall ()
4027 Catchpoint 1 (returned from syscall 'close'), \
4028 0xffffe424 in __kernel_vsyscall ()
4032 Here is an example of catching a system call by name:
4035 (@value{GDBP}) catch syscall chroot
4036 Catchpoint 1 (syscall 'chroot' [61])
4038 Starting program: /tmp/catch-syscall
4040 Catchpoint 1 (call to syscall 'chroot'), \
4041 0xffffe424 in __kernel_vsyscall ()
4045 Catchpoint 1 (returned from syscall 'chroot'), \
4046 0xffffe424 in __kernel_vsyscall ()
4050 An example of specifying a system call numerically. In the case
4051 below, the syscall number has a corresponding entry in the XML
4052 file, so @value{GDBN} finds its name and prints it:
4055 (@value{GDBP}) catch syscall 252
4056 Catchpoint 1 (syscall(s) 'exit_group')
4058 Starting program: /tmp/catch-syscall
4060 Catchpoint 1 (call to syscall 'exit_group'), \
4061 0xffffe424 in __kernel_vsyscall ()
4065 Program exited normally.
4069 However, there can be situations when there is no corresponding name
4070 in XML file for that syscall number. In this case, @value{GDBN} prints
4071 a warning message saying that it was not able to find the syscall name,
4072 but the catchpoint will be set anyway. See the example below:
4075 (@value{GDBP}) catch syscall 764
4076 warning: The number '764' does not represent a known syscall.
4077 Catchpoint 2 (syscall 764)
4081 If you configure @value{GDBN} using the @samp{--without-expat} option,
4082 it will not be able to display syscall names. Also, if your
4083 architecture does not have an XML file describing its system calls,
4084 you will not be able to see the syscall names. It is important to
4085 notice that these two features are used for accessing the syscall
4086 name database. In either case, you will see a warning like this:
4089 (@value{GDBP}) catch syscall
4090 warning: Could not open "syscalls/i386-linux.xml"
4091 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4092 GDB will not be able to display syscall names.
4093 Catchpoint 1 (syscall)
4097 Of course, the file name will change depending on your architecture and system.
4099 Still using the example above, you can also try to catch a syscall by its
4100 number. In this case, you would see something like:
4103 (@value{GDBP}) catch syscall 252
4104 Catchpoint 1 (syscall(s) 252)
4107 Again, in this case @value{GDBN} would not be able to display syscall's names.
4110 A call to @code{fork}. This is currently only available for HP-UX
4114 A call to @code{vfork}. This is currently only available for HP-UX
4119 @item tcatch @var{event}
4120 Set a catchpoint that is enabled only for one stop. The catchpoint is
4121 automatically deleted after the first time the event is caught.
4125 Use the @code{info break} command to list the current catchpoints.
4127 There are currently some limitations to C@t{++} exception handling
4128 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4132 If you call a function interactively, @value{GDBN} normally returns
4133 control to you when the function has finished executing. If the call
4134 raises an exception, however, the call may bypass the mechanism that
4135 returns control to you and cause your program either to abort or to
4136 simply continue running until it hits a breakpoint, catches a signal
4137 that @value{GDBN} is listening for, or exits. This is the case even if
4138 you set a catchpoint for the exception; catchpoints on exceptions are
4139 disabled within interactive calls.
4142 You cannot raise an exception interactively.
4145 You cannot install an exception handler interactively.
4148 @cindex raise exceptions
4149 Sometimes @code{catch} is not the best way to debug exception handling:
4150 if you need to know exactly where an exception is raised, it is better to
4151 stop @emph{before} the exception handler is called, since that way you
4152 can see the stack before any unwinding takes place. If you set a
4153 breakpoint in an exception handler instead, it may not be easy to find
4154 out where the exception was raised.
4156 To stop just before an exception handler is called, you need some
4157 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4158 raised by calling a library function named @code{__raise_exception}
4159 which has the following ANSI C interface:
4162 /* @var{addr} is where the exception identifier is stored.
4163 @var{id} is the exception identifier. */
4164 void __raise_exception (void **addr, void *id);
4168 To make the debugger catch all exceptions before any stack
4169 unwinding takes place, set a breakpoint on @code{__raise_exception}
4170 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4172 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4173 that depends on the value of @var{id}, you can stop your program when
4174 a specific exception is raised. You can use multiple conditional
4175 breakpoints to stop your program when any of a number of exceptions are
4180 @subsection Deleting Breakpoints
4182 @cindex clearing breakpoints, watchpoints, catchpoints
4183 @cindex deleting breakpoints, watchpoints, catchpoints
4184 It is often necessary to eliminate a breakpoint, watchpoint, or
4185 catchpoint once it has done its job and you no longer want your program
4186 to stop there. This is called @dfn{deleting} the breakpoint. A
4187 breakpoint that has been deleted no longer exists; it is forgotten.
4189 With the @code{clear} command you can delete breakpoints according to
4190 where they are in your program. With the @code{delete} command you can
4191 delete individual breakpoints, watchpoints, or catchpoints by specifying
4192 their breakpoint numbers.
4194 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4195 automatically ignores breakpoints on the first instruction to be executed
4196 when you continue execution without changing the execution address.
4201 Delete any breakpoints at the next instruction to be executed in the
4202 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4203 the innermost frame is selected, this is a good way to delete a
4204 breakpoint where your program just stopped.
4206 @item clear @var{location}
4207 Delete any breakpoints set at the specified @var{location}.
4208 @xref{Specify Location}, for the various forms of @var{location}; the
4209 most useful ones are listed below:
4212 @item clear @var{function}
4213 @itemx clear @var{filename}:@var{function}
4214 Delete any breakpoints set at entry to the named @var{function}.
4216 @item clear @var{linenum}
4217 @itemx clear @var{filename}:@var{linenum}
4218 Delete any breakpoints set at or within the code of the specified
4219 @var{linenum} of the specified @var{filename}.
4222 @cindex delete breakpoints
4224 @kindex d @r{(@code{delete})}
4225 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4226 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4227 ranges specified as arguments. If no argument is specified, delete all
4228 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4229 confirm off}). You can abbreviate this command as @code{d}.
4233 @subsection Disabling Breakpoints
4235 @cindex enable/disable a breakpoint
4236 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4237 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4238 it had been deleted, but remembers the information on the breakpoint so
4239 that you can @dfn{enable} it again later.
4241 You disable and enable breakpoints, watchpoints, and catchpoints with
4242 the @code{enable} and @code{disable} commands, optionally specifying
4243 one or more breakpoint numbers as arguments. Use @code{info break} to
4244 print a list of all breakpoints, watchpoints, and catchpoints if you
4245 do not know which numbers to use.
4247 Disabling and enabling a breakpoint that has multiple locations
4248 affects all of its locations.
4250 A breakpoint, watchpoint, or catchpoint can have any of four different
4251 states of enablement:
4255 Enabled. The breakpoint stops your program. A breakpoint set
4256 with the @code{break} command starts out in this state.
4258 Disabled. The breakpoint has no effect on your program.
4260 Enabled once. The breakpoint stops your program, but then becomes
4263 Enabled for deletion. The breakpoint stops your program, but
4264 immediately after it does so it is deleted permanently. A breakpoint
4265 set with the @code{tbreak} command starts out in this state.
4268 You can use the following commands to enable or disable breakpoints,
4269 watchpoints, and catchpoints:
4273 @kindex dis @r{(@code{disable})}
4274 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4275 Disable the specified breakpoints---or all breakpoints, if none are
4276 listed. A disabled breakpoint has no effect but is not forgotten. All
4277 options such as ignore-counts, conditions and commands are remembered in
4278 case the breakpoint is enabled again later. You may abbreviate
4279 @code{disable} as @code{dis}.
4282 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4283 Enable the specified breakpoints (or all defined breakpoints). They
4284 become effective once again in stopping your program.
4286 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4287 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4288 of these breakpoints immediately after stopping your program.
4290 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4291 Enable the specified breakpoints to work once, then die. @value{GDBN}
4292 deletes any of these breakpoints as soon as your program stops there.
4293 Breakpoints set by the @code{tbreak} command start out in this state.
4296 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4297 @c confusing: tbreak is also initially enabled.
4298 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4299 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4300 subsequently, they become disabled or enabled only when you use one of
4301 the commands above. (The command @code{until} can set and delete a
4302 breakpoint of its own, but it does not change the state of your other
4303 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4307 @subsection Break Conditions
4308 @cindex conditional breakpoints
4309 @cindex breakpoint conditions
4311 @c FIXME what is scope of break condition expr? Context where wanted?
4312 @c in particular for a watchpoint?
4313 The simplest sort of breakpoint breaks every time your program reaches a
4314 specified place. You can also specify a @dfn{condition} for a
4315 breakpoint. A condition is just a Boolean expression in your
4316 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4317 a condition evaluates the expression each time your program reaches it,
4318 and your program stops only if the condition is @emph{true}.
4320 This is the converse of using assertions for program validation; in that
4321 situation, you want to stop when the assertion is violated---that is,
4322 when the condition is false. In C, if you want to test an assertion expressed
4323 by the condition @var{assert}, you should set the condition
4324 @samp{! @var{assert}} on the appropriate breakpoint.
4326 Conditions are also accepted for watchpoints; you may not need them,
4327 since a watchpoint is inspecting the value of an expression anyhow---but
4328 it might be simpler, say, to just set a watchpoint on a variable name,
4329 and specify a condition that tests whether the new value is an interesting
4332 Break conditions can have side effects, and may even call functions in
4333 your program. This can be useful, for example, to activate functions
4334 that log program progress, or to use your own print functions to
4335 format special data structures. The effects are completely predictable
4336 unless there is another enabled breakpoint at the same address. (In
4337 that case, @value{GDBN} might see the other breakpoint first and stop your
4338 program without checking the condition of this one.) Note that
4339 breakpoint commands are usually more convenient and flexible than break
4341 purpose of performing side effects when a breakpoint is reached
4342 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4344 Break conditions can be specified when a breakpoint is set, by using
4345 @samp{if} in the arguments to the @code{break} command. @xref{Set
4346 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4347 with the @code{condition} command.
4349 You can also use the @code{if} keyword with the @code{watch} command.
4350 The @code{catch} command does not recognize the @code{if} keyword;
4351 @code{condition} is the only way to impose a further condition on a
4356 @item condition @var{bnum} @var{expression}
4357 Specify @var{expression} as the break condition for breakpoint,
4358 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4359 breakpoint @var{bnum} stops your program only if the value of
4360 @var{expression} is true (nonzero, in C). When you use
4361 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4362 syntactic correctness, and to determine whether symbols in it have
4363 referents in the context of your breakpoint. If @var{expression} uses
4364 symbols not referenced in the context of the breakpoint, @value{GDBN}
4365 prints an error message:
4368 No symbol "foo" in current context.
4373 not actually evaluate @var{expression} at the time the @code{condition}
4374 command (or a command that sets a breakpoint with a condition, like
4375 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4377 @item condition @var{bnum}
4378 Remove the condition from breakpoint number @var{bnum}. It becomes
4379 an ordinary unconditional breakpoint.
4382 @cindex ignore count (of breakpoint)
4383 A special case of a breakpoint condition is to stop only when the
4384 breakpoint has been reached a certain number of times. This is so
4385 useful that there is a special way to do it, using the @dfn{ignore
4386 count} of the breakpoint. Every breakpoint has an ignore count, which
4387 is an integer. Most of the time, the ignore count is zero, and
4388 therefore has no effect. But if your program reaches a breakpoint whose
4389 ignore count is positive, then instead of stopping, it just decrements
4390 the ignore count by one and continues. As a result, if the ignore count
4391 value is @var{n}, the breakpoint does not stop the next @var{n} times
4392 your program reaches it.
4396 @item ignore @var{bnum} @var{count}
4397 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4398 The next @var{count} times the breakpoint is reached, your program's
4399 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4402 To make the breakpoint stop the next time it is reached, specify
4405 When you use @code{continue} to resume execution of your program from a
4406 breakpoint, you can specify an ignore count directly as an argument to
4407 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4408 Stepping,,Continuing and Stepping}.
4410 If a breakpoint has a positive ignore count and a condition, the
4411 condition is not checked. Once the ignore count reaches zero,
4412 @value{GDBN} resumes checking the condition.
4414 You could achieve the effect of the ignore count with a condition such
4415 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4416 is decremented each time. @xref{Convenience Vars, ,Convenience
4420 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4423 @node Break Commands
4424 @subsection Breakpoint Command Lists
4426 @cindex breakpoint commands
4427 You can give any breakpoint (or watchpoint or catchpoint) a series of
4428 commands to execute when your program stops due to that breakpoint. For
4429 example, you might want to print the values of certain expressions, or
4430 enable other breakpoints.
4434 @kindex end@r{ (breakpoint commands)}
4435 @item commands @r{[}@var{range}@dots{}@r{]}
4436 @itemx @dots{} @var{command-list} @dots{}
4438 Specify a list of commands for the given breakpoints. The commands
4439 themselves appear on the following lines. Type a line containing just
4440 @code{end} to terminate the commands.
4442 To remove all commands from a breakpoint, type @code{commands} and
4443 follow it immediately with @code{end}; that is, give no commands.
4445 With no argument, @code{commands} refers to the last breakpoint,
4446 watchpoint, or catchpoint set (not to the breakpoint most recently
4447 encountered). If the most recent breakpoints were set with a single
4448 command, then the @code{commands} will apply to all the breakpoints
4449 set by that command. This applies to breakpoints set by
4450 @code{rbreak}, and also applies when a single @code{break} command
4451 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4455 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4456 disabled within a @var{command-list}.
4458 You can use breakpoint commands to start your program up again. Simply
4459 use the @code{continue} command, or @code{step}, or any other command
4460 that resumes execution.
4462 Any other commands in the command list, after a command that resumes
4463 execution, are ignored. This is because any time you resume execution
4464 (even with a simple @code{next} or @code{step}), you may encounter
4465 another breakpoint---which could have its own command list, leading to
4466 ambiguities about which list to execute.
4469 If the first command you specify in a command list is @code{silent}, the
4470 usual message about stopping at a breakpoint is not printed. This may
4471 be desirable for breakpoints that are to print a specific message and
4472 then continue. If none of the remaining commands print anything, you
4473 see no sign that the breakpoint was reached. @code{silent} is
4474 meaningful only at the beginning of a breakpoint command list.
4476 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4477 print precisely controlled output, and are often useful in silent
4478 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4480 For example, here is how you could use breakpoint commands to print the
4481 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4487 printf "x is %d\n",x
4492 One application for breakpoint commands is to compensate for one bug so
4493 you can test for another. Put a breakpoint just after the erroneous line
4494 of code, give it a condition to detect the case in which something
4495 erroneous has been done, and give it commands to assign correct values
4496 to any variables that need them. End with the @code{continue} command
4497 so that your program does not stop, and start with the @code{silent}
4498 command so that no output is produced. Here is an example:
4509 @node Save Breakpoints
4510 @subsection How to save breakpoints to a file
4512 To save breakpoint definitions to a file use the @w{@code{save
4513 breakpoints}} command.
4516 @kindex save breakpoints
4517 @cindex save breakpoints to a file for future sessions
4518 @item save breakpoints [@var{filename}]
4519 This command saves all current breakpoint definitions together with
4520 their commands and ignore counts, into a file @file{@var{filename}}
4521 suitable for use in a later debugging session. This includes all
4522 types of breakpoints (breakpoints, watchpoints, catchpoints,
4523 tracepoints). To read the saved breakpoint definitions, use the
4524 @code{source} command (@pxref{Command Files}). Note that watchpoints
4525 with expressions involving local variables may fail to be recreated
4526 because it may not be possible to access the context where the
4527 watchpoint is valid anymore. Because the saved breakpoint definitions
4528 are simply a sequence of @value{GDBN} commands that recreate the
4529 breakpoints, you can edit the file in your favorite editing program,
4530 and remove the breakpoint definitions you're not interested in, or
4531 that can no longer be recreated.
4534 @c @ifclear BARETARGET
4535 @node Error in Breakpoints
4536 @subsection ``Cannot insert breakpoints''
4538 If you request too many active hardware-assisted breakpoints and
4539 watchpoints, you will see this error message:
4541 @c FIXME: the precise wording of this message may change; the relevant
4542 @c source change is not committed yet (Sep 3, 1999).
4544 Stopped; cannot insert breakpoints.
4545 You may have requested too many hardware breakpoints and watchpoints.
4549 This message is printed when you attempt to resume the program, since
4550 only then @value{GDBN} knows exactly how many hardware breakpoints and
4551 watchpoints it needs to insert.
4553 When this message is printed, you need to disable or remove some of the
4554 hardware-assisted breakpoints and watchpoints, and then continue.
4556 @node Breakpoint-related Warnings
4557 @subsection ``Breakpoint address adjusted...''
4558 @cindex breakpoint address adjusted
4560 Some processor architectures place constraints on the addresses at
4561 which breakpoints may be placed. For architectures thus constrained,
4562 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4563 with the constraints dictated by the architecture.
4565 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4566 a VLIW architecture in which a number of RISC-like instructions may be
4567 bundled together for parallel execution. The FR-V architecture
4568 constrains the location of a breakpoint instruction within such a
4569 bundle to the instruction with the lowest address. @value{GDBN}
4570 honors this constraint by adjusting a breakpoint's address to the
4571 first in the bundle.
4573 It is not uncommon for optimized code to have bundles which contain
4574 instructions from different source statements, thus it may happen that
4575 a breakpoint's address will be adjusted from one source statement to
4576 another. Since this adjustment may significantly alter @value{GDBN}'s
4577 breakpoint related behavior from what the user expects, a warning is
4578 printed when the breakpoint is first set and also when the breakpoint
4581 A warning like the one below is printed when setting a breakpoint
4582 that's been subject to address adjustment:
4585 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4588 Such warnings are printed both for user settable and @value{GDBN}'s
4589 internal breakpoints. If you see one of these warnings, you should
4590 verify that a breakpoint set at the adjusted address will have the
4591 desired affect. If not, the breakpoint in question may be removed and
4592 other breakpoints may be set which will have the desired behavior.
4593 E.g., it may be sufficient to place the breakpoint at a later
4594 instruction. A conditional breakpoint may also be useful in some
4595 cases to prevent the breakpoint from triggering too often.
4597 @value{GDBN} will also issue a warning when stopping at one of these
4598 adjusted breakpoints:
4601 warning: Breakpoint 1 address previously adjusted from 0x00010414
4605 When this warning is encountered, it may be too late to take remedial
4606 action except in cases where the breakpoint is hit earlier or more
4607 frequently than expected.
4609 @node Continuing and Stepping
4610 @section Continuing and Stepping
4614 @cindex resuming execution
4615 @dfn{Continuing} means resuming program execution until your program
4616 completes normally. In contrast, @dfn{stepping} means executing just
4617 one more ``step'' of your program, where ``step'' may mean either one
4618 line of source code, or one machine instruction (depending on what
4619 particular command you use). Either when continuing or when stepping,
4620 your program may stop even sooner, due to a breakpoint or a signal. (If
4621 it stops due to a signal, you may want to use @code{handle}, or use
4622 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4626 @kindex c @r{(@code{continue})}
4627 @kindex fg @r{(resume foreground execution)}
4628 @item continue @r{[}@var{ignore-count}@r{]}
4629 @itemx c @r{[}@var{ignore-count}@r{]}
4630 @itemx fg @r{[}@var{ignore-count}@r{]}
4631 Resume program execution, at the address where your program last stopped;
4632 any breakpoints set at that address are bypassed. The optional argument
4633 @var{ignore-count} allows you to specify a further number of times to
4634 ignore a breakpoint at this location; its effect is like that of
4635 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4637 The argument @var{ignore-count} is meaningful only when your program
4638 stopped due to a breakpoint. At other times, the argument to
4639 @code{continue} is ignored.
4641 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4642 debugged program is deemed to be the foreground program) are provided
4643 purely for convenience, and have exactly the same behavior as
4647 To resume execution at a different place, you can use @code{return}
4648 (@pxref{Returning, ,Returning from a Function}) to go back to the
4649 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4650 Different Address}) to go to an arbitrary location in your program.
4652 A typical technique for using stepping is to set a breakpoint
4653 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4654 beginning of the function or the section of your program where a problem
4655 is believed to lie, run your program until it stops at that breakpoint,
4656 and then step through the suspect area, examining the variables that are
4657 interesting, until you see the problem happen.
4661 @kindex s @r{(@code{step})}
4663 Continue running your program until control reaches a different source
4664 line, then stop it and return control to @value{GDBN}. This command is
4665 abbreviated @code{s}.
4668 @c "without debugging information" is imprecise; actually "without line
4669 @c numbers in the debugging information". (gcc -g1 has debugging info but
4670 @c not line numbers). But it seems complex to try to make that
4671 @c distinction here.
4672 @emph{Warning:} If you use the @code{step} command while control is
4673 within a function that was compiled without debugging information,
4674 execution proceeds until control reaches a function that does have
4675 debugging information. Likewise, it will not step into a function which
4676 is compiled without debugging information. To step through functions
4677 without debugging information, use the @code{stepi} command, described
4681 The @code{step} command only stops at the first instruction of a source
4682 line. This prevents the multiple stops that could otherwise occur in
4683 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4684 to stop if a function that has debugging information is called within
4685 the line. In other words, @code{step} @emph{steps inside} any functions
4686 called within the line.
4688 Also, the @code{step} command only enters a function if there is line
4689 number information for the function. Otherwise it acts like the
4690 @code{next} command. This avoids problems when using @code{cc -gl}
4691 on MIPS machines. Previously, @code{step} entered subroutines if there
4692 was any debugging information about the routine.
4694 @item step @var{count}
4695 Continue running as in @code{step}, but do so @var{count} times. If a
4696 breakpoint is reached, or a signal not related to stepping occurs before
4697 @var{count} steps, stepping stops right away.
4700 @kindex n @r{(@code{next})}
4701 @item next @r{[}@var{count}@r{]}
4702 Continue to the next source line in the current (innermost) stack frame.
4703 This is similar to @code{step}, but function calls that appear within
4704 the line of code are executed without stopping. Execution stops when
4705 control reaches a different line of code at the original stack level
4706 that was executing when you gave the @code{next} command. This command
4707 is abbreviated @code{n}.
4709 An argument @var{count} is a repeat count, as for @code{step}.
4712 @c FIX ME!! Do we delete this, or is there a way it fits in with
4713 @c the following paragraph? --- Vctoria
4715 @c @code{next} within a function that lacks debugging information acts like
4716 @c @code{step}, but any function calls appearing within the code of the
4717 @c function are executed without stopping.
4719 The @code{next} command only stops at the first instruction of a
4720 source line. This prevents multiple stops that could otherwise occur in
4721 @code{switch} statements, @code{for} loops, etc.
4723 @kindex set step-mode
4725 @cindex functions without line info, and stepping
4726 @cindex stepping into functions with no line info
4727 @itemx set step-mode on
4728 The @code{set step-mode on} command causes the @code{step} command to
4729 stop at the first instruction of a function which contains no debug line
4730 information rather than stepping over it.
4732 This is useful in cases where you may be interested in inspecting the
4733 machine instructions of a function which has no symbolic info and do not
4734 want @value{GDBN} to automatically skip over this function.
4736 @item set step-mode off
4737 Causes the @code{step} command to step over any functions which contains no
4738 debug information. This is the default.
4740 @item show step-mode
4741 Show whether @value{GDBN} will stop in or step over functions without
4742 source line debug information.
4745 @kindex fin @r{(@code{finish})}
4747 Continue running until just after function in the selected stack frame
4748 returns. Print the returned value (if any). This command can be
4749 abbreviated as @code{fin}.
4751 Contrast this with the @code{return} command (@pxref{Returning,
4752 ,Returning from a Function}).
4755 @kindex u @r{(@code{until})}
4756 @cindex run until specified location
4759 Continue running until a source line past the current line, in the
4760 current stack frame, is reached. This command is used to avoid single
4761 stepping through a loop more than once. It is like the @code{next}
4762 command, except that when @code{until} encounters a jump, it
4763 automatically continues execution until the program counter is greater
4764 than the address of the jump.
4766 This means that when you reach the end of a loop after single stepping
4767 though it, @code{until} makes your program continue execution until it
4768 exits the loop. In contrast, a @code{next} command at the end of a loop
4769 simply steps back to the beginning of the loop, which forces you to step
4770 through the next iteration.
4772 @code{until} always stops your program if it attempts to exit the current
4775 @code{until} may produce somewhat counterintuitive results if the order
4776 of machine code does not match the order of the source lines. For
4777 example, in the following excerpt from a debugging session, the @code{f}
4778 (@code{frame}) command shows that execution is stopped at line
4779 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4783 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4785 (@value{GDBP}) until
4786 195 for ( ; argc > 0; NEXTARG) @{
4789 This happened because, for execution efficiency, the compiler had
4790 generated code for the loop closure test at the end, rather than the
4791 start, of the loop---even though the test in a C @code{for}-loop is
4792 written before the body of the loop. The @code{until} command appeared
4793 to step back to the beginning of the loop when it advanced to this
4794 expression; however, it has not really gone to an earlier
4795 statement---not in terms of the actual machine code.
4797 @code{until} with no argument works by means of single
4798 instruction stepping, and hence is slower than @code{until} with an
4801 @item until @var{location}
4802 @itemx u @var{location}
4803 Continue running your program until either the specified location is
4804 reached, or the current stack frame returns. @var{location} is any of
4805 the forms described in @ref{Specify Location}.
4806 This form of the command uses temporary breakpoints, and
4807 hence is quicker than @code{until} without an argument. The specified
4808 location is actually reached only if it is in the current frame. This
4809 implies that @code{until} can be used to skip over recursive function
4810 invocations. For instance in the code below, if the current location is
4811 line @code{96}, issuing @code{until 99} will execute the program up to
4812 line @code{99} in the same invocation of factorial, i.e., after the inner
4813 invocations have returned.
4816 94 int factorial (int value)
4818 96 if (value > 1) @{
4819 97 value *= factorial (value - 1);
4826 @kindex advance @var{location}
4827 @itemx advance @var{location}
4828 Continue running the program up to the given @var{location}. An argument is
4829 required, which should be of one of the forms described in
4830 @ref{Specify Location}.
4831 Execution will also stop upon exit from the current stack
4832 frame. This command is similar to @code{until}, but @code{advance} will
4833 not skip over recursive function calls, and the target location doesn't
4834 have to be in the same frame as the current one.
4838 @kindex si @r{(@code{stepi})}
4840 @itemx stepi @var{arg}
4842 Execute one machine instruction, then stop and return to the debugger.
4844 It is often useful to do @samp{display/i $pc} when stepping by machine
4845 instructions. This makes @value{GDBN} automatically display the next
4846 instruction to be executed, each time your program stops. @xref{Auto
4847 Display,, Automatic Display}.
4849 An argument is a repeat count, as in @code{step}.
4853 @kindex ni @r{(@code{nexti})}
4855 @itemx nexti @var{arg}
4857 Execute one machine instruction, but if it is a function call,
4858 proceed until the function returns.
4860 An argument is a repeat count, as in @code{next}.
4863 @node Skipping Over Functions and Files
4864 @section Skipping Over Functions and Files
4865 @cindex skipping over functions and files
4867 The program you are debugging may contain some functions which are
4868 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4869 skip a function or all functions in a file when stepping.
4871 For example, consider the following C function:
4882 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4883 are not interested in stepping through @code{boring}. If you run @code{step}
4884 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4885 step over both @code{foo} and @code{boring}!
4887 One solution is to @code{step} into @code{boring} and use the @code{finish}
4888 command to immediately exit it. But this can become tedious if @code{boring}
4889 is called from many places.
4891 A more flexible solution is to execute @kbd{skip boring}. This instructs
4892 @value{GDBN} never to step into @code{boring}. Now when you execute
4893 @code{step} at line 103, you'll step over @code{boring} and directly into
4896 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4897 example, @code{skip file boring.c}.
4900 @kindex skip function
4901 @item skip @r{[}@var{linespec}@r{]}
4902 @itemx skip function @r{[}@var{linespec}@r{]}
4903 After running this command, the function named by @var{linespec} or the
4904 function containing the line named by @var{linespec} will be skipped over when
4905 stepping. @xref{Specify Location}.
4907 If you do not specify @var{linespec}, the function you're currently debugging
4910 (If you have a function called @code{file} that you want to skip, use
4911 @kbd{skip function file}.)
4914 @item skip file @r{[}@var{filename}@r{]}
4915 After running this command, any function whose source lives in @var{filename}
4916 will be skipped over when stepping.
4918 If you do not specify @var{filename}, functions whose source lives in the file
4919 you're currently debugging will be skipped.
4922 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4923 These are the commands for managing your list of skips:
4927 @item info skip @r{[}@var{range}@r{]}
4928 Print details about the specified skip(s). If @var{range} is not specified,
4929 print a table with details about all functions and files marked for skipping.
4930 @code{info skip} prints the following information about each skip:
4934 A number identifying this skip.
4936 The type of this skip, either @samp{function} or @samp{file}.
4937 @item Enabled or Disabled
4938 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4940 For function skips, this column indicates the address in memory of the function
4941 being skipped. If you've set a function skip on a function which has not yet
4942 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4943 which has the function is loaded, @code{info skip} will show the function's
4946 For file skips, this field contains the filename being skipped. For functions
4947 skips, this field contains the function name and its line number in the file
4948 where it is defined.
4952 @item skip delete @r{[}@var{range}@r{]}
4953 Delete the specified skip(s). If @var{range} is not specified, delete all
4957 @item skip enable @r{[}@var{range}@r{]}
4958 Enable the specified skip(s). If @var{range} is not specified, enable all
4961 @kindex skip disable
4962 @item skip disable @r{[}@var{range}@r{]}
4963 Disable the specified skip(s). If @var{range} is not specified, disable all
4972 A signal is an asynchronous event that can happen in a program. The
4973 operating system defines the possible kinds of signals, and gives each
4974 kind a name and a number. For example, in Unix @code{SIGINT} is the
4975 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4976 @code{SIGSEGV} is the signal a program gets from referencing a place in
4977 memory far away from all the areas in use; @code{SIGALRM} occurs when
4978 the alarm clock timer goes off (which happens only if your program has
4979 requested an alarm).
4981 @cindex fatal signals
4982 Some signals, including @code{SIGALRM}, are a normal part of the
4983 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4984 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4985 program has not specified in advance some other way to handle the signal.
4986 @code{SIGINT} does not indicate an error in your program, but it is normally
4987 fatal so it can carry out the purpose of the interrupt: to kill the program.
4989 @value{GDBN} has the ability to detect any occurrence of a signal in your
4990 program. You can tell @value{GDBN} in advance what to do for each kind of
4993 @cindex handling signals
4994 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4995 @code{SIGALRM} be silently passed to your program
4996 (so as not to interfere with their role in the program's functioning)
4997 but to stop your program immediately whenever an error signal happens.
4998 You can change these settings with the @code{handle} command.
5001 @kindex info signals
5005 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5006 handle each one. You can use this to see the signal numbers of all
5007 the defined types of signals.
5009 @item info signals @var{sig}
5010 Similar, but print information only about the specified signal number.
5012 @code{info handle} is an alias for @code{info signals}.
5015 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5016 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5017 can be the number of a signal or its name (with or without the
5018 @samp{SIG} at the beginning); a list of signal numbers of the form
5019 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5020 known signals. Optional arguments @var{keywords}, described below,
5021 say what change to make.
5025 The keywords allowed by the @code{handle} command can be abbreviated.
5026 Their full names are:
5030 @value{GDBN} should not stop your program when this signal happens. It may
5031 still print a message telling you that the signal has come in.
5034 @value{GDBN} should stop your program when this signal happens. This implies
5035 the @code{print} keyword as well.
5038 @value{GDBN} should print a message when this signal happens.
5041 @value{GDBN} should not mention the occurrence of the signal at all. This
5042 implies the @code{nostop} keyword as well.
5046 @value{GDBN} should allow your program to see this signal; your program
5047 can handle the signal, or else it may terminate if the signal is fatal
5048 and not handled. @code{pass} and @code{noignore} are synonyms.
5052 @value{GDBN} should not allow your program to see this signal.
5053 @code{nopass} and @code{ignore} are synonyms.
5057 When a signal stops your program, the signal is not visible to the
5059 continue. Your program sees the signal then, if @code{pass} is in
5060 effect for the signal in question @emph{at that time}. In other words,
5061 after @value{GDBN} reports a signal, you can use the @code{handle}
5062 command with @code{pass} or @code{nopass} to control whether your
5063 program sees that signal when you continue.
5065 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5066 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5067 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5070 You can also use the @code{signal} command to prevent your program from
5071 seeing a signal, or cause it to see a signal it normally would not see,
5072 or to give it any signal at any time. For example, if your program stopped
5073 due to some sort of memory reference error, you might store correct
5074 values into the erroneous variables and continue, hoping to see more
5075 execution; but your program would probably terminate immediately as
5076 a result of the fatal signal once it saw the signal. To prevent this,
5077 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5080 @cindex extra signal information
5081 @anchor{extra signal information}
5083 On some targets, @value{GDBN} can inspect extra signal information
5084 associated with the intercepted signal, before it is actually
5085 delivered to the program being debugged. This information is exported
5086 by the convenience variable @code{$_siginfo}, and consists of data
5087 that is passed by the kernel to the signal handler at the time of the
5088 receipt of a signal. The data type of the information itself is
5089 target dependent. You can see the data type using the @code{ptype
5090 $_siginfo} command. On Unix systems, it typically corresponds to the
5091 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5094 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5095 referenced address that raised a segmentation fault.
5099 (@value{GDBP}) continue
5100 Program received signal SIGSEGV, Segmentation fault.
5101 0x0000000000400766 in main ()
5103 (@value{GDBP}) ptype $_siginfo
5110 struct @{...@} _kill;
5111 struct @{...@} _timer;
5113 struct @{...@} _sigchld;
5114 struct @{...@} _sigfault;
5115 struct @{...@} _sigpoll;
5118 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5122 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5123 $1 = (void *) 0x7ffff7ff7000
5127 Depending on target support, @code{$_siginfo} may also be writable.
5130 @section Stopping and Starting Multi-thread Programs
5132 @cindex stopped threads
5133 @cindex threads, stopped
5135 @cindex continuing threads
5136 @cindex threads, continuing
5138 @value{GDBN} supports debugging programs with multiple threads
5139 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5140 are two modes of controlling execution of your program within the
5141 debugger. In the default mode, referred to as @dfn{all-stop mode},
5142 when any thread in your program stops (for example, at a breakpoint
5143 or while being stepped), all other threads in the program are also stopped by
5144 @value{GDBN}. On some targets, @value{GDBN} also supports
5145 @dfn{non-stop mode}, in which other threads can continue to run freely while
5146 you examine the stopped thread in the debugger.
5149 * All-Stop Mode:: All threads stop when GDB takes control
5150 * Non-Stop Mode:: Other threads continue to execute
5151 * Background Execution:: Running your program asynchronously
5152 * Thread-Specific Breakpoints:: Controlling breakpoints
5153 * Interrupted System Calls:: GDB may interfere with system calls
5154 * Observer Mode:: GDB does not alter program behavior
5158 @subsection All-Stop Mode
5160 @cindex all-stop mode
5162 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5163 @emph{all} threads of execution stop, not just the current thread. This
5164 allows you to examine the overall state of the program, including
5165 switching between threads, without worrying that things may change
5168 Conversely, whenever you restart the program, @emph{all} threads start
5169 executing. @emph{This is true even when single-stepping} with commands
5170 like @code{step} or @code{next}.
5172 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5173 Since thread scheduling is up to your debugging target's operating
5174 system (not controlled by @value{GDBN}), other threads may
5175 execute more than one statement while the current thread completes a
5176 single step. Moreover, in general other threads stop in the middle of a
5177 statement, rather than at a clean statement boundary, when the program
5180 You might even find your program stopped in another thread after
5181 continuing or even single-stepping. This happens whenever some other
5182 thread runs into a breakpoint, a signal, or an exception before the
5183 first thread completes whatever you requested.
5185 @cindex automatic thread selection
5186 @cindex switching threads automatically
5187 @cindex threads, automatic switching
5188 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5189 signal, it automatically selects the thread where that breakpoint or
5190 signal happened. @value{GDBN} alerts you to the context switch with a
5191 message such as @samp{[Switching to Thread @var{n}]} to identify the
5194 On some OSes, you can modify @value{GDBN}'s default behavior by
5195 locking the OS scheduler to allow only a single thread to run.
5198 @item set scheduler-locking @var{mode}
5199 @cindex scheduler locking mode
5200 @cindex lock scheduler
5201 Set the scheduler locking mode. If it is @code{off}, then there is no
5202 locking and any thread may run at any time. If @code{on}, then only the
5203 current thread may run when the inferior is resumed. The @code{step}
5204 mode optimizes for single-stepping; it prevents other threads
5205 from preempting the current thread while you are stepping, so that
5206 the focus of debugging does not change unexpectedly.
5207 Other threads only rarely (or never) get a chance to run
5208 when you step. They are more likely to run when you @samp{next} over a
5209 function call, and they are completely free to run when you use commands
5210 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5211 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5212 the current thread away from the thread that you are debugging.
5214 @item show scheduler-locking
5215 Display the current scheduler locking mode.
5218 @cindex resume threads of multiple processes simultaneously
5219 By default, when you issue one of the execution commands such as
5220 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5221 threads of the current inferior to run. For example, if @value{GDBN}
5222 is attached to two inferiors, each with two threads, the
5223 @code{continue} command resumes only the two threads of the current
5224 inferior. This is useful, for example, when you debug a program that
5225 forks and you want to hold the parent stopped (so that, for instance,
5226 it doesn't run to exit), while you debug the child. In other
5227 situations, you may not be interested in inspecting the current state
5228 of any of the processes @value{GDBN} is attached to, and you may want
5229 to resume them all until some breakpoint is hit. In the latter case,
5230 you can instruct @value{GDBN} to allow all threads of all the
5231 inferiors to run with the @w{@code{set schedule-multiple}} command.
5234 @kindex set schedule-multiple
5235 @item set schedule-multiple
5236 Set the mode for allowing threads of multiple processes to be resumed
5237 when an execution command is issued. When @code{on}, all threads of
5238 all processes are allowed to run. When @code{off}, only the threads
5239 of the current process are resumed. The default is @code{off}. The
5240 @code{scheduler-locking} mode takes precedence when set to @code{on},
5241 or while you are stepping and set to @code{step}.
5243 @item show schedule-multiple
5244 Display the current mode for resuming the execution of threads of
5249 @subsection Non-Stop Mode
5251 @cindex non-stop mode
5253 @c This section is really only a place-holder, and needs to be expanded
5254 @c with more details.
5256 For some multi-threaded targets, @value{GDBN} supports an optional
5257 mode of operation in which you can examine stopped program threads in
5258 the debugger while other threads continue to execute freely. This
5259 minimizes intrusion when debugging live systems, such as programs
5260 where some threads have real-time constraints or must continue to
5261 respond to external events. This is referred to as @dfn{non-stop} mode.
5263 In non-stop mode, when a thread stops to report a debugging event,
5264 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5265 threads as well, in contrast to the all-stop mode behavior. Additionally,
5266 execution commands such as @code{continue} and @code{step} apply by default
5267 only to the current thread in non-stop mode, rather than all threads as
5268 in all-stop mode. This allows you to control threads explicitly in
5269 ways that are not possible in all-stop mode --- for example, stepping
5270 one thread while allowing others to run freely, stepping
5271 one thread while holding all others stopped, or stepping several threads
5272 independently and simultaneously.
5274 To enter non-stop mode, use this sequence of commands before you run
5275 or attach to your program:
5278 # Enable the async interface.
5281 # If using the CLI, pagination breaks non-stop.
5284 # Finally, turn it on!
5288 You can use these commands to manipulate the non-stop mode setting:
5291 @kindex set non-stop
5292 @item set non-stop on
5293 Enable selection of non-stop mode.
5294 @item set non-stop off
5295 Disable selection of non-stop mode.
5296 @kindex show non-stop
5298 Show the current non-stop enablement setting.
5301 Note these commands only reflect whether non-stop mode is enabled,
5302 not whether the currently-executing program is being run in non-stop mode.
5303 In particular, the @code{set non-stop} preference is only consulted when
5304 @value{GDBN} starts or connects to the target program, and it is generally
5305 not possible to switch modes once debugging has started. Furthermore,
5306 since not all targets support non-stop mode, even when you have enabled
5307 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5310 In non-stop mode, all execution commands apply only to the current thread
5311 by default. That is, @code{continue} only continues one thread.
5312 To continue all threads, issue @code{continue -a} or @code{c -a}.
5314 You can use @value{GDBN}'s background execution commands
5315 (@pxref{Background Execution}) to run some threads in the background
5316 while you continue to examine or step others from @value{GDBN}.
5317 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5318 always executed asynchronously in non-stop mode.
5320 Suspending execution is done with the @code{interrupt} command when
5321 running in the background, or @kbd{Ctrl-c} during foreground execution.
5322 In all-stop mode, this stops the whole process;
5323 but in non-stop mode the interrupt applies only to the current thread.
5324 To stop the whole program, use @code{interrupt -a}.
5326 Other execution commands do not currently support the @code{-a} option.
5328 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5329 that thread current, as it does in all-stop mode. This is because the
5330 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5331 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5332 changed to a different thread just as you entered a command to operate on the
5333 previously current thread.
5335 @node Background Execution
5336 @subsection Background Execution
5338 @cindex foreground execution
5339 @cindex background execution
5340 @cindex asynchronous execution
5341 @cindex execution, foreground, background and asynchronous
5343 @value{GDBN}'s execution commands have two variants: the normal
5344 foreground (synchronous) behavior, and a background
5345 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5346 the program to report that some thread has stopped before prompting for
5347 another command. In background execution, @value{GDBN} immediately gives
5348 a command prompt so that you can issue other commands while your program runs.
5350 You need to explicitly enable asynchronous mode before you can use
5351 background execution commands. You can use these commands to
5352 manipulate the asynchronous mode setting:
5355 @kindex set target-async
5356 @item set target-async on
5357 Enable asynchronous mode.
5358 @item set target-async off
5359 Disable asynchronous mode.
5360 @kindex show target-async
5361 @item show target-async
5362 Show the current target-async setting.
5365 If the target doesn't support async mode, @value{GDBN} issues an error
5366 message if you attempt to use the background execution commands.
5368 To specify background execution, add a @code{&} to the command. For example,
5369 the background form of the @code{continue} command is @code{continue&}, or
5370 just @code{c&}. The execution commands that accept background execution
5376 @xref{Starting, , Starting your Program}.
5380 @xref{Attach, , Debugging an Already-running Process}.
5384 @xref{Continuing and Stepping, step}.
5388 @xref{Continuing and Stepping, stepi}.
5392 @xref{Continuing and Stepping, next}.
5396 @xref{Continuing and Stepping, nexti}.
5400 @xref{Continuing and Stepping, continue}.
5404 @xref{Continuing and Stepping, finish}.
5408 @xref{Continuing and Stepping, until}.
5412 Background execution is especially useful in conjunction with non-stop
5413 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5414 However, you can also use these commands in the normal all-stop mode with
5415 the restriction that you cannot issue another execution command until the
5416 previous one finishes. Examples of commands that are valid in all-stop
5417 mode while the program is running include @code{help} and @code{info break}.
5419 You can interrupt your program while it is running in the background by
5420 using the @code{interrupt} command.
5427 Suspend execution of the running program. In all-stop mode,
5428 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5429 only the current thread. To stop the whole program in non-stop mode,
5430 use @code{interrupt -a}.
5433 @node Thread-Specific Breakpoints
5434 @subsection Thread-Specific Breakpoints
5436 When your program has multiple threads (@pxref{Threads,, Debugging
5437 Programs with Multiple Threads}), you can choose whether to set
5438 breakpoints on all threads, or on a particular thread.
5441 @cindex breakpoints and threads
5442 @cindex thread breakpoints
5443 @kindex break @dots{} thread @var{threadno}
5444 @item break @var{linespec} thread @var{threadno}
5445 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5446 @var{linespec} specifies source lines; there are several ways of
5447 writing them (@pxref{Specify Location}), but the effect is always to
5448 specify some source line.
5450 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5451 to specify that you only want @value{GDBN} to stop the program when a
5452 particular thread reaches this breakpoint. @var{threadno} is one of the
5453 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5454 column of the @samp{info threads} display.
5456 If you do not specify @samp{thread @var{threadno}} when you set a
5457 breakpoint, the breakpoint applies to @emph{all} threads of your
5460 You can use the @code{thread} qualifier on conditional breakpoints as
5461 well; in this case, place @samp{thread @var{threadno}} before or
5462 after the breakpoint condition, like this:
5465 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5470 @node Interrupted System Calls
5471 @subsection Interrupted System Calls
5473 @cindex thread breakpoints and system calls
5474 @cindex system calls and thread breakpoints
5475 @cindex premature return from system calls
5476 There is an unfortunate side effect when using @value{GDBN} to debug
5477 multi-threaded programs. If one thread stops for a
5478 breakpoint, or for some other reason, and another thread is blocked in a
5479 system call, then the system call may return prematurely. This is a
5480 consequence of the interaction between multiple threads and the signals
5481 that @value{GDBN} uses to implement breakpoints and other events that
5484 To handle this problem, your program should check the return value of
5485 each system call and react appropriately. This is good programming
5488 For example, do not write code like this:
5494 The call to @code{sleep} will return early if a different thread stops
5495 at a breakpoint or for some other reason.
5497 Instead, write this:
5502 unslept = sleep (unslept);
5505 A system call is allowed to return early, so the system is still
5506 conforming to its specification. But @value{GDBN} does cause your
5507 multi-threaded program to behave differently than it would without
5510 Also, @value{GDBN} uses internal breakpoints in the thread library to
5511 monitor certain events such as thread creation and thread destruction.
5512 When such an event happens, a system call in another thread may return
5513 prematurely, even though your program does not appear to stop.
5516 @subsection Observer Mode
5518 If you want to build on non-stop mode and observe program behavior
5519 without any chance of disruption by @value{GDBN}, you can set
5520 variables to disable all of the debugger's attempts to modify state,
5521 whether by writing memory, inserting breakpoints, etc. These operate
5522 at a low level, intercepting operations from all commands.
5524 When all of these are set to @code{off}, then @value{GDBN} is said to
5525 be @dfn{observer mode}. As a convenience, the variable
5526 @code{observer} can be set to disable these, plus enable non-stop
5529 Note that @value{GDBN} will not prevent you from making nonsensical
5530 combinations of these settings. For instance, if you have enabled
5531 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5532 then breakpoints that work by writing trap instructions into the code
5533 stream will still not be able to be placed.
5538 @item set observer on
5539 @itemx set observer off
5540 When set to @code{on}, this disables all the permission variables
5541 below (except for @code{insert-fast-tracepoints}), plus enables
5542 non-stop debugging. Setting this to @code{off} switches back to
5543 normal debugging, though remaining in non-stop mode.
5546 Show whether observer mode is on or off.
5548 @kindex may-write-registers
5549 @item set may-write-registers on
5550 @itemx set may-write-registers off
5551 This controls whether @value{GDBN} will attempt to alter the values of
5552 registers, such as with assignment expressions in @code{print}, or the
5553 @code{jump} command. It defaults to @code{on}.
5555 @item show may-write-registers
5556 Show the current permission to write registers.
5558 @kindex may-write-memory
5559 @item set may-write-memory on
5560 @itemx set may-write-memory off
5561 This controls whether @value{GDBN} will attempt to alter the contents
5562 of memory, such as with assignment expressions in @code{print}. It
5563 defaults to @code{on}.
5565 @item show may-write-memory
5566 Show the current permission to write memory.
5568 @kindex may-insert-breakpoints
5569 @item set may-insert-breakpoints on
5570 @itemx set may-insert-breakpoints off
5571 This controls whether @value{GDBN} will attempt to insert breakpoints.
5572 This affects all breakpoints, including internal breakpoints defined
5573 by @value{GDBN}. It defaults to @code{on}.
5575 @item show may-insert-breakpoints
5576 Show the current permission to insert breakpoints.
5578 @kindex may-insert-tracepoints
5579 @item set may-insert-tracepoints on
5580 @itemx set may-insert-tracepoints off
5581 This controls whether @value{GDBN} will attempt to insert (regular)
5582 tracepoints at the beginning of a tracing experiment. It affects only
5583 non-fast tracepoints, fast tracepoints being under the control of
5584 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5586 @item show may-insert-tracepoints
5587 Show the current permission to insert tracepoints.
5589 @kindex may-insert-fast-tracepoints
5590 @item set may-insert-fast-tracepoints on
5591 @itemx set may-insert-fast-tracepoints off
5592 This controls whether @value{GDBN} will attempt to insert fast
5593 tracepoints at the beginning of a tracing experiment. It affects only
5594 fast tracepoints, regular (non-fast) tracepoints being under the
5595 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5597 @item show may-insert-fast-tracepoints
5598 Show the current permission to insert fast tracepoints.
5600 @kindex may-interrupt
5601 @item set may-interrupt on
5602 @itemx set may-interrupt off
5603 This controls whether @value{GDBN} will attempt to interrupt or stop
5604 program execution. When this variable is @code{off}, the
5605 @code{interrupt} command will have no effect, nor will
5606 @kbd{Ctrl-c}. It defaults to @code{on}.
5608 @item show may-interrupt
5609 Show the current permission to interrupt or stop the program.
5613 @node Reverse Execution
5614 @chapter Running programs backward
5615 @cindex reverse execution
5616 @cindex running programs backward
5618 When you are debugging a program, it is not unusual to realize that
5619 you have gone too far, and some event of interest has already happened.
5620 If the target environment supports it, @value{GDBN} can allow you to
5621 ``rewind'' the program by running it backward.
5623 A target environment that supports reverse execution should be able
5624 to ``undo'' the changes in machine state that have taken place as the
5625 program was executing normally. Variables, registers etc.@: should
5626 revert to their previous values. Obviously this requires a great
5627 deal of sophistication on the part of the target environment; not
5628 all target environments can support reverse execution.
5630 When a program is executed in reverse, the instructions that
5631 have most recently been executed are ``un-executed'', in reverse
5632 order. The program counter runs backward, following the previous
5633 thread of execution in reverse. As each instruction is ``un-executed'',
5634 the values of memory and/or registers that were changed by that
5635 instruction are reverted to their previous states. After executing
5636 a piece of source code in reverse, all side effects of that code
5637 should be ``undone'', and all variables should be returned to their
5638 prior values@footnote{
5639 Note that some side effects are easier to undo than others. For instance,
5640 memory and registers are relatively easy, but device I/O is hard. Some
5641 targets may be able undo things like device I/O, and some may not.
5643 The contract between @value{GDBN} and the reverse executing target
5644 requires only that the target do something reasonable when
5645 @value{GDBN} tells it to execute backwards, and then report the
5646 results back to @value{GDBN}. Whatever the target reports back to
5647 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5648 assumes that the memory and registers that the target reports are in a
5649 consistant state, but @value{GDBN} accepts whatever it is given.
5652 If you are debugging in a target environment that supports
5653 reverse execution, @value{GDBN} provides the following commands.
5656 @kindex reverse-continue
5657 @kindex rc @r{(@code{reverse-continue})}
5658 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5659 @itemx rc @r{[}@var{ignore-count}@r{]}
5660 Beginning at the point where your program last stopped, start executing
5661 in reverse. Reverse execution will stop for breakpoints and synchronous
5662 exceptions (signals), just like normal execution. Behavior of
5663 asynchronous signals depends on the target environment.
5665 @kindex reverse-step
5666 @kindex rs @r{(@code{step})}
5667 @item reverse-step @r{[}@var{count}@r{]}
5668 Run the program backward until control reaches the start of a
5669 different source line; then stop it, and return control to @value{GDBN}.
5671 Like the @code{step} command, @code{reverse-step} will only stop
5672 at the beginning of a source line. It ``un-executes'' the previously
5673 executed source line. If the previous source line included calls to
5674 debuggable functions, @code{reverse-step} will step (backward) into
5675 the called function, stopping at the beginning of the @emph{last}
5676 statement in the called function (typically a return statement).
5678 Also, as with the @code{step} command, if non-debuggable functions are
5679 called, @code{reverse-step} will run thru them backward without stopping.
5681 @kindex reverse-stepi
5682 @kindex rsi @r{(@code{reverse-stepi})}
5683 @item reverse-stepi @r{[}@var{count}@r{]}
5684 Reverse-execute one machine instruction. Note that the instruction
5685 to be reverse-executed is @emph{not} the one pointed to by the program
5686 counter, but the instruction executed prior to that one. For instance,
5687 if the last instruction was a jump, @code{reverse-stepi} will take you
5688 back from the destination of the jump to the jump instruction itself.
5690 @kindex reverse-next
5691 @kindex rn @r{(@code{reverse-next})}
5692 @item reverse-next @r{[}@var{count}@r{]}
5693 Run backward to the beginning of the previous line executed in
5694 the current (innermost) stack frame. If the line contains function
5695 calls, they will be ``un-executed'' without stopping. Starting from
5696 the first line of a function, @code{reverse-next} will take you back
5697 to the caller of that function, @emph{before} the function was called,
5698 just as the normal @code{next} command would take you from the last
5699 line of a function back to its return to its caller
5700 @footnote{Unless the code is too heavily optimized.}.
5702 @kindex reverse-nexti
5703 @kindex rni @r{(@code{reverse-nexti})}
5704 @item reverse-nexti @r{[}@var{count}@r{]}
5705 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5706 in reverse, except that called functions are ``un-executed'' atomically.
5707 That is, if the previously executed instruction was a return from
5708 another function, @code{reverse-nexti} will continue to execute
5709 in reverse until the call to that function (from the current stack
5712 @kindex reverse-finish
5713 @item reverse-finish
5714 Just as the @code{finish} command takes you to the point where the
5715 current function returns, @code{reverse-finish} takes you to the point
5716 where it was called. Instead of ending up at the end of the current
5717 function invocation, you end up at the beginning.
5719 @kindex set exec-direction
5720 @item set exec-direction
5721 Set the direction of target execution.
5722 @itemx set exec-direction reverse
5723 @cindex execute forward or backward in time
5724 @value{GDBN} will perform all execution commands in reverse, until the
5725 exec-direction mode is changed to ``forward''. Affected commands include
5726 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5727 command cannot be used in reverse mode.
5728 @item set exec-direction forward
5729 @value{GDBN} will perform all execution commands in the normal fashion.
5730 This is the default.
5734 @node Process Record and Replay
5735 @chapter Recording Inferior's Execution and Replaying It
5736 @cindex process record and replay
5737 @cindex recording inferior's execution and replaying it
5739 On some platforms, @value{GDBN} provides a special @dfn{process record
5740 and replay} target that can record a log of the process execution, and
5741 replay it later with both forward and reverse execution commands.
5744 When this target is in use, if the execution log includes the record
5745 for the next instruction, @value{GDBN} will debug in @dfn{replay
5746 mode}. In the replay mode, the inferior does not really execute code
5747 instructions. Instead, all the events that normally happen during
5748 code execution are taken from the execution log. While code is not
5749 really executed in replay mode, the values of registers (including the
5750 program counter register) and the memory of the inferior are still
5751 changed as they normally would. Their contents are taken from the
5755 If the record for the next instruction is not in the execution log,
5756 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5757 inferior executes normally, and @value{GDBN} records the execution log
5760 The process record and replay target supports reverse execution
5761 (@pxref{Reverse Execution}), even if the platform on which the
5762 inferior runs does not. However, the reverse execution is limited in
5763 this case by the range of the instructions recorded in the execution
5764 log. In other words, reverse execution on platforms that don't
5765 support it directly can only be done in the replay mode.
5767 When debugging in the reverse direction, @value{GDBN} will work in
5768 replay mode as long as the execution log includes the record for the
5769 previous instruction; otherwise, it will work in record mode, if the
5770 platform supports reverse execution, or stop if not.
5772 For architecture environments that support process record and replay,
5773 @value{GDBN} provides the following commands:
5776 @kindex target record
5780 This command starts the process record and replay target. The process
5781 record and replay target can only debug a process that is already
5782 running. Therefore, you need first to start the process with the
5783 @kbd{run} or @kbd{start} commands, and then start the recording with
5784 the @kbd{target record} command.
5786 Both @code{record} and @code{rec} are aliases of @code{target record}.
5788 @cindex displaced stepping, and process record and replay
5789 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5790 will be automatically disabled when process record and replay target
5791 is started. That's because the process record and replay target
5792 doesn't support displaced stepping.
5794 @cindex non-stop mode, and process record and replay
5795 @cindex asynchronous execution, and process record and replay
5796 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5797 the asynchronous execution mode (@pxref{Background Execution}), the
5798 process record and replay target cannot be started because it doesn't
5799 support these two modes.
5804 Stop the process record and replay target. When process record and
5805 replay target stops, the entire execution log will be deleted and the
5806 inferior will either be terminated, or will remain in its final state.
5808 When you stop the process record and replay target in record mode (at
5809 the end of the execution log), the inferior will be stopped at the
5810 next instruction that would have been recorded. In other words, if
5811 you record for a while and then stop recording, the inferior process
5812 will be left in the same state as if the recording never happened.
5814 On the other hand, if the process record and replay target is stopped
5815 while in replay mode (that is, not at the end of the execution log,
5816 but at some earlier point), the inferior process will become ``live''
5817 at that earlier state, and it will then be possible to continue the
5818 usual ``live'' debugging of the process from that state.
5820 When the inferior process exits, or @value{GDBN} detaches from it,
5821 process record and replay target will automatically stop itself.
5824 @item record save @var{filename}
5825 Save the execution log to a file @file{@var{filename}}.
5826 Default filename is @file{gdb_record.@var{process_id}}, where
5827 @var{process_id} is the process ID of the inferior.
5829 @kindex record restore
5830 @item record restore @var{filename}
5831 Restore the execution log from a file @file{@var{filename}}.
5832 File must have been created with @code{record save}.
5834 @kindex set record insn-number-max
5835 @item set record insn-number-max @var{limit}
5836 Set the limit of instructions to be recorded. Default value is 200000.
5838 If @var{limit} is a positive number, then @value{GDBN} will start
5839 deleting instructions from the log once the number of the record
5840 instructions becomes greater than @var{limit}. For every new recorded
5841 instruction, @value{GDBN} will delete the earliest recorded
5842 instruction to keep the number of recorded instructions at the limit.
5843 (Since deleting recorded instructions loses information, @value{GDBN}
5844 lets you control what happens when the limit is reached, by means of
5845 the @code{stop-at-limit} option, described below.)
5847 If @var{limit} is zero, @value{GDBN} will never delete recorded
5848 instructions from the execution log. The number of recorded
5849 instructions is unlimited in this case.
5851 @kindex show record insn-number-max
5852 @item show record insn-number-max
5853 Show the limit of instructions to be recorded.
5855 @kindex set record stop-at-limit
5856 @item set record stop-at-limit
5857 Control the behavior when the number of recorded instructions reaches
5858 the limit. If ON (the default), @value{GDBN} will stop when the limit
5859 is reached for the first time and ask you whether you want to stop the
5860 inferior or continue running it and recording the execution log. If
5861 you decide to continue recording, each new recorded instruction will
5862 cause the oldest one to be deleted.
5864 If this option is OFF, @value{GDBN} will automatically delete the
5865 oldest record to make room for each new one, without asking.
5867 @kindex show record stop-at-limit
5868 @item show record stop-at-limit
5869 Show the current setting of @code{stop-at-limit}.
5871 @kindex set record memory-query
5872 @item set record memory-query
5873 Control the behavior when @value{GDBN} is unable to record memory
5874 changes caused by an instruction. If ON, @value{GDBN} will query
5875 whether to stop the inferior in that case.
5877 If this option is OFF (the default), @value{GDBN} will automatically
5878 ignore the effect of such instructions on memory. Later, when
5879 @value{GDBN} replays this execution log, it will mark the log of this
5880 instruction as not accessible, and it will not affect the replay
5883 @kindex show record memory-query
5884 @item show record memory-query
5885 Show the current setting of @code{memory-query}.
5889 Show various statistics about the state of process record and its
5890 in-memory execution log buffer, including:
5894 Whether in record mode or replay mode.
5896 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5898 Highest recorded instruction number.
5900 Current instruction about to be replayed (if in replay mode).
5902 Number of instructions contained in the execution log.
5904 Maximum number of instructions that may be contained in the execution log.
5907 @kindex record delete
5910 When record target runs in replay mode (``in the past''), delete the
5911 subsequent execution log and begin to record a new execution log starting
5912 from the current address. This means you will abandon the previously
5913 recorded ``future'' and begin recording a new ``future''.
5918 @chapter Examining the Stack
5920 When your program has stopped, the first thing you need to know is where it
5921 stopped and how it got there.
5924 Each time your program performs a function call, information about the call
5926 That information includes the location of the call in your program,
5927 the arguments of the call,
5928 and the local variables of the function being called.
5929 The information is saved in a block of data called a @dfn{stack frame}.
5930 The stack frames are allocated in a region of memory called the @dfn{call
5933 When your program stops, the @value{GDBN} commands for examining the
5934 stack allow you to see all of this information.
5936 @cindex selected frame
5937 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5938 @value{GDBN} commands refer implicitly to the selected frame. In
5939 particular, whenever you ask @value{GDBN} for the value of a variable in
5940 your program, the value is found in the selected frame. There are
5941 special @value{GDBN} commands to select whichever frame you are
5942 interested in. @xref{Selection, ,Selecting a Frame}.
5944 When your program stops, @value{GDBN} automatically selects the
5945 currently executing frame and describes it briefly, similar to the
5946 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5949 * Frames:: Stack frames
5950 * Backtrace:: Backtraces
5951 * Selection:: Selecting a frame
5952 * Frame Info:: Information on a frame
5957 @section Stack Frames
5959 @cindex frame, definition
5961 The call stack is divided up into contiguous pieces called @dfn{stack
5962 frames}, or @dfn{frames} for short; each frame is the data associated
5963 with one call to one function. The frame contains the arguments given
5964 to the function, the function's local variables, and the address at
5965 which the function is executing.
5967 @cindex initial frame
5968 @cindex outermost frame
5969 @cindex innermost frame
5970 When your program is started, the stack has only one frame, that of the
5971 function @code{main}. This is called the @dfn{initial} frame or the
5972 @dfn{outermost} frame. Each time a function is called, a new frame is
5973 made. Each time a function returns, the frame for that function invocation
5974 is eliminated. If a function is recursive, there can be many frames for
5975 the same function. The frame for the function in which execution is
5976 actually occurring is called the @dfn{innermost} frame. This is the most
5977 recently created of all the stack frames that still exist.
5979 @cindex frame pointer
5980 Inside your program, stack frames are identified by their addresses. A
5981 stack frame consists of many bytes, each of which has its own address; each
5982 kind of computer has a convention for choosing one byte whose
5983 address serves as the address of the frame. Usually this address is kept
5984 in a register called the @dfn{frame pointer register}
5985 (@pxref{Registers, $fp}) while execution is going on in that frame.
5987 @cindex frame number
5988 @value{GDBN} assigns numbers to all existing stack frames, starting with
5989 zero for the innermost frame, one for the frame that called it,
5990 and so on upward. These numbers do not really exist in your program;
5991 they are assigned by @value{GDBN} to give you a way of designating stack
5992 frames in @value{GDBN} commands.
5994 @c The -fomit-frame-pointer below perennially causes hbox overflow
5995 @c underflow problems.
5996 @cindex frameless execution
5997 Some compilers provide a way to compile functions so that they operate
5998 without stack frames. (For example, the @value{NGCC} option
6000 @samp{-fomit-frame-pointer}
6002 generates functions without a frame.)
6003 This is occasionally done with heavily used library functions to save
6004 the frame setup time. @value{GDBN} has limited facilities for dealing
6005 with these function invocations. If the innermost function invocation
6006 has no stack frame, @value{GDBN} nevertheless regards it as though
6007 it had a separate frame, which is numbered zero as usual, allowing
6008 correct tracing of the function call chain. However, @value{GDBN} has
6009 no provision for frameless functions elsewhere in the stack.
6012 @kindex frame@r{, command}
6013 @cindex current stack frame
6014 @item frame @var{args}
6015 The @code{frame} command allows you to move from one stack frame to another,
6016 and to print the stack frame you select. @var{args} may be either the
6017 address of the frame or the stack frame number. Without an argument,
6018 @code{frame} prints the current stack frame.
6020 @kindex select-frame
6021 @cindex selecting frame silently
6023 The @code{select-frame} command allows you to move from one stack frame
6024 to another without printing the frame. This is the silent version of
6032 @cindex call stack traces
6033 A backtrace is a summary of how your program got where it is. It shows one
6034 line per frame, for many frames, starting with the currently executing
6035 frame (frame zero), followed by its caller (frame one), and on up the
6040 @kindex bt @r{(@code{backtrace})}
6043 Print a backtrace of the entire stack: one line per frame for all
6044 frames in the stack.
6046 You can stop the backtrace at any time by typing the system interrupt
6047 character, normally @kbd{Ctrl-c}.
6049 @item backtrace @var{n}
6051 Similar, but print only the innermost @var{n} frames.
6053 @item backtrace -@var{n}
6055 Similar, but print only the outermost @var{n} frames.
6057 @item backtrace full
6059 @itemx bt full @var{n}
6060 @itemx bt full -@var{n}
6061 Print the values of the local variables also. @var{n} specifies the
6062 number of frames to print, as described above.
6067 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6068 are additional aliases for @code{backtrace}.
6070 @cindex multiple threads, backtrace
6071 In a multi-threaded program, @value{GDBN} by default shows the
6072 backtrace only for the current thread. To display the backtrace for
6073 several or all of the threads, use the command @code{thread apply}
6074 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6075 apply all backtrace}, @value{GDBN} will display the backtrace for all
6076 the threads; this is handy when you debug a core dump of a
6077 multi-threaded program.
6079 Each line in the backtrace shows the frame number and the function name.
6080 The program counter value is also shown---unless you use @code{set
6081 print address off}. The backtrace also shows the source file name and
6082 line number, as well as the arguments to the function. The program
6083 counter value is omitted if it is at the beginning of the code for that
6086 Here is an example of a backtrace. It was made with the command
6087 @samp{bt 3}, so it shows the innermost three frames.
6091 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6093 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6094 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6096 (More stack frames follow...)
6101 The display for frame zero does not begin with a program counter
6102 value, indicating that your program has stopped at the beginning of the
6103 code for line @code{993} of @code{builtin.c}.
6106 The value of parameter @code{data} in frame 1 has been replaced by
6107 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6108 only if it is a scalar (integer, pointer, enumeration, etc). See command
6109 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6110 on how to configure the way function parameter values are printed.
6112 @cindex optimized out, in backtrace
6113 @cindex function call arguments, optimized out
6114 If your program was compiled with optimizations, some compilers will
6115 optimize away arguments passed to functions if those arguments are
6116 never used after the call. Such optimizations generate code that
6117 passes arguments through registers, but doesn't store those arguments
6118 in the stack frame. @value{GDBN} has no way of displaying such
6119 arguments in stack frames other than the innermost one. Here's what
6120 such a backtrace might look like:
6124 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6126 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6127 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6129 (More stack frames follow...)
6134 The values of arguments that were not saved in their stack frames are
6135 shown as @samp{<optimized out>}.
6137 If you need to display the values of such optimized-out arguments,
6138 either deduce that from other variables whose values depend on the one
6139 you are interested in, or recompile without optimizations.
6141 @cindex backtrace beyond @code{main} function
6142 @cindex program entry point
6143 @cindex startup code, and backtrace
6144 Most programs have a standard user entry point---a place where system
6145 libraries and startup code transition into user code. For C this is
6146 @code{main}@footnote{
6147 Note that embedded programs (the so-called ``free-standing''
6148 environment) are not required to have a @code{main} function as the
6149 entry point. They could even have multiple entry points.}.
6150 When @value{GDBN} finds the entry function in a backtrace
6151 it will terminate the backtrace, to avoid tracing into highly
6152 system-specific (and generally uninteresting) code.
6154 If you need to examine the startup code, or limit the number of levels
6155 in a backtrace, you can change this behavior:
6158 @item set backtrace past-main
6159 @itemx set backtrace past-main on
6160 @kindex set backtrace
6161 Backtraces will continue past the user entry point.
6163 @item set backtrace past-main off
6164 Backtraces will stop when they encounter the user entry point. This is the
6167 @item show backtrace past-main
6168 @kindex show backtrace
6169 Display the current user entry point backtrace policy.
6171 @item set backtrace past-entry
6172 @itemx set backtrace past-entry on
6173 Backtraces will continue past the internal entry point of an application.
6174 This entry point is encoded by the linker when the application is built,
6175 and is likely before the user entry point @code{main} (or equivalent) is called.
6177 @item set backtrace past-entry off
6178 Backtraces will stop when they encounter the internal entry point of an
6179 application. This is the default.
6181 @item show backtrace past-entry
6182 Display the current internal entry point backtrace policy.
6184 @item set backtrace limit @var{n}
6185 @itemx set backtrace limit 0
6186 @cindex backtrace limit
6187 Limit the backtrace to @var{n} levels. A value of zero means
6190 @item show backtrace limit
6191 Display the current limit on backtrace levels.
6195 @section Selecting a Frame
6197 Most commands for examining the stack and other data in your program work on
6198 whichever stack frame is selected at the moment. Here are the commands for
6199 selecting a stack frame; all of them finish by printing a brief description
6200 of the stack frame just selected.
6203 @kindex frame@r{, selecting}
6204 @kindex f @r{(@code{frame})}
6207 Select frame number @var{n}. Recall that frame zero is the innermost
6208 (currently executing) frame, frame one is the frame that called the
6209 innermost one, and so on. The highest-numbered frame is the one for
6212 @item frame @var{addr}
6214 Select the frame at address @var{addr}. This is useful mainly if the
6215 chaining of stack frames has been damaged by a bug, making it
6216 impossible for @value{GDBN} to assign numbers properly to all frames. In
6217 addition, this can be useful when your program has multiple stacks and
6218 switches between them.
6220 On the SPARC architecture, @code{frame} needs two addresses to
6221 select an arbitrary frame: a frame pointer and a stack pointer.
6223 On the MIPS and Alpha architecture, it needs two addresses: a stack
6224 pointer and a program counter.
6226 On the 29k architecture, it needs three addresses: a register stack
6227 pointer, a program counter, and a memory stack pointer.
6231 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6232 advances toward the outermost frame, to higher frame numbers, to frames
6233 that have existed longer. @var{n} defaults to one.
6236 @kindex do @r{(@code{down})}
6238 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6239 advances toward the innermost frame, to lower frame numbers, to frames
6240 that were created more recently. @var{n} defaults to one. You may
6241 abbreviate @code{down} as @code{do}.
6244 All of these commands end by printing two lines of output describing the
6245 frame. The first line shows the frame number, the function name, the
6246 arguments, and the source file and line number of execution in that
6247 frame. The second line shows the text of that source line.
6255 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6257 10 read_input_file (argv[i]);
6261 After such a printout, the @code{list} command with no arguments
6262 prints ten lines centered on the point of execution in the frame.
6263 You can also edit the program at the point of execution with your favorite
6264 editing program by typing @code{edit}.
6265 @xref{List, ,Printing Source Lines},
6269 @kindex down-silently
6271 @item up-silently @var{n}
6272 @itemx down-silently @var{n}
6273 These two commands are variants of @code{up} and @code{down},
6274 respectively; they differ in that they do their work silently, without
6275 causing display of the new frame. They are intended primarily for use
6276 in @value{GDBN} command scripts, where the output might be unnecessary and
6281 @section Information About a Frame
6283 There are several other commands to print information about the selected
6289 When used without any argument, this command does not change which
6290 frame is selected, but prints a brief description of the currently
6291 selected stack frame. It can be abbreviated @code{f}. With an
6292 argument, this command is used to select a stack frame.
6293 @xref{Selection, ,Selecting a Frame}.
6296 @kindex info f @r{(@code{info frame})}
6299 This command prints a verbose description of the selected stack frame,
6304 the address of the frame
6306 the address of the next frame down (called by this frame)
6308 the address of the next frame up (caller of this frame)
6310 the language in which the source code corresponding to this frame is written
6312 the address of the frame's arguments
6314 the address of the frame's local variables
6316 the program counter saved in it (the address of execution in the caller frame)
6318 which registers were saved in the frame
6321 @noindent The verbose description is useful when
6322 something has gone wrong that has made the stack format fail to fit
6323 the usual conventions.
6325 @item info frame @var{addr}
6326 @itemx info f @var{addr}
6327 Print a verbose description of the frame at address @var{addr}, without
6328 selecting that frame. The selected frame remains unchanged by this
6329 command. This requires the same kind of address (more than one for some
6330 architectures) that you specify in the @code{frame} command.
6331 @xref{Selection, ,Selecting a Frame}.
6335 Print the arguments of the selected frame, each on a separate line.
6339 Print the local variables of the selected frame, each on a separate
6340 line. These are all variables (declared either static or automatic)
6341 accessible at the point of execution of the selected frame.
6344 @cindex catch exceptions, list active handlers
6345 @cindex exception handlers, how to list
6347 Print a list of all the exception handlers that are active in the
6348 current stack frame at the current point of execution. To see other
6349 exception handlers, visit the associated frame (using the @code{up},
6350 @code{down}, or @code{frame} commands); then type @code{info catch}.
6351 @xref{Set Catchpoints, , Setting Catchpoints}.
6357 @chapter Examining Source Files
6359 @value{GDBN} can print parts of your program's source, since the debugging
6360 information recorded in the program tells @value{GDBN} what source files were
6361 used to build it. When your program stops, @value{GDBN} spontaneously prints
6362 the line where it stopped. Likewise, when you select a stack frame
6363 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6364 execution in that frame has stopped. You can print other portions of
6365 source files by explicit command.
6367 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6368 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6369 @value{GDBN} under @sc{gnu} Emacs}.
6372 * List:: Printing source lines
6373 * Specify Location:: How to specify code locations
6374 * Edit:: Editing source files
6375 * Search:: Searching source files
6376 * Source Path:: Specifying source directories
6377 * Machine Code:: Source and machine code
6381 @section Printing Source Lines
6384 @kindex l @r{(@code{list})}
6385 To print lines from a source file, use the @code{list} command
6386 (abbreviated @code{l}). By default, ten lines are printed.
6387 There are several ways to specify what part of the file you want to
6388 print; see @ref{Specify Location}, for the full list.
6390 Here are the forms of the @code{list} command most commonly used:
6393 @item list @var{linenum}
6394 Print lines centered around line number @var{linenum} in the
6395 current source file.
6397 @item list @var{function}
6398 Print lines centered around the beginning of function
6402 Print more lines. If the last lines printed were printed with a
6403 @code{list} command, this prints lines following the last lines
6404 printed; however, if the last line printed was a solitary line printed
6405 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6406 Stack}), this prints lines centered around that line.
6409 Print lines just before the lines last printed.
6412 @cindex @code{list}, how many lines to display
6413 By default, @value{GDBN} prints ten source lines with any of these forms of
6414 the @code{list} command. You can change this using @code{set listsize}:
6417 @kindex set listsize
6418 @item set listsize @var{count}
6419 Make the @code{list} command display @var{count} source lines (unless
6420 the @code{list} argument explicitly specifies some other number).
6422 @kindex show listsize
6424 Display the number of lines that @code{list} prints.
6427 Repeating a @code{list} command with @key{RET} discards the argument,
6428 so it is equivalent to typing just @code{list}. This is more useful
6429 than listing the same lines again. An exception is made for an
6430 argument of @samp{-}; that argument is preserved in repetition so that
6431 each repetition moves up in the source file.
6433 In general, the @code{list} command expects you to supply zero, one or two
6434 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6435 of writing them (@pxref{Specify Location}), but the effect is always
6436 to specify some source line.
6438 Here is a complete description of the possible arguments for @code{list}:
6441 @item list @var{linespec}
6442 Print lines centered around the line specified by @var{linespec}.
6444 @item list @var{first},@var{last}
6445 Print lines from @var{first} to @var{last}. Both arguments are
6446 linespecs. When a @code{list} command has two linespecs, and the
6447 source file of the second linespec is omitted, this refers to
6448 the same source file as the first linespec.
6450 @item list ,@var{last}
6451 Print lines ending with @var{last}.
6453 @item list @var{first},
6454 Print lines starting with @var{first}.
6457 Print lines just after the lines last printed.
6460 Print lines just before the lines last printed.
6463 As described in the preceding table.
6466 @node Specify Location
6467 @section Specifying a Location
6468 @cindex specifying location
6471 Several @value{GDBN} commands accept arguments that specify a location
6472 of your program's code. Since @value{GDBN} is a source-level
6473 debugger, a location usually specifies some line in the source code;
6474 for that reason, locations are also known as @dfn{linespecs}.
6476 Here are all the different ways of specifying a code location that
6477 @value{GDBN} understands:
6481 Specifies the line number @var{linenum} of the current source file.
6484 @itemx +@var{offset}
6485 Specifies the line @var{offset} lines before or after the @dfn{current
6486 line}. For the @code{list} command, the current line is the last one
6487 printed; for the breakpoint commands, this is the line at which
6488 execution stopped in the currently selected @dfn{stack frame}
6489 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6490 used as the second of the two linespecs in a @code{list} command,
6491 this specifies the line @var{offset} lines up or down from the first
6494 @item @var{filename}:@var{linenum}
6495 Specifies the line @var{linenum} in the source file @var{filename}.
6497 @item @var{function}
6498 Specifies the line that begins the body of the function @var{function}.
6499 For example, in C, this is the line with the open brace.
6501 @item @var{function}:@var{label}
6502 Specifies the line where @var{label} appears in @var{function}.
6504 @item @var{filename}:@var{function}
6505 Specifies the line that begins the body of the function @var{function}
6506 in the file @var{filename}. You only need the file name with a
6507 function name to avoid ambiguity when there are identically named
6508 functions in different source files.
6511 Specifies the line at which the label named @var{label} appears.
6512 @value{GDBN} searches for the label in the function corresponding to
6513 the currently selected stack frame. If there is no current selected
6514 stack frame (for instance, if the inferior is not running), then
6515 @value{GDBN} will not search for a label.
6517 @item *@var{address}
6518 Specifies the program address @var{address}. For line-oriented
6519 commands, such as @code{list} and @code{edit}, this specifies a source
6520 line that contains @var{address}. For @code{break} and other
6521 breakpoint oriented commands, this can be used to set breakpoints in
6522 parts of your program which do not have debugging information or
6525 Here @var{address} may be any expression valid in the current working
6526 language (@pxref{Languages, working language}) that specifies a code
6527 address. In addition, as a convenience, @value{GDBN} extends the
6528 semantics of expressions used in locations to cover the situations
6529 that frequently happen during debugging. Here are the various forms
6533 @item @var{expression}
6534 Any expression valid in the current working language.
6536 @item @var{funcaddr}
6537 An address of a function or procedure derived from its name. In C,
6538 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6539 simply the function's name @var{function} (and actually a special case
6540 of a valid expression). In Pascal and Modula-2, this is
6541 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6542 (although the Pascal form also works).
6544 This form specifies the address of the function's first instruction,
6545 before the stack frame and arguments have been set up.
6547 @item '@var{filename}'::@var{funcaddr}
6548 Like @var{funcaddr} above, but also specifies the name of the source
6549 file explicitly. This is useful if the name of the function does not
6550 specify the function unambiguously, e.g., if there are several
6551 functions with identical names in different source files.
6558 @section Editing Source Files
6559 @cindex editing source files
6562 @kindex e @r{(@code{edit})}
6563 To edit the lines in a source file, use the @code{edit} command.
6564 The editing program of your choice
6565 is invoked with the current line set to
6566 the active line in the program.
6567 Alternatively, there are several ways to specify what part of the file you
6568 want to print if you want to see other parts of the program:
6571 @item edit @var{location}
6572 Edit the source file specified by @code{location}. Editing starts at
6573 that @var{location}, e.g., at the specified source line of the
6574 specified file. @xref{Specify Location}, for all the possible forms
6575 of the @var{location} argument; here are the forms of the @code{edit}
6576 command most commonly used:
6579 @item edit @var{number}
6580 Edit the current source file with @var{number} as the active line number.
6582 @item edit @var{function}
6583 Edit the file containing @var{function} at the beginning of its definition.
6588 @subsection Choosing your Editor
6589 You can customize @value{GDBN} to use any editor you want
6591 The only restriction is that your editor (say @code{ex}), recognizes the
6592 following command-line syntax:
6594 ex +@var{number} file
6596 The optional numeric value +@var{number} specifies the number of the line in
6597 the file where to start editing.}.
6598 By default, it is @file{@value{EDITOR}}, but you can change this
6599 by setting the environment variable @code{EDITOR} before using
6600 @value{GDBN}. For example, to configure @value{GDBN} to use the
6601 @code{vi} editor, you could use these commands with the @code{sh} shell:
6607 or in the @code{csh} shell,
6609 setenv EDITOR /usr/bin/vi
6614 @section Searching Source Files
6615 @cindex searching source files
6617 There are two commands for searching through the current source file for a
6622 @kindex forward-search
6623 @item forward-search @var{regexp}
6624 @itemx search @var{regexp}
6625 The command @samp{forward-search @var{regexp}} checks each line,
6626 starting with the one following the last line listed, for a match for
6627 @var{regexp}. It lists the line that is found. You can use the
6628 synonym @samp{search @var{regexp}} or abbreviate the command name as
6631 @kindex reverse-search
6632 @item reverse-search @var{regexp}
6633 The command @samp{reverse-search @var{regexp}} checks each line, starting
6634 with the one before the last line listed and going backward, for a match
6635 for @var{regexp}. It lists the line that is found. You can abbreviate
6636 this command as @code{rev}.
6640 @section Specifying Source Directories
6643 @cindex directories for source files
6644 Executable programs sometimes do not record the directories of the source
6645 files from which they were compiled, just the names. Even when they do,
6646 the directories could be moved between the compilation and your debugging
6647 session. @value{GDBN} has a list of directories to search for source files;
6648 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6649 it tries all the directories in the list, in the order they are present
6650 in the list, until it finds a file with the desired name.
6652 For example, suppose an executable references the file
6653 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6654 @file{/mnt/cross}. The file is first looked up literally; if this
6655 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6656 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6657 message is printed. @value{GDBN} does not look up the parts of the
6658 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6659 Likewise, the subdirectories of the source path are not searched: if
6660 the source path is @file{/mnt/cross}, and the binary refers to
6661 @file{foo.c}, @value{GDBN} would not find it under
6662 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6664 Plain file names, relative file names with leading directories, file
6665 names containing dots, etc.@: are all treated as described above; for
6666 instance, if the source path is @file{/mnt/cross}, and the source file
6667 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6668 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6669 that---@file{/mnt/cross/foo.c}.
6671 Note that the executable search path is @emph{not} used to locate the
6674 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6675 any information it has cached about where source files are found and where
6676 each line is in the file.
6680 When you start @value{GDBN}, its source path includes only @samp{cdir}
6681 and @samp{cwd}, in that order.
6682 To add other directories, use the @code{directory} command.
6684 The search path is used to find both program source files and @value{GDBN}
6685 script files (read using the @samp{-command} option and @samp{source} command).
6687 In addition to the source path, @value{GDBN} provides a set of commands
6688 that manage a list of source path substitution rules. A @dfn{substitution
6689 rule} specifies how to rewrite source directories stored in the program's
6690 debug information in case the sources were moved to a different
6691 directory between compilation and debugging. A rule is made of
6692 two strings, the first specifying what needs to be rewritten in
6693 the path, and the second specifying how it should be rewritten.
6694 In @ref{set substitute-path}, we name these two parts @var{from} and
6695 @var{to} respectively. @value{GDBN} does a simple string replacement
6696 of @var{from} with @var{to} at the start of the directory part of the
6697 source file name, and uses that result instead of the original file
6698 name to look up the sources.
6700 Using the previous example, suppose the @file{foo-1.0} tree has been
6701 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6702 @value{GDBN} to replace @file{/usr/src} in all source path names with
6703 @file{/mnt/cross}. The first lookup will then be
6704 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6705 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6706 substitution rule, use the @code{set substitute-path} command
6707 (@pxref{set substitute-path}).
6709 To avoid unexpected substitution results, a rule is applied only if the
6710 @var{from} part of the directory name ends at a directory separator.
6711 For instance, a rule substituting @file{/usr/source} into
6712 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6713 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6714 is applied only at the beginning of the directory name, this rule will
6715 not be applied to @file{/root/usr/source/baz.c} either.
6717 In many cases, you can achieve the same result using the @code{directory}
6718 command. However, @code{set substitute-path} can be more efficient in
6719 the case where the sources are organized in a complex tree with multiple
6720 subdirectories. With the @code{directory} command, you need to add each
6721 subdirectory of your project. If you moved the entire tree while
6722 preserving its internal organization, then @code{set substitute-path}
6723 allows you to direct the debugger to all the sources with one single
6726 @code{set substitute-path} is also more than just a shortcut command.
6727 The source path is only used if the file at the original location no
6728 longer exists. On the other hand, @code{set substitute-path} modifies
6729 the debugger behavior to look at the rewritten location instead. So, if
6730 for any reason a source file that is not relevant to your executable is
6731 located at the original location, a substitution rule is the only
6732 method available to point @value{GDBN} at the new location.
6734 @cindex @samp{--with-relocated-sources}
6735 @cindex default source path substitution
6736 You can configure a default source path substitution rule by
6737 configuring @value{GDBN} with the
6738 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6739 should be the name of a directory under @value{GDBN}'s configured
6740 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6741 directory names in debug information under @var{dir} will be adjusted
6742 automatically if the installed @value{GDBN} is moved to a new
6743 location. This is useful if @value{GDBN}, libraries or executables
6744 with debug information and corresponding source code are being moved
6748 @item directory @var{dirname} @dots{}
6749 @item dir @var{dirname} @dots{}
6750 Add directory @var{dirname} to the front of the source path. Several
6751 directory names may be given to this command, separated by @samp{:}
6752 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6753 part of absolute file names) or
6754 whitespace. You may specify a directory that is already in the source
6755 path; this moves it forward, so @value{GDBN} searches it sooner.
6759 @vindex $cdir@r{, convenience variable}
6760 @vindex $cwd@r{, convenience variable}
6761 @cindex compilation directory
6762 @cindex current directory
6763 @cindex working directory
6764 @cindex directory, current
6765 @cindex directory, compilation
6766 You can use the string @samp{$cdir} to refer to the compilation
6767 directory (if one is recorded), and @samp{$cwd} to refer to the current
6768 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6769 tracks the current working directory as it changes during your @value{GDBN}
6770 session, while the latter is immediately expanded to the current
6771 directory at the time you add an entry to the source path.
6774 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6776 @c RET-repeat for @code{directory} is explicitly disabled, but since
6777 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6779 @item set directories @var{path-list}
6780 @kindex set directories
6781 Set the source path to @var{path-list}.
6782 @samp{$cdir:$cwd} are added if missing.
6784 @item show directories
6785 @kindex show directories
6786 Print the source path: show which directories it contains.
6788 @anchor{set substitute-path}
6789 @item set substitute-path @var{from} @var{to}
6790 @kindex set substitute-path
6791 Define a source path substitution rule, and add it at the end of the
6792 current list of existing substitution rules. If a rule with the same
6793 @var{from} was already defined, then the old rule is also deleted.
6795 For example, if the file @file{/foo/bar/baz.c} was moved to
6796 @file{/mnt/cross/baz.c}, then the command
6799 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6803 will tell @value{GDBN} to replace @samp{/usr/src} with
6804 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6805 @file{baz.c} even though it was moved.
6807 In the case when more than one substitution rule have been defined,
6808 the rules are evaluated one by one in the order where they have been
6809 defined. The first one matching, if any, is selected to perform
6812 For instance, if we had entered the following commands:
6815 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6816 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6820 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6821 @file{/mnt/include/defs.h} by using the first rule. However, it would
6822 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6823 @file{/mnt/src/lib/foo.c}.
6826 @item unset substitute-path [path]
6827 @kindex unset substitute-path
6828 If a path is specified, search the current list of substitution rules
6829 for a rule that would rewrite that path. Delete that rule if found.
6830 A warning is emitted by the debugger if no rule could be found.
6832 If no path is specified, then all substitution rules are deleted.
6834 @item show substitute-path [path]
6835 @kindex show substitute-path
6836 If a path is specified, then print the source path substitution rule
6837 which would rewrite that path, if any.
6839 If no path is specified, then print all existing source path substitution
6844 If your source path is cluttered with directories that are no longer of
6845 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6846 versions of source. You can correct the situation as follows:
6850 Use @code{directory} with no argument to reset the source path to its default value.
6853 Use @code{directory} with suitable arguments to reinstall the
6854 directories you want in the source path. You can add all the
6855 directories in one command.
6859 @section Source and Machine Code
6860 @cindex source line and its code address
6862 You can use the command @code{info line} to map source lines to program
6863 addresses (and vice versa), and the command @code{disassemble} to display
6864 a range of addresses as machine instructions. You can use the command
6865 @code{set disassemble-next-line} to set whether to disassemble next
6866 source line when execution stops. When run under @sc{gnu} Emacs
6867 mode, the @code{info line} command causes the arrow to point to the
6868 line specified. Also, @code{info line} prints addresses in symbolic form as
6873 @item info line @var{linespec}
6874 Print the starting and ending addresses of the compiled code for
6875 source line @var{linespec}. You can specify source lines in any of
6876 the ways documented in @ref{Specify Location}.
6879 For example, we can use @code{info line} to discover the location of
6880 the object code for the first line of function
6881 @code{m4_changequote}:
6883 @c FIXME: I think this example should also show the addresses in
6884 @c symbolic form, as they usually would be displayed.
6886 (@value{GDBP}) info line m4_changequote
6887 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6891 @cindex code address and its source line
6892 We can also inquire (using @code{*@var{addr}} as the form for
6893 @var{linespec}) what source line covers a particular address:
6895 (@value{GDBP}) info line *0x63ff
6896 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6899 @cindex @code{$_} and @code{info line}
6900 @cindex @code{x} command, default address
6901 @kindex x@r{(examine), and} info line
6902 After @code{info line}, the default address for the @code{x} command
6903 is changed to the starting address of the line, so that @samp{x/i} is
6904 sufficient to begin examining the machine code (@pxref{Memory,
6905 ,Examining Memory}). Also, this address is saved as the value of the
6906 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6911 @cindex assembly instructions
6912 @cindex instructions, assembly
6913 @cindex machine instructions
6914 @cindex listing machine instructions
6916 @itemx disassemble /m
6917 @itemx disassemble /r
6918 This specialized command dumps a range of memory as machine
6919 instructions. It can also print mixed source+disassembly by specifying
6920 the @code{/m} modifier and print the raw instructions in hex as well as
6921 in symbolic form by specifying the @code{/r}.
6922 The default memory range is the function surrounding the
6923 program counter of the selected frame. A single argument to this
6924 command is a program counter value; @value{GDBN} dumps the function
6925 surrounding this value. When two arguments are given, they should
6926 be separated by a comma, possibly surrounded by whitespace. The
6927 arguments specify a range of addresses to dump, in one of two forms:
6930 @item @var{start},@var{end}
6931 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6932 @item @var{start},+@var{length}
6933 the addresses from @var{start} (inclusive) to
6934 @code{@var{start}+@var{length}} (exclusive).
6938 When 2 arguments are specified, the name of the function is also
6939 printed (since there could be several functions in the given range).
6941 The argument(s) can be any expression yielding a numeric value, such as
6942 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6944 If the range of memory being disassembled contains current program counter,
6945 the instruction at that location is shown with a @code{=>} marker.
6948 The following example shows the disassembly of a range of addresses of
6949 HP PA-RISC 2.0 code:
6952 (@value{GDBP}) disas 0x32c4, 0x32e4
6953 Dump of assembler code from 0x32c4 to 0x32e4:
6954 0x32c4 <main+204>: addil 0,dp
6955 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6956 0x32cc <main+212>: ldil 0x3000,r31
6957 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6958 0x32d4 <main+220>: ldo 0(r31),rp
6959 0x32d8 <main+224>: addil -0x800,dp
6960 0x32dc <main+228>: ldo 0x588(r1),r26
6961 0x32e0 <main+232>: ldil 0x3000,r31
6962 End of assembler dump.
6965 Here is an example showing mixed source+assembly for Intel x86, when the
6966 program is stopped just after function prologue:
6969 (@value{GDBP}) disas /m main
6970 Dump of assembler code for function main:
6972 0x08048330 <+0>: push %ebp
6973 0x08048331 <+1>: mov %esp,%ebp
6974 0x08048333 <+3>: sub $0x8,%esp
6975 0x08048336 <+6>: and $0xfffffff0,%esp
6976 0x08048339 <+9>: sub $0x10,%esp
6978 6 printf ("Hello.\n");
6979 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6980 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6984 0x08048348 <+24>: mov $0x0,%eax
6985 0x0804834d <+29>: leave
6986 0x0804834e <+30>: ret
6988 End of assembler dump.
6991 Here is another example showing raw instructions in hex for AMD x86-64,
6994 (gdb) disas /r 0x400281,+10
6995 Dump of assembler code from 0x400281 to 0x40028b:
6996 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6997 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6998 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6999 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7000 End of assembler dump.
7003 Some architectures have more than one commonly-used set of instruction
7004 mnemonics or other syntax.
7006 For programs that were dynamically linked and use shared libraries,
7007 instructions that call functions or branch to locations in the shared
7008 libraries might show a seemingly bogus location---it's actually a
7009 location of the relocation table. On some architectures, @value{GDBN}
7010 might be able to resolve these to actual function names.
7013 @kindex set disassembly-flavor
7014 @cindex Intel disassembly flavor
7015 @cindex AT&T disassembly flavor
7016 @item set disassembly-flavor @var{instruction-set}
7017 Select the instruction set to use when disassembling the
7018 program via the @code{disassemble} or @code{x/i} commands.
7020 Currently this command is only defined for the Intel x86 family. You
7021 can set @var{instruction-set} to either @code{intel} or @code{att}.
7022 The default is @code{att}, the AT&T flavor used by default by Unix
7023 assemblers for x86-based targets.
7025 @kindex show disassembly-flavor
7026 @item show disassembly-flavor
7027 Show the current setting of the disassembly flavor.
7031 @kindex set disassemble-next-line
7032 @kindex show disassemble-next-line
7033 @item set disassemble-next-line
7034 @itemx show disassemble-next-line
7035 Control whether or not @value{GDBN} will disassemble the next source
7036 line or instruction when execution stops. If ON, @value{GDBN} will
7037 display disassembly of the next source line when execution of the
7038 program being debugged stops. This is @emph{in addition} to
7039 displaying the source line itself, which @value{GDBN} always does if
7040 possible. If the next source line cannot be displayed for some reason
7041 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7042 info in the debug info), @value{GDBN} will display disassembly of the
7043 next @emph{instruction} instead of showing the next source line. If
7044 AUTO, @value{GDBN} will display disassembly of next instruction only
7045 if the source line cannot be displayed. This setting causes
7046 @value{GDBN} to display some feedback when you step through a function
7047 with no line info or whose source file is unavailable. The default is
7048 OFF, which means never display the disassembly of the next line or
7054 @chapter Examining Data
7056 @cindex printing data
7057 @cindex examining data
7060 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7061 @c document because it is nonstandard... Under Epoch it displays in a
7062 @c different window or something like that.
7063 The usual way to examine data in your program is with the @code{print}
7064 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7065 evaluates and prints the value of an expression of the language your
7066 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7067 Different Languages}). It may also print the expression using a
7068 Python-based pretty-printer (@pxref{Pretty Printing}).
7071 @item print @var{expr}
7072 @itemx print /@var{f} @var{expr}
7073 @var{expr} is an expression (in the source language). By default the
7074 value of @var{expr} is printed in a format appropriate to its data type;
7075 you can choose a different format by specifying @samp{/@var{f}}, where
7076 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7080 @itemx print /@var{f}
7081 @cindex reprint the last value
7082 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7083 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7084 conveniently inspect the same value in an alternative format.
7087 A more low-level way of examining data is with the @code{x} command.
7088 It examines data in memory at a specified address and prints it in a
7089 specified format. @xref{Memory, ,Examining Memory}.
7091 If you are interested in information about types, or about how the
7092 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7093 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7097 * Expressions:: Expressions
7098 * Ambiguous Expressions:: Ambiguous Expressions
7099 * Variables:: Program variables
7100 * Arrays:: Artificial arrays
7101 * Output Formats:: Output formats
7102 * Memory:: Examining memory
7103 * Auto Display:: Automatic display
7104 * Print Settings:: Print settings
7105 * Pretty Printing:: Python pretty printing
7106 * Value History:: Value history
7107 * Convenience Vars:: Convenience variables
7108 * Registers:: Registers
7109 * Floating Point Hardware:: Floating point hardware
7110 * Vector Unit:: Vector Unit
7111 * OS Information:: Auxiliary data provided by operating system
7112 * Memory Region Attributes:: Memory region attributes
7113 * Dump/Restore Files:: Copy between memory and a file
7114 * Core File Generation:: Cause a program dump its core
7115 * Character Sets:: Debugging programs that use a different
7116 character set than GDB does
7117 * Caching Remote Data:: Data caching for remote targets
7118 * Searching Memory:: Searching memory for a sequence of bytes
7122 @section Expressions
7125 @code{print} and many other @value{GDBN} commands accept an expression and
7126 compute its value. Any kind of constant, variable or operator defined
7127 by the programming language you are using is valid in an expression in
7128 @value{GDBN}. This includes conditional expressions, function calls,
7129 casts, and string constants. It also includes preprocessor macros, if
7130 you compiled your program to include this information; see
7133 @cindex arrays in expressions
7134 @value{GDBN} supports array constants in expressions input by
7135 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7136 you can use the command @code{print @{1, 2, 3@}} to create an array
7137 of three integers. If you pass an array to a function or assign it
7138 to a program variable, @value{GDBN} copies the array to memory that
7139 is @code{malloc}ed in the target program.
7141 Because C is so widespread, most of the expressions shown in examples in
7142 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7143 Languages}, for information on how to use expressions in other
7146 In this section, we discuss operators that you can use in @value{GDBN}
7147 expressions regardless of your programming language.
7149 @cindex casts, in expressions
7150 Casts are supported in all languages, not just in C, because it is so
7151 useful to cast a number into a pointer in order to examine a structure
7152 at that address in memory.
7153 @c FIXME: casts supported---Mod2 true?
7155 @value{GDBN} supports these operators, in addition to those common
7156 to programming languages:
7160 @samp{@@} is a binary operator for treating parts of memory as arrays.
7161 @xref{Arrays, ,Artificial Arrays}, for more information.
7164 @samp{::} allows you to specify a variable in terms of the file or
7165 function where it is defined. @xref{Variables, ,Program Variables}.
7167 @cindex @{@var{type}@}
7168 @cindex type casting memory
7169 @cindex memory, viewing as typed object
7170 @cindex casts, to view memory
7171 @item @{@var{type}@} @var{addr}
7172 Refers to an object of type @var{type} stored at address @var{addr} in
7173 memory. @var{addr} may be any expression whose value is an integer or
7174 pointer (but parentheses are required around binary operators, just as in
7175 a cast). This construct is allowed regardless of what kind of data is
7176 normally supposed to reside at @var{addr}.
7179 @node Ambiguous Expressions
7180 @section Ambiguous Expressions
7181 @cindex ambiguous expressions
7183 Expressions can sometimes contain some ambiguous elements. For instance,
7184 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7185 a single function name to be defined several times, for application in
7186 different contexts. This is called @dfn{overloading}. Another example
7187 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7188 templates and is typically instantiated several times, resulting in
7189 the same function name being defined in different contexts.
7191 In some cases and depending on the language, it is possible to adjust
7192 the expression to remove the ambiguity. For instance in C@t{++}, you
7193 can specify the signature of the function you want to break on, as in
7194 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7195 qualified name of your function often makes the expression unambiguous
7198 When an ambiguity that needs to be resolved is detected, the debugger
7199 has the capability to display a menu of numbered choices for each
7200 possibility, and then waits for the selection with the prompt @samp{>}.
7201 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7202 aborts the current command. If the command in which the expression was
7203 used allows more than one choice to be selected, the next option in the
7204 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7207 For example, the following session excerpt shows an attempt to set a
7208 breakpoint at the overloaded symbol @code{String::after}.
7209 We choose three particular definitions of that function name:
7211 @c FIXME! This is likely to change to show arg type lists, at least
7214 (@value{GDBP}) b String::after
7217 [2] file:String.cc; line number:867
7218 [3] file:String.cc; line number:860
7219 [4] file:String.cc; line number:875
7220 [5] file:String.cc; line number:853
7221 [6] file:String.cc; line number:846
7222 [7] file:String.cc; line number:735
7224 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7225 Breakpoint 2 at 0xb344: file String.cc, line 875.
7226 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7227 Multiple breakpoints were set.
7228 Use the "delete" command to delete unwanted
7235 @kindex set multiple-symbols
7236 @item set multiple-symbols @var{mode}
7237 @cindex multiple-symbols menu
7239 This option allows you to adjust the debugger behavior when an expression
7242 By default, @var{mode} is set to @code{all}. If the command with which
7243 the expression is used allows more than one choice, then @value{GDBN}
7244 automatically selects all possible choices. For instance, inserting
7245 a breakpoint on a function using an ambiguous name results in a breakpoint
7246 inserted on each possible match. However, if a unique choice must be made,
7247 then @value{GDBN} uses the menu to help you disambiguate the expression.
7248 For instance, printing the address of an overloaded function will result
7249 in the use of the menu.
7251 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7252 when an ambiguity is detected.
7254 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7255 an error due to the ambiguity and the command is aborted.
7257 @kindex show multiple-symbols
7258 @item show multiple-symbols
7259 Show the current value of the @code{multiple-symbols} setting.
7263 @section Program Variables
7265 The most common kind of expression to use is the name of a variable
7268 Variables in expressions are understood in the selected stack frame
7269 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7273 global (or file-static)
7280 visible according to the scope rules of the
7281 programming language from the point of execution in that frame
7284 @noindent This means that in the function
7299 you can examine and use the variable @code{a} whenever your program is
7300 executing within the function @code{foo}, but you can only use or
7301 examine the variable @code{b} while your program is executing inside
7302 the block where @code{b} is declared.
7304 @cindex variable name conflict
7305 There is an exception: you can refer to a variable or function whose
7306 scope is a single source file even if the current execution point is not
7307 in this file. But it is possible to have more than one such variable or
7308 function with the same name (in different source files). If that
7309 happens, referring to that name has unpredictable effects. If you wish,
7310 you can specify a static variable in a particular function or file,
7311 using the colon-colon (@code{::}) notation:
7313 @cindex colon-colon, context for variables/functions
7315 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7316 @cindex @code{::}, context for variables/functions
7319 @var{file}::@var{variable}
7320 @var{function}::@var{variable}
7324 Here @var{file} or @var{function} is the name of the context for the
7325 static @var{variable}. In the case of file names, you can use quotes to
7326 make sure @value{GDBN} parses the file name as a single word---for example,
7327 to print a global value of @code{x} defined in @file{f2.c}:
7330 (@value{GDBP}) p 'f2.c'::x
7333 @cindex C@t{++} scope resolution
7334 This use of @samp{::} is very rarely in conflict with the very similar
7335 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7336 scope resolution operator in @value{GDBN} expressions.
7337 @c FIXME: Um, so what happens in one of those rare cases where it's in
7340 @cindex wrong values
7341 @cindex variable values, wrong
7342 @cindex function entry/exit, wrong values of variables
7343 @cindex optimized code, wrong values of variables
7345 @emph{Warning:} Occasionally, a local variable may appear to have the
7346 wrong value at certain points in a function---just after entry to a new
7347 scope, and just before exit.
7349 You may see this problem when you are stepping by machine instructions.
7350 This is because, on most machines, it takes more than one instruction to
7351 set up a stack frame (including local variable definitions); if you are
7352 stepping by machine instructions, variables may appear to have the wrong
7353 values until the stack frame is completely built. On exit, it usually
7354 also takes more than one machine instruction to destroy a stack frame;
7355 after you begin stepping through that group of instructions, local
7356 variable definitions may be gone.
7358 This may also happen when the compiler does significant optimizations.
7359 To be sure of always seeing accurate values, turn off all optimization
7362 @cindex ``No symbol "foo" in current context''
7363 Another possible effect of compiler optimizations is to optimize
7364 unused variables out of existence, or assign variables to registers (as
7365 opposed to memory addresses). Depending on the support for such cases
7366 offered by the debug info format used by the compiler, @value{GDBN}
7367 might not be able to display values for such local variables. If that
7368 happens, @value{GDBN} will print a message like this:
7371 No symbol "foo" in current context.
7374 To solve such problems, either recompile without optimizations, or use a
7375 different debug info format, if the compiler supports several such
7376 formats. @xref{Compilation}, for more information on choosing compiler
7377 options. @xref{C, ,C and C@t{++}}, for more information about debug
7378 info formats that are best suited to C@t{++} programs.
7380 If you ask to print an object whose contents are unknown to
7381 @value{GDBN}, e.g., because its data type is not completely specified
7382 by the debug information, @value{GDBN} will say @samp{<incomplete
7383 type>}. @xref{Symbols, incomplete type}, for more about this.
7385 If you append @kbd{@@entry} string to a function parameter name you get its
7386 value at the time the function got called. If the value is not available an
7387 error message is printed. Entry values are available only with some compilers.
7388 Entry values are normally also printed at the function parameter list according
7389 to @ref{set print entry-values}.
7392 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7398 (gdb) print i@@entry
7402 Strings are identified as arrays of @code{char} values without specified
7403 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7404 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7405 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7406 defines literal string type @code{"char"} as @code{char} without a sign.
7411 signed char var1[] = "A";
7414 You get during debugging
7419 $2 = @{65 'A', 0 '\0'@}
7423 @section Artificial Arrays
7425 @cindex artificial array
7427 @kindex @@@r{, referencing memory as an array}
7428 It is often useful to print out several successive objects of the
7429 same type in memory; a section of an array, or an array of
7430 dynamically determined size for which only a pointer exists in the
7433 You can do this by referring to a contiguous span of memory as an
7434 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7435 operand of @samp{@@} should be the first element of the desired array
7436 and be an individual object. The right operand should be the desired length
7437 of the array. The result is an array value whose elements are all of
7438 the type of the left argument. The first element is actually the left
7439 argument; the second element comes from bytes of memory immediately
7440 following those that hold the first element, and so on. Here is an
7441 example. If a program says
7444 int *array = (int *) malloc (len * sizeof (int));
7448 you can print the contents of @code{array} with
7454 The left operand of @samp{@@} must reside in memory. Array values made
7455 with @samp{@@} in this way behave just like other arrays in terms of
7456 subscripting, and are coerced to pointers when used in expressions.
7457 Artificial arrays most often appear in expressions via the value history
7458 (@pxref{Value History, ,Value History}), after printing one out.
7460 Another way to create an artificial array is to use a cast.
7461 This re-interprets a value as if it were an array.
7462 The value need not be in memory:
7464 (@value{GDBP}) p/x (short[2])0x12345678
7465 $1 = @{0x1234, 0x5678@}
7468 As a convenience, if you leave the array length out (as in
7469 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7470 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7472 (@value{GDBP}) p/x (short[])0x12345678
7473 $2 = @{0x1234, 0x5678@}
7476 Sometimes the artificial array mechanism is not quite enough; in
7477 moderately complex data structures, the elements of interest may not
7478 actually be adjacent---for example, if you are interested in the values
7479 of pointers in an array. One useful work-around in this situation is
7480 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7481 Variables}) as a counter in an expression that prints the first
7482 interesting value, and then repeat that expression via @key{RET}. For
7483 instance, suppose you have an array @code{dtab} of pointers to
7484 structures, and you are interested in the values of a field @code{fv}
7485 in each structure. Here is an example of what you might type:
7495 @node Output Formats
7496 @section Output Formats
7498 @cindex formatted output
7499 @cindex output formats
7500 By default, @value{GDBN} prints a value according to its data type. Sometimes
7501 this is not what you want. For example, you might want to print a number
7502 in hex, or a pointer in decimal. Or you might want to view data in memory
7503 at a certain address as a character string or as an instruction. To do
7504 these things, specify an @dfn{output format} when you print a value.
7506 The simplest use of output formats is to say how to print a value
7507 already computed. This is done by starting the arguments of the
7508 @code{print} command with a slash and a format letter. The format
7509 letters supported are:
7513 Regard the bits of the value as an integer, and print the integer in
7517 Print as integer in signed decimal.
7520 Print as integer in unsigned decimal.
7523 Print as integer in octal.
7526 Print as integer in binary. The letter @samp{t} stands for ``two''.
7527 @footnote{@samp{b} cannot be used because these format letters are also
7528 used with the @code{x} command, where @samp{b} stands for ``byte'';
7529 see @ref{Memory,,Examining Memory}.}
7532 @cindex unknown address, locating
7533 @cindex locate address
7534 Print as an address, both absolute in hexadecimal and as an offset from
7535 the nearest preceding symbol. You can use this format used to discover
7536 where (in what function) an unknown address is located:
7539 (@value{GDBP}) p/a 0x54320
7540 $3 = 0x54320 <_initialize_vx+396>
7544 The command @code{info symbol 0x54320} yields similar results.
7545 @xref{Symbols, info symbol}.
7548 Regard as an integer and print it as a character constant. This
7549 prints both the numerical value and its character representation. The
7550 character representation is replaced with the octal escape @samp{\nnn}
7551 for characters outside the 7-bit @sc{ascii} range.
7553 Without this format, @value{GDBN} displays @code{char},
7554 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7555 constants. Single-byte members of vectors are displayed as integer
7559 Regard the bits of the value as a floating point number and print
7560 using typical floating point syntax.
7563 @cindex printing strings
7564 @cindex printing byte arrays
7565 Regard as a string, if possible. With this format, pointers to single-byte
7566 data are displayed as null-terminated strings and arrays of single-byte data
7567 are displayed as fixed-length strings. Other values are displayed in their
7570 Without this format, @value{GDBN} displays pointers to and arrays of
7571 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7572 strings. Single-byte members of a vector are displayed as an integer
7576 @cindex raw printing
7577 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7578 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7579 Printing}). This typically results in a higher-level display of the
7580 value's contents. The @samp{r} format bypasses any Python
7581 pretty-printer which might exist.
7584 For example, to print the program counter in hex (@pxref{Registers}), type
7591 Note that no space is required before the slash; this is because command
7592 names in @value{GDBN} cannot contain a slash.
7594 To reprint the last value in the value history with a different format,
7595 you can use the @code{print} command with just a format and no
7596 expression. For example, @samp{p/x} reprints the last value in hex.
7599 @section Examining Memory
7601 You can use the command @code{x} (for ``examine'') to examine memory in
7602 any of several formats, independently of your program's data types.
7604 @cindex examining memory
7606 @kindex x @r{(examine memory)}
7607 @item x/@var{nfu} @var{addr}
7610 Use the @code{x} command to examine memory.
7613 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7614 much memory to display and how to format it; @var{addr} is an
7615 expression giving the address where you want to start displaying memory.
7616 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7617 Several commands set convenient defaults for @var{addr}.
7620 @item @var{n}, the repeat count
7621 The repeat count is a decimal integer; the default is 1. It specifies
7622 how much memory (counting by units @var{u}) to display.
7623 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7626 @item @var{f}, the display format
7627 The display format is one of the formats used by @code{print}
7628 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7629 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7630 The default is @samp{x} (hexadecimal) initially. The default changes
7631 each time you use either @code{x} or @code{print}.
7633 @item @var{u}, the unit size
7634 The unit size is any of
7640 Halfwords (two bytes).
7642 Words (four bytes). This is the initial default.
7644 Giant words (eight bytes).
7647 Each time you specify a unit size with @code{x}, that size becomes the
7648 default unit the next time you use @code{x}. For the @samp{i} format,
7649 the unit size is ignored and is normally not written. For the @samp{s} format,
7650 the unit size defaults to @samp{b}, unless it is explicitly given.
7651 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7652 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7653 Note that the results depend on the programming language of the
7654 current compilation unit. If the language is C, the @samp{s}
7655 modifier will use the UTF-16 encoding while @samp{w} will use
7656 UTF-32. The encoding is set by the programming language and cannot
7659 @item @var{addr}, starting display address
7660 @var{addr} is the address where you want @value{GDBN} to begin displaying
7661 memory. The expression need not have a pointer value (though it may);
7662 it is always interpreted as an integer address of a byte of memory.
7663 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7664 @var{addr} is usually just after the last address examined---but several
7665 other commands also set the default address: @code{info breakpoints} (to
7666 the address of the last breakpoint listed), @code{info line} (to the
7667 starting address of a line), and @code{print} (if you use it to display
7668 a value from memory).
7671 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7672 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7673 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7674 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7675 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7677 Since the letters indicating unit sizes are all distinct from the
7678 letters specifying output formats, you do not have to remember whether
7679 unit size or format comes first; either order works. The output
7680 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7681 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7683 Even though the unit size @var{u} is ignored for the formats @samp{s}
7684 and @samp{i}, you might still want to use a count @var{n}; for example,
7685 @samp{3i} specifies that you want to see three machine instructions,
7686 including any operands. For convenience, especially when used with
7687 the @code{display} command, the @samp{i} format also prints branch delay
7688 slot instructions, if any, beyond the count specified, which immediately
7689 follow the last instruction that is within the count. The command
7690 @code{disassemble} gives an alternative way of inspecting machine
7691 instructions; see @ref{Machine Code,,Source and Machine Code}.
7693 All the defaults for the arguments to @code{x} are designed to make it
7694 easy to continue scanning memory with minimal specifications each time
7695 you use @code{x}. For example, after you have inspected three machine
7696 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7697 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7698 the repeat count @var{n} is used again; the other arguments default as
7699 for successive uses of @code{x}.
7701 When examining machine instructions, the instruction at current program
7702 counter is shown with a @code{=>} marker. For example:
7705 (@value{GDBP}) x/5i $pc-6
7706 0x804837f <main+11>: mov %esp,%ebp
7707 0x8048381 <main+13>: push %ecx
7708 0x8048382 <main+14>: sub $0x4,%esp
7709 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7710 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7713 @cindex @code{$_}, @code{$__}, and value history
7714 The addresses and contents printed by the @code{x} command are not saved
7715 in the value history because there is often too much of them and they
7716 would get in the way. Instead, @value{GDBN} makes these values available for
7717 subsequent use in expressions as values of the convenience variables
7718 @code{$_} and @code{$__}. After an @code{x} command, the last address
7719 examined is available for use in expressions in the convenience variable
7720 @code{$_}. The contents of that address, as examined, are available in
7721 the convenience variable @code{$__}.
7723 If the @code{x} command has a repeat count, the address and contents saved
7724 are from the last memory unit printed; this is not the same as the last
7725 address printed if several units were printed on the last line of output.
7727 @cindex remote memory comparison
7728 @cindex verify remote memory image
7729 When you are debugging a program running on a remote target machine
7730 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7731 remote machine's memory against the executable file you downloaded to
7732 the target. The @code{compare-sections} command is provided for such
7736 @kindex compare-sections
7737 @item compare-sections @r{[}@var{section-name}@r{]}
7738 Compare the data of a loadable section @var{section-name} in the
7739 executable file of the program being debugged with the same section in
7740 the remote machine's memory, and report any mismatches. With no
7741 arguments, compares all loadable sections. This command's
7742 availability depends on the target's support for the @code{"qCRC"}
7747 @section Automatic Display
7748 @cindex automatic display
7749 @cindex display of expressions
7751 If you find that you want to print the value of an expression frequently
7752 (to see how it changes), you might want to add it to the @dfn{automatic
7753 display list} so that @value{GDBN} prints its value each time your program stops.
7754 Each expression added to the list is given a number to identify it;
7755 to remove an expression from the list, you specify that number.
7756 The automatic display looks like this:
7760 3: bar[5] = (struct hack *) 0x3804
7764 This display shows item numbers, expressions and their current values. As with
7765 displays you request manually using @code{x} or @code{print}, you can
7766 specify the output format you prefer; in fact, @code{display} decides
7767 whether to use @code{print} or @code{x} depending your format
7768 specification---it uses @code{x} if you specify either the @samp{i}
7769 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7773 @item display @var{expr}
7774 Add the expression @var{expr} to the list of expressions to display
7775 each time your program stops. @xref{Expressions, ,Expressions}.
7777 @code{display} does not repeat if you press @key{RET} again after using it.
7779 @item display/@var{fmt} @var{expr}
7780 For @var{fmt} specifying only a display format and not a size or
7781 count, add the expression @var{expr} to the auto-display list but
7782 arrange to display it each time in the specified format @var{fmt}.
7783 @xref{Output Formats,,Output Formats}.
7785 @item display/@var{fmt} @var{addr}
7786 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7787 number of units, add the expression @var{addr} as a memory address to
7788 be examined each time your program stops. Examining means in effect
7789 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7792 For example, @samp{display/i $pc} can be helpful, to see the machine
7793 instruction about to be executed each time execution stops (@samp{$pc}
7794 is a common name for the program counter; @pxref{Registers, ,Registers}).
7797 @kindex delete display
7799 @item undisplay @var{dnums}@dots{}
7800 @itemx delete display @var{dnums}@dots{}
7801 Remove items from the list of expressions to display. Specify the
7802 numbers of the displays that you want affected with the command
7803 argument @var{dnums}. It can be a single display number, one of the
7804 numbers shown in the first field of the @samp{info display} display;
7805 or it could be a range of display numbers, as in @code{2-4}.
7807 @code{undisplay} does not repeat if you press @key{RET} after using it.
7808 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7810 @kindex disable display
7811 @item disable display @var{dnums}@dots{}
7812 Disable the display of item numbers @var{dnums}. A disabled display
7813 item is not printed automatically, but is not forgotten. It may be
7814 enabled again later. Specify the numbers of the displays that you
7815 want affected with the command argument @var{dnums}. It can be a
7816 single display number, one of the numbers shown in the first field of
7817 the @samp{info display} display; or it could be a range of display
7818 numbers, as in @code{2-4}.
7820 @kindex enable display
7821 @item enable display @var{dnums}@dots{}
7822 Enable display of item numbers @var{dnums}. It becomes effective once
7823 again in auto display of its expression, until you specify otherwise.
7824 Specify the numbers of the displays that you want affected with the
7825 command argument @var{dnums}. It can be a single display number, one
7826 of the numbers shown in the first field of the @samp{info display}
7827 display; or it could be a range of display numbers, as in @code{2-4}.
7830 Display the current values of the expressions on the list, just as is
7831 done when your program stops.
7833 @kindex info display
7835 Print the list of expressions previously set up to display
7836 automatically, each one with its item number, but without showing the
7837 values. This includes disabled expressions, which are marked as such.
7838 It also includes expressions which would not be displayed right now
7839 because they refer to automatic variables not currently available.
7842 @cindex display disabled out of scope
7843 If a display expression refers to local variables, then it does not make
7844 sense outside the lexical context for which it was set up. Such an
7845 expression is disabled when execution enters a context where one of its
7846 variables is not defined. For example, if you give the command
7847 @code{display last_char} while inside a function with an argument
7848 @code{last_char}, @value{GDBN} displays this argument while your program
7849 continues to stop inside that function. When it stops elsewhere---where
7850 there is no variable @code{last_char}---the display is disabled
7851 automatically. The next time your program stops where @code{last_char}
7852 is meaningful, you can enable the display expression once again.
7854 @node Print Settings
7855 @section Print Settings
7857 @cindex format options
7858 @cindex print settings
7859 @value{GDBN} provides the following ways to control how arrays, structures,
7860 and symbols are printed.
7863 These settings are useful for debugging programs in any language:
7867 @item set print address
7868 @itemx set print address on
7869 @cindex print/don't print memory addresses
7870 @value{GDBN} prints memory addresses showing the location of stack
7871 traces, structure values, pointer values, breakpoints, and so forth,
7872 even when it also displays the contents of those addresses. The default
7873 is @code{on}. For example, this is what a stack frame display looks like with
7874 @code{set print address on}:
7879 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7881 530 if (lquote != def_lquote)
7885 @item set print address off
7886 Do not print addresses when displaying their contents. For example,
7887 this is the same stack frame displayed with @code{set print address off}:
7891 (@value{GDBP}) set print addr off
7893 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7894 530 if (lquote != def_lquote)
7898 You can use @samp{set print address off} to eliminate all machine
7899 dependent displays from the @value{GDBN} interface. For example, with
7900 @code{print address off}, you should get the same text for backtraces on
7901 all machines---whether or not they involve pointer arguments.
7904 @item show print address
7905 Show whether or not addresses are to be printed.
7908 When @value{GDBN} prints a symbolic address, it normally prints the
7909 closest earlier symbol plus an offset. If that symbol does not uniquely
7910 identify the address (for example, it is a name whose scope is a single
7911 source file), you may need to clarify. One way to do this is with
7912 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7913 you can set @value{GDBN} to print the source file and line number when
7914 it prints a symbolic address:
7917 @item set print symbol-filename on
7918 @cindex source file and line of a symbol
7919 @cindex symbol, source file and line
7920 Tell @value{GDBN} to print the source file name and line number of a
7921 symbol in the symbolic form of an address.
7923 @item set print symbol-filename off
7924 Do not print source file name and line number of a symbol. This is the
7927 @item show print symbol-filename
7928 Show whether or not @value{GDBN} will print the source file name and
7929 line number of a symbol in the symbolic form of an address.
7932 Another situation where it is helpful to show symbol filenames and line
7933 numbers is when disassembling code; @value{GDBN} shows you the line
7934 number and source file that corresponds to each instruction.
7936 Also, you may wish to see the symbolic form only if the address being
7937 printed is reasonably close to the closest earlier symbol:
7940 @item set print max-symbolic-offset @var{max-offset}
7941 @cindex maximum value for offset of closest symbol
7942 Tell @value{GDBN} to only display the symbolic form of an address if the
7943 offset between the closest earlier symbol and the address is less than
7944 @var{max-offset}. The default is 0, which tells @value{GDBN}
7945 to always print the symbolic form of an address if any symbol precedes it.
7947 @item show print max-symbolic-offset
7948 Ask how large the maximum offset is that @value{GDBN} prints in a
7952 @cindex wild pointer, interpreting
7953 @cindex pointer, finding referent
7954 If you have a pointer and you are not sure where it points, try
7955 @samp{set print symbol-filename on}. Then you can determine the name
7956 and source file location of the variable where it points, using
7957 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7958 For example, here @value{GDBN} shows that a variable @code{ptt} points
7959 at another variable @code{t}, defined in @file{hi2.c}:
7962 (@value{GDBP}) set print symbol-filename on
7963 (@value{GDBP}) p/a ptt
7964 $4 = 0xe008 <t in hi2.c>
7968 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7969 does not show the symbol name and filename of the referent, even with
7970 the appropriate @code{set print} options turned on.
7973 Other settings control how different kinds of objects are printed:
7976 @item set print array
7977 @itemx set print array on
7978 @cindex pretty print arrays
7979 Pretty print arrays. This format is more convenient to read,
7980 but uses more space. The default is off.
7982 @item set print array off
7983 Return to compressed format for arrays.
7985 @item show print array
7986 Show whether compressed or pretty format is selected for displaying
7989 @cindex print array indexes
7990 @item set print array-indexes
7991 @itemx set print array-indexes on
7992 Print the index of each element when displaying arrays. May be more
7993 convenient to locate a given element in the array or quickly find the
7994 index of a given element in that printed array. The default is off.
7996 @item set print array-indexes off
7997 Stop printing element indexes when displaying arrays.
7999 @item show print array-indexes
8000 Show whether the index of each element is printed when displaying
8003 @item set print elements @var{number-of-elements}
8004 @cindex number of array elements to print
8005 @cindex limit on number of printed array elements
8006 Set a limit on how many elements of an array @value{GDBN} will print.
8007 If @value{GDBN} is printing a large array, it stops printing after it has
8008 printed the number of elements set by the @code{set print elements} command.
8009 This limit also applies to the display of strings.
8010 When @value{GDBN} starts, this limit is set to 200.
8011 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8013 @item show print elements
8014 Display the number of elements of a large array that @value{GDBN} will print.
8015 If the number is 0, then the printing is unlimited.
8017 @item set print frame-arguments @var{value}
8018 @kindex set print frame-arguments
8019 @cindex printing frame argument values
8020 @cindex print all frame argument values
8021 @cindex print frame argument values for scalars only
8022 @cindex do not print frame argument values
8023 This command allows to control how the values of arguments are printed
8024 when the debugger prints a frame (@pxref{Frames}). The possible
8029 The values of all arguments are printed.
8032 Print the value of an argument only if it is a scalar. The value of more
8033 complex arguments such as arrays, structures, unions, etc, is replaced
8034 by @code{@dots{}}. This is the default. Here is an example where
8035 only scalar arguments are shown:
8038 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8043 None of the argument values are printed. Instead, the value of each argument
8044 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8047 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8052 By default, only scalar arguments are printed. This command can be used
8053 to configure the debugger to print the value of all arguments, regardless
8054 of their type. However, it is often advantageous to not print the value
8055 of more complex parameters. For instance, it reduces the amount of
8056 information printed in each frame, making the backtrace more readable.
8057 Also, it improves performance when displaying Ada frames, because
8058 the computation of large arguments can sometimes be CPU-intensive,
8059 especially in large applications. Setting @code{print frame-arguments}
8060 to @code{scalars} (the default) or @code{none} avoids this computation,
8061 thus speeding up the display of each Ada frame.
8063 @item show print frame-arguments
8064 Show how the value of arguments should be displayed when printing a frame.
8066 @anchor{set print entry-values}
8067 @item set print entry-values @var{value}
8068 @kindex set print entry-values
8069 Set printing of frame argument values at function entry. In some cases
8070 @value{GDBN} can determine the value of function argument which was passed by
8071 the function caller, even if the value was modified inside the called function
8072 and therefore is different. With optimized code, the current value could be
8073 unavailable, but the entry value may still be known.
8075 The default value is @code{default} (see below for its description). Older
8076 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8077 this feature will behave in the @code{default} setting the same way as with the
8080 This functionality is currently supported only by DWARF 2 debugging format and
8081 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8082 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8085 The @var{value} parameter can be one of the following:
8089 Print only actual parameter values, never print values from function entry
8093 #0 different (val=6)
8094 #0 lost (val=<optimized out>)
8096 #0 invalid (val=<optimized out>)
8100 Print only parameter values from function entry point. The actual parameter
8101 values are never printed.
8103 #0 equal (val@@entry=5)
8104 #0 different (val@@entry=5)
8105 #0 lost (val@@entry=5)
8106 #0 born (val@@entry=<optimized out>)
8107 #0 invalid (val@@entry=<optimized out>)
8111 Print only parameter values from function entry point. If value from function
8112 entry point is not known while the actual value is known, print the actual
8113 value for such parameter.
8115 #0 equal (val@@entry=5)
8116 #0 different (val@@entry=5)
8117 #0 lost (val@@entry=5)
8119 #0 invalid (val@@entry=<optimized out>)
8123 Print actual parameter values. If actual parameter value is not known while
8124 value from function entry point is known, print the entry point value for such
8128 #0 different (val=6)
8129 #0 lost (val@@entry=5)
8131 #0 invalid (val=<optimized out>)
8135 Always print both the actual parameter value and its value from function entry
8136 point, even if values of one or both are not available due to compiler
8139 #0 equal (val=5, val@@entry=5)
8140 #0 different (val=6, val@@entry=5)
8141 #0 lost (val=<optimized out>, val@@entry=5)
8142 #0 born (val=10, val@@entry=<optimized out>)
8143 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8147 Print the actual parameter value if it is known and also its value from
8148 function entry point if it is known. If neither is known, print for the actual
8149 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8150 values are known and identical, print the shortened
8151 @code{param=param@@entry=VALUE} notation.
8153 #0 equal (val=val@@entry=5)
8154 #0 different (val=6, val@@entry=5)
8155 #0 lost (val@@entry=5)
8157 #0 invalid (val=<optimized out>)
8161 Always print the actual parameter value. Print also its value from function
8162 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8163 if both values are known and identical, print the shortened
8164 @code{param=param@@entry=VALUE} notation.
8166 #0 equal (val=val@@entry=5)
8167 #0 different (val=6, val@@entry=5)
8168 #0 lost (val=<optimized out>, val@@entry=5)
8170 #0 invalid (val=<optimized out>)
8174 For analysis messages on possible failures of frame argument values at function
8175 entry resolution see @ref{set debug entry-values}.
8177 @item show print entry-values
8178 Show the method being used for printing of frame argument values at function
8181 @item set print repeats
8182 @cindex repeated array elements
8183 Set the threshold for suppressing display of repeated array
8184 elements. When the number of consecutive identical elements of an
8185 array exceeds the threshold, @value{GDBN} prints the string
8186 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8187 identical repetitions, instead of displaying the identical elements
8188 themselves. Setting the threshold to zero will cause all elements to
8189 be individually printed. The default threshold is 10.
8191 @item show print repeats
8192 Display the current threshold for printing repeated identical
8195 @item set print null-stop
8196 @cindex @sc{null} elements in arrays
8197 Cause @value{GDBN} to stop printing the characters of an array when the first
8198 @sc{null} is encountered. This is useful when large arrays actually
8199 contain only short strings.
8202 @item show print null-stop
8203 Show whether @value{GDBN} stops printing an array on the first
8204 @sc{null} character.
8206 @item set print pretty on
8207 @cindex print structures in indented form
8208 @cindex indentation in structure display
8209 Cause @value{GDBN} to print structures in an indented format with one member
8210 per line, like this:
8225 @item set print pretty off
8226 Cause @value{GDBN} to print structures in a compact format, like this:
8230 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8231 meat = 0x54 "Pork"@}
8236 This is the default format.
8238 @item show print pretty
8239 Show which format @value{GDBN} is using to print structures.
8241 @item set print sevenbit-strings on
8242 @cindex eight-bit characters in strings
8243 @cindex octal escapes in strings
8244 Print using only seven-bit characters; if this option is set,
8245 @value{GDBN} displays any eight-bit characters (in strings or
8246 character values) using the notation @code{\}@var{nnn}. This setting is
8247 best if you are working in English (@sc{ascii}) and you use the
8248 high-order bit of characters as a marker or ``meta'' bit.
8250 @item set print sevenbit-strings off
8251 Print full eight-bit characters. This allows the use of more
8252 international character sets, and is the default.
8254 @item show print sevenbit-strings
8255 Show whether or not @value{GDBN} is printing only seven-bit characters.
8257 @item set print union on
8258 @cindex unions in structures, printing
8259 Tell @value{GDBN} to print unions which are contained in structures
8260 and other unions. This is the default setting.
8262 @item set print union off
8263 Tell @value{GDBN} not to print unions which are contained in
8264 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8267 @item show print union
8268 Ask @value{GDBN} whether or not it will print unions which are contained in
8269 structures and other unions.
8271 For example, given the declarations
8274 typedef enum @{Tree, Bug@} Species;
8275 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8276 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8287 struct thing foo = @{Tree, @{Acorn@}@};
8291 with @code{set print union on} in effect @samp{p foo} would print
8294 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8298 and with @code{set print union off} in effect it would print
8301 $1 = @{it = Tree, form = @{...@}@}
8305 @code{set print union} affects programs written in C-like languages
8311 These settings are of interest when debugging C@t{++} programs:
8314 @cindex demangling C@t{++} names
8315 @item set print demangle
8316 @itemx set print demangle on
8317 Print C@t{++} names in their source form rather than in the encoded
8318 (``mangled'') form passed to the assembler and linker for type-safe
8319 linkage. The default is on.
8321 @item show print demangle
8322 Show whether C@t{++} names are printed in mangled or demangled form.
8324 @item set print asm-demangle
8325 @itemx set print asm-demangle on
8326 Print C@t{++} names in their source form rather than their mangled form, even
8327 in assembler code printouts such as instruction disassemblies.
8330 @item show print asm-demangle
8331 Show whether C@t{++} names in assembly listings are printed in mangled
8334 @cindex C@t{++} symbol decoding style
8335 @cindex symbol decoding style, C@t{++}
8336 @kindex set demangle-style
8337 @item set demangle-style @var{style}
8338 Choose among several encoding schemes used by different compilers to
8339 represent C@t{++} names. The choices for @var{style} are currently:
8343 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8346 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8347 This is the default.
8350 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8353 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8356 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8357 @strong{Warning:} this setting alone is not sufficient to allow
8358 debugging @code{cfront}-generated executables. @value{GDBN} would
8359 require further enhancement to permit that.
8362 If you omit @var{style}, you will see a list of possible formats.
8364 @item show demangle-style
8365 Display the encoding style currently in use for decoding C@t{++} symbols.
8367 @item set print object
8368 @itemx set print object on
8369 @cindex derived type of an object, printing
8370 @cindex display derived types
8371 When displaying a pointer to an object, identify the @emph{actual}
8372 (derived) type of the object rather than the @emph{declared} type, using
8373 the virtual function table. Note that the virtual function table is
8374 required---this feature can only work for objects that have run-time
8375 type identification; a single virtual method in the object's declared
8378 @item set print object off
8379 Display only the declared type of objects, without reference to the
8380 virtual function table. This is the default setting.
8382 @item show print object
8383 Show whether actual, or declared, object types are displayed.
8385 @item set print static-members
8386 @itemx set print static-members on
8387 @cindex static members of C@t{++} objects
8388 Print static members when displaying a C@t{++} object. The default is on.
8390 @item set print static-members off
8391 Do not print static members when displaying a C@t{++} object.
8393 @item show print static-members
8394 Show whether C@t{++} static members are printed or not.
8396 @item set print pascal_static-members
8397 @itemx set print pascal_static-members on
8398 @cindex static members of Pascal objects
8399 @cindex Pascal objects, static members display
8400 Print static members when displaying a Pascal object. The default is on.
8402 @item set print pascal_static-members off
8403 Do not print static members when displaying a Pascal object.
8405 @item show print pascal_static-members
8406 Show whether Pascal static members are printed or not.
8408 @c These don't work with HP ANSI C++ yet.
8409 @item set print vtbl
8410 @itemx set print vtbl on
8411 @cindex pretty print C@t{++} virtual function tables
8412 @cindex virtual functions (C@t{++}) display
8413 @cindex VTBL display
8414 Pretty print C@t{++} virtual function tables. The default is off.
8415 (The @code{vtbl} commands do not work on programs compiled with the HP
8416 ANSI C@t{++} compiler (@code{aCC}).)
8418 @item set print vtbl off
8419 Do not pretty print C@t{++} virtual function tables.
8421 @item show print vtbl
8422 Show whether C@t{++} virtual function tables are pretty printed, or not.
8425 @node Pretty Printing
8426 @section Pretty Printing
8428 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8429 Python code. It greatly simplifies the display of complex objects. This
8430 mechanism works for both MI and the CLI.
8433 * Pretty-Printer Introduction:: Introduction to pretty-printers
8434 * Pretty-Printer Example:: An example pretty-printer
8435 * Pretty-Printer Commands:: Pretty-printer commands
8438 @node Pretty-Printer Introduction
8439 @subsection Pretty-Printer Introduction
8441 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8442 registered for the value. If there is then @value{GDBN} invokes the
8443 pretty-printer to print the value. Otherwise the value is printed normally.
8445 Pretty-printers are normally named. This makes them easy to manage.
8446 The @samp{info pretty-printer} command will list all the installed
8447 pretty-printers with their names.
8448 If a pretty-printer can handle multiple data types, then its
8449 @dfn{subprinters} are the printers for the individual data types.
8450 Each such subprinter has its own name.
8451 The format of the name is @var{printer-name};@var{subprinter-name}.
8453 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8454 Typically they are automatically loaded and registered when the corresponding
8455 debug information is loaded, thus making them available without having to
8456 do anything special.
8458 There are three places where a pretty-printer can be registered.
8462 Pretty-printers registered globally are available when debugging
8466 Pretty-printers registered with a program space are available only
8467 when debugging that program.
8468 @xref{Progspaces In Python}, for more details on program spaces in Python.
8471 Pretty-printers registered with an objfile are loaded and unloaded
8472 with the corresponding objfile (e.g., shared library).
8473 @xref{Objfiles In Python}, for more details on objfiles in Python.
8476 @xref{Selecting Pretty-Printers}, for further information on how
8477 pretty-printers are selected,
8479 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8482 @node Pretty-Printer Example
8483 @subsection Pretty-Printer Example
8485 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8488 (@value{GDBP}) print s
8490 static npos = 4294967295,
8492 <std::allocator<char>> = @{
8493 <__gnu_cxx::new_allocator<char>> = @{
8494 <No data fields>@}, <No data fields>
8496 members of std::basic_string<char, std::char_traits<char>,
8497 std::allocator<char> >::_Alloc_hider:
8498 _M_p = 0x804a014 "abcd"
8503 With a pretty-printer for @code{std::string} only the contents are printed:
8506 (@value{GDBP}) print s
8510 @node Pretty-Printer Commands
8511 @subsection Pretty-Printer Commands
8512 @cindex pretty-printer commands
8515 @kindex info pretty-printer
8516 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8517 Print the list of installed pretty-printers.
8518 This includes disabled pretty-printers, which are marked as such.
8520 @var{object-regexp} is a regular expression matching the objects
8521 whose pretty-printers to list.
8522 Objects can be @code{global}, the program space's file
8523 (@pxref{Progspaces In Python}),
8524 and the object files within that program space (@pxref{Objfiles In Python}).
8525 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8526 looks up a printer from these three objects.
8528 @var{name-regexp} is a regular expression matching the name of the printers
8531 @kindex disable pretty-printer
8532 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8533 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8534 A disabled pretty-printer is not forgotten, it may be enabled again later.
8536 @kindex enable pretty-printer
8537 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8538 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8543 Suppose we have three pretty-printers installed: one from library1.so
8544 named @code{foo} that prints objects of type @code{foo}, and
8545 another from library2.so named @code{bar} that prints two types of objects,
8546 @code{bar1} and @code{bar2}.
8549 (gdb) info pretty-printer
8556 (gdb) info pretty-printer library2
8561 (gdb) disable pretty-printer library1
8563 2 of 3 printers enabled
8564 (gdb) info pretty-printer
8571 (gdb) disable pretty-printer library2 bar:bar1
8573 1 of 3 printers enabled
8574 (gdb) info pretty-printer library2
8581 (gdb) disable pretty-printer library2 bar
8583 0 of 3 printers enabled
8584 (gdb) info pretty-printer library2
8593 Note that for @code{bar} the entire printer can be disabled,
8594 as can each individual subprinter.
8597 @section Value History
8599 @cindex value history
8600 @cindex history of values printed by @value{GDBN}
8601 Values printed by the @code{print} command are saved in the @value{GDBN}
8602 @dfn{value history}. This allows you to refer to them in other expressions.
8603 Values are kept until the symbol table is re-read or discarded
8604 (for example with the @code{file} or @code{symbol-file} commands).
8605 When the symbol table changes, the value history is discarded,
8606 since the values may contain pointers back to the types defined in the
8611 @cindex history number
8612 The values printed are given @dfn{history numbers} by which you can
8613 refer to them. These are successive integers starting with one.
8614 @code{print} shows you the history number assigned to a value by
8615 printing @samp{$@var{num} = } before the value; here @var{num} is the
8618 To refer to any previous value, use @samp{$} followed by the value's
8619 history number. The way @code{print} labels its output is designed to
8620 remind you of this. Just @code{$} refers to the most recent value in
8621 the history, and @code{$$} refers to the value before that.
8622 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8623 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8624 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8626 For example, suppose you have just printed a pointer to a structure and
8627 want to see the contents of the structure. It suffices to type
8633 If you have a chain of structures where the component @code{next} points
8634 to the next one, you can print the contents of the next one with this:
8641 You can print successive links in the chain by repeating this
8642 command---which you can do by just typing @key{RET}.
8644 Note that the history records values, not expressions. If the value of
8645 @code{x} is 4 and you type these commands:
8653 then the value recorded in the value history by the @code{print} command
8654 remains 4 even though the value of @code{x} has changed.
8659 Print the last ten values in the value history, with their item numbers.
8660 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8661 values} does not change the history.
8663 @item show values @var{n}
8664 Print ten history values centered on history item number @var{n}.
8667 Print ten history values just after the values last printed. If no more
8668 values are available, @code{show values +} produces no display.
8671 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8672 same effect as @samp{show values +}.
8674 @node Convenience Vars
8675 @section Convenience Variables
8677 @cindex convenience variables
8678 @cindex user-defined variables
8679 @value{GDBN} provides @dfn{convenience variables} that you can use within
8680 @value{GDBN} to hold on to a value and refer to it later. These variables
8681 exist entirely within @value{GDBN}; they are not part of your program, and
8682 setting a convenience variable has no direct effect on further execution
8683 of your program. That is why you can use them freely.
8685 Convenience variables are prefixed with @samp{$}. Any name preceded by
8686 @samp{$} can be used for a convenience variable, unless it is one of
8687 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8688 (Value history references, in contrast, are @emph{numbers} preceded
8689 by @samp{$}. @xref{Value History, ,Value History}.)
8691 You can save a value in a convenience variable with an assignment
8692 expression, just as you would set a variable in your program.
8696 set $foo = *object_ptr
8700 would save in @code{$foo} the value contained in the object pointed to by
8703 Using a convenience variable for the first time creates it, but its
8704 value is @code{void} until you assign a new value. You can alter the
8705 value with another assignment at any time.
8707 Convenience variables have no fixed types. You can assign a convenience
8708 variable any type of value, including structures and arrays, even if
8709 that variable already has a value of a different type. The convenience
8710 variable, when used as an expression, has the type of its current value.
8713 @kindex show convenience
8714 @cindex show all user variables
8715 @item show convenience
8716 Print a list of convenience variables used so far, and their values.
8717 Abbreviated @code{show conv}.
8719 @kindex init-if-undefined
8720 @cindex convenience variables, initializing
8721 @item init-if-undefined $@var{variable} = @var{expression}
8722 Set a convenience variable if it has not already been set. This is useful
8723 for user-defined commands that keep some state. It is similar, in concept,
8724 to using local static variables with initializers in C (except that
8725 convenience variables are global). It can also be used to allow users to
8726 override default values used in a command script.
8728 If the variable is already defined then the expression is not evaluated so
8729 any side-effects do not occur.
8732 One of the ways to use a convenience variable is as a counter to be
8733 incremented or a pointer to be advanced. For example, to print
8734 a field from successive elements of an array of structures:
8738 print bar[$i++]->contents
8742 Repeat that command by typing @key{RET}.
8744 Some convenience variables are created automatically by @value{GDBN} and given
8745 values likely to be useful.
8748 @vindex $_@r{, convenience variable}
8750 The variable @code{$_} is automatically set by the @code{x} command to
8751 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8752 commands which provide a default address for @code{x} to examine also
8753 set @code{$_} to that address; these commands include @code{info line}
8754 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8755 except when set by the @code{x} command, in which case it is a pointer
8756 to the type of @code{$__}.
8758 @vindex $__@r{, convenience variable}
8760 The variable @code{$__} is automatically set by the @code{x} command
8761 to the value found in the last address examined. Its type is chosen
8762 to match the format in which the data was printed.
8765 @vindex $_exitcode@r{, convenience variable}
8766 The variable @code{$_exitcode} is automatically set to the exit code when
8767 the program being debugged terminates.
8770 @vindex $_sdata@r{, inspect, convenience variable}
8771 The variable @code{$_sdata} contains extra collected static tracepoint
8772 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8773 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8774 if extra static tracepoint data has not been collected.
8777 @vindex $_siginfo@r{, convenience variable}
8778 The variable @code{$_siginfo} contains extra signal information
8779 (@pxref{extra signal information}). Note that @code{$_siginfo}
8780 could be empty, if the application has not yet received any signals.
8781 For example, it will be empty before you execute the @code{run} command.
8784 @vindex $_tlb@r{, convenience variable}
8785 The variable @code{$_tlb} is automatically set when debugging
8786 applications running on MS-Windows in native mode or connected to
8787 gdbserver that supports the @code{qGetTIBAddr} request.
8788 @xref{General Query Packets}.
8789 This variable contains the address of the thread information block.
8793 On HP-UX systems, if you refer to a function or variable name that
8794 begins with a dollar sign, @value{GDBN} searches for a user or system
8795 name first, before it searches for a convenience variable.
8797 @cindex convenience functions
8798 @value{GDBN} also supplies some @dfn{convenience functions}. These
8799 have a syntax similar to convenience variables. A convenience
8800 function can be used in an expression just like an ordinary function;
8801 however, a convenience function is implemented internally to
8806 @kindex help function
8807 @cindex show all convenience functions
8808 Print a list of all convenience functions.
8815 You can refer to machine register contents, in expressions, as variables
8816 with names starting with @samp{$}. The names of registers are different
8817 for each machine; use @code{info registers} to see the names used on
8821 @kindex info registers
8822 @item info registers
8823 Print the names and values of all registers except floating-point
8824 and vector registers (in the selected stack frame).
8826 @kindex info all-registers
8827 @cindex floating point registers
8828 @item info all-registers
8829 Print the names and values of all registers, including floating-point
8830 and vector registers (in the selected stack frame).
8832 @item info registers @var{regname} @dots{}
8833 Print the @dfn{relativized} value of each specified register @var{regname}.
8834 As discussed in detail below, register values are normally relative to
8835 the selected stack frame. @var{regname} may be any register name valid on
8836 the machine you are using, with or without the initial @samp{$}.
8839 @cindex stack pointer register
8840 @cindex program counter register
8841 @cindex process status register
8842 @cindex frame pointer register
8843 @cindex standard registers
8844 @value{GDBN} has four ``standard'' register names that are available (in
8845 expressions) on most machines---whenever they do not conflict with an
8846 architecture's canonical mnemonics for registers. The register names
8847 @code{$pc} and @code{$sp} are used for the program counter register and
8848 the stack pointer. @code{$fp} is used for a register that contains a
8849 pointer to the current stack frame, and @code{$ps} is used for a
8850 register that contains the processor status. For example,
8851 you could print the program counter in hex with
8858 or print the instruction to be executed next with
8865 or add four to the stack pointer@footnote{This is a way of removing
8866 one word from the stack, on machines where stacks grow downward in
8867 memory (most machines, nowadays). This assumes that the innermost
8868 stack frame is selected; setting @code{$sp} is not allowed when other
8869 stack frames are selected. To pop entire frames off the stack,
8870 regardless of machine architecture, use @code{return};
8871 see @ref{Returning, ,Returning from a Function}.} with
8877 Whenever possible, these four standard register names are available on
8878 your machine even though the machine has different canonical mnemonics,
8879 so long as there is no conflict. The @code{info registers} command
8880 shows the canonical names. For example, on the SPARC, @code{info
8881 registers} displays the processor status register as @code{$psr} but you
8882 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8883 is an alias for the @sc{eflags} register.
8885 @value{GDBN} always considers the contents of an ordinary register as an
8886 integer when the register is examined in this way. Some machines have
8887 special registers which can hold nothing but floating point; these
8888 registers are considered to have floating point values. There is no way
8889 to refer to the contents of an ordinary register as floating point value
8890 (although you can @emph{print} it as a floating point value with
8891 @samp{print/f $@var{regname}}).
8893 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8894 means that the data format in which the register contents are saved by
8895 the operating system is not the same one that your program normally
8896 sees. For example, the registers of the 68881 floating point
8897 coprocessor are always saved in ``extended'' (raw) format, but all C
8898 programs expect to work with ``double'' (virtual) format. In such
8899 cases, @value{GDBN} normally works with the virtual format only (the format
8900 that makes sense for your program), but the @code{info registers} command
8901 prints the data in both formats.
8903 @cindex SSE registers (x86)
8904 @cindex MMX registers (x86)
8905 Some machines have special registers whose contents can be interpreted
8906 in several different ways. For example, modern x86-based machines
8907 have SSE and MMX registers that can hold several values packed
8908 together in several different formats. @value{GDBN} refers to such
8909 registers in @code{struct} notation:
8912 (@value{GDBP}) print $xmm1
8914 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8915 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8916 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8917 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8918 v4_int32 = @{0, 20657912, 11, 13@},
8919 v2_int64 = @{88725056443645952, 55834574859@},
8920 uint128 = 0x0000000d0000000b013b36f800000000
8925 To set values of such registers, you need to tell @value{GDBN} which
8926 view of the register you wish to change, as if you were assigning
8927 value to a @code{struct} member:
8930 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8933 Normally, register values are relative to the selected stack frame
8934 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8935 value that the register would contain if all stack frames farther in
8936 were exited and their saved registers restored. In order to see the
8937 true contents of hardware registers, you must select the innermost
8938 frame (with @samp{frame 0}).
8940 However, @value{GDBN} must deduce where registers are saved, from the machine
8941 code generated by your compiler. If some registers are not saved, or if
8942 @value{GDBN} is unable to locate the saved registers, the selected stack
8943 frame makes no difference.
8945 @node Floating Point Hardware
8946 @section Floating Point Hardware
8947 @cindex floating point
8949 Depending on the configuration, @value{GDBN} may be able to give
8950 you more information about the status of the floating point hardware.
8955 Display hardware-dependent information about the floating
8956 point unit. The exact contents and layout vary depending on the
8957 floating point chip. Currently, @samp{info float} is supported on
8958 the ARM and x86 machines.
8962 @section Vector Unit
8965 Depending on the configuration, @value{GDBN} may be able to give you
8966 more information about the status of the vector unit.
8971 Display information about the vector unit. The exact contents and
8972 layout vary depending on the hardware.
8975 @node OS Information
8976 @section Operating System Auxiliary Information
8977 @cindex OS information
8979 @value{GDBN} provides interfaces to useful OS facilities that can help
8980 you debug your program.
8982 @cindex @code{ptrace} system call
8983 @cindex @code{struct user} contents
8984 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8985 machines), it interfaces with the inferior via the @code{ptrace}
8986 system call. The operating system creates a special sata structure,
8987 called @code{struct user}, for this interface. You can use the
8988 command @code{info udot} to display the contents of this data
8994 Display the contents of the @code{struct user} maintained by the OS
8995 kernel for the program being debugged. @value{GDBN} displays the
8996 contents of @code{struct user} as a list of hex numbers, similar to
8997 the @code{examine} command.
9000 @cindex auxiliary vector
9001 @cindex vector, auxiliary
9002 Some operating systems supply an @dfn{auxiliary vector} to programs at
9003 startup. This is akin to the arguments and environment that you
9004 specify for a program, but contains a system-dependent variety of
9005 binary values that tell system libraries important details about the
9006 hardware, operating system, and process. Each value's purpose is
9007 identified by an integer tag; the meanings are well-known but system-specific.
9008 Depending on the configuration and operating system facilities,
9009 @value{GDBN} may be able to show you this information. For remote
9010 targets, this functionality may further depend on the remote stub's
9011 support of the @samp{qXfer:auxv:read} packet, see
9012 @ref{qXfer auxiliary vector read}.
9017 Display the auxiliary vector of the inferior, which can be either a
9018 live process or a core dump file. @value{GDBN} prints each tag value
9019 numerically, and also shows names and text descriptions for recognized
9020 tags. Some values in the vector are numbers, some bit masks, and some
9021 pointers to strings or other data. @value{GDBN} displays each value in the
9022 most appropriate form for a recognized tag, and in hexadecimal for
9023 an unrecognized tag.
9026 On some targets, @value{GDBN} can access operating-system-specific information
9027 and display it to user, without interpretation. For remote targets,
9028 this functionality depends on the remote stub's support of the
9029 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9034 List the types of OS information available for the target. If the
9035 target does not return a list of possible types, this command will
9038 @kindex info os processes
9039 @item info os processes
9040 Display the list of processes on the target. For each process,
9041 @value{GDBN} prints the process identifier, the name of the user, and
9042 the command corresponding to the process.
9045 @node Memory Region Attributes
9046 @section Memory Region Attributes
9047 @cindex memory region attributes
9049 @dfn{Memory region attributes} allow you to describe special handling
9050 required by regions of your target's memory. @value{GDBN} uses
9051 attributes to determine whether to allow certain types of memory
9052 accesses; whether to use specific width accesses; and whether to cache
9053 target memory. By default the description of memory regions is
9054 fetched from the target (if the current target supports this), but the
9055 user can override the fetched regions.
9057 Defined memory regions can be individually enabled and disabled. When a
9058 memory region is disabled, @value{GDBN} uses the default attributes when
9059 accessing memory in that region. Similarly, if no memory regions have
9060 been defined, @value{GDBN} uses the default attributes when accessing
9063 When a memory region is defined, it is given a number to identify it;
9064 to enable, disable, or remove a memory region, you specify that number.
9068 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9069 Define a memory region bounded by @var{lower} and @var{upper} with
9070 attributes @var{attributes}@dots{}, and add it to the list of regions
9071 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9072 case: it is treated as the target's maximum memory address.
9073 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9076 Discard any user changes to the memory regions and use target-supplied
9077 regions, if available, or no regions if the target does not support.
9080 @item delete mem @var{nums}@dots{}
9081 Remove memory regions @var{nums}@dots{} from the list of regions
9082 monitored by @value{GDBN}.
9085 @item disable mem @var{nums}@dots{}
9086 Disable monitoring of memory regions @var{nums}@dots{}.
9087 A disabled memory region is not forgotten.
9088 It may be enabled again later.
9091 @item enable mem @var{nums}@dots{}
9092 Enable monitoring of memory regions @var{nums}@dots{}.
9096 Print a table of all defined memory regions, with the following columns
9100 @item Memory Region Number
9101 @item Enabled or Disabled.
9102 Enabled memory regions are marked with @samp{y}.
9103 Disabled memory regions are marked with @samp{n}.
9106 The address defining the inclusive lower bound of the memory region.
9109 The address defining the exclusive upper bound of the memory region.
9112 The list of attributes set for this memory region.
9117 @subsection Attributes
9119 @subsubsection Memory Access Mode
9120 The access mode attributes set whether @value{GDBN} may make read or
9121 write accesses to a memory region.
9123 While these attributes prevent @value{GDBN} from performing invalid
9124 memory accesses, they do nothing to prevent the target system, I/O DMA,
9125 etc.@: from accessing memory.
9129 Memory is read only.
9131 Memory is write only.
9133 Memory is read/write. This is the default.
9136 @subsubsection Memory Access Size
9137 The access size attribute tells @value{GDBN} to use specific sized
9138 accesses in the memory region. Often memory mapped device registers
9139 require specific sized accesses. If no access size attribute is
9140 specified, @value{GDBN} may use accesses of any size.
9144 Use 8 bit memory accesses.
9146 Use 16 bit memory accesses.
9148 Use 32 bit memory accesses.
9150 Use 64 bit memory accesses.
9153 @c @subsubsection Hardware/Software Breakpoints
9154 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9155 @c will use hardware or software breakpoints for the internal breakpoints
9156 @c used by the step, next, finish, until, etc. commands.
9160 @c Always use hardware breakpoints
9161 @c @item swbreak (default)
9164 @subsubsection Data Cache
9165 The data cache attributes set whether @value{GDBN} will cache target
9166 memory. While this generally improves performance by reducing debug
9167 protocol overhead, it can lead to incorrect results because @value{GDBN}
9168 does not know about volatile variables or memory mapped device
9173 Enable @value{GDBN} to cache target memory.
9175 Disable @value{GDBN} from caching target memory. This is the default.
9178 @subsection Memory Access Checking
9179 @value{GDBN} can be instructed to refuse accesses to memory that is
9180 not explicitly described. This can be useful if accessing such
9181 regions has undesired effects for a specific target, or to provide
9182 better error checking. The following commands control this behaviour.
9185 @kindex set mem inaccessible-by-default
9186 @item set mem inaccessible-by-default [on|off]
9187 If @code{on} is specified, make @value{GDBN} treat memory not
9188 explicitly described by the memory ranges as non-existent and refuse accesses
9189 to such memory. The checks are only performed if there's at least one
9190 memory range defined. If @code{off} is specified, make @value{GDBN}
9191 treat the memory not explicitly described by the memory ranges as RAM.
9192 The default value is @code{on}.
9193 @kindex show mem inaccessible-by-default
9194 @item show mem inaccessible-by-default
9195 Show the current handling of accesses to unknown memory.
9199 @c @subsubsection Memory Write Verification
9200 @c The memory write verification attributes set whether @value{GDBN}
9201 @c will re-reads data after each write to verify the write was successful.
9205 @c @item noverify (default)
9208 @node Dump/Restore Files
9209 @section Copy Between Memory and a File
9210 @cindex dump/restore files
9211 @cindex append data to a file
9212 @cindex dump data to a file
9213 @cindex restore data from a file
9215 You can use the commands @code{dump}, @code{append}, and
9216 @code{restore} to copy data between target memory and a file. The
9217 @code{dump} and @code{append} commands write data to a file, and the
9218 @code{restore} command reads data from a file back into the inferior's
9219 memory. Files may be in binary, Motorola S-record, Intel hex, or
9220 Tektronix Hex format; however, @value{GDBN} can only append to binary
9226 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9227 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9228 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9229 or the value of @var{expr}, to @var{filename} in the given format.
9231 The @var{format} parameter may be any one of:
9238 Motorola S-record format.
9240 Tektronix Hex format.
9243 @value{GDBN} uses the same definitions of these formats as the
9244 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9245 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9249 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9250 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9251 Append the contents of memory from @var{start_addr} to @var{end_addr},
9252 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9253 (@value{GDBN} can only append data to files in raw binary form.)
9256 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9257 Restore the contents of file @var{filename} into memory. The
9258 @code{restore} command can automatically recognize any known @sc{bfd}
9259 file format, except for raw binary. To restore a raw binary file you
9260 must specify the optional keyword @code{binary} after the filename.
9262 If @var{bias} is non-zero, its value will be added to the addresses
9263 contained in the file. Binary files always start at address zero, so
9264 they will be restored at address @var{bias}. Other bfd files have
9265 a built-in location; they will be restored at offset @var{bias}
9268 If @var{start} and/or @var{end} are non-zero, then only data between
9269 file offset @var{start} and file offset @var{end} will be restored.
9270 These offsets are relative to the addresses in the file, before
9271 the @var{bias} argument is applied.
9275 @node Core File Generation
9276 @section How to Produce a Core File from Your Program
9277 @cindex dump core from inferior
9279 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9280 image of a running process and its process status (register values
9281 etc.). Its primary use is post-mortem debugging of a program that
9282 crashed while it ran outside a debugger. A program that crashes
9283 automatically produces a core file, unless this feature is disabled by
9284 the user. @xref{Files}, for information on invoking @value{GDBN} in
9285 the post-mortem debugging mode.
9287 Occasionally, you may wish to produce a core file of the program you
9288 are debugging in order to preserve a snapshot of its state.
9289 @value{GDBN} has a special command for that.
9293 @kindex generate-core-file
9294 @item generate-core-file [@var{file}]
9295 @itemx gcore [@var{file}]
9296 Produce a core dump of the inferior process. The optional argument
9297 @var{file} specifies the file name where to put the core dump. If not
9298 specified, the file name defaults to @file{core.@var{pid}}, where
9299 @var{pid} is the inferior process ID.
9301 Note that this command is implemented only for some systems (as of
9302 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9305 @node Character Sets
9306 @section Character Sets
9307 @cindex character sets
9309 @cindex translating between character sets
9310 @cindex host character set
9311 @cindex target character set
9313 If the program you are debugging uses a different character set to
9314 represent characters and strings than the one @value{GDBN} uses itself,
9315 @value{GDBN} can automatically translate between the character sets for
9316 you. The character set @value{GDBN} uses we call the @dfn{host
9317 character set}; the one the inferior program uses we call the
9318 @dfn{target character set}.
9320 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9321 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9322 remote protocol (@pxref{Remote Debugging}) to debug a program
9323 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9324 then the host character set is Latin-1, and the target character set is
9325 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9326 target-charset EBCDIC-US}, then @value{GDBN} translates between
9327 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9328 character and string literals in expressions.
9330 @value{GDBN} has no way to automatically recognize which character set
9331 the inferior program uses; you must tell it, using the @code{set
9332 target-charset} command, described below.
9334 Here are the commands for controlling @value{GDBN}'s character set
9338 @item set target-charset @var{charset}
9339 @kindex set target-charset
9340 Set the current target character set to @var{charset}. To display the
9341 list of supported target character sets, type
9342 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9344 @item set host-charset @var{charset}
9345 @kindex set host-charset
9346 Set the current host character set to @var{charset}.
9348 By default, @value{GDBN} uses a host character set appropriate to the
9349 system it is running on; you can override that default using the
9350 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9351 automatically determine the appropriate host character set. In this
9352 case, @value{GDBN} uses @samp{UTF-8}.
9354 @value{GDBN} can only use certain character sets as its host character
9355 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9356 @value{GDBN} will list the host character sets it supports.
9358 @item set charset @var{charset}
9360 Set the current host and target character sets to @var{charset}. As
9361 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9362 @value{GDBN} will list the names of the character sets that can be used
9363 for both host and target.
9366 @kindex show charset
9367 Show the names of the current host and target character sets.
9369 @item show host-charset
9370 @kindex show host-charset
9371 Show the name of the current host character set.
9373 @item show target-charset
9374 @kindex show target-charset
9375 Show the name of the current target character set.
9377 @item set target-wide-charset @var{charset}
9378 @kindex set target-wide-charset
9379 Set the current target's wide character set to @var{charset}. This is
9380 the character set used by the target's @code{wchar_t} type. To
9381 display the list of supported wide character sets, type
9382 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9384 @item show target-wide-charset
9385 @kindex show target-wide-charset
9386 Show the name of the current target's wide character set.
9389 Here is an example of @value{GDBN}'s character set support in action.
9390 Assume that the following source code has been placed in the file
9391 @file{charset-test.c}:
9397 = @{72, 101, 108, 108, 111, 44, 32, 119,
9398 111, 114, 108, 100, 33, 10, 0@};
9399 char ibm1047_hello[]
9400 = @{200, 133, 147, 147, 150, 107, 64, 166,
9401 150, 153, 147, 132, 90, 37, 0@};
9405 printf ("Hello, world!\n");
9409 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9410 containing the string @samp{Hello, world!} followed by a newline,
9411 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9413 We compile the program, and invoke the debugger on it:
9416 $ gcc -g charset-test.c -o charset-test
9417 $ gdb -nw charset-test
9418 GNU gdb 2001-12-19-cvs
9419 Copyright 2001 Free Software Foundation, Inc.
9424 We can use the @code{show charset} command to see what character sets
9425 @value{GDBN} is currently using to interpret and display characters and
9429 (@value{GDBP}) show charset
9430 The current host and target character set is `ISO-8859-1'.
9434 For the sake of printing this manual, let's use @sc{ascii} as our
9435 initial character set:
9437 (@value{GDBP}) set charset ASCII
9438 (@value{GDBP}) show charset
9439 The current host and target character set is `ASCII'.
9443 Let's assume that @sc{ascii} is indeed the correct character set for our
9444 host system --- in other words, let's assume that if @value{GDBN} prints
9445 characters using the @sc{ascii} character set, our terminal will display
9446 them properly. Since our current target character set is also
9447 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9450 (@value{GDBP}) print ascii_hello
9451 $1 = 0x401698 "Hello, world!\n"
9452 (@value{GDBP}) print ascii_hello[0]
9457 @value{GDBN} uses the target character set for character and string
9458 literals you use in expressions:
9461 (@value{GDBP}) print '+'
9466 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9469 @value{GDBN} relies on the user to tell it which character set the
9470 target program uses. If we print @code{ibm1047_hello} while our target
9471 character set is still @sc{ascii}, we get jibberish:
9474 (@value{GDBP}) print ibm1047_hello
9475 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9476 (@value{GDBP}) print ibm1047_hello[0]
9481 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9482 @value{GDBN} tells us the character sets it supports:
9485 (@value{GDBP}) set target-charset
9486 ASCII EBCDIC-US IBM1047 ISO-8859-1
9487 (@value{GDBP}) set target-charset
9490 We can select @sc{ibm1047} as our target character set, and examine the
9491 program's strings again. Now the @sc{ascii} string is wrong, but
9492 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9493 target character set, @sc{ibm1047}, to the host character set,
9494 @sc{ascii}, and they display correctly:
9497 (@value{GDBP}) set target-charset IBM1047
9498 (@value{GDBP}) show charset
9499 The current host character set is `ASCII'.
9500 The current target character set is `IBM1047'.
9501 (@value{GDBP}) print ascii_hello
9502 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9503 (@value{GDBP}) print ascii_hello[0]
9505 (@value{GDBP}) print ibm1047_hello
9506 $8 = 0x4016a8 "Hello, world!\n"
9507 (@value{GDBP}) print ibm1047_hello[0]
9512 As above, @value{GDBN} uses the target character set for character and
9513 string literals you use in expressions:
9516 (@value{GDBP}) print '+'
9521 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9524 @node Caching Remote Data
9525 @section Caching Data of Remote Targets
9526 @cindex caching data of remote targets
9528 @value{GDBN} caches data exchanged between the debugger and a
9529 remote target (@pxref{Remote Debugging}). Such caching generally improves
9530 performance, because it reduces the overhead of the remote protocol by
9531 bundling memory reads and writes into large chunks. Unfortunately, simply
9532 caching everything would lead to incorrect results, since @value{GDBN}
9533 does not necessarily know anything about volatile values, memory-mapped I/O
9534 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9535 memory can be changed @emph{while} a gdb command is executing.
9536 Therefore, by default, @value{GDBN} only caches data
9537 known to be on the stack@footnote{In non-stop mode, it is moderately
9538 rare for a running thread to modify the stack of a stopped thread
9539 in a way that would interfere with a backtrace, and caching of
9540 stack reads provides a significant speed up of remote backtraces.}.
9541 Other regions of memory can be explicitly marked as
9542 cacheable; see @pxref{Memory Region Attributes}.
9545 @kindex set remotecache
9546 @item set remotecache on
9547 @itemx set remotecache off
9548 This option no longer does anything; it exists for compatibility
9551 @kindex show remotecache
9552 @item show remotecache
9553 Show the current state of the obsolete remotecache flag.
9555 @kindex set stack-cache
9556 @item set stack-cache on
9557 @itemx set stack-cache off
9558 Enable or disable caching of stack accesses. When @code{ON}, use
9559 caching. By default, this option is @code{ON}.
9561 @kindex show stack-cache
9562 @item show stack-cache
9563 Show the current state of data caching for memory accesses.
9566 @item info dcache @r{[}line@r{]}
9567 Print the information about the data cache performance. The
9568 information displayed includes the dcache width and depth, and for
9569 each cache line, its number, address, and how many times it was
9570 referenced. This command is useful for debugging the data cache
9573 If a line number is specified, the contents of that line will be
9576 @item set dcache size @var{size}
9578 @kindex set dcache size
9579 Set maximum number of entries in dcache (dcache depth above).
9581 @item set dcache line-size @var{line-size}
9582 @cindex dcache line-size
9583 @kindex set dcache line-size
9584 Set number of bytes each dcache entry caches (dcache width above).
9585 Must be a power of 2.
9587 @item show dcache size
9588 @kindex show dcache size
9589 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9591 @item show dcache line-size
9592 @kindex show dcache line-size
9593 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9597 @node Searching Memory
9598 @section Search Memory
9599 @cindex searching memory
9601 Memory can be searched for a particular sequence of bytes with the
9602 @code{find} command.
9606 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9607 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9608 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9609 etc. The search begins at address @var{start_addr} and continues for either
9610 @var{len} bytes or through to @var{end_addr} inclusive.
9613 @var{s} and @var{n} are optional parameters.
9614 They may be specified in either order, apart or together.
9617 @item @var{s}, search query size
9618 The size of each search query value.
9624 halfwords (two bytes)
9628 giant words (eight bytes)
9631 All values are interpreted in the current language.
9632 This means, for example, that if the current source language is C/C@t{++}
9633 then searching for the string ``hello'' includes the trailing '\0'.
9635 If the value size is not specified, it is taken from the
9636 value's type in the current language.
9637 This is useful when one wants to specify the search
9638 pattern as a mixture of types.
9639 Note that this means, for example, that in the case of C-like languages
9640 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9641 which is typically four bytes.
9643 @item @var{n}, maximum number of finds
9644 The maximum number of matches to print. The default is to print all finds.
9647 You can use strings as search values. Quote them with double-quotes
9649 The string value is copied into the search pattern byte by byte,
9650 regardless of the endianness of the target and the size specification.
9652 The address of each match found is printed as well as a count of the
9653 number of matches found.
9655 The address of the last value found is stored in convenience variable
9657 A count of the number of matches is stored in @samp{$numfound}.
9659 For example, if stopped at the @code{printf} in this function:
9665 static char hello[] = "hello-hello";
9666 static struct @{ char c; short s; int i; @}
9667 __attribute__ ((packed)) mixed
9668 = @{ 'c', 0x1234, 0x87654321 @};
9669 printf ("%s\n", hello);
9674 you get during debugging:
9677 (gdb) find &hello[0], +sizeof(hello), "hello"
9678 0x804956d <hello.1620+6>
9680 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9681 0x8049567 <hello.1620>
9682 0x804956d <hello.1620+6>
9684 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9685 0x8049567 <hello.1620>
9687 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9688 0x8049560 <mixed.1625>
9690 (gdb) print $numfound
9693 $2 = (void *) 0x8049560
9696 @node Optimized Code
9697 @chapter Debugging Optimized Code
9698 @cindex optimized code, debugging
9699 @cindex debugging optimized code
9701 Almost all compilers support optimization. With optimization
9702 disabled, the compiler generates assembly code that corresponds
9703 directly to your source code, in a simplistic way. As the compiler
9704 applies more powerful optimizations, the generated assembly code
9705 diverges from your original source code. With help from debugging
9706 information generated by the compiler, @value{GDBN} can map from
9707 the running program back to constructs from your original source.
9709 @value{GDBN} is more accurate with optimization disabled. If you
9710 can recompile without optimization, it is easier to follow the
9711 progress of your program during debugging. But, there are many cases
9712 where you may need to debug an optimized version.
9714 When you debug a program compiled with @samp{-g -O}, remember that the
9715 optimizer has rearranged your code; the debugger shows you what is
9716 really there. Do not be too surprised when the execution path does not
9717 exactly match your source file! An extreme example: if you define a
9718 variable, but never use it, @value{GDBN} never sees that
9719 variable---because the compiler optimizes it out of existence.
9721 Some things do not work as well with @samp{-g -O} as with just
9722 @samp{-g}, particularly on machines with instruction scheduling. If in
9723 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9724 please report it to us as a bug (including a test case!).
9725 @xref{Variables}, for more information about debugging optimized code.
9728 * Inline Functions:: How @value{GDBN} presents inlining
9729 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9732 @node Inline Functions
9733 @section Inline Functions
9734 @cindex inline functions, debugging
9736 @dfn{Inlining} is an optimization that inserts a copy of the function
9737 body directly at each call site, instead of jumping to a shared
9738 routine. @value{GDBN} displays inlined functions just like
9739 non-inlined functions. They appear in backtraces. You can view their
9740 arguments and local variables, step into them with @code{step}, skip
9741 them with @code{next}, and escape from them with @code{finish}.
9742 You can check whether a function was inlined by using the
9743 @code{info frame} command.
9745 For @value{GDBN} to support inlined functions, the compiler must
9746 record information about inlining in the debug information ---
9747 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9748 other compilers do also. @value{GDBN} only supports inlined functions
9749 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9750 do not emit two required attributes (@samp{DW_AT_call_file} and
9751 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9752 function calls with earlier versions of @value{NGCC}. It instead
9753 displays the arguments and local variables of inlined functions as
9754 local variables in the caller.
9756 The body of an inlined function is directly included at its call site;
9757 unlike a non-inlined function, there are no instructions devoted to
9758 the call. @value{GDBN} still pretends that the call site and the
9759 start of the inlined function are different instructions. Stepping to
9760 the call site shows the call site, and then stepping again shows
9761 the first line of the inlined function, even though no additional
9762 instructions are executed.
9764 This makes source-level debugging much clearer; you can see both the
9765 context of the call and then the effect of the call. Only stepping by
9766 a single instruction using @code{stepi} or @code{nexti} does not do
9767 this; single instruction steps always show the inlined body.
9769 There are some ways that @value{GDBN} does not pretend that inlined
9770 function calls are the same as normal calls:
9774 You cannot set breakpoints on inlined functions. @value{GDBN}
9775 either reports that there is no symbol with that name, or else sets the
9776 breakpoint only on non-inlined copies of the function. This limitation
9777 will be removed in a future version of @value{GDBN}; until then,
9778 set a breakpoint by line number on the first line of the inlined
9782 Setting breakpoints at the call site of an inlined function may not
9783 work, because the call site does not contain any code. @value{GDBN}
9784 may incorrectly move the breakpoint to the next line of the enclosing
9785 function, after the call. This limitation will be removed in a future
9786 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9787 or inside the inlined function instead.
9790 @value{GDBN} cannot locate the return value of inlined calls after
9791 using the @code{finish} command. This is a limitation of compiler-generated
9792 debugging information; after @code{finish}, you can step to the next line
9793 and print a variable where your program stored the return value.
9797 @node Tail Call Frames
9798 @section Tail Call Frames
9799 @cindex tail call frames, debugging
9801 Function @code{B} can call function @code{C} in its very last statement. In
9802 unoptimized compilation the call of @code{C} is immediately followed by return
9803 instruction at the end of @code{B} code. Optimizing compiler may replace the
9804 call and return in function @code{B} into one jump to function @code{C}
9805 instead. Such use of a jump instruction is called @dfn{tail call}.
9807 During execution of function @code{C}, there will be no indication in the
9808 function call stack frames that it was tail-called from @code{B}. If function
9809 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9810 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9811 some cases @value{GDBN} can determine that @code{C} was tail-called from
9812 @code{B}, and it will then create fictitious call frame for that, with the
9813 return address set up as if @code{B} called @code{C} normally.
9815 This functionality is currently supported only by DWARF 2 debugging format and
9816 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9817 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9820 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9821 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9825 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9827 Stack level 1, frame at 0x7fffffffda30:
9828 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9829 tail call frame, caller of frame at 0x7fffffffda30
9830 source language c++.
9831 Arglist at unknown address.
9832 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9835 The detection of all the possible code path executions can find them ambiguous.
9836 There is no execution history stored (possible @ref{Reverse Execution} is never
9837 used for this purpose) and the last known caller could have reached the known
9838 callee by multiple different jump sequences. In such case @value{GDBN} still
9839 tries to show at least all the unambiguous top tail callers and all the
9840 unambiguous bottom tail calees, if any.
9843 @anchor{set debug entry-values}
9844 @item set debug entry-values
9845 @kindex set debug entry-values
9846 When set to on, enables printing of analysis messages for both frame argument
9847 values at function entry and tail calls. It will show all the possible valid
9848 tail calls code paths it has considered. It will also print the intersection
9849 of them with the final unambiguous (possibly partial or even empty) code path
9852 @item show debug entry-values
9853 @kindex show debug entry-values
9854 Show the current state of analysis messages printing for both frame argument
9855 values at function entry and tail calls.
9858 The analysis messages for tail calls can for example show why the virtual tail
9859 call frame for function @code{c} has not been recognized (due to the indirect
9860 reference by variable @code{x}):
9863 static void __attribute__((noinline, noclone)) c (void);
9864 void (*x) (void) = c;
9865 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9866 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9867 int main (void) @{ x (); return 0; @}
9869 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9870 DW_TAG_GNU_call_site 0x40039a in main
9872 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9875 #1 0x000000000040039a in main () at t.c:5
9878 Another possibility is an ambiguous virtual tail call frames resolution:
9882 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9883 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9884 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9885 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9886 static void __attribute__((noinline, noclone)) b (void)
9887 @{ if (i) c (); else e (); @}
9888 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9889 int main (void) @{ a (); return 0; @}
9891 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9892 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9893 tailcall: reduced: 0x4004d2(a) |
9896 #1 0x00000000004004d2 in a () at t.c:8
9897 #2 0x0000000000400395 in main () at t.c:9
9900 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9901 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9903 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9904 @ifset HAVE_MAKEINFO_CLICK
9906 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9907 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9909 @ifclear HAVE_MAKEINFO_CLICK
9911 @set CALLSEQ1B @value{CALLSEQ1A}
9912 @set CALLSEQ2B @value{CALLSEQ2A}
9915 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9916 The code can have possible execution paths @value{CALLSEQ1B} or
9917 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9919 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9920 has found. It then finds another possible calling sequcen - that one is
9921 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9922 printed as the @code{reduced:} calling sequence. That one could have many
9923 futher @code{compare:} and @code{reduced:} statements as long as there remain
9924 any non-ambiguous sequence entries.
9926 For the frame of function @code{b} in both cases there are different possible
9927 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9928 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9929 therefore this one is displayed to the user while the ambiguous frames are
9932 There can be also reasons why printing of frame argument values at function
9937 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9938 static void __attribute__((noinline, noclone)) a (int i);
9939 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9940 static void __attribute__((noinline, noclone)) a (int i)
9941 @{ if (i) b (i - 1); else c (0); @}
9942 int main (void) @{ a (5); return 0; @}
9945 #0 c (i=i@@entry=0) at t.c:2
9946 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9947 function "a" at 0x400420 can call itself via tail calls
9948 i=<optimized out>) at t.c:6
9949 #2 0x000000000040036e in main () at t.c:7
9952 @value{GDBN} cannot find out from the inferior state if and how many times did
9953 function @code{a} call itself (via function @code{b}) as these calls would be
9954 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9955 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9956 prints @code{<optimized out>} instead.
9959 @chapter C Preprocessor Macros
9961 Some languages, such as C and C@t{++}, provide a way to define and invoke
9962 ``preprocessor macros'' which expand into strings of tokens.
9963 @value{GDBN} can evaluate expressions containing macro invocations, show
9964 the result of macro expansion, and show a macro's definition, including
9965 where it was defined.
9967 You may need to compile your program specially to provide @value{GDBN}
9968 with information about preprocessor macros. Most compilers do not
9969 include macros in their debugging information, even when you compile
9970 with the @option{-g} flag. @xref{Compilation}.
9972 A program may define a macro at one point, remove that definition later,
9973 and then provide a different definition after that. Thus, at different
9974 points in the program, a macro may have different definitions, or have
9975 no definition at all. If there is a current stack frame, @value{GDBN}
9976 uses the macros in scope at that frame's source code line. Otherwise,
9977 @value{GDBN} uses the macros in scope at the current listing location;
9980 Whenever @value{GDBN} evaluates an expression, it always expands any
9981 macro invocations present in the expression. @value{GDBN} also provides
9982 the following commands for working with macros explicitly.
9986 @kindex macro expand
9987 @cindex macro expansion, showing the results of preprocessor
9988 @cindex preprocessor macro expansion, showing the results of
9989 @cindex expanding preprocessor macros
9990 @item macro expand @var{expression}
9991 @itemx macro exp @var{expression}
9992 Show the results of expanding all preprocessor macro invocations in
9993 @var{expression}. Since @value{GDBN} simply expands macros, but does
9994 not parse the result, @var{expression} need not be a valid expression;
9995 it can be any string of tokens.
9998 @item macro expand-once @var{expression}
9999 @itemx macro exp1 @var{expression}
10000 @cindex expand macro once
10001 @i{(This command is not yet implemented.)} Show the results of
10002 expanding those preprocessor macro invocations that appear explicitly in
10003 @var{expression}. Macro invocations appearing in that expansion are
10004 left unchanged. This command allows you to see the effect of a
10005 particular macro more clearly, without being confused by further
10006 expansions. Since @value{GDBN} simply expands macros, but does not
10007 parse the result, @var{expression} need not be a valid expression; it
10008 can be any string of tokens.
10011 @cindex macro definition, showing
10012 @cindex definition of a macro, showing
10013 @cindex macros, from debug info
10014 @item info macro [-a|-all] [--] @var{macro}
10015 Show the current definition or all definitions of the named @var{macro},
10016 and describe the source location or compiler command-line where that
10017 definition was established. The optional double dash is to signify the end of
10018 argument processing and the beginning of @var{macro} for non C-like macros where
10019 the macro may begin with a hyphen.
10021 @kindex info macros
10022 @item info macros @var{linespec}
10023 Show all macro definitions that are in effect at the location specified
10024 by @var{linespec}, and describe the source location or compiler
10025 command-line where those definitions were established.
10027 @kindex macro define
10028 @cindex user-defined macros
10029 @cindex defining macros interactively
10030 @cindex macros, user-defined
10031 @item macro define @var{macro} @var{replacement-list}
10032 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10033 Introduce a definition for a preprocessor macro named @var{macro},
10034 invocations of which are replaced by the tokens given in
10035 @var{replacement-list}. The first form of this command defines an
10036 ``object-like'' macro, which takes no arguments; the second form
10037 defines a ``function-like'' macro, which takes the arguments given in
10040 A definition introduced by this command is in scope in every
10041 expression evaluated in @value{GDBN}, until it is removed with the
10042 @code{macro undef} command, described below. The definition overrides
10043 all definitions for @var{macro} present in the program being debugged,
10044 as well as any previous user-supplied definition.
10046 @kindex macro undef
10047 @item macro undef @var{macro}
10048 Remove any user-supplied definition for the macro named @var{macro}.
10049 This command only affects definitions provided with the @code{macro
10050 define} command, described above; it cannot remove definitions present
10051 in the program being debugged.
10055 List all the macros defined using the @code{macro define} command.
10058 @cindex macros, example of debugging with
10059 Here is a transcript showing the above commands in action. First, we
10060 show our source files:
10065 #include "sample.h"
10068 #define ADD(x) (M + x)
10073 printf ("Hello, world!\n");
10075 printf ("We're so creative.\n");
10077 printf ("Goodbye, world!\n");
10084 Now, we compile the program using the @sc{gnu} C compiler,
10085 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10086 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10087 and @option{-gdwarf-4}; we recommend always choosing the most recent
10088 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10089 includes information about preprocessor macros in the debugging
10093 $ gcc -gdwarf-2 -g3 sample.c -o sample
10097 Now, we start @value{GDBN} on our sample program:
10101 GNU gdb 2002-05-06-cvs
10102 Copyright 2002 Free Software Foundation, Inc.
10103 GDB is free software, @dots{}
10107 We can expand macros and examine their definitions, even when the
10108 program is not running. @value{GDBN} uses the current listing position
10109 to decide which macro definitions are in scope:
10112 (@value{GDBP}) list main
10115 5 #define ADD(x) (M + x)
10120 10 printf ("Hello, world!\n");
10122 12 printf ("We're so creative.\n");
10123 (@value{GDBP}) info macro ADD
10124 Defined at /home/jimb/gdb/macros/play/sample.c:5
10125 #define ADD(x) (M + x)
10126 (@value{GDBP}) info macro Q
10127 Defined at /home/jimb/gdb/macros/play/sample.h:1
10128 included at /home/jimb/gdb/macros/play/sample.c:2
10130 (@value{GDBP}) macro expand ADD(1)
10131 expands to: (42 + 1)
10132 (@value{GDBP}) macro expand-once ADD(1)
10133 expands to: once (M + 1)
10137 In the example above, note that @code{macro expand-once} expands only
10138 the macro invocation explicit in the original text --- the invocation of
10139 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10140 which was introduced by @code{ADD}.
10142 Once the program is running, @value{GDBN} uses the macro definitions in
10143 force at the source line of the current stack frame:
10146 (@value{GDBP}) break main
10147 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10149 Starting program: /home/jimb/gdb/macros/play/sample
10151 Breakpoint 1, main () at sample.c:10
10152 10 printf ("Hello, world!\n");
10156 At line 10, the definition of the macro @code{N} at line 9 is in force:
10159 (@value{GDBP}) info macro N
10160 Defined at /home/jimb/gdb/macros/play/sample.c:9
10162 (@value{GDBP}) macro expand N Q M
10163 expands to: 28 < 42
10164 (@value{GDBP}) print N Q M
10169 As we step over directives that remove @code{N}'s definition, and then
10170 give it a new definition, @value{GDBN} finds the definition (or lack
10171 thereof) in force at each point:
10174 (@value{GDBP}) next
10176 12 printf ("We're so creative.\n");
10177 (@value{GDBP}) info macro N
10178 The symbol `N' has no definition as a C/C++ preprocessor macro
10179 at /home/jimb/gdb/macros/play/sample.c:12
10180 (@value{GDBP}) next
10182 14 printf ("Goodbye, world!\n");
10183 (@value{GDBP}) info macro N
10184 Defined at /home/jimb/gdb/macros/play/sample.c:13
10186 (@value{GDBP}) macro expand N Q M
10187 expands to: 1729 < 42
10188 (@value{GDBP}) print N Q M
10193 In addition to source files, macros can be defined on the compilation command
10194 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10195 such a way, @value{GDBN} displays the location of their definition as line zero
10196 of the source file submitted to the compiler.
10199 (@value{GDBP}) info macro __STDC__
10200 Defined at /home/jimb/gdb/macros/play/sample.c:0
10207 @chapter Tracepoints
10208 @c This chapter is based on the documentation written by Michael
10209 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10211 @cindex tracepoints
10212 In some applications, it is not feasible for the debugger to interrupt
10213 the program's execution long enough for the developer to learn
10214 anything helpful about its behavior. If the program's correctness
10215 depends on its real-time behavior, delays introduced by a debugger
10216 might cause the program to change its behavior drastically, or perhaps
10217 fail, even when the code itself is correct. It is useful to be able
10218 to observe the program's behavior without interrupting it.
10220 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10221 specify locations in the program, called @dfn{tracepoints}, and
10222 arbitrary expressions to evaluate when those tracepoints are reached.
10223 Later, using the @code{tfind} command, you can examine the values
10224 those expressions had when the program hit the tracepoints. The
10225 expressions may also denote objects in memory---structures or arrays,
10226 for example---whose values @value{GDBN} should record; while visiting
10227 a particular tracepoint, you may inspect those objects as if they were
10228 in memory at that moment. However, because @value{GDBN} records these
10229 values without interacting with you, it can do so quickly and
10230 unobtrusively, hopefully not disturbing the program's behavior.
10232 The tracepoint facility is currently available only for remote
10233 targets. @xref{Targets}. In addition, your remote target must know
10234 how to collect trace data. This functionality is implemented in the
10235 remote stub; however, none of the stubs distributed with @value{GDBN}
10236 support tracepoints as of this writing. The format of the remote
10237 packets used to implement tracepoints are described in @ref{Tracepoint
10240 It is also possible to get trace data from a file, in a manner reminiscent
10241 of corefiles; you specify the filename, and use @code{tfind} to search
10242 through the file. @xref{Trace Files}, for more details.
10244 This chapter describes the tracepoint commands and features.
10247 * Set Tracepoints::
10248 * Analyze Collected Data::
10249 * Tracepoint Variables::
10253 @node Set Tracepoints
10254 @section Commands to Set Tracepoints
10256 Before running such a @dfn{trace experiment}, an arbitrary number of
10257 tracepoints can be set. A tracepoint is actually a special type of
10258 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10259 standard breakpoint commands. For instance, as with breakpoints,
10260 tracepoint numbers are successive integers starting from one, and many
10261 of the commands associated with tracepoints take the tracepoint number
10262 as their argument, to identify which tracepoint to work on.
10264 For each tracepoint, you can specify, in advance, some arbitrary set
10265 of data that you want the target to collect in the trace buffer when
10266 it hits that tracepoint. The collected data can include registers,
10267 local variables, or global data. Later, you can use @value{GDBN}
10268 commands to examine the values these data had at the time the
10269 tracepoint was hit.
10271 Tracepoints do not support every breakpoint feature. Ignore counts on
10272 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10273 commands when they are hit. Tracepoints may not be thread-specific
10276 @cindex fast tracepoints
10277 Some targets may support @dfn{fast tracepoints}, which are inserted in
10278 a different way (such as with a jump instead of a trap), that is
10279 faster but possibly restricted in where they may be installed.
10281 @cindex static tracepoints
10282 @cindex markers, static tracepoints
10283 @cindex probing markers, static tracepoints
10284 Regular and fast tracepoints are dynamic tracing facilities, meaning
10285 that they can be used to insert tracepoints at (almost) any location
10286 in the target. Some targets may also support controlling @dfn{static
10287 tracepoints} from @value{GDBN}. With static tracing, a set of
10288 instrumentation points, also known as @dfn{markers}, are embedded in
10289 the target program, and can be activated or deactivated by name or
10290 address. These are usually placed at locations which facilitate
10291 investigating what the target is actually doing. @value{GDBN}'s
10292 support for static tracing includes being able to list instrumentation
10293 points, and attach them with @value{GDBN} defined high level
10294 tracepoints that expose the whole range of convenience of
10295 @value{GDBN}'s tracepoints support. Namely, support for collecting
10296 registers values and values of global or local (to the instrumentation
10297 point) variables; tracepoint conditions and trace state variables.
10298 The act of installing a @value{GDBN} static tracepoint on an
10299 instrumentation point, or marker, is referred to as @dfn{probing} a
10300 static tracepoint marker.
10302 @code{gdbserver} supports tracepoints on some target systems.
10303 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10305 This section describes commands to set tracepoints and associated
10306 conditions and actions.
10309 * Create and Delete Tracepoints::
10310 * Enable and Disable Tracepoints::
10311 * Tracepoint Passcounts::
10312 * Tracepoint Conditions::
10313 * Trace State Variables::
10314 * Tracepoint Actions::
10315 * Listing Tracepoints::
10316 * Listing Static Tracepoint Markers::
10317 * Starting and Stopping Trace Experiments::
10318 * Tracepoint Restrictions::
10321 @node Create and Delete Tracepoints
10322 @subsection Create and Delete Tracepoints
10325 @cindex set tracepoint
10327 @item trace @var{location}
10328 The @code{trace} command is very similar to the @code{break} command.
10329 Its argument @var{location} can be a source line, a function name, or
10330 an address in the target program. @xref{Specify Location}. The
10331 @code{trace} command defines a tracepoint, which is a point in the
10332 target program where the debugger will briefly stop, collect some
10333 data, and then allow the program to continue. Setting a tracepoint or
10334 changing its actions doesn't take effect until the next @code{tstart}
10335 command, and once a trace experiment is running, further changes will
10336 not have any effect until the next trace experiment starts.
10338 Here are some examples of using the @code{trace} command:
10341 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10343 (@value{GDBP}) @b{trace +2} // 2 lines forward
10345 (@value{GDBP}) @b{trace my_function} // first source line of function
10347 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10349 (@value{GDBP}) @b{trace *0x2117c4} // an address
10353 You can abbreviate @code{trace} as @code{tr}.
10355 @item trace @var{location} if @var{cond}
10356 Set a tracepoint with condition @var{cond}; evaluate the expression
10357 @var{cond} each time the tracepoint is reached, and collect data only
10358 if the value is nonzero---that is, if @var{cond} evaluates as true.
10359 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10360 information on tracepoint conditions.
10362 @item ftrace @var{location} [ if @var{cond} ]
10363 @cindex set fast tracepoint
10364 @cindex fast tracepoints, setting
10366 The @code{ftrace} command sets a fast tracepoint. For targets that
10367 support them, fast tracepoints will use a more efficient but possibly
10368 less general technique to trigger data collection, such as a jump
10369 instruction instead of a trap, or some sort of hardware support. It
10370 may not be possible to create a fast tracepoint at the desired
10371 location, in which case the command will exit with an explanatory
10374 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10377 @item strace @var{location} [ if @var{cond} ]
10378 @cindex set static tracepoint
10379 @cindex static tracepoints, setting
10380 @cindex probe static tracepoint marker
10382 The @code{strace} command sets a static tracepoint. For targets that
10383 support it, setting a static tracepoint probes a static
10384 instrumentation point, or marker, found at @var{location}. It may not
10385 be possible to set a static tracepoint at the desired location, in
10386 which case the command will exit with an explanatory message.
10388 @value{GDBN} handles arguments to @code{strace} exactly as for
10389 @code{trace}, with the addition that the user can also specify
10390 @code{-m @var{marker}} as @var{location}. This probes the marker
10391 identified by the @var{marker} string identifier. This identifier
10392 depends on the static tracepoint backend library your program is
10393 using. You can find all the marker identifiers in the @samp{ID} field
10394 of the @code{info static-tracepoint-markers} command output.
10395 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10396 Markers}. For example, in the following small program using the UST
10402 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10407 the marker id is composed of joining the first two arguments to the
10408 @code{trace_mark} call with a slash, which translates to:
10411 (@value{GDBP}) info static-tracepoint-markers
10412 Cnt Enb ID Address What
10413 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10419 so you may probe the marker above with:
10422 (@value{GDBP}) strace -m ust/bar33
10425 Static tracepoints accept an extra collect action --- @code{collect
10426 $_sdata}. This collects arbitrary user data passed in the probe point
10427 call to the tracing library. In the UST example above, you'll see
10428 that the third argument to @code{trace_mark} is a printf-like format
10429 string. The user data is then the result of running that formating
10430 string against the following arguments. Note that @code{info
10431 static-tracepoint-markers} command output lists that format string in
10432 the @samp{Data:} field.
10434 You can inspect this data when analyzing the trace buffer, by printing
10435 the $_sdata variable like any other variable available to
10436 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10439 @cindex last tracepoint number
10440 @cindex recent tracepoint number
10441 @cindex tracepoint number
10442 The convenience variable @code{$tpnum} records the tracepoint number
10443 of the most recently set tracepoint.
10445 @kindex delete tracepoint
10446 @cindex tracepoint deletion
10447 @item delete tracepoint @r{[}@var{num}@r{]}
10448 Permanently delete one or more tracepoints. With no argument, the
10449 default is to delete all tracepoints. Note that the regular
10450 @code{delete} command can remove tracepoints also.
10455 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10457 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10461 You can abbreviate this command as @code{del tr}.
10464 @node Enable and Disable Tracepoints
10465 @subsection Enable and Disable Tracepoints
10467 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10470 @kindex disable tracepoint
10471 @item disable tracepoint @r{[}@var{num}@r{]}
10472 Disable tracepoint @var{num}, or all tracepoints if no argument
10473 @var{num} is given. A disabled tracepoint will have no effect during
10474 a trace experiment, but it is not forgotten. You can re-enable
10475 a disabled tracepoint using the @code{enable tracepoint} command.
10476 If the command is issued during a trace experiment and the debug target
10477 has support for disabling tracepoints during a trace experiment, then the
10478 change will be effective immediately. Otherwise, it will be applied to the
10479 next trace experiment.
10481 @kindex enable tracepoint
10482 @item enable tracepoint @r{[}@var{num}@r{]}
10483 Enable tracepoint @var{num}, or all tracepoints. If this command is
10484 issued during a trace experiment and the debug target supports enabling
10485 tracepoints during a trace experiment, then the enabled tracepoints will
10486 become effective immediately. Otherwise, they will become effective the
10487 next time a trace experiment is run.
10490 @node Tracepoint Passcounts
10491 @subsection Tracepoint Passcounts
10495 @cindex tracepoint pass count
10496 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10497 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10498 automatically stop a trace experiment. If a tracepoint's passcount is
10499 @var{n}, then the trace experiment will be automatically stopped on
10500 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10501 @var{num} is not specified, the @code{passcount} command sets the
10502 passcount of the most recently defined tracepoint. If no passcount is
10503 given, the trace experiment will run until stopped explicitly by the
10509 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10510 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10512 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10513 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10514 (@value{GDBP}) @b{trace foo}
10515 (@value{GDBP}) @b{pass 3}
10516 (@value{GDBP}) @b{trace bar}
10517 (@value{GDBP}) @b{pass 2}
10518 (@value{GDBP}) @b{trace baz}
10519 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10520 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10521 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10522 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10526 @node Tracepoint Conditions
10527 @subsection Tracepoint Conditions
10528 @cindex conditional tracepoints
10529 @cindex tracepoint conditions
10531 The simplest sort of tracepoint collects data every time your program
10532 reaches a specified place. You can also specify a @dfn{condition} for
10533 a tracepoint. A condition is just a Boolean expression in your
10534 programming language (@pxref{Expressions, ,Expressions}). A
10535 tracepoint with a condition evaluates the expression each time your
10536 program reaches it, and data collection happens only if the condition
10539 Tracepoint conditions can be specified when a tracepoint is set, by
10540 using @samp{if} in the arguments to the @code{trace} command.
10541 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10542 also be set or changed at any time with the @code{condition} command,
10543 just as with breakpoints.
10545 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10546 the conditional expression itself. Instead, @value{GDBN} encodes the
10547 expression into an agent expression (@pxref{Agent Expressions})
10548 suitable for execution on the target, independently of @value{GDBN}.
10549 Global variables become raw memory locations, locals become stack
10550 accesses, and so forth.
10552 For instance, suppose you have a function that is usually called
10553 frequently, but should not be called after an error has occurred. You
10554 could use the following tracepoint command to collect data about calls
10555 of that function that happen while the error code is propagating
10556 through the program; an unconditional tracepoint could end up
10557 collecting thousands of useless trace frames that you would have to
10561 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10564 @node Trace State Variables
10565 @subsection Trace State Variables
10566 @cindex trace state variables
10568 A @dfn{trace state variable} is a special type of variable that is
10569 created and managed by target-side code. The syntax is the same as
10570 that for GDB's convenience variables (a string prefixed with ``$''),
10571 but they are stored on the target. They must be created explicitly,
10572 using a @code{tvariable} command. They are always 64-bit signed
10575 Trace state variables are remembered by @value{GDBN}, and downloaded
10576 to the target along with tracepoint information when the trace
10577 experiment starts. There are no intrinsic limits on the number of
10578 trace state variables, beyond memory limitations of the target.
10580 @cindex convenience variables, and trace state variables
10581 Although trace state variables are managed by the target, you can use
10582 them in print commands and expressions as if they were convenience
10583 variables; @value{GDBN} will get the current value from the target
10584 while the trace experiment is running. Trace state variables share
10585 the same namespace as other ``$'' variables, which means that you
10586 cannot have trace state variables with names like @code{$23} or
10587 @code{$pc}, nor can you have a trace state variable and a convenience
10588 variable with the same name.
10592 @item tvariable $@var{name} [ = @var{expression} ]
10594 The @code{tvariable} command creates a new trace state variable named
10595 @code{$@var{name}}, and optionally gives it an initial value of
10596 @var{expression}. @var{expression} is evaluated when this command is
10597 entered; the result will be converted to an integer if possible,
10598 otherwise @value{GDBN} will report an error. A subsequent
10599 @code{tvariable} command specifying the same name does not create a
10600 variable, but instead assigns the supplied initial value to the
10601 existing variable of that name, overwriting any previous initial
10602 value. The default initial value is 0.
10604 @item info tvariables
10605 @kindex info tvariables
10606 List all the trace state variables along with their initial values.
10607 Their current values may also be displayed, if the trace experiment is
10610 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10611 @kindex delete tvariable
10612 Delete the given trace state variables, or all of them if no arguments
10617 @node Tracepoint Actions
10618 @subsection Tracepoint Action Lists
10622 @cindex tracepoint actions
10623 @item actions @r{[}@var{num}@r{]}
10624 This command will prompt for a list of actions to be taken when the
10625 tracepoint is hit. If the tracepoint number @var{num} is not
10626 specified, this command sets the actions for the one that was most
10627 recently defined (so that you can define a tracepoint and then say
10628 @code{actions} without bothering about its number). You specify the
10629 actions themselves on the following lines, one action at a time, and
10630 terminate the actions list with a line containing just @code{end}. So
10631 far, the only defined actions are @code{collect}, @code{teval}, and
10632 @code{while-stepping}.
10634 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10635 Commands, ,Breakpoint Command Lists}), except that only the defined
10636 actions are allowed; any other @value{GDBN} command is rejected.
10638 @cindex remove actions from a tracepoint
10639 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10640 and follow it immediately with @samp{end}.
10643 (@value{GDBP}) @b{collect @var{data}} // collect some data
10645 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10647 (@value{GDBP}) @b{end} // signals the end of actions.
10650 In the following example, the action list begins with @code{collect}
10651 commands indicating the things to be collected when the tracepoint is
10652 hit. Then, in order to single-step and collect additional data
10653 following the tracepoint, a @code{while-stepping} command is used,
10654 followed by the list of things to be collected after each step in a
10655 sequence of single steps. The @code{while-stepping} command is
10656 terminated by its own separate @code{end} command. Lastly, the action
10657 list is terminated by an @code{end} command.
10660 (@value{GDBP}) @b{trace foo}
10661 (@value{GDBP}) @b{actions}
10662 Enter actions for tracepoint 1, one per line:
10665 > while-stepping 12
10666 > collect $pc, arr[i]
10671 @kindex collect @r{(tracepoints)}
10672 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10673 Collect values of the given expressions when the tracepoint is hit.
10674 This command accepts a comma-separated list of any valid expressions.
10675 In addition to global, static, or local variables, the following
10676 special arguments are supported:
10680 Collect all registers.
10683 Collect all function arguments.
10686 Collect all local variables.
10689 Collect the return address. This is helpful if you want to see more
10693 @vindex $_sdata@r{, collect}
10694 Collect static tracepoint marker specific data. Only available for
10695 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10696 Lists}. On the UST static tracepoints library backend, an
10697 instrumentation point resembles a @code{printf} function call. The
10698 tracing library is able to collect user specified data formatted to a
10699 character string using the format provided by the programmer that
10700 instrumented the program. Other backends have similar mechanisms.
10701 Here's an example of a UST marker call:
10704 const char master_name[] = "$your_name";
10705 trace_mark(channel1, marker1, "hello %s", master_name)
10708 In this case, collecting @code{$_sdata} collects the string
10709 @samp{hello $yourname}. When analyzing the trace buffer, you can
10710 inspect @samp{$_sdata} like any other variable available to
10714 You can give several consecutive @code{collect} commands, each one
10715 with a single argument, or one @code{collect} command with several
10716 arguments separated by commas; the effect is the same.
10718 The optional @var{mods} changes the usual handling of the arguments.
10719 @code{s} requests that pointers to chars be handled as strings, in
10720 particular collecting the contents of the memory being pointed at, up
10721 to the first zero. The upper bound is by default the value of the
10722 @code{print elements} variable; if @code{s} is followed by a decimal
10723 number, that is the upper bound instead. So for instance
10724 @samp{collect/s25 mystr} collects as many as 25 characters at
10727 The command @code{info scope} (@pxref{Symbols, info scope}) is
10728 particularly useful for figuring out what data to collect.
10730 @kindex teval @r{(tracepoints)}
10731 @item teval @var{expr1}, @var{expr2}, @dots{}
10732 Evaluate the given expressions when the tracepoint is hit. This
10733 command accepts a comma-separated list of expressions. The results
10734 are discarded, so this is mainly useful for assigning values to trace
10735 state variables (@pxref{Trace State Variables}) without adding those
10736 values to the trace buffer, as would be the case if the @code{collect}
10739 @kindex while-stepping @r{(tracepoints)}
10740 @item while-stepping @var{n}
10741 Perform @var{n} single-step instruction traces after the tracepoint,
10742 collecting new data after each step. The @code{while-stepping}
10743 command is followed by the list of what to collect while stepping
10744 (followed by its own @code{end} command):
10747 > while-stepping 12
10748 > collect $regs, myglobal
10754 Note that @code{$pc} is not automatically collected by
10755 @code{while-stepping}; you need to explicitly collect that register if
10756 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10759 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10760 @kindex set default-collect
10761 @cindex default collection action
10762 This variable is a list of expressions to collect at each tracepoint
10763 hit. It is effectively an additional @code{collect} action prepended
10764 to every tracepoint action list. The expressions are parsed
10765 individually for each tracepoint, so for instance a variable named
10766 @code{xyz} may be interpreted as a global for one tracepoint, and a
10767 local for another, as appropriate to the tracepoint's location.
10769 @item show default-collect
10770 @kindex show default-collect
10771 Show the list of expressions that are collected by default at each
10776 @node Listing Tracepoints
10777 @subsection Listing Tracepoints
10780 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10781 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10782 @cindex information about tracepoints
10783 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10784 Display information about the tracepoint @var{num}. If you don't
10785 specify a tracepoint number, displays information about all the
10786 tracepoints defined so far. The format is similar to that used for
10787 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10788 command, simply restricting itself to tracepoints.
10790 A tracepoint's listing may include additional information specific to
10795 its passcount as given by the @code{passcount @var{n}} command
10799 (@value{GDBP}) @b{info trace}
10800 Num Type Disp Enb Address What
10801 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10803 collect globfoo, $regs
10812 This command can be abbreviated @code{info tp}.
10815 @node Listing Static Tracepoint Markers
10816 @subsection Listing Static Tracepoint Markers
10819 @kindex info static-tracepoint-markers
10820 @cindex information about static tracepoint markers
10821 @item info static-tracepoint-markers
10822 Display information about all static tracepoint markers defined in the
10825 For each marker, the following columns are printed:
10829 An incrementing counter, output to help readability. This is not a
10832 The marker ID, as reported by the target.
10833 @item Enabled or Disabled
10834 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10835 that are not enabled.
10837 Where the marker is in your program, as a memory address.
10839 Where the marker is in the source for your program, as a file and line
10840 number. If the debug information included in the program does not
10841 allow @value{GDBN} to locate the source of the marker, this column
10842 will be left blank.
10846 In addition, the following information may be printed for each marker:
10850 User data passed to the tracing library by the marker call. In the
10851 UST backend, this is the format string passed as argument to the
10853 @item Static tracepoints probing the marker
10854 The list of static tracepoints attached to the marker.
10858 (@value{GDBP}) info static-tracepoint-markers
10859 Cnt ID Enb Address What
10860 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10861 Data: number1 %d number2 %d
10862 Probed by static tracepoints: #2
10863 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10869 @node Starting and Stopping Trace Experiments
10870 @subsection Starting and Stopping Trace Experiments
10874 @cindex start a new trace experiment
10875 @cindex collected data discarded
10877 This command takes no arguments. It starts the trace experiment, and
10878 begins collecting data. This has the side effect of discarding all
10879 the data collected in the trace buffer during the previous trace
10883 @cindex stop a running trace experiment
10885 This command takes no arguments. It ends the trace experiment, and
10886 stops collecting data.
10888 @strong{Note}: a trace experiment and data collection may stop
10889 automatically if any tracepoint's passcount is reached
10890 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10893 @cindex status of trace data collection
10894 @cindex trace experiment, status of
10896 This command displays the status of the current trace data
10900 Here is an example of the commands we described so far:
10903 (@value{GDBP}) @b{trace gdb_c_test}
10904 (@value{GDBP}) @b{actions}
10905 Enter actions for tracepoint #1, one per line.
10906 > collect $regs,$locals,$args
10907 > while-stepping 11
10911 (@value{GDBP}) @b{tstart}
10912 [time passes @dots{}]
10913 (@value{GDBP}) @b{tstop}
10916 @anchor{disconnected tracing}
10917 @cindex disconnected tracing
10918 You can choose to continue running the trace experiment even if
10919 @value{GDBN} disconnects from the target, voluntarily or
10920 involuntarily. For commands such as @code{detach}, the debugger will
10921 ask what you want to do with the trace. But for unexpected
10922 terminations (@value{GDBN} crash, network outage), it would be
10923 unfortunate to lose hard-won trace data, so the variable
10924 @code{disconnected-tracing} lets you decide whether the trace should
10925 continue running without @value{GDBN}.
10928 @item set disconnected-tracing on
10929 @itemx set disconnected-tracing off
10930 @kindex set disconnected-tracing
10931 Choose whether a tracing run should continue to run if @value{GDBN}
10932 has disconnected from the target. Note that @code{detach} or
10933 @code{quit} will ask you directly what to do about a running trace no
10934 matter what this variable's setting, so the variable is mainly useful
10935 for handling unexpected situations, such as loss of the network.
10937 @item show disconnected-tracing
10938 @kindex show disconnected-tracing
10939 Show the current choice for disconnected tracing.
10943 When you reconnect to the target, the trace experiment may or may not
10944 still be running; it might have filled the trace buffer in the
10945 meantime, or stopped for one of the other reasons. If it is running,
10946 it will continue after reconnection.
10948 Upon reconnection, the target will upload information about the
10949 tracepoints in effect. @value{GDBN} will then compare that
10950 information to the set of tracepoints currently defined, and attempt
10951 to match them up, allowing for the possibility that the numbers may
10952 have changed due to creation and deletion in the meantime. If one of
10953 the target's tracepoints does not match any in @value{GDBN}, the
10954 debugger will create a new tracepoint, so that you have a number with
10955 which to specify that tracepoint. This matching-up process is
10956 necessarily heuristic, and it may result in useless tracepoints being
10957 created; you may simply delete them if they are of no use.
10959 @cindex circular trace buffer
10960 If your target agent supports a @dfn{circular trace buffer}, then you
10961 can run a trace experiment indefinitely without filling the trace
10962 buffer; when space runs out, the agent deletes already-collected trace
10963 frames, oldest first, until there is enough room to continue
10964 collecting. This is especially useful if your tracepoints are being
10965 hit too often, and your trace gets terminated prematurely because the
10966 buffer is full. To ask for a circular trace buffer, simply set
10967 @samp{circular-trace-buffer} to on. You can set this at any time,
10968 including during tracing; if the agent can do it, it will change
10969 buffer handling on the fly, otherwise it will not take effect until
10973 @item set circular-trace-buffer on
10974 @itemx set circular-trace-buffer off
10975 @kindex set circular-trace-buffer
10976 Choose whether a tracing run should use a linear or circular buffer
10977 for trace data. A linear buffer will not lose any trace data, but may
10978 fill up prematurely, while a circular buffer will discard old trace
10979 data, but it will have always room for the latest tracepoint hits.
10981 @item show circular-trace-buffer
10982 @kindex show circular-trace-buffer
10983 Show the current choice for the trace buffer. Note that this may not
10984 match the agent's current buffer handling, nor is it guaranteed to
10985 match the setting that might have been in effect during a past run,
10986 for instance if you are looking at frames from a trace file.
10990 @node Tracepoint Restrictions
10991 @subsection Tracepoint Restrictions
10993 @cindex tracepoint restrictions
10994 There are a number of restrictions on the use of tracepoints. As
10995 described above, tracepoint data gathering occurs on the target
10996 without interaction from @value{GDBN}. Thus the full capabilities of
10997 the debugger are not available during data gathering, and then at data
10998 examination time, you will be limited by only having what was
10999 collected. The following items describe some common problems, but it
11000 is not exhaustive, and you may run into additional difficulties not
11006 Tracepoint expressions are intended to gather objects (lvalues). Thus
11007 the full flexibility of GDB's expression evaluator is not available.
11008 You cannot call functions, cast objects to aggregate types, access
11009 convenience variables or modify values (except by assignment to trace
11010 state variables). Some language features may implicitly call
11011 functions (for instance Objective-C fields with accessors), and therefore
11012 cannot be collected either.
11015 Collection of local variables, either individually or in bulk with
11016 @code{$locals} or @code{$args}, during @code{while-stepping} may
11017 behave erratically. The stepping action may enter a new scope (for
11018 instance by stepping into a function), or the location of the variable
11019 may change (for instance it is loaded into a register). The
11020 tracepoint data recorded uses the location information for the
11021 variables that is correct for the tracepoint location. When the
11022 tracepoint is created, it is not possible, in general, to determine
11023 where the steps of a @code{while-stepping} sequence will advance the
11024 program---particularly if a conditional branch is stepped.
11027 Collection of an incompletely-initialized or partially-destroyed object
11028 may result in something that @value{GDBN} cannot display, or displays
11029 in a misleading way.
11032 When @value{GDBN} displays a pointer to character it automatically
11033 dereferences the pointer to also display characters of the string
11034 being pointed to. However, collecting the pointer during tracing does
11035 not automatically collect the string. You need to explicitly
11036 dereference the pointer and provide size information if you want to
11037 collect not only the pointer, but the memory pointed to. For example,
11038 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11042 It is not possible to collect a complete stack backtrace at a
11043 tracepoint. Instead, you may collect the registers and a few hundred
11044 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11045 (adjust to use the name of the actual stack pointer register on your
11046 target architecture, and the amount of stack you wish to capture).
11047 Then the @code{backtrace} command will show a partial backtrace when
11048 using a trace frame. The number of stack frames that can be examined
11049 depends on the sizes of the frames in the collected stack. Note that
11050 if you ask for a block so large that it goes past the bottom of the
11051 stack, the target agent may report an error trying to read from an
11055 If you do not collect registers at a tracepoint, @value{GDBN} can
11056 infer that the value of @code{$pc} must be the same as the address of
11057 the tracepoint and use that when you are looking at a trace frame
11058 for that tracepoint. However, this cannot work if the tracepoint has
11059 multiple locations (for instance if it was set in a function that was
11060 inlined), or if it has a @code{while-stepping} loop. In those cases
11061 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11066 @node Analyze Collected Data
11067 @section Using the Collected Data
11069 After the tracepoint experiment ends, you use @value{GDBN} commands
11070 for examining the trace data. The basic idea is that each tracepoint
11071 collects a trace @dfn{snapshot} every time it is hit and another
11072 snapshot every time it single-steps. All these snapshots are
11073 consecutively numbered from zero and go into a buffer, and you can
11074 examine them later. The way you examine them is to @dfn{focus} on a
11075 specific trace snapshot. When the remote stub is focused on a trace
11076 snapshot, it will respond to all @value{GDBN} requests for memory and
11077 registers by reading from the buffer which belongs to that snapshot,
11078 rather than from @emph{real} memory or registers of the program being
11079 debugged. This means that @strong{all} @value{GDBN} commands
11080 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11081 behave as if we were currently debugging the program state as it was
11082 when the tracepoint occurred. Any requests for data that are not in
11083 the buffer will fail.
11086 * tfind:: How to select a trace snapshot
11087 * tdump:: How to display all data for a snapshot
11088 * save tracepoints:: How to save tracepoints for a future run
11092 @subsection @code{tfind @var{n}}
11095 @cindex select trace snapshot
11096 @cindex find trace snapshot
11097 The basic command for selecting a trace snapshot from the buffer is
11098 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11099 counting from zero. If no argument @var{n} is given, the next
11100 snapshot is selected.
11102 Here are the various forms of using the @code{tfind} command.
11106 Find the first snapshot in the buffer. This is a synonym for
11107 @code{tfind 0} (since 0 is the number of the first snapshot).
11110 Stop debugging trace snapshots, resume @emph{live} debugging.
11113 Same as @samp{tfind none}.
11116 No argument means find the next trace snapshot.
11119 Find the previous trace snapshot before the current one. This permits
11120 retracing earlier steps.
11122 @item tfind tracepoint @var{num}
11123 Find the next snapshot associated with tracepoint @var{num}. Search
11124 proceeds forward from the last examined trace snapshot. If no
11125 argument @var{num} is given, it means find the next snapshot collected
11126 for the same tracepoint as the current snapshot.
11128 @item tfind pc @var{addr}
11129 Find the next snapshot associated with the value @var{addr} of the
11130 program counter. Search proceeds forward from the last examined trace
11131 snapshot. If no argument @var{addr} is given, it means find the next
11132 snapshot with the same value of PC as the current snapshot.
11134 @item tfind outside @var{addr1}, @var{addr2}
11135 Find the next snapshot whose PC is outside the given range of
11136 addresses (exclusive).
11138 @item tfind range @var{addr1}, @var{addr2}
11139 Find the next snapshot whose PC is between @var{addr1} and
11140 @var{addr2} (inclusive).
11142 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11143 Find the next snapshot associated with the source line @var{n}. If
11144 the optional argument @var{file} is given, refer to line @var{n} in
11145 that source file. Search proceeds forward from the last examined
11146 trace snapshot. If no argument @var{n} is given, it means find the
11147 next line other than the one currently being examined; thus saying
11148 @code{tfind line} repeatedly can appear to have the same effect as
11149 stepping from line to line in a @emph{live} debugging session.
11152 The default arguments for the @code{tfind} commands are specifically
11153 designed to make it easy to scan through the trace buffer. For
11154 instance, @code{tfind} with no argument selects the next trace
11155 snapshot, and @code{tfind -} with no argument selects the previous
11156 trace snapshot. So, by giving one @code{tfind} command, and then
11157 simply hitting @key{RET} repeatedly you can examine all the trace
11158 snapshots in order. Or, by saying @code{tfind -} and then hitting
11159 @key{RET} repeatedly you can examine the snapshots in reverse order.
11160 The @code{tfind line} command with no argument selects the snapshot
11161 for the next source line executed. The @code{tfind pc} command with
11162 no argument selects the next snapshot with the same program counter
11163 (PC) as the current frame. The @code{tfind tracepoint} command with
11164 no argument selects the next trace snapshot collected by the same
11165 tracepoint as the current one.
11167 In addition to letting you scan through the trace buffer manually,
11168 these commands make it easy to construct @value{GDBN} scripts that
11169 scan through the trace buffer and print out whatever collected data
11170 you are interested in. Thus, if we want to examine the PC, FP, and SP
11171 registers from each trace frame in the buffer, we can say this:
11174 (@value{GDBP}) @b{tfind start}
11175 (@value{GDBP}) @b{while ($trace_frame != -1)}
11176 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11177 $trace_frame, $pc, $sp, $fp
11181 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11182 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11183 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11184 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11185 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11186 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11187 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11188 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11189 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11190 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11191 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11194 Or, if we want to examine the variable @code{X} at each source line in
11198 (@value{GDBP}) @b{tfind start}
11199 (@value{GDBP}) @b{while ($trace_frame != -1)}
11200 > printf "Frame %d, X == %d\n", $trace_frame, X
11210 @subsection @code{tdump}
11212 @cindex dump all data collected at tracepoint
11213 @cindex tracepoint data, display
11215 This command takes no arguments. It prints all the data collected at
11216 the current trace snapshot.
11219 (@value{GDBP}) @b{trace 444}
11220 (@value{GDBP}) @b{actions}
11221 Enter actions for tracepoint #2, one per line:
11222 > collect $regs, $locals, $args, gdb_long_test
11225 (@value{GDBP}) @b{tstart}
11227 (@value{GDBP}) @b{tfind line 444}
11228 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11230 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11232 (@value{GDBP}) @b{tdump}
11233 Data collected at tracepoint 2, trace frame 1:
11234 d0 0xc4aa0085 -995491707
11238 d4 0x71aea3d 119204413
11241 d7 0x380035 3670069
11242 a0 0x19e24a 1696330
11243 a1 0x3000668 50333288
11245 a3 0x322000 3284992
11246 a4 0x3000698 50333336
11247 a5 0x1ad3cc 1758156
11248 fp 0x30bf3c 0x30bf3c
11249 sp 0x30bf34 0x30bf34
11251 pc 0x20b2c8 0x20b2c8
11255 p = 0x20e5b4 "gdb-test"
11262 gdb_long_test = 17 '\021'
11267 @code{tdump} works by scanning the tracepoint's current collection
11268 actions and printing the value of each expression listed. So
11269 @code{tdump} can fail, if after a run, you change the tracepoint's
11270 actions to mention variables that were not collected during the run.
11272 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11273 uses the collected value of @code{$pc} to distinguish between trace
11274 frames that were collected at the tracepoint hit, and frames that were
11275 collected while stepping. This allows it to correctly choose whether
11276 to display the basic list of collections, or the collections from the
11277 body of the while-stepping loop. However, if @code{$pc} was not collected,
11278 then @code{tdump} will always attempt to dump using the basic collection
11279 list, and may fail if a while-stepping frame does not include all the
11280 same data that is collected at the tracepoint hit.
11281 @c This is getting pretty arcane, example would be good.
11283 @node save tracepoints
11284 @subsection @code{save tracepoints @var{filename}}
11285 @kindex save tracepoints
11286 @kindex save-tracepoints
11287 @cindex save tracepoints for future sessions
11289 This command saves all current tracepoint definitions together with
11290 their actions and passcounts, into a file @file{@var{filename}}
11291 suitable for use in a later debugging session. To read the saved
11292 tracepoint definitions, use the @code{source} command (@pxref{Command
11293 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11294 alias for @w{@code{save tracepoints}}
11296 @node Tracepoint Variables
11297 @section Convenience Variables for Tracepoints
11298 @cindex tracepoint variables
11299 @cindex convenience variables for tracepoints
11302 @vindex $trace_frame
11303 @item (int) $trace_frame
11304 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11305 snapshot is selected.
11307 @vindex $tracepoint
11308 @item (int) $tracepoint
11309 The tracepoint for the current trace snapshot.
11311 @vindex $trace_line
11312 @item (int) $trace_line
11313 The line number for the current trace snapshot.
11315 @vindex $trace_file
11316 @item (char []) $trace_file
11317 The source file for the current trace snapshot.
11319 @vindex $trace_func
11320 @item (char []) $trace_func
11321 The name of the function containing @code{$tracepoint}.
11324 Note: @code{$trace_file} is not suitable for use in @code{printf},
11325 use @code{output} instead.
11327 Here's a simple example of using these convenience variables for
11328 stepping through all the trace snapshots and printing some of their
11329 data. Note that these are not the same as trace state variables,
11330 which are managed by the target.
11333 (@value{GDBP}) @b{tfind start}
11335 (@value{GDBP}) @b{while $trace_frame != -1}
11336 > output $trace_file
11337 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11343 @section Using Trace Files
11344 @cindex trace files
11346 In some situations, the target running a trace experiment may no
11347 longer be available; perhaps it crashed, or the hardware was needed
11348 for a different activity. To handle these cases, you can arrange to
11349 dump the trace data into a file, and later use that file as a source
11350 of trace data, via the @code{target tfile} command.
11355 @item tsave [ -r ] @var{filename}
11356 Save the trace data to @var{filename}. By default, this command
11357 assumes that @var{filename} refers to the host filesystem, so if
11358 necessary @value{GDBN} will copy raw trace data up from the target and
11359 then save it. If the target supports it, you can also supply the
11360 optional argument @code{-r} (``remote'') to direct the target to save
11361 the data directly into @var{filename} in its own filesystem, which may be
11362 more efficient if the trace buffer is very large. (Note, however, that
11363 @code{target tfile} can only read from files accessible to the host.)
11365 @kindex target tfile
11367 @item target tfile @var{filename}
11368 Use the file named @var{filename} as a source of trace data. Commands
11369 that examine data work as they do with a live target, but it is not
11370 possible to run any new trace experiments. @code{tstatus} will report
11371 the state of the trace run at the moment the data was saved, as well
11372 as the current trace frame you are examining. @var{filename} must be
11373 on a filesystem accessible to the host.
11378 @chapter Debugging Programs That Use Overlays
11381 If your program is too large to fit completely in your target system's
11382 memory, you can sometimes use @dfn{overlays} to work around this
11383 problem. @value{GDBN} provides some support for debugging programs that
11387 * How Overlays Work:: A general explanation of overlays.
11388 * Overlay Commands:: Managing overlays in @value{GDBN}.
11389 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11390 mapped by asking the inferior.
11391 * Overlay Sample Program:: A sample program using overlays.
11394 @node How Overlays Work
11395 @section How Overlays Work
11396 @cindex mapped overlays
11397 @cindex unmapped overlays
11398 @cindex load address, overlay's
11399 @cindex mapped address
11400 @cindex overlay area
11402 Suppose you have a computer whose instruction address space is only 64
11403 kilobytes long, but which has much more memory which can be accessed by
11404 other means: special instructions, segment registers, or memory
11405 management hardware, for example. Suppose further that you want to
11406 adapt a program which is larger than 64 kilobytes to run on this system.
11408 One solution is to identify modules of your program which are relatively
11409 independent, and need not call each other directly; call these modules
11410 @dfn{overlays}. Separate the overlays from the main program, and place
11411 their machine code in the larger memory. Place your main program in
11412 instruction memory, but leave at least enough space there to hold the
11413 largest overlay as well.
11415 Now, to call a function located in an overlay, you must first copy that
11416 overlay's machine code from the large memory into the space set aside
11417 for it in the instruction memory, and then jump to its entry point
11420 @c NB: In the below the mapped area's size is greater or equal to the
11421 @c size of all overlays. This is intentional to remind the developer
11422 @c that overlays don't necessarily need to be the same size.
11426 Data Instruction Larger
11427 Address Space Address Space Address Space
11428 +-----------+ +-----------+ +-----------+
11430 +-----------+ +-----------+ +-----------+<-- overlay 1
11431 | program | | main | .----| overlay 1 | load address
11432 | variables | | program | | +-----------+
11433 | and heap | | | | | |
11434 +-----------+ | | | +-----------+<-- overlay 2
11435 | | +-----------+ | | | load address
11436 +-----------+ | | | .-| overlay 2 |
11438 mapped --->+-----------+ | | +-----------+
11439 address | | | | | |
11440 | overlay | <-' | | |
11441 | area | <---' +-----------+<-- overlay 3
11442 | | <---. | | load address
11443 +-----------+ `--| overlay 3 |
11450 @anchor{A code overlay}A code overlay
11454 The diagram (@pxref{A code overlay}) shows a system with separate data
11455 and instruction address spaces. To map an overlay, the program copies
11456 its code from the larger address space to the instruction address space.
11457 Since the overlays shown here all use the same mapped address, only one
11458 may be mapped at a time. For a system with a single address space for
11459 data and instructions, the diagram would be similar, except that the
11460 program variables and heap would share an address space with the main
11461 program and the overlay area.
11463 An overlay loaded into instruction memory and ready for use is called a
11464 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11465 instruction memory. An overlay not present (or only partially present)
11466 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11467 is its address in the larger memory. The mapped address is also called
11468 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11469 called the @dfn{load memory address}, or @dfn{LMA}.
11471 Unfortunately, overlays are not a completely transparent way to adapt a
11472 program to limited instruction memory. They introduce a new set of
11473 global constraints you must keep in mind as you design your program:
11478 Before calling or returning to a function in an overlay, your program
11479 must make sure that overlay is actually mapped. Otherwise, the call or
11480 return will transfer control to the right address, but in the wrong
11481 overlay, and your program will probably crash.
11484 If the process of mapping an overlay is expensive on your system, you
11485 will need to choose your overlays carefully to minimize their effect on
11486 your program's performance.
11489 The executable file you load onto your system must contain each
11490 overlay's instructions, appearing at the overlay's load address, not its
11491 mapped address. However, each overlay's instructions must be relocated
11492 and its symbols defined as if the overlay were at its mapped address.
11493 You can use GNU linker scripts to specify different load and relocation
11494 addresses for pieces of your program; see @ref{Overlay Description,,,
11495 ld.info, Using ld: the GNU linker}.
11498 The procedure for loading executable files onto your system must be able
11499 to load their contents into the larger address space as well as the
11500 instruction and data spaces.
11504 The overlay system described above is rather simple, and could be
11505 improved in many ways:
11510 If your system has suitable bank switch registers or memory management
11511 hardware, you could use those facilities to make an overlay's load area
11512 contents simply appear at their mapped address in instruction space.
11513 This would probably be faster than copying the overlay to its mapped
11514 area in the usual way.
11517 If your overlays are small enough, you could set aside more than one
11518 overlay area, and have more than one overlay mapped at a time.
11521 You can use overlays to manage data, as well as instructions. In
11522 general, data overlays are even less transparent to your design than
11523 code overlays: whereas code overlays only require care when you call or
11524 return to functions, data overlays require care every time you access
11525 the data. Also, if you change the contents of a data overlay, you
11526 must copy its contents back out to its load address before you can copy a
11527 different data overlay into the same mapped area.
11532 @node Overlay Commands
11533 @section Overlay Commands
11535 To use @value{GDBN}'s overlay support, each overlay in your program must
11536 correspond to a separate section of the executable file. The section's
11537 virtual memory address and load memory address must be the overlay's
11538 mapped and load addresses. Identifying overlays with sections allows
11539 @value{GDBN} to determine the appropriate address of a function or
11540 variable, depending on whether the overlay is mapped or not.
11542 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11543 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11548 Disable @value{GDBN}'s overlay support. When overlay support is
11549 disabled, @value{GDBN} assumes that all functions and variables are
11550 always present at their mapped addresses. By default, @value{GDBN}'s
11551 overlay support is disabled.
11553 @item overlay manual
11554 @cindex manual overlay debugging
11555 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11556 relies on you to tell it which overlays are mapped, and which are not,
11557 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11558 commands described below.
11560 @item overlay map-overlay @var{overlay}
11561 @itemx overlay map @var{overlay}
11562 @cindex map an overlay
11563 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11564 be the name of the object file section containing the overlay. When an
11565 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11566 functions and variables at their mapped addresses. @value{GDBN} assumes
11567 that any other overlays whose mapped ranges overlap that of
11568 @var{overlay} are now unmapped.
11570 @item overlay unmap-overlay @var{overlay}
11571 @itemx overlay unmap @var{overlay}
11572 @cindex unmap an overlay
11573 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11574 must be the name of the object file section containing the overlay.
11575 When an overlay is unmapped, @value{GDBN} assumes it can find the
11576 overlay's functions and variables at their load addresses.
11579 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11580 consults a data structure the overlay manager maintains in the inferior
11581 to see which overlays are mapped. For details, see @ref{Automatic
11582 Overlay Debugging}.
11584 @item overlay load-target
11585 @itemx overlay load
11586 @cindex reloading the overlay table
11587 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11588 re-reads the table @value{GDBN} automatically each time the inferior
11589 stops, so this command should only be necessary if you have changed the
11590 overlay mapping yourself using @value{GDBN}. This command is only
11591 useful when using automatic overlay debugging.
11593 @item overlay list-overlays
11594 @itemx overlay list
11595 @cindex listing mapped overlays
11596 Display a list of the overlays currently mapped, along with their mapped
11597 addresses, load addresses, and sizes.
11601 Normally, when @value{GDBN} prints a code address, it includes the name
11602 of the function the address falls in:
11605 (@value{GDBP}) print main
11606 $3 = @{int ()@} 0x11a0 <main>
11609 When overlay debugging is enabled, @value{GDBN} recognizes code in
11610 unmapped overlays, and prints the names of unmapped functions with
11611 asterisks around them. For example, if @code{foo} is a function in an
11612 unmapped overlay, @value{GDBN} prints it this way:
11615 (@value{GDBP}) overlay list
11616 No sections are mapped.
11617 (@value{GDBP}) print foo
11618 $5 = @{int (int)@} 0x100000 <*foo*>
11621 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11625 (@value{GDBP}) overlay list
11626 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11627 mapped at 0x1016 - 0x104a
11628 (@value{GDBP}) print foo
11629 $6 = @{int (int)@} 0x1016 <foo>
11632 When overlay debugging is enabled, @value{GDBN} can find the correct
11633 address for functions and variables in an overlay, whether or not the
11634 overlay is mapped. This allows most @value{GDBN} commands, like
11635 @code{break} and @code{disassemble}, to work normally, even on unmapped
11636 code. However, @value{GDBN}'s breakpoint support has some limitations:
11640 @cindex breakpoints in overlays
11641 @cindex overlays, setting breakpoints in
11642 You can set breakpoints in functions in unmapped overlays, as long as
11643 @value{GDBN} can write to the overlay at its load address.
11645 @value{GDBN} can not set hardware or simulator-based breakpoints in
11646 unmapped overlays. However, if you set a breakpoint at the end of your
11647 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11648 you are using manual overlay management), @value{GDBN} will re-set its
11649 breakpoints properly.
11653 @node Automatic Overlay Debugging
11654 @section Automatic Overlay Debugging
11655 @cindex automatic overlay debugging
11657 @value{GDBN} can automatically track which overlays are mapped and which
11658 are not, given some simple co-operation from the overlay manager in the
11659 inferior. If you enable automatic overlay debugging with the
11660 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11661 looks in the inferior's memory for certain variables describing the
11662 current state of the overlays.
11664 Here are the variables your overlay manager must define to support
11665 @value{GDBN}'s automatic overlay debugging:
11669 @item @code{_ovly_table}:
11670 This variable must be an array of the following structures:
11675 /* The overlay's mapped address. */
11678 /* The size of the overlay, in bytes. */
11679 unsigned long size;
11681 /* The overlay's load address. */
11684 /* Non-zero if the overlay is currently mapped;
11686 unsigned long mapped;
11690 @item @code{_novlys}:
11691 This variable must be a four-byte signed integer, holding the total
11692 number of elements in @code{_ovly_table}.
11696 To decide whether a particular overlay is mapped or not, @value{GDBN}
11697 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11698 @code{lma} members equal the VMA and LMA of the overlay's section in the
11699 executable file. When @value{GDBN} finds a matching entry, it consults
11700 the entry's @code{mapped} member to determine whether the overlay is
11703 In addition, your overlay manager may define a function called
11704 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11705 will silently set a breakpoint there. If the overlay manager then
11706 calls this function whenever it has changed the overlay table, this
11707 will enable @value{GDBN} to accurately keep track of which overlays
11708 are in program memory, and update any breakpoints that may be set
11709 in overlays. This will allow breakpoints to work even if the
11710 overlays are kept in ROM or other non-writable memory while they
11711 are not being executed.
11713 @node Overlay Sample Program
11714 @section Overlay Sample Program
11715 @cindex overlay example program
11717 When linking a program which uses overlays, you must place the overlays
11718 at their load addresses, while relocating them to run at their mapped
11719 addresses. To do this, you must write a linker script (@pxref{Overlay
11720 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11721 since linker scripts are specific to a particular host system, target
11722 architecture, and target memory layout, this manual cannot provide
11723 portable sample code demonstrating @value{GDBN}'s overlay support.
11725 However, the @value{GDBN} source distribution does contain an overlaid
11726 program, with linker scripts for a few systems, as part of its test
11727 suite. The program consists of the following files from
11728 @file{gdb/testsuite/gdb.base}:
11732 The main program file.
11734 A simple overlay manager, used by @file{overlays.c}.
11739 Overlay modules, loaded and used by @file{overlays.c}.
11742 Linker scripts for linking the test program on the @code{d10v-elf}
11743 and @code{m32r-elf} targets.
11746 You can build the test program using the @code{d10v-elf} GCC
11747 cross-compiler like this:
11750 $ d10v-elf-gcc -g -c overlays.c
11751 $ d10v-elf-gcc -g -c ovlymgr.c
11752 $ d10v-elf-gcc -g -c foo.c
11753 $ d10v-elf-gcc -g -c bar.c
11754 $ d10v-elf-gcc -g -c baz.c
11755 $ d10v-elf-gcc -g -c grbx.c
11756 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11757 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11760 The build process is identical for any other architecture, except that
11761 you must substitute the appropriate compiler and linker script for the
11762 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11766 @chapter Using @value{GDBN} with Different Languages
11769 Although programming languages generally have common aspects, they are
11770 rarely expressed in the same manner. For instance, in ANSI C,
11771 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11772 Modula-2, it is accomplished by @code{p^}. Values can also be
11773 represented (and displayed) differently. Hex numbers in C appear as
11774 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11776 @cindex working language
11777 Language-specific information is built into @value{GDBN} for some languages,
11778 allowing you to express operations like the above in your program's
11779 native language, and allowing @value{GDBN} to output values in a manner
11780 consistent with the syntax of your program's native language. The
11781 language you use to build expressions is called the @dfn{working
11785 * Setting:: Switching between source languages
11786 * Show:: Displaying the language
11787 * Checks:: Type and range checks
11788 * Supported Languages:: Supported languages
11789 * Unsupported Languages:: Unsupported languages
11793 @section Switching Between Source Languages
11795 There are two ways to control the working language---either have @value{GDBN}
11796 set it automatically, or select it manually yourself. You can use the
11797 @code{set language} command for either purpose. On startup, @value{GDBN}
11798 defaults to setting the language automatically. The working language is
11799 used to determine how expressions you type are interpreted, how values
11802 In addition to the working language, every source file that
11803 @value{GDBN} knows about has its own working language. For some object
11804 file formats, the compiler might indicate which language a particular
11805 source file is in. However, most of the time @value{GDBN} infers the
11806 language from the name of the file. The language of a source file
11807 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11808 show each frame appropriately for its own language. There is no way to
11809 set the language of a source file from within @value{GDBN}, but you can
11810 set the language associated with a filename extension. @xref{Show, ,
11811 Displaying the Language}.
11813 This is most commonly a problem when you use a program, such
11814 as @code{cfront} or @code{f2c}, that generates C but is written in
11815 another language. In that case, make the
11816 program use @code{#line} directives in its C output; that way
11817 @value{GDBN} will know the correct language of the source code of the original
11818 program, and will display that source code, not the generated C code.
11821 * Filenames:: Filename extensions and languages.
11822 * Manually:: Setting the working language manually
11823 * Automatically:: Having @value{GDBN} infer the source language
11827 @subsection List of Filename Extensions and Languages
11829 If a source file name ends in one of the following extensions, then
11830 @value{GDBN} infers that its language is the one indicated.
11848 C@t{++} source file
11854 Objective-C source file
11858 Fortran source file
11861 Modula-2 source file
11865 Assembler source file. This actually behaves almost like C, but
11866 @value{GDBN} does not skip over function prologues when stepping.
11869 In addition, you may set the language associated with a filename
11870 extension. @xref{Show, , Displaying the Language}.
11873 @subsection Setting the Working Language
11875 If you allow @value{GDBN} to set the language automatically,
11876 expressions are interpreted the same way in your debugging session and
11879 @kindex set language
11880 If you wish, you may set the language manually. To do this, issue the
11881 command @samp{set language @var{lang}}, where @var{lang} is the name of
11882 a language, such as
11883 @code{c} or @code{modula-2}.
11884 For a list of the supported languages, type @samp{set language}.
11886 Setting the language manually prevents @value{GDBN} from updating the working
11887 language automatically. This can lead to confusion if you try
11888 to debug a program when the working language is not the same as the
11889 source language, when an expression is acceptable to both
11890 languages---but means different things. For instance, if the current
11891 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11899 might not have the effect you intended. In C, this means to add
11900 @code{b} and @code{c} and place the result in @code{a}. The result
11901 printed would be the value of @code{a}. In Modula-2, this means to compare
11902 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11904 @node Automatically
11905 @subsection Having @value{GDBN} Infer the Source Language
11907 To have @value{GDBN} set the working language automatically, use
11908 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11909 then infers the working language. That is, when your program stops in a
11910 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11911 working language to the language recorded for the function in that
11912 frame. If the language for a frame is unknown (that is, if the function
11913 or block corresponding to the frame was defined in a source file that
11914 does not have a recognized extension), the current working language is
11915 not changed, and @value{GDBN} issues a warning.
11917 This may not seem necessary for most programs, which are written
11918 entirely in one source language. However, program modules and libraries
11919 written in one source language can be used by a main program written in
11920 a different source language. Using @samp{set language auto} in this
11921 case frees you from having to set the working language manually.
11924 @section Displaying the Language
11926 The following commands help you find out which language is the
11927 working language, and also what language source files were written in.
11930 @item show language
11931 @kindex show language
11932 Display the current working language. This is the
11933 language you can use with commands such as @code{print} to
11934 build and compute expressions that may involve variables in your program.
11937 @kindex info frame@r{, show the source language}
11938 Display the source language for this frame. This language becomes the
11939 working language if you use an identifier from this frame.
11940 @xref{Frame Info, ,Information about a Frame}, to identify the other
11941 information listed here.
11944 @kindex info source@r{, show the source language}
11945 Display the source language of this source file.
11946 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11947 information listed here.
11950 In unusual circumstances, you may have source files with extensions
11951 not in the standard list. You can then set the extension associated
11952 with a language explicitly:
11955 @item set extension-language @var{ext} @var{language}
11956 @kindex set extension-language
11957 Tell @value{GDBN} that source files with extension @var{ext} are to be
11958 assumed as written in the source language @var{language}.
11960 @item info extensions
11961 @kindex info extensions
11962 List all the filename extensions and the associated languages.
11966 @section Type and Range Checking
11969 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11970 checking are included, but they do not yet have any effect. This
11971 section documents the intended facilities.
11973 @c FIXME remove warning when type/range code added
11975 Some languages are designed to guard you against making seemingly common
11976 errors through a series of compile- and run-time checks. These include
11977 checking the type of arguments to functions and operators, and making
11978 sure mathematical overflows are caught at run time. Checks such as
11979 these help to ensure a program's correctness once it has been compiled
11980 by eliminating type mismatches, and providing active checks for range
11981 errors when your program is running.
11983 @value{GDBN} can check for conditions like the above if you wish.
11984 Although @value{GDBN} does not check the statements in your program,
11985 it can check expressions entered directly into @value{GDBN} for
11986 evaluation via the @code{print} command, for example. As with the
11987 working language, @value{GDBN} can also decide whether or not to check
11988 automatically based on your program's source language.
11989 @xref{Supported Languages, ,Supported Languages}, for the default
11990 settings of supported languages.
11993 * Type Checking:: An overview of type checking
11994 * Range Checking:: An overview of range checking
11997 @cindex type checking
11998 @cindex checks, type
11999 @node Type Checking
12000 @subsection An Overview of Type Checking
12002 Some languages, such as Modula-2, are strongly typed, meaning that the
12003 arguments to operators and functions have to be of the correct type,
12004 otherwise an error occurs. These checks prevent type mismatch
12005 errors from ever causing any run-time problems. For example,
12013 The second example fails because the @code{CARDINAL} 1 is not
12014 type-compatible with the @code{REAL} 2.3.
12016 For the expressions you use in @value{GDBN} commands, you can tell the
12017 @value{GDBN} type checker to skip checking;
12018 to treat any mismatches as errors and abandon the expression;
12019 or to only issue warnings when type mismatches occur,
12020 but evaluate the expression anyway. When you choose the last of
12021 these, @value{GDBN} evaluates expressions like the second example above, but
12022 also issues a warning.
12024 Even if you turn type checking off, there may be other reasons
12025 related to type that prevent @value{GDBN} from evaluating an expression.
12026 For instance, @value{GDBN} does not know how to add an @code{int} and
12027 a @code{struct foo}. These particular type errors have nothing to do
12028 with the language in use, and usually arise from expressions, such as
12029 the one described above, which make little sense to evaluate anyway.
12031 Each language defines to what degree it is strict about type. For
12032 instance, both Modula-2 and C require the arguments to arithmetical
12033 operators to be numbers. In C, enumerated types and pointers can be
12034 represented as numbers, so that they are valid arguments to mathematical
12035 operators. @xref{Supported Languages, ,Supported Languages}, for further
12036 details on specific languages.
12038 @value{GDBN} provides some additional commands for controlling the type checker:
12040 @kindex set check type
12041 @kindex show check type
12043 @item set check type auto
12044 Set type checking on or off based on the current working language.
12045 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12048 @item set check type on
12049 @itemx set check type off
12050 Set type checking on or off, overriding the default setting for the
12051 current working language. Issue a warning if the setting does not
12052 match the language default. If any type mismatches occur in
12053 evaluating an expression while type checking is on, @value{GDBN} prints a
12054 message and aborts evaluation of the expression.
12056 @item set check type warn
12057 Cause the type checker to issue warnings, but to always attempt to
12058 evaluate the expression. Evaluating the expression may still
12059 be impossible for other reasons. For example, @value{GDBN} cannot add
12060 numbers and structures.
12063 Show the current setting of the type checker, and whether or not @value{GDBN}
12064 is setting it automatically.
12067 @cindex range checking
12068 @cindex checks, range
12069 @node Range Checking
12070 @subsection An Overview of Range Checking
12072 In some languages (such as Modula-2), it is an error to exceed the
12073 bounds of a type; this is enforced with run-time checks. Such range
12074 checking is meant to ensure program correctness by making sure
12075 computations do not overflow, or indices on an array element access do
12076 not exceed the bounds of the array.
12078 For expressions you use in @value{GDBN} commands, you can tell
12079 @value{GDBN} to treat range errors in one of three ways: ignore them,
12080 always treat them as errors and abandon the expression, or issue
12081 warnings but evaluate the expression anyway.
12083 A range error can result from numerical overflow, from exceeding an
12084 array index bound, or when you type a constant that is not a member
12085 of any type. Some languages, however, do not treat overflows as an
12086 error. In many implementations of C, mathematical overflow causes the
12087 result to ``wrap around'' to lower values---for example, if @var{m} is
12088 the largest integer value, and @var{s} is the smallest, then
12091 @var{m} + 1 @result{} @var{s}
12094 This, too, is specific to individual languages, and in some cases
12095 specific to individual compilers or machines. @xref{Supported Languages, ,
12096 Supported Languages}, for further details on specific languages.
12098 @value{GDBN} provides some additional commands for controlling the range checker:
12100 @kindex set check range
12101 @kindex show check range
12103 @item set check range auto
12104 Set range checking on or off based on the current working language.
12105 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12108 @item set check range on
12109 @itemx set check range off
12110 Set range checking on or off, overriding the default setting for the
12111 current working language. A warning is issued if the setting does not
12112 match the language default. If a range error occurs and range checking is on,
12113 then a message is printed and evaluation of the expression is aborted.
12115 @item set check range warn
12116 Output messages when the @value{GDBN} range checker detects a range error,
12117 but attempt to evaluate the expression anyway. Evaluating the
12118 expression may still be impossible for other reasons, such as accessing
12119 memory that the process does not own (a typical example from many Unix
12123 Show the current setting of the range checker, and whether or not it is
12124 being set automatically by @value{GDBN}.
12127 @node Supported Languages
12128 @section Supported Languages
12130 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12131 assembly, Modula-2, and Ada.
12132 @c This is false ...
12133 Some @value{GDBN} features may be used in expressions regardless of the
12134 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12135 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12136 ,Expressions}) can be used with the constructs of any supported
12139 The following sections detail to what degree each source language is
12140 supported by @value{GDBN}. These sections are not meant to be language
12141 tutorials or references, but serve only as a reference guide to what the
12142 @value{GDBN} expression parser accepts, and what input and output
12143 formats should look like for different languages. There are many good
12144 books written on each of these languages; please look to these for a
12145 language reference or tutorial.
12148 * C:: C and C@t{++}
12150 * Objective-C:: Objective-C
12151 * OpenCL C:: OpenCL C
12152 * Fortran:: Fortran
12154 * Modula-2:: Modula-2
12159 @subsection C and C@t{++}
12161 @cindex C and C@t{++}
12162 @cindex expressions in C or C@t{++}
12164 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12165 to both languages. Whenever this is the case, we discuss those languages
12169 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12170 @cindex @sc{gnu} C@t{++}
12171 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12172 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12173 effectively, you must compile your C@t{++} programs with a supported
12174 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12175 compiler (@code{aCC}).
12178 * C Operators:: C and C@t{++} operators
12179 * C Constants:: C and C@t{++} constants
12180 * C Plus Plus Expressions:: C@t{++} expressions
12181 * C Defaults:: Default settings for C and C@t{++}
12182 * C Checks:: C and C@t{++} type and range checks
12183 * Debugging C:: @value{GDBN} and C
12184 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12185 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12189 @subsubsection C and C@t{++} Operators
12191 @cindex C and C@t{++} operators
12193 Operators must be defined on values of specific types. For instance,
12194 @code{+} is defined on numbers, but not on structures. Operators are
12195 often defined on groups of types.
12197 For the purposes of C and C@t{++}, the following definitions hold:
12202 @emph{Integral types} include @code{int} with any of its storage-class
12203 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12206 @emph{Floating-point types} include @code{float}, @code{double}, and
12207 @code{long double} (if supported by the target platform).
12210 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12213 @emph{Scalar types} include all of the above.
12218 The following operators are supported. They are listed here
12219 in order of increasing precedence:
12223 The comma or sequencing operator. Expressions in a comma-separated list
12224 are evaluated from left to right, with the result of the entire
12225 expression being the last expression evaluated.
12228 Assignment. The value of an assignment expression is the value
12229 assigned. Defined on scalar types.
12232 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12233 and translated to @w{@code{@var{a} = @var{a op b}}}.
12234 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12235 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12236 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12239 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12240 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12244 Logical @sc{or}. Defined on integral types.
12247 Logical @sc{and}. Defined on integral types.
12250 Bitwise @sc{or}. Defined on integral types.
12253 Bitwise exclusive-@sc{or}. Defined on integral types.
12256 Bitwise @sc{and}. Defined on integral types.
12259 Equality and inequality. Defined on scalar types. The value of these
12260 expressions is 0 for false and non-zero for true.
12262 @item <@r{, }>@r{, }<=@r{, }>=
12263 Less than, greater than, less than or equal, greater than or equal.
12264 Defined on scalar types. The value of these expressions is 0 for false
12265 and non-zero for true.
12268 left shift, and right shift. Defined on integral types.
12271 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12274 Addition and subtraction. Defined on integral types, floating-point types and
12277 @item *@r{, }/@r{, }%
12278 Multiplication, division, and modulus. Multiplication and division are
12279 defined on integral and floating-point types. Modulus is defined on
12283 Increment and decrement. When appearing before a variable, the
12284 operation is performed before the variable is used in an expression;
12285 when appearing after it, the variable's value is used before the
12286 operation takes place.
12289 Pointer dereferencing. Defined on pointer types. Same precedence as
12293 Address operator. Defined on variables. Same precedence as @code{++}.
12295 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12296 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12297 to examine the address
12298 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12302 Negative. Defined on integral and floating-point types. Same
12303 precedence as @code{++}.
12306 Logical negation. Defined on integral types. Same precedence as
12310 Bitwise complement operator. Defined on integral types. Same precedence as
12315 Structure member, and pointer-to-structure member. For convenience,
12316 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12317 pointer based on the stored type information.
12318 Defined on @code{struct} and @code{union} data.
12321 Dereferences of pointers to members.
12324 Array indexing. @code{@var{a}[@var{i}]} is defined as
12325 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12328 Function parameter list. Same precedence as @code{->}.
12331 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12332 and @code{class} types.
12335 Doubled colons also represent the @value{GDBN} scope operator
12336 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12340 If an operator is redefined in the user code, @value{GDBN} usually
12341 attempts to invoke the redefined version instead of using the operator's
12342 predefined meaning.
12345 @subsubsection C and C@t{++} Constants
12347 @cindex C and C@t{++} constants
12349 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12354 Integer constants are a sequence of digits. Octal constants are
12355 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12356 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12357 @samp{l}, specifying that the constant should be treated as a
12361 Floating point constants are a sequence of digits, followed by a decimal
12362 point, followed by a sequence of digits, and optionally followed by an
12363 exponent. An exponent is of the form:
12364 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12365 sequence of digits. The @samp{+} is optional for positive exponents.
12366 A floating-point constant may also end with a letter @samp{f} or
12367 @samp{F}, specifying that the constant should be treated as being of
12368 the @code{float} (as opposed to the default @code{double}) type; or with
12369 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12373 Enumerated constants consist of enumerated identifiers, or their
12374 integral equivalents.
12377 Character constants are a single character surrounded by single quotes
12378 (@code{'}), or a number---the ordinal value of the corresponding character
12379 (usually its @sc{ascii} value). Within quotes, the single character may
12380 be represented by a letter or by @dfn{escape sequences}, which are of
12381 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12382 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12383 @samp{@var{x}} is a predefined special character---for example,
12384 @samp{\n} for newline.
12386 Wide character constants can be written by prefixing a character
12387 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12388 form of @samp{x}. The target wide character set is used when
12389 computing the value of this constant (@pxref{Character Sets}).
12392 String constants are a sequence of character constants surrounded by
12393 double quotes (@code{"}). Any valid character constant (as described
12394 above) may appear. Double quotes within the string must be preceded by
12395 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12398 Wide string constants can be written by prefixing a string constant
12399 with @samp{L}, as in C. The target wide character set is used when
12400 computing the value of this constant (@pxref{Character Sets}).
12403 Pointer constants are an integral value. You can also write pointers
12404 to constants using the C operator @samp{&}.
12407 Array constants are comma-separated lists surrounded by braces @samp{@{}
12408 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12409 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12410 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12413 @node C Plus Plus Expressions
12414 @subsubsection C@t{++} Expressions
12416 @cindex expressions in C@t{++}
12417 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12419 @cindex debugging C@t{++} programs
12420 @cindex C@t{++} compilers
12421 @cindex debug formats and C@t{++}
12422 @cindex @value{NGCC} and C@t{++}
12424 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12425 the proper compiler and the proper debug format. Currently,
12426 @value{GDBN} works best when debugging C@t{++} code that is compiled
12427 with the most recent version of @value{NGCC} possible. The DWARF
12428 debugging format is preferred; @value{NGCC} defaults to this on most
12429 popular platforms. Other compilers and/or debug formats are likely to
12430 work badly or not at all when using @value{GDBN} to debug C@t{++}
12431 code. @xref{Compilation}.
12436 @cindex member functions
12438 Member function calls are allowed; you can use expressions like
12441 count = aml->GetOriginal(x, y)
12444 @vindex this@r{, inside C@t{++} member functions}
12445 @cindex namespace in C@t{++}
12447 While a member function is active (in the selected stack frame), your
12448 expressions have the same namespace available as the member function;
12449 that is, @value{GDBN} allows implicit references to the class instance
12450 pointer @code{this} following the same rules as C@t{++}. @code{using}
12451 declarations in the current scope are also respected by @value{GDBN}.
12453 @cindex call overloaded functions
12454 @cindex overloaded functions, calling
12455 @cindex type conversions in C@t{++}
12457 You can call overloaded functions; @value{GDBN} resolves the function
12458 call to the right definition, with some restrictions. @value{GDBN} does not
12459 perform overload resolution involving user-defined type conversions,
12460 calls to constructors, or instantiations of templates that do not exist
12461 in the program. It also cannot handle ellipsis argument lists or
12464 It does perform integral conversions and promotions, floating-point
12465 promotions, arithmetic conversions, pointer conversions, conversions of
12466 class objects to base classes, and standard conversions such as those of
12467 functions or arrays to pointers; it requires an exact match on the
12468 number of function arguments.
12470 Overload resolution is always performed, unless you have specified
12471 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12472 ,@value{GDBN} Features for C@t{++}}.
12474 You must specify @code{set overload-resolution off} in order to use an
12475 explicit function signature to call an overloaded function, as in
12477 p 'foo(char,int)'('x', 13)
12480 The @value{GDBN} command-completion facility can simplify this;
12481 see @ref{Completion, ,Command Completion}.
12483 @cindex reference declarations
12485 @value{GDBN} understands variables declared as C@t{++} references; you can use
12486 them in expressions just as you do in C@t{++} source---they are automatically
12489 In the parameter list shown when @value{GDBN} displays a frame, the values of
12490 reference variables are not displayed (unlike other variables); this
12491 avoids clutter, since references are often used for large structures.
12492 The @emph{address} of a reference variable is always shown, unless
12493 you have specified @samp{set print address off}.
12496 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12497 expressions can use it just as expressions in your program do. Since
12498 one scope may be defined in another, you can use @code{::} repeatedly if
12499 necessary, for example in an expression like
12500 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12501 resolving name scope by reference to source files, in both C and C@t{++}
12502 debugging (@pxref{Variables, ,Program Variables}).
12505 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12510 @subsubsection C and C@t{++} Defaults
12512 @cindex C and C@t{++} defaults
12514 If you allow @value{GDBN} to set type and range checking automatically, they
12515 both default to @code{off} whenever the working language changes to
12516 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12517 selects the working language.
12519 If you allow @value{GDBN} to set the language automatically, it
12520 recognizes source files whose names end with @file{.c}, @file{.C}, or
12521 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12522 these files, it sets the working language to C or C@t{++}.
12523 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12524 for further details.
12526 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12527 @c unimplemented. If (b) changes, it might make sense to let this node
12528 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12531 @subsubsection C and C@t{++} Type and Range Checks
12533 @cindex C and C@t{++} checks
12535 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12536 is not used. However, if you turn type checking on, @value{GDBN}
12537 considers two variables type equivalent if:
12541 The two variables are structured and have the same structure, union, or
12545 The two variables have the same type name, or types that have been
12546 declared equivalent through @code{typedef}.
12549 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12552 The two @code{struct}, @code{union}, or @code{enum} variables are
12553 declared in the same declaration. (Note: this may not be true for all C
12558 Range checking, if turned on, is done on mathematical operations. Array
12559 indices are not checked, since they are often used to index a pointer
12560 that is not itself an array.
12563 @subsubsection @value{GDBN} and C
12565 The @code{set print union} and @code{show print union} commands apply to
12566 the @code{union} type. When set to @samp{on}, any @code{union} that is
12567 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12568 appears as @samp{@{...@}}.
12570 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12571 with pointers and a memory allocation function. @xref{Expressions,
12574 @node Debugging C Plus Plus
12575 @subsubsection @value{GDBN} Features for C@t{++}
12577 @cindex commands for C@t{++}
12579 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12580 designed specifically for use with C@t{++}. Here is a summary:
12583 @cindex break in overloaded functions
12584 @item @r{breakpoint menus}
12585 When you want a breakpoint in a function whose name is overloaded,
12586 @value{GDBN} has the capability to display a menu of possible breakpoint
12587 locations to help you specify which function definition you want.
12588 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12590 @cindex overloading in C@t{++}
12591 @item rbreak @var{regex}
12592 Setting breakpoints using regular expressions is helpful for setting
12593 breakpoints on overloaded functions that are not members of any special
12595 @xref{Set Breaks, ,Setting Breakpoints}.
12597 @cindex C@t{++} exception handling
12600 Debug C@t{++} exception handling using these commands. @xref{Set
12601 Catchpoints, , Setting Catchpoints}.
12603 @cindex inheritance
12604 @item ptype @var{typename}
12605 Print inheritance relationships as well as other information for type
12607 @xref{Symbols, ,Examining the Symbol Table}.
12609 @cindex C@t{++} symbol display
12610 @item set print demangle
12611 @itemx show print demangle
12612 @itemx set print asm-demangle
12613 @itemx show print asm-demangle
12614 Control whether C@t{++} symbols display in their source form, both when
12615 displaying code as C@t{++} source and when displaying disassemblies.
12616 @xref{Print Settings, ,Print Settings}.
12618 @item set print object
12619 @itemx show print object
12620 Choose whether to print derived (actual) or declared types of objects.
12621 @xref{Print Settings, ,Print Settings}.
12623 @item set print vtbl
12624 @itemx show print vtbl
12625 Control the format for printing virtual function tables.
12626 @xref{Print Settings, ,Print Settings}.
12627 (The @code{vtbl} commands do not work on programs compiled with the HP
12628 ANSI C@t{++} compiler (@code{aCC}).)
12630 @kindex set overload-resolution
12631 @cindex overloaded functions, overload resolution
12632 @item set overload-resolution on
12633 Enable overload resolution for C@t{++} expression evaluation. The default
12634 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12635 and searches for a function whose signature matches the argument types,
12636 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12637 Expressions, ,C@t{++} Expressions}, for details).
12638 If it cannot find a match, it emits a message.
12640 @item set overload-resolution off
12641 Disable overload resolution for C@t{++} expression evaluation. For
12642 overloaded functions that are not class member functions, @value{GDBN}
12643 chooses the first function of the specified name that it finds in the
12644 symbol table, whether or not its arguments are of the correct type. For
12645 overloaded functions that are class member functions, @value{GDBN}
12646 searches for a function whose signature @emph{exactly} matches the
12649 @kindex show overload-resolution
12650 @item show overload-resolution
12651 Show the current setting of overload resolution.
12653 @item @r{Overloaded symbol names}
12654 You can specify a particular definition of an overloaded symbol, using
12655 the same notation that is used to declare such symbols in C@t{++}: type
12656 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12657 also use the @value{GDBN} command-line word completion facilities to list the
12658 available choices, or to finish the type list for you.
12659 @xref{Completion,, Command Completion}, for details on how to do this.
12662 @node Decimal Floating Point
12663 @subsubsection Decimal Floating Point format
12664 @cindex decimal floating point format
12666 @value{GDBN} can examine, set and perform computations with numbers in
12667 decimal floating point format, which in the C language correspond to the
12668 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12669 specified by the extension to support decimal floating-point arithmetic.
12671 There are two encodings in use, depending on the architecture: BID (Binary
12672 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12673 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12676 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12677 to manipulate decimal floating point numbers, it is not possible to convert
12678 (using a cast, for example) integers wider than 32-bit to decimal float.
12680 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12681 point computations, error checking in decimal float operations ignores
12682 underflow, overflow and divide by zero exceptions.
12684 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12685 to inspect @code{_Decimal128} values stored in floating point registers.
12686 See @ref{PowerPC,,PowerPC} for more details.
12692 @value{GDBN} can be used to debug programs written in D and compiled with
12693 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12694 specific feature --- dynamic arrays.
12697 @subsection Objective-C
12699 @cindex Objective-C
12700 This section provides information about some commands and command
12701 options that are useful for debugging Objective-C code. See also
12702 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12703 few more commands specific to Objective-C support.
12706 * Method Names in Commands::
12707 * The Print Command with Objective-C::
12710 @node Method Names in Commands
12711 @subsubsection Method Names in Commands
12713 The following commands have been extended to accept Objective-C method
12714 names as line specifications:
12716 @kindex clear@r{, and Objective-C}
12717 @kindex break@r{, and Objective-C}
12718 @kindex info line@r{, and Objective-C}
12719 @kindex jump@r{, and Objective-C}
12720 @kindex list@r{, and Objective-C}
12724 @item @code{info line}
12729 A fully qualified Objective-C method name is specified as
12732 -[@var{Class} @var{methodName}]
12735 where the minus sign is used to indicate an instance method and a
12736 plus sign (not shown) is used to indicate a class method. The class
12737 name @var{Class} and method name @var{methodName} are enclosed in
12738 brackets, similar to the way messages are specified in Objective-C
12739 source code. For example, to set a breakpoint at the @code{create}
12740 instance method of class @code{Fruit} in the program currently being
12744 break -[Fruit create]
12747 To list ten program lines around the @code{initialize} class method,
12751 list +[NSText initialize]
12754 In the current version of @value{GDBN}, the plus or minus sign is
12755 required. In future versions of @value{GDBN}, the plus or minus
12756 sign will be optional, but you can use it to narrow the search. It
12757 is also possible to specify just a method name:
12763 You must specify the complete method name, including any colons. If
12764 your program's source files contain more than one @code{create} method,
12765 you'll be presented with a numbered list of classes that implement that
12766 method. Indicate your choice by number, or type @samp{0} to exit if
12769 As another example, to clear a breakpoint established at the
12770 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12773 clear -[NSWindow makeKeyAndOrderFront:]
12776 @node The Print Command with Objective-C
12777 @subsubsection The Print Command With Objective-C
12778 @cindex Objective-C, print objects
12779 @kindex print-object
12780 @kindex po @r{(@code{print-object})}
12782 The print command has also been extended to accept methods. For example:
12785 print -[@var{object} hash]
12788 @cindex print an Objective-C object description
12789 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12791 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12792 and print the result. Also, an additional command has been added,
12793 @code{print-object} or @code{po} for short, which is meant to print
12794 the description of an object. However, this command may only work
12795 with certain Objective-C libraries that have a particular hook
12796 function, @code{_NSPrintForDebugger}, defined.
12799 @subsection OpenCL C
12802 This section provides information about @value{GDBN}s OpenCL C support.
12805 * OpenCL C Datatypes::
12806 * OpenCL C Expressions::
12807 * OpenCL C Operators::
12810 @node OpenCL C Datatypes
12811 @subsubsection OpenCL C Datatypes
12813 @cindex OpenCL C Datatypes
12814 @value{GDBN} supports the builtin scalar and vector datatypes specified
12815 by OpenCL 1.1. In addition the half- and double-precision floating point
12816 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12817 extensions are also known to @value{GDBN}.
12819 @node OpenCL C Expressions
12820 @subsubsection OpenCL C Expressions
12822 @cindex OpenCL C Expressions
12823 @value{GDBN} supports accesses to vector components including the access as
12824 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12825 supported by @value{GDBN} can be used as well.
12827 @node OpenCL C Operators
12828 @subsubsection OpenCL C Operators
12830 @cindex OpenCL C Operators
12831 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12835 @subsection Fortran
12836 @cindex Fortran-specific support in @value{GDBN}
12838 @value{GDBN} can be used to debug programs written in Fortran, but it
12839 currently supports only the features of Fortran 77 language.
12841 @cindex trailing underscore, in Fortran symbols
12842 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12843 among them) append an underscore to the names of variables and
12844 functions. When you debug programs compiled by those compilers, you
12845 will need to refer to variables and functions with a trailing
12849 * Fortran Operators:: Fortran operators and expressions
12850 * Fortran Defaults:: Default settings for Fortran
12851 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12854 @node Fortran Operators
12855 @subsubsection Fortran Operators and Expressions
12857 @cindex Fortran operators and expressions
12859 Operators must be defined on values of specific types. For instance,
12860 @code{+} is defined on numbers, but not on characters or other non-
12861 arithmetic types. Operators are often defined on groups of types.
12865 The exponentiation operator. It raises the first operand to the power
12869 The range operator. Normally used in the form of array(low:high) to
12870 represent a section of array.
12873 The access component operator. Normally used to access elements in derived
12874 types. Also suitable for unions. As unions aren't part of regular Fortran,
12875 this can only happen when accessing a register that uses a gdbarch-defined
12879 @node Fortran Defaults
12880 @subsubsection Fortran Defaults
12882 @cindex Fortran Defaults
12884 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12885 default uses case-insensitive matches for Fortran symbols. You can
12886 change that with the @samp{set case-insensitive} command, see
12887 @ref{Symbols}, for the details.
12889 @node Special Fortran Commands
12890 @subsubsection Special Fortran Commands
12892 @cindex Special Fortran commands
12894 @value{GDBN} has some commands to support Fortran-specific features,
12895 such as displaying common blocks.
12898 @cindex @code{COMMON} blocks, Fortran
12899 @kindex info common
12900 @item info common @r{[}@var{common-name}@r{]}
12901 This command prints the values contained in the Fortran @code{COMMON}
12902 block whose name is @var{common-name}. With no argument, the names of
12903 all @code{COMMON} blocks visible at the current program location are
12910 @cindex Pascal support in @value{GDBN}, limitations
12911 Debugging Pascal programs which use sets, subranges, file variables, or
12912 nested functions does not currently work. @value{GDBN} does not support
12913 entering expressions, printing values, or similar features using Pascal
12916 The Pascal-specific command @code{set print pascal_static-members}
12917 controls whether static members of Pascal objects are displayed.
12918 @xref{Print Settings, pascal_static-members}.
12921 @subsection Modula-2
12923 @cindex Modula-2, @value{GDBN} support
12925 The extensions made to @value{GDBN} to support Modula-2 only support
12926 output from the @sc{gnu} Modula-2 compiler (which is currently being
12927 developed). Other Modula-2 compilers are not currently supported, and
12928 attempting to debug executables produced by them is most likely
12929 to give an error as @value{GDBN} reads in the executable's symbol
12932 @cindex expressions in Modula-2
12934 * M2 Operators:: Built-in operators
12935 * Built-In Func/Proc:: Built-in functions and procedures
12936 * M2 Constants:: Modula-2 constants
12937 * M2 Types:: Modula-2 types
12938 * M2 Defaults:: Default settings for Modula-2
12939 * Deviations:: Deviations from standard Modula-2
12940 * M2 Checks:: Modula-2 type and range checks
12941 * M2 Scope:: The scope operators @code{::} and @code{.}
12942 * GDB/M2:: @value{GDBN} and Modula-2
12946 @subsubsection Operators
12947 @cindex Modula-2 operators
12949 Operators must be defined on values of specific types. For instance,
12950 @code{+} is defined on numbers, but not on structures. Operators are
12951 often defined on groups of types. For the purposes of Modula-2, the
12952 following definitions hold:
12957 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12961 @emph{Character types} consist of @code{CHAR} and its subranges.
12964 @emph{Floating-point types} consist of @code{REAL}.
12967 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12971 @emph{Scalar types} consist of all of the above.
12974 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12977 @emph{Boolean types} consist of @code{BOOLEAN}.
12981 The following operators are supported, and appear in order of
12982 increasing precedence:
12986 Function argument or array index separator.
12989 Assignment. The value of @var{var} @code{:=} @var{value} is
12993 Less than, greater than on integral, floating-point, or enumerated
12997 Less than or equal to, greater than or equal to
12998 on integral, floating-point and enumerated types, or set inclusion on
12999 set types. Same precedence as @code{<}.
13001 @item =@r{, }<>@r{, }#
13002 Equality and two ways of expressing inequality, valid on scalar types.
13003 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13004 available for inequality, since @code{#} conflicts with the script
13008 Set membership. Defined on set types and the types of their members.
13009 Same precedence as @code{<}.
13012 Boolean disjunction. Defined on boolean types.
13015 Boolean conjunction. Defined on boolean types.
13018 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13021 Addition and subtraction on integral and floating-point types, or union
13022 and difference on set types.
13025 Multiplication on integral and floating-point types, or set intersection
13029 Division on floating-point types, or symmetric set difference on set
13030 types. Same precedence as @code{*}.
13033 Integer division and remainder. Defined on integral types. Same
13034 precedence as @code{*}.
13037 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13040 Pointer dereferencing. Defined on pointer types.
13043 Boolean negation. Defined on boolean types. Same precedence as
13047 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13048 precedence as @code{^}.
13051 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13054 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13058 @value{GDBN} and Modula-2 scope operators.
13062 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13063 treats the use of the operator @code{IN}, or the use of operators
13064 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13065 @code{<=}, and @code{>=} on sets as an error.
13069 @node Built-In Func/Proc
13070 @subsubsection Built-in Functions and Procedures
13071 @cindex Modula-2 built-ins
13073 Modula-2 also makes available several built-in procedures and functions.
13074 In describing these, the following metavariables are used:
13079 represents an @code{ARRAY} variable.
13082 represents a @code{CHAR} constant or variable.
13085 represents a variable or constant of integral type.
13088 represents an identifier that belongs to a set. Generally used in the
13089 same function with the metavariable @var{s}. The type of @var{s} should
13090 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13093 represents a variable or constant of integral or floating-point type.
13096 represents a variable or constant of floating-point type.
13102 represents a variable.
13105 represents a variable or constant of one of many types. See the
13106 explanation of the function for details.
13109 All Modula-2 built-in procedures also return a result, described below.
13113 Returns the absolute value of @var{n}.
13116 If @var{c} is a lower case letter, it returns its upper case
13117 equivalent, otherwise it returns its argument.
13120 Returns the character whose ordinal value is @var{i}.
13123 Decrements the value in the variable @var{v} by one. Returns the new value.
13125 @item DEC(@var{v},@var{i})
13126 Decrements the value in the variable @var{v} by @var{i}. Returns the
13129 @item EXCL(@var{m},@var{s})
13130 Removes the element @var{m} from the set @var{s}. Returns the new
13133 @item FLOAT(@var{i})
13134 Returns the floating point equivalent of the integer @var{i}.
13136 @item HIGH(@var{a})
13137 Returns the index of the last member of @var{a}.
13140 Increments the value in the variable @var{v} by one. Returns the new value.
13142 @item INC(@var{v},@var{i})
13143 Increments the value in the variable @var{v} by @var{i}. Returns the
13146 @item INCL(@var{m},@var{s})
13147 Adds the element @var{m} to the set @var{s} if it is not already
13148 there. Returns the new set.
13151 Returns the maximum value of the type @var{t}.
13154 Returns the minimum value of the type @var{t}.
13157 Returns boolean TRUE if @var{i} is an odd number.
13160 Returns the ordinal value of its argument. For example, the ordinal
13161 value of a character is its @sc{ascii} value (on machines supporting the
13162 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13163 integral, character and enumerated types.
13165 @item SIZE(@var{x})
13166 Returns the size of its argument. @var{x} can be a variable or a type.
13168 @item TRUNC(@var{r})
13169 Returns the integral part of @var{r}.
13171 @item TSIZE(@var{x})
13172 Returns the size of its argument. @var{x} can be a variable or a type.
13174 @item VAL(@var{t},@var{i})
13175 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13179 @emph{Warning:} Sets and their operations are not yet supported, so
13180 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13184 @cindex Modula-2 constants
13186 @subsubsection Constants
13188 @value{GDBN} allows you to express the constants of Modula-2 in the following
13194 Integer constants are simply a sequence of digits. When used in an
13195 expression, a constant is interpreted to be type-compatible with the
13196 rest of the expression. Hexadecimal integers are specified by a
13197 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13200 Floating point constants appear as a sequence of digits, followed by a
13201 decimal point and another sequence of digits. An optional exponent can
13202 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13203 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13204 digits of the floating point constant must be valid decimal (base 10)
13208 Character constants consist of a single character enclosed by a pair of
13209 like quotes, either single (@code{'}) or double (@code{"}). They may
13210 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13211 followed by a @samp{C}.
13214 String constants consist of a sequence of characters enclosed by a
13215 pair of like quotes, either single (@code{'}) or double (@code{"}).
13216 Escape sequences in the style of C are also allowed. @xref{C
13217 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13221 Enumerated constants consist of an enumerated identifier.
13224 Boolean constants consist of the identifiers @code{TRUE} and
13228 Pointer constants consist of integral values only.
13231 Set constants are not yet supported.
13235 @subsubsection Modula-2 Types
13236 @cindex Modula-2 types
13238 Currently @value{GDBN} can print the following data types in Modula-2
13239 syntax: array types, record types, set types, pointer types, procedure
13240 types, enumerated types, subrange types and base types. You can also
13241 print the contents of variables declared using these type.
13242 This section gives a number of simple source code examples together with
13243 sample @value{GDBN} sessions.
13245 The first example contains the following section of code:
13254 and you can request @value{GDBN} to interrogate the type and value of
13255 @code{r} and @code{s}.
13258 (@value{GDBP}) print s
13260 (@value{GDBP}) ptype s
13262 (@value{GDBP}) print r
13264 (@value{GDBP}) ptype r
13269 Likewise if your source code declares @code{s} as:
13273 s: SET ['A'..'Z'] ;
13277 then you may query the type of @code{s} by:
13280 (@value{GDBP}) ptype s
13281 type = SET ['A'..'Z']
13285 Note that at present you cannot interactively manipulate set
13286 expressions using the debugger.
13288 The following example shows how you might declare an array in Modula-2
13289 and how you can interact with @value{GDBN} to print its type and contents:
13293 s: ARRAY [-10..10] OF CHAR ;
13297 (@value{GDBP}) ptype s
13298 ARRAY [-10..10] OF CHAR
13301 Note that the array handling is not yet complete and although the type
13302 is printed correctly, expression handling still assumes that all
13303 arrays have a lower bound of zero and not @code{-10} as in the example
13306 Here are some more type related Modula-2 examples:
13310 colour = (blue, red, yellow, green) ;
13311 t = [blue..yellow] ;
13319 The @value{GDBN} interaction shows how you can query the data type
13320 and value of a variable.
13323 (@value{GDBP}) print s
13325 (@value{GDBP}) ptype t
13326 type = [blue..yellow]
13330 In this example a Modula-2 array is declared and its contents
13331 displayed. Observe that the contents are written in the same way as
13332 their @code{C} counterparts.
13336 s: ARRAY [1..5] OF CARDINAL ;
13342 (@value{GDBP}) print s
13343 $1 = @{1, 0, 0, 0, 0@}
13344 (@value{GDBP}) ptype s
13345 type = ARRAY [1..5] OF CARDINAL
13348 The Modula-2 language interface to @value{GDBN} also understands
13349 pointer types as shown in this example:
13353 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13360 and you can request that @value{GDBN} describes the type of @code{s}.
13363 (@value{GDBP}) ptype s
13364 type = POINTER TO ARRAY [1..5] OF CARDINAL
13367 @value{GDBN} handles compound types as we can see in this example.
13368 Here we combine array types, record types, pointer types and subrange
13379 myarray = ARRAY myrange OF CARDINAL ;
13380 myrange = [-2..2] ;
13382 s: POINTER TO ARRAY myrange OF foo ;
13386 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13390 (@value{GDBP}) ptype s
13391 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13394 f3 : ARRAY [-2..2] OF CARDINAL;
13399 @subsubsection Modula-2 Defaults
13400 @cindex Modula-2 defaults
13402 If type and range checking are set automatically by @value{GDBN}, they
13403 both default to @code{on} whenever the working language changes to
13404 Modula-2. This happens regardless of whether you or @value{GDBN}
13405 selected the working language.
13407 If you allow @value{GDBN} to set the language automatically, then entering
13408 code compiled from a file whose name ends with @file{.mod} sets the
13409 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13410 Infer the Source Language}, for further details.
13413 @subsubsection Deviations from Standard Modula-2
13414 @cindex Modula-2, deviations from
13416 A few changes have been made to make Modula-2 programs easier to debug.
13417 This is done primarily via loosening its type strictness:
13421 Unlike in standard Modula-2, pointer constants can be formed by
13422 integers. This allows you to modify pointer variables during
13423 debugging. (In standard Modula-2, the actual address contained in a
13424 pointer variable is hidden from you; it can only be modified
13425 through direct assignment to another pointer variable or expression that
13426 returned a pointer.)
13429 C escape sequences can be used in strings and characters to represent
13430 non-printable characters. @value{GDBN} prints out strings with these
13431 escape sequences embedded. Single non-printable characters are
13432 printed using the @samp{CHR(@var{nnn})} format.
13435 The assignment operator (@code{:=}) returns the value of its right-hand
13439 All built-in procedures both modify @emph{and} return their argument.
13443 @subsubsection Modula-2 Type and Range Checks
13444 @cindex Modula-2 checks
13447 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13450 @c FIXME remove warning when type/range checks added
13452 @value{GDBN} considers two Modula-2 variables type equivalent if:
13456 They are of types that have been declared equivalent via a @code{TYPE
13457 @var{t1} = @var{t2}} statement
13460 They have been declared on the same line. (Note: This is true of the
13461 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13464 As long as type checking is enabled, any attempt to combine variables
13465 whose types are not equivalent is an error.
13467 Range checking is done on all mathematical operations, assignment, array
13468 index bounds, and all built-in functions and procedures.
13471 @subsubsection The Scope Operators @code{::} and @code{.}
13473 @cindex @code{.}, Modula-2 scope operator
13474 @cindex colon, doubled as scope operator
13476 @vindex colon-colon@r{, in Modula-2}
13477 @c Info cannot handle :: but TeX can.
13480 @vindex ::@r{, in Modula-2}
13483 There are a few subtle differences between the Modula-2 scope operator
13484 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13489 @var{module} . @var{id}
13490 @var{scope} :: @var{id}
13494 where @var{scope} is the name of a module or a procedure,
13495 @var{module} the name of a module, and @var{id} is any declared
13496 identifier within your program, except another module.
13498 Using the @code{::} operator makes @value{GDBN} search the scope
13499 specified by @var{scope} for the identifier @var{id}. If it is not
13500 found in the specified scope, then @value{GDBN} searches all scopes
13501 enclosing the one specified by @var{scope}.
13503 Using the @code{.} operator makes @value{GDBN} search the current scope for
13504 the identifier specified by @var{id} that was imported from the
13505 definition module specified by @var{module}. With this operator, it is
13506 an error if the identifier @var{id} was not imported from definition
13507 module @var{module}, or if @var{id} is not an identifier in
13511 @subsubsection @value{GDBN} and Modula-2
13513 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13514 Five subcommands of @code{set print} and @code{show print} apply
13515 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13516 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13517 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13518 analogue in Modula-2.
13520 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13521 with any language, is not useful with Modula-2. Its
13522 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13523 created in Modula-2 as they can in C or C@t{++}. However, because an
13524 address can be specified by an integral constant, the construct
13525 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13527 @cindex @code{#} in Modula-2
13528 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13529 interpreted as the beginning of a comment. Use @code{<>} instead.
13535 The extensions made to @value{GDBN} for Ada only support
13536 output from the @sc{gnu} Ada (GNAT) compiler.
13537 Other Ada compilers are not currently supported, and
13538 attempting to debug executables produced by them is most likely
13542 @cindex expressions in Ada
13544 * Ada Mode Intro:: General remarks on the Ada syntax
13545 and semantics supported by Ada mode
13547 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13548 * Additions to Ada:: Extensions of the Ada expression syntax.
13549 * Stopping Before Main Program:: Debugging the program during elaboration.
13550 * Ada Tasks:: Listing and setting breakpoints in tasks.
13551 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13552 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13554 * Ada Glitches:: Known peculiarities of Ada mode.
13557 @node Ada Mode Intro
13558 @subsubsection Introduction
13559 @cindex Ada mode, general
13561 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13562 syntax, with some extensions.
13563 The philosophy behind the design of this subset is
13567 That @value{GDBN} should provide basic literals and access to operations for
13568 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13569 leaving more sophisticated computations to subprograms written into the
13570 program (which therefore may be called from @value{GDBN}).
13573 That type safety and strict adherence to Ada language restrictions
13574 are not particularly important to the @value{GDBN} user.
13577 That brevity is important to the @value{GDBN} user.
13580 Thus, for brevity, the debugger acts as if all names declared in
13581 user-written packages are directly visible, even if they are not visible
13582 according to Ada rules, thus making it unnecessary to fully qualify most
13583 names with their packages, regardless of context. Where this causes
13584 ambiguity, @value{GDBN} asks the user's intent.
13586 The debugger will start in Ada mode if it detects an Ada main program.
13587 As for other languages, it will enter Ada mode when stopped in a program that
13588 was translated from an Ada source file.
13590 While in Ada mode, you may use `@t{--}' for comments. This is useful
13591 mostly for documenting command files. The standard @value{GDBN} comment
13592 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13593 middle (to allow based literals).
13595 The debugger supports limited overloading. Given a subprogram call in which
13596 the function symbol has multiple definitions, it will use the number of
13597 actual parameters and some information about their types to attempt to narrow
13598 the set of definitions. It also makes very limited use of context, preferring
13599 procedures to functions in the context of the @code{call} command, and
13600 functions to procedures elsewhere.
13602 @node Omissions from Ada
13603 @subsubsection Omissions from Ada
13604 @cindex Ada, omissions from
13606 Here are the notable omissions from the subset:
13610 Only a subset of the attributes are supported:
13614 @t{'First}, @t{'Last}, and @t{'Length}
13615 on array objects (not on types and subtypes).
13618 @t{'Min} and @t{'Max}.
13621 @t{'Pos} and @t{'Val}.
13627 @t{'Range} on array objects (not subtypes), but only as the right
13628 operand of the membership (@code{in}) operator.
13631 @t{'Access}, @t{'Unchecked_Access}, and
13632 @t{'Unrestricted_Access} (a GNAT extension).
13640 @code{Characters.Latin_1} are not available and
13641 concatenation is not implemented. Thus, escape characters in strings are
13642 not currently available.
13645 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13646 equality of representations. They will generally work correctly
13647 for strings and arrays whose elements have integer or enumeration types.
13648 They may not work correctly for arrays whose element
13649 types have user-defined equality, for arrays of real values
13650 (in particular, IEEE-conformant floating point, because of negative
13651 zeroes and NaNs), and for arrays whose elements contain unused bits with
13652 indeterminate values.
13655 The other component-by-component array operations (@code{and}, @code{or},
13656 @code{xor}, @code{not}, and relational tests other than equality)
13657 are not implemented.
13660 @cindex array aggregates (Ada)
13661 @cindex record aggregates (Ada)
13662 @cindex aggregates (Ada)
13663 There is limited support for array and record aggregates. They are
13664 permitted only on the right sides of assignments, as in these examples:
13667 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13668 (@value{GDBP}) set An_Array := (1, others => 0)
13669 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13670 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13671 (@value{GDBP}) set A_Record := (1, "Peter", True);
13672 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13676 discriminant's value by assigning an aggregate has an
13677 undefined effect if that discriminant is used within the record.
13678 However, you can first modify discriminants by directly assigning to
13679 them (which normally would not be allowed in Ada), and then performing an
13680 aggregate assignment. For example, given a variable @code{A_Rec}
13681 declared to have a type such as:
13684 type Rec (Len : Small_Integer := 0) is record
13686 Vals : IntArray (1 .. Len);
13690 you can assign a value with a different size of @code{Vals} with two
13694 (@value{GDBP}) set A_Rec.Len := 4
13695 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13698 As this example also illustrates, @value{GDBN} is very loose about the usual
13699 rules concerning aggregates. You may leave out some of the
13700 components of an array or record aggregate (such as the @code{Len}
13701 component in the assignment to @code{A_Rec} above); they will retain their
13702 original values upon assignment. You may freely use dynamic values as
13703 indices in component associations. You may even use overlapping or
13704 redundant component associations, although which component values are
13705 assigned in such cases is not defined.
13708 Calls to dispatching subprograms are not implemented.
13711 The overloading algorithm is much more limited (i.e., less selective)
13712 than that of real Ada. It makes only limited use of the context in
13713 which a subexpression appears to resolve its meaning, and it is much
13714 looser in its rules for allowing type matches. As a result, some
13715 function calls will be ambiguous, and the user will be asked to choose
13716 the proper resolution.
13719 The @code{new} operator is not implemented.
13722 Entry calls are not implemented.
13725 Aside from printing, arithmetic operations on the native VAX floating-point
13726 formats are not supported.
13729 It is not possible to slice a packed array.
13732 The names @code{True} and @code{False}, when not part of a qualified name,
13733 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13735 Should your program
13736 redefine these names in a package or procedure (at best a dubious practice),
13737 you will have to use fully qualified names to access their new definitions.
13740 @node Additions to Ada
13741 @subsubsection Additions to Ada
13742 @cindex Ada, deviations from
13744 As it does for other languages, @value{GDBN} makes certain generic
13745 extensions to Ada (@pxref{Expressions}):
13749 If the expression @var{E} is a variable residing in memory (typically
13750 a local variable or array element) and @var{N} is a positive integer,
13751 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13752 @var{N}-1 adjacent variables following it in memory as an array. In
13753 Ada, this operator is generally not necessary, since its prime use is
13754 in displaying parts of an array, and slicing will usually do this in
13755 Ada. However, there are occasional uses when debugging programs in
13756 which certain debugging information has been optimized away.
13759 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13760 appears in function or file @var{B}.'' When @var{B} is a file name,
13761 you must typically surround it in single quotes.
13764 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13765 @var{type} that appears at address @var{addr}.''
13768 A name starting with @samp{$} is a convenience variable
13769 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13772 In addition, @value{GDBN} provides a few other shortcuts and outright
13773 additions specific to Ada:
13777 The assignment statement is allowed as an expression, returning
13778 its right-hand operand as its value. Thus, you may enter
13781 (@value{GDBP}) set x := y + 3
13782 (@value{GDBP}) print A(tmp := y + 1)
13786 The semicolon is allowed as an ``operator,'' returning as its value
13787 the value of its right-hand operand.
13788 This allows, for example,
13789 complex conditional breaks:
13792 (@value{GDBP}) break f
13793 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13797 Rather than use catenation and symbolic character names to introduce special
13798 characters into strings, one may instead use a special bracket notation,
13799 which is also used to print strings. A sequence of characters of the form
13800 @samp{["@var{XX}"]} within a string or character literal denotes the
13801 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13802 sequence of characters @samp{["""]} also denotes a single quotation mark
13803 in strings. For example,
13805 "One line.["0a"]Next line.["0a"]"
13808 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13812 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13813 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13817 (@value{GDBP}) print 'max(x, y)
13821 When printing arrays, @value{GDBN} uses positional notation when the
13822 array has a lower bound of 1, and uses a modified named notation otherwise.
13823 For example, a one-dimensional array of three integers with a lower bound
13824 of 3 might print as
13831 That is, in contrast to valid Ada, only the first component has a @code{=>}
13835 You may abbreviate attributes in expressions with any unique,
13836 multi-character subsequence of
13837 their names (an exact match gets preference).
13838 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13839 in place of @t{a'length}.
13842 @cindex quoting Ada internal identifiers
13843 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13844 to lower case. The GNAT compiler uses upper-case characters for
13845 some of its internal identifiers, which are normally of no interest to users.
13846 For the rare occasions when you actually have to look at them,
13847 enclose them in angle brackets to avoid the lower-case mapping.
13850 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13854 Printing an object of class-wide type or dereferencing an
13855 access-to-class-wide value will display all the components of the object's
13856 specific type (as indicated by its run-time tag). Likewise, component
13857 selection on such a value will operate on the specific type of the
13862 @node Stopping Before Main Program
13863 @subsubsection Stopping at the Very Beginning
13865 @cindex breakpointing Ada elaboration code
13866 It is sometimes necessary to debug the program during elaboration, and
13867 before reaching the main procedure.
13868 As defined in the Ada Reference
13869 Manual, the elaboration code is invoked from a procedure called
13870 @code{adainit}. To run your program up to the beginning of
13871 elaboration, simply use the following two commands:
13872 @code{tbreak adainit} and @code{run}.
13875 @subsubsection Extensions for Ada Tasks
13876 @cindex Ada, tasking
13878 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13879 @value{GDBN} provides the following task-related commands:
13884 This command shows a list of current Ada tasks, as in the following example:
13891 (@value{GDBP}) info tasks
13892 ID TID P-ID Pri State Name
13893 1 8088000 0 15 Child Activation Wait main_task
13894 2 80a4000 1 15 Accept Statement b
13895 3 809a800 1 15 Child Activation Wait a
13896 * 4 80ae800 3 15 Runnable c
13901 In this listing, the asterisk before the last task indicates it to be the
13902 task currently being inspected.
13906 Represents @value{GDBN}'s internal task number.
13912 The parent's task ID (@value{GDBN}'s internal task number).
13915 The base priority of the task.
13918 Current state of the task.
13922 The task has been created but has not been activated. It cannot be
13926 The task is not blocked for any reason known to Ada. (It may be waiting
13927 for a mutex, though.) It is conceptually "executing" in normal mode.
13930 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13931 that were waiting on terminate alternatives have been awakened and have
13932 terminated themselves.
13934 @item Child Activation Wait
13935 The task is waiting for created tasks to complete activation.
13937 @item Accept Statement
13938 The task is waiting on an accept or selective wait statement.
13940 @item Waiting on entry call
13941 The task is waiting on an entry call.
13943 @item Async Select Wait
13944 The task is waiting to start the abortable part of an asynchronous
13948 The task is waiting on a select statement with only a delay
13951 @item Child Termination Wait
13952 The task is sleeping having completed a master within itself, and is
13953 waiting for the tasks dependent on that master to become terminated or
13954 waiting on a terminate Phase.
13956 @item Wait Child in Term Alt
13957 The task is sleeping waiting for tasks on terminate alternatives to
13958 finish terminating.
13960 @item Accepting RV with @var{taskno}
13961 The task is accepting a rendez-vous with the task @var{taskno}.
13965 Name of the task in the program.
13969 @kindex info task @var{taskno}
13970 @item info task @var{taskno}
13971 This command shows detailled informations on the specified task, as in
13972 the following example:
13977 (@value{GDBP}) info tasks
13978 ID TID P-ID Pri State Name
13979 1 8077880 0 15 Child Activation Wait main_task
13980 * 2 807c468 1 15 Runnable task_1
13981 (@value{GDBP}) info task 2
13982 Ada Task: 0x807c468
13985 Parent: 1 (main_task)
13991 @kindex task@r{ (Ada)}
13992 @cindex current Ada task ID
13993 This command prints the ID of the current task.
13999 (@value{GDBP}) info tasks
14000 ID TID P-ID Pri State Name
14001 1 8077870 0 15 Child Activation Wait main_task
14002 * 2 807c458 1 15 Runnable t
14003 (@value{GDBP}) task
14004 [Current task is 2]
14007 @item task @var{taskno}
14008 @cindex Ada task switching
14009 This command is like the @code{thread @var{threadno}}
14010 command (@pxref{Threads}). It switches the context of debugging
14011 from the current task to the given task.
14017 (@value{GDBP}) info tasks
14018 ID TID P-ID Pri State Name
14019 1 8077870 0 15 Child Activation Wait main_task
14020 * 2 807c458 1 15 Runnable t
14021 (@value{GDBP}) task 1
14022 [Switching to task 1]
14023 #0 0x8067726 in pthread_cond_wait ()
14025 #0 0x8067726 in pthread_cond_wait ()
14026 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14027 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14028 #3 0x806153e in system.tasking.stages.activate_tasks ()
14029 #4 0x804aacc in un () at un.adb:5
14032 @item break @var{linespec} task @var{taskno}
14033 @itemx break @var{linespec} task @var{taskno} if @dots{}
14034 @cindex breakpoints and tasks, in Ada
14035 @cindex task breakpoints, in Ada
14036 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14037 These commands are like the @code{break @dots{} thread @dots{}}
14038 command (@pxref{Thread Stops}).
14039 @var{linespec} specifies source lines, as described
14040 in @ref{Specify Location}.
14042 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14043 to specify that you only want @value{GDBN} to stop the program when a
14044 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14045 numeric task identifiers assigned by @value{GDBN}, shown in the first
14046 column of the @samp{info tasks} display.
14048 If you do not specify @samp{task @var{taskno}} when you set a
14049 breakpoint, the breakpoint applies to @emph{all} tasks of your
14052 You can use the @code{task} qualifier on conditional breakpoints as
14053 well; in this case, place @samp{task @var{taskno}} before the
14054 breakpoint condition (before the @code{if}).
14062 (@value{GDBP}) info tasks
14063 ID TID P-ID Pri State Name
14064 1 140022020 0 15 Child Activation Wait main_task
14065 2 140045060 1 15 Accept/Select Wait t2
14066 3 140044840 1 15 Runnable t1
14067 * 4 140056040 1 15 Runnable t3
14068 (@value{GDBP}) b 15 task 2
14069 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14070 (@value{GDBP}) cont
14075 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14077 (@value{GDBP}) info tasks
14078 ID TID P-ID Pri State Name
14079 1 140022020 0 15 Child Activation Wait main_task
14080 * 2 140045060 1 15 Runnable t2
14081 3 140044840 1 15 Runnable t1
14082 4 140056040 1 15 Delay Sleep t3
14086 @node Ada Tasks and Core Files
14087 @subsubsection Tasking Support when Debugging Core Files
14088 @cindex Ada tasking and core file debugging
14090 When inspecting a core file, as opposed to debugging a live program,
14091 tasking support may be limited or even unavailable, depending on
14092 the platform being used.
14093 For instance, on x86-linux, the list of tasks is available, but task
14094 switching is not supported. On Tru64, however, task switching will work
14097 On certain platforms, including Tru64, the debugger needs to perform some
14098 memory writes in order to provide Ada tasking support. When inspecting
14099 a core file, this means that the core file must be opened with read-write
14100 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14101 Under these circumstances, you should make a backup copy of the core
14102 file before inspecting it with @value{GDBN}.
14104 @node Ravenscar Profile
14105 @subsubsection Tasking Support when using the Ravenscar Profile
14106 @cindex Ravenscar Profile
14108 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14109 specifically designed for systems with safety-critical real-time
14113 @kindex set ravenscar task-switching on
14114 @cindex task switching with program using Ravenscar Profile
14115 @item set ravenscar task-switching on
14116 Allows task switching when debugging a program that uses the Ravenscar
14117 Profile. This is the default.
14119 @kindex set ravenscar task-switching off
14120 @item set ravenscar task-switching off
14121 Turn off task switching when debugging a program that uses the Ravenscar
14122 Profile. This is mostly intended to disable the code that adds support
14123 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14124 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14125 To be effective, this command should be run before the program is started.
14127 @kindex show ravenscar task-switching
14128 @item show ravenscar task-switching
14129 Show whether it is possible to switch from task to task in a program
14130 using the Ravenscar Profile.
14135 @subsubsection Known Peculiarities of Ada Mode
14136 @cindex Ada, problems
14138 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14139 we know of several problems with and limitations of Ada mode in
14141 some of which will be fixed with planned future releases of the debugger
14142 and the GNU Ada compiler.
14146 Static constants that the compiler chooses not to materialize as objects in
14147 storage are invisible to the debugger.
14150 Named parameter associations in function argument lists are ignored (the
14151 argument lists are treated as positional).
14154 Many useful library packages are currently invisible to the debugger.
14157 Fixed-point arithmetic, conversions, input, and output is carried out using
14158 floating-point arithmetic, and may give results that only approximate those on
14162 The GNAT compiler never generates the prefix @code{Standard} for any of
14163 the standard symbols defined by the Ada language. @value{GDBN} knows about
14164 this: it will strip the prefix from names when you use it, and will never
14165 look for a name you have so qualified among local symbols, nor match against
14166 symbols in other packages or subprograms. If you have
14167 defined entities anywhere in your program other than parameters and
14168 local variables whose simple names match names in @code{Standard},
14169 GNAT's lack of qualification here can cause confusion. When this happens,
14170 you can usually resolve the confusion
14171 by qualifying the problematic names with package
14172 @code{Standard} explicitly.
14175 Older versions of the compiler sometimes generate erroneous debugging
14176 information, resulting in the debugger incorrectly printing the value
14177 of affected entities. In some cases, the debugger is able to work
14178 around an issue automatically. In other cases, the debugger is able
14179 to work around the issue, but the work-around has to be specifically
14182 @kindex set ada trust-PAD-over-XVS
14183 @kindex show ada trust-PAD-over-XVS
14186 @item set ada trust-PAD-over-XVS on
14187 Configure GDB to strictly follow the GNAT encoding when computing the
14188 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14189 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14190 a complete description of the encoding used by the GNAT compiler).
14191 This is the default.
14193 @item set ada trust-PAD-over-XVS off
14194 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14195 sometimes prints the wrong value for certain entities, changing @code{ada
14196 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14197 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14198 @code{off}, but this incurs a slight performance penalty, so it is
14199 recommended to leave this setting to @code{on} unless necessary.
14203 @node Unsupported Languages
14204 @section Unsupported Languages
14206 @cindex unsupported languages
14207 @cindex minimal language
14208 In addition to the other fully-supported programming languages,
14209 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14210 It does not represent a real programming language, but provides a set
14211 of capabilities close to what the C or assembly languages provide.
14212 This should allow most simple operations to be performed while debugging
14213 an application that uses a language currently not supported by @value{GDBN}.
14215 If the language is set to @code{auto}, @value{GDBN} will automatically
14216 select this language if the current frame corresponds to an unsupported
14220 @chapter Examining the Symbol Table
14222 The commands described in this chapter allow you to inquire about the
14223 symbols (names of variables, functions and types) defined in your
14224 program. This information is inherent in the text of your program and
14225 does not change as your program executes. @value{GDBN} finds it in your
14226 program's symbol table, in the file indicated when you started @value{GDBN}
14227 (@pxref{File Options, ,Choosing Files}), or by one of the
14228 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14230 @cindex symbol names
14231 @cindex names of symbols
14232 @cindex quoting names
14233 Occasionally, you may need to refer to symbols that contain unusual
14234 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14235 most frequent case is in referring to static variables in other
14236 source files (@pxref{Variables,,Program Variables}). File names
14237 are recorded in object files as debugging symbols, but @value{GDBN} would
14238 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14239 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14240 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14247 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14250 @cindex case-insensitive symbol names
14251 @cindex case sensitivity in symbol names
14252 @kindex set case-sensitive
14253 @item set case-sensitive on
14254 @itemx set case-sensitive off
14255 @itemx set case-sensitive auto
14256 Normally, when @value{GDBN} looks up symbols, it matches their names
14257 with case sensitivity determined by the current source language.
14258 Occasionally, you may wish to control that. The command @code{set
14259 case-sensitive} lets you do that by specifying @code{on} for
14260 case-sensitive matches or @code{off} for case-insensitive ones. If
14261 you specify @code{auto}, case sensitivity is reset to the default
14262 suitable for the source language. The default is case-sensitive
14263 matches for all languages except for Fortran, for which the default is
14264 case-insensitive matches.
14266 @kindex show case-sensitive
14267 @item show case-sensitive
14268 This command shows the current setting of case sensitivity for symbols
14271 @kindex info address
14272 @cindex address of a symbol
14273 @item info address @var{symbol}
14274 Describe where the data for @var{symbol} is stored. For a register
14275 variable, this says which register it is kept in. For a non-register
14276 local variable, this prints the stack-frame offset at which the variable
14279 Note the contrast with @samp{print &@var{symbol}}, which does not work
14280 at all for a register variable, and for a stack local variable prints
14281 the exact address of the current instantiation of the variable.
14283 @kindex info symbol
14284 @cindex symbol from address
14285 @cindex closest symbol and offset for an address
14286 @item info symbol @var{addr}
14287 Print the name of a symbol which is stored at the address @var{addr}.
14288 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14289 nearest symbol and an offset from it:
14292 (@value{GDBP}) info symbol 0x54320
14293 _initialize_vx + 396 in section .text
14297 This is the opposite of the @code{info address} command. You can use
14298 it to find out the name of a variable or a function given its address.
14300 For dynamically linked executables, the name of executable or shared
14301 library containing the symbol is also printed:
14304 (@value{GDBP}) info symbol 0x400225
14305 _start + 5 in section .text of /tmp/a.out
14306 (@value{GDBP}) info symbol 0x2aaaac2811cf
14307 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14311 @item whatis [@var{arg}]
14312 Print the data type of @var{arg}, which can be either an expression
14313 or a name of a data type. With no argument, print the data type of
14314 @code{$}, the last value in the value history.
14316 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14317 is not actually evaluated, and any side-effecting operations (such as
14318 assignments or function calls) inside it do not take place.
14320 If @var{arg} is a variable or an expression, @code{whatis} prints its
14321 literal type as it is used in the source code. If the type was
14322 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14323 the data type underlying the @code{typedef}. If the type of the
14324 variable or the expression is a compound data type, such as
14325 @code{struct} or @code{class}, @code{whatis} never prints their
14326 fields or methods. It just prints the @code{struct}/@code{class}
14327 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14328 such a compound data type, use @code{ptype}.
14330 If @var{arg} is a type name that was defined using @code{typedef},
14331 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14332 Unrolling means that @code{whatis} will show the underlying type used
14333 in the @code{typedef} declaration of @var{arg}. However, if that
14334 underlying type is also a @code{typedef}, @code{whatis} will not
14337 For C code, the type names may also have the form @samp{class
14338 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14339 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14342 @item ptype [@var{arg}]
14343 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14344 detailed description of the type, instead of just the name of the type.
14345 @xref{Expressions, ,Expressions}.
14347 Contrary to @code{whatis}, @code{ptype} always unrolls any
14348 @code{typedef}s in its argument declaration, whether the argument is
14349 a variable, expression, or a data type. This means that @code{ptype}
14350 of a variable or an expression will not print literally its type as
14351 present in the source code---use @code{whatis} for that. @code{typedef}s at
14352 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14353 fields, methods and inner @code{class typedef}s of @code{struct}s,
14354 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14356 For example, for this variable declaration:
14359 typedef double real_t;
14360 struct complex @{ real_t real; double imag; @};
14361 typedef struct complex complex_t;
14363 real_t *real_pointer_var;
14367 the two commands give this output:
14371 (@value{GDBP}) whatis var
14373 (@value{GDBP}) ptype var
14374 type = struct complex @{
14378 (@value{GDBP}) whatis complex_t
14379 type = struct complex
14380 (@value{GDBP}) whatis struct complex
14381 type = struct complex
14382 (@value{GDBP}) ptype struct complex
14383 type = struct complex @{
14387 (@value{GDBP}) whatis real_pointer_var
14389 (@value{GDBP}) ptype real_pointer_var
14395 As with @code{whatis}, using @code{ptype} without an argument refers to
14396 the type of @code{$}, the last value in the value history.
14398 @cindex incomplete type
14399 Sometimes, programs use opaque data types or incomplete specifications
14400 of complex data structure. If the debug information included in the
14401 program does not allow @value{GDBN} to display a full declaration of
14402 the data type, it will say @samp{<incomplete type>}. For example,
14403 given these declarations:
14407 struct foo *fooptr;
14411 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14414 (@value{GDBP}) ptype foo
14415 $1 = <incomplete type>
14419 ``Incomplete type'' is C terminology for data types that are not
14420 completely specified.
14423 @item info types @var{regexp}
14425 Print a brief description of all types whose names match the regular
14426 expression @var{regexp} (or all types in your program, if you supply
14427 no argument). Each complete typename is matched as though it were a
14428 complete line; thus, @samp{i type value} gives information on all
14429 types in your program whose names include the string @code{value}, but
14430 @samp{i type ^value$} gives information only on types whose complete
14431 name is @code{value}.
14433 This command differs from @code{ptype} in two ways: first, like
14434 @code{whatis}, it does not print a detailed description; second, it
14435 lists all source files where a type is defined.
14438 @cindex local variables
14439 @item info scope @var{location}
14440 List all the variables local to a particular scope. This command
14441 accepts a @var{location} argument---a function name, a source line, or
14442 an address preceded by a @samp{*}, and prints all the variables local
14443 to the scope defined by that location. (@xref{Specify Location}, for
14444 details about supported forms of @var{location}.) For example:
14447 (@value{GDBP}) @b{info scope command_line_handler}
14448 Scope for command_line_handler:
14449 Symbol rl is an argument at stack/frame offset 8, length 4.
14450 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14451 Symbol linelength is in static storage at address 0x150a1c, length 4.
14452 Symbol p is a local variable in register $esi, length 4.
14453 Symbol p1 is a local variable in register $ebx, length 4.
14454 Symbol nline is a local variable in register $edx, length 4.
14455 Symbol repeat is a local variable at frame offset -8, length 4.
14459 This command is especially useful for determining what data to collect
14460 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14463 @kindex info source
14465 Show information about the current source file---that is, the source file for
14466 the function containing the current point of execution:
14469 the name of the source file, and the directory containing it,
14471 the directory it was compiled in,
14473 its length, in lines,
14475 which programming language it is written in,
14477 whether the executable includes debugging information for that file, and
14478 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14480 whether the debugging information includes information about
14481 preprocessor macros.
14485 @kindex info sources
14487 Print the names of all source files in your program for which there is
14488 debugging information, organized into two lists: files whose symbols
14489 have already been read, and files whose symbols will be read when needed.
14491 @kindex info functions
14492 @item info functions
14493 Print the names and data types of all defined functions.
14495 @item info functions @var{regexp}
14496 Print the names and data types of all defined functions
14497 whose names contain a match for regular expression @var{regexp}.
14498 Thus, @samp{info fun step} finds all functions whose names
14499 include @code{step}; @samp{info fun ^step} finds those whose names
14500 start with @code{step}. If a function name contains characters
14501 that conflict with the regular expression language (e.g.@:
14502 @samp{operator*()}), they may be quoted with a backslash.
14504 @kindex info variables
14505 @item info variables
14506 Print the names and data types of all variables that are defined
14507 outside of functions (i.e.@: excluding local variables).
14509 @item info variables @var{regexp}
14510 Print the names and data types of all variables (except for local
14511 variables) whose names contain a match for regular expression
14514 @kindex info classes
14515 @cindex Objective-C, classes and selectors
14517 @itemx info classes @var{regexp}
14518 Display all Objective-C classes in your program, or
14519 (with the @var{regexp} argument) all those matching a particular regular
14522 @kindex info selectors
14523 @item info selectors
14524 @itemx info selectors @var{regexp}
14525 Display all Objective-C selectors in your program, or
14526 (with the @var{regexp} argument) all those matching a particular regular
14530 This was never implemented.
14531 @kindex info methods
14533 @itemx info methods @var{regexp}
14534 The @code{info methods} command permits the user to examine all defined
14535 methods within C@t{++} program, or (with the @var{regexp} argument) a
14536 specific set of methods found in the various C@t{++} classes. Many
14537 C@t{++} classes provide a large number of methods. Thus, the output
14538 from the @code{ptype} command can be overwhelming and hard to use. The
14539 @code{info-methods} command filters the methods, printing only those
14540 which match the regular-expression @var{regexp}.
14543 @cindex reloading symbols
14544 Some systems allow individual object files that make up your program to
14545 be replaced without stopping and restarting your program. For example,
14546 in VxWorks you can simply recompile a defective object file and keep on
14547 running. If you are running on one of these systems, you can allow
14548 @value{GDBN} to reload the symbols for automatically relinked modules:
14551 @kindex set symbol-reloading
14552 @item set symbol-reloading on
14553 Replace symbol definitions for the corresponding source file when an
14554 object file with a particular name is seen again.
14556 @item set symbol-reloading off
14557 Do not replace symbol definitions when encountering object files of the
14558 same name more than once. This is the default state; if you are not
14559 running on a system that permits automatic relinking of modules, you
14560 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14561 may discard symbols when linking large programs, that may contain
14562 several modules (from different directories or libraries) with the same
14565 @kindex show symbol-reloading
14566 @item show symbol-reloading
14567 Show the current @code{on} or @code{off} setting.
14570 @cindex opaque data types
14571 @kindex set opaque-type-resolution
14572 @item set opaque-type-resolution on
14573 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14574 declared as a pointer to a @code{struct}, @code{class}, or
14575 @code{union}---for example, @code{struct MyType *}---that is used in one
14576 source file although the full declaration of @code{struct MyType} is in
14577 another source file. The default is on.
14579 A change in the setting of this subcommand will not take effect until
14580 the next time symbols for a file are loaded.
14582 @item set opaque-type-resolution off
14583 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14584 is printed as follows:
14586 @{<no data fields>@}
14589 @kindex show opaque-type-resolution
14590 @item show opaque-type-resolution
14591 Show whether opaque types are resolved or not.
14593 @kindex maint print symbols
14594 @cindex symbol dump
14595 @kindex maint print psymbols
14596 @cindex partial symbol dump
14597 @item maint print symbols @var{filename}
14598 @itemx maint print psymbols @var{filename}
14599 @itemx maint print msymbols @var{filename}
14600 Write a dump of debugging symbol data into the file @var{filename}.
14601 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14602 symbols with debugging data are included. If you use @samp{maint print
14603 symbols}, @value{GDBN} includes all the symbols for which it has already
14604 collected full details: that is, @var{filename} reflects symbols for
14605 only those files whose symbols @value{GDBN} has read. You can use the
14606 command @code{info sources} to find out which files these are. If you
14607 use @samp{maint print psymbols} instead, the dump shows information about
14608 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14609 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14610 @samp{maint print msymbols} dumps just the minimal symbol information
14611 required for each object file from which @value{GDBN} has read some symbols.
14612 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14613 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14615 @kindex maint info symtabs
14616 @kindex maint info psymtabs
14617 @cindex listing @value{GDBN}'s internal symbol tables
14618 @cindex symbol tables, listing @value{GDBN}'s internal
14619 @cindex full symbol tables, listing @value{GDBN}'s internal
14620 @cindex partial symbol tables, listing @value{GDBN}'s internal
14621 @item maint info symtabs @r{[} @var{regexp} @r{]}
14622 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14624 List the @code{struct symtab} or @code{struct partial_symtab}
14625 structures whose names match @var{regexp}. If @var{regexp} is not
14626 given, list them all. The output includes expressions which you can
14627 copy into a @value{GDBN} debugging this one to examine a particular
14628 structure in more detail. For example:
14631 (@value{GDBP}) maint info psymtabs dwarf2read
14632 @{ objfile /home/gnu/build/gdb/gdb
14633 ((struct objfile *) 0x82e69d0)
14634 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14635 ((struct partial_symtab *) 0x8474b10)
14638 text addresses 0x814d3c8 -- 0x8158074
14639 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14640 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14641 dependencies (none)
14644 (@value{GDBP}) maint info symtabs
14648 We see that there is one partial symbol table whose filename contains
14649 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14650 and we see that @value{GDBN} has not read in any symtabs yet at all.
14651 If we set a breakpoint on a function, that will cause @value{GDBN} to
14652 read the symtab for the compilation unit containing that function:
14655 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14656 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14658 (@value{GDBP}) maint info symtabs
14659 @{ objfile /home/gnu/build/gdb/gdb
14660 ((struct objfile *) 0x82e69d0)
14661 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14662 ((struct symtab *) 0x86c1f38)
14665 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14666 linetable ((struct linetable *) 0x8370fa0)
14667 debugformat DWARF 2
14676 @chapter Altering Execution
14678 Once you think you have found an error in your program, you might want to
14679 find out for certain whether correcting the apparent error would lead to
14680 correct results in the rest of the run. You can find the answer by
14681 experiment, using the @value{GDBN} features for altering execution of the
14684 For example, you can store new values into variables or memory
14685 locations, give your program a signal, restart it at a different
14686 address, or even return prematurely from a function.
14689 * Assignment:: Assignment to variables
14690 * Jumping:: Continuing at a different address
14691 * Signaling:: Giving your program a signal
14692 * Returning:: Returning from a function
14693 * Calling:: Calling your program's functions
14694 * Patching:: Patching your program
14698 @section Assignment to Variables
14701 @cindex setting variables
14702 To alter the value of a variable, evaluate an assignment expression.
14703 @xref{Expressions, ,Expressions}. For example,
14710 stores the value 4 into the variable @code{x}, and then prints the
14711 value of the assignment expression (which is 4).
14712 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14713 information on operators in supported languages.
14715 @kindex set variable
14716 @cindex variables, setting
14717 If you are not interested in seeing the value of the assignment, use the
14718 @code{set} command instead of the @code{print} command. @code{set} is
14719 really the same as @code{print} except that the expression's value is
14720 not printed and is not put in the value history (@pxref{Value History,
14721 ,Value History}). The expression is evaluated only for its effects.
14723 If the beginning of the argument string of the @code{set} command
14724 appears identical to a @code{set} subcommand, use the @code{set
14725 variable} command instead of just @code{set}. This command is identical
14726 to @code{set} except for its lack of subcommands. For example, if your
14727 program has a variable @code{width}, you get an error if you try to set
14728 a new value with just @samp{set width=13}, because @value{GDBN} has the
14729 command @code{set width}:
14732 (@value{GDBP}) whatis width
14734 (@value{GDBP}) p width
14736 (@value{GDBP}) set width=47
14737 Invalid syntax in expression.
14741 The invalid expression, of course, is @samp{=47}. In
14742 order to actually set the program's variable @code{width}, use
14745 (@value{GDBP}) set var width=47
14748 Because the @code{set} command has many subcommands that can conflict
14749 with the names of program variables, it is a good idea to use the
14750 @code{set variable} command instead of just @code{set}. For example, if
14751 your program has a variable @code{g}, you run into problems if you try
14752 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14753 the command @code{set gnutarget}, abbreviated @code{set g}:
14757 (@value{GDBP}) whatis g
14761 (@value{GDBP}) set g=4
14765 The program being debugged has been started already.
14766 Start it from the beginning? (y or n) y
14767 Starting program: /home/smith/cc_progs/a.out
14768 "/home/smith/cc_progs/a.out": can't open to read symbols:
14769 Invalid bfd target.
14770 (@value{GDBP}) show g
14771 The current BFD target is "=4".
14776 The program variable @code{g} did not change, and you silently set the
14777 @code{gnutarget} to an invalid value. In order to set the variable
14781 (@value{GDBP}) set var g=4
14784 @value{GDBN} allows more implicit conversions in assignments than C; you can
14785 freely store an integer value into a pointer variable or vice versa,
14786 and you can convert any structure to any other structure that is the
14787 same length or shorter.
14788 @comment FIXME: how do structs align/pad in these conversions?
14789 @comment /doc@cygnus.com 18dec1990
14791 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14792 construct to generate a value of specified type at a specified address
14793 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14794 to memory location @code{0x83040} as an integer (which implies a certain size
14795 and representation in memory), and
14798 set @{int@}0x83040 = 4
14802 stores the value 4 into that memory location.
14805 @section Continuing at a Different Address
14807 Ordinarily, when you continue your program, you do so at the place where
14808 it stopped, with the @code{continue} command. You can instead continue at
14809 an address of your own choosing, with the following commands:
14813 @item jump @var{linespec}
14814 @itemx jump @var{location}
14815 Resume execution at line @var{linespec} or at address given by
14816 @var{location}. Execution stops again immediately if there is a
14817 breakpoint there. @xref{Specify Location}, for a description of the
14818 different forms of @var{linespec} and @var{location}. It is common
14819 practice to use the @code{tbreak} command in conjunction with
14820 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14822 The @code{jump} command does not change the current stack frame, or
14823 the stack pointer, or the contents of any memory location or any
14824 register other than the program counter. If line @var{linespec} is in
14825 a different function from the one currently executing, the results may
14826 be bizarre if the two functions expect different patterns of arguments or
14827 of local variables. For this reason, the @code{jump} command requests
14828 confirmation if the specified line is not in the function currently
14829 executing. However, even bizarre results are predictable if you are
14830 well acquainted with the machine-language code of your program.
14833 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14834 On many systems, you can get much the same effect as the @code{jump}
14835 command by storing a new value into the register @code{$pc}. The
14836 difference is that this does not start your program running; it only
14837 changes the address of where it @emph{will} run when you continue. For
14845 makes the next @code{continue} command or stepping command execute at
14846 address @code{0x485}, rather than at the address where your program stopped.
14847 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14849 The most common occasion to use the @code{jump} command is to back
14850 up---perhaps with more breakpoints set---over a portion of a program
14851 that has already executed, in order to examine its execution in more
14856 @section Giving your Program a Signal
14857 @cindex deliver a signal to a program
14861 @item signal @var{signal}
14862 Resume execution where your program stopped, but immediately give it the
14863 signal @var{signal}. @var{signal} can be the name or the number of a
14864 signal. For example, on many systems @code{signal 2} and @code{signal
14865 SIGINT} are both ways of sending an interrupt signal.
14867 Alternatively, if @var{signal} is zero, continue execution without
14868 giving a signal. This is useful when your program stopped on account of
14869 a signal and would ordinary see the signal when resumed with the
14870 @code{continue} command; @samp{signal 0} causes it to resume without a
14873 @code{signal} does not repeat when you press @key{RET} a second time
14874 after executing the command.
14878 Invoking the @code{signal} command is not the same as invoking the
14879 @code{kill} utility from the shell. Sending a signal with @code{kill}
14880 causes @value{GDBN} to decide what to do with the signal depending on
14881 the signal handling tables (@pxref{Signals}). The @code{signal} command
14882 passes the signal directly to your program.
14886 @section Returning from a Function
14889 @cindex returning from a function
14892 @itemx return @var{expression}
14893 You can cancel execution of a function call with the @code{return}
14894 command. If you give an
14895 @var{expression} argument, its value is used as the function's return
14899 When you use @code{return}, @value{GDBN} discards the selected stack frame
14900 (and all frames within it). You can think of this as making the
14901 discarded frame return prematurely. If you wish to specify a value to
14902 be returned, give that value as the argument to @code{return}.
14904 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14905 Frame}), and any other frames inside of it, leaving its caller as the
14906 innermost remaining frame. That frame becomes selected. The
14907 specified value is stored in the registers used for returning values
14910 The @code{return} command does not resume execution; it leaves the
14911 program stopped in the state that would exist if the function had just
14912 returned. In contrast, the @code{finish} command (@pxref{Continuing
14913 and Stepping, ,Continuing and Stepping}) resumes execution until the
14914 selected stack frame returns naturally.
14916 @value{GDBN} needs to know how the @var{expression} argument should be set for
14917 the inferior. The concrete registers assignment depends on the OS ABI and the
14918 type being returned by the selected stack frame. For example it is common for
14919 OS ABI to return floating point values in FPU registers while integer values in
14920 CPU registers. Still some ABIs return even floating point values in CPU
14921 registers. Larger integer widths (such as @code{long long int}) also have
14922 specific placement rules. @value{GDBN} already knows the OS ABI from its
14923 current target so it needs to find out also the type being returned to make the
14924 assignment into the right register(s).
14926 Normally, the selected stack frame has debug info. @value{GDBN} will always
14927 use the debug info instead of the implicit type of @var{expression} when the
14928 debug info is available. For example, if you type @kbd{return -1}, and the
14929 function in the current stack frame is declared to return a @code{long long
14930 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14931 into a @code{long long int}:
14934 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14936 (@value{GDBP}) return -1
14937 Make func return now? (y or n) y
14938 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14939 43 printf ("result=%lld\n", func ());
14943 However, if the selected stack frame does not have a debug info, e.g., if the
14944 function was compiled without debug info, @value{GDBN} has to find out the type
14945 to return from user. Specifying a different type by mistake may set the value
14946 in different inferior registers than the caller code expects. For example,
14947 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14948 of a @code{long long int} result for a debug info less function (on 32-bit
14949 architectures). Therefore the user is required to specify the return type by
14950 an appropriate cast explicitly:
14953 Breakpoint 2, 0x0040050b in func ()
14954 (@value{GDBP}) return -1
14955 Return value type not available for selected stack frame.
14956 Please use an explicit cast of the value to return.
14957 (@value{GDBP}) return (long long int) -1
14958 Make selected stack frame return now? (y or n) y
14959 #0 0x00400526 in main ()
14964 @section Calling Program Functions
14967 @cindex calling functions
14968 @cindex inferior functions, calling
14969 @item print @var{expr}
14970 Evaluate the expression @var{expr} and display the resulting value.
14971 @var{expr} may include calls to functions in the program being
14975 @item call @var{expr}
14976 Evaluate the expression @var{expr} without displaying @code{void}
14979 You can use this variant of the @code{print} command if you want to
14980 execute a function from your program that does not return anything
14981 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14982 with @code{void} returned values that @value{GDBN} will otherwise
14983 print. If the result is not void, it is printed and saved in the
14987 It is possible for the function you call via the @code{print} or
14988 @code{call} command to generate a signal (e.g., if there's a bug in
14989 the function, or if you passed it incorrect arguments). What happens
14990 in that case is controlled by the @code{set unwindonsignal} command.
14992 Similarly, with a C@t{++} program it is possible for the function you
14993 call via the @code{print} or @code{call} command to generate an
14994 exception that is not handled due to the constraints of the dummy
14995 frame. In this case, any exception that is raised in the frame, but has
14996 an out-of-frame exception handler will not be found. GDB builds a
14997 dummy-frame for the inferior function call, and the unwinder cannot
14998 seek for exception handlers outside of this dummy-frame. What happens
14999 in that case is controlled by the
15000 @code{set unwind-on-terminating-exception} command.
15003 @item set unwindonsignal
15004 @kindex set unwindonsignal
15005 @cindex unwind stack in called functions
15006 @cindex call dummy stack unwinding
15007 Set unwinding of the stack if a signal is received while in a function
15008 that @value{GDBN} called in the program being debugged. If set to on,
15009 @value{GDBN} unwinds the stack it created for the call and restores
15010 the context to what it was before the call. If set to off (the
15011 default), @value{GDBN} stops in the frame where the signal was
15014 @item show unwindonsignal
15015 @kindex show unwindonsignal
15016 Show the current setting of stack unwinding in the functions called by
15019 @item set unwind-on-terminating-exception
15020 @kindex set unwind-on-terminating-exception
15021 @cindex unwind stack in called functions with unhandled exceptions
15022 @cindex call dummy stack unwinding on unhandled exception.
15023 Set unwinding of the stack if a C@t{++} exception is raised, but left
15024 unhandled while in a function that @value{GDBN} called in the program being
15025 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15026 it created for the call and restores the context to what it was before
15027 the call. If set to off, @value{GDBN} the exception is delivered to
15028 the default C@t{++} exception handler and the inferior terminated.
15030 @item show unwind-on-terminating-exception
15031 @kindex show unwind-on-terminating-exception
15032 Show the current setting of stack unwinding in the functions called by
15037 @cindex weak alias functions
15038 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15039 for another function. In such case, @value{GDBN} might not pick up
15040 the type information, including the types of the function arguments,
15041 which causes @value{GDBN} to call the inferior function incorrectly.
15042 As a result, the called function will function erroneously and may
15043 even crash. A solution to that is to use the name of the aliased
15047 @section Patching Programs
15049 @cindex patching binaries
15050 @cindex writing into executables
15051 @cindex writing into corefiles
15053 By default, @value{GDBN} opens the file containing your program's
15054 executable code (or the corefile) read-only. This prevents accidental
15055 alterations to machine code; but it also prevents you from intentionally
15056 patching your program's binary.
15058 If you'd like to be able to patch the binary, you can specify that
15059 explicitly with the @code{set write} command. For example, you might
15060 want to turn on internal debugging flags, or even to make emergency
15066 @itemx set write off
15067 If you specify @samp{set write on}, @value{GDBN} opens executable and
15068 core files for both reading and writing; if you specify @kbd{set write
15069 off} (the default), @value{GDBN} opens them read-only.
15071 If you have already loaded a file, you must load it again (using the
15072 @code{exec-file} or @code{core-file} command) after changing @code{set
15073 write}, for your new setting to take effect.
15077 Display whether executable files and core files are opened for writing
15078 as well as reading.
15082 @chapter @value{GDBN} Files
15084 @value{GDBN} needs to know the file name of the program to be debugged,
15085 both in order to read its symbol table and in order to start your
15086 program. To debug a core dump of a previous run, you must also tell
15087 @value{GDBN} the name of the core dump file.
15090 * Files:: Commands to specify files
15091 * Separate Debug Files:: Debugging information in separate files
15092 * Index Files:: Index files speed up GDB
15093 * Symbol Errors:: Errors reading symbol files
15094 * Data Files:: GDB data files
15098 @section Commands to Specify Files
15100 @cindex symbol table
15101 @cindex core dump file
15103 You may want to specify executable and core dump file names. The usual
15104 way to do this is at start-up time, using the arguments to
15105 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15106 Out of @value{GDBN}}).
15108 Occasionally it is necessary to change to a different file during a
15109 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15110 specify a file you want to use. Or you are debugging a remote target
15111 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15112 Program}). In these situations the @value{GDBN} commands to specify
15113 new files are useful.
15116 @cindex executable file
15118 @item file @var{filename}
15119 Use @var{filename} as the program to be debugged. It is read for its
15120 symbols and for the contents of pure memory. It is also the program
15121 executed when you use the @code{run} command. If you do not specify a
15122 directory and the file is not found in the @value{GDBN} working directory,
15123 @value{GDBN} uses the environment variable @code{PATH} as a list of
15124 directories to search, just as the shell does when looking for a program
15125 to run. You can change the value of this variable, for both @value{GDBN}
15126 and your program, using the @code{path} command.
15128 @cindex unlinked object files
15129 @cindex patching object files
15130 You can load unlinked object @file{.o} files into @value{GDBN} using
15131 the @code{file} command. You will not be able to ``run'' an object
15132 file, but you can disassemble functions and inspect variables. Also,
15133 if the underlying BFD functionality supports it, you could use
15134 @kbd{gdb -write} to patch object files using this technique. Note
15135 that @value{GDBN} can neither interpret nor modify relocations in this
15136 case, so branches and some initialized variables will appear to go to
15137 the wrong place. But this feature is still handy from time to time.
15140 @code{file} with no argument makes @value{GDBN} discard any information it
15141 has on both executable file and the symbol table.
15144 @item exec-file @r{[} @var{filename} @r{]}
15145 Specify that the program to be run (but not the symbol table) is found
15146 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15147 if necessary to locate your program. Omitting @var{filename} means to
15148 discard information on the executable file.
15150 @kindex symbol-file
15151 @item symbol-file @r{[} @var{filename} @r{]}
15152 Read symbol table information from file @var{filename}. @code{PATH} is
15153 searched when necessary. Use the @code{file} command to get both symbol
15154 table and program to run from the same file.
15156 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15157 program's symbol table.
15159 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15160 some breakpoints and auto-display expressions. This is because they may
15161 contain pointers to the internal data recording symbols and data types,
15162 which are part of the old symbol table data being discarded inside
15165 @code{symbol-file} does not repeat if you press @key{RET} again after
15168 When @value{GDBN} is configured for a particular environment, it
15169 understands debugging information in whatever format is the standard
15170 generated for that environment; you may use either a @sc{gnu} compiler, or
15171 other compilers that adhere to the local conventions.
15172 Best results are usually obtained from @sc{gnu} compilers; for example,
15173 using @code{@value{NGCC}} you can generate debugging information for
15176 For most kinds of object files, with the exception of old SVR3 systems
15177 using COFF, the @code{symbol-file} command does not normally read the
15178 symbol table in full right away. Instead, it scans the symbol table
15179 quickly to find which source files and which symbols are present. The
15180 details are read later, one source file at a time, as they are needed.
15182 The purpose of this two-stage reading strategy is to make @value{GDBN}
15183 start up faster. For the most part, it is invisible except for
15184 occasional pauses while the symbol table details for a particular source
15185 file are being read. (The @code{set verbose} command can turn these
15186 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15187 Warnings and Messages}.)
15189 We have not implemented the two-stage strategy for COFF yet. When the
15190 symbol table is stored in COFF format, @code{symbol-file} reads the
15191 symbol table data in full right away. Note that ``stabs-in-COFF''
15192 still does the two-stage strategy, since the debug info is actually
15196 @cindex reading symbols immediately
15197 @cindex symbols, reading immediately
15198 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15199 @itemx file @r{[} -readnow @r{]} @var{filename}
15200 You can override the @value{GDBN} two-stage strategy for reading symbol
15201 tables by using the @samp{-readnow} option with any of the commands that
15202 load symbol table information, if you want to be sure @value{GDBN} has the
15203 entire symbol table available.
15205 @c FIXME: for now no mention of directories, since this seems to be in
15206 @c flux. 13mar1992 status is that in theory GDB would look either in
15207 @c current dir or in same dir as myprog; but issues like competing
15208 @c GDB's, or clutter in system dirs, mean that in practice right now
15209 @c only current dir is used. FFish says maybe a special GDB hierarchy
15210 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15214 @item core-file @r{[}@var{filename}@r{]}
15216 Specify the whereabouts of a core dump file to be used as the ``contents
15217 of memory''. Traditionally, core files contain only some parts of the
15218 address space of the process that generated them; @value{GDBN} can access the
15219 executable file itself for other parts.
15221 @code{core-file} with no argument specifies that no core file is
15224 Note that the core file is ignored when your program is actually running
15225 under @value{GDBN}. So, if you have been running your program and you
15226 wish to debug a core file instead, you must kill the subprocess in which
15227 the program is running. To do this, use the @code{kill} command
15228 (@pxref{Kill Process, ,Killing the Child Process}).
15230 @kindex add-symbol-file
15231 @cindex dynamic linking
15232 @item add-symbol-file @var{filename} @var{address}
15233 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15234 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15235 The @code{add-symbol-file} command reads additional symbol table
15236 information from the file @var{filename}. You would use this command
15237 when @var{filename} has been dynamically loaded (by some other means)
15238 into the program that is running. @var{address} should be the memory
15239 address at which the file has been loaded; @value{GDBN} cannot figure
15240 this out for itself. You can additionally specify an arbitrary number
15241 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15242 section name and base address for that section. You can specify any
15243 @var{address} as an expression.
15245 The symbol table of the file @var{filename} is added to the symbol table
15246 originally read with the @code{symbol-file} command. You can use the
15247 @code{add-symbol-file} command any number of times; the new symbol data
15248 thus read keeps adding to the old. To discard all old symbol data
15249 instead, use the @code{symbol-file} command without any arguments.
15251 @cindex relocatable object files, reading symbols from
15252 @cindex object files, relocatable, reading symbols from
15253 @cindex reading symbols from relocatable object files
15254 @cindex symbols, reading from relocatable object files
15255 @cindex @file{.o} files, reading symbols from
15256 Although @var{filename} is typically a shared library file, an
15257 executable file, or some other object file which has been fully
15258 relocated for loading into a process, you can also load symbolic
15259 information from relocatable @file{.o} files, as long as:
15263 the file's symbolic information refers only to linker symbols defined in
15264 that file, not to symbols defined by other object files,
15266 every section the file's symbolic information refers to has actually
15267 been loaded into the inferior, as it appears in the file, and
15269 you can determine the address at which every section was loaded, and
15270 provide these to the @code{add-symbol-file} command.
15274 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15275 relocatable files into an already running program; such systems
15276 typically make the requirements above easy to meet. However, it's
15277 important to recognize that many native systems use complex link
15278 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15279 assembly, for example) that make the requirements difficult to meet. In
15280 general, one cannot assume that using @code{add-symbol-file} to read a
15281 relocatable object file's symbolic information will have the same effect
15282 as linking the relocatable object file into the program in the normal
15285 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15287 @kindex add-symbol-file-from-memory
15288 @cindex @code{syscall DSO}
15289 @cindex load symbols from memory
15290 @item add-symbol-file-from-memory @var{address}
15291 Load symbols from the given @var{address} in a dynamically loaded
15292 object file whose image is mapped directly into the inferior's memory.
15293 For example, the Linux kernel maps a @code{syscall DSO} into each
15294 process's address space; this DSO provides kernel-specific code for
15295 some system calls. The argument can be any expression whose
15296 evaluation yields the address of the file's shared object file header.
15297 For this command to work, you must have used @code{symbol-file} or
15298 @code{exec-file} commands in advance.
15300 @kindex add-shared-symbol-files
15302 @item add-shared-symbol-files @var{library-file}
15303 @itemx assf @var{library-file}
15304 The @code{add-shared-symbol-files} command can currently be used only
15305 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15306 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15307 @value{GDBN} automatically looks for shared libraries, however if
15308 @value{GDBN} does not find yours, you can invoke
15309 @code{add-shared-symbol-files}. It takes one argument: the shared
15310 library's file name. @code{assf} is a shorthand alias for
15311 @code{add-shared-symbol-files}.
15314 @item section @var{section} @var{addr}
15315 The @code{section} command changes the base address of the named
15316 @var{section} of the exec file to @var{addr}. This can be used if the
15317 exec file does not contain section addresses, (such as in the
15318 @code{a.out} format), or when the addresses specified in the file
15319 itself are wrong. Each section must be changed separately. The
15320 @code{info files} command, described below, lists all the sections and
15324 @kindex info target
15327 @code{info files} and @code{info target} are synonymous; both print the
15328 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15329 including the names of the executable and core dump files currently in
15330 use by @value{GDBN}, and the files from which symbols were loaded. The
15331 command @code{help target} lists all possible targets rather than
15334 @kindex maint info sections
15335 @item maint info sections
15336 Another command that can give you extra information about program sections
15337 is @code{maint info sections}. In addition to the section information
15338 displayed by @code{info files}, this command displays the flags and file
15339 offset of each section in the executable and core dump files. In addition,
15340 @code{maint info sections} provides the following command options (which
15341 may be arbitrarily combined):
15345 Display sections for all loaded object files, including shared libraries.
15346 @item @var{sections}
15347 Display info only for named @var{sections}.
15348 @item @var{section-flags}
15349 Display info only for sections for which @var{section-flags} are true.
15350 The section flags that @value{GDBN} currently knows about are:
15353 Section will have space allocated in the process when loaded.
15354 Set for all sections except those containing debug information.
15356 Section will be loaded from the file into the child process memory.
15357 Set for pre-initialized code and data, clear for @code{.bss} sections.
15359 Section needs to be relocated before loading.
15361 Section cannot be modified by the child process.
15363 Section contains executable code only.
15365 Section contains data only (no executable code).
15367 Section will reside in ROM.
15369 Section contains data for constructor/destructor lists.
15371 Section is not empty.
15373 An instruction to the linker to not output the section.
15374 @item COFF_SHARED_LIBRARY
15375 A notification to the linker that the section contains
15376 COFF shared library information.
15378 Section contains common symbols.
15381 @kindex set trust-readonly-sections
15382 @cindex read-only sections
15383 @item set trust-readonly-sections on
15384 Tell @value{GDBN} that readonly sections in your object file
15385 really are read-only (i.e.@: that their contents will not change).
15386 In that case, @value{GDBN} can fetch values from these sections
15387 out of the object file, rather than from the target program.
15388 For some targets (notably embedded ones), this can be a significant
15389 enhancement to debugging performance.
15391 The default is off.
15393 @item set trust-readonly-sections off
15394 Tell @value{GDBN} not to trust readonly sections. This means that
15395 the contents of the section might change while the program is running,
15396 and must therefore be fetched from the target when needed.
15398 @item show trust-readonly-sections
15399 Show the current setting of trusting readonly sections.
15402 All file-specifying commands allow both absolute and relative file names
15403 as arguments. @value{GDBN} always converts the file name to an absolute file
15404 name and remembers it that way.
15406 @cindex shared libraries
15407 @anchor{Shared Libraries}
15408 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15409 and IBM RS/6000 AIX shared libraries.
15411 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15412 shared libraries. @xref{Expat}.
15414 @value{GDBN} automatically loads symbol definitions from shared libraries
15415 when you use the @code{run} command, or when you examine a core file.
15416 (Before you issue the @code{run} command, @value{GDBN} does not understand
15417 references to a function in a shared library, however---unless you are
15418 debugging a core file).
15420 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15421 automatically loads the symbols at the time of the @code{shl_load} call.
15423 @c FIXME: some @value{GDBN} release may permit some refs to undef
15424 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15425 @c FIXME...lib; check this from time to time when updating manual
15427 There are times, however, when you may wish to not automatically load
15428 symbol definitions from shared libraries, such as when they are
15429 particularly large or there are many of them.
15431 To control the automatic loading of shared library symbols, use the
15435 @kindex set auto-solib-add
15436 @item set auto-solib-add @var{mode}
15437 If @var{mode} is @code{on}, symbols from all shared object libraries
15438 will be loaded automatically when the inferior begins execution, you
15439 attach to an independently started inferior, or when the dynamic linker
15440 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15441 is @code{off}, symbols must be loaded manually, using the
15442 @code{sharedlibrary} command. The default value is @code{on}.
15444 @cindex memory used for symbol tables
15445 If your program uses lots of shared libraries with debug info that
15446 takes large amounts of memory, you can decrease the @value{GDBN}
15447 memory footprint by preventing it from automatically loading the
15448 symbols from shared libraries. To that end, type @kbd{set
15449 auto-solib-add off} before running the inferior, then load each
15450 library whose debug symbols you do need with @kbd{sharedlibrary
15451 @var{regexp}}, where @var{regexp} is a regular expression that matches
15452 the libraries whose symbols you want to be loaded.
15454 @kindex show auto-solib-add
15455 @item show auto-solib-add
15456 Display the current autoloading mode.
15459 @cindex load shared library
15460 To explicitly load shared library symbols, use the @code{sharedlibrary}
15464 @kindex info sharedlibrary
15466 @item info share @var{regex}
15467 @itemx info sharedlibrary @var{regex}
15468 Print the names of the shared libraries which are currently loaded
15469 that match @var{regex}. If @var{regex} is omitted then print
15470 all shared libraries that are loaded.
15472 @kindex sharedlibrary
15474 @item sharedlibrary @var{regex}
15475 @itemx share @var{regex}
15476 Load shared object library symbols for files matching a
15477 Unix regular expression.
15478 As with files loaded automatically, it only loads shared libraries
15479 required by your program for a core file or after typing @code{run}. If
15480 @var{regex} is omitted all shared libraries required by your program are
15483 @item nosharedlibrary
15484 @kindex nosharedlibrary
15485 @cindex unload symbols from shared libraries
15486 Unload all shared object library symbols. This discards all symbols
15487 that have been loaded from all shared libraries. Symbols from shared
15488 libraries that were loaded by explicit user requests are not
15492 Sometimes you may wish that @value{GDBN} stops and gives you control
15493 when any of shared library events happen. Use the @code{set
15494 stop-on-solib-events} command for this:
15497 @item set stop-on-solib-events
15498 @kindex set stop-on-solib-events
15499 This command controls whether @value{GDBN} should give you control
15500 when the dynamic linker notifies it about some shared library event.
15501 The most common event of interest is loading or unloading of a new
15504 @item show stop-on-solib-events
15505 @kindex show stop-on-solib-events
15506 Show whether @value{GDBN} stops and gives you control when shared
15507 library events happen.
15510 Shared libraries are also supported in many cross or remote debugging
15511 configurations. @value{GDBN} needs to have access to the target's libraries;
15512 this can be accomplished either by providing copies of the libraries
15513 on the host system, or by asking @value{GDBN} to automatically retrieve the
15514 libraries from the target. If copies of the target libraries are
15515 provided, they need to be the same as the target libraries, although the
15516 copies on the target can be stripped as long as the copies on the host are
15519 @cindex where to look for shared libraries
15520 For remote debugging, you need to tell @value{GDBN} where the target
15521 libraries are, so that it can load the correct copies---otherwise, it
15522 may try to load the host's libraries. @value{GDBN} has two variables
15523 to specify the search directories for target libraries.
15526 @cindex prefix for shared library file names
15527 @cindex system root, alternate
15528 @kindex set solib-absolute-prefix
15529 @kindex set sysroot
15530 @item set sysroot @var{path}
15531 Use @var{path} as the system root for the program being debugged. Any
15532 absolute shared library paths will be prefixed with @var{path}; many
15533 runtime loaders store the absolute paths to the shared library in the
15534 target program's memory. If you use @code{set sysroot} to find shared
15535 libraries, they need to be laid out in the same way that they are on
15536 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15539 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15540 retrieve the target libraries from the remote system. This is only
15541 supported when using a remote target that supports the @code{remote get}
15542 command (@pxref{File Transfer,,Sending files to a remote system}).
15543 The part of @var{path} following the initial @file{remote:}
15544 (if present) is used as system root prefix on the remote file system.
15545 @footnote{If you want to specify a local system root using a directory
15546 that happens to be named @file{remote:}, you need to use some equivalent
15547 variant of the name like @file{./remote:}.}
15549 For targets with an MS-DOS based filesystem, such as MS-Windows and
15550 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15551 absolute file name with @var{path}. But first, on Unix hosts,
15552 @value{GDBN} converts all backslash directory separators into forward
15553 slashes, because the backslash is not a directory separator on Unix:
15556 c:\foo\bar.dll @result{} c:/foo/bar.dll
15559 Then, @value{GDBN} attempts prefixing the target file name with
15560 @var{path}, and looks for the resulting file name in the host file
15564 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15567 If that does not find the shared library, @value{GDBN} tries removing
15568 the @samp{:} character from the drive spec, both for convenience, and,
15569 for the case of the host file system not supporting file names with
15573 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15576 This makes it possible to have a system root that mirrors a target
15577 with more than one drive. E.g., you may want to setup your local
15578 copies of the target system shared libraries like so (note @samp{c} vs
15582 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15583 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15584 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15588 and point the system root at @file{/path/to/sysroot}, so that
15589 @value{GDBN} can find the correct copies of both
15590 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15592 If that still does not find the shared library, @value{GDBN} tries
15593 removing the whole drive spec from the target file name:
15596 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15599 This last lookup makes it possible to not care about the drive name,
15600 if you don't want or need to.
15602 The @code{set solib-absolute-prefix} command is an alias for @code{set
15605 @cindex default system root
15606 @cindex @samp{--with-sysroot}
15607 You can set the default system root by using the configure-time
15608 @samp{--with-sysroot} option. If the system root is inside
15609 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15610 @samp{--exec-prefix}), then the default system root will be updated
15611 automatically if the installed @value{GDBN} is moved to a new
15614 @kindex show sysroot
15616 Display the current shared library prefix.
15618 @kindex set solib-search-path
15619 @item set solib-search-path @var{path}
15620 If this variable is set, @var{path} is a colon-separated list of
15621 directories to search for shared libraries. @samp{solib-search-path}
15622 is used after @samp{sysroot} fails to locate the library, or if the
15623 path to the library is relative instead of absolute. If you want to
15624 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15625 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15626 finding your host's libraries. @samp{sysroot} is preferred; setting
15627 it to a nonexistent directory may interfere with automatic loading
15628 of shared library symbols.
15630 @kindex show solib-search-path
15631 @item show solib-search-path
15632 Display the current shared library search path.
15634 @cindex DOS file-name semantics of file names.
15635 @kindex set target-file-system-kind (unix|dos-based|auto)
15636 @kindex show target-file-system-kind
15637 @item set target-file-system-kind @var{kind}
15638 Set assumed file system kind for target reported file names.
15640 Shared library file names as reported by the target system may not
15641 make sense as is on the system @value{GDBN} is running on. For
15642 example, when remote debugging a target that has MS-DOS based file
15643 system semantics, from a Unix host, the target may be reporting to
15644 @value{GDBN} a list of loaded shared libraries with file names such as
15645 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15646 drive letters, so the @samp{c:\} prefix is not normally understood as
15647 indicating an absolute file name, and neither is the backslash
15648 normally considered a directory separator character. In that case,
15649 the native file system would interpret this whole absolute file name
15650 as a relative file name with no directory components. This would make
15651 it impossible to point @value{GDBN} at a copy of the remote target's
15652 shared libraries on the host using @code{set sysroot}, and impractical
15653 with @code{set solib-search-path}. Setting
15654 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15655 to interpret such file names similarly to how the target would, and to
15656 map them to file names valid on @value{GDBN}'s native file system
15657 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15658 to one of the supported file system kinds. In that case, @value{GDBN}
15659 tries to determine the appropriate file system variant based on the
15660 current target's operating system (@pxref{ABI, ,Configuring the
15661 Current ABI}). The supported file system settings are:
15665 Instruct @value{GDBN} to assume the target file system is of Unix
15666 kind. Only file names starting the forward slash (@samp{/}) character
15667 are considered absolute, and the directory separator character is also
15671 Instruct @value{GDBN} to assume the target file system is DOS based.
15672 File names starting with either a forward slash, or a drive letter
15673 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15674 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15675 considered directory separators.
15678 Instruct @value{GDBN} to use the file system kind associated with the
15679 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15680 This is the default.
15685 @node Separate Debug Files
15686 @section Debugging Information in Separate Files
15687 @cindex separate debugging information files
15688 @cindex debugging information in separate files
15689 @cindex @file{.debug} subdirectories
15690 @cindex debugging information directory, global
15691 @cindex global debugging information directory
15692 @cindex build ID, and separate debugging files
15693 @cindex @file{.build-id} directory
15695 @value{GDBN} allows you to put a program's debugging information in a
15696 file separate from the executable itself, in a way that allows
15697 @value{GDBN} to find and load the debugging information automatically.
15698 Since debugging information can be very large---sometimes larger
15699 than the executable code itself---some systems distribute debugging
15700 information for their executables in separate files, which users can
15701 install only when they need to debug a problem.
15703 @value{GDBN} supports two ways of specifying the separate debug info
15708 The executable contains a @dfn{debug link} that specifies the name of
15709 the separate debug info file. The separate debug file's name is
15710 usually @file{@var{executable}.debug}, where @var{executable} is the
15711 name of the corresponding executable file without leading directories
15712 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15713 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15714 checksum for the debug file, which @value{GDBN} uses to validate that
15715 the executable and the debug file came from the same build.
15718 The executable contains a @dfn{build ID}, a unique bit string that is
15719 also present in the corresponding debug info file. (This is supported
15720 only on some operating systems, notably those which use the ELF format
15721 for binary files and the @sc{gnu} Binutils.) For more details about
15722 this feature, see the description of the @option{--build-id}
15723 command-line option in @ref{Options, , Command Line Options, ld.info,
15724 The GNU Linker}. The debug info file's name is not specified
15725 explicitly by the build ID, but can be computed from the build ID, see
15729 Depending on the way the debug info file is specified, @value{GDBN}
15730 uses two different methods of looking for the debug file:
15734 For the ``debug link'' method, @value{GDBN} looks up the named file in
15735 the directory of the executable file, then in a subdirectory of that
15736 directory named @file{.debug}, and finally under the global debug
15737 directory, in a subdirectory whose name is identical to the leading
15738 directories of the executable's absolute file name.
15741 For the ``build ID'' method, @value{GDBN} looks in the
15742 @file{.build-id} subdirectory of the global debug directory for a file
15743 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15744 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15745 are the rest of the bit string. (Real build ID strings are 32 or more
15746 hex characters, not 10.)
15749 So, for example, suppose you ask @value{GDBN} to debug
15750 @file{/usr/bin/ls}, which has a debug link that specifies the
15751 file @file{ls.debug}, and a build ID whose value in hex is
15752 @code{abcdef1234}. If the global debug directory is
15753 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15754 debug information files, in the indicated order:
15758 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15760 @file{/usr/bin/ls.debug}
15762 @file{/usr/bin/.debug/ls.debug}
15764 @file{/usr/lib/debug/usr/bin/ls.debug}.
15767 You can set the global debugging info directory's name, and view the
15768 name @value{GDBN} is currently using.
15772 @kindex set debug-file-directory
15773 @item set debug-file-directory @var{directories}
15774 Set the directories which @value{GDBN} searches for separate debugging
15775 information files to @var{directory}. Multiple directory components can be set
15776 concatenating them by a directory separator.
15778 @kindex show debug-file-directory
15779 @item show debug-file-directory
15780 Show the directories @value{GDBN} searches for separate debugging
15785 @cindex @code{.gnu_debuglink} sections
15786 @cindex debug link sections
15787 A debug link is a special section of the executable file named
15788 @code{.gnu_debuglink}. The section must contain:
15792 A filename, with any leading directory components removed, followed by
15795 zero to three bytes of padding, as needed to reach the next four-byte
15796 boundary within the section, and
15798 a four-byte CRC checksum, stored in the same endianness used for the
15799 executable file itself. The checksum is computed on the debugging
15800 information file's full contents by the function given below, passing
15801 zero as the @var{crc} argument.
15804 Any executable file format can carry a debug link, as long as it can
15805 contain a section named @code{.gnu_debuglink} with the contents
15808 @cindex @code{.note.gnu.build-id} sections
15809 @cindex build ID sections
15810 The build ID is a special section in the executable file (and in other
15811 ELF binary files that @value{GDBN} may consider). This section is
15812 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15813 It contains unique identification for the built files---the ID remains
15814 the same across multiple builds of the same build tree. The default
15815 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15816 content for the build ID string. The same section with an identical
15817 value is present in the original built binary with symbols, in its
15818 stripped variant, and in the separate debugging information file.
15820 The debugging information file itself should be an ordinary
15821 executable, containing a full set of linker symbols, sections, and
15822 debugging information. The sections of the debugging information file
15823 should have the same names, addresses, and sizes as the original file,
15824 but they need not contain any data---much like a @code{.bss} section
15825 in an ordinary executable.
15827 The @sc{gnu} binary utilities (Binutils) package includes the
15828 @samp{objcopy} utility that can produce
15829 the separated executable / debugging information file pairs using the
15830 following commands:
15833 @kbd{objcopy --only-keep-debug foo foo.debug}
15838 These commands remove the debugging
15839 information from the executable file @file{foo} and place it in the file
15840 @file{foo.debug}. You can use the first, second or both methods to link the
15845 The debug link method needs the following additional command to also leave
15846 behind a debug link in @file{foo}:
15849 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15852 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15853 a version of the @code{strip} command such that the command @kbd{strip foo -f
15854 foo.debug} has the same functionality as the two @code{objcopy} commands and
15855 the @code{ln -s} command above, together.
15858 Build ID gets embedded into the main executable using @code{ld --build-id} or
15859 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15860 compatibility fixes for debug files separation are present in @sc{gnu} binary
15861 utilities (Binutils) package since version 2.18.
15866 @cindex CRC algorithm definition
15867 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15868 IEEE 802.3 using the polynomial:
15870 @c TexInfo requires naked braces for multi-digit exponents for Tex
15871 @c output, but this causes HTML output to barf. HTML has to be set using
15872 @c raw commands. So we end up having to specify this equation in 2
15877 <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>
15878 + <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
15884 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15885 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15889 The function is computed byte at a time, taking the least
15890 significant bit of each byte first. The initial pattern
15891 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15892 the final result is inverted to ensure trailing zeros also affect the
15895 @emph{Note:} This is the same CRC polynomial as used in handling the
15896 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15897 , @value{GDBN} Remote Serial Protocol}). However in the
15898 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15899 significant bit first, and the result is not inverted, so trailing
15900 zeros have no effect on the CRC value.
15902 To complete the description, we show below the code of the function
15903 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15904 initially supplied @code{crc} argument means that an initial call to
15905 this function passing in zero will start computing the CRC using
15908 @kindex gnu_debuglink_crc32
15911 gnu_debuglink_crc32 (unsigned long crc,
15912 unsigned char *buf, size_t len)
15914 static const unsigned long crc32_table[256] =
15916 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15917 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15918 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15919 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15920 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15921 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15922 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15923 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15924 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15925 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15926 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15927 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15928 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15929 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15930 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15931 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15932 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15933 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15934 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15935 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15936 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15937 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15938 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15939 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15940 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15941 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15942 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15943 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15944 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15945 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15946 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15947 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15948 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15949 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15950 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15951 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15952 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15953 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15954 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15955 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15956 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15957 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15958 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15959 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15960 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15961 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15962 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15963 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15964 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15965 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15966 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15969 unsigned char *end;
15971 crc = ~crc & 0xffffffff;
15972 for (end = buf + len; buf < end; ++buf)
15973 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15974 return ~crc & 0xffffffff;
15979 This computation does not apply to the ``build ID'' method.
15983 @section Index Files Speed Up @value{GDBN}
15984 @cindex index files
15985 @cindex @samp{.gdb_index} section
15987 When @value{GDBN} finds a symbol file, it scans the symbols in the
15988 file in order to construct an internal symbol table. This lets most
15989 @value{GDBN} operations work quickly---at the cost of a delay early
15990 on. For large programs, this delay can be quite lengthy, so
15991 @value{GDBN} provides a way to build an index, which speeds up
15994 The index is stored as a section in the symbol file. @value{GDBN} can
15995 write the index to a file, then you can put it into the symbol file
15996 using @command{objcopy}.
15998 To create an index file, use the @code{save gdb-index} command:
16001 @item save gdb-index @var{directory}
16002 @kindex save gdb-index
16003 Create an index file for each symbol file currently known by
16004 @value{GDBN}. Each file is named after its corresponding symbol file,
16005 with @samp{.gdb-index} appended, and is written into the given
16009 Once you have created an index file you can merge it into your symbol
16010 file, here named @file{symfile}, using @command{objcopy}:
16013 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16014 --set-section-flags .gdb_index=readonly symfile symfile
16017 There are currently some limitation on indices. They only work when
16018 for DWARF debugging information, not stabs. And, they do not
16019 currently work for programs using Ada.
16021 @node Symbol Errors
16022 @section Errors Reading Symbol Files
16024 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16025 such as symbol types it does not recognize, or known bugs in compiler
16026 output. By default, @value{GDBN} does not notify you of such problems, since
16027 they are relatively common and primarily of interest to people
16028 debugging compilers. If you are interested in seeing information
16029 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16030 only one message about each such type of problem, no matter how many
16031 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16032 to see how many times the problems occur, with the @code{set
16033 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16036 The messages currently printed, and their meanings, include:
16039 @item inner block not inside outer block in @var{symbol}
16041 The symbol information shows where symbol scopes begin and end
16042 (such as at the start of a function or a block of statements). This
16043 error indicates that an inner scope block is not fully contained
16044 in its outer scope blocks.
16046 @value{GDBN} circumvents the problem by treating the inner block as if it had
16047 the same scope as the outer block. In the error message, @var{symbol}
16048 may be shown as ``@code{(don't know)}'' if the outer block is not a
16051 @item block at @var{address} out of order
16053 The symbol information for symbol scope blocks should occur in
16054 order of increasing addresses. This error indicates that it does not
16057 @value{GDBN} does not circumvent this problem, and has trouble
16058 locating symbols in the source file whose symbols it is reading. (You
16059 can often determine what source file is affected by specifying
16060 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16063 @item bad block start address patched
16065 The symbol information for a symbol scope block has a start address
16066 smaller than the address of the preceding source line. This is known
16067 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16069 @value{GDBN} circumvents the problem by treating the symbol scope block as
16070 starting on the previous source line.
16072 @item bad string table offset in symbol @var{n}
16075 Symbol number @var{n} contains a pointer into the string table which is
16076 larger than the size of the string table.
16078 @value{GDBN} circumvents the problem by considering the symbol to have the
16079 name @code{foo}, which may cause other problems if many symbols end up
16082 @item unknown symbol type @code{0x@var{nn}}
16084 The symbol information contains new data types that @value{GDBN} does
16085 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16086 uncomprehended information, in hexadecimal.
16088 @value{GDBN} circumvents the error by ignoring this symbol information.
16089 This usually allows you to debug your program, though certain symbols
16090 are not accessible. If you encounter such a problem and feel like
16091 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16092 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16093 and examine @code{*bufp} to see the symbol.
16095 @item stub type has NULL name
16097 @value{GDBN} could not find the full definition for a struct or class.
16099 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16100 The symbol information for a C@t{++} member function is missing some
16101 information that recent versions of the compiler should have output for
16104 @item info mismatch between compiler and debugger
16106 @value{GDBN} could not parse a type specification output by the compiler.
16111 @section GDB Data Files
16113 @cindex prefix for data files
16114 @value{GDBN} will sometimes read an auxiliary data file. These files
16115 are kept in a directory known as the @dfn{data directory}.
16117 You can set the data directory's name, and view the name @value{GDBN}
16118 is currently using.
16121 @kindex set data-directory
16122 @item set data-directory @var{directory}
16123 Set the directory which @value{GDBN} searches for auxiliary data files
16124 to @var{directory}.
16126 @kindex show data-directory
16127 @item show data-directory
16128 Show the directory @value{GDBN} searches for auxiliary data files.
16131 @cindex default data directory
16132 @cindex @samp{--with-gdb-datadir}
16133 You can set the default data directory by using the configure-time
16134 @samp{--with-gdb-datadir} option. If the data directory is inside
16135 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16136 @samp{--exec-prefix}), then the default data directory will be updated
16137 automatically if the installed @value{GDBN} is moved to a new
16140 The data directory may also be specified with the
16141 @code{--data-directory} command line option.
16142 @xref{Mode Options}.
16145 @chapter Specifying a Debugging Target
16147 @cindex debugging target
16148 A @dfn{target} is the execution environment occupied by your program.
16150 Often, @value{GDBN} runs in the same host environment as your program;
16151 in that case, the debugging target is specified as a side effect when
16152 you use the @code{file} or @code{core} commands. When you need more
16153 flexibility---for example, running @value{GDBN} on a physically separate
16154 host, or controlling a standalone system over a serial port or a
16155 realtime system over a TCP/IP connection---you can use the @code{target}
16156 command to specify one of the target types configured for @value{GDBN}
16157 (@pxref{Target Commands, ,Commands for Managing Targets}).
16159 @cindex target architecture
16160 It is possible to build @value{GDBN} for several different @dfn{target
16161 architectures}. When @value{GDBN} is built like that, you can choose
16162 one of the available architectures with the @kbd{set architecture}
16166 @kindex set architecture
16167 @kindex show architecture
16168 @item set architecture @var{arch}
16169 This command sets the current target architecture to @var{arch}. The
16170 value of @var{arch} can be @code{"auto"}, in addition to one of the
16171 supported architectures.
16173 @item show architecture
16174 Show the current target architecture.
16176 @item set processor
16178 @kindex set processor
16179 @kindex show processor
16180 These are alias commands for, respectively, @code{set architecture}
16181 and @code{show architecture}.
16185 * Active Targets:: Active targets
16186 * Target Commands:: Commands for managing targets
16187 * Byte Order:: Choosing target byte order
16190 @node Active Targets
16191 @section Active Targets
16193 @cindex stacking targets
16194 @cindex active targets
16195 @cindex multiple targets
16197 There are multiple classes of targets such as: processes, executable files or
16198 recording sessions. Core files belong to the process class, making core file
16199 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16200 on multiple active targets, one in each class. This allows you to (for
16201 example) start a process and inspect its activity, while still having access to
16202 the executable file after the process finishes. Or if you start process
16203 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16204 presented a virtual layer of the recording target, while the process target
16205 remains stopped at the chronologically last point of the process execution.
16207 Use the @code{core-file} and @code{exec-file} commands to select a new core
16208 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16209 specify as a target a process that is already running, use the @code{attach}
16210 command (@pxref{Attach, ,Debugging an Already-running Process}).
16212 @node Target Commands
16213 @section Commands for Managing Targets
16216 @item target @var{type} @var{parameters}
16217 Connects the @value{GDBN} host environment to a target machine or
16218 process. A target is typically a protocol for talking to debugging
16219 facilities. You use the argument @var{type} to specify the type or
16220 protocol of the target machine.
16222 Further @var{parameters} are interpreted by the target protocol, but
16223 typically include things like device names or host names to connect
16224 with, process numbers, and baud rates.
16226 The @code{target} command does not repeat if you press @key{RET} again
16227 after executing the command.
16229 @kindex help target
16231 Displays the names of all targets available. To display targets
16232 currently selected, use either @code{info target} or @code{info files}
16233 (@pxref{Files, ,Commands to Specify Files}).
16235 @item help target @var{name}
16236 Describe a particular target, including any parameters necessary to
16239 @kindex set gnutarget
16240 @item set gnutarget @var{args}
16241 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16242 knows whether it is reading an @dfn{executable},
16243 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16244 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16245 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16248 @emph{Warning:} To specify a file format with @code{set gnutarget},
16249 you must know the actual BFD name.
16253 @xref{Files, , Commands to Specify Files}.
16255 @kindex show gnutarget
16256 @item show gnutarget
16257 Use the @code{show gnutarget} command to display what file format
16258 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16259 @value{GDBN} will determine the file format for each file automatically,
16260 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16263 @cindex common targets
16264 Here are some common targets (available, or not, depending on the GDB
16269 @item target exec @var{program}
16270 @cindex executable file target
16271 An executable file. @samp{target exec @var{program}} is the same as
16272 @samp{exec-file @var{program}}.
16274 @item target core @var{filename}
16275 @cindex core dump file target
16276 A core dump file. @samp{target core @var{filename}} is the same as
16277 @samp{core-file @var{filename}}.
16279 @item target remote @var{medium}
16280 @cindex remote target
16281 A remote system connected to @value{GDBN} via a serial line or network
16282 connection. This command tells @value{GDBN} to use its own remote
16283 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16285 For example, if you have a board connected to @file{/dev/ttya} on the
16286 machine running @value{GDBN}, you could say:
16289 target remote /dev/ttya
16292 @code{target remote} supports the @code{load} command. This is only
16293 useful if you have some other way of getting the stub to the target
16294 system, and you can put it somewhere in memory where it won't get
16295 clobbered by the download.
16297 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16298 @cindex built-in simulator target
16299 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16307 works; however, you cannot assume that a specific memory map, device
16308 drivers, or even basic I/O is available, although some simulators do
16309 provide these. For info about any processor-specific simulator details,
16310 see the appropriate section in @ref{Embedded Processors, ,Embedded
16315 Some configurations may include these targets as well:
16319 @item target nrom @var{dev}
16320 @cindex NetROM ROM emulator target
16321 NetROM ROM emulator. This target only supports downloading.
16325 Different targets are available on different configurations of @value{GDBN};
16326 your configuration may have more or fewer targets.
16328 Many remote targets require you to download the executable's code once
16329 you've successfully established a connection. You may wish to control
16330 various aspects of this process.
16335 @kindex set hash@r{, for remote monitors}
16336 @cindex hash mark while downloading
16337 This command controls whether a hash mark @samp{#} is displayed while
16338 downloading a file to the remote monitor. If on, a hash mark is
16339 displayed after each S-record is successfully downloaded to the
16343 @kindex show hash@r{, for remote monitors}
16344 Show the current status of displaying the hash mark.
16346 @item set debug monitor
16347 @kindex set debug monitor
16348 @cindex display remote monitor communications
16349 Enable or disable display of communications messages between
16350 @value{GDBN} and the remote monitor.
16352 @item show debug monitor
16353 @kindex show debug monitor
16354 Show the current status of displaying communications between
16355 @value{GDBN} and the remote monitor.
16360 @kindex load @var{filename}
16361 @item load @var{filename}
16363 Depending on what remote debugging facilities are configured into
16364 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16365 is meant to make @var{filename} (an executable) available for debugging
16366 on the remote system---by downloading, or dynamic linking, for example.
16367 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16368 the @code{add-symbol-file} command.
16370 If your @value{GDBN} does not have a @code{load} command, attempting to
16371 execute it gets the error message ``@code{You can't do that when your
16372 target is @dots{}}''
16374 The file is loaded at whatever address is specified in the executable.
16375 For some object file formats, you can specify the load address when you
16376 link the program; for other formats, like a.out, the object file format
16377 specifies a fixed address.
16378 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16380 Depending on the remote side capabilities, @value{GDBN} may be able to
16381 load programs into flash memory.
16383 @code{load} does not repeat if you press @key{RET} again after using it.
16387 @section Choosing Target Byte Order
16389 @cindex choosing target byte order
16390 @cindex target byte order
16392 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16393 offer the ability to run either big-endian or little-endian byte
16394 orders. Usually the executable or symbol will include a bit to
16395 designate the endian-ness, and you will not need to worry about
16396 which to use. However, you may still find it useful to adjust
16397 @value{GDBN}'s idea of processor endian-ness manually.
16401 @item set endian big
16402 Instruct @value{GDBN} to assume the target is big-endian.
16404 @item set endian little
16405 Instruct @value{GDBN} to assume the target is little-endian.
16407 @item set endian auto
16408 Instruct @value{GDBN} to use the byte order associated with the
16412 Display @value{GDBN}'s current idea of the target byte order.
16416 Note that these commands merely adjust interpretation of symbolic
16417 data on the host, and that they have absolutely no effect on the
16421 @node Remote Debugging
16422 @chapter Debugging Remote Programs
16423 @cindex remote debugging
16425 If you are trying to debug a program running on a machine that cannot run
16426 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16427 For example, you might use remote debugging on an operating system kernel,
16428 or on a small system which does not have a general purpose operating system
16429 powerful enough to run a full-featured debugger.
16431 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16432 to make this work with particular debugging targets. In addition,
16433 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16434 but not specific to any particular target system) which you can use if you
16435 write the remote stubs---the code that runs on the remote system to
16436 communicate with @value{GDBN}.
16438 Other remote targets may be available in your
16439 configuration of @value{GDBN}; use @code{help target} to list them.
16442 * Connecting:: Connecting to a remote target
16443 * File Transfer:: Sending files to a remote system
16444 * Server:: Using the gdbserver program
16445 * Remote Configuration:: Remote configuration
16446 * Remote Stub:: Implementing a remote stub
16450 @section Connecting to a Remote Target
16452 On the @value{GDBN} host machine, you will need an unstripped copy of
16453 your program, since @value{GDBN} needs symbol and debugging information.
16454 Start up @value{GDBN} as usual, using the name of the local copy of your
16455 program as the first argument.
16457 @cindex @code{target remote}
16458 @value{GDBN} can communicate with the target over a serial line, or
16459 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16460 each case, @value{GDBN} uses the same protocol for debugging your
16461 program; only the medium carrying the debugging packets varies. The
16462 @code{target remote} command establishes a connection to the target.
16463 Its arguments indicate which medium to use:
16467 @item target remote @var{serial-device}
16468 @cindex serial line, @code{target remote}
16469 Use @var{serial-device} to communicate with the target. For example,
16470 to use a serial line connected to the device named @file{/dev/ttyb}:
16473 target remote /dev/ttyb
16476 If you're using a serial line, you may want to give @value{GDBN} the
16477 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16478 (@pxref{Remote Configuration, set remotebaud}) before the
16479 @code{target} command.
16481 @item target remote @code{@var{host}:@var{port}}
16482 @itemx target remote @code{tcp:@var{host}:@var{port}}
16483 @cindex @acronym{TCP} port, @code{target remote}
16484 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16485 The @var{host} may be either a host name or a numeric @acronym{IP}
16486 address; @var{port} must be a decimal number. The @var{host} could be
16487 the target machine itself, if it is directly connected to the net, or
16488 it might be a terminal server which in turn has a serial line to the
16491 For example, to connect to port 2828 on a terminal server named
16495 target remote manyfarms:2828
16498 If your remote target is actually running on the same machine as your
16499 debugger session (e.g.@: a simulator for your target running on the
16500 same host), you can omit the hostname. For example, to connect to
16501 port 1234 on your local machine:
16504 target remote :1234
16508 Note that the colon is still required here.
16510 @item target remote @code{udp:@var{host}:@var{port}}
16511 @cindex @acronym{UDP} port, @code{target remote}
16512 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16513 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16516 target remote udp:manyfarms:2828
16519 When using a @acronym{UDP} connection for remote debugging, you should
16520 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16521 can silently drop packets on busy or unreliable networks, which will
16522 cause havoc with your debugging session.
16524 @item target remote | @var{command}
16525 @cindex pipe, @code{target remote} to
16526 Run @var{command} in the background and communicate with it using a
16527 pipe. The @var{command} is a shell command, to be parsed and expanded
16528 by the system's command shell, @code{/bin/sh}; it should expect remote
16529 protocol packets on its standard input, and send replies on its
16530 standard output. You could use this to run a stand-alone simulator
16531 that speaks the remote debugging protocol, to make net connections
16532 using programs like @code{ssh}, or for other similar tricks.
16534 If @var{command} closes its standard output (perhaps by exiting),
16535 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16536 program has already exited, this will have no effect.)
16540 Once the connection has been established, you can use all the usual
16541 commands to examine and change data. The remote program is already
16542 running; you can use @kbd{step} and @kbd{continue}, and you do not
16543 need to use @kbd{run}.
16545 @cindex interrupting remote programs
16546 @cindex remote programs, interrupting
16547 Whenever @value{GDBN} is waiting for the remote program, if you type the
16548 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16549 program. This may or may not succeed, depending in part on the hardware
16550 and the serial drivers the remote system uses. If you type the
16551 interrupt character once again, @value{GDBN} displays this prompt:
16554 Interrupted while waiting for the program.
16555 Give up (and stop debugging it)? (y or n)
16558 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16559 (If you decide you want to try again later, you can use @samp{target
16560 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16561 goes back to waiting.
16564 @kindex detach (remote)
16566 When you have finished debugging the remote program, you can use the
16567 @code{detach} command to release it from @value{GDBN} control.
16568 Detaching from the target normally resumes its execution, but the results
16569 will depend on your particular remote stub. After the @code{detach}
16570 command, @value{GDBN} is free to connect to another target.
16574 The @code{disconnect} command behaves like @code{detach}, except that
16575 the target is generally not resumed. It will wait for @value{GDBN}
16576 (this instance or another one) to connect and continue debugging. After
16577 the @code{disconnect} command, @value{GDBN} is again free to connect to
16580 @cindex send command to remote monitor
16581 @cindex extend @value{GDBN} for remote targets
16582 @cindex add new commands for external monitor
16584 @item monitor @var{cmd}
16585 This command allows you to send arbitrary commands directly to the
16586 remote monitor. Since @value{GDBN} doesn't care about the commands it
16587 sends like this, this command is the way to extend @value{GDBN}---you
16588 can add new commands that only the external monitor will understand
16592 @node File Transfer
16593 @section Sending files to a remote system
16594 @cindex remote target, file transfer
16595 @cindex file transfer
16596 @cindex sending files to remote systems
16598 Some remote targets offer the ability to transfer files over the same
16599 connection used to communicate with @value{GDBN}. This is convenient
16600 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16601 running @code{gdbserver} over a network interface. For other targets,
16602 e.g.@: embedded devices with only a single serial port, this may be
16603 the only way to upload or download files.
16605 Not all remote targets support these commands.
16609 @item remote put @var{hostfile} @var{targetfile}
16610 Copy file @var{hostfile} from the host system (the machine running
16611 @value{GDBN}) to @var{targetfile} on the target system.
16614 @item remote get @var{targetfile} @var{hostfile}
16615 Copy file @var{targetfile} from the target system to @var{hostfile}
16616 on the host system.
16618 @kindex remote delete
16619 @item remote delete @var{targetfile}
16620 Delete @var{targetfile} from the target system.
16625 @section Using the @code{gdbserver} Program
16628 @cindex remote connection without stubs
16629 @code{gdbserver} is a control program for Unix-like systems, which
16630 allows you to connect your program with a remote @value{GDBN} via
16631 @code{target remote}---but without linking in the usual debugging stub.
16633 @code{gdbserver} is not a complete replacement for the debugging stubs,
16634 because it requires essentially the same operating-system facilities
16635 that @value{GDBN} itself does. In fact, a system that can run
16636 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16637 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16638 because it is a much smaller program than @value{GDBN} itself. It is
16639 also easier to port than all of @value{GDBN}, so you may be able to get
16640 started more quickly on a new system by using @code{gdbserver}.
16641 Finally, if you develop code for real-time systems, you may find that
16642 the tradeoffs involved in real-time operation make it more convenient to
16643 do as much development work as possible on another system, for example
16644 by cross-compiling. You can use @code{gdbserver} to make a similar
16645 choice for debugging.
16647 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16648 or a TCP connection, using the standard @value{GDBN} remote serial
16652 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16653 Do not run @code{gdbserver} connected to any public network; a
16654 @value{GDBN} connection to @code{gdbserver} provides access to the
16655 target system with the same privileges as the user running
16659 @subsection Running @code{gdbserver}
16660 @cindex arguments, to @code{gdbserver}
16661 @cindex @code{gdbserver}, command-line arguments
16663 Run @code{gdbserver} on the target system. You need a copy of the
16664 program you want to debug, including any libraries it requires.
16665 @code{gdbserver} does not need your program's symbol table, so you can
16666 strip the program if necessary to save space. @value{GDBN} on the host
16667 system does all the symbol handling.
16669 To use the server, you must tell it how to communicate with @value{GDBN};
16670 the name of your program; and the arguments for your program. The usual
16674 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16677 @var{comm} is either a device name (to use a serial line) or a TCP
16678 hostname and portnumber. For example, to debug Emacs with the argument
16679 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16683 target> gdbserver /dev/com1 emacs foo.txt
16686 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16689 To use a TCP connection instead of a serial line:
16692 target> gdbserver host:2345 emacs foo.txt
16695 The only difference from the previous example is the first argument,
16696 specifying that you are communicating with the host @value{GDBN} via
16697 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16698 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16699 (Currently, the @samp{host} part is ignored.) You can choose any number
16700 you want for the port number as long as it does not conflict with any
16701 TCP ports already in use on the target system (for example, @code{23} is
16702 reserved for @code{telnet}).@footnote{If you choose a port number that
16703 conflicts with another service, @code{gdbserver} prints an error message
16704 and exits.} You must use the same port number with the host @value{GDBN}
16705 @code{target remote} command.
16707 @subsubsection Attaching to a Running Program
16708 @cindex attach to a program, @code{gdbserver}
16709 @cindex @option{--attach}, @code{gdbserver} option
16711 On some targets, @code{gdbserver} can also attach to running programs.
16712 This is accomplished via the @code{--attach} argument. The syntax is:
16715 target> gdbserver --attach @var{comm} @var{pid}
16718 @var{pid} is the process ID of a currently running process. It isn't necessary
16719 to point @code{gdbserver} at a binary for the running process.
16722 You can debug processes by name instead of process ID if your target has the
16723 @code{pidof} utility:
16726 target> gdbserver --attach @var{comm} `pidof @var{program}`
16729 In case more than one copy of @var{program} is running, or @var{program}
16730 has multiple threads, most versions of @code{pidof} support the
16731 @code{-s} option to only return the first process ID.
16733 @subsubsection Multi-Process Mode for @code{gdbserver}
16734 @cindex @code{gdbserver}, multiple processes
16735 @cindex multiple processes with @code{gdbserver}
16737 When you connect to @code{gdbserver} using @code{target remote},
16738 @code{gdbserver} debugs the specified program only once. When the
16739 program exits, or you detach from it, @value{GDBN} closes the connection
16740 and @code{gdbserver} exits.
16742 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16743 enters multi-process mode. When the debugged program exits, or you
16744 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16745 though no program is running. The @code{run} and @code{attach}
16746 commands instruct @code{gdbserver} to run or attach to a new program.
16747 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16748 remote exec-file}) to select the program to run. Command line
16749 arguments are supported, except for wildcard expansion and I/O
16750 redirection (@pxref{Arguments}).
16752 @cindex @option{--multi}, @code{gdbserver} option
16753 To start @code{gdbserver} without supplying an initial command to run
16754 or process ID to attach, use the @option{--multi} command line option.
16755 Then you can connect using @kbd{target extended-remote} and start
16756 the program you want to debug.
16758 In multi-process mode @code{gdbserver} does not automatically exit unless you
16759 use the option @option{--once}. You can terminate it by using
16760 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16761 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16762 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16763 @option{--multi} option to @code{gdbserver} has no influence on that.
16765 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16767 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16769 @code{gdbserver} normally terminates after all of its debugged processes have
16770 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16771 extended-remote}, @code{gdbserver} stays running even with no processes left.
16772 @value{GDBN} normally terminates the spawned debugged process on its exit,
16773 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16774 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16775 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16776 stays running even in the @kbd{target remote} mode.
16778 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16779 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16780 completeness, at most one @value{GDBN} can be connected at a time.
16782 @cindex @option{--once}, @code{gdbserver} option
16783 By default, @code{gdbserver} keeps the listening TCP port open, so that
16784 additional connections are possible. However, if you start @code{gdbserver}
16785 with the @option{--once} option, it will stop listening for any further
16786 connection attempts after connecting to the first @value{GDBN} session. This
16787 means no further connections to @code{gdbserver} will be possible after the
16788 first one. It also means @code{gdbserver} will terminate after the first
16789 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16790 connections and even in the @kbd{target extended-remote} mode. The
16791 @option{--once} option allows reusing the same port number for connecting to
16792 multiple instances of @code{gdbserver} running on the same host, since each
16793 instance closes its port after the first connection.
16795 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16797 @cindex @option{--debug}, @code{gdbserver} option
16798 The @option{--debug} option tells @code{gdbserver} to display extra
16799 status information about the debugging process.
16800 @cindex @option{--remote-debug}, @code{gdbserver} option
16801 The @option{--remote-debug} option tells @code{gdbserver} to display
16802 remote protocol debug output. These options are intended for
16803 @code{gdbserver} development and for bug reports to the developers.
16805 @cindex @option{--wrapper}, @code{gdbserver} option
16806 The @option{--wrapper} option specifies a wrapper to launch programs
16807 for debugging. The option should be followed by the name of the
16808 wrapper, then any command-line arguments to pass to the wrapper, then
16809 @kbd{--} indicating the end of the wrapper arguments.
16811 @code{gdbserver} runs the specified wrapper program with a combined
16812 command line including the wrapper arguments, then the name of the
16813 program to debug, then any arguments to the program. The wrapper
16814 runs until it executes your program, and then @value{GDBN} gains control.
16816 You can use any program that eventually calls @code{execve} with
16817 its arguments as a wrapper. Several standard Unix utilities do
16818 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16819 with @code{exec "$@@"} will also work.
16821 For example, you can use @code{env} to pass an environment variable to
16822 the debugged program, without setting the variable in @code{gdbserver}'s
16826 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16829 @subsection Connecting to @code{gdbserver}
16831 Run @value{GDBN} on the host system.
16833 First make sure you have the necessary symbol files. Load symbols for
16834 your application using the @code{file} command before you connect. Use
16835 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16836 was compiled with the correct sysroot using @code{--with-sysroot}).
16838 The symbol file and target libraries must exactly match the executable
16839 and libraries on the target, with one exception: the files on the host
16840 system should not be stripped, even if the files on the target system
16841 are. Mismatched or missing files will lead to confusing results
16842 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16843 files may also prevent @code{gdbserver} from debugging multi-threaded
16846 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16847 For TCP connections, you must start up @code{gdbserver} prior to using
16848 the @code{target remote} command. Otherwise you may get an error whose
16849 text depends on the host system, but which usually looks something like
16850 @samp{Connection refused}. Don't use the @code{load}
16851 command in @value{GDBN} when using @code{gdbserver}, since the program is
16852 already on the target.
16854 @subsection Monitor Commands for @code{gdbserver}
16855 @cindex monitor commands, for @code{gdbserver}
16856 @anchor{Monitor Commands for gdbserver}
16858 During a @value{GDBN} session using @code{gdbserver}, you can use the
16859 @code{monitor} command to send special requests to @code{gdbserver}.
16860 Here are the available commands.
16864 List the available monitor commands.
16866 @item monitor set debug 0
16867 @itemx monitor set debug 1
16868 Disable or enable general debugging messages.
16870 @item monitor set remote-debug 0
16871 @itemx monitor set remote-debug 1
16872 Disable or enable specific debugging messages associated with the remote
16873 protocol (@pxref{Remote Protocol}).
16875 @item monitor set libthread-db-search-path [PATH]
16876 @cindex gdbserver, search path for @code{libthread_db}
16877 When this command is issued, @var{path} is a colon-separated list of
16878 directories to search for @code{libthread_db} (@pxref{Threads,,set
16879 libthread-db-search-path}). If you omit @var{path},
16880 @samp{libthread-db-search-path} will be reset to its default value.
16882 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16883 not supported in @code{gdbserver}.
16886 Tell gdbserver to exit immediately. This command should be followed by
16887 @code{disconnect} to close the debugging session. @code{gdbserver} will
16888 detach from any attached processes and kill any processes it created.
16889 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16890 of a multi-process mode debug session.
16894 @subsection Tracepoints support in @code{gdbserver}
16895 @cindex tracepoints support in @code{gdbserver}
16897 On some targets, @code{gdbserver} supports tracepoints, fast
16898 tracepoints and static tracepoints.
16900 For fast or static tracepoints to work, a special library called the
16901 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16902 This library is built and distributed as an integral part of
16903 @code{gdbserver}. In addition, support for static tracepoints
16904 requires building the in-process agent library with static tracepoints
16905 support. At present, the UST (LTTng Userspace Tracer,
16906 @url{http://lttng.org/ust}) tracing engine is supported. This support
16907 is automatically available if UST development headers are found in the
16908 standard include path when @code{gdbserver} is built, or if
16909 @code{gdbserver} was explicitly configured using @option{--with-ust}
16910 to point at such headers. You can explicitly disable the support
16911 using @option{--with-ust=no}.
16913 There are several ways to load the in-process agent in your program:
16916 @item Specifying it as dependency at link time
16918 You can link your program dynamically with the in-process agent
16919 library. On most systems, this is accomplished by adding
16920 @code{-linproctrace} to the link command.
16922 @item Using the system's preloading mechanisms
16924 You can force loading the in-process agent at startup time by using
16925 your system's support for preloading shared libraries. Many Unixes
16926 support the concept of preloading user defined libraries. In most
16927 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16928 in the environment. See also the description of @code{gdbserver}'s
16929 @option{--wrapper} command line option.
16931 @item Using @value{GDBN} to force loading the agent at run time
16933 On some systems, you can force the inferior to load a shared library,
16934 by calling a dynamic loader function in the inferior that takes care
16935 of dynamically looking up and loading a shared library. On most Unix
16936 systems, the function is @code{dlopen}. You'll use the @code{call}
16937 command for that. For example:
16940 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16943 Note that on most Unix systems, for the @code{dlopen} function to be
16944 available, the program needs to be linked with @code{-ldl}.
16947 On systems that have a userspace dynamic loader, like most Unix
16948 systems, when you connect to @code{gdbserver} using @code{target
16949 remote}, you'll find that the program is stopped at the dynamic
16950 loader's entry point, and no shared library has been loaded in the
16951 program's address space yet, including the in-process agent. In that
16952 case, before being able to use any of the fast or static tracepoints
16953 features, you need to let the loader run and load the shared
16954 libraries. The simplest way to do that is to run the program to the
16955 main procedure. E.g., if debugging a C or C@t{++} program, start
16956 @code{gdbserver} like so:
16959 $ gdbserver :9999 myprogram
16962 Start GDB and connect to @code{gdbserver} like so, and run to main:
16966 (@value{GDBP}) target remote myhost:9999
16967 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16968 (@value{GDBP}) b main
16969 (@value{GDBP}) continue
16972 The in-process tracing agent library should now be loaded into the
16973 process; you can confirm it with the @code{info sharedlibrary}
16974 command, which will list @file{libinproctrace.so} as loaded in the
16975 process. You are now ready to install fast tracepoints, list static
16976 tracepoint markers, probe static tracepoints markers, and start
16979 @node Remote Configuration
16980 @section Remote Configuration
16983 @kindex show remote
16984 This section documents the configuration options available when
16985 debugging remote programs. For the options related to the File I/O
16986 extensions of the remote protocol, see @ref{system,
16987 system-call-allowed}.
16990 @item set remoteaddresssize @var{bits}
16991 @cindex address size for remote targets
16992 @cindex bits in remote address
16993 Set the maximum size of address in a memory packet to the specified
16994 number of bits. @value{GDBN} will mask off the address bits above
16995 that number, when it passes addresses to the remote target. The
16996 default value is the number of bits in the target's address.
16998 @item show remoteaddresssize
16999 Show the current value of remote address size in bits.
17001 @item set remotebaud @var{n}
17002 @cindex baud rate for remote targets
17003 Set the baud rate for the remote serial I/O to @var{n} baud. The
17004 value is used to set the speed of the serial port used for debugging
17007 @item show remotebaud
17008 Show the current speed of the remote connection.
17010 @item set remotebreak
17011 @cindex interrupt remote programs
17012 @cindex BREAK signal instead of Ctrl-C
17013 @anchor{set remotebreak}
17014 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17015 when you type @kbd{Ctrl-c} to interrupt the program running
17016 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17017 character instead. The default is off, since most remote systems
17018 expect to see @samp{Ctrl-C} as the interrupt signal.
17020 @item show remotebreak
17021 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17022 interrupt the remote program.
17024 @item set remoteflow on
17025 @itemx set remoteflow off
17026 @kindex set remoteflow
17027 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17028 on the serial port used to communicate to the remote target.
17030 @item show remoteflow
17031 @kindex show remoteflow
17032 Show the current setting of hardware flow control.
17034 @item set remotelogbase @var{base}
17035 Set the base (a.k.a.@: radix) of logging serial protocol
17036 communications to @var{base}. Supported values of @var{base} are:
17037 @code{ascii}, @code{octal}, and @code{hex}. The default is
17040 @item show remotelogbase
17041 Show the current setting of the radix for logging remote serial
17044 @item set remotelogfile @var{file}
17045 @cindex record serial communications on file
17046 Record remote serial communications on the named @var{file}. The
17047 default is not to record at all.
17049 @item show remotelogfile.
17050 Show the current setting of the file name on which to record the
17051 serial communications.
17053 @item set remotetimeout @var{num}
17054 @cindex timeout for serial communications
17055 @cindex remote timeout
17056 Set the timeout limit to wait for the remote target to respond to
17057 @var{num} seconds. The default is 2 seconds.
17059 @item show remotetimeout
17060 Show the current number of seconds to wait for the remote target
17063 @cindex limit hardware breakpoints and watchpoints
17064 @cindex remote target, limit break- and watchpoints
17065 @anchor{set remote hardware-watchpoint-limit}
17066 @anchor{set remote hardware-breakpoint-limit}
17067 @item set remote hardware-watchpoint-limit @var{limit}
17068 @itemx set remote hardware-breakpoint-limit @var{limit}
17069 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17070 watchpoints. A limit of -1, the default, is treated as unlimited.
17072 @cindex limit hardware watchpoints length
17073 @cindex remote target, limit watchpoints length
17074 @anchor{set remote hardware-watchpoint-length-limit}
17075 @item set remote hardware-watchpoint-length-limit @var{limit}
17076 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17077 a remote hardware watchpoint. A limit of -1, the default, is treated
17080 @item show remote hardware-watchpoint-length-limit
17081 Show the current limit (in bytes) of the maximum length of
17082 a remote hardware watchpoint.
17084 @item set remote exec-file @var{filename}
17085 @itemx show remote exec-file
17086 @anchor{set remote exec-file}
17087 @cindex executable file, for remote target
17088 Select the file used for @code{run} with @code{target
17089 extended-remote}. This should be set to a filename valid on the
17090 target system. If it is not set, the target will use a default
17091 filename (e.g.@: the last program run).
17093 @item set remote interrupt-sequence
17094 @cindex interrupt remote programs
17095 @cindex select Ctrl-C, BREAK or BREAK-g
17096 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17097 @samp{BREAK-g} as the
17098 sequence to the remote target in order to interrupt the execution.
17099 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17100 is high level of serial line for some certain time.
17101 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17102 It is @code{BREAK} signal followed by character @code{g}.
17104 @item show interrupt-sequence
17105 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17106 is sent by @value{GDBN} to interrupt the remote program.
17107 @code{BREAK-g} is BREAK signal followed by @code{g} and
17108 also known as Magic SysRq g.
17110 @item set remote interrupt-on-connect
17111 @cindex send interrupt-sequence on start
17112 Specify whether interrupt-sequence is sent to remote target when
17113 @value{GDBN} connects to it. This is mostly needed when you debug
17114 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17115 which is known as Magic SysRq g in order to connect @value{GDBN}.
17117 @item show interrupt-on-connect
17118 Show whether interrupt-sequence is sent
17119 to remote target when @value{GDBN} connects to it.
17123 @item set tcp auto-retry on
17124 @cindex auto-retry, for remote TCP target
17125 Enable auto-retry for remote TCP connections. This is useful if the remote
17126 debugging agent is launched in parallel with @value{GDBN}; there is a race
17127 condition because the agent may not become ready to accept the connection
17128 before @value{GDBN} attempts to connect. When auto-retry is
17129 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17130 to establish the connection using the timeout specified by
17131 @code{set tcp connect-timeout}.
17133 @item set tcp auto-retry off
17134 Do not auto-retry failed TCP connections.
17136 @item show tcp auto-retry
17137 Show the current auto-retry setting.
17139 @item set tcp connect-timeout @var{seconds}
17140 @cindex connection timeout, for remote TCP target
17141 @cindex timeout, for remote target connection
17142 Set the timeout for establishing a TCP connection to the remote target to
17143 @var{seconds}. The timeout affects both polling to retry failed connections
17144 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17145 that are merely slow to complete, and represents an approximate cumulative
17148 @item show tcp connect-timeout
17149 Show the current connection timeout setting.
17152 @cindex remote packets, enabling and disabling
17153 The @value{GDBN} remote protocol autodetects the packets supported by
17154 your debugging stub. If you need to override the autodetection, you
17155 can use these commands to enable or disable individual packets. Each
17156 packet can be set to @samp{on} (the remote target supports this
17157 packet), @samp{off} (the remote target does not support this packet),
17158 or @samp{auto} (detect remote target support for this packet). They
17159 all default to @samp{auto}. For more information about each packet,
17160 see @ref{Remote Protocol}.
17162 During normal use, you should not have to use any of these commands.
17163 If you do, that may be a bug in your remote debugging stub, or a bug
17164 in @value{GDBN}. You may want to report the problem to the
17165 @value{GDBN} developers.
17167 For each packet @var{name}, the command to enable or disable the
17168 packet is @code{set remote @var{name}-packet}. The available settings
17171 @multitable @columnfractions 0.28 0.32 0.25
17174 @tab Related Features
17176 @item @code{fetch-register}
17178 @tab @code{info registers}
17180 @item @code{set-register}
17184 @item @code{binary-download}
17186 @tab @code{load}, @code{set}
17188 @item @code{read-aux-vector}
17189 @tab @code{qXfer:auxv:read}
17190 @tab @code{info auxv}
17192 @item @code{symbol-lookup}
17193 @tab @code{qSymbol}
17194 @tab Detecting multiple threads
17196 @item @code{attach}
17197 @tab @code{vAttach}
17200 @item @code{verbose-resume}
17202 @tab Stepping or resuming multiple threads
17208 @item @code{software-breakpoint}
17212 @item @code{hardware-breakpoint}
17216 @item @code{write-watchpoint}
17220 @item @code{read-watchpoint}
17224 @item @code{access-watchpoint}
17228 @item @code{target-features}
17229 @tab @code{qXfer:features:read}
17230 @tab @code{set architecture}
17232 @item @code{library-info}
17233 @tab @code{qXfer:libraries:read}
17234 @tab @code{info sharedlibrary}
17236 @item @code{memory-map}
17237 @tab @code{qXfer:memory-map:read}
17238 @tab @code{info mem}
17240 @item @code{read-sdata-object}
17241 @tab @code{qXfer:sdata:read}
17242 @tab @code{print $_sdata}
17244 @item @code{read-spu-object}
17245 @tab @code{qXfer:spu:read}
17246 @tab @code{info spu}
17248 @item @code{write-spu-object}
17249 @tab @code{qXfer:spu:write}
17250 @tab @code{info spu}
17252 @item @code{read-siginfo-object}
17253 @tab @code{qXfer:siginfo:read}
17254 @tab @code{print $_siginfo}
17256 @item @code{write-siginfo-object}
17257 @tab @code{qXfer:siginfo:write}
17258 @tab @code{set $_siginfo}
17260 @item @code{threads}
17261 @tab @code{qXfer:threads:read}
17262 @tab @code{info threads}
17264 @item @code{get-thread-local-@*storage-address}
17265 @tab @code{qGetTLSAddr}
17266 @tab Displaying @code{__thread} variables
17268 @item @code{get-thread-information-block-address}
17269 @tab @code{qGetTIBAddr}
17270 @tab Display MS-Windows Thread Information Block.
17272 @item @code{search-memory}
17273 @tab @code{qSearch:memory}
17276 @item @code{supported-packets}
17277 @tab @code{qSupported}
17278 @tab Remote communications parameters
17280 @item @code{pass-signals}
17281 @tab @code{QPassSignals}
17282 @tab @code{handle @var{signal}}
17284 @item @code{hostio-close-packet}
17285 @tab @code{vFile:close}
17286 @tab @code{remote get}, @code{remote put}
17288 @item @code{hostio-open-packet}
17289 @tab @code{vFile:open}
17290 @tab @code{remote get}, @code{remote put}
17292 @item @code{hostio-pread-packet}
17293 @tab @code{vFile:pread}
17294 @tab @code{remote get}, @code{remote put}
17296 @item @code{hostio-pwrite-packet}
17297 @tab @code{vFile:pwrite}
17298 @tab @code{remote get}, @code{remote put}
17300 @item @code{hostio-unlink-packet}
17301 @tab @code{vFile:unlink}
17302 @tab @code{remote delete}
17304 @item @code{noack-packet}
17305 @tab @code{QStartNoAckMode}
17306 @tab Packet acknowledgment
17308 @item @code{osdata}
17309 @tab @code{qXfer:osdata:read}
17310 @tab @code{info os}
17312 @item @code{query-attached}
17313 @tab @code{qAttached}
17314 @tab Querying remote process attach state.
17316 @item @code{traceframe-info}
17317 @tab @code{qXfer:traceframe-info:read}
17318 @tab Traceframe info
17320 @item @code{disable-randomization}
17321 @tab @code{QDisableRandomization}
17322 @tab @code{set disable-randomization}
17326 @section Implementing a Remote Stub
17328 @cindex debugging stub, example
17329 @cindex remote stub, example
17330 @cindex stub example, remote debugging
17331 The stub files provided with @value{GDBN} implement the target side of the
17332 communication protocol, and the @value{GDBN} side is implemented in the
17333 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17334 these subroutines to communicate, and ignore the details. (If you're
17335 implementing your own stub file, you can still ignore the details: start
17336 with one of the existing stub files. @file{sparc-stub.c} is the best
17337 organized, and therefore the easiest to read.)
17339 @cindex remote serial debugging, overview
17340 To debug a program running on another machine (the debugging
17341 @dfn{target} machine), you must first arrange for all the usual
17342 prerequisites for the program to run by itself. For example, for a C
17347 A startup routine to set up the C runtime environment; these usually
17348 have a name like @file{crt0}. The startup routine may be supplied by
17349 your hardware supplier, or you may have to write your own.
17352 A C subroutine library to support your program's
17353 subroutine calls, notably managing input and output.
17356 A way of getting your program to the other machine---for example, a
17357 download program. These are often supplied by the hardware
17358 manufacturer, but you may have to write your own from hardware
17362 The next step is to arrange for your program to use a serial port to
17363 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17364 machine). In general terms, the scheme looks like this:
17368 @value{GDBN} already understands how to use this protocol; when everything
17369 else is set up, you can simply use the @samp{target remote} command
17370 (@pxref{Targets,,Specifying a Debugging Target}).
17372 @item On the target,
17373 you must link with your program a few special-purpose subroutines that
17374 implement the @value{GDBN} remote serial protocol. The file containing these
17375 subroutines is called a @dfn{debugging stub}.
17377 On certain remote targets, you can use an auxiliary program
17378 @code{gdbserver} instead of linking a stub into your program.
17379 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17382 The debugging stub is specific to the architecture of the remote
17383 machine; for example, use @file{sparc-stub.c} to debug programs on
17386 @cindex remote serial stub list
17387 These working remote stubs are distributed with @value{GDBN}:
17392 @cindex @file{i386-stub.c}
17395 For Intel 386 and compatible architectures.
17398 @cindex @file{m68k-stub.c}
17399 @cindex Motorola 680x0
17401 For Motorola 680x0 architectures.
17404 @cindex @file{sh-stub.c}
17407 For Renesas SH architectures.
17410 @cindex @file{sparc-stub.c}
17412 For @sc{sparc} architectures.
17414 @item sparcl-stub.c
17415 @cindex @file{sparcl-stub.c}
17418 For Fujitsu @sc{sparclite} architectures.
17422 The @file{README} file in the @value{GDBN} distribution may list other
17423 recently added stubs.
17426 * Stub Contents:: What the stub can do for you
17427 * Bootstrapping:: What you must do for the stub
17428 * Debug Session:: Putting it all together
17431 @node Stub Contents
17432 @subsection What the Stub Can Do for You
17434 @cindex remote serial stub
17435 The debugging stub for your architecture supplies these three
17439 @item set_debug_traps
17440 @findex set_debug_traps
17441 @cindex remote serial stub, initialization
17442 This routine arranges for @code{handle_exception} to run when your
17443 program stops. You must call this subroutine explicitly near the
17444 beginning of your program.
17446 @item handle_exception
17447 @findex handle_exception
17448 @cindex remote serial stub, main routine
17449 This is the central workhorse, but your program never calls it
17450 explicitly---the setup code arranges for @code{handle_exception} to
17451 run when a trap is triggered.
17453 @code{handle_exception} takes control when your program stops during
17454 execution (for example, on a breakpoint), and mediates communications
17455 with @value{GDBN} on the host machine. This is where the communications
17456 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17457 representative on the target machine. It begins by sending summary
17458 information on the state of your program, then continues to execute,
17459 retrieving and transmitting any information @value{GDBN} needs, until you
17460 execute a @value{GDBN} command that makes your program resume; at that point,
17461 @code{handle_exception} returns control to your own code on the target
17465 @cindex @code{breakpoint} subroutine, remote
17466 Use this auxiliary subroutine to make your program contain a
17467 breakpoint. Depending on the particular situation, this may be the only
17468 way for @value{GDBN} to get control. For instance, if your target
17469 machine has some sort of interrupt button, you won't need to call this;
17470 pressing the interrupt button transfers control to
17471 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17472 simply receiving characters on the serial port may also trigger a trap;
17473 again, in that situation, you don't need to call @code{breakpoint} from
17474 your own program---simply running @samp{target remote} from the host
17475 @value{GDBN} session gets control.
17477 Call @code{breakpoint} if none of these is true, or if you simply want
17478 to make certain your program stops at a predetermined point for the
17479 start of your debugging session.
17482 @node Bootstrapping
17483 @subsection What You Must Do for the Stub
17485 @cindex remote stub, support routines
17486 The debugging stubs that come with @value{GDBN} are set up for a particular
17487 chip architecture, but they have no information about the rest of your
17488 debugging target machine.
17490 First of all you need to tell the stub how to communicate with the
17494 @item int getDebugChar()
17495 @findex getDebugChar
17496 Write this subroutine to read a single character from the serial port.
17497 It may be identical to @code{getchar} for your target system; a
17498 different name is used to allow you to distinguish the two if you wish.
17500 @item void putDebugChar(int)
17501 @findex putDebugChar
17502 Write this subroutine to write a single character to the serial port.
17503 It may be identical to @code{putchar} for your target system; a
17504 different name is used to allow you to distinguish the two if you wish.
17507 @cindex control C, and remote debugging
17508 @cindex interrupting remote targets
17509 If you want @value{GDBN} to be able to stop your program while it is
17510 running, you need to use an interrupt-driven serial driver, and arrange
17511 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17512 character). That is the character which @value{GDBN} uses to tell the
17513 remote system to stop.
17515 Getting the debugging target to return the proper status to @value{GDBN}
17516 probably requires changes to the standard stub; one quick and dirty way
17517 is to just execute a breakpoint instruction (the ``dirty'' part is that
17518 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17520 Other routines you need to supply are:
17523 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17524 @findex exceptionHandler
17525 Write this function to install @var{exception_address} in the exception
17526 handling tables. You need to do this because the stub does not have any
17527 way of knowing what the exception handling tables on your target system
17528 are like (for example, the processor's table might be in @sc{rom},
17529 containing entries which point to a table in @sc{ram}).
17530 @var{exception_number} is the exception number which should be changed;
17531 its meaning is architecture-dependent (for example, different numbers
17532 might represent divide by zero, misaligned access, etc). When this
17533 exception occurs, control should be transferred directly to
17534 @var{exception_address}, and the processor state (stack, registers,
17535 and so on) should be just as it is when a processor exception occurs. So if
17536 you want to use a jump instruction to reach @var{exception_address}, it
17537 should be a simple jump, not a jump to subroutine.
17539 For the 386, @var{exception_address} should be installed as an interrupt
17540 gate so that interrupts are masked while the handler runs. The gate
17541 should be at privilege level 0 (the most privileged level). The
17542 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17543 help from @code{exceptionHandler}.
17545 @item void flush_i_cache()
17546 @findex flush_i_cache
17547 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17548 instruction cache, if any, on your target machine. If there is no
17549 instruction cache, this subroutine may be a no-op.
17551 On target machines that have instruction caches, @value{GDBN} requires this
17552 function to make certain that the state of your program is stable.
17556 You must also make sure this library routine is available:
17559 @item void *memset(void *, int, int)
17561 This is the standard library function @code{memset} that sets an area of
17562 memory to a known value. If you have one of the free versions of
17563 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17564 either obtain it from your hardware manufacturer, or write your own.
17567 If you do not use the GNU C compiler, you may need other standard
17568 library subroutines as well; this varies from one stub to another,
17569 but in general the stubs are likely to use any of the common library
17570 subroutines which @code{@value{NGCC}} generates as inline code.
17573 @node Debug Session
17574 @subsection Putting it All Together
17576 @cindex remote serial debugging summary
17577 In summary, when your program is ready to debug, you must follow these
17582 Make sure you have defined the supporting low-level routines
17583 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17585 @code{getDebugChar}, @code{putDebugChar},
17586 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17590 Insert these lines near the top of your program:
17598 For the 680x0 stub only, you need to provide a variable called
17599 @code{exceptionHook}. Normally you just use:
17602 void (*exceptionHook)() = 0;
17606 but if before calling @code{set_debug_traps}, you set it to point to a
17607 function in your program, that function is called when
17608 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17609 error). The function indicated by @code{exceptionHook} is called with
17610 one parameter: an @code{int} which is the exception number.
17613 Compile and link together: your program, the @value{GDBN} debugging stub for
17614 your target architecture, and the supporting subroutines.
17617 Make sure you have a serial connection between your target machine and
17618 the @value{GDBN} host, and identify the serial port on the host.
17621 @c The "remote" target now provides a `load' command, so we should
17622 @c document that. FIXME.
17623 Download your program to your target machine (or get it there by
17624 whatever means the manufacturer provides), and start it.
17627 Start @value{GDBN} on the host, and connect to the target
17628 (@pxref{Connecting,,Connecting to a Remote Target}).
17632 @node Configurations
17633 @chapter Configuration-Specific Information
17635 While nearly all @value{GDBN} commands are available for all native and
17636 cross versions of the debugger, there are some exceptions. This chapter
17637 describes things that are only available in certain configurations.
17639 There are three major categories of configurations: native
17640 configurations, where the host and target are the same, embedded
17641 operating system configurations, which are usually the same for several
17642 different processor architectures, and bare embedded processors, which
17643 are quite different from each other.
17648 * Embedded Processors::
17655 This section describes details specific to particular native
17660 * BSD libkvm Interface:: Debugging BSD kernel memory images
17661 * SVR4 Process Information:: SVR4 process information
17662 * DJGPP Native:: Features specific to the DJGPP port
17663 * Cygwin Native:: Features specific to the Cygwin port
17664 * Hurd Native:: Features specific to @sc{gnu} Hurd
17665 * Neutrino:: Features specific to QNX Neutrino
17666 * Darwin:: Features specific to Darwin
17672 On HP-UX systems, if you refer to a function or variable name that
17673 begins with a dollar sign, @value{GDBN} searches for a user or system
17674 name first, before it searches for a convenience variable.
17677 @node BSD libkvm Interface
17678 @subsection BSD libkvm Interface
17681 @cindex kernel memory image
17682 @cindex kernel crash dump
17684 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17685 interface that provides a uniform interface for accessing kernel virtual
17686 memory images, including live systems and crash dumps. @value{GDBN}
17687 uses this interface to allow you to debug live kernels and kernel crash
17688 dumps on many native BSD configurations. This is implemented as a
17689 special @code{kvm} debugging target. For debugging a live system, load
17690 the currently running kernel into @value{GDBN} and connect to the
17694 (@value{GDBP}) @b{target kvm}
17697 For debugging crash dumps, provide the file name of the crash dump as an
17701 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17704 Once connected to the @code{kvm} target, the following commands are
17710 Set current context from the @dfn{Process Control Block} (PCB) address.
17713 Set current context from proc address. This command isn't available on
17714 modern FreeBSD systems.
17717 @node SVR4 Process Information
17718 @subsection SVR4 Process Information
17720 @cindex examine process image
17721 @cindex process info via @file{/proc}
17723 Many versions of SVR4 and compatible systems provide a facility called
17724 @samp{/proc} that can be used to examine the image of a running
17725 process using file-system subroutines. If @value{GDBN} is configured
17726 for an operating system with this facility, the command @code{info
17727 proc} is available to report information about the process running
17728 your program, or about any process running on your system. @code{info
17729 proc} works only on SVR4 systems that include the @code{procfs} code.
17730 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17731 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17737 @itemx info proc @var{process-id}
17738 Summarize available information about any running process. If a
17739 process ID is specified by @var{process-id}, display information about
17740 that process; otherwise display information about the program being
17741 debugged. The summary includes the debugged process ID, the command
17742 line used to invoke it, its current working directory, and its
17743 executable file's absolute file name.
17745 On some systems, @var{process-id} can be of the form
17746 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17747 within a process. If the optional @var{pid} part is missing, it means
17748 a thread from the process being debugged (the leading @samp{/} still
17749 needs to be present, or else @value{GDBN} will interpret the number as
17750 a process ID rather than a thread ID).
17752 @item info proc mappings
17753 @cindex memory address space mappings
17754 Report the memory address space ranges accessible in the program, with
17755 information on whether the process has read, write, or execute access
17756 rights to each range. On @sc{gnu}/Linux systems, each memory range
17757 includes the object file which is mapped to that range, instead of the
17758 memory access rights to that range.
17760 @item info proc stat
17761 @itemx info proc status
17762 @cindex process detailed status information
17763 These subcommands are specific to @sc{gnu}/Linux systems. They show
17764 the process-related information, including the user ID and group ID;
17765 how many threads are there in the process; its virtual memory usage;
17766 the signals that are pending, blocked, and ignored; its TTY; its
17767 consumption of system and user time; its stack size; its @samp{nice}
17768 value; etc. For more information, see the @samp{proc} man page
17769 (type @kbd{man 5 proc} from your shell prompt).
17771 @item info proc all
17772 Show all the information about the process described under all of the
17773 above @code{info proc} subcommands.
17776 @comment These sub-options of 'info proc' were not included when
17777 @comment procfs.c was re-written. Keep their descriptions around
17778 @comment against the day when someone finds the time to put them back in.
17779 @kindex info proc times
17780 @item info proc times
17781 Starting time, user CPU time, and system CPU time for your program and
17784 @kindex info proc id
17786 Report on the process IDs related to your program: its own process ID,
17787 the ID of its parent, the process group ID, and the session ID.
17790 @item set procfs-trace
17791 @kindex set procfs-trace
17792 @cindex @code{procfs} API calls
17793 This command enables and disables tracing of @code{procfs} API calls.
17795 @item show procfs-trace
17796 @kindex show procfs-trace
17797 Show the current state of @code{procfs} API call tracing.
17799 @item set procfs-file @var{file}
17800 @kindex set procfs-file
17801 Tell @value{GDBN} to write @code{procfs} API trace to the named
17802 @var{file}. @value{GDBN} appends the trace info to the previous
17803 contents of the file. The default is to display the trace on the
17806 @item show procfs-file
17807 @kindex show procfs-file
17808 Show the file to which @code{procfs} API trace is written.
17810 @item proc-trace-entry
17811 @itemx proc-trace-exit
17812 @itemx proc-untrace-entry
17813 @itemx proc-untrace-exit
17814 @kindex proc-trace-entry
17815 @kindex proc-trace-exit
17816 @kindex proc-untrace-entry
17817 @kindex proc-untrace-exit
17818 These commands enable and disable tracing of entries into and exits
17819 from the @code{syscall} interface.
17822 @kindex info pidlist
17823 @cindex process list, QNX Neutrino
17824 For QNX Neutrino only, this command displays the list of all the
17825 processes and all the threads within each process.
17828 @kindex info meminfo
17829 @cindex mapinfo list, QNX Neutrino
17830 For QNX Neutrino only, this command displays the list of all mapinfos.
17834 @subsection Features for Debugging @sc{djgpp} Programs
17835 @cindex @sc{djgpp} debugging
17836 @cindex native @sc{djgpp} debugging
17837 @cindex MS-DOS-specific commands
17840 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17841 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17842 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17843 top of real-mode DOS systems and their emulations.
17845 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17846 defines a few commands specific to the @sc{djgpp} port. This
17847 subsection describes those commands.
17852 This is a prefix of @sc{djgpp}-specific commands which print
17853 information about the target system and important OS structures.
17856 @cindex MS-DOS system info
17857 @cindex free memory information (MS-DOS)
17858 @item info dos sysinfo
17859 This command displays assorted information about the underlying
17860 platform: the CPU type and features, the OS version and flavor, the
17861 DPMI version, and the available conventional and DPMI memory.
17866 @cindex segment descriptor tables
17867 @cindex descriptor tables display
17869 @itemx info dos ldt
17870 @itemx info dos idt
17871 These 3 commands display entries from, respectively, Global, Local,
17872 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17873 tables are data structures which store a descriptor for each segment
17874 that is currently in use. The segment's selector is an index into a
17875 descriptor table; the table entry for that index holds the
17876 descriptor's base address and limit, and its attributes and access
17879 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17880 segment (used for both data and the stack), and a DOS segment (which
17881 allows access to DOS/BIOS data structures and absolute addresses in
17882 conventional memory). However, the DPMI host will usually define
17883 additional segments in order to support the DPMI environment.
17885 @cindex garbled pointers
17886 These commands allow to display entries from the descriptor tables.
17887 Without an argument, all entries from the specified table are
17888 displayed. An argument, which should be an integer expression, means
17889 display a single entry whose index is given by the argument. For
17890 example, here's a convenient way to display information about the
17891 debugged program's data segment:
17894 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17895 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17899 This comes in handy when you want to see whether a pointer is outside
17900 the data segment's limit (i.e.@: @dfn{garbled}).
17902 @cindex page tables display (MS-DOS)
17904 @itemx info dos pte
17905 These two commands display entries from, respectively, the Page
17906 Directory and the Page Tables. Page Directories and Page Tables are
17907 data structures which control how virtual memory addresses are mapped
17908 into physical addresses. A Page Table includes an entry for every
17909 page of memory that is mapped into the program's address space; there
17910 may be several Page Tables, each one holding up to 4096 entries. A
17911 Page Directory has up to 4096 entries, one each for every Page Table
17912 that is currently in use.
17914 Without an argument, @kbd{info dos pde} displays the entire Page
17915 Directory, and @kbd{info dos pte} displays all the entries in all of
17916 the Page Tables. An argument, an integer expression, given to the
17917 @kbd{info dos pde} command means display only that entry from the Page
17918 Directory table. An argument given to the @kbd{info dos pte} command
17919 means display entries from a single Page Table, the one pointed to by
17920 the specified entry in the Page Directory.
17922 @cindex direct memory access (DMA) on MS-DOS
17923 These commands are useful when your program uses @dfn{DMA} (Direct
17924 Memory Access), which needs physical addresses to program the DMA
17927 These commands are supported only with some DPMI servers.
17929 @cindex physical address from linear address
17930 @item info dos address-pte @var{addr}
17931 This command displays the Page Table entry for a specified linear
17932 address. The argument @var{addr} is a linear address which should
17933 already have the appropriate segment's base address added to it,
17934 because this command accepts addresses which may belong to @emph{any}
17935 segment. For example, here's how to display the Page Table entry for
17936 the page where a variable @code{i} is stored:
17939 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17940 @exdent @code{Page Table entry for address 0x11a00d30:}
17941 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17945 This says that @code{i} is stored at offset @code{0xd30} from the page
17946 whose physical base address is @code{0x02698000}, and shows all the
17947 attributes of that page.
17949 Note that you must cast the addresses of variables to a @code{char *},
17950 since otherwise the value of @code{__djgpp_base_address}, the base
17951 address of all variables and functions in a @sc{djgpp} program, will
17952 be added using the rules of C pointer arithmetics: if @code{i} is
17953 declared an @code{int}, @value{GDBN} will add 4 times the value of
17954 @code{__djgpp_base_address} to the address of @code{i}.
17956 Here's another example, it displays the Page Table entry for the
17960 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17961 @exdent @code{Page Table entry for address 0x29110:}
17962 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17966 (The @code{+ 3} offset is because the transfer buffer's address is the
17967 3rd member of the @code{_go32_info_block} structure.) The output
17968 clearly shows that this DPMI server maps the addresses in conventional
17969 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17970 linear (@code{0x29110}) addresses are identical.
17972 This command is supported only with some DPMI servers.
17975 @cindex DOS serial data link, remote debugging
17976 In addition to native debugging, the DJGPP port supports remote
17977 debugging via a serial data link. The following commands are specific
17978 to remote serial debugging in the DJGPP port of @value{GDBN}.
17981 @kindex set com1base
17982 @kindex set com1irq
17983 @kindex set com2base
17984 @kindex set com2irq
17985 @kindex set com3base
17986 @kindex set com3irq
17987 @kindex set com4base
17988 @kindex set com4irq
17989 @item set com1base @var{addr}
17990 This command sets the base I/O port address of the @file{COM1} serial
17993 @item set com1irq @var{irq}
17994 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17995 for the @file{COM1} serial port.
17997 There are similar commands @samp{set com2base}, @samp{set com3irq},
17998 etc.@: for setting the port address and the @code{IRQ} lines for the
18001 @kindex show com1base
18002 @kindex show com1irq
18003 @kindex show com2base
18004 @kindex show com2irq
18005 @kindex show com3base
18006 @kindex show com3irq
18007 @kindex show com4base
18008 @kindex show com4irq
18009 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18010 display the current settings of the base address and the @code{IRQ}
18011 lines used by the COM ports.
18014 @kindex info serial
18015 @cindex DOS serial port status
18016 This command prints the status of the 4 DOS serial ports. For each
18017 port, it prints whether it's active or not, its I/O base address and
18018 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18019 counts of various errors encountered so far.
18023 @node Cygwin Native
18024 @subsection Features for Debugging MS Windows PE Executables
18025 @cindex MS Windows debugging
18026 @cindex native Cygwin debugging
18027 @cindex Cygwin-specific commands
18029 @value{GDBN} supports native debugging of MS Windows programs, including
18030 DLLs with and without symbolic debugging information.
18032 @cindex Ctrl-BREAK, MS-Windows
18033 @cindex interrupt debuggee on MS-Windows
18034 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18035 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18036 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18037 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18038 sequence, which can be used to interrupt the debuggee even if it
18041 There are various additional Cygwin-specific commands, described in
18042 this section. Working with DLLs that have no debugging symbols is
18043 described in @ref{Non-debug DLL Symbols}.
18048 This is a prefix of MS Windows-specific commands which print
18049 information about the target system and important OS structures.
18051 @item info w32 selector
18052 This command displays information returned by
18053 the Win32 API @code{GetThreadSelectorEntry} function.
18054 It takes an optional argument that is evaluated to
18055 a long value to give the information about this given selector.
18056 Without argument, this command displays information
18057 about the six segment registers.
18059 @item info w32 thread-information-block
18060 This command displays thread specific information stored in the
18061 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18062 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18066 This is a Cygwin-specific alias of @code{info shared}.
18068 @kindex dll-symbols
18070 This command loads symbols from a dll similarly to
18071 add-sym command but without the need to specify a base address.
18073 @kindex set cygwin-exceptions
18074 @cindex debugging the Cygwin DLL
18075 @cindex Cygwin DLL, debugging
18076 @item set cygwin-exceptions @var{mode}
18077 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18078 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18079 @value{GDBN} will delay recognition of exceptions, and may ignore some
18080 exceptions which seem to be caused by internal Cygwin DLL
18081 ``bookkeeping''. This option is meant primarily for debugging the
18082 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18083 @value{GDBN} users with false @code{SIGSEGV} signals.
18085 @kindex show cygwin-exceptions
18086 @item show cygwin-exceptions
18087 Displays whether @value{GDBN} will break on exceptions that happen
18088 inside the Cygwin DLL itself.
18090 @kindex set new-console
18091 @item set new-console @var{mode}
18092 If @var{mode} is @code{on} the debuggee will
18093 be started in a new console on next start.
18094 If @var{mode} is @code{off}, the debuggee will
18095 be started in the same console as the debugger.
18097 @kindex show new-console
18098 @item show new-console
18099 Displays whether a new console is used
18100 when the debuggee is started.
18102 @kindex set new-group
18103 @item set new-group @var{mode}
18104 This boolean value controls whether the debuggee should
18105 start a new group or stay in the same group as the debugger.
18106 This affects the way the Windows OS handles
18109 @kindex show new-group
18110 @item show new-group
18111 Displays current value of new-group boolean.
18113 @kindex set debugevents
18114 @item set debugevents
18115 This boolean value adds debug output concerning kernel events related
18116 to the debuggee seen by the debugger. This includes events that
18117 signal thread and process creation and exit, DLL loading and
18118 unloading, console interrupts, and debugging messages produced by the
18119 Windows @code{OutputDebugString} API call.
18121 @kindex set debugexec
18122 @item set debugexec
18123 This boolean value adds debug output concerning execute events
18124 (such as resume thread) seen by the debugger.
18126 @kindex set debugexceptions
18127 @item set debugexceptions
18128 This boolean value adds debug output concerning exceptions in the
18129 debuggee seen by the debugger.
18131 @kindex set debugmemory
18132 @item set debugmemory
18133 This boolean value adds debug output concerning debuggee memory reads
18134 and writes by the debugger.
18138 This boolean values specifies whether the debuggee is called
18139 via a shell or directly (default value is on).
18143 Displays if the debuggee will be started with a shell.
18148 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18151 @node Non-debug DLL Symbols
18152 @subsubsection Support for DLLs without Debugging Symbols
18153 @cindex DLLs with no debugging symbols
18154 @cindex Minimal symbols and DLLs
18156 Very often on windows, some of the DLLs that your program relies on do
18157 not include symbolic debugging information (for example,
18158 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18159 symbols in a DLL, it relies on the minimal amount of symbolic
18160 information contained in the DLL's export table. This section
18161 describes working with such symbols, known internally to @value{GDBN} as
18162 ``minimal symbols''.
18164 Note that before the debugged program has started execution, no DLLs
18165 will have been loaded. The easiest way around this problem is simply to
18166 start the program --- either by setting a breakpoint or letting the
18167 program run once to completion. It is also possible to force
18168 @value{GDBN} to load a particular DLL before starting the executable ---
18169 see the shared library information in @ref{Files}, or the
18170 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18171 explicitly loading symbols from a DLL with no debugging information will
18172 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18173 which may adversely affect symbol lookup performance.
18175 @subsubsection DLL Name Prefixes
18177 In keeping with the naming conventions used by the Microsoft debugging
18178 tools, DLL export symbols are made available with a prefix based on the
18179 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18180 also entered into the symbol table, so @code{CreateFileA} is often
18181 sufficient. In some cases there will be name clashes within a program
18182 (particularly if the executable itself includes full debugging symbols)
18183 necessitating the use of the fully qualified name when referring to the
18184 contents of the DLL. Use single-quotes around the name to avoid the
18185 exclamation mark (``!'') being interpreted as a language operator.
18187 Note that the internal name of the DLL may be all upper-case, even
18188 though the file name of the DLL is lower-case, or vice-versa. Since
18189 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18190 some confusion. If in doubt, try the @code{info functions} and
18191 @code{info variables} commands or even @code{maint print msymbols}
18192 (@pxref{Symbols}). Here's an example:
18195 (@value{GDBP}) info function CreateFileA
18196 All functions matching regular expression "CreateFileA":
18198 Non-debugging symbols:
18199 0x77e885f4 CreateFileA
18200 0x77e885f4 KERNEL32!CreateFileA
18204 (@value{GDBP}) info function !
18205 All functions matching regular expression "!":
18207 Non-debugging symbols:
18208 0x6100114c cygwin1!__assert
18209 0x61004034 cygwin1!_dll_crt0@@0
18210 0x61004240 cygwin1!dll_crt0(per_process *)
18214 @subsubsection Working with Minimal Symbols
18216 Symbols extracted from a DLL's export table do not contain very much
18217 type information. All that @value{GDBN} can do is guess whether a symbol
18218 refers to a function or variable depending on the linker section that
18219 contains the symbol. Also note that the actual contents of the memory
18220 contained in a DLL are not available unless the program is running. This
18221 means that you cannot examine the contents of a variable or disassemble
18222 a function within a DLL without a running program.
18224 Variables are generally treated as pointers and dereferenced
18225 automatically. For this reason, it is often necessary to prefix a
18226 variable name with the address-of operator (``&'') and provide explicit
18227 type information in the command. Here's an example of the type of
18231 (@value{GDBP}) print 'cygwin1!__argv'
18236 (@value{GDBP}) x 'cygwin1!__argv'
18237 0x10021610: "\230y\""
18240 And two possible solutions:
18243 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18244 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18248 (@value{GDBP}) x/2x &'cygwin1!__argv'
18249 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18250 (@value{GDBP}) x/x 0x10021608
18251 0x10021608: 0x0022fd98
18252 (@value{GDBP}) x/s 0x0022fd98
18253 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18256 Setting a break point within a DLL is possible even before the program
18257 starts execution. However, under these circumstances, @value{GDBN} can't
18258 examine the initial instructions of the function in order to skip the
18259 function's frame set-up code. You can work around this by using ``*&''
18260 to set the breakpoint at a raw memory address:
18263 (@value{GDBP}) break *&'python22!PyOS_Readline'
18264 Breakpoint 1 at 0x1e04eff0
18267 The author of these extensions is not entirely convinced that setting a
18268 break point within a shared DLL like @file{kernel32.dll} is completely
18272 @subsection Commands Specific to @sc{gnu} Hurd Systems
18273 @cindex @sc{gnu} Hurd debugging
18275 This subsection describes @value{GDBN} commands specific to the
18276 @sc{gnu} Hurd native debugging.
18281 @kindex set signals@r{, Hurd command}
18282 @kindex set sigs@r{, Hurd command}
18283 This command toggles the state of inferior signal interception by
18284 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18285 affected by this command. @code{sigs} is a shorthand alias for
18290 @kindex show signals@r{, Hurd command}
18291 @kindex show sigs@r{, Hurd command}
18292 Show the current state of intercepting inferior's signals.
18294 @item set signal-thread
18295 @itemx set sigthread
18296 @kindex set signal-thread
18297 @kindex set sigthread
18298 This command tells @value{GDBN} which thread is the @code{libc} signal
18299 thread. That thread is run when a signal is delivered to a running
18300 process. @code{set sigthread} is the shorthand alias of @code{set
18303 @item show signal-thread
18304 @itemx show sigthread
18305 @kindex show signal-thread
18306 @kindex show sigthread
18307 These two commands show which thread will run when the inferior is
18308 delivered a signal.
18311 @kindex set stopped@r{, Hurd command}
18312 This commands tells @value{GDBN} that the inferior process is stopped,
18313 as with the @code{SIGSTOP} signal. The stopped process can be
18314 continued by delivering a signal to it.
18317 @kindex show stopped@r{, Hurd command}
18318 This command shows whether @value{GDBN} thinks the debuggee is
18321 @item set exceptions
18322 @kindex set exceptions@r{, Hurd command}
18323 Use this command to turn off trapping of exceptions in the inferior.
18324 When exception trapping is off, neither breakpoints nor
18325 single-stepping will work. To restore the default, set exception
18328 @item show exceptions
18329 @kindex show exceptions@r{, Hurd command}
18330 Show the current state of trapping exceptions in the inferior.
18332 @item set task pause
18333 @kindex set task@r{, Hurd commands}
18334 @cindex task attributes (@sc{gnu} Hurd)
18335 @cindex pause current task (@sc{gnu} Hurd)
18336 This command toggles task suspension when @value{GDBN} has control.
18337 Setting it to on takes effect immediately, and the task is suspended
18338 whenever @value{GDBN} gets control. Setting it to off will take
18339 effect the next time the inferior is continued. If this option is set
18340 to off, you can use @code{set thread default pause on} or @code{set
18341 thread pause on} (see below) to pause individual threads.
18343 @item show task pause
18344 @kindex show task@r{, Hurd commands}
18345 Show the current state of task suspension.
18347 @item set task detach-suspend-count
18348 @cindex task suspend count
18349 @cindex detach from task, @sc{gnu} Hurd
18350 This command sets the suspend count the task will be left with when
18351 @value{GDBN} detaches from it.
18353 @item show task detach-suspend-count
18354 Show the suspend count the task will be left with when detaching.
18356 @item set task exception-port
18357 @itemx set task excp
18358 @cindex task exception port, @sc{gnu} Hurd
18359 This command sets the task exception port to which @value{GDBN} will
18360 forward exceptions. The argument should be the value of the @dfn{send
18361 rights} of the task. @code{set task excp} is a shorthand alias.
18363 @item set noninvasive
18364 @cindex noninvasive task options
18365 This command switches @value{GDBN} to a mode that is the least
18366 invasive as far as interfering with the inferior is concerned. This
18367 is the same as using @code{set task pause}, @code{set exceptions}, and
18368 @code{set signals} to values opposite to the defaults.
18370 @item info send-rights
18371 @itemx info receive-rights
18372 @itemx info port-rights
18373 @itemx info port-sets
18374 @itemx info dead-names
18377 @cindex send rights, @sc{gnu} Hurd
18378 @cindex receive rights, @sc{gnu} Hurd
18379 @cindex port rights, @sc{gnu} Hurd
18380 @cindex port sets, @sc{gnu} Hurd
18381 @cindex dead names, @sc{gnu} Hurd
18382 These commands display information about, respectively, send rights,
18383 receive rights, port rights, port sets, and dead names of a task.
18384 There are also shorthand aliases: @code{info ports} for @code{info
18385 port-rights} and @code{info psets} for @code{info port-sets}.
18387 @item set thread pause
18388 @kindex set thread@r{, Hurd command}
18389 @cindex thread properties, @sc{gnu} Hurd
18390 @cindex pause current thread (@sc{gnu} Hurd)
18391 This command toggles current thread suspension when @value{GDBN} has
18392 control. Setting it to on takes effect immediately, and the current
18393 thread is suspended whenever @value{GDBN} gets control. Setting it to
18394 off will take effect the next time the inferior is continued.
18395 Normally, this command has no effect, since when @value{GDBN} has
18396 control, the whole task is suspended. However, if you used @code{set
18397 task pause off} (see above), this command comes in handy to suspend
18398 only the current thread.
18400 @item show thread pause
18401 @kindex show thread@r{, Hurd command}
18402 This command shows the state of current thread suspension.
18404 @item set thread run
18405 This command sets whether the current thread is allowed to run.
18407 @item show thread run
18408 Show whether the current thread is allowed to run.
18410 @item set thread detach-suspend-count
18411 @cindex thread suspend count, @sc{gnu} Hurd
18412 @cindex detach from thread, @sc{gnu} Hurd
18413 This command sets the suspend count @value{GDBN} will leave on a
18414 thread when detaching. This number is relative to the suspend count
18415 found by @value{GDBN} when it notices the thread; use @code{set thread
18416 takeover-suspend-count} to force it to an absolute value.
18418 @item show thread detach-suspend-count
18419 Show the suspend count @value{GDBN} will leave on the thread when
18422 @item set thread exception-port
18423 @itemx set thread excp
18424 Set the thread exception port to which to forward exceptions. This
18425 overrides the port set by @code{set task exception-port} (see above).
18426 @code{set thread excp} is the shorthand alias.
18428 @item set thread takeover-suspend-count
18429 Normally, @value{GDBN}'s thread suspend counts are relative to the
18430 value @value{GDBN} finds when it notices each thread. This command
18431 changes the suspend counts to be absolute instead.
18433 @item set thread default
18434 @itemx show thread default
18435 @cindex thread default settings, @sc{gnu} Hurd
18436 Each of the above @code{set thread} commands has a @code{set thread
18437 default} counterpart (e.g., @code{set thread default pause}, @code{set
18438 thread default exception-port}, etc.). The @code{thread default}
18439 variety of commands sets the default thread properties for all
18440 threads; you can then change the properties of individual threads with
18441 the non-default commands.
18446 @subsection QNX Neutrino
18447 @cindex QNX Neutrino
18449 @value{GDBN} provides the following commands specific to the QNX
18453 @item set debug nto-debug
18454 @kindex set debug nto-debug
18455 When set to on, enables debugging messages specific to the QNX
18458 @item show debug nto-debug
18459 @kindex show debug nto-debug
18460 Show the current state of QNX Neutrino messages.
18467 @value{GDBN} provides the following commands specific to the Darwin target:
18470 @item set debug darwin @var{num}
18471 @kindex set debug darwin
18472 When set to a non zero value, enables debugging messages specific to
18473 the Darwin support. Higher values produce more verbose output.
18475 @item show debug darwin
18476 @kindex show debug darwin
18477 Show the current state of Darwin messages.
18479 @item set debug mach-o @var{num}
18480 @kindex set debug mach-o
18481 When set to a non zero value, enables debugging messages while
18482 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18483 file format used on Darwin for object and executable files.) Higher
18484 values produce more verbose output. This is a command to diagnose
18485 problems internal to @value{GDBN} and should not be needed in normal
18488 @item show debug mach-o
18489 @kindex show debug mach-o
18490 Show the current state of Mach-O file messages.
18492 @item set mach-exceptions on
18493 @itemx set mach-exceptions off
18494 @kindex set mach-exceptions
18495 On Darwin, faults are first reported as a Mach exception and are then
18496 mapped to a Posix signal. Use this command to turn on trapping of
18497 Mach exceptions in the inferior. This might be sometimes useful to
18498 better understand the cause of a fault. The default is off.
18500 @item show mach-exceptions
18501 @kindex show mach-exceptions
18502 Show the current state of exceptions trapping.
18507 @section Embedded Operating Systems
18509 This section describes configurations involving the debugging of
18510 embedded operating systems that are available for several different
18514 * VxWorks:: Using @value{GDBN} with VxWorks
18517 @value{GDBN} includes the ability to debug programs running on
18518 various real-time operating systems.
18521 @subsection Using @value{GDBN} with VxWorks
18527 @kindex target vxworks
18528 @item target vxworks @var{machinename}
18529 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18530 is the target system's machine name or IP address.
18534 On VxWorks, @code{load} links @var{filename} dynamically on the
18535 current target system as well as adding its symbols in @value{GDBN}.
18537 @value{GDBN} enables developers to spawn and debug tasks running on networked
18538 VxWorks targets from a Unix host. Already-running tasks spawned from
18539 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18540 both the Unix host and on the VxWorks target. The program
18541 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18542 installed with the name @code{vxgdb}, to distinguish it from a
18543 @value{GDBN} for debugging programs on the host itself.)
18546 @item VxWorks-timeout @var{args}
18547 @kindex vxworks-timeout
18548 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18549 This option is set by the user, and @var{args} represents the number of
18550 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18551 your VxWorks target is a slow software simulator or is on the far side
18552 of a thin network line.
18555 The following information on connecting to VxWorks was current when
18556 this manual was produced; newer releases of VxWorks may use revised
18559 @findex INCLUDE_RDB
18560 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18561 to include the remote debugging interface routines in the VxWorks
18562 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18563 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18564 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18565 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18566 information on configuring and remaking VxWorks, see the manufacturer's
18568 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18570 Once you have included @file{rdb.a} in your VxWorks system image and set
18571 your Unix execution search path to find @value{GDBN}, you are ready to
18572 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18573 @code{vxgdb}, depending on your installation).
18575 @value{GDBN} comes up showing the prompt:
18582 * VxWorks Connection:: Connecting to VxWorks
18583 * VxWorks Download:: VxWorks download
18584 * VxWorks Attach:: Running tasks
18587 @node VxWorks Connection
18588 @subsubsection Connecting to VxWorks
18590 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18591 network. To connect to a target whose host name is ``@code{tt}'', type:
18594 (vxgdb) target vxworks tt
18598 @value{GDBN} displays messages like these:
18601 Attaching remote machine across net...
18606 @value{GDBN} then attempts to read the symbol tables of any object modules
18607 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18608 these files by searching the directories listed in the command search
18609 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18610 to find an object file, it displays a message such as:
18613 prog.o: No such file or directory.
18616 When this happens, add the appropriate directory to the search path with
18617 the @value{GDBN} command @code{path}, and execute the @code{target}
18620 @node VxWorks Download
18621 @subsubsection VxWorks Download
18623 @cindex download to VxWorks
18624 If you have connected to the VxWorks target and you want to debug an
18625 object that has not yet been loaded, you can use the @value{GDBN}
18626 @code{load} command to download a file from Unix to VxWorks
18627 incrementally. The object file given as an argument to the @code{load}
18628 command is actually opened twice: first by the VxWorks target in order
18629 to download the code, then by @value{GDBN} in order to read the symbol
18630 table. This can lead to problems if the current working directories on
18631 the two systems differ. If both systems have NFS mounted the same
18632 filesystems, you can avoid these problems by using absolute paths.
18633 Otherwise, it is simplest to set the working directory on both systems
18634 to the directory in which the object file resides, and then to reference
18635 the file by its name, without any path. For instance, a program
18636 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18637 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18638 program, type this on VxWorks:
18641 -> cd "@var{vxpath}/vw/demo/rdb"
18645 Then, in @value{GDBN}, type:
18648 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18649 (vxgdb) load prog.o
18652 @value{GDBN} displays a response similar to this:
18655 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18658 You can also use the @code{load} command to reload an object module
18659 after editing and recompiling the corresponding source file. Note that
18660 this makes @value{GDBN} delete all currently-defined breakpoints,
18661 auto-displays, and convenience variables, and to clear the value
18662 history. (This is necessary in order to preserve the integrity of
18663 debugger's data structures that reference the target system's symbol
18666 @node VxWorks Attach
18667 @subsubsection Running Tasks
18669 @cindex running VxWorks tasks
18670 You can also attach to an existing task using the @code{attach} command as
18674 (vxgdb) attach @var{task}
18678 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18679 or suspended when you attach to it. Running tasks are suspended at
18680 the time of attachment.
18682 @node Embedded Processors
18683 @section Embedded Processors
18685 This section goes into details specific to particular embedded
18688 @cindex send command to simulator
18689 Whenever a specific embedded processor has a simulator, @value{GDBN}
18690 allows to send an arbitrary command to the simulator.
18693 @item sim @var{command}
18694 @kindex sim@r{, a command}
18695 Send an arbitrary @var{command} string to the simulator. Consult the
18696 documentation for the specific simulator in use for information about
18697 acceptable commands.
18703 * M32R/D:: Renesas M32R/D
18704 * M68K:: Motorola M68K
18705 * MicroBlaze:: Xilinx MicroBlaze
18706 * MIPS Embedded:: MIPS Embedded
18707 * OpenRISC 1000:: OpenRisc 1000
18708 * PA:: HP PA Embedded
18709 * PowerPC Embedded:: PowerPC Embedded
18710 * Sparclet:: Tsqware Sparclet
18711 * Sparclite:: Fujitsu Sparclite
18712 * Z8000:: Zilog Z8000
18715 * Super-H:: Renesas Super-H
18724 @item target rdi @var{dev}
18725 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18726 use this target to communicate with both boards running the Angel
18727 monitor, or with the EmbeddedICE JTAG debug device.
18730 @item target rdp @var{dev}
18735 @value{GDBN} provides the following ARM-specific commands:
18738 @item set arm disassembler
18740 This commands selects from a list of disassembly styles. The
18741 @code{"std"} style is the standard style.
18743 @item show arm disassembler
18745 Show the current disassembly style.
18747 @item set arm apcs32
18748 @cindex ARM 32-bit mode
18749 This command toggles ARM operation mode between 32-bit and 26-bit.
18751 @item show arm apcs32
18752 Display the current usage of the ARM 32-bit mode.
18754 @item set arm fpu @var{fputype}
18755 This command sets the ARM floating-point unit (FPU) type. The
18756 argument @var{fputype} can be one of these:
18760 Determine the FPU type by querying the OS ABI.
18762 Software FPU, with mixed-endian doubles on little-endian ARM
18765 GCC-compiled FPA co-processor.
18767 Software FPU with pure-endian doubles.
18773 Show the current type of the FPU.
18776 This command forces @value{GDBN} to use the specified ABI.
18779 Show the currently used ABI.
18781 @item set arm fallback-mode (arm|thumb|auto)
18782 @value{GDBN} uses the symbol table, when available, to determine
18783 whether instructions are ARM or Thumb. This command controls
18784 @value{GDBN}'s default behavior when the symbol table is not
18785 available. The default is @samp{auto}, which causes @value{GDBN} to
18786 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18789 @item show arm fallback-mode
18790 Show the current fallback instruction mode.
18792 @item set arm force-mode (arm|thumb|auto)
18793 This command overrides use of the symbol table to determine whether
18794 instructions are ARM or Thumb. The default is @samp{auto}, which
18795 causes @value{GDBN} to use the symbol table and then the setting
18796 of @samp{set arm fallback-mode}.
18798 @item show arm force-mode
18799 Show the current forced instruction mode.
18801 @item set debug arm
18802 Toggle whether to display ARM-specific debugging messages from the ARM
18803 target support subsystem.
18805 @item show debug arm
18806 Show whether ARM-specific debugging messages are enabled.
18809 The following commands are available when an ARM target is debugged
18810 using the RDI interface:
18813 @item rdilogfile @r{[}@var{file}@r{]}
18815 @cindex ADP (Angel Debugger Protocol) logging
18816 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18817 With an argument, sets the log file to the specified @var{file}. With
18818 no argument, show the current log file name. The default log file is
18821 @item rdilogenable @r{[}@var{arg}@r{]}
18822 @kindex rdilogenable
18823 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18824 enables logging, with an argument 0 or @code{"no"} disables it. With
18825 no arguments displays the current setting. When logging is enabled,
18826 ADP packets exchanged between @value{GDBN} and the RDI target device
18827 are logged to a file.
18829 @item set rdiromatzero
18830 @kindex set rdiromatzero
18831 @cindex ROM at zero address, RDI
18832 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18833 vector catching is disabled, so that zero address can be used. If off
18834 (the default), vector catching is enabled. For this command to take
18835 effect, it needs to be invoked prior to the @code{target rdi} command.
18837 @item show rdiromatzero
18838 @kindex show rdiromatzero
18839 Show the current setting of ROM at zero address.
18841 @item set rdiheartbeat
18842 @kindex set rdiheartbeat
18843 @cindex RDI heartbeat
18844 Enable or disable RDI heartbeat packets. It is not recommended to
18845 turn on this option, since it confuses ARM and EPI JTAG interface, as
18846 well as the Angel monitor.
18848 @item show rdiheartbeat
18849 @kindex show rdiheartbeat
18850 Show the setting of RDI heartbeat packets.
18854 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18855 The @value{GDBN} ARM simulator accepts the following optional arguments.
18858 @item --swi-support=@var{type}
18859 Tell the simulator which SWI interfaces to support.
18860 @var{type} may be a comma separated list of the following values.
18861 The default value is @code{all}.
18874 @subsection Renesas M32R/D and M32R/SDI
18877 @kindex target m32r
18878 @item target m32r @var{dev}
18879 Renesas M32R/D ROM monitor.
18881 @kindex target m32rsdi
18882 @item target m32rsdi @var{dev}
18883 Renesas M32R SDI server, connected via parallel port to the board.
18886 The following @value{GDBN} commands are specific to the M32R monitor:
18889 @item set download-path @var{path}
18890 @kindex set download-path
18891 @cindex find downloadable @sc{srec} files (M32R)
18892 Set the default path for finding downloadable @sc{srec} files.
18894 @item show download-path
18895 @kindex show download-path
18896 Show the default path for downloadable @sc{srec} files.
18898 @item set board-address @var{addr}
18899 @kindex set board-address
18900 @cindex M32-EVA target board address
18901 Set the IP address for the M32R-EVA target board.
18903 @item show board-address
18904 @kindex show board-address
18905 Show the current IP address of the target board.
18907 @item set server-address @var{addr}
18908 @kindex set server-address
18909 @cindex download server address (M32R)
18910 Set the IP address for the download server, which is the @value{GDBN}'s
18913 @item show server-address
18914 @kindex show server-address
18915 Display the IP address of the download server.
18917 @item upload @r{[}@var{file}@r{]}
18918 @kindex upload@r{, M32R}
18919 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18920 upload capability. If no @var{file} argument is given, the current
18921 executable file is uploaded.
18923 @item tload @r{[}@var{file}@r{]}
18924 @kindex tload@r{, M32R}
18925 Test the @code{upload} command.
18928 The following commands are available for M32R/SDI:
18933 @cindex reset SDI connection, M32R
18934 This command resets the SDI connection.
18938 This command shows the SDI connection status.
18941 @kindex debug_chaos
18942 @cindex M32R/Chaos debugging
18943 Instructs the remote that M32R/Chaos debugging is to be used.
18945 @item use_debug_dma
18946 @kindex use_debug_dma
18947 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18950 @kindex use_mon_code
18951 Instructs the remote to use the MON_CODE method of accessing memory.
18954 @kindex use_ib_break
18955 Instructs the remote to set breakpoints by IB break.
18957 @item use_dbt_break
18958 @kindex use_dbt_break
18959 Instructs the remote to set breakpoints by DBT.
18965 The Motorola m68k configuration includes ColdFire support, and a
18966 target command for the following ROM monitor.
18970 @kindex target dbug
18971 @item target dbug @var{dev}
18972 dBUG ROM monitor for Motorola ColdFire.
18977 @subsection MicroBlaze
18978 @cindex Xilinx MicroBlaze
18979 @cindex XMD, Xilinx Microprocessor Debugger
18981 The MicroBlaze is a soft-core processor supported on various Xilinx
18982 FPGAs, such as Spartan or Virtex series. Boards with these processors
18983 usually have JTAG ports which connect to a host system running the Xilinx
18984 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18985 This host system is used to download the configuration bitstream to
18986 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18987 communicates with the target board using the JTAG interface and
18988 presents a @code{gdbserver} interface to the board. By default
18989 @code{xmd} uses port @code{1234}. (While it is possible to change
18990 this default port, it requires the use of undocumented @code{xmd}
18991 commands. Contact Xilinx support if you need to do this.)
18993 Use these GDB commands to connect to the MicroBlaze target processor.
18996 @item target remote :1234
18997 Use this command to connect to the target if you are running @value{GDBN}
18998 on the same system as @code{xmd}.
19000 @item target remote @var{xmd-host}:1234
19001 Use this command to connect to the target if it is connected to @code{xmd}
19002 running on a different system named @var{xmd-host}.
19005 Use this command to download a program to the MicroBlaze target.
19007 @item set debug microblaze @var{n}
19008 Enable MicroBlaze-specific debugging messages if non-zero.
19010 @item show debug microblaze @var{n}
19011 Show MicroBlaze-specific debugging level.
19014 @node MIPS Embedded
19015 @subsection MIPS Embedded
19017 @cindex MIPS boards
19018 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19019 MIPS board attached to a serial line. This is available when
19020 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19023 Use these @value{GDBN} commands to specify the connection to your target board:
19026 @item target mips @var{port}
19027 @kindex target mips @var{port}
19028 To run a program on the board, start up @code{@value{GDBP}} with the
19029 name of your program as the argument. To connect to the board, use the
19030 command @samp{target mips @var{port}}, where @var{port} is the name of
19031 the serial port connected to the board. If the program has not already
19032 been downloaded to the board, you may use the @code{load} command to
19033 download it. You can then use all the usual @value{GDBN} commands.
19035 For example, this sequence connects to the target board through a serial
19036 port, and loads and runs a program called @var{prog} through the
19040 host$ @value{GDBP} @var{prog}
19041 @value{GDBN} is free software and @dots{}
19042 (@value{GDBP}) target mips /dev/ttyb
19043 (@value{GDBP}) load @var{prog}
19047 @item target mips @var{hostname}:@var{portnumber}
19048 On some @value{GDBN} host configurations, you can specify a TCP
19049 connection (for instance, to a serial line managed by a terminal
19050 concentrator) instead of a serial port, using the syntax
19051 @samp{@var{hostname}:@var{portnumber}}.
19053 @item target pmon @var{port}
19054 @kindex target pmon @var{port}
19057 @item target ddb @var{port}
19058 @kindex target ddb @var{port}
19059 NEC's DDB variant of PMON for Vr4300.
19061 @item target lsi @var{port}
19062 @kindex target lsi @var{port}
19063 LSI variant of PMON.
19065 @kindex target r3900
19066 @item target r3900 @var{dev}
19067 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19069 @kindex target array
19070 @item target array @var{dev}
19071 Array Tech LSI33K RAID controller board.
19077 @value{GDBN} also supports these special commands for MIPS targets:
19080 @item set mipsfpu double
19081 @itemx set mipsfpu single
19082 @itemx set mipsfpu none
19083 @itemx set mipsfpu auto
19084 @itemx show mipsfpu
19085 @kindex set mipsfpu
19086 @kindex show mipsfpu
19087 @cindex MIPS remote floating point
19088 @cindex floating point, MIPS remote
19089 If your target board does not support the MIPS floating point
19090 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19091 need this, you may wish to put the command in your @value{GDBN} init
19092 file). This tells @value{GDBN} how to find the return value of
19093 functions which return floating point values. It also allows
19094 @value{GDBN} to avoid saving the floating point registers when calling
19095 functions on the board. If you are using a floating point coprocessor
19096 with only single precision floating point support, as on the @sc{r4650}
19097 processor, use the command @samp{set mipsfpu single}. The default
19098 double precision floating point coprocessor may be selected using
19099 @samp{set mipsfpu double}.
19101 In previous versions the only choices were double precision or no
19102 floating point, so @samp{set mipsfpu on} will select double precision
19103 and @samp{set mipsfpu off} will select no floating point.
19105 As usual, you can inquire about the @code{mipsfpu} variable with
19106 @samp{show mipsfpu}.
19108 @item set timeout @var{seconds}
19109 @itemx set retransmit-timeout @var{seconds}
19110 @itemx show timeout
19111 @itemx show retransmit-timeout
19112 @cindex @code{timeout}, MIPS protocol
19113 @cindex @code{retransmit-timeout}, MIPS protocol
19114 @kindex set timeout
19115 @kindex show timeout
19116 @kindex set retransmit-timeout
19117 @kindex show retransmit-timeout
19118 You can control the timeout used while waiting for a packet, in the MIPS
19119 remote protocol, with the @code{set timeout @var{seconds}} command. The
19120 default is 5 seconds. Similarly, you can control the timeout used while
19121 waiting for an acknowledgment of a packet with the @code{set
19122 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19123 You can inspect both values with @code{show timeout} and @code{show
19124 retransmit-timeout}. (These commands are @emph{only} available when
19125 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19127 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19128 is waiting for your program to stop. In that case, @value{GDBN} waits
19129 forever because it has no way of knowing how long the program is going
19130 to run before stopping.
19132 @item set syn-garbage-limit @var{num}
19133 @kindex set syn-garbage-limit@r{, MIPS remote}
19134 @cindex synchronize with remote MIPS target
19135 Limit the maximum number of characters @value{GDBN} should ignore when
19136 it tries to synchronize with the remote target. The default is 10
19137 characters. Setting the limit to -1 means there's no limit.
19139 @item show syn-garbage-limit
19140 @kindex show syn-garbage-limit@r{, MIPS remote}
19141 Show the current limit on the number of characters to ignore when
19142 trying to synchronize with the remote system.
19144 @item set monitor-prompt @var{prompt}
19145 @kindex set monitor-prompt@r{, MIPS remote}
19146 @cindex remote monitor prompt
19147 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19148 remote monitor. The default depends on the target:
19158 @item show monitor-prompt
19159 @kindex show monitor-prompt@r{, MIPS remote}
19160 Show the current strings @value{GDBN} expects as the prompt from the
19163 @item set monitor-warnings
19164 @kindex set monitor-warnings@r{, MIPS remote}
19165 Enable or disable monitor warnings about hardware breakpoints. This
19166 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19167 display warning messages whose codes are returned by the @code{lsi}
19168 PMON monitor for breakpoint commands.
19170 @item show monitor-warnings
19171 @kindex show monitor-warnings@r{, MIPS remote}
19172 Show the current setting of printing monitor warnings.
19174 @item pmon @var{command}
19175 @kindex pmon@r{, MIPS remote}
19176 @cindex send PMON command
19177 This command allows sending an arbitrary @var{command} string to the
19178 monitor. The monitor must be in debug mode for this to work.
19181 @node OpenRISC 1000
19182 @subsection OpenRISC 1000
19183 @cindex OpenRISC 1000
19185 @cindex or1k boards
19186 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19187 about platform and commands.
19191 @kindex target jtag
19192 @item target jtag jtag://@var{host}:@var{port}
19194 Connects to remote JTAG server.
19195 JTAG remote server can be either an or1ksim or JTAG server,
19196 connected via parallel port to the board.
19198 Example: @code{target jtag jtag://localhost:9999}
19201 @item or1ksim @var{command}
19202 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19203 Simulator, proprietary commands can be executed.
19205 @kindex info or1k spr
19206 @item info or1k spr
19207 Displays spr groups.
19209 @item info or1k spr @var{group}
19210 @itemx info or1k spr @var{groupno}
19211 Displays register names in selected group.
19213 @item info or1k spr @var{group} @var{register}
19214 @itemx info or1k spr @var{register}
19215 @itemx info or1k spr @var{groupno} @var{registerno}
19216 @itemx info or1k spr @var{registerno}
19217 Shows information about specified spr register.
19220 @item spr @var{group} @var{register} @var{value}
19221 @itemx spr @var{register @var{value}}
19222 @itemx spr @var{groupno} @var{registerno @var{value}}
19223 @itemx spr @var{registerno @var{value}}
19224 Writes @var{value} to specified spr register.
19227 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19228 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19229 program execution and is thus much faster. Hardware breakpoints/watchpoint
19230 triggers can be set using:
19233 Load effective address/data
19235 Store effective address/data
19237 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19242 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19243 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19245 @code{htrace} commands:
19246 @cindex OpenRISC 1000 htrace
19249 @item hwatch @var{conditional}
19250 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19251 or Data. For example:
19253 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19255 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19259 Display information about current HW trace configuration.
19261 @item htrace trigger @var{conditional}
19262 Set starting criteria for HW trace.
19264 @item htrace qualifier @var{conditional}
19265 Set acquisition qualifier for HW trace.
19267 @item htrace stop @var{conditional}
19268 Set HW trace stopping criteria.
19270 @item htrace record [@var{data}]*
19271 Selects the data to be recorded, when qualifier is met and HW trace was
19274 @item htrace enable
19275 @itemx htrace disable
19276 Enables/disables the HW trace.
19278 @item htrace rewind [@var{filename}]
19279 Clears currently recorded trace data.
19281 If filename is specified, new trace file is made and any newly collected data
19282 will be written there.
19284 @item htrace print [@var{start} [@var{len}]]
19285 Prints trace buffer, using current record configuration.
19287 @item htrace mode continuous
19288 Set continuous trace mode.
19290 @item htrace mode suspend
19291 Set suspend trace mode.
19295 @node PowerPC Embedded
19296 @subsection PowerPC Embedded
19298 @cindex DVC register
19299 @value{GDBN} supports using the DVC (Data Value Compare) register to
19300 implement in hardware simple hardware watchpoint conditions of the form:
19303 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19304 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19307 The DVC register will be automatically used when @value{GDBN} detects
19308 such pattern in a condition expression, and the created watchpoint uses one
19309 debug register (either the @code{exact-watchpoints} option is on and the
19310 variable is scalar, or the variable has a length of one byte). This feature
19311 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19314 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19315 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19316 in which case watchpoints using only one debug register are created when
19317 watching variables of scalar types.
19319 You can create an artificial array to watch an arbitrary memory
19320 region using one of the following commands (@pxref{Expressions}):
19323 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19324 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19327 PowerPC embedded processors support masked watchpoints. See the discussion
19328 about the @code{mask} argument in @ref{Set Watchpoints}.
19330 @cindex ranged breakpoint
19331 PowerPC embedded processors support hardware accelerated
19332 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19333 the inferior whenever it executes an instruction at any address within
19334 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19335 use the @code{break-range} command.
19337 @value{GDBN} provides the following PowerPC-specific commands:
19340 @kindex break-range
19341 @item break-range @var{start-location}, @var{end-location}
19342 Set a breakpoint for an address range.
19343 @var{start-location} and @var{end-location} can specify a function name,
19344 a line number, an offset of lines from the current line or from the start
19345 location, or an address of an instruction (see @ref{Specify Location},
19346 for a list of all the possible ways to specify a @var{location}.)
19347 The breakpoint will stop execution of the inferior whenever it
19348 executes an instruction at any address within the specified range,
19349 (including @var{start-location} and @var{end-location}.)
19351 @kindex set powerpc
19352 @item set powerpc soft-float
19353 @itemx show powerpc soft-float
19354 Force @value{GDBN} to use (or not use) a software floating point calling
19355 convention. By default, @value{GDBN} selects the calling convention based
19356 on the selected architecture and the provided executable file.
19358 @item set powerpc vector-abi
19359 @itemx show powerpc vector-abi
19360 Force @value{GDBN} to use the specified calling convention for vector
19361 arguments and return values. The valid options are @samp{auto};
19362 @samp{generic}, to avoid vector registers even if they are present;
19363 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19364 registers. By default, @value{GDBN} selects the calling convention
19365 based on the selected architecture and the provided executable file.
19367 @item set powerpc exact-watchpoints
19368 @itemx show powerpc exact-watchpoints
19369 Allow @value{GDBN} to use only one debug register when watching a variable
19370 of scalar type, thus assuming that the variable is accessed through the
19371 address of its first byte.
19373 @kindex target dink32
19374 @item target dink32 @var{dev}
19375 DINK32 ROM monitor.
19377 @kindex target ppcbug
19378 @item target ppcbug @var{dev}
19379 @kindex target ppcbug1
19380 @item target ppcbug1 @var{dev}
19381 PPCBUG ROM monitor for PowerPC.
19384 @item target sds @var{dev}
19385 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19388 @cindex SDS protocol
19389 The following commands specific to the SDS protocol are supported
19393 @item set sdstimeout @var{nsec}
19394 @kindex set sdstimeout
19395 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19396 default is 2 seconds.
19398 @item show sdstimeout
19399 @kindex show sdstimeout
19400 Show the current value of the SDS timeout.
19402 @item sds @var{command}
19403 @kindex sds@r{, a command}
19404 Send the specified @var{command} string to the SDS monitor.
19409 @subsection HP PA Embedded
19413 @kindex target op50n
19414 @item target op50n @var{dev}
19415 OP50N monitor, running on an OKI HPPA board.
19417 @kindex target w89k
19418 @item target w89k @var{dev}
19419 W89K monitor, running on a Winbond HPPA board.
19424 @subsection Tsqware Sparclet
19428 @value{GDBN} enables developers to debug tasks running on
19429 Sparclet targets from a Unix host.
19430 @value{GDBN} uses code that runs on
19431 both the Unix host and on the Sparclet target. The program
19432 @code{@value{GDBP}} is installed and executed on the Unix host.
19435 @item remotetimeout @var{args}
19436 @kindex remotetimeout
19437 @value{GDBN} supports the option @code{remotetimeout}.
19438 This option is set by the user, and @var{args} represents the number of
19439 seconds @value{GDBN} waits for responses.
19442 @cindex compiling, on Sparclet
19443 When compiling for debugging, include the options @samp{-g} to get debug
19444 information and @samp{-Ttext} to relocate the program to where you wish to
19445 load it on the target. You may also want to add the options @samp{-n} or
19446 @samp{-N} in order to reduce the size of the sections. Example:
19449 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19452 You can use @code{objdump} to verify that the addresses are what you intended:
19455 sparclet-aout-objdump --headers --syms prog
19458 @cindex running, on Sparclet
19460 your Unix execution search path to find @value{GDBN}, you are ready to
19461 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19462 (or @code{sparclet-aout-gdb}, depending on your installation).
19464 @value{GDBN} comes up showing the prompt:
19471 * Sparclet File:: Setting the file to debug
19472 * Sparclet Connection:: Connecting to Sparclet
19473 * Sparclet Download:: Sparclet download
19474 * Sparclet Execution:: Running and debugging
19477 @node Sparclet File
19478 @subsubsection Setting File to Debug
19480 The @value{GDBN} command @code{file} lets you choose with program to debug.
19483 (gdbslet) file prog
19487 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19488 @value{GDBN} locates
19489 the file by searching the directories listed in the command search
19491 If the file was compiled with debug information (option @samp{-g}), source
19492 files will be searched as well.
19493 @value{GDBN} locates
19494 the source files by searching the directories listed in the directory search
19495 path (@pxref{Environment, ,Your Program's Environment}).
19497 to find a file, it displays a message such as:
19500 prog: No such file or directory.
19503 When this happens, add the appropriate directories to the search paths with
19504 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19505 @code{target} command again.
19507 @node Sparclet Connection
19508 @subsubsection Connecting to Sparclet
19510 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19511 To connect to a target on serial port ``@code{ttya}'', type:
19514 (gdbslet) target sparclet /dev/ttya
19515 Remote target sparclet connected to /dev/ttya
19516 main () at ../prog.c:3
19520 @value{GDBN} displays messages like these:
19526 @node Sparclet Download
19527 @subsubsection Sparclet Download
19529 @cindex download to Sparclet
19530 Once connected to the Sparclet target,
19531 you can use the @value{GDBN}
19532 @code{load} command to download the file from the host to the target.
19533 The file name and load offset should be given as arguments to the @code{load}
19535 Since the file format is aout, the program must be loaded to the starting
19536 address. You can use @code{objdump} to find out what this value is. The load
19537 offset is an offset which is added to the VMA (virtual memory address)
19538 of each of the file's sections.
19539 For instance, if the program
19540 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19541 and bss at 0x12010170, in @value{GDBN}, type:
19544 (gdbslet) load prog 0x12010000
19545 Loading section .text, size 0xdb0 vma 0x12010000
19548 If the code is loaded at a different address then what the program was linked
19549 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19550 to tell @value{GDBN} where to map the symbol table.
19552 @node Sparclet Execution
19553 @subsubsection Running and Debugging
19555 @cindex running and debugging Sparclet programs
19556 You can now begin debugging the task using @value{GDBN}'s execution control
19557 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19558 manual for the list of commands.
19562 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19564 Starting program: prog
19565 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19566 3 char *symarg = 0;
19568 4 char *execarg = "hello!";
19573 @subsection Fujitsu Sparclite
19577 @kindex target sparclite
19578 @item target sparclite @var{dev}
19579 Fujitsu sparclite boards, used only for the purpose of loading.
19580 You must use an additional command to debug the program.
19581 For example: target remote @var{dev} using @value{GDBN} standard
19587 @subsection Zilog Z8000
19590 @cindex simulator, Z8000
19591 @cindex Zilog Z8000 simulator
19593 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19596 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19597 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19598 segmented variant). The simulator recognizes which architecture is
19599 appropriate by inspecting the object code.
19602 @item target sim @var{args}
19604 @kindex target sim@r{, with Z8000}
19605 Debug programs on a simulated CPU. If the simulator supports setup
19606 options, specify them via @var{args}.
19610 After specifying this target, you can debug programs for the simulated
19611 CPU in the same style as programs for your host computer; use the
19612 @code{file} command to load a new program image, the @code{run} command
19613 to run your program, and so on.
19615 As well as making available all the usual machine registers
19616 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19617 additional items of information as specially named registers:
19622 Counts clock-ticks in the simulator.
19625 Counts instructions run in the simulator.
19628 Execution time in 60ths of a second.
19632 You can refer to these values in @value{GDBN} expressions with the usual
19633 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19634 conditional breakpoint that suspends only after at least 5000
19635 simulated clock ticks.
19638 @subsection Atmel AVR
19641 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19642 following AVR-specific commands:
19645 @item info io_registers
19646 @kindex info io_registers@r{, AVR}
19647 @cindex I/O registers (Atmel AVR)
19648 This command displays information about the AVR I/O registers. For
19649 each register, @value{GDBN} prints its number and value.
19656 When configured for debugging CRIS, @value{GDBN} provides the
19657 following CRIS-specific commands:
19660 @item set cris-version @var{ver}
19661 @cindex CRIS version
19662 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19663 The CRIS version affects register names and sizes. This command is useful in
19664 case autodetection of the CRIS version fails.
19666 @item show cris-version
19667 Show the current CRIS version.
19669 @item set cris-dwarf2-cfi
19670 @cindex DWARF-2 CFI and CRIS
19671 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19672 Change to @samp{off} when using @code{gcc-cris} whose version is below
19675 @item show cris-dwarf2-cfi
19676 Show the current state of using DWARF-2 CFI.
19678 @item set cris-mode @var{mode}
19680 Set the current CRIS mode to @var{mode}. It should only be changed when
19681 debugging in guru mode, in which case it should be set to
19682 @samp{guru} (the default is @samp{normal}).
19684 @item show cris-mode
19685 Show the current CRIS mode.
19689 @subsection Renesas Super-H
19692 For the Renesas Super-H processor, @value{GDBN} provides these
19697 @kindex regs@r{, Super-H}
19698 Show the values of all Super-H registers.
19700 @item set sh calling-convention @var{convention}
19701 @kindex set sh calling-convention
19702 Set the calling-convention used when calling functions from @value{GDBN}.
19703 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19704 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19705 convention. If the DWARF-2 information of the called function specifies
19706 that the function follows the Renesas calling convention, the function
19707 is called using the Renesas calling convention. If the calling convention
19708 is set to @samp{renesas}, the Renesas calling convention is always used,
19709 regardless of the DWARF-2 information. This can be used to override the
19710 default of @samp{gcc} if debug information is missing, or the compiler
19711 does not emit the DWARF-2 calling convention entry for a function.
19713 @item show sh calling-convention
19714 @kindex show sh calling-convention
19715 Show the current calling convention setting.
19720 @node Architectures
19721 @section Architectures
19723 This section describes characteristics of architectures that affect
19724 all uses of @value{GDBN} with the architecture, both native and cross.
19731 * HPPA:: HP PA architecture
19732 * SPU:: Cell Broadband Engine SPU architecture
19737 @subsection x86 Architecture-specific Issues
19740 @item set struct-convention @var{mode}
19741 @kindex set struct-convention
19742 @cindex struct return convention
19743 @cindex struct/union returned in registers
19744 Set the convention used by the inferior to return @code{struct}s and
19745 @code{union}s from functions to @var{mode}. Possible values of
19746 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19747 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19748 are returned on the stack, while @code{"reg"} means that a
19749 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19750 be returned in a register.
19752 @item show struct-convention
19753 @kindex show struct-convention
19754 Show the current setting of the convention to return @code{struct}s
19763 @kindex set rstack_high_address
19764 @cindex AMD 29K register stack
19765 @cindex register stack, AMD29K
19766 @item set rstack_high_address @var{address}
19767 On AMD 29000 family processors, registers are saved in a separate
19768 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19769 extent of this stack. Normally, @value{GDBN} just assumes that the
19770 stack is ``large enough''. This may result in @value{GDBN} referencing
19771 memory locations that do not exist. If necessary, you can get around
19772 this problem by specifying the ending address of the register stack with
19773 the @code{set rstack_high_address} command. The argument should be an
19774 address, which you probably want to precede with @samp{0x} to specify in
19777 @kindex show rstack_high_address
19778 @item show rstack_high_address
19779 Display the current limit of the register stack, on AMD 29000 family
19787 See the following section.
19792 @cindex stack on Alpha
19793 @cindex stack on MIPS
19794 @cindex Alpha stack
19796 Alpha- and MIPS-based computers use an unusual stack frame, which
19797 sometimes requires @value{GDBN} to search backward in the object code to
19798 find the beginning of a function.
19800 @cindex response time, MIPS debugging
19801 To improve response time (especially for embedded applications, where
19802 @value{GDBN} may be restricted to a slow serial line for this search)
19803 you may want to limit the size of this search, using one of these
19807 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19808 @item set heuristic-fence-post @var{limit}
19809 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19810 search for the beginning of a function. A value of @var{0} (the
19811 default) means there is no limit. However, except for @var{0}, the
19812 larger the limit the more bytes @code{heuristic-fence-post} must search
19813 and therefore the longer it takes to run. You should only need to use
19814 this command when debugging a stripped executable.
19816 @item show heuristic-fence-post
19817 Display the current limit.
19821 These commands are available @emph{only} when @value{GDBN} is configured
19822 for debugging programs on Alpha or MIPS processors.
19824 Several MIPS-specific commands are available when debugging MIPS
19828 @item set mips abi @var{arg}
19829 @kindex set mips abi
19830 @cindex set ABI for MIPS
19831 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19832 values of @var{arg} are:
19836 The default ABI associated with the current binary (this is the
19846 @item show mips abi
19847 @kindex show mips abi
19848 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19851 @itemx show mipsfpu
19852 @xref{MIPS Embedded, set mipsfpu}.
19854 @item set mips mask-address @var{arg}
19855 @kindex set mips mask-address
19856 @cindex MIPS addresses, masking
19857 This command determines whether the most-significant 32 bits of 64-bit
19858 MIPS addresses are masked off. The argument @var{arg} can be
19859 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19860 setting, which lets @value{GDBN} determine the correct value.
19862 @item show mips mask-address
19863 @kindex show mips mask-address
19864 Show whether the upper 32 bits of MIPS addresses are masked off or
19867 @item set remote-mips64-transfers-32bit-regs
19868 @kindex set remote-mips64-transfers-32bit-regs
19869 This command controls compatibility with 64-bit MIPS targets that
19870 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19871 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19872 and 64 bits for other registers, set this option to @samp{on}.
19874 @item show remote-mips64-transfers-32bit-regs
19875 @kindex show remote-mips64-transfers-32bit-regs
19876 Show the current setting of compatibility with older MIPS 64 targets.
19878 @item set debug mips
19879 @kindex set debug mips
19880 This command turns on and off debugging messages for the MIPS-specific
19881 target code in @value{GDBN}.
19883 @item show debug mips
19884 @kindex show debug mips
19885 Show the current setting of MIPS debugging messages.
19891 @cindex HPPA support
19893 When @value{GDBN} is debugging the HP PA architecture, it provides the
19894 following special commands:
19897 @item set debug hppa
19898 @kindex set debug hppa
19899 This command determines whether HPPA architecture-specific debugging
19900 messages are to be displayed.
19902 @item show debug hppa
19903 Show whether HPPA debugging messages are displayed.
19905 @item maint print unwind @var{address}
19906 @kindex maint print unwind@r{, HPPA}
19907 This command displays the contents of the unwind table entry at the
19908 given @var{address}.
19914 @subsection Cell Broadband Engine SPU architecture
19915 @cindex Cell Broadband Engine
19918 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19919 it provides the following special commands:
19922 @item info spu event
19924 Display SPU event facility status. Shows current event mask
19925 and pending event status.
19927 @item info spu signal
19928 Display SPU signal notification facility status. Shows pending
19929 signal-control word and signal notification mode of both signal
19930 notification channels.
19932 @item info spu mailbox
19933 Display SPU mailbox facility status. Shows all pending entries,
19934 in order of processing, in each of the SPU Write Outbound,
19935 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19938 Display MFC DMA status. Shows all pending commands in the MFC
19939 DMA queue. For each entry, opcode, tag, class IDs, effective
19940 and local store addresses and transfer size are shown.
19942 @item info spu proxydma
19943 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19944 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19945 and local store addresses and transfer size are shown.
19949 When @value{GDBN} is debugging a combined PowerPC/SPU application
19950 on the Cell Broadband Engine, it provides in addition the following
19954 @item set spu stop-on-load @var{arg}
19956 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19957 will give control to the user when a new SPE thread enters its @code{main}
19958 function. The default is @code{off}.
19960 @item show spu stop-on-load
19962 Show whether to stop for new SPE threads.
19964 @item set spu auto-flush-cache @var{arg}
19965 Set whether to automatically flush the software-managed cache. When set to
19966 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19967 cache to be flushed whenever SPE execution stops. This provides a consistent
19968 view of PowerPC memory that is accessed via the cache. If an application
19969 does not use the software-managed cache, this option has no effect.
19971 @item show spu auto-flush-cache
19972 Show whether to automatically flush the software-managed cache.
19977 @subsection PowerPC
19978 @cindex PowerPC architecture
19980 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19981 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19982 numbers stored in the floating point registers. These values must be stored
19983 in two consecutive registers, always starting at an even register like
19984 @code{f0} or @code{f2}.
19986 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19987 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19988 @code{f2} and @code{f3} for @code{$dl1} and so on.
19990 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19991 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19994 @node Controlling GDB
19995 @chapter Controlling @value{GDBN}
19997 You can alter the way @value{GDBN} interacts with you by using the
19998 @code{set} command. For commands controlling how @value{GDBN} displays
19999 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20004 * Editing:: Command editing
20005 * Command History:: Command history
20006 * Screen Size:: Screen size
20007 * Numbers:: Numbers
20008 * ABI:: Configuring the current ABI
20009 * Messages/Warnings:: Optional warnings and messages
20010 * Debugging Output:: Optional messages about internal happenings
20011 * Other Misc Settings:: Other Miscellaneous Settings
20019 @value{GDBN} indicates its readiness to read a command by printing a string
20020 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20021 can change the prompt string with the @code{set prompt} command. For
20022 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20023 the prompt in one of the @value{GDBN} sessions so that you can always tell
20024 which one you are talking to.
20026 @emph{Note:} @code{set prompt} does not add a space for you after the
20027 prompt you set. This allows you to set a prompt which ends in a space
20028 or a prompt that does not.
20032 @item set prompt @var{newprompt}
20033 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20035 @kindex show prompt
20037 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20040 Versions of @value{GDBN} that ship with Python scripting enabled have
20041 prompt extensions. The commands for interacting with these extensions
20045 @kindex set extended-prompt
20046 @item set extended-prompt @var{prompt}
20047 Set an extended prompt that allows for substitutions.
20048 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20049 substitution. Any escape sequences specified as part of the prompt
20050 string are replaced with the corresponding strings each time the prompt
20056 set extended-prompt Current working directory: \w (gdb)
20059 Note that when an extended-prompt is set, it takes control of the
20060 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20062 @kindex show extended-prompt
20063 @item show extended-prompt
20064 Prints the extended prompt. Any escape sequences specified as part of
20065 the prompt string with @code{set extended-prompt}, are replaced with the
20066 corresponding strings each time the prompt is displayed.
20070 @section Command Editing
20072 @cindex command line editing
20074 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20075 @sc{gnu} library provides consistent behavior for programs which provide a
20076 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20077 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20078 substitution, and a storage and recall of command history across
20079 debugging sessions.
20081 You may control the behavior of command line editing in @value{GDBN} with the
20082 command @code{set}.
20085 @kindex set editing
20088 @itemx set editing on
20089 Enable command line editing (enabled by default).
20091 @item set editing off
20092 Disable command line editing.
20094 @kindex show editing
20096 Show whether command line editing is enabled.
20099 @ifset SYSTEM_READLINE
20100 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20102 @ifclear SYSTEM_READLINE
20103 @xref{Command Line Editing},
20105 for more details about the Readline
20106 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20107 encouraged to read that chapter.
20109 @node Command History
20110 @section Command History
20111 @cindex command history
20113 @value{GDBN} can keep track of the commands you type during your
20114 debugging sessions, so that you can be certain of precisely what
20115 happened. Use these commands to manage the @value{GDBN} command
20118 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20119 package, to provide the history facility.
20120 @ifset SYSTEM_READLINE
20121 @xref{Using History Interactively, , , history, GNU History Library},
20123 @ifclear SYSTEM_READLINE
20124 @xref{Using History Interactively},
20126 for the detailed description of the History library.
20128 To issue a command to @value{GDBN} without affecting certain aspects of
20129 the state which is seen by users, prefix it with @samp{server }
20130 (@pxref{Server Prefix}). This
20131 means that this command will not affect the command history, nor will it
20132 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20133 pressed on a line by itself.
20135 @cindex @code{server}, command prefix
20136 The server prefix does not affect the recording of values into the value
20137 history; to print a value without recording it into the value history,
20138 use the @code{output} command instead of the @code{print} command.
20140 Here is the description of @value{GDBN} commands related to command
20144 @cindex history substitution
20145 @cindex history file
20146 @kindex set history filename
20147 @cindex @env{GDBHISTFILE}, environment variable
20148 @item set history filename @var{fname}
20149 Set the name of the @value{GDBN} command history file to @var{fname}.
20150 This is the file where @value{GDBN} reads an initial command history
20151 list, and where it writes the command history from this session when it
20152 exits. You can access this list through history expansion or through
20153 the history command editing characters listed below. This file defaults
20154 to the value of the environment variable @code{GDBHISTFILE}, or to
20155 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20158 @cindex save command history
20159 @kindex set history save
20160 @item set history save
20161 @itemx set history save on
20162 Record command history in a file, whose name may be specified with the
20163 @code{set history filename} command. By default, this option is disabled.
20165 @item set history save off
20166 Stop recording command history in a file.
20168 @cindex history size
20169 @kindex set history size
20170 @cindex @env{HISTSIZE}, environment variable
20171 @item set history size @var{size}
20172 Set the number of commands which @value{GDBN} keeps in its history list.
20173 This defaults to the value of the environment variable
20174 @code{HISTSIZE}, or to 256 if this variable is not set.
20177 History expansion assigns special meaning to the character @kbd{!}.
20178 @ifset SYSTEM_READLINE
20179 @xref{Event Designators, , , history, GNU History Library},
20181 @ifclear SYSTEM_READLINE
20182 @xref{Event Designators},
20186 @cindex history expansion, turn on/off
20187 Since @kbd{!} is also the logical not operator in C, history expansion
20188 is off by default. If you decide to enable history expansion with the
20189 @code{set history expansion on} command, you may sometimes need to
20190 follow @kbd{!} (when it is used as logical not, in an expression) with
20191 a space or a tab to prevent it from being expanded. The readline
20192 history facilities do not attempt substitution on the strings
20193 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20195 The commands to control history expansion are:
20198 @item set history expansion on
20199 @itemx set history expansion
20200 @kindex set history expansion
20201 Enable history expansion. History expansion is off by default.
20203 @item set history expansion off
20204 Disable history expansion.
20207 @kindex show history
20209 @itemx show history filename
20210 @itemx show history save
20211 @itemx show history size
20212 @itemx show history expansion
20213 These commands display the state of the @value{GDBN} history parameters.
20214 @code{show history} by itself displays all four states.
20219 @kindex show commands
20220 @cindex show last commands
20221 @cindex display command history
20222 @item show commands
20223 Display the last ten commands in the command history.
20225 @item show commands @var{n}
20226 Print ten commands centered on command number @var{n}.
20228 @item show commands +
20229 Print ten commands just after the commands last printed.
20233 @section Screen Size
20234 @cindex size of screen
20235 @cindex pauses in output
20237 Certain commands to @value{GDBN} may produce large amounts of
20238 information output to the screen. To help you read all of it,
20239 @value{GDBN} pauses and asks you for input at the end of each page of
20240 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20241 to discard the remaining output. Also, the screen width setting
20242 determines when to wrap lines of output. Depending on what is being
20243 printed, @value{GDBN} tries to break the line at a readable place,
20244 rather than simply letting it overflow onto the following line.
20246 Normally @value{GDBN} knows the size of the screen from the terminal
20247 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20248 together with the value of the @code{TERM} environment variable and the
20249 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20250 you can override it with the @code{set height} and @code{set
20257 @kindex show height
20258 @item set height @var{lpp}
20260 @itemx set width @var{cpl}
20262 These @code{set} commands specify a screen height of @var{lpp} lines and
20263 a screen width of @var{cpl} characters. The associated @code{show}
20264 commands display the current settings.
20266 If you specify a height of zero lines, @value{GDBN} does not pause during
20267 output no matter how long the output is. This is useful if output is to a
20268 file or to an editor buffer.
20270 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20271 from wrapping its output.
20273 @item set pagination on
20274 @itemx set pagination off
20275 @kindex set pagination
20276 Turn the output pagination on or off; the default is on. Turning
20277 pagination off is the alternative to @code{set height 0}. Note that
20278 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20279 Options, -batch}) also automatically disables pagination.
20281 @item show pagination
20282 @kindex show pagination
20283 Show the current pagination mode.
20288 @cindex number representation
20289 @cindex entering numbers
20291 You can always enter numbers in octal, decimal, or hexadecimal in
20292 @value{GDBN} by the usual conventions: octal numbers begin with
20293 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20294 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20295 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20296 10; likewise, the default display for numbers---when no particular
20297 format is specified---is base 10. You can change the default base for
20298 both input and output with the commands described below.
20301 @kindex set input-radix
20302 @item set input-radix @var{base}
20303 Set the default base for numeric input. Supported choices
20304 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20305 specified either unambiguously or using the current input radix; for
20309 set input-radix 012
20310 set input-radix 10.
20311 set input-radix 0xa
20315 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20316 leaves the input radix unchanged, no matter what it was, since
20317 @samp{10}, being without any leading or trailing signs of its base, is
20318 interpreted in the current radix. Thus, if the current radix is 16,
20319 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20322 @kindex set output-radix
20323 @item set output-radix @var{base}
20324 Set the default base for numeric display. Supported choices
20325 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20326 specified either unambiguously or using the current input radix.
20328 @kindex show input-radix
20329 @item show input-radix
20330 Display the current default base for numeric input.
20332 @kindex show output-radix
20333 @item show output-radix
20334 Display the current default base for numeric display.
20336 @item set radix @r{[}@var{base}@r{]}
20340 These commands set and show the default base for both input and output
20341 of numbers. @code{set radix} sets the radix of input and output to
20342 the same base; without an argument, it resets the radix back to its
20343 default value of 10.
20348 @section Configuring the Current ABI
20350 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20351 application automatically. However, sometimes you need to override its
20352 conclusions. Use these commands to manage @value{GDBN}'s view of the
20359 One @value{GDBN} configuration can debug binaries for multiple operating
20360 system targets, either via remote debugging or native emulation.
20361 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20362 but you can override its conclusion using the @code{set osabi} command.
20363 One example where this is useful is in debugging of binaries which use
20364 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20365 not have the same identifying marks that the standard C library for your
20370 Show the OS ABI currently in use.
20373 With no argument, show the list of registered available OS ABI's.
20375 @item set osabi @var{abi}
20376 Set the current OS ABI to @var{abi}.
20379 @cindex float promotion
20381 Generally, the way that an argument of type @code{float} is passed to a
20382 function depends on whether the function is prototyped. For a prototyped
20383 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20384 according to the architecture's convention for @code{float}. For unprototyped
20385 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20386 @code{double} and then passed.
20388 Unfortunately, some forms of debug information do not reliably indicate whether
20389 a function is prototyped. If @value{GDBN} calls a function that is not marked
20390 as prototyped, it consults @kbd{set coerce-float-to-double}.
20393 @kindex set coerce-float-to-double
20394 @item set coerce-float-to-double
20395 @itemx set coerce-float-to-double on
20396 Arguments of type @code{float} will be promoted to @code{double} when passed
20397 to an unprototyped function. This is the default setting.
20399 @item set coerce-float-to-double off
20400 Arguments of type @code{float} will be passed directly to unprototyped
20403 @kindex show coerce-float-to-double
20404 @item show coerce-float-to-double
20405 Show the current setting of promoting @code{float} to @code{double}.
20409 @kindex show cp-abi
20410 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20411 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20412 used to build your application. @value{GDBN} only fully supports
20413 programs with a single C@t{++} ABI; if your program contains code using
20414 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20415 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20416 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20417 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20418 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20419 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20424 Show the C@t{++} ABI currently in use.
20427 With no argument, show the list of supported C@t{++} ABI's.
20429 @item set cp-abi @var{abi}
20430 @itemx set cp-abi auto
20431 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20434 @node Messages/Warnings
20435 @section Optional Warnings and Messages
20437 @cindex verbose operation
20438 @cindex optional warnings
20439 By default, @value{GDBN} is silent about its inner workings. If you are
20440 running on a slow machine, you may want to use the @code{set verbose}
20441 command. This makes @value{GDBN} tell you when it does a lengthy
20442 internal operation, so you will not think it has crashed.
20444 Currently, the messages controlled by @code{set verbose} are those
20445 which announce that the symbol table for a source file is being read;
20446 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20449 @kindex set verbose
20450 @item set verbose on
20451 Enables @value{GDBN} output of certain informational messages.
20453 @item set verbose off
20454 Disables @value{GDBN} output of certain informational messages.
20456 @kindex show verbose
20458 Displays whether @code{set verbose} is on or off.
20461 By default, if @value{GDBN} encounters bugs in the symbol table of an
20462 object file, it is silent; but if you are debugging a compiler, you may
20463 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20468 @kindex set complaints
20469 @item set complaints @var{limit}
20470 Permits @value{GDBN} to output @var{limit} complaints about each type of
20471 unusual symbols before becoming silent about the problem. Set
20472 @var{limit} to zero to suppress all complaints; set it to a large number
20473 to prevent complaints from being suppressed.
20475 @kindex show complaints
20476 @item show complaints
20477 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20481 @anchor{confirmation requests}
20482 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20483 lot of stupid questions to confirm certain commands. For example, if
20484 you try to run a program which is already running:
20488 The program being debugged has been started already.
20489 Start it from the beginning? (y or n)
20492 If you are willing to unflinchingly face the consequences of your own
20493 commands, you can disable this ``feature'':
20497 @kindex set confirm
20499 @cindex confirmation
20500 @cindex stupid questions
20501 @item set confirm off
20502 Disables confirmation requests. Note that running @value{GDBN} with
20503 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20504 automatically disables confirmation requests.
20506 @item set confirm on
20507 Enables confirmation requests (the default).
20509 @kindex show confirm
20511 Displays state of confirmation requests.
20515 @cindex command tracing
20516 If you need to debug user-defined commands or sourced files you may find it
20517 useful to enable @dfn{command tracing}. In this mode each command will be
20518 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20519 quantity denoting the call depth of each command.
20522 @kindex set trace-commands
20523 @cindex command scripts, debugging
20524 @item set trace-commands on
20525 Enable command tracing.
20526 @item set trace-commands off
20527 Disable command tracing.
20528 @item show trace-commands
20529 Display the current state of command tracing.
20532 @node Debugging Output
20533 @section Optional Messages about Internal Happenings
20534 @cindex optional debugging messages
20536 @value{GDBN} has commands that enable optional debugging messages from
20537 various @value{GDBN} subsystems; normally these commands are of
20538 interest to @value{GDBN} maintainers, or when reporting a bug. This
20539 section documents those commands.
20542 @kindex set exec-done-display
20543 @item set exec-done-display
20544 Turns on or off the notification of asynchronous commands'
20545 completion. When on, @value{GDBN} will print a message when an
20546 asynchronous command finishes its execution. The default is off.
20547 @kindex show exec-done-display
20548 @item show exec-done-display
20549 Displays the current setting of asynchronous command completion
20552 @cindex gdbarch debugging info
20553 @cindex architecture debugging info
20554 @item set debug arch
20555 Turns on or off display of gdbarch debugging info. The default is off
20557 @item show debug arch
20558 Displays the current state of displaying gdbarch debugging info.
20559 @item set debug aix-thread
20560 @cindex AIX threads
20561 Display debugging messages about inner workings of the AIX thread
20563 @item show debug aix-thread
20564 Show the current state of AIX thread debugging info display.
20565 @item set debug check-physname
20567 Check the results of the ``physname'' computation. When reading DWARF
20568 debugging information for C@t{++}, @value{GDBN} attempts to compute
20569 each entity's name. @value{GDBN} can do this computation in two
20570 different ways, depending on exactly what information is present.
20571 When enabled, this setting causes @value{GDBN} to compute the names
20572 both ways and display any discrepancies.
20573 @item show debug check-physname
20574 Show the current state of ``physname'' checking.
20575 @item set debug dwarf2-die
20576 @cindex DWARF2 DIEs
20577 Dump DWARF2 DIEs after they are read in.
20578 The value is the number of nesting levels to print.
20579 A value of zero turns off the display.
20580 @item show debug dwarf2-die
20581 Show the current state of DWARF2 DIE debugging.
20582 @item set debug displaced
20583 @cindex displaced stepping debugging info
20584 Turns on or off display of @value{GDBN} debugging info for the
20585 displaced stepping support. The default is off.
20586 @item show debug displaced
20587 Displays the current state of displaying @value{GDBN} debugging info
20588 related to displaced stepping.
20589 @item set debug event
20590 @cindex event debugging info
20591 Turns on or off display of @value{GDBN} event debugging info. The
20593 @item show debug event
20594 Displays the current state of displaying @value{GDBN} event debugging
20596 @item set debug expression
20597 @cindex expression debugging info
20598 Turns on or off display of debugging info about @value{GDBN}
20599 expression parsing. The default is off.
20600 @item show debug expression
20601 Displays the current state of displaying debugging info about
20602 @value{GDBN} expression parsing.
20603 @item set debug frame
20604 @cindex frame debugging info
20605 Turns on or off display of @value{GDBN} frame debugging info. The
20607 @item show debug frame
20608 Displays the current state of displaying @value{GDBN} frame debugging
20610 @item set debug gnu-nat
20611 @cindex @sc{gnu}/Hurd debug messages
20612 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20613 @item show debug gnu-nat
20614 Show the current state of @sc{gnu}/Hurd debugging messages.
20615 @item set debug infrun
20616 @cindex inferior debugging info
20617 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20618 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20619 for implementing operations such as single-stepping the inferior.
20620 @item show debug infrun
20621 Displays the current state of @value{GDBN} inferior debugging.
20622 @item set debug jit
20623 @cindex just-in-time compilation, debugging messages
20624 Turns on or off debugging messages from JIT debug support.
20625 @item show debug jit
20626 Displays the current state of @value{GDBN} JIT debugging.
20627 @item set debug lin-lwp
20628 @cindex @sc{gnu}/Linux LWP debug messages
20629 @cindex Linux lightweight processes
20630 Turns on or off debugging messages from the Linux LWP debug support.
20631 @item show debug lin-lwp
20632 Show the current state of Linux LWP debugging messages.
20633 @item set debug observer
20634 @cindex observer debugging info
20635 Turns on or off display of @value{GDBN} observer debugging. This
20636 includes info such as the notification of observable events.
20637 @item show debug observer
20638 Displays the current state of observer debugging.
20639 @item set debug overload
20640 @cindex C@t{++} overload debugging info
20641 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20642 info. This includes info such as ranking of functions, etc. The default
20644 @item show debug overload
20645 Displays the current state of displaying @value{GDBN} C@t{++} overload
20647 @cindex expression parser, debugging info
20648 @cindex debug expression parser
20649 @item set debug parser
20650 Turns on or off the display of expression parser debugging output.
20651 Internally, this sets the @code{yydebug} variable in the expression
20652 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20653 details. The default is off.
20654 @item show debug parser
20655 Show the current state of expression parser debugging.
20656 @cindex packets, reporting on stdout
20657 @cindex serial connections, debugging
20658 @cindex debug remote protocol
20659 @cindex remote protocol debugging
20660 @cindex display remote packets
20661 @item set debug remote
20662 Turns on or off display of reports on all packets sent back and forth across
20663 the serial line to the remote machine. The info is printed on the
20664 @value{GDBN} standard output stream. The default is off.
20665 @item show debug remote
20666 Displays the state of display of remote packets.
20667 @item set debug serial
20668 Turns on or off display of @value{GDBN} serial debugging info. The
20670 @item show debug serial
20671 Displays the current state of displaying @value{GDBN} serial debugging
20673 @item set debug solib-frv
20674 @cindex FR-V shared-library debugging
20675 Turns on or off debugging messages for FR-V shared-library code.
20676 @item show debug solib-frv
20677 Display the current state of FR-V shared-library code debugging
20679 @item set debug target
20680 @cindex target debugging info
20681 Turns on or off display of @value{GDBN} target debugging info. This info
20682 includes what is going on at the target level of GDB, as it happens. The
20683 default is 0. Set it to 1 to track events, and to 2 to also track the
20684 value of large memory transfers. Changes to this flag do not take effect
20685 until the next time you connect to a target or use the @code{run} command.
20686 @item show debug target
20687 Displays the current state of displaying @value{GDBN} target debugging
20689 @item set debug timestamp
20690 @cindex timestampping debugging info
20691 Turns on or off display of timestamps with @value{GDBN} debugging info.
20692 When enabled, seconds and microseconds are displayed before each debugging
20694 @item show debug timestamp
20695 Displays the current state of displaying timestamps with @value{GDBN}
20697 @item set debugvarobj
20698 @cindex variable object debugging info
20699 Turns on or off display of @value{GDBN} variable object debugging
20700 info. The default is off.
20701 @item show debugvarobj
20702 Displays the current state of displaying @value{GDBN} variable object
20704 @item set debug xml
20705 @cindex XML parser debugging
20706 Turns on or off debugging messages for built-in XML parsers.
20707 @item show debug xml
20708 Displays the current state of XML debugging messages.
20711 @node Other Misc Settings
20712 @section Other Miscellaneous Settings
20713 @cindex miscellaneous settings
20716 @kindex set interactive-mode
20717 @item set interactive-mode
20718 If @code{on}, forces @value{GDBN} to assume that GDB was started
20719 in a terminal. In practice, this means that @value{GDBN} should wait
20720 for the user to answer queries generated by commands entered at
20721 the command prompt. If @code{off}, forces @value{GDBN} to operate
20722 in the opposite mode, and it uses the default answers to all queries.
20723 If @code{auto} (the default), @value{GDBN} tries to determine whether
20724 its standard input is a terminal, and works in interactive-mode if it
20725 is, non-interactively otherwise.
20727 In the vast majority of cases, the debugger should be able to guess
20728 correctly which mode should be used. But this setting can be useful
20729 in certain specific cases, such as running a MinGW @value{GDBN}
20730 inside a cygwin window.
20732 @kindex show interactive-mode
20733 @item show interactive-mode
20734 Displays whether the debugger is operating in interactive mode or not.
20737 @node Extending GDB
20738 @chapter Extending @value{GDBN}
20739 @cindex extending GDB
20741 @value{GDBN} provides three mechanisms for extension. The first is based
20742 on composition of @value{GDBN} commands, the second is based on the
20743 Python scripting language, and the third is for defining new aliases of
20746 To facilitate the use of the first two extensions, @value{GDBN} is capable
20747 of evaluating the contents of a file. When doing so, @value{GDBN}
20748 can recognize which scripting language is being used by looking at
20749 the filename extension. Files with an unrecognized filename extension
20750 are always treated as a @value{GDBN} Command Files.
20751 @xref{Command Files,, Command files}.
20753 You can control how @value{GDBN} evaluates these files with the following
20757 @kindex set script-extension
20758 @kindex show script-extension
20759 @item set script-extension off
20760 All scripts are always evaluated as @value{GDBN} Command Files.
20762 @item set script-extension soft
20763 The debugger determines the scripting language based on filename
20764 extension. If this scripting language is supported, @value{GDBN}
20765 evaluates the script using that language. Otherwise, it evaluates
20766 the file as a @value{GDBN} Command File.
20768 @item set script-extension strict
20769 The debugger determines the scripting language based on filename
20770 extension, and evaluates the script using that language. If the
20771 language is not supported, then the evaluation fails.
20773 @item show script-extension
20774 Display the current value of the @code{script-extension} option.
20779 * Sequences:: Canned Sequences of Commands
20780 * Python:: Scripting @value{GDBN} using Python
20781 * Aliases:: Creating new spellings of existing commands
20785 @section Canned Sequences of Commands
20787 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20788 Command Lists}), @value{GDBN} provides two ways to store sequences of
20789 commands for execution as a unit: user-defined commands and command
20793 * Define:: How to define your own commands
20794 * Hooks:: Hooks for user-defined commands
20795 * Command Files:: How to write scripts of commands to be stored in a file
20796 * Output:: Commands for controlled output
20800 @subsection User-defined Commands
20802 @cindex user-defined command
20803 @cindex arguments, to user-defined commands
20804 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20805 which you assign a new name as a command. This is done with the
20806 @code{define} command. User commands may accept up to 10 arguments
20807 separated by whitespace. Arguments are accessed within the user command
20808 via @code{$arg0@dots{}$arg9}. A trivial example:
20812 print $arg0 + $arg1 + $arg2
20817 To execute the command use:
20824 This defines the command @code{adder}, which prints the sum of
20825 its three arguments. Note the arguments are text substitutions, so they may
20826 reference variables, use complex expressions, or even perform inferior
20829 @cindex argument count in user-defined commands
20830 @cindex how many arguments (user-defined commands)
20831 In addition, @code{$argc} may be used to find out how many arguments have
20832 been passed. This expands to a number in the range 0@dots{}10.
20837 print $arg0 + $arg1
20840 print $arg0 + $arg1 + $arg2
20848 @item define @var{commandname}
20849 Define a command named @var{commandname}. If there is already a command
20850 by that name, you are asked to confirm that you want to redefine it.
20851 @var{commandname} may be a bare command name consisting of letters,
20852 numbers, dashes, and underscores. It may also start with any predefined
20853 prefix command. For example, @samp{define target my-target} creates
20854 a user-defined @samp{target my-target} command.
20856 The definition of the command is made up of other @value{GDBN} command lines,
20857 which are given following the @code{define} command. The end of these
20858 commands is marked by a line containing @code{end}.
20861 @kindex end@r{ (user-defined commands)}
20862 @item document @var{commandname}
20863 Document the user-defined command @var{commandname}, so that it can be
20864 accessed by @code{help}. The command @var{commandname} must already be
20865 defined. This command reads lines of documentation just as @code{define}
20866 reads the lines of the command definition, ending with @code{end}.
20867 After the @code{document} command is finished, @code{help} on command
20868 @var{commandname} displays the documentation you have written.
20870 You may use the @code{document} command again to change the
20871 documentation of a command. Redefining the command with @code{define}
20872 does not change the documentation.
20874 @kindex dont-repeat
20875 @cindex don't repeat command
20877 Used inside a user-defined command, this tells @value{GDBN} that this
20878 command should not be repeated when the user hits @key{RET}
20879 (@pxref{Command Syntax, repeat last command}).
20881 @kindex help user-defined
20882 @item help user-defined
20883 List all user-defined commands, with the first line of the documentation
20888 @itemx show user @var{commandname}
20889 Display the @value{GDBN} commands used to define @var{commandname} (but
20890 not its documentation). If no @var{commandname} is given, display the
20891 definitions for all user-defined commands.
20893 @cindex infinite recursion in user-defined commands
20894 @kindex show max-user-call-depth
20895 @kindex set max-user-call-depth
20896 @item show max-user-call-depth
20897 @itemx set max-user-call-depth
20898 The value of @code{max-user-call-depth} controls how many recursion
20899 levels are allowed in user-defined commands before @value{GDBN} suspects an
20900 infinite recursion and aborts the command.
20903 In addition to the above commands, user-defined commands frequently
20904 use control flow commands, described in @ref{Command Files}.
20906 When user-defined commands are executed, the
20907 commands of the definition are not printed. An error in any command
20908 stops execution of the user-defined command.
20910 If used interactively, commands that would ask for confirmation proceed
20911 without asking when used inside a user-defined command. Many @value{GDBN}
20912 commands that normally print messages to say what they are doing omit the
20913 messages when used in a user-defined command.
20916 @subsection User-defined Command Hooks
20917 @cindex command hooks
20918 @cindex hooks, for commands
20919 @cindex hooks, pre-command
20922 You may define @dfn{hooks}, which are a special kind of user-defined
20923 command. Whenever you run the command @samp{foo}, if the user-defined
20924 command @samp{hook-foo} exists, it is executed (with no arguments)
20925 before that command.
20927 @cindex hooks, post-command
20929 A hook may also be defined which is run after the command you executed.
20930 Whenever you run the command @samp{foo}, if the user-defined command
20931 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20932 that command. Post-execution hooks may exist simultaneously with
20933 pre-execution hooks, for the same command.
20935 It is valid for a hook to call the command which it hooks. If this
20936 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20938 @c It would be nice if hookpost could be passed a parameter indicating
20939 @c if the command it hooks executed properly or not. FIXME!
20941 @kindex stop@r{, a pseudo-command}
20942 In addition, a pseudo-command, @samp{stop} exists. Defining
20943 (@samp{hook-stop}) makes the associated commands execute every time
20944 execution stops in your program: before breakpoint commands are run,
20945 displays are printed, or the stack frame is printed.
20947 For example, to ignore @code{SIGALRM} signals while
20948 single-stepping, but treat them normally during normal execution,
20953 handle SIGALRM nopass
20957 handle SIGALRM pass
20960 define hook-continue
20961 handle SIGALRM pass
20965 As a further example, to hook at the beginning and end of the @code{echo}
20966 command, and to add extra text to the beginning and end of the message,
20974 define hookpost-echo
20978 (@value{GDBP}) echo Hello World
20979 <<<---Hello World--->>>
20984 You can define a hook for any single-word command in @value{GDBN}, but
20985 not for command aliases; you should define a hook for the basic command
20986 name, e.g.@: @code{backtrace} rather than @code{bt}.
20987 @c FIXME! So how does Joe User discover whether a command is an alias
20989 You can hook a multi-word command by adding @code{hook-} or
20990 @code{hookpost-} to the last word of the command, e.g.@:
20991 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20993 If an error occurs during the execution of your hook, execution of
20994 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20995 (before the command that you actually typed had a chance to run).
20997 If you try to define a hook which does not match any known command, you
20998 get a warning from the @code{define} command.
21000 @node Command Files
21001 @subsection Command Files
21003 @cindex command files
21004 @cindex scripting commands
21005 A command file for @value{GDBN} is a text file made of lines that are
21006 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21007 also be included. An empty line in a command file does nothing; it
21008 does not mean to repeat the last command, as it would from the
21011 You can request the execution of a command file with the @code{source}
21012 command. Note that the @code{source} command is also used to evaluate
21013 scripts that are not Command Files. The exact behavior can be configured
21014 using the @code{script-extension} setting.
21015 @xref{Extending GDB,, Extending GDB}.
21019 @cindex execute commands from a file
21020 @item source [-s] [-v] @var{filename}
21021 Execute the command file @var{filename}.
21024 The lines in a command file are generally executed sequentially,
21025 unless the order of execution is changed by one of the
21026 @emph{flow-control commands} described below. The commands are not
21027 printed as they are executed. An error in any command terminates
21028 execution of the command file and control is returned to the console.
21030 @value{GDBN} first searches for @var{filename} in the current directory.
21031 If the file is not found there, and @var{filename} does not specify a
21032 directory, then @value{GDBN} also looks for the file on the source search path
21033 (specified with the @samp{directory} command);
21034 except that @file{$cdir} is not searched because the compilation directory
21035 is not relevant to scripts.
21037 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21038 on the search path even if @var{filename} specifies a directory.
21039 The search is done by appending @var{filename} to each element of the
21040 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21041 and the search path contains @file{/home/user} then @value{GDBN} will
21042 look for the script @file{/home/user/mylib/myscript}.
21043 The search is also done if @var{filename} is an absolute path.
21044 For example, if @var{filename} is @file{/tmp/myscript} and
21045 the search path contains @file{/home/user} then @value{GDBN} will
21046 look for the script @file{/home/user/tmp/myscript}.
21047 For DOS-like systems, if @var{filename} contains a drive specification,
21048 it is stripped before concatenation. For example, if @var{filename} is
21049 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21050 will look for the script @file{c:/tmp/myscript}.
21052 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21053 each command as it is executed. The option must be given before
21054 @var{filename}, and is interpreted as part of the filename anywhere else.
21056 Commands that would ask for confirmation if used interactively proceed
21057 without asking when used in a command file. Many @value{GDBN} commands that
21058 normally print messages to say what they are doing omit the messages
21059 when called from command files.
21061 @value{GDBN} also accepts command input from standard input. In this
21062 mode, normal output goes to standard output and error output goes to
21063 standard error. Errors in a command file supplied on standard input do
21064 not terminate execution of the command file---execution continues with
21068 gdb < cmds > log 2>&1
21071 (The syntax above will vary depending on the shell used.) This example
21072 will execute commands from the file @file{cmds}. All output and errors
21073 would be directed to @file{log}.
21075 Since commands stored on command files tend to be more general than
21076 commands typed interactively, they frequently need to deal with
21077 complicated situations, such as different or unexpected values of
21078 variables and symbols, changes in how the program being debugged is
21079 built, etc. @value{GDBN} provides a set of flow-control commands to
21080 deal with these complexities. Using these commands, you can write
21081 complex scripts that loop over data structures, execute commands
21082 conditionally, etc.
21089 This command allows to include in your script conditionally executed
21090 commands. The @code{if} command takes a single argument, which is an
21091 expression to evaluate. It is followed by a series of commands that
21092 are executed only if the expression is true (its value is nonzero).
21093 There can then optionally be an @code{else} line, followed by a series
21094 of commands that are only executed if the expression was false. The
21095 end of the list is marked by a line containing @code{end}.
21099 This command allows to write loops. Its syntax is similar to
21100 @code{if}: the command takes a single argument, which is an expression
21101 to evaluate, and must be followed by the commands to execute, one per
21102 line, terminated by an @code{end}. These commands are called the
21103 @dfn{body} of the loop. The commands in the body of @code{while} are
21104 executed repeatedly as long as the expression evaluates to true.
21108 This command exits the @code{while} loop in whose body it is included.
21109 Execution of the script continues after that @code{while}s @code{end}
21112 @kindex loop_continue
21113 @item loop_continue
21114 This command skips the execution of the rest of the body of commands
21115 in the @code{while} loop in whose body it is included. Execution
21116 branches to the beginning of the @code{while} loop, where it evaluates
21117 the controlling expression.
21119 @kindex end@r{ (if/else/while commands)}
21121 Terminate the block of commands that are the body of @code{if},
21122 @code{else}, or @code{while} flow-control commands.
21127 @subsection Commands for Controlled Output
21129 During the execution of a command file or a user-defined command, normal
21130 @value{GDBN} output is suppressed; the only output that appears is what is
21131 explicitly printed by the commands in the definition. This section
21132 describes three commands useful for generating exactly the output you
21137 @item echo @var{text}
21138 @c I do not consider backslash-space a standard C escape sequence
21139 @c because it is not in ANSI.
21140 Print @var{text}. Nonprinting characters can be included in
21141 @var{text} using C escape sequences, such as @samp{\n} to print a
21142 newline. @strong{No newline is printed unless you specify one.}
21143 In addition to the standard C escape sequences, a backslash followed
21144 by a space stands for a space. This is useful for displaying a
21145 string with spaces at the beginning or the end, since leading and
21146 trailing spaces are otherwise trimmed from all arguments.
21147 To print @samp{@w{ }and foo =@w{ }}, use the command
21148 @samp{echo \@w{ }and foo = \@w{ }}.
21150 A backslash at the end of @var{text} can be used, as in C, to continue
21151 the command onto subsequent lines. For example,
21154 echo This is some text\n\
21155 which is continued\n\
21156 onto several lines.\n
21159 produces the same output as
21162 echo This is some text\n
21163 echo which is continued\n
21164 echo onto several lines.\n
21168 @item output @var{expression}
21169 Print the value of @var{expression} and nothing but that value: no
21170 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21171 value history either. @xref{Expressions, ,Expressions}, for more information
21174 @item output/@var{fmt} @var{expression}
21175 Print the value of @var{expression} in format @var{fmt}. You can use
21176 the same formats as for @code{print}. @xref{Output Formats,,Output
21177 Formats}, for more information.
21180 @item printf @var{template}, @var{expressions}@dots{}
21181 Print the values of one or more @var{expressions} under the control of
21182 the string @var{template}. To print several values, make
21183 @var{expressions} be a comma-separated list of individual expressions,
21184 which may be either numbers or pointers. Their values are printed as
21185 specified by @var{template}, exactly as a C program would do by
21186 executing the code below:
21189 printf (@var{template}, @var{expressions}@dots{});
21192 As in @code{C} @code{printf}, ordinary characters in @var{template}
21193 are printed verbatim, while @dfn{conversion specification} introduced
21194 by the @samp{%} character cause subsequent @var{expressions} to be
21195 evaluated, their values converted and formatted according to type and
21196 style information encoded in the conversion specifications, and then
21199 For example, you can print two values in hex like this:
21202 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21205 @code{printf} supports all the standard @code{C} conversion
21206 specifications, including the flags and modifiers between the @samp{%}
21207 character and the conversion letter, with the following exceptions:
21211 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21214 The modifier @samp{*} is not supported for specifying precision or
21218 The @samp{'} flag (for separation of digits into groups according to
21219 @code{LC_NUMERIC'}) is not supported.
21222 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21226 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21229 The conversion letters @samp{a} and @samp{A} are not supported.
21233 Note that the @samp{ll} type modifier is supported only if the
21234 underlying @code{C} implementation used to build @value{GDBN} supports
21235 the @code{long long int} type, and the @samp{L} type modifier is
21236 supported only if @code{long double} type is available.
21238 As in @code{C}, @code{printf} supports simple backslash-escape
21239 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21240 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21241 single character. Octal and hexadecimal escape sequences are not
21244 Additionally, @code{printf} supports conversion specifications for DFP
21245 (@dfn{Decimal Floating Point}) types using the following length modifiers
21246 together with a floating point specifier.
21251 @samp{H} for printing @code{Decimal32} types.
21254 @samp{D} for printing @code{Decimal64} types.
21257 @samp{DD} for printing @code{Decimal128} types.
21260 If the underlying @code{C} implementation used to build @value{GDBN} has
21261 support for the three length modifiers for DFP types, other modifiers
21262 such as width and precision will also be available for @value{GDBN} to use.
21264 In case there is no such @code{C} support, no additional modifiers will be
21265 available and the value will be printed in the standard way.
21267 Here's an example of printing DFP types using the above conversion letters:
21269 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21273 @item eval @var{template}, @var{expressions}@dots{}
21274 Convert the values of one or more @var{expressions} under the control of
21275 the string @var{template} to a command line, and call it.
21280 @section Scripting @value{GDBN} using Python
21281 @cindex python scripting
21282 @cindex scripting with python
21284 You can script @value{GDBN} using the @uref{http://www.python.org/,
21285 Python programming language}. This feature is available only if
21286 @value{GDBN} was configured using @option{--with-python}.
21288 @cindex python directory
21289 Python scripts used by @value{GDBN} should be installed in
21290 @file{@var{data-directory}/python}, where @var{data-directory} is
21291 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21292 This directory, known as the @dfn{python directory},
21293 is automatically added to the Python Search Path in order to allow
21294 the Python interpreter to locate all scripts installed at this location.
21296 Additionally, @value{GDBN} commands and convenience functions which
21297 are written in Python and are located in the
21298 @file{@var{data-directory}/python/gdb/command} or
21299 @file{@var{data-directory}/python/gdb/function} directories are
21300 automatically imported when @value{GDBN} starts.
21303 * Python Commands:: Accessing Python from @value{GDBN}.
21304 * Python API:: Accessing @value{GDBN} from Python.
21305 * Auto-loading:: Automatically loading Python code.
21306 * Python modules:: Python modules provided by @value{GDBN}.
21309 @node Python Commands
21310 @subsection Python Commands
21311 @cindex python commands
21312 @cindex commands to access python
21314 @value{GDBN} provides one command for accessing the Python interpreter,
21315 and one related setting:
21319 @item python @r{[}@var{code}@r{]}
21320 The @code{python} command can be used to evaluate Python code.
21322 If given an argument, the @code{python} command will evaluate the
21323 argument as a Python command. For example:
21326 (@value{GDBP}) python print 23
21330 If you do not provide an argument to @code{python}, it will act as a
21331 multi-line command, like @code{define}. In this case, the Python
21332 script is made up of subsequent command lines, given after the
21333 @code{python} command. This command list is terminated using a line
21334 containing @code{end}. For example:
21337 (@value{GDBP}) python
21339 End with a line saying just "end".
21345 @kindex maint set python print-stack
21346 @item maint set python print-stack
21347 This command is now deprecated. Instead use @code{set python
21350 @kindex set python print-stack
21351 @item set python print-stack
21352 By default, @value{GDBN} will not print a stack trace when an error
21353 occurs in a Python script. This can be controlled using @code{set
21354 python print-stack}: if @code{on}, then Python stack printing is
21355 enabled; if @code{off}, the default, then Python stack printing is
21359 It is also possible to execute a Python script from the @value{GDBN}
21363 @item source @file{script-name}
21364 The script name must end with @samp{.py} and @value{GDBN} must be configured
21365 to recognize the script language based on filename extension using
21366 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21368 @item python execfile ("script-name")
21369 This method is based on the @code{execfile} Python built-in function,
21370 and thus is always available.
21374 @subsection Python API
21376 @cindex programming in python
21378 @cindex python stdout
21379 @cindex python pagination
21380 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21381 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21382 A Python program which outputs to one of these streams may have its
21383 output interrupted by the user (@pxref{Screen Size}). In this
21384 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21387 * Basic Python:: Basic Python Functions.
21388 * Exception Handling:: How Python exceptions are translated.
21389 * Values From Inferior:: Python representation of values.
21390 * Types In Python:: Python representation of types.
21391 * Pretty Printing API:: Pretty-printing values.
21392 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21393 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21394 * Inferiors In Python:: Python representation of inferiors (processes)
21395 * Events In Python:: Listening for events from @value{GDBN}.
21396 * Threads In Python:: Accessing inferior threads from Python.
21397 * Commands In Python:: Implementing new commands in Python.
21398 * Parameters In Python:: Adding new @value{GDBN} parameters.
21399 * Functions In Python:: Writing new convenience functions.
21400 * Progspaces In Python:: Program spaces.
21401 * Objfiles In Python:: Object files.
21402 * Frames In Python:: Accessing inferior stack frames from Python.
21403 * Blocks In Python:: Accessing frame blocks from Python.
21404 * Symbols In Python:: Python representation of symbols.
21405 * Symbol Tables In Python:: Python representation of symbol tables.
21406 * Lazy Strings In Python:: Python representation of lazy strings.
21407 * Breakpoints In Python:: Manipulating breakpoints using Python.
21411 @subsubsection Basic Python
21413 @cindex python functions
21414 @cindex python module
21416 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21417 methods and classes added by @value{GDBN} are placed in this module.
21418 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21419 use in all scripts evaluated by the @code{python} command.
21421 @findex gdb.PYTHONDIR
21422 @defvar gdb.PYTHONDIR
21423 A string containing the python directory (@pxref{Python}).
21426 @findex gdb.execute
21427 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21428 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21429 If a GDB exception happens while @var{command} runs, it is
21430 translated as described in @ref{Exception Handling,,Exception Handling}.
21432 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21433 command as having originated from the user invoking it interactively.
21434 It must be a boolean value. If omitted, it defaults to @code{False}.
21436 By default, any output produced by @var{command} is sent to
21437 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21438 @code{True}, then output will be collected by @code{gdb.execute} and
21439 returned as a string. The default is @code{False}, in which case the
21440 return value is @code{None}. If @var{to_string} is @code{True}, the
21441 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21442 and height, and its pagination will be disabled; @pxref{Screen Size}.
21445 @findex gdb.breakpoints
21446 @defun gdb.breakpoints ()
21447 Return a sequence holding all of @value{GDBN}'s breakpoints.
21448 @xref{Breakpoints In Python}, for more information.
21451 @findex gdb.parameter
21452 @defun gdb.parameter (parameter)
21453 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21454 string naming the parameter to look up; @var{parameter} may contain
21455 spaces if the parameter has a multi-part name. For example,
21456 @samp{print object} is a valid parameter name.
21458 If the named parameter does not exist, this function throws a
21459 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21460 parameter's value is converted to a Python value of the appropriate
21461 type, and returned.
21464 @findex gdb.history
21465 @defun gdb.history (number)
21466 Return a value from @value{GDBN}'s value history (@pxref{Value
21467 History}). @var{number} indicates which history element to return.
21468 If @var{number} is negative, then @value{GDBN} will take its absolute value
21469 and count backward from the last element (i.e., the most recent element) to
21470 find the value to return. If @var{number} is zero, then @value{GDBN} will
21471 return the most recent element. If the element specified by @var{number}
21472 doesn't exist in the value history, a @code{gdb.error} exception will be
21475 If no exception is raised, the return value is always an instance of
21476 @code{gdb.Value} (@pxref{Values From Inferior}).
21479 @findex gdb.parse_and_eval
21480 @defun gdb.parse_and_eval (expression)
21481 Parse @var{expression} as an expression in the current language,
21482 evaluate it, and return the result as a @code{gdb.Value}.
21483 @var{expression} must be a string.
21485 This function can be useful when implementing a new command
21486 (@pxref{Commands In Python}), as it provides a way to parse the
21487 command's argument as an expression. It is also useful simply to
21488 compute values, for example, it is the only way to get the value of a
21489 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21492 @findex gdb.post_event
21493 @defun gdb.post_event (event)
21494 Put @var{event}, a callable object taking no arguments, into
21495 @value{GDBN}'s internal event queue. This callable will be invoked at
21496 some later point, during @value{GDBN}'s event processing. Events
21497 posted using @code{post_event} will be run in the order in which they
21498 were posted; however, there is no way to know when they will be
21499 processed relative to other events inside @value{GDBN}.
21501 @value{GDBN} is not thread-safe. If your Python program uses multiple
21502 threads, you must be careful to only call @value{GDBN}-specific
21503 functions in the main @value{GDBN} thread. @code{post_event} ensures
21507 (@value{GDBP}) python
21511 > def __init__(self, message):
21512 > self.message = message;
21513 > def __call__(self):
21514 > gdb.write(self.message)
21516 >class MyThread1 (threading.Thread):
21518 > gdb.post_event(Writer("Hello "))
21520 >class MyThread2 (threading.Thread):
21522 > gdb.post_event(Writer("World\n"))
21524 >MyThread1().start()
21525 >MyThread2().start()
21527 (@value{GDBP}) Hello World
21532 @defun gdb.write (string @r{[}, stream{]})
21533 Print a string to @value{GDBN}'s paginated output stream. The
21534 optional @var{stream} determines the stream to print to. The default
21535 stream is @value{GDBN}'s standard output stream. Possible stream
21542 @value{GDBN}'s standard output stream.
21547 @value{GDBN}'s standard error stream.
21552 @value{GDBN}'s log stream (@pxref{Logging Output}).
21555 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21556 call this function and will automatically direct the output to the
21561 @defun gdb.flush ()
21562 Flush the buffer of a @value{GDBN} paginated stream so that the
21563 contents are displayed immediately. @value{GDBN} will flush the
21564 contents of a stream automatically when it encounters a newline in the
21565 buffer. The optional @var{stream} determines the stream to flush. The
21566 default stream is @value{GDBN}'s standard output stream. Possible
21573 @value{GDBN}'s standard output stream.
21578 @value{GDBN}'s standard error stream.
21583 @value{GDBN}'s log stream (@pxref{Logging Output}).
21587 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21588 call this function for the relevant stream.
21591 @findex gdb.target_charset
21592 @defun gdb.target_charset ()
21593 Return the name of the current target character set (@pxref{Character
21594 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21595 that @samp{auto} is never returned.
21598 @findex gdb.target_wide_charset
21599 @defun gdb.target_wide_charset ()
21600 Return the name of the current target wide character set
21601 (@pxref{Character Sets}). This differs from
21602 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21606 @findex gdb.solib_name
21607 @defun gdb.solib_name (address)
21608 Return the name of the shared library holding the given @var{address}
21609 as a string, or @code{None}.
21612 @findex gdb.decode_line
21613 @defun gdb.decode_line @r{[}expression@r{]}
21614 Return locations of the line specified by @var{expression}, or of the
21615 current line if no argument was given. This function returns a Python
21616 tuple containing two elements. The first element contains a string
21617 holding any unparsed section of @var{expression} (or @code{None} if
21618 the expression has been fully parsed). The second element contains
21619 either @code{None} or another tuple that contains all the locations
21620 that match the expression represented as @code{gdb.Symtab_and_line}
21621 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21622 provided, it is decoded the way that @value{GDBN}'s inbuilt
21623 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21626 @defun gdb.prompt_hook (current_prompt)
21627 @anchor{prompt_hook}
21629 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21630 assigned to this operation before a prompt is displayed by
21633 The parameter @code{current_prompt} contains the current @value{GDBN}
21634 prompt. This method must return a Python string, or @code{None}. If
21635 a string is returned, the @value{GDBN} prompt will be set to that
21636 string. If @code{None} is returned, @value{GDBN} will continue to use
21637 the current prompt.
21639 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21640 such as those used by readline for command input, and annotation
21641 related prompts are prohibited from being changed.
21644 @node Exception Handling
21645 @subsubsection Exception Handling
21646 @cindex python exceptions
21647 @cindex exceptions, python
21649 When executing the @code{python} command, Python exceptions
21650 uncaught within the Python code are translated to calls to
21651 @value{GDBN} error-reporting mechanism. If the command that called
21652 @code{python} does not handle the error, @value{GDBN} will
21653 terminate it and print an error message containing the Python
21654 exception name, the associated value, and the Python call stack
21655 backtrace at the point where the exception was raised. Example:
21658 (@value{GDBP}) python print foo
21659 Traceback (most recent call last):
21660 File "<string>", line 1, in <module>
21661 NameError: name 'foo' is not defined
21664 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21665 Python code are converted to Python exceptions. The type of the
21666 Python exception depends on the error.
21670 This is the base class for most exceptions generated by @value{GDBN}.
21671 It is derived from @code{RuntimeError}, for compatibility with earlier
21672 versions of @value{GDBN}.
21674 If an error occurring in @value{GDBN} does not fit into some more
21675 specific category, then the generated exception will have this type.
21677 @item gdb.MemoryError
21678 This is a subclass of @code{gdb.error} which is thrown when an
21679 operation tried to access invalid memory in the inferior.
21681 @item KeyboardInterrupt
21682 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21683 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21686 In all cases, your exception handler will see the @value{GDBN} error
21687 message as its value and the Python call stack backtrace at the Python
21688 statement closest to where the @value{GDBN} error occured as the
21691 @findex gdb.GdbError
21692 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21693 it is useful to be able to throw an exception that doesn't cause a
21694 traceback to be printed. For example, the user may have invoked the
21695 command incorrectly. Use the @code{gdb.GdbError} exception
21696 to handle this case. Example:
21700 >class HelloWorld (gdb.Command):
21701 > """Greet the whole world."""
21702 > def __init__ (self):
21703 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21704 > def invoke (self, args, from_tty):
21705 > argv = gdb.string_to_argv (args)
21706 > if len (argv) != 0:
21707 > raise gdb.GdbError ("hello-world takes no arguments")
21708 > print "Hello, World!"
21711 (gdb) hello-world 42
21712 hello-world takes no arguments
21715 @node Values From Inferior
21716 @subsubsection Values From Inferior
21717 @cindex values from inferior, with Python
21718 @cindex python, working with values from inferior
21720 @cindex @code{gdb.Value}
21721 @value{GDBN} provides values it obtains from the inferior program in
21722 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21723 for its internal bookkeeping of the inferior's values, and for
21724 fetching values when necessary.
21726 Inferior values that are simple scalars can be used directly in
21727 Python expressions that are valid for the value's data type. Here's
21728 an example for an integer or floating-point value @code{some_val}:
21735 As result of this, @code{bar} will also be a @code{gdb.Value} object
21736 whose values are of the same type as those of @code{some_val}.
21738 Inferior values that are structures or instances of some class can
21739 be accessed using the Python @dfn{dictionary syntax}. For example, if
21740 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21741 can access its @code{foo} element with:
21744 bar = some_val['foo']
21747 Again, @code{bar} will also be a @code{gdb.Value} object.
21749 A @code{gdb.Value} that represents a function can be executed via
21750 inferior function call. Any arguments provided to the call must match
21751 the function's prototype, and must be provided in the order specified
21754 For example, @code{some_val} is a @code{gdb.Value} instance
21755 representing a function that takes two integers as arguments. To
21756 execute this function, call it like so:
21759 result = some_val (10,20)
21762 Any values returned from a function call will be stored as a
21765 The following attributes are provided:
21768 @defvar Value.address
21769 If this object is addressable, this read-only attribute holds a
21770 @code{gdb.Value} object representing the address. Otherwise,
21771 this attribute holds @code{None}.
21774 @cindex optimized out value in Python
21775 @defvar Value.is_optimized_out
21776 This read-only boolean attribute is true if the compiler optimized out
21777 this value, thus it is not available for fetching from the inferior.
21781 The type of this @code{gdb.Value}. The value of this attribute is a
21782 @code{gdb.Type} object (@pxref{Types In Python}).
21785 @defvar Value.dynamic_type
21786 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21787 type information (@acronym{RTTI}) to determine the dynamic type of the
21788 value. If this value is of class type, it will return the class in
21789 which the value is embedded, if any. If this value is of pointer or
21790 reference to a class type, it will compute the dynamic type of the
21791 referenced object, and return a pointer or reference to that type,
21792 respectively. In all other cases, it will return the value's static
21795 Note that this feature will only work when debugging a C@t{++} program
21796 that includes @acronym{RTTI} for the object in question. Otherwise,
21797 it will just return the static type of the value as in @kbd{ptype foo}
21798 (@pxref{Symbols, ptype}).
21801 @defvar Value.is_lazy
21802 The value of this read-only boolean attribute is @code{True} if this
21803 @code{gdb.Value} has not yet been fetched from the inferior.
21804 @value{GDBN} does not fetch values until necessary, for efficiency.
21808 myval = gdb.parse_and_eval ('somevar')
21811 The value of @code{somevar} is not fetched at this time. It will be
21812 fetched when the value is needed, or when the @code{fetch_lazy}
21817 The following methods are provided:
21820 @defun Value.__init__ (@var{val})
21821 Many Python values can be converted directly to a @code{gdb.Value} via
21822 this object initializer. Specifically:
21825 @item Python boolean
21826 A Python boolean is converted to the boolean type from the current
21829 @item Python integer
21830 A Python integer is converted to the C @code{long} type for the
21831 current architecture.
21834 A Python long is converted to the C @code{long long} type for the
21835 current architecture.
21838 A Python float is converted to the C @code{double} type for the
21839 current architecture.
21841 @item Python string
21842 A Python string is converted to a target string, using the current
21845 @item @code{gdb.Value}
21846 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21848 @item @code{gdb.LazyString}
21849 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21850 Python}), then the lazy string's @code{value} method is called, and
21851 its result is used.
21855 @defun Value.cast (type)
21856 Return a new instance of @code{gdb.Value} that is the result of
21857 casting this instance to the type described by @var{type}, which must
21858 be a @code{gdb.Type} object. If the cast cannot be performed for some
21859 reason, this method throws an exception.
21862 @defun Value.dereference ()
21863 For pointer data types, this method returns a new @code{gdb.Value} object
21864 whose contents is the object pointed to by the pointer. For example, if
21865 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21872 then you can use the corresponding @code{gdb.Value} to access what
21873 @code{foo} points to like this:
21876 bar = foo.dereference ()
21879 The result @code{bar} will be a @code{gdb.Value} object holding the
21880 value pointed to by @code{foo}.
21883 @defun Value.dynamic_cast (type)
21884 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21885 operator were used. Consult a C@t{++} reference for details.
21888 @defun Value.reinterpret_cast (type)
21889 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21890 operator were used. Consult a C@t{++} reference for details.
21893 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
21894 If this @code{gdb.Value} represents a string, then this method
21895 converts the contents to a Python string. Otherwise, this method will
21896 throw an exception.
21898 Strings are recognized in a language-specific way; whether a given
21899 @code{gdb.Value} represents a string is determined by the current
21902 For C-like languages, a value is a string if it is a pointer to or an
21903 array of characters or ints. The string is assumed to be terminated
21904 by a zero of the appropriate width. However if the optional length
21905 argument is given, the string will be converted to that given length,
21906 ignoring any embedded zeros that the string may contain.
21908 If the optional @var{encoding} argument is given, it must be a string
21909 naming the encoding of the string in the @code{gdb.Value}, such as
21910 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21911 the same encodings as the corresponding argument to Python's
21912 @code{string.decode} method, and the Python codec machinery will be used
21913 to convert the string. If @var{encoding} is not given, or if
21914 @var{encoding} is the empty string, then either the @code{target-charset}
21915 (@pxref{Character Sets}) will be used, or a language-specific encoding
21916 will be used, if the current language is able to supply one.
21918 The optional @var{errors} argument is the same as the corresponding
21919 argument to Python's @code{string.decode} method.
21921 If the optional @var{length} argument is given, the string will be
21922 fetched and converted to the given length.
21925 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
21926 If this @code{gdb.Value} represents a string, then this method
21927 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21928 In Python}). Otherwise, this method will throw an exception.
21930 If the optional @var{encoding} argument is given, it must be a string
21931 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21932 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21933 @var{encoding} argument is an encoding that @value{GDBN} does
21934 recognize, @value{GDBN} will raise an error.
21936 When a lazy string is printed, the @value{GDBN} encoding machinery is
21937 used to convert the string during printing. If the optional
21938 @var{encoding} argument is not provided, or is an empty string,
21939 @value{GDBN} will automatically select the encoding most suitable for
21940 the string type. For further information on encoding in @value{GDBN}
21941 please see @ref{Character Sets}.
21943 If the optional @var{length} argument is given, the string will be
21944 fetched and encoded to the length of characters specified. If
21945 the @var{length} argument is not provided, the string will be fetched
21946 and encoded until a null of appropriate width is found.
21949 @defun Value.fetch_lazy ()
21950 If the @code{gdb.Value} object is currently a lazy value
21951 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
21952 fetched from the inferior. Any errors that occur in the process
21953 will produce a Python exception.
21955 If the @code{gdb.Value} object is not a lazy value, this method
21958 This method does not return a value.
21963 @node Types In Python
21964 @subsubsection Types In Python
21965 @cindex types in Python
21966 @cindex Python, working with types
21969 @value{GDBN} represents types from the inferior using the class
21972 The following type-related functions are available in the @code{gdb}
21975 @findex gdb.lookup_type
21976 @defun gdb.lookup_type (name @r{[}, block@r{]})
21977 This function looks up a type by name. @var{name} is the name of the
21978 type to look up. It must be a string.
21980 If @var{block} is given, then @var{name} is looked up in that scope.
21981 Otherwise, it is searched for globally.
21983 Ordinarily, this function will return an instance of @code{gdb.Type}.
21984 If the named type cannot be found, it will throw an exception.
21987 If the type is a structure or class type, or an enum type, the fields
21988 of that type can be accessed using the Python @dfn{dictionary syntax}.
21989 For example, if @code{some_type} is a @code{gdb.Type} instance holding
21990 a structure type, you can access its @code{foo} field with:
21993 bar = some_type['foo']
21996 @code{bar} will be a @code{gdb.Field} object; see below under the
21997 description of the @code{Type.fields} method for a description of the
21998 @code{gdb.Field} class.
22000 An instance of @code{Type} has the following attributes:
22004 The type code for this type. The type code will be one of the
22005 @code{TYPE_CODE_} constants defined below.
22008 @defvar Type.sizeof
22009 The size of this type, in target @code{char} units. Usually, a
22010 target's @code{char} type will be an 8-bit byte. However, on some
22011 unusual platforms, this type may have a different size.
22015 The tag name for this type. The tag name is the name after
22016 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22017 languages have this concept. If this type has no tag name, then
22018 @code{None} is returned.
22022 The following methods are provided:
22025 @defun Type.fields ()
22026 For structure and union types, this method returns the fields. Range
22027 types have two fields, the minimum and maximum values. Enum types
22028 have one field per enum constant. Function and method types have one
22029 field per parameter. The base types of C@t{++} classes are also
22030 represented as fields. If the type has no fields, or does not fit
22031 into one of these categories, an empty sequence will be returned.
22033 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22036 This attribute is not available for @code{static} fields (as in
22037 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22038 position of the field. For @code{enum} fields, the value is the
22039 enumeration member's integer representation.
22042 The name of the field, or @code{None} for anonymous fields.
22045 This is @code{True} if the field is artificial, usually meaning that
22046 it was provided by the compiler and not the user. This attribute is
22047 always provided, and is @code{False} if the field is not artificial.
22049 @item is_base_class
22050 This is @code{True} if the field represents a base class of a C@t{++}
22051 structure. This attribute is always provided, and is @code{False}
22052 if the field is not a base class of the type that is the argument of
22053 @code{fields}, or if that type was not a C@t{++} class.
22056 If the field is packed, or is a bitfield, then this will have a
22057 non-zero value, which is the size of the field in bits. Otherwise,
22058 this will be zero; in this case the field's size is given by its type.
22061 The type of the field. This is usually an instance of @code{Type},
22062 but it can be @code{None} in some situations.
22066 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22067 Return a new @code{gdb.Type} object which represents an array of this
22068 type. If one argument is given, it is the inclusive upper bound of
22069 the array; in this case the lower bound is zero. If two arguments are
22070 given, the first argument is the lower bound of the array, and the
22071 second argument is the upper bound of the array. An array's length
22072 must not be negative, but the bounds can be.
22075 @defun Type.const ()
22076 Return a new @code{gdb.Type} object which represents a
22077 @code{const}-qualified variant of this type.
22080 @defun Type.volatile ()
22081 Return a new @code{gdb.Type} object which represents a
22082 @code{volatile}-qualified variant of this type.
22085 @defun Type.unqualified ()
22086 Return a new @code{gdb.Type} object which represents an unqualified
22087 variant of this type. That is, the result is neither @code{const} nor
22091 @defun Type.range ()
22092 Return a Python @code{Tuple} object that contains two elements: the
22093 low bound of the argument type and the high bound of that type. If
22094 the type does not have a range, @value{GDBN} will raise a
22095 @code{gdb.error} exception (@pxref{Exception Handling}).
22098 @defun Type.reference ()
22099 Return a new @code{gdb.Type} object which represents a reference to this
22103 @defun Type.pointer ()
22104 Return a new @code{gdb.Type} object which represents a pointer to this
22108 @defun Type.strip_typedefs ()
22109 Return a new @code{gdb.Type} that represents the real type,
22110 after removing all layers of typedefs.
22113 @defun Type.target ()
22114 Return a new @code{gdb.Type} object which represents the target type
22117 For a pointer type, the target type is the type of the pointed-to
22118 object. For an array type (meaning C-like arrays), the target type is
22119 the type of the elements of the array. For a function or method type,
22120 the target type is the type of the return value. For a complex type,
22121 the target type is the type of the elements. For a typedef, the
22122 target type is the aliased type.
22124 If the type does not have a target, this method will throw an
22128 @defun Type.template_argument (n @r{[}, block@r{]})
22129 If this @code{gdb.Type} is an instantiation of a template, this will
22130 return a new @code{gdb.Type} which represents the type of the
22131 @var{n}th template argument.
22133 If this @code{gdb.Type} is not a template type, this will throw an
22134 exception. Ordinarily, only C@t{++} code will have template types.
22136 If @var{block} is given, then @var{name} is looked up in that scope.
22137 Otherwise, it is searched for globally.
22142 Each type has a code, which indicates what category this type falls
22143 into. The available type categories are represented by constants
22144 defined in the @code{gdb} module:
22147 @findex TYPE_CODE_PTR
22148 @findex gdb.TYPE_CODE_PTR
22149 @item gdb.TYPE_CODE_PTR
22150 The type is a pointer.
22152 @findex TYPE_CODE_ARRAY
22153 @findex gdb.TYPE_CODE_ARRAY
22154 @item gdb.TYPE_CODE_ARRAY
22155 The type is an array.
22157 @findex TYPE_CODE_STRUCT
22158 @findex gdb.TYPE_CODE_STRUCT
22159 @item gdb.TYPE_CODE_STRUCT
22160 The type is a structure.
22162 @findex TYPE_CODE_UNION
22163 @findex gdb.TYPE_CODE_UNION
22164 @item gdb.TYPE_CODE_UNION
22165 The type is a union.
22167 @findex TYPE_CODE_ENUM
22168 @findex gdb.TYPE_CODE_ENUM
22169 @item gdb.TYPE_CODE_ENUM
22170 The type is an enum.
22172 @findex TYPE_CODE_FLAGS
22173 @findex gdb.TYPE_CODE_FLAGS
22174 @item gdb.TYPE_CODE_FLAGS
22175 A bit flags type, used for things such as status registers.
22177 @findex TYPE_CODE_FUNC
22178 @findex gdb.TYPE_CODE_FUNC
22179 @item gdb.TYPE_CODE_FUNC
22180 The type is a function.
22182 @findex TYPE_CODE_INT
22183 @findex gdb.TYPE_CODE_INT
22184 @item gdb.TYPE_CODE_INT
22185 The type is an integer type.
22187 @findex TYPE_CODE_FLT
22188 @findex gdb.TYPE_CODE_FLT
22189 @item gdb.TYPE_CODE_FLT
22190 A floating point type.
22192 @findex TYPE_CODE_VOID
22193 @findex gdb.TYPE_CODE_VOID
22194 @item gdb.TYPE_CODE_VOID
22195 The special type @code{void}.
22197 @findex TYPE_CODE_SET
22198 @findex gdb.TYPE_CODE_SET
22199 @item gdb.TYPE_CODE_SET
22202 @findex TYPE_CODE_RANGE
22203 @findex gdb.TYPE_CODE_RANGE
22204 @item gdb.TYPE_CODE_RANGE
22205 A range type, that is, an integer type with bounds.
22207 @findex TYPE_CODE_STRING
22208 @findex gdb.TYPE_CODE_STRING
22209 @item gdb.TYPE_CODE_STRING
22210 A string type. Note that this is only used for certain languages with
22211 language-defined string types; C strings are not represented this way.
22213 @findex TYPE_CODE_BITSTRING
22214 @findex gdb.TYPE_CODE_BITSTRING
22215 @item gdb.TYPE_CODE_BITSTRING
22218 @findex TYPE_CODE_ERROR
22219 @findex gdb.TYPE_CODE_ERROR
22220 @item gdb.TYPE_CODE_ERROR
22221 An unknown or erroneous type.
22223 @findex TYPE_CODE_METHOD
22224 @findex gdb.TYPE_CODE_METHOD
22225 @item gdb.TYPE_CODE_METHOD
22226 A method type, as found in C@t{++} or Java.
22228 @findex TYPE_CODE_METHODPTR
22229 @findex gdb.TYPE_CODE_METHODPTR
22230 @item gdb.TYPE_CODE_METHODPTR
22231 A pointer-to-member-function.
22233 @findex TYPE_CODE_MEMBERPTR
22234 @findex gdb.TYPE_CODE_MEMBERPTR
22235 @item gdb.TYPE_CODE_MEMBERPTR
22236 A pointer-to-member.
22238 @findex TYPE_CODE_REF
22239 @findex gdb.TYPE_CODE_REF
22240 @item gdb.TYPE_CODE_REF
22243 @findex TYPE_CODE_CHAR
22244 @findex gdb.TYPE_CODE_CHAR
22245 @item gdb.TYPE_CODE_CHAR
22248 @findex TYPE_CODE_BOOL
22249 @findex gdb.TYPE_CODE_BOOL
22250 @item gdb.TYPE_CODE_BOOL
22253 @findex TYPE_CODE_COMPLEX
22254 @findex gdb.TYPE_CODE_COMPLEX
22255 @item gdb.TYPE_CODE_COMPLEX
22256 A complex float type.
22258 @findex TYPE_CODE_TYPEDEF
22259 @findex gdb.TYPE_CODE_TYPEDEF
22260 @item gdb.TYPE_CODE_TYPEDEF
22261 A typedef to some other type.
22263 @findex TYPE_CODE_NAMESPACE
22264 @findex gdb.TYPE_CODE_NAMESPACE
22265 @item gdb.TYPE_CODE_NAMESPACE
22266 A C@t{++} namespace.
22268 @findex TYPE_CODE_DECFLOAT
22269 @findex gdb.TYPE_CODE_DECFLOAT
22270 @item gdb.TYPE_CODE_DECFLOAT
22271 A decimal floating point type.
22273 @findex TYPE_CODE_INTERNAL_FUNCTION
22274 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22275 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22276 A function internal to @value{GDBN}. This is the type used to represent
22277 convenience functions.
22280 Further support for types is provided in the @code{gdb.types}
22281 Python module (@pxref{gdb.types}).
22283 @node Pretty Printing API
22284 @subsubsection Pretty Printing API
22286 An example output is provided (@pxref{Pretty Printing}).
22288 A pretty-printer is just an object that holds a value and implements a
22289 specific interface, defined here.
22291 @defun pretty_printer.children (self)
22292 @value{GDBN} will call this method on a pretty-printer to compute the
22293 children of the pretty-printer's value.
22295 This method must return an object conforming to the Python iterator
22296 protocol. Each item returned by the iterator must be a tuple holding
22297 two elements. The first element is the ``name'' of the child; the
22298 second element is the child's value. The value can be any Python
22299 object which is convertible to a @value{GDBN} value.
22301 This method is optional. If it does not exist, @value{GDBN} will act
22302 as though the value has no children.
22305 @defun pretty_printer.display_hint (self)
22306 The CLI may call this method and use its result to change the
22307 formatting of a value. The result will also be supplied to an MI
22308 consumer as a @samp{displayhint} attribute of the variable being
22311 This method is optional. If it does exist, this method must return a
22314 Some display hints are predefined by @value{GDBN}:
22318 Indicate that the object being printed is ``array-like''. The CLI
22319 uses this to respect parameters such as @code{set print elements} and
22320 @code{set print array}.
22323 Indicate that the object being printed is ``map-like'', and that the
22324 children of this value can be assumed to alternate between keys and
22328 Indicate that the object being printed is ``string-like''. If the
22329 printer's @code{to_string} method returns a Python string of some
22330 kind, then @value{GDBN} will call its internal language-specific
22331 string-printing function to format the string. For the CLI this means
22332 adding quotation marks, possibly escaping some characters, respecting
22333 @code{set print elements}, and the like.
22337 @defun pretty_printer.to_string (self)
22338 @value{GDBN} will call this method to display the string
22339 representation of the value passed to the object's constructor.
22341 When printing from the CLI, if the @code{to_string} method exists,
22342 then @value{GDBN} will prepend its result to the values returned by
22343 @code{children}. Exactly how this formatting is done is dependent on
22344 the display hint, and may change as more hints are added. Also,
22345 depending on the print settings (@pxref{Print Settings}), the CLI may
22346 print just the result of @code{to_string} in a stack trace, omitting
22347 the result of @code{children}.
22349 If this method returns a string, it is printed verbatim.
22351 Otherwise, if this method returns an instance of @code{gdb.Value},
22352 then @value{GDBN} prints this value. This may result in a call to
22353 another pretty-printer.
22355 If instead the method returns a Python value which is convertible to a
22356 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22357 the resulting value. Again, this may result in a call to another
22358 pretty-printer. Python scalars (integers, floats, and booleans) and
22359 strings are convertible to @code{gdb.Value}; other types are not.
22361 Finally, if this method returns @code{None} then no further operations
22362 are peformed in this method and nothing is printed.
22364 If the result is not one of these types, an exception is raised.
22367 @value{GDBN} provides a function which can be used to look up the
22368 default pretty-printer for a @code{gdb.Value}:
22370 @findex gdb.default_visualizer
22371 @defun gdb.default_visualizer (value)
22372 This function takes a @code{gdb.Value} object as an argument. If a
22373 pretty-printer for this value exists, then it is returned. If no such
22374 printer exists, then this returns @code{None}.
22377 @node Selecting Pretty-Printers
22378 @subsubsection Selecting Pretty-Printers
22380 The Python list @code{gdb.pretty_printers} contains an array of
22381 functions or callable objects that have been registered via addition
22382 as a pretty-printer. Printers in this list are called @code{global}
22383 printers, they're available when debugging all inferiors.
22384 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22385 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22388 Each function on these lists is passed a single @code{gdb.Value}
22389 argument and should return a pretty-printer object conforming to the
22390 interface definition above (@pxref{Pretty Printing API}). If a function
22391 cannot create a pretty-printer for the value, it should return
22394 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22395 @code{gdb.Objfile} in the current program space and iteratively calls
22396 each enabled lookup routine in the list for that @code{gdb.Objfile}
22397 until it receives a pretty-printer object.
22398 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22399 searches the pretty-printer list of the current program space,
22400 calling each enabled function until an object is returned.
22401 After these lists have been exhausted, it tries the global
22402 @code{gdb.pretty_printers} list, again calling each enabled function until an
22403 object is returned.
22405 The order in which the objfiles are searched is not specified. For a
22406 given list, functions are always invoked from the head of the list,
22407 and iterated over sequentially until the end of the list, or a printer
22408 object is returned.
22410 For various reasons a pretty-printer may not work.
22411 For example, the underlying data structure may have changed and
22412 the pretty-printer is out of date.
22414 The consequences of a broken pretty-printer are severe enough that
22415 @value{GDBN} provides support for enabling and disabling individual
22416 printers. For example, if @code{print frame-arguments} is on,
22417 a backtrace can become highly illegible if any argument is printed
22418 with a broken printer.
22420 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22421 attribute to the registered function or callable object. If this attribute
22422 is present and its value is @code{False}, the printer is disabled, otherwise
22423 the printer is enabled.
22425 @node Writing a Pretty-Printer
22426 @subsubsection Writing a Pretty-Printer
22427 @cindex writing a pretty-printer
22429 A pretty-printer consists of two parts: a lookup function to detect
22430 if the type is supported, and the printer itself.
22432 Here is an example showing how a @code{std::string} printer might be
22433 written. @xref{Pretty Printing API}, for details on the API this class
22437 class StdStringPrinter(object):
22438 "Print a std::string"
22440 def __init__(self, val):
22443 def to_string(self):
22444 return self.val['_M_dataplus']['_M_p']
22446 def display_hint(self):
22450 And here is an example showing how a lookup function for the printer
22451 example above might be written.
22454 def str_lookup_function(val):
22455 lookup_tag = val.type.tag
22456 if lookup_tag == None:
22458 regex = re.compile("^std::basic_string<char,.*>$")
22459 if regex.match(lookup_tag):
22460 return StdStringPrinter(val)
22464 The example lookup function extracts the value's type, and attempts to
22465 match it to a type that it can pretty-print. If it is a type the
22466 printer can pretty-print, it will return a printer object. If not, it
22467 returns @code{None}.
22469 We recommend that you put your core pretty-printers into a Python
22470 package. If your pretty-printers are for use with a library, we
22471 further recommend embedding a version number into the package name.
22472 This practice will enable @value{GDBN} to load multiple versions of
22473 your pretty-printers at the same time, because they will have
22476 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22477 can be evaluated multiple times without changing its meaning. An
22478 ideal auto-load file will consist solely of @code{import}s of your
22479 printer modules, followed by a call to a register pretty-printers with
22480 the current objfile.
22482 Taken as a whole, this approach will scale nicely to multiple
22483 inferiors, each potentially using a different library version.
22484 Embedding a version number in the Python package name will ensure that
22485 @value{GDBN} is able to load both sets of printers simultaneously.
22486 Then, because the search for pretty-printers is done by objfile, and
22487 because your auto-loaded code took care to register your library's
22488 printers with a specific objfile, @value{GDBN} will find the correct
22489 printers for the specific version of the library used by each
22492 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22493 this code might appear in @code{gdb.libstdcxx.v6}:
22496 def register_printers(objfile):
22497 objfile.pretty_printers.add(str_lookup_function)
22501 And then the corresponding contents of the auto-load file would be:
22504 import gdb.libstdcxx.v6
22505 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22508 The previous example illustrates a basic pretty-printer.
22509 There are a few things that can be improved on.
22510 The printer doesn't have a name, making it hard to identify in a
22511 list of installed printers. The lookup function has a name, but
22512 lookup functions can have arbitrary, even identical, names.
22514 Second, the printer only handles one type, whereas a library typically has
22515 several types. One could install a lookup function for each desired type
22516 in the library, but one could also have a single lookup function recognize
22517 several types. The latter is the conventional way this is handled.
22518 If a pretty-printer can handle multiple data types, then its
22519 @dfn{subprinters} are the printers for the individual data types.
22521 The @code{gdb.printing} module provides a formal way of solving these
22522 problems (@pxref{gdb.printing}).
22523 Here is another example that handles multiple types.
22525 These are the types we are going to pretty-print:
22528 struct foo @{ int a, b; @};
22529 struct bar @{ struct foo x, y; @};
22532 Here are the printers:
22536 """Print a foo object."""
22538 def __init__(self, val):
22541 def to_string(self):
22542 return ("a=<" + str(self.val["a"]) +
22543 "> b=<" + str(self.val["b"]) + ">")
22546 """Print a bar object."""
22548 def __init__(self, val):
22551 def to_string(self):
22552 return ("x=<" + str(self.val["x"]) +
22553 "> y=<" + str(self.val["y"]) + ">")
22556 This example doesn't need a lookup function, that is handled by the
22557 @code{gdb.printing} module. Instead a function is provided to build up
22558 the object that handles the lookup.
22561 import gdb.printing
22563 def build_pretty_printer():
22564 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22566 pp.add_printer('foo', '^foo$', fooPrinter)
22567 pp.add_printer('bar', '^bar$', barPrinter)
22571 And here is the autoload support:
22574 import gdb.printing
22576 gdb.printing.register_pretty_printer(
22577 gdb.current_objfile(),
22578 my_library.build_pretty_printer())
22581 Finally, when this printer is loaded into @value{GDBN}, here is the
22582 corresponding output of @samp{info pretty-printer}:
22585 (gdb) info pretty-printer
22592 @node Inferiors In Python
22593 @subsubsection Inferiors In Python
22594 @cindex inferiors in Python
22596 @findex gdb.Inferior
22597 Programs which are being run under @value{GDBN} are called inferiors
22598 (@pxref{Inferiors and Programs}). Python scripts can access
22599 information about and manipulate inferiors controlled by @value{GDBN}
22600 via objects of the @code{gdb.Inferior} class.
22602 The following inferior-related functions are available in the @code{gdb}
22605 @defun gdb.inferiors ()
22606 Return a tuple containing all inferior objects.
22609 @defun gdb.selected_inferior ()
22610 Return an object representing the current inferior.
22613 A @code{gdb.Inferior} object has the following attributes:
22616 @defvar Inferior.num
22617 ID of inferior, as assigned by GDB.
22620 @defvar Inferior.pid
22621 Process ID of the inferior, as assigned by the underlying operating
22625 @defvar Inferior.was_attached
22626 Boolean signaling whether the inferior was created using `attach', or
22627 started by @value{GDBN} itself.
22631 A @code{gdb.Inferior} object has the following methods:
22634 @defun Inferior.is_valid ()
22635 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22636 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22637 if the inferior no longer exists within @value{GDBN}. All other
22638 @code{gdb.Inferior} methods will throw an exception if it is invalid
22639 at the time the method is called.
22642 @defun Inferior.threads ()
22643 This method returns a tuple holding all the threads which are valid
22644 when it is called. If there are no valid threads, the method will
22645 return an empty tuple.
22648 @findex gdb.read_memory
22649 @defun Inferior.read_memory (address, length)
22650 Read @var{length} bytes of memory from the inferior, starting at
22651 @var{address}. Returns a buffer object, which behaves much like an array
22652 or a string. It can be modified and given to the @code{gdb.write_memory}
22656 @findex gdb.write_memory
22657 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22658 Write the contents of @var{buffer} to the inferior, starting at
22659 @var{address}. The @var{buffer} parameter must be a Python object
22660 which supports the buffer protocol, i.e., a string, an array or the
22661 object returned from @code{gdb.read_memory}. If given, @var{length}
22662 determines the number of bytes from @var{buffer} to be written.
22665 @findex gdb.search_memory
22666 @defun Inferior.search_memory (address, length, pattern)
22667 Search a region of the inferior memory starting at @var{address} with
22668 the given @var{length} using the search pattern supplied in
22669 @var{pattern}. The @var{pattern} parameter must be a Python object
22670 which supports the buffer protocol, i.e., a string, an array or the
22671 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22672 containing the address where the pattern was found, or @code{None} if
22673 the pattern could not be found.
22677 @node Events In Python
22678 @subsubsection Events In Python
22679 @cindex inferior events in Python
22681 @value{GDBN} provides a general event facility so that Python code can be
22682 notified of various state changes, particularly changes that occur in
22685 An @dfn{event} is just an object that describes some state change. The
22686 type of the object and its attributes will vary depending on the details
22687 of the change. All the existing events are described below.
22689 In order to be notified of an event, you must register an event handler
22690 with an @dfn{event registry}. An event registry is an object in the
22691 @code{gdb.events} module which dispatches particular events. A registry
22692 provides methods to register and unregister event handlers:
22695 @defun EventRegistry.connect (object)
22696 Add the given callable @var{object} to the registry. This object will be
22697 called when an event corresponding to this registry occurs.
22700 @defun EventRegistry.disconnect (object)
22701 Remove the given @var{object} from the registry. Once removed, the object
22702 will no longer receive notifications of events.
22706 Here is an example:
22709 def exit_handler (event):
22710 print "event type: exit"
22711 print "exit code: %d" % (event.exit_code)
22713 gdb.events.exited.connect (exit_handler)
22716 In the above example we connect our handler @code{exit_handler} to the
22717 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22718 called when the inferior exits. The argument @dfn{event} in this example is
22719 of type @code{gdb.ExitedEvent}. As you can see in the example the
22720 @code{ExitedEvent} object has an attribute which indicates the exit code of
22723 The following is a listing of the event registries that are available and
22724 details of the events they emit:
22729 Emits @code{gdb.ThreadEvent}.
22731 Some events can be thread specific when @value{GDBN} is running in non-stop
22732 mode. When represented in Python, these events all extend
22733 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22734 events which are emitted by this or other modules might extend this event.
22735 Examples of these events are @code{gdb.BreakpointEvent} and
22736 @code{gdb.ContinueEvent}.
22739 @defvar ThreadEvent.inferior_thread
22740 In non-stop mode this attribute will be set to the specific thread which was
22741 involved in the emitted event. Otherwise, it will be set to @code{None}.
22745 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22747 This event indicates that the inferior has been continued after a stop. For
22748 inherited attribute refer to @code{gdb.ThreadEvent} above.
22750 @item events.exited
22751 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22752 @code{events.ExitedEvent} has two attributes:
22754 @defvar ExitedEvent.exit_code
22755 An integer representing the exit code, if available, which the inferior
22756 has returned. (The exit code could be unavailable if, for example,
22757 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22758 the attribute does not exist.
22760 @defvar ExitedEvent inferior
22761 A reference to the inferior which triggered the @code{exited} event.
22766 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22768 Indicates that the inferior has stopped. All events emitted by this registry
22769 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22770 will indicate the stopped thread when @value{GDBN} is running in non-stop
22771 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22773 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22775 This event indicates that the inferior or one of its threads has received as
22776 signal. @code{gdb.SignalEvent} has the following attributes:
22779 @defvar SignalEvent.stop_signal
22780 A string representing the signal received by the inferior. A list of possible
22781 signal values can be obtained by running the command @code{info signals} in
22782 the @value{GDBN} command prompt.
22786 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22788 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22789 been hit, and has the following attributes:
22792 @defvar BreakpointEvent.breakpoints
22793 A sequence containing references to all the breakpoints (type
22794 @code{gdb.Breakpoint}) that were hit.
22795 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22797 @defvar BreakpointEvent.breakpoint
22798 A reference to the first breakpoint that was hit.
22799 This function is maintained for backward compatibility and is now deprecated
22800 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22804 @item events.new_objfile
22805 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22806 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22809 @defvar NewObjFileEvent.new_objfile
22810 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22811 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22817 @node Threads In Python
22818 @subsubsection Threads In Python
22819 @cindex threads in python
22821 @findex gdb.InferiorThread
22822 Python scripts can access information about, and manipulate inferior threads
22823 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22825 The following thread-related functions are available in the @code{gdb}
22828 @findex gdb.selected_thread
22829 @defun gdb.selected_thread ()
22830 This function returns the thread object for the selected thread. If there
22831 is no selected thread, this will return @code{None}.
22834 A @code{gdb.InferiorThread} object has the following attributes:
22837 @defvar InferiorThread.name
22838 The name of the thread. If the user specified a name using
22839 @code{thread name}, then this returns that name. Otherwise, if an
22840 OS-supplied name is available, then it is returned. Otherwise, this
22841 returns @code{None}.
22843 This attribute can be assigned to. The new value must be a string
22844 object, which sets the new name, or @code{None}, which removes any
22845 user-specified thread name.
22848 @defvar InferiorThread.num
22849 ID of the thread, as assigned by GDB.
22852 @defvar InferiorThread.ptid
22853 ID of the thread, as assigned by the operating system. This attribute is a
22854 tuple containing three integers. The first is the Process ID (PID); the second
22855 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22856 Either the LWPID or TID may be 0, which indicates that the operating system
22857 does not use that identifier.
22861 A @code{gdb.InferiorThread} object has the following methods:
22864 @defun InferiorThread.is_valid ()
22865 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22866 @code{False} if not. A @code{gdb.InferiorThread} object will become
22867 invalid if the thread exits, or the inferior that the thread belongs
22868 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22869 exception if it is invalid at the time the method is called.
22872 @defun InferiorThread.switch ()
22873 This changes @value{GDBN}'s currently selected thread to the one represented
22877 @defun InferiorThread.is_stopped ()
22878 Return a Boolean indicating whether the thread is stopped.
22881 @defun InferiorThread.is_running ()
22882 Return a Boolean indicating whether the thread is running.
22885 @defun InferiorThread.is_exited ()
22886 Return a Boolean indicating whether the thread is exited.
22890 @node Commands In Python
22891 @subsubsection Commands In Python
22893 @cindex commands in python
22894 @cindex python commands
22895 You can implement new @value{GDBN} CLI commands in Python. A CLI
22896 command is implemented using an instance of the @code{gdb.Command}
22897 class, most commonly using a subclass.
22899 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
22900 The object initializer for @code{Command} registers the new command
22901 with @value{GDBN}. This initializer is normally invoked from the
22902 subclass' own @code{__init__} method.
22904 @var{name} is the name of the command. If @var{name} consists of
22905 multiple words, then the initial words are looked for as prefix
22906 commands. In this case, if one of the prefix commands does not exist,
22907 an exception is raised.
22909 There is no support for multi-line commands.
22911 @var{command_class} should be one of the @samp{COMMAND_} constants
22912 defined below. This argument tells @value{GDBN} how to categorize the
22913 new command in the help system.
22915 @var{completer_class} is an optional argument. If given, it should be
22916 one of the @samp{COMPLETE_} constants defined below. This argument
22917 tells @value{GDBN} how to perform completion for this command. If not
22918 given, @value{GDBN} will attempt to complete using the object's
22919 @code{complete} method (see below); if no such method is found, an
22920 error will occur when completion is attempted.
22922 @var{prefix} is an optional argument. If @code{True}, then the new
22923 command is a prefix command; sub-commands of this command may be
22926 The help text for the new command is taken from the Python
22927 documentation string for the command's class, if there is one. If no
22928 documentation string is provided, the default value ``This command is
22929 not documented.'' is used.
22932 @cindex don't repeat Python command
22933 @defun Command.dont_repeat ()
22934 By default, a @value{GDBN} command is repeated when the user enters a
22935 blank line at the command prompt. A command can suppress this
22936 behavior by invoking the @code{dont_repeat} method. This is similar
22937 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22940 @defun Command.invoke (argument, from_tty)
22941 This method is called by @value{GDBN} when this command is invoked.
22943 @var{argument} is a string. It is the argument to the command, after
22944 leading and trailing whitespace has been stripped.
22946 @var{from_tty} is a boolean argument. When true, this means that the
22947 command was entered by the user at the terminal; when false it means
22948 that the command came from elsewhere.
22950 If this method throws an exception, it is turned into a @value{GDBN}
22951 @code{error} call. Otherwise, the return value is ignored.
22953 @findex gdb.string_to_argv
22954 To break @var{argument} up into an argv-like string use
22955 @code{gdb.string_to_argv}. This function behaves identically to
22956 @value{GDBN}'s internal argument lexer @code{buildargv}.
22957 It is recommended to use this for consistency.
22958 Arguments are separated by spaces and may be quoted.
22962 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22963 ['1', '2 "3', '4 "5', "6 '7"]
22968 @cindex completion of Python commands
22969 @defun Command.complete (text, word)
22970 This method is called by @value{GDBN} when the user attempts
22971 completion on this command. All forms of completion are handled by
22972 this method, that is, the @key{TAB} and @key{M-?} key bindings
22973 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22976 The arguments @var{text} and @var{word} are both strings. @var{text}
22977 holds the complete command line up to the cursor's location.
22978 @var{word} holds the last word of the command line; this is computed
22979 using a word-breaking heuristic.
22981 The @code{complete} method can return several values:
22984 If the return value is a sequence, the contents of the sequence are
22985 used as the completions. It is up to @code{complete} to ensure that the
22986 contents actually do complete the word. A zero-length sequence is
22987 allowed, it means that there were no completions available. Only
22988 string elements of the sequence are used; other elements in the
22989 sequence are ignored.
22992 If the return value is one of the @samp{COMPLETE_} constants defined
22993 below, then the corresponding @value{GDBN}-internal completion
22994 function is invoked, and its result is used.
22997 All other results are treated as though there were no available
23002 When a new command is registered, it must be declared as a member of
23003 some general class of commands. This is used to classify top-level
23004 commands in the on-line help system; note that prefix commands are not
23005 listed under their own category but rather that of their top-level
23006 command. The available classifications are represented by constants
23007 defined in the @code{gdb} module:
23010 @findex COMMAND_NONE
23011 @findex gdb.COMMAND_NONE
23012 @item gdb.COMMAND_NONE
23013 The command does not belong to any particular class. A command in
23014 this category will not be displayed in any of the help categories.
23016 @findex COMMAND_RUNNING
23017 @findex gdb.COMMAND_RUNNING
23018 @item gdb.COMMAND_RUNNING
23019 The command is related to running the inferior. For example,
23020 @code{start}, @code{step}, and @code{continue} are in this category.
23021 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23022 commands in this category.
23024 @findex COMMAND_DATA
23025 @findex gdb.COMMAND_DATA
23026 @item gdb.COMMAND_DATA
23027 The command is related to data or variables. For example,
23028 @code{call}, @code{find}, and @code{print} are in this category. Type
23029 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23032 @findex COMMAND_STACK
23033 @findex gdb.COMMAND_STACK
23034 @item gdb.COMMAND_STACK
23035 The command has to do with manipulation of the stack. For example,
23036 @code{backtrace}, @code{frame}, and @code{return} are in this
23037 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23038 list of commands in this category.
23040 @findex COMMAND_FILES
23041 @findex gdb.COMMAND_FILES
23042 @item gdb.COMMAND_FILES
23043 This class is used for file-related commands. For example,
23044 @code{file}, @code{list} and @code{section} are in this category.
23045 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23046 commands in this category.
23048 @findex COMMAND_SUPPORT
23049 @findex gdb.COMMAND_SUPPORT
23050 @item gdb.COMMAND_SUPPORT
23051 This should be used for ``support facilities'', generally meaning
23052 things that are useful to the user when interacting with @value{GDBN},
23053 but not related to the state of the inferior. For example,
23054 @code{help}, @code{make}, and @code{shell} are in this category. Type
23055 @kbd{help support} at the @value{GDBN} prompt to see a list of
23056 commands in this category.
23058 @findex COMMAND_STATUS
23059 @findex gdb.COMMAND_STATUS
23060 @item gdb.COMMAND_STATUS
23061 The command is an @samp{info}-related command, that is, related to the
23062 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23063 and @code{show} are in this category. Type @kbd{help status} at the
23064 @value{GDBN} prompt to see a list of commands in this category.
23066 @findex COMMAND_BREAKPOINTS
23067 @findex gdb.COMMAND_BREAKPOINTS
23068 @item gdb.COMMAND_BREAKPOINTS
23069 The command has to do with breakpoints. For example, @code{break},
23070 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23071 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23074 @findex COMMAND_TRACEPOINTS
23075 @findex gdb.COMMAND_TRACEPOINTS
23076 @item gdb.COMMAND_TRACEPOINTS
23077 The command has to do with tracepoints. For example, @code{trace},
23078 @code{actions}, and @code{tfind} are in this category. Type
23079 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23080 commands in this category.
23082 @findex COMMAND_OBSCURE
23083 @findex gdb.COMMAND_OBSCURE
23084 @item gdb.COMMAND_OBSCURE
23085 The command is only used in unusual circumstances, or is not of
23086 general interest to users. For example, @code{checkpoint},
23087 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23088 obscure} at the @value{GDBN} prompt to see a list of commands in this
23091 @findex COMMAND_MAINTENANCE
23092 @findex gdb.COMMAND_MAINTENANCE
23093 @item gdb.COMMAND_MAINTENANCE
23094 The command is only useful to @value{GDBN} maintainers. The
23095 @code{maintenance} and @code{flushregs} commands are in this category.
23096 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23097 commands in this category.
23100 A new command can use a predefined completion function, either by
23101 specifying it via an argument at initialization, or by returning it
23102 from the @code{complete} method. These predefined completion
23103 constants are all defined in the @code{gdb} module:
23106 @findex COMPLETE_NONE
23107 @findex gdb.COMPLETE_NONE
23108 @item gdb.COMPLETE_NONE
23109 This constant means that no completion should be done.
23111 @findex COMPLETE_FILENAME
23112 @findex gdb.COMPLETE_FILENAME
23113 @item gdb.COMPLETE_FILENAME
23114 This constant means that filename completion should be performed.
23116 @findex COMPLETE_LOCATION
23117 @findex gdb.COMPLETE_LOCATION
23118 @item gdb.COMPLETE_LOCATION
23119 This constant means that location completion should be done.
23120 @xref{Specify Location}.
23122 @findex COMPLETE_COMMAND
23123 @findex gdb.COMPLETE_COMMAND
23124 @item gdb.COMPLETE_COMMAND
23125 This constant means that completion should examine @value{GDBN}
23128 @findex COMPLETE_SYMBOL
23129 @findex gdb.COMPLETE_SYMBOL
23130 @item gdb.COMPLETE_SYMBOL
23131 This constant means that completion should be done using symbol names
23135 The following code snippet shows how a trivial CLI command can be
23136 implemented in Python:
23139 class HelloWorld (gdb.Command):
23140 """Greet the whole world."""
23142 def __init__ (self):
23143 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23145 def invoke (self, arg, from_tty):
23146 print "Hello, World!"
23151 The last line instantiates the class, and is necessary to trigger the
23152 registration of the command with @value{GDBN}. Depending on how the
23153 Python code is read into @value{GDBN}, you may need to import the
23154 @code{gdb} module explicitly.
23156 @node Parameters In Python
23157 @subsubsection Parameters In Python
23159 @cindex parameters in python
23160 @cindex python parameters
23161 @tindex gdb.Parameter
23163 You can implement new @value{GDBN} parameters using Python. A new
23164 parameter is implemented as an instance of the @code{gdb.Parameter}
23167 Parameters are exposed to the user via the @code{set} and
23168 @code{show} commands. @xref{Help}.
23170 There are many parameters that already exist and can be set in
23171 @value{GDBN}. Two examples are: @code{set follow fork} and
23172 @code{set charset}. Setting these parameters influences certain
23173 behavior in @value{GDBN}. Similarly, you can define parameters that
23174 can be used to influence behavior in custom Python scripts and commands.
23176 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23177 The object initializer for @code{Parameter} registers the new
23178 parameter with @value{GDBN}. This initializer is normally invoked
23179 from the subclass' own @code{__init__} method.
23181 @var{name} is the name of the new parameter. If @var{name} consists
23182 of multiple words, then the initial words are looked for as prefix
23183 parameters. An example of this can be illustrated with the
23184 @code{set print} set of parameters. If @var{name} is
23185 @code{print foo}, then @code{print} will be searched as the prefix
23186 parameter. In this case the parameter can subsequently be accessed in
23187 @value{GDBN} as @code{set print foo}.
23189 If @var{name} consists of multiple words, and no prefix parameter group
23190 can be found, an exception is raised.
23192 @var{command-class} should be one of the @samp{COMMAND_} constants
23193 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23194 categorize the new parameter in the help system.
23196 @var{parameter-class} should be one of the @samp{PARAM_} constants
23197 defined below. This argument tells @value{GDBN} the type of the new
23198 parameter; this information is used for input validation and
23201 If @var{parameter-class} is @code{PARAM_ENUM}, then
23202 @var{enum-sequence} must be a sequence of strings. These strings
23203 represent the possible values for the parameter.
23205 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23206 of a fourth argument will cause an exception to be thrown.
23208 The help text for the new parameter is taken from the Python
23209 documentation string for the parameter's class, if there is one. If
23210 there is no documentation string, a default value is used.
23213 @defvar Parameter.set_doc
23214 If this attribute exists, and is a string, then its value is used as
23215 the help text for this parameter's @code{set} command. The value is
23216 examined when @code{Parameter.__init__} is invoked; subsequent changes
23220 @defvar Parameter.show_doc
23221 If this attribute exists, and is a string, then its value is used as
23222 the help text for this parameter's @code{show} command. The value is
23223 examined when @code{Parameter.__init__} is invoked; subsequent changes
23227 @defvar Parameter.value
23228 The @code{value} attribute holds the underlying value of the
23229 parameter. It can be read and assigned to just as any other
23230 attribute. @value{GDBN} does validation when assignments are made.
23233 There are two methods that should be implemented in any
23234 @code{Parameter} class. These are:
23236 @defun Parameter.get_set_string (self)
23237 @value{GDBN} will call this method when a @var{parameter}'s value has
23238 been changed via the @code{set} API (for example, @kbd{set foo off}).
23239 The @code{value} attribute has already been populated with the new
23240 value and may be used in output. This method must return a string.
23243 @defun Parameter.get_show_string (self, svalue)
23244 @value{GDBN} will call this method when a @var{parameter}'s
23245 @code{show} API has been invoked (for example, @kbd{show foo}). The
23246 argument @code{svalue} receives the string representation of the
23247 current value. This method must return a string.
23250 When a new parameter is defined, its type must be specified. The
23251 available types are represented by constants defined in the @code{gdb}
23255 @findex PARAM_BOOLEAN
23256 @findex gdb.PARAM_BOOLEAN
23257 @item gdb.PARAM_BOOLEAN
23258 The value is a plain boolean. The Python boolean values, @code{True}
23259 and @code{False} are the only valid values.
23261 @findex PARAM_AUTO_BOOLEAN
23262 @findex gdb.PARAM_AUTO_BOOLEAN
23263 @item gdb.PARAM_AUTO_BOOLEAN
23264 The value has three possible states: true, false, and @samp{auto}. In
23265 Python, true and false are represented using boolean constants, and
23266 @samp{auto} is represented using @code{None}.
23268 @findex PARAM_UINTEGER
23269 @findex gdb.PARAM_UINTEGER
23270 @item gdb.PARAM_UINTEGER
23271 The value is an unsigned integer. The value of 0 should be
23272 interpreted to mean ``unlimited''.
23274 @findex PARAM_INTEGER
23275 @findex gdb.PARAM_INTEGER
23276 @item gdb.PARAM_INTEGER
23277 The value is a signed integer. The value of 0 should be interpreted
23278 to mean ``unlimited''.
23280 @findex PARAM_STRING
23281 @findex gdb.PARAM_STRING
23282 @item gdb.PARAM_STRING
23283 The value is a string. When the user modifies the string, any escape
23284 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23285 translated into corresponding characters and encoded into the current
23288 @findex PARAM_STRING_NOESCAPE
23289 @findex gdb.PARAM_STRING_NOESCAPE
23290 @item gdb.PARAM_STRING_NOESCAPE
23291 The value is a string. When the user modifies the string, escapes are
23292 passed through untranslated.
23294 @findex PARAM_OPTIONAL_FILENAME
23295 @findex gdb.PARAM_OPTIONAL_FILENAME
23296 @item gdb.PARAM_OPTIONAL_FILENAME
23297 The value is a either a filename (a string), or @code{None}.
23299 @findex PARAM_FILENAME
23300 @findex gdb.PARAM_FILENAME
23301 @item gdb.PARAM_FILENAME
23302 The value is a filename. This is just like
23303 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23305 @findex PARAM_ZINTEGER
23306 @findex gdb.PARAM_ZINTEGER
23307 @item gdb.PARAM_ZINTEGER
23308 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23309 is interpreted as itself.
23312 @findex gdb.PARAM_ENUM
23313 @item gdb.PARAM_ENUM
23314 The value is a string, which must be one of a collection string
23315 constants provided when the parameter is created.
23318 @node Functions In Python
23319 @subsubsection Writing new convenience functions
23321 @cindex writing convenience functions
23322 @cindex convenience functions in python
23323 @cindex python convenience functions
23324 @tindex gdb.Function
23326 You can implement new convenience functions (@pxref{Convenience Vars})
23327 in Python. A convenience function is an instance of a subclass of the
23328 class @code{gdb.Function}.
23330 @defun Function.__init__ (name)
23331 The initializer for @code{Function} registers the new function with
23332 @value{GDBN}. The argument @var{name} is the name of the function,
23333 a string. The function will be visible to the user as a convenience
23334 variable of type @code{internal function}, whose name is the same as
23335 the given @var{name}.
23337 The documentation for the new function is taken from the documentation
23338 string for the new class.
23341 @defun Function.invoke (@var{*args})
23342 When a convenience function is evaluated, its arguments are converted
23343 to instances of @code{gdb.Value}, and then the function's
23344 @code{invoke} method is called. Note that @value{GDBN} does not
23345 predetermine the arity of convenience functions. Instead, all
23346 available arguments are passed to @code{invoke}, following the
23347 standard Python calling convention. In particular, a convenience
23348 function can have default values for parameters without ill effect.
23350 The return value of this method is used as its value in the enclosing
23351 expression. If an ordinary Python value is returned, it is converted
23352 to a @code{gdb.Value} following the usual rules.
23355 The following code snippet shows how a trivial convenience function can
23356 be implemented in Python:
23359 class Greet (gdb.Function):
23360 """Return string to greet someone.
23361 Takes a name as argument."""
23363 def __init__ (self):
23364 super (Greet, self).__init__ ("greet")
23366 def invoke (self, name):
23367 return "Hello, %s!" % name.string ()
23372 The last line instantiates the class, and is necessary to trigger the
23373 registration of the function with @value{GDBN}. Depending on how the
23374 Python code is read into @value{GDBN}, you may need to import the
23375 @code{gdb} module explicitly.
23377 @node Progspaces In Python
23378 @subsubsection Program Spaces In Python
23380 @cindex progspaces in python
23381 @tindex gdb.Progspace
23383 A program space, or @dfn{progspace}, represents a symbolic view
23384 of an address space.
23385 It consists of all of the objfiles of the program.
23386 @xref{Objfiles In Python}.
23387 @xref{Inferiors and Programs, program spaces}, for more details
23388 about program spaces.
23390 The following progspace-related functions are available in the
23393 @findex gdb.current_progspace
23394 @defun gdb.current_progspace ()
23395 This function returns the program space of the currently selected inferior.
23396 @xref{Inferiors and Programs}.
23399 @findex gdb.progspaces
23400 @defun gdb.progspaces ()
23401 Return a sequence of all the progspaces currently known to @value{GDBN}.
23404 Each progspace is represented by an instance of the @code{gdb.Progspace}
23407 @defvar Progspace.filename
23408 The file name of the progspace as a string.
23411 @defvar Progspace.pretty_printers
23412 The @code{pretty_printers} attribute is a list of functions. It is
23413 used to look up pretty-printers. A @code{Value} is passed to each
23414 function in order; if the function returns @code{None}, then the
23415 search continues. Otherwise, the return value should be an object
23416 which is used to format the value. @xref{Pretty Printing API}, for more
23420 @node Objfiles In Python
23421 @subsubsection Objfiles In Python
23423 @cindex objfiles in python
23424 @tindex gdb.Objfile
23426 @value{GDBN} loads symbols for an inferior from various
23427 symbol-containing files (@pxref{Files}). These include the primary
23428 executable file, any shared libraries used by the inferior, and any
23429 separate debug info files (@pxref{Separate Debug Files}).
23430 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23432 The following objfile-related functions are available in the
23435 @findex gdb.current_objfile
23436 @defun gdb.current_objfile ()
23437 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23438 sets the ``current objfile'' to the corresponding objfile. This
23439 function returns the current objfile. If there is no current objfile,
23440 this function returns @code{None}.
23443 @findex gdb.objfiles
23444 @defun gdb.objfiles ()
23445 Return a sequence of all the objfiles current known to @value{GDBN}.
23446 @xref{Objfiles In Python}.
23449 Each objfile is represented by an instance of the @code{gdb.Objfile}
23452 @defvar Objfile.filename
23453 The file name of the objfile as a string.
23456 @defvar Objfile.pretty_printers
23457 The @code{pretty_printers} attribute is a list of functions. It is
23458 used to look up pretty-printers. A @code{Value} is passed to each
23459 function in order; if the function returns @code{None}, then the
23460 search continues. Otherwise, the return value should be an object
23461 which is used to format the value. @xref{Pretty Printing API}, for more
23465 A @code{gdb.Objfile} object has the following methods:
23467 @defun Objfile.is_valid ()
23468 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23469 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23470 if the object file it refers to is not loaded in @value{GDBN} any
23471 longer. All other @code{gdb.Objfile} methods will throw an exception
23472 if it is invalid at the time the method is called.
23475 @node Frames In Python
23476 @subsubsection Accessing inferior stack frames from Python.
23478 @cindex frames in python
23479 When the debugged program stops, @value{GDBN} is able to analyze its call
23480 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23481 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23482 while its corresponding frame exists in the inferior's stack. If you try
23483 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23484 exception (@pxref{Exception Handling}).
23486 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23490 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23494 The following frame-related functions are available in the @code{gdb} module:
23496 @findex gdb.selected_frame
23497 @defun gdb.selected_frame ()
23498 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23501 @findex gdb.newest_frame
23502 @defun gdb.newest_frame ()
23503 Return the newest frame object for the selected thread.
23506 @defun gdb.frame_stop_reason_string (reason)
23507 Return a string explaining the reason why @value{GDBN} stopped unwinding
23508 frames, as expressed by the given @var{reason} code (an integer, see the
23509 @code{unwind_stop_reason} method further down in this section).
23512 A @code{gdb.Frame} object has the following methods:
23515 @defun Frame.is_valid ()
23516 Returns true if the @code{gdb.Frame} object is valid, false if not.
23517 A frame object can become invalid if the frame it refers to doesn't
23518 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23519 an exception if it is invalid at the time the method is called.
23522 @defun Frame.name ()
23523 Returns the function name of the frame, or @code{None} if it can't be
23527 @defun Frame.type ()
23528 Returns the type of the frame. The value can be one of:
23530 @item gdb.NORMAL_FRAME
23531 An ordinary stack frame.
23533 @item gdb.DUMMY_FRAME
23534 A fake stack frame that was created by @value{GDBN} when performing an
23535 inferior function call.
23537 @item gdb.INLINE_FRAME
23538 A frame representing an inlined function. The function was inlined
23539 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23541 @item gdb.TAILCALL_FRAME
23542 A frame representing a tail call. @xref{Tail Call Frames}.
23544 @item gdb.SIGTRAMP_FRAME
23545 A signal trampoline frame. This is the frame created by the OS when
23546 it calls into a signal handler.
23548 @item gdb.ARCH_FRAME
23549 A fake stack frame representing a cross-architecture call.
23551 @item gdb.SENTINEL_FRAME
23552 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23557 @defun Frame.unwind_stop_reason ()
23558 Return an integer representing the reason why it's not possible to find
23559 more frames toward the outermost frame. Use
23560 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23561 function to a string. The value can be one of:
23564 @item gdb.FRAME_UNWIND_NO_REASON
23565 No particular reason (older frames should be available).
23567 @item gdb.FRAME_UNWIND_NULL_ID
23568 The previous frame's analyzer returns an invalid result.
23570 @item gdb.FRAME_UNWIND_OUTERMOST
23571 This frame is the outermost.
23573 @item gdb.FRAME_UNWIND_UNAVAILABLE
23574 Cannot unwind further, because that would require knowing the
23575 values of registers or memory that have not been collected.
23577 @item gdb.FRAME_UNWIND_INNER_ID
23578 This frame ID looks like it ought to belong to a NEXT frame,
23579 but we got it for a PREV frame. Normally, this is a sign of
23580 unwinder failure. It could also indicate stack corruption.
23582 @item gdb.FRAME_UNWIND_SAME_ID
23583 This frame has the same ID as the previous one. That means
23584 that unwinding further would almost certainly give us another
23585 frame with exactly the same ID, so break the chain. Normally,
23586 this is a sign of unwinder failure. It could also indicate
23589 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23590 The frame unwinder did not find any saved PC, but we needed
23591 one to unwind further.
23593 @item gdb.FRAME_UNWIND_FIRST_ERROR
23594 Any stop reason greater or equal to this value indicates some kind
23595 of error. This special value facilitates writing code that tests
23596 for errors in unwinding in a way that will work correctly even if
23597 the list of the other values is modified in future @value{GDBN}
23598 versions. Using it, you could write:
23600 reason = gdb.selected_frame().unwind_stop_reason ()
23601 reason_str = gdb.frame_stop_reason_string (reason)
23602 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23603 print "An error occured: %s" % reason_str
23610 Returns the frame's resume address.
23613 @defun Frame.block ()
23614 Return the frame's code block. @xref{Blocks In Python}.
23617 @defun Frame.function ()
23618 Return the symbol for the function corresponding to this frame.
23619 @xref{Symbols In Python}.
23622 @defun Frame.older ()
23623 Return the frame that called this frame.
23626 @defun Frame.newer ()
23627 Return the frame called by this frame.
23630 @defun Frame.find_sal ()
23631 Return the frame's symtab and line object.
23632 @xref{Symbol Tables In Python}.
23635 @defun Frame.read_var (variable @r{[}, block@r{]})
23636 Return the value of @var{variable} in this frame. If the optional
23637 argument @var{block} is provided, search for the variable from that
23638 block; otherwise start at the frame's current block (which is
23639 determined by the frame's current program counter). @var{variable}
23640 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23641 @code{gdb.Block} object.
23644 @defun Frame.select ()
23645 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23650 @node Blocks In Python
23651 @subsubsection Accessing frame blocks from Python.
23653 @cindex blocks in python
23656 Within each frame, @value{GDBN} maintains information on each block
23657 stored in that frame. These blocks are organized hierarchically, and
23658 are represented individually in Python as a @code{gdb.Block}.
23659 Please see @ref{Frames In Python}, for a more in-depth discussion on
23660 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23661 detailed technical information on @value{GDBN}'s book-keeping of the
23664 The following block-related functions are available in the @code{gdb}
23667 @findex gdb.block_for_pc
23668 @defun gdb.block_for_pc (pc)
23669 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23670 block cannot be found for the @var{pc} value specified, the function
23671 will return @code{None}.
23674 A @code{gdb.Block} object has the following methods:
23677 @defun Block.is_valid ()
23678 Returns @code{True} if the @code{gdb.Block} object is valid,
23679 @code{False} if not. A block object can become invalid if the block it
23680 refers to doesn't exist anymore in the inferior. All other
23681 @code{gdb.Block} methods will throw an exception if it is invalid at
23682 the time the method is called. This method is also made available to
23683 the Python iterator object that @code{gdb.Block} provides in an iteration
23684 context and via the Python @code{iter} built-in function.
23688 A @code{gdb.Block} object has the following attributes:
23691 @defvar Block.start
23692 The start address of the block. This attribute is not writable.
23696 The end address of the block. This attribute is not writable.
23699 @defvar Block.function
23700 The name of the block represented as a @code{gdb.Symbol}. If the
23701 block is not named, then this attribute holds @code{None}. This
23702 attribute is not writable.
23705 @defvar Block.superblock
23706 The block containing this block. If this parent block does not exist,
23707 this attribute holds @code{None}. This attribute is not writable.
23710 @defvar Block.global_block
23711 The global block associated with this block. This attribute is not
23715 @defvar Block.static_block
23716 The static block associated with this block. This attribute is not
23720 @defvar Block.is_global
23721 @code{True} if the @code{gdb.Block} object is a global block,
23722 @code{False} if not. This attribute is not
23726 @defvar Block.is_static
23727 @code{True} if the @code{gdb.Block} object is a static block,
23728 @code{False} if not. This attribute is not writable.
23732 @node Symbols In Python
23733 @subsubsection Python representation of Symbols.
23735 @cindex symbols in python
23738 @value{GDBN} represents every variable, function and type as an
23739 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23740 Similarly, Python represents these symbols in @value{GDBN} with the
23741 @code{gdb.Symbol} object.
23743 The following symbol-related functions are available in the @code{gdb}
23746 @findex gdb.lookup_symbol
23747 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23748 This function searches for a symbol by name. The search scope can be
23749 restricted to the parameters defined in the optional domain and block
23752 @var{name} is the name of the symbol. It must be a string. The
23753 optional @var{block} argument restricts the search to symbols visible
23754 in that @var{block}. The @var{block} argument must be a
23755 @code{gdb.Block} object. If omitted, the block for the current frame
23756 is used. The optional @var{domain} argument restricts
23757 the search to the domain type. The @var{domain} argument must be a
23758 domain constant defined in the @code{gdb} module and described later
23761 The result is a tuple of two elements.
23762 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23764 If the symbol is found, the second element is @code{True} if the symbol
23765 is a field of a method's object (e.g., @code{this} in C@t{++}),
23766 otherwise it is @code{False}.
23767 If the symbol is not found, the second element is @code{False}.
23770 @findex gdb.lookup_global_symbol
23771 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23772 This function searches for a global symbol by name.
23773 The search scope can be restricted to by the domain argument.
23775 @var{name} is the name of the symbol. It must be a string.
23776 The optional @var{domain} argument restricts the search to the domain type.
23777 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23778 module and described later in this chapter.
23780 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23784 A @code{gdb.Symbol} object has the following attributes:
23787 @defvar Symbol.type
23788 The type of the symbol or @code{None} if no type is recorded.
23789 This attribute is represented as a @code{gdb.Type} object.
23790 @xref{Types In Python}. This attribute is not writable.
23793 @defvar Symbol.symtab
23794 The symbol table in which the symbol appears. This attribute is
23795 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23796 Python}. This attribute is not writable.
23799 @defvar Symbol.name
23800 The name of the symbol as a string. This attribute is not writable.
23803 @defvar Symbol.linkage_name
23804 The name of the symbol, as used by the linker (i.e., may be mangled).
23805 This attribute is not writable.
23808 @defvar Symbol.print_name
23809 The name of the symbol in a form suitable for output. This is either
23810 @code{name} or @code{linkage_name}, depending on whether the user
23811 asked @value{GDBN} to display demangled or mangled names.
23814 @defvar Symbol.addr_class
23815 The address class of the symbol. This classifies how to find the value
23816 of a symbol. Each address class is a constant defined in the
23817 @code{gdb} module and described later in this chapter.
23820 @defvar Symbol.is_argument
23821 @code{True} if the symbol is an argument of a function.
23824 @defvar Symbol.is_constant
23825 @code{True} if the symbol is a constant.
23828 @defvar Symbol.is_function
23829 @code{True} if the symbol is a function or a method.
23832 @defvar Symbol.is_variable
23833 @code{True} if the symbol is a variable.
23837 A @code{gdb.Symbol} object has the following methods:
23840 @defun Symbol.is_valid ()
23841 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23842 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23843 the symbol it refers to does not exist in @value{GDBN} any longer.
23844 All other @code{gdb.Symbol} methods will throw an exception if it is
23845 invalid at the time the method is called.
23849 The available domain categories in @code{gdb.Symbol} are represented
23850 as constants in the @code{gdb} module:
23853 @findex SYMBOL_UNDEF_DOMAIN
23854 @findex gdb.SYMBOL_UNDEF_DOMAIN
23855 @item gdb.SYMBOL_UNDEF_DOMAIN
23856 This is used when a domain has not been discovered or none of the
23857 following domains apply. This usually indicates an error either
23858 in the symbol information or in @value{GDBN}'s handling of symbols.
23859 @findex SYMBOL_VAR_DOMAIN
23860 @findex gdb.SYMBOL_VAR_DOMAIN
23861 @item gdb.SYMBOL_VAR_DOMAIN
23862 This domain contains variables, function names, typedef names and enum
23864 @findex SYMBOL_STRUCT_DOMAIN
23865 @findex gdb.SYMBOL_STRUCT_DOMAIN
23866 @item gdb.SYMBOL_STRUCT_DOMAIN
23867 This domain holds struct, union and enum type names.
23868 @findex SYMBOL_LABEL_DOMAIN
23869 @findex gdb.SYMBOL_LABEL_DOMAIN
23870 @item gdb.SYMBOL_LABEL_DOMAIN
23871 This domain contains names of labels (for gotos).
23872 @findex SYMBOL_VARIABLES_DOMAIN
23873 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23874 @item gdb.SYMBOL_VARIABLES_DOMAIN
23875 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23876 contains everything minus functions and types.
23877 @findex SYMBOL_FUNCTIONS_DOMAIN
23878 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23879 @item gdb.SYMBOL_FUNCTION_DOMAIN
23880 This domain contains all functions.
23881 @findex SYMBOL_TYPES_DOMAIN
23882 @findex gdb.SYMBOL_TYPES_DOMAIN
23883 @item gdb.SYMBOL_TYPES_DOMAIN
23884 This domain contains all types.
23887 The available address class categories in @code{gdb.Symbol} are represented
23888 as constants in the @code{gdb} module:
23891 @findex SYMBOL_LOC_UNDEF
23892 @findex gdb.SYMBOL_LOC_UNDEF
23893 @item gdb.SYMBOL_LOC_UNDEF
23894 If this is returned by address class, it indicates an error either in
23895 the symbol information or in @value{GDBN}'s handling of symbols.
23896 @findex SYMBOL_LOC_CONST
23897 @findex gdb.SYMBOL_LOC_CONST
23898 @item gdb.SYMBOL_LOC_CONST
23899 Value is constant int.
23900 @findex SYMBOL_LOC_STATIC
23901 @findex gdb.SYMBOL_LOC_STATIC
23902 @item gdb.SYMBOL_LOC_STATIC
23903 Value is at a fixed address.
23904 @findex SYMBOL_LOC_REGISTER
23905 @findex gdb.SYMBOL_LOC_REGISTER
23906 @item gdb.SYMBOL_LOC_REGISTER
23907 Value is in a register.
23908 @findex SYMBOL_LOC_ARG
23909 @findex gdb.SYMBOL_LOC_ARG
23910 @item gdb.SYMBOL_LOC_ARG
23911 Value is an argument. This value is at the offset stored within the
23912 symbol inside the frame's argument list.
23913 @findex SYMBOL_LOC_REF_ARG
23914 @findex gdb.SYMBOL_LOC_REF_ARG
23915 @item gdb.SYMBOL_LOC_REF_ARG
23916 Value address is stored in the frame's argument list. Just like
23917 @code{LOC_ARG} except that the value's address is stored at the
23918 offset, not the value itself.
23919 @findex SYMBOL_LOC_REGPARM_ADDR
23920 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23921 @item gdb.SYMBOL_LOC_REGPARM_ADDR
23922 Value is a specified register. Just like @code{LOC_REGISTER} except
23923 the register holds the address of the argument instead of the argument
23925 @findex SYMBOL_LOC_LOCAL
23926 @findex gdb.SYMBOL_LOC_LOCAL
23927 @item gdb.SYMBOL_LOC_LOCAL
23928 Value is a local variable.
23929 @findex SYMBOL_LOC_TYPEDEF
23930 @findex gdb.SYMBOL_LOC_TYPEDEF
23931 @item gdb.SYMBOL_LOC_TYPEDEF
23932 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23934 @findex SYMBOL_LOC_BLOCK
23935 @findex gdb.SYMBOL_LOC_BLOCK
23936 @item gdb.SYMBOL_LOC_BLOCK
23938 @findex SYMBOL_LOC_CONST_BYTES
23939 @findex gdb.SYMBOL_LOC_CONST_BYTES
23940 @item gdb.SYMBOL_LOC_CONST_BYTES
23941 Value is a byte-sequence.
23942 @findex SYMBOL_LOC_UNRESOLVED
23943 @findex gdb.SYMBOL_LOC_UNRESOLVED
23944 @item gdb.SYMBOL_LOC_UNRESOLVED
23945 Value is at a fixed address, but the address of the variable has to be
23946 determined from the minimal symbol table whenever the variable is
23948 @findex SYMBOL_LOC_OPTIMIZED_OUT
23949 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23950 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
23951 The value does not actually exist in the program.
23952 @findex SYMBOL_LOC_COMPUTED
23953 @findex gdb.SYMBOL_LOC_COMPUTED
23954 @item gdb.SYMBOL_LOC_COMPUTED
23955 The value's address is a computed location.
23958 @node Symbol Tables In Python
23959 @subsubsection Symbol table representation in Python.
23961 @cindex symbol tables in python
23963 @tindex gdb.Symtab_and_line
23965 Access to symbol table data maintained by @value{GDBN} on the inferior
23966 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23967 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23968 from the @code{find_sal} method in @code{gdb.Frame} object.
23969 @xref{Frames In Python}.
23971 For more information on @value{GDBN}'s symbol table management, see
23972 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23974 A @code{gdb.Symtab_and_line} object has the following attributes:
23977 @defvar Symtab_and_line.symtab
23978 The symbol table object (@code{gdb.Symtab}) for this frame.
23979 This attribute is not writable.
23982 @defvar Symtab_and_line.pc
23983 Indicates the current program counter address. This attribute is not
23987 @defvar Symtab_and_line.line
23988 Indicates the current line number for this object. This
23989 attribute is not writable.
23993 A @code{gdb.Symtab_and_line} object has the following methods:
23996 @defun Symtab_and_line.is_valid ()
23997 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23998 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23999 invalid if the Symbol table and line object it refers to does not
24000 exist in @value{GDBN} any longer. All other
24001 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24002 invalid at the time the method is called.
24006 A @code{gdb.Symtab} object has the following attributes:
24009 @defvar Symtab.filename
24010 The symbol table's source filename. This attribute is not writable.
24013 @defvar Symtab.objfile
24014 The symbol table's backing object file. @xref{Objfiles In Python}.
24015 This attribute is not writable.
24019 A @code{gdb.Symtab} object has the following methods:
24022 @defun Symtab.is_valid ()
24023 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24024 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24025 the symbol table it refers to does not exist in @value{GDBN} any
24026 longer. All other @code{gdb.Symtab} methods will throw an exception
24027 if it is invalid at the time the method is called.
24030 @defun Symtab.fullname ()
24031 Return the symbol table's source absolute file name.
24035 @node Breakpoints In Python
24036 @subsubsection Manipulating breakpoints using Python
24038 @cindex breakpoints in python
24039 @tindex gdb.Breakpoint
24041 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24044 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24045 Create a new breakpoint. @var{spec} is a string naming the
24046 location of the breakpoint, or an expression that defines a
24047 watchpoint. The contents can be any location recognized by the
24048 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24049 command. The optional @var{type} denotes the breakpoint to create
24050 from the types defined later in this chapter. This argument can be
24051 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24052 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24053 allows the breakpoint to become invisible to the user. The breakpoint
24054 will neither be reported when created, nor will it be listed in the
24055 output from @code{info breakpoints} (but will be listed with the
24056 @code{maint info breakpoints} command). The optional @var{wp_class}
24057 argument defines the class of watchpoint to create, if @var{type} is
24058 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24059 assumed to be a @code{gdb.WP_WRITE} class.
24062 @defun Breakpoint.stop (self)
24063 The @code{gdb.Breakpoint} class can be sub-classed and, in
24064 particular, you may choose to implement the @code{stop} method.
24065 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24066 it will be called when the inferior reaches any location of a
24067 breakpoint which instantiates that sub-class. If the method returns
24068 @code{True}, the inferior will be stopped at the location of the
24069 breakpoint, otherwise the inferior will continue.
24071 If there are multiple breakpoints at the same location with a
24072 @code{stop} method, each one will be called regardless of the
24073 return status of the previous. This ensures that all @code{stop}
24074 methods have a chance to execute at that location. In this scenario
24075 if one of the methods returns @code{True} but the others return
24076 @code{False}, the inferior will still be stopped.
24078 You should not alter the execution state of the inferior (i.e.@:, step,
24079 next, etc.), alter the current frame context (i.e.@:, change the current
24080 active frame), or alter, add or delete any breakpoint. As a general
24081 rule, you should not alter any data within @value{GDBN} or the inferior
24084 Example @code{stop} implementation:
24087 class MyBreakpoint (gdb.Breakpoint):
24089 inf_val = gdb.parse_and_eval("foo")
24096 The available watchpoint types represented by constants are defined in the
24101 @findex gdb.WP_READ
24103 Read only watchpoint.
24106 @findex gdb.WP_WRITE
24108 Write only watchpoint.
24111 @findex gdb.WP_ACCESS
24112 @item gdb.WP_ACCESS
24113 Read/Write watchpoint.
24116 @defun Breakpoint.is_valid ()
24117 Return @code{True} if this @code{Breakpoint} object is valid,
24118 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24119 if the user deletes the breakpoint. In this case, the object still
24120 exists, but the underlying breakpoint does not. In the cases of
24121 watchpoint scope, the watchpoint remains valid even if execution of the
24122 inferior leaves the scope of that watchpoint.
24125 @defun Breakpoint.delete
24126 Permanently deletes the @value{GDBN} breakpoint. This also
24127 invalidates the Python @code{Breakpoint} object. Any further access
24128 to this object's attributes or methods will raise an error.
24131 @defvar Breakpoint.enabled
24132 This attribute is @code{True} if the breakpoint is enabled, and
24133 @code{False} otherwise. This attribute is writable.
24136 @defvar Breakpoint.silent
24137 This attribute is @code{True} if the breakpoint is silent, and
24138 @code{False} otherwise. This attribute is writable.
24140 Note that a breakpoint can also be silent if it has commands and the
24141 first command is @code{silent}. This is not reported by the
24142 @code{silent} attribute.
24145 @defvar Breakpoint.thread
24146 If the breakpoint is thread-specific, this attribute holds the thread
24147 id. If the breakpoint is not thread-specific, this attribute is
24148 @code{None}. This attribute is writable.
24151 @defvar Breakpoint.task
24152 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24153 id. If the breakpoint is not task-specific (or the underlying
24154 language is not Ada), this attribute is @code{None}. This attribute
24158 @defvar Breakpoint.ignore_count
24159 This attribute holds the ignore count for the breakpoint, an integer.
24160 This attribute is writable.
24163 @defvar Breakpoint.number
24164 This attribute holds the breakpoint's number --- the identifier used by
24165 the user to manipulate the breakpoint. This attribute is not writable.
24168 @defvar Breakpoint.type
24169 This attribute holds the breakpoint's type --- the identifier used to
24170 determine the actual breakpoint type or use-case. This attribute is not
24174 @defvar Breakpoint.visible
24175 This attribute tells whether the breakpoint is visible to the user
24176 when set, or when the @samp{info breakpoints} command is run. This
24177 attribute is not writable.
24180 The available types are represented by constants defined in the @code{gdb}
24184 @findex BP_BREAKPOINT
24185 @findex gdb.BP_BREAKPOINT
24186 @item gdb.BP_BREAKPOINT
24187 Normal code breakpoint.
24189 @findex BP_WATCHPOINT
24190 @findex gdb.BP_WATCHPOINT
24191 @item gdb.BP_WATCHPOINT
24192 Watchpoint breakpoint.
24194 @findex BP_HARDWARE_WATCHPOINT
24195 @findex gdb.BP_HARDWARE_WATCHPOINT
24196 @item gdb.BP_HARDWARE_WATCHPOINT
24197 Hardware assisted watchpoint.
24199 @findex BP_READ_WATCHPOINT
24200 @findex gdb.BP_READ_WATCHPOINT
24201 @item gdb.BP_READ_WATCHPOINT
24202 Hardware assisted read watchpoint.
24204 @findex BP_ACCESS_WATCHPOINT
24205 @findex gdb.BP_ACCESS_WATCHPOINT
24206 @item gdb.BP_ACCESS_WATCHPOINT
24207 Hardware assisted access watchpoint.
24210 @defvar Breakpoint.hit_count
24211 This attribute holds the hit count for the breakpoint, an integer.
24212 This attribute is writable, but currently it can only be set to zero.
24215 @defvar Breakpoint.location
24216 This attribute holds the location of the breakpoint, as specified by
24217 the user. It is a string. If the breakpoint does not have a location
24218 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24219 attribute is not writable.
24222 @defvar Breakpoint.expression
24223 This attribute holds a breakpoint expression, as specified by
24224 the user. It is a string. If the breakpoint does not have an
24225 expression (the breakpoint is not a watchpoint) the attribute's value
24226 is @code{None}. This attribute is not writable.
24229 @defvar Breakpoint.condition
24230 This attribute holds the condition of the breakpoint, as specified by
24231 the user. It is a string. If there is no condition, this attribute's
24232 value is @code{None}. This attribute is writable.
24235 @defvar Breakpoint.commands
24236 This attribute holds the commands attached to the breakpoint. If
24237 there are commands, this attribute's value is a string holding all the
24238 commands, separated by newlines. If there are no commands, this
24239 attribute is @code{None}. This attribute is not writable.
24242 @node Lazy Strings In Python
24243 @subsubsection Python representation of lazy strings.
24245 @cindex lazy strings in python
24246 @tindex gdb.LazyString
24248 A @dfn{lazy string} is a string whose contents is not retrieved or
24249 encoded until it is needed.
24251 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24252 @code{address} that points to a region of memory, an @code{encoding}
24253 that will be used to encode that region of memory, and a @code{length}
24254 to delimit the region of memory that represents the string. The
24255 difference between a @code{gdb.LazyString} and a string wrapped within
24256 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24257 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24258 retrieved and encoded during printing, while a @code{gdb.Value}
24259 wrapping a string is immediately retrieved and encoded on creation.
24261 A @code{gdb.LazyString} object has the following functions:
24263 @defun LazyString.value ()
24264 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24265 will point to the string in memory, but will lose all the delayed
24266 retrieval, encoding and handling that @value{GDBN} applies to a
24267 @code{gdb.LazyString}.
24270 @defvar LazyString.address
24271 This attribute holds the address of the string. This attribute is not
24275 @defvar LazyString.length
24276 This attribute holds the length of the string in characters. If the
24277 length is -1, then the string will be fetched and encoded up to the
24278 first null of appropriate width. This attribute is not writable.
24281 @defvar LazyString.encoding
24282 This attribute holds the encoding that will be applied to the string
24283 when the string is printed by @value{GDBN}. If the encoding is not
24284 set, or contains an empty string, then @value{GDBN} will select the
24285 most appropriate encoding when the string is printed. This attribute
24289 @defvar LazyString.type
24290 This attribute holds the type that is represented by the lazy string's
24291 type. For a lazy string this will always be a pointer type. To
24292 resolve this to the lazy string's character type, use the type's
24293 @code{target} method. @xref{Types In Python}. This attribute is not
24298 @subsection Auto-loading
24299 @cindex auto-loading, Python
24301 When a new object file is read (for example, due to the @code{file}
24302 command, or because the inferior has loaded a shared library),
24303 @value{GDBN} will look for Python support scripts in several ways:
24304 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24307 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24308 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24309 * Which flavor to choose?::
24312 The auto-loading feature is useful for supplying application-specific
24313 debugging commands and scripts.
24315 Auto-loading can be enabled or disabled,
24316 and the list of auto-loaded scripts can be printed.
24319 @kindex set auto-load-scripts
24320 @item set auto-load-scripts [yes|no]
24321 Enable or disable the auto-loading of Python scripts.
24323 @kindex show auto-load-scripts
24324 @item show auto-load-scripts
24325 Show whether auto-loading of Python scripts is enabled or disabled.
24327 @kindex info auto-load-scripts
24328 @cindex print list of auto-loaded scripts
24329 @item info auto-load-scripts [@var{regexp}]
24330 Print the list of all scripts that @value{GDBN} auto-loaded.
24332 Also printed is the list of scripts that were mentioned in
24333 the @code{.debug_gdb_scripts} section and were not found
24334 (@pxref{.debug_gdb_scripts section}).
24335 This is useful because their names are not printed when @value{GDBN}
24336 tries to load them and fails. There may be many of them, and printing
24337 an error message for each one is problematic.
24339 If @var{regexp} is supplied only scripts with matching names are printed.
24344 (gdb) info auto-load-scripts
24346 Yes py-section-script.py
24347 full name: /tmp/py-section-script.py
24348 Missing my-foo-pretty-printers.py
24352 When reading an auto-loaded file, @value{GDBN} sets the
24353 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24354 function (@pxref{Objfiles In Python}). This can be useful for
24355 registering objfile-specific pretty-printers.
24357 @node objfile-gdb.py file
24358 @subsubsection The @file{@var{objfile}-gdb.py} file
24359 @cindex @file{@var{objfile}-gdb.py}
24361 When a new object file is read, @value{GDBN} looks for
24362 a file named @file{@var{objfile}-gdb.py},
24363 where @var{objfile} is the object file's real name, formed by ensuring
24364 that the file name is absolute, following all symlinks, and resolving
24365 @code{.} and @code{..} components. If this file exists and is
24366 readable, @value{GDBN} will evaluate it as a Python script.
24368 If this file does not exist, and if the parameter
24369 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24370 then @value{GDBN} will look for @var{real-name} in all of the
24371 directories mentioned in the value of @code{debug-file-directory}.
24373 Finally, if this file does not exist, then @value{GDBN} will look for
24374 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24375 @var{data-directory} is @value{GDBN}'s data directory (available via
24376 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24377 is the object file's real name, as described above.
24379 @value{GDBN} does not track which files it has already auto-loaded this way.
24380 @value{GDBN} will load the associated script every time the corresponding
24381 @var{objfile} is opened.
24382 So your @file{-gdb.py} file should be careful to avoid errors if it
24383 is evaluated more than once.
24385 @node .debug_gdb_scripts section
24386 @subsubsection The @code{.debug_gdb_scripts} section
24387 @cindex @code{.debug_gdb_scripts} section
24389 For systems using file formats like ELF and COFF,
24390 when @value{GDBN} loads a new object file
24391 it will look for a special section named @samp{.debug_gdb_scripts}.
24392 If this section exists, its contents is a list of names of scripts to load.
24394 @value{GDBN} will look for each specified script file first in the
24395 current directory and then along the source search path
24396 (@pxref{Source Path, ,Specifying Source Directories}),
24397 except that @file{$cdir} is not searched, since the compilation
24398 directory is not relevant to scripts.
24400 Entries can be placed in section @code{.debug_gdb_scripts} with,
24401 for example, this GCC macro:
24404 /* Note: The "MS" section flags are to remove duplicates. */
24405 #define DEFINE_GDB_SCRIPT(script_name) \
24407 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24409 .asciz \"" script_name "\"\n\
24415 Then one can reference the macro in a header or source file like this:
24418 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24421 The script name may include directories if desired.
24423 If the macro is put in a header, any application or library
24424 using this header will get a reference to the specified script.
24426 @node Which flavor to choose?
24427 @subsubsection Which flavor to choose?
24429 Given the multiple ways of auto-loading Python scripts, it might not always
24430 be clear which one to choose. This section provides some guidance.
24432 Benefits of the @file{-gdb.py} way:
24436 Can be used with file formats that don't support multiple sections.
24439 Ease of finding scripts for public libraries.
24441 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24442 in the source search path.
24443 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24444 isn't a source directory in which to find the script.
24447 Doesn't require source code additions.
24450 Benefits of the @code{.debug_gdb_scripts} way:
24454 Works with static linking.
24456 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24457 trigger their loading. When an application is statically linked the only
24458 objfile available is the executable, and it is cumbersome to attach all the
24459 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24462 Works with classes that are entirely inlined.
24464 Some classes can be entirely inlined, and thus there may not be an associated
24465 shared library to attach a @file{-gdb.py} script to.
24468 Scripts needn't be copied out of the source tree.
24470 In some circumstances, apps can be built out of large collections of internal
24471 libraries, and the build infrastructure necessary to install the
24472 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24473 cumbersome. It may be easier to specify the scripts in the
24474 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24475 top of the source tree to the source search path.
24478 @node Python modules
24479 @subsection Python modules
24480 @cindex python modules
24482 @value{GDBN} comes with several modules to assist writing Python code.
24485 * gdb.printing:: Building and registering pretty-printers.
24486 * gdb.types:: Utilities for working with types.
24487 * gdb.prompt:: Utilities for prompt value substitution.
24491 @subsubsection gdb.printing
24492 @cindex gdb.printing
24494 This module provides a collection of utilities for working with
24498 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24499 This class specifies the API that makes @samp{info pretty-printer},
24500 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24501 Pretty-printers should generally inherit from this class.
24503 @item SubPrettyPrinter (@var{name})
24504 For printers that handle multiple types, this class specifies the
24505 corresponding API for the subprinters.
24507 @item RegexpCollectionPrettyPrinter (@var{name})
24508 Utility class for handling multiple printers, all recognized via
24509 regular expressions.
24510 @xref{Writing a Pretty-Printer}, for an example.
24512 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24513 Register @var{printer} with the pretty-printer list of @var{obj}.
24514 If @var{replace} is @code{True} then any existing copy of the printer
24515 is replaced. Otherwise a @code{RuntimeError} exception is raised
24516 if a printer with the same name already exists.
24520 @subsubsection gdb.types
24523 This module provides a collection of utilities for working with
24524 @code{gdb.Types} objects.
24527 @item get_basic_type (@var{type})
24528 Return @var{type} with const and volatile qualifiers stripped,
24529 and with typedefs and C@t{++} references converted to the underlying type.
24534 typedef const int const_int;
24536 const_int& foo_ref (foo);
24537 int main () @{ return 0; @}
24544 (gdb) python import gdb.types
24545 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24546 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24550 @item has_field (@var{type}, @var{field})
24551 Return @code{True} if @var{type}, assumed to be a type with fields
24552 (e.g., a structure or union), has field @var{field}.
24554 @item make_enum_dict (@var{enum_type})
24555 Return a Python @code{dictionary} type produced from @var{enum_type}.
24557 @item deep_items (@var{type})
24558 Returns a Python iterator similar to the standard
24559 @code{gdb.Type.iteritems} method, except that the iterator returned
24560 by @code{deep_items} will recursively traverse anonymous struct or
24561 union fields. For example:
24575 Then in @value{GDBN}:
24577 (@value{GDBP}) python import gdb.types
24578 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24579 (@value{GDBP}) python print struct_a.keys ()
24581 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24582 @{['a', 'b0', 'b1']@}
24588 @subsubsection gdb.prompt
24591 This module provides a method for prompt value-substitution.
24594 @item substitute_prompt (@var{string})
24595 Return @var{string} with escape sequences substituted by values. Some
24596 escape sequences take arguments. You can specify arguments inside
24597 ``@{@}'' immediately following the escape sequence.
24599 The escape sequences you can pass to this function are:
24603 Substitute a backslash.
24605 Substitute an ESC character.
24607 Substitute the selected frame; an argument names a frame parameter.
24609 Substitute a newline.
24611 Substitute a parameter's value; the argument names the parameter.
24613 Substitute a carriage return.
24615 Substitute the selected thread; an argument names a thread parameter.
24617 Substitute the version of GDB.
24619 Substitute the current working directory.
24621 Begin a sequence of non-printing characters. These sequences are
24622 typically used with the ESC character, and are not counted in the string
24623 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24624 blue-colored ``(gdb)'' prompt where the length is five.
24626 End a sequence of non-printing characters.
24632 substitute_prompt (``frame: \f,
24633 print arguments: \p@{print frame-arguments@}'')
24636 @exdent will return the string:
24639 "frame: main, print arguments: scalars"
24644 @section Creating new spellings of existing commands
24645 @cindex aliases for commands
24647 It is often useful to define alternate spellings of existing commands.
24648 For example, if a new @value{GDBN} command defined in Python has
24649 a long name to type, it is handy to have an abbreviated version of it
24650 that involves less typing.
24652 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24653 of the @samp{step} command even though it is otherwise an ambiguous
24654 abbreviation of other commands like @samp{set} and @samp{show}.
24656 Aliases are also used to provide shortened or more common versions
24657 of multi-word commands. For example, @value{GDBN} provides the
24658 @samp{tty} alias of the @samp{set inferior-tty} command.
24660 You can define a new alias with the @samp{alias} command.
24665 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24669 @var{ALIAS} specifies the name of the new alias.
24670 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24673 @var{COMMAND} specifies the name of an existing command
24674 that is being aliased.
24676 The @samp{-a} option specifies that the new alias is an abbreviation
24677 of the command. Abbreviations are not shown in command
24678 lists displayed by the @samp{help} command.
24680 The @samp{--} option specifies the end of options,
24681 and is useful when @var{ALIAS} begins with a dash.
24683 Here is a simple example showing how to make an abbreviation
24684 of a command so that there is less to type.
24685 Suppose you were tired of typing @samp{disas}, the current
24686 shortest unambiguous abbreviation of the @samp{disassemble} command
24687 and you wanted an even shorter version named @samp{di}.
24688 The following will accomplish this.
24691 (gdb) alias -a di = disas
24694 Note that aliases are different from user-defined commands.
24695 With a user-defined command, you also need to write documentation
24696 for it with the @samp{document} command.
24697 An alias automatically picks up the documentation of the existing command.
24699 Here is an example where we make @samp{elms} an abbreviation of
24700 @samp{elements} in the @samp{set print elements} command.
24701 This is to show that you can make an abbreviation of any part
24705 (gdb) alias -a set print elms = set print elements
24706 (gdb) alias -a show print elms = show print elements
24707 (gdb) set p elms 20
24709 Limit on string chars or array elements to print is 200.
24712 Note that if you are defining an alias of a @samp{set} command,
24713 and you want to have an alias for the corresponding @samp{show}
24714 command, then you need to define the latter separately.
24716 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24717 @var{ALIAS}, just as they are normally.
24720 (gdb) alias -a set pr elms = set p ele
24723 Finally, here is an example showing the creation of a one word
24724 alias for a more complex command.
24725 This creates alias @samp{spe} of the command @samp{set print elements}.
24728 (gdb) alias spe = set print elements
24733 @chapter Command Interpreters
24734 @cindex command interpreters
24736 @value{GDBN} supports multiple command interpreters, and some command
24737 infrastructure to allow users or user interface writers to switch
24738 between interpreters or run commands in other interpreters.
24740 @value{GDBN} currently supports two command interpreters, the console
24741 interpreter (sometimes called the command-line interpreter or @sc{cli})
24742 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24743 describes both of these interfaces in great detail.
24745 By default, @value{GDBN} will start with the console interpreter.
24746 However, the user may choose to start @value{GDBN} with another
24747 interpreter by specifying the @option{-i} or @option{--interpreter}
24748 startup options. Defined interpreters include:
24752 @cindex console interpreter
24753 The traditional console or command-line interpreter. This is the most often
24754 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24755 @value{GDBN} will use this interpreter.
24758 @cindex mi interpreter
24759 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24760 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24761 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24765 @cindex mi2 interpreter
24766 The current @sc{gdb/mi} interface.
24769 @cindex mi1 interpreter
24770 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24774 @cindex invoke another interpreter
24775 The interpreter being used by @value{GDBN} may not be dynamically
24776 switched at runtime. Although possible, this could lead to a very
24777 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24778 enters the command "interpreter-set console" in a console view,
24779 @value{GDBN} would switch to using the console interpreter, rendering
24780 the IDE inoperable!
24782 @kindex interpreter-exec
24783 Although you may only choose a single interpreter at startup, you may execute
24784 commands in any interpreter from the current interpreter using the appropriate
24785 command. If you are running the console interpreter, simply use the
24786 @code{interpreter-exec} command:
24789 interpreter-exec mi "-data-list-register-names"
24792 @sc{gdb/mi} has a similar command, although it is only available in versions of
24793 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24796 @chapter @value{GDBN} Text User Interface
24798 @cindex Text User Interface
24801 * TUI Overview:: TUI overview
24802 * TUI Keys:: TUI key bindings
24803 * TUI Single Key Mode:: TUI single key mode
24804 * TUI Commands:: TUI-specific commands
24805 * TUI Configuration:: TUI configuration variables
24808 The @value{GDBN} Text User Interface (TUI) is a terminal
24809 interface which uses the @code{curses} library to show the source
24810 file, the assembly output, the program registers and @value{GDBN}
24811 commands in separate text windows. The TUI mode is supported only
24812 on platforms where a suitable version of the @code{curses} library
24815 @pindex @value{GDBTUI}
24816 The TUI mode is enabled by default when you invoke @value{GDBN} as
24817 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
24818 You can also switch in and out of TUI mode while @value{GDBN} runs by
24819 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24820 @xref{TUI Keys, ,TUI Key Bindings}.
24823 @section TUI Overview
24825 In TUI mode, @value{GDBN} can display several text windows:
24829 This window is the @value{GDBN} command window with the @value{GDBN}
24830 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24831 managed using readline.
24834 The source window shows the source file of the program. The current
24835 line and active breakpoints are displayed in this window.
24838 The assembly window shows the disassembly output of the program.
24841 This window shows the processor registers. Registers are highlighted
24842 when their values change.
24845 The source and assembly windows show the current program position
24846 by highlighting the current line and marking it with a @samp{>} marker.
24847 Breakpoints are indicated with two markers. The first marker
24848 indicates the breakpoint type:
24852 Breakpoint which was hit at least once.
24855 Breakpoint which was never hit.
24858 Hardware breakpoint which was hit at least once.
24861 Hardware breakpoint which was never hit.
24864 The second marker indicates whether the breakpoint is enabled or not:
24868 Breakpoint is enabled.
24871 Breakpoint is disabled.
24874 The source, assembly and register windows are updated when the current
24875 thread changes, when the frame changes, or when the program counter
24878 These windows are not all visible at the same time. The command
24879 window is always visible. The others can be arranged in several
24890 source and assembly,
24893 source and registers, or
24896 assembly and registers.
24899 A status line above the command window shows the following information:
24903 Indicates the current @value{GDBN} target.
24904 (@pxref{Targets, ,Specifying a Debugging Target}).
24907 Gives the current process or thread number.
24908 When no process is being debugged, this field is set to @code{No process}.
24911 Gives the current function name for the selected frame.
24912 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24913 When there is no symbol corresponding to the current program counter,
24914 the string @code{??} is displayed.
24917 Indicates the current line number for the selected frame.
24918 When the current line number is not known, the string @code{??} is displayed.
24921 Indicates the current program counter address.
24925 @section TUI Key Bindings
24926 @cindex TUI key bindings
24928 The TUI installs several key bindings in the readline keymaps
24929 @ifset SYSTEM_READLINE
24930 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24932 @ifclear SYSTEM_READLINE
24933 (@pxref{Command Line Editing}).
24935 The following key bindings are installed for both TUI mode and the
24936 @value{GDBN} standard mode.
24945 Enter or leave the TUI mode. When leaving the TUI mode,
24946 the curses window management stops and @value{GDBN} operates using
24947 its standard mode, writing on the terminal directly. When reentering
24948 the TUI mode, control is given back to the curses windows.
24949 The screen is then refreshed.
24953 Use a TUI layout with only one window. The layout will
24954 either be @samp{source} or @samp{assembly}. When the TUI mode
24955 is not active, it will switch to the TUI mode.
24957 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24961 Use a TUI layout with at least two windows. When the current
24962 layout already has two windows, the next layout with two windows is used.
24963 When a new layout is chosen, one window will always be common to the
24964 previous layout and the new one.
24966 Think of it as the Emacs @kbd{C-x 2} binding.
24970 Change the active window. The TUI associates several key bindings
24971 (like scrolling and arrow keys) with the active window. This command
24972 gives the focus to the next TUI window.
24974 Think of it as the Emacs @kbd{C-x o} binding.
24978 Switch in and out of the TUI SingleKey mode that binds single
24979 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24982 The following key bindings only work in the TUI mode:
24987 Scroll the active window one page up.
24991 Scroll the active window one page down.
24995 Scroll the active window one line up.
24999 Scroll the active window one line down.
25003 Scroll the active window one column left.
25007 Scroll the active window one column right.
25011 Refresh the screen.
25014 Because the arrow keys scroll the active window in the TUI mode, they
25015 are not available for their normal use by readline unless the command
25016 window has the focus. When another window is active, you must use
25017 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25018 and @kbd{C-f} to control the command window.
25020 @node TUI Single Key Mode
25021 @section TUI Single Key Mode
25022 @cindex TUI single key mode
25024 The TUI also provides a @dfn{SingleKey} mode, which binds several
25025 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25026 switch into this mode, where the following key bindings are used:
25029 @kindex c @r{(SingleKey TUI key)}
25033 @kindex d @r{(SingleKey TUI key)}
25037 @kindex f @r{(SingleKey TUI key)}
25041 @kindex n @r{(SingleKey TUI key)}
25045 @kindex q @r{(SingleKey TUI key)}
25047 exit the SingleKey mode.
25049 @kindex r @r{(SingleKey TUI key)}
25053 @kindex s @r{(SingleKey TUI key)}
25057 @kindex u @r{(SingleKey TUI key)}
25061 @kindex v @r{(SingleKey TUI key)}
25065 @kindex w @r{(SingleKey TUI key)}
25070 Other keys temporarily switch to the @value{GDBN} command prompt.
25071 The key that was pressed is inserted in the editing buffer so that
25072 it is possible to type most @value{GDBN} commands without interaction
25073 with the TUI SingleKey mode. Once the command is entered the TUI
25074 SingleKey mode is restored. The only way to permanently leave
25075 this mode is by typing @kbd{q} or @kbd{C-x s}.
25079 @section TUI-specific Commands
25080 @cindex TUI commands
25082 The TUI has specific commands to control the text windows.
25083 These commands are always available, even when @value{GDBN} is not in
25084 the TUI mode. When @value{GDBN} is in the standard mode, most
25085 of these commands will automatically switch to the TUI mode.
25087 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25088 terminal, or @value{GDBN} has been started with the machine interface
25089 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25090 these commands will fail with an error, because it would not be
25091 possible or desirable to enable curses window management.
25096 List and give the size of all displayed windows.
25100 Display the next layout.
25103 Display the previous layout.
25106 Display the source window only.
25109 Display the assembly window only.
25112 Display the source and assembly window.
25115 Display the register window together with the source or assembly window.
25119 Make the next window active for scrolling.
25122 Make the previous window active for scrolling.
25125 Make the source window active for scrolling.
25128 Make the assembly window active for scrolling.
25131 Make the register window active for scrolling.
25134 Make the command window active for scrolling.
25138 Refresh the screen. This is similar to typing @kbd{C-L}.
25140 @item tui reg float
25142 Show the floating point registers in the register window.
25144 @item tui reg general
25145 Show the general registers in the register window.
25148 Show the next register group. The list of register groups as well as
25149 their order is target specific. The predefined register groups are the
25150 following: @code{general}, @code{float}, @code{system}, @code{vector},
25151 @code{all}, @code{save}, @code{restore}.
25153 @item tui reg system
25154 Show the system registers in the register window.
25158 Update the source window and the current execution point.
25160 @item winheight @var{name} +@var{count}
25161 @itemx winheight @var{name} -@var{count}
25163 Change the height of the window @var{name} by @var{count}
25164 lines. Positive counts increase the height, while negative counts
25167 @item tabset @var{nchars}
25169 Set the width of tab stops to be @var{nchars} characters.
25172 @node TUI Configuration
25173 @section TUI Configuration Variables
25174 @cindex TUI configuration variables
25176 Several configuration variables control the appearance of TUI windows.
25179 @item set tui border-kind @var{kind}
25180 @kindex set tui border-kind
25181 Select the border appearance for the source, assembly and register windows.
25182 The possible values are the following:
25185 Use a space character to draw the border.
25188 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25191 Use the Alternate Character Set to draw the border. The border is
25192 drawn using character line graphics if the terminal supports them.
25195 @item set tui border-mode @var{mode}
25196 @kindex set tui border-mode
25197 @itemx set tui active-border-mode @var{mode}
25198 @kindex set tui active-border-mode
25199 Select the display attributes for the borders of the inactive windows
25200 or the active window. The @var{mode} can be one of the following:
25203 Use normal attributes to display the border.
25209 Use reverse video mode.
25212 Use half bright mode.
25214 @item half-standout
25215 Use half bright and standout mode.
25218 Use extra bright or bold mode.
25220 @item bold-standout
25221 Use extra bright or bold and standout mode.
25226 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25229 @cindex @sc{gnu} Emacs
25230 A special interface allows you to use @sc{gnu} Emacs to view (and
25231 edit) the source files for the program you are debugging with
25234 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25235 executable file you want to debug as an argument. This command starts
25236 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25237 created Emacs buffer.
25238 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25240 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25245 All ``terminal'' input and output goes through an Emacs buffer, called
25248 This applies both to @value{GDBN} commands and their output, and to the input
25249 and output done by the program you are debugging.
25251 This is useful because it means that you can copy the text of previous
25252 commands and input them again; you can even use parts of the output
25255 All the facilities of Emacs' Shell mode are available for interacting
25256 with your program. In particular, you can send signals the usual
25257 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25261 @value{GDBN} displays source code through Emacs.
25263 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25264 source file for that frame and puts an arrow (@samp{=>}) at the
25265 left margin of the current line. Emacs uses a separate buffer for
25266 source display, and splits the screen to show both your @value{GDBN} session
25269 Explicit @value{GDBN} @code{list} or search commands still produce output as
25270 usual, but you probably have no reason to use them from Emacs.
25273 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25274 a graphical mode, enabled by default, which provides further buffers
25275 that can control the execution and describe the state of your program.
25276 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25278 If you specify an absolute file name when prompted for the @kbd{M-x
25279 gdb} argument, then Emacs sets your current working directory to where
25280 your program resides. If you only specify the file name, then Emacs
25281 sets your current working directory to the directory associated
25282 with the previous buffer. In this case, @value{GDBN} may find your
25283 program by searching your environment's @code{PATH} variable, but on
25284 some operating systems it might not find the source. So, although the
25285 @value{GDBN} input and output session proceeds normally, the auxiliary
25286 buffer does not display the current source and line of execution.
25288 The initial working directory of @value{GDBN} is printed on the top
25289 line of the GUD buffer and this serves as a default for the commands
25290 that specify files for @value{GDBN} to operate on. @xref{Files,
25291 ,Commands to Specify Files}.
25293 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25294 need to call @value{GDBN} by a different name (for example, if you
25295 keep several configurations around, with different names) you can
25296 customize the Emacs variable @code{gud-gdb-command-name} to run the
25299 In the GUD buffer, you can use these special Emacs commands in
25300 addition to the standard Shell mode commands:
25304 Describe the features of Emacs' GUD Mode.
25307 Execute to another source line, like the @value{GDBN} @code{step} command; also
25308 update the display window to show the current file and location.
25311 Execute to next source line in this function, skipping all function
25312 calls, like the @value{GDBN} @code{next} command. Then update the display window
25313 to show the current file and location.
25316 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25317 display window accordingly.
25320 Execute until exit from the selected stack frame, like the @value{GDBN}
25321 @code{finish} command.
25324 Continue execution of your program, like the @value{GDBN} @code{continue}
25328 Go up the number of frames indicated by the numeric argument
25329 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25330 like the @value{GDBN} @code{up} command.
25333 Go down the number of frames indicated by the numeric argument, like the
25334 @value{GDBN} @code{down} command.
25337 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25338 tells @value{GDBN} to set a breakpoint on the source line point is on.
25340 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25341 separate frame which shows a backtrace when the GUD buffer is current.
25342 Move point to any frame in the stack and type @key{RET} to make it
25343 become the current frame and display the associated source in the
25344 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25345 selected frame become the current one. In graphical mode, the
25346 speedbar displays watch expressions.
25348 If you accidentally delete the source-display buffer, an easy way to get
25349 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25350 request a frame display; when you run under Emacs, this recreates
25351 the source buffer if necessary to show you the context of the current
25354 The source files displayed in Emacs are in ordinary Emacs buffers
25355 which are visiting the source files in the usual way. You can edit
25356 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25357 communicates with Emacs in terms of line numbers. If you add or
25358 delete lines from the text, the line numbers that @value{GDBN} knows cease
25359 to correspond properly with the code.
25361 A more detailed description of Emacs' interaction with @value{GDBN} is
25362 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25365 @c The following dropped because Epoch is nonstandard. Reactivate
25366 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25368 @kindex Emacs Epoch environment
25372 Version 18 of @sc{gnu} Emacs has a built-in window system
25373 called the @code{epoch}
25374 environment. Users of this environment can use a new command,
25375 @code{inspect} which performs identically to @code{print} except that
25376 each value is printed in its own window.
25381 @chapter The @sc{gdb/mi} Interface
25383 @unnumberedsec Function and Purpose
25385 @cindex @sc{gdb/mi}, its purpose
25386 @sc{gdb/mi} is a line based machine oriented text interface to
25387 @value{GDBN} and is activated by specifying using the
25388 @option{--interpreter} command line option (@pxref{Mode Options}). It
25389 is specifically intended to support the development of systems which
25390 use the debugger as just one small component of a larger system.
25392 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25393 in the form of a reference manual.
25395 Note that @sc{gdb/mi} is still under construction, so some of the
25396 features described below are incomplete and subject to change
25397 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25399 @unnumberedsec Notation and Terminology
25401 @cindex notational conventions, for @sc{gdb/mi}
25402 This chapter uses the following notation:
25406 @code{|} separates two alternatives.
25409 @code{[ @var{something} ]} indicates that @var{something} is optional:
25410 it may or may not be given.
25413 @code{( @var{group} )*} means that @var{group} inside the parentheses
25414 may repeat zero or more times.
25417 @code{( @var{group} )+} means that @var{group} inside the parentheses
25418 may repeat one or more times.
25421 @code{"@var{string}"} means a literal @var{string}.
25425 @heading Dependencies
25429 * GDB/MI General Design::
25430 * GDB/MI Command Syntax::
25431 * GDB/MI Compatibility with CLI::
25432 * GDB/MI Development and Front Ends::
25433 * GDB/MI Output Records::
25434 * GDB/MI Simple Examples::
25435 * GDB/MI Command Description Format::
25436 * GDB/MI Breakpoint Commands::
25437 * GDB/MI Program Context::
25438 * GDB/MI Thread Commands::
25439 * GDB/MI Ada Tasking Commands::
25440 * GDB/MI Program Execution::
25441 * GDB/MI Stack Manipulation::
25442 * GDB/MI Variable Objects::
25443 * GDB/MI Data Manipulation::
25444 * GDB/MI Tracepoint Commands::
25445 * GDB/MI Symbol Query::
25446 * GDB/MI File Commands::
25448 * GDB/MI Kod Commands::
25449 * GDB/MI Memory Overlay Commands::
25450 * GDB/MI Signal Handling Commands::
25452 * GDB/MI Target Manipulation::
25453 * GDB/MI File Transfer Commands::
25454 * GDB/MI Miscellaneous Commands::
25457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25458 @node GDB/MI General Design
25459 @section @sc{gdb/mi} General Design
25460 @cindex GDB/MI General Design
25462 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25463 parts---commands sent to @value{GDBN}, responses to those commands
25464 and notifications. Each command results in exactly one response,
25465 indicating either successful completion of the command, or an error.
25466 For the commands that do not resume the target, the response contains the
25467 requested information. For the commands that resume the target, the
25468 response only indicates whether the target was successfully resumed.
25469 Notifications is the mechanism for reporting changes in the state of the
25470 target, or in @value{GDBN} state, that cannot conveniently be associated with
25471 a command and reported as part of that command response.
25473 The important examples of notifications are:
25477 Exec notifications. These are used to report changes in
25478 target state---when a target is resumed, or stopped. It would not
25479 be feasible to include this information in response of resuming
25480 commands, because one resume commands can result in multiple events in
25481 different threads. Also, quite some time may pass before any event
25482 happens in the target, while a frontend needs to know whether the resuming
25483 command itself was successfully executed.
25486 Console output, and status notifications. Console output
25487 notifications are used to report output of CLI commands, as well as
25488 diagnostics for other commands. Status notifications are used to
25489 report the progress of a long-running operation. Naturally, including
25490 this information in command response would mean no output is produced
25491 until the command is finished, which is undesirable.
25494 General notifications. Commands may have various side effects on
25495 the @value{GDBN} or target state beyond their official purpose. For example,
25496 a command may change the selected thread. Although such changes can
25497 be included in command response, using notification allows for more
25498 orthogonal frontend design.
25502 There's no guarantee that whenever an MI command reports an error,
25503 @value{GDBN} or the target are in any specific state, and especially,
25504 the state is not reverted to the state before the MI command was
25505 processed. Therefore, whenever an MI command results in an error,
25506 we recommend that the frontend refreshes all the information shown in
25507 the user interface.
25511 * Context management::
25512 * Asynchronous and non-stop modes::
25516 @node Context management
25517 @subsection Context management
25519 In most cases when @value{GDBN} accesses the target, this access is
25520 done in context of a specific thread and frame (@pxref{Frames}).
25521 Often, even when accessing global data, the target requires that a thread
25522 be specified. The CLI interface maintains the selected thread and frame,
25523 and supplies them to target on each command. This is convenient,
25524 because a command line user would not want to specify that information
25525 explicitly on each command, and because user interacts with
25526 @value{GDBN} via a single terminal, so no confusion is possible as
25527 to what thread and frame are the current ones.
25529 In the case of MI, the concept of selected thread and frame is less
25530 useful. First, a frontend can easily remember this information
25531 itself. Second, a graphical frontend can have more than one window,
25532 each one used for debugging a different thread, and the frontend might
25533 want to access additional threads for internal purposes. This
25534 increases the risk that by relying on implicitly selected thread, the
25535 frontend may be operating on a wrong one. Therefore, each MI command
25536 should explicitly specify which thread and frame to operate on. To
25537 make it possible, each MI command accepts the @samp{--thread} and
25538 @samp{--frame} options, the value to each is @value{GDBN} identifier
25539 for thread and frame to operate on.
25541 Usually, each top-level window in a frontend allows the user to select
25542 a thread and a frame, and remembers the user selection for further
25543 operations. However, in some cases @value{GDBN} may suggest that the
25544 current thread be changed. For example, when stopping on a breakpoint
25545 it is reasonable to switch to the thread where breakpoint is hit. For
25546 another example, if the user issues the CLI @samp{thread} command via
25547 the frontend, it is desirable to change the frontend's selected thread to the
25548 one specified by user. @value{GDBN} communicates the suggestion to
25549 change current thread using the @samp{=thread-selected} notification.
25550 No such notification is available for the selected frame at the moment.
25552 Note that historically, MI shares the selected thread with CLI, so
25553 frontends used the @code{-thread-select} to execute commands in the
25554 right context. However, getting this to work right is cumbersome. The
25555 simplest way is for frontend to emit @code{-thread-select} command
25556 before every command. This doubles the number of commands that need
25557 to be sent. The alternative approach is to suppress @code{-thread-select}
25558 if the selected thread in @value{GDBN} is supposed to be identical to the
25559 thread the frontend wants to operate on. However, getting this
25560 optimization right can be tricky. In particular, if the frontend
25561 sends several commands to @value{GDBN}, and one of the commands changes the
25562 selected thread, then the behaviour of subsequent commands will
25563 change. So, a frontend should either wait for response from such
25564 problematic commands, or explicitly add @code{-thread-select} for
25565 all subsequent commands. No frontend is known to do this exactly
25566 right, so it is suggested to just always pass the @samp{--thread} and
25567 @samp{--frame} options.
25569 @node Asynchronous and non-stop modes
25570 @subsection Asynchronous command execution and non-stop mode
25572 On some targets, @value{GDBN} is capable of processing MI commands
25573 even while the target is running. This is called @dfn{asynchronous
25574 command execution} (@pxref{Background Execution}). The frontend may
25575 specify a preferrence for asynchronous execution using the
25576 @code{-gdb-set target-async 1} command, which should be emitted before
25577 either running the executable or attaching to the target. After the
25578 frontend has started the executable or attached to the target, it can
25579 find if asynchronous execution is enabled using the
25580 @code{-list-target-features} command.
25582 Even if @value{GDBN} can accept a command while target is running,
25583 many commands that access the target do not work when the target is
25584 running. Therefore, asynchronous command execution is most useful
25585 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25586 it is possible to examine the state of one thread, while other threads
25589 When a given thread is running, MI commands that try to access the
25590 target in the context of that thread may not work, or may work only on
25591 some targets. In particular, commands that try to operate on thread's
25592 stack will not work, on any target. Commands that read memory, or
25593 modify breakpoints, may work or not work, depending on the target. Note
25594 that even commands that operate on global state, such as @code{print},
25595 @code{set}, and breakpoint commands, still access the target in the
25596 context of a specific thread, so frontend should try to find a
25597 stopped thread and perform the operation on that thread (using the
25598 @samp{--thread} option).
25600 Which commands will work in the context of a running thread is
25601 highly target dependent. However, the two commands
25602 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25603 to find the state of a thread, will always work.
25605 @node Thread groups
25606 @subsection Thread groups
25607 @value{GDBN} may be used to debug several processes at the same time.
25608 On some platfroms, @value{GDBN} may support debugging of several
25609 hardware systems, each one having several cores with several different
25610 processes running on each core. This section describes the MI
25611 mechanism to support such debugging scenarios.
25613 The key observation is that regardless of the structure of the
25614 target, MI can have a global list of threads, because most commands that
25615 accept the @samp{--thread} option do not need to know what process that
25616 thread belongs to. Therefore, it is not necessary to introduce
25617 neither additional @samp{--process} option, nor an notion of the
25618 current process in the MI interface. The only strictly new feature
25619 that is required is the ability to find how the threads are grouped
25622 To allow the user to discover such grouping, and to support arbitrary
25623 hierarchy of machines/cores/processes, MI introduces the concept of a
25624 @dfn{thread group}. Thread group is a collection of threads and other
25625 thread groups. A thread group always has a string identifier, a type,
25626 and may have additional attributes specific to the type. A new
25627 command, @code{-list-thread-groups}, returns the list of top-level
25628 thread groups, which correspond to processes that @value{GDBN} is
25629 debugging at the moment. By passing an identifier of a thread group
25630 to the @code{-list-thread-groups} command, it is possible to obtain
25631 the members of specific thread group.
25633 To allow the user to easily discover processes, and other objects, he
25634 wishes to debug, a concept of @dfn{available thread group} is
25635 introduced. Available thread group is an thread group that
25636 @value{GDBN} is not debugging, but that can be attached to, using the
25637 @code{-target-attach} command. The list of available top-level thread
25638 groups can be obtained using @samp{-list-thread-groups --available}.
25639 In general, the content of a thread group may be only retrieved only
25640 after attaching to that thread group.
25642 Thread groups are related to inferiors (@pxref{Inferiors and
25643 Programs}). Each inferior corresponds to a thread group of a special
25644 type @samp{process}, and some additional operations are permitted on
25645 such thread groups.
25647 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25648 @node GDB/MI Command Syntax
25649 @section @sc{gdb/mi} Command Syntax
25652 * GDB/MI Input Syntax::
25653 * GDB/MI Output Syntax::
25656 @node GDB/MI Input Syntax
25657 @subsection @sc{gdb/mi} Input Syntax
25659 @cindex input syntax for @sc{gdb/mi}
25660 @cindex @sc{gdb/mi}, input syntax
25662 @item @var{command} @expansion{}
25663 @code{@var{cli-command} | @var{mi-command}}
25665 @item @var{cli-command} @expansion{}
25666 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25667 @var{cli-command} is any existing @value{GDBN} CLI command.
25669 @item @var{mi-command} @expansion{}
25670 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25671 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25673 @item @var{token} @expansion{}
25674 "any sequence of digits"
25676 @item @var{option} @expansion{}
25677 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25679 @item @var{parameter} @expansion{}
25680 @code{@var{non-blank-sequence} | @var{c-string}}
25682 @item @var{operation} @expansion{}
25683 @emph{any of the operations described in this chapter}
25685 @item @var{non-blank-sequence} @expansion{}
25686 @emph{anything, provided it doesn't contain special characters such as
25687 "-", @var{nl}, """ and of course " "}
25689 @item @var{c-string} @expansion{}
25690 @code{""" @var{seven-bit-iso-c-string-content} """}
25692 @item @var{nl} @expansion{}
25701 The CLI commands are still handled by the @sc{mi} interpreter; their
25702 output is described below.
25705 The @code{@var{token}}, when present, is passed back when the command
25709 Some @sc{mi} commands accept optional arguments as part of the parameter
25710 list. Each option is identified by a leading @samp{-} (dash) and may be
25711 followed by an optional argument parameter. Options occur first in the
25712 parameter list and can be delimited from normal parameters using
25713 @samp{--} (this is useful when some parameters begin with a dash).
25720 We want easy access to the existing CLI syntax (for debugging).
25723 We want it to be easy to spot a @sc{mi} operation.
25726 @node GDB/MI Output Syntax
25727 @subsection @sc{gdb/mi} Output Syntax
25729 @cindex output syntax of @sc{gdb/mi}
25730 @cindex @sc{gdb/mi}, output syntax
25731 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25732 followed, optionally, by a single result record. This result record
25733 is for the most recent command. The sequence of output records is
25734 terminated by @samp{(gdb)}.
25736 If an input command was prefixed with a @code{@var{token}} then the
25737 corresponding output for that command will also be prefixed by that same
25741 @item @var{output} @expansion{}
25742 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25744 @item @var{result-record} @expansion{}
25745 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25747 @item @var{out-of-band-record} @expansion{}
25748 @code{@var{async-record} | @var{stream-record}}
25750 @item @var{async-record} @expansion{}
25751 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25753 @item @var{exec-async-output} @expansion{}
25754 @code{[ @var{token} ] "*" @var{async-output}}
25756 @item @var{status-async-output} @expansion{}
25757 @code{[ @var{token} ] "+" @var{async-output}}
25759 @item @var{notify-async-output} @expansion{}
25760 @code{[ @var{token} ] "=" @var{async-output}}
25762 @item @var{async-output} @expansion{}
25763 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25765 @item @var{result-class} @expansion{}
25766 @code{"done" | "running" | "connected" | "error" | "exit"}
25768 @item @var{async-class} @expansion{}
25769 @code{"stopped" | @var{others}} (where @var{others} will be added
25770 depending on the needs---this is still in development).
25772 @item @var{result} @expansion{}
25773 @code{ @var{variable} "=" @var{value}}
25775 @item @var{variable} @expansion{}
25776 @code{ @var{string} }
25778 @item @var{value} @expansion{}
25779 @code{ @var{const} | @var{tuple} | @var{list} }
25781 @item @var{const} @expansion{}
25782 @code{@var{c-string}}
25784 @item @var{tuple} @expansion{}
25785 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25787 @item @var{list} @expansion{}
25788 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25789 @var{result} ( "," @var{result} )* "]" }
25791 @item @var{stream-record} @expansion{}
25792 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25794 @item @var{console-stream-output} @expansion{}
25795 @code{"~" @var{c-string}}
25797 @item @var{target-stream-output} @expansion{}
25798 @code{"@@" @var{c-string}}
25800 @item @var{log-stream-output} @expansion{}
25801 @code{"&" @var{c-string}}
25803 @item @var{nl} @expansion{}
25806 @item @var{token} @expansion{}
25807 @emph{any sequence of digits}.
25815 All output sequences end in a single line containing a period.
25818 The @code{@var{token}} is from the corresponding request. Note that
25819 for all async output, while the token is allowed by the grammar and
25820 may be output by future versions of @value{GDBN} for select async
25821 output messages, it is generally omitted. Frontends should treat
25822 all async output as reporting general changes in the state of the
25823 target and there should be no need to associate async output to any
25827 @cindex status output in @sc{gdb/mi}
25828 @var{status-async-output} contains on-going status information about the
25829 progress of a slow operation. It can be discarded. All status output is
25830 prefixed by @samp{+}.
25833 @cindex async output in @sc{gdb/mi}
25834 @var{exec-async-output} contains asynchronous state change on the target
25835 (stopped, started, disappeared). All async output is prefixed by
25839 @cindex notify output in @sc{gdb/mi}
25840 @var{notify-async-output} contains supplementary information that the
25841 client should handle (e.g., a new breakpoint information). All notify
25842 output is prefixed by @samp{=}.
25845 @cindex console output in @sc{gdb/mi}
25846 @var{console-stream-output} is output that should be displayed as is in the
25847 console. It is the textual response to a CLI command. All the console
25848 output is prefixed by @samp{~}.
25851 @cindex target output in @sc{gdb/mi}
25852 @var{target-stream-output} is the output produced by the target program.
25853 All the target output is prefixed by @samp{@@}.
25856 @cindex log output in @sc{gdb/mi}
25857 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25858 instance messages that should be displayed as part of an error log. All
25859 the log output is prefixed by @samp{&}.
25862 @cindex list output in @sc{gdb/mi}
25863 New @sc{gdb/mi} commands should only output @var{lists} containing
25869 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25870 details about the various output records.
25872 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25873 @node GDB/MI Compatibility with CLI
25874 @section @sc{gdb/mi} Compatibility with CLI
25876 @cindex compatibility, @sc{gdb/mi} and CLI
25877 @cindex @sc{gdb/mi}, compatibility with CLI
25879 For the developers convenience CLI commands can be entered directly,
25880 but there may be some unexpected behaviour. For example, commands
25881 that query the user will behave as if the user replied yes, breakpoint
25882 command lists are not executed and some CLI commands, such as
25883 @code{if}, @code{when} and @code{define}, prompt for further input with
25884 @samp{>}, which is not valid MI output.
25886 This feature may be removed at some stage in the future and it is
25887 recommended that front ends use the @code{-interpreter-exec} command
25888 (@pxref{-interpreter-exec}).
25890 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25891 @node GDB/MI Development and Front Ends
25892 @section @sc{gdb/mi} Development and Front Ends
25893 @cindex @sc{gdb/mi} development
25895 The application which takes the MI output and presents the state of the
25896 program being debugged to the user is called a @dfn{front end}.
25898 Although @sc{gdb/mi} is still incomplete, it is currently being used
25899 by a variety of front ends to @value{GDBN}. This makes it difficult
25900 to introduce new functionality without breaking existing usage. This
25901 section tries to minimize the problems by describing how the protocol
25904 Some changes in MI need not break a carefully designed front end, and
25905 for these the MI version will remain unchanged. The following is a
25906 list of changes that may occur within one level, so front ends should
25907 parse MI output in a way that can handle them:
25911 New MI commands may be added.
25914 New fields may be added to the output of any MI command.
25917 The range of values for fields with specified values, e.g.,
25918 @code{in_scope} (@pxref{-var-update}) may be extended.
25920 @c The format of field's content e.g type prefix, may change so parse it
25921 @c at your own risk. Yes, in general?
25923 @c The order of fields may change? Shouldn't really matter but it might
25924 @c resolve inconsistencies.
25927 If the changes are likely to break front ends, the MI version level
25928 will be increased by one. This will allow the front end to parse the
25929 output according to the MI version. Apart from mi0, new versions of
25930 @value{GDBN} will not support old versions of MI and it will be the
25931 responsibility of the front end to work with the new one.
25933 @c Starting with mi3, add a new command -mi-version that prints the MI
25936 The best way to avoid unexpected changes in MI that might break your front
25937 end is to make your project known to @value{GDBN} developers and
25938 follow development on @email{gdb@@sourceware.org} and
25939 @email{gdb-patches@@sourceware.org}.
25940 @cindex mailing lists
25942 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25943 @node GDB/MI Output Records
25944 @section @sc{gdb/mi} Output Records
25947 * GDB/MI Result Records::
25948 * GDB/MI Stream Records::
25949 * GDB/MI Async Records::
25950 * GDB/MI Frame Information::
25951 * GDB/MI Thread Information::
25952 * GDB/MI Ada Exception Information::
25955 @node GDB/MI Result Records
25956 @subsection @sc{gdb/mi} Result Records
25958 @cindex result records in @sc{gdb/mi}
25959 @cindex @sc{gdb/mi}, result records
25960 In addition to a number of out-of-band notifications, the response to a
25961 @sc{gdb/mi} command includes one of the following result indications:
25965 @item "^done" [ "," @var{results} ]
25966 The synchronous operation was successful, @code{@var{results}} are the return
25971 This result record is equivalent to @samp{^done}. Historically, it
25972 was output instead of @samp{^done} if the command has resumed the
25973 target. This behaviour is maintained for backward compatibility, but
25974 all frontends should treat @samp{^done} and @samp{^running}
25975 identically and rely on the @samp{*running} output record to determine
25976 which threads are resumed.
25980 @value{GDBN} has connected to a remote target.
25982 @item "^error" "," @var{c-string}
25984 The operation failed. The @code{@var{c-string}} contains the corresponding
25989 @value{GDBN} has terminated.
25993 @node GDB/MI Stream Records
25994 @subsection @sc{gdb/mi} Stream Records
25996 @cindex @sc{gdb/mi}, stream records
25997 @cindex stream records in @sc{gdb/mi}
25998 @value{GDBN} internally maintains a number of output streams: the console, the
25999 target, and the log. The output intended for each of these streams is
26000 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26002 Each stream record begins with a unique @dfn{prefix character} which
26003 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26004 Syntax}). In addition to the prefix, each stream record contains a
26005 @code{@var{string-output}}. This is either raw text (with an implicit new
26006 line) or a quoted C string (which does not contain an implicit newline).
26009 @item "~" @var{string-output}
26010 The console output stream contains text that should be displayed in the
26011 CLI console window. It contains the textual responses to CLI commands.
26013 @item "@@" @var{string-output}
26014 The target output stream contains any textual output from the running
26015 target. This is only present when GDB's event loop is truly
26016 asynchronous, which is currently only the case for remote targets.
26018 @item "&" @var{string-output}
26019 The log stream contains debugging messages being produced by @value{GDBN}'s
26023 @node GDB/MI Async Records
26024 @subsection @sc{gdb/mi} Async Records
26026 @cindex async records in @sc{gdb/mi}
26027 @cindex @sc{gdb/mi}, async records
26028 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26029 additional changes that have occurred. Those changes can either be a
26030 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26031 target activity (e.g., target stopped).
26033 The following is the list of possible async records:
26037 @item *running,thread-id="@var{thread}"
26038 The target is now running. The @var{thread} field tells which
26039 specific thread is now running, and can be @samp{all} if all threads
26040 are running. The frontend should assume that no interaction with a
26041 running thread is possible after this notification is produced.
26042 The frontend should not assume that this notification is output
26043 only once for any command. @value{GDBN} may emit this notification
26044 several times, either for different threads, because it cannot resume
26045 all threads together, or even for a single thread, if the thread must
26046 be stepped though some code before letting it run freely.
26048 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26049 The target has stopped. The @var{reason} field can have one of the
26053 @item breakpoint-hit
26054 A breakpoint was reached.
26055 @item watchpoint-trigger
26056 A watchpoint was triggered.
26057 @item read-watchpoint-trigger
26058 A read watchpoint was triggered.
26059 @item access-watchpoint-trigger
26060 An access watchpoint was triggered.
26061 @item function-finished
26062 An -exec-finish or similar CLI command was accomplished.
26063 @item location-reached
26064 An -exec-until or similar CLI command was accomplished.
26065 @item watchpoint-scope
26066 A watchpoint has gone out of scope.
26067 @item end-stepping-range
26068 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26069 similar CLI command was accomplished.
26070 @item exited-signalled
26071 The inferior exited because of a signal.
26073 The inferior exited.
26074 @item exited-normally
26075 The inferior exited normally.
26076 @item signal-received
26077 A signal was received by the inferior.
26080 The @var{id} field identifies the thread that directly caused the stop
26081 -- for example by hitting a breakpoint. Depending on whether all-stop
26082 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26083 stop all threads, or only the thread that directly triggered the stop.
26084 If all threads are stopped, the @var{stopped} field will have the
26085 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26086 field will be a list of thread identifiers. Presently, this list will
26087 always include a single thread, but frontend should be prepared to see
26088 several threads in the list. The @var{core} field reports the
26089 processor core on which the stop event has happened. This field may be absent
26090 if such information is not available.
26092 @item =thread-group-added,id="@var{id}"
26093 @itemx =thread-group-removed,id="@var{id}"
26094 A thread group was either added or removed. The @var{id} field
26095 contains the @value{GDBN} identifier of the thread group. When a thread
26096 group is added, it generally might not be associated with a running
26097 process. When a thread group is removed, its id becomes invalid and
26098 cannot be used in any way.
26100 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26101 A thread group became associated with a running program,
26102 either because the program was just started or the thread group
26103 was attached to a program. The @var{id} field contains the
26104 @value{GDBN} identifier of the thread group. The @var{pid} field
26105 contains process identifier, specific to the operating system.
26107 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26108 A thread group is no longer associated with a running program,
26109 either because the program has exited, or because it was detached
26110 from. The @var{id} field contains the @value{GDBN} identifier of the
26111 thread group. @var{code} is the exit code of the inferior; it exists
26112 only when the inferior exited with some code.
26114 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26115 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26116 A thread either was created, or has exited. The @var{id} field
26117 contains the @value{GDBN} identifier of the thread. The @var{gid}
26118 field identifies the thread group this thread belongs to.
26120 @item =thread-selected,id="@var{id}"
26121 Informs that the selected thread was changed as result of the last
26122 command. This notification is not emitted as result of @code{-thread-select}
26123 command but is emitted whenever an MI command that is not documented
26124 to change the selected thread actually changes it. In particular,
26125 invoking, directly or indirectly (via user-defined command), the CLI
26126 @code{thread} command, will generate this notification.
26128 We suggest that in response to this notification, front ends
26129 highlight the selected thread and cause subsequent commands to apply to
26132 @item =library-loaded,...
26133 Reports that a new library file was loaded by the program. This
26134 notification has 4 fields---@var{id}, @var{target-name},
26135 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26136 opaque identifier of the library. For remote debugging case,
26137 @var{target-name} and @var{host-name} fields give the name of the
26138 library file on the target, and on the host respectively. For native
26139 debugging, both those fields have the same value. The
26140 @var{symbols-loaded} field is emitted only for backward compatibility
26141 and should not be relied on to convey any useful information. The
26142 @var{thread-group} field, if present, specifies the id of the thread
26143 group in whose context the library was loaded. If the field is
26144 absent, it means the library was loaded in the context of all present
26147 @item =library-unloaded,...
26148 Reports that a library was unloaded by the program. This notification
26149 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26150 the same meaning as for the @code{=library-loaded} notification.
26151 The @var{thread-group} field, if present, specifies the id of the
26152 thread group in whose context the library was unloaded. If the field is
26153 absent, it means the library was unloaded in the context of all present
26156 @item =breakpoint-created,bkpt=@{...@}
26157 @itemx =breakpoint-modified,bkpt=@{...@}
26158 @itemx =breakpoint-deleted,bkpt=@{...@}
26159 Reports that a breakpoint was created, modified, or deleted,
26160 respectively. Only user-visible breakpoints are reported to the MI
26163 The @var{bkpt} argument is of the same form as returned by the various
26164 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26166 Note that if a breakpoint is emitted in the result record of a
26167 command, then it will not also be emitted in an async record.
26171 @node GDB/MI Frame Information
26172 @subsection @sc{gdb/mi} Frame Information
26174 Response from many MI commands includes an information about stack
26175 frame. This information is a tuple that may have the following
26180 The level of the stack frame. The innermost frame has the level of
26181 zero. This field is always present.
26184 The name of the function corresponding to the frame. This field may
26185 be absent if @value{GDBN} is unable to determine the function name.
26188 The code address for the frame. This field is always present.
26191 The name of the source files that correspond to the frame's code
26192 address. This field may be absent.
26195 The source line corresponding to the frames' code address. This field
26199 The name of the binary file (either executable or shared library) the
26200 corresponds to the frame's code address. This field may be absent.
26204 @node GDB/MI Thread Information
26205 @subsection @sc{gdb/mi} Thread Information
26207 Whenever @value{GDBN} has to report an information about a thread, it
26208 uses a tuple with the following fields:
26212 The numeric id assigned to the thread by @value{GDBN}. This field is
26216 Target-specific string identifying the thread. This field is always present.
26219 Additional information about the thread provided by the target.
26220 It is supposed to be human-readable and not interpreted by the
26221 frontend. This field is optional.
26224 Either @samp{stopped} or @samp{running}, depending on whether the
26225 thread is presently running. This field is always present.
26228 The value of this field is an integer number of the processor core the
26229 thread was last seen on. This field is optional.
26232 @node GDB/MI Ada Exception Information
26233 @subsection @sc{gdb/mi} Ada Exception Information
26235 Whenever a @code{*stopped} record is emitted because the program
26236 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26237 @value{GDBN} provides the name of the exception that was raised via
26238 the @code{exception-name} field.
26240 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26241 @node GDB/MI Simple Examples
26242 @section Simple Examples of @sc{gdb/mi} Interaction
26243 @cindex @sc{gdb/mi}, simple examples
26245 This subsection presents several simple examples of interaction using
26246 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26247 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26248 the output received from @sc{gdb/mi}.
26250 Note the line breaks shown in the examples are here only for
26251 readability, they don't appear in the real output.
26253 @subheading Setting a Breakpoint
26255 Setting a breakpoint generates synchronous output which contains detailed
26256 information of the breakpoint.
26259 -> -break-insert main
26260 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26261 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26262 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26266 @subheading Program Execution
26268 Program execution generates asynchronous records and MI gives the
26269 reason that execution stopped.
26275 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26276 frame=@{addr="0x08048564",func="main",
26277 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26278 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26283 <- *stopped,reason="exited-normally"
26287 @subheading Quitting @value{GDBN}
26289 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26297 Please note that @samp{^exit} is printed immediately, but it might
26298 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26299 performs necessary cleanups, including killing programs being debugged
26300 or disconnecting from debug hardware, so the frontend should wait till
26301 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26302 fails to exit in reasonable time.
26304 @subheading A Bad Command
26306 Here's what happens if you pass a non-existent command:
26310 <- ^error,msg="Undefined MI command: rubbish"
26315 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26316 @node GDB/MI Command Description Format
26317 @section @sc{gdb/mi} Command Description Format
26319 The remaining sections describe blocks of commands. Each block of
26320 commands is laid out in a fashion similar to this section.
26322 @subheading Motivation
26324 The motivation for this collection of commands.
26326 @subheading Introduction
26328 A brief introduction to this collection of commands as a whole.
26330 @subheading Commands
26332 For each command in the block, the following is described:
26334 @subsubheading Synopsis
26337 -command @var{args}@dots{}
26340 @subsubheading Result
26342 @subsubheading @value{GDBN} Command
26344 The corresponding @value{GDBN} CLI command(s), if any.
26346 @subsubheading Example
26348 Example(s) formatted for readability. Some of the described commands have
26349 not been implemented yet and these are labeled N.A.@: (not available).
26352 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26353 @node GDB/MI Breakpoint Commands
26354 @section @sc{gdb/mi} Breakpoint Commands
26356 @cindex breakpoint commands for @sc{gdb/mi}
26357 @cindex @sc{gdb/mi}, breakpoint commands
26358 This section documents @sc{gdb/mi} commands for manipulating
26361 @subheading The @code{-break-after} Command
26362 @findex -break-after
26364 @subsubheading Synopsis
26367 -break-after @var{number} @var{count}
26370 The breakpoint number @var{number} is not in effect until it has been
26371 hit @var{count} times. To see how this is reflected in the output of
26372 the @samp{-break-list} command, see the description of the
26373 @samp{-break-list} command below.
26375 @subsubheading @value{GDBN} Command
26377 The corresponding @value{GDBN} command is @samp{ignore}.
26379 @subsubheading Example
26384 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26385 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26386 fullname="/home/foo/hello.c",line="5",times="0"@}
26393 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26394 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26395 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26396 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26397 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26398 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26399 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26400 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26401 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26402 line="5",times="0",ignore="3"@}]@}
26407 @subheading The @code{-break-catch} Command
26408 @findex -break-catch
26411 @subheading The @code{-break-commands} Command
26412 @findex -break-commands
26414 @subsubheading Synopsis
26417 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26420 Specifies the CLI commands that should be executed when breakpoint
26421 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26422 are the commands. If no command is specified, any previously-set
26423 commands are cleared. @xref{Break Commands}. Typical use of this
26424 functionality is tracing a program, that is, printing of values of
26425 some variables whenever breakpoint is hit and then continuing.
26427 @subsubheading @value{GDBN} Command
26429 The corresponding @value{GDBN} command is @samp{commands}.
26431 @subsubheading Example
26436 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26437 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26438 fullname="/home/foo/hello.c",line="5",times="0"@}
26440 -break-commands 1 "print v" "continue"
26445 @subheading The @code{-break-condition} Command
26446 @findex -break-condition
26448 @subsubheading Synopsis
26451 -break-condition @var{number} @var{expr}
26454 Breakpoint @var{number} will stop the program only if the condition in
26455 @var{expr} is true. The condition becomes part of the
26456 @samp{-break-list} output (see the description of the @samp{-break-list}
26459 @subsubheading @value{GDBN} Command
26461 The corresponding @value{GDBN} command is @samp{condition}.
26463 @subsubheading Example
26467 -break-condition 1 1
26471 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26472 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26473 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26474 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26475 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26476 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26477 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26478 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26479 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26480 line="5",cond="1",times="0",ignore="3"@}]@}
26484 @subheading The @code{-break-delete} Command
26485 @findex -break-delete
26487 @subsubheading Synopsis
26490 -break-delete ( @var{breakpoint} )+
26493 Delete the breakpoint(s) whose number(s) are specified in the argument
26494 list. This is obviously reflected in the breakpoint list.
26496 @subsubheading @value{GDBN} Command
26498 The corresponding @value{GDBN} command is @samp{delete}.
26500 @subsubheading Example
26508 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26509 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26510 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26511 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26512 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26513 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26514 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26519 @subheading The @code{-break-disable} Command
26520 @findex -break-disable
26522 @subsubheading Synopsis
26525 -break-disable ( @var{breakpoint} )+
26528 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26529 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26531 @subsubheading @value{GDBN} Command
26533 The corresponding @value{GDBN} command is @samp{disable}.
26535 @subsubheading Example
26543 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26544 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26545 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26546 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26547 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26548 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26549 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26550 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26551 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26552 line="5",times="0"@}]@}
26556 @subheading The @code{-break-enable} Command
26557 @findex -break-enable
26559 @subsubheading Synopsis
26562 -break-enable ( @var{breakpoint} )+
26565 Enable (previously disabled) @var{breakpoint}(s).
26567 @subsubheading @value{GDBN} Command
26569 The corresponding @value{GDBN} command is @samp{enable}.
26571 @subsubheading Example
26579 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26580 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26581 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26582 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26583 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26584 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26585 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26586 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26587 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26588 line="5",times="0"@}]@}
26592 @subheading The @code{-break-info} Command
26593 @findex -break-info
26595 @subsubheading Synopsis
26598 -break-info @var{breakpoint}
26602 Get information about a single breakpoint.
26604 @subsubheading @value{GDBN} Command
26606 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26608 @subsubheading Example
26611 @subheading The @code{-break-insert} Command
26612 @findex -break-insert
26614 @subsubheading Synopsis
26617 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26618 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26619 [ -p @var{thread} ] [ @var{location} ]
26623 If specified, @var{location}, can be one of:
26630 @item filename:linenum
26631 @item filename:function
26635 The possible optional parameters of this command are:
26639 Insert a temporary breakpoint.
26641 Insert a hardware breakpoint.
26642 @item -c @var{condition}
26643 Make the breakpoint conditional on @var{condition}.
26644 @item -i @var{ignore-count}
26645 Initialize the @var{ignore-count}.
26647 If @var{location} cannot be parsed (for example if it
26648 refers to unknown files or functions), create a pending
26649 breakpoint. Without this flag, @value{GDBN} will report
26650 an error, and won't create a breakpoint, if @var{location}
26653 Create a disabled breakpoint.
26655 Create a tracepoint. @xref{Tracepoints}. When this parameter
26656 is used together with @samp{-h}, a fast tracepoint is created.
26659 @subsubheading Result
26661 The result is in the form:
26664 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26665 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26666 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26667 times="@var{times}"@}
26671 where @var{number} is the @value{GDBN} number for this breakpoint,
26672 @var{funcname} is the name of the function where the breakpoint was
26673 inserted, @var{filename} is the name of the source file which contains
26674 this function, @var{lineno} is the source line number within that file
26675 and @var{times} the number of times that the breakpoint has been hit
26676 (always 0 for -break-insert but may be greater for -break-info or -break-list
26677 which use the same output).
26679 Note: this format is open to change.
26680 @c An out-of-band breakpoint instead of part of the result?
26682 @subsubheading @value{GDBN} Command
26684 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26685 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26687 @subsubheading Example
26692 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26693 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26695 -break-insert -t foo
26696 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26697 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26700 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26701 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26702 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26703 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26704 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26705 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26706 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26707 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26708 addr="0x0001072c", func="main",file="recursive2.c",
26709 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26710 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26711 addr="0x00010774",func="foo",file="recursive2.c",
26712 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26714 -break-insert -r foo.*
26715 ~int foo(int, int);
26716 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26717 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26721 @subheading The @code{-break-list} Command
26722 @findex -break-list
26724 @subsubheading Synopsis
26730 Displays the list of inserted breakpoints, showing the following fields:
26734 number of the breakpoint
26736 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26738 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26741 is the breakpoint enabled or no: @samp{y} or @samp{n}
26743 memory location at which the breakpoint is set
26745 logical location of the breakpoint, expressed by function name, file
26748 number of times the breakpoint has been hit
26751 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26752 @code{body} field is an empty list.
26754 @subsubheading @value{GDBN} Command
26756 The corresponding @value{GDBN} command is @samp{info break}.
26758 @subsubheading Example
26763 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26764 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26765 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26766 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26767 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26768 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26769 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26770 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26771 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26772 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26773 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26774 line="13",times="0"@}]@}
26778 Here's an example of the result when there are no breakpoints:
26783 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26784 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26785 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26786 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26787 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26788 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26789 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26794 @subheading The @code{-break-passcount} Command
26795 @findex -break-passcount
26797 @subsubheading Synopsis
26800 -break-passcount @var{tracepoint-number} @var{passcount}
26803 Set the passcount for tracepoint @var{tracepoint-number} to
26804 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26805 is not a tracepoint, error is emitted. This corresponds to CLI
26806 command @samp{passcount}.
26808 @subheading The @code{-break-watch} Command
26809 @findex -break-watch
26811 @subsubheading Synopsis
26814 -break-watch [ -a | -r ]
26817 Create a watchpoint. With the @samp{-a} option it will create an
26818 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26819 read from or on a write to the memory location. With the @samp{-r}
26820 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26821 trigger only when the memory location is accessed for reading. Without
26822 either of the options, the watchpoint created is a regular watchpoint,
26823 i.e., it will trigger when the memory location is accessed for writing.
26824 @xref{Set Watchpoints, , Setting Watchpoints}.
26826 Note that @samp{-break-list} will report a single list of watchpoints and
26827 breakpoints inserted.
26829 @subsubheading @value{GDBN} Command
26831 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26834 @subsubheading Example
26836 Setting a watchpoint on a variable in the @code{main} function:
26841 ^done,wpt=@{number="2",exp="x"@}
26846 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26847 value=@{old="-268439212",new="55"@},
26848 frame=@{func="main",args=[],file="recursive2.c",
26849 fullname="/home/foo/bar/recursive2.c",line="5"@}
26853 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26854 the program execution twice: first for the variable changing value, then
26855 for the watchpoint going out of scope.
26860 ^done,wpt=@{number="5",exp="C"@}
26865 *stopped,reason="watchpoint-trigger",
26866 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26867 frame=@{func="callee4",args=[],
26868 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26869 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26874 *stopped,reason="watchpoint-scope",wpnum="5",
26875 frame=@{func="callee3",args=[@{name="strarg",
26876 value="0x11940 \"A string argument.\""@}],
26877 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26878 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26882 Listing breakpoints and watchpoints, at different points in the program
26883 execution. Note that once the watchpoint goes out of scope, it is
26889 ^done,wpt=@{number="2",exp="C"@}
26892 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26893 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26894 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26895 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26896 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26897 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26898 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26899 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26900 addr="0x00010734",func="callee4",
26901 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26902 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
26903 bkpt=@{number="2",type="watchpoint",disp="keep",
26904 enabled="y",addr="",what="C",times="0"@}]@}
26909 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26910 value=@{old="-276895068",new="3"@},
26911 frame=@{func="callee4",args=[],
26912 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26913 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26916 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26917 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26918 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26919 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26920 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26921 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26922 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26923 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26924 addr="0x00010734",func="callee4",
26925 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26926 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
26927 bkpt=@{number="2",type="watchpoint",disp="keep",
26928 enabled="y",addr="",what="C",times="-5"@}]@}
26932 ^done,reason="watchpoint-scope",wpnum="2",
26933 frame=@{func="callee3",args=[@{name="strarg",
26934 value="0x11940 \"A string argument.\""@}],
26935 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26936 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26939 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26940 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26941 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26942 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26943 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26944 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26945 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26946 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26947 addr="0x00010734",func="callee4",
26948 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26949 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26954 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26955 @node GDB/MI Program Context
26956 @section @sc{gdb/mi} Program Context
26958 @subheading The @code{-exec-arguments} Command
26959 @findex -exec-arguments
26962 @subsubheading Synopsis
26965 -exec-arguments @var{args}
26968 Set the inferior program arguments, to be used in the next
26971 @subsubheading @value{GDBN} Command
26973 The corresponding @value{GDBN} command is @samp{set args}.
26975 @subsubheading Example
26979 -exec-arguments -v word
26986 @subheading The @code{-exec-show-arguments} Command
26987 @findex -exec-show-arguments
26989 @subsubheading Synopsis
26992 -exec-show-arguments
26995 Print the arguments of the program.
26997 @subsubheading @value{GDBN} Command
26999 The corresponding @value{GDBN} command is @samp{show args}.
27001 @subsubheading Example
27006 @subheading The @code{-environment-cd} Command
27007 @findex -environment-cd
27009 @subsubheading Synopsis
27012 -environment-cd @var{pathdir}
27015 Set @value{GDBN}'s working directory.
27017 @subsubheading @value{GDBN} Command
27019 The corresponding @value{GDBN} command is @samp{cd}.
27021 @subsubheading Example
27025 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27031 @subheading The @code{-environment-directory} Command
27032 @findex -environment-directory
27034 @subsubheading Synopsis
27037 -environment-directory [ -r ] [ @var{pathdir} ]+
27040 Add directories @var{pathdir} to beginning of search path for source files.
27041 If the @samp{-r} option is used, the search path is reset to the default
27042 search path. If directories @var{pathdir} are supplied in addition to the
27043 @samp{-r} option, the search path is first reset and then addition
27045 Multiple directories may be specified, separated by blanks. Specifying
27046 multiple directories in a single command
27047 results in the directories added to the beginning of the
27048 search path in the same order they were presented in the command.
27049 If blanks are needed as
27050 part of a directory name, double-quotes should be used around
27051 the name. In the command output, the path will show up separated
27052 by the system directory-separator character. The directory-separator
27053 character must not be used
27054 in any directory name.
27055 If no directories are specified, the current search path is displayed.
27057 @subsubheading @value{GDBN} Command
27059 The corresponding @value{GDBN} command is @samp{dir}.
27061 @subsubheading Example
27065 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27066 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27068 -environment-directory ""
27069 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27071 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27072 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27074 -environment-directory -r
27075 ^done,source-path="$cdir:$cwd"
27080 @subheading The @code{-environment-path} Command
27081 @findex -environment-path
27083 @subsubheading Synopsis
27086 -environment-path [ -r ] [ @var{pathdir} ]+
27089 Add directories @var{pathdir} to beginning of search path for object files.
27090 If the @samp{-r} option is used, the search path is reset to the original
27091 search path that existed at gdb start-up. If directories @var{pathdir} are
27092 supplied in addition to the
27093 @samp{-r} option, the search path is first reset and then addition
27095 Multiple directories may be specified, separated by blanks. Specifying
27096 multiple directories in a single command
27097 results in the directories added to the beginning of the
27098 search path in the same order they were presented in the command.
27099 If blanks are needed as
27100 part of a directory name, double-quotes should be used around
27101 the name. In the command output, the path will show up separated
27102 by the system directory-separator character. The directory-separator
27103 character must not be used
27104 in any directory name.
27105 If no directories are specified, the current path is displayed.
27108 @subsubheading @value{GDBN} Command
27110 The corresponding @value{GDBN} command is @samp{path}.
27112 @subsubheading Example
27117 ^done,path="/usr/bin"
27119 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27120 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27122 -environment-path -r /usr/local/bin
27123 ^done,path="/usr/local/bin:/usr/bin"
27128 @subheading The @code{-environment-pwd} Command
27129 @findex -environment-pwd
27131 @subsubheading Synopsis
27137 Show the current working directory.
27139 @subsubheading @value{GDBN} Command
27141 The corresponding @value{GDBN} command is @samp{pwd}.
27143 @subsubheading Example
27148 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27152 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27153 @node GDB/MI Thread Commands
27154 @section @sc{gdb/mi} Thread Commands
27157 @subheading The @code{-thread-info} Command
27158 @findex -thread-info
27160 @subsubheading Synopsis
27163 -thread-info [ @var{thread-id} ]
27166 Reports information about either a specific thread, if
27167 the @var{thread-id} parameter is present, or about all
27168 threads. When printing information about all threads,
27169 also reports the current thread.
27171 @subsubheading @value{GDBN} Command
27173 The @samp{info thread} command prints the same information
27176 @subsubheading Result
27178 The result is a list of threads. The following attributes are
27179 defined for a given thread:
27183 This field exists only for the current thread. It has the value @samp{*}.
27186 The identifier that @value{GDBN} uses to refer to the thread.
27189 The identifier that the target uses to refer to the thread.
27192 Extra information about the thread, in a target-specific format. This
27196 The name of the thread. If the user specified a name using the
27197 @code{thread name} command, then this name is given. Otherwise, if
27198 @value{GDBN} can extract the thread name from the target, then that
27199 name is given. If @value{GDBN} cannot find the thread name, then this
27203 The stack frame currently executing in the thread.
27206 The thread's state. The @samp{state} field may have the following
27211 The thread is stopped. Frame information is available for stopped
27215 The thread is running. There's no frame information for running
27221 If @value{GDBN} can find the CPU core on which this thread is running,
27222 then this field is the core identifier. This field is optional.
27226 @subsubheading Example
27231 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27232 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27233 args=[]@},state="running"@},
27234 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27235 frame=@{level="0",addr="0x0804891f",func="foo",
27236 args=[@{name="i",value="10"@}],
27237 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27238 state="running"@}],
27239 current-thread-id="1"
27243 @subheading The @code{-thread-list-ids} Command
27244 @findex -thread-list-ids
27246 @subsubheading Synopsis
27252 Produces a list of the currently known @value{GDBN} thread ids. At the
27253 end of the list it also prints the total number of such threads.
27255 This command is retained for historical reasons, the
27256 @code{-thread-info} command should be used instead.
27258 @subsubheading @value{GDBN} Command
27260 Part of @samp{info threads} supplies the same information.
27262 @subsubheading Example
27267 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27268 current-thread-id="1",number-of-threads="3"
27273 @subheading The @code{-thread-select} Command
27274 @findex -thread-select
27276 @subsubheading Synopsis
27279 -thread-select @var{threadnum}
27282 Make @var{threadnum} the current thread. It prints the number of the new
27283 current thread, and the topmost frame for that thread.
27285 This command is deprecated in favor of explicitly using the
27286 @samp{--thread} option to each command.
27288 @subsubheading @value{GDBN} Command
27290 The corresponding @value{GDBN} command is @samp{thread}.
27292 @subsubheading Example
27299 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27300 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27304 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27305 number-of-threads="3"
27308 ^done,new-thread-id="3",
27309 frame=@{level="0",func="vprintf",
27310 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27311 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27315 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27316 @node GDB/MI Ada Tasking Commands
27317 @section @sc{gdb/mi} Ada Tasking Commands
27319 @subheading The @code{-ada-task-info} Command
27320 @findex -ada-task-info
27322 @subsubheading Synopsis
27325 -ada-task-info [ @var{task-id} ]
27328 Reports information about either a specific Ada task, if the
27329 @var{task-id} parameter is present, or about all Ada tasks.
27331 @subsubheading @value{GDBN} Command
27333 The @samp{info tasks} command prints the same information
27334 about all Ada tasks (@pxref{Ada Tasks}).
27336 @subsubheading Result
27338 The result is a table of Ada tasks. The following columns are
27339 defined for each Ada task:
27343 This field exists only for the current thread. It has the value @samp{*}.
27346 The identifier that @value{GDBN} uses to refer to the Ada task.
27349 The identifier that the target uses to refer to the Ada task.
27352 The identifier of the thread corresponding to the Ada task.
27354 This field should always exist, as Ada tasks are always implemented
27355 on top of a thread. But if @value{GDBN} cannot find this corresponding
27356 thread for any reason, the field is omitted.
27359 This field exists only when the task was created by another task.
27360 In this case, it provides the ID of the parent task.
27363 The base priority of the task.
27366 The current state of the task. For a detailed description of the
27367 possible states, see @ref{Ada Tasks}.
27370 The name of the task.
27374 @subsubheading Example
27378 ^done,tasks=@{nr_rows="3",nr_cols="8",
27379 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27380 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27381 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27382 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27383 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27384 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27385 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27386 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27387 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27388 state="Child Termination Wait",name="main_task"@}]@}
27392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27393 @node GDB/MI Program Execution
27394 @section @sc{gdb/mi} Program Execution
27396 These are the asynchronous commands which generate the out-of-band
27397 record @samp{*stopped}. Currently @value{GDBN} only really executes
27398 asynchronously with remote targets and this interaction is mimicked in
27401 @subheading The @code{-exec-continue} Command
27402 @findex -exec-continue
27404 @subsubheading Synopsis
27407 -exec-continue [--reverse] [--all|--thread-group N]
27410 Resumes the execution of the inferior program, which will continue
27411 to execute until it reaches a debugger stop event. If the
27412 @samp{--reverse} option is specified, execution resumes in reverse until
27413 it reaches a stop event. Stop events may include
27416 breakpoints or watchpoints
27418 signals or exceptions
27420 the end of the process (or its beginning under @samp{--reverse})
27422 the end or beginning of a replay log if one is being used.
27424 In all-stop mode (@pxref{All-Stop
27425 Mode}), may resume only one thread, or all threads, depending on the
27426 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27427 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27428 ignored in all-stop mode. If the @samp{--thread-group} options is
27429 specified, then all threads in that thread group are resumed.
27431 @subsubheading @value{GDBN} Command
27433 The corresponding @value{GDBN} corresponding is @samp{continue}.
27435 @subsubheading Example
27442 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27443 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27449 @subheading The @code{-exec-finish} Command
27450 @findex -exec-finish
27452 @subsubheading Synopsis
27455 -exec-finish [--reverse]
27458 Resumes the execution of the inferior program until the current
27459 function is exited. Displays the results returned by the function.
27460 If the @samp{--reverse} option is specified, resumes the reverse
27461 execution of the inferior program until the point where current
27462 function was called.
27464 @subsubheading @value{GDBN} Command
27466 The corresponding @value{GDBN} command is @samp{finish}.
27468 @subsubheading Example
27470 Function returning @code{void}.
27477 *stopped,reason="function-finished",frame=@{func="main",args=[],
27478 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27482 Function returning other than @code{void}. The name of the internal
27483 @value{GDBN} variable storing the result is printed, together with the
27490 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27491 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27492 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27493 gdb-result-var="$1",return-value="0"
27498 @subheading The @code{-exec-interrupt} Command
27499 @findex -exec-interrupt
27501 @subsubheading Synopsis
27504 -exec-interrupt [--all|--thread-group N]
27507 Interrupts the background execution of the target. Note how the token
27508 associated with the stop message is the one for the execution command
27509 that has been interrupted. The token for the interrupt itself only
27510 appears in the @samp{^done} output. If the user is trying to
27511 interrupt a non-running program, an error message will be printed.
27513 Note that when asynchronous execution is enabled, this command is
27514 asynchronous just like other execution commands. That is, first the
27515 @samp{^done} response will be printed, and the target stop will be
27516 reported after that using the @samp{*stopped} notification.
27518 In non-stop mode, only the context thread is interrupted by default.
27519 All threads (in all inferiors) will be interrupted if the
27520 @samp{--all} option is specified. If the @samp{--thread-group}
27521 option is specified, all threads in that group will be interrupted.
27523 @subsubheading @value{GDBN} Command
27525 The corresponding @value{GDBN} command is @samp{interrupt}.
27527 @subsubheading Example
27538 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27539 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27540 fullname="/home/foo/bar/try.c",line="13"@}
27545 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27549 @subheading The @code{-exec-jump} Command
27552 @subsubheading Synopsis
27555 -exec-jump @var{location}
27558 Resumes execution of the inferior program at the location specified by
27559 parameter. @xref{Specify Location}, for a description of the
27560 different forms of @var{location}.
27562 @subsubheading @value{GDBN} Command
27564 The corresponding @value{GDBN} command is @samp{jump}.
27566 @subsubheading Example
27569 -exec-jump foo.c:10
27570 *running,thread-id="all"
27575 @subheading The @code{-exec-next} Command
27578 @subsubheading Synopsis
27581 -exec-next [--reverse]
27584 Resumes execution of the inferior program, stopping when the beginning
27585 of the next source line is reached.
27587 If the @samp{--reverse} option is specified, resumes reverse execution
27588 of the inferior program, stopping at the beginning of the previous
27589 source line. If you issue this command on the first line of a
27590 function, it will take you back to the caller of that function, to the
27591 source line where the function was called.
27594 @subsubheading @value{GDBN} Command
27596 The corresponding @value{GDBN} command is @samp{next}.
27598 @subsubheading Example
27604 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27609 @subheading The @code{-exec-next-instruction} Command
27610 @findex -exec-next-instruction
27612 @subsubheading Synopsis
27615 -exec-next-instruction [--reverse]
27618 Executes one machine instruction. If the instruction is a function
27619 call, continues until the function returns. If the program stops at an
27620 instruction in the middle of a source line, the address will be
27623 If the @samp{--reverse} option is specified, resumes reverse execution
27624 of the inferior program, stopping at the previous instruction. If the
27625 previously executed instruction was a return from another function,
27626 it will continue to execute in reverse until the call to that function
27627 (from the current stack frame) is reached.
27629 @subsubheading @value{GDBN} Command
27631 The corresponding @value{GDBN} command is @samp{nexti}.
27633 @subsubheading Example
27637 -exec-next-instruction
27641 *stopped,reason="end-stepping-range",
27642 addr="0x000100d4",line="5",file="hello.c"
27647 @subheading The @code{-exec-return} Command
27648 @findex -exec-return
27650 @subsubheading Synopsis
27656 Makes current function return immediately. Doesn't execute the inferior.
27657 Displays the new current frame.
27659 @subsubheading @value{GDBN} Command
27661 The corresponding @value{GDBN} command is @samp{return}.
27663 @subsubheading Example
27667 200-break-insert callee4
27668 200^done,bkpt=@{number="1",addr="0x00010734",
27669 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27674 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27675 frame=@{func="callee4",args=[],
27676 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27677 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27683 111^done,frame=@{level="0",func="callee3",
27684 args=[@{name="strarg",
27685 value="0x11940 \"A string argument.\""@}],
27686 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27687 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27692 @subheading The @code{-exec-run} Command
27695 @subsubheading Synopsis
27698 -exec-run [--all | --thread-group N]
27701 Starts execution of the inferior from the beginning. The inferior
27702 executes until either a breakpoint is encountered or the program
27703 exits. In the latter case the output will include an exit code, if
27704 the program has exited exceptionally.
27706 When no option is specified, the current inferior is started. If the
27707 @samp{--thread-group} option is specified, it should refer to a thread
27708 group of type @samp{process}, and that thread group will be started.
27709 If the @samp{--all} option is specified, then all inferiors will be started.
27711 @subsubheading @value{GDBN} Command
27713 The corresponding @value{GDBN} command is @samp{run}.
27715 @subsubheading Examples
27720 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27725 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27726 frame=@{func="main",args=[],file="recursive2.c",
27727 fullname="/home/foo/bar/recursive2.c",line="4"@}
27732 Program exited normally:
27740 *stopped,reason="exited-normally"
27745 Program exited exceptionally:
27753 *stopped,reason="exited",exit-code="01"
27757 Another way the program can terminate is if it receives a signal such as
27758 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27762 *stopped,reason="exited-signalled",signal-name="SIGINT",
27763 signal-meaning="Interrupt"
27767 @c @subheading -exec-signal
27770 @subheading The @code{-exec-step} Command
27773 @subsubheading Synopsis
27776 -exec-step [--reverse]
27779 Resumes execution of the inferior program, stopping when the beginning
27780 of the next source line is reached, if the next source line is not a
27781 function call. If it is, stop at the first instruction of the called
27782 function. If the @samp{--reverse} option is specified, resumes reverse
27783 execution of the inferior program, stopping at the beginning of the
27784 previously executed source line.
27786 @subsubheading @value{GDBN} Command
27788 The corresponding @value{GDBN} command is @samp{step}.
27790 @subsubheading Example
27792 Stepping into a function:
27798 *stopped,reason="end-stepping-range",
27799 frame=@{func="foo",args=[@{name="a",value="10"@},
27800 @{name="b",value="0"@}],file="recursive2.c",
27801 fullname="/home/foo/bar/recursive2.c",line="11"@}
27811 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27816 @subheading The @code{-exec-step-instruction} Command
27817 @findex -exec-step-instruction
27819 @subsubheading Synopsis
27822 -exec-step-instruction [--reverse]
27825 Resumes the inferior which executes one machine instruction. If the
27826 @samp{--reverse} option is specified, resumes reverse execution of the
27827 inferior program, stopping at the previously executed instruction.
27828 The output, once @value{GDBN} has stopped, will vary depending on
27829 whether we have stopped in the middle of a source line or not. In the
27830 former case, the address at which the program stopped will be printed
27833 @subsubheading @value{GDBN} Command
27835 The corresponding @value{GDBN} command is @samp{stepi}.
27837 @subsubheading Example
27841 -exec-step-instruction
27845 *stopped,reason="end-stepping-range",
27846 frame=@{func="foo",args=[],file="try.c",
27847 fullname="/home/foo/bar/try.c",line="10"@}
27849 -exec-step-instruction
27853 *stopped,reason="end-stepping-range",
27854 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27855 fullname="/home/foo/bar/try.c",line="10"@}
27860 @subheading The @code{-exec-until} Command
27861 @findex -exec-until
27863 @subsubheading Synopsis
27866 -exec-until [ @var{location} ]
27869 Executes the inferior until the @var{location} specified in the
27870 argument is reached. If there is no argument, the inferior executes
27871 until a source line greater than the current one is reached. The
27872 reason for stopping in this case will be @samp{location-reached}.
27874 @subsubheading @value{GDBN} Command
27876 The corresponding @value{GDBN} command is @samp{until}.
27878 @subsubheading Example
27882 -exec-until recursive2.c:6
27886 *stopped,reason="location-reached",frame=@{func="main",args=[],
27887 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27892 @subheading -file-clear
27893 Is this going away????
27896 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27897 @node GDB/MI Stack Manipulation
27898 @section @sc{gdb/mi} Stack Manipulation Commands
27901 @subheading The @code{-stack-info-frame} Command
27902 @findex -stack-info-frame
27904 @subsubheading Synopsis
27910 Get info on the selected frame.
27912 @subsubheading @value{GDBN} Command
27914 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27915 (without arguments).
27917 @subsubheading Example
27922 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27923 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27924 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27928 @subheading The @code{-stack-info-depth} Command
27929 @findex -stack-info-depth
27931 @subsubheading Synopsis
27934 -stack-info-depth [ @var{max-depth} ]
27937 Return the depth of the stack. If the integer argument @var{max-depth}
27938 is specified, do not count beyond @var{max-depth} frames.
27940 @subsubheading @value{GDBN} Command
27942 There's no equivalent @value{GDBN} command.
27944 @subsubheading Example
27946 For a stack with frame levels 0 through 11:
27953 -stack-info-depth 4
27956 -stack-info-depth 12
27959 -stack-info-depth 11
27962 -stack-info-depth 13
27967 @subheading The @code{-stack-list-arguments} Command
27968 @findex -stack-list-arguments
27970 @subsubheading Synopsis
27973 -stack-list-arguments @var{print-values}
27974 [ @var{low-frame} @var{high-frame} ]
27977 Display a list of the arguments for the frames between @var{low-frame}
27978 and @var{high-frame} (inclusive). If @var{low-frame} and
27979 @var{high-frame} are not provided, list the arguments for the whole
27980 call stack. If the two arguments are equal, show the single frame
27981 at the corresponding level. It is an error if @var{low-frame} is
27982 larger than the actual number of frames. On the other hand,
27983 @var{high-frame} may be larger than the actual number of frames, in
27984 which case only existing frames will be returned.
27986 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27987 the variables; if it is 1 or @code{--all-values}, print also their
27988 values; and if it is 2 or @code{--simple-values}, print the name,
27989 type and value for simple data types, and the name and type for arrays,
27990 structures and unions.
27992 Use of this command to obtain arguments in a single frame is
27993 deprecated in favor of the @samp{-stack-list-variables} command.
27995 @subsubheading @value{GDBN} Command
27997 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27998 @samp{gdb_get_args} command which partially overlaps with the
27999 functionality of @samp{-stack-list-arguments}.
28001 @subsubheading Example
28008 frame=@{level="0",addr="0x00010734",func="callee4",
28009 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28010 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28011 frame=@{level="1",addr="0x0001076c",func="callee3",
28012 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28013 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28014 frame=@{level="2",addr="0x0001078c",func="callee2",
28015 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28016 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28017 frame=@{level="3",addr="0x000107b4",func="callee1",
28018 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28019 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28020 frame=@{level="4",addr="0x000107e0",func="main",
28021 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28022 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28024 -stack-list-arguments 0
28027 frame=@{level="0",args=[]@},
28028 frame=@{level="1",args=[name="strarg"]@},
28029 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28030 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28031 frame=@{level="4",args=[]@}]
28033 -stack-list-arguments 1
28036 frame=@{level="0",args=[]@},
28038 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28039 frame=@{level="2",args=[
28040 @{name="intarg",value="2"@},
28041 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28042 @{frame=@{level="3",args=[
28043 @{name="intarg",value="2"@},
28044 @{name="strarg",value="0x11940 \"A string argument.\""@},
28045 @{name="fltarg",value="3.5"@}]@},
28046 frame=@{level="4",args=[]@}]
28048 -stack-list-arguments 0 2 2
28049 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28051 -stack-list-arguments 1 2 2
28052 ^done,stack-args=[frame=@{level="2",
28053 args=[@{name="intarg",value="2"@},
28054 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28058 @c @subheading -stack-list-exception-handlers
28061 @subheading The @code{-stack-list-frames} Command
28062 @findex -stack-list-frames
28064 @subsubheading Synopsis
28067 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28070 List the frames currently on the stack. For each frame it displays the
28075 The frame number, 0 being the topmost frame, i.e., the innermost function.
28077 The @code{$pc} value for that frame.
28081 File name of the source file where the function lives.
28082 @item @var{fullname}
28083 The full file name of the source file where the function lives.
28085 Line number corresponding to the @code{$pc}.
28087 The shared library where this function is defined. This is only given
28088 if the frame's function is not known.
28091 If invoked without arguments, this command prints a backtrace for the
28092 whole stack. If given two integer arguments, it shows the frames whose
28093 levels are between the two arguments (inclusive). If the two arguments
28094 are equal, it shows the single frame at the corresponding level. It is
28095 an error if @var{low-frame} is larger than the actual number of
28096 frames. On the other hand, @var{high-frame} may be larger than the
28097 actual number of frames, in which case only existing frames will be returned.
28099 @subsubheading @value{GDBN} Command
28101 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28103 @subsubheading Example
28105 Full stack backtrace:
28111 [frame=@{level="0",addr="0x0001076c",func="foo",
28112 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28113 frame=@{level="1",addr="0x000107a4",func="foo",
28114 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28115 frame=@{level="2",addr="0x000107a4",func="foo",
28116 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28117 frame=@{level="3",addr="0x000107a4",func="foo",
28118 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28119 frame=@{level="4",addr="0x000107a4",func="foo",
28120 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28121 frame=@{level="5",addr="0x000107a4",func="foo",
28122 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28123 frame=@{level="6",addr="0x000107a4",func="foo",
28124 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28125 frame=@{level="7",addr="0x000107a4",func="foo",
28126 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28127 frame=@{level="8",addr="0x000107a4",func="foo",
28128 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28129 frame=@{level="9",addr="0x000107a4",func="foo",
28130 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28131 frame=@{level="10",addr="0x000107a4",func="foo",
28132 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28133 frame=@{level="11",addr="0x00010738",func="main",
28134 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28138 Show frames between @var{low_frame} and @var{high_frame}:
28142 -stack-list-frames 3 5
28144 [frame=@{level="3",addr="0x000107a4",func="foo",
28145 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28146 frame=@{level="4",addr="0x000107a4",func="foo",
28147 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28148 frame=@{level="5",addr="0x000107a4",func="foo",
28149 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28153 Show a single frame:
28157 -stack-list-frames 3 3
28159 [frame=@{level="3",addr="0x000107a4",func="foo",
28160 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28165 @subheading The @code{-stack-list-locals} Command
28166 @findex -stack-list-locals
28168 @subsubheading Synopsis
28171 -stack-list-locals @var{print-values}
28174 Display the local variable names for the selected frame. If
28175 @var{print-values} is 0 or @code{--no-values}, print only the names of
28176 the variables; if it is 1 or @code{--all-values}, print also their
28177 values; and if it is 2 or @code{--simple-values}, print the name,
28178 type and value for simple data types, and the name and type for arrays,
28179 structures and unions. In this last case, a frontend can immediately
28180 display the value of simple data types and create variable objects for
28181 other data types when the user wishes to explore their values in
28184 This command is deprecated in favor of the
28185 @samp{-stack-list-variables} command.
28187 @subsubheading @value{GDBN} Command
28189 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28191 @subsubheading Example
28195 -stack-list-locals 0
28196 ^done,locals=[name="A",name="B",name="C"]
28198 -stack-list-locals --all-values
28199 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28200 @{name="C",value="@{1, 2, 3@}"@}]
28201 -stack-list-locals --simple-values
28202 ^done,locals=[@{name="A",type="int",value="1"@},
28203 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28207 @subheading The @code{-stack-list-variables} Command
28208 @findex -stack-list-variables
28210 @subsubheading Synopsis
28213 -stack-list-variables @var{print-values}
28216 Display the names of local variables and function arguments for the selected frame. If
28217 @var{print-values} is 0 or @code{--no-values}, print only the names of
28218 the variables; if it is 1 or @code{--all-values}, print also their
28219 values; and if it is 2 or @code{--simple-values}, print the name,
28220 type and value for simple data types, and the name and type for arrays,
28221 structures and unions.
28223 @subsubheading Example
28227 -stack-list-variables --thread 1 --frame 0 --all-values
28228 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28233 @subheading The @code{-stack-select-frame} Command
28234 @findex -stack-select-frame
28236 @subsubheading Synopsis
28239 -stack-select-frame @var{framenum}
28242 Change the selected frame. Select a different frame @var{framenum} on
28245 This command in deprecated in favor of passing the @samp{--frame}
28246 option to every command.
28248 @subsubheading @value{GDBN} Command
28250 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28251 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28253 @subsubheading Example
28257 -stack-select-frame 2
28262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28263 @node GDB/MI Variable Objects
28264 @section @sc{gdb/mi} Variable Objects
28268 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28270 For the implementation of a variable debugger window (locals, watched
28271 expressions, etc.), we are proposing the adaptation of the existing code
28272 used by @code{Insight}.
28274 The two main reasons for that are:
28278 It has been proven in practice (it is already on its second generation).
28281 It will shorten development time (needless to say how important it is
28285 The original interface was designed to be used by Tcl code, so it was
28286 slightly changed so it could be used through @sc{gdb/mi}. This section
28287 describes the @sc{gdb/mi} operations that will be available and gives some
28288 hints about their use.
28290 @emph{Note}: In addition to the set of operations described here, we
28291 expect the @sc{gui} implementation of a variable window to require, at
28292 least, the following operations:
28295 @item @code{-gdb-show} @code{output-radix}
28296 @item @code{-stack-list-arguments}
28297 @item @code{-stack-list-locals}
28298 @item @code{-stack-select-frame}
28303 @subheading Introduction to Variable Objects
28305 @cindex variable objects in @sc{gdb/mi}
28307 Variable objects are "object-oriented" MI interface for examining and
28308 changing values of expressions. Unlike some other MI interfaces that
28309 work with expressions, variable objects are specifically designed for
28310 simple and efficient presentation in the frontend. A variable object
28311 is identified by string name. When a variable object is created, the
28312 frontend specifies the expression for that variable object. The
28313 expression can be a simple variable, or it can be an arbitrary complex
28314 expression, and can even involve CPU registers. After creating a
28315 variable object, the frontend can invoke other variable object
28316 operations---for example to obtain or change the value of a variable
28317 object, or to change display format.
28319 Variable objects have hierarchical tree structure. Any variable object
28320 that corresponds to a composite type, such as structure in C, has
28321 a number of child variable objects, for example corresponding to each
28322 element of a structure. A child variable object can itself have
28323 children, recursively. Recursion ends when we reach
28324 leaf variable objects, which always have built-in types. Child variable
28325 objects are created only by explicit request, so if a frontend
28326 is not interested in the children of a particular variable object, no
28327 child will be created.
28329 For a leaf variable object it is possible to obtain its value as a
28330 string, or set the value from a string. String value can be also
28331 obtained for a non-leaf variable object, but it's generally a string
28332 that only indicates the type of the object, and does not list its
28333 contents. Assignment to a non-leaf variable object is not allowed.
28335 A frontend does not need to read the values of all variable objects each time
28336 the program stops. Instead, MI provides an update command that lists all
28337 variable objects whose values has changed since the last update
28338 operation. This considerably reduces the amount of data that must
28339 be transferred to the frontend. As noted above, children variable
28340 objects are created on demand, and only leaf variable objects have a
28341 real value. As result, gdb will read target memory only for leaf
28342 variables that frontend has created.
28344 The automatic update is not always desirable. For example, a frontend
28345 might want to keep a value of some expression for future reference,
28346 and never update it. For another example, fetching memory is
28347 relatively slow for embedded targets, so a frontend might want
28348 to disable automatic update for the variables that are either not
28349 visible on the screen, or ``closed''. This is possible using so
28350 called ``frozen variable objects''. Such variable objects are never
28351 implicitly updated.
28353 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28354 fixed variable object, the expression is parsed when the variable
28355 object is created, including associating identifiers to specific
28356 variables. The meaning of expression never changes. For a floating
28357 variable object the values of variables whose names appear in the
28358 expressions are re-evaluated every time in the context of the current
28359 frame. Consider this example:
28364 struct work_state state;
28371 If a fixed variable object for the @code{state} variable is created in
28372 this function, and we enter the recursive call, the variable
28373 object will report the value of @code{state} in the top-level
28374 @code{do_work} invocation. On the other hand, a floating variable
28375 object will report the value of @code{state} in the current frame.
28377 If an expression specified when creating a fixed variable object
28378 refers to a local variable, the variable object becomes bound to the
28379 thread and frame in which the variable object is created. When such
28380 variable object is updated, @value{GDBN} makes sure that the
28381 thread/frame combination the variable object is bound to still exists,
28382 and re-evaluates the variable object in context of that thread/frame.
28384 The following is the complete set of @sc{gdb/mi} operations defined to
28385 access this functionality:
28387 @multitable @columnfractions .4 .6
28388 @item @strong{Operation}
28389 @tab @strong{Description}
28391 @item @code{-enable-pretty-printing}
28392 @tab enable Python-based pretty-printing
28393 @item @code{-var-create}
28394 @tab create a variable object
28395 @item @code{-var-delete}
28396 @tab delete the variable object and/or its children
28397 @item @code{-var-set-format}
28398 @tab set the display format of this variable
28399 @item @code{-var-show-format}
28400 @tab show the display format of this variable
28401 @item @code{-var-info-num-children}
28402 @tab tells how many children this object has
28403 @item @code{-var-list-children}
28404 @tab return a list of the object's children
28405 @item @code{-var-info-type}
28406 @tab show the type of this variable object
28407 @item @code{-var-info-expression}
28408 @tab print parent-relative expression that this variable object represents
28409 @item @code{-var-info-path-expression}
28410 @tab print full expression that this variable object represents
28411 @item @code{-var-show-attributes}
28412 @tab is this variable editable? does it exist here?
28413 @item @code{-var-evaluate-expression}
28414 @tab get the value of this variable
28415 @item @code{-var-assign}
28416 @tab set the value of this variable
28417 @item @code{-var-update}
28418 @tab update the variable and its children
28419 @item @code{-var-set-frozen}
28420 @tab set frozeness attribute
28421 @item @code{-var-set-update-range}
28422 @tab set range of children to display on update
28425 In the next subsection we describe each operation in detail and suggest
28426 how it can be used.
28428 @subheading Description And Use of Operations on Variable Objects
28430 @subheading The @code{-enable-pretty-printing} Command
28431 @findex -enable-pretty-printing
28434 -enable-pretty-printing
28437 @value{GDBN} allows Python-based visualizers to affect the output of the
28438 MI variable object commands. However, because there was no way to
28439 implement this in a fully backward-compatible way, a front end must
28440 request that this functionality be enabled.
28442 Once enabled, this feature cannot be disabled.
28444 Note that if Python support has not been compiled into @value{GDBN},
28445 this command will still succeed (and do nothing).
28447 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28448 may work differently in future versions of @value{GDBN}.
28450 @subheading The @code{-var-create} Command
28451 @findex -var-create
28453 @subsubheading Synopsis
28456 -var-create @{@var{name} | "-"@}
28457 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28460 This operation creates a variable object, which allows the monitoring of
28461 a variable, the result of an expression, a memory cell or a CPU
28464 The @var{name} parameter is the string by which the object can be
28465 referenced. It must be unique. If @samp{-} is specified, the varobj
28466 system will generate a string ``varNNNNNN'' automatically. It will be
28467 unique provided that one does not specify @var{name} of that format.
28468 The command fails if a duplicate name is found.
28470 The frame under which the expression should be evaluated can be
28471 specified by @var{frame-addr}. A @samp{*} indicates that the current
28472 frame should be used. A @samp{@@} indicates that a floating variable
28473 object must be created.
28475 @var{expression} is any expression valid on the current language set (must not
28476 begin with a @samp{*}), or one of the following:
28480 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28483 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28486 @samp{$@var{regname}} --- a CPU register name
28489 @cindex dynamic varobj
28490 A varobj's contents may be provided by a Python-based pretty-printer. In this
28491 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28492 have slightly different semantics in some cases. If the
28493 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28494 will never create a dynamic varobj. This ensures backward
28495 compatibility for existing clients.
28497 @subsubheading Result
28499 This operation returns attributes of the newly-created varobj. These
28504 The name of the varobj.
28507 The number of children of the varobj. This number is not necessarily
28508 reliable for a dynamic varobj. Instead, you must examine the
28509 @samp{has_more} attribute.
28512 The varobj's scalar value. For a varobj whose type is some sort of
28513 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28514 will not be interesting.
28517 The varobj's type. This is a string representation of the type, as
28518 would be printed by the @value{GDBN} CLI.
28521 If a variable object is bound to a specific thread, then this is the
28522 thread's identifier.
28525 For a dynamic varobj, this indicates whether there appear to be any
28526 children available. For a non-dynamic varobj, this will be 0.
28529 This attribute will be present and have the value @samp{1} if the
28530 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28531 then this attribute will not be present.
28534 A dynamic varobj can supply a display hint to the front end. The
28535 value comes directly from the Python pretty-printer object's
28536 @code{display_hint} method. @xref{Pretty Printing API}.
28539 Typical output will look like this:
28542 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28543 has_more="@var{has_more}"
28547 @subheading The @code{-var-delete} Command
28548 @findex -var-delete
28550 @subsubheading Synopsis
28553 -var-delete [ -c ] @var{name}
28556 Deletes a previously created variable object and all of its children.
28557 With the @samp{-c} option, just deletes the children.
28559 Returns an error if the object @var{name} is not found.
28562 @subheading The @code{-var-set-format} Command
28563 @findex -var-set-format
28565 @subsubheading Synopsis
28568 -var-set-format @var{name} @var{format-spec}
28571 Sets the output format for the value of the object @var{name} to be
28574 @anchor{-var-set-format}
28575 The syntax for the @var{format-spec} is as follows:
28578 @var{format-spec} @expansion{}
28579 @{binary | decimal | hexadecimal | octal | natural@}
28582 The natural format is the default format choosen automatically
28583 based on the variable type (like decimal for an @code{int}, hex
28584 for pointers, etc.).
28586 For a variable with children, the format is set only on the
28587 variable itself, and the children are not affected.
28589 @subheading The @code{-var-show-format} Command
28590 @findex -var-show-format
28592 @subsubheading Synopsis
28595 -var-show-format @var{name}
28598 Returns the format used to display the value of the object @var{name}.
28601 @var{format} @expansion{}
28606 @subheading The @code{-var-info-num-children} Command
28607 @findex -var-info-num-children
28609 @subsubheading Synopsis
28612 -var-info-num-children @var{name}
28615 Returns the number of children of a variable object @var{name}:
28621 Note that this number is not completely reliable for a dynamic varobj.
28622 It will return the current number of children, but more children may
28626 @subheading The @code{-var-list-children} Command
28627 @findex -var-list-children
28629 @subsubheading Synopsis
28632 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28634 @anchor{-var-list-children}
28636 Return a list of the children of the specified variable object and
28637 create variable objects for them, if they do not already exist. With
28638 a single argument or if @var{print-values} has a value of 0 or
28639 @code{--no-values}, print only the names of the variables; if
28640 @var{print-values} is 1 or @code{--all-values}, also print their
28641 values; and if it is 2 or @code{--simple-values} print the name and
28642 value for simple data types and just the name for arrays, structures
28645 @var{from} and @var{to}, if specified, indicate the range of children
28646 to report. If @var{from} or @var{to} is less than zero, the range is
28647 reset and all children will be reported. Otherwise, children starting
28648 at @var{from} (zero-based) and up to and excluding @var{to} will be
28651 If a child range is requested, it will only affect the current call to
28652 @code{-var-list-children}, but not future calls to @code{-var-update}.
28653 For this, you must instead use @code{-var-set-update-range}. The
28654 intent of this approach is to enable a front end to implement any
28655 update approach it likes; for example, scrolling a view may cause the
28656 front end to request more children with @code{-var-list-children}, and
28657 then the front end could call @code{-var-set-update-range} with a
28658 different range to ensure that future updates are restricted to just
28661 For each child the following results are returned:
28666 Name of the variable object created for this child.
28669 The expression to be shown to the user by the front end to designate this child.
28670 For example this may be the name of a structure member.
28672 For a dynamic varobj, this value cannot be used to form an
28673 expression. There is no way to do this at all with a dynamic varobj.
28675 For C/C@t{++} structures there are several pseudo children returned to
28676 designate access qualifiers. For these pseudo children @var{exp} is
28677 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28678 type and value are not present.
28680 A dynamic varobj will not report the access qualifying
28681 pseudo-children, regardless of the language. This information is not
28682 available at all with a dynamic varobj.
28685 Number of children this child has. For a dynamic varobj, this will be
28689 The type of the child.
28692 If values were requested, this is the value.
28695 If this variable object is associated with a thread, this is the thread id.
28696 Otherwise this result is not present.
28699 If the variable object is frozen, this variable will be present with a value of 1.
28702 The result may have its own attributes:
28706 A dynamic varobj can supply a display hint to the front end. The
28707 value comes directly from the Python pretty-printer object's
28708 @code{display_hint} method. @xref{Pretty Printing API}.
28711 This is an integer attribute which is nonzero if there are children
28712 remaining after the end of the selected range.
28715 @subsubheading Example
28719 -var-list-children n
28720 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28721 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28723 -var-list-children --all-values n
28724 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28725 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28729 @subheading The @code{-var-info-type} Command
28730 @findex -var-info-type
28732 @subsubheading Synopsis
28735 -var-info-type @var{name}
28738 Returns the type of the specified variable @var{name}. The type is
28739 returned as a string in the same format as it is output by the
28743 type=@var{typename}
28747 @subheading The @code{-var-info-expression} Command
28748 @findex -var-info-expression
28750 @subsubheading Synopsis
28753 -var-info-expression @var{name}
28756 Returns a string that is suitable for presenting this
28757 variable object in user interface. The string is generally
28758 not valid expression in the current language, and cannot be evaluated.
28760 For example, if @code{a} is an array, and variable object
28761 @code{A} was created for @code{a}, then we'll get this output:
28764 (gdb) -var-info-expression A.1
28765 ^done,lang="C",exp="1"
28769 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28771 Note that the output of the @code{-var-list-children} command also
28772 includes those expressions, so the @code{-var-info-expression} command
28775 @subheading The @code{-var-info-path-expression} Command
28776 @findex -var-info-path-expression
28778 @subsubheading Synopsis
28781 -var-info-path-expression @var{name}
28784 Returns an expression that can be evaluated in the current
28785 context and will yield the same value that a variable object has.
28786 Compare this with the @code{-var-info-expression} command, which
28787 result can be used only for UI presentation. Typical use of
28788 the @code{-var-info-path-expression} command is creating a
28789 watchpoint from a variable object.
28791 This command is currently not valid for children of a dynamic varobj,
28792 and will give an error when invoked on one.
28794 For example, suppose @code{C} is a C@t{++} class, derived from class
28795 @code{Base}, and that the @code{Base} class has a member called
28796 @code{m_size}. Assume a variable @code{c} is has the type of
28797 @code{C} and a variable object @code{C} was created for variable
28798 @code{c}. Then, we'll get this output:
28800 (gdb) -var-info-path-expression C.Base.public.m_size
28801 ^done,path_expr=((Base)c).m_size)
28804 @subheading The @code{-var-show-attributes} Command
28805 @findex -var-show-attributes
28807 @subsubheading Synopsis
28810 -var-show-attributes @var{name}
28813 List attributes of the specified variable object @var{name}:
28816 status=@var{attr} [ ( ,@var{attr} )* ]
28820 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28822 @subheading The @code{-var-evaluate-expression} Command
28823 @findex -var-evaluate-expression
28825 @subsubheading Synopsis
28828 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28831 Evaluates the expression that is represented by the specified variable
28832 object and returns its value as a string. The format of the string
28833 can be specified with the @samp{-f} option. The possible values of
28834 this option are the same as for @code{-var-set-format}
28835 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28836 the current display format will be used. The current display format
28837 can be changed using the @code{-var-set-format} command.
28843 Note that one must invoke @code{-var-list-children} for a variable
28844 before the value of a child variable can be evaluated.
28846 @subheading The @code{-var-assign} Command
28847 @findex -var-assign
28849 @subsubheading Synopsis
28852 -var-assign @var{name} @var{expression}
28855 Assigns the value of @var{expression} to the variable object specified
28856 by @var{name}. The object must be @samp{editable}. If the variable's
28857 value is altered by the assign, the variable will show up in any
28858 subsequent @code{-var-update} list.
28860 @subsubheading Example
28868 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28872 @subheading The @code{-var-update} Command
28873 @findex -var-update
28875 @subsubheading Synopsis
28878 -var-update [@var{print-values}] @{@var{name} | "*"@}
28881 Reevaluate the expressions corresponding to the variable object
28882 @var{name} and all its direct and indirect children, and return the
28883 list of variable objects whose values have changed; @var{name} must
28884 be a root variable object. Here, ``changed'' means that the result of
28885 @code{-var-evaluate-expression} before and after the
28886 @code{-var-update} is different. If @samp{*} is used as the variable
28887 object names, all existing variable objects are updated, except
28888 for frozen ones (@pxref{-var-set-frozen}). The option
28889 @var{print-values} determines whether both names and values, or just
28890 names are printed. The possible values of this option are the same
28891 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28892 recommended to use the @samp{--all-values} option, to reduce the
28893 number of MI commands needed on each program stop.
28895 With the @samp{*} parameter, if a variable object is bound to a
28896 currently running thread, it will not be updated, without any
28899 If @code{-var-set-update-range} was previously used on a varobj, then
28900 only the selected range of children will be reported.
28902 @code{-var-update} reports all the changed varobjs in a tuple named
28905 Each item in the change list is itself a tuple holding:
28909 The name of the varobj.
28912 If values were requested for this update, then this field will be
28913 present and will hold the value of the varobj.
28916 @anchor{-var-update}
28917 This field is a string which may take one of three values:
28921 The variable object's current value is valid.
28924 The variable object does not currently hold a valid value but it may
28925 hold one in the future if its associated expression comes back into
28929 The variable object no longer holds a valid value.
28930 This can occur when the executable file being debugged has changed,
28931 either through recompilation or by using the @value{GDBN} @code{file}
28932 command. The front end should normally choose to delete these variable
28936 In the future new values may be added to this list so the front should
28937 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28940 This is only present if the varobj is still valid. If the type
28941 changed, then this will be the string @samp{true}; otherwise it will
28945 If the varobj's type changed, then this field will be present and will
28948 @item new_num_children
28949 For a dynamic varobj, if the number of children changed, or if the
28950 type changed, this will be the new number of children.
28952 The @samp{numchild} field in other varobj responses is generally not
28953 valid for a dynamic varobj -- it will show the number of children that
28954 @value{GDBN} knows about, but because dynamic varobjs lazily
28955 instantiate their children, this will not reflect the number of
28956 children which may be available.
28958 The @samp{new_num_children} attribute only reports changes to the
28959 number of children known by @value{GDBN}. This is the only way to
28960 detect whether an update has removed children (which necessarily can
28961 only happen at the end of the update range).
28964 The display hint, if any.
28967 This is an integer value, which will be 1 if there are more children
28968 available outside the varobj's update range.
28971 This attribute will be present and have the value @samp{1} if the
28972 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28973 then this attribute will not be present.
28976 If new children were added to a dynamic varobj within the selected
28977 update range (as set by @code{-var-set-update-range}), then they will
28978 be listed in this attribute.
28981 @subsubheading Example
28988 -var-update --all-values var1
28989 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28990 type_changed="false"@}]
28994 @subheading The @code{-var-set-frozen} Command
28995 @findex -var-set-frozen
28996 @anchor{-var-set-frozen}
28998 @subsubheading Synopsis
29001 -var-set-frozen @var{name} @var{flag}
29004 Set the frozenness flag on the variable object @var{name}. The
29005 @var{flag} parameter should be either @samp{1} to make the variable
29006 frozen or @samp{0} to make it unfrozen. If a variable object is
29007 frozen, then neither itself, nor any of its children, are
29008 implicitly updated by @code{-var-update} of
29009 a parent variable or by @code{-var-update *}. Only
29010 @code{-var-update} of the variable itself will update its value and
29011 values of its children. After a variable object is unfrozen, it is
29012 implicitly updated by all subsequent @code{-var-update} operations.
29013 Unfreezing a variable does not update it, only subsequent
29014 @code{-var-update} does.
29016 @subsubheading Example
29020 -var-set-frozen V 1
29025 @subheading The @code{-var-set-update-range} command
29026 @findex -var-set-update-range
29027 @anchor{-var-set-update-range}
29029 @subsubheading Synopsis
29032 -var-set-update-range @var{name} @var{from} @var{to}
29035 Set the range of children to be returned by future invocations of
29036 @code{-var-update}.
29038 @var{from} and @var{to} indicate the range of children to report. If
29039 @var{from} or @var{to} is less than zero, the range is reset and all
29040 children will be reported. Otherwise, children starting at @var{from}
29041 (zero-based) and up to and excluding @var{to} will be reported.
29043 @subsubheading Example
29047 -var-set-update-range V 1 2
29051 @subheading The @code{-var-set-visualizer} command
29052 @findex -var-set-visualizer
29053 @anchor{-var-set-visualizer}
29055 @subsubheading Synopsis
29058 -var-set-visualizer @var{name} @var{visualizer}
29061 Set a visualizer for the variable object @var{name}.
29063 @var{visualizer} is the visualizer to use. The special value
29064 @samp{None} means to disable any visualizer in use.
29066 If not @samp{None}, @var{visualizer} must be a Python expression.
29067 This expression must evaluate to a callable object which accepts a
29068 single argument. @value{GDBN} will call this object with the value of
29069 the varobj @var{name} as an argument (this is done so that the same
29070 Python pretty-printing code can be used for both the CLI and MI).
29071 When called, this object must return an object which conforms to the
29072 pretty-printing interface (@pxref{Pretty Printing API}).
29074 The pre-defined function @code{gdb.default_visualizer} may be used to
29075 select a visualizer by following the built-in process
29076 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29077 a varobj is created, and so ordinarily is not needed.
29079 This feature is only available if Python support is enabled. The MI
29080 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29081 can be used to check this.
29083 @subsubheading Example
29085 Resetting the visualizer:
29089 -var-set-visualizer V None
29093 Reselecting the default (type-based) visualizer:
29097 -var-set-visualizer V gdb.default_visualizer
29101 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29102 can be used to instantiate this class for a varobj:
29106 -var-set-visualizer V "lambda val: SomeClass()"
29110 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29111 @node GDB/MI Data Manipulation
29112 @section @sc{gdb/mi} Data Manipulation
29114 @cindex data manipulation, in @sc{gdb/mi}
29115 @cindex @sc{gdb/mi}, data manipulation
29116 This section describes the @sc{gdb/mi} commands that manipulate data:
29117 examine memory and registers, evaluate expressions, etc.
29119 @c REMOVED FROM THE INTERFACE.
29120 @c @subheading -data-assign
29121 @c Change the value of a program variable. Plenty of side effects.
29122 @c @subsubheading GDB Command
29124 @c @subsubheading Example
29127 @subheading The @code{-data-disassemble} Command
29128 @findex -data-disassemble
29130 @subsubheading Synopsis
29134 [ -s @var{start-addr} -e @var{end-addr} ]
29135 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29143 @item @var{start-addr}
29144 is the beginning address (or @code{$pc})
29145 @item @var{end-addr}
29147 @item @var{filename}
29148 is the name of the file to disassemble
29149 @item @var{linenum}
29150 is the line number to disassemble around
29152 is the number of disassembly lines to be produced. If it is -1,
29153 the whole function will be disassembled, in case no @var{end-addr} is
29154 specified. If @var{end-addr} is specified as a non-zero value, and
29155 @var{lines} is lower than the number of disassembly lines between
29156 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29157 displayed; if @var{lines} is higher than the number of lines between
29158 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29161 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29162 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29163 mixed source and disassembly with raw opcodes).
29166 @subsubheading Result
29168 The output for each instruction is composed of four fields:
29177 Note that whatever included in the instruction field, is not manipulated
29178 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29180 @subsubheading @value{GDBN} Command
29182 There's no direct mapping from this command to the CLI.
29184 @subsubheading Example
29186 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29190 -data-disassemble -s $pc -e "$pc + 20" -- 0
29193 @{address="0x000107c0",func-name="main",offset="4",
29194 inst="mov 2, %o0"@},
29195 @{address="0x000107c4",func-name="main",offset="8",
29196 inst="sethi %hi(0x11800), %o2"@},
29197 @{address="0x000107c8",func-name="main",offset="12",
29198 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29199 @{address="0x000107cc",func-name="main",offset="16",
29200 inst="sethi %hi(0x11800), %o2"@},
29201 @{address="0x000107d0",func-name="main",offset="20",
29202 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29206 Disassemble the whole @code{main} function. Line 32 is part of
29210 -data-disassemble -f basics.c -l 32 -- 0
29212 @{address="0x000107bc",func-name="main",offset="0",
29213 inst="save %sp, -112, %sp"@},
29214 @{address="0x000107c0",func-name="main",offset="4",
29215 inst="mov 2, %o0"@},
29216 @{address="0x000107c4",func-name="main",offset="8",
29217 inst="sethi %hi(0x11800), %o2"@},
29219 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29220 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29224 Disassemble 3 instructions from the start of @code{main}:
29228 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29230 @{address="0x000107bc",func-name="main",offset="0",
29231 inst="save %sp, -112, %sp"@},
29232 @{address="0x000107c0",func-name="main",offset="4",
29233 inst="mov 2, %o0"@},
29234 @{address="0x000107c4",func-name="main",offset="8",
29235 inst="sethi %hi(0x11800), %o2"@}]
29239 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29243 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29245 src_and_asm_line=@{line="31",
29246 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29247 testsuite/gdb.mi/basics.c",line_asm_insn=[
29248 @{address="0x000107bc",func-name="main",offset="0",
29249 inst="save %sp, -112, %sp"@}]@},
29250 src_and_asm_line=@{line="32",
29251 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29252 testsuite/gdb.mi/basics.c",line_asm_insn=[
29253 @{address="0x000107c0",func-name="main",offset="4",
29254 inst="mov 2, %o0"@},
29255 @{address="0x000107c4",func-name="main",offset="8",
29256 inst="sethi %hi(0x11800), %o2"@}]@}]
29261 @subheading The @code{-data-evaluate-expression} Command
29262 @findex -data-evaluate-expression
29264 @subsubheading Synopsis
29267 -data-evaluate-expression @var{expr}
29270 Evaluate @var{expr} as an expression. The expression could contain an
29271 inferior function call. The function call will execute synchronously.
29272 If the expression contains spaces, it must be enclosed in double quotes.
29274 @subsubheading @value{GDBN} Command
29276 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29277 @samp{call}. In @code{gdbtk} only, there's a corresponding
29278 @samp{gdb_eval} command.
29280 @subsubheading Example
29282 In the following example, the numbers that precede the commands are the
29283 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29284 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29288 211-data-evaluate-expression A
29291 311-data-evaluate-expression &A
29292 311^done,value="0xefffeb7c"
29294 411-data-evaluate-expression A+3
29297 511-data-evaluate-expression "A + 3"
29303 @subheading The @code{-data-list-changed-registers} Command
29304 @findex -data-list-changed-registers
29306 @subsubheading Synopsis
29309 -data-list-changed-registers
29312 Display a list of the registers that have changed.
29314 @subsubheading @value{GDBN} Command
29316 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29317 has the corresponding command @samp{gdb_changed_register_list}.
29319 @subsubheading Example
29321 On a PPC MBX board:
29329 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29330 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29333 -data-list-changed-registers
29334 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29335 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29336 "24","25","26","27","28","30","31","64","65","66","67","69"]
29341 @subheading The @code{-data-list-register-names} Command
29342 @findex -data-list-register-names
29344 @subsubheading Synopsis
29347 -data-list-register-names [ ( @var{regno} )+ ]
29350 Show a list of register names for the current target. If no arguments
29351 are given, it shows a list of the names of all the registers. If
29352 integer numbers are given as arguments, it will print a list of the
29353 names of the registers corresponding to the arguments. To ensure
29354 consistency between a register name and its number, the output list may
29355 include empty register names.
29357 @subsubheading @value{GDBN} Command
29359 @value{GDBN} does not have a command which corresponds to
29360 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29361 corresponding command @samp{gdb_regnames}.
29363 @subsubheading Example
29365 For the PPC MBX board:
29368 -data-list-register-names
29369 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29370 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29371 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29372 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29373 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29374 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29375 "", "pc","ps","cr","lr","ctr","xer"]
29377 -data-list-register-names 1 2 3
29378 ^done,register-names=["r1","r2","r3"]
29382 @subheading The @code{-data-list-register-values} Command
29383 @findex -data-list-register-values
29385 @subsubheading Synopsis
29388 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29391 Display the registers' contents. @var{fmt} is the format according to
29392 which the registers' contents are to be returned, followed by an optional
29393 list of numbers specifying the registers to display. A missing list of
29394 numbers indicates that the contents of all the registers must be returned.
29396 Allowed formats for @var{fmt} are:
29413 @subsubheading @value{GDBN} Command
29415 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29416 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29418 @subsubheading Example
29420 For a PPC MBX board (note: line breaks are for readability only, they
29421 don't appear in the actual output):
29425 -data-list-register-values r 64 65
29426 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29427 @{number="65",value="0x00029002"@}]
29429 -data-list-register-values x
29430 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29431 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29432 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29433 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29434 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29435 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29436 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29437 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29438 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29439 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29440 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29441 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29442 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29443 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29444 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29445 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29446 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29447 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29448 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29449 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29450 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29451 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29452 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29453 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29454 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29455 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29456 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29457 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29458 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29459 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29460 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29461 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29462 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29463 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29464 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29465 @{number="69",value="0x20002b03"@}]
29470 @subheading The @code{-data-read-memory} Command
29471 @findex -data-read-memory
29473 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29475 @subsubheading Synopsis
29478 -data-read-memory [ -o @var{byte-offset} ]
29479 @var{address} @var{word-format} @var{word-size}
29480 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29487 @item @var{address}
29488 An expression specifying the address of the first memory word to be
29489 read. Complex expressions containing embedded white space should be
29490 quoted using the C convention.
29492 @item @var{word-format}
29493 The format to be used to print the memory words. The notation is the
29494 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29497 @item @var{word-size}
29498 The size of each memory word in bytes.
29500 @item @var{nr-rows}
29501 The number of rows in the output table.
29503 @item @var{nr-cols}
29504 The number of columns in the output table.
29507 If present, indicates that each row should include an @sc{ascii} dump. The
29508 value of @var{aschar} is used as a padding character when a byte is not a
29509 member of the printable @sc{ascii} character set (printable @sc{ascii}
29510 characters are those whose code is between 32 and 126, inclusively).
29512 @item @var{byte-offset}
29513 An offset to add to the @var{address} before fetching memory.
29516 This command displays memory contents as a table of @var{nr-rows} by
29517 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29518 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29519 (returned as @samp{total-bytes}). Should less than the requested number
29520 of bytes be returned by the target, the missing words are identified
29521 using @samp{N/A}. The number of bytes read from the target is returned
29522 in @samp{nr-bytes} and the starting address used to read memory in
29525 The address of the next/previous row or page is available in
29526 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29529 @subsubheading @value{GDBN} Command
29531 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29532 @samp{gdb_get_mem} memory read command.
29534 @subsubheading Example
29536 Read six bytes of memory starting at @code{bytes+6} but then offset by
29537 @code{-6} bytes. Format as three rows of two columns. One byte per
29538 word. Display each word in hex.
29542 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29543 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29544 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29545 prev-page="0x0000138a",memory=[
29546 @{addr="0x00001390",data=["0x00","0x01"]@},
29547 @{addr="0x00001392",data=["0x02","0x03"]@},
29548 @{addr="0x00001394",data=["0x04","0x05"]@}]
29552 Read two bytes of memory starting at address @code{shorts + 64} and
29553 display as a single word formatted in decimal.
29557 5-data-read-memory shorts+64 d 2 1 1
29558 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29559 next-row="0x00001512",prev-row="0x0000150e",
29560 next-page="0x00001512",prev-page="0x0000150e",memory=[
29561 @{addr="0x00001510",data=["128"]@}]
29565 Read thirty two bytes of memory starting at @code{bytes+16} and format
29566 as eight rows of four columns. Include a string encoding with @samp{x}
29567 used as the non-printable character.
29571 4-data-read-memory bytes+16 x 1 8 4 x
29572 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29573 next-row="0x000013c0",prev-row="0x0000139c",
29574 next-page="0x000013c0",prev-page="0x00001380",memory=[
29575 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29576 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29577 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29578 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29579 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29580 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29581 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29582 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29586 @subheading The @code{-data-read-memory-bytes} Command
29587 @findex -data-read-memory-bytes
29589 @subsubheading Synopsis
29592 -data-read-memory-bytes [ -o @var{byte-offset} ]
29593 @var{address} @var{count}
29600 @item @var{address}
29601 An expression specifying the address of the first memory word to be
29602 read. Complex expressions containing embedded white space should be
29603 quoted using the C convention.
29606 The number of bytes to read. This should be an integer literal.
29608 @item @var{byte-offset}
29609 The offsets in bytes relative to @var{address} at which to start
29610 reading. This should be an integer literal. This option is provided
29611 so that a frontend is not required to first evaluate address and then
29612 perform address arithmetics itself.
29616 This command attempts to read all accessible memory regions in the
29617 specified range. First, all regions marked as unreadable in the memory
29618 map (if one is defined) will be skipped. @xref{Memory Region
29619 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29620 regions. For each one, if reading full region results in an errors,
29621 @value{GDBN} will try to read a subset of the region.
29623 In general, every single byte in the region may be readable or not,
29624 and the only way to read every readable byte is to try a read at
29625 every address, which is not practical. Therefore, @value{GDBN} will
29626 attempt to read all accessible bytes at either beginning or the end
29627 of the region, using a binary division scheme. This heuristic works
29628 well for reading accross a memory map boundary. Note that if a region
29629 has a readable range that is neither at the beginning or the end,
29630 @value{GDBN} will not read it.
29632 The result record (@pxref{GDB/MI Result Records}) that is output of
29633 the command includes a field named @samp{memory} whose content is a
29634 list of tuples. Each tuple represent a successfully read memory block
29635 and has the following fields:
29639 The start address of the memory block, as hexadecimal literal.
29642 The end address of the memory block, as hexadecimal literal.
29645 The offset of the memory block, as hexadecimal literal, relative to
29646 the start address passed to @code{-data-read-memory-bytes}.
29649 The contents of the memory block, in hex.
29655 @subsubheading @value{GDBN} Command
29657 The corresponding @value{GDBN} command is @samp{x}.
29659 @subsubheading Example
29663 -data-read-memory-bytes &a 10
29664 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29666 contents="01000000020000000300"@}]
29671 @subheading The @code{-data-write-memory-bytes} Command
29672 @findex -data-write-memory-bytes
29674 @subsubheading Synopsis
29677 -data-write-memory-bytes @var{address} @var{contents}
29684 @item @var{address}
29685 An expression specifying the address of the first memory word to be
29686 read. Complex expressions containing embedded white space should be
29687 quoted using the C convention.
29689 @item @var{contents}
29690 The hex-encoded bytes to write.
29694 @subsubheading @value{GDBN} Command
29696 There's no corresponding @value{GDBN} command.
29698 @subsubheading Example
29702 -data-write-memory-bytes &a "aabbccdd"
29708 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29709 @node GDB/MI Tracepoint Commands
29710 @section @sc{gdb/mi} Tracepoint Commands
29712 The commands defined in this section implement MI support for
29713 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29715 @subheading The @code{-trace-find} Command
29716 @findex -trace-find
29718 @subsubheading Synopsis
29721 -trace-find @var{mode} [@var{parameters}@dots{}]
29724 Find a trace frame using criteria defined by @var{mode} and
29725 @var{parameters}. The following table lists permissible
29726 modes and their parameters. For details of operation, see @ref{tfind}.
29731 No parameters are required. Stops examining trace frames.
29734 An integer is required as parameter. Selects tracepoint frame with
29737 @item tracepoint-number
29738 An integer is required as parameter. Finds next
29739 trace frame that corresponds to tracepoint with the specified number.
29742 An address is required as parameter. Finds
29743 next trace frame that corresponds to any tracepoint at the specified
29746 @item pc-inside-range
29747 Two addresses are required as parameters. Finds next trace
29748 frame that corresponds to a tracepoint at an address inside the
29749 specified range. Both bounds are considered to be inside the range.
29751 @item pc-outside-range
29752 Two addresses are required as parameters. Finds
29753 next trace frame that corresponds to a tracepoint at an address outside
29754 the specified range. Both bounds are considered to be inside the range.
29757 Line specification is required as parameter. @xref{Specify Location}.
29758 Finds next trace frame that corresponds to a tracepoint at
29759 the specified location.
29763 If @samp{none} was passed as @var{mode}, the response does not
29764 have fields. Otherwise, the response may have the following fields:
29768 This field has either @samp{0} or @samp{1} as the value, depending
29769 on whether a matching tracepoint was found.
29772 The index of the found traceframe. This field is present iff
29773 the @samp{found} field has value of @samp{1}.
29776 The index of the found tracepoint. This field is present iff
29777 the @samp{found} field has value of @samp{1}.
29780 The information about the frame corresponding to the found trace
29781 frame. This field is present only if a trace frame was found.
29782 @xref{GDB/MI Frame Information}, for description of this field.
29786 @subsubheading @value{GDBN} Command
29788 The corresponding @value{GDBN} command is @samp{tfind}.
29790 @subheading -trace-define-variable
29791 @findex -trace-define-variable
29793 @subsubheading Synopsis
29796 -trace-define-variable @var{name} [ @var{value} ]
29799 Create trace variable @var{name} if it does not exist. If
29800 @var{value} is specified, sets the initial value of the specified
29801 trace variable to that value. Note that the @var{name} should start
29802 with the @samp{$} character.
29804 @subsubheading @value{GDBN} Command
29806 The corresponding @value{GDBN} command is @samp{tvariable}.
29808 @subheading -trace-list-variables
29809 @findex -trace-list-variables
29811 @subsubheading Synopsis
29814 -trace-list-variables
29817 Return a table of all defined trace variables. Each element of the
29818 table has the following fields:
29822 The name of the trace variable. This field is always present.
29825 The initial value. This is a 64-bit signed integer. This
29826 field is always present.
29829 The value the trace variable has at the moment. This is a 64-bit
29830 signed integer. This field is absent iff current value is
29831 not defined, for example if the trace was never run, or is
29836 @subsubheading @value{GDBN} Command
29838 The corresponding @value{GDBN} command is @samp{tvariables}.
29840 @subsubheading Example
29844 -trace-list-variables
29845 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29846 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29847 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29848 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29849 body=[variable=@{name="$trace_timestamp",initial="0"@}
29850 variable=@{name="$foo",initial="10",current="15"@}]@}
29854 @subheading -trace-save
29855 @findex -trace-save
29857 @subsubheading Synopsis
29860 -trace-save [-r ] @var{filename}
29863 Saves the collected trace data to @var{filename}. Without the
29864 @samp{-r} option, the data is downloaded from the target and saved
29865 in a local file. With the @samp{-r} option the target is asked
29866 to perform the save.
29868 @subsubheading @value{GDBN} Command
29870 The corresponding @value{GDBN} command is @samp{tsave}.
29873 @subheading -trace-start
29874 @findex -trace-start
29876 @subsubheading Synopsis
29882 Starts a tracing experiments. The result of this command does not
29885 @subsubheading @value{GDBN} Command
29887 The corresponding @value{GDBN} command is @samp{tstart}.
29889 @subheading -trace-status
29890 @findex -trace-status
29892 @subsubheading Synopsis
29898 Obtains the status of a tracing experiment. The result may include
29899 the following fields:
29904 May have a value of either @samp{0}, when no tracing operations are
29905 supported, @samp{1}, when all tracing operations are supported, or
29906 @samp{file} when examining trace file. In the latter case, examining
29907 of trace frame is possible but new tracing experiement cannot be
29908 started. This field is always present.
29911 May have a value of either @samp{0} or @samp{1} depending on whether
29912 tracing experiement is in progress on target. This field is present
29913 if @samp{supported} field is not @samp{0}.
29916 Report the reason why the tracing was stopped last time. This field
29917 may be absent iff tracing was never stopped on target yet. The
29918 value of @samp{request} means the tracing was stopped as result of
29919 the @code{-trace-stop} command. The value of @samp{overflow} means
29920 the tracing buffer is full. The value of @samp{disconnection} means
29921 tracing was automatically stopped when @value{GDBN} has disconnected.
29922 The value of @samp{passcount} means tracing was stopped when a
29923 tracepoint was passed a maximal number of times for that tracepoint.
29924 This field is present if @samp{supported} field is not @samp{0}.
29926 @item stopping-tracepoint
29927 The number of tracepoint whose passcount as exceeded. This field is
29928 present iff the @samp{stop-reason} field has the value of
29932 @itemx frames-created
29933 The @samp{frames} field is a count of the total number of trace frames
29934 in the trace buffer, while @samp{frames-created} is the total created
29935 during the run, including ones that were discarded, such as when a
29936 circular trace buffer filled up. Both fields are optional.
29940 These fields tell the current size of the tracing buffer and the
29941 remaining space. These fields are optional.
29944 The value of the circular trace buffer flag. @code{1} means that the
29945 trace buffer is circular and old trace frames will be discarded if
29946 necessary to make room, @code{0} means that the trace buffer is linear
29950 The value of the disconnected tracing flag. @code{1} means that
29951 tracing will continue after @value{GDBN} disconnects, @code{0} means
29952 that the trace run will stop.
29956 @subsubheading @value{GDBN} Command
29958 The corresponding @value{GDBN} command is @samp{tstatus}.
29960 @subheading -trace-stop
29961 @findex -trace-stop
29963 @subsubheading Synopsis
29969 Stops a tracing experiment. The result of this command has the same
29970 fields as @code{-trace-status}, except that the @samp{supported} and
29971 @samp{running} fields are not output.
29973 @subsubheading @value{GDBN} Command
29975 The corresponding @value{GDBN} command is @samp{tstop}.
29978 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29979 @node GDB/MI Symbol Query
29980 @section @sc{gdb/mi} Symbol Query Commands
29984 @subheading The @code{-symbol-info-address} Command
29985 @findex -symbol-info-address
29987 @subsubheading Synopsis
29990 -symbol-info-address @var{symbol}
29993 Describe where @var{symbol} is stored.
29995 @subsubheading @value{GDBN} Command
29997 The corresponding @value{GDBN} command is @samp{info address}.
29999 @subsubheading Example
30003 @subheading The @code{-symbol-info-file} Command
30004 @findex -symbol-info-file
30006 @subsubheading Synopsis
30012 Show the file for the symbol.
30014 @subsubheading @value{GDBN} Command
30016 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30017 @samp{gdb_find_file}.
30019 @subsubheading Example
30023 @subheading The @code{-symbol-info-function} Command
30024 @findex -symbol-info-function
30026 @subsubheading Synopsis
30029 -symbol-info-function
30032 Show which function the symbol lives in.
30034 @subsubheading @value{GDBN} Command
30036 @samp{gdb_get_function} in @code{gdbtk}.
30038 @subsubheading Example
30042 @subheading The @code{-symbol-info-line} Command
30043 @findex -symbol-info-line
30045 @subsubheading Synopsis
30051 Show the core addresses of the code for a source line.
30053 @subsubheading @value{GDBN} Command
30055 The corresponding @value{GDBN} command is @samp{info line}.
30056 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30058 @subsubheading Example
30062 @subheading The @code{-symbol-info-symbol} Command
30063 @findex -symbol-info-symbol
30065 @subsubheading Synopsis
30068 -symbol-info-symbol @var{addr}
30071 Describe what symbol is at location @var{addr}.
30073 @subsubheading @value{GDBN} Command
30075 The corresponding @value{GDBN} command is @samp{info symbol}.
30077 @subsubheading Example
30081 @subheading The @code{-symbol-list-functions} Command
30082 @findex -symbol-list-functions
30084 @subsubheading Synopsis
30087 -symbol-list-functions
30090 List the functions in the executable.
30092 @subsubheading @value{GDBN} Command
30094 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30095 @samp{gdb_search} in @code{gdbtk}.
30097 @subsubheading Example
30102 @subheading The @code{-symbol-list-lines} Command
30103 @findex -symbol-list-lines
30105 @subsubheading Synopsis
30108 -symbol-list-lines @var{filename}
30111 Print the list of lines that contain code and their associated program
30112 addresses for the given source filename. The entries are sorted in
30113 ascending PC order.
30115 @subsubheading @value{GDBN} Command
30117 There is no corresponding @value{GDBN} command.
30119 @subsubheading Example
30122 -symbol-list-lines basics.c
30123 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30129 @subheading The @code{-symbol-list-types} Command
30130 @findex -symbol-list-types
30132 @subsubheading Synopsis
30138 List all the type names.
30140 @subsubheading @value{GDBN} Command
30142 The corresponding commands are @samp{info types} in @value{GDBN},
30143 @samp{gdb_search} in @code{gdbtk}.
30145 @subsubheading Example
30149 @subheading The @code{-symbol-list-variables} Command
30150 @findex -symbol-list-variables
30152 @subsubheading Synopsis
30155 -symbol-list-variables
30158 List all the global and static variable names.
30160 @subsubheading @value{GDBN} Command
30162 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30164 @subsubheading Example
30168 @subheading The @code{-symbol-locate} Command
30169 @findex -symbol-locate
30171 @subsubheading Synopsis
30177 @subsubheading @value{GDBN} Command
30179 @samp{gdb_loc} in @code{gdbtk}.
30181 @subsubheading Example
30185 @subheading The @code{-symbol-type} Command
30186 @findex -symbol-type
30188 @subsubheading Synopsis
30191 -symbol-type @var{variable}
30194 Show type of @var{variable}.
30196 @subsubheading @value{GDBN} Command
30198 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30199 @samp{gdb_obj_variable}.
30201 @subsubheading Example
30206 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30207 @node GDB/MI File Commands
30208 @section @sc{gdb/mi} File Commands
30210 This section describes the GDB/MI commands to specify executable file names
30211 and to read in and obtain symbol table information.
30213 @subheading The @code{-file-exec-and-symbols} Command
30214 @findex -file-exec-and-symbols
30216 @subsubheading Synopsis
30219 -file-exec-and-symbols @var{file}
30222 Specify the executable file to be debugged. This file is the one from
30223 which the symbol table is also read. If no file is specified, the
30224 command clears the executable and symbol information. If breakpoints
30225 are set when using this command with no arguments, @value{GDBN} will produce
30226 error messages. Otherwise, no output is produced, except a completion
30229 @subsubheading @value{GDBN} Command
30231 The corresponding @value{GDBN} command is @samp{file}.
30233 @subsubheading Example
30237 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30243 @subheading The @code{-file-exec-file} Command
30244 @findex -file-exec-file
30246 @subsubheading Synopsis
30249 -file-exec-file @var{file}
30252 Specify the executable file to be debugged. Unlike
30253 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30254 from this file. If used without argument, @value{GDBN} clears the information
30255 about the executable file. No output is produced, except a completion
30258 @subsubheading @value{GDBN} Command
30260 The corresponding @value{GDBN} command is @samp{exec-file}.
30262 @subsubheading Example
30266 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30273 @subheading The @code{-file-list-exec-sections} Command
30274 @findex -file-list-exec-sections
30276 @subsubheading Synopsis
30279 -file-list-exec-sections
30282 List the sections of the current executable file.
30284 @subsubheading @value{GDBN} Command
30286 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30287 information as this command. @code{gdbtk} has a corresponding command
30288 @samp{gdb_load_info}.
30290 @subsubheading Example
30295 @subheading The @code{-file-list-exec-source-file} Command
30296 @findex -file-list-exec-source-file
30298 @subsubheading Synopsis
30301 -file-list-exec-source-file
30304 List the line number, the current source file, and the absolute path
30305 to the current source file for the current executable. The macro
30306 information field has a value of @samp{1} or @samp{0} depending on
30307 whether or not the file includes preprocessor macro information.
30309 @subsubheading @value{GDBN} Command
30311 The @value{GDBN} equivalent is @samp{info source}
30313 @subsubheading Example
30317 123-file-list-exec-source-file
30318 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30323 @subheading The @code{-file-list-exec-source-files} Command
30324 @findex -file-list-exec-source-files
30326 @subsubheading Synopsis
30329 -file-list-exec-source-files
30332 List the source files for the current executable.
30334 It will always output the filename, but only when @value{GDBN} can find
30335 the absolute file name of a source file, will it output the fullname.
30337 @subsubheading @value{GDBN} Command
30339 The @value{GDBN} equivalent is @samp{info sources}.
30340 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30342 @subsubheading Example
30345 -file-list-exec-source-files
30347 @{file=foo.c,fullname=/home/foo.c@},
30348 @{file=/home/bar.c,fullname=/home/bar.c@},
30349 @{file=gdb_could_not_find_fullpath.c@}]
30354 @subheading The @code{-file-list-shared-libraries} Command
30355 @findex -file-list-shared-libraries
30357 @subsubheading Synopsis
30360 -file-list-shared-libraries
30363 List the shared libraries in the program.
30365 @subsubheading @value{GDBN} Command
30367 The corresponding @value{GDBN} command is @samp{info shared}.
30369 @subsubheading Example
30373 @subheading The @code{-file-list-symbol-files} Command
30374 @findex -file-list-symbol-files
30376 @subsubheading Synopsis
30379 -file-list-symbol-files
30384 @subsubheading @value{GDBN} Command
30386 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30388 @subsubheading Example
30393 @subheading The @code{-file-symbol-file} Command
30394 @findex -file-symbol-file
30396 @subsubheading Synopsis
30399 -file-symbol-file @var{file}
30402 Read symbol table info from the specified @var{file} argument. When
30403 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30404 produced, except for a completion notification.
30406 @subsubheading @value{GDBN} Command
30408 The corresponding @value{GDBN} command is @samp{symbol-file}.
30410 @subsubheading Example
30414 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30420 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30421 @node GDB/MI Memory Overlay Commands
30422 @section @sc{gdb/mi} Memory Overlay Commands
30424 The memory overlay commands are not implemented.
30426 @c @subheading -overlay-auto
30428 @c @subheading -overlay-list-mapping-state
30430 @c @subheading -overlay-list-overlays
30432 @c @subheading -overlay-map
30434 @c @subheading -overlay-off
30436 @c @subheading -overlay-on
30438 @c @subheading -overlay-unmap
30440 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30441 @node GDB/MI Signal Handling Commands
30442 @section @sc{gdb/mi} Signal Handling Commands
30444 Signal handling commands are not implemented.
30446 @c @subheading -signal-handle
30448 @c @subheading -signal-list-handle-actions
30450 @c @subheading -signal-list-signal-types
30454 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30455 @node GDB/MI Target Manipulation
30456 @section @sc{gdb/mi} Target Manipulation Commands
30459 @subheading The @code{-target-attach} Command
30460 @findex -target-attach
30462 @subsubheading Synopsis
30465 -target-attach @var{pid} | @var{gid} | @var{file}
30468 Attach to a process @var{pid} or a file @var{file} outside of
30469 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30470 group, the id previously returned by
30471 @samp{-list-thread-groups --available} must be used.
30473 @subsubheading @value{GDBN} Command
30475 The corresponding @value{GDBN} command is @samp{attach}.
30477 @subsubheading Example
30481 =thread-created,id="1"
30482 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30488 @subheading The @code{-target-compare-sections} Command
30489 @findex -target-compare-sections
30491 @subsubheading Synopsis
30494 -target-compare-sections [ @var{section} ]
30497 Compare data of section @var{section} on target to the exec file.
30498 Without the argument, all sections are compared.
30500 @subsubheading @value{GDBN} Command
30502 The @value{GDBN} equivalent is @samp{compare-sections}.
30504 @subsubheading Example
30509 @subheading The @code{-target-detach} Command
30510 @findex -target-detach
30512 @subsubheading Synopsis
30515 -target-detach [ @var{pid} | @var{gid} ]
30518 Detach from the remote target which normally resumes its execution.
30519 If either @var{pid} or @var{gid} is specified, detaches from either
30520 the specified process, or specified thread group. There's no output.
30522 @subsubheading @value{GDBN} Command
30524 The corresponding @value{GDBN} command is @samp{detach}.
30526 @subsubheading Example
30536 @subheading The @code{-target-disconnect} Command
30537 @findex -target-disconnect
30539 @subsubheading Synopsis
30545 Disconnect from the remote target. There's no output and the target is
30546 generally not resumed.
30548 @subsubheading @value{GDBN} Command
30550 The corresponding @value{GDBN} command is @samp{disconnect}.
30552 @subsubheading Example
30562 @subheading The @code{-target-download} Command
30563 @findex -target-download
30565 @subsubheading Synopsis
30571 Loads the executable onto the remote target.
30572 It prints out an update message every half second, which includes the fields:
30576 The name of the section.
30578 The size of what has been sent so far for that section.
30580 The size of the section.
30582 The total size of what was sent so far (the current and the previous sections).
30584 The size of the overall executable to download.
30588 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30589 @sc{gdb/mi} Output Syntax}).
30591 In addition, it prints the name and size of the sections, as they are
30592 downloaded. These messages include the following fields:
30596 The name of the section.
30598 The size of the section.
30600 The size of the overall executable to download.
30604 At the end, a summary is printed.
30606 @subsubheading @value{GDBN} Command
30608 The corresponding @value{GDBN} command is @samp{load}.
30610 @subsubheading Example
30612 Note: each status message appears on a single line. Here the messages
30613 have been broken down so that they can fit onto a page.
30618 +download,@{section=".text",section-size="6668",total-size="9880"@}
30619 +download,@{section=".text",section-sent="512",section-size="6668",
30620 total-sent="512",total-size="9880"@}
30621 +download,@{section=".text",section-sent="1024",section-size="6668",
30622 total-sent="1024",total-size="9880"@}
30623 +download,@{section=".text",section-sent="1536",section-size="6668",
30624 total-sent="1536",total-size="9880"@}
30625 +download,@{section=".text",section-sent="2048",section-size="6668",
30626 total-sent="2048",total-size="9880"@}
30627 +download,@{section=".text",section-sent="2560",section-size="6668",
30628 total-sent="2560",total-size="9880"@}
30629 +download,@{section=".text",section-sent="3072",section-size="6668",
30630 total-sent="3072",total-size="9880"@}
30631 +download,@{section=".text",section-sent="3584",section-size="6668",
30632 total-sent="3584",total-size="9880"@}
30633 +download,@{section=".text",section-sent="4096",section-size="6668",
30634 total-sent="4096",total-size="9880"@}
30635 +download,@{section=".text",section-sent="4608",section-size="6668",
30636 total-sent="4608",total-size="9880"@}
30637 +download,@{section=".text",section-sent="5120",section-size="6668",
30638 total-sent="5120",total-size="9880"@}
30639 +download,@{section=".text",section-sent="5632",section-size="6668",
30640 total-sent="5632",total-size="9880"@}
30641 +download,@{section=".text",section-sent="6144",section-size="6668",
30642 total-sent="6144",total-size="9880"@}
30643 +download,@{section=".text",section-sent="6656",section-size="6668",
30644 total-sent="6656",total-size="9880"@}
30645 +download,@{section=".init",section-size="28",total-size="9880"@}
30646 +download,@{section=".fini",section-size="28",total-size="9880"@}
30647 +download,@{section=".data",section-size="3156",total-size="9880"@}
30648 +download,@{section=".data",section-sent="512",section-size="3156",
30649 total-sent="7236",total-size="9880"@}
30650 +download,@{section=".data",section-sent="1024",section-size="3156",
30651 total-sent="7748",total-size="9880"@}
30652 +download,@{section=".data",section-sent="1536",section-size="3156",
30653 total-sent="8260",total-size="9880"@}
30654 +download,@{section=".data",section-sent="2048",section-size="3156",
30655 total-sent="8772",total-size="9880"@}
30656 +download,@{section=".data",section-sent="2560",section-size="3156",
30657 total-sent="9284",total-size="9880"@}
30658 +download,@{section=".data",section-sent="3072",section-size="3156",
30659 total-sent="9796",total-size="9880"@}
30660 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30667 @subheading The @code{-target-exec-status} Command
30668 @findex -target-exec-status
30670 @subsubheading Synopsis
30673 -target-exec-status
30676 Provide information on the state of the target (whether it is running or
30677 not, for instance).
30679 @subsubheading @value{GDBN} Command
30681 There's no equivalent @value{GDBN} command.
30683 @subsubheading Example
30687 @subheading The @code{-target-list-available-targets} Command
30688 @findex -target-list-available-targets
30690 @subsubheading Synopsis
30693 -target-list-available-targets
30696 List the possible targets to connect to.
30698 @subsubheading @value{GDBN} Command
30700 The corresponding @value{GDBN} command is @samp{help target}.
30702 @subsubheading Example
30706 @subheading The @code{-target-list-current-targets} Command
30707 @findex -target-list-current-targets
30709 @subsubheading Synopsis
30712 -target-list-current-targets
30715 Describe the current target.
30717 @subsubheading @value{GDBN} Command
30719 The corresponding information is printed by @samp{info file} (among
30722 @subsubheading Example
30726 @subheading The @code{-target-list-parameters} Command
30727 @findex -target-list-parameters
30729 @subsubheading Synopsis
30732 -target-list-parameters
30738 @subsubheading @value{GDBN} Command
30742 @subsubheading Example
30746 @subheading The @code{-target-select} Command
30747 @findex -target-select
30749 @subsubheading Synopsis
30752 -target-select @var{type} @var{parameters @dots{}}
30755 Connect @value{GDBN} to the remote target. This command takes two args:
30759 The type of target, for instance @samp{remote}, etc.
30760 @item @var{parameters}
30761 Device names, host names and the like. @xref{Target Commands, ,
30762 Commands for Managing Targets}, for more details.
30765 The output is a connection notification, followed by the address at
30766 which the target program is, in the following form:
30769 ^connected,addr="@var{address}",func="@var{function name}",
30770 args=[@var{arg list}]
30773 @subsubheading @value{GDBN} Command
30775 The corresponding @value{GDBN} command is @samp{target}.
30777 @subsubheading Example
30781 -target-select remote /dev/ttya
30782 ^connected,addr="0xfe00a300",func="??",args=[]
30786 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30787 @node GDB/MI File Transfer Commands
30788 @section @sc{gdb/mi} File Transfer Commands
30791 @subheading The @code{-target-file-put} Command
30792 @findex -target-file-put
30794 @subsubheading Synopsis
30797 -target-file-put @var{hostfile} @var{targetfile}
30800 Copy file @var{hostfile} from the host system (the machine running
30801 @value{GDBN}) to @var{targetfile} on the target system.
30803 @subsubheading @value{GDBN} Command
30805 The corresponding @value{GDBN} command is @samp{remote put}.
30807 @subsubheading Example
30811 -target-file-put localfile remotefile
30817 @subheading The @code{-target-file-get} Command
30818 @findex -target-file-get
30820 @subsubheading Synopsis
30823 -target-file-get @var{targetfile} @var{hostfile}
30826 Copy file @var{targetfile} from the target system to @var{hostfile}
30827 on the host system.
30829 @subsubheading @value{GDBN} Command
30831 The corresponding @value{GDBN} command is @samp{remote get}.
30833 @subsubheading Example
30837 -target-file-get remotefile localfile
30843 @subheading The @code{-target-file-delete} Command
30844 @findex -target-file-delete
30846 @subsubheading Synopsis
30849 -target-file-delete @var{targetfile}
30852 Delete @var{targetfile} from the target system.
30854 @subsubheading @value{GDBN} Command
30856 The corresponding @value{GDBN} command is @samp{remote delete}.
30858 @subsubheading Example
30862 -target-file-delete remotefile
30868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30869 @node GDB/MI Miscellaneous Commands
30870 @section Miscellaneous @sc{gdb/mi} Commands
30872 @c @subheading -gdb-complete
30874 @subheading The @code{-gdb-exit} Command
30877 @subsubheading Synopsis
30883 Exit @value{GDBN} immediately.
30885 @subsubheading @value{GDBN} Command
30887 Approximately corresponds to @samp{quit}.
30889 @subsubheading Example
30899 @subheading The @code{-exec-abort} Command
30900 @findex -exec-abort
30902 @subsubheading Synopsis
30908 Kill the inferior running program.
30910 @subsubheading @value{GDBN} Command
30912 The corresponding @value{GDBN} command is @samp{kill}.
30914 @subsubheading Example
30919 @subheading The @code{-gdb-set} Command
30922 @subsubheading Synopsis
30928 Set an internal @value{GDBN} variable.
30929 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
30931 @subsubheading @value{GDBN} Command
30933 The corresponding @value{GDBN} command is @samp{set}.
30935 @subsubheading Example
30945 @subheading The @code{-gdb-show} Command
30948 @subsubheading Synopsis
30954 Show the current value of a @value{GDBN} variable.
30956 @subsubheading @value{GDBN} Command
30958 The corresponding @value{GDBN} command is @samp{show}.
30960 @subsubheading Example
30969 @c @subheading -gdb-source
30972 @subheading The @code{-gdb-version} Command
30973 @findex -gdb-version
30975 @subsubheading Synopsis
30981 Show version information for @value{GDBN}. Used mostly in testing.
30983 @subsubheading @value{GDBN} Command
30985 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
30986 default shows this information when you start an interactive session.
30988 @subsubheading Example
30990 @c This example modifies the actual output from GDB to avoid overfull
30996 ~Copyright 2000 Free Software Foundation, Inc.
30997 ~GDB is free software, covered by the GNU General Public License, and
30998 ~you are welcome to change it and/or distribute copies of it under
30999 ~ certain conditions.
31000 ~Type "show copying" to see the conditions.
31001 ~There is absolutely no warranty for GDB. Type "show warranty" for
31003 ~This GDB was configured as
31004 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31009 @subheading The @code{-list-features} Command
31010 @findex -list-features
31012 Returns a list of particular features of the MI protocol that
31013 this version of gdb implements. A feature can be a command,
31014 or a new field in an output of some command, or even an
31015 important bugfix. While a frontend can sometimes detect presence
31016 of a feature at runtime, it is easier to perform detection at debugger
31019 The command returns a list of strings, with each string naming an
31020 available feature. Each returned string is just a name, it does not
31021 have any internal structure. The list of possible feature names
31027 (gdb) -list-features
31028 ^done,result=["feature1","feature2"]
31031 The current list of features is:
31034 @item frozen-varobjs
31035 Indicates support for the @code{-var-set-frozen} command, as well
31036 as possible presense of the @code{frozen} field in the output
31037 of @code{-varobj-create}.
31038 @item pending-breakpoints
31039 Indicates support for the @option{-f} option to the @code{-break-insert}
31042 Indicates Python scripting support, Python-based
31043 pretty-printing commands, and possible presence of the
31044 @samp{display_hint} field in the output of @code{-var-list-children}
31046 Indicates support for the @code{-thread-info} command.
31047 @item data-read-memory-bytes
31048 Indicates support for the @code{-data-read-memory-bytes} and the
31049 @code{-data-write-memory-bytes} commands.
31050 @item breakpoint-notifications
31051 Indicates that changes to breakpoints and breakpoints created via the
31052 CLI will be announced via async records.
31053 @item ada-task-info
31054 Indicates support for the @code{-ada-task-info} command.
31057 @subheading The @code{-list-target-features} Command
31058 @findex -list-target-features
31060 Returns a list of particular features that are supported by the
31061 target. Those features affect the permitted MI commands, but
31062 unlike the features reported by the @code{-list-features} command, the
31063 features depend on which target GDB is using at the moment. Whenever
31064 a target can change, due to commands such as @code{-target-select},
31065 @code{-target-attach} or @code{-exec-run}, the list of target features
31066 may change, and the frontend should obtain it again.
31070 (gdb) -list-features
31071 ^done,result=["async"]
31074 The current list of features is:
31078 Indicates that the target is capable of asynchronous command
31079 execution, which means that @value{GDBN} will accept further commands
31080 while the target is running.
31083 Indicates that the target is capable of reverse execution.
31084 @xref{Reverse Execution}, for more information.
31088 @subheading The @code{-list-thread-groups} Command
31089 @findex -list-thread-groups
31091 @subheading Synopsis
31094 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31097 Lists thread groups (@pxref{Thread groups}). When a single thread
31098 group is passed as the argument, lists the children of that group.
31099 When several thread group are passed, lists information about those
31100 thread groups. Without any parameters, lists information about all
31101 top-level thread groups.
31103 Normally, thread groups that are being debugged are reported.
31104 With the @samp{--available} option, @value{GDBN} reports thread groups
31105 available on the target.
31107 The output of this command may have either a @samp{threads} result or
31108 a @samp{groups} result. The @samp{thread} result has a list of tuples
31109 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31110 Information}). The @samp{groups} result has a list of tuples as value,
31111 each tuple describing a thread group. If top-level groups are
31112 requested (that is, no parameter is passed), or when several groups
31113 are passed, the output always has a @samp{groups} result. The format
31114 of the @samp{group} result is described below.
31116 To reduce the number of roundtrips it's possible to list thread groups
31117 together with their children, by passing the @samp{--recurse} option
31118 and the recursion depth. Presently, only recursion depth of 1 is
31119 permitted. If this option is present, then every reported thread group
31120 will also include its children, either as @samp{group} or
31121 @samp{threads} field.
31123 In general, any combination of option and parameters is permitted, with
31124 the following caveats:
31128 When a single thread group is passed, the output will typically
31129 be the @samp{threads} result. Because threads may not contain
31130 anything, the @samp{recurse} option will be ignored.
31133 When the @samp{--available} option is passed, limited information may
31134 be available. In particular, the list of threads of a process might
31135 be inaccessible. Further, specifying specific thread groups might
31136 not give any performance advantage over listing all thread groups.
31137 The frontend should assume that @samp{-list-thread-groups --available}
31138 is always an expensive operation and cache the results.
31142 The @samp{groups} result is a list of tuples, where each tuple may
31143 have the following fields:
31147 Identifier of the thread group. This field is always present.
31148 The identifier is an opaque string; frontends should not try to
31149 convert it to an integer, even though it might look like one.
31152 The type of the thread group. At present, only @samp{process} is a
31156 The target-specific process identifier. This field is only present
31157 for thread groups of type @samp{process} and only if the process exists.
31160 The number of children this thread group has. This field may be
31161 absent for an available thread group.
31164 This field has a list of tuples as value, each tuple describing a
31165 thread. It may be present if the @samp{--recurse} option is
31166 specified, and it's actually possible to obtain the threads.
31169 This field is a list of integers, each identifying a core that one
31170 thread of the group is running on. This field may be absent if
31171 such information is not available.
31174 The name of the executable file that corresponds to this thread group.
31175 The field is only present for thread groups of type @samp{process},
31176 and only if there is a corresponding executable file.
31180 @subheading Example
31184 -list-thread-groups
31185 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31186 -list-thread-groups 17
31187 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31188 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31189 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31190 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31191 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31192 -list-thread-groups --available
31193 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31194 -list-thread-groups --available --recurse 1
31195 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31196 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31197 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31198 -list-thread-groups --available --recurse 1 17 18
31199 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31200 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31201 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31205 @subheading The @code{-add-inferior} Command
31206 @findex -add-inferior
31208 @subheading Synopsis
31214 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31215 inferior is not associated with any executable. Such association may
31216 be established with the @samp{-file-exec-and-symbols} command
31217 (@pxref{GDB/MI File Commands}). The command response has a single
31218 field, @samp{thread-group}, whose value is the identifier of the
31219 thread group corresponding to the new inferior.
31221 @subheading Example
31226 ^done,thread-group="i3"
31229 @subheading The @code{-interpreter-exec} Command
31230 @findex -interpreter-exec
31232 @subheading Synopsis
31235 -interpreter-exec @var{interpreter} @var{command}
31237 @anchor{-interpreter-exec}
31239 Execute the specified @var{command} in the given @var{interpreter}.
31241 @subheading @value{GDBN} Command
31243 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31245 @subheading Example
31249 -interpreter-exec console "break main"
31250 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31251 &"During symbol reading, bad structure-type format.\n"
31252 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31257 @subheading The @code{-inferior-tty-set} Command
31258 @findex -inferior-tty-set
31260 @subheading Synopsis
31263 -inferior-tty-set /dev/pts/1
31266 Set terminal for future runs of the program being debugged.
31268 @subheading @value{GDBN} Command
31270 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31272 @subheading Example
31276 -inferior-tty-set /dev/pts/1
31281 @subheading The @code{-inferior-tty-show} Command
31282 @findex -inferior-tty-show
31284 @subheading Synopsis
31290 Show terminal for future runs of program being debugged.
31292 @subheading @value{GDBN} Command
31294 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31296 @subheading Example
31300 -inferior-tty-set /dev/pts/1
31304 ^done,inferior_tty_terminal="/dev/pts/1"
31308 @subheading The @code{-enable-timings} Command
31309 @findex -enable-timings
31311 @subheading Synopsis
31314 -enable-timings [yes | no]
31317 Toggle the printing of the wallclock, user and system times for an MI
31318 command as a field in its output. This command is to help frontend
31319 developers optimize the performance of their code. No argument is
31320 equivalent to @samp{yes}.
31322 @subheading @value{GDBN} Command
31326 @subheading Example
31334 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31335 addr="0x080484ed",func="main",file="myprog.c",
31336 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31337 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31345 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31346 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31347 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31348 fullname="/home/nickrob/myprog.c",line="73"@}
31353 @chapter @value{GDBN} Annotations
31355 This chapter describes annotations in @value{GDBN}. Annotations were
31356 designed to interface @value{GDBN} to graphical user interfaces or other
31357 similar programs which want to interact with @value{GDBN} at a
31358 relatively high level.
31360 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31364 This is Edition @value{EDITION}, @value{DATE}.
31368 * Annotations Overview:: What annotations are; the general syntax.
31369 * Server Prefix:: Issuing a command without affecting user state.
31370 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31371 * Errors:: Annotations for error messages.
31372 * Invalidation:: Some annotations describe things now invalid.
31373 * Annotations for Running::
31374 Whether the program is running, how it stopped, etc.
31375 * Source Annotations:: Annotations describing source code.
31378 @node Annotations Overview
31379 @section What is an Annotation?
31380 @cindex annotations
31382 Annotations start with a newline character, two @samp{control-z}
31383 characters, and the name of the annotation. If there is no additional
31384 information associated with this annotation, the name of the annotation
31385 is followed immediately by a newline. If there is additional
31386 information, the name of the annotation is followed by a space, the
31387 additional information, and a newline. The additional information
31388 cannot contain newline characters.
31390 Any output not beginning with a newline and two @samp{control-z}
31391 characters denotes literal output from @value{GDBN}. Currently there is
31392 no need for @value{GDBN} to output a newline followed by two
31393 @samp{control-z} characters, but if there was such a need, the
31394 annotations could be extended with an @samp{escape} annotation which
31395 means those three characters as output.
31397 The annotation @var{level}, which is specified using the
31398 @option{--annotate} command line option (@pxref{Mode Options}), controls
31399 how much information @value{GDBN} prints together with its prompt,
31400 values of expressions, source lines, and other types of output. Level 0
31401 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31402 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31403 for programs that control @value{GDBN}, and level 2 annotations have
31404 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31405 Interface, annotate, GDB's Obsolete Annotations}).
31408 @kindex set annotate
31409 @item set annotate @var{level}
31410 The @value{GDBN} command @code{set annotate} sets the level of
31411 annotations to the specified @var{level}.
31413 @item show annotate
31414 @kindex show annotate
31415 Show the current annotation level.
31418 This chapter describes level 3 annotations.
31420 A simple example of starting up @value{GDBN} with annotations is:
31423 $ @kbd{gdb --annotate=3}
31425 Copyright 2003 Free Software Foundation, Inc.
31426 GDB is free software, covered by the GNU General Public License,
31427 and you are welcome to change it and/or distribute copies of it
31428 under certain conditions.
31429 Type "show copying" to see the conditions.
31430 There is absolutely no warranty for GDB. Type "show warranty"
31432 This GDB was configured as "i386-pc-linux-gnu"
31443 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31444 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31445 denotes a @samp{control-z} character) are annotations; the rest is
31446 output from @value{GDBN}.
31448 @node Server Prefix
31449 @section The Server Prefix
31450 @cindex server prefix
31452 If you prefix a command with @samp{server } then it will not affect
31453 the command history, nor will it affect @value{GDBN}'s notion of which
31454 command to repeat if @key{RET} is pressed on a line by itself. This
31455 means that commands can be run behind a user's back by a front-end in
31456 a transparent manner.
31458 The @code{server } prefix does not affect the recording of values into
31459 the value history; to print a value without recording it into the
31460 value history, use the @code{output} command instead of the
31461 @code{print} command.
31463 Using this prefix also disables confirmation requests
31464 (@pxref{confirmation requests}).
31467 @section Annotation for @value{GDBN} Input
31469 @cindex annotations for prompts
31470 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31471 to know when to send output, when the output from a given command is
31474 Different kinds of input each have a different @dfn{input type}. Each
31475 input type has three annotations: a @code{pre-} annotation, which
31476 denotes the beginning of any prompt which is being output, a plain
31477 annotation, which denotes the end of the prompt, and then a @code{post-}
31478 annotation which denotes the end of any echo which may (or may not) be
31479 associated with the input. For example, the @code{prompt} input type
31480 features the following annotations:
31488 The input types are
31491 @findex pre-prompt annotation
31492 @findex prompt annotation
31493 @findex post-prompt annotation
31495 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31497 @findex pre-commands annotation
31498 @findex commands annotation
31499 @findex post-commands annotation
31501 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31502 command. The annotations are repeated for each command which is input.
31504 @findex pre-overload-choice annotation
31505 @findex overload-choice annotation
31506 @findex post-overload-choice annotation
31507 @item overload-choice
31508 When @value{GDBN} wants the user to select between various overloaded functions.
31510 @findex pre-query annotation
31511 @findex query annotation
31512 @findex post-query annotation
31514 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31516 @findex pre-prompt-for-continue annotation
31517 @findex prompt-for-continue annotation
31518 @findex post-prompt-for-continue annotation
31519 @item prompt-for-continue
31520 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31521 expect this to work well; instead use @code{set height 0} to disable
31522 prompting. This is because the counting of lines is buggy in the
31523 presence of annotations.
31528 @cindex annotations for errors, warnings and interrupts
31530 @findex quit annotation
31535 This annotation occurs right before @value{GDBN} responds to an interrupt.
31537 @findex error annotation
31542 This annotation occurs right before @value{GDBN} responds to an error.
31544 Quit and error annotations indicate that any annotations which @value{GDBN} was
31545 in the middle of may end abruptly. For example, if a
31546 @code{value-history-begin} annotation is followed by a @code{error}, one
31547 cannot expect to receive the matching @code{value-history-end}. One
31548 cannot expect not to receive it either, however; an error annotation
31549 does not necessarily mean that @value{GDBN} is immediately returning all the way
31552 @findex error-begin annotation
31553 A quit or error annotation may be preceded by
31559 Any output between that and the quit or error annotation is the error
31562 Warning messages are not yet annotated.
31563 @c If we want to change that, need to fix warning(), type_error(),
31564 @c range_error(), and possibly other places.
31567 @section Invalidation Notices
31569 @cindex annotations for invalidation messages
31570 The following annotations say that certain pieces of state may have
31574 @findex frames-invalid annotation
31575 @item ^Z^Zframes-invalid
31577 The frames (for example, output from the @code{backtrace} command) may
31580 @findex breakpoints-invalid annotation
31581 @item ^Z^Zbreakpoints-invalid
31583 The breakpoints may have changed. For example, the user just added or
31584 deleted a breakpoint.
31587 @node Annotations for Running
31588 @section Running the Program
31589 @cindex annotations for running programs
31591 @findex starting annotation
31592 @findex stopping annotation
31593 When the program starts executing due to a @value{GDBN} command such as
31594 @code{step} or @code{continue},
31600 is output. When the program stops,
31606 is output. Before the @code{stopped} annotation, a variety of
31607 annotations describe how the program stopped.
31610 @findex exited annotation
31611 @item ^Z^Zexited @var{exit-status}
31612 The program exited, and @var{exit-status} is the exit status (zero for
31613 successful exit, otherwise nonzero).
31615 @findex signalled annotation
31616 @findex signal-name annotation
31617 @findex signal-name-end annotation
31618 @findex signal-string annotation
31619 @findex signal-string-end annotation
31620 @item ^Z^Zsignalled
31621 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31622 annotation continues:
31628 ^Z^Zsignal-name-end
31632 ^Z^Zsignal-string-end
31637 where @var{name} is the name of the signal, such as @code{SIGILL} or
31638 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31639 as @code{Illegal Instruction} or @code{Segmentation fault}.
31640 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31641 user's benefit and have no particular format.
31643 @findex signal annotation
31645 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31646 just saying that the program received the signal, not that it was
31647 terminated with it.
31649 @findex breakpoint annotation
31650 @item ^Z^Zbreakpoint @var{number}
31651 The program hit breakpoint number @var{number}.
31653 @findex watchpoint annotation
31654 @item ^Z^Zwatchpoint @var{number}
31655 The program hit watchpoint number @var{number}.
31658 @node Source Annotations
31659 @section Displaying Source
31660 @cindex annotations for source display
31662 @findex source annotation
31663 The following annotation is used instead of displaying source code:
31666 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31669 where @var{filename} is an absolute file name indicating which source
31670 file, @var{line} is the line number within that file (where 1 is the
31671 first line in the file), @var{character} is the character position
31672 within the file (where 0 is the first character in the file) (for most
31673 debug formats this will necessarily point to the beginning of a line),
31674 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31675 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31676 @var{addr} is the address in the target program associated with the
31677 source which is being displayed. @var{addr} is in the form @samp{0x}
31678 followed by one or more lowercase hex digits (note that this does not
31679 depend on the language).
31681 @node JIT Interface
31682 @chapter JIT Compilation Interface
31683 @cindex just-in-time compilation
31684 @cindex JIT compilation interface
31686 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31687 interface. A JIT compiler is a program or library that generates native
31688 executable code at runtime and executes it, usually in order to achieve good
31689 performance while maintaining platform independence.
31691 Programs that use JIT compilation are normally difficult to debug because
31692 portions of their code are generated at runtime, instead of being loaded from
31693 object files, which is where @value{GDBN} normally finds the program's symbols
31694 and debug information. In order to debug programs that use JIT compilation,
31695 @value{GDBN} has an interface that allows the program to register in-memory
31696 symbol files with @value{GDBN} at runtime.
31698 If you are using @value{GDBN} to debug a program that uses this interface, then
31699 it should work transparently so long as you have not stripped the binary. If
31700 you are developing a JIT compiler, then the interface is documented in the rest
31701 of this chapter. At this time, the only known client of this interface is the
31704 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31705 JIT compiler communicates with @value{GDBN} by writing data into a global
31706 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31707 attaches, it reads a linked list of symbol files from the global variable to
31708 find existing code, and puts a breakpoint in the function so that it can find
31709 out about additional code.
31712 * Declarations:: Relevant C struct declarations
31713 * Registering Code:: Steps to register code
31714 * Unregistering Code:: Steps to unregister code
31718 @section JIT Declarations
31720 These are the relevant struct declarations that a C program should include to
31721 implement the interface:
31731 struct jit_code_entry
31733 struct jit_code_entry *next_entry;
31734 struct jit_code_entry *prev_entry;
31735 const char *symfile_addr;
31736 uint64_t symfile_size;
31739 struct jit_descriptor
31742 /* This type should be jit_actions_t, but we use uint32_t
31743 to be explicit about the bitwidth. */
31744 uint32_t action_flag;
31745 struct jit_code_entry *relevant_entry;
31746 struct jit_code_entry *first_entry;
31749 /* GDB puts a breakpoint in this function. */
31750 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31752 /* Make sure to specify the version statically, because the
31753 debugger may check the version before we can set it. */
31754 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31757 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31758 modifications to this global data properly, which can easily be done by putting
31759 a global mutex around modifications to these structures.
31761 @node Registering Code
31762 @section Registering Code
31764 To register code with @value{GDBN}, the JIT should follow this protocol:
31768 Generate an object file in memory with symbols and other desired debug
31769 information. The file must include the virtual addresses of the sections.
31772 Create a code entry for the file, which gives the start and size of the symbol
31776 Add it to the linked list in the JIT descriptor.
31779 Point the relevant_entry field of the descriptor at the entry.
31782 Set @code{action_flag} to @code{JIT_REGISTER} and call
31783 @code{__jit_debug_register_code}.
31786 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31787 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31788 new code. However, the linked list must still be maintained in order to allow
31789 @value{GDBN} to attach to a running process and still find the symbol files.
31791 @node Unregistering Code
31792 @section Unregistering Code
31794 If code is freed, then the JIT should use the following protocol:
31798 Remove the code entry corresponding to the code from the linked list.
31801 Point the @code{relevant_entry} field of the descriptor at the code entry.
31804 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31805 @code{__jit_debug_register_code}.
31808 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31809 and the JIT will leak the memory used for the associated symbol files.
31812 @chapter Reporting Bugs in @value{GDBN}
31813 @cindex bugs in @value{GDBN}
31814 @cindex reporting bugs in @value{GDBN}
31816 Your bug reports play an essential role in making @value{GDBN} reliable.
31818 Reporting a bug may help you by bringing a solution to your problem, or it
31819 may not. But in any case the principal function of a bug report is to help
31820 the entire community by making the next version of @value{GDBN} work better. Bug
31821 reports are your contribution to the maintenance of @value{GDBN}.
31823 In order for a bug report to serve its purpose, you must include the
31824 information that enables us to fix the bug.
31827 * Bug Criteria:: Have you found a bug?
31828 * Bug Reporting:: How to report bugs
31832 @section Have You Found a Bug?
31833 @cindex bug criteria
31835 If you are not sure whether you have found a bug, here are some guidelines:
31838 @cindex fatal signal
31839 @cindex debugger crash
31840 @cindex crash of debugger
31842 If the debugger gets a fatal signal, for any input whatever, that is a
31843 @value{GDBN} bug. Reliable debuggers never crash.
31845 @cindex error on valid input
31847 If @value{GDBN} produces an error message for valid input, that is a
31848 bug. (Note that if you're cross debugging, the problem may also be
31849 somewhere in the connection to the target.)
31851 @cindex invalid input
31853 If @value{GDBN} does not produce an error message for invalid input,
31854 that is a bug. However, you should note that your idea of
31855 ``invalid input'' might be our idea of ``an extension'' or ``support
31856 for traditional practice''.
31859 If you are an experienced user of debugging tools, your suggestions
31860 for improvement of @value{GDBN} are welcome in any case.
31863 @node Bug Reporting
31864 @section How to Report Bugs
31865 @cindex bug reports
31866 @cindex @value{GDBN} bugs, reporting
31868 A number of companies and individuals offer support for @sc{gnu} products.
31869 If you obtained @value{GDBN} from a support organization, we recommend you
31870 contact that organization first.
31872 You can find contact information for many support companies and
31873 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
31875 @c should add a web page ref...
31878 @ifset BUGURL_DEFAULT
31879 In any event, we also recommend that you submit bug reports for
31880 @value{GDBN}. The preferred method is to submit them directly using
31881 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
31882 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
31885 @strong{Do not send bug reports to @samp{info-gdb}, or to
31886 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
31887 not want to receive bug reports. Those that do have arranged to receive
31890 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
31891 serves as a repeater. The mailing list and the newsgroup carry exactly
31892 the same messages. Often people think of posting bug reports to the
31893 newsgroup instead of mailing them. This appears to work, but it has one
31894 problem which can be crucial: a newsgroup posting often lacks a mail
31895 path back to the sender. Thus, if we need to ask for more information,
31896 we may be unable to reach you. For this reason, it is better to send
31897 bug reports to the mailing list.
31899 @ifclear BUGURL_DEFAULT
31900 In any event, we also recommend that you submit bug reports for
31901 @value{GDBN} to @value{BUGURL}.
31905 The fundamental principle of reporting bugs usefully is this:
31906 @strong{report all the facts}. If you are not sure whether to state a
31907 fact or leave it out, state it!
31909 Often people omit facts because they think they know what causes the
31910 problem and assume that some details do not matter. Thus, you might
31911 assume that the name of the variable you use in an example does not matter.
31912 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
31913 stray memory reference which happens to fetch from the location where that
31914 name is stored in memory; perhaps, if the name were different, the contents
31915 of that location would fool the debugger into doing the right thing despite
31916 the bug. Play it safe and give a specific, complete example. That is the
31917 easiest thing for you to do, and the most helpful.
31919 Keep in mind that the purpose of a bug report is to enable us to fix the
31920 bug. It may be that the bug has been reported previously, but neither
31921 you nor we can know that unless your bug report is complete and
31924 Sometimes people give a few sketchy facts and ask, ``Does this ring a
31925 bell?'' Those bug reports are useless, and we urge everyone to
31926 @emph{refuse to respond to them} except to chide the sender to report
31929 To enable us to fix the bug, you should include all these things:
31933 The version of @value{GDBN}. @value{GDBN} announces it if you start
31934 with no arguments; you can also print it at any time using @code{show
31937 Without this, we will not know whether there is any point in looking for
31938 the bug in the current version of @value{GDBN}.
31941 The type of machine you are using, and the operating system name and
31945 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
31946 ``@value{GCC}--2.8.1''.
31949 What compiler (and its version) was used to compile the program you are
31950 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
31951 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
31952 to get this information; for other compilers, see the documentation for
31956 The command arguments you gave the compiler to compile your example and
31957 observe the bug. For example, did you use @samp{-O}? To guarantee
31958 you will not omit something important, list them all. A copy of the
31959 Makefile (or the output from make) is sufficient.
31961 If we were to try to guess the arguments, we would probably guess wrong
31962 and then we might not encounter the bug.
31965 A complete input script, and all necessary source files, that will
31969 A description of what behavior you observe that you believe is
31970 incorrect. For example, ``It gets a fatal signal.''
31972 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
31973 will certainly notice it. But if the bug is incorrect output, we might
31974 not notice unless it is glaringly wrong. You might as well not give us
31975 a chance to make a mistake.
31977 Even if the problem you experience is a fatal signal, you should still
31978 say so explicitly. Suppose something strange is going on, such as, your
31979 copy of @value{GDBN} is out of synch, or you have encountered a bug in
31980 the C library on your system. (This has happened!) Your copy might
31981 crash and ours would not. If you told us to expect a crash, then when
31982 ours fails to crash, we would know that the bug was not happening for
31983 us. If you had not told us to expect a crash, then we would not be able
31984 to draw any conclusion from our observations.
31987 @cindex recording a session script
31988 To collect all this information, you can use a session recording program
31989 such as @command{script}, which is available on many Unix systems.
31990 Just run your @value{GDBN} session inside @command{script} and then
31991 include the @file{typescript} file with your bug report.
31993 Another way to record a @value{GDBN} session is to run @value{GDBN}
31994 inside Emacs and then save the entire buffer to a file.
31997 If you wish to suggest changes to the @value{GDBN} source, send us context
31998 diffs. If you even discuss something in the @value{GDBN} source, refer to
31999 it by context, not by line number.
32001 The line numbers in our development sources will not match those in your
32002 sources. Your line numbers would convey no useful information to us.
32006 Here are some things that are not necessary:
32010 A description of the envelope of the bug.
32012 Often people who encounter a bug spend a lot of time investigating
32013 which changes to the input file will make the bug go away and which
32014 changes will not affect it.
32016 This is often time consuming and not very useful, because the way we
32017 will find the bug is by running a single example under the debugger
32018 with breakpoints, not by pure deduction from a series of examples.
32019 We recommend that you save your time for something else.
32021 Of course, if you can find a simpler example to report @emph{instead}
32022 of the original one, that is a convenience for us. Errors in the
32023 output will be easier to spot, running under the debugger will take
32024 less time, and so on.
32026 However, simplification is not vital; if you do not want to do this,
32027 report the bug anyway and send us the entire test case you used.
32030 A patch for the bug.
32032 A patch for the bug does help us if it is a good one. But do not omit
32033 the necessary information, such as the test case, on the assumption that
32034 a patch is all we need. We might see problems with your patch and decide
32035 to fix the problem another way, or we might not understand it at all.
32037 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32038 construct an example that will make the program follow a certain path
32039 through the code. If you do not send us the example, we will not be able
32040 to construct one, so we will not be able to verify that the bug is fixed.
32042 And if we cannot understand what bug you are trying to fix, or why your
32043 patch should be an improvement, we will not install it. A test case will
32044 help us to understand.
32047 A guess about what the bug is or what it depends on.
32049 Such guesses are usually wrong. Even we cannot guess right about such
32050 things without first using the debugger to find the facts.
32053 @c The readline documentation is distributed with the readline code
32054 @c and consists of the two following files:
32057 @c Use -I with makeinfo to point to the appropriate directory,
32058 @c environment var TEXINPUTS with TeX.
32059 @ifclear SYSTEM_READLINE
32060 @include rluser.texi
32061 @include hsuser.texi
32065 @appendix In Memoriam
32067 The @value{GDBN} project mourns the loss of the following long-time
32072 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32073 to Free Software in general. Outside of @value{GDBN}, he was known in
32074 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32076 @item Michael Snyder
32077 Michael was one of the Global Maintainers of the @value{GDBN} project,
32078 with contributions recorded as early as 1996, until 2011. In addition
32079 to his day to day participation, he was a large driving force behind
32080 adding Reverse Debugging to @value{GDBN}.
32083 Beyond their technical contributions to the project, they were also
32084 enjoyable members of the Free Software Community. We will miss them.
32086 @node Formatting Documentation
32087 @appendix Formatting Documentation
32089 @cindex @value{GDBN} reference card
32090 @cindex reference card
32091 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32092 for printing with PostScript or Ghostscript, in the @file{gdb}
32093 subdirectory of the main source directory@footnote{In
32094 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32095 release.}. If you can use PostScript or Ghostscript with your printer,
32096 you can print the reference card immediately with @file{refcard.ps}.
32098 The release also includes the source for the reference card. You
32099 can format it, using @TeX{}, by typing:
32105 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32106 mode on US ``letter'' size paper;
32107 that is, on a sheet 11 inches wide by 8.5 inches
32108 high. You will need to specify this form of printing as an option to
32109 your @sc{dvi} output program.
32111 @cindex documentation
32113 All the documentation for @value{GDBN} comes as part of the machine-readable
32114 distribution. The documentation is written in Texinfo format, which is
32115 a documentation system that uses a single source file to produce both
32116 on-line information and a printed manual. You can use one of the Info
32117 formatting commands to create the on-line version of the documentation
32118 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32120 @value{GDBN} includes an already formatted copy of the on-line Info
32121 version of this manual in the @file{gdb} subdirectory. The main Info
32122 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32123 subordinate files matching @samp{gdb.info*} in the same directory. If
32124 necessary, you can print out these files, or read them with any editor;
32125 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32126 Emacs or the standalone @code{info} program, available as part of the
32127 @sc{gnu} Texinfo distribution.
32129 If you want to format these Info files yourself, you need one of the
32130 Info formatting programs, such as @code{texinfo-format-buffer} or
32133 If you have @code{makeinfo} installed, and are in the top level
32134 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32135 version @value{GDBVN}), you can make the Info file by typing:
32142 If you want to typeset and print copies of this manual, you need @TeX{},
32143 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32144 Texinfo definitions file.
32146 @TeX{} is a typesetting program; it does not print files directly, but
32147 produces output files called @sc{dvi} files. To print a typeset
32148 document, you need a program to print @sc{dvi} files. If your system
32149 has @TeX{} installed, chances are it has such a program. The precise
32150 command to use depends on your system; @kbd{lpr -d} is common; another
32151 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32152 require a file name without any extension or a @samp{.dvi} extension.
32154 @TeX{} also requires a macro definitions file called
32155 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32156 written in Texinfo format. On its own, @TeX{} cannot either read or
32157 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32158 and is located in the @file{gdb-@var{version-number}/texinfo}
32161 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32162 typeset and print this manual. First switch to the @file{gdb}
32163 subdirectory of the main source directory (for example, to
32164 @file{gdb-@value{GDBVN}/gdb}) and type:
32170 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32172 @node Installing GDB
32173 @appendix Installing @value{GDBN}
32174 @cindex installation
32177 * Requirements:: Requirements for building @value{GDBN}
32178 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32179 * Separate Objdir:: Compiling @value{GDBN} in another directory
32180 * Config Names:: Specifying names for hosts and targets
32181 * Configure Options:: Summary of options for configure
32182 * System-wide configuration:: Having a system-wide init file
32186 @section Requirements for Building @value{GDBN}
32187 @cindex building @value{GDBN}, requirements for
32189 Building @value{GDBN} requires various tools and packages to be available.
32190 Other packages will be used only if they are found.
32192 @heading Tools/Packages Necessary for Building @value{GDBN}
32194 @item ISO C90 compiler
32195 @value{GDBN} is written in ISO C90. It should be buildable with any
32196 working C90 compiler, e.g.@: GCC.
32200 @heading Tools/Packages Optional for Building @value{GDBN}
32204 @value{GDBN} can use the Expat XML parsing library. This library may be
32205 included with your operating system distribution; if it is not, you
32206 can get the latest version from @url{http://expat.sourceforge.net}.
32207 The @file{configure} script will search for this library in several
32208 standard locations; if it is installed in an unusual path, you can
32209 use the @option{--with-libexpat-prefix} option to specify its location.
32215 Remote protocol memory maps (@pxref{Memory Map Format})
32217 Target descriptions (@pxref{Target Descriptions})
32219 Remote shared library lists (@pxref{Library List Format})
32221 MS-Windows shared libraries (@pxref{Shared Libraries})
32223 Traceframe info (@pxref{Traceframe Info Format})
32227 @cindex compressed debug sections
32228 @value{GDBN} will use the @samp{zlib} library, if available, to read
32229 compressed debug sections. Some linkers, such as GNU gold, are capable
32230 of producing binaries with compressed debug sections. If @value{GDBN}
32231 is compiled with @samp{zlib}, it will be able to read the debug
32232 information in such binaries.
32234 The @samp{zlib} library is likely included with your operating system
32235 distribution; if it is not, you can get the latest version from
32236 @url{http://zlib.net}.
32239 @value{GDBN}'s features related to character sets (@pxref{Character
32240 Sets}) require a functioning @code{iconv} implementation. If you are
32241 on a GNU system, then this is provided by the GNU C Library. Some
32242 other systems also provide a working @code{iconv}.
32244 If @value{GDBN} is using the @code{iconv} program which is installed
32245 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32246 This is done with @option{--with-iconv-bin} which specifies the
32247 directory that contains the @code{iconv} program.
32249 On systems without @code{iconv}, you can install GNU Libiconv. If you
32250 have previously installed Libiconv, you can use the
32251 @option{--with-libiconv-prefix} option to configure.
32253 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32254 arrange to build Libiconv if a directory named @file{libiconv} appears
32255 in the top-most source directory. If Libiconv is built this way, and
32256 if the operating system does not provide a suitable @code{iconv}
32257 implementation, then the just-built library will automatically be used
32258 by @value{GDBN}. One easy way to set this up is to download GNU
32259 Libiconv, unpack it, and then rename the directory holding the
32260 Libiconv source code to @samp{libiconv}.
32263 @node Running Configure
32264 @section Invoking the @value{GDBN} @file{configure} Script
32265 @cindex configuring @value{GDBN}
32266 @value{GDBN} comes with a @file{configure} script that automates the process
32267 of preparing @value{GDBN} for installation; you can then use @code{make} to
32268 build the @code{gdb} program.
32270 @c irrelevant in info file; it's as current as the code it lives with.
32271 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32272 look at the @file{README} file in the sources; we may have improved the
32273 installation procedures since publishing this manual.}
32276 The @value{GDBN} distribution includes all the source code you need for
32277 @value{GDBN} in a single directory, whose name is usually composed by
32278 appending the version number to @samp{gdb}.
32280 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32281 @file{gdb-@value{GDBVN}} directory. That directory contains:
32284 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32285 script for configuring @value{GDBN} and all its supporting libraries
32287 @item gdb-@value{GDBVN}/gdb
32288 the source specific to @value{GDBN} itself
32290 @item gdb-@value{GDBVN}/bfd
32291 source for the Binary File Descriptor library
32293 @item gdb-@value{GDBVN}/include
32294 @sc{gnu} include files
32296 @item gdb-@value{GDBVN}/libiberty
32297 source for the @samp{-liberty} free software library
32299 @item gdb-@value{GDBVN}/opcodes
32300 source for the library of opcode tables and disassemblers
32302 @item gdb-@value{GDBVN}/readline
32303 source for the @sc{gnu} command-line interface
32305 @item gdb-@value{GDBVN}/glob
32306 source for the @sc{gnu} filename pattern-matching subroutine
32308 @item gdb-@value{GDBVN}/mmalloc
32309 source for the @sc{gnu} memory-mapped malloc package
32312 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32313 from the @file{gdb-@var{version-number}} source directory, which in
32314 this example is the @file{gdb-@value{GDBVN}} directory.
32316 First switch to the @file{gdb-@var{version-number}} source directory
32317 if you are not already in it; then run @file{configure}. Pass the
32318 identifier for the platform on which @value{GDBN} will run as an
32324 cd gdb-@value{GDBVN}
32325 ./configure @var{host}
32330 where @var{host} is an identifier such as @samp{sun4} or
32331 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32332 (You can often leave off @var{host}; @file{configure} tries to guess the
32333 correct value by examining your system.)
32335 Running @samp{configure @var{host}} and then running @code{make} builds the
32336 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32337 libraries, then @code{gdb} itself. The configured source files, and the
32338 binaries, are left in the corresponding source directories.
32341 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32342 system does not recognize this automatically when you run a different
32343 shell, you may need to run @code{sh} on it explicitly:
32346 sh configure @var{host}
32349 If you run @file{configure} from a directory that contains source
32350 directories for multiple libraries or programs, such as the
32351 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32353 creates configuration files for every directory level underneath (unless
32354 you tell it not to, with the @samp{--norecursion} option).
32356 You should run the @file{configure} script from the top directory in the
32357 source tree, the @file{gdb-@var{version-number}} directory. If you run
32358 @file{configure} from one of the subdirectories, you will configure only
32359 that subdirectory. That is usually not what you want. In particular,
32360 if you run the first @file{configure} from the @file{gdb} subdirectory
32361 of the @file{gdb-@var{version-number}} directory, you will omit the
32362 configuration of @file{bfd}, @file{readline}, and other sibling
32363 directories of the @file{gdb} subdirectory. This leads to build errors
32364 about missing include files such as @file{bfd/bfd.h}.
32366 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32367 However, you should make sure that the shell on your path (named by
32368 the @samp{SHELL} environment variable) is publicly readable. Remember
32369 that @value{GDBN} uses the shell to start your program---some systems refuse to
32370 let @value{GDBN} debug child processes whose programs are not readable.
32372 @node Separate Objdir
32373 @section Compiling @value{GDBN} in Another Directory
32375 If you want to run @value{GDBN} versions for several host or target machines,
32376 you need a different @code{gdb} compiled for each combination of
32377 host and target. @file{configure} is designed to make this easy by
32378 allowing you to generate each configuration in a separate subdirectory,
32379 rather than in the source directory. If your @code{make} program
32380 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32381 @code{make} in each of these directories builds the @code{gdb}
32382 program specified there.
32384 To build @code{gdb} in a separate directory, run @file{configure}
32385 with the @samp{--srcdir} option to specify where to find the source.
32386 (You also need to specify a path to find @file{configure}
32387 itself from your working directory. If the path to @file{configure}
32388 would be the same as the argument to @samp{--srcdir}, you can leave out
32389 the @samp{--srcdir} option; it is assumed.)
32391 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32392 separate directory for a Sun 4 like this:
32396 cd gdb-@value{GDBVN}
32399 ../gdb-@value{GDBVN}/configure sun4
32404 When @file{configure} builds a configuration using a remote source
32405 directory, it creates a tree for the binaries with the same structure
32406 (and using the same names) as the tree under the source directory. In
32407 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32408 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32409 @file{gdb-sun4/gdb}.
32411 Make sure that your path to the @file{configure} script has just one
32412 instance of @file{gdb} in it. If your path to @file{configure} looks
32413 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32414 one subdirectory of @value{GDBN}, not the whole package. This leads to
32415 build errors about missing include files such as @file{bfd/bfd.h}.
32417 One popular reason to build several @value{GDBN} configurations in separate
32418 directories is to configure @value{GDBN} for cross-compiling (where
32419 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32420 programs that run on another machine---the @dfn{target}).
32421 You specify a cross-debugging target by
32422 giving the @samp{--target=@var{target}} option to @file{configure}.
32424 When you run @code{make} to build a program or library, you must run
32425 it in a configured directory---whatever directory you were in when you
32426 called @file{configure} (or one of its subdirectories).
32428 The @code{Makefile} that @file{configure} generates in each source
32429 directory also runs recursively. If you type @code{make} in a source
32430 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32431 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32432 will build all the required libraries, and then build GDB.
32434 When you have multiple hosts or targets configured in separate
32435 directories, you can run @code{make} on them in parallel (for example,
32436 if they are NFS-mounted on each of the hosts); they will not interfere
32440 @section Specifying Names for Hosts and Targets
32442 The specifications used for hosts and targets in the @file{configure}
32443 script are based on a three-part naming scheme, but some short predefined
32444 aliases are also supported. The full naming scheme encodes three pieces
32445 of information in the following pattern:
32448 @var{architecture}-@var{vendor}-@var{os}
32451 For example, you can use the alias @code{sun4} as a @var{host} argument,
32452 or as the value for @var{target} in a @code{--target=@var{target}}
32453 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32455 The @file{configure} script accompanying @value{GDBN} does not provide
32456 any query facility to list all supported host and target names or
32457 aliases. @file{configure} calls the Bourne shell script
32458 @code{config.sub} to map abbreviations to full names; you can read the
32459 script, if you wish, or you can use it to test your guesses on
32460 abbreviations---for example:
32463 % sh config.sub i386-linux
32465 % sh config.sub alpha-linux
32466 alpha-unknown-linux-gnu
32467 % sh config.sub hp9k700
32469 % sh config.sub sun4
32470 sparc-sun-sunos4.1.1
32471 % sh config.sub sun3
32472 m68k-sun-sunos4.1.1
32473 % sh config.sub i986v
32474 Invalid configuration `i986v': machine `i986v' not recognized
32478 @code{config.sub} is also distributed in the @value{GDBN} source
32479 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32481 @node Configure Options
32482 @section @file{configure} Options
32484 Here is a summary of the @file{configure} options and arguments that
32485 are most often useful for building @value{GDBN}. @file{configure} also has
32486 several other options not listed here. @inforef{What Configure
32487 Does,,configure.info}, for a full explanation of @file{configure}.
32490 configure @r{[}--help@r{]}
32491 @r{[}--prefix=@var{dir}@r{]}
32492 @r{[}--exec-prefix=@var{dir}@r{]}
32493 @r{[}--srcdir=@var{dirname}@r{]}
32494 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32495 @r{[}--target=@var{target}@r{]}
32500 You may introduce options with a single @samp{-} rather than
32501 @samp{--} if you prefer; but you may abbreviate option names if you use
32506 Display a quick summary of how to invoke @file{configure}.
32508 @item --prefix=@var{dir}
32509 Configure the source to install programs and files under directory
32512 @item --exec-prefix=@var{dir}
32513 Configure the source to install programs under directory
32516 @c avoid splitting the warning from the explanation:
32518 @item --srcdir=@var{dirname}
32519 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32520 @code{make} that implements the @code{VPATH} feature.}@*
32521 Use this option to make configurations in directories separate from the
32522 @value{GDBN} source directories. Among other things, you can use this to
32523 build (or maintain) several configurations simultaneously, in separate
32524 directories. @file{configure} writes configuration-specific files in
32525 the current directory, but arranges for them to use the source in the
32526 directory @var{dirname}. @file{configure} creates directories under
32527 the working directory in parallel to the source directories below
32530 @item --norecursion
32531 Configure only the directory level where @file{configure} is executed; do not
32532 propagate configuration to subdirectories.
32534 @item --target=@var{target}
32535 Configure @value{GDBN} for cross-debugging programs running on the specified
32536 @var{target}. Without this option, @value{GDBN} is configured to debug
32537 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32539 There is no convenient way to generate a list of all available targets.
32541 @item @var{host} @dots{}
32542 Configure @value{GDBN} to run on the specified @var{host}.
32544 There is no convenient way to generate a list of all available hosts.
32547 There are many other options available as well, but they are generally
32548 needed for special purposes only.
32550 @node System-wide configuration
32551 @section System-wide configuration and settings
32552 @cindex system-wide init file
32554 @value{GDBN} can be configured to have a system-wide init file;
32555 this file will be read and executed at startup (@pxref{Startup, , What
32556 @value{GDBN} does during startup}).
32558 Here is the corresponding configure option:
32561 @item --with-system-gdbinit=@var{file}
32562 Specify that the default location of the system-wide init file is
32566 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32567 it may be subject to relocation. Two possible cases:
32571 If the default location of this init file contains @file{$prefix},
32572 it will be subject to relocation. Suppose that the configure options
32573 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32574 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32575 init file is looked for as @file{$install/etc/gdbinit} instead of
32576 @file{$prefix/etc/gdbinit}.
32579 By contrast, if the default location does not contain the prefix,
32580 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32581 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32582 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32583 wherever @value{GDBN} is installed.
32586 @node Maintenance Commands
32587 @appendix Maintenance Commands
32588 @cindex maintenance commands
32589 @cindex internal commands
32591 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32592 includes a number of commands intended for @value{GDBN} developers,
32593 that are not documented elsewhere in this manual. These commands are
32594 provided here for reference. (For commands that turn on debugging
32595 messages, see @ref{Debugging Output}.)
32598 @kindex maint agent
32599 @kindex maint agent-eval
32600 @item maint agent @var{expression}
32601 @itemx maint agent-eval @var{expression}
32602 Translate the given @var{expression} into remote agent bytecodes.
32603 This command is useful for debugging the Agent Expression mechanism
32604 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32605 expression useful for data collection, such as by tracepoints, while
32606 @samp{maint agent-eval} produces an expression that evaluates directly
32607 to a result. For instance, a collection expression for @code{globa +
32608 globb} will include bytecodes to record four bytes of memory at each
32609 of the addresses of @code{globa} and @code{globb}, while discarding
32610 the result of the addition, while an evaluation expression will do the
32611 addition and return the sum.
32613 @kindex maint info breakpoints
32614 @item @anchor{maint info breakpoints}maint info breakpoints
32615 Using the same format as @samp{info breakpoints}, display both the
32616 breakpoints you've set explicitly, and those @value{GDBN} is using for
32617 internal purposes. Internal breakpoints are shown with negative
32618 breakpoint numbers. The type column identifies what kind of breakpoint
32623 Normal, explicitly set breakpoint.
32626 Normal, explicitly set watchpoint.
32629 Internal breakpoint, used to handle correctly stepping through
32630 @code{longjmp} calls.
32632 @item longjmp resume
32633 Internal breakpoint at the target of a @code{longjmp}.
32636 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32639 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32642 Shared library events.
32646 @kindex set displaced-stepping
32647 @kindex show displaced-stepping
32648 @cindex displaced stepping support
32649 @cindex out-of-line single-stepping
32650 @item set displaced-stepping
32651 @itemx show displaced-stepping
32652 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32653 if the target supports it. Displaced stepping is a way to single-step
32654 over breakpoints without removing them from the inferior, by executing
32655 an out-of-line copy of the instruction that was originally at the
32656 breakpoint location. It is also known as out-of-line single-stepping.
32659 @item set displaced-stepping on
32660 If the target architecture supports it, @value{GDBN} will use
32661 displaced stepping to step over breakpoints.
32663 @item set displaced-stepping off
32664 @value{GDBN} will not use displaced stepping to step over breakpoints,
32665 even if such is supported by the target architecture.
32667 @cindex non-stop mode, and @samp{set displaced-stepping}
32668 @item set displaced-stepping auto
32669 This is the default mode. @value{GDBN} will use displaced stepping
32670 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32671 architecture supports displaced stepping.
32674 @kindex maint check-symtabs
32675 @item maint check-symtabs
32676 Check the consistency of psymtabs and symtabs.
32678 @kindex maint cplus first_component
32679 @item maint cplus first_component @var{name}
32680 Print the first C@t{++} class/namespace component of @var{name}.
32682 @kindex maint cplus namespace
32683 @item maint cplus namespace
32684 Print the list of possible C@t{++} namespaces.
32686 @kindex maint demangle
32687 @item maint demangle @var{name}
32688 Demangle a C@t{++} or Objective-C mangled @var{name}.
32690 @kindex maint deprecate
32691 @kindex maint undeprecate
32692 @cindex deprecated commands
32693 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
32694 @itemx maint undeprecate @var{command}
32695 Deprecate or undeprecate the named @var{command}. Deprecated commands
32696 cause @value{GDBN} to issue a warning when you use them. The optional
32697 argument @var{replacement} says which newer command should be used in
32698 favor of the deprecated one; if it is given, @value{GDBN} will mention
32699 the replacement as part of the warning.
32701 @kindex maint dump-me
32702 @item maint dump-me
32703 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
32704 Cause a fatal signal in the debugger and force it to dump its core.
32705 This is supported only on systems which support aborting a program
32706 with the @code{SIGQUIT} signal.
32708 @kindex maint internal-error
32709 @kindex maint internal-warning
32710 @item maint internal-error @r{[}@var{message-text}@r{]}
32711 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
32712 Cause @value{GDBN} to call the internal function @code{internal_error}
32713 or @code{internal_warning} and hence behave as though an internal error
32714 or internal warning has been detected. In addition to reporting the
32715 internal problem, these functions give the user the opportunity to
32716 either quit @value{GDBN} or create a core file of the current
32717 @value{GDBN} session.
32719 These commands take an optional parameter @var{message-text} that is
32720 used as the text of the error or warning message.
32722 Here's an example of using @code{internal-error}:
32725 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
32726 @dots{}/maint.c:121: internal-error: testing, 1, 2
32727 A problem internal to GDB has been detected. Further
32728 debugging may prove unreliable.
32729 Quit this debugging session? (y or n) @kbd{n}
32730 Create a core file? (y or n) @kbd{n}
32734 @cindex @value{GDBN} internal error
32735 @cindex internal errors, control of @value{GDBN} behavior
32737 @kindex maint set internal-error
32738 @kindex maint show internal-error
32739 @kindex maint set internal-warning
32740 @kindex maint show internal-warning
32741 @item maint set internal-error @var{action} [ask|yes|no]
32742 @itemx maint show internal-error @var{action}
32743 @itemx maint set internal-warning @var{action} [ask|yes|no]
32744 @itemx maint show internal-warning @var{action}
32745 When @value{GDBN} reports an internal problem (error or warning) it
32746 gives the user the opportunity to both quit @value{GDBN} and create a
32747 core file of the current @value{GDBN} session. These commands let you
32748 override the default behaviour for each particular @var{action},
32749 described in the table below.
32753 You can specify that @value{GDBN} should always (yes) or never (no)
32754 quit. The default is to ask the user what to do.
32757 You can specify that @value{GDBN} should always (yes) or never (no)
32758 create a core file. The default is to ask the user what to do.
32761 @kindex maint packet
32762 @item maint packet @var{text}
32763 If @value{GDBN} is talking to an inferior via the serial protocol,
32764 then this command sends the string @var{text} to the inferior, and
32765 displays the response packet. @value{GDBN} supplies the initial
32766 @samp{$} character, the terminating @samp{#} character, and the
32769 @kindex maint print architecture
32770 @item maint print architecture @r{[}@var{file}@r{]}
32771 Print the entire architecture configuration. The optional argument
32772 @var{file} names the file where the output goes.
32774 @kindex maint print c-tdesc
32775 @item maint print c-tdesc
32776 Print the current target description (@pxref{Target Descriptions}) as
32777 a C source file. The created source file can be used in @value{GDBN}
32778 when an XML parser is not available to parse the description.
32780 @kindex maint print dummy-frames
32781 @item maint print dummy-frames
32782 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
32785 (@value{GDBP}) @kbd{b add}
32787 (@value{GDBP}) @kbd{print add(2,3)}
32788 Breakpoint 2, add (a=2, b=3) at @dots{}
32790 The program being debugged stopped while in a function called from GDB.
32792 (@value{GDBP}) @kbd{maint print dummy-frames}
32793 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
32794 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
32795 call_lo=0x01014000 call_hi=0x01014001
32799 Takes an optional file parameter.
32801 @kindex maint print registers
32802 @kindex maint print raw-registers
32803 @kindex maint print cooked-registers
32804 @kindex maint print register-groups
32805 @kindex maint print remote-registers
32806 @item maint print registers @r{[}@var{file}@r{]}
32807 @itemx maint print raw-registers @r{[}@var{file}@r{]}
32808 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
32809 @itemx maint print register-groups @r{[}@var{file}@r{]}
32810 @itemx maint print remote-registers @r{[}@var{file}@r{]}
32811 Print @value{GDBN}'s internal register data structures.
32813 The command @code{maint print raw-registers} includes the contents of
32814 the raw register cache; the command @code{maint print
32815 cooked-registers} includes the (cooked) value of all registers,
32816 including registers which aren't available on the target nor visible
32817 to user; the command @code{maint print register-groups} includes the
32818 groups that each register is a member of; and the command @code{maint
32819 print remote-registers} includes the remote target's register numbers
32820 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
32821 @value{GDBN} Internals}.
32823 These commands take an optional parameter, a file name to which to
32824 write the information.
32826 @kindex maint print reggroups
32827 @item maint print reggroups @r{[}@var{file}@r{]}
32828 Print @value{GDBN}'s internal register group data structures. The
32829 optional argument @var{file} tells to what file to write the
32832 The register groups info looks like this:
32835 (@value{GDBP}) @kbd{maint print reggroups}
32848 This command forces @value{GDBN} to flush its internal register cache.
32850 @kindex maint print objfiles
32851 @cindex info for known object files
32852 @item maint print objfiles
32853 Print a dump of all known object files. For each object file, this
32854 command prints its name, address in memory, and all of its psymtabs
32857 @kindex maint print section-scripts
32858 @cindex info for known .debug_gdb_scripts-loaded scripts
32859 @item maint print section-scripts [@var{regexp}]
32860 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
32861 If @var{regexp} is specified, only print scripts loaded by object files
32862 matching @var{regexp}.
32863 For each script, this command prints its name as specified in the objfile,
32864 and the full path if known.
32865 @xref{.debug_gdb_scripts section}.
32867 @kindex maint print statistics
32868 @cindex bcache statistics
32869 @item maint print statistics
32870 This command prints, for each object file in the program, various data
32871 about that object file followed by the byte cache (@dfn{bcache})
32872 statistics for the object file. The objfile data includes the number
32873 of minimal, partial, full, and stabs symbols, the number of types
32874 defined by the objfile, the number of as yet unexpanded psym tables,
32875 the number of line tables and string tables, and the amount of memory
32876 used by the various tables. The bcache statistics include the counts,
32877 sizes, and counts of duplicates of all and unique objects, max,
32878 average, and median entry size, total memory used and its overhead and
32879 savings, and various measures of the hash table size and chain
32882 @kindex maint print target-stack
32883 @cindex target stack description
32884 @item maint print target-stack
32885 A @dfn{target} is an interface between the debugger and a particular
32886 kind of file or process. Targets can be stacked in @dfn{strata},
32887 so that more than one target can potentially respond to a request.
32888 In particular, memory accesses will walk down the stack of targets
32889 until they find a target that is interested in handling that particular
32892 This command prints a short description of each layer that was pushed on
32893 the @dfn{target stack}, starting from the top layer down to the bottom one.
32895 @kindex maint print type
32896 @cindex type chain of a data type
32897 @item maint print type @var{expr}
32898 Print the type chain for a type specified by @var{expr}. The argument
32899 can be either a type name or a symbol. If it is a symbol, the type of
32900 that symbol is described. The type chain produced by this command is
32901 a recursive definition of the data type as stored in @value{GDBN}'s
32902 data structures, including its flags and contained types.
32904 @kindex maint set dwarf2 always-disassemble
32905 @kindex maint show dwarf2 always-disassemble
32906 @item maint set dwarf2 always-disassemble
32907 @item maint show dwarf2 always-disassemble
32908 Control the behavior of @code{info address} when using DWARF debugging
32911 The default is @code{off}, which means that @value{GDBN} should try to
32912 describe a variable's location in an easily readable format. When
32913 @code{on}, @value{GDBN} will instead display the DWARF location
32914 expression in an assembly-like format. Note that some locations are
32915 too complex for @value{GDBN} to describe simply; in this case you will
32916 always see the disassembly form.
32918 Here is an example of the resulting disassembly:
32921 (gdb) info addr argc
32922 Symbol "argc" is a complex DWARF expression:
32926 For more information on these expressions, see
32927 @uref{http://www.dwarfstd.org/, the DWARF standard}.
32929 @kindex maint set dwarf2 max-cache-age
32930 @kindex maint show dwarf2 max-cache-age
32931 @item maint set dwarf2 max-cache-age
32932 @itemx maint show dwarf2 max-cache-age
32933 Control the DWARF 2 compilation unit cache.
32935 @cindex DWARF 2 compilation units cache
32936 In object files with inter-compilation-unit references, such as those
32937 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
32938 reader needs to frequently refer to previously read compilation units.
32939 This setting controls how long a compilation unit will remain in the
32940 cache if it is not referenced. A higher limit means that cached
32941 compilation units will be stored in memory longer, and more total
32942 memory will be used. Setting it to zero disables caching, which will
32943 slow down @value{GDBN} startup, but reduce memory consumption.
32945 @kindex maint set profile
32946 @kindex maint show profile
32947 @cindex profiling GDB
32948 @item maint set profile
32949 @itemx maint show profile
32950 Control profiling of @value{GDBN}.
32952 Profiling will be disabled until you use the @samp{maint set profile}
32953 command to enable it. When you enable profiling, the system will begin
32954 collecting timing and execution count data; when you disable profiling or
32955 exit @value{GDBN}, the results will be written to a log file. Remember that
32956 if you use profiling, @value{GDBN} will overwrite the profiling log file
32957 (often called @file{gmon.out}). If you have a record of important profiling
32958 data in a @file{gmon.out} file, be sure to move it to a safe location.
32960 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
32961 compiled with the @samp{-pg} compiler option.
32963 @kindex maint set show-debug-regs
32964 @kindex maint show show-debug-regs
32965 @cindex hardware debug registers
32966 @item maint set show-debug-regs
32967 @itemx maint show show-debug-regs
32968 Control whether to show variables that mirror the hardware debug
32969 registers. Use @code{ON} to enable, @code{OFF} to disable. If
32970 enabled, the debug registers values are shown when @value{GDBN} inserts or
32971 removes a hardware breakpoint or watchpoint, and when the inferior
32972 triggers a hardware-assisted breakpoint or watchpoint.
32974 @kindex maint set show-all-tib
32975 @kindex maint show show-all-tib
32976 @item maint set show-all-tib
32977 @itemx maint show show-all-tib
32978 Control whether to show all non zero areas within a 1k block starting
32979 at thread local base, when using the @samp{info w32 thread-information-block}
32982 @kindex maint space
32983 @cindex memory used by commands
32985 Control whether to display memory usage for each command. If set to a
32986 nonzero value, @value{GDBN} will display how much memory each command
32987 took, following the command's own output. This can also be requested
32988 by invoking @value{GDBN} with the @option{--statistics} command-line
32989 switch (@pxref{Mode Options}).
32992 @cindex time of command execution
32994 Control whether to display the execution time of @value{GDBN} for each command.
32995 If set to a nonzero value, @value{GDBN} will display how much time it
32996 took to execute each command, following the command's own output.
32997 Both CPU time and wallclock time are printed.
32998 Printing both is useful when trying to determine whether the cost is
32999 CPU or, e.g., disk/network, latency.
33000 Note that the CPU time printed is for @value{GDBN} only, it does not include
33001 the execution time of the inferior because there's no mechanism currently
33002 to compute how much time was spent by @value{GDBN} and how much time was
33003 spent by the program been debugged.
33004 This can also be requested by invoking @value{GDBN} with the
33005 @option{--statistics} command-line switch (@pxref{Mode Options}).
33007 @kindex maint translate-address
33008 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33009 Find the symbol stored at the location specified by the address
33010 @var{addr} and an optional section name @var{section}. If found,
33011 @value{GDBN} prints the name of the closest symbol and an offset from
33012 the symbol's location to the specified address. This is similar to
33013 the @code{info address} command (@pxref{Symbols}), except that this
33014 command also allows to find symbols in other sections.
33016 If section was not specified, the section in which the symbol was found
33017 is also printed. For dynamically linked executables, the name of
33018 executable or shared library containing the symbol is printed as well.
33022 The following command is useful for non-interactive invocations of
33023 @value{GDBN}, such as in the test suite.
33026 @item set watchdog @var{nsec}
33027 @kindex set watchdog
33028 @cindex watchdog timer
33029 @cindex timeout for commands
33030 Set the maximum number of seconds @value{GDBN} will wait for the
33031 target operation to finish. If this time expires, @value{GDBN}
33032 reports and error and the command is aborted.
33034 @item show watchdog
33035 Show the current setting of the target wait timeout.
33038 @node Remote Protocol
33039 @appendix @value{GDBN} Remote Serial Protocol
33044 * Stop Reply Packets::
33045 * General Query Packets::
33046 * Architecture-Specific Protocol Details::
33047 * Tracepoint Packets::
33048 * Host I/O Packets::
33050 * Notification Packets::
33051 * Remote Non-Stop::
33052 * Packet Acknowledgment::
33054 * File-I/O Remote Protocol Extension::
33055 * Library List Format::
33056 * Memory Map Format::
33057 * Thread List Format::
33058 * Traceframe Info Format::
33064 There may be occasions when you need to know something about the
33065 protocol---for example, if there is only one serial port to your target
33066 machine, you might want your program to do something special if it
33067 recognizes a packet meant for @value{GDBN}.
33069 In the examples below, @samp{->} and @samp{<-} are used to indicate
33070 transmitted and received data, respectively.
33072 @cindex protocol, @value{GDBN} remote serial
33073 @cindex serial protocol, @value{GDBN} remote
33074 @cindex remote serial protocol
33075 All @value{GDBN} commands and responses (other than acknowledgments
33076 and notifications, see @ref{Notification Packets}) are sent as a
33077 @var{packet}. A @var{packet} is introduced with the character
33078 @samp{$}, the actual @var{packet-data}, and the terminating character
33079 @samp{#} followed by a two-digit @var{checksum}:
33082 @code{$}@var{packet-data}@code{#}@var{checksum}
33086 @cindex checksum, for @value{GDBN} remote
33088 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33089 characters between the leading @samp{$} and the trailing @samp{#} (an
33090 eight bit unsigned checksum).
33092 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33093 specification also included an optional two-digit @var{sequence-id}:
33096 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33099 @cindex sequence-id, for @value{GDBN} remote
33101 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33102 has never output @var{sequence-id}s. Stubs that handle packets added
33103 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33105 When either the host or the target machine receives a packet, the first
33106 response expected is an acknowledgment: either @samp{+} (to indicate
33107 the package was received correctly) or @samp{-} (to request
33111 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33116 The @samp{+}/@samp{-} acknowledgments can be disabled
33117 once a connection is established.
33118 @xref{Packet Acknowledgment}, for details.
33120 The host (@value{GDBN}) sends @var{command}s, and the target (the
33121 debugging stub incorporated in your program) sends a @var{response}. In
33122 the case of step and continue @var{command}s, the response is only sent
33123 when the operation has completed, and the target has again stopped all
33124 threads in all attached processes. This is the default all-stop mode
33125 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33126 execution mode; see @ref{Remote Non-Stop}, for details.
33128 @var{packet-data} consists of a sequence of characters with the
33129 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33132 @cindex remote protocol, field separator
33133 Fields within the packet should be separated using @samp{,} @samp{;} or
33134 @samp{:}. Except where otherwise noted all numbers are represented in
33135 @sc{hex} with leading zeros suppressed.
33137 Implementors should note that prior to @value{GDBN} 5.0, the character
33138 @samp{:} could not appear as the third character in a packet (as it
33139 would potentially conflict with the @var{sequence-id}).
33141 @cindex remote protocol, binary data
33142 @anchor{Binary Data}
33143 Binary data in most packets is encoded either as two hexadecimal
33144 digits per byte of binary data. This allowed the traditional remote
33145 protocol to work over connections which were only seven-bit clean.
33146 Some packets designed more recently assume an eight-bit clean
33147 connection, and use a more efficient encoding to send and receive
33150 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33151 as an escape character. Any escaped byte is transmitted as the escape
33152 character followed by the original character XORed with @code{0x20}.
33153 For example, the byte @code{0x7d} would be transmitted as the two
33154 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33155 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33156 @samp{@}}) must always be escaped. Responses sent by the stub
33157 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33158 is not interpreted as the start of a run-length encoded sequence
33161 Response @var{data} can be run-length encoded to save space.
33162 Run-length encoding replaces runs of identical characters with one
33163 instance of the repeated character, followed by a @samp{*} and a
33164 repeat count. The repeat count is itself sent encoded, to avoid
33165 binary characters in @var{data}: a value of @var{n} is sent as
33166 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33167 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33168 code 32) for a repeat count of 3. (This is because run-length
33169 encoding starts to win for counts 3 or more.) Thus, for example,
33170 @samp{0* } is a run-length encoding of ``0000'': the space character
33171 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33174 The printable characters @samp{#} and @samp{$} or with a numeric value
33175 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33176 seven repeats (@samp{$}) can be expanded using a repeat count of only
33177 five (@samp{"}). For example, @samp{00000000} can be encoded as
33180 The error response returned for some packets includes a two character
33181 error number. That number is not well defined.
33183 @cindex empty response, for unsupported packets
33184 For any @var{command} not supported by the stub, an empty response
33185 (@samp{$#00}) should be returned. That way it is possible to extend the
33186 protocol. A newer @value{GDBN} can tell if a packet is supported based
33189 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33190 commands for register access, and the @samp{m} and @samp{M} commands
33191 for memory access. Stubs that only control single-threaded targets
33192 can implement run control with the @samp{c} (continue), and @samp{s}
33193 (step) commands. Stubs that support multi-threading targets should
33194 support the @samp{vCont} command. All other commands are optional.
33199 The following table provides a complete list of all currently defined
33200 @var{command}s and their corresponding response @var{data}.
33201 @xref{File-I/O Remote Protocol Extension}, for details about the File
33202 I/O extension of the remote protocol.
33204 Each packet's description has a template showing the packet's overall
33205 syntax, followed by an explanation of the packet's meaning. We
33206 include spaces in some of the templates for clarity; these are not
33207 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33208 separate its components. For example, a template like @samp{foo
33209 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33210 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33211 @var{baz}. @value{GDBN} does not transmit a space character between the
33212 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33215 @cindex @var{thread-id}, in remote protocol
33216 @anchor{thread-id syntax}
33217 Several packets and replies include a @var{thread-id} field to identify
33218 a thread. Normally these are positive numbers with a target-specific
33219 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33220 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33223 In addition, the remote protocol supports a multiprocess feature in
33224 which the @var{thread-id} syntax is extended to optionally include both
33225 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33226 The @var{pid} (process) and @var{tid} (thread) components each have the
33227 format described above: a positive number with target-specific
33228 interpretation formatted as a big-endian hex string, literal @samp{-1}
33229 to indicate all processes or threads (respectively), or @samp{0} to
33230 indicate an arbitrary process or thread. Specifying just a process, as
33231 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33232 error to specify all processes but a specific thread, such as
33233 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33234 for those packets and replies explicitly documented to include a process
33235 ID, rather than a @var{thread-id}.
33237 The multiprocess @var{thread-id} syntax extensions are only used if both
33238 @value{GDBN} and the stub report support for the @samp{multiprocess}
33239 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33242 Note that all packet forms beginning with an upper- or lower-case
33243 letter, other than those described here, are reserved for future use.
33245 Here are the packet descriptions.
33250 @cindex @samp{!} packet
33251 @anchor{extended mode}
33252 Enable extended mode. In extended mode, the remote server is made
33253 persistent. The @samp{R} packet is used to restart the program being
33259 The remote target both supports and has enabled extended mode.
33263 @cindex @samp{?} packet
33264 Indicate the reason the target halted. The reply is the same as for
33265 step and continue. This packet has a special interpretation when the
33266 target is in non-stop mode; see @ref{Remote Non-Stop}.
33269 @xref{Stop Reply Packets}, for the reply specifications.
33271 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33272 @cindex @samp{A} packet
33273 Initialized @code{argv[]} array passed into program. @var{arglen}
33274 specifies the number of bytes in the hex encoded byte stream
33275 @var{arg}. See @code{gdbserver} for more details.
33280 The arguments were set.
33286 @cindex @samp{b} packet
33287 (Don't use this packet; its behavior is not well-defined.)
33288 Change the serial line speed to @var{baud}.
33290 JTC: @emph{When does the transport layer state change? When it's
33291 received, or after the ACK is transmitted. In either case, there are
33292 problems if the command or the acknowledgment packet is dropped.}
33294 Stan: @emph{If people really wanted to add something like this, and get
33295 it working for the first time, they ought to modify ser-unix.c to send
33296 some kind of out-of-band message to a specially-setup stub and have the
33297 switch happen "in between" packets, so that from remote protocol's point
33298 of view, nothing actually happened.}
33300 @item B @var{addr},@var{mode}
33301 @cindex @samp{B} packet
33302 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33303 breakpoint at @var{addr}.
33305 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33306 (@pxref{insert breakpoint or watchpoint packet}).
33308 @cindex @samp{bc} packet
33311 Backward continue. Execute the target system in reverse. No parameter.
33312 @xref{Reverse Execution}, for more information.
33315 @xref{Stop Reply Packets}, for the reply specifications.
33317 @cindex @samp{bs} packet
33320 Backward single step. Execute one instruction in reverse. No parameter.
33321 @xref{Reverse Execution}, for more information.
33324 @xref{Stop Reply Packets}, for the reply specifications.
33326 @item c @r{[}@var{addr}@r{]}
33327 @cindex @samp{c} packet
33328 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33329 resume at current address.
33331 This packet is deprecated for multi-threading support. @xref{vCont
33335 @xref{Stop Reply Packets}, for the reply specifications.
33337 @item C @var{sig}@r{[};@var{addr}@r{]}
33338 @cindex @samp{C} packet
33339 Continue with signal @var{sig} (hex signal number). If
33340 @samp{;@var{addr}} is omitted, resume at same address.
33342 This packet is deprecated for multi-threading support. @xref{vCont
33346 @xref{Stop Reply Packets}, for the reply specifications.
33349 @cindex @samp{d} packet
33352 Don't use this packet; instead, define a general set packet
33353 (@pxref{General Query Packets}).
33357 @cindex @samp{D} packet
33358 The first form of the packet is used to detach @value{GDBN} from the
33359 remote system. It is sent to the remote target
33360 before @value{GDBN} disconnects via the @code{detach} command.
33362 The second form, including a process ID, is used when multiprocess
33363 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33364 detach only a specific process. The @var{pid} is specified as a
33365 big-endian hex string.
33375 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33376 @cindex @samp{F} packet
33377 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33378 This is part of the File-I/O protocol extension. @xref{File-I/O
33379 Remote Protocol Extension}, for the specification.
33382 @anchor{read registers packet}
33383 @cindex @samp{g} packet
33384 Read general registers.
33388 @item @var{XX@dots{}}
33389 Each byte of register data is described by two hex digits. The bytes
33390 with the register are transmitted in target byte order. The size of
33391 each register and their position within the @samp{g} packet are
33392 determined by the @value{GDBN} internal gdbarch functions
33393 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33394 specification of several standard @samp{g} packets is specified below.
33396 When reading registers from a trace frame (@pxref{Analyze Collected
33397 Data,,Using the Collected Data}), the stub may also return a string of
33398 literal @samp{x}'s in place of the register data digits, to indicate
33399 that the corresponding register has not been collected, thus its value
33400 is unavailable. For example, for an architecture with 4 registers of
33401 4 bytes each, the following reply indicates to @value{GDBN} that
33402 registers 0 and 2 have not been collected, while registers 1 and 3
33403 have been collected, and both have zero value:
33407 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33414 @item G @var{XX@dots{}}
33415 @cindex @samp{G} packet
33416 Write general registers. @xref{read registers packet}, for a
33417 description of the @var{XX@dots{}} data.
33427 @item H @var{op} @var{thread-id}
33428 @cindex @samp{H} packet
33429 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33430 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33431 it should be @samp{c} for step and continue operations (note that this
33432 is deprecated, supporting the @samp{vCont} command is a better
33433 option), @samp{g} for other operations. The thread designator
33434 @var{thread-id} has the format and interpretation described in
33435 @ref{thread-id syntax}.
33446 @c 'H': How restrictive (or permissive) is the thread model. If a
33447 @c thread is selected and stopped, are other threads allowed
33448 @c to continue to execute? As I mentioned above, I think the
33449 @c semantics of each command when a thread is selected must be
33450 @c described. For example:
33452 @c 'g': If the stub supports threads and a specific thread is
33453 @c selected, returns the register block from that thread;
33454 @c otherwise returns current registers.
33456 @c 'G' If the stub supports threads and a specific thread is
33457 @c selected, sets the registers of the register block of
33458 @c that thread; otherwise sets current registers.
33460 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33461 @anchor{cycle step packet}
33462 @cindex @samp{i} packet
33463 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33464 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33465 step starting at that address.
33468 @cindex @samp{I} packet
33469 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33473 @cindex @samp{k} packet
33476 FIXME: @emph{There is no description of how to operate when a specific
33477 thread context has been selected (i.e.@: does 'k' kill only that
33480 @item m @var{addr},@var{length}
33481 @cindex @samp{m} packet
33482 Read @var{length} bytes of memory starting at address @var{addr}.
33483 Note that @var{addr} may not be aligned to any particular boundary.
33485 The stub need not use any particular size or alignment when gathering
33486 data from memory for the response; even if @var{addr} is word-aligned
33487 and @var{length} is a multiple of the word size, the stub is free to
33488 use byte accesses, or not. For this reason, this packet may not be
33489 suitable for accessing memory-mapped I/O devices.
33490 @cindex alignment of remote memory accesses
33491 @cindex size of remote memory accesses
33492 @cindex memory, alignment and size of remote accesses
33496 @item @var{XX@dots{}}
33497 Memory contents; each byte is transmitted as a two-digit hexadecimal
33498 number. The reply may contain fewer bytes than requested if the
33499 server was able to read only part of the region of memory.
33504 @item M @var{addr},@var{length}:@var{XX@dots{}}
33505 @cindex @samp{M} packet
33506 Write @var{length} bytes of memory starting at address @var{addr}.
33507 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33508 hexadecimal number.
33515 for an error (this includes the case where only part of the data was
33520 @cindex @samp{p} packet
33521 Read the value of register @var{n}; @var{n} is in hex.
33522 @xref{read registers packet}, for a description of how the returned
33523 register value is encoded.
33527 @item @var{XX@dots{}}
33528 the register's value
33532 Indicating an unrecognized @var{query}.
33535 @item P @var{n@dots{}}=@var{r@dots{}}
33536 @anchor{write register packet}
33537 @cindex @samp{P} packet
33538 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33539 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33540 digits for each byte in the register (target byte order).
33550 @item q @var{name} @var{params}@dots{}
33551 @itemx Q @var{name} @var{params}@dots{}
33552 @cindex @samp{q} packet
33553 @cindex @samp{Q} packet
33554 General query (@samp{q}) and set (@samp{Q}). These packets are
33555 described fully in @ref{General Query Packets}.
33558 @cindex @samp{r} packet
33559 Reset the entire system.
33561 Don't use this packet; use the @samp{R} packet instead.
33564 @cindex @samp{R} packet
33565 Restart the program being debugged. @var{XX}, while needed, is ignored.
33566 This packet is only available in extended mode (@pxref{extended mode}).
33568 The @samp{R} packet has no reply.
33570 @item s @r{[}@var{addr}@r{]}
33571 @cindex @samp{s} packet
33572 Single step. @var{addr} is the address at which to resume. If
33573 @var{addr} is omitted, resume at same address.
33575 This packet is deprecated for multi-threading support. @xref{vCont
33579 @xref{Stop Reply Packets}, for the reply specifications.
33581 @item S @var{sig}@r{[};@var{addr}@r{]}
33582 @anchor{step with signal packet}
33583 @cindex @samp{S} packet
33584 Step with signal. This is analogous to the @samp{C} packet, but
33585 requests a single-step, rather than a normal resumption of execution.
33587 This packet is deprecated for multi-threading support. @xref{vCont
33591 @xref{Stop Reply Packets}, for the reply specifications.
33593 @item t @var{addr}:@var{PP},@var{MM}
33594 @cindex @samp{t} packet
33595 Search backwards starting at address @var{addr} for a match with pattern
33596 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33597 @var{addr} must be at least 3 digits.
33599 @item T @var{thread-id}
33600 @cindex @samp{T} packet
33601 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33606 thread is still alive
33612 Packets starting with @samp{v} are identified by a multi-letter name,
33613 up to the first @samp{;} or @samp{?} (or the end of the packet).
33615 @item vAttach;@var{pid}
33616 @cindex @samp{vAttach} packet
33617 Attach to a new process with the specified process ID @var{pid}.
33618 The process ID is a
33619 hexadecimal integer identifying the process. In all-stop mode, all
33620 threads in the attached process are stopped; in non-stop mode, it may be
33621 attached without being stopped if that is supported by the target.
33623 @c In non-stop mode, on a successful vAttach, the stub should set the
33624 @c current thread to a thread of the newly-attached process. After
33625 @c attaching, GDB queries for the attached process's thread ID with qC.
33626 @c Also note that, from a user perspective, whether or not the
33627 @c target is stopped on attach in non-stop mode depends on whether you
33628 @c use the foreground or background version of the attach command, not
33629 @c on what vAttach does; GDB does the right thing with respect to either
33630 @c stopping or restarting threads.
33632 This packet is only available in extended mode (@pxref{extended mode}).
33638 @item @r{Any stop packet}
33639 for success in all-stop mode (@pxref{Stop Reply Packets})
33641 for success in non-stop mode (@pxref{Remote Non-Stop})
33644 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33645 @cindex @samp{vCont} packet
33646 @anchor{vCont packet}
33647 Resume the inferior, specifying different actions for each thread.
33648 If an action is specified with no @var{thread-id}, then it is applied to any
33649 threads that don't have a specific action specified; if no default action is
33650 specified then other threads should remain stopped in all-stop mode and
33651 in their current state in non-stop mode.
33652 Specifying multiple
33653 default actions is an error; specifying no actions is also an error.
33654 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33656 Currently supported actions are:
33662 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33666 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33671 The optional argument @var{addr} normally associated with the
33672 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33673 not supported in @samp{vCont}.
33675 The @samp{t} action is only relevant in non-stop mode
33676 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33677 A stop reply should be generated for any affected thread not already stopped.
33678 When a thread is stopped by means of a @samp{t} action,
33679 the corresponding stop reply should indicate that the thread has stopped with
33680 signal @samp{0}, regardless of whether the target uses some other signal
33681 as an implementation detail.
33684 @xref{Stop Reply Packets}, for the reply specifications.
33687 @cindex @samp{vCont?} packet
33688 Request a list of actions supported by the @samp{vCont} packet.
33692 @item vCont@r{[};@var{action}@dots{}@r{]}
33693 The @samp{vCont} packet is supported. Each @var{action} is a supported
33694 command in the @samp{vCont} packet.
33696 The @samp{vCont} packet is not supported.
33699 @item vFile:@var{operation}:@var{parameter}@dots{}
33700 @cindex @samp{vFile} packet
33701 Perform a file operation on the target system. For details,
33702 see @ref{Host I/O Packets}.
33704 @item vFlashErase:@var{addr},@var{length}
33705 @cindex @samp{vFlashErase} packet
33706 Direct the stub to erase @var{length} bytes of flash starting at
33707 @var{addr}. The region may enclose any number of flash blocks, but
33708 its start and end must fall on block boundaries, as indicated by the
33709 flash block size appearing in the memory map (@pxref{Memory Map
33710 Format}). @value{GDBN} groups flash memory programming operations
33711 together, and sends a @samp{vFlashDone} request after each group; the
33712 stub is allowed to delay erase operation until the @samp{vFlashDone}
33713 packet is received.
33715 The stub must support @samp{vCont} if it reports support for
33716 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
33717 this case @samp{vCont} actions can be specified to apply to all threads
33718 in a process by using the @samp{p@var{pid}.-1} form of the
33729 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
33730 @cindex @samp{vFlashWrite} packet
33731 Direct the stub to write data to flash address @var{addr}. The data
33732 is passed in binary form using the same encoding as for the @samp{X}
33733 packet (@pxref{Binary Data}). The memory ranges specified by
33734 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
33735 not overlap, and must appear in order of increasing addresses
33736 (although @samp{vFlashErase} packets for higher addresses may already
33737 have been received; the ordering is guaranteed only between
33738 @samp{vFlashWrite} packets). If a packet writes to an address that was
33739 neither erased by a preceding @samp{vFlashErase} packet nor by some other
33740 target-specific method, the results are unpredictable.
33748 for vFlashWrite addressing non-flash memory
33754 @cindex @samp{vFlashDone} packet
33755 Indicate to the stub that flash programming operation is finished.
33756 The stub is permitted to delay or batch the effects of a group of
33757 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
33758 @samp{vFlashDone} packet is received. The contents of the affected
33759 regions of flash memory are unpredictable until the @samp{vFlashDone}
33760 request is completed.
33762 @item vKill;@var{pid}
33763 @cindex @samp{vKill} packet
33764 Kill the process with the specified process ID. @var{pid} is a
33765 hexadecimal integer identifying the process. This packet is used in
33766 preference to @samp{k} when multiprocess protocol extensions are
33767 supported; see @ref{multiprocess extensions}.
33777 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
33778 @cindex @samp{vRun} packet
33779 Run the program @var{filename}, passing it each @var{argument} on its
33780 command line. The file and arguments are hex-encoded strings. If
33781 @var{filename} is an empty string, the stub may use a default program
33782 (e.g.@: the last program run). The program is created in the stopped
33785 @c FIXME: What about non-stop mode?
33787 This packet is only available in extended mode (@pxref{extended mode}).
33793 @item @r{Any stop packet}
33794 for success (@pxref{Stop Reply Packets})
33798 @anchor{vStopped packet}
33799 @cindex @samp{vStopped} packet
33801 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
33802 reply and prompt for the stub to report another one.
33806 @item @r{Any stop packet}
33807 if there is another unreported stop event (@pxref{Stop Reply Packets})
33809 if there are no unreported stop events
33812 @item X @var{addr},@var{length}:@var{XX@dots{}}
33814 @cindex @samp{X} packet
33815 Write data to memory, where the data is transmitted in binary.
33816 @var{addr} is address, @var{length} is number of bytes,
33817 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
33827 @item z @var{type},@var{addr},@var{kind}
33828 @itemx Z @var{type},@var{addr},@var{kind}
33829 @anchor{insert breakpoint or watchpoint packet}
33830 @cindex @samp{z} packet
33831 @cindex @samp{Z} packets
33832 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
33833 watchpoint starting at address @var{address} of kind @var{kind}.
33835 Each breakpoint and watchpoint packet @var{type} is documented
33838 @emph{Implementation notes: A remote target shall return an empty string
33839 for an unrecognized breakpoint or watchpoint packet @var{type}. A
33840 remote target shall support either both or neither of a given
33841 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
33842 avoid potential problems with duplicate packets, the operations should
33843 be implemented in an idempotent way.}
33845 @item z0,@var{addr},@var{kind}
33846 @itemx Z0,@var{addr},@var{kind}
33847 @cindex @samp{z0} packet
33848 @cindex @samp{Z0} packet
33849 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
33850 @var{addr} of type @var{kind}.
33852 A memory breakpoint is implemented by replacing the instruction at
33853 @var{addr} with a software breakpoint or trap instruction. The
33854 @var{kind} is target-specific and typically indicates the size of
33855 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
33856 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
33857 architectures have additional meanings for @var{kind};
33858 see @ref{Architecture-Specific Protocol Details}.
33860 @emph{Implementation note: It is possible for a target to copy or move
33861 code that contains memory breakpoints (e.g., when implementing
33862 overlays). The behavior of this packet, in the presence of such a
33863 target, is not defined.}
33875 @item z1,@var{addr},@var{kind}
33876 @itemx Z1,@var{addr},@var{kind}
33877 @cindex @samp{z1} packet
33878 @cindex @samp{Z1} packet
33879 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
33880 address @var{addr}.
33882 A hardware breakpoint is implemented using a mechanism that is not
33883 dependant on being able to modify the target's memory. @var{kind}
33884 has the same meaning as in @samp{Z0} packets.
33886 @emph{Implementation note: A hardware breakpoint is not affected by code
33899 @item z2,@var{addr},@var{kind}
33900 @itemx Z2,@var{addr},@var{kind}
33901 @cindex @samp{z2} packet
33902 @cindex @samp{Z2} packet
33903 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
33904 @var{kind} is interpreted as the number of bytes to watch.
33916 @item z3,@var{addr},@var{kind}
33917 @itemx Z3,@var{addr},@var{kind}
33918 @cindex @samp{z3} packet
33919 @cindex @samp{Z3} packet
33920 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
33921 @var{kind} is interpreted as the number of bytes to watch.
33933 @item z4,@var{addr},@var{kind}
33934 @itemx Z4,@var{addr},@var{kind}
33935 @cindex @samp{z4} packet
33936 @cindex @samp{Z4} packet
33937 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
33938 @var{kind} is interpreted as the number of bytes to watch.
33952 @node Stop Reply Packets
33953 @section Stop Reply Packets
33954 @cindex stop reply packets
33956 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
33957 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
33958 receive any of the below as a reply. Except for @samp{?}
33959 and @samp{vStopped}, that reply is only returned
33960 when the target halts. In the below the exact meaning of @dfn{signal
33961 number} is defined by the header @file{include/gdb/signals.h} in the
33962 @value{GDBN} source code.
33964 As in the description of request packets, we include spaces in the
33965 reply templates for clarity; these are not part of the reply packet's
33966 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
33972 The program received signal number @var{AA} (a two-digit hexadecimal
33973 number). This is equivalent to a @samp{T} response with no
33974 @var{n}:@var{r} pairs.
33976 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
33977 @cindex @samp{T} packet reply
33978 The program received signal number @var{AA} (a two-digit hexadecimal
33979 number). This is equivalent to an @samp{S} response, except that the
33980 @samp{@var{n}:@var{r}} pairs can carry values of important registers
33981 and other information directly in the stop reply packet, reducing
33982 round-trip latency. Single-step and breakpoint traps are reported
33983 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
33987 If @var{n} is a hexadecimal number, it is a register number, and the
33988 corresponding @var{r} gives that register's value. @var{r} is a
33989 series of bytes in target byte order, with each byte given by a
33990 two-digit hex number.
33993 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
33994 the stopped thread, as specified in @ref{thread-id syntax}.
33997 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
33998 the core on which the stop event was detected.
34001 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34002 specific event that stopped the target. The currently defined stop
34003 reasons are listed below. @var{aa} should be @samp{05}, the trap
34004 signal. At most one stop reason should be present.
34007 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34008 and go on to the next; this allows us to extend the protocol in the
34012 The currently defined stop reasons are:
34018 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34021 @cindex shared library events, remote reply
34023 The packet indicates that the loaded libraries have changed.
34024 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34025 list of loaded libraries. @var{r} is ignored.
34027 @cindex replay log events, remote reply
34029 The packet indicates that the target cannot continue replaying
34030 logged execution events, because it has reached the end (or the
34031 beginning when executing backward) of the log. The value of @var{r}
34032 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34033 for more information.
34037 @itemx W @var{AA} ; process:@var{pid}
34038 The process exited, and @var{AA} is the exit status. This is only
34039 applicable to certain targets.
34041 The second form of the response, including the process ID of the exited
34042 process, can be used only when @value{GDBN} has reported support for
34043 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34044 The @var{pid} is formatted as a big-endian hex string.
34047 @itemx X @var{AA} ; process:@var{pid}
34048 The process terminated with signal @var{AA}.
34050 The second form of the response, including the process ID of the
34051 terminated process, can be used only when @value{GDBN} has reported
34052 support for multiprocess protocol extensions; see @ref{multiprocess
34053 extensions}. The @var{pid} is formatted as a big-endian hex string.
34055 @item O @var{XX}@dots{}
34056 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34057 written as the program's console output. This can happen at any time
34058 while the program is running and the debugger should continue to wait
34059 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34061 @item F @var{call-id},@var{parameter}@dots{}
34062 @var{call-id} is the identifier which says which host system call should
34063 be called. This is just the name of the function. Translation into the
34064 correct system call is only applicable as it's defined in @value{GDBN}.
34065 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34068 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34069 this very system call.
34071 The target replies with this packet when it expects @value{GDBN} to
34072 call a host system call on behalf of the target. @value{GDBN} replies
34073 with an appropriate @samp{F} packet and keeps up waiting for the next
34074 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34075 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34076 Protocol Extension}, for more details.
34080 @node General Query Packets
34081 @section General Query Packets
34082 @cindex remote query requests
34084 Packets starting with @samp{q} are @dfn{general query packets};
34085 packets starting with @samp{Q} are @dfn{general set packets}. General
34086 query and set packets are a semi-unified form for retrieving and
34087 sending information to and from the stub.
34089 The initial letter of a query or set packet is followed by a name
34090 indicating what sort of thing the packet applies to. For example,
34091 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34092 definitions with the stub. These packet names follow some
34097 The name must not contain commas, colons or semicolons.
34099 Most @value{GDBN} query and set packets have a leading upper case
34102 The names of custom vendor packets should use a company prefix, in
34103 lower case, followed by a period. For example, packets designed at
34104 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34105 foos) or @samp{Qacme.bar} (for setting bars).
34108 The name of a query or set packet should be separated from any
34109 parameters by a @samp{:}; the parameters themselves should be
34110 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34111 full packet name, and check for a separator or the end of the packet,
34112 in case two packet names share a common prefix. New packets should not begin
34113 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34114 packets predate these conventions, and have arguments without any terminator
34115 for the packet name; we suspect they are in widespread use in places that
34116 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34117 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34120 Like the descriptions of the other packets, each description here
34121 has a template showing the packet's overall syntax, followed by an
34122 explanation of the packet's meaning. We include spaces in some of the
34123 templates for clarity; these are not part of the packet's syntax. No
34124 @value{GDBN} packet uses spaces to separate its components.
34126 Here are the currently defined query and set packets:
34130 @item QAllow:@var{op}:@var{val}@dots{}
34131 @cindex @samp{QAllow} packet
34132 Specify which operations @value{GDBN} expects to request of the
34133 target, as a semicolon-separated list of operation name and value
34134 pairs. Possible values for @var{op} include @samp{WriteReg},
34135 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34136 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34137 indicating that @value{GDBN} will not request the operation, or 1,
34138 indicating that it may. (The target can then use this to set up its
34139 own internals optimally, for instance if the debugger never expects to
34140 insert breakpoints, it may not need to install its own trap handler.)
34143 @cindex current thread, remote request
34144 @cindex @samp{qC} packet
34145 Return the current thread ID.
34149 @item QC @var{thread-id}
34150 Where @var{thread-id} is a thread ID as documented in
34151 @ref{thread-id syntax}.
34152 @item @r{(anything else)}
34153 Any other reply implies the old thread ID.
34156 @item qCRC:@var{addr},@var{length}
34157 @cindex CRC of memory block, remote request
34158 @cindex @samp{qCRC} packet
34159 Compute the CRC checksum of a block of memory using CRC-32 defined in
34160 IEEE 802.3. The CRC is computed byte at a time, taking the most
34161 significant bit of each byte first. The initial pattern code
34162 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34164 @emph{Note:} This is the same CRC used in validating separate debug
34165 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34166 Files}). However the algorithm is slightly different. When validating
34167 separate debug files, the CRC is computed taking the @emph{least}
34168 significant bit of each byte first, and the final result is inverted to
34169 detect trailing zeros.
34174 An error (such as memory fault)
34175 @item C @var{crc32}
34176 The specified memory region's checksum is @var{crc32}.
34179 @item QDisableRandomization:@var{value}
34180 @cindex disable address space randomization, remote request
34181 @cindex @samp{QDisableRandomization} packet
34182 Some target operating systems will randomize the virtual address space
34183 of the inferior process as a security feature, but provide a feature
34184 to disable such randomization, e.g.@: to allow for a more deterministic
34185 debugging experience. On such systems, this packet with a @var{value}
34186 of 1 directs the target to disable address space randomization for
34187 processes subsequently started via @samp{vRun} packets, while a packet
34188 with a @var{value} of 0 tells the target to enable address space
34191 This packet is only available in extended mode (@pxref{extended mode}).
34196 The request succeeded.
34199 An error occurred. @var{nn} are hex digits.
34202 An empty reply indicates that @samp{QDisableRandomization} is not supported
34206 This packet is not probed by default; the remote stub must request it,
34207 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34208 This should only be done on targets that actually support disabling
34209 address space randomization.
34212 @itemx qsThreadInfo
34213 @cindex list active threads, remote request
34214 @cindex @samp{qfThreadInfo} packet
34215 @cindex @samp{qsThreadInfo} packet
34216 Obtain a list of all active thread IDs from the target (OS). Since there
34217 may be too many active threads to fit into one reply packet, this query
34218 works iteratively: it may require more than one query/reply sequence to
34219 obtain the entire list of threads. The first query of the sequence will
34220 be the @samp{qfThreadInfo} query; subsequent queries in the
34221 sequence will be the @samp{qsThreadInfo} query.
34223 NOTE: This packet replaces the @samp{qL} query (see below).
34227 @item m @var{thread-id}
34229 @item m @var{thread-id},@var{thread-id}@dots{}
34230 a comma-separated list of thread IDs
34232 (lower case letter @samp{L}) denotes end of list.
34235 In response to each query, the target will reply with a list of one or
34236 more thread IDs, separated by commas.
34237 @value{GDBN} will respond to each reply with a request for more thread
34238 ids (using the @samp{qs} form of the query), until the target responds
34239 with @samp{l} (lower-case ell, for @dfn{last}).
34240 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34243 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34244 @cindex get thread-local storage address, remote request
34245 @cindex @samp{qGetTLSAddr} packet
34246 Fetch the address associated with thread local storage specified
34247 by @var{thread-id}, @var{offset}, and @var{lm}.
34249 @var{thread-id} is the thread ID associated with the
34250 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34252 @var{offset} is the (big endian, hex encoded) offset associated with the
34253 thread local variable. (This offset is obtained from the debug
34254 information associated with the variable.)
34256 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34257 load module associated with the thread local storage. For example,
34258 a @sc{gnu}/Linux system will pass the link map address of the shared
34259 object associated with the thread local storage under consideration.
34260 Other operating environments may choose to represent the load module
34261 differently, so the precise meaning of this parameter will vary.
34265 @item @var{XX}@dots{}
34266 Hex encoded (big endian) bytes representing the address of the thread
34267 local storage requested.
34270 An error occurred. @var{nn} are hex digits.
34273 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34276 @item qGetTIBAddr:@var{thread-id}
34277 @cindex get thread information block address
34278 @cindex @samp{qGetTIBAddr} packet
34279 Fetch address of the Windows OS specific Thread Information Block.
34281 @var{thread-id} is the thread ID associated with the thread.
34285 @item @var{XX}@dots{}
34286 Hex encoded (big endian) bytes representing the linear address of the
34287 thread information block.
34290 An error occured. This means that either the thread was not found, or the
34291 address could not be retrieved.
34294 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34297 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34298 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34299 digit) is one to indicate the first query and zero to indicate a
34300 subsequent query; @var{threadcount} (two hex digits) is the maximum
34301 number of threads the response packet can contain; and @var{nextthread}
34302 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34303 returned in the response as @var{argthread}.
34305 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34309 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34310 Where: @var{count} (two hex digits) is the number of threads being
34311 returned; @var{done} (one hex digit) is zero to indicate more threads
34312 and one indicates no further threads; @var{argthreadid} (eight hex
34313 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34314 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34315 digits). See @code{remote.c:parse_threadlist_response()}.
34319 @cindex section offsets, remote request
34320 @cindex @samp{qOffsets} packet
34321 Get section offsets that the target used when relocating the downloaded
34326 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34327 Relocate the @code{Text} section by @var{xxx} from its original address.
34328 Relocate the @code{Data} section by @var{yyy} from its original address.
34329 If the object file format provides segment information (e.g.@: @sc{elf}
34330 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34331 segments by the supplied offsets.
34333 @emph{Note: while a @code{Bss} offset may be included in the response,
34334 @value{GDBN} ignores this and instead applies the @code{Data} offset
34335 to the @code{Bss} section.}
34337 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34338 Relocate the first segment of the object file, which conventionally
34339 contains program code, to a starting address of @var{xxx}. If
34340 @samp{DataSeg} is specified, relocate the second segment, which
34341 conventionally contains modifiable data, to a starting address of
34342 @var{yyy}. @value{GDBN} will report an error if the object file
34343 does not contain segment information, or does not contain at least
34344 as many segments as mentioned in the reply. Extra segments are
34345 kept at fixed offsets relative to the last relocated segment.
34348 @item qP @var{mode} @var{thread-id}
34349 @cindex thread information, remote request
34350 @cindex @samp{qP} packet
34351 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34352 encoded 32 bit mode; @var{thread-id} is a thread ID
34353 (@pxref{thread-id syntax}).
34355 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34358 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34362 @cindex non-stop mode, remote request
34363 @cindex @samp{QNonStop} packet
34365 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34366 @xref{Remote Non-Stop}, for more information.
34371 The request succeeded.
34374 An error occurred. @var{nn} are hex digits.
34377 An empty reply indicates that @samp{QNonStop} is not supported by
34381 This packet is not probed by default; the remote stub must request it,
34382 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34383 Use of this packet is controlled by the @code{set non-stop} command;
34384 @pxref{Non-Stop Mode}.
34386 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34387 @cindex pass signals to inferior, remote request
34388 @cindex @samp{QPassSignals} packet
34389 @anchor{QPassSignals}
34390 Each listed @var{signal} should be passed directly to the inferior process.
34391 Signals are numbered identically to continue packets and stop replies
34392 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34393 strictly greater than the previous item. These signals do not need to stop
34394 the inferior, or be reported to @value{GDBN}. All other signals should be
34395 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34396 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34397 new list. This packet improves performance when using @samp{handle
34398 @var{signal} nostop noprint pass}.
34403 The request succeeded.
34406 An error occurred. @var{nn} are hex digits.
34409 An empty reply indicates that @samp{QPassSignals} is not supported by
34413 Use of this packet is controlled by the @code{set remote pass-signals}
34414 command (@pxref{Remote Configuration, set remote pass-signals}).
34415 This packet is not probed by default; the remote stub must request it,
34416 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34418 @item qRcmd,@var{command}
34419 @cindex execute remote command, remote request
34420 @cindex @samp{qRcmd} packet
34421 @var{command} (hex encoded) is passed to the local interpreter for
34422 execution. Invalid commands should be reported using the output
34423 string. Before the final result packet, the target may also respond
34424 with a number of intermediate @samp{O@var{output}} console output
34425 packets. @emph{Implementors should note that providing access to a
34426 stubs's interpreter may have security implications}.
34431 A command response with no output.
34433 A command response with the hex encoded output string @var{OUTPUT}.
34435 Indicate a badly formed request.
34437 An empty reply indicates that @samp{qRcmd} is not recognized.
34440 (Note that the @code{qRcmd} packet's name is separated from the
34441 command by a @samp{,}, not a @samp{:}, contrary to the naming
34442 conventions above. Please don't use this packet as a model for new
34445 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34446 @cindex searching memory, in remote debugging
34447 @cindex @samp{qSearch:memory} packet
34448 @anchor{qSearch memory}
34449 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34450 @var{address} and @var{length} are encoded in hex.
34451 @var{search-pattern} is a sequence of bytes, hex encoded.
34456 The pattern was not found.
34458 The pattern was found at @var{address}.
34460 A badly formed request or an error was encountered while searching memory.
34462 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34465 @item QStartNoAckMode
34466 @cindex @samp{QStartNoAckMode} packet
34467 @anchor{QStartNoAckMode}
34468 Request that the remote stub disable the normal @samp{+}/@samp{-}
34469 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34474 The stub has switched to no-acknowledgment mode.
34475 @value{GDBN} acknowledges this reponse,
34476 but neither the stub nor @value{GDBN} shall send or expect further
34477 @samp{+}/@samp{-} acknowledgments in the current connection.
34479 An empty reply indicates that the stub does not support no-acknowledgment mode.
34482 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34483 @cindex supported packets, remote query
34484 @cindex features of the remote protocol
34485 @cindex @samp{qSupported} packet
34486 @anchor{qSupported}
34487 Tell the remote stub about features supported by @value{GDBN}, and
34488 query the stub for features it supports. This packet allows
34489 @value{GDBN} and the remote stub to take advantage of each others'
34490 features. @samp{qSupported} also consolidates multiple feature probes
34491 at startup, to improve @value{GDBN} performance---a single larger
34492 packet performs better than multiple smaller probe packets on
34493 high-latency links. Some features may enable behavior which must not
34494 be on by default, e.g.@: because it would confuse older clients or
34495 stubs. Other features may describe packets which could be
34496 automatically probed for, but are not. These features must be
34497 reported before @value{GDBN} will use them. This ``default
34498 unsupported'' behavior is not appropriate for all packets, but it
34499 helps to keep the initial connection time under control with new
34500 versions of @value{GDBN} which support increasing numbers of packets.
34504 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34505 The stub supports or does not support each returned @var{stubfeature},
34506 depending on the form of each @var{stubfeature} (see below for the
34509 An empty reply indicates that @samp{qSupported} is not recognized,
34510 or that no features needed to be reported to @value{GDBN}.
34513 The allowed forms for each feature (either a @var{gdbfeature} in the
34514 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34518 @item @var{name}=@var{value}
34519 The remote protocol feature @var{name} is supported, and associated
34520 with the specified @var{value}. The format of @var{value} depends
34521 on the feature, but it must not include a semicolon.
34523 The remote protocol feature @var{name} is supported, and does not
34524 need an associated value.
34526 The remote protocol feature @var{name} is not supported.
34528 The remote protocol feature @var{name} may be supported, and
34529 @value{GDBN} should auto-detect support in some other way when it is
34530 needed. This form will not be used for @var{gdbfeature} notifications,
34531 but may be used for @var{stubfeature} responses.
34534 Whenever the stub receives a @samp{qSupported} request, the
34535 supplied set of @value{GDBN} features should override any previous
34536 request. This allows @value{GDBN} to put the stub in a known
34537 state, even if the stub had previously been communicating with
34538 a different version of @value{GDBN}.
34540 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34545 This feature indicates whether @value{GDBN} supports multiprocess
34546 extensions to the remote protocol. @value{GDBN} does not use such
34547 extensions unless the stub also reports that it supports them by
34548 including @samp{multiprocess+} in its @samp{qSupported} reply.
34549 @xref{multiprocess extensions}, for details.
34552 This feature indicates that @value{GDBN} supports the XML target
34553 description. If the stub sees @samp{xmlRegisters=} with target
34554 specific strings separated by a comma, it will report register
34558 This feature indicates whether @value{GDBN} supports the
34559 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34560 instruction reply packet}).
34563 Stubs should ignore any unknown values for
34564 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34565 packet supports receiving packets of unlimited length (earlier
34566 versions of @value{GDBN} may reject overly long responses). Additional values
34567 for @var{gdbfeature} may be defined in the future to let the stub take
34568 advantage of new features in @value{GDBN}, e.g.@: incompatible
34569 improvements in the remote protocol---the @samp{multiprocess} feature is
34570 an example of such a feature. The stub's reply should be independent
34571 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34572 describes all the features it supports, and then the stub replies with
34573 all the features it supports.
34575 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34576 responses, as long as each response uses one of the standard forms.
34578 Some features are flags. A stub which supports a flag feature
34579 should respond with a @samp{+} form response. Other features
34580 require values, and the stub should respond with an @samp{=}
34583 Each feature has a default value, which @value{GDBN} will use if
34584 @samp{qSupported} is not available or if the feature is not mentioned
34585 in the @samp{qSupported} response. The default values are fixed; a
34586 stub is free to omit any feature responses that match the defaults.
34588 Not all features can be probed, but for those which can, the probing
34589 mechanism is useful: in some cases, a stub's internal
34590 architecture may not allow the protocol layer to know some information
34591 about the underlying target in advance. This is especially common in
34592 stubs which may be configured for multiple targets.
34594 These are the currently defined stub features and their properties:
34596 @multitable @columnfractions 0.35 0.2 0.12 0.2
34597 @c NOTE: The first row should be @headitem, but we do not yet require
34598 @c a new enough version of Texinfo (4.7) to use @headitem.
34600 @tab Value Required
34604 @item @samp{PacketSize}
34609 @item @samp{qXfer:auxv:read}
34614 @item @samp{qXfer:features:read}
34619 @item @samp{qXfer:libraries:read}
34624 @item @samp{qXfer:memory-map:read}
34629 @item @samp{qXfer:sdata:read}
34634 @item @samp{qXfer:spu:read}
34639 @item @samp{qXfer:spu:write}
34644 @item @samp{qXfer:siginfo:read}
34649 @item @samp{qXfer:siginfo:write}
34654 @item @samp{qXfer:threads:read}
34659 @item @samp{qXfer:traceframe-info:read}
34664 @item @samp{qXfer:fdpic:read}
34669 @item @samp{QNonStop}
34674 @item @samp{QPassSignals}
34679 @item @samp{QStartNoAckMode}
34684 @item @samp{multiprocess}
34689 @item @samp{ConditionalTracepoints}
34694 @item @samp{ReverseContinue}
34699 @item @samp{ReverseStep}
34704 @item @samp{TracepointSource}
34709 @item @samp{QAllow}
34714 @item @samp{QDisableRandomization}
34719 @item @samp{EnableDisableTracepoints}
34724 @item @samp{tracenz}
34731 These are the currently defined stub features, in more detail:
34734 @cindex packet size, remote protocol
34735 @item PacketSize=@var{bytes}
34736 The remote stub can accept packets up to at least @var{bytes} in
34737 length. @value{GDBN} will send packets up to this size for bulk
34738 transfers, and will never send larger packets. This is a limit on the
34739 data characters in the packet, including the frame and checksum.
34740 There is no trailing NUL byte in a remote protocol packet; if the stub
34741 stores packets in a NUL-terminated format, it should allow an extra
34742 byte in its buffer for the NUL. If this stub feature is not supported,
34743 @value{GDBN} guesses based on the size of the @samp{g} packet response.
34745 @item qXfer:auxv:read
34746 The remote stub understands the @samp{qXfer:auxv:read} packet
34747 (@pxref{qXfer auxiliary vector read}).
34749 @item qXfer:features:read
34750 The remote stub understands the @samp{qXfer:features:read} packet
34751 (@pxref{qXfer target description read}).
34753 @item qXfer:libraries:read
34754 The remote stub understands the @samp{qXfer:libraries:read} packet
34755 (@pxref{qXfer library list read}).
34757 @item qXfer:memory-map:read
34758 The remote stub understands the @samp{qXfer:memory-map:read} packet
34759 (@pxref{qXfer memory map read}).
34761 @item qXfer:sdata:read
34762 The remote stub understands the @samp{qXfer:sdata:read} packet
34763 (@pxref{qXfer sdata read}).
34765 @item qXfer:spu:read
34766 The remote stub understands the @samp{qXfer:spu:read} packet
34767 (@pxref{qXfer spu read}).
34769 @item qXfer:spu:write
34770 The remote stub understands the @samp{qXfer:spu:write} packet
34771 (@pxref{qXfer spu write}).
34773 @item qXfer:siginfo:read
34774 The remote stub understands the @samp{qXfer:siginfo:read} packet
34775 (@pxref{qXfer siginfo read}).
34777 @item qXfer:siginfo:write
34778 The remote stub understands the @samp{qXfer:siginfo:write} packet
34779 (@pxref{qXfer siginfo write}).
34781 @item qXfer:threads:read
34782 The remote stub understands the @samp{qXfer:threads:read} packet
34783 (@pxref{qXfer threads read}).
34785 @item qXfer:traceframe-info:read
34786 The remote stub understands the @samp{qXfer:traceframe-info:read}
34787 packet (@pxref{qXfer traceframe info read}).
34789 @item qXfer:fdpic:read
34790 The remote stub understands the @samp{qXfer:fdpic:read}
34791 packet (@pxref{qXfer fdpic loadmap read}).
34794 The remote stub understands the @samp{QNonStop} packet
34795 (@pxref{QNonStop}).
34798 The remote stub understands the @samp{QPassSignals} packet
34799 (@pxref{QPassSignals}).
34801 @item QStartNoAckMode
34802 The remote stub understands the @samp{QStartNoAckMode} packet and
34803 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
34806 @anchor{multiprocess extensions}
34807 @cindex multiprocess extensions, in remote protocol
34808 The remote stub understands the multiprocess extensions to the remote
34809 protocol syntax. The multiprocess extensions affect the syntax of
34810 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
34811 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
34812 replies. Note that reporting this feature indicates support for the
34813 syntactic extensions only, not that the stub necessarily supports
34814 debugging of more than one process at a time. The stub must not use
34815 multiprocess extensions in packet replies unless @value{GDBN} has also
34816 indicated it supports them in its @samp{qSupported} request.
34818 @item qXfer:osdata:read
34819 The remote stub understands the @samp{qXfer:osdata:read} packet
34820 ((@pxref{qXfer osdata read}).
34822 @item ConditionalTracepoints
34823 The remote stub accepts and implements conditional expressions defined
34824 for tracepoints (@pxref{Tracepoint Conditions}).
34826 @item ReverseContinue
34827 The remote stub accepts and implements the reverse continue packet
34831 The remote stub accepts and implements the reverse step packet
34834 @item TracepointSource
34835 The remote stub understands the @samp{QTDPsrc} packet that supplies
34836 the source form of tracepoint definitions.
34839 The remote stub understands the @samp{QAllow} packet.
34841 @item QDisableRandomization
34842 The remote stub understands the @samp{QDisableRandomization} packet.
34844 @item StaticTracepoint
34845 @cindex static tracepoints, in remote protocol
34846 The remote stub supports static tracepoints.
34848 @item EnableDisableTracepoints
34849 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
34850 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
34851 to be enabled and disabled while a trace experiment is running.
34854 @cindex string tracing, in remote protocol
34855 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
34856 See @ref{Bytecode Descriptions} for details about the bytecode.
34861 @cindex symbol lookup, remote request
34862 @cindex @samp{qSymbol} packet
34863 Notify the target that @value{GDBN} is prepared to serve symbol lookup
34864 requests. Accept requests from the target for the values of symbols.
34869 The target does not need to look up any (more) symbols.
34870 @item qSymbol:@var{sym_name}
34871 The target requests the value of symbol @var{sym_name} (hex encoded).
34872 @value{GDBN} may provide the value by using the
34873 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
34877 @item qSymbol:@var{sym_value}:@var{sym_name}
34878 Set the value of @var{sym_name} to @var{sym_value}.
34880 @var{sym_name} (hex encoded) is the name of a symbol whose value the
34881 target has previously requested.
34883 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
34884 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
34890 The target does not need to look up any (more) symbols.
34891 @item qSymbol:@var{sym_name}
34892 The target requests the value of a new symbol @var{sym_name} (hex
34893 encoded). @value{GDBN} will continue to supply the values of symbols
34894 (if available), until the target ceases to request them.
34899 @item QTDisconnected
34906 @xref{Tracepoint Packets}.
34908 @item qThreadExtraInfo,@var{thread-id}
34909 @cindex thread attributes info, remote request
34910 @cindex @samp{qThreadExtraInfo} packet
34911 Obtain a printable string description of a thread's attributes from
34912 the target OS. @var{thread-id} is a thread ID;
34913 see @ref{thread-id syntax}. This
34914 string may contain anything that the target OS thinks is interesting
34915 for @value{GDBN} to tell the user about the thread. The string is
34916 displayed in @value{GDBN}'s @code{info threads} display. Some
34917 examples of possible thread extra info strings are @samp{Runnable}, or
34918 @samp{Blocked on Mutex}.
34922 @item @var{XX}@dots{}
34923 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
34924 comprising the printable string containing the extra information about
34925 the thread's attributes.
34928 (Note that the @code{qThreadExtraInfo} packet's name is separated from
34929 the command by a @samp{,}, not a @samp{:}, contrary to the naming
34930 conventions above. Please don't use this packet as a model for new
34947 @xref{Tracepoint Packets}.
34949 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
34950 @cindex read special object, remote request
34951 @cindex @samp{qXfer} packet
34952 @anchor{qXfer read}
34953 Read uninterpreted bytes from the target's special data area
34954 identified by the keyword @var{object}. Request @var{length} bytes
34955 starting at @var{offset} bytes into the data. The content and
34956 encoding of @var{annex} is specific to @var{object}; it can supply
34957 additional details about what data to access.
34959 Here are the specific requests of this form defined so far. All
34960 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
34961 formats, listed below.
34964 @item qXfer:auxv:read::@var{offset},@var{length}
34965 @anchor{qXfer auxiliary vector read}
34966 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
34967 auxiliary vector}. Note @var{annex} must be empty.
34969 This packet is not probed by default; the remote stub must request it,
34970 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34972 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
34973 @anchor{qXfer target description read}
34974 Access the @dfn{target description}. @xref{Target Descriptions}. The
34975 annex specifies which XML document to access. The main description is
34976 always loaded from the @samp{target.xml} annex.
34978 This packet is not probed by default; the remote stub must request it,
34979 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34981 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
34982 @anchor{qXfer library list read}
34983 Access the target's list of loaded libraries. @xref{Library List Format}.
34984 The annex part of the generic @samp{qXfer} packet must be empty
34985 (@pxref{qXfer read}).
34987 Targets which maintain a list of libraries in the program's memory do
34988 not need to implement this packet; it is designed for platforms where
34989 the operating system manages the list of loaded libraries.
34991 This packet is not probed by default; the remote stub must request it,
34992 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34994 @item qXfer:memory-map:read::@var{offset},@var{length}
34995 @anchor{qXfer memory map read}
34996 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
34997 annex part of the generic @samp{qXfer} packet must be empty
34998 (@pxref{qXfer read}).
35000 This packet is not probed by default; the remote stub must request it,
35001 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35003 @item qXfer:sdata:read::@var{offset},@var{length}
35004 @anchor{qXfer sdata read}
35006 Read contents of the extra collected static tracepoint marker
35007 information. The annex part of the generic @samp{qXfer} packet must
35008 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35011 This packet is not probed by default; the remote stub must request it,
35012 by supplying an appropriate @samp{qSupported} response
35013 (@pxref{qSupported}).
35015 @item qXfer:siginfo:read::@var{offset},@var{length}
35016 @anchor{qXfer siginfo read}
35017 Read contents of the extra signal information on the target
35018 system. The annex part of the generic @samp{qXfer} packet must be
35019 empty (@pxref{qXfer read}).
35021 This packet is not probed by default; the remote stub must request it,
35022 by supplying an appropriate @samp{qSupported} response
35023 (@pxref{qSupported}).
35025 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35026 @anchor{qXfer spu read}
35027 Read contents of an @code{spufs} file on the target system. The
35028 annex specifies which file to read; it must be of the form
35029 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35030 in the target process, and @var{name} identifes the @code{spufs} file
35031 in that context to be accessed.
35033 This packet is not probed by default; the remote stub must request it,
35034 by supplying an appropriate @samp{qSupported} response
35035 (@pxref{qSupported}).
35037 @item qXfer:threads:read::@var{offset},@var{length}
35038 @anchor{qXfer threads read}
35039 Access the list of threads on target. @xref{Thread List Format}. The
35040 annex part of the generic @samp{qXfer} packet must be empty
35041 (@pxref{qXfer read}).
35043 This packet is not probed by default; the remote stub must request it,
35044 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35046 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35047 @anchor{qXfer traceframe info read}
35049 Return a description of the current traceframe's contents.
35050 @xref{Traceframe Info Format}. The annex part of the generic
35051 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35053 This packet is not probed by default; the remote stub must request it,
35054 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35056 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35057 @anchor{qXfer fdpic loadmap read}
35058 Read contents of @code{loadmap}s on the target system. The
35059 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35060 executable @code{loadmap} or interpreter @code{loadmap} to read.
35062 This packet is not probed by default; the remote stub must request it,
35063 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35065 @item qXfer:osdata:read::@var{offset},@var{length}
35066 @anchor{qXfer osdata read}
35067 Access the target's @dfn{operating system information}.
35068 @xref{Operating System Information}.
35075 Data @var{data} (@pxref{Binary Data}) has been read from the
35076 target. There may be more data at a higher address (although
35077 it is permitted to return @samp{m} even for the last valid
35078 block of data, as long as at least one byte of data was read).
35079 @var{data} may have fewer bytes than the @var{length} in the
35083 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35084 There is no more data to be read. @var{data} may have fewer bytes
35085 than the @var{length} in the request.
35088 The @var{offset} in the request is at the end of the data.
35089 There is no more data to be read.
35092 The request was malformed, or @var{annex} was invalid.
35095 The offset was invalid, or there was an error encountered reading the data.
35096 @var{nn} is a hex-encoded @code{errno} value.
35099 An empty reply indicates the @var{object} string was not recognized by
35100 the stub, or that the object does not support reading.
35103 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35104 @cindex write data into object, remote request
35105 @anchor{qXfer write}
35106 Write uninterpreted bytes into the target's special data area
35107 identified by the keyword @var{object}, starting at @var{offset} bytes
35108 into the data. @var{data}@dots{} is the binary-encoded data
35109 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35110 is specific to @var{object}; it can supply additional details about what data
35113 Here are the specific requests of this form defined so far. All
35114 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35115 formats, listed below.
35118 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35119 @anchor{qXfer siginfo write}
35120 Write @var{data} to the extra signal information on the target system.
35121 The annex part of the generic @samp{qXfer} packet must be
35122 empty (@pxref{qXfer write}).
35124 This packet is not probed by default; the remote stub must request it,
35125 by supplying an appropriate @samp{qSupported} response
35126 (@pxref{qSupported}).
35128 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35129 @anchor{qXfer spu write}
35130 Write @var{data} to an @code{spufs} file on the target system. The
35131 annex specifies which file to write; it must be of the form
35132 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35133 in the target process, and @var{name} identifes the @code{spufs} file
35134 in that context to be accessed.
35136 This packet is not probed by default; the remote stub must request it,
35137 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35143 @var{nn} (hex encoded) is the number of bytes written.
35144 This may be fewer bytes than supplied in the request.
35147 The request was malformed, or @var{annex} was invalid.
35150 The offset was invalid, or there was an error encountered writing the data.
35151 @var{nn} is a hex-encoded @code{errno} value.
35154 An empty reply indicates the @var{object} string was not
35155 recognized by the stub, or that the object does not support writing.
35158 @item qXfer:@var{object}:@var{operation}:@dots{}
35159 Requests of this form may be added in the future. When a stub does
35160 not recognize the @var{object} keyword, or its support for
35161 @var{object} does not recognize the @var{operation} keyword, the stub
35162 must respond with an empty packet.
35164 @item qAttached:@var{pid}
35165 @cindex query attached, remote request
35166 @cindex @samp{qAttached} packet
35167 Return an indication of whether the remote server attached to an
35168 existing process or created a new process. When the multiprocess
35169 protocol extensions are supported (@pxref{multiprocess extensions}),
35170 @var{pid} is an integer in hexadecimal format identifying the target
35171 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35172 the query packet will be simplified as @samp{qAttached}.
35174 This query is used, for example, to know whether the remote process
35175 should be detached or killed when a @value{GDBN} session is ended with
35176 the @code{quit} command.
35181 The remote server attached to an existing process.
35183 The remote server created a new process.
35185 A badly formed request or an error was encountered.
35190 @node Architecture-Specific Protocol Details
35191 @section Architecture-Specific Protocol Details
35193 This section describes how the remote protocol is applied to specific
35194 target architectures. Also see @ref{Standard Target Features}, for
35195 details of XML target descriptions for each architecture.
35199 @subsubsection Breakpoint Kinds
35201 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35206 16-bit Thumb mode breakpoint.
35209 32-bit Thumb mode (Thumb-2) breakpoint.
35212 32-bit ARM mode breakpoint.
35218 @subsubsection Register Packet Format
35220 The following @code{g}/@code{G} packets have previously been defined.
35221 In the below, some thirty-two bit registers are transferred as
35222 sixty-four bits. Those registers should be zero/sign extended (which?)
35223 to fill the space allocated. Register bytes are transferred in target
35224 byte order. The two nibbles within a register byte are transferred
35225 most-significant - least-significant.
35231 All registers are transferred as thirty-two bit quantities in the order:
35232 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35233 registers; fsr; fir; fp.
35237 All registers are transferred as sixty-four bit quantities (including
35238 thirty-two bit registers such as @code{sr}). The ordering is the same
35243 @node Tracepoint Packets
35244 @section Tracepoint Packets
35245 @cindex tracepoint packets
35246 @cindex packets, tracepoint
35248 Here we describe the packets @value{GDBN} uses to implement
35249 tracepoints (@pxref{Tracepoints}).
35253 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35254 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35255 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35256 the tracepoint is disabled. @var{step} is the tracepoint's step
35257 count, and @var{pass} is its pass count. If an @samp{F} is present,
35258 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35259 the number of bytes that the target should copy elsewhere to make room
35260 for the tracepoint. If an @samp{X} is present, it introduces a
35261 tracepoint condition, which consists of a hexadecimal length, followed
35262 by a comma and hex-encoded bytes, in a manner similar to action
35263 encodings as described below. If the trailing @samp{-} is present,
35264 further @samp{QTDP} packets will follow to specify this tracepoint's
35270 The packet was understood and carried out.
35272 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35274 The packet was not recognized.
35277 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35278 Define actions to be taken when a tracepoint is hit. @var{n} and
35279 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35280 this tracepoint. This packet may only be sent immediately after
35281 another @samp{QTDP} packet that ended with a @samp{-}. If the
35282 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35283 specifying more actions for this tracepoint.
35285 In the series of action packets for a given tracepoint, at most one
35286 can have an @samp{S} before its first @var{action}. If such a packet
35287 is sent, it and the following packets define ``while-stepping''
35288 actions. Any prior packets define ordinary actions --- that is, those
35289 taken when the tracepoint is first hit. If no action packet has an
35290 @samp{S}, then all the packets in the series specify ordinary
35291 tracepoint actions.
35293 The @samp{@var{action}@dots{}} portion of the packet is a series of
35294 actions, concatenated without separators. Each action has one of the
35300 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35301 a hexadecimal number whose @var{i}'th bit is set if register number
35302 @var{i} should be collected. (The least significant bit is numbered
35303 zero.) Note that @var{mask} may be any number of digits long; it may
35304 not fit in a 32-bit word.
35306 @item M @var{basereg},@var{offset},@var{len}
35307 Collect @var{len} bytes of memory starting at the address in register
35308 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35309 @samp{-1}, then the range has a fixed address: @var{offset} is the
35310 address of the lowest byte to collect. The @var{basereg},
35311 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35312 values (the @samp{-1} value for @var{basereg} is a special case).
35314 @item X @var{len},@var{expr}
35315 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35316 it directs. @var{expr} is an agent expression, as described in
35317 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35318 two-digit hex number in the packet; @var{len} is the number of bytes
35319 in the expression (and thus one-half the number of hex digits in the
35324 Any number of actions may be packed together in a single @samp{QTDP}
35325 packet, as long as the packet does not exceed the maximum packet
35326 length (400 bytes, for many stubs). There may be only one @samp{R}
35327 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35328 actions. Any registers referred to by @samp{M} and @samp{X} actions
35329 must be collected by a preceding @samp{R} action. (The
35330 ``while-stepping'' actions are treated as if they were attached to a
35331 separate tracepoint, as far as these restrictions are concerned.)
35336 The packet was understood and carried out.
35338 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35340 The packet was not recognized.
35343 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35344 @cindex @samp{QTDPsrc} packet
35345 Specify a source string of tracepoint @var{n} at address @var{addr}.
35346 This is useful to get accurate reproduction of the tracepoints
35347 originally downloaded at the beginning of the trace run. @var{type}
35348 is the name of the tracepoint part, such as @samp{cond} for the
35349 tracepoint's conditional expression (see below for a list of types), while
35350 @var{bytes} is the string, encoded in hexadecimal.
35352 @var{start} is the offset of the @var{bytes} within the overall source
35353 string, while @var{slen} is the total length of the source string.
35354 This is intended for handling source strings that are longer than will
35355 fit in a single packet.
35356 @c Add detailed example when this info is moved into a dedicated
35357 @c tracepoint descriptions section.
35359 The available string types are @samp{at} for the location,
35360 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35361 @value{GDBN} sends a separate packet for each command in the action
35362 list, in the same order in which the commands are stored in the list.
35364 The target does not need to do anything with source strings except
35365 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35368 Although this packet is optional, and @value{GDBN} will only send it
35369 if the target replies with @samp{TracepointSource} @xref{General
35370 Query Packets}, it makes both disconnected tracing and trace files
35371 much easier to use. Otherwise the user must be careful that the
35372 tracepoints in effect while looking at trace frames are identical to
35373 the ones in effect during the trace run; even a small discrepancy
35374 could cause @samp{tdump} not to work, or a particular trace frame not
35377 @item QTDV:@var{n}:@var{value}
35378 @cindex define trace state variable, remote request
35379 @cindex @samp{QTDV} packet
35380 Create a new trace state variable, number @var{n}, with an initial
35381 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35382 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35383 the option of not using this packet for initial values of zero; the
35384 target should simply create the trace state variables as they are
35385 mentioned in expressions.
35387 @item QTFrame:@var{n}
35388 Select the @var{n}'th tracepoint frame from the buffer, and use the
35389 register and memory contents recorded there to answer subsequent
35390 request packets from @value{GDBN}.
35392 A successful reply from the stub indicates that the stub has found the
35393 requested frame. The response is a series of parts, concatenated
35394 without separators, describing the frame we selected. Each part has
35395 one of the following forms:
35399 The selected frame is number @var{n} in the trace frame buffer;
35400 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35401 was no frame matching the criteria in the request packet.
35404 The selected trace frame records a hit of tracepoint number @var{t};
35405 @var{t} is a hexadecimal number.
35409 @item QTFrame:pc:@var{addr}
35410 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35411 currently selected frame whose PC is @var{addr};
35412 @var{addr} is a hexadecimal number.
35414 @item QTFrame:tdp:@var{t}
35415 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35416 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35417 is a hexadecimal number.
35419 @item QTFrame:range:@var{start}:@var{end}
35420 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35421 currently selected frame whose PC is between @var{start} (inclusive)
35422 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35425 @item QTFrame:outside:@var{start}:@var{end}
35426 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35427 frame @emph{outside} the given range of addresses (exclusive).
35430 Begin the tracepoint experiment. Begin collecting data from
35431 tracepoint hits in the trace frame buffer. This packet supports the
35432 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35433 instruction reply packet}).
35436 End the tracepoint experiment. Stop collecting trace frames.
35438 @item QTEnable:@var{n}:@var{addr}
35440 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35441 experiment. If the tracepoint was previously disabled, then collection
35442 of data from it will resume.
35444 @item QTDisable:@var{n}:@var{addr}
35446 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35447 experiment. No more data will be collected from the tracepoint unless
35448 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35451 Clear the table of tracepoints, and empty the trace frame buffer.
35453 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35454 Establish the given ranges of memory as ``transparent''. The stub
35455 will answer requests for these ranges from memory's current contents,
35456 if they were not collected as part of the tracepoint hit.
35458 @value{GDBN} uses this to mark read-only regions of memory, like those
35459 containing program code. Since these areas never change, they should
35460 still have the same contents they did when the tracepoint was hit, so
35461 there's no reason for the stub to refuse to provide their contents.
35463 @item QTDisconnected:@var{value}
35464 Set the choice to what to do with the tracing run when @value{GDBN}
35465 disconnects from the target. A @var{value} of 1 directs the target to
35466 continue the tracing run, while 0 tells the target to stop tracing if
35467 @value{GDBN} is no longer in the picture.
35470 Ask the stub if there is a trace experiment running right now.
35472 The reply has the form:
35476 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35477 @var{running} is a single digit @code{1} if the trace is presently
35478 running, or @code{0} if not. It is followed by semicolon-separated
35479 optional fields that an agent may use to report additional status.
35483 If the trace is not running, the agent may report any of several
35484 explanations as one of the optional fields:
35489 No trace has been run yet.
35492 The trace was stopped by a user-originated stop command.
35495 The trace stopped because the trace buffer filled up.
35497 @item tdisconnected:0
35498 The trace stopped because @value{GDBN} disconnected from the target.
35500 @item tpasscount:@var{tpnum}
35501 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35503 @item terror:@var{text}:@var{tpnum}
35504 The trace stopped because tracepoint @var{tpnum} had an error. The
35505 string @var{text} is available to describe the nature of the error
35506 (for instance, a divide by zero in the condition expression).
35507 @var{text} is hex encoded.
35510 The trace stopped for some other reason.
35514 Additional optional fields supply statistical and other information.
35515 Although not required, they are extremely useful for users monitoring
35516 the progress of a trace run. If a trace has stopped, and these
35517 numbers are reported, they must reflect the state of the just-stopped
35522 @item tframes:@var{n}
35523 The number of trace frames in the buffer.
35525 @item tcreated:@var{n}
35526 The total number of trace frames created during the run. This may
35527 be larger than the trace frame count, if the buffer is circular.
35529 @item tsize:@var{n}
35530 The total size of the trace buffer, in bytes.
35532 @item tfree:@var{n}
35533 The number of bytes still unused in the buffer.
35535 @item circular:@var{n}
35536 The value of the circular trace buffer flag. @code{1} means that the
35537 trace buffer is circular and old trace frames will be discarded if
35538 necessary to make room, @code{0} means that the trace buffer is linear
35541 @item disconn:@var{n}
35542 The value of the disconnected tracing flag. @code{1} means that
35543 tracing will continue after @value{GDBN} disconnects, @code{0} means
35544 that the trace run will stop.
35548 @item qTV:@var{var}
35549 @cindex trace state variable value, remote request
35550 @cindex @samp{qTV} packet
35551 Ask the stub for the value of the trace state variable number @var{var}.
35556 The value of the variable is @var{value}. This will be the current
35557 value of the variable if the user is examining a running target, or a
35558 saved value if the variable was collected in the trace frame that the
35559 user is looking at. Note that multiple requests may result in
35560 different reply values, such as when requesting values while the
35561 program is running.
35564 The value of the variable is unknown. This would occur, for example,
35565 if the user is examining a trace frame in which the requested variable
35571 These packets request data about tracepoints that are being used by
35572 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35573 of data, and multiple @code{qTsP} to get additional pieces. Replies
35574 to these packets generally take the form of the @code{QTDP} packets
35575 that define tracepoints. (FIXME add detailed syntax)
35579 These packets request data about trace state variables that are on the
35580 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35581 and multiple @code{qTsV} to get additional variables. Replies to
35582 these packets follow the syntax of the @code{QTDV} packets that define
35583 trace state variables.
35587 These packets request data about static tracepoint markers that exist
35588 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35589 first piece of data, and multiple @code{qTsSTM} to get additional
35590 pieces. Replies to these packets take the following form:
35594 @item m @var{address}:@var{id}:@var{extra}
35596 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35597 a comma-separated list of markers
35599 (lower case letter @samp{L}) denotes end of list.
35601 An error occurred. @var{nn} are hex digits.
35603 An empty reply indicates that the request is not supported by the
35607 @var{address} is encoded in hex.
35608 @var{id} and @var{extra} are strings encoded in hex.
35610 In response to each query, the target will reply with a list of one or
35611 more markers, separated by commas. @value{GDBN} will respond to each
35612 reply with a request for more markers (using the @samp{qs} form of the
35613 query), until the target responds with @samp{l} (lower-case ell, for
35616 @item qTSTMat:@var{address}
35617 This packets requests data about static tracepoint markers in the
35618 target program at @var{address}. Replies to this packet follow the
35619 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35620 tracepoint markers.
35622 @item QTSave:@var{filename}
35623 This packet directs the target to save trace data to the file name
35624 @var{filename} in the target's filesystem. @var{filename} is encoded
35625 as a hex string; the interpretation of the file name (relative vs
35626 absolute, wild cards, etc) is up to the target.
35628 @item qTBuffer:@var{offset},@var{len}
35629 Return up to @var{len} bytes of the current contents of trace buffer,
35630 starting at @var{offset}. The trace buffer is treated as if it were
35631 a contiguous collection of traceframes, as per the trace file format.
35632 The reply consists as many hex-encoded bytes as the target can deliver
35633 in a packet; it is not an error to return fewer than were asked for.
35634 A reply consisting of just @code{l} indicates that no bytes are
35637 @item QTBuffer:circular:@var{value}
35638 This packet directs the target to use a circular trace buffer if
35639 @var{value} is 1, or a linear buffer if the value is 0.
35643 @subsection Relocate instruction reply packet
35644 When installing fast tracepoints in memory, the target may need to
35645 relocate the instruction currently at the tracepoint address to a
35646 different address in memory. For most instructions, a simple copy is
35647 enough, but, for example, call instructions that implicitly push the
35648 return address on the stack, and relative branches or other
35649 PC-relative instructions require offset adjustment, so that the effect
35650 of executing the instruction at a different address is the same as if
35651 it had executed in the original location.
35653 In response to several of the tracepoint packets, the target may also
35654 respond with a number of intermediate @samp{qRelocInsn} request
35655 packets before the final result packet, to have @value{GDBN} handle
35656 this relocation operation. If a packet supports this mechanism, its
35657 documentation will explicitly say so. See for example the above
35658 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
35659 format of the request is:
35662 @item qRelocInsn:@var{from};@var{to}
35664 This requests @value{GDBN} to copy instruction at address @var{from}
35665 to address @var{to}, possibly adjusted so that executing the
35666 instruction at @var{to} has the same effect as executing it at
35667 @var{from}. @value{GDBN} writes the adjusted instruction to target
35668 memory starting at @var{to}.
35673 @item qRelocInsn:@var{adjusted_size}
35674 Informs the stub the relocation is complete. @var{adjusted_size} is
35675 the length in bytes of resulting relocated instruction sequence.
35677 A badly formed request was detected, or an error was encountered while
35678 relocating the instruction.
35681 @node Host I/O Packets
35682 @section Host I/O Packets
35683 @cindex Host I/O, remote protocol
35684 @cindex file transfer, remote protocol
35686 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
35687 operations on the far side of a remote link. For example, Host I/O is
35688 used to upload and download files to a remote target with its own
35689 filesystem. Host I/O uses the same constant values and data structure
35690 layout as the target-initiated File-I/O protocol. However, the
35691 Host I/O packets are structured differently. The target-initiated
35692 protocol relies on target memory to store parameters and buffers.
35693 Host I/O requests are initiated by @value{GDBN}, and the
35694 target's memory is not involved. @xref{File-I/O Remote Protocol
35695 Extension}, for more details on the target-initiated protocol.
35697 The Host I/O request packets all encode a single operation along with
35698 its arguments. They have this format:
35702 @item vFile:@var{operation}: @var{parameter}@dots{}
35703 @var{operation} is the name of the particular request; the target
35704 should compare the entire packet name up to the second colon when checking
35705 for a supported operation. The format of @var{parameter} depends on
35706 the operation. Numbers are always passed in hexadecimal. Negative
35707 numbers have an explicit minus sign (i.e.@: two's complement is not
35708 used). Strings (e.g.@: filenames) are encoded as a series of
35709 hexadecimal bytes. The last argument to a system call may be a
35710 buffer of escaped binary data (@pxref{Binary Data}).
35714 The valid responses to Host I/O packets are:
35718 @item F @var{result} [, @var{errno}] [; @var{attachment}]
35719 @var{result} is the integer value returned by this operation, usually
35720 non-negative for success and -1 for errors. If an error has occured,
35721 @var{errno} will be included in the result. @var{errno} will have a
35722 value defined by the File-I/O protocol (@pxref{Errno Values}). For
35723 operations which return data, @var{attachment} supplies the data as a
35724 binary buffer. Binary buffers in response packets are escaped in the
35725 normal way (@pxref{Binary Data}). See the individual packet
35726 documentation for the interpretation of @var{result} and
35730 An empty response indicates that this operation is not recognized.
35734 These are the supported Host I/O operations:
35737 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
35738 Open a file at @var{pathname} and return a file descriptor for it, or
35739 return -1 if an error occurs. @var{pathname} is a string,
35740 @var{flags} is an integer indicating a mask of open flags
35741 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
35742 of mode bits to use if the file is created (@pxref{mode_t Values}).
35743 @xref{open}, for details of the open flags and mode values.
35745 @item vFile:close: @var{fd}
35746 Close the open file corresponding to @var{fd} and return 0, or
35747 -1 if an error occurs.
35749 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
35750 Read data from the open file corresponding to @var{fd}. Up to
35751 @var{count} bytes will be read from the file, starting at @var{offset}
35752 relative to the start of the file. The target may read fewer bytes;
35753 common reasons include packet size limits and an end-of-file
35754 condition. The number of bytes read is returned. Zero should only be
35755 returned for a successful read at the end of the file, or if
35756 @var{count} was zero.
35758 The data read should be returned as a binary attachment on success.
35759 If zero bytes were read, the response should include an empty binary
35760 attachment (i.e.@: a trailing semicolon). The return value is the
35761 number of target bytes read; the binary attachment may be longer if
35762 some characters were escaped.
35764 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
35765 Write @var{data} (a binary buffer) to the open file corresponding
35766 to @var{fd}. Start the write at @var{offset} from the start of the
35767 file. Unlike many @code{write} system calls, there is no
35768 separate @var{count} argument; the length of @var{data} in the
35769 packet is used. @samp{vFile:write} returns the number of bytes written,
35770 which may be shorter than the length of @var{data}, or -1 if an
35773 @item vFile:unlink: @var{pathname}
35774 Delete the file at @var{pathname} on the target. Return 0,
35775 or -1 if an error occurs. @var{pathname} is a string.
35780 @section Interrupts
35781 @cindex interrupts (remote protocol)
35783 When a program on the remote target is running, @value{GDBN} may
35784 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
35785 a @code{BREAK} followed by @code{g},
35786 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
35788 The precise meaning of @code{BREAK} is defined by the transport
35789 mechanism and may, in fact, be undefined. @value{GDBN} does not
35790 currently define a @code{BREAK} mechanism for any of the network
35791 interfaces except for TCP, in which case @value{GDBN} sends the
35792 @code{telnet} BREAK sequence.
35794 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
35795 transport mechanisms. It is represented by sending the single byte
35796 @code{0x03} without any of the usual packet overhead described in
35797 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
35798 transmitted as part of a packet, it is considered to be packet data
35799 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
35800 (@pxref{X packet}), used for binary downloads, may include an unescaped
35801 @code{0x03} as part of its packet.
35803 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
35804 When Linux kernel receives this sequence from serial port,
35805 it stops execution and connects to gdb.
35807 Stubs are not required to recognize these interrupt mechanisms and the
35808 precise meaning associated with receipt of the interrupt is
35809 implementation defined. If the target supports debugging of multiple
35810 threads and/or processes, it should attempt to interrupt all
35811 currently-executing threads and processes.
35812 If the stub is successful at interrupting the
35813 running program, it should send one of the stop
35814 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
35815 of successfully stopping the program in all-stop mode, and a stop reply
35816 for each stopped thread in non-stop mode.
35817 Interrupts received while the
35818 program is stopped are discarded.
35820 @node Notification Packets
35821 @section Notification Packets
35822 @cindex notification packets
35823 @cindex packets, notification
35825 The @value{GDBN} remote serial protocol includes @dfn{notifications},
35826 packets that require no acknowledgment. Both the GDB and the stub
35827 may send notifications (although the only notifications defined at
35828 present are sent by the stub). Notifications carry information
35829 without incurring the round-trip latency of an acknowledgment, and so
35830 are useful for low-impact communications where occasional packet loss
35833 A notification packet has the form @samp{% @var{data} #
35834 @var{checksum}}, where @var{data} is the content of the notification,
35835 and @var{checksum} is a checksum of @var{data}, computed and formatted
35836 as for ordinary @value{GDBN} packets. A notification's @var{data}
35837 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
35838 receiving a notification, the recipient sends no @samp{+} or @samp{-}
35839 to acknowledge the notification's receipt or to report its corruption.
35841 Every notification's @var{data} begins with a name, which contains no
35842 colon characters, followed by a colon character.
35844 Recipients should silently ignore corrupted notifications and
35845 notifications they do not understand. Recipients should restart
35846 timeout periods on receipt of a well-formed notification, whether or
35847 not they understand it.
35849 Senders should only send the notifications described here when this
35850 protocol description specifies that they are permitted. In the
35851 future, we may extend the protocol to permit existing notifications in
35852 new contexts; this rule helps older senders avoid confusing newer
35855 (Older versions of @value{GDBN} ignore bytes received until they see
35856 the @samp{$} byte that begins an ordinary packet, so new stubs may
35857 transmit notifications without fear of confusing older clients. There
35858 are no notifications defined for @value{GDBN} to send at the moment, but we
35859 assume that most older stubs would ignore them, as well.)
35861 The following notification packets from the stub to @value{GDBN} are
35865 @item Stop: @var{reply}
35866 Report an asynchronous stop event in non-stop mode.
35867 The @var{reply} has the form of a stop reply, as
35868 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
35869 for information on how these notifications are acknowledged by
35873 @node Remote Non-Stop
35874 @section Remote Protocol Support for Non-Stop Mode
35876 @value{GDBN}'s remote protocol supports non-stop debugging of
35877 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
35878 supports non-stop mode, it should report that to @value{GDBN} by including
35879 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
35881 @value{GDBN} typically sends a @samp{QNonStop} packet only when
35882 establishing a new connection with the stub. Entering non-stop mode
35883 does not alter the state of any currently-running threads, but targets
35884 must stop all threads in any already-attached processes when entering
35885 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
35886 probe the target state after a mode change.
35888 In non-stop mode, when an attached process encounters an event that
35889 would otherwise be reported with a stop reply, it uses the
35890 asynchronous notification mechanism (@pxref{Notification Packets}) to
35891 inform @value{GDBN}. In contrast to all-stop mode, where all threads
35892 in all processes are stopped when a stop reply is sent, in non-stop
35893 mode only the thread reporting the stop event is stopped. That is,
35894 when reporting a @samp{S} or @samp{T} response to indicate completion
35895 of a step operation, hitting a breakpoint, or a fault, only the
35896 affected thread is stopped; any other still-running threads continue
35897 to run. When reporting a @samp{W} or @samp{X} response, all running
35898 threads belonging to other attached processes continue to run.
35900 Only one stop reply notification at a time may be pending; if
35901 additional stop events occur before @value{GDBN} has acknowledged the
35902 previous notification, they must be queued by the stub for later
35903 synchronous transmission in response to @samp{vStopped} packets from
35904 @value{GDBN}. Because the notification mechanism is unreliable,
35905 the stub is permitted to resend a stop reply notification
35906 if it believes @value{GDBN} may not have received it. @value{GDBN}
35907 ignores additional stop reply notifications received before it has
35908 finished processing a previous notification and the stub has completed
35909 sending any queued stop events.
35911 Otherwise, @value{GDBN} must be prepared to receive a stop reply
35912 notification at any time. Specifically, they may appear when
35913 @value{GDBN} is not otherwise reading input from the stub, or when
35914 @value{GDBN} is expecting to read a normal synchronous response or a
35915 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
35916 Notification packets are distinct from any other communication from
35917 the stub so there is no ambiguity.
35919 After receiving a stop reply notification, @value{GDBN} shall
35920 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
35921 as a regular, synchronous request to the stub. Such acknowledgment
35922 is not required to happen immediately, as @value{GDBN} is permitted to
35923 send other, unrelated packets to the stub first, which the stub should
35926 Upon receiving a @samp{vStopped} packet, if the stub has other queued
35927 stop events to report to @value{GDBN}, it shall respond by sending a
35928 normal stop reply response. @value{GDBN} shall then send another
35929 @samp{vStopped} packet to solicit further responses; again, it is
35930 permitted to send other, unrelated packets as well which the stub
35931 should process normally.
35933 If the stub receives a @samp{vStopped} packet and there are no
35934 additional stop events to report, the stub shall return an @samp{OK}
35935 response. At this point, if further stop events occur, the stub shall
35936 send a new stop reply notification, @value{GDBN} shall accept the
35937 notification, and the process shall be repeated.
35939 In non-stop mode, the target shall respond to the @samp{?} packet as
35940 follows. First, any incomplete stop reply notification/@samp{vStopped}
35941 sequence in progress is abandoned. The target must begin a new
35942 sequence reporting stop events for all stopped threads, whether or not
35943 it has previously reported those events to @value{GDBN}. The first
35944 stop reply is sent as a synchronous reply to the @samp{?} packet, and
35945 subsequent stop replies are sent as responses to @samp{vStopped} packets
35946 using the mechanism described above. The target must not send
35947 asynchronous stop reply notifications until the sequence is complete.
35948 If all threads are running when the target receives the @samp{?} packet,
35949 or if the target is not attached to any process, it shall respond
35952 @node Packet Acknowledgment
35953 @section Packet Acknowledgment
35955 @cindex acknowledgment, for @value{GDBN} remote
35956 @cindex packet acknowledgment, for @value{GDBN} remote
35957 By default, when either the host or the target machine receives a packet,
35958 the first response expected is an acknowledgment: either @samp{+} (to indicate
35959 the package was received correctly) or @samp{-} (to request retransmission).
35960 This mechanism allows the @value{GDBN} remote protocol to operate over
35961 unreliable transport mechanisms, such as a serial line.
35963 In cases where the transport mechanism is itself reliable (such as a pipe or
35964 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
35965 It may be desirable to disable them in that case to reduce communication
35966 overhead, or for other reasons. This can be accomplished by means of the
35967 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
35969 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
35970 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
35971 and response format still includes the normal checksum, as described in
35972 @ref{Overview}, but the checksum may be ignored by the receiver.
35974 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
35975 no-acknowledgment mode, it should report that to @value{GDBN}
35976 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
35977 @pxref{qSupported}.
35978 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
35979 disabled via the @code{set remote noack-packet off} command
35980 (@pxref{Remote Configuration}),
35981 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
35982 Only then may the stub actually turn off packet acknowledgments.
35983 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
35984 response, which can be safely ignored by the stub.
35986 Note that @code{set remote noack-packet} command only affects negotiation
35987 between @value{GDBN} and the stub when subsequent connections are made;
35988 it does not affect the protocol acknowledgment state for any current
35990 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
35991 new connection is established,
35992 there is also no protocol request to re-enable the acknowledgments
35993 for the current connection, once disabled.
35998 Example sequence of a target being re-started. Notice how the restart
35999 does not get any direct output:
36004 @emph{target restarts}
36007 <- @code{T001:1234123412341234}
36011 Example sequence of a target being stepped by a single instruction:
36014 -> @code{G1445@dots{}}
36019 <- @code{T001:1234123412341234}
36023 <- @code{1455@dots{}}
36027 @node File-I/O Remote Protocol Extension
36028 @section File-I/O Remote Protocol Extension
36029 @cindex File-I/O remote protocol extension
36032 * File-I/O Overview::
36033 * Protocol Basics::
36034 * The F Request Packet::
36035 * The F Reply Packet::
36036 * The Ctrl-C Message::
36038 * List of Supported Calls::
36039 * Protocol-specific Representation of Datatypes::
36041 * File-I/O Examples::
36044 @node File-I/O Overview
36045 @subsection File-I/O Overview
36046 @cindex file-i/o overview
36048 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36049 target to use the host's file system and console I/O to perform various
36050 system calls. System calls on the target system are translated into a
36051 remote protocol packet to the host system, which then performs the needed
36052 actions and returns a response packet to the target system.
36053 This simulates file system operations even on targets that lack file systems.
36055 The protocol is defined to be independent of both the host and target systems.
36056 It uses its own internal representation of datatypes and values. Both
36057 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36058 translating the system-dependent value representations into the internal
36059 protocol representations when data is transmitted.
36061 The communication is synchronous. A system call is possible only when
36062 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36063 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36064 the target is stopped to allow deterministic access to the target's
36065 memory. Therefore File-I/O is not interruptible by target signals. On
36066 the other hand, it is possible to interrupt File-I/O by a user interrupt
36067 (@samp{Ctrl-C}) within @value{GDBN}.
36069 The target's request to perform a host system call does not finish
36070 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36071 after finishing the system call, the target returns to continuing the
36072 previous activity (continue, step). No additional continue or step
36073 request from @value{GDBN} is required.
36076 (@value{GDBP}) continue
36077 <- target requests 'system call X'
36078 target is stopped, @value{GDBN} executes system call
36079 -> @value{GDBN} returns result
36080 ... target continues, @value{GDBN} returns to wait for the target
36081 <- target hits breakpoint and sends a Txx packet
36084 The protocol only supports I/O on the console and to regular files on
36085 the host file system. Character or block special devices, pipes,
36086 named pipes, sockets or any other communication method on the host
36087 system are not supported by this protocol.
36089 File I/O is not supported in non-stop mode.
36091 @node Protocol Basics
36092 @subsection Protocol Basics
36093 @cindex protocol basics, file-i/o
36095 The File-I/O protocol uses the @code{F} packet as the request as well
36096 as reply packet. Since a File-I/O system call can only occur when
36097 @value{GDBN} is waiting for a response from the continuing or stepping target,
36098 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36099 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36100 This @code{F} packet contains all information needed to allow @value{GDBN}
36101 to call the appropriate host system call:
36105 A unique identifier for the requested system call.
36108 All parameters to the system call. Pointers are given as addresses
36109 in the target memory address space. Pointers to strings are given as
36110 pointer/length pair. Numerical values are given as they are.
36111 Numerical control flags are given in a protocol-specific representation.
36115 At this point, @value{GDBN} has to perform the following actions.
36119 If the parameters include pointer values to data needed as input to a
36120 system call, @value{GDBN} requests this data from the target with a
36121 standard @code{m} packet request. This additional communication has to be
36122 expected by the target implementation and is handled as any other @code{m}
36126 @value{GDBN} translates all value from protocol representation to host
36127 representation as needed. Datatypes are coerced into the host types.
36130 @value{GDBN} calls the system call.
36133 It then coerces datatypes back to protocol representation.
36136 If the system call is expected to return data in buffer space specified
36137 by pointer parameters to the call, the data is transmitted to the
36138 target using a @code{M} or @code{X} packet. This packet has to be expected
36139 by the target implementation and is handled as any other @code{M} or @code{X}
36144 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36145 necessary information for the target to continue. This at least contains
36152 @code{errno}, if has been changed by the system call.
36159 After having done the needed type and value coercion, the target continues
36160 the latest continue or step action.
36162 @node The F Request Packet
36163 @subsection The @code{F} Request Packet
36164 @cindex file-i/o request packet
36165 @cindex @code{F} request packet
36167 The @code{F} request packet has the following format:
36170 @item F@var{call-id},@var{parameter@dots{}}
36172 @var{call-id} is the identifier to indicate the host system call to be called.
36173 This is just the name of the function.
36175 @var{parameter@dots{}} are the parameters to the system call.
36176 Parameters are hexadecimal integer values, either the actual values in case
36177 of scalar datatypes, pointers to target buffer space in case of compound
36178 datatypes and unspecified memory areas, or pointer/length pairs in case
36179 of string parameters. These are appended to the @var{call-id} as a
36180 comma-delimited list. All values are transmitted in ASCII
36181 string representation, pointer/length pairs separated by a slash.
36187 @node The F Reply Packet
36188 @subsection The @code{F} Reply Packet
36189 @cindex file-i/o reply packet
36190 @cindex @code{F} reply packet
36192 The @code{F} reply packet has the following format:
36196 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36198 @var{retcode} is the return code of the system call as hexadecimal value.
36200 @var{errno} is the @code{errno} set by the call, in protocol-specific
36202 This parameter can be omitted if the call was successful.
36204 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36205 case, @var{errno} must be sent as well, even if the call was successful.
36206 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36213 or, if the call was interrupted before the host call has been performed:
36220 assuming 4 is the protocol-specific representation of @code{EINTR}.
36225 @node The Ctrl-C Message
36226 @subsection The @samp{Ctrl-C} Message
36227 @cindex ctrl-c message, in file-i/o protocol
36229 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36230 reply packet (@pxref{The F Reply Packet}),
36231 the target should behave as if it had
36232 gotten a break message. The meaning for the target is ``system call
36233 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36234 (as with a break message) and return to @value{GDBN} with a @code{T02}
36237 It's important for the target to know in which
36238 state the system call was interrupted. There are two possible cases:
36242 The system call hasn't been performed on the host yet.
36245 The system call on the host has been finished.
36249 These two states can be distinguished by the target by the value of the
36250 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36251 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36252 on POSIX systems. In any other case, the target may presume that the
36253 system call has been finished --- successfully or not --- and should behave
36254 as if the break message arrived right after the system call.
36256 @value{GDBN} must behave reliably. If the system call has not been called
36257 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36258 @code{errno} in the packet. If the system call on the host has been finished
36259 before the user requests a break, the full action must be finished by
36260 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36261 The @code{F} packet may only be sent when either nothing has happened
36262 or the full action has been completed.
36265 @subsection Console I/O
36266 @cindex console i/o as part of file-i/o
36268 By default and if not explicitly closed by the target system, the file
36269 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36270 on the @value{GDBN} console is handled as any other file output operation
36271 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36272 by @value{GDBN} so that after the target read request from file descriptor
36273 0 all following typing is buffered until either one of the following
36278 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36280 system call is treated as finished.
36283 The user presses @key{RET}. This is treated as end of input with a trailing
36287 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36288 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36292 If the user has typed more characters than fit in the buffer given to
36293 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36294 either another @code{read(0, @dots{})} is requested by the target, or debugging
36295 is stopped at the user's request.
36298 @node List of Supported Calls
36299 @subsection List of Supported Calls
36300 @cindex list of supported file-i/o calls
36317 @unnumberedsubsubsec open
36318 @cindex open, file-i/o system call
36323 int open(const char *pathname, int flags);
36324 int open(const char *pathname, int flags, mode_t mode);
36328 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36331 @var{flags} is the bitwise @code{OR} of the following values:
36335 If the file does not exist it will be created. The host
36336 rules apply as far as file ownership and time stamps
36340 When used with @code{O_CREAT}, if the file already exists it is
36341 an error and open() fails.
36344 If the file already exists and the open mode allows
36345 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36346 truncated to zero length.
36349 The file is opened in append mode.
36352 The file is opened for reading only.
36355 The file is opened for writing only.
36358 The file is opened for reading and writing.
36362 Other bits are silently ignored.
36366 @var{mode} is the bitwise @code{OR} of the following values:
36370 User has read permission.
36373 User has write permission.
36376 Group has read permission.
36379 Group has write permission.
36382 Others have read permission.
36385 Others have write permission.
36389 Other bits are silently ignored.
36392 @item Return value:
36393 @code{open} returns the new file descriptor or -1 if an error
36400 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36403 @var{pathname} refers to a directory.
36406 The requested access is not allowed.
36409 @var{pathname} was too long.
36412 A directory component in @var{pathname} does not exist.
36415 @var{pathname} refers to a device, pipe, named pipe or socket.
36418 @var{pathname} refers to a file on a read-only filesystem and
36419 write access was requested.
36422 @var{pathname} is an invalid pointer value.
36425 No space on device to create the file.
36428 The process already has the maximum number of files open.
36431 The limit on the total number of files open on the system
36435 The call was interrupted by the user.
36441 @unnumberedsubsubsec close
36442 @cindex close, file-i/o system call
36451 @samp{Fclose,@var{fd}}
36453 @item Return value:
36454 @code{close} returns zero on success, or -1 if an error occurred.
36460 @var{fd} isn't a valid open file descriptor.
36463 The call was interrupted by the user.
36469 @unnumberedsubsubsec read
36470 @cindex read, file-i/o system call
36475 int read(int fd, void *buf, unsigned int count);
36479 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36481 @item Return value:
36482 On success, the number of bytes read is returned.
36483 Zero indicates end of file. If count is zero, read
36484 returns zero as well. On error, -1 is returned.
36490 @var{fd} is not a valid file descriptor or is not open for
36494 @var{bufptr} is an invalid pointer value.
36497 The call was interrupted by the user.
36503 @unnumberedsubsubsec write
36504 @cindex write, file-i/o system call
36509 int write(int fd, const void *buf, unsigned int count);
36513 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36515 @item Return value:
36516 On success, the number of bytes written are returned.
36517 Zero indicates nothing was written. On error, -1
36524 @var{fd} is not a valid file descriptor or is not open for
36528 @var{bufptr} is an invalid pointer value.
36531 An attempt was made to write a file that exceeds the
36532 host-specific maximum file size allowed.
36535 No space on device to write the data.
36538 The call was interrupted by the user.
36544 @unnumberedsubsubsec lseek
36545 @cindex lseek, file-i/o system call
36550 long lseek (int fd, long offset, int flag);
36554 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36556 @var{flag} is one of:
36560 The offset is set to @var{offset} bytes.
36563 The offset is set to its current location plus @var{offset}
36567 The offset is set to the size of the file plus @var{offset}
36571 @item Return value:
36572 On success, the resulting unsigned offset in bytes from
36573 the beginning of the file is returned. Otherwise, a
36574 value of -1 is returned.
36580 @var{fd} is not a valid open file descriptor.
36583 @var{fd} is associated with the @value{GDBN} console.
36586 @var{flag} is not a proper value.
36589 The call was interrupted by the user.
36595 @unnumberedsubsubsec rename
36596 @cindex rename, file-i/o system call
36601 int rename(const char *oldpath, const char *newpath);
36605 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36607 @item Return value:
36608 On success, zero is returned. On error, -1 is returned.
36614 @var{newpath} is an existing directory, but @var{oldpath} is not a
36618 @var{newpath} is a non-empty directory.
36621 @var{oldpath} or @var{newpath} is a directory that is in use by some
36625 An attempt was made to make a directory a subdirectory
36629 A component used as a directory in @var{oldpath} or new
36630 path is not a directory. Or @var{oldpath} is a directory
36631 and @var{newpath} exists but is not a directory.
36634 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
36637 No access to the file or the path of the file.
36641 @var{oldpath} or @var{newpath} was too long.
36644 A directory component in @var{oldpath} or @var{newpath} does not exist.
36647 The file is on a read-only filesystem.
36650 The device containing the file has no room for the new
36654 The call was interrupted by the user.
36660 @unnumberedsubsubsec unlink
36661 @cindex unlink, file-i/o system call
36666 int unlink(const char *pathname);
36670 @samp{Funlink,@var{pathnameptr}/@var{len}}
36672 @item Return value:
36673 On success, zero is returned. On error, -1 is returned.
36679 No access to the file or the path of the file.
36682 The system does not allow unlinking of directories.
36685 The file @var{pathname} cannot be unlinked because it's
36686 being used by another process.
36689 @var{pathnameptr} is an invalid pointer value.
36692 @var{pathname} was too long.
36695 A directory component in @var{pathname} does not exist.
36698 A component of the path is not a directory.
36701 The file is on a read-only filesystem.
36704 The call was interrupted by the user.
36710 @unnumberedsubsubsec stat/fstat
36711 @cindex fstat, file-i/o system call
36712 @cindex stat, file-i/o system call
36717 int stat(const char *pathname, struct stat *buf);
36718 int fstat(int fd, struct stat *buf);
36722 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
36723 @samp{Ffstat,@var{fd},@var{bufptr}}
36725 @item Return value:
36726 On success, zero is returned. On error, -1 is returned.
36732 @var{fd} is not a valid open file.
36735 A directory component in @var{pathname} does not exist or the
36736 path is an empty string.
36739 A component of the path is not a directory.
36742 @var{pathnameptr} is an invalid pointer value.
36745 No access to the file or the path of the file.
36748 @var{pathname} was too long.
36751 The call was interrupted by the user.
36757 @unnumberedsubsubsec gettimeofday
36758 @cindex gettimeofday, file-i/o system call
36763 int gettimeofday(struct timeval *tv, void *tz);
36767 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
36769 @item Return value:
36770 On success, 0 is returned, -1 otherwise.
36776 @var{tz} is a non-NULL pointer.
36779 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
36785 @unnumberedsubsubsec isatty
36786 @cindex isatty, file-i/o system call
36791 int isatty(int fd);
36795 @samp{Fisatty,@var{fd}}
36797 @item Return value:
36798 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
36804 The call was interrupted by the user.
36809 Note that the @code{isatty} call is treated as a special case: it returns
36810 1 to the target if the file descriptor is attached
36811 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
36812 would require implementing @code{ioctl} and would be more complex than
36817 @unnumberedsubsubsec system
36818 @cindex system, file-i/o system call
36823 int system(const char *command);
36827 @samp{Fsystem,@var{commandptr}/@var{len}}
36829 @item Return value:
36830 If @var{len} is zero, the return value indicates whether a shell is
36831 available. A zero return value indicates a shell is not available.
36832 For non-zero @var{len}, the value returned is -1 on error and the
36833 return status of the command otherwise. Only the exit status of the
36834 command is returned, which is extracted from the host's @code{system}
36835 return value by calling @code{WEXITSTATUS(retval)}. In case
36836 @file{/bin/sh} could not be executed, 127 is returned.
36842 The call was interrupted by the user.
36847 @value{GDBN} takes over the full task of calling the necessary host calls
36848 to perform the @code{system} call. The return value of @code{system} on
36849 the host is simplified before it's returned
36850 to the target. Any termination signal information from the child process
36851 is discarded, and the return value consists
36852 entirely of the exit status of the called command.
36854 Due to security concerns, the @code{system} call is by default refused
36855 by @value{GDBN}. The user has to allow this call explicitly with the
36856 @code{set remote system-call-allowed 1} command.
36859 @item set remote system-call-allowed
36860 @kindex set remote system-call-allowed
36861 Control whether to allow the @code{system} calls in the File I/O
36862 protocol for the remote target. The default is zero (disabled).
36864 @item show remote system-call-allowed
36865 @kindex show remote system-call-allowed
36866 Show whether the @code{system} calls are allowed in the File I/O
36870 @node Protocol-specific Representation of Datatypes
36871 @subsection Protocol-specific Representation of Datatypes
36872 @cindex protocol-specific representation of datatypes, in file-i/o protocol
36875 * Integral Datatypes::
36877 * Memory Transfer::
36882 @node Integral Datatypes
36883 @unnumberedsubsubsec Integral Datatypes
36884 @cindex integral datatypes, in file-i/o protocol
36886 The integral datatypes used in the system calls are @code{int},
36887 @code{unsigned int}, @code{long}, @code{unsigned long},
36888 @code{mode_t}, and @code{time_t}.
36890 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
36891 implemented as 32 bit values in this protocol.
36893 @code{long} and @code{unsigned long} are implemented as 64 bit types.
36895 @xref{Limits}, for corresponding MIN and MAX values (similar to those
36896 in @file{limits.h}) to allow range checking on host and target.
36898 @code{time_t} datatypes are defined as seconds since the Epoch.
36900 All integral datatypes transferred as part of a memory read or write of a
36901 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
36904 @node Pointer Values
36905 @unnumberedsubsubsec Pointer Values
36906 @cindex pointer values, in file-i/o protocol
36908 Pointers to target data are transmitted as they are. An exception
36909 is made for pointers to buffers for which the length isn't
36910 transmitted as part of the function call, namely strings. Strings
36911 are transmitted as a pointer/length pair, both as hex values, e.g.@:
36918 which is a pointer to data of length 18 bytes at position 0x1aaf.
36919 The length is defined as the full string length in bytes, including
36920 the trailing null byte. For example, the string @code{"hello world"}
36921 at address 0x123456 is transmitted as
36927 @node Memory Transfer
36928 @unnumberedsubsubsec Memory Transfer
36929 @cindex memory transfer, in file-i/o protocol
36931 Structured data which is transferred using a memory read or write (for
36932 example, a @code{struct stat}) is expected to be in a protocol-specific format
36933 with all scalar multibyte datatypes being big endian. Translation to
36934 this representation needs to be done both by the target before the @code{F}
36935 packet is sent, and by @value{GDBN} before
36936 it transfers memory to the target. Transferred pointers to structured
36937 data should point to the already-coerced data at any time.
36941 @unnumberedsubsubsec struct stat
36942 @cindex struct stat, in file-i/o protocol
36944 The buffer of type @code{struct stat} used by the target and @value{GDBN}
36945 is defined as follows:
36949 unsigned int st_dev; /* device */
36950 unsigned int st_ino; /* inode */
36951 mode_t st_mode; /* protection */
36952 unsigned int st_nlink; /* number of hard links */
36953 unsigned int st_uid; /* user ID of owner */
36954 unsigned int st_gid; /* group ID of owner */
36955 unsigned int st_rdev; /* device type (if inode device) */
36956 unsigned long st_size; /* total size, in bytes */
36957 unsigned long st_blksize; /* blocksize for filesystem I/O */
36958 unsigned long st_blocks; /* number of blocks allocated */
36959 time_t st_atime; /* time of last access */
36960 time_t st_mtime; /* time of last modification */
36961 time_t st_ctime; /* time of last change */
36965 The integral datatypes conform to the definitions given in the
36966 appropriate section (see @ref{Integral Datatypes}, for details) so this
36967 structure is of size 64 bytes.
36969 The values of several fields have a restricted meaning and/or
36975 A value of 0 represents a file, 1 the console.
36978 No valid meaning for the target. Transmitted unchanged.
36981 Valid mode bits are described in @ref{Constants}. Any other
36982 bits have currently no meaning for the target.
36987 No valid meaning for the target. Transmitted unchanged.
36992 These values have a host and file system dependent
36993 accuracy. Especially on Windows hosts, the file system may not
36994 support exact timing values.
36997 The target gets a @code{struct stat} of the above representation and is
36998 responsible for coercing it to the target representation before
37001 Note that due to size differences between the host, target, and protocol
37002 representations of @code{struct stat} members, these members could eventually
37003 get truncated on the target.
37005 @node struct timeval
37006 @unnumberedsubsubsec struct timeval
37007 @cindex struct timeval, in file-i/o protocol
37009 The buffer of type @code{struct timeval} used by the File-I/O protocol
37010 is defined as follows:
37014 time_t tv_sec; /* second */
37015 long tv_usec; /* microsecond */
37019 The integral datatypes conform to the definitions given in the
37020 appropriate section (see @ref{Integral Datatypes}, for details) so this
37021 structure is of size 8 bytes.
37024 @subsection Constants
37025 @cindex constants, in file-i/o protocol
37027 The following values are used for the constants inside of the
37028 protocol. @value{GDBN} and target are responsible for translating these
37029 values before and after the call as needed.
37040 @unnumberedsubsubsec Open Flags
37041 @cindex open flags, in file-i/o protocol
37043 All values are given in hexadecimal representation.
37055 @node mode_t Values
37056 @unnumberedsubsubsec mode_t Values
37057 @cindex mode_t values, in file-i/o protocol
37059 All values are given in octal representation.
37076 @unnumberedsubsubsec Errno Values
37077 @cindex errno values, in file-i/o protocol
37079 All values are given in decimal representation.
37104 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37105 any error value not in the list of supported error numbers.
37108 @unnumberedsubsubsec Lseek Flags
37109 @cindex lseek flags, in file-i/o protocol
37118 @unnumberedsubsubsec Limits
37119 @cindex limits, in file-i/o protocol
37121 All values are given in decimal representation.
37124 INT_MIN -2147483648
37126 UINT_MAX 4294967295
37127 LONG_MIN -9223372036854775808
37128 LONG_MAX 9223372036854775807
37129 ULONG_MAX 18446744073709551615
37132 @node File-I/O Examples
37133 @subsection File-I/O Examples
37134 @cindex file-i/o examples
37136 Example sequence of a write call, file descriptor 3, buffer is at target
37137 address 0x1234, 6 bytes should be written:
37140 <- @code{Fwrite,3,1234,6}
37141 @emph{request memory read from target}
37144 @emph{return "6 bytes written"}
37148 Example sequence of a read call, file descriptor 3, buffer is at target
37149 address 0x1234, 6 bytes should be read:
37152 <- @code{Fread,3,1234,6}
37153 @emph{request memory write to target}
37154 -> @code{X1234,6:XXXXXX}
37155 @emph{return "6 bytes read"}
37159 Example sequence of a read call, call fails on the host due to invalid
37160 file descriptor (@code{EBADF}):
37163 <- @code{Fread,3,1234,6}
37167 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37171 <- @code{Fread,3,1234,6}
37176 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37180 <- @code{Fread,3,1234,6}
37181 -> @code{X1234,6:XXXXXX}
37185 @node Library List Format
37186 @section Library List Format
37187 @cindex library list format, remote protocol
37189 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37190 same process as your application to manage libraries. In this case,
37191 @value{GDBN} can use the loader's symbol table and normal memory
37192 operations to maintain a list of shared libraries. On other
37193 platforms, the operating system manages loaded libraries.
37194 @value{GDBN} can not retrieve the list of currently loaded libraries
37195 through memory operations, so it uses the @samp{qXfer:libraries:read}
37196 packet (@pxref{qXfer library list read}) instead. The remote stub
37197 queries the target's operating system and reports which libraries
37200 The @samp{qXfer:libraries:read} packet returns an XML document which
37201 lists loaded libraries and their offsets. Each library has an
37202 associated name and one or more segment or section base addresses,
37203 which report where the library was loaded in memory.
37205 For the common case of libraries that are fully linked binaries, the
37206 library should have a list of segments. If the target supports
37207 dynamic linking of a relocatable object file, its library XML element
37208 should instead include a list of allocated sections. The segment or
37209 section bases are start addresses, not relocation offsets; they do not
37210 depend on the library's link-time base addresses.
37212 @value{GDBN} must be linked with the Expat library to support XML
37213 library lists. @xref{Expat}.
37215 A simple memory map, with one loaded library relocated by a single
37216 offset, looks like this:
37220 <library name="/lib/libc.so.6">
37221 <segment address="0x10000000"/>
37226 Another simple memory map, with one loaded library with three
37227 allocated sections (.text, .data, .bss), looks like this:
37231 <library name="sharedlib.o">
37232 <section address="0x10000000"/>
37233 <section address="0x20000000"/>
37234 <section address="0x30000000"/>
37239 The format of a library list is described by this DTD:
37242 <!-- library-list: Root element with versioning -->
37243 <!ELEMENT library-list (library)*>
37244 <!ATTLIST library-list version CDATA #FIXED "1.0">
37245 <!ELEMENT library (segment*, section*)>
37246 <!ATTLIST library name CDATA #REQUIRED>
37247 <!ELEMENT segment EMPTY>
37248 <!ATTLIST segment address CDATA #REQUIRED>
37249 <!ELEMENT section EMPTY>
37250 <!ATTLIST section address CDATA #REQUIRED>
37253 In addition, segments and section descriptors cannot be mixed within a
37254 single library element, and you must supply at least one segment or
37255 section for each library.
37257 @node Memory Map Format
37258 @section Memory Map Format
37259 @cindex memory map format
37261 To be able to write into flash memory, @value{GDBN} needs to obtain a
37262 memory map from the target. This section describes the format of the
37265 The memory map is obtained using the @samp{qXfer:memory-map:read}
37266 (@pxref{qXfer memory map read}) packet and is an XML document that
37267 lists memory regions.
37269 @value{GDBN} must be linked with the Expat library to support XML
37270 memory maps. @xref{Expat}.
37272 The top-level structure of the document is shown below:
37275 <?xml version="1.0"?>
37276 <!DOCTYPE memory-map
37277 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37278 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37284 Each region can be either:
37289 A region of RAM starting at @var{addr} and extending for @var{length}
37293 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37298 A region of read-only memory:
37301 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37306 A region of flash memory, with erasure blocks @var{blocksize}
37310 <memory type="flash" start="@var{addr}" length="@var{length}">
37311 <property name="blocksize">@var{blocksize}</property>
37317 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37318 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37319 packets to write to addresses in such ranges.
37321 The formal DTD for memory map format is given below:
37324 <!-- ................................................... -->
37325 <!-- Memory Map XML DTD ................................ -->
37326 <!-- File: memory-map.dtd .............................. -->
37327 <!-- .................................... .............. -->
37328 <!-- memory-map.dtd -->
37329 <!-- memory-map: Root element with versioning -->
37330 <!ELEMENT memory-map (memory | property)>
37331 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37332 <!ELEMENT memory (property)>
37333 <!-- memory: Specifies a memory region,
37334 and its type, or device. -->
37335 <!ATTLIST memory type CDATA #REQUIRED
37336 start CDATA #REQUIRED
37337 length CDATA #REQUIRED
37338 device CDATA #IMPLIED>
37339 <!-- property: Generic attribute tag -->
37340 <!ELEMENT property (#PCDATA | property)*>
37341 <!ATTLIST property name CDATA #REQUIRED>
37344 @node Thread List Format
37345 @section Thread List Format
37346 @cindex thread list format
37348 To efficiently update the list of threads and their attributes,
37349 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37350 (@pxref{qXfer threads read}) and obtains the XML document with
37351 the following structure:
37354 <?xml version="1.0"?>
37356 <thread id="id" core="0">
37357 ... description ...
37362 Each @samp{thread} element must have the @samp{id} attribute that
37363 identifies the thread (@pxref{thread-id syntax}). The
37364 @samp{core} attribute, if present, specifies which processor core
37365 the thread was last executing on. The content of the of @samp{thread}
37366 element is interpreted as human-readable auxilliary information.
37368 @node Traceframe Info Format
37369 @section Traceframe Info Format
37370 @cindex traceframe info format
37372 To be able to know which objects in the inferior can be examined when
37373 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37374 memory ranges, registers and trace state variables that have been
37375 collected in a traceframe.
37377 This list is obtained using the @samp{qXfer:traceframe-info:read}
37378 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37380 @value{GDBN} must be linked with the Expat library to support XML
37381 traceframe info discovery. @xref{Expat}.
37383 The top-level structure of the document is shown below:
37386 <?xml version="1.0"?>
37387 <!DOCTYPE traceframe-info
37388 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37389 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37395 Each traceframe block can be either:
37400 A region of collected memory starting at @var{addr} and extending for
37401 @var{length} bytes from there:
37404 <memory start="@var{addr}" length="@var{length}"/>
37409 The formal DTD for the traceframe info format is given below:
37412 <!ELEMENT traceframe-info (memory)* >
37413 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37415 <!ELEMENT memory EMPTY>
37416 <!ATTLIST memory start CDATA #REQUIRED
37417 length CDATA #REQUIRED>
37420 @include agentexpr.texi
37422 @node Target Descriptions
37423 @appendix Target Descriptions
37424 @cindex target descriptions
37426 One of the challenges of using @value{GDBN} to debug embedded systems
37427 is that there are so many minor variants of each processor
37428 architecture in use. It is common practice for vendors to start with
37429 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37430 and then make changes to adapt it to a particular market niche. Some
37431 architectures have hundreds of variants, available from dozens of
37432 vendors. This leads to a number of problems:
37436 With so many different customized processors, it is difficult for
37437 the @value{GDBN} maintainers to keep up with the changes.
37439 Since individual variants may have short lifetimes or limited
37440 audiences, it may not be worthwhile to carry information about every
37441 variant in the @value{GDBN} source tree.
37443 When @value{GDBN} does support the architecture of the embedded system
37444 at hand, the task of finding the correct architecture name to give the
37445 @command{set architecture} command can be error-prone.
37448 To address these problems, the @value{GDBN} remote protocol allows a
37449 target system to not only identify itself to @value{GDBN}, but to
37450 actually describe its own features. This lets @value{GDBN} support
37451 processor variants it has never seen before --- to the extent that the
37452 descriptions are accurate, and that @value{GDBN} understands them.
37454 @value{GDBN} must be linked with the Expat library to support XML
37455 target descriptions. @xref{Expat}.
37458 * Retrieving Descriptions:: How descriptions are fetched from a target.
37459 * Target Description Format:: The contents of a target description.
37460 * Predefined Target Types:: Standard types available for target
37462 * Standard Target Features:: Features @value{GDBN} knows about.
37465 @node Retrieving Descriptions
37466 @section Retrieving Descriptions
37468 Target descriptions can be read from the target automatically, or
37469 specified by the user manually. The default behavior is to read the
37470 description from the target. @value{GDBN} retrieves it via the remote
37471 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37472 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37473 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37474 XML document, of the form described in @ref{Target Description
37477 Alternatively, you can specify a file to read for the target description.
37478 If a file is set, the target will not be queried. The commands to
37479 specify a file are:
37482 @cindex set tdesc filename
37483 @item set tdesc filename @var{path}
37484 Read the target description from @var{path}.
37486 @cindex unset tdesc filename
37487 @item unset tdesc filename
37488 Do not read the XML target description from a file. @value{GDBN}
37489 will use the description supplied by the current target.
37491 @cindex show tdesc filename
37492 @item show tdesc filename
37493 Show the filename to read for a target description, if any.
37497 @node Target Description Format
37498 @section Target Description Format
37499 @cindex target descriptions, XML format
37501 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37502 document which complies with the Document Type Definition provided in
37503 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37504 means you can use generally available tools like @command{xmllint} to
37505 check that your feature descriptions are well-formed and valid.
37506 However, to help people unfamiliar with XML write descriptions for
37507 their targets, we also describe the grammar here.
37509 Target descriptions can identify the architecture of the remote target
37510 and (for some architectures) provide information about custom register
37511 sets. They can also identify the OS ABI of the remote target.
37512 @value{GDBN} can use this information to autoconfigure for your
37513 target, or to warn you if you connect to an unsupported target.
37515 Here is a simple target description:
37518 <target version="1.0">
37519 <architecture>i386:x86-64</architecture>
37524 This minimal description only says that the target uses
37525 the x86-64 architecture.
37527 A target description has the following overall form, with [ ] marking
37528 optional elements and @dots{} marking repeatable elements. The elements
37529 are explained further below.
37532 <?xml version="1.0"?>
37533 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37534 <target version="1.0">
37535 @r{[}@var{architecture}@r{]}
37536 @r{[}@var{osabi}@r{]}
37537 @r{[}@var{compatible}@r{]}
37538 @r{[}@var{feature}@dots{}@r{]}
37543 The description is generally insensitive to whitespace and line
37544 breaks, under the usual common-sense rules. The XML version
37545 declaration and document type declaration can generally be omitted
37546 (@value{GDBN} does not require them), but specifying them may be
37547 useful for XML validation tools. The @samp{version} attribute for
37548 @samp{<target>} may also be omitted, but we recommend
37549 including it; if future versions of @value{GDBN} use an incompatible
37550 revision of @file{gdb-target.dtd}, they will detect and report
37551 the version mismatch.
37553 @subsection Inclusion
37554 @cindex target descriptions, inclusion
37557 @cindex <xi:include>
37560 It can sometimes be valuable to split a target description up into
37561 several different annexes, either for organizational purposes, or to
37562 share files between different possible target descriptions. You can
37563 divide a description into multiple files by replacing any element of
37564 the target description with an inclusion directive of the form:
37567 <xi:include href="@var{document}"/>
37571 When @value{GDBN} encounters an element of this form, it will retrieve
37572 the named XML @var{document}, and replace the inclusion directive with
37573 the contents of that document. If the current description was read
37574 using @samp{qXfer}, then so will be the included document;
37575 @var{document} will be interpreted as the name of an annex. If the
37576 current description was read from a file, @value{GDBN} will look for
37577 @var{document} as a file in the same directory where it found the
37578 original description.
37580 @subsection Architecture
37581 @cindex <architecture>
37583 An @samp{<architecture>} element has this form:
37586 <architecture>@var{arch}</architecture>
37589 @var{arch} is one of the architectures from the set accepted by
37590 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37593 @cindex @code{<osabi>}
37595 This optional field was introduced in @value{GDBN} version 7.0.
37596 Previous versions of @value{GDBN} ignore it.
37598 An @samp{<osabi>} element has this form:
37601 <osabi>@var{abi-name}</osabi>
37604 @var{abi-name} is an OS ABI name from the same selection accepted by
37605 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
37607 @subsection Compatible Architecture
37608 @cindex @code{<compatible>}
37610 This optional field was introduced in @value{GDBN} version 7.0.
37611 Previous versions of @value{GDBN} ignore it.
37613 A @samp{<compatible>} element has this form:
37616 <compatible>@var{arch}</compatible>
37619 @var{arch} is one of the architectures from the set accepted by
37620 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37622 A @samp{<compatible>} element is used to specify that the target
37623 is able to run binaries in some other than the main target architecture
37624 given by the @samp{<architecture>} element. For example, on the
37625 Cell Broadband Engine, the main architecture is @code{powerpc:common}
37626 or @code{powerpc:common64}, but the system is able to run binaries
37627 in the @code{spu} architecture as well. The way to describe this
37628 capability with @samp{<compatible>} is as follows:
37631 <architecture>powerpc:common</architecture>
37632 <compatible>spu</compatible>
37635 @subsection Features
37638 Each @samp{<feature>} describes some logical portion of the target
37639 system. Features are currently used to describe available CPU
37640 registers and the types of their contents. A @samp{<feature>} element
37644 <feature name="@var{name}">
37645 @r{[}@var{type}@dots{}@r{]}
37651 Each feature's name should be unique within the description. The name
37652 of a feature does not matter unless @value{GDBN} has some special
37653 knowledge of the contents of that feature; if it does, the feature
37654 should have its standard name. @xref{Standard Target Features}.
37658 Any register's value is a collection of bits which @value{GDBN} must
37659 interpret. The default interpretation is a two's complement integer,
37660 but other types can be requested by name in the register description.
37661 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
37662 Target Types}), and the description can define additional composite types.
37664 Each type element must have an @samp{id} attribute, which gives
37665 a unique (within the containing @samp{<feature>}) name to the type.
37666 Types must be defined before they are used.
37669 Some targets offer vector registers, which can be treated as arrays
37670 of scalar elements. These types are written as @samp{<vector>} elements,
37671 specifying the array element type, @var{type}, and the number of elements,
37675 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
37679 If a register's value is usefully viewed in multiple ways, define it
37680 with a union type containing the useful representations. The
37681 @samp{<union>} element contains one or more @samp{<field>} elements,
37682 each of which has a @var{name} and a @var{type}:
37685 <union id="@var{id}">
37686 <field name="@var{name}" type="@var{type}"/>
37692 If a register's value is composed from several separate values, define
37693 it with a structure type. There are two forms of the @samp{<struct>}
37694 element; a @samp{<struct>} element must either contain only bitfields
37695 or contain no bitfields. If the structure contains only bitfields,
37696 its total size in bytes must be specified, each bitfield must have an
37697 explicit start and end, and bitfields are automatically assigned an
37698 integer type. The field's @var{start} should be less than or
37699 equal to its @var{end}, and zero represents the least significant bit.
37702 <struct id="@var{id}" size="@var{size}">
37703 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37708 If the structure contains no bitfields, then each field has an
37709 explicit type, and no implicit padding is added.
37712 <struct id="@var{id}">
37713 <field name="@var{name}" type="@var{type}"/>
37719 If a register's value is a series of single-bit flags, define it with
37720 a flags type. The @samp{<flags>} element has an explicit @var{size}
37721 and contains one or more @samp{<field>} elements. Each field has a
37722 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
37726 <flags id="@var{id}" size="@var{size}">
37727 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37732 @subsection Registers
37735 Each register is represented as an element with this form:
37738 <reg name="@var{name}"
37739 bitsize="@var{size}"
37740 @r{[}regnum="@var{num}"@r{]}
37741 @r{[}save-restore="@var{save-restore}"@r{]}
37742 @r{[}type="@var{type}"@r{]}
37743 @r{[}group="@var{group}"@r{]}/>
37747 The components are as follows:
37752 The register's name; it must be unique within the target description.
37755 The register's size, in bits.
37758 The register's number. If omitted, a register's number is one greater
37759 than that of the previous register (either in the current feature or in
37760 a preceding feature); the first register in the target description
37761 defaults to zero. This register number is used to read or write
37762 the register; e.g.@: it is used in the remote @code{p} and @code{P}
37763 packets, and registers appear in the @code{g} and @code{G} packets
37764 in order of increasing register number.
37767 Whether the register should be preserved across inferior function
37768 calls; this must be either @code{yes} or @code{no}. The default is
37769 @code{yes}, which is appropriate for most registers except for
37770 some system control registers; this is not related to the target's
37774 The type of the register. @var{type} may be a predefined type, a type
37775 defined in the current feature, or one of the special types @code{int}
37776 and @code{float}. @code{int} is an integer type of the correct size
37777 for @var{bitsize}, and @code{float} is a floating point type (in the
37778 architecture's normal floating point format) of the correct size for
37779 @var{bitsize}. The default is @code{int}.
37782 The register group to which this register belongs. @var{group} must
37783 be either @code{general}, @code{float}, or @code{vector}. If no
37784 @var{group} is specified, @value{GDBN} will not display the register
37785 in @code{info registers}.
37789 @node Predefined Target Types
37790 @section Predefined Target Types
37791 @cindex target descriptions, predefined types
37793 Type definitions in the self-description can build up composite types
37794 from basic building blocks, but can not define fundamental types. Instead,
37795 standard identifiers are provided by @value{GDBN} for the fundamental
37796 types. The currently supported types are:
37805 Signed integer types holding the specified number of bits.
37812 Unsigned integer types holding the specified number of bits.
37816 Pointers to unspecified code and data. The program counter and
37817 any dedicated return address register may be marked as code
37818 pointers; printing a code pointer converts it into a symbolic
37819 address. The stack pointer and any dedicated address registers
37820 may be marked as data pointers.
37823 Single precision IEEE floating point.
37826 Double precision IEEE floating point.
37829 The 12-byte extended precision format used by ARM FPA registers.
37832 The 10-byte extended precision format used by x87 registers.
37835 32bit @sc{eflags} register used by x86.
37838 32bit @sc{mxcsr} register used by x86.
37842 @node Standard Target Features
37843 @section Standard Target Features
37844 @cindex target descriptions, standard features
37846 A target description must contain either no registers or all the
37847 target's registers. If the description contains no registers, then
37848 @value{GDBN} will assume a default register layout, selected based on
37849 the architecture. If the description contains any registers, the
37850 default layout will not be used; the standard registers must be
37851 described in the target description, in such a way that @value{GDBN}
37852 can recognize them.
37854 This is accomplished by giving specific names to feature elements
37855 which contain standard registers. @value{GDBN} will look for features
37856 with those names and verify that they contain the expected registers;
37857 if any known feature is missing required registers, or if any required
37858 feature is missing, @value{GDBN} will reject the target
37859 description. You can add additional registers to any of the
37860 standard features --- @value{GDBN} will display them just as if
37861 they were added to an unrecognized feature.
37863 This section lists the known features and their expected contents.
37864 Sample XML documents for these features are included in the
37865 @value{GDBN} source tree, in the directory @file{gdb/features}.
37867 Names recognized by @value{GDBN} should include the name of the
37868 company or organization which selected the name, and the overall
37869 architecture to which the feature applies; so e.g.@: the feature
37870 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
37872 The names of registers are not case sensitive for the purpose
37873 of recognizing standard features, but @value{GDBN} will only display
37874 registers using the capitalization used in the description.
37881 * PowerPC Features::
37887 @subsection ARM Features
37888 @cindex target descriptions, ARM features
37890 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
37892 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
37893 @samp{lr}, @samp{pc}, and @samp{cpsr}.
37895 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
37896 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
37897 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
37900 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
37901 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
37903 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
37904 it should contain at least registers @samp{wR0} through @samp{wR15} and
37905 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
37906 @samp{wCSSF}, and @samp{wCASF} registers are optional.
37908 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
37909 should contain at least registers @samp{d0} through @samp{d15}. If
37910 they are present, @samp{d16} through @samp{d31} should also be included.
37911 @value{GDBN} will synthesize the single-precision registers from
37912 halves of the double-precision registers.
37914 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
37915 need to contain registers; it instructs @value{GDBN} to display the
37916 VFP double-precision registers as vectors and to synthesize the
37917 quad-precision registers from pairs of double-precision registers.
37918 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
37919 be present and include 32 double-precision registers.
37921 @node i386 Features
37922 @subsection i386 Features
37923 @cindex target descriptions, i386 features
37925 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
37926 targets. It should describe the following registers:
37930 @samp{eax} through @samp{edi} plus @samp{eip} for i386
37932 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
37934 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
37935 @samp{fs}, @samp{gs}
37937 @samp{st0} through @samp{st7}
37939 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
37940 @samp{foseg}, @samp{fooff} and @samp{fop}
37943 The register sets may be different, depending on the target.
37945 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
37946 describe registers:
37950 @samp{xmm0} through @samp{xmm7} for i386
37952 @samp{xmm0} through @samp{xmm15} for amd64
37957 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
37958 @samp{org.gnu.gdb.i386.sse} feature. It should
37959 describe the upper 128 bits of @sc{ymm} registers:
37963 @samp{ymm0h} through @samp{ymm7h} for i386
37965 @samp{ymm0h} through @samp{ymm15h} for amd64
37968 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
37969 describe a single register, @samp{orig_eax}.
37971 @node MIPS Features
37972 @subsection MIPS Features
37973 @cindex target descriptions, MIPS features
37975 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
37976 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
37977 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
37980 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
37981 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
37982 registers. They may be 32-bit or 64-bit depending on the target.
37984 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
37985 it may be optional in a future version of @value{GDBN}. It should
37986 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
37987 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
37989 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
37990 contain a single register, @samp{restart}, which is used by the
37991 Linux kernel to control restartable syscalls.
37993 @node M68K Features
37994 @subsection M68K Features
37995 @cindex target descriptions, M68K features
37998 @item @samp{org.gnu.gdb.m68k.core}
37999 @itemx @samp{org.gnu.gdb.coldfire.core}
38000 @itemx @samp{org.gnu.gdb.fido.core}
38001 One of those features must be always present.
38002 The feature that is present determines which flavor of m68k is
38003 used. The feature that is present should contain registers
38004 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38005 @samp{sp}, @samp{ps} and @samp{pc}.
38007 @item @samp{org.gnu.gdb.coldfire.fp}
38008 This feature is optional. If present, it should contain registers
38009 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38013 @node PowerPC Features
38014 @subsection PowerPC Features
38015 @cindex target descriptions, PowerPC features
38017 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38018 targets. It should contain registers @samp{r0} through @samp{r31},
38019 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38020 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38022 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38023 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38025 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38026 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38029 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38030 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38031 will combine these registers with the floating point registers
38032 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38033 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38034 through @samp{vs63}, the set of vector registers for POWER7.
38036 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38037 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38038 @samp{spefscr}. SPE targets should provide 32-bit registers in
38039 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38040 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38041 these to present registers @samp{ev0} through @samp{ev31} to the
38044 @node TIC6x Features
38045 @subsection TMS320C6x Features
38046 @cindex target descriptions, TIC6x features
38047 @cindex target descriptions, TMS320C6x features
38048 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38049 targets. It should contain registers @samp{A0} through @samp{A15},
38050 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38052 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38053 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38054 through @samp{B31}.
38056 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38057 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38059 @node Operating System Information
38060 @appendix Operating System Information
38061 @cindex operating system information
38067 Users of @value{GDBN} often wish to obtain information about the state of
38068 the operating system running on the target---for example the list of
38069 processes, or the list of open files. This section describes the
38070 mechanism that makes it possible. This mechanism is similar to the
38071 target features mechanism (@pxref{Target Descriptions}), but focuses
38072 on a different aspect of target.
38074 Operating system information is retrived from the target via the
38075 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38076 read}). The object name in the request should be @samp{osdata}, and
38077 the @var{annex} identifies the data to be fetched.
38080 @appendixsection Process list
38081 @cindex operating system information, process list
38083 When requesting the process list, the @var{annex} field in the
38084 @samp{qXfer} request should be @samp{processes}. The returned data is
38085 an XML document. The formal syntax of this document is defined in
38086 @file{gdb/features/osdata.dtd}.
38088 An example document is:
38091 <?xml version="1.0"?>
38092 <!DOCTYPE target SYSTEM "osdata.dtd">
38093 <osdata type="processes">
38095 <column name="pid">1</column>
38096 <column name="user">root</column>
38097 <column name="command">/sbin/init</column>
38098 <column name="cores">1,2,3</column>
38103 Each item should include a column whose name is @samp{pid}. The value
38104 of that column should identify the process on the target. The
38105 @samp{user} and @samp{command} columns are optional, and will be
38106 displayed by @value{GDBN}. The @samp{cores} column, if present,
38107 should contain a comma-separated list of cores that this process
38108 is running on. Target may provide additional columns,
38109 which @value{GDBN} currently ignores.
38111 @node Trace File Format
38112 @appendix Trace File Format
38113 @cindex trace file format
38115 The trace file comes in three parts: a header, a textual description
38116 section, and a trace frame section with binary data.
38118 The header has the form @code{\x7fTRACE0\n}. The first byte is
38119 @code{0x7f} so as to indicate that the file contains binary data,
38120 while the @code{0} is a version number that may have different values
38123 The description section consists of multiple lines of @sc{ascii} text
38124 separated by newline characters (@code{0xa}). The lines may include a
38125 variety of optional descriptive or context-setting information, such
38126 as tracepoint definitions or register set size. @value{GDBN} will
38127 ignore any line that it does not recognize. An empty line marks the end
38130 @c FIXME add some specific types of data
38132 The trace frame section consists of a number of consecutive frames.
38133 Each frame begins with a two-byte tracepoint number, followed by a
38134 four-byte size giving the amount of data in the frame. The data in
38135 the frame consists of a number of blocks, each introduced by a
38136 character indicating its type (at least register, memory, and trace
38137 state variable). The data in this section is raw binary, not a
38138 hexadecimal or other encoding; its endianness matches the target's
38141 @c FIXME bi-arch may require endianness/arch info in description section
38144 @item R @var{bytes}
38145 Register block. The number and ordering of bytes matches that of a
38146 @code{g} packet in the remote protocol. Note that these are the
38147 actual bytes, in target order and @value{GDBN} register order, not a
38148 hexadecimal encoding.
38150 @item M @var{address} @var{length} @var{bytes}...
38151 Memory block. This is a contiguous block of memory, at the 8-byte
38152 address @var{address}, with a 2-byte length @var{length}, followed by
38153 @var{length} bytes.
38155 @item V @var{number} @var{value}
38156 Trace state variable block. This records the 8-byte signed value
38157 @var{value} of trace state variable numbered @var{number}.
38161 Future enhancements of the trace file format may include additional types
38164 @node Index Section Format
38165 @appendix @code{.gdb_index} section format
38166 @cindex .gdb_index section format
38167 @cindex index section format
38169 This section documents the index section that is created by @code{save
38170 gdb-index} (@pxref{Index Files}). The index section is
38171 DWARF-specific; some knowledge of DWARF is assumed in this
38174 The mapped index file format is designed to be directly
38175 @code{mmap}able on any architecture. In most cases, a datum is
38176 represented using a little-endian 32-bit integer value, called an
38177 @code{offset_type}. Big endian machines must byte-swap the values
38178 before using them. Exceptions to this rule are noted. The data is
38179 laid out such that alignment is always respected.
38181 A mapped index consists of several areas, laid out in order.
38185 The file header. This is a sequence of values, of @code{offset_type}
38186 unless otherwise noted:
38190 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38191 Version 4 differs by its hashing function.
38194 The offset, from the start of the file, of the CU list.
38197 The offset, from the start of the file, of the types CU list. Note
38198 that this area can be empty, in which case this offset will be equal
38199 to the next offset.
38202 The offset, from the start of the file, of the address area.
38205 The offset, from the start of the file, of the symbol table.
38208 The offset, from the start of the file, of the constant pool.
38212 The CU list. This is a sequence of pairs of 64-bit little-endian
38213 values, sorted by the CU offset. The first element in each pair is
38214 the offset of a CU in the @code{.debug_info} section. The second
38215 element in each pair is the length of that CU. References to a CU
38216 elsewhere in the map are done using a CU index, which is just the
38217 0-based index into this table. Note that if there are type CUs, then
38218 conceptually CUs and type CUs form a single list for the purposes of
38222 The types CU list. This is a sequence of triplets of 64-bit
38223 little-endian values. In a triplet, the first value is the CU offset,
38224 the second value is the type offset in the CU, and the third value is
38225 the type signature. The types CU list is not sorted.
38228 The address area. The address area consists of a sequence of address
38229 entries. Each address entry has three elements:
38233 The low address. This is a 64-bit little-endian value.
38236 The high address. This is a 64-bit little-endian value. Like
38237 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38240 The CU index. This is an @code{offset_type} value.
38244 The symbol table. This is an open-addressed hash table. The size of
38245 the hash table is always a power of 2.
38247 Each slot in the hash table consists of a pair of @code{offset_type}
38248 values. The first value is the offset of the symbol's name in the
38249 constant pool. The second value is the offset of the CU vector in the
38252 If both values are 0, then this slot in the hash table is empty. This
38253 is ok because while 0 is a valid constant pool index, it cannot be a
38254 valid index for both a string and a CU vector.
38256 The hash value for a table entry is computed by applying an
38257 iterative hash function to the symbol's name. Starting with an
38258 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38259 the string is incorporated into the hash using the formula depending on the
38264 The formula is @code{r = r * 67 + c - 113}.
38267 The formula is @code{r = r * 67 + tolower (c) - 113}.
38270 The terminating @samp{\0} is not incorporated into the hash.
38272 The step size used in the hash table is computed via
38273 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38274 value, and @samp{size} is the size of the hash table. The step size
38275 is used to find the next candidate slot when handling a hash
38278 The names of C@t{++} symbols in the hash table are canonicalized. We
38279 don't currently have a simple description of the canonicalization
38280 algorithm; if you intend to create new index sections, you must read
38284 The constant pool. This is simply a bunch of bytes. It is organized
38285 so that alignment is correct: CU vectors are stored first, followed by
38288 A CU vector in the constant pool is a sequence of @code{offset_type}
38289 values. The first value is the number of CU indices in the vector.
38290 Each subsequent value is the index of a CU in the CU list. This
38291 element in the hash table is used to indicate which CUs define the
38294 A string in the constant pool is zero-terminated.
38299 @node GNU Free Documentation License
38300 @appendix GNU Free Documentation License
38309 % I think something like @colophon should be in texinfo. In the
38311 \long\def\colophon{\hbox to0pt{}\vfill
38312 \centerline{The body of this manual is set in}
38313 \centerline{\fontname\tenrm,}
38314 \centerline{with headings in {\bf\fontname\tenbf}}
38315 \centerline{and examples in {\tt\fontname\tentt}.}
38316 \centerline{{\it\fontname\tenit\/},}
38317 \centerline{{\bf\fontname\tenbf}, and}
38318 \centerline{{\sl\fontname\tensl\/}}
38319 \centerline{are used for emphasis.}\vfill}
38321 % Blame: doc@cygnus.com, 1991.