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}). Do not use this
1185 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1186 Using @value{GDBN} under @sc{gnu} Emacs}).
1189 @c @cindex @code{--xdb}
1190 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1191 @c For information, see the file @file{xdb_trans.html}, which is usually
1192 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1195 @item -interpreter @var{interp}
1196 @cindex @code{--interpreter}
1197 Use the interpreter @var{interp} for interface with the controlling
1198 program or device. This option is meant to be set by programs which
1199 communicate with @value{GDBN} using it as a back end.
1200 @xref{Interpreters, , Command Interpreters}.
1202 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1203 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1204 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1205 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1206 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1207 @sc{gdb/mi} interfaces are no longer supported.
1210 @cindex @code{--write}
1211 Open the executable and core files for both reading and writing. This
1212 is equivalent to the @samp{set write on} command inside @value{GDBN}
1216 @cindex @code{--statistics}
1217 This option causes @value{GDBN} to print statistics about time and
1218 memory usage after it completes each command and returns to the prompt.
1221 @cindex @code{--version}
1222 This option causes @value{GDBN} to print its version number and
1223 no-warranty blurb, and exit.
1228 @subsection What @value{GDBN} Does During Startup
1229 @cindex @value{GDBN} startup
1231 Here's the description of what @value{GDBN} does during session startup:
1235 Sets up the command interpreter as specified by the command line
1236 (@pxref{Mode Options, interpreter}).
1240 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1241 used when building @value{GDBN}; @pxref{System-wide configuration,
1242 ,System-wide configuration and settings}) and executes all the commands in
1246 Reads the init file (if any) in your home directory@footnote{On
1247 DOS/Windows systems, the home directory is the one pointed to by the
1248 @code{HOME} environment variable.} and executes all the commands in
1252 Processes command line options and operands.
1255 Reads and executes the commands from init file (if any) in the current
1256 working directory. This is only done if the current directory is
1257 different from your home directory. Thus, you can have more than one
1258 init file, one generic in your home directory, and another, specific
1259 to the program you are debugging, in the directory where you invoke
1263 If the command line specified a program to debug, or a process to
1264 attach to, or a core file, @value{GDBN} loads any auto-loaded
1265 scripts provided for the program or for its loaded shared libraries.
1266 @xref{Auto-loading}.
1268 If you wish to disable the auto-loading during startup,
1269 you must do something like the following:
1272 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1275 The following does not work because the auto-loading is turned off too late:
1278 $ gdb -ex "set auto-load-scripts off" myprogram
1282 Reads command files specified by the @samp{-x} option. @xref{Command
1283 Files}, for more details about @value{GDBN} command files.
1286 Reads the command history recorded in the @dfn{history file}.
1287 @xref{Command History}, for more details about the command history and the
1288 files where @value{GDBN} records it.
1291 Init files use the same syntax as @dfn{command files} (@pxref{Command
1292 Files}) and are processed by @value{GDBN} in the same way. The init
1293 file in your home directory can set options (such as @samp{set
1294 complaints}) that affect subsequent processing of command line options
1295 and operands. Init files are not executed if you use the @samp{-nx}
1296 option (@pxref{Mode Options, ,Choosing Modes}).
1298 To display the list of init files loaded by gdb at startup, you
1299 can use @kbd{gdb --help}.
1301 @cindex init file name
1302 @cindex @file{.gdbinit}
1303 @cindex @file{gdb.ini}
1304 The @value{GDBN} init files are normally called @file{.gdbinit}.
1305 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1306 the limitations of file names imposed by DOS filesystems. The Windows
1307 ports of @value{GDBN} use the standard name, but if they find a
1308 @file{gdb.ini} file, they warn you about that and suggest to rename
1309 the file to the standard name.
1313 @section Quitting @value{GDBN}
1314 @cindex exiting @value{GDBN}
1315 @cindex leaving @value{GDBN}
1318 @kindex quit @r{[}@var{expression}@r{]}
1319 @kindex q @r{(@code{quit})}
1320 @item quit @r{[}@var{expression}@r{]}
1322 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1323 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1324 do not supply @var{expression}, @value{GDBN} will terminate normally;
1325 otherwise it will terminate using the result of @var{expression} as the
1330 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1331 terminates the action of any @value{GDBN} command that is in progress and
1332 returns to @value{GDBN} command level. It is safe to type the interrupt
1333 character at any time because @value{GDBN} does not allow it to take effect
1334 until a time when it is safe.
1336 If you have been using @value{GDBN} to control an attached process or
1337 device, you can release it with the @code{detach} command
1338 (@pxref{Attach, ,Debugging an Already-running Process}).
1340 @node Shell Commands
1341 @section Shell Commands
1343 If you need to execute occasional shell commands during your
1344 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1345 just use the @code{shell} command.
1350 @cindex shell escape
1351 @item shell @var{command-string}
1352 @itemx !@var{command-string}
1353 Invoke a standard shell to execute @var{command-string}.
1354 Note that no space is needed between @code{!} and @var{command-string}.
1355 If it exists, the environment variable @code{SHELL} determines which
1356 shell to run. Otherwise @value{GDBN} uses the default shell
1357 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1360 The utility @code{make} is often needed in development environments.
1361 You do not have to use the @code{shell} command for this purpose in
1366 @cindex calling make
1367 @item make @var{make-args}
1368 Execute the @code{make} program with the specified
1369 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1372 @node Logging Output
1373 @section Logging Output
1374 @cindex logging @value{GDBN} output
1375 @cindex save @value{GDBN} output to a file
1377 You may want to save the output of @value{GDBN} commands to a file.
1378 There are several commands to control @value{GDBN}'s logging.
1382 @item set logging on
1384 @item set logging off
1386 @cindex logging file name
1387 @item set logging file @var{file}
1388 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1389 @item set logging overwrite [on|off]
1390 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1391 you want @code{set logging on} to overwrite the logfile instead.
1392 @item set logging redirect [on|off]
1393 By default, @value{GDBN} output will go to both the terminal and the logfile.
1394 Set @code{redirect} if you want output to go only to the log file.
1395 @kindex show logging
1397 Show the current values of the logging settings.
1401 @chapter @value{GDBN} Commands
1403 You can abbreviate a @value{GDBN} command to the first few letters of the command
1404 name, if that abbreviation is unambiguous; and you can repeat certain
1405 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1406 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1407 show you the alternatives available, if there is more than one possibility).
1410 * Command Syntax:: How to give commands to @value{GDBN}
1411 * Completion:: Command completion
1412 * Help:: How to ask @value{GDBN} for help
1415 @node Command Syntax
1416 @section Command Syntax
1418 A @value{GDBN} command is a single line of input. There is no limit on
1419 how long it can be. It starts with a command name, which is followed by
1420 arguments whose meaning depends on the command name. For example, the
1421 command @code{step} accepts an argument which is the number of times to
1422 step, as in @samp{step 5}. You can also use the @code{step} command
1423 with no arguments. Some commands do not allow any arguments.
1425 @cindex abbreviation
1426 @value{GDBN} command names may always be truncated if that abbreviation is
1427 unambiguous. Other possible command abbreviations are listed in the
1428 documentation for individual commands. In some cases, even ambiguous
1429 abbreviations are allowed; for example, @code{s} is specially defined as
1430 equivalent to @code{step} even though there are other commands whose
1431 names start with @code{s}. You can test abbreviations by using them as
1432 arguments to the @code{help} command.
1434 @cindex repeating commands
1435 @kindex RET @r{(repeat last command)}
1436 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1437 repeat the previous command. Certain commands (for example, @code{run})
1438 will not repeat this way; these are commands whose unintentional
1439 repetition might cause trouble and which you are unlikely to want to
1440 repeat. User-defined commands can disable this feature; see
1441 @ref{Define, dont-repeat}.
1443 The @code{list} and @code{x} commands, when you repeat them with
1444 @key{RET}, construct new arguments rather than repeating
1445 exactly as typed. This permits easy scanning of source or memory.
1447 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1448 output, in a way similar to the common utility @code{more}
1449 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1450 @key{RET} too many in this situation, @value{GDBN} disables command
1451 repetition after any command that generates this sort of display.
1453 @kindex # @r{(a comment)}
1455 Any text from a @kbd{#} to the end of the line is a comment; it does
1456 nothing. This is useful mainly in command files (@pxref{Command
1457 Files,,Command Files}).
1459 @cindex repeating command sequences
1460 @kindex Ctrl-o @r{(operate-and-get-next)}
1461 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1462 commands. This command accepts the current line, like @key{RET}, and
1463 then fetches the next line relative to the current line from the history
1467 @section Command Completion
1470 @cindex word completion
1471 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1472 only one possibility; it can also show you what the valid possibilities
1473 are for the next word in a command, at any time. This works for @value{GDBN}
1474 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1476 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1477 of a word. If there is only one possibility, @value{GDBN} fills in the
1478 word, and waits for you to finish the command (or press @key{RET} to
1479 enter it). For example, if you type
1481 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1482 @c complete accuracy in these examples; space introduced for clarity.
1483 @c If texinfo enhancements make it unnecessary, it would be nice to
1484 @c replace " @key" by "@key" in the following...
1486 (@value{GDBP}) info bre @key{TAB}
1490 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1491 the only @code{info} subcommand beginning with @samp{bre}:
1494 (@value{GDBP}) info breakpoints
1498 You can either press @key{RET} at this point, to run the @code{info
1499 breakpoints} command, or backspace and enter something else, if
1500 @samp{breakpoints} does not look like the command you expected. (If you
1501 were sure you wanted @code{info breakpoints} in the first place, you
1502 might as well just type @key{RET} immediately after @samp{info bre},
1503 to exploit command abbreviations rather than command completion).
1505 If there is more than one possibility for the next word when you press
1506 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1507 characters and try again, or just press @key{TAB} a second time;
1508 @value{GDBN} displays all the possible completions for that word. For
1509 example, you might want to set a breakpoint on a subroutine whose name
1510 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1511 just sounds the bell. Typing @key{TAB} again displays all the
1512 function names in your program that begin with those characters, for
1516 (@value{GDBP}) b make_ @key{TAB}
1517 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1518 make_a_section_from_file make_environ
1519 make_abs_section make_function_type
1520 make_blockvector make_pointer_type
1521 make_cleanup make_reference_type
1522 make_command make_symbol_completion_list
1523 (@value{GDBP}) b make_
1527 After displaying the available possibilities, @value{GDBN} copies your
1528 partial input (@samp{b make_} in the example) so you can finish the
1531 If you just want to see the list of alternatives in the first place, you
1532 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1533 means @kbd{@key{META} ?}. You can type this either by holding down a
1534 key designated as the @key{META} shift on your keyboard (if there is
1535 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1537 @cindex quotes in commands
1538 @cindex completion of quoted strings
1539 Sometimes the string you need, while logically a ``word'', may contain
1540 parentheses or other characters that @value{GDBN} normally excludes from
1541 its notion of a word. To permit word completion to work in this
1542 situation, you may enclose words in @code{'} (single quote marks) in
1543 @value{GDBN} commands.
1545 The most likely situation where you might need this is in typing the
1546 name of a C@t{++} function. This is because C@t{++} allows function
1547 overloading (multiple definitions of the same function, distinguished
1548 by argument type). For example, when you want to set a breakpoint you
1549 may need to distinguish whether you mean the version of @code{name}
1550 that takes an @code{int} parameter, @code{name(int)}, or the version
1551 that takes a @code{float} parameter, @code{name(float)}. To use the
1552 word-completion facilities in this situation, type a single quote
1553 @code{'} at the beginning of the function name. This alerts
1554 @value{GDBN} that it may need to consider more information than usual
1555 when you press @key{TAB} or @kbd{M-?} to request word completion:
1558 (@value{GDBP}) b 'bubble( @kbd{M-?}
1559 bubble(double,double) bubble(int,int)
1560 (@value{GDBP}) b 'bubble(
1563 In some cases, @value{GDBN} can tell that completing a name requires using
1564 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1565 completing as much as it can) if you do not type the quote in the first
1569 (@value{GDBP}) b bub @key{TAB}
1570 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1571 (@value{GDBP}) b 'bubble(
1575 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1576 you have not yet started typing the argument list when you ask for
1577 completion on an overloaded symbol.
1579 For more information about overloaded functions, see @ref{C Plus Plus
1580 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1581 overload-resolution off} to disable overload resolution;
1582 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1584 @cindex completion of structure field names
1585 @cindex structure field name completion
1586 @cindex completion of union field names
1587 @cindex union field name completion
1588 When completing in an expression which looks up a field in a
1589 structure, @value{GDBN} also tries@footnote{The completer can be
1590 confused by certain kinds of invalid expressions. Also, it only
1591 examines the static type of the expression, not the dynamic type.} to
1592 limit completions to the field names available in the type of the
1596 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1597 magic to_fputs to_rewind
1598 to_data to_isatty to_write
1599 to_delete to_put to_write_async_safe
1604 This is because the @code{gdb_stdout} is a variable of the type
1605 @code{struct ui_file} that is defined in @value{GDBN} sources as
1612 ui_file_flush_ftype *to_flush;
1613 ui_file_write_ftype *to_write;
1614 ui_file_write_async_safe_ftype *to_write_async_safe;
1615 ui_file_fputs_ftype *to_fputs;
1616 ui_file_read_ftype *to_read;
1617 ui_file_delete_ftype *to_delete;
1618 ui_file_isatty_ftype *to_isatty;
1619 ui_file_rewind_ftype *to_rewind;
1620 ui_file_put_ftype *to_put;
1627 @section Getting Help
1628 @cindex online documentation
1631 You can always ask @value{GDBN} itself for information on its commands,
1632 using the command @code{help}.
1635 @kindex h @r{(@code{help})}
1638 You can use @code{help} (abbreviated @code{h}) with no arguments to
1639 display a short list of named classes of commands:
1643 List of classes of commands:
1645 aliases -- Aliases of other commands
1646 breakpoints -- Making program stop at certain points
1647 data -- Examining data
1648 files -- Specifying and examining files
1649 internals -- Maintenance commands
1650 obscure -- Obscure features
1651 running -- Running the program
1652 stack -- Examining the stack
1653 status -- Status inquiries
1654 support -- Support facilities
1655 tracepoints -- Tracing of program execution without
1656 stopping the program
1657 user-defined -- User-defined commands
1659 Type "help" followed by a class name for a list of
1660 commands in that class.
1661 Type "help" followed by command name for full
1663 Command name abbreviations are allowed if unambiguous.
1666 @c the above line break eliminates huge line overfull...
1668 @item help @var{class}
1669 Using one of the general help classes as an argument, you can get a
1670 list of the individual commands in that class. For example, here is the
1671 help display for the class @code{status}:
1674 (@value{GDBP}) help status
1679 @c Line break in "show" line falsifies real output, but needed
1680 @c to fit in smallbook page size.
1681 info -- Generic command for showing things
1682 about the program being debugged
1683 show -- Generic command for showing things
1686 Type "help" followed by command name for full
1688 Command name abbreviations are allowed if unambiguous.
1692 @item help @var{command}
1693 With a command name as @code{help} argument, @value{GDBN} displays a
1694 short paragraph on how to use that command.
1697 @item apropos @var{args}
1698 The @code{apropos} command searches through all of the @value{GDBN}
1699 commands, and their documentation, for the regular expression specified in
1700 @var{args}. It prints out all matches found. For example:
1711 set symbol-reloading -- Set dynamic symbol table reloading
1712 multiple times in one run
1713 show symbol-reloading -- Show dynamic symbol table reloading
1714 multiple times in one run
1719 @item complete @var{args}
1720 The @code{complete @var{args}} command lists all the possible completions
1721 for the beginning of a command. Use @var{args} to specify the beginning of the
1722 command you want completed. For example:
1728 @noindent results in:
1739 @noindent This is intended for use by @sc{gnu} Emacs.
1742 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1743 and @code{show} to inquire about the state of your program, or the state
1744 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1745 manual introduces each of them in the appropriate context. The listings
1746 under @code{info} and under @code{show} in the Index point to
1747 all the sub-commands. @xref{Index}.
1752 @kindex i @r{(@code{info})}
1754 This command (abbreviated @code{i}) is for describing the state of your
1755 program. For example, you can show the arguments passed to a function
1756 with @code{info args}, list the registers currently in use with @code{info
1757 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1758 You can get a complete list of the @code{info} sub-commands with
1759 @w{@code{help info}}.
1763 You can assign the result of an expression to an environment variable with
1764 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1765 @code{set prompt $}.
1769 In contrast to @code{info}, @code{show} is for describing the state of
1770 @value{GDBN} itself.
1771 You can change most of the things you can @code{show}, by using the
1772 related command @code{set}; for example, you can control what number
1773 system is used for displays with @code{set radix}, or simply inquire
1774 which is currently in use with @code{show radix}.
1777 To display all the settable parameters and their current
1778 values, you can use @code{show} with no arguments; you may also use
1779 @code{info set}. Both commands produce the same display.
1780 @c FIXME: "info set" violates the rule that "info" is for state of
1781 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1782 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1786 Here are three miscellaneous @code{show} subcommands, all of which are
1787 exceptional in lacking corresponding @code{set} commands:
1790 @kindex show version
1791 @cindex @value{GDBN} version number
1793 Show what version of @value{GDBN} is running. You should include this
1794 information in @value{GDBN} bug-reports. If multiple versions of
1795 @value{GDBN} are in use at your site, you may need to determine which
1796 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1797 commands are introduced, and old ones may wither away. Also, many
1798 system vendors ship variant versions of @value{GDBN}, and there are
1799 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1800 The version number is the same as the one announced when you start
1803 @kindex show copying
1804 @kindex info copying
1805 @cindex display @value{GDBN} copyright
1808 Display information about permission for copying @value{GDBN}.
1810 @kindex show warranty
1811 @kindex info warranty
1813 @itemx info warranty
1814 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1815 if your version of @value{GDBN} comes with one.
1820 @chapter Running Programs Under @value{GDBN}
1822 When you run a program under @value{GDBN}, you must first generate
1823 debugging information when you compile it.
1825 You may start @value{GDBN} with its arguments, if any, in an environment
1826 of your choice. If you are doing native debugging, you may redirect
1827 your program's input and output, debug an already running process, or
1828 kill a child process.
1831 * Compilation:: Compiling for debugging
1832 * Starting:: Starting your program
1833 * Arguments:: Your program's arguments
1834 * Environment:: Your program's environment
1836 * Working Directory:: Your program's working directory
1837 * Input/Output:: Your program's input and output
1838 * Attach:: Debugging an already-running process
1839 * Kill Process:: Killing the child process
1841 * Inferiors and Programs:: Debugging multiple inferiors and programs
1842 * Threads:: Debugging programs with multiple threads
1843 * Forks:: Debugging forks
1844 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1848 @section Compiling for Debugging
1850 In order to debug a program effectively, you need to generate
1851 debugging information when you compile it. This debugging information
1852 is stored in the object file; it describes the data type of each
1853 variable or function and the correspondence between source line numbers
1854 and addresses in the executable code.
1856 To request debugging information, specify the @samp{-g} option when you run
1859 Programs that are to be shipped to your customers are compiled with
1860 optimizations, using the @samp{-O} compiler option. However, some
1861 compilers are unable to handle the @samp{-g} and @samp{-O} options
1862 together. Using those compilers, you cannot generate optimized
1863 executables containing debugging information.
1865 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1866 without @samp{-O}, making it possible to debug optimized code. We
1867 recommend that you @emph{always} use @samp{-g} whenever you compile a
1868 program. You may think your program is correct, but there is no sense
1869 in pushing your luck. For more information, see @ref{Optimized Code}.
1871 Older versions of the @sc{gnu} C compiler permitted a variant option
1872 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1873 format; if your @sc{gnu} C compiler has this option, do not use it.
1875 @value{GDBN} knows about preprocessor macros and can show you their
1876 expansion (@pxref{Macros}). Most compilers do not include information
1877 about preprocessor macros in the debugging information if you specify
1878 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1879 the @sc{gnu} C compiler, provides macro information if you are using
1880 the DWARF debugging format, and specify the option @option{-g3}.
1882 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1883 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1884 information on @value{NGCC} options affecting debug information.
1886 You will have the best debugging experience if you use the latest
1887 version of the DWARF debugging format that your compiler supports.
1888 DWARF is currently the most expressive and best supported debugging
1889 format in @value{GDBN}.
1893 @section Starting your Program
1899 @kindex r @r{(@code{run})}
1902 Use the @code{run} command to start your program under @value{GDBN}.
1903 You must first specify the program name (except on VxWorks) with an
1904 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1905 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1906 (@pxref{Files, ,Commands to Specify Files}).
1910 If you are running your program in an execution environment that
1911 supports processes, @code{run} creates an inferior process and makes
1912 that process run your program. In some environments without processes,
1913 @code{run} jumps to the start of your program. Other targets,
1914 like @samp{remote}, are always running. If you get an error
1915 message like this one:
1918 The "remote" target does not support "run".
1919 Try "help target" or "continue".
1923 then use @code{continue} to run your program. You may need @code{load}
1924 first (@pxref{load}).
1926 The execution of a program is affected by certain information it
1927 receives from its superior. @value{GDBN} provides ways to specify this
1928 information, which you must do @emph{before} starting your program. (You
1929 can change it after starting your program, but such changes only affect
1930 your program the next time you start it.) This information may be
1931 divided into four categories:
1934 @item The @emph{arguments.}
1935 Specify the arguments to give your program as the arguments of the
1936 @code{run} command. If a shell is available on your target, the shell
1937 is used to pass the arguments, so that you may use normal conventions
1938 (such as wildcard expansion or variable substitution) in describing
1940 In Unix systems, you can control which shell is used with the
1941 @code{SHELL} environment variable.
1942 @xref{Arguments, ,Your Program's Arguments}.
1944 @item The @emph{environment.}
1945 Your program normally inherits its environment from @value{GDBN}, but you can
1946 use the @value{GDBN} commands @code{set environment} and @code{unset
1947 environment} to change parts of the environment that affect
1948 your program. @xref{Environment, ,Your Program's Environment}.
1950 @item The @emph{working directory.}
1951 Your program inherits its working directory from @value{GDBN}. You can set
1952 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1953 @xref{Working Directory, ,Your Program's Working Directory}.
1955 @item The @emph{standard input and output.}
1956 Your program normally uses the same device for standard input and
1957 standard output as @value{GDBN} is using. You can redirect input and output
1958 in the @code{run} command line, or you can use the @code{tty} command to
1959 set a different device for your program.
1960 @xref{Input/Output, ,Your Program's Input and Output}.
1963 @emph{Warning:} While input and output redirection work, you cannot use
1964 pipes to pass the output of the program you are debugging to another
1965 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1969 When you issue the @code{run} command, your program begins to execute
1970 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1971 of how to arrange for your program to stop. Once your program has
1972 stopped, you may call functions in your program, using the @code{print}
1973 or @code{call} commands. @xref{Data, ,Examining Data}.
1975 If the modification time of your symbol file has changed since the last
1976 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1977 table, and reads it again. When it does this, @value{GDBN} tries to retain
1978 your current breakpoints.
1983 @cindex run to main procedure
1984 The name of the main procedure can vary from language to language.
1985 With C or C@t{++}, the main procedure name is always @code{main}, but
1986 other languages such as Ada do not require a specific name for their
1987 main procedure. The debugger provides a convenient way to start the
1988 execution of the program and to stop at the beginning of the main
1989 procedure, depending on the language used.
1991 The @samp{start} command does the equivalent of setting a temporary
1992 breakpoint at the beginning of the main procedure and then invoking
1993 the @samp{run} command.
1995 @cindex elaboration phase
1996 Some programs contain an @dfn{elaboration} phase where some startup code is
1997 executed before the main procedure is called. This depends on the
1998 languages used to write your program. In C@t{++}, for instance,
1999 constructors for static and global objects are executed before
2000 @code{main} is called. It is therefore possible that the debugger stops
2001 before reaching the main procedure. However, the temporary breakpoint
2002 will remain to halt execution.
2004 Specify the arguments to give to your program as arguments to the
2005 @samp{start} command. These arguments will be given verbatim to the
2006 underlying @samp{run} command. Note that the same arguments will be
2007 reused if no argument is provided during subsequent calls to
2008 @samp{start} or @samp{run}.
2010 It is sometimes necessary to debug the program during elaboration. In
2011 these cases, using the @code{start} command would stop the execution of
2012 your program too late, as the program would have already completed the
2013 elaboration phase. Under these circumstances, insert breakpoints in your
2014 elaboration code before running your program.
2016 @kindex set exec-wrapper
2017 @item set exec-wrapper @var{wrapper}
2018 @itemx show exec-wrapper
2019 @itemx unset exec-wrapper
2020 When @samp{exec-wrapper} is set, the specified wrapper is used to
2021 launch programs for debugging. @value{GDBN} starts your program
2022 with a shell command of the form @kbd{exec @var{wrapper}
2023 @var{program}}. Quoting is added to @var{program} and its
2024 arguments, but not to @var{wrapper}, so you should add quotes if
2025 appropriate for your shell. The wrapper runs until it executes
2026 your program, and then @value{GDBN} takes control.
2028 You can use any program that eventually calls @code{execve} with
2029 its arguments as a wrapper. Several standard Unix utilities do
2030 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2031 with @code{exec "$@@"} will also work.
2033 For example, you can use @code{env} to pass an environment variable to
2034 the debugged program, without setting the variable in your shell's
2038 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2042 This command is available when debugging locally on most targets, excluding
2043 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2045 @kindex set disable-randomization
2046 @item set disable-randomization
2047 @itemx set disable-randomization on
2048 This option (enabled by default in @value{GDBN}) will turn off the native
2049 randomization of the virtual address space of the started program. This option
2050 is useful for multiple debugging sessions to make the execution better
2051 reproducible and memory addresses reusable across debugging sessions.
2053 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2054 On @sc{gnu}/Linux you can get the same behavior using
2057 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2060 @item set disable-randomization off
2061 Leave the behavior of the started executable unchanged. Some bugs rear their
2062 ugly heads only when the program is loaded at certain addresses. If your bug
2063 disappears when you run the program under @value{GDBN}, that might be because
2064 @value{GDBN} by default disables the address randomization on platforms, such
2065 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2066 disable-randomization off} to try to reproduce such elusive bugs.
2068 On targets where it is available, virtual address space randomization
2069 protects the programs against certain kinds of security attacks. In these
2070 cases the attacker needs to know the exact location of a concrete executable
2071 code. Randomizing its location makes it impossible to inject jumps misusing
2072 a code at its expected addresses.
2074 Prelinking shared libraries provides a startup performance advantage but it
2075 makes addresses in these libraries predictable for privileged processes by
2076 having just unprivileged access at the target system. Reading the shared
2077 library binary gives enough information for assembling the malicious code
2078 misusing it. Still even a prelinked shared library can get loaded at a new
2079 random address just requiring the regular relocation process during the
2080 startup. Shared libraries not already prelinked are always loaded at
2081 a randomly chosen address.
2083 Position independent executables (PIE) contain position independent code
2084 similar to the shared libraries and therefore such executables get loaded at
2085 a randomly chosen address upon startup. PIE executables always load even
2086 already prelinked shared libraries at a random address. You can build such
2087 executable using @command{gcc -fPIE -pie}.
2089 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2090 (as long as the randomization is enabled).
2092 @item show disable-randomization
2093 Show the current setting of the explicit disable of the native randomization of
2094 the virtual address space of the started program.
2099 @section Your Program's Arguments
2101 @cindex arguments (to your program)
2102 The arguments to your program can be specified by the arguments of the
2104 They are passed to a shell, which expands wildcard characters and
2105 performs redirection of I/O, and thence to your program. Your
2106 @code{SHELL} environment variable (if it exists) specifies what shell
2107 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2108 the default shell (@file{/bin/sh} on Unix).
2110 On non-Unix systems, the program is usually invoked directly by
2111 @value{GDBN}, which emulates I/O redirection via the appropriate system
2112 calls, and the wildcard characters are expanded by the startup code of
2113 the program, not by the shell.
2115 @code{run} with no arguments uses the same arguments used by the previous
2116 @code{run}, or those set by the @code{set args} command.
2121 Specify the arguments to be used the next time your program is run. If
2122 @code{set args} has no arguments, @code{run} executes your program
2123 with no arguments. Once you have run your program with arguments,
2124 using @code{set args} before the next @code{run} is the only way to run
2125 it again without arguments.
2129 Show the arguments to give your program when it is started.
2133 @section Your Program's Environment
2135 @cindex environment (of your program)
2136 The @dfn{environment} consists of a set of environment variables and
2137 their values. Environment variables conventionally record such things as
2138 your user name, your home directory, your terminal type, and your search
2139 path for programs to run. Usually you set up environment variables with
2140 the shell and they are inherited by all the other programs you run. When
2141 debugging, it can be useful to try running your program with a modified
2142 environment without having to start @value{GDBN} over again.
2146 @item path @var{directory}
2147 Add @var{directory} to the front of the @code{PATH} environment variable
2148 (the search path for executables) that will be passed to your program.
2149 The value of @code{PATH} used by @value{GDBN} does not change.
2150 You may specify several directory names, separated by whitespace or by a
2151 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2152 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2153 is moved to the front, so it is searched sooner.
2155 You can use the string @samp{$cwd} to refer to whatever is the current
2156 working directory at the time @value{GDBN} searches the path. If you
2157 use @samp{.} instead, it refers to the directory where you executed the
2158 @code{path} command. @value{GDBN} replaces @samp{.} in the
2159 @var{directory} argument (with the current path) before adding
2160 @var{directory} to the search path.
2161 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2162 @c document that, since repeating it would be a no-op.
2166 Display the list of search paths for executables (the @code{PATH}
2167 environment variable).
2169 @kindex show environment
2170 @item show environment @r{[}@var{varname}@r{]}
2171 Print the value of environment variable @var{varname} to be given to
2172 your program when it starts. If you do not supply @var{varname},
2173 print the names and values of all environment variables to be given to
2174 your program. You can abbreviate @code{environment} as @code{env}.
2176 @kindex set environment
2177 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2178 Set environment variable @var{varname} to @var{value}. The value
2179 changes for your program only, not for @value{GDBN} itself. @var{value} may
2180 be any string; the values of environment variables are just strings, and
2181 any interpretation is supplied by your program itself. The @var{value}
2182 parameter is optional; if it is eliminated, the variable is set to a
2184 @c "any string" here does not include leading, trailing
2185 @c blanks. Gnu asks: does anyone care?
2187 For example, this command:
2194 tells the debugged program, when subsequently run, that its user is named
2195 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2196 are not actually required.)
2198 @kindex unset environment
2199 @item unset environment @var{varname}
2200 Remove variable @var{varname} from the environment to be passed to your
2201 program. This is different from @samp{set env @var{varname} =};
2202 @code{unset environment} removes the variable from the environment,
2203 rather than assigning it an empty value.
2206 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2208 by your @code{SHELL} environment variable if it exists (or
2209 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2210 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2211 @file{.bashrc} for BASH---any variables you set in that file affect
2212 your program. You may wish to move setting of environment variables to
2213 files that are only run when you sign on, such as @file{.login} or
2216 @node Working Directory
2217 @section Your Program's Working Directory
2219 @cindex working directory (of your program)
2220 Each time you start your program with @code{run}, it inherits its
2221 working directory from the current working directory of @value{GDBN}.
2222 The @value{GDBN} working directory is initially whatever it inherited
2223 from its parent process (typically the shell), but you can specify a new
2224 working directory in @value{GDBN} with the @code{cd} command.
2226 The @value{GDBN} working directory also serves as a default for the commands
2227 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2232 @cindex change working directory
2233 @item cd @var{directory}
2234 Set the @value{GDBN} working directory to @var{directory}.
2238 Print the @value{GDBN} working directory.
2241 It is generally impossible to find the current working directory of
2242 the process being debugged (since a program can change its directory
2243 during its run). If you work on a system where @value{GDBN} is
2244 configured with the @file{/proc} support, you can use the @code{info
2245 proc} command (@pxref{SVR4 Process Information}) to find out the
2246 current working directory of the debuggee.
2249 @section Your Program's Input and Output
2254 By default, the program you run under @value{GDBN} does input and output to
2255 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2256 to its own terminal modes to interact with you, but it records the terminal
2257 modes your program was using and switches back to them when you continue
2258 running your program.
2261 @kindex info terminal
2263 Displays information recorded by @value{GDBN} about the terminal modes your
2267 You can redirect your program's input and/or output using shell
2268 redirection with the @code{run} command. For example,
2275 starts your program, diverting its output to the file @file{outfile}.
2278 @cindex controlling terminal
2279 Another way to specify where your program should do input and output is
2280 with the @code{tty} command. This command accepts a file name as
2281 argument, and causes this file to be the default for future @code{run}
2282 commands. It also resets the controlling terminal for the child
2283 process, for future @code{run} commands. For example,
2290 directs that processes started with subsequent @code{run} commands
2291 default to do input and output on the terminal @file{/dev/ttyb} and have
2292 that as their controlling terminal.
2294 An explicit redirection in @code{run} overrides the @code{tty} command's
2295 effect on the input/output device, but not its effect on the controlling
2298 When you use the @code{tty} command or redirect input in the @code{run}
2299 command, only the input @emph{for your program} is affected. The input
2300 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2301 for @code{set inferior-tty}.
2303 @cindex inferior tty
2304 @cindex set inferior controlling terminal
2305 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2306 display the name of the terminal that will be used for future runs of your
2310 @item set inferior-tty /dev/ttyb
2311 @kindex set inferior-tty
2312 Set the tty for the program being debugged to /dev/ttyb.
2314 @item show inferior-tty
2315 @kindex show inferior-tty
2316 Show the current tty for the program being debugged.
2320 @section Debugging an Already-running Process
2325 @item attach @var{process-id}
2326 This command attaches to a running process---one that was started
2327 outside @value{GDBN}. (@code{info files} shows your active
2328 targets.) The command takes as argument a process ID. The usual way to
2329 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2330 or with the @samp{jobs -l} shell command.
2332 @code{attach} does not repeat if you press @key{RET} a second time after
2333 executing the command.
2336 To use @code{attach}, your program must be running in an environment
2337 which supports processes; for example, @code{attach} does not work for
2338 programs on bare-board targets that lack an operating system. You must
2339 also have permission to send the process a signal.
2341 When you use @code{attach}, the debugger finds the program running in
2342 the process first by looking in the current working directory, then (if
2343 the program is not found) by using the source file search path
2344 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2345 the @code{file} command to load the program. @xref{Files, ,Commands to
2348 The first thing @value{GDBN} does after arranging to debug the specified
2349 process is to stop it. You can examine and modify an attached process
2350 with all the @value{GDBN} commands that are ordinarily available when
2351 you start processes with @code{run}. You can insert breakpoints; you
2352 can step and continue; you can modify storage. If you would rather the
2353 process continue running, you may use the @code{continue} command after
2354 attaching @value{GDBN} to the process.
2359 When you have finished debugging the attached process, you can use the
2360 @code{detach} command to release it from @value{GDBN} control. Detaching
2361 the process continues its execution. After the @code{detach} command,
2362 that process and @value{GDBN} become completely independent once more, and you
2363 are ready to @code{attach} another process or start one with @code{run}.
2364 @code{detach} does not repeat if you press @key{RET} again after
2365 executing the command.
2368 If you exit @value{GDBN} while you have an attached process, you detach
2369 that process. If you use the @code{run} command, you kill that process.
2370 By default, @value{GDBN} asks for confirmation if you try to do either of these
2371 things; you can control whether or not you need to confirm by using the
2372 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2376 @section Killing the Child Process
2381 Kill the child process in which your program is running under @value{GDBN}.
2384 This command is useful if you wish to debug a core dump instead of a
2385 running process. @value{GDBN} ignores any core dump file while your program
2388 On some operating systems, a program cannot be executed outside @value{GDBN}
2389 while you have breakpoints set on it inside @value{GDBN}. You can use the
2390 @code{kill} command in this situation to permit running your program
2391 outside the debugger.
2393 The @code{kill} command is also useful if you wish to recompile and
2394 relink your program, since on many systems it is impossible to modify an
2395 executable file while it is running in a process. In this case, when you
2396 next type @code{run}, @value{GDBN} notices that the file has changed, and
2397 reads the symbol table again (while trying to preserve your current
2398 breakpoint settings).
2400 @node Inferiors and Programs
2401 @section Debugging Multiple Inferiors and Programs
2403 @value{GDBN} lets you run and debug multiple programs in a single
2404 session. In addition, @value{GDBN} on some systems may let you run
2405 several programs simultaneously (otherwise you have to exit from one
2406 before starting another). In the most general case, you can have
2407 multiple threads of execution in each of multiple processes, launched
2408 from multiple executables.
2411 @value{GDBN} represents the state of each program execution with an
2412 object called an @dfn{inferior}. An inferior typically corresponds to
2413 a process, but is more general and applies also to targets that do not
2414 have processes. Inferiors may be created before a process runs, and
2415 may be retained after a process exits. Inferiors have unique
2416 identifiers that are different from process ids. Usually each
2417 inferior will also have its own distinct address space, although some
2418 embedded targets may have several inferiors running in different parts
2419 of a single address space. Each inferior may in turn have multiple
2420 threads running in it.
2422 To find out what inferiors exist at any moment, use @w{@code{info
2426 @kindex info inferiors
2427 @item info inferiors
2428 Print a list of all inferiors currently being managed by @value{GDBN}.
2430 @value{GDBN} displays for each inferior (in this order):
2434 the inferior number assigned by @value{GDBN}
2437 the target system's inferior identifier
2440 the name of the executable the inferior is running.
2445 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2446 indicates the current inferior.
2450 @c end table here to get a little more width for example
2453 (@value{GDBP}) info inferiors
2454 Num Description Executable
2455 2 process 2307 hello
2456 * 1 process 3401 goodbye
2459 To switch focus between inferiors, use the @code{inferior} command:
2462 @kindex inferior @var{infno}
2463 @item inferior @var{infno}
2464 Make inferior number @var{infno} the current inferior. The argument
2465 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2466 in the first field of the @samp{info inferiors} display.
2470 You can get multiple executables into a debugging session via the
2471 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2472 systems @value{GDBN} can add inferiors to the debug session
2473 automatically by following calls to @code{fork} and @code{exec}. To
2474 remove inferiors from the debugging session use the
2475 @w{@code{remove-inferiors}} command.
2478 @kindex add-inferior
2479 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2480 Adds @var{n} inferiors to be run using @var{executable} as the
2481 executable. @var{n} defaults to 1. If no executable is specified,
2482 the inferiors begins empty, with no program. You can still assign or
2483 change the program assigned to the inferior at any time by using the
2484 @code{file} command with the executable name as its argument.
2486 @kindex clone-inferior
2487 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2488 Adds @var{n} inferiors ready to execute the same program as inferior
2489 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2490 number of the current inferior. This is a convenient command when you
2491 want to run another instance of the inferior you are debugging.
2494 (@value{GDBP}) info inferiors
2495 Num Description Executable
2496 * 1 process 29964 helloworld
2497 (@value{GDBP}) clone-inferior
2500 (@value{GDBP}) info inferiors
2501 Num Description Executable
2503 * 1 process 29964 helloworld
2506 You can now simply switch focus to inferior 2 and run it.
2508 @kindex remove-inferiors
2509 @item remove-inferiors @var{infno}@dots{}
2510 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2511 possible to remove an inferior that is running with this command. For
2512 those, use the @code{kill} or @code{detach} command first.
2516 To quit debugging one of the running inferiors that is not the current
2517 inferior, you can either detach from it by using the @w{@code{detach
2518 inferior}} command (allowing it to run independently), or kill it
2519 using the @w{@code{kill inferiors}} command:
2522 @kindex detach inferiors @var{infno}@dots{}
2523 @item detach inferior @var{infno}@dots{}
2524 Detach from the inferior or inferiors identified by @value{GDBN}
2525 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2526 still stays on the list of inferiors shown by @code{info inferiors},
2527 but its Description will show @samp{<null>}.
2529 @kindex kill inferiors @var{infno}@dots{}
2530 @item kill inferiors @var{infno}@dots{}
2531 Kill the inferior or inferiors identified by @value{GDBN} inferior
2532 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2533 stays on the list of inferiors shown by @code{info inferiors}, but its
2534 Description will show @samp{<null>}.
2537 After the successful completion of a command such as @code{detach},
2538 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2539 a normal process exit, the inferior is still valid and listed with
2540 @code{info inferiors}, ready to be restarted.
2543 To be notified when inferiors are started or exit under @value{GDBN}'s
2544 control use @w{@code{set print inferior-events}}:
2547 @kindex set print inferior-events
2548 @cindex print messages on inferior start and exit
2549 @item set print inferior-events
2550 @itemx set print inferior-events on
2551 @itemx set print inferior-events off
2552 The @code{set print inferior-events} command allows you to enable or
2553 disable printing of messages when @value{GDBN} notices that new
2554 inferiors have started or that inferiors have exited or have been
2555 detached. By default, these messages will not be printed.
2557 @kindex show print inferior-events
2558 @item show print inferior-events
2559 Show whether messages will be printed when @value{GDBN} detects that
2560 inferiors have started, exited or have been detached.
2563 Many commands will work the same with multiple programs as with a
2564 single program: e.g., @code{print myglobal} will simply display the
2565 value of @code{myglobal} in the current inferior.
2568 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2569 get more info about the relationship of inferiors, programs, address
2570 spaces in a debug session. You can do that with the @w{@code{maint
2571 info program-spaces}} command.
2574 @kindex maint info program-spaces
2575 @item maint info program-spaces
2576 Print a list of all program spaces currently being managed by
2579 @value{GDBN} displays for each program space (in this order):
2583 the program space number assigned by @value{GDBN}
2586 the name of the executable loaded into the program space, with e.g.,
2587 the @code{file} command.
2592 An asterisk @samp{*} preceding the @value{GDBN} program space number
2593 indicates the current program space.
2595 In addition, below each program space line, @value{GDBN} prints extra
2596 information that isn't suitable to display in tabular form. For
2597 example, the list of inferiors bound to the program space.
2600 (@value{GDBP}) maint info program-spaces
2603 Bound inferiors: ID 1 (process 21561)
2607 Here we can see that no inferior is running the program @code{hello},
2608 while @code{process 21561} is running the program @code{goodbye}. On
2609 some targets, it is possible that multiple inferiors are bound to the
2610 same program space. The most common example is that of debugging both
2611 the parent and child processes of a @code{vfork} call. For example,
2614 (@value{GDBP}) maint info program-spaces
2617 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2620 Here, both inferior 2 and inferior 1 are running in the same program
2621 space as a result of inferior 1 having executed a @code{vfork} call.
2625 @section Debugging Programs with Multiple Threads
2627 @cindex threads of execution
2628 @cindex multiple threads
2629 @cindex switching threads
2630 In some operating systems, such as HP-UX and Solaris, a single program
2631 may have more than one @dfn{thread} of execution. The precise semantics
2632 of threads differ from one operating system to another, but in general
2633 the threads of a single program are akin to multiple processes---except
2634 that they share one address space (that is, they can all examine and
2635 modify the same variables). On the other hand, each thread has its own
2636 registers and execution stack, and perhaps private memory.
2638 @value{GDBN} provides these facilities for debugging multi-thread
2642 @item automatic notification of new threads
2643 @item @samp{thread @var{threadno}}, a command to switch among threads
2644 @item @samp{info threads}, a command to inquire about existing threads
2645 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2646 a command to apply a command to a list of threads
2647 @item thread-specific breakpoints
2648 @item @samp{set print thread-events}, which controls printing of
2649 messages on thread start and exit.
2650 @item @samp{set libthread-db-search-path @var{path}}, which lets
2651 the user specify which @code{libthread_db} to use if the default choice
2652 isn't compatible with the program.
2656 @emph{Warning:} These facilities are not yet available on every
2657 @value{GDBN} configuration where the operating system supports threads.
2658 If your @value{GDBN} does not support threads, these commands have no
2659 effect. For example, a system without thread support shows no output
2660 from @samp{info threads}, and always rejects the @code{thread} command,
2664 (@value{GDBP}) info threads
2665 (@value{GDBP}) thread 1
2666 Thread ID 1 not known. Use the "info threads" command to
2667 see the IDs of currently known threads.
2669 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2670 @c doesn't support threads"?
2673 @cindex focus of debugging
2674 @cindex current thread
2675 The @value{GDBN} thread debugging facility allows you to observe all
2676 threads while your program runs---but whenever @value{GDBN} takes
2677 control, one thread in particular is always the focus of debugging.
2678 This thread is called the @dfn{current thread}. Debugging commands show
2679 program information from the perspective of the current thread.
2681 @cindex @code{New} @var{systag} message
2682 @cindex thread identifier (system)
2683 @c FIXME-implementors!! It would be more helpful if the [New...] message
2684 @c included GDB's numeric thread handle, so you could just go to that
2685 @c thread without first checking `info threads'.
2686 Whenever @value{GDBN} detects a new thread in your program, it displays
2687 the target system's identification for the thread with a message in the
2688 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2689 whose form varies depending on the particular system. For example, on
2690 @sc{gnu}/Linux, you might see
2693 [New Thread 0x41e02940 (LWP 25582)]
2697 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2698 the @var{systag} is simply something like @samp{process 368}, with no
2701 @c FIXME!! (1) Does the [New...] message appear even for the very first
2702 @c thread of a program, or does it only appear for the
2703 @c second---i.e.@: when it becomes obvious we have a multithread
2705 @c (2) *Is* there necessarily a first thread always? Or do some
2706 @c multithread systems permit starting a program with multiple
2707 @c threads ab initio?
2709 @cindex thread number
2710 @cindex thread identifier (GDB)
2711 For debugging purposes, @value{GDBN} associates its own thread
2712 number---always a single integer---with each thread in your program.
2715 @kindex info threads
2716 @item info threads @r{[}@var{id}@dots{}@r{]}
2717 Display a summary of all threads currently in your program. Optional
2718 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2719 means to print information only about the specified thread or threads.
2720 @value{GDBN} displays for each thread (in this order):
2724 the thread number assigned by @value{GDBN}
2727 the target system's thread identifier (@var{systag})
2730 the thread's name, if one is known. A thread can either be named by
2731 the user (see @code{thread name}, below), or, in some cases, by the
2735 the current stack frame summary for that thread
2739 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2740 indicates the current thread.
2744 @c end table here to get a little more width for example
2747 (@value{GDBP}) info threads
2749 3 process 35 thread 27 0x34e5 in sigpause ()
2750 2 process 35 thread 23 0x34e5 in sigpause ()
2751 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2755 On Solaris, you can display more information about user threads with a
2756 Solaris-specific command:
2759 @item maint info sol-threads
2760 @kindex maint info sol-threads
2761 @cindex thread info (Solaris)
2762 Display info on Solaris user threads.
2766 @kindex thread @var{threadno}
2767 @item thread @var{threadno}
2768 Make thread number @var{threadno} the current thread. The command
2769 argument @var{threadno} is the internal @value{GDBN} thread number, as
2770 shown in the first field of the @samp{info threads} display.
2771 @value{GDBN} responds by displaying the system identifier of the thread
2772 you selected, and its current stack frame summary:
2775 (@value{GDBP}) thread 2
2776 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2777 #0 some_function (ignore=0x0) at example.c:8
2778 8 printf ("hello\n");
2782 As with the @samp{[New @dots{}]} message, the form of the text after
2783 @samp{Switching to} depends on your system's conventions for identifying
2786 @vindex $_thread@r{, convenience variable}
2787 The debugger convenience variable @samp{$_thread} contains the number
2788 of the current thread. You may find this useful in writing breakpoint
2789 conditional expressions, command scripts, and so forth. See
2790 @xref{Convenience Vars,, Convenience Variables}, for general
2791 information on convenience variables.
2793 @kindex thread apply
2794 @cindex apply command to several threads
2795 @item thread apply [@var{threadno} | all] @var{command}
2796 The @code{thread apply} command allows you to apply the named
2797 @var{command} to one or more threads. Specify the numbers of the
2798 threads that you want affected with the command argument
2799 @var{threadno}. It can be a single thread number, one of the numbers
2800 shown in the first field of the @samp{info threads} display; or it
2801 could be a range of thread numbers, as in @code{2-4}. To apply a
2802 command to all threads, type @kbd{thread apply all @var{command}}.
2805 @cindex name a thread
2806 @item thread name [@var{name}]
2807 This command assigns a name to the current thread. If no argument is
2808 given, any existing user-specified name is removed. The thread name
2809 appears in the @samp{info threads} display.
2811 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2812 determine the name of the thread as given by the OS. On these
2813 systems, a name specified with @samp{thread name} will override the
2814 system-give name, and removing the user-specified name will cause
2815 @value{GDBN} to once again display the system-specified name.
2818 @cindex search for a thread
2819 @item thread find [@var{regexp}]
2820 Search for and display thread ids whose name or @var{systag}
2821 matches the supplied regular expression.
2823 As well as being the complement to the @samp{thread name} command,
2824 this command also allows you to identify a thread by its target
2825 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2829 (@value{GDBN}) thread find 26688
2830 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2831 (@value{GDBN}) info thread 4
2833 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2836 @kindex set print thread-events
2837 @cindex print messages on thread start and exit
2838 @item set print thread-events
2839 @itemx set print thread-events on
2840 @itemx set print thread-events off
2841 The @code{set print thread-events} command allows you to enable or
2842 disable printing of messages when @value{GDBN} notices that new threads have
2843 started or that threads have exited. By default, these messages will
2844 be printed if detection of these events is supported by the target.
2845 Note that these messages cannot be disabled on all targets.
2847 @kindex show print thread-events
2848 @item show print thread-events
2849 Show whether messages will be printed when @value{GDBN} detects that threads
2850 have started and exited.
2853 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2854 more information about how @value{GDBN} behaves when you stop and start
2855 programs with multiple threads.
2857 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2858 watchpoints in programs with multiple threads.
2861 @kindex set libthread-db-search-path
2862 @cindex search path for @code{libthread_db}
2863 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2864 If this variable is set, @var{path} is a colon-separated list of
2865 directories @value{GDBN} will use to search for @code{libthread_db}.
2866 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2867 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2868 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2871 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2872 @code{libthread_db} library to obtain information about threads in the
2873 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2874 to find @code{libthread_db}.
2876 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2877 refers to the default system directories that are
2878 normally searched for loading shared libraries.
2880 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2881 refers to the directory from which @code{libpthread}
2882 was loaded in the inferior process.
2884 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2885 @value{GDBN} attempts to initialize it with the current inferior process.
2886 If this initialization fails (which could happen because of a version
2887 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2888 will unload @code{libthread_db}, and continue with the next directory.
2889 If none of @code{libthread_db} libraries initialize successfully,
2890 @value{GDBN} will issue a warning and thread debugging will be disabled.
2892 Setting @code{libthread-db-search-path} is currently implemented
2893 only on some platforms.
2895 @kindex show libthread-db-search-path
2896 @item show libthread-db-search-path
2897 Display current libthread_db search path.
2899 @kindex set debug libthread-db
2900 @kindex show debug libthread-db
2901 @cindex debugging @code{libthread_db}
2902 @item set debug libthread-db
2903 @itemx show debug libthread-db
2904 Turns on or off display of @code{libthread_db}-related events.
2905 Use @code{1} to enable, @code{0} to disable.
2909 @section Debugging Forks
2911 @cindex fork, debugging programs which call
2912 @cindex multiple processes
2913 @cindex processes, multiple
2914 On most systems, @value{GDBN} has no special support for debugging
2915 programs which create additional processes using the @code{fork}
2916 function. When a program forks, @value{GDBN} will continue to debug the
2917 parent process and the child process will run unimpeded. If you have
2918 set a breakpoint in any code which the child then executes, the child
2919 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2920 will cause it to terminate.
2922 However, if you want to debug the child process there is a workaround
2923 which isn't too painful. Put a call to @code{sleep} in the code which
2924 the child process executes after the fork. It may be useful to sleep
2925 only if a certain environment variable is set, or a certain file exists,
2926 so that the delay need not occur when you don't want to run @value{GDBN}
2927 on the child. While the child is sleeping, use the @code{ps} program to
2928 get its process ID. Then tell @value{GDBN} (a new invocation of
2929 @value{GDBN} if you are also debugging the parent process) to attach to
2930 the child process (@pxref{Attach}). From that point on you can debug
2931 the child process just like any other process which you attached to.
2933 On some systems, @value{GDBN} provides support for debugging programs that
2934 create additional processes using the @code{fork} or @code{vfork} functions.
2935 Currently, the only platforms with this feature are HP-UX (11.x and later
2936 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2938 By default, when a program forks, @value{GDBN} will continue to debug
2939 the parent process and the child process will run unimpeded.
2941 If you want to follow the child process instead of the parent process,
2942 use the command @w{@code{set follow-fork-mode}}.
2945 @kindex set follow-fork-mode
2946 @item set follow-fork-mode @var{mode}
2947 Set the debugger response to a program call of @code{fork} or
2948 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2949 process. The @var{mode} argument can be:
2953 The original process is debugged after a fork. The child process runs
2954 unimpeded. This is the default.
2957 The new process is debugged after a fork. The parent process runs
2962 @kindex show follow-fork-mode
2963 @item show follow-fork-mode
2964 Display the current debugger response to a @code{fork} or @code{vfork} call.
2967 @cindex debugging multiple processes
2968 On Linux, if you want to debug both the parent and child processes, use the
2969 command @w{@code{set detach-on-fork}}.
2972 @kindex set detach-on-fork
2973 @item set detach-on-fork @var{mode}
2974 Tells gdb whether to detach one of the processes after a fork, or
2975 retain debugger control over them both.
2979 The child process (or parent process, depending on the value of
2980 @code{follow-fork-mode}) will be detached and allowed to run
2981 independently. This is the default.
2984 Both processes will be held under the control of @value{GDBN}.
2985 One process (child or parent, depending on the value of
2986 @code{follow-fork-mode}) is debugged as usual, while the other
2991 @kindex show detach-on-fork
2992 @item show detach-on-fork
2993 Show whether detach-on-fork mode is on/off.
2996 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2997 will retain control of all forked processes (including nested forks).
2998 You can list the forked processes under the control of @value{GDBN} by
2999 using the @w{@code{info inferiors}} command, and switch from one fork
3000 to another by using the @code{inferior} command (@pxref{Inferiors and
3001 Programs, ,Debugging Multiple Inferiors and Programs}).
3003 To quit debugging one of the forked processes, you can either detach
3004 from it by using the @w{@code{detach inferiors}} command (allowing it
3005 to run independently), or kill it using the @w{@code{kill inferiors}}
3006 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3009 If you ask to debug a child process and a @code{vfork} is followed by an
3010 @code{exec}, @value{GDBN} executes the new target up to the first
3011 breakpoint in the new target. If you have a breakpoint set on
3012 @code{main} in your original program, the breakpoint will also be set on
3013 the child process's @code{main}.
3015 On some systems, when a child process is spawned by @code{vfork}, you
3016 cannot debug the child or parent until an @code{exec} call completes.
3018 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3019 call executes, the new target restarts. To restart the parent
3020 process, use the @code{file} command with the parent executable name
3021 as its argument. By default, after an @code{exec} call executes,
3022 @value{GDBN} discards the symbols of the previous executable image.
3023 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3027 @kindex set follow-exec-mode
3028 @item set follow-exec-mode @var{mode}
3030 Set debugger response to a program call of @code{exec}. An
3031 @code{exec} call replaces the program image of a process.
3033 @code{follow-exec-mode} can be:
3037 @value{GDBN} creates a new inferior and rebinds the process to this
3038 new inferior. The program the process was running before the
3039 @code{exec} call can be restarted afterwards by restarting the
3045 (@value{GDBP}) info inferiors
3047 Id Description Executable
3050 process 12020 is executing new program: prog2
3051 Program exited normally.
3052 (@value{GDBP}) info inferiors
3053 Id Description Executable
3059 @value{GDBN} keeps the process bound to the same inferior. The new
3060 executable image replaces the previous executable loaded in the
3061 inferior. Restarting the inferior after the @code{exec} call, with
3062 e.g., the @code{run} command, restarts the executable the process was
3063 running after the @code{exec} call. This is the default mode.
3068 (@value{GDBP}) info inferiors
3069 Id Description Executable
3072 process 12020 is executing new program: prog2
3073 Program exited normally.
3074 (@value{GDBP}) info inferiors
3075 Id Description Executable
3082 You can use the @code{catch} command to make @value{GDBN} stop whenever
3083 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3084 Catchpoints, ,Setting Catchpoints}.
3086 @node Checkpoint/Restart
3087 @section Setting a @emph{Bookmark} to Return to Later
3092 @cindex snapshot of a process
3093 @cindex rewind program state
3095 On certain operating systems@footnote{Currently, only
3096 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3097 program's state, called a @dfn{checkpoint}, and come back to it
3100 Returning to a checkpoint effectively undoes everything that has
3101 happened in the program since the @code{checkpoint} was saved. This
3102 includes changes in memory, registers, and even (within some limits)
3103 system state. Effectively, it is like going back in time to the
3104 moment when the checkpoint was saved.
3106 Thus, if you're stepping thru a program and you think you're
3107 getting close to the point where things go wrong, you can save
3108 a checkpoint. Then, if you accidentally go too far and miss
3109 the critical statement, instead of having to restart your program
3110 from the beginning, you can just go back to the checkpoint and
3111 start again from there.
3113 This can be especially useful if it takes a lot of time or
3114 steps to reach the point where you think the bug occurs.
3116 To use the @code{checkpoint}/@code{restart} method of debugging:
3121 Save a snapshot of the debugged program's current execution state.
3122 The @code{checkpoint} command takes no arguments, but each checkpoint
3123 is assigned a small integer id, similar to a breakpoint id.
3125 @kindex info checkpoints
3126 @item info checkpoints
3127 List the checkpoints that have been saved in the current debugging
3128 session. For each checkpoint, the following information will be
3135 @item Source line, or label
3138 @kindex restart @var{checkpoint-id}
3139 @item restart @var{checkpoint-id}
3140 Restore the program state that was saved as checkpoint number
3141 @var{checkpoint-id}. All program variables, registers, stack frames
3142 etc.@: will be returned to the values that they had when the checkpoint
3143 was saved. In essence, gdb will ``wind back the clock'' to the point
3144 in time when the checkpoint was saved.
3146 Note that breakpoints, @value{GDBN} variables, command history etc.
3147 are not affected by restoring a checkpoint. In general, a checkpoint
3148 only restores things that reside in the program being debugged, not in
3151 @kindex delete checkpoint @var{checkpoint-id}
3152 @item delete checkpoint @var{checkpoint-id}
3153 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3157 Returning to a previously saved checkpoint will restore the user state
3158 of the program being debugged, plus a significant subset of the system
3159 (OS) state, including file pointers. It won't ``un-write'' data from
3160 a file, but it will rewind the file pointer to the previous location,
3161 so that the previously written data can be overwritten. For files
3162 opened in read mode, the pointer will also be restored so that the
3163 previously read data can be read again.
3165 Of course, characters that have been sent to a printer (or other
3166 external device) cannot be ``snatched back'', and characters received
3167 from eg.@: a serial device can be removed from internal program buffers,
3168 but they cannot be ``pushed back'' into the serial pipeline, ready to
3169 be received again. Similarly, the actual contents of files that have
3170 been changed cannot be restored (at this time).
3172 However, within those constraints, you actually can ``rewind'' your
3173 program to a previously saved point in time, and begin debugging it
3174 again --- and you can change the course of events so as to debug a
3175 different execution path this time.
3177 @cindex checkpoints and process id
3178 Finally, there is one bit of internal program state that will be
3179 different when you return to a checkpoint --- the program's process
3180 id. Each checkpoint will have a unique process id (or @var{pid}),
3181 and each will be different from the program's original @var{pid}.
3182 If your program has saved a local copy of its process id, this could
3183 potentially pose a problem.
3185 @subsection A Non-obvious Benefit of Using Checkpoints
3187 On some systems such as @sc{gnu}/Linux, address space randomization
3188 is performed on new processes for security reasons. This makes it
3189 difficult or impossible to set a breakpoint, or watchpoint, on an
3190 absolute address if you have to restart the program, since the
3191 absolute location of a symbol will change from one execution to the
3194 A checkpoint, however, is an @emph{identical} copy of a process.
3195 Therefore if you create a checkpoint at (eg.@:) the start of main,
3196 and simply return to that checkpoint instead of restarting the
3197 process, you can avoid the effects of address randomization and
3198 your symbols will all stay in the same place.
3201 @chapter Stopping and Continuing
3203 The principal purposes of using a debugger are so that you can stop your
3204 program before it terminates; or so that, if your program runs into
3205 trouble, you can investigate and find out why.
3207 Inside @value{GDBN}, your program may stop for any of several reasons,
3208 such as a signal, a breakpoint, or reaching a new line after a
3209 @value{GDBN} command such as @code{step}. You may then examine and
3210 change variables, set new breakpoints or remove old ones, and then
3211 continue execution. Usually, the messages shown by @value{GDBN} provide
3212 ample explanation of the status of your program---but you can also
3213 explicitly request this information at any time.
3216 @kindex info program
3218 Display information about the status of your program: whether it is
3219 running or not, what process it is, and why it stopped.
3223 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3224 * Continuing and Stepping:: Resuming execution
3225 * Skipping Over Functions and Files::
3226 Skipping over functions and files
3228 * Thread Stops:: Stopping and starting multi-thread programs
3232 @section Breakpoints, Watchpoints, and Catchpoints
3235 A @dfn{breakpoint} makes your program stop whenever a certain point in
3236 the program is reached. For each breakpoint, you can add conditions to
3237 control in finer detail whether your program stops. You can set
3238 breakpoints with the @code{break} command and its variants (@pxref{Set
3239 Breaks, ,Setting Breakpoints}), to specify the place where your program
3240 should stop by line number, function name or exact address in the
3243 On some systems, you can set breakpoints in shared libraries before
3244 the executable is run. There is a minor limitation on HP-UX systems:
3245 you must wait until the executable is run in order to set breakpoints
3246 in shared library routines that are not called directly by the program
3247 (for example, routines that are arguments in a @code{pthread_create}
3251 @cindex data breakpoints
3252 @cindex memory tracing
3253 @cindex breakpoint on memory address
3254 @cindex breakpoint on variable modification
3255 A @dfn{watchpoint} is a special breakpoint that stops your program
3256 when the value of an expression changes. The expression may be a value
3257 of a variable, or it could involve values of one or more variables
3258 combined by operators, such as @samp{a + b}. This is sometimes called
3259 @dfn{data breakpoints}. You must use a different command to set
3260 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3261 from that, you can manage a watchpoint like any other breakpoint: you
3262 enable, disable, and delete both breakpoints and watchpoints using the
3265 You can arrange to have values from your program displayed automatically
3266 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3270 @cindex breakpoint on events
3271 A @dfn{catchpoint} is another special breakpoint that stops your program
3272 when a certain kind of event occurs, such as the throwing of a C@t{++}
3273 exception or the loading of a library. As with watchpoints, you use a
3274 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3275 Catchpoints}), but aside from that, you can manage a catchpoint like any
3276 other breakpoint. (To stop when your program receives a signal, use the
3277 @code{handle} command; see @ref{Signals, ,Signals}.)
3279 @cindex breakpoint numbers
3280 @cindex numbers for breakpoints
3281 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3282 catchpoint when you create it; these numbers are successive integers
3283 starting with one. In many of the commands for controlling various
3284 features of breakpoints you use the breakpoint number to say which
3285 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3286 @dfn{disabled}; if disabled, it has no effect on your program until you
3289 @cindex breakpoint ranges
3290 @cindex ranges of breakpoints
3291 Some @value{GDBN} commands accept a range of breakpoints on which to
3292 operate. A breakpoint range is either a single breakpoint number, like
3293 @samp{5}, or two such numbers, in increasing order, separated by a
3294 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3295 all breakpoints in that range are operated on.
3298 * Set Breaks:: Setting breakpoints
3299 * Set Watchpoints:: Setting watchpoints
3300 * Set Catchpoints:: Setting catchpoints
3301 * Delete Breaks:: Deleting breakpoints
3302 * Disabling:: Disabling breakpoints
3303 * Conditions:: Break conditions
3304 * Break Commands:: Breakpoint command lists
3305 * Save Breakpoints:: How to save breakpoints in a file
3306 * Error in Breakpoints:: ``Cannot insert breakpoints''
3307 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3311 @subsection Setting Breakpoints
3313 @c FIXME LMB what does GDB do if no code on line of breakpt?
3314 @c consider in particular declaration with/without initialization.
3316 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3319 @kindex b @r{(@code{break})}
3320 @vindex $bpnum@r{, convenience variable}
3321 @cindex latest breakpoint
3322 Breakpoints are set with the @code{break} command (abbreviated
3323 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3324 number of the breakpoint you've set most recently; see @ref{Convenience
3325 Vars,, Convenience Variables}, for a discussion of what you can do with
3326 convenience variables.
3329 @item break @var{location}
3330 Set a breakpoint at the given @var{location}, which can specify a
3331 function name, a line number, or an address of an instruction.
3332 (@xref{Specify Location}, for a list of all the possible ways to
3333 specify a @var{location}.) The breakpoint will stop your program just
3334 before it executes any of the code in the specified @var{location}.
3336 When using source languages that permit overloading of symbols, such as
3337 C@t{++}, a function name may refer to more than one possible place to break.
3338 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3341 It is also possible to insert a breakpoint that will stop the program
3342 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3343 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3346 When called without any arguments, @code{break} sets a breakpoint at
3347 the next instruction to be executed in the selected stack frame
3348 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3349 innermost, this makes your program stop as soon as control
3350 returns to that frame. This is similar to the effect of a
3351 @code{finish} command in the frame inside the selected frame---except
3352 that @code{finish} does not leave an active breakpoint. If you use
3353 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3354 the next time it reaches the current location; this may be useful
3357 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3358 least one instruction has been executed. If it did not do this, you
3359 would be unable to proceed past a breakpoint without first disabling the
3360 breakpoint. This rule applies whether or not the breakpoint already
3361 existed when your program stopped.
3363 @item break @dots{} if @var{cond}
3364 Set a breakpoint with condition @var{cond}; evaluate the expression
3365 @var{cond} each time the breakpoint is reached, and stop only if the
3366 value is nonzero---that is, if @var{cond} evaluates as true.
3367 @samp{@dots{}} stands for one of the possible arguments described
3368 above (or no argument) specifying where to break. @xref{Conditions,
3369 ,Break Conditions}, for more information on breakpoint conditions.
3372 @item tbreak @var{args}
3373 Set a breakpoint enabled only for one stop. @var{args} are the
3374 same as for the @code{break} command, and the breakpoint is set in the same
3375 way, but the breakpoint is automatically deleted after the first time your
3376 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3379 @cindex hardware breakpoints
3380 @item hbreak @var{args}
3381 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3382 @code{break} command and the breakpoint is set in the same way, but the
3383 breakpoint requires hardware support and some target hardware may not
3384 have this support. The main purpose of this is EPROM/ROM code
3385 debugging, so you can set a breakpoint at an instruction without
3386 changing the instruction. This can be used with the new trap-generation
3387 provided by SPARClite DSU and most x86-based targets. These targets
3388 will generate traps when a program accesses some data or instruction
3389 address that is assigned to the debug registers. However the hardware
3390 breakpoint registers can take a limited number of breakpoints. For
3391 example, on the DSU, only two data breakpoints can be set at a time, and
3392 @value{GDBN} will reject this command if more than two are used. Delete
3393 or disable unused hardware breakpoints before setting new ones
3394 (@pxref{Disabling, ,Disabling Breakpoints}).
3395 @xref{Conditions, ,Break Conditions}.
3396 For remote targets, you can restrict the number of hardware
3397 breakpoints @value{GDBN} will use, see @ref{set remote
3398 hardware-breakpoint-limit}.
3401 @item thbreak @var{args}
3402 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3403 are the same as for the @code{hbreak} command and the breakpoint is set in
3404 the same way. However, like the @code{tbreak} command,
3405 the breakpoint is automatically deleted after the
3406 first time your program stops there. Also, like the @code{hbreak}
3407 command, the breakpoint requires hardware support and some target hardware
3408 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3409 See also @ref{Conditions, ,Break Conditions}.
3412 @cindex regular expression
3413 @cindex breakpoints at functions matching a regexp
3414 @cindex set breakpoints in many functions
3415 @item rbreak @var{regex}
3416 Set breakpoints on all functions matching the regular expression
3417 @var{regex}. This command sets an unconditional breakpoint on all
3418 matches, printing a list of all breakpoints it set. Once these
3419 breakpoints are set, they are treated just like the breakpoints set with
3420 the @code{break} command. You can delete them, disable them, or make
3421 them conditional the same way as any other breakpoint.
3423 The syntax of the regular expression is the standard one used with tools
3424 like @file{grep}. Note that this is different from the syntax used by
3425 shells, so for instance @code{foo*} matches all functions that include
3426 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3427 @code{.*} leading and trailing the regular expression you supply, so to
3428 match only functions that begin with @code{foo}, use @code{^foo}.
3430 @cindex non-member C@t{++} functions, set breakpoint in
3431 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3432 breakpoints on overloaded functions that are not members of any special
3435 @cindex set breakpoints on all functions
3436 The @code{rbreak} command can be used to set breakpoints in
3437 @strong{all} the functions in a program, like this:
3440 (@value{GDBP}) rbreak .
3443 @item rbreak @var{file}:@var{regex}
3444 If @code{rbreak} is called with a filename qualification, it limits
3445 the search for functions matching the given regular expression to the
3446 specified @var{file}. This can be used, for example, to set breakpoints on
3447 every function in a given file:
3450 (@value{GDBP}) rbreak file.c:.
3453 The colon separating the filename qualifier from the regex may
3454 optionally be surrounded by spaces.
3456 @kindex info breakpoints
3457 @cindex @code{$_} and @code{info breakpoints}
3458 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3459 @itemx info break @r{[}@var{n}@dots{}@r{]}
3460 Print a table of all breakpoints, watchpoints, and catchpoints set and
3461 not deleted. Optional argument @var{n} means print information only
3462 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3463 For each breakpoint, following columns are printed:
3466 @item Breakpoint Numbers
3468 Breakpoint, watchpoint, or catchpoint.
3470 Whether the breakpoint is marked to be disabled or deleted when hit.
3471 @item Enabled or Disabled
3472 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3473 that are not enabled.
3475 Where the breakpoint is in your program, as a memory address. For a
3476 pending breakpoint whose address is not yet known, this field will
3477 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3478 library that has the symbol or line referred by breakpoint is loaded.
3479 See below for details. A breakpoint with several locations will
3480 have @samp{<MULTIPLE>} in this field---see below for details.
3482 Where the breakpoint is in the source for your program, as a file and
3483 line number. For a pending breakpoint, the original string passed to
3484 the breakpoint command will be listed as it cannot be resolved until
3485 the appropriate shared library is loaded in the future.
3489 If a breakpoint is conditional, @code{info break} shows the condition on
3490 the line following the affected breakpoint; breakpoint commands, if any,
3491 are listed after that. A pending breakpoint is allowed to have a condition
3492 specified for it. The condition is not parsed for validity until a shared
3493 library is loaded that allows the pending breakpoint to resolve to a
3497 @code{info break} with a breakpoint
3498 number @var{n} as argument lists only that breakpoint. The
3499 convenience variable @code{$_} and the default examining-address for
3500 the @code{x} command are set to the address of the last breakpoint
3501 listed (@pxref{Memory, ,Examining Memory}).
3504 @code{info break} displays a count of the number of times the breakpoint
3505 has been hit. This is especially useful in conjunction with the
3506 @code{ignore} command. You can ignore a large number of breakpoint
3507 hits, look at the breakpoint info to see how many times the breakpoint
3508 was hit, and then run again, ignoring one less than that number. This
3509 will get you quickly to the last hit of that breakpoint.
3512 @value{GDBN} allows you to set any number of breakpoints at the same place in
3513 your program. There is nothing silly or meaningless about this. When
3514 the breakpoints are conditional, this is even useful
3515 (@pxref{Conditions, ,Break Conditions}).
3517 @cindex multiple locations, breakpoints
3518 @cindex breakpoints, multiple locations
3519 It is possible that a breakpoint corresponds to several locations
3520 in your program. Examples of this situation are:
3524 Multiple functions in the program may have the same name.
3527 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3528 instances of the function body, used in different cases.
3531 For a C@t{++} template function, a given line in the function can
3532 correspond to any number of instantiations.
3535 For an inlined function, a given source line can correspond to
3536 several places where that function is inlined.
3539 In all those cases, @value{GDBN} will insert a breakpoint at all
3540 the relevant locations.
3542 A breakpoint with multiple locations is displayed in the breakpoint
3543 table using several rows---one header row, followed by one row for
3544 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3545 address column. The rows for individual locations contain the actual
3546 addresses for locations, and show the functions to which those
3547 locations belong. The number column for a location is of the form
3548 @var{breakpoint-number}.@var{location-number}.
3553 Num Type Disp Enb Address What
3554 1 breakpoint keep y <MULTIPLE>
3556 breakpoint already hit 1 time
3557 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3558 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3561 Each location can be individually enabled or disabled by passing
3562 @var{breakpoint-number}.@var{location-number} as argument to the
3563 @code{enable} and @code{disable} commands. Note that you cannot
3564 delete the individual locations from the list, you can only delete the
3565 entire list of locations that belong to their parent breakpoint (with
3566 the @kbd{delete @var{num}} command, where @var{num} is the number of
3567 the parent breakpoint, 1 in the above example). Disabling or enabling
3568 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3569 that belong to that breakpoint.
3571 @cindex pending breakpoints
3572 It's quite common to have a breakpoint inside a shared library.
3573 Shared libraries can be loaded and unloaded explicitly,
3574 and possibly repeatedly, as the program is executed. To support
3575 this use case, @value{GDBN} updates breakpoint locations whenever
3576 any shared library is loaded or unloaded. Typically, you would
3577 set a breakpoint in a shared library at the beginning of your
3578 debugging session, when the library is not loaded, and when the
3579 symbols from the library are not available. When you try to set
3580 breakpoint, @value{GDBN} will ask you if you want to set
3581 a so called @dfn{pending breakpoint}---breakpoint whose address
3582 is not yet resolved.
3584 After the program is run, whenever a new shared library is loaded,
3585 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3586 shared library contains the symbol or line referred to by some
3587 pending breakpoint, that breakpoint is resolved and becomes an
3588 ordinary breakpoint. When a library is unloaded, all breakpoints
3589 that refer to its symbols or source lines become pending again.
3591 This logic works for breakpoints with multiple locations, too. For
3592 example, if you have a breakpoint in a C@t{++} template function, and
3593 a newly loaded shared library has an instantiation of that template,
3594 a new location is added to the list of locations for the breakpoint.
3596 Except for having unresolved address, pending breakpoints do not
3597 differ from regular breakpoints. You can set conditions or commands,
3598 enable and disable them and perform other breakpoint operations.
3600 @value{GDBN} provides some additional commands for controlling what
3601 happens when the @samp{break} command cannot resolve breakpoint
3602 address specification to an address:
3604 @kindex set breakpoint pending
3605 @kindex show breakpoint pending
3607 @item set breakpoint pending auto
3608 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3609 location, it queries you whether a pending breakpoint should be created.
3611 @item set breakpoint pending on
3612 This indicates that an unrecognized breakpoint location should automatically
3613 result in a pending breakpoint being created.
3615 @item set breakpoint pending off
3616 This indicates that pending breakpoints are not to be created. Any
3617 unrecognized breakpoint location results in an error. This setting does
3618 not affect any pending breakpoints previously created.
3620 @item show breakpoint pending
3621 Show the current behavior setting for creating pending breakpoints.
3624 The settings above only affect the @code{break} command and its
3625 variants. Once breakpoint is set, it will be automatically updated
3626 as shared libraries are loaded and unloaded.
3628 @cindex automatic hardware breakpoints
3629 For some targets, @value{GDBN} can automatically decide if hardware or
3630 software breakpoints should be used, depending on whether the
3631 breakpoint address is read-only or read-write. This applies to
3632 breakpoints set with the @code{break} command as well as to internal
3633 breakpoints set by commands like @code{next} and @code{finish}. For
3634 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3637 You can control this automatic behaviour with the following commands::
3639 @kindex set breakpoint auto-hw
3640 @kindex show breakpoint auto-hw
3642 @item set breakpoint auto-hw on
3643 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3644 will try to use the target memory map to decide if software or hardware
3645 breakpoint must be used.
3647 @item set breakpoint auto-hw off
3648 This indicates @value{GDBN} should not automatically select breakpoint
3649 type. If the target provides a memory map, @value{GDBN} will warn when
3650 trying to set software breakpoint at a read-only address.
3653 @value{GDBN} normally implements breakpoints by replacing the program code
3654 at the breakpoint address with a special instruction, which, when
3655 executed, given control to the debugger. By default, the program
3656 code is so modified only when the program is resumed. As soon as
3657 the program stops, @value{GDBN} restores the original instructions. This
3658 behaviour guards against leaving breakpoints inserted in the
3659 target should gdb abrubptly disconnect. However, with slow remote
3660 targets, inserting and removing breakpoint can reduce the performance.
3661 This behavior can be controlled with the following commands::
3663 @kindex set breakpoint always-inserted
3664 @kindex show breakpoint always-inserted
3666 @item set breakpoint always-inserted off
3667 All breakpoints, including newly added by the user, are inserted in
3668 the target only when the target is resumed. All breakpoints are
3669 removed from the target when it stops.
3671 @item set breakpoint always-inserted on
3672 Causes all breakpoints to be inserted in the target at all times. If
3673 the user adds a new breakpoint, or changes an existing breakpoint, the
3674 breakpoints in the target are updated immediately. A breakpoint is
3675 removed from the target only when breakpoint itself is removed.
3677 @cindex non-stop mode, and @code{breakpoint always-inserted}
3678 @item set breakpoint always-inserted auto
3679 This is the default mode. If @value{GDBN} is controlling the inferior
3680 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3681 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3682 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3683 @code{breakpoint always-inserted} mode is off.
3686 @cindex negative breakpoint numbers
3687 @cindex internal @value{GDBN} breakpoints
3688 @value{GDBN} itself sometimes sets breakpoints in your program for
3689 special purposes, such as proper handling of @code{longjmp} (in C
3690 programs). These internal breakpoints are assigned negative numbers,
3691 starting with @code{-1}; @samp{info breakpoints} does not display them.
3692 You can see these breakpoints with the @value{GDBN} maintenance command
3693 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3696 @node Set Watchpoints
3697 @subsection Setting Watchpoints
3699 @cindex setting watchpoints
3700 You can use a watchpoint to stop execution whenever the value of an
3701 expression changes, without having to predict a particular place where
3702 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3703 The expression may be as simple as the value of a single variable, or
3704 as complex as many variables combined by operators. Examples include:
3708 A reference to the value of a single variable.
3711 An address cast to an appropriate data type. For example,
3712 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3713 address (assuming an @code{int} occupies 4 bytes).
3716 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3717 expression can use any operators valid in the program's native
3718 language (@pxref{Languages}).
3721 You can set a watchpoint on an expression even if the expression can
3722 not be evaluated yet. For instance, you can set a watchpoint on
3723 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3724 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3725 the expression produces a valid value. If the expression becomes
3726 valid in some other way than changing a variable (e.g.@: if the memory
3727 pointed to by @samp{*global_ptr} becomes readable as the result of a
3728 @code{malloc} call), @value{GDBN} may not stop until the next time
3729 the expression changes.
3731 @cindex software watchpoints
3732 @cindex hardware watchpoints
3733 Depending on your system, watchpoints may be implemented in software or
3734 hardware. @value{GDBN} does software watchpointing by single-stepping your
3735 program and testing the variable's value each time, which is hundreds of
3736 times slower than normal execution. (But this may still be worth it, to
3737 catch errors where you have no clue what part of your program is the
3740 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3741 x86-based targets, @value{GDBN} includes support for hardware
3742 watchpoints, which do not slow down the running of your program.
3746 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3747 Set a watchpoint for an expression. @value{GDBN} will break when the
3748 expression @var{expr} is written into by the program and its value
3749 changes. The simplest (and the most popular) use of this command is
3750 to watch the value of a single variable:
3753 (@value{GDBP}) watch foo
3756 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3757 argument, @value{GDBN} breaks only when the thread identified by
3758 @var{threadnum} changes the value of @var{expr}. If any other threads
3759 change the value of @var{expr}, @value{GDBN} will not break. Note
3760 that watchpoints restricted to a single thread in this way only work
3761 with Hardware Watchpoints.
3763 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3764 (see below). The @code{-location} argument tells @value{GDBN} to
3765 instead watch the memory referred to by @var{expr}. In this case,
3766 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3767 and watch the memory at that address. The type of the result is used
3768 to determine the size of the watched memory. If the expression's
3769 result does not have an address, then @value{GDBN} will print an
3772 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3773 of masked watchpoints, if the current architecture supports this
3774 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3775 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3776 to an address to watch. The mask specifies that some bits of an address
3777 (the bits which are reset in the mask) should be ignored when matching
3778 the address accessed by the inferior against the watchpoint address.
3779 Thus, a masked watchpoint watches many addresses simultaneously---those
3780 addresses whose unmasked bits are identical to the unmasked bits in the
3781 watchpoint address. The @code{mask} argument implies @code{-location}.
3785 (@value{GDBP}) watch foo mask 0xffff00ff
3786 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3790 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3791 Set a watchpoint that will break when the value of @var{expr} is read
3795 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3796 Set a watchpoint that will break when @var{expr} is either read from
3797 or written into by the program.
3799 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3800 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3801 This command prints a list of watchpoints, using the same format as
3802 @code{info break} (@pxref{Set Breaks}).
3805 If you watch for a change in a numerically entered address you need to
3806 dereference it, as the address itself is just a constant number which will
3807 never change. @value{GDBN} refuses to create a watchpoint that watches
3808 a never-changing value:
3811 (@value{GDBP}) watch 0x600850
3812 Cannot watch constant value 0x600850.
3813 (@value{GDBP}) watch *(int *) 0x600850
3814 Watchpoint 1: *(int *) 6293584
3817 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3818 watchpoints execute very quickly, and the debugger reports a change in
3819 value at the exact instruction where the change occurs. If @value{GDBN}
3820 cannot set a hardware watchpoint, it sets a software watchpoint, which
3821 executes more slowly and reports the change in value at the next
3822 @emph{statement}, not the instruction, after the change occurs.
3824 @cindex use only software watchpoints
3825 You can force @value{GDBN} to use only software watchpoints with the
3826 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3827 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3828 the underlying system supports them. (Note that hardware-assisted
3829 watchpoints that were set @emph{before} setting
3830 @code{can-use-hw-watchpoints} to zero will still use the hardware
3831 mechanism of watching expression values.)
3834 @item set can-use-hw-watchpoints
3835 @kindex set can-use-hw-watchpoints
3836 Set whether or not to use hardware watchpoints.
3838 @item show can-use-hw-watchpoints
3839 @kindex show can-use-hw-watchpoints
3840 Show the current mode of using hardware watchpoints.
3843 For remote targets, you can restrict the number of hardware
3844 watchpoints @value{GDBN} will use, see @ref{set remote
3845 hardware-breakpoint-limit}.
3847 When you issue the @code{watch} command, @value{GDBN} reports
3850 Hardware watchpoint @var{num}: @var{expr}
3854 if it was able to set a hardware watchpoint.
3856 Currently, the @code{awatch} and @code{rwatch} commands can only set
3857 hardware watchpoints, because accesses to data that don't change the
3858 value of the watched expression cannot be detected without examining
3859 every instruction as it is being executed, and @value{GDBN} does not do
3860 that currently. If @value{GDBN} finds that it is unable to set a
3861 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3862 will print a message like this:
3865 Expression cannot be implemented with read/access watchpoint.
3868 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3869 data type of the watched expression is wider than what a hardware
3870 watchpoint on the target machine can handle. For example, some systems
3871 can only watch regions that are up to 4 bytes wide; on such systems you
3872 cannot set hardware watchpoints for an expression that yields a
3873 double-precision floating-point number (which is typically 8 bytes
3874 wide). As a work-around, it might be possible to break the large region
3875 into a series of smaller ones and watch them with separate watchpoints.
3877 If you set too many hardware watchpoints, @value{GDBN} might be unable
3878 to insert all of them when you resume the execution of your program.
3879 Since the precise number of active watchpoints is unknown until such
3880 time as the program is about to be resumed, @value{GDBN} might not be
3881 able to warn you about this when you set the watchpoints, and the
3882 warning will be printed only when the program is resumed:
3885 Hardware watchpoint @var{num}: Could not insert watchpoint
3889 If this happens, delete or disable some of the watchpoints.
3891 Watching complex expressions that reference many variables can also
3892 exhaust the resources available for hardware-assisted watchpoints.
3893 That's because @value{GDBN} needs to watch every variable in the
3894 expression with separately allocated resources.
3896 If you call a function interactively using @code{print} or @code{call},
3897 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3898 kind of breakpoint or the call completes.
3900 @value{GDBN} automatically deletes watchpoints that watch local
3901 (automatic) variables, or expressions that involve such variables, when
3902 they go out of scope, that is, when the execution leaves the block in
3903 which these variables were defined. In particular, when the program
3904 being debugged terminates, @emph{all} local variables go out of scope,
3905 and so only watchpoints that watch global variables remain set. If you
3906 rerun the program, you will need to set all such watchpoints again. One
3907 way of doing that would be to set a code breakpoint at the entry to the
3908 @code{main} function and when it breaks, set all the watchpoints.
3910 @cindex watchpoints and threads
3911 @cindex threads and watchpoints
3912 In multi-threaded programs, watchpoints will detect changes to the
3913 watched expression from every thread.
3916 @emph{Warning:} In multi-threaded programs, software watchpoints
3917 have only limited usefulness. If @value{GDBN} creates a software
3918 watchpoint, it can only watch the value of an expression @emph{in a
3919 single thread}. If you are confident that the expression can only
3920 change due to the current thread's activity (and if you are also
3921 confident that no other thread can become current), then you can use
3922 software watchpoints as usual. However, @value{GDBN} may not notice
3923 when a non-current thread's activity changes the expression. (Hardware
3924 watchpoints, in contrast, watch an expression in all threads.)
3927 @xref{set remote hardware-watchpoint-limit}.
3929 @node Set Catchpoints
3930 @subsection Setting Catchpoints
3931 @cindex catchpoints, setting
3932 @cindex exception handlers
3933 @cindex event handling
3935 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3936 kinds of program events, such as C@t{++} exceptions or the loading of a
3937 shared library. Use the @code{catch} command to set a catchpoint.
3941 @item catch @var{event}
3942 Stop when @var{event} occurs. @var{event} can be any of the following:
3945 @cindex stop on C@t{++} exceptions
3946 The throwing of a C@t{++} exception.
3949 The catching of a C@t{++} exception.
3952 @cindex Ada exception catching
3953 @cindex catch Ada exceptions
3954 An Ada exception being raised. If an exception name is specified
3955 at the end of the command (eg @code{catch exception Program_Error}),
3956 the debugger will stop only when this specific exception is raised.
3957 Otherwise, the debugger stops execution when any Ada exception is raised.
3959 When inserting an exception catchpoint on a user-defined exception whose
3960 name is identical to one of the exceptions defined by the language, the
3961 fully qualified name must be used as the exception name. Otherwise,
3962 @value{GDBN} will assume that it should stop on the pre-defined exception
3963 rather than the user-defined one. For instance, assuming an exception
3964 called @code{Constraint_Error} is defined in package @code{Pck}, then
3965 the command to use to catch such exceptions is @kbd{catch exception
3966 Pck.Constraint_Error}.
3968 @item exception unhandled
3969 An exception that was raised but is not handled by the program.
3972 A failed Ada assertion.
3975 @cindex break on fork/exec
3976 A call to @code{exec}. This is currently only available for HP-UX
3980 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3981 @cindex break on a system call.
3982 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3983 syscall is a mechanism for application programs to request a service
3984 from the operating system (OS) or one of the OS system services.
3985 @value{GDBN} can catch some or all of the syscalls issued by the
3986 debuggee, and show the related information for each syscall. If no
3987 argument is specified, calls to and returns from all system calls
3990 @var{name} can be any system call name that is valid for the
3991 underlying OS. Just what syscalls are valid depends on the OS. On
3992 GNU and Unix systems, you can find the full list of valid syscall
3993 names on @file{/usr/include/asm/unistd.h}.
3995 @c For MS-Windows, the syscall names and the corresponding numbers
3996 @c can be found, e.g., on this URL:
3997 @c http://www.metasploit.com/users/opcode/syscalls.html
3998 @c but we don't support Windows syscalls yet.
4000 Normally, @value{GDBN} knows in advance which syscalls are valid for
4001 each OS, so you can use the @value{GDBN} command-line completion
4002 facilities (@pxref{Completion,, command completion}) to list the
4005 You may also specify the system call numerically. A syscall's
4006 number is the value passed to the OS's syscall dispatcher to
4007 identify the requested service. When you specify the syscall by its
4008 name, @value{GDBN} uses its database of syscalls to convert the name
4009 into the corresponding numeric code, but using the number directly
4010 may be useful if @value{GDBN}'s database does not have the complete
4011 list of syscalls on your system (e.g., because @value{GDBN} lags
4012 behind the OS upgrades).
4014 The example below illustrates how this command works if you don't provide
4018 (@value{GDBP}) catch syscall
4019 Catchpoint 1 (syscall)
4021 Starting program: /tmp/catch-syscall
4023 Catchpoint 1 (call to syscall 'close'), \
4024 0xffffe424 in __kernel_vsyscall ()
4028 Catchpoint 1 (returned from syscall 'close'), \
4029 0xffffe424 in __kernel_vsyscall ()
4033 Here is an example of catching a system call by name:
4036 (@value{GDBP}) catch syscall chroot
4037 Catchpoint 1 (syscall 'chroot' [61])
4039 Starting program: /tmp/catch-syscall
4041 Catchpoint 1 (call to syscall 'chroot'), \
4042 0xffffe424 in __kernel_vsyscall ()
4046 Catchpoint 1 (returned from syscall 'chroot'), \
4047 0xffffe424 in __kernel_vsyscall ()
4051 An example of specifying a system call numerically. In the case
4052 below, the syscall number has a corresponding entry in the XML
4053 file, so @value{GDBN} finds its name and prints it:
4056 (@value{GDBP}) catch syscall 252
4057 Catchpoint 1 (syscall(s) 'exit_group')
4059 Starting program: /tmp/catch-syscall
4061 Catchpoint 1 (call to syscall 'exit_group'), \
4062 0xffffe424 in __kernel_vsyscall ()
4066 Program exited normally.
4070 However, there can be situations when there is no corresponding name
4071 in XML file for that syscall number. In this case, @value{GDBN} prints
4072 a warning message saying that it was not able to find the syscall name,
4073 but the catchpoint will be set anyway. See the example below:
4076 (@value{GDBP}) catch syscall 764
4077 warning: The number '764' does not represent a known syscall.
4078 Catchpoint 2 (syscall 764)
4082 If you configure @value{GDBN} using the @samp{--without-expat} option,
4083 it will not be able to display syscall names. Also, if your
4084 architecture does not have an XML file describing its system calls,
4085 you will not be able to see the syscall names. It is important to
4086 notice that these two features are used for accessing the syscall
4087 name database. In either case, you will see a warning like this:
4090 (@value{GDBP}) catch syscall
4091 warning: Could not open "syscalls/i386-linux.xml"
4092 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4093 GDB will not be able to display syscall names.
4094 Catchpoint 1 (syscall)
4098 Of course, the file name will change depending on your architecture and system.
4100 Still using the example above, you can also try to catch a syscall by its
4101 number. In this case, you would see something like:
4104 (@value{GDBP}) catch syscall 252
4105 Catchpoint 1 (syscall(s) 252)
4108 Again, in this case @value{GDBN} would not be able to display syscall's names.
4111 A call to @code{fork}. This is currently only available for HP-UX
4115 A call to @code{vfork}. This is currently only available for HP-UX
4120 @item tcatch @var{event}
4121 Set a catchpoint that is enabled only for one stop. The catchpoint is
4122 automatically deleted after the first time the event is caught.
4126 Use the @code{info break} command to list the current catchpoints.
4128 There are currently some limitations to C@t{++} exception handling
4129 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4133 If you call a function interactively, @value{GDBN} normally returns
4134 control to you when the function has finished executing. If the call
4135 raises an exception, however, the call may bypass the mechanism that
4136 returns control to you and cause your program either to abort or to
4137 simply continue running until it hits a breakpoint, catches a signal
4138 that @value{GDBN} is listening for, or exits. This is the case even if
4139 you set a catchpoint for the exception; catchpoints on exceptions are
4140 disabled within interactive calls.
4143 You cannot raise an exception interactively.
4146 You cannot install an exception handler interactively.
4149 @cindex raise exceptions
4150 Sometimes @code{catch} is not the best way to debug exception handling:
4151 if you need to know exactly where an exception is raised, it is better to
4152 stop @emph{before} the exception handler is called, since that way you
4153 can see the stack before any unwinding takes place. If you set a
4154 breakpoint in an exception handler instead, it may not be easy to find
4155 out where the exception was raised.
4157 To stop just before an exception handler is called, you need some
4158 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4159 raised by calling a library function named @code{__raise_exception}
4160 which has the following ANSI C interface:
4163 /* @var{addr} is where the exception identifier is stored.
4164 @var{id} is the exception identifier. */
4165 void __raise_exception (void **addr, void *id);
4169 To make the debugger catch all exceptions before any stack
4170 unwinding takes place, set a breakpoint on @code{__raise_exception}
4171 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4173 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4174 that depends on the value of @var{id}, you can stop your program when
4175 a specific exception is raised. You can use multiple conditional
4176 breakpoints to stop your program when any of a number of exceptions are
4181 @subsection Deleting Breakpoints
4183 @cindex clearing breakpoints, watchpoints, catchpoints
4184 @cindex deleting breakpoints, watchpoints, catchpoints
4185 It is often necessary to eliminate a breakpoint, watchpoint, or
4186 catchpoint once it has done its job and you no longer want your program
4187 to stop there. This is called @dfn{deleting} the breakpoint. A
4188 breakpoint that has been deleted no longer exists; it is forgotten.
4190 With the @code{clear} command you can delete breakpoints according to
4191 where they are in your program. With the @code{delete} command you can
4192 delete individual breakpoints, watchpoints, or catchpoints by specifying
4193 their breakpoint numbers.
4195 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4196 automatically ignores breakpoints on the first instruction to be executed
4197 when you continue execution without changing the execution address.
4202 Delete any breakpoints at the next instruction to be executed in the
4203 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4204 the innermost frame is selected, this is a good way to delete a
4205 breakpoint where your program just stopped.
4207 @item clear @var{location}
4208 Delete any breakpoints set at the specified @var{location}.
4209 @xref{Specify Location}, for the various forms of @var{location}; the
4210 most useful ones are listed below:
4213 @item clear @var{function}
4214 @itemx clear @var{filename}:@var{function}
4215 Delete any breakpoints set at entry to the named @var{function}.
4217 @item clear @var{linenum}
4218 @itemx clear @var{filename}:@var{linenum}
4219 Delete any breakpoints set at or within the code of the specified
4220 @var{linenum} of the specified @var{filename}.
4223 @cindex delete breakpoints
4225 @kindex d @r{(@code{delete})}
4226 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4227 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4228 ranges specified as arguments. If no argument is specified, delete all
4229 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4230 confirm off}). You can abbreviate this command as @code{d}.
4234 @subsection Disabling Breakpoints
4236 @cindex enable/disable a breakpoint
4237 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4238 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4239 it had been deleted, but remembers the information on the breakpoint so
4240 that you can @dfn{enable} it again later.
4242 You disable and enable breakpoints, watchpoints, and catchpoints with
4243 the @code{enable} and @code{disable} commands, optionally specifying
4244 one or more breakpoint numbers as arguments. Use @code{info break} to
4245 print a list of all breakpoints, watchpoints, and catchpoints if you
4246 do not know which numbers to use.
4248 Disabling and enabling a breakpoint that has multiple locations
4249 affects all of its locations.
4251 A breakpoint, watchpoint, or catchpoint can have any of four different
4252 states of enablement:
4256 Enabled. The breakpoint stops your program. A breakpoint set
4257 with the @code{break} command starts out in this state.
4259 Disabled. The breakpoint has no effect on your program.
4261 Enabled once. The breakpoint stops your program, but then becomes
4264 Enabled for deletion. The breakpoint stops your program, but
4265 immediately after it does so it is deleted permanently. A breakpoint
4266 set with the @code{tbreak} command starts out in this state.
4269 You can use the following commands to enable or disable breakpoints,
4270 watchpoints, and catchpoints:
4274 @kindex dis @r{(@code{disable})}
4275 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4276 Disable the specified breakpoints---or all breakpoints, if none are
4277 listed. A disabled breakpoint has no effect but is not forgotten. All
4278 options such as ignore-counts, conditions and commands are remembered in
4279 case the breakpoint is enabled again later. You may abbreviate
4280 @code{disable} as @code{dis}.
4283 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4284 Enable the specified breakpoints (or all defined breakpoints). They
4285 become effective once again in stopping your program.
4287 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4288 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4289 of these breakpoints immediately after stopping your program.
4291 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4292 Enable the specified breakpoints to work once, then die. @value{GDBN}
4293 deletes any of these breakpoints as soon as your program stops there.
4294 Breakpoints set by the @code{tbreak} command start out in this state.
4297 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4298 @c confusing: tbreak is also initially enabled.
4299 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4300 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4301 subsequently, they become disabled or enabled only when you use one of
4302 the commands above. (The command @code{until} can set and delete a
4303 breakpoint of its own, but it does not change the state of your other
4304 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4308 @subsection Break Conditions
4309 @cindex conditional breakpoints
4310 @cindex breakpoint conditions
4312 @c FIXME what is scope of break condition expr? Context where wanted?
4313 @c in particular for a watchpoint?
4314 The simplest sort of breakpoint breaks every time your program reaches a
4315 specified place. You can also specify a @dfn{condition} for a
4316 breakpoint. A condition is just a Boolean expression in your
4317 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4318 a condition evaluates the expression each time your program reaches it,
4319 and your program stops only if the condition is @emph{true}.
4321 This is the converse of using assertions for program validation; in that
4322 situation, you want to stop when the assertion is violated---that is,
4323 when the condition is false. In C, if you want to test an assertion expressed
4324 by the condition @var{assert}, you should set the condition
4325 @samp{! @var{assert}} on the appropriate breakpoint.
4327 Conditions are also accepted for watchpoints; you may not need them,
4328 since a watchpoint is inspecting the value of an expression anyhow---but
4329 it might be simpler, say, to just set a watchpoint on a variable name,
4330 and specify a condition that tests whether the new value is an interesting
4333 Break conditions can have side effects, and may even call functions in
4334 your program. This can be useful, for example, to activate functions
4335 that log program progress, or to use your own print functions to
4336 format special data structures. The effects are completely predictable
4337 unless there is another enabled breakpoint at the same address. (In
4338 that case, @value{GDBN} might see the other breakpoint first and stop your
4339 program without checking the condition of this one.) Note that
4340 breakpoint commands are usually more convenient and flexible than break
4342 purpose of performing side effects when a breakpoint is reached
4343 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4345 Break conditions can be specified when a breakpoint is set, by using
4346 @samp{if} in the arguments to the @code{break} command. @xref{Set
4347 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4348 with the @code{condition} command.
4350 You can also use the @code{if} keyword with the @code{watch} command.
4351 The @code{catch} command does not recognize the @code{if} keyword;
4352 @code{condition} is the only way to impose a further condition on a
4357 @item condition @var{bnum} @var{expression}
4358 Specify @var{expression} as the break condition for breakpoint,
4359 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4360 breakpoint @var{bnum} stops your program only if the value of
4361 @var{expression} is true (nonzero, in C). When you use
4362 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4363 syntactic correctness, and to determine whether symbols in it have
4364 referents in the context of your breakpoint. If @var{expression} uses
4365 symbols not referenced in the context of the breakpoint, @value{GDBN}
4366 prints an error message:
4369 No symbol "foo" in current context.
4374 not actually evaluate @var{expression} at the time the @code{condition}
4375 command (or a command that sets a breakpoint with a condition, like
4376 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4378 @item condition @var{bnum}
4379 Remove the condition from breakpoint number @var{bnum}. It becomes
4380 an ordinary unconditional breakpoint.
4383 @cindex ignore count (of breakpoint)
4384 A special case of a breakpoint condition is to stop only when the
4385 breakpoint has been reached a certain number of times. This is so
4386 useful that there is a special way to do it, using the @dfn{ignore
4387 count} of the breakpoint. Every breakpoint has an ignore count, which
4388 is an integer. Most of the time, the ignore count is zero, and
4389 therefore has no effect. But if your program reaches a breakpoint whose
4390 ignore count is positive, then instead of stopping, it just decrements
4391 the ignore count by one and continues. As a result, if the ignore count
4392 value is @var{n}, the breakpoint does not stop the next @var{n} times
4393 your program reaches it.
4397 @item ignore @var{bnum} @var{count}
4398 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4399 The next @var{count} times the breakpoint is reached, your program's
4400 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4403 To make the breakpoint stop the next time it is reached, specify
4406 When you use @code{continue} to resume execution of your program from a
4407 breakpoint, you can specify an ignore count directly as an argument to
4408 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4409 Stepping,,Continuing and Stepping}.
4411 If a breakpoint has a positive ignore count and a condition, the
4412 condition is not checked. Once the ignore count reaches zero,
4413 @value{GDBN} resumes checking the condition.
4415 You could achieve the effect of the ignore count with a condition such
4416 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4417 is decremented each time. @xref{Convenience Vars, ,Convenience
4421 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4424 @node Break Commands
4425 @subsection Breakpoint Command Lists
4427 @cindex breakpoint commands
4428 You can give any breakpoint (or watchpoint or catchpoint) a series of
4429 commands to execute when your program stops due to that breakpoint. For
4430 example, you might want to print the values of certain expressions, or
4431 enable other breakpoints.
4435 @kindex end@r{ (breakpoint commands)}
4436 @item commands @r{[}@var{range}@dots{}@r{]}
4437 @itemx @dots{} @var{command-list} @dots{}
4439 Specify a list of commands for the given breakpoints. The commands
4440 themselves appear on the following lines. Type a line containing just
4441 @code{end} to terminate the commands.
4443 To remove all commands from a breakpoint, type @code{commands} and
4444 follow it immediately with @code{end}; that is, give no commands.
4446 With no argument, @code{commands} refers to the last breakpoint,
4447 watchpoint, or catchpoint set (not to the breakpoint most recently
4448 encountered). If the most recent breakpoints were set with a single
4449 command, then the @code{commands} will apply to all the breakpoints
4450 set by that command. This applies to breakpoints set by
4451 @code{rbreak}, and also applies when a single @code{break} command
4452 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4456 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4457 disabled within a @var{command-list}.
4459 You can use breakpoint commands to start your program up again. Simply
4460 use the @code{continue} command, or @code{step}, or any other command
4461 that resumes execution.
4463 Any other commands in the command list, after a command that resumes
4464 execution, are ignored. This is because any time you resume execution
4465 (even with a simple @code{next} or @code{step}), you may encounter
4466 another breakpoint---which could have its own command list, leading to
4467 ambiguities about which list to execute.
4470 If the first command you specify in a command list is @code{silent}, the
4471 usual message about stopping at a breakpoint is not printed. This may
4472 be desirable for breakpoints that are to print a specific message and
4473 then continue. If none of the remaining commands print anything, you
4474 see no sign that the breakpoint was reached. @code{silent} is
4475 meaningful only at the beginning of a breakpoint command list.
4477 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4478 print precisely controlled output, and are often useful in silent
4479 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4481 For example, here is how you could use breakpoint commands to print the
4482 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4488 printf "x is %d\n",x
4493 One application for breakpoint commands is to compensate for one bug so
4494 you can test for another. Put a breakpoint just after the erroneous line
4495 of code, give it a condition to detect the case in which something
4496 erroneous has been done, and give it commands to assign correct values
4497 to any variables that need them. End with the @code{continue} command
4498 so that your program does not stop, and start with the @code{silent}
4499 command so that no output is produced. Here is an example:
4510 @node Save Breakpoints
4511 @subsection How to save breakpoints to a file
4513 To save breakpoint definitions to a file use the @w{@code{save
4514 breakpoints}} command.
4517 @kindex save breakpoints
4518 @cindex save breakpoints to a file for future sessions
4519 @item save breakpoints [@var{filename}]
4520 This command saves all current breakpoint definitions together with
4521 their commands and ignore counts, into a file @file{@var{filename}}
4522 suitable for use in a later debugging session. This includes all
4523 types of breakpoints (breakpoints, watchpoints, catchpoints,
4524 tracepoints). To read the saved breakpoint definitions, use the
4525 @code{source} command (@pxref{Command Files}). Note that watchpoints
4526 with expressions involving local variables may fail to be recreated
4527 because it may not be possible to access the context where the
4528 watchpoint is valid anymore. Because the saved breakpoint definitions
4529 are simply a sequence of @value{GDBN} commands that recreate the
4530 breakpoints, you can edit the file in your favorite editing program,
4531 and remove the breakpoint definitions you're not interested in, or
4532 that can no longer be recreated.
4535 @c @ifclear BARETARGET
4536 @node Error in Breakpoints
4537 @subsection ``Cannot insert breakpoints''
4539 If you request too many active hardware-assisted breakpoints and
4540 watchpoints, you will see this error message:
4542 @c FIXME: the precise wording of this message may change; the relevant
4543 @c source change is not committed yet (Sep 3, 1999).
4545 Stopped; cannot insert breakpoints.
4546 You may have requested too many hardware breakpoints and watchpoints.
4550 This message is printed when you attempt to resume the program, since
4551 only then @value{GDBN} knows exactly how many hardware breakpoints and
4552 watchpoints it needs to insert.
4554 When this message is printed, you need to disable or remove some of the
4555 hardware-assisted breakpoints and watchpoints, and then continue.
4557 @node Breakpoint-related Warnings
4558 @subsection ``Breakpoint address adjusted...''
4559 @cindex breakpoint address adjusted
4561 Some processor architectures place constraints on the addresses at
4562 which breakpoints may be placed. For architectures thus constrained,
4563 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4564 with the constraints dictated by the architecture.
4566 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4567 a VLIW architecture in which a number of RISC-like instructions may be
4568 bundled together for parallel execution. The FR-V architecture
4569 constrains the location of a breakpoint instruction within such a
4570 bundle to the instruction with the lowest address. @value{GDBN}
4571 honors this constraint by adjusting a breakpoint's address to the
4572 first in the bundle.
4574 It is not uncommon for optimized code to have bundles which contain
4575 instructions from different source statements, thus it may happen that
4576 a breakpoint's address will be adjusted from one source statement to
4577 another. Since this adjustment may significantly alter @value{GDBN}'s
4578 breakpoint related behavior from what the user expects, a warning is
4579 printed when the breakpoint is first set and also when the breakpoint
4582 A warning like the one below is printed when setting a breakpoint
4583 that's been subject to address adjustment:
4586 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4589 Such warnings are printed both for user settable and @value{GDBN}'s
4590 internal breakpoints. If you see one of these warnings, you should
4591 verify that a breakpoint set at the adjusted address will have the
4592 desired affect. If not, the breakpoint in question may be removed and
4593 other breakpoints may be set which will have the desired behavior.
4594 E.g., it may be sufficient to place the breakpoint at a later
4595 instruction. A conditional breakpoint may also be useful in some
4596 cases to prevent the breakpoint from triggering too often.
4598 @value{GDBN} will also issue a warning when stopping at one of these
4599 adjusted breakpoints:
4602 warning: Breakpoint 1 address previously adjusted from 0x00010414
4606 When this warning is encountered, it may be too late to take remedial
4607 action except in cases where the breakpoint is hit earlier or more
4608 frequently than expected.
4610 @node Continuing and Stepping
4611 @section Continuing and Stepping
4615 @cindex resuming execution
4616 @dfn{Continuing} means resuming program execution until your program
4617 completes normally. In contrast, @dfn{stepping} means executing just
4618 one more ``step'' of your program, where ``step'' may mean either one
4619 line of source code, or one machine instruction (depending on what
4620 particular command you use). Either when continuing or when stepping,
4621 your program may stop even sooner, due to a breakpoint or a signal. (If
4622 it stops due to a signal, you may want to use @code{handle}, or use
4623 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4627 @kindex c @r{(@code{continue})}
4628 @kindex fg @r{(resume foreground execution)}
4629 @item continue @r{[}@var{ignore-count}@r{]}
4630 @itemx c @r{[}@var{ignore-count}@r{]}
4631 @itemx fg @r{[}@var{ignore-count}@r{]}
4632 Resume program execution, at the address where your program last stopped;
4633 any breakpoints set at that address are bypassed. The optional argument
4634 @var{ignore-count} allows you to specify a further number of times to
4635 ignore a breakpoint at this location; its effect is like that of
4636 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4638 The argument @var{ignore-count} is meaningful only when your program
4639 stopped due to a breakpoint. At other times, the argument to
4640 @code{continue} is ignored.
4642 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4643 debugged program is deemed to be the foreground program) are provided
4644 purely for convenience, and have exactly the same behavior as
4648 To resume execution at a different place, you can use @code{return}
4649 (@pxref{Returning, ,Returning from a Function}) to go back to the
4650 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4651 Different Address}) to go to an arbitrary location in your program.
4653 A typical technique for using stepping is to set a breakpoint
4654 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4655 beginning of the function or the section of your program where a problem
4656 is believed to lie, run your program until it stops at that breakpoint,
4657 and then step through the suspect area, examining the variables that are
4658 interesting, until you see the problem happen.
4662 @kindex s @r{(@code{step})}
4664 Continue running your program until control reaches a different source
4665 line, then stop it and return control to @value{GDBN}. This command is
4666 abbreviated @code{s}.
4669 @c "without debugging information" is imprecise; actually "without line
4670 @c numbers in the debugging information". (gcc -g1 has debugging info but
4671 @c not line numbers). But it seems complex to try to make that
4672 @c distinction here.
4673 @emph{Warning:} If you use the @code{step} command while control is
4674 within a function that was compiled without debugging information,
4675 execution proceeds until control reaches a function that does have
4676 debugging information. Likewise, it will not step into a function which
4677 is compiled without debugging information. To step through functions
4678 without debugging information, use the @code{stepi} command, described
4682 The @code{step} command only stops at the first instruction of a source
4683 line. This prevents the multiple stops that could otherwise occur in
4684 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4685 to stop if a function that has debugging information is called within
4686 the line. In other words, @code{step} @emph{steps inside} any functions
4687 called within the line.
4689 Also, the @code{step} command only enters a function if there is line
4690 number information for the function. Otherwise it acts like the
4691 @code{next} command. This avoids problems when using @code{cc -gl}
4692 on MIPS machines. Previously, @code{step} entered subroutines if there
4693 was any debugging information about the routine.
4695 @item step @var{count}
4696 Continue running as in @code{step}, but do so @var{count} times. If a
4697 breakpoint is reached, or a signal not related to stepping occurs before
4698 @var{count} steps, stepping stops right away.
4701 @kindex n @r{(@code{next})}
4702 @item next @r{[}@var{count}@r{]}
4703 Continue to the next source line in the current (innermost) stack frame.
4704 This is similar to @code{step}, but function calls that appear within
4705 the line of code are executed without stopping. Execution stops when
4706 control reaches a different line of code at the original stack level
4707 that was executing when you gave the @code{next} command. This command
4708 is abbreviated @code{n}.
4710 An argument @var{count} is a repeat count, as for @code{step}.
4713 @c FIX ME!! Do we delete this, or is there a way it fits in with
4714 @c the following paragraph? --- Vctoria
4716 @c @code{next} within a function that lacks debugging information acts like
4717 @c @code{step}, but any function calls appearing within the code of the
4718 @c function are executed without stopping.
4720 The @code{next} command only stops at the first instruction of a
4721 source line. This prevents multiple stops that could otherwise occur in
4722 @code{switch} statements, @code{for} loops, etc.
4724 @kindex set step-mode
4726 @cindex functions without line info, and stepping
4727 @cindex stepping into functions with no line info
4728 @itemx set step-mode on
4729 The @code{set step-mode on} command causes the @code{step} command to
4730 stop at the first instruction of a function which contains no debug line
4731 information rather than stepping over it.
4733 This is useful in cases where you may be interested in inspecting the
4734 machine instructions of a function which has no symbolic info and do not
4735 want @value{GDBN} to automatically skip over this function.
4737 @item set step-mode off
4738 Causes the @code{step} command to step over any functions which contains no
4739 debug information. This is the default.
4741 @item show step-mode
4742 Show whether @value{GDBN} will stop in or step over functions without
4743 source line debug information.
4746 @kindex fin @r{(@code{finish})}
4748 Continue running until just after function in the selected stack frame
4749 returns. Print the returned value (if any). This command can be
4750 abbreviated as @code{fin}.
4752 Contrast this with the @code{return} command (@pxref{Returning,
4753 ,Returning from a Function}).
4756 @kindex u @r{(@code{until})}
4757 @cindex run until specified location
4760 Continue running until a source line past the current line, in the
4761 current stack frame, is reached. This command is used to avoid single
4762 stepping through a loop more than once. It is like the @code{next}
4763 command, except that when @code{until} encounters a jump, it
4764 automatically continues execution until the program counter is greater
4765 than the address of the jump.
4767 This means that when you reach the end of a loop after single stepping
4768 though it, @code{until} makes your program continue execution until it
4769 exits the loop. In contrast, a @code{next} command at the end of a loop
4770 simply steps back to the beginning of the loop, which forces you to step
4771 through the next iteration.
4773 @code{until} always stops your program if it attempts to exit the current
4776 @code{until} may produce somewhat counterintuitive results if the order
4777 of machine code does not match the order of the source lines. For
4778 example, in the following excerpt from a debugging session, the @code{f}
4779 (@code{frame}) command shows that execution is stopped at line
4780 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4784 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4786 (@value{GDBP}) until
4787 195 for ( ; argc > 0; NEXTARG) @{
4790 This happened because, for execution efficiency, the compiler had
4791 generated code for the loop closure test at the end, rather than the
4792 start, of the loop---even though the test in a C @code{for}-loop is
4793 written before the body of the loop. The @code{until} command appeared
4794 to step back to the beginning of the loop when it advanced to this
4795 expression; however, it has not really gone to an earlier
4796 statement---not in terms of the actual machine code.
4798 @code{until} with no argument works by means of single
4799 instruction stepping, and hence is slower than @code{until} with an
4802 @item until @var{location}
4803 @itemx u @var{location}
4804 Continue running your program until either the specified location is
4805 reached, or the current stack frame returns. @var{location} is any of
4806 the forms described in @ref{Specify Location}.
4807 This form of the command uses temporary breakpoints, and
4808 hence is quicker than @code{until} without an argument. The specified
4809 location is actually reached only if it is in the current frame. This
4810 implies that @code{until} can be used to skip over recursive function
4811 invocations. For instance in the code below, if the current location is
4812 line @code{96}, issuing @code{until 99} will execute the program up to
4813 line @code{99} in the same invocation of factorial, i.e., after the inner
4814 invocations have returned.
4817 94 int factorial (int value)
4819 96 if (value > 1) @{
4820 97 value *= factorial (value - 1);
4827 @kindex advance @var{location}
4828 @itemx advance @var{location}
4829 Continue running the program up to the given @var{location}. An argument is
4830 required, which should be of one of the forms described in
4831 @ref{Specify Location}.
4832 Execution will also stop upon exit from the current stack
4833 frame. This command is similar to @code{until}, but @code{advance} will
4834 not skip over recursive function calls, and the target location doesn't
4835 have to be in the same frame as the current one.
4839 @kindex si @r{(@code{stepi})}
4841 @itemx stepi @var{arg}
4843 Execute one machine instruction, then stop and return to the debugger.
4845 It is often useful to do @samp{display/i $pc} when stepping by machine
4846 instructions. This makes @value{GDBN} automatically display the next
4847 instruction to be executed, each time your program stops. @xref{Auto
4848 Display,, Automatic Display}.
4850 An argument is a repeat count, as in @code{step}.
4854 @kindex ni @r{(@code{nexti})}
4856 @itemx nexti @var{arg}
4858 Execute one machine instruction, but if it is a function call,
4859 proceed until the function returns.
4861 An argument is a repeat count, as in @code{next}.
4864 @node Skipping Over Functions and Files
4865 @section Skipping Over Functions and Files
4866 @cindex skipping over functions and files
4868 The program you are debugging may contain some functions which are
4869 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4870 skip a function or all functions in a file when stepping.
4872 For example, consider the following C function:
4883 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4884 are not interested in stepping through @code{boring}. If you run @code{step}
4885 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4886 step over both @code{foo} and @code{boring}!
4888 One solution is to @code{step} into @code{boring} and use the @code{finish}
4889 command to immediately exit it. But this can become tedious if @code{boring}
4890 is called from many places.
4892 A more flexible solution is to execute @kbd{skip boring}. This instructs
4893 @value{GDBN} never to step into @code{boring}. Now when you execute
4894 @code{step} at line 103, you'll step over @code{boring} and directly into
4897 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4898 example, @code{skip file boring.c}.
4901 @kindex skip function
4902 @item skip @r{[}@var{linespec}@r{]}
4903 @itemx skip function @r{[}@var{linespec}@r{]}
4904 After running this command, the function named by @var{linespec} or the
4905 function containing the line named by @var{linespec} will be skipped over when
4906 stepping. @xref{Specify Location}.
4908 If you do not specify @var{linespec}, the function you're currently debugging
4911 (If you have a function called @code{file} that you want to skip, use
4912 @kbd{skip function file}.)
4915 @item skip file @r{[}@var{filename}@r{]}
4916 After running this command, any function whose source lives in @var{filename}
4917 will be skipped over when stepping.
4919 If you do not specify @var{filename}, functions whose source lives in the file
4920 you're currently debugging will be skipped.
4923 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4924 These are the commands for managing your list of skips:
4928 @item info skip @r{[}@var{range}@r{]}
4929 Print details about the specified skip(s). If @var{range} is not specified,
4930 print a table with details about all functions and files marked for skipping.
4931 @code{info skip} prints the following information about each skip:
4935 A number identifying this skip.
4937 The type of this skip, either @samp{function} or @samp{file}.
4938 @item Enabled or Disabled
4939 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4941 For function skips, this column indicates the address in memory of the function
4942 being skipped. If you've set a function skip on a function which has not yet
4943 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4944 which has the function is loaded, @code{info skip} will show the function's
4947 For file skips, this field contains the filename being skipped. For functions
4948 skips, this field contains the function name and its line number in the file
4949 where it is defined.
4953 @item skip delete @r{[}@var{range}@r{]}
4954 Delete the specified skip(s). If @var{range} is not specified, delete all
4958 @item skip enable @r{[}@var{range}@r{]}
4959 Enable the specified skip(s). If @var{range} is not specified, enable all
4962 @kindex skip disable
4963 @item skip disable @r{[}@var{range}@r{]}
4964 Disable the specified skip(s). If @var{range} is not specified, disable all
4973 A signal is an asynchronous event that can happen in a program. The
4974 operating system defines the possible kinds of signals, and gives each
4975 kind a name and a number. For example, in Unix @code{SIGINT} is the
4976 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4977 @code{SIGSEGV} is the signal a program gets from referencing a place in
4978 memory far away from all the areas in use; @code{SIGALRM} occurs when
4979 the alarm clock timer goes off (which happens only if your program has
4980 requested an alarm).
4982 @cindex fatal signals
4983 Some signals, including @code{SIGALRM}, are a normal part of the
4984 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4985 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4986 program has not specified in advance some other way to handle the signal.
4987 @code{SIGINT} does not indicate an error in your program, but it is normally
4988 fatal so it can carry out the purpose of the interrupt: to kill the program.
4990 @value{GDBN} has the ability to detect any occurrence of a signal in your
4991 program. You can tell @value{GDBN} in advance what to do for each kind of
4994 @cindex handling signals
4995 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4996 @code{SIGALRM} be silently passed to your program
4997 (so as not to interfere with their role in the program's functioning)
4998 but to stop your program immediately whenever an error signal happens.
4999 You can change these settings with the @code{handle} command.
5002 @kindex info signals
5006 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5007 handle each one. You can use this to see the signal numbers of all
5008 the defined types of signals.
5010 @item info signals @var{sig}
5011 Similar, but print information only about the specified signal number.
5013 @code{info handle} is an alias for @code{info signals}.
5016 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5017 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5018 can be the number of a signal or its name (with or without the
5019 @samp{SIG} at the beginning); a list of signal numbers of the form
5020 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5021 known signals. Optional arguments @var{keywords}, described below,
5022 say what change to make.
5026 The keywords allowed by the @code{handle} command can be abbreviated.
5027 Their full names are:
5031 @value{GDBN} should not stop your program when this signal happens. It may
5032 still print a message telling you that the signal has come in.
5035 @value{GDBN} should stop your program when this signal happens. This implies
5036 the @code{print} keyword as well.
5039 @value{GDBN} should print a message when this signal happens.
5042 @value{GDBN} should not mention the occurrence of the signal at all. This
5043 implies the @code{nostop} keyword as well.
5047 @value{GDBN} should allow your program to see this signal; your program
5048 can handle the signal, or else it may terminate if the signal is fatal
5049 and not handled. @code{pass} and @code{noignore} are synonyms.
5053 @value{GDBN} should not allow your program to see this signal.
5054 @code{nopass} and @code{ignore} are synonyms.
5058 When a signal stops your program, the signal is not visible to the
5060 continue. Your program sees the signal then, if @code{pass} is in
5061 effect for the signal in question @emph{at that time}. In other words,
5062 after @value{GDBN} reports a signal, you can use the @code{handle}
5063 command with @code{pass} or @code{nopass} to control whether your
5064 program sees that signal when you continue.
5066 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5067 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5068 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5071 You can also use the @code{signal} command to prevent your program from
5072 seeing a signal, or cause it to see a signal it normally would not see,
5073 or to give it any signal at any time. For example, if your program stopped
5074 due to some sort of memory reference error, you might store correct
5075 values into the erroneous variables and continue, hoping to see more
5076 execution; but your program would probably terminate immediately as
5077 a result of the fatal signal once it saw the signal. To prevent this,
5078 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5081 @cindex extra signal information
5082 @anchor{extra signal information}
5084 On some targets, @value{GDBN} can inspect extra signal information
5085 associated with the intercepted signal, before it is actually
5086 delivered to the program being debugged. This information is exported
5087 by the convenience variable @code{$_siginfo}, and consists of data
5088 that is passed by the kernel to the signal handler at the time of the
5089 receipt of a signal. The data type of the information itself is
5090 target dependent. You can see the data type using the @code{ptype
5091 $_siginfo} command. On Unix systems, it typically corresponds to the
5092 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5095 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5096 referenced address that raised a segmentation fault.
5100 (@value{GDBP}) continue
5101 Program received signal SIGSEGV, Segmentation fault.
5102 0x0000000000400766 in main ()
5104 (@value{GDBP}) ptype $_siginfo
5111 struct @{...@} _kill;
5112 struct @{...@} _timer;
5114 struct @{...@} _sigchld;
5115 struct @{...@} _sigfault;
5116 struct @{...@} _sigpoll;
5119 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5123 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5124 $1 = (void *) 0x7ffff7ff7000
5128 Depending on target support, @code{$_siginfo} may also be writable.
5131 @section Stopping and Starting Multi-thread Programs
5133 @cindex stopped threads
5134 @cindex threads, stopped
5136 @cindex continuing threads
5137 @cindex threads, continuing
5139 @value{GDBN} supports debugging programs with multiple threads
5140 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5141 are two modes of controlling execution of your program within the
5142 debugger. In the default mode, referred to as @dfn{all-stop mode},
5143 when any thread in your program stops (for example, at a breakpoint
5144 or while being stepped), all other threads in the program are also stopped by
5145 @value{GDBN}. On some targets, @value{GDBN} also supports
5146 @dfn{non-stop mode}, in which other threads can continue to run freely while
5147 you examine the stopped thread in the debugger.
5150 * All-Stop Mode:: All threads stop when GDB takes control
5151 * Non-Stop Mode:: Other threads continue to execute
5152 * Background Execution:: Running your program asynchronously
5153 * Thread-Specific Breakpoints:: Controlling breakpoints
5154 * Interrupted System Calls:: GDB may interfere with system calls
5155 * Observer Mode:: GDB does not alter program behavior
5159 @subsection All-Stop Mode
5161 @cindex all-stop mode
5163 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5164 @emph{all} threads of execution stop, not just the current thread. This
5165 allows you to examine the overall state of the program, including
5166 switching between threads, without worrying that things may change
5169 Conversely, whenever you restart the program, @emph{all} threads start
5170 executing. @emph{This is true even when single-stepping} with commands
5171 like @code{step} or @code{next}.
5173 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5174 Since thread scheduling is up to your debugging target's operating
5175 system (not controlled by @value{GDBN}), other threads may
5176 execute more than one statement while the current thread completes a
5177 single step. Moreover, in general other threads stop in the middle of a
5178 statement, rather than at a clean statement boundary, when the program
5181 You might even find your program stopped in another thread after
5182 continuing or even single-stepping. This happens whenever some other
5183 thread runs into a breakpoint, a signal, or an exception before the
5184 first thread completes whatever you requested.
5186 @cindex automatic thread selection
5187 @cindex switching threads automatically
5188 @cindex threads, automatic switching
5189 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5190 signal, it automatically selects the thread where that breakpoint or
5191 signal happened. @value{GDBN} alerts you to the context switch with a
5192 message such as @samp{[Switching to Thread @var{n}]} to identify the
5195 On some OSes, you can modify @value{GDBN}'s default behavior by
5196 locking the OS scheduler to allow only a single thread to run.
5199 @item set scheduler-locking @var{mode}
5200 @cindex scheduler locking mode
5201 @cindex lock scheduler
5202 Set the scheduler locking mode. If it is @code{off}, then there is no
5203 locking and any thread may run at any time. If @code{on}, then only the
5204 current thread may run when the inferior is resumed. The @code{step}
5205 mode optimizes for single-stepping; it prevents other threads
5206 from preempting the current thread while you are stepping, so that
5207 the focus of debugging does not change unexpectedly.
5208 Other threads only rarely (or never) get a chance to run
5209 when you step. They are more likely to run when you @samp{next} over a
5210 function call, and they are completely free to run when you use commands
5211 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5212 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5213 the current thread away from the thread that you are debugging.
5215 @item show scheduler-locking
5216 Display the current scheduler locking mode.
5219 @cindex resume threads of multiple processes simultaneously
5220 By default, when you issue one of the execution commands such as
5221 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5222 threads of the current inferior to run. For example, if @value{GDBN}
5223 is attached to two inferiors, each with two threads, the
5224 @code{continue} command resumes only the two threads of the current
5225 inferior. This is useful, for example, when you debug a program that
5226 forks and you want to hold the parent stopped (so that, for instance,
5227 it doesn't run to exit), while you debug the child. In other
5228 situations, you may not be interested in inspecting the current state
5229 of any of the processes @value{GDBN} is attached to, and you may want
5230 to resume them all until some breakpoint is hit. In the latter case,
5231 you can instruct @value{GDBN} to allow all threads of all the
5232 inferiors to run with the @w{@code{set schedule-multiple}} command.
5235 @kindex set schedule-multiple
5236 @item set schedule-multiple
5237 Set the mode for allowing threads of multiple processes to be resumed
5238 when an execution command is issued. When @code{on}, all threads of
5239 all processes are allowed to run. When @code{off}, only the threads
5240 of the current process are resumed. The default is @code{off}. The
5241 @code{scheduler-locking} mode takes precedence when set to @code{on},
5242 or while you are stepping and set to @code{step}.
5244 @item show schedule-multiple
5245 Display the current mode for resuming the execution of threads of
5250 @subsection Non-Stop Mode
5252 @cindex non-stop mode
5254 @c This section is really only a place-holder, and needs to be expanded
5255 @c with more details.
5257 For some multi-threaded targets, @value{GDBN} supports an optional
5258 mode of operation in which you can examine stopped program threads in
5259 the debugger while other threads continue to execute freely. This
5260 minimizes intrusion when debugging live systems, such as programs
5261 where some threads have real-time constraints or must continue to
5262 respond to external events. This is referred to as @dfn{non-stop} mode.
5264 In non-stop mode, when a thread stops to report a debugging event,
5265 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5266 threads as well, in contrast to the all-stop mode behavior. Additionally,
5267 execution commands such as @code{continue} and @code{step} apply by default
5268 only to the current thread in non-stop mode, rather than all threads as
5269 in all-stop mode. This allows you to control threads explicitly in
5270 ways that are not possible in all-stop mode --- for example, stepping
5271 one thread while allowing others to run freely, stepping
5272 one thread while holding all others stopped, or stepping several threads
5273 independently and simultaneously.
5275 To enter non-stop mode, use this sequence of commands before you run
5276 or attach to your program:
5279 # Enable the async interface.
5282 # If using the CLI, pagination breaks non-stop.
5285 # Finally, turn it on!
5289 You can use these commands to manipulate the non-stop mode setting:
5292 @kindex set non-stop
5293 @item set non-stop on
5294 Enable selection of non-stop mode.
5295 @item set non-stop off
5296 Disable selection of non-stop mode.
5297 @kindex show non-stop
5299 Show the current non-stop enablement setting.
5302 Note these commands only reflect whether non-stop mode is enabled,
5303 not whether the currently-executing program is being run in non-stop mode.
5304 In particular, the @code{set non-stop} preference is only consulted when
5305 @value{GDBN} starts or connects to the target program, and it is generally
5306 not possible to switch modes once debugging has started. Furthermore,
5307 since not all targets support non-stop mode, even when you have enabled
5308 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5311 In non-stop mode, all execution commands apply only to the current thread
5312 by default. That is, @code{continue} only continues one thread.
5313 To continue all threads, issue @code{continue -a} or @code{c -a}.
5315 You can use @value{GDBN}'s background execution commands
5316 (@pxref{Background Execution}) to run some threads in the background
5317 while you continue to examine or step others from @value{GDBN}.
5318 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5319 always executed asynchronously in non-stop mode.
5321 Suspending execution is done with the @code{interrupt} command when
5322 running in the background, or @kbd{Ctrl-c} during foreground execution.
5323 In all-stop mode, this stops the whole process;
5324 but in non-stop mode the interrupt applies only to the current thread.
5325 To stop the whole program, use @code{interrupt -a}.
5327 Other execution commands do not currently support the @code{-a} option.
5329 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5330 that thread current, as it does in all-stop mode. This is because the
5331 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5332 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5333 changed to a different thread just as you entered a command to operate on the
5334 previously current thread.
5336 @node Background Execution
5337 @subsection Background Execution
5339 @cindex foreground execution
5340 @cindex background execution
5341 @cindex asynchronous execution
5342 @cindex execution, foreground, background and asynchronous
5344 @value{GDBN}'s execution commands have two variants: the normal
5345 foreground (synchronous) behavior, and a background
5346 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5347 the program to report that some thread has stopped before prompting for
5348 another command. In background execution, @value{GDBN} immediately gives
5349 a command prompt so that you can issue other commands while your program runs.
5351 You need to explicitly enable asynchronous mode before you can use
5352 background execution commands. You can use these commands to
5353 manipulate the asynchronous mode setting:
5356 @kindex set target-async
5357 @item set target-async on
5358 Enable asynchronous mode.
5359 @item set target-async off
5360 Disable asynchronous mode.
5361 @kindex show target-async
5362 @item show target-async
5363 Show the current target-async setting.
5366 If the target doesn't support async mode, @value{GDBN} issues an error
5367 message if you attempt to use the background execution commands.
5369 To specify background execution, add a @code{&} to the command. For example,
5370 the background form of the @code{continue} command is @code{continue&}, or
5371 just @code{c&}. The execution commands that accept background execution
5377 @xref{Starting, , Starting your Program}.
5381 @xref{Attach, , Debugging an Already-running Process}.
5385 @xref{Continuing and Stepping, step}.
5389 @xref{Continuing and Stepping, stepi}.
5393 @xref{Continuing and Stepping, next}.
5397 @xref{Continuing and Stepping, nexti}.
5401 @xref{Continuing and Stepping, continue}.
5405 @xref{Continuing and Stepping, finish}.
5409 @xref{Continuing and Stepping, until}.
5413 Background execution is especially useful in conjunction with non-stop
5414 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5415 However, you can also use these commands in the normal all-stop mode with
5416 the restriction that you cannot issue another execution command until the
5417 previous one finishes. Examples of commands that are valid in all-stop
5418 mode while the program is running include @code{help} and @code{info break}.
5420 You can interrupt your program while it is running in the background by
5421 using the @code{interrupt} command.
5428 Suspend execution of the running program. In all-stop mode,
5429 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5430 only the current thread. To stop the whole program in non-stop mode,
5431 use @code{interrupt -a}.
5434 @node Thread-Specific Breakpoints
5435 @subsection Thread-Specific Breakpoints
5437 When your program has multiple threads (@pxref{Threads,, Debugging
5438 Programs with Multiple Threads}), you can choose whether to set
5439 breakpoints on all threads, or on a particular thread.
5442 @cindex breakpoints and threads
5443 @cindex thread breakpoints
5444 @kindex break @dots{} thread @var{threadno}
5445 @item break @var{linespec} thread @var{threadno}
5446 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5447 @var{linespec} specifies source lines; there are several ways of
5448 writing them (@pxref{Specify Location}), but the effect is always to
5449 specify some source line.
5451 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5452 to specify that you only want @value{GDBN} to stop the program when a
5453 particular thread reaches this breakpoint. @var{threadno} is one of the
5454 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5455 column of the @samp{info threads} display.
5457 If you do not specify @samp{thread @var{threadno}} when you set a
5458 breakpoint, the breakpoint applies to @emph{all} threads of your
5461 You can use the @code{thread} qualifier on conditional breakpoints as
5462 well; in this case, place @samp{thread @var{threadno}} before or
5463 after the breakpoint condition, like this:
5466 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5471 @node Interrupted System Calls
5472 @subsection Interrupted System Calls
5474 @cindex thread breakpoints and system calls
5475 @cindex system calls and thread breakpoints
5476 @cindex premature return from system calls
5477 There is an unfortunate side effect when using @value{GDBN} to debug
5478 multi-threaded programs. If one thread stops for a
5479 breakpoint, or for some other reason, and another thread is blocked in a
5480 system call, then the system call may return prematurely. This is a
5481 consequence of the interaction between multiple threads and the signals
5482 that @value{GDBN} uses to implement breakpoints and other events that
5485 To handle this problem, your program should check the return value of
5486 each system call and react appropriately. This is good programming
5489 For example, do not write code like this:
5495 The call to @code{sleep} will return early if a different thread stops
5496 at a breakpoint or for some other reason.
5498 Instead, write this:
5503 unslept = sleep (unslept);
5506 A system call is allowed to return early, so the system is still
5507 conforming to its specification. But @value{GDBN} does cause your
5508 multi-threaded program to behave differently than it would without
5511 Also, @value{GDBN} uses internal breakpoints in the thread library to
5512 monitor certain events such as thread creation and thread destruction.
5513 When such an event happens, a system call in another thread may return
5514 prematurely, even though your program does not appear to stop.
5517 @subsection Observer Mode
5519 If you want to build on non-stop mode and observe program behavior
5520 without any chance of disruption by @value{GDBN}, you can set
5521 variables to disable all of the debugger's attempts to modify state,
5522 whether by writing memory, inserting breakpoints, etc. These operate
5523 at a low level, intercepting operations from all commands.
5525 When all of these are set to @code{off}, then @value{GDBN} is said to
5526 be @dfn{observer mode}. As a convenience, the variable
5527 @code{observer} can be set to disable these, plus enable non-stop
5530 Note that @value{GDBN} will not prevent you from making nonsensical
5531 combinations of these settings. For instance, if you have enabled
5532 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5533 then breakpoints that work by writing trap instructions into the code
5534 stream will still not be able to be placed.
5539 @item set observer on
5540 @itemx set observer off
5541 When set to @code{on}, this disables all the permission variables
5542 below (except for @code{insert-fast-tracepoints}), plus enables
5543 non-stop debugging. Setting this to @code{off} switches back to
5544 normal debugging, though remaining in non-stop mode.
5547 Show whether observer mode is on or off.
5549 @kindex may-write-registers
5550 @item set may-write-registers on
5551 @itemx set may-write-registers off
5552 This controls whether @value{GDBN} will attempt to alter the values of
5553 registers, such as with assignment expressions in @code{print}, or the
5554 @code{jump} command. It defaults to @code{on}.
5556 @item show may-write-registers
5557 Show the current permission to write registers.
5559 @kindex may-write-memory
5560 @item set may-write-memory on
5561 @itemx set may-write-memory off
5562 This controls whether @value{GDBN} will attempt to alter the contents
5563 of memory, such as with assignment expressions in @code{print}. It
5564 defaults to @code{on}.
5566 @item show may-write-memory
5567 Show the current permission to write memory.
5569 @kindex may-insert-breakpoints
5570 @item set may-insert-breakpoints on
5571 @itemx set may-insert-breakpoints off
5572 This controls whether @value{GDBN} will attempt to insert breakpoints.
5573 This affects all breakpoints, including internal breakpoints defined
5574 by @value{GDBN}. It defaults to @code{on}.
5576 @item show may-insert-breakpoints
5577 Show the current permission to insert breakpoints.
5579 @kindex may-insert-tracepoints
5580 @item set may-insert-tracepoints on
5581 @itemx set may-insert-tracepoints off
5582 This controls whether @value{GDBN} will attempt to insert (regular)
5583 tracepoints at the beginning of a tracing experiment. It affects only
5584 non-fast tracepoints, fast tracepoints being under the control of
5585 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5587 @item show may-insert-tracepoints
5588 Show the current permission to insert tracepoints.
5590 @kindex may-insert-fast-tracepoints
5591 @item set may-insert-fast-tracepoints on
5592 @itemx set may-insert-fast-tracepoints off
5593 This controls whether @value{GDBN} will attempt to insert fast
5594 tracepoints at the beginning of a tracing experiment. It affects only
5595 fast tracepoints, regular (non-fast) tracepoints being under the
5596 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5598 @item show may-insert-fast-tracepoints
5599 Show the current permission to insert fast tracepoints.
5601 @kindex may-interrupt
5602 @item set may-interrupt on
5603 @itemx set may-interrupt off
5604 This controls whether @value{GDBN} will attempt to interrupt or stop
5605 program execution. When this variable is @code{off}, the
5606 @code{interrupt} command will have no effect, nor will
5607 @kbd{Ctrl-c}. It defaults to @code{on}.
5609 @item show may-interrupt
5610 Show the current permission to interrupt or stop the program.
5614 @node Reverse Execution
5615 @chapter Running programs backward
5616 @cindex reverse execution
5617 @cindex running programs backward
5619 When you are debugging a program, it is not unusual to realize that
5620 you have gone too far, and some event of interest has already happened.
5621 If the target environment supports it, @value{GDBN} can allow you to
5622 ``rewind'' the program by running it backward.
5624 A target environment that supports reverse execution should be able
5625 to ``undo'' the changes in machine state that have taken place as the
5626 program was executing normally. Variables, registers etc.@: should
5627 revert to their previous values. Obviously this requires a great
5628 deal of sophistication on the part of the target environment; not
5629 all target environments can support reverse execution.
5631 When a program is executed in reverse, the instructions that
5632 have most recently been executed are ``un-executed'', in reverse
5633 order. The program counter runs backward, following the previous
5634 thread of execution in reverse. As each instruction is ``un-executed'',
5635 the values of memory and/or registers that were changed by that
5636 instruction are reverted to their previous states. After executing
5637 a piece of source code in reverse, all side effects of that code
5638 should be ``undone'', and all variables should be returned to their
5639 prior values@footnote{
5640 Note that some side effects are easier to undo than others. For instance,
5641 memory and registers are relatively easy, but device I/O is hard. Some
5642 targets may be able undo things like device I/O, and some may not.
5644 The contract between @value{GDBN} and the reverse executing target
5645 requires only that the target do something reasonable when
5646 @value{GDBN} tells it to execute backwards, and then report the
5647 results back to @value{GDBN}. Whatever the target reports back to
5648 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5649 assumes that the memory and registers that the target reports are in a
5650 consistant state, but @value{GDBN} accepts whatever it is given.
5653 If you are debugging in a target environment that supports
5654 reverse execution, @value{GDBN} provides the following commands.
5657 @kindex reverse-continue
5658 @kindex rc @r{(@code{reverse-continue})}
5659 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5660 @itemx rc @r{[}@var{ignore-count}@r{]}
5661 Beginning at the point where your program last stopped, start executing
5662 in reverse. Reverse execution will stop for breakpoints and synchronous
5663 exceptions (signals), just like normal execution. Behavior of
5664 asynchronous signals depends on the target environment.
5666 @kindex reverse-step
5667 @kindex rs @r{(@code{step})}
5668 @item reverse-step @r{[}@var{count}@r{]}
5669 Run the program backward until control reaches the start of a
5670 different source line; then stop it, and return control to @value{GDBN}.
5672 Like the @code{step} command, @code{reverse-step} will only stop
5673 at the beginning of a source line. It ``un-executes'' the previously
5674 executed source line. If the previous source line included calls to
5675 debuggable functions, @code{reverse-step} will step (backward) into
5676 the called function, stopping at the beginning of the @emph{last}
5677 statement in the called function (typically a return statement).
5679 Also, as with the @code{step} command, if non-debuggable functions are
5680 called, @code{reverse-step} will run thru them backward without stopping.
5682 @kindex reverse-stepi
5683 @kindex rsi @r{(@code{reverse-stepi})}
5684 @item reverse-stepi @r{[}@var{count}@r{]}
5685 Reverse-execute one machine instruction. Note that the instruction
5686 to be reverse-executed is @emph{not} the one pointed to by the program
5687 counter, but the instruction executed prior to that one. For instance,
5688 if the last instruction was a jump, @code{reverse-stepi} will take you
5689 back from the destination of the jump to the jump instruction itself.
5691 @kindex reverse-next
5692 @kindex rn @r{(@code{reverse-next})}
5693 @item reverse-next @r{[}@var{count}@r{]}
5694 Run backward to the beginning of the previous line executed in
5695 the current (innermost) stack frame. If the line contains function
5696 calls, they will be ``un-executed'' without stopping. Starting from
5697 the first line of a function, @code{reverse-next} will take you back
5698 to the caller of that function, @emph{before} the function was called,
5699 just as the normal @code{next} command would take you from the last
5700 line of a function back to its return to its caller
5701 @footnote{Unless the code is too heavily optimized.}.
5703 @kindex reverse-nexti
5704 @kindex rni @r{(@code{reverse-nexti})}
5705 @item reverse-nexti @r{[}@var{count}@r{]}
5706 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5707 in reverse, except that called functions are ``un-executed'' atomically.
5708 That is, if the previously executed instruction was a return from
5709 another function, @code{reverse-nexti} will continue to execute
5710 in reverse until the call to that function (from the current stack
5713 @kindex reverse-finish
5714 @item reverse-finish
5715 Just as the @code{finish} command takes you to the point where the
5716 current function returns, @code{reverse-finish} takes you to the point
5717 where it was called. Instead of ending up at the end of the current
5718 function invocation, you end up at the beginning.
5720 @kindex set exec-direction
5721 @item set exec-direction
5722 Set the direction of target execution.
5723 @itemx set exec-direction reverse
5724 @cindex execute forward or backward in time
5725 @value{GDBN} will perform all execution commands in reverse, until the
5726 exec-direction mode is changed to ``forward''. Affected commands include
5727 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5728 command cannot be used in reverse mode.
5729 @item set exec-direction forward
5730 @value{GDBN} will perform all execution commands in the normal fashion.
5731 This is the default.
5735 @node Process Record and Replay
5736 @chapter Recording Inferior's Execution and Replaying It
5737 @cindex process record and replay
5738 @cindex recording inferior's execution and replaying it
5740 On some platforms, @value{GDBN} provides a special @dfn{process record
5741 and replay} target that can record a log of the process execution, and
5742 replay it later with both forward and reverse execution commands.
5745 When this target is in use, if the execution log includes the record
5746 for the next instruction, @value{GDBN} will debug in @dfn{replay
5747 mode}. In the replay mode, the inferior does not really execute code
5748 instructions. Instead, all the events that normally happen during
5749 code execution are taken from the execution log. While code is not
5750 really executed in replay mode, the values of registers (including the
5751 program counter register) and the memory of the inferior are still
5752 changed as they normally would. Their contents are taken from the
5756 If the record for the next instruction is not in the execution log,
5757 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5758 inferior executes normally, and @value{GDBN} records the execution log
5761 The process record and replay target supports reverse execution
5762 (@pxref{Reverse Execution}), even if the platform on which the
5763 inferior runs does not. However, the reverse execution is limited in
5764 this case by the range of the instructions recorded in the execution
5765 log. In other words, reverse execution on platforms that don't
5766 support it directly can only be done in the replay mode.
5768 When debugging in the reverse direction, @value{GDBN} will work in
5769 replay mode as long as the execution log includes the record for the
5770 previous instruction; otherwise, it will work in record mode, if the
5771 platform supports reverse execution, or stop if not.
5773 For architecture environments that support process record and replay,
5774 @value{GDBN} provides the following commands:
5777 @kindex target record
5781 This command starts the process record and replay target. The process
5782 record and replay target can only debug a process that is already
5783 running. Therefore, you need first to start the process with the
5784 @kbd{run} or @kbd{start} commands, and then start the recording with
5785 the @kbd{target record} command.
5787 Both @code{record} and @code{rec} are aliases of @code{target record}.
5789 @cindex displaced stepping, and process record and replay
5790 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5791 will be automatically disabled when process record and replay target
5792 is started. That's because the process record and replay target
5793 doesn't support displaced stepping.
5795 @cindex non-stop mode, and process record and replay
5796 @cindex asynchronous execution, and process record and replay
5797 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5798 the asynchronous execution mode (@pxref{Background Execution}), the
5799 process record and replay target cannot be started because it doesn't
5800 support these two modes.
5805 Stop the process record and replay target. When process record and
5806 replay target stops, the entire execution log will be deleted and the
5807 inferior will either be terminated, or will remain in its final state.
5809 When you stop the process record and replay target in record mode (at
5810 the end of the execution log), the inferior will be stopped at the
5811 next instruction that would have been recorded. In other words, if
5812 you record for a while and then stop recording, the inferior process
5813 will be left in the same state as if the recording never happened.
5815 On the other hand, if the process record and replay target is stopped
5816 while in replay mode (that is, not at the end of the execution log,
5817 but at some earlier point), the inferior process will become ``live''
5818 at that earlier state, and it will then be possible to continue the
5819 usual ``live'' debugging of the process from that state.
5821 When the inferior process exits, or @value{GDBN} detaches from it,
5822 process record and replay target will automatically stop itself.
5825 @item record save @var{filename}
5826 Save the execution log to a file @file{@var{filename}}.
5827 Default filename is @file{gdb_record.@var{process_id}}, where
5828 @var{process_id} is the process ID of the inferior.
5830 @kindex record restore
5831 @item record restore @var{filename}
5832 Restore the execution log from a file @file{@var{filename}}.
5833 File must have been created with @code{record save}.
5835 @kindex set record insn-number-max
5836 @item set record insn-number-max @var{limit}
5837 Set the limit of instructions to be recorded. Default value is 200000.
5839 If @var{limit} is a positive number, then @value{GDBN} will start
5840 deleting instructions from the log once the number of the record
5841 instructions becomes greater than @var{limit}. For every new recorded
5842 instruction, @value{GDBN} will delete the earliest recorded
5843 instruction to keep the number of recorded instructions at the limit.
5844 (Since deleting recorded instructions loses information, @value{GDBN}
5845 lets you control what happens when the limit is reached, by means of
5846 the @code{stop-at-limit} option, described below.)
5848 If @var{limit} is zero, @value{GDBN} will never delete recorded
5849 instructions from the execution log. The number of recorded
5850 instructions is unlimited in this case.
5852 @kindex show record insn-number-max
5853 @item show record insn-number-max
5854 Show the limit of instructions to be recorded.
5856 @kindex set record stop-at-limit
5857 @item set record stop-at-limit
5858 Control the behavior when the number of recorded instructions reaches
5859 the limit. If ON (the default), @value{GDBN} will stop when the limit
5860 is reached for the first time and ask you whether you want to stop the
5861 inferior or continue running it and recording the execution log. If
5862 you decide to continue recording, each new recorded instruction will
5863 cause the oldest one to be deleted.
5865 If this option is OFF, @value{GDBN} will automatically delete the
5866 oldest record to make room for each new one, without asking.
5868 @kindex show record stop-at-limit
5869 @item show record stop-at-limit
5870 Show the current setting of @code{stop-at-limit}.
5872 @kindex set record memory-query
5873 @item set record memory-query
5874 Control the behavior when @value{GDBN} is unable to record memory
5875 changes caused by an instruction. If ON, @value{GDBN} will query
5876 whether to stop the inferior in that case.
5878 If this option is OFF (the default), @value{GDBN} will automatically
5879 ignore the effect of such instructions on memory. Later, when
5880 @value{GDBN} replays this execution log, it will mark the log of this
5881 instruction as not accessible, and it will not affect the replay
5884 @kindex show record memory-query
5885 @item show record memory-query
5886 Show the current setting of @code{memory-query}.
5890 Show various statistics about the state of process record and its
5891 in-memory execution log buffer, including:
5895 Whether in record mode or replay mode.
5897 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5899 Highest recorded instruction number.
5901 Current instruction about to be replayed (if in replay mode).
5903 Number of instructions contained in the execution log.
5905 Maximum number of instructions that may be contained in the execution log.
5908 @kindex record delete
5911 When record target runs in replay mode (``in the past''), delete the
5912 subsequent execution log and begin to record a new execution log starting
5913 from the current address. This means you will abandon the previously
5914 recorded ``future'' and begin recording a new ``future''.
5919 @chapter Examining the Stack
5921 When your program has stopped, the first thing you need to know is where it
5922 stopped and how it got there.
5925 Each time your program performs a function call, information about the call
5927 That information includes the location of the call in your program,
5928 the arguments of the call,
5929 and the local variables of the function being called.
5930 The information is saved in a block of data called a @dfn{stack frame}.
5931 The stack frames are allocated in a region of memory called the @dfn{call
5934 When your program stops, the @value{GDBN} commands for examining the
5935 stack allow you to see all of this information.
5937 @cindex selected frame
5938 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5939 @value{GDBN} commands refer implicitly to the selected frame. In
5940 particular, whenever you ask @value{GDBN} for the value of a variable in
5941 your program, the value is found in the selected frame. There are
5942 special @value{GDBN} commands to select whichever frame you are
5943 interested in. @xref{Selection, ,Selecting a Frame}.
5945 When your program stops, @value{GDBN} automatically selects the
5946 currently executing frame and describes it briefly, similar to the
5947 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5950 * Frames:: Stack frames
5951 * Backtrace:: Backtraces
5952 * Selection:: Selecting a frame
5953 * Frame Info:: Information on a frame
5958 @section Stack Frames
5960 @cindex frame, definition
5962 The call stack is divided up into contiguous pieces called @dfn{stack
5963 frames}, or @dfn{frames} for short; each frame is the data associated
5964 with one call to one function. The frame contains the arguments given
5965 to the function, the function's local variables, and the address at
5966 which the function is executing.
5968 @cindex initial frame
5969 @cindex outermost frame
5970 @cindex innermost frame
5971 When your program is started, the stack has only one frame, that of the
5972 function @code{main}. This is called the @dfn{initial} frame or the
5973 @dfn{outermost} frame. Each time a function is called, a new frame is
5974 made. Each time a function returns, the frame for that function invocation
5975 is eliminated. If a function is recursive, there can be many frames for
5976 the same function. The frame for the function in which execution is
5977 actually occurring is called the @dfn{innermost} frame. This is the most
5978 recently created of all the stack frames that still exist.
5980 @cindex frame pointer
5981 Inside your program, stack frames are identified by their addresses. A
5982 stack frame consists of many bytes, each of which has its own address; each
5983 kind of computer has a convention for choosing one byte whose
5984 address serves as the address of the frame. Usually this address is kept
5985 in a register called the @dfn{frame pointer register}
5986 (@pxref{Registers, $fp}) while execution is going on in that frame.
5988 @cindex frame number
5989 @value{GDBN} assigns numbers to all existing stack frames, starting with
5990 zero for the innermost frame, one for the frame that called it,
5991 and so on upward. These numbers do not really exist in your program;
5992 they are assigned by @value{GDBN} to give you a way of designating stack
5993 frames in @value{GDBN} commands.
5995 @c The -fomit-frame-pointer below perennially causes hbox overflow
5996 @c underflow problems.
5997 @cindex frameless execution
5998 Some compilers provide a way to compile functions so that they operate
5999 without stack frames. (For example, the @value{NGCC} option
6001 @samp{-fomit-frame-pointer}
6003 generates functions without a frame.)
6004 This is occasionally done with heavily used library functions to save
6005 the frame setup time. @value{GDBN} has limited facilities for dealing
6006 with these function invocations. If the innermost function invocation
6007 has no stack frame, @value{GDBN} nevertheless regards it as though
6008 it had a separate frame, which is numbered zero as usual, allowing
6009 correct tracing of the function call chain. However, @value{GDBN} has
6010 no provision for frameless functions elsewhere in the stack.
6013 @kindex frame@r{, command}
6014 @cindex current stack frame
6015 @item frame @var{args}
6016 The @code{frame} command allows you to move from one stack frame to another,
6017 and to print the stack frame you select. @var{args} may be either the
6018 address of the frame or the stack frame number. Without an argument,
6019 @code{frame} prints the current stack frame.
6021 @kindex select-frame
6022 @cindex selecting frame silently
6024 The @code{select-frame} command allows you to move from one stack frame
6025 to another without printing the frame. This is the silent version of
6033 @cindex call stack traces
6034 A backtrace is a summary of how your program got where it is. It shows one
6035 line per frame, for many frames, starting with the currently executing
6036 frame (frame zero), followed by its caller (frame one), and on up the
6041 @kindex bt @r{(@code{backtrace})}
6044 Print a backtrace of the entire stack: one line per frame for all
6045 frames in the stack.
6047 You can stop the backtrace at any time by typing the system interrupt
6048 character, normally @kbd{Ctrl-c}.
6050 @item backtrace @var{n}
6052 Similar, but print only the innermost @var{n} frames.
6054 @item backtrace -@var{n}
6056 Similar, but print only the outermost @var{n} frames.
6058 @item backtrace full
6060 @itemx bt full @var{n}
6061 @itemx bt full -@var{n}
6062 Print the values of the local variables also. @var{n} specifies the
6063 number of frames to print, as described above.
6068 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6069 are additional aliases for @code{backtrace}.
6071 @cindex multiple threads, backtrace
6072 In a multi-threaded program, @value{GDBN} by default shows the
6073 backtrace only for the current thread. To display the backtrace for
6074 several or all of the threads, use the command @code{thread apply}
6075 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6076 apply all backtrace}, @value{GDBN} will display the backtrace for all
6077 the threads; this is handy when you debug a core dump of a
6078 multi-threaded program.
6080 Each line in the backtrace shows the frame number and the function name.
6081 The program counter value is also shown---unless you use @code{set
6082 print address off}. The backtrace also shows the source file name and
6083 line number, as well as the arguments to the function. The program
6084 counter value is omitted if it is at the beginning of the code for that
6087 Here is an example of a backtrace. It was made with the command
6088 @samp{bt 3}, so it shows the innermost three frames.
6092 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6094 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6095 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6097 (More stack frames follow...)
6102 The display for frame zero does not begin with a program counter
6103 value, indicating that your program has stopped at the beginning of the
6104 code for line @code{993} of @code{builtin.c}.
6107 The value of parameter @code{data} in frame 1 has been replaced by
6108 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6109 only if it is a scalar (integer, pointer, enumeration, etc). See command
6110 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6111 on how to configure the way function parameter values are printed.
6113 @cindex optimized out, in backtrace
6114 @cindex function call arguments, optimized out
6115 If your program was compiled with optimizations, some compilers will
6116 optimize away arguments passed to functions if those arguments are
6117 never used after the call. Such optimizations generate code that
6118 passes arguments through registers, but doesn't store those arguments
6119 in the stack frame. @value{GDBN} has no way of displaying such
6120 arguments in stack frames other than the innermost one. Here's what
6121 such a backtrace might look like:
6125 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6127 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6128 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6130 (More stack frames follow...)
6135 The values of arguments that were not saved in their stack frames are
6136 shown as @samp{<optimized out>}.
6138 If you need to display the values of such optimized-out arguments,
6139 either deduce that from other variables whose values depend on the one
6140 you are interested in, or recompile without optimizations.
6142 @cindex backtrace beyond @code{main} function
6143 @cindex program entry point
6144 @cindex startup code, and backtrace
6145 Most programs have a standard user entry point---a place where system
6146 libraries and startup code transition into user code. For C this is
6147 @code{main}@footnote{
6148 Note that embedded programs (the so-called ``free-standing''
6149 environment) are not required to have a @code{main} function as the
6150 entry point. They could even have multiple entry points.}.
6151 When @value{GDBN} finds the entry function in a backtrace
6152 it will terminate the backtrace, to avoid tracing into highly
6153 system-specific (and generally uninteresting) code.
6155 If you need to examine the startup code, or limit the number of levels
6156 in a backtrace, you can change this behavior:
6159 @item set backtrace past-main
6160 @itemx set backtrace past-main on
6161 @kindex set backtrace
6162 Backtraces will continue past the user entry point.
6164 @item set backtrace past-main off
6165 Backtraces will stop when they encounter the user entry point. This is the
6168 @item show backtrace past-main
6169 @kindex show backtrace
6170 Display the current user entry point backtrace policy.
6172 @item set backtrace past-entry
6173 @itemx set backtrace past-entry on
6174 Backtraces will continue past the internal entry point of an application.
6175 This entry point is encoded by the linker when the application is built,
6176 and is likely before the user entry point @code{main} (or equivalent) is called.
6178 @item set backtrace past-entry off
6179 Backtraces will stop when they encounter the internal entry point of an
6180 application. This is the default.
6182 @item show backtrace past-entry
6183 Display the current internal entry point backtrace policy.
6185 @item set backtrace limit @var{n}
6186 @itemx set backtrace limit 0
6187 @cindex backtrace limit
6188 Limit the backtrace to @var{n} levels. A value of zero means
6191 @item show backtrace limit
6192 Display the current limit on backtrace levels.
6196 @section Selecting a Frame
6198 Most commands for examining the stack and other data in your program work on
6199 whichever stack frame is selected at the moment. Here are the commands for
6200 selecting a stack frame; all of them finish by printing a brief description
6201 of the stack frame just selected.
6204 @kindex frame@r{, selecting}
6205 @kindex f @r{(@code{frame})}
6208 Select frame number @var{n}. Recall that frame zero is the innermost
6209 (currently executing) frame, frame one is the frame that called the
6210 innermost one, and so on. The highest-numbered frame is the one for
6213 @item frame @var{addr}
6215 Select the frame at address @var{addr}. This is useful mainly if the
6216 chaining of stack frames has been damaged by a bug, making it
6217 impossible for @value{GDBN} to assign numbers properly to all frames. In
6218 addition, this can be useful when your program has multiple stacks and
6219 switches between them.
6221 On the SPARC architecture, @code{frame} needs two addresses to
6222 select an arbitrary frame: a frame pointer and a stack pointer.
6224 On the MIPS and Alpha architecture, it needs two addresses: a stack
6225 pointer and a program counter.
6227 On the 29k architecture, it needs three addresses: a register stack
6228 pointer, a program counter, and a memory stack pointer.
6232 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6233 advances toward the outermost frame, to higher frame numbers, to frames
6234 that have existed longer. @var{n} defaults to one.
6237 @kindex do @r{(@code{down})}
6239 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6240 advances toward the innermost frame, to lower frame numbers, to frames
6241 that were created more recently. @var{n} defaults to one. You may
6242 abbreviate @code{down} as @code{do}.
6245 All of these commands end by printing two lines of output describing the
6246 frame. The first line shows the frame number, the function name, the
6247 arguments, and the source file and line number of execution in that
6248 frame. The second line shows the text of that source line.
6256 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6258 10 read_input_file (argv[i]);
6262 After such a printout, the @code{list} command with no arguments
6263 prints ten lines centered on the point of execution in the frame.
6264 You can also edit the program at the point of execution with your favorite
6265 editing program by typing @code{edit}.
6266 @xref{List, ,Printing Source Lines},
6270 @kindex down-silently
6272 @item up-silently @var{n}
6273 @itemx down-silently @var{n}
6274 These two commands are variants of @code{up} and @code{down},
6275 respectively; they differ in that they do their work silently, without
6276 causing display of the new frame. They are intended primarily for use
6277 in @value{GDBN} command scripts, where the output might be unnecessary and
6282 @section Information About a Frame
6284 There are several other commands to print information about the selected
6290 When used without any argument, this command does not change which
6291 frame is selected, but prints a brief description of the currently
6292 selected stack frame. It can be abbreviated @code{f}. With an
6293 argument, this command is used to select a stack frame.
6294 @xref{Selection, ,Selecting a Frame}.
6297 @kindex info f @r{(@code{info frame})}
6300 This command prints a verbose description of the selected stack frame,
6305 the address of the frame
6307 the address of the next frame down (called by this frame)
6309 the address of the next frame up (caller of this frame)
6311 the language in which the source code corresponding to this frame is written
6313 the address of the frame's arguments
6315 the address of the frame's local variables
6317 the program counter saved in it (the address of execution in the caller frame)
6319 which registers were saved in the frame
6322 @noindent The verbose description is useful when
6323 something has gone wrong that has made the stack format fail to fit
6324 the usual conventions.
6326 @item info frame @var{addr}
6327 @itemx info f @var{addr}
6328 Print a verbose description of the frame at address @var{addr}, without
6329 selecting that frame. The selected frame remains unchanged by this
6330 command. This requires the same kind of address (more than one for some
6331 architectures) that you specify in the @code{frame} command.
6332 @xref{Selection, ,Selecting a Frame}.
6336 Print the arguments of the selected frame, each on a separate line.
6340 Print the local variables of the selected frame, each on a separate
6341 line. These are all variables (declared either static or automatic)
6342 accessible at the point of execution of the selected frame.
6345 @cindex catch exceptions, list active handlers
6346 @cindex exception handlers, how to list
6348 Print a list of all the exception handlers that are active in the
6349 current stack frame at the current point of execution. To see other
6350 exception handlers, visit the associated frame (using the @code{up},
6351 @code{down}, or @code{frame} commands); then type @code{info catch}.
6352 @xref{Set Catchpoints, , Setting Catchpoints}.
6358 @chapter Examining Source Files
6360 @value{GDBN} can print parts of your program's source, since the debugging
6361 information recorded in the program tells @value{GDBN} what source files were
6362 used to build it. When your program stops, @value{GDBN} spontaneously prints
6363 the line where it stopped. Likewise, when you select a stack frame
6364 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6365 execution in that frame has stopped. You can print other portions of
6366 source files by explicit command.
6368 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6369 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6370 @value{GDBN} under @sc{gnu} Emacs}.
6373 * List:: Printing source lines
6374 * Specify Location:: How to specify code locations
6375 * Edit:: Editing source files
6376 * Search:: Searching source files
6377 * Source Path:: Specifying source directories
6378 * Machine Code:: Source and machine code
6382 @section Printing Source Lines
6385 @kindex l @r{(@code{list})}
6386 To print lines from a source file, use the @code{list} command
6387 (abbreviated @code{l}). By default, ten lines are printed.
6388 There are several ways to specify what part of the file you want to
6389 print; see @ref{Specify Location}, for the full list.
6391 Here are the forms of the @code{list} command most commonly used:
6394 @item list @var{linenum}
6395 Print lines centered around line number @var{linenum} in the
6396 current source file.
6398 @item list @var{function}
6399 Print lines centered around the beginning of function
6403 Print more lines. If the last lines printed were printed with a
6404 @code{list} command, this prints lines following the last lines
6405 printed; however, if the last line printed was a solitary line printed
6406 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6407 Stack}), this prints lines centered around that line.
6410 Print lines just before the lines last printed.
6413 @cindex @code{list}, how many lines to display
6414 By default, @value{GDBN} prints ten source lines with any of these forms of
6415 the @code{list} command. You can change this using @code{set listsize}:
6418 @kindex set listsize
6419 @item set listsize @var{count}
6420 Make the @code{list} command display @var{count} source lines (unless
6421 the @code{list} argument explicitly specifies some other number).
6423 @kindex show listsize
6425 Display the number of lines that @code{list} prints.
6428 Repeating a @code{list} command with @key{RET} discards the argument,
6429 so it is equivalent to typing just @code{list}. This is more useful
6430 than listing the same lines again. An exception is made for an
6431 argument of @samp{-}; that argument is preserved in repetition so that
6432 each repetition moves up in the source file.
6434 In general, the @code{list} command expects you to supply zero, one or two
6435 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6436 of writing them (@pxref{Specify Location}), but the effect is always
6437 to specify some source line.
6439 Here is a complete description of the possible arguments for @code{list}:
6442 @item list @var{linespec}
6443 Print lines centered around the line specified by @var{linespec}.
6445 @item list @var{first},@var{last}
6446 Print lines from @var{first} to @var{last}. Both arguments are
6447 linespecs. When a @code{list} command has two linespecs, and the
6448 source file of the second linespec is omitted, this refers to
6449 the same source file as the first linespec.
6451 @item list ,@var{last}
6452 Print lines ending with @var{last}.
6454 @item list @var{first},
6455 Print lines starting with @var{first}.
6458 Print lines just after the lines last printed.
6461 Print lines just before the lines last printed.
6464 As described in the preceding table.
6467 @node Specify Location
6468 @section Specifying a Location
6469 @cindex specifying location
6472 Several @value{GDBN} commands accept arguments that specify a location
6473 of your program's code. Since @value{GDBN} is a source-level
6474 debugger, a location usually specifies some line in the source code;
6475 for that reason, locations are also known as @dfn{linespecs}.
6477 Here are all the different ways of specifying a code location that
6478 @value{GDBN} understands:
6482 Specifies the line number @var{linenum} of the current source file.
6485 @itemx +@var{offset}
6486 Specifies the line @var{offset} lines before or after the @dfn{current
6487 line}. For the @code{list} command, the current line is the last one
6488 printed; for the breakpoint commands, this is the line at which
6489 execution stopped in the currently selected @dfn{stack frame}
6490 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6491 used as the second of the two linespecs in a @code{list} command,
6492 this specifies the line @var{offset} lines up or down from the first
6495 @item @var{filename}:@var{linenum}
6496 Specifies the line @var{linenum} in the source file @var{filename}.
6498 @item @var{function}
6499 Specifies the line that begins the body of the function @var{function}.
6500 For example, in C, this is the line with the open brace.
6502 @item @var{function}:@var{label}
6503 Specifies the line where @var{label} appears in @var{function}.
6505 @item @var{filename}:@var{function}
6506 Specifies the line that begins the body of the function @var{function}
6507 in the file @var{filename}. You only need the file name with a
6508 function name to avoid ambiguity when there are identically named
6509 functions in different source files.
6512 Specifies the line at which the label named @var{label} appears.
6513 @value{GDBN} searches for the label in the function corresponding to
6514 the currently selected stack frame. If there is no current selected
6515 stack frame (for instance, if the inferior is not running), then
6516 @value{GDBN} will not search for a label.
6518 @item *@var{address}
6519 Specifies the program address @var{address}. For line-oriented
6520 commands, such as @code{list} and @code{edit}, this specifies a source
6521 line that contains @var{address}. For @code{break} and other
6522 breakpoint oriented commands, this can be used to set breakpoints in
6523 parts of your program which do not have debugging information or
6526 Here @var{address} may be any expression valid in the current working
6527 language (@pxref{Languages, working language}) that specifies a code
6528 address. In addition, as a convenience, @value{GDBN} extends the
6529 semantics of expressions used in locations to cover the situations
6530 that frequently happen during debugging. Here are the various forms
6534 @item @var{expression}
6535 Any expression valid in the current working language.
6537 @item @var{funcaddr}
6538 An address of a function or procedure derived from its name. In C,
6539 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6540 simply the function's name @var{function} (and actually a special case
6541 of a valid expression). In Pascal and Modula-2, this is
6542 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6543 (although the Pascal form also works).
6545 This form specifies the address of the function's first instruction,
6546 before the stack frame and arguments have been set up.
6548 @item '@var{filename}'::@var{funcaddr}
6549 Like @var{funcaddr} above, but also specifies the name of the source
6550 file explicitly. This is useful if the name of the function does not
6551 specify the function unambiguously, e.g., if there are several
6552 functions with identical names in different source files.
6559 @section Editing Source Files
6560 @cindex editing source files
6563 @kindex e @r{(@code{edit})}
6564 To edit the lines in a source file, use the @code{edit} command.
6565 The editing program of your choice
6566 is invoked with the current line set to
6567 the active line in the program.
6568 Alternatively, there are several ways to specify what part of the file you
6569 want to print if you want to see other parts of the program:
6572 @item edit @var{location}
6573 Edit the source file specified by @code{location}. Editing starts at
6574 that @var{location}, e.g., at the specified source line of the
6575 specified file. @xref{Specify Location}, for all the possible forms
6576 of the @var{location} argument; here are the forms of the @code{edit}
6577 command most commonly used:
6580 @item edit @var{number}
6581 Edit the current source file with @var{number} as the active line number.
6583 @item edit @var{function}
6584 Edit the file containing @var{function} at the beginning of its definition.
6589 @subsection Choosing your Editor
6590 You can customize @value{GDBN} to use any editor you want
6592 The only restriction is that your editor (say @code{ex}), recognizes the
6593 following command-line syntax:
6595 ex +@var{number} file
6597 The optional numeric value +@var{number} specifies the number of the line in
6598 the file where to start editing.}.
6599 By default, it is @file{@value{EDITOR}}, but you can change this
6600 by setting the environment variable @code{EDITOR} before using
6601 @value{GDBN}. For example, to configure @value{GDBN} to use the
6602 @code{vi} editor, you could use these commands with the @code{sh} shell:
6608 or in the @code{csh} shell,
6610 setenv EDITOR /usr/bin/vi
6615 @section Searching Source Files
6616 @cindex searching source files
6618 There are two commands for searching through the current source file for a
6623 @kindex forward-search
6624 @item forward-search @var{regexp}
6625 @itemx search @var{regexp}
6626 The command @samp{forward-search @var{regexp}} checks each line,
6627 starting with the one following the last line listed, for a match for
6628 @var{regexp}. It lists the line that is found. You can use the
6629 synonym @samp{search @var{regexp}} or abbreviate the command name as
6632 @kindex reverse-search
6633 @item reverse-search @var{regexp}
6634 The command @samp{reverse-search @var{regexp}} checks each line, starting
6635 with the one before the last line listed and going backward, for a match
6636 for @var{regexp}. It lists the line that is found. You can abbreviate
6637 this command as @code{rev}.
6641 @section Specifying Source Directories
6644 @cindex directories for source files
6645 Executable programs sometimes do not record the directories of the source
6646 files from which they were compiled, just the names. Even when they do,
6647 the directories could be moved between the compilation and your debugging
6648 session. @value{GDBN} has a list of directories to search for source files;
6649 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6650 it tries all the directories in the list, in the order they are present
6651 in the list, until it finds a file with the desired name.
6653 For example, suppose an executable references the file
6654 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6655 @file{/mnt/cross}. The file is first looked up literally; if this
6656 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6657 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6658 message is printed. @value{GDBN} does not look up the parts of the
6659 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6660 Likewise, the subdirectories of the source path are not searched: if
6661 the source path is @file{/mnt/cross}, and the binary refers to
6662 @file{foo.c}, @value{GDBN} would not find it under
6663 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6665 Plain file names, relative file names with leading directories, file
6666 names containing dots, etc.@: are all treated as described above; for
6667 instance, if the source path is @file{/mnt/cross}, and the source file
6668 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6669 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6670 that---@file{/mnt/cross/foo.c}.
6672 Note that the executable search path is @emph{not} used to locate the
6675 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6676 any information it has cached about where source files are found and where
6677 each line is in the file.
6681 When you start @value{GDBN}, its source path includes only @samp{cdir}
6682 and @samp{cwd}, in that order.
6683 To add other directories, use the @code{directory} command.
6685 The search path is used to find both program source files and @value{GDBN}
6686 script files (read using the @samp{-command} option and @samp{source} command).
6688 In addition to the source path, @value{GDBN} provides a set of commands
6689 that manage a list of source path substitution rules. A @dfn{substitution
6690 rule} specifies how to rewrite source directories stored in the program's
6691 debug information in case the sources were moved to a different
6692 directory between compilation and debugging. A rule is made of
6693 two strings, the first specifying what needs to be rewritten in
6694 the path, and the second specifying how it should be rewritten.
6695 In @ref{set substitute-path}, we name these two parts @var{from} and
6696 @var{to} respectively. @value{GDBN} does a simple string replacement
6697 of @var{from} with @var{to} at the start of the directory part of the
6698 source file name, and uses that result instead of the original file
6699 name to look up the sources.
6701 Using the previous example, suppose the @file{foo-1.0} tree has been
6702 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6703 @value{GDBN} to replace @file{/usr/src} in all source path names with
6704 @file{/mnt/cross}. The first lookup will then be
6705 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6706 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6707 substitution rule, use the @code{set substitute-path} command
6708 (@pxref{set substitute-path}).
6710 To avoid unexpected substitution results, a rule is applied only if the
6711 @var{from} part of the directory name ends at a directory separator.
6712 For instance, a rule substituting @file{/usr/source} into
6713 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6714 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6715 is applied only at the beginning of the directory name, this rule will
6716 not be applied to @file{/root/usr/source/baz.c} either.
6718 In many cases, you can achieve the same result using the @code{directory}
6719 command. However, @code{set substitute-path} can be more efficient in
6720 the case where the sources are organized in a complex tree with multiple
6721 subdirectories. With the @code{directory} command, you need to add each
6722 subdirectory of your project. If you moved the entire tree while
6723 preserving its internal organization, then @code{set substitute-path}
6724 allows you to direct the debugger to all the sources with one single
6727 @code{set substitute-path} is also more than just a shortcut command.
6728 The source path is only used if the file at the original location no
6729 longer exists. On the other hand, @code{set substitute-path} modifies
6730 the debugger behavior to look at the rewritten location instead. So, if
6731 for any reason a source file that is not relevant to your executable is
6732 located at the original location, a substitution rule is the only
6733 method available to point @value{GDBN} at the new location.
6735 @cindex @samp{--with-relocated-sources}
6736 @cindex default source path substitution
6737 You can configure a default source path substitution rule by
6738 configuring @value{GDBN} with the
6739 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6740 should be the name of a directory under @value{GDBN}'s configured
6741 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6742 directory names in debug information under @var{dir} will be adjusted
6743 automatically if the installed @value{GDBN} is moved to a new
6744 location. This is useful if @value{GDBN}, libraries or executables
6745 with debug information and corresponding source code are being moved
6749 @item directory @var{dirname} @dots{}
6750 @item dir @var{dirname} @dots{}
6751 Add directory @var{dirname} to the front of the source path. Several
6752 directory names may be given to this command, separated by @samp{:}
6753 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6754 part of absolute file names) or
6755 whitespace. You may specify a directory that is already in the source
6756 path; this moves it forward, so @value{GDBN} searches it sooner.
6760 @vindex $cdir@r{, convenience variable}
6761 @vindex $cwd@r{, convenience variable}
6762 @cindex compilation directory
6763 @cindex current directory
6764 @cindex working directory
6765 @cindex directory, current
6766 @cindex directory, compilation
6767 You can use the string @samp{$cdir} to refer to the compilation
6768 directory (if one is recorded), and @samp{$cwd} to refer to the current
6769 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6770 tracks the current working directory as it changes during your @value{GDBN}
6771 session, while the latter is immediately expanded to the current
6772 directory at the time you add an entry to the source path.
6775 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6777 @c RET-repeat for @code{directory} is explicitly disabled, but since
6778 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6780 @item set directories @var{path-list}
6781 @kindex set directories
6782 Set the source path to @var{path-list}.
6783 @samp{$cdir:$cwd} are added if missing.
6785 @item show directories
6786 @kindex show directories
6787 Print the source path: show which directories it contains.
6789 @anchor{set substitute-path}
6790 @item set substitute-path @var{from} @var{to}
6791 @kindex set substitute-path
6792 Define a source path substitution rule, and add it at the end of the
6793 current list of existing substitution rules. If a rule with the same
6794 @var{from} was already defined, then the old rule is also deleted.
6796 For example, if the file @file{/foo/bar/baz.c} was moved to
6797 @file{/mnt/cross/baz.c}, then the command
6800 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6804 will tell @value{GDBN} to replace @samp{/usr/src} with
6805 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6806 @file{baz.c} even though it was moved.
6808 In the case when more than one substitution rule have been defined,
6809 the rules are evaluated one by one in the order where they have been
6810 defined. The first one matching, if any, is selected to perform
6813 For instance, if we had entered the following commands:
6816 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6817 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6821 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6822 @file{/mnt/include/defs.h} by using the first rule. However, it would
6823 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6824 @file{/mnt/src/lib/foo.c}.
6827 @item unset substitute-path [path]
6828 @kindex unset substitute-path
6829 If a path is specified, search the current list of substitution rules
6830 for a rule that would rewrite that path. Delete that rule if found.
6831 A warning is emitted by the debugger if no rule could be found.
6833 If no path is specified, then all substitution rules are deleted.
6835 @item show substitute-path [path]
6836 @kindex show substitute-path
6837 If a path is specified, then print the source path substitution rule
6838 which would rewrite that path, if any.
6840 If no path is specified, then print all existing source path substitution
6845 If your source path is cluttered with directories that are no longer of
6846 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6847 versions of source. You can correct the situation as follows:
6851 Use @code{directory} with no argument to reset the source path to its default value.
6854 Use @code{directory} with suitable arguments to reinstall the
6855 directories you want in the source path. You can add all the
6856 directories in one command.
6860 @section Source and Machine Code
6861 @cindex source line and its code address
6863 You can use the command @code{info line} to map source lines to program
6864 addresses (and vice versa), and the command @code{disassemble} to display
6865 a range of addresses as machine instructions. You can use the command
6866 @code{set disassemble-next-line} to set whether to disassemble next
6867 source line when execution stops. When run under @sc{gnu} Emacs
6868 mode, the @code{info line} command causes the arrow to point to the
6869 line specified. Also, @code{info line} prints addresses in symbolic form as
6874 @item info line @var{linespec}
6875 Print the starting and ending addresses of the compiled code for
6876 source line @var{linespec}. You can specify source lines in any of
6877 the ways documented in @ref{Specify Location}.
6880 For example, we can use @code{info line} to discover the location of
6881 the object code for the first line of function
6882 @code{m4_changequote}:
6884 @c FIXME: I think this example should also show the addresses in
6885 @c symbolic form, as they usually would be displayed.
6887 (@value{GDBP}) info line m4_changequote
6888 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6892 @cindex code address and its source line
6893 We can also inquire (using @code{*@var{addr}} as the form for
6894 @var{linespec}) what source line covers a particular address:
6896 (@value{GDBP}) info line *0x63ff
6897 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6900 @cindex @code{$_} and @code{info line}
6901 @cindex @code{x} command, default address
6902 @kindex x@r{(examine), and} info line
6903 After @code{info line}, the default address for the @code{x} command
6904 is changed to the starting address of the line, so that @samp{x/i} is
6905 sufficient to begin examining the machine code (@pxref{Memory,
6906 ,Examining Memory}). Also, this address is saved as the value of the
6907 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6912 @cindex assembly instructions
6913 @cindex instructions, assembly
6914 @cindex machine instructions
6915 @cindex listing machine instructions
6917 @itemx disassemble /m
6918 @itemx disassemble /r
6919 This specialized command dumps a range of memory as machine
6920 instructions. It can also print mixed source+disassembly by specifying
6921 the @code{/m} modifier and print the raw instructions in hex as well as
6922 in symbolic form by specifying the @code{/r}.
6923 The default memory range is the function surrounding the
6924 program counter of the selected frame. A single argument to this
6925 command is a program counter value; @value{GDBN} dumps the function
6926 surrounding this value. When two arguments are given, they should
6927 be separated by a comma, possibly surrounded by whitespace. The
6928 arguments specify a range of addresses to dump, in one of two forms:
6931 @item @var{start},@var{end}
6932 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6933 @item @var{start},+@var{length}
6934 the addresses from @var{start} (inclusive) to
6935 @code{@var{start}+@var{length}} (exclusive).
6939 When 2 arguments are specified, the name of the function is also
6940 printed (since there could be several functions in the given range).
6942 The argument(s) can be any expression yielding a numeric value, such as
6943 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6945 If the range of memory being disassembled contains current program counter,
6946 the instruction at that location is shown with a @code{=>} marker.
6949 The following example shows the disassembly of a range of addresses of
6950 HP PA-RISC 2.0 code:
6953 (@value{GDBP}) disas 0x32c4, 0x32e4
6954 Dump of assembler code from 0x32c4 to 0x32e4:
6955 0x32c4 <main+204>: addil 0,dp
6956 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6957 0x32cc <main+212>: ldil 0x3000,r31
6958 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6959 0x32d4 <main+220>: ldo 0(r31),rp
6960 0x32d8 <main+224>: addil -0x800,dp
6961 0x32dc <main+228>: ldo 0x588(r1),r26
6962 0x32e0 <main+232>: ldil 0x3000,r31
6963 End of assembler dump.
6966 Here is an example showing mixed source+assembly for Intel x86, when the
6967 program is stopped just after function prologue:
6970 (@value{GDBP}) disas /m main
6971 Dump of assembler code for function main:
6973 0x08048330 <+0>: push %ebp
6974 0x08048331 <+1>: mov %esp,%ebp
6975 0x08048333 <+3>: sub $0x8,%esp
6976 0x08048336 <+6>: and $0xfffffff0,%esp
6977 0x08048339 <+9>: sub $0x10,%esp
6979 6 printf ("Hello.\n");
6980 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6981 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6985 0x08048348 <+24>: mov $0x0,%eax
6986 0x0804834d <+29>: leave
6987 0x0804834e <+30>: ret
6989 End of assembler dump.
6992 Here is another example showing raw instructions in hex for AMD x86-64,
6995 (gdb) disas /r 0x400281,+10
6996 Dump of assembler code from 0x400281 to 0x40028b:
6997 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6998 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6999 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7000 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7001 End of assembler dump.
7004 Some architectures have more than one commonly-used set of instruction
7005 mnemonics or other syntax.
7007 For programs that were dynamically linked and use shared libraries,
7008 instructions that call functions or branch to locations in the shared
7009 libraries might show a seemingly bogus location---it's actually a
7010 location of the relocation table. On some architectures, @value{GDBN}
7011 might be able to resolve these to actual function names.
7014 @kindex set disassembly-flavor
7015 @cindex Intel disassembly flavor
7016 @cindex AT&T disassembly flavor
7017 @item set disassembly-flavor @var{instruction-set}
7018 Select the instruction set to use when disassembling the
7019 program via the @code{disassemble} or @code{x/i} commands.
7021 Currently this command is only defined for the Intel x86 family. You
7022 can set @var{instruction-set} to either @code{intel} or @code{att}.
7023 The default is @code{att}, the AT&T flavor used by default by Unix
7024 assemblers for x86-based targets.
7026 @kindex show disassembly-flavor
7027 @item show disassembly-flavor
7028 Show the current setting of the disassembly flavor.
7032 @kindex set disassemble-next-line
7033 @kindex show disassemble-next-line
7034 @item set disassemble-next-line
7035 @itemx show disassemble-next-line
7036 Control whether or not @value{GDBN} will disassemble the next source
7037 line or instruction when execution stops. If ON, @value{GDBN} will
7038 display disassembly of the next source line when execution of the
7039 program being debugged stops. This is @emph{in addition} to
7040 displaying the source line itself, which @value{GDBN} always does if
7041 possible. If the next source line cannot be displayed for some reason
7042 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7043 info in the debug info), @value{GDBN} will display disassembly of the
7044 next @emph{instruction} instead of showing the next source line. If
7045 AUTO, @value{GDBN} will display disassembly of next instruction only
7046 if the source line cannot be displayed. This setting causes
7047 @value{GDBN} to display some feedback when you step through a function
7048 with no line info or whose source file is unavailable. The default is
7049 OFF, which means never display the disassembly of the next line or
7055 @chapter Examining Data
7057 @cindex printing data
7058 @cindex examining data
7061 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7062 @c document because it is nonstandard... Under Epoch it displays in a
7063 @c different window or something like that.
7064 The usual way to examine data in your program is with the @code{print}
7065 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7066 evaluates and prints the value of an expression of the language your
7067 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7068 Different Languages}). It may also print the expression using a
7069 Python-based pretty-printer (@pxref{Pretty Printing}).
7072 @item print @var{expr}
7073 @itemx print /@var{f} @var{expr}
7074 @var{expr} is an expression (in the source language). By default the
7075 value of @var{expr} is printed in a format appropriate to its data type;
7076 you can choose a different format by specifying @samp{/@var{f}}, where
7077 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7081 @itemx print /@var{f}
7082 @cindex reprint the last value
7083 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7084 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7085 conveniently inspect the same value in an alternative format.
7088 A more low-level way of examining data is with the @code{x} command.
7089 It examines data in memory at a specified address and prints it in a
7090 specified format. @xref{Memory, ,Examining Memory}.
7092 If you are interested in information about types, or about how the
7093 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7094 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7098 * Expressions:: Expressions
7099 * Ambiguous Expressions:: Ambiguous Expressions
7100 * Variables:: Program variables
7101 * Arrays:: Artificial arrays
7102 * Output Formats:: Output formats
7103 * Memory:: Examining memory
7104 * Auto Display:: Automatic display
7105 * Print Settings:: Print settings
7106 * Pretty Printing:: Python pretty printing
7107 * Value History:: Value history
7108 * Convenience Vars:: Convenience variables
7109 * Registers:: Registers
7110 * Floating Point Hardware:: Floating point hardware
7111 * Vector Unit:: Vector Unit
7112 * OS Information:: Auxiliary data provided by operating system
7113 * Memory Region Attributes:: Memory region attributes
7114 * Dump/Restore Files:: Copy between memory and a file
7115 * Core File Generation:: Cause a program dump its core
7116 * Character Sets:: Debugging programs that use a different
7117 character set than GDB does
7118 * Caching Remote Data:: Data caching for remote targets
7119 * Searching Memory:: Searching memory for a sequence of bytes
7123 @section Expressions
7126 @code{print} and many other @value{GDBN} commands accept an expression and
7127 compute its value. Any kind of constant, variable or operator defined
7128 by the programming language you are using is valid in an expression in
7129 @value{GDBN}. This includes conditional expressions, function calls,
7130 casts, and string constants. It also includes preprocessor macros, if
7131 you compiled your program to include this information; see
7134 @cindex arrays in expressions
7135 @value{GDBN} supports array constants in expressions input by
7136 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7137 you can use the command @code{print @{1, 2, 3@}} to create an array
7138 of three integers. If you pass an array to a function or assign it
7139 to a program variable, @value{GDBN} copies the array to memory that
7140 is @code{malloc}ed in the target program.
7142 Because C is so widespread, most of the expressions shown in examples in
7143 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7144 Languages}, for information on how to use expressions in other
7147 In this section, we discuss operators that you can use in @value{GDBN}
7148 expressions regardless of your programming language.
7150 @cindex casts, in expressions
7151 Casts are supported in all languages, not just in C, because it is so
7152 useful to cast a number into a pointer in order to examine a structure
7153 at that address in memory.
7154 @c FIXME: casts supported---Mod2 true?
7156 @value{GDBN} supports these operators, in addition to those common
7157 to programming languages:
7161 @samp{@@} is a binary operator for treating parts of memory as arrays.
7162 @xref{Arrays, ,Artificial Arrays}, for more information.
7165 @samp{::} allows you to specify a variable in terms of the file or
7166 function where it is defined. @xref{Variables, ,Program Variables}.
7168 @cindex @{@var{type}@}
7169 @cindex type casting memory
7170 @cindex memory, viewing as typed object
7171 @cindex casts, to view memory
7172 @item @{@var{type}@} @var{addr}
7173 Refers to an object of type @var{type} stored at address @var{addr} in
7174 memory. @var{addr} may be any expression whose value is an integer or
7175 pointer (but parentheses are required around binary operators, just as in
7176 a cast). This construct is allowed regardless of what kind of data is
7177 normally supposed to reside at @var{addr}.
7180 @node Ambiguous Expressions
7181 @section Ambiguous Expressions
7182 @cindex ambiguous expressions
7184 Expressions can sometimes contain some ambiguous elements. For instance,
7185 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7186 a single function name to be defined several times, for application in
7187 different contexts. This is called @dfn{overloading}. Another example
7188 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7189 templates and is typically instantiated several times, resulting in
7190 the same function name being defined in different contexts.
7192 In some cases and depending on the language, it is possible to adjust
7193 the expression to remove the ambiguity. For instance in C@t{++}, you
7194 can specify the signature of the function you want to break on, as in
7195 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7196 qualified name of your function often makes the expression unambiguous
7199 When an ambiguity that needs to be resolved is detected, the debugger
7200 has the capability to display a menu of numbered choices for each
7201 possibility, and then waits for the selection with the prompt @samp{>}.
7202 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7203 aborts the current command. If the command in which the expression was
7204 used allows more than one choice to be selected, the next option in the
7205 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7208 For example, the following session excerpt shows an attempt to set a
7209 breakpoint at the overloaded symbol @code{String::after}.
7210 We choose three particular definitions of that function name:
7212 @c FIXME! This is likely to change to show arg type lists, at least
7215 (@value{GDBP}) b String::after
7218 [2] file:String.cc; line number:867
7219 [3] file:String.cc; line number:860
7220 [4] file:String.cc; line number:875
7221 [5] file:String.cc; line number:853
7222 [6] file:String.cc; line number:846
7223 [7] file:String.cc; line number:735
7225 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7226 Breakpoint 2 at 0xb344: file String.cc, line 875.
7227 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7228 Multiple breakpoints were set.
7229 Use the "delete" command to delete unwanted
7236 @kindex set multiple-symbols
7237 @item set multiple-symbols @var{mode}
7238 @cindex multiple-symbols menu
7240 This option allows you to adjust the debugger behavior when an expression
7243 By default, @var{mode} is set to @code{all}. If the command with which
7244 the expression is used allows more than one choice, then @value{GDBN}
7245 automatically selects all possible choices. For instance, inserting
7246 a breakpoint on a function using an ambiguous name results in a breakpoint
7247 inserted on each possible match. However, if a unique choice must be made,
7248 then @value{GDBN} uses the menu to help you disambiguate the expression.
7249 For instance, printing the address of an overloaded function will result
7250 in the use of the menu.
7252 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7253 when an ambiguity is detected.
7255 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7256 an error due to the ambiguity and the command is aborted.
7258 @kindex show multiple-symbols
7259 @item show multiple-symbols
7260 Show the current value of the @code{multiple-symbols} setting.
7264 @section Program Variables
7266 The most common kind of expression to use is the name of a variable
7269 Variables in expressions are understood in the selected stack frame
7270 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7274 global (or file-static)
7281 visible according to the scope rules of the
7282 programming language from the point of execution in that frame
7285 @noindent This means that in the function
7300 you can examine and use the variable @code{a} whenever your program is
7301 executing within the function @code{foo}, but you can only use or
7302 examine the variable @code{b} while your program is executing inside
7303 the block where @code{b} is declared.
7305 @cindex variable name conflict
7306 There is an exception: you can refer to a variable or function whose
7307 scope is a single source file even if the current execution point is not
7308 in this file. But it is possible to have more than one such variable or
7309 function with the same name (in different source files). If that
7310 happens, referring to that name has unpredictable effects. If you wish,
7311 you can specify a static variable in a particular function or file,
7312 using the colon-colon (@code{::}) notation:
7314 @cindex colon-colon, context for variables/functions
7316 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7317 @cindex @code{::}, context for variables/functions
7320 @var{file}::@var{variable}
7321 @var{function}::@var{variable}
7325 Here @var{file} or @var{function} is the name of the context for the
7326 static @var{variable}. In the case of file names, you can use quotes to
7327 make sure @value{GDBN} parses the file name as a single word---for example,
7328 to print a global value of @code{x} defined in @file{f2.c}:
7331 (@value{GDBP}) p 'f2.c'::x
7334 @cindex C@t{++} scope resolution
7335 This use of @samp{::} is very rarely in conflict with the very similar
7336 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7337 scope resolution operator in @value{GDBN} expressions.
7338 @c FIXME: Um, so what happens in one of those rare cases where it's in
7341 @cindex wrong values
7342 @cindex variable values, wrong
7343 @cindex function entry/exit, wrong values of variables
7344 @cindex optimized code, wrong values of variables
7346 @emph{Warning:} Occasionally, a local variable may appear to have the
7347 wrong value at certain points in a function---just after entry to a new
7348 scope, and just before exit.
7350 You may see this problem when you are stepping by machine instructions.
7351 This is because, on most machines, it takes more than one instruction to
7352 set up a stack frame (including local variable definitions); if you are
7353 stepping by machine instructions, variables may appear to have the wrong
7354 values until the stack frame is completely built. On exit, it usually
7355 also takes more than one machine instruction to destroy a stack frame;
7356 after you begin stepping through that group of instructions, local
7357 variable definitions may be gone.
7359 This may also happen when the compiler does significant optimizations.
7360 To be sure of always seeing accurate values, turn off all optimization
7363 @cindex ``No symbol "foo" in current context''
7364 Another possible effect of compiler optimizations is to optimize
7365 unused variables out of existence, or assign variables to registers (as
7366 opposed to memory addresses). Depending on the support for such cases
7367 offered by the debug info format used by the compiler, @value{GDBN}
7368 might not be able to display values for such local variables. If that
7369 happens, @value{GDBN} will print a message like this:
7372 No symbol "foo" in current context.
7375 To solve such problems, either recompile without optimizations, or use a
7376 different debug info format, if the compiler supports several such
7377 formats. @xref{Compilation}, for more information on choosing compiler
7378 options. @xref{C, ,C and C@t{++}}, for more information about debug
7379 info formats that are best suited to C@t{++} programs.
7381 If you ask to print an object whose contents are unknown to
7382 @value{GDBN}, e.g., because its data type is not completely specified
7383 by the debug information, @value{GDBN} will say @samp{<incomplete
7384 type>}. @xref{Symbols, incomplete type}, for more about this.
7386 If you append @kbd{@@entry} string to a function parameter name you get its
7387 value at the time the function got called. If the value is not available an
7388 error message is printed. Entry values are available only with some compilers.
7389 Entry values are normally also printed at the function parameter list according
7390 to @ref{set print entry-values}.
7393 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7399 (gdb) print i@@entry
7403 Strings are identified as arrays of @code{char} values without specified
7404 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7405 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7406 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7407 defines literal string type @code{"char"} as @code{char} without a sign.
7412 signed char var1[] = "A";
7415 You get during debugging
7420 $2 = @{65 'A', 0 '\0'@}
7424 @section Artificial Arrays
7426 @cindex artificial array
7428 @kindex @@@r{, referencing memory as an array}
7429 It is often useful to print out several successive objects of the
7430 same type in memory; a section of an array, or an array of
7431 dynamically determined size for which only a pointer exists in the
7434 You can do this by referring to a contiguous span of memory as an
7435 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7436 operand of @samp{@@} should be the first element of the desired array
7437 and be an individual object. The right operand should be the desired length
7438 of the array. The result is an array value whose elements are all of
7439 the type of the left argument. The first element is actually the left
7440 argument; the second element comes from bytes of memory immediately
7441 following those that hold the first element, and so on. Here is an
7442 example. If a program says
7445 int *array = (int *) malloc (len * sizeof (int));
7449 you can print the contents of @code{array} with
7455 The left operand of @samp{@@} must reside in memory. Array values made
7456 with @samp{@@} in this way behave just like other arrays in terms of
7457 subscripting, and are coerced to pointers when used in expressions.
7458 Artificial arrays most often appear in expressions via the value history
7459 (@pxref{Value History, ,Value History}), after printing one out.
7461 Another way to create an artificial array is to use a cast.
7462 This re-interprets a value as if it were an array.
7463 The value need not be in memory:
7465 (@value{GDBP}) p/x (short[2])0x12345678
7466 $1 = @{0x1234, 0x5678@}
7469 As a convenience, if you leave the array length out (as in
7470 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7471 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7473 (@value{GDBP}) p/x (short[])0x12345678
7474 $2 = @{0x1234, 0x5678@}
7477 Sometimes the artificial array mechanism is not quite enough; in
7478 moderately complex data structures, the elements of interest may not
7479 actually be adjacent---for example, if you are interested in the values
7480 of pointers in an array. One useful work-around in this situation is
7481 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7482 Variables}) as a counter in an expression that prints the first
7483 interesting value, and then repeat that expression via @key{RET}. For
7484 instance, suppose you have an array @code{dtab} of pointers to
7485 structures, and you are interested in the values of a field @code{fv}
7486 in each structure. Here is an example of what you might type:
7496 @node Output Formats
7497 @section Output Formats
7499 @cindex formatted output
7500 @cindex output formats
7501 By default, @value{GDBN} prints a value according to its data type. Sometimes
7502 this is not what you want. For example, you might want to print a number
7503 in hex, or a pointer in decimal. Or you might want to view data in memory
7504 at a certain address as a character string or as an instruction. To do
7505 these things, specify an @dfn{output format} when you print a value.
7507 The simplest use of output formats is to say how to print a value
7508 already computed. This is done by starting the arguments of the
7509 @code{print} command with a slash and a format letter. The format
7510 letters supported are:
7514 Regard the bits of the value as an integer, and print the integer in
7518 Print as integer in signed decimal.
7521 Print as integer in unsigned decimal.
7524 Print as integer in octal.
7527 Print as integer in binary. The letter @samp{t} stands for ``two''.
7528 @footnote{@samp{b} cannot be used because these format letters are also
7529 used with the @code{x} command, where @samp{b} stands for ``byte'';
7530 see @ref{Memory,,Examining Memory}.}
7533 @cindex unknown address, locating
7534 @cindex locate address
7535 Print as an address, both absolute in hexadecimal and as an offset from
7536 the nearest preceding symbol. You can use this format used to discover
7537 where (in what function) an unknown address is located:
7540 (@value{GDBP}) p/a 0x54320
7541 $3 = 0x54320 <_initialize_vx+396>
7545 The command @code{info symbol 0x54320} yields similar results.
7546 @xref{Symbols, info symbol}.
7549 Regard as an integer and print it as a character constant. This
7550 prints both the numerical value and its character representation. The
7551 character representation is replaced with the octal escape @samp{\nnn}
7552 for characters outside the 7-bit @sc{ascii} range.
7554 Without this format, @value{GDBN} displays @code{char},
7555 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7556 constants. Single-byte members of vectors are displayed as integer
7560 Regard the bits of the value as a floating point number and print
7561 using typical floating point syntax.
7564 @cindex printing strings
7565 @cindex printing byte arrays
7566 Regard as a string, if possible. With this format, pointers to single-byte
7567 data are displayed as null-terminated strings and arrays of single-byte data
7568 are displayed as fixed-length strings. Other values are displayed in their
7571 Without this format, @value{GDBN} displays pointers to and arrays of
7572 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7573 strings. Single-byte members of a vector are displayed as an integer
7577 @cindex raw printing
7578 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7579 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7580 Printing}). This typically results in a higher-level display of the
7581 value's contents. The @samp{r} format bypasses any Python
7582 pretty-printer which might exist.
7585 For example, to print the program counter in hex (@pxref{Registers}), type
7592 Note that no space is required before the slash; this is because command
7593 names in @value{GDBN} cannot contain a slash.
7595 To reprint the last value in the value history with a different format,
7596 you can use the @code{print} command with just a format and no
7597 expression. For example, @samp{p/x} reprints the last value in hex.
7600 @section Examining Memory
7602 You can use the command @code{x} (for ``examine'') to examine memory in
7603 any of several formats, independently of your program's data types.
7605 @cindex examining memory
7607 @kindex x @r{(examine memory)}
7608 @item x/@var{nfu} @var{addr}
7611 Use the @code{x} command to examine memory.
7614 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7615 much memory to display and how to format it; @var{addr} is an
7616 expression giving the address where you want to start displaying memory.
7617 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7618 Several commands set convenient defaults for @var{addr}.
7621 @item @var{n}, the repeat count
7622 The repeat count is a decimal integer; the default is 1. It specifies
7623 how much memory (counting by units @var{u}) to display.
7624 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7627 @item @var{f}, the display format
7628 The display format is one of the formats used by @code{print}
7629 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7630 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7631 The default is @samp{x} (hexadecimal) initially. The default changes
7632 each time you use either @code{x} or @code{print}.
7634 @item @var{u}, the unit size
7635 The unit size is any of
7641 Halfwords (two bytes).
7643 Words (four bytes). This is the initial default.
7645 Giant words (eight bytes).
7648 Each time you specify a unit size with @code{x}, that size becomes the
7649 default unit the next time you use @code{x}. For the @samp{i} format,
7650 the unit size is ignored and is normally not written. For the @samp{s} format,
7651 the unit size defaults to @samp{b}, unless it is explicitly given.
7652 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7653 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7654 Note that the results depend on the programming language of the
7655 current compilation unit. If the language is C, the @samp{s}
7656 modifier will use the UTF-16 encoding while @samp{w} will use
7657 UTF-32. The encoding is set by the programming language and cannot
7660 @item @var{addr}, starting display address
7661 @var{addr} is the address where you want @value{GDBN} to begin displaying
7662 memory. The expression need not have a pointer value (though it may);
7663 it is always interpreted as an integer address of a byte of memory.
7664 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7665 @var{addr} is usually just after the last address examined---but several
7666 other commands also set the default address: @code{info breakpoints} (to
7667 the address of the last breakpoint listed), @code{info line} (to the
7668 starting address of a line), and @code{print} (if you use it to display
7669 a value from memory).
7672 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7673 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7674 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7675 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7676 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7678 Since the letters indicating unit sizes are all distinct from the
7679 letters specifying output formats, you do not have to remember whether
7680 unit size or format comes first; either order works. The output
7681 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7682 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7684 Even though the unit size @var{u} is ignored for the formats @samp{s}
7685 and @samp{i}, you might still want to use a count @var{n}; for example,
7686 @samp{3i} specifies that you want to see three machine instructions,
7687 including any operands. For convenience, especially when used with
7688 the @code{display} command, the @samp{i} format also prints branch delay
7689 slot instructions, if any, beyond the count specified, which immediately
7690 follow the last instruction that is within the count. The command
7691 @code{disassemble} gives an alternative way of inspecting machine
7692 instructions; see @ref{Machine Code,,Source and Machine Code}.
7694 All the defaults for the arguments to @code{x} are designed to make it
7695 easy to continue scanning memory with minimal specifications each time
7696 you use @code{x}. For example, after you have inspected three machine
7697 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7698 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7699 the repeat count @var{n} is used again; the other arguments default as
7700 for successive uses of @code{x}.
7702 When examining machine instructions, the instruction at current program
7703 counter is shown with a @code{=>} marker. For example:
7706 (@value{GDBP}) x/5i $pc-6
7707 0x804837f <main+11>: mov %esp,%ebp
7708 0x8048381 <main+13>: push %ecx
7709 0x8048382 <main+14>: sub $0x4,%esp
7710 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7711 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7714 @cindex @code{$_}, @code{$__}, and value history
7715 The addresses and contents printed by the @code{x} command are not saved
7716 in the value history because there is often too much of them and they
7717 would get in the way. Instead, @value{GDBN} makes these values available for
7718 subsequent use in expressions as values of the convenience variables
7719 @code{$_} and @code{$__}. After an @code{x} command, the last address
7720 examined is available for use in expressions in the convenience variable
7721 @code{$_}. The contents of that address, as examined, are available in
7722 the convenience variable @code{$__}.
7724 If the @code{x} command has a repeat count, the address and contents saved
7725 are from the last memory unit printed; this is not the same as the last
7726 address printed if several units were printed on the last line of output.
7728 @cindex remote memory comparison
7729 @cindex verify remote memory image
7730 When you are debugging a program running on a remote target machine
7731 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7732 remote machine's memory against the executable file you downloaded to
7733 the target. The @code{compare-sections} command is provided for such
7737 @kindex compare-sections
7738 @item compare-sections @r{[}@var{section-name}@r{]}
7739 Compare the data of a loadable section @var{section-name} in the
7740 executable file of the program being debugged with the same section in
7741 the remote machine's memory, and report any mismatches. With no
7742 arguments, compares all loadable sections. This command's
7743 availability depends on the target's support for the @code{"qCRC"}
7748 @section Automatic Display
7749 @cindex automatic display
7750 @cindex display of expressions
7752 If you find that you want to print the value of an expression frequently
7753 (to see how it changes), you might want to add it to the @dfn{automatic
7754 display list} so that @value{GDBN} prints its value each time your program stops.
7755 Each expression added to the list is given a number to identify it;
7756 to remove an expression from the list, you specify that number.
7757 The automatic display looks like this:
7761 3: bar[5] = (struct hack *) 0x3804
7765 This display shows item numbers, expressions and their current values. As with
7766 displays you request manually using @code{x} or @code{print}, you can
7767 specify the output format you prefer; in fact, @code{display} decides
7768 whether to use @code{print} or @code{x} depending your format
7769 specification---it uses @code{x} if you specify either the @samp{i}
7770 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7774 @item display @var{expr}
7775 Add the expression @var{expr} to the list of expressions to display
7776 each time your program stops. @xref{Expressions, ,Expressions}.
7778 @code{display} does not repeat if you press @key{RET} again after using it.
7780 @item display/@var{fmt} @var{expr}
7781 For @var{fmt} specifying only a display format and not a size or
7782 count, add the expression @var{expr} to the auto-display list but
7783 arrange to display it each time in the specified format @var{fmt}.
7784 @xref{Output Formats,,Output Formats}.
7786 @item display/@var{fmt} @var{addr}
7787 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7788 number of units, add the expression @var{addr} as a memory address to
7789 be examined each time your program stops. Examining means in effect
7790 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7793 For example, @samp{display/i $pc} can be helpful, to see the machine
7794 instruction about to be executed each time execution stops (@samp{$pc}
7795 is a common name for the program counter; @pxref{Registers, ,Registers}).
7798 @kindex delete display
7800 @item undisplay @var{dnums}@dots{}
7801 @itemx delete display @var{dnums}@dots{}
7802 Remove items from the list of expressions to display. Specify the
7803 numbers of the displays that you want affected with the command
7804 argument @var{dnums}. It can be a single display number, one of the
7805 numbers shown in the first field of the @samp{info display} display;
7806 or it could be a range of display numbers, as in @code{2-4}.
7808 @code{undisplay} does not repeat if you press @key{RET} after using it.
7809 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7811 @kindex disable display
7812 @item disable display @var{dnums}@dots{}
7813 Disable the display of item numbers @var{dnums}. A disabled display
7814 item is not printed automatically, but is not forgotten. It may be
7815 enabled again later. Specify the numbers of the displays that you
7816 want affected with the command argument @var{dnums}. It can be a
7817 single display number, one of the numbers shown in the first field of
7818 the @samp{info display} display; or it could be a range of display
7819 numbers, as in @code{2-4}.
7821 @kindex enable display
7822 @item enable display @var{dnums}@dots{}
7823 Enable display of item numbers @var{dnums}. It becomes effective once
7824 again in auto display of its expression, until you specify otherwise.
7825 Specify the numbers of the displays that you want affected with the
7826 command argument @var{dnums}. It can be a single display number, one
7827 of the numbers shown in the first field of the @samp{info display}
7828 display; or it could be a range of display numbers, as in @code{2-4}.
7831 Display the current values of the expressions on the list, just as is
7832 done when your program stops.
7834 @kindex info display
7836 Print the list of expressions previously set up to display
7837 automatically, each one with its item number, but without showing the
7838 values. This includes disabled expressions, which are marked as such.
7839 It also includes expressions which would not be displayed right now
7840 because they refer to automatic variables not currently available.
7843 @cindex display disabled out of scope
7844 If a display expression refers to local variables, then it does not make
7845 sense outside the lexical context for which it was set up. Such an
7846 expression is disabled when execution enters a context where one of its
7847 variables is not defined. For example, if you give the command
7848 @code{display last_char} while inside a function with an argument
7849 @code{last_char}, @value{GDBN} displays this argument while your program
7850 continues to stop inside that function. When it stops elsewhere---where
7851 there is no variable @code{last_char}---the display is disabled
7852 automatically. The next time your program stops where @code{last_char}
7853 is meaningful, you can enable the display expression once again.
7855 @node Print Settings
7856 @section Print Settings
7858 @cindex format options
7859 @cindex print settings
7860 @value{GDBN} provides the following ways to control how arrays, structures,
7861 and symbols are printed.
7864 These settings are useful for debugging programs in any language:
7868 @item set print address
7869 @itemx set print address on
7870 @cindex print/don't print memory addresses
7871 @value{GDBN} prints memory addresses showing the location of stack
7872 traces, structure values, pointer values, breakpoints, and so forth,
7873 even when it also displays the contents of those addresses. The default
7874 is @code{on}. For example, this is what a stack frame display looks like with
7875 @code{set print address on}:
7880 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7882 530 if (lquote != def_lquote)
7886 @item set print address off
7887 Do not print addresses when displaying their contents. For example,
7888 this is the same stack frame displayed with @code{set print address off}:
7892 (@value{GDBP}) set print addr off
7894 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7895 530 if (lquote != def_lquote)
7899 You can use @samp{set print address off} to eliminate all machine
7900 dependent displays from the @value{GDBN} interface. For example, with
7901 @code{print address off}, you should get the same text for backtraces on
7902 all machines---whether or not they involve pointer arguments.
7905 @item show print address
7906 Show whether or not addresses are to be printed.
7909 When @value{GDBN} prints a symbolic address, it normally prints the
7910 closest earlier symbol plus an offset. If that symbol does not uniquely
7911 identify the address (for example, it is a name whose scope is a single
7912 source file), you may need to clarify. One way to do this is with
7913 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7914 you can set @value{GDBN} to print the source file and line number when
7915 it prints a symbolic address:
7918 @item set print symbol-filename on
7919 @cindex source file and line of a symbol
7920 @cindex symbol, source file and line
7921 Tell @value{GDBN} to print the source file name and line number of a
7922 symbol in the symbolic form of an address.
7924 @item set print symbol-filename off
7925 Do not print source file name and line number of a symbol. This is the
7928 @item show print symbol-filename
7929 Show whether or not @value{GDBN} will print the source file name and
7930 line number of a symbol in the symbolic form of an address.
7933 Another situation where it is helpful to show symbol filenames and line
7934 numbers is when disassembling code; @value{GDBN} shows you the line
7935 number and source file that corresponds to each instruction.
7937 Also, you may wish to see the symbolic form only if the address being
7938 printed is reasonably close to the closest earlier symbol:
7941 @item set print max-symbolic-offset @var{max-offset}
7942 @cindex maximum value for offset of closest symbol
7943 Tell @value{GDBN} to only display the symbolic form of an address if the
7944 offset between the closest earlier symbol and the address is less than
7945 @var{max-offset}. The default is 0, which tells @value{GDBN}
7946 to always print the symbolic form of an address if any symbol precedes it.
7948 @item show print max-symbolic-offset
7949 Ask how large the maximum offset is that @value{GDBN} prints in a
7953 @cindex wild pointer, interpreting
7954 @cindex pointer, finding referent
7955 If you have a pointer and you are not sure where it points, try
7956 @samp{set print symbol-filename on}. Then you can determine the name
7957 and source file location of the variable where it points, using
7958 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7959 For example, here @value{GDBN} shows that a variable @code{ptt} points
7960 at another variable @code{t}, defined in @file{hi2.c}:
7963 (@value{GDBP}) set print symbol-filename on
7964 (@value{GDBP}) p/a ptt
7965 $4 = 0xe008 <t in hi2.c>
7969 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7970 does not show the symbol name and filename of the referent, even with
7971 the appropriate @code{set print} options turned on.
7974 Other settings control how different kinds of objects are printed:
7977 @item set print array
7978 @itemx set print array on
7979 @cindex pretty print arrays
7980 Pretty print arrays. This format is more convenient to read,
7981 but uses more space. The default is off.
7983 @item set print array off
7984 Return to compressed format for arrays.
7986 @item show print array
7987 Show whether compressed or pretty format is selected for displaying
7990 @cindex print array indexes
7991 @item set print array-indexes
7992 @itemx set print array-indexes on
7993 Print the index of each element when displaying arrays. May be more
7994 convenient to locate a given element in the array or quickly find the
7995 index of a given element in that printed array. The default is off.
7997 @item set print array-indexes off
7998 Stop printing element indexes when displaying arrays.
8000 @item show print array-indexes
8001 Show whether the index of each element is printed when displaying
8004 @item set print elements @var{number-of-elements}
8005 @cindex number of array elements to print
8006 @cindex limit on number of printed array elements
8007 Set a limit on how many elements of an array @value{GDBN} will print.
8008 If @value{GDBN} is printing a large array, it stops printing after it has
8009 printed the number of elements set by the @code{set print elements} command.
8010 This limit also applies to the display of strings.
8011 When @value{GDBN} starts, this limit is set to 200.
8012 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8014 @item show print elements
8015 Display the number of elements of a large array that @value{GDBN} will print.
8016 If the number is 0, then the printing is unlimited.
8018 @item set print frame-arguments @var{value}
8019 @kindex set print frame-arguments
8020 @cindex printing frame argument values
8021 @cindex print all frame argument values
8022 @cindex print frame argument values for scalars only
8023 @cindex do not print frame argument values
8024 This command allows to control how the values of arguments are printed
8025 when the debugger prints a frame (@pxref{Frames}). The possible
8030 The values of all arguments are printed.
8033 Print the value of an argument only if it is a scalar. The value of more
8034 complex arguments such as arrays, structures, unions, etc, is replaced
8035 by @code{@dots{}}. This is the default. Here is an example where
8036 only scalar arguments are shown:
8039 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8044 None of the argument values are printed. Instead, the value of each argument
8045 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8048 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8053 By default, only scalar arguments are printed. This command can be used
8054 to configure the debugger to print the value of all arguments, regardless
8055 of their type. However, it is often advantageous to not print the value
8056 of more complex parameters. For instance, it reduces the amount of
8057 information printed in each frame, making the backtrace more readable.
8058 Also, it improves performance when displaying Ada frames, because
8059 the computation of large arguments can sometimes be CPU-intensive,
8060 especially in large applications. Setting @code{print frame-arguments}
8061 to @code{scalars} (the default) or @code{none} avoids this computation,
8062 thus speeding up the display of each Ada frame.
8064 @item show print frame-arguments
8065 Show how the value of arguments should be displayed when printing a frame.
8067 @anchor{set print entry-values}
8068 @item set print entry-values @var{value}
8069 @kindex set print entry-values
8070 Set printing of frame argument values at function entry. In some cases
8071 @value{GDBN} can determine the value of function argument which was passed by
8072 the function caller, even if the value was modified inside the called function
8073 and therefore is different. With optimized code, the current value could be
8074 unavailable, but the entry value may still be known.
8076 The default value is @code{default} (see below for its description). Older
8077 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8078 this feature will behave in the @code{default} setting the same way as with the
8081 This functionality is currently supported only by DWARF 2 debugging format and
8082 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8083 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8086 The @var{value} parameter can be one of the following:
8090 Print only actual parameter values, never print values from function entry
8094 #0 different (val=6)
8095 #0 lost (val=<optimized out>)
8097 #0 invalid (val=<optimized out>)
8101 Print only parameter values from function entry point. The actual parameter
8102 values are never printed.
8104 #0 equal (val@@entry=5)
8105 #0 different (val@@entry=5)
8106 #0 lost (val@@entry=5)
8107 #0 born (val@@entry=<optimized out>)
8108 #0 invalid (val@@entry=<optimized out>)
8112 Print only parameter values from function entry point. If value from function
8113 entry point is not known while the actual value is known, print the actual
8114 value for such parameter.
8116 #0 equal (val@@entry=5)
8117 #0 different (val@@entry=5)
8118 #0 lost (val@@entry=5)
8120 #0 invalid (val@@entry=<optimized out>)
8124 Print actual parameter values. If actual parameter value is not known while
8125 value from function entry point is known, print the entry point value for such
8129 #0 different (val=6)
8130 #0 lost (val@@entry=5)
8132 #0 invalid (val=<optimized out>)
8136 Always print both the actual parameter value and its value from function entry
8137 point, even if values of one or both are not available due to compiler
8140 #0 equal (val=5, val@@entry=5)
8141 #0 different (val=6, val@@entry=5)
8142 #0 lost (val=<optimized out>, val@@entry=5)
8143 #0 born (val=10, val@@entry=<optimized out>)
8144 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8148 Print the actual parameter value if it is known and also its value from
8149 function entry point if it is known. If neither is known, print for the actual
8150 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8151 values are known and identical, print the shortened
8152 @code{param=param@@entry=VALUE} notation.
8154 #0 equal (val=val@@entry=5)
8155 #0 different (val=6, val@@entry=5)
8156 #0 lost (val@@entry=5)
8158 #0 invalid (val=<optimized out>)
8162 Always print the actual parameter value. Print also its value from function
8163 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8164 if both values are known and identical, print the shortened
8165 @code{param=param@@entry=VALUE} notation.
8167 #0 equal (val=val@@entry=5)
8168 #0 different (val=6, val@@entry=5)
8169 #0 lost (val=<optimized out>, val@@entry=5)
8171 #0 invalid (val=<optimized out>)
8175 For analysis messages on possible failures of frame argument values at function
8176 entry resolution see @ref{set debug entry-values}.
8178 @item show print entry-values
8179 Show the method being used for printing of frame argument values at function
8182 @item set print repeats
8183 @cindex repeated array elements
8184 Set the threshold for suppressing display of repeated array
8185 elements. When the number of consecutive identical elements of an
8186 array exceeds the threshold, @value{GDBN} prints the string
8187 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8188 identical repetitions, instead of displaying the identical elements
8189 themselves. Setting the threshold to zero will cause all elements to
8190 be individually printed. The default threshold is 10.
8192 @item show print repeats
8193 Display the current threshold for printing repeated identical
8196 @item set print null-stop
8197 @cindex @sc{null} elements in arrays
8198 Cause @value{GDBN} to stop printing the characters of an array when the first
8199 @sc{null} is encountered. This is useful when large arrays actually
8200 contain only short strings.
8203 @item show print null-stop
8204 Show whether @value{GDBN} stops printing an array on the first
8205 @sc{null} character.
8207 @item set print pretty on
8208 @cindex print structures in indented form
8209 @cindex indentation in structure display
8210 Cause @value{GDBN} to print structures in an indented format with one member
8211 per line, like this:
8226 @item set print pretty off
8227 Cause @value{GDBN} to print structures in a compact format, like this:
8231 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8232 meat = 0x54 "Pork"@}
8237 This is the default format.
8239 @item show print pretty
8240 Show which format @value{GDBN} is using to print structures.
8242 @item set print sevenbit-strings on
8243 @cindex eight-bit characters in strings
8244 @cindex octal escapes in strings
8245 Print using only seven-bit characters; if this option is set,
8246 @value{GDBN} displays any eight-bit characters (in strings or
8247 character values) using the notation @code{\}@var{nnn}. This setting is
8248 best if you are working in English (@sc{ascii}) and you use the
8249 high-order bit of characters as a marker or ``meta'' bit.
8251 @item set print sevenbit-strings off
8252 Print full eight-bit characters. This allows the use of more
8253 international character sets, and is the default.
8255 @item show print sevenbit-strings
8256 Show whether or not @value{GDBN} is printing only seven-bit characters.
8258 @item set print union on
8259 @cindex unions in structures, printing
8260 Tell @value{GDBN} to print unions which are contained in structures
8261 and other unions. This is the default setting.
8263 @item set print union off
8264 Tell @value{GDBN} not to print unions which are contained in
8265 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8268 @item show print union
8269 Ask @value{GDBN} whether or not it will print unions which are contained in
8270 structures and other unions.
8272 For example, given the declarations
8275 typedef enum @{Tree, Bug@} Species;
8276 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8277 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8288 struct thing foo = @{Tree, @{Acorn@}@};
8292 with @code{set print union on} in effect @samp{p foo} would print
8295 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8299 and with @code{set print union off} in effect it would print
8302 $1 = @{it = Tree, form = @{...@}@}
8306 @code{set print union} affects programs written in C-like languages
8312 These settings are of interest when debugging C@t{++} programs:
8315 @cindex demangling C@t{++} names
8316 @item set print demangle
8317 @itemx set print demangle on
8318 Print C@t{++} names in their source form rather than in the encoded
8319 (``mangled'') form passed to the assembler and linker for type-safe
8320 linkage. The default is on.
8322 @item show print demangle
8323 Show whether C@t{++} names are printed in mangled or demangled form.
8325 @item set print asm-demangle
8326 @itemx set print asm-demangle on
8327 Print C@t{++} names in their source form rather than their mangled form, even
8328 in assembler code printouts such as instruction disassemblies.
8331 @item show print asm-demangle
8332 Show whether C@t{++} names in assembly listings are printed in mangled
8335 @cindex C@t{++} symbol decoding style
8336 @cindex symbol decoding style, C@t{++}
8337 @kindex set demangle-style
8338 @item set demangle-style @var{style}
8339 Choose among several encoding schemes used by different compilers to
8340 represent C@t{++} names. The choices for @var{style} are currently:
8344 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8347 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8348 This is the default.
8351 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8354 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8357 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8358 @strong{Warning:} this setting alone is not sufficient to allow
8359 debugging @code{cfront}-generated executables. @value{GDBN} would
8360 require further enhancement to permit that.
8363 If you omit @var{style}, you will see a list of possible formats.
8365 @item show demangle-style
8366 Display the encoding style currently in use for decoding C@t{++} symbols.
8368 @item set print object
8369 @itemx set print object on
8370 @cindex derived type of an object, printing
8371 @cindex display derived types
8372 When displaying a pointer to an object, identify the @emph{actual}
8373 (derived) type of the object rather than the @emph{declared} type, using
8374 the virtual function table. Note that the virtual function table is
8375 required---this feature can only work for objects that have run-time
8376 type identification; a single virtual method in the object's declared
8379 @item set print object off
8380 Display only the declared type of objects, without reference to the
8381 virtual function table. This is the default setting.
8383 @item show print object
8384 Show whether actual, or declared, object types are displayed.
8386 @item set print static-members
8387 @itemx set print static-members on
8388 @cindex static members of C@t{++} objects
8389 Print static members when displaying a C@t{++} object. The default is on.
8391 @item set print static-members off
8392 Do not print static members when displaying a C@t{++} object.
8394 @item show print static-members
8395 Show whether C@t{++} static members are printed or not.
8397 @item set print pascal_static-members
8398 @itemx set print pascal_static-members on
8399 @cindex static members of Pascal objects
8400 @cindex Pascal objects, static members display
8401 Print static members when displaying a Pascal object. The default is on.
8403 @item set print pascal_static-members off
8404 Do not print static members when displaying a Pascal object.
8406 @item show print pascal_static-members
8407 Show whether Pascal static members are printed or not.
8409 @c These don't work with HP ANSI C++ yet.
8410 @item set print vtbl
8411 @itemx set print vtbl on
8412 @cindex pretty print C@t{++} virtual function tables
8413 @cindex virtual functions (C@t{++}) display
8414 @cindex VTBL display
8415 Pretty print C@t{++} virtual function tables. The default is off.
8416 (The @code{vtbl} commands do not work on programs compiled with the HP
8417 ANSI C@t{++} compiler (@code{aCC}).)
8419 @item set print vtbl off
8420 Do not pretty print C@t{++} virtual function tables.
8422 @item show print vtbl
8423 Show whether C@t{++} virtual function tables are pretty printed, or not.
8426 @node Pretty Printing
8427 @section Pretty Printing
8429 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8430 Python code. It greatly simplifies the display of complex objects. This
8431 mechanism works for both MI and the CLI.
8434 * Pretty-Printer Introduction:: Introduction to pretty-printers
8435 * Pretty-Printer Example:: An example pretty-printer
8436 * Pretty-Printer Commands:: Pretty-printer commands
8439 @node Pretty-Printer Introduction
8440 @subsection Pretty-Printer Introduction
8442 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8443 registered for the value. If there is then @value{GDBN} invokes the
8444 pretty-printer to print the value. Otherwise the value is printed normally.
8446 Pretty-printers are normally named. This makes them easy to manage.
8447 The @samp{info pretty-printer} command will list all the installed
8448 pretty-printers with their names.
8449 If a pretty-printer can handle multiple data types, then its
8450 @dfn{subprinters} are the printers for the individual data types.
8451 Each such subprinter has its own name.
8452 The format of the name is @var{printer-name};@var{subprinter-name}.
8454 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8455 Typically they are automatically loaded and registered when the corresponding
8456 debug information is loaded, thus making them available without having to
8457 do anything special.
8459 There are three places where a pretty-printer can be registered.
8463 Pretty-printers registered globally are available when debugging
8467 Pretty-printers registered with a program space are available only
8468 when debugging that program.
8469 @xref{Progspaces In Python}, for more details on program spaces in Python.
8472 Pretty-printers registered with an objfile are loaded and unloaded
8473 with the corresponding objfile (e.g., shared library).
8474 @xref{Objfiles In Python}, for more details on objfiles in Python.
8477 @xref{Selecting Pretty-Printers}, for further information on how
8478 pretty-printers are selected,
8480 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8483 @node Pretty-Printer Example
8484 @subsection Pretty-Printer Example
8486 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8489 (@value{GDBP}) print s
8491 static npos = 4294967295,
8493 <std::allocator<char>> = @{
8494 <__gnu_cxx::new_allocator<char>> = @{
8495 <No data fields>@}, <No data fields>
8497 members of std::basic_string<char, std::char_traits<char>,
8498 std::allocator<char> >::_Alloc_hider:
8499 _M_p = 0x804a014 "abcd"
8504 With a pretty-printer for @code{std::string} only the contents are printed:
8507 (@value{GDBP}) print s
8511 @node Pretty-Printer Commands
8512 @subsection Pretty-Printer Commands
8513 @cindex pretty-printer commands
8516 @kindex info pretty-printer
8517 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8518 Print the list of installed pretty-printers.
8519 This includes disabled pretty-printers, which are marked as such.
8521 @var{object-regexp} is a regular expression matching the objects
8522 whose pretty-printers to list.
8523 Objects can be @code{global}, the program space's file
8524 (@pxref{Progspaces In Python}),
8525 and the object files within that program space (@pxref{Objfiles In Python}).
8526 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8527 looks up a printer from these three objects.
8529 @var{name-regexp} is a regular expression matching the name of the printers
8532 @kindex disable pretty-printer
8533 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8534 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8535 A disabled pretty-printer is not forgotten, it may be enabled again later.
8537 @kindex enable pretty-printer
8538 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8539 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8544 Suppose we have three pretty-printers installed: one from library1.so
8545 named @code{foo} that prints objects of type @code{foo}, and
8546 another from library2.so named @code{bar} that prints two types of objects,
8547 @code{bar1} and @code{bar2}.
8550 (gdb) info pretty-printer
8557 (gdb) info pretty-printer library2
8562 (gdb) disable pretty-printer library1
8564 2 of 3 printers enabled
8565 (gdb) info pretty-printer
8572 (gdb) disable pretty-printer library2 bar:bar1
8574 1 of 3 printers enabled
8575 (gdb) info pretty-printer library2
8582 (gdb) disable pretty-printer library2 bar
8584 0 of 3 printers enabled
8585 (gdb) info pretty-printer library2
8594 Note that for @code{bar} the entire printer can be disabled,
8595 as can each individual subprinter.
8598 @section Value History
8600 @cindex value history
8601 @cindex history of values printed by @value{GDBN}
8602 Values printed by the @code{print} command are saved in the @value{GDBN}
8603 @dfn{value history}. This allows you to refer to them in other expressions.
8604 Values are kept until the symbol table is re-read or discarded
8605 (for example with the @code{file} or @code{symbol-file} commands).
8606 When the symbol table changes, the value history is discarded,
8607 since the values may contain pointers back to the types defined in the
8612 @cindex history number
8613 The values printed are given @dfn{history numbers} by which you can
8614 refer to them. These are successive integers starting with one.
8615 @code{print} shows you the history number assigned to a value by
8616 printing @samp{$@var{num} = } before the value; here @var{num} is the
8619 To refer to any previous value, use @samp{$} followed by the value's
8620 history number. The way @code{print} labels its output is designed to
8621 remind you of this. Just @code{$} refers to the most recent value in
8622 the history, and @code{$$} refers to the value before that.
8623 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8624 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8625 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8627 For example, suppose you have just printed a pointer to a structure and
8628 want to see the contents of the structure. It suffices to type
8634 If you have a chain of structures where the component @code{next} points
8635 to the next one, you can print the contents of the next one with this:
8642 You can print successive links in the chain by repeating this
8643 command---which you can do by just typing @key{RET}.
8645 Note that the history records values, not expressions. If the value of
8646 @code{x} is 4 and you type these commands:
8654 then the value recorded in the value history by the @code{print} command
8655 remains 4 even though the value of @code{x} has changed.
8660 Print the last ten values in the value history, with their item numbers.
8661 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8662 values} does not change the history.
8664 @item show values @var{n}
8665 Print ten history values centered on history item number @var{n}.
8668 Print ten history values just after the values last printed. If no more
8669 values are available, @code{show values +} produces no display.
8672 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8673 same effect as @samp{show values +}.
8675 @node Convenience Vars
8676 @section Convenience Variables
8678 @cindex convenience variables
8679 @cindex user-defined variables
8680 @value{GDBN} provides @dfn{convenience variables} that you can use within
8681 @value{GDBN} to hold on to a value and refer to it later. These variables
8682 exist entirely within @value{GDBN}; they are not part of your program, and
8683 setting a convenience variable has no direct effect on further execution
8684 of your program. That is why you can use them freely.
8686 Convenience variables are prefixed with @samp{$}. Any name preceded by
8687 @samp{$} can be used for a convenience variable, unless it is one of
8688 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8689 (Value history references, in contrast, are @emph{numbers} preceded
8690 by @samp{$}. @xref{Value History, ,Value History}.)
8692 You can save a value in a convenience variable with an assignment
8693 expression, just as you would set a variable in your program.
8697 set $foo = *object_ptr
8701 would save in @code{$foo} the value contained in the object pointed to by
8704 Using a convenience variable for the first time creates it, but its
8705 value is @code{void} until you assign a new value. You can alter the
8706 value with another assignment at any time.
8708 Convenience variables have no fixed types. You can assign a convenience
8709 variable any type of value, including structures and arrays, even if
8710 that variable already has a value of a different type. The convenience
8711 variable, when used as an expression, has the type of its current value.
8714 @kindex show convenience
8715 @cindex show all user variables
8716 @item show convenience
8717 Print a list of convenience variables used so far, and their values.
8718 Abbreviated @code{show conv}.
8720 @kindex init-if-undefined
8721 @cindex convenience variables, initializing
8722 @item init-if-undefined $@var{variable} = @var{expression}
8723 Set a convenience variable if it has not already been set. This is useful
8724 for user-defined commands that keep some state. It is similar, in concept,
8725 to using local static variables with initializers in C (except that
8726 convenience variables are global). It can also be used to allow users to
8727 override default values used in a command script.
8729 If the variable is already defined then the expression is not evaluated so
8730 any side-effects do not occur.
8733 One of the ways to use a convenience variable is as a counter to be
8734 incremented or a pointer to be advanced. For example, to print
8735 a field from successive elements of an array of structures:
8739 print bar[$i++]->contents
8743 Repeat that command by typing @key{RET}.
8745 Some convenience variables are created automatically by @value{GDBN} and given
8746 values likely to be useful.
8749 @vindex $_@r{, convenience variable}
8751 The variable @code{$_} is automatically set by the @code{x} command to
8752 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8753 commands which provide a default address for @code{x} to examine also
8754 set @code{$_} to that address; these commands include @code{info line}
8755 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8756 except when set by the @code{x} command, in which case it is a pointer
8757 to the type of @code{$__}.
8759 @vindex $__@r{, convenience variable}
8761 The variable @code{$__} is automatically set by the @code{x} command
8762 to the value found in the last address examined. Its type is chosen
8763 to match the format in which the data was printed.
8766 @vindex $_exitcode@r{, convenience variable}
8767 The variable @code{$_exitcode} is automatically set to the exit code when
8768 the program being debugged terminates.
8771 @vindex $_sdata@r{, inspect, convenience variable}
8772 The variable @code{$_sdata} contains extra collected static tracepoint
8773 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8774 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8775 if extra static tracepoint data has not been collected.
8778 @vindex $_siginfo@r{, convenience variable}
8779 The variable @code{$_siginfo} contains extra signal information
8780 (@pxref{extra signal information}). Note that @code{$_siginfo}
8781 could be empty, if the application has not yet received any signals.
8782 For example, it will be empty before you execute the @code{run} command.
8785 @vindex $_tlb@r{, convenience variable}
8786 The variable @code{$_tlb} is automatically set when debugging
8787 applications running on MS-Windows in native mode or connected to
8788 gdbserver that supports the @code{qGetTIBAddr} request.
8789 @xref{General Query Packets}.
8790 This variable contains the address of the thread information block.
8794 On HP-UX systems, if you refer to a function or variable name that
8795 begins with a dollar sign, @value{GDBN} searches for a user or system
8796 name first, before it searches for a convenience variable.
8798 @cindex convenience functions
8799 @value{GDBN} also supplies some @dfn{convenience functions}. These
8800 have a syntax similar to convenience variables. A convenience
8801 function can be used in an expression just like an ordinary function;
8802 however, a convenience function is implemented internally to
8807 @kindex help function
8808 @cindex show all convenience functions
8809 Print a list of all convenience functions.
8816 You can refer to machine register contents, in expressions, as variables
8817 with names starting with @samp{$}. The names of registers are different
8818 for each machine; use @code{info registers} to see the names used on
8822 @kindex info registers
8823 @item info registers
8824 Print the names and values of all registers except floating-point
8825 and vector registers (in the selected stack frame).
8827 @kindex info all-registers
8828 @cindex floating point registers
8829 @item info all-registers
8830 Print the names and values of all registers, including floating-point
8831 and vector registers (in the selected stack frame).
8833 @item info registers @var{regname} @dots{}
8834 Print the @dfn{relativized} value of each specified register @var{regname}.
8835 As discussed in detail below, register values are normally relative to
8836 the selected stack frame. @var{regname} may be any register name valid on
8837 the machine you are using, with or without the initial @samp{$}.
8840 @cindex stack pointer register
8841 @cindex program counter register
8842 @cindex process status register
8843 @cindex frame pointer register
8844 @cindex standard registers
8845 @value{GDBN} has four ``standard'' register names that are available (in
8846 expressions) on most machines---whenever they do not conflict with an
8847 architecture's canonical mnemonics for registers. The register names
8848 @code{$pc} and @code{$sp} are used for the program counter register and
8849 the stack pointer. @code{$fp} is used for a register that contains a
8850 pointer to the current stack frame, and @code{$ps} is used for a
8851 register that contains the processor status. For example,
8852 you could print the program counter in hex with
8859 or print the instruction to be executed next with
8866 or add four to the stack pointer@footnote{This is a way of removing
8867 one word from the stack, on machines where stacks grow downward in
8868 memory (most machines, nowadays). This assumes that the innermost
8869 stack frame is selected; setting @code{$sp} is not allowed when other
8870 stack frames are selected. To pop entire frames off the stack,
8871 regardless of machine architecture, use @code{return};
8872 see @ref{Returning, ,Returning from a Function}.} with
8878 Whenever possible, these four standard register names are available on
8879 your machine even though the machine has different canonical mnemonics,
8880 so long as there is no conflict. The @code{info registers} command
8881 shows the canonical names. For example, on the SPARC, @code{info
8882 registers} displays the processor status register as @code{$psr} but you
8883 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8884 is an alias for the @sc{eflags} register.
8886 @value{GDBN} always considers the contents of an ordinary register as an
8887 integer when the register is examined in this way. Some machines have
8888 special registers which can hold nothing but floating point; these
8889 registers are considered to have floating point values. There is no way
8890 to refer to the contents of an ordinary register as floating point value
8891 (although you can @emph{print} it as a floating point value with
8892 @samp{print/f $@var{regname}}).
8894 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8895 means that the data format in which the register contents are saved by
8896 the operating system is not the same one that your program normally
8897 sees. For example, the registers of the 68881 floating point
8898 coprocessor are always saved in ``extended'' (raw) format, but all C
8899 programs expect to work with ``double'' (virtual) format. In such
8900 cases, @value{GDBN} normally works with the virtual format only (the format
8901 that makes sense for your program), but the @code{info registers} command
8902 prints the data in both formats.
8904 @cindex SSE registers (x86)
8905 @cindex MMX registers (x86)
8906 Some machines have special registers whose contents can be interpreted
8907 in several different ways. For example, modern x86-based machines
8908 have SSE and MMX registers that can hold several values packed
8909 together in several different formats. @value{GDBN} refers to such
8910 registers in @code{struct} notation:
8913 (@value{GDBP}) print $xmm1
8915 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8916 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8917 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8918 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8919 v4_int32 = @{0, 20657912, 11, 13@},
8920 v2_int64 = @{88725056443645952, 55834574859@},
8921 uint128 = 0x0000000d0000000b013b36f800000000
8926 To set values of such registers, you need to tell @value{GDBN} which
8927 view of the register you wish to change, as if you were assigning
8928 value to a @code{struct} member:
8931 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8934 Normally, register values are relative to the selected stack frame
8935 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8936 value that the register would contain if all stack frames farther in
8937 were exited and their saved registers restored. In order to see the
8938 true contents of hardware registers, you must select the innermost
8939 frame (with @samp{frame 0}).
8941 However, @value{GDBN} must deduce where registers are saved, from the machine
8942 code generated by your compiler. If some registers are not saved, or if
8943 @value{GDBN} is unable to locate the saved registers, the selected stack
8944 frame makes no difference.
8946 @node Floating Point Hardware
8947 @section Floating Point Hardware
8948 @cindex floating point
8950 Depending on the configuration, @value{GDBN} may be able to give
8951 you more information about the status of the floating point hardware.
8956 Display hardware-dependent information about the floating
8957 point unit. The exact contents and layout vary depending on the
8958 floating point chip. Currently, @samp{info float} is supported on
8959 the ARM and x86 machines.
8963 @section Vector Unit
8966 Depending on the configuration, @value{GDBN} may be able to give you
8967 more information about the status of the vector unit.
8972 Display information about the vector unit. The exact contents and
8973 layout vary depending on the hardware.
8976 @node OS Information
8977 @section Operating System Auxiliary Information
8978 @cindex OS information
8980 @value{GDBN} provides interfaces to useful OS facilities that can help
8981 you debug your program.
8983 @cindex @code{ptrace} system call
8984 @cindex @code{struct user} contents
8985 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8986 machines), it interfaces with the inferior via the @code{ptrace}
8987 system call. The operating system creates a special sata structure,
8988 called @code{struct user}, for this interface. You can use the
8989 command @code{info udot} to display the contents of this data
8995 Display the contents of the @code{struct user} maintained by the OS
8996 kernel for the program being debugged. @value{GDBN} displays the
8997 contents of @code{struct user} as a list of hex numbers, similar to
8998 the @code{examine} command.
9001 @cindex auxiliary vector
9002 @cindex vector, auxiliary
9003 Some operating systems supply an @dfn{auxiliary vector} to programs at
9004 startup. This is akin to the arguments and environment that you
9005 specify for a program, but contains a system-dependent variety of
9006 binary values that tell system libraries important details about the
9007 hardware, operating system, and process. Each value's purpose is
9008 identified by an integer tag; the meanings are well-known but system-specific.
9009 Depending on the configuration and operating system facilities,
9010 @value{GDBN} may be able to show you this information. For remote
9011 targets, this functionality may further depend on the remote stub's
9012 support of the @samp{qXfer:auxv:read} packet, see
9013 @ref{qXfer auxiliary vector read}.
9018 Display the auxiliary vector of the inferior, which can be either a
9019 live process or a core dump file. @value{GDBN} prints each tag value
9020 numerically, and also shows names and text descriptions for recognized
9021 tags. Some values in the vector are numbers, some bit masks, and some
9022 pointers to strings or other data. @value{GDBN} displays each value in the
9023 most appropriate form for a recognized tag, and in hexadecimal for
9024 an unrecognized tag.
9027 On some targets, @value{GDBN} can access operating-system-specific information
9028 and display it to user, without interpretation. For remote targets,
9029 this functionality depends on the remote stub's support of the
9030 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9035 List the types of OS information available for the target. If the
9036 target does not return a list of possible types, this command will
9039 @kindex info os processes
9040 @item info os processes
9041 Display the list of processes on the target. For each process,
9042 @value{GDBN} prints the process identifier, the name of the user, and
9043 the command corresponding to the process.
9046 @node Memory Region Attributes
9047 @section Memory Region Attributes
9048 @cindex memory region attributes
9050 @dfn{Memory region attributes} allow you to describe special handling
9051 required by regions of your target's memory. @value{GDBN} uses
9052 attributes to determine whether to allow certain types of memory
9053 accesses; whether to use specific width accesses; and whether to cache
9054 target memory. By default the description of memory regions is
9055 fetched from the target (if the current target supports this), but the
9056 user can override the fetched regions.
9058 Defined memory regions can be individually enabled and disabled. When a
9059 memory region is disabled, @value{GDBN} uses the default attributes when
9060 accessing memory in that region. Similarly, if no memory regions have
9061 been defined, @value{GDBN} uses the default attributes when accessing
9064 When a memory region is defined, it is given a number to identify it;
9065 to enable, disable, or remove a memory region, you specify that number.
9069 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9070 Define a memory region bounded by @var{lower} and @var{upper} with
9071 attributes @var{attributes}@dots{}, and add it to the list of regions
9072 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9073 case: it is treated as the target's maximum memory address.
9074 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9077 Discard any user changes to the memory regions and use target-supplied
9078 regions, if available, or no regions if the target does not support.
9081 @item delete mem @var{nums}@dots{}
9082 Remove memory regions @var{nums}@dots{} from the list of regions
9083 monitored by @value{GDBN}.
9086 @item disable mem @var{nums}@dots{}
9087 Disable monitoring of memory regions @var{nums}@dots{}.
9088 A disabled memory region is not forgotten.
9089 It may be enabled again later.
9092 @item enable mem @var{nums}@dots{}
9093 Enable monitoring of memory regions @var{nums}@dots{}.
9097 Print a table of all defined memory regions, with the following columns
9101 @item Memory Region Number
9102 @item Enabled or Disabled.
9103 Enabled memory regions are marked with @samp{y}.
9104 Disabled memory regions are marked with @samp{n}.
9107 The address defining the inclusive lower bound of the memory region.
9110 The address defining the exclusive upper bound of the memory region.
9113 The list of attributes set for this memory region.
9118 @subsection Attributes
9120 @subsubsection Memory Access Mode
9121 The access mode attributes set whether @value{GDBN} may make read or
9122 write accesses to a memory region.
9124 While these attributes prevent @value{GDBN} from performing invalid
9125 memory accesses, they do nothing to prevent the target system, I/O DMA,
9126 etc.@: from accessing memory.
9130 Memory is read only.
9132 Memory is write only.
9134 Memory is read/write. This is the default.
9137 @subsubsection Memory Access Size
9138 The access size attribute tells @value{GDBN} to use specific sized
9139 accesses in the memory region. Often memory mapped device registers
9140 require specific sized accesses. If no access size attribute is
9141 specified, @value{GDBN} may use accesses of any size.
9145 Use 8 bit memory accesses.
9147 Use 16 bit memory accesses.
9149 Use 32 bit memory accesses.
9151 Use 64 bit memory accesses.
9154 @c @subsubsection Hardware/Software Breakpoints
9155 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9156 @c will use hardware or software breakpoints for the internal breakpoints
9157 @c used by the step, next, finish, until, etc. commands.
9161 @c Always use hardware breakpoints
9162 @c @item swbreak (default)
9165 @subsubsection Data Cache
9166 The data cache attributes set whether @value{GDBN} will cache target
9167 memory. While this generally improves performance by reducing debug
9168 protocol overhead, it can lead to incorrect results because @value{GDBN}
9169 does not know about volatile variables or memory mapped device
9174 Enable @value{GDBN} to cache target memory.
9176 Disable @value{GDBN} from caching target memory. This is the default.
9179 @subsection Memory Access Checking
9180 @value{GDBN} can be instructed to refuse accesses to memory that is
9181 not explicitly described. This can be useful if accessing such
9182 regions has undesired effects for a specific target, or to provide
9183 better error checking. The following commands control this behaviour.
9186 @kindex set mem inaccessible-by-default
9187 @item set mem inaccessible-by-default [on|off]
9188 If @code{on} is specified, make @value{GDBN} treat memory not
9189 explicitly described by the memory ranges as non-existent and refuse accesses
9190 to such memory. The checks are only performed if there's at least one
9191 memory range defined. If @code{off} is specified, make @value{GDBN}
9192 treat the memory not explicitly described by the memory ranges as RAM.
9193 The default value is @code{on}.
9194 @kindex show mem inaccessible-by-default
9195 @item show mem inaccessible-by-default
9196 Show the current handling of accesses to unknown memory.
9200 @c @subsubsection Memory Write Verification
9201 @c The memory write verification attributes set whether @value{GDBN}
9202 @c will re-reads data after each write to verify the write was successful.
9206 @c @item noverify (default)
9209 @node Dump/Restore Files
9210 @section Copy Between Memory and a File
9211 @cindex dump/restore files
9212 @cindex append data to a file
9213 @cindex dump data to a file
9214 @cindex restore data from a file
9216 You can use the commands @code{dump}, @code{append}, and
9217 @code{restore} to copy data between target memory and a file. The
9218 @code{dump} and @code{append} commands write data to a file, and the
9219 @code{restore} command reads data from a file back into the inferior's
9220 memory. Files may be in binary, Motorola S-record, Intel hex, or
9221 Tektronix Hex format; however, @value{GDBN} can only append to binary
9227 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9228 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9229 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9230 or the value of @var{expr}, to @var{filename} in the given format.
9232 The @var{format} parameter may be any one of:
9239 Motorola S-record format.
9241 Tektronix Hex format.
9244 @value{GDBN} uses the same definitions of these formats as the
9245 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9246 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9250 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9251 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9252 Append the contents of memory from @var{start_addr} to @var{end_addr},
9253 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9254 (@value{GDBN} can only append data to files in raw binary form.)
9257 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9258 Restore the contents of file @var{filename} into memory. The
9259 @code{restore} command can automatically recognize any known @sc{bfd}
9260 file format, except for raw binary. To restore a raw binary file you
9261 must specify the optional keyword @code{binary} after the filename.
9263 If @var{bias} is non-zero, its value will be added to the addresses
9264 contained in the file. Binary files always start at address zero, so
9265 they will be restored at address @var{bias}. Other bfd files have
9266 a built-in location; they will be restored at offset @var{bias}
9269 If @var{start} and/or @var{end} are non-zero, then only data between
9270 file offset @var{start} and file offset @var{end} will be restored.
9271 These offsets are relative to the addresses in the file, before
9272 the @var{bias} argument is applied.
9276 @node Core File Generation
9277 @section How to Produce a Core File from Your Program
9278 @cindex dump core from inferior
9280 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9281 image of a running process and its process status (register values
9282 etc.). Its primary use is post-mortem debugging of a program that
9283 crashed while it ran outside a debugger. A program that crashes
9284 automatically produces a core file, unless this feature is disabled by
9285 the user. @xref{Files}, for information on invoking @value{GDBN} in
9286 the post-mortem debugging mode.
9288 Occasionally, you may wish to produce a core file of the program you
9289 are debugging in order to preserve a snapshot of its state.
9290 @value{GDBN} has a special command for that.
9294 @kindex generate-core-file
9295 @item generate-core-file [@var{file}]
9296 @itemx gcore [@var{file}]
9297 Produce a core dump of the inferior process. The optional argument
9298 @var{file} specifies the file name where to put the core dump. If not
9299 specified, the file name defaults to @file{core.@var{pid}}, where
9300 @var{pid} is the inferior process ID.
9302 Note that this command is implemented only for some systems (as of
9303 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9306 @node Character Sets
9307 @section Character Sets
9308 @cindex character sets
9310 @cindex translating between character sets
9311 @cindex host character set
9312 @cindex target character set
9314 If the program you are debugging uses a different character set to
9315 represent characters and strings than the one @value{GDBN} uses itself,
9316 @value{GDBN} can automatically translate between the character sets for
9317 you. The character set @value{GDBN} uses we call the @dfn{host
9318 character set}; the one the inferior program uses we call the
9319 @dfn{target character set}.
9321 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9322 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9323 remote protocol (@pxref{Remote Debugging}) to debug a program
9324 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9325 then the host character set is Latin-1, and the target character set is
9326 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9327 target-charset EBCDIC-US}, then @value{GDBN} translates between
9328 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9329 character and string literals in expressions.
9331 @value{GDBN} has no way to automatically recognize which character set
9332 the inferior program uses; you must tell it, using the @code{set
9333 target-charset} command, described below.
9335 Here are the commands for controlling @value{GDBN}'s character set
9339 @item set target-charset @var{charset}
9340 @kindex set target-charset
9341 Set the current target character set to @var{charset}. To display the
9342 list of supported target character sets, type
9343 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9345 @item set host-charset @var{charset}
9346 @kindex set host-charset
9347 Set the current host character set to @var{charset}.
9349 By default, @value{GDBN} uses a host character set appropriate to the
9350 system it is running on; you can override that default using the
9351 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9352 automatically determine the appropriate host character set. In this
9353 case, @value{GDBN} uses @samp{UTF-8}.
9355 @value{GDBN} can only use certain character sets as its host character
9356 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9357 @value{GDBN} will list the host character sets it supports.
9359 @item set charset @var{charset}
9361 Set the current host and target character sets to @var{charset}. As
9362 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9363 @value{GDBN} will list the names of the character sets that can be used
9364 for both host and target.
9367 @kindex show charset
9368 Show the names of the current host and target character sets.
9370 @item show host-charset
9371 @kindex show host-charset
9372 Show the name of the current host character set.
9374 @item show target-charset
9375 @kindex show target-charset
9376 Show the name of the current target character set.
9378 @item set target-wide-charset @var{charset}
9379 @kindex set target-wide-charset
9380 Set the current target's wide character set to @var{charset}. This is
9381 the character set used by the target's @code{wchar_t} type. To
9382 display the list of supported wide character sets, type
9383 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9385 @item show target-wide-charset
9386 @kindex show target-wide-charset
9387 Show the name of the current target's wide character set.
9390 Here is an example of @value{GDBN}'s character set support in action.
9391 Assume that the following source code has been placed in the file
9392 @file{charset-test.c}:
9398 = @{72, 101, 108, 108, 111, 44, 32, 119,
9399 111, 114, 108, 100, 33, 10, 0@};
9400 char ibm1047_hello[]
9401 = @{200, 133, 147, 147, 150, 107, 64, 166,
9402 150, 153, 147, 132, 90, 37, 0@};
9406 printf ("Hello, world!\n");
9410 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9411 containing the string @samp{Hello, world!} followed by a newline,
9412 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9414 We compile the program, and invoke the debugger on it:
9417 $ gcc -g charset-test.c -o charset-test
9418 $ gdb -nw charset-test
9419 GNU gdb 2001-12-19-cvs
9420 Copyright 2001 Free Software Foundation, Inc.
9425 We can use the @code{show charset} command to see what character sets
9426 @value{GDBN} is currently using to interpret and display characters and
9430 (@value{GDBP}) show charset
9431 The current host and target character set is `ISO-8859-1'.
9435 For the sake of printing this manual, let's use @sc{ascii} as our
9436 initial character set:
9438 (@value{GDBP}) set charset ASCII
9439 (@value{GDBP}) show charset
9440 The current host and target character set is `ASCII'.
9444 Let's assume that @sc{ascii} is indeed the correct character set for our
9445 host system --- in other words, let's assume that if @value{GDBN} prints
9446 characters using the @sc{ascii} character set, our terminal will display
9447 them properly. Since our current target character set is also
9448 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9451 (@value{GDBP}) print ascii_hello
9452 $1 = 0x401698 "Hello, world!\n"
9453 (@value{GDBP}) print ascii_hello[0]
9458 @value{GDBN} uses the target character set for character and string
9459 literals you use in expressions:
9462 (@value{GDBP}) print '+'
9467 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9470 @value{GDBN} relies on the user to tell it which character set the
9471 target program uses. If we print @code{ibm1047_hello} while our target
9472 character set is still @sc{ascii}, we get jibberish:
9475 (@value{GDBP}) print ibm1047_hello
9476 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9477 (@value{GDBP}) print ibm1047_hello[0]
9482 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9483 @value{GDBN} tells us the character sets it supports:
9486 (@value{GDBP}) set target-charset
9487 ASCII EBCDIC-US IBM1047 ISO-8859-1
9488 (@value{GDBP}) set target-charset
9491 We can select @sc{ibm1047} as our target character set, and examine the
9492 program's strings again. Now the @sc{ascii} string is wrong, but
9493 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9494 target character set, @sc{ibm1047}, to the host character set,
9495 @sc{ascii}, and they display correctly:
9498 (@value{GDBP}) set target-charset IBM1047
9499 (@value{GDBP}) show charset
9500 The current host character set is `ASCII'.
9501 The current target character set is `IBM1047'.
9502 (@value{GDBP}) print ascii_hello
9503 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9504 (@value{GDBP}) print ascii_hello[0]
9506 (@value{GDBP}) print ibm1047_hello
9507 $8 = 0x4016a8 "Hello, world!\n"
9508 (@value{GDBP}) print ibm1047_hello[0]
9513 As above, @value{GDBN} uses the target character set for character and
9514 string literals you use in expressions:
9517 (@value{GDBP}) print '+'
9522 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9525 @node Caching Remote Data
9526 @section Caching Data of Remote Targets
9527 @cindex caching data of remote targets
9529 @value{GDBN} caches data exchanged between the debugger and a
9530 remote target (@pxref{Remote Debugging}). Such caching generally improves
9531 performance, because it reduces the overhead of the remote protocol by
9532 bundling memory reads and writes into large chunks. Unfortunately, simply
9533 caching everything would lead to incorrect results, since @value{GDBN}
9534 does not necessarily know anything about volatile values, memory-mapped I/O
9535 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9536 memory can be changed @emph{while} a gdb command is executing.
9537 Therefore, by default, @value{GDBN} only caches data
9538 known to be on the stack@footnote{In non-stop mode, it is moderately
9539 rare for a running thread to modify the stack of a stopped thread
9540 in a way that would interfere with a backtrace, and caching of
9541 stack reads provides a significant speed up of remote backtraces.}.
9542 Other regions of memory can be explicitly marked as
9543 cacheable; see @pxref{Memory Region Attributes}.
9546 @kindex set remotecache
9547 @item set remotecache on
9548 @itemx set remotecache off
9549 This option no longer does anything; it exists for compatibility
9552 @kindex show remotecache
9553 @item show remotecache
9554 Show the current state of the obsolete remotecache flag.
9556 @kindex set stack-cache
9557 @item set stack-cache on
9558 @itemx set stack-cache off
9559 Enable or disable caching of stack accesses. When @code{ON}, use
9560 caching. By default, this option is @code{ON}.
9562 @kindex show stack-cache
9563 @item show stack-cache
9564 Show the current state of data caching for memory accesses.
9567 @item info dcache @r{[}line@r{]}
9568 Print the information about the data cache performance. The
9569 information displayed includes the dcache width and depth, and for
9570 each cache line, its number, address, and how many times it was
9571 referenced. This command is useful for debugging the data cache
9574 If a line number is specified, the contents of that line will be
9577 @item set dcache size @var{size}
9579 @kindex set dcache size
9580 Set maximum number of entries in dcache (dcache depth above).
9582 @item set dcache line-size @var{line-size}
9583 @cindex dcache line-size
9584 @kindex set dcache line-size
9585 Set number of bytes each dcache entry caches (dcache width above).
9586 Must be a power of 2.
9588 @item show dcache size
9589 @kindex show dcache size
9590 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9592 @item show dcache line-size
9593 @kindex show dcache line-size
9594 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9598 @node Searching Memory
9599 @section Search Memory
9600 @cindex searching memory
9602 Memory can be searched for a particular sequence of bytes with the
9603 @code{find} command.
9607 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9608 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9609 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9610 etc. The search begins at address @var{start_addr} and continues for either
9611 @var{len} bytes or through to @var{end_addr} inclusive.
9614 @var{s} and @var{n} are optional parameters.
9615 They may be specified in either order, apart or together.
9618 @item @var{s}, search query size
9619 The size of each search query value.
9625 halfwords (two bytes)
9629 giant words (eight bytes)
9632 All values are interpreted in the current language.
9633 This means, for example, that if the current source language is C/C@t{++}
9634 then searching for the string ``hello'' includes the trailing '\0'.
9636 If the value size is not specified, it is taken from the
9637 value's type in the current language.
9638 This is useful when one wants to specify the search
9639 pattern as a mixture of types.
9640 Note that this means, for example, that in the case of C-like languages
9641 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9642 which is typically four bytes.
9644 @item @var{n}, maximum number of finds
9645 The maximum number of matches to print. The default is to print all finds.
9648 You can use strings as search values. Quote them with double-quotes
9650 The string value is copied into the search pattern byte by byte,
9651 regardless of the endianness of the target and the size specification.
9653 The address of each match found is printed as well as a count of the
9654 number of matches found.
9656 The address of the last value found is stored in convenience variable
9658 A count of the number of matches is stored in @samp{$numfound}.
9660 For example, if stopped at the @code{printf} in this function:
9666 static char hello[] = "hello-hello";
9667 static struct @{ char c; short s; int i; @}
9668 __attribute__ ((packed)) mixed
9669 = @{ 'c', 0x1234, 0x87654321 @};
9670 printf ("%s\n", hello);
9675 you get during debugging:
9678 (gdb) find &hello[0], +sizeof(hello), "hello"
9679 0x804956d <hello.1620+6>
9681 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9682 0x8049567 <hello.1620>
9683 0x804956d <hello.1620+6>
9685 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9686 0x8049567 <hello.1620>
9688 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9689 0x8049560 <mixed.1625>
9691 (gdb) print $numfound
9694 $2 = (void *) 0x8049560
9697 @node Optimized Code
9698 @chapter Debugging Optimized Code
9699 @cindex optimized code, debugging
9700 @cindex debugging optimized code
9702 Almost all compilers support optimization. With optimization
9703 disabled, the compiler generates assembly code that corresponds
9704 directly to your source code, in a simplistic way. As the compiler
9705 applies more powerful optimizations, the generated assembly code
9706 diverges from your original source code. With help from debugging
9707 information generated by the compiler, @value{GDBN} can map from
9708 the running program back to constructs from your original source.
9710 @value{GDBN} is more accurate with optimization disabled. If you
9711 can recompile without optimization, it is easier to follow the
9712 progress of your program during debugging. But, there are many cases
9713 where you may need to debug an optimized version.
9715 When you debug a program compiled with @samp{-g -O}, remember that the
9716 optimizer has rearranged your code; the debugger shows you what is
9717 really there. Do not be too surprised when the execution path does not
9718 exactly match your source file! An extreme example: if you define a
9719 variable, but never use it, @value{GDBN} never sees that
9720 variable---because the compiler optimizes it out of existence.
9722 Some things do not work as well with @samp{-g -O} as with just
9723 @samp{-g}, particularly on machines with instruction scheduling. If in
9724 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9725 please report it to us as a bug (including a test case!).
9726 @xref{Variables}, for more information about debugging optimized code.
9729 * Inline Functions:: How @value{GDBN} presents inlining
9730 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9733 @node Inline Functions
9734 @section Inline Functions
9735 @cindex inline functions, debugging
9737 @dfn{Inlining} is an optimization that inserts a copy of the function
9738 body directly at each call site, instead of jumping to a shared
9739 routine. @value{GDBN} displays inlined functions just like
9740 non-inlined functions. They appear in backtraces. You can view their
9741 arguments and local variables, step into them with @code{step}, skip
9742 them with @code{next}, and escape from them with @code{finish}.
9743 You can check whether a function was inlined by using the
9744 @code{info frame} command.
9746 For @value{GDBN} to support inlined functions, the compiler must
9747 record information about inlining in the debug information ---
9748 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9749 other compilers do also. @value{GDBN} only supports inlined functions
9750 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9751 do not emit two required attributes (@samp{DW_AT_call_file} and
9752 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9753 function calls with earlier versions of @value{NGCC}. It instead
9754 displays the arguments and local variables of inlined functions as
9755 local variables in the caller.
9757 The body of an inlined function is directly included at its call site;
9758 unlike a non-inlined function, there are no instructions devoted to
9759 the call. @value{GDBN} still pretends that the call site and the
9760 start of the inlined function are different instructions. Stepping to
9761 the call site shows the call site, and then stepping again shows
9762 the first line of the inlined function, even though no additional
9763 instructions are executed.
9765 This makes source-level debugging much clearer; you can see both the
9766 context of the call and then the effect of the call. Only stepping by
9767 a single instruction using @code{stepi} or @code{nexti} does not do
9768 this; single instruction steps always show the inlined body.
9770 There are some ways that @value{GDBN} does not pretend that inlined
9771 function calls are the same as normal calls:
9775 You cannot set breakpoints on inlined functions. @value{GDBN}
9776 either reports that there is no symbol with that name, or else sets the
9777 breakpoint only on non-inlined copies of the function. This limitation
9778 will be removed in a future version of @value{GDBN}; until then,
9779 set a breakpoint by line number on the first line of the inlined
9783 Setting breakpoints at the call site of an inlined function may not
9784 work, because the call site does not contain any code. @value{GDBN}
9785 may incorrectly move the breakpoint to the next line of the enclosing
9786 function, after the call. This limitation will be removed in a future
9787 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9788 or inside the inlined function instead.
9791 @value{GDBN} cannot locate the return value of inlined calls after
9792 using the @code{finish} command. This is a limitation of compiler-generated
9793 debugging information; after @code{finish}, you can step to the next line
9794 and print a variable where your program stored the return value.
9798 @node Tail Call Frames
9799 @section Tail Call Frames
9800 @cindex tail call frames, debugging
9802 Function @code{B} can call function @code{C} in its very last statement. In
9803 unoptimized compilation the call of @code{C} is immediately followed by return
9804 instruction at the end of @code{B} code. Optimizing compiler may replace the
9805 call and return in function @code{B} into one jump to function @code{C}
9806 instead. Such use of a jump instruction is called @dfn{tail call}.
9808 During execution of function @code{C}, there will be no indication in the
9809 function call stack frames that it was tail-called from @code{B}. If function
9810 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9811 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9812 some cases @value{GDBN} can determine that @code{C} was tail-called from
9813 @code{B}, and it will then create fictitious call frame for that, with the
9814 return address set up as if @code{B} called @code{C} normally.
9816 This functionality is currently supported only by DWARF 2 debugging format and
9817 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9818 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9821 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9822 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9826 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9828 Stack level 1, frame at 0x7fffffffda30:
9829 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9830 tail call frame, caller of frame at 0x7fffffffda30
9831 source language c++.
9832 Arglist at unknown address.
9833 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9836 The detection of all the possible code path executions can find them ambiguous.
9837 There is no execution history stored (possible @ref{Reverse Execution} is never
9838 used for this purpose) and the last known caller could have reached the known
9839 callee by multiple different jump sequences. In such case @value{GDBN} still
9840 tries to show at least all the unambiguous top tail callers and all the
9841 unambiguous bottom tail calees, if any.
9844 @anchor{set debug entry-values}
9845 @item set debug entry-values
9846 @kindex set debug entry-values
9847 When set to on, enables printing of analysis messages for both frame argument
9848 values at function entry and tail calls. It will show all the possible valid
9849 tail calls code paths it has considered. It will also print the intersection
9850 of them with the final unambiguous (possibly partial or even empty) code path
9853 @item show debug entry-values
9854 @kindex show debug entry-values
9855 Show the current state of analysis messages printing for both frame argument
9856 values at function entry and tail calls.
9859 The analysis messages for tail calls can for example show why the virtual tail
9860 call frame for function @code{c} has not been recognized (due to the indirect
9861 reference by variable @code{x}):
9864 static void __attribute__((noinline, noclone)) c (void);
9865 void (*x) (void) = c;
9866 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9867 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9868 int main (void) @{ x (); return 0; @}
9870 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9871 DW_TAG_GNU_call_site 0x40039a in main
9873 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9876 #1 0x000000000040039a in main () at t.c:5
9879 Another possibility is an ambiguous virtual tail call frames resolution:
9883 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9884 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9885 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9886 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9887 static void __attribute__((noinline, noclone)) b (void)
9888 @{ if (i) c (); else e (); @}
9889 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9890 int main (void) @{ a (); return 0; @}
9892 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9893 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9894 tailcall: reduced: 0x4004d2(a) |
9897 #1 0x00000000004004d2 in a () at t.c:8
9898 #2 0x0000000000400395 in main () at t.c:9
9901 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9902 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9904 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9905 @ifset HAVE_MAKEINFO_CLICK
9907 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9908 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9910 @ifclear HAVE_MAKEINFO_CLICK
9912 @set CALLSEQ1B @value{CALLSEQ1A}
9913 @set CALLSEQ2B @value{CALLSEQ2A}
9916 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9917 The code can have possible execution paths @value{CALLSEQ1B} or
9918 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9920 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9921 has found. It then finds another possible calling sequcen - that one is
9922 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9923 printed as the @code{reduced:} calling sequence. That one could have many
9924 futher @code{compare:} and @code{reduced:} statements as long as there remain
9925 any non-ambiguous sequence entries.
9927 For the frame of function @code{b} in both cases there are different possible
9928 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9929 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9930 therefore this one is displayed to the user while the ambiguous frames are
9933 There can be also reasons why printing of frame argument values at function
9938 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9939 static void __attribute__((noinline, noclone)) a (int i);
9940 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9941 static void __attribute__((noinline, noclone)) a (int i)
9942 @{ if (i) b (i - 1); else c (0); @}
9943 int main (void) @{ a (5); return 0; @}
9946 #0 c (i=i@@entry=0) at t.c:2
9947 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9948 function "a" at 0x400420 can call itself via tail calls
9949 i=<optimized out>) at t.c:6
9950 #2 0x000000000040036e in main () at t.c:7
9953 @value{GDBN} cannot find out from the inferior state if and how many times did
9954 function @code{a} call itself (via function @code{b}) as these calls would be
9955 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9956 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9957 prints @code{<optimized out>} instead.
9960 @chapter C Preprocessor Macros
9962 Some languages, such as C and C@t{++}, provide a way to define and invoke
9963 ``preprocessor macros'' which expand into strings of tokens.
9964 @value{GDBN} can evaluate expressions containing macro invocations, show
9965 the result of macro expansion, and show a macro's definition, including
9966 where it was defined.
9968 You may need to compile your program specially to provide @value{GDBN}
9969 with information about preprocessor macros. Most compilers do not
9970 include macros in their debugging information, even when you compile
9971 with the @option{-g} flag. @xref{Compilation}.
9973 A program may define a macro at one point, remove that definition later,
9974 and then provide a different definition after that. Thus, at different
9975 points in the program, a macro may have different definitions, or have
9976 no definition at all. If there is a current stack frame, @value{GDBN}
9977 uses the macros in scope at that frame's source code line. Otherwise,
9978 @value{GDBN} uses the macros in scope at the current listing location;
9981 Whenever @value{GDBN} evaluates an expression, it always expands any
9982 macro invocations present in the expression. @value{GDBN} also provides
9983 the following commands for working with macros explicitly.
9987 @kindex macro expand
9988 @cindex macro expansion, showing the results of preprocessor
9989 @cindex preprocessor macro expansion, showing the results of
9990 @cindex expanding preprocessor macros
9991 @item macro expand @var{expression}
9992 @itemx macro exp @var{expression}
9993 Show the results of expanding all preprocessor macro invocations in
9994 @var{expression}. Since @value{GDBN} simply expands macros, but does
9995 not parse the result, @var{expression} need not be a valid expression;
9996 it can be any string of tokens.
9999 @item macro expand-once @var{expression}
10000 @itemx macro exp1 @var{expression}
10001 @cindex expand macro once
10002 @i{(This command is not yet implemented.)} Show the results of
10003 expanding those preprocessor macro invocations that appear explicitly in
10004 @var{expression}. Macro invocations appearing in that expansion are
10005 left unchanged. This command allows you to see the effect of a
10006 particular macro more clearly, without being confused by further
10007 expansions. Since @value{GDBN} simply expands macros, but does not
10008 parse the result, @var{expression} need not be a valid expression; it
10009 can be any string of tokens.
10012 @cindex macro definition, showing
10013 @cindex definition of a macro, showing
10014 @cindex macros, from debug info
10015 @item info macro [-a|-all] [--] @var{macro}
10016 Show the current definition or all definitions of the named @var{macro},
10017 and describe the source location or compiler command-line where that
10018 definition was established. The optional double dash is to signify the end of
10019 argument processing and the beginning of @var{macro} for non C-like macros where
10020 the macro may begin with a hyphen.
10022 @kindex info macros
10023 @item info macros @var{linespec}
10024 Show all macro definitions that are in effect at the location specified
10025 by @var{linespec}, and describe the source location or compiler
10026 command-line where those definitions were established.
10028 @kindex macro define
10029 @cindex user-defined macros
10030 @cindex defining macros interactively
10031 @cindex macros, user-defined
10032 @item macro define @var{macro} @var{replacement-list}
10033 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10034 Introduce a definition for a preprocessor macro named @var{macro},
10035 invocations of which are replaced by the tokens given in
10036 @var{replacement-list}. The first form of this command defines an
10037 ``object-like'' macro, which takes no arguments; the second form
10038 defines a ``function-like'' macro, which takes the arguments given in
10041 A definition introduced by this command is in scope in every
10042 expression evaluated in @value{GDBN}, until it is removed with the
10043 @code{macro undef} command, described below. The definition overrides
10044 all definitions for @var{macro} present in the program being debugged,
10045 as well as any previous user-supplied definition.
10047 @kindex macro undef
10048 @item macro undef @var{macro}
10049 Remove any user-supplied definition for the macro named @var{macro}.
10050 This command only affects definitions provided with the @code{macro
10051 define} command, described above; it cannot remove definitions present
10052 in the program being debugged.
10056 List all the macros defined using the @code{macro define} command.
10059 @cindex macros, example of debugging with
10060 Here is a transcript showing the above commands in action. First, we
10061 show our source files:
10066 #include "sample.h"
10069 #define ADD(x) (M + x)
10074 printf ("Hello, world!\n");
10076 printf ("We're so creative.\n");
10078 printf ("Goodbye, world!\n");
10085 Now, we compile the program using the @sc{gnu} C compiler,
10086 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10087 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10088 and @option{-gdwarf-4}; we recommend always choosing the most recent
10089 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10090 includes information about preprocessor macros in the debugging
10094 $ gcc -gdwarf-2 -g3 sample.c -o sample
10098 Now, we start @value{GDBN} on our sample program:
10102 GNU gdb 2002-05-06-cvs
10103 Copyright 2002 Free Software Foundation, Inc.
10104 GDB is free software, @dots{}
10108 We can expand macros and examine their definitions, even when the
10109 program is not running. @value{GDBN} uses the current listing position
10110 to decide which macro definitions are in scope:
10113 (@value{GDBP}) list main
10116 5 #define ADD(x) (M + x)
10121 10 printf ("Hello, world!\n");
10123 12 printf ("We're so creative.\n");
10124 (@value{GDBP}) info macro ADD
10125 Defined at /home/jimb/gdb/macros/play/sample.c:5
10126 #define ADD(x) (M + x)
10127 (@value{GDBP}) info macro Q
10128 Defined at /home/jimb/gdb/macros/play/sample.h:1
10129 included at /home/jimb/gdb/macros/play/sample.c:2
10131 (@value{GDBP}) macro expand ADD(1)
10132 expands to: (42 + 1)
10133 (@value{GDBP}) macro expand-once ADD(1)
10134 expands to: once (M + 1)
10138 In the example above, note that @code{macro expand-once} expands only
10139 the macro invocation explicit in the original text --- the invocation of
10140 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10141 which was introduced by @code{ADD}.
10143 Once the program is running, @value{GDBN} uses the macro definitions in
10144 force at the source line of the current stack frame:
10147 (@value{GDBP}) break main
10148 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10150 Starting program: /home/jimb/gdb/macros/play/sample
10152 Breakpoint 1, main () at sample.c:10
10153 10 printf ("Hello, world!\n");
10157 At line 10, the definition of the macro @code{N} at line 9 is in force:
10160 (@value{GDBP}) info macro N
10161 Defined at /home/jimb/gdb/macros/play/sample.c:9
10163 (@value{GDBP}) macro expand N Q M
10164 expands to: 28 < 42
10165 (@value{GDBP}) print N Q M
10170 As we step over directives that remove @code{N}'s definition, and then
10171 give it a new definition, @value{GDBN} finds the definition (or lack
10172 thereof) in force at each point:
10175 (@value{GDBP}) next
10177 12 printf ("We're so creative.\n");
10178 (@value{GDBP}) info macro N
10179 The symbol `N' has no definition as a C/C++ preprocessor macro
10180 at /home/jimb/gdb/macros/play/sample.c:12
10181 (@value{GDBP}) next
10183 14 printf ("Goodbye, world!\n");
10184 (@value{GDBP}) info macro N
10185 Defined at /home/jimb/gdb/macros/play/sample.c:13
10187 (@value{GDBP}) macro expand N Q M
10188 expands to: 1729 < 42
10189 (@value{GDBP}) print N Q M
10194 In addition to source files, macros can be defined on the compilation command
10195 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10196 such a way, @value{GDBN} displays the location of their definition as line zero
10197 of the source file submitted to the compiler.
10200 (@value{GDBP}) info macro __STDC__
10201 Defined at /home/jimb/gdb/macros/play/sample.c:0
10208 @chapter Tracepoints
10209 @c This chapter is based on the documentation written by Michael
10210 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10212 @cindex tracepoints
10213 In some applications, it is not feasible for the debugger to interrupt
10214 the program's execution long enough for the developer to learn
10215 anything helpful about its behavior. If the program's correctness
10216 depends on its real-time behavior, delays introduced by a debugger
10217 might cause the program to change its behavior drastically, or perhaps
10218 fail, even when the code itself is correct. It is useful to be able
10219 to observe the program's behavior without interrupting it.
10221 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10222 specify locations in the program, called @dfn{tracepoints}, and
10223 arbitrary expressions to evaluate when those tracepoints are reached.
10224 Later, using the @code{tfind} command, you can examine the values
10225 those expressions had when the program hit the tracepoints. The
10226 expressions may also denote objects in memory---structures or arrays,
10227 for example---whose values @value{GDBN} should record; while visiting
10228 a particular tracepoint, you may inspect those objects as if they were
10229 in memory at that moment. However, because @value{GDBN} records these
10230 values without interacting with you, it can do so quickly and
10231 unobtrusively, hopefully not disturbing the program's behavior.
10233 The tracepoint facility is currently available only for remote
10234 targets. @xref{Targets}. In addition, your remote target must know
10235 how to collect trace data. This functionality is implemented in the
10236 remote stub; however, none of the stubs distributed with @value{GDBN}
10237 support tracepoints as of this writing. The format of the remote
10238 packets used to implement tracepoints are described in @ref{Tracepoint
10241 It is also possible to get trace data from a file, in a manner reminiscent
10242 of corefiles; you specify the filename, and use @code{tfind} to search
10243 through the file. @xref{Trace Files}, for more details.
10245 This chapter describes the tracepoint commands and features.
10248 * Set Tracepoints::
10249 * Analyze Collected Data::
10250 * Tracepoint Variables::
10254 @node Set Tracepoints
10255 @section Commands to Set Tracepoints
10257 Before running such a @dfn{trace experiment}, an arbitrary number of
10258 tracepoints can be set. A tracepoint is actually a special type of
10259 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10260 standard breakpoint commands. For instance, as with breakpoints,
10261 tracepoint numbers are successive integers starting from one, and many
10262 of the commands associated with tracepoints take the tracepoint number
10263 as their argument, to identify which tracepoint to work on.
10265 For each tracepoint, you can specify, in advance, some arbitrary set
10266 of data that you want the target to collect in the trace buffer when
10267 it hits that tracepoint. The collected data can include registers,
10268 local variables, or global data. Later, you can use @value{GDBN}
10269 commands to examine the values these data had at the time the
10270 tracepoint was hit.
10272 Tracepoints do not support every breakpoint feature. Ignore counts on
10273 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10274 commands when they are hit. Tracepoints may not be thread-specific
10277 @cindex fast tracepoints
10278 Some targets may support @dfn{fast tracepoints}, which are inserted in
10279 a different way (such as with a jump instead of a trap), that is
10280 faster but possibly restricted in where they may be installed.
10282 @cindex static tracepoints
10283 @cindex markers, static tracepoints
10284 @cindex probing markers, static tracepoints
10285 Regular and fast tracepoints are dynamic tracing facilities, meaning
10286 that they can be used to insert tracepoints at (almost) any location
10287 in the target. Some targets may also support controlling @dfn{static
10288 tracepoints} from @value{GDBN}. With static tracing, a set of
10289 instrumentation points, also known as @dfn{markers}, are embedded in
10290 the target program, and can be activated or deactivated by name or
10291 address. These are usually placed at locations which facilitate
10292 investigating what the target is actually doing. @value{GDBN}'s
10293 support for static tracing includes being able to list instrumentation
10294 points, and attach them with @value{GDBN} defined high level
10295 tracepoints that expose the whole range of convenience of
10296 @value{GDBN}'s tracepoints support. Namely, support for collecting
10297 registers values and values of global or local (to the instrumentation
10298 point) variables; tracepoint conditions and trace state variables.
10299 The act of installing a @value{GDBN} static tracepoint on an
10300 instrumentation point, or marker, is referred to as @dfn{probing} a
10301 static tracepoint marker.
10303 @code{gdbserver} supports tracepoints on some target systems.
10304 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10306 This section describes commands to set tracepoints and associated
10307 conditions and actions.
10310 * Create and Delete Tracepoints::
10311 * Enable and Disable Tracepoints::
10312 * Tracepoint Passcounts::
10313 * Tracepoint Conditions::
10314 * Trace State Variables::
10315 * Tracepoint Actions::
10316 * Listing Tracepoints::
10317 * Listing Static Tracepoint Markers::
10318 * Starting and Stopping Trace Experiments::
10319 * Tracepoint Restrictions::
10322 @node Create and Delete Tracepoints
10323 @subsection Create and Delete Tracepoints
10326 @cindex set tracepoint
10328 @item trace @var{location}
10329 The @code{trace} command is very similar to the @code{break} command.
10330 Its argument @var{location} can be a source line, a function name, or
10331 an address in the target program. @xref{Specify Location}. The
10332 @code{trace} command defines a tracepoint, which is a point in the
10333 target program where the debugger will briefly stop, collect some
10334 data, and then allow the program to continue. Setting a tracepoint or
10335 changing its actions takes effect immediately if the remote stub
10336 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10338 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10339 these changes don't take effect until the next @code{tstart}
10340 command, and once a trace experiment is running, further changes will
10341 not have any effect until the next trace experiment starts. In addition,
10342 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10343 address is not yet resolved. (This is similar to pending breakpoints.)
10344 Pending tracepoints are not downloaded to the target and not installed
10345 until they are resolved. The resolution of pending tracepoints requires
10346 @value{GDBN} support---when debugging with the remote target, and
10347 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10348 tracing}), pending tracepoints can not be resolved (and downloaded to
10349 the remote stub) while @value{GDBN} is disconnected.
10351 Here are some examples of using the @code{trace} command:
10354 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10356 (@value{GDBP}) @b{trace +2} // 2 lines forward
10358 (@value{GDBP}) @b{trace my_function} // first source line of function
10360 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10362 (@value{GDBP}) @b{trace *0x2117c4} // an address
10366 You can abbreviate @code{trace} as @code{tr}.
10368 @item trace @var{location} if @var{cond}
10369 Set a tracepoint with condition @var{cond}; evaluate the expression
10370 @var{cond} each time the tracepoint is reached, and collect data only
10371 if the value is nonzero---that is, if @var{cond} evaluates as true.
10372 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10373 information on tracepoint conditions.
10375 @item ftrace @var{location} [ if @var{cond} ]
10376 @cindex set fast tracepoint
10377 @cindex fast tracepoints, setting
10379 The @code{ftrace} command sets a fast tracepoint. For targets that
10380 support them, fast tracepoints will use a more efficient but possibly
10381 less general technique to trigger data collection, such as a jump
10382 instruction instead of a trap, or some sort of hardware support. It
10383 may not be possible to create a fast tracepoint at the desired
10384 location, in which case the command will exit with an explanatory
10387 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10390 On 32-bit x86-architecture systems, fast tracepoints normally need to
10391 be placed at an instruction that is 5 bytes or longer, but can be
10392 placed at 4-byte instructions if the low 64K of memory of the target
10393 program is available to install trampolines. Some Unix-type systems,
10394 such as @sc{gnu}/Linux, exclude low addresses from the program's
10395 address space; but for instance with the Linux kernel it is possible
10396 to let @value{GDBN} use this area by doing a @command{sysctl} command
10397 to set the @code{mmap_min_addr} kernel parameter, as in
10400 sudo sysctl -w vm.mmap_min_addr=32768
10404 which sets the low address to 32K, which leaves plenty of room for
10405 trampolines. The minimum address should be set to a page boundary.
10407 @item strace @var{location} [ if @var{cond} ]
10408 @cindex set static tracepoint
10409 @cindex static tracepoints, setting
10410 @cindex probe static tracepoint marker
10412 The @code{strace} command sets a static tracepoint. For targets that
10413 support it, setting a static tracepoint probes a static
10414 instrumentation point, or marker, found at @var{location}. It may not
10415 be possible to set a static tracepoint at the desired location, in
10416 which case the command will exit with an explanatory message.
10418 @value{GDBN} handles arguments to @code{strace} exactly as for
10419 @code{trace}, with the addition that the user can also specify
10420 @code{-m @var{marker}} as @var{location}. This probes the marker
10421 identified by the @var{marker} string identifier. This identifier
10422 depends on the static tracepoint backend library your program is
10423 using. You can find all the marker identifiers in the @samp{ID} field
10424 of the @code{info static-tracepoint-markers} command output.
10425 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10426 Markers}. For example, in the following small program using the UST
10432 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10437 the marker id is composed of joining the first two arguments to the
10438 @code{trace_mark} call with a slash, which translates to:
10441 (@value{GDBP}) info static-tracepoint-markers
10442 Cnt Enb ID Address What
10443 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10449 so you may probe the marker above with:
10452 (@value{GDBP}) strace -m ust/bar33
10455 Static tracepoints accept an extra collect action --- @code{collect
10456 $_sdata}. This collects arbitrary user data passed in the probe point
10457 call to the tracing library. In the UST example above, you'll see
10458 that the third argument to @code{trace_mark} is a printf-like format
10459 string. The user data is then the result of running that formating
10460 string against the following arguments. Note that @code{info
10461 static-tracepoint-markers} command output lists that format string in
10462 the @samp{Data:} field.
10464 You can inspect this data when analyzing the trace buffer, by printing
10465 the $_sdata variable like any other variable available to
10466 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10469 @cindex last tracepoint number
10470 @cindex recent tracepoint number
10471 @cindex tracepoint number
10472 The convenience variable @code{$tpnum} records the tracepoint number
10473 of the most recently set tracepoint.
10475 @kindex delete tracepoint
10476 @cindex tracepoint deletion
10477 @item delete tracepoint @r{[}@var{num}@r{]}
10478 Permanently delete one or more tracepoints. With no argument, the
10479 default is to delete all tracepoints. Note that the regular
10480 @code{delete} command can remove tracepoints also.
10485 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10487 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10491 You can abbreviate this command as @code{del tr}.
10494 @node Enable and Disable Tracepoints
10495 @subsection Enable and Disable Tracepoints
10497 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10500 @kindex disable tracepoint
10501 @item disable tracepoint @r{[}@var{num}@r{]}
10502 Disable tracepoint @var{num}, or all tracepoints if no argument
10503 @var{num} is given. A disabled tracepoint will have no effect during
10504 a trace experiment, but it is not forgotten. You can re-enable
10505 a disabled tracepoint using the @code{enable tracepoint} command.
10506 If the command is issued during a trace experiment and the debug target
10507 has support for disabling tracepoints during a trace experiment, then the
10508 change will be effective immediately. Otherwise, it will be applied to the
10509 next trace experiment.
10511 @kindex enable tracepoint
10512 @item enable tracepoint @r{[}@var{num}@r{]}
10513 Enable tracepoint @var{num}, or all tracepoints. If this command is
10514 issued during a trace experiment and the debug target supports enabling
10515 tracepoints during a trace experiment, then the enabled tracepoints will
10516 become effective immediately. Otherwise, they will become effective the
10517 next time a trace experiment is run.
10520 @node Tracepoint Passcounts
10521 @subsection Tracepoint Passcounts
10525 @cindex tracepoint pass count
10526 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10527 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10528 automatically stop a trace experiment. If a tracepoint's passcount is
10529 @var{n}, then the trace experiment will be automatically stopped on
10530 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10531 @var{num} is not specified, the @code{passcount} command sets the
10532 passcount of the most recently defined tracepoint. If no passcount is
10533 given, the trace experiment will run until stopped explicitly by the
10539 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10540 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10542 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10543 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10544 (@value{GDBP}) @b{trace foo}
10545 (@value{GDBP}) @b{pass 3}
10546 (@value{GDBP}) @b{trace bar}
10547 (@value{GDBP}) @b{pass 2}
10548 (@value{GDBP}) @b{trace baz}
10549 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10550 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10551 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10552 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10556 @node Tracepoint Conditions
10557 @subsection Tracepoint Conditions
10558 @cindex conditional tracepoints
10559 @cindex tracepoint conditions
10561 The simplest sort of tracepoint collects data every time your program
10562 reaches a specified place. You can also specify a @dfn{condition} for
10563 a tracepoint. A condition is just a Boolean expression in your
10564 programming language (@pxref{Expressions, ,Expressions}). A
10565 tracepoint with a condition evaluates the expression each time your
10566 program reaches it, and data collection happens only if the condition
10569 Tracepoint conditions can be specified when a tracepoint is set, by
10570 using @samp{if} in the arguments to the @code{trace} command.
10571 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10572 also be set or changed at any time with the @code{condition} command,
10573 just as with breakpoints.
10575 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10576 the conditional expression itself. Instead, @value{GDBN} encodes the
10577 expression into an agent expression (@pxref{Agent Expressions})
10578 suitable for execution on the target, independently of @value{GDBN}.
10579 Global variables become raw memory locations, locals become stack
10580 accesses, and so forth.
10582 For instance, suppose you have a function that is usually called
10583 frequently, but should not be called after an error has occurred. You
10584 could use the following tracepoint command to collect data about calls
10585 of that function that happen while the error code is propagating
10586 through the program; an unconditional tracepoint could end up
10587 collecting thousands of useless trace frames that you would have to
10591 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10594 @node Trace State Variables
10595 @subsection Trace State Variables
10596 @cindex trace state variables
10598 A @dfn{trace state variable} is a special type of variable that is
10599 created and managed by target-side code. The syntax is the same as
10600 that for GDB's convenience variables (a string prefixed with ``$''),
10601 but they are stored on the target. They must be created explicitly,
10602 using a @code{tvariable} command. They are always 64-bit signed
10605 Trace state variables are remembered by @value{GDBN}, and downloaded
10606 to the target along with tracepoint information when the trace
10607 experiment starts. There are no intrinsic limits on the number of
10608 trace state variables, beyond memory limitations of the target.
10610 @cindex convenience variables, and trace state variables
10611 Although trace state variables are managed by the target, you can use
10612 them in print commands and expressions as if they were convenience
10613 variables; @value{GDBN} will get the current value from the target
10614 while the trace experiment is running. Trace state variables share
10615 the same namespace as other ``$'' variables, which means that you
10616 cannot have trace state variables with names like @code{$23} or
10617 @code{$pc}, nor can you have a trace state variable and a convenience
10618 variable with the same name.
10622 @item tvariable $@var{name} [ = @var{expression} ]
10624 The @code{tvariable} command creates a new trace state variable named
10625 @code{$@var{name}}, and optionally gives it an initial value of
10626 @var{expression}. @var{expression} is evaluated when this command is
10627 entered; the result will be converted to an integer if possible,
10628 otherwise @value{GDBN} will report an error. A subsequent
10629 @code{tvariable} command specifying the same name does not create a
10630 variable, but instead assigns the supplied initial value to the
10631 existing variable of that name, overwriting any previous initial
10632 value. The default initial value is 0.
10634 @item info tvariables
10635 @kindex info tvariables
10636 List all the trace state variables along with their initial values.
10637 Their current values may also be displayed, if the trace experiment is
10640 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10641 @kindex delete tvariable
10642 Delete the given trace state variables, or all of them if no arguments
10647 @node Tracepoint Actions
10648 @subsection Tracepoint Action Lists
10652 @cindex tracepoint actions
10653 @item actions @r{[}@var{num}@r{]}
10654 This command will prompt for a list of actions to be taken when the
10655 tracepoint is hit. If the tracepoint number @var{num} is not
10656 specified, this command sets the actions for the one that was most
10657 recently defined (so that you can define a tracepoint and then say
10658 @code{actions} without bothering about its number). You specify the
10659 actions themselves on the following lines, one action at a time, and
10660 terminate the actions list with a line containing just @code{end}. So
10661 far, the only defined actions are @code{collect}, @code{teval}, and
10662 @code{while-stepping}.
10664 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10665 Commands, ,Breakpoint Command Lists}), except that only the defined
10666 actions are allowed; any other @value{GDBN} command is rejected.
10668 @cindex remove actions from a tracepoint
10669 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10670 and follow it immediately with @samp{end}.
10673 (@value{GDBP}) @b{collect @var{data}} // collect some data
10675 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10677 (@value{GDBP}) @b{end} // signals the end of actions.
10680 In the following example, the action list begins with @code{collect}
10681 commands indicating the things to be collected when the tracepoint is
10682 hit. Then, in order to single-step and collect additional data
10683 following the tracepoint, a @code{while-stepping} command is used,
10684 followed by the list of things to be collected after each step in a
10685 sequence of single steps. The @code{while-stepping} command is
10686 terminated by its own separate @code{end} command. Lastly, the action
10687 list is terminated by an @code{end} command.
10690 (@value{GDBP}) @b{trace foo}
10691 (@value{GDBP}) @b{actions}
10692 Enter actions for tracepoint 1, one per line:
10695 > while-stepping 12
10696 > collect $pc, arr[i]
10701 @kindex collect @r{(tracepoints)}
10702 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10703 Collect values of the given expressions when the tracepoint is hit.
10704 This command accepts a comma-separated list of any valid expressions.
10705 In addition to global, static, or local variables, the following
10706 special arguments are supported:
10710 Collect all registers.
10713 Collect all function arguments.
10716 Collect all local variables.
10719 Collect the return address. This is helpful if you want to see more
10723 @vindex $_sdata@r{, collect}
10724 Collect static tracepoint marker specific data. Only available for
10725 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10726 Lists}. On the UST static tracepoints library backend, an
10727 instrumentation point resembles a @code{printf} function call. The
10728 tracing library is able to collect user specified data formatted to a
10729 character string using the format provided by the programmer that
10730 instrumented the program. Other backends have similar mechanisms.
10731 Here's an example of a UST marker call:
10734 const char master_name[] = "$your_name";
10735 trace_mark(channel1, marker1, "hello %s", master_name)
10738 In this case, collecting @code{$_sdata} collects the string
10739 @samp{hello $yourname}. When analyzing the trace buffer, you can
10740 inspect @samp{$_sdata} like any other variable available to
10744 You can give several consecutive @code{collect} commands, each one
10745 with a single argument, or one @code{collect} command with several
10746 arguments separated by commas; the effect is the same.
10748 The optional @var{mods} changes the usual handling of the arguments.
10749 @code{s} requests that pointers to chars be handled as strings, in
10750 particular collecting the contents of the memory being pointed at, up
10751 to the first zero. The upper bound is by default the value of the
10752 @code{print elements} variable; if @code{s} is followed by a decimal
10753 number, that is the upper bound instead. So for instance
10754 @samp{collect/s25 mystr} collects as many as 25 characters at
10757 The command @code{info scope} (@pxref{Symbols, info scope}) is
10758 particularly useful for figuring out what data to collect.
10760 @kindex teval @r{(tracepoints)}
10761 @item teval @var{expr1}, @var{expr2}, @dots{}
10762 Evaluate the given expressions when the tracepoint is hit. This
10763 command accepts a comma-separated list of expressions. The results
10764 are discarded, so this is mainly useful for assigning values to trace
10765 state variables (@pxref{Trace State Variables}) without adding those
10766 values to the trace buffer, as would be the case if the @code{collect}
10769 @kindex while-stepping @r{(tracepoints)}
10770 @item while-stepping @var{n}
10771 Perform @var{n} single-step instruction traces after the tracepoint,
10772 collecting new data after each step. The @code{while-stepping}
10773 command is followed by the list of what to collect while stepping
10774 (followed by its own @code{end} command):
10777 > while-stepping 12
10778 > collect $regs, myglobal
10784 Note that @code{$pc} is not automatically collected by
10785 @code{while-stepping}; you need to explicitly collect that register if
10786 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10789 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10790 @kindex set default-collect
10791 @cindex default collection action
10792 This variable is a list of expressions to collect at each tracepoint
10793 hit. It is effectively an additional @code{collect} action prepended
10794 to every tracepoint action list. The expressions are parsed
10795 individually for each tracepoint, so for instance a variable named
10796 @code{xyz} may be interpreted as a global for one tracepoint, and a
10797 local for another, as appropriate to the tracepoint's location.
10799 @item show default-collect
10800 @kindex show default-collect
10801 Show the list of expressions that are collected by default at each
10806 @node Listing Tracepoints
10807 @subsection Listing Tracepoints
10810 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10811 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10812 @cindex information about tracepoints
10813 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10814 Display information about the tracepoint @var{num}. If you don't
10815 specify a tracepoint number, displays information about all the
10816 tracepoints defined so far. The format is similar to that used for
10817 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10818 command, simply restricting itself to tracepoints.
10820 A tracepoint's listing may include additional information specific to
10825 its passcount as given by the @code{passcount @var{n}} command
10829 (@value{GDBP}) @b{info trace}
10830 Num Type Disp Enb Address What
10831 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10833 collect globfoo, $regs
10842 This command can be abbreviated @code{info tp}.
10845 @node Listing Static Tracepoint Markers
10846 @subsection Listing Static Tracepoint Markers
10849 @kindex info static-tracepoint-markers
10850 @cindex information about static tracepoint markers
10851 @item info static-tracepoint-markers
10852 Display information about all static tracepoint markers defined in the
10855 For each marker, the following columns are printed:
10859 An incrementing counter, output to help readability. This is not a
10862 The marker ID, as reported by the target.
10863 @item Enabled or Disabled
10864 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10865 that are not enabled.
10867 Where the marker is in your program, as a memory address.
10869 Where the marker is in the source for your program, as a file and line
10870 number. If the debug information included in the program does not
10871 allow @value{GDBN} to locate the source of the marker, this column
10872 will be left blank.
10876 In addition, the following information may be printed for each marker:
10880 User data passed to the tracing library by the marker call. In the
10881 UST backend, this is the format string passed as argument to the
10883 @item Static tracepoints probing the marker
10884 The list of static tracepoints attached to the marker.
10888 (@value{GDBP}) info static-tracepoint-markers
10889 Cnt ID Enb Address What
10890 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10891 Data: number1 %d number2 %d
10892 Probed by static tracepoints: #2
10893 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10899 @node Starting and Stopping Trace Experiments
10900 @subsection Starting and Stopping Trace Experiments
10903 @kindex tstart [ @var{notes} ]
10904 @cindex start a new trace experiment
10905 @cindex collected data discarded
10907 This command starts the trace experiment, and begins collecting data.
10908 It has the side effect of discarding all the data collected in the
10909 trace buffer during the previous trace experiment. If any arguments
10910 are supplied, they are taken as a note and stored with the trace
10911 experiment's state. The notes may be arbitrary text, and are
10912 especially useful with disconnected tracing in a multi-user context;
10913 the notes can explain what the trace is doing, supply user contact
10914 information, and so forth.
10916 @kindex tstop [ @var{notes} ]
10917 @cindex stop a running trace experiment
10919 This command stops the trace experiment. If any arguments are
10920 supplied, they are recorded with the experiment as a note. This is
10921 useful if you are stopping a trace started by someone else, for
10922 instance if the trace is interfering with the system's behavior and
10923 needs to be stopped quickly.
10925 @strong{Note}: a trace experiment and data collection may stop
10926 automatically if any tracepoint's passcount is reached
10927 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10930 @cindex status of trace data collection
10931 @cindex trace experiment, status of
10933 This command displays the status of the current trace data
10937 Here is an example of the commands we described so far:
10940 (@value{GDBP}) @b{trace gdb_c_test}
10941 (@value{GDBP}) @b{actions}
10942 Enter actions for tracepoint #1, one per line.
10943 > collect $regs,$locals,$args
10944 > while-stepping 11
10948 (@value{GDBP}) @b{tstart}
10949 [time passes @dots{}]
10950 (@value{GDBP}) @b{tstop}
10953 @anchor{disconnected tracing}
10954 @cindex disconnected tracing
10955 You can choose to continue running the trace experiment even if
10956 @value{GDBN} disconnects from the target, voluntarily or
10957 involuntarily. For commands such as @code{detach}, the debugger will
10958 ask what you want to do with the trace. But for unexpected
10959 terminations (@value{GDBN} crash, network outage), it would be
10960 unfortunate to lose hard-won trace data, so the variable
10961 @code{disconnected-tracing} lets you decide whether the trace should
10962 continue running without @value{GDBN}.
10965 @item set disconnected-tracing on
10966 @itemx set disconnected-tracing off
10967 @kindex set disconnected-tracing
10968 Choose whether a tracing run should continue to run if @value{GDBN}
10969 has disconnected from the target. Note that @code{detach} or
10970 @code{quit} will ask you directly what to do about a running trace no
10971 matter what this variable's setting, so the variable is mainly useful
10972 for handling unexpected situations, such as loss of the network.
10974 @item show disconnected-tracing
10975 @kindex show disconnected-tracing
10976 Show the current choice for disconnected tracing.
10980 When you reconnect to the target, the trace experiment may or may not
10981 still be running; it might have filled the trace buffer in the
10982 meantime, or stopped for one of the other reasons. If it is running,
10983 it will continue after reconnection.
10985 Upon reconnection, the target will upload information about the
10986 tracepoints in effect. @value{GDBN} will then compare that
10987 information to the set of tracepoints currently defined, and attempt
10988 to match them up, allowing for the possibility that the numbers may
10989 have changed due to creation and deletion in the meantime. If one of
10990 the target's tracepoints does not match any in @value{GDBN}, the
10991 debugger will create a new tracepoint, so that you have a number with
10992 which to specify that tracepoint. This matching-up process is
10993 necessarily heuristic, and it may result in useless tracepoints being
10994 created; you may simply delete them if they are of no use.
10996 @cindex circular trace buffer
10997 If your target agent supports a @dfn{circular trace buffer}, then you
10998 can run a trace experiment indefinitely without filling the trace
10999 buffer; when space runs out, the agent deletes already-collected trace
11000 frames, oldest first, until there is enough room to continue
11001 collecting. This is especially useful if your tracepoints are being
11002 hit too often, and your trace gets terminated prematurely because the
11003 buffer is full. To ask for a circular trace buffer, simply set
11004 @samp{circular-trace-buffer} to on. You can set this at any time,
11005 including during tracing; if the agent can do it, it will change
11006 buffer handling on the fly, otherwise it will not take effect until
11010 @item set circular-trace-buffer on
11011 @itemx set circular-trace-buffer off
11012 @kindex set circular-trace-buffer
11013 Choose whether a tracing run should use a linear or circular buffer
11014 for trace data. A linear buffer will not lose any trace data, but may
11015 fill up prematurely, while a circular buffer will discard old trace
11016 data, but it will have always room for the latest tracepoint hits.
11018 @item show circular-trace-buffer
11019 @kindex show circular-trace-buffer
11020 Show the current choice for the trace buffer. Note that this may not
11021 match the agent's current buffer handling, nor is it guaranteed to
11022 match the setting that might have been in effect during a past run,
11023 for instance if you are looking at frames from a trace file.
11028 @item set trace-user @var{text}
11029 @kindex set trace-user
11031 @item show trace-user
11032 @kindex show trace-user
11034 @item set trace-notes @var{text}
11035 @kindex set trace-notes
11036 Set the trace run's notes.
11038 @item show trace-notes
11039 @kindex show trace-notes
11040 Show the trace run's notes.
11042 @item set trace-stop-notes @var{text}
11043 @kindex set trace-stop-notes
11044 Set the trace run's stop notes. The handling of the note is as for
11045 @code{tstop} arguments; the set command is convenient way to fix a
11046 stop note that is mistaken or incomplete.
11048 @item show trace-stop-notes
11049 @kindex show trace-stop-notes
11050 Show the trace run's stop notes.
11054 @node Tracepoint Restrictions
11055 @subsection Tracepoint Restrictions
11057 @cindex tracepoint restrictions
11058 There are a number of restrictions on the use of tracepoints. As
11059 described above, tracepoint data gathering occurs on the target
11060 without interaction from @value{GDBN}. Thus the full capabilities of
11061 the debugger are not available during data gathering, and then at data
11062 examination time, you will be limited by only having what was
11063 collected. The following items describe some common problems, but it
11064 is not exhaustive, and you may run into additional difficulties not
11070 Tracepoint expressions are intended to gather objects (lvalues). Thus
11071 the full flexibility of GDB's expression evaluator is not available.
11072 You cannot call functions, cast objects to aggregate types, access
11073 convenience variables or modify values (except by assignment to trace
11074 state variables). Some language features may implicitly call
11075 functions (for instance Objective-C fields with accessors), and therefore
11076 cannot be collected either.
11079 Collection of local variables, either individually or in bulk with
11080 @code{$locals} or @code{$args}, during @code{while-stepping} may
11081 behave erratically. The stepping action may enter a new scope (for
11082 instance by stepping into a function), or the location of the variable
11083 may change (for instance it is loaded into a register). The
11084 tracepoint data recorded uses the location information for the
11085 variables that is correct for the tracepoint location. When the
11086 tracepoint is created, it is not possible, in general, to determine
11087 where the steps of a @code{while-stepping} sequence will advance the
11088 program---particularly if a conditional branch is stepped.
11091 Collection of an incompletely-initialized or partially-destroyed object
11092 may result in something that @value{GDBN} cannot display, or displays
11093 in a misleading way.
11096 When @value{GDBN} displays a pointer to character it automatically
11097 dereferences the pointer to also display characters of the string
11098 being pointed to. However, collecting the pointer during tracing does
11099 not automatically collect the string. You need to explicitly
11100 dereference the pointer and provide size information if you want to
11101 collect not only the pointer, but the memory pointed to. For example,
11102 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11106 It is not possible to collect a complete stack backtrace at a
11107 tracepoint. Instead, you may collect the registers and a few hundred
11108 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11109 (adjust to use the name of the actual stack pointer register on your
11110 target architecture, and the amount of stack you wish to capture).
11111 Then the @code{backtrace} command will show a partial backtrace when
11112 using a trace frame. The number of stack frames that can be examined
11113 depends on the sizes of the frames in the collected stack. Note that
11114 if you ask for a block so large that it goes past the bottom of the
11115 stack, the target agent may report an error trying to read from an
11119 If you do not collect registers at a tracepoint, @value{GDBN} can
11120 infer that the value of @code{$pc} must be the same as the address of
11121 the tracepoint and use that when you are looking at a trace frame
11122 for that tracepoint. However, this cannot work if the tracepoint has
11123 multiple locations (for instance if it was set in a function that was
11124 inlined), or if it has a @code{while-stepping} loop. In those cases
11125 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11130 @node Analyze Collected Data
11131 @section Using the Collected Data
11133 After the tracepoint experiment ends, you use @value{GDBN} commands
11134 for examining the trace data. The basic idea is that each tracepoint
11135 collects a trace @dfn{snapshot} every time it is hit and another
11136 snapshot every time it single-steps. All these snapshots are
11137 consecutively numbered from zero and go into a buffer, and you can
11138 examine them later. The way you examine them is to @dfn{focus} on a
11139 specific trace snapshot. When the remote stub is focused on a trace
11140 snapshot, it will respond to all @value{GDBN} requests for memory and
11141 registers by reading from the buffer which belongs to that snapshot,
11142 rather than from @emph{real} memory or registers of the program being
11143 debugged. This means that @strong{all} @value{GDBN} commands
11144 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11145 behave as if we were currently debugging the program state as it was
11146 when the tracepoint occurred. Any requests for data that are not in
11147 the buffer will fail.
11150 * tfind:: How to select a trace snapshot
11151 * tdump:: How to display all data for a snapshot
11152 * save tracepoints:: How to save tracepoints for a future run
11156 @subsection @code{tfind @var{n}}
11159 @cindex select trace snapshot
11160 @cindex find trace snapshot
11161 The basic command for selecting a trace snapshot from the buffer is
11162 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11163 counting from zero. If no argument @var{n} is given, the next
11164 snapshot is selected.
11166 Here are the various forms of using the @code{tfind} command.
11170 Find the first snapshot in the buffer. This is a synonym for
11171 @code{tfind 0} (since 0 is the number of the first snapshot).
11174 Stop debugging trace snapshots, resume @emph{live} debugging.
11177 Same as @samp{tfind none}.
11180 No argument means find the next trace snapshot.
11183 Find the previous trace snapshot before the current one. This permits
11184 retracing earlier steps.
11186 @item tfind tracepoint @var{num}
11187 Find the next snapshot associated with tracepoint @var{num}. Search
11188 proceeds forward from the last examined trace snapshot. If no
11189 argument @var{num} is given, it means find the next snapshot collected
11190 for the same tracepoint as the current snapshot.
11192 @item tfind pc @var{addr}
11193 Find the next snapshot associated with the value @var{addr} of the
11194 program counter. Search proceeds forward from the last examined trace
11195 snapshot. If no argument @var{addr} is given, it means find the next
11196 snapshot with the same value of PC as the current snapshot.
11198 @item tfind outside @var{addr1}, @var{addr2}
11199 Find the next snapshot whose PC is outside the given range of
11200 addresses (exclusive).
11202 @item tfind range @var{addr1}, @var{addr2}
11203 Find the next snapshot whose PC is between @var{addr1} and
11204 @var{addr2} (inclusive).
11206 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11207 Find the next snapshot associated with the source line @var{n}. If
11208 the optional argument @var{file} is given, refer to line @var{n} in
11209 that source file. Search proceeds forward from the last examined
11210 trace snapshot. If no argument @var{n} is given, it means find the
11211 next line other than the one currently being examined; thus saying
11212 @code{tfind line} repeatedly can appear to have the same effect as
11213 stepping from line to line in a @emph{live} debugging session.
11216 The default arguments for the @code{tfind} commands are specifically
11217 designed to make it easy to scan through the trace buffer. For
11218 instance, @code{tfind} with no argument selects the next trace
11219 snapshot, and @code{tfind -} with no argument selects the previous
11220 trace snapshot. So, by giving one @code{tfind} command, and then
11221 simply hitting @key{RET} repeatedly you can examine all the trace
11222 snapshots in order. Or, by saying @code{tfind -} and then hitting
11223 @key{RET} repeatedly you can examine the snapshots in reverse order.
11224 The @code{tfind line} command with no argument selects the snapshot
11225 for the next source line executed. The @code{tfind pc} command with
11226 no argument selects the next snapshot with the same program counter
11227 (PC) as the current frame. The @code{tfind tracepoint} command with
11228 no argument selects the next trace snapshot collected by the same
11229 tracepoint as the current one.
11231 In addition to letting you scan through the trace buffer manually,
11232 these commands make it easy to construct @value{GDBN} scripts that
11233 scan through the trace buffer and print out whatever collected data
11234 you are interested in. Thus, if we want to examine the PC, FP, and SP
11235 registers from each trace frame in the buffer, we can say this:
11238 (@value{GDBP}) @b{tfind start}
11239 (@value{GDBP}) @b{while ($trace_frame != -1)}
11240 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11241 $trace_frame, $pc, $sp, $fp
11245 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11246 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11247 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11248 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11249 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11250 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11251 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11252 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11253 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11254 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11255 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11258 Or, if we want to examine the variable @code{X} at each source line in
11262 (@value{GDBP}) @b{tfind start}
11263 (@value{GDBP}) @b{while ($trace_frame != -1)}
11264 > printf "Frame %d, X == %d\n", $trace_frame, X
11274 @subsection @code{tdump}
11276 @cindex dump all data collected at tracepoint
11277 @cindex tracepoint data, display
11279 This command takes no arguments. It prints all the data collected at
11280 the current trace snapshot.
11283 (@value{GDBP}) @b{trace 444}
11284 (@value{GDBP}) @b{actions}
11285 Enter actions for tracepoint #2, one per line:
11286 > collect $regs, $locals, $args, gdb_long_test
11289 (@value{GDBP}) @b{tstart}
11291 (@value{GDBP}) @b{tfind line 444}
11292 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11294 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11296 (@value{GDBP}) @b{tdump}
11297 Data collected at tracepoint 2, trace frame 1:
11298 d0 0xc4aa0085 -995491707
11302 d4 0x71aea3d 119204413
11305 d7 0x380035 3670069
11306 a0 0x19e24a 1696330
11307 a1 0x3000668 50333288
11309 a3 0x322000 3284992
11310 a4 0x3000698 50333336
11311 a5 0x1ad3cc 1758156
11312 fp 0x30bf3c 0x30bf3c
11313 sp 0x30bf34 0x30bf34
11315 pc 0x20b2c8 0x20b2c8
11319 p = 0x20e5b4 "gdb-test"
11326 gdb_long_test = 17 '\021'
11331 @code{tdump} works by scanning the tracepoint's current collection
11332 actions and printing the value of each expression listed. So
11333 @code{tdump} can fail, if after a run, you change the tracepoint's
11334 actions to mention variables that were not collected during the run.
11336 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11337 uses the collected value of @code{$pc} to distinguish between trace
11338 frames that were collected at the tracepoint hit, and frames that were
11339 collected while stepping. This allows it to correctly choose whether
11340 to display the basic list of collections, or the collections from the
11341 body of the while-stepping loop. However, if @code{$pc} was not collected,
11342 then @code{tdump} will always attempt to dump using the basic collection
11343 list, and may fail if a while-stepping frame does not include all the
11344 same data that is collected at the tracepoint hit.
11345 @c This is getting pretty arcane, example would be good.
11347 @node save tracepoints
11348 @subsection @code{save tracepoints @var{filename}}
11349 @kindex save tracepoints
11350 @kindex save-tracepoints
11351 @cindex save tracepoints for future sessions
11353 This command saves all current tracepoint definitions together with
11354 their actions and passcounts, into a file @file{@var{filename}}
11355 suitable for use in a later debugging session. To read the saved
11356 tracepoint definitions, use the @code{source} command (@pxref{Command
11357 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11358 alias for @w{@code{save tracepoints}}
11360 @node Tracepoint Variables
11361 @section Convenience Variables for Tracepoints
11362 @cindex tracepoint variables
11363 @cindex convenience variables for tracepoints
11366 @vindex $trace_frame
11367 @item (int) $trace_frame
11368 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11369 snapshot is selected.
11371 @vindex $tracepoint
11372 @item (int) $tracepoint
11373 The tracepoint for the current trace snapshot.
11375 @vindex $trace_line
11376 @item (int) $trace_line
11377 The line number for the current trace snapshot.
11379 @vindex $trace_file
11380 @item (char []) $trace_file
11381 The source file for the current trace snapshot.
11383 @vindex $trace_func
11384 @item (char []) $trace_func
11385 The name of the function containing @code{$tracepoint}.
11388 Note: @code{$trace_file} is not suitable for use in @code{printf},
11389 use @code{output} instead.
11391 Here's a simple example of using these convenience variables for
11392 stepping through all the trace snapshots and printing some of their
11393 data. Note that these are not the same as trace state variables,
11394 which are managed by the target.
11397 (@value{GDBP}) @b{tfind start}
11399 (@value{GDBP}) @b{while $trace_frame != -1}
11400 > output $trace_file
11401 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11407 @section Using Trace Files
11408 @cindex trace files
11410 In some situations, the target running a trace experiment may no
11411 longer be available; perhaps it crashed, or the hardware was needed
11412 for a different activity. To handle these cases, you can arrange to
11413 dump the trace data into a file, and later use that file as a source
11414 of trace data, via the @code{target tfile} command.
11419 @item tsave [ -r ] @var{filename}
11420 Save the trace data to @var{filename}. By default, this command
11421 assumes that @var{filename} refers to the host filesystem, so if
11422 necessary @value{GDBN} will copy raw trace data up from the target and
11423 then save it. If the target supports it, you can also supply the
11424 optional argument @code{-r} (``remote'') to direct the target to save
11425 the data directly into @var{filename} in its own filesystem, which may be
11426 more efficient if the trace buffer is very large. (Note, however, that
11427 @code{target tfile} can only read from files accessible to the host.)
11429 @kindex target tfile
11431 @item target tfile @var{filename}
11432 Use the file named @var{filename} as a source of trace data. Commands
11433 that examine data work as they do with a live target, but it is not
11434 possible to run any new trace experiments. @code{tstatus} will report
11435 the state of the trace run at the moment the data was saved, as well
11436 as the current trace frame you are examining. @var{filename} must be
11437 on a filesystem accessible to the host.
11442 @chapter Debugging Programs That Use Overlays
11445 If your program is too large to fit completely in your target system's
11446 memory, you can sometimes use @dfn{overlays} to work around this
11447 problem. @value{GDBN} provides some support for debugging programs that
11451 * How Overlays Work:: A general explanation of overlays.
11452 * Overlay Commands:: Managing overlays in @value{GDBN}.
11453 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11454 mapped by asking the inferior.
11455 * Overlay Sample Program:: A sample program using overlays.
11458 @node How Overlays Work
11459 @section How Overlays Work
11460 @cindex mapped overlays
11461 @cindex unmapped overlays
11462 @cindex load address, overlay's
11463 @cindex mapped address
11464 @cindex overlay area
11466 Suppose you have a computer whose instruction address space is only 64
11467 kilobytes long, but which has much more memory which can be accessed by
11468 other means: special instructions, segment registers, or memory
11469 management hardware, for example. Suppose further that you want to
11470 adapt a program which is larger than 64 kilobytes to run on this system.
11472 One solution is to identify modules of your program which are relatively
11473 independent, and need not call each other directly; call these modules
11474 @dfn{overlays}. Separate the overlays from the main program, and place
11475 their machine code in the larger memory. Place your main program in
11476 instruction memory, but leave at least enough space there to hold the
11477 largest overlay as well.
11479 Now, to call a function located in an overlay, you must first copy that
11480 overlay's machine code from the large memory into the space set aside
11481 for it in the instruction memory, and then jump to its entry point
11484 @c NB: In the below the mapped area's size is greater or equal to the
11485 @c size of all overlays. This is intentional to remind the developer
11486 @c that overlays don't necessarily need to be the same size.
11490 Data Instruction Larger
11491 Address Space Address Space Address Space
11492 +-----------+ +-----------+ +-----------+
11494 +-----------+ +-----------+ +-----------+<-- overlay 1
11495 | program | | main | .----| overlay 1 | load address
11496 | variables | | program | | +-----------+
11497 | and heap | | | | | |
11498 +-----------+ | | | +-----------+<-- overlay 2
11499 | | +-----------+ | | | load address
11500 +-----------+ | | | .-| overlay 2 |
11502 mapped --->+-----------+ | | +-----------+
11503 address | | | | | |
11504 | overlay | <-' | | |
11505 | area | <---' +-----------+<-- overlay 3
11506 | | <---. | | load address
11507 +-----------+ `--| overlay 3 |
11514 @anchor{A code overlay}A code overlay
11518 The diagram (@pxref{A code overlay}) shows a system with separate data
11519 and instruction address spaces. To map an overlay, the program copies
11520 its code from the larger address space to the instruction address space.
11521 Since the overlays shown here all use the same mapped address, only one
11522 may be mapped at a time. For a system with a single address space for
11523 data and instructions, the diagram would be similar, except that the
11524 program variables and heap would share an address space with the main
11525 program and the overlay area.
11527 An overlay loaded into instruction memory and ready for use is called a
11528 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11529 instruction memory. An overlay not present (or only partially present)
11530 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11531 is its address in the larger memory. The mapped address is also called
11532 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11533 called the @dfn{load memory address}, or @dfn{LMA}.
11535 Unfortunately, overlays are not a completely transparent way to adapt a
11536 program to limited instruction memory. They introduce a new set of
11537 global constraints you must keep in mind as you design your program:
11542 Before calling or returning to a function in an overlay, your program
11543 must make sure that overlay is actually mapped. Otherwise, the call or
11544 return will transfer control to the right address, but in the wrong
11545 overlay, and your program will probably crash.
11548 If the process of mapping an overlay is expensive on your system, you
11549 will need to choose your overlays carefully to minimize their effect on
11550 your program's performance.
11553 The executable file you load onto your system must contain each
11554 overlay's instructions, appearing at the overlay's load address, not its
11555 mapped address. However, each overlay's instructions must be relocated
11556 and its symbols defined as if the overlay were at its mapped address.
11557 You can use GNU linker scripts to specify different load and relocation
11558 addresses for pieces of your program; see @ref{Overlay Description,,,
11559 ld.info, Using ld: the GNU linker}.
11562 The procedure for loading executable files onto your system must be able
11563 to load their contents into the larger address space as well as the
11564 instruction and data spaces.
11568 The overlay system described above is rather simple, and could be
11569 improved in many ways:
11574 If your system has suitable bank switch registers or memory management
11575 hardware, you could use those facilities to make an overlay's load area
11576 contents simply appear at their mapped address in instruction space.
11577 This would probably be faster than copying the overlay to its mapped
11578 area in the usual way.
11581 If your overlays are small enough, you could set aside more than one
11582 overlay area, and have more than one overlay mapped at a time.
11585 You can use overlays to manage data, as well as instructions. In
11586 general, data overlays are even less transparent to your design than
11587 code overlays: whereas code overlays only require care when you call or
11588 return to functions, data overlays require care every time you access
11589 the data. Also, if you change the contents of a data overlay, you
11590 must copy its contents back out to its load address before you can copy a
11591 different data overlay into the same mapped area.
11596 @node Overlay Commands
11597 @section Overlay Commands
11599 To use @value{GDBN}'s overlay support, each overlay in your program must
11600 correspond to a separate section of the executable file. The section's
11601 virtual memory address and load memory address must be the overlay's
11602 mapped and load addresses. Identifying overlays with sections allows
11603 @value{GDBN} to determine the appropriate address of a function or
11604 variable, depending on whether the overlay is mapped or not.
11606 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11607 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11612 Disable @value{GDBN}'s overlay support. When overlay support is
11613 disabled, @value{GDBN} assumes that all functions and variables are
11614 always present at their mapped addresses. By default, @value{GDBN}'s
11615 overlay support is disabled.
11617 @item overlay manual
11618 @cindex manual overlay debugging
11619 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11620 relies on you to tell it which overlays are mapped, and which are not,
11621 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11622 commands described below.
11624 @item overlay map-overlay @var{overlay}
11625 @itemx overlay map @var{overlay}
11626 @cindex map an overlay
11627 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11628 be the name of the object file section containing the overlay. When an
11629 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11630 functions and variables at their mapped addresses. @value{GDBN} assumes
11631 that any other overlays whose mapped ranges overlap that of
11632 @var{overlay} are now unmapped.
11634 @item overlay unmap-overlay @var{overlay}
11635 @itemx overlay unmap @var{overlay}
11636 @cindex unmap an overlay
11637 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11638 must be the name of the object file section containing the overlay.
11639 When an overlay is unmapped, @value{GDBN} assumes it can find the
11640 overlay's functions and variables at their load addresses.
11643 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11644 consults a data structure the overlay manager maintains in the inferior
11645 to see which overlays are mapped. For details, see @ref{Automatic
11646 Overlay Debugging}.
11648 @item overlay load-target
11649 @itemx overlay load
11650 @cindex reloading the overlay table
11651 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11652 re-reads the table @value{GDBN} automatically each time the inferior
11653 stops, so this command should only be necessary if you have changed the
11654 overlay mapping yourself using @value{GDBN}. This command is only
11655 useful when using automatic overlay debugging.
11657 @item overlay list-overlays
11658 @itemx overlay list
11659 @cindex listing mapped overlays
11660 Display a list of the overlays currently mapped, along with their mapped
11661 addresses, load addresses, and sizes.
11665 Normally, when @value{GDBN} prints a code address, it includes the name
11666 of the function the address falls in:
11669 (@value{GDBP}) print main
11670 $3 = @{int ()@} 0x11a0 <main>
11673 When overlay debugging is enabled, @value{GDBN} recognizes code in
11674 unmapped overlays, and prints the names of unmapped functions with
11675 asterisks around them. For example, if @code{foo} is a function in an
11676 unmapped overlay, @value{GDBN} prints it this way:
11679 (@value{GDBP}) overlay list
11680 No sections are mapped.
11681 (@value{GDBP}) print foo
11682 $5 = @{int (int)@} 0x100000 <*foo*>
11685 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11689 (@value{GDBP}) overlay list
11690 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11691 mapped at 0x1016 - 0x104a
11692 (@value{GDBP}) print foo
11693 $6 = @{int (int)@} 0x1016 <foo>
11696 When overlay debugging is enabled, @value{GDBN} can find the correct
11697 address for functions and variables in an overlay, whether or not the
11698 overlay is mapped. This allows most @value{GDBN} commands, like
11699 @code{break} and @code{disassemble}, to work normally, even on unmapped
11700 code. However, @value{GDBN}'s breakpoint support has some limitations:
11704 @cindex breakpoints in overlays
11705 @cindex overlays, setting breakpoints in
11706 You can set breakpoints in functions in unmapped overlays, as long as
11707 @value{GDBN} can write to the overlay at its load address.
11709 @value{GDBN} can not set hardware or simulator-based breakpoints in
11710 unmapped overlays. However, if you set a breakpoint at the end of your
11711 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11712 you are using manual overlay management), @value{GDBN} will re-set its
11713 breakpoints properly.
11717 @node Automatic Overlay Debugging
11718 @section Automatic Overlay Debugging
11719 @cindex automatic overlay debugging
11721 @value{GDBN} can automatically track which overlays are mapped and which
11722 are not, given some simple co-operation from the overlay manager in the
11723 inferior. If you enable automatic overlay debugging with the
11724 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11725 looks in the inferior's memory for certain variables describing the
11726 current state of the overlays.
11728 Here are the variables your overlay manager must define to support
11729 @value{GDBN}'s automatic overlay debugging:
11733 @item @code{_ovly_table}:
11734 This variable must be an array of the following structures:
11739 /* The overlay's mapped address. */
11742 /* The size of the overlay, in bytes. */
11743 unsigned long size;
11745 /* The overlay's load address. */
11748 /* Non-zero if the overlay is currently mapped;
11750 unsigned long mapped;
11754 @item @code{_novlys}:
11755 This variable must be a four-byte signed integer, holding the total
11756 number of elements in @code{_ovly_table}.
11760 To decide whether a particular overlay is mapped or not, @value{GDBN}
11761 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11762 @code{lma} members equal the VMA and LMA of the overlay's section in the
11763 executable file. When @value{GDBN} finds a matching entry, it consults
11764 the entry's @code{mapped} member to determine whether the overlay is
11767 In addition, your overlay manager may define a function called
11768 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11769 will silently set a breakpoint there. If the overlay manager then
11770 calls this function whenever it has changed the overlay table, this
11771 will enable @value{GDBN} to accurately keep track of which overlays
11772 are in program memory, and update any breakpoints that may be set
11773 in overlays. This will allow breakpoints to work even if the
11774 overlays are kept in ROM or other non-writable memory while they
11775 are not being executed.
11777 @node Overlay Sample Program
11778 @section Overlay Sample Program
11779 @cindex overlay example program
11781 When linking a program which uses overlays, you must place the overlays
11782 at their load addresses, while relocating them to run at their mapped
11783 addresses. To do this, you must write a linker script (@pxref{Overlay
11784 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11785 since linker scripts are specific to a particular host system, target
11786 architecture, and target memory layout, this manual cannot provide
11787 portable sample code demonstrating @value{GDBN}'s overlay support.
11789 However, the @value{GDBN} source distribution does contain an overlaid
11790 program, with linker scripts for a few systems, as part of its test
11791 suite. The program consists of the following files from
11792 @file{gdb/testsuite/gdb.base}:
11796 The main program file.
11798 A simple overlay manager, used by @file{overlays.c}.
11803 Overlay modules, loaded and used by @file{overlays.c}.
11806 Linker scripts for linking the test program on the @code{d10v-elf}
11807 and @code{m32r-elf} targets.
11810 You can build the test program using the @code{d10v-elf} GCC
11811 cross-compiler like this:
11814 $ d10v-elf-gcc -g -c overlays.c
11815 $ d10v-elf-gcc -g -c ovlymgr.c
11816 $ d10v-elf-gcc -g -c foo.c
11817 $ d10v-elf-gcc -g -c bar.c
11818 $ d10v-elf-gcc -g -c baz.c
11819 $ d10v-elf-gcc -g -c grbx.c
11820 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11821 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11824 The build process is identical for any other architecture, except that
11825 you must substitute the appropriate compiler and linker script for the
11826 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11830 @chapter Using @value{GDBN} with Different Languages
11833 Although programming languages generally have common aspects, they are
11834 rarely expressed in the same manner. For instance, in ANSI C,
11835 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11836 Modula-2, it is accomplished by @code{p^}. Values can also be
11837 represented (and displayed) differently. Hex numbers in C appear as
11838 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11840 @cindex working language
11841 Language-specific information is built into @value{GDBN} for some languages,
11842 allowing you to express operations like the above in your program's
11843 native language, and allowing @value{GDBN} to output values in a manner
11844 consistent with the syntax of your program's native language. The
11845 language you use to build expressions is called the @dfn{working
11849 * Setting:: Switching between source languages
11850 * Show:: Displaying the language
11851 * Checks:: Type and range checks
11852 * Supported Languages:: Supported languages
11853 * Unsupported Languages:: Unsupported languages
11857 @section Switching Between Source Languages
11859 There are two ways to control the working language---either have @value{GDBN}
11860 set it automatically, or select it manually yourself. You can use the
11861 @code{set language} command for either purpose. On startup, @value{GDBN}
11862 defaults to setting the language automatically. The working language is
11863 used to determine how expressions you type are interpreted, how values
11866 In addition to the working language, every source file that
11867 @value{GDBN} knows about has its own working language. For some object
11868 file formats, the compiler might indicate which language a particular
11869 source file is in. However, most of the time @value{GDBN} infers the
11870 language from the name of the file. The language of a source file
11871 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11872 show each frame appropriately for its own language. There is no way to
11873 set the language of a source file from within @value{GDBN}, but you can
11874 set the language associated with a filename extension. @xref{Show, ,
11875 Displaying the Language}.
11877 This is most commonly a problem when you use a program, such
11878 as @code{cfront} or @code{f2c}, that generates C but is written in
11879 another language. In that case, make the
11880 program use @code{#line} directives in its C output; that way
11881 @value{GDBN} will know the correct language of the source code of the original
11882 program, and will display that source code, not the generated C code.
11885 * Filenames:: Filename extensions and languages.
11886 * Manually:: Setting the working language manually
11887 * Automatically:: Having @value{GDBN} infer the source language
11891 @subsection List of Filename Extensions and Languages
11893 If a source file name ends in one of the following extensions, then
11894 @value{GDBN} infers that its language is the one indicated.
11912 C@t{++} source file
11918 Objective-C source file
11922 Fortran source file
11925 Modula-2 source file
11929 Assembler source file. This actually behaves almost like C, but
11930 @value{GDBN} does not skip over function prologues when stepping.
11933 In addition, you may set the language associated with a filename
11934 extension. @xref{Show, , Displaying the Language}.
11937 @subsection Setting the Working Language
11939 If you allow @value{GDBN} to set the language automatically,
11940 expressions are interpreted the same way in your debugging session and
11943 @kindex set language
11944 If you wish, you may set the language manually. To do this, issue the
11945 command @samp{set language @var{lang}}, where @var{lang} is the name of
11946 a language, such as
11947 @code{c} or @code{modula-2}.
11948 For a list of the supported languages, type @samp{set language}.
11950 Setting the language manually prevents @value{GDBN} from updating the working
11951 language automatically. This can lead to confusion if you try
11952 to debug a program when the working language is not the same as the
11953 source language, when an expression is acceptable to both
11954 languages---but means different things. For instance, if the current
11955 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11963 might not have the effect you intended. In C, this means to add
11964 @code{b} and @code{c} and place the result in @code{a}. The result
11965 printed would be the value of @code{a}. In Modula-2, this means to compare
11966 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11968 @node Automatically
11969 @subsection Having @value{GDBN} Infer the Source Language
11971 To have @value{GDBN} set the working language automatically, use
11972 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11973 then infers the working language. That is, when your program stops in a
11974 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11975 working language to the language recorded for the function in that
11976 frame. If the language for a frame is unknown (that is, if the function
11977 or block corresponding to the frame was defined in a source file that
11978 does not have a recognized extension), the current working language is
11979 not changed, and @value{GDBN} issues a warning.
11981 This may not seem necessary for most programs, which are written
11982 entirely in one source language. However, program modules and libraries
11983 written in one source language can be used by a main program written in
11984 a different source language. Using @samp{set language auto} in this
11985 case frees you from having to set the working language manually.
11988 @section Displaying the Language
11990 The following commands help you find out which language is the
11991 working language, and also what language source files were written in.
11994 @item show language
11995 @kindex show language
11996 Display the current working language. This is the
11997 language you can use with commands such as @code{print} to
11998 build and compute expressions that may involve variables in your program.
12001 @kindex info frame@r{, show the source language}
12002 Display the source language for this frame. This language becomes the
12003 working language if you use an identifier from this frame.
12004 @xref{Frame Info, ,Information about a Frame}, to identify the other
12005 information listed here.
12008 @kindex info source@r{, show the source language}
12009 Display the source language of this source file.
12010 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12011 information listed here.
12014 In unusual circumstances, you may have source files with extensions
12015 not in the standard list. You can then set the extension associated
12016 with a language explicitly:
12019 @item set extension-language @var{ext} @var{language}
12020 @kindex set extension-language
12021 Tell @value{GDBN} that source files with extension @var{ext} are to be
12022 assumed as written in the source language @var{language}.
12024 @item info extensions
12025 @kindex info extensions
12026 List all the filename extensions and the associated languages.
12030 @section Type and Range Checking
12033 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12034 checking are included, but they do not yet have any effect. This
12035 section documents the intended facilities.
12037 @c FIXME remove warning when type/range code added
12039 Some languages are designed to guard you against making seemingly common
12040 errors through a series of compile- and run-time checks. These include
12041 checking the type of arguments to functions and operators, and making
12042 sure mathematical overflows are caught at run time. Checks such as
12043 these help to ensure a program's correctness once it has been compiled
12044 by eliminating type mismatches, and providing active checks for range
12045 errors when your program is running.
12047 @value{GDBN} can check for conditions like the above if you wish.
12048 Although @value{GDBN} does not check the statements in your program,
12049 it can check expressions entered directly into @value{GDBN} for
12050 evaluation via the @code{print} command, for example. As with the
12051 working language, @value{GDBN} can also decide whether or not to check
12052 automatically based on your program's source language.
12053 @xref{Supported Languages, ,Supported Languages}, for the default
12054 settings of supported languages.
12057 * Type Checking:: An overview of type checking
12058 * Range Checking:: An overview of range checking
12061 @cindex type checking
12062 @cindex checks, type
12063 @node Type Checking
12064 @subsection An Overview of Type Checking
12066 Some languages, such as Modula-2, are strongly typed, meaning that the
12067 arguments to operators and functions have to be of the correct type,
12068 otherwise an error occurs. These checks prevent type mismatch
12069 errors from ever causing any run-time problems. For example,
12077 The second example fails because the @code{CARDINAL} 1 is not
12078 type-compatible with the @code{REAL} 2.3.
12080 For the expressions you use in @value{GDBN} commands, you can tell the
12081 @value{GDBN} type checker to skip checking;
12082 to treat any mismatches as errors and abandon the expression;
12083 or to only issue warnings when type mismatches occur,
12084 but evaluate the expression anyway. When you choose the last of
12085 these, @value{GDBN} evaluates expressions like the second example above, but
12086 also issues a warning.
12088 Even if you turn type checking off, there may be other reasons
12089 related to type that prevent @value{GDBN} from evaluating an expression.
12090 For instance, @value{GDBN} does not know how to add an @code{int} and
12091 a @code{struct foo}. These particular type errors have nothing to do
12092 with the language in use, and usually arise from expressions, such as
12093 the one described above, which make little sense to evaluate anyway.
12095 Each language defines to what degree it is strict about type. For
12096 instance, both Modula-2 and C require the arguments to arithmetical
12097 operators to be numbers. In C, enumerated types and pointers can be
12098 represented as numbers, so that they are valid arguments to mathematical
12099 operators. @xref{Supported Languages, ,Supported Languages}, for further
12100 details on specific languages.
12102 @value{GDBN} provides some additional commands for controlling the type checker:
12104 @kindex set check type
12105 @kindex show check type
12107 @item set check type auto
12108 Set type checking on or off based on the current working language.
12109 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12112 @item set check type on
12113 @itemx set check type off
12114 Set type checking on or off, overriding the default setting for the
12115 current working language. Issue a warning if the setting does not
12116 match the language default. If any type mismatches occur in
12117 evaluating an expression while type checking is on, @value{GDBN} prints a
12118 message and aborts evaluation of the expression.
12120 @item set check type warn
12121 Cause the type checker to issue warnings, but to always attempt to
12122 evaluate the expression. Evaluating the expression may still
12123 be impossible for other reasons. For example, @value{GDBN} cannot add
12124 numbers and structures.
12127 Show the current setting of the type checker, and whether or not @value{GDBN}
12128 is setting it automatically.
12131 @cindex range checking
12132 @cindex checks, range
12133 @node Range Checking
12134 @subsection An Overview of Range Checking
12136 In some languages (such as Modula-2), it is an error to exceed the
12137 bounds of a type; this is enforced with run-time checks. Such range
12138 checking is meant to ensure program correctness by making sure
12139 computations do not overflow, or indices on an array element access do
12140 not exceed the bounds of the array.
12142 For expressions you use in @value{GDBN} commands, you can tell
12143 @value{GDBN} to treat range errors in one of three ways: ignore them,
12144 always treat them as errors and abandon the expression, or issue
12145 warnings but evaluate the expression anyway.
12147 A range error can result from numerical overflow, from exceeding an
12148 array index bound, or when you type a constant that is not a member
12149 of any type. Some languages, however, do not treat overflows as an
12150 error. In many implementations of C, mathematical overflow causes the
12151 result to ``wrap around'' to lower values---for example, if @var{m} is
12152 the largest integer value, and @var{s} is the smallest, then
12155 @var{m} + 1 @result{} @var{s}
12158 This, too, is specific to individual languages, and in some cases
12159 specific to individual compilers or machines. @xref{Supported Languages, ,
12160 Supported Languages}, for further details on specific languages.
12162 @value{GDBN} provides some additional commands for controlling the range checker:
12164 @kindex set check range
12165 @kindex show check range
12167 @item set check range auto
12168 Set range checking on or off based on the current working language.
12169 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12172 @item set check range on
12173 @itemx set check range off
12174 Set range checking on or off, overriding the default setting for the
12175 current working language. A warning is issued if the setting does not
12176 match the language default. If a range error occurs and range checking is on,
12177 then a message is printed and evaluation of the expression is aborted.
12179 @item set check range warn
12180 Output messages when the @value{GDBN} range checker detects a range error,
12181 but attempt to evaluate the expression anyway. Evaluating the
12182 expression may still be impossible for other reasons, such as accessing
12183 memory that the process does not own (a typical example from many Unix
12187 Show the current setting of the range checker, and whether or not it is
12188 being set automatically by @value{GDBN}.
12191 @node Supported Languages
12192 @section Supported Languages
12194 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12195 assembly, Modula-2, and Ada.
12196 @c This is false ...
12197 Some @value{GDBN} features may be used in expressions regardless of the
12198 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12199 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12200 ,Expressions}) can be used with the constructs of any supported
12203 The following sections detail to what degree each source language is
12204 supported by @value{GDBN}. These sections are not meant to be language
12205 tutorials or references, but serve only as a reference guide to what the
12206 @value{GDBN} expression parser accepts, and what input and output
12207 formats should look like for different languages. There are many good
12208 books written on each of these languages; please look to these for a
12209 language reference or tutorial.
12212 * C:: C and C@t{++}
12214 * Objective-C:: Objective-C
12215 * OpenCL C:: OpenCL C
12216 * Fortran:: Fortran
12218 * Modula-2:: Modula-2
12223 @subsection C and C@t{++}
12225 @cindex C and C@t{++}
12226 @cindex expressions in C or C@t{++}
12228 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12229 to both languages. Whenever this is the case, we discuss those languages
12233 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12234 @cindex @sc{gnu} C@t{++}
12235 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12236 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12237 effectively, you must compile your C@t{++} programs with a supported
12238 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12239 compiler (@code{aCC}).
12242 * C Operators:: C and C@t{++} operators
12243 * C Constants:: C and C@t{++} constants
12244 * C Plus Plus Expressions:: C@t{++} expressions
12245 * C Defaults:: Default settings for C and C@t{++}
12246 * C Checks:: C and C@t{++} type and range checks
12247 * Debugging C:: @value{GDBN} and C
12248 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12249 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12253 @subsubsection C and C@t{++} Operators
12255 @cindex C and C@t{++} operators
12257 Operators must be defined on values of specific types. For instance,
12258 @code{+} is defined on numbers, but not on structures. Operators are
12259 often defined on groups of types.
12261 For the purposes of C and C@t{++}, the following definitions hold:
12266 @emph{Integral types} include @code{int} with any of its storage-class
12267 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12270 @emph{Floating-point types} include @code{float}, @code{double}, and
12271 @code{long double} (if supported by the target platform).
12274 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12277 @emph{Scalar types} include all of the above.
12282 The following operators are supported. They are listed here
12283 in order of increasing precedence:
12287 The comma or sequencing operator. Expressions in a comma-separated list
12288 are evaluated from left to right, with the result of the entire
12289 expression being the last expression evaluated.
12292 Assignment. The value of an assignment expression is the value
12293 assigned. Defined on scalar types.
12296 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12297 and translated to @w{@code{@var{a} = @var{a op b}}}.
12298 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12299 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12300 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12303 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12304 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12308 Logical @sc{or}. Defined on integral types.
12311 Logical @sc{and}. Defined on integral types.
12314 Bitwise @sc{or}. Defined on integral types.
12317 Bitwise exclusive-@sc{or}. Defined on integral types.
12320 Bitwise @sc{and}. Defined on integral types.
12323 Equality and inequality. Defined on scalar types. The value of these
12324 expressions is 0 for false and non-zero for true.
12326 @item <@r{, }>@r{, }<=@r{, }>=
12327 Less than, greater than, less than or equal, greater than or equal.
12328 Defined on scalar types. The value of these expressions is 0 for false
12329 and non-zero for true.
12332 left shift, and right shift. Defined on integral types.
12335 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12338 Addition and subtraction. Defined on integral types, floating-point types and
12341 @item *@r{, }/@r{, }%
12342 Multiplication, division, and modulus. Multiplication and division are
12343 defined on integral and floating-point types. Modulus is defined on
12347 Increment and decrement. When appearing before a variable, the
12348 operation is performed before the variable is used in an expression;
12349 when appearing after it, the variable's value is used before the
12350 operation takes place.
12353 Pointer dereferencing. Defined on pointer types. Same precedence as
12357 Address operator. Defined on variables. Same precedence as @code{++}.
12359 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12360 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12361 to examine the address
12362 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12366 Negative. Defined on integral and floating-point types. Same
12367 precedence as @code{++}.
12370 Logical negation. Defined on integral types. Same precedence as
12374 Bitwise complement operator. Defined on integral types. Same precedence as
12379 Structure member, and pointer-to-structure member. For convenience,
12380 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12381 pointer based on the stored type information.
12382 Defined on @code{struct} and @code{union} data.
12385 Dereferences of pointers to members.
12388 Array indexing. @code{@var{a}[@var{i}]} is defined as
12389 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12392 Function parameter list. Same precedence as @code{->}.
12395 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12396 and @code{class} types.
12399 Doubled colons also represent the @value{GDBN} scope operator
12400 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12404 If an operator is redefined in the user code, @value{GDBN} usually
12405 attempts to invoke the redefined version instead of using the operator's
12406 predefined meaning.
12409 @subsubsection C and C@t{++} Constants
12411 @cindex C and C@t{++} constants
12413 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12418 Integer constants are a sequence of digits. Octal constants are
12419 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12420 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12421 @samp{l}, specifying that the constant should be treated as a
12425 Floating point constants are a sequence of digits, followed by a decimal
12426 point, followed by a sequence of digits, and optionally followed by an
12427 exponent. An exponent is of the form:
12428 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12429 sequence of digits. The @samp{+} is optional for positive exponents.
12430 A floating-point constant may also end with a letter @samp{f} or
12431 @samp{F}, specifying that the constant should be treated as being of
12432 the @code{float} (as opposed to the default @code{double}) type; or with
12433 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12437 Enumerated constants consist of enumerated identifiers, or their
12438 integral equivalents.
12441 Character constants are a single character surrounded by single quotes
12442 (@code{'}), or a number---the ordinal value of the corresponding character
12443 (usually its @sc{ascii} value). Within quotes, the single character may
12444 be represented by a letter or by @dfn{escape sequences}, which are of
12445 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12446 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12447 @samp{@var{x}} is a predefined special character---for example,
12448 @samp{\n} for newline.
12450 Wide character constants can be written by prefixing a character
12451 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12452 form of @samp{x}. The target wide character set is used when
12453 computing the value of this constant (@pxref{Character Sets}).
12456 String constants are a sequence of character constants surrounded by
12457 double quotes (@code{"}). Any valid character constant (as described
12458 above) may appear. Double quotes within the string must be preceded by
12459 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12462 Wide string constants can be written by prefixing a string constant
12463 with @samp{L}, as in C. The target wide character set is used when
12464 computing the value of this constant (@pxref{Character Sets}).
12467 Pointer constants are an integral value. You can also write pointers
12468 to constants using the C operator @samp{&}.
12471 Array constants are comma-separated lists surrounded by braces @samp{@{}
12472 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12473 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12474 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12477 @node C Plus Plus Expressions
12478 @subsubsection C@t{++} Expressions
12480 @cindex expressions in C@t{++}
12481 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12483 @cindex debugging C@t{++} programs
12484 @cindex C@t{++} compilers
12485 @cindex debug formats and C@t{++}
12486 @cindex @value{NGCC} and C@t{++}
12488 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12489 the proper compiler and the proper debug format. Currently,
12490 @value{GDBN} works best when debugging C@t{++} code that is compiled
12491 with the most recent version of @value{NGCC} possible. The DWARF
12492 debugging format is preferred; @value{NGCC} defaults to this on most
12493 popular platforms. Other compilers and/or debug formats are likely to
12494 work badly or not at all when using @value{GDBN} to debug C@t{++}
12495 code. @xref{Compilation}.
12500 @cindex member functions
12502 Member function calls are allowed; you can use expressions like
12505 count = aml->GetOriginal(x, y)
12508 @vindex this@r{, inside C@t{++} member functions}
12509 @cindex namespace in C@t{++}
12511 While a member function is active (in the selected stack frame), your
12512 expressions have the same namespace available as the member function;
12513 that is, @value{GDBN} allows implicit references to the class instance
12514 pointer @code{this} following the same rules as C@t{++}. @code{using}
12515 declarations in the current scope are also respected by @value{GDBN}.
12517 @cindex call overloaded functions
12518 @cindex overloaded functions, calling
12519 @cindex type conversions in C@t{++}
12521 You can call overloaded functions; @value{GDBN} resolves the function
12522 call to the right definition, with some restrictions. @value{GDBN} does not
12523 perform overload resolution involving user-defined type conversions,
12524 calls to constructors, or instantiations of templates that do not exist
12525 in the program. It also cannot handle ellipsis argument lists or
12528 It does perform integral conversions and promotions, floating-point
12529 promotions, arithmetic conversions, pointer conversions, conversions of
12530 class objects to base classes, and standard conversions such as those of
12531 functions or arrays to pointers; it requires an exact match on the
12532 number of function arguments.
12534 Overload resolution is always performed, unless you have specified
12535 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12536 ,@value{GDBN} Features for C@t{++}}.
12538 You must specify @code{set overload-resolution off} in order to use an
12539 explicit function signature to call an overloaded function, as in
12541 p 'foo(char,int)'('x', 13)
12544 The @value{GDBN} command-completion facility can simplify this;
12545 see @ref{Completion, ,Command Completion}.
12547 @cindex reference declarations
12549 @value{GDBN} understands variables declared as C@t{++} references; you can use
12550 them in expressions just as you do in C@t{++} source---they are automatically
12553 In the parameter list shown when @value{GDBN} displays a frame, the values of
12554 reference variables are not displayed (unlike other variables); this
12555 avoids clutter, since references are often used for large structures.
12556 The @emph{address} of a reference variable is always shown, unless
12557 you have specified @samp{set print address off}.
12560 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12561 expressions can use it just as expressions in your program do. Since
12562 one scope may be defined in another, you can use @code{::} repeatedly if
12563 necessary, for example in an expression like
12564 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12565 resolving name scope by reference to source files, in both C and C@t{++}
12566 debugging (@pxref{Variables, ,Program Variables}).
12569 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12574 @subsubsection C and C@t{++} Defaults
12576 @cindex C and C@t{++} defaults
12578 If you allow @value{GDBN} to set type and range checking automatically, they
12579 both default to @code{off} whenever the working language changes to
12580 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12581 selects the working language.
12583 If you allow @value{GDBN} to set the language automatically, it
12584 recognizes source files whose names end with @file{.c}, @file{.C}, or
12585 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12586 these files, it sets the working language to C or C@t{++}.
12587 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12588 for further details.
12590 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12591 @c unimplemented. If (b) changes, it might make sense to let this node
12592 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12595 @subsubsection C and C@t{++} Type and Range Checks
12597 @cindex C and C@t{++} checks
12599 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12600 is not used. However, if you turn type checking on, @value{GDBN}
12601 considers two variables type equivalent if:
12605 The two variables are structured and have the same structure, union, or
12609 The two variables have the same type name, or types that have been
12610 declared equivalent through @code{typedef}.
12613 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12616 The two @code{struct}, @code{union}, or @code{enum} variables are
12617 declared in the same declaration. (Note: this may not be true for all C
12622 Range checking, if turned on, is done on mathematical operations. Array
12623 indices are not checked, since they are often used to index a pointer
12624 that is not itself an array.
12627 @subsubsection @value{GDBN} and C
12629 The @code{set print union} and @code{show print union} commands apply to
12630 the @code{union} type. When set to @samp{on}, any @code{union} that is
12631 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12632 appears as @samp{@{...@}}.
12634 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12635 with pointers and a memory allocation function. @xref{Expressions,
12638 @node Debugging C Plus Plus
12639 @subsubsection @value{GDBN} Features for C@t{++}
12641 @cindex commands for C@t{++}
12643 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12644 designed specifically for use with C@t{++}. Here is a summary:
12647 @cindex break in overloaded functions
12648 @item @r{breakpoint menus}
12649 When you want a breakpoint in a function whose name is overloaded,
12650 @value{GDBN} has the capability to display a menu of possible breakpoint
12651 locations to help you specify which function definition you want.
12652 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12654 @cindex overloading in C@t{++}
12655 @item rbreak @var{regex}
12656 Setting breakpoints using regular expressions is helpful for setting
12657 breakpoints on overloaded functions that are not members of any special
12659 @xref{Set Breaks, ,Setting Breakpoints}.
12661 @cindex C@t{++} exception handling
12664 Debug C@t{++} exception handling using these commands. @xref{Set
12665 Catchpoints, , Setting Catchpoints}.
12667 @cindex inheritance
12668 @item ptype @var{typename}
12669 Print inheritance relationships as well as other information for type
12671 @xref{Symbols, ,Examining the Symbol Table}.
12673 @cindex C@t{++} symbol display
12674 @item set print demangle
12675 @itemx show print demangle
12676 @itemx set print asm-demangle
12677 @itemx show print asm-demangle
12678 Control whether C@t{++} symbols display in their source form, both when
12679 displaying code as C@t{++} source and when displaying disassemblies.
12680 @xref{Print Settings, ,Print Settings}.
12682 @item set print object
12683 @itemx show print object
12684 Choose whether to print derived (actual) or declared types of objects.
12685 @xref{Print Settings, ,Print Settings}.
12687 @item set print vtbl
12688 @itemx show print vtbl
12689 Control the format for printing virtual function tables.
12690 @xref{Print Settings, ,Print Settings}.
12691 (The @code{vtbl} commands do not work on programs compiled with the HP
12692 ANSI C@t{++} compiler (@code{aCC}).)
12694 @kindex set overload-resolution
12695 @cindex overloaded functions, overload resolution
12696 @item set overload-resolution on
12697 Enable overload resolution for C@t{++} expression evaluation. The default
12698 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12699 and searches for a function whose signature matches the argument types,
12700 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12701 Expressions, ,C@t{++} Expressions}, for details).
12702 If it cannot find a match, it emits a message.
12704 @item set overload-resolution off
12705 Disable overload resolution for C@t{++} expression evaluation. For
12706 overloaded functions that are not class member functions, @value{GDBN}
12707 chooses the first function of the specified name that it finds in the
12708 symbol table, whether or not its arguments are of the correct type. For
12709 overloaded functions that are class member functions, @value{GDBN}
12710 searches for a function whose signature @emph{exactly} matches the
12713 @kindex show overload-resolution
12714 @item show overload-resolution
12715 Show the current setting of overload resolution.
12717 @item @r{Overloaded symbol names}
12718 You can specify a particular definition of an overloaded symbol, using
12719 the same notation that is used to declare such symbols in C@t{++}: type
12720 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12721 also use the @value{GDBN} command-line word completion facilities to list the
12722 available choices, or to finish the type list for you.
12723 @xref{Completion,, Command Completion}, for details on how to do this.
12726 @node Decimal Floating Point
12727 @subsubsection Decimal Floating Point format
12728 @cindex decimal floating point format
12730 @value{GDBN} can examine, set and perform computations with numbers in
12731 decimal floating point format, which in the C language correspond to the
12732 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12733 specified by the extension to support decimal floating-point arithmetic.
12735 There are two encodings in use, depending on the architecture: BID (Binary
12736 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12737 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12740 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12741 to manipulate decimal floating point numbers, it is not possible to convert
12742 (using a cast, for example) integers wider than 32-bit to decimal float.
12744 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12745 point computations, error checking in decimal float operations ignores
12746 underflow, overflow and divide by zero exceptions.
12748 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12749 to inspect @code{_Decimal128} values stored in floating point registers.
12750 See @ref{PowerPC,,PowerPC} for more details.
12756 @value{GDBN} can be used to debug programs written in D and compiled with
12757 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12758 specific feature --- dynamic arrays.
12761 @subsection Objective-C
12763 @cindex Objective-C
12764 This section provides information about some commands and command
12765 options that are useful for debugging Objective-C code. See also
12766 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12767 few more commands specific to Objective-C support.
12770 * Method Names in Commands::
12771 * The Print Command with Objective-C::
12774 @node Method Names in Commands
12775 @subsubsection Method Names in Commands
12777 The following commands have been extended to accept Objective-C method
12778 names as line specifications:
12780 @kindex clear@r{, and Objective-C}
12781 @kindex break@r{, and Objective-C}
12782 @kindex info line@r{, and Objective-C}
12783 @kindex jump@r{, and Objective-C}
12784 @kindex list@r{, and Objective-C}
12788 @item @code{info line}
12793 A fully qualified Objective-C method name is specified as
12796 -[@var{Class} @var{methodName}]
12799 where the minus sign is used to indicate an instance method and a
12800 plus sign (not shown) is used to indicate a class method. The class
12801 name @var{Class} and method name @var{methodName} are enclosed in
12802 brackets, similar to the way messages are specified in Objective-C
12803 source code. For example, to set a breakpoint at the @code{create}
12804 instance method of class @code{Fruit} in the program currently being
12808 break -[Fruit create]
12811 To list ten program lines around the @code{initialize} class method,
12815 list +[NSText initialize]
12818 In the current version of @value{GDBN}, the plus or minus sign is
12819 required. In future versions of @value{GDBN}, the plus or minus
12820 sign will be optional, but you can use it to narrow the search. It
12821 is also possible to specify just a method name:
12827 You must specify the complete method name, including any colons. If
12828 your program's source files contain more than one @code{create} method,
12829 you'll be presented with a numbered list of classes that implement that
12830 method. Indicate your choice by number, or type @samp{0} to exit if
12833 As another example, to clear a breakpoint established at the
12834 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12837 clear -[NSWindow makeKeyAndOrderFront:]
12840 @node The Print Command with Objective-C
12841 @subsubsection The Print Command With Objective-C
12842 @cindex Objective-C, print objects
12843 @kindex print-object
12844 @kindex po @r{(@code{print-object})}
12846 The print command has also been extended to accept methods. For example:
12849 print -[@var{object} hash]
12852 @cindex print an Objective-C object description
12853 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12855 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12856 and print the result. Also, an additional command has been added,
12857 @code{print-object} or @code{po} for short, which is meant to print
12858 the description of an object. However, this command may only work
12859 with certain Objective-C libraries that have a particular hook
12860 function, @code{_NSPrintForDebugger}, defined.
12863 @subsection OpenCL C
12866 This section provides information about @value{GDBN}s OpenCL C support.
12869 * OpenCL C Datatypes::
12870 * OpenCL C Expressions::
12871 * OpenCL C Operators::
12874 @node OpenCL C Datatypes
12875 @subsubsection OpenCL C Datatypes
12877 @cindex OpenCL C Datatypes
12878 @value{GDBN} supports the builtin scalar and vector datatypes specified
12879 by OpenCL 1.1. In addition the half- and double-precision floating point
12880 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12881 extensions are also known to @value{GDBN}.
12883 @node OpenCL C Expressions
12884 @subsubsection OpenCL C Expressions
12886 @cindex OpenCL C Expressions
12887 @value{GDBN} supports accesses to vector components including the access as
12888 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12889 supported by @value{GDBN} can be used as well.
12891 @node OpenCL C Operators
12892 @subsubsection OpenCL C Operators
12894 @cindex OpenCL C Operators
12895 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12899 @subsection Fortran
12900 @cindex Fortran-specific support in @value{GDBN}
12902 @value{GDBN} can be used to debug programs written in Fortran, but it
12903 currently supports only the features of Fortran 77 language.
12905 @cindex trailing underscore, in Fortran symbols
12906 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12907 among them) append an underscore to the names of variables and
12908 functions. When you debug programs compiled by those compilers, you
12909 will need to refer to variables and functions with a trailing
12913 * Fortran Operators:: Fortran operators and expressions
12914 * Fortran Defaults:: Default settings for Fortran
12915 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12918 @node Fortran Operators
12919 @subsubsection Fortran Operators and Expressions
12921 @cindex Fortran operators and expressions
12923 Operators must be defined on values of specific types. For instance,
12924 @code{+} is defined on numbers, but not on characters or other non-
12925 arithmetic types. Operators are often defined on groups of types.
12929 The exponentiation operator. It raises the first operand to the power
12933 The range operator. Normally used in the form of array(low:high) to
12934 represent a section of array.
12937 The access component operator. Normally used to access elements in derived
12938 types. Also suitable for unions. As unions aren't part of regular Fortran,
12939 this can only happen when accessing a register that uses a gdbarch-defined
12943 @node Fortran Defaults
12944 @subsubsection Fortran Defaults
12946 @cindex Fortran Defaults
12948 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12949 default uses case-insensitive matches for Fortran symbols. You can
12950 change that with the @samp{set case-insensitive} command, see
12951 @ref{Symbols}, for the details.
12953 @node Special Fortran Commands
12954 @subsubsection Special Fortran Commands
12956 @cindex Special Fortran commands
12958 @value{GDBN} has some commands to support Fortran-specific features,
12959 such as displaying common blocks.
12962 @cindex @code{COMMON} blocks, Fortran
12963 @kindex info common
12964 @item info common @r{[}@var{common-name}@r{]}
12965 This command prints the values contained in the Fortran @code{COMMON}
12966 block whose name is @var{common-name}. With no argument, the names of
12967 all @code{COMMON} blocks visible at the current program location are
12974 @cindex Pascal support in @value{GDBN}, limitations
12975 Debugging Pascal programs which use sets, subranges, file variables, or
12976 nested functions does not currently work. @value{GDBN} does not support
12977 entering expressions, printing values, or similar features using Pascal
12980 The Pascal-specific command @code{set print pascal_static-members}
12981 controls whether static members of Pascal objects are displayed.
12982 @xref{Print Settings, pascal_static-members}.
12985 @subsection Modula-2
12987 @cindex Modula-2, @value{GDBN} support
12989 The extensions made to @value{GDBN} to support Modula-2 only support
12990 output from the @sc{gnu} Modula-2 compiler (which is currently being
12991 developed). Other Modula-2 compilers are not currently supported, and
12992 attempting to debug executables produced by them is most likely
12993 to give an error as @value{GDBN} reads in the executable's symbol
12996 @cindex expressions in Modula-2
12998 * M2 Operators:: Built-in operators
12999 * Built-In Func/Proc:: Built-in functions and procedures
13000 * M2 Constants:: Modula-2 constants
13001 * M2 Types:: Modula-2 types
13002 * M2 Defaults:: Default settings for Modula-2
13003 * Deviations:: Deviations from standard Modula-2
13004 * M2 Checks:: Modula-2 type and range checks
13005 * M2 Scope:: The scope operators @code{::} and @code{.}
13006 * GDB/M2:: @value{GDBN} and Modula-2
13010 @subsubsection Operators
13011 @cindex Modula-2 operators
13013 Operators must be defined on values of specific types. For instance,
13014 @code{+} is defined on numbers, but not on structures. Operators are
13015 often defined on groups of types. For the purposes of Modula-2, the
13016 following definitions hold:
13021 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13025 @emph{Character types} consist of @code{CHAR} and its subranges.
13028 @emph{Floating-point types} consist of @code{REAL}.
13031 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13035 @emph{Scalar types} consist of all of the above.
13038 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13041 @emph{Boolean types} consist of @code{BOOLEAN}.
13045 The following operators are supported, and appear in order of
13046 increasing precedence:
13050 Function argument or array index separator.
13053 Assignment. The value of @var{var} @code{:=} @var{value} is
13057 Less than, greater than on integral, floating-point, or enumerated
13061 Less than or equal to, greater than or equal to
13062 on integral, floating-point and enumerated types, or set inclusion on
13063 set types. Same precedence as @code{<}.
13065 @item =@r{, }<>@r{, }#
13066 Equality and two ways of expressing inequality, valid on scalar types.
13067 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13068 available for inequality, since @code{#} conflicts with the script
13072 Set membership. Defined on set types and the types of their members.
13073 Same precedence as @code{<}.
13076 Boolean disjunction. Defined on boolean types.
13079 Boolean conjunction. Defined on boolean types.
13082 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13085 Addition and subtraction on integral and floating-point types, or union
13086 and difference on set types.
13089 Multiplication on integral and floating-point types, or set intersection
13093 Division on floating-point types, or symmetric set difference on set
13094 types. Same precedence as @code{*}.
13097 Integer division and remainder. Defined on integral types. Same
13098 precedence as @code{*}.
13101 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13104 Pointer dereferencing. Defined on pointer types.
13107 Boolean negation. Defined on boolean types. Same precedence as
13111 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13112 precedence as @code{^}.
13115 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13118 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13122 @value{GDBN} and Modula-2 scope operators.
13126 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13127 treats the use of the operator @code{IN}, or the use of operators
13128 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13129 @code{<=}, and @code{>=} on sets as an error.
13133 @node Built-In Func/Proc
13134 @subsubsection Built-in Functions and Procedures
13135 @cindex Modula-2 built-ins
13137 Modula-2 also makes available several built-in procedures and functions.
13138 In describing these, the following metavariables are used:
13143 represents an @code{ARRAY} variable.
13146 represents a @code{CHAR} constant or variable.
13149 represents a variable or constant of integral type.
13152 represents an identifier that belongs to a set. Generally used in the
13153 same function with the metavariable @var{s}. The type of @var{s} should
13154 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13157 represents a variable or constant of integral or floating-point type.
13160 represents a variable or constant of floating-point type.
13166 represents a variable.
13169 represents a variable or constant of one of many types. See the
13170 explanation of the function for details.
13173 All Modula-2 built-in procedures also return a result, described below.
13177 Returns the absolute value of @var{n}.
13180 If @var{c} is a lower case letter, it returns its upper case
13181 equivalent, otherwise it returns its argument.
13184 Returns the character whose ordinal value is @var{i}.
13187 Decrements the value in the variable @var{v} by one. Returns the new value.
13189 @item DEC(@var{v},@var{i})
13190 Decrements the value in the variable @var{v} by @var{i}. Returns the
13193 @item EXCL(@var{m},@var{s})
13194 Removes the element @var{m} from the set @var{s}. Returns the new
13197 @item FLOAT(@var{i})
13198 Returns the floating point equivalent of the integer @var{i}.
13200 @item HIGH(@var{a})
13201 Returns the index of the last member of @var{a}.
13204 Increments the value in the variable @var{v} by one. Returns the new value.
13206 @item INC(@var{v},@var{i})
13207 Increments the value in the variable @var{v} by @var{i}. Returns the
13210 @item INCL(@var{m},@var{s})
13211 Adds the element @var{m} to the set @var{s} if it is not already
13212 there. Returns the new set.
13215 Returns the maximum value of the type @var{t}.
13218 Returns the minimum value of the type @var{t}.
13221 Returns boolean TRUE if @var{i} is an odd number.
13224 Returns the ordinal value of its argument. For example, the ordinal
13225 value of a character is its @sc{ascii} value (on machines supporting the
13226 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13227 integral, character and enumerated types.
13229 @item SIZE(@var{x})
13230 Returns the size of its argument. @var{x} can be a variable or a type.
13232 @item TRUNC(@var{r})
13233 Returns the integral part of @var{r}.
13235 @item TSIZE(@var{x})
13236 Returns the size of its argument. @var{x} can be a variable or a type.
13238 @item VAL(@var{t},@var{i})
13239 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13243 @emph{Warning:} Sets and their operations are not yet supported, so
13244 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13248 @cindex Modula-2 constants
13250 @subsubsection Constants
13252 @value{GDBN} allows you to express the constants of Modula-2 in the following
13258 Integer constants are simply a sequence of digits. When used in an
13259 expression, a constant is interpreted to be type-compatible with the
13260 rest of the expression. Hexadecimal integers are specified by a
13261 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13264 Floating point constants appear as a sequence of digits, followed by a
13265 decimal point and another sequence of digits. An optional exponent can
13266 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13267 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13268 digits of the floating point constant must be valid decimal (base 10)
13272 Character constants consist of a single character enclosed by a pair of
13273 like quotes, either single (@code{'}) or double (@code{"}). They may
13274 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13275 followed by a @samp{C}.
13278 String constants consist of a sequence of characters enclosed by a
13279 pair of like quotes, either single (@code{'}) or double (@code{"}).
13280 Escape sequences in the style of C are also allowed. @xref{C
13281 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13285 Enumerated constants consist of an enumerated identifier.
13288 Boolean constants consist of the identifiers @code{TRUE} and
13292 Pointer constants consist of integral values only.
13295 Set constants are not yet supported.
13299 @subsubsection Modula-2 Types
13300 @cindex Modula-2 types
13302 Currently @value{GDBN} can print the following data types in Modula-2
13303 syntax: array types, record types, set types, pointer types, procedure
13304 types, enumerated types, subrange types and base types. You can also
13305 print the contents of variables declared using these type.
13306 This section gives a number of simple source code examples together with
13307 sample @value{GDBN} sessions.
13309 The first example contains the following section of code:
13318 and you can request @value{GDBN} to interrogate the type and value of
13319 @code{r} and @code{s}.
13322 (@value{GDBP}) print s
13324 (@value{GDBP}) ptype s
13326 (@value{GDBP}) print r
13328 (@value{GDBP}) ptype r
13333 Likewise if your source code declares @code{s} as:
13337 s: SET ['A'..'Z'] ;
13341 then you may query the type of @code{s} by:
13344 (@value{GDBP}) ptype s
13345 type = SET ['A'..'Z']
13349 Note that at present you cannot interactively manipulate set
13350 expressions using the debugger.
13352 The following example shows how you might declare an array in Modula-2
13353 and how you can interact with @value{GDBN} to print its type and contents:
13357 s: ARRAY [-10..10] OF CHAR ;
13361 (@value{GDBP}) ptype s
13362 ARRAY [-10..10] OF CHAR
13365 Note that the array handling is not yet complete and although the type
13366 is printed correctly, expression handling still assumes that all
13367 arrays have a lower bound of zero and not @code{-10} as in the example
13370 Here are some more type related Modula-2 examples:
13374 colour = (blue, red, yellow, green) ;
13375 t = [blue..yellow] ;
13383 The @value{GDBN} interaction shows how you can query the data type
13384 and value of a variable.
13387 (@value{GDBP}) print s
13389 (@value{GDBP}) ptype t
13390 type = [blue..yellow]
13394 In this example a Modula-2 array is declared and its contents
13395 displayed. Observe that the contents are written in the same way as
13396 their @code{C} counterparts.
13400 s: ARRAY [1..5] OF CARDINAL ;
13406 (@value{GDBP}) print s
13407 $1 = @{1, 0, 0, 0, 0@}
13408 (@value{GDBP}) ptype s
13409 type = ARRAY [1..5] OF CARDINAL
13412 The Modula-2 language interface to @value{GDBN} also understands
13413 pointer types as shown in this example:
13417 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13424 and you can request that @value{GDBN} describes the type of @code{s}.
13427 (@value{GDBP}) ptype s
13428 type = POINTER TO ARRAY [1..5] OF CARDINAL
13431 @value{GDBN} handles compound types as we can see in this example.
13432 Here we combine array types, record types, pointer types and subrange
13443 myarray = ARRAY myrange OF CARDINAL ;
13444 myrange = [-2..2] ;
13446 s: POINTER TO ARRAY myrange OF foo ;
13450 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13454 (@value{GDBP}) ptype s
13455 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13458 f3 : ARRAY [-2..2] OF CARDINAL;
13463 @subsubsection Modula-2 Defaults
13464 @cindex Modula-2 defaults
13466 If type and range checking are set automatically by @value{GDBN}, they
13467 both default to @code{on} whenever the working language changes to
13468 Modula-2. This happens regardless of whether you or @value{GDBN}
13469 selected the working language.
13471 If you allow @value{GDBN} to set the language automatically, then entering
13472 code compiled from a file whose name ends with @file{.mod} sets the
13473 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13474 Infer the Source Language}, for further details.
13477 @subsubsection Deviations from Standard Modula-2
13478 @cindex Modula-2, deviations from
13480 A few changes have been made to make Modula-2 programs easier to debug.
13481 This is done primarily via loosening its type strictness:
13485 Unlike in standard Modula-2, pointer constants can be formed by
13486 integers. This allows you to modify pointer variables during
13487 debugging. (In standard Modula-2, the actual address contained in a
13488 pointer variable is hidden from you; it can only be modified
13489 through direct assignment to another pointer variable or expression that
13490 returned a pointer.)
13493 C escape sequences can be used in strings and characters to represent
13494 non-printable characters. @value{GDBN} prints out strings with these
13495 escape sequences embedded. Single non-printable characters are
13496 printed using the @samp{CHR(@var{nnn})} format.
13499 The assignment operator (@code{:=}) returns the value of its right-hand
13503 All built-in procedures both modify @emph{and} return their argument.
13507 @subsubsection Modula-2 Type and Range Checks
13508 @cindex Modula-2 checks
13511 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13514 @c FIXME remove warning when type/range checks added
13516 @value{GDBN} considers two Modula-2 variables type equivalent if:
13520 They are of types that have been declared equivalent via a @code{TYPE
13521 @var{t1} = @var{t2}} statement
13524 They have been declared on the same line. (Note: This is true of the
13525 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13528 As long as type checking is enabled, any attempt to combine variables
13529 whose types are not equivalent is an error.
13531 Range checking is done on all mathematical operations, assignment, array
13532 index bounds, and all built-in functions and procedures.
13535 @subsubsection The Scope Operators @code{::} and @code{.}
13537 @cindex @code{.}, Modula-2 scope operator
13538 @cindex colon, doubled as scope operator
13540 @vindex colon-colon@r{, in Modula-2}
13541 @c Info cannot handle :: but TeX can.
13544 @vindex ::@r{, in Modula-2}
13547 There are a few subtle differences between the Modula-2 scope operator
13548 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13553 @var{module} . @var{id}
13554 @var{scope} :: @var{id}
13558 where @var{scope} is the name of a module or a procedure,
13559 @var{module} the name of a module, and @var{id} is any declared
13560 identifier within your program, except another module.
13562 Using the @code{::} operator makes @value{GDBN} search the scope
13563 specified by @var{scope} for the identifier @var{id}. If it is not
13564 found in the specified scope, then @value{GDBN} searches all scopes
13565 enclosing the one specified by @var{scope}.
13567 Using the @code{.} operator makes @value{GDBN} search the current scope for
13568 the identifier specified by @var{id} that was imported from the
13569 definition module specified by @var{module}. With this operator, it is
13570 an error if the identifier @var{id} was not imported from definition
13571 module @var{module}, or if @var{id} is not an identifier in
13575 @subsubsection @value{GDBN} and Modula-2
13577 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13578 Five subcommands of @code{set print} and @code{show print} apply
13579 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13580 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13581 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13582 analogue in Modula-2.
13584 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13585 with any language, is not useful with Modula-2. Its
13586 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13587 created in Modula-2 as they can in C or C@t{++}. However, because an
13588 address can be specified by an integral constant, the construct
13589 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13591 @cindex @code{#} in Modula-2
13592 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13593 interpreted as the beginning of a comment. Use @code{<>} instead.
13599 The extensions made to @value{GDBN} for Ada only support
13600 output from the @sc{gnu} Ada (GNAT) compiler.
13601 Other Ada compilers are not currently supported, and
13602 attempting to debug executables produced by them is most likely
13606 @cindex expressions in Ada
13608 * Ada Mode Intro:: General remarks on the Ada syntax
13609 and semantics supported by Ada mode
13611 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13612 * Additions to Ada:: Extensions of the Ada expression syntax.
13613 * Stopping Before Main Program:: Debugging the program during elaboration.
13614 * Ada Tasks:: Listing and setting breakpoints in tasks.
13615 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13616 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13618 * Ada Glitches:: Known peculiarities of Ada mode.
13621 @node Ada Mode Intro
13622 @subsubsection Introduction
13623 @cindex Ada mode, general
13625 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13626 syntax, with some extensions.
13627 The philosophy behind the design of this subset is
13631 That @value{GDBN} should provide basic literals and access to operations for
13632 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13633 leaving more sophisticated computations to subprograms written into the
13634 program (which therefore may be called from @value{GDBN}).
13637 That type safety and strict adherence to Ada language restrictions
13638 are not particularly important to the @value{GDBN} user.
13641 That brevity is important to the @value{GDBN} user.
13644 Thus, for brevity, the debugger acts as if all names declared in
13645 user-written packages are directly visible, even if they are not visible
13646 according to Ada rules, thus making it unnecessary to fully qualify most
13647 names with their packages, regardless of context. Where this causes
13648 ambiguity, @value{GDBN} asks the user's intent.
13650 The debugger will start in Ada mode if it detects an Ada main program.
13651 As for other languages, it will enter Ada mode when stopped in a program that
13652 was translated from an Ada source file.
13654 While in Ada mode, you may use `@t{--}' for comments. This is useful
13655 mostly for documenting command files. The standard @value{GDBN} comment
13656 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13657 middle (to allow based literals).
13659 The debugger supports limited overloading. Given a subprogram call in which
13660 the function symbol has multiple definitions, it will use the number of
13661 actual parameters and some information about their types to attempt to narrow
13662 the set of definitions. It also makes very limited use of context, preferring
13663 procedures to functions in the context of the @code{call} command, and
13664 functions to procedures elsewhere.
13666 @node Omissions from Ada
13667 @subsubsection Omissions from Ada
13668 @cindex Ada, omissions from
13670 Here are the notable omissions from the subset:
13674 Only a subset of the attributes are supported:
13678 @t{'First}, @t{'Last}, and @t{'Length}
13679 on array objects (not on types and subtypes).
13682 @t{'Min} and @t{'Max}.
13685 @t{'Pos} and @t{'Val}.
13691 @t{'Range} on array objects (not subtypes), but only as the right
13692 operand of the membership (@code{in}) operator.
13695 @t{'Access}, @t{'Unchecked_Access}, and
13696 @t{'Unrestricted_Access} (a GNAT extension).
13704 @code{Characters.Latin_1} are not available and
13705 concatenation is not implemented. Thus, escape characters in strings are
13706 not currently available.
13709 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13710 equality of representations. They will generally work correctly
13711 for strings and arrays whose elements have integer or enumeration types.
13712 They may not work correctly for arrays whose element
13713 types have user-defined equality, for arrays of real values
13714 (in particular, IEEE-conformant floating point, because of negative
13715 zeroes and NaNs), and for arrays whose elements contain unused bits with
13716 indeterminate values.
13719 The other component-by-component array operations (@code{and}, @code{or},
13720 @code{xor}, @code{not}, and relational tests other than equality)
13721 are not implemented.
13724 @cindex array aggregates (Ada)
13725 @cindex record aggregates (Ada)
13726 @cindex aggregates (Ada)
13727 There is limited support for array and record aggregates. They are
13728 permitted only on the right sides of assignments, as in these examples:
13731 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13732 (@value{GDBP}) set An_Array := (1, others => 0)
13733 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13734 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13735 (@value{GDBP}) set A_Record := (1, "Peter", True);
13736 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13740 discriminant's value by assigning an aggregate has an
13741 undefined effect if that discriminant is used within the record.
13742 However, you can first modify discriminants by directly assigning to
13743 them (which normally would not be allowed in Ada), and then performing an
13744 aggregate assignment. For example, given a variable @code{A_Rec}
13745 declared to have a type such as:
13748 type Rec (Len : Small_Integer := 0) is record
13750 Vals : IntArray (1 .. Len);
13754 you can assign a value with a different size of @code{Vals} with two
13758 (@value{GDBP}) set A_Rec.Len := 4
13759 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13762 As this example also illustrates, @value{GDBN} is very loose about the usual
13763 rules concerning aggregates. You may leave out some of the
13764 components of an array or record aggregate (such as the @code{Len}
13765 component in the assignment to @code{A_Rec} above); they will retain their
13766 original values upon assignment. You may freely use dynamic values as
13767 indices in component associations. You may even use overlapping or
13768 redundant component associations, although which component values are
13769 assigned in such cases is not defined.
13772 Calls to dispatching subprograms are not implemented.
13775 The overloading algorithm is much more limited (i.e., less selective)
13776 than that of real Ada. It makes only limited use of the context in
13777 which a subexpression appears to resolve its meaning, and it is much
13778 looser in its rules for allowing type matches. As a result, some
13779 function calls will be ambiguous, and the user will be asked to choose
13780 the proper resolution.
13783 The @code{new} operator is not implemented.
13786 Entry calls are not implemented.
13789 Aside from printing, arithmetic operations on the native VAX floating-point
13790 formats are not supported.
13793 It is not possible to slice a packed array.
13796 The names @code{True} and @code{False}, when not part of a qualified name,
13797 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13799 Should your program
13800 redefine these names in a package or procedure (at best a dubious practice),
13801 you will have to use fully qualified names to access their new definitions.
13804 @node Additions to Ada
13805 @subsubsection Additions to Ada
13806 @cindex Ada, deviations from
13808 As it does for other languages, @value{GDBN} makes certain generic
13809 extensions to Ada (@pxref{Expressions}):
13813 If the expression @var{E} is a variable residing in memory (typically
13814 a local variable or array element) and @var{N} is a positive integer,
13815 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13816 @var{N}-1 adjacent variables following it in memory as an array. In
13817 Ada, this operator is generally not necessary, since its prime use is
13818 in displaying parts of an array, and slicing will usually do this in
13819 Ada. However, there are occasional uses when debugging programs in
13820 which certain debugging information has been optimized away.
13823 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13824 appears in function or file @var{B}.'' When @var{B} is a file name,
13825 you must typically surround it in single quotes.
13828 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13829 @var{type} that appears at address @var{addr}.''
13832 A name starting with @samp{$} is a convenience variable
13833 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13836 In addition, @value{GDBN} provides a few other shortcuts and outright
13837 additions specific to Ada:
13841 The assignment statement is allowed as an expression, returning
13842 its right-hand operand as its value. Thus, you may enter
13845 (@value{GDBP}) set x := y + 3
13846 (@value{GDBP}) print A(tmp := y + 1)
13850 The semicolon is allowed as an ``operator,'' returning as its value
13851 the value of its right-hand operand.
13852 This allows, for example,
13853 complex conditional breaks:
13856 (@value{GDBP}) break f
13857 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13861 Rather than use catenation and symbolic character names to introduce special
13862 characters into strings, one may instead use a special bracket notation,
13863 which is also used to print strings. A sequence of characters of the form
13864 @samp{["@var{XX}"]} within a string or character literal denotes the
13865 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13866 sequence of characters @samp{["""]} also denotes a single quotation mark
13867 in strings. For example,
13869 "One line.["0a"]Next line.["0a"]"
13872 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13876 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13877 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13881 (@value{GDBP}) print 'max(x, y)
13885 When printing arrays, @value{GDBN} uses positional notation when the
13886 array has a lower bound of 1, and uses a modified named notation otherwise.
13887 For example, a one-dimensional array of three integers with a lower bound
13888 of 3 might print as
13895 That is, in contrast to valid Ada, only the first component has a @code{=>}
13899 You may abbreviate attributes in expressions with any unique,
13900 multi-character subsequence of
13901 their names (an exact match gets preference).
13902 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13903 in place of @t{a'length}.
13906 @cindex quoting Ada internal identifiers
13907 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13908 to lower case. The GNAT compiler uses upper-case characters for
13909 some of its internal identifiers, which are normally of no interest to users.
13910 For the rare occasions when you actually have to look at them,
13911 enclose them in angle brackets to avoid the lower-case mapping.
13914 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13918 Printing an object of class-wide type or dereferencing an
13919 access-to-class-wide value will display all the components of the object's
13920 specific type (as indicated by its run-time tag). Likewise, component
13921 selection on such a value will operate on the specific type of the
13926 @node Stopping Before Main Program
13927 @subsubsection Stopping at the Very Beginning
13929 @cindex breakpointing Ada elaboration code
13930 It is sometimes necessary to debug the program during elaboration, and
13931 before reaching the main procedure.
13932 As defined in the Ada Reference
13933 Manual, the elaboration code is invoked from a procedure called
13934 @code{adainit}. To run your program up to the beginning of
13935 elaboration, simply use the following two commands:
13936 @code{tbreak adainit} and @code{run}.
13939 @subsubsection Extensions for Ada Tasks
13940 @cindex Ada, tasking
13942 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13943 @value{GDBN} provides the following task-related commands:
13948 This command shows a list of current Ada tasks, as in the following example:
13955 (@value{GDBP}) info tasks
13956 ID TID P-ID Pri State Name
13957 1 8088000 0 15 Child Activation Wait main_task
13958 2 80a4000 1 15 Accept Statement b
13959 3 809a800 1 15 Child Activation Wait a
13960 * 4 80ae800 3 15 Runnable c
13965 In this listing, the asterisk before the last task indicates it to be the
13966 task currently being inspected.
13970 Represents @value{GDBN}'s internal task number.
13976 The parent's task ID (@value{GDBN}'s internal task number).
13979 The base priority of the task.
13982 Current state of the task.
13986 The task has been created but has not been activated. It cannot be
13990 The task is not blocked for any reason known to Ada. (It may be waiting
13991 for a mutex, though.) It is conceptually "executing" in normal mode.
13994 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13995 that were waiting on terminate alternatives have been awakened and have
13996 terminated themselves.
13998 @item Child Activation Wait
13999 The task is waiting for created tasks to complete activation.
14001 @item Accept Statement
14002 The task is waiting on an accept or selective wait statement.
14004 @item Waiting on entry call
14005 The task is waiting on an entry call.
14007 @item Async Select Wait
14008 The task is waiting to start the abortable part of an asynchronous
14012 The task is waiting on a select statement with only a delay
14015 @item Child Termination Wait
14016 The task is sleeping having completed a master within itself, and is
14017 waiting for the tasks dependent on that master to become terminated or
14018 waiting on a terminate Phase.
14020 @item Wait Child in Term Alt
14021 The task is sleeping waiting for tasks on terminate alternatives to
14022 finish terminating.
14024 @item Accepting RV with @var{taskno}
14025 The task is accepting a rendez-vous with the task @var{taskno}.
14029 Name of the task in the program.
14033 @kindex info task @var{taskno}
14034 @item info task @var{taskno}
14035 This command shows detailled informations on the specified task, as in
14036 the following example:
14041 (@value{GDBP}) info tasks
14042 ID TID P-ID Pri State Name
14043 1 8077880 0 15 Child Activation Wait main_task
14044 * 2 807c468 1 15 Runnable task_1
14045 (@value{GDBP}) info task 2
14046 Ada Task: 0x807c468
14049 Parent: 1 (main_task)
14055 @kindex task@r{ (Ada)}
14056 @cindex current Ada task ID
14057 This command prints the ID of the current task.
14063 (@value{GDBP}) info tasks
14064 ID TID P-ID Pri State Name
14065 1 8077870 0 15 Child Activation Wait main_task
14066 * 2 807c458 1 15 Runnable t
14067 (@value{GDBP}) task
14068 [Current task is 2]
14071 @item task @var{taskno}
14072 @cindex Ada task switching
14073 This command is like the @code{thread @var{threadno}}
14074 command (@pxref{Threads}). It switches the context of debugging
14075 from the current task to the given task.
14081 (@value{GDBP}) info tasks
14082 ID TID P-ID Pri State Name
14083 1 8077870 0 15 Child Activation Wait main_task
14084 * 2 807c458 1 15 Runnable t
14085 (@value{GDBP}) task 1
14086 [Switching to task 1]
14087 #0 0x8067726 in pthread_cond_wait ()
14089 #0 0x8067726 in pthread_cond_wait ()
14090 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14091 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14092 #3 0x806153e in system.tasking.stages.activate_tasks ()
14093 #4 0x804aacc in un () at un.adb:5
14096 @item break @var{linespec} task @var{taskno}
14097 @itemx break @var{linespec} task @var{taskno} if @dots{}
14098 @cindex breakpoints and tasks, in Ada
14099 @cindex task breakpoints, in Ada
14100 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14101 These commands are like the @code{break @dots{} thread @dots{}}
14102 command (@pxref{Thread Stops}).
14103 @var{linespec} specifies source lines, as described
14104 in @ref{Specify Location}.
14106 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14107 to specify that you only want @value{GDBN} to stop the program when a
14108 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14109 numeric task identifiers assigned by @value{GDBN}, shown in the first
14110 column of the @samp{info tasks} display.
14112 If you do not specify @samp{task @var{taskno}} when you set a
14113 breakpoint, the breakpoint applies to @emph{all} tasks of your
14116 You can use the @code{task} qualifier on conditional breakpoints as
14117 well; in this case, place @samp{task @var{taskno}} before the
14118 breakpoint condition (before the @code{if}).
14126 (@value{GDBP}) info tasks
14127 ID TID P-ID Pri State Name
14128 1 140022020 0 15 Child Activation Wait main_task
14129 2 140045060 1 15 Accept/Select Wait t2
14130 3 140044840 1 15 Runnable t1
14131 * 4 140056040 1 15 Runnable t3
14132 (@value{GDBP}) b 15 task 2
14133 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14134 (@value{GDBP}) cont
14139 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14141 (@value{GDBP}) info tasks
14142 ID TID P-ID Pri State Name
14143 1 140022020 0 15 Child Activation Wait main_task
14144 * 2 140045060 1 15 Runnable t2
14145 3 140044840 1 15 Runnable t1
14146 4 140056040 1 15 Delay Sleep t3
14150 @node Ada Tasks and Core Files
14151 @subsubsection Tasking Support when Debugging Core Files
14152 @cindex Ada tasking and core file debugging
14154 When inspecting a core file, as opposed to debugging a live program,
14155 tasking support may be limited or even unavailable, depending on
14156 the platform being used.
14157 For instance, on x86-linux, the list of tasks is available, but task
14158 switching is not supported. On Tru64, however, task switching will work
14161 On certain platforms, including Tru64, the debugger needs to perform some
14162 memory writes in order to provide Ada tasking support. When inspecting
14163 a core file, this means that the core file must be opened with read-write
14164 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14165 Under these circumstances, you should make a backup copy of the core
14166 file before inspecting it with @value{GDBN}.
14168 @node Ravenscar Profile
14169 @subsubsection Tasking Support when using the Ravenscar Profile
14170 @cindex Ravenscar Profile
14172 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14173 specifically designed for systems with safety-critical real-time
14177 @kindex set ravenscar task-switching on
14178 @cindex task switching with program using Ravenscar Profile
14179 @item set ravenscar task-switching on
14180 Allows task switching when debugging a program that uses the Ravenscar
14181 Profile. This is the default.
14183 @kindex set ravenscar task-switching off
14184 @item set ravenscar task-switching off
14185 Turn off task switching when debugging a program that uses the Ravenscar
14186 Profile. This is mostly intended to disable the code that adds support
14187 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14188 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14189 To be effective, this command should be run before the program is started.
14191 @kindex show ravenscar task-switching
14192 @item show ravenscar task-switching
14193 Show whether it is possible to switch from task to task in a program
14194 using the Ravenscar Profile.
14199 @subsubsection Known Peculiarities of Ada Mode
14200 @cindex Ada, problems
14202 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14203 we know of several problems with and limitations of Ada mode in
14205 some of which will be fixed with planned future releases of the debugger
14206 and the GNU Ada compiler.
14210 Static constants that the compiler chooses not to materialize as objects in
14211 storage are invisible to the debugger.
14214 Named parameter associations in function argument lists are ignored (the
14215 argument lists are treated as positional).
14218 Many useful library packages are currently invisible to the debugger.
14221 Fixed-point arithmetic, conversions, input, and output is carried out using
14222 floating-point arithmetic, and may give results that only approximate those on
14226 The GNAT compiler never generates the prefix @code{Standard} for any of
14227 the standard symbols defined by the Ada language. @value{GDBN} knows about
14228 this: it will strip the prefix from names when you use it, and will never
14229 look for a name you have so qualified among local symbols, nor match against
14230 symbols in other packages or subprograms. If you have
14231 defined entities anywhere in your program other than parameters and
14232 local variables whose simple names match names in @code{Standard},
14233 GNAT's lack of qualification here can cause confusion. When this happens,
14234 you can usually resolve the confusion
14235 by qualifying the problematic names with package
14236 @code{Standard} explicitly.
14239 Older versions of the compiler sometimes generate erroneous debugging
14240 information, resulting in the debugger incorrectly printing the value
14241 of affected entities. In some cases, the debugger is able to work
14242 around an issue automatically. In other cases, the debugger is able
14243 to work around the issue, but the work-around has to be specifically
14246 @kindex set ada trust-PAD-over-XVS
14247 @kindex show ada trust-PAD-over-XVS
14250 @item set ada trust-PAD-over-XVS on
14251 Configure GDB to strictly follow the GNAT encoding when computing the
14252 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14253 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14254 a complete description of the encoding used by the GNAT compiler).
14255 This is the default.
14257 @item set ada trust-PAD-over-XVS off
14258 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14259 sometimes prints the wrong value for certain entities, changing @code{ada
14260 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14261 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14262 @code{off}, but this incurs a slight performance penalty, so it is
14263 recommended to leave this setting to @code{on} unless necessary.
14267 @node Unsupported Languages
14268 @section Unsupported Languages
14270 @cindex unsupported languages
14271 @cindex minimal language
14272 In addition to the other fully-supported programming languages,
14273 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14274 It does not represent a real programming language, but provides a set
14275 of capabilities close to what the C or assembly languages provide.
14276 This should allow most simple operations to be performed while debugging
14277 an application that uses a language currently not supported by @value{GDBN}.
14279 If the language is set to @code{auto}, @value{GDBN} will automatically
14280 select this language if the current frame corresponds to an unsupported
14284 @chapter Examining the Symbol Table
14286 The commands described in this chapter allow you to inquire about the
14287 symbols (names of variables, functions and types) defined in your
14288 program. This information is inherent in the text of your program and
14289 does not change as your program executes. @value{GDBN} finds it in your
14290 program's symbol table, in the file indicated when you started @value{GDBN}
14291 (@pxref{File Options, ,Choosing Files}), or by one of the
14292 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14294 @cindex symbol names
14295 @cindex names of symbols
14296 @cindex quoting names
14297 Occasionally, you may need to refer to symbols that contain unusual
14298 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14299 most frequent case is in referring to static variables in other
14300 source files (@pxref{Variables,,Program Variables}). File names
14301 are recorded in object files as debugging symbols, but @value{GDBN} would
14302 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14303 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14304 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14311 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14314 @cindex case-insensitive symbol names
14315 @cindex case sensitivity in symbol names
14316 @kindex set case-sensitive
14317 @item set case-sensitive on
14318 @itemx set case-sensitive off
14319 @itemx set case-sensitive auto
14320 Normally, when @value{GDBN} looks up symbols, it matches their names
14321 with case sensitivity determined by the current source language.
14322 Occasionally, you may wish to control that. The command @code{set
14323 case-sensitive} lets you do that by specifying @code{on} for
14324 case-sensitive matches or @code{off} for case-insensitive ones. If
14325 you specify @code{auto}, case sensitivity is reset to the default
14326 suitable for the source language. The default is case-sensitive
14327 matches for all languages except for Fortran, for which the default is
14328 case-insensitive matches.
14330 @kindex show case-sensitive
14331 @item show case-sensitive
14332 This command shows the current setting of case sensitivity for symbols
14335 @kindex info address
14336 @cindex address of a symbol
14337 @item info address @var{symbol}
14338 Describe where the data for @var{symbol} is stored. For a register
14339 variable, this says which register it is kept in. For a non-register
14340 local variable, this prints the stack-frame offset at which the variable
14343 Note the contrast with @samp{print &@var{symbol}}, which does not work
14344 at all for a register variable, and for a stack local variable prints
14345 the exact address of the current instantiation of the variable.
14347 @kindex info symbol
14348 @cindex symbol from address
14349 @cindex closest symbol and offset for an address
14350 @item info symbol @var{addr}
14351 Print the name of a symbol which is stored at the address @var{addr}.
14352 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14353 nearest symbol and an offset from it:
14356 (@value{GDBP}) info symbol 0x54320
14357 _initialize_vx + 396 in section .text
14361 This is the opposite of the @code{info address} command. You can use
14362 it to find out the name of a variable or a function given its address.
14364 For dynamically linked executables, the name of executable or shared
14365 library containing the symbol is also printed:
14368 (@value{GDBP}) info symbol 0x400225
14369 _start + 5 in section .text of /tmp/a.out
14370 (@value{GDBP}) info symbol 0x2aaaac2811cf
14371 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14375 @item whatis [@var{arg}]
14376 Print the data type of @var{arg}, which can be either an expression
14377 or a name of a data type. With no argument, print the data type of
14378 @code{$}, the last value in the value history.
14380 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14381 is not actually evaluated, and any side-effecting operations (such as
14382 assignments or function calls) inside it do not take place.
14384 If @var{arg} is a variable or an expression, @code{whatis} prints its
14385 literal type as it is used in the source code. If the type was
14386 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14387 the data type underlying the @code{typedef}. If the type of the
14388 variable or the expression is a compound data type, such as
14389 @code{struct} or @code{class}, @code{whatis} never prints their
14390 fields or methods. It just prints the @code{struct}/@code{class}
14391 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14392 such a compound data type, use @code{ptype}.
14394 If @var{arg} is a type name that was defined using @code{typedef},
14395 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14396 Unrolling means that @code{whatis} will show the underlying type used
14397 in the @code{typedef} declaration of @var{arg}. However, if that
14398 underlying type is also a @code{typedef}, @code{whatis} will not
14401 For C code, the type names may also have the form @samp{class
14402 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14403 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14406 @item ptype [@var{arg}]
14407 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14408 detailed description of the type, instead of just the name of the type.
14409 @xref{Expressions, ,Expressions}.
14411 Contrary to @code{whatis}, @code{ptype} always unrolls any
14412 @code{typedef}s in its argument declaration, whether the argument is
14413 a variable, expression, or a data type. This means that @code{ptype}
14414 of a variable or an expression will not print literally its type as
14415 present in the source code---use @code{whatis} for that. @code{typedef}s at
14416 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14417 fields, methods and inner @code{class typedef}s of @code{struct}s,
14418 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14420 For example, for this variable declaration:
14423 typedef double real_t;
14424 struct complex @{ real_t real; double imag; @};
14425 typedef struct complex complex_t;
14427 real_t *real_pointer_var;
14431 the two commands give this output:
14435 (@value{GDBP}) whatis var
14437 (@value{GDBP}) ptype var
14438 type = struct complex @{
14442 (@value{GDBP}) whatis complex_t
14443 type = struct complex
14444 (@value{GDBP}) whatis struct complex
14445 type = struct complex
14446 (@value{GDBP}) ptype struct complex
14447 type = struct complex @{
14451 (@value{GDBP}) whatis real_pointer_var
14453 (@value{GDBP}) ptype real_pointer_var
14459 As with @code{whatis}, using @code{ptype} without an argument refers to
14460 the type of @code{$}, the last value in the value history.
14462 @cindex incomplete type
14463 Sometimes, programs use opaque data types or incomplete specifications
14464 of complex data structure. If the debug information included in the
14465 program does not allow @value{GDBN} to display a full declaration of
14466 the data type, it will say @samp{<incomplete type>}. For example,
14467 given these declarations:
14471 struct foo *fooptr;
14475 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14478 (@value{GDBP}) ptype foo
14479 $1 = <incomplete type>
14483 ``Incomplete type'' is C terminology for data types that are not
14484 completely specified.
14487 @item info types @var{regexp}
14489 Print a brief description of all types whose names match the regular
14490 expression @var{regexp} (or all types in your program, if you supply
14491 no argument). Each complete typename is matched as though it were a
14492 complete line; thus, @samp{i type value} gives information on all
14493 types in your program whose names include the string @code{value}, but
14494 @samp{i type ^value$} gives information only on types whose complete
14495 name is @code{value}.
14497 This command differs from @code{ptype} in two ways: first, like
14498 @code{whatis}, it does not print a detailed description; second, it
14499 lists all source files where a type is defined.
14502 @cindex local variables
14503 @item info scope @var{location}
14504 List all the variables local to a particular scope. This command
14505 accepts a @var{location} argument---a function name, a source line, or
14506 an address preceded by a @samp{*}, and prints all the variables local
14507 to the scope defined by that location. (@xref{Specify Location}, for
14508 details about supported forms of @var{location}.) For example:
14511 (@value{GDBP}) @b{info scope command_line_handler}
14512 Scope for command_line_handler:
14513 Symbol rl is an argument at stack/frame offset 8, length 4.
14514 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14515 Symbol linelength is in static storage at address 0x150a1c, length 4.
14516 Symbol p is a local variable in register $esi, length 4.
14517 Symbol p1 is a local variable in register $ebx, length 4.
14518 Symbol nline is a local variable in register $edx, length 4.
14519 Symbol repeat is a local variable at frame offset -8, length 4.
14523 This command is especially useful for determining what data to collect
14524 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14527 @kindex info source
14529 Show information about the current source file---that is, the source file for
14530 the function containing the current point of execution:
14533 the name of the source file, and the directory containing it,
14535 the directory it was compiled in,
14537 its length, in lines,
14539 which programming language it is written in,
14541 whether the executable includes debugging information for that file, and
14542 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14544 whether the debugging information includes information about
14545 preprocessor macros.
14549 @kindex info sources
14551 Print the names of all source files in your program for which there is
14552 debugging information, organized into two lists: files whose symbols
14553 have already been read, and files whose symbols will be read when needed.
14555 @kindex info functions
14556 @item info functions
14557 Print the names and data types of all defined functions.
14559 @item info functions @var{regexp}
14560 Print the names and data types of all defined functions
14561 whose names contain a match for regular expression @var{regexp}.
14562 Thus, @samp{info fun step} finds all functions whose names
14563 include @code{step}; @samp{info fun ^step} finds those whose names
14564 start with @code{step}. If a function name contains characters
14565 that conflict with the regular expression language (e.g.@:
14566 @samp{operator*()}), they may be quoted with a backslash.
14568 @kindex info variables
14569 @item info variables
14570 Print the names and data types of all variables that are defined
14571 outside of functions (i.e.@: excluding local variables).
14573 @item info variables @var{regexp}
14574 Print the names and data types of all variables (except for local
14575 variables) whose names contain a match for regular expression
14578 @kindex info classes
14579 @cindex Objective-C, classes and selectors
14581 @itemx info classes @var{regexp}
14582 Display all Objective-C classes in your program, or
14583 (with the @var{regexp} argument) all those matching a particular regular
14586 @kindex info selectors
14587 @item info selectors
14588 @itemx info selectors @var{regexp}
14589 Display all Objective-C selectors in your program, or
14590 (with the @var{regexp} argument) all those matching a particular regular
14594 This was never implemented.
14595 @kindex info methods
14597 @itemx info methods @var{regexp}
14598 The @code{info methods} command permits the user to examine all defined
14599 methods within C@t{++} program, or (with the @var{regexp} argument) a
14600 specific set of methods found in the various C@t{++} classes. Many
14601 C@t{++} classes provide a large number of methods. Thus, the output
14602 from the @code{ptype} command can be overwhelming and hard to use. The
14603 @code{info-methods} command filters the methods, printing only those
14604 which match the regular-expression @var{regexp}.
14607 @cindex reloading symbols
14608 Some systems allow individual object files that make up your program to
14609 be replaced without stopping and restarting your program. For example,
14610 in VxWorks you can simply recompile a defective object file and keep on
14611 running. If you are running on one of these systems, you can allow
14612 @value{GDBN} to reload the symbols for automatically relinked modules:
14615 @kindex set symbol-reloading
14616 @item set symbol-reloading on
14617 Replace symbol definitions for the corresponding source file when an
14618 object file with a particular name is seen again.
14620 @item set symbol-reloading off
14621 Do not replace symbol definitions when encountering object files of the
14622 same name more than once. This is the default state; if you are not
14623 running on a system that permits automatic relinking of modules, you
14624 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14625 may discard symbols when linking large programs, that may contain
14626 several modules (from different directories or libraries) with the same
14629 @kindex show symbol-reloading
14630 @item show symbol-reloading
14631 Show the current @code{on} or @code{off} setting.
14634 @cindex opaque data types
14635 @kindex set opaque-type-resolution
14636 @item set opaque-type-resolution on
14637 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14638 declared as a pointer to a @code{struct}, @code{class}, or
14639 @code{union}---for example, @code{struct MyType *}---that is used in one
14640 source file although the full declaration of @code{struct MyType} is in
14641 another source file. The default is on.
14643 A change in the setting of this subcommand will not take effect until
14644 the next time symbols for a file are loaded.
14646 @item set opaque-type-resolution off
14647 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14648 is printed as follows:
14650 @{<no data fields>@}
14653 @kindex show opaque-type-resolution
14654 @item show opaque-type-resolution
14655 Show whether opaque types are resolved or not.
14657 @kindex maint print symbols
14658 @cindex symbol dump
14659 @kindex maint print psymbols
14660 @cindex partial symbol dump
14661 @item maint print symbols @var{filename}
14662 @itemx maint print psymbols @var{filename}
14663 @itemx maint print msymbols @var{filename}
14664 Write a dump of debugging symbol data into the file @var{filename}.
14665 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14666 symbols with debugging data are included. If you use @samp{maint print
14667 symbols}, @value{GDBN} includes all the symbols for which it has already
14668 collected full details: that is, @var{filename} reflects symbols for
14669 only those files whose symbols @value{GDBN} has read. You can use the
14670 command @code{info sources} to find out which files these are. If you
14671 use @samp{maint print psymbols} instead, the dump shows information about
14672 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14673 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14674 @samp{maint print msymbols} dumps just the minimal symbol information
14675 required for each object file from which @value{GDBN} has read some symbols.
14676 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14677 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14679 @kindex maint info symtabs
14680 @kindex maint info psymtabs
14681 @cindex listing @value{GDBN}'s internal symbol tables
14682 @cindex symbol tables, listing @value{GDBN}'s internal
14683 @cindex full symbol tables, listing @value{GDBN}'s internal
14684 @cindex partial symbol tables, listing @value{GDBN}'s internal
14685 @item maint info symtabs @r{[} @var{regexp} @r{]}
14686 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14688 List the @code{struct symtab} or @code{struct partial_symtab}
14689 structures whose names match @var{regexp}. If @var{regexp} is not
14690 given, list them all. The output includes expressions which you can
14691 copy into a @value{GDBN} debugging this one to examine a particular
14692 structure in more detail. For example:
14695 (@value{GDBP}) maint info psymtabs dwarf2read
14696 @{ objfile /home/gnu/build/gdb/gdb
14697 ((struct objfile *) 0x82e69d0)
14698 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14699 ((struct partial_symtab *) 0x8474b10)
14702 text addresses 0x814d3c8 -- 0x8158074
14703 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14704 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14705 dependencies (none)
14708 (@value{GDBP}) maint info symtabs
14712 We see that there is one partial symbol table whose filename contains
14713 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14714 and we see that @value{GDBN} has not read in any symtabs yet at all.
14715 If we set a breakpoint on a function, that will cause @value{GDBN} to
14716 read the symtab for the compilation unit containing that function:
14719 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14720 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14722 (@value{GDBP}) maint info symtabs
14723 @{ objfile /home/gnu/build/gdb/gdb
14724 ((struct objfile *) 0x82e69d0)
14725 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14726 ((struct symtab *) 0x86c1f38)
14729 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14730 linetable ((struct linetable *) 0x8370fa0)
14731 debugformat DWARF 2
14740 @chapter Altering Execution
14742 Once you think you have found an error in your program, you might want to
14743 find out for certain whether correcting the apparent error would lead to
14744 correct results in the rest of the run. You can find the answer by
14745 experiment, using the @value{GDBN} features for altering execution of the
14748 For example, you can store new values into variables or memory
14749 locations, give your program a signal, restart it at a different
14750 address, or even return prematurely from a function.
14753 * Assignment:: Assignment to variables
14754 * Jumping:: Continuing at a different address
14755 * Signaling:: Giving your program a signal
14756 * Returning:: Returning from a function
14757 * Calling:: Calling your program's functions
14758 * Patching:: Patching your program
14762 @section Assignment to Variables
14765 @cindex setting variables
14766 To alter the value of a variable, evaluate an assignment expression.
14767 @xref{Expressions, ,Expressions}. For example,
14774 stores the value 4 into the variable @code{x}, and then prints the
14775 value of the assignment expression (which is 4).
14776 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14777 information on operators in supported languages.
14779 @kindex set variable
14780 @cindex variables, setting
14781 If you are not interested in seeing the value of the assignment, use the
14782 @code{set} command instead of the @code{print} command. @code{set} is
14783 really the same as @code{print} except that the expression's value is
14784 not printed and is not put in the value history (@pxref{Value History,
14785 ,Value History}). The expression is evaluated only for its effects.
14787 If the beginning of the argument string of the @code{set} command
14788 appears identical to a @code{set} subcommand, use the @code{set
14789 variable} command instead of just @code{set}. This command is identical
14790 to @code{set} except for its lack of subcommands. For example, if your
14791 program has a variable @code{width}, you get an error if you try to set
14792 a new value with just @samp{set width=13}, because @value{GDBN} has the
14793 command @code{set width}:
14796 (@value{GDBP}) whatis width
14798 (@value{GDBP}) p width
14800 (@value{GDBP}) set width=47
14801 Invalid syntax in expression.
14805 The invalid expression, of course, is @samp{=47}. In
14806 order to actually set the program's variable @code{width}, use
14809 (@value{GDBP}) set var width=47
14812 Because the @code{set} command has many subcommands that can conflict
14813 with the names of program variables, it is a good idea to use the
14814 @code{set variable} command instead of just @code{set}. For example, if
14815 your program has a variable @code{g}, you run into problems if you try
14816 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14817 the command @code{set gnutarget}, abbreviated @code{set g}:
14821 (@value{GDBP}) whatis g
14825 (@value{GDBP}) set g=4
14829 The program being debugged has been started already.
14830 Start it from the beginning? (y or n) y
14831 Starting program: /home/smith/cc_progs/a.out
14832 "/home/smith/cc_progs/a.out": can't open to read symbols:
14833 Invalid bfd target.
14834 (@value{GDBP}) show g
14835 The current BFD target is "=4".
14840 The program variable @code{g} did not change, and you silently set the
14841 @code{gnutarget} to an invalid value. In order to set the variable
14845 (@value{GDBP}) set var g=4
14848 @value{GDBN} allows more implicit conversions in assignments than C; you can
14849 freely store an integer value into a pointer variable or vice versa,
14850 and you can convert any structure to any other structure that is the
14851 same length or shorter.
14852 @comment FIXME: how do structs align/pad in these conversions?
14853 @comment /doc@cygnus.com 18dec1990
14855 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14856 construct to generate a value of specified type at a specified address
14857 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14858 to memory location @code{0x83040} as an integer (which implies a certain size
14859 and representation in memory), and
14862 set @{int@}0x83040 = 4
14866 stores the value 4 into that memory location.
14869 @section Continuing at a Different Address
14871 Ordinarily, when you continue your program, you do so at the place where
14872 it stopped, with the @code{continue} command. You can instead continue at
14873 an address of your own choosing, with the following commands:
14877 @item jump @var{linespec}
14878 @itemx jump @var{location}
14879 Resume execution at line @var{linespec} or at address given by
14880 @var{location}. Execution stops again immediately if there is a
14881 breakpoint there. @xref{Specify Location}, for a description of the
14882 different forms of @var{linespec} and @var{location}. It is common
14883 practice to use the @code{tbreak} command in conjunction with
14884 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14886 The @code{jump} command does not change the current stack frame, or
14887 the stack pointer, or the contents of any memory location or any
14888 register other than the program counter. If line @var{linespec} is in
14889 a different function from the one currently executing, the results may
14890 be bizarre if the two functions expect different patterns of arguments or
14891 of local variables. For this reason, the @code{jump} command requests
14892 confirmation if the specified line is not in the function currently
14893 executing. However, even bizarre results are predictable if you are
14894 well acquainted with the machine-language code of your program.
14897 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14898 On many systems, you can get much the same effect as the @code{jump}
14899 command by storing a new value into the register @code{$pc}. The
14900 difference is that this does not start your program running; it only
14901 changes the address of where it @emph{will} run when you continue. For
14909 makes the next @code{continue} command or stepping command execute at
14910 address @code{0x485}, rather than at the address where your program stopped.
14911 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14913 The most common occasion to use the @code{jump} command is to back
14914 up---perhaps with more breakpoints set---over a portion of a program
14915 that has already executed, in order to examine its execution in more
14920 @section Giving your Program a Signal
14921 @cindex deliver a signal to a program
14925 @item signal @var{signal}
14926 Resume execution where your program stopped, but immediately give it the
14927 signal @var{signal}. @var{signal} can be the name or the number of a
14928 signal. For example, on many systems @code{signal 2} and @code{signal
14929 SIGINT} are both ways of sending an interrupt signal.
14931 Alternatively, if @var{signal} is zero, continue execution without
14932 giving a signal. This is useful when your program stopped on account of
14933 a signal and would ordinary see the signal when resumed with the
14934 @code{continue} command; @samp{signal 0} causes it to resume without a
14937 @code{signal} does not repeat when you press @key{RET} a second time
14938 after executing the command.
14942 Invoking the @code{signal} command is not the same as invoking the
14943 @code{kill} utility from the shell. Sending a signal with @code{kill}
14944 causes @value{GDBN} to decide what to do with the signal depending on
14945 the signal handling tables (@pxref{Signals}). The @code{signal} command
14946 passes the signal directly to your program.
14950 @section Returning from a Function
14953 @cindex returning from a function
14956 @itemx return @var{expression}
14957 You can cancel execution of a function call with the @code{return}
14958 command. If you give an
14959 @var{expression} argument, its value is used as the function's return
14963 When you use @code{return}, @value{GDBN} discards the selected stack frame
14964 (and all frames within it). You can think of this as making the
14965 discarded frame return prematurely. If you wish to specify a value to
14966 be returned, give that value as the argument to @code{return}.
14968 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14969 Frame}), and any other frames inside of it, leaving its caller as the
14970 innermost remaining frame. That frame becomes selected. The
14971 specified value is stored in the registers used for returning values
14974 The @code{return} command does not resume execution; it leaves the
14975 program stopped in the state that would exist if the function had just
14976 returned. In contrast, the @code{finish} command (@pxref{Continuing
14977 and Stepping, ,Continuing and Stepping}) resumes execution until the
14978 selected stack frame returns naturally.
14980 @value{GDBN} needs to know how the @var{expression} argument should be set for
14981 the inferior. The concrete registers assignment depends on the OS ABI and the
14982 type being returned by the selected stack frame. For example it is common for
14983 OS ABI to return floating point values in FPU registers while integer values in
14984 CPU registers. Still some ABIs return even floating point values in CPU
14985 registers. Larger integer widths (such as @code{long long int}) also have
14986 specific placement rules. @value{GDBN} already knows the OS ABI from its
14987 current target so it needs to find out also the type being returned to make the
14988 assignment into the right register(s).
14990 Normally, the selected stack frame has debug info. @value{GDBN} will always
14991 use the debug info instead of the implicit type of @var{expression} when the
14992 debug info is available. For example, if you type @kbd{return -1}, and the
14993 function in the current stack frame is declared to return a @code{long long
14994 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14995 into a @code{long long int}:
14998 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15000 (@value{GDBP}) return -1
15001 Make func return now? (y or n) y
15002 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15003 43 printf ("result=%lld\n", func ());
15007 However, if the selected stack frame does not have a debug info, e.g., if the
15008 function was compiled without debug info, @value{GDBN} has to find out the type
15009 to return from user. Specifying a different type by mistake may set the value
15010 in different inferior registers than the caller code expects. For example,
15011 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15012 of a @code{long long int} result for a debug info less function (on 32-bit
15013 architectures). Therefore the user is required to specify the return type by
15014 an appropriate cast explicitly:
15017 Breakpoint 2, 0x0040050b in func ()
15018 (@value{GDBP}) return -1
15019 Return value type not available for selected stack frame.
15020 Please use an explicit cast of the value to return.
15021 (@value{GDBP}) return (long long int) -1
15022 Make selected stack frame return now? (y or n) y
15023 #0 0x00400526 in main ()
15028 @section Calling Program Functions
15031 @cindex calling functions
15032 @cindex inferior functions, calling
15033 @item print @var{expr}
15034 Evaluate the expression @var{expr} and display the resulting value.
15035 @var{expr} may include calls to functions in the program being
15039 @item call @var{expr}
15040 Evaluate the expression @var{expr} without displaying @code{void}
15043 You can use this variant of the @code{print} command if you want to
15044 execute a function from your program that does not return anything
15045 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15046 with @code{void} returned values that @value{GDBN} will otherwise
15047 print. If the result is not void, it is printed and saved in the
15051 It is possible for the function you call via the @code{print} or
15052 @code{call} command to generate a signal (e.g., if there's a bug in
15053 the function, or if you passed it incorrect arguments). What happens
15054 in that case is controlled by the @code{set unwindonsignal} command.
15056 Similarly, with a C@t{++} program it is possible for the function you
15057 call via the @code{print} or @code{call} command to generate an
15058 exception that is not handled due to the constraints of the dummy
15059 frame. In this case, any exception that is raised in the frame, but has
15060 an out-of-frame exception handler will not be found. GDB builds a
15061 dummy-frame for the inferior function call, and the unwinder cannot
15062 seek for exception handlers outside of this dummy-frame. What happens
15063 in that case is controlled by the
15064 @code{set unwind-on-terminating-exception} command.
15067 @item set unwindonsignal
15068 @kindex set unwindonsignal
15069 @cindex unwind stack in called functions
15070 @cindex call dummy stack unwinding
15071 Set unwinding of the stack if a signal is received while in a function
15072 that @value{GDBN} called in the program being debugged. If set to on,
15073 @value{GDBN} unwinds the stack it created for the call and restores
15074 the context to what it was before the call. If set to off (the
15075 default), @value{GDBN} stops in the frame where the signal was
15078 @item show unwindonsignal
15079 @kindex show unwindonsignal
15080 Show the current setting of stack unwinding in the functions called by
15083 @item set unwind-on-terminating-exception
15084 @kindex set unwind-on-terminating-exception
15085 @cindex unwind stack in called functions with unhandled exceptions
15086 @cindex call dummy stack unwinding on unhandled exception.
15087 Set unwinding of the stack if a C@t{++} exception is raised, but left
15088 unhandled while in a function that @value{GDBN} called in the program being
15089 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15090 it created for the call and restores the context to what it was before
15091 the call. If set to off, @value{GDBN} the exception is delivered to
15092 the default C@t{++} exception handler and the inferior terminated.
15094 @item show unwind-on-terminating-exception
15095 @kindex show unwind-on-terminating-exception
15096 Show the current setting of stack unwinding in the functions called by
15101 @cindex weak alias functions
15102 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15103 for another function. In such case, @value{GDBN} might not pick up
15104 the type information, including the types of the function arguments,
15105 which causes @value{GDBN} to call the inferior function incorrectly.
15106 As a result, the called function will function erroneously and may
15107 even crash. A solution to that is to use the name of the aliased
15111 @section Patching Programs
15113 @cindex patching binaries
15114 @cindex writing into executables
15115 @cindex writing into corefiles
15117 By default, @value{GDBN} opens the file containing your program's
15118 executable code (or the corefile) read-only. This prevents accidental
15119 alterations to machine code; but it also prevents you from intentionally
15120 patching your program's binary.
15122 If you'd like to be able to patch the binary, you can specify that
15123 explicitly with the @code{set write} command. For example, you might
15124 want to turn on internal debugging flags, or even to make emergency
15130 @itemx set write off
15131 If you specify @samp{set write on}, @value{GDBN} opens executable and
15132 core files for both reading and writing; if you specify @kbd{set write
15133 off} (the default), @value{GDBN} opens them read-only.
15135 If you have already loaded a file, you must load it again (using the
15136 @code{exec-file} or @code{core-file} command) after changing @code{set
15137 write}, for your new setting to take effect.
15141 Display whether executable files and core files are opened for writing
15142 as well as reading.
15146 @chapter @value{GDBN} Files
15148 @value{GDBN} needs to know the file name of the program to be debugged,
15149 both in order to read its symbol table and in order to start your
15150 program. To debug a core dump of a previous run, you must also tell
15151 @value{GDBN} the name of the core dump file.
15154 * Files:: Commands to specify files
15155 * Separate Debug Files:: Debugging information in separate files
15156 * Index Files:: Index files speed up GDB
15157 * Symbol Errors:: Errors reading symbol files
15158 * Data Files:: GDB data files
15162 @section Commands to Specify Files
15164 @cindex symbol table
15165 @cindex core dump file
15167 You may want to specify executable and core dump file names. The usual
15168 way to do this is at start-up time, using the arguments to
15169 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15170 Out of @value{GDBN}}).
15172 Occasionally it is necessary to change to a different file during a
15173 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15174 specify a file you want to use. Or you are debugging a remote target
15175 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15176 Program}). In these situations the @value{GDBN} commands to specify
15177 new files are useful.
15180 @cindex executable file
15182 @item file @var{filename}
15183 Use @var{filename} as the program to be debugged. It is read for its
15184 symbols and for the contents of pure memory. It is also the program
15185 executed when you use the @code{run} command. If you do not specify a
15186 directory and the file is not found in the @value{GDBN} working directory,
15187 @value{GDBN} uses the environment variable @code{PATH} as a list of
15188 directories to search, just as the shell does when looking for a program
15189 to run. You can change the value of this variable, for both @value{GDBN}
15190 and your program, using the @code{path} command.
15192 @cindex unlinked object files
15193 @cindex patching object files
15194 You can load unlinked object @file{.o} files into @value{GDBN} using
15195 the @code{file} command. You will not be able to ``run'' an object
15196 file, but you can disassemble functions and inspect variables. Also,
15197 if the underlying BFD functionality supports it, you could use
15198 @kbd{gdb -write} to patch object files using this technique. Note
15199 that @value{GDBN} can neither interpret nor modify relocations in this
15200 case, so branches and some initialized variables will appear to go to
15201 the wrong place. But this feature is still handy from time to time.
15204 @code{file} with no argument makes @value{GDBN} discard any information it
15205 has on both executable file and the symbol table.
15208 @item exec-file @r{[} @var{filename} @r{]}
15209 Specify that the program to be run (but not the symbol table) is found
15210 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15211 if necessary to locate your program. Omitting @var{filename} means to
15212 discard information on the executable file.
15214 @kindex symbol-file
15215 @item symbol-file @r{[} @var{filename} @r{]}
15216 Read symbol table information from file @var{filename}. @code{PATH} is
15217 searched when necessary. Use the @code{file} command to get both symbol
15218 table and program to run from the same file.
15220 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15221 program's symbol table.
15223 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15224 some breakpoints and auto-display expressions. This is because they may
15225 contain pointers to the internal data recording symbols and data types,
15226 which are part of the old symbol table data being discarded inside
15229 @code{symbol-file} does not repeat if you press @key{RET} again after
15232 When @value{GDBN} is configured for a particular environment, it
15233 understands debugging information in whatever format is the standard
15234 generated for that environment; you may use either a @sc{gnu} compiler, or
15235 other compilers that adhere to the local conventions.
15236 Best results are usually obtained from @sc{gnu} compilers; for example,
15237 using @code{@value{NGCC}} you can generate debugging information for
15240 For most kinds of object files, with the exception of old SVR3 systems
15241 using COFF, the @code{symbol-file} command does not normally read the
15242 symbol table in full right away. Instead, it scans the symbol table
15243 quickly to find which source files and which symbols are present. The
15244 details are read later, one source file at a time, as they are needed.
15246 The purpose of this two-stage reading strategy is to make @value{GDBN}
15247 start up faster. For the most part, it is invisible except for
15248 occasional pauses while the symbol table details for a particular source
15249 file are being read. (The @code{set verbose} command can turn these
15250 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15251 Warnings and Messages}.)
15253 We have not implemented the two-stage strategy for COFF yet. When the
15254 symbol table is stored in COFF format, @code{symbol-file} reads the
15255 symbol table data in full right away. Note that ``stabs-in-COFF''
15256 still does the two-stage strategy, since the debug info is actually
15260 @cindex reading symbols immediately
15261 @cindex symbols, reading immediately
15262 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15263 @itemx file @r{[} -readnow @r{]} @var{filename}
15264 You can override the @value{GDBN} two-stage strategy for reading symbol
15265 tables by using the @samp{-readnow} option with any of the commands that
15266 load symbol table information, if you want to be sure @value{GDBN} has the
15267 entire symbol table available.
15269 @c FIXME: for now no mention of directories, since this seems to be in
15270 @c flux. 13mar1992 status is that in theory GDB would look either in
15271 @c current dir or in same dir as myprog; but issues like competing
15272 @c GDB's, or clutter in system dirs, mean that in practice right now
15273 @c only current dir is used. FFish says maybe a special GDB hierarchy
15274 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15278 @item core-file @r{[}@var{filename}@r{]}
15280 Specify the whereabouts of a core dump file to be used as the ``contents
15281 of memory''. Traditionally, core files contain only some parts of the
15282 address space of the process that generated them; @value{GDBN} can access the
15283 executable file itself for other parts.
15285 @code{core-file} with no argument specifies that no core file is
15288 Note that the core file is ignored when your program is actually running
15289 under @value{GDBN}. So, if you have been running your program and you
15290 wish to debug a core file instead, you must kill the subprocess in which
15291 the program is running. To do this, use the @code{kill} command
15292 (@pxref{Kill Process, ,Killing the Child Process}).
15294 @kindex add-symbol-file
15295 @cindex dynamic linking
15296 @item add-symbol-file @var{filename} @var{address}
15297 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15298 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15299 The @code{add-symbol-file} command reads additional symbol table
15300 information from the file @var{filename}. You would use this command
15301 when @var{filename} has been dynamically loaded (by some other means)
15302 into the program that is running. @var{address} should be the memory
15303 address at which the file has been loaded; @value{GDBN} cannot figure
15304 this out for itself. You can additionally specify an arbitrary number
15305 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15306 section name and base address for that section. You can specify any
15307 @var{address} as an expression.
15309 The symbol table of the file @var{filename} is added to the symbol table
15310 originally read with the @code{symbol-file} command. You can use the
15311 @code{add-symbol-file} command any number of times; the new symbol data
15312 thus read keeps adding to the old. To discard all old symbol data
15313 instead, use the @code{symbol-file} command without any arguments.
15315 @cindex relocatable object files, reading symbols from
15316 @cindex object files, relocatable, reading symbols from
15317 @cindex reading symbols from relocatable object files
15318 @cindex symbols, reading from relocatable object files
15319 @cindex @file{.o} files, reading symbols from
15320 Although @var{filename} is typically a shared library file, an
15321 executable file, or some other object file which has been fully
15322 relocated for loading into a process, you can also load symbolic
15323 information from relocatable @file{.o} files, as long as:
15327 the file's symbolic information refers only to linker symbols defined in
15328 that file, not to symbols defined by other object files,
15330 every section the file's symbolic information refers to has actually
15331 been loaded into the inferior, as it appears in the file, and
15333 you can determine the address at which every section was loaded, and
15334 provide these to the @code{add-symbol-file} command.
15338 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15339 relocatable files into an already running program; such systems
15340 typically make the requirements above easy to meet. However, it's
15341 important to recognize that many native systems use complex link
15342 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15343 assembly, for example) that make the requirements difficult to meet. In
15344 general, one cannot assume that using @code{add-symbol-file} to read a
15345 relocatable object file's symbolic information will have the same effect
15346 as linking the relocatable object file into the program in the normal
15349 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15351 @kindex add-symbol-file-from-memory
15352 @cindex @code{syscall DSO}
15353 @cindex load symbols from memory
15354 @item add-symbol-file-from-memory @var{address}
15355 Load symbols from the given @var{address} in a dynamically loaded
15356 object file whose image is mapped directly into the inferior's memory.
15357 For example, the Linux kernel maps a @code{syscall DSO} into each
15358 process's address space; this DSO provides kernel-specific code for
15359 some system calls. The argument can be any expression whose
15360 evaluation yields the address of the file's shared object file header.
15361 For this command to work, you must have used @code{symbol-file} or
15362 @code{exec-file} commands in advance.
15364 @kindex add-shared-symbol-files
15366 @item add-shared-symbol-files @var{library-file}
15367 @itemx assf @var{library-file}
15368 The @code{add-shared-symbol-files} command can currently be used only
15369 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15370 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15371 @value{GDBN} automatically looks for shared libraries, however if
15372 @value{GDBN} does not find yours, you can invoke
15373 @code{add-shared-symbol-files}. It takes one argument: the shared
15374 library's file name. @code{assf} is a shorthand alias for
15375 @code{add-shared-symbol-files}.
15378 @item section @var{section} @var{addr}
15379 The @code{section} command changes the base address of the named
15380 @var{section} of the exec file to @var{addr}. This can be used if the
15381 exec file does not contain section addresses, (such as in the
15382 @code{a.out} format), or when the addresses specified in the file
15383 itself are wrong. Each section must be changed separately. The
15384 @code{info files} command, described below, lists all the sections and
15388 @kindex info target
15391 @code{info files} and @code{info target} are synonymous; both print the
15392 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15393 including the names of the executable and core dump files currently in
15394 use by @value{GDBN}, and the files from which symbols were loaded. The
15395 command @code{help target} lists all possible targets rather than
15398 @kindex maint info sections
15399 @item maint info sections
15400 Another command that can give you extra information about program sections
15401 is @code{maint info sections}. In addition to the section information
15402 displayed by @code{info files}, this command displays the flags and file
15403 offset of each section in the executable and core dump files. In addition,
15404 @code{maint info sections} provides the following command options (which
15405 may be arbitrarily combined):
15409 Display sections for all loaded object files, including shared libraries.
15410 @item @var{sections}
15411 Display info only for named @var{sections}.
15412 @item @var{section-flags}
15413 Display info only for sections for which @var{section-flags} are true.
15414 The section flags that @value{GDBN} currently knows about are:
15417 Section will have space allocated in the process when loaded.
15418 Set for all sections except those containing debug information.
15420 Section will be loaded from the file into the child process memory.
15421 Set for pre-initialized code and data, clear for @code{.bss} sections.
15423 Section needs to be relocated before loading.
15425 Section cannot be modified by the child process.
15427 Section contains executable code only.
15429 Section contains data only (no executable code).
15431 Section will reside in ROM.
15433 Section contains data for constructor/destructor lists.
15435 Section is not empty.
15437 An instruction to the linker to not output the section.
15438 @item COFF_SHARED_LIBRARY
15439 A notification to the linker that the section contains
15440 COFF shared library information.
15442 Section contains common symbols.
15445 @kindex set trust-readonly-sections
15446 @cindex read-only sections
15447 @item set trust-readonly-sections on
15448 Tell @value{GDBN} that readonly sections in your object file
15449 really are read-only (i.e.@: that their contents will not change).
15450 In that case, @value{GDBN} can fetch values from these sections
15451 out of the object file, rather than from the target program.
15452 For some targets (notably embedded ones), this can be a significant
15453 enhancement to debugging performance.
15455 The default is off.
15457 @item set trust-readonly-sections off
15458 Tell @value{GDBN} not to trust readonly sections. This means that
15459 the contents of the section might change while the program is running,
15460 and must therefore be fetched from the target when needed.
15462 @item show trust-readonly-sections
15463 Show the current setting of trusting readonly sections.
15466 All file-specifying commands allow both absolute and relative file names
15467 as arguments. @value{GDBN} always converts the file name to an absolute file
15468 name and remembers it that way.
15470 @cindex shared libraries
15471 @anchor{Shared Libraries}
15472 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15473 and IBM RS/6000 AIX shared libraries.
15475 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15476 shared libraries. @xref{Expat}.
15478 @value{GDBN} automatically loads symbol definitions from shared libraries
15479 when you use the @code{run} command, or when you examine a core file.
15480 (Before you issue the @code{run} command, @value{GDBN} does not understand
15481 references to a function in a shared library, however---unless you are
15482 debugging a core file).
15484 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15485 automatically loads the symbols at the time of the @code{shl_load} call.
15487 @c FIXME: some @value{GDBN} release may permit some refs to undef
15488 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15489 @c FIXME...lib; check this from time to time when updating manual
15491 There are times, however, when you may wish to not automatically load
15492 symbol definitions from shared libraries, such as when they are
15493 particularly large or there are many of them.
15495 To control the automatic loading of shared library symbols, use the
15499 @kindex set auto-solib-add
15500 @item set auto-solib-add @var{mode}
15501 If @var{mode} is @code{on}, symbols from all shared object libraries
15502 will be loaded automatically when the inferior begins execution, you
15503 attach to an independently started inferior, or when the dynamic linker
15504 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15505 is @code{off}, symbols must be loaded manually, using the
15506 @code{sharedlibrary} command. The default value is @code{on}.
15508 @cindex memory used for symbol tables
15509 If your program uses lots of shared libraries with debug info that
15510 takes large amounts of memory, you can decrease the @value{GDBN}
15511 memory footprint by preventing it from automatically loading the
15512 symbols from shared libraries. To that end, type @kbd{set
15513 auto-solib-add off} before running the inferior, then load each
15514 library whose debug symbols you do need with @kbd{sharedlibrary
15515 @var{regexp}}, where @var{regexp} is a regular expression that matches
15516 the libraries whose symbols you want to be loaded.
15518 @kindex show auto-solib-add
15519 @item show auto-solib-add
15520 Display the current autoloading mode.
15523 @cindex load shared library
15524 To explicitly load shared library symbols, use the @code{sharedlibrary}
15528 @kindex info sharedlibrary
15530 @item info share @var{regex}
15531 @itemx info sharedlibrary @var{regex}
15532 Print the names of the shared libraries which are currently loaded
15533 that match @var{regex}. If @var{regex} is omitted then print
15534 all shared libraries that are loaded.
15536 @kindex sharedlibrary
15538 @item sharedlibrary @var{regex}
15539 @itemx share @var{regex}
15540 Load shared object library symbols for files matching a
15541 Unix regular expression.
15542 As with files loaded automatically, it only loads shared libraries
15543 required by your program for a core file or after typing @code{run}. If
15544 @var{regex} is omitted all shared libraries required by your program are
15547 @item nosharedlibrary
15548 @kindex nosharedlibrary
15549 @cindex unload symbols from shared libraries
15550 Unload all shared object library symbols. This discards all symbols
15551 that have been loaded from all shared libraries. Symbols from shared
15552 libraries that were loaded by explicit user requests are not
15556 Sometimes you may wish that @value{GDBN} stops and gives you control
15557 when any of shared library events happen. Use the @code{set
15558 stop-on-solib-events} command for this:
15561 @item set stop-on-solib-events
15562 @kindex set stop-on-solib-events
15563 This command controls whether @value{GDBN} should give you control
15564 when the dynamic linker notifies it about some shared library event.
15565 The most common event of interest is loading or unloading of a new
15568 @item show stop-on-solib-events
15569 @kindex show stop-on-solib-events
15570 Show whether @value{GDBN} stops and gives you control when shared
15571 library events happen.
15574 Shared libraries are also supported in many cross or remote debugging
15575 configurations. @value{GDBN} needs to have access to the target's libraries;
15576 this can be accomplished either by providing copies of the libraries
15577 on the host system, or by asking @value{GDBN} to automatically retrieve the
15578 libraries from the target. If copies of the target libraries are
15579 provided, they need to be the same as the target libraries, although the
15580 copies on the target can be stripped as long as the copies on the host are
15583 @cindex where to look for shared libraries
15584 For remote debugging, you need to tell @value{GDBN} where the target
15585 libraries are, so that it can load the correct copies---otherwise, it
15586 may try to load the host's libraries. @value{GDBN} has two variables
15587 to specify the search directories for target libraries.
15590 @cindex prefix for shared library file names
15591 @cindex system root, alternate
15592 @kindex set solib-absolute-prefix
15593 @kindex set sysroot
15594 @item set sysroot @var{path}
15595 Use @var{path} as the system root for the program being debugged. Any
15596 absolute shared library paths will be prefixed with @var{path}; many
15597 runtime loaders store the absolute paths to the shared library in the
15598 target program's memory. If you use @code{set sysroot} to find shared
15599 libraries, they need to be laid out in the same way that they are on
15600 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15603 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15604 retrieve the target libraries from the remote system. This is only
15605 supported when using a remote target that supports the @code{remote get}
15606 command (@pxref{File Transfer,,Sending files to a remote system}).
15607 The part of @var{path} following the initial @file{remote:}
15608 (if present) is used as system root prefix on the remote file system.
15609 @footnote{If you want to specify a local system root using a directory
15610 that happens to be named @file{remote:}, you need to use some equivalent
15611 variant of the name like @file{./remote:}.}
15613 For targets with an MS-DOS based filesystem, such as MS-Windows and
15614 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15615 absolute file name with @var{path}. But first, on Unix hosts,
15616 @value{GDBN} converts all backslash directory separators into forward
15617 slashes, because the backslash is not a directory separator on Unix:
15620 c:\foo\bar.dll @result{} c:/foo/bar.dll
15623 Then, @value{GDBN} attempts prefixing the target file name with
15624 @var{path}, and looks for the resulting file name in the host file
15628 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15631 If that does not find the shared library, @value{GDBN} tries removing
15632 the @samp{:} character from the drive spec, both for convenience, and,
15633 for the case of the host file system not supporting file names with
15637 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15640 This makes it possible to have a system root that mirrors a target
15641 with more than one drive. E.g., you may want to setup your local
15642 copies of the target system shared libraries like so (note @samp{c} vs
15646 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15647 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15648 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15652 and point the system root at @file{/path/to/sysroot}, so that
15653 @value{GDBN} can find the correct copies of both
15654 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15656 If that still does not find the shared library, @value{GDBN} tries
15657 removing the whole drive spec from the target file name:
15660 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15663 This last lookup makes it possible to not care about the drive name,
15664 if you don't want or need to.
15666 The @code{set solib-absolute-prefix} command is an alias for @code{set
15669 @cindex default system root
15670 @cindex @samp{--with-sysroot}
15671 You can set the default system root by using the configure-time
15672 @samp{--with-sysroot} option. If the system root is inside
15673 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15674 @samp{--exec-prefix}), then the default system root will be updated
15675 automatically if the installed @value{GDBN} is moved to a new
15678 @kindex show sysroot
15680 Display the current shared library prefix.
15682 @kindex set solib-search-path
15683 @item set solib-search-path @var{path}
15684 If this variable is set, @var{path} is a colon-separated list of
15685 directories to search for shared libraries. @samp{solib-search-path}
15686 is used after @samp{sysroot} fails to locate the library, or if the
15687 path to the library is relative instead of absolute. If you want to
15688 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15689 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15690 finding your host's libraries. @samp{sysroot} is preferred; setting
15691 it to a nonexistent directory may interfere with automatic loading
15692 of shared library symbols.
15694 @kindex show solib-search-path
15695 @item show solib-search-path
15696 Display the current shared library search path.
15698 @cindex DOS file-name semantics of file names.
15699 @kindex set target-file-system-kind (unix|dos-based|auto)
15700 @kindex show target-file-system-kind
15701 @item set target-file-system-kind @var{kind}
15702 Set assumed file system kind for target reported file names.
15704 Shared library file names as reported by the target system may not
15705 make sense as is on the system @value{GDBN} is running on. For
15706 example, when remote debugging a target that has MS-DOS based file
15707 system semantics, from a Unix host, the target may be reporting to
15708 @value{GDBN} a list of loaded shared libraries with file names such as
15709 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15710 drive letters, so the @samp{c:\} prefix is not normally understood as
15711 indicating an absolute file name, and neither is the backslash
15712 normally considered a directory separator character. In that case,
15713 the native file system would interpret this whole absolute file name
15714 as a relative file name with no directory components. This would make
15715 it impossible to point @value{GDBN} at a copy of the remote target's
15716 shared libraries on the host using @code{set sysroot}, and impractical
15717 with @code{set solib-search-path}. Setting
15718 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15719 to interpret such file names similarly to how the target would, and to
15720 map them to file names valid on @value{GDBN}'s native file system
15721 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15722 to one of the supported file system kinds. In that case, @value{GDBN}
15723 tries to determine the appropriate file system variant based on the
15724 current target's operating system (@pxref{ABI, ,Configuring the
15725 Current ABI}). The supported file system settings are:
15729 Instruct @value{GDBN} to assume the target file system is of Unix
15730 kind. Only file names starting the forward slash (@samp{/}) character
15731 are considered absolute, and the directory separator character is also
15735 Instruct @value{GDBN} to assume the target file system is DOS based.
15736 File names starting with either a forward slash, or a drive letter
15737 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15738 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15739 considered directory separators.
15742 Instruct @value{GDBN} to use the file system kind associated with the
15743 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15744 This is the default.
15748 @cindex file name canonicalization
15749 @cindex base name differences
15750 When processing file names provided by the user, @value{GDBN}
15751 frequently needs to compare them to the file names recorded in the
15752 program's debug info. Normally, @value{GDBN} compares just the
15753 @dfn{base names} of the files as strings, which is reasonably fast
15754 even for very large programs. (The base name of a file is the last
15755 portion of its name, after stripping all the leading directories.)
15756 This shortcut in comparison is based upon the assumption that files
15757 cannot have more than one base name. This is usually true, but
15758 references to files that use symlinks or similar filesystem
15759 facilities violate that assumption. If your program records files
15760 using such facilities, or if you provide file names to @value{GDBN}
15761 using symlinks etc., you can set @code{basenames-may-differ} to
15762 @code{true} to instruct @value{GDBN} to completely canonicalize each
15763 pair of file names it needs to compare. This will make file-name
15764 comparisons accurate, but at a price of a significant slowdown.
15767 @item set basenames-may-differ
15768 @kindex set basenames-may-differ
15769 Set whether a source file may have multiple base names.
15771 @item show basenames-may-differ
15772 @kindex show basenames-may-differ
15773 Show whether a source file may have multiple base names.
15776 @node Separate Debug Files
15777 @section Debugging Information in Separate Files
15778 @cindex separate debugging information files
15779 @cindex debugging information in separate files
15780 @cindex @file{.debug} subdirectories
15781 @cindex debugging information directory, global
15782 @cindex global debugging information directory
15783 @cindex build ID, and separate debugging files
15784 @cindex @file{.build-id} directory
15786 @value{GDBN} allows you to put a program's debugging information in a
15787 file separate from the executable itself, in a way that allows
15788 @value{GDBN} to find and load the debugging information automatically.
15789 Since debugging information can be very large---sometimes larger
15790 than the executable code itself---some systems distribute debugging
15791 information for their executables in separate files, which users can
15792 install only when they need to debug a problem.
15794 @value{GDBN} supports two ways of specifying the separate debug info
15799 The executable contains a @dfn{debug link} that specifies the name of
15800 the separate debug info file. The separate debug file's name is
15801 usually @file{@var{executable}.debug}, where @var{executable} is the
15802 name of the corresponding executable file without leading directories
15803 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15804 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15805 checksum for the debug file, which @value{GDBN} uses to validate that
15806 the executable and the debug file came from the same build.
15809 The executable contains a @dfn{build ID}, a unique bit string that is
15810 also present in the corresponding debug info file. (This is supported
15811 only on some operating systems, notably those which use the ELF format
15812 for binary files and the @sc{gnu} Binutils.) For more details about
15813 this feature, see the description of the @option{--build-id}
15814 command-line option in @ref{Options, , Command Line Options, ld.info,
15815 The GNU Linker}. The debug info file's name is not specified
15816 explicitly by the build ID, but can be computed from the build ID, see
15820 Depending on the way the debug info file is specified, @value{GDBN}
15821 uses two different methods of looking for the debug file:
15825 For the ``debug link'' method, @value{GDBN} looks up the named file in
15826 the directory of the executable file, then in a subdirectory of that
15827 directory named @file{.debug}, and finally under the global debug
15828 directory, in a subdirectory whose name is identical to the leading
15829 directories of the executable's absolute file name.
15832 For the ``build ID'' method, @value{GDBN} looks in the
15833 @file{.build-id} subdirectory of the global debug directory for a file
15834 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15835 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15836 are the rest of the bit string. (Real build ID strings are 32 or more
15837 hex characters, not 10.)
15840 So, for example, suppose you ask @value{GDBN} to debug
15841 @file{/usr/bin/ls}, which has a debug link that specifies the
15842 file @file{ls.debug}, and a build ID whose value in hex is
15843 @code{abcdef1234}. If the global debug directory is
15844 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15845 debug information files, in the indicated order:
15849 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15851 @file{/usr/bin/ls.debug}
15853 @file{/usr/bin/.debug/ls.debug}
15855 @file{/usr/lib/debug/usr/bin/ls.debug}.
15858 You can set the global debugging info directory's name, and view the
15859 name @value{GDBN} is currently using.
15863 @kindex set debug-file-directory
15864 @item set debug-file-directory @var{directories}
15865 Set the directories which @value{GDBN} searches for separate debugging
15866 information files to @var{directory}. Multiple directory components can be set
15867 concatenating them by a directory separator.
15869 @kindex show debug-file-directory
15870 @item show debug-file-directory
15871 Show the directories @value{GDBN} searches for separate debugging
15876 @cindex @code{.gnu_debuglink} sections
15877 @cindex debug link sections
15878 A debug link is a special section of the executable file named
15879 @code{.gnu_debuglink}. The section must contain:
15883 A filename, with any leading directory components removed, followed by
15886 zero to three bytes of padding, as needed to reach the next four-byte
15887 boundary within the section, and
15889 a four-byte CRC checksum, stored in the same endianness used for the
15890 executable file itself. The checksum is computed on the debugging
15891 information file's full contents by the function given below, passing
15892 zero as the @var{crc} argument.
15895 Any executable file format can carry a debug link, as long as it can
15896 contain a section named @code{.gnu_debuglink} with the contents
15899 @cindex @code{.note.gnu.build-id} sections
15900 @cindex build ID sections
15901 The build ID is a special section in the executable file (and in other
15902 ELF binary files that @value{GDBN} may consider). This section is
15903 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15904 It contains unique identification for the built files---the ID remains
15905 the same across multiple builds of the same build tree. The default
15906 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15907 content for the build ID string. The same section with an identical
15908 value is present in the original built binary with symbols, in its
15909 stripped variant, and in the separate debugging information file.
15911 The debugging information file itself should be an ordinary
15912 executable, containing a full set of linker symbols, sections, and
15913 debugging information. The sections of the debugging information file
15914 should have the same names, addresses, and sizes as the original file,
15915 but they need not contain any data---much like a @code{.bss} section
15916 in an ordinary executable.
15918 The @sc{gnu} binary utilities (Binutils) package includes the
15919 @samp{objcopy} utility that can produce
15920 the separated executable / debugging information file pairs using the
15921 following commands:
15924 @kbd{objcopy --only-keep-debug foo foo.debug}
15929 These commands remove the debugging
15930 information from the executable file @file{foo} and place it in the file
15931 @file{foo.debug}. You can use the first, second or both methods to link the
15936 The debug link method needs the following additional command to also leave
15937 behind a debug link in @file{foo}:
15940 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15943 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15944 a version of the @code{strip} command such that the command @kbd{strip foo -f
15945 foo.debug} has the same functionality as the two @code{objcopy} commands and
15946 the @code{ln -s} command above, together.
15949 Build ID gets embedded into the main executable using @code{ld --build-id} or
15950 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15951 compatibility fixes for debug files separation are present in @sc{gnu} binary
15952 utilities (Binutils) package since version 2.18.
15957 @cindex CRC algorithm definition
15958 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15959 IEEE 802.3 using the polynomial:
15961 @c TexInfo requires naked braces for multi-digit exponents for Tex
15962 @c output, but this causes HTML output to barf. HTML has to be set using
15963 @c raw commands. So we end up having to specify this equation in 2
15968 <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>
15969 + <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
15975 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15976 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15980 The function is computed byte at a time, taking the least
15981 significant bit of each byte first. The initial pattern
15982 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15983 the final result is inverted to ensure trailing zeros also affect the
15986 @emph{Note:} This is the same CRC polynomial as used in handling the
15987 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15988 , @value{GDBN} Remote Serial Protocol}). However in the
15989 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15990 significant bit first, and the result is not inverted, so trailing
15991 zeros have no effect on the CRC value.
15993 To complete the description, we show below the code of the function
15994 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15995 initially supplied @code{crc} argument means that an initial call to
15996 this function passing in zero will start computing the CRC using
15999 @kindex gnu_debuglink_crc32
16002 gnu_debuglink_crc32 (unsigned long crc,
16003 unsigned char *buf, size_t len)
16005 static const unsigned long crc32_table[256] =
16007 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16008 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16009 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16010 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16011 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16012 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16013 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16014 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16015 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16016 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16017 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16018 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16019 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16020 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16021 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16022 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16023 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16024 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16025 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16026 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16027 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16028 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16029 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16030 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16031 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16032 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16033 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16034 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16035 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16036 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16037 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16038 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16039 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16040 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16041 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16042 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16043 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16044 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16045 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16046 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16047 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16048 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16049 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16050 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16051 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16052 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16053 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16054 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16055 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16056 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16057 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16060 unsigned char *end;
16062 crc = ~crc & 0xffffffff;
16063 for (end = buf + len; buf < end; ++buf)
16064 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16065 return ~crc & 0xffffffff;
16070 This computation does not apply to the ``build ID'' method.
16074 @section Index Files Speed Up @value{GDBN}
16075 @cindex index files
16076 @cindex @samp{.gdb_index} section
16078 When @value{GDBN} finds a symbol file, it scans the symbols in the
16079 file in order to construct an internal symbol table. This lets most
16080 @value{GDBN} operations work quickly---at the cost of a delay early
16081 on. For large programs, this delay can be quite lengthy, so
16082 @value{GDBN} provides a way to build an index, which speeds up
16085 The index is stored as a section in the symbol file. @value{GDBN} can
16086 write the index to a file, then you can put it into the symbol file
16087 using @command{objcopy}.
16089 To create an index file, use the @code{save gdb-index} command:
16092 @item save gdb-index @var{directory}
16093 @kindex save gdb-index
16094 Create an index file for each symbol file currently known by
16095 @value{GDBN}. Each file is named after its corresponding symbol file,
16096 with @samp{.gdb-index} appended, and is written into the given
16100 Once you have created an index file you can merge it into your symbol
16101 file, here named @file{symfile}, using @command{objcopy}:
16104 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16105 --set-section-flags .gdb_index=readonly symfile symfile
16108 There are currently some limitation on indices. They only work when
16109 for DWARF debugging information, not stabs. And, they do not
16110 currently work for programs using Ada.
16112 @node Symbol Errors
16113 @section Errors Reading Symbol Files
16115 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16116 such as symbol types it does not recognize, or known bugs in compiler
16117 output. By default, @value{GDBN} does not notify you of such problems, since
16118 they are relatively common and primarily of interest to people
16119 debugging compilers. If you are interested in seeing information
16120 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16121 only one message about each such type of problem, no matter how many
16122 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16123 to see how many times the problems occur, with the @code{set
16124 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16127 The messages currently printed, and their meanings, include:
16130 @item inner block not inside outer block in @var{symbol}
16132 The symbol information shows where symbol scopes begin and end
16133 (such as at the start of a function or a block of statements). This
16134 error indicates that an inner scope block is not fully contained
16135 in its outer scope blocks.
16137 @value{GDBN} circumvents the problem by treating the inner block as if it had
16138 the same scope as the outer block. In the error message, @var{symbol}
16139 may be shown as ``@code{(don't know)}'' if the outer block is not a
16142 @item block at @var{address} out of order
16144 The symbol information for symbol scope blocks should occur in
16145 order of increasing addresses. This error indicates that it does not
16148 @value{GDBN} does not circumvent this problem, and has trouble
16149 locating symbols in the source file whose symbols it is reading. (You
16150 can often determine what source file is affected by specifying
16151 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16154 @item bad block start address patched
16156 The symbol information for a symbol scope block has a start address
16157 smaller than the address of the preceding source line. This is known
16158 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16160 @value{GDBN} circumvents the problem by treating the symbol scope block as
16161 starting on the previous source line.
16163 @item bad string table offset in symbol @var{n}
16166 Symbol number @var{n} contains a pointer into the string table which is
16167 larger than the size of the string table.
16169 @value{GDBN} circumvents the problem by considering the symbol to have the
16170 name @code{foo}, which may cause other problems if many symbols end up
16173 @item unknown symbol type @code{0x@var{nn}}
16175 The symbol information contains new data types that @value{GDBN} does
16176 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16177 uncomprehended information, in hexadecimal.
16179 @value{GDBN} circumvents the error by ignoring this symbol information.
16180 This usually allows you to debug your program, though certain symbols
16181 are not accessible. If you encounter such a problem and feel like
16182 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16183 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16184 and examine @code{*bufp} to see the symbol.
16186 @item stub type has NULL name
16188 @value{GDBN} could not find the full definition for a struct or class.
16190 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16191 The symbol information for a C@t{++} member function is missing some
16192 information that recent versions of the compiler should have output for
16195 @item info mismatch between compiler and debugger
16197 @value{GDBN} could not parse a type specification output by the compiler.
16202 @section GDB Data Files
16204 @cindex prefix for data files
16205 @value{GDBN} will sometimes read an auxiliary data file. These files
16206 are kept in a directory known as the @dfn{data directory}.
16208 You can set the data directory's name, and view the name @value{GDBN}
16209 is currently using.
16212 @kindex set data-directory
16213 @item set data-directory @var{directory}
16214 Set the directory which @value{GDBN} searches for auxiliary data files
16215 to @var{directory}.
16217 @kindex show data-directory
16218 @item show data-directory
16219 Show the directory @value{GDBN} searches for auxiliary data files.
16222 @cindex default data directory
16223 @cindex @samp{--with-gdb-datadir}
16224 You can set the default data directory by using the configure-time
16225 @samp{--with-gdb-datadir} option. If the data directory is inside
16226 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16227 @samp{--exec-prefix}), then the default data directory will be updated
16228 automatically if the installed @value{GDBN} is moved to a new
16231 The data directory may also be specified with the
16232 @code{--data-directory} command line option.
16233 @xref{Mode Options}.
16236 @chapter Specifying a Debugging Target
16238 @cindex debugging target
16239 A @dfn{target} is the execution environment occupied by your program.
16241 Often, @value{GDBN} runs in the same host environment as your program;
16242 in that case, the debugging target is specified as a side effect when
16243 you use the @code{file} or @code{core} commands. When you need more
16244 flexibility---for example, running @value{GDBN} on a physically separate
16245 host, or controlling a standalone system over a serial port or a
16246 realtime system over a TCP/IP connection---you can use the @code{target}
16247 command to specify one of the target types configured for @value{GDBN}
16248 (@pxref{Target Commands, ,Commands for Managing Targets}).
16250 @cindex target architecture
16251 It is possible to build @value{GDBN} for several different @dfn{target
16252 architectures}. When @value{GDBN} is built like that, you can choose
16253 one of the available architectures with the @kbd{set architecture}
16257 @kindex set architecture
16258 @kindex show architecture
16259 @item set architecture @var{arch}
16260 This command sets the current target architecture to @var{arch}. The
16261 value of @var{arch} can be @code{"auto"}, in addition to one of the
16262 supported architectures.
16264 @item show architecture
16265 Show the current target architecture.
16267 @item set processor
16269 @kindex set processor
16270 @kindex show processor
16271 These are alias commands for, respectively, @code{set architecture}
16272 and @code{show architecture}.
16276 * Active Targets:: Active targets
16277 * Target Commands:: Commands for managing targets
16278 * Byte Order:: Choosing target byte order
16281 @node Active Targets
16282 @section Active Targets
16284 @cindex stacking targets
16285 @cindex active targets
16286 @cindex multiple targets
16288 There are multiple classes of targets such as: processes, executable files or
16289 recording sessions. Core files belong to the process class, making core file
16290 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16291 on multiple active targets, one in each class. This allows you to (for
16292 example) start a process and inspect its activity, while still having access to
16293 the executable file after the process finishes. Or if you start process
16294 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16295 presented a virtual layer of the recording target, while the process target
16296 remains stopped at the chronologically last point of the process execution.
16298 Use the @code{core-file} and @code{exec-file} commands to select a new core
16299 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16300 specify as a target a process that is already running, use the @code{attach}
16301 command (@pxref{Attach, ,Debugging an Already-running Process}).
16303 @node Target Commands
16304 @section Commands for Managing Targets
16307 @item target @var{type} @var{parameters}
16308 Connects the @value{GDBN} host environment to a target machine or
16309 process. A target is typically a protocol for talking to debugging
16310 facilities. You use the argument @var{type} to specify the type or
16311 protocol of the target machine.
16313 Further @var{parameters} are interpreted by the target protocol, but
16314 typically include things like device names or host names to connect
16315 with, process numbers, and baud rates.
16317 The @code{target} command does not repeat if you press @key{RET} again
16318 after executing the command.
16320 @kindex help target
16322 Displays the names of all targets available. To display targets
16323 currently selected, use either @code{info target} or @code{info files}
16324 (@pxref{Files, ,Commands to Specify Files}).
16326 @item help target @var{name}
16327 Describe a particular target, including any parameters necessary to
16330 @kindex set gnutarget
16331 @item set gnutarget @var{args}
16332 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16333 knows whether it is reading an @dfn{executable},
16334 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16335 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16336 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16339 @emph{Warning:} To specify a file format with @code{set gnutarget},
16340 you must know the actual BFD name.
16344 @xref{Files, , Commands to Specify Files}.
16346 @kindex show gnutarget
16347 @item show gnutarget
16348 Use the @code{show gnutarget} command to display what file format
16349 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16350 @value{GDBN} will determine the file format for each file automatically,
16351 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16354 @cindex common targets
16355 Here are some common targets (available, or not, depending on the GDB
16360 @item target exec @var{program}
16361 @cindex executable file target
16362 An executable file. @samp{target exec @var{program}} is the same as
16363 @samp{exec-file @var{program}}.
16365 @item target core @var{filename}
16366 @cindex core dump file target
16367 A core dump file. @samp{target core @var{filename}} is the same as
16368 @samp{core-file @var{filename}}.
16370 @item target remote @var{medium}
16371 @cindex remote target
16372 A remote system connected to @value{GDBN} via a serial line or network
16373 connection. This command tells @value{GDBN} to use its own remote
16374 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16376 For example, if you have a board connected to @file{/dev/ttya} on the
16377 machine running @value{GDBN}, you could say:
16380 target remote /dev/ttya
16383 @code{target remote} supports the @code{load} command. This is only
16384 useful if you have some other way of getting the stub to the target
16385 system, and you can put it somewhere in memory where it won't get
16386 clobbered by the download.
16388 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16389 @cindex built-in simulator target
16390 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16398 works; however, you cannot assume that a specific memory map, device
16399 drivers, or even basic I/O is available, although some simulators do
16400 provide these. For info about any processor-specific simulator details,
16401 see the appropriate section in @ref{Embedded Processors, ,Embedded
16406 Some configurations may include these targets as well:
16410 @item target nrom @var{dev}
16411 @cindex NetROM ROM emulator target
16412 NetROM ROM emulator. This target only supports downloading.
16416 Different targets are available on different configurations of @value{GDBN};
16417 your configuration may have more or fewer targets.
16419 Many remote targets require you to download the executable's code once
16420 you've successfully established a connection. You may wish to control
16421 various aspects of this process.
16426 @kindex set hash@r{, for remote monitors}
16427 @cindex hash mark while downloading
16428 This command controls whether a hash mark @samp{#} is displayed while
16429 downloading a file to the remote monitor. If on, a hash mark is
16430 displayed after each S-record is successfully downloaded to the
16434 @kindex show hash@r{, for remote monitors}
16435 Show the current status of displaying the hash mark.
16437 @item set debug monitor
16438 @kindex set debug monitor
16439 @cindex display remote monitor communications
16440 Enable or disable display of communications messages between
16441 @value{GDBN} and the remote monitor.
16443 @item show debug monitor
16444 @kindex show debug monitor
16445 Show the current status of displaying communications between
16446 @value{GDBN} and the remote monitor.
16451 @kindex load @var{filename}
16452 @item load @var{filename}
16454 Depending on what remote debugging facilities are configured into
16455 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16456 is meant to make @var{filename} (an executable) available for debugging
16457 on the remote system---by downloading, or dynamic linking, for example.
16458 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16459 the @code{add-symbol-file} command.
16461 If your @value{GDBN} does not have a @code{load} command, attempting to
16462 execute it gets the error message ``@code{You can't do that when your
16463 target is @dots{}}''
16465 The file is loaded at whatever address is specified in the executable.
16466 For some object file formats, you can specify the load address when you
16467 link the program; for other formats, like a.out, the object file format
16468 specifies a fixed address.
16469 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16471 Depending on the remote side capabilities, @value{GDBN} may be able to
16472 load programs into flash memory.
16474 @code{load} does not repeat if you press @key{RET} again after using it.
16478 @section Choosing Target Byte Order
16480 @cindex choosing target byte order
16481 @cindex target byte order
16483 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16484 offer the ability to run either big-endian or little-endian byte
16485 orders. Usually the executable or symbol will include a bit to
16486 designate the endian-ness, and you will not need to worry about
16487 which to use. However, you may still find it useful to adjust
16488 @value{GDBN}'s idea of processor endian-ness manually.
16492 @item set endian big
16493 Instruct @value{GDBN} to assume the target is big-endian.
16495 @item set endian little
16496 Instruct @value{GDBN} to assume the target is little-endian.
16498 @item set endian auto
16499 Instruct @value{GDBN} to use the byte order associated with the
16503 Display @value{GDBN}'s current idea of the target byte order.
16507 Note that these commands merely adjust interpretation of symbolic
16508 data on the host, and that they have absolutely no effect on the
16512 @node Remote Debugging
16513 @chapter Debugging Remote Programs
16514 @cindex remote debugging
16516 If you are trying to debug a program running on a machine that cannot run
16517 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16518 For example, you might use remote debugging on an operating system kernel,
16519 or on a small system which does not have a general purpose operating system
16520 powerful enough to run a full-featured debugger.
16522 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16523 to make this work with particular debugging targets. In addition,
16524 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16525 but not specific to any particular target system) which you can use if you
16526 write the remote stubs---the code that runs on the remote system to
16527 communicate with @value{GDBN}.
16529 Other remote targets may be available in your
16530 configuration of @value{GDBN}; use @code{help target} to list them.
16533 * Connecting:: Connecting to a remote target
16534 * File Transfer:: Sending files to a remote system
16535 * Server:: Using the gdbserver program
16536 * Remote Configuration:: Remote configuration
16537 * Remote Stub:: Implementing a remote stub
16541 @section Connecting to a Remote Target
16543 On the @value{GDBN} host machine, you will need an unstripped copy of
16544 your program, since @value{GDBN} needs symbol and debugging information.
16545 Start up @value{GDBN} as usual, using the name of the local copy of your
16546 program as the first argument.
16548 @cindex @code{target remote}
16549 @value{GDBN} can communicate with the target over a serial line, or
16550 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16551 each case, @value{GDBN} uses the same protocol for debugging your
16552 program; only the medium carrying the debugging packets varies. The
16553 @code{target remote} command establishes a connection to the target.
16554 Its arguments indicate which medium to use:
16558 @item target remote @var{serial-device}
16559 @cindex serial line, @code{target remote}
16560 Use @var{serial-device} to communicate with the target. For example,
16561 to use a serial line connected to the device named @file{/dev/ttyb}:
16564 target remote /dev/ttyb
16567 If you're using a serial line, you may want to give @value{GDBN} the
16568 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16569 (@pxref{Remote Configuration, set remotebaud}) before the
16570 @code{target} command.
16572 @item target remote @code{@var{host}:@var{port}}
16573 @itemx target remote @code{tcp:@var{host}:@var{port}}
16574 @cindex @acronym{TCP} port, @code{target remote}
16575 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16576 The @var{host} may be either a host name or a numeric @acronym{IP}
16577 address; @var{port} must be a decimal number. The @var{host} could be
16578 the target machine itself, if it is directly connected to the net, or
16579 it might be a terminal server which in turn has a serial line to the
16582 For example, to connect to port 2828 on a terminal server named
16586 target remote manyfarms:2828
16589 If your remote target is actually running on the same machine as your
16590 debugger session (e.g.@: a simulator for your target running on the
16591 same host), you can omit the hostname. For example, to connect to
16592 port 1234 on your local machine:
16595 target remote :1234
16599 Note that the colon is still required here.
16601 @item target remote @code{udp:@var{host}:@var{port}}
16602 @cindex @acronym{UDP} port, @code{target remote}
16603 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16604 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16607 target remote udp:manyfarms:2828
16610 When using a @acronym{UDP} connection for remote debugging, you should
16611 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16612 can silently drop packets on busy or unreliable networks, which will
16613 cause havoc with your debugging session.
16615 @item target remote | @var{command}
16616 @cindex pipe, @code{target remote} to
16617 Run @var{command} in the background and communicate with it using a
16618 pipe. The @var{command} is a shell command, to be parsed and expanded
16619 by the system's command shell, @code{/bin/sh}; it should expect remote
16620 protocol packets on its standard input, and send replies on its
16621 standard output. You could use this to run a stand-alone simulator
16622 that speaks the remote debugging protocol, to make net connections
16623 using programs like @code{ssh}, or for other similar tricks.
16625 If @var{command} closes its standard output (perhaps by exiting),
16626 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16627 program has already exited, this will have no effect.)
16631 Once the connection has been established, you can use all the usual
16632 commands to examine and change data. The remote program is already
16633 running; you can use @kbd{step} and @kbd{continue}, and you do not
16634 need to use @kbd{run}.
16636 @cindex interrupting remote programs
16637 @cindex remote programs, interrupting
16638 Whenever @value{GDBN} is waiting for the remote program, if you type the
16639 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16640 program. This may or may not succeed, depending in part on the hardware
16641 and the serial drivers the remote system uses. If you type the
16642 interrupt character once again, @value{GDBN} displays this prompt:
16645 Interrupted while waiting for the program.
16646 Give up (and stop debugging it)? (y or n)
16649 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16650 (If you decide you want to try again later, you can use @samp{target
16651 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16652 goes back to waiting.
16655 @kindex detach (remote)
16657 When you have finished debugging the remote program, you can use the
16658 @code{detach} command to release it from @value{GDBN} control.
16659 Detaching from the target normally resumes its execution, but the results
16660 will depend on your particular remote stub. After the @code{detach}
16661 command, @value{GDBN} is free to connect to another target.
16665 The @code{disconnect} command behaves like @code{detach}, except that
16666 the target is generally not resumed. It will wait for @value{GDBN}
16667 (this instance or another one) to connect and continue debugging. After
16668 the @code{disconnect} command, @value{GDBN} is again free to connect to
16671 @cindex send command to remote monitor
16672 @cindex extend @value{GDBN} for remote targets
16673 @cindex add new commands for external monitor
16675 @item monitor @var{cmd}
16676 This command allows you to send arbitrary commands directly to the
16677 remote monitor. Since @value{GDBN} doesn't care about the commands it
16678 sends like this, this command is the way to extend @value{GDBN}---you
16679 can add new commands that only the external monitor will understand
16683 @node File Transfer
16684 @section Sending files to a remote system
16685 @cindex remote target, file transfer
16686 @cindex file transfer
16687 @cindex sending files to remote systems
16689 Some remote targets offer the ability to transfer files over the same
16690 connection used to communicate with @value{GDBN}. This is convenient
16691 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16692 running @code{gdbserver} over a network interface. For other targets,
16693 e.g.@: embedded devices with only a single serial port, this may be
16694 the only way to upload or download files.
16696 Not all remote targets support these commands.
16700 @item remote put @var{hostfile} @var{targetfile}
16701 Copy file @var{hostfile} from the host system (the machine running
16702 @value{GDBN}) to @var{targetfile} on the target system.
16705 @item remote get @var{targetfile} @var{hostfile}
16706 Copy file @var{targetfile} from the target system to @var{hostfile}
16707 on the host system.
16709 @kindex remote delete
16710 @item remote delete @var{targetfile}
16711 Delete @var{targetfile} from the target system.
16716 @section Using the @code{gdbserver} Program
16719 @cindex remote connection without stubs
16720 @code{gdbserver} is a control program for Unix-like systems, which
16721 allows you to connect your program with a remote @value{GDBN} via
16722 @code{target remote}---but without linking in the usual debugging stub.
16724 @code{gdbserver} is not a complete replacement for the debugging stubs,
16725 because it requires essentially the same operating-system facilities
16726 that @value{GDBN} itself does. In fact, a system that can run
16727 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16728 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16729 because it is a much smaller program than @value{GDBN} itself. It is
16730 also easier to port than all of @value{GDBN}, so you may be able to get
16731 started more quickly on a new system by using @code{gdbserver}.
16732 Finally, if you develop code for real-time systems, you may find that
16733 the tradeoffs involved in real-time operation make it more convenient to
16734 do as much development work as possible on another system, for example
16735 by cross-compiling. You can use @code{gdbserver} to make a similar
16736 choice for debugging.
16738 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16739 or a TCP connection, using the standard @value{GDBN} remote serial
16743 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16744 Do not run @code{gdbserver} connected to any public network; a
16745 @value{GDBN} connection to @code{gdbserver} provides access to the
16746 target system with the same privileges as the user running
16750 @subsection Running @code{gdbserver}
16751 @cindex arguments, to @code{gdbserver}
16752 @cindex @code{gdbserver}, command-line arguments
16754 Run @code{gdbserver} on the target system. You need a copy of the
16755 program you want to debug, including any libraries it requires.
16756 @code{gdbserver} does not need your program's symbol table, so you can
16757 strip the program if necessary to save space. @value{GDBN} on the host
16758 system does all the symbol handling.
16760 To use the server, you must tell it how to communicate with @value{GDBN};
16761 the name of your program; and the arguments for your program. The usual
16765 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16768 @var{comm} is either a device name (to use a serial line), or a TCP
16769 hostname and portnumber, or @code{-} or @code{stdio} to use
16770 stdin/stdout of @code{gdbserver}.
16771 For example, to debug Emacs with the argument
16772 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16776 target> gdbserver /dev/com1 emacs foo.txt
16779 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16782 To use a TCP connection instead of a serial line:
16785 target> gdbserver host:2345 emacs foo.txt
16788 The only difference from the previous example is the first argument,
16789 specifying that you are communicating with the host @value{GDBN} via
16790 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16791 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16792 (Currently, the @samp{host} part is ignored.) You can choose any number
16793 you want for the port number as long as it does not conflict with any
16794 TCP ports already in use on the target system (for example, @code{23} is
16795 reserved for @code{telnet}).@footnote{If you choose a port number that
16796 conflicts with another service, @code{gdbserver} prints an error message
16797 and exits.} You must use the same port number with the host @value{GDBN}
16798 @code{target remote} command.
16800 The @code{stdio} connection is useful when starting @code{gdbserver}
16804 (gdb) target remote | ssh -T hostname gdbserver - hello
16807 The @samp{-T} option to ssh is provided because we don't need a remote pty,
16808 and we don't want escape-character handling. Ssh does this by default when
16809 a command is provided, the flag is provided to make it explicit.
16810 You could elide it if you want to.
16812 Programs started with stdio-connected gdbserver have @file{/dev/null} for
16813 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
16814 display through a pipe connected to gdbserver.
16815 Both @code{stdout} and @code{stderr} use the same pipe.
16817 @subsubsection Attaching to a Running Program
16818 @cindex attach to a program, @code{gdbserver}
16819 @cindex @option{--attach}, @code{gdbserver} option
16821 On some targets, @code{gdbserver} can also attach to running programs.
16822 This is accomplished via the @code{--attach} argument. The syntax is:
16825 target> gdbserver --attach @var{comm} @var{pid}
16828 @var{pid} is the process ID of a currently running process. It isn't necessary
16829 to point @code{gdbserver} at a binary for the running process.
16832 You can debug processes by name instead of process ID if your target has the
16833 @code{pidof} utility:
16836 target> gdbserver --attach @var{comm} `pidof @var{program}`
16839 In case more than one copy of @var{program} is running, or @var{program}
16840 has multiple threads, most versions of @code{pidof} support the
16841 @code{-s} option to only return the first process ID.
16843 @subsubsection Multi-Process Mode for @code{gdbserver}
16844 @cindex @code{gdbserver}, multiple processes
16845 @cindex multiple processes with @code{gdbserver}
16847 When you connect to @code{gdbserver} using @code{target remote},
16848 @code{gdbserver} debugs the specified program only once. When the
16849 program exits, or you detach from it, @value{GDBN} closes the connection
16850 and @code{gdbserver} exits.
16852 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16853 enters multi-process mode. When the debugged program exits, or you
16854 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16855 though no program is running. The @code{run} and @code{attach}
16856 commands instruct @code{gdbserver} to run or attach to a new program.
16857 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16858 remote exec-file}) to select the program to run. Command line
16859 arguments are supported, except for wildcard expansion and I/O
16860 redirection (@pxref{Arguments}).
16862 @cindex @option{--multi}, @code{gdbserver} option
16863 To start @code{gdbserver} without supplying an initial command to run
16864 or process ID to attach, use the @option{--multi} command line option.
16865 Then you can connect using @kbd{target extended-remote} and start
16866 the program you want to debug.
16868 In multi-process mode @code{gdbserver} does not automatically exit unless you
16869 use the option @option{--once}. You can terminate it by using
16870 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16871 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16872 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16873 @option{--multi} option to @code{gdbserver} has no influence on that.
16875 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16877 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16879 @code{gdbserver} normally terminates after all of its debugged processes have
16880 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16881 extended-remote}, @code{gdbserver} stays running even with no processes left.
16882 @value{GDBN} normally terminates the spawned debugged process on its exit,
16883 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16884 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16885 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16886 stays running even in the @kbd{target remote} mode.
16888 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16889 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16890 completeness, at most one @value{GDBN} can be connected at a time.
16892 @cindex @option{--once}, @code{gdbserver} option
16893 By default, @code{gdbserver} keeps the listening TCP port open, so that
16894 additional connections are possible. However, if you start @code{gdbserver}
16895 with the @option{--once} option, it will stop listening for any further
16896 connection attempts after connecting to the first @value{GDBN} session. This
16897 means no further connections to @code{gdbserver} will be possible after the
16898 first one. It also means @code{gdbserver} will terminate after the first
16899 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16900 connections and even in the @kbd{target extended-remote} mode. The
16901 @option{--once} option allows reusing the same port number for connecting to
16902 multiple instances of @code{gdbserver} running on the same host, since each
16903 instance closes its port after the first connection.
16905 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16907 @cindex @option{--debug}, @code{gdbserver} option
16908 The @option{--debug} option tells @code{gdbserver} to display extra
16909 status information about the debugging process.
16910 @cindex @option{--remote-debug}, @code{gdbserver} option
16911 The @option{--remote-debug} option tells @code{gdbserver} to display
16912 remote protocol debug output. These options are intended for
16913 @code{gdbserver} development and for bug reports to the developers.
16915 @cindex @option{--wrapper}, @code{gdbserver} option
16916 The @option{--wrapper} option specifies a wrapper to launch programs
16917 for debugging. The option should be followed by the name of the
16918 wrapper, then any command-line arguments to pass to the wrapper, then
16919 @kbd{--} indicating the end of the wrapper arguments.
16921 @code{gdbserver} runs the specified wrapper program with a combined
16922 command line including the wrapper arguments, then the name of the
16923 program to debug, then any arguments to the program. The wrapper
16924 runs until it executes your program, and then @value{GDBN} gains control.
16926 You can use any program that eventually calls @code{execve} with
16927 its arguments as a wrapper. Several standard Unix utilities do
16928 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16929 with @code{exec "$@@"} will also work.
16931 For example, you can use @code{env} to pass an environment variable to
16932 the debugged program, without setting the variable in @code{gdbserver}'s
16936 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16939 @subsection Connecting to @code{gdbserver}
16941 Run @value{GDBN} on the host system.
16943 First make sure you have the necessary symbol files. Load symbols for
16944 your application using the @code{file} command before you connect. Use
16945 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16946 was compiled with the correct sysroot using @code{--with-sysroot}).
16948 The symbol file and target libraries must exactly match the executable
16949 and libraries on the target, with one exception: the files on the host
16950 system should not be stripped, even if the files on the target system
16951 are. Mismatched or missing files will lead to confusing results
16952 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16953 files may also prevent @code{gdbserver} from debugging multi-threaded
16956 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16957 For TCP connections, you must start up @code{gdbserver} prior to using
16958 the @code{target remote} command. Otherwise you may get an error whose
16959 text depends on the host system, but which usually looks something like
16960 @samp{Connection refused}. Don't use the @code{load}
16961 command in @value{GDBN} when using @code{gdbserver}, since the program is
16962 already on the target.
16964 @subsection Monitor Commands for @code{gdbserver}
16965 @cindex monitor commands, for @code{gdbserver}
16966 @anchor{Monitor Commands for gdbserver}
16968 During a @value{GDBN} session using @code{gdbserver}, you can use the
16969 @code{monitor} command to send special requests to @code{gdbserver}.
16970 Here are the available commands.
16974 List the available monitor commands.
16976 @item monitor set debug 0
16977 @itemx monitor set debug 1
16978 Disable or enable general debugging messages.
16980 @item monitor set remote-debug 0
16981 @itemx monitor set remote-debug 1
16982 Disable or enable specific debugging messages associated with the remote
16983 protocol (@pxref{Remote Protocol}).
16985 @item monitor set libthread-db-search-path [PATH]
16986 @cindex gdbserver, search path for @code{libthread_db}
16987 When this command is issued, @var{path} is a colon-separated list of
16988 directories to search for @code{libthread_db} (@pxref{Threads,,set
16989 libthread-db-search-path}). If you omit @var{path},
16990 @samp{libthread-db-search-path} will be reset to its default value.
16992 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16993 not supported in @code{gdbserver}.
16996 Tell gdbserver to exit immediately. This command should be followed by
16997 @code{disconnect} to close the debugging session. @code{gdbserver} will
16998 detach from any attached processes and kill any processes it created.
16999 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17000 of a multi-process mode debug session.
17004 @subsection Tracepoints support in @code{gdbserver}
17005 @cindex tracepoints support in @code{gdbserver}
17007 On some targets, @code{gdbserver} supports tracepoints, fast
17008 tracepoints and static tracepoints.
17010 For fast or static tracepoints to work, a special library called the
17011 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17012 This library is built and distributed as an integral part of
17013 @code{gdbserver}. In addition, support for static tracepoints
17014 requires building the in-process agent library with static tracepoints
17015 support. At present, the UST (LTTng Userspace Tracer,
17016 @url{http://lttng.org/ust}) tracing engine is supported. This support
17017 is automatically available if UST development headers are found in the
17018 standard include path when @code{gdbserver} is built, or if
17019 @code{gdbserver} was explicitly configured using @option{--with-ust}
17020 to point at such headers. You can explicitly disable the support
17021 using @option{--with-ust=no}.
17023 There are several ways to load the in-process agent in your program:
17026 @item Specifying it as dependency at link time
17028 You can link your program dynamically with the in-process agent
17029 library. On most systems, this is accomplished by adding
17030 @code{-linproctrace} to the link command.
17032 @item Using the system's preloading mechanisms
17034 You can force loading the in-process agent at startup time by using
17035 your system's support for preloading shared libraries. Many Unixes
17036 support the concept of preloading user defined libraries. In most
17037 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17038 in the environment. See also the description of @code{gdbserver}'s
17039 @option{--wrapper} command line option.
17041 @item Using @value{GDBN} to force loading the agent at run time
17043 On some systems, you can force the inferior to load a shared library,
17044 by calling a dynamic loader function in the inferior that takes care
17045 of dynamically looking up and loading a shared library. On most Unix
17046 systems, the function is @code{dlopen}. You'll use the @code{call}
17047 command for that. For example:
17050 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17053 Note that on most Unix systems, for the @code{dlopen} function to be
17054 available, the program needs to be linked with @code{-ldl}.
17057 On systems that have a userspace dynamic loader, like most Unix
17058 systems, when you connect to @code{gdbserver} using @code{target
17059 remote}, you'll find that the program is stopped at the dynamic
17060 loader's entry point, and no shared library has been loaded in the
17061 program's address space yet, including the in-process agent. In that
17062 case, before being able to use any of the fast or static tracepoints
17063 features, you need to let the loader run and load the shared
17064 libraries. The simplest way to do that is to run the program to the
17065 main procedure. E.g., if debugging a C or C@t{++} program, start
17066 @code{gdbserver} like so:
17069 $ gdbserver :9999 myprogram
17072 Start GDB and connect to @code{gdbserver} like so, and run to main:
17076 (@value{GDBP}) target remote myhost:9999
17077 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17078 (@value{GDBP}) b main
17079 (@value{GDBP}) continue
17082 The in-process tracing agent library should now be loaded into the
17083 process; you can confirm it with the @code{info sharedlibrary}
17084 command, which will list @file{libinproctrace.so} as loaded in the
17085 process. You are now ready to install fast tracepoints, list static
17086 tracepoint markers, probe static tracepoints markers, and start
17089 @node Remote Configuration
17090 @section Remote Configuration
17093 @kindex show remote
17094 This section documents the configuration options available when
17095 debugging remote programs. For the options related to the File I/O
17096 extensions of the remote protocol, see @ref{system,
17097 system-call-allowed}.
17100 @item set remoteaddresssize @var{bits}
17101 @cindex address size for remote targets
17102 @cindex bits in remote address
17103 Set the maximum size of address in a memory packet to the specified
17104 number of bits. @value{GDBN} will mask off the address bits above
17105 that number, when it passes addresses to the remote target. The
17106 default value is the number of bits in the target's address.
17108 @item show remoteaddresssize
17109 Show the current value of remote address size in bits.
17111 @item set remotebaud @var{n}
17112 @cindex baud rate for remote targets
17113 Set the baud rate for the remote serial I/O to @var{n} baud. The
17114 value is used to set the speed of the serial port used for debugging
17117 @item show remotebaud
17118 Show the current speed of the remote connection.
17120 @item set remotebreak
17121 @cindex interrupt remote programs
17122 @cindex BREAK signal instead of Ctrl-C
17123 @anchor{set remotebreak}
17124 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17125 when you type @kbd{Ctrl-c} to interrupt the program running
17126 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17127 character instead. The default is off, since most remote systems
17128 expect to see @samp{Ctrl-C} as the interrupt signal.
17130 @item show remotebreak
17131 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17132 interrupt the remote program.
17134 @item set remoteflow on
17135 @itemx set remoteflow off
17136 @kindex set remoteflow
17137 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17138 on the serial port used to communicate to the remote target.
17140 @item show remoteflow
17141 @kindex show remoteflow
17142 Show the current setting of hardware flow control.
17144 @item set remotelogbase @var{base}
17145 Set the base (a.k.a.@: radix) of logging serial protocol
17146 communications to @var{base}. Supported values of @var{base} are:
17147 @code{ascii}, @code{octal}, and @code{hex}. The default is
17150 @item show remotelogbase
17151 Show the current setting of the radix for logging remote serial
17154 @item set remotelogfile @var{file}
17155 @cindex record serial communications on file
17156 Record remote serial communications on the named @var{file}. The
17157 default is not to record at all.
17159 @item show remotelogfile.
17160 Show the current setting of the file name on which to record the
17161 serial communications.
17163 @item set remotetimeout @var{num}
17164 @cindex timeout for serial communications
17165 @cindex remote timeout
17166 Set the timeout limit to wait for the remote target to respond to
17167 @var{num} seconds. The default is 2 seconds.
17169 @item show remotetimeout
17170 Show the current number of seconds to wait for the remote target
17173 @cindex limit hardware breakpoints and watchpoints
17174 @cindex remote target, limit break- and watchpoints
17175 @anchor{set remote hardware-watchpoint-limit}
17176 @anchor{set remote hardware-breakpoint-limit}
17177 @item set remote hardware-watchpoint-limit @var{limit}
17178 @itemx set remote hardware-breakpoint-limit @var{limit}
17179 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17180 watchpoints. A limit of -1, the default, is treated as unlimited.
17182 @cindex limit hardware watchpoints length
17183 @cindex remote target, limit watchpoints length
17184 @anchor{set remote hardware-watchpoint-length-limit}
17185 @item set remote hardware-watchpoint-length-limit @var{limit}
17186 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17187 a remote hardware watchpoint. A limit of -1, the default, is treated
17190 @item show remote hardware-watchpoint-length-limit
17191 Show the current limit (in bytes) of the maximum length of
17192 a remote hardware watchpoint.
17194 @item set remote exec-file @var{filename}
17195 @itemx show remote exec-file
17196 @anchor{set remote exec-file}
17197 @cindex executable file, for remote target
17198 Select the file used for @code{run} with @code{target
17199 extended-remote}. This should be set to a filename valid on the
17200 target system. If it is not set, the target will use a default
17201 filename (e.g.@: the last program run).
17203 @item set remote interrupt-sequence
17204 @cindex interrupt remote programs
17205 @cindex select Ctrl-C, BREAK or BREAK-g
17206 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17207 @samp{BREAK-g} as the
17208 sequence to the remote target in order to interrupt the execution.
17209 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17210 is high level of serial line for some certain time.
17211 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17212 It is @code{BREAK} signal followed by character @code{g}.
17214 @item show interrupt-sequence
17215 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17216 is sent by @value{GDBN} to interrupt the remote program.
17217 @code{BREAK-g} is BREAK signal followed by @code{g} and
17218 also known as Magic SysRq g.
17220 @item set remote interrupt-on-connect
17221 @cindex send interrupt-sequence on start
17222 Specify whether interrupt-sequence is sent to remote target when
17223 @value{GDBN} connects to it. This is mostly needed when you debug
17224 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17225 which is known as Magic SysRq g in order to connect @value{GDBN}.
17227 @item show interrupt-on-connect
17228 Show whether interrupt-sequence is sent
17229 to remote target when @value{GDBN} connects to it.
17233 @item set tcp auto-retry on
17234 @cindex auto-retry, for remote TCP target
17235 Enable auto-retry for remote TCP connections. This is useful if the remote
17236 debugging agent is launched in parallel with @value{GDBN}; there is a race
17237 condition because the agent may not become ready to accept the connection
17238 before @value{GDBN} attempts to connect. When auto-retry is
17239 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17240 to establish the connection using the timeout specified by
17241 @code{set tcp connect-timeout}.
17243 @item set tcp auto-retry off
17244 Do not auto-retry failed TCP connections.
17246 @item show tcp auto-retry
17247 Show the current auto-retry setting.
17249 @item set tcp connect-timeout @var{seconds}
17250 @cindex connection timeout, for remote TCP target
17251 @cindex timeout, for remote target connection
17252 Set the timeout for establishing a TCP connection to the remote target to
17253 @var{seconds}. The timeout affects both polling to retry failed connections
17254 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17255 that are merely slow to complete, and represents an approximate cumulative
17258 @item show tcp connect-timeout
17259 Show the current connection timeout setting.
17262 @cindex remote packets, enabling and disabling
17263 The @value{GDBN} remote protocol autodetects the packets supported by
17264 your debugging stub. If you need to override the autodetection, you
17265 can use these commands to enable or disable individual packets. Each
17266 packet can be set to @samp{on} (the remote target supports this
17267 packet), @samp{off} (the remote target does not support this packet),
17268 or @samp{auto} (detect remote target support for this packet). They
17269 all default to @samp{auto}. For more information about each packet,
17270 see @ref{Remote Protocol}.
17272 During normal use, you should not have to use any of these commands.
17273 If you do, that may be a bug in your remote debugging stub, or a bug
17274 in @value{GDBN}. You may want to report the problem to the
17275 @value{GDBN} developers.
17277 For each packet @var{name}, the command to enable or disable the
17278 packet is @code{set remote @var{name}-packet}. The available settings
17281 @multitable @columnfractions 0.28 0.32 0.25
17284 @tab Related Features
17286 @item @code{fetch-register}
17288 @tab @code{info registers}
17290 @item @code{set-register}
17294 @item @code{binary-download}
17296 @tab @code{load}, @code{set}
17298 @item @code{read-aux-vector}
17299 @tab @code{qXfer:auxv:read}
17300 @tab @code{info auxv}
17302 @item @code{symbol-lookup}
17303 @tab @code{qSymbol}
17304 @tab Detecting multiple threads
17306 @item @code{attach}
17307 @tab @code{vAttach}
17310 @item @code{verbose-resume}
17312 @tab Stepping or resuming multiple threads
17318 @item @code{software-breakpoint}
17322 @item @code{hardware-breakpoint}
17326 @item @code{write-watchpoint}
17330 @item @code{read-watchpoint}
17334 @item @code{access-watchpoint}
17338 @item @code{target-features}
17339 @tab @code{qXfer:features:read}
17340 @tab @code{set architecture}
17342 @item @code{library-info}
17343 @tab @code{qXfer:libraries:read}
17344 @tab @code{info sharedlibrary}
17346 @item @code{memory-map}
17347 @tab @code{qXfer:memory-map:read}
17348 @tab @code{info mem}
17350 @item @code{read-sdata-object}
17351 @tab @code{qXfer:sdata:read}
17352 @tab @code{print $_sdata}
17354 @item @code{read-spu-object}
17355 @tab @code{qXfer:spu:read}
17356 @tab @code{info spu}
17358 @item @code{write-spu-object}
17359 @tab @code{qXfer:spu:write}
17360 @tab @code{info spu}
17362 @item @code{read-siginfo-object}
17363 @tab @code{qXfer:siginfo:read}
17364 @tab @code{print $_siginfo}
17366 @item @code{write-siginfo-object}
17367 @tab @code{qXfer:siginfo:write}
17368 @tab @code{set $_siginfo}
17370 @item @code{threads}
17371 @tab @code{qXfer:threads:read}
17372 @tab @code{info threads}
17374 @item @code{get-thread-local-@*storage-address}
17375 @tab @code{qGetTLSAddr}
17376 @tab Displaying @code{__thread} variables
17378 @item @code{get-thread-information-block-address}
17379 @tab @code{qGetTIBAddr}
17380 @tab Display MS-Windows Thread Information Block.
17382 @item @code{search-memory}
17383 @tab @code{qSearch:memory}
17386 @item @code{supported-packets}
17387 @tab @code{qSupported}
17388 @tab Remote communications parameters
17390 @item @code{pass-signals}
17391 @tab @code{QPassSignals}
17392 @tab @code{handle @var{signal}}
17394 @item @code{hostio-close-packet}
17395 @tab @code{vFile:close}
17396 @tab @code{remote get}, @code{remote put}
17398 @item @code{hostio-open-packet}
17399 @tab @code{vFile:open}
17400 @tab @code{remote get}, @code{remote put}
17402 @item @code{hostio-pread-packet}
17403 @tab @code{vFile:pread}
17404 @tab @code{remote get}, @code{remote put}
17406 @item @code{hostio-pwrite-packet}
17407 @tab @code{vFile:pwrite}
17408 @tab @code{remote get}, @code{remote put}
17410 @item @code{hostio-unlink-packet}
17411 @tab @code{vFile:unlink}
17412 @tab @code{remote delete}
17414 @item @code{noack-packet}
17415 @tab @code{QStartNoAckMode}
17416 @tab Packet acknowledgment
17418 @item @code{osdata}
17419 @tab @code{qXfer:osdata:read}
17420 @tab @code{info os}
17422 @item @code{query-attached}
17423 @tab @code{qAttached}
17424 @tab Querying remote process attach state.
17426 @item @code{traceframe-info}
17427 @tab @code{qXfer:traceframe-info:read}
17428 @tab Traceframe info
17430 @item @code{install-in-trace}
17431 @tab @code{InstallInTrace}
17432 @tab Install tracepoint in tracing
17434 @item @code{disable-randomization}
17435 @tab @code{QDisableRandomization}
17436 @tab @code{set disable-randomization}
17440 @section Implementing a Remote Stub
17442 @cindex debugging stub, example
17443 @cindex remote stub, example
17444 @cindex stub example, remote debugging
17445 The stub files provided with @value{GDBN} implement the target side of the
17446 communication protocol, and the @value{GDBN} side is implemented in the
17447 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17448 these subroutines to communicate, and ignore the details. (If you're
17449 implementing your own stub file, you can still ignore the details: start
17450 with one of the existing stub files. @file{sparc-stub.c} is the best
17451 organized, and therefore the easiest to read.)
17453 @cindex remote serial debugging, overview
17454 To debug a program running on another machine (the debugging
17455 @dfn{target} machine), you must first arrange for all the usual
17456 prerequisites for the program to run by itself. For example, for a C
17461 A startup routine to set up the C runtime environment; these usually
17462 have a name like @file{crt0}. The startup routine may be supplied by
17463 your hardware supplier, or you may have to write your own.
17466 A C subroutine library to support your program's
17467 subroutine calls, notably managing input and output.
17470 A way of getting your program to the other machine---for example, a
17471 download program. These are often supplied by the hardware
17472 manufacturer, but you may have to write your own from hardware
17476 The next step is to arrange for your program to use a serial port to
17477 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17478 machine). In general terms, the scheme looks like this:
17482 @value{GDBN} already understands how to use this protocol; when everything
17483 else is set up, you can simply use the @samp{target remote} command
17484 (@pxref{Targets,,Specifying a Debugging Target}).
17486 @item On the target,
17487 you must link with your program a few special-purpose subroutines that
17488 implement the @value{GDBN} remote serial protocol. The file containing these
17489 subroutines is called a @dfn{debugging stub}.
17491 On certain remote targets, you can use an auxiliary program
17492 @code{gdbserver} instead of linking a stub into your program.
17493 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17496 The debugging stub is specific to the architecture of the remote
17497 machine; for example, use @file{sparc-stub.c} to debug programs on
17500 @cindex remote serial stub list
17501 These working remote stubs are distributed with @value{GDBN}:
17506 @cindex @file{i386-stub.c}
17509 For Intel 386 and compatible architectures.
17512 @cindex @file{m68k-stub.c}
17513 @cindex Motorola 680x0
17515 For Motorola 680x0 architectures.
17518 @cindex @file{sh-stub.c}
17521 For Renesas SH architectures.
17524 @cindex @file{sparc-stub.c}
17526 For @sc{sparc} architectures.
17528 @item sparcl-stub.c
17529 @cindex @file{sparcl-stub.c}
17532 For Fujitsu @sc{sparclite} architectures.
17536 The @file{README} file in the @value{GDBN} distribution may list other
17537 recently added stubs.
17540 * Stub Contents:: What the stub can do for you
17541 * Bootstrapping:: What you must do for the stub
17542 * Debug Session:: Putting it all together
17545 @node Stub Contents
17546 @subsection What the Stub Can Do for You
17548 @cindex remote serial stub
17549 The debugging stub for your architecture supplies these three
17553 @item set_debug_traps
17554 @findex set_debug_traps
17555 @cindex remote serial stub, initialization
17556 This routine arranges for @code{handle_exception} to run when your
17557 program stops. You must call this subroutine explicitly in your
17558 program's startup code.
17560 @item handle_exception
17561 @findex handle_exception
17562 @cindex remote serial stub, main routine
17563 This is the central workhorse, but your program never calls it
17564 explicitly---the setup code arranges for @code{handle_exception} to
17565 run when a trap is triggered.
17567 @code{handle_exception} takes control when your program stops during
17568 execution (for example, on a breakpoint), and mediates communications
17569 with @value{GDBN} on the host machine. This is where the communications
17570 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17571 representative on the target machine. It begins by sending summary
17572 information on the state of your program, then continues to execute,
17573 retrieving and transmitting any information @value{GDBN} needs, until you
17574 execute a @value{GDBN} command that makes your program resume; at that point,
17575 @code{handle_exception} returns control to your own code on the target
17579 @cindex @code{breakpoint} subroutine, remote
17580 Use this auxiliary subroutine to make your program contain a
17581 breakpoint. Depending on the particular situation, this may be the only
17582 way for @value{GDBN} to get control. For instance, if your target
17583 machine has some sort of interrupt button, you won't need to call this;
17584 pressing the interrupt button transfers control to
17585 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17586 simply receiving characters on the serial port may also trigger a trap;
17587 again, in that situation, you don't need to call @code{breakpoint} from
17588 your own program---simply running @samp{target remote} from the host
17589 @value{GDBN} session gets control.
17591 Call @code{breakpoint} if none of these is true, or if you simply want
17592 to make certain your program stops at a predetermined point for the
17593 start of your debugging session.
17596 @node Bootstrapping
17597 @subsection What You Must Do for the Stub
17599 @cindex remote stub, support routines
17600 The debugging stubs that come with @value{GDBN} are set up for a particular
17601 chip architecture, but they have no information about the rest of your
17602 debugging target machine.
17604 First of all you need to tell the stub how to communicate with the
17608 @item int getDebugChar()
17609 @findex getDebugChar
17610 Write this subroutine to read a single character from the serial port.
17611 It may be identical to @code{getchar} for your target system; a
17612 different name is used to allow you to distinguish the two if you wish.
17614 @item void putDebugChar(int)
17615 @findex putDebugChar
17616 Write this subroutine to write a single character to the serial port.
17617 It may be identical to @code{putchar} for your target system; a
17618 different name is used to allow you to distinguish the two if you wish.
17621 @cindex control C, and remote debugging
17622 @cindex interrupting remote targets
17623 If you want @value{GDBN} to be able to stop your program while it is
17624 running, you need to use an interrupt-driven serial driver, and arrange
17625 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17626 character). That is the character which @value{GDBN} uses to tell the
17627 remote system to stop.
17629 Getting the debugging target to return the proper status to @value{GDBN}
17630 probably requires changes to the standard stub; one quick and dirty way
17631 is to just execute a breakpoint instruction (the ``dirty'' part is that
17632 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17634 Other routines you need to supply are:
17637 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17638 @findex exceptionHandler
17639 Write this function to install @var{exception_address} in the exception
17640 handling tables. You need to do this because the stub does not have any
17641 way of knowing what the exception handling tables on your target system
17642 are like (for example, the processor's table might be in @sc{rom},
17643 containing entries which point to a table in @sc{ram}).
17644 @var{exception_number} is the exception number which should be changed;
17645 its meaning is architecture-dependent (for example, different numbers
17646 might represent divide by zero, misaligned access, etc). When this
17647 exception occurs, control should be transferred directly to
17648 @var{exception_address}, and the processor state (stack, registers,
17649 and so on) should be just as it is when a processor exception occurs. So if
17650 you want to use a jump instruction to reach @var{exception_address}, it
17651 should be a simple jump, not a jump to subroutine.
17653 For the 386, @var{exception_address} should be installed as an interrupt
17654 gate so that interrupts are masked while the handler runs. The gate
17655 should be at privilege level 0 (the most privileged level). The
17656 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17657 help from @code{exceptionHandler}.
17659 @item void flush_i_cache()
17660 @findex flush_i_cache
17661 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17662 instruction cache, if any, on your target machine. If there is no
17663 instruction cache, this subroutine may be a no-op.
17665 On target machines that have instruction caches, @value{GDBN} requires this
17666 function to make certain that the state of your program is stable.
17670 You must also make sure this library routine is available:
17673 @item void *memset(void *, int, int)
17675 This is the standard library function @code{memset} that sets an area of
17676 memory to a known value. If you have one of the free versions of
17677 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17678 either obtain it from your hardware manufacturer, or write your own.
17681 If you do not use the GNU C compiler, you may need other standard
17682 library subroutines as well; this varies from one stub to another,
17683 but in general the stubs are likely to use any of the common library
17684 subroutines which @code{@value{NGCC}} generates as inline code.
17687 @node Debug Session
17688 @subsection Putting it All Together
17690 @cindex remote serial debugging summary
17691 In summary, when your program is ready to debug, you must follow these
17696 Make sure you have defined the supporting low-level routines
17697 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17699 @code{getDebugChar}, @code{putDebugChar},
17700 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17704 Insert these lines in your program's startup code, before the main
17705 procedure is called:
17712 On some machines, when a breakpoint trap is raised, the hardware
17713 automatically makes the PC point to the instruction after the
17714 breakpoint. If your machine doesn't do that, you may need to adjust
17715 @code{handle_exception} to arrange for it to return to the instruction
17716 after the breakpoint on this first invocation, so that your program
17717 doesn't keep hitting the initial breakpoint instead of making
17721 For the 680x0 stub only, you need to provide a variable called
17722 @code{exceptionHook}. Normally you just use:
17725 void (*exceptionHook)() = 0;
17729 but if before calling @code{set_debug_traps}, you set it to point to a
17730 function in your program, that function is called when
17731 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17732 error). The function indicated by @code{exceptionHook} is called with
17733 one parameter: an @code{int} which is the exception number.
17736 Compile and link together: your program, the @value{GDBN} debugging stub for
17737 your target architecture, and the supporting subroutines.
17740 Make sure you have a serial connection between your target machine and
17741 the @value{GDBN} host, and identify the serial port on the host.
17744 @c The "remote" target now provides a `load' command, so we should
17745 @c document that. FIXME.
17746 Download your program to your target machine (or get it there by
17747 whatever means the manufacturer provides), and start it.
17750 Start @value{GDBN} on the host, and connect to the target
17751 (@pxref{Connecting,,Connecting to a Remote Target}).
17755 @node Configurations
17756 @chapter Configuration-Specific Information
17758 While nearly all @value{GDBN} commands are available for all native and
17759 cross versions of the debugger, there are some exceptions. This chapter
17760 describes things that are only available in certain configurations.
17762 There are three major categories of configurations: native
17763 configurations, where the host and target are the same, embedded
17764 operating system configurations, which are usually the same for several
17765 different processor architectures, and bare embedded processors, which
17766 are quite different from each other.
17771 * Embedded Processors::
17778 This section describes details specific to particular native
17783 * BSD libkvm Interface:: Debugging BSD kernel memory images
17784 * SVR4 Process Information:: SVR4 process information
17785 * DJGPP Native:: Features specific to the DJGPP port
17786 * Cygwin Native:: Features specific to the Cygwin port
17787 * Hurd Native:: Features specific to @sc{gnu} Hurd
17788 * Neutrino:: Features specific to QNX Neutrino
17789 * Darwin:: Features specific to Darwin
17795 On HP-UX systems, if you refer to a function or variable name that
17796 begins with a dollar sign, @value{GDBN} searches for a user or system
17797 name first, before it searches for a convenience variable.
17800 @node BSD libkvm Interface
17801 @subsection BSD libkvm Interface
17804 @cindex kernel memory image
17805 @cindex kernel crash dump
17807 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17808 interface that provides a uniform interface for accessing kernel virtual
17809 memory images, including live systems and crash dumps. @value{GDBN}
17810 uses this interface to allow you to debug live kernels and kernel crash
17811 dumps on many native BSD configurations. This is implemented as a
17812 special @code{kvm} debugging target. For debugging a live system, load
17813 the currently running kernel into @value{GDBN} and connect to the
17817 (@value{GDBP}) @b{target kvm}
17820 For debugging crash dumps, provide the file name of the crash dump as an
17824 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17827 Once connected to the @code{kvm} target, the following commands are
17833 Set current context from the @dfn{Process Control Block} (PCB) address.
17836 Set current context from proc address. This command isn't available on
17837 modern FreeBSD systems.
17840 @node SVR4 Process Information
17841 @subsection SVR4 Process Information
17843 @cindex examine process image
17844 @cindex process info via @file{/proc}
17846 Many versions of SVR4 and compatible systems provide a facility called
17847 @samp{/proc} that can be used to examine the image of a running
17848 process using file-system subroutines. If @value{GDBN} is configured
17849 for an operating system with this facility, the command @code{info
17850 proc} is available to report information about the process running
17851 your program, or about any process running on your system. @code{info
17852 proc} works only on SVR4 systems that include the @code{procfs} code.
17853 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17854 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17860 @itemx info proc @var{process-id}
17861 Summarize available information about any running process. If a
17862 process ID is specified by @var{process-id}, display information about
17863 that process; otherwise display information about the program being
17864 debugged. The summary includes the debugged process ID, the command
17865 line used to invoke it, its current working directory, and its
17866 executable file's absolute file name.
17868 On some systems, @var{process-id} can be of the form
17869 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17870 within a process. If the optional @var{pid} part is missing, it means
17871 a thread from the process being debugged (the leading @samp{/} still
17872 needs to be present, or else @value{GDBN} will interpret the number as
17873 a process ID rather than a thread ID).
17875 @item info proc mappings
17876 @cindex memory address space mappings
17877 Report the memory address space ranges accessible in the program, with
17878 information on whether the process has read, write, or execute access
17879 rights to each range. On @sc{gnu}/Linux systems, each memory range
17880 includes the object file which is mapped to that range, instead of the
17881 memory access rights to that range.
17883 @item info proc stat
17884 @itemx info proc status
17885 @cindex process detailed status information
17886 These subcommands are specific to @sc{gnu}/Linux systems. They show
17887 the process-related information, including the user ID and group ID;
17888 how many threads are there in the process; its virtual memory usage;
17889 the signals that are pending, blocked, and ignored; its TTY; its
17890 consumption of system and user time; its stack size; its @samp{nice}
17891 value; etc. For more information, see the @samp{proc} man page
17892 (type @kbd{man 5 proc} from your shell prompt).
17894 @item info proc all
17895 Show all the information about the process described under all of the
17896 above @code{info proc} subcommands.
17899 @comment These sub-options of 'info proc' were not included when
17900 @comment procfs.c was re-written. Keep their descriptions around
17901 @comment against the day when someone finds the time to put them back in.
17902 @kindex info proc times
17903 @item info proc times
17904 Starting time, user CPU time, and system CPU time for your program and
17907 @kindex info proc id
17909 Report on the process IDs related to your program: its own process ID,
17910 the ID of its parent, the process group ID, and the session ID.
17913 @item set procfs-trace
17914 @kindex set procfs-trace
17915 @cindex @code{procfs} API calls
17916 This command enables and disables tracing of @code{procfs} API calls.
17918 @item show procfs-trace
17919 @kindex show procfs-trace
17920 Show the current state of @code{procfs} API call tracing.
17922 @item set procfs-file @var{file}
17923 @kindex set procfs-file
17924 Tell @value{GDBN} to write @code{procfs} API trace to the named
17925 @var{file}. @value{GDBN} appends the trace info to the previous
17926 contents of the file. The default is to display the trace on the
17929 @item show procfs-file
17930 @kindex show procfs-file
17931 Show the file to which @code{procfs} API trace is written.
17933 @item proc-trace-entry
17934 @itemx proc-trace-exit
17935 @itemx proc-untrace-entry
17936 @itemx proc-untrace-exit
17937 @kindex proc-trace-entry
17938 @kindex proc-trace-exit
17939 @kindex proc-untrace-entry
17940 @kindex proc-untrace-exit
17941 These commands enable and disable tracing of entries into and exits
17942 from the @code{syscall} interface.
17945 @kindex info pidlist
17946 @cindex process list, QNX Neutrino
17947 For QNX Neutrino only, this command displays the list of all the
17948 processes and all the threads within each process.
17951 @kindex info meminfo
17952 @cindex mapinfo list, QNX Neutrino
17953 For QNX Neutrino only, this command displays the list of all mapinfos.
17957 @subsection Features for Debugging @sc{djgpp} Programs
17958 @cindex @sc{djgpp} debugging
17959 @cindex native @sc{djgpp} debugging
17960 @cindex MS-DOS-specific commands
17963 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17964 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17965 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17966 top of real-mode DOS systems and their emulations.
17968 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17969 defines a few commands specific to the @sc{djgpp} port. This
17970 subsection describes those commands.
17975 This is a prefix of @sc{djgpp}-specific commands which print
17976 information about the target system and important OS structures.
17979 @cindex MS-DOS system info
17980 @cindex free memory information (MS-DOS)
17981 @item info dos sysinfo
17982 This command displays assorted information about the underlying
17983 platform: the CPU type and features, the OS version and flavor, the
17984 DPMI version, and the available conventional and DPMI memory.
17989 @cindex segment descriptor tables
17990 @cindex descriptor tables display
17992 @itemx info dos ldt
17993 @itemx info dos idt
17994 These 3 commands display entries from, respectively, Global, Local,
17995 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17996 tables are data structures which store a descriptor for each segment
17997 that is currently in use. The segment's selector is an index into a
17998 descriptor table; the table entry for that index holds the
17999 descriptor's base address and limit, and its attributes and access
18002 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18003 segment (used for both data and the stack), and a DOS segment (which
18004 allows access to DOS/BIOS data structures and absolute addresses in
18005 conventional memory). However, the DPMI host will usually define
18006 additional segments in order to support the DPMI environment.
18008 @cindex garbled pointers
18009 These commands allow to display entries from the descriptor tables.
18010 Without an argument, all entries from the specified table are
18011 displayed. An argument, which should be an integer expression, means
18012 display a single entry whose index is given by the argument. For
18013 example, here's a convenient way to display information about the
18014 debugged program's data segment:
18017 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18018 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18022 This comes in handy when you want to see whether a pointer is outside
18023 the data segment's limit (i.e.@: @dfn{garbled}).
18025 @cindex page tables display (MS-DOS)
18027 @itemx info dos pte
18028 These two commands display entries from, respectively, the Page
18029 Directory and the Page Tables. Page Directories and Page Tables are
18030 data structures which control how virtual memory addresses are mapped
18031 into physical addresses. A Page Table includes an entry for every
18032 page of memory that is mapped into the program's address space; there
18033 may be several Page Tables, each one holding up to 4096 entries. A
18034 Page Directory has up to 4096 entries, one each for every Page Table
18035 that is currently in use.
18037 Without an argument, @kbd{info dos pde} displays the entire Page
18038 Directory, and @kbd{info dos pte} displays all the entries in all of
18039 the Page Tables. An argument, an integer expression, given to the
18040 @kbd{info dos pde} command means display only that entry from the Page
18041 Directory table. An argument given to the @kbd{info dos pte} command
18042 means display entries from a single Page Table, the one pointed to by
18043 the specified entry in the Page Directory.
18045 @cindex direct memory access (DMA) on MS-DOS
18046 These commands are useful when your program uses @dfn{DMA} (Direct
18047 Memory Access), which needs physical addresses to program the DMA
18050 These commands are supported only with some DPMI servers.
18052 @cindex physical address from linear address
18053 @item info dos address-pte @var{addr}
18054 This command displays the Page Table entry for a specified linear
18055 address. The argument @var{addr} is a linear address which should
18056 already have the appropriate segment's base address added to it,
18057 because this command accepts addresses which may belong to @emph{any}
18058 segment. For example, here's how to display the Page Table entry for
18059 the page where a variable @code{i} is stored:
18062 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18063 @exdent @code{Page Table entry for address 0x11a00d30:}
18064 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18068 This says that @code{i} is stored at offset @code{0xd30} from the page
18069 whose physical base address is @code{0x02698000}, and shows all the
18070 attributes of that page.
18072 Note that you must cast the addresses of variables to a @code{char *},
18073 since otherwise the value of @code{__djgpp_base_address}, the base
18074 address of all variables and functions in a @sc{djgpp} program, will
18075 be added using the rules of C pointer arithmetics: if @code{i} is
18076 declared an @code{int}, @value{GDBN} will add 4 times the value of
18077 @code{__djgpp_base_address} to the address of @code{i}.
18079 Here's another example, it displays the Page Table entry for the
18083 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18084 @exdent @code{Page Table entry for address 0x29110:}
18085 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18089 (The @code{+ 3} offset is because the transfer buffer's address is the
18090 3rd member of the @code{_go32_info_block} structure.) The output
18091 clearly shows that this DPMI server maps the addresses in conventional
18092 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18093 linear (@code{0x29110}) addresses are identical.
18095 This command is supported only with some DPMI servers.
18098 @cindex DOS serial data link, remote debugging
18099 In addition to native debugging, the DJGPP port supports remote
18100 debugging via a serial data link. The following commands are specific
18101 to remote serial debugging in the DJGPP port of @value{GDBN}.
18104 @kindex set com1base
18105 @kindex set com1irq
18106 @kindex set com2base
18107 @kindex set com2irq
18108 @kindex set com3base
18109 @kindex set com3irq
18110 @kindex set com4base
18111 @kindex set com4irq
18112 @item set com1base @var{addr}
18113 This command sets the base I/O port address of the @file{COM1} serial
18116 @item set com1irq @var{irq}
18117 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18118 for the @file{COM1} serial port.
18120 There are similar commands @samp{set com2base}, @samp{set com3irq},
18121 etc.@: for setting the port address and the @code{IRQ} lines for the
18124 @kindex show com1base
18125 @kindex show com1irq
18126 @kindex show com2base
18127 @kindex show com2irq
18128 @kindex show com3base
18129 @kindex show com3irq
18130 @kindex show com4base
18131 @kindex show com4irq
18132 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18133 display the current settings of the base address and the @code{IRQ}
18134 lines used by the COM ports.
18137 @kindex info serial
18138 @cindex DOS serial port status
18139 This command prints the status of the 4 DOS serial ports. For each
18140 port, it prints whether it's active or not, its I/O base address and
18141 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18142 counts of various errors encountered so far.
18146 @node Cygwin Native
18147 @subsection Features for Debugging MS Windows PE Executables
18148 @cindex MS Windows debugging
18149 @cindex native Cygwin debugging
18150 @cindex Cygwin-specific commands
18152 @value{GDBN} supports native debugging of MS Windows programs, including
18153 DLLs with and without symbolic debugging information.
18155 @cindex Ctrl-BREAK, MS-Windows
18156 @cindex interrupt debuggee on MS-Windows
18157 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18158 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18159 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18160 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18161 sequence, which can be used to interrupt the debuggee even if it
18164 There are various additional Cygwin-specific commands, described in
18165 this section. Working with DLLs that have no debugging symbols is
18166 described in @ref{Non-debug DLL Symbols}.
18171 This is a prefix of MS Windows-specific commands which print
18172 information about the target system and important OS structures.
18174 @item info w32 selector
18175 This command displays information returned by
18176 the Win32 API @code{GetThreadSelectorEntry} function.
18177 It takes an optional argument that is evaluated to
18178 a long value to give the information about this given selector.
18179 Without argument, this command displays information
18180 about the six segment registers.
18182 @item info w32 thread-information-block
18183 This command displays thread specific information stored in the
18184 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18185 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18189 This is a Cygwin-specific alias of @code{info shared}.
18191 @kindex dll-symbols
18193 This command loads symbols from a dll similarly to
18194 add-sym command but without the need to specify a base address.
18196 @kindex set cygwin-exceptions
18197 @cindex debugging the Cygwin DLL
18198 @cindex Cygwin DLL, debugging
18199 @item set cygwin-exceptions @var{mode}
18200 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18201 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18202 @value{GDBN} will delay recognition of exceptions, and may ignore some
18203 exceptions which seem to be caused by internal Cygwin DLL
18204 ``bookkeeping''. This option is meant primarily for debugging the
18205 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18206 @value{GDBN} users with false @code{SIGSEGV} signals.
18208 @kindex show cygwin-exceptions
18209 @item show cygwin-exceptions
18210 Displays whether @value{GDBN} will break on exceptions that happen
18211 inside the Cygwin DLL itself.
18213 @kindex set new-console
18214 @item set new-console @var{mode}
18215 If @var{mode} is @code{on} the debuggee will
18216 be started in a new console on next start.
18217 If @var{mode} is @code{off}, the debuggee will
18218 be started in the same console as the debugger.
18220 @kindex show new-console
18221 @item show new-console
18222 Displays whether a new console is used
18223 when the debuggee is started.
18225 @kindex set new-group
18226 @item set new-group @var{mode}
18227 This boolean value controls whether the debuggee should
18228 start a new group or stay in the same group as the debugger.
18229 This affects the way the Windows OS handles
18232 @kindex show new-group
18233 @item show new-group
18234 Displays current value of new-group boolean.
18236 @kindex set debugevents
18237 @item set debugevents
18238 This boolean value adds debug output concerning kernel events related
18239 to the debuggee seen by the debugger. This includes events that
18240 signal thread and process creation and exit, DLL loading and
18241 unloading, console interrupts, and debugging messages produced by the
18242 Windows @code{OutputDebugString} API call.
18244 @kindex set debugexec
18245 @item set debugexec
18246 This boolean value adds debug output concerning execute events
18247 (such as resume thread) seen by the debugger.
18249 @kindex set debugexceptions
18250 @item set debugexceptions
18251 This boolean value adds debug output concerning exceptions in the
18252 debuggee seen by the debugger.
18254 @kindex set debugmemory
18255 @item set debugmemory
18256 This boolean value adds debug output concerning debuggee memory reads
18257 and writes by the debugger.
18261 This boolean values specifies whether the debuggee is called
18262 via a shell or directly (default value is on).
18266 Displays if the debuggee will be started with a shell.
18271 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18274 @node Non-debug DLL Symbols
18275 @subsubsection Support for DLLs without Debugging Symbols
18276 @cindex DLLs with no debugging symbols
18277 @cindex Minimal symbols and DLLs
18279 Very often on windows, some of the DLLs that your program relies on do
18280 not include symbolic debugging information (for example,
18281 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18282 symbols in a DLL, it relies on the minimal amount of symbolic
18283 information contained in the DLL's export table. This section
18284 describes working with such symbols, known internally to @value{GDBN} as
18285 ``minimal symbols''.
18287 Note that before the debugged program has started execution, no DLLs
18288 will have been loaded. The easiest way around this problem is simply to
18289 start the program --- either by setting a breakpoint or letting the
18290 program run once to completion. It is also possible to force
18291 @value{GDBN} to load a particular DLL before starting the executable ---
18292 see the shared library information in @ref{Files}, or the
18293 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18294 explicitly loading symbols from a DLL with no debugging information will
18295 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18296 which may adversely affect symbol lookup performance.
18298 @subsubsection DLL Name Prefixes
18300 In keeping with the naming conventions used by the Microsoft debugging
18301 tools, DLL export symbols are made available with a prefix based on the
18302 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18303 also entered into the symbol table, so @code{CreateFileA} is often
18304 sufficient. In some cases there will be name clashes within a program
18305 (particularly if the executable itself includes full debugging symbols)
18306 necessitating the use of the fully qualified name when referring to the
18307 contents of the DLL. Use single-quotes around the name to avoid the
18308 exclamation mark (``!'') being interpreted as a language operator.
18310 Note that the internal name of the DLL may be all upper-case, even
18311 though the file name of the DLL is lower-case, or vice-versa. Since
18312 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18313 some confusion. If in doubt, try the @code{info functions} and
18314 @code{info variables} commands or even @code{maint print msymbols}
18315 (@pxref{Symbols}). Here's an example:
18318 (@value{GDBP}) info function CreateFileA
18319 All functions matching regular expression "CreateFileA":
18321 Non-debugging symbols:
18322 0x77e885f4 CreateFileA
18323 0x77e885f4 KERNEL32!CreateFileA
18327 (@value{GDBP}) info function !
18328 All functions matching regular expression "!":
18330 Non-debugging symbols:
18331 0x6100114c cygwin1!__assert
18332 0x61004034 cygwin1!_dll_crt0@@0
18333 0x61004240 cygwin1!dll_crt0(per_process *)
18337 @subsubsection Working with Minimal Symbols
18339 Symbols extracted from a DLL's export table do not contain very much
18340 type information. All that @value{GDBN} can do is guess whether a symbol
18341 refers to a function or variable depending on the linker section that
18342 contains the symbol. Also note that the actual contents of the memory
18343 contained in a DLL are not available unless the program is running. This
18344 means that you cannot examine the contents of a variable or disassemble
18345 a function within a DLL without a running program.
18347 Variables are generally treated as pointers and dereferenced
18348 automatically. For this reason, it is often necessary to prefix a
18349 variable name with the address-of operator (``&'') and provide explicit
18350 type information in the command. Here's an example of the type of
18354 (@value{GDBP}) print 'cygwin1!__argv'
18359 (@value{GDBP}) x 'cygwin1!__argv'
18360 0x10021610: "\230y\""
18363 And two possible solutions:
18366 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18367 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18371 (@value{GDBP}) x/2x &'cygwin1!__argv'
18372 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18373 (@value{GDBP}) x/x 0x10021608
18374 0x10021608: 0x0022fd98
18375 (@value{GDBP}) x/s 0x0022fd98
18376 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18379 Setting a break point within a DLL is possible even before the program
18380 starts execution. However, under these circumstances, @value{GDBN} can't
18381 examine the initial instructions of the function in order to skip the
18382 function's frame set-up code. You can work around this by using ``*&''
18383 to set the breakpoint at a raw memory address:
18386 (@value{GDBP}) break *&'python22!PyOS_Readline'
18387 Breakpoint 1 at 0x1e04eff0
18390 The author of these extensions is not entirely convinced that setting a
18391 break point within a shared DLL like @file{kernel32.dll} is completely
18395 @subsection Commands Specific to @sc{gnu} Hurd Systems
18396 @cindex @sc{gnu} Hurd debugging
18398 This subsection describes @value{GDBN} commands specific to the
18399 @sc{gnu} Hurd native debugging.
18404 @kindex set signals@r{, Hurd command}
18405 @kindex set sigs@r{, Hurd command}
18406 This command toggles the state of inferior signal interception by
18407 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18408 affected by this command. @code{sigs} is a shorthand alias for
18413 @kindex show signals@r{, Hurd command}
18414 @kindex show sigs@r{, Hurd command}
18415 Show the current state of intercepting inferior's signals.
18417 @item set signal-thread
18418 @itemx set sigthread
18419 @kindex set signal-thread
18420 @kindex set sigthread
18421 This command tells @value{GDBN} which thread is the @code{libc} signal
18422 thread. That thread is run when a signal is delivered to a running
18423 process. @code{set sigthread} is the shorthand alias of @code{set
18426 @item show signal-thread
18427 @itemx show sigthread
18428 @kindex show signal-thread
18429 @kindex show sigthread
18430 These two commands show which thread will run when the inferior is
18431 delivered a signal.
18434 @kindex set stopped@r{, Hurd command}
18435 This commands tells @value{GDBN} that the inferior process is stopped,
18436 as with the @code{SIGSTOP} signal. The stopped process can be
18437 continued by delivering a signal to it.
18440 @kindex show stopped@r{, Hurd command}
18441 This command shows whether @value{GDBN} thinks the debuggee is
18444 @item set exceptions
18445 @kindex set exceptions@r{, Hurd command}
18446 Use this command to turn off trapping of exceptions in the inferior.
18447 When exception trapping is off, neither breakpoints nor
18448 single-stepping will work. To restore the default, set exception
18451 @item show exceptions
18452 @kindex show exceptions@r{, Hurd command}
18453 Show the current state of trapping exceptions in the inferior.
18455 @item set task pause
18456 @kindex set task@r{, Hurd commands}
18457 @cindex task attributes (@sc{gnu} Hurd)
18458 @cindex pause current task (@sc{gnu} Hurd)
18459 This command toggles task suspension when @value{GDBN} has control.
18460 Setting it to on takes effect immediately, and the task is suspended
18461 whenever @value{GDBN} gets control. Setting it to off will take
18462 effect the next time the inferior is continued. If this option is set
18463 to off, you can use @code{set thread default pause on} or @code{set
18464 thread pause on} (see below) to pause individual threads.
18466 @item show task pause
18467 @kindex show task@r{, Hurd commands}
18468 Show the current state of task suspension.
18470 @item set task detach-suspend-count
18471 @cindex task suspend count
18472 @cindex detach from task, @sc{gnu} Hurd
18473 This command sets the suspend count the task will be left with when
18474 @value{GDBN} detaches from it.
18476 @item show task detach-suspend-count
18477 Show the suspend count the task will be left with when detaching.
18479 @item set task exception-port
18480 @itemx set task excp
18481 @cindex task exception port, @sc{gnu} Hurd
18482 This command sets the task exception port to which @value{GDBN} will
18483 forward exceptions. The argument should be the value of the @dfn{send
18484 rights} of the task. @code{set task excp} is a shorthand alias.
18486 @item set noninvasive
18487 @cindex noninvasive task options
18488 This command switches @value{GDBN} to a mode that is the least
18489 invasive as far as interfering with the inferior is concerned. This
18490 is the same as using @code{set task pause}, @code{set exceptions}, and
18491 @code{set signals} to values opposite to the defaults.
18493 @item info send-rights
18494 @itemx info receive-rights
18495 @itemx info port-rights
18496 @itemx info port-sets
18497 @itemx info dead-names
18500 @cindex send rights, @sc{gnu} Hurd
18501 @cindex receive rights, @sc{gnu} Hurd
18502 @cindex port rights, @sc{gnu} Hurd
18503 @cindex port sets, @sc{gnu} Hurd
18504 @cindex dead names, @sc{gnu} Hurd
18505 These commands display information about, respectively, send rights,
18506 receive rights, port rights, port sets, and dead names of a task.
18507 There are also shorthand aliases: @code{info ports} for @code{info
18508 port-rights} and @code{info psets} for @code{info port-sets}.
18510 @item set thread pause
18511 @kindex set thread@r{, Hurd command}
18512 @cindex thread properties, @sc{gnu} Hurd
18513 @cindex pause current thread (@sc{gnu} Hurd)
18514 This command toggles current thread suspension when @value{GDBN} has
18515 control. Setting it to on takes effect immediately, and the current
18516 thread is suspended whenever @value{GDBN} gets control. Setting it to
18517 off will take effect the next time the inferior is continued.
18518 Normally, this command has no effect, since when @value{GDBN} has
18519 control, the whole task is suspended. However, if you used @code{set
18520 task pause off} (see above), this command comes in handy to suspend
18521 only the current thread.
18523 @item show thread pause
18524 @kindex show thread@r{, Hurd command}
18525 This command shows the state of current thread suspension.
18527 @item set thread run
18528 This command sets whether the current thread is allowed to run.
18530 @item show thread run
18531 Show whether the current thread is allowed to run.
18533 @item set thread detach-suspend-count
18534 @cindex thread suspend count, @sc{gnu} Hurd
18535 @cindex detach from thread, @sc{gnu} Hurd
18536 This command sets the suspend count @value{GDBN} will leave on a
18537 thread when detaching. This number is relative to the suspend count
18538 found by @value{GDBN} when it notices the thread; use @code{set thread
18539 takeover-suspend-count} to force it to an absolute value.
18541 @item show thread detach-suspend-count
18542 Show the suspend count @value{GDBN} will leave on the thread when
18545 @item set thread exception-port
18546 @itemx set thread excp
18547 Set the thread exception port to which to forward exceptions. This
18548 overrides the port set by @code{set task exception-port} (see above).
18549 @code{set thread excp} is the shorthand alias.
18551 @item set thread takeover-suspend-count
18552 Normally, @value{GDBN}'s thread suspend counts are relative to the
18553 value @value{GDBN} finds when it notices each thread. This command
18554 changes the suspend counts to be absolute instead.
18556 @item set thread default
18557 @itemx show thread default
18558 @cindex thread default settings, @sc{gnu} Hurd
18559 Each of the above @code{set thread} commands has a @code{set thread
18560 default} counterpart (e.g., @code{set thread default pause}, @code{set
18561 thread default exception-port}, etc.). The @code{thread default}
18562 variety of commands sets the default thread properties for all
18563 threads; you can then change the properties of individual threads with
18564 the non-default commands.
18569 @subsection QNX Neutrino
18570 @cindex QNX Neutrino
18572 @value{GDBN} provides the following commands specific to the QNX
18576 @item set debug nto-debug
18577 @kindex set debug nto-debug
18578 When set to on, enables debugging messages specific to the QNX
18581 @item show debug nto-debug
18582 @kindex show debug nto-debug
18583 Show the current state of QNX Neutrino messages.
18590 @value{GDBN} provides the following commands specific to the Darwin target:
18593 @item set debug darwin @var{num}
18594 @kindex set debug darwin
18595 When set to a non zero value, enables debugging messages specific to
18596 the Darwin support. Higher values produce more verbose output.
18598 @item show debug darwin
18599 @kindex show debug darwin
18600 Show the current state of Darwin messages.
18602 @item set debug mach-o @var{num}
18603 @kindex set debug mach-o
18604 When set to a non zero value, enables debugging messages while
18605 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18606 file format used on Darwin for object and executable files.) Higher
18607 values produce more verbose output. This is a command to diagnose
18608 problems internal to @value{GDBN} and should not be needed in normal
18611 @item show debug mach-o
18612 @kindex show debug mach-o
18613 Show the current state of Mach-O file messages.
18615 @item set mach-exceptions on
18616 @itemx set mach-exceptions off
18617 @kindex set mach-exceptions
18618 On Darwin, faults are first reported as a Mach exception and are then
18619 mapped to a Posix signal. Use this command to turn on trapping of
18620 Mach exceptions in the inferior. This might be sometimes useful to
18621 better understand the cause of a fault. The default is off.
18623 @item show mach-exceptions
18624 @kindex show mach-exceptions
18625 Show the current state of exceptions trapping.
18630 @section Embedded Operating Systems
18632 This section describes configurations involving the debugging of
18633 embedded operating systems that are available for several different
18637 * VxWorks:: Using @value{GDBN} with VxWorks
18640 @value{GDBN} includes the ability to debug programs running on
18641 various real-time operating systems.
18644 @subsection Using @value{GDBN} with VxWorks
18650 @kindex target vxworks
18651 @item target vxworks @var{machinename}
18652 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18653 is the target system's machine name or IP address.
18657 On VxWorks, @code{load} links @var{filename} dynamically on the
18658 current target system as well as adding its symbols in @value{GDBN}.
18660 @value{GDBN} enables developers to spawn and debug tasks running on networked
18661 VxWorks targets from a Unix host. Already-running tasks spawned from
18662 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18663 both the Unix host and on the VxWorks target. The program
18664 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18665 installed with the name @code{vxgdb}, to distinguish it from a
18666 @value{GDBN} for debugging programs on the host itself.)
18669 @item VxWorks-timeout @var{args}
18670 @kindex vxworks-timeout
18671 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18672 This option is set by the user, and @var{args} represents the number of
18673 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18674 your VxWorks target is a slow software simulator or is on the far side
18675 of a thin network line.
18678 The following information on connecting to VxWorks was current when
18679 this manual was produced; newer releases of VxWorks may use revised
18682 @findex INCLUDE_RDB
18683 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18684 to include the remote debugging interface routines in the VxWorks
18685 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18686 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18687 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18688 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18689 information on configuring and remaking VxWorks, see the manufacturer's
18691 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18693 Once you have included @file{rdb.a} in your VxWorks system image and set
18694 your Unix execution search path to find @value{GDBN}, you are ready to
18695 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18696 @code{vxgdb}, depending on your installation).
18698 @value{GDBN} comes up showing the prompt:
18705 * VxWorks Connection:: Connecting to VxWorks
18706 * VxWorks Download:: VxWorks download
18707 * VxWorks Attach:: Running tasks
18710 @node VxWorks Connection
18711 @subsubsection Connecting to VxWorks
18713 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18714 network. To connect to a target whose host name is ``@code{tt}'', type:
18717 (vxgdb) target vxworks tt
18721 @value{GDBN} displays messages like these:
18724 Attaching remote machine across net...
18729 @value{GDBN} then attempts to read the symbol tables of any object modules
18730 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18731 these files by searching the directories listed in the command search
18732 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18733 to find an object file, it displays a message such as:
18736 prog.o: No such file or directory.
18739 When this happens, add the appropriate directory to the search path with
18740 the @value{GDBN} command @code{path}, and execute the @code{target}
18743 @node VxWorks Download
18744 @subsubsection VxWorks Download
18746 @cindex download to VxWorks
18747 If you have connected to the VxWorks target and you want to debug an
18748 object that has not yet been loaded, you can use the @value{GDBN}
18749 @code{load} command to download a file from Unix to VxWorks
18750 incrementally. The object file given as an argument to the @code{load}
18751 command is actually opened twice: first by the VxWorks target in order
18752 to download the code, then by @value{GDBN} in order to read the symbol
18753 table. This can lead to problems if the current working directories on
18754 the two systems differ. If both systems have NFS mounted the same
18755 filesystems, you can avoid these problems by using absolute paths.
18756 Otherwise, it is simplest to set the working directory on both systems
18757 to the directory in which the object file resides, and then to reference
18758 the file by its name, without any path. For instance, a program
18759 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18760 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18761 program, type this on VxWorks:
18764 -> cd "@var{vxpath}/vw/demo/rdb"
18768 Then, in @value{GDBN}, type:
18771 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18772 (vxgdb) load prog.o
18775 @value{GDBN} displays a response similar to this:
18778 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18781 You can also use the @code{load} command to reload an object module
18782 after editing and recompiling the corresponding source file. Note that
18783 this makes @value{GDBN} delete all currently-defined breakpoints,
18784 auto-displays, and convenience variables, and to clear the value
18785 history. (This is necessary in order to preserve the integrity of
18786 debugger's data structures that reference the target system's symbol
18789 @node VxWorks Attach
18790 @subsubsection Running Tasks
18792 @cindex running VxWorks tasks
18793 You can also attach to an existing task using the @code{attach} command as
18797 (vxgdb) attach @var{task}
18801 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18802 or suspended when you attach to it. Running tasks are suspended at
18803 the time of attachment.
18805 @node Embedded Processors
18806 @section Embedded Processors
18808 This section goes into details specific to particular embedded
18811 @cindex send command to simulator
18812 Whenever a specific embedded processor has a simulator, @value{GDBN}
18813 allows to send an arbitrary command to the simulator.
18816 @item sim @var{command}
18817 @kindex sim@r{, a command}
18818 Send an arbitrary @var{command} string to the simulator. Consult the
18819 documentation for the specific simulator in use for information about
18820 acceptable commands.
18826 * M32R/D:: Renesas M32R/D
18827 * M68K:: Motorola M68K
18828 * MicroBlaze:: Xilinx MicroBlaze
18829 * MIPS Embedded:: MIPS Embedded
18830 * OpenRISC 1000:: OpenRisc 1000
18831 * PA:: HP PA Embedded
18832 * PowerPC Embedded:: PowerPC Embedded
18833 * Sparclet:: Tsqware Sparclet
18834 * Sparclite:: Fujitsu Sparclite
18835 * Z8000:: Zilog Z8000
18838 * Super-H:: Renesas Super-H
18847 @item target rdi @var{dev}
18848 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18849 use this target to communicate with both boards running the Angel
18850 monitor, or with the EmbeddedICE JTAG debug device.
18853 @item target rdp @var{dev}
18858 @value{GDBN} provides the following ARM-specific commands:
18861 @item set arm disassembler
18863 This commands selects from a list of disassembly styles. The
18864 @code{"std"} style is the standard style.
18866 @item show arm disassembler
18868 Show the current disassembly style.
18870 @item set arm apcs32
18871 @cindex ARM 32-bit mode
18872 This command toggles ARM operation mode between 32-bit and 26-bit.
18874 @item show arm apcs32
18875 Display the current usage of the ARM 32-bit mode.
18877 @item set arm fpu @var{fputype}
18878 This command sets the ARM floating-point unit (FPU) type. The
18879 argument @var{fputype} can be one of these:
18883 Determine the FPU type by querying the OS ABI.
18885 Software FPU, with mixed-endian doubles on little-endian ARM
18888 GCC-compiled FPA co-processor.
18890 Software FPU with pure-endian doubles.
18896 Show the current type of the FPU.
18899 This command forces @value{GDBN} to use the specified ABI.
18902 Show the currently used ABI.
18904 @item set arm fallback-mode (arm|thumb|auto)
18905 @value{GDBN} uses the symbol table, when available, to determine
18906 whether instructions are ARM or Thumb. This command controls
18907 @value{GDBN}'s default behavior when the symbol table is not
18908 available. The default is @samp{auto}, which causes @value{GDBN} to
18909 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18912 @item show arm fallback-mode
18913 Show the current fallback instruction mode.
18915 @item set arm force-mode (arm|thumb|auto)
18916 This command overrides use of the symbol table to determine whether
18917 instructions are ARM or Thumb. The default is @samp{auto}, which
18918 causes @value{GDBN} to use the symbol table and then the setting
18919 of @samp{set arm fallback-mode}.
18921 @item show arm force-mode
18922 Show the current forced instruction mode.
18924 @item set debug arm
18925 Toggle whether to display ARM-specific debugging messages from the ARM
18926 target support subsystem.
18928 @item show debug arm
18929 Show whether ARM-specific debugging messages are enabled.
18932 The following commands are available when an ARM target is debugged
18933 using the RDI interface:
18936 @item rdilogfile @r{[}@var{file}@r{]}
18938 @cindex ADP (Angel Debugger Protocol) logging
18939 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18940 With an argument, sets the log file to the specified @var{file}. With
18941 no argument, show the current log file name. The default log file is
18944 @item rdilogenable @r{[}@var{arg}@r{]}
18945 @kindex rdilogenable
18946 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18947 enables logging, with an argument 0 or @code{"no"} disables it. With
18948 no arguments displays the current setting. When logging is enabled,
18949 ADP packets exchanged between @value{GDBN} and the RDI target device
18950 are logged to a file.
18952 @item set rdiromatzero
18953 @kindex set rdiromatzero
18954 @cindex ROM at zero address, RDI
18955 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18956 vector catching is disabled, so that zero address can be used. If off
18957 (the default), vector catching is enabled. For this command to take
18958 effect, it needs to be invoked prior to the @code{target rdi} command.
18960 @item show rdiromatzero
18961 @kindex show rdiromatzero
18962 Show the current setting of ROM at zero address.
18964 @item set rdiheartbeat
18965 @kindex set rdiheartbeat
18966 @cindex RDI heartbeat
18967 Enable or disable RDI heartbeat packets. It is not recommended to
18968 turn on this option, since it confuses ARM and EPI JTAG interface, as
18969 well as the Angel monitor.
18971 @item show rdiheartbeat
18972 @kindex show rdiheartbeat
18973 Show the setting of RDI heartbeat packets.
18977 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18978 The @value{GDBN} ARM simulator accepts the following optional arguments.
18981 @item --swi-support=@var{type}
18982 Tell the simulator which SWI interfaces to support.
18983 @var{type} may be a comma separated list of the following values.
18984 The default value is @code{all}.
18997 @subsection Renesas M32R/D and M32R/SDI
19000 @kindex target m32r
19001 @item target m32r @var{dev}
19002 Renesas M32R/D ROM monitor.
19004 @kindex target m32rsdi
19005 @item target m32rsdi @var{dev}
19006 Renesas M32R SDI server, connected via parallel port to the board.
19009 The following @value{GDBN} commands are specific to the M32R monitor:
19012 @item set download-path @var{path}
19013 @kindex set download-path
19014 @cindex find downloadable @sc{srec} files (M32R)
19015 Set the default path for finding downloadable @sc{srec} files.
19017 @item show download-path
19018 @kindex show download-path
19019 Show the default path for downloadable @sc{srec} files.
19021 @item set board-address @var{addr}
19022 @kindex set board-address
19023 @cindex M32-EVA target board address
19024 Set the IP address for the M32R-EVA target board.
19026 @item show board-address
19027 @kindex show board-address
19028 Show the current IP address of the target board.
19030 @item set server-address @var{addr}
19031 @kindex set server-address
19032 @cindex download server address (M32R)
19033 Set the IP address for the download server, which is the @value{GDBN}'s
19036 @item show server-address
19037 @kindex show server-address
19038 Display the IP address of the download server.
19040 @item upload @r{[}@var{file}@r{]}
19041 @kindex upload@r{, M32R}
19042 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19043 upload capability. If no @var{file} argument is given, the current
19044 executable file is uploaded.
19046 @item tload @r{[}@var{file}@r{]}
19047 @kindex tload@r{, M32R}
19048 Test the @code{upload} command.
19051 The following commands are available for M32R/SDI:
19056 @cindex reset SDI connection, M32R
19057 This command resets the SDI connection.
19061 This command shows the SDI connection status.
19064 @kindex debug_chaos
19065 @cindex M32R/Chaos debugging
19066 Instructs the remote that M32R/Chaos debugging is to be used.
19068 @item use_debug_dma
19069 @kindex use_debug_dma
19070 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19073 @kindex use_mon_code
19074 Instructs the remote to use the MON_CODE method of accessing memory.
19077 @kindex use_ib_break
19078 Instructs the remote to set breakpoints by IB break.
19080 @item use_dbt_break
19081 @kindex use_dbt_break
19082 Instructs the remote to set breakpoints by DBT.
19088 The Motorola m68k configuration includes ColdFire support, and a
19089 target command for the following ROM monitor.
19093 @kindex target dbug
19094 @item target dbug @var{dev}
19095 dBUG ROM monitor for Motorola ColdFire.
19100 @subsection MicroBlaze
19101 @cindex Xilinx MicroBlaze
19102 @cindex XMD, Xilinx Microprocessor Debugger
19104 The MicroBlaze is a soft-core processor supported on various Xilinx
19105 FPGAs, such as Spartan or Virtex series. Boards with these processors
19106 usually have JTAG ports which connect to a host system running the Xilinx
19107 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19108 This host system is used to download the configuration bitstream to
19109 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19110 communicates with the target board using the JTAG interface and
19111 presents a @code{gdbserver} interface to the board. By default
19112 @code{xmd} uses port @code{1234}. (While it is possible to change
19113 this default port, it requires the use of undocumented @code{xmd}
19114 commands. Contact Xilinx support if you need to do this.)
19116 Use these GDB commands to connect to the MicroBlaze target processor.
19119 @item target remote :1234
19120 Use this command to connect to the target if you are running @value{GDBN}
19121 on the same system as @code{xmd}.
19123 @item target remote @var{xmd-host}:1234
19124 Use this command to connect to the target if it is connected to @code{xmd}
19125 running on a different system named @var{xmd-host}.
19128 Use this command to download a program to the MicroBlaze target.
19130 @item set debug microblaze @var{n}
19131 Enable MicroBlaze-specific debugging messages if non-zero.
19133 @item show debug microblaze @var{n}
19134 Show MicroBlaze-specific debugging level.
19137 @node MIPS Embedded
19138 @subsection MIPS Embedded
19140 @cindex MIPS boards
19141 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19142 MIPS board attached to a serial line. This is available when
19143 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19146 Use these @value{GDBN} commands to specify the connection to your target board:
19149 @item target mips @var{port}
19150 @kindex target mips @var{port}
19151 To run a program on the board, start up @code{@value{GDBP}} with the
19152 name of your program as the argument. To connect to the board, use the
19153 command @samp{target mips @var{port}}, where @var{port} is the name of
19154 the serial port connected to the board. If the program has not already
19155 been downloaded to the board, you may use the @code{load} command to
19156 download it. You can then use all the usual @value{GDBN} commands.
19158 For example, this sequence connects to the target board through a serial
19159 port, and loads and runs a program called @var{prog} through the
19163 host$ @value{GDBP} @var{prog}
19164 @value{GDBN} is free software and @dots{}
19165 (@value{GDBP}) target mips /dev/ttyb
19166 (@value{GDBP}) load @var{prog}
19170 @item target mips @var{hostname}:@var{portnumber}
19171 On some @value{GDBN} host configurations, you can specify a TCP
19172 connection (for instance, to a serial line managed by a terminal
19173 concentrator) instead of a serial port, using the syntax
19174 @samp{@var{hostname}:@var{portnumber}}.
19176 @item target pmon @var{port}
19177 @kindex target pmon @var{port}
19180 @item target ddb @var{port}
19181 @kindex target ddb @var{port}
19182 NEC's DDB variant of PMON for Vr4300.
19184 @item target lsi @var{port}
19185 @kindex target lsi @var{port}
19186 LSI variant of PMON.
19188 @kindex target r3900
19189 @item target r3900 @var{dev}
19190 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19192 @kindex target array
19193 @item target array @var{dev}
19194 Array Tech LSI33K RAID controller board.
19200 @value{GDBN} also supports these special commands for MIPS targets:
19203 @item set mipsfpu double
19204 @itemx set mipsfpu single
19205 @itemx set mipsfpu none
19206 @itemx set mipsfpu auto
19207 @itemx show mipsfpu
19208 @kindex set mipsfpu
19209 @kindex show mipsfpu
19210 @cindex MIPS remote floating point
19211 @cindex floating point, MIPS remote
19212 If your target board does not support the MIPS floating point
19213 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19214 need this, you may wish to put the command in your @value{GDBN} init
19215 file). This tells @value{GDBN} how to find the return value of
19216 functions which return floating point values. It also allows
19217 @value{GDBN} to avoid saving the floating point registers when calling
19218 functions on the board. If you are using a floating point coprocessor
19219 with only single precision floating point support, as on the @sc{r4650}
19220 processor, use the command @samp{set mipsfpu single}. The default
19221 double precision floating point coprocessor may be selected using
19222 @samp{set mipsfpu double}.
19224 In previous versions the only choices were double precision or no
19225 floating point, so @samp{set mipsfpu on} will select double precision
19226 and @samp{set mipsfpu off} will select no floating point.
19228 As usual, you can inquire about the @code{mipsfpu} variable with
19229 @samp{show mipsfpu}.
19231 @item set timeout @var{seconds}
19232 @itemx set retransmit-timeout @var{seconds}
19233 @itemx show timeout
19234 @itemx show retransmit-timeout
19235 @cindex @code{timeout}, MIPS protocol
19236 @cindex @code{retransmit-timeout}, MIPS protocol
19237 @kindex set timeout
19238 @kindex show timeout
19239 @kindex set retransmit-timeout
19240 @kindex show retransmit-timeout
19241 You can control the timeout used while waiting for a packet, in the MIPS
19242 remote protocol, with the @code{set timeout @var{seconds}} command. The
19243 default is 5 seconds. Similarly, you can control the timeout used while
19244 waiting for an acknowledgment of a packet with the @code{set
19245 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19246 You can inspect both values with @code{show timeout} and @code{show
19247 retransmit-timeout}. (These commands are @emph{only} available when
19248 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19250 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19251 is waiting for your program to stop. In that case, @value{GDBN} waits
19252 forever because it has no way of knowing how long the program is going
19253 to run before stopping.
19255 @item set syn-garbage-limit @var{num}
19256 @kindex set syn-garbage-limit@r{, MIPS remote}
19257 @cindex synchronize with remote MIPS target
19258 Limit the maximum number of characters @value{GDBN} should ignore when
19259 it tries to synchronize with the remote target. The default is 10
19260 characters. Setting the limit to -1 means there's no limit.
19262 @item show syn-garbage-limit
19263 @kindex show syn-garbage-limit@r{, MIPS remote}
19264 Show the current limit on the number of characters to ignore when
19265 trying to synchronize with the remote system.
19267 @item set monitor-prompt @var{prompt}
19268 @kindex set monitor-prompt@r{, MIPS remote}
19269 @cindex remote monitor prompt
19270 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19271 remote monitor. The default depends on the target:
19281 @item show monitor-prompt
19282 @kindex show monitor-prompt@r{, MIPS remote}
19283 Show the current strings @value{GDBN} expects as the prompt from the
19286 @item set monitor-warnings
19287 @kindex set monitor-warnings@r{, MIPS remote}
19288 Enable or disable monitor warnings about hardware breakpoints. This
19289 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19290 display warning messages whose codes are returned by the @code{lsi}
19291 PMON monitor for breakpoint commands.
19293 @item show monitor-warnings
19294 @kindex show monitor-warnings@r{, MIPS remote}
19295 Show the current setting of printing monitor warnings.
19297 @item pmon @var{command}
19298 @kindex pmon@r{, MIPS remote}
19299 @cindex send PMON command
19300 This command allows sending an arbitrary @var{command} string to the
19301 monitor. The monitor must be in debug mode for this to work.
19304 @node OpenRISC 1000
19305 @subsection OpenRISC 1000
19306 @cindex OpenRISC 1000
19308 @cindex or1k boards
19309 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19310 about platform and commands.
19314 @kindex target jtag
19315 @item target jtag jtag://@var{host}:@var{port}
19317 Connects to remote JTAG server.
19318 JTAG remote server can be either an or1ksim or JTAG server,
19319 connected via parallel port to the board.
19321 Example: @code{target jtag jtag://localhost:9999}
19324 @item or1ksim @var{command}
19325 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19326 Simulator, proprietary commands can be executed.
19328 @kindex info or1k spr
19329 @item info or1k spr
19330 Displays spr groups.
19332 @item info or1k spr @var{group}
19333 @itemx info or1k spr @var{groupno}
19334 Displays register names in selected group.
19336 @item info or1k spr @var{group} @var{register}
19337 @itemx info or1k spr @var{register}
19338 @itemx info or1k spr @var{groupno} @var{registerno}
19339 @itemx info or1k spr @var{registerno}
19340 Shows information about specified spr register.
19343 @item spr @var{group} @var{register} @var{value}
19344 @itemx spr @var{register @var{value}}
19345 @itemx spr @var{groupno} @var{registerno @var{value}}
19346 @itemx spr @var{registerno @var{value}}
19347 Writes @var{value} to specified spr register.
19350 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19351 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19352 program execution and is thus much faster. Hardware breakpoints/watchpoint
19353 triggers can be set using:
19356 Load effective address/data
19358 Store effective address/data
19360 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19365 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19366 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19368 @code{htrace} commands:
19369 @cindex OpenRISC 1000 htrace
19372 @item hwatch @var{conditional}
19373 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19374 or Data. For example:
19376 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19378 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19382 Display information about current HW trace configuration.
19384 @item htrace trigger @var{conditional}
19385 Set starting criteria for HW trace.
19387 @item htrace qualifier @var{conditional}
19388 Set acquisition qualifier for HW trace.
19390 @item htrace stop @var{conditional}
19391 Set HW trace stopping criteria.
19393 @item htrace record [@var{data}]*
19394 Selects the data to be recorded, when qualifier is met and HW trace was
19397 @item htrace enable
19398 @itemx htrace disable
19399 Enables/disables the HW trace.
19401 @item htrace rewind [@var{filename}]
19402 Clears currently recorded trace data.
19404 If filename is specified, new trace file is made and any newly collected data
19405 will be written there.
19407 @item htrace print [@var{start} [@var{len}]]
19408 Prints trace buffer, using current record configuration.
19410 @item htrace mode continuous
19411 Set continuous trace mode.
19413 @item htrace mode suspend
19414 Set suspend trace mode.
19418 @node PowerPC Embedded
19419 @subsection PowerPC Embedded
19421 @cindex DVC register
19422 @value{GDBN} supports using the DVC (Data Value Compare) register to
19423 implement in hardware simple hardware watchpoint conditions of the form:
19426 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19427 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19430 The DVC register will be automatically used when @value{GDBN} detects
19431 such pattern in a condition expression, and the created watchpoint uses one
19432 debug register (either the @code{exact-watchpoints} option is on and the
19433 variable is scalar, or the variable has a length of one byte). This feature
19434 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19437 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19438 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19439 in which case watchpoints using only one debug register are created when
19440 watching variables of scalar types.
19442 You can create an artificial array to watch an arbitrary memory
19443 region using one of the following commands (@pxref{Expressions}):
19446 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19447 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19450 PowerPC embedded processors support masked watchpoints. See the discussion
19451 about the @code{mask} argument in @ref{Set Watchpoints}.
19453 @cindex ranged breakpoint
19454 PowerPC embedded processors support hardware accelerated
19455 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19456 the inferior whenever it executes an instruction at any address within
19457 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19458 use the @code{break-range} command.
19460 @value{GDBN} provides the following PowerPC-specific commands:
19463 @kindex break-range
19464 @item break-range @var{start-location}, @var{end-location}
19465 Set a breakpoint for an address range.
19466 @var{start-location} and @var{end-location} can specify a function name,
19467 a line number, an offset of lines from the current line or from the start
19468 location, or an address of an instruction (see @ref{Specify Location},
19469 for a list of all the possible ways to specify a @var{location}.)
19470 The breakpoint will stop execution of the inferior whenever it
19471 executes an instruction at any address within the specified range,
19472 (including @var{start-location} and @var{end-location}.)
19474 @kindex set powerpc
19475 @item set powerpc soft-float
19476 @itemx show powerpc soft-float
19477 Force @value{GDBN} to use (or not use) a software floating point calling
19478 convention. By default, @value{GDBN} selects the calling convention based
19479 on the selected architecture and the provided executable file.
19481 @item set powerpc vector-abi
19482 @itemx show powerpc vector-abi
19483 Force @value{GDBN} to use the specified calling convention for vector
19484 arguments and return values. The valid options are @samp{auto};
19485 @samp{generic}, to avoid vector registers even if they are present;
19486 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19487 registers. By default, @value{GDBN} selects the calling convention
19488 based on the selected architecture and the provided executable file.
19490 @item set powerpc exact-watchpoints
19491 @itemx show powerpc exact-watchpoints
19492 Allow @value{GDBN} to use only one debug register when watching a variable
19493 of scalar type, thus assuming that the variable is accessed through the
19494 address of its first byte.
19496 @kindex target dink32
19497 @item target dink32 @var{dev}
19498 DINK32 ROM monitor.
19500 @kindex target ppcbug
19501 @item target ppcbug @var{dev}
19502 @kindex target ppcbug1
19503 @item target ppcbug1 @var{dev}
19504 PPCBUG ROM monitor for PowerPC.
19507 @item target sds @var{dev}
19508 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19511 @cindex SDS protocol
19512 The following commands specific to the SDS protocol are supported
19516 @item set sdstimeout @var{nsec}
19517 @kindex set sdstimeout
19518 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19519 default is 2 seconds.
19521 @item show sdstimeout
19522 @kindex show sdstimeout
19523 Show the current value of the SDS timeout.
19525 @item sds @var{command}
19526 @kindex sds@r{, a command}
19527 Send the specified @var{command} string to the SDS monitor.
19532 @subsection HP PA Embedded
19536 @kindex target op50n
19537 @item target op50n @var{dev}
19538 OP50N monitor, running on an OKI HPPA board.
19540 @kindex target w89k
19541 @item target w89k @var{dev}
19542 W89K monitor, running on a Winbond HPPA board.
19547 @subsection Tsqware Sparclet
19551 @value{GDBN} enables developers to debug tasks running on
19552 Sparclet targets from a Unix host.
19553 @value{GDBN} uses code that runs on
19554 both the Unix host and on the Sparclet target. The program
19555 @code{@value{GDBP}} is installed and executed on the Unix host.
19558 @item remotetimeout @var{args}
19559 @kindex remotetimeout
19560 @value{GDBN} supports the option @code{remotetimeout}.
19561 This option is set by the user, and @var{args} represents the number of
19562 seconds @value{GDBN} waits for responses.
19565 @cindex compiling, on Sparclet
19566 When compiling for debugging, include the options @samp{-g} to get debug
19567 information and @samp{-Ttext} to relocate the program to where you wish to
19568 load it on the target. You may also want to add the options @samp{-n} or
19569 @samp{-N} in order to reduce the size of the sections. Example:
19572 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19575 You can use @code{objdump} to verify that the addresses are what you intended:
19578 sparclet-aout-objdump --headers --syms prog
19581 @cindex running, on Sparclet
19583 your Unix execution search path to find @value{GDBN}, you are ready to
19584 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19585 (or @code{sparclet-aout-gdb}, depending on your installation).
19587 @value{GDBN} comes up showing the prompt:
19594 * Sparclet File:: Setting the file to debug
19595 * Sparclet Connection:: Connecting to Sparclet
19596 * Sparclet Download:: Sparclet download
19597 * Sparclet Execution:: Running and debugging
19600 @node Sparclet File
19601 @subsubsection Setting File to Debug
19603 The @value{GDBN} command @code{file} lets you choose with program to debug.
19606 (gdbslet) file prog
19610 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19611 @value{GDBN} locates
19612 the file by searching the directories listed in the command search
19614 If the file was compiled with debug information (option @samp{-g}), source
19615 files will be searched as well.
19616 @value{GDBN} locates
19617 the source files by searching the directories listed in the directory search
19618 path (@pxref{Environment, ,Your Program's Environment}).
19620 to find a file, it displays a message such as:
19623 prog: No such file or directory.
19626 When this happens, add the appropriate directories to the search paths with
19627 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19628 @code{target} command again.
19630 @node Sparclet Connection
19631 @subsubsection Connecting to Sparclet
19633 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19634 To connect to a target on serial port ``@code{ttya}'', type:
19637 (gdbslet) target sparclet /dev/ttya
19638 Remote target sparclet connected to /dev/ttya
19639 main () at ../prog.c:3
19643 @value{GDBN} displays messages like these:
19649 @node Sparclet Download
19650 @subsubsection Sparclet Download
19652 @cindex download to Sparclet
19653 Once connected to the Sparclet target,
19654 you can use the @value{GDBN}
19655 @code{load} command to download the file from the host to the target.
19656 The file name and load offset should be given as arguments to the @code{load}
19658 Since the file format is aout, the program must be loaded to the starting
19659 address. You can use @code{objdump} to find out what this value is. The load
19660 offset is an offset which is added to the VMA (virtual memory address)
19661 of each of the file's sections.
19662 For instance, if the program
19663 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19664 and bss at 0x12010170, in @value{GDBN}, type:
19667 (gdbslet) load prog 0x12010000
19668 Loading section .text, size 0xdb0 vma 0x12010000
19671 If the code is loaded at a different address then what the program was linked
19672 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19673 to tell @value{GDBN} where to map the symbol table.
19675 @node Sparclet Execution
19676 @subsubsection Running and Debugging
19678 @cindex running and debugging Sparclet programs
19679 You can now begin debugging the task using @value{GDBN}'s execution control
19680 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19681 manual for the list of commands.
19685 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19687 Starting program: prog
19688 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19689 3 char *symarg = 0;
19691 4 char *execarg = "hello!";
19696 @subsection Fujitsu Sparclite
19700 @kindex target sparclite
19701 @item target sparclite @var{dev}
19702 Fujitsu sparclite boards, used only for the purpose of loading.
19703 You must use an additional command to debug the program.
19704 For example: target remote @var{dev} using @value{GDBN} standard
19710 @subsection Zilog Z8000
19713 @cindex simulator, Z8000
19714 @cindex Zilog Z8000 simulator
19716 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19719 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19720 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19721 segmented variant). The simulator recognizes which architecture is
19722 appropriate by inspecting the object code.
19725 @item target sim @var{args}
19727 @kindex target sim@r{, with Z8000}
19728 Debug programs on a simulated CPU. If the simulator supports setup
19729 options, specify them via @var{args}.
19733 After specifying this target, you can debug programs for the simulated
19734 CPU in the same style as programs for your host computer; use the
19735 @code{file} command to load a new program image, the @code{run} command
19736 to run your program, and so on.
19738 As well as making available all the usual machine registers
19739 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19740 additional items of information as specially named registers:
19745 Counts clock-ticks in the simulator.
19748 Counts instructions run in the simulator.
19751 Execution time in 60ths of a second.
19755 You can refer to these values in @value{GDBN} expressions with the usual
19756 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19757 conditional breakpoint that suspends only after at least 5000
19758 simulated clock ticks.
19761 @subsection Atmel AVR
19764 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19765 following AVR-specific commands:
19768 @item info io_registers
19769 @kindex info io_registers@r{, AVR}
19770 @cindex I/O registers (Atmel AVR)
19771 This command displays information about the AVR I/O registers. For
19772 each register, @value{GDBN} prints its number and value.
19779 When configured for debugging CRIS, @value{GDBN} provides the
19780 following CRIS-specific commands:
19783 @item set cris-version @var{ver}
19784 @cindex CRIS version
19785 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19786 The CRIS version affects register names and sizes. This command is useful in
19787 case autodetection of the CRIS version fails.
19789 @item show cris-version
19790 Show the current CRIS version.
19792 @item set cris-dwarf2-cfi
19793 @cindex DWARF-2 CFI and CRIS
19794 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19795 Change to @samp{off} when using @code{gcc-cris} whose version is below
19798 @item show cris-dwarf2-cfi
19799 Show the current state of using DWARF-2 CFI.
19801 @item set cris-mode @var{mode}
19803 Set the current CRIS mode to @var{mode}. It should only be changed when
19804 debugging in guru mode, in which case it should be set to
19805 @samp{guru} (the default is @samp{normal}).
19807 @item show cris-mode
19808 Show the current CRIS mode.
19812 @subsection Renesas Super-H
19815 For the Renesas Super-H processor, @value{GDBN} provides these
19820 @kindex regs@r{, Super-H}
19821 Show the values of all Super-H registers.
19823 @item set sh calling-convention @var{convention}
19824 @kindex set sh calling-convention
19825 Set the calling-convention used when calling functions from @value{GDBN}.
19826 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19827 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19828 convention. If the DWARF-2 information of the called function specifies
19829 that the function follows the Renesas calling convention, the function
19830 is called using the Renesas calling convention. If the calling convention
19831 is set to @samp{renesas}, the Renesas calling convention is always used,
19832 regardless of the DWARF-2 information. This can be used to override the
19833 default of @samp{gcc} if debug information is missing, or the compiler
19834 does not emit the DWARF-2 calling convention entry for a function.
19836 @item show sh calling-convention
19837 @kindex show sh calling-convention
19838 Show the current calling convention setting.
19843 @node Architectures
19844 @section Architectures
19846 This section describes characteristics of architectures that affect
19847 all uses of @value{GDBN} with the architecture, both native and cross.
19854 * HPPA:: HP PA architecture
19855 * SPU:: Cell Broadband Engine SPU architecture
19860 @subsection x86 Architecture-specific Issues
19863 @item set struct-convention @var{mode}
19864 @kindex set struct-convention
19865 @cindex struct return convention
19866 @cindex struct/union returned in registers
19867 Set the convention used by the inferior to return @code{struct}s and
19868 @code{union}s from functions to @var{mode}. Possible values of
19869 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19870 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19871 are returned on the stack, while @code{"reg"} means that a
19872 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19873 be returned in a register.
19875 @item show struct-convention
19876 @kindex show struct-convention
19877 Show the current setting of the convention to return @code{struct}s
19886 @kindex set rstack_high_address
19887 @cindex AMD 29K register stack
19888 @cindex register stack, AMD29K
19889 @item set rstack_high_address @var{address}
19890 On AMD 29000 family processors, registers are saved in a separate
19891 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19892 extent of this stack. Normally, @value{GDBN} just assumes that the
19893 stack is ``large enough''. This may result in @value{GDBN} referencing
19894 memory locations that do not exist. If necessary, you can get around
19895 this problem by specifying the ending address of the register stack with
19896 the @code{set rstack_high_address} command. The argument should be an
19897 address, which you probably want to precede with @samp{0x} to specify in
19900 @kindex show rstack_high_address
19901 @item show rstack_high_address
19902 Display the current limit of the register stack, on AMD 29000 family
19910 See the following section.
19915 @cindex stack on Alpha
19916 @cindex stack on MIPS
19917 @cindex Alpha stack
19919 Alpha- and MIPS-based computers use an unusual stack frame, which
19920 sometimes requires @value{GDBN} to search backward in the object code to
19921 find the beginning of a function.
19923 @cindex response time, MIPS debugging
19924 To improve response time (especially for embedded applications, where
19925 @value{GDBN} may be restricted to a slow serial line for this search)
19926 you may want to limit the size of this search, using one of these
19930 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19931 @item set heuristic-fence-post @var{limit}
19932 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19933 search for the beginning of a function. A value of @var{0} (the
19934 default) means there is no limit. However, except for @var{0}, the
19935 larger the limit the more bytes @code{heuristic-fence-post} must search
19936 and therefore the longer it takes to run. You should only need to use
19937 this command when debugging a stripped executable.
19939 @item show heuristic-fence-post
19940 Display the current limit.
19944 These commands are available @emph{only} when @value{GDBN} is configured
19945 for debugging programs on Alpha or MIPS processors.
19947 Several MIPS-specific commands are available when debugging MIPS
19951 @item set mips abi @var{arg}
19952 @kindex set mips abi
19953 @cindex set ABI for MIPS
19954 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19955 values of @var{arg} are:
19959 The default ABI associated with the current binary (this is the
19969 @item show mips abi
19970 @kindex show mips abi
19971 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19974 @itemx show mipsfpu
19975 @xref{MIPS Embedded, set mipsfpu}.
19977 @item set mips mask-address @var{arg}
19978 @kindex set mips mask-address
19979 @cindex MIPS addresses, masking
19980 This command determines whether the most-significant 32 bits of 64-bit
19981 MIPS addresses are masked off. The argument @var{arg} can be
19982 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19983 setting, which lets @value{GDBN} determine the correct value.
19985 @item show mips mask-address
19986 @kindex show mips mask-address
19987 Show whether the upper 32 bits of MIPS addresses are masked off or
19990 @item set remote-mips64-transfers-32bit-regs
19991 @kindex set remote-mips64-transfers-32bit-regs
19992 This command controls compatibility with 64-bit MIPS targets that
19993 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19994 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19995 and 64 bits for other registers, set this option to @samp{on}.
19997 @item show remote-mips64-transfers-32bit-regs
19998 @kindex show remote-mips64-transfers-32bit-regs
19999 Show the current setting of compatibility with older MIPS 64 targets.
20001 @item set debug mips
20002 @kindex set debug mips
20003 This command turns on and off debugging messages for the MIPS-specific
20004 target code in @value{GDBN}.
20006 @item show debug mips
20007 @kindex show debug mips
20008 Show the current setting of MIPS debugging messages.
20014 @cindex HPPA support
20016 When @value{GDBN} is debugging the HP PA architecture, it provides the
20017 following special commands:
20020 @item set debug hppa
20021 @kindex set debug hppa
20022 This command determines whether HPPA architecture-specific debugging
20023 messages are to be displayed.
20025 @item show debug hppa
20026 Show whether HPPA debugging messages are displayed.
20028 @item maint print unwind @var{address}
20029 @kindex maint print unwind@r{, HPPA}
20030 This command displays the contents of the unwind table entry at the
20031 given @var{address}.
20037 @subsection Cell Broadband Engine SPU architecture
20038 @cindex Cell Broadband Engine
20041 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20042 it provides the following special commands:
20045 @item info spu event
20047 Display SPU event facility status. Shows current event mask
20048 and pending event status.
20050 @item info spu signal
20051 Display SPU signal notification facility status. Shows pending
20052 signal-control word and signal notification mode of both signal
20053 notification channels.
20055 @item info spu mailbox
20056 Display SPU mailbox facility status. Shows all pending entries,
20057 in order of processing, in each of the SPU Write Outbound,
20058 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20061 Display MFC DMA status. Shows all pending commands in the MFC
20062 DMA queue. For each entry, opcode, tag, class IDs, effective
20063 and local store addresses and transfer size are shown.
20065 @item info spu proxydma
20066 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20067 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20068 and local store addresses and transfer size are shown.
20072 When @value{GDBN} is debugging a combined PowerPC/SPU application
20073 on the Cell Broadband Engine, it provides in addition the following
20077 @item set spu stop-on-load @var{arg}
20079 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20080 will give control to the user when a new SPE thread enters its @code{main}
20081 function. The default is @code{off}.
20083 @item show spu stop-on-load
20085 Show whether to stop for new SPE threads.
20087 @item set spu auto-flush-cache @var{arg}
20088 Set whether to automatically flush the software-managed cache. When set to
20089 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20090 cache to be flushed whenever SPE execution stops. This provides a consistent
20091 view of PowerPC memory that is accessed via the cache. If an application
20092 does not use the software-managed cache, this option has no effect.
20094 @item show spu auto-flush-cache
20095 Show whether to automatically flush the software-managed cache.
20100 @subsection PowerPC
20101 @cindex PowerPC architecture
20103 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20104 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20105 numbers stored in the floating point registers. These values must be stored
20106 in two consecutive registers, always starting at an even register like
20107 @code{f0} or @code{f2}.
20109 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20110 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20111 @code{f2} and @code{f3} for @code{$dl1} and so on.
20113 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20114 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20117 @node Controlling GDB
20118 @chapter Controlling @value{GDBN}
20120 You can alter the way @value{GDBN} interacts with you by using the
20121 @code{set} command. For commands controlling how @value{GDBN} displays
20122 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20127 * Editing:: Command editing
20128 * Command History:: Command history
20129 * Screen Size:: Screen size
20130 * Numbers:: Numbers
20131 * ABI:: Configuring the current ABI
20132 * Messages/Warnings:: Optional warnings and messages
20133 * Debugging Output:: Optional messages about internal happenings
20134 * Other Misc Settings:: Other Miscellaneous Settings
20142 @value{GDBN} indicates its readiness to read a command by printing a string
20143 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20144 can change the prompt string with the @code{set prompt} command. For
20145 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20146 the prompt in one of the @value{GDBN} sessions so that you can always tell
20147 which one you are talking to.
20149 @emph{Note:} @code{set prompt} does not add a space for you after the
20150 prompt you set. This allows you to set a prompt which ends in a space
20151 or a prompt that does not.
20155 @item set prompt @var{newprompt}
20156 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20158 @kindex show prompt
20160 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20163 Versions of @value{GDBN} that ship with Python scripting enabled have
20164 prompt extensions. The commands for interacting with these extensions
20168 @kindex set extended-prompt
20169 @item set extended-prompt @var{prompt}
20170 Set an extended prompt that allows for substitutions.
20171 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20172 substitution. Any escape sequences specified as part of the prompt
20173 string are replaced with the corresponding strings each time the prompt
20179 set extended-prompt Current working directory: \w (gdb)
20182 Note that when an extended-prompt is set, it takes control of the
20183 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20185 @kindex show extended-prompt
20186 @item show extended-prompt
20187 Prints the extended prompt. Any escape sequences specified as part of
20188 the prompt string with @code{set extended-prompt}, are replaced with the
20189 corresponding strings each time the prompt is displayed.
20193 @section Command Editing
20195 @cindex command line editing
20197 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20198 @sc{gnu} library provides consistent behavior for programs which provide a
20199 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20200 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20201 substitution, and a storage and recall of command history across
20202 debugging sessions.
20204 You may control the behavior of command line editing in @value{GDBN} with the
20205 command @code{set}.
20208 @kindex set editing
20211 @itemx set editing on
20212 Enable command line editing (enabled by default).
20214 @item set editing off
20215 Disable command line editing.
20217 @kindex show editing
20219 Show whether command line editing is enabled.
20222 @ifset SYSTEM_READLINE
20223 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20225 @ifclear SYSTEM_READLINE
20226 @xref{Command Line Editing},
20228 for more details about the Readline
20229 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20230 encouraged to read that chapter.
20232 @node Command History
20233 @section Command History
20234 @cindex command history
20236 @value{GDBN} can keep track of the commands you type during your
20237 debugging sessions, so that you can be certain of precisely what
20238 happened. Use these commands to manage the @value{GDBN} command
20241 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20242 package, to provide the history facility.
20243 @ifset SYSTEM_READLINE
20244 @xref{Using History Interactively, , , history, GNU History Library},
20246 @ifclear SYSTEM_READLINE
20247 @xref{Using History Interactively},
20249 for the detailed description of the History library.
20251 To issue a command to @value{GDBN} without affecting certain aspects of
20252 the state which is seen by users, prefix it with @samp{server }
20253 (@pxref{Server Prefix}). This
20254 means that this command will not affect the command history, nor will it
20255 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20256 pressed on a line by itself.
20258 @cindex @code{server}, command prefix
20259 The server prefix does not affect the recording of values into the value
20260 history; to print a value without recording it into the value history,
20261 use the @code{output} command instead of the @code{print} command.
20263 Here is the description of @value{GDBN} commands related to command
20267 @cindex history substitution
20268 @cindex history file
20269 @kindex set history filename
20270 @cindex @env{GDBHISTFILE}, environment variable
20271 @item set history filename @var{fname}
20272 Set the name of the @value{GDBN} command history file to @var{fname}.
20273 This is the file where @value{GDBN} reads an initial command history
20274 list, and where it writes the command history from this session when it
20275 exits. You can access this list through history expansion or through
20276 the history command editing characters listed below. This file defaults
20277 to the value of the environment variable @code{GDBHISTFILE}, or to
20278 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20281 @cindex save command history
20282 @kindex set history save
20283 @item set history save
20284 @itemx set history save on
20285 Record command history in a file, whose name may be specified with the
20286 @code{set history filename} command. By default, this option is disabled.
20288 @item set history save off
20289 Stop recording command history in a file.
20291 @cindex history size
20292 @kindex set history size
20293 @cindex @env{HISTSIZE}, environment variable
20294 @item set history size @var{size}
20295 Set the number of commands which @value{GDBN} keeps in its history list.
20296 This defaults to the value of the environment variable
20297 @code{HISTSIZE}, or to 256 if this variable is not set.
20300 History expansion assigns special meaning to the character @kbd{!}.
20301 @ifset SYSTEM_READLINE
20302 @xref{Event Designators, , , history, GNU History Library},
20304 @ifclear SYSTEM_READLINE
20305 @xref{Event Designators},
20309 @cindex history expansion, turn on/off
20310 Since @kbd{!} is also the logical not operator in C, history expansion
20311 is off by default. If you decide to enable history expansion with the
20312 @code{set history expansion on} command, you may sometimes need to
20313 follow @kbd{!} (when it is used as logical not, in an expression) with
20314 a space or a tab to prevent it from being expanded. The readline
20315 history facilities do not attempt substitution on the strings
20316 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20318 The commands to control history expansion are:
20321 @item set history expansion on
20322 @itemx set history expansion
20323 @kindex set history expansion
20324 Enable history expansion. History expansion is off by default.
20326 @item set history expansion off
20327 Disable history expansion.
20330 @kindex show history
20332 @itemx show history filename
20333 @itemx show history save
20334 @itemx show history size
20335 @itemx show history expansion
20336 These commands display the state of the @value{GDBN} history parameters.
20337 @code{show history} by itself displays all four states.
20342 @kindex show commands
20343 @cindex show last commands
20344 @cindex display command history
20345 @item show commands
20346 Display the last ten commands in the command history.
20348 @item show commands @var{n}
20349 Print ten commands centered on command number @var{n}.
20351 @item show commands +
20352 Print ten commands just after the commands last printed.
20356 @section Screen Size
20357 @cindex size of screen
20358 @cindex pauses in output
20360 Certain commands to @value{GDBN} may produce large amounts of
20361 information output to the screen. To help you read all of it,
20362 @value{GDBN} pauses and asks you for input at the end of each page of
20363 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20364 to discard the remaining output. Also, the screen width setting
20365 determines when to wrap lines of output. Depending on what is being
20366 printed, @value{GDBN} tries to break the line at a readable place,
20367 rather than simply letting it overflow onto the following line.
20369 Normally @value{GDBN} knows the size of the screen from the terminal
20370 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20371 together with the value of the @code{TERM} environment variable and the
20372 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20373 you can override it with the @code{set height} and @code{set
20380 @kindex show height
20381 @item set height @var{lpp}
20383 @itemx set width @var{cpl}
20385 These @code{set} commands specify a screen height of @var{lpp} lines and
20386 a screen width of @var{cpl} characters. The associated @code{show}
20387 commands display the current settings.
20389 If you specify a height of zero lines, @value{GDBN} does not pause during
20390 output no matter how long the output is. This is useful if output is to a
20391 file or to an editor buffer.
20393 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20394 from wrapping its output.
20396 @item set pagination on
20397 @itemx set pagination off
20398 @kindex set pagination
20399 Turn the output pagination on or off; the default is on. Turning
20400 pagination off is the alternative to @code{set height 0}. Note that
20401 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20402 Options, -batch}) also automatically disables pagination.
20404 @item show pagination
20405 @kindex show pagination
20406 Show the current pagination mode.
20411 @cindex number representation
20412 @cindex entering numbers
20414 You can always enter numbers in octal, decimal, or hexadecimal in
20415 @value{GDBN} by the usual conventions: octal numbers begin with
20416 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20417 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20418 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20419 10; likewise, the default display for numbers---when no particular
20420 format is specified---is base 10. You can change the default base for
20421 both input and output with the commands described below.
20424 @kindex set input-radix
20425 @item set input-radix @var{base}
20426 Set the default base for numeric input. Supported choices
20427 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20428 specified either unambiguously or using the current input radix; for
20432 set input-radix 012
20433 set input-radix 10.
20434 set input-radix 0xa
20438 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20439 leaves the input radix unchanged, no matter what it was, since
20440 @samp{10}, being without any leading or trailing signs of its base, is
20441 interpreted in the current radix. Thus, if the current radix is 16,
20442 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20445 @kindex set output-radix
20446 @item set output-radix @var{base}
20447 Set the default base for numeric display. Supported choices
20448 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20449 specified either unambiguously or using the current input radix.
20451 @kindex show input-radix
20452 @item show input-radix
20453 Display the current default base for numeric input.
20455 @kindex show output-radix
20456 @item show output-radix
20457 Display the current default base for numeric display.
20459 @item set radix @r{[}@var{base}@r{]}
20463 These commands set and show the default base for both input and output
20464 of numbers. @code{set radix} sets the radix of input and output to
20465 the same base; without an argument, it resets the radix back to its
20466 default value of 10.
20471 @section Configuring the Current ABI
20473 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20474 application automatically. However, sometimes you need to override its
20475 conclusions. Use these commands to manage @value{GDBN}'s view of the
20482 One @value{GDBN} configuration can debug binaries for multiple operating
20483 system targets, either via remote debugging or native emulation.
20484 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20485 but you can override its conclusion using the @code{set osabi} command.
20486 One example where this is useful is in debugging of binaries which use
20487 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20488 not have the same identifying marks that the standard C library for your
20493 Show the OS ABI currently in use.
20496 With no argument, show the list of registered available OS ABI's.
20498 @item set osabi @var{abi}
20499 Set the current OS ABI to @var{abi}.
20502 @cindex float promotion
20504 Generally, the way that an argument of type @code{float} is passed to a
20505 function depends on whether the function is prototyped. For a prototyped
20506 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20507 according to the architecture's convention for @code{float}. For unprototyped
20508 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20509 @code{double} and then passed.
20511 Unfortunately, some forms of debug information do not reliably indicate whether
20512 a function is prototyped. If @value{GDBN} calls a function that is not marked
20513 as prototyped, it consults @kbd{set coerce-float-to-double}.
20516 @kindex set coerce-float-to-double
20517 @item set coerce-float-to-double
20518 @itemx set coerce-float-to-double on
20519 Arguments of type @code{float} will be promoted to @code{double} when passed
20520 to an unprototyped function. This is the default setting.
20522 @item set coerce-float-to-double off
20523 Arguments of type @code{float} will be passed directly to unprototyped
20526 @kindex show coerce-float-to-double
20527 @item show coerce-float-to-double
20528 Show the current setting of promoting @code{float} to @code{double}.
20532 @kindex show cp-abi
20533 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20534 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20535 used to build your application. @value{GDBN} only fully supports
20536 programs with a single C@t{++} ABI; if your program contains code using
20537 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20538 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20539 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20540 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20541 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20542 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20547 Show the C@t{++} ABI currently in use.
20550 With no argument, show the list of supported C@t{++} ABI's.
20552 @item set cp-abi @var{abi}
20553 @itemx set cp-abi auto
20554 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20557 @node Messages/Warnings
20558 @section Optional Warnings and Messages
20560 @cindex verbose operation
20561 @cindex optional warnings
20562 By default, @value{GDBN} is silent about its inner workings. If you are
20563 running on a slow machine, you may want to use the @code{set verbose}
20564 command. This makes @value{GDBN} tell you when it does a lengthy
20565 internal operation, so you will not think it has crashed.
20567 Currently, the messages controlled by @code{set verbose} are those
20568 which announce that the symbol table for a source file is being read;
20569 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20572 @kindex set verbose
20573 @item set verbose on
20574 Enables @value{GDBN} output of certain informational messages.
20576 @item set verbose off
20577 Disables @value{GDBN} output of certain informational messages.
20579 @kindex show verbose
20581 Displays whether @code{set verbose} is on or off.
20584 By default, if @value{GDBN} encounters bugs in the symbol table of an
20585 object file, it is silent; but if you are debugging a compiler, you may
20586 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20591 @kindex set complaints
20592 @item set complaints @var{limit}
20593 Permits @value{GDBN} to output @var{limit} complaints about each type of
20594 unusual symbols before becoming silent about the problem. Set
20595 @var{limit} to zero to suppress all complaints; set it to a large number
20596 to prevent complaints from being suppressed.
20598 @kindex show complaints
20599 @item show complaints
20600 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20604 @anchor{confirmation requests}
20605 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20606 lot of stupid questions to confirm certain commands. For example, if
20607 you try to run a program which is already running:
20611 The program being debugged has been started already.
20612 Start it from the beginning? (y or n)
20615 If you are willing to unflinchingly face the consequences of your own
20616 commands, you can disable this ``feature'':
20620 @kindex set confirm
20622 @cindex confirmation
20623 @cindex stupid questions
20624 @item set confirm off
20625 Disables confirmation requests. Note that running @value{GDBN} with
20626 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20627 automatically disables confirmation requests.
20629 @item set confirm on
20630 Enables confirmation requests (the default).
20632 @kindex show confirm
20634 Displays state of confirmation requests.
20638 @cindex command tracing
20639 If you need to debug user-defined commands or sourced files you may find it
20640 useful to enable @dfn{command tracing}. In this mode each command will be
20641 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20642 quantity denoting the call depth of each command.
20645 @kindex set trace-commands
20646 @cindex command scripts, debugging
20647 @item set trace-commands on
20648 Enable command tracing.
20649 @item set trace-commands off
20650 Disable command tracing.
20651 @item show trace-commands
20652 Display the current state of command tracing.
20655 @node Debugging Output
20656 @section Optional Messages about Internal Happenings
20657 @cindex optional debugging messages
20659 @value{GDBN} has commands that enable optional debugging messages from
20660 various @value{GDBN} subsystems; normally these commands are of
20661 interest to @value{GDBN} maintainers, or when reporting a bug. This
20662 section documents those commands.
20665 @kindex set exec-done-display
20666 @item set exec-done-display
20667 Turns on or off the notification of asynchronous commands'
20668 completion. When on, @value{GDBN} will print a message when an
20669 asynchronous command finishes its execution. The default is off.
20670 @kindex show exec-done-display
20671 @item show exec-done-display
20672 Displays the current setting of asynchronous command completion
20675 @cindex gdbarch debugging info
20676 @cindex architecture debugging info
20677 @item set debug arch
20678 Turns on or off display of gdbarch debugging info. The default is off
20680 @item show debug arch
20681 Displays the current state of displaying gdbarch debugging info.
20682 @item set debug aix-thread
20683 @cindex AIX threads
20684 Display debugging messages about inner workings of the AIX thread
20686 @item show debug aix-thread
20687 Show the current state of AIX thread debugging info display.
20688 @item set debug check-physname
20690 Check the results of the ``physname'' computation. When reading DWARF
20691 debugging information for C@t{++}, @value{GDBN} attempts to compute
20692 each entity's name. @value{GDBN} can do this computation in two
20693 different ways, depending on exactly what information is present.
20694 When enabled, this setting causes @value{GDBN} to compute the names
20695 both ways and display any discrepancies.
20696 @item show debug check-physname
20697 Show the current state of ``physname'' checking.
20698 @item set debug dwarf2-die
20699 @cindex DWARF2 DIEs
20700 Dump DWARF2 DIEs after they are read in.
20701 The value is the number of nesting levels to print.
20702 A value of zero turns off the display.
20703 @item show debug dwarf2-die
20704 Show the current state of DWARF2 DIE debugging.
20705 @item set debug displaced
20706 @cindex displaced stepping debugging info
20707 Turns on or off display of @value{GDBN} debugging info for the
20708 displaced stepping support. The default is off.
20709 @item show debug displaced
20710 Displays the current state of displaying @value{GDBN} debugging info
20711 related to displaced stepping.
20712 @item set debug event
20713 @cindex event debugging info
20714 Turns on or off display of @value{GDBN} event debugging info. The
20716 @item show debug event
20717 Displays the current state of displaying @value{GDBN} event debugging
20719 @item set debug expression
20720 @cindex expression debugging info
20721 Turns on or off display of debugging info about @value{GDBN}
20722 expression parsing. The default is off.
20723 @item show debug expression
20724 Displays the current state of displaying debugging info about
20725 @value{GDBN} expression parsing.
20726 @item set debug frame
20727 @cindex frame debugging info
20728 Turns on or off display of @value{GDBN} frame debugging info. The
20730 @item show debug frame
20731 Displays the current state of displaying @value{GDBN} frame debugging
20733 @item set debug gnu-nat
20734 @cindex @sc{gnu}/Hurd debug messages
20735 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20736 @item show debug gnu-nat
20737 Show the current state of @sc{gnu}/Hurd debugging messages.
20738 @item set debug infrun
20739 @cindex inferior debugging info
20740 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20741 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20742 for implementing operations such as single-stepping the inferior.
20743 @item show debug infrun
20744 Displays the current state of @value{GDBN} inferior debugging.
20745 @item set debug jit
20746 @cindex just-in-time compilation, debugging messages
20747 Turns on or off debugging messages from JIT debug support.
20748 @item show debug jit
20749 Displays the current state of @value{GDBN} JIT debugging.
20750 @item set debug lin-lwp
20751 @cindex @sc{gnu}/Linux LWP debug messages
20752 @cindex Linux lightweight processes
20753 Turns on or off debugging messages from the Linux LWP debug support.
20754 @item show debug lin-lwp
20755 Show the current state of Linux LWP debugging messages.
20756 @item set debug observer
20757 @cindex observer debugging info
20758 Turns on or off display of @value{GDBN} observer debugging. This
20759 includes info such as the notification of observable events.
20760 @item show debug observer
20761 Displays the current state of observer debugging.
20762 @item set debug overload
20763 @cindex C@t{++} overload debugging info
20764 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20765 info. This includes info such as ranking of functions, etc. The default
20767 @item show debug overload
20768 Displays the current state of displaying @value{GDBN} C@t{++} overload
20770 @cindex expression parser, debugging info
20771 @cindex debug expression parser
20772 @item set debug parser
20773 Turns on or off the display of expression parser debugging output.
20774 Internally, this sets the @code{yydebug} variable in the expression
20775 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20776 details. The default is off.
20777 @item show debug parser
20778 Show the current state of expression parser debugging.
20779 @cindex packets, reporting on stdout
20780 @cindex serial connections, debugging
20781 @cindex debug remote protocol
20782 @cindex remote protocol debugging
20783 @cindex display remote packets
20784 @item set debug remote
20785 Turns on or off display of reports on all packets sent back and forth across
20786 the serial line to the remote machine. The info is printed on the
20787 @value{GDBN} standard output stream. The default is off.
20788 @item show debug remote
20789 Displays the state of display of remote packets.
20790 @item set debug serial
20791 Turns on or off display of @value{GDBN} serial debugging info. The
20793 @item show debug serial
20794 Displays the current state of displaying @value{GDBN} serial debugging
20796 @item set debug solib-frv
20797 @cindex FR-V shared-library debugging
20798 Turns on or off debugging messages for FR-V shared-library code.
20799 @item show debug solib-frv
20800 Display the current state of FR-V shared-library code debugging
20802 @item set debug target
20803 @cindex target debugging info
20804 Turns on or off display of @value{GDBN} target debugging info. This info
20805 includes what is going on at the target level of GDB, as it happens. The
20806 default is 0. Set it to 1 to track events, and to 2 to also track the
20807 value of large memory transfers. Changes to this flag do not take effect
20808 until the next time you connect to a target or use the @code{run} command.
20809 @item show debug target
20810 Displays the current state of displaying @value{GDBN} target debugging
20812 @item set debug timestamp
20813 @cindex timestampping debugging info
20814 Turns on or off display of timestamps with @value{GDBN} debugging info.
20815 When enabled, seconds and microseconds are displayed before each debugging
20817 @item show debug timestamp
20818 Displays the current state of displaying timestamps with @value{GDBN}
20820 @item set debugvarobj
20821 @cindex variable object debugging info
20822 Turns on or off display of @value{GDBN} variable object debugging
20823 info. The default is off.
20824 @item show debugvarobj
20825 Displays the current state of displaying @value{GDBN} variable object
20827 @item set debug xml
20828 @cindex XML parser debugging
20829 Turns on or off debugging messages for built-in XML parsers.
20830 @item show debug xml
20831 Displays the current state of XML debugging messages.
20834 @node Other Misc Settings
20835 @section Other Miscellaneous Settings
20836 @cindex miscellaneous settings
20839 @kindex set interactive-mode
20840 @item set interactive-mode
20841 If @code{on}, forces @value{GDBN} to assume that GDB was started
20842 in a terminal. In practice, this means that @value{GDBN} should wait
20843 for the user to answer queries generated by commands entered at
20844 the command prompt. If @code{off}, forces @value{GDBN} to operate
20845 in the opposite mode, and it uses the default answers to all queries.
20846 If @code{auto} (the default), @value{GDBN} tries to determine whether
20847 its standard input is a terminal, and works in interactive-mode if it
20848 is, non-interactively otherwise.
20850 In the vast majority of cases, the debugger should be able to guess
20851 correctly which mode should be used. But this setting can be useful
20852 in certain specific cases, such as running a MinGW @value{GDBN}
20853 inside a cygwin window.
20855 @kindex show interactive-mode
20856 @item show interactive-mode
20857 Displays whether the debugger is operating in interactive mode or not.
20860 @node Extending GDB
20861 @chapter Extending @value{GDBN}
20862 @cindex extending GDB
20864 @value{GDBN} provides three mechanisms for extension. The first is based
20865 on composition of @value{GDBN} commands, the second is based on the
20866 Python scripting language, and the third is for defining new aliases of
20869 To facilitate the use of the first two extensions, @value{GDBN} is capable
20870 of evaluating the contents of a file. When doing so, @value{GDBN}
20871 can recognize which scripting language is being used by looking at
20872 the filename extension. Files with an unrecognized filename extension
20873 are always treated as a @value{GDBN} Command Files.
20874 @xref{Command Files,, Command files}.
20876 You can control how @value{GDBN} evaluates these files with the following
20880 @kindex set script-extension
20881 @kindex show script-extension
20882 @item set script-extension off
20883 All scripts are always evaluated as @value{GDBN} Command Files.
20885 @item set script-extension soft
20886 The debugger determines the scripting language based on filename
20887 extension. If this scripting language is supported, @value{GDBN}
20888 evaluates the script using that language. Otherwise, it evaluates
20889 the file as a @value{GDBN} Command File.
20891 @item set script-extension strict
20892 The debugger determines the scripting language based on filename
20893 extension, and evaluates the script using that language. If the
20894 language is not supported, then the evaluation fails.
20896 @item show script-extension
20897 Display the current value of the @code{script-extension} option.
20902 * Sequences:: Canned Sequences of Commands
20903 * Python:: Scripting @value{GDBN} using Python
20904 * Aliases:: Creating new spellings of existing commands
20908 @section Canned Sequences of Commands
20910 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20911 Command Lists}), @value{GDBN} provides two ways to store sequences of
20912 commands for execution as a unit: user-defined commands and command
20916 * Define:: How to define your own commands
20917 * Hooks:: Hooks for user-defined commands
20918 * Command Files:: How to write scripts of commands to be stored in a file
20919 * Output:: Commands for controlled output
20923 @subsection User-defined Commands
20925 @cindex user-defined command
20926 @cindex arguments, to user-defined commands
20927 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20928 which you assign a new name as a command. This is done with the
20929 @code{define} command. User commands may accept up to 10 arguments
20930 separated by whitespace. Arguments are accessed within the user command
20931 via @code{$arg0@dots{}$arg9}. A trivial example:
20935 print $arg0 + $arg1 + $arg2
20940 To execute the command use:
20947 This defines the command @code{adder}, which prints the sum of
20948 its three arguments. Note the arguments are text substitutions, so they may
20949 reference variables, use complex expressions, or even perform inferior
20952 @cindex argument count in user-defined commands
20953 @cindex how many arguments (user-defined commands)
20954 In addition, @code{$argc} may be used to find out how many arguments have
20955 been passed. This expands to a number in the range 0@dots{}10.
20960 print $arg0 + $arg1
20963 print $arg0 + $arg1 + $arg2
20971 @item define @var{commandname}
20972 Define a command named @var{commandname}. If there is already a command
20973 by that name, you are asked to confirm that you want to redefine it.
20974 @var{commandname} may be a bare command name consisting of letters,
20975 numbers, dashes, and underscores. It may also start with any predefined
20976 prefix command. For example, @samp{define target my-target} creates
20977 a user-defined @samp{target my-target} command.
20979 The definition of the command is made up of other @value{GDBN} command lines,
20980 which are given following the @code{define} command. The end of these
20981 commands is marked by a line containing @code{end}.
20984 @kindex end@r{ (user-defined commands)}
20985 @item document @var{commandname}
20986 Document the user-defined command @var{commandname}, so that it can be
20987 accessed by @code{help}. The command @var{commandname} must already be
20988 defined. This command reads lines of documentation just as @code{define}
20989 reads the lines of the command definition, ending with @code{end}.
20990 After the @code{document} command is finished, @code{help} on command
20991 @var{commandname} displays the documentation you have written.
20993 You may use the @code{document} command again to change the
20994 documentation of a command. Redefining the command with @code{define}
20995 does not change the documentation.
20997 @kindex dont-repeat
20998 @cindex don't repeat command
21000 Used inside a user-defined command, this tells @value{GDBN} that this
21001 command should not be repeated when the user hits @key{RET}
21002 (@pxref{Command Syntax, repeat last command}).
21004 @kindex help user-defined
21005 @item help user-defined
21006 List all user-defined commands, with the first line of the documentation
21011 @itemx show user @var{commandname}
21012 Display the @value{GDBN} commands used to define @var{commandname} (but
21013 not its documentation). If no @var{commandname} is given, display the
21014 definitions for all user-defined commands.
21016 @cindex infinite recursion in user-defined commands
21017 @kindex show max-user-call-depth
21018 @kindex set max-user-call-depth
21019 @item show max-user-call-depth
21020 @itemx set max-user-call-depth
21021 The value of @code{max-user-call-depth} controls how many recursion
21022 levels are allowed in user-defined commands before @value{GDBN} suspects an
21023 infinite recursion and aborts the command.
21026 In addition to the above commands, user-defined commands frequently
21027 use control flow commands, described in @ref{Command Files}.
21029 When user-defined commands are executed, the
21030 commands of the definition are not printed. An error in any command
21031 stops execution of the user-defined command.
21033 If used interactively, commands that would ask for confirmation proceed
21034 without asking when used inside a user-defined command. Many @value{GDBN}
21035 commands that normally print messages to say what they are doing omit the
21036 messages when used in a user-defined command.
21039 @subsection User-defined Command Hooks
21040 @cindex command hooks
21041 @cindex hooks, for commands
21042 @cindex hooks, pre-command
21045 You may define @dfn{hooks}, which are a special kind of user-defined
21046 command. Whenever you run the command @samp{foo}, if the user-defined
21047 command @samp{hook-foo} exists, it is executed (with no arguments)
21048 before that command.
21050 @cindex hooks, post-command
21052 A hook may also be defined which is run after the command you executed.
21053 Whenever you run the command @samp{foo}, if the user-defined command
21054 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21055 that command. Post-execution hooks may exist simultaneously with
21056 pre-execution hooks, for the same command.
21058 It is valid for a hook to call the command which it hooks. If this
21059 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21061 @c It would be nice if hookpost could be passed a parameter indicating
21062 @c if the command it hooks executed properly or not. FIXME!
21064 @kindex stop@r{, a pseudo-command}
21065 In addition, a pseudo-command, @samp{stop} exists. Defining
21066 (@samp{hook-stop}) makes the associated commands execute every time
21067 execution stops in your program: before breakpoint commands are run,
21068 displays are printed, or the stack frame is printed.
21070 For example, to ignore @code{SIGALRM} signals while
21071 single-stepping, but treat them normally during normal execution,
21076 handle SIGALRM nopass
21080 handle SIGALRM pass
21083 define hook-continue
21084 handle SIGALRM pass
21088 As a further example, to hook at the beginning and end of the @code{echo}
21089 command, and to add extra text to the beginning and end of the message,
21097 define hookpost-echo
21101 (@value{GDBP}) echo Hello World
21102 <<<---Hello World--->>>
21107 You can define a hook for any single-word command in @value{GDBN}, but
21108 not for command aliases; you should define a hook for the basic command
21109 name, e.g.@: @code{backtrace} rather than @code{bt}.
21110 @c FIXME! So how does Joe User discover whether a command is an alias
21112 You can hook a multi-word command by adding @code{hook-} or
21113 @code{hookpost-} to the last word of the command, e.g.@:
21114 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21116 If an error occurs during the execution of your hook, execution of
21117 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21118 (before the command that you actually typed had a chance to run).
21120 If you try to define a hook which does not match any known command, you
21121 get a warning from the @code{define} command.
21123 @node Command Files
21124 @subsection Command Files
21126 @cindex command files
21127 @cindex scripting commands
21128 A command file for @value{GDBN} is a text file made of lines that are
21129 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21130 also be included. An empty line in a command file does nothing; it
21131 does not mean to repeat the last command, as it would from the
21134 You can request the execution of a command file with the @code{source}
21135 command. Note that the @code{source} command is also used to evaluate
21136 scripts that are not Command Files. The exact behavior can be configured
21137 using the @code{script-extension} setting.
21138 @xref{Extending GDB,, Extending GDB}.
21142 @cindex execute commands from a file
21143 @item source [-s] [-v] @var{filename}
21144 Execute the command file @var{filename}.
21147 The lines in a command file are generally executed sequentially,
21148 unless the order of execution is changed by one of the
21149 @emph{flow-control commands} described below. The commands are not
21150 printed as they are executed. An error in any command terminates
21151 execution of the command file and control is returned to the console.
21153 @value{GDBN} first searches for @var{filename} in the current directory.
21154 If the file is not found there, and @var{filename} does not specify a
21155 directory, then @value{GDBN} also looks for the file on the source search path
21156 (specified with the @samp{directory} command);
21157 except that @file{$cdir} is not searched because the compilation directory
21158 is not relevant to scripts.
21160 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21161 on the search path even if @var{filename} specifies a directory.
21162 The search is done by appending @var{filename} to each element of the
21163 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21164 and the search path contains @file{/home/user} then @value{GDBN} will
21165 look for the script @file{/home/user/mylib/myscript}.
21166 The search is also done if @var{filename} is an absolute path.
21167 For example, if @var{filename} is @file{/tmp/myscript} and
21168 the search path contains @file{/home/user} then @value{GDBN} will
21169 look for the script @file{/home/user/tmp/myscript}.
21170 For DOS-like systems, if @var{filename} contains a drive specification,
21171 it is stripped before concatenation. For example, if @var{filename} is
21172 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21173 will look for the script @file{c:/tmp/myscript}.
21175 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21176 each command as it is executed. The option must be given before
21177 @var{filename}, and is interpreted as part of the filename anywhere else.
21179 Commands that would ask for confirmation if used interactively proceed
21180 without asking when used in a command file. Many @value{GDBN} commands that
21181 normally print messages to say what they are doing omit the messages
21182 when called from command files.
21184 @value{GDBN} also accepts command input from standard input. In this
21185 mode, normal output goes to standard output and error output goes to
21186 standard error. Errors in a command file supplied on standard input do
21187 not terminate execution of the command file---execution continues with
21191 gdb < cmds > log 2>&1
21194 (The syntax above will vary depending on the shell used.) This example
21195 will execute commands from the file @file{cmds}. All output and errors
21196 would be directed to @file{log}.
21198 Since commands stored on command files tend to be more general than
21199 commands typed interactively, they frequently need to deal with
21200 complicated situations, such as different or unexpected values of
21201 variables and symbols, changes in how the program being debugged is
21202 built, etc. @value{GDBN} provides a set of flow-control commands to
21203 deal with these complexities. Using these commands, you can write
21204 complex scripts that loop over data structures, execute commands
21205 conditionally, etc.
21212 This command allows to include in your script conditionally executed
21213 commands. The @code{if} command takes a single argument, which is an
21214 expression to evaluate. It is followed by a series of commands that
21215 are executed only if the expression is true (its value is nonzero).
21216 There can then optionally be an @code{else} line, followed by a series
21217 of commands that are only executed if the expression was false. The
21218 end of the list is marked by a line containing @code{end}.
21222 This command allows to write loops. Its syntax is similar to
21223 @code{if}: the command takes a single argument, which is an expression
21224 to evaluate, and must be followed by the commands to execute, one per
21225 line, terminated by an @code{end}. These commands are called the
21226 @dfn{body} of the loop. The commands in the body of @code{while} are
21227 executed repeatedly as long as the expression evaluates to true.
21231 This command exits the @code{while} loop in whose body it is included.
21232 Execution of the script continues after that @code{while}s @code{end}
21235 @kindex loop_continue
21236 @item loop_continue
21237 This command skips the execution of the rest of the body of commands
21238 in the @code{while} loop in whose body it is included. Execution
21239 branches to the beginning of the @code{while} loop, where it evaluates
21240 the controlling expression.
21242 @kindex end@r{ (if/else/while commands)}
21244 Terminate the block of commands that are the body of @code{if},
21245 @code{else}, or @code{while} flow-control commands.
21250 @subsection Commands for Controlled Output
21252 During the execution of a command file or a user-defined command, normal
21253 @value{GDBN} output is suppressed; the only output that appears is what is
21254 explicitly printed by the commands in the definition. This section
21255 describes three commands useful for generating exactly the output you
21260 @item echo @var{text}
21261 @c I do not consider backslash-space a standard C escape sequence
21262 @c because it is not in ANSI.
21263 Print @var{text}. Nonprinting characters can be included in
21264 @var{text} using C escape sequences, such as @samp{\n} to print a
21265 newline. @strong{No newline is printed unless you specify one.}
21266 In addition to the standard C escape sequences, a backslash followed
21267 by a space stands for a space. This is useful for displaying a
21268 string with spaces at the beginning or the end, since leading and
21269 trailing spaces are otherwise trimmed from all arguments.
21270 To print @samp{@w{ }and foo =@w{ }}, use the command
21271 @samp{echo \@w{ }and foo = \@w{ }}.
21273 A backslash at the end of @var{text} can be used, as in C, to continue
21274 the command onto subsequent lines. For example,
21277 echo This is some text\n\
21278 which is continued\n\
21279 onto several lines.\n
21282 produces the same output as
21285 echo This is some text\n
21286 echo which is continued\n
21287 echo onto several lines.\n
21291 @item output @var{expression}
21292 Print the value of @var{expression} and nothing but that value: no
21293 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21294 value history either. @xref{Expressions, ,Expressions}, for more information
21297 @item output/@var{fmt} @var{expression}
21298 Print the value of @var{expression} in format @var{fmt}. You can use
21299 the same formats as for @code{print}. @xref{Output Formats,,Output
21300 Formats}, for more information.
21303 @item printf @var{template}, @var{expressions}@dots{}
21304 Print the values of one or more @var{expressions} under the control of
21305 the string @var{template}. To print several values, make
21306 @var{expressions} be a comma-separated list of individual expressions,
21307 which may be either numbers or pointers. Their values are printed as
21308 specified by @var{template}, exactly as a C program would do by
21309 executing the code below:
21312 printf (@var{template}, @var{expressions}@dots{});
21315 As in @code{C} @code{printf}, ordinary characters in @var{template}
21316 are printed verbatim, while @dfn{conversion specification} introduced
21317 by the @samp{%} character cause subsequent @var{expressions} to be
21318 evaluated, their values converted and formatted according to type and
21319 style information encoded in the conversion specifications, and then
21322 For example, you can print two values in hex like this:
21325 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21328 @code{printf} supports all the standard @code{C} conversion
21329 specifications, including the flags and modifiers between the @samp{%}
21330 character and the conversion letter, with the following exceptions:
21334 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21337 The modifier @samp{*} is not supported for specifying precision or
21341 The @samp{'} flag (for separation of digits into groups according to
21342 @code{LC_NUMERIC'}) is not supported.
21345 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21349 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21352 The conversion letters @samp{a} and @samp{A} are not supported.
21356 Note that the @samp{ll} type modifier is supported only if the
21357 underlying @code{C} implementation used to build @value{GDBN} supports
21358 the @code{long long int} type, and the @samp{L} type modifier is
21359 supported only if @code{long double} type is available.
21361 As in @code{C}, @code{printf} supports simple backslash-escape
21362 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21363 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21364 single character. Octal and hexadecimal escape sequences are not
21367 Additionally, @code{printf} supports conversion specifications for DFP
21368 (@dfn{Decimal Floating Point}) types using the following length modifiers
21369 together with a floating point specifier.
21374 @samp{H} for printing @code{Decimal32} types.
21377 @samp{D} for printing @code{Decimal64} types.
21380 @samp{DD} for printing @code{Decimal128} types.
21383 If the underlying @code{C} implementation used to build @value{GDBN} has
21384 support for the three length modifiers for DFP types, other modifiers
21385 such as width and precision will also be available for @value{GDBN} to use.
21387 In case there is no such @code{C} support, no additional modifiers will be
21388 available and the value will be printed in the standard way.
21390 Here's an example of printing DFP types using the above conversion letters:
21392 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21396 @item eval @var{template}, @var{expressions}@dots{}
21397 Convert the values of one or more @var{expressions} under the control of
21398 the string @var{template} to a command line, and call it.
21403 @section Scripting @value{GDBN} using Python
21404 @cindex python scripting
21405 @cindex scripting with python
21407 You can script @value{GDBN} using the @uref{http://www.python.org/,
21408 Python programming language}. This feature is available only if
21409 @value{GDBN} was configured using @option{--with-python}.
21411 @cindex python directory
21412 Python scripts used by @value{GDBN} should be installed in
21413 @file{@var{data-directory}/python}, where @var{data-directory} is
21414 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21415 This directory, known as the @dfn{python directory},
21416 is automatically added to the Python Search Path in order to allow
21417 the Python interpreter to locate all scripts installed at this location.
21419 Additionally, @value{GDBN} commands and convenience functions which
21420 are written in Python and are located in the
21421 @file{@var{data-directory}/python/gdb/command} or
21422 @file{@var{data-directory}/python/gdb/function} directories are
21423 automatically imported when @value{GDBN} starts.
21426 * Python Commands:: Accessing Python from @value{GDBN}.
21427 * Python API:: Accessing @value{GDBN} from Python.
21428 * Auto-loading:: Automatically loading Python code.
21429 * Python modules:: Python modules provided by @value{GDBN}.
21432 @node Python Commands
21433 @subsection Python Commands
21434 @cindex python commands
21435 @cindex commands to access python
21437 @value{GDBN} provides one command for accessing the Python interpreter,
21438 and one related setting:
21442 @item python @r{[}@var{code}@r{]}
21443 The @code{python} command can be used to evaluate Python code.
21445 If given an argument, the @code{python} command will evaluate the
21446 argument as a Python command. For example:
21449 (@value{GDBP}) python print 23
21453 If you do not provide an argument to @code{python}, it will act as a
21454 multi-line command, like @code{define}. In this case, the Python
21455 script is made up of subsequent command lines, given after the
21456 @code{python} command. This command list is terminated using a line
21457 containing @code{end}. For example:
21460 (@value{GDBP}) python
21462 End with a line saying just "end".
21468 @kindex set python print-stack
21469 @item set python print-stack
21470 By default, @value{GDBN} will print only the message component of a
21471 Python exception when an error occurs in a Python script. This can be
21472 controlled using @code{set python print-stack}: if @code{full}, then
21473 full Python stack printing is enabled; if @code{none}, then Python stack
21474 and message printing is disabled; if @code{message}, the default, only
21475 the message component of the error is printed.
21478 It is also possible to execute a Python script from the @value{GDBN}
21482 @item source @file{script-name}
21483 The script name must end with @samp{.py} and @value{GDBN} must be configured
21484 to recognize the script language based on filename extension using
21485 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21487 @item python execfile ("script-name")
21488 This method is based on the @code{execfile} Python built-in function,
21489 and thus is always available.
21493 @subsection Python API
21495 @cindex programming in python
21497 @cindex python stdout
21498 @cindex python pagination
21499 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21500 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21501 A Python program which outputs to one of these streams may have its
21502 output interrupted by the user (@pxref{Screen Size}). In this
21503 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21506 * Basic Python:: Basic Python Functions.
21507 * Exception Handling:: How Python exceptions are translated.
21508 * Values From Inferior:: Python representation of values.
21509 * Types In Python:: Python representation of types.
21510 * Pretty Printing API:: Pretty-printing values.
21511 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21512 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21513 * Inferiors In Python:: Python representation of inferiors (processes)
21514 * Events In Python:: Listening for events from @value{GDBN}.
21515 * Threads In Python:: Accessing inferior threads from Python.
21516 * Commands In Python:: Implementing new commands in Python.
21517 * Parameters In Python:: Adding new @value{GDBN} parameters.
21518 * Functions In Python:: Writing new convenience functions.
21519 * Progspaces In Python:: Program spaces.
21520 * Objfiles In Python:: Object files.
21521 * Frames In Python:: Accessing inferior stack frames from Python.
21522 * Blocks In Python:: Accessing frame blocks from Python.
21523 * Symbols In Python:: Python representation of symbols.
21524 * Symbol Tables In Python:: Python representation of symbol tables.
21525 * Lazy Strings In Python:: Python representation of lazy strings.
21526 * Breakpoints In Python:: Manipulating breakpoints using Python.
21527 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21532 @subsubsection Basic Python
21534 @cindex python functions
21535 @cindex python module
21537 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21538 methods and classes added by @value{GDBN} are placed in this module.
21539 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21540 use in all scripts evaluated by the @code{python} command.
21542 @findex gdb.PYTHONDIR
21543 @defvar gdb.PYTHONDIR
21544 A string containing the python directory (@pxref{Python}).
21547 @findex gdb.execute
21548 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21549 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21550 If a GDB exception happens while @var{command} runs, it is
21551 translated as described in @ref{Exception Handling,,Exception Handling}.
21553 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21554 command as having originated from the user invoking it interactively.
21555 It must be a boolean value. If omitted, it defaults to @code{False}.
21557 By default, any output produced by @var{command} is sent to
21558 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21559 @code{True}, then output will be collected by @code{gdb.execute} and
21560 returned as a string. The default is @code{False}, in which case the
21561 return value is @code{None}. If @var{to_string} is @code{True}, the
21562 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21563 and height, and its pagination will be disabled; @pxref{Screen Size}.
21566 @findex gdb.breakpoints
21567 @defun gdb.breakpoints ()
21568 Return a sequence holding all of @value{GDBN}'s breakpoints.
21569 @xref{Breakpoints In Python}, for more information.
21572 @findex gdb.parameter
21573 @defun gdb.parameter (parameter)
21574 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21575 string naming the parameter to look up; @var{parameter} may contain
21576 spaces if the parameter has a multi-part name. For example,
21577 @samp{print object} is a valid parameter name.
21579 If the named parameter does not exist, this function throws a
21580 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21581 parameter's value is converted to a Python value of the appropriate
21582 type, and returned.
21585 @findex gdb.history
21586 @defun gdb.history (number)
21587 Return a value from @value{GDBN}'s value history (@pxref{Value
21588 History}). @var{number} indicates which history element to return.
21589 If @var{number} is negative, then @value{GDBN} will take its absolute value
21590 and count backward from the last element (i.e., the most recent element) to
21591 find the value to return. If @var{number} is zero, then @value{GDBN} will
21592 return the most recent element. If the element specified by @var{number}
21593 doesn't exist in the value history, a @code{gdb.error} exception will be
21596 If no exception is raised, the return value is always an instance of
21597 @code{gdb.Value} (@pxref{Values From Inferior}).
21600 @findex gdb.parse_and_eval
21601 @defun gdb.parse_and_eval (expression)
21602 Parse @var{expression} as an expression in the current language,
21603 evaluate it, and return the result as a @code{gdb.Value}.
21604 @var{expression} must be a string.
21606 This function can be useful when implementing a new command
21607 (@pxref{Commands In Python}), as it provides a way to parse the
21608 command's argument as an expression. It is also useful simply to
21609 compute values, for example, it is the only way to get the value of a
21610 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21613 @findex gdb.post_event
21614 @defun gdb.post_event (event)
21615 Put @var{event}, a callable object taking no arguments, into
21616 @value{GDBN}'s internal event queue. This callable will be invoked at
21617 some later point, during @value{GDBN}'s event processing. Events
21618 posted using @code{post_event} will be run in the order in which they
21619 were posted; however, there is no way to know when they will be
21620 processed relative to other events inside @value{GDBN}.
21622 @value{GDBN} is not thread-safe. If your Python program uses multiple
21623 threads, you must be careful to only call @value{GDBN}-specific
21624 functions in the main @value{GDBN} thread. @code{post_event} ensures
21628 (@value{GDBP}) python
21632 > def __init__(self, message):
21633 > self.message = message;
21634 > def __call__(self):
21635 > gdb.write(self.message)
21637 >class MyThread1 (threading.Thread):
21639 > gdb.post_event(Writer("Hello "))
21641 >class MyThread2 (threading.Thread):
21643 > gdb.post_event(Writer("World\n"))
21645 >MyThread1().start()
21646 >MyThread2().start()
21648 (@value{GDBP}) Hello World
21653 @defun gdb.write (string @r{[}, stream{]})
21654 Print a string to @value{GDBN}'s paginated output stream. The
21655 optional @var{stream} determines the stream to print to. The default
21656 stream is @value{GDBN}'s standard output stream. Possible stream
21663 @value{GDBN}'s standard output stream.
21668 @value{GDBN}'s standard error stream.
21673 @value{GDBN}'s log stream (@pxref{Logging Output}).
21676 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21677 call this function and will automatically direct the output to the
21682 @defun gdb.flush ()
21683 Flush the buffer of a @value{GDBN} paginated stream so that the
21684 contents are displayed immediately. @value{GDBN} will flush the
21685 contents of a stream automatically when it encounters a newline in the
21686 buffer. The optional @var{stream} determines the stream to flush. The
21687 default stream is @value{GDBN}'s standard output stream. Possible
21694 @value{GDBN}'s standard output stream.
21699 @value{GDBN}'s standard error stream.
21704 @value{GDBN}'s log stream (@pxref{Logging Output}).
21708 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21709 call this function for the relevant stream.
21712 @findex gdb.target_charset
21713 @defun gdb.target_charset ()
21714 Return the name of the current target character set (@pxref{Character
21715 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21716 that @samp{auto} is never returned.
21719 @findex gdb.target_wide_charset
21720 @defun gdb.target_wide_charset ()
21721 Return the name of the current target wide character set
21722 (@pxref{Character Sets}). This differs from
21723 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21727 @findex gdb.solib_name
21728 @defun gdb.solib_name (address)
21729 Return the name of the shared library holding the given @var{address}
21730 as a string, or @code{None}.
21733 @findex gdb.decode_line
21734 @defun gdb.decode_line @r{[}expression@r{]}
21735 Return locations of the line specified by @var{expression}, or of the
21736 current line if no argument was given. This function returns a Python
21737 tuple containing two elements. The first element contains a string
21738 holding any unparsed section of @var{expression} (or @code{None} if
21739 the expression has been fully parsed). The second element contains
21740 either @code{None} or another tuple that contains all the locations
21741 that match the expression represented as @code{gdb.Symtab_and_line}
21742 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21743 provided, it is decoded the way that @value{GDBN}'s inbuilt
21744 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21747 @defun gdb.prompt_hook (current_prompt)
21748 @anchor{prompt_hook}
21750 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21751 assigned to this operation before a prompt is displayed by
21754 The parameter @code{current_prompt} contains the current @value{GDBN}
21755 prompt. This method must return a Python string, or @code{None}. If
21756 a string is returned, the @value{GDBN} prompt will be set to that
21757 string. If @code{None} is returned, @value{GDBN} will continue to use
21758 the current prompt.
21760 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21761 such as those used by readline for command input, and annotation
21762 related prompts are prohibited from being changed.
21765 @node Exception Handling
21766 @subsubsection Exception Handling
21767 @cindex python exceptions
21768 @cindex exceptions, python
21770 When executing the @code{python} command, Python exceptions
21771 uncaught within the Python code are translated to calls to
21772 @value{GDBN} error-reporting mechanism. If the command that called
21773 @code{python} does not handle the error, @value{GDBN} will
21774 terminate it and print an error message containing the Python
21775 exception name, the associated value, and the Python call stack
21776 backtrace at the point where the exception was raised. Example:
21779 (@value{GDBP}) python print foo
21780 Traceback (most recent call last):
21781 File "<string>", line 1, in <module>
21782 NameError: name 'foo' is not defined
21785 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21786 Python code are converted to Python exceptions. The type of the
21787 Python exception depends on the error.
21791 This is the base class for most exceptions generated by @value{GDBN}.
21792 It is derived from @code{RuntimeError}, for compatibility with earlier
21793 versions of @value{GDBN}.
21795 If an error occurring in @value{GDBN} does not fit into some more
21796 specific category, then the generated exception will have this type.
21798 @item gdb.MemoryError
21799 This is a subclass of @code{gdb.error} which is thrown when an
21800 operation tried to access invalid memory in the inferior.
21802 @item KeyboardInterrupt
21803 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21804 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21807 In all cases, your exception handler will see the @value{GDBN} error
21808 message as its value and the Python call stack backtrace at the Python
21809 statement closest to where the @value{GDBN} error occured as the
21812 @findex gdb.GdbError
21813 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21814 it is useful to be able to throw an exception that doesn't cause a
21815 traceback to be printed. For example, the user may have invoked the
21816 command incorrectly. Use the @code{gdb.GdbError} exception
21817 to handle this case. Example:
21821 >class HelloWorld (gdb.Command):
21822 > """Greet the whole world."""
21823 > def __init__ (self):
21824 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21825 > def invoke (self, args, from_tty):
21826 > argv = gdb.string_to_argv (args)
21827 > if len (argv) != 0:
21828 > raise gdb.GdbError ("hello-world takes no arguments")
21829 > print "Hello, World!"
21832 (gdb) hello-world 42
21833 hello-world takes no arguments
21836 @node Values From Inferior
21837 @subsubsection Values From Inferior
21838 @cindex values from inferior, with Python
21839 @cindex python, working with values from inferior
21841 @cindex @code{gdb.Value}
21842 @value{GDBN} provides values it obtains from the inferior program in
21843 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21844 for its internal bookkeeping of the inferior's values, and for
21845 fetching values when necessary.
21847 Inferior values that are simple scalars can be used directly in
21848 Python expressions that are valid for the value's data type. Here's
21849 an example for an integer or floating-point value @code{some_val}:
21856 As result of this, @code{bar} will also be a @code{gdb.Value} object
21857 whose values are of the same type as those of @code{some_val}.
21859 Inferior values that are structures or instances of some class can
21860 be accessed using the Python @dfn{dictionary syntax}. For example, if
21861 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21862 can access its @code{foo} element with:
21865 bar = some_val['foo']
21868 Again, @code{bar} will also be a @code{gdb.Value} object.
21870 A @code{gdb.Value} that represents a function can be executed via
21871 inferior function call. Any arguments provided to the call must match
21872 the function's prototype, and must be provided in the order specified
21875 For example, @code{some_val} is a @code{gdb.Value} instance
21876 representing a function that takes two integers as arguments. To
21877 execute this function, call it like so:
21880 result = some_val (10,20)
21883 Any values returned from a function call will be stored as a
21886 The following attributes are provided:
21889 @defvar Value.address
21890 If this object is addressable, this read-only attribute holds a
21891 @code{gdb.Value} object representing the address. Otherwise,
21892 this attribute holds @code{None}.
21895 @cindex optimized out value in Python
21896 @defvar Value.is_optimized_out
21897 This read-only boolean attribute is true if the compiler optimized out
21898 this value, thus it is not available for fetching from the inferior.
21902 The type of this @code{gdb.Value}. The value of this attribute is a
21903 @code{gdb.Type} object (@pxref{Types In Python}).
21906 @defvar Value.dynamic_type
21907 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21908 type information (@acronym{RTTI}) to determine the dynamic type of the
21909 value. If this value is of class type, it will return the class in
21910 which the value is embedded, if any. If this value is of pointer or
21911 reference to a class type, it will compute the dynamic type of the
21912 referenced object, and return a pointer or reference to that type,
21913 respectively. In all other cases, it will return the value's static
21916 Note that this feature will only work when debugging a C@t{++} program
21917 that includes @acronym{RTTI} for the object in question. Otherwise,
21918 it will just return the static type of the value as in @kbd{ptype foo}
21919 (@pxref{Symbols, ptype}).
21922 @defvar Value.is_lazy
21923 The value of this read-only boolean attribute is @code{True} if this
21924 @code{gdb.Value} has not yet been fetched from the inferior.
21925 @value{GDBN} does not fetch values until necessary, for efficiency.
21929 myval = gdb.parse_and_eval ('somevar')
21932 The value of @code{somevar} is not fetched at this time. It will be
21933 fetched when the value is needed, or when the @code{fetch_lazy}
21938 The following methods are provided:
21941 @defun Value.__init__ (@var{val})
21942 Many Python values can be converted directly to a @code{gdb.Value} via
21943 this object initializer. Specifically:
21946 @item Python boolean
21947 A Python boolean is converted to the boolean type from the current
21950 @item Python integer
21951 A Python integer is converted to the C @code{long} type for the
21952 current architecture.
21955 A Python long is converted to the C @code{long long} type for the
21956 current architecture.
21959 A Python float is converted to the C @code{double} type for the
21960 current architecture.
21962 @item Python string
21963 A Python string is converted to a target string, using the current
21966 @item @code{gdb.Value}
21967 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21969 @item @code{gdb.LazyString}
21970 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21971 Python}), then the lazy string's @code{value} method is called, and
21972 its result is used.
21976 @defun Value.cast (type)
21977 Return a new instance of @code{gdb.Value} that is the result of
21978 casting this instance to the type described by @var{type}, which must
21979 be a @code{gdb.Type} object. If the cast cannot be performed for some
21980 reason, this method throws an exception.
21983 @defun Value.dereference ()
21984 For pointer data types, this method returns a new @code{gdb.Value} object
21985 whose contents is the object pointed to by the pointer. For example, if
21986 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21993 then you can use the corresponding @code{gdb.Value} to access what
21994 @code{foo} points to like this:
21997 bar = foo.dereference ()
22000 The result @code{bar} will be a @code{gdb.Value} object holding the
22001 value pointed to by @code{foo}.
22004 @defun Value.dynamic_cast (type)
22005 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22006 operator were used. Consult a C@t{++} reference for details.
22009 @defun Value.reinterpret_cast (type)
22010 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22011 operator were used. Consult a C@t{++} reference for details.
22014 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22015 If this @code{gdb.Value} represents a string, then this method
22016 converts the contents to a Python string. Otherwise, this method will
22017 throw an exception.
22019 Strings are recognized in a language-specific way; whether a given
22020 @code{gdb.Value} represents a string is determined by the current
22023 For C-like languages, a value is a string if it is a pointer to or an
22024 array of characters or ints. The string is assumed to be terminated
22025 by a zero of the appropriate width. However if the optional length
22026 argument is given, the string will be converted to that given length,
22027 ignoring any embedded zeros that the string may contain.
22029 If the optional @var{encoding} argument is given, it must be a string
22030 naming the encoding of the string in the @code{gdb.Value}, such as
22031 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22032 the same encodings as the corresponding argument to Python's
22033 @code{string.decode} method, and the Python codec machinery will be used
22034 to convert the string. If @var{encoding} is not given, or if
22035 @var{encoding} is the empty string, then either the @code{target-charset}
22036 (@pxref{Character Sets}) will be used, or a language-specific encoding
22037 will be used, if the current language is able to supply one.
22039 The optional @var{errors} argument is the same as the corresponding
22040 argument to Python's @code{string.decode} method.
22042 If the optional @var{length} argument is given, the string will be
22043 fetched and converted to the given length.
22046 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22047 If this @code{gdb.Value} represents a string, then this method
22048 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22049 In Python}). Otherwise, this method will throw an exception.
22051 If the optional @var{encoding} argument is given, it must be a string
22052 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22053 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22054 @var{encoding} argument is an encoding that @value{GDBN} does
22055 recognize, @value{GDBN} will raise an error.
22057 When a lazy string is printed, the @value{GDBN} encoding machinery is
22058 used to convert the string during printing. If the optional
22059 @var{encoding} argument is not provided, or is an empty string,
22060 @value{GDBN} will automatically select the encoding most suitable for
22061 the string type. For further information on encoding in @value{GDBN}
22062 please see @ref{Character Sets}.
22064 If the optional @var{length} argument is given, the string will be
22065 fetched and encoded to the length of characters specified. If
22066 the @var{length} argument is not provided, the string will be fetched
22067 and encoded until a null of appropriate width is found.
22070 @defun Value.fetch_lazy ()
22071 If the @code{gdb.Value} object is currently a lazy value
22072 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22073 fetched from the inferior. Any errors that occur in the process
22074 will produce a Python exception.
22076 If the @code{gdb.Value} object is not a lazy value, this method
22079 This method does not return a value.
22084 @node Types In Python
22085 @subsubsection Types In Python
22086 @cindex types in Python
22087 @cindex Python, working with types
22090 @value{GDBN} represents types from the inferior using the class
22093 The following type-related functions are available in the @code{gdb}
22096 @findex gdb.lookup_type
22097 @defun gdb.lookup_type (name @r{[}, block@r{]})
22098 This function looks up a type by name. @var{name} is the name of the
22099 type to look up. It must be a string.
22101 If @var{block} is given, then @var{name} is looked up in that scope.
22102 Otherwise, it is searched for globally.
22104 Ordinarily, this function will return an instance of @code{gdb.Type}.
22105 If the named type cannot be found, it will throw an exception.
22108 If the type is a structure or class type, or an enum type, the fields
22109 of that type can be accessed using the Python @dfn{dictionary syntax}.
22110 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22111 a structure type, you can access its @code{foo} field with:
22114 bar = some_type['foo']
22117 @code{bar} will be a @code{gdb.Field} object; see below under the
22118 description of the @code{Type.fields} method for a description of the
22119 @code{gdb.Field} class.
22121 An instance of @code{Type} has the following attributes:
22125 The type code for this type. The type code will be one of the
22126 @code{TYPE_CODE_} constants defined below.
22129 @defvar Type.sizeof
22130 The size of this type, in target @code{char} units. Usually, a
22131 target's @code{char} type will be an 8-bit byte. However, on some
22132 unusual platforms, this type may have a different size.
22136 The tag name for this type. The tag name is the name after
22137 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22138 languages have this concept. If this type has no tag name, then
22139 @code{None} is returned.
22143 The following methods are provided:
22146 @defun Type.fields ()
22147 For structure and union types, this method returns the fields. Range
22148 types have two fields, the minimum and maximum values. Enum types
22149 have one field per enum constant. Function and method types have one
22150 field per parameter. The base types of C@t{++} classes are also
22151 represented as fields. If the type has no fields, or does not fit
22152 into one of these categories, an empty sequence will be returned.
22154 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22157 This attribute is not available for @code{static} fields (as in
22158 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22159 position of the field. For @code{enum} fields, the value is the
22160 enumeration member's integer representation.
22163 The name of the field, or @code{None} for anonymous fields.
22166 This is @code{True} if the field is artificial, usually meaning that
22167 it was provided by the compiler and not the user. This attribute is
22168 always provided, and is @code{False} if the field is not artificial.
22170 @item is_base_class
22171 This is @code{True} if the field represents a base class of a C@t{++}
22172 structure. This attribute is always provided, and is @code{False}
22173 if the field is not a base class of the type that is the argument of
22174 @code{fields}, or if that type was not a C@t{++} class.
22177 If the field is packed, or is a bitfield, then this will have a
22178 non-zero value, which is the size of the field in bits. Otherwise,
22179 this will be zero; in this case the field's size is given by its type.
22182 The type of the field. This is usually an instance of @code{Type},
22183 but it can be @code{None} in some situations.
22187 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22188 Return a new @code{gdb.Type} object which represents an array of this
22189 type. If one argument is given, it is the inclusive upper bound of
22190 the array; in this case the lower bound is zero. If two arguments are
22191 given, the first argument is the lower bound of the array, and the
22192 second argument is the upper bound of the array. An array's length
22193 must not be negative, but the bounds can be.
22196 @defun Type.const ()
22197 Return a new @code{gdb.Type} object which represents a
22198 @code{const}-qualified variant of this type.
22201 @defun Type.volatile ()
22202 Return a new @code{gdb.Type} object which represents a
22203 @code{volatile}-qualified variant of this type.
22206 @defun Type.unqualified ()
22207 Return a new @code{gdb.Type} object which represents an unqualified
22208 variant of this type. That is, the result is neither @code{const} nor
22212 @defun Type.range ()
22213 Return a Python @code{Tuple} object that contains two elements: the
22214 low bound of the argument type and the high bound of that type. If
22215 the type does not have a range, @value{GDBN} will raise a
22216 @code{gdb.error} exception (@pxref{Exception Handling}).
22219 @defun Type.reference ()
22220 Return a new @code{gdb.Type} object which represents a reference to this
22224 @defun Type.pointer ()
22225 Return a new @code{gdb.Type} object which represents a pointer to this
22229 @defun Type.strip_typedefs ()
22230 Return a new @code{gdb.Type} that represents the real type,
22231 after removing all layers of typedefs.
22234 @defun Type.target ()
22235 Return a new @code{gdb.Type} object which represents the target type
22238 For a pointer type, the target type is the type of the pointed-to
22239 object. For an array type (meaning C-like arrays), the target type is
22240 the type of the elements of the array. For a function or method type,
22241 the target type is the type of the return value. For a complex type,
22242 the target type is the type of the elements. For a typedef, the
22243 target type is the aliased type.
22245 If the type does not have a target, this method will throw an
22249 @defun Type.template_argument (n @r{[}, block@r{]})
22250 If this @code{gdb.Type} is an instantiation of a template, this will
22251 return a new @code{gdb.Type} which represents the type of the
22252 @var{n}th template argument.
22254 If this @code{gdb.Type} is not a template type, this will throw an
22255 exception. Ordinarily, only C@t{++} code will have template types.
22257 If @var{block} is given, then @var{name} is looked up in that scope.
22258 Otherwise, it is searched for globally.
22263 Each type has a code, which indicates what category this type falls
22264 into. The available type categories are represented by constants
22265 defined in the @code{gdb} module:
22268 @findex TYPE_CODE_PTR
22269 @findex gdb.TYPE_CODE_PTR
22270 @item gdb.TYPE_CODE_PTR
22271 The type is a pointer.
22273 @findex TYPE_CODE_ARRAY
22274 @findex gdb.TYPE_CODE_ARRAY
22275 @item gdb.TYPE_CODE_ARRAY
22276 The type is an array.
22278 @findex TYPE_CODE_STRUCT
22279 @findex gdb.TYPE_CODE_STRUCT
22280 @item gdb.TYPE_CODE_STRUCT
22281 The type is a structure.
22283 @findex TYPE_CODE_UNION
22284 @findex gdb.TYPE_CODE_UNION
22285 @item gdb.TYPE_CODE_UNION
22286 The type is a union.
22288 @findex TYPE_CODE_ENUM
22289 @findex gdb.TYPE_CODE_ENUM
22290 @item gdb.TYPE_CODE_ENUM
22291 The type is an enum.
22293 @findex TYPE_CODE_FLAGS
22294 @findex gdb.TYPE_CODE_FLAGS
22295 @item gdb.TYPE_CODE_FLAGS
22296 A bit flags type, used for things such as status registers.
22298 @findex TYPE_CODE_FUNC
22299 @findex gdb.TYPE_CODE_FUNC
22300 @item gdb.TYPE_CODE_FUNC
22301 The type is a function.
22303 @findex TYPE_CODE_INT
22304 @findex gdb.TYPE_CODE_INT
22305 @item gdb.TYPE_CODE_INT
22306 The type is an integer type.
22308 @findex TYPE_CODE_FLT
22309 @findex gdb.TYPE_CODE_FLT
22310 @item gdb.TYPE_CODE_FLT
22311 A floating point type.
22313 @findex TYPE_CODE_VOID
22314 @findex gdb.TYPE_CODE_VOID
22315 @item gdb.TYPE_CODE_VOID
22316 The special type @code{void}.
22318 @findex TYPE_CODE_SET
22319 @findex gdb.TYPE_CODE_SET
22320 @item gdb.TYPE_CODE_SET
22323 @findex TYPE_CODE_RANGE
22324 @findex gdb.TYPE_CODE_RANGE
22325 @item gdb.TYPE_CODE_RANGE
22326 A range type, that is, an integer type with bounds.
22328 @findex TYPE_CODE_STRING
22329 @findex gdb.TYPE_CODE_STRING
22330 @item gdb.TYPE_CODE_STRING
22331 A string type. Note that this is only used for certain languages with
22332 language-defined string types; C strings are not represented this way.
22334 @findex TYPE_CODE_BITSTRING
22335 @findex gdb.TYPE_CODE_BITSTRING
22336 @item gdb.TYPE_CODE_BITSTRING
22339 @findex TYPE_CODE_ERROR
22340 @findex gdb.TYPE_CODE_ERROR
22341 @item gdb.TYPE_CODE_ERROR
22342 An unknown or erroneous type.
22344 @findex TYPE_CODE_METHOD
22345 @findex gdb.TYPE_CODE_METHOD
22346 @item gdb.TYPE_CODE_METHOD
22347 A method type, as found in C@t{++} or Java.
22349 @findex TYPE_CODE_METHODPTR
22350 @findex gdb.TYPE_CODE_METHODPTR
22351 @item gdb.TYPE_CODE_METHODPTR
22352 A pointer-to-member-function.
22354 @findex TYPE_CODE_MEMBERPTR
22355 @findex gdb.TYPE_CODE_MEMBERPTR
22356 @item gdb.TYPE_CODE_MEMBERPTR
22357 A pointer-to-member.
22359 @findex TYPE_CODE_REF
22360 @findex gdb.TYPE_CODE_REF
22361 @item gdb.TYPE_CODE_REF
22364 @findex TYPE_CODE_CHAR
22365 @findex gdb.TYPE_CODE_CHAR
22366 @item gdb.TYPE_CODE_CHAR
22369 @findex TYPE_CODE_BOOL
22370 @findex gdb.TYPE_CODE_BOOL
22371 @item gdb.TYPE_CODE_BOOL
22374 @findex TYPE_CODE_COMPLEX
22375 @findex gdb.TYPE_CODE_COMPLEX
22376 @item gdb.TYPE_CODE_COMPLEX
22377 A complex float type.
22379 @findex TYPE_CODE_TYPEDEF
22380 @findex gdb.TYPE_CODE_TYPEDEF
22381 @item gdb.TYPE_CODE_TYPEDEF
22382 A typedef to some other type.
22384 @findex TYPE_CODE_NAMESPACE
22385 @findex gdb.TYPE_CODE_NAMESPACE
22386 @item gdb.TYPE_CODE_NAMESPACE
22387 A C@t{++} namespace.
22389 @findex TYPE_CODE_DECFLOAT
22390 @findex gdb.TYPE_CODE_DECFLOAT
22391 @item gdb.TYPE_CODE_DECFLOAT
22392 A decimal floating point type.
22394 @findex TYPE_CODE_INTERNAL_FUNCTION
22395 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22396 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22397 A function internal to @value{GDBN}. This is the type used to represent
22398 convenience functions.
22401 Further support for types is provided in the @code{gdb.types}
22402 Python module (@pxref{gdb.types}).
22404 @node Pretty Printing API
22405 @subsubsection Pretty Printing API
22407 An example output is provided (@pxref{Pretty Printing}).
22409 A pretty-printer is just an object that holds a value and implements a
22410 specific interface, defined here.
22412 @defun pretty_printer.children (self)
22413 @value{GDBN} will call this method on a pretty-printer to compute the
22414 children of the pretty-printer's value.
22416 This method must return an object conforming to the Python iterator
22417 protocol. Each item returned by the iterator must be a tuple holding
22418 two elements. The first element is the ``name'' of the child; the
22419 second element is the child's value. The value can be any Python
22420 object which is convertible to a @value{GDBN} value.
22422 This method is optional. If it does not exist, @value{GDBN} will act
22423 as though the value has no children.
22426 @defun pretty_printer.display_hint (self)
22427 The CLI may call this method and use its result to change the
22428 formatting of a value. The result will also be supplied to an MI
22429 consumer as a @samp{displayhint} attribute of the variable being
22432 This method is optional. If it does exist, this method must return a
22435 Some display hints are predefined by @value{GDBN}:
22439 Indicate that the object being printed is ``array-like''. The CLI
22440 uses this to respect parameters such as @code{set print elements} and
22441 @code{set print array}.
22444 Indicate that the object being printed is ``map-like'', and that the
22445 children of this value can be assumed to alternate between keys and
22449 Indicate that the object being printed is ``string-like''. If the
22450 printer's @code{to_string} method returns a Python string of some
22451 kind, then @value{GDBN} will call its internal language-specific
22452 string-printing function to format the string. For the CLI this means
22453 adding quotation marks, possibly escaping some characters, respecting
22454 @code{set print elements}, and the like.
22458 @defun pretty_printer.to_string (self)
22459 @value{GDBN} will call this method to display the string
22460 representation of the value passed to the object's constructor.
22462 When printing from the CLI, if the @code{to_string} method exists,
22463 then @value{GDBN} will prepend its result to the values returned by
22464 @code{children}. Exactly how this formatting is done is dependent on
22465 the display hint, and may change as more hints are added. Also,
22466 depending on the print settings (@pxref{Print Settings}), the CLI may
22467 print just the result of @code{to_string} in a stack trace, omitting
22468 the result of @code{children}.
22470 If this method returns a string, it is printed verbatim.
22472 Otherwise, if this method returns an instance of @code{gdb.Value},
22473 then @value{GDBN} prints this value. This may result in a call to
22474 another pretty-printer.
22476 If instead the method returns a Python value which is convertible to a
22477 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22478 the resulting value. Again, this may result in a call to another
22479 pretty-printer. Python scalars (integers, floats, and booleans) and
22480 strings are convertible to @code{gdb.Value}; other types are not.
22482 Finally, if this method returns @code{None} then no further operations
22483 are peformed in this method and nothing is printed.
22485 If the result is not one of these types, an exception is raised.
22488 @value{GDBN} provides a function which can be used to look up the
22489 default pretty-printer for a @code{gdb.Value}:
22491 @findex gdb.default_visualizer
22492 @defun gdb.default_visualizer (value)
22493 This function takes a @code{gdb.Value} object as an argument. If a
22494 pretty-printer for this value exists, then it is returned. If no such
22495 printer exists, then this returns @code{None}.
22498 @node Selecting Pretty-Printers
22499 @subsubsection Selecting Pretty-Printers
22501 The Python list @code{gdb.pretty_printers} contains an array of
22502 functions or callable objects that have been registered via addition
22503 as a pretty-printer. Printers in this list are called @code{global}
22504 printers, they're available when debugging all inferiors.
22505 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22506 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22509 Each function on these lists is passed a single @code{gdb.Value}
22510 argument and should return a pretty-printer object conforming to the
22511 interface definition above (@pxref{Pretty Printing API}). If a function
22512 cannot create a pretty-printer for the value, it should return
22515 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22516 @code{gdb.Objfile} in the current program space and iteratively calls
22517 each enabled lookup routine in the list for that @code{gdb.Objfile}
22518 until it receives a pretty-printer object.
22519 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22520 searches the pretty-printer list of the current program space,
22521 calling each enabled function until an object is returned.
22522 After these lists have been exhausted, it tries the global
22523 @code{gdb.pretty_printers} list, again calling each enabled function until an
22524 object is returned.
22526 The order in which the objfiles are searched is not specified. For a
22527 given list, functions are always invoked from the head of the list,
22528 and iterated over sequentially until the end of the list, or a printer
22529 object is returned.
22531 For various reasons a pretty-printer may not work.
22532 For example, the underlying data structure may have changed and
22533 the pretty-printer is out of date.
22535 The consequences of a broken pretty-printer are severe enough that
22536 @value{GDBN} provides support for enabling and disabling individual
22537 printers. For example, if @code{print frame-arguments} is on,
22538 a backtrace can become highly illegible if any argument is printed
22539 with a broken printer.
22541 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22542 attribute to the registered function or callable object. If this attribute
22543 is present and its value is @code{False}, the printer is disabled, otherwise
22544 the printer is enabled.
22546 @node Writing a Pretty-Printer
22547 @subsubsection Writing a Pretty-Printer
22548 @cindex writing a pretty-printer
22550 A pretty-printer consists of two parts: a lookup function to detect
22551 if the type is supported, and the printer itself.
22553 Here is an example showing how a @code{std::string} printer might be
22554 written. @xref{Pretty Printing API}, for details on the API this class
22558 class StdStringPrinter(object):
22559 "Print a std::string"
22561 def __init__(self, val):
22564 def to_string(self):
22565 return self.val['_M_dataplus']['_M_p']
22567 def display_hint(self):
22571 And here is an example showing how a lookup function for the printer
22572 example above might be written.
22575 def str_lookup_function(val):
22576 lookup_tag = val.type.tag
22577 if lookup_tag == None:
22579 regex = re.compile("^std::basic_string<char,.*>$")
22580 if regex.match(lookup_tag):
22581 return StdStringPrinter(val)
22585 The example lookup function extracts the value's type, and attempts to
22586 match it to a type that it can pretty-print. If it is a type the
22587 printer can pretty-print, it will return a printer object. If not, it
22588 returns @code{None}.
22590 We recommend that you put your core pretty-printers into a Python
22591 package. If your pretty-printers are for use with a library, we
22592 further recommend embedding a version number into the package name.
22593 This practice will enable @value{GDBN} to load multiple versions of
22594 your pretty-printers at the same time, because they will have
22597 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22598 can be evaluated multiple times without changing its meaning. An
22599 ideal auto-load file will consist solely of @code{import}s of your
22600 printer modules, followed by a call to a register pretty-printers with
22601 the current objfile.
22603 Taken as a whole, this approach will scale nicely to multiple
22604 inferiors, each potentially using a different library version.
22605 Embedding a version number in the Python package name will ensure that
22606 @value{GDBN} is able to load both sets of printers simultaneously.
22607 Then, because the search for pretty-printers is done by objfile, and
22608 because your auto-loaded code took care to register your library's
22609 printers with a specific objfile, @value{GDBN} will find the correct
22610 printers for the specific version of the library used by each
22613 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22614 this code might appear in @code{gdb.libstdcxx.v6}:
22617 def register_printers(objfile):
22618 objfile.pretty_printers.append(str_lookup_function)
22622 And then the corresponding contents of the auto-load file would be:
22625 import gdb.libstdcxx.v6
22626 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22629 The previous example illustrates a basic pretty-printer.
22630 There are a few things that can be improved on.
22631 The printer doesn't have a name, making it hard to identify in a
22632 list of installed printers. The lookup function has a name, but
22633 lookup functions can have arbitrary, even identical, names.
22635 Second, the printer only handles one type, whereas a library typically has
22636 several types. One could install a lookup function for each desired type
22637 in the library, but one could also have a single lookup function recognize
22638 several types. The latter is the conventional way this is handled.
22639 If a pretty-printer can handle multiple data types, then its
22640 @dfn{subprinters} are the printers for the individual data types.
22642 The @code{gdb.printing} module provides a formal way of solving these
22643 problems (@pxref{gdb.printing}).
22644 Here is another example that handles multiple types.
22646 These are the types we are going to pretty-print:
22649 struct foo @{ int a, b; @};
22650 struct bar @{ struct foo x, y; @};
22653 Here are the printers:
22657 """Print a foo object."""
22659 def __init__(self, val):
22662 def to_string(self):
22663 return ("a=<" + str(self.val["a"]) +
22664 "> b=<" + str(self.val["b"]) + ">")
22667 """Print a bar object."""
22669 def __init__(self, val):
22672 def to_string(self):
22673 return ("x=<" + str(self.val["x"]) +
22674 "> y=<" + str(self.val["y"]) + ">")
22677 This example doesn't need a lookup function, that is handled by the
22678 @code{gdb.printing} module. Instead a function is provided to build up
22679 the object that handles the lookup.
22682 import gdb.printing
22684 def build_pretty_printer():
22685 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22687 pp.add_printer('foo', '^foo$', fooPrinter)
22688 pp.add_printer('bar', '^bar$', barPrinter)
22692 And here is the autoload support:
22695 import gdb.printing
22697 gdb.printing.register_pretty_printer(
22698 gdb.current_objfile(),
22699 my_library.build_pretty_printer())
22702 Finally, when this printer is loaded into @value{GDBN}, here is the
22703 corresponding output of @samp{info pretty-printer}:
22706 (gdb) info pretty-printer
22713 @node Inferiors In Python
22714 @subsubsection Inferiors In Python
22715 @cindex inferiors in Python
22717 @findex gdb.Inferior
22718 Programs which are being run under @value{GDBN} are called inferiors
22719 (@pxref{Inferiors and Programs}). Python scripts can access
22720 information about and manipulate inferiors controlled by @value{GDBN}
22721 via objects of the @code{gdb.Inferior} class.
22723 The following inferior-related functions are available in the @code{gdb}
22726 @defun gdb.inferiors ()
22727 Return a tuple containing all inferior objects.
22730 @defun gdb.selected_inferior ()
22731 Return an object representing the current inferior.
22734 A @code{gdb.Inferior} object has the following attributes:
22737 @defvar Inferior.num
22738 ID of inferior, as assigned by GDB.
22741 @defvar Inferior.pid
22742 Process ID of the inferior, as assigned by the underlying operating
22746 @defvar Inferior.was_attached
22747 Boolean signaling whether the inferior was created using `attach', or
22748 started by @value{GDBN} itself.
22752 A @code{gdb.Inferior} object has the following methods:
22755 @defun Inferior.is_valid ()
22756 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22757 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22758 if the inferior no longer exists within @value{GDBN}. All other
22759 @code{gdb.Inferior} methods will throw an exception if it is invalid
22760 at the time the method is called.
22763 @defun Inferior.threads ()
22764 This method returns a tuple holding all the threads which are valid
22765 when it is called. If there are no valid threads, the method will
22766 return an empty tuple.
22769 @findex gdb.read_memory
22770 @defun Inferior.read_memory (address, length)
22771 Read @var{length} bytes of memory from the inferior, starting at
22772 @var{address}. Returns a buffer object, which behaves much like an array
22773 or a string. It can be modified and given to the @code{gdb.write_memory}
22777 @findex gdb.write_memory
22778 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22779 Write the contents of @var{buffer} to the inferior, starting at
22780 @var{address}. The @var{buffer} parameter must be a Python object
22781 which supports the buffer protocol, i.e., a string, an array or the
22782 object returned from @code{gdb.read_memory}. If given, @var{length}
22783 determines the number of bytes from @var{buffer} to be written.
22786 @findex gdb.search_memory
22787 @defun Inferior.search_memory (address, length, pattern)
22788 Search a region of the inferior memory starting at @var{address} with
22789 the given @var{length} using the search pattern supplied in
22790 @var{pattern}. The @var{pattern} parameter must be a Python object
22791 which supports the buffer protocol, i.e., a string, an array or the
22792 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22793 containing the address where the pattern was found, or @code{None} if
22794 the pattern could not be found.
22798 @node Events In Python
22799 @subsubsection Events In Python
22800 @cindex inferior events in Python
22802 @value{GDBN} provides a general event facility so that Python code can be
22803 notified of various state changes, particularly changes that occur in
22806 An @dfn{event} is just an object that describes some state change. The
22807 type of the object and its attributes will vary depending on the details
22808 of the change. All the existing events are described below.
22810 In order to be notified of an event, you must register an event handler
22811 with an @dfn{event registry}. An event registry is an object in the
22812 @code{gdb.events} module which dispatches particular events. A registry
22813 provides methods to register and unregister event handlers:
22816 @defun EventRegistry.connect (object)
22817 Add the given callable @var{object} to the registry. This object will be
22818 called when an event corresponding to this registry occurs.
22821 @defun EventRegistry.disconnect (object)
22822 Remove the given @var{object} from the registry. Once removed, the object
22823 will no longer receive notifications of events.
22827 Here is an example:
22830 def exit_handler (event):
22831 print "event type: exit"
22832 print "exit code: %d" % (event.exit_code)
22834 gdb.events.exited.connect (exit_handler)
22837 In the above example we connect our handler @code{exit_handler} to the
22838 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22839 called when the inferior exits. The argument @dfn{event} in this example is
22840 of type @code{gdb.ExitedEvent}. As you can see in the example the
22841 @code{ExitedEvent} object has an attribute which indicates the exit code of
22844 The following is a listing of the event registries that are available and
22845 details of the events they emit:
22850 Emits @code{gdb.ThreadEvent}.
22852 Some events can be thread specific when @value{GDBN} is running in non-stop
22853 mode. When represented in Python, these events all extend
22854 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22855 events which are emitted by this or other modules might extend this event.
22856 Examples of these events are @code{gdb.BreakpointEvent} and
22857 @code{gdb.ContinueEvent}.
22860 @defvar ThreadEvent.inferior_thread
22861 In non-stop mode this attribute will be set to the specific thread which was
22862 involved in the emitted event. Otherwise, it will be set to @code{None}.
22866 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22868 This event indicates that the inferior has been continued after a stop. For
22869 inherited attribute refer to @code{gdb.ThreadEvent} above.
22871 @item events.exited
22872 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22873 @code{events.ExitedEvent} has two attributes:
22875 @defvar ExitedEvent.exit_code
22876 An integer representing the exit code, if available, which the inferior
22877 has returned. (The exit code could be unavailable if, for example,
22878 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22879 the attribute does not exist.
22881 @defvar ExitedEvent inferior
22882 A reference to the inferior which triggered the @code{exited} event.
22887 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22889 Indicates that the inferior has stopped. All events emitted by this registry
22890 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22891 will indicate the stopped thread when @value{GDBN} is running in non-stop
22892 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22894 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22896 This event indicates that the inferior or one of its threads has received as
22897 signal. @code{gdb.SignalEvent} has the following attributes:
22900 @defvar SignalEvent.stop_signal
22901 A string representing the signal received by the inferior. A list of possible
22902 signal values can be obtained by running the command @code{info signals} in
22903 the @value{GDBN} command prompt.
22907 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22909 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22910 been hit, and has the following attributes:
22913 @defvar BreakpointEvent.breakpoints
22914 A sequence containing references to all the breakpoints (type
22915 @code{gdb.Breakpoint}) that were hit.
22916 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22918 @defvar BreakpointEvent.breakpoint
22919 A reference to the first breakpoint that was hit.
22920 This function is maintained for backward compatibility and is now deprecated
22921 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22925 @item events.new_objfile
22926 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22927 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22930 @defvar NewObjFileEvent.new_objfile
22931 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22932 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22938 @node Threads In Python
22939 @subsubsection Threads In Python
22940 @cindex threads in python
22942 @findex gdb.InferiorThread
22943 Python scripts can access information about, and manipulate inferior threads
22944 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22946 The following thread-related functions are available in the @code{gdb}
22949 @findex gdb.selected_thread
22950 @defun gdb.selected_thread ()
22951 This function returns the thread object for the selected thread. If there
22952 is no selected thread, this will return @code{None}.
22955 A @code{gdb.InferiorThread} object has the following attributes:
22958 @defvar InferiorThread.name
22959 The name of the thread. If the user specified a name using
22960 @code{thread name}, then this returns that name. Otherwise, if an
22961 OS-supplied name is available, then it is returned. Otherwise, this
22962 returns @code{None}.
22964 This attribute can be assigned to. The new value must be a string
22965 object, which sets the new name, or @code{None}, which removes any
22966 user-specified thread name.
22969 @defvar InferiorThread.num
22970 ID of the thread, as assigned by GDB.
22973 @defvar InferiorThread.ptid
22974 ID of the thread, as assigned by the operating system. This attribute is a
22975 tuple containing three integers. The first is the Process ID (PID); the second
22976 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22977 Either the LWPID or TID may be 0, which indicates that the operating system
22978 does not use that identifier.
22982 A @code{gdb.InferiorThread} object has the following methods:
22985 @defun InferiorThread.is_valid ()
22986 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22987 @code{False} if not. A @code{gdb.InferiorThread} object will become
22988 invalid if the thread exits, or the inferior that the thread belongs
22989 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22990 exception if it is invalid at the time the method is called.
22993 @defun InferiorThread.switch ()
22994 This changes @value{GDBN}'s currently selected thread to the one represented
22998 @defun InferiorThread.is_stopped ()
22999 Return a Boolean indicating whether the thread is stopped.
23002 @defun InferiorThread.is_running ()
23003 Return a Boolean indicating whether the thread is running.
23006 @defun InferiorThread.is_exited ()
23007 Return a Boolean indicating whether the thread is exited.
23011 @node Commands In Python
23012 @subsubsection Commands In Python
23014 @cindex commands in python
23015 @cindex python commands
23016 You can implement new @value{GDBN} CLI commands in Python. A CLI
23017 command is implemented using an instance of the @code{gdb.Command}
23018 class, most commonly using a subclass.
23020 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23021 The object initializer for @code{Command} registers the new command
23022 with @value{GDBN}. This initializer is normally invoked from the
23023 subclass' own @code{__init__} method.
23025 @var{name} is the name of the command. If @var{name} consists of
23026 multiple words, then the initial words are looked for as prefix
23027 commands. In this case, if one of the prefix commands does not exist,
23028 an exception is raised.
23030 There is no support for multi-line commands.
23032 @var{command_class} should be one of the @samp{COMMAND_} constants
23033 defined below. This argument tells @value{GDBN} how to categorize the
23034 new command in the help system.
23036 @var{completer_class} is an optional argument. If given, it should be
23037 one of the @samp{COMPLETE_} constants defined below. This argument
23038 tells @value{GDBN} how to perform completion for this command. If not
23039 given, @value{GDBN} will attempt to complete using the object's
23040 @code{complete} method (see below); if no such method is found, an
23041 error will occur when completion is attempted.
23043 @var{prefix} is an optional argument. If @code{True}, then the new
23044 command is a prefix command; sub-commands of this command may be
23047 The help text for the new command is taken from the Python
23048 documentation string for the command's class, if there is one. If no
23049 documentation string is provided, the default value ``This command is
23050 not documented.'' is used.
23053 @cindex don't repeat Python command
23054 @defun Command.dont_repeat ()
23055 By default, a @value{GDBN} command is repeated when the user enters a
23056 blank line at the command prompt. A command can suppress this
23057 behavior by invoking the @code{dont_repeat} method. This is similar
23058 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23061 @defun Command.invoke (argument, from_tty)
23062 This method is called by @value{GDBN} when this command is invoked.
23064 @var{argument} is a string. It is the argument to the command, after
23065 leading and trailing whitespace has been stripped.
23067 @var{from_tty} is a boolean argument. When true, this means that the
23068 command was entered by the user at the terminal; when false it means
23069 that the command came from elsewhere.
23071 If this method throws an exception, it is turned into a @value{GDBN}
23072 @code{error} call. Otherwise, the return value is ignored.
23074 @findex gdb.string_to_argv
23075 To break @var{argument} up into an argv-like string use
23076 @code{gdb.string_to_argv}. This function behaves identically to
23077 @value{GDBN}'s internal argument lexer @code{buildargv}.
23078 It is recommended to use this for consistency.
23079 Arguments are separated by spaces and may be quoted.
23083 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23084 ['1', '2 "3', '4 "5', "6 '7"]
23089 @cindex completion of Python commands
23090 @defun Command.complete (text, word)
23091 This method is called by @value{GDBN} when the user attempts
23092 completion on this command. All forms of completion are handled by
23093 this method, that is, the @key{TAB} and @key{M-?} key bindings
23094 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23097 The arguments @var{text} and @var{word} are both strings. @var{text}
23098 holds the complete command line up to the cursor's location.
23099 @var{word} holds the last word of the command line; this is computed
23100 using a word-breaking heuristic.
23102 The @code{complete} method can return several values:
23105 If the return value is a sequence, the contents of the sequence are
23106 used as the completions. It is up to @code{complete} to ensure that the
23107 contents actually do complete the word. A zero-length sequence is
23108 allowed, it means that there were no completions available. Only
23109 string elements of the sequence are used; other elements in the
23110 sequence are ignored.
23113 If the return value is one of the @samp{COMPLETE_} constants defined
23114 below, then the corresponding @value{GDBN}-internal completion
23115 function is invoked, and its result is used.
23118 All other results are treated as though there were no available
23123 When a new command is registered, it must be declared as a member of
23124 some general class of commands. This is used to classify top-level
23125 commands in the on-line help system; note that prefix commands are not
23126 listed under their own category but rather that of their top-level
23127 command. The available classifications are represented by constants
23128 defined in the @code{gdb} module:
23131 @findex COMMAND_NONE
23132 @findex gdb.COMMAND_NONE
23133 @item gdb.COMMAND_NONE
23134 The command does not belong to any particular class. A command in
23135 this category will not be displayed in any of the help categories.
23137 @findex COMMAND_RUNNING
23138 @findex gdb.COMMAND_RUNNING
23139 @item gdb.COMMAND_RUNNING
23140 The command is related to running the inferior. For example,
23141 @code{start}, @code{step}, and @code{continue} are in this category.
23142 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23143 commands in this category.
23145 @findex COMMAND_DATA
23146 @findex gdb.COMMAND_DATA
23147 @item gdb.COMMAND_DATA
23148 The command is related to data or variables. For example,
23149 @code{call}, @code{find}, and @code{print} are in this category. Type
23150 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23153 @findex COMMAND_STACK
23154 @findex gdb.COMMAND_STACK
23155 @item gdb.COMMAND_STACK
23156 The command has to do with manipulation of the stack. For example,
23157 @code{backtrace}, @code{frame}, and @code{return} are in this
23158 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23159 list of commands in this category.
23161 @findex COMMAND_FILES
23162 @findex gdb.COMMAND_FILES
23163 @item gdb.COMMAND_FILES
23164 This class is used for file-related commands. For example,
23165 @code{file}, @code{list} and @code{section} are in this category.
23166 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23167 commands in this category.
23169 @findex COMMAND_SUPPORT
23170 @findex gdb.COMMAND_SUPPORT
23171 @item gdb.COMMAND_SUPPORT
23172 This should be used for ``support facilities'', generally meaning
23173 things that are useful to the user when interacting with @value{GDBN},
23174 but not related to the state of the inferior. For example,
23175 @code{help}, @code{make}, and @code{shell} are in this category. Type
23176 @kbd{help support} at the @value{GDBN} prompt to see a list of
23177 commands in this category.
23179 @findex COMMAND_STATUS
23180 @findex gdb.COMMAND_STATUS
23181 @item gdb.COMMAND_STATUS
23182 The command is an @samp{info}-related command, that is, related to the
23183 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23184 and @code{show} are in this category. Type @kbd{help status} at the
23185 @value{GDBN} prompt to see a list of commands in this category.
23187 @findex COMMAND_BREAKPOINTS
23188 @findex gdb.COMMAND_BREAKPOINTS
23189 @item gdb.COMMAND_BREAKPOINTS
23190 The command has to do with breakpoints. For example, @code{break},
23191 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23192 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23195 @findex COMMAND_TRACEPOINTS
23196 @findex gdb.COMMAND_TRACEPOINTS
23197 @item gdb.COMMAND_TRACEPOINTS
23198 The command has to do with tracepoints. For example, @code{trace},
23199 @code{actions}, and @code{tfind} are in this category. Type
23200 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23201 commands in this category.
23203 @findex COMMAND_OBSCURE
23204 @findex gdb.COMMAND_OBSCURE
23205 @item gdb.COMMAND_OBSCURE
23206 The command is only used in unusual circumstances, or is not of
23207 general interest to users. For example, @code{checkpoint},
23208 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23209 obscure} at the @value{GDBN} prompt to see a list of commands in this
23212 @findex COMMAND_MAINTENANCE
23213 @findex gdb.COMMAND_MAINTENANCE
23214 @item gdb.COMMAND_MAINTENANCE
23215 The command is only useful to @value{GDBN} maintainers. The
23216 @code{maintenance} and @code{flushregs} commands are in this category.
23217 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23218 commands in this category.
23221 A new command can use a predefined completion function, either by
23222 specifying it via an argument at initialization, or by returning it
23223 from the @code{complete} method. These predefined completion
23224 constants are all defined in the @code{gdb} module:
23227 @findex COMPLETE_NONE
23228 @findex gdb.COMPLETE_NONE
23229 @item gdb.COMPLETE_NONE
23230 This constant means that no completion should be done.
23232 @findex COMPLETE_FILENAME
23233 @findex gdb.COMPLETE_FILENAME
23234 @item gdb.COMPLETE_FILENAME
23235 This constant means that filename completion should be performed.
23237 @findex COMPLETE_LOCATION
23238 @findex gdb.COMPLETE_LOCATION
23239 @item gdb.COMPLETE_LOCATION
23240 This constant means that location completion should be done.
23241 @xref{Specify Location}.
23243 @findex COMPLETE_COMMAND
23244 @findex gdb.COMPLETE_COMMAND
23245 @item gdb.COMPLETE_COMMAND
23246 This constant means that completion should examine @value{GDBN}
23249 @findex COMPLETE_SYMBOL
23250 @findex gdb.COMPLETE_SYMBOL
23251 @item gdb.COMPLETE_SYMBOL
23252 This constant means that completion should be done using symbol names
23256 The following code snippet shows how a trivial CLI command can be
23257 implemented in Python:
23260 class HelloWorld (gdb.Command):
23261 """Greet the whole world."""
23263 def __init__ (self):
23264 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23266 def invoke (self, arg, from_tty):
23267 print "Hello, World!"
23272 The last line instantiates the class, and is necessary to trigger the
23273 registration of the command with @value{GDBN}. Depending on how the
23274 Python code is read into @value{GDBN}, you may need to import the
23275 @code{gdb} module explicitly.
23277 @node Parameters In Python
23278 @subsubsection Parameters In Python
23280 @cindex parameters in python
23281 @cindex python parameters
23282 @tindex gdb.Parameter
23284 You can implement new @value{GDBN} parameters using Python. A new
23285 parameter is implemented as an instance of the @code{gdb.Parameter}
23288 Parameters are exposed to the user via the @code{set} and
23289 @code{show} commands. @xref{Help}.
23291 There are many parameters that already exist and can be set in
23292 @value{GDBN}. Two examples are: @code{set follow fork} and
23293 @code{set charset}. Setting these parameters influences certain
23294 behavior in @value{GDBN}. Similarly, you can define parameters that
23295 can be used to influence behavior in custom Python scripts and commands.
23297 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23298 The object initializer for @code{Parameter} registers the new
23299 parameter with @value{GDBN}. This initializer is normally invoked
23300 from the subclass' own @code{__init__} method.
23302 @var{name} is the name of the new parameter. If @var{name} consists
23303 of multiple words, then the initial words are looked for as prefix
23304 parameters. An example of this can be illustrated with the
23305 @code{set print} set of parameters. If @var{name} is
23306 @code{print foo}, then @code{print} will be searched as the prefix
23307 parameter. In this case the parameter can subsequently be accessed in
23308 @value{GDBN} as @code{set print foo}.
23310 If @var{name} consists of multiple words, and no prefix parameter group
23311 can be found, an exception is raised.
23313 @var{command-class} should be one of the @samp{COMMAND_} constants
23314 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23315 categorize the new parameter in the help system.
23317 @var{parameter-class} should be one of the @samp{PARAM_} constants
23318 defined below. This argument tells @value{GDBN} the type of the new
23319 parameter; this information is used for input validation and
23322 If @var{parameter-class} is @code{PARAM_ENUM}, then
23323 @var{enum-sequence} must be a sequence of strings. These strings
23324 represent the possible values for the parameter.
23326 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23327 of a fourth argument will cause an exception to be thrown.
23329 The help text for the new parameter is taken from the Python
23330 documentation string for the parameter's class, if there is one. If
23331 there is no documentation string, a default value is used.
23334 @defvar Parameter.set_doc
23335 If this attribute exists, and is a string, then its value is used as
23336 the help text for this parameter's @code{set} command. The value is
23337 examined when @code{Parameter.__init__} is invoked; subsequent changes
23341 @defvar Parameter.show_doc
23342 If this attribute exists, and is a string, then its value is used as
23343 the help text for this parameter's @code{show} command. The value is
23344 examined when @code{Parameter.__init__} is invoked; subsequent changes
23348 @defvar Parameter.value
23349 The @code{value} attribute holds the underlying value of the
23350 parameter. It can be read and assigned to just as any other
23351 attribute. @value{GDBN} does validation when assignments are made.
23354 There are two methods that should be implemented in any
23355 @code{Parameter} class. These are:
23357 @defun Parameter.get_set_string (self)
23358 @value{GDBN} will call this method when a @var{parameter}'s value has
23359 been changed via the @code{set} API (for example, @kbd{set foo off}).
23360 The @code{value} attribute has already been populated with the new
23361 value and may be used in output. This method must return a string.
23364 @defun Parameter.get_show_string (self, svalue)
23365 @value{GDBN} will call this method when a @var{parameter}'s
23366 @code{show} API has been invoked (for example, @kbd{show foo}). The
23367 argument @code{svalue} receives the string representation of the
23368 current value. This method must return a string.
23371 When a new parameter is defined, its type must be specified. The
23372 available types are represented by constants defined in the @code{gdb}
23376 @findex PARAM_BOOLEAN
23377 @findex gdb.PARAM_BOOLEAN
23378 @item gdb.PARAM_BOOLEAN
23379 The value is a plain boolean. The Python boolean values, @code{True}
23380 and @code{False} are the only valid values.
23382 @findex PARAM_AUTO_BOOLEAN
23383 @findex gdb.PARAM_AUTO_BOOLEAN
23384 @item gdb.PARAM_AUTO_BOOLEAN
23385 The value has three possible states: true, false, and @samp{auto}. In
23386 Python, true and false are represented using boolean constants, and
23387 @samp{auto} is represented using @code{None}.
23389 @findex PARAM_UINTEGER
23390 @findex gdb.PARAM_UINTEGER
23391 @item gdb.PARAM_UINTEGER
23392 The value is an unsigned integer. The value of 0 should be
23393 interpreted to mean ``unlimited''.
23395 @findex PARAM_INTEGER
23396 @findex gdb.PARAM_INTEGER
23397 @item gdb.PARAM_INTEGER
23398 The value is a signed integer. The value of 0 should be interpreted
23399 to mean ``unlimited''.
23401 @findex PARAM_STRING
23402 @findex gdb.PARAM_STRING
23403 @item gdb.PARAM_STRING
23404 The value is a string. When the user modifies the string, any escape
23405 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23406 translated into corresponding characters and encoded into the current
23409 @findex PARAM_STRING_NOESCAPE
23410 @findex gdb.PARAM_STRING_NOESCAPE
23411 @item gdb.PARAM_STRING_NOESCAPE
23412 The value is a string. When the user modifies the string, escapes are
23413 passed through untranslated.
23415 @findex PARAM_OPTIONAL_FILENAME
23416 @findex gdb.PARAM_OPTIONAL_FILENAME
23417 @item gdb.PARAM_OPTIONAL_FILENAME
23418 The value is a either a filename (a string), or @code{None}.
23420 @findex PARAM_FILENAME
23421 @findex gdb.PARAM_FILENAME
23422 @item gdb.PARAM_FILENAME
23423 The value is a filename. This is just like
23424 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23426 @findex PARAM_ZINTEGER
23427 @findex gdb.PARAM_ZINTEGER
23428 @item gdb.PARAM_ZINTEGER
23429 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23430 is interpreted as itself.
23433 @findex gdb.PARAM_ENUM
23434 @item gdb.PARAM_ENUM
23435 The value is a string, which must be one of a collection string
23436 constants provided when the parameter is created.
23439 @node Functions In Python
23440 @subsubsection Writing new convenience functions
23442 @cindex writing convenience functions
23443 @cindex convenience functions in python
23444 @cindex python convenience functions
23445 @tindex gdb.Function
23447 You can implement new convenience functions (@pxref{Convenience Vars})
23448 in Python. A convenience function is an instance of a subclass of the
23449 class @code{gdb.Function}.
23451 @defun Function.__init__ (name)
23452 The initializer for @code{Function} registers the new function with
23453 @value{GDBN}. The argument @var{name} is the name of the function,
23454 a string. The function will be visible to the user as a convenience
23455 variable of type @code{internal function}, whose name is the same as
23456 the given @var{name}.
23458 The documentation for the new function is taken from the documentation
23459 string for the new class.
23462 @defun Function.invoke (@var{*args})
23463 When a convenience function is evaluated, its arguments are converted
23464 to instances of @code{gdb.Value}, and then the function's
23465 @code{invoke} method is called. Note that @value{GDBN} does not
23466 predetermine the arity of convenience functions. Instead, all
23467 available arguments are passed to @code{invoke}, following the
23468 standard Python calling convention. In particular, a convenience
23469 function can have default values for parameters without ill effect.
23471 The return value of this method is used as its value in the enclosing
23472 expression. If an ordinary Python value is returned, it is converted
23473 to a @code{gdb.Value} following the usual rules.
23476 The following code snippet shows how a trivial convenience function can
23477 be implemented in Python:
23480 class Greet (gdb.Function):
23481 """Return string to greet someone.
23482 Takes a name as argument."""
23484 def __init__ (self):
23485 super (Greet, self).__init__ ("greet")
23487 def invoke (self, name):
23488 return "Hello, %s!" % name.string ()
23493 The last line instantiates the class, and is necessary to trigger the
23494 registration of the function with @value{GDBN}. Depending on how the
23495 Python code is read into @value{GDBN}, you may need to import the
23496 @code{gdb} module explicitly.
23498 @node Progspaces In Python
23499 @subsubsection Program Spaces In Python
23501 @cindex progspaces in python
23502 @tindex gdb.Progspace
23504 A program space, or @dfn{progspace}, represents a symbolic view
23505 of an address space.
23506 It consists of all of the objfiles of the program.
23507 @xref{Objfiles In Python}.
23508 @xref{Inferiors and Programs, program spaces}, for more details
23509 about program spaces.
23511 The following progspace-related functions are available in the
23514 @findex gdb.current_progspace
23515 @defun gdb.current_progspace ()
23516 This function returns the program space of the currently selected inferior.
23517 @xref{Inferiors and Programs}.
23520 @findex gdb.progspaces
23521 @defun gdb.progspaces ()
23522 Return a sequence of all the progspaces currently known to @value{GDBN}.
23525 Each progspace is represented by an instance of the @code{gdb.Progspace}
23528 @defvar Progspace.filename
23529 The file name of the progspace as a string.
23532 @defvar Progspace.pretty_printers
23533 The @code{pretty_printers} attribute is a list of functions. It is
23534 used to look up pretty-printers. A @code{Value} is passed to each
23535 function in order; if the function returns @code{None}, then the
23536 search continues. Otherwise, the return value should be an object
23537 which is used to format the value. @xref{Pretty Printing API}, for more
23541 @node Objfiles In Python
23542 @subsubsection Objfiles In Python
23544 @cindex objfiles in python
23545 @tindex gdb.Objfile
23547 @value{GDBN} loads symbols for an inferior from various
23548 symbol-containing files (@pxref{Files}). These include the primary
23549 executable file, any shared libraries used by the inferior, and any
23550 separate debug info files (@pxref{Separate Debug Files}).
23551 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23553 The following objfile-related functions are available in the
23556 @findex gdb.current_objfile
23557 @defun gdb.current_objfile ()
23558 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23559 sets the ``current objfile'' to the corresponding objfile. This
23560 function returns the current objfile. If there is no current objfile,
23561 this function returns @code{None}.
23564 @findex gdb.objfiles
23565 @defun gdb.objfiles ()
23566 Return a sequence of all the objfiles current known to @value{GDBN}.
23567 @xref{Objfiles In Python}.
23570 Each objfile is represented by an instance of the @code{gdb.Objfile}
23573 @defvar Objfile.filename
23574 The file name of the objfile as a string.
23577 @defvar Objfile.pretty_printers
23578 The @code{pretty_printers} attribute is a list of functions. It is
23579 used to look up pretty-printers. A @code{Value} is passed to each
23580 function in order; if the function returns @code{None}, then the
23581 search continues. Otherwise, the return value should be an object
23582 which is used to format the value. @xref{Pretty Printing API}, for more
23586 A @code{gdb.Objfile} object has the following methods:
23588 @defun Objfile.is_valid ()
23589 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23590 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23591 if the object file it refers to is not loaded in @value{GDBN} any
23592 longer. All other @code{gdb.Objfile} methods will throw an exception
23593 if it is invalid at the time the method is called.
23596 @node Frames In Python
23597 @subsubsection Accessing inferior stack frames from Python.
23599 @cindex frames in python
23600 When the debugged program stops, @value{GDBN} is able to analyze its call
23601 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23602 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23603 while its corresponding frame exists in the inferior's stack. If you try
23604 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23605 exception (@pxref{Exception Handling}).
23607 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23611 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23615 The following frame-related functions are available in the @code{gdb} module:
23617 @findex gdb.selected_frame
23618 @defun gdb.selected_frame ()
23619 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23622 @findex gdb.newest_frame
23623 @defun gdb.newest_frame ()
23624 Return the newest frame object for the selected thread.
23627 @defun gdb.frame_stop_reason_string (reason)
23628 Return a string explaining the reason why @value{GDBN} stopped unwinding
23629 frames, as expressed by the given @var{reason} code (an integer, see the
23630 @code{unwind_stop_reason} method further down in this section).
23633 A @code{gdb.Frame} object has the following methods:
23636 @defun Frame.is_valid ()
23637 Returns true if the @code{gdb.Frame} object is valid, false if not.
23638 A frame object can become invalid if the frame it refers to doesn't
23639 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23640 an exception if it is invalid at the time the method is called.
23643 @defun Frame.name ()
23644 Returns the function name of the frame, or @code{None} if it can't be
23648 @defun Frame.type ()
23649 Returns the type of the frame. The value can be one of:
23651 @item gdb.NORMAL_FRAME
23652 An ordinary stack frame.
23654 @item gdb.DUMMY_FRAME
23655 A fake stack frame that was created by @value{GDBN} when performing an
23656 inferior function call.
23658 @item gdb.INLINE_FRAME
23659 A frame representing an inlined function. The function was inlined
23660 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23662 @item gdb.TAILCALL_FRAME
23663 A frame representing a tail call. @xref{Tail Call Frames}.
23665 @item gdb.SIGTRAMP_FRAME
23666 A signal trampoline frame. This is the frame created by the OS when
23667 it calls into a signal handler.
23669 @item gdb.ARCH_FRAME
23670 A fake stack frame representing a cross-architecture call.
23672 @item gdb.SENTINEL_FRAME
23673 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23678 @defun Frame.unwind_stop_reason ()
23679 Return an integer representing the reason why it's not possible to find
23680 more frames toward the outermost frame. Use
23681 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23682 function to a string. The value can be one of:
23685 @item gdb.FRAME_UNWIND_NO_REASON
23686 No particular reason (older frames should be available).
23688 @item gdb.FRAME_UNWIND_NULL_ID
23689 The previous frame's analyzer returns an invalid result.
23691 @item gdb.FRAME_UNWIND_OUTERMOST
23692 This frame is the outermost.
23694 @item gdb.FRAME_UNWIND_UNAVAILABLE
23695 Cannot unwind further, because that would require knowing the
23696 values of registers or memory that have not been collected.
23698 @item gdb.FRAME_UNWIND_INNER_ID
23699 This frame ID looks like it ought to belong to a NEXT frame,
23700 but we got it for a PREV frame. Normally, this is a sign of
23701 unwinder failure. It could also indicate stack corruption.
23703 @item gdb.FRAME_UNWIND_SAME_ID
23704 This frame has the same ID as the previous one. That means
23705 that unwinding further would almost certainly give us another
23706 frame with exactly the same ID, so break the chain. Normally,
23707 this is a sign of unwinder failure. It could also indicate
23710 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23711 The frame unwinder did not find any saved PC, but we needed
23712 one to unwind further.
23714 @item gdb.FRAME_UNWIND_FIRST_ERROR
23715 Any stop reason greater or equal to this value indicates some kind
23716 of error. This special value facilitates writing code that tests
23717 for errors in unwinding in a way that will work correctly even if
23718 the list of the other values is modified in future @value{GDBN}
23719 versions. Using it, you could write:
23721 reason = gdb.selected_frame().unwind_stop_reason ()
23722 reason_str = gdb.frame_stop_reason_string (reason)
23723 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23724 print "An error occured: %s" % reason_str
23731 Returns the frame's resume address.
23734 @defun Frame.block ()
23735 Return the frame's code block. @xref{Blocks In Python}.
23738 @defun Frame.function ()
23739 Return the symbol for the function corresponding to this frame.
23740 @xref{Symbols In Python}.
23743 @defun Frame.older ()
23744 Return the frame that called this frame.
23747 @defun Frame.newer ()
23748 Return the frame called by this frame.
23751 @defun Frame.find_sal ()
23752 Return the frame's symtab and line object.
23753 @xref{Symbol Tables In Python}.
23756 @defun Frame.read_var (variable @r{[}, block@r{]})
23757 Return the value of @var{variable} in this frame. If the optional
23758 argument @var{block} is provided, search for the variable from that
23759 block; otherwise start at the frame's current block (which is
23760 determined by the frame's current program counter). @var{variable}
23761 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23762 @code{gdb.Block} object.
23765 @defun Frame.select ()
23766 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23771 @node Blocks In Python
23772 @subsubsection Accessing frame blocks from Python.
23774 @cindex blocks in python
23777 Within each frame, @value{GDBN} maintains information on each block
23778 stored in that frame. These blocks are organized hierarchically, and
23779 are represented individually in Python as a @code{gdb.Block}.
23780 Please see @ref{Frames In Python}, for a more in-depth discussion on
23781 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23782 detailed technical information on @value{GDBN}'s book-keeping of the
23785 The following block-related functions are available in the @code{gdb}
23788 @findex gdb.block_for_pc
23789 @defun gdb.block_for_pc (pc)
23790 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23791 block cannot be found for the @var{pc} value specified, the function
23792 will return @code{None}.
23795 A @code{gdb.Block} object has the following methods:
23798 @defun Block.is_valid ()
23799 Returns @code{True} if the @code{gdb.Block} object is valid,
23800 @code{False} if not. A block object can become invalid if the block it
23801 refers to doesn't exist anymore in the inferior. All other
23802 @code{gdb.Block} methods will throw an exception if it is invalid at
23803 the time the method is called. This method is also made available to
23804 the Python iterator object that @code{gdb.Block} provides in an iteration
23805 context and via the Python @code{iter} built-in function.
23809 A @code{gdb.Block} object has the following attributes:
23812 @defvar Block.start
23813 The start address of the block. This attribute is not writable.
23817 The end address of the block. This attribute is not writable.
23820 @defvar Block.function
23821 The name of the block represented as a @code{gdb.Symbol}. If the
23822 block is not named, then this attribute holds @code{None}. This
23823 attribute is not writable.
23826 @defvar Block.superblock
23827 The block containing this block. If this parent block does not exist,
23828 this attribute holds @code{None}. This attribute is not writable.
23831 @defvar Block.global_block
23832 The global block associated with this block. This attribute is not
23836 @defvar Block.static_block
23837 The static block associated with this block. This attribute is not
23841 @defvar Block.is_global
23842 @code{True} if the @code{gdb.Block} object is a global block,
23843 @code{False} if not. This attribute is not
23847 @defvar Block.is_static
23848 @code{True} if the @code{gdb.Block} object is a static block,
23849 @code{False} if not. This attribute is not writable.
23853 @node Symbols In Python
23854 @subsubsection Python representation of Symbols.
23856 @cindex symbols in python
23859 @value{GDBN} represents every variable, function and type as an
23860 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23861 Similarly, Python represents these symbols in @value{GDBN} with the
23862 @code{gdb.Symbol} object.
23864 The following symbol-related functions are available in the @code{gdb}
23867 @findex gdb.lookup_symbol
23868 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23869 This function searches for a symbol by name. The search scope can be
23870 restricted to the parameters defined in the optional domain and block
23873 @var{name} is the name of the symbol. It must be a string. The
23874 optional @var{block} argument restricts the search to symbols visible
23875 in that @var{block}. The @var{block} argument must be a
23876 @code{gdb.Block} object. If omitted, the block for the current frame
23877 is used. The optional @var{domain} argument restricts
23878 the search to the domain type. The @var{domain} argument must be a
23879 domain constant defined in the @code{gdb} module and described later
23882 The result is a tuple of two elements.
23883 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23885 If the symbol is found, the second element is @code{True} if the symbol
23886 is a field of a method's object (e.g., @code{this} in C@t{++}),
23887 otherwise it is @code{False}.
23888 If the symbol is not found, the second element is @code{False}.
23891 @findex gdb.lookup_global_symbol
23892 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23893 This function searches for a global symbol by name.
23894 The search scope can be restricted to by the domain argument.
23896 @var{name} is the name of the symbol. It must be a string.
23897 The optional @var{domain} argument restricts the search to the domain type.
23898 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23899 module and described later in this chapter.
23901 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23905 A @code{gdb.Symbol} object has the following attributes:
23908 @defvar Symbol.type
23909 The type of the symbol or @code{None} if no type is recorded.
23910 This attribute is represented as a @code{gdb.Type} object.
23911 @xref{Types In Python}. This attribute is not writable.
23914 @defvar Symbol.symtab
23915 The symbol table in which the symbol appears. This attribute is
23916 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23917 Python}. This attribute is not writable.
23920 @defvar Symbol.name
23921 The name of the symbol as a string. This attribute is not writable.
23924 @defvar Symbol.linkage_name
23925 The name of the symbol, as used by the linker (i.e., may be mangled).
23926 This attribute is not writable.
23929 @defvar Symbol.print_name
23930 The name of the symbol in a form suitable for output. This is either
23931 @code{name} or @code{linkage_name}, depending on whether the user
23932 asked @value{GDBN} to display demangled or mangled names.
23935 @defvar Symbol.addr_class
23936 The address class of the symbol. This classifies how to find the value
23937 of a symbol. Each address class is a constant defined in the
23938 @code{gdb} module and described later in this chapter.
23941 @defvar Symbol.is_argument
23942 @code{True} if the symbol is an argument of a function.
23945 @defvar Symbol.is_constant
23946 @code{True} if the symbol is a constant.
23949 @defvar Symbol.is_function
23950 @code{True} if the symbol is a function or a method.
23953 @defvar Symbol.is_variable
23954 @code{True} if the symbol is a variable.
23958 A @code{gdb.Symbol} object has the following methods:
23961 @defun Symbol.is_valid ()
23962 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23963 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23964 the symbol it refers to does not exist in @value{GDBN} any longer.
23965 All other @code{gdb.Symbol} methods will throw an exception if it is
23966 invalid at the time the method is called.
23970 The available domain categories in @code{gdb.Symbol} are represented
23971 as constants in the @code{gdb} module:
23974 @findex SYMBOL_UNDEF_DOMAIN
23975 @findex gdb.SYMBOL_UNDEF_DOMAIN
23976 @item gdb.SYMBOL_UNDEF_DOMAIN
23977 This is used when a domain has not been discovered or none of the
23978 following domains apply. This usually indicates an error either
23979 in the symbol information or in @value{GDBN}'s handling of symbols.
23980 @findex SYMBOL_VAR_DOMAIN
23981 @findex gdb.SYMBOL_VAR_DOMAIN
23982 @item gdb.SYMBOL_VAR_DOMAIN
23983 This domain contains variables, function names, typedef names and enum
23985 @findex SYMBOL_STRUCT_DOMAIN
23986 @findex gdb.SYMBOL_STRUCT_DOMAIN
23987 @item gdb.SYMBOL_STRUCT_DOMAIN
23988 This domain holds struct, union and enum type names.
23989 @findex SYMBOL_LABEL_DOMAIN
23990 @findex gdb.SYMBOL_LABEL_DOMAIN
23991 @item gdb.SYMBOL_LABEL_DOMAIN
23992 This domain contains names of labels (for gotos).
23993 @findex SYMBOL_VARIABLES_DOMAIN
23994 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23995 @item gdb.SYMBOL_VARIABLES_DOMAIN
23996 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23997 contains everything minus functions and types.
23998 @findex SYMBOL_FUNCTIONS_DOMAIN
23999 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24000 @item gdb.SYMBOL_FUNCTION_DOMAIN
24001 This domain contains all functions.
24002 @findex SYMBOL_TYPES_DOMAIN
24003 @findex gdb.SYMBOL_TYPES_DOMAIN
24004 @item gdb.SYMBOL_TYPES_DOMAIN
24005 This domain contains all types.
24008 The available address class categories in @code{gdb.Symbol} are represented
24009 as constants in the @code{gdb} module:
24012 @findex SYMBOL_LOC_UNDEF
24013 @findex gdb.SYMBOL_LOC_UNDEF
24014 @item gdb.SYMBOL_LOC_UNDEF
24015 If this is returned by address class, it indicates an error either in
24016 the symbol information or in @value{GDBN}'s handling of symbols.
24017 @findex SYMBOL_LOC_CONST
24018 @findex gdb.SYMBOL_LOC_CONST
24019 @item gdb.SYMBOL_LOC_CONST
24020 Value is constant int.
24021 @findex SYMBOL_LOC_STATIC
24022 @findex gdb.SYMBOL_LOC_STATIC
24023 @item gdb.SYMBOL_LOC_STATIC
24024 Value is at a fixed address.
24025 @findex SYMBOL_LOC_REGISTER
24026 @findex gdb.SYMBOL_LOC_REGISTER
24027 @item gdb.SYMBOL_LOC_REGISTER
24028 Value is in a register.
24029 @findex SYMBOL_LOC_ARG
24030 @findex gdb.SYMBOL_LOC_ARG
24031 @item gdb.SYMBOL_LOC_ARG
24032 Value is an argument. This value is at the offset stored within the
24033 symbol inside the frame's argument list.
24034 @findex SYMBOL_LOC_REF_ARG
24035 @findex gdb.SYMBOL_LOC_REF_ARG
24036 @item gdb.SYMBOL_LOC_REF_ARG
24037 Value address is stored in the frame's argument list. Just like
24038 @code{LOC_ARG} except that the value's address is stored at the
24039 offset, not the value itself.
24040 @findex SYMBOL_LOC_REGPARM_ADDR
24041 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24042 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24043 Value is a specified register. Just like @code{LOC_REGISTER} except
24044 the register holds the address of the argument instead of the argument
24046 @findex SYMBOL_LOC_LOCAL
24047 @findex gdb.SYMBOL_LOC_LOCAL
24048 @item gdb.SYMBOL_LOC_LOCAL
24049 Value is a local variable.
24050 @findex SYMBOL_LOC_TYPEDEF
24051 @findex gdb.SYMBOL_LOC_TYPEDEF
24052 @item gdb.SYMBOL_LOC_TYPEDEF
24053 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24055 @findex SYMBOL_LOC_BLOCK
24056 @findex gdb.SYMBOL_LOC_BLOCK
24057 @item gdb.SYMBOL_LOC_BLOCK
24059 @findex SYMBOL_LOC_CONST_BYTES
24060 @findex gdb.SYMBOL_LOC_CONST_BYTES
24061 @item gdb.SYMBOL_LOC_CONST_BYTES
24062 Value is a byte-sequence.
24063 @findex SYMBOL_LOC_UNRESOLVED
24064 @findex gdb.SYMBOL_LOC_UNRESOLVED
24065 @item gdb.SYMBOL_LOC_UNRESOLVED
24066 Value is at a fixed address, but the address of the variable has to be
24067 determined from the minimal symbol table whenever the variable is
24069 @findex SYMBOL_LOC_OPTIMIZED_OUT
24070 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24071 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24072 The value does not actually exist in the program.
24073 @findex SYMBOL_LOC_COMPUTED
24074 @findex gdb.SYMBOL_LOC_COMPUTED
24075 @item gdb.SYMBOL_LOC_COMPUTED
24076 The value's address is a computed location.
24079 @node Symbol Tables In Python
24080 @subsubsection Symbol table representation in Python.
24082 @cindex symbol tables in python
24084 @tindex gdb.Symtab_and_line
24086 Access to symbol table data maintained by @value{GDBN} on the inferior
24087 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24088 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24089 from the @code{find_sal} method in @code{gdb.Frame} object.
24090 @xref{Frames In Python}.
24092 For more information on @value{GDBN}'s symbol table management, see
24093 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24095 A @code{gdb.Symtab_and_line} object has the following attributes:
24098 @defvar Symtab_and_line.symtab
24099 The symbol table object (@code{gdb.Symtab}) for this frame.
24100 This attribute is not writable.
24103 @defvar Symtab_and_line.pc
24104 Indicates the current program counter address. This attribute is not
24108 @defvar Symtab_and_line.line
24109 Indicates the current line number for this object. This
24110 attribute is not writable.
24114 A @code{gdb.Symtab_and_line} object has the following methods:
24117 @defun Symtab_and_line.is_valid ()
24118 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24119 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24120 invalid if the Symbol table and line object it refers to does not
24121 exist in @value{GDBN} any longer. All other
24122 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24123 invalid at the time the method is called.
24127 A @code{gdb.Symtab} object has the following attributes:
24130 @defvar Symtab.filename
24131 The symbol table's source filename. This attribute is not writable.
24134 @defvar Symtab.objfile
24135 The symbol table's backing object file. @xref{Objfiles In Python}.
24136 This attribute is not writable.
24140 A @code{gdb.Symtab} object has the following methods:
24143 @defun Symtab.is_valid ()
24144 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24145 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24146 the symbol table it refers to does not exist in @value{GDBN} any
24147 longer. All other @code{gdb.Symtab} methods will throw an exception
24148 if it is invalid at the time the method is called.
24151 @defun Symtab.fullname ()
24152 Return the symbol table's source absolute file name.
24156 @node Breakpoints In Python
24157 @subsubsection Manipulating breakpoints using Python
24159 @cindex breakpoints in python
24160 @tindex gdb.Breakpoint
24162 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24165 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24166 Create a new breakpoint. @var{spec} is a string naming the
24167 location of the breakpoint, or an expression that defines a
24168 watchpoint. The contents can be any location recognized by the
24169 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24170 command. The optional @var{type} denotes the breakpoint to create
24171 from the types defined later in this chapter. This argument can be
24172 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24173 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24174 allows the breakpoint to become invisible to the user. The breakpoint
24175 will neither be reported when created, nor will it be listed in the
24176 output from @code{info breakpoints} (but will be listed with the
24177 @code{maint info breakpoints} command). The optional @var{wp_class}
24178 argument defines the class of watchpoint to create, if @var{type} is
24179 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24180 assumed to be a @code{gdb.WP_WRITE} class.
24183 @defun Breakpoint.stop (self)
24184 The @code{gdb.Breakpoint} class can be sub-classed and, in
24185 particular, you may choose to implement the @code{stop} method.
24186 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24187 it will be called when the inferior reaches any location of a
24188 breakpoint which instantiates that sub-class. If the method returns
24189 @code{True}, the inferior will be stopped at the location of the
24190 breakpoint, otherwise the inferior will continue.
24192 If there are multiple breakpoints at the same location with a
24193 @code{stop} method, each one will be called regardless of the
24194 return status of the previous. This ensures that all @code{stop}
24195 methods have a chance to execute at that location. In this scenario
24196 if one of the methods returns @code{True} but the others return
24197 @code{False}, the inferior will still be stopped.
24199 You should not alter the execution state of the inferior (i.e.@:, step,
24200 next, etc.), alter the current frame context (i.e.@:, change the current
24201 active frame), or alter, add or delete any breakpoint. As a general
24202 rule, you should not alter any data within @value{GDBN} or the inferior
24205 Example @code{stop} implementation:
24208 class MyBreakpoint (gdb.Breakpoint):
24210 inf_val = gdb.parse_and_eval("foo")
24217 The available watchpoint types represented by constants are defined in the
24222 @findex gdb.WP_READ
24224 Read only watchpoint.
24227 @findex gdb.WP_WRITE
24229 Write only watchpoint.
24232 @findex gdb.WP_ACCESS
24233 @item gdb.WP_ACCESS
24234 Read/Write watchpoint.
24237 @defun Breakpoint.is_valid ()
24238 Return @code{True} if this @code{Breakpoint} object is valid,
24239 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24240 if the user deletes the breakpoint. In this case, the object still
24241 exists, but the underlying breakpoint does not. In the cases of
24242 watchpoint scope, the watchpoint remains valid even if execution of the
24243 inferior leaves the scope of that watchpoint.
24246 @defun Breakpoint.delete
24247 Permanently deletes the @value{GDBN} breakpoint. This also
24248 invalidates the Python @code{Breakpoint} object. Any further access
24249 to this object's attributes or methods will raise an error.
24252 @defvar Breakpoint.enabled
24253 This attribute is @code{True} if the breakpoint is enabled, and
24254 @code{False} otherwise. This attribute is writable.
24257 @defvar Breakpoint.silent
24258 This attribute is @code{True} if the breakpoint is silent, and
24259 @code{False} otherwise. This attribute is writable.
24261 Note that a breakpoint can also be silent if it has commands and the
24262 first command is @code{silent}. This is not reported by the
24263 @code{silent} attribute.
24266 @defvar Breakpoint.thread
24267 If the breakpoint is thread-specific, this attribute holds the thread
24268 id. If the breakpoint is not thread-specific, this attribute is
24269 @code{None}. This attribute is writable.
24272 @defvar Breakpoint.task
24273 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24274 id. If the breakpoint is not task-specific (or the underlying
24275 language is not Ada), this attribute is @code{None}. This attribute
24279 @defvar Breakpoint.ignore_count
24280 This attribute holds the ignore count for the breakpoint, an integer.
24281 This attribute is writable.
24284 @defvar Breakpoint.number
24285 This attribute holds the breakpoint's number --- the identifier used by
24286 the user to manipulate the breakpoint. This attribute is not writable.
24289 @defvar Breakpoint.type
24290 This attribute holds the breakpoint's type --- the identifier used to
24291 determine the actual breakpoint type or use-case. This attribute is not
24295 @defvar Breakpoint.visible
24296 This attribute tells whether the breakpoint is visible to the user
24297 when set, or when the @samp{info breakpoints} command is run. This
24298 attribute is not writable.
24301 The available types are represented by constants defined in the @code{gdb}
24305 @findex BP_BREAKPOINT
24306 @findex gdb.BP_BREAKPOINT
24307 @item gdb.BP_BREAKPOINT
24308 Normal code breakpoint.
24310 @findex BP_WATCHPOINT
24311 @findex gdb.BP_WATCHPOINT
24312 @item gdb.BP_WATCHPOINT
24313 Watchpoint breakpoint.
24315 @findex BP_HARDWARE_WATCHPOINT
24316 @findex gdb.BP_HARDWARE_WATCHPOINT
24317 @item gdb.BP_HARDWARE_WATCHPOINT
24318 Hardware assisted watchpoint.
24320 @findex BP_READ_WATCHPOINT
24321 @findex gdb.BP_READ_WATCHPOINT
24322 @item gdb.BP_READ_WATCHPOINT
24323 Hardware assisted read watchpoint.
24325 @findex BP_ACCESS_WATCHPOINT
24326 @findex gdb.BP_ACCESS_WATCHPOINT
24327 @item gdb.BP_ACCESS_WATCHPOINT
24328 Hardware assisted access watchpoint.
24331 @defvar Breakpoint.hit_count
24332 This attribute holds the hit count for the breakpoint, an integer.
24333 This attribute is writable, but currently it can only be set to zero.
24336 @defvar Breakpoint.location
24337 This attribute holds the location of the breakpoint, as specified by
24338 the user. It is a string. If the breakpoint does not have a location
24339 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24340 attribute is not writable.
24343 @defvar Breakpoint.expression
24344 This attribute holds a breakpoint expression, as specified by
24345 the user. It is a string. If the breakpoint does not have an
24346 expression (the breakpoint is not a watchpoint) the attribute's value
24347 is @code{None}. This attribute is not writable.
24350 @defvar Breakpoint.condition
24351 This attribute holds the condition of the breakpoint, as specified by
24352 the user. It is a string. If there is no condition, this attribute's
24353 value is @code{None}. This attribute is writable.
24356 @defvar Breakpoint.commands
24357 This attribute holds the commands attached to the breakpoint. If
24358 there are commands, this attribute's value is a string holding all the
24359 commands, separated by newlines. If there are no commands, this
24360 attribute is @code{None}. This attribute is not writable.
24363 @node Finish Breakpoints in Python
24364 @subsubsection Finish Breakpoints
24366 @cindex python finish breakpoints
24367 @tindex gdb.FinishBreakpoint
24369 A finish breakpoint is a temporary breakpoint set at the return address of
24370 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24371 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24372 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24373 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24374 Finish breakpoints are thread specific and must be create with the right
24377 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24378 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24379 object @var{frame}. If @var{frame} is not provided, this defaults to the
24380 newest frame. The optional @var{internal} argument allows the breakpoint to
24381 become invisible to the user. @xref{Breakpoints In Python}, for further
24382 details about this argument.
24385 @defun FinishBreakpoint.out_of_scope (self)
24386 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24387 @code{return} command, @dots{}), a function may not properly terminate, and
24388 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24389 situation, the @code{out_of_scope} callback will be triggered.
24391 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24395 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24397 print "normal finish"
24400 def out_of_scope ():
24401 print "abnormal finish"
24405 @defvar FinishBreakpoint.return_value
24406 When @value{GDBN} is stopped at a finish breakpoint and the frame
24407 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24408 attribute will contain a @code{gdb.Value} object corresponding to the return
24409 value of the function. The value will be @code{None} if the function return
24410 type is @code{void} or if the return value was not computable. This attribute
24414 @node Lazy Strings In Python
24415 @subsubsection Python representation of lazy strings.
24417 @cindex lazy strings in python
24418 @tindex gdb.LazyString
24420 A @dfn{lazy string} is a string whose contents is not retrieved or
24421 encoded until it is needed.
24423 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24424 @code{address} that points to a region of memory, an @code{encoding}
24425 that will be used to encode that region of memory, and a @code{length}
24426 to delimit the region of memory that represents the string. The
24427 difference between a @code{gdb.LazyString} and a string wrapped within
24428 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24429 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24430 retrieved and encoded during printing, while a @code{gdb.Value}
24431 wrapping a string is immediately retrieved and encoded on creation.
24433 A @code{gdb.LazyString} object has the following functions:
24435 @defun LazyString.value ()
24436 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24437 will point to the string in memory, but will lose all the delayed
24438 retrieval, encoding and handling that @value{GDBN} applies to a
24439 @code{gdb.LazyString}.
24442 @defvar LazyString.address
24443 This attribute holds the address of the string. This attribute is not
24447 @defvar LazyString.length
24448 This attribute holds the length of the string in characters. If the
24449 length is -1, then the string will be fetched and encoded up to the
24450 first null of appropriate width. This attribute is not writable.
24453 @defvar LazyString.encoding
24454 This attribute holds the encoding that will be applied to the string
24455 when the string is printed by @value{GDBN}. If the encoding is not
24456 set, or contains an empty string, then @value{GDBN} will select the
24457 most appropriate encoding when the string is printed. This attribute
24461 @defvar LazyString.type
24462 This attribute holds the type that is represented by the lazy string's
24463 type. For a lazy string this will always be a pointer type. To
24464 resolve this to the lazy string's character type, use the type's
24465 @code{target} method. @xref{Types In Python}. This attribute is not
24470 @subsection Auto-loading
24471 @cindex auto-loading, Python
24473 When a new object file is read (for example, due to the @code{file}
24474 command, or because the inferior has loaded a shared library),
24475 @value{GDBN} will look for Python support scripts in several ways:
24476 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24479 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24480 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24481 * Which flavor to choose?::
24484 The auto-loading feature is useful for supplying application-specific
24485 debugging commands and scripts.
24487 Auto-loading can be enabled or disabled,
24488 and the list of auto-loaded scripts can be printed.
24491 @kindex set auto-load-scripts
24492 @item set auto-load-scripts [yes|no]
24493 Enable or disable the auto-loading of Python scripts.
24495 @kindex show auto-load-scripts
24496 @item show auto-load-scripts
24497 Show whether auto-loading of Python scripts is enabled or disabled.
24499 @kindex info auto-load-scripts
24500 @cindex print list of auto-loaded scripts
24501 @item info auto-load-scripts [@var{regexp}]
24502 Print the list of all scripts that @value{GDBN} auto-loaded.
24504 Also printed is the list of scripts that were mentioned in
24505 the @code{.debug_gdb_scripts} section and were not found
24506 (@pxref{.debug_gdb_scripts section}).
24507 This is useful because their names are not printed when @value{GDBN}
24508 tries to load them and fails. There may be many of them, and printing
24509 an error message for each one is problematic.
24511 If @var{regexp} is supplied only scripts with matching names are printed.
24516 (gdb) info auto-load-scripts
24518 Yes py-section-script.py
24519 full name: /tmp/py-section-script.py
24520 Missing my-foo-pretty-printers.py
24524 When reading an auto-loaded file, @value{GDBN} sets the
24525 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24526 function (@pxref{Objfiles In Python}). This can be useful for
24527 registering objfile-specific pretty-printers.
24529 @node objfile-gdb.py file
24530 @subsubsection The @file{@var{objfile}-gdb.py} file
24531 @cindex @file{@var{objfile}-gdb.py}
24533 When a new object file is read, @value{GDBN} looks for
24534 a file named @file{@var{objfile}-gdb.py},
24535 where @var{objfile} is the object file's real name, formed by ensuring
24536 that the file name is absolute, following all symlinks, and resolving
24537 @code{.} and @code{..} components. If this file exists and is
24538 readable, @value{GDBN} will evaluate it as a Python script.
24540 If this file does not exist, and if the parameter
24541 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24542 then @value{GDBN} will look for @var{real-name} in all of the
24543 directories mentioned in the value of @code{debug-file-directory}.
24545 Finally, if this file does not exist, then @value{GDBN} will look for
24546 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24547 @var{data-directory} is @value{GDBN}'s data directory (available via
24548 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24549 is the object file's real name, as described above.
24551 @value{GDBN} does not track which files it has already auto-loaded this way.
24552 @value{GDBN} will load the associated script every time the corresponding
24553 @var{objfile} is opened.
24554 So your @file{-gdb.py} file should be careful to avoid errors if it
24555 is evaluated more than once.
24557 @node .debug_gdb_scripts section
24558 @subsubsection The @code{.debug_gdb_scripts} section
24559 @cindex @code{.debug_gdb_scripts} section
24561 For systems using file formats like ELF and COFF,
24562 when @value{GDBN} loads a new object file
24563 it will look for a special section named @samp{.debug_gdb_scripts}.
24564 If this section exists, its contents is a list of names of scripts to load.
24566 @value{GDBN} will look for each specified script file first in the
24567 current directory and then along the source search path
24568 (@pxref{Source Path, ,Specifying Source Directories}),
24569 except that @file{$cdir} is not searched, since the compilation
24570 directory is not relevant to scripts.
24572 Entries can be placed in section @code{.debug_gdb_scripts} with,
24573 for example, this GCC macro:
24576 /* Note: The "MS" section flags are to remove duplicates. */
24577 #define DEFINE_GDB_SCRIPT(script_name) \
24579 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24581 .asciz \"" script_name "\"\n\
24587 Then one can reference the macro in a header or source file like this:
24590 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24593 The script name may include directories if desired.
24595 If the macro is put in a header, any application or library
24596 using this header will get a reference to the specified script.
24598 @node Which flavor to choose?
24599 @subsubsection Which flavor to choose?
24601 Given the multiple ways of auto-loading Python scripts, it might not always
24602 be clear which one to choose. This section provides some guidance.
24604 Benefits of the @file{-gdb.py} way:
24608 Can be used with file formats that don't support multiple sections.
24611 Ease of finding scripts for public libraries.
24613 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24614 in the source search path.
24615 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24616 isn't a source directory in which to find the script.
24619 Doesn't require source code additions.
24622 Benefits of the @code{.debug_gdb_scripts} way:
24626 Works with static linking.
24628 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24629 trigger their loading. When an application is statically linked the only
24630 objfile available is the executable, and it is cumbersome to attach all the
24631 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24634 Works with classes that are entirely inlined.
24636 Some classes can be entirely inlined, and thus there may not be an associated
24637 shared library to attach a @file{-gdb.py} script to.
24640 Scripts needn't be copied out of the source tree.
24642 In some circumstances, apps can be built out of large collections of internal
24643 libraries, and the build infrastructure necessary to install the
24644 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24645 cumbersome. It may be easier to specify the scripts in the
24646 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24647 top of the source tree to the source search path.
24650 @node Python modules
24651 @subsection Python modules
24652 @cindex python modules
24654 @value{GDBN} comes with several modules to assist writing Python code.
24657 * gdb.printing:: Building and registering pretty-printers.
24658 * gdb.types:: Utilities for working with types.
24659 * gdb.prompt:: Utilities for prompt value substitution.
24663 @subsubsection gdb.printing
24664 @cindex gdb.printing
24666 This module provides a collection of utilities for working with
24670 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24671 This class specifies the API that makes @samp{info pretty-printer},
24672 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24673 Pretty-printers should generally inherit from this class.
24675 @item SubPrettyPrinter (@var{name})
24676 For printers that handle multiple types, this class specifies the
24677 corresponding API for the subprinters.
24679 @item RegexpCollectionPrettyPrinter (@var{name})
24680 Utility class for handling multiple printers, all recognized via
24681 regular expressions.
24682 @xref{Writing a Pretty-Printer}, for an example.
24684 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24685 Register @var{printer} with the pretty-printer list of @var{obj}.
24686 If @var{replace} is @code{True} then any existing copy of the printer
24687 is replaced. Otherwise a @code{RuntimeError} exception is raised
24688 if a printer with the same name already exists.
24692 @subsubsection gdb.types
24695 This module provides a collection of utilities for working with
24696 @code{gdb.Types} objects.
24699 @item get_basic_type (@var{type})
24700 Return @var{type} with const and volatile qualifiers stripped,
24701 and with typedefs and C@t{++} references converted to the underlying type.
24706 typedef const int const_int;
24708 const_int& foo_ref (foo);
24709 int main () @{ return 0; @}
24716 (gdb) python import gdb.types
24717 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24718 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24722 @item has_field (@var{type}, @var{field})
24723 Return @code{True} if @var{type}, assumed to be a type with fields
24724 (e.g., a structure or union), has field @var{field}.
24726 @item make_enum_dict (@var{enum_type})
24727 Return a Python @code{dictionary} type produced from @var{enum_type}.
24729 @item deep_items (@var{type})
24730 Returns a Python iterator similar to the standard
24731 @code{gdb.Type.iteritems} method, except that the iterator returned
24732 by @code{deep_items} will recursively traverse anonymous struct or
24733 union fields. For example:
24747 Then in @value{GDBN}:
24749 (@value{GDBP}) python import gdb.types
24750 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24751 (@value{GDBP}) python print struct_a.keys ()
24753 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24754 @{['a', 'b0', 'b1']@}
24760 @subsubsection gdb.prompt
24763 This module provides a method for prompt value-substitution.
24766 @item substitute_prompt (@var{string})
24767 Return @var{string} with escape sequences substituted by values. Some
24768 escape sequences take arguments. You can specify arguments inside
24769 ``@{@}'' immediately following the escape sequence.
24771 The escape sequences you can pass to this function are:
24775 Substitute a backslash.
24777 Substitute an ESC character.
24779 Substitute the selected frame; an argument names a frame parameter.
24781 Substitute a newline.
24783 Substitute a parameter's value; the argument names the parameter.
24785 Substitute a carriage return.
24787 Substitute the selected thread; an argument names a thread parameter.
24789 Substitute the version of GDB.
24791 Substitute the current working directory.
24793 Begin a sequence of non-printing characters. These sequences are
24794 typically used with the ESC character, and are not counted in the string
24795 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24796 blue-colored ``(gdb)'' prompt where the length is five.
24798 End a sequence of non-printing characters.
24804 substitute_prompt (``frame: \f,
24805 print arguments: \p@{print frame-arguments@}'')
24808 @exdent will return the string:
24811 "frame: main, print arguments: scalars"
24816 @section Creating new spellings of existing commands
24817 @cindex aliases for commands
24819 It is often useful to define alternate spellings of existing commands.
24820 For example, if a new @value{GDBN} command defined in Python has
24821 a long name to type, it is handy to have an abbreviated version of it
24822 that involves less typing.
24824 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24825 of the @samp{step} command even though it is otherwise an ambiguous
24826 abbreviation of other commands like @samp{set} and @samp{show}.
24828 Aliases are also used to provide shortened or more common versions
24829 of multi-word commands. For example, @value{GDBN} provides the
24830 @samp{tty} alias of the @samp{set inferior-tty} command.
24832 You can define a new alias with the @samp{alias} command.
24837 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24841 @var{ALIAS} specifies the name of the new alias.
24842 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24845 @var{COMMAND} specifies the name of an existing command
24846 that is being aliased.
24848 The @samp{-a} option specifies that the new alias is an abbreviation
24849 of the command. Abbreviations are not shown in command
24850 lists displayed by the @samp{help} command.
24852 The @samp{--} option specifies the end of options,
24853 and is useful when @var{ALIAS} begins with a dash.
24855 Here is a simple example showing how to make an abbreviation
24856 of a command so that there is less to type.
24857 Suppose you were tired of typing @samp{disas}, the current
24858 shortest unambiguous abbreviation of the @samp{disassemble} command
24859 and you wanted an even shorter version named @samp{di}.
24860 The following will accomplish this.
24863 (gdb) alias -a di = disas
24866 Note that aliases are different from user-defined commands.
24867 With a user-defined command, you also need to write documentation
24868 for it with the @samp{document} command.
24869 An alias automatically picks up the documentation of the existing command.
24871 Here is an example where we make @samp{elms} an abbreviation of
24872 @samp{elements} in the @samp{set print elements} command.
24873 This is to show that you can make an abbreviation of any part
24877 (gdb) alias -a set print elms = set print elements
24878 (gdb) alias -a show print elms = show print elements
24879 (gdb) set p elms 20
24881 Limit on string chars or array elements to print is 200.
24884 Note that if you are defining an alias of a @samp{set} command,
24885 and you want to have an alias for the corresponding @samp{show}
24886 command, then you need to define the latter separately.
24888 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24889 @var{ALIAS}, just as they are normally.
24892 (gdb) alias -a set pr elms = set p ele
24895 Finally, here is an example showing the creation of a one word
24896 alias for a more complex command.
24897 This creates alias @samp{spe} of the command @samp{set print elements}.
24900 (gdb) alias spe = set print elements
24905 @chapter Command Interpreters
24906 @cindex command interpreters
24908 @value{GDBN} supports multiple command interpreters, and some command
24909 infrastructure to allow users or user interface writers to switch
24910 between interpreters or run commands in other interpreters.
24912 @value{GDBN} currently supports two command interpreters, the console
24913 interpreter (sometimes called the command-line interpreter or @sc{cli})
24914 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24915 describes both of these interfaces in great detail.
24917 By default, @value{GDBN} will start with the console interpreter.
24918 However, the user may choose to start @value{GDBN} with another
24919 interpreter by specifying the @option{-i} or @option{--interpreter}
24920 startup options. Defined interpreters include:
24924 @cindex console interpreter
24925 The traditional console or command-line interpreter. This is the most often
24926 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24927 @value{GDBN} will use this interpreter.
24930 @cindex mi interpreter
24931 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24932 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24933 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24937 @cindex mi2 interpreter
24938 The current @sc{gdb/mi} interface.
24941 @cindex mi1 interpreter
24942 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24946 @cindex invoke another interpreter
24947 The interpreter being used by @value{GDBN} may not be dynamically
24948 switched at runtime. Although possible, this could lead to a very
24949 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24950 enters the command "interpreter-set console" in a console view,
24951 @value{GDBN} would switch to using the console interpreter, rendering
24952 the IDE inoperable!
24954 @kindex interpreter-exec
24955 Although you may only choose a single interpreter at startup, you may execute
24956 commands in any interpreter from the current interpreter using the appropriate
24957 command. If you are running the console interpreter, simply use the
24958 @code{interpreter-exec} command:
24961 interpreter-exec mi "-data-list-register-names"
24964 @sc{gdb/mi} has a similar command, although it is only available in versions of
24965 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24968 @chapter @value{GDBN} Text User Interface
24970 @cindex Text User Interface
24973 * TUI Overview:: TUI overview
24974 * TUI Keys:: TUI key bindings
24975 * TUI Single Key Mode:: TUI single key mode
24976 * TUI Commands:: TUI-specific commands
24977 * TUI Configuration:: TUI configuration variables
24980 The @value{GDBN} Text User Interface (TUI) is a terminal
24981 interface which uses the @code{curses} library to show the source
24982 file, the assembly output, the program registers and @value{GDBN}
24983 commands in separate text windows. The TUI mode is supported only
24984 on platforms where a suitable version of the @code{curses} library
24987 The TUI mode is enabled by default when you invoke @value{GDBN} as
24988 @samp{@value{GDBP} -tui}.
24989 You can also switch in and out of TUI mode while @value{GDBN} runs by
24990 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24991 @xref{TUI Keys, ,TUI Key Bindings}.
24994 @section TUI Overview
24996 In TUI mode, @value{GDBN} can display several text windows:
25000 This window is the @value{GDBN} command window with the @value{GDBN}
25001 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25002 managed using readline.
25005 The source window shows the source file of the program. The current
25006 line and active breakpoints are displayed in this window.
25009 The assembly window shows the disassembly output of the program.
25012 This window shows the processor registers. Registers are highlighted
25013 when their values change.
25016 The source and assembly windows show the current program position
25017 by highlighting the current line and marking it with a @samp{>} marker.
25018 Breakpoints are indicated with two markers. The first marker
25019 indicates the breakpoint type:
25023 Breakpoint which was hit at least once.
25026 Breakpoint which was never hit.
25029 Hardware breakpoint which was hit at least once.
25032 Hardware breakpoint which was never hit.
25035 The second marker indicates whether the breakpoint is enabled or not:
25039 Breakpoint is enabled.
25042 Breakpoint is disabled.
25045 The source, assembly and register windows are updated when the current
25046 thread changes, when the frame changes, or when the program counter
25049 These windows are not all visible at the same time. The command
25050 window is always visible. The others can be arranged in several
25061 source and assembly,
25064 source and registers, or
25067 assembly and registers.
25070 A status line above the command window shows the following information:
25074 Indicates the current @value{GDBN} target.
25075 (@pxref{Targets, ,Specifying a Debugging Target}).
25078 Gives the current process or thread number.
25079 When no process is being debugged, this field is set to @code{No process}.
25082 Gives the current function name for the selected frame.
25083 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25084 When there is no symbol corresponding to the current program counter,
25085 the string @code{??} is displayed.
25088 Indicates the current line number for the selected frame.
25089 When the current line number is not known, the string @code{??} is displayed.
25092 Indicates the current program counter address.
25096 @section TUI Key Bindings
25097 @cindex TUI key bindings
25099 The TUI installs several key bindings in the readline keymaps
25100 @ifset SYSTEM_READLINE
25101 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25103 @ifclear SYSTEM_READLINE
25104 (@pxref{Command Line Editing}).
25106 The following key bindings are installed for both TUI mode and the
25107 @value{GDBN} standard mode.
25116 Enter or leave the TUI mode. When leaving the TUI mode,
25117 the curses window management stops and @value{GDBN} operates using
25118 its standard mode, writing on the terminal directly. When reentering
25119 the TUI mode, control is given back to the curses windows.
25120 The screen is then refreshed.
25124 Use a TUI layout with only one window. The layout will
25125 either be @samp{source} or @samp{assembly}. When the TUI mode
25126 is not active, it will switch to the TUI mode.
25128 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25132 Use a TUI layout with at least two windows. When the current
25133 layout already has two windows, the next layout with two windows is used.
25134 When a new layout is chosen, one window will always be common to the
25135 previous layout and the new one.
25137 Think of it as the Emacs @kbd{C-x 2} binding.
25141 Change the active window. The TUI associates several key bindings
25142 (like scrolling and arrow keys) with the active window. This command
25143 gives the focus to the next TUI window.
25145 Think of it as the Emacs @kbd{C-x o} binding.
25149 Switch in and out of the TUI SingleKey mode that binds single
25150 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25153 The following key bindings only work in the TUI mode:
25158 Scroll the active window one page up.
25162 Scroll the active window one page down.
25166 Scroll the active window one line up.
25170 Scroll the active window one line down.
25174 Scroll the active window one column left.
25178 Scroll the active window one column right.
25182 Refresh the screen.
25185 Because the arrow keys scroll the active window in the TUI mode, they
25186 are not available for their normal use by readline unless the command
25187 window has the focus. When another window is active, you must use
25188 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25189 and @kbd{C-f} to control the command window.
25191 @node TUI Single Key Mode
25192 @section TUI Single Key Mode
25193 @cindex TUI single key mode
25195 The TUI also provides a @dfn{SingleKey} mode, which binds several
25196 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25197 switch into this mode, where the following key bindings are used:
25200 @kindex c @r{(SingleKey TUI key)}
25204 @kindex d @r{(SingleKey TUI key)}
25208 @kindex f @r{(SingleKey TUI key)}
25212 @kindex n @r{(SingleKey TUI key)}
25216 @kindex q @r{(SingleKey TUI key)}
25218 exit the SingleKey mode.
25220 @kindex r @r{(SingleKey TUI key)}
25224 @kindex s @r{(SingleKey TUI key)}
25228 @kindex u @r{(SingleKey TUI key)}
25232 @kindex v @r{(SingleKey TUI key)}
25236 @kindex w @r{(SingleKey TUI key)}
25241 Other keys temporarily switch to the @value{GDBN} command prompt.
25242 The key that was pressed is inserted in the editing buffer so that
25243 it is possible to type most @value{GDBN} commands without interaction
25244 with the TUI SingleKey mode. Once the command is entered the TUI
25245 SingleKey mode is restored. The only way to permanently leave
25246 this mode is by typing @kbd{q} or @kbd{C-x s}.
25250 @section TUI-specific Commands
25251 @cindex TUI commands
25253 The TUI has specific commands to control the text windows.
25254 These commands are always available, even when @value{GDBN} is not in
25255 the TUI mode. When @value{GDBN} is in the standard mode, most
25256 of these commands will automatically switch to the TUI mode.
25258 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25259 terminal, or @value{GDBN} has been started with the machine interface
25260 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25261 these commands will fail with an error, because it would not be
25262 possible or desirable to enable curses window management.
25267 List and give the size of all displayed windows.
25271 Display the next layout.
25274 Display the previous layout.
25277 Display the source window only.
25280 Display the assembly window only.
25283 Display the source and assembly window.
25286 Display the register window together with the source or assembly window.
25290 Make the next window active for scrolling.
25293 Make the previous window active for scrolling.
25296 Make the source window active for scrolling.
25299 Make the assembly window active for scrolling.
25302 Make the register window active for scrolling.
25305 Make the command window active for scrolling.
25309 Refresh the screen. This is similar to typing @kbd{C-L}.
25311 @item tui reg float
25313 Show the floating point registers in the register window.
25315 @item tui reg general
25316 Show the general registers in the register window.
25319 Show the next register group. The list of register groups as well as
25320 their order is target specific. The predefined register groups are the
25321 following: @code{general}, @code{float}, @code{system}, @code{vector},
25322 @code{all}, @code{save}, @code{restore}.
25324 @item tui reg system
25325 Show the system registers in the register window.
25329 Update the source window and the current execution point.
25331 @item winheight @var{name} +@var{count}
25332 @itemx winheight @var{name} -@var{count}
25334 Change the height of the window @var{name} by @var{count}
25335 lines. Positive counts increase the height, while negative counts
25338 @item tabset @var{nchars}
25340 Set the width of tab stops to be @var{nchars} characters.
25343 @node TUI Configuration
25344 @section TUI Configuration Variables
25345 @cindex TUI configuration variables
25347 Several configuration variables control the appearance of TUI windows.
25350 @item set tui border-kind @var{kind}
25351 @kindex set tui border-kind
25352 Select the border appearance for the source, assembly and register windows.
25353 The possible values are the following:
25356 Use a space character to draw the border.
25359 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25362 Use the Alternate Character Set to draw the border. The border is
25363 drawn using character line graphics if the terminal supports them.
25366 @item set tui border-mode @var{mode}
25367 @kindex set tui border-mode
25368 @itemx set tui active-border-mode @var{mode}
25369 @kindex set tui active-border-mode
25370 Select the display attributes for the borders of the inactive windows
25371 or the active window. The @var{mode} can be one of the following:
25374 Use normal attributes to display the border.
25380 Use reverse video mode.
25383 Use half bright mode.
25385 @item half-standout
25386 Use half bright and standout mode.
25389 Use extra bright or bold mode.
25391 @item bold-standout
25392 Use extra bright or bold and standout mode.
25397 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25400 @cindex @sc{gnu} Emacs
25401 A special interface allows you to use @sc{gnu} Emacs to view (and
25402 edit) the source files for the program you are debugging with
25405 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25406 executable file you want to debug as an argument. This command starts
25407 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25408 created Emacs buffer.
25409 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25411 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25416 All ``terminal'' input and output goes through an Emacs buffer, called
25419 This applies both to @value{GDBN} commands and their output, and to the input
25420 and output done by the program you are debugging.
25422 This is useful because it means that you can copy the text of previous
25423 commands and input them again; you can even use parts of the output
25426 All the facilities of Emacs' Shell mode are available for interacting
25427 with your program. In particular, you can send signals the usual
25428 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25432 @value{GDBN} displays source code through Emacs.
25434 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25435 source file for that frame and puts an arrow (@samp{=>}) at the
25436 left margin of the current line. Emacs uses a separate buffer for
25437 source display, and splits the screen to show both your @value{GDBN} session
25440 Explicit @value{GDBN} @code{list} or search commands still produce output as
25441 usual, but you probably have no reason to use them from Emacs.
25444 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25445 a graphical mode, enabled by default, which provides further buffers
25446 that can control the execution and describe the state of your program.
25447 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25449 If you specify an absolute file name when prompted for the @kbd{M-x
25450 gdb} argument, then Emacs sets your current working directory to where
25451 your program resides. If you only specify the file name, then Emacs
25452 sets your current working directory to the directory associated
25453 with the previous buffer. In this case, @value{GDBN} may find your
25454 program by searching your environment's @code{PATH} variable, but on
25455 some operating systems it might not find the source. So, although the
25456 @value{GDBN} input and output session proceeds normally, the auxiliary
25457 buffer does not display the current source and line of execution.
25459 The initial working directory of @value{GDBN} is printed on the top
25460 line of the GUD buffer and this serves as a default for the commands
25461 that specify files for @value{GDBN} to operate on. @xref{Files,
25462 ,Commands to Specify Files}.
25464 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25465 need to call @value{GDBN} by a different name (for example, if you
25466 keep several configurations around, with different names) you can
25467 customize the Emacs variable @code{gud-gdb-command-name} to run the
25470 In the GUD buffer, you can use these special Emacs commands in
25471 addition to the standard Shell mode commands:
25475 Describe the features of Emacs' GUD Mode.
25478 Execute to another source line, like the @value{GDBN} @code{step} command; also
25479 update the display window to show the current file and location.
25482 Execute to next source line in this function, skipping all function
25483 calls, like the @value{GDBN} @code{next} command. Then update the display window
25484 to show the current file and location.
25487 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25488 display window accordingly.
25491 Execute until exit from the selected stack frame, like the @value{GDBN}
25492 @code{finish} command.
25495 Continue execution of your program, like the @value{GDBN} @code{continue}
25499 Go up the number of frames indicated by the numeric argument
25500 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25501 like the @value{GDBN} @code{up} command.
25504 Go down the number of frames indicated by the numeric argument, like the
25505 @value{GDBN} @code{down} command.
25508 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25509 tells @value{GDBN} to set a breakpoint on the source line point is on.
25511 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25512 separate frame which shows a backtrace when the GUD buffer is current.
25513 Move point to any frame in the stack and type @key{RET} to make it
25514 become the current frame and display the associated source in the
25515 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25516 selected frame become the current one. In graphical mode, the
25517 speedbar displays watch expressions.
25519 If you accidentally delete the source-display buffer, an easy way to get
25520 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25521 request a frame display; when you run under Emacs, this recreates
25522 the source buffer if necessary to show you the context of the current
25525 The source files displayed in Emacs are in ordinary Emacs buffers
25526 which are visiting the source files in the usual way. You can edit
25527 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25528 communicates with Emacs in terms of line numbers. If you add or
25529 delete lines from the text, the line numbers that @value{GDBN} knows cease
25530 to correspond properly with the code.
25532 A more detailed description of Emacs' interaction with @value{GDBN} is
25533 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25536 @c The following dropped because Epoch is nonstandard. Reactivate
25537 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25539 @kindex Emacs Epoch environment
25543 Version 18 of @sc{gnu} Emacs has a built-in window system
25544 called the @code{epoch}
25545 environment. Users of this environment can use a new command,
25546 @code{inspect} which performs identically to @code{print} except that
25547 each value is printed in its own window.
25552 @chapter The @sc{gdb/mi} Interface
25554 @unnumberedsec Function and Purpose
25556 @cindex @sc{gdb/mi}, its purpose
25557 @sc{gdb/mi} is a line based machine oriented text interface to
25558 @value{GDBN} and is activated by specifying using the
25559 @option{--interpreter} command line option (@pxref{Mode Options}). It
25560 is specifically intended to support the development of systems which
25561 use the debugger as just one small component of a larger system.
25563 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25564 in the form of a reference manual.
25566 Note that @sc{gdb/mi} is still under construction, so some of the
25567 features described below are incomplete and subject to change
25568 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25570 @unnumberedsec Notation and Terminology
25572 @cindex notational conventions, for @sc{gdb/mi}
25573 This chapter uses the following notation:
25577 @code{|} separates two alternatives.
25580 @code{[ @var{something} ]} indicates that @var{something} is optional:
25581 it may or may not be given.
25584 @code{( @var{group} )*} means that @var{group} inside the parentheses
25585 may repeat zero or more times.
25588 @code{( @var{group} )+} means that @var{group} inside the parentheses
25589 may repeat one or more times.
25592 @code{"@var{string}"} means a literal @var{string}.
25596 @heading Dependencies
25600 * GDB/MI General Design::
25601 * GDB/MI Command Syntax::
25602 * GDB/MI Compatibility with CLI::
25603 * GDB/MI Development and Front Ends::
25604 * GDB/MI Output Records::
25605 * GDB/MI Simple Examples::
25606 * GDB/MI Command Description Format::
25607 * GDB/MI Breakpoint Commands::
25608 * GDB/MI Program Context::
25609 * GDB/MI Thread Commands::
25610 * GDB/MI Ada Tasking Commands::
25611 * GDB/MI Program Execution::
25612 * GDB/MI Stack Manipulation::
25613 * GDB/MI Variable Objects::
25614 * GDB/MI Data Manipulation::
25615 * GDB/MI Tracepoint Commands::
25616 * GDB/MI Symbol Query::
25617 * GDB/MI File Commands::
25619 * GDB/MI Kod Commands::
25620 * GDB/MI Memory Overlay Commands::
25621 * GDB/MI Signal Handling Commands::
25623 * GDB/MI Target Manipulation::
25624 * GDB/MI File Transfer Commands::
25625 * GDB/MI Miscellaneous Commands::
25628 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25629 @node GDB/MI General Design
25630 @section @sc{gdb/mi} General Design
25631 @cindex GDB/MI General Design
25633 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25634 parts---commands sent to @value{GDBN}, responses to those commands
25635 and notifications. Each command results in exactly one response,
25636 indicating either successful completion of the command, or an error.
25637 For the commands that do not resume the target, the response contains the
25638 requested information. For the commands that resume the target, the
25639 response only indicates whether the target was successfully resumed.
25640 Notifications is the mechanism for reporting changes in the state of the
25641 target, or in @value{GDBN} state, that cannot conveniently be associated with
25642 a command and reported as part of that command response.
25644 The important examples of notifications are:
25648 Exec notifications. These are used to report changes in
25649 target state---when a target is resumed, or stopped. It would not
25650 be feasible to include this information in response of resuming
25651 commands, because one resume commands can result in multiple events in
25652 different threads. Also, quite some time may pass before any event
25653 happens in the target, while a frontend needs to know whether the resuming
25654 command itself was successfully executed.
25657 Console output, and status notifications. Console output
25658 notifications are used to report output of CLI commands, as well as
25659 diagnostics for other commands. Status notifications are used to
25660 report the progress of a long-running operation. Naturally, including
25661 this information in command response would mean no output is produced
25662 until the command is finished, which is undesirable.
25665 General notifications. Commands may have various side effects on
25666 the @value{GDBN} or target state beyond their official purpose. For example,
25667 a command may change the selected thread. Although such changes can
25668 be included in command response, using notification allows for more
25669 orthogonal frontend design.
25673 There's no guarantee that whenever an MI command reports an error,
25674 @value{GDBN} or the target are in any specific state, and especially,
25675 the state is not reverted to the state before the MI command was
25676 processed. Therefore, whenever an MI command results in an error,
25677 we recommend that the frontend refreshes all the information shown in
25678 the user interface.
25682 * Context management::
25683 * Asynchronous and non-stop modes::
25687 @node Context management
25688 @subsection Context management
25690 In most cases when @value{GDBN} accesses the target, this access is
25691 done in context of a specific thread and frame (@pxref{Frames}).
25692 Often, even when accessing global data, the target requires that a thread
25693 be specified. The CLI interface maintains the selected thread and frame,
25694 and supplies them to target on each command. This is convenient,
25695 because a command line user would not want to specify that information
25696 explicitly on each command, and because user interacts with
25697 @value{GDBN} via a single terminal, so no confusion is possible as
25698 to what thread and frame are the current ones.
25700 In the case of MI, the concept of selected thread and frame is less
25701 useful. First, a frontend can easily remember this information
25702 itself. Second, a graphical frontend can have more than one window,
25703 each one used for debugging a different thread, and the frontend might
25704 want to access additional threads for internal purposes. This
25705 increases the risk that by relying on implicitly selected thread, the
25706 frontend may be operating on a wrong one. Therefore, each MI command
25707 should explicitly specify which thread and frame to operate on. To
25708 make it possible, each MI command accepts the @samp{--thread} and
25709 @samp{--frame} options, the value to each is @value{GDBN} identifier
25710 for thread and frame to operate on.
25712 Usually, each top-level window in a frontend allows the user to select
25713 a thread and a frame, and remembers the user selection for further
25714 operations. However, in some cases @value{GDBN} may suggest that the
25715 current thread be changed. For example, when stopping on a breakpoint
25716 it is reasonable to switch to the thread where breakpoint is hit. For
25717 another example, if the user issues the CLI @samp{thread} command via
25718 the frontend, it is desirable to change the frontend's selected thread to the
25719 one specified by user. @value{GDBN} communicates the suggestion to
25720 change current thread using the @samp{=thread-selected} notification.
25721 No such notification is available for the selected frame at the moment.
25723 Note that historically, MI shares the selected thread with CLI, so
25724 frontends used the @code{-thread-select} to execute commands in the
25725 right context. However, getting this to work right is cumbersome. The
25726 simplest way is for frontend to emit @code{-thread-select} command
25727 before every command. This doubles the number of commands that need
25728 to be sent. The alternative approach is to suppress @code{-thread-select}
25729 if the selected thread in @value{GDBN} is supposed to be identical to the
25730 thread the frontend wants to operate on. However, getting this
25731 optimization right can be tricky. In particular, if the frontend
25732 sends several commands to @value{GDBN}, and one of the commands changes the
25733 selected thread, then the behaviour of subsequent commands will
25734 change. So, a frontend should either wait for response from such
25735 problematic commands, or explicitly add @code{-thread-select} for
25736 all subsequent commands. No frontend is known to do this exactly
25737 right, so it is suggested to just always pass the @samp{--thread} and
25738 @samp{--frame} options.
25740 @node Asynchronous and non-stop modes
25741 @subsection Asynchronous command execution and non-stop mode
25743 On some targets, @value{GDBN} is capable of processing MI commands
25744 even while the target is running. This is called @dfn{asynchronous
25745 command execution} (@pxref{Background Execution}). The frontend may
25746 specify a preferrence for asynchronous execution using the
25747 @code{-gdb-set target-async 1} command, which should be emitted before
25748 either running the executable or attaching to the target. After the
25749 frontend has started the executable or attached to the target, it can
25750 find if asynchronous execution is enabled using the
25751 @code{-list-target-features} command.
25753 Even if @value{GDBN} can accept a command while target is running,
25754 many commands that access the target do not work when the target is
25755 running. Therefore, asynchronous command execution is most useful
25756 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25757 it is possible to examine the state of one thread, while other threads
25760 When a given thread is running, MI commands that try to access the
25761 target in the context of that thread may not work, or may work only on
25762 some targets. In particular, commands that try to operate on thread's
25763 stack will not work, on any target. Commands that read memory, or
25764 modify breakpoints, may work or not work, depending on the target. Note
25765 that even commands that operate on global state, such as @code{print},
25766 @code{set}, and breakpoint commands, still access the target in the
25767 context of a specific thread, so frontend should try to find a
25768 stopped thread and perform the operation on that thread (using the
25769 @samp{--thread} option).
25771 Which commands will work in the context of a running thread is
25772 highly target dependent. However, the two commands
25773 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25774 to find the state of a thread, will always work.
25776 @node Thread groups
25777 @subsection Thread groups
25778 @value{GDBN} may be used to debug several processes at the same time.
25779 On some platfroms, @value{GDBN} may support debugging of several
25780 hardware systems, each one having several cores with several different
25781 processes running on each core. This section describes the MI
25782 mechanism to support such debugging scenarios.
25784 The key observation is that regardless of the structure of the
25785 target, MI can have a global list of threads, because most commands that
25786 accept the @samp{--thread} option do not need to know what process that
25787 thread belongs to. Therefore, it is not necessary to introduce
25788 neither additional @samp{--process} option, nor an notion of the
25789 current process in the MI interface. The only strictly new feature
25790 that is required is the ability to find how the threads are grouped
25793 To allow the user to discover such grouping, and to support arbitrary
25794 hierarchy of machines/cores/processes, MI introduces the concept of a
25795 @dfn{thread group}. Thread group is a collection of threads and other
25796 thread groups. A thread group always has a string identifier, a type,
25797 and may have additional attributes specific to the type. A new
25798 command, @code{-list-thread-groups}, returns the list of top-level
25799 thread groups, which correspond to processes that @value{GDBN} is
25800 debugging at the moment. By passing an identifier of a thread group
25801 to the @code{-list-thread-groups} command, it is possible to obtain
25802 the members of specific thread group.
25804 To allow the user to easily discover processes, and other objects, he
25805 wishes to debug, a concept of @dfn{available thread group} is
25806 introduced. Available thread group is an thread group that
25807 @value{GDBN} is not debugging, but that can be attached to, using the
25808 @code{-target-attach} command. The list of available top-level thread
25809 groups can be obtained using @samp{-list-thread-groups --available}.
25810 In general, the content of a thread group may be only retrieved only
25811 after attaching to that thread group.
25813 Thread groups are related to inferiors (@pxref{Inferiors and
25814 Programs}). Each inferior corresponds to a thread group of a special
25815 type @samp{process}, and some additional operations are permitted on
25816 such thread groups.
25818 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25819 @node GDB/MI Command Syntax
25820 @section @sc{gdb/mi} Command Syntax
25823 * GDB/MI Input Syntax::
25824 * GDB/MI Output Syntax::
25827 @node GDB/MI Input Syntax
25828 @subsection @sc{gdb/mi} Input Syntax
25830 @cindex input syntax for @sc{gdb/mi}
25831 @cindex @sc{gdb/mi}, input syntax
25833 @item @var{command} @expansion{}
25834 @code{@var{cli-command} | @var{mi-command}}
25836 @item @var{cli-command} @expansion{}
25837 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25838 @var{cli-command} is any existing @value{GDBN} CLI command.
25840 @item @var{mi-command} @expansion{}
25841 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25842 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25844 @item @var{token} @expansion{}
25845 "any sequence of digits"
25847 @item @var{option} @expansion{}
25848 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25850 @item @var{parameter} @expansion{}
25851 @code{@var{non-blank-sequence} | @var{c-string}}
25853 @item @var{operation} @expansion{}
25854 @emph{any of the operations described in this chapter}
25856 @item @var{non-blank-sequence} @expansion{}
25857 @emph{anything, provided it doesn't contain special characters such as
25858 "-", @var{nl}, """ and of course " "}
25860 @item @var{c-string} @expansion{}
25861 @code{""" @var{seven-bit-iso-c-string-content} """}
25863 @item @var{nl} @expansion{}
25872 The CLI commands are still handled by the @sc{mi} interpreter; their
25873 output is described below.
25876 The @code{@var{token}}, when present, is passed back when the command
25880 Some @sc{mi} commands accept optional arguments as part of the parameter
25881 list. Each option is identified by a leading @samp{-} (dash) and may be
25882 followed by an optional argument parameter. Options occur first in the
25883 parameter list and can be delimited from normal parameters using
25884 @samp{--} (this is useful when some parameters begin with a dash).
25891 We want easy access to the existing CLI syntax (for debugging).
25894 We want it to be easy to spot a @sc{mi} operation.
25897 @node GDB/MI Output Syntax
25898 @subsection @sc{gdb/mi} Output Syntax
25900 @cindex output syntax of @sc{gdb/mi}
25901 @cindex @sc{gdb/mi}, output syntax
25902 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25903 followed, optionally, by a single result record. This result record
25904 is for the most recent command. The sequence of output records is
25905 terminated by @samp{(gdb)}.
25907 If an input command was prefixed with a @code{@var{token}} then the
25908 corresponding output for that command will also be prefixed by that same
25912 @item @var{output} @expansion{}
25913 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25915 @item @var{result-record} @expansion{}
25916 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25918 @item @var{out-of-band-record} @expansion{}
25919 @code{@var{async-record} | @var{stream-record}}
25921 @item @var{async-record} @expansion{}
25922 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25924 @item @var{exec-async-output} @expansion{}
25925 @code{[ @var{token} ] "*" @var{async-output}}
25927 @item @var{status-async-output} @expansion{}
25928 @code{[ @var{token} ] "+" @var{async-output}}
25930 @item @var{notify-async-output} @expansion{}
25931 @code{[ @var{token} ] "=" @var{async-output}}
25933 @item @var{async-output} @expansion{}
25934 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25936 @item @var{result-class} @expansion{}
25937 @code{"done" | "running" | "connected" | "error" | "exit"}
25939 @item @var{async-class} @expansion{}
25940 @code{"stopped" | @var{others}} (where @var{others} will be added
25941 depending on the needs---this is still in development).
25943 @item @var{result} @expansion{}
25944 @code{ @var{variable} "=" @var{value}}
25946 @item @var{variable} @expansion{}
25947 @code{ @var{string} }
25949 @item @var{value} @expansion{}
25950 @code{ @var{const} | @var{tuple} | @var{list} }
25952 @item @var{const} @expansion{}
25953 @code{@var{c-string}}
25955 @item @var{tuple} @expansion{}
25956 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25958 @item @var{list} @expansion{}
25959 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25960 @var{result} ( "," @var{result} )* "]" }
25962 @item @var{stream-record} @expansion{}
25963 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25965 @item @var{console-stream-output} @expansion{}
25966 @code{"~" @var{c-string}}
25968 @item @var{target-stream-output} @expansion{}
25969 @code{"@@" @var{c-string}}
25971 @item @var{log-stream-output} @expansion{}
25972 @code{"&" @var{c-string}}
25974 @item @var{nl} @expansion{}
25977 @item @var{token} @expansion{}
25978 @emph{any sequence of digits}.
25986 All output sequences end in a single line containing a period.
25989 The @code{@var{token}} is from the corresponding request. Note that
25990 for all async output, while the token is allowed by the grammar and
25991 may be output by future versions of @value{GDBN} for select async
25992 output messages, it is generally omitted. Frontends should treat
25993 all async output as reporting general changes in the state of the
25994 target and there should be no need to associate async output to any
25998 @cindex status output in @sc{gdb/mi}
25999 @var{status-async-output} contains on-going status information about the
26000 progress of a slow operation. It can be discarded. All status output is
26001 prefixed by @samp{+}.
26004 @cindex async output in @sc{gdb/mi}
26005 @var{exec-async-output} contains asynchronous state change on the target
26006 (stopped, started, disappeared). All async output is prefixed by
26010 @cindex notify output in @sc{gdb/mi}
26011 @var{notify-async-output} contains supplementary information that the
26012 client should handle (e.g., a new breakpoint information). All notify
26013 output is prefixed by @samp{=}.
26016 @cindex console output in @sc{gdb/mi}
26017 @var{console-stream-output} is output that should be displayed as is in the
26018 console. It is the textual response to a CLI command. All the console
26019 output is prefixed by @samp{~}.
26022 @cindex target output in @sc{gdb/mi}
26023 @var{target-stream-output} is the output produced by the target program.
26024 All the target output is prefixed by @samp{@@}.
26027 @cindex log output in @sc{gdb/mi}
26028 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26029 instance messages that should be displayed as part of an error log. All
26030 the log output is prefixed by @samp{&}.
26033 @cindex list output in @sc{gdb/mi}
26034 New @sc{gdb/mi} commands should only output @var{lists} containing
26040 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26041 details about the various output records.
26043 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26044 @node GDB/MI Compatibility with CLI
26045 @section @sc{gdb/mi} Compatibility with CLI
26047 @cindex compatibility, @sc{gdb/mi} and CLI
26048 @cindex @sc{gdb/mi}, compatibility with CLI
26050 For the developers convenience CLI commands can be entered directly,
26051 but there may be some unexpected behaviour. For example, commands
26052 that query the user will behave as if the user replied yes, breakpoint
26053 command lists are not executed and some CLI commands, such as
26054 @code{if}, @code{when} and @code{define}, prompt for further input with
26055 @samp{>}, which is not valid MI output.
26057 This feature may be removed at some stage in the future and it is
26058 recommended that front ends use the @code{-interpreter-exec} command
26059 (@pxref{-interpreter-exec}).
26061 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26062 @node GDB/MI Development and Front Ends
26063 @section @sc{gdb/mi} Development and Front Ends
26064 @cindex @sc{gdb/mi} development
26066 The application which takes the MI output and presents the state of the
26067 program being debugged to the user is called a @dfn{front end}.
26069 Although @sc{gdb/mi} is still incomplete, it is currently being used
26070 by a variety of front ends to @value{GDBN}. This makes it difficult
26071 to introduce new functionality without breaking existing usage. This
26072 section tries to minimize the problems by describing how the protocol
26075 Some changes in MI need not break a carefully designed front end, and
26076 for these the MI version will remain unchanged. The following is a
26077 list of changes that may occur within one level, so front ends should
26078 parse MI output in a way that can handle them:
26082 New MI commands may be added.
26085 New fields may be added to the output of any MI command.
26088 The range of values for fields with specified values, e.g.,
26089 @code{in_scope} (@pxref{-var-update}) may be extended.
26091 @c The format of field's content e.g type prefix, may change so parse it
26092 @c at your own risk. Yes, in general?
26094 @c The order of fields may change? Shouldn't really matter but it might
26095 @c resolve inconsistencies.
26098 If the changes are likely to break front ends, the MI version level
26099 will be increased by one. This will allow the front end to parse the
26100 output according to the MI version. Apart from mi0, new versions of
26101 @value{GDBN} will not support old versions of MI and it will be the
26102 responsibility of the front end to work with the new one.
26104 @c Starting with mi3, add a new command -mi-version that prints the MI
26107 The best way to avoid unexpected changes in MI that might break your front
26108 end is to make your project known to @value{GDBN} developers and
26109 follow development on @email{gdb@@sourceware.org} and
26110 @email{gdb-patches@@sourceware.org}.
26111 @cindex mailing lists
26113 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26114 @node GDB/MI Output Records
26115 @section @sc{gdb/mi} Output Records
26118 * GDB/MI Result Records::
26119 * GDB/MI Stream Records::
26120 * GDB/MI Async Records::
26121 * GDB/MI Frame Information::
26122 * GDB/MI Thread Information::
26123 * GDB/MI Ada Exception Information::
26126 @node GDB/MI Result Records
26127 @subsection @sc{gdb/mi} Result Records
26129 @cindex result records in @sc{gdb/mi}
26130 @cindex @sc{gdb/mi}, result records
26131 In addition to a number of out-of-band notifications, the response to a
26132 @sc{gdb/mi} command includes one of the following result indications:
26136 @item "^done" [ "," @var{results} ]
26137 The synchronous operation was successful, @code{@var{results}} are the return
26142 This result record is equivalent to @samp{^done}. Historically, it
26143 was output instead of @samp{^done} if the command has resumed the
26144 target. This behaviour is maintained for backward compatibility, but
26145 all frontends should treat @samp{^done} and @samp{^running}
26146 identically and rely on the @samp{*running} output record to determine
26147 which threads are resumed.
26151 @value{GDBN} has connected to a remote target.
26153 @item "^error" "," @var{c-string}
26155 The operation failed. The @code{@var{c-string}} contains the corresponding
26160 @value{GDBN} has terminated.
26164 @node GDB/MI Stream Records
26165 @subsection @sc{gdb/mi} Stream Records
26167 @cindex @sc{gdb/mi}, stream records
26168 @cindex stream records in @sc{gdb/mi}
26169 @value{GDBN} internally maintains a number of output streams: the console, the
26170 target, and the log. The output intended for each of these streams is
26171 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26173 Each stream record begins with a unique @dfn{prefix character} which
26174 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26175 Syntax}). In addition to the prefix, each stream record contains a
26176 @code{@var{string-output}}. This is either raw text (with an implicit new
26177 line) or a quoted C string (which does not contain an implicit newline).
26180 @item "~" @var{string-output}
26181 The console output stream contains text that should be displayed in the
26182 CLI console window. It contains the textual responses to CLI commands.
26184 @item "@@" @var{string-output}
26185 The target output stream contains any textual output from the running
26186 target. This is only present when GDB's event loop is truly
26187 asynchronous, which is currently only the case for remote targets.
26189 @item "&" @var{string-output}
26190 The log stream contains debugging messages being produced by @value{GDBN}'s
26194 @node GDB/MI Async Records
26195 @subsection @sc{gdb/mi} Async Records
26197 @cindex async records in @sc{gdb/mi}
26198 @cindex @sc{gdb/mi}, async records
26199 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26200 additional changes that have occurred. Those changes can either be a
26201 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26202 target activity (e.g., target stopped).
26204 The following is the list of possible async records:
26208 @item *running,thread-id="@var{thread}"
26209 The target is now running. The @var{thread} field tells which
26210 specific thread is now running, and can be @samp{all} if all threads
26211 are running. The frontend should assume that no interaction with a
26212 running thread is possible after this notification is produced.
26213 The frontend should not assume that this notification is output
26214 only once for any command. @value{GDBN} may emit this notification
26215 several times, either for different threads, because it cannot resume
26216 all threads together, or even for a single thread, if the thread must
26217 be stepped though some code before letting it run freely.
26219 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26220 The target has stopped. The @var{reason} field can have one of the
26224 @item breakpoint-hit
26225 A breakpoint was reached.
26226 @item watchpoint-trigger
26227 A watchpoint was triggered.
26228 @item read-watchpoint-trigger
26229 A read watchpoint was triggered.
26230 @item access-watchpoint-trigger
26231 An access watchpoint was triggered.
26232 @item function-finished
26233 An -exec-finish or similar CLI command was accomplished.
26234 @item location-reached
26235 An -exec-until or similar CLI command was accomplished.
26236 @item watchpoint-scope
26237 A watchpoint has gone out of scope.
26238 @item end-stepping-range
26239 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26240 similar CLI command was accomplished.
26241 @item exited-signalled
26242 The inferior exited because of a signal.
26244 The inferior exited.
26245 @item exited-normally
26246 The inferior exited normally.
26247 @item signal-received
26248 A signal was received by the inferior.
26250 The inferior has stopped due to a library being loaded or unloaded.
26251 This can only happen when @code{stop-on-solib-events} (@pxref{Files})
26254 The inferior has forked. This is reported when @code{catch fork}
26255 (@pxref{Set Catchpoints}) has been used.
26257 The inferior has vforked. This is reported in when @code{catch vfork}
26258 (@pxref{Set Catchpoints}) has been used.
26259 @item syscall-entry
26260 The inferior entered a system call. This is reported when @code{catch
26261 syscall} (@pxref{Set Catchpoints}) has been used.
26262 @item syscall-entry
26263 The inferior returned from a system call. This is reported when
26264 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26266 The inferior called @code{exec}. This is reported when @code{catch exec}
26267 (@pxref{Set Catchpoints}) has been used.
26270 The @var{id} field identifies the thread that directly caused the stop
26271 -- for example by hitting a breakpoint. Depending on whether all-stop
26272 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26273 stop all threads, or only the thread that directly triggered the stop.
26274 If all threads are stopped, the @var{stopped} field will have the
26275 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26276 field will be a list of thread identifiers. Presently, this list will
26277 always include a single thread, but frontend should be prepared to see
26278 several threads in the list. The @var{core} field reports the
26279 processor core on which the stop event has happened. This field may be absent
26280 if such information is not available.
26282 @item =thread-group-added,id="@var{id}"
26283 @itemx =thread-group-removed,id="@var{id}"
26284 A thread group was either added or removed. The @var{id} field
26285 contains the @value{GDBN} identifier of the thread group. When a thread
26286 group is added, it generally might not be associated with a running
26287 process. When a thread group is removed, its id becomes invalid and
26288 cannot be used in any way.
26290 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26291 A thread group became associated with a running program,
26292 either because the program was just started or the thread group
26293 was attached to a program. The @var{id} field contains the
26294 @value{GDBN} identifier of the thread group. The @var{pid} field
26295 contains process identifier, specific to the operating system.
26297 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26298 A thread group is no longer associated with a running program,
26299 either because the program has exited, or because it was detached
26300 from. The @var{id} field contains the @value{GDBN} identifier of the
26301 thread group. @var{code} is the exit code of the inferior; it exists
26302 only when the inferior exited with some code.
26304 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26305 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26306 A thread either was created, or has exited. The @var{id} field
26307 contains the @value{GDBN} identifier of the thread. The @var{gid}
26308 field identifies the thread group this thread belongs to.
26310 @item =thread-selected,id="@var{id}"
26311 Informs that the selected thread was changed as result of the last
26312 command. This notification is not emitted as result of @code{-thread-select}
26313 command but is emitted whenever an MI command that is not documented
26314 to change the selected thread actually changes it. In particular,
26315 invoking, directly or indirectly (via user-defined command), the CLI
26316 @code{thread} command, will generate this notification.
26318 We suggest that in response to this notification, front ends
26319 highlight the selected thread and cause subsequent commands to apply to
26322 @item =library-loaded,...
26323 Reports that a new library file was loaded by the program. This
26324 notification has 4 fields---@var{id}, @var{target-name},
26325 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26326 opaque identifier of the library. For remote debugging case,
26327 @var{target-name} and @var{host-name} fields give the name of the
26328 library file on the target, and on the host respectively. For native
26329 debugging, both those fields have the same value. The
26330 @var{symbols-loaded} field is emitted only for backward compatibility
26331 and should not be relied on to convey any useful information. The
26332 @var{thread-group} field, if present, specifies the id of the thread
26333 group in whose context the library was loaded. If the field is
26334 absent, it means the library was loaded in the context of all present
26337 @item =library-unloaded,...
26338 Reports that a library was unloaded by the program. This notification
26339 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26340 the same meaning as for the @code{=library-loaded} notification.
26341 The @var{thread-group} field, if present, specifies the id of the
26342 thread group in whose context the library was unloaded. If the field is
26343 absent, it means the library was unloaded in the context of all present
26346 @item =breakpoint-created,bkpt=@{...@}
26347 @itemx =breakpoint-modified,bkpt=@{...@}
26348 @itemx =breakpoint-deleted,bkpt=@{...@}
26349 Reports that a breakpoint was created, modified, or deleted,
26350 respectively. Only user-visible breakpoints are reported to the MI
26353 The @var{bkpt} argument is of the same form as returned by the various
26354 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26356 Note that if a breakpoint is emitted in the result record of a
26357 command, then it will not also be emitted in an async record.
26361 @node GDB/MI Frame Information
26362 @subsection @sc{gdb/mi} Frame Information
26364 Response from many MI commands includes an information about stack
26365 frame. This information is a tuple that may have the following
26370 The level of the stack frame. The innermost frame has the level of
26371 zero. This field is always present.
26374 The name of the function corresponding to the frame. This field may
26375 be absent if @value{GDBN} is unable to determine the function name.
26378 The code address for the frame. This field is always present.
26381 The name of the source files that correspond to the frame's code
26382 address. This field may be absent.
26385 The source line corresponding to the frames' code address. This field
26389 The name of the binary file (either executable or shared library) the
26390 corresponds to the frame's code address. This field may be absent.
26394 @node GDB/MI Thread Information
26395 @subsection @sc{gdb/mi} Thread Information
26397 Whenever @value{GDBN} has to report an information about a thread, it
26398 uses a tuple with the following fields:
26402 The numeric id assigned to the thread by @value{GDBN}. This field is
26406 Target-specific string identifying the thread. This field is always present.
26409 Additional information about the thread provided by the target.
26410 It is supposed to be human-readable and not interpreted by the
26411 frontend. This field is optional.
26414 Either @samp{stopped} or @samp{running}, depending on whether the
26415 thread is presently running. This field is always present.
26418 The value of this field is an integer number of the processor core the
26419 thread was last seen on. This field is optional.
26422 @node GDB/MI Ada Exception Information
26423 @subsection @sc{gdb/mi} Ada Exception Information
26425 Whenever a @code{*stopped} record is emitted because the program
26426 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26427 @value{GDBN} provides the name of the exception that was raised via
26428 the @code{exception-name} field.
26430 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26431 @node GDB/MI Simple Examples
26432 @section Simple Examples of @sc{gdb/mi} Interaction
26433 @cindex @sc{gdb/mi}, simple examples
26435 This subsection presents several simple examples of interaction using
26436 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26437 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26438 the output received from @sc{gdb/mi}.
26440 Note the line breaks shown in the examples are here only for
26441 readability, they don't appear in the real output.
26443 @subheading Setting a Breakpoint
26445 Setting a breakpoint generates synchronous output which contains detailed
26446 information of the breakpoint.
26449 -> -break-insert main
26450 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26451 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26452 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26456 @subheading Program Execution
26458 Program execution generates asynchronous records and MI gives the
26459 reason that execution stopped.
26465 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26466 frame=@{addr="0x08048564",func="main",
26467 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26468 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26473 <- *stopped,reason="exited-normally"
26477 @subheading Quitting @value{GDBN}
26479 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26487 Please note that @samp{^exit} is printed immediately, but it might
26488 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26489 performs necessary cleanups, including killing programs being debugged
26490 or disconnecting from debug hardware, so the frontend should wait till
26491 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26492 fails to exit in reasonable time.
26494 @subheading A Bad Command
26496 Here's what happens if you pass a non-existent command:
26500 <- ^error,msg="Undefined MI command: rubbish"
26505 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26506 @node GDB/MI Command Description Format
26507 @section @sc{gdb/mi} Command Description Format
26509 The remaining sections describe blocks of commands. Each block of
26510 commands is laid out in a fashion similar to this section.
26512 @subheading Motivation
26514 The motivation for this collection of commands.
26516 @subheading Introduction
26518 A brief introduction to this collection of commands as a whole.
26520 @subheading Commands
26522 For each command in the block, the following is described:
26524 @subsubheading Synopsis
26527 -command @var{args}@dots{}
26530 @subsubheading Result
26532 @subsubheading @value{GDBN} Command
26534 The corresponding @value{GDBN} CLI command(s), if any.
26536 @subsubheading Example
26538 Example(s) formatted for readability. Some of the described commands have
26539 not been implemented yet and these are labeled N.A.@: (not available).
26542 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26543 @node GDB/MI Breakpoint Commands
26544 @section @sc{gdb/mi} Breakpoint Commands
26546 @cindex breakpoint commands for @sc{gdb/mi}
26547 @cindex @sc{gdb/mi}, breakpoint commands
26548 This section documents @sc{gdb/mi} commands for manipulating
26551 @subheading The @code{-break-after} Command
26552 @findex -break-after
26554 @subsubheading Synopsis
26557 -break-after @var{number} @var{count}
26560 The breakpoint number @var{number} is not in effect until it has been
26561 hit @var{count} times. To see how this is reflected in the output of
26562 the @samp{-break-list} command, see the description of the
26563 @samp{-break-list} command below.
26565 @subsubheading @value{GDBN} Command
26567 The corresponding @value{GDBN} command is @samp{ignore}.
26569 @subsubheading Example
26574 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26575 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26576 fullname="/home/foo/hello.c",line="5",times="0"@}
26583 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26584 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26585 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26586 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26587 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26588 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26589 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26590 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26591 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26592 line="5",times="0",ignore="3"@}]@}
26597 @subheading The @code{-break-catch} Command
26598 @findex -break-catch
26601 @subheading The @code{-break-commands} Command
26602 @findex -break-commands
26604 @subsubheading Synopsis
26607 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26610 Specifies the CLI commands that should be executed when breakpoint
26611 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26612 are the commands. If no command is specified, any previously-set
26613 commands are cleared. @xref{Break Commands}. Typical use of this
26614 functionality is tracing a program, that is, printing of values of
26615 some variables whenever breakpoint is hit and then continuing.
26617 @subsubheading @value{GDBN} Command
26619 The corresponding @value{GDBN} command is @samp{commands}.
26621 @subsubheading Example
26626 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26627 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26628 fullname="/home/foo/hello.c",line="5",times="0"@}
26630 -break-commands 1 "print v" "continue"
26635 @subheading The @code{-break-condition} Command
26636 @findex -break-condition
26638 @subsubheading Synopsis
26641 -break-condition @var{number} @var{expr}
26644 Breakpoint @var{number} will stop the program only if the condition in
26645 @var{expr} is true. The condition becomes part of the
26646 @samp{-break-list} output (see the description of the @samp{-break-list}
26649 @subsubheading @value{GDBN} Command
26651 The corresponding @value{GDBN} command is @samp{condition}.
26653 @subsubheading Example
26657 -break-condition 1 1
26661 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26662 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26663 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26664 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26665 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26666 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26667 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26668 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26669 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26670 line="5",cond="1",times="0",ignore="3"@}]@}
26674 @subheading The @code{-break-delete} Command
26675 @findex -break-delete
26677 @subsubheading Synopsis
26680 -break-delete ( @var{breakpoint} )+
26683 Delete the breakpoint(s) whose number(s) are specified in the argument
26684 list. This is obviously reflected in the breakpoint list.
26686 @subsubheading @value{GDBN} Command
26688 The corresponding @value{GDBN} command is @samp{delete}.
26690 @subsubheading Example
26698 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26699 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26700 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26701 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26702 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26703 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26704 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26709 @subheading The @code{-break-disable} Command
26710 @findex -break-disable
26712 @subsubheading Synopsis
26715 -break-disable ( @var{breakpoint} )+
26718 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26719 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26721 @subsubheading @value{GDBN} Command
26723 The corresponding @value{GDBN} command is @samp{disable}.
26725 @subsubheading Example
26733 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26734 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26735 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26736 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26737 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26738 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26739 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26740 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26741 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26742 line="5",times="0"@}]@}
26746 @subheading The @code{-break-enable} Command
26747 @findex -break-enable
26749 @subsubheading Synopsis
26752 -break-enable ( @var{breakpoint} )+
26755 Enable (previously disabled) @var{breakpoint}(s).
26757 @subsubheading @value{GDBN} Command
26759 The corresponding @value{GDBN} command is @samp{enable}.
26761 @subsubheading Example
26769 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26770 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26771 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26772 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26773 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26774 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26775 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26776 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26777 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26778 line="5",times="0"@}]@}
26782 @subheading The @code{-break-info} Command
26783 @findex -break-info
26785 @subsubheading Synopsis
26788 -break-info @var{breakpoint}
26792 Get information about a single breakpoint.
26794 @subsubheading @value{GDBN} Command
26796 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26798 @subsubheading Example
26801 @subheading The @code{-break-insert} Command
26802 @findex -break-insert
26804 @subsubheading Synopsis
26807 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26808 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26809 [ -p @var{thread} ] [ @var{location} ]
26813 If specified, @var{location}, can be one of:
26820 @item filename:linenum
26821 @item filename:function
26825 The possible optional parameters of this command are:
26829 Insert a temporary breakpoint.
26831 Insert a hardware breakpoint.
26832 @item -c @var{condition}
26833 Make the breakpoint conditional on @var{condition}.
26834 @item -i @var{ignore-count}
26835 Initialize the @var{ignore-count}.
26837 If @var{location} cannot be parsed (for example if it
26838 refers to unknown files or functions), create a pending
26839 breakpoint. Without this flag, @value{GDBN} will report
26840 an error, and won't create a breakpoint, if @var{location}
26843 Create a disabled breakpoint.
26845 Create a tracepoint. @xref{Tracepoints}. When this parameter
26846 is used together with @samp{-h}, a fast tracepoint is created.
26849 @subsubheading Result
26851 The result is in the form:
26854 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26855 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26856 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26857 times="@var{times}"@}
26861 where @var{number} is the @value{GDBN} number for this breakpoint,
26862 @var{funcname} is the name of the function where the breakpoint was
26863 inserted, @var{filename} is the name of the source file which contains
26864 this function, @var{lineno} is the source line number within that file
26865 and @var{times} the number of times that the breakpoint has been hit
26866 (always 0 for -break-insert but may be greater for -break-info or -break-list
26867 which use the same output).
26869 Note: this format is open to change.
26870 @c An out-of-band breakpoint instead of part of the result?
26872 @subsubheading @value{GDBN} Command
26874 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26875 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26877 @subsubheading Example
26882 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26883 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26885 -break-insert -t foo
26886 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26887 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26890 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26891 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26892 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26893 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26894 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26895 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26896 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26897 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26898 addr="0x0001072c", func="main",file="recursive2.c",
26899 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26900 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26901 addr="0x00010774",func="foo",file="recursive2.c",
26902 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26904 -break-insert -r foo.*
26905 ~int foo(int, int);
26906 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26907 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26911 @subheading The @code{-break-list} Command
26912 @findex -break-list
26914 @subsubheading Synopsis
26920 Displays the list of inserted breakpoints, showing the following fields:
26924 number of the breakpoint
26926 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26928 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26931 is the breakpoint enabled or no: @samp{y} or @samp{n}
26933 memory location at which the breakpoint is set
26935 logical location of the breakpoint, expressed by function name, file
26938 number of times the breakpoint has been hit
26941 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26942 @code{body} field is an empty list.
26944 @subsubheading @value{GDBN} Command
26946 The corresponding @value{GDBN} command is @samp{info break}.
26948 @subsubheading Example
26953 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26954 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26955 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26956 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26957 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26958 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26959 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26960 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26961 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26962 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26963 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26964 line="13",times="0"@}]@}
26968 Here's an example of the result when there are no breakpoints:
26973 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26974 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26975 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26976 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26977 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26978 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26979 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26984 @subheading The @code{-break-passcount} Command
26985 @findex -break-passcount
26987 @subsubheading Synopsis
26990 -break-passcount @var{tracepoint-number} @var{passcount}
26993 Set the passcount for tracepoint @var{tracepoint-number} to
26994 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26995 is not a tracepoint, error is emitted. This corresponds to CLI
26996 command @samp{passcount}.
26998 @subheading The @code{-break-watch} Command
26999 @findex -break-watch
27001 @subsubheading Synopsis
27004 -break-watch [ -a | -r ]
27007 Create a watchpoint. With the @samp{-a} option it will create an
27008 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27009 read from or on a write to the memory location. With the @samp{-r}
27010 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27011 trigger only when the memory location is accessed for reading. Without
27012 either of the options, the watchpoint created is a regular watchpoint,
27013 i.e., it will trigger when the memory location is accessed for writing.
27014 @xref{Set Watchpoints, , Setting Watchpoints}.
27016 Note that @samp{-break-list} will report a single list of watchpoints and
27017 breakpoints inserted.
27019 @subsubheading @value{GDBN} Command
27021 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27024 @subsubheading Example
27026 Setting a watchpoint on a variable in the @code{main} function:
27031 ^done,wpt=@{number="2",exp="x"@}
27036 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27037 value=@{old="-268439212",new="55"@},
27038 frame=@{func="main",args=[],file="recursive2.c",
27039 fullname="/home/foo/bar/recursive2.c",line="5"@}
27043 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27044 the program execution twice: first for the variable changing value, then
27045 for the watchpoint going out of scope.
27050 ^done,wpt=@{number="5",exp="C"@}
27055 *stopped,reason="watchpoint-trigger",
27056 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27057 frame=@{func="callee4",args=[],
27058 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27059 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27064 *stopped,reason="watchpoint-scope",wpnum="5",
27065 frame=@{func="callee3",args=[@{name="strarg",
27066 value="0x11940 \"A string argument.\""@}],
27067 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27068 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27072 Listing breakpoints and watchpoints, at different points in the program
27073 execution. Note that once the watchpoint goes out of scope, it is
27079 ^done,wpt=@{number="2",exp="C"@}
27082 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27083 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27084 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27085 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27086 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27087 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27088 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27089 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27090 addr="0x00010734",func="callee4",
27091 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27092 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27093 bkpt=@{number="2",type="watchpoint",disp="keep",
27094 enabled="y",addr="",what="C",times="0"@}]@}
27099 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27100 value=@{old="-276895068",new="3"@},
27101 frame=@{func="callee4",args=[],
27102 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27103 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27106 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27107 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27108 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27109 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27110 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27111 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27112 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27113 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27114 addr="0x00010734",func="callee4",
27115 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27116 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27117 bkpt=@{number="2",type="watchpoint",disp="keep",
27118 enabled="y",addr="",what="C",times="-5"@}]@}
27122 ^done,reason="watchpoint-scope",wpnum="2",
27123 frame=@{func="callee3",args=[@{name="strarg",
27124 value="0x11940 \"A string argument.\""@}],
27125 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27126 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27129 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27130 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27131 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27132 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27133 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27134 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27135 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27136 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27137 addr="0x00010734",func="callee4",
27138 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27139 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27144 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27145 @node GDB/MI Program Context
27146 @section @sc{gdb/mi} Program Context
27148 @subheading The @code{-exec-arguments} Command
27149 @findex -exec-arguments
27152 @subsubheading Synopsis
27155 -exec-arguments @var{args}
27158 Set the inferior program arguments, to be used in the next
27161 @subsubheading @value{GDBN} Command
27163 The corresponding @value{GDBN} command is @samp{set args}.
27165 @subsubheading Example
27169 -exec-arguments -v word
27176 @subheading The @code{-exec-show-arguments} Command
27177 @findex -exec-show-arguments
27179 @subsubheading Synopsis
27182 -exec-show-arguments
27185 Print the arguments of the program.
27187 @subsubheading @value{GDBN} Command
27189 The corresponding @value{GDBN} command is @samp{show args}.
27191 @subsubheading Example
27196 @subheading The @code{-environment-cd} Command
27197 @findex -environment-cd
27199 @subsubheading Synopsis
27202 -environment-cd @var{pathdir}
27205 Set @value{GDBN}'s working directory.
27207 @subsubheading @value{GDBN} Command
27209 The corresponding @value{GDBN} command is @samp{cd}.
27211 @subsubheading Example
27215 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27221 @subheading The @code{-environment-directory} Command
27222 @findex -environment-directory
27224 @subsubheading Synopsis
27227 -environment-directory [ -r ] [ @var{pathdir} ]+
27230 Add directories @var{pathdir} to beginning of search path for source files.
27231 If the @samp{-r} option is used, the search path is reset to the default
27232 search path. If directories @var{pathdir} are supplied in addition to the
27233 @samp{-r} option, the search path is first reset and then addition
27235 Multiple directories may be specified, separated by blanks. Specifying
27236 multiple directories in a single command
27237 results in the directories added to the beginning of the
27238 search path in the same order they were presented in the command.
27239 If blanks are needed as
27240 part of a directory name, double-quotes should be used around
27241 the name. In the command output, the path will show up separated
27242 by the system directory-separator character. The directory-separator
27243 character must not be used
27244 in any directory name.
27245 If no directories are specified, the current search path is displayed.
27247 @subsubheading @value{GDBN} Command
27249 The corresponding @value{GDBN} command is @samp{dir}.
27251 @subsubheading Example
27255 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27256 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27258 -environment-directory ""
27259 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27261 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27262 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27264 -environment-directory -r
27265 ^done,source-path="$cdir:$cwd"
27270 @subheading The @code{-environment-path} Command
27271 @findex -environment-path
27273 @subsubheading Synopsis
27276 -environment-path [ -r ] [ @var{pathdir} ]+
27279 Add directories @var{pathdir} to beginning of search path for object files.
27280 If the @samp{-r} option is used, the search path is reset to the original
27281 search path that existed at gdb start-up. If directories @var{pathdir} are
27282 supplied in addition to the
27283 @samp{-r} option, the search path is first reset and then addition
27285 Multiple directories may be specified, separated by blanks. Specifying
27286 multiple directories in a single command
27287 results in the directories added to the beginning of the
27288 search path in the same order they were presented in the command.
27289 If blanks are needed as
27290 part of a directory name, double-quotes should be used around
27291 the name. In the command output, the path will show up separated
27292 by the system directory-separator character. The directory-separator
27293 character must not be used
27294 in any directory name.
27295 If no directories are specified, the current path is displayed.
27298 @subsubheading @value{GDBN} Command
27300 The corresponding @value{GDBN} command is @samp{path}.
27302 @subsubheading Example
27307 ^done,path="/usr/bin"
27309 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27310 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27312 -environment-path -r /usr/local/bin
27313 ^done,path="/usr/local/bin:/usr/bin"
27318 @subheading The @code{-environment-pwd} Command
27319 @findex -environment-pwd
27321 @subsubheading Synopsis
27327 Show the current working directory.
27329 @subsubheading @value{GDBN} Command
27331 The corresponding @value{GDBN} command is @samp{pwd}.
27333 @subsubheading Example
27338 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27342 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27343 @node GDB/MI Thread Commands
27344 @section @sc{gdb/mi} Thread Commands
27347 @subheading The @code{-thread-info} Command
27348 @findex -thread-info
27350 @subsubheading Synopsis
27353 -thread-info [ @var{thread-id} ]
27356 Reports information about either a specific thread, if
27357 the @var{thread-id} parameter is present, or about all
27358 threads. When printing information about all threads,
27359 also reports the current thread.
27361 @subsubheading @value{GDBN} Command
27363 The @samp{info thread} command prints the same information
27366 @subsubheading Result
27368 The result is a list of threads. The following attributes are
27369 defined for a given thread:
27373 This field exists only for the current thread. It has the value @samp{*}.
27376 The identifier that @value{GDBN} uses to refer to the thread.
27379 The identifier that the target uses to refer to the thread.
27382 Extra information about the thread, in a target-specific format. This
27386 The name of the thread. If the user specified a name using the
27387 @code{thread name} command, then this name is given. Otherwise, if
27388 @value{GDBN} can extract the thread name from the target, then that
27389 name is given. If @value{GDBN} cannot find the thread name, then this
27393 The stack frame currently executing in the thread.
27396 The thread's state. The @samp{state} field may have the following
27401 The thread is stopped. Frame information is available for stopped
27405 The thread is running. There's no frame information for running
27411 If @value{GDBN} can find the CPU core on which this thread is running,
27412 then this field is the core identifier. This field is optional.
27416 @subsubheading Example
27421 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27422 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27423 args=[]@},state="running"@},
27424 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27425 frame=@{level="0",addr="0x0804891f",func="foo",
27426 args=[@{name="i",value="10"@}],
27427 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27428 state="running"@}],
27429 current-thread-id="1"
27433 @subheading The @code{-thread-list-ids} Command
27434 @findex -thread-list-ids
27436 @subsubheading Synopsis
27442 Produces a list of the currently known @value{GDBN} thread ids. At the
27443 end of the list it also prints the total number of such threads.
27445 This command is retained for historical reasons, the
27446 @code{-thread-info} command should be used instead.
27448 @subsubheading @value{GDBN} Command
27450 Part of @samp{info threads} supplies the same information.
27452 @subsubheading Example
27457 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27458 current-thread-id="1",number-of-threads="3"
27463 @subheading The @code{-thread-select} Command
27464 @findex -thread-select
27466 @subsubheading Synopsis
27469 -thread-select @var{threadnum}
27472 Make @var{threadnum} the current thread. It prints the number of the new
27473 current thread, and the topmost frame for that thread.
27475 This command is deprecated in favor of explicitly using the
27476 @samp{--thread} option to each command.
27478 @subsubheading @value{GDBN} Command
27480 The corresponding @value{GDBN} command is @samp{thread}.
27482 @subsubheading Example
27489 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27490 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27494 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27495 number-of-threads="3"
27498 ^done,new-thread-id="3",
27499 frame=@{level="0",func="vprintf",
27500 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27501 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27505 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27506 @node GDB/MI Ada Tasking Commands
27507 @section @sc{gdb/mi} Ada Tasking Commands
27509 @subheading The @code{-ada-task-info} Command
27510 @findex -ada-task-info
27512 @subsubheading Synopsis
27515 -ada-task-info [ @var{task-id} ]
27518 Reports information about either a specific Ada task, if the
27519 @var{task-id} parameter is present, or about all Ada tasks.
27521 @subsubheading @value{GDBN} Command
27523 The @samp{info tasks} command prints the same information
27524 about all Ada tasks (@pxref{Ada Tasks}).
27526 @subsubheading Result
27528 The result is a table of Ada tasks. The following columns are
27529 defined for each Ada task:
27533 This field exists only for the current thread. It has the value @samp{*}.
27536 The identifier that @value{GDBN} uses to refer to the Ada task.
27539 The identifier that the target uses to refer to the Ada task.
27542 The identifier of the thread corresponding to the Ada task.
27544 This field should always exist, as Ada tasks are always implemented
27545 on top of a thread. But if @value{GDBN} cannot find this corresponding
27546 thread for any reason, the field is omitted.
27549 This field exists only when the task was created by another task.
27550 In this case, it provides the ID of the parent task.
27553 The base priority of the task.
27556 The current state of the task. For a detailed description of the
27557 possible states, see @ref{Ada Tasks}.
27560 The name of the task.
27564 @subsubheading Example
27568 ^done,tasks=@{nr_rows="3",nr_cols="8",
27569 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27570 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27571 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27572 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27573 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27574 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27575 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27576 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27577 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27578 state="Child Termination Wait",name="main_task"@}]@}
27582 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27583 @node GDB/MI Program Execution
27584 @section @sc{gdb/mi} Program Execution
27586 These are the asynchronous commands which generate the out-of-band
27587 record @samp{*stopped}. Currently @value{GDBN} only really executes
27588 asynchronously with remote targets and this interaction is mimicked in
27591 @subheading The @code{-exec-continue} Command
27592 @findex -exec-continue
27594 @subsubheading Synopsis
27597 -exec-continue [--reverse] [--all|--thread-group N]
27600 Resumes the execution of the inferior program, which will continue
27601 to execute until it reaches a debugger stop event. If the
27602 @samp{--reverse} option is specified, execution resumes in reverse until
27603 it reaches a stop event. Stop events may include
27606 breakpoints or watchpoints
27608 signals or exceptions
27610 the end of the process (or its beginning under @samp{--reverse})
27612 the end or beginning of a replay log if one is being used.
27614 In all-stop mode (@pxref{All-Stop
27615 Mode}), may resume only one thread, or all threads, depending on the
27616 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27617 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27618 ignored in all-stop mode. If the @samp{--thread-group} options is
27619 specified, then all threads in that thread group are resumed.
27621 @subsubheading @value{GDBN} Command
27623 The corresponding @value{GDBN} corresponding is @samp{continue}.
27625 @subsubheading Example
27632 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27633 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27639 @subheading The @code{-exec-finish} Command
27640 @findex -exec-finish
27642 @subsubheading Synopsis
27645 -exec-finish [--reverse]
27648 Resumes the execution of the inferior program until the current
27649 function is exited. Displays the results returned by the function.
27650 If the @samp{--reverse} option is specified, resumes the reverse
27651 execution of the inferior program until the point where current
27652 function was called.
27654 @subsubheading @value{GDBN} Command
27656 The corresponding @value{GDBN} command is @samp{finish}.
27658 @subsubheading Example
27660 Function returning @code{void}.
27667 *stopped,reason="function-finished",frame=@{func="main",args=[],
27668 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27672 Function returning other than @code{void}. The name of the internal
27673 @value{GDBN} variable storing the result is printed, together with the
27680 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27681 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27682 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27683 gdb-result-var="$1",return-value="0"
27688 @subheading The @code{-exec-interrupt} Command
27689 @findex -exec-interrupt
27691 @subsubheading Synopsis
27694 -exec-interrupt [--all|--thread-group N]
27697 Interrupts the background execution of the target. Note how the token
27698 associated with the stop message is the one for the execution command
27699 that has been interrupted. The token for the interrupt itself only
27700 appears in the @samp{^done} output. If the user is trying to
27701 interrupt a non-running program, an error message will be printed.
27703 Note that when asynchronous execution is enabled, this command is
27704 asynchronous just like other execution commands. That is, first the
27705 @samp{^done} response will be printed, and the target stop will be
27706 reported after that using the @samp{*stopped} notification.
27708 In non-stop mode, only the context thread is interrupted by default.
27709 All threads (in all inferiors) will be interrupted if the
27710 @samp{--all} option is specified. If the @samp{--thread-group}
27711 option is specified, all threads in that group will be interrupted.
27713 @subsubheading @value{GDBN} Command
27715 The corresponding @value{GDBN} command is @samp{interrupt}.
27717 @subsubheading Example
27728 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27729 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27730 fullname="/home/foo/bar/try.c",line="13"@}
27735 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27739 @subheading The @code{-exec-jump} Command
27742 @subsubheading Synopsis
27745 -exec-jump @var{location}
27748 Resumes execution of the inferior program at the location specified by
27749 parameter. @xref{Specify Location}, for a description of the
27750 different forms of @var{location}.
27752 @subsubheading @value{GDBN} Command
27754 The corresponding @value{GDBN} command is @samp{jump}.
27756 @subsubheading Example
27759 -exec-jump foo.c:10
27760 *running,thread-id="all"
27765 @subheading The @code{-exec-next} Command
27768 @subsubheading Synopsis
27771 -exec-next [--reverse]
27774 Resumes execution of the inferior program, stopping when the beginning
27775 of the next source line is reached.
27777 If the @samp{--reverse} option is specified, resumes reverse execution
27778 of the inferior program, stopping at the beginning of the previous
27779 source line. If you issue this command on the first line of a
27780 function, it will take you back to the caller of that function, to the
27781 source line where the function was called.
27784 @subsubheading @value{GDBN} Command
27786 The corresponding @value{GDBN} command is @samp{next}.
27788 @subsubheading Example
27794 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27799 @subheading The @code{-exec-next-instruction} Command
27800 @findex -exec-next-instruction
27802 @subsubheading Synopsis
27805 -exec-next-instruction [--reverse]
27808 Executes one machine instruction. If the instruction is a function
27809 call, continues until the function returns. If the program stops at an
27810 instruction in the middle of a source line, the address will be
27813 If the @samp{--reverse} option is specified, resumes reverse execution
27814 of the inferior program, stopping at the previous instruction. If the
27815 previously executed instruction was a return from another function,
27816 it will continue to execute in reverse until the call to that function
27817 (from the current stack frame) is reached.
27819 @subsubheading @value{GDBN} Command
27821 The corresponding @value{GDBN} command is @samp{nexti}.
27823 @subsubheading Example
27827 -exec-next-instruction
27831 *stopped,reason="end-stepping-range",
27832 addr="0x000100d4",line="5",file="hello.c"
27837 @subheading The @code{-exec-return} Command
27838 @findex -exec-return
27840 @subsubheading Synopsis
27846 Makes current function return immediately. Doesn't execute the inferior.
27847 Displays the new current frame.
27849 @subsubheading @value{GDBN} Command
27851 The corresponding @value{GDBN} command is @samp{return}.
27853 @subsubheading Example
27857 200-break-insert callee4
27858 200^done,bkpt=@{number="1",addr="0x00010734",
27859 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27864 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27865 frame=@{func="callee4",args=[],
27866 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27867 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27873 111^done,frame=@{level="0",func="callee3",
27874 args=[@{name="strarg",
27875 value="0x11940 \"A string argument.\""@}],
27876 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27877 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27882 @subheading The @code{-exec-run} Command
27885 @subsubheading Synopsis
27888 -exec-run [--all | --thread-group N]
27891 Starts execution of the inferior from the beginning. The inferior
27892 executes until either a breakpoint is encountered or the program
27893 exits. In the latter case the output will include an exit code, if
27894 the program has exited exceptionally.
27896 When no option is specified, the current inferior is started. If the
27897 @samp{--thread-group} option is specified, it should refer to a thread
27898 group of type @samp{process}, and that thread group will be started.
27899 If the @samp{--all} option is specified, then all inferiors will be started.
27901 @subsubheading @value{GDBN} Command
27903 The corresponding @value{GDBN} command is @samp{run}.
27905 @subsubheading Examples
27910 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27915 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27916 frame=@{func="main",args=[],file="recursive2.c",
27917 fullname="/home/foo/bar/recursive2.c",line="4"@}
27922 Program exited normally:
27930 *stopped,reason="exited-normally"
27935 Program exited exceptionally:
27943 *stopped,reason="exited",exit-code="01"
27947 Another way the program can terminate is if it receives a signal such as
27948 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27952 *stopped,reason="exited-signalled",signal-name="SIGINT",
27953 signal-meaning="Interrupt"
27957 @c @subheading -exec-signal
27960 @subheading The @code{-exec-step} Command
27963 @subsubheading Synopsis
27966 -exec-step [--reverse]
27969 Resumes execution of the inferior program, stopping when the beginning
27970 of the next source line is reached, if the next source line is not a
27971 function call. If it is, stop at the first instruction of the called
27972 function. If the @samp{--reverse} option is specified, resumes reverse
27973 execution of the inferior program, stopping at the beginning of the
27974 previously executed source line.
27976 @subsubheading @value{GDBN} Command
27978 The corresponding @value{GDBN} command is @samp{step}.
27980 @subsubheading Example
27982 Stepping into a function:
27988 *stopped,reason="end-stepping-range",
27989 frame=@{func="foo",args=[@{name="a",value="10"@},
27990 @{name="b",value="0"@}],file="recursive2.c",
27991 fullname="/home/foo/bar/recursive2.c",line="11"@}
28001 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28006 @subheading The @code{-exec-step-instruction} Command
28007 @findex -exec-step-instruction
28009 @subsubheading Synopsis
28012 -exec-step-instruction [--reverse]
28015 Resumes the inferior which executes one machine instruction. If the
28016 @samp{--reverse} option is specified, resumes reverse execution of the
28017 inferior program, stopping at the previously executed instruction.
28018 The output, once @value{GDBN} has stopped, will vary depending on
28019 whether we have stopped in the middle of a source line or not. In the
28020 former case, the address at which the program stopped will be printed
28023 @subsubheading @value{GDBN} Command
28025 The corresponding @value{GDBN} command is @samp{stepi}.
28027 @subsubheading Example
28031 -exec-step-instruction
28035 *stopped,reason="end-stepping-range",
28036 frame=@{func="foo",args=[],file="try.c",
28037 fullname="/home/foo/bar/try.c",line="10"@}
28039 -exec-step-instruction
28043 *stopped,reason="end-stepping-range",
28044 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28045 fullname="/home/foo/bar/try.c",line="10"@}
28050 @subheading The @code{-exec-until} Command
28051 @findex -exec-until
28053 @subsubheading Synopsis
28056 -exec-until [ @var{location} ]
28059 Executes the inferior until the @var{location} specified in the
28060 argument is reached. If there is no argument, the inferior executes
28061 until a source line greater than the current one is reached. The
28062 reason for stopping in this case will be @samp{location-reached}.
28064 @subsubheading @value{GDBN} Command
28066 The corresponding @value{GDBN} command is @samp{until}.
28068 @subsubheading Example
28072 -exec-until recursive2.c:6
28076 *stopped,reason="location-reached",frame=@{func="main",args=[],
28077 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28082 @subheading -file-clear
28083 Is this going away????
28086 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28087 @node GDB/MI Stack Manipulation
28088 @section @sc{gdb/mi} Stack Manipulation Commands
28091 @subheading The @code{-stack-info-frame} Command
28092 @findex -stack-info-frame
28094 @subsubheading Synopsis
28100 Get info on the selected frame.
28102 @subsubheading @value{GDBN} Command
28104 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28105 (without arguments).
28107 @subsubheading Example
28112 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28113 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28114 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28118 @subheading The @code{-stack-info-depth} Command
28119 @findex -stack-info-depth
28121 @subsubheading Synopsis
28124 -stack-info-depth [ @var{max-depth} ]
28127 Return the depth of the stack. If the integer argument @var{max-depth}
28128 is specified, do not count beyond @var{max-depth} frames.
28130 @subsubheading @value{GDBN} Command
28132 There's no equivalent @value{GDBN} command.
28134 @subsubheading Example
28136 For a stack with frame levels 0 through 11:
28143 -stack-info-depth 4
28146 -stack-info-depth 12
28149 -stack-info-depth 11
28152 -stack-info-depth 13
28157 @subheading The @code{-stack-list-arguments} Command
28158 @findex -stack-list-arguments
28160 @subsubheading Synopsis
28163 -stack-list-arguments @var{print-values}
28164 [ @var{low-frame} @var{high-frame} ]
28167 Display a list of the arguments for the frames between @var{low-frame}
28168 and @var{high-frame} (inclusive). If @var{low-frame} and
28169 @var{high-frame} are not provided, list the arguments for the whole
28170 call stack. If the two arguments are equal, show the single frame
28171 at the corresponding level. It is an error if @var{low-frame} is
28172 larger than the actual number of frames. On the other hand,
28173 @var{high-frame} may be larger than the actual number of frames, in
28174 which case only existing frames will be returned.
28176 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28177 the variables; if it is 1 or @code{--all-values}, print also their
28178 values; and if it is 2 or @code{--simple-values}, print the name,
28179 type and value for simple data types, and the name and type for arrays,
28180 structures and unions.
28182 Use of this command to obtain arguments in a single frame is
28183 deprecated in favor of the @samp{-stack-list-variables} command.
28185 @subsubheading @value{GDBN} Command
28187 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28188 @samp{gdb_get_args} command which partially overlaps with the
28189 functionality of @samp{-stack-list-arguments}.
28191 @subsubheading Example
28198 frame=@{level="0",addr="0x00010734",func="callee4",
28199 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28200 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28201 frame=@{level="1",addr="0x0001076c",func="callee3",
28202 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28203 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28204 frame=@{level="2",addr="0x0001078c",func="callee2",
28205 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28206 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28207 frame=@{level="3",addr="0x000107b4",func="callee1",
28208 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28209 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28210 frame=@{level="4",addr="0x000107e0",func="main",
28211 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28212 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28214 -stack-list-arguments 0
28217 frame=@{level="0",args=[]@},
28218 frame=@{level="1",args=[name="strarg"]@},
28219 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28220 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28221 frame=@{level="4",args=[]@}]
28223 -stack-list-arguments 1
28226 frame=@{level="0",args=[]@},
28228 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28229 frame=@{level="2",args=[
28230 @{name="intarg",value="2"@},
28231 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28232 @{frame=@{level="3",args=[
28233 @{name="intarg",value="2"@},
28234 @{name="strarg",value="0x11940 \"A string argument.\""@},
28235 @{name="fltarg",value="3.5"@}]@},
28236 frame=@{level="4",args=[]@}]
28238 -stack-list-arguments 0 2 2
28239 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28241 -stack-list-arguments 1 2 2
28242 ^done,stack-args=[frame=@{level="2",
28243 args=[@{name="intarg",value="2"@},
28244 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28248 @c @subheading -stack-list-exception-handlers
28251 @subheading The @code{-stack-list-frames} Command
28252 @findex -stack-list-frames
28254 @subsubheading Synopsis
28257 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28260 List the frames currently on the stack. For each frame it displays the
28265 The frame number, 0 being the topmost frame, i.e., the innermost function.
28267 The @code{$pc} value for that frame.
28271 File name of the source file where the function lives.
28272 @item @var{fullname}
28273 The full file name of the source file where the function lives.
28275 Line number corresponding to the @code{$pc}.
28277 The shared library where this function is defined. This is only given
28278 if the frame's function is not known.
28281 If invoked without arguments, this command prints a backtrace for the
28282 whole stack. If given two integer arguments, it shows the frames whose
28283 levels are between the two arguments (inclusive). If the two arguments
28284 are equal, it shows the single frame at the corresponding level. It is
28285 an error if @var{low-frame} is larger than the actual number of
28286 frames. On the other hand, @var{high-frame} may be larger than the
28287 actual number of frames, in which case only existing frames will be returned.
28289 @subsubheading @value{GDBN} Command
28291 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28293 @subsubheading Example
28295 Full stack backtrace:
28301 [frame=@{level="0",addr="0x0001076c",func="foo",
28302 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28303 frame=@{level="1",addr="0x000107a4",func="foo",
28304 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28305 frame=@{level="2",addr="0x000107a4",func="foo",
28306 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28307 frame=@{level="3",addr="0x000107a4",func="foo",
28308 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28309 frame=@{level="4",addr="0x000107a4",func="foo",
28310 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28311 frame=@{level="5",addr="0x000107a4",func="foo",
28312 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28313 frame=@{level="6",addr="0x000107a4",func="foo",
28314 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28315 frame=@{level="7",addr="0x000107a4",func="foo",
28316 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28317 frame=@{level="8",addr="0x000107a4",func="foo",
28318 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28319 frame=@{level="9",addr="0x000107a4",func="foo",
28320 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28321 frame=@{level="10",addr="0x000107a4",func="foo",
28322 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28323 frame=@{level="11",addr="0x00010738",func="main",
28324 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28328 Show frames between @var{low_frame} and @var{high_frame}:
28332 -stack-list-frames 3 5
28334 [frame=@{level="3",addr="0x000107a4",func="foo",
28335 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28336 frame=@{level="4",addr="0x000107a4",func="foo",
28337 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28338 frame=@{level="5",addr="0x000107a4",func="foo",
28339 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28343 Show a single frame:
28347 -stack-list-frames 3 3
28349 [frame=@{level="3",addr="0x000107a4",func="foo",
28350 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28355 @subheading The @code{-stack-list-locals} Command
28356 @findex -stack-list-locals
28358 @subsubheading Synopsis
28361 -stack-list-locals @var{print-values}
28364 Display the local variable names for the selected frame. If
28365 @var{print-values} is 0 or @code{--no-values}, print only the names of
28366 the variables; if it is 1 or @code{--all-values}, print also their
28367 values; and if it is 2 or @code{--simple-values}, print the name,
28368 type and value for simple data types, and the name and type for arrays,
28369 structures and unions. In this last case, a frontend can immediately
28370 display the value of simple data types and create variable objects for
28371 other data types when the user wishes to explore their values in
28374 This command is deprecated in favor of the
28375 @samp{-stack-list-variables} command.
28377 @subsubheading @value{GDBN} Command
28379 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28381 @subsubheading Example
28385 -stack-list-locals 0
28386 ^done,locals=[name="A",name="B",name="C"]
28388 -stack-list-locals --all-values
28389 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28390 @{name="C",value="@{1, 2, 3@}"@}]
28391 -stack-list-locals --simple-values
28392 ^done,locals=[@{name="A",type="int",value="1"@},
28393 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28397 @subheading The @code{-stack-list-variables} Command
28398 @findex -stack-list-variables
28400 @subsubheading Synopsis
28403 -stack-list-variables @var{print-values}
28406 Display the names of local variables and function arguments for the selected frame. If
28407 @var{print-values} is 0 or @code{--no-values}, print only the names of
28408 the variables; if it is 1 or @code{--all-values}, print also their
28409 values; and if it is 2 or @code{--simple-values}, print the name,
28410 type and value for simple data types, and the name and type for arrays,
28411 structures and unions.
28413 @subsubheading Example
28417 -stack-list-variables --thread 1 --frame 0 --all-values
28418 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28423 @subheading The @code{-stack-select-frame} Command
28424 @findex -stack-select-frame
28426 @subsubheading Synopsis
28429 -stack-select-frame @var{framenum}
28432 Change the selected frame. Select a different frame @var{framenum} on
28435 This command in deprecated in favor of passing the @samp{--frame}
28436 option to every command.
28438 @subsubheading @value{GDBN} Command
28440 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28441 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28443 @subsubheading Example
28447 -stack-select-frame 2
28452 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28453 @node GDB/MI Variable Objects
28454 @section @sc{gdb/mi} Variable Objects
28458 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28460 For the implementation of a variable debugger window (locals, watched
28461 expressions, etc.), we are proposing the adaptation of the existing code
28462 used by @code{Insight}.
28464 The two main reasons for that are:
28468 It has been proven in practice (it is already on its second generation).
28471 It will shorten development time (needless to say how important it is
28475 The original interface was designed to be used by Tcl code, so it was
28476 slightly changed so it could be used through @sc{gdb/mi}. This section
28477 describes the @sc{gdb/mi} operations that will be available and gives some
28478 hints about their use.
28480 @emph{Note}: In addition to the set of operations described here, we
28481 expect the @sc{gui} implementation of a variable window to require, at
28482 least, the following operations:
28485 @item @code{-gdb-show} @code{output-radix}
28486 @item @code{-stack-list-arguments}
28487 @item @code{-stack-list-locals}
28488 @item @code{-stack-select-frame}
28493 @subheading Introduction to Variable Objects
28495 @cindex variable objects in @sc{gdb/mi}
28497 Variable objects are "object-oriented" MI interface for examining and
28498 changing values of expressions. Unlike some other MI interfaces that
28499 work with expressions, variable objects are specifically designed for
28500 simple and efficient presentation in the frontend. A variable object
28501 is identified by string name. When a variable object is created, the
28502 frontend specifies the expression for that variable object. The
28503 expression can be a simple variable, or it can be an arbitrary complex
28504 expression, and can even involve CPU registers. After creating a
28505 variable object, the frontend can invoke other variable object
28506 operations---for example to obtain or change the value of a variable
28507 object, or to change display format.
28509 Variable objects have hierarchical tree structure. Any variable object
28510 that corresponds to a composite type, such as structure in C, has
28511 a number of child variable objects, for example corresponding to each
28512 element of a structure. A child variable object can itself have
28513 children, recursively. Recursion ends when we reach
28514 leaf variable objects, which always have built-in types. Child variable
28515 objects are created only by explicit request, so if a frontend
28516 is not interested in the children of a particular variable object, no
28517 child will be created.
28519 For a leaf variable object it is possible to obtain its value as a
28520 string, or set the value from a string. String value can be also
28521 obtained for a non-leaf variable object, but it's generally a string
28522 that only indicates the type of the object, and does not list its
28523 contents. Assignment to a non-leaf variable object is not allowed.
28525 A frontend does not need to read the values of all variable objects each time
28526 the program stops. Instead, MI provides an update command that lists all
28527 variable objects whose values has changed since the last update
28528 operation. This considerably reduces the amount of data that must
28529 be transferred to the frontend. As noted above, children variable
28530 objects are created on demand, and only leaf variable objects have a
28531 real value. As result, gdb will read target memory only for leaf
28532 variables that frontend has created.
28534 The automatic update is not always desirable. For example, a frontend
28535 might want to keep a value of some expression for future reference,
28536 and never update it. For another example, fetching memory is
28537 relatively slow for embedded targets, so a frontend might want
28538 to disable automatic update for the variables that are either not
28539 visible on the screen, or ``closed''. This is possible using so
28540 called ``frozen variable objects''. Such variable objects are never
28541 implicitly updated.
28543 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28544 fixed variable object, the expression is parsed when the variable
28545 object is created, including associating identifiers to specific
28546 variables. The meaning of expression never changes. For a floating
28547 variable object the values of variables whose names appear in the
28548 expressions are re-evaluated every time in the context of the current
28549 frame. Consider this example:
28554 struct work_state state;
28561 If a fixed variable object for the @code{state} variable is created in
28562 this function, and we enter the recursive call, the variable
28563 object will report the value of @code{state} in the top-level
28564 @code{do_work} invocation. On the other hand, a floating variable
28565 object will report the value of @code{state} in the current frame.
28567 If an expression specified when creating a fixed variable object
28568 refers to a local variable, the variable object becomes bound to the
28569 thread and frame in which the variable object is created. When such
28570 variable object is updated, @value{GDBN} makes sure that the
28571 thread/frame combination the variable object is bound to still exists,
28572 and re-evaluates the variable object in context of that thread/frame.
28574 The following is the complete set of @sc{gdb/mi} operations defined to
28575 access this functionality:
28577 @multitable @columnfractions .4 .6
28578 @item @strong{Operation}
28579 @tab @strong{Description}
28581 @item @code{-enable-pretty-printing}
28582 @tab enable Python-based pretty-printing
28583 @item @code{-var-create}
28584 @tab create a variable object
28585 @item @code{-var-delete}
28586 @tab delete the variable object and/or its children
28587 @item @code{-var-set-format}
28588 @tab set the display format of this variable
28589 @item @code{-var-show-format}
28590 @tab show the display format of this variable
28591 @item @code{-var-info-num-children}
28592 @tab tells how many children this object has
28593 @item @code{-var-list-children}
28594 @tab return a list of the object's children
28595 @item @code{-var-info-type}
28596 @tab show the type of this variable object
28597 @item @code{-var-info-expression}
28598 @tab print parent-relative expression that this variable object represents
28599 @item @code{-var-info-path-expression}
28600 @tab print full expression that this variable object represents
28601 @item @code{-var-show-attributes}
28602 @tab is this variable editable? does it exist here?
28603 @item @code{-var-evaluate-expression}
28604 @tab get the value of this variable
28605 @item @code{-var-assign}
28606 @tab set the value of this variable
28607 @item @code{-var-update}
28608 @tab update the variable and its children
28609 @item @code{-var-set-frozen}
28610 @tab set frozeness attribute
28611 @item @code{-var-set-update-range}
28612 @tab set range of children to display on update
28615 In the next subsection we describe each operation in detail and suggest
28616 how it can be used.
28618 @subheading Description And Use of Operations on Variable Objects
28620 @subheading The @code{-enable-pretty-printing} Command
28621 @findex -enable-pretty-printing
28624 -enable-pretty-printing
28627 @value{GDBN} allows Python-based visualizers to affect the output of the
28628 MI variable object commands. However, because there was no way to
28629 implement this in a fully backward-compatible way, a front end must
28630 request that this functionality be enabled.
28632 Once enabled, this feature cannot be disabled.
28634 Note that if Python support has not been compiled into @value{GDBN},
28635 this command will still succeed (and do nothing).
28637 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28638 may work differently in future versions of @value{GDBN}.
28640 @subheading The @code{-var-create} Command
28641 @findex -var-create
28643 @subsubheading Synopsis
28646 -var-create @{@var{name} | "-"@}
28647 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28650 This operation creates a variable object, which allows the monitoring of
28651 a variable, the result of an expression, a memory cell or a CPU
28654 The @var{name} parameter is the string by which the object can be
28655 referenced. It must be unique. If @samp{-} is specified, the varobj
28656 system will generate a string ``varNNNNNN'' automatically. It will be
28657 unique provided that one does not specify @var{name} of that format.
28658 The command fails if a duplicate name is found.
28660 The frame under which the expression should be evaluated can be
28661 specified by @var{frame-addr}. A @samp{*} indicates that the current
28662 frame should be used. A @samp{@@} indicates that a floating variable
28663 object must be created.
28665 @var{expression} is any expression valid on the current language set (must not
28666 begin with a @samp{*}), or one of the following:
28670 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28673 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28676 @samp{$@var{regname}} --- a CPU register name
28679 @cindex dynamic varobj
28680 A varobj's contents may be provided by a Python-based pretty-printer. In this
28681 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28682 have slightly different semantics in some cases. If the
28683 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28684 will never create a dynamic varobj. This ensures backward
28685 compatibility for existing clients.
28687 @subsubheading Result
28689 This operation returns attributes of the newly-created varobj. These
28694 The name of the varobj.
28697 The number of children of the varobj. This number is not necessarily
28698 reliable for a dynamic varobj. Instead, you must examine the
28699 @samp{has_more} attribute.
28702 The varobj's scalar value. For a varobj whose type is some sort of
28703 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28704 will not be interesting.
28707 The varobj's type. This is a string representation of the type, as
28708 would be printed by the @value{GDBN} CLI.
28711 If a variable object is bound to a specific thread, then this is the
28712 thread's identifier.
28715 For a dynamic varobj, this indicates whether there appear to be any
28716 children available. For a non-dynamic varobj, this will be 0.
28719 This attribute will be present and have the value @samp{1} if the
28720 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28721 then this attribute will not be present.
28724 A dynamic varobj can supply a display hint to the front end. The
28725 value comes directly from the Python pretty-printer object's
28726 @code{display_hint} method. @xref{Pretty Printing API}.
28729 Typical output will look like this:
28732 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28733 has_more="@var{has_more}"
28737 @subheading The @code{-var-delete} Command
28738 @findex -var-delete
28740 @subsubheading Synopsis
28743 -var-delete [ -c ] @var{name}
28746 Deletes a previously created variable object and all of its children.
28747 With the @samp{-c} option, just deletes the children.
28749 Returns an error if the object @var{name} is not found.
28752 @subheading The @code{-var-set-format} Command
28753 @findex -var-set-format
28755 @subsubheading Synopsis
28758 -var-set-format @var{name} @var{format-spec}
28761 Sets the output format for the value of the object @var{name} to be
28764 @anchor{-var-set-format}
28765 The syntax for the @var{format-spec} is as follows:
28768 @var{format-spec} @expansion{}
28769 @{binary | decimal | hexadecimal | octal | natural@}
28772 The natural format is the default format choosen automatically
28773 based on the variable type (like decimal for an @code{int}, hex
28774 for pointers, etc.).
28776 For a variable with children, the format is set only on the
28777 variable itself, and the children are not affected.
28779 @subheading The @code{-var-show-format} Command
28780 @findex -var-show-format
28782 @subsubheading Synopsis
28785 -var-show-format @var{name}
28788 Returns the format used to display the value of the object @var{name}.
28791 @var{format} @expansion{}
28796 @subheading The @code{-var-info-num-children} Command
28797 @findex -var-info-num-children
28799 @subsubheading Synopsis
28802 -var-info-num-children @var{name}
28805 Returns the number of children of a variable object @var{name}:
28811 Note that this number is not completely reliable for a dynamic varobj.
28812 It will return the current number of children, but more children may
28816 @subheading The @code{-var-list-children} Command
28817 @findex -var-list-children
28819 @subsubheading Synopsis
28822 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28824 @anchor{-var-list-children}
28826 Return a list of the children of the specified variable object and
28827 create variable objects for them, if they do not already exist. With
28828 a single argument or if @var{print-values} has a value of 0 or
28829 @code{--no-values}, print only the names of the variables; if
28830 @var{print-values} is 1 or @code{--all-values}, also print their
28831 values; and if it is 2 or @code{--simple-values} print the name and
28832 value for simple data types and just the name for arrays, structures
28835 @var{from} and @var{to}, if specified, indicate the range of children
28836 to report. If @var{from} or @var{to} is less than zero, the range is
28837 reset and all children will be reported. Otherwise, children starting
28838 at @var{from} (zero-based) and up to and excluding @var{to} will be
28841 If a child range is requested, it will only affect the current call to
28842 @code{-var-list-children}, but not future calls to @code{-var-update}.
28843 For this, you must instead use @code{-var-set-update-range}. The
28844 intent of this approach is to enable a front end to implement any
28845 update approach it likes; for example, scrolling a view may cause the
28846 front end to request more children with @code{-var-list-children}, and
28847 then the front end could call @code{-var-set-update-range} with a
28848 different range to ensure that future updates are restricted to just
28851 For each child the following results are returned:
28856 Name of the variable object created for this child.
28859 The expression to be shown to the user by the front end to designate this child.
28860 For example this may be the name of a structure member.
28862 For a dynamic varobj, this value cannot be used to form an
28863 expression. There is no way to do this at all with a dynamic varobj.
28865 For C/C@t{++} structures there are several pseudo children returned to
28866 designate access qualifiers. For these pseudo children @var{exp} is
28867 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28868 type and value are not present.
28870 A dynamic varobj will not report the access qualifying
28871 pseudo-children, regardless of the language. This information is not
28872 available at all with a dynamic varobj.
28875 Number of children this child has. For a dynamic varobj, this will be
28879 The type of the child.
28882 If values were requested, this is the value.
28885 If this variable object is associated with a thread, this is the thread id.
28886 Otherwise this result is not present.
28889 If the variable object is frozen, this variable will be present with a value of 1.
28892 The result may have its own attributes:
28896 A dynamic varobj can supply a display hint to the front end. The
28897 value comes directly from the Python pretty-printer object's
28898 @code{display_hint} method. @xref{Pretty Printing API}.
28901 This is an integer attribute which is nonzero if there are children
28902 remaining after the end of the selected range.
28905 @subsubheading Example
28909 -var-list-children n
28910 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28911 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28913 -var-list-children --all-values n
28914 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28915 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28919 @subheading The @code{-var-info-type} Command
28920 @findex -var-info-type
28922 @subsubheading Synopsis
28925 -var-info-type @var{name}
28928 Returns the type of the specified variable @var{name}. The type is
28929 returned as a string in the same format as it is output by the
28933 type=@var{typename}
28937 @subheading The @code{-var-info-expression} Command
28938 @findex -var-info-expression
28940 @subsubheading Synopsis
28943 -var-info-expression @var{name}
28946 Returns a string that is suitable for presenting this
28947 variable object in user interface. The string is generally
28948 not valid expression in the current language, and cannot be evaluated.
28950 For example, if @code{a} is an array, and variable object
28951 @code{A} was created for @code{a}, then we'll get this output:
28954 (gdb) -var-info-expression A.1
28955 ^done,lang="C",exp="1"
28959 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28961 Note that the output of the @code{-var-list-children} command also
28962 includes those expressions, so the @code{-var-info-expression} command
28965 @subheading The @code{-var-info-path-expression} Command
28966 @findex -var-info-path-expression
28968 @subsubheading Synopsis
28971 -var-info-path-expression @var{name}
28974 Returns an expression that can be evaluated in the current
28975 context and will yield the same value that a variable object has.
28976 Compare this with the @code{-var-info-expression} command, which
28977 result can be used only for UI presentation. Typical use of
28978 the @code{-var-info-path-expression} command is creating a
28979 watchpoint from a variable object.
28981 This command is currently not valid for children of a dynamic varobj,
28982 and will give an error when invoked on one.
28984 For example, suppose @code{C} is a C@t{++} class, derived from class
28985 @code{Base}, and that the @code{Base} class has a member called
28986 @code{m_size}. Assume a variable @code{c} is has the type of
28987 @code{C} and a variable object @code{C} was created for variable
28988 @code{c}. Then, we'll get this output:
28990 (gdb) -var-info-path-expression C.Base.public.m_size
28991 ^done,path_expr=((Base)c).m_size)
28994 @subheading The @code{-var-show-attributes} Command
28995 @findex -var-show-attributes
28997 @subsubheading Synopsis
29000 -var-show-attributes @var{name}
29003 List attributes of the specified variable object @var{name}:
29006 status=@var{attr} [ ( ,@var{attr} )* ]
29010 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29012 @subheading The @code{-var-evaluate-expression} Command
29013 @findex -var-evaluate-expression
29015 @subsubheading Synopsis
29018 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29021 Evaluates the expression that is represented by the specified variable
29022 object and returns its value as a string. The format of the string
29023 can be specified with the @samp{-f} option. The possible values of
29024 this option are the same as for @code{-var-set-format}
29025 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29026 the current display format will be used. The current display format
29027 can be changed using the @code{-var-set-format} command.
29033 Note that one must invoke @code{-var-list-children} for a variable
29034 before the value of a child variable can be evaluated.
29036 @subheading The @code{-var-assign} Command
29037 @findex -var-assign
29039 @subsubheading Synopsis
29042 -var-assign @var{name} @var{expression}
29045 Assigns the value of @var{expression} to the variable object specified
29046 by @var{name}. The object must be @samp{editable}. If the variable's
29047 value is altered by the assign, the variable will show up in any
29048 subsequent @code{-var-update} list.
29050 @subsubheading Example
29058 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29062 @subheading The @code{-var-update} Command
29063 @findex -var-update
29065 @subsubheading Synopsis
29068 -var-update [@var{print-values}] @{@var{name} | "*"@}
29071 Reevaluate the expressions corresponding to the variable object
29072 @var{name} and all its direct and indirect children, and return the
29073 list of variable objects whose values have changed; @var{name} must
29074 be a root variable object. Here, ``changed'' means that the result of
29075 @code{-var-evaluate-expression} before and after the
29076 @code{-var-update} is different. If @samp{*} is used as the variable
29077 object names, all existing variable objects are updated, except
29078 for frozen ones (@pxref{-var-set-frozen}). The option
29079 @var{print-values} determines whether both names and values, or just
29080 names are printed. The possible values of this option are the same
29081 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29082 recommended to use the @samp{--all-values} option, to reduce the
29083 number of MI commands needed on each program stop.
29085 With the @samp{*} parameter, if a variable object is bound to a
29086 currently running thread, it will not be updated, without any
29089 If @code{-var-set-update-range} was previously used on a varobj, then
29090 only the selected range of children will be reported.
29092 @code{-var-update} reports all the changed varobjs in a tuple named
29095 Each item in the change list is itself a tuple holding:
29099 The name of the varobj.
29102 If values were requested for this update, then this field will be
29103 present and will hold the value of the varobj.
29106 @anchor{-var-update}
29107 This field is a string which may take one of three values:
29111 The variable object's current value is valid.
29114 The variable object does not currently hold a valid value but it may
29115 hold one in the future if its associated expression comes back into
29119 The variable object no longer holds a valid value.
29120 This can occur when the executable file being debugged has changed,
29121 either through recompilation or by using the @value{GDBN} @code{file}
29122 command. The front end should normally choose to delete these variable
29126 In the future new values may be added to this list so the front should
29127 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29130 This is only present if the varobj is still valid. If the type
29131 changed, then this will be the string @samp{true}; otherwise it will
29135 If the varobj's type changed, then this field will be present and will
29138 @item new_num_children
29139 For a dynamic varobj, if the number of children changed, or if the
29140 type changed, this will be the new number of children.
29142 The @samp{numchild} field in other varobj responses is generally not
29143 valid for a dynamic varobj -- it will show the number of children that
29144 @value{GDBN} knows about, but because dynamic varobjs lazily
29145 instantiate their children, this will not reflect the number of
29146 children which may be available.
29148 The @samp{new_num_children} attribute only reports changes to the
29149 number of children known by @value{GDBN}. This is the only way to
29150 detect whether an update has removed children (which necessarily can
29151 only happen at the end of the update range).
29154 The display hint, if any.
29157 This is an integer value, which will be 1 if there are more children
29158 available outside the varobj's update range.
29161 This attribute will be present and have the value @samp{1} if the
29162 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29163 then this attribute will not be present.
29166 If new children were added to a dynamic varobj within the selected
29167 update range (as set by @code{-var-set-update-range}), then they will
29168 be listed in this attribute.
29171 @subsubheading Example
29178 -var-update --all-values var1
29179 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29180 type_changed="false"@}]
29184 @subheading The @code{-var-set-frozen} Command
29185 @findex -var-set-frozen
29186 @anchor{-var-set-frozen}
29188 @subsubheading Synopsis
29191 -var-set-frozen @var{name} @var{flag}
29194 Set the frozenness flag on the variable object @var{name}. The
29195 @var{flag} parameter should be either @samp{1} to make the variable
29196 frozen or @samp{0} to make it unfrozen. If a variable object is
29197 frozen, then neither itself, nor any of its children, are
29198 implicitly updated by @code{-var-update} of
29199 a parent variable or by @code{-var-update *}. Only
29200 @code{-var-update} of the variable itself will update its value and
29201 values of its children. After a variable object is unfrozen, it is
29202 implicitly updated by all subsequent @code{-var-update} operations.
29203 Unfreezing a variable does not update it, only subsequent
29204 @code{-var-update} does.
29206 @subsubheading Example
29210 -var-set-frozen V 1
29215 @subheading The @code{-var-set-update-range} command
29216 @findex -var-set-update-range
29217 @anchor{-var-set-update-range}
29219 @subsubheading Synopsis
29222 -var-set-update-range @var{name} @var{from} @var{to}
29225 Set the range of children to be returned by future invocations of
29226 @code{-var-update}.
29228 @var{from} and @var{to} indicate the range of children to report. If
29229 @var{from} or @var{to} is less than zero, the range is reset and all
29230 children will be reported. Otherwise, children starting at @var{from}
29231 (zero-based) and up to and excluding @var{to} will be reported.
29233 @subsubheading Example
29237 -var-set-update-range V 1 2
29241 @subheading The @code{-var-set-visualizer} command
29242 @findex -var-set-visualizer
29243 @anchor{-var-set-visualizer}
29245 @subsubheading Synopsis
29248 -var-set-visualizer @var{name} @var{visualizer}
29251 Set a visualizer for the variable object @var{name}.
29253 @var{visualizer} is the visualizer to use. The special value
29254 @samp{None} means to disable any visualizer in use.
29256 If not @samp{None}, @var{visualizer} must be a Python expression.
29257 This expression must evaluate to a callable object which accepts a
29258 single argument. @value{GDBN} will call this object with the value of
29259 the varobj @var{name} as an argument (this is done so that the same
29260 Python pretty-printing code can be used for both the CLI and MI).
29261 When called, this object must return an object which conforms to the
29262 pretty-printing interface (@pxref{Pretty Printing API}).
29264 The pre-defined function @code{gdb.default_visualizer} may be used to
29265 select a visualizer by following the built-in process
29266 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29267 a varobj is created, and so ordinarily is not needed.
29269 This feature is only available if Python support is enabled. The MI
29270 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29271 can be used to check this.
29273 @subsubheading Example
29275 Resetting the visualizer:
29279 -var-set-visualizer V None
29283 Reselecting the default (type-based) visualizer:
29287 -var-set-visualizer V gdb.default_visualizer
29291 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29292 can be used to instantiate this class for a varobj:
29296 -var-set-visualizer V "lambda val: SomeClass()"
29300 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29301 @node GDB/MI Data Manipulation
29302 @section @sc{gdb/mi} Data Manipulation
29304 @cindex data manipulation, in @sc{gdb/mi}
29305 @cindex @sc{gdb/mi}, data manipulation
29306 This section describes the @sc{gdb/mi} commands that manipulate data:
29307 examine memory and registers, evaluate expressions, etc.
29309 @c REMOVED FROM THE INTERFACE.
29310 @c @subheading -data-assign
29311 @c Change the value of a program variable. Plenty of side effects.
29312 @c @subsubheading GDB Command
29314 @c @subsubheading Example
29317 @subheading The @code{-data-disassemble} Command
29318 @findex -data-disassemble
29320 @subsubheading Synopsis
29324 [ -s @var{start-addr} -e @var{end-addr} ]
29325 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29333 @item @var{start-addr}
29334 is the beginning address (or @code{$pc})
29335 @item @var{end-addr}
29337 @item @var{filename}
29338 is the name of the file to disassemble
29339 @item @var{linenum}
29340 is the line number to disassemble around
29342 is the number of disassembly lines to be produced. If it is -1,
29343 the whole function will be disassembled, in case no @var{end-addr} is
29344 specified. If @var{end-addr} is specified as a non-zero value, and
29345 @var{lines} is lower than the number of disassembly lines between
29346 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29347 displayed; if @var{lines} is higher than the number of lines between
29348 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29351 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29352 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29353 mixed source and disassembly with raw opcodes).
29356 @subsubheading Result
29358 The output for each instruction is composed of four fields:
29367 Note that whatever included in the instruction field, is not manipulated
29368 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29370 @subsubheading @value{GDBN} Command
29372 There's no direct mapping from this command to the CLI.
29374 @subsubheading Example
29376 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29380 -data-disassemble -s $pc -e "$pc + 20" -- 0
29383 @{address="0x000107c0",func-name="main",offset="4",
29384 inst="mov 2, %o0"@},
29385 @{address="0x000107c4",func-name="main",offset="8",
29386 inst="sethi %hi(0x11800), %o2"@},
29387 @{address="0x000107c8",func-name="main",offset="12",
29388 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29389 @{address="0x000107cc",func-name="main",offset="16",
29390 inst="sethi %hi(0x11800), %o2"@},
29391 @{address="0x000107d0",func-name="main",offset="20",
29392 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29396 Disassemble the whole @code{main} function. Line 32 is part of
29400 -data-disassemble -f basics.c -l 32 -- 0
29402 @{address="0x000107bc",func-name="main",offset="0",
29403 inst="save %sp, -112, %sp"@},
29404 @{address="0x000107c0",func-name="main",offset="4",
29405 inst="mov 2, %o0"@},
29406 @{address="0x000107c4",func-name="main",offset="8",
29407 inst="sethi %hi(0x11800), %o2"@},
29409 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29410 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29414 Disassemble 3 instructions from the start of @code{main}:
29418 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29420 @{address="0x000107bc",func-name="main",offset="0",
29421 inst="save %sp, -112, %sp"@},
29422 @{address="0x000107c0",func-name="main",offset="4",
29423 inst="mov 2, %o0"@},
29424 @{address="0x000107c4",func-name="main",offset="8",
29425 inst="sethi %hi(0x11800), %o2"@}]
29429 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29433 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29435 src_and_asm_line=@{line="31",
29436 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29437 testsuite/gdb.mi/basics.c",line_asm_insn=[
29438 @{address="0x000107bc",func-name="main",offset="0",
29439 inst="save %sp, -112, %sp"@}]@},
29440 src_and_asm_line=@{line="32",
29441 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29442 testsuite/gdb.mi/basics.c",line_asm_insn=[
29443 @{address="0x000107c0",func-name="main",offset="4",
29444 inst="mov 2, %o0"@},
29445 @{address="0x000107c4",func-name="main",offset="8",
29446 inst="sethi %hi(0x11800), %o2"@}]@}]
29451 @subheading The @code{-data-evaluate-expression} Command
29452 @findex -data-evaluate-expression
29454 @subsubheading Synopsis
29457 -data-evaluate-expression @var{expr}
29460 Evaluate @var{expr} as an expression. The expression could contain an
29461 inferior function call. The function call will execute synchronously.
29462 If the expression contains spaces, it must be enclosed in double quotes.
29464 @subsubheading @value{GDBN} Command
29466 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29467 @samp{call}. In @code{gdbtk} only, there's a corresponding
29468 @samp{gdb_eval} command.
29470 @subsubheading Example
29472 In the following example, the numbers that precede the commands are the
29473 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29474 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29478 211-data-evaluate-expression A
29481 311-data-evaluate-expression &A
29482 311^done,value="0xefffeb7c"
29484 411-data-evaluate-expression A+3
29487 511-data-evaluate-expression "A + 3"
29493 @subheading The @code{-data-list-changed-registers} Command
29494 @findex -data-list-changed-registers
29496 @subsubheading Synopsis
29499 -data-list-changed-registers
29502 Display a list of the registers that have changed.
29504 @subsubheading @value{GDBN} Command
29506 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29507 has the corresponding command @samp{gdb_changed_register_list}.
29509 @subsubheading Example
29511 On a PPC MBX board:
29519 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29520 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29523 -data-list-changed-registers
29524 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29525 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29526 "24","25","26","27","28","30","31","64","65","66","67","69"]
29531 @subheading The @code{-data-list-register-names} Command
29532 @findex -data-list-register-names
29534 @subsubheading Synopsis
29537 -data-list-register-names [ ( @var{regno} )+ ]
29540 Show a list of register names for the current target. If no arguments
29541 are given, it shows a list of the names of all the registers. If
29542 integer numbers are given as arguments, it will print a list of the
29543 names of the registers corresponding to the arguments. To ensure
29544 consistency between a register name and its number, the output list may
29545 include empty register names.
29547 @subsubheading @value{GDBN} Command
29549 @value{GDBN} does not have a command which corresponds to
29550 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29551 corresponding command @samp{gdb_regnames}.
29553 @subsubheading Example
29555 For the PPC MBX board:
29558 -data-list-register-names
29559 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29560 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29561 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29562 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29563 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29564 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29565 "", "pc","ps","cr","lr","ctr","xer"]
29567 -data-list-register-names 1 2 3
29568 ^done,register-names=["r1","r2","r3"]
29572 @subheading The @code{-data-list-register-values} Command
29573 @findex -data-list-register-values
29575 @subsubheading Synopsis
29578 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29581 Display the registers' contents. @var{fmt} is the format according to
29582 which the registers' contents are to be returned, followed by an optional
29583 list of numbers specifying the registers to display. A missing list of
29584 numbers indicates that the contents of all the registers must be returned.
29586 Allowed formats for @var{fmt} are:
29603 @subsubheading @value{GDBN} Command
29605 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29606 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29608 @subsubheading Example
29610 For a PPC MBX board (note: line breaks are for readability only, they
29611 don't appear in the actual output):
29615 -data-list-register-values r 64 65
29616 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29617 @{number="65",value="0x00029002"@}]
29619 -data-list-register-values x
29620 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29621 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29622 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29623 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29624 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29625 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29626 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29627 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29628 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29629 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29630 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29631 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29632 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29633 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29634 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29635 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29636 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29637 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29638 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29639 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29640 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29641 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29642 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29643 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29644 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29645 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29646 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29647 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29648 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29649 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29650 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29651 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29652 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29653 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29654 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29655 @{number="69",value="0x20002b03"@}]
29660 @subheading The @code{-data-read-memory} Command
29661 @findex -data-read-memory
29663 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29665 @subsubheading Synopsis
29668 -data-read-memory [ -o @var{byte-offset} ]
29669 @var{address} @var{word-format} @var{word-size}
29670 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29677 @item @var{address}
29678 An expression specifying the address of the first memory word to be
29679 read. Complex expressions containing embedded white space should be
29680 quoted using the C convention.
29682 @item @var{word-format}
29683 The format to be used to print the memory words. The notation is the
29684 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29687 @item @var{word-size}
29688 The size of each memory word in bytes.
29690 @item @var{nr-rows}
29691 The number of rows in the output table.
29693 @item @var{nr-cols}
29694 The number of columns in the output table.
29697 If present, indicates that each row should include an @sc{ascii} dump. The
29698 value of @var{aschar} is used as a padding character when a byte is not a
29699 member of the printable @sc{ascii} character set (printable @sc{ascii}
29700 characters are those whose code is between 32 and 126, inclusively).
29702 @item @var{byte-offset}
29703 An offset to add to the @var{address} before fetching memory.
29706 This command displays memory contents as a table of @var{nr-rows} by
29707 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29708 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29709 (returned as @samp{total-bytes}). Should less than the requested number
29710 of bytes be returned by the target, the missing words are identified
29711 using @samp{N/A}. The number of bytes read from the target is returned
29712 in @samp{nr-bytes} and the starting address used to read memory in
29715 The address of the next/previous row or page is available in
29716 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29719 @subsubheading @value{GDBN} Command
29721 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29722 @samp{gdb_get_mem} memory read command.
29724 @subsubheading Example
29726 Read six bytes of memory starting at @code{bytes+6} but then offset by
29727 @code{-6} bytes. Format as three rows of two columns. One byte per
29728 word. Display each word in hex.
29732 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29733 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29734 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29735 prev-page="0x0000138a",memory=[
29736 @{addr="0x00001390",data=["0x00","0x01"]@},
29737 @{addr="0x00001392",data=["0x02","0x03"]@},
29738 @{addr="0x00001394",data=["0x04","0x05"]@}]
29742 Read two bytes of memory starting at address @code{shorts + 64} and
29743 display as a single word formatted in decimal.
29747 5-data-read-memory shorts+64 d 2 1 1
29748 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29749 next-row="0x00001512",prev-row="0x0000150e",
29750 next-page="0x00001512",prev-page="0x0000150e",memory=[
29751 @{addr="0x00001510",data=["128"]@}]
29755 Read thirty two bytes of memory starting at @code{bytes+16} and format
29756 as eight rows of four columns. Include a string encoding with @samp{x}
29757 used as the non-printable character.
29761 4-data-read-memory bytes+16 x 1 8 4 x
29762 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29763 next-row="0x000013c0",prev-row="0x0000139c",
29764 next-page="0x000013c0",prev-page="0x00001380",memory=[
29765 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29766 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29767 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29768 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29769 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29770 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29771 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29772 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29776 @subheading The @code{-data-read-memory-bytes} Command
29777 @findex -data-read-memory-bytes
29779 @subsubheading Synopsis
29782 -data-read-memory-bytes [ -o @var{byte-offset} ]
29783 @var{address} @var{count}
29790 @item @var{address}
29791 An expression specifying the address of the first memory word to be
29792 read. Complex expressions containing embedded white space should be
29793 quoted using the C convention.
29796 The number of bytes to read. This should be an integer literal.
29798 @item @var{byte-offset}
29799 The offsets in bytes relative to @var{address} at which to start
29800 reading. This should be an integer literal. This option is provided
29801 so that a frontend is not required to first evaluate address and then
29802 perform address arithmetics itself.
29806 This command attempts to read all accessible memory regions in the
29807 specified range. First, all regions marked as unreadable in the memory
29808 map (if one is defined) will be skipped. @xref{Memory Region
29809 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29810 regions. For each one, if reading full region results in an errors,
29811 @value{GDBN} will try to read a subset of the region.
29813 In general, every single byte in the region may be readable or not,
29814 and the only way to read every readable byte is to try a read at
29815 every address, which is not practical. Therefore, @value{GDBN} will
29816 attempt to read all accessible bytes at either beginning or the end
29817 of the region, using a binary division scheme. This heuristic works
29818 well for reading accross a memory map boundary. Note that if a region
29819 has a readable range that is neither at the beginning or the end,
29820 @value{GDBN} will not read it.
29822 The result record (@pxref{GDB/MI Result Records}) that is output of
29823 the command includes a field named @samp{memory} whose content is a
29824 list of tuples. Each tuple represent a successfully read memory block
29825 and has the following fields:
29829 The start address of the memory block, as hexadecimal literal.
29832 The end address of the memory block, as hexadecimal literal.
29835 The offset of the memory block, as hexadecimal literal, relative to
29836 the start address passed to @code{-data-read-memory-bytes}.
29839 The contents of the memory block, in hex.
29845 @subsubheading @value{GDBN} Command
29847 The corresponding @value{GDBN} command is @samp{x}.
29849 @subsubheading Example
29853 -data-read-memory-bytes &a 10
29854 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29856 contents="01000000020000000300"@}]
29861 @subheading The @code{-data-write-memory-bytes} Command
29862 @findex -data-write-memory-bytes
29864 @subsubheading Synopsis
29867 -data-write-memory-bytes @var{address} @var{contents}
29874 @item @var{address}
29875 An expression specifying the address of the first memory word to be
29876 read. Complex expressions containing embedded white space should be
29877 quoted using the C convention.
29879 @item @var{contents}
29880 The hex-encoded bytes to write.
29884 @subsubheading @value{GDBN} Command
29886 There's no corresponding @value{GDBN} command.
29888 @subsubheading Example
29892 -data-write-memory-bytes &a "aabbccdd"
29898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29899 @node GDB/MI Tracepoint Commands
29900 @section @sc{gdb/mi} Tracepoint Commands
29902 The commands defined in this section implement MI support for
29903 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29905 @subheading The @code{-trace-find} Command
29906 @findex -trace-find
29908 @subsubheading Synopsis
29911 -trace-find @var{mode} [@var{parameters}@dots{}]
29914 Find a trace frame using criteria defined by @var{mode} and
29915 @var{parameters}. The following table lists permissible
29916 modes and their parameters. For details of operation, see @ref{tfind}.
29921 No parameters are required. Stops examining trace frames.
29924 An integer is required as parameter. Selects tracepoint frame with
29927 @item tracepoint-number
29928 An integer is required as parameter. Finds next
29929 trace frame that corresponds to tracepoint with the specified number.
29932 An address is required as parameter. Finds
29933 next trace frame that corresponds to any tracepoint at the specified
29936 @item pc-inside-range
29937 Two addresses are required as parameters. Finds next trace
29938 frame that corresponds to a tracepoint at an address inside the
29939 specified range. Both bounds are considered to be inside the range.
29941 @item pc-outside-range
29942 Two addresses are required as parameters. Finds
29943 next trace frame that corresponds to a tracepoint at an address outside
29944 the specified range. Both bounds are considered to be inside the range.
29947 Line specification is required as parameter. @xref{Specify Location}.
29948 Finds next trace frame that corresponds to a tracepoint at
29949 the specified location.
29953 If @samp{none} was passed as @var{mode}, the response does not
29954 have fields. Otherwise, the response may have the following fields:
29958 This field has either @samp{0} or @samp{1} as the value, depending
29959 on whether a matching tracepoint was found.
29962 The index of the found traceframe. This field is present iff
29963 the @samp{found} field has value of @samp{1}.
29966 The index of the found tracepoint. This field is present iff
29967 the @samp{found} field has value of @samp{1}.
29970 The information about the frame corresponding to the found trace
29971 frame. This field is present only if a trace frame was found.
29972 @xref{GDB/MI Frame Information}, for description of this field.
29976 @subsubheading @value{GDBN} Command
29978 The corresponding @value{GDBN} command is @samp{tfind}.
29980 @subheading -trace-define-variable
29981 @findex -trace-define-variable
29983 @subsubheading Synopsis
29986 -trace-define-variable @var{name} [ @var{value} ]
29989 Create trace variable @var{name} if it does not exist. If
29990 @var{value} is specified, sets the initial value of the specified
29991 trace variable to that value. Note that the @var{name} should start
29992 with the @samp{$} character.
29994 @subsubheading @value{GDBN} Command
29996 The corresponding @value{GDBN} command is @samp{tvariable}.
29998 @subheading -trace-list-variables
29999 @findex -trace-list-variables
30001 @subsubheading Synopsis
30004 -trace-list-variables
30007 Return a table of all defined trace variables. Each element of the
30008 table has the following fields:
30012 The name of the trace variable. This field is always present.
30015 The initial value. This is a 64-bit signed integer. This
30016 field is always present.
30019 The value the trace variable has at the moment. This is a 64-bit
30020 signed integer. This field is absent iff current value is
30021 not defined, for example if the trace was never run, or is
30026 @subsubheading @value{GDBN} Command
30028 The corresponding @value{GDBN} command is @samp{tvariables}.
30030 @subsubheading Example
30034 -trace-list-variables
30035 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30036 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30037 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30038 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30039 body=[variable=@{name="$trace_timestamp",initial="0"@}
30040 variable=@{name="$foo",initial="10",current="15"@}]@}
30044 @subheading -trace-save
30045 @findex -trace-save
30047 @subsubheading Synopsis
30050 -trace-save [-r ] @var{filename}
30053 Saves the collected trace data to @var{filename}. Without the
30054 @samp{-r} option, the data is downloaded from the target and saved
30055 in a local file. With the @samp{-r} option the target is asked
30056 to perform the save.
30058 @subsubheading @value{GDBN} Command
30060 The corresponding @value{GDBN} command is @samp{tsave}.
30063 @subheading -trace-start
30064 @findex -trace-start
30066 @subsubheading Synopsis
30072 Starts a tracing experiments. The result of this command does not
30075 @subsubheading @value{GDBN} Command
30077 The corresponding @value{GDBN} command is @samp{tstart}.
30079 @subheading -trace-status
30080 @findex -trace-status
30082 @subsubheading Synopsis
30088 Obtains the status of a tracing experiment. The result may include
30089 the following fields:
30094 May have a value of either @samp{0}, when no tracing operations are
30095 supported, @samp{1}, when all tracing operations are supported, or
30096 @samp{file} when examining trace file. In the latter case, examining
30097 of trace frame is possible but new tracing experiement cannot be
30098 started. This field is always present.
30101 May have a value of either @samp{0} or @samp{1} depending on whether
30102 tracing experiement is in progress on target. This field is present
30103 if @samp{supported} field is not @samp{0}.
30106 Report the reason why the tracing was stopped last time. This field
30107 may be absent iff tracing was never stopped on target yet. The
30108 value of @samp{request} means the tracing was stopped as result of
30109 the @code{-trace-stop} command. The value of @samp{overflow} means
30110 the tracing buffer is full. The value of @samp{disconnection} means
30111 tracing was automatically stopped when @value{GDBN} has disconnected.
30112 The value of @samp{passcount} means tracing was stopped when a
30113 tracepoint was passed a maximal number of times for that tracepoint.
30114 This field is present if @samp{supported} field is not @samp{0}.
30116 @item stopping-tracepoint
30117 The number of tracepoint whose passcount as exceeded. This field is
30118 present iff the @samp{stop-reason} field has the value of
30122 @itemx frames-created
30123 The @samp{frames} field is a count of the total number of trace frames
30124 in the trace buffer, while @samp{frames-created} is the total created
30125 during the run, including ones that were discarded, such as when a
30126 circular trace buffer filled up. Both fields are optional.
30130 These fields tell the current size of the tracing buffer and the
30131 remaining space. These fields are optional.
30134 The value of the circular trace buffer flag. @code{1} means that the
30135 trace buffer is circular and old trace frames will be discarded if
30136 necessary to make room, @code{0} means that the trace buffer is linear
30140 The value of the disconnected tracing flag. @code{1} means that
30141 tracing will continue after @value{GDBN} disconnects, @code{0} means
30142 that the trace run will stop.
30146 @subsubheading @value{GDBN} Command
30148 The corresponding @value{GDBN} command is @samp{tstatus}.
30150 @subheading -trace-stop
30151 @findex -trace-stop
30153 @subsubheading Synopsis
30159 Stops a tracing experiment. The result of this command has the same
30160 fields as @code{-trace-status}, except that the @samp{supported} and
30161 @samp{running} fields are not output.
30163 @subsubheading @value{GDBN} Command
30165 The corresponding @value{GDBN} command is @samp{tstop}.
30168 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30169 @node GDB/MI Symbol Query
30170 @section @sc{gdb/mi} Symbol Query Commands
30174 @subheading The @code{-symbol-info-address} Command
30175 @findex -symbol-info-address
30177 @subsubheading Synopsis
30180 -symbol-info-address @var{symbol}
30183 Describe where @var{symbol} is stored.
30185 @subsubheading @value{GDBN} Command
30187 The corresponding @value{GDBN} command is @samp{info address}.
30189 @subsubheading Example
30193 @subheading The @code{-symbol-info-file} Command
30194 @findex -symbol-info-file
30196 @subsubheading Synopsis
30202 Show the file for the symbol.
30204 @subsubheading @value{GDBN} Command
30206 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30207 @samp{gdb_find_file}.
30209 @subsubheading Example
30213 @subheading The @code{-symbol-info-function} Command
30214 @findex -symbol-info-function
30216 @subsubheading Synopsis
30219 -symbol-info-function
30222 Show which function the symbol lives in.
30224 @subsubheading @value{GDBN} Command
30226 @samp{gdb_get_function} in @code{gdbtk}.
30228 @subsubheading Example
30232 @subheading The @code{-symbol-info-line} Command
30233 @findex -symbol-info-line
30235 @subsubheading Synopsis
30241 Show the core addresses of the code for a source line.
30243 @subsubheading @value{GDBN} Command
30245 The corresponding @value{GDBN} command is @samp{info line}.
30246 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30248 @subsubheading Example
30252 @subheading The @code{-symbol-info-symbol} Command
30253 @findex -symbol-info-symbol
30255 @subsubheading Synopsis
30258 -symbol-info-symbol @var{addr}
30261 Describe what symbol is at location @var{addr}.
30263 @subsubheading @value{GDBN} Command
30265 The corresponding @value{GDBN} command is @samp{info symbol}.
30267 @subsubheading Example
30271 @subheading The @code{-symbol-list-functions} Command
30272 @findex -symbol-list-functions
30274 @subsubheading Synopsis
30277 -symbol-list-functions
30280 List the functions in the executable.
30282 @subsubheading @value{GDBN} Command
30284 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30285 @samp{gdb_search} in @code{gdbtk}.
30287 @subsubheading Example
30292 @subheading The @code{-symbol-list-lines} Command
30293 @findex -symbol-list-lines
30295 @subsubheading Synopsis
30298 -symbol-list-lines @var{filename}
30301 Print the list of lines that contain code and their associated program
30302 addresses for the given source filename. The entries are sorted in
30303 ascending PC order.
30305 @subsubheading @value{GDBN} Command
30307 There is no corresponding @value{GDBN} command.
30309 @subsubheading Example
30312 -symbol-list-lines basics.c
30313 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30319 @subheading The @code{-symbol-list-types} Command
30320 @findex -symbol-list-types
30322 @subsubheading Synopsis
30328 List all the type names.
30330 @subsubheading @value{GDBN} Command
30332 The corresponding commands are @samp{info types} in @value{GDBN},
30333 @samp{gdb_search} in @code{gdbtk}.
30335 @subsubheading Example
30339 @subheading The @code{-symbol-list-variables} Command
30340 @findex -symbol-list-variables
30342 @subsubheading Synopsis
30345 -symbol-list-variables
30348 List all the global and static variable names.
30350 @subsubheading @value{GDBN} Command
30352 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30354 @subsubheading Example
30358 @subheading The @code{-symbol-locate} Command
30359 @findex -symbol-locate
30361 @subsubheading Synopsis
30367 @subsubheading @value{GDBN} Command
30369 @samp{gdb_loc} in @code{gdbtk}.
30371 @subsubheading Example
30375 @subheading The @code{-symbol-type} Command
30376 @findex -symbol-type
30378 @subsubheading Synopsis
30381 -symbol-type @var{variable}
30384 Show type of @var{variable}.
30386 @subsubheading @value{GDBN} Command
30388 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30389 @samp{gdb_obj_variable}.
30391 @subsubheading Example
30396 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30397 @node GDB/MI File Commands
30398 @section @sc{gdb/mi} File Commands
30400 This section describes the GDB/MI commands to specify executable file names
30401 and to read in and obtain symbol table information.
30403 @subheading The @code{-file-exec-and-symbols} Command
30404 @findex -file-exec-and-symbols
30406 @subsubheading Synopsis
30409 -file-exec-and-symbols @var{file}
30412 Specify the executable file to be debugged. This file is the one from
30413 which the symbol table is also read. If no file is specified, the
30414 command clears the executable and symbol information. If breakpoints
30415 are set when using this command with no arguments, @value{GDBN} will produce
30416 error messages. Otherwise, no output is produced, except a completion
30419 @subsubheading @value{GDBN} Command
30421 The corresponding @value{GDBN} command is @samp{file}.
30423 @subsubheading Example
30427 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30433 @subheading The @code{-file-exec-file} Command
30434 @findex -file-exec-file
30436 @subsubheading Synopsis
30439 -file-exec-file @var{file}
30442 Specify the executable file to be debugged. Unlike
30443 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30444 from this file. If used without argument, @value{GDBN} clears the information
30445 about the executable file. No output is produced, except a completion
30448 @subsubheading @value{GDBN} Command
30450 The corresponding @value{GDBN} command is @samp{exec-file}.
30452 @subsubheading Example
30456 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30463 @subheading The @code{-file-list-exec-sections} Command
30464 @findex -file-list-exec-sections
30466 @subsubheading Synopsis
30469 -file-list-exec-sections
30472 List the sections of the current executable file.
30474 @subsubheading @value{GDBN} Command
30476 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30477 information as this command. @code{gdbtk} has a corresponding command
30478 @samp{gdb_load_info}.
30480 @subsubheading Example
30485 @subheading The @code{-file-list-exec-source-file} Command
30486 @findex -file-list-exec-source-file
30488 @subsubheading Synopsis
30491 -file-list-exec-source-file
30494 List the line number, the current source file, and the absolute path
30495 to the current source file for the current executable. The macro
30496 information field has a value of @samp{1} or @samp{0} depending on
30497 whether or not the file includes preprocessor macro information.
30499 @subsubheading @value{GDBN} Command
30501 The @value{GDBN} equivalent is @samp{info source}
30503 @subsubheading Example
30507 123-file-list-exec-source-file
30508 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30513 @subheading The @code{-file-list-exec-source-files} Command
30514 @findex -file-list-exec-source-files
30516 @subsubheading Synopsis
30519 -file-list-exec-source-files
30522 List the source files for the current executable.
30524 It will always output the filename, but only when @value{GDBN} can find
30525 the absolute file name of a source file, will it output the fullname.
30527 @subsubheading @value{GDBN} Command
30529 The @value{GDBN} equivalent is @samp{info sources}.
30530 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30532 @subsubheading Example
30535 -file-list-exec-source-files
30537 @{file=foo.c,fullname=/home/foo.c@},
30538 @{file=/home/bar.c,fullname=/home/bar.c@},
30539 @{file=gdb_could_not_find_fullpath.c@}]
30544 @subheading The @code{-file-list-shared-libraries} Command
30545 @findex -file-list-shared-libraries
30547 @subsubheading Synopsis
30550 -file-list-shared-libraries
30553 List the shared libraries in the program.
30555 @subsubheading @value{GDBN} Command
30557 The corresponding @value{GDBN} command is @samp{info shared}.
30559 @subsubheading Example
30563 @subheading The @code{-file-list-symbol-files} Command
30564 @findex -file-list-symbol-files
30566 @subsubheading Synopsis
30569 -file-list-symbol-files
30574 @subsubheading @value{GDBN} Command
30576 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30578 @subsubheading Example
30583 @subheading The @code{-file-symbol-file} Command
30584 @findex -file-symbol-file
30586 @subsubheading Synopsis
30589 -file-symbol-file @var{file}
30592 Read symbol table info from the specified @var{file} argument. When
30593 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30594 produced, except for a completion notification.
30596 @subsubheading @value{GDBN} Command
30598 The corresponding @value{GDBN} command is @samp{symbol-file}.
30600 @subsubheading Example
30604 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30610 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30611 @node GDB/MI Memory Overlay Commands
30612 @section @sc{gdb/mi} Memory Overlay Commands
30614 The memory overlay commands are not implemented.
30616 @c @subheading -overlay-auto
30618 @c @subheading -overlay-list-mapping-state
30620 @c @subheading -overlay-list-overlays
30622 @c @subheading -overlay-map
30624 @c @subheading -overlay-off
30626 @c @subheading -overlay-on
30628 @c @subheading -overlay-unmap
30630 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30631 @node GDB/MI Signal Handling Commands
30632 @section @sc{gdb/mi} Signal Handling Commands
30634 Signal handling commands are not implemented.
30636 @c @subheading -signal-handle
30638 @c @subheading -signal-list-handle-actions
30640 @c @subheading -signal-list-signal-types
30644 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30645 @node GDB/MI Target Manipulation
30646 @section @sc{gdb/mi} Target Manipulation Commands
30649 @subheading The @code{-target-attach} Command
30650 @findex -target-attach
30652 @subsubheading Synopsis
30655 -target-attach @var{pid} | @var{gid} | @var{file}
30658 Attach to a process @var{pid} or a file @var{file} outside of
30659 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30660 group, the id previously returned by
30661 @samp{-list-thread-groups --available} must be used.
30663 @subsubheading @value{GDBN} Command
30665 The corresponding @value{GDBN} command is @samp{attach}.
30667 @subsubheading Example
30671 =thread-created,id="1"
30672 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30678 @subheading The @code{-target-compare-sections} Command
30679 @findex -target-compare-sections
30681 @subsubheading Synopsis
30684 -target-compare-sections [ @var{section} ]
30687 Compare data of section @var{section} on target to the exec file.
30688 Without the argument, all sections are compared.
30690 @subsubheading @value{GDBN} Command
30692 The @value{GDBN} equivalent is @samp{compare-sections}.
30694 @subsubheading Example
30699 @subheading The @code{-target-detach} Command
30700 @findex -target-detach
30702 @subsubheading Synopsis
30705 -target-detach [ @var{pid} | @var{gid} ]
30708 Detach from the remote target which normally resumes its execution.
30709 If either @var{pid} or @var{gid} is specified, detaches from either
30710 the specified process, or specified thread group. There's no output.
30712 @subsubheading @value{GDBN} Command
30714 The corresponding @value{GDBN} command is @samp{detach}.
30716 @subsubheading Example
30726 @subheading The @code{-target-disconnect} Command
30727 @findex -target-disconnect
30729 @subsubheading Synopsis
30735 Disconnect from the remote target. There's no output and the target is
30736 generally not resumed.
30738 @subsubheading @value{GDBN} Command
30740 The corresponding @value{GDBN} command is @samp{disconnect}.
30742 @subsubheading Example
30752 @subheading The @code{-target-download} Command
30753 @findex -target-download
30755 @subsubheading Synopsis
30761 Loads the executable onto the remote target.
30762 It prints out an update message every half second, which includes the fields:
30766 The name of the section.
30768 The size of what has been sent so far for that section.
30770 The size of the section.
30772 The total size of what was sent so far (the current and the previous sections).
30774 The size of the overall executable to download.
30778 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30779 @sc{gdb/mi} Output Syntax}).
30781 In addition, it prints the name and size of the sections, as they are
30782 downloaded. These messages include the following fields:
30786 The name of the section.
30788 The size of the section.
30790 The size of the overall executable to download.
30794 At the end, a summary is printed.
30796 @subsubheading @value{GDBN} Command
30798 The corresponding @value{GDBN} command is @samp{load}.
30800 @subsubheading Example
30802 Note: each status message appears on a single line. Here the messages
30803 have been broken down so that they can fit onto a page.
30808 +download,@{section=".text",section-size="6668",total-size="9880"@}
30809 +download,@{section=".text",section-sent="512",section-size="6668",
30810 total-sent="512",total-size="9880"@}
30811 +download,@{section=".text",section-sent="1024",section-size="6668",
30812 total-sent="1024",total-size="9880"@}
30813 +download,@{section=".text",section-sent="1536",section-size="6668",
30814 total-sent="1536",total-size="9880"@}
30815 +download,@{section=".text",section-sent="2048",section-size="6668",
30816 total-sent="2048",total-size="9880"@}
30817 +download,@{section=".text",section-sent="2560",section-size="6668",
30818 total-sent="2560",total-size="9880"@}
30819 +download,@{section=".text",section-sent="3072",section-size="6668",
30820 total-sent="3072",total-size="9880"@}
30821 +download,@{section=".text",section-sent="3584",section-size="6668",
30822 total-sent="3584",total-size="9880"@}
30823 +download,@{section=".text",section-sent="4096",section-size="6668",
30824 total-sent="4096",total-size="9880"@}
30825 +download,@{section=".text",section-sent="4608",section-size="6668",
30826 total-sent="4608",total-size="9880"@}
30827 +download,@{section=".text",section-sent="5120",section-size="6668",
30828 total-sent="5120",total-size="9880"@}
30829 +download,@{section=".text",section-sent="5632",section-size="6668",
30830 total-sent="5632",total-size="9880"@}
30831 +download,@{section=".text",section-sent="6144",section-size="6668",
30832 total-sent="6144",total-size="9880"@}
30833 +download,@{section=".text",section-sent="6656",section-size="6668",
30834 total-sent="6656",total-size="9880"@}
30835 +download,@{section=".init",section-size="28",total-size="9880"@}
30836 +download,@{section=".fini",section-size="28",total-size="9880"@}
30837 +download,@{section=".data",section-size="3156",total-size="9880"@}
30838 +download,@{section=".data",section-sent="512",section-size="3156",
30839 total-sent="7236",total-size="9880"@}
30840 +download,@{section=".data",section-sent="1024",section-size="3156",
30841 total-sent="7748",total-size="9880"@}
30842 +download,@{section=".data",section-sent="1536",section-size="3156",
30843 total-sent="8260",total-size="9880"@}
30844 +download,@{section=".data",section-sent="2048",section-size="3156",
30845 total-sent="8772",total-size="9880"@}
30846 +download,@{section=".data",section-sent="2560",section-size="3156",
30847 total-sent="9284",total-size="9880"@}
30848 +download,@{section=".data",section-sent="3072",section-size="3156",
30849 total-sent="9796",total-size="9880"@}
30850 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30857 @subheading The @code{-target-exec-status} Command
30858 @findex -target-exec-status
30860 @subsubheading Synopsis
30863 -target-exec-status
30866 Provide information on the state of the target (whether it is running or
30867 not, for instance).
30869 @subsubheading @value{GDBN} Command
30871 There's no equivalent @value{GDBN} command.
30873 @subsubheading Example
30877 @subheading The @code{-target-list-available-targets} Command
30878 @findex -target-list-available-targets
30880 @subsubheading Synopsis
30883 -target-list-available-targets
30886 List the possible targets to connect to.
30888 @subsubheading @value{GDBN} Command
30890 The corresponding @value{GDBN} command is @samp{help target}.
30892 @subsubheading Example
30896 @subheading The @code{-target-list-current-targets} Command
30897 @findex -target-list-current-targets
30899 @subsubheading Synopsis
30902 -target-list-current-targets
30905 Describe the current target.
30907 @subsubheading @value{GDBN} Command
30909 The corresponding information is printed by @samp{info file} (among
30912 @subsubheading Example
30916 @subheading The @code{-target-list-parameters} Command
30917 @findex -target-list-parameters
30919 @subsubheading Synopsis
30922 -target-list-parameters
30928 @subsubheading @value{GDBN} Command
30932 @subsubheading Example
30936 @subheading The @code{-target-select} Command
30937 @findex -target-select
30939 @subsubheading Synopsis
30942 -target-select @var{type} @var{parameters @dots{}}
30945 Connect @value{GDBN} to the remote target. This command takes two args:
30949 The type of target, for instance @samp{remote}, etc.
30950 @item @var{parameters}
30951 Device names, host names and the like. @xref{Target Commands, ,
30952 Commands for Managing Targets}, for more details.
30955 The output is a connection notification, followed by the address at
30956 which the target program is, in the following form:
30959 ^connected,addr="@var{address}",func="@var{function name}",
30960 args=[@var{arg list}]
30963 @subsubheading @value{GDBN} Command
30965 The corresponding @value{GDBN} command is @samp{target}.
30967 @subsubheading Example
30971 -target-select remote /dev/ttya
30972 ^connected,addr="0xfe00a300",func="??",args=[]
30976 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30977 @node GDB/MI File Transfer Commands
30978 @section @sc{gdb/mi} File Transfer Commands
30981 @subheading The @code{-target-file-put} Command
30982 @findex -target-file-put
30984 @subsubheading Synopsis
30987 -target-file-put @var{hostfile} @var{targetfile}
30990 Copy file @var{hostfile} from the host system (the machine running
30991 @value{GDBN}) to @var{targetfile} on the target system.
30993 @subsubheading @value{GDBN} Command
30995 The corresponding @value{GDBN} command is @samp{remote put}.
30997 @subsubheading Example
31001 -target-file-put localfile remotefile
31007 @subheading The @code{-target-file-get} Command
31008 @findex -target-file-get
31010 @subsubheading Synopsis
31013 -target-file-get @var{targetfile} @var{hostfile}
31016 Copy file @var{targetfile} from the target system to @var{hostfile}
31017 on the host system.
31019 @subsubheading @value{GDBN} Command
31021 The corresponding @value{GDBN} command is @samp{remote get}.
31023 @subsubheading Example
31027 -target-file-get remotefile localfile
31033 @subheading The @code{-target-file-delete} Command
31034 @findex -target-file-delete
31036 @subsubheading Synopsis
31039 -target-file-delete @var{targetfile}
31042 Delete @var{targetfile} from the target system.
31044 @subsubheading @value{GDBN} Command
31046 The corresponding @value{GDBN} command is @samp{remote delete}.
31048 @subsubheading Example
31052 -target-file-delete remotefile
31058 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31059 @node GDB/MI Miscellaneous Commands
31060 @section Miscellaneous @sc{gdb/mi} Commands
31062 @c @subheading -gdb-complete
31064 @subheading The @code{-gdb-exit} Command
31067 @subsubheading Synopsis
31073 Exit @value{GDBN} immediately.
31075 @subsubheading @value{GDBN} Command
31077 Approximately corresponds to @samp{quit}.
31079 @subsubheading Example
31089 @subheading The @code{-exec-abort} Command
31090 @findex -exec-abort
31092 @subsubheading Synopsis
31098 Kill the inferior running program.
31100 @subsubheading @value{GDBN} Command
31102 The corresponding @value{GDBN} command is @samp{kill}.
31104 @subsubheading Example
31109 @subheading The @code{-gdb-set} Command
31112 @subsubheading Synopsis
31118 Set an internal @value{GDBN} variable.
31119 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31121 @subsubheading @value{GDBN} Command
31123 The corresponding @value{GDBN} command is @samp{set}.
31125 @subsubheading Example
31135 @subheading The @code{-gdb-show} Command
31138 @subsubheading Synopsis
31144 Show the current value of a @value{GDBN} variable.
31146 @subsubheading @value{GDBN} Command
31148 The corresponding @value{GDBN} command is @samp{show}.
31150 @subsubheading Example
31159 @c @subheading -gdb-source
31162 @subheading The @code{-gdb-version} Command
31163 @findex -gdb-version
31165 @subsubheading Synopsis
31171 Show version information for @value{GDBN}. Used mostly in testing.
31173 @subsubheading @value{GDBN} Command
31175 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31176 default shows this information when you start an interactive session.
31178 @subsubheading Example
31180 @c This example modifies the actual output from GDB to avoid overfull
31186 ~Copyright 2000 Free Software Foundation, Inc.
31187 ~GDB is free software, covered by the GNU General Public License, and
31188 ~you are welcome to change it and/or distribute copies of it under
31189 ~ certain conditions.
31190 ~Type "show copying" to see the conditions.
31191 ~There is absolutely no warranty for GDB. Type "show warranty" for
31193 ~This GDB was configured as
31194 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31199 @subheading The @code{-list-features} Command
31200 @findex -list-features
31202 Returns a list of particular features of the MI protocol that
31203 this version of gdb implements. A feature can be a command,
31204 or a new field in an output of some command, or even an
31205 important bugfix. While a frontend can sometimes detect presence
31206 of a feature at runtime, it is easier to perform detection at debugger
31209 The command returns a list of strings, with each string naming an
31210 available feature. Each returned string is just a name, it does not
31211 have any internal structure. The list of possible feature names
31217 (gdb) -list-features
31218 ^done,result=["feature1","feature2"]
31221 The current list of features is:
31224 @item frozen-varobjs
31225 Indicates support for the @code{-var-set-frozen} command, as well
31226 as possible presense of the @code{frozen} field in the output
31227 of @code{-varobj-create}.
31228 @item pending-breakpoints
31229 Indicates support for the @option{-f} option to the @code{-break-insert}
31232 Indicates Python scripting support, Python-based
31233 pretty-printing commands, and possible presence of the
31234 @samp{display_hint} field in the output of @code{-var-list-children}
31236 Indicates support for the @code{-thread-info} command.
31237 @item data-read-memory-bytes
31238 Indicates support for the @code{-data-read-memory-bytes} and the
31239 @code{-data-write-memory-bytes} commands.
31240 @item breakpoint-notifications
31241 Indicates that changes to breakpoints and breakpoints created via the
31242 CLI will be announced via async records.
31243 @item ada-task-info
31244 Indicates support for the @code{-ada-task-info} command.
31247 @subheading The @code{-list-target-features} Command
31248 @findex -list-target-features
31250 Returns a list of particular features that are supported by the
31251 target. Those features affect the permitted MI commands, but
31252 unlike the features reported by the @code{-list-features} command, the
31253 features depend on which target GDB is using at the moment. Whenever
31254 a target can change, due to commands such as @code{-target-select},
31255 @code{-target-attach} or @code{-exec-run}, the list of target features
31256 may change, and the frontend should obtain it again.
31260 (gdb) -list-features
31261 ^done,result=["async"]
31264 The current list of features is:
31268 Indicates that the target is capable of asynchronous command
31269 execution, which means that @value{GDBN} will accept further commands
31270 while the target is running.
31273 Indicates that the target is capable of reverse execution.
31274 @xref{Reverse Execution}, for more information.
31278 @subheading The @code{-list-thread-groups} Command
31279 @findex -list-thread-groups
31281 @subheading Synopsis
31284 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31287 Lists thread groups (@pxref{Thread groups}). When a single thread
31288 group is passed as the argument, lists the children of that group.
31289 When several thread group are passed, lists information about those
31290 thread groups. Without any parameters, lists information about all
31291 top-level thread groups.
31293 Normally, thread groups that are being debugged are reported.
31294 With the @samp{--available} option, @value{GDBN} reports thread groups
31295 available on the target.
31297 The output of this command may have either a @samp{threads} result or
31298 a @samp{groups} result. The @samp{thread} result has a list of tuples
31299 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31300 Information}). The @samp{groups} result has a list of tuples as value,
31301 each tuple describing a thread group. If top-level groups are
31302 requested (that is, no parameter is passed), or when several groups
31303 are passed, the output always has a @samp{groups} result. The format
31304 of the @samp{group} result is described below.
31306 To reduce the number of roundtrips it's possible to list thread groups
31307 together with their children, by passing the @samp{--recurse} option
31308 and the recursion depth. Presently, only recursion depth of 1 is
31309 permitted. If this option is present, then every reported thread group
31310 will also include its children, either as @samp{group} or
31311 @samp{threads} field.
31313 In general, any combination of option and parameters is permitted, with
31314 the following caveats:
31318 When a single thread group is passed, the output will typically
31319 be the @samp{threads} result. Because threads may not contain
31320 anything, the @samp{recurse} option will be ignored.
31323 When the @samp{--available} option is passed, limited information may
31324 be available. In particular, the list of threads of a process might
31325 be inaccessible. Further, specifying specific thread groups might
31326 not give any performance advantage over listing all thread groups.
31327 The frontend should assume that @samp{-list-thread-groups --available}
31328 is always an expensive operation and cache the results.
31332 The @samp{groups} result is a list of tuples, where each tuple may
31333 have the following fields:
31337 Identifier of the thread group. This field is always present.
31338 The identifier is an opaque string; frontends should not try to
31339 convert it to an integer, even though it might look like one.
31342 The type of the thread group. At present, only @samp{process} is a
31346 The target-specific process identifier. This field is only present
31347 for thread groups of type @samp{process} and only if the process exists.
31350 The number of children this thread group has. This field may be
31351 absent for an available thread group.
31354 This field has a list of tuples as value, each tuple describing a
31355 thread. It may be present if the @samp{--recurse} option is
31356 specified, and it's actually possible to obtain the threads.
31359 This field is a list of integers, each identifying a core that one
31360 thread of the group is running on. This field may be absent if
31361 such information is not available.
31364 The name of the executable file that corresponds to this thread group.
31365 The field is only present for thread groups of type @samp{process},
31366 and only if there is a corresponding executable file.
31370 @subheading Example
31374 -list-thread-groups
31375 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31376 -list-thread-groups 17
31377 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31378 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31379 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31380 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31381 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31382 -list-thread-groups --available
31383 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31384 -list-thread-groups --available --recurse 1
31385 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31386 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31387 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31388 -list-thread-groups --available --recurse 1 17 18
31389 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31390 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31391 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31395 @subheading The @code{-add-inferior} Command
31396 @findex -add-inferior
31398 @subheading Synopsis
31404 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31405 inferior is not associated with any executable. Such association may
31406 be established with the @samp{-file-exec-and-symbols} command
31407 (@pxref{GDB/MI File Commands}). The command response has a single
31408 field, @samp{thread-group}, whose value is the identifier of the
31409 thread group corresponding to the new inferior.
31411 @subheading Example
31416 ^done,thread-group="i3"
31419 @subheading The @code{-interpreter-exec} Command
31420 @findex -interpreter-exec
31422 @subheading Synopsis
31425 -interpreter-exec @var{interpreter} @var{command}
31427 @anchor{-interpreter-exec}
31429 Execute the specified @var{command} in the given @var{interpreter}.
31431 @subheading @value{GDBN} Command
31433 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31435 @subheading Example
31439 -interpreter-exec console "break main"
31440 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31441 &"During symbol reading, bad structure-type format.\n"
31442 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31447 @subheading The @code{-inferior-tty-set} Command
31448 @findex -inferior-tty-set
31450 @subheading Synopsis
31453 -inferior-tty-set /dev/pts/1
31456 Set terminal for future runs of the program being debugged.
31458 @subheading @value{GDBN} Command
31460 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31462 @subheading Example
31466 -inferior-tty-set /dev/pts/1
31471 @subheading The @code{-inferior-tty-show} Command
31472 @findex -inferior-tty-show
31474 @subheading Synopsis
31480 Show terminal for future runs of program being debugged.
31482 @subheading @value{GDBN} Command
31484 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31486 @subheading Example
31490 -inferior-tty-set /dev/pts/1
31494 ^done,inferior_tty_terminal="/dev/pts/1"
31498 @subheading The @code{-enable-timings} Command
31499 @findex -enable-timings
31501 @subheading Synopsis
31504 -enable-timings [yes | no]
31507 Toggle the printing of the wallclock, user and system times for an MI
31508 command as a field in its output. This command is to help frontend
31509 developers optimize the performance of their code. No argument is
31510 equivalent to @samp{yes}.
31512 @subheading @value{GDBN} Command
31516 @subheading Example
31524 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31525 addr="0x080484ed",func="main",file="myprog.c",
31526 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31527 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31535 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31536 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31537 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31538 fullname="/home/nickrob/myprog.c",line="73"@}
31543 @chapter @value{GDBN} Annotations
31545 This chapter describes annotations in @value{GDBN}. Annotations were
31546 designed to interface @value{GDBN} to graphical user interfaces or other
31547 similar programs which want to interact with @value{GDBN} at a
31548 relatively high level.
31550 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31554 This is Edition @value{EDITION}, @value{DATE}.
31558 * Annotations Overview:: What annotations are; the general syntax.
31559 * Server Prefix:: Issuing a command without affecting user state.
31560 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31561 * Errors:: Annotations for error messages.
31562 * Invalidation:: Some annotations describe things now invalid.
31563 * Annotations for Running::
31564 Whether the program is running, how it stopped, etc.
31565 * Source Annotations:: Annotations describing source code.
31568 @node Annotations Overview
31569 @section What is an Annotation?
31570 @cindex annotations
31572 Annotations start with a newline character, two @samp{control-z}
31573 characters, and the name of the annotation. If there is no additional
31574 information associated with this annotation, the name of the annotation
31575 is followed immediately by a newline. If there is additional
31576 information, the name of the annotation is followed by a space, the
31577 additional information, and a newline. The additional information
31578 cannot contain newline characters.
31580 Any output not beginning with a newline and two @samp{control-z}
31581 characters denotes literal output from @value{GDBN}. Currently there is
31582 no need for @value{GDBN} to output a newline followed by two
31583 @samp{control-z} characters, but if there was such a need, the
31584 annotations could be extended with an @samp{escape} annotation which
31585 means those three characters as output.
31587 The annotation @var{level}, which is specified using the
31588 @option{--annotate} command line option (@pxref{Mode Options}), controls
31589 how much information @value{GDBN} prints together with its prompt,
31590 values of expressions, source lines, and other types of output. Level 0
31591 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31592 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31593 for programs that control @value{GDBN}, and level 2 annotations have
31594 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31595 Interface, annotate, GDB's Obsolete Annotations}).
31598 @kindex set annotate
31599 @item set annotate @var{level}
31600 The @value{GDBN} command @code{set annotate} sets the level of
31601 annotations to the specified @var{level}.
31603 @item show annotate
31604 @kindex show annotate
31605 Show the current annotation level.
31608 This chapter describes level 3 annotations.
31610 A simple example of starting up @value{GDBN} with annotations is:
31613 $ @kbd{gdb --annotate=3}
31615 Copyright 2003 Free Software Foundation, Inc.
31616 GDB is free software, covered by the GNU General Public License,
31617 and you are welcome to change it and/or distribute copies of it
31618 under certain conditions.
31619 Type "show copying" to see the conditions.
31620 There is absolutely no warranty for GDB. Type "show warranty"
31622 This GDB was configured as "i386-pc-linux-gnu"
31633 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31634 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31635 denotes a @samp{control-z} character) are annotations; the rest is
31636 output from @value{GDBN}.
31638 @node Server Prefix
31639 @section The Server Prefix
31640 @cindex server prefix
31642 If you prefix a command with @samp{server } then it will not affect
31643 the command history, nor will it affect @value{GDBN}'s notion of which
31644 command to repeat if @key{RET} is pressed on a line by itself. This
31645 means that commands can be run behind a user's back by a front-end in
31646 a transparent manner.
31648 The @code{server } prefix does not affect the recording of values into
31649 the value history; to print a value without recording it into the
31650 value history, use the @code{output} command instead of the
31651 @code{print} command.
31653 Using this prefix also disables confirmation requests
31654 (@pxref{confirmation requests}).
31657 @section Annotation for @value{GDBN} Input
31659 @cindex annotations for prompts
31660 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31661 to know when to send output, when the output from a given command is
31664 Different kinds of input each have a different @dfn{input type}. Each
31665 input type has three annotations: a @code{pre-} annotation, which
31666 denotes the beginning of any prompt which is being output, a plain
31667 annotation, which denotes the end of the prompt, and then a @code{post-}
31668 annotation which denotes the end of any echo which may (or may not) be
31669 associated with the input. For example, the @code{prompt} input type
31670 features the following annotations:
31678 The input types are
31681 @findex pre-prompt annotation
31682 @findex prompt annotation
31683 @findex post-prompt annotation
31685 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31687 @findex pre-commands annotation
31688 @findex commands annotation
31689 @findex post-commands annotation
31691 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31692 command. The annotations are repeated for each command which is input.
31694 @findex pre-overload-choice annotation
31695 @findex overload-choice annotation
31696 @findex post-overload-choice annotation
31697 @item overload-choice
31698 When @value{GDBN} wants the user to select between various overloaded functions.
31700 @findex pre-query annotation
31701 @findex query annotation
31702 @findex post-query annotation
31704 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31706 @findex pre-prompt-for-continue annotation
31707 @findex prompt-for-continue annotation
31708 @findex post-prompt-for-continue annotation
31709 @item prompt-for-continue
31710 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31711 expect this to work well; instead use @code{set height 0} to disable
31712 prompting. This is because the counting of lines is buggy in the
31713 presence of annotations.
31718 @cindex annotations for errors, warnings and interrupts
31720 @findex quit annotation
31725 This annotation occurs right before @value{GDBN} responds to an interrupt.
31727 @findex error annotation
31732 This annotation occurs right before @value{GDBN} responds to an error.
31734 Quit and error annotations indicate that any annotations which @value{GDBN} was
31735 in the middle of may end abruptly. For example, if a
31736 @code{value-history-begin} annotation is followed by a @code{error}, one
31737 cannot expect to receive the matching @code{value-history-end}. One
31738 cannot expect not to receive it either, however; an error annotation
31739 does not necessarily mean that @value{GDBN} is immediately returning all the way
31742 @findex error-begin annotation
31743 A quit or error annotation may be preceded by
31749 Any output between that and the quit or error annotation is the error
31752 Warning messages are not yet annotated.
31753 @c If we want to change that, need to fix warning(), type_error(),
31754 @c range_error(), and possibly other places.
31757 @section Invalidation Notices
31759 @cindex annotations for invalidation messages
31760 The following annotations say that certain pieces of state may have
31764 @findex frames-invalid annotation
31765 @item ^Z^Zframes-invalid
31767 The frames (for example, output from the @code{backtrace} command) may
31770 @findex breakpoints-invalid annotation
31771 @item ^Z^Zbreakpoints-invalid
31773 The breakpoints may have changed. For example, the user just added or
31774 deleted a breakpoint.
31777 @node Annotations for Running
31778 @section Running the Program
31779 @cindex annotations for running programs
31781 @findex starting annotation
31782 @findex stopping annotation
31783 When the program starts executing due to a @value{GDBN} command such as
31784 @code{step} or @code{continue},
31790 is output. When the program stops,
31796 is output. Before the @code{stopped} annotation, a variety of
31797 annotations describe how the program stopped.
31800 @findex exited annotation
31801 @item ^Z^Zexited @var{exit-status}
31802 The program exited, and @var{exit-status} is the exit status (zero for
31803 successful exit, otherwise nonzero).
31805 @findex signalled annotation
31806 @findex signal-name annotation
31807 @findex signal-name-end annotation
31808 @findex signal-string annotation
31809 @findex signal-string-end annotation
31810 @item ^Z^Zsignalled
31811 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31812 annotation continues:
31818 ^Z^Zsignal-name-end
31822 ^Z^Zsignal-string-end
31827 where @var{name} is the name of the signal, such as @code{SIGILL} or
31828 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31829 as @code{Illegal Instruction} or @code{Segmentation fault}.
31830 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31831 user's benefit and have no particular format.
31833 @findex signal annotation
31835 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31836 just saying that the program received the signal, not that it was
31837 terminated with it.
31839 @findex breakpoint annotation
31840 @item ^Z^Zbreakpoint @var{number}
31841 The program hit breakpoint number @var{number}.
31843 @findex watchpoint annotation
31844 @item ^Z^Zwatchpoint @var{number}
31845 The program hit watchpoint number @var{number}.
31848 @node Source Annotations
31849 @section Displaying Source
31850 @cindex annotations for source display
31852 @findex source annotation
31853 The following annotation is used instead of displaying source code:
31856 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31859 where @var{filename} is an absolute file name indicating which source
31860 file, @var{line} is the line number within that file (where 1 is the
31861 first line in the file), @var{character} is the character position
31862 within the file (where 0 is the first character in the file) (for most
31863 debug formats this will necessarily point to the beginning of a line),
31864 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31865 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31866 @var{addr} is the address in the target program associated with the
31867 source which is being displayed. @var{addr} is in the form @samp{0x}
31868 followed by one or more lowercase hex digits (note that this does not
31869 depend on the language).
31871 @node JIT Interface
31872 @chapter JIT Compilation Interface
31873 @cindex just-in-time compilation
31874 @cindex JIT compilation interface
31876 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31877 interface. A JIT compiler is a program or library that generates native
31878 executable code at runtime and executes it, usually in order to achieve good
31879 performance while maintaining platform independence.
31881 Programs that use JIT compilation are normally difficult to debug because
31882 portions of their code are generated at runtime, instead of being loaded from
31883 object files, which is where @value{GDBN} normally finds the program's symbols
31884 and debug information. In order to debug programs that use JIT compilation,
31885 @value{GDBN} has an interface that allows the program to register in-memory
31886 symbol files with @value{GDBN} at runtime.
31888 If you are using @value{GDBN} to debug a program that uses this interface, then
31889 it should work transparently so long as you have not stripped the binary. If
31890 you are developing a JIT compiler, then the interface is documented in the rest
31891 of this chapter. At this time, the only known client of this interface is the
31894 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31895 JIT compiler communicates with @value{GDBN} by writing data into a global
31896 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31897 attaches, it reads a linked list of symbol files from the global variable to
31898 find existing code, and puts a breakpoint in the function so that it can find
31899 out about additional code.
31902 * Declarations:: Relevant C struct declarations
31903 * Registering Code:: Steps to register code
31904 * Unregistering Code:: Steps to unregister code
31905 * Custom Debug Info:: Emit debug information in a custom format
31909 @section JIT Declarations
31911 These are the relevant struct declarations that a C program should include to
31912 implement the interface:
31922 struct jit_code_entry
31924 struct jit_code_entry *next_entry;
31925 struct jit_code_entry *prev_entry;
31926 const char *symfile_addr;
31927 uint64_t symfile_size;
31930 struct jit_descriptor
31933 /* This type should be jit_actions_t, but we use uint32_t
31934 to be explicit about the bitwidth. */
31935 uint32_t action_flag;
31936 struct jit_code_entry *relevant_entry;
31937 struct jit_code_entry *first_entry;
31940 /* GDB puts a breakpoint in this function. */
31941 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31943 /* Make sure to specify the version statically, because the
31944 debugger may check the version before we can set it. */
31945 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31948 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31949 modifications to this global data properly, which can easily be done by putting
31950 a global mutex around modifications to these structures.
31952 @node Registering Code
31953 @section Registering Code
31955 To register code with @value{GDBN}, the JIT should follow this protocol:
31959 Generate an object file in memory with symbols and other desired debug
31960 information. The file must include the virtual addresses of the sections.
31963 Create a code entry for the file, which gives the start and size of the symbol
31967 Add it to the linked list in the JIT descriptor.
31970 Point the relevant_entry field of the descriptor at the entry.
31973 Set @code{action_flag} to @code{JIT_REGISTER} and call
31974 @code{__jit_debug_register_code}.
31977 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31978 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31979 new code. However, the linked list must still be maintained in order to allow
31980 @value{GDBN} to attach to a running process and still find the symbol files.
31982 @node Unregistering Code
31983 @section Unregistering Code
31985 If code is freed, then the JIT should use the following protocol:
31989 Remove the code entry corresponding to the code from the linked list.
31992 Point the @code{relevant_entry} field of the descriptor at the code entry.
31995 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31996 @code{__jit_debug_register_code}.
31999 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32000 and the JIT will leak the memory used for the associated symbol files.
32002 @node Custom Debug Info
32003 @section Custom Debug Info
32004 @cindex custom JIT debug info
32005 @cindex JIT debug info reader
32007 Generating debug information in platform-native file formats (like ELF
32008 or COFF) may be an overkill for JIT compilers; especially if all the
32009 debug info is used for is displaying a meaningful backtrace. The
32010 issue can be resolved by having the JIT writers decide on a debug info
32011 format and also provide a reader that parses the debug info generated
32012 by the JIT compiler. This section gives a brief overview on writing
32013 such a parser. More specific details can be found in the source file
32014 @file{gdb/jit-reader.in}, which is also installed as a header at
32015 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32017 The reader is implemented as a shared object (so this functionality is
32018 not available on platforms which don't allow loading shared objects at
32019 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32020 @code{jit-reader-unload} are provided, to be used to load and unload
32021 the readers from a preconfigured directory. Once loaded, the shared
32022 object is used the parse the debug information emitted by the JIT
32026 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32027 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32030 @node Using JIT Debug Info Readers
32031 @subsection Using JIT Debug Info Readers
32032 @kindex jit-reader-load
32033 @kindex jit-reader-unload
32035 Readers can be loaded and unloaded using the @code{jit-reader-load}
32036 and @code{jit-reader-unload} commands.
32039 @item jit-reader-load @var{reader-name}
32040 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32041 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32042 @var{libdir} is the system library directory, usually
32043 @file{/usr/local/lib}. Only one reader can be active at a time;
32044 trying to load a second reader when one is already loaded will result
32045 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32046 first unloading the current one using @code{jit-reader-load} and then
32047 invoking @code{jit-reader-load}.
32049 @item jit-reader-unload
32050 Unload the currently loaded JIT reader.
32054 @node Writing JIT Debug Info Readers
32055 @subsection Writing JIT Debug Info Readers
32056 @cindex writing JIT debug info readers
32058 As mentioned, a reader is essentially a shared object conforming to a
32059 certain ABI. This ABI is described in @file{jit-reader.h}.
32061 @file{jit-reader.h} defines the structures, macros and functions
32062 required to write a reader. It is installed (along with
32063 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32064 the system include directory.
32066 Readers need to be released under a GPL compatible license. A reader
32067 can be declared as released under such a license by placing the macro
32068 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32070 The entry point for readers is the symbol @code{gdb_init_reader},
32071 which is expected to be a function with the prototype
32073 @findex gdb_init_reader
32075 extern struct gdb_reader_funcs *gdb_init_reader (void);
32078 @cindex @code{struct gdb_reader_funcs}
32080 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32081 functions. These functions are executed to read the debug info
32082 generated by the JIT compiler (@code{read}), to unwind stack frames
32083 (@code{unwind}) and to create canonical frame IDs
32084 (@code{get_Frame_id}). It also has a callback that is called when the
32085 reader is being unloaded (@code{destroy}). The struct looks like this
32088 struct gdb_reader_funcs
32090 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32091 int reader_version;
32093 /* For use by the reader. */
32096 gdb_read_debug_info *read;
32097 gdb_unwind_frame *unwind;
32098 gdb_get_frame_id *get_frame_id;
32099 gdb_destroy_reader *destroy;
32103 @cindex @code{struct gdb_symbol_callbacks}
32104 @cindex @code{struct gdb_unwind_callbacks}
32106 The callbacks are provided with another set of callbacks by
32107 @value{GDBN} to do their job. For @code{read}, these callbacks are
32108 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32109 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32110 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32111 files and new symbol tables inside those object files. @code{struct
32112 gdb_unwind_callbacks} has callbacks to read registers off the current
32113 frame and to write out the values of the registers in the previous
32114 frame. Both have a callback (@code{target_read}) to read bytes off the
32115 target's address space.
32118 @chapter Reporting Bugs in @value{GDBN}
32119 @cindex bugs in @value{GDBN}
32120 @cindex reporting bugs in @value{GDBN}
32122 Your bug reports play an essential role in making @value{GDBN} reliable.
32124 Reporting a bug may help you by bringing a solution to your problem, or it
32125 may not. But in any case the principal function of a bug report is to help
32126 the entire community by making the next version of @value{GDBN} work better. Bug
32127 reports are your contribution to the maintenance of @value{GDBN}.
32129 In order for a bug report to serve its purpose, you must include the
32130 information that enables us to fix the bug.
32133 * Bug Criteria:: Have you found a bug?
32134 * Bug Reporting:: How to report bugs
32138 @section Have You Found a Bug?
32139 @cindex bug criteria
32141 If you are not sure whether you have found a bug, here are some guidelines:
32144 @cindex fatal signal
32145 @cindex debugger crash
32146 @cindex crash of debugger
32148 If the debugger gets a fatal signal, for any input whatever, that is a
32149 @value{GDBN} bug. Reliable debuggers never crash.
32151 @cindex error on valid input
32153 If @value{GDBN} produces an error message for valid input, that is a
32154 bug. (Note that if you're cross debugging, the problem may also be
32155 somewhere in the connection to the target.)
32157 @cindex invalid input
32159 If @value{GDBN} does not produce an error message for invalid input,
32160 that is a bug. However, you should note that your idea of
32161 ``invalid input'' might be our idea of ``an extension'' or ``support
32162 for traditional practice''.
32165 If you are an experienced user of debugging tools, your suggestions
32166 for improvement of @value{GDBN} are welcome in any case.
32169 @node Bug Reporting
32170 @section How to Report Bugs
32171 @cindex bug reports
32172 @cindex @value{GDBN} bugs, reporting
32174 A number of companies and individuals offer support for @sc{gnu} products.
32175 If you obtained @value{GDBN} from a support organization, we recommend you
32176 contact that organization first.
32178 You can find contact information for many support companies and
32179 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32181 @c should add a web page ref...
32184 @ifset BUGURL_DEFAULT
32185 In any event, we also recommend that you submit bug reports for
32186 @value{GDBN}. The preferred method is to submit them directly using
32187 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32188 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32191 @strong{Do not send bug reports to @samp{info-gdb}, or to
32192 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32193 not want to receive bug reports. Those that do have arranged to receive
32196 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32197 serves as a repeater. The mailing list and the newsgroup carry exactly
32198 the same messages. Often people think of posting bug reports to the
32199 newsgroup instead of mailing them. This appears to work, but it has one
32200 problem which can be crucial: a newsgroup posting often lacks a mail
32201 path back to the sender. Thus, if we need to ask for more information,
32202 we may be unable to reach you. For this reason, it is better to send
32203 bug reports to the mailing list.
32205 @ifclear BUGURL_DEFAULT
32206 In any event, we also recommend that you submit bug reports for
32207 @value{GDBN} to @value{BUGURL}.
32211 The fundamental principle of reporting bugs usefully is this:
32212 @strong{report all the facts}. If you are not sure whether to state a
32213 fact or leave it out, state it!
32215 Often people omit facts because they think they know what causes the
32216 problem and assume that some details do not matter. Thus, you might
32217 assume that the name of the variable you use in an example does not matter.
32218 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32219 stray memory reference which happens to fetch from the location where that
32220 name is stored in memory; perhaps, if the name were different, the contents
32221 of that location would fool the debugger into doing the right thing despite
32222 the bug. Play it safe and give a specific, complete example. That is the
32223 easiest thing for you to do, and the most helpful.
32225 Keep in mind that the purpose of a bug report is to enable us to fix the
32226 bug. It may be that the bug has been reported previously, but neither
32227 you nor we can know that unless your bug report is complete and
32230 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32231 bell?'' Those bug reports are useless, and we urge everyone to
32232 @emph{refuse to respond to them} except to chide the sender to report
32235 To enable us to fix the bug, you should include all these things:
32239 The version of @value{GDBN}. @value{GDBN} announces it if you start
32240 with no arguments; you can also print it at any time using @code{show
32243 Without this, we will not know whether there is any point in looking for
32244 the bug in the current version of @value{GDBN}.
32247 The type of machine you are using, and the operating system name and
32251 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32252 ``@value{GCC}--2.8.1''.
32255 What compiler (and its version) was used to compile the program you are
32256 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32257 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32258 to get this information; for other compilers, see the documentation for
32262 The command arguments you gave the compiler to compile your example and
32263 observe the bug. For example, did you use @samp{-O}? To guarantee
32264 you will not omit something important, list them all. A copy of the
32265 Makefile (or the output from make) is sufficient.
32267 If we were to try to guess the arguments, we would probably guess wrong
32268 and then we might not encounter the bug.
32271 A complete input script, and all necessary source files, that will
32275 A description of what behavior you observe that you believe is
32276 incorrect. For example, ``It gets a fatal signal.''
32278 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32279 will certainly notice it. But if the bug is incorrect output, we might
32280 not notice unless it is glaringly wrong. You might as well not give us
32281 a chance to make a mistake.
32283 Even if the problem you experience is a fatal signal, you should still
32284 say so explicitly. Suppose something strange is going on, such as, your
32285 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32286 the C library on your system. (This has happened!) Your copy might
32287 crash and ours would not. If you told us to expect a crash, then when
32288 ours fails to crash, we would know that the bug was not happening for
32289 us. If you had not told us to expect a crash, then we would not be able
32290 to draw any conclusion from our observations.
32293 @cindex recording a session script
32294 To collect all this information, you can use a session recording program
32295 such as @command{script}, which is available on many Unix systems.
32296 Just run your @value{GDBN} session inside @command{script} and then
32297 include the @file{typescript} file with your bug report.
32299 Another way to record a @value{GDBN} session is to run @value{GDBN}
32300 inside Emacs and then save the entire buffer to a file.
32303 If you wish to suggest changes to the @value{GDBN} source, send us context
32304 diffs. If you even discuss something in the @value{GDBN} source, refer to
32305 it by context, not by line number.
32307 The line numbers in our development sources will not match those in your
32308 sources. Your line numbers would convey no useful information to us.
32312 Here are some things that are not necessary:
32316 A description of the envelope of the bug.
32318 Often people who encounter a bug spend a lot of time investigating
32319 which changes to the input file will make the bug go away and which
32320 changes will not affect it.
32322 This is often time consuming and not very useful, because the way we
32323 will find the bug is by running a single example under the debugger
32324 with breakpoints, not by pure deduction from a series of examples.
32325 We recommend that you save your time for something else.
32327 Of course, if you can find a simpler example to report @emph{instead}
32328 of the original one, that is a convenience for us. Errors in the
32329 output will be easier to spot, running under the debugger will take
32330 less time, and so on.
32332 However, simplification is not vital; if you do not want to do this,
32333 report the bug anyway and send us the entire test case you used.
32336 A patch for the bug.
32338 A patch for the bug does help us if it is a good one. But do not omit
32339 the necessary information, such as the test case, on the assumption that
32340 a patch is all we need. We might see problems with your patch and decide
32341 to fix the problem another way, or we might not understand it at all.
32343 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32344 construct an example that will make the program follow a certain path
32345 through the code. If you do not send us the example, we will not be able
32346 to construct one, so we will not be able to verify that the bug is fixed.
32348 And if we cannot understand what bug you are trying to fix, or why your
32349 patch should be an improvement, we will not install it. A test case will
32350 help us to understand.
32353 A guess about what the bug is or what it depends on.
32355 Such guesses are usually wrong. Even we cannot guess right about such
32356 things without first using the debugger to find the facts.
32359 @c The readline documentation is distributed with the readline code
32360 @c and consists of the two following files:
32363 @c Use -I with makeinfo to point to the appropriate directory,
32364 @c environment var TEXINPUTS with TeX.
32365 @ifclear SYSTEM_READLINE
32366 @include rluser.texi
32367 @include hsuser.texi
32371 @appendix In Memoriam
32373 The @value{GDBN} project mourns the loss of the following long-time
32378 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32379 to Free Software in general. Outside of @value{GDBN}, he was known in
32380 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32382 @item Michael Snyder
32383 Michael was one of the Global Maintainers of the @value{GDBN} project,
32384 with contributions recorded as early as 1996, until 2011. In addition
32385 to his day to day participation, he was a large driving force behind
32386 adding Reverse Debugging to @value{GDBN}.
32389 Beyond their technical contributions to the project, they were also
32390 enjoyable members of the Free Software Community. We will miss them.
32392 @node Formatting Documentation
32393 @appendix Formatting Documentation
32395 @cindex @value{GDBN} reference card
32396 @cindex reference card
32397 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32398 for printing with PostScript or Ghostscript, in the @file{gdb}
32399 subdirectory of the main source directory@footnote{In
32400 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32401 release.}. If you can use PostScript or Ghostscript with your printer,
32402 you can print the reference card immediately with @file{refcard.ps}.
32404 The release also includes the source for the reference card. You
32405 can format it, using @TeX{}, by typing:
32411 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32412 mode on US ``letter'' size paper;
32413 that is, on a sheet 11 inches wide by 8.5 inches
32414 high. You will need to specify this form of printing as an option to
32415 your @sc{dvi} output program.
32417 @cindex documentation
32419 All the documentation for @value{GDBN} comes as part of the machine-readable
32420 distribution. The documentation is written in Texinfo format, which is
32421 a documentation system that uses a single source file to produce both
32422 on-line information and a printed manual. You can use one of the Info
32423 formatting commands to create the on-line version of the documentation
32424 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32426 @value{GDBN} includes an already formatted copy of the on-line Info
32427 version of this manual in the @file{gdb} subdirectory. The main Info
32428 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32429 subordinate files matching @samp{gdb.info*} in the same directory. If
32430 necessary, you can print out these files, or read them with any editor;
32431 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32432 Emacs or the standalone @code{info} program, available as part of the
32433 @sc{gnu} Texinfo distribution.
32435 If you want to format these Info files yourself, you need one of the
32436 Info formatting programs, such as @code{texinfo-format-buffer} or
32439 If you have @code{makeinfo} installed, and are in the top level
32440 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32441 version @value{GDBVN}), you can make the Info file by typing:
32448 If you want to typeset and print copies of this manual, you need @TeX{},
32449 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32450 Texinfo definitions file.
32452 @TeX{} is a typesetting program; it does not print files directly, but
32453 produces output files called @sc{dvi} files. To print a typeset
32454 document, you need a program to print @sc{dvi} files. If your system
32455 has @TeX{} installed, chances are it has such a program. The precise
32456 command to use depends on your system; @kbd{lpr -d} is common; another
32457 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32458 require a file name without any extension or a @samp{.dvi} extension.
32460 @TeX{} also requires a macro definitions file called
32461 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32462 written in Texinfo format. On its own, @TeX{} cannot either read or
32463 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32464 and is located in the @file{gdb-@var{version-number}/texinfo}
32467 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32468 typeset and print this manual. First switch to the @file{gdb}
32469 subdirectory of the main source directory (for example, to
32470 @file{gdb-@value{GDBVN}/gdb}) and type:
32476 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32478 @node Installing GDB
32479 @appendix Installing @value{GDBN}
32480 @cindex installation
32483 * Requirements:: Requirements for building @value{GDBN}
32484 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32485 * Separate Objdir:: Compiling @value{GDBN} in another directory
32486 * Config Names:: Specifying names for hosts and targets
32487 * Configure Options:: Summary of options for configure
32488 * System-wide configuration:: Having a system-wide init file
32492 @section Requirements for Building @value{GDBN}
32493 @cindex building @value{GDBN}, requirements for
32495 Building @value{GDBN} requires various tools and packages to be available.
32496 Other packages will be used only if they are found.
32498 @heading Tools/Packages Necessary for Building @value{GDBN}
32500 @item ISO C90 compiler
32501 @value{GDBN} is written in ISO C90. It should be buildable with any
32502 working C90 compiler, e.g.@: GCC.
32506 @heading Tools/Packages Optional for Building @value{GDBN}
32510 @value{GDBN} can use the Expat XML parsing library. This library may be
32511 included with your operating system distribution; if it is not, you
32512 can get the latest version from @url{http://expat.sourceforge.net}.
32513 The @file{configure} script will search for this library in several
32514 standard locations; if it is installed in an unusual path, you can
32515 use the @option{--with-libexpat-prefix} option to specify its location.
32521 Remote protocol memory maps (@pxref{Memory Map Format})
32523 Target descriptions (@pxref{Target Descriptions})
32525 Remote shared library lists (@xref{Library List Format},
32526 or alternatively @pxref{Library List Format for SVR4 Targets})
32528 MS-Windows shared libraries (@pxref{Shared Libraries})
32530 Traceframe info (@pxref{Traceframe Info Format})
32534 @cindex compressed debug sections
32535 @value{GDBN} will use the @samp{zlib} library, if available, to read
32536 compressed debug sections. Some linkers, such as GNU gold, are capable
32537 of producing binaries with compressed debug sections. If @value{GDBN}
32538 is compiled with @samp{zlib}, it will be able to read the debug
32539 information in such binaries.
32541 The @samp{zlib} library is likely included with your operating system
32542 distribution; if it is not, you can get the latest version from
32543 @url{http://zlib.net}.
32546 @value{GDBN}'s features related to character sets (@pxref{Character
32547 Sets}) require a functioning @code{iconv} implementation. If you are
32548 on a GNU system, then this is provided by the GNU C Library. Some
32549 other systems also provide a working @code{iconv}.
32551 If @value{GDBN} is using the @code{iconv} program which is installed
32552 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32553 This is done with @option{--with-iconv-bin} which specifies the
32554 directory that contains the @code{iconv} program.
32556 On systems without @code{iconv}, you can install GNU Libiconv. If you
32557 have previously installed Libiconv, you can use the
32558 @option{--with-libiconv-prefix} option to configure.
32560 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32561 arrange to build Libiconv if a directory named @file{libiconv} appears
32562 in the top-most source directory. If Libiconv is built this way, and
32563 if the operating system does not provide a suitable @code{iconv}
32564 implementation, then the just-built library will automatically be used
32565 by @value{GDBN}. One easy way to set this up is to download GNU
32566 Libiconv, unpack it, and then rename the directory holding the
32567 Libiconv source code to @samp{libiconv}.
32570 @node Running Configure
32571 @section Invoking the @value{GDBN} @file{configure} Script
32572 @cindex configuring @value{GDBN}
32573 @value{GDBN} comes with a @file{configure} script that automates the process
32574 of preparing @value{GDBN} for installation; you can then use @code{make} to
32575 build the @code{gdb} program.
32577 @c irrelevant in info file; it's as current as the code it lives with.
32578 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32579 look at the @file{README} file in the sources; we may have improved the
32580 installation procedures since publishing this manual.}
32583 The @value{GDBN} distribution includes all the source code you need for
32584 @value{GDBN} in a single directory, whose name is usually composed by
32585 appending the version number to @samp{gdb}.
32587 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32588 @file{gdb-@value{GDBVN}} directory. That directory contains:
32591 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32592 script for configuring @value{GDBN} and all its supporting libraries
32594 @item gdb-@value{GDBVN}/gdb
32595 the source specific to @value{GDBN} itself
32597 @item gdb-@value{GDBVN}/bfd
32598 source for the Binary File Descriptor library
32600 @item gdb-@value{GDBVN}/include
32601 @sc{gnu} include files
32603 @item gdb-@value{GDBVN}/libiberty
32604 source for the @samp{-liberty} free software library
32606 @item gdb-@value{GDBVN}/opcodes
32607 source for the library of opcode tables and disassemblers
32609 @item gdb-@value{GDBVN}/readline
32610 source for the @sc{gnu} command-line interface
32612 @item gdb-@value{GDBVN}/glob
32613 source for the @sc{gnu} filename pattern-matching subroutine
32615 @item gdb-@value{GDBVN}/mmalloc
32616 source for the @sc{gnu} memory-mapped malloc package
32619 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32620 from the @file{gdb-@var{version-number}} source directory, which in
32621 this example is the @file{gdb-@value{GDBVN}} directory.
32623 First switch to the @file{gdb-@var{version-number}} source directory
32624 if you are not already in it; then run @file{configure}. Pass the
32625 identifier for the platform on which @value{GDBN} will run as an
32631 cd gdb-@value{GDBVN}
32632 ./configure @var{host}
32637 where @var{host} is an identifier such as @samp{sun4} or
32638 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32639 (You can often leave off @var{host}; @file{configure} tries to guess the
32640 correct value by examining your system.)
32642 Running @samp{configure @var{host}} and then running @code{make} builds the
32643 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32644 libraries, then @code{gdb} itself. The configured source files, and the
32645 binaries, are left in the corresponding source directories.
32648 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32649 system does not recognize this automatically when you run a different
32650 shell, you may need to run @code{sh} on it explicitly:
32653 sh configure @var{host}
32656 If you run @file{configure} from a directory that contains source
32657 directories for multiple libraries or programs, such as the
32658 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32660 creates configuration files for every directory level underneath (unless
32661 you tell it not to, with the @samp{--norecursion} option).
32663 You should run the @file{configure} script from the top directory in the
32664 source tree, the @file{gdb-@var{version-number}} directory. If you run
32665 @file{configure} from one of the subdirectories, you will configure only
32666 that subdirectory. That is usually not what you want. In particular,
32667 if you run the first @file{configure} from the @file{gdb} subdirectory
32668 of the @file{gdb-@var{version-number}} directory, you will omit the
32669 configuration of @file{bfd}, @file{readline}, and other sibling
32670 directories of the @file{gdb} subdirectory. This leads to build errors
32671 about missing include files such as @file{bfd/bfd.h}.
32673 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32674 However, you should make sure that the shell on your path (named by
32675 the @samp{SHELL} environment variable) is publicly readable. Remember
32676 that @value{GDBN} uses the shell to start your program---some systems refuse to
32677 let @value{GDBN} debug child processes whose programs are not readable.
32679 @node Separate Objdir
32680 @section Compiling @value{GDBN} in Another Directory
32682 If you want to run @value{GDBN} versions for several host or target machines,
32683 you need a different @code{gdb} compiled for each combination of
32684 host and target. @file{configure} is designed to make this easy by
32685 allowing you to generate each configuration in a separate subdirectory,
32686 rather than in the source directory. If your @code{make} program
32687 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32688 @code{make} in each of these directories builds the @code{gdb}
32689 program specified there.
32691 To build @code{gdb} in a separate directory, run @file{configure}
32692 with the @samp{--srcdir} option to specify where to find the source.
32693 (You also need to specify a path to find @file{configure}
32694 itself from your working directory. If the path to @file{configure}
32695 would be the same as the argument to @samp{--srcdir}, you can leave out
32696 the @samp{--srcdir} option; it is assumed.)
32698 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32699 separate directory for a Sun 4 like this:
32703 cd gdb-@value{GDBVN}
32706 ../gdb-@value{GDBVN}/configure sun4
32711 When @file{configure} builds a configuration using a remote source
32712 directory, it creates a tree for the binaries with the same structure
32713 (and using the same names) as the tree under the source directory. In
32714 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32715 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32716 @file{gdb-sun4/gdb}.
32718 Make sure that your path to the @file{configure} script has just one
32719 instance of @file{gdb} in it. If your path to @file{configure} looks
32720 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32721 one subdirectory of @value{GDBN}, not the whole package. This leads to
32722 build errors about missing include files such as @file{bfd/bfd.h}.
32724 One popular reason to build several @value{GDBN} configurations in separate
32725 directories is to configure @value{GDBN} for cross-compiling (where
32726 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32727 programs that run on another machine---the @dfn{target}).
32728 You specify a cross-debugging target by
32729 giving the @samp{--target=@var{target}} option to @file{configure}.
32731 When you run @code{make} to build a program or library, you must run
32732 it in a configured directory---whatever directory you were in when you
32733 called @file{configure} (or one of its subdirectories).
32735 The @code{Makefile} that @file{configure} generates in each source
32736 directory also runs recursively. If you type @code{make} in a source
32737 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32738 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32739 will build all the required libraries, and then build GDB.
32741 When you have multiple hosts or targets configured in separate
32742 directories, you can run @code{make} on them in parallel (for example,
32743 if they are NFS-mounted on each of the hosts); they will not interfere
32747 @section Specifying Names for Hosts and Targets
32749 The specifications used for hosts and targets in the @file{configure}
32750 script are based on a three-part naming scheme, but some short predefined
32751 aliases are also supported. The full naming scheme encodes three pieces
32752 of information in the following pattern:
32755 @var{architecture}-@var{vendor}-@var{os}
32758 For example, you can use the alias @code{sun4} as a @var{host} argument,
32759 or as the value for @var{target} in a @code{--target=@var{target}}
32760 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32762 The @file{configure} script accompanying @value{GDBN} does not provide
32763 any query facility to list all supported host and target names or
32764 aliases. @file{configure} calls the Bourne shell script
32765 @code{config.sub} to map abbreviations to full names; you can read the
32766 script, if you wish, or you can use it to test your guesses on
32767 abbreviations---for example:
32770 % sh config.sub i386-linux
32772 % sh config.sub alpha-linux
32773 alpha-unknown-linux-gnu
32774 % sh config.sub hp9k700
32776 % sh config.sub sun4
32777 sparc-sun-sunos4.1.1
32778 % sh config.sub sun3
32779 m68k-sun-sunos4.1.1
32780 % sh config.sub i986v
32781 Invalid configuration `i986v': machine `i986v' not recognized
32785 @code{config.sub} is also distributed in the @value{GDBN} source
32786 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32788 @node Configure Options
32789 @section @file{configure} Options
32791 Here is a summary of the @file{configure} options and arguments that
32792 are most often useful for building @value{GDBN}. @file{configure} also has
32793 several other options not listed here. @inforef{What Configure
32794 Does,,configure.info}, for a full explanation of @file{configure}.
32797 configure @r{[}--help@r{]}
32798 @r{[}--prefix=@var{dir}@r{]}
32799 @r{[}--exec-prefix=@var{dir}@r{]}
32800 @r{[}--srcdir=@var{dirname}@r{]}
32801 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32802 @r{[}--target=@var{target}@r{]}
32807 You may introduce options with a single @samp{-} rather than
32808 @samp{--} if you prefer; but you may abbreviate option names if you use
32813 Display a quick summary of how to invoke @file{configure}.
32815 @item --prefix=@var{dir}
32816 Configure the source to install programs and files under directory
32819 @item --exec-prefix=@var{dir}
32820 Configure the source to install programs under directory
32823 @c avoid splitting the warning from the explanation:
32825 @item --srcdir=@var{dirname}
32826 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32827 @code{make} that implements the @code{VPATH} feature.}@*
32828 Use this option to make configurations in directories separate from the
32829 @value{GDBN} source directories. Among other things, you can use this to
32830 build (or maintain) several configurations simultaneously, in separate
32831 directories. @file{configure} writes configuration-specific files in
32832 the current directory, but arranges for them to use the source in the
32833 directory @var{dirname}. @file{configure} creates directories under
32834 the working directory in parallel to the source directories below
32837 @item --norecursion
32838 Configure only the directory level where @file{configure} is executed; do not
32839 propagate configuration to subdirectories.
32841 @item --target=@var{target}
32842 Configure @value{GDBN} for cross-debugging programs running on the specified
32843 @var{target}. Without this option, @value{GDBN} is configured to debug
32844 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32846 There is no convenient way to generate a list of all available targets.
32848 @item @var{host} @dots{}
32849 Configure @value{GDBN} to run on the specified @var{host}.
32851 There is no convenient way to generate a list of all available hosts.
32854 There are many other options available as well, but they are generally
32855 needed for special purposes only.
32857 @node System-wide configuration
32858 @section System-wide configuration and settings
32859 @cindex system-wide init file
32861 @value{GDBN} can be configured to have a system-wide init file;
32862 this file will be read and executed at startup (@pxref{Startup, , What
32863 @value{GDBN} does during startup}).
32865 Here is the corresponding configure option:
32868 @item --with-system-gdbinit=@var{file}
32869 Specify that the default location of the system-wide init file is
32873 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32874 it may be subject to relocation. Two possible cases:
32878 If the default location of this init file contains @file{$prefix},
32879 it will be subject to relocation. Suppose that the configure options
32880 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32881 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32882 init file is looked for as @file{$install/etc/gdbinit} instead of
32883 @file{$prefix/etc/gdbinit}.
32886 By contrast, if the default location does not contain the prefix,
32887 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32888 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32889 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32890 wherever @value{GDBN} is installed.
32893 @node Maintenance Commands
32894 @appendix Maintenance Commands
32895 @cindex maintenance commands
32896 @cindex internal commands
32898 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32899 includes a number of commands intended for @value{GDBN} developers,
32900 that are not documented elsewhere in this manual. These commands are
32901 provided here for reference. (For commands that turn on debugging
32902 messages, see @ref{Debugging Output}.)
32905 @kindex maint agent
32906 @kindex maint agent-eval
32907 @item maint agent @var{expression}
32908 @itemx maint agent-eval @var{expression}
32909 Translate the given @var{expression} into remote agent bytecodes.
32910 This command is useful for debugging the Agent Expression mechanism
32911 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32912 expression useful for data collection, such as by tracepoints, while
32913 @samp{maint agent-eval} produces an expression that evaluates directly
32914 to a result. For instance, a collection expression for @code{globa +
32915 globb} will include bytecodes to record four bytes of memory at each
32916 of the addresses of @code{globa} and @code{globb}, while discarding
32917 the result of the addition, while an evaluation expression will do the
32918 addition and return the sum.
32920 @kindex maint info breakpoints
32921 @item @anchor{maint info breakpoints}maint info breakpoints
32922 Using the same format as @samp{info breakpoints}, display both the
32923 breakpoints you've set explicitly, and those @value{GDBN} is using for
32924 internal purposes. Internal breakpoints are shown with negative
32925 breakpoint numbers. The type column identifies what kind of breakpoint
32930 Normal, explicitly set breakpoint.
32933 Normal, explicitly set watchpoint.
32936 Internal breakpoint, used to handle correctly stepping through
32937 @code{longjmp} calls.
32939 @item longjmp resume
32940 Internal breakpoint at the target of a @code{longjmp}.
32943 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32946 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32949 Shared library events.
32953 @kindex set displaced-stepping
32954 @kindex show displaced-stepping
32955 @cindex displaced stepping support
32956 @cindex out-of-line single-stepping
32957 @item set displaced-stepping
32958 @itemx show displaced-stepping
32959 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32960 if the target supports it. Displaced stepping is a way to single-step
32961 over breakpoints without removing them from the inferior, by executing
32962 an out-of-line copy of the instruction that was originally at the
32963 breakpoint location. It is also known as out-of-line single-stepping.
32966 @item set displaced-stepping on
32967 If the target architecture supports it, @value{GDBN} will use
32968 displaced stepping to step over breakpoints.
32970 @item set displaced-stepping off
32971 @value{GDBN} will not use displaced stepping to step over breakpoints,
32972 even if such is supported by the target architecture.
32974 @cindex non-stop mode, and @samp{set displaced-stepping}
32975 @item set displaced-stepping auto
32976 This is the default mode. @value{GDBN} will use displaced stepping
32977 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32978 architecture supports displaced stepping.
32981 @kindex maint check-symtabs
32982 @item maint check-symtabs
32983 Check the consistency of psymtabs and symtabs.
32985 @kindex maint cplus first_component
32986 @item maint cplus first_component @var{name}
32987 Print the first C@t{++} class/namespace component of @var{name}.
32989 @kindex maint cplus namespace
32990 @item maint cplus namespace
32991 Print the list of possible C@t{++} namespaces.
32993 @kindex maint demangle
32994 @item maint demangle @var{name}
32995 Demangle a C@t{++} or Objective-C mangled @var{name}.
32997 @kindex maint deprecate
32998 @kindex maint undeprecate
32999 @cindex deprecated commands
33000 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33001 @itemx maint undeprecate @var{command}
33002 Deprecate or undeprecate the named @var{command}. Deprecated commands
33003 cause @value{GDBN} to issue a warning when you use them. The optional
33004 argument @var{replacement} says which newer command should be used in
33005 favor of the deprecated one; if it is given, @value{GDBN} will mention
33006 the replacement as part of the warning.
33008 @kindex maint dump-me
33009 @item maint dump-me
33010 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33011 Cause a fatal signal in the debugger and force it to dump its core.
33012 This is supported only on systems which support aborting a program
33013 with the @code{SIGQUIT} signal.
33015 @kindex maint internal-error
33016 @kindex maint internal-warning
33017 @item maint internal-error @r{[}@var{message-text}@r{]}
33018 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33019 Cause @value{GDBN} to call the internal function @code{internal_error}
33020 or @code{internal_warning} and hence behave as though an internal error
33021 or internal warning has been detected. In addition to reporting the
33022 internal problem, these functions give the user the opportunity to
33023 either quit @value{GDBN} or create a core file of the current
33024 @value{GDBN} session.
33026 These commands take an optional parameter @var{message-text} that is
33027 used as the text of the error or warning message.
33029 Here's an example of using @code{internal-error}:
33032 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33033 @dots{}/maint.c:121: internal-error: testing, 1, 2
33034 A problem internal to GDB has been detected. Further
33035 debugging may prove unreliable.
33036 Quit this debugging session? (y or n) @kbd{n}
33037 Create a core file? (y or n) @kbd{n}
33041 @cindex @value{GDBN} internal error
33042 @cindex internal errors, control of @value{GDBN} behavior
33044 @kindex maint set internal-error
33045 @kindex maint show internal-error
33046 @kindex maint set internal-warning
33047 @kindex maint show internal-warning
33048 @item maint set internal-error @var{action} [ask|yes|no]
33049 @itemx maint show internal-error @var{action}
33050 @itemx maint set internal-warning @var{action} [ask|yes|no]
33051 @itemx maint show internal-warning @var{action}
33052 When @value{GDBN} reports an internal problem (error or warning) it
33053 gives the user the opportunity to both quit @value{GDBN} and create a
33054 core file of the current @value{GDBN} session. These commands let you
33055 override the default behaviour for each particular @var{action},
33056 described in the table below.
33060 You can specify that @value{GDBN} should always (yes) or never (no)
33061 quit. The default is to ask the user what to do.
33064 You can specify that @value{GDBN} should always (yes) or never (no)
33065 create a core file. The default is to ask the user what to do.
33068 @kindex maint packet
33069 @item maint packet @var{text}
33070 If @value{GDBN} is talking to an inferior via the serial protocol,
33071 then this command sends the string @var{text} to the inferior, and
33072 displays the response packet. @value{GDBN} supplies the initial
33073 @samp{$} character, the terminating @samp{#} character, and the
33076 @kindex maint print architecture
33077 @item maint print architecture @r{[}@var{file}@r{]}
33078 Print the entire architecture configuration. The optional argument
33079 @var{file} names the file where the output goes.
33081 @kindex maint print c-tdesc
33082 @item maint print c-tdesc
33083 Print the current target description (@pxref{Target Descriptions}) as
33084 a C source file. The created source file can be used in @value{GDBN}
33085 when an XML parser is not available to parse the description.
33087 @kindex maint print dummy-frames
33088 @item maint print dummy-frames
33089 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33092 (@value{GDBP}) @kbd{b add}
33094 (@value{GDBP}) @kbd{print add(2,3)}
33095 Breakpoint 2, add (a=2, b=3) at @dots{}
33097 The program being debugged stopped while in a function called from GDB.
33099 (@value{GDBP}) @kbd{maint print dummy-frames}
33100 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33101 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33102 call_lo=0x01014000 call_hi=0x01014001
33106 Takes an optional file parameter.
33108 @kindex maint print registers
33109 @kindex maint print raw-registers
33110 @kindex maint print cooked-registers
33111 @kindex maint print register-groups
33112 @kindex maint print remote-registers
33113 @item maint print registers @r{[}@var{file}@r{]}
33114 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33115 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33116 @itemx maint print register-groups @r{[}@var{file}@r{]}
33117 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33118 Print @value{GDBN}'s internal register data structures.
33120 The command @code{maint print raw-registers} includes the contents of
33121 the raw register cache; the command @code{maint print
33122 cooked-registers} includes the (cooked) value of all registers,
33123 including registers which aren't available on the target nor visible
33124 to user; the command @code{maint print register-groups} includes the
33125 groups that each register is a member of; and the command @code{maint
33126 print remote-registers} includes the remote target's register numbers
33127 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33128 @value{GDBN} Internals}.
33130 These commands take an optional parameter, a file name to which to
33131 write the information.
33133 @kindex maint print reggroups
33134 @item maint print reggroups @r{[}@var{file}@r{]}
33135 Print @value{GDBN}'s internal register group data structures. The
33136 optional argument @var{file} tells to what file to write the
33139 The register groups info looks like this:
33142 (@value{GDBP}) @kbd{maint print reggroups}
33155 This command forces @value{GDBN} to flush its internal register cache.
33157 @kindex maint print objfiles
33158 @cindex info for known object files
33159 @item maint print objfiles
33160 Print a dump of all known object files. For each object file, this
33161 command prints its name, address in memory, and all of its psymtabs
33164 @kindex maint print section-scripts
33165 @cindex info for known .debug_gdb_scripts-loaded scripts
33166 @item maint print section-scripts [@var{regexp}]
33167 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33168 If @var{regexp} is specified, only print scripts loaded by object files
33169 matching @var{regexp}.
33170 For each script, this command prints its name as specified in the objfile,
33171 and the full path if known.
33172 @xref{.debug_gdb_scripts section}.
33174 @kindex maint print statistics
33175 @cindex bcache statistics
33176 @item maint print statistics
33177 This command prints, for each object file in the program, various data
33178 about that object file followed by the byte cache (@dfn{bcache})
33179 statistics for the object file. The objfile data includes the number
33180 of minimal, partial, full, and stabs symbols, the number of types
33181 defined by the objfile, the number of as yet unexpanded psym tables,
33182 the number of line tables and string tables, and the amount of memory
33183 used by the various tables. The bcache statistics include the counts,
33184 sizes, and counts of duplicates of all and unique objects, max,
33185 average, and median entry size, total memory used and its overhead and
33186 savings, and various measures of the hash table size and chain
33189 @kindex maint print target-stack
33190 @cindex target stack description
33191 @item maint print target-stack
33192 A @dfn{target} is an interface between the debugger and a particular
33193 kind of file or process. Targets can be stacked in @dfn{strata},
33194 so that more than one target can potentially respond to a request.
33195 In particular, memory accesses will walk down the stack of targets
33196 until they find a target that is interested in handling that particular
33199 This command prints a short description of each layer that was pushed on
33200 the @dfn{target stack}, starting from the top layer down to the bottom one.
33202 @kindex maint print type
33203 @cindex type chain of a data type
33204 @item maint print type @var{expr}
33205 Print the type chain for a type specified by @var{expr}. The argument
33206 can be either a type name or a symbol. If it is a symbol, the type of
33207 that symbol is described. The type chain produced by this command is
33208 a recursive definition of the data type as stored in @value{GDBN}'s
33209 data structures, including its flags and contained types.
33211 @kindex maint set dwarf2 always-disassemble
33212 @kindex maint show dwarf2 always-disassemble
33213 @item maint set dwarf2 always-disassemble
33214 @item maint show dwarf2 always-disassemble
33215 Control the behavior of @code{info address} when using DWARF debugging
33218 The default is @code{off}, which means that @value{GDBN} should try to
33219 describe a variable's location in an easily readable format. When
33220 @code{on}, @value{GDBN} will instead display the DWARF location
33221 expression in an assembly-like format. Note that some locations are
33222 too complex for @value{GDBN} to describe simply; in this case you will
33223 always see the disassembly form.
33225 Here is an example of the resulting disassembly:
33228 (gdb) info addr argc
33229 Symbol "argc" is a complex DWARF expression:
33233 For more information on these expressions, see
33234 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33236 @kindex maint set dwarf2 max-cache-age
33237 @kindex maint show dwarf2 max-cache-age
33238 @item maint set dwarf2 max-cache-age
33239 @itemx maint show dwarf2 max-cache-age
33240 Control the DWARF 2 compilation unit cache.
33242 @cindex DWARF 2 compilation units cache
33243 In object files with inter-compilation-unit references, such as those
33244 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33245 reader needs to frequently refer to previously read compilation units.
33246 This setting controls how long a compilation unit will remain in the
33247 cache if it is not referenced. A higher limit means that cached
33248 compilation units will be stored in memory longer, and more total
33249 memory will be used. Setting it to zero disables caching, which will
33250 slow down @value{GDBN} startup, but reduce memory consumption.
33252 @kindex maint set profile
33253 @kindex maint show profile
33254 @cindex profiling GDB
33255 @item maint set profile
33256 @itemx maint show profile
33257 Control profiling of @value{GDBN}.
33259 Profiling will be disabled until you use the @samp{maint set profile}
33260 command to enable it. When you enable profiling, the system will begin
33261 collecting timing and execution count data; when you disable profiling or
33262 exit @value{GDBN}, the results will be written to a log file. Remember that
33263 if you use profiling, @value{GDBN} will overwrite the profiling log file
33264 (often called @file{gmon.out}). If you have a record of important profiling
33265 data in a @file{gmon.out} file, be sure to move it to a safe location.
33267 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33268 compiled with the @samp{-pg} compiler option.
33270 @kindex maint set show-debug-regs
33271 @kindex maint show show-debug-regs
33272 @cindex hardware debug registers
33273 @item maint set show-debug-regs
33274 @itemx maint show show-debug-regs
33275 Control whether to show variables that mirror the hardware debug
33276 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33277 enabled, the debug registers values are shown when @value{GDBN} inserts or
33278 removes a hardware breakpoint or watchpoint, and when the inferior
33279 triggers a hardware-assisted breakpoint or watchpoint.
33281 @kindex maint set show-all-tib
33282 @kindex maint show show-all-tib
33283 @item maint set show-all-tib
33284 @itemx maint show show-all-tib
33285 Control whether to show all non zero areas within a 1k block starting
33286 at thread local base, when using the @samp{info w32 thread-information-block}
33289 @kindex maint space
33290 @cindex memory used by commands
33292 Control whether to display memory usage for each command. If set to a
33293 nonzero value, @value{GDBN} will display how much memory each command
33294 took, following the command's own output. This can also be requested
33295 by invoking @value{GDBN} with the @option{--statistics} command-line
33296 switch (@pxref{Mode Options}).
33299 @cindex time of command execution
33301 Control whether to display the execution time of @value{GDBN} for each command.
33302 If set to a nonzero value, @value{GDBN} will display how much time it
33303 took to execute each command, following the command's own output.
33304 Both CPU time and wallclock time are printed.
33305 Printing both is useful when trying to determine whether the cost is
33306 CPU or, e.g., disk/network, latency.
33307 Note that the CPU time printed is for @value{GDBN} only, it does not include
33308 the execution time of the inferior because there's no mechanism currently
33309 to compute how much time was spent by @value{GDBN} and how much time was
33310 spent by the program been debugged.
33311 This can also be requested by invoking @value{GDBN} with the
33312 @option{--statistics} command-line switch (@pxref{Mode Options}).
33314 @kindex maint translate-address
33315 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33316 Find the symbol stored at the location specified by the address
33317 @var{addr} and an optional section name @var{section}. If found,
33318 @value{GDBN} prints the name of the closest symbol and an offset from
33319 the symbol's location to the specified address. This is similar to
33320 the @code{info address} command (@pxref{Symbols}), except that this
33321 command also allows to find symbols in other sections.
33323 If section was not specified, the section in which the symbol was found
33324 is also printed. For dynamically linked executables, the name of
33325 executable or shared library containing the symbol is printed as well.
33329 The following command is useful for non-interactive invocations of
33330 @value{GDBN}, such as in the test suite.
33333 @item set watchdog @var{nsec}
33334 @kindex set watchdog
33335 @cindex watchdog timer
33336 @cindex timeout for commands
33337 Set the maximum number of seconds @value{GDBN} will wait for the
33338 target operation to finish. If this time expires, @value{GDBN}
33339 reports and error and the command is aborted.
33341 @item show watchdog
33342 Show the current setting of the target wait timeout.
33345 @node Remote Protocol
33346 @appendix @value{GDBN} Remote Serial Protocol
33351 * Stop Reply Packets::
33352 * General Query Packets::
33353 * Architecture-Specific Protocol Details::
33354 * Tracepoint Packets::
33355 * Host I/O Packets::
33357 * Notification Packets::
33358 * Remote Non-Stop::
33359 * Packet Acknowledgment::
33361 * File-I/O Remote Protocol Extension::
33362 * Library List Format::
33363 * Library List Format for SVR4 Targets::
33364 * Memory Map Format::
33365 * Thread List Format::
33366 * Traceframe Info Format::
33372 There may be occasions when you need to know something about the
33373 protocol---for example, if there is only one serial port to your target
33374 machine, you might want your program to do something special if it
33375 recognizes a packet meant for @value{GDBN}.
33377 In the examples below, @samp{->} and @samp{<-} are used to indicate
33378 transmitted and received data, respectively.
33380 @cindex protocol, @value{GDBN} remote serial
33381 @cindex serial protocol, @value{GDBN} remote
33382 @cindex remote serial protocol
33383 All @value{GDBN} commands and responses (other than acknowledgments
33384 and notifications, see @ref{Notification Packets}) are sent as a
33385 @var{packet}. A @var{packet} is introduced with the character
33386 @samp{$}, the actual @var{packet-data}, and the terminating character
33387 @samp{#} followed by a two-digit @var{checksum}:
33390 @code{$}@var{packet-data}@code{#}@var{checksum}
33394 @cindex checksum, for @value{GDBN} remote
33396 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33397 characters between the leading @samp{$} and the trailing @samp{#} (an
33398 eight bit unsigned checksum).
33400 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33401 specification also included an optional two-digit @var{sequence-id}:
33404 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33407 @cindex sequence-id, for @value{GDBN} remote
33409 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33410 has never output @var{sequence-id}s. Stubs that handle packets added
33411 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33413 When either the host or the target machine receives a packet, the first
33414 response expected is an acknowledgment: either @samp{+} (to indicate
33415 the package was received correctly) or @samp{-} (to request
33419 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33424 The @samp{+}/@samp{-} acknowledgments can be disabled
33425 once a connection is established.
33426 @xref{Packet Acknowledgment}, for details.
33428 The host (@value{GDBN}) sends @var{command}s, and the target (the
33429 debugging stub incorporated in your program) sends a @var{response}. In
33430 the case of step and continue @var{command}s, the response is only sent
33431 when the operation has completed, and the target has again stopped all
33432 threads in all attached processes. This is the default all-stop mode
33433 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33434 execution mode; see @ref{Remote Non-Stop}, for details.
33436 @var{packet-data} consists of a sequence of characters with the
33437 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33440 @cindex remote protocol, field separator
33441 Fields within the packet should be separated using @samp{,} @samp{;} or
33442 @samp{:}. Except where otherwise noted all numbers are represented in
33443 @sc{hex} with leading zeros suppressed.
33445 Implementors should note that prior to @value{GDBN} 5.0, the character
33446 @samp{:} could not appear as the third character in a packet (as it
33447 would potentially conflict with the @var{sequence-id}).
33449 @cindex remote protocol, binary data
33450 @anchor{Binary Data}
33451 Binary data in most packets is encoded either as two hexadecimal
33452 digits per byte of binary data. This allowed the traditional remote
33453 protocol to work over connections which were only seven-bit clean.
33454 Some packets designed more recently assume an eight-bit clean
33455 connection, and use a more efficient encoding to send and receive
33458 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33459 as an escape character. Any escaped byte is transmitted as the escape
33460 character followed by the original character XORed with @code{0x20}.
33461 For example, the byte @code{0x7d} would be transmitted as the two
33462 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33463 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33464 @samp{@}}) must always be escaped. Responses sent by the stub
33465 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33466 is not interpreted as the start of a run-length encoded sequence
33469 Response @var{data} can be run-length encoded to save space.
33470 Run-length encoding replaces runs of identical characters with one
33471 instance of the repeated character, followed by a @samp{*} and a
33472 repeat count. The repeat count is itself sent encoded, to avoid
33473 binary characters in @var{data}: a value of @var{n} is sent as
33474 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33475 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33476 code 32) for a repeat count of 3. (This is because run-length
33477 encoding starts to win for counts 3 or more.) Thus, for example,
33478 @samp{0* } is a run-length encoding of ``0000'': the space character
33479 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33482 The printable characters @samp{#} and @samp{$} or with a numeric value
33483 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33484 seven repeats (@samp{$}) can be expanded using a repeat count of only
33485 five (@samp{"}). For example, @samp{00000000} can be encoded as
33488 The error response returned for some packets includes a two character
33489 error number. That number is not well defined.
33491 @cindex empty response, for unsupported packets
33492 For any @var{command} not supported by the stub, an empty response
33493 (@samp{$#00}) should be returned. That way it is possible to extend the
33494 protocol. A newer @value{GDBN} can tell if a packet is supported based
33497 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33498 commands for register access, and the @samp{m} and @samp{M} commands
33499 for memory access. Stubs that only control single-threaded targets
33500 can implement run control with the @samp{c} (continue), and @samp{s}
33501 (step) commands. Stubs that support multi-threading targets should
33502 support the @samp{vCont} command. All other commands are optional.
33507 The following table provides a complete list of all currently defined
33508 @var{command}s and their corresponding response @var{data}.
33509 @xref{File-I/O Remote Protocol Extension}, for details about the File
33510 I/O extension of the remote protocol.
33512 Each packet's description has a template showing the packet's overall
33513 syntax, followed by an explanation of the packet's meaning. We
33514 include spaces in some of the templates for clarity; these are not
33515 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33516 separate its components. For example, a template like @samp{foo
33517 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33518 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33519 @var{baz}. @value{GDBN} does not transmit a space character between the
33520 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33523 @cindex @var{thread-id}, in remote protocol
33524 @anchor{thread-id syntax}
33525 Several packets and replies include a @var{thread-id} field to identify
33526 a thread. Normally these are positive numbers with a target-specific
33527 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33528 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33531 In addition, the remote protocol supports a multiprocess feature in
33532 which the @var{thread-id} syntax is extended to optionally include both
33533 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33534 The @var{pid} (process) and @var{tid} (thread) components each have the
33535 format described above: a positive number with target-specific
33536 interpretation formatted as a big-endian hex string, literal @samp{-1}
33537 to indicate all processes or threads (respectively), or @samp{0} to
33538 indicate an arbitrary process or thread. Specifying just a process, as
33539 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33540 error to specify all processes but a specific thread, such as
33541 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33542 for those packets and replies explicitly documented to include a process
33543 ID, rather than a @var{thread-id}.
33545 The multiprocess @var{thread-id} syntax extensions are only used if both
33546 @value{GDBN} and the stub report support for the @samp{multiprocess}
33547 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33550 Note that all packet forms beginning with an upper- or lower-case
33551 letter, other than those described here, are reserved for future use.
33553 Here are the packet descriptions.
33558 @cindex @samp{!} packet
33559 @anchor{extended mode}
33560 Enable extended mode. In extended mode, the remote server is made
33561 persistent. The @samp{R} packet is used to restart the program being
33567 The remote target both supports and has enabled extended mode.
33571 @cindex @samp{?} packet
33572 Indicate the reason the target halted. The reply is the same as for
33573 step and continue. This packet has a special interpretation when the
33574 target is in non-stop mode; see @ref{Remote Non-Stop}.
33577 @xref{Stop Reply Packets}, for the reply specifications.
33579 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33580 @cindex @samp{A} packet
33581 Initialized @code{argv[]} array passed into program. @var{arglen}
33582 specifies the number of bytes in the hex encoded byte stream
33583 @var{arg}. See @code{gdbserver} for more details.
33588 The arguments were set.
33594 @cindex @samp{b} packet
33595 (Don't use this packet; its behavior is not well-defined.)
33596 Change the serial line speed to @var{baud}.
33598 JTC: @emph{When does the transport layer state change? When it's
33599 received, or after the ACK is transmitted. In either case, there are
33600 problems if the command or the acknowledgment packet is dropped.}
33602 Stan: @emph{If people really wanted to add something like this, and get
33603 it working for the first time, they ought to modify ser-unix.c to send
33604 some kind of out-of-band message to a specially-setup stub and have the
33605 switch happen "in between" packets, so that from remote protocol's point
33606 of view, nothing actually happened.}
33608 @item B @var{addr},@var{mode}
33609 @cindex @samp{B} packet
33610 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33611 breakpoint at @var{addr}.
33613 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33614 (@pxref{insert breakpoint or watchpoint packet}).
33616 @cindex @samp{bc} packet
33619 Backward continue. Execute the target system in reverse. No parameter.
33620 @xref{Reverse Execution}, for more information.
33623 @xref{Stop Reply Packets}, for the reply specifications.
33625 @cindex @samp{bs} packet
33628 Backward single step. Execute one instruction in reverse. No parameter.
33629 @xref{Reverse Execution}, for more information.
33632 @xref{Stop Reply Packets}, for the reply specifications.
33634 @item c @r{[}@var{addr}@r{]}
33635 @cindex @samp{c} packet
33636 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33637 resume at current address.
33639 This packet is deprecated for multi-threading support. @xref{vCont
33643 @xref{Stop Reply Packets}, for the reply specifications.
33645 @item C @var{sig}@r{[};@var{addr}@r{]}
33646 @cindex @samp{C} packet
33647 Continue with signal @var{sig} (hex signal number). If
33648 @samp{;@var{addr}} is omitted, resume at same address.
33650 This packet is deprecated for multi-threading support. @xref{vCont
33654 @xref{Stop Reply Packets}, for the reply specifications.
33657 @cindex @samp{d} packet
33660 Don't use this packet; instead, define a general set packet
33661 (@pxref{General Query Packets}).
33665 @cindex @samp{D} packet
33666 The first form of the packet is used to detach @value{GDBN} from the
33667 remote system. It is sent to the remote target
33668 before @value{GDBN} disconnects via the @code{detach} command.
33670 The second form, including a process ID, is used when multiprocess
33671 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33672 detach only a specific process. The @var{pid} is specified as a
33673 big-endian hex string.
33683 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33684 @cindex @samp{F} packet
33685 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33686 This is part of the File-I/O protocol extension. @xref{File-I/O
33687 Remote Protocol Extension}, for the specification.
33690 @anchor{read registers packet}
33691 @cindex @samp{g} packet
33692 Read general registers.
33696 @item @var{XX@dots{}}
33697 Each byte of register data is described by two hex digits. The bytes
33698 with the register are transmitted in target byte order. The size of
33699 each register and their position within the @samp{g} packet are
33700 determined by the @value{GDBN} internal gdbarch functions
33701 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33702 specification of several standard @samp{g} packets is specified below.
33704 When reading registers from a trace frame (@pxref{Analyze Collected
33705 Data,,Using the Collected Data}), the stub may also return a string of
33706 literal @samp{x}'s in place of the register data digits, to indicate
33707 that the corresponding register has not been collected, thus its value
33708 is unavailable. For example, for an architecture with 4 registers of
33709 4 bytes each, the following reply indicates to @value{GDBN} that
33710 registers 0 and 2 have not been collected, while registers 1 and 3
33711 have been collected, and both have zero value:
33715 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33722 @item G @var{XX@dots{}}
33723 @cindex @samp{G} packet
33724 Write general registers. @xref{read registers packet}, for a
33725 description of the @var{XX@dots{}} data.
33735 @item H @var{op} @var{thread-id}
33736 @cindex @samp{H} packet
33737 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33738 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33739 it should be @samp{c} for step and continue operations (note that this
33740 is deprecated, supporting the @samp{vCont} command is a better
33741 option), @samp{g} for other operations. The thread designator
33742 @var{thread-id} has the format and interpretation described in
33743 @ref{thread-id syntax}.
33754 @c 'H': How restrictive (or permissive) is the thread model. If a
33755 @c thread is selected and stopped, are other threads allowed
33756 @c to continue to execute? As I mentioned above, I think the
33757 @c semantics of each command when a thread is selected must be
33758 @c described. For example:
33760 @c 'g': If the stub supports threads and a specific thread is
33761 @c selected, returns the register block from that thread;
33762 @c otherwise returns current registers.
33764 @c 'G' If the stub supports threads and a specific thread is
33765 @c selected, sets the registers of the register block of
33766 @c that thread; otherwise sets current registers.
33768 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33769 @anchor{cycle step packet}
33770 @cindex @samp{i} packet
33771 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33772 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33773 step starting at that address.
33776 @cindex @samp{I} packet
33777 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33781 @cindex @samp{k} packet
33784 FIXME: @emph{There is no description of how to operate when a specific
33785 thread context has been selected (i.e.@: does 'k' kill only that
33788 @item m @var{addr},@var{length}
33789 @cindex @samp{m} packet
33790 Read @var{length} bytes of memory starting at address @var{addr}.
33791 Note that @var{addr} may not be aligned to any particular boundary.
33793 The stub need not use any particular size or alignment when gathering
33794 data from memory for the response; even if @var{addr} is word-aligned
33795 and @var{length} is a multiple of the word size, the stub is free to
33796 use byte accesses, or not. For this reason, this packet may not be
33797 suitable for accessing memory-mapped I/O devices.
33798 @cindex alignment of remote memory accesses
33799 @cindex size of remote memory accesses
33800 @cindex memory, alignment and size of remote accesses
33804 @item @var{XX@dots{}}
33805 Memory contents; each byte is transmitted as a two-digit hexadecimal
33806 number. The reply may contain fewer bytes than requested if the
33807 server was able to read only part of the region of memory.
33812 @item M @var{addr},@var{length}:@var{XX@dots{}}
33813 @cindex @samp{M} packet
33814 Write @var{length} bytes of memory starting at address @var{addr}.
33815 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33816 hexadecimal number.
33823 for an error (this includes the case where only part of the data was
33828 @cindex @samp{p} packet
33829 Read the value of register @var{n}; @var{n} is in hex.
33830 @xref{read registers packet}, for a description of how the returned
33831 register value is encoded.
33835 @item @var{XX@dots{}}
33836 the register's value
33840 Indicating an unrecognized @var{query}.
33843 @item P @var{n@dots{}}=@var{r@dots{}}
33844 @anchor{write register packet}
33845 @cindex @samp{P} packet
33846 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33847 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33848 digits for each byte in the register (target byte order).
33858 @item q @var{name} @var{params}@dots{}
33859 @itemx Q @var{name} @var{params}@dots{}
33860 @cindex @samp{q} packet
33861 @cindex @samp{Q} packet
33862 General query (@samp{q}) and set (@samp{Q}). These packets are
33863 described fully in @ref{General Query Packets}.
33866 @cindex @samp{r} packet
33867 Reset the entire system.
33869 Don't use this packet; use the @samp{R} packet instead.
33872 @cindex @samp{R} packet
33873 Restart the program being debugged. @var{XX}, while needed, is ignored.
33874 This packet is only available in extended mode (@pxref{extended mode}).
33876 The @samp{R} packet has no reply.
33878 @item s @r{[}@var{addr}@r{]}
33879 @cindex @samp{s} packet
33880 Single step. @var{addr} is the address at which to resume. If
33881 @var{addr} is omitted, resume at same address.
33883 This packet is deprecated for multi-threading support. @xref{vCont
33887 @xref{Stop Reply Packets}, for the reply specifications.
33889 @item S @var{sig}@r{[};@var{addr}@r{]}
33890 @anchor{step with signal packet}
33891 @cindex @samp{S} packet
33892 Step with signal. This is analogous to the @samp{C} packet, but
33893 requests a single-step, rather than a normal resumption of execution.
33895 This packet is deprecated for multi-threading support. @xref{vCont
33899 @xref{Stop Reply Packets}, for the reply specifications.
33901 @item t @var{addr}:@var{PP},@var{MM}
33902 @cindex @samp{t} packet
33903 Search backwards starting at address @var{addr} for a match with pattern
33904 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33905 @var{addr} must be at least 3 digits.
33907 @item T @var{thread-id}
33908 @cindex @samp{T} packet
33909 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33914 thread is still alive
33920 Packets starting with @samp{v} are identified by a multi-letter name,
33921 up to the first @samp{;} or @samp{?} (or the end of the packet).
33923 @item vAttach;@var{pid}
33924 @cindex @samp{vAttach} packet
33925 Attach to a new process with the specified process ID @var{pid}.
33926 The process ID is a
33927 hexadecimal integer identifying the process. In all-stop mode, all
33928 threads in the attached process are stopped; in non-stop mode, it may be
33929 attached without being stopped if that is supported by the target.
33931 @c In non-stop mode, on a successful vAttach, the stub should set the
33932 @c current thread to a thread of the newly-attached process. After
33933 @c attaching, GDB queries for the attached process's thread ID with qC.
33934 @c Also note that, from a user perspective, whether or not the
33935 @c target is stopped on attach in non-stop mode depends on whether you
33936 @c use the foreground or background version of the attach command, not
33937 @c on what vAttach does; GDB does the right thing with respect to either
33938 @c stopping or restarting threads.
33940 This packet is only available in extended mode (@pxref{extended mode}).
33946 @item @r{Any stop packet}
33947 for success in all-stop mode (@pxref{Stop Reply Packets})
33949 for success in non-stop mode (@pxref{Remote Non-Stop})
33952 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33953 @cindex @samp{vCont} packet
33954 @anchor{vCont packet}
33955 Resume the inferior, specifying different actions for each thread.
33956 If an action is specified with no @var{thread-id}, then it is applied to any
33957 threads that don't have a specific action specified; if no default action is
33958 specified then other threads should remain stopped in all-stop mode and
33959 in their current state in non-stop mode.
33960 Specifying multiple
33961 default actions is an error; specifying no actions is also an error.
33962 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33964 Currently supported actions are:
33970 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33974 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33979 The optional argument @var{addr} normally associated with the
33980 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33981 not supported in @samp{vCont}.
33983 The @samp{t} action is only relevant in non-stop mode
33984 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33985 A stop reply should be generated for any affected thread not already stopped.
33986 When a thread is stopped by means of a @samp{t} action,
33987 the corresponding stop reply should indicate that the thread has stopped with
33988 signal @samp{0}, regardless of whether the target uses some other signal
33989 as an implementation detail.
33992 @xref{Stop Reply Packets}, for the reply specifications.
33995 @cindex @samp{vCont?} packet
33996 Request a list of actions supported by the @samp{vCont} packet.
34000 @item vCont@r{[};@var{action}@dots{}@r{]}
34001 The @samp{vCont} packet is supported. Each @var{action} is a supported
34002 command in the @samp{vCont} packet.
34004 The @samp{vCont} packet is not supported.
34007 @item vFile:@var{operation}:@var{parameter}@dots{}
34008 @cindex @samp{vFile} packet
34009 Perform a file operation on the target system. For details,
34010 see @ref{Host I/O Packets}.
34012 @item vFlashErase:@var{addr},@var{length}
34013 @cindex @samp{vFlashErase} packet
34014 Direct the stub to erase @var{length} bytes of flash starting at
34015 @var{addr}. The region may enclose any number of flash blocks, but
34016 its start and end must fall on block boundaries, as indicated by the
34017 flash block size appearing in the memory map (@pxref{Memory Map
34018 Format}). @value{GDBN} groups flash memory programming operations
34019 together, and sends a @samp{vFlashDone} request after each group; the
34020 stub is allowed to delay erase operation until the @samp{vFlashDone}
34021 packet is received.
34023 The stub must support @samp{vCont} if it reports support for
34024 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34025 this case @samp{vCont} actions can be specified to apply to all threads
34026 in a process by using the @samp{p@var{pid}.-1} form of the
34037 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34038 @cindex @samp{vFlashWrite} packet
34039 Direct the stub to write data to flash address @var{addr}. The data
34040 is passed in binary form using the same encoding as for the @samp{X}
34041 packet (@pxref{Binary Data}). The memory ranges specified by
34042 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34043 not overlap, and must appear in order of increasing addresses
34044 (although @samp{vFlashErase} packets for higher addresses may already
34045 have been received; the ordering is guaranteed only between
34046 @samp{vFlashWrite} packets). If a packet writes to an address that was
34047 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34048 target-specific method, the results are unpredictable.
34056 for vFlashWrite addressing non-flash memory
34062 @cindex @samp{vFlashDone} packet
34063 Indicate to the stub that flash programming operation is finished.
34064 The stub is permitted to delay or batch the effects of a group of
34065 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34066 @samp{vFlashDone} packet is received. The contents of the affected
34067 regions of flash memory are unpredictable until the @samp{vFlashDone}
34068 request is completed.
34070 @item vKill;@var{pid}
34071 @cindex @samp{vKill} packet
34072 Kill the process with the specified process ID. @var{pid} is a
34073 hexadecimal integer identifying the process. This packet is used in
34074 preference to @samp{k} when multiprocess protocol extensions are
34075 supported; see @ref{multiprocess extensions}.
34085 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34086 @cindex @samp{vRun} packet
34087 Run the program @var{filename}, passing it each @var{argument} on its
34088 command line. The file and arguments are hex-encoded strings. If
34089 @var{filename} is an empty string, the stub may use a default program
34090 (e.g.@: the last program run). The program is created in the stopped
34093 @c FIXME: What about non-stop mode?
34095 This packet is only available in extended mode (@pxref{extended mode}).
34101 @item @r{Any stop packet}
34102 for success (@pxref{Stop Reply Packets})
34106 @anchor{vStopped packet}
34107 @cindex @samp{vStopped} packet
34109 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34110 reply and prompt for the stub to report another one.
34114 @item @r{Any stop packet}
34115 if there is another unreported stop event (@pxref{Stop Reply Packets})
34117 if there are no unreported stop events
34120 @item X @var{addr},@var{length}:@var{XX@dots{}}
34122 @cindex @samp{X} packet
34123 Write data to memory, where the data is transmitted in binary.
34124 @var{addr} is address, @var{length} is number of bytes,
34125 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34135 @item z @var{type},@var{addr},@var{kind}
34136 @itemx Z @var{type},@var{addr},@var{kind}
34137 @anchor{insert breakpoint or watchpoint packet}
34138 @cindex @samp{z} packet
34139 @cindex @samp{Z} packets
34140 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34141 watchpoint starting at address @var{address} of kind @var{kind}.
34143 Each breakpoint and watchpoint packet @var{type} is documented
34146 @emph{Implementation notes: A remote target shall return an empty string
34147 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34148 remote target shall support either both or neither of a given
34149 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34150 avoid potential problems with duplicate packets, the operations should
34151 be implemented in an idempotent way.}
34153 @item z0,@var{addr},@var{kind}
34154 @itemx Z0,@var{addr},@var{kind}
34155 @cindex @samp{z0} packet
34156 @cindex @samp{Z0} packet
34157 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34158 @var{addr} of type @var{kind}.
34160 A memory breakpoint is implemented by replacing the instruction at
34161 @var{addr} with a software breakpoint or trap instruction. The
34162 @var{kind} is target-specific and typically indicates the size of
34163 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34164 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34165 architectures have additional meanings for @var{kind};
34166 see @ref{Architecture-Specific Protocol Details}.
34168 @emph{Implementation note: It is possible for a target to copy or move
34169 code that contains memory breakpoints (e.g., when implementing
34170 overlays). The behavior of this packet, in the presence of such a
34171 target, is not defined.}
34183 @item z1,@var{addr},@var{kind}
34184 @itemx Z1,@var{addr},@var{kind}
34185 @cindex @samp{z1} packet
34186 @cindex @samp{Z1} packet
34187 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34188 address @var{addr}.
34190 A hardware breakpoint is implemented using a mechanism that is not
34191 dependant on being able to modify the target's memory. @var{kind}
34192 has the same meaning as in @samp{Z0} packets.
34194 @emph{Implementation note: A hardware breakpoint is not affected by code
34207 @item z2,@var{addr},@var{kind}
34208 @itemx Z2,@var{addr},@var{kind}
34209 @cindex @samp{z2} packet
34210 @cindex @samp{Z2} packet
34211 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34212 @var{kind} is interpreted as the number of bytes to watch.
34224 @item z3,@var{addr},@var{kind}
34225 @itemx Z3,@var{addr},@var{kind}
34226 @cindex @samp{z3} packet
34227 @cindex @samp{Z3} packet
34228 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34229 @var{kind} is interpreted as the number of bytes to watch.
34241 @item z4,@var{addr},@var{kind}
34242 @itemx Z4,@var{addr},@var{kind}
34243 @cindex @samp{z4} packet
34244 @cindex @samp{Z4} packet
34245 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34246 @var{kind} is interpreted as the number of bytes to watch.
34260 @node Stop Reply Packets
34261 @section Stop Reply Packets
34262 @cindex stop reply packets
34264 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34265 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34266 receive any of the below as a reply. Except for @samp{?}
34267 and @samp{vStopped}, that reply is only returned
34268 when the target halts. In the below the exact meaning of @dfn{signal
34269 number} is defined by the header @file{include/gdb/signals.h} in the
34270 @value{GDBN} source code.
34272 As in the description of request packets, we include spaces in the
34273 reply templates for clarity; these are not part of the reply packet's
34274 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34280 The program received signal number @var{AA} (a two-digit hexadecimal
34281 number). This is equivalent to a @samp{T} response with no
34282 @var{n}:@var{r} pairs.
34284 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34285 @cindex @samp{T} packet reply
34286 The program received signal number @var{AA} (a two-digit hexadecimal
34287 number). This is equivalent to an @samp{S} response, except that the
34288 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34289 and other information directly in the stop reply packet, reducing
34290 round-trip latency. Single-step and breakpoint traps are reported
34291 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34295 If @var{n} is a hexadecimal number, it is a register number, and the
34296 corresponding @var{r} gives that register's value. @var{r} is a
34297 series of bytes in target byte order, with each byte given by a
34298 two-digit hex number.
34301 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34302 the stopped thread, as specified in @ref{thread-id syntax}.
34305 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34306 the core on which the stop event was detected.
34309 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34310 specific event that stopped the target. The currently defined stop
34311 reasons are listed below. @var{aa} should be @samp{05}, the trap
34312 signal. At most one stop reason should be present.
34315 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34316 and go on to the next; this allows us to extend the protocol in the
34320 The currently defined stop reasons are:
34326 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34329 @cindex shared library events, remote reply
34331 The packet indicates that the loaded libraries have changed.
34332 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34333 list of loaded libraries. @var{r} is ignored.
34335 @cindex replay log events, remote reply
34337 The packet indicates that the target cannot continue replaying
34338 logged execution events, because it has reached the end (or the
34339 beginning when executing backward) of the log. The value of @var{r}
34340 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34341 for more information.
34345 @itemx W @var{AA} ; process:@var{pid}
34346 The process exited, and @var{AA} is the exit status. This is only
34347 applicable to certain targets.
34349 The second form of the response, including the process ID of the exited
34350 process, can be used only when @value{GDBN} has reported support for
34351 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34352 The @var{pid} is formatted as a big-endian hex string.
34355 @itemx X @var{AA} ; process:@var{pid}
34356 The process terminated with signal @var{AA}.
34358 The second form of the response, including the process ID of the
34359 terminated process, can be used only when @value{GDBN} has reported
34360 support for multiprocess protocol extensions; see @ref{multiprocess
34361 extensions}. The @var{pid} is formatted as a big-endian hex string.
34363 @item O @var{XX}@dots{}
34364 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34365 written as the program's console output. This can happen at any time
34366 while the program is running and the debugger should continue to wait
34367 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34369 @item F @var{call-id},@var{parameter}@dots{}
34370 @var{call-id} is the identifier which says which host system call should
34371 be called. This is just the name of the function. Translation into the
34372 correct system call is only applicable as it's defined in @value{GDBN}.
34373 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34376 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34377 this very system call.
34379 The target replies with this packet when it expects @value{GDBN} to
34380 call a host system call on behalf of the target. @value{GDBN} replies
34381 with an appropriate @samp{F} packet and keeps up waiting for the next
34382 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34383 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34384 Protocol Extension}, for more details.
34388 @node General Query Packets
34389 @section General Query Packets
34390 @cindex remote query requests
34392 Packets starting with @samp{q} are @dfn{general query packets};
34393 packets starting with @samp{Q} are @dfn{general set packets}. General
34394 query and set packets are a semi-unified form for retrieving and
34395 sending information to and from the stub.
34397 The initial letter of a query or set packet is followed by a name
34398 indicating what sort of thing the packet applies to. For example,
34399 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34400 definitions with the stub. These packet names follow some
34405 The name must not contain commas, colons or semicolons.
34407 Most @value{GDBN} query and set packets have a leading upper case
34410 The names of custom vendor packets should use a company prefix, in
34411 lower case, followed by a period. For example, packets designed at
34412 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34413 foos) or @samp{Qacme.bar} (for setting bars).
34416 The name of a query or set packet should be separated from any
34417 parameters by a @samp{:}; the parameters themselves should be
34418 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34419 full packet name, and check for a separator or the end of the packet,
34420 in case two packet names share a common prefix. New packets should not begin
34421 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34422 packets predate these conventions, and have arguments without any terminator
34423 for the packet name; we suspect they are in widespread use in places that
34424 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34425 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34428 Like the descriptions of the other packets, each description here
34429 has a template showing the packet's overall syntax, followed by an
34430 explanation of the packet's meaning. We include spaces in some of the
34431 templates for clarity; these are not part of the packet's syntax. No
34432 @value{GDBN} packet uses spaces to separate its components.
34434 Here are the currently defined query and set packets:
34438 @item QAllow:@var{op}:@var{val}@dots{}
34439 @cindex @samp{QAllow} packet
34440 Specify which operations @value{GDBN} expects to request of the
34441 target, as a semicolon-separated list of operation name and value
34442 pairs. Possible values for @var{op} include @samp{WriteReg},
34443 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34444 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34445 indicating that @value{GDBN} will not request the operation, or 1,
34446 indicating that it may. (The target can then use this to set up its
34447 own internals optimally, for instance if the debugger never expects to
34448 insert breakpoints, it may not need to install its own trap handler.)
34451 @cindex current thread, remote request
34452 @cindex @samp{qC} packet
34453 Return the current thread ID.
34457 @item QC @var{thread-id}
34458 Where @var{thread-id} is a thread ID as documented in
34459 @ref{thread-id syntax}.
34460 @item @r{(anything else)}
34461 Any other reply implies the old thread ID.
34464 @item qCRC:@var{addr},@var{length}
34465 @cindex CRC of memory block, remote request
34466 @cindex @samp{qCRC} packet
34467 Compute the CRC checksum of a block of memory using CRC-32 defined in
34468 IEEE 802.3. The CRC is computed byte at a time, taking the most
34469 significant bit of each byte first. The initial pattern code
34470 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34472 @emph{Note:} This is the same CRC used in validating separate debug
34473 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34474 Files}). However the algorithm is slightly different. When validating
34475 separate debug files, the CRC is computed taking the @emph{least}
34476 significant bit of each byte first, and the final result is inverted to
34477 detect trailing zeros.
34482 An error (such as memory fault)
34483 @item C @var{crc32}
34484 The specified memory region's checksum is @var{crc32}.
34487 @item QDisableRandomization:@var{value}
34488 @cindex disable address space randomization, remote request
34489 @cindex @samp{QDisableRandomization} packet
34490 Some target operating systems will randomize the virtual address space
34491 of the inferior process as a security feature, but provide a feature
34492 to disable such randomization, e.g.@: to allow for a more deterministic
34493 debugging experience. On such systems, this packet with a @var{value}
34494 of 1 directs the target to disable address space randomization for
34495 processes subsequently started via @samp{vRun} packets, while a packet
34496 with a @var{value} of 0 tells the target to enable address space
34499 This packet is only available in extended mode (@pxref{extended mode}).
34504 The request succeeded.
34507 An error occurred. @var{nn} are hex digits.
34510 An empty reply indicates that @samp{QDisableRandomization} is not supported
34514 This packet is not probed by default; the remote stub must request it,
34515 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34516 This should only be done on targets that actually support disabling
34517 address space randomization.
34520 @itemx qsThreadInfo
34521 @cindex list active threads, remote request
34522 @cindex @samp{qfThreadInfo} packet
34523 @cindex @samp{qsThreadInfo} packet
34524 Obtain a list of all active thread IDs from the target (OS). Since there
34525 may be too many active threads to fit into one reply packet, this query
34526 works iteratively: it may require more than one query/reply sequence to
34527 obtain the entire list of threads. The first query of the sequence will
34528 be the @samp{qfThreadInfo} query; subsequent queries in the
34529 sequence will be the @samp{qsThreadInfo} query.
34531 NOTE: This packet replaces the @samp{qL} query (see below).
34535 @item m @var{thread-id}
34537 @item m @var{thread-id},@var{thread-id}@dots{}
34538 a comma-separated list of thread IDs
34540 (lower case letter @samp{L}) denotes end of list.
34543 In response to each query, the target will reply with a list of one or
34544 more thread IDs, separated by commas.
34545 @value{GDBN} will respond to each reply with a request for more thread
34546 ids (using the @samp{qs} form of the query), until the target responds
34547 with @samp{l} (lower-case ell, for @dfn{last}).
34548 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34551 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34552 @cindex get thread-local storage address, remote request
34553 @cindex @samp{qGetTLSAddr} packet
34554 Fetch the address associated with thread local storage specified
34555 by @var{thread-id}, @var{offset}, and @var{lm}.
34557 @var{thread-id} is the thread ID associated with the
34558 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34560 @var{offset} is the (big endian, hex encoded) offset associated with the
34561 thread local variable. (This offset is obtained from the debug
34562 information associated with the variable.)
34564 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34565 load module associated with the thread local storage. For example,
34566 a @sc{gnu}/Linux system will pass the link map address of the shared
34567 object associated with the thread local storage under consideration.
34568 Other operating environments may choose to represent the load module
34569 differently, so the precise meaning of this parameter will vary.
34573 @item @var{XX}@dots{}
34574 Hex encoded (big endian) bytes representing the address of the thread
34575 local storage requested.
34578 An error occurred. @var{nn} are hex digits.
34581 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34584 @item qGetTIBAddr:@var{thread-id}
34585 @cindex get thread information block address
34586 @cindex @samp{qGetTIBAddr} packet
34587 Fetch address of the Windows OS specific Thread Information Block.
34589 @var{thread-id} is the thread ID associated with the thread.
34593 @item @var{XX}@dots{}
34594 Hex encoded (big endian) bytes representing the linear address of the
34595 thread information block.
34598 An error occured. This means that either the thread was not found, or the
34599 address could not be retrieved.
34602 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34605 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34606 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34607 digit) is one to indicate the first query and zero to indicate a
34608 subsequent query; @var{threadcount} (two hex digits) is the maximum
34609 number of threads the response packet can contain; and @var{nextthread}
34610 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34611 returned in the response as @var{argthread}.
34613 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34617 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34618 Where: @var{count} (two hex digits) is the number of threads being
34619 returned; @var{done} (one hex digit) is zero to indicate more threads
34620 and one indicates no further threads; @var{argthreadid} (eight hex
34621 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34622 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34623 digits). See @code{remote.c:parse_threadlist_response()}.
34627 @cindex section offsets, remote request
34628 @cindex @samp{qOffsets} packet
34629 Get section offsets that the target used when relocating the downloaded
34634 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34635 Relocate the @code{Text} section by @var{xxx} from its original address.
34636 Relocate the @code{Data} section by @var{yyy} from its original address.
34637 If the object file format provides segment information (e.g.@: @sc{elf}
34638 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34639 segments by the supplied offsets.
34641 @emph{Note: while a @code{Bss} offset may be included in the response,
34642 @value{GDBN} ignores this and instead applies the @code{Data} offset
34643 to the @code{Bss} section.}
34645 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34646 Relocate the first segment of the object file, which conventionally
34647 contains program code, to a starting address of @var{xxx}. If
34648 @samp{DataSeg} is specified, relocate the second segment, which
34649 conventionally contains modifiable data, to a starting address of
34650 @var{yyy}. @value{GDBN} will report an error if the object file
34651 does not contain segment information, or does not contain at least
34652 as many segments as mentioned in the reply. Extra segments are
34653 kept at fixed offsets relative to the last relocated segment.
34656 @item qP @var{mode} @var{thread-id}
34657 @cindex thread information, remote request
34658 @cindex @samp{qP} packet
34659 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34660 encoded 32 bit mode; @var{thread-id} is a thread ID
34661 (@pxref{thread-id syntax}).
34663 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34666 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34670 @cindex non-stop mode, remote request
34671 @cindex @samp{QNonStop} packet
34673 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34674 @xref{Remote Non-Stop}, for more information.
34679 The request succeeded.
34682 An error occurred. @var{nn} are hex digits.
34685 An empty reply indicates that @samp{QNonStop} is not supported by
34689 This packet is not probed by default; the remote stub must request it,
34690 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34691 Use of this packet is controlled by the @code{set non-stop} command;
34692 @pxref{Non-Stop Mode}.
34694 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34695 @cindex pass signals to inferior, remote request
34696 @cindex @samp{QPassSignals} packet
34697 @anchor{QPassSignals}
34698 Each listed @var{signal} should be passed directly to the inferior process.
34699 Signals are numbered identically to continue packets and stop replies
34700 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34701 strictly greater than the previous item. These signals do not need to stop
34702 the inferior, or be reported to @value{GDBN}. All other signals should be
34703 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34704 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34705 new list. This packet improves performance when using @samp{handle
34706 @var{signal} nostop noprint pass}.
34711 The request succeeded.
34714 An error occurred. @var{nn} are hex digits.
34717 An empty reply indicates that @samp{QPassSignals} is not supported by
34721 Use of this packet is controlled by the @code{set remote pass-signals}
34722 command (@pxref{Remote Configuration, set remote pass-signals}).
34723 This packet is not probed by default; the remote stub must request it,
34724 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34726 @item qRcmd,@var{command}
34727 @cindex execute remote command, remote request
34728 @cindex @samp{qRcmd} packet
34729 @var{command} (hex encoded) is passed to the local interpreter for
34730 execution. Invalid commands should be reported using the output
34731 string. Before the final result packet, the target may also respond
34732 with a number of intermediate @samp{O@var{output}} console output
34733 packets. @emph{Implementors should note that providing access to a
34734 stubs's interpreter may have security implications}.
34739 A command response with no output.
34741 A command response with the hex encoded output string @var{OUTPUT}.
34743 Indicate a badly formed request.
34745 An empty reply indicates that @samp{qRcmd} is not recognized.
34748 (Note that the @code{qRcmd} packet's name is separated from the
34749 command by a @samp{,}, not a @samp{:}, contrary to the naming
34750 conventions above. Please don't use this packet as a model for new
34753 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34754 @cindex searching memory, in remote debugging
34755 @cindex @samp{qSearch:memory} packet
34756 @anchor{qSearch memory}
34757 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34758 @var{address} and @var{length} are encoded in hex.
34759 @var{search-pattern} is a sequence of bytes, hex encoded.
34764 The pattern was not found.
34766 The pattern was found at @var{address}.
34768 A badly formed request or an error was encountered while searching memory.
34770 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34773 @item QStartNoAckMode
34774 @cindex @samp{QStartNoAckMode} packet
34775 @anchor{QStartNoAckMode}
34776 Request that the remote stub disable the normal @samp{+}/@samp{-}
34777 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34782 The stub has switched to no-acknowledgment mode.
34783 @value{GDBN} acknowledges this reponse,
34784 but neither the stub nor @value{GDBN} shall send or expect further
34785 @samp{+}/@samp{-} acknowledgments in the current connection.
34787 An empty reply indicates that the stub does not support no-acknowledgment mode.
34790 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34791 @cindex supported packets, remote query
34792 @cindex features of the remote protocol
34793 @cindex @samp{qSupported} packet
34794 @anchor{qSupported}
34795 Tell the remote stub about features supported by @value{GDBN}, and
34796 query the stub for features it supports. This packet allows
34797 @value{GDBN} and the remote stub to take advantage of each others'
34798 features. @samp{qSupported} also consolidates multiple feature probes
34799 at startup, to improve @value{GDBN} performance---a single larger
34800 packet performs better than multiple smaller probe packets on
34801 high-latency links. Some features may enable behavior which must not
34802 be on by default, e.g.@: because it would confuse older clients or
34803 stubs. Other features may describe packets which could be
34804 automatically probed for, but are not. These features must be
34805 reported before @value{GDBN} will use them. This ``default
34806 unsupported'' behavior is not appropriate for all packets, but it
34807 helps to keep the initial connection time under control with new
34808 versions of @value{GDBN} which support increasing numbers of packets.
34812 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34813 The stub supports or does not support each returned @var{stubfeature},
34814 depending on the form of each @var{stubfeature} (see below for the
34817 An empty reply indicates that @samp{qSupported} is not recognized,
34818 or that no features needed to be reported to @value{GDBN}.
34821 The allowed forms for each feature (either a @var{gdbfeature} in the
34822 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34826 @item @var{name}=@var{value}
34827 The remote protocol feature @var{name} is supported, and associated
34828 with the specified @var{value}. The format of @var{value} depends
34829 on the feature, but it must not include a semicolon.
34831 The remote protocol feature @var{name} is supported, and does not
34832 need an associated value.
34834 The remote protocol feature @var{name} is not supported.
34836 The remote protocol feature @var{name} may be supported, and
34837 @value{GDBN} should auto-detect support in some other way when it is
34838 needed. This form will not be used for @var{gdbfeature} notifications,
34839 but may be used for @var{stubfeature} responses.
34842 Whenever the stub receives a @samp{qSupported} request, the
34843 supplied set of @value{GDBN} features should override any previous
34844 request. This allows @value{GDBN} to put the stub in a known
34845 state, even if the stub had previously been communicating with
34846 a different version of @value{GDBN}.
34848 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34853 This feature indicates whether @value{GDBN} supports multiprocess
34854 extensions to the remote protocol. @value{GDBN} does not use such
34855 extensions unless the stub also reports that it supports them by
34856 including @samp{multiprocess+} in its @samp{qSupported} reply.
34857 @xref{multiprocess extensions}, for details.
34860 This feature indicates that @value{GDBN} supports the XML target
34861 description. If the stub sees @samp{xmlRegisters=} with target
34862 specific strings separated by a comma, it will report register
34866 This feature indicates whether @value{GDBN} supports the
34867 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34868 instruction reply packet}).
34871 Stubs should ignore any unknown values for
34872 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34873 packet supports receiving packets of unlimited length (earlier
34874 versions of @value{GDBN} may reject overly long responses). Additional values
34875 for @var{gdbfeature} may be defined in the future to let the stub take
34876 advantage of new features in @value{GDBN}, e.g.@: incompatible
34877 improvements in the remote protocol---the @samp{multiprocess} feature is
34878 an example of such a feature. The stub's reply should be independent
34879 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34880 describes all the features it supports, and then the stub replies with
34881 all the features it supports.
34883 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34884 responses, as long as each response uses one of the standard forms.
34886 Some features are flags. A stub which supports a flag feature
34887 should respond with a @samp{+} form response. Other features
34888 require values, and the stub should respond with an @samp{=}
34891 Each feature has a default value, which @value{GDBN} will use if
34892 @samp{qSupported} is not available or if the feature is not mentioned
34893 in the @samp{qSupported} response. The default values are fixed; a
34894 stub is free to omit any feature responses that match the defaults.
34896 Not all features can be probed, but for those which can, the probing
34897 mechanism is useful: in some cases, a stub's internal
34898 architecture may not allow the protocol layer to know some information
34899 about the underlying target in advance. This is especially common in
34900 stubs which may be configured for multiple targets.
34902 These are the currently defined stub features and their properties:
34904 @multitable @columnfractions 0.35 0.2 0.12 0.2
34905 @c NOTE: The first row should be @headitem, but we do not yet require
34906 @c a new enough version of Texinfo (4.7) to use @headitem.
34908 @tab Value Required
34912 @item @samp{PacketSize}
34917 @item @samp{qXfer:auxv:read}
34922 @item @samp{qXfer:features:read}
34927 @item @samp{qXfer:libraries:read}
34932 @item @samp{qXfer:memory-map:read}
34937 @item @samp{qXfer:sdata:read}
34942 @item @samp{qXfer:spu:read}
34947 @item @samp{qXfer:spu:write}
34952 @item @samp{qXfer:siginfo:read}
34957 @item @samp{qXfer:siginfo:write}
34962 @item @samp{qXfer:threads:read}
34967 @item @samp{qXfer:traceframe-info:read}
34972 @item @samp{qXfer:fdpic:read}
34977 @item @samp{QNonStop}
34982 @item @samp{QPassSignals}
34987 @item @samp{QStartNoAckMode}
34992 @item @samp{multiprocess}
34997 @item @samp{ConditionalTracepoints}
35002 @item @samp{ReverseContinue}
35007 @item @samp{ReverseStep}
35012 @item @samp{TracepointSource}
35017 @item @samp{QAllow}
35022 @item @samp{QDisableRandomization}
35027 @item @samp{EnableDisableTracepoints}
35032 @item @samp{tracenz}
35039 These are the currently defined stub features, in more detail:
35042 @cindex packet size, remote protocol
35043 @item PacketSize=@var{bytes}
35044 The remote stub can accept packets up to at least @var{bytes} in
35045 length. @value{GDBN} will send packets up to this size for bulk
35046 transfers, and will never send larger packets. This is a limit on the
35047 data characters in the packet, including the frame and checksum.
35048 There is no trailing NUL byte in a remote protocol packet; if the stub
35049 stores packets in a NUL-terminated format, it should allow an extra
35050 byte in its buffer for the NUL. If this stub feature is not supported,
35051 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35053 @item qXfer:auxv:read
35054 The remote stub understands the @samp{qXfer:auxv:read} packet
35055 (@pxref{qXfer auxiliary vector read}).
35057 @item qXfer:features:read
35058 The remote stub understands the @samp{qXfer:features:read} packet
35059 (@pxref{qXfer target description read}).
35061 @item qXfer:libraries:read
35062 The remote stub understands the @samp{qXfer:libraries:read} packet
35063 (@pxref{qXfer library list read}).
35065 @item qXfer:libraries-svr4:read
35066 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35067 (@pxref{qXfer svr4 library list read}).
35069 @item qXfer:memory-map:read
35070 The remote stub understands the @samp{qXfer:memory-map:read} packet
35071 (@pxref{qXfer memory map read}).
35073 @item qXfer:sdata:read
35074 The remote stub understands the @samp{qXfer:sdata:read} packet
35075 (@pxref{qXfer sdata read}).
35077 @item qXfer:spu:read
35078 The remote stub understands the @samp{qXfer:spu:read} packet
35079 (@pxref{qXfer spu read}).
35081 @item qXfer:spu:write
35082 The remote stub understands the @samp{qXfer:spu:write} packet
35083 (@pxref{qXfer spu write}).
35085 @item qXfer:siginfo:read
35086 The remote stub understands the @samp{qXfer:siginfo:read} packet
35087 (@pxref{qXfer siginfo read}).
35089 @item qXfer:siginfo:write
35090 The remote stub understands the @samp{qXfer:siginfo:write} packet
35091 (@pxref{qXfer siginfo write}).
35093 @item qXfer:threads:read
35094 The remote stub understands the @samp{qXfer:threads:read} packet
35095 (@pxref{qXfer threads read}).
35097 @item qXfer:traceframe-info:read
35098 The remote stub understands the @samp{qXfer:traceframe-info:read}
35099 packet (@pxref{qXfer traceframe info read}).
35101 @item qXfer:fdpic:read
35102 The remote stub understands the @samp{qXfer:fdpic:read}
35103 packet (@pxref{qXfer fdpic loadmap read}).
35106 The remote stub understands the @samp{QNonStop} packet
35107 (@pxref{QNonStop}).
35110 The remote stub understands the @samp{QPassSignals} packet
35111 (@pxref{QPassSignals}).
35113 @item QStartNoAckMode
35114 The remote stub understands the @samp{QStartNoAckMode} packet and
35115 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35118 @anchor{multiprocess extensions}
35119 @cindex multiprocess extensions, in remote protocol
35120 The remote stub understands the multiprocess extensions to the remote
35121 protocol syntax. The multiprocess extensions affect the syntax of
35122 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35123 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35124 replies. Note that reporting this feature indicates support for the
35125 syntactic extensions only, not that the stub necessarily supports
35126 debugging of more than one process at a time. The stub must not use
35127 multiprocess extensions in packet replies unless @value{GDBN} has also
35128 indicated it supports them in its @samp{qSupported} request.
35130 @item qXfer:osdata:read
35131 The remote stub understands the @samp{qXfer:osdata:read} packet
35132 ((@pxref{qXfer osdata read}).
35134 @item ConditionalTracepoints
35135 The remote stub accepts and implements conditional expressions defined
35136 for tracepoints (@pxref{Tracepoint Conditions}).
35138 @item ReverseContinue
35139 The remote stub accepts and implements the reverse continue packet
35143 The remote stub accepts and implements the reverse step packet
35146 @item TracepointSource
35147 The remote stub understands the @samp{QTDPsrc} packet that supplies
35148 the source form of tracepoint definitions.
35151 The remote stub understands the @samp{QAllow} packet.
35153 @item QDisableRandomization
35154 The remote stub understands the @samp{QDisableRandomization} packet.
35156 @item StaticTracepoint
35157 @cindex static tracepoints, in remote protocol
35158 The remote stub supports static tracepoints.
35160 @item InstallInTrace
35161 @anchor{install tracepoint in tracing}
35162 The remote stub supports installing tracepoint in tracing.
35164 @item EnableDisableTracepoints
35165 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35166 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35167 to be enabled and disabled while a trace experiment is running.
35170 @cindex string tracing, in remote protocol
35171 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35172 See @ref{Bytecode Descriptions} for details about the bytecode.
35177 @cindex symbol lookup, remote request
35178 @cindex @samp{qSymbol} packet
35179 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35180 requests. Accept requests from the target for the values of symbols.
35185 The target does not need to look up any (more) symbols.
35186 @item qSymbol:@var{sym_name}
35187 The target requests the value of symbol @var{sym_name} (hex encoded).
35188 @value{GDBN} may provide the value by using the
35189 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35193 @item qSymbol:@var{sym_value}:@var{sym_name}
35194 Set the value of @var{sym_name} to @var{sym_value}.
35196 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35197 target has previously requested.
35199 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35200 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35206 The target does not need to look up any (more) symbols.
35207 @item qSymbol:@var{sym_name}
35208 The target requests the value of a new symbol @var{sym_name} (hex
35209 encoded). @value{GDBN} will continue to supply the values of symbols
35210 (if available), until the target ceases to request them.
35215 @item QTDisconnected
35222 @itemx qTMinFTPILen
35224 @xref{Tracepoint Packets}.
35226 @item qThreadExtraInfo,@var{thread-id}
35227 @cindex thread attributes info, remote request
35228 @cindex @samp{qThreadExtraInfo} packet
35229 Obtain a printable string description of a thread's attributes from
35230 the target OS. @var{thread-id} is a thread ID;
35231 see @ref{thread-id syntax}. This
35232 string may contain anything that the target OS thinks is interesting
35233 for @value{GDBN} to tell the user about the thread. The string is
35234 displayed in @value{GDBN}'s @code{info threads} display. Some
35235 examples of possible thread extra info strings are @samp{Runnable}, or
35236 @samp{Blocked on Mutex}.
35240 @item @var{XX}@dots{}
35241 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35242 comprising the printable string containing the extra information about
35243 the thread's attributes.
35246 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35247 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35248 conventions above. Please don't use this packet as a model for new
35267 @xref{Tracepoint Packets}.
35269 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35270 @cindex read special object, remote request
35271 @cindex @samp{qXfer} packet
35272 @anchor{qXfer read}
35273 Read uninterpreted bytes from the target's special data area
35274 identified by the keyword @var{object}. Request @var{length} bytes
35275 starting at @var{offset} bytes into the data. The content and
35276 encoding of @var{annex} is specific to @var{object}; it can supply
35277 additional details about what data to access.
35279 Here are the specific requests of this form defined so far. All
35280 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35281 formats, listed below.
35284 @item qXfer:auxv:read::@var{offset},@var{length}
35285 @anchor{qXfer auxiliary vector read}
35286 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35287 auxiliary vector}. Note @var{annex} must be empty.
35289 This packet is not probed by default; the remote stub must request it,
35290 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35292 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35293 @anchor{qXfer target description read}
35294 Access the @dfn{target description}. @xref{Target Descriptions}. The
35295 annex specifies which XML document to access. The main description is
35296 always loaded from the @samp{target.xml} annex.
35298 This packet is not probed by default; the remote stub must request it,
35299 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35301 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35302 @anchor{qXfer library list read}
35303 Access the target's list of loaded libraries. @xref{Library List Format}.
35304 The annex part of the generic @samp{qXfer} packet must be empty
35305 (@pxref{qXfer read}).
35307 Targets which maintain a list of libraries in the program's memory do
35308 not need to implement this packet; it is designed for platforms where
35309 the operating system manages the list of loaded libraries.
35311 This packet is not probed by default; the remote stub must request it,
35312 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35314 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35315 @anchor{qXfer svr4 library list read}
35316 Access the target's list of loaded libraries when the target is an SVR4
35317 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35318 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35320 This packet is optional for better performance on SVR4 targets.
35321 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35323 This packet is not probed by default; the remote stub must request it,
35324 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35326 @item qXfer:memory-map:read::@var{offset},@var{length}
35327 @anchor{qXfer memory map read}
35328 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35329 annex part of the generic @samp{qXfer} packet must be empty
35330 (@pxref{qXfer read}).
35332 This packet is not probed by default; the remote stub must request it,
35333 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35335 @item qXfer:sdata:read::@var{offset},@var{length}
35336 @anchor{qXfer sdata read}
35338 Read contents of the extra collected static tracepoint marker
35339 information. The annex part of the generic @samp{qXfer} packet must
35340 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35343 This packet is not probed by default; the remote stub must request it,
35344 by supplying an appropriate @samp{qSupported} response
35345 (@pxref{qSupported}).
35347 @item qXfer:siginfo:read::@var{offset},@var{length}
35348 @anchor{qXfer siginfo read}
35349 Read contents of the extra signal information on the target
35350 system. The annex part of the generic @samp{qXfer} packet must be
35351 empty (@pxref{qXfer read}).
35353 This packet is not probed by default; the remote stub must request it,
35354 by supplying an appropriate @samp{qSupported} response
35355 (@pxref{qSupported}).
35357 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35358 @anchor{qXfer spu read}
35359 Read contents of an @code{spufs} file on the target system. The
35360 annex specifies which file to read; it must be of the form
35361 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35362 in the target process, and @var{name} identifes the @code{spufs} file
35363 in that context to be accessed.
35365 This packet is not probed by default; the remote stub must request it,
35366 by supplying an appropriate @samp{qSupported} response
35367 (@pxref{qSupported}).
35369 @item qXfer:threads:read::@var{offset},@var{length}
35370 @anchor{qXfer threads read}
35371 Access the list of threads on target. @xref{Thread List Format}. The
35372 annex part of the generic @samp{qXfer} packet must be empty
35373 (@pxref{qXfer read}).
35375 This packet is not probed by default; the remote stub must request it,
35376 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35378 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35379 @anchor{qXfer traceframe info read}
35381 Return a description of the current traceframe's contents.
35382 @xref{Traceframe Info Format}. The annex part of the generic
35383 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35385 This packet is not probed by default; the remote stub must request it,
35386 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35388 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35389 @anchor{qXfer fdpic loadmap read}
35390 Read contents of @code{loadmap}s on the target system. The
35391 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35392 executable @code{loadmap} or interpreter @code{loadmap} to read.
35394 This packet is not probed by default; the remote stub must request it,
35395 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35397 @item qXfer:osdata:read::@var{offset},@var{length}
35398 @anchor{qXfer osdata read}
35399 Access the target's @dfn{operating system information}.
35400 @xref{Operating System Information}.
35407 Data @var{data} (@pxref{Binary Data}) has been read from the
35408 target. There may be more data at a higher address (although
35409 it is permitted to return @samp{m} even for the last valid
35410 block of data, as long as at least one byte of data was read).
35411 @var{data} may have fewer bytes than the @var{length} in the
35415 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35416 There is no more data to be read. @var{data} may have fewer bytes
35417 than the @var{length} in the request.
35420 The @var{offset} in the request is at the end of the data.
35421 There is no more data to be read.
35424 The request was malformed, or @var{annex} was invalid.
35427 The offset was invalid, or there was an error encountered reading the data.
35428 @var{nn} is a hex-encoded @code{errno} value.
35431 An empty reply indicates the @var{object} string was not recognized by
35432 the stub, or that the object does not support reading.
35435 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35436 @cindex write data into object, remote request
35437 @anchor{qXfer write}
35438 Write uninterpreted bytes into the target's special data area
35439 identified by the keyword @var{object}, starting at @var{offset} bytes
35440 into the data. @var{data}@dots{} is the binary-encoded data
35441 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35442 is specific to @var{object}; it can supply additional details about what data
35445 Here are the specific requests of this form defined so far. All
35446 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35447 formats, listed below.
35450 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35451 @anchor{qXfer siginfo write}
35452 Write @var{data} to the extra signal information on the target system.
35453 The annex part of the generic @samp{qXfer} packet must be
35454 empty (@pxref{qXfer write}).
35456 This packet is not probed by default; the remote stub must request it,
35457 by supplying an appropriate @samp{qSupported} response
35458 (@pxref{qSupported}).
35460 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35461 @anchor{qXfer spu write}
35462 Write @var{data} to an @code{spufs} file on the target system. The
35463 annex specifies which file to write; it must be of the form
35464 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35465 in the target process, and @var{name} identifes the @code{spufs} file
35466 in that context to be accessed.
35468 This packet is not probed by default; the remote stub must request it,
35469 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35475 @var{nn} (hex encoded) is the number of bytes written.
35476 This may be fewer bytes than supplied in the request.
35479 The request was malformed, or @var{annex} was invalid.
35482 The offset was invalid, or there was an error encountered writing the data.
35483 @var{nn} is a hex-encoded @code{errno} value.
35486 An empty reply indicates the @var{object} string was not
35487 recognized by the stub, or that the object does not support writing.
35490 @item qXfer:@var{object}:@var{operation}:@dots{}
35491 Requests of this form may be added in the future. When a stub does
35492 not recognize the @var{object} keyword, or its support for
35493 @var{object} does not recognize the @var{operation} keyword, the stub
35494 must respond with an empty packet.
35496 @item qAttached:@var{pid}
35497 @cindex query attached, remote request
35498 @cindex @samp{qAttached} packet
35499 Return an indication of whether the remote server attached to an
35500 existing process or created a new process. When the multiprocess
35501 protocol extensions are supported (@pxref{multiprocess extensions}),
35502 @var{pid} is an integer in hexadecimal format identifying the target
35503 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35504 the query packet will be simplified as @samp{qAttached}.
35506 This query is used, for example, to know whether the remote process
35507 should be detached or killed when a @value{GDBN} session is ended with
35508 the @code{quit} command.
35513 The remote server attached to an existing process.
35515 The remote server created a new process.
35517 A badly formed request or an error was encountered.
35522 @node Architecture-Specific Protocol Details
35523 @section Architecture-Specific Protocol Details
35525 This section describes how the remote protocol is applied to specific
35526 target architectures. Also see @ref{Standard Target Features}, for
35527 details of XML target descriptions for each architecture.
35531 @subsubsection Breakpoint Kinds
35533 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35538 16-bit Thumb mode breakpoint.
35541 32-bit Thumb mode (Thumb-2) breakpoint.
35544 32-bit ARM mode breakpoint.
35550 @subsubsection Register Packet Format
35552 The following @code{g}/@code{G} packets have previously been defined.
35553 In the below, some thirty-two bit registers are transferred as
35554 sixty-four bits. Those registers should be zero/sign extended (which?)
35555 to fill the space allocated. Register bytes are transferred in target
35556 byte order. The two nibbles within a register byte are transferred
35557 most-significant - least-significant.
35563 All registers are transferred as thirty-two bit quantities in the order:
35564 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35565 registers; fsr; fir; fp.
35569 All registers are transferred as sixty-four bit quantities (including
35570 thirty-two bit registers such as @code{sr}). The ordering is the same
35575 @node Tracepoint Packets
35576 @section Tracepoint Packets
35577 @cindex tracepoint packets
35578 @cindex packets, tracepoint
35580 Here we describe the packets @value{GDBN} uses to implement
35581 tracepoints (@pxref{Tracepoints}).
35585 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35586 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35587 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35588 the tracepoint is disabled. @var{step} is the tracepoint's step
35589 count, and @var{pass} is its pass count. If an @samp{F} is present,
35590 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35591 the number of bytes that the target should copy elsewhere to make room
35592 for the tracepoint. If an @samp{X} is present, it introduces a
35593 tracepoint condition, which consists of a hexadecimal length, followed
35594 by a comma and hex-encoded bytes, in a manner similar to action
35595 encodings as described below. If the trailing @samp{-} is present,
35596 further @samp{QTDP} packets will follow to specify this tracepoint's
35602 The packet was understood and carried out.
35604 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35606 The packet was not recognized.
35609 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35610 Define actions to be taken when a tracepoint is hit. @var{n} and
35611 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35612 this tracepoint. This packet may only be sent immediately after
35613 another @samp{QTDP} packet that ended with a @samp{-}. If the
35614 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35615 specifying more actions for this tracepoint.
35617 In the series of action packets for a given tracepoint, at most one
35618 can have an @samp{S} before its first @var{action}. If such a packet
35619 is sent, it and the following packets define ``while-stepping''
35620 actions. Any prior packets define ordinary actions --- that is, those
35621 taken when the tracepoint is first hit. If no action packet has an
35622 @samp{S}, then all the packets in the series specify ordinary
35623 tracepoint actions.
35625 The @samp{@var{action}@dots{}} portion of the packet is a series of
35626 actions, concatenated without separators. Each action has one of the
35632 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35633 a hexadecimal number whose @var{i}'th bit is set if register number
35634 @var{i} should be collected. (The least significant bit is numbered
35635 zero.) Note that @var{mask} may be any number of digits long; it may
35636 not fit in a 32-bit word.
35638 @item M @var{basereg},@var{offset},@var{len}
35639 Collect @var{len} bytes of memory starting at the address in register
35640 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35641 @samp{-1}, then the range has a fixed address: @var{offset} is the
35642 address of the lowest byte to collect. The @var{basereg},
35643 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35644 values (the @samp{-1} value for @var{basereg} is a special case).
35646 @item X @var{len},@var{expr}
35647 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35648 it directs. @var{expr} is an agent expression, as described in
35649 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35650 two-digit hex number in the packet; @var{len} is the number of bytes
35651 in the expression (and thus one-half the number of hex digits in the
35656 Any number of actions may be packed together in a single @samp{QTDP}
35657 packet, as long as the packet does not exceed the maximum packet
35658 length (400 bytes, for many stubs). There may be only one @samp{R}
35659 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35660 actions. Any registers referred to by @samp{M} and @samp{X} actions
35661 must be collected by a preceding @samp{R} action. (The
35662 ``while-stepping'' actions are treated as if they were attached to a
35663 separate tracepoint, as far as these restrictions are concerned.)
35668 The packet was understood and carried out.
35670 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35672 The packet was not recognized.
35675 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35676 @cindex @samp{QTDPsrc} packet
35677 Specify a source string of tracepoint @var{n} at address @var{addr}.
35678 This is useful to get accurate reproduction of the tracepoints
35679 originally downloaded at the beginning of the trace run. @var{type}
35680 is the name of the tracepoint part, such as @samp{cond} for the
35681 tracepoint's conditional expression (see below for a list of types), while
35682 @var{bytes} is the string, encoded in hexadecimal.
35684 @var{start} is the offset of the @var{bytes} within the overall source
35685 string, while @var{slen} is the total length of the source string.
35686 This is intended for handling source strings that are longer than will
35687 fit in a single packet.
35688 @c Add detailed example when this info is moved into a dedicated
35689 @c tracepoint descriptions section.
35691 The available string types are @samp{at} for the location,
35692 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35693 @value{GDBN} sends a separate packet for each command in the action
35694 list, in the same order in which the commands are stored in the list.
35696 The target does not need to do anything with source strings except
35697 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35700 Although this packet is optional, and @value{GDBN} will only send it
35701 if the target replies with @samp{TracepointSource} @xref{General
35702 Query Packets}, it makes both disconnected tracing and trace files
35703 much easier to use. Otherwise the user must be careful that the
35704 tracepoints in effect while looking at trace frames are identical to
35705 the ones in effect during the trace run; even a small discrepancy
35706 could cause @samp{tdump} not to work, or a particular trace frame not
35709 @item QTDV:@var{n}:@var{value}
35710 @cindex define trace state variable, remote request
35711 @cindex @samp{QTDV} packet
35712 Create a new trace state variable, number @var{n}, with an initial
35713 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35714 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35715 the option of not using this packet for initial values of zero; the
35716 target should simply create the trace state variables as they are
35717 mentioned in expressions.
35719 @item QTFrame:@var{n}
35720 Select the @var{n}'th tracepoint frame from the buffer, and use the
35721 register and memory contents recorded there to answer subsequent
35722 request packets from @value{GDBN}.
35724 A successful reply from the stub indicates that the stub has found the
35725 requested frame. The response is a series of parts, concatenated
35726 without separators, describing the frame we selected. Each part has
35727 one of the following forms:
35731 The selected frame is number @var{n} in the trace frame buffer;
35732 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35733 was no frame matching the criteria in the request packet.
35736 The selected trace frame records a hit of tracepoint number @var{t};
35737 @var{t} is a hexadecimal number.
35741 @item QTFrame:pc:@var{addr}
35742 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35743 currently selected frame whose PC is @var{addr};
35744 @var{addr} is a hexadecimal number.
35746 @item QTFrame:tdp:@var{t}
35747 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35748 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35749 is a hexadecimal number.
35751 @item QTFrame:range:@var{start}:@var{end}
35752 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35753 currently selected frame whose PC is between @var{start} (inclusive)
35754 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35757 @item QTFrame:outside:@var{start}:@var{end}
35758 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35759 frame @emph{outside} the given range of addresses (exclusive).
35762 This packet requests the minimum length of instruction at which a fast
35763 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
35764 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
35765 it depends on the target system being able to create trampolines in
35766 the first 64K of memory, which might or might not be possible for that
35767 system. So the reply to this packet will be 4 if it is able to
35774 The minimum instruction length is currently unknown.
35776 The minimum instruction length is @var{length}, where @var{length} is greater
35777 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
35778 that a fast tracepoint may be placed on any instruction regardless of size.
35780 An error has occurred.
35782 An empty reply indicates that the request is not supported by the stub.
35786 Begin the tracepoint experiment. Begin collecting data from
35787 tracepoint hits in the trace frame buffer. This packet supports the
35788 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35789 instruction reply packet}).
35792 End the tracepoint experiment. Stop collecting trace frames.
35794 @item QTEnable:@var{n}:@var{addr}
35796 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35797 experiment. If the tracepoint was previously disabled, then collection
35798 of data from it will resume.
35800 @item QTDisable:@var{n}:@var{addr}
35802 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35803 experiment. No more data will be collected from the tracepoint unless
35804 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35807 Clear the table of tracepoints, and empty the trace frame buffer.
35809 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35810 Establish the given ranges of memory as ``transparent''. The stub
35811 will answer requests for these ranges from memory's current contents,
35812 if they were not collected as part of the tracepoint hit.
35814 @value{GDBN} uses this to mark read-only regions of memory, like those
35815 containing program code. Since these areas never change, they should
35816 still have the same contents they did when the tracepoint was hit, so
35817 there's no reason for the stub to refuse to provide their contents.
35819 @item QTDisconnected:@var{value}
35820 Set the choice to what to do with the tracing run when @value{GDBN}
35821 disconnects from the target. A @var{value} of 1 directs the target to
35822 continue the tracing run, while 0 tells the target to stop tracing if
35823 @value{GDBN} is no longer in the picture.
35826 Ask the stub if there is a trace experiment running right now.
35828 The reply has the form:
35832 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35833 @var{running} is a single digit @code{1} if the trace is presently
35834 running, or @code{0} if not. It is followed by semicolon-separated
35835 optional fields that an agent may use to report additional status.
35839 If the trace is not running, the agent may report any of several
35840 explanations as one of the optional fields:
35845 No trace has been run yet.
35847 @item tstop[:@var{text}]:0
35848 The trace was stopped by a user-originated stop command. The optional
35849 @var{text} field is a user-supplied string supplied as part of the
35850 stop command (for instance, an explanation of why the trace was
35851 stopped manually). It is hex-encoded.
35854 The trace stopped because the trace buffer filled up.
35856 @item tdisconnected:0
35857 The trace stopped because @value{GDBN} disconnected from the target.
35859 @item tpasscount:@var{tpnum}
35860 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35862 @item terror:@var{text}:@var{tpnum}
35863 The trace stopped because tracepoint @var{tpnum} had an error. The
35864 string @var{text} is available to describe the nature of the error
35865 (for instance, a divide by zero in the condition expression).
35866 @var{text} is hex encoded.
35869 The trace stopped for some other reason.
35873 Additional optional fields supply statistical and other information.
35874 Although not required, they are extremely useful for users monitoring
35875 the progress of a trace run. If a trace has stopped, and these
35876 numbers are reported, they must reflect the state of the just-stopped
35881 @item tframes:@var{n}
35882 The number of trace frames in the buffer.
35884 @item tcreated:@var{n}
35885 The total number of trace frames created during the run. This may
35886 be larger than the trace frame count, if the buffer is circular.
35888 @item tsize:@var{n}
35889 The total size of the trace buffer, in bytes.
35891 @item tfree:@var{n}
35892 The number of bytes still unused in the buffer.
35894 @item circular:@var{n}
35895 The value of the circular trace buffer flag. @code{1} means that the
35896 trace buffer is circular and old trace frames will be discarded if
35897 necessary to make room, @code{0} means that the trace buffer is linear
35900 @item disconn:@var{n}
35901 The value of the disconnected tracing flag. @code{1} means that
35902 tracing will continue after @value{GDBN} disconnects, @code{0} means
35903 that the trace run will stop.
35907 @item qTP:@var{tp}:@var{addr}
35908 @cindex tracepoint status, remote request
35909 @cindex @samp{qTP} packet
35910 Ask the stub for the current state of tracepoint number @var{tp} at
35911 address @var{addr}.
35915 @item V@var{hits}:@var{usage}
35916 The tracepoint has been hit @var{hits} times so far during the trace
35917 run, and accounts for @var{usage} in the trace buffer. Note that
35918 @code{while-stepping} steps are not counted as separate hits, but the
35919 steps' space consumption is added into the usage number.
35923 @item qTV:@var{var}
35924 @cindex trace state variable value, remote request
35925 @cindex @samp{qTV} packet
35926 Ask the stub for the value of the trace state variable number @var{var}.
35931 The value of the variable is @var{value}. This will be the current
35932 value of the variable if the user is examining a running target, or a
35933 saved value if the variable was collected in the trace frame that the
35934 user is looking at. Note that multiple requests may result in
35935 different reply values, such as when requesting values while the
35936 program is running.
35939 The value of the variable is unknown. This would occur, for example,
35940 if the user is examining a trace frame in which the requested variable
35946 These packets request data about tracepoints that are being used by
35947 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35948 of data, and multiple @code{qTsP} to get additional pieces. Replies
35949 to these packets generally take the form of the @code{QTDP} packets
35950 that define tracepoints. (FIXME add detailed syntax)
35954 These packets request data about trace state variables that are on the
35955 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35956 and multiple @code{qTsV} to get additional variables. Replies to
35957 these packets follow the syntax of the @code{QTDV} packets that define
35958 trace state variables.
35962 These packets request data about static tracepoint markers that exist
35963 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35964 first piece of data, and multiple @code{qTsSTM} to get additional
35965 pieces. Replies to these packets take the following form:
35969 @item m @var{address}:@var{id}:@var{extra}
35971 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35972 a comma-separated list of markers
35974 (lower case letter @samp{L}) denotes end of list.
35976 An error occurred. @var{nn} are hex digits.
35978 An empty reply indicates that the request is not supported by the
35982 @var{address} is encoded in hex.
35983 @var{id} and @var{extra} are strings encoded in hex.
35985 In response to each query, the target will reply with a list of one or
35986 more markers, separated by commas. @value{GDBN} will respond to each
35987 reply with a request for more markers (using the @samp{qs} form of the
35988 query), until the target responds with @samp{l} (lower-case ell, for
35991 @item qTSTMat:@var{address}
35992 This packets requests data about static tracepoint markers in the
35993 target program at @var{address}. Replies to this packet follow the
35994 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35995 tracepoint markers.
35997 @item QTSave:@var{filename}
35998 This packet directs the target to save trace data to the file name
35999 @var{filename} in the target's filesystem. @var{filename} is encoded
36000 as a hex string; the interpretation of the file name (relative vs
36001 absolute, wild cards, etc) is up to the target.
36003 @item qTBuffer:@var{offset},@var{len}
36004 Return up to @var{len} bytes of the current contents of trace buffer,
36005 starting at @var{offset}. The trace buffer is treated as if it were
36006 a contiguous collection of traceframes, as per the trace file format.
36007 The reply consists as many hex-encoded bytes as the target can deliver
36008 in a packet; it is not an error to return fewer than were asked for.
36009 A reply consisting of just @code{l} indicates that no bytes are
36012 @item QTBuffer:circular:@var{value}
36013 This packet directs the target to use a circular trace buffer if
36014 @var{value} is 1, or a linear buffer if the value is 0.
36016 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36017 This packet adds optional textual notes to the trace run. Allowable
36018 types include @code{user}, @code{notes}, and @code{tstop}, the
36019 @var{text} fields are arbitrary strings, hex-encoded.
36023 @subsection Relocate instruction reply packet
36024 When installing fast tracepoints in memory, the target may need to
36025 relocate the instruction currently at the tracepoint address to a
36026 different address in memory. For most instructions, a simple copy is
36027 enough, but, for example, call instructions that implicitly push the
36028 return address on the stack, and relative branches or other
36029 PC-relative instructions require offset adjustment, so that the effect
36030 of executing the instruction at a different address is the same as if
36031 it had executed in the original location.
36033 In response to several of the tracepoint packets, the target may also
36034 respond with a number of intermediate @samp{qRelocInsn} request
36035 packets before the final result packet, to have @value{GDBN} handle
36036 this relocation operation. If a packet supports this mechanism, its
36037 documentation will explicitly say so. See for example the above
36038 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36039 format of the request is:
36042 @item qRelocInsn:@var{from};@var{to}
36044 This requests @value{GDBN} to copy instruction at address @var{from}
36045 to address @var{to}, possibly adjusted so that executing the
36046 instruction at @var{to} has the same effect as executing it at
36047 @var{from}. @value{GDBN} writes the adjusted instruction to target
36048 memory starting at @var{to}.
36053 @item qRelocInsn:@var{adjusted_size}
36054 Informs the stub the relocation is complete. @var{adjusted_size} is
36055 the length in bytes of resulting relocated instruction sequence.
36057 A badly formed request was detected, or an error was encountered while
36058 relocating the instruction.
36061 @node Host I/O Packets
36062 @section Host I/O Packets
36063 @cindex Host I/O, remote protocol
36064 @cindex file transfer, remote protocol
36066 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36067 operations on the far side of a remote link. For example, Host I/O is
36068 used to upload and download files to a remote target with its own
36069 filesystem. Host I/O uses the same constant values and data structure
36070 layout as the target-initiated File-I/O protocol. However, the
36071 Host I/O packets are structured differently. The target-initiated
36072 protocol relies on target memory to store parameters and buffers.
36073 Host I/O requests are initiated by @value{GDBN}, and the
36074 target's memory is not involved. @xref{File-I/O Remote Protocol
36075 Extension}, for more details on the target-initiated protocol.
36077 The Host I/O request packets all encode a single operation along with
36078 its arguments. They have this format:
36082 @item vFile:@var{operation}: @var{parameter}@dots{}
36083 @var{operation} is the name of the particular request; the target
36084 should compare the entire packet name up to the second colon when checking
36085 for a supported operation. The format of @var{parameter} depends on
36086 the operation. Numbers are always passed in hexadecimal. Negative
36087 numbers have an explicit minus sign (i.e.@: two's complement is not
36088 used). Strings (e.g.@: filenames) are encoded as a series of
36089 hexadecimal bytes. The last argument to a system call may be a
36090 buffer of escaped binary data (@pxref{Binary Data}).
36094 The valid responses to Host I/O packets are:
36098 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36099 @var{result} is the integer value returned by this operation, usually
36100 non-negative for success and -1 for errors. If an error has occured,
36101 @var{errno} will be included in the result. @var{errno} will have a
36102 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36103 operations which return data, @var{attachment} supplies the data as a
36104 binary buffer. Binary buffers in response packets are escaped in the
36105 normal way (@pxref{Binary Data}). See the individual packet
36106 documentation for the interpretation of @var{result} and
36110 An empty response indicates that this operation is not recognized.
36114 These are the supported Host I/O operations:
36117 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36118 Open a file at @var{pathname} and return a file descriptor for it, or
36119 return -1 if an error occurs. @var{pathname} is a string,
36120 @var{flags} is an integer indicating a mask of open flags
36121 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36122 of mode bits to use if the file is created (@pxref{mode_t Values}).
36123 @xref{open}, for details of the open flags and mode values.
36125 @item vFile:close: @var{fd}
36126 Close the open file corresponding to @var{fd} and return 0, or
36127 -1 if an error occurs.
36129 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36130 Read data from the open file corresponding to @var{fd}. Up to
36131 @var{count} bytes will be read from the file, starting at @var{offset}
36132 relative to the start of the file. The target may read fewer bytes;
36133 common reasons include packet size limits and an end-of-file
36134 condition. The number of bytes read is returned. Zero should only be
36135 returned for a successful read at the end of the file, or if
36136 @var{count} was zero.
36138 The data read should be returned as a binary attachment on success.
36139 If zero bytes were read, the response should include an empty binary
36140 attachment (i.e.@: a trailing semicolon). The return value is the
36141 number of target bytes read; the binary attachment may be longer if
36142 some characters were escaped.
36144 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36145 Write @var{data} (a binary buffer) to the open file corresponding
36146 to @var{fd}. Start the write at @var{offset} from the start of the
36147 file. Unlike many @code{write} system calls, there is no
36148 separate @var{count} argument; the length of @var{data} in the
36149 packet is used. @samp{vFile:write} returns the number of bytes written,
36150 which may be shorter than the length of @var{data}, or -1 if an
36153 @item vFile:unlink: @var{pathname}
36154 Delete the file at @var{pathname} on the target. Return 0,
36155 or -1 if an error occurs. @var{pathname} is a string.
36160 @section Interrupts
36161 @cindex interrupts (remote protocol)
36163 When a program on the remote target is running, @value{GDBN} may
36164 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36165 a @code{BREAK} followed by @code{g},
36166 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36168 The precise meaning of @code{BREAK} is defined by the transport
36169 mechanism and may, in fact, be undefined. @value{GDBN} does not
36170 currently define a @code{BREAK} mechanism for any of the network
36171 interfaces except for TCP, in which case @value{GDBN} sends the
36172 @code{telnet} BREAK sequence.
36174 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36175 transport mechanisms. It is represented by sending the single byte
36176 @code{0x03} without any of the usual packet overhead described in
36177 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36178 transmitted as part of a packet, it is considered to be packet data
36179 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36180 (@pxref{X packet}), used for binary downloads, may include an unescaped
36181 @code{0x03} as part of its packet.
36183 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36184 When Linux kernel receives this sequence from serial port,
36185 it stops execution and connects to gdb.
36187 Stubs are not required to recognize these interrupt mechanisms and the
36188 precise meaning associated with receipt of the interrupt is
36189 implementation defined. If the target supports debugging of multiple
36190 threads and/or processes, it should attempt to interrupt all
36191 currently-executing threads and processes.
36192 If the stub is successful at interrupting the
36193 running program, it should send one of the stop
36194 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36195 of successfully stopping the program in all-stop mode, and a stop reply
36196 for each stopped thread in non-stop mode.
36197 Interrupts received while the
36198 program is stopped are discarded.
36200 @node Notification Packets
36201 @section Notification Packets
36202 @cindex notification packets
36203 @cindex packets, notification
36205 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36206 packets that require no acknowledgment. Both the GDB and the stub
36207 may send notifications (although the only notifications defined at
36208 present are sent by the stub). Notifications carry information
36209 without incurring the round-trip latency of an acknowledgment, and so
36210 are useful for low-impact communications where occasional packet loss
36213 A notification packet has the form @samp{% @var{data} #
36214 @var{checksum}}, where @var{data} is the content of the notification,
36215 and @var{checksum} is a checksum of @var{data}, computed and formatted
36216 as for ordinary @value{GDBN} packets. A notification's @var{data}
36217 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36218 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36219 to acknowledge the notification's receipt or to report its corruption.
36221 Every notification's @var{data} begins with a name, which contains no
36222 colon characters, followed by a colon character.
36224 Recipients should silently ignore corrupted notifications and
36225 notifications they do not understand. Recipients should restart
36226 timeout periods on receipt of a well-formed notification, whether or
36227 not they understand it.
36229 Senders should only send the notifications described here when this
36230 protocol description specifies that they are permitted. In the
36231 future, we may extend the protocol to permit existing notifications in
36232 new contexts; this rule helps older senders avoid confusing newer
36235 (Older versions of @value{GDBN} ignore bytes received until they see
36236 the @samp{$} byte that begins an ordinary packet, so new stubs may
36237 transmit notifications without fear of confusing older clients. There
36238 are no notifications defined for @value{GDBN} to send at the moment, but we
36239 assume that most older stubs would ignore them, as well.)
36241 The following notification packets from the stub to @value{GDBN} are
36245 @item Stop: @var{reply}
36246 Report an asynchronous stop event in non-stop mode.
36247 The @var{reply} has the form of a stop reply, as
36248 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36249 for information on how these notifications are acknowledged by
36253 @node Remote Non-Stop
36254 @section Remote Protocol Support for Non-Stop Mode
36256 @value{GDBN}'s remote protocol supports non-stop debugging of
36257 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36258 supports non-stop mode, it should report that to @value{GDBN} by including
36259 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36261 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36262 establishing a new connection with the stub. Entering non-stop mode
36263 does not alter the state of any currently-running threads, but targets
36264 must stop all threads in any already-attached processes when entering
36265 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36266 probe the target state after a mode change.
36268 In non-stop mode, when an attached process encounters an event that
36269 would otherwise be reported with a stop reply, it uses the
36270 asynchronous notification mechanism (@pxref{Notification Packets}) to
36271 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36272 in all processes are stopped when a stop reply is sent, in non-stop
36273 mode only the thread reporting the stop event is stopped. That is,
36274 when reporting a @samp{S} or @samp{T} response to indicate completion
36275 of a step operation, hitting a breakpoint, or a fault, only the
36276 affected thread is stopped; any other still-running threads continue
36277 to run. When reporting a @samp{W} or @samp{X} response, all running
36278 threads belonging to other attached processes continue to run.
36280 Only one stop reply notification at a time may be pending; if
36281 additional stop events occur before @value{GDBN} has acknowledged the
36282 previous notification, they must be queued by the stub for later
36283 synchronous transmission in response to @samp{vStopped} packets from
36284 @value{GDBN}. Because the notification mechanism is unreliable,
36285 the stub is permitted to resend a stop reply notification
36286 if it believes @value{GDBN} may not have received it. @value{GDBN}
36287 ignores additional stop reply notifications received before it has
36288 finished processing a previous notification and the stub has completed
36289 sending any queued stop events.
36291 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36292 notification at any time. Specifically, they may appear when
36293 @value{GDBN} is not otherwise reading input from the stub, or when
36294 @value{GDBN} is expecting to read a normal synchronous response or a
36295 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36296 Notification packets are distinct from any other communication from
36297 the stub so there is no ambiguity.
36299 After receiving a stop reply notification, @value{GDBN} shall
36300 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36301 as a regular, synchronous request to the stub. Such acknowledgment
36302 is not required to happen immediately, as @value{GDBN} is permitted to
36303 send other, unrelated packets to the stub first, which the stub should
36306 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36307 stop events to report to @value{GDBN}, it shall respond by sending a
36308 normal stop reply response. @value{GDBN} shall then send another
36309 @samp{vStopped} packet to solicit further responses; again, it is
36310 permitted to send other, unrelated packets as well which the stub
36311 should process normally.
36313 If the stub receives a @samp{vStopped} packet and there are no
36314 additional stop events to report, the stub shall return an @samp{OK}
36315 response. At this point, if further stop events occur, the stub shall
36316 send a new stop reply notification, @value{GDBN} shall accept the
36317 notification, and the process shall be repeated.
36319 In non-stop mode, the target shall respond to the @samp{?} packet as
36320 follows. First, any incomplete stop reply notification/@samp{vStopped}
36321 sequence in progress is abandoned. The target must begin a new
36322 sequence reporting stop events for all stopped threads, whether or not
36323 it has previously reported those events to @value{GDBN}. The first
36324 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36325 subsequent stop replies are sent as responses to @samp{vStopped} packets
36326 using the mechanism described above. The target must not send
36327 asynchronous stop reply notifications until the sequence is complete.
36328 If all threads are running when the target receives the @samp{?} packet,
36329 or if the target is not attached to any process, it shall respond
36332 @node Packet Acknowledgment
36333 @section Packet Acknowledgment
36335 @cindex acknowledgment, for @value{GDBN} remote
36336 @cindex packet acknowledgment, for @value{GDBN} remote
36337 By default, when either the host or the target machine receives a packet,
36338 the first response expected is an acknowledgment: either @samp{+} (to indicate
36339 the package was received correctly) or @samp{-} (to request retransmission).
36340 This mechanism allows the @value{GDBN} remote protocol to operate over
36341 unreliable transport mechanisms, such as a serial line.
36343 In cases where the transport mechanism is itself reliable (such as a pipe or
36344 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36345 It may be desirable to disable them in that case to reduce communication
36346 overhead, or for other reasons. This can be accomplished by means of the
36347 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36349 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36350 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36351 and response format still includes the normal checksum, as described in
36352 @ref{Overview}, but the checksum may be ignored by the receiver.
36354 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36355 no-acknowledgment mode, it should report that to @value{GDBN}
36356 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36357 @pxref{qSupported}.
36358 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36359 disabled via the @code{set remote noack-packet off} command
36360 (@pxref{Remote Configuration}),
36361 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36362 Only then may the stub actually turn off packet acknowledgments.
36363 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36364 response, which can be safely ignored by the stub.
36366 Note that @code{set remote noack-packet} command only affects negotiation
36367 between @value{GDBN} and the stub when subsequent connections are made;
36368 it does not affect the protocol acknowledgment state for any current
36370 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36371 new connection is established,
36372 there is also no protocol request to re-enable the acknowledgments
36373 for the current connection, once disabled.
36378 Example sequence of a target being re-started. Notice how the restart
36379 does not get any direct output:
36384 @emph{target restarts}
36387 <- @code{T001:1234123412341234}
36391 Example sequence of a target being stepped by a single instruction:
36394 -> @code{G1445@dots{}}
36399 <- @code{T001:1234123412341234}
36403 <- @code{1455@dots{}}
36407 @node File-I/O Remote Protocol Extension
36408 @section File-I/O Remote Protocol Extension
36409 @cindex File-I/O remote protocol extension
36412 * File-I/O Overview::
36413 * Protocol Basics::
36414 * The F Request Packet::
36415 * The F Reply Packet::
36416 * The Ctrl-C Message::
36418 * List of Supported Calls::
36419 * Protocol-specific Representation of Datatypes::
36421 * File-I/O Examples::
36424 @node File-I/O Overview
36425 @subsection File-I/O Overview
36426 @cindex file-i/o overview
36428 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36429 target to use the host's file system and console I/O to perform various
36430 system calls. System calls on the target system are translated into a
36431 remote protocol packet to the host system, which then performs the needed
36432 actions and returns a response packet to the target system.
36433 This simulates file system operations even on targets that lack file systems.
36435 The protocol is defined to be independent of both the host and target systems.
36436 It uses its own internal representation of datatypes and values. Both
36437 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36438 translating the system-dependent value representations into the internal
36439 protocol representations when data is transmitted.
36441 The communication is synchronous. A system call is possible only when
36442 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36443 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36444 the target is stopped to allow deterministic access to the target's
36445 memory. Therefore File-I/O is not interruptible by target signals. On
36446 the other hand, it is possible to interrupt File-I/O by a user interrupt
36447 (@samp{Ctrl-C}) within @value{GDBN}.
36449 The target's request to perform a host system call does not finish
36450 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36451 after finishing the system call, the target returns to continuing the
36452 previous activity (continue, step). No additional continue or step
36453 request from @value{GDBN} is required.
36456 (@value{GDBP}) continue
36457 <- target requests 'system call X'
36458 target is stopped, @value{GDBN} executes system call
36459 -> @value{GDBN} returns result
36460 ... target continues, @value{GDBN} returns to wait for the target
36461 <- target hits breakpoint and sends a Txx packet
36464 The protocol only supports I/O on the console and to regular files on
36465 the host file system. Character or block special devices, pipes,
36466 named pipes, sockets or any other communication method on the host
36467 system are not supported by this protocol.
36469 File I/O is not supported in non-stop mode.
36471 @node Protocol Basics
36472 @subsection Protocol Basics
36473 @cindex protocol basics, file-i/o
36475 The File-I/O protocol uses the @code{F} packet as the request as well
36476 as reply packet. Since a File-I/O system call can only occur when
36477 @value{GDBN} is waiting for a response from the continuing or stepping target,
36478 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36479 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36480 This @code{F} packet contains all information needed to allow @value{GDBN}
36481 to call the appropriate host system call:
36485 A unique identifier for the requested system call.
36488 All parameters to the system call. Pointers are given as addresses
36489 in the target memory address space. Pointers to strings are given as
36490 pointer/length pair. Numerical values are given as they are.
36491 Numerical control flags are given in a protocol-specific representation.
36495 At this point, @value{GDBN} has to perform the following actions.
36499 If the parameters include pointer values to data needed as input to a
36500 system call, @value{GDBN} requests this data from the target with a
36501 standard @code{m} packet request. This additional communication has to be
36502 expected by the target implementation and is handled as any other @code{m}
36506 @value{GDBN} translates all value from protocol representation to host
36507 representation as needed. Datatypes are coerced into the host types.
36510 @value{GDBN} calls the system call.
36513 It then coerces datatypes back to protocol representation.
36516 If the system call is expected to return data in buffer space specified
36517 by pointer parameters to the call, the data is transmitted to the
36518 target using a @code{M} or @code{X} packet. This packet has to be expected
36519 by the target implementation and is handled as any other @code{M} or @code{X}
36524 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36525 necessary information for the target to continue. This at least contains
36532 @code{errno}, if has been changed by the system call.
36539 After having done the needed type and value coercion, the target continues
36540 the latest continue or step action.
36542 @node The F Request Packet
36543 @subsection The @code{F} Request Packet
36544 @cindex file-i/o request packet
36545 @cindex @code{F} request packet
36547 The @code{F} request packet has the following format:
36550 @item F@var{call-id},@var{parameter@dots{}}
36552 @var{call-id} is the identifier to indicate the host system call to be called.
36553 This is just the name of the function.
36555 @var{parameter@dots{}} are the parameters to the system call.
36556 Parameters are hexadecimal integer values, either the actual values in case
36557 of scalar datatypes, pointers to target buffer space in case of compound
36558 datatypes and unspecified memory areas, or pointer/length pairs in case
36559 of string parameters. These are appended to the @var{call-id} as a
36560 comma-delimited list. All values are transmitted in ASCII
36561 string representation, pointer/length pairs separated by a slash.
36567 @node The F Reply Packet
36568 @subsection The @code{F} Reply Packet
36569 @cindex file-i/o reply packet
36570 @cindex @code{F} reply packet
36572 The @code{F} reply packet has the following format:
36576 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36578 @var{retcode} is the return code of the system call as hexadecimal value.
36580 @var{errno} is the @code{errno} set by the call, in protocol-specific
36582 This parameter can be omitted if the call was successful.
36584 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36585 case, @var{errno} must be sent as well, even if the call was successful.
36586 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36593 or, if the call was interrupted before the host call has been performed:
36600 assuming 4 is the protocol-specific representation of @code{EINTR}.
36605 @node The Ctrl-C Message
36606 @subsection The @samp{Ctrl-C} Message
36607 @cindex ctrl-c message, in file-i/o protocol
36609 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36610 reply packet (@pxref{The F Reply Packet}),
36611 the target should behave as if it had
36612 gotten a break message. The meaning for the target is ``system call
36613 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36614 (as with a break message) and return to @value{GDBN} with a @code{T02}
36617 It's important for the target to know in which
36618 state the system call was interrupted. There are two possible cases:
36622 The system call hasn't been performed on the host yet.
36625 The system call on the host has been finished.
36629 These two states can be distinguished by the target by the value of the
36630 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36631 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36632 on POSIX systems. In any other case, the target may presume that the
36633 system call has been finished --- successfully or not --- and should behave
36634 as if the break message arrived right after the system call.
36636 @value{GDBN} must behave reliably. If the system call has not been called
36637 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36638 @code{errno} in the packet. If the system call on the host has been finished
36639 before the user requests a break, the full action must be finished by
36640 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36641 The @code{F} packet may only be sent when either nothing has happened
36642 or the full action has been completed.
36645 @subsection Console I/O
36646 @cindex console i/o as part of file-i/o
36648 By default and if not explicitly closed by the target system, the file
36649 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36650 on the @value{GDBN} console is handled as any other file output operation
36651 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36652 by @value{GDBN} so that after the target read request from file descriptor
36653 0 all following typing is buffered until either one of the following
36658 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36660 system call is treated as finished.
36663 The user presses @key{RET}. This is treated as end of input with a trailing
36667 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36668 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36672 If the user has typed more characters than fit in the buffer given to
36673 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36674 either another @code{read(0, @dots{})} is requested by the target, or debugging
36675 is stopped at the user's request.
36678 @node List of Supported Calls
36679 @subsection List of Supported Calls
36680 @cindex list of supported file-i/o calls
36697 @unnumberedsubsubsec open
36698 @cindex open, file-i/o system call
36703 int open(const char *pathname, int flags);
36704 int open(const char *pathname, int flags, mode_t mode);
36708 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36711 @var{flags} is the bitwise @code{OR} of the following values:
36715 If the file does not exist it will be created. The host
36716 rules apply as far as file ownership and time stamps
36720 When used with @code{O_CREAT}, if the file already exists it is
36721 an error and open() fails.
36724 If the file already exists and the open mode allows
36725 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36726 truncated to zero length.
36729 The file is opened in append mode.
36732 The file is opened for reading only.
36735 The file is opened for writing only.
36738 The file is opened for reading and writing.
36742 Other bits are silently ignored.
36746 @var{mode} is the bitwise @code{OR} of the following values:
36750 User has read permission.
36753 User has write permission.
36756 Group has read permission.
36759 Group has write permission.
36762 Others have read permission.
36765 Others have write permission.
36769 Other bits are silently ignored.
36772 @item Return value:
36773 @code{open} returns the new file descriptor or -1 if an error
36780 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36783 @var{pathname} refers to a directory.
36786 The requested access is not allowed.
36789 @var{pathname} was too long.
36792 A directory component in @var{pathname} does not exist.
36795 @var{pathname} refers to a device, pipe, named pipe or socket.
36798 @var{pathname} refers to a file on a read-only filesystem and
36799 write access was requested.
36802 @var{pathname} is an invalid pointer value.
36805 No space on device to create the file.
36808 The process already has the maximum number of files open.
36811 The limit on the total number of files open on the system
36815 The call was interrupted by the user.
36821 @unnumberedsubsubsec close
36822 @cindex close, file-i/o system call
36831 @samp{Fclose,@var{fd}}
36833 @item Return value:
36834 @code{close} returns zero on success, or -1 if an error occurred.
36840 @var{fd} isn't a valid open file descriptor.
36843 The call was interrupted by the user.
36849 @unnumberedsubsubsec read
36850 @cindex read, file-i/o system call
36855 int read(int fd, void *buf, unsigned int count);
36859 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36861 @item Return value:
36862 On success, the number of bytes read is returned.
36863 Zero indicates end of file. If count is zero, read
36864 returns zero as well. On error, -1 is returned.
36870 @var{fd} is not a valid file descriptor or is not open for
36874 @var{bufptr} is an invalid pointer value.
36877 The call was interrupted by the user.
36883 @unnumberedsubsubsec write
36884 @cindex write, file-i/o system call
36889 int write(int fd, const void *buf, unsigned int count);
36893 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36895 @item Return value:
36896 On success, the number of bytes written are returned.
36897 Zero indicates nothing was written. On error, -1
36904 @var{fd} is not a valid file descriptor or is not open for
36908 @var{bufptr} is an invalid pointer value.
36911 An attempt was made to write a file that exceeds the
36912 host-specific maximum file size allowed.
36915 No space on device to write the data.
36918 The call was interrupted by the user.
36924 @unnumberedsubsubsec lseek
36925 @cindex lseek, file-i/o system call
36930 long lseek (int fd, long offset, int flag);
36934 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36936 @var{flag} is one of:
36940 The offset is set to @var{offset} bytes.
36943 The offset is set to its current location plus @var{offset}
36947 The offset is set to the size of the file plus @var{offset}
36951 @item Return value:
36952 On success, the resulting unsigned offset in bytes from
36953 the beginning of the file is returned. Otherwise, a
36954 value of -1 is returned.
36960 @var{fd} is not a valid open file descriptor.
36963 @var{fd} is associated with the @value{GDBN} console.
36966 @var{flag} is not a proper value.
36969 The call was interrupted by the user.
36975 @unnumberedsubsubsec rename
36976 @cindex rename, file-i/o system call
36981 int rename(const char *oldpath, const char *newpath);
36985 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36987 @item Return value:
36988 On success, zero is returned. On error, -1 is returned.
36994 @var{newpath} is an existing directory, but @var{oldpath} is not a
36998 @var{newpath} is a non-empty directory.
37001 @var{oldpath} or @var{newpath} is a directory that is in use by some
37005 An attempt was made to make a directory a subdirectory
37009 A component used as a directory in @var{oldpath} or new
37010 path is not a directory. Or @var{oldpath} is a directory
37011 and @var{newpath} exists but is not a directory.
37014 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37017 No access to the file or the path of the file.
37021 @var{oldpath} or @var{newpath} was too long.
37024 A directory component in @var{oldpath} or @var{newpath} does not exist.
37027 The file is on a read-only filesystem.
37030 The device containing the file has no room for the new
37034 The call was interrupted by the user.
37040 @unnumberedsubsubsec unlink
37041 @cindex unlink, file-i/o system call
37046 int unlink(const char *pathname);
37050 @samp{Funlink,@var{pathnameptr}/@var{len}}
37052 @item Return value:
37053 On success, zero is returned. On error, -1 is returned.
37059 No access to the file or the path of the file.
37062 The system does not allow unlinking of directories.
37065 The file @var{pathname} cannot be unlinked because it's
37066 being used by another process.
37069 @var{pathnameptr} is an invalid pointer value.
37072 @var{pathname} was too long.
37075 A directory component in @var{pathname} does not exist.
37078 A component of the path is not a directory.
37081 The file is on a read-only filesystem.
37084 The call was interrupted by the user.
37090 @unnumberedsubsubsec stat/fstat
37091 @cindex fstat, file-i/o system call
37092 @cindex stat, file-i/o system call
37097 int stat(const char *pathname, struct stat *buf);
37098 int fstat(int fd, struct stat *buf);
37102 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37103 @samp{Ffstat,@var{fd},@var{bufptr}}
37105 @item Return value:
37106 On success, zero is returned. On error, -1 is returned.
37112 @var{fd} is not a valid open file.
37115 A directory component in @var{pathname} does not exist or the
37116 path is an empty string.
37119 A component of the path is not a directory.
37122 @var{pathnameptr} is an invalid pointer value.
37125 No access to the file or the path of the file.
37128 @var{pathname} was too long.
37131 The call was interrupted by the user.
37137 @unnumberedsubsubsec gettimeofday
37138 @cindex gettimeofday, file-i/o system call
37143 int gettimeofday(struct timeval *tv, void *tz);
37147 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37149 @item Return value:
37150 On success, 0 is returned, -1 otherwise.
37156 @var{tz} is a non-NULL pointer.
37159 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37165 @unnumberedsubsubsec isatty
37166 @cindex isatty, file-i/o system call
37171 int isatty(int fd);
37175 @samp{Fisatty,@var{fd}}
37177 @item Return value:
37178 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37184 The call was interrupted by the user.
37189 Note that the @code{isatty} call is treated as a special case: it returns
37190 1 to the target if the file descriptor is attached
37191 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37192 would require implementing @code{ioctl} and would be more complex than
37197 @unnumberedsubsubsec system
37198 @cindex system, file-i/o system call
37203 int system(const char *command);
37207 @samp{Fsystem,@var{commandptr}/@var{len}}
37209 @item Return value:
37210 If @var{len} is zero, the return value indicates whether a shell is
37211 available. A zero return value indicates a shell is not available.
37212 For non-zero @var{len}, the value returned is -1 on error and the
37213 return status of the command otherwise. Only the exit status of the
37214 command is returned, which is extracted from the host's @code{system}
37215 return value by calling @code{WEXITSTATUS(retval)}. In case
37216 @file{/bin/sh} could not be executed, 127 is returned.
37222 The call was interrupted by the user.
37227 @value{GDBN} takes over the full task of calling the necessary host calls
37228 to perform the @code{system} call. The return value of @code{system} on
37229 the host is simplified before it's returned
37230 to the target. Any termination signal information from the child process
37231 is discarded, and the return value consists
37232 entirely of the exit status of the called command.
37234 Due to security concerns, the @code{system} call is by default refused
37235 by @value{GDBN}. The user has to allow this call explicitly with the
37236 @code{set remote system-call-allowed 1} command.
37239 @item set remote system-call-allowed
37240 @kindex set remote system-call-allowed
37241 Control whether to allow the @code{system} calls in the File I/O
37242 protocol for the remote target. The default is zero (disabled).
37244 @item show remote system-call-allowed
37245 @kindex show remote system-call-allowed
37246 Show whether the @code{system} calls are allowed in the File I/O
37250 @node Protocol-specific Representation of Datatypes
37251 @subsection Protocol-specific Representation of Datatypes
37252 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37255 * Integral Datatypes::
37257 * Memory Transfer::
37262 @node Integral Datatypes
37263 @unnumberedsubsubsec Integral Datatypes
37264 @cindex integral datatypes, in file-i/o protocol
37266 The integral datatypes used in the system calls are @code{int},
37267 @code{unsigned int}, @code{long}, @code{unsigned long},
37268 @code{mode_t}, and @code{time_t}.
37270 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37271 implemented as 32 bit values in this protocol.
37273 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37275 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37276 in @file{limits.h}) to allow range checking on host and target.
37278 @code{time_t} datatypes are defined as seconds since the Epoch.
37280 All integral datatypes transferred as part of a memory read or write of a
37281 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37284 @node Pointer Values
37285 @unnumberedsubsubsec Pointer Values
37286 @cindex pointer values, in file-i/o protocol
37288 Pointers to target data are transmitted as they are. An exception
37289 is made for pointers to buffers for which the length isn't
37290 transmitted as part of the function call, namely strings. Strings
37291 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37298 which is a pointer to data of length 18 bytes at position 0x1aaf.
37299 The length is defined as the full string length in bytes, including
37300 the trailing null byte. For example, the string @code{"hello world"}
37301 at address 0x123456 is transmitted as
37307 @node Memory Transfer
37308 @unnumberedsubsubsec Memory Transfer
37309 @cindex memory transfer, in file-i/o protocol
37311 Structured data which is transferred using a memory read or write (for
37312 example, a @code{struct stat}) is expected to be in a protocol-specific format
37313 with all scalar multibyte datatypes being big endian. Translation to
37314 this representation needs to be done both by the target before the @code{F}
37315 packet is sent, and by @value{GDBN} before
37316 it transfers memory to the target. Transferred pointers to structured
37317 data should point to the already-coerced data at any time.
37321 @unnumberedsubsubsec struct stat
37322 @cindex struct stat, in file-i/o protocol
37324 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37325 is defined as follows:
37329 unsigned int st_dev; /* device */
37330 unsigned int st_ino; /* inode */
37331 mode_t st_mode; /* protection */
37332 unsigned int st_nlink; /* number of hard links */
37333 unsigned int st_uid; /* user ID of owner */
37334 unsigned int st_gid; /* group ID of owner */
37335 unsigned int st_rdev; /* device type (if inode device) */
37336 unsigned long st_size; /* total size, in bytes */
37337 unsigned long st_blksize; /* blocksize for filesystem I/O */
37338 unsigned long st_blocks; /* number of blocks allocated */
37339 time_t st_atime; /* time of last access */
37340 time_t st_mtime; /* time of last modification */
37341 time_t st_ctime; /* time of last change */
37345 The integral datatypes conform to the definitions given in the
37346 appropriate section (see @ref{Integral Datatypes}, for details) so this
37347 structure is of size 64 bytes.
37349 The values of several fields have a restricted meaning and/or
37355 A value of 0 represents a file, 1 the console.
37358 No valid meaning for the target. Transmitted unchanged.
37361 Valid mode bits are described in @ref{Constants}. Any other
37362 bits have currently no meaning for the target.
37367 No valid meaning for the target. Transmitted unchanged.
37372 These values have a host and file system dependent
37373 accuracy. Especially on Windows hosts, the file system may not
37374 support exact timing values.
37377 The target gets a @code{struct stat} of the above representation and is
37378 responsible for coercing it to the target representation before
37381 Note that due to size differences between the host, target, and protocol
37382 representations of @code{struct stat} members, these members could eventually
37383 get truncated on the target.
37385 @node struct timeval
37386 @unnumberedsubsubsec struct timeval
37387 @cindex struct timeval, in file-i/o protocol
37389 The buffer of type @code{struct timeval} used by the File-I/O protocol
37390 is defined as follows:
37394 time_t tv_sec; /* second */
37395 long tv_usec; /* microsecond */
37399 The integral datatypes conform to the definitions given in the
37400 appropriate section (see @ref{Integral Datatypes}, for details) so this
37401 structure is of size 8 bytes.
37404 @subsection Constants
37405 @cindex constants, in file-i/o protocol
37407 The following values are used for the constants inside of the
37408 protocol. @value{GDBN} and target are responsible for translating these
37409 values before and after the call as needed.
37420 @unnumberedsubsubsec Open Flags
37421 @cindex open flags, in file-i/o protocol
37423 All values are given in hexadecimal representation.
37435 @node mode_t Values
37436 @unnumberedsubsubsec mode_t Values
37437 @cindex mode_t values, in file-i/o protocol
37439 All values are given in octal representation.
37456 @unnumberedsubsubsec Errno Values
37457 @cindex errno values, in file-i/o protocol
37459 All values are given in decimal representation.
37484 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37485 any error value not in the list of supported error numbers.
37488 @unnumberedsubsubsec Lseek Flags
37489 @cindex lseek flags, in file-i/o protocol
37498 @unnumberedsubsubsec Limits
37499 @cindex limits, in file-i/o protocol
37501 All values are given in decimal representation.
37504 INT_MIN -2147483648
37506 UINT_MAX 4294967295
37507 LONG_MIN -9223372036854775808
37508 LONG_MAX 9223372036854775807
37509 ULONG_MAX 18446744073709551615
37512 @node File-I/O Examples
37513 @subsection File-I/O Examples
37514 @cindex file-i/o examples
37516 Example sequence of a write call, file descriptor 3, buffer is at target
37517 address 0x1234, 6 bytes should be written:
37520 <- @code{Fwrite,3,1234,6}
37521 @emph{request memory read from target}
37524 @emph{return "6 bytes written"}
37528 Example sequence of a read call, file descriptor 3, buffer is at target
37529 address 0x1234, 6 bytes should be read:
37532 <- @code{Fread,3,1234,6}
37533 @emph{request memory write to target}
37534 -> @code{X1234,6:XXXXXX}
37535 @emph{return "6 bytes read"}
37539 Example sequence of a read call, call fails on the host due to invalid
37540 file descriptor (@code{EBADF}):
37543 <- @code{Fread,3,1234,6}
37547 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37551 <- @code{Fread,3,1234,6}
37556 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37560 <- @code{Fread,3,1234,6}
37561 -> @code{X1234,6:XXXXXX}
37565 @node Library List Format
37566 @section Library List Format
37567 @cindex library list format, remote protocol
37569 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37570 same process as your application to manage libraries. In this case,
37571 @value{GDBN} can use the loader's symbol table and normal memory
37572 operations to maintain a list of shared libraries. On other
37573 platforms, the operating system manages loaded libraries.
37574 @value{GDBN} can not retrieve the list of currently loaded libraries
37575 through memory operations, so it uses the @samp{qXfer:libraries:read}
37576 packet (@pxref{qXfer library list read}) instead. The remote stub
37577 queries the target's operating system and reports which libraries
37580 The @samp{qXfer:libraries:read} packet returns an XML document which
37581 lists loaded libraries and their offsets. Each library has an
37582 associated name and one or more segment or section base addresses,
37583 which report where the library was loaded in memory.
37585 For the common case of libraries that are fully linked binaries, the
37586 library should have a list of segments. If the target supports
37587 dynamic linking of a relocatable object file, its library XML element
37588 should instead include a list of allocated sections. The segment or
37589 section bases are start addresses, not relocation offsets; they do not
37590 depend on the library's link-time base addresses.
37592 @value{GDBN} must be linked with the Expat library to support XML
37593 library lists. @xref{Expat}.
37595 A simple memory map, with one loaded library relocated by a single
37596 offset, looks like this:
37600 <library name="/lib/libc.so.6">
37601 <segment address="0x10000000"/>
37606 Another simple memory map, with one loaded library with three
37607 allocated sections (.text, .data, .bss), looks like this:
37611 <library name="sharedlib.o">
37612 <section address="0x10000000"/>
37613 <section address="0x20000000"/>
37614 <section address="0x30000000"/>
37619 The format of a library list is described by this DTD:
37622 <!-- library-list: Root element with versioning -->
37623 <!ELEMENT library-list (library)*>
37624 <!ATTLIST library-list version CDATA #FIXED "1.0">
37625 <!ELEMENT library (segment*, section*)>
37626 <!ATTLIST library name CDATA #REQUIRED>
37627 <!ELEMENT segment EMPTY>
37628 <!ATTLIST segment address CDATA #REQUIRED>
37629 <!ELEMENT section EMPTY>
37630 <!ATTLIST section address CDATA #REQUIRED>
37633 In addition, segments and section descriptors cannot be mixed within a
37634 single library element, and you must supply at least one segment or
37635 section for each library.
37637 @node Library List Format for SVR4 Targets
37638 @section Library List Format for SVR4 Targets
37639 @cindex library list format, remote protocol
37641 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
37642 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
37643 shared libraries. Still a special library list provided by this packet is
37644 more efficient for the @value{GDBN} remote protocol.
37646 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
37647 loaded libraries and their SVR4 linker parameters. For each library on SVR4
37648 target, the following parameters are reported:
37652 @code{name}, the absolute file name from the @code{l_name} field of
37653 @code{struct link_map}.
37655 @code{lm} with address of @code{struct link_map} used for TLS
37656 (Thread Local Storage) access.
37658 @code{l_addr}, the displacement as read from the field @code{l_addr} of
37659 @code{struct link_map}. For prelinked libraries this is not an absolute
37660 memory address. It is a displacement of absolute memory address against
37661 address the file was prelinked to during the library load.
37663 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
37666 Additionally the single @code{main-lm} attribute specifies address of
37667 @code{struct link_map} used for the main executable. This parameter is used
37668 for TLS access and its presence is optional.
37670 @value{GDBN} must be linked with the Expat library to support XML
37671 SVR4 library lists. @xref{Expat}.
37673 A simple memory map, with two loaded libraries (which do not use prelink),
37677 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
37678 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
37680 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
37682 </library-list-svr>
37685 The format of an SVR4 library list is described by this DTD:
37688 <!-- library-list-svr4: Root element with versioning -->
37689 <!ELEMENT library-list-svr4 (library)*>
37690 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
37691 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
37692 <!ELEMENT library EMPTY>
37693 <!ATTLIST library name CDATA #REQUIRED>
37694 <!ATTLIST library lm CDATA #REQUIRED>
37695 <!ATTLIST library l_addr CDATA #REQUIRED>
37696 <!ATTLIST library l_ld CDATA #REQUIRED>
37699 @node Memory Map Format
37700 @section Memory Map Format
37701 @cindex memory map format
37703 To be able to write into flash memory, @value{GDBN} needs to obtain a
37704 memory map from the target. This section describes the format of the
37707 The memory map is obtained using the @samp{qXfer:memory-map:read}
37708 (@pxref{qXfer memory map read}) packet and is an XML document that
37709 lists memory regions.
37711 @value{GDBN} must be linked with the Expat library to support XML
37712 memory maps. @xref{Expat}.
37714 The top-level structure of the document is shown below:
37717 <?xml version="1.0"?>
37718 <!DOCTYPE memory-map
37719 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37720 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37726 Each region can be either:
37731 A region of RAM starting at @var{addr} and extending for @var{length}
37735 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37740 A region of read-only memory:
37743 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37748 A region of flash memory, with erasure blocks @var{blocksize}
37752 <memory type="flash" start="@var{addr}" length="@var{length}">
37753 <property name="blocksize">@var{blocksize}</property>
37759 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37760 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37761 packets to write to addresses in such ranges.
37763 The formal DTD for memory map format is given below:
37766 <!-- ................................................... -->
37767 <!-- Memory Map XML DTD ................................ -->
37768 <!-- File: memory-map.dtd .............................. -->
37769 <!-- .................................... .............. -->
37770 <!-- memory-map.dtd -->
37771 <!-- memory-map: Root element with versioning -->
37772 <!ELEMENT memory-map (memory | property)>
37773 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37774 <!ELEMENT memory (property)>
37775 <!-- memory: Specifies a memory region,
37776 and its type, or device. -->
37777 <!ATTLIST memory type CDATA #REQUIRED
37778 start CDATA #REQUIRED
37779 length CDATA #REQUIRED
37780 device CDATA #IMPLIED>
37781 <!-- property: Generic attribute tag -->
37782 <!ELEMENT property (#PCDATA | property)*>
37783 <!ATTLIST property name CDATA #REQUIRED>
37786 @node Thread List Format
37787 @section Thread List Format
37788 @cindex thread list format
37790 To efficiently update the list of threads and their attributes,
37791 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37792 (@pxref{qXfer threads read}) and obtains the XML document with
37793 the following structure:
37796 <?xml version="1.0"?>
37798 <thread id="id" core="0">
37799 ... description ...
37804 Each @samp{thread} element must have the @samp{id} attribute that
37805 identifies the thread (@pxref{thread-id syntax}). The
37806 @samp{core} attribute, if present, specifies which processor core
37807 the thread was last executing on. The content of the of @samp{thread}
37808 element is interpreted as human-readable auxilliary information.
37810 @node Traceframe Info Format
37811 @section Traceframe Info Format
37812 @cindex traceframe info format
37814 To be able to know which objects in the inferior can be examined when
37815 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37816 memory ranges, registers and trace state variables that have been
37817 collected in a traceframe.
37819 This list is obtained using the @samp{qXfer:traceframe-info:read}
37820 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37822 @value{GDBN} must be linked with the Expat library to support XML
37823 traceframe info discovery. @xref{Expat}.
37825 The top-level structure of the document is shown below:
37828 <?xml version="1.0"?>
37829 <!DOCTYPE traceframe-info
37830 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37831 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37837 Each traceframe block can be either:
37842 A region of collected memory starting at @var{addr} and extending for
37843 @var{length} bytes from there:
37846 <memory start="@var{addr}" length="@var{length}"/>
37851 The formal DTD for the traceframe info format is given below:
37854 <!ELEMENT traceframe-info (memory)* >
37855 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37857 <!ELEMENT memory EMPTY>
37858 <!ATTLIST memory start CDATA #REQUIRED
37859 length CDATA #REQUIRED>
37862 @include agentexpr.texi
37864 @node Target Descriptions
37865 @appendix Target Descriptions
37866 @cindex target descriptions
37868 One of the challenges of using @value{GDBN} to debug embedded systems
37869 is that there are so many minor variants of each processor
37870 architecture in use. It is common practice for vendors to start with
37871 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37872 and then make changes to adapt it to a particular market niche. Some
37873 architectures have hundreds of variants, available from dozens of
37874 vendors. This leads to a number of problems:
37878 With so many different customized processors, it is difficult for
37879 the @value{GDBN} maintainers to keep up with the changes.
37881 Since individual variants may have short lifetimes or limited
37882 audiences, it may not be worthwhile to carry information about every
37883 variant in the @value{GDBN} source tree.
37885 When @value{GDBN} does support the architecture of the embedded system
37886 at hand, the task of finding the correct architecture name to give the
37887 @command{set architecture} command can be error-prone.
37890 To address these problems, the @value{GDBN} remote protocol allows a
37891 target system to not only identify itself to @value{GDBN}, but to
37892 actually describe its own features. This lets @value{GDBN} support
37893 processor variants it has never seen before --- to the extent that the
37894 descriptions are accurate, and that @value{GDBN} understands them.
37896 @value{GDBN} must be linked with the Expat library to support XML
37897 target descriptions. @xref{Expat}.
37900 * Retrieving Descriptions:: How descriptions are fetched from a target.
37901 * Target Description Format:: The contents of a target description.
37902 * Predefined Target Types:: Standard types available for target
37904 * Standard Target Features:: Features @value{GDBN} knows about.
37907 @node Retrieving Descriptions
37908 @section Retrieving Descriptions
37910 Target descriptions can be read from the target automatically, or
37911 specified by the user manually. The default behavior is to read the
37912 description from the target. @value{GDBN} retrieves it via the remote
37913 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37914 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37915 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37916 XML document, of the form described in @ref{Target Description
37919 Alternatively, you can specify a file to read for the target description.
37920 If a file is set, the target will not be queried. The commands to
37921 specify a file are:
37924 @cindex set tdesc filename
37925 @item set tdesc filename @var{path}
37926 Read the target description from @var{path}.
37928 @cindex unset tdesc filename
37929 @item unset tdesc filename
37930 Do not read the XML target description from a file. @value{GDBN}
37931 will use the description supplied by the current target.
37933 @cindex show tdesc filename
37934 @item show tdesc filename
37935 Show the filename to read for a target description, if any.
37939 @node Target Description Format
37940 @section Target Description Format
37941 @cindex target descriptions, XML format
37943 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37944 document which complies with the Document Type Definition provided in
37945 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37946 means you can use generally available tools like @command{xmllint} to
37947 check that your feature descriptions are well-formed and valid.
37948 However, to help people unfamiliar with XML write descriptions for
37949 their targets, we also describe the grammar here.
37951 Target descriptions can identify the architecture of the remote target
37952 and (for some architectures) provide information about custom register
37953 sets. They can also identify the OS ABI of the remote target.
37954 @value{GDBN} can use this information to autoconfigure for your
37955 target, or to warn you if you connect to an unsupported target.
37957 Here is a simple target description:
37960 <target version="1.0">
37961 <architecture>i386:x86-64</architecture>
37966 This minimal description only says that the target uses
37967 the x86-64 architecture.
37969 A target description has the following overall form, with [ ] marking
37970 optional elements and @dots{} marking repeatable elements. The elements
37971 are explained further below.
37974 <?xml version="1.0"?>
37975 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37976 <target version="1.0">
37977 @r{[}@var{architecture}@r{]}
37978 @r{[}@var{osabi}@r{]}
37979 @r{[}@var{compatible}@r{]}
37980 @r{[}@var{feature}@dots{}@r{]}
37985 The description is generally insensitive to whitespace and line
37986 breaks, under the usual common-sense rules. The XML version
37987 declaration and document type declaration can generally be omitted
37988 (@value{GDBN} does not require them), but specifying them may be
37989 useful for XML validation tools. The @samp{version} attribute for
37990 @samp{<target>} may also be omitted, but we recommend
37991 including it; if future versions of @value{GDBN} use an incompatible
37992 revision of @file{gdb-target.dtd}, they will detect and report
37993 the version mismatch.
37995 @subsection Inclusion
37996 @cindex target descriptions, inclusion
37999 @cindex <xi:include>
38002 It can sometimes be valuable to split a target description up into
38003 several different annexes, either for organizational purposes, or to
38004 share files between different possible target descriptions. You can
38005 divide a description into multiple files by replacing any element of
38006 the target description with an inclusion directive of the form:
38009 <xi:include href="@var{document}"/>
38013 When @value{GDBN} encounters an element of this form, it will retrieve
38014 the named XML @var{document}, and replace the inclusion directive with
38015 the contents of that document. If the current description was read
38016 using @samp{qXfer}, then so will be the included document;
38017 @var{document} will be interpreted as the name of an annex. If the
38018 current description was read from a file, @value{GDBN} will look for
38019 @var{document} as a file in the same directory where it found the
38020 original description.
38022 @subsection Architecture
38023 @cindex <architecture>
38025 An @samp{<architecture>} element has this form:
38028 <architecture>@var{arch}</architecture>
38031 @var{arch} is one of the architectures from the set accepted by
38032 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38035 @cindex @code{<osabi>}
38037 This optional field was introduced in @value{GDBN} version 7.0.
38038 Previous versions of @value{GDBN} ignore it.
38040 An @samp{<osabi>} element has this form:
38043 <osabi>@var{abi-name}</osabi>
38046 @var{abi-name} is an OS ABI name from the same selection accepted by
38047 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38049 @subsection Compatible Architecture
38050 @cindex @code{<compatible>}
38052 This optional field was introduced in @value{GDBN} version 7.0.
38053 Previous versions of @value{GDBN} ignore it.
38055 A @samp{<compatible>} element has this form:
38058 <compatible>@var{arch}</compatible>
38061 @var{arch} is one of the architectures from the set accepted by
38062 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38064 A @samp{<compatible>} element is used to specify that the target
38065 is able to run binaries in some other than the main target architecture
38066 given by the @samp{<architecture>} element. For example, on the
38067 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38068 or @code{powerpc:common64}, but the system is able to run binaries
38069 in the @code{spu} architecture as well. The way to describe this
38070 capability with @samp{<compatible>} is as follows:
38073 <architecture>powerpc:common</architecture>
38074 <compatible>spu</compatible>
38077 @subsection Features
38080 Each @samp{<feature>} describes some logical portion of the target
38081 system. Features are currently used to describe available CPU
38082 registers and the types of their contents. A @samp{<feature>} element
38086 <feature name="@var{name}">
38087 @r{[}@var{type}@dots{}@r{]}
38093 Each feature's name should be unique within the description. The name
38094 of a feature does not matter unless @value{GDBN} has some special
38095 knowledge of the contents of that feature; if it does, the feature
38096 should have its standard name. @xref{Standard Target Features}.
38100 Any register's value is a collection of bits which @value{GDBN} must
38101 interpret. The default interpretation is a two's complement integer,
38102 but other types can be requested by name in the register description.
38103 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38104 Target Types}), and the description can define additional composite types.
38106 Each type element must have an @samp{id} attribute, which gives
38107 a unique (within the containing @samp{<feature>}) name to the type.
38108 Types must be defined before they are used.
38111 Some targets offer vector registers, which can be treated as arrays
38112 of scalar elements. These types are written as @samp{<vector>} elements,
38113 specifying the array element type, @var{type}, and the number of elements,
38117 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38121 If a register's value is usefully viewed in multiple ways, define it
38122 with a union type containing the useful representations. The
38123 @samp{<union>} element contains one or more @samp{<field>} elements,
38124 each of which has a @var{name} and a @var{type}:
38127 <union id="@var{id}">
38128 <field name="@var{name}" type="@var{type}"/>
38134 If a register's value is composed from several separate values, define
38135 it with a structure type. There are two forms of the @samp{<struct>}
38136 element; a @samp{<struct>} element must either contain only bitfields
38137 or contain no bitfields. If the structure contains only bitfields,
38138 its total size in bytes must be specified, each bitfield must have an
38139 explicit start and end, and bitfields are automatically assigned an
38140 integer type. The field's @var{start} should be less than or
38141 equal to its @var{end}, and zero represents the least significant bit.
38144 <struct id="@var{id}" size="@var{size}">
38145 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38150 If the structure contains no bitfields, then each field has an
38151 explicit type, and no implicit padding is added.
38154 <struct id="@var{id}">
38155 <field name="@var{name}" type="@var{type}"/>
38161 If a register's value is a series of single-bit flags, define it with
38162 a flags type. The @samp{<flags>} element has an explicit @var{size}
38163 and contains one or more @samp{<field>} elements. Each field has a
38164 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38168 <flags id="@var{id}" size="@var{size}">
38169 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38174 @subsection Registers
38177 Each register is represented as an element with this form:
38180 <reg name="@var{name}"
38181 bitsize="@var{size}"
38182 @r{[}regnum="@var{num}"@r{]}
38183 @r{[}save-restore="@var{save-restore}"@r{]}
38184 @r{[}type="@var{type}"@r{]}
38185 @r{[}group="@var{group}"@r{]}/>
38189 The components are as follows:
38194 The register's name; it must be unique within the target description.
38197 The register's size, in bits.
38200 The register's number. If omitted, a register's number is one greater
38201 than that of the previous register (either in the current feature or in
38202 a preceding feature); the first register in the target description
38203 defaults to zero. This register number is used to read or write
38204 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38205 packets, and registers appear in the @code{g} and @code{G} packets
38206 in order of increasing register number.
38209 Whether the register should be preserved across inferior function
38210 calls; this must be either @code{yes} or @code{no}. The default is
38211 @code{yes}, which is appropriate for most registers except for
38212 some system control registers; this is not related to the target's
38216 The type of the register. @var{type} may be a predefined type, a type
38217 defined in the current feature, or one of the special types @code{int}
38218 and @code{float}. @code{int} is an integer type of the correct size
38219 for @var{bitsize}, and @code{float} is a floating point type (in the
38220 architecture's normal floating point format) of the correct size for
38221 @var{bitsize}. The default is @code{int}.
38224 The register group to which this register belongs. @var{group} must
38225 be either @code{general}, @code{float}, or @code{vector}. If no
38226 @var{group} is specified, @value{GDBN} will not display the register
38227 in @code{info registers}.
38231 @node Predefined Target Types
38232 @section Predefined Target Types
38233 @cindex target descriptions, predefined types
38235 Type definitions in the self-description can build up composite types
38236 from basic building blocks, but can not define fundamental types. Instead,
38237 standard identifiers are provided by @value{GDBN} for the fundamental
38238 types. The currently supported types are:
38247 Signed integer types holding the specified number of bits.
38254 Unsigned integer types holding the specified number of bits.
38258 Pointers to unspecified code and data. The program counter and
38259 any dedicated return address register may be marked as code
38260 pointers; printing a code pointer converts it into a symbolic
38261 address. The stack pointer and any dedicated address registers
38262 may be marked as data pointers.
38265 Single precision IEEE floating point.
38268 Double precision IEEE floating point.
38271 The 12-byte extended precision format used by ARM FPA registers.
38274 The 10-byte extended precision format used by x87 registers.
38277 32bit @sc{eflags} register used by x86.
38280 32bit @sc{mxcsr} register used by x86.
38284 @node Standard Target Features
38285 @section Standard Target Features
38286 @cindex target descriptions, standard features
38288 A target description must contain either no registers or all the
38289 target's registers. If the description contains no registers, then
38290 @value{GDBN} will assume a default register layout, selected based on
38291 the architecture. If the description contains any registers, the
38292 default layout will not be used; the standard registers must be
38293 described in the target description, in such a way that @value{GDBN}
38294 can recognize them.
38296 This is accomplished by giving specific names to feature elements
38297 which contain standard registers. @value{GDBN} will look for features
38298 with those names and verify that they contain the expected registers;
38299 if any known feature is missing required registers, or if any required
38300 feature is missing, @value{GDBN} will reject the target
38301 description. You can add additional registers to any of the
38302 standard features --- @value{GDBN} will display them just as if
38303 they were added to an unrecognized feature.
38305 This section lists the known features and their expected contents.
38306 Sample XML documents for these features are included in the
38307 @value{GDBN} source tree, in the directory @file{gdb/features}.
38309 Names recognized by @value{GDBN} should include the name of the
38310 company or organization which selected the name, and the overall
38311 architecture to which the feature applies; so e.g.@: the feature
38312 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38314 The names of registers are not case sensitive for the purpose
38315 of recognizing standard features, but @value{GDBN} will only display
38316 registers using the capitalization used in the description.
38323 * PowerPC Features::
38329 @subsection ARM Features
38330 @cindex target descriptions, ARM features
38332 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38334 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38335 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38337 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38338 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38339 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38342 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38343 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38345 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38346 it should contain at least registers @samp{wR0} through @samp{wR15} and
38347 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38348 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38350 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38351 should contain at least registers @samp{d0} through @samp{d15}. If
38352 they are present, @samp{d16} through @samp{d31} should also be included.
38353 @value{GDBN} will synthesize the single-precision registers from
38354 halves of the double-precision registers.
38356 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38357 need to contain registers; it instructs @value{GDBN} to display the
38358 VFP double-precision registers as vectors and to synthesize the
38359 quad-precision registers from pairs of double-precision registers.
38360 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38361 be present and include 32 double-precision registers.
38363 @node i386 Features
38364 @subsection i386 Features
38365 @cindex target descriptions, i386 features
38367 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38368 targets. It should describe the following registers:
38372 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38374 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38376 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38377 @samp{fs}, @samp{gs}
38379 @samp{st0} through @samp{st7}
38381 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38382 @samp{foseg}, @samp{fooff} and @samp{fop}
38385 The register sets may be different, depending on the target.
38387 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38388 describe registers:
38392 @samp{xmm0} through @samp{xmm7} for i386
38394 @samp{xmm0} through @samp{xmm15} for amd64
38399 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38400 @samp{org.gnu.gdb.i386.sse} feature. It should
38401 describe the upper 128 bits of @sc{ymm} registers:
38405 @samp{ymm0h} through @samp{ymm7h} for i386
38407 @samp{ymm0h} through @samp{ymm15h} for amd64
38410 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38411 describe a single register, @samp{orig_eax}.
38413 @node MIPS Features
38414 @subsection MIPS Features
38415 @cindex target descriptions, MIPS features
38417 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38418 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38419 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38422 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38423 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38424 registers. They may be 32-bit or 64-bit depending on the target.
38426 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38427 it may be optional in a future version of @value{GDBN}. It should
38428 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38429 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38431 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38432 contain a single register, @samp{restart}, which is used by the
38433 Linux kernel to control restartable syscalls.
38435 @node M68K Features
38436 @subsection M68K Features
38437 @cindex target descriptions, M68K features
38440 @item @samp{org.gnu.gdb.m68k.core}
38441 @itemx @samp{org.gnu.gdb.coldfire.core}
38442 @itemx @samp{org.gnu.gdb.fido.core}
38443 One of those features must be always present.
38444 The feature that is present determines which flavor of m68k is
38445 used. The feature that is present should contain registers
38446 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38447 @samp{sp}, @samp{ps} and @samp{pc}.
38449 @item @samp{org.gnu.gdb.coldfire.fp}
38450 This feature is optional. If present, it should contain registers
38451 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38455 @node PowerPC Features
38456 @subsection PowerPC Features
38457 @cindex target descriptions, PowerPC features
38459 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38460 targets. It should contain registers @samp{r0} through @samp{r31},
38461 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38462 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38464 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38465 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38467 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38468 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38471 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38472 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38473 will combine these registers with the floating point registers
38474 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38475 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38476 through @samp{vs63}, the set of vector registers for POWER7.
38478 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38479 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38480 @samp{spefscr}. SPE targets should provide 32-bit registers in
38481 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38482 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38483 these to present registers @samp{ev0} through @samp{ev31} to the
38486 @node TIC6x Features
38487 @subsection TMS320C6x Features
38488 @cindex target descriptions, TIC6x features
38489 @cindex target descriptions, TMS320C6x features
38490 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38491 targets. It should contain registers @samp{A0} through @samp{A15},
38492 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38494 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38495 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38496 through @samp{B31}.
38498 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38499 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38501 @node Operating System Information
38502 @appendix Operating System Information
38503 @cindex operating system information
38509 Users of @value{GDBN} often wish to obtain information about the state of
38510 the operating system running on the target---for example the list of
38511 processes, or the list of open files. This section describes the
38512 mechanism that makes it possible. This mechanism is similar to the
38513 target features mechanism (@pxref{Target Descriptions}), but focuses
38514 on a different aspect of target.
38516 Operating system information is retrived from the target via the
38517 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38518 read}). The object name in the request should be @samp{osdata}, and
38519 the @var{annex} identifies the data to be fetched.
38522 @appendixsection Process list
38523 @cindex operating system information, process list
38525 When requesting the process list, the @var{annex} field in the
38526 @samp{qXfer} request should be @samp{processes}. The returned data is
38527 an XML document. The formal syntax of this document is defined in
38528 @file{gdb/features/osdata.dtd}.
38530 An example document is:
38533 <?xml version="1.0"?>
38534 <!DOCTYPE target SYSTEM "osdata.dtd">
38535 <osdata type="processes">
38537 <column name="pid">1</column>
38538 <column name="user">root</column>
38539 <column name="command">/sbin/init</column>
38540 <column name="cores">1,2,3</column>
38545 Each item should include a column whose name is @samp{pid}. The value
38546 of that column should identify the process on the target. The
38547 @samp{user} and @samp{command} columns are optional, and will be
38548 displayed by @value{GDBN}. The @samp{cores} column, if present,
38549 should contain a comma-separated list of cores that this process
38550 is running on. Target may provide additional columns,
38551 which @value{GDBN} currently ignores.
38553 @node Trace File Format
38554 @appendix Trace File Format
38555 @cindex trace file format
38557 The trace file comes in three parts: a header, a textual description
38558 section, and a trace frame section with binary data.
38560 The header has the form @code{\x7fTRACE0\n}. The first byte is
38561 @code{0x7f} so as to indicate that the file contains binary data,
38562 while the @code{0} is a version number that may have different values
38565 The description section consists of multiple lines of @sc{ascii} text
38566 separated by newline characters (@code{0xa}). The lines may include a
38567 variety of optional descriptive or context-setting information, such
38568 as tracepoint definitions or register set size. @value{GDBN} will
38569 ignore any line that it does not recognize. An empty line marks the end
38572 @c FIXME add some specific types of data
38574 The trace frame section consists of a number of consecutive frames.
38575 Each frame begins with a two-byte tracepoint number, followed by a
38576 four-byte size giving the amount of data in the frame. The data in
38577 the frame consists of a number of blocks, each introduced by a
38578 character indicating its type (at least register, memory, and trace
38579 state variable). The data in this section is raw binary, not a
38580 hexadecimal or other encoding; its endianness matches the target's
38583 @c FIXME bi-arch may require endianness/arch info in description section
38586 @item R @var{bytes}
38587 Register block. The number and ordering of bytes matches that of a
38588 @code{g} packet in the remote protocol. Note that these are the
38589 actual bytes, in target order and @value{GDBN} register order, not a
38590 hexadecimal encoding.
38592 @item M @var{address} @var{length} @var{bytes}...
38593 Memory block. This is a contiguous block of memory, at the 8-byte
38594 address @var{address}, with a 2-byte length @var{length}, followed by
38595 @var{length} bytes.
38597 @item V @var{number} @var{value}
38598 Trace state variable block. This records the 8-byte signed value
38599 @var{value} of trace state variable numbered @var{number}.
38603 Future enhancements of the trace file format may include additional types
38606 @node Index Section Format
38607 @appendix @code{.gdb_index} section format
38608 @cindex .gdb_index section format
38609 @cindex index section format
38611 This section documents the index section that is created by @code{save
38612 gdb-index} (@pxref{Index Files}). The index section is
38613 DWARF-specific; some knowledge of DWARF is assumed in this
38616 The mapped index file format is designed to be directly
38617 @code{mmap}able on any architecture. In most cases, a datum is
38618 represented using a little-endian 32-bit integer value, called an
38619 @code{offset_type}. Big endian machines must byte-swap the values
38620 before using them. Exceptions to this rule are noted. The data is
38621 laid out such that alignment is always respected.
38623 A mapped index consists of several areas, laid out in order.
38627 The file header. This is a sequence of values, of @code{offset_type}
38628 unless otherwise noted:
38632 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38633 Version 4 differs by its hashing function.
38636 The offset, from the start of the file, of the CU list.
38639 The offset, from the start of the file, of the types CU list. Note
38640 that this area can be empty, in which case this offset will be equal
38641 to the next offset.
38644 The offset, from the start of the file, of the address area.
38647 The offset, from the start of the file, of the symbol table.
38650 The offset, from the start of the file, of the constant pool.
38654 The CU list. This is a sequence of pairs of 64-bit little-endian
38655 values, sorted by the CU offset. The first element in each pair is
38656 the offset of a CU in the @code{.debug_info} section. The second
38657 element in each pair is the length of that CU. References to a CU
38658 elsewhere in the map are done using a CU index, which is just the
38659 0-based index into this table. Note that if there are type CUs, then
38660 conceptually CUs and type CUs form a single list for the purposes of
38664 The types CU list. This is a sequence of triplets of 64-bit
38665 little-endian values. In a triplet, the first value is the CU offset,
38666 the second value is the type offset in the CU, and the third value is
38667 the type signature. The types CU list is not sorted.
38670 The address area. The address area consists of a sequence of address
38671 entries. Each address entry has three elements:
38675 The low address. This is a 64-bit little-endian value.
38678 The high address. This is a 64-bit little-endian value. Like
38679 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38682 The CU index. This is an @code{offset_type} value.
38686 The symbol table. This is an open-addressed hash table. The size of
38687 the hash table is always a power of 2.
38689 Each slot in the hash table consists of a pair of @code{offset_type}
38690 values. The first value is the offset of the symbol's name in the
38691 constant pool. The second value is the offset of the CU vector in the
38694 If both values are 0, then this slot in the hash table is empty. This
38695 is ok because while 0 is a valid constant pool index, it cannot be a
38696 valid index for both a string and a CU vector.
38698 The hash value for a table entry is computed by applying an
38699 iterative hash function to the symbol's name. Starting with an
38700 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38701 the string is incorporated into the hash using the formula depending on the
38706 The formula is @code{r = r * 67 + c - 113}.
38709 The formula is @code{r = r * 67 + tolower (c) - 113}.
38712 The terminating @samp{\0} is not incorporated into the hash.
38714 The step size used in the hash table is computed via
38715 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38716 value, and @samp{size} is the size of the hash table. The step size
38717 is used to find the next candidate slot when handling a hash
38720 The names of C@t{++} symbols in the hash table are canonicalized. We
38721 don't currently have a simple description of the canonicalization
38722 algorithm; if you intend to create new index sections, you must read
38726 The constant pool. This is simply a bunch of bytes. It is organized
38727 so that alignment is correct: CU vectors are stored first, followed by
38730 A CU vector in the constant pool is a sequence of @code{offset_type}
38731 values. The first value is the number of CU indices in the vector.
38732 Each subsequent value is the index of a CU in the CU list. This
38733 element in the hash table is used to indicate which CUs define the
38736 A string in the constant pool is zero-terminated.
38741 @node GNU Free Documentation License
38742 @appendix GNU Free Documentation License
38751 % I think something like @colophon should be in texinfo. In the
38753 \long\def\colophon{\hbox to0pt{}\vfill
38754 \centerline{The body of this manual is set in}
38755 \centerline{\fontname\tenrm,}
38756 \centerline{with headings in {\bf\fontname\tenbf}}
38757 \centerline{and examples in {\tt\fontname\tentt}.}
38758 \centerline{{\it\fontname\tenit\/},}
38759 \centerline{{\bf\fontname\tenbf}, and}
38760 \centerline{{\sl\fontname\tensl\/}}
38761 \centerline{are used for emphasis.}\vfill}
38763 % Blame: doc@cygnus.com, 1991.