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 1-882114-77-9 @*
107 @node Top, Summary, (dir), (dir)
109 @top Debugging with @value{GDBN}
111 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
113 This is the @value{EDITION} Edition, for @value{GDBN}
114 @ifset VERSION_PACKAGE
115 @value{VERSION_PACKAGE}
117 Version @value{GDBVN}.
119 Copyright (C) 1988-2010 Free Software Foundation, Inc.
121 This edition of the GDB manual is dedicated to the memory of Fred
122 Fish. Fred was a long-standing contributor to GDB and to Free
123 software in general. We will miss him.
126 * Summary:: Summary of @value{GDBN}
127 * Sample Session:: A sample @value{GDBN} session
129 * Invocation:: Getting in and out of @value{GDBN}
130 * Commands:: @value{GDBN} commands
131 * Running:: Running programs under @value{GDBN}
132 * Stopping:: Stopping and continuing
133 * Reverse Execution:: Running programs backward
134 * Process Record and Replay:: Recording inferior's execution and replaying it
135 * Stack:: Examining the stack
136 * Source:: Examining source files
137 * Data:: Examining data
138 * Optimized Code:: Debugging optimized code
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Extending GDB:: Extending @value{GDBN}
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
158 * JIT Interface:: Using the JIT debugging interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 @ifset SYSTEM_READLINE
163 * Command Line Editing: (rluserman). Command Line Editing
164 * Using History Interactively: (history). Using History Interactively
166 @ifclear SYSTEM_READLINE
167 * Command Line Editing:: Command Line Editing
168 * Using History Interactively:: Using History Interactively
170 * In Memoriam:: In Memoriam
171 * Formatting Documentation:: How to format and print @value{GDBN} documentation
172 * Installing GDB:: Installing GDB
173 * Maintenance Commands:: Maintenance Commands
174 * Remote Protocol:: GDB Remote Serial Protocol
175 * Agent Expressions:: The GDB Agent Expression Mechanism
176 * Target Descriptions:: How targets can describe themselves to
178 * Operating System Information:: Getting additional information from
180 * Trace File Format:: GDB trace file format
181 * Index Section Format:: .gdb_index section format
182 * Copying:: GNU General Public License says
183 how you can copy and share GDB
184 * GNU Free Documentation License:: The license for this documentation
193 @unnumbered Summary of @value{GDBN}
195 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
196 going on ``inside'' another program while it executes---or what another
197 program was doing at the moment it crashed.
199 @value{GDBN} can do four main kinds of things (plus other things in support of
200 these) to help you catch bugs in the act:
204 Start your program, specifying anything that might affect its behavior.
207 Make your program stop on specified conditions.
210 Examine what has happened, when your program has stopped.
213 Change things in your program, so you can experiment with correcting the
214 effects of one bug and go on to learn about another.
217 You can use @value{GDBN} to debug programs written in C and C@t{++}.
218 For more information, see @ref{Supported Languages,,Supported Languages}.
219 For more information, see @ref{C,,C and C++}.
221 Support for D is partial. For information on D, see
225 Support for Modula-2 is partial. For information on Modula-2, see
226 @ref{Modula-2,,Modula-2}.
228 Support for OpenCL C is partial. For information on OpenCL C, see
229 @ref{OpenCL C,,OpenCL C}.
232 Debugging Pascal programs which use sets, subranges, file variables, or
233 nested functions does not currently work. @value{GDBN} does not support
234 entering expressions, printing values, or similar features using Pascal
238 @value{GDBN} can be used to debug programs written in Fortran, although
239 it may be necessary to refer to some variables with a trailing
242 @value{GDBN} can be used to debug programs written in Objective-C,
243 using either the Apple/NeXT or the GNU Objective-C runtime.
246 * Free Software:: Freely redistributable software
247 * Contributors:: Contributors to GDB
251 @unnumberedsec Free Software
253 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
254 General Public License
255 (GPL). The GPL gives you the freedom to copy or adapt a licensed
256 program---but every person getting a copy also gets with it the
257 freedom to modify that copy (which means that they must get access to
258 the source code), and the freedom to distribute further copies.
259 Typical software companies use copyrights to limit your freedoms; the
260 Free Software Foundation uses the GPL to preserve these freedoms.
262 Fundamentally, the General Public License is a license which says that
263 you have these freedoms and that you cannot take these freedoms away
266 @unnumberedsec Free Software Needs Free Documentation
268 The biggest deficiency in the free software community today is not in
269 the software---it is the lack of good free documentation that we can
270 include with the free software. Many of our most important
271 programs do not come with free reference manuals and free introductory
272 texts. Documentation is an essential part of any software package;
273 when an important free software package does not come with a free
274 manual and a free tutorial, that is a major gap. We have many such
277 Consider Perl, for instance. The tutorial manuals that people
278 normally use are non-free. How did this come about? Because the
279 authors of those manuals published them with restrictive terms---no
280 copying, no modification, source files not available---which exclude
281 them from the free software world.
283 That wasn't the first time this sort of thing happened, and it was far
284 from the last. Many times we have heard a GNU user eagerly describe a
285 manual that he is writing, his intended contribution to the community,
286 only to learn that he had ruined everything by signing a publication
287 contract to make it non-free.
289 Free documentation, like free software, is a matter of freedom, not
290 price. The problem with the non-free manual is not that publishers
291 charge a price for printed copies---that in itself is fine. (The Free
292 Software Foundation sells printed copies of manuals, too.) The
293 problem is the restrictions on the use of the manual. Free manuals
294 are available in source code form, and give you permission to copy and
295 modify. Non-free manuals do not allow this.
297 The criteria of freedom for a free manual are roughly the same as for
298 free software. Redistribution (including the normal kinds of
299 commercial redistribution) must be permitted, so that the manual can
300 accompany every copy of the program, both on-line and on paper.
302 Permission for modification of the technical content is crucial too.
303 When people modify the software, adding or changing features, if they
304 are conscientious they will change the manual too---so they can
305 provide accurate and clear documentation for the modified program. A
306 manual that leaves you no choice but to write a new manual to document
307 a changed version of the program is not really available to our
310 Some kinds of limits on the way modification is handled are
311 acceptable. For example, requirements to preserve the original
312 author's copyright notice, the distribution terms, or the list of
313 authors, are ok. It is also no problem to require modified versions
314 to include notice that they were modified. Even entire sections that
315 may not be deleted or changed are acceptable, as long as they deal
316 with nontechnical topics (like this one). These kinds of restrictions
317 are acceptable because they don't obstruct the community's normal use
320 However, it must be possible to modify all the @emph{technical}
321 content of the manual, and then distribute the result in all the usual
322 media, through all the usual channels. Otherwise, the restrictions
323 obstruct the use of the manual, it is not free, and we need another
324 manual to replace it.
326 Please spread the word about this issue. Our community continues to
327 lose manuals to proprietary publishing. If we spread the word that
328 free software needs free reference manuals and free tutorials, perhaps
329 the next person who wants to contribute by writing documentation will
330 realize, before it is too late, that only free manuals contribute to
331 the free software community.
333 If you are writing documentation, please insist on publishing it under
334 the GNU Free Documentation License or another free documentation
335 license. Remember that this decision requires your approval---you
336 don't have to let the publisher decide. Some commercial publishers
337 will use a free license if you insist, but they will not propose the
338 option; it is up to you to raise the issue and say firmly that this is
339 what you want. If the publisher you are dealing with refuses, please
340 try other publishers. If you're not sure whether a proposed license
341 is free, write to @email{licensing@@gnu.org}.
343 You can encourage commercial publishers to sell more free, copylefted
344 manuals and tutorials by buying them, and particularly by buying
345 copies from the publishers that paid for their writing or for major
346 improvements. Meanwhile, try to avoid buying non-free documentation
347 at all. Check the distribution terms of a manual before you buy it,
348 and insist that whoever seeks your business must respect your freedom.
349 Check the history of the book, and try to reward the publishers that
350 have paid or pay the authors to work on it.
352 The Free Software Foundation maintains a list of free documentation
353 published by other publishers, at
354 @url{http://www.fsf.org/doc/other-free-books.html}.
357 @unnumberedsec Contributors to @value{GDBN}
359 Richard Stallman was the original author of @value{GDBN}, and of many
360 other @sc{gnu} programs. Many others have contributed to its
361 development. This section attempts to credit major contributors. One
362 of the virtues of free software is that everyone is free to contribute
363 to it; with regret, we cannot actually acknowledge everyone here. The
364 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
365 blow-by-blow account.
367 Changes much prior to version 2.0 are lost in the mists of time.
370 @emph{Plea:} Additions to this section are particularly welcome. If you
371 or your friends (or enemies, to be evenhanded) have been unfairly
372 omitted from this list, we would like to add your names!
375 So that they may not regard their many labors as thankless, we
376 particularly thank those who shepherded @value{GDBN} through major
378 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
379 Jim Blandy (release 4.18);
380 Jason Molenda (release 4.17);
381 Stan Shebs (release 4.14);
382 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
383 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
384 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
385 Jim Kingdon (releases 3.5, 3.4, and 3.3);
386 and Randy Smith (releases 3.2, 3.1, and 3.0).
388 Richard Stallman, assisted at various times by Peter TerMaat, Chris
389 Hanson, and Richard Mlynarik, handled releases through 2.8.
391 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
392 in @value{GDBN}, with significant additional contributions from Per
393 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
394 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
395 much general update work leading to release 3.0).
397 @value{GDBN} uses the BFD subroutine library to examine multiple
398 object-file formats; BFD was a joint project of David V.
399 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
401 David Johnson wrote the original COFF support; Pace Willison did
402 the original support for encapsulated COFF.
404 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
406 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
407 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
409 Jean-Daniel Fekete contributed Sun 386i support.
410 Chris Hanson improved the HP9000 support.
411 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
412 David Johnson contributed Encore Umax support.
413 Jyrki Kuoppala contributed Altos 3068 support.
414 Jeff Law contributed HP PA and SOM support.
415 Keith Packard contributed NS32K support.
416 Doug Rabson contributed Acorn Risc Machine support.
417 Bob Rusk contributed Harris Nighthawk CX-UX support.
418 Chris Smith contributed Convex support (and Fortran debugging).
419 Jonathan Stone contributed Pyramid support.
420 Michael Tiemann contributed SPARC support.
421 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
422 Pace Willison contributed Intel 386 support.
423 Jay Vosburgh contributed Symmetry support.
424 Marko Mlinar contributed OpenRISC 1000 support.
426 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
428 Rich Schaefer and Peter Schauer helped with support of SunOS shared
431 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
432 about several machine instruction sets.
434 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
435 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
436 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
437 and RDI targets, respectively.
439 Brian Fox is the author of the readline libraries providing
440 command-line editing and command history.
442 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
443 Modula-2 support, and contributed the Languages chapter of this manual.
445 Fred Fish wrote most of the support for Unix System Vr4.
446 He also enhanced the command-completion support to cover C@t{++} overloaded
449 Hitachi America (now Renesas America), Ltd. sponsored the support for
450 H8/300, H8/500, and Super-H processors.
452 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
454 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
457 Toshiba sponsored the support for the TX39 Mips processor.
459 Matsushita sponsored the support for the MN10200 and MN10300 processors.
461 Fujitsu sponsored the support for SPARClite and FR30 processors.
463 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
466 Michael Snyder added support for tracepoints.
468 Stu Grossman wrote gdbserver.
470 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
471 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
473 The following people at the Hewlett-Packard Company contributed
474 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
475 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
476 compiler, and the Text User Interface (nee Terminal User Interface):
477 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
478 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
479 provided HP-specific information in this manual.
481 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
482 Robert Hoehne made significant contributions to the DJGPP port.
484 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
485 development since 1991. Cygnus engineers who have worked on @value{GDBN}
486 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
487 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
488 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
489 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
490 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
491 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
492 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
493 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
494 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
495 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
496 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
497 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
498 Zuhn have made contributions both large and small.
500 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
501 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
503 Jim Blandy added support for preprocessor macros, while working for Red
506 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
507 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
508 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
509 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
510 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
511 with the migration of old architectures to this new framework.
513 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
514 unwinder framework, this consisting of a fresh new design featuring
515 frame IDs, independent frame sniffers, and the sentinel frame. Mark
516 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
517 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
518 trad unwinders. The architecture-specific changes, each involving a
519 complete rewrite of the architecture's frame code, were carried out by
520 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
521 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
522 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
523 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
526 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
527 Tensilica, Inc.@: contributed support for Xtensa processors. Others
528 who have worked on the Xtensa port of @value{GDBN} in the past include
529 Steve Tjiang, John Newlin, and Scott Foehner.
531 Michael Eager and staff of Xilinx, Inc., contributed support for the
532 Xilinx MicroBlaze architecture.
535 @chapter A Sample @value{GDBN} Session
537 You can use this manual at your leisure to read all about @value{GDBN}.
538 However, a handful of commands are enough to get started using the
539 debugger. This chapter illustrates those commands.
542 In this sample session, we emphasize user input like this: @b{input},
543 to make it easier to pick out from the surrounding output.
546 @c FIXME: this example may not be appropriate for some configs, where
547 @c FIXME...primary interest is in remote use.
549 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
550 processor) exhibits the following bug: sometimes, when we change its
551 quote strings from the default, the commands used to capture one macro
552 definition within another stop working. In the following short @code{m4}
553 session, we define a macro @code{foo} which expands to @code{0000}; we
554 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
555 same thing. However, when we change the open quote string to
556 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
557 procedure fails to define a new synonym @code{baz}:
566 @b{define(bar,defn(`foo'))}
570 @b{changequote(<QUOTE>,<UNQUOTE>)}
572 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
575 m4: End of input: 0: fatal error: EOF in string
579 Let us use @value{GDBN} to try to see what is going on.
582 $ @b{@value{GDBP} m4}
583 @c FIXME: this falsifies the exact text played out, to permit smallbook
584 @c FIXME... format to come out better.
585 @value{GDBN} is free software and you are welcome to distribute copies
586 of it under certain conditions; type "show copying" to see
588 There is absolutely no warranty for @value{GDBN}; type "show warranty"
591 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
596 @value{GDBN} reads only enough symbol data to know where to find the
597 rest when needed; as a result, the first prompt comes up very quickly.
598 We now tell @value{GDBN} to use a narrower display width than usual, so
599 that examples fit in this manual.
602 (@value{GDBP}) @b{set width 70}
606 We need to see how the @code{m4} built-in @code{changequote} works.
607 Having looked at the source, we know the relevant subroutine is
608 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
609 @code{break} command.
612 (@value{GDBP}) @b{break m4_changequote}
613 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
617 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
618 control; as long as control does not reach the @code{m4_changequote}
619 subroutine, the program runs as usual:
622 (@value{GDBP}) @b{run}
623 Starting program: /work/Editorial/gdb/gnu/m4/m4
631 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
632 suspends execution of @code{m4}, displaying information about the
633 context where it stops.
636 @b{changequote(<QUOTE>,<UNQUOTE>)}
638 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
640 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
644 Now we use the command @code{n} (@code{next}) to advance execution to
645 the next line of the current function.
649 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
654 @code{set_quotes} looks like a promising subroutine. We can go into it
655 by using the command @code{s} (@code{step}) instead of @code{next}.
656 @code{step} goes to the next line to be executed in @emph{any}
657 subroutine, so it steps into @code{set_quotes}.
661 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
663 530 if (lquote != def_lquote)
667 The display that shows the subroutine where @code{m4} is now
668 suspended (and its arguments) is called a stack frame display. It
669 shows a summary of the stack. We can use the @code{backtrace}
670 command (which can also be spelled @code{bt}), to see where we are
671 in the stack as a whole: the @code{backtrace} command displays a
672 stack frame for each active subroutine.
675 (@value{GDBP}) @b{bt}
676 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
680 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
681 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
683 #4 0x79dc in expand_input () at macro.c:40
684 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
688 We step through a few more lines to see what happens. The first two
689 times, we can use @samp{s}; the next two times we use @code{n} to avoid
690 falling into the @code{xstrdup} subroutine.
694 0x3b5c 532 if (rquote != def_rquote)
696 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
697 def_lquote : xstrdup(lq);
699 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
702 538 len_lquote = strlen(rquote);
706 The last line displayed looks a little odd; we can examine the variables
707 @code{lquote} and @code{rquote} to see if they are in fact the new left
708 and right quotes we specified. We use the command @code{p}
709 (@code{print}) to see their values.
712 (@value{GDBP}) @b{p lquote}
713 $1 = 0x35d40 "<QUOTE>"
714 (@value{GDBP}) @b{p rquote}
715 $2 = 0x35d50 "<UNQUOTE>"
719 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
720 To look at some context, we can display ten lines of source
721 surrounding the current line with the @code{l} (@code{list}) command.
727 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
729 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
732 538 len_lquote = strlen(rquote);
733 539 len_rquote = strlen(lquote);
740 Let us step past the two lines that set @code{len_lquote} and
741 @code{len_rquote}, and then examine the values of those variables.
745 539 len_rquote = strlen(lquote);
748 (@value{GDBP}) @b{p len_lquote}
750 (@value{GDBP}) @b{p len_rquote}
755 That certainly looks wrong, assuming @code{len_lquote} and
756 @code{len_rquote} are meant to be the lengths of @code{lquote} and
757 @code{rquote} respectively. We can set them to better values using
758 the @code{p} command, since it can print the value of
759 any expression---and that expression can include subroutine calls and
763 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
765 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
770 Is that enough to fix the problem of using the new quotes with the
771 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
772 executing with the @code{c} (@code{continue}) command, and then try the
773 example that caused trouble initially:
779 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
786 Success! The new quotes now work just as well as the default ones. The
787 problem seems to have been just the two typos defining the wrong
788 lengths. We allow @code{m4} exit by giving it an EOF as input:
792 Program exited normally.
796 The message @samp{Program exited normally.} is from @value{GDBN}; it
797 indicates @code{m4} has finished executing. We can end our @value{GDBN}
798 session with the @value{GDBN} @code{quit} command.
801 (@value{GDBP}) @b{quit}
805 @chapter Getting In and Out of @value{GDBN}
807 This chapter discusses how to start @value{GDBN}, and how to get out of it.
811 type @samp{@value{GDBP}} to start @value{GDBN}.
813 type @kbd{quit} or @kbd{Ctrl-d} to exit.
817 * Invoking GDB:: How to start @value{GDBN}
818 * Quitting GDB:: How to quit @value{GDBN}
819 * Shell Commands:: How to use shell commands inside @value{GDBN}
820 * Logging Output:: How to log @value{GDBN}'s output to a file
824 @section Invoking @value{GDBN}
826 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
827 @value{GDBN} reads commands from the terminal until you tell it to exit.
829 You can also run @code{@value{GDBP}} with a variety of arguments and options,
830 to specify more of your debugging environment at the outset.
832 The command-line options described here are designed
833 to cover a variety of situations; in some environments, some of these
834 options may effectively be unavailable.
836 The most usual way to start @value{GDBN} is with one argument,
837 specifying an executable program:
840 @value{GDBP} @var{program}
844 You can also start with both an executable program and a core file
848 @value{GDBP} @var{program} @var{core}
851 You can, instead, specify a process ID as a second argument, if you want
852 to debug a running process:
855 @value{GDBP} @var{program} 1234
859 would attach @value{GDBN} to process @code{1234} (unless you also have a file
860 named @file{1234}; @value{GDBN} does check for a core file first).
862 Taking advantage of the second command-line argument requires a fairly
863 complete operating system; when you use @value{GDBN} as a remote
864 debugger attached to a bare board, there may not be any notion of
865 ``process'', and there is often no way to get a core dump. @value{GDBN}
866 will warn you if it is unable to attach or to read core dumps.
868 You can optionally have @code{@value{GDBP}} pass any arguments after the
869 executable file to the inferior using @code{--args}. This option stops
872 @value{GDBP} --args gcc -O2 -c foo.c
874 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
875 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
877 You can run @code{@value{GDBP}} without printing the front material, which describes
878 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
885 You can further control how @value{GDBN} starts up by using command-line
886 options. @value{GDBN} itself can remind you of the options available.
896 to display all available options and briefly describe their use
897 (@samp{@value{GDBP} -h} is a shorter equivalent).
899 All options and command line arguments you give are processed
900 in sequential order. The order makes a difference when the
901 @samp{-x} option is used.
905 * File Options:: Choosing files
906 * Mode Options:: Choosing modes
907 * Startup:: What @value{GDBN} does during startup
911 @subsection Choosing Files
913 When @value{GDBN} starts, it reads any arguments other than options as
914 specifying an executable file and core file (or process ID). This is
915 the same as if the arguments were specified by the @samp{-se} and
916 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
917 first argument that does not have an associated option flag as
918 equivalent to the @samp{-se} option followed by that argument; and the
919 second argument that does not have an associated option flag, if any, as
920 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
921 If the second argument begins with a decimal digit, @value{GDBN} will
922 first attempt to attach to it as a process, and if that fails, attempt
923 to open it as a corefile. If you have a corefile whose name begins with
924 a digit, you can prevent @value{GDBN} from treating it as a pid by
925 prefixing it with @file{./}, e.g.@: @file{./12345}.
927 If @value{GDBN} has not been configured to included core file support,
928 such as for most embedded targets, then it will complain about a second
929 argument and ignore it.
931 Many options have both long and short forms; both are shown in the
932 following list. @value{GDBN} also recognizes the long forms if you truncate
933 them, so long as enough of the option is present to be unambiguous.
934 (If you prefer, you can flag option arguments with @samp{--} rather
935 than @samp{-}, though we illustrate the more usual convention.)
937 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
938 @c way, both those who look for -foo and --foo in the index, will find
942 @item -symbols @var{file}
944 @cindex @code{--symbols}
946 Read symbol table from file @var{file}.
948 @item -exec @var{file}
950 @cindex @code{--exec}
952 Use file @var{file} as the executable file to execute when appropriate,
953 and for examining pure data in conjunction with a core dump.
957 Read symbol table from file @var{file} and use it as the executable
960 @item -core @var{file}
962 @cindex @code{--core}
964 Use file @var{file} as a core dump to examine.
966 @item -pid @var{number}
967 @itemx -p @var{number}
970 Connect to process ID @var{number}, as with the @code{attach} command.
972 @item -command @var{file}
974 @cindex @code{--command}
976 Execute commands from file @var{file}. The contents of this file is
977 evaluated exactly as the @code{source} command would.
978 @xref{Command Files,, Command files}.
980 @item -eval-command @var{command}
981 @itemx -ex @var{command}
982 @cindex @code{--eval-command}
984 Execute a single @value{GDBN} command.
986 This option may be used multiple times to call multiple commands. It may
987 also be interleaved with @samp{-command} as required.
990 @value{GDBP} -ex 'target sim' -ex 'load' \
991 -x setbreakpoints -ex 'run' a.out
994 @item -directory @var{directory}
995 @itemx -d @var{directory}
996 @cindex @code{--directory}
998 Add @var{directory} to the path to search for source and script files.
1002 @cindex @code{--readnow}
1004 Read each symbol file's entire symbol table immediately, rather than
1005 the default, which is to read it incrementally as it is needed.
1006 This makes startup slower, but makes future operations faster.
1011 @subsection Choosing Modes
1013 You can run @value{GDBN} in various alternative modes---for example, in
1014 batch mode or quiet mode.
1021 Do not execute commands found in any initialization files. Normally,
1022 @value{GDBN} executes the commands in these files after all the command
1023 options and arguments have been processed. @xref{Command Files,,Command
1029 @cindex @code{--quiet}
1030 @cindex @code{--silent}
1032 ``Quiet''. Do not print the introductory and copyright messages. These
1033 messages are also suppressed in batch mode.
1036 @cindex @code{--batch}
1037 Run in batch mode. Exit with status @code{0} after processing all the
1038 command files specified with @samp{-x} (and all commands from
1039 initialization files, if not inhibited with @samp{-n}). Exit with
1040 nonzero status if an error occurs in executing the @value{GDBN} commands
1041 in the command files. Batch mode also disables pagination, sets unlimited
1042 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1043 off} were in effect (@pxref{Messages/Warnings}).
1045 Batch mode may be useful for running @value{GDBN} as a filter, for
1046 example to download and run a program on another computer; in order to
1047 make this more useful, the message
1050 Program exited normally.
1054 (which is ordinarily issued whenever a program running under
1055 @value{GDBN} control terminates) is not issued when running in batch
1059 @cindex @code{--batch-silent}
1060 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1061 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1062 unaffected). This is much quieter than @samp{-silent} and would be useless
1063 for an interactive session.
1065 This is particularly useful when using targets that give @samp{Loading section}
1066 messages, for example.
1068 Note that targets that give their output via @value{GDBN}, as opposed to
1069 writing directly to @code{stdout}, will also be made silent.
1071 @item -return-child-result
1072 @cindex @code{--return-child-result}
1073 The return code from @value{GDBN} will be the return code from the child
1074 process (the process being debugged), with the following exceptions:
1078 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1079 internal error. In this case the exit code is the same as it would have been
1080 without @samp{-return-child-result}.
1082 The user quits with an explicit value. E.g., @samp{quit 1}.
1084 The child process never runs, or is not allowed to terminate, in which case
1085 the exit code will be -1.
1088 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1089 when @value{GDBN} is being used as a remote program loader or simulator
1094 @cindex @code{--nowindows}
1096 ``No windows''. If @value{GDBN} comes with a graphical user interface
1097 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1098 interface. If no GUI is available, this option has no effect.
1102 @cindex @code{--windows}
1104 If @value{GDBN} includes a GUI, then this option requires it to be
1107 @item -cd @var{directory}
1109 Run @value{GDBN} using @var{directory} as its working directory,
1110 instead of the current directory.
1112 @item -data-directory @var{directory}
1113 @cindex @code{--data-directory}
1114 Run @value{GDBN} using @var{directory} as its data directory.
1115 The data directory is where @value{GDBN} searches for its
1116 auxiliary files. @xref{Data Files}.
1120 @cindex @code{--fullname}
1122 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1123 subprocess. It tells @value{GDBN} to output the full file name and line
1124 number in a standard, recognizable fashion each time a stack frame is
1125 displayed (which includes each time your program stops). This
1126 recognizable format looks like two @samp{\032} characters, followed by
1127 the file name, line number and character position separated by colons,
1128 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1129 @samp{\032} characters as a signal to display the source code for the
1133 @cindex @code{--epoch}
1134 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1135 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1136 routines so as to allow Epoch to display values of expressions in a
1139 @item -annotate @var{level}
1140 @cindex @code{--annotate}
1141 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1142 effect is identical to using @samp{set annotate @var{level}}
1143 (@pxref{Annotations}). The annotation @var{level} controls how much
1144 information @value{GDBN} prints together with its prompt, values of
1145 expressions, source lines, and other types of output. Level 0 is the
1146 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1147 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1148 that control @value{GDBN}, and level 2 has been deprecated.
1150 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1154 @cindex @code{--args}
1155 Change interpretation of command line so that arguments following the
1156 executable file are passed as command line arguments to the inferior.
1157 This option stops option processing.
1159 @item -baud @var{bps}
1161 @cindex @code{--baud}
1163 Set the line speed (baud rate or bits per second) of any serial
1164 interface used by @value{GDBN} for remote debugging.
1166 @item -l @var{timeout}
1168 Set the timeout (in seconds) of any communication used by @value{GDBN}
1169 for remote debugging.
1171 @item -tty @var{device}
1172 @itemx -t @var{device}
1173 @cindex @code{--tty}
1175 Run using @var{device} for your program's standard input and output.
1176 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1178 @c resolve the situation of these eventually
1180 @cindex @code{--tui}
1181 Activate the @dfn{Text User Interface} when starting. The Text User
1182 Interface manages several text windows on the terminal, showing
1183 source, assembly, registers and @value{GDBN} command outputs
1184 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1185 Text User Interface can be enabled by invoking the program
1186 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1187 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1190 @c @cindex @code{--xdb}
1191 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1192 @c For information, see the file @file{xdb_trans.html}, which is usually
1193 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1196 @item -interpreter @var{interp}
1197 @cindex @code{--interpreter}
1198 Use the interpreter @var{interp} for interface with the controlling
1199 program or device. This option is meant to be set by programs which
1200 communicate with @value{GDBN} using it as a back end.
1201 @xref{Interpreters, , Command Interpreters}.
1203 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1204 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1205 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1206 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1207 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1208 @sc{gdb/mi} interfaces are no longer supported.
1211 @cindex @code{--write}
1212 Open the executable and core files for both reading and writing. This
1213 is equivalent to the @samp{set write on} command inside @value{GDBN}
1217 @cindex @code{--statistics}
1218 This option causes @value{GDBN} to print statistics about time and
1219 memory usage after it completes each command and returns to the prompt.
1222 @cindex @code{--version}
1223 This option causes @value{GDBN} to print its version number and
1224 no-warranty blurb, and exit.
1229 @subsection What @value{GDBN} Does During Startup
1230 @cindex @value{GDBN} startup
1232 Here's the description of what @value{GDBN} does during session startup:
1236 Sets up the command interpreter as specified by the command line
1237 (@pxref{Mode Options, interpreter}).
1241 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1242 used when building @value{GDBN}; @pxref{System-wide configuration,
1243 ,System-wide configuration and settings}) and executes all the commands in
1247 Reads the init file (if any) in your home directory@footnote{On
1248 DOS/Windows systems, the home directory is the one pointed to by the
1249 @code{HOME} environment variable.} and executes all the commands in
1253 Processes command line options and operands.
1256 Reads and executes the commands from init file (if any) in the current
1257 working directory. This is only done if the current directory is
1258 different from your home directory. Thus, you can have more than one
1259 init file, one generic in your home directory, and another, specific
1260 to the program you are debugging, in the directory where you invoke
1264 If the command line specified a program to debug, or a process to
1265 attach to, or a core file, @value{GDBN} loads any auto-loaded
1266 scripts provided for the program or for its loaded shared libraries.
1267 @xref{Auto-loading}.
1269 If you wish to disable the auto-loading during startup,
1270 you must do something like the following:
1273 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1276 The following does not work because the auto-loading is turned off too late:
1279 $ gdb -ex "set auto-load-scripts off" myprogram
1283 Reads command files specified by the @samp{-x} option. @xref{Command
1284 Files}, for more details about @value{GDBN} command files.
1287 Reads the command history recorded in the @dfn{history file}.
1288 @xref{Command History}, for more details about the command history and the
1289 files where @value{GDBN} records it.
1292 Init files use the same syntax as @dfn{command files} (@pxref{Command
1293 Files}) and are processed by @value{GDBN} in the same way. The init
1294 file in your home directory can set options (such as @samp{set
1295 complaints}) that affect subsequent processing of command line options
1296 and operands. Init files are not executed if you use the @samp{-nx}
1297 option (@pxref{Mode Options, ,Choosing Modes}).
1299 To display the list of init files loaded by gdb at startup, you
1300 can use @kbd{gdb --help}.
1302 @cindex init file name
1303 @cindex @file{.gdbinit}
1304 @cindex @file{gdb.ini}
1305 The @value{GDBN} init files are normally called @file{.gdbinit}.
1306 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1307 the limitations of file names imposed by DOS filesystems. The Windows
1308 ports of @value{GDBN} use the standard name, but if they find a
1309 @file{gdb.ini} file, they warn you about that and suggest to rename
1310 the file to the standard name.
1314 @section Quitting @value{GDBN}
1315 @cindex exiting @value{GDBN}
1316 @cindex leaving @value{GDBN}
1319 @kindex quit @r{[}@var{expression}@r{]}
1320 @kindex q @r{(@code{quit})}
1321 @item quit @r{[}@var{expression}@r{]}
1323 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1324 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1325 do not supply @var{expression}, @value{GDBN} will terminate normally;
1326 otherwise it will terminate using the result of @var{expression} as the
1331 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1332 terminates the action of any @value{GDBN} command that is in progress and
1333 returns to @value{GDBN} command level. It is safe to type the interrupt
1334 character at any time because @value{GDBN} does not allow it to take effect
1335 until a time when it is safe.
1337 If you have been using @value{GDBN} to control an attached process or
1338 device, you can release it with the @code{detach} command
1339 (@pxref{Attach, ,Debugging an Already-running Process}).
1341 @node Shell Commands
1342 @section Shell Commands
1344 If you need to execute occasional shell commands during your
1345 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1346 just use the @code{shell} command.
1350 @cindex shell escape
1351 @item shell @var{command string}
1352 Invoke a standard shell to execute @var{command string}.
1353 If it exists, the environment variable @code{SHELL} determines which
1354 shell to run. Otherwise @value{GDBN} uses the default shell
1355 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1358 The utility @code{make} is often needed in development environments.
1359 You do not have to use the @code{shell} command for this purpose in
1364 @cindex calling make
1365 @item make @var{make-args}
1366 Execute the @code{make} program with the specified
1367 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1370 @node Logging Output
1371 @section Logging Output
1372 @cindex logging @value{GDBN} output
1373 @cindex save @value{GDBN} output to a file
1375 You may want to save the output of @value{GDBN} commands to a file.
1376 There are several commands to control @value{GDBN}'s logging.
1380 @item set logging on
1382 @item set logging off
1384 @cindex logging file name
1385 @item set logging file @var{file}
1386 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1387 @item set logging overwrite [on|off]
1388 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1389 you want @code{set logging on} to overwrite the logfile instead.
1390 @item set logging redirect [on|off]
1391 By default, @value{GDBN} output will go to both the terminal and the logfile.
1392 Set @code{redirect} if you want output to go only to the log file.
1393 @kindex show logging
1395 Show the current values of the logging settings.
1399 @chapter @value{GDBN} Commands
1401 You can abbreviate a @value{GDBN} command to the first few letters of the command
1402 name, if that abbreviation is unambiguous; and you can repeat certain
1403 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1404 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1405 show you the alternatives available, if there is more than one possibility).
1408 * Command Syntax:: How to give commands to @value{GDBN}
1409 * Completion:: Command completion
1410 * Help:: How to ask @value{GDBN} for help
1413 @node Command Syntax
1414 @section Command Syntax
1416 A @value{GDBN} command is a single line of input. There is no limit on
1417 how long it can be. It starts with a command name, which is followed by
1418 arguments whose meaning depends on the command name. For example, the
1419 command @code{step} accepts an argument which is the number of times to
1420 step, as in @samp{step 5}. You can also use the @code{step} command
1421 with no arguments. Some commands do not allow any arguments.
1423 @cindex abbreviation
1424 @value{GDBN} command names may always be truncated if that abbreviation is
1425 unambiguous. Other possible command abbreviations are listed in the
1426 documentation for individual commands. In some cases, even ambiguous
1427 abbreviations are allowed; for example, @code{s} is specially defined as
1428 equivalent to @code{step} even though there are other commands whose
1429 names start with @code{s}. You can test abbreviations by using them as
1430 arguments to the @code{help} command.
1432 @cindex repeating commands
1433 @kindex RET @r{(repeat last command)}
1434 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1435 repeat the previous command. Certain commands (for example, @code{run})
1436 will not repeat this way; these are commands whose unintentional
1437 repetition might cause trouble and which you are unlikely to want to
1438 repeat. User-defined commands can disable this feature; see
1439 @ref{Define, dont-repeat}.
1441 The @code{list} and @code{x} commands, when you repeat them with
1442 @key{RET}, construct new arguments rather than repeating
1443 exactly as typed. This permits easy scanning of source or memory.
1445 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1446 output, in a way similar to the common utility @code{more}
1447 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1448 @key{RET} too many in this situation, @value{GDBN} disables command
1449 repetition after any command that generates this sort of display.
1451 @kindex # @r{(a comment)}
1453 Any text from a @kbd{#} to the end of the line is a comment; it does
1454 nothing. This is useful mainly in command files (@pxref{Command
1455 Files,,Command Files}).
1457 @cindex repeating command sequences
1458 @kindex Ctrl-o @r{(operate-and-get-next)}
1459 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1460 commands. This command accepts the current line, like @key{RET}, and
1461 then fetches the next line relative to the current line from the history
1465 @section Command Completion
1468 @cindex word completion
1469 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1470 only one possibility; it can also show you what the valid possibilities
1471 are for the next word in a command, at any time. This works for @value{GDBN}
1472 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1474 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1475 of a word. If there is only one possibility, @value{GDBN} fills in the
1476 word, and waits for you to finish the command (or press @key{RET} to
1477 enter it). For example, if you type
1479 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1480 @c complete accuracy in these examples; space introduced for clarity.
1481 @c If texinfo enhancements make it unnecessary, it would be nice to
1482 @c replace " @key" by "@key" in the following...
1484 (@value{GDBP}) info bre @key{TAB}
1488 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1489 the only @code{info} subcommand beginning with @samp{bre}:
1492 (@value{GDBP}) info breakpoints
1496 You can either press @key{RET} at this point, to run the @code{info
1497 breakpoints} command, or backspace and enter something else, if
1498 @samp{breakpoints} does not look like the command you expected. (If you
1499 were sure you wanted @code{info breakpoints} in the first place, you
1500 might as well just type @key{RET} immediately after @samp{info bre},
1501 to exploit command abbreviations rather than command completion).
1503 If there is more than one possibility for the next word when you press
1504 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1505 characters and try again, or just press @key{TAB} a second time;
1506 @value{GDBN} displays all the possible completions for that word. For
1507 example, you might want to set a breakpoint on a subroutine whose name
1508 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1509 just sounds the bell. Typing @key{TAB} again displays all the
1510 function names in your program that begin with those characters, for
1514 (@value{GDBP}) b make_ @key{TAB}
1515 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1516 make_a_section_from_file make_environ
1517 make_abs_section make_function_type
1518 make_blockvector make_pointer_type
1519 make_cleanup make_reference_type
1520 make_command make_symbol_completion_list
1521 (@value{GDBP}) b make_
1525 After displaying the available possibilities, @value{GDBN} copies your
1526 partial input (@samp{b make_} in the example) so you can finish the
1529 If you just want to see the list of alternatives in the first place, you
1530 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1531 means @kbd{@key{META} ?}. You can type this either by holding down a
1532 key designated as the @key{META} shift on your keyboard (if there is
1533 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1535 @cindex quotes in commands
1536 @cindex completion of quoted strings
1537 Sometimes the string you need, while logically a ``word'', may contain
1538 parentheses or other characters that @value{GDBN} normally excludes from
1539 its notion of a word. To permit word completion to work in this
1540 situation, you may enclose words in @code{'} (single quote marks) in
1541 @value{GDBN} commands.
1543 The most likely situation where you might need this is in typing the
1544 name of a C@t{++} function. This is because C@t{++} allows function
1545 overloading (multiple definitions of the same function, distinguished
1546 by argument type). For example, when you want to set a breakpoint you
1547 may need to distinguish whether you mean the version of @code{name}
1548 that takes an @code{int} parameter, @code{name(int)}, or the version
1549 that takes a @code{float} parameter, @code{name(float)}. To use the
1550 word-completion facilities in this situation, type a single quote
1551 @code{'} at the beginning of the function name. This alerts
1552 @value{GDBN} that it may need to consider more information than usual
1553 when you press @key{TAB} or @kbd{M-?} to request word completion:
1556 (@value{GDBP}) b 'bubble( @kbd{M-?}
1557 bubble(double,double) bubble(int,int)
1558 (@value{GDBP}) b 'bubble(
1561 In some cases, @value{GDBN} can tell that completing a name requires using
1562 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1563 completing as much as it can) if you do not type the quote in the first
1567 (@value{GDBP}) b bub @key{TAB}
1568 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1569 (@value{GDBP}) b 'bubble(
1573 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1574 you have not yet started typing the argument list when you ask for
1575 completion on an overloaded symbol.
1577 For more information about overloaded functions, see @ref{C Plus Plus
1578 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1579 overload-resolution off} to disable overload resolution;
1580 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1582 @cindex completion of structure field names
1583 @cindex structure field name completion
1584 @cindex completion of union field names
1585 @cindex union field name completion
1586 When completing in an expression which looks up a field in a
1587 structure, @value{GDBN} also tries@footnote{The completer can be
1588 confused by certain kinds of invalid expressions. Also, it only
1589 examines the static type of the expression, not the dynamic type.} to
1590 limit completions to the field names available in the type of the
1594 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1595 magic to_fputs to_rewind
1596 to_data to_isatty to_write
1597 to_delete to_put to_write_async_safe
1602 This is because the @code{gdb_stdout} is a variable of the type
1603 @code{struct ui_file} that is defined in @value{GDBN} sources as
1610 ui_file_flush_ftype *to_flush;
1611 ui_file_write_ftype *to_write;
1612 ui_file_write_async_safe_ftype *to_write_async_safe;
1613 ui_file_fputs_ftype *to_fputs;
1614 ui_file_read_ftype *to_read;
1615 ui_file_delete_ftype *to_delete;
1616 ui_file_isatty_ftype *to_isatty;
1617 ui_file_rewind_ftype *to_rewind;
1618 ui_file_put_ftype *to_put;
1625 @section Getting Help
1626 @cindex online documentation
1629 You can always ask @value{GDBN} itself for information on its commands,
1630 using the command @code{help}.
1633 @kindex h @r{(@code{help})}
1636 You can use @code{help} (abbreviated @code{h}) with no arguments to
1637 display a short list of named classes of commands:
1641 List of classes of commands:
1643 aliases -- Aliases of other commands
1644 breakpoints -- Making program stop at certain points
1645 data -- Examining data
1646 files -- Specifying and examining files
1647 internals -- Maintenance commands
1648 obscure -- Obscure features
1649 running -- Running the program
1650 stack -- Examining the stack
1651 status -- Status inquiries
1652 support -- Support facilities
1653 tracepoints -- Tracing of program execution without
1654 stopping the program
1655 user-defined -- User-defined commands
1657 Type "help" followed by a class name for a list of
1658 commands in that class.
1659 Type "help" followed by command name for full
1661 Command name abbreviations are allowed if unambiguous.
1664 @c the above line break eliminates huge line overfull...
1666 @item help @var{class}
1667 Using one of the general help classes as an argument, you can get a
1668 list of the individual commands in that class. For example, here is the
1669 help display for the class @code{status}:
1672 (@value{GDBP}) help status
1677 @c Line break in "show" line falsifies real output, but needed
1678 @c to fit in smallbook page size.
1679 info -- Generic command for showing things
1680 about the program being debugged
1681 show -- Generic command for showing things
1684 Type "help" followed by command name for full
1686 Command name abbreviations are allowed if unambiguous.
1690 @item help @var{command}
1691 With a command name as @code{help} argument, @value{GDBN} displays a
1692 short paragraph on how to use that command.
1695 @item apropos @var{args}
1696 The @code{apropos} command searches through all of the @value{GDBN}
1697 commands, and their documentation, for the regular expression specified in
1698 @var{args}. It prints out all matches found. For example:
1709 set symbol-reloading -- Set dynamic symbol table reloading
1710 multiple times in one run
1711 show symbol-reloading -- Show dynamic symbol table reloading
1712 multiple times in one run
1717 @item complete @var{args}
1718 The @code{complete @var{args}} command lists all the possible completions
1719 for the beginning of a command. Use @var{args} to specify the beginning of the
1720 command you want completed. For example:
1726 @noindent results in:
1737 @noindent This is intended for use by @sc{gnu} Emacs.
1740 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1741 and @code{show} to inquire about the state of your program, or the state
1742 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1743 manual introduces each of them in the appropriate context. The listings
1744 under @code{info} and under @code{show} in the Index point to
1745 all the sub-commands. @xref{Index}.
1750 @kindex i @r{(@code{info})}
1752 This command (abbreviated @code{i}) is for describing the state of your
1753 program. For example, you can show the arguments passed to a function
1754 with @code{info args}, list the registers currently in use with @code{info
1755 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1756 You can get a complete list of the @code{info} sub-commands with
1757 @w{@code{help info}}.
1761 You can assign the result of an expression to an environment variable with
1762 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1763 @code{set prompt $}.
1767 In contrast to @code{info}, @code{show} is for describing the state of
1768 @value{GDBN} itself.
1769 You can change most of the things you can @code{show}, by using the
1770 related command @code{set}; for example, you can control what number
1771 system is used for displays with @code{set radix}, or simply inquire
1772 which is currently in use with @code{show radix}.
1775 To display all the settable parameters and their current
1776 values, you can use @code{show} with no arguments; you may also use
1777 @code{info set}. Both commands produce the same display.
1778 @c FIXME: "info set" violates the rule that "info" is for state of
1779 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1780 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1784 Here are three miscellaneous @code{show} subcommands, all of which are
1785 exceptional in lacking corresponding @code{set} commands:
1788 @kindex show version
1789 @cindex @value{GDBN} version number
1791 Show what version of @value{GDBN} is running. You should include this
1792 information in @value{GDBN} bug-reports. If multiple versions of
1793 @value{GDBN} are in use at your site, you may need to determine which
1794 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1795 commands are introduced, and old ones may wither away. Also, many
1796 system vendors ship variant versions of @value{GDBN}, and there are
1797 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1798 The version number is the same as the one announced when you start
1801 @kindex show copying
1802 @kindex info copying
1803 @cindex display @value{GDBN} copyright
1806 Display information about permission for copying @value{GDBN}.
1808 @kindex show warranty
1809 @kindex info warranty
1811 @itemx info warranty
1812 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1813 if your version of @value{GDBN} comes with one.
1818 @chapter Running Programs Under @value{GDBN}
1820 When you run a program under @value{GDBN}, you must first generate
1821 debugging information when you compile it.
1823 You may start @value{GDBN} with its arguments, if any, in an environment
1824 of your choice. If you are doing native debugging, you may redirect
1825 your program's input and output, debug an already running process, or
1826 kill a child process.
1829 * Compilation:: Compiling for debugging
1830 * Starting:: Starting your program
1831 * Arguments:: Your program's arguments
1832 * Environment:: Your program's environment
1834 * Working Directory:: Your program's working directory
1835 * Input/Output:: Your program's input and output
1836 * Attach:: Debugging an already-running process
1837 * Kill Process:: Killing the child process
1839 * Inferiors and Programs:: Debugging multiple inferiors and programs
1840 * Threads:: Debugging programs with multiple threads
1841 * Forks:: Debugging forks
1842 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1846 @section Compiling for Debugging
1848 In order to debug a program effectively, you need to generate
1849 debugging information when you compile it. This debugging information
1850 is stored in the object file; it describes the data type of each
1851 variable or function and the correspondence between source line numbers
1852 and addresses in the executable code.
1854 To request debugging information, specify the @samp{-g} option when you run
1857 Programs that are to be shipped to your customers are compiled with
1858 optimizations, using the @samp{-O} compiler option. However, some
1859 compilers are unable to handle the @samp{-g} and @samp{-O} options
1860 together. Using those compilers, you cannot generate optimized
1861 executables containing debugging information.
1863 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1864 without @samp{-O}, making it possible to debug optimized code. We
1865 recommend that you @emph{always} use @samp{-g} whenever you compile a
1866 program. You may think your program is correct, but there is no sense
1867 in pushing your luck. For more information, see @ref{Optimized Code}.
1869 Older versions of the @sc{gnu} C compiler permitted a variant option
1870 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1871 format; if your @sc{gnu} C compiler has this option, do not use it.
1873 @value{GDBN} knows about preprocessor macros and can show you their
1874 expansion (@pxref{Macros}). Most compilers do not include information
1875 about preprocessor macros in the debugging information if you specify
1876 the @option{-g} flag alone, because this information is rather large.
1877 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1878 provides macro information if you specify the options
1879 @option{-gdwarf-2} and @option{-g3}; the former option requests
1880 debugging information in the Dwarf 2 format, and the latter requests
1881 ``extra information''. In the future, we hope to find more compact
1882 ways to represent macro information, so that it can be included with
1887 @section Starting your Program
1893 @kindex r @r{(@code{run})}
1896 Use the @code{run} command to start your program under @value{GDBN}.
1897 You must first specify the program name (except on VxWorks) with an
1898 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1899 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1900 (@pxref{Files, ,Commands to Specify Files}).
1904 If you are running your program in an execution environment that
1905 supports processes, @code{run} creates an inferior process and makes
1906 that process run your program. In some environments without processes,
1907 @code{run} jumps to the start of your program. Other targets,
1908 like @samp{remote}, are always running. If you get an error
1909 message like this one:
1912 The "remote" target does not support "run".
1913 Try "help target" or "continue".
1917 then use @code{continue} to run your program. You may need @code{load}
1918 first (@pxref{load}).
1920 The execution of a program is affected by certain information it
1921 receives from its superior. @value{GDBN} provides ways to specify this
1922 information, which you must do @emph{before} starting your program. (You
1923 can change it after starting your program, but such changes only affect
1924 your program the next time you start it.) This information may be
1925 divided into four categories:
1928 @item The @emph{arguments.}
1929 Specify the arguments to give your program as the arguments of the
1930 @code{run} command. If a shell is available on your target, the shell
1931 is used to pass the arguments, so that you may use normal conventions
1932 (such as wildcard expansion or variable substitution) in describing
1934 In Unix systems, you can control which shell is used with the
1935 @code{SHELL} environment variable.
1936 @xref{Arguments, ,Your Program's Arguments}.
1938 @item The @emph{environment.}
1939 Your program normally inherits its environment from @value{GDBN}, but you can
1940 use the @value{GDBN} commands @code{set environment} and @code{unset
1941 environment} to change parts of the environment that affect
1942 your program. @xref{Environment, ,Your Program's Environment}.
1944 @item The @emph{working directory.}
1945 Your program inherits its working directory from @value{GDBN}. You can set
1946 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1947 @xref{Working Directory, ,Your Program's Working Directory}.
1949 @item The @emph{standard input and output.}
1950 Your program normally uses the same device for standard input and
1951 standard output as @value{GDBN} is using. You can redirect input and output
1952 in the @code{run} command line, or you can use the @code{tty} command to
1953 set a different device for your program.
1954 @xref{Input/Output, ,Your Program's Input and Output}.
1957 @emph{Warning:} While input and output redirection work, you cannot use
1958 pipes to pass the output of the program you are debugging to another
1959 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1963 When you issue the @code{run} command, your program begins to execute
1964 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1965 of how to arrange for your program to stop. Once your program has
1966 stopped, you may call functions in your program, using the @code{print}
1967 or @code{call} commands. @xref{Data, ,Examining Data}.
1969 If the modification time of your symbol file has changed since the last
1970 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1971 table, and reads it again. When it does this, @value{GDBN} tries to retain
1972 your current breakpoints.
1977 @cindex run to main procedure
1978 The name of the main procedure can vary from language to language.
1979 With C or C@t{++}, the main procedure name is always @code{main}, but
1980 other languages such as Ada do not require a specific name for their
1981 main procedure. The debugger provides a convenient way to start the
1982 execution of the program and to stop at the beginning of the main
1983 procedure, depending on the language used.
1985 The @samp{start} command does the equivalent of setting a temporary
1986 breakpoint at the beginning of the main procedure and then invoking
1987 the @samp{run} command.
1989 @cindex elaboration phase
1990 Some programs contain an @dfn{elaboration} phase where some startup code is
1991 executed before the main procedure is called. This depends on the
1992 languages used to write your program. In C@t{++}, for instance,
1993 constructors for static and global objects are executed before
1994 @code{main} is called. It is therefore possible that the debugger stops
1995 before reaching the main procedure. However, the temporary breakpoint
1996 will remain to halt execution.
1998 Specify the arguments to give to your program as arguments to the
1999 @samp{start} command. These arguments will be given verbatim to the
2000 underlying @samp{run} command. Note that the same arguments will be
2001 reused if no argument is provided during subsequent calls to
2002 @samp{start} or @samp{run}.
2004 It is sometimes necessary to debug the program during elaboration. In
2005 these cases, using the @code{start} command would stop the execution of
2006 your program too late, as the program would have already completed the
2007 elaboration phase. Under these circumstances, insert breakpoints in your
2008 elaboration code before running your program.
2010 @kindex set exec-wrapper
2011 @item set exec-wrapper @var{wrapper}
2012 @itemx show exec-wrapper
2013 @itemx unset exec-wrapper
2014 When @samp{exec-wrapper} is set, the specified wrapper is used to
2015 launch programs for debugging. @value{GDBN} starts your program
2016 with a shell command of the form @kbd{exec @var{wrapper}
2017 @var{program}}. Quoting is added to @var{program} and its
2018 arguments, but not to @var{wrapper}, so you should add quotes if
2019 appropriate for your shell. The wrapper runs until it executes
2020 your program, and then @value{GDBN} takes control.
2022 You can use any program that eventually calls @code{execve} with
2023 its arguments as a wrapper. Several standard Unix utilities do
2024 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2025 with @code{exec "$@@"} will also work.
2027 For example, you can use @code{env} to pass an environment variable to
2028 the debugged program, without setting the variable in your shell's
2032 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2036 This command is available when debugging locally on most targets, excluding
2037 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2039 @kindex set disable-randomization
2040 @item set disable-randomization
2041 @itemx set disable-randomization on
2042 This option (enabled by default in @value{GDBN}) will turn off the native
2043 randomization of the virtual address space of the started program. This option
2044 is useful for multiple debugging sessions to make the execution better
2045 reproducible and memory addresses reusable across debugging sessions.
2047 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2051 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2054 @item set disable-randomization off
2055 Leave the behavior of the started executable unchanged. Some bugs rear their
2056 ugly heads only when the program is loaded at certain addresses. If your bug
2057 disappears when you run the program under @value{GDBN}, that might be because
2058 @value{GDBN} by default disables the address randomization on platforms, such
2059 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2060 disable-randomization off} to try to reproduce such elusive bugs.
2062 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2063 It protects the programs against some kinds of security attacks. In these
2064 cases the attacker needs to know the exact location of a concrete executable
2065 code. Randomizing its location makes it impossible to inject jumps misusing
2066 a code at its expected addresses.
2068 Prelinking shared libraries provides a startup performance advantage but it
2069 makes addresses in these libraries predictable for privileged processes by
2070 having just unprivileged access at the target system. Reading the shared
2071 library binary gives enough information for assembling the malicious code
2072 misusing it. Still even a prelinked shared library can get loaded at a new
2073 random address just requiring the regular relocation process during the
2074 startup. Shared libraries not already prelinked are always loaded at
2075 a randomly chosen address.
2077 Position independent executables (PIE) contain position independent code
2078 similar to the shared libraries and therefore such executables get loaded at
2079 a randomly chosen address upon startup. PIE executables always load even
2080 already prelinked shared libraries at a random address. You can build such
2081 executable using @command{gcc -fPIE -pie}.
2083 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2084 (as long as the randomization is enabled).
2086 @item show disable-randomization
2087 Show the current setting of the explicit disable of the native randomization of
2088 the virtual address space of the started program.
2093 @section Your Program's Arguments
2095 @cindex arguments (to your program)
2096 The arguments to your program can be specified by the arguments of the
2098 They are passed to a shell, which expands wildcard characters and
2099 performs redirection of I/O, and thence to your program. Your
2100 @code{SHELL} environment variable (if it exists) specifies what shell
2101 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2102 the default shell (@file{/bin/sh} on Unix).
2104 On non-Unix systems, the program is usually invoked directly by
2105 @value{GDBN}, which emulates I/O redirection via the appropriate system
2106 calls, and the wildcard characters are expanded by the startup code of
2107 the program, not by the shell.
2109 @code{run} with no arguments uses the same arguments used by the previous
2110 @code{run}, or those set by the @code{set args} command.
2115 Specify the arguments to be used the next time your program is run. If
2116 @code{set args} has no arguments, @code{run} executes your program
2117 with no arguments. Once you have run your program with arguments,
2118 using @code{set args} before the next @code{run} is the only way to run
2119 it again without arguments.
2123 Show the arguments to give your program when it is started.
2127 @section Your Program's Environment
2129 @cindex environment (of your program)
2130 The @dfn{environment} consists of a set of environment variables and
2131 their values. Environment variables conventionally record such things as
2132 your user name, your home directory, your terminal type, and your search
2133 path for programs to run. Usually you set up environment variables with
2134 the shell and they are inherited by all the other programs you run. When
2135 debugging, it can be useful to try running your program with a modified
2136 environment without having to start @value{GDBN} over again.
2140 @item path @var{directory}
2141 Add @var{directory} to the front of the @code{PATH} environment variable
2142 (the search path for executables) that will be passed to your program.
2143 The value of @code{PATH} used by @value{GDBN} does not change.
2144 You may specify several directory names, separated by whitespace or by a
2145 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2146 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2147 is moved to the front, so it is searched sooner.
2149 You can use the string @samp{$cwd} to refer to whatever is the current
2150 working directory at the time @value{GDBN} searches the path. If you
2151 use @samp{.} instead, it refers to the directory where you executed the
2152 @code{path} command. @value{GDBN} replaces @samp{.} in the
2153 @var{directory} argument (with the current path) before adding
2154 @var{directory} to the search path.
2155 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2156 @c document that, since repeating it would be a no-op.
2160 Display the list of search paths for executables (the @code{PATH}
2161 environment variable).
2163 @kindex show environment
2164 @item show environment @r{[}@var{varname}@r{]}
2165 Print the value of environment variable @var{varname} to be given to
2166 your program when it starts. If you do not supply @var{varname},
2167 print the names and values of all environment variables to be given to
2168 your program. You can abbreviate @code{environment} as @code{env}.
2170 @kindex set environment
2171 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2172 Set environment variable @var{varname} to @var{value}. The value
2173 changes for your program only, not for @value{GDBN} itself. @var{value} may
2174 be any string; the values of environment variables are just strings, and
2175 any interpretation is supplied by your program itself. The @var{value}
2176 parameter is optional; if it is eliminated, the variable is set to a
2178 @c "any string" here does not include leading, trailing
2179 @c blanks. Gnu asks: does anyone care?
2181 For example, this command:
2188 tells the debugged program, when subsequently run, that its user is named
2189 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2190 are not actually required.)
2192 @kindex unset environment
2193 @item unset environment @var{varname}
2194 Remove variable @var{varname} from the environment to be passed to your
2195 program. This is different from @samp{set env @var{varname} =};
2196 @code{unset environment} removes the variable from the environment,
2197 rather than assigning it an empty value.
2200 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2202 by your @code{SHELL} environment variable if it exists (or
2203 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2204 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2205 @file{.bashrc} for BASH---any variables you set in that file affect
2206 your program. You may wish to move setting of environment variables to
2207 files that are only run when you sign on, such as @file{.login} or
2210 @node Working Directory
2211 @section Your Program's Working Directory
2213 @cindex working directory (of your program)
2214 Each time you start your program with @code{run}, it inherits its
2215 working directory from the current working directory of @value{GDBN}.
2216 The @value{GDBN} working directory is initially whatever it inherited
2217 from its parent process (typically the shell), but you can specify a new
2218 working directory in @value{GDBN} with the @code{cd} command.
2220 The @value{GDBN} working directory also serves as a default for the commands
2221 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2226 @cindex change working directory
2227 @item cd @var{directory}
2228 Set the @value{GDBN} working directory to @var{directory}.
2232 Print the @value{GDBN} working directory.
2235 It is generally impossible to find the current working directory of
2236 the process being debugged (since a program can change its directory
2237 during its run). If you work on a system where @value{GDBN} is
2238 configured with the @file{/proc} support, you can use the @code{info
2239 proc} command (@pxref{SVR4 Process Information}) to find out the
2240 current working directory of the debuggee.
2243 @section Your Program's Input and Output
2248 By default, the program you run under @value{GDBN} does input and output to
2249 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2250 to its own terminal modes to interact with you, but it records the terminal
2251 modes your program was using and switches back to them when you continue
2252 running your program.
2255 @kindex info terminal
2257 Displays information recorded by @value{GDBN} about the terminal modes your
2261 You can redirect your program's input and/or output using shell
2262 redirection with the @code{run} command. For example,
2269 starts your program, diverting its output to the file @file{outfile}.
2272 @cindex controlling terminal
2273 Another way to specify where your program should do input and output is
2274 with the @code{tty} command. This command accepts a file name as
2275 argument, and causes this file to be the default for future @code{run}
2276 commands. It also resets the controlling terminal for the child
2277 process, for future @code{run} commands. For example,
2284 directs that processes started with subsequent @code{run} commands
2285 default to do input and output on the terminal @file{/dev/ttyb} and have
2286 that as their controlling terminal.
2288 An explicit redirection in @code{run} overrides the @code{tty} command's
2289 effect on the input/output device, but not its effect on the controlling
2292 When you use the @code{tty} command or redirect input in the @code{run}
2293 command, only the input @emph{for your program} is affected. The input
2294 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2295 for @code{set inferior-tty}.
2297 @cindex inferior tty
2298 @cindex set inferior controlling terminal
2299 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2300 display the name of the terminal that will be used for future runs of your
2304 @item set inferior-tty /dev/ttyb
2305 @kindex set inferior-tty
2306 Set the tty for the program being debugged to /dev/ttyb.
2308 @item show inferior-tty
2309 @kindex show inferior-tty
2310 Show the current tty for the program being debugged.
2314 @section Debugging an Already-running Process
2319 @item attach @var{process-id}
2320 This command attaches to a running process---one that was started
2321 outside @value{GDBN}. (@code{info files} shows your active
2322 targets.) The command takes as argument a process ID. The usual way to
2323 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2324 or with the @samp{jobs -l} shell command.
2326 @code{attach} does not repeat if you press @key{RET} a second time after
2327 executing the command.
2330 To use @code{attach}, your program must be running in an environment
2331 which supports processes; for example, @code{attach} does not work for
2332 programs on bare-board targets that lack an operating system. You must
2333 also have permission to send the process a signal.
2335 When you use @code{attach}, the debugger finds the program running in
2336 the process first by looking in the current working directory, then (if
2337 the program is not found) by using the source file search path
2338 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2339 the @code{file} command to load the program. @xref{Files, ,Commands to
2342 The first thing @value{GDBN} does after arranging to debug the specified
2343 process is to stop it. You can examine and modify an attached process
2344 with all the @value{GDBN} commands that are ordinarily available when
2345 you start processes with @code{run}. You can insert breakpoints; you
2346 can step and continue; you can modify storage. If you would rather the
2347 process continue running, you may use the @code{continue} command after
2348 attaching @value{GDBN} to the process.
2353 When you have finished debugging the attached process, you can use the
2354 @code{detach} command to release it from @value{GDBN} control. Detaching
2355 the process continues its execution. After the @code{detach} command,
2356 that process and @value{GDBN} become completely independent once more, and you
2357 are ready to @code{attach} another process or start one with @code{run}.
2358 @code{detach} does not repeat if you press @key{RET} again after
2359 executing the command.
2362 If you exit @value{GDBN} while you have an attached process, you detach
2363 that process. If you use the @code{run} command, you kill that process.
2364 By default, @value{GDBN} asks for confirmation if you try to do either of these
2365 things; you can control whether or not you need to confirm by using the
2366 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2370 @section Killing the Child Process
2375 Kill the child process in which your program is running under @value{GDBN}.
2378 This command is useful if you wish to debug a core dump instead of a
2379 running process. @value{GDBN} ignores any core dump file while your program
2382 On some operating systems, a program cannot be executed outside @value{GDBN}
2383 while you have breakpoints set on it inside @value{GDBN}. You can use the
2384 @code{kill} command in this situation to permit running your program
2385 outside the debugger.
2387 The @code{kill} command is also useful if you wish to recompile and
2388 relink your program, since on many systems it is impossible to modify an
2389 executable file while it is running in a process. In this case, when you
2390 next type @code{run}, @value{GDBN} notices that the file has changed, and
2391 reads the symbol table again (while trying to preserve your current
2392 breakpoint settings).
2394 @node Inferiors and Programs
2395 @section Debugging Multiple Inferiors and Programs
2397 @value{GDBN} lets you run and debug multiple programs in a single
2398 session. In addition, @value{GDBN} on some systems may let you run
2399 several programs simultaneously (otherwise you have to exit from one
2400 before starting another). In the most general case, you can have
2401 multiple threads of execution in each of multiple processes, launched
2402 from multiple executables.
2405 @value{GDBN} represents the state of each program execution with an
2406 object called an @dfn{inferior}. An inferior typically corresponds to
2407 a process, but is more general and applies also to targets that do not
2408 have processes. Inferiors may be created before a process runs, and
2409 may be retained after a process exits. Inferiors have unique
2410 identifiers that are different from process ids. Usually each
2411 inferior will also have its own distinct address space, although some
2412 embedded targets may have several inferiors running in different parts
2413 of a single address space. Each inferior may in turn have multiple
2414 threads running in it.
2416 To find out what inferiors exist at any moment, use @w{@code{info
2420 @kindex info inferiors
2421 @item info inferiors
2422 Print a list of all inferiors currently being managed by @value{GDBN}.
2424 @value{GDBN} displays for each inferior (in this order):
2428 the inferior number assigned by @value{GDBN}
2431 the target system's inferior identifier
2434 the name of the executable the inferior is running.
2439 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2440 indicates the current inferior.
2444 @c end table here to get a little more width for example
2447 (@value{GDBP}) info inferiors
2448 Num Description Executable
2449 2 process 2307 hello
2450 * 1 process 3401 goodbye
2453 To switch focus between inferiors, use the @code{inferior} command:
2456 @kindex inferior @var{infno}
2457 @item inferior @var{infno}
2458 Make inferior number @var{infno} the current inferior. The argument
2459 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2460 in the first field of the @samp{info inferiors} display.
2464 You can get multiple executables into a debugging session via the
2465 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2466 systems @value{GDBN} can add inferiors to the debug session
2467 automatically by following calls to @code{fork} and @code{exec}. To
2468 remove inferiors from the debugging session use the
2469 @w{@code{remove-inferiors}} command.
2472 @kindex add-inferior
2473 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2474 Adds @var{n} inferiors to be run using @var{executable} as the
2475 executable. @var{n} defaults to 1. If no executable is specified,
2476 the inferiors begins empty, with no program. You can still assign or
2477 change the program assigned to the inferior at any time by using the
2478 @code{file} command with the executable name as its argument.
2480 @kindex clone-inferior
2481 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2482 Adds @var{n} inferiors ready to execute the same program as inferior
2483 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2484 number of the current inferior. This is a convenient command when you
2485 want to run another instance of the inferior you are debugging.
2488 (@value{GDBP}) info inferiors
2489 Num Description Executable
2490 * 1 process 29964 helloworld
2491 (@value{GDBP}) clone-inferior
2494 (@value{GDBP}) info inferiors
2495 Num Description Executable
2497 * 1 process 29964 helloworld
2500 You can now simply switch focus to inferior 2 and run it.
2502 @kindex remove-inferiors
2503 @item remove-inferiors @var{infno}@dots{}
2504 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2505 possible to remove an inferior that is running with this command. For
2506 those, use the @code{kill} or @code{detach} command first.
2510 To quit debugging one of the running inferiors that is not the current
2511 inferior, you can either detach from it by using the @w{@code{detach
2512 inferior}} command (allowing it to run independently), or kill it
2513 using the @w{@code{kill inferiors}} command:
2516 @kindex detach inferiors @var{infno}@dots{}
2517 @item detach inferior @var{infno}@dots{}
2518 Detach from the inferior or inferiors identified by @value{GDBN}
2519 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2520 still stays on the list of inferiors shown by @code{info inferiors},
2521 but its Description will show @samp{<null>}.
2523 @kindex kill inferiors @var{infno}@dots{}
2524 @item kill inferiors @var{infno}@dots{}
2525 Kill the inferior or inferiors identified by @value{GDBN} inferior
2526 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2527 stays on the list of inferiors shown by @code{info inferiors}, but its
2528 Description will show @samp{<null>}.
2531 After the successful completion of a command such as @code{detach},
2532 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2533 a normal process exit, the inferior is still valid and listed with
2534 @code{info inferiors}, ready to be restarted.
2537 To be notified when inferiors are started or exit under @value{GDBN}'s
2538 control use @w{@code{set print inferior-events}}:
2541 @kindex set print inferior-events
2542 @cindex print messages on inferior start and exit
2543 @item set print inferior-events
2544 @itemx set print inferior-events on
2545 @itemx set print inferior-events off
2546 The @code{set print inferior-events} command allows you to enable or
2547 disable printing of messages when @value{GDBN} notices that new
2548 inferiors have started or that inferiors have exited or have been
2549 detached. By default, these messages will not be printed.
2551 @kindex show print inferior-events
2552 @item show print inferior-events
2553 Show whether messages will be printed when @value{GDBN} detects that
2554 inferiors have started, exited or have been detached.
2557 Many commands will work the same with multiple programs as with a
2558 single program: e.g., @code{print myglobal} will simply display the
2559 value of @code{myglobal} in the current inferior.
2562 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2563 get more info about the relationship of inferiors, programs, address
2564 spaces in a debug session. You can do that with the @w{@code{maint
2565 info program-spaces}} command.
2568 @kindex maint info program-spaces
2569 @item maint info program-spaces
2570 Print a list of all program spaces currently being managed by
2573 @value{GDBN} displays for each program space (in this order):
2577 the program space number assigned by @value{GDBN}
2580 the name of the executable loaded into the program space, with e.g.,
2581 the @code{file} command.
2586 An asterisk @samp{*} preceding the @value{GDBN} program space number
2587 indicates the current program space.
2589 In addition, below each program space line, @value{GDBN} prints extra
2590 information that isn't suitable to display in tabular form. For
2591 example, the list of inferiors bound to the program space.
2594 (@value{GDBP}) maint info program-spaces
2597 Bound inferiors: ID 1 (process 21561)
2601 Here we can see that no inferior is running the program @code{hello},
2602 while @code{process 21561} is running the program @code{goodbye}. On
2603 some targets, it is possible that multiple inferiors are bound to the
2604 same program space. The most common example is that of debugging both
2605 the parent and child processes of a @code{vfork} call. For example,
2608 (@value{GDBP}) maint info program-spaces
2611 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2614 Here, both inferior 2 and inferior 1 are running in the same program
2615 space as a result of inferior 1 having executed a @code{vfork} call.
2619 @section Debugging Programs with Multiple Threads
2621 @cindex threads of execution
2622 @cindex multiple threads
2623 @cindex switching threads
2624 In some operating systems, such as HP-UX and Solaris, a single program
2625 may have more than one @dfn{thread} of execution. The precise semantics
2626 of threads differ from one operating system to another, but in general
2627 the threads of a single program are akin to multiple processes---except
2628 that they share one address space (that is, they can all examine and
2629 modify the same variables). On the other hand, each thread has its own
2630 registers and execution stack, and perhaps private memory.
2632 @value{GDBN} provides these facilities for debugging multi-thread
2636 @item automatic notification of new threads
2637 @item @samp{thread @var{threadno}}, a command to switch among threads
2638 @item @samp{info threads}, a command to inquire about existing threads
2639 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2640 a command to apply a command to a list of threads
2641 @item thread-specific breakpoints
2642 @item @samp{set print thread-events}, which controls printing of
2643 messages on thread start and exit.
2644 @item @samp{set libthread-db-search-path @var{path}}, which lets
2645 the user specify which @code{libthread_db} to use if the default choice
2646 isn't compatible with the program.
2650 @emph{Warning:} These facilities are not yet available on every
2651 @value{GDBN} configuration where the operating system supports threads.
2652 If your @value{GDBN} does not support threads, these commands have no
2653 effect. For example, a system without thread support shows no output
2654 from @samp{info threads}, and always rejects the @code{thread} command,
2658 (@value{GDBP}) info threads
2659 (@value{GDBP}) thread 1
2660 Thread ID 1 not known. Use the "info threads" command to
2661 see the IDs of currently known threads.
2663 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2664 @c doesn't support threads"?
2667 @cindex focus of debugging
2668 @cindex current thread
2669 The @value{GDBN} thread debugging facility allows you to observe all
2670 threads while your program runs---but whenever @value{GDBN} takes
2671 control, one thread in particular is always the focus of debugging.
2672 This thread is called the @dfn{current thread}. Debugging commands show
2673 program information from the perspective of the current thread.
2675 @cindex @code{New} @var{systag} message
2676 @cindex thread identifier (system)
2677 @c FIXME-implementors!! It would be more helpful if the [New...] message
2678 @c included GDB's numeric thread handle, so you could just go to that
2679 @c thread without first checking `info threads'.
2680 Whenever @value{GDBN} detects a new thread in your program, it displays
2681 the target system's identification for the thread with a message in the
2682 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2683 whose form varies depending on the particular system. For example, on
2684 @sc{gnu}/Linux, you might see
2687 [New Thread 0x41e02940 (LWP 25582)]
2691 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2692 the @var{systag} is simply something like @samp{process 368}, with no
2695 @c FIXME!! (1) Does the [New...] message appear even for the very first
2696 @c thread of a program, or does it only appear for the
2697 @c second---i.e.@: when it becomes obvious we have a multithread
2699 @c (2) *Is* there necessarily a first thread always? Or do some
2700 @c multithread systems permit starting a program with multiple
2701 @c threads ab initio?
2703 @cindex thread number
2704 @cindex thread identifier (GDB)
2705 For debugging purposes, @value{GDBN} associates its own thread
2706 number---always a single integer---with each thread in your program.
2709 @kindex info threads
2710 @item info threads @r{[}@var{id}@dots{}@r{]}
2711 Display a summary of all threads currently in your program. Optional
2712 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2713 means to print information only about the specified thread or threads.
2714 @value{GDBN} displays for each thread (in this order):
2718 the thread number assigned by @value{GDBN}
2721 the target system's thread identifier (@var{systag})
2724 the thread's name, if one is known. A thread can either be named by
2725 the user (see @code{thread name}, below), or, in some cases, by the
2729 the current stack frame summary for that thread
2733 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2734 indicates the current thread.
2738 @c end table here to get a little more width for example
2741 (@value{GDBP}) info threads
2743 3 process 35 thread 27 0x34e5 in sigpause ()
2744 2 process 35 thread 23 0x34e5 in sigpause ()
2745 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2749 On Solaris, you can display more information about user threads with a
2750 Solaris-specific command:
2753 @item maint info sol-threads
2754 @kindex maint info sol-threads
2755 @cindex thread info (Solaris)
2756 Display info on Solaris user threads.
2760 @kindex thread @var{threadno}
2761 @item thread @var{threadno}
2762 Make thread number @var{threadno} the current thread. The command
2763 argument @var{threadno} is the internal @value{GDBN} thread number, as
2764 shown in the first field of the @samp{info threads} display.
2765 @value{GDBN} responds by displaying the system identifier of the thread
2766 you selected, and its current stack frame summary:
2769 (@value{GDBP}) thread 2
2770 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2771 #0 some_function (ignore=0x0) at example.c:8
2772 8 printf ("hello\n");
2776 As with the @samp{[New @dots{}]} message, the form of the text after
2777 @samp{Switching to} depends on your system's conventions for identifying
2780 @vindex $_thread@r{, convenience variable}
2781 The debugger convenience variable @samp{$_thread} contains the number
2782 of the current thread. You may find this useful in writing breakpoint
2783 conditional expressions, command scripts, and so forth. See
2784 @xref{Convenience Vars,, Convenience Variables}, for general
2785 information on convenience variables.
2787 @kindex thread apply
2788 @cindex apply command to several threads
2789 @item thread apply [@var{threadno} | all] @var{command}
2790 The @code{thread apply} command allows you to apply the named
2791 @var{command} to one or more threads. Specify the numbers of the
2792 threads that you want affected with the command argument
2793 @var{threadno}. It can be a single thread number, one of the numbers
2794 shown in the first field of the @samp{info threads} display; or it
2795 could be a range of thread numbers, as in @code{2-4}. To apply a
2796 command to all threads, type @kbd{thread apply all @var{command}}.
2799 @cindex name a thread
2800 @item thread name [@var{name}]
2801 This command assigns a name to the current thread. If no argument is
2802 given, any existing user-specified name is removed. The thread name
2803 appears in the @samp{info threads} display.
2805 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2806 determine the name of the thread as given by the OS. On these
2807 systems, a name specified with @samp{thread name} will override the
2808 system-give name, and removing the user-specified name will cause
2809 @value{GDBN} to once again display the system-specified name.
2812 @cindex search for a thread
2813 @item thread find [@var{regexp}]
2814 Search for and display thread ids whose name or @var{systag}
2815 matches the supplied regular expression.
2817 As well as being the complement to the @samp{thread name} command,
2818 this command also allows you to identify a thread by its target
2819 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2823 (@value{GDBN}) thread find 26688
2824 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2825 (@value{GDBN}) info thread 4
2827 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2830 @kindex set print thread-events
2831 @cindex print messages on thread start and exit
2832 @item set print thread-events
2833 @itemx set print thread-events on
2834 @itemx set print thread-events off
2835 The @code{set print thread-events} command allows you to enable or
2836 disable printing of messages when @value{GDBN} notices that new threads have
2837 started or that threads have exited. By default, these messages will
2838 be printed if detection of these events is supported by the target.
2839 Note that these messages cannot be disabled on all targets.
2841 @kindex show print thread-events
2842 @item show print thread-events
2843 Show whether messages will be printed when @value{GDBN} detects that threads
2844 have started and exited.
2847 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2848 more information about how @value{GDBN} behaves when you stop and start
2849 programs with multiple threads.
2851 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2852 watchpoints in programs with multiple threads.
2855 @kindex set libthread-db-search-path
2856 @cindex search path for @code{libthread_db}
2857 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2858 If this variable is set, @var{path} is a colon-separated list of
2859 directories @value{GDBN} will use to search for @code{libthread_db}.
2860 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2861 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2862 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2865 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2866 @code{libthread_db} library to obtain information about threads in the
2867 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2868 to find @code{libthread_db}.
2870 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2871 refers to the default system directories that are
2872 normally searched for loading shared libraries.
2874 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2875 refers to the directory from which @code{libpthread}
2876 was loaded in the inferior process.
2878 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2879 @value{GDBN} attempts to initialize it with the current inferior process.
2880 If this initialization fails (which could happen because of a version
2881 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2882 will unload @code{libthread_db}, and continue with the next directory.
2883 If none of @code{libthread_db} libraries initialize successfully,
2884 @value{GDBN} will issue a warning and thread debugging will be disabled.
2886 Setting @code{libthread-db-search-path} is currently implemented
2887 only on some platforms.
2889 @kindex show libthread-db-search-path
2890 @item show libthread-db-search-path
2891 Display current libthread_db search path.
2893 @kindex set debug libthread-db
2894 @kindex show debug libthread-db
2895 @cindex debugging @code{libthread_db}
2896 @item set debug libthread-db
2897 @itemx show debug libthread-db
2898 Turns on or off display of @code{libthread_db}-related events.
2899 Use @code{1} to enable, @code{0} to disable.
2903 @section Debugging Forks
2905 @cindex fork, debugging programs which call
2906 @cindex multiple processes
2907 @cindex processes, multiple
2908 On most systems, @value{GDBN} has no special support for debugging
2909 programs which create additional processes using the @code{fork}
2910 function. When a program forks, @value{GDBN} will continue to debug the
2911 parent process and the child process will run unimpeded. If you have
2912 set a breakpoint in any code which the child then executes, the child
2913 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2914 will cause it to terminate.
2916 However, if you want to debug the child process there is a workaround
2917 which isn't too painful. Put a call to @code{sleep} in the code which
2918 the child process executes after the fork. It may be useful to sleep
2919 only if a certain environment variable is set, or a certain file exists,
2920 so that the delay need not occur when you don't want to run @value{GDBN}
2921 on the child. While the child is sleeping, use the @code{ps} program to
2922 get its process ID. Then tell @value{GDBN} (a new invocation of
2923 @value{GDBN} if you are also debugging the parent process) to attach to
2924 the child process (@pxref{Attach}). From that point on you can debug
2925 the child process just like any other process which you attached to.
2927 On some systems, @value{GDBN} provides support for debugging programs that
2928 create additional processes using the @code{fork} or @code{vfork} functions.
2929 Currently, the only platforms with this feature are HP-UX (11.x and later
2930 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2932 By default, when a program forks, @value{GDBN} will continue to debug
2933 the parent process and the child process will run unimpeded.
2935 If you want to follow the child process instead of the parent process,
2936 use the command @w{@code{set follow-fork-mode}}.
2939 @kindex set follow-fork-mode
2940 @item set follow-fork-mode @var{mode}
2941 Set the debugger response to a program call of @code{fork} or
2942 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2943 process. The @var{mode} argument can be:
2947 The original process is debugged after a fork. The child process runs
2948 unimpeded. This is the default.
2951 The new process is debugged after a fork. The parent process runs
2956 @kindex show follow-fork-mode
2957 @item show follow-fork-mode
2958 Display the current debugger response to a @code{fork} or @code{vfork} call.
2961 @cindex debugging multiple processes
2962 On Linux, if you want to debug both the parent and child processes, use the
2963 command @w{@code{set detach-on-fork}}.
2966 @kindex set detach-on-fork
2967 @item set detach-on-fork @var{mode}
2968 Tells gdb whether to detach one of the processes after a fork, or
2969 retain debugger control over them both.
2973 The child process (or parent process, depending on the value of
2974 @code{follow-fork-mode}) will be detached and allowed to run
2975 independently. This is the default.
2978 Both processes will be held under the control of @value{GDBN}.
2979 One process (child or parent, depending on the value of
2980 @code{follow-fork-mode}) is debugged as usual, while the other
2985 @kindex show detach-on-fork
2986 @item show detach-on-fork
2987 Show whether detach-on-fork mode is on/off.
2990 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2991 will retain control of all forked processes (including nested forks).
2992 You can list the forked processes under the control of @value{GDBN} by
2993 using the @w{@code{info inferiors}} command, and switch from one fork
2994 to another by using the @code{inferior} command (@pxref{Inferiors and
2995 Programs, ,Debugging Multiple Inferiors and Programs}).
2997 To quit debugging one of the forked processes, you can either detach
2998 from it by using the @w{@code{detach inferiors}} command (allowing it
2999 to run independently), or kill it using the @w{@code{kill inferiors}}
3000 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3003 If you ask to debug a child process and a @code{vfork} is followed by an
3004 @code{exec}, @value{GDBN} executes the new target up to the first
3005 breakpoint in the new target. If you have a breakpoint set on
3006 @code{main} in your original program, the breakpoint will also be set on
3007 the child process's @code{main}.
3009 On some systems, when a child process is spawned by @code{vfork}, you
3010 cannot debug the child or parent until an @code{exec} call completes.
3012 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3013 call executes, the new target restarts. To restart the parent
3014 process, use the @code{file} command with the parent executable name
3015 as its argument. By default, after an @code{exec} call executes,
3016 @value{GDBN} discards the symbols of the previous executable image.
3017 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3021 @kindex set follow-exec-mode
3022 @item set follow-exec-mode @var{mode}
3024 Set debugger response to a program call of @code{exec}. An
3025 @code{exec} call replaces the program image of a process.
3027 @code{follow-exec-mode} can be:
3031 @value{GDBN} creates a new inferior and rebinds the process to this
3032 new inferior. The program the process was running before the
3033 @code{exec} call can be restarted afterwards by restarting the
3039 (@value{GDBP}) info inferiors
3041 Id Description Executable
3044 process 12020 is executing new program: prog2
3045 Program exited normally.
3046 (@value{GDBP}) info inferiors
3047 Id Description Executable
3053 @value{GDBN} keeps the process bound to the same inferior. The new
3054 executable image replaces the previous executable loaded in the
3055 inferior. Restarting the inferior after the @code{exec} call, with
3056 e.g., the @code{run} command, restarts the executable the process was
3057 running after the @code{exec} call. This is the default mode.
3062 (@value{GDBP}) info inferiors
3063 Id Description Executable
3066 process 12020 is executing new program: prog2
3067 Program exited normally.
3068 (@value{GDBP}) info inferiors
3069 Id Description Executable
3076 You can use the @code{catch} command to make @value{GDBN} stop whenever
3077 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3078 Catchpoints, ,Setting Catchpoints}.
3080 @node Checkpoint/Restart
3081 @section Setting a @emph{Bookmark} to Return to Later
3086 @cindex snapshot of a process
3087 @cindex rewind program state
3089 On certain operating systems@footnote{Currently, only
3090 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3091 program's state, called a @dfn{checkpoint}, and come back to it
3094 Returning to a checkpoint effectively undoes everything that has
3095 happened in the program since the @code{checkpoint} was saved. This
3096 includes changes in memory, registers, and even (within some limits)
3097 system state. Effectively, it is like going back in time to the
3098 moment when the checkpoint was saved.
3100 Thus, if you're stepping thru a program and you think you're
3101 getting close to the point where things go wrong, you can save
3102 a checkpoint. Then, if you accidentally go too far and miss
3103 the critical statement, instead of having to restart your program
3104 from the beginning, you can just go back to the checkpoint and
3105 start again from there.
3107 This can be especially useful if it takes a lot of time or
3108 steps to reach the point where you think the bug occurs.
3110 To use the @code{checkpoint}/@code{restart} method of debugging:
3115 Save a snapshot of the debugged program's current execution state.
3116 The @code{checkpoint} command takes no arguments, but each checkpoint
3117 is assigned a small integer id, similar to a breakpoint id.
3119 @kindex info checkpoints
3120 @item info checkpoints
3121 List the checkpoints that have been saved in the current debugging
3122 session. For each checkpoint, the following information will be
3129 @item Source line, or label
3132 @kindex restart @var{checkpoint-id}
3133 @item restart @var{checkpoint-id}
3134 Restore the program state that was saved as checkpoint number
3135 @var{checkpoint-id}. All program variables, registers, stack frames
3136 etc.@: will be returned to the values that they had when the checkpoint
3137 was saved. In essence, gdb will ``wind back the clock'' to the point
3138 in time when the checkpoint was saved.
3140 Note that breakpoints, @value{GDBN} variables, command history etc.
3141 are not affected by restoring a checkpoint. In general, a checkpoint
3142 only restores things that reside in the program being debugged, not in
3145 @kindex delete checkpoint @var{checkpoint-id}
3146 @item delete checkpoint @var{checkpoint-id}
3147 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3151 Returning to a previously saved checkpoint will restore the user state
3152 of the program being debugged, plus a significant subset of the system
3153 (OS) state, including file pointers. It won't ``un-write'' data from
3154 a file, but it will rewind the file pointer to the previous location,
3155 so that the previously written data can be overwritten. For files
3156 opened in read mode, the pointer will also be restored so that the
3157 previously read data can be read again.
3159 Of course, characters that have been sent to a printer (or other
3160 external device) cannot be ``snatched back'', and characters received
3161 from eg.@: a serial device can be removed from internal program buffers,
3162 but they cannot be ``pushed back'' into the serial pipeline, ready to
3163 be received again. Similarly, the actual contents of files that have
3164 been changed cannot be restored (at this time).
3166 However, within those constraints, you actually can ``rewind'' your
3167 program to a previously saved point in time, and begin debugging it
3168 again --- and you can change the course of events so as to debug a
3169 different execution path this time.
3171 @cindex checkpoints and process id
3172 Finally, there is one bit of internal program state that will be
3173 different when you return to a checkpoint --- the program's process
3174 id. Each checkpoint will have a unique process id (or @var{pid}),
3175 and each will be different from the program's original @var{pid}.
3176 If your program has saved a local copy of its process id, this could
3177 potentially pose a problem.
3179 @subsection A Non-obvious Benefit of Using Checkpoints
3181 On some systems such as @sc{gnu}/Linux, address space randomization
3182 is performed on new processes for security reasons. This makes it
3183 difficult or impossible to set a breakpoint, or watchpoint, on an
3184 absolute address if you have to restart the program, since the
3185 absolute location of a symbol will change from one execution to the
3188 A checkpoint, however, is an @emph{identical} copy of a process.
3189 Therefore if you create a checkpoint at (eg.@:) the start of main,
3190 and simply return to that checkpoint instead of restarting the
3191 process, you can avoid the effects of address randomization and
3192 your symbols will all stay in the same place.
3195 @chapter Stopping and Continuing
3197 The principal purposes of using a debugger are so that you can stop your
3198 program before it terminates; or so that, if your program runs into
3199 trouble, you can investigate and find out why.
3201 Inside @value{GDBN}, your program may stop for any of several reasons,
3202 such as a signal, a breakpoint, or reaching a new line after a
3203 @value{GDBN} command such as @code{step}. You may then examine and
3204 change variables, set new breakpoints or remove old ones, and then
3205 continue execution. Usually, the messages shown by @value{GDBN} provide
3206 ample explanation of the status of your program---but you can also
3207 explicitly request this information at any time.
3210 @kindex info program
3212 Display information about the status of your program: whether it is
3213 running or not, what process it is, and why it stopped.
3217 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3218 * Continuing and Stepping:: Resuming execution
3220 * Thread Stops:: Stopping and starting multi-thread programs
3224 @section Breakpoints, Watchpoints, and Catchpoints
3227 A @dfn{breakpoint} makes your program stop whenever a certain point in
3228 the program is reached. For each breakpoint, you can add conditions to
3229 control in finer detail whether your program stops. You can set
3230 breakpoints with the @code{break} command and its variants (@pxref{Set
3231 Breaks, ,Setting Breakpoints}), to specify the place where your program
3232 should stop by line number, function name or exact address in the
3235 On some systems, you can set breakpoints in shared libraries before
3236 the executable is run. There is a minor limitation on HP-UX systems:
3237 you must wait until the executable is run in order to set breakpoints
3238 in shared library routines that are not called directly by the program
3239 (for example, routines that are arguments in a @code{pthread_create}
3243 @cindex data breakpoints
3244 @cindex memory tracing
3245 @cindex breakpoint on memory address
3246 @cindex breakpoint on variable modification
3247 A @dfn{watchpoint} is a special breakpoint that stops your program
3248 when the value of an expression changes. The expression may be a value
3249 of a variable, or it could involve values of one or more variables
3250 combined by operators, such as @samp{a + b}. This is sometimes called
3251 @dfn{data breakpoints}. You must use a different command to set
3252 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3253 from that, you can manage a watchpoint like any other breakpoint: you
3254 enable, disable, and delete both breakpoints and watchpoints using the
3257 You can arrange to have values from your program displayed automatically
3258 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3262 @cindex breakpoint on events
3263 A @dfn{catchpoint} is another special breakpoint that stops your program
3264 when a certain kind of event occurs, such as the throwing of a C@t{++}
3265 exception or the loading of a library. As with watchpoints, you use a
3266 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3267 Catchpoints}), but aside from that, you can manage a catchpoint like any
3268 other breakpoint. (To stop when your program receives a signal, use the
3269 @code{handle} command; see @ref{Signals, ,Signals}.)
3271 @cindex breakpoint numbers
3272 @cindex numbers for breakpoints
3273 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3274 catchpoint when you create it; these numbers are successive integers
3275 starting with one. In many of the commands for controlling various
3276 features of breakpoints you use the breakpoint number to say which
3277 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3278 @dfn{disabled}; if disabled, it has no effect on your program until you
3281 @cindex breakpoint ranges
3282 @cindex ranges of breakpoints
3283 Some @value{GDBN} commands accept a range of breakpoints on which to
3284 operate. A breakpoint range is either a single breakpoint number, like
3285 @samp{5}, or two such numbers, in increasing order, separated by a
3286 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3287 all breakpoints in that range are operated on.
3290 * Set Breaks:: Setting breakpoints
3291 * Set Watchpoints:: Setting watchpoints
3292 * Set Catchpoints:: Setting catchpoints
3293 * Delete Breaks:: Deleting breakpoints
3294 * Disabling:: Disabling breakpoints
3295 * Conditions:: Break conditions
3296 * Break Commands:: Breakpoint command lists
3297 * Save Breakpoints:: How to save breakpoints in a file
3298 * Error in Breakpoints:: ``Cannot insert breakpoints''
3299 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3303 @subsection Setting Breakpoints
3305 @c FIXME LMB what does GDB do if no code on line of breakpt?
3306 @c consider in particular declaration with/without initialization.
3308 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3311 @kindex b @r{(@code{break})}
3312 @vindex $bpnum@r{, convenience variable}
3313 @cindex latest breakpoint
3314 Breakpoints are set with the @code{break} command (abbreviated
3315 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3316 number of the breakpoint you've set most recently; see @ref{Convenience
3317 Vars,, Convenience Variables}, for a discussion of what you can do with
3318 convenience variables.
3321 @item break @var{location}
3322 Set a breakpoint at the given @var{location}, which can specify a
3323 function name, a line number, or an address of an instruction.
3324 (@xref{Specify Location}, for a list of all the possible ways to
3325 specify a @var{location}.) The breakpoint will stop your program just
3326 before it executes any of the code in the specified @var{location}.
3328 When using source languages that permit overloading of symbols, such as
3329 C@t{++}, a function name may refer to more than one possible place to break.
3330 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3333 It is also possible to insert a breakpoint that will stop the program
3334 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3335 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3338 When called without any arguments, @code{break} sets a breakpoint at
3339 the next instruction to be executed in the selected stack frame
3340 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3341 innermost, this makes your program stop as soon as control
3342 returns to that frame. This is similar to the effect of a
3343 @code{finish} command in the frame inside the selected frame---except
3344 that @code{finish} does not leave an active breakpoint. If you use
3345 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3346 the next time it reaches the current location; this may be useful
3349 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3350 least one instruction has been executed. If it did not do this, you
3351 would be unable to proceed past a breakpoint without first disabling the
3352 breakpoint. This rule applies whether or not the breakpoint already
3353 existed when your program stopped.
3355 @item break @dots{} if @var{cond}
3356 Set a breakpoint with condition @var{cond}; evaluate the expression
3357 @var{cond} each time the breakpoint is reached, and stop only if the
3358 value is nonzero---that is, if @var{cond} evaluates as true.
3359 @samp{@dots{}} stands for one of the possible arguments described
3360 above (or no argument) specifying where to break. @xref{Conditions,
3361 ,Break Conditions}, for more information on breakpoint conditions.
3364 @item tbreak @var{args}
3365 Set a breakpoint enabled only for one stop. @var{args} are the
3366 same as for the @code{break} command, and the breakpoint is set in the same
3367 way, but the breakpoint is automatically deleted after the first time your
3368 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3371 @cindex hardware breakpoints
3372 @item hbreak @var{args}
3373 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3374 @code{break} command and the breakpoint is set in the same way, but the
3375 breakpoint requires hardware support and some target hardware may not
3376 have this support. The main purpose of this is EPROM/ROM code
3377 debugging, so you can set a breakpoint at an instruction without
3378 changing the instruction. This can be used with the new trap-generation
3379 provided by SPARClite DSU and most x86-based targets. These targets
3380 will generate traps when a program accesses some data or instruction
3381 address that is assigned to the debug registers. However the hardware
3382 breakpoint registers can take a limited number of breakpoints. For
3383 example, on the DSU, only two data breakpoints can be set at a time, and
3384 @value{GDBN} will reject this command if more than two are used. Delete
3385 or disable unused hardware breakpoints before setting new ones
3386 (@pxref{Disabling, ,Disabling Breakpoints}).
3387 @xref{Conditions, ,Break Conditions}.
3388 For remote targets, you can restrict the number of hardware
3389 breakpoints @value{GDBN} will use, see @ref{set remote
3390 hardware-breakpoint-limit}.
3393 @item thbreak @var{args}
3394 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3395 are the same as for the @code{hbreak} command and the breakpoint is set in
3396 the same way. However, like the @code{tbreak} command,
3397 the breakpoint is automatically deleted after the
3398 first time your program stops there. Also, like the @code{hbreak}
3399 command, the breakpoint requires hardware support and some target hardware
3400 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3401 See also @ref{Conditions, ,Break Conditions}.
3404 @cindex regular expression
3405 @cindex breakpoints at functions matching a regexp
3406 @cindex set breakpoints in many functions
3407 @item rbreak @var{regex}
3408 Set breakpoints on all functions matching the regular expression
3409 @var{regex}. This command sets an unconditional breakpoint on all
3410 matches, printing a list of all breakpoints it set. Once these
3411 breakpoints are set, they are treated just like the breakpoints set with
3412 the @code{break} command. You can delete them, disable them, or make
3413 them conditional the same way as any other breakpoint.
3415 The syntax of the regular expression is the standard one used with tools
3416 like @file{grep}. Note that this is different from the syntax used by
3417 shells, so for instance @code{foo*} matches all functions that include
3418 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3419 @code{.*} leading and trailing the regular expression you supply, so to
3420 match only functions that begin with @code{foo}, use @code{^foo}.
3422 @cindex non-member C@t{++} functions, set breakpoint in
3423 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3424 breakpoints on overloaded functions that are not members of any special
3427 @cindex set breakpoints on all functions
3428 The @code{rbreak} command can be used to set breakpoints in
3429 @strong{all} the functions in a program, like this:
3432 (@value{GDBP}) rbreak .
3435 @item rbreak @var{file}:@var{regex}
3436 If @code{rbreak} is called with a filename qualification, it limits
3437 the search for functions matching the given regular expression to the
3438 specified @var{file}. This can be used, for example, to set breakpoints on
3439 every function in a given file:
3442 (@value{GDBP}) rbreak file.c:.
3445 The colon separating the filename qualifier from the regex may
3446 optionally be surrounded by spaces.
3448 @kindex info breakpoints
3449 @cindex @code{$_} and @code{info breakpoints}
3450 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3451 @itemx info break @r{[}@var{n}@dots{}@r{]}
3452 Print a table of all breakpoints, watchpoints, and catchpoints set and
3453 not deleted. Optional argument @var{n} means print information only
3454 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3455 For each breakpoint, following columns are printed:
3458 @item Breakpoint Numbers
3460 Breakpoint, watchpoint, or catchpoint.
3462 Whether the breakpoint is marked to be disabled or deleted when hit.
3463 @item Enabled or Disabled
3464 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3465 that are not enabled.
3467 Where the breakpoint is in your program, as a memory address. For a
3468 pending breakpoint whose address is not yet known, this field will
3469 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3470 library that has the symbol or line referred by breakpoint is loaded.
3471 See below for details. A breakpoint with several locations will
3472 have @samp{<MULTIPLE>} in this field---see below for details.
3474 Where the breakpoint is in the source for your program, as a file and
3475 line number. For a pending breakpoint, the original string passed to
3476 the breakpoint command will be listed as it cannot be resolved until
3477 the appropriate shared library is loaded in the future.
3481 If a breakpoint is conditional, @code{info break} shows the condition on
3482 the line following the affected breakpoint; breakpoint commands, if any,
3483 are listed after that. A pending breakpoint is allowed to have a condition
3484 specified for it. The condition is not parsed for validity until a shared
3485 library is loaded that allows the pending breakpoint to resolve to a
3489 @code{info break} with a breakpoint
3490 number @var{n} as argument lists only that breakpoint. The
3491 convenience variable @code{$_} and the default examining-address for
3492 the @code{x} command are set to the address of the last breakpoint
3493 listed (@pxref{Memory, ,Examining Memory}).
3496 @code{info break} displays a count of the number of times the breakpoint
3497 has been hit. This is especially useful in conjunction with the
3498 @code{ignore} command. You can ignore a large number of breakpoint
3499 hits, look at the breakpoint info to see how many times the breakpoint
3500 was hit, and then run again, ignoring one less than that number. This
3501 will get you quickly to the last hit of that breakpoint.
3504 @value{GDBN} allows you to set any number of breakpoints at the same place in
3505 your program. There is nothing silly or meaningless about this. When
3506 the breakpoints are conditional, this is even useful
3507 (@pxref{Conditions, ,Break Conditions}).
3509 @cindex multiple locations, breakpoints
3510 @cindex breakpoints, multiple locations
3511 It is possible that a breakpoint corresponds to several locations
3512 in your program. Examples of this situation are:
3516 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3517 instances of the function body, used in different cases.
3520 For a C@t{++} template function, a given line in the function can
3521 correspond to any number of instantiations.
3524 For an inlined function, a given source line can correspond to
3525 several places where that function is inlined.
3528 In all those cases, @value{GDBN} will insert a breakpoint at all
3529 the relevant locations@footnote{
3530 As of this writing, multiple-location breakpoints work only if there's
3531 line number information for all the locations. This means that they
3532 will generally not work in system libraries, unless you have debug
3533 info with line numbers for them.}.
3535 A breakpoint with multiple locations is displayed in the breakpoint
3536 table using several rows---one header row, followed by one row for
3537 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3538 address column. The rows for individual locations contain the actual
3539 addresses for locations, and show the functions to which those
3540 locations belong. The number column for a location is of the form
3541 @var{breakpoint-number}.@var{location-number}.
3546 Num Type Disp Enb Address What
3547 1 breakpoint keep y <MULTIPLE>
3549 breakpoint already hit 1 time
3550 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3551 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3554 Each location can be individually enabled or disabled by passing
3555 @var{breakpoint-number}.@var{location-number} as argument to the
3556 @code{enable} and @code{disable} commands. Note that you cannot
3557 delete the individual locations from the list, you can only delete the
3558 entire list of locations that belong to their parent breakpoint (with
3559 the @kbd{delete @var{num}} command, where @var{num} is the number of
3560 the parent breakpoint, 1 in the above example). Disabling or enabling
3561 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3562 that belong to that breakpoint.
3564 @cindex pending breakpoints
3565 It's quite common to have a breakpoint inside a shared library.
3566 Shared libraries can be loaded and unloaded explicitly,
3567 and possibly repeatedly, as the program is executed. To support
3568 this use case, @value{GDBN} updates breakpoint locations whenever
3569 any shared library is loaded or unloaded. Typically, you would
3570 set a breakpoint in a shared library at the beginning of your
3571 debugging session, when the library is not loaded, and when the
3572 symbols from the library are not available. When you try to set
3573 breakpoint, @value{GDBN} will ask you if you want to set
3574 a so called @dfn{pending breakpoint}---breakpoint whose address
3575 is not yet resolved.
3577 After the program is run, whenever a new shared library is loaded,
3578 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3579 shared library contains the symbol or line referred to by some
3580 pending breakpoint, that breakpoint is resolved and becomes an
3581 ordinary breakpoint. When a library is unloaded, all breakpoints
3582 that refer to its symbols or source lines become pending again.
3584 This logic works for breakpoints with multiple locations, too. For
3585 example, if you have a breakpoint in a C@t{++} template function, and
3586 a newly loaded shared library has an instantiation of that template,
3587 a new location is added to the list of locations for the breakpoint.
3589 Except for having unresolved address, pending breakpoints do not
3590 differ from regular breakpoints. You can set conditions or commands,
3591 enable and disable them and perform other breakpoint operations.
3593 @value{GDBN} provides some additional commands for controlling what
3594 happens when the @samp{break} command cannot resolve breakpoint
3595 address specification to an address:
3597 @kindex set breakpoint pending
3598 @kindex show breakpoint pending
3600 @item set breakpoint pending auto
3601 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3602 location, it queries you whether a pending breakpoint should be created.
3604 @item set breakpoint pending on
3605 This indicates that an unrecognized breakpoint location should automatically
3606 result in a pending breakpoint being created.
3608 @item set breakpoint pending off
3609 This indicates that pending breakpoints are not to be created. Any
3610 unrecognized breakpoint location results in an error. This setting does
3611 not affect any pending breakpoints previously created.
3613 @item show breakpoint pending
3614 Show the current behavior setting for creating pending breakpoints.
3617 The settings above only affect the @code{break} command and its
3618 variants. Once breakpoint is set, it will be automatically updated
3619 as shared libraries are loaded and unloaded.
3621 @cindex automatic hardware breakpoints
3622 For some targets, @value{GDBN} can automatically decide if hardware or
3623 software breakpoints should be used, depending on whether the
3624 breakpoint address is read-only or read-write. This applies to
3625 breakpoints set with the @code{break} command as well as to internal
3626 breakpoints set by commands like @code{next} and @code{finish}. For
3627 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3630 You can control this automatic behaviour with the following commands::
3632 @kindex set breakpoint auto-hw
3633 @kindex show breakpoint auto-hw
3635 @item set breakpoint auto-hw on
3636 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3637 will try to use the target memory map to decide if software or hardware
3638 breakpoint must be used.
3640 @item set breakpoint auto-hw off
3641 This indicates @value{GDBN} should not automatically select breakpoint
3642 type. If the target provides a memory map, @value{GDBN} will warn when
3643 trying to set software breakpoint at a read-only address.
3646 @value{GDBN} normally implements breakpoints by replacing the program code
3647 at the breakpoint address with a special instruction, which, when
3648 executed, given control to the debugger. By default, the program
3649 code is so modified only when the program is resumed. As soon as
3650 the program stops, @value{GDBN} restores the original instructions. This
3651 behaviour guards against leaving breakpoints inserted in the
3652 target should gdb abrubptly disconnect. However, with slow remote
3653 targets, inserting and removing breakpoint can reduce the performance.
3654 This behavior can be controlled with the following commands::
3656 @kindex set breakpoint always-inserted
3657 @kindex show breakpoint always-inserted
3659 @item set breakpoint always-inserted off
3660 All breakpoints, including newly added by the user, are inserted in
3661 the target only when the target is resumed. All breakpoints are
3662 removed from the target when it stops.
3664 @item set breakpoint always-inserted on
3665 Causes all breakpoints to be inserted in the target at all times. If
3666 the user adds a new breakpoint, or changes an existing breakpoint, the
3667 breakpoints in the target are updated immediately. A breakpoint is
3668 removed from the target only when breakpoint itself is removed.
3670 @cindex non-stop mode, and @code{breakpoint always-inserted}
3671 @item set breakpoint always-inserted auto
3672 This is the default mode. If @value{GDBN} is controlling the inferior
3673 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3674 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3675 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3676 @code{breakpoint always-inserted} mode is off.
3679 @cindex negative breakpoint numbers
3680 @cindex internal @value{GDBN} breakpoints
3681 @value{GDBN} itself sometimes sets breakpoints in your program for
3682 special purposes, such as proper handling of @code{longjmp} (in C
3683 programs). These internal breakpoints are assigned negative numbers,
3684 starting with @code{-1}; @samp{info breakpoints} does not display them.
3685 You can see these breakpoints with the @value{GDBN} maintenance command
3686 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3689 @node Set Watchpoints
3690 @subsection Setting Watchpoints
3692 @cindex setting watchpoints
3693 You can use a watchpoint to stop execution whenever the value of an
3694 expression changes, without having to predict a particular place where
3695 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3696 The expression may be as simple as the value of a single variable, or
3697 as complex as many variables combined by operators. Examples include:
3701 A reference to the value of a single variable.
3704 An address cast to an appropriate data type. For example,
3705 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3706 address (assuming an @code{int} occupies 4 bytes).
3709 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3710 expression can use any operators valid in the program's native
3711 language (@pxref{Languages}).
3714 You can set a watchpoint on an expression even if the expression can
3715 not be evaluated yet. For instance, you can set a watchpoint on
3716 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3717 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3718 the expression produces a valid value. If the expression becomes
3719 valid in some other way than changing a variable (e.g.@: if the memory
3720 pointed to by @samp{*global_ptr} becomes readable as the result of a
3721 @code{malloc} call), @value{GDBN} may not stop until the next time
3722 the expression changes.
3724 @cindex software watchpoints
3725 @cindex hardware watchpoints
3726 Depending on your system, watchpoints may be implemented in software or
3727 hardware. @value{GDBN} does software watchpointing by single-stepping your
3728 program and testing the variable's value each time, which is hundreds of
3729 times slower than normal execution. (But this may still be worth it, to
3730 catch errors where you have no clue what part of your program is the
3733 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3734 x86-based targets, @value{GDBN} includes support for hardware
3735 watchpoints, which do not slow down the running of your program.
3739 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3740 Set a watchpoint for an expression. @value{GDBN} will break when the
3741 expression @var{expr} is written into by the program and its value
3742 changes. The simplest (and the most popular) use of this command is
3743 to watch the value of a single variable:
3746 (@value{GDBP}) watch foo
3749 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3750 argument, @value{GDBN} breaks only when the thread identified by
3751 @var{threadnum} changes the value of @var{expr}. If any other threads
3752 change the value of @var{expr}, @value{GDBN} will not break. Note
3753 that watchpoints restricted to a single thread in this way only work
3754 with Hardware Watchpoints.
3756 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3757 (see below). The @code{-location} argument tells @value{GDBN} to
3758 instead watch the memory referred to by @var{expr}. In this case,
3759 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3760 and watch the memory at that address. The type of the result is used
3761 to determine the size of the watched memory. If the expression's
3762 result does not have an address, then @value{GDBN} will print an
3765 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3766 of masked watchpoints, if the current architecture supports this
3767 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3768 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3769 to an address to watch. The mask specifies that some bits of an address
3770 (the bits which are reset in the mask) should be ignored when matching
3771 the address accessed by the inferior against the watchpoint address.
3772 Thus, a masked watchpoint watches many addresses simultaneously---those
3773 addresses whose unmasked bits are identical to the unmasked bits in the
3774 watchpoint address. The @code{mask} argument implies @code{-location}.
3778 (@value{GDBP}) watch foo mask 0xffff00ff
3779 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3783 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3784 Set a watchpoint that will break when the value of @var{expr} is read
3788 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3789 Set a watchpoint that will break when @var{expr} is either read from
3790 or written into by the program.
3792 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3793 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3794 This command prints a list of watchpoints, using the same format as
3795 @code{info break} (@pxref{Set Breaks}).
3798 If you watch for a change in a numerically entered address you need to
3799 dereference it, as the address itself is just a constant number which will
3800 never change. @value{GDBN} refuses to create a watchpoint that watches
3801 a never-changing value:
3804 (@value{GDBP}) watch 0x600850
3805 Cannot watch constant value 0x600850.
3806 (@value{GDBP}) watch *(int *) 0x600850
3807 Watchpoint 1: *(int *) 6293584
3810 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3811 watchpoints execute very quickly, and the debugger reports a change in
3812 value at the exact instruction where the change occurs. If @value{GDBN}
3813 cannot set a hardware watchpoint, it sets a software watchpoint, which
3814 executes more slowly and reports the change in value at the next
3815 @emph{statement}, not the instruction, after the change occurs.
3817 @cindex use only software watchpoints
3818 You can force @value{GDBN} to use only software watchpoints with the
3819 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3820 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3821 the underlying system supports them. (Note that hardware-assisted
3822 watchpoints that were set @emph{before} setting
3823 @code{can-use-hw-watchpoints} to zero will still use the hardware
3824 mechanism of watching expression values.)
3827 @item set can-use-hw-watchpoints
3828 @kindex set can-use-hw-watchpoints
3829 Set whether or not to use hardware watchpoints.
3831 @item show can-use-hw-watchpoints
3832 @kindex show can-use-hw-watchpoints
3833 Show the current mode of using hardware watchpoints.
3836 For remote targets, you can restrict the number of hardware
3837 watchpoints @value{GDBN} will use, see @ref{set remote
3838 hardware-breakpoint-limit}.
3840 When you issue the @code{watch} command, @value{GDBN} reports
3843 Hardware watchpoint @var{num}: @var{expr}
3847 if it was able to set a hardware watchpoint.
3849 Currently, the @code{awatch} and @code{rwatch} commands can only set
3850 hardware watchpoints, because accesses to data that don't change the
3851 value of the watched expression cannot be detected without examining
3852 every instruction as it is being executed, and @value{GDBN} does not do
3853 that currently. If @value{GDBN} finds that it is unable to set a
3854 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3855 will print a message like this:
3858 Expression cannot be implemented with read/access watchpoint.
3861 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3862 data type of the watched expression is wider than what a hardware
3863 watchpoint on the target machine can handle. For example, some systems
3864 can only watch regions that are up to 4 bytes wide; on such systems you
3865 cannot set hardware watchpoints for an expression that yields a
3866 double-precision floating-point number (which is typically 8 bytes
3867 wide). As a work-around, it might be possible to break the large region
3868 into a series of smaller ones and watch them with separate watchpoints.
3870 If you set too many hardware watchpoints, @value{GDBN} might be unable
3871 to insert all of them when you resume the execution of your program.
3872 Since the precise number of active watchpoints is unknown until such
3873 time as the program is about to be resumed, @value{GDBN} might not be
3874 able to warn you about this when you set the watchpoints, and the
3875 warning will be printed only when the program is resumed:
3878 Hardware watchpoint @var{num}: Could not insert watchpoint
3882 If this happens, delete or disable some of the watchpoints.
3884 Watching complex expressions that reference many variables can also
3885 exhaust the resources available for hardware-assisted watchpoints.
3886 That's because @value{GDBN} needs to watch every variable in the
3887 expression with separately allocated resources.
3889 If you call a function interactively using @code{print} or @code{call},
3890 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3891 kind of breakpoint or the call completes.
3893 @value{GDBN} automatically deletes watchpoints that watch local
3894 (automatic) variables, or expressions that involve such variables, when
3895 they go out of scope, that is, when the execution leaves the block in
3896 which these variables were defined. In particular, when the program
3897 being debugged terminates, @emph{all} local variables go out of scope,
3898 and so only watchpoints that watch global variables remain set. If you
3899 rerun the program, you will need to set all such watchpoints again. One
3900 way of doing that would be to set a code breakpoint at the entry to the
3901 @code{main} function and when it breaks, set all the watchpoints.
3903 @cindex watchpoints and threads
3904 @cindex threads and watchpoints
3905 In multi-threaded programs, watchpoints will detect changes to the
3906 watched expression from every thread.
3909 @emph{Warning:} In multi-threaded programs, software watchpoints
3910 have only limited usefulness. If @value{GDBN} creates a software
3911 watchpoint, it can only watch the value of an expression @emph{in a
3912 single thread}. If you are confident that the expression can only
3913 change due to the current thread's activity (and if you are also
3914 confident that no other thread can become current), then you can use
3915 software watchpoints as usual. However, @value{GDBN} may not notice
3916 when a non-current thread's activity changes the expression. (Hardware
3917 watchpoints, in contrast, watch an expression in all threads.)
3920 @xref{set remote hardware-watchpoint-limit}.
3922 @node Set Catchpoints
3923 @subsection Setting Catchpoints
3924 @cindex catchpoints, setting
3925 @cindex exception handlers
3926 @cindex event handling
3928 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3929 kinds of program events, such as C@t{++} exceptions or the loading of a
3930 shared library. Use the @code{catch} command to set a catchpoint.
3934 @item catch @var{event}
3935 Stop when @var{event} occurs. @var{event} can be any of the following:
3938 @cindex stop on C@t{++} exceptions
3939 The throwing of a C@t{++} exception.
3942 The catching of a C@t{++} exception.
3945 @cindex Ada exception catching
3946 @cindex catch Ada exceptions
3947 An Ada exception being raised. If an exception name is specified
3948 at the end of the command (eg @code{catch exception Program_Error}),
3949 the debugger will stop only when this specific exception is raised.
3950 Otherwise, the debugger stops execution when any Ada exception is raised.
3952 When inserting an exception catchpoint on a user-defined exception whose
3953 name is identical to one of the exceptions defined by the language, the
3954 fully qualified name must be used as the exception name. Otherwise,
3955 @value{GDBN} will assume that it should stop on the pre-defined exception
3956 rather than the user-defined one. For instance, assuming an exception
3957 called @code{Constraint_Error} is defined in package @code{Pck}, then
3958 the command to use to catch such exceptions is @kbd{catch exception
3959 Pck.Constraint_Error}.
3961 @item exception unhandled
3962 An exception that was raised but is not handled by the program.
3965 A failed Ada assertion.
3968 @cindex break on fork/exec
3969 A call to @code{exec}. This is currently only available for HP-UX
3973 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3974 @cindex break on a system call.
3975 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3976 syscall is a mechanism for application programs to request a service
3977 from the operating system (OS) or one of the OS system services.
3978 @value{GDBN} can catch some or all of the syscalls issued by the
3979 debuggee, and show the related information for each syscall. If no
3980 argument is specified, calls to and returns from all system calls
3983 @var{name} can be any system call name that is valid for the
3984 underlying OS. Just what syscalls are valid depends on the OS. On
3985 GNU and Unix systems, you can find the full list of valid syscall
3986 names on @file{/usr/include/asm/unistd.h}.
3988 @c For MS-Windows, the syscall names and the corresponding numbers
3989 @c can be found, e.g., on this URL:
3990 @c http://www.metasploit.com/users/opcode/syscalls.html
3991 @c but we don't support Windows syscalls yet.
3993 Normally, @value{GDBN} knows in advance which syscalls are valid for
3994 each OS, so you can use the @value{GDBN} command-line completion
3995 facilities (@pxref{Completion,, command completion}) to list the
3998 You may also specify the system call numerically. A syscall's
3999 number is the value passed to the OS's syscall dispatcher to
4000 identify the requested service. When you specify the syscall by its
4001 name, @value{GDBN} uses its database of syscalls to convert the name
4002 into the corresponding numeric code, but using the number directly
4003 may be useful if @value{GDBN}'s database does not have the complete
4004 list of syscalls on your system (e.g., because @value{GDBN} lags
4005 behind the OS upgrades).
4007 The example below illustrates how this command works if you don't provide
4011 (@value{GDBP}) catch syscall
4012 Catchpoint 1 (syscall)
4014 Starting program: /tmp/catch-syscall
4016 Catchpoint 1 (call to syscall 'close'), \
4017 0xffffe424 in __kernel_vsyscall ()
4021 Catchpoint 1 (returned from syscall 'close'), \
4022 0xffffe424 in __kernel_vsyscall ()
4026 Here is an example of catching a system call by name:
4029 (@value{GDBP}) catch syscall chroot
4030 Catchpoint 1 (syscall 'chroot' [61])
4032 Starting program: /tmp/catch-syscall
4034 Catchpoint 1 (call to syscall 'chroot'), \
4035 0xffffe424 in __kernel_vsyscall ()
4039 Catchpoint 1 (returned from syscall 'chroot'), \
4040 0xffffe424 in __kernel_vsyscall ()
4044 An example of specifying a system call numerically. In the case
4045 below, the syscall number has a corresponding entry in the XML
4046 file, so @value{GDBN} finds its name and prints it:
4049 (@value{GDBP}) catch syscall 252
4050 Catchpoint 1 (syscall(s) 'exit_group')
4052 Starting program: /tmp/catch-syscall
4054 Catchpoint 1 (call to syscall 'exit_group'), \
4055 0xffffe424 in __kernel_vsyscall ()
4059 Program exited normally.
4063 However, there can be situations when there is no corresponding name
4064 in XML file for that syscall number. In this case, @value{GDBN} prints
4065 a warning message saying that it was not able to find the syscall name,
4066 but the catchpoint will be set anyway. See the example below:
4069 (@value{GDBP}) catch syscall 764
4070 warning: The number '764' does not represent a known syscall.
4071 Catchpoint 2 (syscall 764)
4075 If you configure @value{GDBN} using the @samp{--without-expat} option,
4076 it will not be able to display syscall names. Also, if your
4077 architecture does not have an XML file describing its system calls,
4078 you will not be able to see the syscall names. It is important to
4079 notice that these two features are used for accessing the syscall
4080 name database. In either case, you will see a warning like this:
4083 (@value{GDBP}) catch syscall
4084 warning: Could not open "syscalls/i386-linux.xml"
4085 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4086 GDB will not be able to display syscall names.
4087 Catchpoint 1 (syscall)
4091 Of course, the file name will change depending on your architecture and system.
4093 Still using the example above, you can also try to catch a syscall by its
4094 number. In this case, you would see something like:
4097 (@value{GDBP}) catch syscall 252
4098 Catchpoint 1 (syscall(s) 252)
4101 Again, in this case @value{GDBN} would not be able to display syscall's names.
4104 A call to @code{fork}. This is currently only available for HP-UX
4108 A call to @code{vfork}. This is currently only available for HP-UX
4113 @item tcatch @var{event}
4114 Set a catchpoint that is enabled only for one stop. The catchpoint is
4115 automatically deleted after the first time the event is caught.
4119 Use the @code{info break} command to list the current catchpoints.
4121 There are currently some limitations to C@t{++} exception handling
4122 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4126 If you call a function interactively, @value{GDBN} normally returns
4127 control to you when the function has finished executing. If the call
4128 raises an exception, however, the call may bypass the mechanism that
4129 returns control to you and cause your program either to abort or to
4130 simply continue running until it hits a breakpoint, catches a signal
4131 that @value{GDBN} is listening for, or exits. This is the case even if
4132 you set a catchpoint for the exception; catchpoints on exceptions are
4133 disabled within interactive calls.
4136 You cannot raise an exception interactively.
4139 You cannot install an exception handler interactively.
4142 @cindex raise exceptions
4143 Sometimes @code{catch} is not the best way to debug exception handling:
4144 if you need to know exactly where an exception is raised, it is better to
4145 stop @emph{before} the exception handler is called, since that way you
4146 can see the stack before any unwinding takes place. If you set a
4147 breakpoint in an exception handler instead, it may not be easy to find
4148 out where the exception was raised.
4150 To stop just before an exception handler is called, you need some
4151 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4152 raised by calling a library function named @code{__raise_exception}
4153 which has the following ANSI C interface:
4156 /* @var{addr} is where the exception identifier is stored.
4157 @var{id} is the exception identifier. */
4158 void __raise_exception (void **addr, void *id);
4162 To make the debugger catch all exceptions before any stack
4163 unwinding takes place, set a breakpoint on @code{__raise_exception}
4164 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4166 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4167 that depends on the value of @var{id}, you can stop your program when
4168 a specific exception is raised. You can use multiple conditional
4169 breakpoints to stop your program when any of a number of exceptions are
4174 @subsection Deleting Breakpoints
4176 @cindex clearing breakpoints, watchpoints, catchpoints
4177 @cindex deleting breakpoints, watchpoints, catchpoints
4178 It is often necessary to eliminate a breakpoint, watchpoint, or
4179 catchpoint once it has done its job and you no longer want your program
4180 to stop there. This is called @dfn{deleting} the breakpoint. A
4181 breakpoint that has been deleted no longer exists; it is forgotten.
4183 With the @code{clear} command you can delete breakpoints according to
4184 where they are in your program. With the @code{delete} command you can
4185 delete individual breakpoints, watchpoints, or catchpoints by specifying
4186 their breakpoint numbers.
4188 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4189 automatically ignores breakpoints on the first instruction to be executed
4190 when you continue execution without changing the execution address.
4195 Delete any breakpoints at the next instruction to be executed in the
4196 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4197 the innermost frame is selected, this is a good way to delete a
4198 breakpoint where your program just stopped.
4200 @item clear @var{location}
4201 Delete any breakpoints set at the specified @var{location}.
4202 @xref{Specify Location}, for the various forms of @var{location}; the
4203 most useful ones are listed below:
4206 @item clear @var{function}
4207 @itemx clear @var{filename}:@var{function}
4208 Delete any breakpoints set at entry to the named @var{function}.
4210 @item clear @var{linenum}
4211 @itemx clear @var{filename}:@var{linenum}
4212 Delete any breakpoints set at or within the code of the specified
4213 @var{linenum} of the specified @var{filename}.
4216 @cindex delete breakpoints
4218 @kindex d @r{(@code{delete})}
4219 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4220 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4221 ranges specified as arguments. If no argument is specified, delete all
4222 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4223 confirm off}). You can abbreviate this command as @code{d}.
4227 @subsection Disabling Breakpoints
4229 @cindex enable/disable a breakpoint
4230 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4231 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4232 it had been deleted, but remembers the information on the breakpoint so
4233 that you can @dfn{enable} it again later.
4235 You disable and enable breakpoints, watchpoints, and catchpoints with
4236 the @code{enable} and @code{disable} commands, optionally specifying
4237 one or more breakpoint numbers as arguments. Use @code{info break} to
4238 print a list of all breakpoints, watchpoints, and catchpoints if you
4239 do not know which numbers to use.
4241 Disabling and enabling a breakpoint that has multiple locations
4242 affects all of its locations.
4244 A breakpoint, watchpoint, or catchpoint can have any of four different
4245 states of enablement:
4249 Enabled. The breakpoint stops your program. A breakpoint set
4250 with the @code{break} command starts out in this state.
4252 Disabled. The breakpoint has no effect on your program.
4254 Enabled once. The breakpoint stops your program, but then becomes
4257 Enabled for deletion. The breakpoint stops your program, but
4258 immediately after it does so it is deleted permanently. A breakpoint
4259 set with the @code{tbreak} command starts out in this state.
4262 You can use the following commands to enable or disable breakpoints,
4263 watchpoints, and catchpoints:
4267 @kindex dis @r{(@code{disable})}
4268 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4269 Disable the specified breakpoints---or all breakpoints, if none are
4270 listed. A disabled breakpoint has no effect but is not forgotten. All
4271 options such as ignore-counts, conditions and commands are remembered in
4272 case the breakpoint is enabled again later. You may abbreviate
4273 @code{disable} as @code{dis}.
4276 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4277 Enable the specified breakpoints (or all defined breakpoints). They
4278 become effective once again in stopping your program.
4280 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4281 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4282 of these breakpoints immediately after stopping your program.
4284 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4285 Enable the specified breakpoints to work once, then die. @value{GDBN}
4286 deletes any of these breakpoints as soon as your program stops there.
4287 Breakpoints set by the @code{tbreak} command start out in this state.
4290 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4291 @c confusing: tbreak is also initially enabled.
4292 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4293 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4294 subsequently, they become disabled or enabled only when you use one of
4295 the commands above. (The command @code{until} can set and delete a
4296 breakpoint of its own, but it does not change the state of your other
4297 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4301 @subsection Break Conditions
4302 @cindex conditional breakpoints
4303 @cindex breakpoint conditions
4305 @c FIXME what is scope of break condition expr? Context where wanted?
4306 @c in particular for a watchpoint?
4307 The simplest sort of breakpoint breaks every time your program reaches a
4308 specified place. You can also specify a @dfn{condition} for a
4309 breakpoint. A condition is just a Boolean expression in your
4310 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4311 a condition evaluates the expression each time your program reaches it,
4312 and your program stops only if the condition is @emph{true}.
4314 This is the converse of using assertions for program validation; in that
4315 situation, you want to stop when the assertion is violated---that is,
4316 when the condition is false. In C, if you want to test an assertion expressed
4317 by the condition @var{assert}, you should set the condition
4318 @samp{! @var{assert}} on the appropriate breakpoint.
4320 Conditions are also accepted for watchpoints; you may not need them,
4321 since a watchpoint is inspecting the value of an expression anyhow---but
4322 it might be simpler, say, to just set a watchpoint on a variable name,
4323 and specify a condition that tests whether the new value is an interesting
4326 Break conditions can have side effects, and may even call functions in
4327 your program. This can be useful, for example, to activate functions
4328 that log program progress, or to use your own print functions to
4329 format special data structures. The effects are completely predictable
4330 unless there is another enabled breakpoint at the same address. (In
4331 that case, @value{GDBN} might see the other breakpoint first and stop your
4332 program without checking the condition of this one.) Note that
4333 breakpoint commands are usually more convenient and flexible than break
4335 purpose of performing side effects when a breakpoint is reached
4336 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4338 Break conditions can be specified when a breakpoint is set, by using
4339 @samp{if} in the arguments to the @code{break} command. @xref{Set
4340 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4341 with the @code{condition} command.
4343 You can also use the @code{if} keyword with the @code{watch} command.
4344 The @code{catch} command does not recognize the @code{if} keyword;
4345 @code{condition} is the only way to impose a further condition on a
4350 @item condition @var{bnum} @var{expression}
4351 Specify @var{expression} as the break condition for breakpoint,
4352 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4353 breakpoint @var{bnum} stops your program only if the value of
4354 @var{expression} is true (nonzero, in C). When you use
4355 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4356 syntactic correctness, and to determine whether symbols in it have
4357 referents in the context of your breakpoint. If @var{expression} uses
4358 symbols not referenced in the context of the breakpoint, @value{GDBN}
4359 prints an error message:
4362 No symbol "foo" in current context.
4367 not actually evaluate @var{expression} at the time the @code{condition}
4368 command (or a command that sets a breakpoint with a condition, like
4369 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4371 @item condition @var{bnum}
4372 Remove the condition from breakpoint number @var{bnum}. It becomes
4373 an ordinary unconditional breakpoint.
4376 @cindex ignore count (of breakpoint)
4377 A special case of a breakpoint condition is to stop only when the
4378 breakpoint has been reached a certain number of times. This is so
4379 useful that there is a special way to do it, using the @dfn{ignore
4380 count} of the breakpoint. Every breakpoint has an ignore count, which
4381 is an integer. Most of the time, the ignore count is zero, and
4382 therefore has no effect. But if your program reaches a breakpoint whose
4383 ignore count is positive, then instead of stopping, it just decrements
4384 the ignore count by one and continues. As a result, if the ignore count
4385 value is @var{n}, the breakpoint does not stop the next @var{n} times
4386 your program reaches it.
4390 @item ignore @var{bnum} @var{count}
4391 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4392 The next @var{count} times the breakpoint is reached, your program's
4393 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4396 To make the breakpoint stop the next time it is reached, specify
4399 When you use @code{continue} to resume execution of your program from a
4400 breakpoint, you can specify an ignore count directly as an argument to
4401 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4402 Stepping,,Continuing and Stepping}.
4404 If a breakpoint has a positive ignore count and a condition, the
4405 condition is not checked. Once the ignore count reaches zero,
4406 @value{GDBN} resumes checking the condition.
4408 You could achieve the effect of the ignore count with a condition such
4409 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4410 is decremented each time. @xref{Convenience Vars, ,Convenience
4414 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4417 @node Break Commands
4418 @subsection Breakpoint Command Lists
4420 @cindex breakpoint commands
4421 You can give any breakpoint (or watchpoint or catchpoint) a series of
4422 commands to execute when your program stops due to that breakpoint. For
4423 example, you might want to print the values of certain expressions, or
4424 enable other breakpoints.
4428 @kindex end@r{ (breakpoint commands)}
4429 @item commands @r{[}@var{range}@dots{}@r{]}
4430 @itemx @dots{} @var{command-list} @dots{}
4432 Specify a list of commands for the given breakpoints. The commands
4433 themselves appear on the following lines. Type a line containing just
4434 @code{end} to terminate the commands.
4436 To remove all commands from a breakpoint, type @code{commands} and
4437 follow it immediately with @code{end}; that is, give no commands.
4439 With no argument, @code{commands} refers to the last breakpoint,
4440 watchpoint, or catchpoint set (not to the breakpoint most recently
4441 encountered). If the most recent breakpoints were set with a single
4442 command, then the @code{commands} will apply to all the breakpoints
4443 set by that command. This applies to breakpoints set by
4444 @code{rbreak}, and also applies when a single @code{break} command
4445 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4449 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4450 disabled within a @var{command-list}.
4452 You can use breakpoint commands to start your program up again. Simply
4453 use the @code{continue} command, or @code{step}, or any other command
4454 that resumes execution.
4456 Any other commands in the command list, after a command that resumes
4457 execution, are ignored. This is because any time you resume execution
4458 (even with a simple @code{next} or @code{step}), you may encounter
4459 another breakpoint---which could have its own command list, leading to
4460 ambiguities about which list to execute.
4463 If the first command you specify in a command list is @code{silent}, the
4464 usual message about stopping at a breakpoint is not printed. This may
4465 be desirable for breakpoints that are to print a specific message and
4466 then continue. If none of the remaining commands print anything, you
4467 see no sign that the breakpoint was reached. @code{silent} is
4468 meaningful only at the beginning of a breakpoint command list.
4470 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4471 print precisely controlled output, and are often useful in silent
4472 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4474 For example, here is how you could use breakpoint commands to print the
4475 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4481 printf "x is %d\n",x
4486 One application for breakpoint commands is to compensate for one bug so
4487 you can test for another. Put a breakpoint just after the erroneous line
4488 of code, give it a condition to detect the case in which something
4489 erroneous has been done, and give it commands to assign correct values
4490 to any variables that need them. End with the @code{continue} command
4491 so that your program does not stop, and start with the @code{silent}
4492 command so that no output is produced. Here is an example:
4503 @node Save Breakpoints
4504 @subsection How to save breakpoints to a file
4506 To save breakpoint definitions to a file use the @w{@code{save
4507 breakpoints}} command.
4510 @kindex save breakpoints
4511 @cindex save breakpoints to a file for future sessions
4512 @item save breakpoints [@var{filename}]
4513 This command saves all current breakpoint definitions together with
4514 their commands and ignore counts, into a file @file{@var{filename}}
4515 suitable for use in a later debugging session. This includes all
4516 types of breakpoints (breakpoints, watchpoints, catchpoints,
4517 tracepoints). To read the saved breakpoint definitions, use the
4518 @code{source} command (@pxref{Command Files}). Note that watchpoints
4519 with expressions involving local variables may fail to be recreated
4520 because it may not be possible to access the context where the
4521 watchpoint is valid anymore. Because the saved breakpoint definitions
4522 are simply a sequence of @value{GDBN} commands that recreate the
4523 breakpoints, you can edit the file in your favorite editing program,
4524 and remove the breakpoint definitions you're not interested in, or
4525 that can no longer be recreated.
4528 @c @ifclear BARETARGET
4529 @node Error in Breakpoints
4530 @subsection ``Cannot insert breakpoints''
4532 If you request too many active hardware-assisted breakpoints and
4533 watchpoints, you will see this error message:
4535 @c FIXME: the precise wording of this message may change; the relevant
4536 @c source change is not committed yet (Sep 3, 1999).
4538 Stopped; cannot insert breakpoints.
4539 You may have requested too many hardware breakpoints and watchpoints.
4543 This message is printed when you attempt to resume the program, since
4544 only then @value{GDBN} knows exactly how many hardware breakpoints and
4545 watchpoints it needs to insert.
4547 When this message is printed, you need to disable or remove some of the
4548 hardware-assisted breakpoints and watchpoints, and then continue.
4550 @node Breakpoint-related Warnings
4551 @subsection ``Breakpoint address adjusted...''
4552 @cindex breakpoint address adjusted
4554 Some processor architectures place constraints on the addresses at
4555 which breakpoints may be placed. For architectures thus constrained,
4556 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4557 with the constraints dictated by the architecture.
4559 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4560 a VLIW architecture in which a number of RISC-like instructions may be
4561 bundled together for parallel execution. The FR-V architecture
4562 constrains the location of a breakpoint instruction within such a
4563 bundle to the instruction with the lowest address. @value{GDBN}
4564 honors this constraint by adjusting a breakpoint's address to the
4565 first in the bundle.
4567 It is not uncommon for optimized code to have bundles which contain
4568 instructions from different source statements, thus it may happen that
4569 a breakpoint's address will be adjusted from one source statement to
4570 another. Since this adjustment may significantly alter @value{GDBN}'s
4571 breakpoint related behavior from what the user expects, a warning is
4572 printed when the breakpoint is first set and also when the breakpoint
4575 A warning like the one below is printed when setting a breakpoint
4576 that's been subject to address adjustment:
4579 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4582 Such warnings are printed both for user settable and @value{GDBN}'s
4583 internal breakpoints. If you see one of these warnings, you should
4584 verify that a breakpoint set at the adjusted address will have the
4585 desired affect. If not, the breakpoint in question may be removed and
4586 other breakpoints may be set which will have the desired behavior.
4587 E.g., it may be sufficient to place the breakpoint at a later
4588 instruction. A conditional breakpoint may also be useful in some
4589 cases to prevent the breakpoint from triggering too often.
4591 @value{GDBN} will also issue a warning when stopping at one of these
4592 adjusted breakpoints:
4595 warning: Breakpoint 1 address previously adjusted from 0x00010414
4599 When this warning is encountered, it may be too late to take remedial
4600 action except in cases where the breakpoint is hit earlier or more
4601 frequently than expected.
4603 @node Continuing and Stepping
4604 @section Continuing and Stepping
4608 @cindex resuming execution
4609 @dfn{Continuing} means resuming program execution until your program
4610 completes normally. In contrast, @dfn{stepping} means executing just
4611 one more ``step'' of your program, where ``step'' may mean either one
4612 line of source code, or one machine instruction (depending on what
4613 particular command you use). Either when continuing or when stepping,
4614 your program may stop even sooner, due to a breakpoint or a signal. (If
4615 it stops due to a signal, you may want to use @code{handle}, or use
4616 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4620 @kindex c @r{(@code{continue})}
4621 @kindex fg @r{(resume foreground execution)}
4622 @item continue @r{[}@var{ignore-count}@r{]}
4623 @itemx c @r{[}@var{ignore-count}@r{]}
4624 @itemx fg @r{[}@var{ignore-count}@r{]}
4625 Resume program execution, at the address where your program last stopped;
4626 any breakpoints set at that address are bypassed. The optional argument
4627 @var{ignore-count} allows you to specify a further number of times to
4628 ignore a breakpoint at this location; its effect is like that of
4629 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4631 The argument @var{ignore-count} is meaningful only when your program
4632 stopped due to a breakpoint. At other times, the argument to
4633 @code{continue} is ignored.
4635 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4636 debugged program is deemed to be the foreground program) are provided
4637 purely for convenience, and have exactly the same behavior as
4641 To resume execution at a different place, you can use @code{return}
4642 (@pxref{Returning, ,Returning from a Function}) to go back to the
4643 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4644 Different Address}) to go to an arbitrary location in your program.
4646 A typical technique for using stepping is to set a breakpoint
4647 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4648 beginning of the function or the section of your program where a problem
4649 is believed to lie, run your program until it stops at that breakpoint,
4650 and then step through the suspect area, examining the variables that are
4651 interesting, until you see the problem happen.
4655 @kindex s @r{(@code{step})}
4657 Continue running your program until control reaches a different source
4658 line, then stop it and return control to @value{GDBN}. This command is
4659 abbreviated @code{s}.
4662 @c "without debugging information" is imprecise; actually "without line
4663 @c numbers in the debugging information". (gcc -g1 has debugging info but
4664 @c not line numbers). But it seems complex to try to make that
4665 @c distinction here.
4666 @emph{Warning:} If you use the @code{step} command while control is
4667 within a function that was compiled without debugging information,
4668 execution proceeds until control reaches a function that does have
4669 debugging information. Likewise, it will not step into a function which
4670 is compiled without debugging information. To step through functions
4671 without debugging information, use the @code{stepi} command, described
4675 The @code{step} command only stops at the first instruction of a source
4676 line. This prevents the multiple stops that could otherwise occur in
4677 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4678 to stop if a function that has debugging information is called within
4679 the line. In other words, @code{step} @emph{steps inside} any functions
4680 called within the line.
4682 Also, the @code{step} command only enters a function if there is line
4683 number information for the function. Otherwise it acts like the
4684 @code{next} command. This avoids problems when using @code{cc -gl}
4685 on MIPS machines. Previously, @code{step} entered subroutines if there
4686 was any debugging information about the routine.
4688 @item step @var{count}
4689 Continue running as in @code{step}, but do so @var{count} times. If a
4690 breakpoint is reached, or a signal not related to stepping occurs before
4691 @var{count} steps, stepping stops right away.
4694 @kindex n @r{(@code{next})}
4695 @item next @r{[}@var{count}@r{]}
4696 Continue to the next source line in the current (innermost) stack frame.
4697 This is similar to @code{step}, but function calls that appear within
4698 the line of code are executed without stopping. Execution stops when
4699 control reaches a different line of code at the original stack level
4700 that was executing when you gave the @code{next} command. This command
4701 is abbreviated @code{n}.
4703 An argument @var{count} is a repeat count, as for @code{step}.
4706 @c FIX ME!! Do we delete this, or is there a way it fits in with
4707 @c the following paragraph? --- Vctoria
4709 @c @code{next} within a function that lacks debugging information acts like
4710 @c @code{step}, but any function calls appearing within the code of the
4711 @c function are executed without stopping.
4713 The @code{next} command only stops at the first instruction of a
4714 source line. This prevents multiple stops that could otherwise occur in
4715 @code{switch} statements, @code{for} loops, etc.
4717 @kindex set step-mode
4719 @cindex functions without line info, and stepping
4720 @cindex stepping into functions with no line info
4721 @itemx set step-mode on
4722 The @code{set step-mode on} command causes the @code{step} command to
4723 stop at the first instruction of a function which contains no debug line
4724 information rather than stepping over it.
4726 This is useful in cases where you may be interested in inspecting the
4727 machine instructions of a function which has no symbolic info and do not
4728 want @value{GDBN} to automatically skip over this function.
4730 @item set step-mode off
4731 Causes the @code{step} command to step over any functions which contains no
4732 debug information. This is the default.
4734 @item show step-mode
4735 Show whether @value{GDBN} will stop in or step over functions without
4736 source line debug information.
4739 @kindex fin @r{(@code{finish})}
4741 Continue running until just after function in the selected stack frame
4742 returns. Print the returned value (if any). This command can be
4743 abbreviated as @code{fin}.
4745 Contrast this with the @code{return} command (@pxref{Returning,
4746 ,Returning from a Function}).
4749 @kindex u @r{(@code{until})}
4750 @cindex run until specified location
4753 Continue running until a source line past the current line, in the
4754 current stack frame, is reached. This command is used to avoid single
4755 stepping through a loop more than once. It is like the @code{next}
4756 command, except that when @code{until} encounters a jump, it
4757 automatically continues execution until the program counter is greater
4758 than the address of the jump.
4760 This means that when you reach the end of a loop after single stepping
4761 though it, @code{until} makes your program continue execution until it
4762 exits the loop. In contrast, a @code{next} command at the end of a loop
4763 simply steps back to the beginning of the loop, which forces you to step
4764 through the next iteration.
4766 @code{until} always stops your program if it attempts to exit the current
4769 @code{until} may produce somewhat counterintuitive results if the order
4770 of machine code does not match the order of the source lines. For
4771 example, in the following excerpt from a debugging session, the @code{f}
4772 (@code{frame}) command shows that execution is stopped at line
4773 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4777 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4779 (@value{GDBP}) until
4780 195 for ( ; argc > 0; NEXTARG) @{
4783 This happened because, for execution efficiency, the compiler had
4784 generated code for the loop closure test at the end, rather than the
4785 start, of the loop---even though the test in a C @code{for}-loop is
4786 written before the body of the loop. The @code{until} command appeared
4787 to step back to the beginning of the loop when it advanced to this
4788 expression; however, it has not really gone to an earlier
4789 statement---not in terms of the actual machine code.
4791 @code{until} with no argument works by means of single
4792 instruction stepping, and hence is slower than @code{until} with an
4795 @item until @var{location}
4796 @itemx u @var{location}
4797 Continue running your program until either the specified location is
4798 reached, or the current stack frame returns. @var{location} is any of
4799 the forms described in @ref{Specify Location}.
4800 This form of the command uses temporary breakpoints, and
4801 hence is quicker than @code{until} without an argument. The specified
4802 location is actually reached only if it is in the current frame. This
4803 implies that @code{until} can be used to skip over recursive function
4804 invocations. For instance in the code below, if the current location is
4805 line @code{96}, issuing @code{until 99} will execute the program up to
4806 line @code{99} in the same invocation of factorial, i.e., after the inner
4807 invocations have returned.
4810 94 int factorial (int value)
4812 96 if (value > 1) @{
4813 97 value *= factorial (value - 1);
4820 @kindex advance @var{location}
4821 @itemx advance @var{location}
4822 Continue running the program up to the given @var{location}. An argument is
4823 required, which should be of one of the forms described in
4824 @ref{Specify Location}.
4825 Execution will also stop upon exit from the current stack
4826 frame. This command is similar to @code{until}, but @code{advance} will
4827 not skip over recursive function calls, and the target location doesn't
4828 have to be in the same frame as the current one.
4832 @kindex si @r{(@code{stepi})}
4834 @itemx stepi @var{arg}
4836 Execute one machine instruction, then stop and return to the debugger.
4838 It is often useful to do @samp{display/i $pc} when stepping by machine
4839 instructions. This makes @value{GDBN} automatically display the next
4840 instruction to be executed, each time your program stops. @xref{Auto
4841 Display,, Automatic Display}.
4843 An argument is a repeat count, as in @code{step}.
4847 @kindex ni @r{(@code{nexti})}
4849 @itemx nexti @var{arg}
4851 Execute one machine instruction, but if it is a function call,
4852 proceed until the function returns.
4854 An argument is a repeat count, as in @code{next}.
4861 A signal is an asynchronous event that can happen in a program. The
4862 operating system defines the possible kinds of signals, and gives each
4863 kind a name and a number. For example, in Unix @code{SIGINT} is the
4864 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4865 @code{SIGSEGV} is the signal a program gets from referencing a place in
4866 memory far away from all the areas in use; @code{SIGALRM} occurs when
4867 the alarm clock timer goes off (which happens only if your program has
4868 requested an alarm).
4870 @cindex fatal signals
4871 Some signals, including @code{SIGALRM}, are a normal part of the
4872 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4873 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4874 program has not specified in advance some other way to handle the signal.
4875 @code{SIGINT} does not indicate an error in your program, but it is normally
4876 fatal so it can carry out the purpose of the interrupt: to kill the program.
4878 @value{GDBN} has the ability to detect any occurrence of a signal in your
4879 program. You can tell @value{GDBN} in advance what to do for each kind of
4882 @cindex handling signals
4883 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4884 @code{SIGALRM} be silently passed to your program
4885 (so as not to interfere with their role in the program's functioning)
4886 but to stop your program immediately whenever an error signal happens.
4887 You can change these settings with the @code{handle} command.
4890 @kindex info signals
4894 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4895 handle each one. You can use this to see the signal numbers of all
4896 the defined types of signals.
4898 @item info signals @var{sig}
4899 Similar, but print information only about the specified signal number.
4901 @code{info handle} is an alias for @code{info signals}.
4904 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4905 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4906 can be the number of a signal or its name (with or without the
4907 @samp{SIG} at the beginning); a list of signal numbers of the form
4908 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4909 known signals. Optional arguments @var{keywords}, described below,
4910 say what change to make.
4914 The keywords allowed by the @code{handle} command can be abbreviated.
4915 Their full names are:
4919 @value{GDBN} should not stop your program when this signal happens. It may
4920 still print a message telling you that the signal has come in.
4923 @value{GDBN} should stop your program when this signal happens. This implies
4924 the @code{print} keyword as well.
4927 @value{GDBN} should print a message when this signal happens.
4930 @value{GDBN} should not mention the occurrence of the signal at all. This
4931 implies the @code{nostop} keyword as well.
4935 @value{GDBN} should allow your program to see this signal; your program
4936 can handle the signal, or else it may terminate if the signal is fatal
4937 and not handled. @code{pass} and @code{noignore} are synonyms.
4941 @value{GDBN} should not allow your program to see this signal.
4942 @code{nopass} and @code{ignore} are synonyms.
4946 When a signal stops your program, the signal is not visible to the
4948 continue. Your program sees the signal then, if @code{pass} is in
4949 effect for the signal in question @emph{at that time}. In other words,
4950 after @value{GDBN} reports a signal, you can use the @code{handle}
4951 command with @code{pass} or @code{nopass} to control whether your
4952 program sees that signal when you continue.
4954 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4955 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4956 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4959 You can also use the @code{signal} command to prevent your program from
4960 seeing a signal, or cause it to see a signal it normally would not see,
4961 or to give it any signal at any time. For example, if your program stopped
4962 due to some sort of memory reference error, you might store correct
4963 values into the erroneous variables and continue, hoping to see more
4964 execution; but your program would probably terminate immediately as
4965 a result of the fatal signal once it saw the signal. To prevent this,
4966 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4969 @cindex extra signal information
4970 @anchor{extra signal information}
4972 On some targets, @value{GDBN} can inspect extra signal information
4973 associated with the intercepted signal, before it is actually
4974 delivered to the program being debugged. This information is exported
4975 by the convenience variable @code{$_siginfo}, and consists of data
4976 that is passed by the kernel to the signal handler at the time of the
4977 receipt of a signal. The data type of the information itself is
4978 target dependent. You can see the data type using the @code{ptype
4979 $_siginfo} command. On Unix systems, it typically corresponds to the
4980 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4983 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4984 referenced address that raised a segmentation fault.
4988 (@value{GDBP}) continue
4989 Program received signal SIGSEGV, Segmentation fault.
4990 0x0000000000400766 in main ()
4992 (@value{GDBP}) ptype $_siginfo
4999 struct @{...@} _kill;
5000 struct @{...@} _timer;
5002 struct @{...@} _sigchld;
5003 struct @{...@} _sigfault;
5004 struct @{...@} _sigpoll;
5007 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5011 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5012 $1 = (void *) 0x7ffff7ff7000
5016 Depending on target support, @code{$_siginfo} may also be writable.
5019 @section Stopping and Starting Multi-thread Programs
5021 @cindex stopped threads
5022 @cindex threads, stopped
5024 @cindex continuing threads
5025 @cindex threads, continuing
5027 @value{GDBN} supports debugging programs with multiple threads
5028 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5029 are two modes of controlling execution of your program within the
5030 debugger. In the default mode, referred to as @dfn{all-stop mode},
5031 when any thread in your program stops (for example, at a breakpoint
5032 or while being stepped), all other threads in the program are also stopped by
5033 @value{GDBN}. On some targets, @value{GDBN} also supports
5034 @dfn{non-stop mode}, in which other threads can continue to run freely while
5035 you examine the stopped thread in the debugger.
5038 * All-Stop Mode:: All threads stop when GDB takes control
5039 * Non-Stop Mode:: Other threads continue to execute
5040 * Background Execution:: Running your program asynchronously
5041 * Thread-Specific Breakpoints:: Controlling breakpoints
5042 * Interrupted System Calls:: GDB may interfere with system calls
5043 * Observer Mode:: GDB does not alter program behavior
5047 @subsection All-Stop Mode
5049 @cindex all-stop mode
5051 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5052 @emph{all} threads of execution stop, not just the current thread. This
5053 allows you to examine the overall state of the program, including
5054 switching between threads, without worrying that things may change
5057 Conversely, whenever you restart the program, @emph{all} threads start
5058 executing. @emph{This is true even when single-stepping} with commands
5059 like @code{step} or @code{next}.
5061 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5062 Since thread scheduling is up to your debugging target's operating
5063 system (not controlled by @value{GDBN}), other threads may
5064 execute more than one statement while the current thread completes a
5065 single step. Moreover, in general other threads stop in the middle of a
5066 statement, rather than at a clean statement boundary, when the program
5069 You might even find your program stopped in another thread after
5070 continuing or even single-stepping. This happens whenever some other
5071 thread runs into a breakpoint, a signal, or an exception before the
5072 first thread completes whatever you requested.
5074 @cindex automatic thread selection
5075 @cindex switching threads automatically
5076 @cindex threads, automatic switching
5077 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5078 signal, it automatically selects the thread where that breakpoint or
5079 signal happened. @value{GDBN} alerts you to the context switch with a
5080 message such as @samp{[Switching to Thread @var{n}]} to identify the
5083 On some OSes, you can modify @value{GDBN}'s default behavior by
5084 locking the OS scheduler to allow only a single thread to run.
5087 @item set scheduler-locking @var{mode}
5088 @cindex scheduler locking mode
5089 @cindex lock scheduler
5090 Set the scheduler locking mode. If it is @code{off}, then there is no
5091 locking and any thread may run at any time. If @code{on}, then only the
5092 current thread may run when the inferior is resumed. The @code{step}
5093 mode optimizes for single-stepping; it prevents other threads
5094 from preempting the current thread while you are stepping, so that
5095 the focus of debugging does not change unexpectedly.
5096 Other threads only rarely (or never) get a chance to run
5097 when you step. They are more likely to run when you @samp{next} over a
5098 function call, and they are completely free to run when you use commands
5099 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5100 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5101 the current thread away from the thread that you are debugging.
5103 @item show scheduler-locking
5104 Display the current scheduler locking mode.
5107 @cindex resume threads of multiple processes simultaneously
5108 By default, when you issue one of the execution commands such as
5109 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5110 threads of the current inferior to run. For example, if @value{GDBN}
5111 is attached to two inferiors, each with two threads, the
5112 @code{continue} command resumes only the two threads of the current
5113 inferior. This is useful, for example, when you debug a program that
5114 forks and you want to hold the parent stopped (so that, for instance,
5115 it doesn't run to exit), while you debug the child. In other
5116 situations, you may not be interested in inspecting the current state
5117 of any of the processes @value{GDBN} is attached to, and you may want
5118 to resume them all until some breakpoint is hit. In the latter case,
5119 you can instruct @value{GDBN} to allow all threads of all the
5120 inferiors to run with the @w{@code{set schedule-multiple}} command.
5123 @kindex set schedule-multiple
5124 @item set schedule-multiple
5125 Set the mode for allowing threads of multiple processes to be resumed
5126 when an execution command is issued. When @code{on}, all threads of
5127 all processes are allowed to run. When @code{off}, only the threads
5128 of the current process are resumed. The default is @code{off}. The
5129 @code{scheduler-locking} mode takes precedence when set to @code{on},
5130 or while you are stepping and set to @code{step}.
5132 @item show schedule-multiple
5133 Display the current mode for resuming the execution of threads of
5138 @subsection Non-Stop Mode
5140 @cindex non-stop mode
5142 @c This section is really only a place-holder, and needs to be expanded
5143 @c with more details.
5145 For some multi-threaded targets, @value{GDBN} supports an optional
5146 mode of operation in which you can examine stopped program threads in
5147 the debugger while other threads continue to execute freely. This
5148 minimizes intrusion when debugging live systems, such as programs
5149 where some threads have real-time constraints or must continue to
5150 respond to external events. This is referred to as @dfn{non-stop} mode.
5152 In non-stop mode, when a thread stops to report a debugging event,
5153 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5154 threads as well, in contrast to the all-stop mode behavior. Additionally,
5155 execution commands such as @code{continue} and @code{step} apply by default
5156 only to the current thread in non-stop mode, rather than all threads as
5157 in all-stop mode. This allows you to control threads explicitly in
5158 ways that are not possible in all-stop mode --- for example, stepping
5159 one thread while allowing others to run freely, stepping
5160 one thread while holding all others stopped, or stepping several threads
5161 independently and simultaneously.
5163 To enter non-stop mode, use this sequence of commands before you run
5164 or attach to your program:
5167 # Enable the async interface.
5170 # If using the CLI, pagination breaks non-stop.
5173 # Finally, turn it on!
5177 You can use these commands to manipulate the non-stop mode setting:
5180 @kindex set non-stop
5181 @item set non-stop on
5182 Enable selection of non-stop mode.
5183 @item set non-stop off
5184 Disable selection of non-stop mode.
5185 @kindex show non-stop
5187 Show the current non-stop enablement setting.
5190 Note these commands only reflect whether non-stop mode is enabled,
5191 not whether the currently-executing program is being run in non-stop mode.
5192 In particular, the @code{set non-stop} preference is only consulted when
5193 @value{GDBN} starts or connects to the target program, and it is generally
5194 not possible to switch modes once debugging has started. Furthermore,
5195 since not all targets support non-stop mode, even when you have enabled
5196 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5199 In non-stop mode, all execution commands apply only to the current thread
5200 by default. That is, @code{continue} only continues one thread.
5201 To continue all threads, issue @code{continue -a} or @code{c -a}.
5203 You can use @value{GDBN}'s background execution commands
5204 (@pxref{Background Execution}) to run some threads in the background
5205 while you continue to examine or step others from @value{GDBN}.
5206 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5207 always executed asynchronously in non-stop mode.
5209 Suspending execution is done with the @code{interrupt} command when
5210 running in the background, or @kbd{Ctrl-c} during foreground execution.
5211 In all-stop mode, this stops the whole process;
5212 but in non-stop mode the interrupt applies only to the current thread.
5213 To stop the whole program, use @code{interrupt -a}.
5215 Other execution commands do not currently support the @code{-a} option.
5217 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5218 that thread current, as it does in all-stop mode. This is because the
5219 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5220 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5221 changed to a different thread just as you entered a command to operate on the
5222 previously current thread.
5224 @node Background Execution
5225 @subsection Background Execution
5227 @cindex foreground execution
5228 @cindex background execution
5229 @cindex asynchronous execution
5230 @cindex execution, foreground, background and asynchronous
5232 @value{GDBN}'s execution commands have two variants: the normal
5233 foreground (synchronous) behavior, and a background
5234 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5235 the program to report that some thread has stopped before prompting for
5236 another command. In background execution, @value{GDBN} immediately gives
5237 a command prompt so that you can issue other commands while your program runs.
5239 You need to explicitly enable asynchronous mode before you can use
5240 background execution commands. You can use these commands to
5241 manipulate the asynchronous mode setting:
5244 @kindex set target-async
5245 @item set target-async on
5246 Enable asynchronous mode.
5247 @item set target-async off
5248 Disable asynchronous mode.
5249 @kindex show target-async
5250 @item show target-async
5251 Show the current target-async setting.
5254 If the target doesn't support async mode, @value{GDBN} issues an error
5255 message if you attempt to use the background execution commands.
5257 To specify background execution, add a @code{&} to the command. For example,
5258 the background form of the @code{continue} command is @code{continue&}, or
5259 just @code{c&}. The execution commands that accept background execution
5265 @xref{Starting, , Starting your Program}.
5269 @xref{Attach, , Debugging an Already-running Process}.
5273 @xref{Continuing and Stepping, step}.
5277 @xref{Continuing and Stepping, stepi}.
5281 @xref{Continuing and Stepping, next}.
5285 @xref{Continuing and Stepping, nexti}.
5289 @xref{Continuing and Stepping, continue}.
5293 @xref{Continuing and Stepping, finish}.
5297 @xref{Continuing and Stepping, until}.
5301 Background execution is especially useful in conjunction with non-stop
5302 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5303 However, you can also use these commands in the normal all-stop mode with
5304 the restriction that you cannot issue another execution command until the
5305 previous one finishes. Examples of commands that are valid in all-stop
5306 mode while the program is running include @code{help} and @code{info break}.
5308 You can interrupt your program while it is running in the background by
5309 using the @code{interrupt} command.
5316 Suspend execution of the running program. In all-stop mode,
5317 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5318 only the current thread. To stop the whole program in non-stop mode,
5319 use @code{interrupt -a}.
5322 @node Thread-Specific Breakpoints
5323 @subsection Thread-Specific Breakpoints
5325 When your program has multiple threads (@pxref{Threads,, Debugging
5326 Programs with Multiple Threads}), you can choose whether to set
5327 breakpoints on all threads, or on a particular thread.
5330 @cindex breakpoints and threads
5331 @cindex thread breakpoints
5332 @kindex break @dots{} thread @var{threadno}
5333 @item break @var{linespec} thread @var{threadno}
5334 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5335 @var{linespec} specifies source lines; there are several ways of
5336 writing them (@pxref{Specify Location}), but the effect is always to
5337 specify some source line.
5339 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5340 to specify that you only want @value{GDBN} to stop the program when a
5341 particular thread reaches this breakpoint. @var{threadno} is one of the
5342 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5343 column of the @samp{info threads} display.
5345 If you do not specify @samp{thread @var{threadno}} when you set a
5346 breakpoint, the breakpoint applies to @emph{all} threads of your
5349 You can use the @code{thread} qualifier on conditional breakpoints as
5350 well; in this case, place @samp{thread @var{threadno}} before or
5351 after the breakpoint condition, like this:
5354 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5359 @node Interrupted System Calls
5360 @subsection Interrupted System Calls
5362 @cindex thread breakpoints and system calls
5363 @cindex system calls and thread breakpoints
5364 @cindex premature return from system calls
5365 There is an unfortunate side effect when using @value{GDBN} to debug
5366 multi-threaded programs. If one thread stops for a
5367 breakpoint, or for some other reason, and another thread is blocked in a
5368 system call, then the system call may return prematurely. This is a
5369 consequence of the interaction between multiple threads and the signals
5370 that @value{GDBN} uses to implement breakpoints and other events that
5373 To handle this problem, your program should check the return value of
5374 each system call and react appropriately. This is good programming
5377 For example, do not write code like this:
5383 The call to @code{sleep} will return early if a different thread stops
5384 at a breakpoint or for some other reason.
5386 Instead, write this:
5391 unslept = sleep (unslept);
5394 A system call is allowed to return early, so the system is still
5395 conforming to its specification. But @value{GDBN} does cause your
5396 multi-threaded program to behave differently than it would without
5399 Also, @value{GDBN} uses internal breakpoints in the thread library to
5400 monitor certain events such as thread creation and thread destruction.
5401 When such an event happens, a system call in another thread may return
5402 prematurely, even though your program does not appear to stop.
5405 @subsection Observer Mode
5407 If you want to build on non-stop mode and observe program behavior
5408 without any chance of disruption by @value{GDBN}, you can set
5409 variables to disable all of the debugger's attempts to modify state,
5410 whether by writing memory, inserting breakpoints, etc. These operate
5411 at a low level, intercepting operations from all commands.
5413 When all of these are set to @code{off}, then @value{GDBN} is said to
5414 be @dfn{observer mode}. As a convenience, the variable
5415 @code{observer} can be set to disable these, plus enable non-stop
5418 Note that @value{GDBN} will not prevent you from making nonsensical
5419 combinations of these settings. For instance, if you have enabled
5420 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5421 then breakpoints that work by writing trap instructions into the code
5422 stream will still not be able to be placed.
5427 @item set observer on
5428 @itemx set observer off
5429 When set to @code{on}, this disables all the permission variables
5430 below (except for @code{insert-fast-tracepoints}), plus enables
5431 non-stop debugging. Setting this to @code{off} switches back to
5432 normal debugging, though remaining in non-stop mode.
5435 Show whether observer mode is on or off.
5437 @kindex may-write-registers
5438 @item set may-write-registers on
5439 @itemx set may-write-registers off
5440 This controls whether @value{GDBN} will attempt to alter the values of
5441 registers, such as with assignment expressions in @code{print}, or the
5442 @code{jump} command. It defaults to @code{on}.
5444 @item show may-write-registers
5445 Show the current permission to write registers.
5447 @kindex may-write-memory
5448 @item set may-write-memory on
5449 @itemx set may-write-memory off
5450 This controls whether @value{GDBN} will attempt to alter the contents
5451 of memory, such as with assignment expressions in @code{print}. It
5452 defaults to @code{on}.
5454 @item show may-write-memory
5455 Show the current permission to write memory.
5457 @kindex may-insert-breakpoints
5458 @item set may-insert-breakpoints on
5459 @itemx set may-insert-breakpoints off
5460 This controls whether @value{GDBN} will attempt to insert breakpoints.
5461 This affects all breakpoints, including internal breakpoints defined
5462 by @value{GDBN}. It defaults to @code{on}.
5464 @item show may-insert-breakpoints
5465 Show the current permission to insert breakpoints.
5467 @kindex may-insert-tracepoints
5468 @item set may-insert-tracepoints on
5469 @itemx set may-insert-tracepoints off
5470 This controls whether @value{GDBN} will attempt to insert (regular)
5471 tracepoints at the beginning of a tracing experiment. It affects only
5472 non-fast tracepoints, fast tracepoints being under the control of
5473 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5475 @item show may-insert-tracepoints
5476 Show the current permission to insert tracepoints.
5478 @kindex may-insert-fast-tracepoints
5479 @item set may-insert-fast-tracepoints on
5480 @itemx set may-insert-fast-tracepoints off
5481 This controls whether @value{GDBN} will attempt to insert fast
5482 tracepoints at the beginning of a tracing experiment. It affects only
5483 fast tracepoints, regular (non-fast) tracepoints being under the
5484 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5486 @item show may-insert-fast-tracepoints
5487 Show the current permission to insert fast tracepoints.
5489 @kindex may-interrupt
5490 @item set may-interrupt on
5491 @itemx set may-interrupt off
5492 This controls whether @value{GDBN} will attempt to interrupt or stop
5493 program execution. When this variable is @code{off}, the
5494 @code{interrupt} command will have no effect, nor will
5495 @kbd{Ctrl-c}. It defaults to @code{on}.
5497 @item show may-interrupt
5498 Show the current permission to interrupt or stop the program.
5502 @node Reverse Execution
5503 @chapter Running programs backward
5504 @cindex reverse execution
5505 @cindex running programs backward
5507 When you are debugging a program, it is not unusual to realize that
5508 you have gone too far, and some event of interest has already happened.
5509 If the target environment supports it, @value{GDBN} can allow you to
5510 ``rewind'' the program by running it backward.
5512 A target environment that supports reverse execution should be able
5513 to ``undo'' the changes in machine state that have taken place as the
5514 program was executing normally. Variables, registers etc.@: should
5515 revert to their previous values. Obviously this requires a great
5516 deal of sophistication on the part of the target environment; not
5517 all target environments can support reverse execution.
5519 When a program is executed in reverse, the instructions that
5520 have most recently been executed are ``un-executed'', in reverse
5521 order. The program counter runs backward, following the previous
5522 thread of execution in reverse. As each instruction is ``un-executed'',
5523 the values of memory and/or registers that were changed by that
5524 instruction are reverted to their previous states. After executing
5525 a piece of source code in reverse, all side effects of that code
5526 should be ``undone'', and all variables should be returned to their
5527 prior values@footnote{
5528 Note that some side effects are easier to undo than others. For instance,
5529 memory and registers are relatively easy, but device I/O is hard. Some
5530 targets may be able undo things like device I/O, and some may not.
5532 The contract between @value{GDBN} and the reverse executing target
5533 requires only that the target do something reasonable when
5534 @value{GDBN} tells it to execute backwards, and then report the
5535 results back to @value{GDBN}. Whatever the target reports back to
5536 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5537 assumes that the memory and registers that the target reports are in a
5538 consistant state, but @value{GDBN} accepts whatever it is given.
5541 If you are debugging in a target environment that supports
5542 reverse execution, @value{GDBN} provides the following commands.
5545 @kindex reverse-continue
5546 @kindex rc @r{(@code{reverse-continue})}
5547 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5548 @itemx rc @r{[}@var{ignore-count}@r{]}
5549 Beginning at the point where your program last stopped, start executing
5550 in reverse. Reverse execution will stop for breakpoints and synchronous
5551 exceptions (signals), just like normal execution. Behavior of
5552 asynchronous signals depends on the target environment.
5554 @kindex reverse-step
5555 @kindex rs @r{(@code{step})}
5556 @item reverse-step @r{[}@var{count}@r{]}
5557 Run the program backward until control reaches the start of a
5558 different source line; then stop it, and return control to @value{GDBN}.
5560 Like the @code{step} command, @code{reverse-step} will only stop
5561 at the beginning of a source line. It ``un-executes'' the previously
5562 executed source line. If the previous source line included calls to
5563 debuggable functions, @code{reverse-step} will step (backward) into
5564 the called function, stopping at the beginning of the @emph{last}
5565 statement in the called function (typically a return statement).
5567 Also, as with the @code{step} command, if non-debuggable functions are
5568 called, @code{reverse-step} will run thru them backward without stopping.
5570 @kindex reverse-stepi
5571 @kindex rsi @r{(@code{reverse-stepi})}
5572 @item reverse-stepi @r{[}@var{count}@r{]}
5573 Reverse-execute one machine instruction. Note that the instruction
5574 to be reverse-executed is @emph{not} the one pointed to by the program
5575 counter, but the instruction executed prior to that one. For instance,
5576 if the last instruction was a jump, @code{reverse-stepi} will take you
5577 back from the destination of the jump to the jump instruction itself.
5579 @kindex reverse-next
5580 @kindex rn @r{(@code{reverse-next})}
5581 @item reverse-next @r{[}@var{count}@r{]}
5582 Run backward to the beginning of the previous line executed in
5583 the current (innermost) stack frame. If the line contains function
5584 calls, they will be ``un-executed'' without stopping. Starting from
5585 the first line of a function, @code{reverse-next} will take you back
5586 to the caller of that function, @emph{before} the function was called,
5587 just as the normal @code{next} command would take you from the last
5588 line of a function back to its return to its caller
5589 @footnote{Unless the code is too heavily optimized.}.
5591 @kindex reverse-nexti
5592 @kindex rni @r{(@code{reverse-nexti})}
5593 @item reverse-nexti @r{[}@var{count}@r{]}
5594 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5595 in reverse, except that called functions are ``un-executed'' atomically.
5596 That is, if the previously executed instruction was a return from
5597 another function, @code{reverse-nexti} will continue to execute
5598 in reverse until the call to that function (from the current stack
5601 @kindex reverse-finish
5602 @item reverse-finish
5603 Just as the @code{finish} command takes you to the point where the
5604 current function returns, @code{reverse-finish} takes you to the point
5605 where it was called. Instead of ending up at the end of the current
5606 function invocation, you end up at the beginning.
5608 @kindex set exec-direction
5609 @item set exec-direction
5610 Set the direction of target execution.
5611 @itemx set exec-direction reverse
5612 @cindex execute forward or backward in time
5613 @value{GDBN} will perform all execution commands in reverse, until the
5614 exec-direction mode is changed to ``forward''. Affected commands include
5615 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5616 command cannot be used in reverse mode.
5617 @item set exec-direction forward
5618 @value{GDBN} will perform all execution commands in the normal fashion.
5619 This is the default.
5623 @node Process Record and Replay
5624 @chapter Recording Inferior's Execution and Replaying It
5625 @cindex process record and replay
5626 @cindex recording inferior's execution and replaying it
5628 On some platforms, @value{GDBN} provides a special @dfn{process record
5629 and replay} target that can record a log of the process execution, and
5630 replay it later with both forward and reverse execution commands.
5633 When this target is in use, if the execution log includes the record
5634 for the next instruction, @value{GDBN} will debug in @dfn{replay
5635 mode}. In the replay mode, the inferior does not really execute code
5636 instructions. Instead, all the events that normally happen during
5637 code execution are taken from the execution log. While code is not
5638 really executed in replay mode, the values of registers (including the
5639 program counter register) and the memory of the inferior are still
5640 changed as they normally would. Their contents are taken from the
5644 If the record for the next instruction is not in the execution log,
5645 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5646 inferior executes normally, and @value{GDBN} records the execution log
5649 The process record and replay target supports reverse execution
5650 (@pxref{Reverse Execution}), even if the platform on which the
5651 inferior runs does not. However, the reverse execution is limited in
5652 this case by the range of the instructions recorded in the execution
5653 log. In other words, reverse execution on platforms that don't
5654 support it directly can only be done in the replay mode.
5656 When debugging in the reverse direction, @value{GDBN} will work in
5657 replay mode as long as the execution log includes the record for the
5658 previous instruction; otherwise, it will work in record mode, if the
5659 platform supports reverse execution, or stop if not.
5661 For architecture environments that support process record and replay,
5662 @value{GDBN} provides the following commands:
5665 @kindex target record
5669 This command starts the process record and replay target. The process
5670 record and replay target can only debug a process that is already
5671 running. Therefore, you need first to start the process with the
5672 @kbd{run} or @kbd{start} commands, and then start the recording with
5673 the @kbd{target record} command.
5675 Both @code{record} and @code{rec} are aliases of @code{target record}.
5677 @cindex displaced stepping, and process record and replay
5678 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5679 will be automatically disabled when process record and replay target
5680 is started. That's because the process record and replay target
5681 doesn't support displaced stepping.
5683 @cindex non-stop mode, and process record and replay
5684 @cindex asynchronous execution, and process record and replay
5685 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5686 the asynchronous execution mode (@pxref{Background Execution}), the
5687 process record and replay target cannot be started because it doesn't
5688 support these two modes.
5693 Stop the process record and replay target. When process record and
5694 replay target stops, the entire execution log will be deleted and the
5695 inferior will either be terminated, or will remain in its final state.
5697 When you stop the process record and replay target in record mode (at
5698 the end of the execution log), the inferior will be stopped at the
5699 next instruction that would have been recorded. In other words, if
5700 you record for a while and then stop recording, the inferior process
5701 will be left in the same state as if the recording never happened.
5703 On the other hand, if the process record and replay target is stopped
5704 while in replay mode (that is, not at the end of the execution log,
5705 but at some earlier point), the inferior process will become ``live''
5706 at that earlier state, and it will then be possible to continue the
5707 usual ``live'' debugging of the process from that state.
5709 When the inferior process exits, or @value{GDBN} detaches from it,
5710 process record and replay target will automatically stop itself.
5713 @item record save @var{filename}
5714 Save the execution log to a file @file{@var{filename}}.
5715 Default filename is @file{gdb_record.@var{process_id}}, where
5716 @var{process_id} is the process ID of the inferior.
5718 @kindex record restore
5719 @item record restore @var{filename}
5720 Restore the execution log from a file @file{@var{filename}}.
5721 File must have been created with @code{record save}.
5723 @kindex set record insn-number-max
5724 @item set record insn-number-max @var{limit}
5725 Set the limit of instructions to be recorded. Default value is 200000.
5727 If @var{limit} is a positive number, then @value{GDBN} will start
5728 deleting instructions from the log once the number of the record
5729 instructions becomes greater than @var{limit}. For every new recorded
5730 instruction, @value{GDBN} will delete the earliest recorded
5731 instruction to keep the number of recorded instructions at the limit.
5732 (Since deleting recorded instructions loses information, @value{GDBN}
5733 lets you control what happens when the limit is reached, by means of
5734 the @code{stop-at-limit} option, described below.)
5736 If @var{limit} is zero, @value{GDBN} will never delete recorded
5737 instructions from the execution log. The number of recorded
5738 instructions is unlimited in this case.
5740 @kindex show record insn-number-max
5741 @item show record insn-number-max
5742 Show the limit of instructions to be recorded.
5744 @kindex set record stop-at-limit
5745 @item set record stop-at-limit
5746 Control the behavior when the number of recorded instructions reaches
5747 the limit. If ON (the default), @value{GDBN} will stop when the limit
5748 is reached for the first time and ask you whether you want to stop the
5749 inferior or continue running it and recording the execution log. If
5750 you decide to continue recording, each new recorded instruction will
5751 cause the oldest one to be deleted.
5753 If this option is OFF, @value{GDBN} will automatically delete the
5754 oldest record to make room for each new one, without asking.
5756 @kindex show record stop-at-limit
5757 @item show record stop-at-limit
5758 Show the current setting of @code{stop-at-limit}.
5760 @kindex set record memory-query
5761 @item set record memory-query
5762 Control the behavior when @value{GDBN} is unable to record memory
5763 changes caused by an instruction. If ON, @value{GDBN} will query
5764 whether to stop the inferior in that case.
5766 If this option is OFF (the default), @value{GDBN} will automatically
5767 ignore the effect of such instructions on memory. Later, when
5768 @value{GDBN} replays this execution log, it will mark the log of this
5769 instruction as not accessible, and it will not affect the replay
5772 @kindex show record memory-query
5773 @item show record memory-query
5774 Show the current setting of @code{memory-query}.
5778 Show various statistics about the state of process record and its
5779 in-memory execution log buffer, including:
5783 Whether in record mode or replay mode.
5785 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5787 Highest recorded instruction number.
5789 Current instruction about to be replayed (if in replay mode).
5791 Number of instructions contained in the execution log.
5793 Maximum number of instructions that may be contained in the execution log.
5796 @kindex record delete
5799 When record target runs in replay mode (``in the past''), delete the
5800 subsequent execution log and begin to record a new execution log starting
5801 from the current address. This means you will abandon the previously
5802 recorded ``future'' and begin recording a new ``future''.
5807 @chapter Examining the Stack
5809 When your program has stopped, the first thing you need to know is where it
5810 stopped and how it got there.
5813 Each time your program performs a function call, information about the call
5815 That information includes the location of the call in your program,
5816 the arguments of the call,
5817 and the local variables of the function being called.
5818 The information is saved in a block of data called a @dfn{stack frame}.
5819 The stack frames are allocated in a region of memory called the @dfn{call
5822 When your program stops, the @value{GDBN} commands for examining the
5823 stack allow you to see all of this information.
5825 @cindex selected frame
5826 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5827 @value{GDBN} commands refer implicitly to the selected frame. In
5828 particular, whenever you ask @value{GDBN} for the value of a variable in
5829 your program, the value is found in the selected frame. There are
5830 special @value{GDBN} commands to select whichever frame you are
5831 interested in. @xref{Selection, ,Selecting a Frame}.
5833 When your program stops, @value{GDBN} automatically selects the
5834 currently executing frame and describes it briefly, similar to the
5835 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5838 * Frames:: Stack frames
5839 * Backtrace:: Backtraces
5840 * Selection:: Selecting a frame
5841 * Frame Info:: Information on a frame
5846 @section Stack Frames
5848 @cindex frame, definition
5850 The call stack is divided up into contiguous pieces called @dfn{stack
5851 frames}, or @dfn{frames} for short; each frame is the data associated
5852 with one call to one function. The frame contains the arguments given
5853 to the function, the function's local variables, and the address at
5854 which the function is executing.
5856 @cindex initial frame
5857 @cindex outermost frame
5858 @cindex innermost frame
5859 When your program is started, the stack has only one frame, that of the
5860 function @code{main}. This is called the @dfn{initial} frame or the
5861 @dfn{outermost} frame. Each time a function is called, a new frame is
5862 made. Each time a function returns, the frame for that function invocation
5863 is eliminated. If a function is recursive, there can be many frames for
5864 the same function. The frame for the function in which execution is
5865 actually occurring is called the @dfn{innermost} frame. This is the most
5866 recently created of all the stack frames that still exist.
5868 @cindex frame pointer
5869 Inside your program, stack frames are identified by their addresses. A
5870 stack frame consists of many bytes, each of which has its own address; each
5871 kind of computer has a convention for choosing one byte whose
5872 address serves as the address of the frame. Usually this address is kept
5873 in a register called the @dfn{frame pointer register}
5874 (@pxref{Registers, $fp}) while execution is going on in that frame.
5876 @cindex frame number
5877 @value{GDBN} assigns numbers to all existing stack frames, starting with
5878 zero for the innermost frame, one for the frame that called it,
5879 and so on upward. These numbers do not really exist in your program;
5880 they are assigned by @value{GDBN} to give you a way of designating stack
5881 frames in @value{GDBN} commands.
5883 @c The -fomit-frame-pointer below perennially causes hbox overflow
5884 @c underflow problems.
5885 @cindex frameless execution
5886 Some compilers provide a way to compile functions so that they operate
5887 without stack frames. (For example, the @value{NGCC} option
5889 @samp{-fomit-frame-pointer}
5891 generates functions without a frame.)
5892 This is occasionally done with heavily used library functions to save
5893 the frame setup time. @value{GDBN} has limited facilities for dealing
5894 with these function invocations. If the innermost function invocation
5895 has no stack frame, @value{GDBN} nevertheless regards it as though
5896 it had a separate frame, which is numbered zero as usual, allowing
5897 correct tracing of the function call chain. However, @value{GDBN} has
5898 no provision for frameless functions elsewhere in the stack.
5901 @kindex frame@r{, command}
5902 @cindex current stack frame
5903 @item frame @var{args}
5904 The @code{frame} command allows you to move from one stack frame to another,
5905 and to print the stack frame you select. @var{args} may be either the
5906 address of the frame or the stack frame number. Without an argument,
5907 @code{frame} prints the current stack frame.
5909 @kindex select-frame
5910 @cindex selecting frame silently
5912 The @code{select-frame} command allows you to move from one stack frame
5913 to another without printing the frame. This is the silent version of
5921 @cindex call stack traces
5922 A backtrace is a summary of how your program got where it is. It shows one
5923 line per frame, for many frames, starting with the currently executing
5924 frame (frame zero), followed by its caller (frame one), and on up the
5929 @kindex bt @r{(@code{backtrace})}
5932 Print a backtrace of the entire stack: one line per frame for all
5933 frames in the stack.
5935 You can stop the backtrace at any time by typing the system interrupt
5936 character, normally @kbd{Ctrl-c}.
5938 @item backtrace @var{n}
5940 Similar, but print only the innermost @var{n} frames.
5942 @item backtrace -@var{n}
5944 Similar, but print only the outermost @var{n} frames.
5946 @item backtrace full
5948 @itemx bt full @var{n}
5949 @itemx bt full -@var{n}
5950 Print the values of the local variables also. @var{n} specifies the
5951 number of frames to print, as described above.
5956 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5957 are additional aliases for @code{backtrace}.
5959 @cindex multiple threads, backtrace
5960 In a multi-threaded program, @value{GDBN} by default shows the
5961 backtrace only for the current thread. To display the backtrace for
5962 several or all of the threads, use the command @code{thread apply}
5963 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5964 apply all backtrace}, @value{GDBN} will display the backtrace for all
5965 the threads; this is handy when you debug a core dump of a
5966 multi-threaded program.
5968 Each line in the backtrace shows the frame number and the function name.
5969 The program counter value is also shown---unless you use @code{set
5970 print address off}. The backtrace also shows the source file name and
5971 line number, as well as the arguments to the function. The program
5972 counter value is omitted if it is at the beginning of the code for that
5975 Here is an example of a backtrace. It was made with the command
5976 @samp{bt 3}, so it shows the innermost three frames.
5980 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5982 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5983 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5985 (More stack frames follow...)
5990 The display for frame zero does not begin with a program counter
5991 value, indicating that your program has stopped at the beginning of the
5992 code for line @code{993} of @code{builtin.c}.
5995 The value of parameter @code{data} in frame 1 has been replaced by
5996 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5997 only if it is a scalar (integer, pointer, enumeration, etc). See command
5998 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5999 on how to configure the way function parameter values are printed.
6001 @cindex optimized out, in backtrace
6002 @cindex function call arguments, optimized out
6003 If your program was compiled with optimizations, some compilers will
6004 optimize away arguments passed to functions if those arguments are
6005 never used after the call. Such optimizations generate code that
6006 passes arguments through registers, but doesn't store those arguments
6007 in the stack frame. @value{GDBN} has no way of displaying such
6008 arguments in stack frames other than the innermost one. Here's what
6009 such a backtrace might look like:
6013 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6015 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6016 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6018 (More stack frames follow...)
6023 The values of arguments that were not saved in their stack frames are
6024 shown as @samp{<optimized out>}.
6026 If you need to display the values of such optimized-out arguments,
6027 either deduce that from other variables whose values depend on the one
6028 you are interested in, or recompile without optimizations.
6030 @cindex backtrace beyond @code{main} function
6031 @cindex program entry point
6032 @cindex startup code, and backtrace
6033 Most programs have a standard user entry point---a place where system
6034 libraries and startup code transition into user code. For C this is
6035 @code{main}@footnote{
6036 Note that embedded programs (the so-called ``free-standing''
6037 environment) are not required to have a @code{main} function as the
6038 entry point. They could even have multiple entry points.}.
6039 When @value{GDBN} finds the entry function in a backtrace
6040 it will terminate the backtrace, to avoid tracing into highly
6041 system-specific (and generally uninteresting) code.
6043 If you need to examine the startup code, or limit the number of levels
6044 in a backtrace, you can change this behavior:
6047 @item set backtrace past-main
6048 @itemx set backtrace past-main on
6049 @kindex set backtrace
6050 Backtraces will continue past the user entry point.
6052 @item set backtrace past-main off
6053 Backtraces will stop when they encounter the user entry point. This is the
6056 @item show backtrace past-main
6057 @kindex show backtrace
6058 Display the current user entry point backtrace policy.
6060 @item set backtrace past-entry
6061 @itemx set backtrace past-entry on
6062 Backtraces will continue past the internal entry point of an application.
6063 This entry point is encoded by the linker when the application is built,
6064 and is likely before the user entry point @code{main} (or equivalent) is called.
6066 @item set backtrace past-entry off
6067 Backtraces will stop when they encounter the internal entry point of an
6068 application. This is the default.
6070 @item show backtrace past-entry
6071 Display the current internal entry point backtrace policy.
6073 @item set backtrace limit @var{n}
6074 @itemx set backtrace limit 0
6075 @cindex backtrace limit
6076 Limit the backtrace to @var{n} levels. A value of zero means
6079 @item show backtrace limit
6080 Display the current limit on backtrace levels.
6084 @section Selecting a Frame
6086 Most commands for examining the stack and other data in your program work on
6087 whichever stack frame is selected at the moment. Here are the commands for
6088 selecting a stack frame; all of them finish by printing a brief description
6089 of the stack frame just selected.
6092 @kindex frame@r{, selecting}
6093 @kindex f @r{(@code{frame})}
6096 Select frame number @var{n}. Recall that frame zero is the innermost
6097 (currently executing) frame, frame one is the frame that called the
6098 innermost one, and so on. The highest-numbered frame is the one for
6101 @item frame @var{addr}
6103 Select the frame at address @var{addr}. This is useful mainly if the
6104 chaining of stack frames has been damaged by a bug, making it
6105 impossible for @value{GDBN} to assign numbers properly to all frames. In
6106 addition, this can be useful when your program has multiple stacks and
6107 switches between them.
6109 On the SPARC architecture, @code{frame} needs two addresses to
6110 select an arbitrary frame: a frame pointer and a stack pointer.
6112 On the MIPS and Alpha architecture, it needs two addresses: a stack
6113 pointer and a program counter.
6115 On the 29k architecture, it needs three addresses: a register stack
6116 pointer, a program counter, and a memory stack pointer.
6120 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6121 advances toward the outermost frame, to higher frame numbers, to frames
6122 that have existed longer. @var{n} defaults to one.
6125 @kindex do @r{(@code{down})}
6127 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6128 advances toward the innermost frame, to lower frame numbers, to frames
6129 that were created more recently. @var{n} defaults to one. You may
6130 abbreviate @code{down} as @code{do}.
6133 All of these commands end by printing two lines of output describing the
6134 frame. The first line shows the frame number, the function name, the
6135 arguments, and the source file and line number of execution in that
6136 frame. The second line shows the text of that source line.
6144 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6146 10 read_input_file (argv[i]);
6150 After such a printout, the @code{list} command with no arguments
6151 prints ten lines centered on the point of execution in the frame.
6152 You can also edit the program at the point of execution with your favorite
6153 editing program by typing @code{edit}.
6154 @xref{List, ,Printing Source Lines},
6158 @kindex down-silently
6160 @item up-silently @var{n}
6161 @itemx down-silently @var{n}
6162 These two commands are variants of @code{up} and @code{down},
6163 respectively; they differ in that they do their work silently, without
6164 causing display of the new frame. They are intended primarily for use
6165 in @value{GDBN} command scripts, where the output might be unnecessary and
6170 @section Information About a Frame
6172 There are several other commands to print information about the selected
6178 When used without any argument, this command does not change which
6179 frame is selected, but prints a brief description of the currently
6180 selected stack frame. It can be abbreviated @code{f}. With an
6181 argument, this command is used to select a stack frame.
6182 @xref{Selection, ,Selecting a Frame}.
6185 @kindex info f @r{(@code{info frame})}
6188 This command prints a verbose description of the selected stack frame,
6193 the address of the frame
6195 the address of the next frame down (called by this frame)
6197 the address of the next frame up (caller of this frame)
6199 the language in which the source code corresponding to this frame is written
6201 the address of the frame's arguments
6203 the address of the frame's local variables
6205 the program counter saved in it (the address of execution in the caller frame)
6207 which registers were saved in the frame
6210 @noindent The verbose description is useful when
6211 something has gone wrong that has made the stack format fail to fit
6212 the usual conventions.
6214 @item info frame @var{addr}
6215 @itemx info f @var{addr}
6216 Print a verbose description of the frame at address @var{addr}, without
6217 selecting that frame. The selected frame remains unchanged by this
6218 command. This requires the same kind of address (more than one for some
6219 architectures) that you specify in the @code{frame} command.
6220 @xref{Selection, ,Selecting a Frame}.
6224 Print the arguments of the selected frame, each on a separate line.
6228 Print the local variables of the selected frame, each on a separate
6229 line. These are all variables (declared either static or automatic)
6230 accessible at the point of execution of the selected frame.
6233 @cindex catch exceptions, list active handlers
6234 @cindex exception handlers, how to list
6236 Print a list of all the exception handlers that are active in the
6237 current stack frame at the current point of execution. To see other
6238 exception handlers, visit the associated frame (using the @code{up},
6239 @code{down}, or @code{frame} commands); then type @code{info catch}.
6240 @xref{Set Catchpoints, , Setting Catchpoints}.
6246 @chapter Examining Source Files
6248 @value{GDBN} can print parts of your program's source, since the debugging
6249 information recorded in the program tells @value{GDBN} what source files were
6250 used to build it. When your program stops, @value{GDBN} spontaneously prints
6251 the line where it stopped. Likewise, when you select a stack frame
6252 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6253 execution in that frame has stopped. You can print other portions of
6254 source files by explicit command.
6256 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6257 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6258 @value{GDBN} under @sc{gnu} Emacs}.
6261 * List:: Printing source lines
6262 * Specify Location:: How to specify code locations
6263 * Edit:: Editing source files
6264 * Search:: Searching source files
6265 * Source Path:: Specifying source directories
6266 * Machine Code:: Source and machine code
6270 @section Printing Source Lines
6273 @kindex l @r{(@code{list})}
6274 To print lines from a source file, use the @code{list} command
6275 (abbreviated @code{l}). By default, ten lines are printed.
6276 There are several ways to specify what part of the file you want to
6277 print; see @ref{Specify Location}, for the full list.
6279 Here are the forms of the @code{list} command most commonly used:
6282 @item list @var{linenum}
6283 Print lines centered around line number @var{linenum} in the
6284 current source file.
6286 @item list @var{function}
6287 Print lines centered around the beginning of function
6291 Print more lines. If the last lines printed were printed with a
6292 @code{list} command, this prints lines following the last lines
6293 printed; however, if the last line printed was a solitary line printed
6294 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6295 Stack}), this prints lines centered around that line.
6298 Print lines just before the lines last printed.
6301 @cindex @code{list}, how many lines to display
6302 By default, @value{GDBN} prints ten source lines with any of these forms of
6303 the @code{list} command. You can change this using @code{set listsize}:
6306 @kindex set listsize
6307 @item set listsize @var{count}
6308 Make the @code{list} command display @var{count} source lines (unless
6309 the @code{list} argument explicitly specifies some other number).
6311 @kindex show listsize
6313 Display the number of lines that @code{list} prints.
6316 Repeating a @code{list} command with @key{RET} discards the argument,
6317 so it is equivalent to typing just @code{list}. This is more useful
6318 than listing the same lines again. An exception is made for an
6319 argument of @samp{-}; that argument is preserved in repetition so that
6320 each repetition moves up in the source file.
6322 In general, the @code{list} command expects you to supply zero, one or two
6323 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6324 of writing them (@pxref{Specify Location}), but the effect is always
6325 to specify some source line.
6327 Here is a complete description of the possible arguments for @code{list}:
6330 @item list @var{linespec}
6331 Print lines centered around the line specified by @var{linespec}.
6333 @item list @var{first},@var{last}
6334 Print lines from @var{first} to @var{last}. Both arguments are
6335 linespecs. When a @code{list} command has two linespecs, and the
6336 source file of the second linespec is omitted, this refers to
6337 the same source file as the first linespec.
6339 @item list ,@var{last}
6340 Print lines ending with @var{last}.
6342 @item list @var{first},
6343 Print lines starting with @var{first}.
6346 Print lines just after the lines last printed.
6349 Print lines just before the lines last printed.
6352 As described in the preceding table.
6355 @node Specify Location
6356 @section Specifying a Location
6357 @cindex specifying location
6360 Several @value{GDBN} commands accept arguments that specify a location
6361 of your program's code. Since @value{GDBN} is a source-level
6362 debugger, a location usually specifies some line in the source code;
6363 for that reason, locations are also known as @dfn{linespecs}.
6365 Here are all the different ways of specifying a code location that
6366 @value{GDBN} understands:
6370 Specifies the line number @var{linenum} of the current source file.
6373 @itemx +@var{offset}
6374 Specifies the line @var{offset} lines before or after the @dfn{current
6375 line}. For the @code{list} command, the current line is the last one
6376 printed; for the breakpoint commands, this is the line at which
6377 execution stopped in the currently selected @dfn{stack frame}
6378 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6379 used as the second of the two linespecs in a @code{list} command,
6380 this specifies the line @var{offset} lines up or down from the first
6383 @item @var{filename}:@var{linenum}
6384 Specifies the line @var{linenum} in the source file @var{filename}.
6386 @item @var{function}
6387 Specifies the line that begins the body of the function @var{function}.
6388 For example, in C, this is the line with the open brace.
6390 @item @var{function}:@var{label}
6391 Specifies the line where @var{label} appears in @var{function}.
6393 @item @var{filename}:@var{function}
6394 Specifies the line that begins the body of the function @var{function}
6395 in the file @var{filename}. You only need the file name with a
6396 function name to avoid ambiguity when there are identically named
6397 functions in different source files.
6400 Specifies the line at which the label named @var{label} appears.
6401 @value{GDBN} searches for the label in the function corresponding to
6402 the currently selected stack frame. If there is no current selected
6403 stack frame (for instance, if the inferior is not running), then
6404 @value{GDBN} will not search for a label.
6406 @item *@var{address}
6407 Specifies the program address @var{address}. For line-oriented
6408 commands, such as @code{list} and @code{edit}, this specifies a source
6409 line that contains @var{address}. For @code{break} and other
6410 breakpoint oriented commands, this can be used to set breakpoints in
6411 parts of your program which do not have debugging information or
6414 Here @var{address} may be any expression valid in the current working
6415 language (@pxref{Languages, working language}) that specifies a code
6416 address. In addition, as a convenience, @value{GDBN} extends the
6417 semantics of expressions used in locations to cover the situations
6418 that frequently happen during debugging. Here are the various forms
6422 @item @var{expression}
6423 Any expression valid in the current working language.
6425 @item @var{funcaddr}
6426 An address of a function or procedure derived from its name. In C,
6427 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6428 simply the function's name @var{function} (and actually a special case
6429 of a valid expression). In Pascal and Modula-2, this is
6430 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6431 (although the Pascal form also works).
6433 This form specifies the address of the function's first instruction,
6434 before the stack frame and arguments have been set up.
6436 @item '@var{filename}'::@var{funcaddr}
6437 Like @var{funcaddr} above, but also specifies the name of the source
6438 file explicitly. This is useful if the name of the function does not
6439 specify the function unambiguously, e.g., if there are several
6440 functions with identical names in different source files.
6447 @section Editing Source Files
6448 @cindex editing source files
6451 @kindex e @r{(@code{edit})}
6452 To edit the lines in a source file, use the @code{edit} command.
6453 The editing program of your choice
6454 is invoked with the current line set to
6455 the active line in the program.
6456 Alternatively, there are several ways to specify what part of the file you
6457 want to print if you want to see other parts of the program:
6460 @item edit @var{location}
6461 Edit the source file specified by @code{location}. Editing starts at
6462 that @var{location}, e.g., at the specified source line of the
6463 specified file. @xref{Specify Location}, for all the possible forms
6464 of the @var{location} argument; here are the forms of the @code{edit}
6465 command most commonly used:
6468 @item edit @var{number}
6469 Edit the current source file with @var{number} as the active line number.
6471 @item edit @var{function}
6472 Edit the file containing @var{function} at the beginning of its definition.
6477 @subsection Choosing your Editor
6478 You can customize @value{GDBN} to use any editor you want
6480 The only restriction is that your editor (say @code{ex}), recognizes the
6481 following command-line syntax:
6483 ex +@var{number} file
6485 The optional numeric value +@var{number} specifies the number of the line in
6486 the file where to start editing.}.
6487 By default, it is @file{@value{EDITOR}}, but you can change this
6488 by setting the environment variable @code{EDITOR} before using
6489 @value{GDBN}. For example, to configure @value{GDBN} to use the
6490 @code{vi} editor, you could use these commands with the @code{sh} shell:
6496 or in the @code{csh} shell,
6498 setenv EDITOR /usr/bin/vi
6503 @section Searching Source Files
6504 @cindex searching source files
6506 There are two commands for searching through the current source file for a
6511 @kindex forward-search
6512 @item forward-search @var{regexp}
6513 @itemx search @var{regexp}
6514 The command @samp{forward-search @var{regexp}} checks each line,
6515 starting with the one following the last line listed, for a match for
6516 @var{regexp}. It lists the line that is found. You can use the
6517 synonym @samp{search @var{regexp}} or abbreviate the command name as
6520 @kindex reverse-search
6521 @item reverse-search @var{regexp}
6522 The command @samp{reverse-search @var{regexp}} checks each line, starting
6523 with the one before the last line listed and going backward, for a match
6524 for @var{regexp}. It lists the line that is found. You can abbreviate
6525 this command as @code{rev}.
6529 @section Specifying Source Directories
6532 @cindex directories for source files
6533 Executable programs sometimes do not record the directories of the source
6534 files from which they were compiled, just the names. Even when they do,
6535 the directories could be moved between the compilation and your debugging
6536 session. @value{GDBN} has a list of directories to search for source files;
6537 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6538 it tries all the directories in the list, in the order they are present
6539 in the list, until it finds a file with the desired name.
6541 For example, suppose an executable references the file
6542 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6543 @file{/mnt/cross}. The file is first looked up literally; if this
6544 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6545 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6546 message is printed. @value{GDBN} does not look up the parts of the
6547 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6548 Likewise, the subdirectories of the source path are not searched: if
6549 the source path is @file{/mnt/cross}, and the binary refers to
6550 @file{foo.c}, @value{GDBN} would not find it under
6551 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6553 Plain file names, relative file names with leading directories, file
6554 names containing dots, etc.@: are all treated as described above; for
6555 instance, if the source path is @file{/mnt/cross}, and the source file
6556 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6557 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6558 that---@file{/mnt/cross/foo.c}.
6560 Note that the executable search path is @emph{not} used to locate the
6563 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6564 any information it has cached about where source files are found and where
6565 each line is in the file.
6569 When you start @value{GDBN}, its source path includes only @samp{cdir}
6570 and @samp{cwd}, in that order.
6571 To add other directories, use the @code{directory} command.
6573 The search path is used to find both program source files and @value{GDBN}
6574 script files (read using the @samp{-command} option and @samp{source} command).
6576 In addition to the source path, @value{GDBN} provides a set of commands
6577 that manage a list of source path substitution rules. A @dfn{substitution
6578 rule} specifies how to rewrite source directories stored in the program's
6579 debug information in case the sources were moved to a different
6580 directory between compilation and debugging. A rule is made of
6581 two strings, the first specifying what needs to be rewritten in
6582 the path, and the second specifying how it should be rewritten.
6583 In @ref{set substitute-path}, we name these two parts @var{from} and
6584 @var{to} respectively. @value{GDBN} does a simple string replacement
6585 of @var{from} with @var{to} at the start of the directory part of the
6586 source file name, and uses that result instead of the original file
6587 name to look up the sources.
6589 Using the previous example, suppose the @file{foo-1.0} tree has been
6590 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6591 @value{GDBN} to replace @file{/usr/src} in all source path names with
6592 @file{/mnt/cross}. The first lookup will then be
6593 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6594 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6595 substitution rule, use the @code{set substitute-path} command
6596 (@pxref{set substitute-path}).
6598 To avoid unexpected substitution results, a rule is applied only if the
6599 @var{from} part of the directory name ends at a directory separator.
6600 For instance, a rule substituting @file{/usr/source} into
6601 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6602 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6603 is applied only at the beginning of the directory name, this rule will
6604 not be applied to @file{/root/usr/source/baz.c} either.
6606 In many cases, you can achieve the same result using the @code{directory}
6607 command. However, @code{set substitute-path} can be more efficient in
6608 the case where the sources are organized in a complex tree with multiple
6609 subdirectories. With the @code{directory} command, you need to add each
6610 subdirectory of your project. If you moved the entire tree while
6611 preserving its internal organization, then @code{set substitute-path}
6612 allows you to direct the debugger to all the sources with one single
6615 @code{set substitute-path} is also more than just a shortcut command.
6616 The source path is only used if the file at the original location no
6617 longer exists. On the other hand, @code{set substitute-path} modifies
6618 the debugger behavior to look at the rewritten location instead. So, if
6619 for any reason a source file that is not relevant to your executable is
6620 located at the original location, a substitution rule is the only
6621 method available to point @value{GDBN} at the new location.
6623 @cindex @samp{--with-relocated-sources}
6624 @cindex default source path substitution
6625 You can configure a default source path substitution rule by
6626 configuring @value{GDBN} with the
6627 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6628 should be the name of a directory under @value{GDBN}'s configured
6629 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6630 directory names in debug information under @var{dir} will be adjusted
6631 automatically if the installed @value{GDBN} is moved to a new
6632 location. This is useful if @value{GDBN}, libraries or executables
6633 with debug information and corresponding source code are being moved
6637 @item directory @var{dirname} @dots{}
6638 @item dir @var{dirname} @dots{}
6639 Add directory @var{dirname} to the front of the source path. Several
6640 directory names may be given to this command, separated by @samp{:}
6641 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6642 part of absolute file names) or
6643 whitespace. You may specify a directory that is already in the source
6644 path; this moves it forward, so @value{GDBN} searches it sooner.
6648 @vindex $cdir@r{, convenience variable}
6649 @vindex $cwd@r{, convenience variable}
6650 @cindex compilation directory
6651 @cindex current directory
6652 @cindex working directory
6653 @cindex directory, current
6654 @cindex directory, compilation
6655 You can use the string @samp{$cdir} to refer to the compilation
6656 directory (if one is recorded), and @samp{$cwd} to refer to the current
6657 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6658 tracks the current working directory as it changes during your @value{GDBN}
6659 session, while the latter is immediately expanded to the current
6660 directory at the time you add an entry to the source path.
6663 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6665 @c RET-repeat for @code{directory} is explicitly disabled, but since
6666 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6668 @item set directories @var{path-list}
6669 @kindex set directories
6670 Set the source path to @var{path-list}.
6671 @samp{$cdir:$cwd} are added if missing.
6673 @item show directories
6674 @kindex show directories
6675 Print the source path: show which directories it contains.
6677 @anchor{set substitute-path}
6678 @item set substitute-path @var{from} @var{to}
6679 @kindex set substitute-path
6680 Define a source path substitution rule, and add it at the end of the
6681 current list of existing substitution rules. If a rule with the same
6682 @var{from} was already defined, then the old rule is also deleted.
6684 For example, if the file @file{/foo/bar/baz.c} was moved to
6685 @file{/mnt/cross/baz.c}, then the command
6688 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6692 will tell @value{GDBN} to replace @samp{/usr/src} with
6693 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6694 @file{baz.c} even though it was moved.
6696 In the case when more than one substitution rule have been defined,
6697 the rules are evaluated one by one in the order where they have been
6698 defined. The first one matching, if any, is selected to perform
6701 For instance, if we had entered the following commands:
6704 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6705 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6709 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6710 @file{/mnt/include/defs.h} by using the first rule. However, it would
6711 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6712 @file{/mnt/src/lib/foo.c}.
6715 @item unset substitute-path [path]
6716 @kindex unset substitute-path
6717 If a path is specified, search the current list of substitution rules
6718 for a rule that would rewrite that path. Delete that rule if found.
6719 A warning is emitted by the debugger if no rule could be found.
6721 If no path is specified, then all substitution rules are deleted.
6723 @item show substitute-path [path]
6724 @kindex show substitute-path
6725 If a path is specified, then print the source path substitution rule
6726 which would rewrite that path, if any.
6728 If no path is specified, then print all existing source path substitution
6733 If your source path is cluttered with directories that are no longer of
6734 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6735 versions of source. You can correct the situation as follows:
6739 Use @code{directory} with no argument to reset the source path to its default value.
6742 Use @code{directory} with suitable arguments to reinstall the
6743 directories you want in the source path. You can add all the
6744 directories in one command.
6748 @section Source and Machine Code
6749 @cindex source line and its code address
6751 You can use the command @code{info line} to map source lines to program
6752 addresses (and vice versa), and the command @code{disassemble} to display
6753 a range of addresses as machine instructions. You can use the command
6754 @code{set disassemble-next-line} to set whether to disassemble next
6755 source line when execution stops. When run under @sc{gnu} Emacs
6756 mode, the @code{info line} command causes the arrow to point to the
6757 line specified. Also, @code{info line} prints addresses in symbolic form as
6762 @item info line @var{linespec}
6763 Print the starting and ending addresses of the compiled code for
6764 source line @var{linespec}. You can specify source lines in any of
6765 the ways documented in @ref{Specify Location}.
6768 For example, we can use @code{info line} to discover the location of
6769 the object code for the first line of function
6770 @code{m4_changequote}:
6772 @c FIXME: I think this example should also show the addresses in
6773 @c symbolic form, as they usually would be displayed.
6775 (@value{GDBP}) info line m4_changequote
6776 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6780 @cindex code address and its source line
6781 We can also inquire (using @code{*@var{addr}} as the form for
6782 @var{linespec}) what source line covers a particular address:
6784 (@value{GDBP}) info line *0x63ff
6785 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6788 @cindex @code{$_} and @code{info line}
6789 @cindex @code{x} command, default address
6790 @kindex x@r{(examine), and} info line
6791 After @code{info line}, the default address for the @code{x} command
6792 is changed to the starting address of the line, so that @samp{x/i} is
6793 sufficient to begin examining the machine code (@pxref{Memory,
6794 ,Examining Memory}). Also, this address is saved as the value of the
6795 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6800 @cindex assembly instructions
6801 @cindex instructions, assembly
6802 @cindex machine instructions
6803 @cindex listing machine instructions
6805 @itemx disassemble /m
6806 @itemx disassemble /r
6807 This specialized command dumps a range of memory as machine
6808 instructions. It can also print mixed source+disassembly by specifying
6809 the @code{/m} modifier and print the raw instructions in hex as well as
6810 in symbolic form by specifying the @code{/r}.
6811 The default memory range is the function surrounding the
6812 program counter of the selected frame. A single argument to this
6813 command is a program counter value; @value{GDBN} dumps the function
6814 surrounding this value. When two arguments are given, they should
6815 be separated by a comma, possibly surrounded by whitespace. The
6816 arguments specify a range of addresses to dump, in one of two forms:
6819 @item @var{start},@var{end}
6820 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6821 @item @var{start},+@var{length}
6822 the addresses from @var{start} (inclusive) to
6823 @code{@var{start}+@var{length}} (exclusive).
6827 When 2 arguments are specified, the name of the function is also
6828 printed (since there could be several functions in the given range).
6830 The argument(s) can be any expression yielding a numeric value, such as
6831 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6833 If the range of memory being disassembled contains current program counter,
6834 the instruction at that location is shown with a @code{=>} marker.
6837 The following example shows the disassembly of a range of addresses of
6838 HP PA-RISC 2.0 code:
6841 (@value{GDBP}) disas 0x32c4, 0x32e4
6842 Dump of assembler code from 0x32c4 to 0x32e4:
6843 0x32c4 <main+204>: addil 0,dp
6844 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6845 0x32cc <main+212>: ldil 0x3000,r31
6846 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6847 0x32d4 <main+220>: ldo 0(r31),rp
6848 0x32d8 <main+224>: addil -0x800,dp
6849 0x32dc <main+228>: ldo 0x588(r1),r26
6850 0x32e0 <main+232>: ldil 0x3000,r31
6851 End of assembler dump.
6854 Here is an example showing mixed source+assembly for Intel x86, when the
6855 program is stopped just after function prologue:
6858 (@value{GDBP}) disas /m main
6859 Dump of assembler code for function main:
6861 0x08048330 <+0>: push %ebp
6862 0x08048331 <+1>: mov %esp,%ebp
6863 0x08048333 <+3>: sub $0x8,%esp
6864 0x08048336 <+6>: and $0xfffffff0,%esp
6865 0x08048339 <+9>: sub $0x10,%esp
6867 6 printf ("Hello.\n");
6868 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6869 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6873 0x08048348 <+24>: mov $0x0,%eax
6874 0x0804834d <+29>: leave
6875 0x0804834e <+30>: ret
6877 End of assembler dump.
6880 Here is another example showing raw instructions in hex for AMD x86-64,
6883 (gdb) disas /r 0x400281,+10
6884 Dump of assembler code from 0x400281 to 0x40028b:
6885 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6886 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6887 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6888 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6889 End of assembler dump.
6892 Some architectures have more than one commonly-used set of instruction
6893 mnemonics or other syntax.
6895 For programs that were dynamically linked and use shared libraries,
6896 instructions that call functions or branch to locations in the shared
6897 libraries might show a seemingly bogus location---it's actually a
6898 location of the relocation table. On some architectures, @value{GDBN}
6899 might be able to resolve these to actual function names.
6902 @kindex set disassembly-flavor
6903 @cindex Intel disassembly flavor
6904 @cindex AT&T disassembly flavor
6905 @item set disassembly-flavor @var{instruction-set}
6906 Select the instruction set to use when disassembling the
6907 program via the @code{disassemble} or @code{x/i} commands.
6909 Currently this command is only defined for the Intel x86 family. You
6910 can set @var{instruction-set} to either @code{intel} or @code{att}.
6911 The default is @code{att}, the AT&T flavor used by default by Unix
6912 assemblers for x86-based targets.
6914 @kindex show disassembly-flavor
6915 @item show disassembly-flavor
6916 Show the current setting of the disassembly flavor.
6920 @kindex set disassemble-next-line
6921 @kindex show disassemble-next-line
6922 @item set disassemble-next-line
6923 @itemx show disassemble-next-line
6924 Control whether or not @value{GDBN} will disassemble the next source
6925 line or instruction when execution stops. If ON, @value{GDBN} will
6926 display disassembly of the next source line when execution of the
6927 program being debugged stops. This is @emph{in addition} to
6928 displaying the source line itself, which @value{GDBN} always does if
6929 possible. If the next source line cannot be displayed for some reason
6930 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6931 info in the debug info), @value{GDBN} will display disassembly of the
6932 next @emph{instruction} instead of showing the next source line. If
6933 AUTO, @value{GDBN} will display disassembly of next instruction only
6934 if the source line cannot be displayed. This setting causes
6935 @value{GDBN} to display some feedback when you step through a function
6936 with no line info or whose source file is unavailable. The default is
6937 OFF, which means never display the disassembly of the next line or
6943 @chapter Examining Data
6945 @cindex printing data
6946 @cindex examining data
6949 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6950 @c document because it is nonstandard... Under Epoch it displays in a
6951 @c different window or something like that.
6952 The usual way to examine data in your program is with the @code{print}
6953 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6954 evaluates and prints the value of an expression of the language your
6955 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6956 Different Languages}). It may also print the expression using a
6957 Python-based pretty-printer (@pxref{Pretty Printing}).
6960 @item print @var{expr}
6961 @itemx print /@var{f} @var{expr}
6962 @var{expr} is an expression (in the source language). By default the
6963 value of @var{expr} is printed in a format appropriate to its data type;
6964 you can choose a different format by specifying @samp{/@var{f}}, where
6965 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6969 @itemx print /@var{f}
6970 @cindex reprint the last value
6971 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6972 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6973 conveniently inspect the same value in an alternative format.
6976 A more low-level way of examining data is with the @code{x} command.
6977 It examines data in memory at a specified address and prints it in a
6978 specified format. @xref{Memory, ,Examining Memory}.
6980 If you are interested in information about types, or about how the
6981 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6982 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6986 * Expressions:: Expressions
6987 * Ambiguous Expressions:: Ambiguous Expressions
6988 * Variables:: Program variables
6989 * Arrays:: Artificial arrays
6990 * Output Formats:: Output formats
6991 * Memory:: Examining memory
6992 * Auto Display:: Automatic display
6993 * Print Settings:: Print settings
6994 * Pretty Printing:: Python pretty printing
6995 * Value History:: Value history
6996 * Convenience Vars:: Convenience variables
6997 * Registers:: Registers
6998 * Floating Point Hardware:: Floating point hardware
6999 * Vector Unit:: Vector Unit
7000 * OS Information:: Auxiliary data provided by operating system
7001 * Memory Region Attributes:: Memory region attributes
7002 * Dump/Restore Files:: Copy between memory and a file
7003 * Core File Generation:: Cause a program dump its core
7004 * Character Sets:: Debugging programs that use a different
7005 character set than GDB does
7006 * Caching Remote Data:: Data caching for remote targets
7007 * Searching Memory:: Searching memory for a sequence of bytes
7011 @section Expressions
7014 @code{print} and many other @value{GDBN} commands accept an expression and
7015 compute its value. Any kind of constant, variable or operator defined
7016 by the programming language you are using is valid in an expression in
7017 @value{GDBN}. This includes conditional expressions, function calls,
7018 casts, and string constants. It also includes preprocessor macros, if
7019 you compiled your program to include this information; see
7022 @cindex arrays in expressions
7023 @value{GDBN} supports array constants in expressions input by
7024 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7025 you can use the command @code{print @{1, 2, 3@}} to create an array
7026 of three integers. If you pass an array to a function or assign it
7027 to a program variable, @value{GDBN} copies the array to memory that
7028 is @code{malloc}ed in the target program.
7030 Because C is so widespread, most of the expressions shown in examples in
7031 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7032 Languages}, for information on how to use expressions in other
7035 In this section, we discuss operators that you can use in @value{GDBN}
7036 expressions regardless of your programming language.
7038 @cindex casts, in expressions
7039 Casts are supported in all languages, not just in C, because it is so
7040 useful to cast a number into a pointer in order to examine a structure
7041 at that address in memory.
7042 @c FIXME: casts supported---Mod2 true?
7044 @value{GDBN} supports these operators, in addition to those common
7045 to programming languages:
7049 @samp{@@} is a binary operator for treating parts of memory as arrays.
7050 @xref{Arrays, ,Artificial Arrays}, for more information.
7053 @samp{::} allows you to specify a variable in terms of the file or
7054 function where it is defined. @xref{Variables, ,Program Variables}.
7056 @cindex @{@var{type}@}
7057 @cindex type casting memory
7058 @cindex memory, viewing as typed object
7059 @cindex casts, to view memory
7060 @item @{@var{type}@} @var{addr}
7061 Refers to an object of type @var{type} stored at address @var{addr} in
7062 memory. @var{addr} may be any expression whose value is an integer or
7063 pointer (but parentheses are required around binary operators, just as in
7064 a cast). This construct is allowed regardless of what kind of data is
7065 normally supposed to reside at @var{addr}.
7068 @node Ambiguous Expressions
7069 @section Ambiguous Expressions
7070 @cindex ambiguous expressions
7072 Expressions can sometimes contain some ambiguous elements. For instance,
7073 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7074 a single function name to be defined several times, for application in
7075 different contexts. This is called @dfn{overloading}. Another example
7076 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7077 templates and is typically instantiated several times, resulting in
7078 the same function name being defined in different contexts.
7080 In some cases and depending on the language, it is possible to adjust
7081 the expression to remove the ambiguity. For instance in C@t{++}, you
7082 can specify the signature of the function you want to break on, as in
7083 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7084 qualified name of your function often makes the expression unambiguous
7087 When an ambiguity that needs to be resolved is detected, the debugger
7088 has the capability to display a menu of numbered choices for each
7089 possibility, and then waits for the selection with the prompt @samp{>}.
7090 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7091 aborts the current command. If the command in which the expression was
7092 used allows more than one choice to be selected, the next option in the
7093 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7096 For example, the following session excerpt shows an attempt to set a
7097 breakpoint at the overloaded symbol @code{String::after}.
7098 We choose three particular definitions of that function name:
7100 @c FIXME! This is likely to change to show arg type lists, at least
7103 (@value{GDBP}) b String::after
7106 [2] file:String.cc; line number:867
7107 [3] file:String.cc; line number:860
7108 [4] file:String.cc; line number:875
7109 [5] file:String.cc; line number:853
7110 [6] file:String.cc; line number:846
7111 [7] file:String.cc; line number:735
7113 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7114 Breakpoint 2 at 0xb344: file String.cc, line 875.
7115 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7116 Multiple breakpoints were set.
7117 Use the "delete" command to delete unwanted
7124 @kindex set multiple-symbols
7125 @item set multiple-symbols @var{mode}
7126 @cindex multiple-symbols menu
7128 This option allows you to adjust the debugger behavior when an expression
7131 By default, @var{mode} is set to @code{all}. If the command with which
7132 the expression is used allows more than one choice, then @value{GDBN}
7133 automatically selects all possible choices. For instance, inserting
7134 a breakpoint on a function using an ambiguous name results in a breakpoint
7135 inserted on each possible match. However, if a unique choice must be made,
7136 then @value{GDBN} uses the menu to help you disambiguate the expression.
7137 For instance, printing the address of an overloaded function will result
7138 in the use of the menu.
7140 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7141 when an ambiguity is detected.
7143 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7144 an error due to the ambiguity and the command is aborted.
7146 @kindex show multiple-symbols
7147 @item show multiple-symbols
7148 Show the current value of the @code{multiple-symbols} setting.
7152 @section Program Variables
7154 The most common kind of expression to use is the name of a variable
7157 Variables in expressions are understood in the selected stack frame
7158 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7162 global (or file-static)
7169 visible according to the scope rules of the
7170 programming language from the point of execution in that frame
7173 @noindent This means that in the function
7188 you can examine and use the variable @code{a} whenever your program is
7189 executing within the function @code{foo}, but you can only use or
7190 examine the variable @code{b} while your program is executing inside
7191 the block where @code{b} is declared.
7193 @cindex variable name conflict
7194 There is an exception: you can refer to a variable or function whose
7195 scope is a single source file even if the current execution point is not
7196 in this file. But it is possible to have more than one such variable or
7197 function with the same name (in different source files). If that
7198 happens, referring to that name has unpredictable effects. If you wish,
7199 you can specify a static variable in a particular function or file,
7200 using the colon-colon (@code{::}) notation:
7202 @cindex colon-colon, context for variables/functions
7204 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7205 @cindex @code{::}, context for variables/functions
7208 @var{file}::@var{variable}
7209 @var{function}::@var{variable}
7213 Here @var{file} or @var{function} is the name of the context for the
7214 static @var{variable}. In the case of file names, you can use quotes to
7215 make sure @value{GDBN} parses the file name as a single word---for example,
7216 to print a global value of @code{x} defined in @file{f2.c}:
7219 (@value{GDBP}) p 'f2.c'::x
7222 @cindex C@t{++} scope resolution
7223 This use of @samp{::} is very rarely in conflict with the very similar
7224 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7225 scope resolution operator in @value{GDBN} expressions.
7226 @c FIXME: Um, so what happens in one of those rare cases where it's in
7229 @cindex wrong values
7230 @cindex variable values, wrong
7231 @cindex function entry/exit, wrong values of variables
7232 @cindex optimized code, wrong values of variables
7234 @emph{Warning:} Occasionally, a local variable may appear to have the
7235 wrong value at certain points in a function---just after entry to a new
7236 scope, and just before exit.
7238 You may see this problem when you are stepping by machine instructions.
7239 This is because, on most machines, it takes more than one instruction to
7240 set up a stack frame (including local variable definitions); if you are
7241 stepping by machine instructions, variables may appear to have the wrong
7242 values until the stack frame is completely built. On exit, it usually
7243 also takes more than one machine instruction to destroy a stack frame;
7244 after you begin stepping through that group of instructions, local
7245 variable definitions may be gone.
7247 This may also happen when the compiler does significant optimizations.
7248 To be sure of always seeing accurate values, turn off all optimization
7251 @cindex ``No symbol "foo" in current context''
7252 Another possible effect of compiler optimizations is to optimize
7253 unused variables out of existence, or assign variables to registers (as
7254 opposed to memory addresses). Depending on the support for such cases
7255 offered by the debug info format used by the compiler, @value{GDBN}
7256 might not be able to display values for such local variables. If that
7257 happens, @value{GDBN} will print a message like this:
7260 No symbol "foo" in current context.
7263 To solve such problems, either recompile without optimizations, or use a
7264 different debug info format, if the compiler supports several such
7265 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7266 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7267 produces debug info in a format that is superior to formats such as
7268 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7269 an effective form for debug info. @xref{Debugging Options,,Options
7270 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7271 Compiler Collection (GCC)}.
7272 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7273 that are best suited to C@t{++} programs.
7275 If you ask to print an object whose contents are unknown to
7276 @value{GDBN}, e.g., because its data type is not completely specified
7277 by the debug information, @value{GDBN} will say @samp{<incomplete
7278 type>}. @xref{Symbols, incomplete type}, for more about this.
7280 Strings are identified as arrays of @code{char} values without specified
7281 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7282 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7283 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7284 defines literal string type @code{"char"} as @code{char} without a sign.
7289 signed char var1[] = "A";
7292 You get during debugging
7297 $2 = @{65 'A', 0 '\0'@}
7301 @section Artificial Arrays
7303 @cindex artificial array
7305 @kindex @@@r{, referencing memory as an array}
7306 It is often useful to print out several successive objects of the
7307 same type in memory; a section of an array, or an array of
7308 dynamically determined size for which only a pointer exists in the
7311 You can do this by referring to a contiguous span of memory as an
7312 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7313 operand of @samp{@@} should be the first element of the desired array
7314 and be an individual object. The right operand should be the desired length
7315 of the array. The result is an array value whose elements are all of
7316 the type of the left argument. The first element is actually the left
7317 argument; the second element comes from bytes of memory immediately
7318 following those that hold the first element, and so on. Here is an
7319 example. If a program says
7322 int *array = (int *) malloc (len * sizeof (int));
7326 you can print the contents of @code{array} with
7332 The left operand of @samp{@@} must reside in memory. Array values made
7333 with @samp{@@} in this way behave just like other arrays in terms of
7334 subscripting, and are coerced to pointers when used in expressions.
7335 Artificial arrays most often appear in expressions via the value history
7336 (@pxref{Value History, ,Value History}), after printing one out.
7338 Another way to create an artificial array is to use a cast.
7339 This re-interprets a value as if it were an array.
7340 The value need not be in memory:
7342 (@value{GDBP}) p/x (short[2])0x12345678
7343 $1 = @{0x1234, 0x5678@}
7346 As a convenience, if you leave the array length out (as in
7347 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7348 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7350 (@value{GDBP}) p/x (short[])0x12345678
7351 $2 = @{0x1234, 0x5678@}
7354 Sometimes the artificial array mechanism is not quite enough; in
7355 moderately complex data structures, the elements of interest may not
7356 actually be adjacent---for example, if you are interested in the values
7357 of pointers in an array. One useful work-around in this situation is
7358 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7359 Variables}) as a counter in an expression that prints the first
7360 interesting value, and then repeat that expression via @key{RET}. For
7361 instance, suppose you have an array @code{dtab} of pointers to
7362 structures, and you are interested in the values of a field @code{fv}
7363 in each structure. Here is an example of what you might type:
7373 @node Output Formats
7374 @section Output Formats
7376 @cindex formatted output
7377 @cindex output formats
7378 By default, @value{GDBN} prints a value according to its data type. Sometimes
7379 this is not what you want. For example, you might want to print a number
7380 in hex, or a pointer in decimal. Or you might want to view data in memory
7381 at a certain address as a character string or as an instruction. To do
7382 these things, specify an @dfn{output format} when you print a value.
7384 The simplest use of output formats is to say how to print a value
7385 already computed. This is done by starting the arguments of the
7386 @code{print} command with a slash and a format letter. The format
7387 letters supported are:
7391 Regard the bits of the value as an integer, and print the integer in
7395 Print as integer in signed decimal.
7398 Print as integer in unsigned decimal.
7401 Print as integer in octal.
7404 Print as integer in binary. The letter @samp{t} stands for ``two''.
7405 @footnote{@samp{b} cannot be used because these format letters are also
7406 used with the @code{x} command, where @samp{b} stands for ``byte'';
7407 see @ref{Memory,,Examining Memory}.}
7410 @cindex unknown address, locating
7411 @cindex locate address
7412 Print as an address, both absolute in hexadecimal and as an offset from
7413 the nearest preceding symbol. You can use this format used to discover
7414 where (in what function) an unknown address is located:
7417 (@value{GDBP}) p/a 0x54320
7418 $3 = 0x54320 <_initialize_vx+396>
7422 The command @code{info symbol 0x54320} yields similar results.
7423 @xref{Symbols, info symbol}.
7426 Regard as an integer and print it as a character constant. This
7427 prints both the numerical value and its character representation. The
7428 character representation is replaced with the octal escape @samp{\nnn}
7429 for characters outside the 7-bit @sc{ascii} range.
7431 Without this format, @value{GDBN} displays @code{char},
7432 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7433 constants. Single-byte members of vectors are displayed as integer
7437 Regard the bits of the value as a floating point number and print
7438 using typical floating point syntax.
7441 @cindex printing strings
7442 @cindex printing byte arrays
7443 Regard as a string, if possible. With this format, pointers to single-byte
7444 data are displayed as null-terminated strings and arrays of single-byte data
7445 are displayed as fixed-length strings. Other values are displayed in their
7448 Without this format, @value{GDBN} displays pointers to and arrays of
7449 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7450 strings. Single-byte members of a vector are displayed as an integer
7454 @cindex raw printing
7455 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7456 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7457 Printing}). This typically results in a higher-level display of the
7458 value's contents. The @samp{r} format bypasses any Python
7459 pretty-printer which might exist.
7462 For example, to print the program counter in hex (@pxref{Registers}), type
7469 Note that no space is required before the slash; this is because command
7470 names in @value{GDBN} cannot contain a slash.
7472 To reprint the last value in the value history with a different format,
7473 you can use the @code{print} command with just a format and no
7474 expression. For example, @samp{p/x} reprints the last value in hex.
7477 @section Examining Memory
7479 You can use the command @code{x} (for ``examine'') to examine memory in
7480 any of several formats, independently of your program's data types.
7482 @cindex examining memory
7484 @kindex x @r{(examine memory)}
7485 @item x/@var{nfu} @var{addr}
7488 Use the @code{x} command to examine memory.
7491 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7492 much memory to display and how to format it; @var{addr} is an
7493 expression giving the address where you want to start displaying memory.
7494 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7495 Several commands set convenient defaults for @var{addr}.
7498 @item @var{n}, the repeat count
7499 The repeat count is a decimal integer; the default is 1. It specifies
7500 how much memory (counting by units @var{u}) to display.
7501 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7504 @item @var{f}, the display format
7505 The display format is one of the formats used by @code{print}
7506 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7507 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7508 The default is @samp{x} (hexadecimal) initially. The default changes
7509 each time you use either @code{x} or @code{print}.
7511 @item @var{u}, the unit size
7512 The unit size is any of
7518 Halfwords (two bytes).
7520 Words (four bytes). This is the initial default.
7522 Giant words (eight bytes).
7525 Each time you specify a unit size with @code{x}, that size becomes the
7526 default unit the next time you use @code{x}. For the @samp{i} format,
7527 the unit size is ignored and is normally not written. For the @samp{s} format,
7528 the unit size defaults to @samp{b}, unless it is explicitly given.
7529 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7530 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7531 Note that the results depend on the programming language of the
7532 current compilation unit. If the language is C, the @samp{s}
7533 modifier will use the UTF-16 encoding while @samp{w} will use
7534 UTF-32. The encoding is set by the programming language and cannot
7537 @item @var{addr}, starting display address
7538 @var{addr} is the address where you want @value{GDBN} to begin displaying
7539 memory. The expression need not have a pointer value (though it may);
7540 it is always interpreted as an integer address of a byte of memory.
7541 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7542 @var{addr} is usually just after the last address examined---but several
7543 other commands also set the default address: @code{info breakpoints} (to
7544 the address of the last breakpoint listed), @code{info line} (to the
7545 starting address of a line), and @code{print} (if you use it to display
7546 a value from memory).
7549 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7550 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7551 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7552 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7553 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7555 Since the letters indicating unit sizes are all distinct from the
7556 letters specifying output formats, you do not have to remember whether
7557 unit size or format comes first; either order works. The output
7558 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7559 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7561 Even though the unit size @var{u} is ignored for the formats @samp{s}
7562 and @samp{i}, you might still want to use a count @var{n}; for example,
7563 @samp{3i} specifies that you want to see three machine instructions,
7564 including any operands. For convenience, especially when used with
7565 the @code{display} command, the @samp{i} format also prints branch delay
7566 slot instructions, if any, beyond the count specified, which immediately
7567 follow the last instruction that is within the count. The command
7568 @code{disassemble} gives an alternative way of inspecting machine
7569 instructions; see @ref{Machine Code,,Source and Machine Code}.
7571 All the defaults for the arguments to @code{x} are designed to make it
7572 easy to continue scanning memory with minimal specifications each time
7573 you use @code{x}. For example, after you have inspected three machine
7574 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7575 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7576 the repeat count @var{n} is used again; the other arguments default as
7577 for successive uses of @code{x}.
7579 When examining machine instructions, the instruction at current program
7580 counter is shown with a @code{=>} marker. For example:
7583 (@value{GDBP}) x/5i $pc-6
7584 0x804837f <main+11>: mov %esp,%ebp
7585 0x8048381 <main+13>: push %ecx
7586 0x8048382 <main+14>: sub $0x4,%esp
7587 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7588 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7591 @cindex @code{$_}, @code{$__}, and value history
7592 The addresses and contents printed by the @code{x} command are not saved
7593 in the value history because there is often too much of them and they
7594 would get in the way. Instead, @value{GDBN} makes these values available for
7595 subsequent use in expressions as values of the convenience variables
7596 @code{$_} and @code{$__}. After an @code{x} command, the last address
7597 examined is available for use in expressions in the convenience variable
7598 @code{$_}. The contents of that address, as examined, are available in
7599 the convenience variable @code{$__}.
7601 If the @code{x} command has a repeat count, the address and contents saved
7602 are from the last memory unit printed; this is not the same as the last
7603 address printed if several units were printed on the last line of output.
7605 @cindex remote memory comparison
7606 @cindex verify remote memory image
7607 When you are debugging a program running on a remote target machine
7608 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7609 remote machine's memory against the executable file you downloaded to
7610 the target. The @code{compare-sections} command is provided for such
7614 @kindex compare-sections
7615 @item compare-sections @r{[}@var{section-name}@r{]}
7616 Compare the data of a loadable section @var{section-name} in the
7617 executable file of the program being debugged with the same section in
7618 the remote machine's memory, and report any mismatches. With no
7619 arguments, compares all loadable sections. This command's
7620 availability depends on the target's support for the @code{"qCRC"}
7625 @section Automatic Display
7626 @cindex automatic display
7627 @cindex display of expressions
7629 If you find that you want to print the value of an expression frequently
7630 (to see how it changes), you might want to add it to the @dfn{automatic
7631 display list} so that @value{GDBN} prints its value each time your program stops.
7632 Each expression added to the list is given a number to identify it;
7633 to remove an expression from the list, you specify that number.
7634 The automatic display looks like this:
7638 3: bar[5] = (struct hack *) 0x3804
7642 This display shows item numbers, expressions and their current values. As with
7643 displays you request manually using @code{x} or @code{print}, you can
7644 specify the output format you prefer; in fact, @code{display} decides
7645 whether to use @code{print} or @code{x} depending your format
7646 specification---it uses @code{x} if you specify either the @samp{i}
7647 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7651 @item display @var{expr}
7652 Add the expression @var{expr} to the list of expressions to display
7653 each time your program stops. @xref{Expressions, ,Expressions}.
7655 @code{display} does not repeat if you press @key{RET} again after using it.
7657 @item display/@var{fmt} @var{expr}
7658 For @var{fmt} specifying only a display format and not a size or
7659 count, add the expression @var{expr} to the auto-display list but
7660 arrange to display it each time in the specified format @var{fmt}.
7661 @xref{Output Formats,,Output Formats}.
7663 @item display/@var{fmt} @var{addr}
7664 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7665 number of units, add the expression @var{addr} as a memory address to
7666 be examined each time your program stops. Examining means in effect
7667 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7670 For example, @samp{display/i $pc} can be helpful, to see the machine
7671 instruction about to be executed each time execution stops (@samp{$pc}
7672 is a common name for the program counter; @pxref{Registers, ,Registers}).
7675 @kindex delete display
7677 @item undisplay @var{dnums}@dots{}
7678 @itemx delete display @var{dnums}@dots{}
7679 Remove items from the list of expressions to display. Specify the
7680 numbers of the displays that you want affected with the command
7681 argument @var{dnums}. It can be a single display number, one of the
7682 numbers shown in the first field of the @samp{info display} display;
7683 or it could be a range of display numbers, as in @code{2-4}.
7685 @code{undisplay} does not repeat if you press @key{RET} after using it.
7686 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7688 @kindex disable display
7689 @item disable display @var{dnums}@dots{}
7690 Disable the display of item numbers @var{dnums}. A disabled display
7691 item is not printed automatically, but is not forgotten. It may be
7692 enabled again later. Specify the numbers of the displays that you
7693 want affected with the command argument @var{dnums}. It can be a
7694 single display number, one of the numbers shown in the first field of
7695 the @samp{info display} display; or it could be a range of display
7696 numbers, as in @code{2-4}.
7698 @kindex enable display
7699 @item enable display @var{dnums}@dots{}
7700 Enable display of item numbers @var{dnums}. It becomes effective once
7701 again in auto display of its expression, until you specify otherwise.
7702 Specify the numbers of the displays that you want affected with the
7703 command argument @var{dnums}. It can be a single display number, one
7704 of the numbers shown in the first field of the @samp{info display}
7705 display; or it could be a range of display numbers, as in @code{2-4}.
7708 Display the current values of the expressions on the list, just as is
7709 done when your program stops.
7711 @kindex info display
7713 Print the list of expressions previously set up to display
7714 automatically, each one with its item number, but without showing the
7715 values. This includes disabled expressions, which are marked as such.
7716 It also includes expressions which would not be displayed right now
7717 because they refer to automatic variables not currently available.
7720 @cindex display disabled out of scope
7721 If a display expression refers to local variables, then it does not make
7722 sense outside the lexical context for which it was set up. Such an
7723 expression is disabled when execution enters a context where one of its
7724 variables is not defined. For example, if you give the command
7725 @code{display last_char} while inside a function with an argument
7726 @code{last_char}, @value{GDBN} displays this argument while your program
7727 continues to stop inside that function. When it stops elsewhere---where
7728 there is no variable @code{last_char}---the display is disabled
7729 automatically. The next time your program stops where @code{last_char}
7730 is meaningful, you can enable the display expression once again.
7732 @node Print Settings
7733 @section Print Settings
7735 @cindex format options
7736 @cindex print settings
7737 @value{GDBN} provides the following ways to control how arrays, structures,
7738 and symbols are printed.
7741 These settings are useful for debugging programs in any language:
7745 @item set print address
7746 @itemx set print address on
7747 @cindex print/don't print memory addresses
7748 @value{GDBN} prints memory addresses showing the location of stack
7749 traces, structure values, pointer values, breakpoints, and so forth,
7750 even when it also displays the contents of those addresses. The default
7751 is @code{on}. For example, this is what a stack frame display looks like with
7752 @code{set print address on}:
7757 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7759 530 if (lquote != def_lquote)
7763 @item set print address off
7764 Do not print addresses when displaying their contents. For example,
7765 this is the same stack frame displayed with @code{set print address off}:
7769 (@value{GDBP}) set print addr off
7771 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7772 530 if (lquote != def_lquote)
7776 You can use @samp{set print address off} to eliminate all machine
7777 dependent displays from the @value{GDBN} interface. For example, with
7778 @code{print address off}, you should get the same text for backtraces on
7779 all machines---whether or not they involve pointer arguments.
7782 @item show print address
7783 Show whether or not addresses are to be printed.
7786 When @value{GDBN} prints a symbolic address, it normally prints the
7787 closest earlier symbol plus an offset. If that symbol does not uniquely
7788 identify the address (for example, it is a name whose scope is a single
7789 source file), you may need to clarify. One way to do this is with
7790 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7791 you can set @value{GDBN} to print the source file and line number when
7792 it prints a symbolic address:
7795 @item set print symbol-filename on
7796 @cindex source file and line of a symbol
7797 @cindex symbol, source file and line
7798 Tell @value{GDBN} to print the source file name and line number of a
7799 symbol in the symbolic form of an address.
7801 @item set print symbol-filename off
7802 Do not print source file name and line number of a symbol. This is the
7805 @item show print symbol-filename
7806 Show whether or not @value{GDBN} will print the source file name and
7807 line number of a symbol in the symbolic form of an address.
7810 Another situation where it is helpful to show symbol filenames and line
7811 numbers is when disassembling code; @value{GDBN} shows you the line
7812 number and source file that corresponds to each instruction.
7814 Also, you may wish to see the symbolic form only if the address being
7815 printed is reasonably close to the closest earlier symbol:
7818 @item set print max-symbolic-offset @var{max-offset}
7819 @cindex maximum value for offset of closest symbol
7820 Tell @value{GDBN} to only display the symbolic form of an address if the
7821 offset between the closest earlier symbol and the address is less than
7822 @var{max-offset}. The default is 0, which tells @value{GDBN}
7823 to always print the symbolic form of an address if any symbol precedes it.
7825 @item show print max-symbolic-offset
7826 Ask how large the maximum offset is that @value{GDBN} prints in a
7830 @cindex wild pointer, interpreting
7831 @cindex pointer, finding referent
7832 If you have a pointer and you are not sure where it points, try
7833 @samp{set print symbol-filename on}. Then you can determine the name
7834 and source file location of the variable where it points, using
7835 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7836 For example, here @value{GDBN} shows that a variable @code{ptt} points
7837 at another variable @code{t}, defined in @file{hi2.c}:
7840 (@value{GDBP}) set print symbol-filename on
7841 (@value{GDBP}) p/a ptt
7842 $4 = 0xe008 <t in hi2.c>
7846 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7847 does not show the symbol name and filename of the referent, even with
7848 the appropriate @code{set print} options turned on.
7851 Other settings control how different kinds of objects are printed:
7854 @item set print array
7855 @itemx set print array on
7856 @cindex pretty print arrays
7857 Pretty print arrays. This format is more convenient to read,
7858 but uses more space. The default is off.
7860 @item set print array off
7861 Return to compressed format for arrays.
7863 @item show print array
7864 Show whether compressed or pretty format is selected for displaying
7867 @cindex print array indexes
7868 @item set print array-indexes
7869 @itemx set print array-indexes on
7870 Print the index of each element when displaying arrays. May be more
7871 convenient to locate a given element in the array or quickly find the
7872 index of a given element in that printed array. The default is off.
7874 @item set print array-indexes off
7875 Stop printing element indexes when displaying arrays.
7877 @item show print array-indexes
7878 Show whether the index of each element is printed when displaying
7881 @item set print elements @var{number-of-elements}
7882 @cindex number of array elements to print
7883 @cindex limit on number of printed array elements
7884 Set a limit on how many elements of an array @value{GDBN} will print.
7885 If @value{GDBN} is printing a large array, it stops printing after it has
7886 printed the number of elements set by the @code{set print elements} command.
7887 This limit also applies to the display of strings.
7888 When @value{GDBN} starts, this limit is set to 200.
7889 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7891 @item show print elements
7892 Display the number of elements of a large array that @value{GDBN} will print.
7893 If the number is 0, then the printing is unlimited.
7895 @item set print frame-arguments @var{value}
7896 @kindex set print frame-arguments
7897 @cindex printing frame argument values
7898 @cindex print all frame argument values
7899 @cindex print frame argument values for scalars only
7900 @cindex do not print frame argument values
7901 This command allows to control how the values of arguments are printed
7902 when the debugger prints a frame (@pxref{Frames}). The possible
7907 The values of all arguments are printed.
7910 Print the value of an argument only if it is a scalar. The value of more
7911 complex arguments such as arrays, structures, unions, etc, is replaced
7912 by @code{@dots{}}. This is the default. Here is an example where
7913 only scalar arguments are shown:
7916 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7921 None of the argument values are printed. Instead, the value of each argument
7922 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7925 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7930 By default, only scalar arguments are printed. This command can be used
7931 to configure the debugger to print the value of all arguments, regardless
7932 of their type. However, it is often advantageous to not print the value
7933 of more complex parameters. For instance, it reduces the amount of
7934 information printed in each frame, making the backtrace more readable.
7935 Also, it improves performance when displaying Ada frames, because
7936 the computation of large arguments can sometimes be CPU-intensive,
7937 especially in large applications. Setting @code{print frame-arguments}
7938 to @code{scalars} (the default) or @code{none} avoids this computation,
7939 thus speeding up the display of each Ada frame.
7941 @item show print frame-arguments
7942 Show how the value of arguments should be displayed when printing a frame.
7944 @item set print repeats
7945 @cindex repeated array elements
7946 Set the threshold for suppressing display of repeated array
7947 elements. When the number of consecutive identical elements of an
7948 array exceeds the threshold, @value{GDBN} prints the string
7949 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7950 identical repetitions, instead of displaying the identical elements
7951 themselves. Setting the threshold to zero will cause all elements to
7952 be individually printed. The default threshold is 10.
7954 @item show print repeats
7955 Display the current threshold for printing repeated identical
7958 @item set print null-stop
7959 @cindex @sc{null} elements in arrays
7960 Cause @value{GDBN} to stop printing the characters of an array when the first
7961 @sc{null} is encountered. This is useful when large arrays actually
7962 contain only short strings.
7965 @item show print null-stop
7966 Show whether @value{GDBN} stops printing an array on the first
7967 @sc{null} character.
7969 @item set print pretty on
7970 @cindex print structures in indented form
7971 @cindex indentation in structure display
7972 Cause @value{GDBN} to print structures in an indented format with one member
7973 per line, like this:
7988 @item set print pretty off
7989 Cause @value{GDBN} to print structures in a compact format, like this:
7993 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7994 meat = 0x54 "Pork"@}
7999 This is the default format.
8001 @item show print pretty
8002 Show which format @value{GDBN} is using to print structures.
8004 @item set print sevenbit-strings on
8005 @cindex eight-bit characters in strings
8006 @cindex octal escapes in strings
8007 Print using only seven-bit characters; if this option is set,
8008 @value{GDBN} displays any eight-bit characters (in strings or
8009 character values) using the notation @code{\}@var{nnn}. This setting is
8010 best if you are working in English (@sc{ascii}) and you use the
8011 high-order bit of characters as a marker or ``meta'' bit.
8013 @item set print sevenbit-strings off
8014 Print full eight-bit characters. This allows the use of more
8015 international character sets, and is the default.
8017 @item show print sevenbit-strings
8018 Show whether or not @value{GDBN} is printing only seven-bit characters.
8020 @item set print union on
8021 @cindex unions in structures, printing
8022 Tell @value{GDBN} to print unions which are contained in structures
8023 and other unions. This is the default setting.
8025 @item set print union off
8026 Tell @value{GDBN} not to print unions which are contained in
8027 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8030 @item show print union
8031 Ask @value{GDBN} whether or not it will print unions which are contained in
8032 structures and other unions.
8034 For example, given the declarations
8037 typedef enum @{Tree, Bug@} Species;
8038 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8039 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8050 struct thing foo = @{Tree, @{Acorn@}@};
8054 with @code{set print union on} in effect @samp{p foo} would print
8057 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8061 and with @code{set print union off} in effect it would print
8064 $1 = @{it = Tree, form = @{...@}@}
8068 @code{set print union} affects programs written in C-like languages
8074 These settings are of interest when debugging C@t{++} programs:
8077 @cindex demangling C@t{++} names
8078 @item set print demangle
8079 @itemx set print demangle on
8080 Print C@t{++} names in their source form rather than in the encoded
8081 (``mangled'') form passed to the assembler and linker for type-safe
8082 linkage. The default is on.
8084 @item show print demangle
8085 Show whether C@t{++} names are printed in mangled or demangled form.
8087 @item set print asm-demangle
8088 @itemx set print asm-demangle on
8089 Print C@t{++} names in their source form rather than their mangled form, even
8090 in assembler code printouts such as instruction disassemblies.
8093 @item show print asm-demangle
8094 Show whether C@t{++} names in assembly listings are printed in mangled
8097 @cindex C@t{++} symbol decoding style
8098 @cindex symbol decoding style, C@t{++}
8099 @kindex set demangle-style
8100 @item set demangle-style @var{style}
8101 Choose among several encoding schemes used by different compilers to
8102 represent C@t{++} names. The choices for @var{style} are currently:
8106 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8109 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8110 This is the default.
8113 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8116 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8119 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8120 @strong{Warning:} this setting alone is not sufficient to allow
8121 debugging @code{cfront}-generated executables. @value{GDBN} would
8122 require further enhancement to permit that.
8125 If you omit @var{style}, you will see a list of possible formats.
8127 @item show demangle-style
8128 Display the encoding style currently in use for decoding C@t{++} symbols.
8130 @item set print object
8131 @itemx set print object on
8132 @cindex derived type of an object, printing
8133 @cindex display derived types
8134 When displaying a pointer to an object, identify the @emph{actual}
8135 (derived) type of the object rather than the @emph{declared} type, using
8136 the virtual function table.
8138 @item set print object off
8139 Display only the declared type of objects, without reference to the
8140 virtual function table. This is the default setting.
8142 @item show print object
8143 Show whether actual, or declared, object types are displayed.
8145 @item set print static-members
8146 @itemx set print static-members on
8147 @cindex static members of C@t{++} objects
8148 Print static members when displaying a C@t{++} object. The default is on.
8150 @item set print static-members off
8151 Do not print static members when displaying a C@t{++} object.
8153 @item show print static-members
8154 Show whether C@t{++} static members are printed or not.
8156 @item set print pascal_static-members
8157 @itemx set print pascal_static-members on
8158 @cindex static members of Pascal objects
8159 @cindex Pascal objects, static members display
8160 Print static members when displaying a Pascal object. The default is on.
8162 @item set print pascal_static-members off
8163 Do not print static members when displaying a Pascal object.
8165 @item show print pascal_static-members
8166 Show whether Pascal static members are printed or not.
8168 @c These don't work with HP ANSI C++ yet.
8169 @item set print vtbl
8170 @itemx set print vtbl on
8171 @cindex pretty print C@t{++} virtual function tables
8172 @cindex virtual functions (C@t{++}) display
8173 @cindex VTBL display
8174 Pretty print C@t{++} virtual function tables. The default is off.
8175 (The @code{vtbl} commands do not work on programs compiled with the HP
8176 ANSI C@t{++} compiler (@code{aCC}).)
8178 @item set print vtbl off
8179 Do not pretty print C@t{++} virtual function tables.
8181 @item show print vtbl
8182 Show whether C@t{++} virtual function tables are pretty printed, or not.
8185 @node Pretty Printing
8186 @section Pretty Printing
8188 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8189 Python code. It greatly simplifies the display of complex objects. This
8190 mechanism works for both MI and the CLI.
8193 * Pretty-Printer Introduction:: Introduction to pretty-printers
8194 * Pretty-Printer Example:: An example pretty-printer
8195 * Pretty-Printer Commands:: Pretty-printer commands
8198 @node Pretty-Printer Introduction
8199 @subsection Pretty-Printer Introduction
8201 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8202 registered for the value. If there is then @value{GDBN} invokes the
8203 pretty-printer to print the value. Otherwise the value is printed normally.
8205 Pretty-printers are normally named. This makes them easy to manage.
8206 The @samp{info pretty-printer} command will list all the installed
8207 pretty-printers with their names.
8208 If a pretty-printer can handle multiple data types, then its
8209 @dfn{subprinters} are the printers for the individual data types.
8210 Each such subprinter has its own name.
8211 The format of the name is @var{printer-name};@var{subprinter-name}.
8213 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8214 Typically they are automatically loaded and registered when the corresponding
8215 debug information is loaded, thus making them available without having to
8216 do anything special.
8218 There are three places where a pretty-printer can be registered.
8222 Pretty-printers registered globally are available when debugging
8226 Pretty-printers registered with a program space are available only
8227 when debugging that program.
8228 @xref{Progspaces In Python}, for more details on program spaces in Python.
8231 Pretty-printers registered with an objfile are loaded and unloaded
8232 with the corresponding objfile (e.g., shared library).
8233 @xref{Objfiles In Python}, for more details on objfiles in Python.
8236 @xref{Selecting Pretty-Printers}, for further information on how
8237 pretty-printers are selected,
8239 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8242 @node Pretty-Printer Example
8243 @subsection Pretty-Printer Example
8245 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8248 (@value{GDBP}) print s
8250 static npos = 4294967295,
8252 <std::allocator<char>> = @{
8253 <__gnu_cxx::new_allocator<char>> = @{
8254 <No data fields>@}, <No data fields>
8256 members of std::basic_string<char, std::char_traits<char>,
8257 std::allocator<char> >::_Alloc_hider:
8258 _M_p = 0x804a014 "abcd"
8263 With a pretty-printer for @code{std::string} only the contents are printed:
8266 (@value{GDBP}) print s
8270 @node Pretty-Printer Commands
8271 @subsection Pretty-Printer Commands
8272 @cindex pretty-printer commands
8275 @kindex info pretty-printer
8276 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8277 Print the list of installed pretty-printers.
8278 This includes disabled pretty-printers, which are marked as such.
8280 @var{object-regexp} is a regular expression matching the objects
8281 whose pretty-printers to list.
8282 Objects can be @code{global}, the program space's file
8283 (@pxref{Progspaces In Python}),
8284 and the object files within that program space (@pxref{Objfiles In Python}).
8285 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8286 looks up a printer from these three objects.
8288 @var{name-regexp} is a regular expression matching the name of the printers
8291 @kindex disable pretty-printer
8292 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8293 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8294 A disabled pretty-printer is not forgotten, it may be enabled again later.
8296 @kindex enable pretty-printer
8297 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8298 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8303 Suppose we have three pretty-printers installed: one from library1.so
8304 named @code{foo} that prints objects of type @code{foo}, and
8305 another from library2.so named @code{bar} that prints two types of objects,
8306 @code{bar1} and @code{bar2}.
8309 (gdb) info pretty-printer
8316 (gdb) info pretty-printer library2
8321 (gdb) disable pretty-printer library1
8323 2 of 3 printers enabled
8324 (gdb) info pretty-printer
8331 (gdb) disable pretty-printer library2 bar:bar1
8333 1 of 3 printers enabled
8334 (gdb) info pretty-printer library2
8341 (gdb) disable pretty-printer library2 bar
8343 0 of 3 printers enabled
8344 (gdb) info pretty-printer library2
8353 Note that for @code{bar} the entire printer can be disabled,
8354 as can each individual subprinter.
8357 @section Value History
8359 @cindex value history
8360 @cindex history of values printed by @value{GDBN}
8361 Values printed by the @code{print} command are saved in the @value{GDBN}
8362 @dfn{value history}. This allows you to refer to them in other expressions.
8363 Values are kept until the symbol table is re-read or discarded
8364 (for example with the @code{file} or @code{symbol-file} commands).
8365 When the symbol table changes, the value history is discarded,
8366 since the values may contain pointers back to the types defined in the
8371 @cindex history number
8372 The values printed are given @dfn{history numbers} by which you can
8373 refer to them. These are successive integers starting with one.
8374 @code{print} shows you the history number assigned to a value by
8375 printing @samp{$@var{num} = } before the value; here @var{num} is the
8378 To refer to any previous value, use @samp{$} followed by the value's
8379 history number. The way @code{print} labels its output is designed to
8380 remind you of this. Just @code{$} refers to the most recent value in
8381 the history, and @code{$$} refers to the value before that.
8382 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8383 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8384 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8386 For example, suppose you have just printed a pointer to a structure and
8387 want to see the contents of the structure. It suffices to type
8393 If you have a chain of structures where the component @code{next} points
8394 to the next one, you can print the contents of the next one with this:
8401 You can print successive links in the chain by repeating this
8402 command---which you can do by just typing @key{RET}.
8404 Note that the history records values, not expressions. If the value of
8405 @code{x} is 4 and you type these commands:
8413 then the value recorded in the value history by the @code{print} command
8414 remains 4 even though the value of @code{x} has changed.
8419 Print the last ten values in the value history, with their item numbers.
8420 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8421 values} does not change the history.
8423 @item show values @var{n}
8424 Print ten history values centered on history item number @var{n}.
8427 Print ten history values just after the values last printed. If no more
8428 values are available, @code{show values +} produces no display.
8431 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8432 same effect as @samp{show values +}.
8434 @node Convenience Vars
8435 @section Convenience Variables
8437 @cindex convenience variables
8438 @cindex user-defined variables
8439 @value{GDBN} provides @dfn{convenience variables} that you can use within
8440 @value{GDBN} to hold on to a value and refer to it later. These variables
8441 exist entirely within @value{GDBN}; they are not part of your program, and
8442 setting a convenience variable has no direct effect on further execution
8443 of your program. That is why you can use them freely.
8445 Convenience variables are prefixed with @samp{$}. Any name preceded by
8446 @samp{$} can be used for a convenience variable, unless it is one of
8447 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8448 (Value history references, in contrast, are @emph{numbers} preceded
8449 by @samp{$}. @xref{Value History, ,Value History}.)
8451 You can save a value in a convenience variable with an assignment
8452 expression, just as you would set a variable in your program.
8456 set $foo = *object_ptr
8460 would save in @code{$foo} the value contained in the object pointed to by
8463 Using a convenience variable for the first time creates it, but its
8464 value is @code{void} until you assign a new value. You can alter the
8465 value with another assignment at any time.
8467 Convenience variables have no fixed types. You can assign a convenience
8468 variable any type of value, including structures and arrays, even if
8469 that variable already has a value of a different type. The convenience
8470 variable, when used as an expression, has the type of its current value.
8473 @kindex show convenience
8474 @cindex show all user variables
8475 @item show convenience
8476 Print a list of convenience variables used so far, and their values.
8477 Abbreviated @code{show conv}.
8479 @kindex init-if-undefined
8480 @cindex convenience variables, initializing
8481 @item init-if-undefined $@var{variable} = @var{expression}
8482 Set a convenience variable if it has not already been set. This is useful
8483 for user-defined commands that keep some state. It is similar, in concept,
8484 to using local static variables with initializers in C (except that
8485 convenience variables are global). It can also be used to allow users to
8486 override default values used in a command script.
8488 If the variable is already defined then the expression is not evaluated so
8489 any side-effects do not occur.
8492 One of the ways to use a convenience variable is as a counter to be
8493 incremented or a pointer to be advanced. For example, to print
8494 a field from successive elements of an array of structures:
8498 print bar[$i++]->contents
8502 Repeat that command by typing @key{RET}.
8504 Some convenience variables are created automatically by @value{GDBN} and given
8505 values likely to be useful.
8508 @vindex $_@r{, convenience variable}
8510 The variable @code{$_} is automatically set by the @code{x} command to
8511 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8512 commands which provide a default address for @code{x} to examine also
8513 set @code{$_} to that address; these commands include @code{info line}
8514 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8515 except when set by the @code{x} command, in which case it is a pointer
8516 to the type of @code{$__}.
8518 @vindex $__@r{, convenience variable}
8520 The variable @code{$__} is automatically set by the @code{x} command
8521 to the value found in the last address examined. Its type is chosen
8522 to match the format in which the data was printed.
8525 @vindex $_exitcode@r{, convenience variable}
8526 The variable @code{$_exitcode} is automatically set to the exit code when
8527 the program being debugged terminates.
8530 @vindex $_sdata@r{, inspect, convenience variable}
8531 The variable @code{$_sdata} contains extra collected static tracepoint
8532 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8533 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8534 if extra static tracepoint data has not been collected.
8537 @vindex $_siginfo@r{, convenience variable}
8538 The variable @code{$_siginfo} contains extra signal information
8539 (@pxref{extra signal information}). Note that @code{$_siginfo}
8540 could be empty, if the application has not yet received any signals.
8541 For example, it will be empty before you execute the @code{run} command.
8544 @vindex $_tlb@r{, convenience variable}
8545 The variable @code{$_tlb} is automatically set when debugging
8546 applications running on MS-Windows in native mode or connected to
8547 gdbserver that supports the @code{qGetTIBAddr} request.
8548 @xref{General Query Packets}.
8549 This variable contains the address of the thread information block.
8553 On HP-UX systems, if you refer to a function or variable name that
8554 begins with a dollar sign, @value{GDBN} searches for a user or system
8555 name first, before it searches for a convenience variable.
8557 @cindex convenience functions
8558 @value{GDBN} also supplies some @dfn{convenience functions}. These
8559 have a syntax similar to convenience variables. A convenience
8560 function can be used in an expression just like an ordinary function;
8561 however, a convenience function is implemented internally to
8566 @kindex help function
8567 @cindex show all convenience functions
8568 Print a list of all convenience functions.
8575 You can refer to machine register contents, in expressions, as variables
8576 with names starting with @samp{$}. The names of registers are different
8577 for each machine; use @code{info registers} to see the names used on
8581 @kindex info registers
8582 @item info registers
8583 Print the names and values of all registers except floating-point
8584 and vector registers (in the selected stack frame).
8586 @kindex info all-registers
8587 @cindex floating point registers
8588 @item info all-registers
8589 Print the names and values of all registers, including floating-point
8590 and vector registers (in the selected stack frame).
8592 @item info registers @var{regname} @dots{}
8593 Print the @dfn{relativized} value of each specified register @var{regname}.
8594 As discussed in detail below, register values are normally relative to
8595 the selected stack frame. @var{regname} may be any register name valid on
8596 the machine you are using, with or without the initial @samp{$}.
8599 @cindex stack pointer register
8600 @cindex program counter register
8601 @cindex process status register
8602 @cindex frame pointer register
8603 @cindex standard registers
8604 @value{GDBN} has four ``standard'' register names that are available (in
8605 expressions) on most machines---whenever they do not conflict with an
8606 architecture's canonical mnemonics for registers. The register names
8607 @code{$pc} and @code{$sp} are used for the program counter register and
8608 the stack pointer. @code{$fp} is used for a register that contains a
8609 pointer to the current stack frame, and @code{$ps} is used for a
8610 register that contains the processor status. For example,
8611 you could print the program counter in hex with
8618 or print the instruction to be executed next with
8625 or add four to the stack pointer@footnote{This is a way of removing
8626 one word from the stack, on machines where stacks grow downward in
8627 memory (most machines, nowadays). This assumes that the innermost
8628 stack frame is selected; setting @code{$sp} is not allowed when other
8629 stack frames are selected. To pop entire frames off the stack,
8630 regardless of machine architecture, use @code{return};
8631 see @ref{Returning, ,Returning from a Function}.} with
8637 Whenever possible, these four standard register names are available on
8638 your machine even though the machine has different canonical mnemonics,
8639 so long as there is no conflict. The @code{info registers} command
8640 shows the canonical names. For example, on the SPARC, @code{info
8641 registers} displays the processor status register as @code{$psr} but you
8642 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8643 is an alias for the @sc{eflags} register.
8645 @value{GDBN} always considers the contents of an ordinary register as an
8646 integer when the register is examined in this way. Some machines have
8647 special registers which can hold nothing but floating point; these
8648 registers are considered to have floating point values. There is no way
8649 to refer to the contents of an ordinary register as floating point value
8650 (although you can @emph{print} it as a floating point value with
8651 @samp{print/f $@var{regname}}).
8653 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8654 means that the data format in which the register contents are saved by
8655 the operating system is not the same one that your program normally
8656 sees. For example, the registers of the 68881 floating point
8657 coprocessor are always saved in ``extended'' (raw) format, but all C
8658 programs expect to work with ``double'' (virtual) format. In such
8659 cases, @value{GDBN} normally works with the virtual format only (the format
8660 that makes sense for your program), but the @code{info registers} command
8661 prints the data in both formats.
8663 @cindex SSE registers (x86)
8664 @cindex MMX registers (x86)
8665 Some machines have special registers whose contents can be interpreted
8666 in several different ways. For example, modern x86-based machines
8667 have SSE and MMX registers that can hold several values packed
8668 together in several different formats. @value{GDBN} refers to such
8669 registers in @code{struct} notation:
8672 (@value{GDBP}) print $xmm1
8674 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8675 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8676 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8677 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8678 v4_int32 = @{0, 20657912, 11, 13@},
8679 v2_int64 = @{88725056443645952, 55834574859@},
8680 uint128 = 0x0000000d0000000b013b36f800000000
8685 To set values of such registers, you need to tell @value{GDBN} which
8686 view of the register you wish to change, as if you were assigning
8687 value to a @code{struct} member:
8690 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8693 Normally, register values are relative to the selected stack frame
8694 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8695 value that the register would contain if all stack frames farther in
8696 were exited and their saved registers restored. In order to see the
8697 true contents of hardware registers, you must select the innermost
8698 frame (with @samp{frame 0}).
8700 However, @value{GDBN} must deduce where registers are saved, from the machine
8701 code generated by your compiler. If some registers are not saved, or if
8702 @value{GDBN} is unable to locate the saved registers, the selected stack
8703 frame makes no difference.
8705 @node Floating Point Hardware
8706 @section Floating Point Hardware
8707 @cindex floating point
8709 Depending on the configuration, @value{GDBN} may be able to give
8710 you more information about the status of the floating point hardware.
8715 Display hardware-dependent information about the floating
8716 point unit. The exact contents and layout vary depending on the
8717 floating point chip. Currently, @samp{info float} is supported on
8718 the ARM and x86 machines.
8722 @section Vector Unit
8725 Depending on the configuration, @value{GDBN} may be able to give you
8726 more information about the status of the vector unit.
8731 Display information about the vector unit. The exact contents and
8732 layout vary depending on the hardware.
8735 @node OS Information
8736 @section Operating System Auxiliary Information
8737 @cindex OS information
8739 @value{GDBN} provides interfaces to useful OS facilities that can help
8740 you debug your program.
8742 @cindex @code{ptrace} system call
8743 @cindex @code{struct user} contents
8744 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8745 machines), it interfaces with the inferior via the @code{ptrace}
8746 system call. The operating system creates a special sata structure,
8747 called @code{struct user}, for this interface. You can use the
8748 command @code{info udot} to display the contents of this data
8754 Display the contents of the @code{struct user} maintained by the OS
8755 kernel for the program being debugged. @value{GDBN} displays the
8756 contents of @code{struct user} as a list of hex numbers, similar to
8757 the @code{examine} command.
8760 @cindex auxiliary vector
8761 @cindex vector, auxiliary
8762 Some operating systems supply an @dfn{auxiliary vector} to programs at
8763 startup. This is akin to the arguments and environment that you
8764 specify for a program, but contains a system-dependent variety of
8765 binary values that tell system libraries important details about the
8766 hardware, operating system, and process. Each value's purpose is
8767 identified by an integer tag; the meanings are well-known but system-specific.
8768 Depending on the configuration and operating system facilities,
8769 @value{GDBN} may be able to show you this information. For remote
8770 targets, this functionality may further depend on the remote stub's
8771 support of the @samp{qXfer:auxv:read} packet, see
8772 @ref{qXfer auxiliary vector read}.
8777 Display the auxiliary vector of the inferior, which can be either a
8778 live process or a core dump file. @value{GDBN} prints each tag value
8779 numerically, and also shows names and text descriptions for recognized
8780 tags. Some values in the vector are numbers, some bit masks, and some
8781 pointers to strings or other data. @value{GDBN} displays each value in the
8782 most appropriate form for a recognized tag, and in hexadecimal for
8783 an unrecognized tag.
8786 On some targets, @value{GDBN} can access operating-system-specific information
8787 and display it to user, without interpretation. For remote targets,
8788 this functionality depends on the remote stub's support of the
8789 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8794 List the types of OS information available for the target. If the
8795 target does not return a list of possible types, this command will
8798 @kindex info os processes
8799 @item info os processes
8800 Display the list of processes on the target. For each process,
8801 @value{GDBN} prints the process identifier, the name of the user, and
8802 the command corresponding to the process.
8805 @node Memory Region Attributes
8806 @section Memory Region Attributes
8807 @cindex memory region attributes
8809 @dfn{Memory region attributes} allow you to describe special handling
8810 required by regions of your target's memory. @value{GDBN} uses
8811 attributes to determine whether to allow certain types of memory
8812 accesses; whether to use specific width accesses; and whether to cache
8813 target memory. By default the description of memory regions is
8814 fetched from the target (if the current target supports this), but the
8815 user can override the fetched regions.
8817 Defined memory regions can be individually enabled and disabled. When a
8818 memory region is disabled, @value{GDBN} uses the default attributes when
8819 accessing memory in that region. Similarly, if no memory regions have
8820 been defined, @value{GDBN} uses the default attributes when accessing
8823 When a memory region is defined, it is given a number to identify it;
8824 to enable, disable, or remove a memory region, you specify that number.
8828 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8829 Define a memory region bounded by @var{lower} and @var{upper} with
8830 attributes @var{attributes}@dots{}, and add it to the list of regions
8831 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8832 case: it is treated as the target's maximum memory address.
8833 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8836 Discard any user changes to the memory regions and use target-supplied
8837 regions, if available, or no regions if the target does not support.
8840 @item delete mem @var{nums}@dots{}
8841 Remove memory regions @var{nums}@dots{} from the list of regions
8842 monitored by @value{GDBN}.
8845 @item disable mem @var{nums}@dots{}
8846 Disable monitoring of memory regions @var{nums}@dots{}.
8847 A disabled memory region is not forgotten.
8848 It may be enabled again later.
8851 @item enable mem @var{nums}@dots{}
8852 Enable monitoring of memory regions @var{nums}@dots{}.
8856 Print a table of all defined memory regions, with the following columns
8860 @item Memory Region Number
8861 @item Enabled or Disabled.
8862 Enabled memory regions are marked with @samp{y}.
8863 Disabled memory regions are marked with @samp{n}.
8866 The address defining the inclusive lower bound of the memory region.
8869 The address defining the exclusive upper bound of the memory region.
8872 The list of attributes set for this memory region.
8877 @subsection Attributes
8879 @subsubsection Memory Access Mode
8880 The access mode attributes set whether @value{GDBN} may make read or
8881 write accesses to a memory region.
8883 While these attributes prevent @value{GDBN} from performing invalid
8884 memory accesses, they do nothing to prevent the target system, I/O DMA,
8885 etc.@: from accessing memory.
8889 Memory is read only.
8891 Memory is write only.
8893 Memory is read/write. This is the default.
8896 @subsubsection Memory Access Size
8897 The access size attribute tells @value{GDBN} to use specific sized
8898 accesses in the memory region. Often memory mapped device registers
8899 require specific sized accesses. If no access size attribute is
8900 specified, @value{GDBN} may use accesses of any size.
8904 Use 8 bit memory accesses.
8906 Use 16 bit memory accesses.
8908 Use 32 bit memory accesses.
8910 Use 64 bit memory accesses.
8913 @c @subsubsection Hardware/Software Breakpoints
8914 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8915 @c will use hardware or software breakpoints for the internal breakpoints
8916 @c used by the step, next, finish, until, etc. commands.
8920 @c Always use hardware breakpoints
8921 @c @item swbreak (default)
8924 @subsubsection Data Cache
8925 The data cache attributes set whether @value{GDBN} will cache target
8926 memory. While this generally improves performance by reducing debug
8927 protocol overhead, it can lead to incorrect results because @value{GDBN}
8928 does not know about volatile variables or memory mapped device
8933 Enable @value{GDBN} to cache target memory.
8935 Disable @value{GDBN} from caching target memory. This is the default.
8938 @subsection Memory Access Checking
8939 @value{GDBN} can be instructed to refuse accesses to memory that is
8940 not explicitly described. This can be useful if accessing such
8941 regions has undesired effects for a specific target, or to provide
8942 better error checking. The following commands control this behaviour.
8945 @kindex set mem inaccessible-by-default
8946 @item set mem inaccessible-by-default [on|off]
8947 If @code{on} is specified, make @value{GDBN} treat memory not
8948 explicitly described by the memory ranges as non-existent and refuse accesses
8949 to such memory. The checks are only performed if there's at least one
8950 memory range defined. If @code{off} is specified, make @value{GDBN}
8951 treat the memory not explicitly described by the memory ranges as RAM.
8952 The default value is @code{on}.
8953 @kindex show mem inaccessible-by-default
8954 @item show mem inaccessible-by-default
8955 Show the current handling of accesses to unknown memory.
8959 @c @subsubsection Memory Write Verification
8960 @c The memory write verification attributes set whether @value{GDBN}
8961 @c will re-reads data after each write to verify the write was successful.
8965 @c @item noverify (default)
8968 @node Dump/Restore Files
8969 @section Copy Between Memory and a File
8970 @cindex dump/restore files
8971 @cindex append data to a file
8972 @cindex dump data to a file
8973 @cindex restore data from a file
8975 You can use the commands @code{dump}, @code{append}, and
8976 @code{restore} to copy data between target memory and a file. The
8977 @code{dump} and @code{append} commands write data to a file, and the
8978 @code{restore} command reads data from a file back into the inferior's
8979 memory. Files may be in binary, Motorola S-record, Intel hex, or
8980 Tektronix Hex format; however, @value{GDBN} can only append to binary
8986 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8987 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8988 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8989 or the value of @var{expr}, to @var{filename} in the given format.
8991 The @var{format} parameter may be any one of:
8998 Motorola S-record format.
9000 Tektronix Hex format.
9003 @value{GDBN} uses the same definitions of these formats as the
9004 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9005 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9009 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9010 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9011 Append the contents of memory from @var{start_addr} to @var{end_addr},
9012 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9013 (@value{GDBN} can only append data to files in raw binary form.)
9016 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9017 Restore the contents of file @var{filename} into memory. The
9018 @code{restore} command can automatically recognize any known @sc{bfd}
9019 file format, except for raw binary. To restore a raw binary file you
9020 must specify the optional keyword @code{binary} after the filename.
9022 If @var{bias} is non-zero, its value will be added to the addresses
9023 contained in the file. Binary files always start at address zero, so
9024 they will be restored at address @var{bias}. Other bfd files have
9025 a built-in location; they will be restored at offset @var{bias}
9028 If @var{start} and/or @var{end} are non-zero, then only data between
9029 file offset @var{start} and file offset @var{end} will be restored.
9030 These offsets are relative to the addresses in the file, before
9031 the @var{bias} argument is applied.
9035 @node Core File Generation
9036 @section How to Produce a Core File from Your Program
9037 @cindex dump core from inferior
9039 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9040 image of a running process and its process status (register values
9041 etc.). Its primary use is post-mortem debugging of a program that
9042 crashed while it ran outside a debugger. A program that crashes
9043 automatically produces a core file, unless this feature is disabled by
9044 the user. @xref{Files}, for information on invoking @value{GDBN} in
9045 the post-mortem debugging mode.
9047 Occasionally, you may wish to produce a core file of the program you
9048 are debugging in order to preserve a snapshot of its state.
9049 @value{GDBN} has a special command for that.
9053 @kindex generate-core-file
9054 @item generate-core-file [@var{file}]
9055 @itemx gcore [@var{file}]
9056 Produce a core dump of the inferior process. The optional argument
9057 @var{file} specifies the file name where to put the core dump. If not
9058 specified, the file name defaults to @file{core.@var{pid}}, where
9059 @var{pid} is the inferior process ID.
9061 Note that this command is implemented only for some systems (as of
9062 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9065 @node Character Sets
9066 @section Character Sets
9067 @cindex character sets
9069 @cindex translating between character sets
9070 @cindex host character set
9071 @cindex target character set
9073 If the program you are debugging uses a different character set to
9074 represent characters and strings than the one @value{GDBN} uses itself,
9075 @value{GDBN} can automatically translate between the character sets for
9076 you. The character set @value{GDBN} uses we call the @dfn{host
9077 character set}; the one the inferior program uses we call the
9078 @dfn{target character set}.
9080 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9081 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9082 remote protocol (@pxref{Remote Debugging}) to debug a program
9083 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9084 then the host character set is Latin-1, and the target character set is
9085 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9086 target-charset EBCDIC-US}, then @value{GDBN} translates between
9087 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9088 character and string literals in expressions.
9090 @value{GDBN} has no way to automatically recognize which character set
9091 the inferior program uses; you must tell it, using the @code{set
9092 target-charset} command, described below.
9094 Here are the commands for controlling @value{GDBN}'s character set
9098 @item set target-charset @var{charset}
9099 @kindex set target-charset
9100 Set the current target character set to @var{charset}. To display the
9101 list of supported target character sets, type
9102 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9104 @item set host-charset @var{charset}
9105 @kindex set host-charset
9106 Set the current host character set to @var{charset}.
9108 By default, @value{GDBN} uses a host character set appropriate to the
9109 system it is running on; you can override that default using the
9110 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9111 automatically determine the appropriate host character set. In this
9112 case, @value{GDBN} uses @samp{UTF-8}.
9114 @value{GDBN} can only use certain character sets as its host character
9115 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9116 @value{GDBN} will list the host character sets it supports.
9118 @item set charset @var{charset}
9120 Set the current host and target character sets to @var{charset}. As
9121 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9122 @value{GDBN} will list the names of the character sets that can be used
9123 for both host and target.
9126 @kindex show charset
9127 Show the names of the current host and target character sets.
9129 @item show host-charset
9130 @kindex show host-charset
9131 Show the name of the current host character set.
9133 @item show target-charset
9134 @kindex show target-charset
9135 Show the name of the current target character set.
9137 @item set target-wide-charset @var{charset}
9138 @kindex set target-wide-charset
9139 Set the current target's wide character set to @var{charset}. This is
9140 the character set used by the target's @code{wchar_t} type. To
9141 display the list of supported wide character sets, type
9142 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9144 @item show target-wide-charset
9145 @kindex show target-wide-charset
9146 Show the name of the current target's wide character set.
9149 Here is an example of @value{GDBN}'s character set support in action.
9150 Assume that the following source code has been placed in the file
9151 @file{charset-test.c}:
9157 = @{72, 101, 108, 108, 111, 44, 32, 119,
9158 111, 114, 108, 100, 33, 10, 0@};
9159 char ibm1047_hello[]
9160 = @{200, 133, 147, 147, 150, 107, 64, 166,
9161 150, 153, 147, 132, 90, 37, 0@};
9165 printf ("Hello, world!\n");
9169 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9170 containing the string @samp{Hello, world!} followed by a newline,
9171 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9173 We compile the program, and invoke the debugger on it:
9176 $ gcc -g charset-test.c -o charset-test
9177 $ gdb -nw charset-test
9178 GNU gdb 2001-12-19-cvs
9179 Copyright 2001 Free Software Foundation, Inc.
9184 We can use the @code{show charset} command to see what character sets
9185 @value{GDBN} is currently using to interpret and display characters and
9189 (@value{GDBP}) show charset
9190 The current host and target character set is `ISO-8859-1'.
9194 For the sake of printing this manual, let's use @sc{ascii} as our
9195 initial character set:
9197 (@value{GDBP}) set charset ASCII
9198 (@value{GDBP}) show charset
9199 The current host and target character set is `ASCII'.
9203 Let's assume that @sc{ascii} is indeed the correct character set for our
9204 host system --- in other words, let's assume that if @value{GDBN} prints
9205 characters using the @sc{ascii} character set, our terminal will display
9206 them properly. Since our current target character set is also
9207 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9210 (@value{GDBP}) print ascii_hello
9211 $1 = 0x401698 "Hello, world!\n"
9212 (@value{GDBP}) print ascii_hello[0]
9217 @value{GDBN} uses the target character set for character and string
9218 literals you use in expressions:
9221 (@value{GDBP}) print '+'
9226 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9229 @value{GDBN} relies on the user to tell it which character set the
9230 target program uses. If we print @code{ibm1047_hello} while our target
9231 character set is still @sc{ascii}, we get jibberish:
9234 (@value{GDBP}) print ibm1047_hello
9235 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9236 (@value{GDBP}) print ibm1047_hello[0]
9241 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9242 @value{GDBN} tells us the character sets it supports:
9245 (@value{GDBP}) set target-charset
9246 ASCII EBCDIC-US IBM1047 ISO-8859-1
9247 (@value{GDBP}) set target-charset
9250 We can select @sc{ibm1047} as our target character set, and examine the
9251 program's strings again. Now the @sc{ascii} string is wrong, but
9252 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9253 target character set, @sc{ibm1047}, to the host character set,
9254 @sc{ascii}, and they display correctly:
9257 (@value{GDBP}) set target-charset IBM1047
9258 (@value{GDBP}) show charset
9259 The current host character set is `ASCII'.
9260 The current target character set is `IBM1047'.
9261 (@value{GDBP}) print ascii_hello
9262 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9263 (@value{GDBP}) print ascii_hello[0]
9265 (@value{GDBP}) print ibm1047_hello
9266 $8 = 0x4016a8 "Hello, world!\n"
9267 (@value{GDBP}) print ibm1047_hello[0]
9272 As above, @value{GDBN} uses the target character set for character and
9273 string literals you use in expressions:
9276 (@value{GDBP}) print '+'
9281 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9284 @node Caching Remote Data
9285 @section Caching Data of Remote Targets
9286 @cindex caching data of remote targets
9288 @value{GDBN} caches data exchanged between the debugger and a
9289 remote target (@pxref{Remote Debugging}). Such caching generally improves
9290 performance, because it reduces the overhead of the remote protocol by
9291 bundling memory reads and writes into large chunks. Unfortunately, simply
9292 caching everything would lead to incorrect results, since @value{GDBN}
9293 does not necessarily know anything about volatile values, memory-mapped I/O
9294 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9295 memory can be changed @emph{while} a gdb command is executing.
9296 Therefore, by default, @value{GDBN} only caches data
9297 known to be on the stack@footnote{In non-stop mode, it is moderately
9298 rare for a running thread to modify the stack of a stopped thread
9299 in a way that would interfere with a backtrace, and caching of
9300 stack reads provides a significant speed up of remote backtraces.}.
9301 Other regions of memory can be explicitly marked as
9302 cacheable; see @pxref{Memory Region Attributes}.
9305 @kindex set remotecache
9306 @item set remotecache on
9307 @itemx set remotecache off
9308 This option no longer does anything; it exists for compatibility
9311 @kindex show remotecache
9312 @item show remotecache
9313 Show the current state of the obsolete remotecache flag.
9315 @kindex set stack-cache
9316 @item set stack-cache on
9317 @itemx set stack-cache off
9318 Enable or disable caching of stack accesses. When @code{ON}, use
9319 caching. By default, this option is @code{ON}.
9321 @kindex show stack-cache
9322 @item show stack-cache
9323 Show the current state of data caching for memory accesses.
9326 @item info dcache @r{[}line@r{]}
9327 Print the information about the data cache performance. The
9328 information displayed includes the dcache width and depth, and for
9329 each cache line, its number, address, and how many times it was
9330 referenced. This command is useful for debugging the data cache
9333 If a line number is specified, the contents of that line will be
9336 @item set dcache size @var{size}
9338 @kindex set dcache size
9339 Set maximum number of entries in dcache (dcache depth above).
9341 @item set dcache line-size @var{line-size}
9342 @cindex dcache line-size
9343 @kindex set dcache line-size
9344 Set number of bytes each dcache entry caches (dcache width above).
9345 Must be a power of 2.
9347 @item show dcache size
9348 @kindex show dcache size
9349 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9351 @item show dcache line-size
9352 @kindex show dcache line-size
9353 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9357 @node Searching Memory
9358 @section Search Memory
9359 @cindex searching memory
9361 Memory can be searched for a particular sequence of bytes with the
9362 @code{find} command.
9366 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9367 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9368 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9369 etc. The search begins at address @var{start_addr} and continues for either
9370 @var{len} bytes or through to @var{end_addr} inclusive.
9373 @var{s} and @var{n} are optional parameters.
9374 They may be specified in either order, apart or together.
9377 @item @var{s}, search query size
9378 The size of each search query value.
9384 halfwords (two bytes)
9388 giant words (eight bytes)
9391 All values are interpreted in the current language.
9392 This means, for example, that if the current source language is C/C@t{++}
9393 then searching for the string ``hello'' includes the trailing '\0'.
9395 If the value size is not specified, it is taken from the
9396 value's type in the current language.
9397 This is useful when one wants to specify the search
9398 pattern as a mixture of types.
9399 Note that this means, for example, that in the case of C-like languages
9400 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9401 which is typically four bytes.
9403 @item @var{n}, maximum number of finds
9404 The maximum number of matches to print. The default is to print all finds.
9407 You can use strings as search values. Quote them with double-quotes
9409 The string value is copied into the search pattern byte by byte,
9410 regardless of the endianness of the target and the size specification.
9412 The address of each match found is printed as well as a count of the
9413 number of matches found.
9415 The address of the last value found is stored in convenience variable
9417 A count of the number of matches is stored in @samp{$numfound}.
9419 For example, if stopped at the @code{printf} in this function:
9425 static char hello[] = "hello-hello";
9426 static struct @{ char c; short s; int i; @}
9427 __attribute__ ((packed)) mixed
9428 = @{ 'c', 0x1234, 0x87654321 @};
9429 printf ("%s\n", hello);
9434 you get during debugging:
9437 (gdb) find &hello[0], +sizeof(hello), "hello"
9438 0x804956d <hello.1620+6>
9440 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9441 0x8049567 <hello.1620>
9442 0x804956d <hello.1620+6>
9444 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9445 0x8049567 <hello.1620>
9447 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9448 0x8049560 <mixed.1625>
9450 (gdb) print $numfound
9453 $2 = (void *) 0x8049560
9456 @node Optimized Code
9457 @chapter Debugging Optimized Code
9458 @cindex optimized code, debugging
9459 @cindex debugging optimized code
9461 Almost all compilers support optimization. With optimization
9462 disabled, the compiler generates assembly code that corresponds
9463 directly to your source code, in a simplistic way. As the compiler
9464 applies more powerful optimizations, the generated assembly code
9465 diverges from your original source code. With help from debugging
9466 information generated by the compiler, @value{GDBN} can map from
9467 the running program back to constructs from your original source.
9469 @value{GDBN} is more accurate with optimization disabled. If you
9470 can recompile without optimization, it is easier to follow the
9471 progress of your program during debugging. But, there are many cases
9472 where you may need to debug an optimized version.
9474 When you debug a program compiled with @samp{-g -O}, remember that the
9475 optimizer has rearranged your code; the debugger shows you what is
9476 really there. Do not be too surprised when the execution path does not
9477 exactly match your source file! An extreme example: if you define a
9478 variable, but never use it, @value{GDBN} never sees that
9479 variable---because the compiler optimizes it out of existence.
9481 Some things do not work as well with @samp{-g -O} as with just
9482 @samp{-g}, particularly on machines with instruction scheduling. If in
9483 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9484 please report it to us as a bug (including a test case!).
9485 @xref{Variables}, for more information about debugging optimized code.
9488 * Inline Functions:: How @value{GDBN} presents inlining
9491 @node Inline Functions
9492 @section Inline Functions
9493 @cindex inline functions, debugging
9495 @dfn{Inlining} is an optimization that inserts a copy of the function
9496 body directly at each call site, instead of jumping to a shared
9497 routine. @value{GDBN} displays inlined functions just like
9498 non-inlined functions. They appear in backtraces. You can view their
9499 arguments and local variables, step into them with @code{step}, skip
9500 them with @code{next}, and escape from them with @code{finish}.
9501 You can check whether a function was inlined by using the
9502 @code{info frame} command.
9504 For @value{GDBN} to support inlined functions, the compiler must
9505 record information about inlining in the debug information ---
9506 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9507 other compilers do also. @value{GDBN} only supports inlined functions
9508 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9509 do not emit two required attributes (@samp{DW_AT_call_file} and
9510 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9511 function calls with earlier versions of @value{NGCC}. It instead
9512 displays the arguments and local variables of inlined functions as
9513 local variables in the caller.
9515 The body of an inlined function is directly included at its call site;
9516 unlike a non-inlined function, there are no instructions devoted to
9517 the call. @value{GDBN} still pretends that the call site and the
9518 start of the inlined function are different instructions. Stepping to
9519 the call site shows the call site, and then stepping again shows
9520 the first line of the inlined function, even though no additional
9521 instructions are executed.
9523 This makes source-level debugging much clearer; you can see both the
9524 context of the call and then the effect of the call. Only stepping by
9525 a single instruction using @code{stepi} or @code{nexti} does not do
9526 this; single instruction steps always show the inlined body.
9528 There are some ways that @value{GDBN} does not pretend that inlined
9529 function calls are the same as normal calls:
9533 You cannot set breakpoints on inlined functions. @value{GDBN}
9534 either reports that there is no symbol with that name, or else sets the
9535 breakpoint only on non-inlined copies of the function. This limitation
9536 will be removed in a future version of @value{GDBN}; until then,
9537 set a breakpoint by line number on the first line of the inlined
9541 Setting breakpoints at the call site of an inlined function may not
9542 work, because the call site does not contain any code. @value{GDBN}
9543 may incorrectly move the breakpoint to the next line of the enclosing
9544 function, after the call. This limitation will be removed in a future
9545 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9546 or inside the inlined function instead.
9549 @value{GDBN} cannot locate the return value of inlined calls after
9550 using the @code{finish} command. This is a limitation of compiler-generated
9551 debugging information; after @code{finish}, you can step to the next line
9552 and print a variable where your program stored the return value.
9558 @chapter C Preprocessor Macros
9560 Some languages, such as C and C@t{++}, provide a way to define and invoke
9561 ``preprocessor macros'' which expand into strings of tokens.
9562 @value{GDBN} can evaluate expressions containing macro invocations, show
9563 the result of macro expansion, and show a macro's definition, including
9564 where it was defined.
9566 You may need to compile your program specially to provide @value{GDBN}
9567 with information about preprocessor macros. Most compilers do not
9568 include macros in their debugging information, even when you compile
9569 with the @option{-g} flag. @xref{Compilation}.
9571 A program may define a macro at one point, remove that definition later,
9572 and then provide a different definition after that. Thus, at different
9573 points in the program, a macro may have different definitions, or have
9574 no definition at all. If there is a current stack frame, @value{GDBN}
9575 uses the macros in scope at that frame's source code line. Otherwise,
9576 @value{GDBN} uses the macros in scope at the current listing location;
9579 Whenever @value{GDBN} evaluates an expression, it always expands any
9580 macro invocations present in the expression. @value{GDBN} also provides
9581 the following commands for working with macros explicitly.
9585 @kindex macro expand
9586 @cindex macro expansion, showing the results of preprocessor
9587 @cindex preprocessor macro expansion, showing the results of
9588 @cindex expanding preprocessor macros
9589 @item macro expand @var{expression}
9590 @itemx macro exp @var{expression}
9591 Show the results of expanding all preprocessor macro invocations in
9592 @var{expression}. Since @value{GDBN} simply expands macros, but does
9593 not parse the result, @var{expression} need not be a valid expression;
9594 it can be any string of tokens.
9597 @item macro expand-once @var{expression}
9598 @itemx macro exp1 @var{expression}
9599 @cindex expand macro once
9600 @i{(This command is not yet implemented.)} Show the results of
9601 expanding those preprocessor macro invocations that appear explicitly in
9602 @var{expression}. Macro invocations appearing in that expansion are
9603 left unchanged. This command allows you to see the effect of a
9604 particular macro more clearly, without being confused by further
9605 expansions. Since @value{GDBN} simply expands macros, but does not
9606 parse the result, @var{expression} need not be a valid expression; it
9607 can be any string of tokens.
9610 @cindex macro definition, showing
9611 @cindex definition of a macro, showing
9612 @cindex macros, from debug info
9613 @item info macro @var{macro}
9614 Show the current definition of the named @var{macro}, and describe the
9615 source location or compiler command-line where that definition was established.
9618 @item info macros @var{linespec}
9619 Show all macro definitions that are in effect at the location specified
9620 by @var{linespec}, and describe the source location or compiler
9621 command-line where those definitions were established.
9623 @kindex info definitions
9624 @item info definitions @var{macro}
9625 Show all definitions of the named @var{macro} that are defined in the current
9626 compilation unit, and describe the source location or compiler command-line
9627 where those definitions were established.
9629 @kindex macro define
9630 @cindex user-defined macros
9631 @cindex defining macros interactively
9632 @cindex macros, user-defined
9633 @item macro define @var{macro} @var{replacement-list}
9634 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9635 Introduce a definition for a preprocessor macro named @var{macro},
9636 invocations of which are replaced by the tokens given in
9637 @var{replacement-list}. The first form of this command defines an
9638 ``object-like'' macro, which takes no arguments; the second form
9639 defines a ``function-like'' macro, which takes the arguments given in
9642 A definition introduced by this command is in scope in every
9643 expression evaluated in @value{GDBN}, until it is removed with the
9644 @code{macro undef} command, described below. The definition overrides
9645 all definitions for @var{macro} present in the program being debugged,
9646 as well as any previous user-supplied definition.
9649 @item macro undef @var{macro}
9650 Remove any user-supplied definition for the macro named @var{macro}.
9651 This command only affects definitions provided with the @code{macro
9652 define} command, described above; it cannot remove definitions present
9653 in the program being debugged.
9657 List all the macros defined using the @code{macro define} command.
9660 @cindex macros, example of debugging with
9661 Here is a transcript showing the above commands in action. First, we
9662 show our source files:
9670 #define ADD(x) (M + x)
9675 printf ("Hello, world!\n");
9677 printf ("We're so creative.\n");
9679 printf ("Goodbye, world!\n");
9686 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9687 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9688 compiler includes information about preprocessor macros in the debugging
9692 $ gcc -gdwarf-2 -g3 sample.c -o sample
9696 Now, we start @value{GDBN} on our sample program:
9700 GNU gdb 2002-05-06-cvs
9701 Copyright 2002 Free Software Foundation, Inc.
9702 GDB is free software, @dots{}
9706 We can expand macros and examine their definitions, even when the
9707 program is not running. @value{GDBN} uses the current listing position
9708 to decide which macro definitions are in scope:
9711 (@value{GDBP}) list main
9714 5 #define ADD(x) (M + x)
9719 10 printf ("Hello, world!\n");
9721 12 printf ("We're so creative.\n");
9722 (@value{GDBP}) info macro ADD
9723 Defined at /home/jimb/gdb/macros/play/sample.c:5
9724 #define ADD(x) (M + x)
9725 (@value{GDBP}) info macro Q
9726 Defined at /home/jimb/gdb/macros/play/sample.h:1
9727 included at /home/jimb/gdb/macros/play/sample.c:2
9729 (@value{GDBP}) macro expand ADD(1)
9730 expands to: (42 + 1)
9731 (@value{GDBP}) macro expand-once ADD(1)
9732 expands to: once (M + 1)
9736 In the example above, note that @code{macro expand-once} expands only
9737 the macro invocation explicit in the original text --- the invocation of
9738 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9739 which was introduced by @code{ADD}.
9741 Once the program is running, @value{GDBN} uses the macro definitions in
9742 force at the source line of the current stack frame:
9745 (@value{GDBP}) break main
9746 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9748 Starting program: /home/jimb/gdb/macros/play/sample
9750 Breakpoint 1, main () at sample.c:10
9751 10 printf ("Hello, world!\n");
9755 At line 10, the definition of the macro @code{N} at line 9 is in force:
9758 (@value{GDBP}) info macro N
9759 Defined at /home/jimb/gdb/macros/play/sample.c:9
9761 (@value{GDBP}) macro expand N Q M
9763 (@value{GDBP}) print N Q M
9768 As we step over directives that remove @code{N}'s definition, and then
9769 give it a new definition, @value{GDBN} finds the definition (or lack
9770 thereof) in force at each point:
9775 12 printf ("We're so creative.\n");
9776 (@value{GDBP}) info macro N
9777 The symbol `N' has no definition as a C/C++ preprocessor macro
9778 at /home/jimb/gdb/macros/play/sample.c:12
9781 14 printf ("Goodbye, world!\n");
9782 (@value{GDBP}) info macro N
9783 Defined at /home/jimb/gdb/macros/play/sample.c:13
9785 (@value{GDBP}) macro expand N Q M
9786 expands to: 1729 < 42
9787 (@value{GDBP}) print N Q M
9792 In addition to source files, macros can be defined on the compilation command
9793 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9794 such a way, @value{GDBN} displays the location of their definition as line zero
9795 of the source file submitted to the compiler.
9798 (@value{GDBP}) info macro __STDC__
9799 Defined at /home/jimb/gdb/macros/play/sample.c:0
9806 @chapter Tracepoints
9807 @c This chapter is based on the documentation written by Michael
9808 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9811 In some applications, it is not feasible for the debugger to interrupt
9812 the program's execution long enough for the developer to learn
9813 anything helpful about its behavior. If the program's correctness
9814 depends on its real-time behavior, delays introduced by a debugger
9815 might cause the program to change its behavior drastically, or perhaps
9816 fail, even when the code itself is correct. It is useful to be able
9817 to observe the program's behavior without interrupting it.
9819 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9820 specify locations in the program, called @dfn{tracepoints}, and
9821 arbitrary expressions to evaluate when those tracepoints are reached.
9822 Later, using the @code{tfind} command, you can examine the values
9823 those expressions had when the program hit the tracepoints. The
9824 expressions may also denote objects in memory---structures or arrays,
9825 for example---whose values @value{GDBN} should record; while visiting
9826 a particular tracepoint, you may inspect those objects as if they were
9827 in memory at that moment. However, because @value{GDBN} records these
9828 values without interacting with you, it can do so quickly and
9829 unobtrusively, hopefully not disturbing the program's behavior.
9831 The tracepoint facility is currently available only for remote
9832 targets. @xref{Targets}. In addition, your remote target must know
9833 how to collect trace data. This functionality is implemented in the
9834 remote stub; however, none of the stubs distributed with @value{GDBN}
9835 support tracepoints as of this writing. The format of the remote
9836 packets used to implement tracepoints are described in @ref{Tracepoint
9839 It is also possible to get trace data from a file, in a manner reminiscent
9840 of corefiles; you specify the filename, and use @code{tfind} to search
9841 through the file. @xref{Trace Files}, for more details.
9843 This chapter describes the tracepoint commands and features.
9847 * Analyze Collected Data::
9848 * Tracepoint Variables::
9852 @node Set Tracepoints
9853 @section Commands to Set Tracepoints
9855 Before running such a @dfn{trace experiment}, an arbitrary number of
9856 tracepoints can be set. A tracepoint is actually a special type of
9857 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9858 standard breakpoint commands. For instance, as with breakpoints,
9859 tracepoint numbers are successive integers starting from one, and many
9860 of the commands associated with tracepoints take the tracepoint number
9861 as their argument, to identify which tracepoint to work on.
9863 For each tracepoint, you can specify, in advance, some arbitrary set
9864 of data that you want the target to collect in the trace buffer when
9865 it hits that tracepoint. The collected data can include registers,
9866 local variables, or global data. Later, you can use @value{GDBN}
9867 commands to examine the values these data had at the time the
9870 Tracepoints do not support every breakpoint feature. Ignore counts on
9871 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9872 commands when they are hit. Tracepoints may not be thread-specific
9875 @cindex fast tracepoints
9876 Some targets may support @dfn{fast tracepoints}, which are inserted in
9877 a different way (such as with a jump instead of a trap), that is
9878 faster but possibly restricted in where they may be installed.
9880 @cindex static tracepoints
9881 @cindex markers, static tracepoints
9882 @cindex probing markers, static tracepoints
9883 Regular and fast tracepoints are dynamic tracing facilities, meaning
9884 that they can be used to insert tracepoints at (almost) any location
9885 in the target. Some targets may also support controlling @dfn{static
9886 tracepoints} from @value{GDBN}. With static tracing, a set of
9887 instrumentation points, also known as @dfn{markers}, are embedded in
9888 the target program, and can be activated or deactivated by name or
9889 address. These are usually placed at locations which facilitate
9890 investigating what the target is actually doing. @value{GDBN}'s
9891 support for static tracing includes being able to list instrumentation
9892 points, and attach them with @value{GDBN} defined high level
9893 tracepoints that expose the whole range of convenience of
9894 @value{GDBN}'s tracepoints support. Namely, support for collecting
9895 registers values and values of global or local (to the instrumentation
9896 point) variables; tracepoint conditions and trace state variables.
9897 The act of installing a @value{GDBN} static tracepoint on an
9898 instrumentation point, or marker, is referred to as @dfn{probing} a
9899 static tracepoint marker.
9901 @code{gdbserver} supports tracepoints on some target systems.
9902 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9904 This section describes commands to set tracepoints and associated
9905 conditions and actions.
9908 * Create and Delete Tracepoints::
9909 * Enable and Disable Tracepoints::
9910 * Tracepoint Passcounts::
9911 * Tracepoint Conditions::
9912 * Trace State Variables::
9913 * Tracepoint Actions::
9914 * Listing Tracepoints::
9915 * Listing Static Tracepoint Markers::
9916 * Starting and Stopping Trace Experiments::
9917 * Tracepoint Restrictions::
9920 @node Create and Delete Tracepoints
9921 @subsection Create and Delete Tracepoints
9924 @cindex set tracepoint
9926 @item trace @var{location}
9927 The @code{trace} command is very similar to the @code{break} command.
9928 Its argument @var{location} can be a source line, a function name, or
9929 an address in the target program. @xref{Specify Location}. The
9930 @code{trace} command defines a tracepoint, which is a point in the
9931 target program where the debugger will briefly stop, collect some
9932 data, and then allow the program to continue. Setting a tracepoint or
9933 changing its actions doesn't take effect until the next @code{tstart}
9934 command, and once a trace experiment is running, further changes will
9935 not have any effect until the next trace experiment starts.
9937 Here are some examples of using the @code{trace} command:
9940 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9942 (@value{GDBP}) @b{trace +2} // 2 lines forward
9944 (@value{GDBP}) @b{trace my_function} // first source line of function
9946 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9948 (@value{GDBP}) @b{trace *0x2117c4} // an address
9952 You can abbreviate @code{trace} as @code{tr}.
9954 @item trace @var{location} if @var{cond}
9955 Set a tracepoint with condition @var{cond}; evaluate the expression
9956 @var{cond} each time the tracepoint is reached, and collect data only
9957 if the value is nonzero---that is, if @var{cond} evaluates as true.
9958 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9959 information on tracepoint conditions.
9961 @item ftrace @var{location} [ if @var{cond} ]
9962 @cindex set fast tracepoint
9963 @cindex fast tracepoints, setting
9965 The @code{ftrace} command sets a fast tracepoint. For targets that
9966 support them, fast tracepoints will use a more efficient but possibly
9967 less general technique to trigger data collection, such as a jump
9968 instruction instead of a trap, or some sort of hardware support. It
9969 may not be possible to create a fast tracepoint at the desired
9970 location, in which case the command will exit with an explanatory
9973 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9976 @item strace @var{location} [ if @var{cond} ]
9977 @cindex set static tracepoint
9978 @cindex static tracepoints, setting
9979 @cindex probe static tracepoint marker
9981 The @code{strace} command sets a static tracepoint. For targets that
9982 support it, setting a static tracepoint probes a static
9983 instrumentation point, or marker, found at @var{location}. It may not
9984 be possible to set a static tracepoint at the desired location, in
9985 which case the command will exit with an explanatory message.
9987 @value{GDBN} handles arguments to @code{strace} exactly as for
9988 @code{trace}, with the addition that the user can also specify
9989 @code{-m @var{marker}} as @var{location}. This probes the marker
9990 identified by the @var{marker} string identifier. This identifier
9991 depends on the static tracepoint backend library your program is
9992 using. You can find all the marker identifiers in the @samp{ID} field
9993 of the @code{info static-tracepoint-markers} command output.
9994 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9995 Markers}. For example, in the following small program using the UST
10001 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10006 the marker id is composed of joining the first two arguments to the
10007 @code{trace_mark} call with a slash, which translates to:
10010 (@value{GDBP}) info static-tracepoint-markers
10011 Cnt Enb ID Address What
10012 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10018 so you may probe the marker above with:
10021 (@value{GDBP}) strace -m ust/bar33
10024 Static tracepoints accept an extra collect action --- @code{collect
10025 $_sdata}. This collects arbitrary user data passed in the probe point
10026 call to the tracing library. In the UST example above, you'll see
10027 that the third argument to @code{trace_mark} is a printf-like format
10028 string. The user data is then the result of running that formating
10029 string against the following arguments. Note that @code{info
10030 static-tracepoint-markers} command output lists that format string in
10031 the @samp{Data:} field.
10033 You can inspect this data when analyzing the trace buffer, by printing
10034 the $_sdata variable like any other variable available to
10035 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10038 @cindex last tracepoint number
10039 @cindex recent tracepoint number
10040 @cindex tracepoint number
10041 The convenience variable @code{$tpnum} records the tracepoint number
10042 of the most recently set tracepoint.
10044 @kindex delete tracepoint
10045 @cindex tracepoint deletion
10046 @item delete tracepoint @r{[}@var{num}@r{]}
10047 Permanently delete one or more tracepoints. With no argument, the
10048 default is to delete all tracepoints. Note that the regular
10049 @code{delete} command can remove tracepoints also.
10054 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10056 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10060 You can abbreviate this command as @code{del tr}.
10063 @node Enable and Disable Tracepoints
10064 @subsection Enable and Disable Tracepoints
10066 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10069 @kindex disable tracepoint
10070 @item disable tracepoint @r{[}@var{num}@r{]}
10071 Disable tracepoint @var{num}, or all tracepoints if no argument
10072 @var{num} is given. A disabled tracepoint will have no effect during
10073 a trace experiment, but it is not forgotten. You can re-enable
10074 a disabled tracepoint using the @code{enable tracepoint} command.
10075 If the command is issued during a trace experiment and the debug target
10076 has support for disabling tracepoints during a trace experiment, then the
10077 change will be effective immediately. Otherwise, it will be applied to the
10078 next trace experiment.
10080 @kindex enable tracepoint
10081 @item enable tracepoint @r{[}@var{num}@r{]}
10082 Enable tracepoint @var{num}, or all tracepoints. If this command is
10083 issued during a trace experiment and the debug target supports enabling
10084 tracepoints during a trace experiment, then the enabled tracepoints will
10085 become effective immediately. Otherwise, they will become effective the
10086 next time a trace experiment is run.
10089 @node Tracepoint Passcounts
10090 @subsection Tracepoint Passcounts
10094 @cindex tracepoint pass count
10095 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10096 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10097 automatically stop a trace experiment. If a tracepoint's passcount is
10098 @var{n}, then the trace experiment will be automatically stopped on
10099 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10100 @var{num} is not specified, the @code{passcount} command sets the
10101 passcount of the most recently defined tracepoint. If no passcount is
10102 given, the trace experiment will run until stopped explicitly by the
10108 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10109 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10111 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10112 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10113 (@value{GDBP}) @b{trace foo}
10114 (@value{GDBP}) @b{pass 3}
10115 (@value{GDBP}) @b{trace bar}
10116 (@value{GDBP}) @b{pass 2}
10117 (@value{GDBP}) @b{trace baz}
10118 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10119 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10120 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10121 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10125 @node Tracepoint Conditions
10126 @subsection Tracepoint Conditions
10127 @cindex conditional tracepoints
10128 @cindex tracepoint conditions
10130 The simplest sort of tracepoint collects data every time your program
10131 reaches a specified place. You can also specify a @dfn{condition} for
10132 a tracepoint. A condition is just a Boolean expression in your
10133 programming language (@pxref{Expressions, ,Expressions}). A
10134 tracepoint with a condition evaluates the expression each time your
10135 program reaches it, and data collection happens only if the condition
10138 Tracepoint conditions can be specified when a tracepoint is set, by
10139 using @samp{if} in the arguments to the @code{trace} command.
10140 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10141 also be set or changed at any time with the @code{condition} command,
10142 just as with breakpoints.
10144 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10145 the conditional expression itself. Instead, @value{GDBN} encodes the
10146 expression into an agent expression (@pxref{Agent Expressions})
10147 suitable for execution on the target, independently of @value{GDBN}.
10148 Global variables become raw memory locations, locals become stack
10149 accesses, and so forth.
10151 For instance, suppose you have a function that is usually called
10152 frequently, but should not be called after an error has occurred. You
10153 could use the following tracepoint command to collect data about calls
10154 of that function that happen while the error code is propagating
10155 through the program; an unconditional tracepoint could end up
10156 collecting thousands of useless trace frames that you would have to
10160 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10163 @node Trace State Variables
10164 @subsection Trace State Variables
10165 @cindex trace state variables
10167 A @dfn{trace state variable} is a special type of variable that is
10168 created and managed by target-side code. The syntax is the same as
10169 that for GDB's convenience variables (a string prefixed with ``$''),
10170 but they are stored on the target. They must be created explicitly,
10171 using a @code{tvariable} command. They are always 64-bit signed
10174 Trace state variables are remembered by @value{GDBN}, and downloaded
10175 to the target along with tracepoint information when the trace
10176 experiment starts. There are no intrinsic limits on the number of
10177 trace state variables, beyond memory limitations of the target.
10179 @cindex convenience variables, and trace state variables
10180 Although trace state variables are managed by the target, you can use
10181 them in print commands and expressions as if they were convenience
10182 variables; @value{GDBN} will get the current value from the target
10183 while the trace experiment is running. Trace state variables share
10184 the same namespace as other ``$'' variables, which means that you
10185 cannot have trace state variables with names like @code{$23} or
10186 @code{$pc}, nor can you have a trace state variable and a convenience
10187 variable with the same name.
10191 @item tvariable $@var{name} [ = @var{expression} ]
10193 The @code{tvariable} command creates a new trace state variable named
10194 @code{$@var{name}}, and optionally gives it an initial value of
10195 @var{expression}. @var{expression} is evaluated when this command is
10196 entered; the result will be converted to an integer if possible,
10197 otherwise @value{GDBN} will report an error. A subsequent
10198 @code{tvariable} command specifying the same name does not create a
10199 variable, but instead assigns the supplied initial value to the
10200 existing variable of that name, overwriting any previous initial
10201 value. The default initial value is 0.
10203 @item info tvariables
10204 @kindex info tvariables
10205 List all the trace state variables along with their initial values.
10206 Their current values may also be displayed, if the trace experiment is
10209 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10210 @kindex delete tvariable
10211 Delete the given trace state variables, or all of them if no arguments
10216 @node Tracepoint Actions
10217 @subsection Tracepoint Action Lists
10221 @cindex tracepoint actions
10222 @item actions @r{[}@var{num}@r{]}
10223 This command will prompt for a list of actions to be taken when the
10224 tracepoint is hit. If the tracepoint number @var{num} is not
10225 specified, this command sets the actions for the one that was most
10226 recently defined (so that you can define a tracepoint and then say
10227 @code{actions} without bothering about its number). You specify the
10228 actions themselves on the following lines, one action at a time, and
10229 terminate the actions list with a line containing just @code{end}. So
10230 far, the only defined actions are @code{collect}, @code{teval}, and
10231 @code{while-stepping}.
10233 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10234 Commands, ,Breakpoint Command Lists}), except that only the defined
10235 actions are allowed; any other @value{GDBN} command is rejected.
10237 @cindex remove actions from a tracepoint
10238 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10239 and follow it immediately with @samp{end}.
10242 (@value{GDBP}) @b{collect @var{data}} // collect some data
10244 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10246 (@value{GDBP}) @b{end} // signals the end of actions.
10249 In the following example, the action list begins with @code{collect}
10250 commands indicating the things to be collected when the tracepoint is
10251 hit. Then, in order to single-step and collect additional data
10252 following the tracepoint, a @code{while-stepping} command is used,
10253 followed by the list of things to be collected after each step in a
10254 sequence of single steps. The @code{while-stepping} command is
10255 terminated by its own separate @code{end} command. Lastly, the action
10256 list is terminated by an @code{end} command.
10259 (@value{GDBP}) @b{trace foo}
10260 (@value{GDBP}) @b{actions}
10261 Enter actions for tracepoint 1, one per line:
10264 > while-stepping 12
10265 > collect $pc, arr[i]
10270 @kindex collect @r{(tracepoints)}
10271 @item collect @var{expr1}, @var{expr2}, @dots{}
10272 Collect values of the given expressions when the tracepoint is hit.
10273 This command accepts a comma-separated list of any valid expressions.
10274 In addition to global, static, or local variables, the following
10275 special arguments are supported:
10279 Collect all registers.
10282 Collect all function arguments.
10285 Collect all local variables.
10288 @vindex $_sdata@r{, collect}
10289 Collect static tracepoint marker specific data. Only available for
10290 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10291 Lists}. On the UST static tracepoints library backend, an
10292 instrumentation point resembles a @code{printf} function call. The
10293 tracing library is able to collect user specified data formatted to a
10294 character string using the format provided by the programmer that
10295 instrumented the program. Other backends have similar mechanisms.
10296 Here's an example of a UST marker call:
10299 const char master_name[] = "$your_name";
10300 trace_mark(channel1, marker1, "hello %s", master_name)
10303 In this case, collecting @code{$_sdata} collects the string
10304 @samp{hello $yourname}. When analyzing the trace buffer, you can
10305 inspect @samp{$_sdata} like any other variable available to
10309 You can give several consecutive @code{collect} commands, each one
10310 with a single argument, or one @code{collect} command with several
10311 arguments separated by commas; the effect is the same.
10313 The command @code{info scope} (@pxref{Symbols, info scope}) is
10314 particularly useful for figuring out what data to collect.
10316 @kindex teval @r{(tracepoints)}
10317 @item teval @var{expr1}, @var{expr2}, @dots{}
10318 Evaluate the given expressions when the tracepoint is hit. This
10319 command accepts a comma-separated list of expressions. The results
10320 are discarded, so this is mainly useful for assigning values to trace
10321 state variables (@pxref{Trace State Variables}) without adding those
10322 values to the trace buffer, as would be the case if the @code{collect}
10325 @kindex while-stepping @r{(tracepoints)}
10326 @item while-stepping @var{n}
10327 Perform @var{n} single-step instruction traces after the tracepoint,
10328 collecting new data after each step. The @code{while-stepping}
10329 command is followed by the list of what to collect while stepping
10330 (followed by its own @code{end} command):
10333 > while-stepping 12
10334 > collect $regs, myglobal
10340 Note that @code{$pc} is not automatically collected by
10341 @code{while-stepping}; you need to explicitly collect that register if
10342 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10345 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10346 @kindex set default-collect
10347 @cindex default collection action
10348 This variable is a list of expressions to collect at each tracepoint
10349 hit. It is effectively an additional @code{collect} action prepended
10350 to every tracepoint action list. The expressions are parsed
10351 individually for each tracepoint, so for instance a variable named
10352 @code{xyz} may be interpreted as a global for one tracepoint, and a
10353 local for another, as appropriate to the tracepoint's location.
10355 @item show default-collect
10356 @kindex show default-collect
10357 Show the list of expressions that are collected by default at each
10362 @node Listing Tracepoints
10363 @subsection Listing Tracepoints
10366 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10367 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10368 @cindex information about tracepoints
10369 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10370 Display information about the tracepoint @var{num}. If you don't
10371 specify a tracepoint number, displays information about all the
10372 tracepoints defined so far. The format is similar to that used for
10373 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10374 command, simply restricting itself to tracepoints.
10376 A tracepoint's listing may include additional information specific to
10381 its passcount as given by the @code{passcount @var{n}} command
10385 (@value{GDBP}) @b{info trace}
10386 Num Type Disp Enb Address What
10387 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10389 collect globfoo, $regs
10398 This command can be abbreviated @code{info tp}.
10401 @node Listing Static Tracepoint Markers
10402 @subsection Listing Static Tracepoint Markers
10405 @kindex info static-tracepoint-markers
10406 @cindex information about static tracepoint markers
10407 @item info static-tracepoint-markers
10408 Display information about all static tracepoint markers defined in the
10411 For each marker, the following columns are printed:
10415 An incrementing counter, output to help readability. This is not a
10418 The marker ID, as reported by the target.
10419 @item Enabled or Disabled
10420 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10421 that are not enabled.
10423 Where the marker is in your program, as a memory address.
10425 Where the marker is in the source for your program, as a file and line
10426 number. If the debug information included in the program does not
10427 allow @value{GDBN} to locate the source of the marker, this column
10428 will be left blank.
10432 In addition, the following information may be printed for each marker:
10436 User data passed to the tracing library by the marker call. In the
10437 UST backend, this is the format string passed as argument to the
10439 @item Static tracepoints probing the marker
10440 The list of static tracepoints attached to the marker.
10444 (@value{GDBP}) info static-tracepoint-markers
10445 Cnt ID Enb Address What
10446 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10447 Data: number1 %d number2 %d
10448 Probed by static tracepoints: #2
10449 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10455 @node Starting and Stopping Trace Experiments
10456 @subsection Starting and Stopping Trace Experiments
10460 @cindex start a new trace experiment
10461 @cindex collected data discarded
10463 This command takes no arguments. It starts the trace experiment, and
10464 begins collecting data. This has the side effect of discarding all
10465 the data collected in the trace buffer during the previous trace
10469 @cindex stop a running trace experiment
10471 This command takes no arguments. It ends the trace experiment, and
10472 stops collecting data.
10474 @strong{Note}: a trace experiment and data collection may stop
10475 automatically if any tracepoint's passcount is reached
10476 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10479 @cindex status of trace data collection
10480 @cindex trace experiment, status of
10482 This command displays the status of the current trace data
10486 Here is an example of the commands we described so far:
10489 (@value{GDBP}) @b{trace gdb_c_test}
10490 (@value{GDBP}) @b{actions}
10491 Enter actions for tracepoint #1, one per line.
10492 > collect $regs,$locals,$args
10493 > while-stepping 11
10497 (@value{GDBP}) @b{tstart}
10498 [time passes @dots{}]
10499 (@value{GDBP}) @b{tstop}
10502 @anchor{disconnected tracing}
10503 @cindex disconnected tracing
10504 You can choose to continue running the trace experiment even if
10505 @value{GDBN} disconnects from the target, voluntarily or
10506 involuntarily. For commands such as @code{detach}, the debugger will
10507 ask what you want to do with the trace. But for unexpected
10508 terminations (@value{GDBN} crash, network outage), it would be
10509 unfortunate to lose hard-won trace data, so the variable
10510 @code{disconnected-tracing} lets you decide whether the trace should
10511 continue running without @value{GDBN}.
10514 @item set disconnected-tracing on
10515 @itemx set disconnected-tracing off
10516 @kindex set disconnected-tracing
10517 Choose whether a tracing run should continue to run if @value{GDBN}
10518 has disconnected from the target. Note that @code{detach} or
10519 @code{quit} will ask you directly what to do about a running trace no
10520 matter what this variable's setting, so the variable is mainly useful
10521 for handling unexpected situations, such as loss of the network.
10523 @item show disconnected-tracing
10524 @kindex show disconnected-tracing
10525 Show the current choice for disconnected tracing.
10529 When you reconnect to the target, the trace experiment may or may not
10530 still be running; it might have filled the trace buffer in the
10531 meantime, or stopped for one of the other reasons. If it is running,
10532 it will continue after reconnection.
10534 Upon reconnection, the target will upload information about the
10535 tracepoints in effect. @value{GDBN} will then compare that
10536 information to the set of tracepoints currently defined, and attempt
10537 to match them up, allowing for the possibility that the numbers may
10538 have changed due to creation and deletion in the meantime. If one of
10539 the target's tracepoints does not match any in @value{GDBN}, the
10540 debugger will create a new tracepoint, so that you have a number with
10541 which to specify that tracepoint. This matching-up process is
10542 necessarily heuristic, and it may result in useless tracepoints being
10543 created; you may simply delete them if they are of no use.
10545 @cindex circular trace buffer
10546 If your target agent supports a @dfn{circular trace buffer}, then you
10547 can run a trace experiment indefinitely without filling the trace
10548 buffer; when space runs out, the agent deletes already-collected trace
10549 frames, oldest first, until there is enough room to continue
10550 collecting. This is especially useful if your tracepoints are being
10551 hit too often, and your trace gets terminated prematurely because the
10552 buffer is full. To ask for a circular trace buffer, simply set
10553 @samp{circular-trace-buffer} to on. You can set this at any time,
10554 including during tracing; if the agent can do it, it will change
10555 buffer handling on the fly, otherwise it will not take effect until
10559 @item set circular-trace-buffer on
10560 @itemx set circular-trace-buffer off
10561 @kindex set circular-trace-buffer
10562 Choose whether a tracing run should use a linear or circular buffer
10563 for trace data. A linear buffer will not lose any trace data, but may
10564 fill up prematurely, while a circular buffer will discard old trace
10565 data, but it will have always room for the latest tracepoint hits.
10567 @item show circular-trace-buffer
10568 @kindex show circular-trace-buffer
10569 Show the current choice for the trace buffer. Note that this may not
10570 match the agent's current buffer handling, nor is it guaranteed to
10571 match the setting that might have been in effect during a past run,
10572 for instance if you are looking at frames from a trace file.
10576 @node Tracepoint Restrictions
10577 @subsection Tracepoint Restrictions
10579 @cindex tracepoint restrictions
10580 There are a number of restrictions on the use of tracepoints. As
10581 described above, tracepoint data gathering occurs on the target
10582 without interaction from @value{GDBN}. Thus the full capabilities of
10583 the debugger are not available during data gathering, and then at data
10584 examination time, you will be limited by only having what was
10585 collected. The following items describe some common problems, but it
10586 is not exhaustive, and you may run into additional difficulties not
10592 Tracepoint expressions are intended to gather objects (lvalues). Thus
10593 the full flexibility of GDB's expression evaluator is not available.
10594 You cannot call functions, cast objects to aggregate types, access
10595 convenience variables or modify values (except by assignment to trace
10596 state variables). Some language features may implicitly call
10597 functions (for instance Objective-C fields with accessors), and therefore
10598 cannot be collected either.
10601 Collection of local variables, either individually or in bulk with
10602 @code{$locals} or @code{$args}, during @code{while-stepping} may
10603 behave erratically. The stepping action may enter a new scope (for
10604 instance by stepping into a function), or the location of the variable
10605 may change (for instance it is loaded into a register). The
10606 tracepoint data recorded uses the location information for the
10607 variables that is correct for the tracepoint location. When the
10608 tracepoint is created, it is not possible, in general, to determine
10609 where the steps of a @code{while-stepping} sequence will advance the
10610 program---particularly if a conditional branch is stepped.
10613 Collection of an incompletely-initialized or partially-destroyed object
10614 may result in something that @value{GDBN} cannot display, or displays
10615 in a misleading way.
10618 When @value{GDBN} displays a pointer to character it automatically
10619 dereferences the pointer to also display characters of the string
10620 being pointed to. However, collecting the pointer during tracing does
10621 not automatically collect the string. You need to explicitly
10622 dereference the pointer and provide size information if you want to
10623 collect not only the pointer, but the memory pointed to. For example,
10624 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10628 It is not possible to collect a complete stack backtrace at a
10629 tracepoint. Instead, you may collect the registers and a few hundred
10630 bytes from the stack pointer with something like @code{*$esp@@300}
10631 (adjust to use the name of the actual stack pointer register on your
10632 target architecture, and the amount of stack you wish to capture).
10633 Then the @code{backtrace} command will show a partial backtrace when
10634 using a trace frame. The number of stack frames that can be examined
10635 depends on the sizes of the frames in the collected stack. Note that
10636 if you ask for a block so large that it goes past the bottom of the
10637 stack, the target agent may report an error trying to read from an
10641 If you do not collect registers at a tracepoint, @value{GDBN} can
10642 infer that the value of @code{$pc} must be the same as the address of
10643 the tracepoint and use that when you are looking at a trace frame
10644 for that tracepoint. However, this cannot work if the tracepoint has
10645 multiple locations (for instance if it was set in a function that was
10646 inlined), or if it has a @code{while-stepping} loop. In those cases
10647 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10652 @node Analyze Collected Data
10653 @section Using the Collected Data
10655 After the tracepoint experiment ends, you use @value{GDBN} commands
10656 for examining the trace data. The basic idea is that each tracepoint
10657 collects a trace @dfn{snapshot} every time it is hit and another
10658 snapshot every time it single-steps. All these snapshots are
10659 consecutively numbered from zero and go into a buffer, and you can
10660 examine them later. The way you examine them is to @dfn{focus} on a
10661 specific trace snapshot. When the remote stub is focused on a trace
10662 snapshot, it will respond to all @value{GDBN} requests for memory and
10663 registers by reading from the buffer which belongs to that snapshot,
10664 rather than from @emph{real} memory or registers of the program being
10665 debugged. This means that @strong{all} @value{GDBN} commands
10666 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10667 behave as if we were currently debugging the program state as it was
10668 when the tracepoint occurred. Any requests for data that are not in
10669 the buffer will fail.
10672 * tfind:: How to select a trace snapshot
10673 * tdump:: How to display all data for a snapshot
10674 * save tracepoints:: How to save tracepoints for a future run
10678 @subsection @code{tfind @var{n}}
10681 @cindex select trace snapshot
10682 @cindex find trace snapshot
10683 The basic command for selecting a trace snapshot from the buffer is
10684 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10685 counting from zero. If no argument @var{n} is given, the next
10686 snapshot is selected.
10688 Here are the various forms of using the @code{tfind} command.
10692 Find the first snapshot in the buffer. This is a synonym for
10693 @code{tfind 0} (since 0 is the number of the first snapshot).
10696 Stop debugging trace snapshots, resume @emph{live} debugging.
10699 Same as @samp{tfind none}.
10702 No argument means find the next trace snapshot.
10705 Find the previous trace snapshot before the current one. This permits
10706 retracing earlier steps.
10708 @item tfind tracepoint @var{num}
10709 Find the next snapshot associated with tracepoint @var{num}. Search
10710 proceeds forward from the last examined trace snapshot. If no
10711 argument @var{num} is given, it means find the next snapshot collected
10712 for the same tracepoint as the current snapshot.
10714 @item tfind pc @var{addr}
10715 Find the next snapshot associated with the value @var{addr} of the
10716 program counter. Search proceeds forward from the last examined trace
10717 snapshot. If no argument @var{addr} is given, it means find the next
10718 snapshot with the same value of PC as the current snapshot.
10720 @item tfind outside @var{addr1}, @var{addr2}
10721 Find the next snapshot whose PC is outside the given range of
10722 addresses (exclusive).
10724 @item tfind range @var{addr1}, @var{addr2}
10725 Find the next snapshot whose PC is between @var{addr1} and
10726 @var{addr2} (inclusive).
10728 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10729 Find the next snapshot associated with the source line @var{n}. If
10730 the optional argument @var{file} is given, refer to line @var{n} in
10731 that source file. Search proceeds forward from the last examined
10732 trace snapshot. If no argument @var{n} is given, it means find the
10733 next line other than the one currently being examined; thus saying
10734 @code{tfind line} repeatedly can appear to have the same effect as
10735 stepping from line to line in a @emph{live} debugging session.
10738 The default arguments for the @code{tfind} commands are specifically
10739 designed to make it easy to scan through the trace buffer. For
10740 instance, @code{tfind} with no argument selects the next trace
10741 snapshot, and @code{tfind -} with no argument selects the previous
10742 trace snapshot. So, by giving one @code{tfind} command, and then
10743 simply hitting @key{RET} repeatedly you can examine all the trace
10744 snapshots in order. Or, by saying @code{tfind -} and then hitting
10745 @key{RET} repeatedly you can examine the snapshots in reverse order.
10746 The @code{tfind line} command with no argument selects the snapshot
10747 for the next source line executed. The @code{tfind pc} command with
10748 no argument selects the next snapshot with the same program counter
10749 (PC) as the current frame. The @code{tfind tracepoint} command with
10750 no argument selects the next trace snapshot collected by the same
10751 tracepoint as the current one.
10753 In addition to letting you scan through the trace buffer manually,
10754 these commands make it easy to construct @value{GDBN} scripts that
10755 scan through the trace buffer and print out whatever collected data
10756 you are interested in. Thus, if we want to examine the PC, FP, and SP
10757 registers from each trace frame in the buffer, we can say this:
10760 (@value{GDBP}) @b{tfind start}
10761 (@value{GDBP}) @b{while ($trace_frame != -1)}
10762 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10763 $trace_frame, $pc, $sp, $fp
10767 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10768 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10769 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10770 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10771 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10772 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10773 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10774 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10775 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10776 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10777 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10780 Or, if we want to examine the variable @code{X} at each source line in
10784 (@value{GDBP}) @b{tfind start}
10785 (@value{GDBP}) @b{while ($trace_frame != -1)}
10786 > printf "Frame %d, X == %d\n", $trace_frame, X
10796 @subsection @code{tdump}
10798 @cindex dump all data collected at tracepoint
10799 @cindex tracepoint data, display
10801 This command takes no arguments. It prints all the data collected at
10802 the current trace snapshot.
10805 (@value{GDBP}) @b{trace 444}
10806 (@value{GDBP}) @b{actions}
10807 Enter actions for tracepoint #2, one per line:
10808 > collect $regs, $locals, $args, gdb_long_test
10811 (@value{GDBP}) @b{tstart}
10813 (@value{GDBP}) @b{tfind line 444}
10814 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10816 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10818 (@value{GDBP}) @b{tdump}
10819 Data collected at tracepoint 2, trace frame 1:
10820 d0 0xc4aa0085 -995491707
10824 d4 0x71aea3d 119204413
10827 d7 0x380035 3670069
10828 a0 0x19e24a 1696330
10829 a1 0x3000668 50333288
10831 a3 0x322000 3284992
10832 a4 0x3000698 50333336
10833 a5 0x1ad3cc 1758156
10834 fp 0x30bf3c 0x30bf3c
10835 sp 0x30bf34 0x30bf34
10837 pc 0x20b2c8 0x20b2c8
10841 p = 0x20e5b4 "gdb-test"
10848 gdb_long_test = 17 '\021'
10853 @code{tdump} works by scanning the tracepoint's current collection
10854 actions and printing the value of each expression listed. So
10855 @code{tdump} can fail, if after a run, you change the tracepoint's
10856 actions to mention variables that were not collected during the run.
10858 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10859 uses the collected value of @code{$pc} to distinguish between trace
10860 frames that were collected at the tracepoint hit, and frames that were
10861 collected while stepping. This allows it to correctly choose whether
10862 to display the basic list of collections, or the collections from the
10863 body of the while-stepping loop. However, if @code{$pc} was not collected,
10864 then @code{tdump} will always attempt to dump using the basic collection
10865 list, and may fail if a while-stepping frame does not include all the
10866 same data that is collected at the tracepoint hit.
10867 @c This is getting pretty arcane, example would be good.
10869 @node save tracepoints
10870 @subsection @code{save tracepoints @var{filename}}
10871 @kindex save tracepoints
10872 @kindex save-tracepoints
10873 @cindex save tracepoints for future sessions
10875 This command saves all current tracepoint definitions together with
10876 their actions and passcounts, into a file @file{@var{filename}}
10877 suitable for use in a later debugging session. To read the saved
10878 tracepoint definitions, use the @code{source} command (@pxref{Command
10879 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10880 alias for @w{@code{save tracepoints}}
10882 @node Tracepoint Variables
10883 @section Convenience Variables for Tracepoints
10884 @cindex tracepoint variables
10885 @cindex convenience variables for tracepoints
10888 @vindex $trace_frame
10889 @item (int) $trace_frame
10890 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10891 snapshot is selected.
10893 @vindex $tracepoint
10894 @item (int) $tracepoint
10895 The tracepoint for the current trace snapshot.
10897 @vindex $trace_line
10898 @item (int) $trace_line
10899 The line number for the current trace snapshot.
10901 @vindex $trace_file
10902 @item (char []) $trace_file
10903 The source file for the current trace snapshot.
10905 @vindex $trace_func
10906 @item (char []) $trace_func
10907 The name of the function containing @code{$tracepoint}.
10910 Note: @code{$trace_file} is not suitable for use in @code{printf},
10911 use @code{output} instead.
10913 Here's a simple example of using these convenience variables for
10914 stepping through all the trace snapshots and printing some of their
10915 data. Note that these are not the same as trace state variables,
10916 which are managed by the target.
10919 (@value{GDBP}) @b{tfind start}
10921 (@value{GDBP}) @b{while $trace_frame != -1}
10922 > output $trace_file
10923 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10929 @section Using Trace Files
10930 @cindex trace files
10932 In some situations, the target running a trace experiment may no
10933 longer be available; perhaps it crashed, or the hardware was needed
10934 for a different activity. To handle these cases, you can arrange to
10935 dump the trace data into a file, and later use that file as a source
10936 of trace data, via the @code{target tfile} command.
10941 @item tsave [ -r ] @var{filename}
10942 Save the trace data to @var{filename}. By default, this command
10943 assumes that @var{filename} refers to the host filesystem, so if
10944 necessary @value{GDBN} will copy raw trace data up from the target and
10945 then save it. If the target supports it, you can also supply the
10946 optional argument @code{-r} (``remote'') to direct the target to save
10947 the data directly into @var{filename} in its own filesystem, which may be
10948 more efficient if the trace buffer is very large. (Note, however, that
10949 @code{target tfile} can only read from files accessible to the host.)
10951 @kindex target tfile
10953 @item target tfile @var{filename}
10954 Use the file named @var{filename} as a source of trace data. Commands
10955 that examine data work as they do with a live target, but it is not
10956 possible to run any new trace experiments. @code{tstatus} will report
10957 the state of the trace run at the moment the data was saved, as well
10958 as the current trace frame you are examining. @var{filename} must be
10959 on a filesystem accessible to the host.
10964 @chapter Debugging Programs That Use Overlays
10967 If your program is too large to fit completely in your target system's
10968 memory, you can sometimes use @dfn{overlays} to work around this
10969 problem. @value{GDBN} provides some support for debugging programs that
10973 * How Overlays Work:: A general explanation of overlays.
10974 * Overlay Commands:: Managing overlays in @value{GDBN}.
10975 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10976 mapped by asking the inferior.
10977 * Overlay Sample Program:: A sample program using overlays.
10980 @node How Overlays Work
10981 @section How Overlays Work
10982 @cindex mapped overlays
10983 @cindex unmapped overlays
10984 @cindex load address, overlay's
10985 @cindex mapped address
10986 @cindex overlay area
10988 Suppose you have a computer whose instruction address space is only 64
10989 kilobytes long, but which has much more memory which can be accessed by
10990 other means: special instructions, segment registers, or memory
10991 management hardware, for example. Suppose further that you want to
10992 adapt a program which is larger than 64 kilobytes to run on this system.
10994 One solution is to identify modules of your program which are relatively
10995 independent, and need not call each other directly; call these modules
10996 @dfn{overlays}. Separate the overlays from the main program, and place
10997 their machine code in the larger memory. Place your main program in
10998 instruction memory, but leave at least enough space there to hold the
10999 largest overlay as well.
11001 Now, to call a function located in an overlay, you must first copy that
11002 overlay's machine code from the large memory into the space set aside
11003 for it in the instruction memory, and then jump to its entry point
11006 @c NB: In the below the mapped area's size is greater or equal to the
11007 @c size of all overlays. This is intentional to remind the developer
11008 @c that overlays don't necessarily need to be the same size.
11012 Data Instruction Larger
11013 Address Space Address Space Address Space
11014 +-----------+ +-----------+ +-----------+
11016 +-----------+ +-----------+ +-----------+<-- overlay 1
11017 | program | | main | .----| overlay 1 | load address
11018 | variables | | program | | +-----------+
11019 | and heap | | | | | |
11020 +-----------+ | | | +-----------+<-- overlay 2
11021 | | +-----------+ | | | load address
11022 +-----------+ | | | .-| overlay 2 |
11024 mapped --->+-----------+ | | +-----------+
11025 address | | | | | |
11026 | overlay | <-' | | |
11027 | area | <---' +-----------+<-- overlay 3
11028 | | <---. | | load address
11029 +-----------+ `--| overlay 3 |
11036 @anchor{A code overlay}A code overlay
11040 The diagram (@pxref{A code overlay}) shows a system with separate data
11041 and instruction address spaces. To map an overlay, the program copies
11042 its code from the larger address space to the instruction address space.
11043 Since the overlays shown here all use the same mapped address, only one
11044 may be mapped at a time. For a system with a single address space for
11045 data and instructions, the diagram would be similar, except that the
11046 program variables and heap would share an address space with the main
11047 program and the overlay area.
11049 An overlay loaded into instruction memory and ready for use is called a
11050 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11051 instruction memory. An overlay not present (or only partially present)
11052 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11053 is its address in the larger memory. The mapped address is also called
11054 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11055 called the @dfn{load memory address}, or @dfn{LMA}.
11057 Unfortunately, overlays are not a completely transparent way to adapt a
11058 program to limited instruction memory. They introduce a new set of
11059 global constraints you must keep in mind as you design your program:
11064 Before calling or returning to a function in an overlay, your program
11065 must make sure that overlay is actually mapped. Otherwise, the call or
11066 return will transfer control to the right address, but in the wrong
11067 overlay, and your program will probably crash.
11070 If the process of mapping an overlay is expensive on your system, you
11071 will need to choose your overlays carefully to minimize their effect on
11072 your program's performance.
11075 The executable file you load onto your system must contain each
11076 overlay's instructions, appearing at the overlay's load address, not its
11077 mapped address. However, each overlay's instructions must be relocated
11078 and its symbols defined as if the overlay were at its mapped address.
11079 You can use GNU linker scripts to specify different load and relocation
11080 addresses for pieces of your program; see @ref{Overlay Description,,,
11081 ld.info, Using ld: the GNU linker}.
11084 The procedure for loading executable files onto your system must be able
11085 to load their contents into the larger address space as well as the
11086 instruction and data spaces.
11090 The overlay system described above is rather simple, and could be
11091 improved in many ways:
11096 If your system has suitable bank switch registers or memory management
11097 hardware, you could use those facilities to make an overlay's load area
11098 contents simply appear at their mapped address in instruction space.
11099 This would probably be faster than copying the overlay to its mapped
11100 area in the usual way.
11103 If your overlays are small enough, you could set aside more than one
11104 overlay area, and have more than one overlay mapped at a time.
11107 You can use overlays to manage data, as well as instructions. In
11108 general, data overlays are even less transparent to your design than
11109 code overlays: whereas code overlays only require care when you call or
11110 return to functions, data overlays require care every time you access
11111 the data. Also, if you change the contents of a data overlay, you
11112 must copy its contents back out to its load address before you can copy a
11113 different data overlay into the same mapped area.
11118 @node Overlay Commands
11119 @section Overlay Commands
11121 To use @value{GDBN}'s overlay support, each overlay in your program must
11122 correspond to a separate section of the executable file. The section's
11123 virtual memory address and load memory address must be the overlay's
11124 mapped and load addresses. Identifying overlays with sections allows
11125 @value{GDBN} to determine the appropriate address of a function or
11126 variable, depending on whether the overlay is mapped or not.
11128 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11129 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11134 Disable @value{GDBN}'s overlay support. When overlay support is
11135 disabled, @value{GDBN} assumes that all functions and variables are
11136 always present at their mapped addresses. By default, @value{GDBN}'s
11137 overlay support is disabled.
11139 @item overlay manual
11140 @cindex manual overlay debugging
11141 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11142 relies on you to tell it which overlays are mapped, and which are not,
11143 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11144 commands described below.
11146 @item overlay map-overlay @var{overlay}
11147 @itemx overlay map @var{overlay}
11148 @cindex map an overlay
11149 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11150 be the name of the object file section containing the overlay. When an
11151 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11152 functions and variables at their mapped addresses. @value{GDBN} assumes
11153 that any other overlays whose mapped ranges overlap that of
11154 @var{overlay} are now unmapped.
11156 @item overlay unmap-overlay @var{overlay}
11157 @itemx overlay unmap @var{overlay}
11158 @cindex unmap an overlay
11159 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11160 must be the name of the object file section containing the overlay.
11161 When an overlay is unmapped, @value{GDBN} assumes it can find the
11162 overlay's functions and variables at their load addresses.
11165 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11166 consults a data structure the overlay manager maintains in the inferior
11167 to see which overlays are mapped. For details, see @ref{Automatic
11168 Overlay Debugging}.
11170 @item overlay load-target
11171 @itemx overlay load
11172 @cindex reloading the overlay table
11173 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11174 re-reads the table @value{GDBN} automatically each time the inferior
11175 stops, so this command should only be necessary if you have changed the
11176 overlay mapping yourself using @value{GDBN}. This command is only
11177 useful when using automatic overlay debugging.
11179 @item overlay list-overlays
11180 @itemx overlay list
11181 @cindex listing mapped overlays
11182 Display a list of the overlays currently mapped, along with their mapped
11183 addresses, load addresses, and sizes.
11187 Normally, when @value{GDBN} prints a code address, it includes the name
11188 of the function the address falls in:
11191 (@value{GDBP}) print main
11192 $3 = @{int ()@} 0x11a0 <main>
11195 When overlay debugging is enabled, @value{GDBN} recognizes code in
11196 unmapped overlays, and prints the names of unmapped functions with
11197 asterisks around them. For example, if @code{foo} is a function in an
11198 unmapped overlay, @value{GDBN} prints it this way:
11201 (@value{GDBP}) overlay list
11202 No sections are mapped.
11203 (@value{GDBP}) print foo
11204 $5 = @{int (int)@} 0x100000 <*foo*>
11207 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11211 (@value{GDBP}) overlay list
11212 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11213 mapped at 0x1016 - 0x104a
11214 (@value{GDBP}) print foo
11215 $6 = @{int (int)@} 0x1016 <foo>
11218 When overlay debugging is enabled, @value{GDBN} can find the correct
11219 address for functions and variables in an overlay, whether or not the
11220 overlay is mapped. This allows most @value{GDBN} commands, like
11221 @code{break} and @code{disassemble}, to work normally, even on unmapped
11222 code. However, @value{GDBN}'s breakpoint support has some limitations:
11226 @cindex breakpoints in overlays
11227 @cindex overlays, setting breakpoints in
11228 You can set breakpoints in functions in unmapped overlays, as long as
11229 @value{GDBN} can write to the overlay at its load address.
11231 @value{GDBN} can not set hardware or simulator-based breakpoints in
11232 unmapped overlays. However, if you set a breakpoint at the end of your
11233 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11234 you are using manual overlay management), @value{GDBN} will re-set its
11235 breakpoints properly.
11239 @node Automatic Overlay Debugging
11240 @section Automatic Overlay Debugging
11241 @cindex automatic overlay debugging
11243 @value{GDBN} can automatically track which overlays are mapped and which
11244 are not, given some simple co-operation from the overlay manager in the
11245 inferior. If you enable automatic overlay debugging with the
11246 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11247 looks in the inferior's memory for certain variables describing the
11248 current state of the overlays.
11250 Here are the variables your overlay manager must define to support
11251 @value{GDBN}'s automatic overlay debugging:
11255 @item @code{_ovly_table}:
11256 This variable must be an array of the following structures:
11261 /* The overlay's mapped address. */
11264 /* The size of the overlay, in bytes. */
11265 unsigned long size;
11267 /* The overlay's load address. */
11270 /* Non-zero if the overlay is currently mapped;
11272 unsigned long mapped;
11276 @item @code{_novlys}:
11277 This variable must be a four-byte signed integer, holding the total
11278 number of elements in @code{_ovly_table}.
11282 To decide whether a particular overlay is mapped or not, @value{GDBN}
11283 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11284 @code{lma} members equal the VMA and LMA of the overlay's section in the
11285 executable file. When @value{GDBN} finds a matching entry, it consults
11286 the entry's @code{mapped} member to determine whether the overlay is
11289 In addition, your overlay manager may define a function called
11290 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11291 will silently set a breakpoint there. If the overlay manager then
11292 calls this function whenever it has changed the overlay table, this
11293 will enable @value{GDBN} to accurately keep track of which overlays
11294 are in program memory, and update any breakpoints that may be set
11295 in overlays. This will allow breakpoints to work even if the
11296 overlays are kept in ROM or other non-writable memory while they
11297 are not being executed.
11299 @node Overlay Sample Program
11300 @section Overlay Sample Program
11301 @cindex overlay example program
11303 When linking a program which uses overlays, you must place the overlays
11304 at their load addresses, while relocating them to run at their mapped
11305 addresses. To do this, you must write a linker script (@pxref{Overlay
11306 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11307 since linker scripts are specific to a particular host system, target
11308 architecture, and target memory layout, this manual cannot provide
11309 portable sample code demonstrating @value{GDBN}'s overlay support.
11311 However, the @value{GDBN} source distribution does contain an overlaid
11312 program, with linker scripts for a few systems, as part of its test
11313 suite. The program consists of the following files from
11314 @file{gdb/testsuite/gdb.base}:
11318 The main program file.
11320 A simple overlay manager, used by @file{overlays.c}.
11325 Overlay modules, loaded and used by @file{overlays.c}.
11328 Linker scripts for linking the test program on the @code{d10v-elf}
11329 and @code{m32r-elf} targets.
11332 You can build the test program using the @code{d10v-elf} GCC
11333 cross-compiler like this:
11336 $ d10v-elf-gcc -g -c overlays.c
11337 $ d10v-elf-gcc -g -c ovlymgr.c
11338 $ d10v-elf-gcc -g -c foo.c
11339 $ d10v-elf-gcc -g -c bar.c
11340 $ d10v-elf-gcc -g -c baz.c
11341 $ d10v-elf-gcc -g -c grbx.c
11342 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11343 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11346 The build process is identical for any other architecture, except that
11347 you must substitute the appropriate compiler and linker script for the
11348 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11352 @chapter Using @value{GDBN} with Different Languages
11355 Although programming languages generally have common aspects, they are
11356 rarely expressed in the same manner. For instance, in ANSI C,
11357 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11358 Modula-2, it is accomplished by @code{p^}. Values can also be
11359 represented (and displayed) differently. Hex numbers in C appear as
11360 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11362 @cindex working language
11363 Language-specific information is built into @value{GDBN} for some languages,
11364 allowing you to express operations like the above in your program's
11365 native language, and allowing @value{GDBN} to output values in a manner
11366 consistent with the syntax of your program's native language. The
11367 language you use to build expressions is called the @dfn{working
11371 * Setting:: Switching between source languages
11372 * Show:: Displaying the language
11373 * Checks:: Type and range checks
11374 * Supported Languages:: Supported languages
11375 * Unsupported Languages:: Unsupported languages
11379 @section Switching Between Source Languages
11381 There are two ways to control the working language---either have @value{GDBN}
11382 set it automatically, or select it manually yourself. You can use the
11383 @code{set language} command for either purpose. On startup, @value{GDBN}
11384 defaults to setting the language automatically. The working language is
11385 used to determine how expressions you type are interpreted, how values
11388 In addition to the working language, every source file that
11389 @value{GDBN} knows about has its own working language. For some object
11390 file formats, the compiler might indicate which language a particular
11391 source file is in. However, most of the time @value{GDBN} infers the
11392 language from the name of the file. The language of a source file
11393 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11394 show each frame appropriately for its own language. There is no way to
11395 set the language of a source file from within @value{GDBN}, but you can
11396 set the language associated with a filename extension. @xref{Show, ,
11397 Displaying the Language}.
11399 This is most commonly a problem when you use a program, such
11400 as @code{cfront} or @code{f2c}, that generates C but is written in
11401 another language. In that case, make the
11402 program use @code{#line} directives in its C output; that way
11403 @value{GDBN} will know the correct language of the source code of the original
11404 program, and will display that source code, not the generated C code.
11407 * Filenames:: Filename extensions and languages.
11408 * Manually:: Setting the working language manually
11409 * Automatically:: Having @value{GDBN} infer the source language
11413 @subsection List of Filename Extensions and Languages
11415 If a source file name ends in one of the following extensions, then
11416 @value{GDBN} infers that its language is the one indicated.
11434 C@t{++} source file
11440 Objective-C source file
11444 Fortran source file
11447 Modula-2 source file
11451 Assembler source file. This actually behaves almost like C, but
11452 @value{GDBN} does not skip over function prologues when stepping.
11455 In addition, you may set the language associated with a filename
11456 extension. @xref{Show, , Displaying the Language}.
11459 @subsection Setting the Working Language
11461 If you allow @value{GDBN} to set the language automatically,
11462 expressions are interpreted the same way in your debugging session and
11465 @kindex set language
11466 If you wish, you may set the language manually. To do this, issue the
11467 command @samp{set language @var{lang}}, where @var{lang} is the name of
11468 a language, such as
11469 @code{c} or @code{modula-2}.
11470 For a list of the supported languages, type @samp{set language}.
11472 Setting the language manually prevents @value{GDBN} from updating the working
11473 language automatically. This can lead to confusion if you try
11474 to debug a program when the working language is not the same as the
11475 source language, when an expression is acceptable to both
11476 languages---but means different things. For instance, if the current
11477 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11485 might not have the effect you intended. In C, this means to add
11486 @code{b} and @code{c} and place the result in @code{a}. The result
11487 printed would be the value of @code{a}. In Modula-2, this means to compare
11488 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11490 @node Automatically
11491 @subsection Having @value{GDBN} Infer the Source Language
11493 To have @value{GDBN} set the working language automatically, use
11494 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11495 then infers the working language. That is, when your program stops in a
11496 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11497 working language to the language recorded for the function in that
11498 frame. If the language for a frame is unknown (that is, if the function
11499 or block corresponding to the frame was defined in a source file that
11500 does not have a recognized extension), the current working language is
11501 not changed, and @value{GDBN} issues a warning.
11503 This may not seem necessary for most programs, which are written
11504 entirely in one source language. However, program modules and libraries
11505 written in one source language can be used by a main program written in
11506 a different source language. Using @samp{set language auto} in this
11507 case frees you from having to set the working language manually.
11510 @section Displaying the Language
11512 The following commands help you find out which language is the
11513 working language, and also what language source files were written in.
11516 @item show language
11517 @kindex show language
11518 Display the current working language. This is the
11519 language you can use with commands such as @code{print} to
11520 build and compute expressions that may involve variables in your program.
11523 @kindex info frame@r{, show the source language}
11524 Display the source language for this frame. This language becomes the
11525 working language if you use an identifier from this frame.
11526 @xref{Frame Info, ,Information about a Frame}, to identify the other
11527 information listed here.
11530 @kindex info source@r{, show the source language}
11531 Display the source language of this source file.
11532 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11533 information listed here.
11536 In unusual circumstances, you may have source files with extensions
11537 not in the standard list. You can then set the extension associated
11538 with a language explicitly:
11541 @item set extension-language @var{ext} @var{language}
11542 @kindex set extension-language
11543 Tell @value{GDBN} that source files with extension @var{ext} are to be
11544 assumed as written in the source language @var{language}.
11546 @item info extensions
11547 @kindex info extensions
11548 List all the filename extensions and the associated languages.
11552 @section Type and Range Checking
11555 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11556 checking are included, but they do not yet have any effect. This
11557 section documents the intended facilities.
11559 @c FIXME remove warning when type/range code added
11561 Some languages are designed to guard you against making seemingly common
11562 errors through a series of compile- and run-time checks. These include
11563 checking the type of arguments to functions and operators, and making
11564 sure mathematical overflows are caught at run time. Checks such as
11565 these help to ensure a program's correctness once it has been compiled
11566 by eliminating type mismatches, and providing active checks for range
11567 errors when your program is running.
11569 @value{GDBN} can check for conditions like the above if you wish.
11570 Although @value{GDBN} does not check the statements in your program,
11571 it can check expressions entered directly into @value{GDBN} for
11572 evaluation via the @code{print} command, for example. As with the
11573 working language, @value{GDBN} can also decide whether or not to check
11574 automatically based on your program's source language.
11575 @xref{Supported Languages, ,Supported Languages}, for the default
11576 settings of supported languages.
11579 * Type Checking:: An overview of type checking
11580 * Range Checking:: An overview of range checking
11583 @cindex type checking
11584 @cindex checks, type
11585 @node Type Checking
11586 @subsection An Overview of Type Checking
11588 Some languages, such as Modula-2, are strongly typed, meaning that the
11589 arguments to operators and functions have to be of the correct type,
11590 otherwise an error occurs. These checks prevent type mismatch
11591 errors from ever causing any run-time problems. For example,
11599 The second example fails because the @code{CARDINAL} 1 is not
11600 type-compatible with the @code{REAL} 2.3.
11602 For the expressions you use in @value{GDBN} commands, you can tell the
11603 @value{GDBN} type checker to skip checking;
11604 to treat any mismatches as errors and abandon the expression;
11605 or to only issue warnings when type mismatches occur,
11606 but evaluate the expression anyway. When you choose the last of
11607 these, @value{GDBN} evaluates expressions like the second example above, but
11608 also issues a warning.
11610 Even if you turn type checking off, there may be other reasons
11611 related to type that prevent @value{GDBN} from evaluating an expression.
11612 For instance, @value{GDBN} does not know how to add an @code{int} and
11613 a @code{struct foo}. These particular type errors have nothing to do
11614 with the language in use, and usually arise from expressions, such as
11615 the one described above, which make little sense to evaluate anyway.
11617 Each language defines to what degree it is strict about type. For
11618 instance, both Modula-2 and C require the arguments to arithmetical
11619 operators to be numbers. In C, enumerated types and pointers can be
11620 represented as numbers, so that they are valid arguments to mathematical
11621 operators. @xref{Supported Languages, ,Supported Languages}, for further
11622 details on specific languages.
11624 @value{GDBN} provides some additional commands for controlling the type checker:
11626 @kindex set check type
11627 @kindex show check type
11629 @item set check type auto
11630 Set type checking on or off based on the current working language.
11631 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11634 @item set check type on
11635 @itemx set check type off
11636 Set type checking on or off, overriding the default setting for the
11637 current working language. Issue a warning if the setting does not
11638 match the language default. If any type mismatches occur in
11639 evaluating an expression while type checking is on, @value{GDBN} prints a
11640 message and aborts evaluation of the expression.
11642 @item set check type warn
11643 Cause the type checker to issue warnings, but to always attempt to
11644 evaluate the expression. Evaluating the expression may still
11645 be impossible for other reasons. For example, @value{GDBN} cannot add
11646 numbers and structures.
11649 Show the current setting of the type checker, and whether or not @value{GDBN}
11650 is setting it automatically.
11653 @cindex range checking
11654 @cindex checks, range
11655 @node Range Checking
11656 @subsection An Overview of Range Checking
11658 In some languages (such as Modula-2), it is an error to exceed the
11659 bounds of a type; this is enforced with run-time checks. Such range
11660 checking is meant to ensure program correctness by making sure
11661 computations do not overflow, or indices on an array element access do
11662 not exceed the bounds of the array.
11664 For expressions you use in @value{GDBN} commands, you can tell
11665 @value{GDBN} to treat range errors in one of three ways: ignore them,
11666 always treat them as errors and abandon the expression, or issue
11667 warnings but evaluate the expression anyway.
11669 A range error can result from numerical overflow, from exceeding an
11670 array index bound, or when you type a constant that is not a member
11671 of any type. Some languages, however, do not treat overflows as an
11672 error. In many implementations of C, mathematical overflow causes the
11673 result to ``wrap around'' to lower values---for example, if @var{m} is
11674 the largest integer value, and @var{s} is the smallest, then
11677 @var{m} + 1 @result{} @var{s}
11680 This, too, is specific to individual languages, and in some cases
11681 specific to individual compilers or machines. @xref{Supported Languages, ,
11682 Supported Languages}, for further details on specific languages.
11684 @value{GDBN} provides some additional commands for controlling the range checker:
11686 @kindex set check range
11687 @kindex show check range
11689 @item set check range auto
11690 Set range checking on or off based on the current working language.
11691 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11694 @item set check range on
11695 @itemx set check range off
11696 Set range checking on or off, overriding the default setting for the
11697 current working language. A warning is issued if the setting does not
11698 match the language default. If a range error occurs and range checking is on,
11699 then a message is printed and evaluation of the expression is aborted.
11701 @item set check range warn
11702 Output messages when the @value{GDBN} range checker detects a range error,
11703 but attempt to evaluate the expression anyway. Evaluating the
11704 expression may still be impossible for other reasons, such as accessing
11705 memory that the process does not own (a typical example from many Unix
11709 Show the current setting of the range checker, and whether or not it is
11710 being set automatically by @value{GDBN}.
11713 @node Supported Languages
11714 @section Supported Languages
11716 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11717 assembly, Modula-2, and Ada.
11718 @c This is false ...
11719 Some @value{GDBN} features may be used in expressions regardless of the
11720 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11721 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11722 ,Expressions}) can be used with the constructs of any supported
11725 The following sections detail to what degree each source language is
11726 supported by @value{GDBN}. These sections are not meant to be language
11727 tutorials or references, but serve only as a reference guide to what the
11728 @value{GDBN} expression parser accepts, and what input and output
11729 formats should look like for different languages. There are many good
11730 books written on each of these languages; please look to these for a
11731 language reference or tutorial.
11734 * C:: C and C@t{++}
11736 * Objective-C:: Objective-C
11737 * OpenCL C:: OpenCL C
11738 * Fortran:: Fortran
11740 * Modula-2:: Modula-2
11745 @subsection C and C@t{++}
11747 @cindex C and C@t{++}
11748 @cindex expressions in C or C@t{++}
11750 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11751 to both languages. Whenever this is the case, we discuss those languages
11755 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11756 @cindex @sc{gnu} C@t{++}
11757 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11758 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11759 effectively, you must compile your C@t{++} programs with a supported
11760 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11761 compiler (@code{aCC}).
11763 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11764 format; if it doesn't work on your system, try the stabs+ debugging
11765 format. You can select those formats explicitly with the @code{g++}
11766 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11767 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11768 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11771 * C Operators:: C and C@t{++} operators
11772 * C Constants:: C and C@t{++} constants
11773 * C Plus Plus Expressions:: C@t{++} expressions
11774 * C Defaults:: Default settings for C and C@t{++}
11775 * C Checks:: C and C@t{++} type and range checks
11776 * Debugging C:: @value{GDBN} and C
11777 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11778 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11782 @subsubsection C and C@t{++} Operators
11784 @cindex C and C@t{++} operators
11786 Operators must be defined on values of specific types. For instance,
11787 @code{+} is defined on numbers, but not on structures. Operators are
11788 often defined on groups of types.
11790 For the purposes of C and C@t{++}, the following definitions hold:
11795 @emph{Integral types} include @code{int} with any of its storage-class
11796 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11799 @emph{Floating-point types} include @code{float}, @code{double}, and
11800 @code{long double} (if supported by the target platform).
11803 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11806 @emph{Scalar types} include all of the above.
11811 The following operators are supported. They are listed here
11812 in order of increasing precedence:
11816 The comma or sequencing operator. Expressions in a comma-separated list
11817 are evaluated from left to right, with the result of the entire
11818 expression being the last expression evaluated.
11821 Assignment. The value of an assignment expression is the value
11822 assigned. Defined on scalar types.
11825 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11826 and translated to @w{@code{@var{a} = @var{a op b}}}.
11827 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11828 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11829 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11832 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11833 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11837 Logical @sc{or}. Defined on integral types.
11840 Logical @sc{and}. Defined on integral types.
11843 Bitwise @sc{or}. Defined on integral types.
11846 Bitwise exclusive-@sc{or}. Defined on integral types.
11849 Bitwise @sc{and}. Defined on integral types.
11852 Equality and inequality. Defined on scalar types. The value of these
11853 expressions is 0 for false and non-zero for true.
11855 @item <@r{, }>@r{, }<=@r{, }>=
11856 Less than, greater than, less than or equal, greater than or equal.
11857 Defined on scalar types. The value of these expressions is 0 for false
11858 and non-zero for true.
11861 left shift, and right shift. Defined on integral types.
11864 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11867 Addition and subtraction. Defined on integral types, floating-point types and
11870 @item *@r{, }/@r{, }%
11871 Multiplication, division, and modulus. Multiplication and division are
11872 defined on integral and floating-point types. Modulus is defined on
11876 Increment and decrement. When appearing before a variable, the
11877 operation is performed before the variable is used in an expression;
11878 when appearing after it, the variable's value is used before the
11879 operation takes place.
11882 Pointer dereferencing. Defined on pointer types. Same precedence as
11886 Address operator. Defined on variables. Same precedence as @code{++}.
11888 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11889 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11890 to examine the address
11891 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11895 Negative. Defined on integral and floating-point types. Same
11896 precedence as @code{++}.
11899 Logical negation. Defined on integral types. Same precedence as
11903 Bitwise complement operator. Defined on integral types. Same precedence as
11908 Structure member, and pointer-to-structure member. For convenience,
11909 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11910 pointer based on the stored type information.
11911 Defined on @code{struct} and @code{union} data.
11914 Dereferences of pointers to members.
11917 Array indexing. @code{@var{a}[@var{i}]} is defined as
11918 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11921 Function parameter list. Same precedence as @code{->}.
11924 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11925 and @code{class} types.
11928 Doubled colons also represent the @value{GDBN} scope operator
11929 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11933 If an operator is redefined in the user code, @value{GDBN} usually
11934 attempts to invoke the redefined version instead of using the operator's
11935 predefined meaning.
11938 @subsubsection C and C@t{++} Constants
11940 @cindex C and C@t{++} constants
11942 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11947 Integer constants are a sequence of digits. Octal constants are
11948 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11949 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11950 @samp{l}, specifying that the constant should be treated as a
11954 Floating point constants are a sequence of digits, followed by a decimal
11955 point, followed by a sequence of digits, and optionally followed by an
11956 exponent. An exponent is of the form:
11957 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11958 sequence of digits. The @samp{+} is optional for positive exponents.
11959 A floating-point constant may also end with a letter @samp{f} or
11960 @samp{F}, specifying that the constant should be treated as being of
11961 the @code{float} (as opposed to the default @code{double}) type; or with
11962 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11966 Enumerated constants consist of enumerated identifiers, or their
11967 integral equivalents.
11970 Character constants are a single character surrounded by single quotes
11971 (@code{'}), or a number---the ordinal value of the corresponding character
11972 (usually its @sc{ascii} value). Within quotes, the single character may
11973 be represented by a letter or by @dfn{escape sequences}, which are of
11974 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11975 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11976 @samp{@var{x}} is a predefined special character---for example,
11977 @samp{\n} for newline.
11980 String constants are a sequence of character constants surrounded by
11981 double quotes (@code{"}). Any valid character constant (as described
11982 above) may appear. Double quotes within the string must be preceded by
11983 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11987 Pointer constants are an integral value. You can also write pointers
11988 to constants using the C operator @samp{&}.
11991 Array constants are comma-separated lists surrounded by braces @samp{@{}
11992 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11993 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11994 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11997 @node C Plus Plus Expressions
11998 @subsubsection C@t{++} Expressions
12000 @cindex expressions in C@t{++}
12001 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12003 @cindex debugging C@t{++} programs
12004 @cindex C@t{++} compilers
12005 @cindex debug formats and C@t{++}
12006 @cindex @value{NGCC} and C@t{++}
12008 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
12009 proper compiler and the proper debug format. Currently, @value{GDBN}
12010 works best when debugging C@t{++} code that is compiled with
12011 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
12012 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
12013 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
12014 stabs+ as their default debug format, so you usually don't need to
12015 specify a debug format explicitly. Other compilers and/or debug formats
12016 are likely to work badly or not at all when using @value{GDBN} to debug
12022 @cindex member functions
12024 Member function calls are allowed; you can use expressions like
12027 count = aml->GetOriginal(x, y)
12030 @vindex this@r{, inside C@t{++} member functions}
12031 @cindex namespace in C@t{++}
12033 While a member function is active (in the selected stack frame), your
12034 expressions have the same namespace available as the member function;
12035 that is, @value{GDBN} allows implicit references to the class instance
12036 pointer @code{this} following the same rules as C@t{++}.
12038 @cindex call overloaded functions
12039 @cindex overloaded functions, calling
12040 @cindex type conversions in C@t{++}
12042 You can call overloaded functions; @value{GDBN} resolves the function
12043 call to the right definition, with some restrictions. @value{GDBN} does not
12044 perform overload resolution involving user-defined type conversions,
12045 calls to constructors, or instantiations of templates that do not exist
12046 in the program. It also cannot handle ellipsis argument lists or
12049 It does perform integral conversions and promotions, floating-point
12050 promotions, arithmetic conversions, pointer conversions, conversions of
12051 class objects to base classes, and standard conversions such as those of
12052 functions or arrays to pointers; it requires an exact match on the
12053 number of function arguments.
12055 Overload resolution is always performed, unless you have specified
12056 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12057 ,@value{GDBN} Features for C@t{++}}.
12059 You must specify @code{set overload-resolution off} in order to use an
12060 explicit function signature to call an overloaded function, as in
12062 p 'foo(char,int)'('x', 13)
12065 The @value{GDBN} command-completion facility can simplify this;
12066 see @ref{Completion, ,Command Completion}.
12068 @cindex reference declarations
12070 @value{GDBN} understands variables declared as C@t{++} references; you can use
12071 them in expressions just as you do in C@t{++} source---they are automatically
12074 In the parameter list shown when @value{GDBN} displays a frame, the values of
12075 reference variables are not displayed (unlike other variables); this
12076 avoids clutter, since references are often used for large structures.
12077 The @emph{address} of a reference variable is always shown, unless
12078 you have specified @samp{set print address off}.
12081 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12082 expressions can use it just as expressions in your program do. Since
12083 one scope may be defined in another, you can use @code{::} repeatedly if
12084 necessary, for example in an expression like
12085 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12086 resolving name scope by reference to source files, in both C and C@t{++}
12087 debugging (@pxref{Variables, ,Program Variables}).
12090 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12091 calling virtual functions correctly, printing out virtual bases of
12092 objects, calling functions in a base subobject, casting objects, and
12093 invoking user-defined operators.
12096 @subsubsection C and C@t{++} Defaults
12098 @cindex C and C@t{++} defaults
12100 If you allow @value{GDBN} to set type and range checking automatically, they
12101 both default to @code{off} whenever the working language changes to
12102 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12103 selects the working language.
12105 If you allow @value{GDBN} to set the language automatically, it
12106 recognizes source files whose names end with @file{.c}, @file{.C}, or
12107 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12108 these files, it sets the working language to C or C@t{++}.
12109 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12110 for further details.
12112 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12113 @c unimplemented. If (b) changes, it might make sense to let this node
12114 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12117 @subsubsection C and C@t{++} Type and Range Checks
12119 @cindex C and C@t{++} checks
12121 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12122 is not used. However, if you turn type checking on, @value{GDBN}
12123 considers two variables type equivalent if:
12127 The two variables are structured and have the same structure, union, or
12131 The two variables have the same type name, or types that have been
12132 declared equivalent through @code{typedef}.
12135 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12138 The two @code{struct}, @code{union}, or @code{enum} variables are
12139 declared in the same declaration. (Note: this may not be true for all C
12144 Range checking, if turned on, is done on mathematical operations. Array
12145 indices are not checked, since they are often used to index a pointer
12146 that is not itself an array.
12149 @subsubsection @value{GDBN} and C
12151 The @code{set print union} and @code{show print union} commands apply to
12152 the @code{union} type. When set to @samp{on}, any @code{union} that is
12153 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12154 appears as @samp{@{...@}}.
12156 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12157 with pointers and a memory allocation function. @xref{Expressions,
12160 @node Debugging C Plus Plus
12161 @subsubsection @value{GDBN} Features for C@t{++}
12163 @cindex commands for C@t{++}
12165 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12166 designed specifically for use with C@t{++}. Here is a summary:
12169 @cindex break in overloaded functions
12170 @item @r{breakpoint menus}
12171 When you want a breakpoint in a function whose name is overloaded,
12172 @value{GDBN} has the capability to display a menu of possible breakpoint
12173 locations to help you specify which function definition you want.
12174 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12176 @cindex overloading in C@t{++}
12177 @item rbreak @var{regex}
12178 Setting breakpoints using regular expressions is helpful for setting
12179 breakpoints on overloaded functions that are not members of any special
12181 @xref{Set Breaks, ,Setting Breakpoints}.
12183 @cindex C@t{++} exception handling
12186 Debug C@t{++} exception handling using these commands. @xref{Set
12187 Catchpoints, , Setting Catchpoints}.
12189 @cindex inheritance
12190 @item ptype @var{typename}
12191 Print inheritance relationships as well as other information for type
12193 @xref{Symbols, ,Examining the Symbol Table}.
12195 @cindex C@t{++} symbol display
12196 @item set print demangle
12197 @itemx show print demangle
12198 @itemx set print asm-demangle
12199 @itemx show print asm-demangle
12200 Control whether C@t{++} symbols display in their source form, both when
12201 displaying code as C@t{++} source and when displaying disassemblies.
12202 @xref{Print Settings, ,Print Settings}.
12204 @item set print object
12205 @itemx show print object
12206 Choose whether to print derived (actual) or declared types of objects.
12207 @xref{Print Settings, ,Print Settings}.
12209 @item set print vtbl
12210 @itemx show print vtbl
12211 Control the format for printing virtual function tables.
12212 @xref{Print Settings, ,Print Settings}.
12213 (The @code{vtbl} commands do not work on programs compiled with the HP
12214 ANSI C@t{++} compiler (@code{aCC}).)
12216 @kindex set overload-resolution
12217 @cindex overloaded functions, overload resolution
12218 @item set overload-resolution on
12219 Enable overload resolution for C@t{++} expression evaluation. The default
12220 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12221 and searches for a function whose signature matches the argument types,
12222 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12223 Expressions, ,C@t{++} Expressions}, for details).
12224 If it cannot find a match, it emits a message.
12226 @item set overload-resolution off
12227 Disable overload resolution for C@t{++} expression evaluation. For
12228 overloaded functions that are not class member functions, @value{GDBN}
12229 chooses the first function of the specified name that it finds in the
12230 symbol table, whether or not its arguments are of the correct type. For
12231 overloaded functions that are class member functions, @value{GDBN}
12232 searches for a function whose signature @emph{exactly} matches the
12235 @kindex show overload-resolution
12236 @item show overload-resolution
12237 Show the current setting of overload resolution.
12239 @item @r{Overloaded symbol names}
12240 You can specify a particular definition of an overloaded symbol, using
12241 the same notation that is used to declare such symbols in C@t{++}: type
12242 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12243 also use the @value{GDBN} command-line word completion facilities to list the
12244 available choices, or to finish the type list for you.
12245 @xref{Completion,, Command Completion}, for details on how to do this.
12248 @node Decimal Floating Point
12249 @subsubsection Decimal Floating Point format
12250 @cindex decimal floating point format
12252 @value{GDBN} can examine, set and perform computations with numbers in
12253 decimal floating point format, which in the C language correspond to the
12254 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12255 specified by the extension to support decimal floating-point arithmetic.
12257 There are two encodings in use, depending on the architecture: BID (Binary
12258 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12259 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12262 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12263 to manipulate decimal floating point numbers, it is not possible to convert
12264 (using a cast, for example) integers wider than 32-bit to decimal float.
12266 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12267 point computations, error checking in decimal float operations ignores
12268 underflow, overflow and divide by zero exceptions.
12270 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12271 to inspect @code{_Decimal128} values stored in floating point registers.
12272 See @ref{PowerPC,,PowerPC} for more details.
12278 @value{GDBN} can be used to debug programs written in D and compiled with
12279 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12280 specific feature --- dynamic arrays.
12283 @subsection Objective-C
12285 @cindex Objective-C
12286 This section provides information about some commands and command
12287 options that are useful for debugging Objective-C code. See also
12288 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12289 few more commands specific to Objective-C support.
12292 * Method Names in Commands::
12293 * The Print Command with Objective-C::
12296 @node Method Names in Commands
12297 @subsubsection Method Names in Commands
12299 The following commands have been extended to accept Objective-C method
12300 names as line specifications:
12302 @kindex clear@r{, and Objective-C}
12303 @kindex break@r{, and Objective-C}
12304 @kindex info line@r{, and Objective-C}
12305 @kindex jump@r{, and Objective-C}
12306 @kindex list@r{, and Objective-C}
12310 @item @code{info line}
12315 A fully qualified Objective-C method name is specified as
12318 -[@var{Class} @var{methodName}]
12321 where the minus sign is used to indicate an instance method and a
12322 plus sign (not shown) is used to indicate a class method. The class
12323 name @var{Class} and method name @var{methodName} are enclosed in
12324 brackets, similar to the way messages are specified in Objective-C
12325 source code. For example, to set a breakpoint at the @code{create}
12326 instance method of class @code{Fruit} in the program currently being
12330 break -[Fruit create]
12333 To list ten program lines around the @code{initialize} class method,
12337 list +[NSText initialize]
12340 In the current version of @value{GDBN}, the plus or minus sign is
12341 required. In future versions of @value{GDBN}, the plus or minus
12342 sign will be optional, but you can use it to narrow the search. It
12343 is also possible to specify just a method name:
12349 You must specify the complete method name, including any colons. If
12350 your program's source files contain more than one @code{create} method,
12351 you'll be presented with a numbered list of classes that implement that
12352 method. Indicate your choice by number, or type @samp{0} to exit if
12355 As another example, to clear a breakpoint established at the
12356 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12359 clear -[NSWindow makeKeyAndOrderFront:]
12362 @node The Print Command with Objective-C
12363 @subsubsection The Print Command With Objective-C
12364 @cindex Objective-C, print objects
12365 @kindex print-object
12366 @kindex po @r{(@code{print-object})}
12368 The print command has also been extended to accept methods. For example:
12371 print -[@var{object} hash]
12374 @cindex print an Objective-C object description
12375 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12377 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12378 and print the result. Also, an additional command has been added,
12379 @code{print-object} or @code{po} for short, which is meant to print
12380 the description of an object. However, this command may only work
12381 with certain Objective-C libraries that have a particular hook
12382 function, @code{_NSPrintForDebugger}, defined.
12385 @subsection OpenCL C
12388 This section provides information about @value{GDBN}s OpenCL C support.
12391 * OpenCL C Datatypes::
12392 * OpenCL C Expressions::
12393 * OpenCL C Operators::
12396 @node OpenCL C Datatypes
12397 @subsubsection OpenCL C Datatypes
12399 @cindex OpenCL C Datatypes
12400 @value{GDBN} supports the builtin scalar and vector datatypes specified
12401 by OpenCL 1.1. In addition the half- and double-precision floating point
12402 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12403 extensions are also known to @value{GDBN}.
12405 @node OpenCL C Expressions
12406 @subsubsection OpenCL C Expressions
12408 @cindex OpenCL C Expressions
12409 @value{GDBN} supports accesses to vector components including the access as
12410 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12411 supported by @value{GDBN} can be used as well.
12413 @node OpenCL C Operators
12414 @subsubsection OpenCL C Operators
12416 @cindex OpenCL C Operators
12417 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12421 @subsection Fortran
12422 @cindex Fortran-specific support in @value{GDBN}
12424 @value{GDBN} can be used to debug programs written in Fortran, but it
12425 currently supports only the features of Fortran 77 language.
12427 @cindex trailing underscore, in Fortran symbols
12428 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12429 among them) append an underscore to the names of variables and
12430 functions. When you debug programs compiled by those compilers, you
12431 will need to refer to variables and functions with a trailing
12435 * Fortran Operators:: Fortran operators and expressions
12436 * Fortran Defaults:: Default settings for Fortran
12437 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12440 @node Fortran Operators
12441 @subsubsection Fortran Operators and Expressions
12443 @cindex Fortran operators and expressions
12445 Operators must be defined on values of specific types. For instance,
12446 @code{+} is defined on numbers, but not on characters or other non-
12447 arithmetic types. Operators are often defined on groups of types.
12451 The exponentiation operator. It raises the first operand to the power
12455 The range operator. Normally used in the form of array(low:high) to
12456 represent a section of array.
12459 The access component operator. Normally used to access elements in derived
12460 types. Also suitable for unions. As unions aren't part of regular Fortran,
12461 this can only happen when accessing a register that uses a gdbarch-defined
12465 @node Fortran Defaults
12466 @subsubsection Fortran Defaults
12468 @cindex Fortran Defaults
12470 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12471 default uses case-insensitive matches for Fortran symbols. You can
12472 change that with the @samp{set case-insensitive} command, see
12473 @ref{Symbols}, for the details.
12475 @node Special Fortran Commands
12476 @subsubsection Special Fortran Commands
12478 @cindex Special Fortran commands
12480 @value{GDBN} has some commands to support Fortran-specific features,
12481 such as displaying common blocks.
12484 @cindex @code{COMMON} blocks, Fortran
12485 @kindex info common
12486 @item info common @r{[}@var{common-name}@r{]}
12487 This command prints the values contained in the Fortran @code{COMMON}
12488 block whose name is @var{common-name}. With no argument, the names of
12489 all @code{COMMON} blocks visible at the current program location are
12496 @cindex Pascal support in @value{GDBN}, limitations
12497 Debugging Pascal programs which use sets, subranges, file variables, or
12498 nested functions does not currently work. @value{GDBN} does not support
12499 entering expressions, printing values, or similar features using Pascal
12502 The Pascal-specific command @code{set print pascal_static-members}
12503 controls whether static members of Pascal objects are displayed.
12504 @xref{Print Settings, pascal_static-members}.
12507 @subsection Modula-2
12509 @cindex Modula-2, @value{GDBN} support
12511 The extensions made to @value{GDBN} to support Modula-2 only support
12512 output from the @sc{gnu} Modula-2 compiler (which is currently being
12513 developed). Other Modula-2 compilers are not currently supported, and
12514 attempting to debug executables produced by them is most likely
12515 to give an error as @value{GDBN} reads in the executable's symbol
12518 @cindex expressions in Modula-2
12520 * M2 Operators:: Built-in operators
12521 * Built-In Func/Proc:: Built-in functions and procedures
12522 * M2 Constants:: Modula-2 constants
12523 * M2 Types:: Modula-2 types
12524 * M2 Defaults:: Default settings for Modula-2
12525 * Deviations:: Deviations from standard Modula-2
12526 * M2 Checks:: Modula-2 type and range checks
12527 * M2 Scope:: The scope operators @code{::} and @code{.}
12528 * GDB/M2:: @value{GDBN} and Modula-2
12532 @subsubsection Operators
12533 @cindex Modula-2 operators
12535 Operators must be defined on values of specific types. For instance,
12536 @code{+} is defined on numbers, but not on structures. Operators are
12537 often defined on groups of types. For the purposes of Modula-2, the
12538 following definitions hold:
12543 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12547 @emph{Character types} consist of @code{CHAR} and its subranges.
12550 @emph{Floating-point types} consist of @code{REAL}.
12553 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12557 @emph{Scalar types} consist of all of the above.
12560 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12563 @emph{Boolean types} consist of @code{BOOLEAN}.
12567 The following operators are supported, and appear in order of
12568 increasing precedence:
12572 Function argument or array index separator.
12575 Assignment. The value of @var{var} @code{:=} @var{value} is
12579 Less than, greater than on integral, floating-point, or enumerated
12583 Less than or equal to, greater than or equal to
12584 on integral, floating-point and enumerated types, or set inclusion on
12585 set types. Same precedence as @code{<}.
12587 @item =@r{, }<>@r{, }#
12588 Equality and two ways of expressing inequality, valid on scalar types.
12589 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12590 available for inequality, since @code{#} conflicts with the script
12594 Set membership. Defined on set types and the types of their members.
12595 Same precedence as @code{<}.
12598 Boolean disjunction. Defined on boolean types.
12601 Boolean conjunction. Defined on boolean types.
12604 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12607 Addition and subtraction on integral and floating-point types, or union
12608 and difference on set types.
12611 Multiplication on integral and floating-point types, or set intersection
12615 Division on floating-point types, or symmetric set difference on set
12616 types. Same precedence as @code{*}.
12619 Integer division and remainder. Defined on integral types. Same
12620 precedence as @code{*}.
12623 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12626 Pointer dereferencing. Defined on pointer types.
12629 Boolean negation. Defined on boolean types. Same precedence as
12633 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12634 precedence as @code{^}.
12637 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12640 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12644 @value{GDBN} and Modula-2 scope operators.
12648 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12649 treats the use of the operator @code{IN}, or the use of operators
12650 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12651 @code{<=}, and @code{>=} on sets as an error.
12655 @node Built-In Func/Proc
12656 @subsubsection Built-in Functions and Procedures
12657 @cindex Modula-2 built-ins
12659 Modula-2 also makes available several built-in procedures and functions.
12660 In describing these, the following metavariables are used:
12665 represents an @code{ARRAY} variable.
12668 represents a @code{CHAR} constant or variable.
12671 represents a variable or constant of integral type.
12674 represents an identifier that belongs to a set. Generally used in the
12675 same function with the metavariable @var{s}. The type of @var{s} should
12676 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12679 represents a variable or constant of integral or floating-point type.
12682 represents a variable or constant of floating-point type.
12688 represents a variable.
12691 represents a variable or constant of one of many types. See the
12692 explanation of the function for details.
12695 All Modula-2 built-in procedures also return a result, described below.
12699 Returns the absolute value of @var{n}.
12702 If @var{c} is a lower case letter, it returns its upper case
12703 equivalent, otherwise it returns its argument.
12706 Returns the character whose ordinal value is @var{i}.
12709 Decrements the value in the variable @var{v} by one. Returns the new value.
12711 @item DEC(@var{v},@var{i})
12712 Decrements the value in the variable @var{v} by @var{i}. Returns the
12715 @item EXCL(@var{m},@var{s})
12716 Removes the element @var{m} from the set @var{s}. Returns the new
12719 @item FLOAT(@var{i})
12720 Returns the floating point equivalent of the integer @var{i}.
12722 @item HIGH(@var{a})
12723 Returns the index of the last member of @var{a}.
12726 Increments the value in the variable @var{v} by one. Returns the new value.
12728 @item INC(@var{v},@var{i})
12729 Increments the value in the variable @var{v} by @var{i}. Returns the
12732 @item INCL(@var{m},@var{s})
12733 Adds the element @var{m} to the set @var{s} if it is not already
12734 there. Returns the new set.
12737 Returns the maximum value of the type @var{t}.
12740 Returns the minimum value of the type @var{t}.
12743 Returns boolean TRUE if @var{i} is an odd number.
12746 Returns the ordinal value of its argument. For example, the ordinal
12747 value of a character is its @sc{ascii} value (on machines supporting the
12748 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12749 integral, character and enumerated types.
12751 @item SIZE(@var{x})
12752 Returns the size of its argument. @var{x} can be a variable or a type.
12754 @item TRUNC(@var{r})
12755 Returns the integral part of @var{r}.
12757 @item TSIZE(@var{x})
12758 Returns the size of its argument. @var{x} can be a variable or a type.
12760 @item VAL(@var{t},@var{i})
12761 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12765 @emph{Warning:} Sets and their operations are not yet supported, so
12766 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12770 @cindex Modula-2 constants
12772 @subsubsection Constants
12774 @value{GDBN} allows you to express the constants of Modula-2 in the following
12780 Integer constants are simply a sequence of digits. When used in an
12781 expression, a constant is interpreted to be type-compatible with the
12782 rest of the expression. Hexadecimal integers are specified by a
12783 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12786 Floating point constants appear as a sequence of digits, followed by a
12787 decimal point and another sequence of digits. An optional exponent can
12788 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12789 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12790 digits of the floating point constant must be valid decimal (base 10)
12794 Character constants consist of a single character enclosed by a pair of
12795 like quotes, either single (@code{'}) or double (@code{"}). They may
12796 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12797 followed by a @samp{C}.
12800 String constants consist of a sequence of characters enclosed by a
12801 pair of like quotes, either single (@code{'}) or double (@code{"}).
12802 Escape sequences in the style of C are also allowed. @xref{C
12803 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12807 Enumerated constants consist of an enumerated identifier.
12810 Boolean constants consist of the identifiers @code{TRUE} and
12814 Pointer constants consist of integral values only.
12817 Set constants are not yet supported.
12821 @subsubsection Modula-2 Types
12822 @cindex Modula-2 types
12824 Currently @value{GDBN} can print the following data types in Modula-2
12825 syntax: array types, record types, set types, pointer types, procedure
12826 types, enumerated types, subrange types and base types. You can also
12827 print the contents of variables declared using these type.
12828 This section gives a number of simple source code examples together with
12829 sample @value{GDBN} sessions.
12831 The first example contains the following section of code:
12840 and you can request @value{GDBN} to interrogate the type and value of
12841 @code{r} and @code{s}.
12844 (@value{GDBP}) print s
12846 (@value{GDBP}) ptype s
12848 (@value{GDBP}) print r
12850 (@value{GDBP}) ptype r
12855 Likewise if your source code declares @code{s} as:
12859 s: SET ['A'..'Z'] ;
12863 then you may query the type of @code{s} by:
12866 (@value{GDBP}) ptype s
12867 type = SET ['A'..'Z']
12871 Note that at present you cannot interactively manipulate set
12872 expressions using the debugger.
12874 The following example shows how you might declare an array in Modula-2
12875 and how you can interact with @value{GDBN} to print its type and contents:
12879 s: ARRAY [-10..10] OF CHAR ;
12883 (@value{GDBP}) ptype s
12884 ARRAY [-10..10] OF CHAR
12887 Note that the array handling is not yet complete and although the type
12888 is printed correctly, expression handling still assumes that all
12889 arrays have a lower bound of zero and not @code{-10} as in the example
12892 Here are some more type related Modula-2 examples:
12896 colour = (blue, red, yellow, green) ;
12897 t = [blue..yellow] ;
12905 The @value{GDBN} interaction shows how you can query the data type
12906 and value of a variable.
12909 (@value{GDBP}) print s
12911 (@value{GDBP}) ptype t
12912 type = [blue..yellow]
12916 In this example a Modula-2 array is declared and its contents
12917 displayed. Observe that the contents are written in the same way as
12918 their @code{C} counterparts.
12922 s: ARRAY [1..5] OF CARDINAL ;
12928 (@value{GDBP}) print s
12929 $1 = @{1, 0, 0, 0, 0@}
12930 (@value{GDBP}) ptype s
12931 type = ARRAY [1..5] OF CARDINAL
12934 The Modula-2 language interface to @value{GDBN} also understands
12935 pointer types as shown in this example:
12939 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12946 and you can request that @value{GDBN} describes the type of @code{s}.
12949 (@value{GDBP}) ptype s
12950 type = POINTER TO ARRAY [1..5] OF CARDINAL
12953 @value{GDBN} handles compound types as we can see in this example.
12954 Here we combine array types, record types, pointer types and subrange
12965 myarray = ARRAY myrange OF CARDINAL ;
12966 myrange = [-2..2] ;
12968 s: POINTER TO ARRAY myrange OF foo ;
12972 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12976 (@value{GDBP}) ptype s
12977 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12980 f3 : ARRAY [-2..2] OF CARDINAL;
12985 @subsubsection Modula-2 Defaults
12986 @cindex Modula-2 defaults
12988 If type and range checking are set automatically by @value{GDBN}, they
12989 both default to @code{on} whenever the working language changes to
12990 Modula-2. This happens regardless of whether you or @value{GDBN}
12991 selected the working language.
12993 If you allow @value{GDBN} to set the language automatically, then entering
12994 code compiled from a file whose name ends with @file{.mod} sets the
12995 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12996 Infer the Source Language}, for further details.
12999 @subsubsection Deviations from Standard Modula-2
13000 @cindex Modula-2, deviations from
13002 A few changes have been made to make Modula-2 programs easier to debug.
13003 This is done primarily via loosening its type strictness:
13007 Unlike in standard Modula-2, pointer constants can be formed by
13008 integers. This allows you to modify pointer variables during
13009 debugging. (In standard Modula-2, the actual address contained in a
13010 pointer variable is hidden from you; it can only be modified
13011 through direct assignment to another pointer variable or expression that
13012 returned a pointer.)
13015 C escape sequences can be used in strings and characters to represent
13016 non-printable characters. @value{GDBN} prints out strings with these
13017 escape sequences embedded. Single non-printable characters are
13018 printed using the @samp{CHR(@var{nnn})} format.
13021 The assignment operator (@code{:=}) returns the value of its right-hand
13025 All built-in procedures both modify @emph{and} return their argument.
13029 @subsubsection Modula-2 Type and Range Checks
13030 @cindex Modula-2 checks
13033 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13036 @c FIXME remove warning when type/range checks added
13038 @value{GDBN} considers two Modula-2 variables type equivalent if:
13042 They are of types that have been declared equivalent via a @code{TYPE
13043 @var{t1} = @var{t2}} statement
13046 They have been declared on the same line. (Note: This is true of the
13047 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13050 As long as type checking is enabled, any attempt to combine variables
13051 whose types are not equivalent is an error.
13053 Range checking is done on all mathematical operations, assignment, array
13054 index bounds, and all built-in functions and procedures.
13057 @subsubsection The Scope Operators @code{::} and @code{.}
13059 @cindex @code{.}, Modula-2 scope operator
13060 @cindex colon, doubled as scope operator
13062 @vindex colon-colon@r{, in Modula-2}
13063 @c Info cannot handle :: but TeX can.
13066 @vindex ::@r{, in Modula-2}
13069 There are a few subtle differences between the Modula-2 scope operator
13070 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13075 @var{module} . @var{id}
13076 @var{scope} :: @var{id}
13080 where @var{scope} is the name of a module or a procedure,
13081 @var{module} the name of a module, and @var{id} is any declared
13082 identifier within your program, except another module.
13084 Using the @code{::} operator makes @value{GDBN} search the scope
13085 specified by @var{scope} for the identifier @var{id}. If it is not
13086 found in the specified scope, then @value{GDBN} searches all scopes
13087 enclosing the one specified by @var{scope}.
13089 Using the @code{.} operator makes @value{GDBN} search the current scope for
13090 the identifier specified by @var{id} that was imported from the
13091 definition module specified by @var{module}. With this operator, it is
13092 an error if the identifier @var{id} was not imported from definition
13093 module @var{module}, or if @var{id} is not an identifier in
13097 @subsubsection @value{GDBN} and Modula-2
13099 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13100 Five subcommands of @code{set print} and @code{show print} apply
13101 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13102 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13103 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13104 analogue in Modula-2.
13106 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13107 with any language, is not useful with Modula-2. Its
13108 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13109 created in Modula-2 as they can in C or C@t{++}. However, because an
13110 address can be specified by an integral constant, the construct
13111 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13113 @cindex @code{#} in Modula-2
13114 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13115 interpreted as the beginning of a comment. Use @code{<>} instead.
13121 The extensions made to @value{GDBN} for Ada only support
13122 output from the @sc{gnu} Ada (GNAT) compiler.
13123 Other Ada compilers are not currently supported, and
13124 attempting to debug executables produced by them is most likely
13128 @cindex expressions in Ada
13130 * Ada Mode Intro:: General remarks on the Ada syntax
13131 and semantics supported by Ada mode
13133 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13134 * Additions to Ada:: Extensions of the Ada expression syntax.
13135 * Stopping Before Main Program:: Debugging the program during elaboration.
13136 * Ada Tasks:: Listing and setting breakpoints in tasks.
13137 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13138 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13140 * Ada Glitches:: Known peculiarities of Ada mode.
13143 @node Ada Mode Intro
13144 @subsubsection Introduction
13145 @cindex Ada mode, general
13147 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13148 syntax, with some extensions.
13149 The philosophy behind the design of this subset is
13153 That @value{GDBN} should provide basic literals and access to operations for
13154 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13155 leaving more sophisticated computations to subprograms written into the
13156 program (which therefore may be called from @value{GDBN}).
13159 That type safety and strict adherence to Ada language restrictions
13160 are not particularly important to the @value{GDBN} user.
13163 That brevity is important to the @value{GDBN} user.
13166 Thus, for brevity, the debugger acts as if all names declared in
13167 user-written packages are directly visible, even if they are not visible
13168 according to Ada rules, thus making it unnecessary to fully qualify most
13169 names with their packages, regardless of context. Where this causes
13170 ambiguity, @value{GDBN} asks the user's intent.
13172 The debugger will start in Ada mode if it detects an Ada main program.
13173 As for other languages, it will enter Ada mode when stopped in a program that
13174 was translated from an Ada source file.
13176 While in Ada mode, you may use `@t{--}' for comments. This is useful
13177 mostly for documenting command files. The standard @value{GDBN} comment
13178 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13179 middle (to allow based literals).
13181 The debugger supports limited overloading. Given a subprogram call in which
13182 the function symbol has multiple definitions, it will use the number of
13183 actual parameters and some information about their types to attempt to narrow
13184 the set of definitions. It also makes very limited use of context, preferring
13185 procedures to functions in the context of the @code{call} command, and
13186 functions to procedures elsewhere.
13188 @node Omissions from Ada
13189 @subsubsection Omissions from Ada
13190 @cindex Ada, omissions from
13192 Here are the notable omissions from the subset:
13196 Only a subset of the attributes are supported:
13200 @t{'First}, @t{'Last}, and @t{'Length}
13201 on array objects (not on types and subtypes).
13204 @t{'Min} and @t{'Max}.
13207 @t{'Pos} and @t{'Val}.
13213 @t{'Range} on array objects (not subtypes), but only as the right
13214 operand of the membership (@code{in}) operator.
13217 @t{'Access}, @t{'Unchecked_Access}, and
13218 @t{'Unrestricted_Access} (a GNAT extension).
13226 @code{Characters.Latin_1} are not available and
13227 concatenation is not implemented. Thus, escape characters in strings are
13228 not currently available.
13231 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13232 equality of representations. They will generally work correctly
13233 for strings and arrays whose elements have integer or enumeration types.
13234 They may not work correctly for arrays whose element
13235 types have user-defined equality, for arrays of real values
13236 (in particular, IEEE-conformant floating point, because of negative
13237 zeroes and NaNs), and for arrays whose elements contain unused bits with
13238 indeterminate values.
13241 The other component-by-component array operations (@code{and}, @code{or},
13242 @code{xor}, @code{not}, and relational tests other than equality)
13243 are not implemented.
13246 @cindex array aggregates (Ada)
13247 @cindex record aggregates (Ada)
13248 @cindex aggregates (Ada)
13249 There is limited support for array and record aggregates. They are
13250 permitted only on the right sides of assignments, as in these examples:
13253 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13254 (@value{GDBP}) set An_Array := (1, others => 0)
13255 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13256 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13257 (@value{GDBP}) set A_Record := (1, "Peter", True);
13258 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13262 discriminant's value by assigning an aggregate has an
13263 undefined effect if that discriminant is used within the record.
13264 However, you can first modify discriminants by directly assigning to
13265 them (which normally would not be allowed in Ada), and then performing an
13266 aggregate assignment. For example, given a variable @code{A_Rec}
13267 declared to have a type such as:
13270 type Rec (Len : Small_Integer := 0) is record
13272 Vals : IntArray (1 .. Len);
13276 you can assign a value with a different size of @code{Vals} with two
13280 (@value{GDBP}) set A_Rec.Len := 4
13281 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13284 As this example also illustrates, @value{GDBN} is very loose about the usual
13285 rules concerning aggregates. You may leave out some of the
13286 components of an array or record aggregate (such as the @code{Len}
13287 component in the assignment to @code{A_Rec} above); they will retain their
13288 original values upon assignment. You may freely use dynamic values as
13289 indices in component associations. You may even use overlapping or
13290 redundant component associations, although which component values are
13291 assigned in such cases is not defined.
13294 Calls to dispatching subprograms are not implemented.
13297 The overloading algorithm is much more limited (i.e., less selective)
13298 than that of real Ada. It makes only limited use of the context in
13299 which a subexpression appears to resolve its meaning, and it is much
13300 looser in its rules for allowing type matches. As a result, some
13301 function calls will be ambiguous, and the user will be asked to choose
13302 the proper resolution.
13305 The @code{new} operator is not implemented.
13308 Entry calls are not implemented.
13311 Aside from printing, arithmetic operations on the native VAX floating-point
13312 formats are not supported.
13315 It is not possible to slice a packed array.
13318 The names @code{True} and @code{False}, when not part of a qualified name,
13319 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13321 Should your program
13322 redefine these names in a package or procedure (at best a dubious practice),
13323 you will have to use fully qualified names to access their new definitions.
13326 @node Additions to Ada
13327 @subsubsection Additions to Ada
13328 @cindex Ada, deviations from
13330 As it does for other languages, @value{GDBN} makes certain generic
13331 extensions to Ada (@pxref{Expressions}):
13335 If the expression @var{E} is a variable residing in memory (typically
13336 a local variable or array element) and @var{N} is a positive integer,
13337 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13338 @var{N}-1 adjacent variables following it in memory as an array. In
13339 Ada, this operator is generally not necessary, since its prime use is
13340 in displaying parts of an array, and slicing will usually do this in
13341 Ada. However, there are occasional uses when debugging programs in
13342 which certain debugging information has been optimized away.
13345 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13346 appears in function or file @var{B}.'' When @var{B} is a file name,
13347 you must typically surround it in single quotes.
13350 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13351 @var{type} that appears at address @var{addr}.''
13354 A name starting with @samp{$} is a convenience variable
13355 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13358 In addition, @value{GDBN} provides a few other shortcuts and outright
13359 additions specific to Ada:
13363 The assignment statement is allowed as an expression, returning
13364 its right-hand operand as its value. Thus, you may enter
13367 (@value{GDBP}) set x := y + 3
13368 (@value{GDBP}) print A(tmp := y + 1)
13372 The semicolon is allowed as an ``operator,'' returning as its value
13373 the value of its right-hand operand.
13374 This allows, for example,
13375 complex conditional breaks:
13378 (@value{GDBP}) break f
13379 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13383 Rather than use catenation and symbolic character names to introduce special
13384 characters into strings, one may instead use a special bracket notation,
13385 which is also used to print strings. A sequence of characters of the form
13386 @samp{["@var{XX}"]} within a string or character literal denotes the
13387 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13388 sequence of characters @samp{["""]} also denotes a single quotation mark
13389 in strings. For example,
13391 "One line.["0a"]Next line.["0a"]"
13394 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13398 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13399 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13403 (@value{GDBP}) print 'max(x, y)
13407 When printing arrays, @value{GDBN} uses positional notation when the
13408 array has a lower bound of 1, and uses a modified named notation otherwise.
13409 For example, a one-dimensional array of three integers with a lower bound
13410 of 3 might print as
13417 That is, in contrast to valid Ada, only the first component has a @code{=>}
13421 You may abbreviate attributes in expressions with any unique,
13422 multi-character subsequence of
13423 their names (an exact match gets preference).
13424 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13425 in place of @t{a'length}.
13428 @cindex quoting Ada internal identifiers
13429 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13430 to lower case. The GNAT compiler uses upper-case characters for
13431 some of its internal identifiers, which are normally of no interest to users.
13432 For the rare occasions when you actually have to look at them,
13433 enclose them in angle brackets to avoid the lower-case mapping.
13436 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13440 Printing an object of class-wide type or dereferencing an
13441 access-to-class-wide value will display all the components of the object's
13442 specific type (as indicated by its run-time tag). Likewise, component
13443 selection on such a value will operate on the specific type of the
13448 @node Stopping Before Main Program
13449 @subsubsection Stopping at the Very Beginning
13451 @cindex breakpointing Ada elaboration code
13452 It is sometimes necessary to debug the program during elaboration, and
13453 before reaching the main procedure.
13454 As defined in the Ada Reference
13455 Manual, the elaboration code is invoked from a procedure called
13456 @code{adainit}. To run your program up to the beginning of
13457 elaboration, simply use the following two commands:
13458 @code{tbreak adainit} and @code{run}.
13461 @subsubsection Extensions for Ada Tasks
13462 @cindex Ada, tasking
13464 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13465 @value{GDBN} provides the following task-related commands:
13470 This command shows a list of current Ada tasks, as in the following example:
13477 (@value{GDBP}) info tasks
13478 ID TID P-ID Pri State Name
13479 1 8088000 0 15 Child Activation Wait main_task
13480 2 80a4000 1 15 Accept Statement b
13481 3 809a800 1 15 Child Activation Wait a
13482 * 4 80ae800 3 15 Runnable c
13487 In this listing, the asterisk before the last task indicates it to be the
13488 task currently being inspected.
13492 Represents @value{GDBN}'s internal task number.
13498 The parent's task ID (@value{GDBN}'s internal task number).
13501 The base priority of the task.
13504 Current state of the task.
13508 The task has been created but has not been activated. It cannot be
13512 The task is not blocked for any reason known to Ada. (It may be waiting
13513 for a mutex, though.) It is conceptually "executing" in normal mode.
13516 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13517 that were waiting on terminate alternatives have been awakened and have
13518 terminated themselves.
13520 @item Child Activation Wait
13521 The task is waiting for created tasks to complete activation.
13523 @item Accept Statement
13524 The task is waiting on an accept or selective wait statement.
13526 @item Waiting on entry call
13527 The task is waiting on an entry call.
13529 @item Async Select Wait
13530 The task is waiting to start the abortable part of an asynchronous
13534 The task is waiting on a select statement with only a delay
13537 @item Child Termination Wait
13538 The task is sleeping having completed a master within itself, and is
13539 waiting for the tasks dependent on that master to become terminated or
13540 waiting on a terminate Phase.
13542 @item Wait Child in Term Alt
13543 The task is sleeping waiting for tasks on terminate alternatives to
13544 finish terminating.
13546 @item Accepting RV with @var{taskno}
13547 The task is accepting a rendez-vous with the task @var{taskno}.
13551 Name of the task in the program.
13555 @kindex info task @var{taskno}
13556 @item info task @var{taskno}
13557 This command shows detailled informations on the specified task, as in
13558 the following example:
13563 (@value{GDBP}) info tasks
13564 ID TID P-ID Pri State Name
13565 1 8077880 0 15 Child Activation Wait main_task
13566 * 2 807c468 1 15 Runnable task_1
13567 (@value{GDBP}) info task 2
13568 Ada Task: 0x807c468
13571 Parent: 1 (main_task)
13577 @kindex task@r{ (Ada)}
13578 @cindex current Ada task ID
13579 This command prints the ID of the current task.
13585 (@value{GDBP}) info tasks
13586 ID TID P-ID Pri State Name
13587 1 8077870 0 15 Child Activation Wait main_task
13588 * 2 807c458 1 15 Runnable t
13589 (@value{GDBP}) task
13590 [Current task is 2]
13593 @item task @var{taskno}
13594 @cindex Ada task switching
13595 This command is like the @code{thread @var{threadno}}
13596 command (@pxref{Threads}). It switches the context of debugging
13597 from the current task to the given task.
13603 (@value{GDBP}) info tasks
13604 ID TID P-ID Pri State Name
13605 1 8077870 0 15 Child Activation Wait main_task
13606 * 2 807c458 1 15 Runnable t
13607 (@value{GDBP}) task 1
13608 [Switching to task 1]
13609 #0 0x8067726 in pthread_cond_wait ()
13611 #0 0x8067726 in pthread_cond_wait ()
13612 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13613 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13614 #3 0x806153e in system.tasking.stages.activate_tasks ()
13615 #4 0x804aacc in un () at un.adb:5
13618 @item break @var{linespec} task @var{taskno}
13619 @itemx break @var{linespec} task @var{taskno} if @dots{}
13620 @cindex breakpoints and tasks, in Ada
13621 @cindex task breakpoints, in Ada
13622 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13623 These commands are like the @code{break @dots{} thread @dots{}}
13624 command (@pxref{Thread Stops}).
13625 @var{linespec} specifies source lines, as described
13626 in @ref{Specify Location}.
13628 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13629 to specify that you only want @value{GDBN} to stop the program when a
13630 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13631 numeric task identifiers assigned by @value{GDBN}, shown in the first
13632 column of the @samp{info tasks} display.
13634 If you do not specify @samp{task @var{taskno}} when you set a
13635 breakpoint, the breakpoint applies to @emph{all} tasks of your
13638 You can use the @code{task} qualifier on conditional breakpoints as
13639 well; in this case, place @samp{task @var{taskno}} before the
13640 breakpoint condition (before the @code{if}).
13648 (@value{GDBP}) info tasks
13649 ID TID P-ID Pri State Name
13650 1 140022020 0 15 Child Activation Wait main_task
13651 2 140045060 1 15 Accept/Select Wait t2
13652 3 140044840 1 15 Runnable t1
13653 * 4 140056040 1 15 Runnable t3
13654 (@value{GDBP}) b 15 task 2
13655 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13656 (@value{GDBP}) cont
13661 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13663 (@value{GDBP}) info tasks
13664 ID TID P-ID Pri State Name
13665 1 140022020 0 15 Child Activation Wait main_task
13666 * 2 140045060 1 15 Runnable t2
13667 3 140044840 1 15 Runnable t1
13668 4 140056040 1 15 Delay Sleep t3
13672 @node Ada Tasks and Core Files
13673 @subsubsection Tasking Support when Debugging Core Files
13674 @cindex Ada tasking and core file debugging
13676 When inspecting a core file, as opposed to debugging a live program,
13677 tasking support may be limited or even unavailable, depending on
13678 the platform being used.
13679 For instance, on x86-linux, the list of tasks is available, but task
13680 switching is not supported. On Tru64, however, task switching will work
13683 On certain platforms, including Tru64, the debugger needs to perform some
13684 memory writes in order to provide Ada tasking support. When inspecting
13685 a core file, this means that the core file must be opened with read-write
13686 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13687 Under these circumstances, you should make a backup copy of the core
13688 file before inspecting it with @value{GDBN}.
13690 @node Ravenscar Profile
13691 @subsubsection Tasking Support when using the Ravenscar Profile
13692 @cindex Ravenscar Profile
13694 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13695 specifically designed for systems with safety-critical real-time
13699 @kindex set ravenscar task-switching on
13700 @cindex task switching with program using Ravenscar Profile
13701 @item set ravenscar task-switching on
13702 Allows task switching when debugging a program that uses the Ravenscar
13703 Profile. This is the default.
13705 @kindex set ravenscar task-switching off
13706 @item set ravenscar task-switching off
13707 Turn off task switching when debugging a program that uses the Ravenscar
13708 Profile. This is mostly intended to disable the code that adds support
13709 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13710 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13711 To be effective, this command should be run before the program is started.
13713 @kindex show ravenscar task-switching
13714 @item show ravenscar task-switching
13715 Show whether it is possible to switch from task to task in a program
13716 using the Ravenscar Profile.
13721 @subsubsection Known Peculiarities of Ada Mode
13722 @cindex Ada, problems
13724 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13725 we know of several problems with and limitations of Ada mode in
13727 some of which will be fixed with planned future releases of the debugger
13728 and the GNU Ada compiler.
13732 Static constants that the compiler chooses not to materialize as objects in
13733 storage are invisible to the debugger.
13736 Named parameter associations in function argument lists are ignored (the
13737 argument lists are treated as positional).
13740 Many useful library packages are currently invisible to the debugger.
13743 Fixed-point arithmetic, conversions, input, and output is carried out using
13744 floating-point arithmetic, and may give results that only approximate those on
13748 The GNAT compiler never generates the prefix @code{Standard} for any of
13749 the standard symbols defined by the Ada language. @value{GDBN} knows about
13750 this: it will strip the prefix from names when you use it, and will never
13751 look for a name you have so qualified among local symbols, nor match against
13752 symbols in other packages or subprograms. If you have
13753 defined entities anywhere in your program other than parameters and
13754 local variables whose simple names match names in @code{Standard},
13755 GNAT's lack of qualification here can cause confusion. When this happens,
13756 you can usually resolve the confusion
13757 by qualifying the problematic names with package
13758 @code{Standard} explicitly.
13761 Older versions of the compiler sometimes generate erroneous debugging
13762 information, resulting in the debugger incorrectly printing the value
13763 of affected entities. In some cases, the debugger is able to work
13764 around an issue automatically. In other cases, the debugger is able
13765 to work around the issue, but the work-around has to be specifically
13768 @kindex set ada trust-PAD-over-XVS
13769 @kindex show ada trust-PAD-over-XVS
13772 @item set ada trust-PAD-over-XVS on
13773 Configure GDB to strictly follow the GNAT encoding when computing the
13774 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13775 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13776 a complete description of the encoding used by the GNAT compiler).
13777 This is the default.
13779 @item set ada trust-PAD-over-XVS off
13780 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13781 sometimes prints the wrong value for certain entities, changing @code{ada
13782 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13783 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13784 @code{off}, but this incurs a slight performance penalty, so it is
13785 recommended to leave this setting to @code{on} unless necessary.
13789 @node Unsupported Languages
13790 @section Unsupported Languages
13792 @cindex unsupported languages
13793 @cindex minimal language
13794 In addition to the other fully-supported programming languages,
13795 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13796 It does not represent a real programming language, but provides a set
13797 of capabilities close to what the C or assembly languages provide.
13798 This should allow most simple operations to be performed while debugging
13799 an application that uses a language currently not supported by @value{GDBN}.
13801 If the language is set to @code{auto}, @value{GDBN} will automatically
13802 select this language if the current frame corresponds to an unsupported
13806 @chapter Examining the Symbol Table
13808 The commands described in this chapter allow you to inquire about the
13809 symbols (names of variables, functions and types) defined in your
13810 program. This information is inherent in the text of your program and
13811 does not change as your program executes. @value{GDBN} finds it in your
13812 program's symbol table, in the file indicated when you started @value{GDBN}
13813 (@pxref{File Options, ,Choosing Files}), or by one of the
13814 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13816 @cindex symbol names
13817 @cindex names of symbols
13818 @cindex quoting names
13819 Occasionally, you may need to refer to symbols that contain unusual
13820 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13821 most frequent case is in referring to static variables in other
13822 source files (@pxref{Variables,,Program Variables}). File names
13823 are recorded in object files as debugging symbols, but @value{GDBN} would
13824 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13825 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13826 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13833 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13836 @cindex case-insensitive symbol names
13837 @cindex case sensitivity in symbol names
13838 @kindex set case-sensitive
13839 @item set case-sensitive on
13840 @itemx set case-sensitive off
13841 @itemx set case-sensitive auto
13842 Normally, when @value{GDBN} looks up symbols, it matches their names
13843 with case sensitivity determined by the current source language.
13844 Occasionally, you may wish to control that. The command @code{set
13845 case-sensitive} lets you do that by specifying @code{on} for
13846 case-sensitive matches or @code{off} for case-insensitive ones. If
13847 you specify @code{auto}, case sensitivity is reset to the default
13848 suitable for the source language. The default is case-sensitive
13849 matches for all languages except for Fortran, for which the default is
13850 case-insensitive matches.
13852 @kindex show case-sensitive
13853 @item show case-sensitive
13854 This command shows the current setting of case sensitivity for symbols
13857 @kindex info address
13858 @cindex address of a symbol
13859 @item info address @var{symbol}
13860 Describe where the data for @var{symbol} is stored. For a register
13861 variable, this says which register it is kept in. For a non-register
13862 local variable, this prints the stack-frame offset at which the variable
13865 Note the contrast with @samp{print &@var{symbol}}, which does not work
13866 at all for a register variable, and for a stack local variable prints
13867 the exact address of the current instantiation of the variable.
13869 @kindex info symbol
13870 @cindex symbol from address
13871 @cindex closest symbol and offset for an address
13872 @item info symbol @var{addr}
13873 Print the name of a symbol which is stored at the address @var{addr}.
13874 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13875 nearest symbol and an offset from it:
13878 (@value{GDBP}) info symbol 0x54320
13879 _initialize_vx + 396 in section .text
13883 This is the opposite of the @code{info address} command. You can use
13884 it to find out the name of a variable or a function given its address.
13886 For dynamically linked executables, the name of executable or shared
13887 library containing the symbol is also printed:
13890 (@value{GDBP}) info symbol 0x400225
13891 _start + 5 in section .text of /tmp/a.out
13892 (@value{GDBP}) info symbol 0x2aaaac2811cf
13893 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13897 @item whatis [@var{arg}]
13898 Print the data type of @var{arg}, which can be either an expression or
13899 a data type. With no argument, print the data type of @code{$}, the
13900 last value in the value history. If @var{arg} is an expression, it is
13901 not actually evaluated, and any side-effecting operations (such as
13902 assignments or function calls) inside it do not take place. If
13903 @var{arg} is a type name, it may be the name of a type or typedef, or
13904 for C code it may have the form @samp{class @var{class-name}},
13905 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13906 @samp{enum @var{enum-tag}}.
13907 @xref{Expressions, ,Expressions}.
13910 @item ptype [@var{arg}]
13911 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13912 detailed description of the type, instead of just the name of the type.
13913 @xref{Expressions, ,Expressions}.
13915 For example, for this variable declaration:
13918 struct complex @{double real; double imag;@} v;
13922 the two commands give this output:
13926 (@value{GDBP}) whatis v
13927 type = struct complex
13928 (@value{GDBP}) ptype v
13929 type = struct complex @{
13937 As with @code{whatis}, using @code{ptype} without an argument refers to
13938 the type of @code{$}, the last value in the value history.
13940 @cindex incomplete type
13941 Sometimes, programs use opaque data types or incomplete specifications
13942 of complex data structure. If the debug information included in the
13943 program does not allow @value{GDBN} to display a full declaration of
13944 the data type, it will say @samp{<incomplete type>}. For example,
13945 given these declarations:
13949 struct foo *fooptr;
13953 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13956 (@value{GDBP}) ptype foo
13957 $1 = <incomplete type>
13961 ``Incomplete type'' is C terminology for data types that are not
13962 completely specified.
13965 @item info types @var{regexp}
13967 Print a brief description of all types whose names match the regular
13968 expression @var{regexp} (or all types in your program, if you supply
13969 no argument). Each complete typename is matched as though it were a
13970 complete line; thus, @samp{i type value} gives information on all
13971 types in your program whose names include the string @code{value}, but
13972 @samp{i type ^value$} gives information only on types whose complete
13973 name is @code{value}.
13975 This command differs from @code{ptype} in two ways: first, like
13976 @code{whatis}, it does not print a detailed description; second, it
13977 lists all source files where a type is defined.
13980 @cindex local variables
13981 @item info scope @var{location}
13982 List all the variables local to a particular scope. This command
13983 accepts a @var{location} argument---a function name, a source line, or
13984 an address preceded by a @samp{*}, and prints all the variables local
13985 to the scope defined by that location. (@xref{Specify Location}, for
13986 details about supported forms of @var{location}.) For example:
13989 (@value{GDBP}) @b{info scope command_line_handler}
13990 Scope for command_line_handler:
13991 Symbol rl is an argument at stack/frame offset 8, length 4.
13992 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13993 Symbol linelength is in static storage at address 0x150a1c, length 4.
13994 Symbol p is a local variable in register $esi, length 4.
13995 Symbol p1 is a local variable in register $ebx, length 4.
13996 Symbol nline is a local variable in register $edx, length 4.
13997 Symbol repeat is a local variable at frame offset -8, length 4.
14001 This command is especially useful for determining what data to collect
14002 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14005 @kindex info source
14007 Show information about the current source file---that is, the source file for
14008 the function containing the current point of execution:
14011 the name of the source file, and the directory containing it,
14013 the directory it was compiled in,
14015 its length, in lines,
14017 which programming language it is written in,
14019 whether the executable includes debugging information for that file, and
14020 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14022 whether the debugging information includes information about
14023 preprocessor macros.
14027 @kindex info sources
14029 Print the names of all source files in your program for which there is
14030 debugging information, organized into two lists: files whose symbols
14031 have already been read, and files whose symbols will be read when needed.
14033 @kindex info functions
14034 @item info functions
14035 Print the names and data types of all defined functions.
14037 @item info functions @var{regexp}
14038 Print the names and data types of all defined functions
14039 whose names contain a match for regular expression @var{regexp}.
14040 Thus, @samp{info fun step} finds all functions whose names
14041 include @code{step}; @samp{info fun ^step} finds those whose names
14042 start with @code{step}. If a function name contains characters
14043 that conflict with the regular expression language (e.g.@:
14044 @samp{operator*()}), they may be quoted with a backslash.
14046 @kindex info variables
14047 @item info variables
14048 Print the names and data types of all variables that are defined
14049 outside of functions (i.e.@: excluding local variables).
14051 @item info variables @var{regexp}
14052 Print the names and data types of all variables (except for local
14053 variables) whose names contain a match for regular expression
14056 @kindex info classes
14057 @cindex Objective-C, classes and selectors
14059 @itemx info classes @var{regexp}
14060 Display all Objective-C classes in your program, or
14061 (with the @var{regexp} argument) all those matching a particular regular
14064 @kindex info selectors
14065 @item info selectors
14066 @itemx info selectors @var{regexp}
14067 Display all Objective-C selectors in your program, or
14068 (with the @var{regexp} argument) all those matching a particular regular
14072 This was never implemented.
14073 @kindex info methods
14075 @itemx info methods @var{regexp}
14076 The @code{info methods} command permits the user to examine all defined
14077 methods within C@t{++} program, or (with the @var{regexp} argument) a
14078 specific set of methods found in the various C@t{++} classes. Many
14079 C@t{++} classes provide a large number of methods. Thus, the output
14080 from the @code{ptype} command can be overwhelming and hard to use. The
14081 @code{info-methods} command filters the methods, printing only those
14082 which match the regular-expression @var{regexp}.
14085 @cindex reloading symbols
14086 Some systems allow individual object files that make up your program to
14087 be replaced without stopping and restarting your program. For example,
14088 in VxWorks you can simply recompile a defective object file and keep on
14089 running. If you are running on one of these systems, you can allow
14090 @value{GDBN} to reload the symbols for automatically relinked modules:
14093 @kindex set symbol-reloading
14094 @item set symbol-reloading on
14095 Replace symbol definitions for the corresponding source file when an
14096 object file with a particular name is seen again.
14098 @item set symbol-reloading off
14099 Do not replace symbol definitions when encountering object files of the
14100 same name more than once. This is the default state; if you are not
14101 running on a system that permits automatic relinking of modules, you
14102 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14103 may discard symbols when linking large programs, that may contain
14104 several modules (from different directories or libraries) with the same
14107 @kindex show symbol-reloading
14108 @item show symbol-reloading
14109 Show the current @code{on} or @code{off} setting.
14112 @cindex opaque data types
14113 @kindex set opaque-type-resolution
14114 @item set opaque-type-resolution on
14115 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14116 declared as a pointer to a @code{struct}, @code{class}, or
14117 @code{union}---for example, @code{struct MyType *}---that is used in one
14118 source file although the full declaration of @code{struct MyType} is in
14119 another source file. The default is on.
14121 A change in the setting of this subcommand will not take effect until
14122 the next time symbols for a file are loaded.
14124 @item set opaque-type-resolution off
14125 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14126 is printed as follows:
14128 @{<no data fields>@}
14131 @kindex show opaque-type-resolution
14132 @item show opaque-type-resolution
14133 Show whether opaque types are resolved or not.
14135 @kindex maint print symbols
14136 @cindex symbol dump
14137 @kindex maint print psymbols
14138 @cindex partial symbol dump
14139 @item maint print symbols @var{filename}
14140 @itemx maint print psymbols @var{filename}
14141 @itemx maint print msymbols @var{filename}
14142 Write a dump of debugging symbol data into the file @var{filename}.
14143 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14144 symbols with debugging data are included. If you use @samp{maint print
14145 symbols}, @value{GDBN} includes all the symbols for which it has already
14146 collected full details: that is, @var{filename} reflects symbols for
14147 only those files whose symbols @value{GDBN} has read. You can use the
14148 command @code{info sources} to find out which files these are. If you
14149 use @samp{maint print psymbols} instead, the dump shows information about
14150 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14151 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14152 @samp{maint print msymbols} dumps just the minimal symbol information
14153 required for each object file from which @value{GDBN} has read some symbols.
14154 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14155 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14157 @kindex maint info symtabs
14158 @kindex maint info psymtabs
14159 @cindex listing @value{GDBN}'s internal symbol tables
14160 @cindex symbol tables, listing @value{GDBN}'s internal
14161 @cindex full symbol tables, listing @value{GDBN}'s internal
14162 @cindex partial symbol tables, listing @value{GDBN}'s internal
14163 @item maint info symtabs @r{[} @var{regexp} @r{]}
14164 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14166 List the @code{struct symtab} or @code{struct partial_symtab}
14167 structures whose names match @var{regexp}. If @var{regexp} is not
14168 given, list them all. The output includes expressions which you can
14169 copy into a @value{GDBN} debugging this one to examine a particular
14170 structure in more detail. For example:
14173 (@value{GDBP}) maint info psymtabs dwarf2read
14174 @{ objfile /home/gnu/build/gdb/gdb
14175 ((struct objfile *) 0x82e69d0)
14176 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14177 ((struct partial_symtab *) 0x8474b10)
14180 text addresses 0x814d3c8 -- 0x8158074
14181 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14182 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14183 dependencies (none)
14186 (@value{GDBP}) maint info symtabs
14190 We see that there is one partial symbol table whose filename contains
14191 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14192 and we see that @value{GDBN} has not read in any symtabs yet at all.
14193 If we set a breakpoint on a function, that will cause @value{GDBN} to
14194 read the symtab for the compilation unit containing that function:
14197 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14198 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14200 (@value{GDBP}) maint info symtabs
14201 @{ objfile /home/gnu/build/gdb/gdb
14202 ((struct objfile *) 0x82e69d0)
14203 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14204 ((struct symtab *) 0x86c1f38)
14207 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14208 linetable ((struct linetable *) 0x8370fa0)
14209 debugformat DWARF 2
14218 @chapter Altering Execution
14220 Once you think you have found an error in your program, you might want to
14221 find out for certain whether correcting the apparent error would lead to
14222 correct results in the rest of the run. You can find the answer by
14223 experiment, using the @value{GDBN} features for altering execution of the
14226 For example, you can store new values into variables or memory
14227 locations, give your program a signal, restart it at a different
14228 address, or even return prematurely from a function.
14231 * Assignment:: Assignment to variables
14232 * Jumping:: Continuing at a different address
14233 * Signaling:: Giving your program a signal
14234 * Returning:: Returning from a function
14235 * Calling:: Calling your program's functions
14236 * Patching:: Patching your program
14240 @section Assignment to Variables
14243 @cindex setting variables
14244 To alter the value of a variable, evaluate an assignment expression.
14245 @xref{Expressions, ,Expressions}. For example,
14252 stores the value 4 into the variable @code{x}, and then prints the
14253 value of the assignment expression (which is 4).
14254 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14255 information on operators in supported languages.
14257 @kindex set variable
14258 @cindex variables, setting
14259 If you are not interested in seeing the value of the assignment, use the
14260 @code{set} command instead of the @code{print} command. @code{set} is
14261 really the same as @code{print} except that the expression's value is
14262 not printed and is not put in the value history (@pxref{Value History,
14263 ,Value History}). The expression is evaluated only for its effects.
14265 If the beginning of the argument string of the @code{set} command
14266 appears identical to a @code{set} subcommand, use the @code{set
14267 variable} command instead of just @code{set}. This command is identical
14268 to @code{set} except for its lack of subcommands. For example, if your
14269 program has a variable @code{width}, you get an error if you try to set
14270 a new value with just @samp{set width=13}, because @value{GDBN} has the
14271 command @code{set width}:
14274 (@value{GDBP}) whatis width
14276 (@value{GDBP}) p width
14278 (@value{GDBP}) set width=47
14279 Invalid syntax in expression.
14283 The invalid expression, of course, is @samp{=47}. In
14284 order to actually set the program's variable @code{width}, use
14287 (@value{GDBP}) set var width=47
14290 Because the @code{set} command has many subcommands that can conflict
14291 with the names of program variables, it is a good idea to use the
14292 @code{set variable} command instead of just @code{set}. For example, if
14293 your program has a variable @code{g}, you run into problems if you try
14294 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14295 the command @code{set gnutarget}, abbreviated @code{set g}:
14299 (@value{GDBP}) whatis g
14303 (@value{GDBP}) set g=4
14307 The program being debugged has been started already.
14308 Start it from the beginning? (y or n) y
14309 Starting program: /home/smith/cc_progs/a.out
14310 "/home/smith/cc_progs/a.out": can't open to read symbols:
14311 Invalid bfd target.
14312 (@value{GDBP}) show g
14313 The current BFD target is "=4".
14318 The program variable @code{g} did not change, and you silently set the
14319 @code{gnutarget} to an invalid value. In order to set the variable
14323 (@value{GDBP}) set var g=4
14326 @value{GDBN} allows more implicit conversions in assignments than C; you can
14327 freely store an integer value into a pointer variable or vice versa,
14328 and you can convert any structure to any other structure that is the
14329 same length or shorter.
14330 @comment FIXME: how do structs align/pad in these conversions?
14331 @comment /doc@cygnus.com 18dec1990
14333 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14334 construct to generate a value of specified type at a specified address
14335 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14336 to memory location @code{0x83040} as an integer (which implies a certain size
14337 and representation in memory), and
14340 set @{int@}0x83040 = 4
14344 stores the value 4 into that memory location.
14347 @section Continuing at a Different Address
14349 Ordinarily, when you continue your program, you do so at the place where
14350 it stopped, with the @code{continue} command. You can instead continue at
14351 an address of your own choosing, with the following commands:
14355 @item jump @var{linespec}
14356 @itemx jump @var{location}
14357 Resume execution at line @var{linespec} or at address given by
14358 @var{location}. Execution stops again immediately if there is a
14359 breakpoint there. @xref{Specify Location}, for a description of the
14360 different forms of @var{linespec} and @var{location}. It is common
14361 practice to use the @code{tbreak} command in conjunction with
14362 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14364 The @code{jump} command does not change the current stack frame, or
14365 the stack pointer, or the contents of any memory location or any
14366 register other than the program counter. If line @var{linespec} is in
14367 a different function from the one currently executing, the results may
14368 be bizarre if the two functions expect different patterns of arguments or
14369 of local variables. For this reason, the @code{jump} command requests
14370 confirmation if the specified line is not in the function currently
14371 executing. However, even bizarre results are predictable if you are
14372 well acquainted with the machine-language code of your program.
14375 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14376 On many systems, you can get much the same effect as the @code{jump}
14377 command by storing a new value into the register @code{$pc}. The
14378 difference is that this does not start your program running; it only
14379 changes the address of where it @emph{will} run when you continue. For
14387 makes the next @code{continue} command or stepping command execute at
14388 address @code{0x485}, rather than at the address where your program stopped.
14389 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14391 The most common occasion to use the @code{jump} command is to back
14392 up---perhaps with more breakpoints set---over a portion of a program
14393 that has already executed, in order to examine its execution in more
14398 @section Giving your Program a Signal
14399 @cindex deliver a signal to a program
14403 @item signal @var{signal}
14404 Resume execution where your program stopped, but immediately give it the
14405 signal @var{signal}. @var{signal} can be the name or the number of a
14406 signal. For example, on many systems @code{signal 2} and @code{signal
14407 SIGINT} are both ways of sending an interrupt signal.
14409 Alternatively, if @var{signal} is zero, continue execution without
14410 giving a signal. This is useful when your program stopped on account of
14411 a signal and would ordinary see the signal when resumed with the
14412 @code{continue} command; @samp{signal 0} causes it to resume without a
14415 @code{signal} does not repeat when you press @key{RET} a second time
14416 after executing the command.
14420 Invoking the @code{signal} command is not the same as invoking the
14421 @code{kill} utility from the shell. Sending a signal with @code{kill}
14422 causes @value{GDBN} to decide what to do with the signal depending on
14423 the signal handling tables (@pxref{Signals}). The @code{signal} command
14424 passes the signal directly to your program.
14428 @section Returning from a Function
14431 @cindex returning from a function
14434 @itemx return @var{expression}
14435 You can cancel execution of a function call with the @code{return}
14436 command. If you give an
14437 @var{expression} argument, its value is used as the function's return
14441 When you use @code{return}, @value{GDBN} discards the selected stack frame
14442 (and all frames within it). You can think of this as making the
14443 discarded frame return prematurely. If you wish to specify a value to
14444 be returned, give that value as the argument to @code{return}.
14446 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14447 Frame}), and any other frames inside of it, leaving its caller as the
14448 innermost remaining frame. That frame becomes selected. The
14449 specified value is stored in the registers used for returning values
14452 The @code{return} command does not resume execution; it leaves the
14453 program stopped in the state that would exist if the function had just
14454 returned. In contrast, the @code{finish} command (@pxref{Continuing
14455 and Stepping, ,Continuing and Stepping}) resumes execution until the
14456 selected stack frame returns naturally.
14458 @value{GDBN} needs to know how the @var{expression} argument should be set for
14459 the inferior. The concrete registers assignment depends on the OS ABI and the
14460 type being returned by the selected stack frame. For example it is common for
14461 OS ABI to return floating point values in FPU registers while integer values in
14462 CPU registers. Still some ABIs return even floating point values in CPU
14463 registers. Larger integer widths (such as @code{long long int}) also have
14464 specific placement rules. @value{GDBN} already knows the OS ABI from its
14465 current target so it needs to find out also the type being returned to make the
14466 assignment into the right register(s).
14468 Normally, the selected stack frame has debug info. @value{GDBN} will always
14469 use the debug info instead of the implicit type of @var{expression} when the
14470 debug info is available. For example, if you type @kbd{return -1}, and the
14471 function in the current stack frame is declared to return a @code{long long
14472 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14473 into a @code{long long int}:
14476 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14478 (@value{GDBP}) return -1
14479 Make func return now? (y or n) y
14480 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14481 43 printf ("result=%lld\n", func ());
14485 However, if the selected stack frame does not have a debug info, e.g., if the
14486 function was compiled without debug info, @value{GDBN} has to find out the type
14487 to return from user. Specifying a different type by mistake may set the value
14488 in different inferior registers than the caller code expects. For example,
14489 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14490 of a @code{long long int} result for a debug info less function (on 32-bit
14491 architectures). Therefore the user is required to specify the return type by
14492 an appropriate cast explicitly:
14495 Breakpoint 2, 0x0040050b in func ()
14496 (@value{GDBP}) return -1
14497 Return value type not available for selected stack frame.
14498 Please use an explicit cast of the value to return.
14499 (@value{GDBP}) return (long long int) -1
14500 Make selected stack frame return now? (y or n) y
14501 #0 0x00400526 in main ()
14506 @section Calling Program Functions
14509 @cindex calling functions
14510 @cindex inferior functions, calling
14511 @item print @var{expr}
14512 Evaluate the expression @var{expr} and display the resulting value.
14513 @var{expr} may include calls to functions in the program being
14517 @item call @var{expr}
14518 Evaluate the expression @var{expr} without displaying @code{void}
14521 You can use this variant of the @code{print} command if you want to
14522 execute a function from your program that does not return anything
14523 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14524 with @code{void} returned values that @value{GDBN} will otherwise
14525 print. If the result is not void, it is printed and saved in the
14529 It is possible for the function you call via the @code{print} or
14530 @code{call} command to generate a signal (e.g., if there's a bug in
14531 the function, or if you passed it incorrect arguments). What happens
14532 in that case is controlled by the @code{set unwindonsignal} command.
14534 Similarly, with a C@t{++} program it is possible for the function you
14535 call via the @code{print} or @code{call} command to generate an
14536 exception that is not handled due to the constraints of the dummy
14537 frame. In this case, any exception that is raised in the frame, but has
14538 an out-of-frame exception handler will not be found. GDB builds a
14539 dummy-frame for the inferior function call, and the unwinder cannot
14540 seek for exception handlers outside of this dummy-frame. What happens
14541 in that case is controlled by the
14542 @code{set unwind-on-terminating-exception} command.
14545 @item set unwindonsignal
14546 @kindex set unwindonsignal
14547 @cindex unwind stack in called functions
14548 @cindex call dummy stack unwinding
14549 Set unwinding of the stack if a signal is received while in a function
14550 that @value{GDBN} called in the program being debugged. If set to on,
14551 @value{GDBN} unwinds the stack it created for the call and restores
14552 the context to what it was before the call. If set to off (the
14553 default), @value{GDBN} stops in the frame where the signal was
14556 @item show unwindonsignal
14557 @kindex show unwindonsignal
14558 Show the current setting of stack unwinding in the functions called by
14561 @item set unwind-on-terminating-exception
14562 @kindex set unwind-on-terminating-exception
14563 @cindex unwind stack in called functions with unhandled exceptions
14564 @cindex call dummy stack unwinding on unhandled exception.
14565 Set unwinding of the stack if a C@t{++} exception is raised, but left
14566 unhandled while in a function that @value{GDBN} called in the program being
14567 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14568 it created for the call and restores the context to what it was before
14569 the call. If set to off, @value{GDBN} the exception is delivered to
14570 the default C@t{++} exception handler and the inferior terminated.
14572 @item show unwind-on-terminating-exception
14573 @kindex show unwind-on-terminating-exception
14574 Show the current setting of stack unwinding in the functions called by
14579 @cindex weak alias functions
14580 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14581 for another function. In such case, @value{GDBN} might not pick up
14582 the type information, including the types of the function arguments,
14583 which causes @value{GDBN} to call the inferior function incorrectly.
14584 As a result, the called function will function erroneously and may
14585 even crash. A solution to that is to use the name of the aliased
14589 @section Patching Programs
14591 @cindex patching binaries
14592 @cindex writing into executables
14593 @cindex writing into corefiles
14595 By default, @value{GDBN} opens the file containing your program's
14596 executable code (or the corefile) read-only. This prevents accidental
14597 alterations to machine code; but it also prevents you from intentionally
14598 patching your program's binary.
14600 If you'd like to be able to patch the binary, you can specify that
14601 explicitly with the @code{set write} command. For example, you might
14602 want to turn on internal debugging flags, or even to make emergency
14608 @itemx set write off
14609 If you specify @samp{set write on}, @value{GDBN} opens executable and
14610 core files for both reading and writing; if you specify @kbd{set write
14611 off} (the default), @value{GDBN} opens them read-only.
14613 If you have already loaded a file, you must load it again (using the
14614 @code{exec-file} or @code{core-file} command) after changing @code{set
14615 write}, for your new setting to take effect.
14619 Display whether executable files and core files are opened for writing
14620 as well as reading.
14624 @chapter @value{GDBN} Files
14626 @value{GDBN} needs to know the file name of the program to be debugged,
14627 both in order to read its symbol table and in order to start your
14628 program. To debug a core dump of a previous run, you must also tell
14629 @value{GDBN} the name of the core dump file.
14632 * Files:: Commands to specify files
14633 * Separate Debug Files:: Debugging information in separate files
14634 * Index Files:: Index files speed up GDB
14635 * Symbol Errors:: Errors reading symbol files
14636 * Data Files:: GDB data files
14640 @section Commands to Specify Files
14642 @cindex symbol table
14643 @cindex core dump file
14645 You may want to specify executable and core dump file names. The usual
14646 way to do this is at start-up time, using the arguments to
14647 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14648 Out of @value{GDBN}}).
14650 Occasionally it is necessary to change to a different file during a
14651 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14652 specify a file you want to use. Or you are debugging a remote target
14653 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14654 Program}). In these situations the @value{GDBN} commands to specify
14655 new files are useful.
14658 @cindex executable file
14660 @item file @var{filename}
14661 Use @var{filename} as the program to be debugged. It is read for its
14662 symbols and for the contents of pure memory. It is also the program
14663 executed when you use the @code{run} command. If you do not specify a
14664 directory and the file is not found in the @value{GDBN} working directory,
14665 @value{GDBN} uses the environment variable @code{PATH} as a list of
14666 directories to search, just as the shell does when looking for a program
14667 to run. You can change the value of this variable, for both @value{GDBN}
14668 and your program, using the @code{path} command.
14670 @cindex unlinked object files
14671 @cindex patching object files
14672 You can load unlinked object @file{.o} files into @value{GDBN} using
14673 the @code{file} command. You will not be able to ``run'' an object
14674 file, but you can disassemble functions and inspect variables. Also,
14675 if the underlying BFD functionality supports it, you could use
14676 @kbd{gdb -write} to patch object files using this technique. Note
14677 that @value{GDBN} can neither interpret nor modify relocations in this
14678 case, so branches and some initialized variables will appear to go to
14679 the wrong place. But this feature is still handy from time to time.
14682 @code{file} with no argument makes @value{GDBN} discard any information it
14683 has on both executable file and the symbol table.
14686 @item exec-file @r{[} @var{filename} @r{]}
14687 Specify that the program to be run (but not the symbol table) is found
14688 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14689 if necessary to locate your program. Omitting @var{filename} means to
14690 discard information on the executable file.
14692 @kindex symbol-file
14693 @item symbol-file @r{[} @var{filename} @r{]}
14694 Read symbol table information from file @var{filename}. @code{PATH} is
14695 searched when necessary. Use the @code{file} command to get both symbol
14696 table and program to run from the same file.
14698 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14699 program's symbol table.
14701 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14702 some breakpoints and auto-display expressions. This is because they may
14703 contain pointers to the internal data recording symbols and data types,
14704 which are part of the old symbol table data being discarded inside
14707 @code{symbol-file} does not repeat if you press @key{RET} again after
14710 When @value{GDBN} is configured for a particular environment, it
14711 understands debugging information in whatever format is the standard
14712 generated for that environment; you may use either a @sc{gnu} compiler, or
14713 other compilers that adhere to the local conventions.
14714 Best results are usually obtained from @sc{gnu} compilers; for example,
14715 using @code{@value{NGCC}} you can generate debugging information for
14718 For most kinds of object files, with the exception of old SVR3 systems
14719 using COFF, the @code{symbol-file} command does not normally read the
14720 symbol table in full right away. Instead, it scans the symbol table
14721 quickly to find which source files and which symbols are present. The
14722 details are read later, one source file at a time, as they are needed.
14724 The purpose of this two-stage reading strategy is to make @value{GDBN}
14725 start up faster. For the most part, it is invisible except for
14726 occasional pauses while the symbol table details for a particular source
14727 file are being read. (The @code{set verbose} command can turn these
14728 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14729 Warnings and Messages}.)
14731 We have not implemented the two-stage strategy for COFF yet. When the
14732 symbol table is stored in COFF format, @code{symbol-file} reads the
14733 symbol table data in full right away. Note that ``stabs-in-COFF''
14734 still does the two-stage strategy, since the debug info is actually
14738 @cindex reading symbols immediately
14739 @cindex symbols, reading immediately
14740 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14741 @itemx file @r{[} -readnow @r{]} @var{filename}
14742 You can override the @value{GDBN} two-stage strategy for reading symbol
14743 tables by using the @samp{-readnow} option with any of the commands that
14744 load symbol table information, if you want to be sure @value{GDBN} has the
14745 entire symbol table available.
14747 @c FIXME: for now no mention of directories, since this seems to be in
14748 @c flux. 13mar1992 status is that in theory GDB would look either in
14749 @c current dir or in same dir as myprog; but issues like competing
14750 @c GDB's, or clutter in system dirs, mean that in practice right now
14751 @c only current dir is used. FFish says maybe a special GDB hierarchy
14752 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14756 @item core-file @r{[}@var{filename}@r{]}
14758 Specify the whereabouts of a core dump file to be used as the ``contents
14759 of memory''. Traditionally, core files contain only some parts of the
14760 address space of the process that generated them; @value{GDBN} can access the
14761 executable file itself for other parts.
14763 @code{core-file} with no argument specifies that no core file is
14766 Note that the core file is ignored when your program is actually running
14767 under @value{GDBN}. So, if you have been running your program and you
14768 wish to debug a core file instead, you must kill the subprocess in which
14769 the program is running. To do this, use the @code{kill} command
14770 (@pxref{Kill Process, ,Killing the Child Process}).
14772 @kindex add-symbol-file
14773 @cindex dynamic linking
14774 @item add-symbol-file @var{filename} @var{address}
14775 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14776 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14777 The @code{add-symbol-file} command reads additional symbol table
14778 information from the file @var{filename}. You would use this command
14779 when @var{filename} has been dynamically loaded (by some other means)
14780 into the program that is running. @var{address} should be the memory
14781 address at which the file has been loaded; @value{GDBN} cannot figure
14782 this out for itself. You can additionally specify an arbitrary number
14783 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14784 section name and base address for that section. You can specify any
14785 @var{address} as an expression.
14787 The symbol table of the file @var{filename} is added to the symbol table
14788 originally read with the @code{symbol-file} command. You can use the
14789 @code{add-symbol-file} command any number of times; the new symbol data
14790 thus read keeps adding to the old. To discard all old symbol data
14791 instead, use the @code{symbol-file} command without any arguments.
14793 @cindex relocatable object files, reading symbols from
14794 @cindex object files, relocatable, reading symbols from
14795 @cindex reading symbols from relocatable object files
14796 @cindex symbols, reading from relocatable object files
14797 @cindex @file{.o} files, reading symbols from
14798 Although @var{filename} is typically a shared library file, an
14799 executable file, or some other object file which has been fully
14800 relocated for loading into a process, you can also load symbolic
14801 information from relocatable @file{.o} files, as long as:
14805 the file's symbolic information refers only to linker symbols defined in
14806 that file, not to symbols defined by other object files,
14808 every section the file's symbolic information refers to has actually
14809 been loaded into the inferior, as it appears in the file, and
14811 you can determine the address at which every section was loaded, and
14812 provide these to the @code{add-symbol-file} command.
14816 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14817 relocatable files into an already running program; such systems
14818 typically make the requirements above easy to meet. However, it's
14819 important to recognize that many native systems use complex link
14820 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14821 assembly, for example) that make the requirements difficult to meet. In
14822 general, one cannot assume that using @code{add-symbol-file} to read a
14823 relocatable object file's symbolic information will have the same effect
14824 as linking the relocatable object file into the program in the normal
14827 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14829 @kindex add-symbol-file-from-memory
14830 @cindex @code{syscall DSO}
14831 @cindex load symbols from memory
14832 @item add-symbol-file-from-memory @var{address}
14833 Load symbols from the given @var{address} in a dynamically loaded
14834 object file whose image is mapped directly into the inferior's memory.
14835 For example, the Linux kernel maps a @code{syscall DSO} into each
14836 process's address space; this DSO provides kernel-specific code for
14837 some system calls. The argument can be any expression whose
14838 evaluation yields the address of the file's shared object file header.
14839 For this command to work, you must have used @code{symbol-file} or
14840 @code{exec-file} commands in advance.
14842 @kindex add-shared-symbol-files
14844 @item add-shared-symbol-files @var{library-file}
14845 @itemx assf @var{library-file}
14846 The @code{add-shared-symbol-files} command can currently be used only
14847 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14848 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14849 @value{GDBN} automatically looks for shared libraries, however if
14850 @value{GDBN} does not find yours, you can invoke
14851 @code{add-shared-symbol-files}. It takes one argument: the shared
14852 library's file name. @code{assf} is a shorthand alias for
14853 @code{add-shared-symbol-files}.
14856 @item section @var{section} @var{addr}
14857 The @code{section} command changes the base address of the named
14858 @var{section} of the exec file to @var{addr}. This can be used if the
14859 exec file does not contain section addresses, (such as in the
14860 @code{a.out} format), or when the addresses specified in the file
14861 itself are wrong. Each section must be changed separately. The
14862 @code{info files} command, described below, lists all the sections and
14866 @kindex info target
14869 @code{info files} and @code{info target} are synonymous; both print the
14870 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14871 including the names of the executable and core dump files currently in
14872 use by @value{GDBN}, and the files from which symbols were loaded. The
14873 command @code{help target} lists all possible targets rather than
14876 @kindex maint info sections
14877 @item maint info sections
14878 Another command that can give you extra information about program sections
14879 is @code{maint info sections}. In addition to the section information
14880 displayed by @code{info files}, this command displays the flags and file
14881 offset of each section in the executable and core dump files. In addition,
14882 @code{maint info sections} provides the following command options (which
14883 may be arbitrarily combined):
14887 Display sections for all loaded object files, including shared libraries.
14888 @item @var{sections}
14889 Display info only for named @var{sections}.
14890 @item @var{section-flags}
14891 Display info only for sections for which @var{section-flags} are true.
14892 The section flags that @value{GDBN} currently knows about are:
14895 Section will have space allocated in the process when loaded.
14896 Set for all sections except those containing debug information.
14898 Section will be loaded from the file into the child process memory.
14899 Set for pre-initialized code and data, clear for @code{.bss} sections.
14901 Section needs to be relocated before loading.
14903 Section cannot be modified by the child process.
14905 Section contains executable code only.
14907 Section contains data only (no executable code).
14909 Section will reside in ROM.
14911 Section contains data for constructor/destructor lists.
14913 Section is not empty.
14915 An instruction to the linker to not output the section.
14916 @item COFF_SHARED_LIBRARY
14917 A notification to the linker that the section contains
14918 COFF shared library information.
14920 Section contains common symbols.
14923 @kindex set trust-readonly-sections
14924 @cindex read-only sections
14925 @item set trust-readonly-sections on
14926 Tell @value{GDBN} that readonly sections in your object file
14927 really are read-only (i.e.@: that their contents will not change).
14928 In that case, @value{GDBN} can fetch values from these sections
14929 out of the object file, rather than from the target program.
14930 For some targets (notably embedded ones), this can be a significant
14931 enhancement to debugging performance.
14933 The default is off.
14935 @item set trust-readonly-sections off
14936 Tell @value{GDBN} not to trust readonly sections. This means that
14937 the contents of the section might change while the program is running,
14938 and must therefore be fetched from the target when needed.
14940 @item show trust-readonly-sections
14941 Show the current setting of trusting readonly sections.
14944 All file-specifying commands allow both absolute and relative file names
14945 as arguments. @value{GDBN} always converts the file name to an absolute file
14946 name and remembers it that way.
14948 @cindex shared libraries
14949 @anchor{Shared Libraries}
14950 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14951 and IBM RS/6000 AIX shared libraries.
14953 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14954 shared libraries. @xref{Expat}.
14956 @value{GDBN} automatically loads symbol definitions from shared libraries
14957 when you use the @code{run} command, or when you examine a core file.
14958 (Before you issue the @code{run} command, @value{GDBN} does not understand
14959 references to a function in a shared library, however---unless you are
14960 debugging a core file).
14962 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14963 automatically loads the symbols at the time of the @code{shl_load} call.
14965 @c FIXME: some @value{GDBN} release may permit some refs to undef
14966 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14967 @c FIXME...lib; check this from time to time when updating manual
14969 There are times, however, when you may wish to not automatically load
14970 symbol definitions from shared libraries, such as when they are
14971 particularly large or there are many of them.
14973 To control the automatic loading of shared library symbols, use the
14977 @kindex set auto-solib-add
14978 @item set auto-solib-add @var{mode}
14979 If @var{mode} is @code{on}, symbols from all shared object libraries
14980 will be loaded automatically when the inferior begins execution, you
14981 attach to an independently started inferior, or when the dynamic linker
14982 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14983 is @code{off}, symbols must be loaded manually, using the
14984 @code{sharedlibrary} command. The default value is @code{on}.
14986 @cindex memory used for symbol tables
14987 If your program uses lots of shared libraries with debug info that
14988 takes large amounts of memory, you can decrease the @value{GDBN}
14989 memory footprint by preventing it from automatically loading the
14990 symbols from shared libraries. To that end, type @kbd{set
14991 auto-solib-add off} before running the inferior, then load each
14992 library whose debug symbols you do need with @kbd{sharedlibrary
14993 @var{regexp}}, where @var{regexp} is a regular expression that matches
14994 the libraries whose symbols you want to be loaded.
14996 @kindex show auto-solib-add
14997 @item show auto-solib-add
14998 Display the current autoloading mode.
15001 @cindex load shared library
15002 To explicitly load shared library symbols, use the @code{sharedlibrary}
15006 @kindex info sharedlibrary
15008 @item info share @var{regex}
15009 @itemx info sharedlibrary @var{regex}
15010 Print the names of the shared libraries which are currently loaded
15011 that match @var{regex}. If @var{regex} is omitted then print
15012 all shared libraries that are loaded.
15014 @kindex sharedlibrary
15016 @item sharedlibrary @var{regex}
15017 @itemx share @var{regex}
15018 Load shared object library symbols for files matching a
15019 Unix regular expression.
15020 As with files loaded automatically, it only loads shared libraries
15021 required by your program for a core file or after typing @code{run}. If
15022 @var{regex} is omitted all shared libraries required by your program are
15025 @item nosharedlibrary
15026 @kindex nosharedlibrary
15027 @cindex unload symbols from shared libraries
15028 Unload all shared object library symbols. This discards all symbols
15029 that have been loaded from all shared libraries. Symbols from shared
15030 libraries that were loaded by explicit user requests are not
15034 Sometimes you may wish that @value{GDBN} stops and gives you control
15035 when any of shared library events happen. Use the @code{set
15036 stop-on-solib-events} command for this:
15039 @item set stop-on-solib-events
15040 @kindex set stop-on-solib-events
15041 This command controls whether @value{GDBN} should give you control
15042 when the dynamic linker notifies it about some shared library event.
15043 The most common event of interest is loading or unloading of a new
15046 @item show stop-on-solib-events
15047 @kindex show stop-on-solib-events
15048 Show whether @value{GDBN} stops and gives you control when shared
15049 library events happen.
15052 Shared libraries are also supported in many cross or remote debugging
15053 configurations. @value{GDBN} needs to have access to the target's libraries;
15054 this can be accomplished either by providing copies of the libraries
15055 on the host system, or by asking @value{GDBN} to automatically retrieve the
15056 libraries from the target. If copies of the target libraries are
15057 provided, they need to be the same as the target libraries, although the
15058 copies on the target can be stripped as long as the copies on the host are
15061 @cindex where to look for shared libraries
15062 For remote debugging, you need to tell @value{GDBN} where the target
15063 libraries are, so that it can load the correct copies---otherwise, it
15064 may try to load the host's libraries. @value{GDBN} has two variables
15065 to specify the search directories for target libraries.
15068 @cindex prefix for shared library file names
15069 @cindex system root, alternate
15070 @kindex set solib-absolute-prefix
15071 @kindex set sysroot
15072 @item set sysroot @var{path}
15073 Use @var{path} as the system root for the program being debugged. Any
15074 absolute shared library paths will be prefixed with @var{path}; many
15075 runtime loaders store the absolute paths to the shared library in the
15076 target program's memory. If you use @code{set sysroot} to find shared
15077 libraries, they need to be laid out in the same way that they are on
15078 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15081 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15082 retrieve the target libraries from the remote system. This is only
15083 supported when using a remote target that supports the @code{remote get}
15084 command (@pxref{File Transfer,,Sending files to a remote system}).
15085 The part of @var{path} following the initial @file{remote:}
15086 (if present) is used as system root prefix on the remote file system.
15087 @footnote{If you want to specify a local system root using a directory
15088 that happens to be named @file{remote:}, you need to use some equivalent
15089 variant of the name like @file{./remote:}.}
15091 For targets with an MS-DOS based filesystem, such as MS-Windows and
15092 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15093 absolute file name with @var{path}. But first, on Unix hosts,
15094 @value{GDBN} converts all backslash directory separators into forward
15095 slashes, because the backslash is not a directory separator on Unix:
15098 c:\foo\bar.dll @result{} c:/foo/bar.dll
15101 Then, @value{GDBN} attempts prefixing the target file name with
15102 @var{path}, and looks for the resulting file name in the host file
15106 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15109 If that does not find the shared library, @value{GDBN} tries removing
15110 the @samp{:} character from the drive spec, both for convenience, and,
15111 for the case of the host file system not supporting file names with
15115 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15118 This makes it possible to have a system root that mirrors a target
15119 with more than one drive. E.g., you may want to setup your local
15120 copies of the target system shared libraries like so (note @samp{c} vs
15124 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15125 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15126 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15130 and point the system root at @file{/path/to/sysroot}, so that
15131 @value{GDBN} can find the correct copies of both
15132 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15134 If that still does not find the shared library, @value{GDBN} tries
15135 removing the whole drive spec from the target file name:
15138 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15141 This last lookup makes it possible to not care about the drive name,
15142 if you don't want or need to.
15144 The @code{set solib-absolute-prefix} command is an alias for @code{set
15147 @cindex default system root
15148 @cindex @samp{--with-sysroot}
15149 You can set the default system root by using the configure-time
15150 @samp{--with-sysroot} option. If the system root is inside
15151 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15152 @samp{--exec-prefix}), then the default system root will be updated
15153 automatically if the installed @value{GDBN} is moved to a new
15156 @kindex show sysroot
15158 Display the current shared library prefix.
15160 @kindex set solib-search-path
15161 @item set solib-search-path @var{path}
15162 If this variable is set, @var{path} is a colon-separated list of
15163 directories to search for shared libraries. @samp{solib-search-path}
15164 is used after @samp{sysroot} fails to locate the library, or if the
15165 path to the library is relative instead of absolute. If you want to
15166 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15167 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15168 finding your host's libraries. @samp{sysroot} is preferred; setting
15169 it to a nonexistent directory may interfere with automatic loading
15170 of shared library symbols.
15172 @kindex show solib-search-path
15173 @item show solib-search-path
15174 Display the current shared library search path.
15176 @cindex DOS file-name semantics of file names.
15177 @kindex set target-file-system-kind (unix|dos-based|auto)
15178 @kindex show target-file-system-kind
15179 @item set target-file-system-kind @var{kind}
15180 Set assumed file system kind for target reported file names.
15182 Shared library file names as reported by the target system may not
15183 make sense as is on the system @value{GDBN} is running on. For
15184 example, when remote debugging a target that has MS-DOS based file
15185 system semantics, from a Unix host, the target may be reporting to
15186 @value{GDBN} a list of loaded shared libraries with file names such as
15187 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15188 drive letters, so the @samp{c:\} prefix is not normally understood as
15189 indicating an absolute file name, and neither is the backslash
15190 normally considered a directory separator character. In that case,
15191 the native file system would interpret this whole absolute file name
15192 as a relative file name with no directory components. This would make
15193 it impossible to point @value{GDBN} at a copy of the remote target's
15194 shared libraries on the host using @code{set sysroot}, and impractical
15195 with @code{set solib-search-path}. Setting
15196 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15197 to interpret such file names similarly to how the target would, and to
15198 map them to file names valid on @value{GDBN}'s native file system
15199 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15200 to one of the supported file system kinds. In that case, @value{GDBN}
15201 tries to determine the appropriate file system variant based on the
15202 current target's operating system (@pxref{ABI, ,Configuring the
15203 Current ABI}). The supported file system settings are:
15207 Instruct @value{GDBN} to assume the target file system is of Unix
15208 kind. Only file names starting the forward slash (@samp{/}) character
15209 are considered absolute, and the directory separator character is also
15213 Instruct @value{GDBN} to assume the target file system is DOS based.
15214 File names starting with either a forward slash, or a drive letter
15215 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15216 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15217 considered directory separators.
15220 Instruct @value{GDBN} to use the file system kind associated with the
15221 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15222 This is the default.
15227 @node Separate Debug Files
15228 @section Debugging Information in Separate Files
15229 @cindex separate debugging information files
15230 @cindex debugging information in separate files
15231 @cindex @file{.debug} subdirectories
15232 @cindex debugging information directory, global
15233 @cindex global debugging information directory
15234 @cindex build ID, and separate debugging files
15235 @cindex @file{.build-id} directory
15237 @value{GDBN} allows you to put a program's debugging information in a
15238 file separate from the executable itself, in a way that allows
15239 @value{GDBN} to find and load the debugging information automatically.
15240 Since debugging information can be very large---sometimes larger
15241 than the executable code itself---some systems distribute debugging
15242 information for their executables in separate files, which users can
15243 install only when they need to debug a problem.
15245 @value{GDBN} supports two ways of specifying the separate debug info
15250 The executable contains a @dfn{debug link} that specifies the name of
15251 the separate debug info file. The separate debug file's name is
15252 usually @file{@var{executable}.debug}, where @var{executable} is the
15253 name of the corresponding executable file without leading directories
15254 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15255 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15256 checksum for the debug file, which @value{GDBN} uses to validate that
15257 the executable and the debug file came from the same build.
15260 The executable contains a @dfn{build ID}, a unique bit string that is
15261 also present in the corresponding debug info file. (This is supported
15262 only on some operating systems, notably those which use the ELF format
15263 for binary files and the @sc{gnu} Binutils.) For more details about
15264 this feature, see the description of the @option{--build-id}
15265 command-line option in @ref{Options, , Command Line Options, ld.info,
15266 The GNU Linker}. The debug info file's name is not specified
15267 explicitly by the build ID, but can be computed from the build ID, see
15271 Depending on the way the debug info file is specified, @value{GDBN}
15272 uses two different methods of looking for the debug file:
15276 For the ``debug link'' method, @value{GDBN} looks up the named file in
15277 the directory of the executable file, then in a subdirectory of that
15278 directory named @file{.debug}, and finally under the global debug
15279 directory, in a subdirectory whose name is identical to the leading
15280 directories of the executable's absolute file name.
15283 For the ``build ID'' method, @value{GDBN} looks in the
15284 @file{.build-id} subdirectory of the global debug directory for a file
15285 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15286 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15287 are the rest of the bit string. (Real build ID strings are 32 or more
15288 hex characters, not 10.)
15291 So, for example, suppose you ask @value{GDBN} to debug
15292 @file{/usr/bin/ls}, which has a debug link that specifies the
15293 file @file{ls.debug}, and a build ID whose value in hex is
15294 @code{abcdef1234}. If the global debug directory is
15295 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15296 debug information files, in the indicated order:
15300 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15302 @file{/usr/bin/ls.debug}
15304 @file{/usr/bin/.debug/ls.debug}
15306 @file{/usr/lib/debug/usr/bin/ls.debug}.
15309 You can set the global debugging info directory's name, and view the
15310 name @value{GDBN} is currently using.
15314 @kindex set debug-file-directory
15315 @item set debug-file-directory @var{directories}
15316 Set the directories which @value{GDBN} searches for separate debugging
15317 information files to @var{directory}. Multiple directory components can be set
15318 concatenating them by a directory separator.
15320 @kindex show debug-file-directory
15321 @item show debug-file-directory
15322 Show the directories @value{GDBN} searches for separate debugging
15327 @cindex @code{.gnu_debuglink} sections
15328 @cindex debug link sections
15329 A debug link is a special section of the executable file named
15330 @code{.gnu_debuglink}. The section must contain:
15334 A filename, with any leading directory components removed, followed by
15337 zero to three bytes of padding, as needed to reach the next four-byte
15338 boundary within the section, and
15340 a four-byte CRC checksum, stored in the same endianness used for the
15341 executable file itself. The checksum is computed on the debugging
15342 information file's full contents by the function given below, passing
15343 zero as the @var{crc} argument.
15346 Any executable file format can carry a debug link, as long as it can
15347 contain a section named @code{.gnu_debuglink} with the contents
15350 @cindex @code{.note.gnu.build-id} sections
15351 @cindex build ID sections
15352 The build ID is a special section in the executable file (and in other
15353 ELF binary files that @value{GDBN} may consider). This section is
15354 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15355 It contains unique identification for the built files---the ID remains
15356 the same across multiple builds of the same build tree. The default
15357 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15358 content for the build ID string. The same section with an identical
15359 value is present in the original built binary with symbols, in its
15360 stripped variant, and in the separate debugging information file.
15362 The debugging information file itself should be an ordinary
15363 executable, containing a full set of linker symbols, sections, and
15364 debugging information. The sections of the debugging information file
15365 should have the same names, addresses, and sizes as the original file,
15366 but they need not contain any data---much like a @code{.bss} section
15367 in an ordinary executable.
15369 The @sc{gnu} binary utilities (Binutils) package includes the
15370 @samp{objcopy} utility that can produce
15371 the separated executable / debugging information file pairs using the
15372 following commands:
15375 @kbd{objcopy --only-keep-debug foo foo.debug}
15380 These commands remove the debugging
15381 information from the executable file @file{foo} and place it in the file
15382 @file{foo.debug}. You can use the first, second or both methods to link the
15387 The debug link method needs the following additional command to also leave
15388 behind a debug link in @file{foo}:
15391 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15394 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15395 a version of the @code{strip} command such that the command @kbd{strip foo -f
15396 foo.debug} has the same functionality as the two @code{objcopy} commands and
15397 the @code{ln -s} command above, together.
15400 Build ID gets embedded into the main executable using @code{ld --build-id} or
15401 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15402 compatibility fixes for debug files separation are present in @sc{gnu} binary
15403 utilities (Binutils) package since version 2.18.
15408 @cindex CRC algorithm definition
15409 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15410 IEEE 802.3 using the polynomial:
15412 @c TexInfo requires naked braces for multi-digit exponents for Tex
15413 @c output, but this causes HTML output to barf. HTML has to be set using
15414 @c raw commands. So we end up having to specify this equation in 2
15419 <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>
15420 + <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
15426 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15427 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15431 The function is computed byte at a time, taking the least
15432 significant bit of each byte first. The initial pattern
15433 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15434 the final result is inverted to ensure trailing zeros also affect the
15437 @emph{Note:} This is the same CRC polynomial as used in handling the
15438 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15439 , @value{GDBN} Remote Serial Protocol}). However in the
15440 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15441 significant bit first, and the result is not inverted, so trailing
15442 zeros have no effect on the CRC value.
15444 To complete the description, we show below the code of the function
15445 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15446 initially supplied @code{crc} argument means that an initial call to
15447 this function passing in zero will start computing the CRC using
15450 @kindex gnu_debuglink_crc32
15453 gnu_debuglink_crc32 (unsigned long crc,
15454 unsigned char *buf, size_t len)
15456 static const unsigned long crc32_table[256] =
15458 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15459 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15460 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15461 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15462 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15463 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15464 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15465 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15466 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15467 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15468 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15469 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15470 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15471 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15472 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15473 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15474 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15475 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15476 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15477 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15478 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15479 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15480 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15481 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15482 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15483 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15484 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15485 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15486 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15487 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15488 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15489 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15490 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15491 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15492 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15493 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15494 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15495 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15496 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15497 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15498 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15499 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15500 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15501 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15502 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15503 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15504 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15505 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15506 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15507 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15508 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15511 unsigned char *end;
15513 crc = ~crc & 0xffffffff;
15514 for (end = buf + len; buf < end; ++buf)
15515 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15516 return ~crc & 0xffffffff;
15521 This computation does not apply to the ``build ID'' method.
15525 @section Index Files Speed Up @value{GDBN}
15526 @cindex index files
15527 @cindex @samp{.gdb_index} section
15529 When @value{GDBN} finds a symbol file, it scans the symbols in the
15530 file in order to construct an internal symbol table. This lets most
15531 @value{GDBN} operations work quickly---at the cost of a delay early
15532 on. For large programs, this delay can be quite lengthy, so
15533 @value{GDBN} provides a way to build an index, which speeds up
15536 The index is stored as a section in the symbol file. @value{GDBN} can
15537 write the index to a file, then you can put it into the symbol file
15538 using @command{objcopy}.
15540 To create an index file, use the @code{save gdb-index} command:
15543 @item save gdb-index @var{directory}
15544 @kindex save gdb-index
15545 Create an index file for each symbol file currently known by
15546 @value{GDBN}. Each file is named after its corresponding symbol file,
15547 with @samp{.gdb-index} appended, and is written into the given
15551 Once you have created an index file you can merge it into your symbol
15552 file, here named @file{symfile}, using @command{objcopy}:
15555 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15556 --set-section-flags .gdb_index=readonly symfile symfile
15559 There are currently some limitation on indices. They only work when
15560 for DWARF debugging information, not stabs. And, they do not
15561 currently work for programs using Ada.
15563 @node Symbol Errors
15564 @section Errors Reading Symbol Files
15566 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15567 such as symbol types it does not recognize, or known bugs in compiler
15568 output. By default, @value{GDBN} does not notify you of such problems, since
15569 they are relatively common and primarily of interest to people
15570 debugging compilers. If you are interested in seeing information
15571 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15572 only one message about each such type of problem, no matter how many
15573 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15574 to see how many times the problems occur, with the @code{set
15575 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15578 The messages currently printed, and their meanings, include:
15581 @item inner block not inside outer block in @var{symbol}
15583 The symbol information shows where symbol scopes begin and end
15584 (such as at the start of a function or a block of statements). This
15585 error indicates that an inner scope block is not fully contained
15586 in its outer scope blocks.
15588 @value{GDBN} circumvents the problem by treating the inner block as if it had
15589 the same scope as the outer block. In the error message, @var{symbol}
15590 may be shown as ``@code{(don't know)}'' if the outer block is not a
15593 @item block at @var{address} out of order
15595 The symbol information for symbol scope blocks should occur in
15596 order of increasing addresses. This error indicates that it does not
15599 @value{GDBN} does not circumvent this problem, and has trouble
15600 locating symbols in the source file whose symbols it is reading. (You
15601 can often determine what source file is affected by specifying
15602 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15605 @item bad block start address patched
15607 The symbol information for a symbol scope block has a start address
15608 smaller than the address of the preceding source line. This is known
15609 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15611 @value{GDBN} circumvents the problem by treating the symbol scope block as
15612 starting on the previous source line.
15614 @item bad string table offset in symbol @var{n}
15617 Symbol number @var{n} contains a pointer into the string table which is
15618 larger than the size of the string table.
15620 @value{GDBN} circumvents the problem by considering the symbol to have the
15621 name @code{foo}, which may cause other problems if many symbols end up
15624 @item unknown symbol type @code{0x@var{nn}}
15626 The symbol information contains new data types that @value{GDBN} does
15627 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15628 uncomprehended information, in hexadecimal.
15630 @value{GDBN} circumvents the error by ignoring this symbol information.
15631 This usually allows you to debug your program, though certain symbols
15632 are not accessible. If you encounter such a problem and feel like
15633 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15634 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15635 and examine @code{*bufp} to see the symbol.
15637 @item stub type has NULL name
15639 @value{GDBN} could not find the full definition for a struct or class.
15641 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15642 The symbol information for a C@t{++} member function is missing some
15643 information that recent versions of the compiler should have output for
15646 @item info mismatch between compiler and debugger
15648 @value{GDBN} could not parse a type specification output by the compiler.
15653 @section GDB Data Files
15655 @cindex prefix for data files
15656 @value{GDBN} will sometimes read an auxiliary data file. These files
15657 are kept in a directory known as the @dfn{data directory}.
15659 You can set the data directory's name, and view the name @value{GDBN}
15660 is currently using.
15663 @kindex set data-directory
15664 @item set data-directory @var{directory}
15665 Set the directory which @value{GDBN} searches for auxiliary data files
15666 to @var{directory}.
15668 @kindex show data-directory
15669 @item show data-directory
15670 Show the directory @value{GDBN} searches for auxiliary data files.
15673 @cindex default data directory
15674 @cindex @samp{--with-gdb-datadir}
15675 You can set the default data directory by using the configure-time
15676 @samp{--with-gdb-datadir} option. If the data directory is inside
15677 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15678 @samp{--exec-prefix}), then the default data directory will be updated
15679 automatically if the installed @value{GDBN} is moved to a new
15682 The data directory may also be specified with the
15683 @code{--data-directory} command line option.
15684 @xref{Mode Options}.
15687 @chapter Specifying a Debugging Target
15689 @cindex debugging target
15690 A @dfn{target} is the execution environment occupied by your program.
15692 Often, @value{GDBN} runs in the same host environment as your program;
15693 in that case, the debugging target is specified as a side effect when
15694 you use the @code{file} or @code{core} commands. When you need more
15695 flexibility---for example, running @value{GDBN} on a physically separate
15696 host, or controlling a standalone system over a serial port or a
15697 realtime system over a TCP/IP connection---you can use the @code{target}
15698 command to specify one of the target types configured for @value{GDBN}
15699 (@pxref{Target Commands, ,Commands for Managing Targets}).
15701 @cindex target architecture
15702 It is possible to build @value{GDBN} for several different @dfn{target
15703 architectures}. When @value{GDBN} is built like that, you can choose
15704 one of the available architectures with the @kbd{set architecture}
15708 @kindex set architecture
15709 @kindex show architecture
15710 @item set architecture @var{arch}
15711 This command sets the current target architecture to @var{arch}. The
15712 value of @var{arch} can be @code{"auto"}, in addition to one of the
15713 supported architectures.
15715 @item show architecture
15716 Show the current target architecture.
15718 @item set processor
15720 @kindex set processor
15721 @kindex show processor
15722 These are alias commands for, respectively, @code{set architecture}
15723 and @code{show architecture}.
15727 * Active Targets:: Active targets
15728 * Target Commands:: Commands for managing targets
15729 * Byte Order:: Choosing target byte order
15732 @node Active Targets
15733 @section Active Targets
15735 @cindex stacking targets
15736 @cindex active targets
15737 @cindex multiple targets
15739 There are multiple classes of targets such as: processes, executable files or
15740 recording sessions. Core files belong to the process class, making core file
15741 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15742 on multiple active targets, one in each class. This allows you to (for
15743 example) start a process and inspect its activity, while still having access to
15744 the executable file after the process finishes. Or if you start process
15745 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15746 presented a virtual layer of the recording target, while the process target
15747 remains stopped at the chronologically last point of the process execution.
15749 Use the @code{core-file} and @code{exec-file} commands to select a new core
15750 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15751 specify as a target a process that is already running, use the @code{attach}
15752 command (@pxref{Attach, ,Debugging an Already-running Process}).
15754 @node Target Commands
15755 @section Commands for Managing Targets
15758 @item target @var{type} @var{parameters}
15759 Connects the @value{GDBN} host environment to a target machine or
15760 process. A target is typically a protocol for talking to debugging
15761 facilities. You use the argument @var{type} to specify the type or
15762 protocol of the target machine.
15764 Further @var{parameters} are interpreted by the target protocol, but
15765 typically include things like device names or host names to connect
15766 with, process numbers, and baud rates.
15768 The @code{target} command does not repeat if you press @key{RET} again
15769 after executing the command.
15771 @kindex help target
15773 Displays the names of all targets available. To display targets
15774 currently selected, use either @code{info target} or @code{info files}
15775 (@pxref{Files, ,Commands to Specify Files}).
15777 @item help target @var{name}
15778 Describe a particular target, including any parameters necessary to
15781 @kindex set gnutarget
15782 @item set gnutarget @var{args}
15783 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15784 knows whether it is reading an @dfn{executable},
15785 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15786 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15787 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15790 @emph{Warning:} To specify a file format with @code{set gnutarget},
15791 you must know the actual BFD name.
15795 @xref{Files, , Commands to Specify Files}.
15797 @kindex show gnutarget
15798 @item show gnutarget
15799 Use the @code{show gnutarget} command to display what file format
15800 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15801 @value{GDBN} will determine the file format for each file automatically,
15802 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15805 @cindex common targets
15806 Here are some common targets (available, or not, depending on the GDB
15811 @item target exec @var{program}
15812 @cindex executable file target
15813 An executable file. @samp{target exec @var{program}} is the same as
15814 @samp{exec-file @var{program}}.
15816 @item target core @var{filename}
15817 @cindex core dump file target
15818 A core dump file. @samp{target core @var{filename}} is the same as
15819 @samp{core-file @var{filename}}.
15821 @item target remote @var{medium}
15822 @cindex remote target
15823 A remote system connected to @value{GDBN} via a serial line or network
15824 connection. This command tells @value{GDBN} to use its own remote
15825 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15827 For example, if you have a board connected to @file{/dev/ttya} on the
15828 machine running @value{GDBN}, you could say:
15831 target remote /dev/ttya
15834 @code{target remote} supports the @code{load} command. This is only
15835 useful if you have some other way of getting the stub to the target
15836 system, and you can put it somewhere in memory where it won't get
15837 clobbered by the download.
15839 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15840 @cindex built-in simulator target
15841 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15849 works; however, you cannot assume that a specific memory map, device
15850 drivers, or even basic I/O is available, although some simulators do
15851 provide these. For info about any processor-specific simulator details,
15852 see the appropriate section in @ref{Embedded Processors, ,Embedded
15857 Some configurations may include these targets as well:
15861 @item target nrom @var{dev}
15862 @cindex NetROM ROM emulator target
15863 NetROM ROM emulator. This target only supports downloading.
15867 Different targets are available on different configurations of @value{GDBN};
15868 your configuration may have more or fewer targets.
15870 Many remote targets require you to download the executable's code once
15871 you've successfully established a connection. You may wish to control
15872 various aspects of this process.
15877 @kindex set hash@r{, for remote monitors}
15878 @cindex hash mark while downloading
15879 This command controls whether a hash mark @samp{#} is displayed while
15880 downloading a file to the remote monitor. If on, a hash mark is
15881 displayed after each S-record is successfully downloaded to the
15885 @kindex show hash@r{, for remote monitors}
15886 Show the current status of displaying the hash mark.
15888 @item set debug monitor
15889 @kindex set debug monitor
15890 @cindex display remote monitor communications
15891 Enable or disable display of communications messages between
15892 @value{GDBN} and the remote monitor.
15894 @item show debug monitor
15895 @kindex show debug monitor
15896 Show the current status of displaying communications between
15897 @value{GDBN} and the remote monitor.
15902 @kindex load @var{filename}
15903 @item load @var{filename}
15905 Depending on what remote debugging facilities are configured into
15906 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15907 is meant to make @var{filename} (an executable) available for debugging
15908 on the remote system---by downloading, or dynamic linking, for example.
15909 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15910 the @code{add-symbol-file} command.
15912 If your @value{GDBN} does not have a @code{load} command, attempting to
15913 execute it gets the error message ``@code{You can't do that when your
15914 target is @dots{}}''
15916 The file is loaded at whatever address is specified in the executable.
15917 For some object file formats, you can specify the load address when you
15918 link the program; for other formats, like a.out, the object file format
15919 specifies a fixed address.
15920 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15922 Depending on the remote side capabilities, @value{GDBN} may be able to
15923 load programs into flash memory.
15925 @code{load} does not repeat if you press @key{RET} again after using it.
15929 @section Choosing Target Byte Order
15931 @cindex choosing target byte order
15932 @cindex target byte order
15934 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15935 offer the ability to run either big-endian or little-endian byte
15936 orders. Usually the executable or symbol will include a bit to
15937 designate the endian-ness, and you will not need to worry about
15938 which to use. However, you may still find it useful to adjust
15939 @value{GDBN}'s idea of processor endian-ness manually.
15943 @item set endian big
15944 Instruct @value{GDBN} to assume the target is big-endian.
15946 @item set endian little
15947 Instruct @value{GDBN} to assume the target is little-endian.
15949 @item set endian auto
15950 Instruct @value{GDBN} to use the byte order associated with the
15954 Display @value{GDBN}'s current idea of the target byte order.
15958 Note that these commands merely adjust interpretation of symbolic
15959 data on the host, and that they have absolutely no effect on the
15963 @node Remote Debugging
15964 @chapter Debugging Remote Programs
15965 @cindex remote debugging
15967 If you are trying to debug a program running on a machine that cannot run
15968 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15969 For example, you might use remote debugging on an operating system kernel,
15970 or on a small system which does not have a general purpose operating system
15971 powerful enough to run a full-featured debugger.
15973 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15974 to make this work with particular debugging targets. In addition,
15975 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15976 but not specific to any particular target system) which you can use if you
15977 write the remote stubs---the code that runs on the remote system to
15978 communicate with @value{GDBN}.
15980 Other remote targets may be available in your
15981 configuration of @value{GDBN}; use @code{help target} to list them.
15984 * Connecting:: Connecting to a remote target
15985 * File Transfer:: Sending files to a remote system
15986 * Server:: Using the gdbserver program
15987 * Remote Configuration:: Remote configuration
15988 * Remote Stub:: Implementing a remote stub
15992 @section Connecting to a Remote Target
15994 On the @value{GDBN} host machine, you will need an unstripped copy of
15995 your program, since @value{GDBN} needs symbol and debugging information.
15996 Start up @value{GDBN} as usual, using the name of the local copy of your
15997 program as the first argument.
15999 @cindex @code{target remote}
16000 @value{GDBN} can communicate with the target over a serial line, or
16001 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16002 each case, @value{GDBN} uses the same protocol for debugging your
16003 program; only the medium carrying the debugging packets varies. The
16004 @code{target remote} command establishes a connection to the target.
16005 Its arguments indicate which medium to use:
16009 @item target remote @var{serial-device}
16010 @cindex serial line, @code{target remote}
16011 Use @var{serial-device} to communicate with the target. For example,
16012 to use a serial line connected to the device named @file{/dev/ttyb}:
16015 target remote /dev/ttyb
16018 If you're using a serial line, you may want to give @value{GDBN} the
16019 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16020 (@pxref{Remote Configuration, set remotebaud}) before the
16021 @code{target} command.
16023 @item target remote @code{@var{host}:@var{port}}
16024 @itemx target remote @code{tcp:@var{host}:@var{port}}
16025 @cindex @acronym{TCP} port, @code{target remote}
16026 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16027 The @var{host} may be either a host name or a numeric @acronym{IP}
16028 address; @var{port} must be a decimal number. The @var{host} could be
16029 the target machine itself, if it is directly connected to the net, or
16030 it might be a terminal server which in turn has a serial line to the
16033 For example, to connect to port 2828 on a terminal server named
16037 target remote manyfarms:2828
16040 If your remote target is actually running on the same machine as your
16041 debugger session (e.g.@: a simulator for your target running on the
16042 same host), you can omit the hostname. For example, to connect to
16043 port 1234 on your local machine:
16046 target remote :1234
16050 Note that the colon is still required here.
16052 @item target remote @code{udp:@var{host}:@var{port}}
16053 @cindex @acronym{UDP} port, @code{target remote}
16054 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16055 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16058 target remote udp:manyfarms:2828
16061 When using a @acronym{UDP} connection for remote debugging, you should
16062 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16063 can silently drop packets on busy or unreliable networks, which will
16064 cause havoc with your debugging session.
16066 @item target remote | @var{command}
16067 @cindex pipe, @code{target remote} to
16068 Run @var{command} in the background and communicate with it using a
16069 pipe. The @var{command} is a shell command, to be parsed and expanded
16070 by the system's command shell, @code{/bin/sh}; it should expect remote
16071 protocol packets on its standard input, and send replies on its
16072 standard output. You could use this to run a stand-alone simulator
16073 that speaks the remote debugging protocol, to make net connections
16074 using programs like @code{ssh}, or for other similar tricks.
16076 If @var{command} closes its standard output (perhaps by exiting),
16077 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16078 program has already exited, this will have no effect.)
16082 Once the connection has been established, you can use all the usual
16083 commands to examine and change data. The remote program is already
16084 running; you can use @kbd{step} and @kbd{continue}, and you do not
16085 need to use @kbd{run}.
16087 @cindex interrupting remote programs
16088 @cindex remote programs, interrupting
16089 Whenever @value{GDBN} is waiting for the remote program, if you type the
16090 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16091 program. This may or may not succeed, depending in part on the hardware
16092 and the serial drivers the remote system uses. If you type the
16093 interrupt character once again, @value{GDBN} displays this prompt:
16096 Interrupted while waiting for the program.
16097 Give up (and stop debugging it)? (y or n)
16100 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16101 (If you decide you want to try again later, you can use @samp{target
16102 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16103 goes back to waiting.
16106 @kindex detach (remote)
16108 When you have finished debugging the remote program, you can use the
16109 @code{detach} command to release it from @value{GDBN} control.
16110 Detaching from the target normally resumes its execution, but the results
16111 will depend on your particular remote stub. After the @code{detach}
16112 command, @value{GDBN} is free to connect to another target.
16116 The @code{disconnect} command behaves like @code{detach}, except that
16117 the target is generally not resumed. It will wait for @value{GDBN}
16118 (this instance or another one) to connect and continue debugging. After
16119 the @code{disconnect} command, @value{GDBN} is again free to connect to
16122 @cindex send command to remote monitor
16123 @cindex extend @value{GDBN} for remote targets
16124 @cindex add new commands for external monitor
16126 @item monitor @var{cmd}
16127 This command allows you to send arbitrary commands directly to the
16128 remote monitor. Since @value{GDBN} doesn't care about the commands it
16129 sends like this, this command is the way to extend @value{GDBN}---you
16130 can add new commands that only the external monitor will understand
16134 @node File Transfer
16135 @section Sending files to a remote system
16136 @cindex remote target, file transfer
16137 @cindex file transfer
16138 @cindex sending files to remote systems
16140 Some remote targets offer the ability to transfer files over the same
16141 connection used to communicate with @value{GDBN}. This is convenient
16142 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16143 running @code{gdbserver} over a network interface. For other targets,
16144 e.g.@: embedded devices with only a single serial port, this may be
16145 the only way to upload or download files.
16147 Not all remote targets support these commands.
16151 @item remote put @var{hostfile} @var{targetfile}
16152 Copy file @var{hostfile} from the host system (the machine running
16153 @value{GDBN}) to @var{targetfile} on the target system.
16156 @item remote get @var{targetfile} @var{hostfile}
16157 Copy file @var{targetfile} from the target system to @var{hostfile}
16158 on the host system.
16160 @kindex remote delete
16161 @item remote delete @var{targetfile}
16162 Delete @var{targetfile} from the target system.
16167 @section Using the @code{gdbserver} Program
16170 @cindex remote connection without stubs
16171 @code{gdbserver} is a control program for Unix-like systems, which
16172 allows you to connect your program with a remote @value{GDBN} via
16173 @code{target remote}---but without linking in the usual debugging stub.
16175 @code{gdbserver} is not a complete replacement for the debugging stubs,
16176 because it requires essentially the same operating-system facilities
16177 that @value{GDBN} itself does. In fact, a system that can run
16178 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16179 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16180 because it is a much smaller program than @value{GDBN} itself. It is
16181 also easier to port than all of @value{GDBN}, so you may be able to get
16182 started more quickly on a new system by using @code{gdbserver}.
16183 Finally, if you develop code for real-time systems, you may find that
16184 the tradeoffs involved in real-time operation make it more convenient to
16185 do as much development work as possible on another system, for example
16186 by cross-compiling. You can use @code{gdbserver} to make a similar
16187 choice for debugging.
16189 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16190 or a TCP connection, using the standard @value{GDBN} remote serial
16194 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16195 Do not run @code{gdbserver} connected to any public network; a
16196 @value{GDBN} connection to @code{gdbserver} provides access to the
16197 target system with the same privileges as the user running
16201 @subsection Running @code{gdbserver}
16202 @cindex arguments, to @code{gdbserver}
16203 @cindex @code{gdbserver}, command-line arguments
16205 Run @code{gdbserver} on the target system. You need a copy of the
16206 program you want to debug, including any libraries it requires.
16207 @code{gdbserver} does not need your program's symbol table, so you can
16208 strip the program if necessary to save space. @value{GDBN} on the host
16209 system does all the symbol handling.
16211 To use the server, you must tell it how to communicate with @value{GDBN};
16212 the name of your program; and the arguments for your program. The usual
16216 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16219 @var{comm} is either a device name (to use a serial line) or a TCP
16220 hostname and portnumber. For example, to debug Emacs with the argument
16221 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16225 target> gdbserver /dev/com1 emacs foo.txt
16228 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16231 To use a TCP connection instead of a serial line:
16234 target> gdbserver host:2345 emacs foo.txt
16237 The only difference from the previous example is the first argument,
16238 specifying that you are communicating with the host @value{GDBN} via
16239 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16240 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16241 (Currently, the @samp{host} part is ignored.) You can choose any number
16242 you want for the port number as long as it does not conflict with any
16243 TCP ports already in use on the target system (for example, @code{23} is
16244 reserved for @code{telnet}).@footnote{If you choose a port number that
16245 conflicts with another service, @code{gdbserver} prints an error message
16246 and exits.} You must use the same port number with the host @value{GDBN}
16247 @code{target remote} command.
16249 @subsubsection Attaching to a Running Program
16250 @cindex attach to a program, @code{gdbserver}
16251 @cindex @option{--attach}, @code{gdbserver} option
16253 On some targets, @code{gdbserver} can also attach to running programs.
16254 This is accomplished via the @code{--attach} argument. The syntax is:
16257 target> gdbserver --attach @var{comm} @var{pid}
16260 @var{pid} is the process ID of a currently running process. It isn't necessary
16261 to point @code{gdbserver} at a binary for the running process.
16264 You can debug processes by name instead of process ID if your target has the
16265 @code{pidof} utility:
16268 target> gdbserver --attach @var{comm} `pidof @var{program}`
16271 In case more than one copy of @var{program} is running, or @var{program}
16272 has multiple threads, most versions of @code{pidof} support the
16273 @code{-s} option to only return the first process ID.
16275 @subsubsection Multi-Process Mode for @code{gdbserver}
16276 @cindex @code{gdbserver}, multiple processes
16277 @cindex multiple processes with @code{gdbserver}
16279 When you connect to @code{gdbserver} using @code{target remote},
16280 @code{gdbserver} debugs the specified program only once. When the
16281 program exits, or you detach from it, @value{GDBN} closes the connection
16282 and @code{gdbserver} exits.
16284 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16285 enters multi-process mode. When the debugged program exits, or you
16286 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16287 though no program is running. The @code{run} and @code{attach}
16288 commands instruct @code{gdbserver} to run or attach to a new program.
16289 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16290 remote exec-file}) to select the program to run. Command line
16291 arguments are supported, except for wildcard expansion and I/O
16292 redirection (@pxref{Arguments}).
16294 @cindex @option{--multi}, @code{gdbserver} option
16295 To start @code{gdbserver} without supplying an initial command to run
16296 or process ID to attach, use the @option{--multi} command line option.
16297 Then you can connect using @kbd{target extended-remote} and start
16298 the program you want to debug.
16300 In multi-process mode @code{gdbserver} does not automatically exit unless you
16301 use the option @option{--once}. You can terminate it by using
16302 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16303 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16304 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16305 @option{--multi} option to @code{gdbserver} has no influence on that.
16307 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16309 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16311 @code{gdbserver} normally terminates after all of its debugged processes have
16312 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16313 extended-remote}, @code{gdbserver} stays running even with no processes left.
16314 @value{GDBN} normally terminates the spawned debugged process on its exit,
16315 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16316 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16317 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16318 stays running even in the @kbd{target remote} mode.
16320 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16321 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16322 completeness, at most one @value{GDBN} can be connected at a time.
16324 @cindex @option{--once}, @code{gdbserver} option
16325 By default, @code{gdbserver} keeps the listening TCP port open, so that
16326 additional connections are possible. However, if you start @code{gdbserver}
16327 with the @option{--once} option, it will stop listening for any further
16328 connection attempts after connecting to the first @value{GDBN} session. This
16329 means no further connections to @code{gdbserver} will be possible after the
16330 first one. It also means @code{gdbserver} will terminate after the first
16331 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16332 connections and even in the @kbd{target extended-remote} mode. The
16333 @option{--once} option allows reusing the same port number for connecting to
16334 multiple instances of @code{gdbserver} running on the same host, since each
16335 instance closes its port after the first connection.
16337 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16339 @cindex @option{--debug}, @code{gdbserver} option
16340 The @option{--debug} option tells @code{gdbserver} to display extra
16341 status information about the debugging process.
16342 @cindex @option{--remote-debug}, @code{gdbserver} option
16343 The @option{--remote-debug} option tells @code{gdbserver} to display
16344 remote protocol debug output. These options are intended for
16345 @code{gdbserver} development and for bug reports to the developers.
16347 @cindex @option{--wrapper}, @code{gdbserver} option
16348 The @option{--wrapper} option specifies a wrapper to launch programs
16349 for debugging. The option should be followed by the name of the
16350 wrapper, then any command-line arguments to pass to the wrapper, then
16351 @kbd{--} indicating the end of the wrapper arguments.
16353 @code{gdbserver} runs the specified wrapper program with a combined
16354 command line including the wrapper arguments, then the name of the
16355 program to debug, then any arguments to the program. The wrapper
16356 runs until it executes your program, and then @value{GDBN} gains control.
16358 You can use any program that eventually calls @code{execve} with
16359 its arguments as a wrapper. Several standard Unix utilities do
16360 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16361 with @code{exec "$@@"} will also work.
16363 For example, you can use @code{env} to pass an environment variable to
16364 the debugged program, without setting the variable in @code{gdbserver}'s
16368 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16371 @subsection Connecting to @code{gdbserver}
16373 Run @value{GDBN} on the host system.
16375 First make sure you have the necessary symbol files. Load symbols for
16376 your application using the @code{file} command before you connect. Use
16377 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16378 was compiled with the correct sysroot using @code{--with-sysroot}).
16380 The symbol file and target libraries must exactly match the executable
16381 and libraries on the target, with one exception: the files on the host
16382 system should not be stripped, even if the files on the target system
16383 are. Mismatched or missing files will lead to confusing results
16384 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16385 files may also prevent @code{gdbserver} from debugging multi-threaded
16388 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16389 For TCP connections, you must start up @code{gdbserver} prior to using
16390 the @code{target remote} command. Otherwise you may get an error whose
16391 text depends on the host system, but which usually looks something like
16392 @samp{Connection refused}. Don't use the @code{load}
16393 command in @value{GDBN} when using @code{gdbserver}, since the program is
16394 already on the target.
16396 @subsection Monitor Commands for @code{gdbserver}
16397 @cindex monitor commands, for @code{gdbserver}
16398 @anchor{Monitor Commands for gdbserver}
16400 During a @value{GDBN} session using @code{gdbserver}, you can use the
16401 @code{monitor} command to send special requests to @code{gdbserver}.
16402 Here are the available commands.
16406 List the available monitor commands.
16408 @item monitor set debug 0
16409 @itemx monitor set debug 1
16410 Disable or enable general debugging messages.
16412 @item monitor set remote-debug 0
16413 @itemx monitor set remote-debug 1
16414 Disable or enable specific debugging messages associated with the remote
16415 protocol (@pxref{Remote Protocol}).
16417 @item monitor set libthread-db-search-path [PATH]
16418 @cindex gdbserver, search path for @code{libthread_db}
16419 When this command is issued, @var{path} is a colon-separated list of
16420 directories to search for @code{libthread_db} (@pxref{Threads,,set
16421 libthread-db-search-path}). If you omit @var{path},
16422 @samp{libthread-db-search-path} will be reset to its default value.
16424 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16425 not supported in @code{gdbserver}.
16428 Tell gdbserver to exit immediately. This command should be followed by
16429 @code{disconnect} to close the debugging session. @code{gdbserver} will
16430 detach from any attached processes and kill any processes it created.
16431 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16432 of a multi-process mode debug session.
16436 @subsection Tracepoints support in @code{gdbserver}
16437 @cindex tracepoints support in @code{gdbserver}
16439 On some targets, @code{gdbserver} supports tracepoints, fast
16440 tracepoints and static tracepoints.
16442 For fast or static tracepoints to work, a special library called the
16443 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16444 This library is built and distributed as an integral part of
16445 @code{gdbserver}. In addition, support for static tracepoints
16446 requires building the in-process agent library with static tracepoints
16447 support. At present, the UST (LTTng Userspace Tracer,
16448 @url{http://lttng.org/ust}) tracing engine is supported. This support
16449 is automatically available if UST development headers are found in the
16450 standard include path when @code{gdbserver} is built, or if
16451 @code{gdbserver} was explicitly configured using @option{--with-ust}
16452 to point at such headers. You can explicitly disable the support
16453 using @option{--with-ust=no}.
16455 There are several ways to load the in-process agent in your program:
16458 @item Specifying it as dependency at link time
16460 You can link your program dynamically with the in-process agent
16461 library. On most systems, this is accomplished by adding
16462 @code{-linproctrace} to the link command.
16464 @item Using the system's preloading mechanisms
16466 You can force loading the in-process agent at startup time by using
16467 your system's support for preloading shared libraries. Many Unixes
16468 support the concept of preloading user defined libraries. In most
16469 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16470 in the environment. See also the description of @code{gdbserver}'s
16471 @option{--wrapper} command line option.
16473 @item Using @value{GDBN} to force loading the agent at run time
16475 On some systems, you can force the inferior to load a shared library,
16476 by calling a dynamic loader function in the inferior that takes care
16477 of dynamically looking up and loading a shared library. On most Unix
16478 systems, the function is @code{dlopen}. You'll use the @code{call}
16479 command for that. For example:
16482 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16485 Note that on most Unix systems, for the @code{dlopen} function to be
16486 available, the program needs to be linked with @code{-ldl}.
16489 On systems that have a userspace dynamic loader, like most Unix
16490 systems, when you connect to @code{gdbserver} using @code{target
16491 remote}, you'll find that the program is stopped at the dynamic
16492 loader's entry point, and no shared library has been loaded in the
16493 program's address space yet, including the in-process agent. In that
16494 case, before being able to use any of the fast or static tracepoints
16495 features, you need to let the loader run and load the shared
16496 libraries. The simplest way to do that is to run the program to the
16497 main procedure. E.g., if debugging a C or C@t{++} program, start
16498 @code{gdbserver} like so:
16501 $ gdbserver :9999 myprogram
16504 Start GDB and connect to @code{gdbserver} like so, and run to main:
16508 (@value{GDBP}) target remote myhost:9999
16509 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16510 (@value{GDBP}) b main
16511 (@value{GDBP}) continue
16514 The in-process tracing agent library should now be loaded into the
16515 process; you can confirm it with the @code{info sharedlibrary}
16516 command, which will list @file{libinproctrace.so} as loaded in the
16517 process. You are now ready to install fast tracepoints, list static
16518 tracepoint markers, probe static tracepoints markers, and start
16521 @node Remote Configuration
16522 @section Remote Configuration
16525 @kindex show remote
16526 This section documents the configuration options available when
16527 debugging remote programs. For the options related to the File I/O
16528 extensions of the remote protocol, see @ref{system,
16529 system-call-allowed}.
16532 @item set remoteaddresssize @var{bits}
16533 @cindex address size for remote targets
16534 @cindex bits in remote address
16535 Set the maximum size of address in a memory packet to the specified
16536 number of bits. @value{GDBN} will mask off the address bits above
16537 that number, when it passes addresses to the remote target. The
16538 default value is the number of bits in the target's address.
16540 @item show remoteaddresssize
16541 Show the current value of remote address size in bits.
16543 @item set remotebaud @var{n}
16544 @cindex baud rate for remote targets
16545 Set the baud rate for the remote serial I/O to @var{n} baud. The
16546 value is used to set the speed of the serial port used for debugging
16549 @item show remotebaud
16550 Show the current speed of the remote connection.
16552 @item set remotebreak
16553 @cindex interrupt remote programs
16554 @cindex BREAK signal instead of Ctrl-C
16555 @anchor{set remotebreak}
16556 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16557 when you type @kbd{Ctrl-c} to interrupt the program running
16558 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16559 character instead. The default is off, since most remote systems
16560 expect to see @samp{Ctrl-C} as the interrupt signal.
16562 @item show remotebreak
16563 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16564 interrupt the remote program.
16566 @item set remoteflow on
16567 @itemx set remoteflow off
16568 @kindex set remoteflow
16569 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16570 on the serial port used to communicate to the remote target.
16572 @item show remoteflow
16573 @kindex show remoteflow
16574 Show the current setting of hardware flow control.
16576 @item set remotelogbase @var{base}
16577 Set the base (a.k.a.@: radix) of logging serial protocol
16578 communications to @var{base}. Supported values of @var{base} are:
16579 @code{ascii}, @code{octal}, and @code{hex}. The default is
16582 @item show remotelogbase
16583 Show the current setting of the radix for logging remote serial
16586 @item set remotelogfile @var{file}
16587 @cindex record serial communications on file
16588 Record remote serial communications on the named @var{file}. The
16589 default is not to record at all.
16591 @item show remotelogfile.
16592 Show the current setting of the file name on which to record the
16593 serial communications.
16595 @item set remotetimeout @var{num}
16596 @cindex timeout for serial communications
16597 @cindex remote timeout
16598 Set the timeout limit to wait for the remote target to respond to
16599 @var{num} seconds. The default is 2 seconds.
16601 @item show remotetimeout
16602 Show the current number of seconds to wait for the remote target
16605 @cindex limit hardware breakpoints and watchpoints
16606 @cindex remote target, limit break- and watchpoints
16607 @anchor{set remote hardware-watchpoint-limit}
16608 @anchor{set remote hardware-breakpoint-limit}
16609 @item set remote hardware-watchpoint-limit @var{limit}
16610 @itemx set remote hardware-breakpoint-limit @var{limit}
16611 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16612 watchpoints. A limit of -1, the default, is treated as unlimited.
16614 @item set remote exec-file @var{filename}
16615 @itemx show remote exec-file
16616 @anchor{set remote exec-file}
16617 @cindex executable file, for remote target
16618 Select the file used for @code{run} with @code{target
16619 extended-remote}. This should be set to a filename valid on the
16620 target system. If it is not set, the target will use a default
16621 filename (e.g.@: the last program run).
16623 @item set remote interrupt-sequence
16624 @cindex interrupt remote programs
16625 @cindex select Ctrl-C, BREAK or BREAK-g
16626 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16627 @samp{BREAK-g} as the
16628 sequence to the remote target in order to interrupt the execution.
16629 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16630 is high level of serial line for some certain time.
16631 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16632 It is @code{BREAK} signal followed by character @code{g}.
16634 @item show interrupt-sequence
16635 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16636 is sent by @value{GDBN} to interrupt the remote program.
16637 @code{BREAK-g} is BREAK signal followed by @code{g} and
16638 also known as Magic SysRq g.
16640 @item set remote interrupt-on-connect
16641 @cindex send interrupt-sequence on start
16642 Specify whether interrupt-sequence is sent to remote target when
16643 @value{GDBN} connects to it. This is mostly needed when you debug
16644 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16645 which is known as Magic SysRq g in order to connect @value{GDBN}.
16647 @item show interrupt-on-connect
16648 Show whether interrupt-sequence is sent
16649 to remote target when @value{GDBN} connects to it.
16653 @item set tcp auto-retry on
16654 @cindex auto-retry, for remote TCP target
16655 Enable auto-retry for remote TCP connections. This is useful if the remote
16656 debugging agent is launched in parallel with @value{GDBN}; there is a race
16657 condition because the agent may not become ready to accept the connection
16658 before @value{GDBN} attempts to connect. When auto-retry is
16659 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16660 to establish the connection using the timeout specified by
16661 @code{set tcp connect-timeout}.
16663 @item set tcp auto-retry off
16664 Do not auto-retry failed TCP connections.
16666 @item show tcp auto-retry
16667 Show the current auto-retry setting.
16669 @item set tcp connect-timeout @var{seconds}
16670 @cindex connection timeout, for remote TCP target
16671 @cindex timeout, for remote target connection
16672 Set the timeout for establishing a TCP connection to the remote target to
16673 @var{seconds}. The timeout affects both polling to retry failed connections
16674 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16675 that are merely slow to complete, and represents an approximate cumulative
16678 @item show tcp connect-timeout
16679 Show the current connection timeout setting.
16682 @cindex remote packets, enabling and disabling
16683 The @value{GDBN} remote protocol autodetects the packets supported by
16684 your debugging stub. If you need to override the autodetection, you
16685 can use these commands to enable or disable individual packets. Each
16686 packet can be set to @samp{on} (the remote target supports this
16687 packet), @samp{off} (the remote target does not support this packet),
16688 or @samp{auto} (detect remote target support for this packet). They
16689 all default to @samp{auto}. For more information about each packet,
16690 see @ref{Remote Protocol}.
16692 During normal use, you should not have to use any of these commands.
16693 If you do, that may be a bug in your remote debugging stub, or a bug
16694 in @value{GDBN}. You may want to report the problem to the
16695 @value{GDBN} developers.
16697 For each packet @var{name}, the command to enable or disable the
16698 packet is @code{set remote @var{name}-packet}. The available settings
16701 @multitable @columnfractions 0.28 0.32 0.25
16704 @tab Related Features
16706 @item @code{fetch-register}
16708 @tab @code{info registers}
16710 @item @code{set-register}
16714 @item @code{binary-download}
16716 @tab @code{load}, @code{set}
16718 @item @code{read-aux-vector}
16719 @tab @code{qXfer:auxv:read}
16720 @tab @code{info auxv}
16722 @item @code{symbol-lookup}
16723 @tab @code{qSymbol}
16724 @tab Detecting multiple threads
16726 @item @code{attach}
16727 @tab @code{vAttach}
16730 @item @code{verbose-resume}
16732 @tab Stepping or resuming multiple threads
16738 @item @code{software-breakpoint}
16742 @item @code{hardware-breakpoint}
16746 @item @code{write-watchpoint}
16750 @item @code{read-watchpoint}
16754 @item @code{access-watchpoint}
16758 @item @code{target-features}
16759 @tab @code{qXfer:features:read}
16760 @tab @code{set architecture}
16762 @item @code{library-info}
16763 @tab @code{qXfer:libraries:read}
16764 @tab @code{info sharedlibrary}
16766 @item @code{memory-map}
16767 @tab @code{qXfer:memory-map:read}
16768 @tab @code{info mem}
16770 @item @code{read-sdata-object}
16771 @tab @code{qXfer:sdata:read}
16772 @tab @code{print $_sdata}
16774 @item @code{read-spu-object}
16775 @tab @code{qXfer:spu:read}
16776 @tab @code{info spu}
16778 @item @code{write-spu-object}
16779 @tab @code{qXfer:spu:write}
16780 @tab @code{info spu}
16782 @item @code{read-siginfo-object}
16783 @tab @code{qXfer:siginfo:read}
16784 @tab @code{print $_siginfo}
16786 @item @code{write-siginfo-object}
16787 @tab @code{qXfer:siginfo:write}
16788 @tab @code{set $_siginfo}
16790 @item @code{threads}
16791 @tab @code{qXfer:threads:read}
16792 @tab @code{info threads}
16794 @item @code{get-thread-local-@*storage-address}
16795 @tab @code{qGetTLSAddr}
16796 @tab Displaying @code{__thread} variables
16798 @item @code{get-thread-information-block-address}
16799 @tab @code{qGetTIBAddr}
16800 @tab Display MS-Windows Thread Information Block.
16802 @item @code{search-memory}
16803 @tab @code{qSearch:memory}
16806 @item @code{supported-packets}
16807 @tab @code{qSupported}
16808 @tab Remote communications parameters
16810 @item @code{pass-signals}
16811 @tab @code{QPassSignals}
16812 @tab @code{handle @var{signal}}
16814 @item @code{hostio-close-packet}
16815 @tab @code{vFile:close}
16816 @tab @code{remote get}, @code{remote put}
16818 @item @code{hostio-open-packet}
16819 @tab @code{vFile:open}
16820 @tab @code{remote get}, @code{remote put}
16822 @item @code{hostio-pread-packet}
16823 @tab @code{vFile:pread}
16824 @tab @code{remote get}, @code{remote put}
16826 @item @code{hostio-pwrite-packet}
16827 @tab @code{vFile:pwrite}
16828 @tab @code{remote get}, @code{remote put}
16830 @item @code{hostio-unlink-packet}
16831 @tab @code{vFile:unlink}
16832 @tab @code{remote delete}
16834 @item @code{noack-packet}
16835 @tab @code{QStartNoAckMode}
16836 @tab Packet acknowledgment
16838 @item @code{osdata}
16839 @tab @code{qXfer:osdata:read}
16840 @tab @code{info os}
16842 @item @code{query-attached}
16843 @tab @code{qAttached}
16844 @tab Querying remote process attach state.
16846 @item @code{traceframe-info}
16847 @tab @code{qXfer:traceframe-info:read}
16848 @tab Traceframe info
16852 @section Implementing a Remote Stub
16854 @cindex debugging stub, example
16855 @cindex remote stub, example
16856 @cindex stub example, remote debugging
16857 The stub files provided with @value{GDBN} implement the target side of the
16858 communication protocol, and the @value{GDBN} side is implemented in the
16859 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16860 these subroutines to communicate, and ignore the details. (If you're
16861 implementing your own stub file, you can still ignore the details: start
16862 with one of the existing stub files. @file{sparc-stub.c} is the best
16863 organized, and therefore the easiest to read.)
16865 @cindex remote serial debugging, overview
16866 To debug a program running on another machine (the debugging
16867 @dfn{target} machine), you must first arrange for all the usual
16868 prerequisites for the program to run by itself. For example, for a C
16873 A startup routine to set up the C runtime environment; these usually
16874 have a name like @file{crt0}. The startup routine may be supplied by
16875 your hardware supplier, or you may have to write your own.
16878 A C subroutine library to support your program's
16879 subroutine calls, notably managing input and output.
16882 A way of getting your program to the other machine---for example, a
16883 download program. These are often supplied by the hardware
16884 manufacturer, but you may have to write your own from hardware
16888 The next step is to arrange for your program to use a serial port to
16889 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16890 machine). In general terms, the scheme looks like this:
16894 @value{GDBN} already understands how to use this protocol; when everything
16895 else is set up, you can simply use the @samp{target remote} command
16896 (@pxref{Targets,,Specifying a Debugging Target}).
16898 @item On the target,
16899 you must link with your program a few special-purpose subroutines that
16900 implement the @value{GDBN} remote serial protocol. The file containing these
16901 subroutines is called a @dfn{debugging stub}.
16903 On certain remote targets, you can use an auxiliary program
16904 @code{gdbserver} instead of linking a stub into your program.
16905 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16908 The debugging stub is specific to the architecture of the remote
16909 machine; for example, use @file{sparc-stub.c} to debug programs on
16912 @cindex remote serial stub list
16913 These working remote stubs are distributed with @value{GDBN}:
16918 @cindex @file{i386-stub.c}
16921 For Intel 386 and compatible architectures.
16924 @cindex @file{m68k-stub.c}
16925 @cindex Motorola 680x0
16927 For Motorola 680x0 architectures.
16930 @cindex @file{sh-stub.c}
16933 For Renesas SH architectures.
16936 @cindex @file{sparc-stub.c}
16938 For @sc{sparc} architectures.
16940 @item sparcl-stub.c
16941 @cindex @file{sparcl-stub.c}
16944 For Fujitsu @sc{sparclite} architectures.
16948 The @file{README} file in the @value{GDBN} distribution may list other
16949 recently added stubs.
16952 * Stub Contents:: What the stub can do for you
16953 * Bootstrapping:: What you must do for the stub
16954 * Debug Session:: Putting it all together
16957 @node Stub Contents
16958 @subsection What the Stub Can Do for You
16960 @cindex remote serial stub
16961 The debugging stub for your architecture supplies these three
16965 @item set_debug_traps
16966 @findex set_debug_traps
16967 @cindex remote serial stub, initialization
16968 This routine arranges for @code{handle_exception} to run when your
16969 program stops. You must call this subroutine explicitly near the
16970 beginning of your program.
16972 @item handle_exception
16973 @findex handle_exception
16974 @cindex remote serial stub, main routine
16975 This is the central workhorse, but your program never calls it
16976 explicitly---the setup code arranges for @code{handle_exception} to
16977 run when a trap is triggered.
16979 @code{handle_exception} takes control when your program stops during
16980 execution (for example, on a breakpoint), and mediates communications
16981 with @value{GDBN} on the host machine. This is where the communications
16982 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16983 representative on the target machine. It begins by sending summary
16984 information on the state of your program, then continues to execute,
16985 retrieving and transmitting any information @value{GDBN} needs, until you
16986 execute a @value{GDBN} command that makes your program resume; at that point,
16987 @code{handle_exception} returns control to your own code on the target
16991 @cindex @code{breakpoint} subroutine, remote
16992 Use this auxiliary subroutine to make your program contain a
16993 breakpoint. Depending on the particular situation, this may be the only
16994 way for @value{GDBN} to get control. For instance, if your target
16995 machine has some sort of interrupt button, you won't need to call this;
16996 pressing the interrupt button transfers control to
16997 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16998 simply receiving characters on the serial port may also trigger a trap;
16999 again, in that situation, you don't need to call @code{breakpoint} from
17000 your own program---simply running @samp{target remote} from the host
17001 @value{GDBN} session gets control.
17003 Call @code{breakpoint} if none of these is true, or if you simply want
17004 to make certain your program stops at a predetermined point for the
17005 start of your debugging session.
17008 @node Bootstrapping
17009 @subsection What You Must Do for the Stub
17011 @cindex remote stub, support routines
17012 The debugging stubs that come with @value{GDBN} are set up for a particular
17013 chip architecture, but they have no information about the rest of your
17014 debugging target machine.
17016 First of all you need to tell the stub how to communicate with the
17020 @item int getDebugChar()
17021 @findex getDebugChar
17022 Write this subroutine to read a single character from the serial port.
17023 It may be identical to @code{getchar} for your target system; a
17024 different name is used to allow you to distinguish the two if you wish.
17026 @item void putDebugChar(int)
17027 @findex putDebugChar
17028 Write this subroutine to write a single character to the serial port.
17029 It may be identical to @code{putchar} for your target system; a
17030 different name is used to allow you to distinguish the two if you wish.
17033 @cindex control C, and remote debugging
17034 @cindex interrupting remote targets
17035 If you want @value{GDBN} to be able to stop your program while it is
17036 running, you need to use an interrupt-driven serial driver, and arrange
17037 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17038 character). That is the character which @value{GDBN} uses to tell the
17039 remote system to stop.
17041 Getting the debugging target to return the proper status to @value{GDBN}
17042 probably requires changes to the standard stub; one quick and dirty way
17043 is to just execute a breakpoint instruction (the ``dirty'' part is that
17044 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17046 Other routines you need to supply are:
17049 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17050 @findex exceptionHandler
17051 Write this function to install @var{exception_address} in the exception
17052 handling tables. You need to do this because the stub does not have any
17053 way of knowing what the exception handling tables on your target system
17054 are like (for example, the processor's table might be in @sc{rom},
17055 containing entries which point to a table in @sc{ram}).
17056 @var{exception_number} is the exception number which should be changed;
17057 its meaning is architecture-dependent (for example, different numbers
17058 might represent divide by zero, misaligned access, etc). When this
17059 exception occurs, control should be transferred directly to
17060 @var{exception_address}, and the processor state (stack, registers,
17061 and so on) should be just as it is when a processor exception occurs. So if
17062 you want to use a jump instruction to reach @var{exception_address}, it
17063 should be a simple jump, not a jump to subroutine.
17065 For the 386, @var{exception_address} should be installed as an interrupt
17066 gate so that interrupts are masked while the handler runs. The gate
17067 should be at privilege level 0 (the most privileged level). The
17068 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17069 help from @code{exceptionHandler}.
17071 @item void flush_i_cache()
17072 @findex flush_i_cache
17073 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17074 instruction cache, if any, on your target machine. If there is no
17075 instruction cache, this subroutine may be a no-op.
17077 On target machines that have instruction caches, @value{GDBN} requires this
17078 function to make certain that the state of your program is stable.
17082 You must also make sure this library routine is available:
17085 @item void *memset(void *, int, int)
17087 This is the standard library function @code{memset} that sets an area of
17088 memory to a known value. If you have one of the free versions of
17089 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17090 either obtain it from your hardware manufacturer, or write your own.
17093 If you do not use the GNU C compiler, you may need other standard
17094 library subroutines as well; this varies from one stub to another,
17095 but in general the stubs are likely to use any of the common library
17096 subroutines which @code{@value{NGCC}} generates as inline code.
17099 @node Debug Session
17100 @subsection Putting it All Together
17102 @cindex remote serial debugging summary
17103 In summary, when your program is ready to debug, you must follow these
17108 Make sure you have defined the supporting low-level routines
17109 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17111 @code{getDebugChar}, @code{putDebugChar},
17112 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17116 Insert these lines near the top of your program:
17124 For the 680x0 stub only, you need to provide a variable called
17125 @code{exceptionHook}. Normally you just use:
17128 void (*exceptionHook)() = 0;
17132 but if before calling @code{set_debug_traps}, you set it to point to a
17133 function in your program, that function is called when
17134 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17135 error). The function indicated by @code{exceptionHook} is called with
17136 one parameter: an @code{int} which is the exception number.
17139 Compile and link together: your program, the @value{GDBN} debugging stub for
17140 your target architecture, and the supporting subroutines.
17143 Make sure you have a serial connection between your target machine and
17144 the @value{GDBN} host, and identify the serial port on the host.
17147 @c The "remote" target now provides a `load' command, so we should
17148 @c document that. FIXME.
17149 Download your program to your target machine (or get it there by
17150 whatever means the manufacturer provides), and start it.
17153 Start @value{GDBN} on the host, and connect to the target
17154 (@pxref{Connecting,,Connecting to a Remote Target}).
17158 @node Configurations
17159 @chapter Configuration-Specific Information
17161 While nearly all @value{GDBN} commands are available for all native and
17162 cross versions of the debugger, there are some exceptions. This chapter
17163 describes things that are only available in certain configurations.
17165 There are three major categories of configurations: native
17166 configurations, where the host and target are the same, embedded
17167 operating system configurations, which are usually the same for several
17168 different processor architectures, and bare embedded processors, which
17169 are quite different from each other.
17174 * Embedded Processors::
17181 This section describes details specific to particular native
17186 * BSD libkvm Interface:: Debugging BSD kernel memory images
17187 * SVR4 Process Information:: SVR4 process information
17188 * DJGPP Native:: Features specific to the DJGPP port
17189 * Cygwin Native:: Features specific to the Cygwin port
17190 * Hurd Native:: Features specific to @sc{gnu} Hurd
17191 * Neutrino:: Features specific to QNX Neutrino
17192 * Darwin:: Features specific to Darwin
17198 On HP-UX systems, if you refer to a function or variable name that
17199 begins with a dollar sign, @value{GDBN} searches for a user or system
17200 name first, before it searches for a convenience variable.
17203 @node BSD libkvm Interface
17204 @subsection BSD libkvm Interface
17207 @cindex kernel memory image
17208 @cindex kernel crash dump
17210 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17211 interface that provides a uniform interface for accessing kernel virtual
17212 memory images, including live systems and crash dumps. @value{GDBN}
17213 uses this interface to allow you to debug live kernels and kernel crash
17214 dumps on many native BSD configurations. This is implemented as a
17215 special @code{kvm} debugging target. For debugging a live system, load
17216 the currently running kernel into @value{GDBN} and connect to the
17220 (@value{GDBP}) @b{target kvm}
17223 For debugging crash dumps, provide the file name of the crash dump as an
17227 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17230 Once connected to the @code{kvm} target, the following commands are
17236 Set current context from the @dfn{Process Control Block} (PCB) address.
17239 Set current context from proc address. This command isn't available on
17240 modern FreeBSD systems.
17243 @node SVR4 Process Information
17244 @subsection SVR4 Process Information
17246 @cindex examine process image
17247 @cindex process info via @file{/proc}
17249 Many versions of SVR4 and compatible systems provide a facility called
17250 @samp{/proc} that can be used to examine the image of a running
17251 process using file-system subroutines. If @value{GDBN} is configured
17252 for an operating system with this facility, the command @code{info
17253 proc} is available to report information about the process running
17254 your program, or about any process running on your system. @code{info
17255 proc} works only on SVR4 systems that include the @code{procfs} code.
17256 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17257 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17263 @itemx info proc @var{process-id}
17264 Summarize available information about any running process. If a
17265 process ID is specified by @var{process-id}, display information about
17266 that process; otherwise display information about the program being
17267 debugged. The summary includes the debugged process ID, the command
17268 line used to invoke it, its current working directory, and its
17269 executable file's absolute file name.
17271 On some systems, @var{process-id} can be of the form
17272 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17273 within a process. If the optional @var{pid} part is missing, it means
17274 a thread from the process being debugged (the leading @samp{/} still
17275 needs to be present, or else @value{GDBN} will interpret the number as
17276 a process ID rather than a thread ID).
17278 @item info proc mappings
17279 @cindex memory address space mappings
17280 Report the memory address space ranges accessible in the program, with
17281 information on whether the process has read, write, or execute access
17282 rights to each range. On @sc{gnu}/Linux systems, each memory range
17283 includes the object file which is mapped to that range, instead of the
17284 memory access rights to that range.
17286 @item info proc stat
17287 @itemx info proc status
17288 @cindex process detailed status information
17289 These subcommands are specific to @sc{gnu}/Linux systems. They show
17290 the process-related information, including the user ID and group ID;
17291 how many threads are there in the process; its virtual memory usage;
17292 the signals that are pending, blocked, and ignored; its TTY; its
17293 consumption of system and user time; its stack size; its @samp{nice}
17294 value; etc. For more information, see the @samp{proc} man page
17295 (type @kbd{man 5 proc} from your shell prompt).
17297 @item info proc all
17298 Show all the information about the process described under all of the
17299 above @code{info proc} subcommands.
17302 @comment These sub-options of 'info proc' were not included when
17303 @comment procfs.c was re-written. Keep their descriptions around
17304 @comment against the day when someone finds the time to put them back in.
17305 @kindex info proc times
17306 @item info proc times
17307 Starting time, user CPU time, and system CPU time for your program and
17310 @kindex info proc id
17312 Report on the process IDs related to your program: its own process ID,
17313 the ID of its parent, the process group ID, and the session ID.
17316 @item set procfs-trace
17317 @kindex set procfs-trace
17318 @cindex @code{procfs} API calls
17319 This command enables and disables tracing of @code{procfs} API calls.
17321 @item show procfs-trace
17322 @kindex show procfs-trace
17323 Show the current state of @code{procfs} API call tracing.
17325 @item set procfs-file @var{file}
17326 @kindex set procfs-file
17327 Tell @value{GDBN} to write @code{procfs} API trace to the named
17328 @var{file}. @value{GDBN} appends the trace info to the previous
17329 contents of the file. The default is to display the trace on the
17332 @item show procfs-file
17333 @kindex show procfs-file
17334 Show the file to which @code{procfs} API trace is written.
17336 @item proc-trace-entry
17337 @itemx proc-trace-exit
17338 @itemx proc-untrace-entry
17339 @itemx proc-untrace-exit
17340 @kindex proc-trace-entry
17341 @kindex proc-trace-exit
17342 @kindex proc-untrace-entry
17343 @kindex proc-untrace-exit
17344 These commands enable and disable tracing of entries into and exits
17345 from the @code{syscall} interface.
17348 @kindex info pidlist
17349 @cindex process list, QNX Neutrino
17350 For QNX Neutrino only, this command displays the list of all the
17351 processes and all the threads within each process.
17354 @kindex info meminfo
17355 @cindex mapinfo list, QNX Neutrino
17356 For QNX Neutrino only, this command displays the list of all mapinfos.
17360 @subsection Features for Debugging @sc{djgpp} Programs
17361 @cindex @sc{djgpp} debugging
17362 @cindex native @sc{djgpp} debugging
17363 @cindex MS-DOS-specific commands
17366 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17367 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17368 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17369 top of real-mode DOS systems and their emulations.
17371 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17372 defines a few commands specific to the @sc{djgpp} port. This
17373 subsection describes those commands.
17378 This is a prefix of @sc{djgpp}-specific commands which print
17379 information about the target system and important OS structures.
17382 @cindex MS-DOS system info
17383 @cindex free memory information (MS-DOS)
17384 @item info dos sysinfo
17385 This command displays assorted information about the underlying
17386 platform: the CPU type and features, the OS version and flavor, the
17387 DPMI version, and the available conventional and DPMI memory.
17392 @cindex segment descriptor tables
17393 @cindex descriptor tables display
17395 @itemx info dos ldt
17396 @itemx info dos idt
17397 These 3 commands display entries from, respectively, Global, Local,
17398 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17399 tables are data structures which store a descriptor for each segment
17400 that is currently in use. The segment's selector is an index into a
17401 descriptor table; the table entry for that index holds the
17402 descriptor's base address and limit, and its attributes and access
17405 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17406 segment (used for both data and the stack), and a DOS segment (which
17407 allows access to DOS/BIOS data structures and absolute addresses in
17408 conventional memory). However, the DPMI host will usually define
17409 additional segments in order to support the DPMI environment.
17411 @cindex garbled pointers
17412 These commands allow to display entries from the descriptor tables.
17413 Without an argument, all entries from the specified table are
17414 displayed. An argument, which should be an integer expression, means
17415 display a single entry whose index is given by the argument. For
17416 example, here's a convenient way to display information about the
17417 debugged program's data segment:
17420 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17421 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17425 This comes in handy when you want to see whether a pointer is outside
17426 the data segment's limit (i.e.@: @dfn{garbled}).
17428 @cindex page tables display (MS-DOS)
17430 @itemx info dos pte
17431 These two commands display entries from, respectively, the Page
17432 Directory and the Page Tables. Page Directories and Page Tables are
17433 data structures which control how virtual memory addresses are mapped
17434 into physical addresses. A Page Table includes an entry for every
17435 page of memory that is mapped into the program's address space; there
17436 may be several Page Tables, each one holding up to 4096 entries. A
17437 Page Directory has up to 4096 entries, one each for every Page Table
17438 that is currently in use.
17440 Without an argument, @kbd{info dos pde} displays the entire Page
17441 Directory, and @kbd{info dos pte} displays all the entries in all of
17442 the Page Tables. An argument, an integer expression, given to the
17443 @kbd{info dos pde} command means display only that entry from the Page
17444 Directory table. An argument given to the @kbd{info dos pte} command
17445 means display entries from a single Page Table, the one pointed to by
17446 the specified entry in the Page Directory.
17448 @cindex direct memory access (DMA) on MS-DOS
17449 These commands are useful when your program uses @dfn{DMA} (Direct
17450 Memory Access), which needs physical addresses to program the DMA
17453 These commands are supported only with some DPMI servers.
17455 @cindex physical address from linear address
17456 @item info dos address-pte @var{addr}
17457 This command displays the Page Table entry for a specified linear
17458 address. The argument @var{addr} is a linear address which should
17459 already have the appropriate segment's base address added to it,
17460 because this command accepts addresses which may belong to @emph{any}
17461 segment. For example, here's how to display the Page Table entry for
17462 the page where a variable @code{i} is stored:
17465 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17466 @exdent @code{Page Table entry for address 0x11a00d30:}
17467 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17471 This says that @code{i} is stored at offset @code{0xd30} from the page
17472 whose physical base address is @code{0x02698000}, and shows all the
17473 attributes of that page.
17475 Note that you must cast the addresses of variables to a @code{char *},
17476 since otherwise the value of @code{__djgpp_base_address}, the base
17477 address of all variables and functions in a @sc{djgpp} program, will
17478 be added using the rules of C pointer arithmetics: if @code{i} is
17479 declared an @code{int}, @value{GDBN} will add 4 times the value of
17480 @code{__djgpp_base_address} to the address of @code{i}.
17482 Here's another example, it displays the Page Table entry for the
17486 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17487 @exdent @code{Page Table entry for address 0x29110:}
17488 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17492 (The @code{+ 3} offset is because the transfer buffer's address is the
17493 3rd member of the @code{_go32_info_block} structure.) The output
17494 clearly shows that this DPMI server maps the addresses in conventional
17495 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17496 linear (@code{0x29110}) addresses are identical.
17498 This command is supported only with some DPMI servers.
17501 @cindex DOS serial data link, remote debugging
17502 In addition to native debugging, the DJGPP port supports remote
17503 debugging via a serial data link. The following commands are specific
17504 to remote serial debugging in the DJGPP port of @value{GDBN}.
17507 @kindex set com1base
17508 @kindex set com1irq
17509 @kindex set com2base
17510 @kindex set com2irq
17511 @kindex set com3base
17512 @kindex set com3irq
17513 @kindex set com4base
17514 @kindex set com4irq
17515 @item set com1base @var{addr}
17516 This command sets the base I/O port address of the @file{COM1} serial
17519 @item set com1irq @var{irq}
17520 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17521 for the @file{COM1} serial port.
17523 There are similar commands @samp{set com2base}, @samp{set com3irq},
17524 etc.@: for setting the port address and the @code{IRQ} lines for the
17527 @kindex show com1base
17528 @kindex show com1irq
17529 @kindex show com2base
17530 @kindex show com2irq
17531 @kindex show com3base
17532 @kindex show com3irq
17533 @kindex show com4base
17534 @kindex show com4irq
17535 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17536 display the current settings of the base address and the @code{IRQ}
17537 lines used by the COM ports.
17540 @kindex info serial
17541 @cindex DOS serial port status
17542 This command prints the status of the 4 DOS serial ports. For each
17543 port, it prints whether it's active or not, its I/O base address and
17544 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17545 counts of various errors encountered so far.
17549 @node Cygwin Native
17550 @subsection Features for Debugging MS Windows PE Executables
17551 @cindex MS Windows debugging
17552 @cindex native Cygwin debugging
17553 @cindex Cygwin-specific commands
17555 @value{GDBN} supports native debugging of MS Windows programs, including
17556 DLLs with and without symbolic debugging information.
17558 @cindex Ctrl-BREAK, MS-Windows
17559 @cindex interrupt debuggee on MS-Windows
17560 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17561 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17562 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17563 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17564 sequence, which can be used to interrupt the debuggee even if it
17567 There are various additional Cygwin-specific commands, described in
17568 this section. Working with DLLs that have no debugging symbols is
17569 described in @ref{Non-debug DLL Symbols}.
17574 This is a prefix of MS Windows-specific commands which print
17575 information about the target system and important OS structures.
17577 @item info w32 selector
17578 This command displays information returned by
17579 the Win32 API @code{GetThreadSelectorEntry} function.
17580 It takes an optional argument that is evaluated to
17581 a long value to give the information about this given selector.
17582 Without argument, this command displays information
17583 about the six segment registers.
17585 @item info w32 thread-information-block
17586 This command displays thread specific information stored in the
17587 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17588 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17592 This is a Cygwin-specific alias of @code{info shared}.
17594 @kindex dll-symbols
17596 This command loads symbols from a dll similarly to
17597 add-sym command but without the need to specify a base address.
17599 @kindex set cygwin-exceptions
17600 @cindex debugging the Cygwin DLL
17601 @cindex Cygwin DLL, debugging
17602 @item set cygwin-exceptions @var{mode}
17603 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17604 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17605 @value{GDBN} will delay recognition of exceptions, and may ignore some
17606 exceptions which seem to be caused by internal Cygwin DLL
17607 ``bookkeeping''. This option is meant primarily for debugging the
17608 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17609 @value{GDBN} users with false @code{SIGSEGV} signals.
17611 @kindex show cygwin-exceptions
17612 @item show cygwin-exceptions
17613 Displays whether @value{GDBN} will break on exceptions that happen
17614 inside the Cygwin DLL itself.
17616 @kindex set new-console
17617 @item set new-console @var{mode}
17618 If @var{mode} is @code{on} the debuggee will
17619 be started in a new console on next start.
17620 If @var{mode} is @code{off}, the debuggee will
17621 be started in the same console as the debugger.
17623 @kindex show new-console
17624 @item show new-console
17625 Displays whether a new console is used
17626 when the debuggee is started.
17628 @kindex set new-group
17629 @item set new-group @var{mode}
17630 This boolean value controls whether the debuggee should
17631 start a new group or stay in the same group as the debugger.
17632 This affects the way the Windows OS handles
17635 @kindex show new-group
17636 @item show new-group
17637 Displays current value of new-group boolean.
17639 @kindex set debugevents
17640 @item set debugevents
17641 This boolean value adds debug output concerning kernel events related
17642 to the debuggee seen by the debugger. This includes events that
17643 signal thread and process creation and exit, DLL loading and
17644 unloading, console interrupts, and debugging messages produced by the
17645 Windows @code{OutputDebugString} API call.
17647 @kindex set debugexec
17648 @item set debugexec
17649 This boolean value adds debug output concerning execute events
17650 (such as resume thread) seen by the debugger.
17652 @kindex set debugexceptions
17653 @item set debugexceptions
17654 This boolean value adds debug output concerning exceptions in the
17655 debuggee seen by the debugger.
17657 @kindex set debugmemory
17658 @item set debugmemory
17659 This boolean value adds debug output concerning debuggee memory reads
17660 and writes by the debugger.
17664 This boolean values specifies whether the debuggee is called
17665 via a shell or directly (default value is on).
17669 Displays if the debuggee will be started with a shell.
17674 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17677 @node Non-debug DLL Symbols
17678 @subsubsection Support for DLLs without Debugging Symbols
17679 @cindex DLLs with no debugging symbols
17680 @cindex Minimal symbols and DLLs
17682 Very often on windows, some of the DLLs that your program relies on do
17683 not include symbolic debugging information (for example,
17684 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17685 symbols in a DLL, it relies on the minimal amount of symbolic
17686 information contained in the DLL's export table. This section
17687 describes working with such symbols, known internally to @value{GDBN} as
17688 ``minimal symbols''.
17690 Note that before the debugged program has started execution, no DLLs
17691 will have been loaded. The easiest way around this problem is simply to
17692 start the program --- either by setting a breakpoint or letting the
17693 program run once to completion. It is also possible to force
17694 @value{GDBN} to load a particular DLL before starting the executable ---
17695 see the shared library information in @ref{Files}, or the
17696 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17697 explicitly loading symbols from a DLL with no debugging information will
17698 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17699 which may adversely affect symbol lookup performance.
17701 @subsubsection DLL Name Prefixes
17703 In keeping with the naming conventions used by the Microsoft debugging
17704 tools, DLL export symbols are made available with a prefix based on the
17705 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17706 also entered into the symbol table, so @code{CreateFileA} is often
17707 sufficient. In some cases there will be name clashes within a program
17708 (particularly if the executable itself includes full debugging symbols)
17709 necessitating the use of the fully qualified name when referring to the
17710 contents of the DLL. Use single-quotes around the name to avoid the
17711 exclamation mark (``!'') being interpreted as a language operator.
17713 Note that the internal name of the DLL may be all upper-case, even
17714 though the file name of the DLL is lower-case, or vice-versa. Since
17715 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17716 some confusion. If in doubt, try the @code{info functions} and
17717 @code{info variables} commands or even @code{maint print msymbols}
17718 (@pxref{Symbols}). Here's an example:
17721 (@value{GDBP}) info function CreateFileA
17722 All functions matching regular expression "CreateFileA":
17724 Non-debugging symbols:
17725 0x77e885f4 CreateFileA
17726 0x77e885f4 KERNEL32!CreateFileA
17730 (@value{GDBP}) info function !
17731 All functions matching regular expression "!":
17733 Non-debugging symbols:
17734 0x6100114c cygwin1!__assert
17735 0x61004034 cygwin1!_dll_crt0@@0
17736 0x61004240 cygwin1!dll_crt0(per_process *)
17740 @subsubsection Working with Minimal Symbols
17742 Symbols extracted from a DLL's export table do not contain very much
17743 type information. All that @value{GDBN} can do is guess whether a symbol
17744 refers to a function or variable depending on the linker section that
17745 contains the symbol. Also note that the actual contents of the memory
17746 contained in a DLL are not available unless the program is running. This
17747 means that you cannot examine the contents of a variable or disassemble
17748 a function within a DLL without a running program.
17750 Variables are generally treated as pointers and dereferenced
17751 automatically. For this reason, it is often necessary to prefix a
17752 variable name with the address-of operator (``&'') and provide explicit
17753 type information in the command. Here's an example of the type of
17757 (@value{GDBP}) print 'cygwin1!__argv'
17762 (@value{GDBP}) x 'cygwin1!__argv'
17763 0x10021610: "\230y\""
17766 And two possible solutions:
17769 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17770 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17774 (@value{GDBP}) x/2x &'cygwin1!__argv'
17775 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17776 (@value{GDBP}) x/x 0x10021608
17777 0x10021608: 0x0022fd98
17778 (@value{GDBP}) x/s 0x0022fd98
17779 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17782 Setting a break point within a DLL is possible even before the program
17783 starts execution. However, under these circumstances, @value{GDBN} can't
17784 examine the initial instructions of the function in order to skip the
17785 function's frame set-up code. You can work around this by using ``*&''
17786 to set the breakpoint at a raw memory address:
17789 (@value{GDBP}) break *&'python22!PyOS_Readline'
17790 Breakpoint 1 at 0x1e04eff0
17793 The author of these extensions is not entirely convinced that setting a
17794 break point within a shared DLL like @file{kernel32.dll} is completely
17798 @subsection Commands Specific to @sc{gnu} Hurd Systems
17799 @cindex @sc{gnu} Hurd debugging
17801 This subsection describes @value{GDBN} commands specific to the
17802 @sc{gnu} Hurd native debugging.
17807 @kindex set signals@r{, Hurd command}
17808 @kindex set sigs@r{, Hurd command}
17809 This command toggles the state of inferior signal interception by
17810 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17811 affected by this command. @code{sigs} is a shorthand alias for
17816 @kindex show signals@r{, Hurd command}
17817 @kindex show sigs@r{, Hurd command}
17818 Show the current state of intercepting inferior's signals.
17820 @item set signal-thread
17821 @itemx set sigthread
17822 @kindex set signal-thread
17823 @kindex set sigthread
17824 This command tells @value{GDBN} which thread is the @code{libc} signal
17825 thread. That thread is run when a signal is delivered to a running
17826 process. @code{set sigthread} is the shorthand alias of @code{set
17829 @item show signal-thread
17830 @itemx show sigthread
17831 @kindex show signal-thread
17832 @kindex show sigthread
17833 These two commands show which thread will run when the inferior is
17834 delivered a signal.
17837 @kindex set stopped@r{, Hurd command}
17838 This commands tells @value{GDBN} that the inferior process is stopped,
17839 as with the @code{SIGSTOP} signal. The stopped process can be
17840 continued by delivering a signal to it.
17843 @kindex show stopped@r{, Hurd command}
17844 This command shows whether @value{GDBN} thinks the debuggee is
17847 @item set exceptions
17848 @kindex set exceptions@r{, Hurd command}
17849 Use this command to turn off trapping of exceptions in the inferior.
17850 When exception trapping is off, neither breakpoints nor
17851 single-stepping will work. To restore the default, set exception
17854 @item show exceptions
17855 @kindex show exceptions@r{, Hurd command}
17856 Show the current state of trapping exceptions in the inferior.
17858 @item set task pause
17859 @kindex set task@r{, Hurd commands}
17860 @cindex task attributes (@sc{gnu} Hurd)
17861 @cindex pause current task (@sc{gnu} Hurd)
17862 This command toggles task suspension when @value{GDBN} has control.
17863 Setting it to on takes effect immediately, and the task is suspended
17864 whenever @value{GDBN} gets control. Setting it to off will take
17865 effect the next time the inferior is continued. If this option is set
17866 to off, you can use @code{set thread default pause on} or @code{set
17867 thread pause on} (see below) to pause individual threads.
17869 @item show task pause
17870 @kindex show task@r{, Hurd commands}
17871 Show the current state of task suspension.
17873 @item set task detach-suspend-count
17874 @cindex task suspend count
17875 @cindex detach from task, @sc{gnu} Hurd
17876 This command sets the suspend count the task will be left with when
17877 @value{GDBN} detaches from it.
17879 @item show task detach-suspend-count
17880 Show the suspend count the task will be left with when detaching.
17882 @item set task exception-port
17883 @itemx set task excp
17884 @cindex task exception port, @sc{gnu} Hurd
17885 This command sets the task exception port to which @value{GDBN} will
17886 forward exceptions. The argument should be the value of the @dfn{send
17887 rights} of the task. @code{set task excp} is a shorthand alias.
17889 @item set noninvasive
17890 @cindex noninvasive task options
17891 This command switches @value{GDBN} to a mode that is the least
17892 invasive as far as interfering with the inferior is concerned. This
17893 is the same as using @code{set task pause}, @code{set exceptions}, and
17894 @code{set signals} to values opposite to the defaults.
17896 @item info send-rights
17897 @itemx info receive-rights
17898 @itemx info port-rights
17899 @itemx info port-sets
17900 @itemx info dead-names
17903 @cindex send rights, @sc{gnu} Hurd
17904 @cindex receive rights, @sc{gnu} Hurd
17905 @cindex port rights, @sc{gnu} Hurd
17906 @cindex port sets, @sc{gnu} Hurd
17907 @cindex dead names, @sc{gnu} Hurd
17908 These commands display information about, respectively, send rights,
17909 receive rights, port rights, port sets, and dead names of a task.
17910 There are also shorthand aliases: @code{info ports} for @code{info
17911 port-rights} and @code{info psets} for @code{info port-sets}.
17913 @item set thread pause
17914 @kindex set thread@r{, Hurd command}
17915 @cindex thread properties, @sc{gnu} Hurd
17916 @cindex pause current thread (@sc{gnu} Hurd)
17917 This command toggles current thread suspension when @value{GDBN} has
17918 control. Setting it to on takes effect immediately, and the current
17919 thread is suspended whenever @value{GDBN} gets control. Setting it to
17920 off will take effect the next time the inferior is continued.
17921 Normally, this command has no effect, since when @value{GDBN} has
17922 control, the whole task is suspended. However, if you used @code{set
17923 task pause off} (see above), this command comes in handy to suspend
17924 only the current thread.
17926 @item show thread pause
17927 @kindex show thread@r{, Hurd command}
17928 This command shows the state of current thread suspension.
17930 @item set thread run
17931 This command sets whether the current thread is allowed to run.
17933 @item show thread run
17934 Show whether the current thread is allowed to run.
17936 @item set thread detach-suspend-count
17937 @cindex thread suspend count, @sc{gnu} Hurd
17938 @cindex detach from thread, @sc{gnu} Hurd
17939 This command sets the suspend count @value{GDBN} will leave on a
17940 thread when detaching. This number is relative to the suspend count
17941 found by @value{GDBN} when it notices the thread; use @code{set thread
17942 takeover-suspend-count} to force it to an absolute value.
17944 @item show thread detach-suspend-count
17945 Show the suspend count @value{GDBN} will leave on the thread when
17948 @item set thread exception-port
17949 @itemx set thread excp
17950 Set the thread exception port to which to forward exceptions. This
17951 overrides the port set by @code{set task exception-port} (see above).
17952 @code{set thread excp} is the shorthand alias.
17954 @item set thread takeover-suspend-count
17955 Normally, @value{GDBN}'s thread suspend counts are relative to the
17956 value @value{GDBN} finds when it notices each thread. This command
17957 changes the suspend counts to be absolute instead.
17959 @item set thread default
17960 @itemx show thread default
17961 @cindex thread default settings, @sc{gnu} Hurd
17962 Each of the above @code{set thread} commands has a @code{set thread
17963 default} counterpart (e.g., @code{set thread default pause}, @code{set
17964 thread default exception-port}, etc.). The @code{thread default}
17965 variety of commands sets the default thread properties for all
17966 threads; you can then change the properties of individual threads with
17967 the non-default commands.
17972 @subsection QNX Neutrino
17973 @cindex QNX Neutrino
17975 @value{GDBN} provides the following commands specific to the QNX
17979 @item set debug nto-debug
17980 @kindex set debug nto-debug
17981 When set to on, enables debugging messages specific to the QNX
17984 @item show debug nto-debug
17985 @kindex show debug nto-debug
17986 Show the current state of QNX Neutrino messages.
17993 @value{GDBN} provides the following commands specific to the Darwin target:
17996 @item set debug darwin @var{num}
17997 @kindex set debug darwin
17998 When set to a non zero value, enables debugging messages specific to
17999 the Darwin support. Higher values produce more verbose output.
18001 @item show debug darwin
18002 @kindex show debug darwin
18003 Show the current state of Darwin messages.
18005 @item set debug mach-o @var{num}
18006 @kindex set debug mach-o
18007 When set to a non zero value, enables debugging messages while
18008 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18009 file format used on Darwin for object and executable files.) Higher
18010 values produce more verbose output. This is a command to diagnose
18011 problems internal to @value{GDBN} and should not be needed in normal
18014 @item show debug mach-o
18015 @kindex show debug mach-o
18016 Show the current state of Mach-O file messages.
18018 @item set mach-exceptions on
18019 @itemx set mach-exceptions off
18020 @kindex set mach-exceptions
18021 On Darwin, faults are first reported as a Mach exception and are then
18022 mapped to a Posix signal. Use this command to turn on trapping of
18023 Mach exceptions in the inferior. This might be sometimes useful to
18024 better understand the cause of a fault. The default is off.
18026 @item show mach-exceptions
18027 @kindex show mach-exceptions
18028 Show the current state of exceptions trapping.
18033 @section Embedded Operating Systems
18035 This section describes configurations involving the debugging of
18036 embedded operating systems that are available for several different
18040 * VxWorks:: Using @value{GDBN} with VxWorks
18043 @value{GDBN} includes the ability to debug programs running on
18044 various real-time operating systems.
18047 @subsection Using @value{GDBN} with VxWorks
18053 @kindex target vxworks
18054 @item target vxworks @var{machinename}
18055 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18056 is the target system's machine name or IP address.
18060 On VxWorks, @code{load} links @var{filename} dynamically on the
18061 current target system as well as adding its symbols in @value{GDBN}.
18063 @value{GDBN} enables developers to spawn and debug tasks running on networked
18064 VxWorks targets from a Unix host. Already-running tasks spawned from
18065 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18066 both the Unix host and on the VxWorks target. The program
18067 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18068 installed with the name @code{vxgdb}, to distinguish it from a
18069 @value{GDBN} for debugging programs on the host itself.)
18072 @item VxWorks-timeout @var{args}
18073 @kindex vxworks-timeout
18074 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18075 This option is set by the user, and @var{args} represents the number of
18076 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18077 your VxWorks target is a slow software simulator or is on the far side
18078 of a thin network line.
18081 The following information on connecting to VxWorks was current when
18082 this manual was produced; newer releases of VxWorks may use revised
18085 @findex INCLUDE_RDB
18086 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18087 to include the remote debugging interface routines in the VxWorks
18088 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18089 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18090 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18091 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18092 information on configuring and remaking VxWorks, see the manufacturer's
18094 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18096 Once you have included @file{rdb.a} in your VxWorks system image and set
18097 your Unix execution search path to find @value{GDBN}, you are ready to
18098 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18099 @code{vxgdb}, depending on your installation).
18101 @value{GDBN} comes up showing the prompt:
18108 * VxWorks Connection:: Connecting to VxWorks
18109 * VxWorks Download:: VxWorks download
18110 * VxWorks Attach:: Running tasks
18113 @node VxWorks Connection
18114 @subsubsection Connecting to VxWorks
18116 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18117 network. To connect to a target whose host name is ``@code{tt}'', type:
18120 (vxgdb) target vxworks tt
18124 @value{GDBN} displays messages like these:
18127 Attaching remote machine across net...
18132 @value{GDBN} then attempts to read the symbol tables of any object modules
18133 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18134 these files by searching the directories listed in the command search
18135 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18136 to find an object file, it displays a message such as:
18139 prog.o: No such file or directory.
18142 When this happens, add the appropriate directory to the search path with
18143 the @value{GDBN} command @code{path}, and execute the @code{target}
18146 @node VxWorks Download
18147 @subsubsection VxWorks Download
18149 @cindex download to VxWorks
18150 If you have connected to the VxWorks target and you want to debug an
18151 object that has not yet been loaded, you can use the @value{GDBN}
18152 @code{load} command to download a file from Unix to VxWorks
18153 incrementally. The object file given as an argument to the @code{load}
18154 command is actually opened twice: first by the VxWorks target in order
18155 to download the code, then by @value{GDBN} in order to read the symbol
18156 table. This can lead to problems if the current working directories on
18157 the two systems differ. If both systems have NFS mounted the same
18158 filesystems, you can avoid these problems by using absolute paths.
18159 Otherwise, it is simplest to set the working directory on both systems
18160 to the directory in which the object file resides, and then to reference
18161 the file by its name, without any path. For instance, a program
18162 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18163 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18164 program, type this on VxWorks:
18167 -> cd "@var{vxpath}/vw/demo/rdb"
18171 Then, in @value{GDBN}, type:
18174 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18175 (vxgdb) load prog.o
18178 @value{GDBN} displays a response similar to this:
18181 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18184 You can also use the @code{load} command to reload an object module
18185 after editing and recompiling the corresponding source file. Note that
18186 this makes @value{GDBN} delete all currently-defined breakpoints,
18187 auto-displays, and convenience variables, and to clear the value
18188 history. (This is necessary in order to preserve the integrity of
18189 debugger's data structures that reference the target system's symbol
18192 @node VxWorks Attach
18193 @subsubsection Running Tasks
18195 @cindex running VxWorks tasks
18196 You can also attach to an existing task using the @code{attach} command as
18200 (vxgdb) attach @var{task}
18204 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18205 or suspended when you attach to it. Running tasks are suspended at
18206 the time of attachment.
18208 @node Embedded Processors
18209 @section Embedded Processors
18211 This section goes into details specific to particular embedded
18214 @cindex send command to simulator
18215 Whenever a specific embedded processor has a simulator, @value{GDBN}
18216 allows to send an arbitrary command to the simulator.
18219 @item sim @var{command}
18220 @kindex sim@r{, a command}
18221 Send an arbitrary @var{command} string to the simulator. Consult the
18222 documentation for the specific simulator in use for information about
18223 acceptable commands.
18229 * M32R/D:: Renesas M32R/D
18230 * M68K:: Motorola M68K
18231 * MicroBlaze:: Xilinx MicroBlaze
18232 * MIPS Embedded:: MIPS Embedded
18233 * OpenRISC 1000:: OpenRisc 1000
18234 * PA:: HP PA Embedded
18235 * PowerPC Embedded:: PowerPC Embedded
18236 * Sparclet:: Tsqware Sparclet
18237 * Sparclite:: Fujitsu Sparclite
18238 * Z8000:: Zilog Z8000
18241 * Super-H:: Renesas Super-H
18250 @item target rdi @var{dev}
18251 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18252 use this target to communicate with both boards running the Angel
18253 monitor, or with the EmbeddedICE JTAG debug device.
18256 @item target rdp @var{dev}
18261 @value{GDBN} provides the following ARM-specific commands:
18264 @item set arm disassembler
18266 This commands selects from a list of disassembly styles. The
18267 @code{"std"} style is the standard style.
18269 @item show arm disassembler
18271 Show the current disassembly style.
18273 @item set arm apcs32
18274 @cindex ARM 32-bit mode
18275 This command toggles ARM operation mode between 32-bit and 26-bit.
18277 @item show arm apcs32
18278 Display the current usage of the ARM 32-bit mode.
18280 @item set arm fpu @var{fputype}
18281 This command sets the ARM floating-point unit (FPU) type. The
18282 argument @var{fputype} can be one of these:
18286 Determine the FPU type by querying the OS ABI.
18288 Software FPU, with mixed-endian doubles on little-endian ARM
18291 GCC-compiled FPA co-processor.
18293 Software FPU with pure-endian doubles.
18299 Show the current type of the FPU.
18302 This command forces @value{GDBN} to use the specified ABI.
18305 Show the currently used ABI.
18307 @item set arm fallback-mode (arm|thumb|auto)
18308 @value{GDBN} uses the symbol table, when available, to determine
18309 whether instructions are ARM or Thumb. This command controls
18310 @value{GDBN}'s default behavior when the symbol table is not
18311 available. The default is @samp{auto}, which causes @value{GDBN} to
18312 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18315 @item show arm fallback-mode
18316 Show the current fallback instruction mode.
18318 @item set arm force-mode (arm|thumb|auto)
18319 This command overrides use of the symbol table to determine whether
18320 instructions are ARM or Thumb. The default is @samp{auto}, which
18321 causes @value{GDBN} to use the symbol table and then the setting
18322 of @samp{set arm fallback-mode}.
18324 @item show arm force-mode
18325 Show the current forced instruction mode.
18327 @item set debug arm
18328 Toggle whether to display ARM-specific debugging messages from the ARM
18329 target support subsystem.
18331 @item show debug arm
18332 Show whether ARM-specific debugging messages are enabled.
18335 The following commands are available when an ARM target is debugged
18336 using the RDI interface:
18339 @item rdilogfile @r{[}@var{file}@r{]}
18341 @cindex ADP (Angel Debugger Protocol) logging
18342 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18343 With an argument, sets the log file to the specified @var{file}. With
18344 no argument, show the current log file name. The default log file is
18347 @item rdilogenable @r{[}@var{arg}@r{]}
18348 @kindex rdilogenable
18349 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18350 enables logging, with an argument 0 or @code{"no"} disables it. With
18351 no arguments displays the current setting. When logging is enabled,
18352 ADP packets exchanged between @value{GDBN} and the RDI target device
18353 are logged to a file.
18355 @item set rdiromatzero
18356 @kindex set rdiromatzero
18357 @cindex ROM at zero address, RDI
18358 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18359 vector catching is disabled, so that zero address can be used. If off
18360 (the default), vector catching is enabled. For this command to take
18361 effect, it needs to be invoked prior to the @code{target rdi} command.
18363 @item show rdiromatzero
18364 @kindex show rdiromatzero
18365 Show the current setting of ROM at zero address.
18367 @item set rdiheartbeat
18368 @kindex set rdiheartbeat
18369 @cindex RDI heartbeat
18370 Enable or disable RDI heartbeat packets. It is not recommended to
18371 turn on this option, since it confuses ARM and EPI JTAG interface, as
18372 well as the Angel monitor.
18374 @item show rdiheartbeat
18375 @kindex show rdiheartbeat
18376 Show the setting of RDI heartbeat packets.
18380 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18381 The @value{GDBN} ARM simulator accepts the following optional arguments.
18384 @item --swi-support=@var{type}
18385 Tell the simulator which SWI interfaces to support.
18386 @var{type} may be a comma separated list of the following values.
18387 The default value is @code{all}.
18400 @subsection Renesas M32R/D and M32R/SDI
18403 @kindex target m32r
18404 @item target m32r @var{dev}
18405 Renesas M32R/D ROM monitor.
18407 @kindex target m32rsdi
18408 @item target m32rsdi @var{dev}
18409 Renesas M32R SDI server, connected via parallel port to the board.
18412 The following @value{GDBN} commands are specific to the M32R monitor:
18415 @item set download-path @var{path}
18416 @kindex set download-path
18417 @cindex find downloadable @sc{srec} files (M32R)
18418 Set the default path for finding downloadable @sc{srec} files.
18420 @item show download-path
18421 @kindex show download-path
18422 Show the default path for downloadable @sc{srec} files.
18424 @item set board-address @var{addr}
18425 @kindex set board-address
18426 @cindex M32-EVA target board address
18427 Set the IP address for the M32R-EVA target board.
18429 @item show board-address
18430 @kindex show board-address
18431 Show the current IP address of the target board.
18433 @item set server-address @var{addr}
18434 @kindex set server-address
18435 @cindex download server address (M32R)
18436 Set the IP address for the download server, which is the @value{GDBN}'s
18439 @item show server-address
18440 @kindex show server-address
18441 Display the IP address of the download server.
18443 @item upload @r{[}@var{file}@r{]}
18444 @kindex upload@r{, M32R}
18445 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18446 upload capability. If no @var{file} argument is given, the current
18447 executable file is uploaded.
18449 @item tload @r{[}@var{file}@r{]}
18450 @kindex tload@r{, M32R}
18451 Test the @code{upload} command.
18454 The following commands are available for M32R/SDI:
18459 @cindex reset SDI connection, M32R
18460 This command resets the SDI connection.
18464 This command shows the SDI connection status.
18467 @kindex debug_chaos
18468 @cindex M32R/Chaos debugging
18469 Instructs the remote that M32R/Chaos debugging is to be used.
18471 @item use_debug_dma
18472 @kindex use_debug_dma
18473 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18476 @kindex use_mon_code
18477 Instructs the remote to use the MON_CODE method of accessing memory.
18480 @kindex use_ib_break
18481 Instructs the remote to set breakpoints by IB break.
18483 @item use_dbt_break
18484 @kindex use_dbt_break
18485 Instructs the remote to set breakpoints by DBT.
18491 The Motorola m68k configuration includes ColdFire support, and a
18492 target command for the following ROM monitor.
18496 @kindex target dbug
18497 @item target dbug @var{dev}
18498 dBUG ROM monitor for Motorola ColdFire.
18503 @subsection MicroBlaze
18504 @cindex Xilinx MicroBlaze
18505 @cindex XMD, Xilinx Microprocessor Debugger
18507 The MicroBlaze is a soft-core processor supported on various Xilinx
18508 FPGAs, such as Spartan or Virtex series. Boards with these processors
18509 usually have JTAG ports which connect to a host system running the Xilinx
18510 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18511 This host system is used to download the configuration bitstream to
18512 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18513 communicates with the target board using the JTAG interface and
18514 presents a @code{gdbserver} interface to the board. By default
18515 @code{xmd} uses port @code{1234}. (While it is possible to change
18516 this default port, it requires the use of undocumented @code{xmd}
18517 commands. Contact Xilinx support if you need to do this.)
18519 Use these GDB commands to connect to the MicroBlaze target processor.
18522 @item target remote :1234
18523 Use this command to connect to the target if you are running @value{GDBN}
18524 on the same system as @code{xmd}.
18526 @item target remote @var{xmd-host}:1234
18527 Use this command to connect to the target if it is connected to @code{xmd}
18528 running on a different system named @var{xmd-host}.
18531 Use this command to download a program to the MicroBlaze target.
18533 @item set debug microblaze @var{n}
18534 Enable MicroBlaze-specific debugging messages if non-zero.
18536 @item show debug microblaze @var{n}
18537 Show MicroBlaze-specific debugging level.
18540 @node MIPS Embedded
18541 @subsection MIPS Embedded
18543 @cindex MIPS boards
18544 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18545 MIPS board attached to a serial line. This is available when
18546 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18549 Use these @value{GDBN} commands to specify the connection to your target board:
18552 @item target mips @var{port}
18553 @kindex target mips @var{port}
18554 To run a program on the board, start up @code{@value{GDBP}} with the
18555 name of your program as the argument. To connect to the board, use the
18556 command @samp{target mips @var{port}}, where @var{port} is the name of
18557 the serial port connected to the board. If the program has not already
18558 been downloaded to the board, you may use the @code{load} command to
18559 download it. You can then use all the usual @value{GDBN} commands.
18561 For example, this sequence connects to the target board through a serial
18562 port, and loads and runs a program called @var{prog} through the
18566 host$ @value{GDBP} @var{prog}
18567 @value{GDBN} is free software and @dots{}
18568 (@value{GDBP}) target mips /dev/ttyb
18569 (@value{GDBP}) load @var{prog}
18573 @item target mips @var{hostname}:@var{portnumber}
18574 On some @value{GDBN} host configurations, you can specify a TCP
18575 connection (for instance, to a serial line managed by a terminal
18576 concentrator) instead of a serial port, using the syntax
18577 @samp{@var{hostname}:@var{portnumber}}.
18579 @item target pmon @var{port}
18580 @kindex target pmon @var{port}
18583 @item target ddb @var{port}
18584 @kindex target ddb @var{port}
18585 NEC's DDB variant of PMON for Vr4300.
18587 @item target lsi @var{port}
18588 @kindex target lsi @var{port}
18589 LSI variant of PMON.
18591 @kindex target r3900
18592 @item target r3900 @var{dev}
18593 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18595 @kindex target array
18596 @item target array @var{dev}
18597 Array Tech LSI33K RAID controller board.
18603 @value{GDBN} also supports these special commands for MIPS targets:
18606 @item set mipsfpu double
18607 @itemx set mipsfpu single
18608 @itemx set mipsfpu none
18609 @itemx set mipsfpu auto
18610 @itemx show mipsfpu
18611 @kindex set mipsfpu
18612 @kindex show mipsfpu
18613 @cindex MIPS remote floating point
18614 @cindex floating point, MIPS remote
18615 If your target board does not support the MIPS floating point
18616 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18617 need this, you may wish to put the command in your @value{GDBN} init
18618 file). This tells @value{GDBN} how to find the return value of
18619 functions which return floating point values. It also allows
18620 @value{GDBN} to avoid saving the floating point registers when calling
18621 functions on the board. If you are using a floating point coprocessor
18622 with only single precision floating point support, as on the @sc{r4650}
18623 processor, use the command @samp{set mipsfpu single}. The default
18624 double precision floating point coprocessor may be selected using
18625 @samp{set mipsfpu double}.
18627 In previous versions the only choices were double precision or no
18628 floating point, so @samp{set mipsfpu on} will select double precision
18629 and @samp{set mipsfpu off} will select no floating point.
18631 As usual, you can inquire about the @code{mipsfpu} variable with
18632 @samp{show mipsfpu}.
18634 @item set timeout @var{seconds}
18635 @itemx set retransmit-timeout @var{seconds}
18636 @itemx show timeout
18637 @itemx show retransmit-timeout
18638 @cindex @code{timeout}, MIPS protocol
18639 @cindex @code{retransmit-timeout}, MIPS protocol
18640 @kindex set timeout
18641 @kindex show timeout
18642 @kindex set retransmit-timeout
18643 @kindex show retransmit-timeout
18644 You can control the timeout used while waiting for a packet, in the MIPS
18645 remote protocol, with the @code{set timeout @var{seconds}} command. The
18646 default is 5 seconds. Similarly, you can control the timeout used while
18647 waiting for an acknowledgment of a packet with the @code{set
18648 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18649 You can inspect both values with @code{show timeout} and @code{show
18650 retransmit-timeout}. (These commands are @emph{only} available when
18651 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18653 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18654 is waiting for your program to stop. In that case, @value{GDBN} waits
18655 forever because it has no way of knowing how long the program is going
18656 to run before stopping.
18658 @item set syn-garbage-limit @var{num}
18659 @kindex set syn-garbage-limit@r{, MIPS remote}
18660 @cindex synchronize with remote MIPS target
18661 Limit the maximum number of characters @value{GDBN} should ignore when
18662 it tries to synchronize with the remote target. The default is 10
18663 characters. Setting the limit to -1 means there's no limit.
18665 @item show syn-garbage-limit
18666 @kindex show syn-garbage-limit@r{, MIPS remote}
18667 Show the current limit on the number of characters to ignore when
18668 trying to synchronize with the remote system.
18670 @item set monitor-prompt @var{prompt}
18671 @kindex set monitor-prompt@r{, MIPS remote}
18672 @cindex remote monitor prompt
18673 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18674 remote monitor. The default depends on the target:
18684 @item show monitor-prompt
18685 @kindex show monitor-prompt@r{, MIPS remote}
18686 Show the current strings @value{GDBN} expects as the prompt from the
18689 @item set monitor-warnings
18690 @kindex set monitor-warnings@r{, MIPS remote}
18691 Enable or disable monitor warnings about hardware breakpoints. This
18692 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18693 display warning messages whose codes are returned by the @code{lsi}
18694 PMON monitor for breakpoint commands.
18696 @item show monitor-warnings
18697 @kindex show monitor-warnings@r{, MIPS remote}
18698 Show the current setting of printing monitor warnings.
18700 @item pmon @var{command}
18701 @kindex pmon@r{, MIPS remote}
18702 @cindex send PMON command
18703 This command allows sending an arbitrary @var{command} string to the
18704 monitor. The monitor must be in debug mode for this to work.
18707 @node OpenRISC 1000
18708 @subsection OpenRISC 1000
18709 @cindex OpenRISC 1000
18711 @cindex or1k boards
18712 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18713 about platform and commands.
18717 @kindex target jtag
18718 @item target jtag jtag://@var{host}:@var{port}
18720 Connects to remote JTAG server.
18721 JTAG remote server can be either an or1ksim or JTAG server,
18722 connected via parallel port to the board.
18724 Example: @code{target jtag jtag://localhost:9999}
18727 @item or1ksim @var{command}
18728 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18729 Simulator, proprietary commands can be executed.
18731 @kindex info or1k spr
18732 @item info or1k spr
18733 Displays spr groups.
18735 @item info or1k spr @var{group}
18736 @itemx info or1k spr @var{groupno}
18737 Displays register names in selected group.
18739 @item info or1k spr @var{group} @var{register}
18740 @itemx info or1k spr @var{register}
18741 @itemx info or1k spr @var{groupno} @var{registerno}
18742 @itemx info or1k spr @var{registerno}
18743 Shows information about specified spr register.
18746 @item spr @var{group} @var{register} @var{value}
18747 @itemx spr @var{register @var{value}}
18748 @itemx spr @var{groupno} @var{registerno @var{value}}
18749 @itemx spr @var{registerno @var{value}}
18750 Writes @var{value} to specified spr register.
18753 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18754 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18755 program execution and is thus much faster. Hardware breakpoints/watchpoint
18756 triggers can be set using:
18759 Load effective address/data
18761 Store effective address/data
18763 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18768 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18769 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18771 @code{htrace} commands:
18772 @cindex OpenRISC 1000 htrace
18775 @item hwatch @var{conditional}
18776 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18777 or Data. For example:
18779 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18781 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18785 Display information about current HW trace configuration.
18787 @item htrace trigger @var{conditional}
18788 Set starting criteria for HW trace.
18790 @item htrace qualifier @var{conditional}
18791 Set acquisition qualifier for HW trace.
18793 @item htrace stop @var{conditional}
18794 Set HW trace stopping criteria.
18796 @item htrace record [@var{data}]*
18797 Selects the data to be recorded, when qualifier is met and HW trace was
18800 @item htrace enable
18801 @itemx htrace disable
18802 Enables/disables the HW trace.
18804 @item htrace rewind [@var{filename}]
18805 Clears currently recorded trace data.
18807 If filename is specified, new trace file is made and any newly collected data
18808 will be written there.
18810 @item htrace print [@var{start} [@var{len}]]
18811 Prints trace buffer, using current record configuration.
18813 @item htrace mode continuous
18814 Set continuous trace mode.
18816 @item htrace mode suspend
18817 Set suspend trace mode.
18821 @node PowerPC Embedded
18822 @subsection PowerPC Embedded
18824 @cindex DVC register
18825 @value{GDBN} supports using the DVC (Data Value Compare) register to
18826 implement in hardware simple hardware watchpoint conditions of the form:
18829 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18830 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18833 The DVC register will be automatically used when @value{GDBN} detects
18834 such pattern in a condition expression, and the created watchpoint uses one
18835 debug register (either the @code{exact-watchpoints} option is on and the
18836 variable is scalar, or the variable has a length of one byte). This feature
18837 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
18840 When running on PowerPC embedded processors, @value{GDBN} automatically uses
18841 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
18842 in which case watchpoints using only one debug register are created when
18843 watching variables of scalar types.
18845 You can create an artificial array to watch an arbitrary memory
18846 region using one of the following commands (@pxref{Expressions}):
18849 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
18850 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
18853 PowerPC embedded processors support masked watchpoints. See the discussion
18854 about the @code{mask} argument in @ref{Set Watchpoints}.
18856 @cindex ranged breakpoint
18857 PowerPC embedded processors support hardware accelerated
18858 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
18859 the inferior whenever it executes an instruction at any address within
18860 the range it specifies. To set a ranged breakpoint in @value{GDBN},
18861 use the @code{break-range} command.
18863 @value{GDBN} provides the following PowerPC-specific commands:
18866 @kindex break-range
18867 @item break-range @var{start-location}, @var{end-location}
18868 Set a breakpoint for an address range.
18869 @var{start-location} and @var{end-location} can specify a function name,
18870 a line number, an offset of lines from the current line or from the start
18871 location, or an address of an instruction (see @ref{Specify Location},
18872 for a list of all the possible ways to specify a @var{location}.)
18873 The breakpoint will stop execution of the inferior whenever it
18874 executes an instruction at any address within the specified range,
18875 (including @var{start-location} and @var{end-location}.)
18877 @kindex set powerpc
18878 @item set powerpc soft-float
18879 @itemx show powerpc soft-float
18880 Force @value{GDBN} to use (or not use) a software floating point calling
18881 convention. By default, @value{GDBN} selects the calling convention based
18882 on the selected architecture and the provided executable file.
18884 @item set powerpc vector-abi
18885 @itemx show powerpc vector-abi
18886 Force @value{GDBN} to use the specified calling convention for vector
18887 arguments and return values. The valid options are @samp{auto};
18888 @samp{generic}, to avoid vector registers even if they are present;
18889 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18890 registers. By default, @value{GDBN} selects the calling convention
18891 based on the selected architecture and the provided executable file.
18893 @item set powerpc exact-watchpoints
18894 @itemx show powerpc exact-watchpoints
18895 Allow @value{GDBN} to use only one debug register when watching a variable
18896 of scalar type, thus assuming that the variable is accessed through the
18897 address of its first byte.
18899 @kindex target dink32
18900 @item target dink32 @var{dev}
18901 DINK32 ROM monitor.
18903 @kindex target ppcbug
18904 @item target ppcbug @var{dev}
18905 @kindex target ppcbug1
18906 @item target ppcbug1 @var{dev}
18907 PPCBUG ROM monitor for PowerPC.
18910 @item target sds @var{dev}
18911 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18914 @cindex SDS protocol
18915 The following commands specific to the SDS protocol are supported
18919 @item set sdstimeout @var{nsec}
18920 @kindex set sdstimeout
18921 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18922 default is 2 seconds.
18924 @item show sdstimeout
18925 @kindex show sdstimeout
18926 Show the current value of the SDS timeout.
18928 @item sds @var{command}
18929 @kindex sds@r{, a command}
18930 Send the specified @var{command} string to the SDS monitor.
18935 @subsection HP PA Embedded
18939 @kindex target op50n
18940 @item target op50n @var{dev}
18941 OP50N monitor, running on an OKI HPPA board.
18943 @kindex target w89k
18944 @item target w89k @var{dev}
18945 W89K monitor, running on a Winbond HPPA board.
18950 @subsection Tsqware Sparclet
18954 @value{GDBN} enables developers to debug tasks running on
18955 Sparclet targets from a Unix host.
18956 @value{GDBN} uses code that runs on
18957 both the Unix host and on the Sparclet target. The program
18958 @code{@value{GDBP}} is installed and executed on the Unix host.
18961 @item remotetimeout @var{args}
18962 @kindex remotetimeout
18963 @value{GDBN} supports the option @code{remotetimeout}.
18964 This option is set by the user, and @var{args} represents the number of
18965 seconds @value{GDBN} waits for responses.
18968 @cindex compiling, on Sparclet
18969 When compiling for debugging, include the options @samp{-g} to get debug
18970 information and @samp{-Ttext} to relocate the program to where you wish to
18971 load it on the target. You may also want to add the options @samp{-n} or
18972 @samp{-N} in order to reduce the size of the sections. Example:
18975 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18978 You can use @code{objdump} to verify that the addresses are what you intended:
18981 sparclet-aout-objdump --headers --syms prog
18984 @cindex running, on Sparclet
18986 your Unix execution search path to find @value{GDBN}, you are ready to
18987 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18988 (or @code{sparclet-aout-gdb}, depending on your installation).
18990 @value{GDBN} comes up showing the prompt:
18997 * Sparclet File:: Setting the file to debug
18998 * Sparclet Connection:: Connecting to Sparclet
18999 * Sparclet Download:: Sparclet download
19000 * Sparclet Execution:: Running and debugging
19003 @node Sparclet File
19004 @subsubsection Setting File to Debug
19006 The @value{GDBN} command @code{file} lets you choose with program to debug.
19009 (gdbslet) file prog
19013 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19014 @value{GDBN} locates
19015 the file by searching the directories listed in the command search
19017 If the file was compiled with debug information (option @samp{-g}), source
19018 files will be searched as well.
19019 @value{GDBN} locates
19020 the source files by searching the directories listed in the directory search
19021 path (@pxref{Environment, ,Your Program's Environment}).
19023 to find a file, it displays a message such as:
19026 prog: No such file or directory.
19029 When this happens, add the appropriate directories to the search paths with
19030 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19031 @code{target} command again.
19033 @node Sparclet Connection
19034 @subsubsection Connecting to Sparclet
19036 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19037 To connect to a target on serial port ``@code{ttya}'', type:
19040 (gdbslet) target sparclet /dev/ttya
19041 Remote target sparclet connected to /dev/ttya
19042 main () at ../prog.c:3
19046 @value{GDBN} displays messages like these:
19052 @node Sparclet Download
19053 @subsubsection Sparclet Download
19055 @cindex download to Sparclet
19056 Once connected to the Sparclet target,
19057 you can use the @value{GDBN}
19058 @code{load} command to download the file from the host to the target.
19059 The file name and load offset should be given as arguments to the @code{load}
19061 Since the file format is aout, the program must be loaded to the starting
19062 address. You can use @code{objdump} to find out what this value is. The load
19063 offset is an offset which is added to the VMA (virtual memory address)
19064 of each of the file's sections.
19065 For instance, if the program
19066 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19067 and bss at 0x12010170, in @value{GDBN}, type:
19070 (gdbslet) load prog 0x12010000
19071 Loading section .text, size 0xdb0 vma 0x12010000
19074 If the code is loaded at a different address then what the program was linked
19075 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19076 to tell @value{GDBN} where to map the symbol table.
19078 @node Sparclet Execution
19079 @subsubsection Running and Debugging
19081 @cindex running and debugging Sparclet programs
19082 You can now begin debugging the task using @value{GDBN}'s execution control
19083 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19084 manual for the list of commands.
19088 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19090 Starting program: prog
19091 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19092 3 char *symarg = 0;
19094 4 char *execarg = "hello!";
19099 @subsection Fujitsu Sparclite
19103 @kindex target sparclite
19104 @item target sparclite @var{dev}
19105 Fujitsu sparclite boards, used only for the purpose of loading.
19106 You must use an additional command to debug the program.
19107 For example: target remote @var{dev} using @value{GDBN} standard
19113 @subsection Zilog Z8000
19116 @cindex simulator, Z8000
19117 @cindex Zilog Z8000 simulator
19119 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19122 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19123 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19124 segmented variant). The simulator recognizes which architecture is
19125 appropriate by inspecting the object code.
19128 @item target sim @var{args}
19130 @kindex target sim@r{, with Z8000}
19131 Debug programs on a simulated CPU. If the simulator supports setup
19132 options, specify them via @var{args}.
19136 After specifying this target, you can debug programs for the simulated
19137 CPU in the same style as programs for your host computer; use the
19138 @code{file} command to load a new program image, the @code{run} command
19139 to run your program, and so on.
19141 As well as making available all the usual machine registers
19142 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19143 additional items of information as specially named registers:
19148 Counts clock-ticks in the simulator.
19151 Counts instructions run in the simulator.
19154 Execution time in 60ths of a second.
19158 You can refer to these values in @value{GDBN} expressions with the usual
19159 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19160 conditional breakpoint that suspends only after at least 5000
19161 simulated clock ticks.
19164 @subsection Atmel AVR
19167 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19168 following AVR-specific commands:
19171 @item info io_registers
19172 @kindex info io_registers@r{, AVR}
19173 @cindex I/O registers (Atmel AVR)
19174 This command displays information about the AVR I/O registers. For
19175 each register, @value{GDBN} prints its number and value.
19182 When configured for debugging CRIS, @value{GDBN} provides the
19183 following CRIS-specific commands:
19186 @item set cris-version @var{ver}
19187 @cindex CRIS version
19188 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19189 The CRIS version affects register names and sizes. This command is useful in
19190 case autodetection of the CRIS version fails.
19192 @item show cris-version
19193 Show the current CRIS version.
19195 @item set cris-dwarf2-cfi
19196 @cindex DWARF-2 CFI and CRIS
19197 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19198 Change to @samp{off} when using @code{gcc-cris} whose version is below
19201 @item show cris-dwarf2-cfi
19202 Show the current state of using DWARF-2 CFI.
19204 @item set cris-mode @var{mode}
19206 Set the current CRIS mode to @var{mode}. It should only be changed when
19207 debugging in guru mode, in which case it should be set to
19208 @samp{guru} (the default is @samp{normal}).
19210 @item show cris-mode
19211 Show the current CRIS mode.
19215 @subsection Renesas Super-H
19218 For the Renesas Super-H processor, @value{GDBN} provides these
19223 @kindex regs@r{, Super-H}
19224 Show the values of all Super-H registers.
19226 @item set sh calling-convention @var{convention}
19227 @kindex set sh calling-convention
19228 Set the calling-convention used when calling functions from @value{GDBN}.
19229 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19230 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19231 convention. If the DWARF-2 information of the called function specifies
19232 that the function follows the Renesas calling convention, the function
19233 is called using the Renesas calling convention. If the calling convention
19234 is set to @samp{renesas}, the Renesas calling convention is always used,
19235 regardless of the DWARF-2 information. This can be used to override the
19236 default of @samp{gcc} if debug information is missing, or the compiler
19237 does not emit the DWARF-2 calling convention entry for a function.
19239 @item show sh calling-convention
19240 @kindex show sh calling-convention
19241 Show the current calling convention setting.
19246 @node Architectures
19247 @section Architectures
19249 This section describes characteristics of architectures that affect
19250 all uses of @value{GDBN} with the architecture, both native and cross.
19257 * HPPA:: HP PA architecture
19258 * SPU:: Cell Broadband Engine SPU architecture
19263 @subsection x86 Architecture-specific Issues
19266 @item set struct-convention @var{mode}
19267 @kindex set struct-convention
19268 @cindex struct return convention
19269 @cindex struct/union returned in registers
19270 Set the convention used by the inferior to return @code{struct}s and
19271 @code{union}s from functions to @var{mode}. Possible values of
19272 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19273 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19274 are returned on the stack, while @code{"reg"} means that a
19275 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19276 be returned in a register.
19278 @item show struct-convention
19279 @kindex show struct-convention
19280 Show the current setting of the convention to return @code{struct}s
19289 @kindex set rstack_high_address
19290 @cindex AMD 29K register stack
19291 @cindex register stack, AMD29K
19292 @item set rstack_high_address @var{address}
19293 On AMD 29000 family processors, registers are saved in a separate
19294 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19295 extent of this stack. Normally, @value{GDBN} just assumes that the
19296 stack is ``large enough''. This may result in @value{GDBN} referencing
19297 memory locations that do not exist. If necessary, you can get around
19298 this problem by specifying the ending address of the register stack with
19299 the @code{set rstack_high_address} command. The argument should be an
19300 address, which you probably want to precede with @samp{0x} to specify in
19303 @kindex show rstack_high_address
19304 @item show rstack_high_address
19305 Display the current limit of the register stack, on AMD 29000 family
19313 See the following section.
19318 @cindex stack on Alpha
19319 @cindex stack on MIPS
19320 @cindex Alpha stack
19322 Alpha- and MIPS-based computers use an unusual stack frame, which
19323 sometimes requires @value{GDBN} to search backward in the object code to
19324 find the beginning of a function.
19326 @cindex response time, MIPS debugging
19327 To improve response time (especially for embedded applications, where
19328 @value{GDBN} may be restricted to a slow serial line for this search)
19329 you may want to limit the size of this search, using one of these
19333 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19334 @item set heuristic-fence-post @var{limit}
19335 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19336 search for the beginning of a function. A value of @var{0} (the
19337 default) means there is no limit. However, except for @var{0}, the
19338 larger the limit the more bytes @code{heuristic-fence-post} must search
19339 and therefore the longer it takes to run. You should only need to use
19340 this command when debugging a stripped executable.
19342 @item show heuristic-fence-post
19343 Display the current limit.
19347 These commands are available @emph{only} when @value{GDBN} is configured
19348 for debugging programs on Alpha or MIPS processors.
19350 Several MIPS-specific commands are available when debugging MIPS
19354 @item set mips abi @var{arg}
19355 @kindex set mips abi
19356 @cindex set ABI for MIPS
19357 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19358 values of @var{arg} are:
19362 The default ABI associated with the current binary (this is the
19373 @item show mips abi
19374 @kindex show mips abi
19375 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19378 @itemx show mipsfpu
19379 @xref{MIPS Embedded, set mipsfpu}.
19381 @item set mips mask-address @var{arg}
19382 @kindex set mips mask-address
19383 @cindex MIPS addresses, masking
19384 This command determines whether the most-significant 32 bits of 64-bit
19385 MIPS addresses are masked off. The argument @var{arg} can be
19386 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19387 setting, which lets @value{GDBN} determine the correct value.
19389 @item show mips mask-address
19390 @kindex show mips mask-address
19391 Show whether the upper 32 bits of MIPS addresses are masked off or
19394 @item set remote-mips64-transfers-32bit-regs
19395 @kindex set remote-mips64-transfers-32bit-regs
19396 This command controls compatibility with 64-bit MIPS targets that
19397 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19398 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19399 and 64 bits for other registers, set this option to @samp{on}.
19401 @item show remote-mips64-transfers-32bit-regs
19402 @kindex show remote-mips64-transfers-32bit-regs
19403 Show the current setting of compatibility with older MIPS 64 targets.
19405 @item set debug mips
19406 @kindex set debug mips
19407 This command turns on and off debugging messages for the MIPS-specific
19408 target code in @value{GDBN}.
19410 @item show debug mips
19411 @kindex show debug mips
19412 Show the current setting of MIPS debugging messages.
19418 @cindex HPPA support
19420 When @value{GDBN} is debugging the HP PA architecture, it provides the
19421 following special commands:
19424 @item set debug hppa
19425 @kindex set debug hppa
19426 This command determines whether HPPA architecture-specific debugging
19427 messages are to be displayed.
19429 @item show debug hppa
19430 Show whether HPPA debugging messages are displayed.
19432 @item maint print unwind @var{address}
19433 @kindex maint print unwind@r{, HPPA}
19434 This command displays the contents of the unwind table entry at the
19435 given @var{address}.
19441 @subsection Cell Broadband Engine SPU architecture
19442 @cindex Cell Broadband Engine
19445 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19446 it provides the following special commands:
19449 @item info spu event
19451 Display SPU event facility status. Shows current event mask
19452 and pending event status.
19454 @item info spu signal
19455 Display SPU signal notification facility status. Shows pending
19456 signal-control word and signal notification mode of both signal
19457 notification channels.
19459 @item info spu mailbox
19460 Display SPU mailbox facility status. Shows all pending entries,
19461 in order of processing, in each of the SPU Write Outbound,
19462 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19465 Display MFC DMA status. Shows all pending commands in the MFC
19466 DMA queue. For each entry, opcode, tag, class IDs, effective
19467 and local store addresses and transfer size are shown.
19469 @item info spu proxydma
19470 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19471 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19472 and local store addresses and transfer size are shown.
19476 When @value{GDBN} is debugging a combined PowerPC/SPU application
19477 on the Cell Broadband Engine, it provides in addition the following
19481 @item set spu stop-on-load @var{arg}
19483 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19484 will give control to the user when a new SPE thread enters its @code{main}
19485 function. The default is @code{off}.
19487 @item show spu stop-on-load
19489 Show whether to stop for new SPE threads.
19491 @item set spu auto-flush-cache @var{arg}
19492 Set whether to automatically flush the software-managed cache. When set to
19493 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19494 cache to be flushed whenever SPE execution stops. This provides a consistent
19495 view of PowerPC memory that is accessed via the cache. If an application
19496 does not use the software-managed cache, this option has no effect.
19498 @item show spu auto-flush-cache
19499 Show whether to automatically flush the software-managed cache.
19504 @subsection PowerPC
19505 @cindex PowerPC architecture
19507 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19508 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19509 numbers stored in the floating point registers. These values must be stored
19510 in two consecutive registers, always starting at an even register like
19511 @code{f0} or @code{f2}.
19513 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19514 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19515 @code{f2} and @code{f3} for @code{$dl1} and so on.
19517 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19518 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19521 @node Controlling GDB
19522 @chapter Controlling @value{GDBN}
19524 You can alter the way @value{GDBN} interacts with you by using the
19525 @code{set} command. For commands controlling how @value{GDBN} displays
19526 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19531 * Editing:: Command editing
19532 * Command History:: Command history
19533 * Screen Size:: Screen size
19534 * Numbers:: Numbers
19535 * ABI:: Configuring the current ABI
19536 * Messages/Warnings:: Optional warnings and messages
19537 * Debugging Output:: Optional messages about internal happenings
19538 * Other Misc Settings:: Other Miscellaneous Settings
19546 @value{GDBN} indicates its readiness to read a command by printing a string
19547 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19548 can change the prompt string with the @code{set prompt} command. For
19549 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19550 the prompt in one of the @value{GDBN} sessions so that you can always tell
19551 which one you are talking to.
19553 @emph{Note:} @code{set prompt} does not add a space for you after the
19554 prompt you set. This allows you to set a prompt which ends in a space
19555 or a prompt that does not.
19559 @item set prompt @var{newprompt}
19560 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19562 @kindex show prompt
19564 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19568 @section Command Editing
19570 @cindex command line editing
19572 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19573 @sc{gnu} library provides consistent behavior for programs which provide a
19574 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19575 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19576 substitution, and a storage and recall of command history across
19577 debugging sessions.
19579 You may control the behavior of command line editing in @value{GDBN} with the
19580 command @code{set}.
19583 @kindex set editing
19586 @itemx set editing on
19587 Enable command line editing (enabled by default).
19589 @item set editing off
19590 Disable command line editing.
19592 @kindex show editing
19594 Show whether command line editing is enabled.
19597 @ifset SYSTEM_READLINE
19598 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19600 @ifclear SYSTEM_READLINE
19601 @xref{Command Line Editing},
19603 for more details about the Readline
19604 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19605 encouraged to read that chapter.
19607 @node Command History
19608 @section Command History
19609 @cindex command history
19611 @value{GDBN} can keep track of the commands you type during your
19612 debugging sessions, so that you can be certain of precisely what
19613 happened. Use these commands to manage the @value{GDBN} command
19616 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19617 package, to provide the history facility.
19618 @ifset SYSTEM_READLINE
19619 @xref{Using History Interactively, , , history, GNU History Library},
19621 @ifclear SYSTEM_READLINE
19622 @xref{Using History Interactively},
19624 for the detailed description of the History library.
19626 To issue a command to @value{GDBN} without affecting certain aspects of
19627 the state which is seen by users, prefix it with @samp{server }
19628 (@pxref{Server Prefix}). This
19629 means that this command will not affect the command history, nor will it
19630 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19631 pressed on a line by itself.
19633 @cindex @code{server}, command prefix
19634 The server prefix does not affect the recording of values into the value
19635 history; to print a value without recording it into the value history,
19636 use the @code{output} command instead of the @code{print} command.
19638 Here is the description of @value{GDBN} commands related to command
19642 @cindex history substitution
19643 @cindex history file
19644 @kindex set history filename
19645 @cindex @env{GDBHISTFILE}, environment variable
19646 @item set history filename @var{fname}
19647 Set the name of the @value{GDBN} command history file to @var{fname}.
19648 This is the file where @value{GDBN} reads an initial command history
19649 list, and where it writes the command history from this session when it
19650 exits. You can access this list through history expansion or through
19651 the history command editing characters listed below. This file defaults
19652 to the value of the environment variable @code{GDBHISTFILE}, or to
19653 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19656 @cindex save command history
19657 @kindex set history save
19658 @item set history save
19659 @itemx set history save on
19660 Record command history in a file, whose name may be specified with the
19661 @code{set history filename} command. By default, this option is disabled.
19663 @item set history save off
19664 Stop recording command history in a file.
19666 @cindex history size
19667 @kindex set history size
19668 @cindex @env{HISTSIZE}, environment variable
19669 @item set history size @var{size}
19670 Set the number of commands which @value{GDBN} keeps in its history list.
19671 This defaults to the value of the environment variable
19672 @code{HISTSIZE}, or to 256 if this variable is not set.
19675 History expansion assigns special meaning to the character @kbd{!}.
19676 @ifset SYSTEM_READLINE
19677 @xref{Event Designators, , , history, GNU History Library},
19679 @ifclear SYSTEM_READLINE
19680 @xref{Event Designators},
19684 @cindex history expansion, turn on/off
19685 Since @kbd{!} is also the logical not operator in C, history expansion
19686 is off by default. If you decide to enable history expansion with the
19687 @code{set history expansion on} command, you may sometimes need to
19688 follow @kbd{!} (when it is used as logical not, in an expression) with
19689 a space or a tab to prevent it from being expanded. The readline
19690 history facilities do not attempt substitution on the strings
19691 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19693 The commands to control history expansion are:
19696 @item set history expansion on
19697 @itemx set history expansion
19698 @kindex set history expansion
19699 Enable history expansion. History expansion is off by default.
19701 @item set history expansion off
19702 Disable history expansion.
19705 @kindex show history
19707 @itemx show history filename
19708 @itemx show history save
19709 @itemx show history size
19710 @itemx show history expansion
19711 These commands display the state of the @value{GDBN} history parameters.
19712 @code{show history} by itself displays all four states.
19717 @kindex show commands
19718 @cindex show last commands
19719 @cindex display command history
19720 @item show commands
19721 Display the last ten commands in the command history.
19723 @item show commands @var{n}
19724 Print ten commands centered on command number @var{n}.
19726 @item show commands +
19727 Print ten commands just after the commands last printed.
19731 @section Screen Size
19732 @cindex size of screen
19733 @cindex pauses in output
19735 Certain commands to @value{GDBN} may produce large amounts of
19736 information output to the screen. To help you read all of it,
19737 @value{GDBN} pauses and asks you for input at the end of each page of
19738 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19739 to discard the remaining output. Also, the screen width setting
19740 determines when to wrap lines of output. Depending on what is being
19741 printed, @value{GDBN} tries to break the line at a readable place,
19742 rather than simply letting it overflow onto the following line.
19744 Normally @value{GDBN} knows the size of the screen from the terminal
19745 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19746 together with the value of the @code{TERM} environment variable and the
19747 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19748 you can override it with the @code{set height} and @code{set
19755 @kindex show height
19756 @item set height @var{lpp}
19758 @itemx set width @var{cpl}
19760 These @code{set} commands specify a screen height of @var{lpp} lines and
19761 a screen width of @var{cpl} characters. The associated @code{show}
19762 commands display the current settings.
19764 If you specify a height of zero lines, @value{GDBN} does not pause during
19765 output no matter how long the output is. This is useful if output is to a
19766 file or to an editor buffer.
19768 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19769 from wrapping its output.
19771 @item set pagination on
19772 @itemx set pagination off
19773 @kindex set pagination
19774 Turn the output pagination on or off; the default is on. Turning
19775 pagination off is the alternative to @code{set height 0}. Note that
19776 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19777 Options, -batch}) also automatically disables pagination.
19779 @item show pagination
19780 @kindex show pagination
19781 Show the current pagination mode.
19786 @cindex number representation
19787 @cindex entering numbers
19789 You can always enter numbers in octal, decimal, or hexadecimal in
19790 @value{GDBN} by the usual conventions: octal numbers begin with
19791 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19792 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19793 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19794 10; likewise, the default display for numbers---when no particular
19795 format is specified---is base 10. You can change the default base for
19796 both input and output with the commands described below.
19799 @kindex set input-radix
19800 @item set input-radix @var{base}
19801 Set the default base for numeric input. Supported choices
19802 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19803 specified either unambiguously or using the current input radix; for
19807 set input-radix 012
19808 set input-radix 10.
19809 set input-radix 0xa
19813 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19814 leaves the input radix unchanged, no matter what it was, since
19815 @samp{10}, being without any leading or trailing signs of its base, is
19816 interpreted in the current radix. Thus, if the current radix is 16,
19817 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19820 @kindex set output-radix
19821 @item set output-radix @var{base}
19822 Set the default base for numeric display. Supported choices
19823 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19824 specified either unambiguously or using the current input radix.
19826 @kindex show input-radix
19827 @item show input-radix
19828 Display the current default base for numeric input.
19830 @kindex show output-radix
19831 @item show output-radix
19832 Display the current default base for numeric display.
19834 @item set radix @r{[}@var{base}@r{]}
19838 These commands set and show the default base for both input and output
19839 of numbers. @code{set radix} sets the radix of input and output to
19840 the same base; without an argument, it resets the radix back to its
19841 default value of 10.
19846 @section Configuring the Current ABI
19848 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19849 application automatically. However, sometimes you need to override its
19850 conclusions. Use these commands to manage @value{GDBN}'s view of the
19857 One @value{GDBN} configuration can debug binaries for multiple operating
19858 system targets, either via remote debugging or native emulation.
19859 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19860 but you can override its conclusion using the @code{set osabi} command.
19861 One example where this is useful is in debugging of binaries which use
19862 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19863 not have the same identifying marks that the standard C library for your
19868 Show the OS ABI currently in use.
19871 With no argument, show the list of registered available OS ABI's.
19873 @item set osabi @var{abi}
19874 Set the current OS ABI to @var{abi}.
19877 @cindex float promotion
19879 Generally, the way that an argument of type @code{float} is passed to a
19880 function depends on whether the function is prototyped. For a prototyped
19881 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19882 according to the architecture's convention for @code{float}. For unprototyped
19883 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19884 @code{double} and then passed.
19886 Unfortunately, some forms of debug information do not reliably indicate whether
19887 a function is prototyped. If @value{GDBN} calls a function that is not marked
19888 as prototyped, it consults @kbd{set coerce-float-to-double}.
19891 @kindex set coerce-float-to-double
19892 @item set coerce-float-to-double
19893 @itemx set coerce-float-to-double on
19894 Arguments of type @code{float} will be promoted to @code{double} when passed
19895 to an unprototyped function. This is the default setting.
19897 @item set coerce-float-to-double off
19898 Arguments of type @code{float} will be passed directly to unprototyped
19901 @kindex show coerce-float-to-double
19902 @item show coerce-float-to-double
19903 Show the current setting of promoting @code{float} to @code{double}.
19907 @kindex show cp-abi
19908 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19909 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19910 used to build your application. @value{GDBN} only fully supports
19911 programs with a single C@t{++} ABI; if your program contains code using
19912 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19913 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19914 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19915 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19916 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19917 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19922 Show the C@t{++} ABI currently in use.
19925 With no argument, show the list of supported C@t{++} ABI's.
19927 @item set cp-abi @var{abi}
19928 @itemx set cp-abi auto
19929 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19932 @node Messages/Warnings
19933 @section Optional Warnings and Messages
19935 @cindex verbose operation
19936 @cindex optional warnings
19937 By default, @value{GDBN} is silent about its inner workings. If you are
19938 running on a slow machine, you may want to use the @code{set verbose}
19939 command. This makes @value{GDBN} tell you when it does a lengthy
19940 internal operation, so you will not think it has crashed.
19942 Currently, the messages controlled by @code{set verbose} are those
19943 which announce that the symbol table for a source file is being read;
19944 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19947 @kindex set verbose
19948 @item set verbose on
19949 Enables @value{GDBN} output of certain informational messages.
19951 @item set verbose off
19952 Disables @value{GDBN} output of certain informational messages.
19954 @kindex show verbose
19956 Displays whether @code{set verbose} is on or off.
19959 By default, if @value{GDBN} encounters bugs in the symbol table of an
19960 object file, it is silent; but if you are debugging a compiler, you may
19961 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19966 @kindex set complaints
19967 @item set complaints @var{limit}
19968 Permits @value{GDBN} to output @var{limit} complaints about each type of
19969 unusual symbols before becoming silent about the problem. Set
19970 @var{limit} to zero to suppress all complaints; set it to a large number
19971 to prevent complaints from being suppressed.
19973 @kindex show complaints
19974 @item show complaints
19975 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19979 @anchor{confirmation requests}
19980 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19981 lot of stupid questions to confirm certain commands. For example, if
19982 you try to run a program which is already running:
19986 The program being debugged has been started already.
19987 Start it from the beginning? (y or n)
19990 If you are willing to unflinchingly face the consequences of your own
19991 commands, you can disable this ``feature'':
19995 @kindex set confirm
19997 @cindex confirmation
19998 @cindex stupid questions
19999 @item set confirm off
20000 Disables confirmation requests. Note that running @value{GDBN} with
20001 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20002 automatically disables confirmation requests.
20004 @item set confirm on
20005 Enables confirmation requests (the default).
20007 @kindex show confirm
20009 Displays state of confirmation requests.
20013 @cindex command tracing
20014 If you need to debug user-defined commands or sourced files you may find it
20015 useful to enable @dfn{command tracing}. In this mode each command will be
20016 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20017 quantity denoting the call depth of each command.
20020 @kindex set trace-commands
20021 @cindex command scripts, debugging
20022 @item set trace-commands on
20023 Enable command tracing.
20024 @item set trace-commands off
20025 Disable command tracing.
20026 @item show trace-commands
20027 Display the current state of command tracing.
20030 @node Debugging Output
20031 @section Optional Messages about Internal Happenings
20032 @cindex optional debugging messages
20034 @value{GDBN} has commands that enable optional debugging messages from
20035 various @value{GDBN} subsystems; normally these commands are of
20036 interest to @value{GDBN} maintainers, or when reporting a bug. This
20037 section documents those commands.
20040 @kindex set exec-done-display
20041 @item set exec-done-display
20042 Turns on or off the notification of asynchronous commands'
20043 completion. When on, @value{GDBN} will print a message when an
20044 asynchronous command finishes its execution. The default is off.
20045 @kindex show exec-done-display
20046 @item show exec-done-display
20047 Displays the current setting of asynchronous command completion
20050 @cindex gdbarch debugging info
20051 @cindex architecture debugging info
20052 @item set debug arch
20053 Turns on or off display of gdbarch debugging info. The default is off
20055 @item show debug arch
20056 Displays the current state of displaying gdbarch debugging info.
20057 @item set debug aix-thread
20058 @cindex AIX threads
20059 Display debugging messages about inner workings of the AIX thread
20061 @item show debug aix-thread
20062 Show the current state of AIX thread debugging info display.
20063 @item set debug check-physname
20065 Check the results of the ``physname'' computation. When reading DWARF
20066 debugging information for C@t{++}, @value{GDBN} attempts to compute
20067 each entity's name. @value{GDBN} can do this computation in two
20068 different ways, depending on exactly what information is present.
20069 When enabled, this setting causes @value{GDBN} to compute the names
20070 both ways and display any discrepancies.
20071 @item show debug check-physname
20072 Show the current state of ``physname'' checking.
20073 @item set debug dwarf2-die
20074 @cindex DWARF2 DIEs
20075 Dump DWARF2 DIEs after they are read in.
20076 The value is the number of nesting levels to print.
20077 A value of zero turns off the display.
20078 @item show debug dwarf2-die
20079 Show the current state of DWARF2 DIE debugging.
20080 @item set debug displaced
20081 @cindex displaced stepping debugging info
20082 Turns on or off display of @value{GDBN} debugging info for the
20083 displaced stepping support. The default is off.
20084 @item show debug displaced
20085 Displays the current state of displaying @value{GDBN} debugging info
20086 related to displaced stepping.
20087 @item set debug event
20088 @cindex event debugging info
20089 Turns on or off display of @value{GDBN} event debugging info. The
20091 @item show debug event
20092 Displays the current state of displaying @value{GDBN} event debugging
20094 @item set debug expression
20095 @cindex expression debugging info
20096 Turns on or off display of debugging info about @value{GDBN}
20097 expression parsing. The default is off.
20098 @item show debug expression
20099 Displays the current state of displaying debugging info about
20100 @value{GDBN} expression parsing.
20101 @item set debug frame
20102 @cindex frame debugging info
20103 Turns on or off display of @value{GDBN} frame debugging info. The
20105 @item show debug frame
20106 Displays the current state of displaying @value{GDBN} frame debugging
20108 @item set debug gnu-nat
20109 @cindex @sc{gnu}/Hurd debug messages
20110 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20111 @item show debug gnu-nat
20112 Show the current state of @sc{gnu}/Hurd debugging messages.
20113 @item set debug infrun
20114 @cindex inferior debugging info
20115 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20116 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20117 for implementing operations such as single-stepping the inferior.
20118 @item show debug infrun
20119 Displays the current state of @value{GDBN} inferior debugging.
20120 @item set debug jit
20121 @cindex just-in-time compilation, debugging messages
20122 Turns on or off debugging messages from JIT debug support.
20123 @item show debug jit
20124 Displays the current state of @value{GDBN} JIT debugging.
20125 @item set debug lin-lwp
20126 @cindex @sc{gnu}/Linux LWP debug messages
20127 @cindex Linux lightweight processes
20128 Turns on or off debugging messages from the Linux LWP debug support.
20129 @item show debug lin-lwp
20130 Show the current state of Linux LWP debugging messages.
20131 @item set debug observer
20132 @cindex observer debugging info
20133 Turns on or off display of @value{GDBN} observer debugging. This
20134 includes info such as the notification of observable events.
20135 @item show debug observer
20136 Displays the current state of observer debugging.
20137 @item set debug overload
20138 @cindex C@t{++} overload debugging info
20139 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20140 info. This includes info such as ranking of functions, etc. The default
20142 @item show debug overload
20143 Displays the current state of displaying @value{GDBN} C@t{++} overload
20145 @cindex expression parser, debugging info
20146 @cindex debug expression parser
20147 @item set debug parser
20148 Turns on or off the display of expression parser debugging output.
20149 Internally, this sets the @code{yydebug} variable in the expression
20150 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20151 details. The default is off.
20152 @item show debug parser
20153 Show the current state of expression parser debugging.
20154 @cindex packets, reporting on stdout
20155 @cindex serial connections, debugging
20156 @cindex debug remote protocol
20157 @cindex remote protocol debugging
20158 @cindex display remote packets
20159 @item set debug remote
20160 Turns on or off display of reports on all packets sent back and forth across
20161 the serial line to the remote machine. The info is printed on the
20162 @value{GDBN} standard output stream. The default is off.
20163 @item show debug remote
20164 Displays the state of display of remote packets.
20165 @item set debug serial
20166 Turns on or off display of @value{GDBN} serial debugging info. The
20168 @item show debug serial
20169 Displays the current state of displaying @value{GDBN} serial debugging
20171 @item set debug solib-frv
20172 @cindex FR-V shared-library debugging
20173 Turns on or off debugging messages for FR-V shared-library code.
20174 @item show debug solib-frv
20175 Display the current state of FR-V shared-library code debugging
20177 @item set debug target
20178 @cindex target debugging info
20179 Turns on or off display of @value{GDBN} target debugging info. This info
20180 includes what is going on at the target level of GDB, as it happens. The
20181 default is 0. Set it to 1 to track events, and to 2 to also track the
20182 value of large memory transfers. Changes to this flag do not take effect
20183 until the next time you connect to a target or use the @code{run} command.
20184 @item show debug target
20185 Displays the current state of displaying @value{GDBN} target debugging
20187 @item set debug timestamp
20188 @cindex timestampping debugging info
20189 Turns on or off display of timestamps with @value{GDBN} debugging info.
20190 When enabled, seconds and microseconds are displayed before each debugging
20192 @item show debug timestamp
20193 Displays the current state of displaying timestamps with @value{GDBN}
20195 @item set debugvarobj
20196 @cindex variable object debugging info
20197 Turns on or off display of @value{GDBN} variable object debugging
20198 info. The default is off.
20199 @item show debugvarobj
20200 Displays the current state of displaying @value{GDBN} variable object
20202 @item set debug xml
20203 @cindex XML parser debugging
20204 Turns on or off debugging messages for built-in XML parsers.
20205 @item show debug xml
20206 Displays the current state of XML debugging messages.
20209 @node Other Misc Settings
20210 @section Other Miscellaneous Settings
20211 @cindex miscellaneous settings
20214 @kindex set interactive-mode
20215 @item set interactive-mode
20216 If @code{on}, forces @value{GDBN} to assume that GDB was started
20217 in a terminal. In practice, this means that @value{GDBN} should wait
20218 for the user to answer queries generated by commands entered at
20219 the command prompt. If @code{off}, forces @value{GDBN} to operate
20220 in the opposite mode, and it uses the default answers to all queries.
20221 If @code{auto} (the default), @value{GDBN} tries to determine whether
20222 its standard input is a terminal, and works in interactive-mode if it
20223 is, non-interactively otherwise.
20225 In the vast majority of cases, the debugger should be able to guess
20226 correctly which mode should be used. But this setting can be useful
20227 in certain specific cases, such as running a MinGW @value{GDBN}
20228 inside a cygwin window.
20230 @kindex show interactive-mode
20231 @item show interactive-mode
20232 Displays whether the debugger is operating in interactive mode or not.
20235 @node Extending GDB
20236 @chapter Extending @value{GDBN}
20237 @cindex extending GDB
20239 @value{GDBN} provides two mechanisms for extension. The first is based
20240 on composition of @value{GDBN} commands, and the second is based on the
20241 Python scripting language.
20243 To facilitate the use of these extensions, @value{GDBN} is capable
20244 of evaluating the contents of a file. When doing so, @value{GDBN}
20245 can recognize which scripting language is being used by looking at
20246 the filename extension. Files with an unrecognized filename extension
20247 are always treated as a @value{GDBN} Command Files.
20248 @xref{Command Files,, Command files}.
20250 You can control how @value{GDBN} evaluates these files with the following
20254 @kindex set script-extension
20255 @kindex show script-extension
20256 @item set script-extension off
20257 All scripts are always evaluated as @value{GDBN} Command Files.
20259 @item set script-extension soft
20260 The debugger determines the scripting language based on filename
20261 extension. If this scripting language is supported, @value{GDBN}
20262 evaluates the script using that language. Otherwise, it evaluates
20263 the file as a @value{GDBN} Command File.
20265 @item set script-extension strict
20266 The debugger determines the scripting language based on filename
20267 extension, and evaluates the script using that language. If the
20268 language is not supported, then the evaluation fails.
20270 @item show script-extension
20271 Display the current value of the @code{script-extension} option.
20276 * Sequences:: Canned Sequences of Commands
20277 * Python:: Scripting @value{GDBN} using Python
20281 @section Canned Sequences of Commands
20283 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20284 Command Lists}), @value{GDBN} provides two ways to store sequences of
20285 commands for execution as a unit: user-defined commands and command
20289 * Define:: How to define your own commands
20290 * Hooks:: Hooks for user-defined commands
20291 * Command Files:: How to write scripts of commands to be stored in a file
20292 * Output:: Commands for controlled output
20296 @subsection User-defined Commands
20298 @cindex user-defined command
20299 @cindex arguments, to user-defined commands
20300 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20301 which you assign a new name as a command. This is done with the
20302 @code{define} command. User commands may accept up to 10 arguments
20303 separated by whitespace. Arguments are accessed within the user command
20304 via @code{$arg0@dots{}$arg9}. A trivial example:
20308 print $arg0 + $arg1 + $arg2
20313 To execute the command use:
20320 This defines the command @code{adder}, which prints the sum of
20321 its three arguments. Note the arguments are text substitutions, so they may
20322 reference variables, use complex expressions, or even perform inferior
20325 @cindex argument count in user-defined commands
20326 @cindex how many arguments (user-defined commands)
20327 In addition, @code{$argc} may be used to find out how many arguments have
20328 been passed. This expands to a number in the range 0@dots{}10.
20333 print $arg0 + $arg1
20336 print $arg0 + $arg1 + $arg2
20344 @item define @var{commandname}
20345 Define a command named @var{commandname}. If there is already a command
20346 by that name, you are asked to confirm that you want to redefine it.
20347 @var{commandname} may be a bare command name consisting of letters,
20348 numbers, dashes, and underscores. It may also start with any predefined
20349 prefix command. For example, @samp{define target my-target} creates
20350 a user-defined @samp{target my-target} command.
20352 The definition of the command is made up of other @value{GDBN} command lines,
20353 which are given following the @code{define} command. The end of these
20354 commands is marked by a line containing @code{end}.
20357 @kindex end@r{ (user-defined commands)}
20358 @item document @var{commandname}
20359 Document the user-defined command @var{commandname}, so that it can be
20360 accessed by @code{help}. The command @var{commandname} must already be
20361 defined. This command reads lines of documentation just as @code{define}
20362 reads the lines of the command definition, ending with @code{end}.
20363 After the @code{document} command is finished, @code{help} on command
20364 @var{commandname} displays the documentation you have written.
20366 You may use the @code{document} command again to change the
20367 documentation of a command. Redefining the command with @code{define}
20368 does not change the documentation.
20370 @kindex dont-repeat
20371 @cindex don't repeat command
20373 Used inside a user-defined command, this tells @value{GDBN} that this
20374 command should not be repeated when the user hits @key{RET}
20375 (@pxref{Command Syntax, repeat last command}).
20377 @kindex help user-defined
20378 @item help user-defined
20379 List all user-defined commands, with the first line of the documentation
20384 @itemx show user @var{commandname}
20385 Display the @value{GDBN} commands used to define @var{commandname} (but
20386 not its documentation). If no @var{commandname} is given, display the
20387 definitions for all user-defined commands.
20389 @cindex infinite recursion in user-defined commands
20390 @kindex show max-user-call-depth
20391 @kindex set max-user-call-depth
20392 @item show max-user-call-depth
20393 @itemx set max-user-call-depth
20394 The value of @code{max-user-call-depth} controls how many recursion
20395 levels are allowed in user-defined commands before @value{GDBN} suspects an
20396 infinite recursion and aborts the command.
20399 In addition to the above commands, user-defined commands frequently
20400 use control flow commands, described in @ref{Command Files}.
20402 When user-defined commands are executed, the
20403 commands of the definition are not printed. An error in any command
20404 stops execution of the user-defined command.
20406 If used interactively, commands that would ask for confirmation proceed
20407 without asking when used inside a user-defined command. Many @value{GDBN}
20408 commands that normally print messages to say what they are doing omit the
20409 messages when used in a user-defined command.
20412 @subsection User-defined Command Hooks
20413 @cindex command hooks
20414 @cindex hooks, for commands
20415 @cindex hooks, pre-command
20418 You may define @dfn{hooks}, which are a special kind of user-defined
20419 command. Whenever you run the command @samp{foo}, if the user-defined
20420 command @samp{hook-foo} exists, it is executed (with no arguments)
20421 before that command.
20423 @cindex hooks, post-command
20425 A hook may also be defined which is run after the command you executed.
20426 Whenever you run the command @samp{foo}, if the user-defined command
20427 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20428 that command. Post-execution hooks may exist simultaneously with
20429 pre-execution hooks, for the same command.
20431 It is valid for a hook to call the command which it hooks. If this
20432 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20434 @c It would be nice if hookpost could be passed a parameter indicating
20435 @c if the command it hooks executed properly or not. FIXME!
20437 @kindex stop@r{, a pseudo-command}
20438 In addition, a pseudo-command, @samp{stop} exists. Defining
20439 (@samp{hook-stop}) makes the associated commands execute every time
20440 execution stops in your program: before breakpoint commands are run,
20441 displays are printed, or the stack frame is printed.
20443 For example, to ignore @code{SIGALRM} signals while
20444 single-stepping, but treat them normally during normal execution,
20449 handle SIGALRM nopass
20453 handle SIGALRM pass
20456 define hook-continue
20457 handle SIGALRM pass
20461 As a further example, to hook at the beginning and end of the @code{echo}
20462 command, and to add extra text to the beginning and end of the message,
20470 define hookpost-echo
20474 (@value{GDBP}) echo Hello World
20475 <<<---Hello World--->>>
20480 You can define a hook for any single-word command in @value{GDBN}, but
20481 not for command aliases; you should define a hook for the basic command
20482 name, e.g.@: @code{backtrace} rather than @code{bt}.
20483 @c FIXME! So how does Joe User discover whether a command is an alias
20485 You can hook a multi-word command by adding @code{hook-} or
20486 @code{hookpost-} to the last word of the command, e.g.@:
20487 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20489 If an error occurs during the execution of your hook, execution of
20490 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20491 (before the command that you actually typed had a chance to run).
20493 If you try to define a hook which does not match any known command, you
20494 get a warning from the @code{define} command.
20496 @node Command Files
20497 @subsection Command Files
20499 @cindex command files
20500 @cindex scripting commands
20501 A command file for @value{GDBN} is a text file made of lines that are
20502 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20503 also be included. An empty line in a command file does nothing; it
20504 does not mean to repeat the last command, as it would from the
20507 You can request the execution of a command file with the @code{source}
20508 command. Note that the @code{source} command is also used to evaluate
20509 scripts that are not Command Files. The exact behavior can be configured
20510 using the @code{script-extension} setting.
20511 @xref{Extending GDB,, Extending GDB}.
20515 @cindex execute commands from a file
20516 @item source [-s] [-v] @var{filename}
20517 Execute the command file @var{filename}.
20520 The lines in a command file are generally executed sequentially,
20521 unless the order of execution is changed by one of the
20522 @emph{flow-control commands} described below. The commands are not
20523 printed as they are executed. An error in any command terminates
20524 execution of the command file and control is returned to the console.
20526 @value{GDBN} first searches for @var{filename} in the current directory.
20527 If the file is not found there, and @var{filename} does not specify a
20528 directory, then @value{GDBN} also looks for the file on the source search path
20529 (specified with the @samp{directory} command);
20530 except that @file{$cdir} is not searched because the compilation directory
20531 is not relevant to scripts.
20533 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20534 on the search path even if @var{filename} specifies a directory.
20535 The search is done by appending @var{filename} to each element of the
20536 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20537 and the search path contains @file{/home/user} then @value{GDBN} will
20538 look for the script @file{/home/user/mylib/myscript}.
20539 The search is also done if @var{filename} is an absolute path.
20540 For example, if @var{filename} is @file{/tmp/myscript} and
20541 the search path contains @file{/home/user} then @value{GDBN} will
20542 look for the script @file{/home/user/tmp/myscript}.
20543 For DOS-like systems, if @var{filename} contains a drive specification,
20544 it is stripped before concatenation. For example, if @var{filename} is
20545 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20546 will look for the script @file{c:/tmp/myscript}.
20548 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20549 each command as it is executed. The option must be given before
20550 @var{filename}, and is interpreted as part of the filename anywhere else.
20552 Commands that would ask for confirmation if used interactively proceed
20553 without asking when used in a command file. Many @value{GDBN} commands that
20554 normally print messages to say what they are doing omit the messages
20555 when called from command files.
20557 @value{GDBN} also accepts command input from standard input. In this
20558 mode, normal output goes to standard output and error output goes to
20559 standard error. Errors in a command file supplied on standard input do
20560 not terminate execution of the command file---execution continues with
20564 gdb < cmds > log 2>&1
20567 (The syntax above will vary depending on the shell used.) This example
20568 will execute commands from the file @file{cmds}. All output and errors
20569 would be directed to @file{log}.
20571 Since commands stored on command files tend to be more general than
20572 commands typed interactively, they frequently need to deal with
20573 complicated situations, such as different or unexpected values of
20574 variables and symbols, changes in how the program being debugged is
20575 built, etc. @value{GDBN} provides a set of flow-control commands to
20576 deal with these complexities. Using these commands, you can write
20577 complex scripts that loop over data structures, execute commands
20578 conditionally, etc.
20585 This command allows to include in your script conditionally executed
20586 commands. The @code{if} command takes a single argument, which is an
20587 expression to evaluate. It is followed by a series of commands that
20588 are executed only if the expression is true (its value is nonzero).
20589 There can then optionally be an @code{else} line, followed by a series
20590 of commands that are only executed if the expression was false. The
20591 end of the list is marked by a line containing @code{end}.
20595 This command allows to write loops. Its syntax is similar to
20596 @code{if}: the command takes a single argument, which is an expression
20597 to evaluate, and must be followed by the commands to execute, one per
20598 line, terminated by an @code{end}. These commands are called the
20599 @dfn{body} of the loop. The commands in the body of @code{while} are
20600 executed repeatedly as long as the expression evaluates to true.
20604 This command exits the @code{while} loop in whose body it is included.
20605 Execution of the script continues after that @code{while}s @code{end}
20608 @kindex loop_continue
20609 @item loop_continue
20610 This command skips the execution of the rest of the body of commands
20611 in the @code{while} loop in whose body it is included. Execution
20612 branches to the beginning of the @code{while} loop, where it evaluates
20613 the controlling expression.
20615 @kindex end@r{ (if/else/while commands)}
20617 Terminate the block of commands that are the body of @code{if},
20618 @code{else}, or @code{while} flow-control commands.
20623 @subsection Commands for Controlled Output
20625 During the execution of a command file or a user-defined command, normal
20626 @value{GDBN} output is suppressed; the only output that appears is what is
20627 explicitly printed by the commands in the definition. This section
20628 describes three commands useful for generating exactly the output you
20633 @item echo @var{text}
20634 @c I do not consider backslash-space a standard C escape sequence
20635 @c because it is not in ANSI.
20636 Print @var{text}. Nonprinting characters can be included in
20637 @var{text} using C escape sequences, such as @samp{\n} to print a
20638 newline. @strong{No newline is printed unless you specify one.}
20639 In addition to the standard C escape sequences, a backslash followed
20640 by a space stands for a space. This is useful for displaying a
20641 string with spaces at the beginning or the end, since leading and
20642 trailing spaces are otherwise trimmed from all arguments.
20643 To print @samp{@w{ }and foo =@w{ }}, use the command
20644 @samp{echo \@w{ }and foo = \@w{ }}.
20646 A backslash at the end of @var{text} can be used, as in C, to continue
20647 the command onto subsequent lines. For example,
20650 echo This is some text\n\
20651 which is continued\n\
20652 onto several lines.\n
20655 produces the same output as
20658 echo This is some text\n
20659 echo which is continued\n
20660 echo onto several lines.\n
20664 @item output @var{expression}
20665 Print the value of @var{expression} and nothing but that value: no
20666 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20667 value history either. @xref{Expressions, ,Expressions}, for more information
20670 @item output/@var{fmt} @var{expression}
20671 Print the value of @var{expression} in format @var{fmt}. You can use
20672 the same formats as for @code{print}. @xref{Output Formats,,Output
20673 Formats}, for more information.
20676 @item printf @var{template}, @var{expressions}@dots{}
20677 Print the values of one or more @var{expressions} under the control of
20678 the string @var{template}. To print several values, make
20679 @var{expressions} be a comma-separated list of individual expressions,
20680 which may be either numbers or pointers. Their values are printed as
20681 specified by @var{template}, exactly as a C program would do by
20682 executing the code below:
20685 printf (@var{template}, @var{expressions}@dots{});
20688 As in @code{C} @code{printf}, ordinary characters in @var{template}
20689 are printed verbatim, while @dfn{conversion specification} introduced
20690 by the @samp{%} character cause subsequent @var{expressions} to be
20691 evaluated, their values converted and formatted according to type and
20692 style information encoded in the conversion specifications, and then
20695 For example, you can print two values in hex like this:
20698 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20701 @code{printf} supports all the standard @code{C} conversion
20702 specifications, including the flags and modifiers between the @samp{%}
20703 character and the conversion letter, with the following exceptions:
20707 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20710 The modifier @samp{*} is not supported for specifying precision or
20714 The @samp{'} flag (for separation of digits into groups according to
20715 @code{LC_NUMERIC'}) is not supported.
20718 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20722 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20725 The conversion letters @samp{a} and @samp{A} are not supported.
20729 Note that the @samp{ll} type modifier is supported only if the
20730 underlying @code{C} implementation used to build @value{GDBN} supports
20731 the @code{long long int} type, and the @samp{L} type modifier is
20732 supported only if @code{long double} type is available.
20734 As in @code{C}, @code{printf} supports simple backslash-escape
20735 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20736 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20737 single character. Octal and hexadecimal escape sequences are not
20740 Additionally, @code{printf} supports conversion specifications for DFP
20741 (@dfn{Decimal Floating Point}) types using the following length modifiers
20742 together with a floating point specifier.
20747 @samp{H} for printing @code{Decimal32} types.
20750 @samp{D} for printing @code{Decimal64} types.
20753 @samp{DD} for printing @code{Decimal128} types.
20756 If the underlying @code{C} implementation used to build @value{GDBN} has
20757 support for the three length modifiers for DFP types, other modifiers
20758 such as width and precision will also be available for @value{GDBN} to use.
20760 In case there is no such @code{C} support, no additional modifiers will be
20761 available and the value will be printed in the standard way.
20763 Here's an example of printing DFP types using the above conversion letters:
20765 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20769 @item eval @var{template}, @var{expressions}@dots{}
20770 Convert the values of one or more @var{expressions} under the control of
20771 the string @var{template} to a command line, and call it.
20776 @section Scripting @value{GDBN} using Python
20777 @cindex python scripting
20778 @cindex scripting with python
20780 You can script @value{GDBN} using the @uref{http://www.python.org/,
20781 Python programming language}. This feature is available only if
20782 @value{GDBN} was configured using @option{--with-python}.
20784 @cindex python directory
20785 Python scripts used by @value{GDBN} should be installed in
20786 @file{@var{data-directory}/python}, where @var{data-directory} is
20787 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20788 This directory, known as the @dfn{python directory},
20789 is automatically added to the Python Search Path in order to allow
20790 the Python interpreter to locate all scripts installed at this location.
20793 * Python Commands:: Accessing Python from @value{GDBN}.
20794 * Python API:: Accessing @value{GDBN} from Python.
20795 * Auto-loading:: Automatically loading Python code.
20796 * Python modules:: Python modules provided by @value{GDBN}.
20799 @node Python Commands
20800 @subsection Python Commands
20801 @cindex python commands
20802 @cindex commands to access python
20804 @value{GDBN} provides one command for accessing the Python interpreter,
20805 and one related setting:
20809 @item python @r{[}@var{code}@r{]}
20810 The @code{python} command can be used to evaluate Python code.
20812 If given an argument, the @code{python} command will evaluate the
20813 argument as a Python command. For example:
20816 (@value{GDBP}) python print 23
20820 If you do not provide an argument to @code{python}, it will act as a
20821 multi-line command, like @code{define}. In this case, the Python
20822 script is made up of subsequent command lines, given after the
20823 @code{python} command. This command list is terminated using a line
20824 containing @code{end}. For example:
20827 (@value{GDBP}) python
20829 End with a line saying just "end".
20835 @kindex maint set python print-stack
20836 @item maint set python print-stack
20837 This command is now deprecated. Instead use @code{set python
20840 @kindex set python print-stack
20841 @item set python print-stack
20842 By default, @value{GDBN} will not print a stack trace when an error
20843 occurs in a Python script. This can be controlled using @code{set
20844 python print-stack}: if @code{on}, then Python stack printing is
20845 enabled; if @code{off}, the default, then Python stack printing is
20849 It is also possible to execute a Python script from the @value{GDBN}
20853 @item source @file{script-name}
20854 The script name must end with @samp{.py} and @value{GDBN} must be configured
20855 to recognize the script language based on filename extension using
20856 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20858 @item python execfile ("script-name")
20859 This method is based on the @code{execfile} Python built-in function,
20860 and thus is always available.
20864 @subsection Python API
20866 @cindex programming in python
20868 @cindex python stdout
20869 @cindex python pagination
20870 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20871 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20872 A Python program which outputs to one of these streams may have its
20873 output interrupted by the user (@pxref{Screen Size}). In this
20874 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20877 * Basic Python:: Basic Python Functions.
20878 * Exception Handling:: How Python exceptions are translated.
20879 * Values From Inferior:: Python representation of values.
20880 * Types In Python:: Python representation of types.
20881 * Pretty Printing API:: Pretty-printing values.
20882 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20883 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20884 * Inferiors In Python:: Python representation of inferiors (processes)
20885 * Events In Python:: Listening for events from @value{GDBN}.
20886 * Threads In Python:: Accessing inferior threads from Python.
20887 * Commands In Python:: Implementing new commands in Python.
20888 * Parameters In Python:: Adding new @value{GDBN} parameters.
20889 * Functions In Python:: Writing new convenience functions.
20890 * Progspaces In Python:: Program spaces.
20891 * Objfiles In Python:: Object files.
20892 * Frames In Python:: Accessing inferior stack frames from Python.
20893 * Blocks In Python:: Accessing frame blocks from Python.
20894 * Symbols In Python:: Python representation of symbols.
20895 * Symbol Tables In Python:: Python representation of symbol tables.
20896 * Lazy Strings In Python:: Python representation of lazy strings.
20897 * Breakpoints In Python:: Manipulating breakpoints using Python.
20901 @subsubsection Basic Python
20903 @cindex python functions
20904 @cindex python module
20906 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20907 methods and classes added by @value{GDBN} are placed in this module.
20908 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20909 use in all scripts evaluated by the @code{python} command.
20911 @findex gdb.PYTHONDIR
20913 A string containing the python directory (@pxref{Python}).
20916 @findex gdb.execute
20917 @defun execute command [from_tty] [to_string]
20918 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20919 If a GDB exception happens while @var{command} runs, it is
20920 translated as described in @ref{Exception Handling,,Exception Handling}.
20922 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20923 command as having originated from the user invoking it interactively.
20924 It must be a boolean value. If omitted, it defaults to @code{False}.
20926 By default, any output produced by @var{command} is sent to
20927 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20928 @code{True}, then output will be collected by @code{gdb.execute} and
20929 returned as a string. The default is @code{False}, in which case the
20930 return value is @code{None}. If @var{to_string} is @code{True}, the
20931 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20932 and height, and its pagination will be disabled; @pxref{Screen Size}.
20935 @findex gdb.breakpoints
20937 Return a sequence holding all of @value{GDBN}'s breakpoints.
20938 @xref{Breakpoints In Python}, for more information.
20941 @findex gdb.parameter
20942 @defun parameter parameter
20943 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20944 string naming the parameter to look up; @var{parameter} may contain
20945 spaces if the parameter has a multi-part name. For example,
20946 @samp{print object} is a valid parameter name.
20948 If the named parameter does not exist, this function throws a
20949 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
20950 parameter's value is converted to a Python value of the appropriate
20951 type, and returned.
20954 @findex gdb.history
20955 @defun history number
20956 Return a value from @value{GDBN}'s value history (@pxref{Value
20957 History}). @var{number} indicates which history element to return.
20958 If @var{number} is negative, then @value{GDBN} will take its absolute value
20959 and count backward from the last element (i.e., the most recent element) to
20960 find the value to return. If @var{number} is zero, then @value{GDBN} will
20961 return the most recent element. If the element specified by @var{number}
20962 doesn't exist in the value history, a @code{gdb.error} exception will be
20965 If no exception is raised, the return value is always an instance of
20966 @code{gdb.Value} (@pxref{Values From Inferior}).
20969 @findex gdb.parse_and_eval
20970 @defun parse_and_eval expression
20971 Parse @var{expression} as an expression in the current language,
20972 evaluate it, and return the result as a @code{gdb.Value}.
20973 @var{expression} must be a string.
20975 This function can be useful when implementing a new command
20976 (@pxref{Commands In Python}), as it provides a way to parse the
20977 command's argument as an expression. It is also useful simply to
20978 compute values, for example, it is the only way to get the value of a
20979 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20982 @findex gdb.post_event
20983 @defun post_event event
20984 Put @var{event}, a callable object taking no arguments, into
20985 @value{GDBN}'s internal event queue. This callable will be invoked at
20986 some later point, during @value{GDBN}'s event processing. Events
20987 posted using @code{post_event} will be run in the order in which they
20988 were posted; however, there is no way to know when they will be
20989 processed relative to other events inside @value{GDBN}.
20991 @value{GDBN} is not thread-safe. If your Python program uses multiple
20992 threads, you must be careful to only call @value{GDBN}-specific
20993 functions in the main @value{GDBN} thread. @code{post_event} ensures
20997 (@value{GDBP}) python
21001 > def __init__(self, message):
21002 > self.message = message;
21003 > def __call__(self):
21004 > gdb.write(self.message)
21006 >class MyThread1 (threading.Thread):
21008 > gdb.post_event(Writer("Hello "))
21010 >class MyThread2 (threading.Thread):
21012 > gdb.post_event(Writer("World\n"))
21014 >MyThread1().start()
21015 >MyThread2().start()
21017 (@value{GDBP}) Hello World
21022 @defun write string @r{[}stream{]}
21023 Print a string to @value{GDBN}'s paginated output stream. The
21024 optional @var{stream} determines the stream to print to. The default
21025 stream is @value{GDBN}'s standard output stream. Possible stream
21032 @value{GDBN}'s standard output stream.
21037 @value{GDBN}'s standard error stream.
21042 @value{GDBN}'s log stream (@pxref{Logging Output}).
21045 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21046 call this function and will automatically direct the output to the
21052 Flush the buffer of a @value{GDBN} paginated stream so that the
21053 contents are displayed immediately. @value{GDBN} will flush the
21054 contents of a stream automatically when it encounters a newline in the
21055 buffer. The optional @var{stream} determines the stream to flush. The
21056 default stream is @value{GDBN}'s standard output stream. Possible
21063 @value{GDBN}'s standard output stream.
21068 @value{GDBN}'s standard error stream.
21073 @value{GDBN}'s log stream (@pxref{Logging Output}).
21077 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21078 call this function for the relevant stream.
21081 @findex gdb.target_charset
21082 @defun target_charset
21083 Return the name of the current target character set (@pxref{Character
21084 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21085 that @samp{auto} is never returned.
21088 @findex gdb.target_wide_charset
21089 @defun target_wide_charset
21090 Return the name of the current target wide character set
21091 (@pxref{Character Sets}). This differs from
21092 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21096 @findex gdb.solib_name
21097 @defun solib_name address
21098 Return the name of the shared library holding the given @var{address}
21099 as a string, or @code{None}.
21102 @findex gdb.decode_line
21103 @defun decode_line @r{[}expression@r{]}
21104 Return locations of the line specified by @var{expression}, or of the
21105 current line if no argument was given. This function returns a Python
21106 tuple containing two elements. The first element contains a string
21107 holding any unparsed section of @var{expression} (or @code{None} if
21108 the expression has been fully parsed). The second element contains
21109 either @code{None} or another tuple that contains all the locations
21110 that match the expression represented as @code{gdb.Symtab_and_line}
21111 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21112 provided, it is decoded the way that @value{GDBN}'s inbuilt
21113 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21116 @defop Operation {@value{GDBN}} prompt_hook current_prompt
21117 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21118 assigned to this operation before a prompt is displayed by
21121 The parameter @code{current_prompt} contains the current @value{GDBN}
21122 prompt. This method must return a Python string, or @code{None}. If
21123 a string is returned, the @value{GDBN} prompt will be set to that
21124 string. If @code{None} is returned, @value{GDBN} will continue to use
21125 the current prompt.
21127 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21128 such as those used by readline for command input, and annotation
21129 related prompts are prohibited from being changed.
21132 @node Exception Handling
21133 @subsubsection Exception Handling
21134 @cindex python exceptions
21135 @cindex exceptions, python
21137 When executing the @code{python} command, Python exceptions
21138 uncaught within the Python code are translated to calls to
21139 @value{GDBN} error-reporting mechanism. If the command that called
21140 @code{python} does not handle the error, @value{GDBN} will
21141 terminate it and print an error message containing the Python
21142 exception name, the associated value, and the Python call stack
21143 backtrace at the point where the exception was raised. Example:
21146 (@value{GDBP}) python print foo
21147 Traceback (most recent call last):
21148 File "<string>", line 1, in <module>
21149 NameError: name 'foo' is not defined
21152 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21153 Python code are converted to Python exceptions. The type of the
21154 Python exception depends on the error.
21158 This is the base class for most exceptions generated by @value{GDBN}.
21159 It is derived from @code{RuntimeError}, for compatibility with earlier
21160 versions of @value{GDBN}.
21162 If an error occurring in @value{GDBN} does not fit into some more
21163 specific category, then the generated exception will have this type.
21165 @item gdb.MemoryError
21166 This is a subclass of @code{gdb.error} which is thrown when an
21167 operation tried to access invalid memory in the inferior.
21169 @item KeyboardInterrupt
21170 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21171 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21174 In all cases, your exception handler will see the @value{GDBN} error
21175 message as its value and the Python call stack backtrace at the Python
21176 statement closest to where the @value{GDBN} error occured as the
21179 @findex gdb.GdbError
21180 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21181 it is useful to be able to throw an exception that doesn't cause a
21182 traceback to be printed. For example, the user may have invoked the
21183 command incorrectly. Use the @code{gdb.GdbError} exception
21184 to handle this case. Example:
21188 >class HelloWorld (gdb.Command):
21189 > """Greet the whole world."""
21190 > def __init__ (self):
21191 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21192 > def invoke (self, args, from_tty):
21193 > argv = gdb.string_to_argv (args)
21194 > if len (argv) != 0:
21195 > raise gdb.GdbError ("hello-world takes no arguments")
21196 > print "Hello, World!"
21199 (gdb) hello-world 42
21200 hello-world takes no arguments
21203 @node Values From Inferior
21204 @subsubsection Values From Inferior
21205 @cindex values from inferior, with Python
21206 @cindex python, working with values from inferior
21208 @cindex @code{gdb.Value}
21209 @value{GDBN} provides values it obtains from the inferior program in
21210 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21211 for its internal bookkeeping of the inferior's values, and for
21212 fetching values when necessary.
21214 Inferior values that are simple scalars can be used directly in
21215 Python expressions that are valid for the value's data type. Here's
21216 an example for an integer or floating-point value @code{some_val}:
21223 As result of this, @code{bar} will also be a @code{gdb.Value} object
21224 whose values are of the same type as those of @code{some_val}.
21226 Inferior values that are structures or instances of some class can
21227 be accessed using the Python @dfn{dictionary syntax}. For example, if
21228 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21229 can access its @code{foo} element with:
21232 bar = some_val['foo']
21235 Again, @code{bar} will also be a @code{gdb.Value} object.
21237 A @code{gdb.Value} that represents a function can be executed via
21238 inferior function call. Any arguments provided to the call must match
21239 the function's prototype, and must be provided in the order specified
21242 For example, @code{some_val} is a @code{gdb.Value} instance
21243 representing a function that takes two integers as arguments. To
21244 execute this function, call it like so:
21247 result = some_val (10,20)
21250 Any values returned from a function call will be stored as a
21253 The following attributes are provided:
21256 @defivar Value address
21257 If this object is addressable, this read-only attribute holds a
21258 @code{gdb.Value} object representing the address. Otherwise,
21259 this attribute holds @code{None}.
21262 @cindex optimized out value in Python
21263 @defivar Value is_optimized_out
21264 This read-only boolean attribute is true if the compiler optimized out
21265 this value, thus it is not available for fetching from the inferior.
21268 @defivar Value type
21269 The type of this @code{gdb.Value}. The value of this attribute is a
21270 @code{gdb.Type} object (@pxref{Types In Python}).
21273 @defivar Value dynamic_type
21274 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21275 type information (@acronym{RTTI}) to determine the dynamic type of the
21276 value. If this value is of class type, it will return the class in
21277 which the value is embedded, if any. If this value is of pointer or
21278 reference to a class type, it will compute the dynamic type of the
21279 referenced object, and return a pointer or reference to that type,
21280 respectively. In all other cases, it will return the value's static
21283 Note that this feature will only work when debugging a C@t{++} program
21284 that includes @acronym{RTTI} for the object in question. Otherwise,
21285 it will just return the static type of the value as in @kbd{ptype foo}
21286 (@pxref{Symbols, ptype}).
21290 The following methods are provided:
21293 @defmethod Value __init__ @var{val}
21294 Many Python values can be converted directly to a @code{gdb.Value} via
21295 this object initializer. Specifically:
21298 @item Python boolean
21299 A Python boolean is converted to the boolean type from the current
21302 @item Python integer
21303 A Python integer is converted to the C @code{long} type for the
21304 current architecture.
21307 A Python long is converted to the C @code{long long} type for the
21308 current architecture.
21311 A Python float is converted to the C @code{double} type for the
21312 current architecture.
21314 @item Python string
21315 A Python string is converted to a target string, using the current
21318 @item @code{gdb.Value}
21319 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21321 @item @code{gdb.LazyString}
21322 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21323 Python}), then the lazy string's @code{value} method is called, and
21324 its result is used.
21328 @defmethod Value cast type
21329 Return a new instance of @code{gdb.Value} that is the result of
21330 casting this instance to the type described by @var{type}, which must
21331 be a @code{gdb.Type} object. If the cast cannot be performed for some
21332 reason, this method throws an exception.
21335 @defmethod Value dereference
21336 For pointer data types, this method returns a new @code{gdb.Value} object
21337 whose contents is the object pointed to by the pointer. For example, if
21338 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21345 then you can use the corresponding @code{gdb.Value} to access what
21346 @code{foo} points to like this:
21349 bar = foo.dereference ()
21352 The result @code{bar} will be a @code{gdb.Value} object holding the
21353 value pointed to by @code{foo}.
21356 @defmethod Value dynamic_cast type
21357 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21358 operator were used. Consult a C@t{++} reference for details.
21361 @defmethod Value reinterpret_cast type
21362 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21363 operator were used. Consult a C@t{++} reference for details.
21366 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
21367 If this @code{gdb.Value} represents a string, then this method
21368 converts the contents to a Python string. Otherwise, this method will
21369 throw an exception.
21371 Strings are recognized in a language-specific way; whether a given
21372 @code{gdb.Value} represents a string is determined by the current
21375 For C-like languages, a value is a string if it is a pointer to or an
21376 array of characters or ints. The string is assumed to be terminated
21377 by a zero of the appropriate width. However if the optional length
21378 argument is given, the string will be converted to that given length,
21379 ignoring any embedded zeros that the string may contain.
21381 If the optional @var{encoding} argument is given, it must be a string
21382 naming the encoding of the string in the @code{gdb.Value}, such as
21383 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21384 the same encodings as the corresponding argument to Python's
21385 @code{string.decode} method, and the Python codec machinery will be used
21386 to convert the string. If @var{encoding} is not given, or if
21387 @var{encoding} is the empty string, then either the @code{target-charset}
21388 (@pxref{Character Sets}) will be used, or a language-specific encoding
21389 will be used, if the current language is able to supply one.
21391 The optional @var{errors} argument is the same as the corresponding
21392 argument to Python's @code{string.decode} method.
21394 If the optional @var{length} argument is given, the string will be
21395 fetched and converted to the given length.
21398 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
21399 If this @code{gdb.Value} represents a string, then this method
21400 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21401 In Python}). Otherwise, this method will throw an exception.
21403 If the optional @var{encoding} argument is given, it must be a string
21404 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21405 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21406 @var{encoding} argument is an encoding that @value{GDBN} does
21407 recognize, @value{GDBN} will raise an error.
21409 When a lazy string is printed, the @value{GDBN} encoding machinery is
21410 used to convert the string during printing. If the optional
21411 @var{encoding} argument is not provided, or is an empty string,
21412 @value{GDBN} will automatically select the encoding most suitable for
21413 the string type. For further information on encoding in @value{GDBN}
21414 please see @ref{Character Sets}.
21416 If the optional @var{length} argument is given, the string will be
21417 fetched and encoded to the length of characters specified. If
21418 the @var{length} argument is not provided, the string will be fetched
21419 and encoded until a null of appropriate width is found.
21423 @node Types In Python
21424 @subsubsection Types In Python
21425 @cindex types in Python
21426 @cindex Python, working with types
21429 @value{GDBN} represents types from the inferior using the class
21432 The following type-related functions are available in the @code{gdb}
21435 @findex gdb.lookup_type
21436 @defun lookup_type name [block]
21437 This function looks up a type by name. @var{name} is the name of the
21438 type to look up. It must be a string.
21440 If @var{block} is given, then @var{name} is looked up in that scope.
21441 Otherwise, it is searched for globally.
21443 Ordinarily, this function will return an instance of @code{gdb.Type}.
21444 If the named type cannot be found, it will throw an exception.
21447 An instance of @code{Type} has the following attributes:
21451 The type code for this type. The type code will be one of the
21452 @code{TYPE_CODE_} constants defined below.
21455 @defivar Type sizeof
21456 The size of this type, in target @code{char} units. Usually, a
21457 target's @code{char} type will be an 8-bit byte. However, on some
21458 unusual platforms, this type may have a different size.
21462 The tag name for this type. The tag name is the name after
21463 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21464 languages have this concept. If this type has no tag name, then
21465 @code{None} is returned.
21469 The following methods are provided:
21472 @defmethod Type fields
21473 For structure and union types, this method returns the fields. Range
21474 types have two fields, the minimum and maximum values. Enum types
21475 have one field per enum constant. Function and method types have one
21476 field per parameter. The base types of C@t{++} classes are also
21477 represented as fields. If the type has no fields, or does not fit
21478 into one of these categories, an empty sequence will be returned.
21480 Each field is an object, with some pre-defined attributes:
21483 This attribute is not available for @code{static} fields (as in
21484 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21485 position of the field.
21488 The name of the field, or @code{None} for anonymous fields.
21491 This is @code{True} if the field is artificial, usually meaning that
21492 it was provided by the compiler and not the user. This attribute is
21493 always provided, and is @code{False} if the field is not artificial.
21495 @item is_base_class
21496 This is @code{True} if the field represents a base class of a C@t{++}
21497 structure. This attribute is always provided, and is @code{False}
21498 if the field is not a base class of the type that is the argument of
21499 @code{fields}, or if that type was not a C@t{++} class.
21502 If the field is packed, or is a bitfield, then this will have a
21503 non-zero value, which is the size of the field in bits. Otherwise,
21504 this will be zero; in this case the field's size is given by its type.
21507 The type of the field. This is usually an instance of @code{Type},
21508 but it can be @code{None} in some situations.
21512 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21513 Return a new @code{gdb.Type} object which represents an array of this
21514 type. If one argument is given, it is the inclusive upper bound of
21515 the array; in this case the lower bound is zero. If two arguments are
21516 given, the first argument is the lower bound of the array, and the
21517 second argument is the upper bound of the array. An array's length
21518 must not be negative, but the bounds can be.
21521 @defmethod Type const
21522 Return a new @code{gdb.Type} object which represents a
21523 @code{const}-qualified variant of this type.
21526 @defmethod Type volatile
21527 Return a new @code{gdb.Type} object which represents a
21528 @code{volatile}-qualified variant of this type.
21531 @defmethod Type unqualified
21532 Return a new @code{gdb.Type} object which represents an unqualified
21533 variant of this type. That is, the result is neither @code{const} nor
21537 @defmethod Type range
21538 Return a Python @code{Tuple} object that contains two elements: the
21539 low bound of the argument type and the high bound of that type. If
21540 the type does not have a range, @value{GDBN} will raise a
21541 @code{gdb.error} exception (@pxref{Exception Handling}).
21544 @defmethod Type reference
21545 Return a new @code{gdb.Type} object which represents a reference to this
21549 @defmethod Type pointer
21550 Return a new @code{gdb.Type} object which represents a pointer to this
21554 @defmethod Type strip_typedefs
21555 Return a new @code{gdb.Type} that represents the real type,
21556 after removing all layers of typedefs.
21559 @defmethod Type target
21560 Return a new @code{gdb.Type} object which represents the target type
21563 For a pointer type, the target type is the type of the pointed-to
21564 object. For an array type (meaning C-like arrays), the target type is
21565 the type of the elements of the array. For a function or method type,
21566 the target type is the type of the return value. For a complex type,
21567 the target type is the type of the elements. For a typedef, the
21568 target type is the aliased type.
21570 If the type does not have a target, this method will throw an
21574 @defmethod Type template_argument n [block]
21575 If this @code{gdb.Type} is an instantiation of a template, this will
21576 return a new @code{gdb.Type} which represents the type of the
21577 @var{n}th template argument.
21579 If this @code{gdb.Type} is not a template type, this will throw an
21580 exception. Ordinarily, only C@t{++} code will have template types.
21582 If @var{block} is given, then @var{name} is looked up in that scope.
21583 Otherwise, it is searched for globally.
21588 Each type has a code, which indicates what category this type falls
21589 into. The available type categories are represented by constants
21590 defined in the @code{gdb} module:
21593 @findex TYPE_CODE_PTR
21594 @findex gdb.TYPE_CODE_PTR
21595 @item TYPE_CODE_PTR
21596 The type is a pointer.
21598 @findex TYPE_CODE_ARRAY
21599 @findex gdb.TYPE_CODE_ARRAY
21600 @item TYPE_CODE_ARRAY
21601 The type is an array.
21603 @findex TYPE_CODE_STRUCT
21604 @findex gdb.TYPE_CODE_STRUCT
21605 @item TYPE_CODE_STRUCT
21606 The type is a structure.
21608 @findex TYPE_CODE_UNION
21609 @findex gdb.TYPE_CODE_UNION
21610 @item TYPE_CODE_UNION
21611 The type is a union.
21613 @findex TYPE_CODE_ENUM
21614 @findex gdb.TYPE_CODE_ENUM
21615 @item TYPE_CODE_ENUM
21616 The type is an enum.
21618 @findex TYPE_CODE_FLAGS
21619 @findex gdb.TYPE_CODE_FLAGS
21620 @item TYPE_CODE_FLAGS
21621 A bit flags type, used for things such as status registers.
21623 @findex TYPE_CODE_FUNC
21624 @findex gdb.TYPE_CODE_FUNC
21625 @item TYPE_CODE_FUNC
21626 The type is a function.
21628 @findex TYPE_CODE_INT
21629 @findex gdb.TYPE_CODE_INT
21630 @item TYPE_CODE_INT
21631 The type is an integer type.
21633 @findex TYPE_CODE_FLT
21634 @findex gdb.TYPE_CODE_FLT
21635 @item TYPE_CODE_FLT
21636 A floating point type.
21638 @findex TYPE_CODE_VOID
21639 @findex gdb.TYPE_CODE_VOID
21640 @item TYPE_CODE_VOID
21641 The special type @code{void}.
21643 @findex TYPE_CODE_SET
21644 @findex gdb.TYPE_CODE_SET
21645 @item TYPE_CODE_SET
21648 @findex TYPE_CODE_RANGE
21649 @findex gdb.TYPE_CODE_RANGE
21650 @item TYPE_CODE_RANGE
21651 A range type, that is, an integer type with bounds.
21653 @findex TYPE_CODE_STRING
21654 @findex gdb.TYPE_CODE_STRING
21655 @item TYPE_CODE_STRING
21656 A string type. Note that this is only used for certain languages with
21657 language-defined string types; C strings are not represented this way.
21659 @findex TYPE_CODE_BITSTRING
21660 @findex gdb.TYPE_CODE_BITSTRING
21661 @item TYPE_CODE_BITSTRING
21664 @findex TYPE_CODE_ERROR
21665 @findex gdb.TYPE_CODE_ERROR
21666 @item TYPE_CODE_ERROR
21667 An unknown or erroneous type.
21669 @findex TYPE_CODE_METHOD
21670 @findex gdb.TYPE_CODE_METHOD
21671 @item TYPE_CODE_METHOD
21672 A method type, as found in C@t{++} or Java.
21674 @findex TYPE_CODE_METHODPTR
21675 @findex gdb.TYPE_CODE_METHODPTR
21676 @item TYPE_CODE_METHODPTR
21677 A pointer-to-member-function.
21679 @findex TYPE_CODE_MEMBERPTR
21680 @findex gdb.TYPE_CODE_MEMBERPTR
21681 @item TYPE_CODE_MEMBERPTR
21682 A pointer-to-member.
21684 @findex TYPE_CODE_REF
21685 @findex gdb.TYPE_CODE_REF
21686 @item TYPE_CODE_REF
21689 @findex TYPE_CODE_CHAR
21690 @findex gdb.TYPE_CODE_CHAR
21691 @item TYPE_CODE_CHAR
21694 @findex TYPE_CODE_BOOL
21695 @findex gdb.TYPE_CODE_BOOL
21696 @item TYPE_CODE_BOOL
21699 @findex TYPE_CODE_COMPLEX
21700 @findex gdb.TYPE_CODE_COMPLEX
21701 @item TYPE_CODE_COMPLEX
21702 A complex float type.
21704 @findex TYPE_CODE_TYPEDEF
21705 @findex gdb.TYPE_CODE_TYPEDEF
21706 @item TYPE_CODE_TYPEDEF
21707 A typedef to some other type.
21709 @findex TYPE_CODE_NAMESPACE
21710 @findex gdb.TYPE_CODE_NAMESPACE
21711 @item TYPE_CODE_NAMESPACE
21712 A C@t{++} namespace.
21714 @findex TYPE_CODE_DECFLOAT
21715 @findex gdb.TYPE_CODE_DECFLOAT
21716 @item TYPE_CODE_DECFLOAT
21717 A decimal floating point type.
21719 @findex TYPE_CODE_INTERNAL_FUNCTION
21720 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21721 @item TYPE_CODE_INTERNAL_FUNCTION
21722 A function internal to @value{GDBN}. This is the type used to represent
21723 convenience functions.
21726 Further support for types is provided in the @code{gdb.types}
21727 Python module (@pxref{gdb.types}).
21729 @node Pretty Printing API
21730 @subsubsection Pretty Printing API
21732 An example output is provided (@pxref{Pretty Printing}).
21734 A pretty-printer is just an object that holds a value and implements a
21735 specific interface, defined here.
21737 @defop Operation {pretty printer} children (self)
21738 @value{GDBN} will call this method on a pretty-printer to compute the
21739 children of the pretty-printer's value.
21741 This method must return an object conforming to the Python iterator
21742 protocol. Each item returned by the iterator must be a tuple holding
21743 two elements. The first element is the ``name'' of the child; the
21744 second element is the child's value. The value can be any Python
21745 object which is convertible to a @value{GDBN} value.
21747 This method is optional. If it does not exist, @value{GDBN} will act
21748 as though the value has no children.
21751 @defop Operation {pretty printer} display_hint (self)
21752 The CLI may call this method and use its result to change the
21753 formatting of a value. The result will also be supplied to an MI
21754 consumer as a @samp{displayhint} attribute of the variable being
21757 This method is optional. If it does exist, this method must return a
21760 Some display hints are predefined by @value{GDBN}:
21764 Indicate that the object being printed is ``array-like''. The CLI
21765 uses this to respect parameters such as @code{set print elements} and
21766 @code{set print array}.
21769 Indicate that the object being printed is ``map-like'', and that the
21770 children of this value can be assumed to alternate between keys and
21774 Indicate that the object being printed is ``string-like''. If the
21775 printer's @code{to_string} method returns a Python string of some
21776 kind, then @value{GDBN} will call its internal language-specific
21777 string-printing function to format the string. For the CLI this means
21778 adding quotation marks, possibly escaping some characters, respecting
21779 @code{set print elements}, and the like.
21783 @defop Operation {pretty printer} to_string (self)
21784 @value{GDBN} will call this method to display the string
21785 representation of the value passed to the object's constructor.
21787 When printing from the CLI, if the @code{to_string} method exists,
21788 then @value{GDBN} will prepend its result to the values returned by
21789 @code{children}. Exactly how this formatting is done is dependent on
21790 the display hint, and may change as more hints are added. Also,
21791 depending on the print settings (@pxref{Print Settings}), the CLI may
21792 print just the result of @code{to_string} in a stack trace, omitting
21793 the result of @code{children}.
21795 If this method returns a string, it is printed verbatim.
21797 Otherwise, if this method returns an instance of @code{gdb.Value},
21798 then @value{GDBN} prints this value. This may result in a call to
21799 another pretty-printer.
21801 If instead the method returns a Python value which is convertible to a
21802 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21803 the resulting value. Again, this may result in a call to another
21804 pretty-printer. Python scalars (integers, floats, and booleans) and
21805 strings are convertible to @code{gdb.Value}; other types are not.
21807 Finally, if this method returns @code{None} then no further operations
21808 are peformed in this method and nothing is printed.
21810 If the result is not one of these types, an exception is raised.
21813 @value{GDBN} provides a function which can be used to look up the
21814 default pretty-printer for a @code{gdb.Value}:
21816 @findex gdb.default_visualizer
21817 @defun default_visualizer value
21818 This function takes a @code{gdb.Value} object as an argument. If a
21819 pretty-printer for this value exists, then it is returned. If no such
21820 printer exists, then this returns @code{None}.
21823 @node Selecting Pretty-Printers
21824 @subsubsection Selecting Pretty-Printers
21826 The Python list @code{gdb.pretty_printers} contains an array of
21827 functions or callable objects that have been registered via addition
21828 as a pretty-printer. Printers in this list are called @code{global}
21829 printers, they're available when debugging all inferiors.
21830 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21831 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21834 Each function on these lists is passed a single @code{gdb.Value}
21835 argument and should return a pretty-printer object conforming to the
21836 interface definition above (@pxref{Pretty Printing API}). If a function
21837 cannot create a pretty-printer for the value, it should return
21840 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21841 @code{gdb.Objfile} in the current program space and iteratively calls
21842 each enabled lookup routine in the list for that @code{gdb.Objfile}
21843 until it receives a pretty-printer object.
21844 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21845 searches the pretty-printer list of the current program space,
21846 calling each enabled function until an object is returned.
21847 After these lists have been exhausted, it tries the global
21848 @code{gdb.pretty_printers} list, again calling each enabled function until an
21849 object is returned.
21851 The order in which the objfiles are searched is not specified. For a
21852 given list, functions are always invoked from the head of the list,
21853 and iterated over sequentially until the end of the list, or a printer
21854 object is returned.
21856 For various reasons a pretty-printer may not work.
21857 For example, the underlying data structure may have changed and
21858 the pretty-printer is out of date.
21860 The consequences of a broken pretty-printer are severe enough that
21861 @value{GDBN} provides support for enabling and disabling individual
21862 printers. For example, if @code{print frame-arguments} is on,
21863 a backtrace can become highly illegible if any argument is printed
21864 with a broken printer.
21866 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21867 attribute to the registered function or callable object. If this attribute
21868 is present and its value is @code{False}, the printer is disabled, otherwise
21869 the printer is enabled.
21871 @node Writing a Pretty-Printer
21872 @subsubsection Writing a Pretty-Printer
21873 @cindex writing a pretty-printer
21875 A pretty-printer consists of two parts: a lookup function to detect
21876 if the type is supported, and the printer itself.
21878 Here is an example showing how a @code{std::string} printer might be
21879 written. @xref{Pretty Printing API}, for details on the API this class
21883 class StdStringPrinter(object):
21884 "Print a std::string"
21886 def __init__(self, val):
21889 def to_string(self):
21890 return self.val['_M_dataplus']['_M_p']
21892 def display_hint(self):
21896 And here is an example showing how a lookup function for the printer
21897 example above might be written.
21900 def str_lookup_function(val):
21901 lookup_tag = val.type.tag
21902 if lookup_tag == None:
21904 regex = re.compile("^std::basic_string<char,.*>$")
21905 if regex.match(lookup_tag):
21906 return StdStringPrinter(val)
21910 The example lookup function extracts the value's type, and attempts to
21911 match it to a type that it can pretty-print. If it is a type the
21912 printer can pretty-print, it will return a printer object. If not, it
21913 returns @code{None}.
21915 We recommend that you put your core pretty-printers into a Python
21916 package. If your pretty-printers are for use with a library, we
21917 further recommend embedding a version number into the package name.
21918 This practice will enable @value{GDBN} to load multiple versions of
21919 your pretty-printers at the same time, because they will have
21922 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21923 can be evaluated multiple times without changing its meaning. An
21924 ideal auto-load file will consist solely of @code{import}s of your
21925 printer modules, followed by a call to a register pretty-printers with
21926 the current objfile.
21928 Taken as a whole, this approach will scale nicely to multiple
21929 inferiors, each potentially using a different library version.
21930 Embedding a version number in the Python package name will ensure that
21931 @value{GDBN} is able to load both sets of printers simultaneously.
21932 Then, because the search for pretty-printers is done by objfile, and
21933 because your auto-loaded code took care to register your library's
21934 printers with a specific objfile, @value{GDBN} will find the correct
21935 printers for the specific version of the library used by each
21938 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21939 this code might appear in @code{gdb.libstdcxx.v6}:
21942 def register_printers(objfile):
21943 objfile.pretty_printers.add(str_lookup_function)
21947 And then the corresponding contents of the auto-load file would be:
21950 import gdb.libstdcxx.v6
21951 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
21954 The previous example illustrates a basic pretty-printer.
21955 There are a few things that can be improved on.
21956 The printer doesn't have a name, making it hard to identify in a
21957 list of installed printers. The lookup function has a name, but
21958 lookup functions can have arbitrary, even identical, names.
21960 Second, the printer only handles one type, whereas a library typically has
21961 several types. One could install a lookup function for each desired type
21962 in the library, but one could also have a single lookup function recognize
21963 several types. The latter is the conventional way this is handled.
21964 If a pretty-printer can handle multiple data types, then its
21965 @dfn{subprinters} are the printers for the individual data types.
21967 The @code{gdb.printing} module provides a formal way of solving these
21968 problems (@pxref{gdb.printing}).
21969 Here is another example that handles multiple types.
21971 These are the types we are going to pretty-print:
21974 struct foo @{ int a, b; @};
21975 struct bar @{ struct foo x, y; @};
21978 Here are the printers:
21982 """Print a foo object."""
21984 def __init__(self, val):
21987 def to_string(self):
21988 return ("a=<" + str(self.val["a"]) +
21989 "> b=<" + str(self.val["b"]) + ">")
21992 """Print a bar object."""
21994 def __init__(self, val):
21997 def to_string(self):
21998 return ("x=<" + str(self.val["x"]) +
21999 "> y=<" + str(self.val["y"]) + ">")
22002 This example doesn't need a lookup function, that is handled by the
22003 @code{gdb.printing} module. Instead a function is provided to build up
22004 the object that handles the lookup.
22007 import gdb.printing
22009 def build_pretty_printer():
22010 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22012 pp.add_printer('foo', '^foo$', fooPrinter)
22013 pp.add_printer('bar', '^bar$', barPrinter)
22017 And here is the autoload support:
22020 import gdb.printing
22022 gdb.printing.register_pretty_printer(
22023 gdb.current_objfile(),
22024 my_library.build_pretty_printer())
22027 Finally, when this printer is loaded into @value{GDBN}, here is the
22028 corresponding output of @samp{info pretty-printer}:
22031 (gdb) info pretty-printer
22038 @node Inferiors In Python
22039 @subsubsection Inferiors In Python
22040 @cindex inferiors in Python
22042 @findex gdb.Inferior
22043 Programs which are being run under @value{GDBN} are called inferiors
22044 (@pxref{Inferiors and Programs}). Python scripts can access
22045 information about and manipulate inferiors controlled by @value{GDBN}
22046 via objects of the @code{gdb.Inferior} class.
22048 The following inferior-related functions are available in the @code{gdb}
22052 Return a tuple containing all inferior objects.
22055 A @code{gdb.Inferior} object has the following attributes:
22058 @defivar Inferior num
22059 ID of inferior, as assigned by GDB.
22062 @defivar Inferior pid
22063 Process ID of the inferior, as assigned by the underlying operating
22067 @defivar Inferior was_attached
22068 Boolean signaling whether the inferior was created using `attach', or
22069 started by @value{GDBN} itself.
22073 A @code{gdb.Inferior} object has the following methods:
22076 @defmethod Inferior is_valid
22077 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22078 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22079 if the inferior no longer exists within @value{GDBN}. All other
22080 @code{gdb.Inferior} methods will throw an exception if it is invalid
22081 at the time the method is called.
22084 @defmethod Inferior threads
22085 This method returns a tuple holding all the threads which are valid
22086 when it is called. If there are no valid threads, the method will
22087 return an empty tuple.
22090 @findex gdb.read_memory
22091 @defmethod Inferior read_memory address length
22092 Read @var{length} bytes of memory from the inferior, starting at
22093 @var{address}. Returns a buffer object, which behaves much like an array
22094 or a string. It can be modified and given to the @code{gdb.write_memory}
22098 @findex gdb.write_memory
22099 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
22100 Write the contents of @var{buffer} to the inferior, starting at
22101 @var{address}. The @var{buffer} parameter must be a Python object
22102 which supports the buffer protocol, i.e., a string, an array or the
22103 object returned from @code{gdb.read_memory}. If given, @var{length}
22104 determines the number of bytes from @var{buffer} to be written.
22107 @findex gdb.search_memory
22108 @defmethod Inferior search_memory address length pattern
22109 Search a region of the inferior memory starting at @var{address} with
22110 the given @var{length} using the search pattern supplied in
22111 @var{pattern}. The @var{pattern} parameter must be a Python object
22112 which supports the buffer protocol, i.e., a string, an array or the
22113 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22114 containing the address where the pattern was found, or @code{None} if
22115 the pattern could not be found.
22119 @node Events In Python
22120 @subsubsection Events In Python
22121 @cindex inferior events in Python
22123 @value{GDBN} provides a general event facility so that Python code can be
22124 notified of various state changes, particularly changes that occur in
22127 An @dfn{event} is just an object that describes some state change. The
22128 type of the object and its attributes will vary depending on the details
22129 of the change. All the existing events are described below.
22131 In order to be notified of an event, you must register an event handler
22132 with an @dfn{event registry}. An event registry is an object in the
22133 @code{gdb.events} module which dispatches particular events. A registry
22134 provides methods to register and unregister event handlers:
22137 @defmethod EventRegistry connect object
22138 Add the given callable @var{object} to the registry. This object will be
22139 called when an event corresponding to this registry occurs.
22142 @defmethod EventRegistry disconnect object
22143 Remove the given @var{object} from the registry. Once removed, the object
22144 will no longer receive notifications of events.
22148 Here is an example:
22151 def exit_handler (event):
22152 print "event type: exit"
22153 print "exit code: %d" % (event.exit_code)
22155 gdb.events.exited.connect (exit_handler)
22158 In the above example we connect our handler @code{exit_handler} to the
22159 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22160 called when the inferior exits. The argument @dfn{event} in this example is
22161 of type @code{gdb.ExitedEvent}. As you can see in the example the
22162 @code{ExitedEvent} object has an attribute which indicates the exit code of
22165 The following is a listing of the event registries that are available and
22166 details of the events they emit:
22171 Emits @code{gdb.ThreadEvent}.
22173 Some events can be thread specific when @value{GDBN} is running in non-stop
22174 mode. When represented in Python, these events all extend
22175 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22176 events which are emitted by this or other modules might extend this event.
22177 Examples of these events are @code{gdb.BreakpointEvent} and
22178 @code{gdb.ContinueEvent}.
22181 @defivar ThreadEvent inferior_thread
22182 In non-stop mode this attribute will be set to the specific thread which was
22183 involved in the emitted event. Otherwise, it will be set to @code{None}.
22187 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22189 This event indicates that the inferior has been continued after a stop. For
22190 inherited attribute refer to @code{gdb.ThreadEvent} above.
22192 @item events.exited
22193 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22194 @code{events.ExitedEvent} has one optional attribute. This attribute
22195 will exist only in the case that the inferior exited with some
22198 @defivar ExitedEvent exit_code
22199 An integer representing the exit code which the inferior has returned.
22204 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22206 Indicates that the inferior has stopped. All events emitted by this registry
22207 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22208 will indicate the stopped thread when @value{GDBN} is running in non-stop
22209 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22211 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22213 This event indicates that the inferior or one of its threads has received as
22214 signal. @code{gdb.SignalEvent} has the following attributes:
22217 @defivar SignalEvent stop_signal
22218 A string representing the signal received by the inferior. A list of possible
22219 signal values can be obtained by running the command @code{info signals} in
22220 the @value{GDBN} command prompt.
22224 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22226 @code{gdb.BreakpointEvent} event indicates that a breakpoint has been hit, and
22227 has the following attributes:
22230 @defivar BreakpointEvent breakpoint
22231 A reference to the breakpoint that was hit of type @code{gdb.Breakpoint}.
22232 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22238 @node Threads In Python
22239 @subsubsection Threads In Python
22240 @cindex threads in python
22242 @findex gdb.InferiorThread
22243 Python scripts can access information about, and manipulate inferior threads
22244 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22246 The following thread-related functions are available in the @code{gdb}
22249 @findex gdb.selected_thread
22250 @defun selected_thread
22251 This function returns the thread object for the selected thread. If there
22252 is no selected thread, this will return @code{None}.
22255 A @code{gdb.InferiorThread} object has the following attributes:
22258 @defivar InferiorThread name
22259 The name of the thread. If the user specified a name using
22260 @code{thread name}, then this returns that name. Otherwise, if an
22261 OS-supplied name is available, then it is returned. Otherwise, this
22262 returns @code{None}.
22264 This attribute can be assigned to. The new value must be a string
22265 object, which sets the new name, or @code{None}, which removes any
22266 user-specified thread name.
22269 @defivar InferiorThread num
22270 ID of the thread, as assigned by GDB.
22273 @defivar InferiorThread ptid
22274 ID of the thread, as assigned by the operating system. This attribute is a
22275 tuple containing three integers. The first is the Process ID (PID); the second
22276 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22277 Either the LWPID or TID may be 0, which indicates that the operating system
22278 does not use that identifier.
22282 A @code{gdb.InferiorThread} object has the following methods:
22285 @defmethod InferiorThread is_valid
22286 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22287 @code{False} if not. A @code{gdb.InferiorThread} object will become
22288 invalid if the thread exits, or the inferior that the thread belongs
22289 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22290 exception if it is invalid at the time the method is called.
22293 @defmethod InferiorThread switch
22294 This changes @value{GDBN}'s currently selected thread to the one represented
22298 @defmethod InferiorThread is_stopped
22299 Return a Boolean indicating whether the thread is stopped.
22302 @defmethod InferiorThread is_running
22303 Return a Boolean indicating whether the thread is running.
22306 @defmethod InferiorThread is_exited
22307 Return a Boolean indicating whether the thread is exited.
22311 @node Commands In Python
22312 @subsubsection Commands In Python
22314 @cindex commands in python
22315 @cindex python commands
22316 You can implement new @value{GDBN} CLI commands in Python. A CLI
22317 command is implemented using an instance of the @code{gdb.Command}
22318 class, most commonly using a subclass.
22320 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
22321 The object initializer for @code{Command} registers the new command
22322 with @value{GDBN}. This initializer is normally invoked from the
22323 subclass' own @code{__init__} method.
22325 @var{name} is the name of the command. If @var{name} consists of
22326 multiple words, then the initial words are looked for as prefix
22327 commands. In this case, if one of the prefix commands does not exist,
22328 an exception is raised.
22330 There is no support for multi-line commands.
22332 @var{command_class} should be one of the @samp{COMMAND_} constants
22333 defined below. This argument tells @value{GDBN} how to categorize the
22334 new command in the help system.
22336 @var{completer_class} is an optional argument. If given, it should be
22337 one of the @samp{COMPLETE_} constants defined below. This argument
22338 tells @value{GDBN} how to perform completion for this command. If not
22339 given, @value{GDBN} will attempt to complete using the object's
22340 @code{complete} method (see below); if no such method is found, an
22341 error will occur when completion is attempted.
22343 @var{prefix} is an optional argument. If @code{True}, then the new
22344 command is a prefix command; sub-commands of this command may be
22347 The help text for the new command is taken from the Python
22348 documentation string for the command's class, if there is one. If no
22349 documentation string is provided, the default value ``This command is
22350 not documented.'' is used.
22353 @cindex don't repeat Python command
22354 @defmethod Command dont_repeat
22355 By default, a @value{GDBN} command is repeated when the user enters a
22356 blank line at the command prompt. A command can suppress this
22357 behavior by invoking the @code{dont_repeat} method. This is similar
22358 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22361 @defmethod Command invoke argument from_tty
22362 This method is called by @value{GDBN} when this command is invoked.
22364 @var{argument} is a string. It is the argument to the command, after
22365 leading and trailing whitespace has been stripped.
22367 @var{from_tty} is a boolean argument. When true, this means that the
22368 command was entered by the user at the terminal; when false it means
22369 that the command came from elsewhere.
22371 If this method throws an exception, it is turned into a @value{GDBN}
22372 @code{error} call. Otherwise, the return value is ignored.
22374 @findex gdb.string_to_argv
22375 To break @var{argument} up into an argv-like string use
22376 @code{gdb.string_to_argv}. This function behaves identically to
22377 @value{GDBN}'s internal argument lexer @code{buildargv}.
22378 It is recommended to use this for consistency.
22379 Arguments are separated by spaces and may be quoted.
22383 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22384 ['1', '2 "3', '4 "5', "6 '7"]
22389 @cindex completion of Python commands
22390 @defmethod Command complete text word
22391 This method is called by @value{GDBN} when the user attempts
22392 completion on this command. All forms of completion are handled by
22393 this method, that is, the @key{TAB} and @key{M-?} key bindings
22394 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22397 The arguments @var{text} and @var{word} are both strings. @var{text}
22398 holds the complete command line up to the cursor's location.
22399 @var{word} holds the last word of the command line; this is computed
22400 using a word-breaking heuristic.
22402 The @code{complete} method can return several values:
22405 If the return value is a sequence, the contents of the sequence are
22406 used as the completions. It is up to @code{complete} to ensure that the
22407 contents actually do complete the word. A zero-length sequence is
22408 allowed, it means that there were no completions available. Only
22409 string elements of the sequence are used; other elements in the
22410 sequence are ignored.
22413 If the return value is one of the @samp{COMPLETE_} constants defined
22414 below, then the corresponding @value{GDBN}-internal completion
22415 function is invoked, and its result is used.
22418 All other results are treated as though there were no available
22423 When a new command is registered, it must be declared as a member of
22424 some general class of commands. This is used to classify top-level
22425 commands in the on-line help system; note that prefix commands are not
22426 listed under their own category but rather that of their top-level
22427 command. The available classifications are represented by constants
22428 defined in the @code{gdb} module:
22431 @findex COMMAND_NONE
22432 @findex gdb.COMMAND_NONE
22434 The command does not belong to any particular class. A command in
22435 this category will not be displayed in any of the help categories.
22437 @findex COMMAND_RUNNING
22438 @findex gdb.COMMAND_RUNNING
22439 @item COMMAND_RUNNING
22440 The command is related to running the inferior. For example,
22441 @code{start}, @code{step}, and @code{continue} are in this category.
22442 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22443 commands in this category.
22445 @findex COMMAND_DATA
22446 @findex gdb.COMMAND_DATA
22448 The command is related to data or variables. For example,
22449 @code{call}, @code{find}, and @code{print} are in this category. Type
22450 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22453 @findex COMMAND_STACK
22454 @findex gdb.COMMAND_STACK
22455 @item COMMAND_STACK
22456 The command has to do with manipulation of the stack. For example,
22457 @code{backtrace}, @code{frame}, and @code{return} are in this
22458 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22459 list of commands in this category.
22461 @findex COMMAND_FILES
22462 @findex gdb.COMMAND_FILES
22463 @item COMMAND_FILES
22464 This class is used for file-related commands. For example,
22465 @code{file}, @code{list} and @code{section} are in this category.
22466 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22467 commands in this category.
22469 @findex COMMAND_SUPPORT
22470 @findex gdb.COMMAND_SUPPORT
22471 @item COMMAND_SUPPORT
22472 This should be used for ``support facilities'', generally meaning
22473 things that are useful to the user when interacting with @value{GDBN},
22474 but not related to the state of the inferior. For example,
22475 @code{help}, @code{make}, and @code{shell} are in this category. Type
22476 @kbd{help support} at the @value{GDBN} prompt to see a list of
22477 commands in this category.
22479 @findex COMMAND_STATUS
22480 @findex gdb.COMMAND_STATUS
22481 @item COMMAND_STATUS
22482 The command is an @samp{info}-related command, that is, related to the
22483 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22484 and @code{show} are in this category. Type @kbd{help status} at the
22485 @value{GDBN} prompt to see a list of commands in this category.
22487 @findex COMMAND_BREAKPOINTS
22488 @findex gdb.COMMAND_BREAKPOINTS
22489 @item COMMAND_BREAKPOINTS
22490 The command has to do with breakpoints. For example, @code{break},
22491 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22492 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22495 @findex COMMAND_TRACEPOINTS
22496 @findex gdb.COMMAND_TRACEPOINTS
22497 @item COMMAND_TRACEPOINTS
22498 The command has to do with tracepoints. For example, @code{trace},
22499 @code{actions}, and @code{tfind} are in this category. Type
22500 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22501 commands in this category.
22503 @findex COMMAND_OBSCURE
22504 @findex gdb.COMMAND_OBSCURE
22505 @item COMMAND_OBSCURE
22506 The command is only used in unusual circumstances, or is not of
22507 general interest to users. For example, @code{checkpoint},
22508 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22509 obscure} at the @value{GDBN} prompt to see a list of commands in this
22512 @findex COMMAND_MAINTENANCE
22513 @findex gdb.COMMAND_MAINTENANCE
22514 @item COMMAND_MAINTENANCE
22515 The command is only useful to @value{GDBN} maintainers. The
22516 @code{maintenance} and @code{flushregs} commands are in this category.
22517 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22518 commands in this category.
22521 A new command can use a predefined completion function, either by
22522 specifying it via an argument at initialization, or by returning it
22523 from the @code{complete} method. These predefined completion
22524 constants are all defined in the @code{gdb} module:
22527 @findex COMPLETE_NONE
22528 @findex gdb.COMPLETE_NONE
22529 @item COMPLETE_NONE
22530 This constant means that no completion should be done.
22532 @findex COMPLETE_FILENAME
22533 @findex gdb.COMPLETE_FILENAME
22534 @item COMPLETE_FILENAME
22535 This constant means that filename completion should be performed.
22537 @findex COMPLETE_LOCATION
22538 @findex gdb.COMPLETE_LOCATION
22539 @item COMPLETE_LOCATION
22540 This constant means that location completion should be done.
22541 @xref{Specify Location}.
22543 @findex COMPLETE_COMMAND
22544 @findex gdb.COMPLETE_COMMAND
22545 @item COMPLETE_COMMAND
22546 This constant means that completion should examine @value{GDBN}
22549 @findex COMPLETE_SYMBOL
22550 @findex gdb.COMPLETE_SYMBOL
22551 @item COMPLETE_SYMBOL
22552 This constant means that completion should be done using symbol names
22556 The following code snippet shows how a trivial CLI command can be
22557 implemented in Python:
22560 class HelloWorld (gdb.Command):
22561 """Greet the whole world."""
22563 def __init__ (self):
22564 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22566 def invoke (self, arg, from_tty):
22567 print "Hello, World!"
22572 The last line instantiates the class, and is necessary to trigger the
22573 registration of the command with @value{GDBN}. Depending on how the
22574 Python code is read into @value{GDBN}, you may need to import the
22575 @code{gdb} module explicitly.
22577 @node Parameters In Python
22578 @subsubsection Parameters In Python
22580 @cindex parameters in python
22581 @cindex python parameters
22582 @tindex gdb.Parameter
22584 You can implement new @value{GDBN} parameters using Python. A new
22585 parameter is implemented as an instance of the @code{gdb.Parameter}
22588 Parameters are exposed to the user via the @code{set} and
22589 @code{show} commands. @xref{Help}.
22591 There are many parameters that already exist and can be set in
22592 @value{GDBN}. Two examples are: @code{set follow fork} and
22593 @code{set charset}. Setting these parameters influences certain
22594 behavior in @value{GDBN}. Similarly, you can define parameters that
22595 can be used to influence behavior in custom Python scripts and commands.
22597 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
22598 The object initializer for @code{Parameter} registers the new
22599 parameter with @value{GDBN}. This initializer is normally invoked
22600 from the subclass' own @code{__init__} method.
22602 @var{name} is the name of the new parameter. If @var{name} consists
22603 of multiple words, then the initial words are looked for as prefix
22604 parameters. An example of this can be illustrated with the
22605 @code{set print} set of parameters. If @var{name} is
22606 @code{print foo}, then @code{print} will be searched as the prefix
22607 parameter. In this case the parameter can subsequently be accessed in
22608 @value{GDBN} as @code{set print foo}.
22610 If @var{name} consists of multiple words, and no prefix parameter group
22611 can be found, an exception is raised.
22613 @var{command-class} should be one of the @samp{COMMAND_} constants
22614 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22615 categorize the new parameter in the help system.
22617 @var{parameter-class} should be one of the @samp{PARAM_} constants
22618 defined below. This argument tells @value{GDBN} the type of the new
22619 parameter; this information is used for input validation and
22622 If @var{parameter-class} is @code{PARAM_ENUM}, then
22623 @var{enum-sequence} must be a sequence of strings. These strings
22624 represent the possible values for the parameter.
22626 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22627 of a fourth argument will cause an exception to be thrown.
22629 The help text for the new parameter is taken from the Python
22630 documentation string for the parameter's class, if there is one. If
22631 there is no documentation string, a default value is used.
22634 @defivar Parameter set_doc
22635 If this attribute exists, and is a string, then its value is used as
22636 the help text for this parameter's @code{set} command. The value is
22637 examined when @code{Parameter.__init__} is invoked; subsequent changes
22641 @defivar Parameter show_doc
22642 If this attribute exists, and is a string, then its value is used as
22643 the help text for this parameter's @code{show} command. The value is
22644 examined when @code{Parameter.__init__} is invoked; subsequent changes
22648 @defivar Parameter value
22649 The @code{value} attribute holds the underlying value of the
22650 parameter. It can be read and assigned to just as any other
22651 attribute. @value{GDBN} does validation when assignments are made.
22654 There are two methods that should be implemented in any
22655 @code{Parameter} class. These are:
22657 @defop Operation {parameter} get_set_string self
22658 @value{GDBN} will call this method when a @var{parameter}'s value has
22659 been changed via the @code{set} API (for example, @kbd{set foo off}).
22660 The @code{value} attribute has already been populated with the new
22661 value and may be used in output. This method must return a string.
22664 @defop Operation {parameter} get_show_string self svalue
22665 @value{GDBN} will call this method when a @var{parameter}'s
22666 @code{show} API has been invoked (for example, @kbd{show foo}). The
22667 argument @code{svalue} receives the string representation of the
22668 current value. This method must return a string.
22671 When a new parameter is defined, its type must be specified. The
22672 available types are represented by constants defined in the @code{gdb}
22676 @findex PARAM_BOOLEAN
22677 @findex gdb.PARAM_BOOLEAN
22678 @item PARAM_BOOLEAN
22679 The value is a plain boolean. The Python boolean values, @code{True}
22680 and @code{False} are the only valid values.
22682 @findex PARAM_AUTO_BOOLEAN
22683 @findex gdb.PARAM_AUTO_BOOLEAN
22684 @item PARAM_AUTO_BOOLEAN
22685 The value has three possible states: true, false, and @samp{auto}. In
22686 Python, true and false are represented using boolean constants, and
22687 @samp{auto} is represented using @code{None}.
22689 @findex PARAM_UINTEGER
22690 @findex gdb.PARAM_UINTEGER
22691 @item PARAM_UINTEGER
22692 The value is an unsigned integer. The value of 0 should be
22693 interpreted to mean ``unlimited''.
22695 @findex PARAM_INTEGER
22696 @findex gdb.PARAM_INTEGER
22697 @item PARAM_INTEGER
22698 The value is a signed integer. The value of 0 should be interpreted
22699 to mean ``unlimited''.
22701 @findex PARAM_STRING
22702 @findex gdb.PARAM_STRING
22704 The value is a string. When the user modifies the string, any escape
22705 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22706 translated into corresponding characters and encoded into the current
22709 @findex PARAM_STRING_NOESCAPE
22710 @findex gdb.PARAM_STRING_NOESCAPE
22711 @item PARAM_STRING_NOESCAPE
22712 The value is a string. When the user modifies the string, escapes are
22713 passed through untranslated.
22715 @findex PARAM_OPTIONAL_FILENAME
22716 @findex gdb.PARAM_OPTIONAL_FILENAME
22717 @item PARAM_OPTIONAL_FILENAME
22718 The value is a either a filename (a string), or @code{None}.
22720 @findex PARAM_FILENAME
22721 @findex gdb.PARAM_FILENAME
22722 @item PARAM_FILENAME
22723 The value is a filename. This is just like
22724 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22726 @findex PARAM_ZINTEGER
22727 @findex gdb.PARAM_ZINTEGER
22728 @item PARAM_ZINTEGER
22729 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22730 is interpreted as itself.
22733 @findex gdb.PARAM_ENUM
22735 The value is a string, which must be one of a collection string
22736 constants provided when the parameter is created.
22739 @node Functions In Python
22740 @subsubsection Writing new convenience functions
22742 @cindex writing convenience functions
22743 @cindex convenience functions in python
22744 @cindex python convenience functions
22745 @tindex gdb.Function
22747 You can implement new convenience functions (@pxref{Convenience Vars})
22748 in Python. A convenience function is an instance of a subclass of the
22749 class @code{gdb.Function}.
22751 @defmethod Function __init__ name
22752 The initializer for @code{Function} registers the new function with
22753 @value{GDBN}. The argument @var{name} is the name of the function,
22754 a string. The function will be visible to the user as a convenience
22755 variable of type @code{internal function}, whose name is the same as
22756 the given @var{name}.
22758 The documentation for the new function is taken from the documentation
22759 string for the new class.
22762 @defmethod Function invoke @var{*args}
22763 When a convenience function is evaluated, its arguments are converted
22764 to instances of @code{gdb.Value}, and then the function's
22765 @code{invoke} method is called. Note that @value{GDBN} does not
22766 predetermine the arity of convenience functions. Instead, all
22767 available arguments are passed to @code{invoke}, following the
22768 standard Python calling convention. In particular, a convenience
22769 function can have default values for parameters without ill effect.
22771 The return value of this method is used as its value in the enclosing
22772 expression. If an ordinary Python value is returned, it is converted
22773 to a @code{gdb.Value} following the usual rules.
22776 The following code snippet shows how a trivial convenience function can
22777 be implemented in Python:
22780 class Greet (gdb.Function):
22781 """Return string to greet someone.
22782 Takes a name as argument."""
22784 def __init__ (self):
22785 super (Greet, self).__init__ ("greet")
22787 def invoke (self, name):
22788 return "Hello, %s!" % name.string ()
22793 The last line instantiates the class, and is necessary to trigger the
22794 registration of the function with @value{GDBN}. Depending on how the
22795 Python code is read into @value{GDBN}, you may need to import the
22796 @code{gdb} module explicitly.
22798 @node Progspaces In Python
22799 @subsubsection Program Spaces In Python
22801 @cindex progspaces in python
22802 @tindex gdb.Progspace
22804 A program space, or @dfn{progspace}, represents a symbolic view
22805 of an address space.
22806 It consists of all of the objfiles of the program.
22807 @xref{Objfiles In Python}.
22808 @xref{Inferiors and Programs, program spaces}, for more details
22809 about program spaces.
22811 The following progspace-related functions are available in the
22814 @findex gdb.current_progspace
22815 @defun current_progspace
22816 This function returns the program space of the currently selected inferior.
22817 @xref{Inferiors and Programs}.
22820 @findex gdb.progspaces
22822 Return a sequence of all the progspaces currently known to @value{GDBN}.
22825 Each progspace is represented by an instance of the @code{gdb.Progspace}
22828 @defivar Progspace filename
22829 The file name of the progspace as a string.
22832 @defivar Progspace pretty_printers
22833 The @code{pretty_printers} attribute is a list of functions. It is
22834 used to look up pretty-printers. A @code{Value} is passed to each
22835 function in order; if the function returns @code{None}, then the
22836 search continues. Otherwise, the return value should be an object
22837 which is used to format the value. @xref{Pretty Printing API}, for more
22841 @node Objfiles In Python
22842 @subsubsection Objfiles In Python
22844 @cindex objfiles in python
22845 @tindex gdb.Objfile
22847 @value{GDBN} loads symbols for an inferior from various
22848 symbol-containing files (@pxref{Files}). These include the primary
22849 executable file, any shared libraries used by the inferior, and any
22850 separate debug info files (@pxref{Separate Debug Files}).
22851 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22853 The following objfile-related functions are available in the
22856 @findex gdb.current_objfile
22857 @defun current_objfile
22858 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22859 sets the ``current objfile'' to the corresponding objfile. This
22860 function returns the current objfile. If there is no current objfile,
22861 this function returns @code{None}.
22864 @findex gdb.objfiles
22866 Return a sequence of all the objfiles current known to @value{GDBN}.
22867 @xref{Objfiles In Python}.
22870 Each objfile is represented by an instance of the @code{gdb.Objfile}
22873 @defivar Objfile filename
22874 The file name of the objfile as a string.
22877 @defivar Objfile pretty_printers
22878 The @code{pretty_printers} attribute is a list of functions. It is
22879 used to look up pretty-printers. A @code{Value} is passed to each
22880 function in order; if the function returns @code{None}, then the
22881 search continues. Otherwise, the return value should be an object
22882 which is used to format the value. @xref{Pretty Printing API}, for more
22886 A @code{gdb.Objfile} object has the following methods:
22888 @defmethod Objfile is_valid
22889 Returns @code{True} if the @code{gdb.Objfile} object is valid,
22890 @code{False} if not. A @code{gdb.Objfile} object can become invalid
22891 if the object file it refers to is not loaded in @value{GDBN} any
22892 longer. All other @code{gdb.Objfile} methods will throw an exception
22893 if it is invalid at the time the method is called.
22896 @node Frames In Python
22897 @subsubsection Accessing inferior stack frames from Python.
22899 @cindex frames in python
22900 When the debugged program stops, @value{GDBN} is able to analyze its call
22901 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22902 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22903 while its corresponding frame exists in the inferior's stack. If you try
22904 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
22905 exception (@pxref{Exception Handling}).
22907 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22911 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22915 The following frame-related functions are available in the @code{gdb} module:
22917 @findex gdb.selected_frame
22918 @defun selected_frame
22919 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22922 @findex gdb.newest_frame
22923 @defun newest_frame
22924 Return the newest frame object for the selected thread.
22927 @defun frame_stop_reason_string reason
22928 Return a string explaining the reason why @value{GDBN} stopped unwinding
22929 frames, as expressed by the given @var{reason} code (an integer, see the
22930 @code{unwind_stop_reason} method further down in this section).
22933 A @code{gdb.Frame} object has the following methods:
22936 @defmethod Frame is_valid
22937 Returns true if the @code{gdb.Frame} object is valid, false if not.
22938 A frame object can become invalid if the frame it refers to doesn't
22939 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22940 an exception if it is invalid at the time the method is called.
22943 @defmethod Frame name
22944 Returns the function name of the frame, or @code{None} if it can't be
22948 @defmethod Frame type
22949 Returns the type of the frame. The value can be one of:
22951 @item gdb.NORMAL_FRAME
22952 An ordinary stack frame.
22954 @item gdb.DUMMY_FRAME
22955 A fake stack frame that was created by @value{GDBN} when performing an
22956 inferior function call.
22958 @item gdb.INLINE_FRAME
22959 A frame representing an inlined function. The function was inlined
22960 into a @code{gdb.NORMAL_FRAME} that is older than this one.
22962 @item gdb.SIGTRAMP_FRAME
22963 A signal trampoline frame. This is the frame created by the OS when
22964 it calls into a signal handler.
22966 @item gdb.ARCH_FRAME
22967 A fake stack frame representing a cross-architecture call.
22969 @item gdb.SENTINEL_FRAME
22970 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
22975 @defmethod Frame unwind_stop_reason
22976 Return an integer representing the reason why it's not possible to find
22977 more frames toward the outermost frame. Use
22978 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22979 function to a string.
22982 @defmethod Frame pc
22983 Returns the frame's resume address.
22986 @defmethod Frame block
22987 Return the frame's code block. @xref{Blocks In Python}.
22990 @defmethod Frame function
22991 Return the symbol for the function corresponding to this frame.
22992 @xref{Symbols In Python}.
22995 @defmethod Frame older
22996 Return the frame that called this frame.
22999 @defmethod Frame newer
23000 Return the frame called by this frame.
23003 @defmethod Frame find_sal
23004 Return the frame's symtab and line object.
23005 @xref{Symbol Tables In Python}.
23008 @defmethod Frame read_var variable @r{[}block@r{]}
23009 Return the value of @var{variable} in this frame. If the optional
23010 argument @var{block} is provided, search for the variable from that
23011 block; otherwise start at the frame's current block (which is
23012 determined by the frame's current program counter). @var{variable}
23013 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23014 @code{gdb.Block} object.
23017 @defmethod Frame select
23018 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23023 @node Blocks In Python
23024 @subsubsection Accessing frame blocks from Python.
23026 @cindex blocks in python
23029 Within each frame, @value{GDBN} maintains information on each block
23030 stored in that frame. These blocks are organized hierarchically, and
23031 are represented individually in Python as a @code{gdb.Block}.
23032 Please see @ref{Frames In Python}, for a more in-depth discussion on
23033 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23034 detailed technical information on @value{GDBN}'s book-keeping of the
23037 The following block-related functions are available in the @code{gdb}
23040 @findex gdb.block_for_pc
23041 @defun block_for_pc pc
23042 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23043 block cannot be found for the @var{pc} value specified, the function
23044 will return @code{None}.
23047 A @code{gdb.Block} object has the following methods:
23050 @defmethod Block is_valid
23051 Returns @code{True} if the @code{gdb.Block} object is valid,
23052 @code{False} if not. A block object can become invalid if the block it
23053 refers to doesn't exist anymore in the inferior. All other
23054 @code{gdb.Block} methods will throw an exception if it is invalid at
23055 the time the method is called. This method is also made available to
23056 the Python iterator object that @code{gdb.Block} provides in an iteration
23057 context and via the Python @code{iter} built-in function.
23061 A @code{gdb.Block} object has the following attributes:
23064 @defivar Block start
23065 The start address of the block. This attribute is not writable.
23069 The end address of the block. This attribute is not writable.
23072 @defivar Block function
23073 The name of the block represented as a @code{gdb.Symbol}. If the
23074 block is not named, then this attribute holds @code{None}. This
23075 attribute is not writable.
23078 @defivar Block superblock
23079 The block containing this block. If this parent block does not exist,
23080 this attribute holds @code{None}. This attribute is not writable.
23084 @node Symbols In Python
23085 @subsubsection Python representation of Symbols.
23087 @cindex symbols in python
23090 @value{GDBN} represents every variable, function and type as an
23091 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23092 Similarly, Python represents these symbols in @value{GDBN} with the
23093 @code{gdb.Symbol} object.
23095 The following symbol-related functions are available in the @code{gdb}
23098 @findex gdb.lookup_symbol
23099 @defun lookup_symbol name @r{[}block@r{]} @r{[}domain@r{]}
23100 This function searches for a symbol by name. The search scope can be
23101 restricted to the parameters defined in the optional domain and block
23104 @var{name} is the name of the symbol. It must be a string. The
23105 optional @var{block} argument restricts the search to symbols visible
23106 in that @var{block}. The @var{block} argument must be a
23107 @code{gdb.Block} object. If omitted, the block for the current frame
23108 is used. The optional @var{domain} argument restricts
23109 the search to the domain type. The @var{domain} argument must be a
23110 domain constant defined in the @code{gdb} module and described later
23113 The result is a tuple of two elements.
23114 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23116 If the symbol is found, the second element is @code{True} if the symbol
23117 is a field of a method's object (e.g., @code{this} in C@t{++}),
23118 otherwise it is @code{False}.
23119 If the symbol is not found, the second element is @code{False}.
23122 @findex gdb.lookup_global_symbol
23123 @defun lookup_global_symbol name @r{[}domain@r{]}
23124 This function searches for a global symbol by name.
23125 The search scope can be restricted to by the domain argument.
23127 @var{name} is the name of the symbol. It must be a string.
23128 The optional @var{domain} argument restricts the search to the domain type.
23129 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23130 module and described later in this chapter.
23132 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23136 A @code{gdb.Symbol} object has the following attributes:
23139 @defivar Symbol symtab
23140 The symbol table in which the symbol appears. This attribute is
23141 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23142 Python}. This attribute is not writable.
23145 @defivar Symbol name
23146 The name of the symbol as a string. This attribute is not writable.
23149 @defivar Symbol linkage_name
23150 The name of the symbol, as used by the linker (i.e., may be mangled).
23151 This attribute is not writable.
23154 @defivar Symbol print_name
23155 The name of the symbol in a form suitable for output. This is either
23156 @code{name} or @code{linkage_name}, depending on whether the user
23157 asked @value{GDBN} to display demangled or mangled names.
23160 @defivar Symbol addr_class
23161 The address class of the symbol. This classifies how to find the value
23162 of a symbol. Each address class is a constant defined in the
23163 @code{gdb} module and described later in this chapter.
23166 @defivar Symbol is_argument
23167 @code{True} if the symbol is an argument of a function.
23170 @defivar Symbol is_constant
23171 @code{True} if the symbol is a constant.
23174 @defivar Symbol is_function
23175 @code{True} if the symbol is a function or a method.
23178 @defivar Symbol is_variable
23179 @code{True} if the symbol is a variable.
23183 A @code{gdb.Symbol} object has the following methods:
23186 @defmethod Symbol is_valid
23187 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23188 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23189 the symbol it refers to does not exist in @value{GDBN} any longer.
23190 All other @code{gdb.Symbol} methods will throw an exception if it is
23191 invalid at the time the method is called.
23195 The available domain categories in @code{gdb.Symbol} are represented
23196 as constants in the @code{gdb} module:
23199 @findex SYMBOL_UNDEF_DOMAIN
23200 @findex gdb.SYMBOL_UNDEF_DOMAIN
23201 @item SYMBOL_UNDEF_DOMAIN
23202 This is used when a domain has not been discovered or none of the
23203 following domains apply. This usually indicates an error either
23204 in the symbol information or in @value{GDBN}'s handling of symbols.
23205 @findex SYMBOL_VAR_DOMAIN
23206 @findex gdb.SYMBOL_VAR_DOMAIN
23207 @item SYMBOL_VAR_DOMAIN
23208 This domain contains variables, function names, typedef names and enum
23210 @findex SYMBOL_STRUCT_DOMAIN
23211 @findex gdb.SYMBOL_STRUCT_DOMAIN
23212 @item SYMBOL_STRUCT_DOMAIN
23213 This domain holds struct, union and enum type names.
23214 @findex SYMBOL_LABEL_DOMAIN
23215 @findex gdb.SYMBOL_LABEL_DOMAIN
23216 @item SYMBOL_LABEL_DOMAIN
23217 This domain contains names of labels (for gotos).
23218 @findex SYMBOL_VARIABLES_DOMAIN
23219 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23220 @item SYMBOL_VARIABLES_DOMAIN
23221 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23222 contains everything minus functions and types.
23223 @findex SYMBOL_FUNCTIONS_DOMAIN
23224 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23225 @item SYMBOL_FUNCTION_DOMAIN
23226 This domain contains all functions.
23227 @findex SYMBOL_TYPES_DOMAIN
23228 @findex gdb.SYMBOL_TYPES_DOMAIN
23229 @item SYMBOL_TYPES_DOMAIN
23230 This domain contains all types.
23233 The available address class categories in @code{gdb.Symbol} are represented
23234 as constants in the @code{gdb} module:
23237 @findex SYMBOL_LOC_UNDEF
23238 @findex gdb.SYMBOL_LOC_UNDEF
23239 @item SYMBOL_LOC_UNDEF
23240 If this is returned by address class, it indicates an error either in
23241 the symbol information or in @value{GDBN}'s handling of symbols.
23242 @findex SYMBOL_LOC_CONST
23243 @findex gdb.SYMBOL_LOC_CONST
23244 @item SYMBOL_LOC_CONST
23245 Value is constant int.
23246 @findex SYMBOL_LOC_STATIC
23247 @findex gdb.SYMBOL_LOC_STATIC
23248 @item SYMBOL_LOC_STATIC
23249 Value is at a fixed address.
23250 @findex SYMBOL_LOC_REGISTER
23251 @findex gdb.SYMBOL_LOC_REGISTER
23252 @item SYMBOL_LOC_REGISTER
23253 Value is in a register.
23254 @findex SYMBOL_LOC_ARG
23255 @findex gdb.SYMBOL_LOC_ARG
23256 @item SYMBOL_LOC_ARG
23257 Value is an argument. This value is at the offset stored within the
23258 symbol inside the frame's argument list.
23259 @findex SYMBOL_LOC_REF_ARG
23260 @findex gdb.SYMBOL_LOC_REF_ARG
23261 @item SYMBOL_LOC_REF_ARG
23262 Value address is stored in the frame's argument list. Just like
23263 @code{LOC_ARG} except that the value's address is stored at the
23264 offset, not the value itself.
23265 @findex SYMBOL_LOC_REGPARM_ADDR
23266 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23267 @item SYMBOL_LOC_REGPARM_ADDR
23268 Value is a specified register. Just like @code{LOC_REGISTER} except
23269 the register holds the address of the argument instead of the argument
23271 @findex SYMBOL_LOC_LOCAL
23272 @findex gdb.SYMBOL_LOC_LOCAL
23273 @item SYMBOL_LOC_LOCAL
23274 Value is a local variable.
23275 @findex SYMBOL_LOC_TYPEDEF
23276 @findex gdb.SYMBOL_LOC_TYPEDEF
23277 @item SYMBOL_LOC_TYPEDEF
23278 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23280 @findex SYMBOL_LOC_BLOCK
23281 @findex gdb.SYMBOL_LOC_BLOCK
23282 @item SYMBOL_LOC_BLOCK
23284 @findex SYMBOL_LOC_CONST_BYTES
23285 @findex gdb.SYMBOL_LOC_CONST_BYTES
23286 @item SYMBOL_LOC_CONST_BYTES
23287 Value is a byte-sequence.
23288 @findex SYMBOL_LOC_UNRESOLVED
23289 @findex gdb.SYMBOL_LOC_UNRESOLVED
23290 @item SYMBOL_LOC_UNRESOLVED
23291 Value is at a fixed address, but the address of the variable has to be
23292 determined from the minimal symbol table whenever the variable is
23294 @findex SYMBOL_LOC_OPTIMIZED_OUT
23295 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23296 @item SYMBOL_LOC_OPTIMIZED_OUT
23297 The value does not actually exist in the program.
23298 @findex SYMBOL_LOC_COMPUTED
23299 @findex gdb.SYMBOL_LOC_COMPUTED
23300 @item SYMBOL_LOC_COMPUTED
23301 The value's address is a computed location.
23304 @node Symbol Tables In Python
23305 @subsubsection Symbol table representation in Python.
23307 @cindex symbol tables in python
23309 @tindex gdb.Symtab_and_line
23311 Access to symbol table data maintained by @value{GDBN} on the inferior
23312 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23313 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23314 from the @code{find_sal} method in @code{gdb.Frame} object.
23315 @xref{Frames In Python}.
23317 For more information on @value{GDBN}'s symbol table management, see
23318 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23320 A @code{gdb.Symtab_and_line} object has the following attributes:
23323 @defivar Symtab_and_line symtab
23324 The symbol table object (@code{gdb.Symtab}) for this frame.
23325 This attribute is not writable.
23328 @defivar Symtab_and_line pc
23329 Indicates the current program counter address. This attribute is not
23333 @defivar Symtab_and_line line
23334 Indicates the current line number for this object. This
23335 attribute is not writable.
23339 A @code{gdb.Symtab_and_line} object has the following methods:
23342 @defmethod Symtab_and_line is_valid
23343 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23344 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23345 invalid if the Symbol table and line object it refers to does not
23346 exist in @value{GDBN} any longer. All other
23347 @code{gdb.Symtab_and_line} methods will throw an exception if it is
23348 invalid at the time the method is called.
23352 A @code{gdb.Symtab} object has the following attributes:
23355 @defivar Symtab filename
23356 The symbol table's source filename. This attribute is not writable.
23359 @defivar Symtab objfile
23360 The symbol table's backing object file. @xref{Objfiles In Python}.
23361 This attribute is not writable.
23365 A @code{gdb.Symtab} object has the following methods:
23368 @defmethod Symtab is_valid
23369 Returns @code{True} if the @code{gdb.Symtab} object is valid,
23370 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
23371 the symbol table it refers to does not exist in @value{GDBN} any
23372 longer. All other @code{gdb.Symtab} methods will throw an exception
23373 if it is invalid at the time the method is called.
23376 @defmethod Symtab fullname
23377 Return the symbol table's source absolute file name.
23381 @node Breakpoints In Python
23382 @subsubsection Manipulating breakpoints using Python
23384 @cindex breakpoints in python
23385 @tindex gdb.Breakpoint
23387 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
23390 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]} @r{[}internal@r{]}
23391 Create a new breakpoint. @var{spec} is a string naming the
23392 location of the breakpoint, or an expression that defines a
23393 watchpoint. The contents can be any location recognized by the
23394 @code{break} command, or in the case of a watchpoint, by the @code{watch}
23395 command. The optional @var{type} denotes the breakpoint to create
23396 from the types defined later in this chapter. This argument can be
23397 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
23398 defaults to @code{BP_BREAKPOINT}. The optional @var{internal} argument
23399 allows the breakpoint to become invisible to the user. The breakpoint
23400 will neither be reported when created, nor will it be listed in the
23401 output from @code{info breakpoints} (but will be listed with the
23402 @code{maint info breakpoints} command). The optional @var{wp_class}
23403 argument defines the class of watchpoint to create, if @var{type} is
23404 @code{BP_WATCHPOINT}. If a watchpoint class is not provided, it is
23405 assumed to be a @var{WP_WRITE} class.
23408 @defop Operation {gdb.Breakpoint} stop (self)
23409 The @code{gdb.Breakpoint} class can be sub-classed and, in
23410 particular, you may choose to implement the @code{stop} method.
23411 If this method is defined as a sub-class of @code{gdb.Breakpoint},
23412 it will be called when the inferior reaches any location of a
23413 breakpoint which instantiates that sub-class. If the method returns
23414 @code{True}, the inferior will be stopped at the location of the
23415 breakpoint, otherwise the inferior will continue.
23417 If there are multiple breakpoints at the same location with a
23418 @code{stop} method, each one will be called regardless of the
23419 return status of the previous. This ensures that all @code{stop}
23420 methods have a chance to execute at that location. In this scenario
23421 if one of the methods returns @code{True} but the others return
23422 @code{False}, the inferior will still be stopped.
23424 Example @code{stop} implementation:
23427 class MyBreakpoint (gdb.Breakpoint):
23429 inf_val = gdb.parse_and_eval("foo")
23436 The available watchpoint types represented by constants are defined in the
23441 @findex gdb.WP_READ
23443 Read only watchpoint.
23446 @findex gdb.WP_WRITE
23448 Write only watchpoint.
23451 @findex gdb.WP_ACCESS
23453 Read/Write watchpoint.
23456 @defmethod Breakpoint is_valid
23457 Return @code{True} if this @code{Breakpoint} object is valid,
23458 @code{False} otherwise. A @code{Breakpoint} object can become invalid
23459 if the user deletes the breakpoint. In this case, the object still
23460 exists, but the underlying breakpoint does not. In the cases of
23461 watchpoint scope, the watchpoint remains valid even if execution of the
23462 inferior leaves the scope of that watchpoint.
23465 @defmethod Breakpoint delete
23466 Permanently deletes the @value{GDBN} breakpoint. This also
23467 invalidates the Python @code{Breakpoint} object. Any further access
23468 to this object's attributes or methods will raise an error.
23471 @defivar Breakpoint enabled
23472 This attribute is @code{True} if the breakpoint is enabled, and
23473 @code{False} otherwise. This attribute is writable.
23476 @defivar Breakpoint silent
23477 This attribute is @code{True} if the breakpoint is silent, and
23478 @code{False} otherwise. This attribute is writable.
23480 Note that a breakpoint can also be silent if it has commands and the
23481 first command is @code{silent}. This is not reported by the
23482 @code{silent} attribute.
23485 @defivar Breakpoint thread
23486 If the breakpoint is thread-specific, this attribute holds the thread
23487 id. If the breakpoint is not thread-specific, this attribute is
23488 @code{None}. This attribute is writable.
23491 @defivar Breakpoint task
23492 If the breakpoint is Ada task-specific, this attribute holds the Ada task
23493 id. If the breakpoint is not task-specific (or the underlying
23494 language is not Ada), this attribute is @code{None}. This attribute
23498 @defivar Breakpoint ignore_count
23499 This attribute holds the ignore count for the breakpoint, an integer.
23500 This attribute is writable.
23503 @defivar Breakpoint number
23504 This attribute holds the breakpoint's number --- the identifier used by
23505 the user to manipulate the breakpoint. This attribute is not writable.
23508 @defivar Breakpoint type
23509 This attribute holds the breakpoint's type --- the identifier used to
23510 determine the actual breakpoint type or use-case. This attribute is not
23514 @defivar Breakpoint visible
23515 This attribute tells whether the breakpoint is visible to the user
23516 when set, or when the @samp{info breakpoints} command is run. This
23517 attribute is not writable.
23520 The available types are represented by constants defined in the @code{gdb}
23524 @findex BP_BREAKPOINT
23525 @findex gdb.BP_BREAKPOINT
23526 @item BP_BREAKPOINT
23527 Normal code breakpoint.
23529 @findex BP_WATCHPOINT
23530 @findex gdb.BP_WATCHPOINT
23531 @item BP_WATCHPOINT
23532 Watchpoint breakpoint.
23534 @findex BP_HARDWARE_WATCHPOINT
23535 @findex gdb.BP_HARDWARE_WATCHPOINT
23536 @item BP_HARDWARE_WATCHPOINT
23537 Hardware assisted watchpoint.
23539 @findex BP_READ_WATCHPOINT
23540 @findex gdb.BP_READ_WATCHPOINT
23541 @item BP_READ_WATCHPOINT
23542 Hardware assisted read watchpoint.
23544 @findex BP_ACCESS_WATCHPOINT
23545 @findex gdb.BP_ACCESS_WATCHPOINT
23546 @item BP_ACCESS_WATCHPOINT
23547 Hardware assisted access watchpoint.
23550 @defivar Breakpoint hit_count
23551 This attribute holds the hit count for the breakpoint, an integer.
23552 This attribute is writable, but currently it can only be set to zero.
23555 @defivar Breakpoint location
23556 This attribute holds the location of the breakpoint, as specified by
23557 the user. It is a string. If the breakpoint does not have a location
23558 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23559 attribute is not writable.
23562 @defivar Breakpoint expression
23563 This attribute holds a breakpoint expression, as specified by
23564 the user. It is a string. If the breakpoint does not have an
23565 expression (the breakpoint is not a watchpoint) the attribute's value
23566 is @code{None}. This attribute is not writable.
23569 @defivar Breakpoint condition
23570 This attribute holds the condition of the breakpoint, as specified by
23571 the user. It is a string. If there is no condition, this attribute's
23572 value is @code{None}. This attribute is writable.
23575 @defivar Breakpoint commands
23576 This attribute holds the commands attached to the breakpoint. If
23577 there are commands, this attribute's value is a string holding all the
23578 commands, separated by newlines. If there are no commands, this
23579 attribute is @code{None}. This attribute is not writable.
23582 @node Lazy Strings In Python
23583 @subsubsection Python representation of lazy strings.
23585 @cindex lazy strings in python
23586 @tindex gdb.LazyString
23588 A @dfn{lazy string} is a string whose contents is not retrieved or
23589 encoded until it is needed.
23591 A @code{gdb.LazyString} is represented in @value{GDBN} as an
23592 @code{address} that points to a region of memory, an @code{encoding}
23593 that will be used to encode that region of memory, and a @code{length}
23594 to delimit the region of memory that represents the string. The
23595 difference between a @code{gdb.LazyString} and a string wrapped within
23596 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
23597 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
23598 retrieved and encoded during printing, while a @code{gdb.Value}
23599 wrapping a string is immediately retrieved and encoded on creation.
23601 A @code{gdb.LazyString} object has the following functions:
23603 @defmethod LazyString value
23604 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
23605 will point to the string in memory, but will lose all the delayed
23606 retrieval, encoding and handling that @value{GDBN} applies to a
23607 @code{gdb.LazyString}.
23610 @defivar LazyString address
23611 This attribute holds the address of the string. This attribute is not
23615 @defivar LazyString length
23616 This attribute holds the length of the string in characters. If the
23617 length is -1, then the string will be fetched and encoded up to the
23618 first null of appropriate width. This attribute is not writable.
23621 @defivar LazyString encoding
23622 This attribute holds the encoding that will be applied to the string
23623 when the string is printed by @value{GDBN}. If the encoding is not
23624 set, or contains an empty string, then @value{GDBN} will select the
23625 most appropriate encoding when the string is printed. This attribute
23629 @defivar LazyString type
23630 This attribute holds the type that is represented by the lazy string's
23631 type. For a lazy string this will always be a pointer type. To
23632 resolve this to the lazy string's character type, use the type's
23633 @code{target} method. @xref{Types In Python}. This attribute is not
23638 @subsection Auto-loading
23639 @cindex auto-loading, Python
23641 When a new object file is read (for example, due to the @code{file}
23642 command, or because the inferior has loaded a shared library),
23643 @value{GDBN} will look for Python support scripts in several ways:
23644 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
23647 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
23648 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
23649 * Which flavor to choose?::
23652 The auto-loading feature is useful for supplying application-specific
23653 debugging commands and scripts.
23655 Auto-loading can be enabled or disabled,
23656 and the list of auto-loaded scripts can be printed.
23659 @kindex set auto-load-scripts
23660 @item set auto-load-scripts [yes|no]
23661 Enable or disable the auto-loading of Python scripts.
23663 @kindex show auto-load-scripts
23664 @item show auto-load-scripts
23665 Show whether auto-loading of Python scripts is enabled or disabled.
23667 @kindex info auto-load-scripts
23668 @cindex print list of auto-loaded scripts
23669 @item info auto-load-scripts [@var{regexp}]
23670 Print the list of all scripts that @value{GDBN} auto-loaded.
23672 Also printed is the list of scripts that were mentioned in
23673 the @code{.debug_gdb_scripts} section and were not found
23674 (@pxref{.debug_gdb_scripts section}).
23675 This is useful because their names are not printed when @value{GDBN}
23676 tries to load them and fails. There may be many of them, and printing
23677 an error message for each one is problematic.
23679 If @var{regexp} is supplied only scripts with matching names are printed.
23684 (gdb) info auto-load-scripts
23686 Yes py-section-script.py
23687 full name: /tmp/py-section-script.py
23688 Missing my-foo-pretty-printers.py
23692 When reading an auto-loaded file, @value{GDBN} sets the
23693 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23694 function (@pxref{Objfiles In Python}). This can be useful for
23695 registering objfile-specific pretty-printers.
23697 @node objfile-gdb.py file
23698 @subsubsection The @file{@var{objfile}-gdb.py} file
23699 @cindex @file{@var{objfile}-gdb.py}
23701 When a new object file is read, @value{GDBN} looks for
23702 a file named @file{@var{objfile}-gdb.py},
23703 where @var{objfile} is the object file's real name, formed by ensuring
23704 that the file name is absolute, following all symlinks, and resolving
23705 @code{.} and @code{..} components. If this file exists and is
23706 readable, @value{GDBN} will evaluate it as a Python script.
23708 If this file does not exist, and if the parameter
23709 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23710 then @value{GDBN} will look for @var{real-name} in all of the
23711 directories mentioned in the value of @code{debug-file-directory}.
23713 Finally, if this file does not exist, then @value{GDBN} will look for
23714 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23715 @var{data-directory} is @value{GDBN}'s data directory (available via
23716 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23717 is the object file's real name, as described above.
23719 @value{GDBN} does not track which files it has already auto-loaded this way.
23720 @value{GDBN} will load the associated script every time the corresponding
23721 @var{objfile} is opened.
23722 So your @file{-gdb.py} file should be careful to avoid errors if it
23723 is evaluated more than once.
23725 @node .debug_gdb_scripts section
23726 @subsubsection The @code{.debug_gdb_scripts} section
23727 @cindex @code{.debug_gdb_scripts} section
23729 For systems using file formats like ELF and COFF,
23730 when @value{GDBN} loads a new object file
23731 it will look for a special section named @samp{.debug_gdb_scripts}.
23732 If this section exists, its contents is a list of names of scripts to load.
23734 @value{GDBN} will look for each specified script file first in the
23735 current directory and then along the source search path
23736 (@pxref{Source Path, ,Specifying Source Directories}),
23737 except that @file{$cdir} is not searched, since the compilation
23738 directory is not relevant to scripts.
23740 Entries can be placed in section @code{.debug_gdb_scripts} with,
23741 for example, this GCC macro:
23744 /* Note: The "MS" section flags are to remove duplicates. */
23745 #define DEFINE_GDB_SCRIPT(script_name) \
23747 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23749 .asciz \"" script_name "\"\n\
23755 Then one can reference the macro in a header or source file like this:
23758 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23761 The script name may include directories if desired.
23763 If the macro is put in a header, any application or library
23764 using this header will get a reference to the specified script.
23766 @node Which flavor to choose?
23767 @subsubsection Which flavor to choose?
23769 Given the multiple ways of auto-loading Python scripts, it might not always
23770 be clear which one to choose. This section provides some guidance.
23772 Benefits of the @file{-gdb.py} way:
23776 Can be used with file formats that don't support multiple sections.
23779 Ease of finding scripts for public libraries.
23781 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23782 in the source search path.
23783 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23784 isn't a source directory in which to find the script.
23787 Doesn't require source code additions.
23790 Benefits of the @code{.debug_gdb_scripts} way:
23794 Works with static linking.
23796 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23797 trigger their loading. When an application is statically linked the only
23798 objfile available is the executable, and it is cumbersome to attach all the
23799 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23802 Works with classes that are entirely inlined.
23804 Some classes can be entirely inlined, and thus there may not be an associated
23805 shared library to attach a @file{-gdb.py} script to.
23808 Scripts needn't be copied out of the source tree.
23810 In some circumstances, apps can be built out of large collections of internal
23811 libraries, and the build infrastructure necessary to install the
23812 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23813 cumbersome. It may be easier to specify the scripts in the
23814 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23815 top of the source tree to the source search path.
23818 @node Python modules
23819 @subsection Python modules
23820 @cindex python modules
23822 @value{GDBN} comes with a module to assist writing Python code.
23825 * gdb.printing:: Building and registering pretty-printers.
23826 * gdb.types:: Utilities for working with types.
23830 @subsubsection gdb.printing
23831 @cindex gdb.printing
23833 This module provides a collection of utilities for working with
23837 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23838 This class specifies the API that makes @samp{info pretty-printer},
23839 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23840 Pretty-printers should generally inherit from this class.
23842 @item SubPrettyPrinter (@var{name})
23843 For printers that handle multiple types, this class specifies the
23844 corresponding API for the subprinters.
23846 @item RegexpCollectionPrettyPrinter (@var{name})
23847 Utility class for handling multiple printers, all recognized via
23848 regular expressions.
23849 @xref{Writing a Pretty-Printer}, for an example.
23851 @item register_pretty_printer (@var{obj}, @var{printer})
23852 Register @var{printer} with the pretty-printer list of @var{obj}.
23856 @subsubsection gdb.types
23859 This module provides a collection of utilities for working with
23860 @code{gdb.Types} objects.
23863 @item get_basic_type (@var{type})
23864 Return @var{type} with const and volatile qualifiers stripped,
23865 and with typedefs and C@t{++} references converted to the underlying type.
23870 typedef const int const_int;
23872 const_int& foo_ref (foo);
23873 int main () @{ return 0; @}
23880 (gdb) python import gdb.types
23881 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23882 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23886 @item has_field (@var{type}, @var{field})
23887 Return @code{True} if @var{type}, assumed to be a type with fields
23888 (e.g., a structure or union), has field @var{field}.
23890 @item make_enum_dict (@var{enum_type})
23891 Return a Python @code{dictionary} type produced from @var{enum_type}.
23895 @chapter Command Interpreters
23896 @cindex command interpreters
23898 @value{GDBN} supports multiple command interpreters, and some command
23899 infrastructure to allow users or user interface writers to switch
23900 between interpreters or run commands in other interpreters.
23902 @value{GDBN} currently supports two command interpreters, the console
23903 interpreter (sometimes called the command-line interpreter or @sc{cli})
23904 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23905 describes both of these interfaces in great detail.
23907 By default, @value{GDBN} will start with the console interpreter.
23908 However, the user may choose to start @value{GDBN} with another
23909 interpreter by specifying the @option{-i} or @option{--interpreter}
23910 startup options. Defined interpreters include:
23914 @cindex console interpreter
23915 The traditional console or command-line interpreter. This is the most often
23916 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23917 @value{GDBN} will use this interpreter.
23920 @cindex mi interpreter
23921 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23922 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23923 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23927 @cindex mi2 interpreter
23928 The current @sc{gdb/mi} interface.
23931 @cindex mi1 interpreter
23932 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23936 @cindex invoke another interpreter
23937 The interpreter being used by @value{GDBN} may not be dynamically
23938 switched at runtime. Although possible, this could lead to a very
23939 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23940 enters the command "interpreter-set console" in a console view,
23941 @value{GDBN} would switch to using the console interpreter, rendering
23942 the IDE inoperable!
23944 @kindex interpreter-exec
23945 Although you may only choose a single interpreter at startup, you may execute
23946 commands in any interpreter from the current interpreter using the appropriate
23947 command. If you are running the console interpreter, simply use the
23948 @code{interpreter-exec} command:
23951 interpreter-exec mi "-data-list-register-names"
23954 @sc{gdb/mi} has a similar command, although it is only available in versions of
23955 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23958 @chapter @value{GDBN} Text User Interface
23960 @cindex Text User Interface
23963 * TUI Overview:: TUI overview
23964 * TUI Keys:: TUI key bindings
23965 * TUI Single Key Mode:: TUI single key mode
23966 * TUI Commands:: TUI-specific commands
23967 * TUI Configuration:: TUI configuration variables
23970 The @value{GDBN} Text User Interface (TUI) is a terminal
23971 interface which uses the @code{curses} library to show the source
23972 file, the assembly output, the program registers and @value{GDBN}
23973 commands in separate text windows. The TUI mode is supported only
23974 on platforms where a suitable version of the @code{curses} library
23977 @pindex @value{GDBTUI}
23978 The TUI mode is enabled by default when you invoke @value{GDBN} as
23979 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23980 You can also switch in and out of TUI mode while @value{GDBN} runs by
23981 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23982 @xref{TUI Keys, ,TUI Key Bindings}.
23985 @section TUI Overview
23987 In TUI mode, @value{GDBN} can display several text windows:
23991 This window is the @value{GDBN} command window with the @value{GDBN}
23992 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23993 managed using readline.
23996 The source window shows the source file of the program. The current
23997 line and active breakpoints are displayed in this window.
24000 The assembly window shows the disassembly output of the program.
24003 This window shows the processor registers. Registers are highlighted
24004 when their values change.
24007 The source and assembly windows show the current program position
24008 by highlighting the current line and marking it with a @samp{>} marker.
24009 Breakpoints are indicated with two markers. The first marker
24010 indicates the breakpoint type:
24014 Breakpoint which was hit at least once.
24017 Breakpoint which was never hit.
24020 Hardware breakpoint which was hit at least once.
24023 Hardware breakpoint which was never hit.
24026 The second marker indicates whether the breakpoint is enabled or not:
24030 Breakpoint is enabled.
24033 Breakpoint is disabled.
24036 The source, assembly and register windows are updated when the current
24037 thread changes, when the frame changes, or when the program counter
24040 These windows are not all visible at the same time. The command
24041 window is always visible. The others can be arranged in several
24052 source and assembly,
24055 source and registers, or
24058 assembly and registers.
24061 A status line above the command window shows the following information:
24065 Indicates the current @value{GDBN} target.
24066 (@pxref{Targets, ,Specifying a Debugging Target}).
24069 Gives the current process or thread number.
24070 When no process is being debugged, this field is set to @code{No process}.
24073 Gives the current function name for the selected frame.
24074 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24075 When there is no symbol corresponding to the current program counter,
24076 the string @code{??} is displayed.
24079 Indicates the current line number for the selected frame.
24080 When the current line number is not known, the string @code{??} is displayed.
24083 Indicates the current program counter address.
24087 @section TUI Key Bindings
24088 @cindex TUI key bindings
24090 The TUI installs several key bindings in the readline keymaps
24091 @ifset SYSTEM_READLINE
24092 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24094 @ifclear SYSTEM_READLINE
24095 (@pxref{Command Line Editing}).
24097 The following key bindings are installed for both TUI mode and the
24098 @value{GDBN} standard mode.
24107 Enter or leave the TUI mode. When leaving the TUI mode,
24108 the curses window management stops and @value{GDBN} operates using
24109 its standard mode, writing on the terminal directly. When reentering
24110 the TUI mode, control is given back to the curses windows.
24111 The screen is then refreshed.
24115 Use a TUI layout with only one window. The layout will
24116 either be @samp{source} or @samp{assembly}. When the TUI mode
24117 is not active, it will switch to the TUI mode.
24119 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24123 Use a TUI layout with at least two windows. When the current
24124 layout already has two windows, the next layout with two windows is used.
24125 When a new layout is chosen, one window will always be common to the
24126 previous layout and the new one.
24128 Think of it as the Emacs @kbd{C-x 2} binding.
24132 Change the active window. The TUI associates several key bindings
24133 (like scrolling and arrow keys) with the active window. This command
24134 gives the focus to the next TUI window.
24136 Think of it as the Emacs @kbd{C-x o} binding.
24140 Switch in and out of the TUI SingleKey mode that binds single
24141 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24144 The following key bindings only work in the TUI mode:
24149 Scroll the active window one page up.
24153 Scroll the active window one page down.
24157 Scroll the active window one line up.
24161 Scroll the active window one line down.
24165 Scroll the active window one column left.
24169 Scroll the active window one column right.
24173 Refresh the screen.
24176 Because the arrow keys scroll the active window in the TUI mode, they
24177 are not available for their normal use by readline unless the command
24178 window has the focus. When another window is active, you must use
24179 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24180 and @kbd{C-f} to control the command window.
24182 @node TUI Single Key Mode
24183 @section TUI Single Key Mode
24184 @cindex TUI single key mode
24186 The TUI also provides a @dfn{SingleKey} mode, which binds several
24187 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24188 switch into this mode, where the following key bindings are used:
24191 @kindex c @r{(SingleKey TUI key)}
24195 @kindex d @r{(SingleKey TUI key)}
24199 @kindex f @r{(SingleKey TUI key)}
24203 @kindex n @r{(SingleKey TUI key)}
24207 @kindex q @r{(SingleKey TUI key)}
24209 exit the SingleKey mode.
24211 @kindex r @r{(SingleKey TUI key)}
24215 @kindex s @r{(SingleKey TUI key)}
24219 @kindex u @r{(SingleKey TUI key)}
24223 @kindex v @r{(SingleKey TUI key)}
24227 @kindex w @r{(SingleKey TUI key)}
24232 Other keys temporarily switch to the @value{GDBN} command prompt.
24233 The key that was pressed is inserted in the editing buffer so that
24234 it is possible to type most @value{GDBN} commands without interaction
24235 with the TUI SingleKey mode. Once the command is entered the TUI
24236 SingleKey mode is restored. The only way to permanently leave
24237 this mode is by typing @kbd{q} or @kbd{C-x s}.
24241 @section TUI-specific Commands
24242 @cindex TUI commands
24244 The TUI has specific commands to control the text windows.
24245 These commands are always available, even when @value{GDBN} is not in
24246 the TUI mode. When @value{GDBN} is in the standard mode, most
24247 of these commands will automatically switch to the TUI mode.
24249 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24250 terminal, or @value{GDBN} has been started with the machine interface
24251 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24252 these commands will fail with an error, because it would not be
24253 possible or desirable to enable curses window management.
24258 List and give the size of all displayed windows.
24262 Display the next layout.
24265 Display the previous layout.
24268 Display the source window only.
24271 Display the assembly window only.
24274 Display the source and assembly window.
24277 Display the register window together with the source or assembly window.
24281 Make the next window active for scrolling.
24284 Make the previous window active for scrolling.
24287 Make the source window active for scrolling.
24290 Make the assembly window active for scrolling.
24293 Make the register window active for scrolling.
24296 Make the command window active for scrolling.
24300 Refresh the screen. This is similar to typing @kbd{C-L}.
24302 @item tui reg float
24304 Show the floating point registers in the register window.
24306 @item tui reg general
24307 Show the general registers in the register window.
24310 Show the next register group. The list of register groups as well as
24311 their order is target specific. The predefined register groups are the
24312 following: @code{general}, @code{float}, @code{system}, @code{vector},
24313 @code{all}, @code{save}, @code{restore}.
24315 @item tui reg system
24316 Show the system registers in the register window.
24320 Update the source window and the current execution point.
24322 @item winheight @var{name} +@var{count}
24323 @itemx winheight @var{name} -@var{count}
24325 Change the height of the window @var{name} by @var{count}
24326 lines. Positive counts increase the height, while negative counts
24329 @item tabset @var{nchars}
24331 Set the width of tab stops to be @var{nchars} characters.
24334 @node TUI Configuration
24335 @section TUI Configuration Variables
24336 @cindex TUI configuration variables
24338 Several configuration variables control the appearance of TUI windows.
24341 @item set tui border-kind @var{kind}
24342 @kindex set tui border-kind
24343 Select the border appearance for the source, assembly and register windows.
24344 The possible values are the following:
24347 Use a space character to draw the border.
24350 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24353 Use the Alternate Character Set to draw the border. The border is
24354 drawn using character line graphics if the terminal supports them.
24357 @item set tui border-mode @var{mode}
24358 @kindex set tui border-mode
24359 @itemx set tui active-border-mode @var{mode}
24360 @kindex set tui active-border-mode
24361 Select the display attributes for the borders of the inactive windows
24362 or the active window. The @var{mode} can be one of the following:
24365 Use normal attributes to display the border.
24371 Use reverse video mode.
24374 Use half bright mode.
24376 @item half-standout
24377 Use half bright and standout mode.
24380 Use extra bright or bold mode.
24382 @item bold-standout
24383 Use extra bright or bold and standout mode.
24388 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24391 @cindex @sc{gnu} Emacs
24392 A special interface allows you to use @sc{gnu} Emacs to view (and
24393 edit) the source files for the program you are debugging with
24396 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24397 executable file you want to debug as an argument. This command starts
24398 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24399 created Emacs buffer.
24400 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24402 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24407 All ``terminal'' input and output goes through an Emacs buffer, called
24410 This applies both to @value{GDBN} commands and their output, and to the input
24411 and output done by the program you are debugging.
24413 This is useful because it means that you can copy the text of previous
24414 commands and input them again; you can even use parts of the output
24417 All the facilities of Emacs' Shell mode are available for interacting
24418 with your program. In particular, you can send signals the usual
24419 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24423 @value{GDBN} displays source code through Emacs.
24425 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24426 source file for that frame and puts an arrow (@samp{=>}) at the
24427 left margin of the current line. Emacs uses a separate buffer for
24428 source display, and splits the screen to show both your @value{GDBN} session
24431 Explicit @value{GDBN} @code{list} or search commands still produce output as
24432 usual, but you probably have no reason to use them from Emacs.
24435 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24436 a graphical mode, enabled by default, which provides further buffers
24437 that can control the execution and describe the state of your program.
24438 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24440 If you specify an absolute file name when prompted for the @kbd{M-x
24441 gdb} argument, then Emacs sets your current working directory to where
24442 your program resides. If you only specify the file name, then Emacs
24443 sets your current working directory to the directory associated
24444 with the previous buffer. In this case, @value{GDBN} may find your
24445 program by searching your environment's @code{PATH} variable, but on
24446 some operating systems it might not find the source. So, although the
24447 @value{GDBN} input and output session proceeds normally, the auxiliary
24448 buffer does not display the current source and line of execution.
24450 The initial working directory of @value{GDBN} is printed on the top
24451 line of the GUD buffer and this serves as a default for the commands
24452 that specify files for @value{GDBN} to operate on. @xref{Files,
24453 ,Commands to Specify Files}.
24455 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24456 need to call @value{GDBN} by a different name (for example, if you
24457 keep several configurations around, with different names) you can
24458 customize the Emacs variable @code{gud-gdb-command-name} to run the
24461 In the GUD buffer, you can use these special Emacs commands in
24462 addition to the standard Shell mode commands:
24466 Describe the features of Emacs' GUD Mode.
24469 Execute to another source line, like the @value{GDBN} @code{step} command; also
24470 update the display window to show the current file and location.
24473 Execute to next source line in this function, skipping all function
24474 calls, like the @value{GDBN} @code{next} command. Then update the display window
24475 to show the current file and location.
24478 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24479 display window accordingly.
24482 Execute until exit from the selected stack frame, like the @value{GDBN}
24483 @code{finish} command.
24486 Continue execution of your program, like the @value{GDBN} @code{continue}
24490 Go up the number of frames indicated by the numeric argument
24491 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24492 like the @value{GDBN} @code{up} command.
24495 Go down the number of frames indicated by the numeric argument, like the
24496 @value{GDBN} @code{down} command.
24499 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24500 tells @value{GDBN} to set a breakpoint on the source line point is on.
24502 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24503 separate frame which shows a backtrace when the GUD buffer is current.
24504 Move point to any frame in the stack and type @key{RET} to make it
24505 become the current frame and display the associated source in the
24506 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24507 selected frame become the current one. In graphical mode, the
24508 speedbar displays watch expressions.
24510 If you accidentally delete the source-display buffer, an easy way to get
24511 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24512 request a frame display; when you run under Emacs, this recreates
24513 the source buffer if necessary to show you the context of the current
24516 The source files displayed in Emacs are in ordinary Emacs buffers
24517 which are visiting the source files in the usual way. You can edit
24518 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24519 communicates with Emacs in terms of line numbers. If you add or
24520 delete lines from the text, the line numbers that @value{GDBN} knows cease
24521 to correspond properly with the code.
24523 A more detailed description of Emacs' interaction with @value{GDBN} is
24524 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24527 @c The following dropped because Epoch is nonstandard. Reactivate
24528 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
24530 @kindex Emacs Epoch environment
24534 Version 18 of @sc{gnu} Emacs has a built-in window system
24535 called the @code{epoch}
24536 environment. Users of this environment can use a new command,
24537 @code{inspect} which performs identically to @code{print} except that
24538 each value is printed in its own window.
24543 @chapter The @sc{gdb/mi} Interface
24545 @unnumberedsec Function and Purpose
24547 @cindex @sc{gdb/mi}, its purpose
24548 @sc{gdb/mi} is a line based machine oriented text interface to
24549 @value{GDBN} and is activated by specifying using the
24550 @option{--interpreter} command line option (@pxref{Mode Options}). It
24551 is specifically intended to support the development of systems which
24552 use the debugger as just one small component of a larger system.
24554 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24555 in the form of a reference manual.
24557 Note that @sc{gdb/mi} is still under construction, so some of the
24558 features described below are incomplete and subject to change
24559 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24561 @unnumberedsec Notation and Terminology
24563 @cindex notational conventions, for @sc{gdb/mi}
24564 This chapter uses the following notation:
24568 @code{|} separates two alternatives.
24571 @code{[ @var{something} ]} indicates that @var{something} is optional:
24572 it may or may not be given.
24575 @code{( @var{group} )*} means that @var{group} inside the parentheses
24576 may repeat zero or more times.
24579 @code{( @var{group} )+} means that @var{group} inside the parentheses
24580 may repeat one or more times.
24583 @code{"@var{string}"} means a literal @var{string}.
24587 @heading Dependencies
24591 * GDB/MI General Design::
24592 * GDB/MI Command Syntax::
24593 * GDB/MI Compatibility with CLI::
24594 * GDB/MI Development and Front Ends::
24595 * GDB/MI Output Records::
24596 * GDB/MI Simple Examples::
24597 * GDB/MI Command Description Format::
24598 * GDB/MI Breakpoint Commands::
24599 * GDB/MI Program Context::
24600 * GDB/MI Thread Commands::
24601 * GDB/MI Program Execution::
24602 * GDB/MI Stack Manipulation::
24603 * GDB/MI Variable Objects::
24604 * GDB/MI Data Manipulation::
24605 * GDB/MI Tracepoint Commands::
24606 * GDB/MI Symbol Query::
24607 * GDB/MI File Commands::
24609 * GDB/MI Kod Commands::
24610 * GDB/MI Memory Overlay Commands::
24611 * GDB/MI Signal Handling Commands::
24613 * GDB/MI Target Manipulation::
24614 * GDB/MI File Transfer Commands::
24615 * GDB/MI Miscellaneous Commands::
24618 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24619 @node GDB/MI General Design
24620 @section @sc{gdb/mi} General Design
24621 @cindex GDB/MI General Design
24623 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24624 parts---commands sent to @value{GDBN}, responses to those commands
24625 and notifications. Each command results in exactly one response,
24626 indicating either successful completion of the command, or an error.
24627 For the commands that do not resume the target, the response contains the
24628 requested information. For the commands that resume the target, the
24629 response only indicates whether the target was successfully resumed.
24630 Notifications is the mechanism for reporting changes in the state of the
24631 target, or in @value{GDBN} state, that cannot conveniently be associated with
24632 a command and reported as part of that command response.
24634 The important examples of notifications are:
24638 Exec notifications. These are used to report changes in
24639 target state---when a target is resumed, or stopped. It would not
24640 be feasible to include this information in response of resuming
24641 commands, because one resume commands can result in multiple events in
24642 different threads. Also, quite some time may pass before any event
24643 happens in the target, while a frontend needs to know whether the resuming
24644 command itself was successfully executed.
24647 Console output, and status notifications. Console output
24648 notifications are used to report output of CLI commands, as well as
24649 diagnostics for other commands. Status notifications are used to
24650 report the progress of a long-running operation. Naturally, including
24651 this information in command response would mean no output is produced
24652 until the command is finished, which is undesirable.
24655 General notifications. Commands may have various side effects on
24656 the @value{GDBN} or target state beyond their official purpose. For example,
24657 a command may change the selected thread. Although such changes can
24658 be included in command response, using notification allows for more
24659 orthogonal frontend design.
24663 There's no guarantee that whenever an MI command reports an error,
24664 @value{GDBN} or the target are in any specific state, and especially,
24665 the state is not reverted to the state before the MI command was
24666 processed. Therefore, whenever an MI command results in an error,
24667 we recommend that the frontend refreshes all the information shown in
24668 the user interface.
24672 * Context management::
24673 * Asynchronous and non-stop modes::
24677 @node Context management
24678 @subsection Context management
24680 In most cases when @value{GDBN} accesses the target, this access is
24681 done in context of a specific thread and frame (@pxref{Frames}).
24682 Often, even when accessing global data, the target requires that a thread
24683 be specified. The CLI interface maintains the selected thread and frame,
24684 and supplies them to target on each command. This is convenient,
24685 because a command line user would not want to specify that information
24686 explicitly on each command, and because user interacts with
24687 @value{GDBN} via a single terminal, so no confusion is possible as
24688 to what thread and frame are the current ones.
24690 In the case of MI, the concept of selected thread and frame is less
24691 useful. First, a frontend can easily remember this information
24692 itself. Second, a graphical frontend can have more than one window,
24693 each one used for debugging a different thread, and the frontend might
24694 want to access additional threads for internal purposes. This
24695 increases the risk that by relying on implicitly selected thread, the
24696 frontend may be operating on a wrong one. Therefore, each MI command
24697 should explicitly specify which thread and frame to operate on. To
24698 make it possible, each MI command accepts the @samp{--thread} and
24699 @samp{--frame} options, the value to each is @value{GDBN} identifier
24700 for thread and frame to operate on.
24702 Usually, each top-level window in a frontend allows the user to select
24703 a thread and a frame, and remembers the user selection for further
24704 operations. However, in some cases @value{GDBN} may suggest that the
24705 current thread be changed. For example, when stopping on a breakpoint
24706 it is reasonable to switch to the thread where breakpoint is hit. For
24707 another example, if the user issues the CLI @samp{thread} command via
24708 the frontend, it is desirable to change the frontend's selected thread to the
24709 one specified by user. @value{GDBN} communicates the suggestion to
24710 change current thread using the @samp{=thread-selected} notification.
24711 No such notification is available for the selected frame at the moment.
24713 Note that historically, MI shares the selected thread with CLI, so
24714 frontends used the @code{-thread-select} to execute commands in the
24715 right context. However, getting this to work right is cumbersome. The
24716 simplest way is for frontend to emit @code{-thread-select} command
24717 before every command. This doubles the number of commands that need
24718 to be sent. The alternative approach is to suppress @code{-thread-select}
24719 if the selected thread in @value{GDBN} is supposed to be identical to the
24720 thread the frontend wants to operate on. However, getting this
24721 optimization right can be tricky. In particular, if the frontend
24722 sends several commands to @value{GDBN}, and one of the commands changes the
24723 selected thread, then the behaviour of subsequent commands will
24724 change. So, a frontend should either wait for response from such
24725 problematic commands, or explicitly add @code{-thread-select} for
24726 all subsequent commands. No frontend is known to do this exactly
24727 right, so it is suggested to just always pass the @samp{--thread} and
24728 @samp{--frame} options.
24730 @node Asynchronous and non-stop modes
24731 @subsection Asynchronous command execution and non-stop mode
24733 On some targets, @value{GDBN} is capable of processing MI commands
24734 even while the target is running. This is called @dfn{asynchronous
24735 command execution} (@pxref{Background Execution}). The frontend may
24736 specify a preferrence for asynchronous execution using the
24737 @code{-gdb-set target-async 1} command, which should be emitted before
24738 either running the executable or attaching to the target. After the
24739 frontend has started the executable or attached to the target, it can
24740 find if asynchronous execution is enabled using the
24741 @code{-list-target-features} command.
24743 Even if @value{GDBN} can accept a command while target is running,
24744 many commands that access the target do not work when the target is
24745 running. Therefore, asynchronous command execution is most useful
24746 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24747 it is possible to examine the state of one thread, while other threads
24750 When a given thread is running, MI commands that try to access the
24751 target in the context of that thread may not work, or may work only on
24752 some targets. In particular, commands that try to operate on thread's
24753 stack will not work, on any target. Commands that read memory, or
24754 modify breakpoints, may work or not work, depending on the target. Note
24755 that even commands that operate on global state, such as @code{print},
24756 @code{set}, and breakpoint commands, still access the target in the
24757 context of a specific thread, so frontend should try to find a
24758 stopped thread and perform the operation on that thread (using the
24759 @samp{--thread} option).
24761 Which commands will work in the context of a running thread is
24762 highly target dependent. However, the two commands
24763 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24764 to find the state of a thread, will always work.
24766 @node Thread groups
24767 @subsection Thread groups
24768 @value{GDBN} may be used to debug several processes at the same time.
24769 On some platfroms, @value{GDBN} may support debugging of several
24770 hardware systems, each one having several cores with several different
24771 processes running on each core. This section describes the MI
24772 mechanism to support such debugging scenarios.
24774 The key observation is that regardless of the structure of the
24775 target, MI can have a global list of threads, because most commands that
24776 accept the @samp{--thread} option do not need to know what process that
24777 thread belongs to. Therefore, it is not necessary to introduce
24778 neither additional @samp{--process} option, nor an notion of the
24779 current process in the MI interface. The only strictly new feature
24780 that is required is the ability to find how the threads are grouped
24783 To allow the user to discover such grouping, and to support arbitrary
24784 hierarchy of machines/cores/processes, MI introduces the concept of a
24785 @dfn{thread group}. Thread group is a collection of threads and other
24786 thread groups. A thread group always has a string identifier, a type,
24787 and may have additional attributes specific to the type. A new
24788 command, @code{-list-thread-groups}, returns the list of top-level
24789 thread groups, which correspond to processes that @value{GDBN} is
24790 debugging at the moment. By passing an identifier of a thread group
24791 to the @code{-list-thread-groups} command, it is possible to obtain
24792 the members of specific thread group.
24794 To allow the user to easily discover processes, and other objects, he
24795 wishes to debug, a concept of @dfn{available thread group} is
24796 introduced. Available thread group is an thread group that
24797 @value{GDBN} is not debugging, but that can be attached to, using the
24798 @code{-target-attach} command. The list of available top-level thread
24799 groups can be obtained using @samp{-list-thread-groups --available}.
24800 In general, the content of a thread group may be only retrieved only
24801 after attaching to that thread group.
24803 Thread groups are related to inferiors (@pxref{Inferiors and
24804 Programs}). Each inferior corresponds to a thread group of a special
24805 type @samp{process}, and some additional operations are permitted on
24806 such thread groups.
24808 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24809 @node GDB/MI Command Syntax
24810 @section @sc{gdb/mi} Command Syntax
24813 * GDB/MI Input Syntax::
24814 * GDB/MI Output Syntax::
24817 @node GDB/MI Input Syntax
24818 @subsection @sc{gdb/mi} Input Syntax
24820 @cindex input syntax for @sc{gdb/mi}
24821 @cindex @sc{gdb/mi}, input syntax
24823 @item @var{command} @expansion{}
24824 @code{@var{cli-command} | @var{mi-command}}
24826 @item @var{cli-command} @expansion{}
24827 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24828 @var{cli-command} is any existing @value{GDBN} CLI command.
24830 @item @var{mi-command} @expansion{}
24831 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24832 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24834 @item @var{token} @expansion{}
24835 "any sequence of digits"
24837 @item @var{option} @expansion{}
24838 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24840 @item @var{parameter} @expansion{}
24841 @code{@var{non-blank-sequence} | @var{c-string}}
24843 @item @var{operation} @expansion{}
24844 @emph{any of the operations described in this chapter}
24846 @item @var{non-blank-sequence} @expansion{}
24847 @emph{anything, provided it doesn't contain special characters such as
24848 "-", @var{nl}, """ and of course " "}
24850 @item @var{c-string} @expansion{}
24851 @code{""" @var{seven-bit-iso-c-string-content} """}
24853 @item @var{nl} @expansion{}
24862 The CLI commands are still handled by the @sc{mi} interpreter; their
24863 output is described below.
24866 The @code{@var{token}}, when present, is passed back when the command
24870 Some @sc{mi} commands accept optional arguments as part of the parameter
24871 list. Each option is identified by a leading @samp{-} (dash) and may be
24872 followed by an optional argument parameter. Options occur first in the
24873 parameter list and can be delimited from normal parameters using
24874 @samp{--} (this is useful when some parameters begin with a dash).
24881 We want easy access to the existing CLI syntax (for debugging).
24884 We want it to be easy to spot a @sc{mi} operation.
24887 @node GDB/MI Output Syntax
24888 @subsection @sc{gdb/mi} Output Syntax
24890 @cindex output syntax of @sc{gdb/mi}
24891 @cindex @sc{gdb/mi}, output syntax
24892 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24893 followed, optionally, by a single result record. This result record
24894 is for the most recent command. The sequence of output records is
24895 terminated by @samp{(gdb)}.
24897 If an input command was prefixed with a @code{@var{token}} then the
24898 corresponding output for that command will also be prefixed by that same
24902 @item @var{output} @expansion{}
24903 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24905 @item @var{result-record} @expansion{}
24906 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24908 @item @var{out-of-band-record} @expansion{}
24909 @code{@var{async-record} | @var{stream-record}}
24911 @item @var{async-record} @expansion{}
24912 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24914 @item @var{exec-async-output} @expansion{}
24915 @code{[ @var{token} ] "*" @var{async-output}}
24917 @item @var{status-async-output} @expansion{}
24918 @code{[ @var{token} ] "+" @var{async-output}}
24920 @item @var{notify-async-output} @expansion{}
24921 @code{[ @var{token} ] "=" @var{async-output}}
24923 @item @var{async-output} @expansion{}
24924 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
24926 @item @var{result-class} @expansion{}
24927 @code{"done" | "running" | "connected" | "error" | "exit"}
24929 @item @var{async-class} @expansion{}
24930 @code{"stopped" | @var{others}} (where @var{others} will be added
24931 depending on the needs---this is still in development).
24933 @item @var{result} @expansion{}
24934 @code{ @var{variable} "=" @var{value}}
24936 @item @var{variable} @expansion{}
24937 @code{ @var{string} }
24939 @item @var{value} @expansion{}
24940 @code{ @var{const} | @var{tuple} | @var{list} }
24942 @item @var{const} @expansion{}
24943 @code{@var{c-string}}
24945 @item @var{tuple} @expansion{}
24946 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24948 @item @var{list} @expansion{}
24949 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24950 @var{result} ( "," @var{result} )* "]" }
24952 @item @var{stream-record} @expansion{}
24953 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24955 @item @var{console-stream-output} @expansion{}
24956 @code{"~" @var{c-string}}
24958 @item @var{target-stream-output} @expansion{}
24959 @code{"@@" @var{c-string}}
24961 @item @var{log-stream-output} @expansion{}
24962 @code{"&" @var{c-string}}
24964 @item @var{nl} @expansion{}
24967 @item @var{token} @expansion{}
24968 @emph{any sequence of digits}.
24976 All output sequences end in a single line containing a period.
24979 The @code{@var{token}} is from the corresponding request. Note that
24980 for all async output, while the token is allowed by the grammar and
24981 may be output by future versions of @value{GDBN} for select async
24982 output messages, it is generally omitted. Frontends should treat
24983 all async output as reporting general changes in the state of the
24984 target and there should be no need to associate async output to any
24988 @cindex status output in @sc{gdb/mi}
24989 @var{status-async-output} contains on-going status information about the
24990 progress of a slow operation. It can be discarded. All status output is
24991 prefixed by @samp{+}.
24994 @cindex async output in @sc{gdb/mi}
24995 @var{exec-async-output} contains asynchronous state change on the target
24996 (stopped, started, disappeared). All async output is prefixed by
25000 @cindex notify output in @sc{gdb/mi}
25001 @var{notify-async-output} contains supplementary information that the
25002 client should handle (e.g., a new breakpoint information). All notify
25003 output is prefixed by @samp{=}.
25006 @cindex console output in @sc{gdb/mi}
25007 @var{console-stream-output} is output that should be displayed as is in the
25008 console. It is the textual response to a CLI command. All the console
25009 output is prefixed by @samp{~}.
25012 @cindex target output in @sc{gdb/mi}
25013 @var{target-stream-output} is the output produced by the target program.
25014 All the target output is prefixed by @samp{@@}.
25017 @cindex log output in @sc{gdb/mi}
25018 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25019 instance messages that should be displayed as part of an error log. All
25020 the log output is prefixed by @samp{&}.
25023 @cindex list output in @sc{gdb/mi}
25024 New @sc{gdb/mi} commands should only output @var{lists} containing
25030 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25031 details about the various output records.
25033 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25034 @node GDB/MI Compatibility with CLI
25035 @section @sc{gdb/mi} Compatibility with CLI
25037 @cindex compatibility, @sc{gdb/mi} and CLI
25038 @cindex @sc{gdb/mi}, compatibility with CLI
25040 For the developers convenience CLI commands can be entered directly,
25041 but there may be some unexpected behaviour. For example, commands
25042 that query the user will behave as if the user replied yes, breakpoint
25043 command lists are not executed and some CLI commands, such as
25044 @code{if}, @code{when} and @code{define}, prompt for further input with
25045 @samp{>}, which is not valid MI output.
25047 This feature may be removed at some stage in the future and it is
25048 recommended that front ends use the @code{-interpreter-exec} command
25049 (@pxref{-interpreter-exec}).
25051 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25052 @node GDB/MI Development and Front Ends
25053 @section @sc{gdb/mi} Development and Front Ends
25054 @cindex @sc{gdb/mi} development
25056 The application which takes the MI output and presents the state of the
25057 program being debugged to the user is called a @dfn{front end}.
25059 Although @sc{gdb/mi} is still incomplete, it is currently being used
25060 by a variety of front ends to @value{GDBN}. This makes it difficult
25061 to introduce new functionality without breaking existing usage. This
25062 section tries to minimize the problems by describing how the protocol
25065 Some changes in MI need not break a carefully designed front end, and
25066 for these the MI version will remain unchanged. The following is a
25067 list of changes that may occur within one level, so front ends should
25068 parse MI output in a way that can handle them:
25072 New MI commands may be added.
25075 New fields may be added to the output of any MI command.
25078 The range of values for fields with specified values, e.g.,
25079 @code{in_scope} (@pxref{-var-update}) may be extended.
25081 @c The format of field's content e.g type prefix, may change so parse it
25082 @c at your own risk. Yes, in general?
25084 @c The order of fields may change? Shouldn't really matter but it might
25085 @c resolve inconsistencies.
25088 If the changes are likely to break front ends, the MI version level
25089 will be increased by one. This will allow the front end to parse the
25090 output according to the MI version. Apart from mi0, new versions of
25091 @value{GDBN} will not support old versions of MI and it will be the
25092 responsibility of the front end to work with the new one.
25094 @c Starting with mi3, add a new command -mi-version that prints the MI
25097 The best way to avoid unexpected changes in MI that might break your front
25098 end is to make your project known to @value{GDBN} developers and
25099 follow development on @email{gdb@@sourceware.org} and
25100 @email{gdb-patches@@sourceware.org}.
25101 @cindex mailing lists
25103 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25104 @node GDB/MI Output Records
25105 @section @sc{gdb/mi} Output Records
25108 * GDB/MI Result Records::
25109 * GDB/MI Stream Records::
25110 * GDB/MI Async Records::
25111 * GDB/MI Frame Information::
25112 * GDB/MI Thread Information::
25113 * GDB/MI Ada Exception Information::
25116 @node GDB/MI Result Records
25117 @subsection @sc{gdb/mi} Result Records
25119 @cindex result records in @sc{gdb/mi}
25120 @cindex @sc{gdb/mi}, result records
25121 In addition to a number of out-of-band notifications, the response to a
25122 @sc{gdb/mi} command includes one of the following result indications:
25126 @item "^done" [ "," @var{results} ]
25127 The synchronous operation was successful, @code{@var{results}} are the return
25132 This result record is equivalent to @samp{^done}. Historically, it
25133 was output instead of @samp{^done} if the command has resumed the
25134 target. This behaviour is maintained for backward compatibility, but
25135 all frontends should treat @samp{^done} and @samp{^running}
25136 identically and rely on the @samp{*running} output record to determine
25137 which threads are resumed.
25141 @value{GDBN} has connected to a remote target.
25143 @item "^error" "," @var{c-string}
25145 The operation failed. The @code{@var{c-string}} contains the corresponding
25150 @value{GDBN} has terminated.
25154 @node GDB/MI Stream Records
25155 @subsection @sc{gdb/mi} Stream Records
25157 @cindex @sc{gdb/mi}, stream records
25158 @cindex stream records in @sc{gdb/mi}
25159 @value{GDBN} internally maintains a number of output streams: the console, the
25160 target, and the log. The output intended for each of these streams is
25161 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25163 Each stream record begins with a unique @dfn{prefix character} which
25164 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25165 Syntax}). In addition to the prefix, each stream record contains a
25166 @code{@var{string-output}}. This is either raw text (with an implicit new
25167 line) or a quoted C string (which does not contain an implicit newline).
25170 @item "~" @var{string-output}
25171 The console output stream contains text that should be displayed in the
25172 CLI console window. It contains the textual responses to CLI commands.
25174 @item "@@" @var{string-output}
25175 The target output stream contains any textual output from the running
25176 target. This is only present when GDB's event loop is truly
25177 asynchronous, which is currently only the case for remote targets.
25179 @item "&" @var{string-output}
25180 The log stream contains debugging messages being produced by @value{GDBN}'s
25184 @node GDB/MI Async Records
25185 @subsection @sc{gdb/mi} Async Records
25187 @cindex async records in @sc{gdb/mi}
25188 @cindex @sc{gdb/mi}, async records
25189 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25190 additional changes that have occurred. Those changes can either be a
25191 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25192 target activity (e.g., target stopped).
25194 The following is the list of possible async records:
25198 @item *running,thread-id="@var{thread}"
25199 The target is now running. The @var{thread} field tells which
25200 specific thread is now running, and can be @samp{all} if all threads
25201 are running. The frontend should assume that no interaction with a
25202 running thread is possible after this notification is produced.
25203 The frontend should not assume that this notification is output
25204 only once for any command. @value{GDBN} may emit this notification
25205 several times, either for different threads, because it cannot resume
25206 all threads together, or even for a single thread, if the thread must
25207 be stepped though some code before letting it run freely.
25209 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25210 The target has stopped. The @var{reason} field can have one of the
25214 @item breakpoint-hit
25215 A breakpoint was reached.
25216 @item watchpoint-trigger
25217 A watchpoint was triggered.
25218 @item read-watchpoint-trigger
25219 A read watchpoint was triggered.
25220 @item access-watchpoint-trigger
25221 An access watchpoint was triggered.
25222 @item function-finished
25223 An -exec-finish or similar CLI command was accomplished.
25224 @item location-reached
25225 An -exec-until or similar CLI command was accomplished.
25226 @item watchpoint-scope
25227 A watchpoint has gone out of scope.
25228 @item end-stepping-range
25229 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25230 similar CLI command was accomplished.
25231 @item exited-signalled
25232 The inferior exited because of a signal.
25234 The inferior exited.
25235 @item exited-normally
25236 The inferior exited normally.
25237 @item signal-received
25238 A signal was received by the inferior.
25241 The @var{id} field identifies the thread that directly caused the stop
25242 -- for example by hitting a breakpoint. Depending on whether all-stop
25243 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25244 stop all threads, or only the thread that directly triggered the stop.
25245 If all threads are stopped, the @var{stopped} field will have the
25246 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25247 field will be a list of thread identifiers. Presently, this list will
25248 always include a single thread, but frontend should be prepared to see
25249 several threads in the list. The @var{core} field reports the
25250 processor core on which the stop event has happened. This field may be absent
25251 if such information is not available.
25253 @item =thread-group-added,id="@var{id}"
25254 @itemx =thread-group-removed,id="@var{id}"
25255 A thread group was either added or removed. The @var{id} field
25256 contains the @value{GDBN} identifier of the thread group. When a thread
25257 group is added, it generally might not be associated with a running
25258 process. When a thread group is removed, its id becomes invalid and
25259 cannot be used in any way.
25261 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25262 A thread group became associated with a running program,
25263 either because the program was just started or the thread group
25264 was attached to a program. The @var{id} field contains the
25265 @value{GDBN} identifier of the thread group. The @var{pid} field
25266 contains process identifier, specific to the operating system.
25268 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25269 A thread group is no longer associated with a running program,
25270 either because the program has exited, or because it was detached
25271 from. The @var{id} field contains the @value{GDBN} identifier of the
25272 thread group. @var{code} is the exit code of the inferior; it exists
25273 only when the inferior exited with some code.
25275 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25276 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25277 A thread either was created, or has exited. The @var{id} field
25278 contains the @value{GDBN} identifier of the thread. The @var{gid}
25279 field identifies the thread group this thread belongs to.
25281 @item =thread-selected,id="@var{id}"
25282 Informs that the selected thread was changed as result of the last
25283 command. This notification is not emitted as result of @code{-thread-select}
25284 command but is emitted whenever an MI command that is not documented
25285 to change the selected thread actually changes it. In particular,
25286 invoking, directly or indirectly (via user-defined command), the CLI
25287 @code{thread} command, will generate this notification.
25289 We suggest that in response to this notification, front ends
25290 highlight the selected thread and cause subsequent commands to apply to
25293 @item =library-loaded,...
25294 Reports that a new library file was loaded by the program. This
25295 notification has 4 fields---@var{id}, @var{target-name},
25296 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25297 opaque identifier of the library. For remote debugging case,
25298 @var{target-name} and @var{host-name} fields give the name of the
25299 library file on the target, and on the host respectively. For native
25300 debugging, both those fields have the same value. The
25301 @var{symbols-loaded} field is emitted only for backward compatibility
25302 and should not be relied on to convey any useful information. The
25303 @var{thread-group} field, if present, specifies the id of the thread
25304 group in whose context the library was loaded. If the field is
25305 absent, it means the library was loaded in the context of all present
25308 @item =library-unloaded,...
25309 Reports that a library was unloaded by the program. This notification
25310 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25311 the same meaning as for the @code{=library-loaded} notification.
25312 The @var{thread-group} field, if present, specifies the id of the
25313 thread group in whose context the library was unloaded. If the field is
25314 absent, it means the library was unloaded in the context of all present
25317 @item =breakpoint-created,bkpt=@{...@}
25318 @itemx =breakpoint-modified,bkpt=@{...@}
25319 @itemx =breakpoint-deleted,bkpt=@{...@}
25320 Reports that a breakpoint was created, modified, or deleted,
25321 respectively. Only user-visible breakpoints are reported to the MI
25324 The @var{bkpt} argument is of the same form as returned by the various
25325 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
25327 Note that if a breakpoint is emitted in the result record of a
25328 command, then it will not also be emitted in an async record.
25332 @node GDB/MI Frame Information
25333 @subsection @sc{gdb/mi} Frame Information
25335 Response from many MI commands includes an information about stack
25336 frame. This information is a tuple that may have the following
25341 The level of the stack frame. The innermost frame has the level of
25342 zero. This field is always present.
25345 The name of the function corresponding to the frame. This field may
25346 be absent if @value{GDBN} is unable to determine the function name.
25349 The code address for the frame. This field is always present.
25352 The name of the source files that correspond to the frame's code
25353 address. This field may be absent.
25356 The source line corresponding to the frames' code address. This field
25360 The name of the binary file (either executable or shared library) the
25361 corresponds to the frame's code address. This field may be absent.
25365 @node GDB/MI Thread Information
25366 @subsection @sc{gdb/mi} Thread Information
25368 Whenever @value{GDBN} has to report an information about a thread, it
25369 uses a tuple with the following fields:
25373 The numeric id assigned to the thread by @value{GDBN}. This field is
25377 Target-specific string identifying the thread. This field is always present.
25380 Additional information about the thread provided by the target.
25381 It is supposed to be human-readable and not interpreted by the
25382 frontend. This field is optional.
25385 Either @samp{stopped} or @samp{running}, depending on whether the
25386 thread is presently running. This field is always present.
25389 The value of this field is an integer number of the processor core the
25390 thread was last seen on. This field is optional.
25393 @node GDB/MI Ada Exception Information
25394 @subsection @sc{gdb/mi} Ada Exception Information
25396 Whenever a @code{*stopped} record is emitted because the program
25397 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25398 @value{GDBN} provides the name of the exception that was raised via
25399 the @code{exception-name} field.
25401 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25402 @node GDB/MI Simple Examples
25403 @section Simple Examples of @sc{gdb/mi} Interaction
25404 @cindex @sc{gdb/mi}, simple examples
25406 This subsection presents several simple examples of interaction using
25407 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25408 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25409 the output received from @sc{gdb/mi}.
25411 Note the line breaks shown in the examples are here only for
25412 readability, they don't appear in the real output.
25414 @subheading Setting a Breakpoint
25416 Setting a breakpoint generates synchronous output which contains detailed
25417 information of the breakpoint.
25420 -> -break-insert main
25421 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25422 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25423 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
25427 @subheading Program Execution
25429 Program execution generates asynchronous records and MI gives the
25430 reason that execution stopped.
25436 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25437 frame=@{addr="0x08048564",func="main",
25438 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25439 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25444 <- *stopped,reason="exited-normally"
25448 @subheading Quitting @value{GDBN}
25450 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25458 Please note that @samp{^exit} is printed immediately, but it might
25459 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25460 performs necessary cleanups, including killing programs being debugged
25461 or disconnecting from debug hardware, so the frontend should wait till
25462 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25463 fails to exit in reasonable time.
25465 @subheading A Bad Command
25467 Here's what happens if you pass a non-existent command:
25471 <- ^error,msg="Undefined MI command: rubbish"
25476 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25477 @node GDB/MI Command Description Format
25478 @section @sc{gdb/mi} Command Description Format
25480 The remaining sections describe blocks of commands. Each block of
25481 commands is laid out in a fashion similar to this section.
25483 @subheading Motivation
25485 The motivation for this collection of commands.
25487 @subheading Introduction
25489 A brief introduction to this collection of commands as a whole.
25491 @subheading Commands
25493 For each command in the block, the following is described:
25495 @subsubheading Synopsis
25498 -command @var{args}@dots{}
25501 @subsubheading Result
25503 @subsubheading @value{GDBN} Command
25505 The corresponding @value{GDBN} CLI command(s), if any.
25507 @subsubheading Example
25509 Example(s) formatted for readability. Some of the described commands have
25510 not been implemented yet and these are labeled N.A.@: (not available).
25513 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25514 @node GDB/MI Breakpoint Commands
25515 @section @sc{gdb/mi} Breakpoint Commands
25517 @cindex breakpoint commands for @sc{gdb/mi}
25518 @cindex @sc{gdb/mi}, breakpoint commands
25519 This section documents @sc{gdb/mi} commands for manipulating
25522 @subheading The @code{-break-after} Command
25523 @findex -break-after
25525 @subsubheading Synopsis
25528 -break-after @var{number} @var{count}
25531 The breakpoint number @var{number} is not in effect until it has been
25532 hit @var{count} times. To see how this is reflected in the output of
25533 the @samp{-break-list} command, see the description of the
25534 @samp{-break-list} command below.
25536 @subsubheading @value{GDBN} Command
25538 The corresponding @value{GDBN} command is @samp{ignore}.
25540 @subsubheading Example
25545 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25546 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25547 fullname="/home/foo/hello.c",line="5",times="0"@}
25554 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25555 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25556 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25557 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25558 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25559 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25560 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25561 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25562 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25563 line="5",times="0",ignore="3"@}]@}
25568 @subheading The @code{-break-catch} Command
25569 @findex -break-catch
25572 @subheading The @code{-break-commands} Command
25573 @findex -break-commands
25575 @subsubheading Synopsis
25578 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25581 Specifies the CLI commands that should be executed when breakpoint
25582 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25583 are the commands. If no command is specified, any previously-set
25584 commands are cleared. @xref{Break Commands}. Typical use of this
25585 functionality is tracing a program, that is, printing of values of
25586 some variables whenever breakpoint is hit and then continuing.
25588 @subsubheading @value{GDBN} Command
25590 The corresponding @value{GDBN} command is @samp{commands}.
25592 @subsubheading Example
25597 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25598 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25599 fullname="/home/foo/hello.c",line="5",times="0"@}
25601 -break-commands 1 "print v" "continue"
25606 @subheading The @code{-break-condition} Command
25607 @findex -break-condition
25609 @subsubheading Synopsis
25612 -break-condition @var{number} @var{expr}
25615 Breakpoint @var{number} will stop the program only if the condition in
25616 @var{expr} is true. The condition becomes part of the
25617 @samp{-break-list} output (see the description of the @samp{-break-list}
25620 @subsubheading @value{GDBN} Command
25622 The corresponding @value{GDBN} command is @samp{condition}.
25624 @subsubheading Example
25628 -break-condition 1 1
25632 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25633 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25634 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25635 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25636 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25637 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25638 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25639 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25640 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25641 line="5",cond="1",times="0",ignore="3"@}]@}
25645 @subheading The @code{-break-delete} Command
25646 @findex -break-delete
25648 @subsubheading Synopsis
25651 -break-delete ( @var{breakpoint} )+
25654 Delete the breakpoint(s) whose number(s) are specified in the argument
25655 list. This is obviously reflected in the breakpoint list.
25657 @subsubheading @value{GDBN} Command
25659 The corresponding @value{GDBN} command is @samp{delete}.
25661 @subsubheading Example
25669 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25670 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25671 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25672 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25673 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25674 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25675 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25680 @subheading The @code{-break-disable} Command
25681 @findex -break-disable
25683 @subsubheading Synopsis
25686 -break-disable ( @var{breakpoint} )+
25689 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25690 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25692 @subsubheading @value{GDBN} Command
25694 The corresponding @value{GDBN} command is @samp{disable}.
25696 @subsubheading Example
25704 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25705 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25706 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25707 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25708 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25709 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25710 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25711 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25712 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25713 line="5",times="0"@}]@}
25717 @subheading The @code{-break-enable} Command
25718 @findex -break-enable
25720 @subsubheading Synopsis
25723 -break-enable ( @var{breakpoint} )+
25726 Enable (previously disabled) @var{breakpoint}(s).
25728 @subsubheading @value{GDBN} Command
25730 The corresponding @value{GDBN} command is @samp{enable}.
25732 @subsubheading Example
25740 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25741 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25742 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25743 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25744 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25745 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25746 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25747 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25748 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25749 line="5",times="0"@}]@}
25753 @subheading The @code{-break-info} Command
25754 @findex -break-info
25756 @subsubheading Synopsis
25759 -break-info @var{breakpoint}
25763 Get information about a single breakpoint.
25765 @subsubheading @value{GDBN} Command
25767 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25769 @subsubheading Example
25772 @subheading The @code{-break-insert} Command
25773 @findex -break-insert
25775 @subsubheading Synopsis
25778 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25779 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25780 [ -p @var{thread} ] [ @var{location} ]
25784 If specified, @var{location}, can be one of:
25791 @item filename:linenum
25792 @item filename:function
25796 The possible optional parameters of this command are:
25800 Insert a temporary breakpoint.
25802 Insert a hardware breakpoint.
25803 @item -c @var{condition}
25804 Make the breakpoint conditional on @var{condition}.
25805 @item -i @var{ignore-count}
25806 Initialize the @var{ignore-count}.
25808 If @var{location} cannot be parsed (for example if it
25809 refers to unknown files or functions), create a pending
25810 breakpoint. Without this flag, @value{GDBN} will report
25811 an error, and won't create a breakpoint, if @var{location}
25814 Create a disabled breakpoint.
25816 Create a tracepoint. @xref{Tracepoints}. When this parameter
25817 is used together with @samp{-h}, a fast tracepoint is created.
25820 @subsubheading Result
25822 The result is in the form:
25825 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25826 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25827 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25828 times="@var{times}"@}
25832 where @var{number} is the @value{GDBN} number for this breakpoint,
25833 @var{funcname} is the name of the function where the breakpoint was
25834 inserted, @var{filename} is the name of the source file which contains
25835 this function, @var{lineno} is the source line number within that file
25836 and @var{times} the number of times that the breakpoint has been hit
25837 (always 0 for -break-insert but may be greater for -break-info or -break-list
25838 which use the same output).
25840 Note: this format is open to change.
25841 @c An out-of-band breakpoint instead of part of the result?
25843 @subsubheading @value{GDBN} Command
25845 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
25846 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
25848 @subsubheading Example
25853 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
25854 fullname="/home/foo/recursive2.c,line="4",times="0"@}
25856 -break-insert -t foo
25857 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
25858 fullname="/home/foo/recursive2.c,line="11",times="0"@}
25861 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25862 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25863 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25864 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25865 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25866 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25867 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25868 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25869 addr="0x0001072c", func="main",file="recursive2.c",
25870 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
25871 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
25872 addr="0x00010774",func="foo",file="recursive2.c",
25873 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
25875 -break-insert -r foo.*
25876 ~int foo(int, int);
25877 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
25878 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
25882 @subheading The @code{-break-list} Command
25883 @findex -break-list
25885 @subsubheading Synopsis
25891 Displays the list of inserted breakpoints, showing the following fields:
25895 number of the breakpoint
25897 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
25899 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
25902 is the breakpoint enabled or no: @samp{y} or @samp{n}
25904 memory location at which the breakpoint is set
25906 logical location of the breakpoint, expressed by function name, file
25909 number of times the breakpoint has been hit
25912 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
25913 @code{body} field is an empty list.
25915 @subsubheading @value{GDBN} Command
25917 The corresponding @value{GDBN} command is @samp{info break}.
25919 @subsubheading Example
25924 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25925 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25926 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25927 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25928 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25929 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25930 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25931 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25932 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
25933 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25934 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
25935 line="13",times="0"@}]@}
25939 Here's an example of the result when there are no breakpoints:
25944 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25945 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25946 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25947 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25948 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25949 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25950 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25955 @subheading The @code{-break-passcount} Command
25956 @findex -break-passcount
25958 @subsubheading Synopsis
25961 -break-passcount @var{tracepoint-number} @var{passcount}
25964 Set the passcount for tracepoint @var{tracepoint-number} to
25965 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25966 is not a tracepoint, error is emitted. This corresponds to CLI
25967 command @samp{passcount}.
25969 @subheading The @code{-break-watch} Command
25970 @findex -break-watch
25972 @subsubheading Synopsis
25975 -break-watch [ -a | -r ]
25978 Create a watchpoint. With the @samp{-a} option it will create an
25979 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25980 read from or on a write to the memory location. With the @samp{-r}
25981 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25982 trigger only when the memory location is accessed for reading. Without
25983 either of the options, the watchpoint created is a regular watchpoint,
25984 i.e., it will trigger when the memory location is accessed for writing.
25985 @xref{Set Watchpoints, , Setting Watchpoints}.
25987 Note that @samp{-break-list} will report a single list of watchpoints and
25988 breakpoints inserted.
25990 @subsubheading @value{GDBN} Command
25992 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25995 @subsubheading Example
25997 Setting a watchpoint on a variable in the @code{main} function:
26002 ^done,wpt=@{number="2",exp="x"@}
26007 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26008 value=@{old="-268439212",new="55"@},
26009 frame=@{func="main",args=[],file="recursive2.c",
26010 fullname="/home/foo/bar/recursive2.c",line="5"@}
26014 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26015 the program execution twice: first for the variable changing value, then
26016 for the watchpoint going out of scope.
26021 ^done,wpt=@{number="5",exp="C"@}
26026 *stopped,reason="watchpoint-trigger",
26027 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26028 frame=@{func="callee4",args=[],
26029 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26030 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26035 *stopped,reason="watchpoint-scope",wpnum="5",
26036 frame=@{func="callee3",args=[@{name="strarg",
26037 value="0x11940 \"A string argument.\""@}],
26038 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26039 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26043 Listing breakpoints and watchpoints, at different points in the program
26044 execution. Note that once the watchpoint goes out of scope, it is
26050 ^done,wpt=@{number="2",exp="C"@}
26053 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26054 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26055 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26056 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26057 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26058 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26059 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26060 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26061 addr="0x00010734",func="callee4",
26062 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26063 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
26064 bkpt=@{number="2",type="watchpoint",disp="keep",
26065 enabled="y",addr="",what="C",times="0"@}]@}
26070 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26071 value=@{old="-276895068",new="3"@},
26072 frame=@{func="callee4",args=[],
26073 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26074 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26077 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26078 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26079 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26080 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26081 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26082 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26083 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26084 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26085 addr="0x00010734",func="callee4",
26086 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26087 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
26088 bkpt=@{number="2",type="watchpoint",disp="keep",
26089 enabled="y",addr="",what="C",times="-5"@}]@}
26093 ^done,reason="watchpoint-scope",wpnum="2",
26094 frame=@{func="callee3",args=[@{name="strarg",
26095 value="0x11940 \"A string argument.\""@}],
26096 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26097 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26100 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26101 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26102 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26103 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26104 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26105 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26106 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26107 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26108 addr="0x00010734",func="callee4",
26109 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26110 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26115 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26116 @node GDB/MI Program Context
26117 @section @sc{gdb/mi} Program Context
26119 @subheading The @code{-exec-arguments} Command
26120 @findex -exec-arguments
26123 @subsubheading Synopsis
26126 -exec-arguments @var{args}
26129 Set the inferior program arguments, to be used in the next
26132 @subsubheading @value{GDBN} Command
26134 The corresponding @value{GDBN} command is @samp{set args}.
26136 @subsubheading Example
26140 -exec-arguments -v word
26147 @subheading The @code{-exec-show-arguments} Command
26148 @findex -exec-show-arguments
26150 @subsubheading Synopsis
26153 -exec-show-arguments
26156 Print the arguments of the program.
26158 @subsubheading @value{GDBN} Command
26160 The corresponding @value{GDBN} command is @samp{show args}.
26162 @subsubheading Example
26167 @subheading The @code{-environment-cd} Command
26168 @findex -environment-cd
26170 @subsubheading Synopsis
26173 -environment-cd @var{pathdir}
26176 Set @value{GDBN}'s working directory.
26178 @subsubheading @value{GDBN} Command
26180 The corresponding @value{GDBN} command is @samp{cd}.
26182 @subsubheading Example
26186 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26192 @subheading The @code{-environment-directory} Command
26193 @findex -environment-directory
26195 @subsubheading Synopsis
26198 -environment-directory [ -r ] [ @var{pathdir} ]+
26201 Add directories @var{pathdir} to beginning of search path for source files.
26202 If the @samp{-r} option is used, the search path is reset to the default
26203 search path. If directories @var{pathdir} are supplied in addition to the
26204 @samp{-r} option, the search path is first reset and then addition
26206 Multiple directories may be specified, separated by blanks. Specifying
26207 multiple directories in a single command
26208 results in the directories added to the beginning of the
26209 search path in the same order they were presented in the command.
26210 If blanks are needed as
26211 part of a directory name, double-quotes should be used around
26212 the name. In the command output, the path will show up separated
26213 by the system directory-separator character. The directory-separator
26214 character must not be used
26215 in any directory name.
26216 If no directories are specified, the current search path is displayed.
26218 @subsubheading @value{GDBN} Command
26220 The corresponding @value{GDBN} command is @samp{dir}.
26222 @subsubheading Example
26226 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26227 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26229 -environment-directory ""
26230 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26232 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26233 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26235 -environment-directory -r
26236 ^done,source-path="$cdir:$cwd"
26241 @subheading The @code{-environment-path} Command
26242 @findex -environment-path
26244 @subsubheading Synopsis
26247 -environment-path [ -r ] [ @var{pathdir} ]+
26250 Add directories @var{pathdir} to beginning of search path for object files.
26251 If the @samp{-r} option is used, the search path is reset to the original
26252 search path that existed at gdb start-up. If directories @var{pathdir} are
26253 supplied in addition to the
26254 @samp{-r} option, the search path is first reset and then addition
26256 Multiple directories may be specified, separated by blanks. Specifying
26257 multiple directories in a single command
26258 results in the directories added to the beginning of the
26259 search path in the same order they were presented in the command.
26260 If blanks are needed as
26261 part of a directory name, double-quotes should be used around
26262 the name. In the command output, the path will show up separated
26263 by the system directory-separator character. The directory-separator
26264 character must not be used
26265 in any directory name.
26266 If no directories are specified, the current path is displayed.
26269 @subsubheading @value{GDBN} Command
26271 The corresponding @value{GDBN} command is @samp{path}.
26273 @subsubheading Example
26278 ^done,path="/usr/bin"
26280 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26281 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26283 -environment-path -r /usr/local/bin
26284 ^done,path="/usr/local/bin:/usr/bin"
26289 @subheading The @code{-environment-pwd} Command
26290 @findex -environment-pwd
26292 @subsubheading Synopsis
26298 Show the current working directory.
26300 @subsubheading @value{GDBN} Command
26302 The corresponding @value{GDBN} command is @samp{pwd}.
26304 @subsubheading Example
26309 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26313 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26314 @node GDB/MI Thread Commands
26315 @section @sc{gdb/mi} Thread Commands
26318 @subheading The @code{-thread-info} Command
26319 @findex -thread-info
26321 @subsubheading Synopsis
26324 -thread-info [ @var{thread-id} ]
26327 Reports information about either a specific thread, if
26328 the @var{thread-id} parameter is present, or about all
26329 threads. When printing information about all threads,
26330 also reports the current thread.
26332 @subsubheading @value{GDBN} Command
26334 The @samp{info thread} command prints the same information
26337 @subsubheading Result
26339 The result is a list of threads. The following attributes are
26340 defined for a given thread:
26344 This field exists only for the current thread. It has the value @samp{*}.
26347 The identifier that @value{GDBN} uses to refer to the thread.
26350 The identifier that the target uses to refer to the thread.
26353 Extra information about the thread, in a target-specific format. This
26357 The name of the thread. If the user specified a name using the
26358 @code{thread name} command, then this name is given. Otherwise, if
26359 @value{GDBN} can extract the thread name from the target, then that
26360 name is given. If @value{GDBN} cannot find the thread name, then this
26364 The stack frame currently executing in the thread.
26367 The thread's state. The @samp{state} field may have the following
26372 The thread is stopped. Frame information is available for stopped
26376 The thread is running. There's no frame information for running
26382 If @value{GDBN} can find the CPU core on which this thread is running,
26383 then this field is the core identifier. This field is optional.
26387 @subsubheading Example
26392 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26393 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26394 args=[]@},state="running"@},
26395 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26396 frame=@{level="0",addr="0x0804891f",func="foo",
26397 args=[@{name="i",value="10"@}],
26398 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26399 state="running"@}],
26400 current-thread-id="1"
26404 @subheading The @code{-thread-list-ids} Command
26405 @findex -thread-list-ids
26407 @subsubheading Synopsis
26413 Produces a list of the currently known @value{GDBN} thread ids. At the
26414 end of the list it also prints the total number of such threads.
26416 This command is retained for historical reasons, the
26417 @code{-thread-info} command should be used instead.
26419 @subsubheading @value{GDBN} Command
26421 Part of @samp{info threads} supplies the same information.
26423 @subsubheading Example
26428 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26429 current-thread-id="1",number-of-threads="3"
26434 @subheading The @code{-thread-select} Command
26435 @findex -thread-select
26437 @subsubheading Synopsis
26440 -thread-select @var{threadnum}
26443 Make @var{threadnum} the current thread. It prints the number of the new
26444 current thread, and the topmost frame for that thread.
26446 This command is deprecated in favor of explicitly using the
26447 @samp{--thread} option to each command.
26449 @subsubheading @value{GDBN} Command
26451 The corresponding @value{GDBN} command is @samp{thread}.
26453 @subsubheading Example
26460 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26461 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26465 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26466 number-of-threads="3"
26469 ^done,new-thread-id="3",
26470 frame=@{level="0",func="vprintf",
26471 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26472 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26476 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26477 @node GDB/MI Program Execution
26478 @section @sc{gdb/mi} Program Execution
26480 These are the asynchronous commands which generate the out-of-band
26481 record @samp{*stopped}. Currently @value{GDBN} only really executes
26482 asynchronously with remote targets and this interaction is mimicked in
26485 @subheading The @code{-exec-continue} Command
26486 @findex -exec-continue
26488 @subsubheading Synopsis
26491 -exec-continue [--reverse] [--all|--thread-group N]
26494 Resumes the execution of the inferior program, which will continue
26495 to execute until it reaches a debugger stop event. If the
26496 @samp{--reverse} option is specified, execution resumes in reverse until
26497 it reaches a stop event. Stop events may include
26500 breakpoints or watchpoints
26502 signals or exceptions
26504 the end of the process (or its beginning under @samp{--reverse})
26506 the end or beginning of a replay log if one is being used.
26508 In all-stop mode (@pxref{All-Stop
26509 Mode}), may resume only one thread, or all threads, depending on the
26510 value of the @samp{scheduler-locking} variable. If @samp{--all} is
26511 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
26512 ignored in all-stop mode. If the @samp{--thread-group} options is
26513 specified, then all threads in that thread group are resumed.
26515 @subsubheading @value{GDBN} Command
26517 The corresponding @value{GDBN} corresponding is @samp{continue}.
26519 @subsubheading Example
26526 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
26527 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
26533 @subheading The @code{-exec-finish} Command
26534 @findex -exec-finish
26536 @subsubheading Synopsis
26539 -exec-finish [--reverse]
26542 Resumes the execution of the inferior program until the current
26543 function is exited. Displays the results returned by the function.
26544 If the @samp{--reverse} option is specified, resumes the reverse
26545 execution of the inferior program until the point where current
26546 function was called.
26548 @subsubheading @value{GDBN} Command
26550 The corresponding @value{GDBN} command is @samp{finish}.
26552 @subsubheading Example
26554 Function returning @code{void}.
26561 *stopped,reason="function-finished",frame=@{func="main",args=[],
26562 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
26566 Function returning other than @code{void}. The name of the internal
26567 @value{GDBN} variable storing the result is printed, together with the
26574 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
26575 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
26576 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26577 gdb-result-var="$1",return-value="0"
26582 @subheading The @code{-exec-interrupt} Command
26583 @findex -exec-interrupt
26585 @subsubheading Synopsis
26588 -exec-interrupt [--all|--thread-group N]
26591 Interrupts the background execution of the target. Note how the token
26592 associated with the stop message is the one for the execution command
26593 that has been interrupted. The token for the interrupt itself only
26594 appears in the @samp{^done} output. If the user is trying to
26595 interrupt a non-running program, an error message will be printed.
26597 Note that when asynchronous execution is enabled, this command is
26598 asynchronous just like other execution commands. That is, first the
26599 @samp{^done} response will be printed, and the target stop will be
26600 reported after that using the @samp{*stopped} notification.
26602 In non-stop mode, only the context thread is interrupted by default.
26603 All threads (in all inferiors) will be interrupted if the
26604 @samp{--all} option is specified. If the @samp{--thread-group}
26605 option is specified, all threads in that group will be interrupted.
26607 @subsubheading @value{GDBN} Command
26609 The corresponding @value{GDBN} command is @samp{interrupt}.
26611 @subsubheading Example
26622 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
26623 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
26624 fullname="/home/foo/bar/try.c",line="13"@}
26629 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
26633 @subheading The @code{-exec-jump} Command
26636 @subsubheading Synopsis
26639 -exec-jump @var{location}
26642 Resumes execution of the inferior program at the location specified by
26643 parameter. @xref{Specify Location}, for a description of the
26644 different forms of @var{location}.
26646 @subsubheading @value{GDBN} Command
26648 The corresponding @value{GDBN} command is @samp{jump}.
26650 @subsubheading Example
26653 -exec-jump foo.c:10
26654 *running,thread-id="all"
26659 @subheading The @code{-exec-next} Command
26662 @subsubheading Synopsis
26665 -exec-next [--reverse]
26668 Resumes execution of the inferior program, stopping when the beginning
26669 of the next source line is reached.
26671 If the @samp{--reverse} option is specified, resumes reverse execution
26672 of the inferior program, stopping at the beginning of the previous
26673 source line. If you issue this command on the first line of a
26674 function, it will take you back to the caller of that function, to the
26675 source line where the function was called.
26678 @subsubheading @value{GDBN} Command
26680 The corresponding @value{GDBN} command is @samp{next}.
26682 @subsubheading Example
26688 *stopped,reason="end-stepping-range",line="8",file="hello.c"
26693 @subheading The @code{-exec-next-instruction} Command
26694 @findex -exec-next-instruction
26696 @subsubheading Synopsis
26699 -exec-next-instruction [--reverse]
26702 Executes one machine instruction. If the instruction is a function
26703 call, continues until the function returns. If the program stops at an
26704 instruction in the middle of a source line, the address will be
26707 If the @samp{--reverse} option is specified, resumes reverse execution
26708 of the inferior program, stopping at the previous instruction. If the
26709 previously executed instruction was a return from another function,
26710 it will continue to execute in reverse until the call to that function
26711 (from the current stack frame) is reached.
26713 @subsubheading @value{GDBN} Command
26715 The corresponding @value{GDBN} command is @samp{nexti}.
26717 @subsubheading Example
26721 -exec-next-instruction
26725 *stopped,reason="end-stepping-range",
26726 addr="0x000100d4",line="5",file="hello.c"
26731 @subheading The @code{-exec-return} Command
26732 @findex -exec-return
26734 @subsubheading Synopsis
26740 Makes current function return immediately. Doesn't execute the inferior.
26741 Displays the new current frame.
26743 @subsubheading @value{GDBN} Command
26745 The corresponding @value{GDBN} command is @samp{return}.
26747 @subsubheading Example
26751 200-break-insert callee4
26752 200^done,bkpt=@{number="1",addr="0x00010734",
26753 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26758 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26759 frame=@{func="callee4",args=[],
26760 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26761 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26767 111^done,frame=@{level="0",func="callee3",
26768 args=[@{name="strarg",
26769 value="0x11940 \"A string argument.\""@}],
26770 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26771 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26776 @subheading The @code{-exec-run} Command
26779 @subsubheading Synopsis
26782 -exec-run [--all | --thread-group N]
26785 Starts execution of the inferior from the beginning. The inferior
26786 executes until either a breakpoint is encountered or the program
26787 exits. In the latter case the output will include an exit code, if
26788 the program has exited exceptionally.
26790 When no option is specified, the current inferior is started. If the
26791 @samp{--thread-group} option is specified, it should refer to a thread
26792 group of type @samp{process}, and that thread group will be started.
26793 If the @samp{--all} option is specified, then all inferiors will be started.
26795 @subsubheading @value{GDBN} Command
26797 The corresponding @value{GDBN} command is @samp{run}.
26799 @subsubheading Examples
26804 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26809 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26810 frame=@{func="main",args=[],file="recursive2.c",
26811 fullname="/home/foo/bar/recursive2.c",line="4"@}
26816 Program exited normally:
26824 *stopped,reason="exited-normally"
26829 Program exited exceptionally:
26837 *stopped,reason="exited",exit-code="01"
26841 Another way the program can terminate is if it receives a signal such as
26842 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
26846 *stopped,reason="exited-signalled",signal-name="SIGINT",
26847 signal-meaning="Interrupt"
26851 @c @subheading -exec-signal
26854 @subheading The @code{-exec-step} Command
26857 @subsubheading Synopsis
26860 -exec-step [--reverse]
26863 Resumes execution of the inferior program, stopping when the beginning
26864 of the next source line is reached, if the next source line is not a
26865 function call. If it is, stop at the first instruction of the called
26866 function. If the @samp{--reverse} option is specified, resumes reverse
26867 execution of the inferior program, stopping at the beginning of the
26868 previously executed source line.
26870 @subsubheading @value{GDBN} Command
26872 The corresponding @value{GDBN} command is @samp{step}.
26874 @subsubheading Example
26876 Stepping into a function:
26882 *stopped,reason="end-stepping-range",
26883 frame=@{func="foo",args=[@{name="a",value="10"@},
26884 @{name="b",value="0"@}],file="recursive2.c",
26885 fullname="/home/foo/bar/recursive2.c",line="11"@}
26895 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
26900 @subheading The @code{-exec-step-instruction} Command
26901 @findex -exec-step-instruction
26903 @subsubheading Synopsis
26906 -exec-step-instruction [--reverse]
26909 Resumes the inferior which executes one machine instruction. If the
26910 @samp{--reverse} option is specified, resumes reverse execution of the
26911 inferior program, stopping at the previously executed instruction.
26912 The output, once @value{GDBN} has stopped, will vary depending on
26913 whether we have stopped in the middle of a source line or not. In the
26914 former case, the address at which the program stopped will be printed
26917 @subsubheading @value{GDBN} Command
26919 The corresponding @value{GDBN} command is @samp{stepi}.
26921 @subsubheading Example
26925 -exec-step-instruction
26929 *stopped,reason="end-stepping-range",
26930 frame=@{func="foo",args=[],file="try.c",
26931 fullname="/home/foo/bar/try.c",line="10"@}
26933 -exec-step-instruction
26937 *stopped,reason="end-stepping-range",
26938 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
26939 fullname="/home/foo/bar/try.c",line="10"@}
26944 @subheading The @code{-exec-until} Command
26945 @findex -exec-until
26947 @subsubheading Synopsis
26950 -exec-until [ @var{location} ]
26953 Executes the inferior until the @var{location} specified in the
26954 argument is reached. If there is no argument, the inferior executes
26955 until a source line greater than the current one is reached. The
26956 reason for stopping in this case will be @samp{location-reached}.
26958 @subsubheading @value{GDBN} Command
26960 The corresponding @value{GDBN} command is @samp{until}.
26962 @subsubheading Example
26966 -exec-until recursive2.c:6
26970 *stopped,reason="location-reached",frame=@{func="main",args=[],
26971 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
26976 @subheading -file-clear
26977 Is this going away????
26980 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26981 @node GDB/MI Stack Manipulation
26982 @section @sc{gdb/mi} Stack Manipulation Commands
26985 @subheading The @code{-stack-info-frame} Command
26986 @findex -stack-info-frame
26988 @subsubheading Synopsis
26994 Get info on the selected frame.
26996 @subsubheading @value{GDBN} Command
26998 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26999 (without arguments).
27001 @subsubheading Example
27006 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27007 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27008 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27012 @subheading The @code{-stack-info-depth} Command
27013 @findex -stack-info-depth
27015 @subsubheading Synopsis
27018 -stack-info-depth [ @var{max-depth} ]
27021 Return the depth of the stack. If the integer argument @var{max-depth}
27022 is specified, do not count beyond @var{max-depth} frames.
27024 @subsubheading @value{GDBN} Command
27026 There's no equivalent @value{GDBN} command.
27028 @subsubheading Example
27030 For a stack with frame levels 0 through 11:
27037 -stack-info-depth 4
27040 -stack-info-depth 12
27043 -stack-info-depth 11
27046 -stack-info-depth 13
27051 @subheading The @code{-stack-list-arguments} Command
27052 @findex -stack-list-arguments
27054 @subsubheading Synopsis
27057 -stack-list-arguments @var{print-values}
27058 [ @var{low-frame} @var{high-frame} ]
27061 Display a list of the arguments for the frames between @var{low-frame}
27062 and @var{high-frame} (inclusive). If @var{low-frame} and
27063 @var{high-frame} are not provided, list the arguments for the whole
27064 call stack. If the two arguments are equal, show the single frame
27065 at the corresponding level. It is an error if @var{low-frame} is
27066 larger than the actual number of frames. On the other hand,
27067 @var{high-frame} may be larger than the actual number of frames, in
27068 which case only existing frames will be returned.
27070 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27071 the variables; if it is 1 or @code{--all-values}, print also their
27072 values; and if it is 2 or @code{--simple-values}, print the name,
27073 type and value for simple data types, and the name and type for arrays,
27074 structures and unions.
27076 Use of this command to obtain arguments in a single frame is
27077 deprecated in favor of the @samp{-stack-list-variables} command.
27079 @subsubheading @value{GDBN} Command
27081 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27082 @samp{gdb_get_args} command which partially overlaps with the
27083 functionality of @samp{-stack-list-arguments}.
27085 @subsubheading Example
27092 frame=@{level="0",addr="0x00010734",func="callee4",
27093 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27094 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27095 frame=@{level="1",addr="0x0001076c",func="callee3",
27096 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27097 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27098 frame=@{level="2",addr="0x0001078c",func="callee2",
27099 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27100 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27101 frame=@{level="3",addr="0x000107b4",func="callee1",
27102 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27103 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27104 frame=@{level="4",addr="0x000107e0",func="main",
27105 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27106 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27108 -stack-list-arguments 0
27111 frame=@{level="0",args=[]@},
27112 frame=@{level="1",args=[name="strarg"]@},
27113 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27114 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27115 frame=@{level="4",args=[]@}]
27117 -stack-list-arguments 1
27120 frame=@{level="0",args=[]@},
27122 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27123 frame=@{level="2",args=[
27124 @{name="intarg",value="2"@},
27125 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27126 @{frame=@{level="3",args=[
27127 @{name="intarg",value="2"@},
27128 @{name="strarg",value="0x11940 \"A string argument.\""@},
27129 @{name="fltarg",value="3.5"@}]@},
27130 frame=@{level="4",args=[]@}]
27132 -stack-list-arguments 0 2 2
27133 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27135 -stack-list-arguments 1 2 2
27136 ^done,stack-args=[frame=@{level="2",
27137 args=[@{name="intarg",value="2"@},
27138 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27142 @c @subheading -stack-list-exception-handlers
27145 @subheading The @code{-stack-list-frames} Command
27146 @findex -stack-list-frames
27148 @subsubheading Synopsis
27151 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
27154 List the frames currently on the stack. For each frame it displays the
27159 The frame number, 0 being the topmost frame, i.e., the innermost function.
27161 The @code{$pc} value for that frame.
27165 File name of the source file where the function lives.
27166 @item @var{fullname}
27167 The full file name of the source file where the function lives.
27169 Line number corresponding to the @code{$pc}.
27171 The shared library where this function is defined. This is only given
27172 if the frame's function is not known.
27175 If invoked without arguments, this command prints a backtrace for the
27176 whole stack. If given two integer arguments, it shows the frames whose
27177 levels are between the two arguments (inclusive). If the two arguments
27178 are equal, it shows the single frame at the corresponding level. It is
27179 an error if @var{low-frame} is larger than the actual number of
27180 frames. On the other hand, @var{high-frame} may be larger than the
27181 actual number of frames, in which case only existing frames will be returned.
27183 @subsubheading @value{GDBN} Command
27185 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27187 @subsubheading Example
27189 Full stack backtrace:
27195 [frame=@{level="0",addr="0x0001076c",func="foo",
27196 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27197 frame=@{level="1",addr="0x000107a4",func="foo",
27198 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27199 frame=@{level="2",addr="0x000107a4",func="foo",
27200 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27201 frame=@{level="3",addr="0x000107a4",func="foo",
27202 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27203 frame=@{level="4",addr="0x000107a4",func="foo",
27204 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27205 frame=@{level="5",addr="0x000107a4",func="foo",
27206 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27207 frame=@{level="6",addr="0x000107a4",func="foo",
27208 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27209 frame=@{level="7",addr="0x000107a4",func="foo",
27210 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27211 frame=@{level="8",addr="0x000107a4",func="foo",
27212 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27213 frame=@{level="9",addr="0x000107a4",func="foo",
27214 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27215 frame=@{level="10",addr="0x000107a4",func="foo",
27216 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27217 frame=@{level="11",addr="0x00010738",func="main",
27218 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27222 Show frames between @var{low_frame} and @var{high_frame}:
27226 -stack-list-frames 3 5
27228 [frame=@{level="3",addr="0x000107a4",func="foo",
27229 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27230 frame=@{level="4",addr="0x000107a4",func="foo",
27231 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27232 frame=@{level="5",addr="0x000107a4",func="foo",
27233 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27237 Show a single frame:
27241 -stack-list-frames 3 3
27243 [frame=@{level="3",addr="0x000107a4",func="foo",
27244 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27249 @subheading The @code{-stack-list-locals} Command
27250 @findex -stack-list-locals
27252 @subsubheading Synopsis
27255 -stack-list-locals @var{print-values}
27258 Display the local variable names for the selected frame. If
27259 @var{print-values} is 0 or @code{--no-values}, print only the names of
27260 the variables; if it is 1 or @code{--all-values}, print also their
27261 values; and if it is 2 or @code{--simple-values}, print the name,
27262 type and value for simple data types, and the name and type for arrays,
27263 structures and unions. In this last case, a frontend can immediately
27264 display the value of simple data types and create variable objects for
27265 other data types when the user wishes to explore their values in
27268 This command is deprecated in favor of the
27269 @samp{-stack-list-variables} command.
27271 @subsubheading @value{GDBN} Command
27273 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27275 @subsubheading Example
27279 -stack-list-locals 0
27280 ^done,locals=[name="A",name="B",name="C"]
27282 -stack-list-locals --all-values
27283 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27284 @{name="C",value="@{1, 2, 3@}"@}]
27285 -stack-list-locals --simple-values
27286 ^done,locals=[@{name="A",type="int",value="1"@},
27287 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27291 @subheading The @code{-stack-list-variables} Command
27292 @findex -stack-list-variables
27294 @subsubheading Synopsis
27297 -stack-list-variables @var{print-values}
27300 Display the names of local variables and function arguments for the selected frame. If
27301 @var{print-values} is 0 or @code{--no-values}, print only the names of
27302 the variables; if it is 1 or @code{--all-values}, print also their
27303 values; and if it is 2 or @code{--simple-values}, print the name,
27304 type and value for simple data types, and the name and type for arrays,
27305 structures and unions.
27307 @subsubheading Example
27311 -stack-list-variables --thread 1 --frame 0 --all-values
27312 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27317 @subheading The @code{-stack-select-frame} Command
27318 @findex -stack-select-frame
27320 @subsubheading Synopsis
27323 -stack-select-frame @var{framenum}
27326 Change the selected frame. Select a different frame @var{framenum} on
27329 This command in deprecated in favor of passing the @samp{--frame}
27330 option to every command.
27332 @subsubheading @value{GDBN} Command
27334 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27335 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27337 @subsubheading Example
27341 -stack-select-frame 2
27346 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27347 @node GDB/MI Variable Objects
27348 @section @sc{gdb/mi} Variable Objects
27352 @subheading Motivation for Variable Objects in @sc{gdb/mi}
27354 For the implementation of a variable debugger window (locals, watched
27355 expressions, etc.), we are proposing the adaptation of the existing code
27356 used by @code{Insight}.
27358 The two main reasons for that are:
27362 It has been proven in practice (it is already on its second generation).
27365 It will shorten development time (needless to say how important it is
27369 The original interface was designed to be used by Tcl code, so it was
27370 slightly changed so it could be used through @sc{gdb/mi}. This section
27371 describes the @sc{gdb/mi} operations that will be available and gives some
27372 hints about their use.
27374 @emph{Note}: In addition to the set of operations described here, we
27375 expect the @sc{gui} implementation of a variable window to require, at
27376 least, the following operations:
27379 @item @code{-gdb-show} @code{output-radix}
27380 @item @code{-stack-list-arguments}
27381 @item @code{-stack-list-locals}
27382 @item @code{-stack-select-frame}
27387 @subheading Introduction to Variable Objects
27389 @cindex variable objects in @sc{gdb/mi}
27391 Variable objects are "object-oriented" MI interface for examining and
27392 changing values of expressions. Unlike some other MI interfaces that
27393 work with expressions, variable objects are specifically designed for
27394 simple and efficient presentation in the frontend. A variable object
27395 is identified by string name. When a variable object is created, the
27396 frontend specifies the expression for that variable object. The
27397 expression can be a simple variable, or it can be an arbitrary complex
27398 expression, and can even involve CPU registers. After creating a
27399 variable object, the frontend can invoke other variable object
27400 operations---for example to obtain or change the value of a variable
27401 object, or to change display format.
27403 Variable objects have hierarchical tree structure. Any variable object
27404 that corresponds to a composite type, such as structure in C, has
27405 a number of child variable objects, for example corresponding to each
27406 element of a structure. A child variable object can itself have
27407 children, recursively. Recursion ends when we reach
27408 leaf variable objects, which always have built-in types. Child variable
27409 objects are created only by explicit request, so if a frontend
27410 is not interested in the children of a particular variable object, no
27411 child will be created.
27413 For a leaf variable object it is possible to obtain its value as a
27414 string, or set the value from a string. String value can be also
27415 obtained for a non-leaf variable object, but it's generally a string
27416 that only indicates the type of the object, and does not list its
27417 contents. Assignment to a non-leaf variable object is not allowed.
27419 A frontend does not need to read the values of all variable objects each time
27420 the program stops. Instead, MI provides an update command that lists all
27421 variable objects whose values has changed since the last update
27422 operation. This considerably reduces the amount of data that must
27423 be transferred to the frontend. As noted above, children variable
27424 objects are created on demand, and only leaf variable objects have a
27425 real value. As result, gdb will read target memory only for leaf
27426 variables that frontend has created.
27428 The automatic update is not always desirable. For example, a frontend
27429 might want to keep a value of some expression for future reference,
27430 and never update it. For another example, fetching memory is
27431 relatively slow for embedded targets, so a frontend might want
27432 to disable automatic update for the variables that are either not
27433 visible on the screen, or ``closed''. This is possible using so
27434 called ``frozen variable objects''. Such variable objects are never
27435 implicitly updated.
27437 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
27438 fixed variable object, the expression is parsed when the variable
27439 object is created, including associating identifiers to specific
27440 variables. The meaning of expression never changes. For a floating
27441 variable object the values of variables whose names appear in the
27442 expressions are re-evaluated every time in the context of the current
27443 frame. Consider this example:
27448 struct work_state state;
27455 If a fixed variable object for the @code{state} variable is created in
27456 this function, and we enter the recursive call, the variable
27457 object will report the value of @code{state} in the top-level
27458 @code{do_work} invocation. On the other hand, a floating variable
27459 object will report the value of @code{state} in the current frame.
27461 If an expression specified when creating a fixed variable object
27462 refers to a local variable, the variable object becomes bound to the
27463 thread and frame in which the variable object is created. When such
27464 variable object is updated, @value{GDBN} makes sure that the
27465 thread/frame combination the variable object is bound to still exists,
27466 and re-evaluates the variable object in context of that thread/frame.
27468 The following is the complete set of @sc{gdb/mi} operations defined to
27469 access this functionality:
27471 @multitable @columnfractions .4 .6
27472 @item @strong{Operation}
27473 @tab @strong{Description}
27475 @item @code{-enable-pretty-printing}
27476 @tab enable Python-based pretty-printing
27477 @item @code{-var-create}
27478 @tab create a variable object
27479 @item @code{-var-delete}
27480 @tab delete the variable object and/or its children
27481 @item @code{-var-set-format}
27482 @tab set the display format of this variable
27483 @item @code{-var-show-format}
27484 @tab show the display format of this variable
27485 @item @code{-var-info-num-children}
27486 @tab tells how many children this object has
27487 @item @code{-var-list-children}
27488 @tab return a list of the object's children
27489 @item @code{-var-info-type}
27490 @tab show the type of this variable object
27491 @item @code{-var-info-expression}
27492 @tab print parent-relative expression that this variable object represents
27493 @item @code{-var-info-path-expression}
27494 @tab print full expression that this variable object represents
27495 @item @code{-var-show-attributes}
27496 @tab is this variable editable? does it exist here?
27497 @item @code{-var-evaluate-expression}
27498 @tab get the value of this variable
27499 @item @code{-var-assign}
27500 @tab set the value of this variable
27501 @item @code{-var-update}
27502 @tab update the variable and its children
27503 @item @code{-var-set-frozen}
27504 @tab set frozeness attribute
27505 @item @code{-var-set-update-range}
27506 @tab set range of children to display on update
27509 In the next subsection we describe each operation in detail and suggest
27510 how it can be used.
27512 @subheading Description And Use of Operations on Variable Objects
27514 @subheading The @code{-enable-pretty-printing} Command
27515 @findex -enable-pretty-printing
27518 -enable-pretty-printing
27521 @value{GDBN} allows Python-based visualizers to affect the output of the
27522 MI variable object commands. However, because there was no way to
27523 implement this in a fully backward-compatible way, a front end must
27524 request that this functionality be enabled.
27526 Once enabled, this feature cannot be disabled.
27528 Note that if Python support has not been compiled into @value{GDBN},
27529 this command will still succeed (and do nothing).
27531 This feature is currently (as of @value{GDBN} 7.0) experimental, and
27532 may work differently in future versions of @value{GDBN}.
27534 @subheading The @code{-var-create} Command
27535 @findex -var-create
27537 @subsubheading Synopsis
27540 -var-create @{@var{name} | "-"@}
27541 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
27544 This operation creates a variable object, which allows the monitoring of
27545 a variable, the result of an expression, a memory cell or a CPU
27548 The @var{name} parameter is the string by which the object can be
27549 referenced. It must be unique. If @samp{-} is specified, the varobj
27550 system will generate a string ``varNNNNNN'' automatically. It will be
27551 unique provided that one does not specify @var{name} of that format.
27552 The command fails if a duplicate name is found.
27554 The frame under which the expression should be evaluated can be
27555 specified by @var{frame-addr}. A @samp{*} indicates that the current
27556 frame should be used. A @samp{@@} indicates that a floating variable
27557 object must be created.
27559 @var{expression} is any expression valid on the current language set (must not
27560 begin with a @samp{*}), or one of the following:
27564 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
27567 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
27570 @samp{$@var{regname}} --- a CPU register name
27573 @cindex dynamic varobj
27574 A varobj's contents may be provided by a Python-based pretty-printer. In this
27575 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
27576 have slightly different semantics in some cases. If the
27577 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
27578 will never create a dynamic varobj. This ensures backward
27579 compatibility for existing clients.
27581 @subsubheading Result
27583 This operation returns attributes of the newly-created varobj. These
27588 The name of the varobj.
27591 The number of children of the varobj. This number is not necessarily
27592 reliable for a dynamic varobj. Instead, you must examine the
27593 @samp{has_more} attribute.
27596 The varobj's scalar value. For a varobj whose type is some sort of
27597 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
27598 will not be interesting.
27601 The varobj's type. This is a string representation of the type, as
27602 would be printed by the @value{GDBN} CLI.
27605 If a variable object is bound to a specific thread, then this is the
27606 thread's identifier.
27609 For a dynamic varobj, this indicates whether there appear to be any
27610 children available. For a non-dynamic varobj, this will be 0.
27613 This attribute will be present and have the value @samp{1} if the
27614 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27615 then this attribute will not be present.
27618 A dynamic varobj can supply a display hint to the front end. The
27619 value comes directly from the Python pretty-printer object's
27620 @code{display_hint} method. @xref{Pretty Printing API}.
27623 Typical output will look like this:
27626 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
27627 has_more="@var{has_more}"
27631 @subheading The @code{-var-delete} Command
27632 @findex -var-delete
27634 @subsubheading Synopsis
27637 -var-delete [ -c ] @var{name}
27640 Deletes a previously created variable object and all of its children.
27641 With the @samp{-c} option, just deletes the children.
27643 Returns an error if the object @var{name} is not found.
27646 @subheading The @code{-var-set-format} Command
27647 @findex -var-set-format
27649 @subsubheading Synopsis
27652 -var-set-format @var{name} @var{format-spec}
27655 Sets the output format for the value of the object @var{name} to be
27658 @anchor{-var-set-format}
27659 The syntax for the @var{format-spec} is as follows:
27662 @var{format-spec} @expansion{}
27663 @{binary | decimal | hexadecimal | octal | natural@}
27666 The natural format is the default format choosen automatically
27667 based on the variable type (like decimal for an @code{int}, hex
27668 for pointers, etc.).
27670 For a variable with children, the format is set only on the
27671 variable itself, and the children are not affected.
27673 @subheading The @code{-var-show-format} Command
27674 @findex -var-show-format
27676 @subsubheading Synopsis
27679 -var-show-format @var{name}
27682 Returns the format used to display the value of the object @var{name}.
27685 @var{format} @expansion{}
27690 @subheading The @code{-var-info-num-children} Command
27691 @findex -var-info-num-children
27693 @subsubheading Synopsis
27696 -var-info-num-children @var{name}
27699 Returns the number of children of a variable object @var{name}:
27705 Note that this number is not completely reliable for a dynamic varobj.
27706 It will return the current number of children, but more children may
27710 @subheading The @code{-var-list-children} Command
27711 @findex -var-list-children
27713 @subsubheading Synopsis
27716 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
27718 @anchor{-var-list-children}
27720 Return a list of the children of the specified variable object and
27721 create variable objects for them, if they do not already exist. With
27722 a single argument or if @var{print-values} has a value of 0 or
27723 @code{--no-values}, print only the names of the variables; if
27724 @var{print-values} is 1 or @code{--all-values}, also print their
27725 values; and if it is 2 or @code{--simple-values} print the name and
27726 value for simple data types and just the name for arrays, structures
27729 @var{from} and @var{to}, if specified, indicate the range of children
27730 to report. If @var{from} or @var{to} is less than zero, the range is
27731 reset and all children will be reported. Otherwise, children starting
27732 at @var{from} (zero-based) and up to and excluding @var{to} will be
27735 If a child range is requested, it will only affect the current call to
27736 @code{-var-list-children}, but not future calls to @code{-var-update}.
27737 For this, you must instead use @code{-var-set-update-range}. The
27738 intent of this approach is to enable a front end to implement any
27739 update approach it likes; for example, scrolling a view may cause the
27740 front end to request more children with @code{-var-list-children}, and
27741 then the front end could call @code{-var-set-update-range} with a
27742 different range to ensure that future updates are restricted to just
27745 For each child the following results are returned:
27750 Name of the variable object created for this child.
27753 The expression to be shown to the user by the front end to designate this child.
27754 For example this may be the name of a structure member.
27756 For a dynamic varobj, this value cannot be used to form an
27757 expression. There is no way to do this at all with a dynamic varobj.
27759 For C/C@t{++} structures there are several pseudo children returned to
27760 designate access qualifiers. For these pseudo children @var{exp} is
27761 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27762 type and value are not present.
27764 A dynamic varobj will not report the access qualifying
27765 pseudo-children, regardless of the language. This information is not
27766 available at all with a dynamic varobj.
27769 Number of children this child has. For a dynamic varobj, this will be
27773 The type of the child.
27776 If values were requested, this is the value.
27779 If this variable object is associated with a thread, this is the thread id.
27780 Otherwise this result is not present.
27783 If the variable object is frozen, this variable will be present with a value of 1.
27786 The result may have its own attributes:
27790 A dynamic varobj can supply a display hint to the front end. The
27791 value comes directly from the Python pretty-printer object's
27792 @code{display_hint} method. @xref{Pretty Printing API}.
27795 This is an integer attribute which is nonzero if there are children
27796 remaining after the end of the selected range.
27799 @subsubheading Example
27803 -var-list-children n
27804 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27805 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27807 -var-list-children --all-values n
27808 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27809 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27813 @subheading The @code{-var-info-type} Command
27814 @findex -var-info-type
27816 @subsubheading Synopsis
27819 -var-info-type @var{name}
27822 Returns the type of the specified variable @var{name}. The type is
27823 returned as a string in the same format as it is output by the
27827 type=@var{typename}
27831 @subheading The @code{-var-info-expression} Command
27832 @findex -var-info-expression
27834 @subsubheading Synopsis
27837 -var-info-expression @var{name}
27840 Returns a string that is suitable for presenting this
27841 variable object in user interface. The string is generally
27842 not valid expression in the current language, and cannot be evaluated.
27844 For example, if @code{a} is an array, and variable object
27845 @code{A} was created for @code{a}, then we'll get this output:
27848 (gdb) -var-info-expression A.1
27849 ^done,lang="C",exp="1"
27853 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
27855 Note that the output of the @code{-var-list-children} command also
27856 includes those expressions, so the @code{-var-info-expression} command
27859 @subheading The @code{-var-info-path-expression} Command
27860 @findex -var-info-path-expression
27862 @subsubheading Synopsis
27865 -var-info-path-expression @var{name}
27868 Returns an expression that can be evaluated in the current
27869 context and will yield the same value that a variable object has.
27870 Compare this with the @code{-var-info-expression} command, which
27871 result can be used only for UI presentation. Typical use of
27872 the @code{-var-info-path-expression} command is creating a
27873 watchpoint from a variable object.
27875 This command is currently not valid for children of a dynamic varobj,
27876 and will give an error when invoked on one.
27878 For example, suppose @code{C} is a C@t{++} class, derived from class
27879 @code{Base}, and that the @code{Base} class has a member called
27880 @code{m_size}. Assume a variable @code{c} is has the type of
27881 @code{C} and a variable object @code{C} was created for variable
27882 @code{c}. Then, we'll get this output:
27884 (gdb) -var-info-path-expression C.Base.public.m_size
27885 ^done,path_expr=((Base)c).m_size)
27888 @subheading The @code{-var-show-attributes} Command
27889 @findex -var-show-attributes
27891 @subsubheading Synopsis
27894 -var-show-attributes @var{name}
27897 List attributes of the specified variable object @var{name}:
27900 status=@var{attr} [ ( ,@var{attr} )* ]
27904 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
27906 @subheading The @code{-var-evaluate-expression} Command
27907 @findex -var-evaluate-expression
27909 @subsubheading Synopsis
27912 -var-evaluate-expression [-f @var{format-spec}] @var{name}
27915 Evaluates the expression that is represented by the specified variable
27916 object and returns its value as a string. The format of the string
27917 can be specified with the @samp{-f} option. The possible values of
27918 this option are the same as for @code{-var-set-format}
27919 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
27920 the current display format will be used. The current display format
27921 can be changed using the @code{-var-set-format} command.
27927 Note that one must invoke @code{-var-list-children} for a variable
27928 before the value of a child variable can be evaluated.
27930 @subheading The @code{-var-assign} Command
27931 @findex -var-assign
27933 @subsubheading Synopsis
27936 -var-assign @var{name} @var{expression}
27939 Assigns the value of @var{expression} to the variable object specified
27940 by @var{name}. The object must be @samp{editable}. If the variable's
27941 value is altered by the assign, the variable will show up in any
27942 subsequent @code{-var-update} list.
27944 @subsubheading Example
27952 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
27956 @subheading The @code{-var-update} Command
27957 @findex -var-update
27959 @subsubheading Synopsis
27962 -var-update [@var{print-values}] @{@var{name} | "*"@}
27965 Reevaluate the expressions corresponding to the variable object
27966 @var{name} and all its direct and indirect children, and return the
27967 list of variable objects whose values have changed; @var{name} must
27968 be a root variable object. Here, ``changed'' means that the result of
27969 @code{-var-evaluate-expression} before and after the
27970 @code{-var-update} is different. If @samp{*} is used as the variable
27971 object names, all existing variable objects are updated, except
27972 for frozen ones (@pxref{-var-set-frozen}). The option
27973 @var{print-values} determines whether both names and values, or just
27974 names are printed. The possible values of this option are the same
27975 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
27976 recommended to use the @samp{--all-values} option, to reduce the
27977 number of MI commands needed on each program stop.
27979 With the @samp{*} parameter, if a variable object is bound to a
27980 currently running thread, it will not be updated, without any
27983 If @code{-var-set-update-range} was previously used on a varobj, then
27984 only the selected range of children will be reported.
27986 @code{-var-update} reports all the changed varobjs in a tuple named
27989 Each item in the change list is itself a tuple holding:
27993 The name of the varobj.
27996 If values were requested for this update, then this field will be
27997 present and will hold the value of the varobj.
28000 @anchor{-var-update}
28001 This field is a string which may take one of three values:
28005 The variable object's current value is valid.
28008 The variable object does not currently hold a valid value but it may
28009 hold one in the future if its associated expression comes back into
28013 The variable object no longer holds a valid value.
28014 This can occur when the executable file being debugged has changed,
28015 either through recompilation or by using the @value{GDBN} @code{file}
28016 command. The front end should normally choose to delete these variable
28020 In the future new values may be added to this list so the front should
28021 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28024 This is only present if the varobj is still valid. If the type
28025 changed, then this will be the string @samp{true}; otherwise it will
28029 If the varobj's type changed, then this field will be present and will
28032 @item new_num_children
28033 For a dynamic varobj, if the number of children changed, or if the
28034 type changed, this will be the new number of children.
28036 The @samp{numchild} field in other varobj responses is generally not
28037 valid for a dynamic varobj -- it will show the number of children that
28038 @value{GDBN} knows about, but because dynamic varobjs lazily
28039 instantiate their children, this will not reflect the number of
28040 children which may be available.
28042 The @samp{new_num_children} attribute only reports changes to the
28043 number of children known by @value{GDBN}. This is the only way to
28044 detect whether an update has removed children (which necessarily can
28045 only happen at the end of the update range).
28048 The display hint, if any.
28051 This is an integer value, which will be 1 if there are more children
28052 available outside the varobj's update range.
28055 This attribute will be present and have the value @samp{1} if the
28056 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28057 then this attribute will not be present.
28060 If new children were added to a dynamic varobj within the selected
28061 update range (as set by @code{-var-set-update-range}), then they will
28062 be listed in this attribute.
28065 @subsubheading Example
28072 -var-update --all-values var1
28073 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28074 type_changed="false"@}]
28078 @subheading The @code{-var-set-frozen} Command
28079 @findex -var-set-frozen
28080 @anchor{-var-set-frozen}
28082 @subsubheading Synopsis
28085 -var-set-frozen @var{name} @var{flag}
28088 Set the frozenness flag on the variable object @var{name}. The
28089 @var{flag} parameter should be either @samp{1} to make the variable
28090 frozen or @samp{0} to make it unfrozen. If a variable object is
28091 frozen, then neither itself, nor any of its children, are
28092 implicitly updated by @code{-var-update} of
28093 a parent variable or by @code{-var-update *}. Only
28094 @code{-var-update} of the variable itself will update its value and
28095 values of its children. After a variable object is unfrozen, it is
28096 implicitly updated by all subsequent @code{-var-update} operations.
28097 Unfreezing a variable does not update it, only subsequent
28098 @code{-var-update} does.
28100 @subsubheading Example
28104 -var-set-frozen V 1
28109 @subheading The @code{-var-set-update-range} command
28110 @findex -var-set-update-range
28111 @anchor{-var-set-update-range}
28113 @subsubheading Synopsis
28116 -var-set-update-range @var{name} @var{from} @var{to}
28119 Set the range of children to be returned by future invocations of
28120 @code{-var-update}.
28122 @var{from} and @var{to} indicate the range of children to report. If
28123 @var{from} or @var{to} is less than zero, the range is reset and all
28124 children will be reported. Otherwise, children starting at @var{from}
28125 (zero-based) and up to and excluding @var{to} will be reported.
28127 @subsubheading Example
28131 -var-set-update-range V 1 2
28135 @subheading The @code{-var-set-visualizer} command
28136 @findex -var-set-visualizer
28137 @anchor{-var-set-visualizer}
28139 @subsubheading Synopsis
28142 -var-set-visualizer @var{name} @var{visualizer}
28145 Set a visualizer for the variable object @var{name}.
28147 @var{visualizer} is the visualizer to use. The special value
28148 @samp{None} means to disable any visualizer in use.
28150 If not @samp{None}, @var{visualizer} must be a Python expression.
28151 This expression must evaluate to a callable object which accepts a
28152 single argument. @value{GDBN} will call this object with the value of
28153 the varobj @var{name} as an argument (this is done so that the same
28154 Python pretty-printing code can be used for both the CLI and MI).
28155 When called, this object must return an object which conforms to the
28156 pretty-printing interface (@pxref{Pretty Printing API}).
28158 The pre-defined function @code{gdb.default_visualizer} may be used to
28159 select a visualizer by following the built-in process
28160 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28161 a varobj is created, and so ordinarily is not needed.
28163 This feature is only available if Python support is enabled. The MI
28164 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
28165 can be used to check this.
28167 @subsubheading Example
28169 Resetting the visualizer:
28173 -var-set-visualizer V None
28177 Reselecting the default (type-based) visualizer:
28181 -var-set-visualizer V gdb.default_visualizer
28185 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28186 can be used to instantiate this class for a varobj:
28190 -var-set-visualizer V "lambda val: SomeClass()"
28194 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28195 @node GDB/MI Data Manipulation
28196 @section @sc{gdb/mi} Data Manipulation
28198 @cindex data manipulation, in @sc{gdb/mi}
28199 @cindex @sc{gdb/mi}, data manipulation
28200 This section describes the @sc{gdb/mi} commands that manipulate data:
28201 examine memory and registers, evaluate expressions, etc.
28203 @c REMOVED FROM THE INTERFACE.
28204 @c @subheading -data-assign
28205 @c Change the value of a program variable. Plenty of side effects.
28206 @c @subsubheading GDB Command
28208 @c @subsubheading Example
28211 @subheading The @code{-data-disassemble} Command
28212 @findex -data-disassemble
28214 @subsubheading Synopsis
28218 [ -s @var{start-addr} -e @var{end-addr} ]
28219 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28227 @item @var{start-addr}
28228 is the beginning address (or @code{$pc})
28229 @item @var{end-addr}
28231 @item @var{filename}
28232 is the name of the file to disassemble
28233 @item @var{linenum}
28234 is the line number to disassemble around
28236 is the number of disassembly lines to be produced. If it is -1,
28237 the whole function will be disassembled, in case no @var{end-addr} is
28238 specified. If @var{end-addr} is specified as a non-zero value, and
28239 @var{lines} is lower than the number of disassembly lines between
28240 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28241 displayed; if @var{lines} is higher than the number of lines between
28242 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28245 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28246 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28247 mixed source and disassembly with raw opcodes).
28250 @subsubheading Result
28252 The output for each instruction is composed of four fields:
28261 Note that whatever included in the instruction field, is not manipulated
28262 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
28264 @subsubheading @value{GDBN} Command
28266 There's no direct mapping from this command to the CLI.
28268 @subsubheading Example
28270 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28274 -data-disassemble -s $pc -e "$pc + 20" -- 0
28277 @{address="0x000107c0",func-name="main",offset="4",
28278 inst="mov 2, %o0"@},
28279 @{address="0x000107c4",func-name="main",offset="8",
28280 inst="sethi %hi(0x11800), %o2"@},
28281 @{address="0x000107c8",func-name="main",offset="12",
28282 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
28283 @{address="0x000107cc",func-name="main",offset="16",
28284 inst="sethi %hi(0x11800), %o2"@},
28285 @{address="0x000107d0",func-name="main",offset="20",
28286 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
28290 Disassemble the whole @code{main} function. Line 32 is part of
28294 -data-disassemble -f basics.c -l 32 -- 0
28296 @{address="0x000107bc",func-name="main",offset="0",
28297 inst="save %sp, -112, %sp"@},
28298 @{address="0x000107c0",func-name="main",offset="4",
28299 inst="mov 2, %o0"@},
28300 @{address="0x000107c4",func-name="main",offset="8",
28301 inst="sethi %hi(0x11800), %o2"@},
28303 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
28304 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
28308 Disassemble 3 instructions from the start of @code{main}:
28312 -data-disassemble -f basics.c -l 32 -n 3 -- 0
28314 @{address="0x000107bc",func-name="main",offset="0",
28315 inst="save %sp, -112, %sp"@},
28316 @{address="0x000107c0",func-name="main",offset="4",
28317 inst="mov 2, %o0"@},
28318 @{address="0x000107c4",func-name="main",offset="8",
28319 inst="sethi %hi(0x11800), %o2"@}]
28323 Disassemble 3 instructions from the start of @code{main} in mixed mode:
28327 -data-disassemble -f basics.c -l 32 -n 3 -- 1
28329 src_and_asm_line=@{line="31",
28330 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28331 testsuite/gdb.mi/basics.c",line_asm_insn=[
28332 @{address="0x000107bc",func-name="main",offset="0",
28333 inst="save %sp, -112, %sp"@}]@},
28334 src_and_asm_line=@{line="32",
28335 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28336 testsuite/gdb.mi/basics.c",line_asm_insn=[
28337 @{address="0x000107c0",func-name="main",offset="4",
28338 inst="mov 2, %o0"@},
28339 @{address="0x000107c4",func-name="main",offset="8",
28340 inst="sethi %hi(0x11800), %o2"@}]@}]
28345 @subheading The @code{-data-evaluate-expression} Command
28346 @findex -data-evaluate-expression
28348 @subsubheading Synopsis
28351 -data-evaluate-expression @var{expr}
28354 Evaluate @var{expr} as an expression. The expression could contain an
28355 inferior function call. The function call will execute synchronously.
28356 If the expression contains spaces, it must be enclosed in double quotes.
28358 @subsubheading @value{GDBN} Command
28360 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
28361 @samp{call}. In @code{gdbtk} only, there's a corresponding
28362 @samp{gdb_eval} command.
28364 @subsubheading Example
28366 In the following example, the numbers that precede the commands are the
28367 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
28368 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
28372 211-data-evaluate-expression A
28375 311-data-evaluate-expression &A
28376 311^done,value="0xefffeb7c"
28378 411-data-evaluate-expression A+3
28381 511-data-evaluate-expression "A + 3"
28387 @subheading The @code{-data-list-changed-registers} Command
28388 @findex -data-list-changed-registers
28390 @subsubheading Synopsis
28393 -data-list-changed-registers
28396 Display a list of the registers that have changed.
28398 @subsubheading @value{GDBN} Command
28400 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
28401 has the corresponding command @samp{gdb_changed_register_list}.
28403 @subsubheading Example
28405 On a PPC MBX board:
28413 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
28414 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
28417 -data-list-changed-registers
28418 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
28419 "10","11","13","14","15","16","17","18","19","20","21","22","23",
28420 "24","25","26","27","28","30","31","64","65","66","67","69"]
28425 @subheading The @code{-data-list-register-names} Command
28426 @findex -data-list-register-names
28428 @subsubheading Synopsis
28431 -data-list-register-names [ ( @var{regno} )+ ]
28434 Show a list of register names for the current target. If no arguments
28435 are given, it shows a list of the names of all the registers. If
28436 integer numbers are given as arguments, it will print a list of the
28437 names of the registers corresponding to the arguments. To ensure
28438 consistency between a register name and its number, the output list may
28439 include empty register names.
28441 @subsubheading @value{GDBN} Command
28443 @value{GDBN} does not have a command which corresponds to
28444 @samp{-data-list-register-names}. In @code{gdbtk} there is a
28445 corresponding command @samp{gdb_regnames}.
28447 @subsubheading Example
28449 For the PPC MBX board:
28452 -data-list-register-names
28453 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
28454 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
28455 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
28456 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
28457 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
28458 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
28459 "", "pc","ps","cr","lr","ctr","xer"]
28461 -data-list-register-names 1 2 3
28462 ^done,register-names=["r1","r2","r3"]
28466 @subheading The @code{-data-list-register-values} Command
28467 @findex -data-list-register-values
28469 @subsubheading Synopsis
28472 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
28475 Display the registers' contents. @var{fmt} is the format according to
28476 which the registers' contents are to be returned, followed by an optional
28477 list of numbers specifying the registers to display. A missing list of
28478 numbers indicates that the contents of all the registers must be returned.
28480 Allowed formats for @var{fmt} are:
28497 @subsubheading @value{GDBN} Command
28499 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
28500 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
28502 @subsubheading Example
28504 For a PPC MBX board (note: line breaks are for readability only, they
28505 don't appear in the actual output):
28509 -data-list-register-values r 64 65
28510 ^done,register-values=[@{number="64",value="0xfe00a300"@},
28511 @{number="65",value="0x00029002"@}]
28513 -data-list-register-values x
28514 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
28515 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
28516 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
28517 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
28518 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
28519 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
28520 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
28521 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
28522 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
28523 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
28524 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
28525 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
28526 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
28527 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
28528 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
28529 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
28530 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
28531 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
28532 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
28533 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
28534 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
28535 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
28536 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
28537 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
28538 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
28539 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
28540 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
28541 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
28542 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
28543 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
28544 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
28545 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
28546 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
28547 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
28548 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
28549 @{number="69",value="0x20002b03"@}]
28554 @subheading The @code{-data-read-memory} Command
28555 @findex -data-read-memory
28557 This command is deprecated, use @code{-data-read-memory-bytes} instead.
28559 @subsubheading Synopsis
28562 -data-read-memory [ -o @var{byte-offset} ]
28563 @var{address} @var{word-format} @var{word-size}
28564 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
28571 @item @var{address}
28572 An expression specifying the address of the first memory word to be
28573 read. Complex expressions containing embedded white space should be
28574 quoted using the C convention.
28576 @item @var{word-format}
28577 The format to be used to print the memory words. The notation is the
28578 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
28581 @item @var{word-size}
28582 The size of each memory word in bytes.
28584 @item @var{nr-rows}
28585 The number of rows in the output table.
28587 @item @var{nr-cols}
28588 The number of columns in the output table.
28591 If present, indicates that each row should include an @sc{ascii} dump. The
28592 value of @var{aschar} is used as a padding character when a byte is not a
28593 member of the printable @sc{ascii} character set (printable @sc{ascii}
28594 characters are those whose code is between 32 and 126, inclusively).
28596 @item @var{byte-offset}
28597 An offset to add to the @var{address} before fetching memory.
28600 This command displays memory contents as a table of @var{nr-rows} by
28601 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
28602 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
28603 (returned as @samp{total-bytes}). Should less than the requested number
28604 of bytes be returned by the target, the missing words are identified
28605 using @samp{N/A}. The number of bytes read from the target is returned
28606 in @samp{nr-bytes} and the starting address used to read memory in
28609 The address of the next/previous row or page is available in
28610 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
28613 @subsubheading @value{GDBN} Command
28615 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
28616 @samp{gdb_get_mem} memory read command.
28618 @subsubheading Example
28620 Read six bytes of memory starting at @code{bytes+6} but then offset by
28621 @code{-6} bytes. Format as three rows of two columns. One byte per
28622 word. Display each word in hex.
28626 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
28627 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
28628 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
28629 prev-page="0x0000138a",memory=[
28630 @{addr="0x00001390",data=["0x00","0x01"]@},
28631 @{addr="0x00001392",data=["0x02","0x03"]@},
28632 @{addr="0x00001394",data=["0x04","0x05"]@}]
28636 Read two bytes of memory starting at address @code{shorts + 64} and
28637 display as a single word formatted in decimal.
28641 5-data-read-memory shorts+64 d 2 1 1
28642 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
28643 next-row="0x00001512",prev-row="0x0000150e",
28644 next-page="0x00001512",prev-page="0x0000150e",memory=[
28645 @{addr="0x00001510",data=["128"]@}]
28649 Read thirty two bytes of memory starting at @code{bytes+16} and format
28650 as eight rows of four columns. Include a string encoding with @samp{x}
28651 used as the non-printable character.
28655 4-data-read-memory bytes+16 x 1 8 4 x
28656 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
28657 next-row="0x000013c0",prev-row="0x0000139c",
28658 next-page="0x000013c0",prev-page="0x00001380",memory=[
28659 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
28660 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
28661 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
28662 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
28663 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
28664 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
28665 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
28666 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
28670 @subheading The @code{-data-read-memory-bytes} Command
28671 @findex -data-read-memory-bytes
28673 @subsubheading Synopsis
28676 -data-read-memory-bytes [ -o @var{byte-offset} ]
28677 @var{address} @var{count}
28684 @item @var{address}
28685 An expression specifying the address of the first memory word to be
28686 read. Complex expressions containing embedded white space should be
28687 quoted using the C convention.
28690 The number of bytes to read. This should be an integer literal.
28692 @item @var{byte-offset}
28693 The offsets in bytes relative to @var{address} at which to start
28694 reading. This should be an integer literal. This option is provided
28695 so that a frontend is not required to first evaluate address and then
28696 perform address arithmetics itself.
28700 This command attempts to read all accessible memory regions in the
28701 specified range. First, all regions marked as unreadable in the memory
28702 map (if one is defined) will be skipped. @xref{Memory Region
28703 Attributes}. Second, @value{GDBN} will attempt to read the remaining
28704 regions. For each one, if reading full region results in an errors,
28705 @value{GDBN} will try to read a subset of the region.
28707 In general, every single byte in the region may be readable or not,
28708 and the only way to read every readable byte is to try a read at
28709 every address, which is not practical. Therefore, @value{GDBN} will
28710 attempt to read all accessible bytes at either beginning or the end
28711 of the region, using a binary division scheme. This heuristic works
28712 well for reading accross a memory map boundary. Note that if a region
28713 has a readable range that is neither at the beginning or the end,
28714 @value{GDBN} will not read it.
28716 The result record (@pxref{GDB/MI Result Records}) that is output of
28717 the command includes a field named @samp{memory} whose content is a
28718 list of tuples. Each tuple represent a successfully read memory block
28719 and has the following fields:
28723 The start address of the memory block, as hexadecimal literal.
28726 The end address of the memory block, as hexadecimal literal.
28729 The offset of the memory block, as hexadecimal literal, relative to
28730 the start address passed to @code{-data-read-memory-bytes}.
28733 The contents of the memory block, in hex.
28739 @subsubheading @value{GDBN} Command
28741 The corresponding @value{GDBN} command is @samp{x}.
28743 @subsubheading Example
28747 -data-read-memory-bytes &a 10
28748 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28750 contents="01000000020000000300"@}]
28755 @subheading The @code{-data-write-memory-bytes} Command
28756 @findex -data-write-memory-bytes
28758 @subsubheading Synopsis
28761 -data-write-memory-bytes @var{address} @var{contents}
28768 @item @var{address}
28769 An expression specifying the address of the first memory word to be
28770 read. Complex expressions containing embedded white space should be
28771 quoted using the C convention.
28773 @item @var{contents}
28774 The hex-encoded bytes to write.
28778 @subsubheading @value{GDBN} Command
28780 There's no corresponding @value{GDBN} command.
28782 @subsubheading Example
28786 -data-write-memory-bytes &a "aabbccdd"
28792 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28793 @node GDB/MI Tracepoint Commands
28794 @section @sc{gdb/mi} Tracepoint Commands
28796 The commands defined in this section implement MI support for
28797 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28799 @subheading The @code{-trace-find} Command
28800 @findex -trace-find
28802 @subsubheading Synopsis
28805 -trace-find @var{mode} [@var{parameters}@dots{}]
28808 Find a trace frame using criteria defined by @var{mode} and
28809 @var{parameters}. The following table lists permissible
28810 modes and their parameters. For details of operation, see @ref{tfind}.
28815 No parameters are required. Stops examining trace frames.
28818 An integer is required as parameter. Selects tracepoint frame with
28821 @item tracepoint-number
28822 An integer is required as parameter. Finds next
28823 trace frame that corresponds to tracepoint with the specified number.
28826 An address is required as parameter. Finds
28827 next trace frame that corresponds to any tracepoint at the specified
28830 @item pc-inside-range
28831 Two addresses are required as parameters. Finds next trace
28832 frame that corresponds to a tracepoint at an address inside the
28833 specified range. Both bounds are considered to be inside the range.
28835 @item pc-outside-range
28836 Two addresses are required as parameters. Finds
28837 next trace frame that corresponds to a tracepoint at an address outside
28838 the specified range. Both bounds are considered to be inside the range.
28841 Line specification is required as parameter. @xref{Specify Location}.
28842 Finds next trace frame that corresponds to a tracepoint at
28843 the specified location.
28847 If @samp{none} was passed as @var{mode}, the response does not
28848 have fields. Otherwise, the response may have the following fields:
28852 This field has either @samp{0} or @samp{1} as the value, depending
28853 on whether a matching tracepoint was found.
28856 The index of the found traceframe. This field is present iff
28857 the @samp{found} field has value of @samp{1}.
28860 The index of the found tracepoint. This field is present iff
28861 the @samp{found} field has value of @samp{1}.
28864 The information about the frame corresponding to the found trace
28865 frame. This field is present only if a trace frame was found.
28866 @xref{GDB/MI Frame Information}, for description of this field.
28870 @subsubheading @value{GDBN} Command
28872 The corresponding @value{GDBN} command is @samp{tfind}.
28874 @subheading -trace-define-variable
28875 @findex -trace-define-variable
28877 @subsubheading Synopsis
28880 -trace-define-variable @var{name} [ @var{value} ]
28883 Create trace variable @var{name} if it does not exist. If
28884 @var{value} is specified, sets the initial value of the specified
28885 trace variable to that value. Note that the @var{name} should start
28886 with the @samp{$} character.
28888 @subsubheading @value{GDBN} Command
28890 The corresponding @value{GDBN} command is @samp{tvariable}.
28892 @subheading -trace-list-variables
28893 @findex -trace-list-variables
28895 @subsubheading Synopsis
28898 -trace-list-variables
28901 Return a table of all defined trace variables. Each element of the
28902 table has the following fields:
28906 The name of the trace variable. This field is always present.
28909 The initial value. This is a 64-bit signed integer. This
28910 field is always present.
28913 The value the trace variable has at the moment. This is a 64-bit
28914 signed integer. This field is absent iff current value is
28915 not defined, for example if the trace was never run, or is
28920 @subsubheading @value{GDBN} Command
28922 The corresponding @value{GDBN} command is @samp{tvariables}.
28924 @subsubheading Example
28928 -trace-list-variables
28929 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
28930 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
28931 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
28932 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
28933 body=[variable=@{name="$trace_timestamp",initial="0"@}
28934 variable=@{name="$foo",initial="10",current="15"@}]@}
28938 @subheading -trace-save
28939 @findex -trace-save
28941 @subsubheading Synopsis
28944 -trace-save [-r ] @var{filename}
28947 Saves the collected trace data to @var{filename}. Without the
28948 @samp{-r} option, the data is downloaded from the target and saved
28949 in a local file. With the @samp{-r} option the target is asked
28950 to perform the save.
28952 @subsubheading @value{GDBN} Command
28954 The corresponding @value{GDBN} command is @samp{tsave}.
28957 @subheading -trace-start
28958 @findex -trace-start
28960 @subsubheading Synopsis
28966 Starts a tracing experiments. The result of this command does not
28969 @subsubheading @value{GDBN} Command
28971 The corresponding @value{GDBN} command is @samp{tstart}.
28973 @subheading -trace-status
28974 @findex -trace-status
28976 @subsubheading Synopsis
28982 Obtains the status of a tracing experiment. The result may include
28983 the following fields:
28988 May have a value of either @samp{0}, when no tracing operations are
28989 supported, @samp{1}, when all tracing operations are supported, or
28990 @samp{file} when examining trace file. In the latter case, examining
28991 of trace frame is possible but new tracing experiement cannot be
28992 started. This field is always present.
28995 May have a value of either @samp{0} or @samp{1} depending on whether
28996 tracing experiement is in progress on target. This field is present
28997 if @samp{supported} field is not @samp{0}.
29000 Report the reason why the tracing was stopped last time. This field
29001 may be absent iff tracing was never stopped on target yet. The
29002 value of @samp{request} means the tracing was stopped as result of
29003 the @code{-trace-stop} command. The value of @samp{overflow} means
29004 the tracing buffer is full. The value of @samp{disconnection} means
29005 tracing was automatically stopped when @value{GDBN} has disconnected.
29006 The value of @samp{passcount} means tracing was stopped when a
29007 tracepoint was passed a maximal number of times for that tracepoint.
29008 This field is present if @samp{supported} field is not @samp{0}.
29010 @item stopping-tracepoint
29011 The number of tracepoint whose passcount as exceeded. This field is
29012 present iff the @samp{stop-reason} field has the value of
29016 @itemx frames-created
29017 The @samp{frames} field is a count of the total number of trace frames
29018 in the trace buffer, while @samp{frames-created} is the total created
29019 during the run, including ones that were discarded, such as when a
29020 circular trace buffer filled up. Both fields are optional.
29024 These fields tell the current size of the tracing buffer and the
29025 remaining space. These fields are optional.
29028 The value of the circular trace buffer flag. @code{1} means that the
29029 trace buffer is circular and old trace frames will be discarded if
29030 necessary to make room, @code{0} means that the trace buffer is linear
29034 The value of the disconnected tracing flag. @code{1} means that
29035 tracing will continue after @value{GDBN} disconnects, @code{0} means
29036 that the trace run will stop.
29040 @subsubheading @value{GDBN} Command
29042 The corresponding @value{GDBN} command is @samp{tstatus}.
29044 @subheading -trace-stop
29045 @findex -trace-stop
29047 @subsubheading Synopsis
29053 Stops a tracing experiment. The result of this command has the same
29054 fields as @code{-trace-status}, except that the @samp{supported} and
29055 @samp{running} fields are not output.
29057 @subsubheading @value{GDBN} Command
29059 The corresponding @value{GDBN} command is @samp{tstop}.
29062 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29063 @node GDB/MI Symbol Query
29064 @section @sc{gdb/mi} Symbol Query Commands
29068 @subheading The @code{-symbol-info-address} Command
29069 @findex -symbol-info-address
29071 @subsubheading Synopsis
29074 -symbol-info-address @var{symbol}
29077 Describe where @var{symbol} is stored.
29079 @subsubheading @value{GDBN} Command
29081 The corresponding @value{GDBN} command is @samp{info address}.
29083 @subsubheading Example
29087 @subheading The @code{-symbol-info-file} Command
29088 @findex -symbol-info-file
29090 @subsubheading Synopsis
29096 Show the file for the symbol.
29098 @subsubheading @value{GDBN} Command
29100 There's no equivalent @value{GDBN} command. @code{gdbtk} has
29101 @samp{gdb_find_file}.
29103 @subsubheading Example
29107 @subheading The @code{-symbol-info-function} Command
29108 @findex -symbol-info-function
29110 @subsubheading Synopsis
29113 -symbol-info-function
29116 Show which function the symbol lives in.
29118 @subsubheading @value{GDBN} Command
29120 @samp{gdb_get_function} in @code{gdbtk}.
29122 @subsubheading Example
29126 @subheading The @code{-symbol-info-line} Command
29127 @findex -symbol-info-line
29129 @subsubheading Synopsis
29135 Show the core addresses of the code for a source line.
29137 @subsubheading @value{GDBN} Command
29139 The corresponding @value{GDBN} command is @samp{info line}.
29140 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
29142 @subsubheading Example
29146 @subheading The @code{-symbol-info-symbol} Command
29147 @findex -symbol-info-symbol
29149 @subsubheading Synopsis
29152 -symbol-info-symbol @var{addr}
29155 Describe what symbol is at location @var{addr}.
29157 @subsubheading @value{GDBN} Command
29159 The corresponding @value{GDBN} command is @samp{info symbol}.
29161 @subsubheading Example
29165 @subheading The @code{-symbol-list-functions} Command
29166 @findex -symbol-list-functions
29168 @subsubheading Synopsis
29171 -symbol-list-functions
29174 List the functions in the executable.
29176 @subsubheading @value{GDBN} Command
29178 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
29179 @samp{gdb_search} in @code{gdbtk}.
29181 @subsubheading Example
29186 @subheading The @code{-symbol-list-lines} Command
29187 @findex -symbol-list-lines
29189 @subsubheading Synopsis
29192 -symbol-list-lines @var{filename}
29195 Print the list of lines that contain code and their associated program
29196 addresses for the given source filename. The entries are sorted in
29197 ascending PC order.
29199 @subsubheading @value{GDBN} Command
29201 There is no corresponding @value{GDBN} command.
29203 @subsubheading Example
29206 -symbol-list-lines basics.c
29207 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
29213 @subheading The @code{-symbol-list-types} Command
29214 @findex -symbol-list-types
29216 @subsubheading Synopsis
29222 List all the type names.
29224 @subsubheading @value{GDBN} Command
29226 The corresponding commands are @samp{info types} in @value{GDBN},
29227 @samp{gdb_search} in @code{gdbtk}.
29229 @subsubheading Example
29233 @subheading The @code{-symbol-list-variables} Command
29234 @findex -symbol-list-variables
29236 @subsubheading Synopsis
29239 -symbol-list-variables
29242 List all the global and static variable names.
29244 @subsubheading @value{GDBN} Command
29246 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
29248 @subsubheading Example
29252 @subheading The @code{-symbol-locate} Command
29253 @findex -symbol-locate
29255 @subsubheading Synopsis
29261 @subsubheading @value{GDBN} Command
29263 @samp{gdb_loc} in @code{gdbtk}.
29265 @subsubheading Example
29269 @subheading The @code{-symbol-type} Command
29270 @findex -symbol-type
29272 @subsubheading Synopsis
29275 -symbol-type @var{variable}
29278 Show type of @var{variable}.
29280 @subsubheading @value{GDBN} Command
29282 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
29283 @samp{gdb_obj_variable}.
29285 @subsubheading Example
29290 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29291 @node GDB/MI File Commands
29292 @section @sc{gdb/mi} File Commands
29294 This section describes the GDB/MI commands to specify executable file names
29295 and to read in and obtain symbol table information.
29297 @subheading The @code{-file-exec-and-symbols} Command
29298 @findex -file-exec-and-symbols
29300 @subsubheading Synopsis
29303 -file-exec-and-symbols @var{file}
29306 Specify the executable file to be debugged. This file is the one from
29307 which the symbol table is also read. If no file is specified, the
29308 command clears the executable and symbol information. If breakpoints
29309 are set when using this command with no arguments, @value{GDBN} will produce
29310 error messages. Otherwise, no output is produced, except a completion
29313 @subsubheading @value{GDBN} Command
29315 The corresponding @value{GDBN} command is @samp{file}.
29317 @subsubheading Example
29321 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29327 @subheading The @code{-file-exec-file} Command
29328 @findex -file-exec-file
29330 @subsubheading Synopsis
29333 -file-exec-file @var{file}
29336 Specify the executable file to be debugged. Unlike
29337 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
29338 from this file. If used without argument, @value{GDBN} clears the information
29339 about the executable file. No output is produced, except a completion
29342 @subsubheading @value{GDBN} Command
29344 The corresponding @value{GDBN} command is @samp{exec-file}.
29346 @subsubheading Example
29350 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29357 @subheading The @code{-file-list-exec-sections} Command
29358 @findex -file-list-exec-sections
29360 @subsubheading Synopsis
29363 -file-list-exec-sections
29366 List the sections of the current executable file.
29368 @subsubheading @value{GDBN} Command
29370 The @value{GDBN} command @samp{info file} shows, among the rest, the same
29371 information as this command. @code{gdbtk} has a corresponding command
29372 @samp{gdb_load_info}.
29374 @subsubheading Example
29379 @subheading The @code{-file-list-exec-source-file} Command
29380 @findex -file-list-exec-source-file
29382 @subsubheading Synopsis
29385 -file-list-exec-source-file
29388 List the line number, the current source file, and the absolute path
29389 to the current source file for the current executable. The macro
29390 information field has a value of @samp{1} or @samp{0} depending on
29391 whether or not the file includes preprocessor macro information.
29393 @subsubheading @value{GDBN} Command
29395 The @value{GDBN} equivalent is @samp{info source}
29397 @subsubheading Example
29401 123-file-list-exec-source-file
29402 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
29407 @subheading The @code{-file-list-exec-source-files} Command
29408 @findex -file-list-exec-source-files
29410 @subsubheading Synopsis
29413 -file-list-exec-source-files
29416 List the source files for the current executable.
29418 It will always output the filename, but only when @value{GDBN} can find
29419 the absolute file name of a source file, will it output the fullname.
29421 @subsubheading @value{GDBN} Command
29423 The @value{GDBN} equivalent is @samp{info sources}.
29424 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
29426 @subsubheading Example
29429 -file-list-exec-source-files
29431 @{file=foo.c,fullname=/home/foo.c@},
29432 @{file=/home/bar.c,fullname=/home/bar.c@},
29433 @{file=gdb_could_not_find_fullpath.c@}]
29438 @subheading The @code{-file-list-shared-libraries} Command
29439 @findex -file-list-shared-libraries
29441 @subsubheading Synopsis
29444 -file-list-shared-libraries
29447 List the shared libraries in the program.
29449 @subsubheading @value{GDBN} Command
29451 The corresponding @value{GDBN} command is @samp{info shared}.
29453 @subsubheading Example
29457 @subheading The @code{-file-list-symbol-files} Command
29458 @findex -file-list-symbol-files
29460 @subsubheading Synopsis
29463 -file-list-symbol-files
29468 @subsubheading @value{GDBN} Command
29470 The corresponding @value{GDBN} command is @samp{info file} (part of it).
29472 @subsubheading Example
29477 @subheading The @code{-file-symbol-file} Command
29478 @findex -file-symbol-file
29480 @subsubheading Synopsis
29483 -file-symbol-file @var{file}
29486 Read symbol table info from the specified @var{file} argument. When
29487 used without arguments, clears @value{GDBN}'s symbol table info. No output is
29488 produced, except for a completion notification.
29490 @subsubheading @value{GDBN} Command
29492 The corresponding @value{GDBN} command is @samp{symbol-file}.
29494 @subsubheading Example
29498 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29504 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29505 @node GDB/MI Memory Overlay Commands
29506 @section @sc{gdb/mi} Memory Overlay Commands
29508 The memory overlay commands are not implemented.
29510 @c @subheading -overlay-auto
29512 @c @subheading -overlay-list-mapping-state
29514 @c @subheading -overlay-list-overlays
29516 @c @subheading -overlay-map
29518 @c @subheading -overlay-off
29520 @c @subheading -overlay-on
29522 @c @subheading -overlay-unmap
29524 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29525 @node GDB/MI Signal Handling Commands
29526 @section @sc{gdb/mi} Signal Handling Commands
29528 Signal handling commands are not implemented.
29530 @c @subheading -signal-handle
29532 @c @subheading -signal-list-handle-actions
29534 @c @subheading -signal-list-signal-types
29538 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29539 @node GDB/MI Target Manipulation
29540 @section @sc{gdb/mi} Target Manipulation Commands
29543 @subheading The @code{-target-attach} Command
29544 @findex -target-attach
29546 @subsubheading Synopsis
29549 -target-attach @var{pid} | @var{gid} | @var{file}
29552 Attach to a process @var{pid} or a file @var{file} outside of
29553 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
29554 group, the id previously returned by
29555 @samp{-list-thread-groups --available} must be used.
29557 @subsubheading @value{GDBN} Command
29559 The corresponding @value{GDBN} command is @samp{attach}.
29561 @subsubheading Example
29565 =thread-created,id="1"
29566 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
29572 @subheading The @code{-target-compare-sections} Command
29573 @findex -target-compare-sections
29575 @subsubheading Synopsis
29578 -target-compare-sections [ @var{section} ]
29581 Compare data of section @var{section} on target to the exec file.
29582 Without the argument, all sections are compared.
29584 @subsubheading @value{GDBN} Command
29586 The @value{GDBN} equivalent is @samp{compare-sections}.
29588 @subsubheading Example
29593 @subheading The @code{-target-detach} Command
29594 @findex -target-detach
29596 @subsubheading Synopsis
29599 -target-detach [ @var{pid} | @var{gid} ]
29602 Detach from the remote target which normally resumes its execution.
29603 If either @var{pid} or @var{gid} is specified, detaches from either
29604 the specified process, or specified thread group. There's no output.
29606 @subsubheading @value{GDBN} Command
29608 The corresponding @value{GDBN} command is @samp{detach}.
29610 @subsubheading Example
29620 @subheading The @code{-target-disconnect} Command
29621 @findex -target-disconnect
29623 @subsubheading Synopsis
29629 Disconnect from the remote target. There's no output and the target is
29630 generally not resumed.
29632 @subsubheading @value{GDBN} Command
29634 The corresponding @value{GDBN} command is @samp{disconnect}.
29636 @subsubheading Example
29646 @subheading The @code{-target-download} Command
29647 @findex -target-download
29649 @subsubheading Synopsis
29655 Loads the executable onto the remote target.
29656 It prints out an update message every half second, which includes the fields:
29660 The name of the section.
29662 The size of what has been sent so far for that section.
29664 The size of the section.
29666 The total size of what was sent so far (the current and the previous sections).
29668 The size of the overall executable to download.
29672 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
29673 @sc{gdb/mi} Output Syntax}).
29675 In addition, it prints the name and size of the sections, as they are
29676 downloaded. These messages include the following fields:
29680 The name of the section.
29682 The size of the section.
29684 The size of the overall executable to download.
29688 At the end, a summary is printed.
29690 @subsubheading @value{GDBN} Command
29692 The corresponding @value{GDBN} command is @samp{load}.
29694 @subsubheading Example
29696 Note: each status message appears on a single line. Here the messages
29697 have been broken down so that they can fit onto a page.
29702 +download,@{section=".text",section-size="6668",total-size="9880"@}
29703 +download,@{section=".text",section-sent="512",section-size="6668",
29704 total-sent="512",total-size="9880"@}
29705 +download,@{section=".text",section-sent="1024",section-size="6668",
29706 total-sent="1024",total-size="9880"@}
29707 +download,@{section=".text",section-sent="1536",section-size="6668",
29708 total-sent="1536",total-size="9880"@}
29709 +download,@{section=".text",section-sent="2048",section-size="6668",
29710 total-sent="2048",total-size="9880"@}
29711 +download,@{section=".text",section-sent="2560",section-size="6668",
29712 total-sent="2560",total-size="9880"@}
29713 +download,@{section=".text",section-sent="3072",section-size="6668",
29714 total-sent="3072",total-size="9880"@}
29715 +download,@{section=".text",section-sent="3584",section-size="6668",
29716 total-sent="3584",total-size="9880"@}
29717 +download,@{section=".text",section-sent="4096",section-size="6668",
29718 total-sent="4096",total-size="9880"@}
29719 +download,@{section=".text",section-sent="4608",section-size="6668",
29720 total-sent="4608",total-size="9880"@}
29721 +download,@{section=".text",section-sent="5120",section-size="6668",
29722 total-sent="5120",total-size="9880"@}
29723 +download,@{section=".text",section-sent="5632",section-size="6668",
29724 total-sent="5632",total-size="9880"@}
29725 +download,@{section=".text",section-sent="6144",section-size="6668",
29726 total-sent="6144",total-size="9880"@}
29727 +download,@{section=".text",section-sent="6656",section-size="6668",
29728 total-sent="6656",total-size="9880"@}
29729 +download,@{section=".init",section-size="28",total-size="9880"@}
29730 +download,@{section=".fini",section-size="28",total-size="9880"@}
29731 +download,@{section=".data",section-size="3156",total-size="9880"@}
29732 +download,@{section=".data",section-sent="512",section-size="3156",
29733 total-sent="7236",total-size="9880"@}
29734 +download,@{section=".data",section-sent="1024",section-size="3156",
29735 total-sent="7748",total-size="9880"@}
29736 +download,@{section=".data",section-sent="1536",section-size="3156",
29737 total-sent="8260",total-size="9880"@}
29738 +download,@{section=".data",section-sent="2048",section-size="3156",
29739 total-sent="8772",total-size="9880"@}
29740 +download,@{section=".data",section-sent="2560",section-size="3156",
29741 total-sent="9284",total-size="9880"@}
29742 +download,@{section=".data",section-sent="3072",section-size="3156",
29743 total-sent="9796",total-size="9880"@}
29744 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29751 @subheading The @code{-target-exec-status} Command
29752 @findex -target-exec-status
29754 @subsubheading Synopsis
29757 -target-exec-status
29760 Provide information on the state of the target (whether it is running or
29761 not, for instance).
29763 @subsubheading @value{GDBN} Command
29765 There's no equivalent @value{GDBN} command.
29767 @subsubheading Example
29771 @subheading The @code{-target-list-available-targets} Command
29772 @findex -target-list-available-targets
29774 @subsubheading Synopsis
29777 -target-list-available-targets
29780 List the possible targets to connect to.
29782 @subsubheading @value{GDBN} Command
29784 The corresponding @value{GDBN} command is @samp{help target}.
29786 @subsubheading Example
29790 @subheading The @code{-target-list-current-targets} Command
29791 @findex -target-list-current-targets
29793 @subsubheading Synopsis
29796 -target-list-current-targets
29799 Describe the current target.
29801 @subsubheading @value{GDBN} Command
29803 The corresponding information is printed by @samp{info file} (among
29806 @subsubheading Example
29810 @subheading The @code{-target-list-parameters} Command
29811 @findex -target-list-parameters
29813 @subsubheading Synopsis
29816 -target-list-parameters
29822 @subsubheading @value{GDBN} Command
29826 @subsubheading Example
29830 @subheading The @code{-target-select} Command
29831 @findex -target-select
29833 @subsubheading Synopsis
29836 -target-select @var{type} @var{parameters @dots{}}
29839 Connect @value{GDBN} to the remote target. This command takes two args:
29843 The type of target, for instance @samp{remote}, etc.
29844 @item @var{parameters}
29845 Device names, host names and the like. @xref{Target Commands, ,
29846 Commands for Managing Targets}, for more details.
29849 The output is a connection notification, followed by the address at
29850 which the target program is, in the following form:
29853 ^connected,addr="@var{address}",func="@var{function name}",
29854 args=[@var{arg list}]
29857 @subsubheading @value{GDBN} Command
29859 The corresponding @value{GDBN} command is @samp{target}.
29861 @subsubheading Example
29865 -target-select remote /dev/ttya
29866 ^connected,addr="0xfe00a300",func="??",args=[]
29870 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29871 @node GDB/MI File Transfer Commands
29872 @section @sc{gdb/mi} File Transfer Commands
29875 @subheading The @code{-target-file-put} Command
29876 @findex -target-file-put
29878 @subsubheading Synopsis
29881 -target-file-put @var{hostfile} @var{targetfile}
29884 Copy file @var{hostfile} from the host system (the machine running
29885 @value{GDBN}) to @var{targetfile} on the target system.
29887 @subsubheading @value{GDBN} Command
29889 The corresponding @value{GDBN} command is @samp{remote put}.
29891 @subsubheading Example
29895 -target-file-put localfile remotefile
29901 @subheading The @code{-target-file-get} Command
29902 @findex -target-file-get
29904 @subsubheading Synopsis
29907 -target-file-get @var{targetfile} @var{hostfile}
29910 Copy file @var{targetfile} from the target system to @var{hostfile}
29911 on the host system.
29913 @subsubheading @value{GDBN} Command
29915 The corresponding @value{GDBN} command is @samp{remote get}.
29917 @subsubheading Example
29921 -target-file-get remotefile localfile
29927 @subheading The @code{-target-file-delete} Command
29928 @findex -target-file-delete
29930 @subsubheading Synopsis
29933 -target-file-delete @var{targetfile}
29936 Delete @var{targetfile} from the target system.
29938 @subsubheading @value{GDBN} Command
29940 The corresponding @value{GDBN} command is @samp{remote delete}.
29942 @subsubheading Example
29946 -target-file-delete remotefile
29952 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29953 @node GDB/MI Miscellaneous Commands
29954 @section Miscellaneous @sc{gdb/mi} Commands
29956 @c @subheading -gdb-complete
29958 @subheading The @code{-gdb-exit} Command
29961 @subsubheading Synopsis
29967 Exit @value{GDBN} immediately.
29969 @subsubheading @value{GDBN} Command
29971 Approximately corresponds to @samp{quit}.
29973 @subsubheading Example
29983 @subheading The @code{-exec-abort} Command
29984 @findex -exec-abort
29986 @subsubheading Synopsis
29992 Kill the inferior running program.
29994 @subsubheading @value{GDBN} Command
29996 The corresponding @value{GDBN} command is @samp{kill}.
29998 @subsubheading Example
30003 @subheading The @code{-gdb-set} Command
30006 @subsubheading Synopsis
30012 Set an internal @value{GDBN} variable.
30013 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
30015 @subsubheading @value{GDBN} Command
30017 The corresponding @value{GDBN} command is @samp{set}.
30019 @subsubheading Example
30029 @subheading The @code{-gdb-show} Command
30032 @subsubheading Synopsis
30038 Show the current value of a @value{GDBN} variable.
30040 @subsubheading @value{GDBN} Command
30042 The corresponding @value{GDBN} command is @samp{show}.
30044 @subsubheading Example
30053 @c @subheading -gdb-source
30056 @subheading The @code{-gdb-version} Command
30057 @findex -gdb-version
30059 @subsubheading Synopsis
30065 Show version information for @value{GDBN}. Used mostly in testing.
30067 @subsubheading @value{GDBN} Command
30069 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
30070 default shows this information when you start an interactive session.
30072 @subsubheading Example
30074 @c This example modifies the actual output from GDB to avoid overfull
30080 ~Copyright 2000 Free Software Foundation, Inc.
30081 ~GDB is free software, covered by the GNU General Public License, and
30082 ~you are welcome to change it and/or distribute copies of it under
30083 ~ certain conditions.
30084 ~Type "show copying" to see the conditions.
30085 ~There is absolutely no warranty for GDB. Type "show warranty" for
30087 ~This GDB was configured as
30088 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
30093 @subheading The @code{-list-features} Command
30094 @findex -list-features
30096 Returns a list of particular features of the MI protocol that
30097 this version of gdb implements. A feature can be a command,
30098 or a new field in an output of some command, or even an
30099 important bugfix. While a frontend can sometimes detect presence
30100 of a feature at runtime, it is easier to perform detection at debugger
30103 The command returns a list of strings, with each string naming an
30104 available feature. Each returned string is just a name, it does not
30105 have any internal structure. The list of possible feature names
30111 (gdb) -list-features
30112 ^done,result=["feature1","feature2"]
30115 The current list of features is:
30118 @item frozen-varobjs
30119 Indicates presence of the @code{-var-set-frozen} command, as well
30120 as possible presense of the @code{frozen} field in the output
30121 of @code{-varobj-create}.
30122 @item pending-breakpoints
30123 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
30125 Indicates presence of Python scripting support, Python-based
30126 pretty-printing commands, and possible presence of the
30127 @samp{display_hint} field in the output of @code{-var-list-children}
30129 Indicates presence of the @code{-thread-info} command.
30130 @item data-read-memory-bytes
30131 Indicates presense of the @code{-data-read-memory-bytes} and the
30132 @code{-data-write-memory-bytes} commands.
30133 @item breakpoint-notifications
30134 Indicates that changes to breakpoints and breakpoints created via the
30135 CLI will be announced via async records.
30139 @subheading The @code{-list-target-features} Command
30140 @findex -list-target-features
30142 Returns a list of particular features that are supported by the
30143 target. Those features affect the permitted MI commands, but
30144 unlike the features reported by the @code{-list-features} command, the
30145 features depend on which target GDB is using at the moment. Whenever
30146 a target can change, due to commands such as @code{-target-select},
30147 @code{-target-attach} or @code{-exec-run}, the list of target features
30148 may change, and the frontend should obtain it again.
30152 (gdb) -list-features
30153 ^done,result=["async"]
30156 The current list of features is:
30160 Indicates that the target is capable of asynchronous command
30161 execution, which means that @value{GDBN} will accept further commands
30162 while the target is running.
30165 Indicates that the target is capable of reverse execution.
30166 @xref{Reverse Execution}, for more information.
30170 @subheading The @code{-list-thread-groups} Command
30171 @findex -list-thread-groups
30173 @subheading Synopsis
30176 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
30179 Lists thread groups (@pxref{Thread groups}). When a single thread
30180 group is passed as the argument, lists the children of that group.
30181 When several thread group are passed, lists information about those
30182 thread groups. Without any parameters, lists information about all
30183 top-level thread groups.
30185 Normally, thread groups that are being debugged are reported.
30186 With the @samp{--available} option, @value{GDBN} reports thread groups
30187 available on the target.
30189 The output of this command may have either a @samp{threads} result or
30190 a @samp{groups} result. The @samp{thread} result has a list of tuples
30191 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
30192 Information}). The @samp{groups} result has a list of tuples as value,
30193 each tuple describing a thread group. If top-level groups are
30194 requested (that is, no parameter is passed), or when several groups
30195 are passed, the output always has a @samp{groups} result. The format
30196 of the @samp{group} result is described below.
30198 To reduce the number of roundtrips it's possible to list thread groups
30199 together with their children, by passing the @samp{--recurse} option
30200 and the recursion depth. Presently, only recursion depth of 1 is
30201 permitted. If this option is present, then every reported thread group
30202 will also include its children, either as @samp{group} or
30203 @samp{threads} field.
30205 In general, any combination of option and parameters is permitted, with
30206 the following caveats:
30210 When a single thread group is passed, the output will typically
30211 be the @samp{threads} result. Because threads may not contain
30212 anything, the @samp{recurse} option will be ignored.
30215 When the @samp{--available} option is passed, limited information may
30216 be available. In particular, the list of threads of a process might
30217 be inaccessible. Further, specifying specific thread groups might
30218 not give any performance advantage over listing all thread groups.
30219 The frontend should assume that @samp{-list-thread-groups --available}
30220 is always an expensive operation and cache the results.
30224 The @samp{groups} result is a list of tuples, where each tuple may
30225 have the following fields:
30229 Identifier of the thread group. This field is always present.
30230 The identifier is an opaque string; frontends should not try to
30231 convert it to an integer, even though it might look like one.
30234 The type of the thread group. At present, only @samp{process} is a
30238 The target-specific process identifier. This field is only present
30239 for thread groups of type @samp{process} and only if the process exists.
30242 The number of children this thread group has. This field may be
30243 absent for an available thread group.
30246 This field has a list of tuples as value, each tuple describing a
30247 thread. It may be present if the @samp{--recurse} option is
30248 specified, and it's actually possible to obtain the threads.
30251 This field is a list of integers, each identifying a core that one
30252 thread of the group is running on. This field may be absent if
30253 such information is not available.
30256 The name of the executable file that corresponds to this thread group.
30257 The field is only present for thread groups of type @samp{process},
30258 and only if there is a corresponding executable file.
30262 @subheading Example
30266 -list-thread-groups
30267 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
30268 -list-thread-groups 17
30269 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30270 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
30271 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30272 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
30273 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
30274 -list-thread-groups --available
30275 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
30276 -list-thread-groups --available --recurse 1
30277 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30278 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30279 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
30280 -list-thread-groups --available --recurse 1 17 18
30281 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30282 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30283 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
30287 @subheading The @code{-add-inferior} Command
30288 @findex -add-inferior
30290 @subheading Synopsis
30296 Creates a new inferior (@pxref{Inferiors and Programs}). The created
30297 inferior is not associated with any executable. Such association may
30298 be established with the @samp{-file-exec-and-symbols} command
30299 (@pxref{GDB/MI File Commands}). The command response has a single
30300 field, @samp{thread-group}, whose value is the identifier of the
30301 thread group corresponding to the new inferior.
30303 @subheading Example
30308 ^done,thread-group="i3"
30311 @subheading The @code{-interpreter-exec} Command
30312 @findex -interpreter-exec
30314 @subheading Synopsis
30317 -interpreter-exec @var{interpreter} @var{command}
30319 @anchor{-interpreter-exec}
30321 Execute the specified @var{command} in the given @var{interpreter}.
30323 @subheading @value{GDBN} Command
30325 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
30327 @subheading Example
30331 -interpreter-exec console "break main"
30332 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
30333 &"During symbol reading, bad structure-type format.\n"
30334 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
30339 @subheading The @code{-inferior-tty-set} Command
30340 @findex -inferior-tty-set
30342 @subheading Synopsis
30345 -inferior-tty-set /dev/pts/1
30348 Set terminal for future runs of the program being debugged.
30350 @subheading @value{GDBN} Command
30352 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
30354 @subheading Example
30358 -inferior-tty-set /dev/pts/1
30363 @subheading The @code{-inferior-tty-show} Command
30364 @findex -inferior-tty-show
30366 @subheading Synopsis
30372 Show terminal for future runs of program being debugged.
30374 @subheading @value{GDBN} Command
30376 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
30378 @subheading Example
30382 -inferior-tty-set /dev/pts/1
30386 ^done,inferior_tty_terminal="/dev/pts/1"
30390 @subheading The @code{-enable-timings} Command
30391 @findex -enable-timings
30393 @subheading Synopsis
30396 -enable-timings [yes | no]
30399 Toggle the printing of the wallclock, user and system times for an MI
30400 command as a field in its output. This command is to help frontend
30401 developers optimize the performance of their code. No argument is
30402 equivalent to @samp{yes}.
30404 @subheading @value{GDBN} Command
30408 @subheading Example
30416 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30417 addr="0x080484ed",func="main",file="myprog.c",
30418 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
30419 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
30427 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30428 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
30429 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
30430 fullname="/home/nickrob/myprog.c",line="73"@}
30435 @chapter @value{GDBN} Annotations
30437 This chapter describes annotations in @value{GDBN}. Annotations were
30438 designed to interface @value{GDBN} to graphical user interfaces or other
30439 similar programs which want to interact with @value{GDBN} at a
30440 relatively high level.
30442 The annotation mechanism has largely been superseded by @sc{gdb/mi}
30446 This is Edition @value{EDITION}, @value{DATE}.
30450 * Annotations Overview:: What annotations are; the general syntax.
30451 * Server Prefix:: Issuing a command without affecting user state.
30452 * Prompting:: Annotations marking @value{GDBN}'s need for input.
30453 * Errors:: Annotations for error messages.
30454 * Invalidation:: Some annotations describe things now invalid.
30455 * Annotations for Running::
30456 Whether the program is running, how it stopped, etc.
30457 * Source Annotations:: Annotations describing source code.
30460 @node Annotations Overview
30461 @section What is an Annotation?
30462 @cindex annotations
30464 Annotations start with a newline character, two @samp{control-z}
30465 characters, and the name of the annotation. If there is no additional
30466 information associated with this annotation, the name of the annotation
30467 is followed immediately by a newline. If there is additional
30468 information, the name of the annotation is followed by a space, the
30469 additional information, and a newline. The additional information
30470 cannot contain newline characters.
30472 Any output not beginning with a newline and two @samp{control-z}
30473 characters denotes literal output from @value{GDBN}. Currently there is
30474 no need for @value{GDBN} to output a newline followed by two
30475 @samp{control-z} characters, but if there was such a need, the
30476 annotations could be extended with an @samp{escape} annotation which
30477 means those three characters as output.
30479 The annotation @var{level}, which is specified using the
30480 @option{--annotate} command line option (@pxref{Mode Options}), controls
30481 how much information @value{GDBN} prints together with its prompt,
30482 values of expressions, source lines, and other types of output. Level 0
30483 is for no annotations, level 1 is for use when @value{GDBN} is run as a
30484 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
30485 for programs that control @value{GDBN}, and level 2 annotations have
30486 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
30487 Interface, annotate, GDB's Obsolete Annotations}).
30490 @kindex set annotate
30491 @item set annotate @var{level}
30492 The @value{GDBN} command @code{set annotate} sets the level of
30493 annotations to the specified @var{level}.
30495 @item show annotate
30496 @kindex show annotate
30497 Show the current annotation level.
30500 This chapter describes level 3 annotations.
30502 A simple example of starting up @value{GDBN} with annotations is:
30505 $ @kbd{gdb --annotate=3}
30507 Copyright 2003 Free Software Foundation, Inc.
30508 GDB is free software, covered by the GNU General Public License,
30509 and you are welcome to change it and/or distribute copies of it
30510 under certain conditions.
30511 Type "show copying" to see the conditions.
30512 There is absolutely no warranty for GDB. Type "show warranty"
30514 This GDB was configured as "i386-pc-linux-gnu"
30525 Here @samp{quit} is input to @value{GDBN}; the rest is output from
30526 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
30527 denotes a @samp{control-z} character) are annotations; the rest is
30528 output from @value{GDBN}.
30530 @node Server Prefix
30531 @section The Server Prefix
30532 @cindex server prefix
30534 If you prefix a command with @samp{server } then it will not affect
30535 the command history, nor will it affect @value{GDBN}'s notion of which
30536 command to repeat if @key{RET} is pressed on a line by itself. This
30537 means that commands can be run behind a user's back by a front-end in
30538 a transparent manner.
30540 The @code{server } prefix does not affect the recording of values into
30541 the value history; to print a value without recording it into the
30542 value history, use the @code{output} command instead of the
30543 @code{print} command.
30545 Using this prefix also disables confirmation requests
30546 (@pxref{confirmation requests}).
30549 @section Annotation for @value{GDBN} Input
30551 @cindex annotations for prompts
30552 When @value{GDBN} prompts for input, it annotates this fact so it is possible
30553 to know when to send output, when the output from a given command is
30556 Different kinds of input each have a different @dfn{input type}. Each
30557 input type has three annotations: a @code{pre-} annotation, which
30558 denotes the beginning of any prompt which is being output, a plain
30559 annotation, which denotes the end of the prompt, and then a @code{post-}
30560 annotation which denotes the end of any echo which may (or may not) be
30561 associated with the input. For example, the @code{prompt} input type
30562 features the following annotations:
30570 The input types are
30573 @findex pre-prompt annotation
30574 @findex prompt annotation
30575 @findex post-prompt annotation
30577 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
30579 @findex pre-commands annotation
30580 @findex commands annotation
30581 @findex post-commands annotation
30583 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
30584 command. The annotations are repeated for each command which is input.
30586 @findex pre-overload-choice annotation
30587 @findex overload-choice annotation
30588 @findex post-overload-choice annotation
30589 @item overload-choice
30590 When @value{GDBN} wants the user to select between various overloaded functions.
30592 @findex pre-query annotation
30593 @findex query annotation
30594 @findex post-query annotation
30596 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
30598 @findex pre-prompt-for-continue annotation
30599 @findex prompt-for-continue annotation
30600 @findex post-prompt-for-continue annotation
30601 @item prompt-for-continue
30602 When @value{GDBN} is asking the user to press return to continue. Note: Don't
30603 expect this to work well; instead use @code{set height 0} to disable
30604 prompting. This is because the counting of lines is buggy in the
30605 presence of annotations.
30610 @cindex annotations for errors, warnings and interrupts
30612 @findex quit annotation
30617 This annotation occurs right before @value{GDBN} responds to an interrupt.
30619 @findex error annotation
30624 This annotation occurs right before @value{GDBN} responds to an error.
30626 Quit and error annotations indicate that any annotations which @value{GDBN} was
30627 in the middle of may end abruptly. For example, if a
30628 @code{value-history-begin} annotation is followed by a @code{error}, one
30629 cannot expect to receive the matching @code{value-history-end}. One
30630 cannot expect not to receive it either, however; an error annotation
30631 does not necessarily mean that @value{GDBN} is immediately returning all the way
30634 @findex error-begin annotation
30635 A quit or error annotation may be preceded by
30641 Any output between that and the quit or error annotation is the error
30644 Warning messages are not yet annotated.
30645 @c If we want to change that, need to fix warning(), type_error(),
30646 @c range_error(), and possibly other places.
30649 @section Invalidation Notices
30651 @cindex annotations for invalidation messages
30652 The following annotations say that certain pieces of state may have
30656 @findex frames-invalid annotation
30657 @item ^Z^Zframes-invalid
30659 The frames (for example, output from the @code{backtrace} command) may
30662 @findex breakpoints-invalid annotation
30663 @item ^Z^Zbreakpoints-invalid
30665 The breakpoints may have changed. For example, the user just added or
30666 deleted a breakpoint.
30669 @node Annotations for Running
30670 @section Running the Program
30671 @cindex annotations for running programs
30673 @findex starting annotation
30674 @findex stopping annotation
30675 When the program starts executing due to a @value{GDBN} command such as
30676 @code{step} or @code{continue},
30682 is output. When the program stops,
30688 is output. Before the @code{stopped} annotation, a variety of
30689 annotations describe how the program stopped.
30692 @findex exited annotation
30693 @item ^Z^Zexited @var{exit-status}
30694 The program exited, and @var{exit-status} is the exit status (zero for
30695 successful exit, otherwise nonzero).
30697 @findex signalled annotation
30698 @findex signal-name annotation
30699 @findex signal-name-end annotation
30700 @findex signal-string annotation
30701 @findex signal-string-end annotation
30702 @item ^Z^Zsignalled
30703 The program exited with a signal. After the @code{^Z^Zsignalled}, the
30704 annotation continues:
30710 ^Z^Zsignal-name-end
30714 ^Z^Zsignal-string-end
30719 where @var{name} is the name of the signal, such as @code{SIGILL} or
30720 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
30721 as @code{Illegal Instruction} or @code{Segmentation fault}.
30722 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
30723 user's benefit and have no particular format.
30725 @findex signal annotation
30727 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
30728 just saying that the program received the signal, not that it was
30729 terminated with it.
30731 @findex breakpoint annotation
30732 @item ^Z^Zbreakpoint @var{number}
30733 The program hit breakpoint number @var{number}.
30735 @findex watchpoint annotation
30736 @item ^Z^Zwatchpoint @var{number}
30737 The program hit watchpoint number @var{number}.
30740 @node Source Annotations
30741 @section Displaying Source
30742 @cindex annotations for source display
30744 @findex source annotation
30745 The following annotation is used instead of displaying source code:
30748 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30751 where @var{filename} is an absolute file name indicating which source
30752 file, @var{line} is the line number within that file (where 1 is the
30753 first line in the file), @var{character} is the character position
30754 within the file (where 0 is the first character in the file) (for most
30755 debug formats this will necessarily point to the beginning of a line),
30756 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30757 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30758 @var{addr} is the address in the target program associated with the
30759 source which is being displayed. @var{addr} is in the form @samp{0x}
30760 followed by one or more lowercase hex digits (note that this does not
30761 depend on the language).
30763 @node JIT Interface
30764 @chapter JIT Compilation Interface
30765 @cindex just-in-time compilation
30766 @cindex JIT compilation interface
30768 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30769 interface. A JIT compiler is a program or library that generates native
30770 executable code at runtime and executes it, usually in order to achieve good
30771 performance while maintaining platform independence.
30773 Programs that use JIT compilation are normally difficult to debug because
30774 portions of their code are generated at runtime, instead of being loaded from
30775 object files, which is where @value{GDBN} normally finds the program's symbols
30776 and debug information. In order to debug programs that use JIT compilation,
30777 @value{GDBN} has an interface that allows the program to register in-memory
30778 symbol files with @value{GDBN} at runtime.
30780 If you are using @value{GDBN} to debug a program that uses this interface, then
30781 it should work transparently so long as you have not stripped the binary. If
30782 you are developing a JIT compiler, then the interface is documented in the rest
30783 of this chapter. At this time, the only known client of this interface is the
30786 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30787 JIT compiler communicates with @value{GDBN} by writing data into a global
30788 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30789 attaches, it reads a linked list of symbol files from the global variable to
30790 find existing code, and puts a breakpoint in the function so that it can find
30791 out about additional code.
30794 * Declarations:: Relevant C struct declarations
30795 * Registering Code:: Steps to register code
30796 * Unregistering Code:: Steps to unregister code
30800 @section JIT Declarations
30802 These are the relevant struct declarations that a C program should include to
30803 implement the interface:
30813 struct jit_code_entry
30815 struct jit_code_entry *next_entry;
30816 struct jit_code_entry *prev_entry;
30817 const char *symfile_addr;
30818 uint64_t symfile_size;
30821 struct jit_descriptor
30824 /* This type should be jit_actions_t, but we use uint32_t
30825 to be explicit about the bitwidth. */
30826 uint32_t action_flag;
30827 struct jit_code_entry *relevant_entry;
30828 struct jit_code_entry *first_entry;
30831 /* GDB puts a breakpoint in this function. */
30832 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
30834 /* Make sure to specify the version statically, because the
30835 debugger may check the version before we can set it. */
30836 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
30839 If the JIT is multi-threaded, then it is important that the JIT synchronize any
30840 modifications to this global data properly, which can easily be done by putting
30841 a global mutex around modifications to these structures.
30843 @node Registering Code
30844 @section Registering Code
30846 To register code with @value{GDBN}, the JIT should follow this protocol:
30850 Generate an object file in memory with symbols and other desired debug
30851 information. The file must include the virtual addresses of the sections.
30854 Create a code entry for the file, which gives the start and size of the symbol
30858 Add it to the linked list in the JIT descriptor.
30861 Point the relevant_entry field of the descriptor at the entry.
30864 Set @code{action_flag} to @code{JIT_REGISTER} and call
30865 @code{__jit_debug_register_code}.
30868 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
30869 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
30870 new code. However, the linked list must still be maintained in order to allow
30871 @value{GDBN} to attach to a running process and still find the symbol files.
30873 @node Unregistering Code
30874 @section Unregistering Code
30876 If code is freed, then the JIT should use the following protocol:
30880 Remove the code entry corresponding to the code from the linked list.
30883 Point the @code{relevant_entry} field of the descriptor at the code entry.
30886 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
30887 @code{__jit_debug_register_code}.
30890 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
30891 and the JIT will leak the memory used for the associated symbol files.
30894 @chapter Reporting Bugs in @value{GDBN}
30895 @cindex bugs in @value{GDBN}
30896 @cindex reporting bugs in @value{GDBN}
30898 Your bug reports play an essential role in making @value{GDBN} reliable.
30900 Reporting a bug may help you by bringing a solution to your problem, or it
30901 may not. But in any case the principal function of a bug report is to help
30902 the entire community by making the next version of @value{GDBN} work better. Bug
30903 reports are your contribution to the maintenance of @value{GDBN}.
30905 In order for a bug report to serve its purpose, you must include the
30906 information that enables us to fix the bug.
30909 * Bug Criteria:: Have you found a bug?
30910 * Bug Reporting:: How to report bugs
30914 @section Have You Found a Bug?
30915 @cindex bug criteria
30917 If you are not sure whether you have found a bug, here are some guidelines:
30920 @cindex fatal signal
30921 @cindex debugger crash
30922 @cindex crash of debugger
30924 If the debugger gets a fatal signal, for any input whatever, that is a
30925 @value{GDBN} bug. Reliable debuggers never crash.
30927 @cindex error on valid input
30929 If @value{GDBN} produces an error message for valid input, that is a
30930 bug. (Note that if you're cross debugging, the problem may also be
30931 somewhere in the connection to the target.)
30933 @cindex invalid input
30935 If @value{GDBN} does not produce an error message for invalid input,
30936 that is a bug. However, you should note that your idea of
30937 ``invalid input'' might be our idea of ``an extension'' or ``support
30938 for traditional practice''.
30941 If you are an experienced user of debugging tools, your suggestions
30942 for improvement of @value{GDBN} are welcome in any case.
30945 @node Bug Reporting
30946 @section How to Report Bugs
30947 @cindex bug reports
30948 @cindex @value{GDBN} bugs, reporting
30950 A number of companies and individuals offer support for @sc{gnu} products.
30951 If you obtained @value{GDBN} from a support organization, we recommend you
30952 contact that organization first.
30954 You can find contact information for many support companies and
30955 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
30957 @c should add a web page ref...
30960 @ifset BUGURL_DEFAULT
30961 In any event, we also recommend that you submit bug reports for
30962 @value{GDBN}. The preferred method is to submit them directly using
30963 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
30964 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
30967 @strong{Do not send bug reports to @samp{info-gdb}, or to
30968 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
30969 not want to receive bug reports. Those that do have arranged to receive
30972 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
30973 serves as a repeater. The mailing list and the newsgroup carry exactly
30974 the same messages. Often people think of posting bug reports to the
30975 newsgroup instead of mailing them. This appears to work, but it has one
30976 problem which can be crucial: a newsgroup posting often lacks a mail
30977 path back to the sender. Thus, if we need to ask for more information,
30978 we may be unable to reach you. For this reason, it is better to send
30979 bug reports to the mailing list.
30981 @ifclear BUGURL_DEFAULT
30982 In any event, we also recommend that you submit bug reports for
30983 @value{GDBN} to @value{BUGURL}.
30987 The fundamental principle of reporting bugs usefully is this:
30988 @strong{report all the facts}. If you are not sure whether to state a
30989 fact or leave it out, state it!
30991 Often people omit facts because they think they know what causes the
30992 problem and assume that some details do not matter. Thus, you might
30993 assume that the name of the variable you use in an example does not matter.
30994 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
30995 stray memory reference which happens to fetch from the location where that
30996 name is stored in memory; perhaps, if the name were different, the contents
30997 of that location would fool the debugger into doing the right thing despite
30998 the bug. Play it safe and give a specific, complete example. That is the
30999 easiest thing for you to do, and the most helpful.
31001 Keep in mind that the purpose of a bug report is to enable us to fix the
31002 bug. It may be that the bug has been reported previously, but neither
31003 you nor we can know that unless your bug report is complete and
31006 Sometimes people give a few sketchy facts and ask, ``Does this ring a
31007 bell?'' Those bug reports are useless, and we urge everyone to
31008 @emph{refuse to respond to them} except to chide the sender to report
31011 To enable us to fix the bug, you should include all these things:
31015 The version of @value{GDBN}. @value{GDBN} announces it if you start
31016 with no arguments; you can also print it at any time using @code{show
31019 Without this, we will not know whether there is any point in looking for
31020 the bug in the current version of @value{GDBN}.
31023 The type of machine you are using, and the operating system name and
31027 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
31028 ``@value{GCC}--2.8.1''.
31031 What compiler (and its version) was used to compile the program you are
31032 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
31033 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
31034 to get this information; for other compilers, see the documentation for
31038 The command arguments you gave the compiler to compile your example and
31039 observe the bug. For example, did you use @samp{-O}? To guarantee
31040 you will not omit something important, list them all. A copy of the
31041 Makefile (or the output from make) is sufficient.
31043 If we were to try to guess the arguments, we would probably guess wrong
31044 and then we might not encounter the bug.
31047 A complete input script, and all necessary source files, that will
31051 A description of what behavior you observe that you believe is
31052 incorrect. For example, ``It gets a fatal signal.''
31054 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
31055 will certainly notice it. But if the bug is incorrect output, we might
31056 not notice unless it is glaringly wrong. You might as well not give us
31057 a chance to make a mistake.
31059 Even if the problem you experience is a fatal signal, you should still
31060 say so explicitly. Suppose something strange is going on, such as, your
31061 copy of @value{GDBN} is out of synch, or you have encountered a bug in
31062 the C library on your system. (This has happened!) Your copy might
31063 crash and ours would not. If you told us to expect a crash, then when
31064 ours fails to crash, we would know that the bug was not happening for
31065 us. If you had not told us to expect a crash, then we would not be able
31066 to draw any conclusion from our observations.
31069 @cindex recording a session script
31070 To collect all this information, you can use a session recording program
31071 such as @command{script}, which is available on many Unix systems.
31072 Just run your @value{GDBN} session inside @command{script} and then
31073 include the @file{typescript} file with your bug report.
31075 Another way to record a @value{GDBN} session is to run @value{GDBN}
31076 inside Emacs and then save the entire buffer to a file.
31079 If you wish to suggest changes to the @value{GDBN} source, send us context
31080 diffs. If you even discuss something in the @value{GDBN} source, refer to
31081 it by context, not by line number.
31083 The line numbers in our development sources will not match those in your
31084 sources. Your line numbers would convey no useful information to us.
31088 Here are some things that are not necessary:
31092 A description of the envelope of the bug.
31094 Often people who encounter a bug spend a lot of time investigating
31095 which changes to the input file will make the bug go away and which
31096 changes will not affect it.
31098 This is often time consuming and not very useful, because the way we
31099 will find the bug is by running a single example under the debugger
31100 with breakpoints, not by pure deduction from a series of examples.
31101 We recommend that you save your time for something else.
31103 Of course, if you can find a simpler example to report @emph{instead}
31104 of the original one, that is a convenience for us. Errors in the
31105 output will be easier to spot, running under the debugger will take
31106 less time, and so on.
31108 However, simplification is not vital; if you do not want to do this,
31109 report the bug anyway and send us the entire test case you used.
31112 A patch for the bug.
31114 A patch for the bug does help us if it is a good one. But do not omit
31115 the necessary information, such as the test case, on the assumption that
31116 a patch is all we need. We might see problems with your patch and decide
31117 to fix the problem another way, or we might not understand it at all.
31119 Sometimes with a program as complicated as @value{GDBN} it is very hard to
31120 construct an example that will make the program follow a certain path
31121 through the code. If you do not send us the example, we will not be able
31122 to construct one, so we will not be able to verify that the bug is fixed.
31124 And if we cannot understand what bug you are trying to fix, or why your
31125 patch should be an improvement, we will not install it. A test case will
31126 help us to understand.
31129 A guess about what the bug is or what it depends on.
31131 Such guesses are usually wrong. Even we cannot guess right about such
31132 things without first using the debugger to find the facts.
31135 @c The readline documentation is distributed with the readline code
31136 @c and consists of the two following files:
31139 @c Use -I with makeinfo to point to the appropriate directory,
31140 @c environment var TEXINPUTS with TeX.
31141 @ifclear SYSTEM_READLINE
31142 @include rluser.texi
31143 @include hsuser.texi
31147 @appendix In Memoriam
31149 The @value{GDBN} project mourns the loss of the following long-time
31154 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
31155 to Free Software in general. Outside of @value{GDBN}, he was known in
31156 the Amiga world for his series of Fish Disks, and the GeekGadget project.
31158 @item Michael Snyder
31159 Michael was one of the Global Maintainers of the @value{GDBN} project,
31160 with contributions recorded as early as 1996, until 2011. In addition
31161 to his day to day participation, he was a large driving force behind
31162 adding Reverse Debugging to @value{GDBN}.
31165 Beyond their technical contributions to the project, they were also
31166 enjoyable members of the Free Software Community. We will miss them.
31168 @node Formatting Documentation
31169 @appendix Formatting Documentation
31171 @cindex @value{GDBN} reference card
31172 @cindex reference card
31173 The @value{GDBN} 4 release includes an already-formatted reference card, ready
31174 for printing with PostScript or Ghostscript, in the @file{gdb}
31175 subdirectory of the main source directory@footnote{In
31176 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
31177 release.}. If you can use PostScript or Ghostscript with your printer,
31178 you can print the reference card immediately with @file{refcard.ps}.
31180 The release also includes the source for the reference card. You
31181 can format it, using @TeX{}, by typing:
31187 The @value{GDBN} reference card is designed to print in @dfn{landscape}
31188 mode on US ``letter'' size paper;
31189 that is, on a sheet 11 inches wide by 8.5 inches
31190 high. You will need to specify this form of printing as an option to
31191 your @sc{dvi} output program.
31193 @cindex documentation
31195 All the documentation for @value{GDBN} comes as part of the machine-readable
31196 distribution. The documentation is written in Texinfo format, which is
31197 a documentation system that uses a single source file to produce both
31198 on-line information and a printed manual. You can use one of the Info
31199 formatting commands to create the on-line version of the documentation
31200 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
31202 @value{GDBN} includes an already formatted copy of the on-line Info
31203 version of this manual in the @file{gdb} subdirectory. The main Info
31204 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
31205 subordinate files matching @samp{gdb.info*} in the same directory. If
31206 necessary, you can print out these files, or read them with any editor;
31207 but they are easier to read using the @code{info} subsystem in @sc{gnu}
31208 Emacs or the standalone @code{info} program, available as part of the
31209 @sc{gnu} Texinfo distribution.
31211 If you want to format these Info files yourself, you need one of the
31212 Info formatting programs, such as @code{texinfo-format-buffer} or
31215 If you have @code{makeinfo} installed, and are in the top level
31216 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
31217 version @value{GDBVN}), you can make the Info file by typing:
31224 If you want to typeset and print copies of this manual, you need @TeX{},
31225 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
31226 Texinfo definitions file.
31228 @TeX{} is a typesetting program; it does not print files directly, but
31229 produces output files called @sc{dvi} files. To print a typeset
31230 document, you need a program to print @sc{dvi} files. If your system
31231 has @TeX{} installed, chances are it has such a program. The precise
31232 command to use depends on your system; @kbd{lpr -d} is common; another
31233 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
31234 require a file name without any extension or a @samp{.dvi} extension.
31236 @TeX{} also requires a macro definitions file called
31237 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
31238 written in Texinfo format. On its own, @TeX{} cannot either read or
31239 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
31240 and is located in the @file{gdb-@var{version-number}/texinfo}
31243 If you have @TeX{} and a @sc{dvi} printer program installed, you can
31244 typeset and print this manual. First switch to the @file{gdb}
31245 subdirectory of the main source directory (for example, to
31246 @file{gdb-@value{GDBVN}/gdb}) and type:
31252 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
31254 @node Installing GDB
31255 @appendix Installing @value{GDBN}
31256 @cindex installation
31259 * Requirements:: Requirements for building @value{GDBN}
31260 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
31261 * Separate Objdir:: Compiling @value{GDBN} in another directory
31262 * Config Names:: Specifying names for hosts and targets
31263 * Configure Options:: Summary of options for configure
31264 * System-wide configuration:: Having a system-wide init file
31268 @section Requirements for Building @value{GDBN}
31269 @cindex building @value{GDBN}, requirements for
31271 Building @value{GDBN} requires various tools and packages to be available.
31272 Other packages will be used only if they are found.
31274 @heading Tools/Packages Necessary for Building @value{GDBN}
31276 @item ISO C90 compiler
31277 @value{GDBN} is written in ISO C90. It should be buildable with any
31278 working C90 compiler, e.g.@: GCC.
31282 @heading Tools/Packages Optional for Building @value{GDBN}
31286 @value{GDBN} can use the Expat XML parsing library. This library may be
31287 included with your operating system distribution; if it is not, you
31288 can get the latest version from @url{http://expat.sourceforge.net}.
31289 The @file{configure} script will search for this library in several
31290 standard locations; if it is installed in an unusual path, you can
31291 use the @option{--with-libexpat-prefix} option to specify its location.
31297 Remote protocol memory maps (@pxref{Memory Map Format})
31299 Target descriptions (@pxref{Target Descriptions})
31301 Remote shared library lists (@pxref{Library List Format})
31303 MS-Windows shared libraries (@pxref{Shared Libraries})
31305 Traceframe info (@pxref{Traceframe Info Format})
31309 @cindex compressed debug sections
31310 @value{GDBN} will use the @samp{zlib} library, if available, to read
31311 compressed debug sections. Some linkers, such as GNU gold, are capable
31312 of producing binaries with compressed debug sections. If @value{GDBN}
31313 is compiled with @samp{zlib}, it will be able to read the debug
31314 information in such binaries.
31316 The @samp{zlib} library is likely included with your operating system
31317 distribution; if it is not, you can get the latest version from
31318 @url{http://zlib.net}.
31321 @value{GDBN}'s features related to character sets (@pxref{Character
31322 Sets}) require a functioning @code{iconv} implementation. If you are
31323 on a GNU system, then this is provided by the GNU C Library. Some
31324 other systems also provide a working @code{iconv}.
31326 If @value{GDBN} is using the @code{iconv} program which is installed
31327 in a non-standard place, you will need to tell @value{GDBN} where to find it.
31328 This is done with @option{--with-iconv-bin} which specifies the
31329 directory that contains the @code{iconv} program.
31331 On systems without @code{iconv}, you can install GNU Libiconv. If you
31332 have previously installed Libiconv, you can use the
31333 @option{--with-libiconv-prefix} option to configure.
31335 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
31336 arrange to build Libiconv if a directory named @file{libiconv} appears
31337 in the top-most source directory. If Libiconv is built this way, and
31338 if the operating system does not provide a suitable @code{iconv}
31339 implementation, then the just-built library will automatically be used
31340 by @value{GDBN}. One easy way to set this up is to download GNU
31341 Libiconv, unpack it, and then rename the directory holding the
31342 Libiconv source code to @samp{libiconv}.
31345 @node Running Configure
31346 @section Invoking the @value{GDBN} @file{configure} Script
31347 @cindex configuring @value{GDBN}
31348 @value{GDBN} comes with a @file{configure} script that automates the process
31349 of preparing @value{GDBN} for installation; you can then use @code{make} to
31350 build the @code{gdb} program.
31352 @c irrelevant in info file; it's as current as the code it lives with.
31353 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
31354 look at the @file{README} file in the sources; we may have improved the
31355 installation procedures since publishing this manual.}
31358 The @value{GDBN} distribution includes all the source code you need for
31359 @value{GDBN} in a single directory, whose name is usually composed by
31360 appending the version number to @samp{gdb}.
31362 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
31363 @file{gdb-@value{GDBVN}} directory. That directory contains:
31366 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
31367 script for configuring @value{GDBN} and all its supporting libraries
31369 @item gdb-@value{GDBVN}/gdb
31370 the source specific to @value{GDBN} itself
31372 @item gdb-@value{GDBVN}/bfd
31373 source for the Binary File Descriptor library
31375 @item gdb-@value{GDBVN}/include
31376 @sc{gnu} include files
31378 @item gdb-@value{GDBVN}/libiberty
31379 source for the @samp{-liberty} free software library
31381 @item gdb-@value{GDBVN}/opcodes
31382 source for the library of opcode tables and disassemblers
31384 @item gdb-@value{GDBVN}/readline
31385 source for the @sc{gnu} command-line interface
31387 @item gdb-@value{GDBVN}/glob
31388 source for the @sc{gnu} filename pattern-matching subroutine
31390 @item gdb-@value{GDBVN}/mmalloc
31391 source for the @sc{gnu} memory-mapped malloc package
31394 The simplest way to configure and build @value{GDBN} is to run @file{configure}
31395 from the @file{gdb-@var{version-number}} source directory, which in
31396 this example is the @file{gdb-@value{GDBVN}} directory.
31398 First switch to the @file{gdb-@var{version-number}} source directory
31399 if you are not already in it; then run @file{configure}. Pass the
31400 identifier for the platform on which @value{GDBN} will run as an
31406 cd gdb-@value{GDBVN}
31407 ./configure @var{host}
31412 where @var{host} is an identifier such as @samp{sun4} or
31413 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
31414 (You can often leave off @var{host}; @file{configure} tries to guess the
31415 correct value by examining your system.)
31417 Running @samp{configure @var{host}} and then running @code{make} builds the
31418 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
31419 libraries, then @code{gdb} itself. The configured source files, and the
31420 binaries, are left in the corresponding source directories.
31423 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
31424 system does not recognize this automatically when you run a different
31425 shell, you may need to run @code{sh} on it explicitly:
31428 sh configure @var{host}
31431 If you run @file{configure} from a directory that contains source
31432 directories for multiple libraries or programs, such as the
31433 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
31435 creates configuration files for every directory level underneath (unless
31436 you tell it not to, with the @samp{--norecursion} option).
31438 You should run the @file{configure} script from the top directory in the
31439 source tree, the @file{gdb-@var{version-number}} directory. If you run
31440 @file{configure} from one of the subdirectories, you will configure only
31441 that subdirectory. That is usually not what you want. In particular,
31442 if you run the first @file{configure} from the @file{gdb} subdirectory
31443 of the @file{gdb-@var{version-number}} directory, you will omit the
31444 configuration of @file{bfd}, @file{readline}, and other sibling
31445 directories of the @file{gdb} subdirectory. This leads to build errors
31446 about missing include files such as @file{bfd/bfd.h}.
31448 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
31449 However, you should make sure that the shell on your path (named by
31450 the @samp{SHELL} environment variable) is publicly readable. Remember
31451 that @value{GDBN} uses the shell to start your program---some systems refuse to
31452 let @value{GDBN} debug child processes whose programs are not readable.
31454 @node Separate Objdir
31455 @section Compiling @value{GDBN} in Another Directory
31457 If you want to run @value{GDBN} versions for several host or target machines,
31458 you need a different @code{gdb} compiled for each combination of
31459 host and target. @file{configure} is designed to make this easy by
31460 allowing you to generate each configuration in a separate subdirectory,
31461 rather than in the source directory. If your @code{make} program
31462 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
31463 @code{make} in each of these directories builds the @code{gdb}
31464 program specified there.
31466 To build @code{gdb} in a separate directory, run @file{configure}
31467 with the @samp{--srcdir} option to specify where to find the source.
31468 (You also need to specify a path to find @file{configure}
31469 itself from your working directory. If the path to @file{configure}
31470 would be the same as the argument to @samp{--srcdir}, you can leave out
31471 the @samp{--srcdir} option; it is assumed.)
31473 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
31474 separate directory for a Sun 4 like this:
31478 cd gdb-@value{GDBVN}
31481 ../gdb-@value{GDBVN}/configure sun4
31486 When @file{configure} builds a configuration using a remote source
31487 directory, it creates a tree for the binaries with the same structure
31488 (and using the same names) as the tree under the source directory. In
31489 the example, you'd find the Sun 4 library @file{libiberty.a} in the
31490 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
31491 @file{gdb-sun4/gdb}.
31493 Make sure that your path to the @file{configure} script has just one
31494 instance of @file{gdb} in it. If your path to @file{configure} looks
31495 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
31496 one subdirectory of @value{GDBN}, not the whole package. This leads to
31497 build errors about missing include files such as @file{bfd/bfd.h}.
31499 One popular reason to build several @value{GDBN} configurations in separate
31500 directories is to configure @value{GDBN} for cross-compiling (where
31501 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
31502 programs that run on another machine---the @dfn{target}).
31503 You specify a cross-debugging target by
31504 giving the @samp{--target=@var{target}} option to @file{configure}.
31506 When you run @code{make} to build a program or library, you must run
31507 it in a configured directory---whatever directory you were in when you
31508 called @file{configure} (or one of its subdirectories).
31510 The @code{Makefile} that @file{configure} generates in each source
31511 directory also runs recursively. If you type @code{make} in a source
31512 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
31513 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
31514 will build all the required libraries, and then build GDB.
31516 When you have multiple hosts or targets configured in separate
31517 directories, you can run @code{make} on them in parallel (for example,
31518 if they are NFS-mounted on each of the hosts); they will not interfere
31522 @section Specifying Names for Hosts and Targets
31524 The specifications used for hosts and targets in the @file{configure}
31525 script are based on a three-part naming scheme, but some short predefined
31526 aliases are also supported. The full naming scheme encodes three pieces
31527 of information in the following pattern:
31530 @var{architecture}-@var{vendor}-@var{os}
31533 For example, you can use the alias @code{sun4} as a @var{host} argument,
31534 or as the value for @var{target} in a @code{--target=@var{target}}
31535 option. The equivalent full name is @samp{sparc-sun-sunos4}.
31537 The @file{configure} script accompanying @value{GDBN} does not provide
31538 any query facility to list all supported host and target names or
31539 aliases. @file{configure} calls the Bourne shell script
31540 @code{config.sub} to map abbreviations to full names; you can read the
31541 script, if you wish, or you can use it to test your guesses on
31542 abbreviations---for example:
31545 % sh config.sub i386-linux
31547 % sh config.sub alpha-linux
31548 alpha-unknown-linux-gnu
31549 % sh config.sub hp9k700
31551 % sh config.sub sun4
31552 sparc-sun-sunos4.1.1
31553 % sh config.sub sun3
31554 m68k-sun-sunos4.1.1
31555 % sh config.sub i986v
31556 Invalid configuration `i986v': machine `i986v' not recognized
31560 @code{config.sub} is also distributed in the @value{GDBN} source
31561 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
31563 @node Configure Options
31564 @section @file{configure} Options
31566 Here is a summary of the @file{configure} options and arguments that
31567 are most often useful for building @value{GDBN}. @file{configure} also has
31568 several other options not listed here. @inforef{What Configure
31569 Does,,configure.info}, for a full explanation of @file{configure}.
31572 configure @r{[}--help@r{]}
31573 @r{[}--prefix=@var{dir}@r{]}
31574 @r{[}--exec-prefix=@var{dir}@r{]}
31575 @r{[}--srcdir=@var{dirname}@r{]}
31576 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
31577 @r{[}--target=@var{target}@r{]}
31582 You may introduce options with a single @samp{-} rather than
31583 @samp{--} if you prefer; but you may abbreviate option names if you use
31588 Display a quick summary of how to invoke @file{configure}.
31590 @item --prefix=@var{dir}
31591 Configure the source to install programs and files under directory
31594 @item --exec-prefix=@var{dir}
31595 Configure the source to install programs under directory
31598 @c avoid splitting the warning from the explanation:
31600 @item --srcdir=@var{dirname}
31601 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
31602 @code{make} that implements the @code{VPATH} feature.}@*
31603 Use this option to make configurations in directories separate from the
31604 @value{GDBN} source directories. Among other things, you can use this to
31605 build (or maintain) several configurations simultaneously, in separate
31606 directories. @file{configure} writes configuration-specific files in
31607 the current directory, but arranges for them to use the source in the
31608 directory @var{dirname}. @file{configure} creates directories under
31609 the working directory in parallel to the source directories below
31612 @item --norecursion
31613 Configure only the directory level where @file{configure} is executed; do not
31614 propagate configuration to subdirectories.
31616 @item --target=@var{target}
31617 Configure @value{GDBN} for cross-debugging programs running on the specified
31618 @var{target}. Without this option, @value{GDBN} is configured to debug
31619 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
31621 There is no convenient way to generate a list of all available targets.
31623 @item @var{host} @dots{}
31624 Configure @value{GDBN} to run on the specified @var{host}.
31626 There is no convenient way to generate a list of all available hosts.
31629 There are many other options available as well, but they are generally
31630 needed for special purposes only.
31632 @node System-wide configuration
31633 @section System-wide configuration and settings
31634 @cindex system-wide init file
31636 @value{GDBN} can be configured to have a system-wide init file;
31637 this file will be read and executed at startup (@pxref{Startup, , What
31638 @value{GDBN} does during startup}).
31640 Here is the corresponding configure option:
31643 @item --with-system-gdbinit=@var{file}
31644 Specify that the default location of the system-wide init file is
31648 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
31649 it may be subject to relocation. Two possible cases:
31653 If the default location of this init file contains @file{$prefix},
31654 it will be subject to relocation. Suppose that the configure options
31655 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
31656 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
31657 init file is looked for as @file{$install/etc/gdbinit} instead of
31658 @file{$prefix/etc/gdbinit}.
31661 By contrast, if the default location does not contain the prefix,
31662 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
31663 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
31664 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
31665 wherever @value{GDBN} is installed.
31668 @node Maintenance Commands
31669 @appendix Maintenance Commands
31670 @cindex maintenance commands
31671 @cindex internal commands
31673 In addition to commands intended for @value{GDBN} users, @value{GDBN}
31674 includes a number of commands intended for @value{GDBN} developers,
31675 that are not documented elsewhere in this manual. These commands are
31676 provided here for reference. (For commands that turn on debugging
31677 messages, see @ref{Debugging Output}.)
31680 @kindex maint agent
31681 @kindex maint agent-eval
31682 @item maint agent @var{expression}
31683 @itemx maint agent-eval @var{expression}
31684 Translate the given @var{expression} into remote agent bytecodes.
31685 This command is useful for debugging the Agent Expression mechanism
31686 (@pxref{Agent Expressions}). The @samp{agent} version produces an
31687 expression useful for data collection, such as by tracepoints, while
31688 @samp{maint agent-eval} produces an expression that evaluates directly
31689 to a result. For instance, a collection expression for @code{globa +
31690 globb} will include bytecodes to record four bytes of memory at each
31691 of the addresses of @code{globa} and @code{globb}, while discarding
31692 the result of the addition, while an evaluation expression will do the
31693 addition and return the sum.
31695 @kindex maint info breakpoints
31696 @item @anchor{maint info breakpoints}maint info breakpoints
31697 Using the same format as @samp{info breakpoints}, display both the
31698 breakpoints you've set explicitly, and those @value{GDBN} is using for
31699 internal purposes. Internal breakpoints are shown with negative
31700 breakpoint numbers. The type column identifies what kind of breakpoint
31705 Normal, explicitly set breakpoint.
31708 Normal, explicitly set watchpoint.
31711 Internal breakpoint, used to handle correctly stepping through
31712 @code{longjmp} calls.
31714 @item longjmp resume
31715 Internal breakpoint at the target of a @code{longjmp}.
31718 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
31721 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
31724 Shared library events.
31728 @kindex set displaced-stepping
31729 @kindex show displaced-stepping
31730 @cindex displaced stepping support
31731 @cindex out-of-line single-stepping
31732 @item set displaced-stepping
31733 @itemx show displaced-stepping
31734 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
31735 if the target supports it. Displaced stepping is a way to single-step
31736 over breakpoints without removing them from the inferior, by executing
31737 an out-of-line copy of the instruction that was originally at the
31738 breakpoint location. It is also known as out-of-line single-stepping.
31741 @item set displaced-stepping on
31742 If the target architecture supports it, @value{GDBN} will use
31743 displaced stepping to step over breakpoints.
31745 @item set displaced-stepping off
31746 @value{GDBN} will not use displaced stepping to step over breakpoints,
31747 even if such is supported by the target architecture.
31749 @cindex non-stop mode, and @samp{set displaced-stepping}
31750 @item set displaced-stepping auto
31751 This is the default mode. @value{GDBN} will use displaced stepping
31752 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
31753 architecture supports displaced stepping.
31756 @kindex maint check-symtabs
31757 @item maint check-symtabs
31758 Check the consistency of psymtabs and symtabs.
31760 @kindex maint cplus first_component
31761 @item maint cplus first_component @var{name}
31762 Print the first C@t{++} class/namespace component of @var{name}.
31764 @kindex maint cplus namespace
31765 @item maint cplus namespace
31766 Print the list of possible C@t{++} namespaces.
31768 @kindex maint demangle
31769 @item maint demangle @var{name}
31770 Demangle a C@t{++} or Objective-C mangled @var{name}.
31772 @kindex maint deprecate
31773 @kindex maint undeprecate
31774 @cindex deprecated commands
31775 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
31776 @itemx maint undeprecate @var{command}
31777 Deprecate or undeprecate the named @var{command}. Deprecated commands
31778 cause @value{GDBN} to issue a warning when you use them. The optional
31779 argument @var{replacement} says which newer command should be used in
31780 favor of the deprecated one; if it is given, @value{GDBN} will mention
31781 the replacement as part of the warning.
31783 @kindex maint dump-me
31784 @item maint dump-me
31785 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31786 Cause a fatal signal in the debugger and force it to dump its core.
31787 This is supported only on systems which support aborting a program
31788 with the @code{SIGQUIT} signal.
31790 @kindex maint internal-error
31791 @kindex maint internal-warning
31792 @item maint internal-error @r{[}@var{message-text}@r{]}
31793 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31794 Cause @value{GDBN} to call the internal function @code{internal_error}
31795 or @code{internal_warning} and hence behave as though an internal error
31796 or internal warning has been detected. In addition to reporting the
31797 internal problem, these functions give the user the opportunity to
31798 either quit @value{GDBN} or create a core file of the current
31799 @value{GDBN} session.
31801 These commands take an optional parameter @var{message-text} that is
31802 used as the text of the error or warning message.
31804 Here's an example of using @code{internal-error}:
31807 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31808 @dots{}/maint.c:121: internal-error: testing, 1, 2
31809 A problem internal to GDB has been detected. Further
31810 debugging may prove unreliable.
31811 Quit this debugging session? (y or n) @kbd{n}
31812 Create a core file? (y or n) @kbd{n}
31816 @cindex @value{GDBN} internal error
31817 @cindex internal errors, control of @value{GDBN} behavior
31819 @kindex maint set internal-error
31820 @kindex maint show internal-error
31821 @kindex maint set internal-warning
31822 @kindex maint show internal-warning
31823 @item maint set internal-error @var{action} [ask|yes|no]
31824 @itemx maint show internal-error @var{action}
31825 @itemx maint set internal-warning @var{action} [ask|yes|no]
31826 @itemx maint show internal-warning @var{action}
31827 When @value{GDBN} reports an internal problem (error or warning) it
31828 gives the user the opportunity to both quit @value{GDBN} and create a
31829 core file of the current @value{GDBN} session. These commands let you
31830 override the default behaviour for each particular @var{action},
31831 described in the table below.
31835 You can specify that @value{GDBN} should always (yes) or never (no)
31836 quit. The default is to ask the user what to do.
31839 You can specify that @value{GDBN} should always (yes) or never (no)
31840 create a core file. The default is to ask the user what to do.
31843 @kindex maint packet
31844 @item maint packet @var{text}
31845 If @value{GDBN} is talking to an inferior via the serial protocol,
31846 then this command sends the string @var{text} to the inferior, and
31847 displays the response packet. @value{GDBN} supplies the initial
31848 @samp{$} character, the terminating @samp{#} character, and the
31851 @kindex maint print architecture
31852 @item maint print architecture @r{[}@var{file}@r{]}
31853 Print the entire architecture configuration. The optional argument
31854 @var{file} names the file where the output goes.
31856 @kindex maint print c-tdesc
31857 @item maint print c-tdesc
31858 Print the current target description (@pxref{Target Descriptions}) as
31859 a C source file. The created source file can be used in @value{GDBN}
31860 when an XML parser is not available to parse the description.
31862 @kindex maint print dummy-frames
31863 @item maint print dummy-frames
31864 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
31867 (@value{GDBP}) @kbd{b add}
31869 (@value{GDBP}) @kbd{print add(2,3)}
31870 Breakpoint 2, add (a=2, b=3) at @dots{}
31872 The program being debugged stopped while in a function called from GDB.
31874 (@value{GDBP}) @kbd{maint print dummy-frames}
31875 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
31876 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
31877 call_lo=0x01014000 call_hi=0x01014001
31881 Takes an optional file parameter.
31883 @kindex maint print registers
31884 @kindex maint print raw-registers
31885 @kindex maint print cooked-registers
31886 @kindex maint print register-groups
31887 @kindex maint print remote-registers
31888 @item maint print registers @r{[}@var{file}@r{]}
31889 @itemx maint print raw-registers @r{[}@var{file}@r{]}
31890 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
31891 @itemx maint print register-groups @r{[}@var{file}@r{]}
31892 @itemx maint print remote-registers @r{[}@var{file}@r{]}
31893 Print @value{GDBN}'s internal register data structures.
31895 The command @code{maint print raw-registers} includes the contents of
31896 the raw register cache; the command @code{maint print
31897 cooked-registers} includes the (cooked) value of all registers,
31898 including registers which aren't available on the target nor visible
31899 to user; the command @code{maint print register-groups} includes the
31900 groups that each register is a member of; and the command @code{maint
31901 print remote-registers} includes the remote target's register numbers
31902 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
31903 @value{GDBN} Internals}.
31905 These commands take an optional parameter, a file name to which to
31906 write the information.
31908 @kindex maint print reggroups
31909 @item maint print reggroups @r{[}@var{file}@r{]}
31910 Print @value{GDBN}'s internal register group data structures. The
31911 optional argument @var{file} tells to what file to write the
31914 The register groups info looks like this:
31917 (@value{GDBP}) @kbd{maint print reggroups}
31930 This command forces @value{GDBN} to flush its internal register cache.
31932 @kindex maint print objfiles
31933 @cindex info for known object files
31934 @item maint print objfiles
31935 Print a dump of all known object files. For each object file, this
31936 command prints its name, address in memory, and all of its psymtabs
31939 @kindex maint print section-scripts
31940 @cindex info for known .debug_gdb_scripts-loaded scripts
31941 @item maint print section-scripts [@var{regexp}]
31942 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
31943 If @var{regexp} is specified, only print scripts loaded by object files
31944 matching @var{regexp}.
31945 For each script, this command prints its name as specified in the objfile,
31946 and the full path if known.
31947 @xref{.debug_gdb_scripts section}.
31949 @kindex maint print statistics
31950 @cindex bcache statistics
31951 @item maint print statistics
31952 This command prints, for each object file in the program, various data
31953 about that object file followed by the byte cache (@dfn{bcache})
31954 statistics for the object file. The objfile data includes the number
31955 of minimal, partial, full, and stabs symbols, the number of types
31956 defined by the objfile, the number of as yet unexpanded psym tables,
31957 the number of line tables and string tables, and the amount of memory
31958 used by the various tables. The bcache statistics include the counts,
31959 sizes, and counts of duplicates of all and unique objects, max,
31960 average, and median entry size, total memory used and its overhead and
31961 savings, and various measures of the hash table size and chain
31964 @kindex maint print target-stack
31965 @cindex target stack description
31966 @item maint print target-stack
31967 A @dfn{target} is an interface between the debugger and a particular
31968 kind of file or process. Targets can be stacked in @dfn{strata},
31969 so that more than one target can potentially respond to a request.
31970 In particular, memory accesses will walk down the stack of targets
31971 until they find a target that is interested in handling that particular
31974 This command prints a short description of each layer that was pushed on
31975 the @dfn{target stack}, starting from the top layer down to the bottom one.
31977 @kindex maint print type
31978 @cindex type chain of a data type
31979 @item maint print type @var{expr}
31980 Print the type chain for a type specified by @var{expr}. The argument
31981 can be either a type name or a symbol. If it is a symbol, the type of
31982 that symbol is described. The type chain produced by this command is
31983 a recursive definition of the data type as stored in @value{GDBN}'s
31984 data structures, including its flags and contained types.
31986 @kindex maint set dwarf2 always-disassemble
31987 @kindex maint show dwarf2 always-disassemble
31988 @item maint set dwarf2 always-disassemble
31989 @item maint show dwarf2 always-disassemble
31990 Control the behavior of @code{info address} when using DWARF debugging
31993 The default is @code{off}, which means that @value{GDBN} should try to
31994 describe a variable's location in an easily readable format. When
31995 @code{on}, @value{GDBN} will instead display the DWARF location
31996 expression in an assembly-like format. Note that some locations are
31997 too complex for @value{GDBN} to describe simply; in this case you will
31998 always see the disassembly form.
32000 Here is an example of the resulting disassembly:
32003 (gdb) info addr argc
32004 Symbol "argc" is a complex DWARF expression:
32008 For more information on these expressions, see
32009 @uref{http://www.dwarfstd.org/, the DWARF standard}.
32011 @kindex maint set dwarf2 max-cache-age
32012 @kindex maint show dwarf2 max-cache-age
32013 @item maint set dwarf2 max-cache-age
32014 @itemx maint show dwarf2 max-cache-age
32015 Control the DWARF 2 compilation unit cache.
32017 @cindex DWARF 2 compilation units cache
32018 In object files with inter-compilation-unit references, such as those
32019 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
32020 reader needs to frequently refer to previously read compilation units.
32021 This setting controls how long a compilation unit will remain in the
32022 cache if it is not referenced. A higher limit means that cached
32023 compilation units will be stored in memory longer, and more total
32024 memory will be used. Setting it to zero disables caching, which will
32025 slow down @value{GDBN} startup, but reduce memory consumption.
32027 @kindex maint set profile
32028 @kindex maint show profile
32029 @cindex profiling GDB
32030 @item maint set profile
32031 @itemx maint show profile
32032 Control profiling of @value{GDBN}.
32034 Profiling will be disabled until you use the @samp{maint set profile}
32035 command to enable it. When you enable profiling, the system will begin
32036 collecting timing and execution count data; when you disable profiling or
32037 exit @value{GDBN}, the results will be written to a log file. Remember that
32038 if you use profiling, @value{GDBN} will overwrite the profiling log file
32039 (often called @file{gmon.out}). If you have a record of important profiling
32040 data in a @file{gmon.out} file, be sure to move it to a safe location.
32042 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
32043 compiled with the @samp{-pg} compiler option.
32045 @kindex maint set show-debug-regs
32046 @kindex maint show show-debug-regs
32047 @cindex hardware debug registers
32048 @item maint set show-debug-regs
32049 @itemx maint show show-debug-regs
32050 Control whether to show variables that mirror the hardware debug
32051 registers. Use @code{ON} to enable, @code{OFF} to disable. If
32052 enabled, the debug registers values are shown when @value{GDBN} inserts or
32053 removes a hardware breakpoint or watchpoint, and when the inferior
32054 triggers a hardware-assisted breakpoint or watchpoint.
32056 @kindex maint set show-all-tib
32057 @kindex maint show show-all-tib
32058 @item maint set show-all-tib
32059 @itemx maint show show-all-tib
32060 Control whether to show all non zero areas within a 1k block starting
32061 at thread local base, when using the @samp{info w32 thread-information-block}
32064 @kindex maint space
32065 @cindex memory used by commands
32067 Control whether to display memory usage for each command. If set to a
32068 nonzero value, @value{GDBN} will display how much memory each command
32069 took, following the command's own output. This can also be requested
32070 by invoking @value{GDBN} with the @option{--statistics} command-line
32071 switch (@pxref{Mode Options}).
32074 @cindex time of command execution
32076 Control whether to display the execution time for each command. If
32077 set to a nonzero value, @value{GDBN} will display how much time it
32078 took to execute each command, following the command's own output.
32079 The time is not printed for the commands that run the target, since
32080 there's no mechanism currently to compute how much time was spend
32081 by @value{GDBN} and how much time was spend by the program been debugged.
32082 it's not possibly currently
32083 This can also be requested by invoking @value{GDBN} with the
32084 @option{--statistics} command-line switch (@pxref{Mode Options}).
32086 @kindex maint translate-address
32087 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
32088 Find the symbol stored at the location specified by the address
32089 @var{addr} and an optional section name @var{section}. If found,
32090 @value{GDBN} prints the name of the closest symbol and an offset from
32091 the symbol's location to the specified address. This is similar to
32092 the @code{info address} command (@pxref{Symbols}), except that this
32093 command also allows to find symbols in other sections.
32095 If section was not specified, the section in which the symbol was found
32096 is also printed. For dynamically linked executables, the name of
32097 executable or shared library containing the symbol is printed as well.
32101 The following command is useful for non-interactive invocations of
32102 @value{GDBN}, such as in the test suite.
32105 @item set watchdog @var{nsec}
32106 @kindex set watchdog
32107 @cindex watchdog timer
32108 @cindex timeout for commands
32109 Set the maximum number of seconds @value{GDBN} will wait for the
32110 target operation to finish. If this time expires, @value{GDBN}
32111 reports and error and the command is aborted.
32113 @item show watchdog
32114 Show the current setting of the target wait timeout.
32117 @node Remote Protocol
32118 @appendix @value{GDBN} Remote Serial Protocol
32123 * Stop Reply Packets::
32124 * General Query Packets::
32125 * Architecture-Specific Protocol Details::
32126 * Tracepoint Packets::
32127 * Host I/O Packets::
32129 * Notification Packets::
32130 * Remote Non-Stop::
32131 * Packet Acknowledgment::
32133 * File-I/O Remote Protocol Extension::
32134 * Library List Format::
32135 * Memory Map Format::
32136 * Thread List Format::
32137 * Traceframe Info Format::
32143 There may be occasions when you need to know something about the
32144 protocol---for example, if there is only one serial port to your target
32145 machine, you might want your program to do something special if it
32146 recognizes a packet meant for @value{GDBN}.
32148 In the examples below, @samp{->} and @samp{<-} are used to indicate
32149 transmitted and received data, respectively.
32151 @cindex protocol, @value{GDBN} remote serial
32152 @cindex serial protocol, @value{GDBN} remote
32153 @cindex remote serial protocol
32154 All @value{GDBN} commands and responses (other than acknowledgments
32155 and notifications, see @ref{Notification Packets}) are sent as a
32156 @var{packet}. A @var{packet} is introduced with the character
32157 @samp{$}, the actual @var{packet-data}, and the terminating character
32158 @samp{#} followed by a two-digit @var{checksum}:
32161 @code{$}@var{packet-data}@code{#}@var{checksum}
32165 @cindex checksum, for @value{GDBN} remote
32167 The two-digit @var{checksum} is computed as the modulo 256 sum of all
32168 characters between the leading @samp{$} and the trailing @samp{#} (an
32169 eight bit unsigned checksum).
32171 Implementors should note that prior to @value{GDBN} 5.0 the protocol
32172 specification also included an optional two-digit @var{sequence-id}:
32175 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
32178 @cindex sequence-id, for @value{GDBN} remote
32180 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
32181 has never output @var{sequence-id}s. Stubs that handle packets added
32182 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
32184 When either the host or the target machine receives a packet, the first
32185 response expected is an acknowledgment: either @samp{+} (to indicate
32186 the package was received correctly) or @samp{-} (to request
32190 -> @code{$}@var{packet-data}@code{#}@var{checksum}
32195 The @samp{+}/@samp{-} acknowledgments can be disabled
32196 once a connection is established.
32197 @xref{Packet Acknowledgment}, for details.
32199 The host (@value{GDBN}) sends @var{command}s, and the target (the
32200 debugging stub incorporated in your program) sends a @var{response}. In
32201 the case of step and continue @var{command}s, the response is only sent
32202 when the operation has completed, and the target has again stopped all
32203 threads in all attached processes. This is the default all-stop mode
32204 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
32205 execution mode; see @ref{Remote Non-Stop}, for details.
32207 @var{packet-data} consists of a sequence of characters with the
32208 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
32211 @cindex remote protocol, field separator
32212 Fields within the packet should be separated using @samp{,} @samp{;} or
32213 @samp{:}. Except where otherwise noted all numbers are represented in
32214 @sc{hex} with leading zeros suppressed.
32216 Implementors should note that prior to @value{GDBN} 5.0, the character
32217 @samp{:} could not appear as the third character in a packet (as it
32218 would potentially conflict with the @var{sequence-id}).
32220 @cindex remote protocol, binary data
32221 @anchor{Binary Data}
32222 Binary data in most packets is encoded either as two hexadecimal
32223 digits per byte of binary data. This allowed the traditional remote
32224 protocol to work over connections which were only seven-bit clean.
32225 Some packets designed more recently assume an eight-bit clean
32226 connection, and use a more efficient encoding to send and receive
32229 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
32230 as an escape character. Any escaped byte is transmitted as the escape
32231 character followed by the original character XORed with @code{0x20}.
32232 For example, the byte @code{0x7d} would be transmitted as the two
32233 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
32234 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
32235 @samp{@}}) must always be escaped. Responses sent by the stub
32236 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
32237 is not interpreted as the start of a run-length encoded sequence
32240 Response @var{data} can be run-length encoded to save space.
32241 Run-length encoding replaces runs of identical characters with one
32242 instance of the repeated character, followed by a @samp{*} and a
32243 repeat count. The repeat count is itself sent encoded, to avoid
32244 binary characters in @var{data}: a value of @var{n} is sent as
32245 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
32246 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
32247 code 32) for a repeat count of 3. (This is because run-length
32248 encoding starts to win for counts 3 or more.) Thus, for example,
32249 @samp{0* } is a run-length encoding of ``0000'': the space character
32250 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
32253 The printable characters @samp{#} and @samp{$} or with a numeric value
32254 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
32255 seven repeats (@samp{$}) can be expanded using a repeat count of only
32256 five (@samp{"}). For example, @samp{00000000} can be encoded as
32259 The error response returned for some packets includes a two character
32260 error number. That number is not well defined.
32262 @cindex empty response, for unsupported packets
32263 For any @var{command} not supported by the stub, an empty response
32264 (@samp{$#00}) should be returned. That way it is possible to extend the
32265 protocol. A newer @value{GDBN} can tell if a packet is supported based
32268 At a minimum, a stub is required to support the @samp{g} and @samp{G}
32269 commands for register access, and the @samp{m} and @samp{M} commands
32270 for memory access. Stubs that only control single-threaded targets
32271 can implement run control with the @samp{c} (continue), and @samp{s}
32272 (step) commands. Stubs that support multi-threading targets should
32273 support the @samp{vCont} command. All other commands are optional.
32278 The following table provides a complete list of all currently defined
32279 @var{command}s and their corresponding response @var{data}.
32280 @xref{File-I/O Remote Protocol Extension}, for details about the File
32281 I/O extension of the remote protocol.
32283 Each packet's description has a template showing the packet's overall
32284 syntax, followed by an explanation of the packet's meaning. We
32285 include spaces in some of the templates for clarity; these are not
32286 part of the packet's syntax. No @value{GDBN} packet uses spaces to
32287 separate its components. For example, a template like @samp{foo
32288 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
32289 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
32290 @var{baz}. @value{GDBN} does not transmit a space character between the
32291 @samp{foo} and the @var{bar}, or between the @var{bar} and the
32294 @cindex @var{thread-id}, in remote protocol
32295 @anchor{thread-id syntax}
32296 Several packets and replies include a @var{thread-id} field to identify
32297 a thread. Normally these are positive numbers with a target-specific
32298 interpretation, formatted as big-endian hex strings. A @var{thread-id}
32299 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
32302 In addition, the remote protocol supports a multiprocess feature in
32303 which the @var{thread-id} syntax is extended to optionally include both
32304 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
32305 The @var{pid} (process) and @var{tid} (thread) components each have the
32306 format described above: a positive number with target-specific
32307 interpretation formatted as a big-endian hex string, literal @samp{-1}
32308 to indicate all processes or threads (respectively), or @samp{0} to
32309 indicate an arbitrary process or thread. Specifying just a process, as
32310 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
32311 error to specify all processes but a specific thread, such as
32312 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
32313 for those packets and replies explicitly documented to include a process
32314 ID, rather than a @var{thread-id}.
32316 The multiprocess @var{thread-id} syntax extensions are only used if both
32317 @value{GDBN} and the stub report support for the @samp{multiprocess}
32318 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
32321 Note that all packet forms beginning with an upper- or lower-case
32322 letter, other than those described here, are reserved for future use.
32324 Here are the packet descriptions.
32329 @cindex @samp{!} packet
32330 @anchor{extended mode}
32331 Enable extended mode. In extended mode, the remote server is made
32332 persistent. The @samp{R} packet is used to restart the program being
32338 The remote target both supports and has enabled extended mode.
32342 @cindex @samp{?} packet
32343 Indicate the reason the target halted. The reply is the same as for
32344 step and continue. This packet has a special interpretation when the
32345 target is in non-stop mode; see @ref{Remote Non-Stop}.
32348 @xref{Stop Reply Packets}, for the reply specifications.
32350 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
32351 @cindex @samp{A} packet
32352 Initialized @code{argv[]} array passed into program. @var{arglen}
32353 specifies the number of bytes in the hex encoded byte stream
32354 @var{arg}. See @code{gdbserver} for more details.
32359 The arguments were set.
32365 @cindex @samp{b} packet
32366 (Don't use this packet; its behavior is not well-defined.)
32367 Change the serial line speed to @var{baud}.
32369 JTC: @emph{When does the transport layer state change? When it's
32370 received, or after the ACK is transmitted. In either case, there are
32371 problems if the command or the acknowledgment packet is dropped.}
32373 Stan: @emph{If people really wanted to add something like this, and get
32374 it working for the first time, they ought to modify ser-unix.c to send
32375 some kind of out-of-band message to a specially-setup stub and have the
32376 switch happen "in between" packets, so that from remote protocol's point
32377 of view, nothing actually happened.}
32379 @item B @var{addr},@var{mode}
32380 @cindex @samp{B} packet
32381 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
32382 breakpoint at @var{addr}.
32384 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
32385 (@pxref{insert breakpoint or watchpoint packet}).
32387 @cindex @samp{bc} packet
32390 Backward continue. Execute the target system in reverse. No parameter.
32391 @xref{Reverse Execution}, for more information.
32394 @xref{Stop Reply Packets}, for the reply specifications.
32396 @cindex @samp{bs} packet
32399 Backward single step. Execute one instruction in reverse. No parameter.
32400 @xref{Reverse Execution}, for more information.
32403 @xref{Stop Reply Packets}, for the reply specifications.
32405 @item c @r{[}@var{addr}@r{]}
32406 @cindex @samp{c} packet
32407 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
32408 resume at current address.
32410 This packet is deprecated for multi-threading support. @xref{vCont
32414 @xref{Stop Reply Packets}, for the reply specifications.
32416 @item C @var{sig}@r{[};@var{addr}@r{]}
32417 @cindex @samp{C} packet
32418 Continue with signal @var{sig} (hex signal number). If
32419 @samp{;@var{addr}} is omitted, resume at same address.
32421 This packet is deprecated for multi-threading support. @xref{vCont
32425 @xref{Stop Reply Packets}, for the reply specifications.
32428 @cindex @samp{d} packet
32431 Don't use this packet; instead, define a general set packet
32432 (@pxref{General Query Packets}).
32436 @cindex @samp{D} packet
32437 The first form of the packet is used to detach @value{GDBN} from the
32438 remote system. It is sent to the remote target
32439 before @value{GDBN} disconnects via the @code{detach} command.
32441 The second form, including a process ID, is used when multiprocess
32442 protocol extensions are enabled (@pxref{multiprocess extensions}), to
32443 detach only a specific process. The @var{pid} is specified as a
32444 big-endian hex string.
32454 @item F @var{RC},@var{EE},@var{CF};@var{XX}
32455 @cindex @samp{F} packet
32456 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
32457 This is part of the File-I/O protocol extension. @xref{File-I/O
32458 Remote Protocol Extension}, for the specification.
32461 @anchor{read registers packet}
32462 @cindex @samp{g} packet
32463 Read general registers.
32467 @item @var{XX@dots{}}
32468 Each byte of register data is described by two hex digits. The bytes
32469 with the register are transmitted in target byte order. The size of
32470 each register and their position within the @samp{g} packet are
32471 determined by the @value{GDBN} internal gdbarch functions
32472 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
32473 specification of several standard @samp{g} packets is specified below.
32475 When reading registers from a trace frame (@pxref{Analyze Collected
32476 Data,,Using the Collected Data}), the stub may also return a string of
32477 literal @samp{x}'s in place of the register data digits, to indicate
32478 that the corresponding register has not been collected, thus its value
32479 is unavailable. For example, for an architecture with 4 registers of
32480 4 bytes each, the following reply indicates to @value{GDBN} that
32481 registers 0 and 2 have not been collected, while registers 1 and 3
32482 have been collected, and both have zero value:
32486 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
32493 @item G @var{XX@dots{}}
32494 @cindex @samp{G} packet
32495 Write general registers. @xref{read registers packet}, for a
32496 description of the @var{XX@dots{}} data.
32506 @item H @var{op} @var{thread-id}
32507 @cindex @samp{H} packet
32508 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
32509 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
32510 it should be @samp{c} for step and continue operations (note that this
32511 is deprecated, supporting the @samp{vCont} command is a better
32512 option), @samp{g} for other operations. The thread designator
32513 @var{thread-id} has the format and interpretation described in
32514 @ref{thread-id syntax}.
32525 @c 'H': How restrictive (or permissive) is the thread model. If a
32526 @c thread is selected and stopped, are other threads allowed
32527 @c to continue to execute? As I mentioned above, I think the
32528 @c semantics of each command when a thread is selected must be
32529 @c described. For example:
32531 @c 'g': If the stub supports threads and a specific thread is
32532 @c selected, returns the register block from that thread;
32533 @c otherwise returns current registers.
32535 @c 'G' If the stub supports threads and a specific thread is
32536 @c selected, sets the registers of the register block of
32537 @c that thread; otherwise sets current registers.
32539 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
32540 @anchor{cycle step packet}
32541 @cindex @samp{i} packet
32542 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
32543 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
32544 step starting at that address.
32547 @cindex @samp{I} packet
32548 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
32552 @cindex @samp{k} packet
32555 FIXME: @emph{There is no description of how to operate when a specific
32556 thread context has been selected (i.e.@: does 'k' kill only that
32559 @item m @var{addr},@var{length}
32560 @cindex @samp{m} packet
32561 Read @var{length} bytes of memory starting at address @var{addr}.
32562 Note that @var{addr} may not be aligned to any particular boundary.
32564 The stub need not use any particular size or alignment when gathering
32565 data from memory for the response; even if @var{addr} is word-aligned
32566 and @var{length} is a multiple of the word size, the stub is free to
32567 use byte accesses, or not. For this reason, this packet may not be
32568 suitable for accessing memory-mapped I/O devices.
32569 @cindex alignment of remote memory accesses
32570 @cindex size of remote memory accesses
32571 @cindex memory, alignment and size of remote accesses
32575 @item @var{XX@dots{}}
32576 Memory contents; each byte is transmitted as a two-digit hexadecimal
32577 number. The reply may contain fewer bytes than requested if the
32578 server was able to read only part of the region of memory.
32583 @item M @var{addr},@var{length}:@var{XX@dots{}}
32584 @cindex @samp{M} packet
32585 Write @var{length} bytes of memory starting at address @var{addr}.
32586 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
32587 hexadecimal number.
32594 for an error (this includes the case where only part of the data was
32599 @cindex @samp{p} packet
32600 Read the value of register @var{n}; @var{n} is in hex.
32601 @xref{read registers packet}, for a description of how the returned
32602 register value is encoded.
32606 @item @var{XX@dots{}}
32607 the register's value
32611 Indicating an unrecognized @var{query}.
32614 @item P @var{n@dots{}}=@var{r@dots{}}
32615 @anchor{write register packet}
32616 @cindex @samp{P} packet
32617 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
32618 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
32619 digits for each byte in the register (target byte order).
32629 @item q @var{name} @var{params}@dots{}
32630 @itemx Q @var{name} @var{params}@dots{}
32631 @cindex @samp{q} packet
32632 @cindex @samp{Q} packet
32633 General query (@samp{q}) and set (@samp{Q}). These packets are
32634 described fully in @ref{General Query Packets}.
32637 @cindex @samp{r} packet
32638 Reset the entire system.
32640 Don't use this packet; use the @samp{R} packet instead.
32643 @cindex @samp{R} packet
32644 Restart the program being debugged. @var{XX}, while needed, is ignored.
32645 This packet is only available in extended mode (@pxref{extended mode}).
32647 The @samp{R} packet has no reply.
32649 @item s @r{[}@var{addr}@r{]}
32650 @cindex @samp{s} packet
32651 Single step. @var{addr} is the address at which to resume. If
32652 @var{addr} is omitted, resume at same address.
32654 This packet is deprecated for multi-threading support. @xref{vCont
32658 @xref{Stop Reply Packets}, for the reply specifications.
32660 @item S @var{sig}@r{[};@var{addr}@r{]}
32661 @anchor{step with signal packet}
32662 @cindex @samp{S} packet
32663 Step with signal. This is analogous to the @samp{C} packet, but
32664 requests a single-step, rather than a normal resumption of execution.
32666 This packet is deprecated for multi-threading support. @xref{vCont
32670 @xref{Stop Reply Packets}, for the reply specifications.
32672 @item t @var{addr}:@var{PP},@var{MM}
32673 @cindex @samp{t} packet
32674 Search backwards starting at address @var{addr} for a match with pattern
32675 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
32676 @var{addr} must be at least 3 digits.
32678 @item T @var{thread-id}
32679 @cindex @samp{T} packet
32680 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
32685 thread is still alive
32691 Packets starting with @samp{v} are identified by a multi-letter name,
32692 up to the first @samp{;} or @samp{?} (or the end of the packet).
32694 @item vAttach;@var{pid}
32695 @cindex @samp{vAttach} packet
32696 Attach to a new process with the specified process ID @var{pid}.
32697 The process ID is a
32698 hexadecimal integer identifying the process. In all-stop mode, all
32699 threads in the attached process are stopped; in non-stop mode, it may be
32700 attached without being stopped if that is supported by the target.
32702 @c In non-stop mode, on a successful vAttach, the stub should set the
32703 @c current thread to a thread of the newly-attached process. After
32704 @c attaching, GDB queries for the attached process's thread ID with qC.
32705 @c Also note that, from a user perspective, whether or not the
32706 @c target is stopped on attach in non-stop mode depends on whether you
32707 @c use the foreground or background version of the attach command, not
32708 @c on what vAttach does; GDB does the right thing with respect to either
32709 @c stopping or restarting threads.
32711 This packet is only available in extended mode (@pxref{extended mode}).
32717 @item @r{Any stop packet}
32718 for success in all-stop mode (@pxref{Stop Reply Packets})
32720 for success in non-stop mode (@pxref{Remote Non-Stop})
32723 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
32724 @cindex @samp{vCont} packet
32725 @anchor{vCont packet}
32726 Resume the inferior, specifying different actions for each thread.
32727 If an action is specified with no @var{thread-id}, then it is applied to any
32728 threads that don't have a specific action specified; if no default action is
32729 specified then other threads should remain stopped in all-stop mode and
32730 in their current state in non-stop mode.
32731 Specifying multiple
32732 default actions is an error; specifying no actions is also an error.
32733 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
32735 Currently supported actions are:
32741 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
32745 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
32750 The optional argument @var{addr} normally associated with the
32751 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
32752 not supported in @samp{vCont}.
32754 The @samp{t} action is only relevant in non-stop mode
32755 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
32756 A stop reply should be generated for any affected thread not already stopped.
32757 When a thread is stopped by means of a @samp{t} action,
32758 the corresponding stop reply should indicate that the thread has stopped with
32759 signal @samp{0}, regardless of whether the target uses some other signal
32760 as an implementation detail.
32763 @xref{Stop Reply Packets}, for the reply specifications.
32766 @cindex @samp{vCont?} packet
32767 Request a list of actions supported by the @samp{vCont} packet.
32771 @item vCont@r{[};@var{action}@dots{}@r{]}
32772 The @samp{vCont} packet is supported. Each @var{action} is a supported
32773 command in the @samp{vCont} packet.
32775 The @samp{vCont} packet is not supported.
32778 @item vFile:@var{operation}:@var{parameter}@dots{}
32779 @cindex @samp{vFile} packet
32780 Perform a file operation on the target system. For details,
32781 see @ref{Host I/O Packets}.
32783 @item vFlashErase:@var{addr},@var{length}
32784 @cindex @samp{vFlashErase} packet
32785 Direct the stub to erase @var{length} bytes of flash starting at
32786 @var{addr}. The region may enclose any number of flash blocks, but
32787 its start and end must fall on block boundaries, as indicated by the
32788 flash block size appearing in the memory map (@pxref{Memory Map
32789 Format}). @value{GDBN} groups flash memory programming operations
32790 together, and sends a @samp{vFlashDone} request after each group; the
32791 stub is allowed to delay erase operation until the @samp{vFlashDone}
32792 packet is received.
32794 The stub must support @samp{vCont} if it reports support for
32795 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
32796 this case @samp{vCont} actions can be specified to apply to all threads
32797 in a process by using the @samp{p@var{pid}.-1} form of the
32808 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
32809 @cindex @samp{vFlashWrite} packet
32810 Direct the stub to write data to flash address @var{addr}. The data
32811 is passed in binary form using the same encoding as for the @samp{X}
32812 packet (@pxref{Binary Data}). The memory ranges specified by
32813 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
32814 not overlap, and must appear in order of increasing addresses
32815 (although @samp{vFlashErase} packets for higher addresses may already
32816 have been received; the ordering is guaranteed only between
32817 @samp{vFlashWrite} packets). If a packet writes to an address that was
32818 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32819 target-specific method, the results are unpredictable.
32827 for vFlashWrite addressing non-flash memory
32833 @cindex @samp{vFlashDone} packet
32834 Indicate to the stub that flash programming operation is finished.
32835 The stub is permitted to delay or batch the effects of a group of
32836 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
32837 @samp{vFlashDone} packet is received. The contents of the affected
32838 regions of flash memory are unpredictable until the @samp{vFlashDone}
32839 request is completed.
32841 @item vKill;@var{pid}
32842 @cindex @samp{vKill} packet
32843 Kill the process with the specified process ID. @var{pid} is a
32844 hexadecimal integer identifying the process. This packet is used in
32845 preference to @samp{k} when multiprocess protocol extensions are
32846 supported; see @ref{multiprocess extensions}.
32856 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
32857 @cindex @samp{vRun} packet
32858 Run the program @var{filename}, passing it each @var{argument} on its
32859 command line. The file and arguments are hex-encoded strings. If
32860 @var{filename} is an empty string, the stub may use a default program
32861 (e.g.@: the last program run). The program is created in the stopped
32864 @c FIXME: What about non-stop mode?
32866 This packet is only available in extended mode (@pxref{extended mode}).
32872 @item @r{Any stop packet}
32873 for success (@pxref{Stop Reply Packets})
32877 @anchor{vStopped packet}
32878 @cindex @samp{vStopped} packet
32880 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
32881 reply and prompt for the stub to report another one.
32885 @item @r{Any stop packet}
32886 if there is another unreported stop event (@pxref{Stop Reply Packets})
32888 if there are no unreported stop events
32891 @item X @var{addr},@var{length}:@var{XX@dots{}}
32893 @cindex @samp{X} packet
32894 Write data to memory, where the data is transmitted in binary.
32895 @var{addr} is address, @var{length} is number of bytes,
32896 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
32906 @item z @var{type},@var{addr},@var{kind}
32907 @itemx Z @var{type},@var{addr},@var{kind}
32908 @anchor{insert breakpoint or watchpoint packet}
32909 @cindex @samp{z} packet
32910 @cindex @samp{Z} packets
32911 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
32912 watchpoint starting at address @var{address} of kind @var{kind}.
32914 Each breakpoint and watchpoint packet @var{type} is documented
32917 @emph{Implementation notes: A remote target shall return an empty string
32918 for an unrecognized breakpoint or watchpoint packet @var{type}. A
32919 remote target shall support either both or neither of a given
32920 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
32921 avoid potential problems with duplicate packets, the operations should
32922 be implemented in an idempotent way.}
32924 @item z0,@var{addr},@var{kind}
32925 @itemx Z0,@var{addr},@var{kind}
32926 @cindex @samp{z0} packet
32927 @cindex @samp{Z0} packet
32928 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
32929 @var{addr} of type @var{kind}.
32931 A memory breakpoint is implemented by replacing the instruction at
32932 @var{addr} with a software breakpoint or trap instruction. The
32933 @var{kind} is target-specific and typically indicates the size of
32934 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
32935 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
32936 architectures have additional meanings for @var{kind};
32937 see @ref{Architecture-Specific Protocol Details}.
32939 @emph{Implementation note: It is possible for a target to copy or move
32940 code that contains memory breakpoints (e.g., when implementing
32941 overlays). The behavior of this packet, in the presence of such a
32942 target, is not defined.}
32954 @item z1,@var{addr},@var{kind}
32955 @itemx Z1,@var{addr},@var{kind}
32956 @cindex @samp{z1} packet
32957 @cindex @samp{Z1} packet
32958 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
32959 address @var{addr}.
32961 A hardware breakpoint is implemented using a mechanism that is not
32962 dependant on being able to modify the target's memory. @var{kind}
32963 has the same meaning as in @samp{Z0} packets.
32965 @emph{Implementation note: A hardware breakpoint is not affected by code
32978 @item z2,@var{addr},@var{kind}
32979 @itemx Z2,@var{addr},@var{kind}
32980 @cindex @samp{z2} packet
32981 @cindex @samp{Z2} packet
32982 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
32983 @var{kind} is interpreted as the number of bytes to watch.
32995 @item z3,@var{addr},@var{kind}
32996 @itemx Z3,@var{addr},@var{kind}
32997 @cindex @samp{z3} packet
32998 @cindex @samp{Z3} packet
32999 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
33000 @var{kind} is interpreted as the number of bytes to watch.
33012 @item z4,@var{addr},@var{kind}
33013 @itemx Z4,@var{addr},@var{kind}
33014 @cindex @samp{z4} packet
33015 @cindex @samp{Z4} packet
33016 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
33017 @var{kind} is interpreted as the number of bytes to watch.
33031 @node Stop Reply Packets
33032 @section Stop Reply Packets
33033 @cindex stop reply packets
33035 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
33036 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
33037 receive any of the below as a reply. Except for @samp{?}
33038 and @samp{vStopped}, that reply is only returned
33039 when the target halts. In the below the exact meaning of @dfn{signal
33040 number} is defined by the header @file{include/gdb/signals.h} in the
33041 @value{GDBN} source code.
33043 As in the description of request packets, we include spaces in the
33044 reply templates for clarity; these are not part of the reply packet's
33045 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
33051 The program received signal number @var{AA} (a two-digit hexadecimal
33052 number). This is equivalent to a @samp{T} response with no
33053 @var{n}:@var{r} pairs.
33055 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
33056 @cindex @samp{T} packet reply
33057 The program received signal number @var{AA} (a two-digit hexadecimal
33058 number). This is equivalent to an @samp{S} response, except that the
33059 @samp{@var{n}:@var{r}} pairs can carry values of important registers
33060 and other information directly in the stop reply packet, reducing
33061 round-trip latency. Single-step and breakpoint traps are reported
33062 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
33066 If @var{n} is a hexadecimal number, it is a register number, and the
33067 corresponding @var{r} gives that register's value. @var{r} is a
33068 series of bytes in target byte order, with each byte given by a
33069 two-digit hex number.
33072 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
33073 the stopped thread, as specified in @ref{thread-id syntax}.
33076 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
33077 the core on which the stop event was detected.
33080 If @var{n} is a recognized @dfn{stop reason}, it describes a more
33081 specific event that stopped the target. The currently defined stop
33082 reasons are listed below. @var{aa} should be @samp{05}, the trap
33083 signal. At most one stop reason should be present.
33086 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
33087 and go on to the next; this allows us to extend the protocol in the
33091 The currently defined stop reasons are:
33097 The packet indicates a watchpoint hit, and @var{r} is the data address, in
33100 @cindex shared library events, remote reply
33102 The packet indicates that the loaded libraries have changed.
33103 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
33104 list of loaded libraries. @var{r} is ignored.
33106 @cindex replay log events, remote reply
33108 The packet indicates that the target cannot continue replaying
33109 logged execution events, because it has reached the end (or the
33110 beginning when executing backward) of the log. The value of @var{r}
33111 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
33112 for more information.
33116 @itemx W @var{AA} ; process:@var{pid}
33117 The process exited, and @var{AA} is the exit status. This is only
33118 applicable to certain targets.
33120 The second form of the response, including the process ID of the exited
33121 process, can be used only when @value{GDBN} has reported support for
33122 multiprocess protocol extensions; see @ref{multiprocess extensions}.
33123 The @var{pid} is formatted as a big-endian hex string.
33126 @itemx X @var{AA} ; process:@var{pid}
33127 The process terminated with signal @var{AA}.
33129 The second form of the response, including the process ID of the
33130 terminated process, can be used only when @value{GDBN} has reported
33131 support for multiprocess protocol extensions; see @ref{multiprocess
33132 extensions}. The @var{pid} is formatted as a big-endian hex string.
33134 @item O @var{XX}@dots{}
33135 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
33136 written as the program's console output. This can happen at any time
33137 while the program is running and the debugger should continue to wait
33138 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
33140 @item F @var{call-id},@var{parameter}@dots{}
33141 @var{call-id} is the identifier which says which host system call should
33142 be called. This is just the name of the function. Translation into the
33143 correct system call is only applicable as it's defined in @value{GDBN}.
33144 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
33147 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
33148 this very system call.
33150 The target replies with this packet when it expects @value{GDBN} to
33151 call a host system call on behalf of the target. @value{GDBN} replies
33152 with an appropriate @samp{F} packet and keeps up waiting for the next
33153 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
33154 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
33155 Protocol Extension}, for more details.
33159 @node General Query Packets
33160 @section General Query Packets
33161 @cindex remote query requests
33163 Packets starting with @samp{q} are @dfn{general query packets};
33164 packets starting with @samp{Q} are @dfn{general set packets}. General
33165 query and set packets are a semi-unified form for retrieving and
33166 sending information to and from the stub.
33168 The initial letter of a query or set packet is followed by a name
33169 indicating what sort of thing the packet applies to. For example,
33170 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
33171 definitions with the stub. These packet names follow some
33176 The name must not contain commas, colons or semicolons.
33178 Most @value{GDBN} query and set packets have a leading upper case
33181 The names of custom vendor packets should use a company prefix, in
33182 lower case, followed by a period. For example, packets designed at
33183 the Acme Corporation might begin with @samp{qacme.foo} (for querying
33184 foos) or @samp{Qacme.bar} (for setting bars).
33187 The name of a query or set packet should be separated from any
33188 parameters by a @samp{:}; the parameters themselves should be
33189 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
33190 full packet name, and check for a separator or the end of the packet,
33191 in case two packet names share a common prefix. New packets should not begin
33192 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
33193 packets predate these conventions, and have arguments without any terminator
33194 for the packet name; we suspect they are in widespread use in places that
33195 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
33196 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
33199 Like the descriptions of the other packets, each description here
33200 has a template showing the packet's overall syntax, followed by an
33201 explanation of the packet's meaning. We include spaces in some of the
33202 templates for clarity; these are not part of the packet's syntax. No
33203 @value{GDBN} packet uses spaces to separate its components.
33205 Here are the currently defined query and set packets:
33209 @item QAllow:@var{op}:@var{val}@dots{}
33210 @cindex @samp{QAllow} packet
33211 Specify which operations @value{GDBN} expects to request of the
33212 target, as a semicolon-separated list of operation name and value
33213 pairs. Possible values for @var{op} include @samp{WriteReg},
33214 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
33215 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
33216 indicating that @value{GDBN} will not request the operation, or 1,
33217 indicating that it may. (The target can then use this to set up its
33218 own internals optimally, for instance if the debugger never expects to
33219 insert breakpoints, it may not need to install its own trap handler.)
33222 @cindex current thread, remote request
33223 @cindex @samp{qC} packet
33224 Return the current thread ID.
33228 @item QC @var{thread-id}
33229 Where @var{thread-id} is a thread ID as documented in
33230 @ref{thread-id syntax}.
33231 @item @r{(anything else)}
33232 Any other reply implies the old thread ID.
33235 @item qCRC:@var{addr},@var{length}
33236 @cindex CRC of memory block, remote request
33237 @cindex @samp{qCRC} packet
33238 Compute the CRC checksum of a block of memory using CRC-32 defined in
33239 IEEE 802.3. The CRC is computed byte at a time, taking the most
33240 significant bit of each byte first. The initial pattern code
33241 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
33243 @emph{Note:} This is the same CRC used in validating separate debug
33244 files (@pxref{Separate Debug Files, , Debugging Information in Separate
33245 Files}). However the algorithm is slightly different. When validating
33246 separate debug files, the CRC is computed taking the @emph{least}
33247 significant bit of each byte first, and the final result is inverted to
33248 detect trailing zeros.
33253 An error (such as memory fault)
33254 @item C @var{crc32}
33255 The specified memory region's checksum is @var{crc32}.
33259 @itemx qsThreadInfo
33260 @cindex list active threads, remote request
33261 @cindex @samp{qfThreadInfo} packet
33262 @cindex @samp{qsThreadInfo} packet
33263 Obtain a list of all active thread IDs from the target (OS). Since there
33264 may be too many active threads to fit into one reply packet, this query
33265 works iteratively: it may require more than one query/reply sequence to
33266 obtain the entire list of threads. The first query of the sequence will
33267 be the @samp{qfThreadInfo} query; subsequent queries in the
33268 sequence will be the @samp{qsThreadInfo} query.
33270 NOTE: This packet replaces the @samp{qL} query (see below).
33274 @item m @var{thread-id}
33276 @item m @var{thread-id},@var{thread-id}@dots{}
33277 a comma-separated list of thread IDs
33279 (lower case letter @samp{L}) denotes end of list.
33282 In response to each query, the target will reply with a list of one or
33283 more thread IDs, separated by commas.
33284 @value{GDBN} will respond to each reply with a request for more thread
33285 ids (using the @samp{qs} form of the query), until the target responds
33286 with @samp{l} (lower-case ell, for @dfn{last}).
33287 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
33290 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
33291 @cindex get thread-local storage address, remote request
33292 @cindex @samp{qGetTLSAddr} packet
33293 Fetch the address associated with thread local storage specified
33294 by @var{thread-id}, @var{offset}, and @var{lm}.
33296 @var{thread-id} is the thread ID associated with the
33297 thread for which to fetch the TLS address. @xref{thread-id syntax}.
33299 @var{offset} is the (big endian, hex encoded) offset associated with the
33300 thread local variable. (This offset is obtained from the debug
33301 information associated with the variable.)
33303 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
33304 load module associated with the thread local storage. For example,
33305 a @sc{gnu}/Linux system will pass the link map address of the shared
33306 object associated with the thread local storage under consideration.
33307 Other operating environments may choose to represent the load module
33308 differently, so the precise meaning of this parameter will vary.
33312 @item @var{XX}@dots{}
33313 Hex encoded (big endian) bytes representing the address of the thread
33314 local storage requested.
33317 An error occurred. @var{nn} are hex digits.
33320 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
33323 @item qGetTIBAddr:@var{thread-id}
33324 @cindex get thread information block address
33325 @cindex @samp{qGetTIBAddr} packet
33326 Fetch address of the Windows OS specific Thread Information Block.
33328 @var{thread-id} is the thread ID associated with the thread.
33332 @item @var{XX}@dots{}
33333 Hex encoded (big endian) bytes representing the linear address of the
33334 thread information block.
33337 An error occured. This means that either the thread was not found, or the
33338 address could not be retrieved.
33341 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
33344 @item qL @var{startflag} @var{threadcount} @var{nextthread}
33345 Obtain thread information from RTOS. Where: @var{startflag} (one hex
33346 digit) is one to indicate the first query and zero to indicate a
33347 subsequent query; @var{threadcount} (two hex digits) is the maximum
33348 number of threads the response packet can contain; and @var{nextthread}
33349 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
33350 returned in the response as @var{argthread}.
33352 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
33356 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
33357 Where: @var{count} (two hex digits) is the number of threads being
33358 returned; @var{done} (one hex digit) is zero to indicate more threads
33359 and one indicates no further threads; @var{argthreadid} (eight hex
33360 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
33361 is a sequence of thread IDs from the target. @var{threadid} (eight hex
33362 digits). See @code{remote.c:parse_threadlist_response()}.
33366 @cindex section offsets, remote request
33367 @cindex @samp{qOffsets} packet
33368 Get section offsets that the target used when relocating the downloaded
33373 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
33374 Relocate the @code{Text} section by @var{xxx} from its original address.
33375 Relocate the @code{Data} section by @var{yyy} from its original address.
33376 If the object file format provides segment information (e.g.@: @sc{elf}
33377 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
33378 segments by the supplied offsets.
33380 @emph{Note: while a @code{Bss} offset may be included in the response,
33381 @value{GDBN} ignores this and instead applies the @code{Data} offset
33382 to the @code{Bss} section.}
33384 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
33385 Relocate the first segment of the object file, which conventionally
33386 contains program code, to a starting address of @var{xxx}. If
33387 @samp{DataSeg} is specified, relocate the second segment, which
33388 conventionally contains modifiable data, to a starting address of
33389 @var{yyy}. @value{GDBN} will report an error if the object file
33390 does not contain segment information, or does not contain at least
33391 as many segments as mentioned in the reply. Extra segments are
33392 kept at fixed offsets relative to the last relocated segment.
33395 @item qP @var{mode} @var{thread-id}
33396 @cindex thread information, remote request
33397 @cindex @samp{qP} packet
33398 Returns information on @var{thread-id}. Where: @var{mode} is a hex
33399 encoded 32 bit mode; @var{thread-id} is a thread ID
33400 (@pxref{thread-id syntax}).
33402 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
33405 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
33409 @cindex non-stop mode, remote request
33410 @cindex @samp{QNonStop} packet
33412 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
33413 @xref{Remote Non-Stop}, for more information.
33418 The request succeeded.
33421 An error occurred. @var{nn} are hex digits.
33424 An empty reply indicates that @samp{QNonStop} is not supported by
33428 This packet is not probed by default; the remote stub must request it,
33429 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33430 Use of this packet is controlled by the @code{set non-stop} command;
33431 @pxref{Non-Stop Mode}.
33433 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
33434 @cindex pass signals to inferior, remote request
33435 @cindex @samp{QPassSignals} packet
33436 @anchor{QPassSignals}
33437 Each listed @var{signal} should be passed directly to the inferior process.
33438 Signals are numbered identically to continue packets and stop replies
33439 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
33440 strictly greater than the previous item. These signals do not need to stop
33441 the inferior, or be reported to @value{GDBN}. All other signals should be
33442 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
33443 combine; any earlier @samp{QPassSignals} list is completely replaced by the
33444 new list. This packet improves performance when using @samp{handle
33445 @var{signal} nostop noprint pass}.
33450 The request succeeded.
33453 An error occurred. @var{nn} are hex digits.
33456 An empty reply indicates that @samp{QPassSignals} is not supported by
33460 Use of this packet is controlled by the @code{set remote pass-signals}
33461 command (@pxref{Remote Configuration, set remote pass-signals}).
33462 This packet is not probed by default; the remote stub must request it,
33463 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33465 @item qRcmd,@var{command}
33466 @cindex execute remote command, remote request
33467 @cindex @samp{qRcmd} packet
33468 @var{command} (hex encoded) is passed to the local interpreter for
33469 execution. Invalid commands should be reported using the output
33470 string. Before the final result packet, the target may also respond
33471 with a number of intermediate @samp{O@var{output}} console output
33472 packets. @emph{Implementors should note that providing access to a
33473 stubs's interpreter may have security implications}.
33478 A command response with no output.
33480 A command response with the hex encoded output string @var{OUTPUT}.
33482 Indicate a badly formed request.
33484 An empty reply indicates that @samp{qRcmd} is not recognized.
33487 (Note that the @code{qRcmd} packet's name is separated from the
33488 command by a @samp{,}, not a @samp{:}, contrary to the naming
33489 conventions above. Please don't use this packet as a model for new
33492 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
33493 @cindex searching memory, in remote debugging
33494 @cindex @samp{qSearch:memory} packet
33495 @anchor{qSearch memory}
33496 Search @var{length} bytes at @var{address} for @var{search-pattern}.
33497 @var{address} and @var{length} are encoded in hex.
33498 @var{search-pattern} is a sequence of bytes, hex encoded.
33503 The pattern was not found.
33505 The pattern was found at @var{address}.
33507 A badly formed request or an error was encountered while searching memory.
33509 An empty reply indicates that @samp{qSearch:memory} is not recognized.
33512 @item QStartNoAckMode
33513 @cindex @samp{QStartNoAckMode} packet
33514 @anchor{QStartNoAckMode}
33515 Request that the remote stub disable the normal @samp{+}/@samp{-}
33516 protocol acknowledgments (@pxref{Packet Acknowledgment}).
33521 The stub has switched to no-acknowledgment mode.
33522 @value{GDBN} acknowledges this reponse,
33523 but neither the stub nor @value{GDBN} shall send or expect further
33524 @samp{+}/@samp{-} acknowledgments in the current connection.
33526 An empty reply indicates that the stub does not support no-acknowledgment mode.
33529 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
33530 @cindex supported packets, remote query
33531 @cindex features of the remote protocol
33532 @cindex @samp{qSupported} packet
33533 @anchor{qSupported}
33534 Tell the remote stub about features supported by @value{GDBN}, and
33535 query the stub for features it supports. This packet allows
33536 @value{GDBN} and the remote stub to take advantage of each others'
33537 features. @samp{qSupported} also consolidates multiple feature probes
33538 at startup, to improve @value{GDBN} performance---a single larger
33539 packet performs better than multiple smaller probe packets on
33540 high-latency links. Some features may enable behavior which must not
33541 be on by default, e.g.@: because it would confuse older clients or
33542 stubs. Other features may describe packets which could be
33543 automatically probed for, but are not. These features must be
33544 reported before @value{GDBN} will use them. This ``default
33545 unsupported'' behavior is not appropriate for all packets, but it
33546 helps to keep the initial connection time under control with new
33547 versions of @value{GDBN} which support increasing numbers of packets.
33551 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
33552 The stub supports or does not support each returned @var{stubfeature},
33553 depending on the form of each @var{stubfeature} (see below for the
33556 An empty reply indicates that @samp{qSupported} is not recognized,
33557 or that no features needed to be reported to @value{GDBN}.
33560 The allowed forms for each feature (either a @var{gdbfeature} in the
33561 @samp{qSupported} packet, or a @var{stubfeature} in the response)
33565 @item @var{name}=@var{value}
33566 The remote protocol feature @var{name} is supported, and associated
33567 with the specified @var{value}. The format of @var{value} depends
33568 on the feature, but it must not include a semicolon.
33570 The remote protocol feature @var{name} is supported, and does not
33571 need an associated value.
33573 The remote protocol feature @var{name} is not supported.
33575 The remote protocol feature @var{name} may be supported, and
33576 @value{GDBN} should auto-detect support in some other way when it is
33577 needed. This form will not be used for @var{gdbfeature} notifications,
33578 but may be used for @var{stubfeature} responses.
33581 Whenever the stub receives a @samp{qSupported} request, the
33582 supplied set of @value{GDBN} features should override any previous
33583 request. This allows @value{GDBN} to put the stub in a known
33584 state, even if the stub had previously been communicating with
33585 a different version of @value{GDBN}.
33587 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
33592 This feature indicates whether @value{GDBN} supports multiprocess
33593 extensions to the remote protocol. @value{GDBN} does not use such
33594 extensions unless the stub also reports that it supports them by
33595 including @samp{multiprocess+} in its @samp{qSupported} reply.
33596 @xref{multiprocess extensions}, for details.
33599 This feature indicates that @value{GDBN} supports the XML target
33600 description. If the stub sees @samp{xmlRegisters=} with target
33601 specific strings separated by a comma, it will report register
33605 This feature indicates whether @value{GDBN} supports the
33606 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
33607 instruction reply packet}).
33610 Stubs should ignore any unknown values for
33611 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
33612 packet supports receiving packets of unlimited length (earlier
33613 versions of @value{GDBN} may reject overly long responses). Additional values
33614 for @var{gdbfeature} may be defined in the future to let the stub take
33615 advantage of new features in @value{GDBN}, e.g.@: incompatible
33616 improvements in the remote protocol---the @samp{multiprocess} feature is
33617 an example of such a feature. The stub's reply should be independent
33618 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
33619 describes all the features it supports, and then the stub replies with
33620 all the features it supports.
33622 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
33623 responses, as long as each response uses one of the standard forms.
33625 Some features are flags. A stub which supports a flag feature
33626 should respond with a @samp{+} form response. Other features
33627 require values, and the stub should respond with an @samp{=}
33630 Each feature has a default value, which @value{GDBN} will use if
33631 @samp{qSupported} is not available or if the feature is not mentioned
33632 in the @samp{qSupported} response. The default values are fixed; a
33633 stub is free to omit any feature responses that match the defaults.
33635 Not all features can be probed, but for those which can, the probing
33636 mechanism is useful: in some cases, a stub's internal
33637 architecture may not allow the protocol layer to know some information
33638 about the underlying target in advance. This is especially common in
33639 stubs which may be configured for multiple targets.
33641 These are the currently defined stub features and their properties:
33643 @multitable @columnfractions 0.35 0.2 0.12 0.2
33644 @c NOTE: The first row should be @headitem, but we do not yet require
33645 @c a new enough version of Texinfo (4.7) to use @headitem.
33647 @tab Value Required
33651 @item @samp{PacketSize}
33656 @item @samp{qXfer:auxv:read}
33661 @item @samp{qXfer:features:read}
33666 @item @samp{qXfer:libraries:read}
33671 @item @samp{qXfer:memory-map:read}
33676 @item @samp{qXfer:sdata:read}
33681 @item @samp{qXfer:spu:read}
33686 @item @samp{qXfer:spu:write}
33691 @item @samp{qXfer:siginfo:read}
33696 @item @samp{qXfer:siginfo:write}
33701 @item @samp{qXfer:threads:read}
33706 @item @samp{qXfer:traceframe-info:read}
33712 @item @samp{QNonStop}
33717 @item @samp{QPassSignals}
33722 @item @samp{QStartNoAckMode}
33727 @item @samp{multiprocess}
33732 @item @samp{ConditionalTracepoints}
33737 @item @samp{ReverseContinue}
33742 @item @samp{ReverseStep}
33747 @item @samp{TracepointSource}
33752 @item @samp{QAllow}
33757 @item @samp{EnableDisableTracepoints}
33764 These are the currently defined stub features, in more detail:
33767 @cindex packet size, remote protocol
33768 @item PacketSize=@var{bytes}
33769 The remote stub can accept packets up to at least @var{bytes} in
33770 length. @value{GDBN} will send packets up to this size for bulk
33771 transfers, and will never send larger packets. This is a limit on the
33772 data characters in the packet, including the frame and checksum.
33773 There is no trailing NUL byte in a remote protocol packet; if the stub
33774 stores packets in a NUL-terminated format, it should allow an extra
33775 byte in its buffer for the NUL. If this stub feature is not supported,
33776 @value{GDBN} guesses based on the size of the @samp{g} packet response.
33778 @item qXfer:auxv:read
33779 The remote stub understands the @samp{qXfer:auxv:read} packet
33780 (@pxref{qXfer auxiliary vector read}).
33782 @item qXfer:features:read
33783 The remote stub understands the @samp{qXfer:features:read} packet
33784 (@pxref{qXfer target description read}).
33786 @item qXfer:libraries:read
33787 The remote stub understands the @samp{qXfer:libraries:read} packet
33788 (@pxref{qXfer library list read}).
33790 @item qXfer:memory-map:read
33791 The remote stub understands the @samp{qXfer:memory-map:read} packet
33792 (@pxref{qXfer memory map read}).
33794 @item qXfer:sdata:read
33795 The remote stub understands the @samp{qXfer:sdata:read} packet
33796 (@pxref{qXfer sdata read}).
33798 @item qXfer:spu:read
33799 The remote stub understands the @samp{qXfer:spu:read} packet
33800 (@pxref{qXfer spu read}).
33802 @item qXfer:spu:write
33803 The remote stub understands the @samp{qXfer:spu:write} packet
33804 (@pxref{qXfer spu write}).
33806 @item qXfer:siginfo:read
33807 The remote stub understands the @samp{qXfer:siginfo:read} packet
33808 (@pxref{qXfer siginfo read}).
33810 @item qXfer:siginfo:write
33811 The remote stub understands the @samp{qXfer:siginfo:write} packet
33812 (@pxref{qXfer siginfo write}).
33814 @item qXfer:threads:read
33815 The remote stub understands the @samp{qXfer:threads:read} packet
33816 (@pxref{qXfer threads read}).
33818 @item qXfer:traceframe-info:read
33819 The remote stub understands the @samp{qXfer:traceframe-info:read}
33820 packet (@pxref{qXfer traceframe info read}).
33823 The remote stub understands the @samp{QNonStop} packet
33824 (@pxref{QNonStop}).
33827 The remote stub understands the @samp{QPassSignals} packet
33828 (@pxref{QPassSignals}).
33830 @item QStartNoAckMode
33831 The remote stub understands the @samp{QStartNoAckMode} packet and
33832 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
33835 @anchor{multiprocess extensions}
33836 @cindex multiprocess extensions, in remote protocol
33837 The remote stub understands the multiprocess extensions to the remote
33838 protocol syntax. The multiprocess extensions affect the syntax of
33839 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
33840 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
33841 replies. Note that reporting this feature indicates support for the
33842 syntactic extensions only, not that the stub necessarily supports
33843 debugging of more than one process at a time. The stub must not use
33844 multiprocess extensions in packet replies unless @value{GDBN} has also
33845 indicated it supports them in its @samp{qSupported} request.
33847 @item qXfer:osdata:read
33848 The remote stub understands the @samp{qXfer:osdata:read} packet
33849 ((@pxref{qXfer osdata read}).
33851 @item ConditionalTracepoints
33852 The remote stub accepts and implements conditional expressions defined
33853 for tracepoints (@pxref{Tracepoint Conditions}).
33855 @item ReverseContinue
33856 The remote stub accepts and implements the reverse continue packet
33860 The remote stub accepts and implements the reverse step packet
33863 @item TracepointSource
33864 The remote stub understands the @samp{QTDPsrc} packet that supplies
33865 the source form of tracepoint definitions.
33868 The remote stub understands the @samp{QAllow} packet.
33870 @item StaticTracepoint
33871 @cindex static tracepoints, in remote protocol
33872 The remote stub supports static tracepoints.
33874 @item EnableDisableTracepoints
33875 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
33876 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
33877 to be enabled and disabled while a trace experiment is running.
33882 @cindex symbol lookup, remote request
33883 @cindex @samp{qSymbol} packet
33884 Notify the target that @value{GDBN} is prepared to serve symbol lookup
33885 requests. Accept requests from the target for the values of symbols.
33890 The target does not need to look up any (more) symbols.
33891 @item qSymbol:@var{sym_name}
33892 The target requests the value of symbol @var{sym_name} (hex encoded).
33893 @value{GDBN} may provide the value by using the
33894 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
33898 @item qSymbol:@var{sym_value}:@var{sym_name}
33899 Set the value of @var{sym_name} to @var{sym_value}.
33901 @var{sym_name} (hex encoded) is the name of a symbol whose value the
33902 target has previously requested.
33904 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
33905 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
33911 The target does not need to look up any (more) symbols.
33912 @item qSymbol:@var{sym_name}
33913 The target requests the value of a new symbol @var{sym_name} (hex
33914 encoded). @value{GDBN} will continue to supply the values of symbols
33915 (if available), until the target ceases to request them.
33920 @item QTDisconnected
33927 @xref{Tracepoint Packets}.
33929 @item qThreadExtraInfo,@var{thread-id}
33930 @cindex thread attributes info, remote request
33931 @cindex @samp{qThreadExtraInfo} packet
33932 Obtain a printable string description of a thread's attributes from
33933 the target OS. @var{thread-id} is a thread ID;
33934 see @ref{thread-id syntax}. This
33935 string may contain anything that the target OS thinks is interesting
33936 for @value{GDBN} to tell the user about the thread. The string is
33937 displayed in @value{GDBN}'s @code{info threads} display. Some
33938 examples of possible thread extra info strings are @samp{Runnable}, or
33939 @samp{Blocked on Mutex}.
33943 @item @var{XX}@dots{}
33944 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
33945 comprising the printable string containing the extra information about
33946 the thread's attributes.
33949 (Note that the @code{qThreadExtraInfo} packet's name is separated from
33950 the command by a @samp{,}, not a @samp{:}, contrary to the naming
33951 conventions above. Please don't use this packet as a model for new
33968 @xref{Tracepoint Packets}.
33970 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
33971 @cindex read special object, remote request
33972 @cindex @samp{qXfer} packet
33973 @anchor{qXfer read}
33974 Read uninterpreted bytes from the target's special data area
33975 identified by the keyword @var{object}. Request @var{length} bytes
33976 starting at @var{offset} bytes into the data. The content and
33977 encoding of @var{annex} is specific to @var{object}; it can supply
33978 additional details about what data to access.
33980 Here are the specific requests of this form defined so far. All
33981 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
33982 formats, listed below.
33985 @item qXfer:auxv:read::@var{offset},@var{length}
33986 @anchor{qXfer auxiliary vector read}
33987 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
33988 auxiliary vector}. Note @var{annex} must be empty.
33990 This packet is not probed by default; the remote stub must request it,
33991 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33993 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
33994 @anchor{qXfer target description read}
33995 Access the @dfn{target description}. @xref{Target Descriptions}. The
33996 annex specifies which XML document to access. The main description is
33997 always loaded from the @samp{target.xml} annex.
33999 This packet is not probed by default; the remote stub must request it,
34000 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34002 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
34003 @anchor{qXfer library list read}
34004 Access the target's list of loaded libraries. @xref{Library List Format}.
34005 The annex part of the generic @samp{qXfer} packet must be empty
34006 (@pxref{qXfer read}).
34008 Targets which maintain a list of libraries in the program's memory do
34009 not need to implement this packet; it is designed for platforms where
34010 the operating system manages the list of loaded libraries.
34012 This packet is not probed by default; the remote stub must request it,
34013 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34015 @item qXfer:memory-map:read::@var{offset},@var{length}
34016 @anchor{qXfer memory map read}
34017 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
34018 annex part of the generic @samp{qXfer} packet must be empty
34019 (@pxref{qXfer read}).
34021 This packet is not probed by default; the remote stub must request it,
34022 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34024 @item qXfer:sdata:read::@var{offset},@var{length}
34025 @anchor{qXfer sdata read}
34027 Read contents of the extra collected static tracepoint marker
34028 information. The annex part of the generic @samp{qXfer} packet must
34029 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
34032 This packet is not probed by default; the remote stub must request it,
34033 by supplying an appropriate @samp{qSupported} response
34034 (@pxref{qSupported}).
34036 @item qXfer:siginfo:read::@var{offset},@var{length}
34037 @anchor{qXfer siginfo read}
34038 Read contents of the extra signal information on the target
34039 system. The annex part of the generic @samp{qXfer} packet must be
34040 empty (@pxref{qXfer read}).
34042 This packet is not probed by default; the remote stub must request it,
34043 by supplying an appropriate @samp{qSupported} response
34044 (@pxref{qSupported}).
34046 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
34047 @anchor{qXfer spu read}
34048 Read contents of an @code{spufs} file on the target system. The
34049 annex specifies which file to read; it must be of the form
34050 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
34051 in the target process, and @var{name} identifes the @code{spufs} file
34052 in that context to be accessed.
34054 This packet is not probed by default; the remote stub must request it,
34055 by supplying an appropriate @samp{qSupported} response
34056 (@pxref{qSupported}).
34058 @item qXfer:threads:read::@var{offset},@var{length}
34059 @anchor{qXfer threads read}
34060 Access the list of threads on target. @xref{Thread List Format}. The
34061 annex part of the generic @samp{qXfer} packet must be empty
34062 (@pxref{qXfer read}).
34064 This packet is not probed by default; the remote stub must request it,
34065 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34067 @item qXfer:traceframe-info:read::@var{offset},@var{length}
34068 @anchor{qXfer traceframe info read}
34070 Return a description of the current traceframe's contents.
34071 @xref{Traceframe Info Format}. The annex part of the generic
34072 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
34074 This packet is not probed by default; the remote stub must request it,
34075 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34077 @item qXfer:osdata:read::@var{offset},@var{length}
34078 @anchor{qXfer osdata read}
34079 Access the target's @dfn{operating system information}.
34080 @xref{Operating System Information}.
34087 Data @var{data} (@pxref{Binary Data}) has been read from the
34088 target. There may be more data at a higher address (although
34089 it is permitted to return @samp{m} even for the last valid
34090 block of data, as long as at least one byte of data was read).
34091 @var{data} may have fewer bytes than the @var{length} in the
34095 Data @var{data} (@pxref{Binary Data}) has been read from the target.
34096 There is no more data to be read. @var{data} may have fewer bytes
34097 than the @var{length} in the request.
34100 The @var{offset} in the request is at the end of the data.
34101 There is no more data to be read.
34104 The request was malformed, or @var{annex} was invalid.
34107 The offset was invalid, or there was an error encountered reading the data.
34108 @var{nn} is a hex-encoded @code{errno} value.
34111 An empty reply indicates the @var{object} string was not recognized by
34112 the stub, or that the object does not support reading.
34115 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
34116 @cindex write data into object, remote request
34117 @anchor{qXfer write}
34118 Write uninterpreted bytes into the target's special data area
34119 identified by the keyword @var{object}, starting at @var{offset} bytes
34120 into the data. @var{data}@dots{} is the binary-encoded data
34121 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
34122 is specific to @var{object}; it can supply additional details about what data
34125 Here are the specific requests of this form defined so far. All
34126 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
34127 formats, listed below.
34130 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
34131 @anchor{qXfer siginfo write}
34132 Write @var{data} to the extra signal information on the target system.
34133 The annex part of the generic @samp{qXfer} packet must be
34134 empty (@pxref{qXfer write}).
34136 This packet is not probed by default; the remote stub must request it,
34137 by supplying an appropriate @samp{qSupported} response
34138 (@pxref{qSupported}).
34140 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
34141 @anchor{qXfer spu write}
34142 Write @var{data} to an @code{spufs} file on the target system. The
34143 annex specifies which file to write; it must be of the form
34144 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
34145 in the target process, and @var{name} identifes the @code{spufs} file
34146 in that context to be accessed.
34148 This packet is not probed by default; the remote stub must request it,
34149 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34155 @var{nn} (hex encoded) is the number of bytes written.
34156 This may be fewer bytes than supplied in the request.
34159 The request was malformed, or @var{annex} was invalid.
34162 The offset was invalid, or there was an error encountered writing the data.
34163 @var{nn} is a hex-encoded @code{errno} value.
34166 An empty reply indicates the @var{object} string was not
34167 recognized by the stub, or that the object does not support writing.
34170 @item qXfer:@var{object}:@var{operation}:@dots{}
34171 Requests of this form may be added in the future. When a stub does
34172 not recognize the @var{object} keyword, or its support for
34173 @var{object} does not recognize the @var{operation} keyword, the stub
34174 must respond with an empty packet.
34176 @item qAttached:@var{pid}
34177 @cindex query attached, remote request
34178 @cindex @samp{qAttached} packet
34179 Return an indication of whether the remote server attached to an
34180 existing process or created a new process. When the multiprocess
34181 protocol extensions are supported (@pxref{multiprocess extensions}),
34182 @var{pid} is an integer in hexadecimal format identifying the target
34183 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
34184 the query packet will be simplified as @samp{qAttached}.
34186 This query is used, for example, to know whether the remote process
34187 should be detached or killed when a @value{GDBN} session is ended with
34188 the @code{quit} command.
34193 The remote server attached to an existing process.
34195 The remote server created a new process.
34197 A badly formed request or an error was encountered.
34202 @node Architecture-Specific Protocol Details
34203 @section Architecture-Specific Protocol Details
34205 This section describes how the remote protocol is applied to specific
34206 target architectures. Also see @ref{Standard Target Features}, for
34207 details of XML target descriptions for each architecture.
34211 @subsubsection Breakpoint Kinds
34213 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
34218 16-bit Thumb mode breakpoint.
34221 32-bit Thumb mode (Thumb-2) breakpoint.
34224 32-bit ARM mode breakpoint.
34230 @subsubsection Register Packet Format
34232 The following @code{g}/@code{G} packets have previously been defined.
34233 In the below, some thirty-two bit registers are transferred as
34234 sixty-four bits. Those registers should be zero/sign extended (which?)
34235 to fill the space allocated. Register bytes are transferred in target
34236 byte order. The two nibbles within a register byte are transferred
34237 most-significant - least-significant.
34243 All registers are transferred as thirty-two bit quantities in the order:
34244 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
34245 registers; fsr; fir; fp.
34249 All registers are transferred as sixty-four bit quantities (including
34250 thirty-two bit registers such as @code{sr}). The ordering is the same
34255 @node Tracepoint Packets
34256 @section Tracepoint Packets
34257 @cindex tracepoint packets
34258 @cindex packets, tracepoint
34260 Here we describe the packets @value{GDBN} uses to implement
34261 tracepoints (@pxref{Tracepoints}).
34265 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
34266 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
34267 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
34268 the tracepoint is disabled. @var{step} is the tracepoint's step
34269 count, and @var{pass} is its pass count. If an @samp{F} is present,
34270 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
34271 the number of bytes that the target should copy elsewhere to make room
34272 for the tracepoint. If an @samp{X} is present, it introduces a
34273 tracepoint condition, which consists of a hexadecimal length, followed
34274 by a comma and hex-encoded bytes, in a manner similar to action
34275 encodings as described below. If the trailing @samp{-} is present,
34276 further @samp{QTDP} packets will follow to specify this tracepoint's
34282 The packet was understood and carried out.
34284 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34286 The packet was not recognized.
34289 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
34290 Define actions to be taken when a tracepoint is hit. @var{n} and
34291 @var{addr} must be the same as in the initial @samp{QTDP} packet for
34292 this tracepoint. This packet may only be sent immediately after
34293 another @samp{QTDP} packet that ended with a @samp{-}. If the
34294 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
34295 specifying more actions for this tracepoint.
34297 In the series of action packets for a given tracepoint, at most one
34298 can have an @samp{S} before its first @var{action}. If such a packet
34299 is sent, it and the following packets define ``while-stepping''
34300 actions. Any prior packets define ordinary actions --- that is, those
34301 taken when the tracepoint is first hit. If no action packet has an
34302 @samp{S}, then all the packets in the series specify ordinary
34303 tracepoint actions.
34305 The @samp{@var{action}@dots{}} portion of the packet is a series of
34306 actions, concatenated without separators. Each action has one of the
34312 Collect the registers whose bits are set in @var{mask}. @var{mask} is
34313 a hexadecimal number whose @var{i}'th bit is set if register number
34314 @var{i} should be collected. (The least significant bit is numbered
34315 zero.) Note that @var{mask} may be any number of digits long; it may
34316 not fit in a 32-bit word.
34318 @item M @var{basereg},@var{offset},@var{len}
34319 Collect @var{len} bytes of memory starting at the address in register
34320 number @var{basereg}, plus @var{offset}. If @var{basereg} is
34321 @samp{-1}, then the range has a fixed address: @var{offset} is the
34322 address of the lowest byte to collect. The @var{basereg},
34323 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
34324 values (the @samp{-1} value for @var{basereg} is a special case).
34326 @item X @var{len},@var{expr}
34327 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
34328 it directs. @var{expr} is an agent expression, as described in
34329 @ref{Agent Expressions}. Each byte of the expression is encoded as a
34330 two-digit hex number in the packet; @var{len} is the number of bytes
34331 in the expression (and thus one-half the number of hex digits in the
34336 Any number of actions may be packed together in a single @samp{QTDP}
34337 packet, as long as the packet does not exceed the maximum packet
34338 length (400 bytes, for many stubs). There may be only one @samp{R}
34339 action per tracepoint, and it must precede any @samp{M} or @samp{X}
34340 actions. Any registers referred to by @samp{M} and @samp{X} actions
34341 must be collected by a preceding @samp{R} action. (The
34342 ``while-stepping'' actions are treated as if they were attached to a
34343 separate tracepoint, as far as these restrictions are concerned.)
34348 The packet was understood and carried out.
34350 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34352 The packet was not recognized.
34355 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
34356 @cindex @samp{QTDPsrc} packet
34357 Specify a source string of tracepoint @var{n} at address @var{addr}.
34358 This is useful to get accurate reproduction of the tracepoints
34359 originally downloaded at the beginning of the trace run. @var{type}
34360 is the name of the tracepoint part, such as @samp{cond} for the
34361 tracepoint's conditional expression (see below for a list of types), while
34362 @var{bytes} is the string, encoded in hexadecimal.
34364 @var{start} is the offset of the @var{bytes} within the overall source
34365 string, while @var{slen} is the total length of the source string.
34366 This is intended for handling source strings that are longer than will
34367 fit in a single packet.
34368 @c Add detailed example when this info is moved into a dedicated
34369 @c tracepoint descriptions section.
34371 The available string types are @samp{at} for the location,
34372 @samp{cond} for the conditional, and @samp{cmd} for an action command.
34373 @value{GDBN} sends a separate packet for each command in the action
34374 list, in the same order in which the commands are stored in the list.
34376 The target does not need to do anything with source strings except
34377 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
34380 Although this packet is optional, and @value{GDBN} will only send it
34381 if the target replies with @samp{TracepointSource} @xref{General
34382 Query Packets}, it makes both disconnected tracing and trace files
34383 much easier to use. Otherwise the user must be careful that the
34384 tracepoints in effect while looking at trace frames are identical to
34385 the ones in effect during the trace run; even a small discrepancy
34386 could cause @samp{tdump} not to work, or a particular trace frame not
34389 @item QTDV:@var{n}:@var{value}
34390 @cindex define trace state variable, remote request
34391 @cindex @samp{QTDV} packet
34392 Create a new trace state variable, number @var{n}, with an initial
34393 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
34394 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
34395 the option of not using this packet for initial values of zero; the
34396 target should simply create the trace state variables as they are
34397 mentioned in expressions.
34399 @item QTFrame:@var{n}
34400 Select the @var{n}'th tracepoint frame from the buffer, and use the
34401 register and memory contents recorded there to answer subsequent
34402 request packets from @value{GDBN}.
34404 A successful reply from the stub indicates that the stub has found the
34405 requested frame. The response is a series of parts, concatenated
34406 without separators, describing the frame we selected. Each part has
34407 one of the following forms:
34411 The selected frame is number @var{n} in the trace frame buffer;
34412 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
34413 was no frame matching the criteria in the request packet.
34416 The selected trace frame records a hit of tracepoint number @var{t};
34417 @var{t} is a hexadecimal number.
34421 @item QTFrame:pc:@var{addr}
34422 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34423 currently selected frame whose PC is @var{addr};
34424 @var{addr} is a hexadecimal number.
34426 @item QTFrame:tdp:@var{t}
34427 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34428 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
34429 is a hexadecimal number.
34431 @item QTFrame:range:@var{start}:@var{end}
34432 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34433 currently selected frame whose PC is between @var{start} (inclusive)
34434 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
34437 @item QTFrame:outside:@var{start}:@var{end}
34438 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
34439 frame @emph{outside} the given range of addresses (exclusive).
34442 Begin the tracepoint experiment. Begin collecting data from
34443 tracepoint hits in the trace frame buffer. This packet supports the
34444 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
34445 instruction reply packet}).
34448 End the tracepoint experiment. Stop collecting trace frames.
34450 @item QTEnable:@var{n}:@var{addr}
34452 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
34453 experiment. If the tracepoint was previously disabled, then collection
34454 of data from it will resume.
34456 @item QTDisable:@var{n}:@var{addr}
34458 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
34459 experiment. No more data will be collected from the tracepoint unless
34460 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
34463 Clear the table of tracepoints, and empty the trace frame buffer.
34465 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
34466 Establish the given ranges of memory as ``transparent''. The stub
34467 will answer requests for these ranges from memory's current contents,
34468 if they were not collected as part of the tracepoint hit.
34470 @value{GDBN} uses this to mark read-only regions of memory, like those
34471 containing program code. Since these areas never change, they should
34472 still have the same contents they did when the tracepoint was hit, so
34473 there's no reason for the stub to refuse to provide their contents.
34475 @item QTDisconnected:@var{value}
34476 Set the choice to what to do with the tracing run when @value{GDBN}
34477 disconnects from the target. A @var{value} of 1 directs the target to
34478 continue the tracing run, while 0 tells the target to stop tracing if
34479 @value{GDBN} is no longer in the picture.
34482 Ask the stub if there is a trace experiment running right now.
34484 The reply has the form:
34488 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
34489 @var{running} is a single digit @code{1} if the trace is presently
34490 running, or @code{0} if not. It is followed by semicolon-separated
34491 optional fields that an agent may use to report additional status.
34495 If the trace is not running, the agent may report any of several
34496 explanations as one of the optional fields:
34501 No trace has been run yet.
34504 The trace was stopped by a user-originated stop command.
34507 The trace stopped because the trace buffer filled up.
34509 @item tdisconnected:0
34510 The trace stopped because @value{GDBN} disconnected from the target.
34512 @item tpasscount:@var{tpnum}
34513 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
34515 @item terror:@var{text}:@var{tpnum}
34516 The trace stopped because tracepoint @var{tpnum} had an error. The
34517 string @var{text} is available to describe the nature of the error
34518 (for instance, a divide by zero in the condition expression).
34519 @var{text} is hex encoded.
34522 The trace stopped for some other reason.
34526 Additional optional fields supply statistical and other information.
34527 Although not required, they are extremely useful for users monitoring
34528 the progress of a trace run. If a trace has stopped, and these
34529 numbers are reported, they must reflect the state of the just-stopped
34534 @item tframes:@var{n}
34535 The number of trace frames in the buffer.
34537 @item tcreated:@var{n}
34538 The total number of trace frames created during the run. This may
34539 be larger than the trace frame count, if the buffer is circular.
34541 @item tsize:@var{n}
34542 The total size of the trace buffer, in bytes.
34544 @item tfree:@var{n}
34545 The number of bytes still unused in the buffer.
34547 @item circular:@var{n}
34548 The value of the circular trace buffer flag. @code{1} means that the
34549 trace buffer is circular and old trace frames will be discarded if
34550 necessary to make room, @code{0} means that the trace buffer is linear
34553 @item disconn:@var{n}
34554 The value of the disconnected tracing flag. @code{1} means that
34555 tracing will continue after @value{GDBN} disconnects, @code{0} means
34556 that the trace run will stop.
34560 @item qTV:@var{var}
34561 @cindex trace state variable value, remote request
34562 @cindex @samp{qTV} packet
34563 Ask the stub for the value of the trace state variable number @var{var}.
34568 The value of the variable is @var{value}. This will be the current
34569 value of the variable if the user is examining a running target, or a
34570 saved value if the variable was collected in the trace frame that the
34571 user is looking at. Note that multiple requests may result in
34572 different reply values, such as when requesting values while the
34573 program is running.
34576 The value of the variable is unknown. This would occur, for example,
34577 if the user is examining a trace frame in which the requested variable
34583 These packets request data about tracepoints that are being used by
34584 the target. @value{GDBN} sends @code{qTfP} to get the first piece
34585 of data, and multiple @code{qTsP} to get additional pieces. Replies
34586 to these packets generally take the form of the @code{QTDP} packets
34587 that define tracepoints. (FIXME add detailed syntax)
34591 These packets request data about trace state variables that are on the
34592 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
34593 and multiple @code{qTsV} to get additional variables. Replies to
34594 these packets follow the syntax of the @code{QTDV} packets that define
34595 trace state variables.
34599 These packets request data about static tracepoint markers that exist
34600 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
34601 first piece of data, and multiple @code{qTsSTM} to get additional
34602 pieces. Replies to these packets take the following form:
34606 @item m @var{address}:@var{id}:@var{extra}
34608 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
34609 a comma-separated list of markers
34611 (lower case letter @samp{L}) denotes end of list.
34613 An error occurred. @var{nn} are hex digits.
34615 An empty reply indicates that the request is not supported by the
34619 @var{address} is encoded in hex.
34620 @var{id} and @var{extra} are strings encoded in hex.
34622 In response to each query, the target will reply with a list of one or
34623 more markers, separated by commas. @value{GDBN} will respond to each
34624 reply with a request for more markers (using the @samp{qs} form of the
34625 query), until the target responds with @samp{l} (lower-case ell, for
34628 @item qTSTMat:@var{address}
34629 This packets requests data about static tracepoint markers in the
34630 target program at @var{address}. Replies to this packet follow the
34631 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
34632 tracepoint markers.
34634 @item QTSave:@var{filename}
34635 This packet directs the target to save trace data to the file name
34636 @var{filename} in the target's filesystem. @var{filename} is encoded
34637 as a hex string; the interpretation of the file name (relative vs
34638 absolute, wild cards, etc) is up to the target.
34640 @item qTBuffer:@var{offset},@var{len}
34641 Return up to @var{len} bytes of the current contents of trace buffer,
34642 starting at @var{offset}. The trace buffer is treated as if it were
34643 a contiguous collection of traceframes, as per the trace file format.
34644 The reply consists as many hex-encoded bytes as the target can deliver
34645 in a packet; it is not an error to return fewer than were asked for.
34646 A reply consisting of just @code{l} indicates that no bytes are
34649 @item QTBuffer:circular:@var{value}
34650 This packet directs the target to use a circular trace buffer if
34651 @var{value} is 1, or a linear buffer if the value is 0.
34655 @subsection Relocate instruction reply packet
34656 When installing fast tracepoints in memory, the target may need to
34657 relocate the instruction currently at the tracepoint address to a
34658 different address in memory. For most instructions, a simple copy is
34659 enough, but, for example, call instructions that implicitly push the
34660 return address on the stack, and relative branches or other
34661 PC-relative instructions require offset adjustment, so that the effect
34662 of executing the instruction at a different address is the same as if
34663 it had executed in the original location.
34665 In response to several of the tracepoint packets, the target may also
34666 respond with a number of intermediate @samp{qRelocInsn} request
34667 packets before the final result packet, to have @value{GDBN} handle
34668 this relocation operation. If a packet supports this mechanism, its
34669 documentation will explicitly say so. See for example the above
34670 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
34671 format of the request is:
34674 @item qRelocInsn:@var{from};@var{to}
34676 This requests @value{GDBN} to copy instruction at address @var{from}
34677 to address @var{to}, possibly adjusted so that executing the
34678 instruction at @var{to} has the same effect as executing it at
34679 @var{from}. @value{GDBN} writes the adjusted instruction to target
34680 memory starting at @var{to}.
34685 @item qRelocInsn:@var{adjusted_size}
34686 Informs the stub the relocation is complete. @var{adjusted_size} is
34687 the length in bytes of resulting relocated instruction sequence.
34689 A badly formed request was detected, or an error was encountered while
34690 relocating the instruction.
34693 @node Host I/O Packets
34694 @section Host I/O Packets
34695 @cindex Host I/O, remote protocol
34696 @cindex file transfer, remote protocol
34698 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
34699 operations on the far side of a remote link. For example, Host I/O is
34700 used to upload and download files to a remote target with its own
34701 filesystem. Host I/O uses the same constant values and data structure
34702 layout as the target-initiated File-I/O protocol. However, the
34703 Host I/O packets are structured differently. The target-initiated
34704 protocol relies on target memory to store parameters and buffers.
34705 Host I/O requests are initiated by @value{GDBN}, and the
34706 target's memory is not involved. @xref{File-I/O Remote Protocol
34707 Extension}, for more details on the target-initiated protocol.
34709 The Host I/O request packets all encode a single operation along with
34710 its arguments. They have this format:
34714 @item vFile:@var{operation}: @var{parameter}@dots{}
34715 @var{operation} is the name of the particular request; the target
34716 should compare the entire packet name up to the second colon when checking
34717 for a supported operation. The format of @var{parameter} depends on
34718 the operation. Numbers are always passed in hexadecimal. Negative
34719 numbers have an explicit minus sign (i.e.@: two's complement is not
34720 used). Strings (e.g.@: filenames) are encoded as a series of
34721 hexadecimal bytes. The last argument to a system call may be a
34722 buffer of escaped binary data (@pxref{Binary Data}).
34726 The valid responses to Host I/O packets are:
34730 @item F @var{result} [, @var{errno}] [; @var{attachment}]
34731 @var{result} is the integer value returned by this operation, usually
34732 non-negative for success and -1 for errors. If an error has occured,
34733 @var{errno} will be included in the result. @var{errno} will have a
34734 value defined by the File-I/O protocol (@pxref{Errno Values}). For
34735 operations which return data, @var{attachment} supplies the data as a
34736 binary buffer. Binary buffers in response packets are escaped in the
34737 normal way (@pxref{Binary Data}). See the individual packet
34738 documentation for the interpretation of @var{result} and
34742 An empty response indicates that this operation is not recognized.
34746 These are the supported Host I/O operations:
34749 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
34750 Open a file at @var{pathname} and return a file descriptor for it, or
34751 return -1 if an error occurs. @var{pathname} is a string,
34752 @var{flags} is an integer indicating a mask of open flags
34753 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
34754 of mode bits to use if the file is created (@pxref{mode_t Values}).
34755 @xref{open}, for details of the open flags and mode values.
34757 @item vFile:close: @var{fd}
34758 Close the open file corresponding to @var{fd} and return 0, or
34759 -1 if an error occurs.
34761 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
34762 Read data from the open file corresponding to @var{fd}. Up to
34763 @var{count} bytes will be read from the file, starting at @var{offset}
34764 relative to the start of the file. The target may read fewer bytes;
34765 common reasons include packet size limits and an end-of-file
34766 condition. The number of bytes read is returned. Zero should only be
34767 returned for a successful read at the end of the file, or if
34768 @var{count} was zero.
34770 The data read should be returned as a binary attachment on success.
34771 If zero bytes were read, the response should include an empty binary
34772 attachment (i.e.@: a trailing semicolon). The return value is the
34773 number of target bytes read; the binary attachment may be longer if
34774 some characters were escaped.
34776 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
34777 Write @var{data} (a binary buffer) to the open file corresponding
34778 to @var{fd}. Start the write at @var{offset} from the start of the
34779 file. Unlike many @code{write} system calls, there is no
34780 separate @var{count} argument; the length of @var{data} in the
34781 packet is used. @samp{vFile:write} returns the number of bytes written,
34782 which may be shorter than the length of @var{data}, or -1 if an
34785 @item vFile:unlink: @var{pathname}
34786 Delete the file at @var{pathname} on the target. Return 0,
34787 or -1 if an error occurs. @var{pathname} is a string.
34792 @section Interrupts
34793 @cindex interrupts (remote protocol)
34795 When a program on the remote target is running, @value{GDBN} may
34796 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
34797 a @code{BREAK} followed by @code{g},
34798 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
34800 The precise meaning of @code{BREAK} is defined by the transport
34801 mechanism and may, in fact, be undefined. @value{GDBN} does not
34802 currently define a @code{BREAK} mechanism for any of the network
34803 interfaces except for TCP, in which case @value{GDBN} sends the
34804 @code{telnet} BREAK sequence.
34806 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
34807 transport mechanisms. It is represented by sending the single byte
34808 @code{0x03} without any of the usual packet overhead described in
34809 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
34810 transmitted as part of a packet, it is considered to be packet data
34811 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
34812 (@pxref{X packet}), used for binary downloads, may include an unescaped
34813 @code{0x03} as part of its packet.
34815 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
34816 When Linux kernel receives this sequence from serial port,
34817 it stops execution and connects to gdb.
34819 Stubs are not required to recognize these interrupt mechanisms and the
34820 precise meaning associated with receipt of the interrupt is
34821 implementation defined. If the target supports debugging of multiple
34822 threads and/or processes, it should attempt to interrupt all
34823 currently-executing threads and processes.
34824 If the stub is successful at interrupting the
34825 running program, it should send one of the stop
34826 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
34827 of successfully stopping the program in all-stop mode, and a stop reply
34828 for each stopped thread in non-stop mode.
34829 Interrupts received while the
34830 program is stopped are discarded.
34832 @node Notification Packets
34833 @section Notification Packets
34834 @cindex notification packets
34835 @cindex packets, notification
34837 The @value{GDBN} remote serial protocol includes @dfn{notifications},
34838 packets that require no acknowledgment. Both the GDB and the stub
34839 may send notifications (although the only notifications defined at
34840 present are sent by the stub). Notifications carry information
34841 without incurring the round-trip latency of an acknowledgment, and so
34842 are useful for low-impact communications where occasional packet loss
34845 A notification packet has the form @samp{% @var{data} #
34846 @var{checksum}}, where @var{data} is the content of the notification,
34847 and @var{checksum} is a checksum of @var{data}, computed and formatted
34848 as for ordinary @value{GDBN} packets. A notification's @var{data}
34849 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
34850 receiving a notification, the recipient sends no @samp{+} or @samp{-}
34851 to acknowledge the notification's receipt or to report its corruption.
34853 Every notification's @var{data} begins with a name, which contains no
34854 colon characters, followed by a colon character.
34856 Recipients should silently ignore corrupted notifications and
34857 notifications they do not understand. Recipients should restart
34858 timeout periods on receipt of a well-formed notification, whether or
34859 not they understand it.
34861 Senders should only send the notifications described here when this
34862 protocol description specifies that they are permitted. In the
34863 future, we may extend the protocol to permit existing notifications in
34864 new contexts; this rule helps older senders avoid confusing newer
34867 (Older versions of @value{GDBN} ignore bytes received until they see
34868 the @samp{$} byte that begins an ordinary packet, so new stubs may
34869 transmit notifications without fear of confusing older clients. There
34870 are no notifications defined for @value{GDBN} to send at the moment, but we
34871 assume that most older stubs would ignore them, as well.)
34873 The following notification packets from the stub to @value{GDBN} are
34877 @item Stop: @var{reply}
34878 Report an asynchronous stop event in non-stop mode.
34879 The @var{reply} has the form of a stop reply, as
34880 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
34881 for information on how these notifications are acknowledged by
34885 @node Remote Non-Stop
34886 @section Remote Protocol Support for Non-Stop Mode
34888 @value{GDBN}'s remote protocol supports non-stop debugging of
34889 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
34890 supports non-stop mode, it should report that to @value{GDBN} by including
34891 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
34893 @value{GDBN} typically sends a @samp{QNonStop} packet only when
34894 establishing a new connection with the stub. Entering non-stop mode
34895 does not alter the state of any currently-running threads, but targets
34896 must stop all threads in any already-attached processes when entering
34897 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
34898 probe the target state after a mode change.
34900 In non-stop mode, when an attached process encounters an event that
34901 would otherwise be reported with a stop reply, it uses the
34902 asynchronous notification mechanism (@pxref{Notification Packets}) to
34903 inform @value{GDBN}. In contrast to all-stop mode, where all threads
34904 in all processes are stopped when a stop reply is sent, in non-stop
34905 mode only the thread reporting the stop event is stopped. That is,
34906 when reporting a @samp{S} or @samp{T} response to indicate completion
34907 of a step operation, hitting a breakpoint, or a fault, only the
34908 affected thread is stopped; any other still-running threads continue
34909 to run. When reporting a @samp{W} or @samp{X} response, all running
34910 threads belonging to other attached processes continue to run.
34912 Only one stop reply notification at a time may be pending; if
34913 additional stop events occur before @value{GDBN} has acknowledged the
34914 previous notification, they must be queued by the stub for later
34915 synchronous transmission in response to @samp{vStopped} packets from
34916 @value{GDBN}. Because the notification mechanism is unreliable,
34917 the stub is permitted to resend a stop reply notification
34918 if it believes @value{GDBN} may not have received it. @value{GDBN}
34919 ignores additional stop reply notifications received before it has
34920 finished processing a previous notification and the stub has completed
34921 sending any queued stop events.
34923 Otherwise, @value{GDBN} must be prepared to receive a stop reply
34924 notification at any time. Specifically, they may appear when
34925 @value{GDBN} is not otherwise reading input from the stub, or when
34926 @value{GDBN} is expecting to read a normal synchronous response or a
34927 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
34928 Notification packets are distinct from any other communication from
34929 the stub so there is no ambiguity.
34931 After receiving a stop reply notification, @value{GDBN} shall
34932 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
34933 as a regular, synchronous request to the stub. Such acknowledgment
34934 is not required to happen immediately, as @value{GDBN} is permitted to
34935 send other, unrelated packets to the stub first, which the stub should
34938 Upon receiving a @samp{vStopped} packet, if the stub has other queued
34939 stop events to report to @value{GDBN}, it shall respond by sending a
34940 normal stop reply response. @value{GDBN} shall then send another
34941 @samp{vStopped} packet to solicit further responses; again, it is
34942 permitted to send other, unrelated packets as well which the stub
34943 should process normally.
34945 If the stub receives a @samp{vStopped} packet and there are no
34946 additional stop events to report, the stub shall return an @samp{OK}
34947 response. At this point, if further stop events occur, the stub shall
34948 send a new stop reply notification, @value{GDBN} shall accept the
34949 notification, and the process shall be repeated.
34951 In non-stop mode, the target shall respond to the @samp{?} packet as
34952 follows. First, any incomplete stop reply notification/@samp{vStopped}
34953 sequence in progress is abandoned. The target must begin a new
34954 sequence reporting stop events for all stopped threads, whether or not
34955 it has previously reported those events to @value{GDBN}. The first
34956 stop reply is sent as a synchronous reply to the @samp{?} packet, and
34957 subsequent stop replies are sent as responses to @samp{vStopped} packets
34958 using the mechanism described above. The target must not send
34959 asynchronous stop reply notifications until the sequence is complete.
34960 If all threads are running when the target receives the @samp{?} packet,
34961 or if the target is not attached to any process, it shall respond
34964 @node Packet Acknowledgment
34965 @section Packet Acknowledgment
34967 @cindex acknowledgment, for @value{GDBN} remote
34968 @cindex packet acknowledgment, for @value{GDBN} remote
34969 By default, when either the host or the target machine receives a packet,
34970 the first response expected is an acknowledgment: either @samp{+} (to indicate
34971 the package was received correctly) or @samp{-} (to request retransmission).
34972 This mechanism allows the @value{GDBN} remote protocol to operate over
34973 unreliable transport mechanisms, such as a serial line.
34975 In cases where the transport mechanism is itself reliable (such as a pipe or
34976 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
34977 It may be desirable to disable them in that case to reduce communication
34978 overhead, or for other reasons. This can be accomplished by means of the
34979 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
34981 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
34982 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
34983 and response format still includes the normal checksum, as described in
34984 @ref{Overview}, but the checksum may be ignored by the receiver.
34986 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
34987 no-acknowledgment mode, it should report that to @value{GDBN}
34988 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
34989 @pxref{qSupported}.
34990 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
34991 disabled via the @code{set remote noack-packet off} command
34992 (@pxref{Remote Configuration}),
34993 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
34994 Only then may the stub actually turn off packet acknowledgments.
34995 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
34996 response, which can be safely ignored by the stub.
34998 Note that @code{set remote noack-packet} command only affects negotiation
34999 between @value{GDBN} and the stub when subsequent connections are made;
35000 it does not affect the protocol acknowledgment state for any current
35002 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
35003 new connection is established,
35004 there is also no protocol request to re-enable the acknowledgments
35005 for the current connection, once disabled.
35010 Example sequence of a target being re-started. Notice how the restart
35011 does not get any direct output:
35016 @emph{target restarts}
35019 <- @code{T001:1234123412341234}
35023 Example sequence of a target being stepped by a single instruction:
35026 -> @code{G1445@dots{}}
35031 <- @code{T001:1234123412341234}
35035 <- @code{1455@dots{}}
35039 @node File-I/O Remote Protocol Extension
35040 @section File-I/O Remote Protocol Extension
35041 @cindex File-I/O remote protocol extension
35044 * File-I/O Overview::
35045 * Protocol Basics::
35046 * The F Request Packet::
35047 * The F Reply Packet::
35048 * The Ctrl-C Message::
35050 * List of Supported Calls::
35051 * Protocol-specific Representation of Datatypes::
35053 * File-I/O Examples::
35056 @node File-I/O Overview
35057 @subsection File-I/O Overview
35058 @cindex file-i/o overview
35060 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
35061 target to use the host's file system and console I/O to perform various
35062 system calls. System calls on the target system are translated into a
35063 remote protocol packet to the host system, which then performs the needed
35064 actions and returns a response packet to the target system.
35065 This simulates file system operations even on targets that lack file systems.
35067 The protocol is defined to be independent of both the host and target systems.
35068 It uses its own internal representation of datatypes and values. Both
35069 @value{GDBN} and the target's @value{GDBN} stub are responsible for
35070 translating the system-dependent value representations into the internal
35071 protocol representations when data is transmitted.
35073 The communication is synchronous. A system call is possible only when
35074 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
35075 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
35076 the target is stopped to allow deterministic access to the target's
35077 memory. Therefore File-I/O is not interruptible by target signals. On
35078 the other hand, it is possible to interrupt File-I/O by a user interrupt
35079 (@samp{Ctrl-C}) within @value{GDBN}.
35081 The target's request to perform a host system call does not finish
35082 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
35083 after finishing the system call, the target returns to continuing the
35084 previous activity (continue, step). No additional continue or step
35085 request from @value{GDBN} is required.
35088 (@value{GDBP}) continue
35089 <- target requests 'system call X'
35090 target is stopped, @value{GDBN} executes system call
35091 -> @value{GDBN} returns result
35092 ... target continues, @value{GDBN} returns to wait for the target
35093 <- target hits breakpoint and sends a Txx packet
35096 The protocol only supports I/O on the console and to regular files on
35097 the host file system. Character or block special devices, pipes,
35098 named pipes, sockets or any other communication method on the host
35099 system are not supported by this protocol.
35101 File I/O is not supported in non-stop mode.
35103 @node Protocol Basics
35104 @subsection Protocol Basics
35105 @cindex protocol basics, file-i/o
35107 The File-I/O protocol uses the @code{F} packet as the request as well
35108 as reply packet. Since a File-I/O system call can only occur when
35109 @value{GDBN} is waiting for a response from the continuing or stepping target,
35110 the File-I/O request is a reply that @value{GDBN} has to expect as a result
35111 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
35112 This @code{F} packet contains all information needed to allow @value{GDBN}
35113 to call the appropriate host system call:
35117 A unique identifier for the requested system call.
35120 All parameters to the system call. Pointers are given as addresses
35121 in the target memory address space. Pointers to strings are given as
35122 pointer/length pair. Numerical values are given as they are.
35123 Numerical control flags are given in a protocol-specific representation.
35127 At this point, @value{GDBN} has to perform the following actions.
35131 If the parameters include pointer values to data needed as input to a
35132 system call, @value{GDBN} requests this data from the target with a
35133 standard @code{m} packet request. This additional communication has to be
35134 expected by the target implementation and is handled as any other @code{m}
35138 @value{GDBN} translates all value from protocol representation to host
35139 representation as needed. Datatypes are coerced into the host types.
35142 @value{GDBN} calls the system call.
35145 It then coerces datatypes back to protocol representation.
35148 If the system call is expected to return data in buffer space specified
35149 by pointer parameters to the call, the data is transmitted to the
35150 target using a @code{M} or @code{X} packet. This packet has to be expected
35151 by the target implementation and is handled as any other @code{M} or @code{X}
35156 Eventually @value{GDBN} replies with another @code{F} packet which contains all
35157 necessary information for the target to continue. This at least contains
35164 @code{errno}, if has been changed by the system call.
35171 After having done the needed type and value coercion, the target continues
35172 the latest continue or step action.
35174 @node The F Request Packet
35175 @subsection The @code{F} Request Packet
35176 @cindex file-i/o request packet
35177 @cindex @code{F} request packet
35179 The @code{F} request packet has the following format:
35182 @item F@var{call-id},@var{parameter@dots{}}
35184 @var{call-id} is the identifier to indicate the host system call to be called.
35185 This is just the name of the function.
35187 @var{parameter@dots{}} are the parameters to the system call.
35188 Parameters are hexadecimal integer values, either the actual values in case
35189 of scalar datatypes, pointers to target buffer space in case of compound
35190 datatypes and unspecified memory areas, or pointer/length pairs in case
35191 of string parameters. These are appended to the @var{call-id} as a
35192 comma-delimited list. All values are transmitted in ASCII
35193 string representation, pointer/length pairs separated by a slash.
35199 @node The F Reply Packet
35200 @subsection The @code{F} Reply Packet
35201 @cindex file-i/o reply packet
35202 @cindex @code{F} reply packet
35204 The @code{F} reply packet has the following format:
35208 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
35210 @var{retcode} is the return code of the system call as hexadecimal value.
35212 @var{errno} is the @code{errno} set by the call, in protocol-specific
35214 This parameter can be omitted if the call was successful.
35216 @var{Ctrl-C flag} is only sent if the user requested a break. In this
35217 case, @var{errno} must be sent as well, even if the call was successful.
35218 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
35225 or, if the call was interrupted before the host call has been performed:
35232 assuming 4 is the protocol-specific representation of @code{EINTR}.
35237 @node The Ctrl-C Message
35238 @subsection The @samp{Ctrl-C} Message
35239 @cindex ctrl-c message, in file-i/o protocol
35241 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
35242 reply packet (@pxref{The F Reply Packet}),
35243 the target should behave as if it had
35244 gotten a break message. The meaning for the target is ``system call
35245 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
35246 (as with a break message) and return to @value{GDBN} with a @code{T02}
35249 It's important for the target to know in which
35250 state the system call was interrupted. There are two possible cases:
35254 The system call hasn't been performed on the host yet.
35257 The system call on the host has been finished.
35261 These two states can be distinguished by the target by the value of the
35262 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
35263 call hasn't been performed. This is equivalent to the @code{EINTR} handling
35264 on POSIX systems. In any other case, the target may presume that the
35265 system call has been finished --- successfully or not --- and should behave
35266 as if the break message arrived right after the system call.
35268 @value{GDBN} must behave reliably. If the system call has not been called
35269 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
35270 @code{errno} in the packet. If the system call on the host has been finished
35271 before the user requests a break, the full action must be finished by
35272 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
35273 The @code{F} packet may only be sent when either nothing has happened
35274 or the full action has been completed.
35277 @subsection Console I/O
35278 @cindex console i/o as part of file-i/o
35280 By default and if not explicitly closed by the target system, the file
35281 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
35282 on the @value{GDBN} console is handled as any other file output operation
35283 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
35284 by @value{GDBN} so that after the target read request from file descriptor
35285 0 all following typing is buffered until either one of the following
35290 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
35292 system call is treated as finished.
35295 The user presses @key{RET}. This is treated as end of input with a trailing
35299 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
35300 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
35304 If the user has typed more characters than fit in the buffer given to
35305 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
35306 either another @code{read(0, @dots{})} is requested by the target, or debugging
35307 is stopped at the user's request.
35310 @node List of Supported Calls
35311 @subsection List of Supported Calls
35312 @cindex list of supported file-i/o calls
35329 @unnumberedsubsubsec open
35330 @cindex open, file-i/o system call
35335 int open(const char *pathname, int flags);
35336 int open(const char *pathname, int flags, mode_t mode);
35340 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
35343 @var{flags} is the bitwise @code{OR} of the following values:
35347 If the file does not exist it will be created. The host
35348 rules apply as far as file ownership and time stamps
35352 When used with @code{O_CREAT}, if the file already exists it is
35353 an error and open() fails.
35356 If the file already exists and the open mode allows
35357 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
35358 truncated to zero length.
35361 The file is opened in append mode.
35364 The file is opened for reading only.
35367 The file is opened for writing only.
35370 The file is opened for reading and writing.
35374 Other bits are silently ignored.
35378 @var{mode} is the bitwise @code{OR} of the following values:
35382 User has read permission.
35385 User has write permission.
35388 Group has read permission.
35391 Group has write permission.
35394 Others have read permission.
35397 Others have write permission.
35401 Other bits are silently ignored.
35404 @item Return value:
35405 @code{open} returns the new file descriptor or -1 if an error
35412 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
35415 @var{pathname} refers to a directory.
35418 The requested access is not allowed.
35421 @var{pathname} was too long.
35424 A directory component in @var{pathname} does not exist.
35427 @var{pathname} refers to a device, pipe, named pipe or socket.
35430 @var{pathname} refers to a file on a read-only filesystem and
35431 write access was requested.
35434 @var{pathname} is an invalid pointer value.
35437 No space on device to create the file.
35440 The process already has the maximum number of files open.
35443 The limit on the total number of files open on the system
35447 The call was interrupted by the user.
35453 @unnumberedsubsubsec close
35454 @cindex close, file-i/o system call
35463 @samp{Fclose,@var{fd}}
35465 @item Return value:
35466 @code{close} returns zero on success, or -1 if an error occurred.
35472 @var{fd} isn't a valid open file descriptor.
35475 The call was interrupted by the user.
35481 @unnumberedsubsubsec read
35482 @cindex read, file-i/o system call
35487 int read(int fd, void *buf, unsigned int count);
35491 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
35493 @item Return value:
35494 On success, the number of bytes read is returned.
35495 Zero indicates end of file. If count is zero, read
35496 returns zero as well. On error, -1 is returned.
35502 @var{fd} is not a valid file descriptor or is not open for
35506 @var{bufptr} is an invalid pointer value.
35509 The call was interrupted by the user.
35515 @unnumberedsubsubsec write
35516 @cindex write, file-i/o system call
35521 int write(int fd, const void *buf, unsigned int count);
35525 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
35527 @item Return value:
35528 On success, the number of bytes written are returned.
35529 Zero indicates nothing was written. On error, -1
35536 @var{fd} is not a valid file descriptor or is not open for
35540 @var{bufptr} is an invalid pointer value.
35543 An attempt was made to write a file that exceeds the
35544 host-specific maximum file size allowed.
35547 No space on device to write the data.
35550 The call was interrupted by the user.
35556 @unnumberedsubsubsec lseek
35557 @cindex lseek, file-i/o system call
35562 long lseek (int fd, long offset, int flag);
35566 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
35568 @var{flag} is one of:
35572 The offset is set to @var{offset} bytes.
35575 The offset is set to its current location plus @var{offset}
35579 The offset is set to the size of the file plus @var{offset}
35583 @item Return value:
35584 On success, the resulting unsigned offset in bytes from
35585 the beginning of the file is returned. Otherwise, a
35586 value of -1 is returned.
35592 @var{fd} is not a valid open file descriptor.
35595 @var{fd} is associated with the @value{GDBN} console.
35598 @var{flag} is not a proper value.
35601 The call was interrupted by the user.
35607 @unnumberedsubsubsec rename
35608 @cindex rename, file-i/o system call
35613 int rename(const char *oldpath, const char *newpath);
35617 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
35619 @item Return value:
35620 On success, zero is returned. On error, -1 is returned.
35626 @var{newpath} is an existing directory, but @var{oldpath} is not a
35630 @var{newpath} is a non-empty directory.
35633 @var{oldpath} or @var{newpath} is a directory that is in use by some
35637 An attempt was made to make a directory a subdirectory
35641 A component used as a directory in @var{oldpath} or new
35642 path is not a directory. Or @var{oldpath} is a directory
35643 and @var{newpath} exists but is not a directory.
35646 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
35649 No access to the file or the path of the file.
35653 @var{oldpath} or @var{newpath} was too long.
35656 A directory component in @var{oldpath} or @var{newpath} does not exist.
35659 The file is on a read-only filesystem.
35662 The device containing the file has no room for the new
35666 The call was interrupted by the user.
35672 @unnumberedsubsubsec unlink
35673 @cindex unlink, file-i/o system call
35678 int unlink(const char *pathname);
35682 @samp{Funlink,@var{pathnameptr}/@var{len}}
35684 @item Return value:
35685 On success, zero is returned. On error, -1 is returned.
35691 No access to the file or the path of the file.
35694 The system does not allow unlinking of directories.
35697 The file @var{pathname} cannot be unlinked because it's
35698 being used by another process.
35701 @var{pathnameptr} is an invalid pointer value.
35704 @var{pathname} was too long.
35707 A directory component in @var{pathname} does not exist.
35710 A component of the path is not a directory.
35713 The file is on a read-only filesystem.
35716 The call was interrupted by the user.
35722 @unnumberedsubsubsec stat/fstat
35723 @cindex fstat, file-i/o system call
35724 @cindex stat, file-i/o system call
35729 int stat(const char *pathname, struct stat *buf);
35730 int fstat(int fd, struct stat *buf);
35734 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
35735 @samp{Ffstat,@var{fd},@var{bufptr}}
35737 @item Return value:
35738 On success, zero is returned. On error, -1 is returned.
35744 @var{fd} is not a valid open file.
35747 A directory component in @var{pathname} does not exist or the
35748 path is an empty string.
35751 A component of the path is not a directory.
35754 @var{pathnameptr} is an invalid pointer value.
35757 No access to the file or the path of the file.
35760 @var{pathname} was too long.
35763 The call was interrupted by the user.
35769 @unnumberedsubsubsec gettimeofday
35770 @cindex gettimeofday, file-i/o system call
35775 int gettimeofday(struct timeval *tv, void *tz);
35779 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
35781 @item Return value:
35782 On success, 0 is returned, -1 otherwise.
35788 @var{tz} is a non-NULL pointer.
35791 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
35797 @unnumberedsubsubsec isatty
35798 @cindex isatty, file-i/o system call
35803 int isatty(int fd);
35807 @samp{Fisatty,@var{fd}}
35809 @item Return value:
35810 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
35816 The call was interrupted by the user.
35821 Note that the @code{isatty} call is treated as a special case: it returns
35822 1 to the target if the file descriptor is attached
35823 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
35824 would require implementing @code{ioctl} and would be more complex than
35829 @unnumberedsubsubsec system
35830 @cindex system, file-i/o system call
35835 int system(const char *command);
35839 @samp{Fsystem,@var{commandptr}/@var{len}}
35841 @item Return value:
35842 If @var{len} is zero, the return value indicates whether a shell is
35843 available. A zero return value indicates a shell is not available.
35844 For non-zero @var{len}, the value returned is -1 on error and the
35845 return status of the command otherwise. Only the exit status of the
35846 command is returned, which is extracted from the host's @code{system}
35847 return value by calling @code{WEXITSTATUS(retval)}. In case
35848 @file{/bin/sh} could not be executed, 127 is returned.
35854 The call was interrupted by the user.
35859 @value{GDBN} takes over the full task of calling the necessary host calls
35860 to perform the @code{system} call. The return value of @code{system} on
35861 the host is simplified before it's returned
35862 to the target. Any termination signal information from the child process
35863 is discarded, and the return value consists
35864 entirely of the exit status of the called command.
35866 Due to security concerns, the @code{system} call is by default refused
35867 by @value{GDBN}. The user has to allow this call explicitly with the
35868 @code{set remote system-call-allowed 1} command.
35871 @item set remote system-call-allowed
35872 @kindex set remote system-call-allowed
35873 Control whether to allow the @code{system} calls in the File I/O
35874 protocol for the remote target. The default is zero (disabled).
35876 @item show remote system-call-allowed
35877 @kindex show remote system-call-allowed
35878 Show whether the @code{system} calls are allowed in the File I/O
35882 @node Protocol-specific Representation of Datatypes
35883 @subsection Protocol-specific Representation of Datatypes
35884 @cindex protocol-specific representation of datatypes, in file-i/o protocol
35887 * Integral Datatypes::
35889 * Memory Transfer::
35894 @node Integral Datatypes
35895 @unnumberedsubsubsec Integral Datatypes
35896 @cindex integral datatypes, in file-i/o protocol
35898 The integral datatypes used in the system calls are @code{int},
35899 @code{unsigned int}, @code{long}, @code{unsigned long},
35900 @code{mode_t}, and @code{time_t}.
35902 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
35903 implemented as 32 bit values in this protocol.
35905 @code{long} and @code{unsigned long} are implemented as 64 bit types.
35907 @xref{Limits}, for corresponding MIN and MAX values (similar to those
35908 in @file{limits.h}) to allow range checking on host and target.
35910 @code{time_t} datatypes are defined as seconds since the Epoch.
35912 All integral datatypes transferred as part of a memory read or write of a
35913 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
35916 @node Pointer Values
35917 @unnumberedsubsubsec Pointer Values
35918 @cindex pointer values, in file-i/o protocol
35920 Pointers to target data are transmitted as they are. An exception
35921 is made for pointers to buffers for which the length isn't
35922 transmitted as part of the function call, namely strings. Strings
35923 are transmitted as a pointer/length pair, both as hex values, e.g.@:
35930 which is a pointer to data of length 18 bytes at position 0x1aaf.
35931 The length is defined as the full string length in bytes, including
35932 the trailing null byte. For example, the string @code{"hello world"}
35933 at address 0x123456 is transmitted as
35939 @node Memory Transfer
35940 @unnumberedsubsubsec Memory Transfer
35941 @cindex memory transfer, in file-i/o protocol
35943 Structured data which is transferred using a memory read or write (for
35944 example, a @code{struct stat}) is expected to be in a protocol-specific format
35945 with all scalar multibyte datatypes being big endian. Translation to
35946 this representation needs to be done both by the target before the @code{F}
35947 packet is sent, and by @value{GDBN} before
35948 it transfers memory to the target. Transferred pointers to structured
35949 data should point to the already-coerced data at any time.
35953 @unnumberedsubsubsec struct stat
35954 @cindex struct stat, in file-i/o protocol
35956 The buffer of type @code{struct stat} used by the target and @value{GDBN}
35957 is defined as follows:
35961 unsigned int st_dev; /* device */
35962 unsigned int st_ino; /* inode */
35963 mode_t st_mode; /* protection */
35964 unsigned int st_nlink; /* number of hard links */
35965 unsigned int st_uid; /* user ID of owner */
35966 unsigned int st_gid; /* group ID of owner */
35967 unsigned int st_rdev; /* device type (if inode device) */
35968 unsigned long st_size; /* total size, in bytes */
35969 unsigned long st_blksize; /* blocksize for filesystem I/O */
35970 unsigned long st_blocks; /* number of blocks allocated */
35971 time_t st_atime; /* time of last access */
35972 time_t st_mtime; /* time of last modification */
35973 time_t st_ctime; /* time of last change */
35977 The integral datatypes conform to the definitions given in the
35978 appropriate section (see @ref{Integral Datatypes}, for details) so this
35979 structure is of size 64 bytes.
35981 The values of several fields have a restricted meaning and/or
35987 A value of 0 represents a file, 1 the console.
35990 No valid meaning for the target. Transmitted unchanged.
35993 Valid mode bits are described in @ref{Constants}. Any other
35994 bits have currently no meaning for the target.
35999 No valid meaning for the target. Transmitted unchanged.
36004 These values have a host and file system dependent
36005 accuracy. Especially on Windows hosts, the file system may not
36006 support exact timing values.
36009 The target gets a @code{struct stat} of the above representation and is
36010 responsible for coercing it to the target representation before
36013 Note that due to size differences between the host, target, and protocol
36014 representations of @code{struct stat} members, these members could eventually
36015 get truncated on the target.
36017 @node struct timeval
36018 @unnumberedsubsubsec struct timeval
36019 @cindex struct timeval, in file-i/o protocol
36021 The buffer of type @code{struct timeval} used by the File-I/O protocol
36022 is defined as follows:
36026 time_t tv_sec; /* second */
36027 long tv_usec; /* microsecond */
36031 The integral datatypes conform to the definitions given in the
36032 appropriate section (see @ref{Integral Datatypes}, for details) so this
36033 structure is of size 8 bytes.
36036 @subsection Constants
36037 @cindex constants, in file-i/o protocol
36039 The following values are used for the constants inside of the
36040 protocol. @value{GDBN} and target are responsible for translating these
36041 values before and after the call as needed.
36052 @unnumberedsubsubsec Open Flags
36053 @cindex open flags, in file-i/o protocol
36055 All values are given in hexadecimal representation.
36067 @node mode_t Values
36068 @unnumberedsubsubsec mode_t Values
36069 @cindex mode_t values, in file-i/o protocol
36071 All values are given in octal representation.
36088 @unnumberedsubsubsec Errno Values
36089 @cindex errno values, in file-i/o protocol
36091 All values are given in decimal representation.
36116 @code{EUNKNOWN} is used as a fallback error value if a host system returns
36117 any error value not in the list of supported error numbers.
36120 @unnumberedsubsubsec Lseek Flags
36121 @cindex lseek flags, in file-i/o protocol
36130 @unnumberedsubsubsec Limits
36131 @cindex limits, in file-i/o protocol
36133 All values are given in decimal representation.
36136 INT_MIN -2147483648
36138 UINT_MAX 4294967295
36139 LONG_MIN -9223372036854775808
36140 LONG_MAX 9223372036854775807
36141 ULONG_MAX 18446744073709551615
36144 @node File-I/O Examples
36145 @subsection File-I/O Examples
36146 @cindex file-i/o examples
36148 Example sequence of a write call, file descriptor 3, buffer is at target
36149 address 0x1234, 6 bytes should be written:
36152 <- @code{Fwrite,3,1234,6}
36153 @emph{request memory read from target}
36156 @emph{return "6 bytes written"}
36160 Example sequence of a read call, file descriptor 3, buffer is at target
36161 address 0x1234, 6 bytes should be read:
36164 <- @code{Fread,3,1234,6}
36165 @emph{request memory write to target}
36166 -> @code{X1234,6:XXXXXX}
36167 @emph{return "6 bytes read"}
36171 Example sequence of a read call, call fails on the host due to invalid
36172 file descriptor (@code{EBADF}):
36175 <- @code{Fread,3,1234,6}
36179 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
36183 <- @code{Fread,3,1234,6}
36188 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
36192 <- @code{Fread,3,1234,6}
36193 -> @code{X1234,6:XXXXXX}
36197 @node Library List Format
36198 @section Library List Format
36199 @cindex library list format, remote protocol
36201 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
36202 same process as your application to manage libraries. In this case,
36203 @value{GDBN} can use the loader's symbol table and normal memory
36204 operations to maintain a list of shared libraries. On other
36205 platforms, the operating system manages loaded libraries.
36206 @value{GDBN} can not retrieve the list of currently loaded libraries
36207 through memory operations, so it uses the @samp{qXfer:libraries:read}
36208 packet (@pxref{qXfer library list read}) instead. The remote stub
36209 queries the target's operating system and reports which libraries
36212 The @samp{qXfer:libraries:read} packet returns an XML document which
36213 lists loaded libraries and their offsets. Each library has an
36214 associated name and one or more segment or section base addresses,
36215 which report where the library was loaded in memory.
36217 For the common case of libraries that are fully linked binaries, the
36218 library should have a list of segments. If the target supports
36219 dynamic linking of a relocatable object file, its library XML element
36220 should instead include a list of allocated sections. The segment or
36221 section bases are start addresses, not relocation offsets; they do not
36222 depend on the library's link-time base addresses.
36224 @value{GDBN} must be linked with the Expat library to support XML
36225 library lists. @xref{Expat}.
36227 A simple memory map, with one loaded library relocated by a single
36228 offset, looks like this:
36232 <library name="/lib/libc.so.6">
36233 <segment address="0x10000000"/>
36238 Another simple memory map, with one loaded library with three
36239 allocated sections (.text, .data, .bss), looks like this:
36243 <library name="sharedlib.o">
36244 <section address="0x10000000"/>
36245 <section address="0x20000000"/>
36246 <section address="0x30000000"/>
36251 The format of a library list is described by this DTD:
36254 <!-- library-list: Root element with versioning -->
36255 <!ELEMENT library-list (library)*>
36256 <!ATTLIST library-list version CDATA #FIXED "1.0">
36257 <!ELEMENT library (segment*, section*)>
36258 <!ATTLIST library name CDATA #REQUIRED>
36259 <!ELEMENT segment EMPTY>
36260 <!ATTLIST segment address CDATA #REQUIRED>
36261 <!ELEMENT section EMPTY>
36262 <!ATTLIST section address CDATA #REQUIRED>
36265 In addition, segments and section descriptors cannot be mixed within a
36266 single library element, and you must supply at least one segment or
36267 section for each library.
36269 @node Memory Map Format
36270 @section Memory Map Format
36271 @cindex memory map format
36273 To be able to write into flash memory, @value{GDBN} needs to obtain a
36274 memory map from the target. This section describes the format of the
36277 The memory map is obtained using the @samp{qXfer:memory-map:read}
36278 (@pxref{qXfer memory map read}) packet and is an XML document that
36279 lists memory regions.
36281 @value{GDBN} must be linked with the Expat library to support XML
36282 memory maps. @xref{Expat}.
36284 The top-level structure of the document is shown below:
36287 <?xml version="1.0"?>
36288 <!DOCTYPE memory-map
36289 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36290 "http://sourceware.org/gdb/gdb-memory-map.dtd">
36296 Each region can be either:
36301 A region of RAM starting at @var{addr} and extending for @var{length}
36305 <memory type="ram" start="@var{addr}" length="@var{length}"/>
36310 A region of read-only memory:
36313 <memory type="rom" start="@var{addr}" length="@var{length}"/>
36318 A region of flash memory, with erasure blocks @var{blocksize}
36322 <memory type="flash" start="@var{addr}" length="@var{length}">
36323 <property name="blocksize">@var{blocksize}</property>
36329 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
36330 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
36331 packets to write to addresses in such ranges.
36333 The formal DTD for memory map format is given below:
36336 <!-- ................................................... -->
36337 <!-- Memory Map XML DTD ................................ -->
36338 <!-- File: memory-map.dtd .............................. -->
36339 <!-- .................................... .............. -->
36340 <!-- memory-map.dtd -->
36341 <!-- memory-map: Root element with versioning -->
36342 <!ELEMENT memory-map (memory | property)>
36343 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
36344 <!ELEMENT memory (property)>
36345 <!-- memory: Specifies a memory region,
36346 and its type, or device. -->
36347 <!ATTLIST memory type CDATA #REQUIRED
36348 start CDATA #REQUIRED
36349 length CDATA #REQUIRED
36350 device CDATA #IMPLIED>
36351 <!-- property: Generic attribute tag -->
36352 <!ELEMENT property (#PCDATA | property)*>
36353 <!ATTLIST property name CDATA #REQUIRED>
36356 @node Thread List Format
36357 @section Thread List Format
36358 @cindex thread list format
36360 To efficiently update the list of threads and their attributes,
36361 @value{GDBN} issues the @samp{qXfer:threads:read} packet
36362 (@pxref{qXfer threads read}) and obtains the XML document with
36363 the following structure:
36366 <?xml version="1.0"?>
36368 <thread id="id" core="0">
36369 ... description ...
36374 Each @samp{thread} element must have the @samp{id} attribute that
36375 identifies the thread (@pxref{thread-id syntax}). The
36376 @samp{core} attribute, if present, specifies which processor core
36377 the thread was last executing on. The content of the of @samp{thread}
36378 element is interpreted as human-readable auxilliary information.
36380 @node Traceframe Info Format
36381 @section Traceframe Info Format
36382 @cindex traceframe info format
36384 To be able to know which objects in the inferior can be examined when
36385 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
36386 memory ranges, registers and trace state variables that have been
36387 collected in a traceframe.
36389 This list is obtained using the @samp{qXfer:traceframe-info:read}
36390 (@pxref{qXfer traceframe info read}) packet and is an XML document.
36392 @value{GDBN} must be linked with the Expat library to support XML
36393 traceframe info discovery. @xref{Expat}.
36395 The top-level structure of the document is shown below:
36398 <?xml version="1.0"?>
36399 <!DOCTYPE traceframe-info
36400 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36401 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
36407 Each traceframe block can be either:
36412 A region of collected memory starting at @var{addr} and extending for
36413 @var{length} bytes from there:
36416 <memory start="@var{addr}" length="@var{length}"/>
36421 The formal DTD for the traceframe info format is given below:
36424 <!ELEMENT traceframe-info (memory)* >
36425 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
36427 <!ELEMENT memory EMPTY>
36428 <!ATTLIST memory start CDATA #REQUIRED
36429 length CDATA #REQUIRED>
36432 @include agentexpr.texi
36434 @node Target Descriptions
36435 @appendix Target Descriptions
36436 @cindex target descriptions
36438 One of the challenges of using @value{GDBN} to debug embedded systems
36439 is that there are so many minor variants of each processor
36440 architecture in use. It is common practice for vendors to start with
36441 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
36442 and then make changes to adapt it to a particular market niche. Some
36443 architectures have hundreds of variants, available from dozens of
36444 vendors. This leads to a number of problems:
36448 With so many different customized processors, it is difficult for
36449 the @value{GDBN} maintainers to keep up with the changes.
36451 Since individual variants may have short lifetimes or limited
36452 audiences, it may not be worthwhile to carry information about every
36453 variant in the @value{GDBN} source tree.
36455 When @value{GDBN} does support the architecture of the embedded system
36456 at hand, the task of finding the correct architecture name to give the
36457 @command{set architecture} command can be error-prone.
36460 To address these problems, the @value{GDBN} remote protocol allows a
36461 target system to not only identify itself to @value{GDBN}, but to
36462 actually describe its own features. This lets @value{GDBN} support
36463 processor variants it has never seen before --- to the extent that the
36464 descriptions are accurate, and that @value{GDBN} understands them.
36466 @value{GDBN} must be linked with the Expat library to support XML
36467 target descriptions. @xref{Expat}.
36470 * Retrieving Descriptions:: How descriptions are fetched from a target.
36471 * Target Description Format:: The contents of a target description.
36472 * Predefined Target Types:: Standard types available for target
36474 * Standard Target Features:: Features @value{GDBN} knows about.
36477 @node Retrieving Descriptions
36478 @section Retrieving Descriptions
36480 Target descriptions can be read from the target automatically, or
36481 specified by the user manually. The default behavior is to read the
36482 description from the target. @value{GDBN} retrieves it via the remote
36483 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
36484 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
36485 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
36486 XML document, of the form described in @ref{Target Description
36489 Alternatively, you can specify a file to read for the target description.
36490 If a file is set, the target will not be queried. The commands to
36491 specify a file are:
36494 @cindex set tdesc filename
36495 @item set tdesc filename @var{path}
36496 Read the target description from @var{path}.
36498 @cindex unset tdesc filename
36499 @item unset tdesc filename
36500 Do not read the XML target description from a file. @value{GDBN}
36501 will use the description supplied by the current target.
36503 @cindex show tdesc filename
36504 @item show tdesc filename
36505 Show the filename to read for a target description, if any.
36509 @node Target Description Format
36510 @section Target Description Format
36511 @cindex target descriptions, XML format
36513 A target description annex is an @uref{http://www.w3.org/XML/, XML}
36514 document which complies with the Document Type Definition provided in
36515 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
36516 means you can use generally available tools like @command{xmllint} to
36517 check that your feature descriptions are well-formed and valid.
36518 However, to help people unfamiliar with XML write descriptions for
36519 their targets, we also describe the grammar here.
36521 Target descriptions can identify the architecture of the remote target
36522 and (for some architectures) provide information about custom register
36523 sets. They can also identify the OS ABI of the remote target.
36524 @value{GDBN} can use this information to autoconfigure for your
36525 target, or to warn you if you connect to an unsupported target.
36527 Here is a simple target description:
36530 <target version="1.0">
36531 <architecture>i386:x86-64</architecture>
36536 This minimal description only says that the target uses
36537 the x86-64 architecture.
36539 A target description has the following overall form, with [ ] marking
36540 optional elements and @dots{} marking repeatable elements. The elements
36541 are explained further below.
36544 <?xml version="1.0"?>
36545 <!DOCTYPE target SYSTEM "gdb-target.dtd">
36546 <target version="1.0">
36547 @r{[}@var{architecture}@r{]}
36548 @r{[}@var{osabi}@r{]}
36549 @r{[}@var{compatible}@r{]}
36550 @r{[}@var{feature}@dots{}@r{]}
36555 The description is generally insensitive to whitespace and line
36556 breaks, under the usual common-sense rules. The XML version
36557 declaration and document type declaration can generally be omitted
36558 (@value{GDBN} does not require them), but specifying them may be
36559 useful for XML validation tools. The @samp{version} attribute for
36560 @samp{<target>} may also be omitted, but we recommend
36561 including it; if future versions of @value{GDBN} use an incompatible
36562 revision of @file{gdb-target.dtd}, they will detect and report
36563 the version mismatch.
36565 @subsection Inclusion
36566 @cindex target descriptions, inclusion
36569 @cindex <xi:include>
36572 It can sometimes be valuable to split a target description up into
36573 several different annexes, either for organizational purposes, or to
36574 share files between different possible target descriptions. You can
36575 divide a description into multiple files by replacing any element of
36576 the target description with an inclusion directive of the form:
36579 <xi:include href="@var{document}"/>
36583 When @value{GDBN} encounters an element of this form, it will retrieve
36584 the named XML @var{document}, and replace the inclusion directive with
36585 the contents of that document. If the current description was read
36586 using @samp{qXfer}, then so will be the included document;
36587 @var{document} will be interpreted as the name of an annex. If the
36588 current description was read from a file, @value{GDBN} will look for
36589 @var{document} as a file in the same directory where it found the
36590 original description.
36592 @subsection Architecture
36593 @cindex <architecture>
36595 An @samp{<architecture>} element has this form:
36598 <architecture>@var{arch}</architecture>
36601 @var{arch} is one of the architectures from the set accepted by
36602 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36605 @cindex @code{<osabi>}
36607 This optional field was introduced in @value{GDBN} version 7.0.
36608 Previous versions of @value{GDBN} ignore it.
36610 An @samp{<osabi>} element has this form:
36613 <osabi>@var{abi-name}</osabi>
36616 @var{abi-name} is an OS ABI name from the same selection accepted by
36617 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
36619 @subsection Compatible Architecture
36620 @cindex @code{<compatible>}
36622 This optional field was introduced in @value{GDBN} version 7.0.
36623 Previous versions of @value{GDBN} ignore it.
36625 A @samp{<compatible>} element has this form:
36628 <compatible>@var{arch}</compatible>
36631 @var{arch} is one of the architectures from the set accepted by
36632 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36634 A @samp{<compatible>} element is used to specify that the target
36635 is able to run binaries in some other than the main target architecture
36636 given by the @samp{<architecture>} element. For example, on the
36637 Cell Broadband Engine, the main architecture is @code{powerpc:common}
36638 or @code{powerpc:common64}, but the system is able to run binaries
36639 in the @code{spu} architecture as well. The way to describe this
36640 capability with @samp{<compatible>} is as follows:
36643 <architecture>powerpc:common</architecture>
36644 <compatible>spu</compatible>
36647 @subsection Features
36650 Each @samp{<feature>} describes some logical portion of the target
36651 system. Features are currently used to describe available CPU
36652 registers and the types of their contents. A @samp{<feature>} element
36656 <feature name="@var{name}">
36657 @r{[}@var{type}@dots{}@r{]}
36663 Each feature's name should be unique within the description. The name
36664 of a feature does not matter unless @value{GDBN} has some special
36665 knowledge of the contents of that feature; if it does, the feature
36666 should have its standard name. @xref{Standard Target Features}.
36670 Any register's value is a collection of bits which @value{GDBN} must
36671 interpret. The default interpretation is a two's complement integer,
36672 but other types can be requested by name in the register description.
36673 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
36674 Target Types}), and the description can define additional composite types.
36676 Each type element must have an @samp{id} attribute, which gives
36677 a unique (within the containing @samp{<feature>}) name to the type.
36678 Types must be defined before they are used.
36681 Some targets offer vector registers, which can be treated as arrays
36682 of scalar elements. These types are written as @samp{<vector>} elements,
36683 specifying the array element type, @var{type}, and the number of elements,
36687 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
36691 If a register's value is usefully viewed in multiple ways, define it
36692 with a union type containing the useful representations. The
36693 @samp{<union>} element contains one or more @samp{<field>} elements,
36694 each of which has a @var{name} and a @var{type}:
36697 <union id="@var{id}">
36698 <field name="@var{name}" type="@var{type}"/>
36704 If a register's value is composed from several separate values, define
36705 it with a structure type. There are two forms of the @samp{<struct>}
36706 element; a @samp{<struct>} element must either contain only bitfields
36707 or contain no bitfields. If the structure contains only bitfields,
36708 its total size in bytes must be specified, each bitfield must have an
36709 explicit start and end, and bitfields are automatically assigned an
36710 integer type. The field's @var{start} should be less than or
36711 equal to its @var{end}, and zero represents the least significant bit.
36714 <struct id="@var{id}" size="@var{size}">
36715 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36720 If the structure contains no bitfields, then each field has an
36721 explicit type, and no implicit padding is added.
36724 <struct id="@var{id}">
36725 <field name="@var{name}" type="@var{type}"/>
36731 If a register's value is a series of single-bit flags, define it with
36732 a flags type. The @samp{<flags>} element has an explicit @var{size}
36733 and contains one or more @samp{<field>} elements. Each field has a
36734 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
36738 <flags id="@var{id}" size="@var{size}">
36739 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36744 @subsection Registers
36747 Each register is represented as an element with this form:
36750 <reg name="@var{name}"
36751 bitsize="@var{size}"
36752 @r{[}regnum="@var{num}"@r{]}
36753 @r{[}save-restore="@var{save-restore}"@r{]}
36754 @r{[}type="@var{type}"@r{]}
36755 @r{[}group="@var{group}"@r{]}/>
36759 The components are as follows:
36764 The register's name; it must be unique within the target description.
36767 The register's size, in bits.
36770 The register's number. If omitted, a register's number is one greater
36771 than that of the previous register (either in the current feature or in
36772 a preceding feature); the first register in the target description
36773 defaults to zero. This register number is used to read or write
36774 the register; e.g.@: it is used in the remote @code{p} and @code{P}
36775 packets, and registers appear in the @code{g} and @code{G} packets
36776 in order of increasing register number.
36779 Whether the register should be preserved across inferior function
36780 calls; this must be either @code{yes} or @code{no}. The default is
36781 @code{yes}, which is appropriate for most registers except for
36782 some system control registers; this is not related to the target's
36786 The type of the register. @var{type} may be a predefined type, a type
36787 defined in the current feature, or one of the special types @code{int}
36788 and @code{float}. @code{int} is an integer type of the correct size
36789 for @var{bitsize}, and @code{float} is a floating point type (in the
36790 architecture's normal floating point format) of the correct size for
36791 @var{bitsize}. The default is @code{int}.
36794 The register group to which this register belongs. @var{group} must
36795 be either @code{general}, @code{float}, or @code{vector}. If no
36796 @var{group} is specified, @value{GDBN} will not display the register
36797 in @code{info registers}.
36801 @node Predefined Target Types
36802 @section Predefined Target Types
36803 @cindex target descriptions, predefined types
36805 Type definitions in the self-description can build up composite types
36806 from basic building blocks, but can not define fundamental types. Instead,
36807 standard identifiers are provided by @value{GDBN} for the fundamental
36808 types. The currently supported types are:
36817 Signed integer types holding the specified number of bits.
36824 Unsigned integer types holding the specified number of bits.
36828 Pointers to unspecified code and data. The program counter and
36829 any dedicated return address register may be marked as code
36830 pointers; printing a code pointer converts it into a symbolic
36831 address. The stack pointer and any dedicated address registers
36832 may be marked as data pointers.
36835 Single precision IEEE floating point.
36838 Double precision IEEE floating point.
36841 The 12-byte extended precision format used by ARM FPA registers.
36844 The 10-byte extended precision format used by x87 registers.
36847 32bit @sc{eflags} register used by x86.
36850 32bit @sc{mxcsr} register used by x86.
36854 @node Standard Target Features
36855 @section Standard Target Features
36856 @cindex target descriptions, standard features
36858 A target description must contain either no registers or all the
36859 target's registers. If the description contains no registers, then
36860 @value{GDBN} will assume a default register layout, selected based on
36861 the architecture. If the description contains any registers, the
36862 default layout will not be used; the standard registers must be
36863 described in the target description, in such a way that @value{GDBN}
36864 can recognize them.
36866 This is accomplished by giving specific names to feature elements
36867 which contain standard registers. @value{GDBN} will look for features
36868 with those names and verify that they contain the expected registers;
36869 if any known feature is missing required registers, or if any required
36870 feature is missing, @value{GDBN} will reject the target
36871 description. You can add additional registers to any of the
36872 standard features --- @value{GDBN} will display them just as if
36873 they were added to an unrecognized feature.
36875 This section lists the known features and their expected contents.
36876 Sample XML documents for these features are included in the
36877 @value{GDBN} source tree, in the directory @file{gdb/features}.
36879 Names recognized by @value{GDBN} should include the name of the
36880 company or organization which selected the name, and the overall
36881 architecture to which the feature applies; so e.g.@: the feature
36882 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
36884 The names of registers are not case sensitive for the purpose
36885 of recognizing standard features, but @value{GDBN} will only display
36886 registers using the capitalization used in the description.
36893 * PowerPC Features::
36898 @subsection ARM Features
36899 @cindex target descriptions, ARM features
36901 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
36903 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
36904 @samp{lr}, @samp{pc}, and @samp{cpsr}.
36906 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
36907 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
36908 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
36911 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
36912 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
36914 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
36915 it should contain at least registers @samp{wR0} through @samp{wR15} and
36916 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
36917 @samp{wCSSF}, and @samp{wCASF} registers are optional.
36919 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
36920 should contain at least registers @samp{d0} through @samp{d15}. If
36921 they are present, @samp{d16} through @samp{d31} should also be included.
36922 @value{GDBN} will synthesize the single-precision registers from
36923 halves of the double-precision registers.
36925 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
36926 need to contain registers; it instructs @value{GDBN} to display the
36927 VFP double-precision registers as vectors and to synthesize the
36928 quad-precision registers from pairs of double-precision registers.
36929 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
36930 be present and include 32 double-precision registers.
36932 @node i386 Features
36933 @subsection i386 Features
36934 @cindex target descriptions, i386 features
36936 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
36937 targets. It should describe the following registers:
36941 @samp{eax} through @samp{edi} plus @samp{eip} for i386
36943 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
36945 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
36946 @samp{fs}, @samp{gs}
36948 @samp{st0} through @samp{st7}
36950 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
36951 @samp{foseg}, @samp{fooff} and @samp{fop}
36954 The register sets may be different, depending on the target.
36956 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
36957 describe registers:
36961 @samp{xmm0} through @samp{xmm7} for i386
36963 @samp{xmm0} through @samp{xmm15} for amd64
36968 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
36969 @samp{org.gnu.gdb.i386.sse} feature. It should
36970 describe the upper 128 bits of @sc{ymm} registers:
36974 @samp{ymm0h} through @samp{ymm7h} for i386
36976 @samp{ymm0h} through @samp{ymm15h} for amd64
36979 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
36980 describe a single register, @samp{orig_eax}.
36982 @node MIPS Features
36983 @subsection MIPS Features
36984 @cindex target descriptions, MIPS features
36986 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
36987 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
36988 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
36991 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
36992 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
36993 registers. They may be 32-bit or 64-bit depending on the target.
36995 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
36996 it may be optional in a future version of @value{GDBN}. It should
36997 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
36998 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
37000 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
37001 contain a single register, @samp{restart}, which is used by the
37002 Linux kernel to control restartable syscalls.
37004 @node M68K Features
37005 @subsection M68K Features
37006 @cindex target descriptions, M68K features
37009 @item @samp{org.gnu.gdb.m68k.core}
37010 @itemx @samp{org.gnu.gdb.coldfire.core}
37011 @itemx @samp{org.gnu.gdb.fido.core}
37012 One of those features must be always present.
37013 The feature that is present determines which flavor of m68k is
37014 used. The feature that is present should contain registers
37015 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
37016 @samp{sp}, @samp{ps} and @samp{pc}.
37018 @item @samp{org.gnu.gdb.coldfire.fp}
37019 This feature is optional. If present, it should contain registers
37020 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
37024 @node PowerPC Features
37025 @subsection PowerPC Features
37026 @cindex target descriptions, PowerPC features
37028 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
37029 targets. It should contain registers @samp{r0} through @samp{r31},
37030 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
37031 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
37033 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
37034 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
37036 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
37037 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
37040 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
37041 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
37042 will combine these registers with the floating point registers
37043 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
37044 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
37045 through @samp{vs63}, the set of vector registers for POWER7.
37047 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
37048 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
37049 @samp{spefscr}. SPE targets should provide 32-bit registers in
37050 @samp{org.gnu.gdb.power.core} and provide the upper halves in
37051 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
37052 these to present registers @samp{ev0} through @samp{ev31} to the
37055 @node Operating System Information
37056 @appendix Operating System Information
37057 @cindex operating system information
37063 Users of @value{GDBN} often wish to obtain information about the state of
37064 the operating system running on the target---for example the list of
37065 processes, or the list of open files. This section describes the
37066 mechanism that makes it possible. This mechanism is similar to the
37067 target features mechanism (@pxref{Target Descriptions}), but focuses
37068 on a different aspect of target.
37070 Operating system information is retrived from the target via the
37071 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
37072 read}). The object name in the request should be @samp{osdata}, and
37073 the @var{annex} identifies the data to be fetched.
37076 @appendixsection Process list
37077 @cindex operating system information, process list
37079 When requesting the process list, the @var{annex} field in the
37080 @samp{qXfer} request should be @samp{processes}. The returned data is
37081 an XML document. The formal syntax of this document is defined in
37082 @file{gdb/features/osdata.dtd}.
37084 An example document is:
37087 <?xml version="1.0"?>
37088 <!DOCTYPE target SYSTEM "osdata.dtd">
37089 <osdata type="processes">
37091 <column name="pid">1</column>
37092 <column name="user">root</column>
37093 <column name="command">/sbin/init</column>
37094 <column name="cores">1,2,3</column>
37099 Each item should include a column whose name is @samp{pid}. The value
37100 of that column should identify the process on the target. The
37101 @samp{user} and @samp{command} columns are optional, and will be
37102 displayed by @value{GDBN}. The @samp{cores} column, if present,
37103 should contain a comma-separated list of cores that this process
37104 is running on. Target may provide additional columns,
37105 which @value{GDBN} currently ignores.
37107 @node Trace File Format
37108 @appendix Trace File Format
37109 @cindex trace file format
37111 The trace file comes in three parts: a header, a textual description
37112 section, and a trace frame section with binary data.
37114 The header has the form @code{\x7fTRACE0\n}. The first byte is
37115 @code{0x7f} so as to indicate that the file contains binary data,
37116 while the @code{0} is a version number that may have different values
37119 The description section consists of multiple lines of @sc{ascii} text
37120 separated by newline characters (@code{0xa}). The lines may include a
37121 variety of optional descriptive or context-setting information, such
37122 as tracepoint definitions or register set size. @value{GDBN} will
37123 ignore any line that it does not recognize. An empty line marks the end
37126 @c FIXME add some specific types of data
37128 The trace frame section consists of a number of consecutive frames.
37129 Each frame begins with a two-byte tracepoint number, followed by a
37130 four-byte size giving the amount of data in the frame. The data in
37131 the frame consists of a number of blocks, each introduced by a
37132 character indicating its type (at least register, memory, and trace
37133 state variable). The data in this section is raw binary, not a
37134 hexadecimal or other encoding; its endianness matches the target's
37137 @c FIXME bi-arch may require endianness/arch info in description section
37140 @item R @var{bytes}
37141 Register block. The number and ordering of bytes matches that of a
37142 @code{g} packet in the remote protocol. Note that these are the
37143 actual bytes, in target order and @value{GDBN} register order, not a
37144 hexadecimal encoding.
37146 @item M @var{address} @var{length} @var{bytes}...
37147 Memory block. This is a contiguous block of memory, at the 8-byte
37148 address @var{address}, with a 2-byte length @var{length}, followed by
37149 @var{length} bytes.
37151 @item V @var{number} @var{value}
37152 Trace state variable block. This records the 8-byte signed value
37153 @var{value} of trace state variable numbered @var{number}.
37157 Future enhancements of the trace file format may include additional types
37160 @node Index Section Format
37161 @appendix @code{.gdb_index} section format
37162 @cindex .gdb_index section format
37163 @cindex index section format
37165 This section documents the index section that is created by @code{save
37166 gdb-index} (@pxref{Index Files}). The index section is
37167 DWARF-specific; some knowledge of DWARF is assumed in this
37170 The mapped index file format is designed to be directly
37171 @code{mmap}able on any architecture. In most cases, a datum is
37172 represented using a little-endian 32-bit integer value, called an
37173 @code{offset_type}. Big endian machines must byte-swap the values
37174 before using them. Exceptions to this rule are noted. The data is
37175 laid out such that alignment is always respected.
37177 A mapped index consists of several areas, laid out in order.
37181 The file header. This is a sequence of values, of @code{offset_type}
37182 unless otherwise noted:
37186 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
37187 Version 4 differs by its hashing function.
37190 The offset, from the start of the file, of the CU list.
37193 The offset, from the start of the file, of the types CU list. Note
37194 that this area can be empty, in which case this offset will be equal
37195 to the next offset.
37198 The offset, from the start of the file, of the address area.
37201 The offset, from the start of the file, of the symbol table.
37204 The offset, from the start of the file, of the constant pool.
37208 The CU list. This is a sequence of pairs of 64-bit little-endian
37209 values, sorted by the CU offset. The first element in each pair is
37210 the offset of a CU in the @code{.debug_info} section. The second
37211 element in each pair is the length of that CU. References to a CU
37212 elsewhere in the map are done using a CU index, which is just the
37213 0-based index into this table. Note that if there are type CUs, then
37214 conceptually CUs and type CUs form a single list for the purposes of
37218 The types CU list. This is a sequence of triplets of 64-bit
37219 little-endian values. In a triplet, the first value is the CU offset,
37220 the second value is the type offset in the CU, and the third value is
37221 the type signature. The types CU list is not sorted.
37224 The address area. The address area consists of a sequence of address
37225 entries. Each address entry has three elements:
37229 The low address. This is a 64-bit little-endian value.
37232 The high address. This is a 64-bit little-endian value. Like
37233 @code{DW_AT_high_pc}, the value is one byte beyond the end.
37236 The CU index. This is an @code{offset_type} value.
37240 The symbol table. This is an open-addressed hash table. The size of
37241 the hash table is always a power of 2.
37243 Each slot in the hash table consists of a pair of @code{offset_type}
37244 values. The first value is the offset of the symbol's name in the
37245 constant pool. The second value is the offset of the CU vector in the
37248 If both values are 0, then this slot in the hash table is empty. This
37249 is ok because while 0 is a valid constant pool index, it cannot be a
37250 valid index for both a string and a CU vector.
37252 The hash value for a table entry is computed by applying an
37253 iterative hash function to the symbol's name. Starting with an
37254 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
37255 the string is incorporated into the hash using the formula depending on the
37260 The formula is @code{r = r * 67 + c - 113}.
37263 The formula is @code{r = r * 67 + tolower (c) - 113}.
37266 The terminating @samp{\0} is not incorporated into the hash.
37268 The step size used in the hash table is computed via
37269 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
37270 value, and @samp{size} is the size of the hash table. The step size
37271 is used to find the next candidate slot when handling a hash
37274 The names of C@t{++} symbols in the hash table are canonicalized. We
37275 don't currently have a simple description of the canonicalization
37276 algorithm; if you intend to create new index sections, you must read
37280 The constant pool. This is simply a bunch of bytes. It is organized
37281 so that alignment is correct: CU vectors are stored first, followed by
37284 A CU vector in the constant pool is a sequence of @code{offset_type}
37285 values. The first value is the number of CU indices in the vector.
37286 Each subsequent value is the index of a CU in the CU list. This
37287 element in the hash table is used to indicate which CUs define the
37290 A string in the constant pool is zero-terminated.
37295 @node GNU Free Documentation License
37296 @appendix GNU Free Documentation License
37305 % I think something like @colophon should be in texinfo. In the
37307 \long\def\colophon{\hbox to0pt{}\vfill
37308 \centerline{The body of this manual is set in}
37309 \centerline{\fontname\tenrm,}
37310 \centerline{with headings in {\bf\fontname\tenbf}}
37311 \centerline{and examples in {\tt\fontname\tentt}.}
37312 \centerline{{\it\fontname\tenit\/},}
37313 \centerline{{\bf\fontname\tenbf}, and}
37314 \centerline{{\sl\fontname\tensl\/}}
37315 \centerline{are used for emphasis.}\vfill}
37317 % Blame: doc@cygnus.com, 1991.