1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2013 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
11 @settitle Debugging with @value{GDBN}
12 @setchapternewpage odd
21 @c To avoid file-name clashes between index.html and Index.html, when
22 @c the manual is produced on a Posix host and then moved to a
23 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
24 @c indices into two: Concept Index and all the rest.
28 @c readline appendices use @vindex, @findex and @ftable,
29 @c annotate.texi and gdbmi use @findex.
33 @c !!set GDB manual's edition---not the same as GDB version!
34 @c This is updated by GNU Press.
37 @c !!set GDB edit command default editor
40 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
42 @c This is a dir.info fragment to support semi-automated addition of
43 @c manuals to an info tree.
44 @dircategory Software development
46 * Gdb: (gdb). The GNU debugger.
50 Copyright @copyright{} 1988-2013 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 978-0-9831592-3-0 @*
107 @node Top, Summary, (dir), (dir)
109 @top Debugging with @value{GDBN}
111 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
113 This is the @value{EDITION} Edition, for @value{GDBN}
114 @ifset VERSION_PACKAGE
115 @value{VERSION_PACKAGE}
117 Version @value{GDBVN}.
119 Copyright (C) 1988-2013 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.
159 * In-Process Agent:: In-Process Agent
161 * GDB Bugs:: Reporting bugs in @value{GDBN}
163 @ifset SYSTEM_READLINE
164 * Command Line Editing: (rluserman). Command Line Editing
165 * Using History Interactively: (history). Using History Interactively
167 @ifclear SYSTEM_READLINE
168 * Command Line Editing:: Command Line Editing
169 * Using History Interactively:: Using History Interactively
171 * In Memoriam:: In Memoriam
172 * Formatting Documentation:: How to format and print @value{GDBN} documentation
173 * Installing GDB:: Installing GDB
174 * Maintenance Commands:: Maintenance Commands
175 * Remote Protocol:: GDB Remote Serial Protocol
176 * Agent Expressions:: The GDB Agent Expression Mechanism
177 * Target Descriptions:: How targets can describe themselves to
179 * Operating System Information:: Getting additional information from
181 * Trace File Format:: GDB trace file format
182 * Index Section Format:: .gdb_index section format
183 * Copying:: GNU General Public License says
184 how you can copy and share GDB
185 * GNU Free Documentation License:: The license for this documentation
186 * Concept Index:: Index of @value{GDBN} concepts
187 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
188 functions, and Python data types
196 @unnumbered Summary of @value{GDBN}
198 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
199 going on ``inside'' another program while it executes---or what another
200 program was doing at the moment it crashed.
202 @value{GDBN} can do four main kinds of things (plus other things in support of
203 these) to help you catch bugs in the act:
207 Start your program, specifying anything that might affect its behavior.
210 Make your program stop on specified conditions.
213 Examine what has happened, when your program has stopped.
216 Change things in your program, so you can experiment with correcting the
217 effects of one bug and go on to learn about another.
220 You can use @value{GDBN} to debug programs written in C and C@t{++}.
221 For more information, see @ref{Supported Languages,,Supported Languages}.
222 For more information, see @ref{C,,C and C++}.
224 Support for D is partial. For information on D, see
228 Support for Modula-2 is partial. For information on Modula-2, see
229 @ref{Modula-2,,Modula-2}.
231 Support for OpenCL C is partial. For information on OpenCL C, see
232 @ref{OpenCL C,,OpenCL C}.
235 Debugging Pascal programs which use sets, subranges, file variables, or
236 nested functions does not currently work. @value{GDBN} does not support
237 entering expressions, printing values, or similar features using Pascal
241 @value{GDBN} can be used to debug programs written in Fortran, although
242 it may be necessary to refer to some variables with a trailing
245 @value{GDBN} can be used to debug programs written in Objective-C,
246 using either the Apple/NeXT or the GNU Objective-C runtime.
249 * Free Software:: Freely redistributable software
250 * Free Documentation:: Free Software Needs Free Documentation
251 * Contributors:: Contributors to GDB
255 @unnumberedsec Free Software
257 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
258 General Public License
259 (GPL). The GPL gives you the freedom to copy or adapt a licensed
260 program---but every person getting a copy also gets with it the
261 freedom to modify that copy (which means that they must get access to
262 the source code), and the freedom to distribute further copies.
263 Typical software companies use copyrights to limit your freedoms; the
264 Free Software Foundation uses the GPL to preserve these freedoms.
266 Fundamentally, the General Public License is a license which says that
267 you have these freedoms and that you cannot take these freedoms away
270 @node Free Documentation
271 @unnumberedsec Free Software Needs Free Documentation
273 The biggest deficiency in the free software community today is not in
274 the software---it is the lack of good free documentation that we can
275 include with the free software. Many of our most important
276 programs do not come with free reference manuals and free introductory
277 texts. Documentation is an essential part of any software package;
278 when an important free software package does not come with a free
279 manual and a free tutorial, that is a major gap. We have many such
282 Consider Perl, for instance. The tutorial manuals that people
283 normally use are non-free. How did this come about? Because the
284 authors of those manuals published them with restrictive terms---no
285 copying, no modification, source files not available---which exclude
286 them from the free software world.
288 That wasn't the first time this sort of thing happened, and it was far
289 from the last. Many times we have heard a GNU user eagerly describe a
290 manual that he is writing, his intended contribution to the community,
291 only to learn that he had ruined everything by signing a publication
292 contract to make it non-free.
294 Free documentation, like free software, is a matter of freedom, not
295 price. The problem with the non-free manual is not that publishers
296 charge a price for printed copies---that in itself is fine. (The Free
297 Software Foundation sells printed copies of manuals, too.) The
298 problem is the restrictions on the use of the manual. Free manuals
299 are available in source code form, and give you permission to copy and
300 modify. Non-free manuals do not allow this.
302 The criteria of freedom for a free manual are roughly the same as for
303 free software. Redistribution (including the normal kinds of
304 commercial redistribution) must be permitted, so that the manual can
305 accompany every copy of the program, both on-line and on paper.
307 Permission for modification of the technical content is crucial too.
308 When people modify the software, adding or changing features, if they
309 are conscientious they will change the manual too---so they can
310 provide accurate and clear documentation for the modified program. A
311 manual that leaves you no choice but to write a new manual to document
312 a changed version of the program is not really available to our
315 Some kinds of limits on the way modification is handled are
316 acceptable. For example, requirements to preserve the original
317 author's copyright notice, the distribution terms, or the list of
318 authors, are ok. It is also no problem to require modified versions
319 to include notice that they were modified. Even entire sections that
320 may not be deleted or changed are acceptable, as long as they deal
321 with nontechnical topics (like this one). These kinds of restrictions
322 are acceptable because they don't obstruct the community's normal use
325 However, it must be possible to modify all the @emph{technical}
326 content of the manual, and then distribute the result in all the usual
327 media, through all the usual channels. Otherwise, the restrictions
328 obstruct the use of the manual, it is not free, and we need another
329 manual to replace it.
331 Please spread the word about this issue. Our community continues to
332 lose manuals to proprietary publishing. If we spread the word that
333 free software needs free reference manuals and free tutorials, perhaps
334 the next person who wants to contribute by writing documentation will
335 realize, before it is too late, that only free manuals contribute to
336 the free software community.
338 If you are writing documentation, please insist on publishing it under
339 the GNU Free Documentation License or another free documentation
340 license. Remember that this decision requires your approval---you
341 don't have to let the publisher decide. Some commercial publishers
342 will use a free license if you insist, but they will not propose the
343 option; it is up to you to raise the issue and say firmly that this is
344 what you want. If the publisher you are dealing with refuses, please
345 try other publishers. If you're not sure whether a proposed license
346 is free, write to @email{licensing@@gnu.org}.
348 You can encourage commercial publishers to sell more free, copylefted
349 manuals and tutorials by buying them, and particularly by buying
350 copies from the publishers that paid for their writing or for major
351 improvements. Meanwhile, try to avoid buying non-free documentation
352 at all. Check the distribution terms of a manual before you buy it,
353 and insist that whoever seeks your business must respect your freedom.
354 Check the history of the book, and try to reward the publishers that
355 have paid or pay the authors to work on it.
357 The Free Software Foundation maintains a list of free documentation
358 published by other publishers, at
359 @url{http://www.fsf.org/doc/other-free-books.html}.
362 @unnumberedsec Contributors to @value{GDBN}
364 Richard Stallman was the original author of @value{GDBN}, and of many
365 other @sc{gnu} programs. Many others have contributed to its
366 development. This section attempts to credit major contributors. One
367 of the virtues of free software is that everyone is free to contribute
368 to it; with regret, we cannot actually acknowledge everyone here. The
369 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
370 blow-by-blow account.
372 Changes much prior to version 2.0 are lost in the mists of time.
375 @emph{Plea:} Additions to this section are particularly welcome. If you
376 or your friends (or enemies, to be evenhanded) have been unfairly
377 omitted from this list, we would like to add your names!
380 So that they may not regard their many labors as thankless, we
381 particularly thank those who shepherded @value{GDBN} through major
383 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
384 Jim Blandy (release 4.18);
385 Jason Molenda (release 4.17);
386 Stan Shebs (release 4.14);
387 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
388 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
389 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
390 Jim Kingdon (releases 3.5, 3.4, and 3.3);
391 and Randy Smith (releases 3.2, 3.1, and 3.0).
393 Richard Stallman, assisted at various times by Peter TerMaat, Chris
394 Hanson, and Richard Mlynarik, handled releases through 2.8.
396 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
397 in @value{GDBN}, with significant additional contributions from Per
398 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
399 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
400 much general update work leading to release 3.0).
402 @value{GDBN} uses the BFD subroutine library to examine multiple
403 object-file formats; BFD was a joint project of David V.
404 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
406 David Johnson wrote the original COFF support; Pace Willison did
407 the original support for encapsulated COFF.
409 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
411 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
412 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
414 Jean-Daniel Fekete contributed Sun 386i support.
415 Chris Hanson improved the HP9000 support.
416 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
417 David Johnson contributed Encore Umax support.
418 Jyrki Kuoppala contributed Altos 3068 support.
419 Jeff Law contributed HP PA and SOM support.
420 Keith Packard contributed NS32K support.
421 Doug Rabson contributed Acorn Risc Machine support.
422 Bob Rusk contributed Harris Nighthawk CX-UX support.
423 Chris Smith contributed Convex support (and Fortran debugging).
424 Jonathan Stone contributed Pyramid support.
425 Michael Tiemann contributed SPARC support.
426 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
427 Pace Willison contributed Intel 386 support.
428 Jay Vosburgh contributed Symmetry support.
429 Marko Mlinar contributed OpenRISC 1000 support.
431 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
433 Rich Schaefer and Peter Schauer helped with support of SunOS shared
436 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
437 about several machine instruction sets.
439 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
440 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
441 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
442 and RDI targets, respectively.
444 Brian Fox is the author of the readline libraries providing
445 command-line editing and command history.
447 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
448 Modula-2 support, and contributed the Languages chapter of this manual.
450 Fred Fish wrote most of the support for Unix System Vr4.
451 He also enhanced the command-completion support to cover C@t{++} overloaded
454 Hitachi America (now Renesas America), Ltd. sponsored the support for
455 H8/300, H8/500, and Super-H processors.
457 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
459 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
462 Toshiba sponsored the support for the TX39 Mips processor.
464 Matsushita sponsored the support for the MN10200 and MN10300 processors.
466 Fujitsu sponsored the support for SPARClite and FR30 processors.
468 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
471 Michael Snyder added support for tracepoints.
473 Stu Grossman wrote gdbserver.
475 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
476 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
478 The following people at the Hewlett-Packard Company contributed
479 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
480 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
481 compiler, and the Text User Interface (nee Terminal User Interface):
482 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
483 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
484 provided HP-specific information in this manual.
486 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
487 Robert Hoehne made significant contributions to the DJGPP port.
489 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
490 development since 1991. Cygnus engineers who have worked on @value{GDBN}
491 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
492 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
493 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
494 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
495 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
496 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
497 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
498 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
499 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
500 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
501 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
502 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
503 Zuhn have made contributions both large and small.
505 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
506 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
508 Jim Blandy added support for preprocessor macros, while working for Red
511 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
512 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
513 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
514 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
515 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
516 with the migration of old architectures to this new framework.
518 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
519 unwinder framework, this consisting of a fresh new design featuring
520 frame IDs, independent frame sniffers, and the sentinel frame. Mark
521 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
522 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
523 trad unwinders. The architecture-specific changes, each involving a
524 complete rewrite of the architecture's frame code, were carried out by
525 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
526 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
527 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
528 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
531 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
532 Tensilica, Inc.@: contributed support for Xtensa processors. Others
533 who have worked on the Xtensa port of @value{GDBN} in the past include
534 Steve Tjiang, John Newlin, and Scott Foehner.
536 Michael Eager and staff of Xilinx, Inc., contributed support for the
537 Xilinx MicroBlaze architecture.
540 @chapter A Sample @value{GDBN} Session
542 You can use this manual at your leisure to read all about @value{GDBN}.
543 However, a handful of commands are enough to get started using the
544 debugger. This chapter illustrates those commands.
547 In this sample session, we emphasize user input like this: @b{input},
548 to make it easier to pick out from the surrounding output.
551 @c FIXME: this example may not be appropriate for some configs, where
552 @c FIXME...primary interest is in remote use.
554 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
555 processor) exhibits the following bug: sometimes, when we change its
556 quote strings from the default, the commands used to capture one macro
557 definition within another stop working. In the following short @code{m4}
558 session, we define a macro @code{foo} which expands to @code{0000}; we
559 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
560 same thing. However, when we change the open quote string to
561 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
562 procedure fails to define a new synonym @code{baz}:
571 @b{define(bar,defn(`foo'))}
575 @b{changequote(<QUOTE>,<UNQUOTE>)}
577 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
580 m4: End of input: 0: fatal error: EOF in string
584 Let us use @value{GDBN} to try to see what is going on.
587 $ @b{@value{GDBP} m4}
588 @c FIXME: this falsifies the exact text played out, to permit smallbook
589 @c FIXME... format to come out better.
590 @value{GDBN} is free software and you are welcome to distribute copies
591 of it under certain conditions; type "show copying" to see
593 There is absolutely no warranty for @value{GDBN}; type "show warranty"
596 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
601 @value{GDBN} reads only enough symbol data to know where to find the
602 rest when needed; as a result, the first prompt comes up very quickly.
603 We now tell @value{GDBN} to use a narrower display width than usual, so
604 that examples fit in this manual.
607 (@value{GDBP}) @b{set width 70}
611 We need to see how the @code{m4} built-in @code{changequote} works.
612 Having looked at the source, we know the relevant subroutine is
613 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
614 @code{break} command.
617 (@value{GDBP}) @b{break m4_changequote}
618 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
622 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
623 control; as long as control does not reach the @code{m4_changequote}
624 subroutine, the program runs as usual:
627 (@value{GDBP}) @b{run}
628 Starting program: /work/Editorial/gdb/gnu/m4/m4
636 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
637 suspends execution of @code{m4}, displaying information about the
638 context where it stops.
641 @b{changequote(<QUOTE>,<UNQUOTE>)}
643 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
645 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
649 Now we use the command @code{n} (@code{next}) to advance execution to
650 the next line of the current function.
654 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
659 @code{set_quotes} looks like a promising subroutine. We can go into it
660 by using the command @code{s} (@code{step}) instead of @code{next}.
661 @code{step} goes to the next line to be executed in @emph{any}
662 subroutine, so it steps into @code{set_quotes}.
666 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
668 530 if (lquote != def_lquote)
672 The display that shows the subroutine where @code{m4} is now
673 suspended (and its arguments) is called a stack frame display. It
674 shows a summary of the stack. We can use the @code{backtrace}
675 command (which can also be spelled @code{bt}), to see where we are
676 in the stack as a whole: the @code{backtrace} command displays a
677 stack frame for each active subroutine.
680 (@value{GDBP}) @b{bt}
681 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
683 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
685 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
686 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
688 #4 0x79dc in expand_input () at macro.c:40
689 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
693 We step through a few more lines to see what happens. The first two
694 times, we can use @samp{s}; the next two times we use @code{n} to avoid
695 falling into the @code{xstrdup} subroutine.
699 0x3b5c 532 if (rquote != def_rquote)
701 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
702 def_lquote : xstrdup(lq);
704 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
707 538 len_lquote = strlen(rquote);
711 The last line displayed looks a little odd; we can examine the variables
712 @code{lquote} and @code{rquote} to see if they are in fact the new left
713 and right quotes we specified. We use the command @code{p}
714 (@code{print}) to see their values.
717 (@value{GDBP}) @b{p lquote}
718 $1 = 0x35d40 "<QUOTE>"
719 (@value{GDBP}) @b{p rquote}
720 $2 = 0x35d50 "<UNQUOTE>"
724 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
725 To look at some context, we can display ten lines of source
726 surrounding the current line with the @code{l} (@code{list}) command.
732 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
734 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
737 538 len_lquote = strlen(rquote);
738 539 len_rquote = strlen(lquote);
745 Let us step past the two lines that set @code{len_lquote} and
746 @code{len_rquote}, and then examine the values of those variables.
750 539 len_rquote = strlen(lquote);
753 (@value{GDBP}) @b{p len_lquote}
755 (@value{GDBP}) @b{p len_rquote}
760 That certainly looks wrong, assuming @code{len_lquote} and
761 @code{len_rquote} are meant to be the lengths of @code{lquote} and
762 @code{rquote} respectively. We can set them to better values using
763 the @code{p} command, since it can print the value of
764 any expression---and that expression can include subroutine calls and
768 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
770 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
775 Is that enough to fix the problem of using the new quotes with the
776 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
777 executing with the @code{c} (@code{continue}) command, and then try the
778 example that caused trouble initially:
784 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
791 Success! The new quotes now work just as well as the default ones. The
792 problem seems to have been just the two typos defining the wrong
793 lengths. We allow @code{m4} exit by giving it an EOF as input:
797 Program exited normally.
801 The message @samp{Program exited normally.} is from @value{GDBN}; it
802 indicates @code{m4} has finished executing. We can end our @value{GDBN}
803 session with the @value{GDBN} @code{quit} command.
806 (@value{GDBP}) @b{quit}
810 @chapter Getting In and Out of @value{GDBN}
812 This chapter discusses how to start @value{GDBN}, and how to get out of it.
816 type @samp{@value{GDBP}} to start @value{GDBN}.
818 type @kbd{quit} or @kbd{Ctrl-d} to exit.
822 * Invoking GDB:: How to start @value{GDBN}
823 * Quitting GDB:: How to quit @value{GDBN}
824 * Shell Commands:: How to use shell commands inside @value{GDBN}
825 * Logging Output:: How to log @value{GDBN}'s output to a file
829 @section Invoking @value{GDBN}
831 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
832 @value{GDBN} reads commands from the terminal until you tell it to exit.
834 You can also run @code{@value{GDBP}} with a variety of arguments and options,
835 to specify more of your debugging environment at the outset.
837 The command-line options described here are designed
838 to cover a variety of situations; in some environments, some of these
839 options may effectively be unavailable.
841 The most usual way to start @value{GDBN} is with one argument,
842 specifying an executable program:
845 @value{GDBP} @var{program}
849 You can also start with both an executable program and a core file
853 @value{GDBP} @var{program} @var{core}
856 You can, instead, specify a process ID as a second argument, if you want
857 to debug a running process:
860 @value{GDBP} @var{program} 1234
864 would attach @value{GDBN} to process @code{1234} (unless you also have a file
865 named @file{1234}; @value{GDBN} does check for a core file first).
867 Taking advantage of the second command-line argument requires a fairly
868 complete operating system; when you use @value{GDBN} as a remote
869 debugger attached to a bare board, there may not be any notion of
870 ``process'', and there is often no way to get a core dump. @value{GDBN}
871 will warn you if it is unable to attach or to read core dumps.
873 You can optionally have @code{@value{GDBP}} pass any arguments after the
874 executable file to the inferior using @code{--args}. This option stops
877 @value{GDBP} --args gcc -O2 -c foo.c
879 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
880 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
882 You can run @code{@value{GDBP}} without printing the front material, which describes
883 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
890 You can further control how @value{GDBN} starts up by using command-line
891 options. @value{GDBN} itself can remind you of the options available.
901 to display all available options and briefly describe their use
902 (@samp{@value{GDBP} -h} is a shorter equivalent).
904 All options and command line arguments you give are processed
905 in sequential order. The order makes a difference when the
906 @samp{-x} option is used.
910 * File Options:: Choosing files
911 * Mode Options:: Choosing modes
912 * Startup:: What @value{GDBN} does during startup
916 @subsection Choosing Files
918 When @value{GDBN} starts, it reads any arguments other than options as
919 specifying an executable file and core file (or process ID). This is
920 the same as if the arguments were specified by the @samp{-se} and
921 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
922 first argument that does not have an associated option flag as
923 equivalent to the @samp{-se} option followed by that argument; and the
924 second argument that does not have an associated option flag, if any, as
925 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
926 If the second argument begins with a decimal digit, @value{GDBN} will
927 first attempt to attach to it as a process, and if that fails, attempt
928 to open it as a corefile. If you have a corefile whose name begins with
929 a digit, you can prevent @value{GDBN} from treating it as a pid by
930 prefixing it with @file{./}, e.g.@: @file{./12345}.
932 If @value{GDBN} has not been configured to included core file support,
933 such as for most embedded targets, then it will complain about a second
934 argument and ignore it.
936 Many options have both long and short forms; both are shown in the
937 following list. @value{GDBN} also recognizes the long forms if you truncate
938 them, so long as enough of the option is present to be unambiguous.
939 (If you prefer, you can flag option arguments with @samp{--} rather
940 than @samp{-}, though we illustrate the more usual convention.)
942 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
943 @c way, both those who look for -foo and --foo in the index, will find
947 @item -symbols @var{file}
949 @cindex @code{--symbols}
951 Read symbol table from file @var{file}.
953 @item -exec @var{file}
955 @cindex @code{--exec}
957 Use file @var{file} as the executable file to execute when appropriate,
958 and for examining pure data in conjunction with a core dump.
962 Read symbol table from file @var{file} and use it as the executable
965 @item -core @var{file}
967 @cindex @code{--core}
969 Use file @var{file} as a core dump to examine.
971 @item -pid @var{number}
972 @itemx -p @var{number}
975 Connect to process ID @var{number}, as with the @code{attach} command.
977 @item -command @var{file}
979 @cindex @code{--command}
981 Execute commands from file @var{file}. The contents of this file is
982 evaluated exactly as the @code{source} command would.
983 @xref{Command Files,, Command files}.
985 @item -eval-command @var{command}
986 @itemx -ex @var{command}
987 @cindex @code{--eval-command}
989 Execute a single @value{GDBN} command.
991 This option may be used multiple times to call multiple commands. It may
992 also be interleaved with @samp{-command} as required.
995 @value{GDBP} -ex 'target sim' -ex 'load' \
996 -x setbreakpoints -ex 'run' a.out
999 @item -init-command @var{file}
1000 @itemx -ix @var{file}
1001 @cindex @code{--init-command}
1003 Execute commands from file @var{file} before loading the inferior (but
1004 after loading gdbinit files).
1007 @item -init-eval-command @var{command}
1008 @itemx -iex @var{command}
1009 @cindex @code{--init-eval-command}
1011 Execute a single @value{GDBN} command before loading the inferior (but
1012 after loading gdbinit files).
1015 @item -directory @var{directory}
1016 @itemx -d @var{directory}
1017 @cindex @code{--directory}
1019 Add @var{directory} to the path to search for source and script files.
1023 @cindex @code{--readnow}
1025 Read each symbol file's entire symbol table immediately, rather than
1026 the default, which is to read it incrementally as it is needed.
1027 This makes startup slower, but makes future operations faster.
1032 @subsection Choosing Modes
1034 You can run @value{GDBN} in various alternative modes---for example, in
1035 batch mode or quiet mode.
1043 Do not execute commands found in any initialization file.
1044 There are three init files, loaded in the following order:
1047 @item @file{system.gdbinit}
1048 This is the system-wide init file.
1049 Its location is specified with the @code{--with-system-gdbinit}
1050 configure option (@pxref{System-wide configuration}).
1051 It is loaded first when @value{GDBN} starts, before command line options
1052 have been processed.
1053 @item @file{~/.gdbinit}
1054 This is the init file in your home directory.
1055 It is loaded next, after @file{system.gdbinit}, and before
1056 command options have been processed.
1057 @item @file{./.gdbinit}
1058 This is the init file in the current directory.
1059 It is loaded last, after command line options other than @code{-x} and
1060 @code{-ex} have been processed. Command line options @code{-x} and
1061 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1064 For further documentation on startup processing, @xref{Startup}.
1065 For documentation on how to write command files,
1066 @xref{Command Files,,Command Files}.
1071 Do not execute commands found in @file{~/.gdbinit}, the init file
1072 in your home directory.
1078 @cindex @code{--quiet}
1079 @cindex @code{--silent}
1081 ``Quiet''. Do not print the introductory and copyright messages. These
1082 messages are also suppressed in batch mode.
1085 @cindex @code{--batch}
1086 Run in batch mode. Exit with status @code{0} after processing all the
1087 command files specified with @samp{-x} (and all commands from
1088 initialization files, if not inhibited with @samp{-n}). Exit with
1089 nonzero status if an error occurs in executing the @value{GDBN} commands
1090 in the command files. Batch mode also disables pagination, sets unlimited
1091 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1092 off} were in effect (@pxref{Messages/Warnings}).
1094 Batch mode may be useful for running @value{GDBN} as a filter, for
1095 example to download and run a program on another computer; in order to
1096 make this more useful, the message
1099 Program exited normally.
1103 (which is ordinarily issued whenever a program running under
1104 @value{GDBN} control terminates) is not issued when running in batch
1108 @cindex @code{--batch-silent}
1109 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1110 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1111 unaffected). This is much quieter than @samp{-silent} and would be useless
1112 for an interactive session.
1114 This is particularly useful when using targets that give @samp{Loading section}
1115 messages, for example.
1117 Note that targets that give their output via @value{GDBN}, as opposed to
1118 writing directly to @code{stdout}, will also be made silent.
1120 @item -return-child-result
1121 @cindex @code{--return-child-result}
1122 The return code from @value{GDBN} will be the return code from the child
1123 process (the process being debugged), with the following exceptions:
1127 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1128 internal error. In this case the exit code is the same as it would have been
1129 without @samp{-return-child-result}.
1131 The user quits with an explicit value. E.g., @samp{quit 1}.
1133 The child process never runs, or is not allowed to terminate, in which case
1134 the exit code will be -1.
1137 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1138 when @value{GDBN} is being used as a remote program loader or simulator
1143 @cindex @code{--nowindows}
1145 ``No windows''. If @value{GDBN} comes with a graphical user interface
1146 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1147 interface. If no GUI is available, this option has no effect.
1151 @cindex @code{--windows}
1153 If @value{GDBN} includes a GUI, then this option requires it to be
1156 @item -cd @var{directory}
1158 Run @value{GDBN} using @var{directory} as its working directory,
1159 instead of the current directory.
1161 @item -data-directory @var{directory}
1162 @cindex @code{--data-directory}
1163 Run @value{GDBN} using @var{directory} as its data directory.
1164 The data directory is where @value{GDBN} searches for its
1165 auxiliary files. @xref{Data Files}.
1169 @cindex @code{--fullname}
1171 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1172 subprocess. It tells @value{GDBN} to output the full file name and line
1173 number in a standard, recognizable fashion each time a stack frame is
1174 displayed (which includes each time your program stops). This
1175 recognizable format looks like two @samp{\032} characters, followed by
1176 the file name, line number and character position separated by colons,
1177 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1178 @samp{\032} characters as a signal to display the source code for the
1181 @item -annotate @var{level}
1182 @cindex @code{--annotate}
1183 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1184 effect is identical to using @samp{set annotate @var{level}}
1185 (@pxref{Annotations}). The annotation @var{level} controls how much
1186 information @value{GDBN} prints together with its prompt, values of
1187 expressions, source lines, and other types of output. Level 0 is the
1188 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1189 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1190 that control @value{GDBN}, and level 2 has been deprecated.
1192 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1196 @cindex @code{--args}
1197 Change interpretation of command line so that arguments following the
1198 executable file are passed as command line arguments to the inferior.
1199 This option stops option processing.
1201 @item -baud @var{bps}
1203 @cindex @code{--baud}
1205 Set the line speed (baud rate or bits per second) of any serial
1206 interface used by @value{GDBN} for remote debugging.
1208 @item -l @var{timeout}
1210 Set the timeout (in seconds) of any communication used by @value{GDBN}
1211 for remote debugging.
1213 @item -tty @var{device}
1214 @itemx -t @var{device}
1215 @cindex @code{--tty}
1217 Run using @var{device} for your program's standard input and output.
1218 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1220 @c resolve the situation of these eventually
1222 @cindex @code{--tui}
1223 Activate the @dfn{Text User Interface} when starting. The Text User
1224 Interface manages several text windows on the terminal, showing
1225 source, assembly, registers and @value{GDBN} command outputs
1226 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1227 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1228 Using @value{GDBN} under @sc{gnu} Emacs}).
1231 @c @cindex @code{--xdb}
1232 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1233 @c For information, see the file @file{xdb_trans.html}, which is usually
1234 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1237 @item -interpreter @var{interp}
1238 @cindex @code{--interpreter}
1239 Use the interpreter @var{interp} for interface with the controlling
1240 program or device. This option is meant to be set by programs which
1241 communicate with @value{GDBN} using it as a back end.
1242 @xref{Interpreters, , Command Interpreters}.
1244 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1245 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1246 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1247 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1248 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1249 @sc{gdb/mi} interfaces are no longer supported.
1252 @cindex @code{--write}
1253 Open the executable and core files for both reading and writing. This
1254 is equivalent to the @samp{set write on} command inside @value{GDBN}
1258 @cindex @code{--statistics}
1259 This option causes @value{GDBN} to print statistics about time and
1260 memory usage after it completes each command and returns to the prompt.
1263 @cindex @code{--version}
1264 This option causes @value{GDBN} to print its version number and
1265 no-warranty blurb, and exit.
1270 @subsection What @value{GDBN} Does During Startup
1271 @cindex @value{GDBN} startup
1273 Here's the description of what @value{GDBN} does during session startup:
1277 Sets up the command interpreter as specified by the command line
1278 (@pxref{Mode Options, interpreter}).
1282 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1283 used when building @value{GDBN}; @pxref{System-wide configuration,
1284 ,System-wide configuration and settings}) and executes all the commands in
1287 @anchor{Home Directory Init File}
1289 Reads the init file (if any) in your home directory@footnote{On
1290 DOS/Windows systems, the home directory is the one pointed to by the
1291 @code{HOME} environment variable.} and executes all the commands in
1294 @anchor{Option -init-eval-command}
1296 Executes commands and command files specified by the @samp{-iex} and
1297 @samp{-ix} options in their specified order. Usually you should use the
1298 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1299 settings before @value{GDBN} init files get executed and before inferior
1303 Processes command line options and operands.
1305 @anchor{Init File in the Current Directory during Startup}
1307 Reads and executes the commands from init file (if any) in the current
1308 working directory as long as @samp{set auto-load local-gdbinit} is set to
1309 @samp{on} (@pxref{Init File in the Current Directory}).
1310 This is only done if the current directory is
1311 different from your home directory. Thus, you can have more than one
1312 init file, one generic in your home directory, and another, specific
1313 to the program you are debugging, in the directory where you invoke
1317 If the command line specified a program to debug, or a process to
1318 attach to, or a core file, @value{GDBN} loads any auto-loaded
1319 scripts provided for the program or for its loaded shared libraries.
1320 @xref{Auto-loading}.
1322 If you wish to disable the auto-loading during startup,
1323 you must do something like the following:
1326 $ gdb -iex "set auto-load python-scripts off" myprogram
1329 Option @samp{-ex} does not work because the auto-loading is then turned
1333 Executes commands and command files specified by the @samp{-ex} and
1334 @samp{-x} options in their specified order. @xref{Command Files}, for
1335 more details about @value{GDBN} command files.
1338 Reads the command history recorded in the @dfn{history file}.
1339 @xref{Command History}, for more details about the command history and the
1340 files where @value{GDBN} records it.
1343 Init files use the same syntax as @dfn{command files} (@pxref{Command
1344 Files}) and are processed by @value{GDBN} in the same way. The init
1345 file in your home directory can set options (such as @samp{set
1346 complaints}) that affect subsequent processing of command line options
1347 and operands. Init files are not executed if you use the @samp{-nx}
1348 option (@pxref{Mode Options, ,Choosing Modes}).
1350 To display the list of init files loaded by gdb at startup, you
1351 can use @kbd{gdb --help}.
1353 @cindex init file name
1354 @cindex @file{.gdbinit}
1355 @cindex @file{gdb.ini}
1356 The @value{GDBN} init files are normally called @file{.gdbinit}.
1357 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1358 the limitations of file names imposed by DOS filesystems. The Windows
1359 port of @value{GDBN} uses the standard name, but if it finds a
1360 @file{gdb.ini} file in your home directory, it warns you about that
1361 and suggests to rename the file to the standard name.
1365 @section Quitting @value{GDBN}
1366 @cindex exiting @value{GDBN}
1367 @cindex leaving @value{GDBN}
1370 @kindex quit @r{[}@var{expression}@r{]}
1371 @kindex q @r{(@code{quit})}
1372 @item quit @r{[}@var{expression}@r{]}
1374 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1375 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1376 do not supply @var{expression}, @value{GDBN} will terminate normally;
1377 otherwise it will terminate using the result of @var{expression} as the
1382 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1383 terminates the action of any @value{GDBN} command that is in progress and
1384 returns to @value{GDBN} command level. It is safe to type the interrupt
1385 character at any time because @value{GDBN} does not allow it to take effect
1386 until a time when it is safe.
1388 If you have been using @value{GDBN} to control an attached process or
1389 device, you can release it with the @code{detach} command
1390 (@pxref{Attach, ,Debugging an Already-running Process}).
1392 @node Shell Commands
1393 @section Shell Commands
1395 If you need to execute occasional shell commands during your
1396 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1397 just use the @code{shell} command.
1402 @cindex shell escape
1403 @item shell @var{command-string}
1404 @itemx !@var{command-string}
1405 Invoke a standard shell to execute @var{command-string}.
1406 Note that no space is needed between @code{!} and @var{command-string}.
1407 If it exists, the environment variable @code{SHELL} determines which
1408 shell to run. Otherwise @value{GDBN} uses the default shell
1409 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1412 The utility @code{make} is often needed in development environments.
1413 You do not have to use the @code{shell} command for this purpose in
1418 @cindex calling make
1419 @item make @var{make-args}
1420 Execute the @code{make} program with the specified
1421 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1424 @node Logging Output
1425 @section Logging Output
1426 @cindex logging @value{GDBN} output
1427 @cindex save @value{GDBN} output to a file
1429 You may want to save the output of @value{GDBN} commands to a file.
1430 There are several commands to control @value{GDBN}'s logging.
1434 @item set logging on
1436 @item set logging off
1438 @cindex logging file name
1439 @item set logging file @var{file}
1440 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1441 @item set logging overwrite [on|off]
1442 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1443 you want @code{set logging on} to overwrite the logfile instead.
1444 @item set logging redirect [on|off]
1445 By default, @value{GDBN} output will go to both the terminal and the logfile.
1446 Set @code{redirect} if you want output to go only to the log file.
1447 @kindex show logging
1449 Show the current values of the logging settings.
1453 @chapter @value{GDBN} Commands
1455 You can abbreviate a @value{GDBN} command to the first few letters of the command
1456 name, if that abbreviation is unambiguous; and you can repeat certain
1457 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1458 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1459 show you the alternatives available, if there is more than one possibility).
1462 * Command Syntax:: How to give commands to @value{GDBN}
1463 * Completion:: Command completion
1464 * Help:: How to ask @value{GDBN} for help
1467 @node Command Syntax
1468 @section Command Syntax
1470 A @value{GDBN} command is a single line of input. There is no limit on
1471 how long it can be. It starts with a command name, which is followed by
1472 arguments whose meaning depends on the command name. For example, the
1473 command @code{step} accepts an argument which is the number of times to
1474 step, as in @samp{step 5}. You can also use the @code{step} command
1475 with no arguments. Some commands do not allow any arguments.
1477 @cindex abbreviation
1478 @value{GDBN} command names may always be truncated if that abbreviation is
1479 unambiguous. Other possible command abbreviations are listed in the
1480 documentation for individual commands. In some cases, even ambiguous
1481 abbreviations are allowed; for example, @code{s} is specially defined as
1482 equivalent to @code{step} even though there are other commands whose
1483 names start with @code{s}. You can test abbreviations by using them as
1484 arguments to the @code{help} command.
1486 @cindex repeating commands
1487 @kindex RET @r{(repeat last command)}
1488 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1489 repeat the previous command. Certain commands (for example, @code{run})
1490 will not repeat this way; these are commands whose unintentional
1491 repetition might cause trouble and which you are unlikely to want to
1492 repeat. User-defined commands can disable this feature; see
1493 @ref{Define, dont-repeat}.
1495 The @code{list} and @code{x} commands, when you repeat them with
1496 @key{RET}, construct new arguments rather than repeating
1497 exactly as typed. This permits easy scanning of source or memory.
1499 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1500 output, in a way similar to the common utility @code{more}
1501 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1502 @key{RET} too many in this situation, @value{GDBN} disables command
1503 repetition after any command that generates this sort of display.
1505 @kindex # @r{(a comment)}
1507 Any text from a @kbd{#} to the end of the line is a comment; it does
1508 nothing. This is useful mainly in command files (@pxref{Command
1509 Files,,Command Files}).
1511 @cindex repeating command sequences
1512 @kindex Ctrl-o @r{(operate-and-get-next)}
1513 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1514 commands. This command accepts the current line, like @key{RET}, and
1515 then fetches the next line relative to the current line from the history
1519 @section Command Completion
1522 @cindex word completion
1523 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1524 only one possibility; it can also show you what the valid possibilities
1525 are for the next word in a command, at any time. This works for @value{GDBN}
1526 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1528 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1529 of a word. If there is only one possibility, @value{GDBN} fills in the
1530 word, and waits for you to finish the command (or press @key{RET} to
1531 enter it). For example, if you type
1533 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1534 @c complete accuracy in these examples; space introduced for clarity.
1535 @c If texinfo enhancements make it unnecessary, it would be nice to
1536 @c replace " @key" by "@key" in the following...
1538 (@value{GDBP}) info bre @key{TAB}
1542 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1543 the only @code{info} subcommand beginning with @samp{bre}:
1546 (@value{GDBP}) info breakpoints
1550 You can either press @key{RET} at this point, to run the @code{info
1551 breakpoints} command, or backspace and enter something else, if
1552 @samp{breakpoints} does not look like the command you expected. (If you
1553 were sure you wanted @code{info breakpoints} in the first place, you
1554 might as well just type @key{RET} immediately after @samp{info bre},
1555 to exploit command abbreviations rather than command completion).
1557 If there is more than one possibility for the next word when you press
1558 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1559 characters and try again, or just press @key{TAB} a second time;
1560 @value{GDBN} displays all the possible completions for that word. For
1561 example, you might want to set a breakpoint on a subroutine whose name
1562 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1563 just sounds the bell. Typing @key{TAB} again displays all the
1564 function names in your program that begin with those characters, for
1568 (@value{GDBP}) b make_ @key{TAB}
1569 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1570 make_a_section_from_file make_environ
1571 make_abs_section make_function_type
1572 make_blockvector make_pointer_type
1573 make_cleanup make_reference_type
1574 make_command make_symbol_completion_list
1575 (@value{GDBP}) b make_
1579 After displaying the available possibilities, @value{GDBN} copies your
1580 partial input (@samp{b make_} in the example) so you can finish the
1583 If you just want to see the list of alternatives in the first place, you
1584 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1585 means @kbd{@key{META} ?}. You can type this either by holding down a
1586 key designated as the @key{META} shift on your keyboard (if there is
1587 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1589 @cindex quotes in commands
1590 @cindex completion of quoted strings
1591 Sometimes the string you need, while logically a ``word'', may contain
1592 parentheses or other characters that @value{GDBN} normally excludes from
1593 its notion of a word. To permit word completion to work in this
1594 situation, you may enclose words in @code{'} (single quote marks) in
1595 @value{GDBN} commands.
1597 The most likely situation where you might need this is in typing the
1598 name of a C@t{++} function. This is because C@t{++} allows function
1599 overloading (multiple definitions of the same function, distinguished
1600 by argument type). For example, when you want to set a breakpoint you
1601 may need to distinguish whether you mean the version of @code{name}
1602 that takes an @code{int} parameter, @code{name(int)}, or the version
1603 that takes a @code{float} parameter, @code{name(float)}. To use the
1604 word-completion facilities in this situation, type a single quote
1605 @code{'} at the beginning of the function name. This alerts
1606 @value{GDBN} that it may need to consider more information than usual
1607 when you press @key{TAB} or @kbd{M-?} to request word completion:
1610 (@value{GDBP}) b 'bubble( @kbd{M-?}
1611 bubble(double,double) bubble(int,int)
1612 (@value{GDBP}) b 'bubble(
1615 In some cases, @value{GDBN} can tell that completing a name requires using
1616 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1617 completing as much as it can) if you do not type the quote in the first
1621 (@value{GDBP}) b bub @key{TAB}
1622 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1623 (@value{GDBP}) b 'bubble(
1627 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1628 you have not yet started typing the argument list when you ask for
1629 completion on an overloaded symbol.
1631 For more information about overloaded functions, see @ref{C Plus Plus
1632 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1633 overload-resolution off} to disable overload resolution;
1634 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1636 @cindex completion of structure field names
1637 @cindex structure field name completion
1638 @cindex completion of union field names
1639 @cindex union field name completion
1640 When completing in an expression which looks up a field in a
1641 structure, @value{GDBN} also tries@footnote{The completer can be
1642 confused by certain kinds of invalid expressions. Also, it only
1643 examines the static type of the expression, not the dynamic type.} to
1644 limit completions to the field names available in the type of the
1648 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1649 magic to_fputs to_rewind
1650 to_data to_isatty to_write
1651 to_delete to_put to_write_async_safe
1656 This is because the @code{gdb_stdout} is a variable of the type
1657 @code{struct ui_file} that is defined in @value{GDBN} sources as
1664 ui_file_flush_ftype *to_flush;
1665 ui_file_write_ftype *to_write;
1666 ui_file_write_async_safe_ftype *to_write_async_safe;
1667 ui_file_fputs_ftype *to_fputs;
1668 ui_file_read_ftype *to_read;
1669 ui_file_delete_ftype *to_delete;
1670 ui_file_isatty_ftype *to_isatty;
1671 ui_file_rewind_ftype *to_rewind;
1672 ui_file_put_ftype *to_put;
1679 @section Getting Help
1680 @cindex online documentation
1683 You can always ask @value{GDBN} itself for information on its commands,
1684 using the command @code{help}.
1687 @kindex h @r{(@code{help})}
1690 You can use @code{help} (abbreviated @code{h}) with no arguments to
1691 display a short list of named classes of commands:
1695 List of classes of commands:
1697 aliases -- Aliases of other commands
1698 breakpoints -- Making program stop at certain points
1699 data -- Examining data
1700 files -- Specifying and examining files
1701 internals -- Maintenance commands
1702 obscure -- Obscure features
1703 running -- Running the program
1704 stack -- Examining the stack
1705 status -- Status inquiries
1706 support -- Support facilities
1707 tracepoints -- Tracing of program execution without
1708 stopping the program
1709 user-defined -- User-defined commands
1711 Type "help" followed by a class name for a list of
1712 commands in that class.
1713 Type "help" followed by command name for full
1715 Command name abbreviations are allowed if unambiguous.
1718 @c the above line break eliminates huge line overfull...
1720 @item help @var{class}
1721 Using one of the general help classes as an argument, you can get a
1722 list of the individual commands in that class. For example, here is the
1723 help display for the class @code{status}:
1726 (@value{GDBP}) help status
1731 @c Line break in "show" line falsifies real output, but needed
1732 @c to fit in smallbook page size.
1733 info -- Generic command for showing things
1734 about the program being debugged
1735 show -- Generic command for showing things
1738 Type "help" followed by command name for full
1740 Command name abbreviations are allowed if unambiguous.
1744 @item help @var{command}
1745 With a command name as @code{help} argument, @value{GDBN} displays a
1746 short paragraph on how to use that command.
1749 @item apropos @var{args}
1750 The @code{apropos} command searches through all of the @value{GDBN}
1751 commands, and their documentation, for the regular expression specified in
1752 @var{args}. It prints out all matches found. For example:
1763 alias -- Define a new command that is an alias of an existing command
1764 aliases -- Aliases of other commands
1765 d -- Delete some breakpoints or auto-display expressions
1766 del -- Delete some breakpoints or auto-display expressions
1767 delete -- Delete some breakpoints or auto-display expressions
1772 @item complete @var{args}
1773 The @code{complete @var{args}} command lists all the possible completions
1774 for the beginning of a command. Use @var{args} to specify the beginning of the
1775 command you want completed. For example:
1781 @noindent results in:
1792 @noindent This is intended for use by @sc{gnu} Emacs.
1795 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1796 and @code{show} to inquire about the state of your program, or the state
1797 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1798 manual introduces each of them in the appropriate context. The listings
1799 under @code{info} and under @code{show} in the Command, Variable, and
1800 Function Index point to all the sub-commands. @xref{Command and Variable
1806 @kindex i @r{(@code{info})}
1808 This command (abbreviated @code{i}) is for describing the state of your
1809 program. For example, you can show the arguments passed to a function
1810 with @code{info args}, list the registers currently in use with @code{info
1811 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1812 You can get a complete list of the @code{info} sub-commands with
1813 @w{@code{help info}}.
1817 You can assign the result of an expression to an environment variable with
1818 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1819 @code{set prompt $}.
1823 In contrast to @code{info}, @code{show} is for describing the state of
1824 @value{GDBN} itself.
1825 You can change most of the things you can @code{show}, by using the
1826 related command @code{set}; for example, you can control what number
1827 system is used for displays with @code{set radix}, or simply inquire
1828 which is currently in use with @code{show radix}.
1831 To display all the settable parameters and their current
1832 values, you can use @code{show} with no arguments; you may also use
1833 @code{info set}. Both commands produce the same display.
1834 @c FIXME: "info set" violates the rule that "info" is for state of
1835 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1836 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1840 Here are three miscellaneous @code{show} subcommands, all of which are
1841 exceptional in lacking corresponding @code{set} commands:
1844 @kindex show version
1845 @cindex @value{GDBN} version number
1847 Show what version of @value{GDBN} is running. You should include this
1848 information in @value{GDBN} bug-reports. If multiple versions of
1849 @value{GDBN} are in use at your site, you may need to determine which
1850 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1851 commands are introduced, and old ones may wither away. Also, many
1852 system vendors ship variant versions of @value{GDBN}, and there are
1853 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1854 The version number is the same as the one announced when you start
1857 @kindex show copying
1858 @kindex info copying
1859 @cindex display @value{GDBN} copyright
1862 Display information about permission for copying @value{GDBN}.
1864 @kindex show warranty
1865 @kindex info warranty
1867 @itemx info warranty
1868 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1869 if your version of @value{GDBN} comes with one.
1874 @chapter Running Programs Under @value{GDBN}
1876 When you run a program under @value{GDBN}, you must first generate
1877 debugging information when you compile it.
1879 You may start @value{GDBN} with its arguments, if any, in an environment
1880 of your choice. If you are doing native debugging, you may redirect
1881 your program's input and output, debug an already running process, or
1882 kill a child process.
1885 * Compilation:: Compiling for debugging
1886 * Starting:: Starting your program
1887 * Arguments:: Your program's arguments
1888 * Environment:: Your program's environment
1890 * Working Directory:: Your program's working directory
1891 * Input/Output:: Your program's input and output
1892 * Attach:: Debugging an already-running process
1893 * Kill Process:: Killing the child process
1895 * Inferiors and Programs:: Debugging multiple inferiors and programs
1896 * Threads:: Debugging programs with multiple threads
1897 * Forks:: Debugging forks
1898 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1902 @section Compiling for Debugging
1904 In order to debug a program effectively, you need to generate
1905 debugging information when you compile it. This debugging information
1906 is stored in the object file; it describes the data type of each
1907 variable or function and the correspondence between source line numbers
1908 and addresses in the executable code.
1910 To request debugging information, specify the @samp{-g} option when you run
1913 Programs that are to be shipped to your customers are compiled with
1914 optimizations, using the @samp{-O} compiler option. However, some
1915 compilers are unable to handle the @samp{-g} and @samp{-O} options
1916 together. Using those compilers, you cannot generate optimized
1917 executables containing debugging information.
1919 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1920 without @samp{-O}, making it possible to debug optimized code. We
1921 recommend that you @emph{always} use @samp{-g} whenever you compile a
1922 program. You may think your program is correct, but there is no sense
1923 in pushing your luck. For more information, see @ref{Optimized Code}.
1925 Older versions of the @sc{gnu} C compiler permitted a variant option
1926 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1927 format; if your @sc{gnu} C compiler has this option, do not use it.
1929 @value{GDBN} knows about preprocessor macros and can show you their
1930 expansion (@pxref{Macros}). Most compilers do not include information
1931 about preprocessor macros in the debugging information if you specify
1932 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1933 the @sc{gnu} C compiler, provides macro information if you are using
1934 the DWARF debugging format, and specify the option @option{-g3}.
1936 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1937 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1938 information on @value{NGCC} options affecting debug information.
1940 You will have the best debugging experience if you use the latest
1941 version of the DWARF debugging format that your compiler supports.
1942 DWARF is currently the most expressive and best supported debugging
1943 format in @value{GDBN}.
1947 @section Starting your Program
1953 @kindex r @r{(@code{run})}
1956 Use the @code{run} command to start your program under @value{GDBN}.
1957 You must first specify the program name (except on VxWorks) with an
1958 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1959 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1960 (@pxref{Files, ,Commands to Specify Files}).
1964 If you are running your program in an execution environment that
1965 supports processes, @code{run} creates an inferior process and makes
1966 that process run your program. In some environments without processes,
1967 @code{run} jumps to the start of your program. Other targets,
1968 like @samp{remote}, are always running. If you get an error
1969 message like this one:
1972 The "remote" target does not support "run".
1973 Try "help target" or "continue".
1977 then use @code{continue} to run your program. You may need @code{load}
1978 first (@pxref{load}).
1980 The execution of a program is affected by certain information it
1981 receives from its superior. @value{GDBN} provides ways to specify this
1982 information, which you must do @emph{before} starting your program. (You
1983 can change it after starting your program, but such changes only affect
1984 your program the next time you start it.) This information may be
1985 divided into four categories:
1988 @item The @emph{arguments.}
1989 Specify the arguments to give your program as the arguments of the
1990 @code{run} command. If a shell is available on your target, the shell
1991 is used to pass the arguments, so that you may use normal conventions
1992 (such as wildcard expansion or variable substitution) in describing
1994 In Unix systems, you can control which shell is used with the
1995 @code{SHELL} environment variable.
1996 @xref{Arguments, ,Your Program's Arguments}.
1998 @item The @emph{environment.}
1999 Your program normally inherits its environment from @value{GDBN}, but you can
2000 use the @value{GDBN} commands @code{set environment} and @code{unset
2001 environment} to change parts of the environment that affect
2002 your program. @xref{Environment, ,Your Program's Environment}.
2004 @item The @emph{working directory.}
2005 Your program inherits its working directory from @value{GDBN}. You can set
2006 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2007 @xref{Working Directory, ,Your Program's Working Directory}.
2009 @item The @emph{standard input and output.}
2010 Your program normally uses the same device for standard input and
2011 standard output as @value{GDBN} is using. You can redirect input and output
2012 in the @code{run} command line, or you can use the @code{tty} command to
2013 set a different device for your program.
2014 @xref{Input/Output, ,Your Program's Input and Output}.
2017 @emph{Warning:} While input and output redirection work, you cannot use
2018 pipes to pass the output of the program you are debugging to another
2019 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2023 When you issue the @code{run} command, your program begins to execute
2024 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2025 of how to arrange for your program to stop. Once your program has
2026 stopped, you may call functions in your program, using the @code{print}
2027 or @code{call} commands. @xref{Data, ,Examining Data}.
2029 If the modification time of your symbol file has changed since the last
2030 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2031 table, and reads it again. When it does this, @value{GDBN} tries to retain
2032 your current breakpoints.
2037 @cindex run to main procedure
2038 The name of the main procedure can vary from language to language.
2039 With C or C@t{++}, the main procedure name is always @code{main}, but
2040 other languages such as Ada do not require a specific name for their
2041 main procedure. The debugger provides a convenient way to start the
2042 execution of the program and to stop at the beginning of the main
2043 procedure, depending on the language used.
2045 The @samp{start} command does the equivalent of setting a temporary
2046 breakpoint at the beginning of the main procedure and then invoking
2047 the @samp{run} command.
2049 @cindex elaboration phase
2050 Some programs contain an @dfn{elaboration} phase where some startup code is
2051 executed before the main procedure is called. This depends on the
2052 languages used to write your program. In C@t{++}, for instance,
2053 constructors for static and global objects are executed before
2054 @code{main} is called. It is therefore possible that the debugger stops
2055 before reaching the main procedure. However, the temporary breakpoint
2056 will remain to halt execution.
2058 Specify the arguments to give to your program as arguments to the
2059 @samp{start} command. These arguments will be given verbatim to the
2060 underlying @samp{run} command. Note that the same arguments will be
2061 reused if no argument is provided during subsequent calls to
2062 @samp{start} or @samp{run}.
2064 It is sometimes necessary to debug the program during elaboration. In
2065 these cases, using the @code{start} command would stop the execution of
2066 your program too late, as the program would have already completed the
2067 elaboration phase. Under these circumstances, insert breakpoints in your
2068 elaboration code before running your program.
2070 @kindex set exec-wrapper
2071 @item set exec-wrapper @var{wrapper}
2072 @itemx show exec-wrapper
2073 @itemx unset exec-wrapper
2074 When @samp{exec-wrapper} is set, the specified wrapper is used to
2075 launch programs for debugging. @value{GDBN} starts your program
2076 with a shell command of the form @kbd{exec @var{wrapper}
2077 @var{program}}. Quoting is added to @var{program} and its
2078 arguments, but not to @var{wrapper}, so you should add quotes if
2079 appropriate for your shell. The wrapper runs until it executes
2080 your program, and then @value{GDBN} takes control.
2082 You can use any program that eventually calls @code{execve} with
2083 its arguments as a wrapper. Several standard Unix utilities do
2084 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2085 with @code{exec "$@@"} will also work.
2087 For example, you can use @code{env} to pass an environment variable to
2088 the debugged program, without setting the variable in your shell's
2092 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2096 This command is available when debugging locally on most targets, excluding
2097 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2099 @kindex set disable-randomization
2100 @item set disable-randomization
2101 @itemx set disable-randomization on
2102 This option (enabled by default in @value{GDBN}) will turn off the native
2103 randomization of the virtual address space of the started program. This option
2104 is useful for multiple debugging sessions to make the execution better
2105 reproducible and memory addresses reusable across debugging sessions.
2107 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2108 On @sc{gnu}/Linux you can get the same behavior using
2111 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2114 @item set disable-randomization off
2115 Leave the behavior of the started executable unchanged. Some bugs rear their
2116 ugly heads only when the program is loaded at certain addresses. If your bug
2117 disappears when you run the program under @value{GDBN}, that might be because
2118 @value{GDBN} by default disables the address randomization on platforms, such
2119 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2120 disable-randomization off} to try to reproduce such elusive bugs.
2122 On targets where it is available, virtual address space randomization
2123 protects the programs against certain kinds of security attacks. In these
2124 cases the attacker needs to know the exact location of a concrete executable
2125 code. Randomizing its location makes it impossible to inject jumps misusing
2126 a code at its expected addresses.
2128 Prelinking shared libraries provides a startup performance advantage but it
2129 makes addresses in these libraries predictable for privileged processes by
2130 having just unprivileged access at the target system. Reading the shared
2131 library binary gives enough information for assembling the malicious code
2132 misusing it. Still even a prelinked shared library can get loaded at a new
2133 random address just requiring the regular relocation process during the
2134 startup. Shared libraries not already prelinked are always loaded at
2135 a randomly chosen address.
2137 Position independent executables (PIE) contain position independent code
2138 similar to the shared libraries and therefore such executables get loaded at
2139 a randomly chosen address upon startup. PIE executables always load even
2140 already prelinked shared libraries at a random address. You can build such
2141 executable using @command{gcc -fPIE -pie}.
2143 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2144 (as long as the randomization is enabled).
2146 @item show disable-randomization
2147 Show the current setting of the explicit disable of the native randomization of
2148 the virtual address space of the started program.
2153 @section Your Program's Arguments
2155 @cindex arguments (to your program)
2156 The arguments to your program can be specified by the arguments of the
2158 They are passed to a shell, which expands wildcard characters and
2159 performs redirection of I/O, and thence to your program. Your
2160 @code{SHELL} environment variable (if it exists) specifies what shell
2161 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2162 the default shell (@file{/bin/sh} on Unix).
2164 On non-Unix systems, the program is usually invoked directly by
2165 @value{GDBN}, which emulates I/O redirection via the appropriate system
2166 calls, and the wildcard characters are expanded by the startup code of
2167 the program, not by the shell.
2169 @code{run} with no arguments uses the same arguments used by the previous
2170 @code{run}, or those set by the @code{set args} command.
2175 Specify the arguments to be used the next time your program is run. If
2176 @code{set args} has no arguments, @code{run} executes your program
2177 with no arguments. Once you have run your program with arguments,
2178 using @code{set args} before the next @code{run} is the only way to run
2179 it again without arguments.
2183 Show the arguments to give your program when it is started.
2187 @section Your Program's Environment
2189 @cindex environment (of your program)
2190 The @dfn{environment} consists of a set of environment variables and
2191 their values. Environment variables conventionally record such things as
2192 your user name, your home directory, your terminal type, and your search
2193 path for programs to run. Usually you set up environment variables with
2194 the shell and they are inherited by all the other programs you run. When
2195 debugging, it can be useful to try running your program with a modified
2196 environment without having to start @value{GDBN} over again.
2200 @item path @var{directory}
2201 Add @var{directory} to the front of the @code{PATH} environment variable
2202 (the search path for executables) that will be passed to your program.
2203 The value of @code{PATH} used by @value{GDBN} does not change.
2204 You may specify several directory names, separated by whitespace or by a
2205 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2206 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2207 is moved to the front, so it is searched sooner.
2209 You can use the string @samp{$cwd} to refer to whatever is the current
2210 working directory at the time @value{GDBN} searches the path. If you
2211 use @samp{.} instead, it refers to the directory where you executed the
2212 @code{path} command. @value{GDBN} replaces @samp{.} in the
2213 @var{directory} argument (with the current path) before adding
2214 @var{directory} to the search path.
2215 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2216 @c document that, since repeating it would be a no-op.
2220 Display the list of search paths for executables (the @code{PATH}
2221 environment variable).
2223 @kindex show environment
2224 @item show environment @r{[}@var{varname}@r{]}
2225 Print the value of environment variable @var{varname} to be given to
2226 your program when it starts. If you do not supply @var{varname},
2227 print the names and values of all environment variables to be given to
2228 your program. You can abbreviate @code{environment} as @code{env}.
2230 @kindex set environment
2231 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2232 Set environment variable @var{varname} to @var{value}. The value
2233 changes for your program only, not for @value{GDBN} itself. @var{value} may
2234 be any string; the values of environment variables are just strings, and
2235 any interpretation is supplied by your program itself. The @var{value}
2236 parameter is optional; if it is eliminated, the variable is set to a
2238 @c "any string" here does not include leading, trailing
2239 @c blanks. Gnu asks: does anyone care?
2241 For example, this command:
2248 tells the debugged program, when subsequently run, that its user is named
2249 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2250 are not actually required.)
2252 @kindex unset environment
2253 @item unset environment @var{varname}
2254 Remove variable @var{varname} from the environment to be passed to your
2255 program. This is different from @samp{set env @var{varname} =};
2256 @code{unset environment} removes the variable from the environment,
2257 rather than assigning it an empty value.
2260 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2262 by your @code{SHELL} environment variable if it exists (or
2263 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2264 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2265 @file{.bashrc} for BASH---any variables you set in that file affect
2266 your program. You may wish to move setting of environment variables to
2267 files that are only run when you sign on, such as @file{.login} or
2270 @node Working Directory
2271 @section Your Program's Working Directory
2273 @cindex working directory (of your program)
2274 Each time you start your program with @code{run}, it inherits its
2275 working directory from the current working directory of @value{GDBN}.
2276 The @value{GDBN} working directory is initially whatever it inherited
2277 from its parent process (typically the shell), but you can specify a new
2278 working directory in @value{GDBN} with the @code{cd} command.
2280 The @value{GDBN} working directory also serves as a default for the commands
2281 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2286 @cindex change working directory
2287 @item cd @r{[}@var{directory}@r{]}
2288 Set the @value{GDBN} working directory to @var{directory}. If not
2289 given, @var{directory} uses @file{'~'}.
2293 Print the @value{GDBN} working directory.
2296 It is generally impossible to find the current working directory of
2297 the process being debugged (since a program can change its directory
2298 during its run). If you work on a system where @value{GDBN} is
2299 configured with the @file{/proc} support, you can use the @code{info
2300 proc} command (@pxref{SVR4 Process Information}) to find out the
2301 current working directory of the debuggee.
2304 @section Your Program's Input and Output
2309 By default, the program you run under @value{GDBN} does input and output to
2310 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2311 to its own terminal modes to interact with you, but it records the terminal
2312 modes your program was using and switches back to them when you continue
2313 running your program.
2316 @kindex info terminal
2318 Displays information recorded by @value{GDBN} about the terminal modes your
2322 You can redirect your program's input and/or output using shell
2323 redirection with the @code{run} command. For example,
2330 starts your program, diverting its output to the file @file{outfile}.
2333 @cindex controlling terminal
2334 Another way to specify where your program should do input and output is
2335 with the @code{tty} command. This command accepts a file name as
2336 argument, and causes this file to be the default for future @code{run}
2337 commands. It also resets the controlling terminal for the child
2338 process, for future @code{run} commands. For example,
2345 directs that processes started with subsequent @code{run} commands
2346 default to do input and output on the terminal @file{/dev/ttyb} and have
2347 that as their controlling terminal.
2349 An explicit redirection in @code{run} overrides the @code{tty} command's
2350 effect on the input/output device, but not its effect on the controlling
2353 When you use the @code{tty} command or redirect input in the @code{run}
2354 command, only the input @emph{for your program} is affected. The input
2355 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2356 for @code{set inferior-tty}.
2358 @cindex inferior tty
2359 @cindex set inferior controlling terminal
2360 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2361 display the name of the terminal that will be used for future runs of your
2365 @item set inferior-tty /dev/ttyb
2366 @kindex set inferior-tty
2367 Set the tty for the program being debugged to /dev/ttyb.
2369 @item show inferior-tty
2370 @kindex show inferior-tty
2371 Show the current tty for the program being debugged.
2375 @section Debugging an Already-running Process
2380 @item attach @var{process-id}
2381 This command attaches to a running process---one that was started
2382 outside @value{GDBN}. (@code{info files} shows your active
2383 targets.) The command takes as argument a process ID. The usual way to
2384 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2385 or with the @samp{jobs -l} shell command.
2387 @code{attach} does not repeat if you press @key{RET} a second time after
2388 executing the command.
2391 To use @code{attach}, your program must be running in an environment
2392 which supports processes; for example, @code{attach} does not work for
2393 programs on bare-board targets that lack an operating system. You must
2394 also have permission to send the process a signal.
2396 When you use @code{attach}, the debugger finds the program running in
2397 the process first by looking in the current working directory, then (if
2398 the program is not found) by using the source file search path
2399 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2400 the @code{file} command to load the program. @xref{Files, ,Commands to
2403 The first thing @value{GDBN} does after arranging to debug the specified
2404 process is to stop it. You can examine and modify an attached process
2405 with all the @value{GDBN} commands that are ordinarily available when
2406 you start processes with @code{run}. You can insert breakpoints; you
2407 can step and continue; you can modify storage. If you would rather the
2408 process continue running, you may use the @code{continue} command after
2409 attaching @value{GDBN} to the process.
2414 When you have finished debugging the attached process, you can use the
2415 @code{detach} command to release it from @value{GDBN} control. Detaching
2416 the process continues its execution. After the @code{detach} command,
2417 that process and @value{GDBN} become completely independent once more, and you
2418 are ready to @code{attach} another process or start one with @code{run}.
2419 @code{detach} does not repeat if you press @key{RET} again after
2420 executing the command.
2423 If you exit @value{GDBN} while you have an attached process, you detach
2424 that process. If you use the @code{run} command, you kill that process.
2425 By default, @value{GDBN} asks for confirmation if you try to do either of these
2426 things; you can control whether or not you need to confirm by using the
2427 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2431 @section Killing the Child Process
2436 Kill the child process in which your program is running under @value{GDBN}.
2439 This command is useful if you wish to debug a core dump instead of a
2440 running process. @value{GDBN} ignores any core dump file while your program
2443 On some operating systems, a program cannot be executed outside @value{GDBN}
2444 while you have breakpoints set on it inside @value{GDBN}. You can use the
2445 @code{kill} command in this situation to permit running your program
2446 outside the debugger.
2448 The @code{kill} command is also useful if you wish to recompile and
2449 relink your program, since on many systems it is impossible to modify an
2450 executable file while it is running in a process. In this case, when you
2451 next type @code{run}, @value{GDBN} notices that the file has changed, and
2452 reads the symbol table again (while trying to preserve your current
2453 breakpoint settings).
2455 @node Inferiors and Programs
2456 @section Debugging Multiple Inferiors and Programs
2458 @value{GDBN} lets you run and debug multiple programs in a single
2459 session. In addition, @value{GDBN} on some systems may let you run
2460 several programs simultaneously (otherwise you have to exit from one
2461 before starting another). In the most general case, you can have
2462 multiple threads of execution in each of multiple processes, launched
2463 from multiple executables.
2466 @value{GDBN} represents the state of each program execution with an
2467 object called an @dfn{inferior}. An inferior typically corresponds to
2468 a process, but is more general and applies also to targets that do not
2469 have processes. Inferiors may be created before a process runs, and
2470 may be retained after a process exits. Inferiors have unique
2471 identifiers that are different from process ids. Usually each
2472 inferior will also have its own distinct address space, although some
2473 embedded targets may have several inferiors running in different parts
2474 of a single address space. Each inferior may in turn have multiple
2475 threads running in it.
2477 To find out what inferiors exist at any moment, use @w{@code{info
2481 @kindex info inferiors
2482 @item info inferiors
2483 Print a list of all inferiors currently being managed by @value{GDBN}.
2485 @value{GDBN} displays for each inferior (in this order):
2489 the inferior number assigned by @value{GDBN}
2492 the target system's inferior identifier
2495 the name of the executable the inferior is running.
2500 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2501 indicates the current inferior.
2505 @c end table here to get a little more width for example
2508 (@value{GDBP}) info inferiors
2509 Num Description Executable
2510 2 process 2307 hello
2511 * 1 process 3401 goodbye
2514 To switch focus between inferiors, use the @code{inferior} command:
2517 @kindex inferior @var{infno}
2518 @item inferior @var{infno}
2519 Make inferior number @var{infno} the current inferior. The argument
2520 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2521 in the first field of the @samp{info inferiors} display.
2525 You can get multiple executables into a debugging session via the
2526 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2527 systems @value{GDBN} can add inferiors to the debug session
2528 automatically by following calls to @code{fork} and @code{exec}. To
2529 remove inferiors from the debugging session use the
2530 @w{@code{remove-inferiors}} command.
2533 @kindex add-inferior
2534 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2535 Adds @var{n} inferiors to be run using @var{executable} as the
2536 executable. @var{n} defaults to 1. If no executable is specified,
2537 the inferiors begins empty, with no program. You can still assign or
2538 change the program assigned to the inferior at any time by using the
2539 @code{file} command with the executable name as its argument.
2541 @kindex clone-inferior
2542 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2543 Adds @var{n} inferiors ready to execute the same program as inferior
2544 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2545 number of the current inferior. This is a convenient command when you
2546 want to run another instance of the inferior you are debugging.
2549 (@value{GDBP}) info inferiors
2550 Num Description Executable
2551 * 1 process 29964 helloworld
2552 (@value{GDBP}) clone-inferior
2555 (@value{GDBP}) info inferiors
2556 Num Description Executable
2558 * 1 process 29964 helloworld
2561 You can now simply switch focus to inferior 2 and run it.
2563 @kindex remove-inferiors
2564 @item remove-inferiors @var{infno}@dots{}
2565 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2566 possible to remove an inferior that is running with this command. For
2567 those, use the @code{kill} or @code{detach} command first.
2571 To quit debugging one of the running inferiors that is not the current
2572 inferior, you can either detach from it by using the @w{@code{detach
2573 inferior}} command (allowing it to run independently), or kill it
2574 using the @w{@code{kill inferiors}} command:
2577 @kindex detach inferiors @var{infno}@dots{}
2578 @item detach inferior @var{infno}@dots{}
2579 Detach from the inferior or inferiors identified by @value{GDBN}
2580 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2581 still stays on the list of inferiors shown by @code{info inferiors},
2582 but its Description will show @samp{<null>}.
2584 @kindex kill inferiors @var{infno}@dots{}
2585 @item kill inferiors @var{infno}@dots{}
2586 Kill the inferior or inferiors identified by @value{GDBN} inferior
2587 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2588 stays on the list of inferiors shown by @code{info inferiors}, but its
2589 Description will show @samp{<null>}.
2592 After the successful completion of a command such as @code{detach},
2593 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2594 a normal process exit, the inferior is still valid and listed with
2595 @code{info inferiors}, ready to be restarted.
2598 To be notified when inferiors are started or exit under @value{GDBN}'s
2599 control use @w{@code{set print inferior-events}}:
2602 @kindex set print inferior-events
2603 @cindex print messages on inferior start and exit
2604 @item set print inferior-events
2605 @itemx set print inferior-events on
2606 @itemx set print inferior-events off
2607 The @code{set print inferior-events} command allows you to enable or
2608 disable printing of messages when @value{GDBN} notices that new
2609 inferiors have started or that inferiors have exited or have been
2610 detached. By default, these messages will not be printed.
2612 @kindex show print inferior-events
2613 @item show print inferior-events
2614 Show whether messages will be printed when @value{GDBN} detects that
2615 inferiors have started, exited or have been detached.
2618 Many commands will work the same with multiple programs as with a
2619 single program: e.g., @code{print myglobal} will simply display the
2620 value of @code{myglobal} in the current inferior.
2623 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2624 get more info about the relationship of inferiors, programs, address
2625 spaces in a debug session. You can do that with the @w{@code{maint
2626 info program-spaces}} command.
2629 @kindex maint info program-spaces
2630 @item maint info program-spaces
2631 Print a list of all program spaces currently being managed by
2634 @value{GDBN} displays for each program space (in this order):
2638 the program space number assigned by @value{GDBN}
2641 the name of the executable loaded into the program space, with e.g.,
2642 the @code{file} command.
2647 An asterisk @samp{*} preceding the @value{GDBN} program space number
2648 indicates the current program space.
2650 In addition, below each program space line, @value{GDBN} prints extra
2651 information that isn't suitable to display in tabular form. For
2652 example, the list of inferiors bound to the program space.
2655 (@value{GDBP}) maint info program-spaces
2658 Bound inferiors: ID 1 (process 21561)
2662 Here we can see that no inferior is running the program @code{hello},
2663 while @code{process 21561} is running the program @code{goodbye}. On
2664 some targets, it is possible that multiple inferiors are bound to the
2665 same program space. The most common example is that of debugging both
2666 the parent and child processes of a @code{vfork} call. For example,
2669 (@value{GDBP}) maint info program-spaces
2672 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2675 Here, both inferior 2 and inferior 1 are running in the same program
2676 space as a result of inferior 1 having executed a @code{vfork} call.
2680 @section Debugging Programs with Multiple Threads
2682 @cindex threads of execution
2683 @cindex multiple threads
2684 @cindex switching threads
2685 In some operating systems, such as HP-UX and Solaris, a single program
2686 may have more than one @dfn{thread} of execution. The precise semantics
2687 of threads differ from one operating system to another, but in general
2688 the threads of a single program are akin to multiple processes---except
2689 that they share one address space (that is, they can all examine and
2690 modify the same variables). On the other hand, each thread has its own
2691 registers and execution stack, and perhaps private memory.
2693 @value{GDBN} provides these facilities for debugging multi-thread
2697 @item automatic notification of new threads
2698 @item @samp{thread @var{threadno}}, a command to switch among threads
2699 @item @samp{info threads}, a command to inquire about existing threads
2700 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2701 a command to apply a command to a list of threads
2702 @item thread-specific breakpoints
2703 @item @samp{set print thread-events}, which controls printing of
2704 messages on thread start and exit.
2705 @item @samp{set libthread-db-search-path @var{path}}, which lets
2706 the user specify which @code{libthread_db} to use if the default choice
2707 isn't compatible with the program.
2711 @emph{Warning:} These facilities are not yet available on every
2712 @value{GDBN} configuration where the operating system supports threads.
2713 If your @value{GDBN} does not support threads, these commands have no
2714 effect. For example, a system without thread support shows no output
2715 from @samp{info threads}, and always rejects the @code{thread} command,
2719 (@value{GDBP}) info threads
2720 (@value{GDBP}) thread 1
2721 Thread ID 1 not known. Use the "info threads" command to
2722 see the IDs of currently known threads.
2724 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2725 @c doesn't support threads"?
2728 @cindex focus of debugging
2729 @cindex current thread
2730 The @value{GDBN} thread debugging facility allows you to observe all
2731 threads while your program runs---but whenever @value{GDBN} takes
2732 control, one thread in particular is always the focus of debugging.
2733 This thread is called the @dfn{current thread}. Debugging commands show
2734 program information from the perspective of the current thread.
2736 @cindex @code{New} @var{systag} message
2737 @cindex thread identifier (system)
2738 @c FIXME-implementors!! It would be more helpful if the [New...] message
2739 @c included GDB's numeric thread handle, so you could just go to that
2740 @c thread without first checking `info threads'.
2741 Whenever @value{GDBN} detects a new thread in your program, it displays
2742 the target system's identification for the thread with a message in the
2743 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2744 whose form varies depending on the particular system. For example, on
2745 @sc{gnu}/Linux, you might see
2748 [New Thread 0x41e02940 (LWP 25582)]
2752 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2753 the @var{systag} is simply something like @samp{process 368}, with no
2756 @c FIXME!! (1) Does the [New...] message appear even for the very first
2757 @c thread of a program, or does it only appear for the
2758 @c second---i.e.@: when it becomes obvious we have a multithread
2760 @c (2) *Is* there necessarily a first thread always? Or do some
2761 @c multithread systems permit starting a program with multiple
2762 @c threads ab initio?
2764 @cindex thread number
2765 @cindex thread identifier (GDB)
2766 For debugging purposes, @value{GDBN} associates its own thread
2767 number---always a single integer---with each thread in your program.
2770 @kindex info threads
2771 @item info threads @r{[}@var{id}@dots{}@r{]}
2772 Display a summary of all threads currently in your program. Optional
2773 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2774 means to print information only about the specified thread or threads.
2775 @value{GDBN} displays for each thread (in this order):
2779 the thread number assigned by @value{GDBN}
2782 the target system's thread identifier (@var{systag})
2785 the thread's name, if one is known. A thread can either be named by
2786 the user (see @code{thread name}, below), or, in some cases, by the
2790 the current stack frame summary for that thread
2794 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2795 indicates the current thread.
2799 @c end table here to get a little more width for example
2802 (@value{GDBP}) info threads
2804 3 process 35 thread 27 0x34e5 in sigpause ()
2805 2 process 35 thread 23 0x34e5 in sigpause ()
2806 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2810 On Solaris, you can display more information about user threads with a
2811 Solaris-specific command:
2814 @item maint info sol-threads
2815 @kindex maint info sol-threads
2816 @cindex thread info (Solaris)
2817 Display info on Solaris user threads.
2821 @kindex thread @var{threadno}
2822 @item thread @var{threadno}
2823 Make thread number @var{threadno} the current thread. The command
2824 argument @var{threadno} is the internal @value{GDBN} thread number, as
2825 shown in the first field of the @samp{info threads} display.
2826 @value{GDBN} responds by displaying the system identifier of the thread
2827 you selected, and its current stack frame summary:
2830 (@value{GDBP}) thread 2
2831 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2832 #0 some_function (ignore=0x0) at example.c:8
2833 8 printf ("hello\n");
2837 As with the @samp{[New @dots{}]} message, the form of the text after
2838 @samp{Switching to} depends on your system's conventions for identifying
2841 @vindex $_thread@r{, convenience variable}
2842 The debugger convenience variable @samp{$_thread} contains the number
2843 of the current thread. You may find this useful in writing breakpoint
2844 conditional expressions, command scripts, and so forth. See
2845 @xref{Convenience Vars,, Convenience Variables}, for general
2846 information on convenience variables.
2848 @kindex thread apply
2849 @cindex apply command to several threads
2850 @item thread apply [@var{threadno} | all] @var{command}
2851 The @code{thread apply} command allows you to apply the named
2852 @var{command} to one or more threads. Specify the numbers of the
2853 threads that you want affected with the command argument
2854 @var{threadno}. It can be a single thread number, one of the numbers
2855 shown in the first field of the @samp{info threads} display; or it
2856 could be a range of thread numbers, as in @code{2-4}. To apply a
2857 command to all threads, type @kbd{thread apply all @var{command}}.
2860 @cindex name a thread
2861 @item thread name [@var{name}]
2862 This command assigns a name to the current thread. If no argument is
2863 given, any existing user-specified name is removed. The thread name
2864 appears in the @samp{info threads} display.
2866 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2867 determine the name of the thread as given by the OS. On these
2868 systems, a name specified with @samp{thread name} will override the
2869 system-give name, and removing the user-specified name will cause
2870 @value{GDBN} to once again display the system-specified name.
2873 @cindex search for a thread
2874 @item thread find [@var{regexp}]
2875 Search for and display thread ids whose name or @var{systag}
2876 matches the supplied regular expression.
2878 As well as being the complement to the @samp{thread name} command,
2879 this command also allows you to identify a thread by its target
2880 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2884 (@value{GDBN}) thread find 26688
2885 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2886 (@value{GDBN}) info thread 4
2888 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2891 @kindex set print thread-events
2892 @cindex print messages on thread start and exit
2893 @item set print thread-events
2894 @itemx set print thread-events on
2895 @itemx set print thread-events off
2896 The @code{set print thread-events} command allows you to enable or
2897 disable printing of messages when @value{GDBN} notices that new threads have
2898 started or that threads have exited. By default, these messages will
2899 be printed if detection of these events is supported by the target.
2900 Note that these messages cannot be disabled on all targets.
2902 @kindex show print thread-events
2903 @item show print thread-events
2904 Show whether messages will be printed when @value{GDBN} detects that threads
2905 have started and exited.
2908 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2909 more information about how @value{GDBN} behaves when you stop and start
2910 programs with multiple threads.
2912 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2913 watchpoints in programs with multiple threads.
2915 @anchor{set libthread-db-search-path}
2917 @kindex set libthread-db-search-path
2918 @cindex search path for @code{libthread_db}
2919 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2920 If this variable is set, @var{path} is a colon-separated list of
2921 directories @value{GDBN} will use to search for @code{libthread_db}.
2922 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2923 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2924 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2927 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2928 @code{libthread_db} library to obtain information about threads in the
2929 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2930 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2931 specific thread debugging library loading is enabled
2932 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2934 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2935 refers to the default system directories that are
2936 normally searched for loading shared libraries. The @samp{$sdir} entry
2937 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2938 (@pxref{libthread_db.so.1 file}).
2940 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2941 refers to the directory from which @code{libpthread}
2942 was loaded in the inferior process.
2944 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2945 @value{GDBN} attempts to initialize it with the current inferior process.
2946 If this initialization fails (which could happen because of a version
2947 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2948 will unload @code{libthread_db}, and continue with the next directory.
2949 If none of @code{libthread_db} libraries initialize successfully,
2950 @value{GDBN} will issue a warning and thread debugging will be disabled.
2952 Setting @code{libthread-db-search-path} is currently implemented
2953 only on some platforms.
2955 @kindex show libthread-db-search-path
2956 @item show libthread-db-search-path
2957 Display current libthread_db search path.
2959 @kindex set debug libthread-db
2960 @kindex show debug libthread-db
2961 @cindex debugging @code{libthread_db}
2962 @item set debug libthread-db
2963 @itemx show debug libthread-db
2964 Turns on or off display of @code{libthread_db}-related events.
2965 Use @code{1} to enable, @code{0} to disable.
2969 @section Debugging Forks
2971 @cindex fork, debugging programs which call
2972 @cindex multiple processes
2973 @cindex processes, multiple
2974 On most systems, @value{GDBN} has no special support for debugging
2975 programs which create additional processes using the @code{fork}
2976 function. When a program forks, @value{GDBN} will continue to debug the
2977 parent process and the child process will run unimpeded. If you have
2978 set a breakpoint in any code which the child then executes, the child
2979 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2980 will cause it to terminate.
2982 However, if you want to debug the child process there is a workaround
2983 which isn't too painful. Put a call to @code{sleep} in the code which
2984 the child process executes after the fork. It may be useful to sleep
2985 only if a certain environment variable is set, or a certain file exists,
2986 so that the delay need not occur when you don't want to run @value{GDBN}
2987 on the child. While the child is sleeping, use the @code{ps} program to
2988 get its process ID. Then tell @value{GDBN} (a new invocation of
2989 @value{GDBN} if you are also debugging the parent process) to attach to
2990 the child process (@pxref{Attach}). From that point on you can debug
2991 the child process just like any other process which you attached to.
2993 On some systems, @value{GDBN} provides support for debugging programs that
2994 create additional processes using the @code{fork} or @code{vfork} functions.
2995 Currently, the only platforms with this feature are HP-UX (11.x and later
2996 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2998 By default, when a program forks, @value{GDBN} will continue to debug
2999 the parent process and the child process will run unimpeded.
3001 If you want to follow the child process instead of the parent process,
3002 use the command @w{@code{set follow-fork-mode}}.
3005 @kindex set follow-fork-mode
3006 @item set follow-fork-mode @var{mode}
3007 Set the debugger response to a program call of @code{fork} or
3008 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3009 process. The @var{mode} argument can be:
3013 The original process is debugged after a fork. The child process runs
3014 unimpeded. This is the default.
3017 The new process is debugged after a fork. The parent process runs
3022 @kindex show follow-fork-mode
3023 @item show follow-fork-mode
3024 Display the current debugger response to a @code{fork} or @code{vfork} call.
3027 @cindex debugging multiple processes
3028 On Linux, if you want to debug both the parent and child processes, use the
3029 command @w{@code{set detach-on-fork}}.
3032 @kindex set detach-on-fork
3033 @item set detach-on-fork @var{mode}
3034 Tells gdb whether to detach one of the processes after a fork, or
3035 retain debugger control over them both.
3039 The child process (or parent process, depending on the value of
3040 @code{follow-fork-mode}) will be detached and allowed to run
3041 independently. This is the default.
3044 Both processes will be held under the control of @value{GDBN}.
3045 One process (child or parent, depending on the value of
3046 @code{follow-fork-mode}) is debugged as usual, while the other
3051 @kindex show detach-on-fork
3052 @item show detach-on-fork
3053 Show whether detach-on-fork mode is on/off.
3056 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3057 will retain control of all forked processes (including nested forks).
3058 You can list the forked processes under the control of @value{GDBN} by
3059 using the @w{@code{info inferiors}} command, and switch from one fork
3060 to another by using the @code{inferior} command (@pxref{Inferiors and
3061 Programs, ,Debugging Multiple Inferiors and Programs}).
3063 To quit debugging one of the forked processes, you can either detach
3064 from it by using the @w{@code{detach inferiors}} command (allowing it
3065 to run independently), or kill it using the @w{@code{kill inferiors}}
3066 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3069 If you ask to debug a child process and a @code{vfork} is followed by an
3070 @code{exec}, @value{GDBN} executes the new target up to the first
3071 breakpoint in the new target. If you have a breakpoint set on
3072 @code{main} in your original program, the breakpoint will also be set on
3073 the child process's @code{main}.
3075 On some systems, when a child process is spawned by @code{vfork}, you
3076 cannot debug the child or parent until an @code{exec} call completes.
3078 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3079 call executes, the new target restarts. To restart the parent
3080 process, use the @code{file} command with the parent executable name
3081 as its argument. By default, after an @code{exec} call executes,
3082 @value{GDBN} discards the symbols of the previous executable image.
3083 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3087 @kindex set follow-exec-mode
3088 @item set follow-exec-mode @var{mode}
3090 Set debugger response to a program call of @code{exec}. An
3091 @code{exec} call replaces the program image of a process.
3093 @code{follow-exec-mode} can be:
3097 @value{GDBN} creates a new inferior and rebinds the process to this
3098 new inferior. The program the process was running before the
3099 @code{exec} call can be restarted afterwards by restarting the
3105 (@value{GDBP}) info inferiors
3107 Id Description Executable
3110 process 12020 is executing new program: prog2
3111 Program exited normally.
3112 (@value{GDBP}) info inferiors
3113 Id Description Executable
3119 @value{GDBN} keeps the process bound to the same inferior. The new
3120 executable image replaces the previous executable loaded in the
3121 inferior. Restarting the inferior after the @code{exec} call, with
3122 e.g., the @code{run} command, restarts the executable the process was
3123 running after the @code{exec} call. This is the default mode.
3128 (@value{GDBP}) info inferiors
3129 Id Description Executable
3132 process 12020 is executing new program: prog2
3133 Program exited normally.
3134 (@value{GDBP}) info inferiors
3135 Id Description Executable
3142 You can use the @code{catch} command to make @value{GDBN} stop whenever
3143 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3144 Catchpoints, ,Setting Catchpoints}.
3146 @node Checkpoint/Restart
3147 @section Setting a @emph{Bookmark} to Return to Later
3152 @cindex snapshot of a process
3153 @cindex rewind program state
3155 On certain operating systems@footnote{Currently, only
3156 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3157 program's state, called a @dfn{checkpoint}, and come back to it
3160 Returning to a checkpoint effectively undoes everything that has
3161 happened in the program since the @code{checkpoint} was saved. This
3162 includes changes in memory, registers, and even (within some limits)
3163 system state. Effectively, it is like going back in time to the
3164 moment when the checkpoint was saved.
3166 Thus, if you're stepping thru a program and you think you're
3167 getting close to the point where things go wrong, you can save
3168 a checkpoint. Then, if you accidentally go too far and miss
3169 the critical statement, instead of having to restart your program
3170 from the beginning, you can just go back to the checkpoint and
3171 start again from there.
3173 This can be especially useful if it takes a lot of time or
3174 steps to reach the point where you think the bug occurs.
3176 To use the @code{checkpoint}/@code{restart} method of debugging:
3181 Save a snapshot of the debugged program's current execution state.
3182 The @code{checkpoint} command takes no arguments, but each checkpoint
3183 is assigned a small integer id, similar to a breakpoint id.
3185 @kindex info checkpoints
3186 @item info checkpoints
3187 List the checkpoints that have been saved in the current debugging
3188 session. For each checkpoint, the following information will be
3195 @item Source line, or label
3198 @kindex restart @var{checkpoint-id}
3199 @item restart @var{checkpoint-id}
3200 Restore the program state that was saved as checkpoint number
3201 @var{checkpoint-id}. All program variables, registers, stack frames
3202 etc.@: will be returned to the values that they had when the checkpoint
3203 was saved. In essence, gdb will ``wind back the clock'' to the point
3204 in time when the checkpoint was saved.
3206 Note that breakpoints, @value{GDBN} variables, command history etc.
3207 are not affected by restoring a checkpoint. In general, a checkpoint
3208 only restores things that reside in the program being debugged, not in
3211 @kindex delete checkpoint @var{checkpoint-id}
3212 @item delete checkpoint @var{checkpoint-id}
3213 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3217 Returning to a previously saved checkpoint will restore the user state
3218 of the program being debugged, plus a significant subset of the system
3219 (OS) state, including file pointers. It won't ``un-write'' data from
3220 a file, but it will rewind the file pointer to the previous location,
3221 so that the previously written data can be overwritten. For files
3222 opened in read mode, the pointer will also be restored so that the
3223 previously read data can be read again.
3225 Of course, characters that have been sent to a printer (or other
3226 external device) cannot be ``snatched back'', and characters received
3227 from eg.@: a serial device can be removed from internal program buffers,
3228 but they cannot be ``pushed back'' into the serial pipeline, ready to
3229 be received again. Similarly, the actual contents of files that have
3230 been changed cannot be restored (at this time).
3232 However, within those constraints, you actually can ``rewind'' your
3233 program to a previously saved point in time, and begin debugging it
3234 again --- and you can change the course of events so as to debug a
3235 different execution path this time.
3237 @cindex checkpoints and process id
3238 Finally, there is one bit of internal program state that will be
3239 different when you return to a checkpoint --- the program's process
3240 id. Each checkpoint will have a unique process id (or @var{pid}),
3241 and each will be different from the program's original @var{pid}.
3242 If your program has saved a local copy of its process id, this could
3243 potentially pose a problem.
3245 @subsection A Non-obvious Benefit of Using Checkpoints
3247 On some systems such as @sc{gnu}/Linux, address space randomization
3248 is performed on new processes for security reasons. This makes it
3249 difficult or impossible to set a breakpoint, or watchpoint, on an
3250 absolute address if you have to restart the program, since the
3251 absolute location of a symbol will change from one execution to the
3254 A checkpoint, however, is an @emph{identical} copy of a process.
3255 Therefore if you create a checkpoint at (eg.@:) the start of main,
3256 and simply return to that checkpoint instead of restarting the
3257 process, you can avoid the effects of address randomization and
3258 your symbols will all stay in the same place.
3261 @chapter Stopping and Continuing
3263 The principal purposes of using a debugger are so that you can stop your
3264 program before it terminates; or so that, if your program runs into
3265 trouble, you can investigate and find out why.
3267 Inside @value{GDBN}, your program may stop for any of several reasons,
3268 such as a signal, a breakpoint, or reaching a new line after a
3269 @value{GDBN} command such as @code{step}. You may then examine and
3270 change variables, set new breakpoints or remove old ones, and then
3271 continue execution. Usually, the messages shown by @value{GDBN} provide
3272 ample explanation of the status of your program---but you can also
3273 explicitly request this information at any time.
3276 @kindex info program
3278 Display information about the status of your program: whether it is
3279 running or not, what process it is, and why it stopped.
3283 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3284 * Continuing and Stepping:: Resuming execution
3285 * Skipping Over Functions and Files::
3286 Skipping over functions and files
3288 * Thread Stops:: Stopping and starting multi-thread programs
3292 @section Breakpoints, Watchpoints, and Catchpoints
3295 A @dfn{breakpoint} makes your program stop whenever a certain point in
3296 the program is reached. For each breakpoint, you can add conditions to
3297 control in finer detail whether your program stops. You can set
3298 breakpoints with the @code{break} command and its variants (@pxref{Set
3299 Breaks, ,Setting Breakpoints}), to specify the place where your program
3300 should stop by line number, function name or exact address in the
3303 On some systems, you can set breakpoints in shared libraries before
3304 the executable is run. There is a minor limitation on HP-UX systems:
3305 you must wait until the executable is run in order to set breakpoints
3306 in shared library routines that are not called directly by the program
3307 (for example, routines that are arguments in a @code{pthread_create}
3311 @cindex data breakpoints
3312 @cindex memory tracing
3313 @cindex breakpoint on memory address
3314 @cindex breakpoint on variable modification
3315 A @dfn{watchpoint} is a special breakpoint that stops your program
3316 when the value of an expression changes. The expression may be a value
3317 of a variable, or it could involve values of one or more variables
3318 combined by operators, such as @samp{a + b}. This is sometimes called
3319 @dfn{data breakpoints}. You must use a different command to set
3320 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3321 from that, you can manage a watchpoint like any other breakpoint: you
3322 enable, disable, and delete both breakpoints and watchpoints using the
3325 You can arrange to have values from your program displayed automatically
3326 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3330 @cindex breakpoint on events
3331 A @dfn{catchpoint} is another special breakpoint that stops your program
3332 when a certain kind of event occurs, such as the throwing of a C@t{++}
3333 exception or the loading of a library. As with watchpoints, you use a
3334 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3335 Catchpoints}), but aside from that, you can manage a catchpoint like any
3336 other breakpoint. (To stop when your program receives a signal, use the
3337 @code{handle} command; see @ref{Signals, ,Signals}.)
3339 @cindex breakpoint numbers
3340 @cindex numbers for breakpoints
3341 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3342 catchpoint when you create it; these numbers are successive integers
3343 starting with one. In many of the commands for controlling various
3344 features of breakpoints you use the breakpoint number to say which
3345 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3346 @dfn{disabled}; if disabled, it has no effect on your program until you
3349 @cindex breakpoint ranges
3350 @cindex ranges of breakpoints
3351 Some @value{GDBN} commands accept a range of breakpoints on which to
3352 operate. A breakpoint range is either a single breakpoint number, like
3353 @samp{5}, or two such numbers, in increasing order, separated by a
3354 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3355 all breakpoints in that range are operated on.
3358 * Set Breaks:: Setting breakpoints
3359 * Set Watchpoints:: Setting watchpoints
3360 * Set Catchpoints:: Setting catchpoints
3361 * Delete Breaks:: Deleting breakpoints
3362 * Disabling:: Disabling breakpoints
3363 * Conditions:: Break conditions
3364 * Break Commands:: Breakpoint command lists
3365 * Dynamic Printf:: Dynamic printf
3366 * Save Breakpoints:: How to save breakpoints in a file
3367 * Static Probe Points:: Listing static probe points
3368 * Error in Breakpoints:: ``Cannot insert breakpoints''
3369 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3373 @subsection Setting Breakpoints
3375 @c FIXME LMB what does GDB do if no code on line of breakpt?
3376 @c consider in particular declaration with/without initialization.
3378 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3381 @kindex b @r{(@code{break})}
3382 @vindex $bpnum@r{, convenience variable}
3383 @cindex latest breakpoint
3384 Breakpoints are set with the @code{break} command (abbreviated
3385 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3386 number of the breakpoint you've set most recently; see @ref{Convenience
3387 Vars,, Convenience Variables}, for a discussion of what you can do with
3388 convenience variables.
3391 @item break @var{location}
3392 Set a breakpoint at the given @var{location}, which can specify a
3393 function name, a line number, or an address of an instruction.
3394 (@xref{Specify Location}, for a list of all the possible ways to
3395 specify a @var{location}.) The breakpoint will stop your program just
3396 before it executes any of the code in the specified @var{location}.
3398 When using source languages that permit overloading of symbols, such as
3399 C@t{++}, a function name may refer to more than one possible place to break.
3400 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3403 It is also possible to insert a breakpoint that will stop the program
3404 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3405 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3408 When called without any arguments, @code{break} sets a breakpoint at
3409 the next instruction to be executed in the selected stack frame
3410 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3411 innermost, this makes your program stop as soon as control
3412 returns to that frame. This is similar to the effect of a
3413 @code{finish} command in the frame inside the selected frame---except
3414 that @code{finish} does not leave an active breakpoint. If you use
3415 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3416 the next time it reaches the current location; this may be useful
3419 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3420 least one instruction has been executed. If it did not do this, you
3421 would be unable to proceed past a breakpoint without first disabling the
3422 breakpoint. This rule applies whether or not the breakpoint already
3423 existed when your program stopped.
3425 @item break @dots{} if @var{cond}
3426 Set a breakpoint with condition @var{cond}; evaluate the expression
3427 @var{cond} each time the breakpoint is reached, and stop only if the
3428 value is nonzero---that is, if @var{cond} evaluates as true.
3429 @samp{@dots{}} stands for one of the possible arguments described
3430 above (or no argument) specifying where to break. @xref{Conditions,
3431 ,Break Conditions}, for more information on breakpoint conditions.
3434 @item tbreak @var{args}
3435 Set a breakpoint enabled only for one stop. @var{args} are the
3436 same as for the @code{break} command, and the breakpoint is set in the same
3437 way, but the breakpoint is automatically deleted after the first time your
3438 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3441 @cindex hardware breakpoints
3442 @item hbreak @var{args}
3443 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3444 @code{break} command and the breakpoint is set in the same way, but the
3445 breakpoint requires hardware support and some target hardware may not
3446 have this support. The main purpose of this is EPROM/ROM code
3447 debugging, so you can set a breakpoint at an instruction without
3448 changing the instruction. This can be used with the new trap-generation
3449 provided by SPARClite DSU and most x86-based targets. These targets
3450 will generate traps when a program accesses some data or instruction
3451 address that is assigned to the debug registers. However the hardware
3452 breakpoint registers can take a limited number of breakpoints. For
3453 example, on the DSU, only two data breakpoints can be set at a time, and
3454 @value{GDBN} will reject this command if more than two are used. Delete
3455 or disable unused hardware breakpoints before setting new ones
3456 (@pxref{Disabling, ,Disabling Breakpoints}).
3457 @xref{Conditions, ,Break Conditions}.
3458 For remote targets, you can restrict the number of hardware
3459 breakpoints @value{GDBN} will use, see @ref{set remote
3460 hardware-breakpoint-limit}.
3463 @item thbreak @var{args}
3464 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3465 are the same as for the @code{hbreak} command and the breakpoint is set in
3466 the same way. However, like the @code{tbreak} command,
3467 the breakpoint is automatically deleted after the
3468 first time your program stops there. Also, like the @code{hbreak}
3469 command, the breakpoint requires hardware support and some target hardware
3470 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3471 See also @ref{Conditions, ,Break Conditions}.
3474 @cindex regular expression
3475 @cindex breakpoints at functions matching a regexp
3476 @cindex set breakpoints in many functions
3477 @item rbreak @var{regex}
3478 Set breakpoints on all functions matching the regular expression
3479 @var{regex}. This command sets an unconditional breakpoint on all
3480 matches, printing a list of all breakpoints it set. Once these
3481 breakpoints are set, they are treated just like the breakpoints set with
3482 the @code{break} command. You can delete them, disable them, or make
3483 them conditional the same way as any other breakpoint.
3485 The syntax of the regular expression is the standard one used with tools
3486 like @file{grep}. Note that this is different from the syntax used by
3487 shells, so for instance @code{foo*} matches all functions that include
3488 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3489 @code{.*} leading and trailing the regular expression you supply, so to
3490 match only functions that begin with @code{foo}, use @code{^foo}.
3492 @cindex non-member C@t{++} functions, set breakpoint in
3493 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3494 breakpoints on overloaded functions that are not members of any special
3497 @cindex set breakpoints on all functions
3498 The @code{rbreak} command can be used to set breakpoints in
3499 @strong{all} the functions in a program, like this:
3502 (@value{GDBP}) rbreak .
3505 @item rbreak @var{file}:@var{regex}
3506 If @code{rbreak} is called with a filename qualification, it limits
3507 the search for functions matching the given regular expression to the
3508 specified @var{file}. This can be used, for example, to set breakpoints on
3509 every function in a given file:
3512 (@value{GDBP}) rbreak file.c:.
3515 The colon separating the filename qualifier from the regex may
3516 optionally be surrounded by spaces.
3518 @kindex info breakpoints
3519 @cindex @code{$_} and @code{info breakpoints}
3520 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3521 @itemx info break @r{[}@var{n}@dots{}@r{]}
3522 Print a table of all breakpoints, watchpoints, and catchpoints set and
3523 not deleted. Optional argument @var{n} means print information only
3524 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3525 For each breakpoint, following columns are printed:
3528 @item Breakpoint Numbers
3530 Breakpoint, watchpoint, or catchpoint.
3532 Whether the breakpoint is marked to be disabled or deleted when hit.
3533 @item Enabled or Disabled
3534 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3535 that are not enabled.
3537 Where the breakpoint is in your program, as a memory address. For a
3538 pending breakpoint whose address is not yet known, this field will
3539 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3540 library that has the symbol or line referred by breakpoint is loaded.
3541 See below for details. A breakpoint with several locations will
3542 have @samp{<MULTIPLE>} in this field---see below for details.
3544 Where the breakpoint is in the source for your program, as a file and
3545 line number. For a pending breakpoint, the original string passed to
3546 the breakpoint command will be listed as it cannot be resolved until
3547 the appropriate shared library is loaded in the future.
3551 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3552 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3553 @value{GDBN} on the host's side. If it is ``target'', then the condition
3554 is evaluated by the target. The @code{info break} command shows
3555 the condition on the line following the affected breakpoint, together with
3556 its condition evaluation mode in between parentheses.
3558 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3559 allowed to have a condition specified for it. The condition is not parsed for
3560 validity until a shared library is loaded that allows the pending
3561 breakpoint to resolve to a valid location.
3564 @code{info break} with a breakpoint
3565 number @var{n} as argument lists only that breakpoint. The
3566 convenience variable @code{$_} and the default examining-address for
3567 the @code{x} command are set to the address of the last breakpoint
3568 listed (@pxref{Memory, ,Examining Memory}).
3571 @code{info break} displays a count of the number of times the breakpoint
3572 has been hit. This is especially useful in conjunction with the
3573 @code{ignore} command. You can ignore a large number of breakpoint
3574 hits, look at the breakpoint info to see how many times the breakpoint
3575 was hit, and then run again, ignoring one less than that number. This
3576 will get you quickly to the last hit of that breakpoint.
3579 For a breakpoints with an enable count (xref) greater than 1,
3580 @code{info break} also displays that count.
3584 @value{GDBN} allows you to set any number of breakpoints at the same place in
3585 your program. There is nothing silly or meaningless about this. When
3586 the breakpoints are conditional, this is even useful
3587 (@pxref{Conditions, ,Break Conditions}).
3589 @cindex multiple locations, breakpoints
3590 @cindex breakpoints, multiple locations
3591 It is possible that a breakpoint corresponds to several locations
3592 in your program. Examples of this situation are:
3596 Multiple functions in the program may have the same name.
3599 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3600 instances of the function body, used in different cases.
3603 For a C@t{++} template function, a given line in the function can
3604 correspond to any number of instantiations.
3607 For an inlined function, a given source line can correspond to
3608 several places where that function is inlined.
3611 In all those cases, @value{GDBN} will insert a breakpoint at all
3612 the relevant locations.
3614 A breakpoint with multiple locations is displayed in the breakpoint
3615 table using several rows---one header row, followed by one row for
3616 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3617 address column. The rows for individual locations contain the actual
3618 addresses for locations, and show the functions to which those
3619 locations belong. The number column for a location is of the form
3620 @var{breakpoint-number}.@var{location-number}.
3625 Num Type Disp Enb Address What
3626 1 breakpoint keep y <MULTIPLE>
3628 breakpoint already hit 1 time
3629 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3630 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3633 Each location can be individually enabled or disabled by passing
3634 @var{breakpoint-number}.@var{location-number} as argument to the
3635 @code{enable} and @code{disable} commands. Note that you cannot
3636 delete the individual locations from the list, you can only delete the
3637 entire list of locations that belong to their parent breakpoint (with
3638 the @kbd{delete @var{num}} command, where @var{num} is the number of
3639 the parent breakpoint, 1 in the above example). Disabling or enabling
3640 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3641 that belong to that breakpoint.
3643 @cindex pending breakpoints
3644 It's quite common to have a breakpoint inside a shared library.
3645 Shared libraries can be loaded and unloaded explicitly,
3646 and possibly repeatedly, as the program is executed. To support
3647 this use case, @value{GDBN} updates breakpoint locations whenever
3648 any shared library is loaded or unloaded. Typically, you would
3649 set a breakpoint in a shared library at the beginning of your
3650 debugging session, when the library is not loaded, and when the
3651 symbols from the library are not available. When you try to set
3652 breakpoint, @value{GDBN} will ask you if you want to set
3653 a so called @dfn{pending breakpoint}---breakpoint whose address
3654 is not yet resolved.
3656 After the program is run, whenever a new shared library is loaded,
3657 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3658 shared library contains the symbol or line referred to by some
3659 pending breakpoint, that breakpoint is resolved and becomes an
3660 ordinary breakpoint. When a library is unloaded, all breakpoints
3661 that refer to its symbols or source lines become pending again.
3663 This logic works for breakpoints with multiple locations, too. For
3664 example, if you have a breakpoint in a C@t{++} template function, and
3665 a newly loaded shared library has an instantiation of that template,
3666 a new location is added to the list of locations for the breakpoint.
3668 Except for having unresolved address, pending breakpoints do not
3669 differ from regular breakpoints. You can set conditions or commands,
3670 enable and disable them and perform other breakpoint operations.
3672 @value{GDBN} provides some additional commands for controlling what
3673 happens when the @samp{break} command cannot resolve breakpoint
3674 address specification to an address:
3676 @kindex set breakpoint pending
3677 @kindex show breakpoint pending
3679 @item set breakpoint pending auto
3680 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3681 location, it queries you whether a pending breakpoint should be created.
3683 @item set breakpoint pending on
3684 This indicates that an unrecognized breakpoint location should automatically
3685 result in a pending breakpoint being created.
3687 @item set breakpoint pending off
3688 This indicates that pending breakpoints are not to be created. Any
3689 unrecognized breakpoint location results in an error. This setting does
3690 not affect any pending breakpoints previously created.
3692 @item show breakpoint pending
3693 Show the current behavior setting for creating pending breakpoints.
3696 The settings above only affect the @code{break} command and its
3697 variants. Once breakpoint is set, it will be automatically updated
3698 as shared libraries are loaded and unloaded.
3700 @cindex automatic hardware breakpoints
3701 For some targets, @value{GDBN} can automatically decide if hardware or
3702 software breakpoints should be used, depending on whether the
3703 breakpoint address is read-only or read-write. This applies to
3704 breakpoints set with the @code{break} command as well as to internal
3705 breakpoints set by commands like @code{next} and @code{finish}. For
3706 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3709 You can control this automatic behaviour with the following commands::
3711 @kindex set breakpoint auto-hw
3712 @kindex show breakpoint auto-hw
3714 @item set breakpoint auto-hw on
3715 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3716 will try to use the target memory map to decide if software or hardware
3717 breakpoint must be used.
3719 @item set breakpoint auto-hw off
3720 This indicates @value{GDBN} should not automatically select breakpoint
3721 type. If the target provides a memory map, @value{GDBN} will warn when
3722 trying to set software breakpoint at a read-only address.
3725 @value{GDBN} normally implements breakpoints by replacing the program code
3726 at the breakpoint address with a special instruction, which, when
3727 executed, given control to the debugger. By default, the program
3728 code is so modified only when the program is resumed. As soon as
3729 the program stops, @value{GDBN} restores the original instructions. This
3730 behaviour guards against leaving breakpoints inserted in the
3731 target should gdb abrubptly disconnect. However, with slow remote
3732 targets, inserting and removing breakpoint can reduce the performance.
3733 This behavior can be controlled with the following commands::
3735 @kindex set breakpoint always-inserted
3736 @kindex show breakpoint always-inserted
3738 @item set breakpoint always-inserted off
3739 All breakpoints, including newly added by the user, are inserted in
3740 the target only when the target is resumed. All breakpoints are
3741 removed from the target when it stops.
3743 @item set breakpoint always-inserted on
3744 Causes all breakpoints to be inserted in the target at all times. If
3745 the user adds a new breakpoint, or changes an existing breakpoint, the
3746 breakpoints in the target are updated immediately. A breakpoint is
3747 removed from the target only when breakpoint itself is removed.
3749 @cindex non-stop mode, and @code{breakpoint always-inserted}
3750 @item set breakpoint always-inserted auto
3751 This is the default mode. If @value{GDBN} is controlling the inferior
3752 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3753 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3754 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3755 @code{breakpoint always-inserted} mode is off.
3758 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3759 when a breakpoint breaks. If the condition is true, then the process being
3760 debugged stops, otherwise the process is resumed.
3762 If the target supports evaluating conditions on its end, @value{GDBN} may
3763 download the breakpoint, together with its conditions, to it.
3765 This feature can be controlled via the following commands:
3767 @kindex set breakpoint condition-evaluation
3768 @kindex show breakpoint condition-evaluation
3770 @item set breakpoint condition-evaluation host
3771 This option commands @value{GDBN} to evaluate the breakpoint
3772 conditions on the host's side. Unconditional breakpoints are sent to
3773 the target which in turn receives the triggers and reports them back to GDB
3774 for condition evaluation. This is the standard evaluation mode.
3776 @item set breakpoint condition-evaluation target
3777 This option commands @value{GDBN} to download breakpoint conditions
3778 to the target at the moment of their insertion. The target
3779 is responsible for evaluating the conditional expression and reporting
3780 breakpoint stop events back to @value{GDBN} whenever the condition
3781 is true. Due to limitations of target-side evaluation, some conditions
3782 cannot be evaluated there, e.g., conditions that depend on local data
3783 that is only known to the host. Examples include
3784 conditional expressions involving convenience variables, complex types
3785 that cannot be handled by the agent expression parser and expressions
3786 that are too long to be sent over to the target, specially when the
3787 target is a remote system. In these cases, the conditions will be
3788 evaluated by @value{GDBN}.
3790 @item set breakpoint condition-evaluation auto
3791 This is the default mode. If the target supports evaluating breakpoint
3792 conditions on its end, @value{GDBN} will download breakpoint conditions to
3793 the target (limitations mentioned previously apply). If the target does
3794 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3795 to evaluating all these conditions on the host's side.
3799 @cindex negative breakpoint numbers
3800 @cindex internal @value{GDBN} breakpoints
3801 @value{GDBN} itself sometimes sets breakpoints in your program for
3802 special purposes, such as proper handling of @code{longjmp} (in C
3803 programs). These internal breakpoints are assigned negative numbers,
3804 starting with @code{-1}; @samp{info breakpoints} does not display them.
3805 You can see these breakpoints with the @value{GDBN} maintenance command
3806 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3809 @node Set Watchpoints
3810 @subsection Setting Watchpoints
3812 @cindex setting watchpoints
3813 You can use a watchpoint to stop execution whenever the value of an
3814 expression changes, without having to predict a particular place where
3815 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3816 The expression may be as simple as the value of a single variable, or
3817 as complex as many variables combined by operators. Examples include:
3821 A reference to the value of a single variable.
3824 An address cast to an appropriate data type. For example,
3825 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3826 address (assuming an @code{int} occupies 4 bytes).
3829 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3830 expression can use any operators valid in the program's native
3831 language (@pxref{Languages}).
3834 You can set a watchpoint on an expression even if the expression can
3835 not be evaluated yet. For instance, you can set a watchpoint on
3836 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3837 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3838 the expression produces a valid value. If the expression becomes
3839 valid in some other way than changing a variable (e.g.@: if the memory
3840 pointed to by @samp{*global_ptr} becomes readable as the result of a
3841 @code{malloc} call), @value{GDBN} may not stop until the next time
3842 the expression changes.
3844 @cindex software watchpoints
3845 @cindex hardware watchpoints
3846 Depending on your system, watchpoints may be implemented in software or
3847 hardware. @value{GDBN} does software watchpointing by single-stepping your
3848 program and testing the variable's value each time, which is hundreds of
3849 times slower than normal execution. (But this may still be worth it, to
3850 catch errors where you have no clue what part of your program is the
3853 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3854 x86-based targets, @value{GDBN} includes support for hardware
3855 watchpoints, which do not slow down the running of your program.
3859 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3860 Set a watchpoint for an expression. @value{GDBN} will break when the
3861 expression @var{expr} is written into by the program and its value
3862 changes. The simplest (and the most popular) use of this command is
3863 to watch the value of a single variable:
3866 (@value{GDBP}) watch foo
3869 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3870 argument, @value{GDBN} breaks only when the thread identified by
3871 @var{threadnum} changes the value of @var{expr}. If any other threads
3872 change the value of @var{expr}, @value{GDBN} will not break. Note
3873 that watchpoints restricted to a single thread in this way only work
3874 with Hardware Watchpoints.
3876 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3877 (see below). The @code{-location} argument tells @value{GDBN} to
3878 instead watch the memory referred to by @var{expr}. In this case,
3879 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3880 and watch the memory at that address. The type of the result is used
3881 to determine the size of the watched memory. If the expression's
3882 result does not have an address, then @value{GDBN} will print an
3885 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3886 of masked watchpoints, if the current architecture supports this
3887 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3888 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3889 to an address to watch. The mask specifies that some bits of an address
3890 (the bits which are reset in the mask) should be ignored when matching
3891 the address accessed by the inferior against the watchpoint address.
3892 Thus, a masked watchpoint watches many addresses simultaneously---those
3893 addresses whose unmasked bits are identical to the unmasked bits in the
3894 watchpoint address. The @code{mask} argument implies @code{-location}.
3898 (@value{GDBP}) watch foo mask 0xffff00ff
3899 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3903 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3904 Set a watchpoint that will break when the value of @var{expr} is read
3908 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3909 Set a watchpoint that will break when @var{expr} is either read from
3910 or written into by the program.
3912 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3913 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3914 This command prints a list of watchpoints, using the same format as
3915 @code{info break} (@pxref{Set Breaks}).
3918 If you watch for a change in a numerically entered address you need to
3919 dereference it, as the address itself is just a constant number which will
3920 never change. @value{GDBN} refuses to create a watchpoint that watches
3921 a never-changing value:
3924 (@value{GDBP}) watch 0x600850
3925 Cannot watch constant value 0x600850.
3926 (@value{GDBP}) watch *(int *) 0x600850
3927 Watchpoint 1: *(int *) 6293584
3930 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3931 watchpoints execute very quickly, and the debugger reports a change in
3932 value at the exact instruction where the change occurs. If @value{GDBN}
3933 cannot set a hardware watchpoint, it sets a software watchpoint, which
3934 executes more slowly and reports the change in value at the next
3935 @emph{statement}, not the instruction, after the change occurs.
3937 @cindex use only software watchpoints
3938 You can force @value{GDBN} to use only software watchpoints with the
3939 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3940 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3941 the underlying system supports them. (Note that hardware-assisted
3942 watchpoints that were set @emph{before} setting
3943 @code{can-use-hw-watchpoints} to zero will still use the hardware
3944 mechanism of watching expression values.)
3947 @item set can-use-hw-watchpoints
3948 @kindex set can-use-hw-watchpoints
3949 Set whether or not to use hardware watchpoints.
3951 @item show can-use-hw-watchpoints
3952 @kindex show can-use-hw-watchpoints
3953 Show the current mode of using hardware watchpoints.
3956 For remote targets, you can restrict the number of hardware
3957 watchpoints @value{GDBN} will use, see @ref{set remote
3958 hardware-breakpoint-limit}.
3960 When you issue the @code{watch} command, @value{GDBN} reports
3963 Hardware watchpoint @var{num}: @var{expr}
3967 if it was able to set a hardware watchpoint.
3969 Currently, the @code{awatch} and @code{rwatch} commands can only set
3970 hardware watchpoints, because accesses to data that don't change the
3971 value of the watched expression cannot be detected without examining
3972 every instruction as it is being executed, and @value{GDBN} does not do
3973 that currently. If @value{GDBN} finds that it is unable to set a
3974 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3975 will print a message like this:
3978 Expression cannot be implemented with read/access watchpoint.
3981 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3982 data type of the watched expression is wider than what a hardware
3983 watchpoint on the target machine can handle. For example, some systems
3984 can only watch regions that are up to 4 bytes wide; on such systems you
3985 cannot set hardware watchpoints for an expression that yields a
3986 double-precision floating-point number (which is typically 8 bytes
3987 wide). As a work-around, it might be possible to break the large region
3988 into a series of smaller ones and watch them with separate watchpoints.
3990 If you set too many hardware watchpoints, @value{GDBN} might be unable
3991 to insert all of them when you resume the execution of your program.
3992 Since the precise number of active watchpoints is unknown until such
3993 time as the program is about to be resumed, @value{GDBN} might not be
3994 able to warn you about this when you set the watchpoints, and the
3995 warning will be printed only when the program is resumed:
3998 Hardware watchpoint @var{num}: Could not insert watchpoint
4002 If this happens, delete or disable some of the watchpoints.
4004 Watching complex expressions that reference many variables can also
4005 exhaust the resources available for hardware-assisted watchpoints.
4006 That's because @value{GDBN} needs to watch every variable in the
4007 expression with separately allocated resources.
4009 If you call a function interactively using @code{print} or @code{call},
4010 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4011 kind of breakpoint or the call completes.
4013 @value{GDBN} automatically deletes watchpoints that watch local
4014 (automatic) variables, or expressions that involve such variables, when
4015 they go out of scope, that is, when the execution leaves the block in
4016 which these variables were defined. In particular, when the program
4017 being debugged terminates, @emph{all} local variables go out of scope,
4018 and so only watchpoints that watch global variables remain set. If you
4019 rerun the program, you will need to set all such watchpoints again. One
4020 way of doing that would be to set a code breakpoint at the entry to the
4021 @code{main} function and when it breaks, set all the watchpoints.
4023 @cindex watchpoints and threads
4024 @cindex threads and watchpoints
4025 In multi-threaded programs, watchpoints will detect changes to the
4026 watched expression from every thread.
4029 @emph{Warning:} In multi-threaded programs, software watchpoints
4030 have only limited usefulness. If @value{GDBN} creates a software
4031 watchpoint, it can only watch the value of an expression @emph{in a
4032 single thread}. If you are confident that the expression can only
4033 change due to the current thread's activity (and if you are also
4034 confident that no other thread can become current), then you can use
4035 software watchpoints as usual. However, @value{GDBN} may not notice
4036 when a non-current thread's activity changes the expression. (Hardware
4037 watchpoints, in contrast, watch an expression in all threads.)
4040 @xref{set remote hardware-watchpoint-limit}.
4042 @node Set Catchpoints
4043 @subsection Setting Catchpoints
4044 @cindex catchpoints, setting
4045 @cindex exception handlers
4046 @cindex event handling
4048 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4049 kinds of program events, such as C@t{++} exceptions or the loading of a
4050 shared library. Use the @code{catch} command to set a catchpoint.
4054 @item catch @var{event}
4055 Stop when @var{event} occurs. @var{event} can be any of the following:
4058 @cindex stop on C@t{++} exceptions
4059 The throwing of a C@t{++} exception.
4062 The catching of a C@t{++} exception.
4065 @cindex Ada exception catching
4066 @cindex catch Ada exceptions
4067 An Ada exception being raised. If an exception name is specified
4068 at the end of the command (eg @code{catch exception Program_Error}),
4069 the debugger will stop only when this specific exception is raised.
4070 Otherwise, the debugger stops execution when any Ada exception is raised.
4072 When inserting an exception catchpoint on a user-defined exception whose
4073 name is identical to one of the exceptions defined by the language, the
4074 fully qualified name must be used as the exception name. Otherwise,
4075 @value{GDBN} will assume that it should stop on the pre-defined exception
4076 rather than the user-defined one. For instance, assuming an exception
4077 called @code{Constraint_Error} is defined in package @code{Pck}, then
4078 the command to use to catch such exceptions is @kbd{catch exception
4079 Pck.Constraint_Error}.
4081 @item exception unhandled
4082 An exception that was raised but is not handled by the program.
4085 A failed Ada assertion.
4088 @cindex break on fork/exec
4089 A call to @code{exec}. This is currently only available for HP-UX
4093 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4094 @cindex break on a system call.
4095 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4096 syscall is a mechanism for application programs to request a service
4097 from the operating system (OS) or one of the OS system services.
4098 @value{GDBN} can catch some or all of the syscalls issued by the
4099 debuggee, and show the related information for each syscall. If no
4100 argument is specified, calls to and returns from all system calls
4103 @var{name} can be any system call name that is valid for the
4104 underlying OS. Just what syscalls are valid depends on the OS. On
4105 GNU and Unix systems, you can find the full list of valid syscall
4106 names on @file{/usr/include/asm/unistd.h}.
4108 @c For MS-Windows, the syscall names and the corresponding numbers
4109 @c can be found, e.g., on this URL:
4110 @c http://www.metasploit.com/users/opcode/syscalls.html
4111 @c but we don't support Windows syscalls yet.
4113 Normally, @value{GDBN} knows in advance which syscalls are valid for
4114 each OS, so you can use the @value{GDBN} command-line completion
4115 facilities (@pxref{Completion,, command completion}) to list the
4118 You may also specify the system call numerically. A syscall's
4119 number is the value passed to the OS's syscall dispatcher to
4120 identify the requested service. When you specify the syscall by its
4121 name, @value{GDBN} uses its database of syscalls to convert the name
4122 into the corresponding numeric code, but using the number directly
4123 may be useful if @value{GDBN}'s database does not have the complete
4124 list of syscalls on your system (e.g., because @value{GDBN} lags
4125 behind the OS upgrades).
4127 The example below illustrates how this command works if you don't provide
4131 (@value{GDBP}) catch syscall
4132 Catchpoint 1 (syscall)
4134 Starting program: /tmp/catch-syscall
4136 Catchpoint 1 (call to syscall 'close'), \
4137 0xffffe424 in __kernel_vsyscall ()
4141 Catchpoint 1 (returned from syscall 'close'), \
4142 0xffffe424 in __kernel_vsyscall ()
4146 Here is an example of catching a system call by name:
4149 (@value{GDBP}) catch syscall chroot
4150 Catchpoint 1 (syscall 'chroot' [61])
4152 Starting program: /tmp/catch-syscall
4154 Catchpoint 1 (call to syscall 'chroot'), \
4155 0xffffe424 in __kernel_vsyscall ()
4159 Catchpoint 1 (returned from syscall 'chroot'), \
4160 0xffffe424 in __kernel_vsyscall ()
4164 An example of specifying a system call numerically. In the case
4165 below, the syscall number has a corresponding entry in the XML
4166 file, so @value{GDBN} finds its name and prints it:
4169 (@value{GDBP}) catch syscall 252
4170 Catchpoint 1 (syscall(s) 'exit_group')
4172 Starting program: /tmp/catch-syscall
4174 Catchpoint 1 (call to syscall 'exit_group'), \
4175 0xffffe424 in __kernel_vsyscall ()
4179 Program exited normally.
4183 However, there can be situations when there is no corresponding name
4184 in XML file for that syscall number. In this case, @value{GDBN} prints
4185 a warning message saying that it was not able to find the syscall name,
4186 but the catchpoint will be set anyway. See the example below:
4189 (@value{GDBP}) catch syscall 764
4190 warning: The number '764' does not represent a known syscall.
4191 Catchpoint 2 (syscall 764)
4195 If you configure @value{GDBN} using the @samp{--without-expat} option,
4196 it will not be able to display syscall names. Also, if your
4197 architecture does not have an XML file describing its system calls,
4198 you will not be able to see the syscall names. It is important to
4199 notice that these two features are used for accessing the syscall
4200 name database. In either case, you will see a warning like this:
4203 (@value{GDBP}) catch syscall
4204 warning: Could not open "syscalls/i386-linux.xml"
4205 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4206 GDB will not be able to display syscall names.
4207 Catchpoint 1 (syscall)
4211 Of course, the file name will change depending on your architecture and system.
4213 Still using the example above, you can also try to catch a syscall by its
4214 number. In this case, you would see something like:
4217 (@value{GDBP}) catch syscall 252
4218 Catchpoint 1 (syscall(s) 252)
4221 Again, in this case @value{GDBN} would not be able to display syscall's names.
4224 A call to @code{fork}. This is currently only available for HP-UX
4228 A call to @code{vfork}. This is currently only available for HP-UX
4231 @item load @r{[}regexp@r{]}
4232 @itemx unload @r{[}regexp@r{]}
4233 The loading or unloading of a shared library. If @var{regexp} is
4234 given, then the catchpoint will stop only if the regular expression
4235 matches one of the affected libraries.
4237 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4238 The delivery of a signal.
4240 With no arguments, this catchpoint will catch any signal that is not
4241 used internally by @value{GDBN}, specifically, all signals except
4242 @samp{SIGTRAP} and @samp{SIGINT}.
4244 With the argument @samp{all}, all signals, including those used by
4245 @value{GDBN}, will be caught. This argument cannot be used with other
4248 Otherwise, the arguments are a list of signal names as given to
4249 @code{handle} (@pxref{Signals}). Only signals specified in this list
4252 One reason that @code{catch signal} can be more useful than
4253 @code{handle} is that you can attach commands and conditions to the
4256 When a signal is caught by a catchpoint, the signal's @code{stop} and
4257 @code{print} settings, as specified by @code{handle}, are ignored.
4258 However, whether the signal is still delivered to the inferior depends
4259 on the @code{pass} setting; this can be changed in the catchpoint's
4264 @item tcatch @var{event}
4265 Set a catchpoint that is enabled only for one stop. The catchpoint is
4266 automatically deleted after the first time the event is caught.
4270 Use the @code{info break} command to list the current catchpoints.
4272 There are currently some limitations to C@t{++} exception handling
4273 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4277 If you call a function interactively, @value{GDBN} normally returns
4278 control to you when the function has finished executing. If the call
4279 raises an exception, however, the call may bypass the mechanism that
4280 returns control to you and cause your program either to abort or to
4281 simply continue running until it hits a breakpoint, catches a signal
4282 that @value{GDBN} is listening for, or exits. This is the case even if
4283 you set a catchpoint for the exception; catchpoints on exceptions are
4284 disabled within interactive calls.
4287 You cannot raise an exception interactively.
4290 You cannot install an exception handler interactively.
4293 @cindex raise exceptions
4294 Sometimes @code{catch} is not the best way to debug exception handling:
4295 if you need to know exactly where an exception is raised, it is better to
4296 stop @emph{before} the exception handler is called, since that way you
4297 can see the stack before any unwinding takes place. If you set a
4298 breakpoint in an exception handler instead, it may not be easy to find
4299 out where the exception was raised.
4301 To stop just before an exception handler is called, you need some
4302 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4303 raised by calling a library function named @code{__raise_exception}
4304 which has the following ANSI C interface:
4307 /* @var{addr} is where the exception identifier is stored.
4308 @var{id} is the exception identifier. */
4309 void __raise_exception (void **addr, void *id);
4313 To make the debugger catch all exceptions before any stack
4314 unwinding takes place, set a breakpoint on @code{__raise_exception}
4315 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4317 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4318 that depends on the value of @var{id}, you can stop your program when
4319 a specific exception is raised. You can use multiple conditional
4320 breakpoints to stop your program when any of a number of exceptions are
4325 @subsection Deleting Breakpoints
4327 @cindex clearing breakpoints, watchpoints, catchpoints
4328 @cindex deleting breakpoints, watchpoints, catchpoints
4329 It is often necessary to eliminate a breakpoint, watchpoint, or
4330 catchpoint once it has done its job and you no longer want your program
4331 to stop there. This is called @dfn{deleting} the breakpoint. A
4332 breakpoint that has been deleted no longer exists; it is forgotten.
4334 With the @code{clear} command you can delete breakpoints according to
4335 where they are in your program. With the @code{delete} command you can
4336 delete individual breakpoints, watchpoints, or catchpoints by specifying
4337 their breakpoint numbers.
4339 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4340 automatically ignores breakpoints on the first instruction to be executed
4341 when you continue execution without changing the execution address.
4346 Delete any breakpoints at the next instruction to be executed in the
4347 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4348 the innermost frame is selected, this is a good way to delete a
4349 breakpoint where your program just stopped.
4351 @item clear @var{location}
4352 Delete any breakpoints set at the specified @var{location}.
4353 @xref{Specify Location}, for the various forms of @var{location}; the
4354 most useful ones are listed below:
4357 @item clear @var{function}
4358 @itemx clear @var{filename}:@var{function}
4359 Delete any breakpoints set at entry to the named @var{function}.
4361 @item clear @var{linenum}
4362 @itemx clear @var{filename}:@var{linenum}
4363 Delete any breakpoints set at or within the code of the specified
4364 @var{linenum} of the specified @var{filename}.
4367 @cindex delete breakpoints
4369 @kindex d @r{(@code{delete})}
4370 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4371 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4372 ranges specified as arguments. If no argument is specified, delete all
4373 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4374 confirm off}). You can abbreviate this command as @code{d}.
4378 @subsection Disabling Breakpoints
4380 @cindex enable/disable a breakpoint
4381 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4382 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4383 it had been deleted, but remembers the information on the breakpoint so
4384 that you can @dfn{enable} it again later.
4386 You disable and enable breakpoints, watchpoints, and catchpoints with
4387 the @code{enable} and @code{disable} commands, optionally specifying
4388 one or more breakpoint numbers as arguments. Use @code{info break} to
4389 print a list of all breakpoints, watchpoints, and catchpoints if you
4390 do not know which numbers to use.
4392 Disabling and enabling a breakpoint that has multiple locations
4393 affects all of its locations.
4395 A breakpoint, watchpoint, or catchpoint can have any of several
4396 different states of enablement:
4400 Enabled. The breakpoint stops your program. A breakpoint set
4401 with the @code{break} command starts out in this state.
4403 Disabled. The breakpoint has no effect on your program.
4405 Enabled once. The breakpoint stops your program, but then becomes
4408 Enabled for a count. The breakpoint stops your program for the next
4409 N times, then becomes disabled.
4411 Enabled for deletion. The breakpoint stops your program, but
4412 immediately after it does so it is deleted permanently. A breakpoint
4413 set with the @code{tbreak} command starts out in this state.
4416 You can use the following commands to enable or disable breakpoints,
4417 watchpoints, and catchpoints:
4421 @kindex dis @r{(@code{disable})}
4422 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4423 Disable the specified breakpoints---or all breakpoints, if none are
4424 listed. A disabled breakpoint has no effect but is not forgotten. All
4425 options such as ignore-counts, conditions and commands are remembered in
4426 case the breakpoint is enabled again later. You may abbreviate
4427 @code{disable} as @code{dis}.
4430 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4431 Enable the specified breakpoints (or all defined breakpoints). They
4432 become effective once again in stopping your program.
4434 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4435 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4436 of these breakpoints immediately after stopping your program.
4438 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4439 Enable the specified breakpoints temporarily. @value{GDBN} records
4440 @var{count} with each of the specified breakpoints, and decrements a
4441 breakpoint's count when it is hit. When any count reaches 0,
4442 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4443 count (@pxref{Conditions, ,Break Conditions}), that will be
4444 decremented to 0 before @var{count} is affected.
4446 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4447 Enable the specified breakpoints to work once, then die. @value{GDBN}
4448 deletes any of these breakpoints as soon as your program stops there.
4449 Breakpoints set by the @code{tbreak} command start out in this state.
4452 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4453 @c confusing: tbreak is also initially enabled.
4454 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4455 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4456 subsequently, they become disabled or enabled only when you use one of
4457 the commands above. (The command @code{until} can set and delete a
4458 breakpoint of its own, but it does not change the state of your other
4459 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4463 @subsection Break Conditions
4464 @cindex conditional breakpoints
4465 @cindex breakpoint conditions
4467 @c FIXME what is scope of break condition expr? Context where wanted?
4468 @c in particular for a watchpoint?
4469 The simplest sort of breakpoint breaks every time your program reaches a
4470 specified place. You can also specify a @dfn{condition} for a
4471 breakpoint. A condition is just a Boolean expression in your
4472 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4473 a condition evaluates the expression each time your program reaches it,
4474 and your program stops only if the condition is @emph{true}.
4476 This is the converse of using assertions for program validation; in that
4477 situation, you want to stop when the assertion is violated---that is,
4478 when the condition is false. In C, if you want to test an assertion expressed
4479 by the condition @var{assert}, you should set the condition
4480 @samp{! @var{assert}} on the appropriate breakpoint.
4482 Conditions are also accepted for watchpoints; you may not need them,
4483 since a watchpoint is inspecting the value of an expression anyhow---but
4484 it might be simpler, say, to just set a watchpoint on a variable name,
4485 and specify a condition that tests whether the new value is an interesting
4488 Break conditions can have side effects, and may even call functions in
4489 your program. This can be useful, for example, to activate functions
4490 that log program progress, or to use your own print functions to
4491 format special data structures. The effects are completely predictable
4492 unless there is another enabled breakpoint at the same address. (In
4493 that case, @value{GDBN} might see the other breakpoint first and stop your
4494 program without checking the condition of this one.) Note that
4495 breakpoint commands are usually more convenient and flexible than break
4497 purpose of performing side effects when a breakpoint is reached
4498 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4500 Breakpoint conditions can also be evaluated on the target's side if
4501 the target supports it. Instead of evaluating the conditions locally,
4502 @value{GDBN} encodes the expression into an agent expression
4503 (@pxref{Agent Expressions}) suitable for execution on the target,
4504 independently of @value{GDBN}. Global variables become raw memory
4505 locations, locals become stack accesses, and so forth.
4507 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4508 when its condition evaluates to true. This mechanism may provide faster
4509 response times depending on the performance characteristics of the target
4510 since it does not need to keep @value{GDBN} informed about
4511 every breakpoint trigger, even those with false conditions.
4513 Break conditions can be specified when a breakpoint is set, by using
4514 @samp{if} in the arguments to the @code{break} command. @xref{Set
4515 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4516 with the @code{condition} command.
4518 You can also use the @code{if} keyword with the @code{watch} command.
4519 The @code{catch} command does not recognize the @code{if} keyword;
4520 @code{condition} is the only way to impose a further condition on a
4525 @item condition @var{bnum} @var{expression}
4526 Specify @var{expression} as the break condition for breakpoint,
4527 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4528 breakpoint @var{bnum} stops your program only if the value of
4529 @var{expression} is true (nonzero, in C). When you use
4530 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4531 syntactic correctness, and to determine whether symbols in it have
4532 referents in the context of your breakpoint. If @var{expression} uses
4533 symbols not referenced in the context of the breakpoint, @value{GDBN}
4534 prints an error message:
4537 No symbol "foo" in current context.
4542 not actually evaluate @var{expression} at the time the @code{condition}
4543 command (or a command that sets a breakpoint with a condition, like
4544 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4546 @item condition @var{bnum}
4547 Remove the condition from breakpoint number @var{bnum}. It becomes
4548 an ordinary unconditional breakpoint.
4551 @cindex ignore count (of breakpoint)
4552 A special case of a breakpoint condition is to stop only when the
4553 breakpoint has been reached a certain number of times. This is so
4554 useful that there is a special way to do it, using the @dfn{ignore
4555 count} of the breakpoint. Every breakpoint has an ignore count, which
4556 is an integer. Most of the time, the ignore count is zero, and
4557 therefore has no effect. But if your program reaches a breakpoint whose
4558 ignore count is positive, then instead of stopping, it just decrements
4559 the ignore count by one and continues. As a result, if the ignore count
4560 value is @var{n}, the breakpoint does not stop the next @var{n} times
4561 your program reaches it.
4565 @item ignore @var{bnum} @var{count}
4566 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4567 The next @var{count} times the breakpoint is reached, your program's
4568 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4571 To make the breakpoint stop the next time it is reached, specify
4574 When you use @code{continue} to resume execution of your program from a
4575 breakpoint, you can specify an ignore count directly as an argument to
4576 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4577 Stepping,,Continuing and Stepping}.
4579 If a breakpoint has a positive ignore count and a condition, the
4580 condition is not checked. Once the ignore count reaches zero,
4581 @value{GDBN} resumes checking the condition.
4583 You could achieve the effect of the ignore count with a condition such
4584 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4585 is decremented each time. @xref{Convenience Vars, ,Convenience
4589 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4592 @node Break Commands
4593 @subsection Breakpoint Command Lists
4595 @cindex breakpoint commands
4596 You can give any breakpoint (or watchpoint or catchpoint) a series of
4597 commands to execute when your program stops due to that breakpoint. For
4598 example, you might want to print the values of certain expressions, or
4599 enable other breakpoints.
4603 @kindex end@r{ (breakpoint commands)}
4604 @item commands @r{[}@var{range}@dots{}@r{]}
4605 @itemx @dots{} @var{command-list} @dots{}
4607 Specify a list of commands for the given breakpoints. The commands
4608 themselves appear on the following lines. Type a line containing just
4609 @code{end} to terminate the commands.
4611 To remove all commands from a breakpoint, type @code{commands} and
4612 follow it immediately with @code{end}; that is, give no commands.
4614 With no argument, @code{commands} refers to the last breakpoint,
4615 watchpoint, or catchpoint set (not to the breakpoint most recently
4616 encountered). If the most recent breakpoints were set with a single
4617 command, then the @code{commands} will apply to all the breakpoints
4618 set by that command. This applies to breakpoints set by
4619 @code{rbreak}, and also applies when a single @code{break} command
4620 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4624 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4625 disabled within a @var{command-list}.
4627 You can use breakpoint commands to start your program up again. Simply
4628 use the @code{continue} command, or @code{step}, or any other command
4629 that resumes execution.
4631 Any other commands in the command list, after a command that resumes
4632 execution, are ignored. This is because any time you resume execution
4633 (even with a simple @code{next} or @code{step}), you may encounter
4634 another breakpoint---which could have its own command list, leading to
4635 ambiguities about which list to execute.
4638 If the first command you specify in a command list is @code{silent}, the
4639 usual message about stopping at a breakpoint is not printed. This may
4640 be desirable for breakpoints that are to print a specific message and
4641 then continue. If none of the remaining commands print anything, you
4642 see no sign that the breakpoint was reached. @code{silent} is
4643 meaningful only at the beginning of a breakpoint command list.
4645 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4646 print precisely controlled output, and are often useful in silent
4647 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4649 For example, here is how you could use breakpoint commands to print the
4650 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4656 printf "x is %d\n",x
4661 One application for breakpoint commands is to compensate for one bug so
4662 you can test for another. Put a breakpoint just after the erroneous line
4663 of code, give it a condition to detect the case in which something
4664 erroneous has been done, and give it commands to assign correct values
4665 to any variables that need them. End with the @code{continue} command
4666 so that your program does not stop, and start with the @code{silent}
4667 command so that no output is produced. Here is an example:
4678 @node Dynamic Printf
4679 @subsection Dynamic Printf
4681 @cindex dynamic printf
4683 The dynamic printf command @code{dprintf} combines a breakpoint with
4684 formatted printing of your program's data to give you the effect of
4685 inserting @code{printf} calls into your program on-the-fly, without
4686 having to recompile it.
4688 In its most basic form, the output goes to the GDB console. However,
4689 you can set the variable @code{dprintf-style} for alternate handling.
4690 For instance, you can ask to format the output by calling your
4691 program's @code{printf} function. This has the advantage that the
4692 characters go to the program's output device, so they can recorded in
4693 redirects to files and so forth.
4695 If you are doing remote debugging with a stub or agent, you can also
4696 ask to have the printf handled by the remote agent. In addition to
4697 ensuring that the output goes to the remote program's device along
4698 with any other output the program might produce, you can also ask that
4699 the dprintf remain active even after disconnecting from the remote
4700 target. Using the stub/agent is also more efficient, as it can do
4701 everything without needing to communicate with @value{GDBN}.
4705 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4706 Whenever execution reaches @var{location}, print the values of one or
4707 more @var{expressions} under the control of the string @var{template}.
4708 To print several values, separate them with commas.
4710 @item set dprintf-style @var{style}
4711 Set the dprintf output to be handled in one of several different
4712 styles enumerated below. A change of style affects all existing
4713 dynamic printfs immediately. (If you need individual control over the
4714 print commands, simply define normal breakpoints with
4715 explicitly-supplied command lists.)
4718 @kindex dprintf-style gdb
4719 Handle the output using the @value{GDBN} @code{printf} command.
4722 @kindex dprintf-style call
4723 Handle the output by calling a function in your program (normally
4727 @kindex dprintf-style agent
4728 Have the remote debugging agent (such as @code{gdbserver}) handle
4729 the output itself. This style is only available for agents that
4730 support running commands on the target.
4732 @item set dprintf-function @var{function}
4733 Set the function to call if the dprintf style is @code{call}. By
4734 default its value is @code{printf}. You may set it to any expression.
4735 that @value{GDBN} can evaluate to a function, as per the @code{call}
4738 @item set dprintf-channel @var{channel}
4739 Set a ``channel'' for dprintf. If set to a non-empty value,
4740 @value{GDBN} will evaluate it as an expression and pass the result as
4741 a first argument to the @code{dprintf-function}, in the manner of
4742 @code{fprintf} and similar functions. Otherwise, the dprintf format
4743 string will be the first argument, in the manner of @code{printf}.
4745 As an example, if you wanted @code{dprintf} output to go to a logfile
4746 that is a standard I/O stream assigned to the variable @code{mylog},
4747 you could do the following:
4750 (gdb) set dprintf-style call
4751 (gdb) set dprintf-function fprintf
4752 (gdb) set dprintf-channel mylog
4753 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4754 Dprintf 1 at 0x123456: file main.c, line 25.
4756 1 dprintf keep y 0x00123456 in main at main.c:25
4757 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4762 Note that the @code{info break} displays the dynamic printf commands
4763 as normal breakpoint commands; you can thus easily see the effect of
4764 the variable settings.
4766 @item set disconnected-dprintf on
4767 @itemx set disconnected-dprintf off
4768 @kindex set disconnected-dprintf
4769 Choose whether @code{dprintf} commands should continue to run if
4770 @value{GDBN} has disconnected from the target. This only applies
4771 if the @code{dprintf-style} is @code{agent}.
4773 @item show disconnected-dprintf off
4774 @kindex show disconnected-dprintf
4775 Show the current choice for disconnected @code{dprintf}.
4779 @value{GDBN} does not check the validity of function and channel,
4780 relying on you to supply values that are meaningful for the contexts
4781 in which they are being used. For instance, the function and channel
4782 may be the values of local variables, but if that is the case, then
4783 all enabled dynamic prints must be at locations within the scope of
4784 those locals. If evaluation fails, @value{GDBN} will report an error.
4786 @node Save Breakpoints
4787 @subsection How to save breakpoints to a file
4789 To save breakpoint definitions to a file use the @w{@code{save
4790 breakpoints}} command.
4793 @kindex save breakpoints
4794 @cindex save breakpoints to a file for future sessions
4795 @item save breakpoints [@var{filename}]
4796 This command saves all current breakpoint definitions together with
4797 their commands and ignore counts, into a file @file{@var{filename}}
4798 suitable for use in a later debugging session. This includes all
4799 types of breakpoints (breakpoints, watchpoints, catchpoints,
4800 tracepoints). To read the saved breakpoint definitions, use the
4801 @code{source} command (@pxref{Command Files}). Note that watchpoints
4802 with expressions involving local variables may fail to be recreated
4803 because it may not be possible to access the context where the
4804 watchpoint is valid anymore. Because the saved breakpoint definitions
4805 are simply a sequence of @value{GDBN} commands that recreate the
4806 breakpoints, you can edit the file in your favorite editing program,
4807 and remove the breakpoint definitions you're not interested in, or
4808 that can no longer be recreated.
4811 @node Static Probe Points
4812 @subsection Static Probe Points
4814 @cindex static probe point, SystemTap
4815 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4816 for Statically Defined Tracing, and the probes are designed to have a tiny
4817 runtime code and data footprint, and no dynamic relocations. They are
4818 usable from assembly, C and C@t{++} languages. See
4819 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4820 for a good reference on how the @acronym{SDT} probes are implemented.
4822 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4823 @acronym{SDT} probes are supported on ELF-compatible systems. See
4824 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4825 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4826 in your applications.
4828 @cindex semaphores on static probe points
4829 Some probes have an associated semaphore variable; for instance, this
4830 happens automatically if you defined your probe using a DTrace-style
4831 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4832 automatically enable it when you specify a breakpoint using the
4833 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4834 location by some other method (e.g., @code{break file:line}), then
4835 @value{GDBN} will not automatically set the semaphore.
4837 You can examine the available static static probes using @code{info
4838 probes}, with optional arguments:
4842 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4843 If given, @var{provider} is a regular expression used to match against provider
4844 names when selecting which probes to list. If omitted, probes by all
4845 probes from all providers are listed.
4847 If given, @var{name} is a regular expression to match against probe names
4848 when selecting which probes to list. If omitted, probe names are not
4849 considered when deciding whether to display them.
4851 If given, @var{objfile} is a regular expression used to select which
4852 object files (executable or shared libraries) to examine. If not
4853 given, all object files are considered.
4855 @item info probes all
4856 List the available static probes, from all types.
4859 @vindex $_probe_arg@r{, convenience variable}
4860 A probe may specify up to twelve arguments. These are available at the
4861 point at which the probe is defined---that is, when the current PC is
4862 at the probe's location. The arguments are available using the
4863 convenience variables (@pxref{Convenience Vars})
4864 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4865 an integer of the appropriate size; types are not preserved. The
4866 convenience variable @code{$_probe_argc} holds the number of arguments
4867 at the current probe point.
4869 These variables are always available, but attempts to access them at
4870 any location other than a probe point will cause @value{GDBN} to give
4874 @c @ifclear BARETARGET
4875 @node Error in Breakpoints
4876 @subsection ``Cannot insert breakpoints''
4878 If you request too many active hardware-assisted breakpoints and
4879 watchpoints, you will see this error message:
4881 @c FIXME: the precise wording of this message may change; the relevant
4882 @c source change is not committed yet (Sep 3, 1999).
4884 Stopped; cannot insert breakpoints.
4885 You may have requested too many hardware breakpoints and watchpoints.
4889 This message is printed when you attempt to resume the program, since
4890 only then @value{GDBN} knows exactly how many hardware breakpoints and
4891 watchpoints it needs to insert.
4893 When this message is printed, you need to disable or remove some of the
4894 hardware-assisted breakpoints and watchpoints, and then continue.
4896 @node Breakpoint-related Warnings
4897 @subsection ``Breakpoint address adjusted...''
4898 @cindex breakpoint address adjusted
4900 Some processor architectures place constraints on the addresses at
4901 which breakpoints may be placed. For architectures thus constrained,
4902 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4903 with the constraints dictated by the architecture.
4905 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4906 a VLIW architecture in which a number of RISC-like instructions may be
4907 bundled together for parallel execution. The FR-V architecture
4908 constrains the location of a breakpoint instruction within such a
4909 bundle to the instruction with the lowest address. @value{GDBN}
4910 honors this constraint by adjusting a breakpoint's address to the
4911 first in the bundle.
4913 It is not uncommon for optimized code to have bundles which contain
4914 instructions from different source statements, thus it may happen that
4915 a breakpoint's address will be adjusted from one source statement to
4916 another. Since this adjustment may significantly alter @value{GDBN}'s
4917 breakpoint related behavior from what the user expects, a warning is
4918 printed when the breakpoint is first set and also when the breakpoint
4921 A warning like the one below is printed when setting a breakpoint
4922 that's been subject to address adjustment:
4925 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4928 Such warnings are printed both for user settable and @value{GDBN}'s
4929 internal breakpoints. If you see one of these warnings, you should
4930 verify that a breakpoint set at the adjusted address will have the
4931 desired affect. If not, the breakpoint in question may be removed and
4932 other breakpoints may be set which will have the desired behavior.
4933 E.g., it may be sufficient to place the breakpoint at a later
4934 instruction. A conditional breakpoint may also be useful in some
4935 cases to prevent the breakpoint from triggering too often.
4937 @value{GDBN} will also issue a warning when stopping at one of these
4938 adjusted breakpoints:
4941 warning: Breakpoint 1 address previously adjusted from 0x00010414
4945 When this warning is encountered, it may be too late to take remedial
4946 action except in cases where the breakpoint is hit earlier or more
4947 frequently than expected.
4949 @node Continuing and Stepping
4950 @section Continuing and Stepping
4954 @cindex resuming execution
4955 @dfn{Continuing} means resuming program execution until your program
4956 completes normally. In contrast, @dfn{stepping} means executing just
4957 one more ``step'' of your program, where ``step'' may mean either one
4958 line of source code, or one machine instruction (depending on what
4959 particular command you use). Either when continuing or when stepping,
4960 your program may stop even sooner, due to a breakpoint or a signal. (If
4961 it stops due to a signal, you may want to use @code{handle}, or use
4962 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4966 @kindex c @r{(@code{continue})}
4967 @kindex fg @r{(resume foreground execution)}
4968 @item continue @r{[}@var{ignore-count}@r{]}
4969 @itemx c @r{[}@var{ignore-count}@r{]}
4970 @itemx fg @r{[}@var{ignore-count}@r{]}
4971 Resume program execution, at the address where your program last stopped;
4972 any breakpoints set at that address are bypassed. The optional argument
4973 @var{ignore-count} allows you to specify a further number of times to
4974 ignore a breakpoint at this location; its effect is like that of
4975 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4977 The argument @var{ignore-count} is meaningful only when your program
4978 stopped due to a breakpoint. At other times, the argument to
4979 @code{continue} is ignored.
4981 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4982 debugged program is deemed to be the foreground program) are provided
4983 purely for convenience, and have exactly the same behavior as
4987 To resume execution at a different place, you can use @code{return}
4988 (@pxref{Returning, ,Returning from a Function}) to go back to the
4989 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4990 Different Address}) to go to an arbitrary location in your program.
4992 A typical technique for using stepping is to set a breakpoint
4993 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4994 beginning of the function or the section of your program where a problem
4995 is believed to lie, run your program until it stops at that breakpoint,
4996 and then step through the suspect area, examining the variables that are
4997 interesting, until you see the problem happen.
5001 @kindex s @r{(@code{step})}
5003 Continue running your program until control reaches a different source
5004 line, then stop it and return control to @value{GDBN}. This command is
5005 abbreviated @code{s}.
5008 @c "without debugging information" is imprecise; actually "without line
5009 @c numbers in the debugging information". (gcc -g1 has debugging info but
5010 @c not line numbers). But it seems complex to try to make that
5011 @c distinction here.
5012 @emph{Warning:} If you use the @code{step} command while control is
5013 within a function that was compiled without debugging information,
5014 execution proceeds until control reaches a function that does have
5015 debugging information. Likewise, it will not step into a function which
5016 is compiled without debugging information. To step through functions
5017 without debugging information, use the @code{stepi} command, described
5021 The @code{step} command only stops at the first instruction of a source
5022 line. This prevents the multiple stops that could otherwise occur in
5023 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5024 to stop if a function that has debugging information is called within
5025 the line. In other words, @code{step} @emph{steps inside} any functions
5026 called within the line.
5028 Also, the @code{step} command only enters a function if there is line
5029 number information for the function. Otherwise it acts like the
5030 @code{next} command. This avoids problems when using @code{cc -gl}
5031 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5032 was any debugging information about the routine.
5034 @item step @var{count}
5035 Continue running as in @code{step}, but do so @var{count} times. If a
5036 breakpoint is reached, or a signal not related to stepping occurs before
5037 @var{count} steps, stepping stops right away.
5040 @kindex n @r{(@code{next})}
5041 @item next @r{[}@var{count}@r{]}
5042 Continue to the next source line in the current (innermost) stack frame.
5043 This is similar to @code{step}, but function calls that appear within
5044 the line of code are executed without stopping. Execution stops when
5045 control reaches a different line of code at the original stack level
5046 that was executing when you gave the @code{next} command. This command
5047 is abbreviated @code{n}.
5049 An argument @var{count} is a repeat count, as for @code{step}.
5052 @c FIX ME!! Do we delete this, or is there a way it fits in with
5053 @c the following paragraph? --- Vctoria
5055 @c @code{next} within a function that lacks debugging information acts like
5056 @c @code{step}, but any function calls appearing within the code of the
5057 @c function are executed without stopping.
5059 The @code{next} command only stops at the first instruction of a
5060 source line. This prevents multiple stops that could otherwise occur in
5061 @code{switch} statements, @code{for} loops, etc.
5063 @kindex set step-mode
5065 @cindex functions without line info, and stepping
5066 @cindex stepping into functions with no line info
5067 @itemx set step-mode on
5068 The @code{set step-mode on} command causes the @code{step} command to
5069 stop at the first instruction of a function which contains no debug line
5070 information rather than stepping over it.
5072 This is useful in cases where you may be interested in inspecting the
5073 machine instructions of a function which has no symbolic info and do not
5074 want @value{GDBN} to automatically skip over this function.
5076 @item set step-mode off
5077 Causes the @code{step} command to step over any functions which contains no
5078 debug information. This is the default.
5080 @item show step-mode
5081 Show whether @value{GDBN} will stop in or step over functions without
5082 source line debug information.
5085 @kindex fin @r{(@code{finish})}
5087 Continue running until just after function in the selected stack frame
5088 returns. Print the returned value (if any). This command can be
5089 abbreviated as @code{fin}.
5091 Contrast this with the @code{return} command (@pxref{Returning,
5092 ,Returning from a Function}).
5095 @kindex u @r{(@code{until})}
5096 @cindex run until specified location
5099 Continue running until a source line past the current line, in the
5100 current stack frame, is reached. This command is used to avoid single
5101 stepping through a loop more than once. It is like the @code{next}
5102 command, except that when @code{until} encounters a jump, it
5103 automatically continues execution until the program counter is greater
5104 than the address of the jump.
5106 This means that when you reach the end of a loop after single stepping
5107 though it, @code{until} makes your program continue execution until it
5108 exits the loop. In contrast, a @code{next} command at the end of a loop
5109 simply steps back to the beginning of the loop, which forces you to step
5110 through the next iteration.
5112 @code{until} always stops your program if it attempts to exit the current
5115 @code{until} may produce somewhat counterintuitive results if the order
5116 of machine code does not match the order of the source lines. For
5117 example, in the following excerpt from a debugging session, the @code{f}
5118 (@code{frame}) command shows that execution is stopped at line
5119 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5123 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5125 (@value{GDBP}) until
5126 195 for ( ; argc > 0; NEXTARG) @{
5129 This happened because, for execution efficiency, the compiler had
5130 generated code for the loop closure test at the end, rather than the
5131 start, of the loop---even though the test in a C @code{for}-loop is
5132 written before the body of the loop. The @code{until} command appeared
5133 to step back to the beginning of the loop when it advanced to this
5134 expression; however, it has not really gone to an earlier
5135 statement---not in terms of the actual machine code.
5137 @code{until} with no argument works by means of single
5138 instruction stepping, and hence is slower than @code{until} with an
5141 @item until @var{location}
5142 @itemx u @var{location}
5143 Continue running your program until either the specified location is
5144 reached, or the current stack frame returns. @var{location} is any of
5145 the forms described in @ref{Specify Location}.
5146 This form of the command uses temporary breakpoints, and
5147 hence is quicker than @code{until} without an argument. The specified
5148 location is actually reached only if it is in the current frame. This
5149 implies that @code{until} can be used to skip over recursive function
5150 invocations. For instance in the code below, if the current location is
5151 line @code{96}, issuing @code{until 99} will execute the program up to
5152 line @code{99} in the same invocation of factorial, i.e., after the inner
5153 invocations have returned.
5156 94 int factorial (int value)
5158 96 if (value > 1) @{
5159 97 value *= factorial (value - 1);
5166 @kindex advance @var{location}
5167 @item advance @var{location}
5168 Continue running the program up to the given @var{location}. An argument is
5169 required, which should be of one of the forms described in
5170 @ref{Specify Location}.
5171 Execution will also stop upon exit from the current stack
5172 frame. This command is similar to @code{until}, but @code{advance} will
5173 not skip over recursive function calls, and the target location doesn't
5174 have to be in the same frame as the current one.
5178 @kindex si @r{(@code{stepi})}
5180 @itemx stepi @var{arg}
5182 Execute one machine instruction, then stop and return to the debugger.
5184 It is often useful to do @samp{display/i $pc} when stepping by machine
5185 instructions. This makes @value{GDBN} automatically display the next
5186 instruction to be executed, each time your program stops. @xref{Auto
5187 Display,, Automatic Display}.
5189 An argument is a repeat count, as in @code{step}.
5193 @kindex ni @r{(@code{nexti})}
5195 @itemx nexti @var{arg}
5197 Execute one machine instruction, but if it is a function call,
5198 proceed until the function returns.
5200 An argument is a repeat count, as in @code{next}.
5203 @node Skipping Over Functions and Files
5204 @section Skipping Over Functions and Files
5205 @cindex skipping over functions and files
5207 The program you are debugging may contain some functions which are
5208 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5209 skip a function or all functions in a file when stepping.
5211 For example, consider the following C function:
5222 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5223 are not interested in stepping through @code{boring}. If you run @code{step}
5224 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5225 step over both @code{foo} and @code{boring}!
5227 One solution is to @code{step} into @code{boring} and use the @code{finish}
5228 command to immediately exit it. But this can become tedious if @code{boring}
5229 is called from many places.
5231 A more flexible solution is to execute @kbd{skip boring}. This instructs
5232 @value{GDBN} never to step into @code{boring}. Now when you execute
5233 @code{step} at line 103, you'll step over @code{boring} and directly into
5236 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5237 example, @code{skip file boring.c}.
5240 @kindex skip function
5241 @item skip @r{[}@var{linespec}@r{]}
5242 @itemx skip function @r{[}@var{linespec}@r{]}
5243 After running this command, the function named by @var{linespec} or the
5244 function containing the line named by @var{linespec} will be skipped over when
5245 stepping. @xref{Specify Location}.
5247 If you do not specify @var{linespec}, the function you're currently debugging
5250 (If you have a function called @code{file} that you want to skip, use
5251 @kbd{skip function file}.)
5254 @item skip file @r{[}@var{filename}@r{]}
5255 After running this command, any function whose source lives in @var{filename}
5256 will be skipped over when stepping.
5258 If you do not specify @var{filename}, functions whose source lives in the file
5259 you're currently debugging will be skipped.
5262 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5263 These are the commands for managing your list of skips:
5267 @item info skip @r{[}@var{range}@r{]}
5268 Print details about the specified skip(s). If @var{range} is not specified,
5269 print a table with details about all functions and files marked for skipping.
5270 @code{info skip} prints the following information about each skip:
5274 A number identifying this skip.
5276 The type of this skip, either @samp{function} or @samp{file}.
5277 @item Enabled or Disabled
5278 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5280 For function skips, this column indicates the address in memory of the function
5281 being skipped. If you've set a function skip on a function which has not yet
5282 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5283 which has the function is loaded, @code{info skip} will show the function's
5286 For file skips, this field contains the filename being skipped. For functions
5287 skips, this field contains the function name and its line number in the file
5288 where it is defined.
5292 @item skip delete @r{[}@var{range}@r{]}
5293 Delete the specified skip(s). If @var{range} is not specified, delete all
5297 @item skip enable @r{[}@var{range}@r{]}
5298 Enable the specified skip(s). If @var{range} is not specified, enable all
5301 @kindex skip disable
5302 @item skip disable @r{[}@var{range}@r{]}
5303 Disable the specified skip(s). If @var{range} is not specified, disable all
5312 A signal is an asynchronous event that can happen in a program. The
5313 operating system defines the possible kinds of signals, and gives each
5314 kind a name and a number. For example, in Unix @code{SIGINT} is the
5315 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5316 @code{SIGSEGV} is the signal a program gets from referencing a place in
5317 memory far away from all the areas in use; @code{SIGALRM} occurs when
5318 the alarm clock timer goes off (which happens only if your program has
5319 requested an alarm).
5321 @cindex fatal signals
5322 Some signals, including @code{SIGALRM}, are a normal part of the
5323 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5324 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5325 program has not specified in advance some other way to handle the signal.
5326 @code{SIGINT} does not indicate an error in your program, but it is normally
5327 fatal so it can carry out the purpose of the interrupt: to kill the program.
5329 @value{GDBN} has the ability to detect any occurrence of a signal in your
5330 program. You can tell @value{GDBN} in advance what to do for each kind of
5333 @cindex handling signals
5334 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5335 @code{SIGALRM} be silently passed to your program
5336 (so as not to interfere with their role in the program's functioning)
5337 but to stop your program immediately whenever an error signal happens.
5338 You can change these settings with the @code{handle} command.
5341 @kindex info signals
5345 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5346 handle each one. You can use this to see the signal numbers of all
5347 the defined types of signals.
5349 @item info signals @var{sig}
5350 Similar, but print information only about the specified signal number.
5352 @code{info handle} is an alias for @code{info signals}.
5354 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5355 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5356 for details about this command.
5359 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5360 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5361 can be the number of a signal or its name (with or without the
5362 @samp{SIG} at the beginning); a list of signal numbers of the form
5363 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5364 known signals. Optional arguments @var{keywords}, described below,
5365 say what change to make.
5369 The keywords allowed by the @code{handle} command can be abbreviated.
5370 Their full names are:
5374 @value{GDBN} should not stop your program when this signal happens. It may
5375 still print a message telling you that the signal has come in.
5378 @value{GDBN} should stop your program when this signal happens. This implies
5379 the @code{print} keyword as well.
5382 @value{GDBN} should print a message when this signal happens.
5385 @value{GDBN} should not mention the occurrence of the signal at all. This
5386 implies the @code{nostop} keyword as well.
5390 @value{GDBN} should allow your program to see this signal; your program
5391 can handle the signal, or else it may terminate if the signal is fatal
5392 and not handled. @code{pass} and @code{noignore} are synonyms.
5396 @value{GDBN} should not allow your program to see this signal.
5397 @code{nopass} and @code{ignore} are synonyms.
5401 When a signal stops your program, the signal is not visible to the
5403 continue. Your program sees the signal then, if @code{pass} is in
5404 effect for the signal in question @emph{at that time}. In other words,
5405 after @value{GDBN} reports a signal, you can use the @code{handle}
5406 command with @code{pass} or @code{nopass} to control whether your
5407 program sees that signal when you continue.
5409 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5410 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5411 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5414 You can also use the @code{signal} command to prevent your program from
5415 seeing a signal, or cause it to see a signal it normally would not see,
5416 or to give it any signal at any time. For example, if your program stopped
5417 due to some sort of memory reference error, you might store correct
5418 values into the erroneous variables and continue, hoping to see more
5419 execution; but your program would probably terminate immediately as
5420 a result of the fatal signal once it saw the signal. To prevent this,
5421 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5424 @cindex extra signal information
5425 @anchor{extra signal information}
5427 On some targets, @value{GDBN} can inspect extra signal information
5428 associated with the intercepted signal, before it is actually
5429 delivered to the program being debugged. This information is exported
5430 by the convenience variable @code{$_siginfo}, and consists of data
5431 that is passed by the kernel to the signal handler at the time of the
5432 receipt of a signal. The data type of the information itself is
5433 target dependent. You can see the data type using the @code{ptype
5434 $_siginfo} command. On Unix systems, it typically corresponds to the
5435 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5438 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5439 referenced address that raised a segmentation fault.
5443 (@value{GDBP}) continue
5444 Program received signal SIGSEGV, Segmentation fault.
5445 0x0000000000400766 in main ()
5447 (@value{GDBP}) ptype $_siginfo
5454 struct @{...@} _kill;
5455 struct @{...@} _timer;
5457 struct @{...@} _sigchld;
5458 struct @{...@} _sigfault;
5459 struct @{...@} _sigpoll;
5462 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5466 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5467 $1 = (void *) 0x7ffff7ff7000
5471 Depending on target support, @code{$_siginfo} may also be writable.
5474 @section Stopping and Starting Multi-thread Programs
5476 @cindex stopped threads
5477 @cindex threads, stopped
5479 @cindex continuing threads
5480 @cindex threads, continuing
5482 @value{GDBN} supports debugging programs with multiple threads
5483 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5484 are two modes of controlling execution of your program within the
5485 debugger. In the default mode, referred to as @dfn{all-stop mode},
5486 when any thread in your program stops (for example, at a breakpoint
5487 or while being stepped), all other threads in the program are also stopped by
5488 @value{GDBN}. On some targets, @value{GDBN} also supports
5489 @dfn{non-stop mode}, in which other threads can continue to run freely while
5490 you examine the stopped thread in the debugger.
5493 * All-Stop Mode:: All threads stop when GDB takes control
5494 * Non-Stop Mode:: Other threads continue to execute
5495 * Background Execution:: Running your program asynchronously
5496 * Thread-Specific Breakpoints:: Controlling breakpoints
5497 * Interrupted System Calls:: GDB may interfere with system calls
5498 * Observer Mode:: GDB does not alter program behavior
5502 @subsection All-Stop Mode
5504 @cindex all-stop mode
5506 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5507 @emph{all} threads of execution stop, not just the current thread. This
5508 allows you to examine the overall state of the program, including
5509 switching between threads, without worrying that things may change
5512 Conversely, whenever you restart the program, @emph{all} threads start
5513 executing. @emph{This is true even when single-stepping} with commands
5514 like @code{step} or @code{next}.
5516 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5517 Since thread scheduling is up to your debugging target's operating
5518 system (not controlled by @value{GDBN}), other threads may
5519 execute more than one statement while the current thread completes a
5520 single step. Moreover, in general other threads stop in the middle of a
5521 statement, rather than at a clean statement boundary, when the program
5524 You might even find your program stopped in another thread after
5525 continuing or even single-stepping. This happens whenever some other
5526 thread runs into a breakpoint, a signal, or an exception before the
5527 first thread completes whatever you requested.
5529 @cindex automatic thread selection
5530 @cindex switching threads automatically
5531 @cindex threads, automatic switching
5532 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5533 signal, it automatically selects the thread where that breakpoint or
5534 signal happened. @value{GDBN} alerts you to the context switch with a
5535 message such as @samp{[Switching to Thread @var{n}]} to identify the
5538 On some OSes, you can modify @value{GDBN}'s default behavior by
5539 locking the OS scheduler to allow only a single thread to run.
5542 @item set scheduler-locking @var{mode}
5543 @cindex scheduler locking mode
5544 @cindex lock scheduler
5545 Set the scheduler locking mode. If it is @code{off}, then there is no
5546 locking and any thread may run at any time. If @code{on}, then only the
5547 current thread may run when the inferior is resumed. The @code{step}
5548 mode optimizes for single-stepping; it prevents other threads
5549 from preempting the current thread while you are stepping, so that
5550 the focus of debugging does not change unexpectedly.
5551 Other threads only rarely (or never) get a chance to run
5552 when you step. They are more likely to run when you @samp{next} over a
5553 function call, and they are completely free to run when you use commands
5554 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5555 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5556 the current thread away from the thread that you are debugging.
5558 @item show scheduler-locking
5559 Display the current scheduler locking mode.
5562 @cindex resume threads of multiple processes simultaneously
5563 By default, when you issue one of the execution commands such as
5564 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5565 threads of the current inferior to run. For example, if @value{GDBN}
5566 is attached to two inferiors, each with two threads, the
5567 @code{continue} command resumes only the two threads of the current
5568 inferior. This is useful, for example, when you debug a program that
5569 forks and you want to hold the parent stopped (so that, for instance,
5570 it doesn't run to exit), while you debug the child. In other
5571 situations, you may not be interested in inspecting the current state
5572 of any of the processes @value{GDBN} is attached to, and you may want
5573 to resume them all until some breakpoint is hit. In the latter case,
5574 you can instruct @value{GDBN} to allow all threads of all the
5575 inferiors to run with the @w{@code{set schedule-multiple}} command.
5578 @kindex set schedule-multiple
5579 @item set schedule-multiple
5580 Set the mode for allowing threads of multiple processes to be resumed
5581 when an execution command is issued. When @code{on}, all threads of
5582 all processes are allowed to run. When @code{off}, only the threads
5583 of the current process are resumed. The default is @code{off}. The
5584 @code{scheduler-locking} mode takes precedence when set to @code{on},
5585 or while you are stepping and set to @code{step}.
5587 @item show schedule-multiple
5588 Display the current mode for resuming the execution of threads of
5593 @subsection Non-Stop Mode
5595 @cindex non-stop mode
5597 @c This section is really only a place-holder, and needs to be expanded
5598 @c with more details.
5600 For some multi-threaded targets, @value{GDBN} supports an optional
5601 mode of operation in which you can examine stopped program threads in
5602 the debugger while other threads continue to execute freely. This
5603 minimizes intrusion when debugging live systems, such as programs
5604 where some threads have real-time constraints or must continue to
5605 respond to external events. This is referred to as @dfn{non-stop} mode.
5607 In non-stop mode, when a thread stops to report a debugging event,
5608 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5609 threads as well, in contrast to the all-stop mode behavior. Additionally,
5610 execution commands such as @code{continue} and @code{step} apply by default
5611 only to the current thread in non-stop mode, rather than all threads as
5612 in all-stop mode. This allows you to control threads explicitly in
5613 ways that are not possible in all-stop mode --- for example, stepping
5614 one thread while allowing others to run freely, stepping
5615 one thread while holding all others stopped, or stepping several threads
5616 independently and simultaneously.
5618 To enter non-stop mode, use this sequence of commands before you run
5619 or attach to your program:
5622 # Enable the async interface.
5625 # If using the CLI, pagination breaks non-stop.
5628 # Finally, turn it on!
5632 You can use these commands to manipulate the non-stop mode setting:
5635 @kindex set non-stop
5636 @item set non-stop on
5637 Enable selection of non-stop mode.
5638 @item set non-stop off
5639 Disable selection of non-stop mode.
5640 @kindex show non-stop
5642 Show the current non-stop enablement setting.
5645 Note these commands only reflect whether non-stop mode is enabled,
5646 not whether the currently-executing program is being run in non-stop mode.
5647 In particular, the @code{set non-stop} preference is only consulted when
5648 @value{GDBN} starts or connects to the target program, and it is generally
5649 not possible to switch modes once debugging has started. Furthermore,
5650 since not all targets support non-stop mode, even when you have enabled
5651 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5654 In non-stop mode, all execution commands apply only to the current thread
5655 by default. That is, @code{continue} only continues one thread.
5656 To continue all threads, issue @code{continue -a} or @code{c -a}.
5658 You can use @value{GDBN}'s background execution commands
5659 (@pxref{Background Execution}) to run some threads in the background
5660 while you continue to examine or step others from @value{GDBN}.
5661 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5662 always executed asynchronously in non-stop mode.
5664 Suspending execution is done with the @code{interrupt} command when
5665 running in the background, or @kbd{Ctrl-c} during foreground execution.
5666 In all-stop mode, this stops the whole process;
5667 but in non-stop mode the interrupt applies only to the current thread.
5668 To stop the whole program, use @code{interrupt -a}.
5670 Other execution commands do not currently support the @code{-a} option.
5672 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5673 that thread current, as it does in all-stop mode. This is because the
5674 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5675 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5676 changed to a different thread just as you entered a command to operate on the
5677 previously current thread.
5679 @node Background Execution
5680 @subsection Background Execution
5682 @cindex foreground execution
5683 @cindex background execution
5684 @cindex asynchronous execution
5685 @cindex execution, foreground, background and asynchronous
5687 @value{GDBN}'s execution commands have two variants: the normal
5688 foreground (synchronous) behavior, and a background
5689 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5690 the program to report that some thread has stopped before prompting for
5691 another command. In background execution, @value{GDBN} immediately gives
5692 a command prompt so that you can issue other commands while your program runs.
5694 You need to explicitly enable asynchronous mode before you can use
5695 background execution commands. You can use these commands to
5696 manipulate the asynchronous mode setting:
5699 @kindex set target-async
5700 @item set target-async on
5701 Enable asynchronous mode.
5702 @item set target-async off
5703 Disable asynchronous mode.
5704 @kindex show target-async
5705 @item show target-async
5706 Show the current target-async setting.
5709 If the target doesn't support async mode, @value{GDBN} issues an error
5710 message if you attempt to use the background execution commands.
5712 To specify background execution, add a @code{&} to the command. For example,
5713 the background form of the @code{continue} command is @code{continue&}, or
5714 just @code{c&}. The execution commands that accept background execution
5720 @xref{Starting, , Starting your Program}.
5724 @xref{Attach, , Debugging an Already-running Process}.
5728 @xref{Continuing and Stepping, step}.
5732 @xref{Continuing and Stepping, stepi}.
5736 @xref{Continuing and Stepping, next}.
5740 @xref{Continuing and Stepping, nexti}.
5744 @xref{Continuing and Stepping, continue}.
5748 @xref{Continuing and Stepping, finish}.
5752 @xref{Continuing and Stepping, until}.
5756 Background execution is especially useful in conjunction with non-stop
5757 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5758 However, you can also use these commands in the normal all-stop mode with
5759 the restriction that you cannot issue another execution command until the
5760 previous one finishes. Examples of commands that are valid in all-stop
5761 mode while the program is running include @code{help} and @code{info break}.
5763 You can interrupt your program while it is running in the background by
5764 using the @code{interrupt} command.
5771 Suspend execution of the running program. In all-stop mode,
5772 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5773 only the current thread. To stop the whole program in non-stop mode,
5774 use @code{interrupt -a}.
5777 @node Thread-Specific Breakpoints
5778 @subsection Thread-Specific Breakpoints
5780 When your program has multiple threads (@pxref{Threads,, Debugging
5781 Programs with Multiple Threads}), you can choose whether to set
5782 breakpoints on all threads, or on a particular thread.
5785 @cindex breakpoints and threads
5786 @cindex thread breakpoints
5787 @kindex break @dots{} thread @var{threadno}
5788 @item break @var{linespec} thread @var{threadno}
5789 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5790 @var{linespec} specifies source lines; there are several ways of
5791 writing them (@pxref{Specify Location}), but the effect is always to
5792 specify some source line.
5794 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5795 to specify that you only want @value{GDBN} to stop the program when a
5796 particular thread reaches this breakpoint. @var{threadno} is one of the
5797 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5798 column of the @samp{info threads} display.
5800 If you do not specify @samp{thread @var{threadno}} when you set a
5801 breakpoint, the breakpoint applies to @emph{all} threads of your
5804 You can use the @code{thread} qualifier on conditional breakpoints as
5805 well; in this case, place @samp{thread @var{threadno}} before or
5806 after the breakpoint condition, like this:
5809 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5814 @node Interrupted System Calls
5815 @subsection Interrupted System Calls
5817 @cindex thread breakpoints and system calls
5818 @cindex system calls and thread breakpoints
5819 @cindex premature return from system calls
5820 There is an unfortunate side effect when using @value{GDBN} to debug
5821 multi-threaded programs. If one thread stops for a
5822 breakpoint, or for some other reason, and another thread is blocked in a
5823 system call, then the system call may return prematurely. This is a
5824 consequence of the interaction between multiple threads and the signals
5825 that @value{GDBN} uses to implement breakpoints and other events that
5828 To handle this problem, your program should check the return value of
5829 each system call and react appropriately. This is good programming
5832 For example, do not write code like this:
5838 The call to @code{sleep} will return early if a different thread stops
5839 at a breakpoint or for some other reason.
5841 Instead, write this:
5846 unslept = sleep (unslept);
5849 A system call is allowed to return early, so the system is still
5850 conforming to its specification. But @value{GDBN} does cause your
5851 multi-threaded program to behave differently than it would without
5854 Also, @value{GDBN} uses internal breakpoints in the thread library to
5855 monitor certain events such as thread creation and thread destruction.
5856 When such an event happens, a system call in another thread may return
5857 prematurely, even though your program does not appear to stop.
5860 @subsection Observer Mode
5862 If you want to build on non-stop mode and observe program behavior
5863 without any chance of disruption by @value{GDBN}, you can set
5864 variables to disable all of the debugger's attempts to modify state,
5865 whether by writing memory, inserting breakpoints, etc. These operate
5866 at a low level, intercepting operations from all commands.
5868 When all of these are set to @code{off}, then @value{GDBN} is said to
5869 be @dfn{observer mode}. As a convenience, the variable
5870 @code{observer} can be set to disable these, plus enable non-stop
5873 Note that @value{GDBN} will not prevent you from making nonsensical
5874 combinations of these settings. For instance, if you have enabled
5875 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5876 then breakpoints that work by writing trap instructions into the code
5877 stream will still not be able to be placed.
5882 @item set observer on
5883 @itemx set observer off
5884 When set to @code{on}, this disables all the permission variables
5885 below (except for @code{insert-fast-tracepoints}), plus enables
5886 non-stop debugging. Setting this to @code{off} switches back to
5887 normal debugging, though remaining in non-stop mode.
5890 Show whether observer mode is on or off.
5892 @kindex may-write-registers
5893 @item set may-write-registers on
5894 @itemx set may-write-registers off
5895 This controls whether @value{GDBN} will attempt to alter the values of
5896 registers, such as with assignment expressions in @code{print}, or the
5897 @code{jump} command. It defaults to @code{on}.
5899 @item show may-write-registers
5900 Show the current permission to write registers.
5902 @kindex may-write-memory
5903 @item set may-write-memory on
5904 @itemx set may-write-memory off
5905 This controls whether @value{GDBN} will attempt to alter the contents
5906 of memory, such as with assignment expressions in @code{print}. It
5907 defaults to @code{on}.
5909 @item show may-write-memory
5910 Show the current permission to write memory.
5912 @kindex may-insert-breakpoints
5913 @item set may-insert-breakpoints on
5914 @itemx set may-insert-breakpoints off
5915 This controls whether @value{GDBN} will attempt to insert breakpoints.
5916 This affects all breakpoints, including internal breakpoints defined
5917 by @value{GDBN}. It defaults to @code{on}.
5919 @item show may-insert-breakpoints
5920 Show the current permission to insert breakpoints.
5922 @kindex may-insert-tracepoints
5923 @item set may-insert-tracepoints on
5924 @itemx set may-insert-tracepoints off
5925 This controls whether @value{GDBN} will attempt to insert (regular)
5926 tracepoints at the beginning of a tracing experiment. It affects only
5927 non-fast tracepoints, fast tracepoints being under the control of
5928 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5930 @item show may-insert-tracepoints
5931 Show the current permission to insert tracepoints.
5933 @kindex may-insert-fast-tracepoints
5934 @item set may-insert-fast-tracepoints on
5935 @itemx set may-insert-fast-tracepoints off
5936 This controls whether @value{GDBN} will attempt to insert fast
5937 tracepoints at the beginning of a tracing experiment. It affects only
5938 fast tracepoints, regular (non-fast) tracepoints being under the
5939 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5941 @item show may-insert-fast-tracepoints
5942 Show the current permission to insert fast tracepoints.
5944 @kindex may-interrupt
5945 @item set may-interrupt on
5946 @itemx set may-interrupt off
5947 This controls whether @value{GDBN} will attempt to interrupt or stop
5948 program execution. When this variable is @code{off}, the
5949 @code{interrupt} command will have no effect, nor will
5950 @kbd{Ctrl-c}. It defaults to @code{on}.
5952 @item show may-interrupt
5953 Show the current permission to interrupt or stop the program.
5957 @node Reverse Execution
5958 @chapter Running programs backward
5959 @cindex reverse execution
5960 @cindex running programs backward
5962 When you are debugging a program, it is not unusual to realize that
5963 you have gone too far, and some event of interest has already happened.
5964 If the target environment supports it, @value{GDBN} can allow you to
5965 ``rewind'' the program by running it backward.
5967 A target environment that supports reverse execution should be able
5968 to ``undo'' the changes in machine state that have taken place as the
5969 program was executing normally. Variables, registers etc.@: should
5970 revert to their previous values. Obviously this requires a great
5971 deal of sophistication on the part of the target environment; not
5972 all target environments can support reverse execution.
5974 When a program is executed in reverse, the instructions that
5975 have most recently been executed are ``un-executed'', in reverse
5976 order. The program counter runs backward, following the previous
5977 thread of execution in reverse. As each instruction is ``un-executed'',
5978 the values of memory and/or registers that were changed by that
5979 instruction are reverted to their previous states. After executing
5980 a piece of source code in reverse, all side effects of that code
5981 should be ``undone'', and all variables should be returned to their
5982 prior values@footnote{
5983 Note that some side effects are easier to undo than others. For instance,
5984 memory and registers are relatively easy, but device I/O is hard. Some
5985 targets may be able undo things like device I/O, and some may not.
5987 The contract between @value{GDBN} and the reverse executing target
5988 requires only that the target do something reasonable when
5989 @value{GDBN} tells it to execute backwards, and then report the
5990 results back to @value{GDBN}. Whatever the target reports back to
5991 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5992 assumes that the memory and registers that the target reports are in a
5993 consistant state, but @value{GDBN} accepts whatever it is given.
5996 If you are debugging in a target environment that supports
5997 reverse execution, @value{GDBN} provides the following commands.
6000 @kindex reverse-continue
6001 @kindex rc @r{(@code{reverse-continue})}
6002 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6003 @itemx rc @r{[}@var{ignore-count}@r{]}
6004 Beginning at the point where your program last stopped, start executing
6005 in reverse. Reverse execution will stop for breakpoints and synchronous
6006 exceptions (signals), just like normal execution. Behavior of
6007 asynchronous signals depends on the target environment.
6009 @kindex reverse-step
6010 @kindex rs @r{(@code{step})}
6011 @item reverse-step @r{[}@var{count}@r{]}
6012 Run the program backward until control reaches the start of a
6013 different source line; then stop it, and return control to @value{GDBN}.
6015 Like the @code{step} command, @code{reverse-step} will only stop
6016 at the beginning of a source line. It ``un-executes'' the previously
6017 executed source line. If the previous source line included calls to
6018 debuggable functions, @code{reverse-step} will step (backward) into
6019 the called function, stopping at the beginning of the @emph{last}
6020 statement in the called function (typically a return statement).
6022 Also, as with the @code{step} command, if non-debuggable functions are
6023 called, @code{reverse-step} will run thru them backward without stopping.
6025 @kindex reverse-stepi
6026 @kindex rsi @r{(@code{reverse-stepi})}
6027 @item reverse-stepi @r{[}@var{count}@r{]}
6028 Reverse-execute one machine instruction. Note that the instruction
6029 to be reverse-executed is @emph{not} the one pointed to by the program
6030 counter, but the instruction executed prior to that one. For instance,
6031 if the last instruction was a jump, @code{reverse-stepi} will take you
6032 back from the destination of the jump to the jump instruction itself.
6034 @kindex reverse-next
6035 @kindex rn @r{(@code{reverse-next})}
6036 @item reverse-next @r{[}@var{count}@r{]}
6037 Run backward to the beginning of the previous line executed in
6038 the current (innermost) stack frame. If the line contains function
6039 calls, they will be ``un-executed'' without stopping. Starting from
6040 the first line of a function, @code{reverse-next} will take you back
6041 to the caller of that function, @emph{before} the function was called,
6042 just as the normal @code{next} command would take you from the last
6043 line of a function back to its return to its caller
6044 @footnote{Unless the code is too heavily optimized.}.
6046 @kindex reverse-nexti
6047 @kindex rni @r{(@code{reverse-nexti})}
6048 @item reverse-nexti @r{[}@var{count}@r{]}
6049 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6050 in reverse, except that called functions are ``un-executed'' atomically.
6051 That is, if the previously executed instruction was a return from
6052 another function, @code{reverse-nexti} will continue to execute
6053 in reverse until the call to that function (from the current stack
6056 @kindex reverse-finish
6057 @item reverse-finish
6058 Just as the @code{finish} command takes you to the point where the
6059 current function returns, @code{reverse-finish} takes you to the point
6060 where it was called. Instead of ending up at the end of the current
6061 function invocation, you end up at the beginning.
6063 @kindex set exec-direction
6064 @item set exec-direction
6065 Set the direction of target execution.
6066 @item set exec-direction reverse
6067 @cindex execute forward or backward in time
6068 @value{GDBN} will perform all execution commands in reverse, until the
6069 exec-direction mode is changed to ``forward''. Affected commands include
6070 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6071 command cannot be used in reverse mode.
6072 @item set exec-direction forward
6073 @value{GDBN} will perform all execution commands in the normal fashion.
6074 This is the default.
6078 @node Process Record and Replay
6079 @chapter Recording Inferior's Execution and Replaying It
6080 @cindex process record and replay
6081 @cindex recording inferior's execution and replaying it
6083 On some platforms, @value{GDBN} provides a special @dfn{process record
6084 and replay} target that can record a log of the process execution, and
6085 replay it later with both forward and reverse execution commands.
6088 When this target is in use, if the execution log includes the record
6089 for the next instruction, @value{GDBN} will debug in @dfn{replay
6090 mode}. In the replay mode, the inferior does not really execute code
6091 instructions. Instead, all the events that normally happen during
6092 code execution are taken from the execution log. While code is not
6093 really executed in replay mode, the values of registers (including the
6094 program counter register) and the memory of the inferior are still
6095 changed as they normally would. Their contents are taken from the
6099 If the record for the next instruction is not in the execution log,
6100 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6101 inferior executes normally, and @value{GDBN} records the execution log
6104 The process record and replay target supports reverse execution
6105 (@pxref{Reverse Execution}), even if the platform on which the
6106 inferior runs does not. However, the reverse execution is limited in
6107 this case by the range of the instructions recorded in the execution
6108 log. In other words, reverse execution on platforms that don't
6109 support it directly can only be done in the replay mode.
6111 When debugging in the reverse direction, @value{GDBN} will work in
6112 replay mode as long as the execution log includes the record for the
6113 previous instruction; otherwise, it will work in record mode, if the
6114 platform supports reverse execution, or stop if not.
6116 For architecture environments that support process record and replay,
6117 @value{GDBN} provides the following commands:
6120 @kindex target record
6124 This command starts the process record and replay target. The process
6125 record and replay target can only debug a process that is already
6126 running. Therefore, you need first to start the process with the
6127 @kbd{run} or @kbd{start} commands, and then start the recording with
6128 the @kbd{target record} command.
6130 Both @code{record} and @code{rec} are aliases of @code{target record}.
6132 @cindex displaced stepping, and process record and replay
6133 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6134 will be automatically disabled when process record and replay target
6135 is started. That's because the process record and replay target
6136 doesn't support displaced stepping.
6138 @cindex non-stop mode, and process record and replay
6139 @cindex asynchronous execution, and process record and replay
6140 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6141 the asynchronous execution mode (@pxref{Background Execution}), the
6142 process record and replay target cannot be started because it doesn't
6143 support these two modes.
6148 Stop the process record and replay target. When process record and
6149 replay target stops, the entire execution log will be deleted and the
6150 inferior will either be terminated, or will remain in its final state.
6152 When you stop the process record and replay target in record mode (at
6153 the end of the execution log), the inferior will be stopped at the
6154 next instruction that would have been recorded. In other words, if
6155 you record for a while and then stop recording, the inferior process
6156 will be left in the same state as if the recording never happened.
6158 On the other hand, if the process record and replay target is stopped
6159 while in replay mode (that is, not at the end of the execution log,
6160 but at some earlier point), the inferior process will become ``live''
6161 at that earlier state, and it will then be possible to continue the
6162 usual ``live'' debugging of the process from that state.
6164 When the inferior process exits, or @value{GDBN} detaches from it,
6165 process record and replay target will automatically stop itself.
6168 @item record save @var{filename}
6169 Save the execution log to a file @file{@var{filename}}.
6170 Default filename is @file{gdb_record.@var{process_id}}, where
6171 @var{process_id} is the process ID of the inferior.
6173 @kindex record restore
6174 @item record restore @var{filename}
6175 Restore the execution log from a file @file{@var{filename}}.
6176 File must have been created with @code{record save}.
6178 @kindex set record insn-number-max
6179 @item set record insn-number-max @var{limit}
6180 Set the limit of instructions to be recorded. Default value is 200000.
6182 If @var{limit} is a positive number, then @value{GDBN} will start
6183 deleting instructions from the log once the number of the record
6184 instructions becomes greater than @var{limit}. For every new recorded
6185 instruction, @value{GDBN} will delete the earliest recorded
6186 instruction to keep the number of recorded instructions at the limit.
6187 (Since deleting recorded instructions loses information, @value{GDBN}
6188 lets you control what happens when the limit is reached, by means of
6189 the @code{stop-at-limit} option, described below.)
6191 If @var{limit} is zero, @value{GDBN} will never delete recorded
6192 instructions from the execution log. The number of recorded
6193 instructions is unlimited in this case.
6195 @kindex show record insn-number-max
6196 @item show record insn-number-max
6197 Show the limit of instructions to be recorded.
6199 @kindex set record stop-at-limit
6200 @item set record stop-at-limit
6201 Control the behavior when the number of recorded instructions reaches
6202 the limit. If ON (the default), @value{GDBN} will stop when the limit
6203 is reached for the first time and ask you whether you want to stop the
6204 inferior or continue running it and recording the execution log. If
6205 you decide to continue recording, each new recorded instruction will
6206 cause the oldest one to be deleted.
6208 If this option is OFF, @value{GDBN} will automatically delete the
6209 oldest record to make room for each new one, without asking.
6211 @kindex show record stop-at-limit
6212 @item show record stop-at-limit
6213 Show the current setting of @code{stop-at-limit}.
6215 @kindex set record memory-query
6216 @item set record memory-query
6217 Control the behavior when @value{GDBN} is unable to record memory
6218 changes caused by an instruction. If ON, @value{GDBN} will query
6219 whether to stop the inferior in that case.
6221 If this option is OFF (the default), @value{GDBN} will automatically
6222 ignore the effect of such instructions on memory. Later, when
6223 @value{GDBN} replays this execution log, it will mark the log of this
6224 instruction as not accessible, and it will not affect the replay
6227 @kindex show record memory-query
6228 @item show record memory-query
6229 Show the current setting of @code{memory-query}.
6233 Show various statistics about the state of process record and its
6234 in-memory execution log buffer, including:
6238 Whether in record mode or replay mode.
6240 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6242 Highest recorded instruction number.
6244 Current instruction about to be replayed (if in replay mode).
6246 Number of instructions contained in the execution log.
6248 Maximum number of instructions that may be contained in the execution log.
6251 @kindex record delete
6254 When record target runs in replay mode (``in the past''), delete the
6255 subsequent execution log and begin to record a new execution log starting
6256 from the current address. This means you will abandon the previously
6257 recorded ``future'' and begin recording a new ``future''.
6262 @chapter Examining the Stack
6264 When your program has stopped, the first thing you need to know is where it
6265 stopped and how it got there.
6268 Each time your program performs a function call, information about the call
6270 That information includes the location of the call in your program,
6271 the arguments of the call,
6272 and the local variables of the function being called.
6273 The information is saved in a block of data called a @dfn{stack frame}.
6274 The stack frames are allocated in a region of memory called the @dfn{call
6277 When your program stops, the @value{GDBN} commands for examining the
6278 stack allow you to see all of this information.
6280 @cindex selected frame
6281 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6282 @value{GDBN} commands refer implicitly to the selected frame. In
6283 particular, whenever you ask @value{GDBN} for the value of a variable in
6284 your program, the value is found in the selected frame. There are
6285 special @value{GDBN} commands to select whichever frame you are
6286 interested in. @xref{Selection, ,Selecting a Frame}.
6288 When your program stops, @value{GDBN} automatically selects the
6289 currently executing frame and describes it briefly, similar to the
6290 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6293 * Frames:: Stack frames
6294 * Backtrace:: Backtraces
6295 * Selection:: Selecting a frame
6296 * Frame Info:: Information on a frame
6301 @section Stack Frames
6303 @cindex frame, definition
6305 The call stack is divided up into contiguous pieces called @dfn{stack
6306 frames}, or @dfn{frames} for short; each frame is the data associated
6307 with one call to one function. The frame contains the arguments given
6308 to the function, the function's local variables, and the address at
6309 which the function is executing.
6311 @cindex initial frame
6312 @cindex outermost frame
6313 @cindex innermost frame
6314 When your program is started, the stack has only one frame, that of the
6315 function @code{main}. This is called the @dfn{initial} frame or the
6316 @dfn{outermost} frame. Each time a function is called, a new frame is
6317 made. Each time a function returns, the frame for that function invocation
6318 is eliminated. If a function is recursive, there can be many frames for
6319 the same function. The frame for the function in which execution is
6320 actually occurring is called the @dfn{innermost} frame. This is the most
6321 recently created of all the stack frames that still exist.
6323 @cindex frame pointer
6324 Inside your program, stack frames are identified by their addresses. A
6325 stack frame consists of many bytes, each of which has its own address; each
6326 kind of computer has a convention for choosing one byte whose
6327 address serves as the address of the frame. Usually this address is kept
6328 in a register called the @dfn{frame pointer register}
6329 (@pxref{Registers, $fp}) while execution is going on in that frame.
6331 @cindex frame number
6332 @value{GDBN} assigns numbers to all existing stack frames, starting with
6333 zero for the innermost frame, one for the frame that called it,
6334 and so on upward. These numbers do not really exist in your program;
6335 they are assigned by @value{GDBN} to give you a way of designating stack
6336 frames in @value{GDBN} commands.
6338 @c The -fomit-frame-pointer below perennially causes hbox overflow
6339 @c underflow problems.
6340 @cindex frameless execution
6341 Some compilers provide a way to compile functions so that they operate
6342 without stack frames. (For example, the @value{NGCC} option
6344 @samp{-fomit-frame-pointer}
6346 generates functions without a frame.)
6347 This is occasionally done with heavily used library functions to save
6348 the frame setup time. @value{GDBN} has limited facilities for dealing
6349 with these function invocations. If the innermost function invocation
6350 has no stack frame, @value{GDBN} nevertheless regards it as though
6351 it had a separate frame, which is numbered zero as usual, allowing
6352 correct tracing of the function call chain. However, @value{GDBN} has
6353 no provision for frameless functions elsewhere in the stack.
6356 @kindex frame@r{, command}
6357 @cindex current stack frame
6358 @item frame @var{args}
6359 The @code{frame} command allows you to move from one stack frame to another,
6360 and to print the stack frame you select. @var{args} may be either the
6361 address of the frame or the stack frame number. Without an argument,
6362 @code{frame} prints the current stack frame.
6364 @kindex select-frame
6365 @cindex selecting frame silently
6367 The @code{select-frame} command allows you to move from one stack frame
6368 to another without printing the frame. This is the silent version of
6376 @cindex call stack traces
6377 A backtrace is a summary of how your program got where it is. It shows one
6378 line per frame, for many frames, starting with the currently executing
6379 frame (frame zero), followed by its caller (frame one), and on up the
6384 @kindex bt @r{(@code{backtrace})}
6387 Print a backtrace of the entire stack: one line per frame for all
6388 frames in the stack.
6390 You can stop the backtrace at any time by typing the system interrupt
6391 character, normally @kbd{Ctrl-c}.
6393 @item backtrace @var{n}
6395 Similar, but print only the innermost @var{n} frames.
6397 @item backtrace -@var{n}
6399 Similar, but print only the outermost @var{n} frames.
6401 @item backtrace full
6403 @itemx bt full @var{n}
6404 @itemx bt full -@var{n}
6405 Print the values of the local variables also. @var{n} specifies the
6406 number of frames to print, as described above.
6411 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6412 are additional aliases for @code{backtrace}.
6414 @cindex multiple threads, backtrace
6415 In a multi-threaded program, @value{GDBN} by default shows the
6416 backtrace only for the current thread. To display the backtrace for
6417 several or all of the threads, use the command @code{thread apply}
6418 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6419 apply all backtrace}, @value{GDBN} will display the backtrace for all
6420 the threads; this is handy when you debug a core dump of a
6421 multi-threaded program.
6423 Each line in the backtrace shows the frame number and the function name.
6424 The program counter value is also shown---unless you use @code{set
6425 print address off}. The backtrace also shows the source file name and
6426 line number, as well as the arguments to the function. The program
6427 counter value is omitted if it is at the beginning of the code for that
6430 Here is an example of a backtrace. It was made with the command
6431 @samp{bt 3}, so it shows the innermost three frames.
6435 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6437 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6438 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6440 (More stack frames follow...)
6445 The display for frame zero does not begin with a program counter
6446 value, indicating that your program has stopped at the beginning of the
6447 code for line @code{993} of @code{builtin.c}.
6450 The value of parameter @code{data} in frame 1 has been replaced by
6451 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6452 only if it is a scalar (integer, pointer, enumeration, etc). See command
6453 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6454 on how to configure the way function parameter values are printed.
6456 @cindex optimized out, in backtrace
6457 @cindex function call arguments, optimized out
6458 If your program was compiled with optimizations, some compilers will
6459 optimize away arguments passed to functions if those arguments are
6460 never used after the call. Such optimizations generate code that
6461 passes arguments through registers, but doesn't store those arguments
6462 in the stack frame. @value{GDBN} has no way of displaying such
6463 arguments in stack frames other than the innermost one. Here's what
6464 such a backtrace might look like:
6468 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6470 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6471 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6473 (More stack frames follow...)
6478 The values of arguments that were not saved in their stack frames are
6479 shown as @samp{<optimized out>}.
6481 If you need to display the values of such optimized-out arguments,
6482 either deduce that from other variables whose values depend on the one
6483 you are interested in, or recompile without optimizations.
6485 @cindex backtrace beyond @code{main} function
6486 @cindex program entry point
6487 @cindex startup code, and backtrace
6488 Most programs have a standard user entry point---a place where system
6489 libraries and startup code transition into user code. For C this is
6490 @code{main}@footnote{
6491 Note that embedded programs (the so-called ``free-standing''
6492 environment) are not required to have a @code{main} function as the
6493 entry point. They could even have multiple entry points.}.
6494 When @value{GDBN} finds the entry function in a backtrace
6495 it will terminate the backtrace, to avoid tracing into highly
6496 system-specific (and generally uninteresting) code.
6498 If you need to examine the startup code, or limit the number of levels
6499 in a backtrace, you can change this behavior:
6502 @item set backtrace past-main
6503 @itemx set backtrace past-main on
6504 @kindex set backtrace
6505 Backtraces will continue past the user entry point.
6507 @item set backtrace past-main off
6508 Backtraces will stop when they encounter the user entry point. This is the
6511 @item show backtrace past-main
6512 @kindex show backtrace
6513 Display the current user entry point backtrace policy.
6515 @item set backtrace past-entry
6516 @itemx set backtrace past-entry on
6517 Backtraces will continue past the internal entry point of an application.
6518 This entry point is encoded by the linker when the application is built,
6519 and is likely before the user entry point @code{main} (or equivalent) is called.
6521 @item set backtrace past-entry off
6522 Backtraces will stop when they encounter the internal entry point of an
6523 application. This is the default.
6525 @item show backtrace past-entry
6526 Display the current internal entry point backtrace policy.
6528 @item set backtrace limit @var{n}
6529 @itemx set backtrace limit 0
6530 @cindex backtrace limit
6531 Limit the backtrace to @var{n} levels. A value of zero means
6534 @item show backtrace limit
6535 Display the current limit on backtrace levels.
6538 You can control how file names are displayed.
6541 @item set filename-display
6542 @itemx set filename-display relative
6543 @cindex filename-display
6544 Display file names relative to the compilation directory. This is the default.
6546 @item set filename-display basename
6547 Display only basename of a filename.
6549 @item set filename-display absolute
6550 Display an absolute filename.
6552 @item show filename-display
6553 Show the current way to display filenames.
6557 @section Selecting a Frame
6559 Most commands for examining the stack and other data in your program work on
6560 whichever stack frame is selected at the moment. Here are the commands for
6561 selecting a stack frame; all of them finish by printing a brief description
6562 of the stack frame just selected.
6565 @kindex frame@r{, selecting}
6566 @kindex f @r{(@code{frame})}
6569 Select frame number @var{n}. Recall that frame zero is the innermost
6570 (currently executing) frame, frame one is the frame that called the
6571 innermost one, and so on. The highest-numbered frame is the one for
6574 @item frame @var{addr}
6576 Select the frame at address @var{addr}. This is useful mainly if the
6577 chaining of stack frames has been damaged by a bug, making it
6578 impossible for @value{GDBN} to assign numbers properly to all frames. In
6579 addition, this can be useful when your program has multiple stacks and
6580 switches between them.
6582 On the SPARC architecture, @code{frame} needs two addresses to
6583 select an arbitrary frame: a frame pointer and a stack pointer.
6585 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6586 pointer and a program counter.
6588 On the 29k architecture, it needs three addresses: a register stack
6589 pointer, a program counter, and a memory stack pointer.
6593 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6594 advances toward the outermost frame, to higher frame numbers, to frames
6595 that have existed longer. @var{n} defaults to one.
6598 @kindex do @r{(@code{down})}
6600 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6601 advances toward the innermost frame, to lower frame numbers, to frames
6602 that were created more recently. @var{n} defaults to one. You may
6603 abbreviate @code{down} as @code{do}.
6606 All of these commands end by printing two lines of output describing the
6607 frame. The first line shows the frame number, the function name, the
6608 arguments, and the source file and line number of execution in that
6609 frame. The second line shows the text of that source line.
6617 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6619 10 read_input_file (argv[i]);
6623 After such a printout, the @code{list} command with no arguments
6624 prints ten lines centered on the point of execution in the frame.
6625 You can also edit the program at the point of execution with your favorite
6626 editing program by typing @code{edit}.
6627 @xref{List, ,Printing Source Lines},
6631 @kindex down-silently
6633 @item up-silently @var{n}
6634 @itemx down-silently @var{n}
6635 These two commands are variants of @code{up} and @code{down},
6636 respectively; they differ in that they do their work silently, without
6637 causing display of the new frame. They are intended primarily for use
6638 in @value{GDBN} command scripts, where the output might be unnecessary and
6643 @section Information About a Frame
6645 There are several other commands to print information about the selected
6651 When used without any argument, this command does not change which
6652 frame is selected, but prints a brief description of the currently
6653 selected stack frame. It can be abbreviated @code{f}. With an
6654 argument, this command is used to select a stack frame.
6655 @xref{Selection, ,Selecting a Frame}.
6658 @kindex info f @r{(@code{info frame})}
6661 This command prints a verbose description of the selected stack frame,
6666 the address of the frame
6668 the address of the next frame down (called by this frame)
6670 the address of the next frame up (caller of this frame)
6672 the language in which the source code corresponding to this frame is written
6674 the address of the frame's arguments
6676 the address of the frame's local variables
6678 the program counter saved in it (the address of execution in the caller frame)
6680 which registers were saved in the frame
6683 @noindent The verbose description is useful when
6684 something has gone wrong that has made the stack format fail to fit
6685 the usual conventions.
6687 @item info frame @var{addr}
6688 @itemx info f @var{addr}
6689 Print a verbose description of the frame at address @var{addr}, without
6690 selecting that frame. The selected frame remains unchanged by this
6691 command. This requires the same kind of address (more than one for some
6692 architectures) that you specify in the @code{frame} command.
6693 @xref{Selection, ,Selecting a Frame}.
6697 Print the arguments of the selected frame, each on a separate line.
6701 Print the local variables of the selected frame, each on a separate
6702 line. These are all variables (declared either static or automatic)
6703 accessible at the point of execution of the selected frame.
6709 @chapter Examining Source Files
6711 @value{GDBN} can print parts of your program's source, since the debugging
6712 information recorded in the program tells @value{GDBN} what source files were
6713 used to build it. When your program stops, @value{GDBN} spontaneously prints
6714 the line where it stopped. Likewise, when you select a stack frame
6715 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6716 execution in that frame has stopped. You can print other portions of
6717 source files by explicit command.
6719 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6720 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6721 @value{GDBN} under @sc{gnu} Emacs}.
6724 * List:: Printing source lines
6725 * Specify Location:: How to specify code locations
6726 * Edit:: Editing source files
6727 * Search:: Searching source files
6728 * Source Path:: Specifying source directories
6729 * Machine Code:: Source and machine code
6733 @section Printing Source Lines
6736 @kindex l @r{(@code{list})}
6737 To print lines from a source file, use the @code{list} command
6738 (abbreviated @code{l}). By default, ten lines are printed.
6739 There are several ways to specify what part of the file you want to
6740 print; see @ref{Specify Location}, for the full list.
6742 Here are the forms of the @code{list} command most commonly used:
6745 @item list @var{linenum}
6746 Print lines centered around line number @var{linenum} in the
6747 current source file.
6749 @item list @var{function}
6750 Print lines centered around the beginning of function
6754 Print more lines. If the last lines printed were printed with a
6755 @code{list} command, this prints lines following the last lines
6756 printed; however, if the last line printed was a solitary line printed
6757 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6758 Stack}), this prints lines centered around that line.
6761 Print lines just before the lines last printed.
6764 @cindex @code{list}, how many lines to display
6765 By default, @value{GDBN} prints ten source lines with any of these forms of
6766 the @code{list} command. You can change this using @code{set listsize}:
6769 @kindex set listsize
6770 @item set listsize @var{count}
6771 Make the @code{list} command display @var{count} source lines (unless
6772 the @code{list} argument explicitly specifies some other number).
6773 Setting @var{count} to -1 means there's no limit and 0 means suppress
6774 display of source lines.
6776 @kindex show listsize
6778 Display the number of lines that @code{list} prints.
6781 Repeating a @code{list} command with @key{RET} discards the argument,
6782 so it is equivalent to typing just @code{list}. This is more useful
6783 than listing the same lines again. An exception is made for an
6784 argument of @samp{-}; that argument is preserved in repetition so that
6785 each repetition moves up in the source file.
6787 In general, the @code{list} command expects you to supply zero, one or two
6788 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6789 of writing them (@pxref{Specify Location}), but the effect is always
6790 to specify some source line.
6792 Here is a complete description of the possible arguments for @code{list}:
6795 @item list @var{linespec}
6796 Print lines centered around the line specified by @var{linespec}.
6798 @item list @var{first},@var{last}
6799 Print lines from @var{first} to @var{last}. Both arguments are
6800 linespecs. When a @code{list} command has two linespecs, and the
6801 source file of the second linespec is omitted, this refers to
6802 the same source file as the first linespec.
6804 @item list ,@var{last}
6805 Print lines ending with @var{last}.
6807 @item list @var{first},
6808 Print lines starting with @var{first}.
6811 Print lines just after the lines last printed.
6814 Print lines just before the lines last printed.
6817 As described in the preceding table.
6820 @node Specify Location
6821 @section Specifying a Location
6822 @cindex specifying location
6825 Several @value{GDBN} commands accept arguments that specify a location
6826 of your program's code. Since @value{GDBN} is a source-level
6827 debugger, a location usually specifies some line in the source code;
6828 for that reason, locations are also known as @dfn{linespecs}.
6830 Here are all the different ways of specifying a code location that
6831 @value{GDBN} understands:
6835 Specifies the line number @var{linenum} of the current source file.
6838 @itemx +@var{offset}
6839 Specifies the line @var{offset} lines before or after the @dfn{current
6840 line}. For the @code{list} command, the current line is the last one
6841 printed; for the breakpoint commands, this is the line at which
6842 execution stopped in the currently selected @dfn{stack frame}
6843 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6844 used as the second of the two linespecs in a @code{list} command,
6845 this specifies the line @var{offset} lines up or down from the first
6848 @item @var{filename}:@var{linenum}
6849 Specifies the line @var{linenum} in the source file @var{filename}.
6850 If @var{filename} is a relative file name, then it will match any
6851 source file name with the same trailing components. For example, if
6852 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6853 name of @file{/build/trunk/gcc/expr.c}, but not
6854 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6856 @item @var{function}
6857 Specifies the line that begins the body of the function @var{function}.
6858 For example, in C, this is the line with the open brace.
6860 @item @var{function}:@var{label}
6861 Specifies the line where @var{label} appears in @var{function}.
6863 @item @var{filename}:@var{function}
6864 Specifies the line that begins the body of the function @var{function}
6865 in the file @var{filename}. You only need the file name with a
6866 function name to avoid ambiguity when there are identically named
6867 functions in different source files.
6870 Specifies the line at which the label named @var{label} appears.
6871 @value{GDBN} searches for the label in the function corresponding to
6872 the currently selected stack frame. If there is no current selected
6873 stack frame (for instance, if the inferior is not running), then
6874 @value{GDBN} will not search for a label.
6876 @item *@var{address}
6877 Specifies the program address @var{address}. For line-oriented
6878 commands, such as @code{list} and @code{edit}, this specifies a source
6879 line that contains @var{address}. For @code{break} and other
6880 breakpoint oriented commands, this can be used to set breakpoints in
6881 parts of your program which do not have debugging information or
6884 Here @var{address} may be any expression valid in the current working
6885 language (@pxref{Languages, working language}) that specifies a code
6886 address. In addition, as a convenience, @value{GDBN} extends the
6887 semantics of expressions used in locations to cover the situations
6888 that frequently happen during debugging. Here are the various forms
6892 @item @var{expression}
6893 Any expression valid in the current working language.
6895 @item @var{funcaddr}
6896 An address of a function or procedure derived from its name. In C,
6897 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6898 simply the function's name @var{function} (and actually a special case
6899 of a valid expression). In Pascal and Modula-2, this is
6900 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6901 (although the Pascal form also works).
6903 This form specifies the address of the function's first instruction,
6904 before the stack frame and arguments have been set up.
6906 @item '@var{filename}'::@var{funcaddr}
6907 Like @var{funcaddr} above, but also specifies the name of the source
6908 file explicitly. This is useful if the name of the function does not
6909 specify the function unambiguously, e.g., if there are several
6910 functions with identical names in different source files.
6913 @cindex breakpoint at static probe point
6914 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
6915 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
6916 applications to embed static probes. @xref{Static Probe Points}, for more
6917 information on finding and using static probes. This form of linespec
6918 specifies the location of such a static probe.
6920 If @var{objfile} is given, only probes coming from that shared library
6921 or executable matching @var{objfile} as a regular expression are considered.
6922 If @var{provider} is given, then only probes from that provider are considered.
6923 If several probes match the spec, @value{GDBN} will insert a breakpoint at
6924 each one of those probes.
6930 @section Editing Source Files
6931 @cindex editing source files
6934 @kindex e @r{(@code{edit})}
6935 To edit the lines in a source file, use the @code{edit} command.
6936 The editing program of your choice
6937 is invoked with the current line set to
6938 the active line in the program.
6939 Alternatively, there are several ways to specify what part of the file you
6940 want to print if you want to see other parts of the program:
6943 @item edit @var{location}
6944 Edit the source file specified by @code{location}. Editing starts at
6945 that @var{location}, e.g., at the specified source line of the
6946 specified file. @xref{Specify Location}, for all the possible forms
6947 of the @var{location} argument; here are the forms of the @code{edit}
6948 command most commonly used:
6951 @item edit @var{number}
6952 Edit the current source file with @var{number} as the active line number.
6954 @item edit @var{function}
6955 Edit the file containing @var{function} at the beginning of its definition.
6960 @subsection Choosing your Editor
6961 You can customize @value{GDBN} to use any editor you want
6963 The only restriction is that your editor (say @code{ex}), recognizes the
6964 following command-line syntax:
6966 ex +@var{number} file
6968 The optional numeric value +@var{number} specifies the number of the line in
6969 the file where to start editing.}.
6970 By default, it is @file{@value{EDITOR}}, but you can change this
6971 by setting the environment variable @code{EDITOR} before using
6972 @value{GDBN}. For example, to configure @value{GDBN} to use the
6973 @code{vi} editor, you could use these commands with the @code{sh} shell:
6979 or in the @code{csh} shell,
6981 setenv EDITOR /usr/bin/vi
6986 @section Searching Source Files
6987 @cindex searching source files
6989 There are two commands for searching through the current source file for a
6994 @kindex forward-search
6995 @kindex fo @r{(@code{forward-search})}
6996 @item forward-search @var{regexp}
6997 @itemx search @var{regexp}
6998 The command @samp{forward-search @var{regexp}} checks each line,
6999 starting with the one following the last line listed, for a match for
7000 @var{regexp}. It lists the line that is found. You can use the
7001 synonym @samp{search @var{regexp}} or abbreviate the command name as
7004 @kindex reverse-search
7005 @item reverse-search @var{regexp}
7006 The command @samp{reverse-search @var{regexp}} checks each line, starting
7007 with the one before the last line listed and going backward, for a match
7008 for @var{regexp}. It lists the line that is found. You can abbreviate
7009 this command as @code{rev}.
7013 @section Specifying Source Directories
7016 @cindex directories for source files
7017 Executable programs sometimes do not record the directories of the source
7018 files from which they were compiled, just the names. Even when they do,
7019 the directories could be moved between the compilation and your debugging
7020 session. @value{GDBN} has a list of directories to search for source files;
7021 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7022 it tries all the directories in the list, in the order they are present
7023 in the list, until it finds a file with the desired name.
7025 For example, suppose an executable references the file
7026 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7027 @file{/mnt/cross}. The file is first looked up literally; if this
7028 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7029 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7030 message is printed. @value{GDBN} does not look up the parts of the
7031 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7032 Likewise, the subdirectories of the source path are not searched: if
7033 the source path is @file{/mnt/cross}, and the binary refers to
7034 @file{foo.c}, @value{GDBN} would not find it under
7035 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7037 Plain file names, relative file names with leading directories, file
7038 names containing dots, etc.@: are all treated as described above; for
7039 instance, if the source path is @file{/mnt/cross}, and the source file
7040 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7041 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7042 that---@file{/mnt/cross/foo.c}.
7044 Note that the executable search path is @emph{not} used to locate the
7047 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7048 any information it has cached about where source files are found and where
7049 each line is in the file.
7053 When you start @value{GDBN}, its source path includes only @samp{cdir}
7054 and @samp{cwd}, in that order.
7055 To add other directories, use the @code{directory} command.
7057 The search path is used to find both program source files and @value{GDBN}
7058 script files (read using the @samp{-command} option and @samp{source} command).
7060 In addition to the source path, @value{GDBN} provides a set of commands
7061 that manage a list of source path substitution rules. A @dfn{substitution
7062 rule} specifies how to rewrite source directories stored in the program's
7063 debug information in case the sources were moved to a different
7064 directory between compilation and debugging. A rule is made of
7065 two strings, the first specifying what needs to be rewritten in
7066 the path, and the second specifying how it should be rewritten.
7067 In @ref{set substitute-path}, we name these two parts @var{from} and
7068 @var{to} respectively. @value{GDBN} does a simple string replacement
7069 of @var{from} with @var{to} at the start of the directory part of the
7070 source file name, and uses that result instead of the original file
7071 name to look up the sources.
7073 Using the previous example, suppose the @file{foo-1.0} tree has been
7074 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7075 @value{GDBN} to replace @file{/usr/src} in all source path names with
7076 @file{/mnt/cross}. The first lookup will then be
7077 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7078 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7079 substitution rule, use the @code{set substitute-path} command
7080 (@pxref{set substitute-path}).
7082 To avoid unexpected substitution results, a rule is applied only if the
7083 @var{from} part of the directory name ends at a directory separator.
7084 For instance, a rule substituting @file{/usr/source} into
7085 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7086 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7087 is applied only at the beginning of the directory name, this rule will
7088 not be applied to @file{/root/usr/source/baz.c} either.
7090 In many cases, you can achieve the same result using the @code{directory}
7091 command. However, @code{set substitute-path} can be more efficient in
7092 the case where the sources are organized in a complex tree with multiple
7093 subdirectories. With the @code{directory} command, you need to add each
7094 subdirectory of your project. If you moved the entire tree while
7095 preserving its internal organization, then @code{set substitute-path}
7096 allows you to direct the debugger to all the sources with one single
7099 @code{set substitute-path} is also more than just a shortcut command.
7100 The source path is only used if the file at the original location no
7101 longer exists. On the other hand, @code{set substitute-path} modifies
7102 the debugger behavior to look at the rewritten location instead. So, if
7103 for any reason a source file that is not relevant to your executable is
7104 located at the original location, a substitution rule is the only
7105 method available to point @value{GDBN} at the new location.
7107 @cindex @samp{--with-relocated-sources}
7108 @cindex default source path substitution
7109 You can configure a default source path substitution rule by
7110 configuring @value{GDBN} with the
7111 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7112 should be the name of a directory under @value{GDBN}'s configured
7113 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7114 directory names in debug information under @var{dir} will be adjusted
7115 automatically if the installed @value{GDBN} is moved to a new
7116 location. This is useful if @value{GDBN}, libraries or executables
7117 with debug information and corresponding source code are being moved
7121 @item directory @var{dirname} @dots{}
7122 @item dir @var{dirname} @dots{}
7123 Add directory @var{dirname} to the front of the source path. Several
7124 directory names may be given to this command, separated by @samp{:}
7125 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7126 part of absolute file names) or
7127 whitespace. You may specify a directory that is already in the source
7128 path; this moves it forward, so @value{GDBN} searches it sooner.
7132 @vindex $cdir@r{, convenience variable}
7133 @vindex $cwd@r{, convenience variable}
7134 @cindex compilation directory
7135 @cindex current directory
7136 @cindex working directory
7137 @cindex directory, current
7138 @cindex directory, compilation
7139 You can use the string @samp{$cdir} to refer to the compilation
7140 directory (if one is recorded), and @samp{$cwd} to refer to the current
7141 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7142 tracks the current working directory as it changes during your @value{GDBN}
7143 session, while the latter is immediately expanded to the current
7144 directory at the time you add an entry to the source path.
7147 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7149 @c RET-repeat for @code{directory} is explicitly disabled, but since
7150 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7152 @item set directories @var{path-list}
7153 @kindex set directories
7154 Set the source path to @var{path-list}.
7155 @samp{$cdir:$cwd} are added if missing.
7157 @item show directories
7158 @kindex show directories
7159 Print the source path: show which directories it contains.
7161 @anchor{set substitute-path}
7162 @item set substitute-path @var{from} @var{to}
7163 @kindex set substitute-path
7164 Define a source path substitution rule, and add it at the end of the
7165 current list of existing substitution rules. If a rule with the same
7166 @var{from} was already defined, then the old rule is also deleted.
7168 For example, if the file @file{/foo/bar/baz.c} was moved to
7169 @file{/mnt/cross/baz.c}, then the command
7172 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7176 will tell @value{GDBN} to replace @samp{/usr/src} with
7177 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7178 @file{baz.c} even though it was moved.
7180 In the case when more than one substitution rule have been defined,
7181 the rules are evaluated one by one in the order where they have been
7182 defined. The first one matching, if any, is selected to perform
7185 For instance, if we had entered the following commands:
7188 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7189 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7193 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7194 @file{/mnt/include/defs.h} by using the first rule. However, it would
7195 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7196 @file{/mnt/src/lib/foo.c}.
7199 @item unset substitute-path [path]
7200 @kindex unset substitute-path
7201 If a path is specified, search the current list of substitution rules
7202 for a rule that would rewrite that path. Delete that rule if found.
7203 A warning is emitted by the debugger if no rule could be found.
7205 If no path is specified, then all substitution rules are deleted.
7207 @item show substitute-path [path]
7208 @kindex show substitute-path
7209 If a path is specified, then print the source path substitution rule
7210 which would rewrite that path, if any.
7212 If no path is specified, then print all existing source path substitution
7217 If your source path is cluttered with directories that are no longer of
7218 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7219 versions of source. You can correct the situation as follows:
7223 Use @code{directory} with no argument to reset the source path to its default value.
7226 Use @code{directory} with suitable arguments to reinstall the
7227 directories you want in the source path. You can add all the
7228 directories in one command.
7232 @section Source and Machine Code
7233 @cindex source line and its code address
7235 You can use the command @code{info line} to map source lines to program
7236 addresses (and vice versa), and the command @code{disassemble} to display
7237 a range of addresses as machine instructions. You can use the command
7238 @code{set disassemble-next-line} to set whether to disassemble next
7239 source line when execution stops. When run under @sc{gnu} Emacs
7240 mode, the @code{info line} command causes the arrow to point to the
7241 line specified. Also, @code{info line} prints addresses in symbolic form as
7246 @item info line @var{linespec}
7247 Print the starting and ending addresses of the compiled code for
7248 source line @var{linespec}. You can specify source lines in any of
7249 the ways documented in @ref{Specify Location}.
7252 For example, we can use @code{info line} to discover the location of
7253 the object code for the first line of function
7254 @code{m4_changequote}:
7256 @c FIXME: I think this example should also show the addresses in
7257 @c symbolic form, as they usually would be displayed.
7259 (@value{GDBP}) info line m4_changequote
7260 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7264 @cindex code address and its source line
7265 We can also inquire (using @code{*@var{addr}} as the form for
7266 @var{linespec}) what source line covers a particular address:
7268 (@value{GDBP}) info line *0x63ff
7269 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7272 @cindex @code{$_} and @code{info line}
7273 @cindex @code{x} command, default address
7274 @kindex x@r{(examine), and} info line
7275 After @code{info line}, the default address for the @code{x} command
7276 is changed to the starting address of the line, so that @samp{x/i} is
7277 sufficient to begin examining the machine code (@pxref{Memory,
7278 ,Examining Memory}). Also, this address is saved as the value of the
7279 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7284 @cindex assembly instructions
7285 @cindex instructions, assembly
7286 @cindex machine instructions
7287 @cindex listing machine instructions
7289 @itemx disassemble /m
7290 @itemx disassemble /r
7291 This specialized command dumps a range of memory as machine
7292 instructions. It can also print mixed source+disassembly by specifying
7293 the @code{/m} modifier and print the raw instructions in hex as well as
7294 in symbolic form by specifying the @code{/r}.
7295 The default memory range is the function surrounding the
7296 program counter of the selected frame. A single argument to this
7297 command is a program counter value; @value{GDBN} dumps the function
7298 surrounding this value. When two arguments are given, they should
7299 be separated by a comma, possibly surrounded by whitespace. The
7300 arguments specify a range of addresses to dump, in one of two forms:
7303 @item @var{start},@var{end}
7304 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7305 @item @var{start},+@var{length}
7306 the addresses from @var{start} (inclusive) to
7307 @code{@var{start}+@var{length}} (exclusive).
7311 When 2 arguments are specified, the name of the function is also
7312 printed (since there could be several functions in the given range).
7314 The argument(s) can be any expression yielding a numeric value, such as
7315 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7317 If the range of memory being disassembled contains current program counter,
7318 the instruction at that location is shown with a @code{=>} marker.
7321 The following example shows the disassembly of a range of addresses of
7322 HP PA-RISC 2.0 code:
7325 (@value{GDBP}) disas 0x32c4, 0x32e4
7326 Dump of assembler code from 0x32c4 to 0x32e4:
7327 0x32c4 <main+204>: addil 0,dp
7328 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7329 0x32cc <main+212>: ldil 0x3000,r31
7330 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7331 0x32d4 <main+220>: ldo 0(r31),rp
7332 0x32d8 <main+224>: addil -0x800,dp
7333 0x32dc <main+228>: ldo 0x588(r1),r26
7334 0x32e0 <main+232>: ldil 0x3000,r31
7335 End of assembler dump.
7338 Here is an example showing mixed source+assembly for Intel x86, when the
7339 program is stopped just after function prologue:
7342 (@value{GDBP}) disas /m main
7343 Dump of assembler code for function main:
7345 0x08048330 <+0>: push %ebp
7346 0x08048331 <+1>: mov %esp,%ebp
7347 0x08048333 <+3>: sub $0x8,%esp
7348 0x08048336 <+6>: and $0xfffffff0,%esp
7349 0x08048339 <+9>: sub $0x10,%esp
7351 6 printf ("Hello.\n");
7352 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7353 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7357 0x08048348 <+24>: mov $0x0,%eax
7358 0x0804834d <+29>: leave
7359 0x0804834e <+30>: ret
7361 End of assembler dump.
7364 Here is another example showing raw instructions in hex for AMD x86-64,
7367 (gdb) disas /r 0x400281,+10
7368 Dump of assembler code from 0x400281 to 0x40028b:
7369 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7370 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7371 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7372 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7373 End of assembler dump.
7376 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7377 So, for example, if you want to disassemble function @code{bar}
7378 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7379 and not @samp{disassemble foo.c:bar}.
7381 Some architectures have more than one commonly-used set of instruction
7382 mnemonics or other syntax.
7384 For programs that were dynamically linked and use shared libraries,
7385 instructions that call functions or branch to locations in the shared
7386 libraries might show a seemingly bogus location---it's actually a
7387 location of the relocation table. On some architectures, @value{GDBN}
7388 might be able to resolve these to actual function names.
7391 @kindex set disassembly-flavor
7392 @cindex Intel disassembly flavor
7393 @cindex AT&T disassembly flavor
7394 @item set disassembly-flavor @var{instruction-set}
7395 Select the instruction set to use when disassembling the
7396 program via the @code{disassemble} or @code{x/i} commands.
7398 Currently this command is only defined for the Intel x86 family. You
7399 can set @var{instruction-set} to either @code{intel} or @code{att}.
7400 The default is @code{att}, the AT&T flavor used by default by Unix
7401 assemblers for x86-based targets.
7403 @kindex show disassembly-flavor
7404 @item show disassembly-flavor
7405 Show the current setting of the disassembly flavor.
7409 @kindex set disassemble-next-line
7410 @kindex show disassemble-next-line
7411 @item set disassemble-next-line
7412 @itemx show disassemble-next-line
7413 Control whether or not @value{GDBN} will disassemble the next source
7414 line or instruction when execution stops. If ON, @value{GDBN} will
7415 display disassembly of the next source line when execution of the
7416 program being debugged stops. This is @emph{in addition} to
7417 displaying the source line itself, which @value{GDBN} always does if
7418 possible. If the next source line cannot be displayed for some reason
7419 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7420 info in the debug info), @value{GDBN} will display disassembly of the
7421 next @emph{instruction} instead of showing the next source line. If
7422 AUTO, @value{GDBN} will display disassembly of next instruction only
7423 if the source line cannot be displayed. This setting causes
7424 @value{GDBN} to display some feedback when you step through a function
7425 with no line info or whose source file is unavailable. The default is
7426 OFF, which means never display the disassembly of the next line or
7432 @chapter Examining Data
7434 @cindex printing data
7435 @cindex examining data
7438 The usual way to examine data in your program is with the @code{print}
7439 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7440 evaluates and prints the value of an expression of the language your
7441 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7442 Different Languages}). It may also print the expression using a
7443 Python-based pretty-printer (@pxref{Pretty Printing}).
7446 @item print @var{expr}
7447 @itemx print /@var{f} @var{expr}
7448 @var{expr} is an expression (in the source language). By default the
7449 value of @var{expr} is printed in a format appropriate to its data type;
7450 you can choose a different format by specifying @samp{/@var{f}}, where
7451 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7455 @itemx print /@var{f}
7456 @cindex reprint the last value
7457 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7458 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7459 conveniently inspect the same value in an alternative format.
7462 A more low-level way of examining data is with the @code{x} command.
7463 It examines data in memory at a specified address and prints it in a
7464 specified format. @xref{Memory, ,Examining Memory}.
7466 If you are interested in information about types, or about how the
7467 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7468 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7471 @cindex exploring hierarchical data structures
7473 Another way of examining values of expressions and type information is
7474 through the Python extension command @code{explore} (available only if
7475 the @value{GDBN} build is configured with @code{--with-python}). It
7476 offers an interactive way to start at the highest level (or, the most
7477 abstract level) of the data type of an expression (or, the data type
7478 itself) and explore all the way down to leaf scalar values/fields
7479 embedded in the higher level data types.
7482 @item explore @var{arg}
7483 @var{arg} is either an expression (in the source language), or a type
7484 visible in the current context of the program being debugged.
7487 The working of the @code{explore} command can be illustrated with an
7488 example. If a data type @code{struct ComplexStruct} is defined in your
7498 struct ComplexStruct
7500 struct SimpleStruct *ss_p;
7506 followed by variable declarations as
7509 struct SimpleStruct ss = @{ 10, 1.11 @};
7510 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7514 then, the value of the variable @code{cs} can be explored using the
7515 @code{explore} command as follows.
7519 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7520 the following fields:
7522 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7523 arr = <Enter 1 to explore this field of type `int [10]'>
7525 Enter the field number of choice:
7529 Since the fields of @code{cs} are not scalar values, you are being
7530 prompted to chose the field you want to explore. Let's say you choose
7531 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7532 pointer, you will be asked if it is pointing to a single value. From
7533 the declaration of @code{cs} above, it is indeed pointing to a single
7534 value, hence you enter @code{y}. If you enter @code{n}, then you will
7535 be asked if it were pointing to an array of values, in which case this
7536 field will be explored as if it were an array.
7539 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7540 Continue exploring it as a pointer to a single value [y/n]: y
7541 The value of `*(cs.ss_p)' is a struct/class of type `struct
7542 SimpleStruct' with the following fields:
7544 i = 10 .. (Value of type `int')
7545 d = 1.1100000000000001 .. (Value of type `double')
7547 Press enter to return to parent value:
7551 If the field @code{arr} of @code{cs} was chosen for exploration by
7552 entering @code{1} earlier, then since it is as array, you will be
7553 prompted to enter the index of the element in the array that you want
7557 `cs.arr' is an array of `int'.
7558 Enter the index of the element you want to explore in `cs.arr': 5
7560 `(cs.arr)[5]' is a scalar value of type `int'.
7564 Press enter to return to parent value:
7567 In general, at any stage of exploration, you can go deeper towards the
7568 leaf values by responding to the prompts appropriately, or hit the
7569 return key to return to the enclosing data structure (the @i{higher}
7570 level data structure).
7572 Similar to exploring values, you can use the @code{explore} command to
7573 explore types. Instead of specifying a value (which is typically a
7574 variable name or an expression valid in the current context of the
7575 program being debugged), you specify a type name. If you consider the
7576 same example as above, your can explore the type
7577 @code{struct ComplexStruct} by passing the argument
7578 @code{struct ComplexStruct} to the @code{explore} command.
7581 (gdb) explore struct ComplexStruct
7585 By responding to the prompts appropriately in the subsequent interactive
7586 session, you can explore the type @code{struct ComplexStruct} in a
7587 manner similar to how the value @code{cs} was explored in the above
7590 The @code{explore} command also has two sub-commands,
7591 @code{explore value} and @code{explore type}. The former sub-command is
7592 a way to explicitly specify that value exploration of the argument is
7593 being invoked, while the latter is a way to explicitly specify that type
7594 exploration of the argument is being invoked.
7597 @item explore value @var{expr}
7598 @cindex explore value
7599 This sub-command of @code{explore} explores the value of the
7600 expression @var{expr} (if @var{expr} is an expression valid in the
7601 current context of the program being debugged). The behavior of this
7602 command is identical to that of the behavior of the @code{explore}
7603 command being passed the argument @var{expr}.
7605 @item explore type @var{arg}
7606 @cindex explore type
7607 This sub-command of @code{explore} explores the type of @var{arg} (if
7608 @var{arg} is a type visible in the current context of program being
7609 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7610 is an expression valid in the current context of the program being
7611 debugged). If @var{arg} is a type, then the behavior of this command is
7612 identical to that of the @code{explore} command being passed the
7613 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7614 this command will be identical to that of the @code{explore} command
7615 being passed the type of @var{arg} as the argument.
7619 * Expressions:: Expressions
7620 * Ambiguous Expressions:: Ambiguous Expressions
7621 * Variables:: Program variables
7622 * Arrays:: Artificial arrays
7623 * Output Formats:: Output formats
7624 * Memory:: Examining memory
7625 * Auto Display:: Automatic display
7626 * Print Settings:: Print settings
7627 * Pretty Printing:: Python pretty printing
7628 * Value History:: Value history
7629 * Convenience Vars:: Convenience variables
7630 * Convenience Funs:: Convenience functions
7631 * Registers:: Registers
7632 * Floating Point Hardware:: Floating point hardware
7633 * Vector Unit:: Vector Unit
7634 * OS Information:: Auxiliary data provided by operating system
7635 * Memory Region Attributes:: Memory region attributes
7636 * Dump/Restore Files:: Copy between memory and a file
7637 * Core File Generation:: Cause a program dump its core
7638 * Character Sets:: Debugging programs that use a different
7639 character set than GDB does
7640 * Caching Remote Data:: Data caching for remote targets
7641 * Searching Memory:: Searching memory for a sequence of bytes
7645 @section Expressions
7648 @code{print} and many other @value{GDBN} commands accept an expression and
7649 compute its value. Any kind of constant, variable or operator defined
7650 by the programming language you are using is valid in an expression in
7651 @value{GDBN}. This includes conditional expressions, function calls,
7652 casts, and string constants. It also includes preprocessor macros, if
7653 you compiled your program to include this information; see
7656 @cindex arrays in expressions
7657 @value{GDBN} supports array constants in expressions input by
7658 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7659 you can use the command @code{print @{1, 2, 3@}} to create an array
7660 of three integers. If you pass an array to a function or assign it
7661 to a program variable, @value{GDBN} copies the array to memory that
7662 is @code{malloc}ed in the target program.
7664 Because C is so widespread, most of the expressions shown in examples in
7665 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7666 Languages}, for information on how to use expressions in other
7669 In this section, we discuss operators that you can use in @value{GDBN}
7670 expressions regardless of your programming language.
7672 @cindex casts, in expressions
7673 Casts are supported in all languages, not just in C, because it is so
7674 useful to cast a number into a pointer in order to examine a structure
7675 at that address in memory.
7676 @c FIXME: casts supported---Mod2 true?
7678 @value{GDBN} supports these operators, in addition to those common
7679 to programming languages:
7683 @samp{@@} is a binary operator for treating parts of memory as arrays.
7684 @xref{Arrays, ,Artificial Arrays}, for more information.
7687 @samp{::} allows you to specify a variable in terms of the file or
7688 function where it is defined. @xref{Variables, ,Program Variables}.
7690 @cindex @{@var{type}@}
7691 @cindex type casting memory
7692 @cindex memory, viewing as typed object
7693 @cindex casts, to view memory
7694 @item @{@var{type}@} @var{addr}
7695 Refers to an object of type @var{type} stored at address @var{addr} in
7696 memory. @var{addr} may be any expression whose value is an integer or
7697 pointer (but parentheses are required around binary operators, just as in
7698 a cast). This construct is allowed regardless of what kind of data is
7699 normally supposed to reside at @var{addr}.
7702 @node Ambiguous Expressions
7703 @section Ambiguous Expressions
7704 @cindex ambiguous expressions
7706 Expressions can sometimes contain some ambiguous elements. For instance,
7707 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7708 a single function name to be defined several times, for application in
7709 different contexts. This is called @dfn{overloading}. Another example
7710 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7711 templates and is typically instantiated several times, resulting in
7712 the same function name being defined in different contexts.
7714 In some cases and depending on the language, it is possible to adjust
7715 the expression to remove the ambiguity. For instance in C@t{++}, you
7716 can specify the signature of the function you want to break on, as in
7717 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7718 qualified name of your function often makes the expression unambiguous
7721 When an ambiguity that needs to be resolved is detected, the debugger
7722 has the capability to display a menu of numbered choices for each
7723 possibility, and then waits for the selection with the prompt @samp{>}.
7724 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7725 aborts the current command. If the command in which the expression was
7726 used allows more than one choice to be selected, the next option in the
7727 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7730 For example, the following session excerpt shows an attempt to set a
7731 breakpoint at the overloaded symbol @code{String::after}.
7732 We choose three particular definitions of that function name:
7734 @c FIXME! This is likely to change to show arg type lists, at least
7737 (@value{GDBP}) b String::after
7740 [2] file:String.cc; line number:867
7741 [3] file:String.cc; line number:860
7742 [4] file:String.cc; line number:875
7743 [5] file:String.cc; line number:853
7744 [6] file:String.cc; line number:846
7745 [7] file:String.cc; line number:735
7747 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7748 Breakpoint 2 at 0xb344: file String.cc, line 875.
7749 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7750 Multiple breakpoints were set.
7751 Use the "delete" command to delete unwanted
7758 @kindex set multiple-symbols
7759 @item set multiple-symbols @var{mode}
7760 @cindex multiple-symbols menu
7762 This option allows you to adjust the debugger behavior when an expression
7765 By default, @var{mode} is set to @code{all}. If the command with which
7766 the expression is used allows more than one choice, then @value{GDBN}
7767 automatically selects all possible choices. For instance, inserting
7768 a breakpoint on a function using an ambiguous name results in a breakpoint
7769 inserted on each possible match. However, if a unique choice must be made,
7770 then @value{GDBN} uses the menu to help you disambiguate the expression.
7771 For instance, printing the address of an overloaded function will result
7772 in the use of the menu.
7774 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7775 when an ambiguity is detected.
7777 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7778 an error due to the ambiguity and the command is aborted.
7780 @kindex show multiple-symbols
7781 @item show multiple-symbols
7782 Show the current value of the @code{multiple-symbols} setting.
7786 @section Program Variables
7788 The most common kind of expression to use is the name of a variable
7791 Variables in expressions are understood in the selected stack frame
7792 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7796 global (or file-static)
7803 visible according to the scope rules of the
7804 programming language from the point of execution in that frame
7807 @noindent This means that in the function
7822 you can examine and use the variable @code{a} whenever your program is
7823 executing within the function @code{foo}, but you can only use or
7824 examine the variable @code{b} while your program is executing inside
7825 the block where @code{b} is declared.
7827 @cindex variable name conflict
7828 There is an exception: you can refer to a variable or function whose
7829 scope is a single source file even if the current execution point is not
7830 in this file. But it is possible to have more than one such variable or
7831 function with the same name (in different source files). If that
7832 happens, referring to that name has unpredictable effects. If you wish,
7833 you can specify a static variable in a particular function or file by
7834 using the colon-colon (@code{::}) notation:
7836 @cindex colon-colon, context for variables/functions
7838 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7839 @cindex @code{::}, context for variables/functions
7842 @var{file}::@var{variable}
7843 @var{function}::@var{variable}
7847 Here @var{file} or @var{function} is the name of the context for the
7848 static @var{variable}. In the case of file names, you can use quotes to
7849 make sure @value{GDBN} parses the file name as a single word---for example,
7850 to print a global value of @code{x} defined in @file{f2.c}:
7853 (@value{GDBP}) p 'f2.c'::x
7856 The @code{::} notation is normally used for referring to
7857 static variables, since you typically disambiguate uses of local variables
7858 in functions by selecting the appropriate frame and using the
7859 simple name of the variable. However, you may also use this notation
7860 to refer to local variables in frames enclosing the selected frame:
7869 process (a); /* Stop here */
7880 For example, if there is a breakpoint at the commented line,
7881 here is what you might see
7882 when the program stops after executing the call @code{bar(0)}:
7887 (@value{GDBP}) p bar::a
7890 #2 0x080483d0 in foo (a=5) at foobar.c:12
7893 (@value{GDBP}) p bar::a
7897 @cindex C@t{++} scope resolution
7898 These uses of @samp{::} are very rarely in conflict with the very similar
7899 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7900 scope resolution operator in @value{GDBN} expressions.
7901 @c FIXME: Um, so what happens in one of those rare cases where it's in
7904 @cindex wrong values
7905 @cindex variable values, wrong
7906 @cindex function entry/exit, wrong values of variables
7907 @cindex optimized code, wrong values of variables
7909 @emph{Warning:} Occasionally, a local variable may appear to have the
7910 wrong value at certain points in a function---just after entry to a new
7911 scope, and just before exit.
7913 You may see this problem when you are stepping by machine instructions.
7914 This is because, on most machines, it takes more than one instruction to
7915 set up a stack frame (including local variable definitions); if you are
7916 stepping by machine instructions, variables may appear to have the wrong
7917 values until the stack frame is completely built. On exit, it usually
7918 also takes more than one machine instruction to destroy a stack frame;
7919 after you begin stepping through that group of instructions, local
7920 variable definitions may be gone.
7922 This may also happen when the compiler does significant optimizations.
7923 To be sure of always seeing accurate values, turn off all optimization
7926 @cindex ``No symbol "foo" in current context''
7927 Another possible effect of compiler optimizations is to optimize
7928 unused variables out of existence, or assign variables to registers (as
7929 opposed to memory addresses). Depending on the support for such cases
7930 offered by the debug info format used by the compiler, @value{GDBN}
7931 might not be able to display values for such local variables. If that
7932 happens, @value{GDBN} will print a message like this:
7935 No symbol "foo" in current context.
7938 To solve such problems, either recompile without optimizations, or use a
7939 different debug info format, if the compiler supports several such
7940 formats. @xref{Compilation}, for more information on choosing compiler
7941 options. @xref{C, ,C and C@t{++}}, for more information about debug
7942 info formats that are best suited to C@t{++} programs.
7944 If you ask to print an object whose contents are unknown to
7945 @value{GDBN}, e.g., because its data type is not completely specified
7946 by the debug information, @value{GDBN} will say @samp{<incomplete
7947 type>}. @xref{Symbols, incomplete type}, for more about this.
7949 If you append @kbd{@@entry} string to a function parameter name you get its
7950 value at the time the function got called. If the value is not available an
7951 error message is printed. Entry values are available only with some compilers.
7952 Entry values are normally also printed at the function parameter list according
7953 to @ref{set print entry-values}.
7956 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7962 (gdb) print i@@entry
7966 Strings are identified as arrays of @code{char} values without specified
7967 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7968 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7969 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7970 defines literal string type @code{"char"} as @code{char} without a sign.
7975 signed char var1[] = "A";
7978 You get during debugging
7983 $2 = @{65 'A', 0 '\0'@}
7987 @section Artificial Arrays
7989 @cindex artificial array
7991 @kindex @@@r{, referencing memory as an array}
7992 It is often useful to print out several successive objects of the
7993 same type in memory; a section of an array, or an array of
7994 dynamically determined size for which only a pointer exists in the
7997 You can do this by referring to a contiguous span of memory as an
7998 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7999 operand of @samp{@@} should be the first element of the desired array
8000 and be an individual object. The right operand should be the desired length
8001 of the array. The result is an array value whose elements are all of
8002 the type of the left argument. The first element is actually the left
8003 argument; the second element comes from bytes of memory immediately
8004 following those that hold the first element, and so on. Here is an
8005 example. If a program says
8008 int *array = (int *) malloc (len * sizeof (int));
8012 you can print the contents of @code{array} with
8018 The left operand of @samp{@@} must reside in memory. Array values made
8019 with @samp{@@} in this way behave just like other arrays in terms of
8020 subscripting, and are coerced to pointers when used in expressions.
8021 Artificial arrays most often appear in expressions via the value history
8022 (@pxref{Value History, ,Value History}), after printing one out.
8024 Another way to create an artificial array is to use a cast.
8025 This re-interprets a value as if it were an array.
8026 The value need not be in memory:
8028 (@value{GDBP}) p/x (short[2])0x12345678
8029 $1 = @{0x1234, 0x5678@}
8032 As a convenience, if you leave the array length out (as in
8033 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8034 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8036 (@value{GDBP}) p/x (short[])0x12345678
8037 $2 = @{0x1234, 0x5678@}
8040 Sometimes the artificial array mechanism is not quite enough; in
8041 moderately complex data structures, the elements of interest may not
8042 actually be adjacent---for example, if you are interested in the values
8043 of pointers in an array. One useful work-around in this situation is
8044 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8045 Variables}) as a counter in an expression that prints the first
8046 interesting value, and then repeat that expression via @key{RET}. For
8047 instance, suppose you have an array @code{dtab} of pointers to
8048 structures, and you are interested in the values of a field @code{fv}
8049 in each structure. Here is an example of what you might type:
8059 @node Output Formats
8060 @section Output Formats
8062 @cindex formatted output
8063 @cindex output formats
8064 By default, @value{GDBN} prints a value according to its data type. Sometimes
8065 this is not what you want. For example, you might want to print a number
8066 in hex, or a pointer in decimal. Or you might want to view data in memory
8067 at a certain address as a character string or as an instruction. To do
8068 these things, specify an @dfn{output format} when you print a value.
8070 The simplest use of output formats is to say how to print a value
8071 already computed. This is done by starting the arguments of the
8072 @code{print} command with a slash and a format letter. The format
8073 letters supported are:
8077 Regard the bits of the value as an integer, and print the integer in
8081 Print as integer in signed decimal.
8084 Print as integer in unsigned decimal.
8087 Print as integer in octal.
8090 Print as integer in binary. The letter @samp{t} stands for ``two''.
8091 @footnote{@samp{b} cannot be used because these format letters are also
8092 used with the @code{x} command, where @samp{b} stands for ``byte'';
8093 see @ref{Memory,,Examining Memory}.}
8096 @cindex unknown address, locating
8097 @cindex locate address
8098 Print as an address, both absolute in hexadecimal and as an offset from
8099 the nearest preceding symbol. You can use this format used to discover
8100 where (in what function) an unknown address is located:
8103 (@value{GDBP}) p/a 0x54320
8104 $3 = 0x54320 <_initialize_vx+396>
8108 The command @code{info symbol 0x54320} yields similar results.
8109 @xref{Symbols, info symbol}.
8112 Regard as an integer and print it as a character constant. This
8113 prints both the numerical value and its character representation. The
8114 character representation is replaced with the octal escape @samp{\nnn}
8115 for characters outside the 7-bit @sc{ascii} range.
8117 Without this format, @value{GDBN} displays @code{char},
8118 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8119 constants. Single-byte members of vectors are displayed as integer
8123 Regard the bits of the value as a floating point number and print
8124 using typical floating point syntax.
8127 @cindex printing strings
8128 @cindex printing byte arrays
8129 Regard as a string, if possible. With this format, pointers to single-byte
8130 data are displayed as null-terminated strings and arrays of single-byte data
8131 are displayed as fixed-length strings. Other values are displayed in their
8134 Without this format, @value{GDBN} displays pointers to and arrays of
8135 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8136 strings. Single-byte members of a vector are displayed as an integer
8140 @cindex raw printing
8141 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8142 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8143 Printing}). This typically results in a higher-level display of the
8144 value's contents. The @samp{r} format bypasses any Python
8145 pretty-printer which might exist.
8148 For example, to print the program counter in hex (@pxref{Registers}), type
8155 Note that no space is required before the slash; this is because command
8156 names in @value{GDBN} cannot contain a slash.
8158 To reprint the last value in the value history with a different format,
8159 you can use the @code{print} command with just a format and no
8160 expression. For example, @samp{p/x} reprints the last value in hex.
8163 @section Examining Memory
8165 You can use the command @code{x} (for ``examine'') to examine memory in
8166 any of several formats, independently of your program's data types.
8168 @cindex examining memory
8170 @kindex x @r{(examine memory)}
8171 @item x/@var{nfu} @var{addr}
8174 Use the @code{x} command to examine memory.
8177 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8178 much memory to display and how to format it; @var{addr} is an
8179 expression giving the address where you want to start displaying memory.
8180 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8181 Several commands set convenient defaults for @var{addr}.
8184 @item @var{n}, the repeat count
8185 The repeat count is a decimal integer; the default is 1. It specifies
8186 how much memory (counting by units @var{u}) to display.
8187 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8190 @item @var{f}, the display format
8191 The display format is one of the formats used by @code{print}
8192 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8193 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8194 The default is @samp{x} (hexadecimal) initially. The default changes
8195 each time you use either @code{x} or @code{print}.
8197 @item @var{u}, the unit size
8198 The unit size is any of
8204 Halfwords (two bytes).
8206 Words (four bytes). This is the initial default.
8208 Giant words (eight bytes).
8211 Each time you specify a unit size with @code{x}, that size becomes the
8212 default unit the next time you use @code{x}. For the @samp{i} format,
8213 the unit size is ignored and is normally not written. For the @samp{s} format,
8214 the unit size defaults to @samp{b}, unless it is explicitly given.
8215 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8216 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8217 Note that the results depend on the programming language of the
8218 current compilation unit. If the language is C, the @samp{s}
8219 modifier will use the UTF-16 encoding while @samp{w} will use
8220 UTF-32. The encoding is set by the programming language and cannot
8223 @item @var{addr}, starting display address
8224 @var{addr} is the address where you want @value{GDBN} to begin displaying
8225 memory. The expression need not have a pointer value (though it may);
8226 it is always interpreted as an integer address of a byte of memory.
8227 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8228 @var{addr} is usually just after the last address examined---but several
8229 other commands also set the default address: @code{info breakpoints} (to
8230 the address of the last breakpoint listed), @code{info line} (to the
8231 starting address of a line), and @code{print} (if you use it to display
8232 a value from memory).
8235 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8236 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8237 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8238 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8239 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8241 Since the letters indicating unit sizes are all distinct from the
8242 letters specifying output formats, you do not have to remember whether
8243 unit size or format comes first; either order works. The output
8244 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8245 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8247 Even though the unit size @var{u} is ignored for the formats @samp{s}
8248 and @samp{i}, you might still want to use a count @var{n}; for example,
8249 @samp{3i} specifies that you want to see three machine instructions,
8250 including any operands. For convenience, especially when used with
8251 the @code{display} command, the @samp{i} format also prints branch delay
8252 slot instructions, if any, beyond the count specified, which immediately
8253 follow the last instruction that is within the count. The command
8254 @code{disassemble} gives an alternative way of inspecting machine
8255 instructions; see @ref{Machine Code,,Source and Machine Code}.
8257 All the defaults for the arguments to @code{x} are designed to make it
8258 easy to continue scanning memory with minimal specifications each time
8259 you use @code{x}. For example, after you have inspected three machine
8260 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8261 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8262 the repeat count @var{n} is used again; the other arguments default as
8263 for successive uses of @code{x}.
8265 When examining machine instructions, the instruction at current program
8266 counter is shown with a @code{=>} marker. For example:
8269 (@value{GDBP}) x/5i $pc-6
8270 0x804837f <main+11>: mov %esp,%ebp
8271 0x8048381 <main+13>: push %ecx
8272 0x8048382 <main+14>: sub $0x4,%esp
8273 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8274 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8277 @cindex @code{$_}, @code{$__}, and value history
8278 The addresses and contents printed by the @code{x} command are not saved
8279 in the value history because there is often too much of them and they
8280 would get in the way. Instead, @value{GDBN} makes these values available for
8281 subsequent use in expressions as values of the convenience variables
8282 @code{$_} and @code{$__}. After an @code{x} command, the last address
8283 examined is available for use in expressions in the convenience variable
8284 @code{$_}. The contents of that address, as examined, are available in
8285 the convenience variable @code{$__}.
8287 If the @code{x} command has a repeat count, the address and contents saved
8288 are from the last memory unit printed; this is not the same as the last
8289 address printed if several units were printed on the last line of output.
8291 @cindex remote memory comparison
8292 @cindex verify remote memory image
8293 When you are debugging a program running on a remote target machine
8294 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8295 remote machine's memory against the executable file you downloaded to
8296 the target. The @code{compare-sections} command is provided for such
8300 @kindex compare-sections
8301 @item compare-sections @r{[}@var{section-name}@r{]}
8302 Compare the data of a loadable section @var{section-name} in the
8303 executable file of the program being debugged with the same section in
8304 the remote machine's memory, and report any mismatches. With no
8305 arguments, compares all loadable sections. This command's
8306 availability depends on the target's support for the @code{"qCRC"}
8311 @section Automatic Display
8312 @cindex automatic display
8313 @cindex display of expressions
8315 If you find that you want to print the value of an expression frequently
8316 (to see how it changes), you might want to add it to the @dfn{automatic
8317 display list} so that @value{GDBN} prints its value each time your program stops.
8318 Each expression added to the list is given a number to identify it;
8319 to remove an expression from the list, you specify that number.
8320 The automatic display looks like this:
8324 3: bar[5] = (struct hack *) 0x3804
8328 This display shows item numbers, expressions and their current values. As with
8329 displays you request manually using @code{x} or @code{print}, you can
8330 specify the output format you prefer; in fact, @code{display} decides
8331 whether to use @code{print} or @code{x} depending your format
8332 specification---it uses @code{x} if you specify either the @samp{i}
8333 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8337 @item display @var{expr}
8338 Add the expression @var{expr} to the list of expressions to display
8339 each time your program stops. @xref{Expressions, ,Expressions}.
8341 @code{display} does not repeat if you press @key{RET} again after using it.
8343 @item display/@var{fmt} @var{expr}
8344 For @var{fmt} specifying only a display format and not a size or
8345 count, add the expression @var{expr} to the auto-display list but
8346 arrange to display it each time in the specified format @var{fmt}.
8347 @xref{Output Formats,,Output Formats}.
8349 @item display/@var{fmt} @var{addr}
8350 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8351 number of units, add the expression @var{addr} as a memory address to
8352 be examined each time your program stops. Examining means in effect
8353 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8356 For example, @samp{display/i $pc} can be helpful, to see the machine
8357 instruction about to be executed each time execution stops (@samp{$pc}
8358 is a common name for the program counter; @pxref{Registers, ,Registers}).
8361 @kindex delete display
8363 @item undisplay @var{dnums}@dots{}
8364 @itemx delete display @var{dnums}@dots{}
8365 Remove items from the list of expressions to display. Specify the
8366 numbers of the displays that you want affected with the command
8367 argument @var{dnums}. It can be a single display number, one of the
8368 numbers shown in the first field of the @samp{info display} display;
8369 or it could be a range of display numbers, as in @code{2-4}.
8371 @code{undisplay} does not repeat if you press @key{RET} after using it.
8372 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8374 @kindex disable display
8375 @item disable display @var{dnums}@dots{}
8376 Disable the display of item numbers @var{dnums}. A disabled display
8377 item is not printed automatically, but is not forgotten. It may be
8378 enabled again later. Specify the numbers of the displays that you
8379 want affected with the command argument @var{dnums}. It can be a
8380 single display number, one of the numbers shown in the first field of
8381 the @samp{info display} display; or it could be a range of display
8382 numbers, as in @code{2-4}.
8384 @kindex enable display
8385 @item enable display @var{dnums}@dots{}
8386 Enable display of item numbers @var{dnums}. It becomes effective once
8387 again in auto display of its expression, until you specify otherwise.
8388 Specify the numbers of the displays that you want affected with the
8389 command argument @var{dnums}. It can be a single display number, one
8390 of the numbers shown in the first field of the @samp{info display}
8391 display; or it could be a range of display numbers, as in @code{2-4}.
8394 Display the current values of the expressions on the list, just as is
8395 done when your program stops.
8397 @kindex info display
8399 Print the list of expressions previously set up to display
8400 automatically, each one with its item number, but without showing the
8401 values. This includes disabled expressions, which are marked as such.
8402 It also includes expressions which would not be displayed right now
8403 because they refer to automatic variables not currently available.
8406 @cindex display disabled out of scope
8407 If a display expression refers to local variables, then it does not make
8408 sense outside the lexical context for which it was set up. Such an
8409 expression is disabled when execution enters a context where one of its
8410 variables is not defined. For example, if you give the command
8411 @code{display last_char} while inside a function with an argument
8412 @code{last_char}, @value{GDBN} displays this argument while your program
8413 continues to stop inside that function. When it stops elsewhere---where
8414 there is no variable @code{last_char}---the display is disabled
8415 automatically. The next time your program stops where @code{last_char}
8416 is meaningful, you can enable the display expression once again.
8418 @node Print Settings
8419 @section Print Settings
8421 @cindex format options
8422 @cindex print settings
8423 @value{GDBN} provides the following ways to control how arrays, structures,
8424 and symbols are printed.
8427 These settings are useful for debugging programs in any language:
8431 @item set print address
8432 @itemx set print address on
8433 @cindex print/don't print memory addresses
8434 @value{GDBN} prints memory addresses showing the location of stack
8435 traces, structure values, pointer values, breakpoints, and so forth,
8436 even when it also displays the contents of those addresses. The default
8437 is @code{on}. For example, this is what a stack frame display looks like with
8438 @code{set print address on}:
8443 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8445 530 if (lquote != def_lquote)
8449 @item set print address off
8450 Do not print addresses when displaying their contents. For example,
8451 this is the same stack frame displayed with @code{set print address off}:
8455 (@value{GDBP}) set print addr off
8457 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8458 530 if (lquote != def_lquote)
8462 You can use @samp{set print address off} to eliminate all machine
8463 dependent displays from the @value{GDBN} interface. For example, with
8464 @code{print address off}, you should get the same text for backtraces on
8465 all machines---whether or not they involve pointer arguments.
8468 @item show print address
8469 Show whether or not addresses are to be printed.
8472 When @value{GDBN} prints a symbolic address, it normally prints the
8473 closest earlier symbol plus an offset. If that symbol does not uniquely
8474 identify the address (for example, it is a name whose scope is a single
8475 source file), you may need to clarify. One way to do this is with
8476 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8477 you can set @value{GDBN} to print the source file and line number when
8478 it prints a symbolic address:
8481 @item set print symbol-filename on
8482 @cindex source file and line of a symbol
8483 @cindex symbol, source file and line
8484 Tell @value{GDBN} to print the source file name and line number of a
8485 symbol in the symbolic form of an address.
8487 @item set print symbol-filename off
8488 Do not print source file name and line number of a symbol. This is the
8491 @item show print symbol-filename
8492 Show whether or not @value{GDBN} will print the source file name and
8493 line number of a symbol in the symbolic form of an address.
8496 Another situation where it is helpful to show symbol filenames and line
8497 numbers is when disassembling code; @value{GDBN} shows you the line
8498 number and source file that corresponds to each instruction.
8500 Also, you may wish to see the symbolic form only if the address being
8501 printed is reasonably close to the closest earlier symbol:
8504 @item set print max-symbolic-offset @var{max-offset}
8505 @cindex maximum value for offset of closest symbol
8506 Tell @value{GDBN} to only display the symbolic form of an address if the
8507 offset between the closest earlier symbol and the address is less than
8508 @var{max-offset}. The default is 0, which tells @value{GDBN}
8509 to always print the symbolic form of an address if any symbol precedes it.
8511 @item show print max-symbolic-offset
8512 Ask how large the maximum offset is that @value{GDBN} prints in a
8516 @cindex wild pointer, interpreting
8517 @cindex pointer, finding referent
8518 If you have a pointer and you are not sure where it points, try
8519 @samp{set print symbol-filename on}. Then you can determine the name
8520 and source file location of the variable where it points, using
8521 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8522 For example, here @value{GDBN} shows that a variable @code{ptt} points
8523 at another variable @code{t}, defined in @file{hi2.c}:
8526 (@value{GDBP}) set print symbol-filename on
8527 (@value{GDBP}) p/a ptt
8528 $4 = 0xe008 <t in hi2.c>
8532 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8533 does not show the symbol name and filename of the referent, even with
8534 the appropriate @code{set print} options turned on.
8537 You can also enable @samp{/a}-like formatting all the time using
8538 @samp{set print symbol on}:
8541 @item set print symbol on
8542 Tell @value{GDBN} to print the symbol corresponding to an address, if
8545 @item set print symbol off
8546 Tell @value{GDBN} not to print the symbol corresponding to an
8547 address. In this mode, @value{GDBN} will still print the symbol
8548 corresponding to pointers to functions. This is the default.
8550 @item show print symbol
8551 Show whether @value{GDBN} will display the symbol corresponding to an
8555 Other settings control how different kinds of objects are printed:
8558 @item set print array
8559 @itemx set print array on
8560 @cindex pretty print arrays
8561 Pretty print arrays. This format is more convenient to read,
8562 but uses more space. The default is off.
8564 @item set print array off
8565 Return to compressed format for arrays.
8567 @item show print array
8568 Show whether compressed or pretty format is selected for displaying
8571 @cindex print array indexes
8572 @item set print array-indexes
8573 @itemx set print array-indexes on
8574 Print the index of each element when displaying arrays. May be more
8575 convenient to locate a given element in the array or quickly find the
8576 index of a given element in that printed array. The default is off.
8578 @item set print array-indexes off
8579 Stop printing element indexes when displaying arrays.
8581 @item show print array-indexes
8582 Show whether the index of each element is printed when displaying
8585 @item set print elements @var{number-of-elements}
8586 @cindex number of array elements to print
8587 @cindex limit on number of printed array elements
8588 Set a limit on how many elements of an array @value{GDBN} will print.
8589 If @value{GDBN} is printing a large array, it stops printing after it has
8590 printed the number of elements set by the @code{set print elements} command.
8591 This limit also applies to the display of strings.
8592 When @value{GDBN} starts, this limit is set to 200.
8593 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8595 @item show print elements
8596 Display the number of elements of a large array that @value{GDBN} will print.
8597 If the number is 0, then the printing is unlimited.
8599 @item set print frame-arguments @var{value}
8600 @kindex set print frame-arguments
8601 @cindex printing frame argument values
8602 @cindex print all frame argument values
8603 @cindex print frame argument values for scalars only
8604 @cindex do not print frame argument values
8605 This command allows to control how the values of arguments are printed
8606 when the debugger prints a frame (@pxref{Frames}). The possible
8611 The values of all arguments are printed.
8614 Print the value of an argument only if it is a scalar. The value of more
8615 complex arguments such as arrays, structures, unions, etc, is replaced
8616 by @code{@dots{}}. This is the default. Here is an example where
8617 only scalar arguments are shown:
8620 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8625 None of the argument values are printed. Instead, the value of each argument
8626 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8629 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8634 By default, only scalar arguments are printed. This command can be used
8635 to configure the debugger to print the value of all arguments, regardless
8636 of their type. However, it is often advantageous to not print the value
8637 of more complex parameters. For instance, it reduces the amount of
8638 information printed in each frame, making the backtrace more readable.
8639 Also, it improves performance when displaying Ada frames, because
8640 the computation of large arguments can sometimes be CPU-intensive,
8641 especially in large applications. Setting @code{print frame-arguments}
8642 to @code{scalars} (the default) or @code{none} avoids this computation,
8643 thus speeding up the display of each Ada frame.
8645 @item show print frame-arguments
8646 Show how the value of arguments should be displayed when printing a frame.
8648 @anchor{set print entry-values}
8649 @item set print entry-values @var{value}
8650 @kindex set print entry-values
8651 Set printing of frame argument values at function entry. In some cases
8652 @value{GDBN} can determine the value of function argument which was passed by
8653 the function caller, even if the value was modified inside the called function
8654 and therefore is different. With optimized code, the current value could be
8655 unavailable, but the entry value may still be known.
8657 The default value is @code{default} (see below for its description). Older
8658 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8659 this feature will behave in the @code{default} setting the same way as with the
8662 This functionality is currently supported only by DWARF 2 debugging format and
8663 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8664 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8667 The @var{value} parameter can be one of the following:
8671 Print only actual parameter values, never print values from function entry
8675 #0 different (val=6)
8676 #0 lost (val=<optimized out>)
8678 #0 invalid (val=<optimized out>)
8682 Print only parameter values from function entry point. The actual parameter
8683 values are never printed.
8685 #0 equal (val@@entry=5)
8686 #0 different (val@@entry=5)
8687 #0 lost (val@@entry=5)
8688 #0 born (val@@entry=<optimized out>)
8689 #0 invalid (val@@entry=<optimized out>)
8693 Print only parameter values from function entry point. If value from function
8694 entry point is not known while the actual value is known, print the actual
8695 value for such parameter.
8697 #0 equal (val@@entry=5)
8698 #0 different (val@@entry=5)
8699 #0 lost (val@@entry=5)
8701 #0 invalid (val@@entry=<optimized out>)
8705 Print actual parameter values. If actual parameter value is not known while
8706 value from function entry point is known, print the entry point value for such
8710 #0 different (val=6)
8711 #0 lost (val@@entry=5)
8713 #0 invalid (val=<optimized out>)
8717 Always print both the actual parameter value and its value from function entry
8718 point, even if values of one or both are not available due to compiler
8721 #0 equal (val=5, val@@entry=5)
8722 #0 different (val=6, val@@entry=5)
8723 #0 lost (val=<optimized out>, val@@entry=5)
8724 #0 born (val=10, val@@entry=<optimized out>)
8725 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8729 Print the actual parameter value if it is known and also its value from
8730 function entry point if it is known. If neither is known, print for the actual
8731 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8732 values are known and identical, print the shortened
8733 @code{param=param@@entry=VALUE} notation.
8735 #0 equal (val=val@@entry=5)
8736 #0 different (val=6, val@@entry=5)
8737 #0 lost (val@@entry=5)
8739 #0 invalid (val=<optimized out>)
8743 Always print the actual parameter value. Print also its value from function
8744 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8745 if both values are known and identical, print the shortened
8746 @code{param=param@@entry=VALUE} notation.
8748 #0 equal (val=val@@entry=5)
8749 #0 different (val=6, val@@entry=5)
8750 #0 lost (val=<optimized out>, val@@entry=5)
8752 #0 invalid (val=<optimized out>)
8756 For analysis messages on possible failures of frame argument values at function
8757 entry resolution see @ref{set debug entry-values}.
8759 @item show print entry-values
8760 Show the method being used for printing of frame argument values at function
8763 @item set print repeats
8764 @cindex repeated array elements
8765 Set the threshold for suppressing display of repeated array
8766 elements. When the number of consecutive identical elements of an
8767 array exceeds the threshold, @value{GDBN} prints the string
8768 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8769 identical repetitions, instead of displaying the identical elements
8770 themselves. Setting the threshold to zero will cause all elements to
8771 be individually printed. The default threshold is 10.
8773 @item show print repeats
8774 Display the current threshold for printing repeated identical
8777 @item set print null-stop
8778 @cindex @sc{null} elements in arrays
8779 Cause @value{GDBN} to stop printing the characters of an array when the first
8780 @sc{null} is encountered. This is useful when large arrays actually
8781 contain only short strings.
8784 @item show print null-stop
8785 Show whether @value{GDBN} stops printing an array on the first
8786 @sc{null} character.
8788 @item set print pretty on
8789 @cindex print structures in indented form
8790 @cindex indentation in structure display
8791 Cause @value{GDBN} to print structures in an indented format with one member
8792 per line, like this:
8807 @item set print pretty off
8808 Cause @value{GDBN} to print structures in a compact format, like this:
8812 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8813 meat = 0x54 "Pork"@}
8818 This is the default format.
8820 @item show print pretty
8821 Show which format @value{GDBN} is using to print structures.
8823 @item set print sevenbit-strings on
8824 @cindex eight-bit characters in strings
8825 @cindex octal escapes in strings
8826 Print using only seven-bit characters; if this option is set,
8827 @value{GDBN} displays any eight-bit characters (in strings or
8828 character values) using the notation @code{\}@var{nnn}. This setting is
8829 best if you are working in English (@sc{ascii}) and you use the
8830 high-order bit of characters as a marker or ``meta'' bit.
8832 @item set print sevenbit-strings off
8833 Print full eight-bit characters. This allows the use of more
8834 international character sets, and is the default.
8836 @item show print sevenbit-strings
8837 Show whether or not @value{GDBN} is printing only seven-bit characters.
8839 @item set print union on
8840 @cindex unions in structures, printing
8841 Tell @value{GDBN} to print unions which are contained in structures
8842 and other unions. This is the default setting.
8844 @item set print union off
8845 Tell @value{GDBN} not to print unions which are contained in
8846 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8849 @item show print union
8850 Ask @value{GDBN} whether or not it will print unions which are contained in
8851 structures and other unions.
8853 For example, given the declarations
8856 typedef enum @{Tree, Bug@} Species;
8857 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8858 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8869 struct thing foo = @{Tree, @{Acorn@}@};
8873 with @code{set print union on} in effect @samp{p foo} would print
8876 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8880 and with @code{set print union off} in effect it would print
8883 $1 = @{it = Tree, form = @{...@}@}
8887 @code{set print union} affects programs written in C-like languages
8893 These settings are of interest when debugging C@t{++} programs:
8896 @cindex demangling C@t{++} names
8897 @item set print demangle
8898 @itemx set print demangle on
8899 Print C@t{++} names in their source form rather than in the encoded
8900 (``mangled'') form passed to the assembler and linker for type-safe
8901 linkage. The default is on.
8903 @item show print demangle
8904 Show whether C@t{++} names are printed in mangled or demangled form.
8906 @item set print asm-demangle
8907 @itemx set print asm-demangle on
8908 Print C@t{++} names in their source form rather than their mangled form, even
8909 in assembler code printouts such as instruction disassemblies.
8912 @item show print asm-demangle
8913 Show whether C@t{++} names in assembly listings are printed in mangled
8916 @cindex C@t{++} symbol decoding style
8917 @cindex symbol decoding style, C@t{++}
8918 @kindex set demangle-style
8919 @item set demangle-style @var{style}
8920 Choose among several encoding schemes used by different compilers to
8921 represent C@t{++} names. The choices for @var{style} are currently:
8925 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8926 This is the default.
8929 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8932 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8935 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8938 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8939 @strong{Warning:} this setting alone is not sufficient to allow
8940 debugging @code{cfront}-generated executables. @value{GDBN} would
8941 require further enhancement to permit that.
8944 If you omit @var{style}, you will see a list of possible formats.
8946 @item show demangle-style
8947 Display the encoding style currently in use for decoding C@t{++} symbols.
8949 @item set print object
8950 @itemx set print object on
8951 @cindex derived type of an object, printing
8952 @cindex display derived types
8953 When displaying a pointer to an object, identify the @emph{actual}
8954 (derived) type of the object rather than the @emph{declared} type, using
8955 the virtual function table. Note that the virtual function table is
8956 required---this feature can only work for objects that have run-time
8957 type identification; a single virtual method in the object's declared
8958 type is sufficient. Note that this setting is also taken into account when
8959 working with variable objects via MI (@pxref{GDB/MI}).
8961 @item set print object off
8962 Display only the declared type of objects, without reference to the
8963 virtual function table. This is the default setting.
8965 @item show print object
8966 Show whether actual, or declared, object types are displayed.
8968 @item set print static-members
8969 @itemx set print static-members on
8970 @cindex static members of C@t{++} objects
8971 Print static members when displaying a C@t{++} object. The default is on.
8973 @item set print static-members off
8974 Do not print static members when displaying a C@t{++} object.
8976 @item show print static-members
8977 Show whether C@t{++} static members are printed or not.
8979 @item set print pascal_static-members
8980 @itemx set print pascal_static-members on
8981 @cindex static members of Pascal objects
8982 @cindex Pascal objects, static members display
8983 Print static members when displaying a Pascal object. The default is on.
8985 @item set print pascal_static-members off
8986 Do not print static members when displaying a Pascal object.
8988 @item show print pascal_static-members
8989 Show whether Pascal static members are printed or not.
8991 @c These don't work with HP ANSI C++ yet.
8992 @item set print vtbl
8993 @itemx set print vtbl on
8994 @cindex pretty print C@t{++} virtual function tables
8995 @cindex virtual functions (C@t{++}) display
8996 @cindex VTBL display
8997 Pretty print C@t{++} virtual function tables. The default is off.
8998 (The @code{vtbl} commands do not work on programs compiled with the HP
8999 ANSI C@t{++} compiler (@code{aCC}).)
9001 @item set print vtbl off
9002 Do not pretty print C@t{++} virtual function tables.
9004 @item show print vtbl
9005 Show whether C@t{++} virtual function tables are pretty printed, or not.
9008 @node Pretty Printing
9009 @section Pretty Printing
9011 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9012 Python code. It greatly simplifies the display of complex objects. This
9013 mechanism works for both MI and the CLI.
9016 * Pretty-Printer Introduction:: Introduction to pretty-printers
9017 * Pretty-Printer Example:: An example pretty-printer
9018 * Pretty-Printer Commands:: Pretty-printer commands
9021 @node Pretty-Printer Introduction
9022 @subsection Pretty-Printer Introduction
9024 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9025 registered for the value. If there is then @value{GDBN} invokes the
9026 pretty-printer to print the value. Otherwise the value is printed normally.
9028 Pretty-printers are normally named. This makes them easy to manage.
9029 The @samp{info pretty-printer} command will list all the installed
9030 pretty-printers with their names.
9031 If a pretty-printer can handle multiple data types, then its
9032 @dfn{subprinters} are the printers for the individual data types.
9033 Each such subprinter has its own name.
9034 The format of the name is @var{printer-name};@var{subprinter-name}.
9036 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9037 Typically they are automatically loaded and registered when the corresponding
9038 debug information is loaded, thus making them available without having to
9039 do anything special.
9041 There are three places where a pretty-printer can be registered.
9045 Pretty-printers registered globally are available when debugging
9049 Pretty-printers registered with a program space are available only
9050 when debugging that program.
9051 @xref{Progspaces In Python}, for more details on program spaces in Python.
9054 Pretty-printers registered with an objfile are loaded and unloaded
9055 with the corresponding objfile (e.g., shared library).
9056 @xref{Objfiles In Python}, for more details on objfiles in Python.
9059 @xref{Selecting Pretty-Printers}, for further information on how
9060 pretty-printers are selected,
9062 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9065 @node Pretty-Printer Example
9066 @subsection Pretty-Printer Example
9068 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9071 (@value{GDBP}) print s
9073 static npos = 4294967295,
9075 <std::allocator<char>> = @{
9076 <__gnu_cxx::new_allocator<char>> = @{
9077 <No data fields>@}, <No data fields>
9079 members of std::basic_string<char, std::char_traits<char>,
9080 std::allocator<char> >::_Alloc_hider:
9081 _M_p = 0x804a014 "abcd"
9086 With a pretty-printer for @code{std::string} only the contents are printed:
9089 (@value{GDBP}) print s
9093 @node Pretty-Printer Commands
9094 @subsection Pretty-Printer Commands
9095 @cindex pretty-printer commands
9098 @kindex info pretty-printer
9099 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9100 Print the list of installed pretty-printers.
9101 This includes disabled pretty-printers, which are marked as such.
9103 @var{object-regexp} is a regular expression matching the objects
9104 whose pretty-printers to list.
9105 Objects can be @code{global}, the program space's file
9106 (@pxref{Progspaces In Python}),
9107 and the object files within that program space (@pxref{Objfiles In Python}).
9108 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9109 looks up a printer from these three objects.
9111 @var{name-regexp} is a regular expression matching the name of the printers
9114 @kindex disable pretty-printer
9115 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9116 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9117 A disabled pretty-printer is not forgotten, it may be enabled again later.
9119 @kindex enable pretty-printer
9120 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9121 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9126 Suppose we have three pretty-printers installed: one from library1.so
9127 named @code{foo} that prints objects of type @code{foo}, and
9128 another from library2.so named @code{bar} that prints two types of objects,
9129 @code{bar1} and @code{bar2}.
9132 (gdb) info pretty-printer
9139 (gdb) info pretty-printer library2
9144 (gdb) disable pretty-printer library1
9146 2 of 3 printers enabled
9147 (gdb) info pretty-printer
9154 (gdb) disable pretty-printer library2 bar:bar1
9156 1 of 3 printers enabled
9157 (gdb) info pretty-printer library2
9164 (gdb) disable pretty-printer library2 bar
9166 0 of 3 printers enabled
9167 (gdb) info pretty-printer library2
9176 Note that for @code{bar} the entire printer can be disabled,
9177 as can each individual subprinter.
9180 @section Value History
9182 @cindex value history
9183 @cindex history of values printed by @value{GDBN}
9184 Values printed by the @code{print} command are saved in the @value{GDBN}
9185 @dfn{value history}. This allows you to refer to them in other expressions.
9186 Values are kept until the symbol table is re-read or discarded
9187 (for example with the @code{file} or @code{symbol-file} commands).
9188 When the symbol table changes, the value history is discarded,
9189 since the values may contain pointers back to the types defined in the
9194 @cindex history number
9195 The values printed are given @dfn{history numbers} by which you can
9196 refer to them. These are successive integers starting with one.
9197 @code{print} shows you the history number assigned to a value by
9198 printing @samp{$@var{num} = } before the value; here @var{num} is the
9201 To refer to any previous value, use @samp{$} followed by the value's
9202 history number. The way @code{print} labels its output is designed to
9203 remind you of this. Just @code{$} refers to the most recent value in
9204 the history, and @code{$$} refers to the value before that.
9205 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9206 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9207 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9209 For example, suppose you have just printed a pointer to a structure and
9210 want to see the contents of the structure. It suffices to type
9216 If you have a chain of structures where the component @code{next} points
9217 to the next one, you can print the contents of the next one with this:
9224 You can print successive links in the chain by repeating this
9225 command---which you can do by just typing @key{RET}.
9227 Note that the history records values, not expressions. If the value of
9228 @code{x} is 4 and you type these commands:
9236 then the value recorded in the value history by the @code{print} command
9237 remains 4 even though the value of @code{x} has changed.
9242 Print the last ten values in the value history, with their item numbers.
9243 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9244 values} does not change the history.
9246 @item show values @var{n}
9247 Print ten history values centered on history item number @var{n}.
9250 Print ten history values just after the values last printed. If no more
9251 values are available, @code{show values +} produces no display.
9254 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9255 same effect as @samp{show values +}.
9257 @node Convenience Vars
9258 @section Convenience Variables
9260 @cindex convenience variables
9261 @cindex user-defined variables
9262 @value{GDBN} provides @dfn{convenience variables} that you can use within
9263 @value{GDBN} to hold on to a value and refer to it later. These variables
9264 exist entirely within @value{GDBN}; they are not part of your program, and
9265 setting a convenience variable has no direct effect on further execution
9266 of your program. That is why you can use them freely.
9268 Convenience variables are prefixed with @samp{$}. Any name preceded by
9269 @samp{$} can be used for a convenience variable, unless it is one of
9270 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9271 (Value history references, in contrast, are @emph{numbers} preceded
9272 by @samp{$}. @xref{Value History, ,Value History}.)
9274 You can save a value in a convenience variable with an assignment
9275 expression, just as you would set a variable in your program.
9279 set $foo = *object_ptr
9283 would save in @code{$foo} the value contained in the object pointed to by
9286 Using a convenience variable for the first time creates it, but its
9287 value is @code{void} until you assign a new value. You can alter the
9288 value with another assignment at any time.
9290 Convenience variables have no fixed types. You can assign a convenience
9291 variable any type of value, including structures and arrays, even if
9292 that variable already has a value of a different type. The convenience
9293 variable, when used as an expression, has the type of its current value.
9296 @kindex show convenience
9297 @cindex show all user variables and functions
9298 @item show convenience
9299 Print a list of convenience variables used so far, and their values,
9300 as well as a list of the convenience functions.
9301 Abbreviated @code{show conv}.
9303 @kindex init-if-undefined
9304 @cindex convenience variables, initializing
9305 @item init-if-undefined $@var{variable} = @var{expression}
9306 Set a convenience variable if it has not already been set. This is useful
9307 for user-defined commands that keep some state. It is similar, in concept,
9308 to using local static variables with initializers in C (except that
9309 convenience variables are global). It can also be used to allow users to
9310 override default values used in a command script.
9312 If the variable is already defined then the expression is not evaluated so
9313 any side-effects do not occur.
9316 One of the ways to use a convenience variable is as a counter to be
9317 incremented or a pointer to be advanced. For example, to print
9318 a field from successive elements of an array of structures:
9322 print bar[$i++]->contents
9326 Repeat that command by typing @key{RET}.
9328 Some convenience variables are created automatically by @value{GDBN} and given
9329 values likely to be useful.
9332 @vindex $_@r{, convenience variable}
9334 The variable @code{$_} is automatically set by the @code{x} command to
9335 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9336 commands which provide a default address for @code{x} to examine also
9337 set @code{$_} to that address; these commands include @code{info line}
9338 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9339 except when set by the @code{x} command, in which case it is a pointer
9340 to the type of @code{$__}.
9342 @vindex $__@r{, convenience variable}
9344 The variable @code{$__} is automatically set by the @code{x} command
9345 to the value found in the last address examined. Its type is chosen
9346 to match the format in which the data was printed.
9349 @vindex $_exitcode@r{, convenience variable}
9350 The variable @code{$_exitcode} is automatically set to the exit code when
9351 the program being debugged terminates.
9354 @itemx $_probe_arg0@dots{}$_probe_arg11
9355 Arguments to a static probe. @xref{Static Probe Points}.
9358 @vindex $_sdata@r{, inspect, convenience variable}
9359 The variable @code{$_sdata} contains extra collected static tracepoint
9360 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9361 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9362 if extra static tracepoint data has not been collected.
9365 @vindex $_siginfo@r{, convenience variable}
9366 The variable @code{$_siginfo} contains extra signal information
9367 (@pxref{extra signal information}). Note that @code{$_siginfo}
9368 could be empty, if the application has not yet received any signals.
9369 For example, it will be empty before you execute the @code{run} command.
9372 @vindex $_tlb@r{, convenience variable}
9373 The variable @code{$_tlb} is automatically set when debugging
9374 applications running on MS-Windows in native mode or connected to
9375 gdbserver that supports the @code{qGetTIBAddr} request.
9376 @xref{General Query Packets}.
9377 This variable contains the address of the thread information block.
9381 On HP-UX systems, if you refer to a function or variable name that
9382 begins with a dollar sign, @value{GDBN} searches for a user or system
9383 name first, before it searches for a convenience variable.
9385 @node Convenience Funs
9386 @section Convenience Functions
9388 @cindex convenience functions
9389 @value{GDBN} also supplies some @dfn{convenience functions}. These
9390 have a syntax similar to convenience variables. A convenience
9391 function can be used in an expression just like an ordinary function;
9392 however, a convenience function is implemented internally to
9395 These functions require @value{GDBN} to be configured with
9396 @code{Python} support.
9400 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9401 @findex $_memeq@r{, convenience function}
9402 Returns one if the @var{length} bytes at the addresses given by
9403 @var{buf1} and @var{buf2} are equal.
9404 Otherwise it returns zero.
9406 @item $_regex(@var{str}, @var{regex})
9407 @findex $_regex@r{, convenience function}
9408 Returns one if the string @var{str} matches the regular expression
9409 @var{regex}. Otherwise it returns zero.
9410 The syntax of the regular expression is that specified by @code{Python}'s
9411 regular expression support.
9413 @item $_streq(@var{str1}, @var{str2})
9414 @findex $_streq@r{, convenience function}
9415 Returns one if the strings @var{str1} and @var{str2} are equal.
9416 Otherwise it returns zero.
9418 @item $_strlen(@var{str})
9419 @findex $_strlen@r{, convenience function}
9420 Returns the length of string @var{str}.
9424 @value{GDBN} provides the ability to list and get help on
9425 convenience functions.
9429 @kindex help function
9430 @cindex show all convenience functions
9431 Print a list of all convenience functions.
9438 You can refer to machine register contents, in expressions, as variables
9439 with names starting with @samp{$}. The names of registers are different
9440 for each machine; use @code{info registers} to see the names used on
9444 @kindex info registers
9445 @item info registers
9446 Print the names and values of all registers except floating-point
9447 and vector registers (in the selected stack frame).
9449 @kindex info all-registers
9450 @cindex floating point registers
9451 @item info all-registers
9452 Print the names and values of all registers, including floating-point
9453 and vector registers (in the selected stack frame).
9455 @item info registers @var{regname} @dots{}
9456 Print the @dfn{relativized} value of each specified register @var{regname}.
9457 As discussed in detail below, register values are normally relative to
9458 the selected stack frame. @var{regname} may be any register name valid on
9459 the machine you are using, with or without the initial @samp{$}.
9462 @cindex stack pointer register
9463 @cindex program counter register
9464 @cindex process status register
9465 @cindex frame pointer register
9466 @cindex standard registers
9467 @value{GDBN} has four ``standard'' register names that are available (in
9468 expressions) on most machines---whenever they do not conflict with an
9469 architecture's canonical mnemonics for registers. The register names
9470 @code{$pc} and @code{$sp} are used for the program counter register and
9471 the stack pointer. @code{$fp} is used for a register that contains a
9472 pointer to the current stack frame, and @code{$ps} is used for a
9473 register that contains the processor status. For example,
9474 you could print the program counter in hex with
9481 or print the instruction to be executed next with
9488 or add four to the stack pointer@footnote{This is a way of removing
9489 one word from the stack, on machines where stacks grow downward in
9490 memory (most machines, nowadays). This assumes that the innermost
9491 stack frame is selected; setting @code{$sp} is not allowed when other
9492 stack frames are selected. To pop entire frames off the stack,
9493 regardless of machine architecture, use @code{return};
9494 see @ref{Returning, ,Returning from a Function}.} with
9500 Whenever possible, these four standard register names are available on
9501 your machine even though the machine has different canonical mnemonics,
9502 so long as there is no conflict. The @code{info registers} command
9503 shows the canonical names. For example, on the SPARC, @code{info
9504 registers} displays the processor status register as @code{$psr} but you
9505 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9506 is an alias for the @sc{eflags} register.
9508 @value{GDBN} always considers the contents of an ordinary register as an
9509 integer when the register is examined in this way. Some machines have
9510 special registers which can hold nothing but floating point; these
9511 registers are considered to have floating point values. There is no way
9512 to refer to the contents of an ordinary register as floating point value
9513 (although you can @emph{print} it as a floating point value with
9514 @samp{print/f $@var{regname}}).
9516 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9517 means that the data format in which the register contents are saved by
9518 the operating system is not the same one that your program normally
9519 sees. For example, the registers of the 68881 floating point
9520 coprocessor are always saved in ``extended'' (raw) format, but all C
9521 programs expect to work with ``double'' (virtual) format. In such
9522 cases, @value{GDBN} normally works with the virtual format only (the format
9523 that makes sense for your program), but the @code{info registers} command
9524 prints the data in both formats.
9526 @cindex SSE registers (x86)
9527 @cindex MMX registers (x86)
9528 Some machines have special registers whose contents can be interpreted
9529 in several different ways. For example, modern x86-based machines
9530 have SSE and MMX registers that can hold several values packed
9531 together in several different formats. @value{GDBN} refers to such
9532 registers in @code{struct} notation:
9535 (@value{GDBP}) print $xmm1
9537 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9538 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9539 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9540 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9541 v4_int32 = @{0, 20657912, 11, 13@},
9542 v2_int64 = @{88725056443645952, 55834574859@},
9543 uint128 = 0x0000000d0000000b013b36f800000000
9548 To set values of such registers, you need to tell @value{GDBN} which
9549 view of the register you wish to change, as if you were assigning
9550 value to a @code{struct} member:
9553 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9556 Normally, register values are relative to the selected stack frame
9557 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9558 value that the register would contain if all stack frames farther in
9559 were exited and their saved registers restored. In order to see the
9560 true contents of hardware registers, you must select the innermost
9561 frame (with @samp{frame 0}).
9563 However, @value{GDBN} must deduce where registers are saved, from the machine
9564 code generated by your compiler. If some registers are not saved, or if
9565 @value{GDBN} is unable to locate the saved registers, the selected stack
9566 frame makes no difference.
9568 @node Floating Point Hardware
9569 @section Floating Point Hardware
9570 @cindex floating point
9572 Depending on the configuration, @value{GDBN} may be able to give
9573 you more information about the status of the floating point hardware.
9578 Display hardware-dependent information about the floating
9579 point unit. The exact contents and layout vary depending on the
9580 floating point chip. Currently, @samp{info float} is supported on
9581 the ARM and x86 machines.
9585 @section Vector Unit
9588 Depending on the configuration, @value{GDBN} may be able to give you
9589 more information about the status of the vector unit.
9594 Display information about the vector unit. The exact contents and
9595 layout vary depending on the hardware.
9598 @node OS Information
9599 @section Operating System Auxiliary Information
9600 @cindex OS information
9602 @value{GDBN} provides interfaces to useful OS facilities that can help
9603 you debug your program.
9605 @cindex auxiliary vector
9606 @cindex vector, auxiliary
9607 Some operating systems supply an @dfn{auxiliary vector} to programs at
9608 startup. This is akin to the arguments and environment that you
9609 specify for a program, but contains a system-dependent variety of
9610 binary values that tell system libraries important details about the
9611 hardware, operating system, and process. Each value's purpose is
9612 identified by an integer tag; the meanings are well-known but system-specific.
9613 Depending on the configuration and operating system facilities,
9614 @value{GDBN} may be able to show you this information. For remote
9615 targets, this functionality may further depend on the remote stub's
9616 support of the @samp{qXfer:auxv:read} packet, see
9617 @ref{qXfer auxiliary vector read}.
9622 Display the auxiliary vector of the inferior, which can be either a
9623 live process or a core dump file. @value{GDBN} prints each tag value
9624 numerically, and also shows names and text descriptions for recognized
9625 tags. Some values in the vector are numbers, some bit masks, and some
9626 pointers to strings or other data. @value{GDBN} displays each value in the
9627 most appropriate form for a recognized tag, and in hexadecimal for
9628 an unrecognized tag.
9631 On some targets, @value{GDBN} can access operating system-specific
9632 information and show it to you. The types of information available
9633 will differ depending on the type of operating system running on the
9634 target. The mechanism used to fetch the data is described in
9635 @ref{Operating System Information}. For remote targets, this
9636 functionality depends on the remote stub's support of the
9637 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9641 @item info os @var{infotype}
9643 Display OS information of the requested type.
9645 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9647 @anchor{linux info os infotypes}
9649 @kindex info os processes
9651 Display the list of processes on the target. For each process,
9652 @value{GDBN} prints the process identifier, the name of the user, the
9653 command corresponding to the process, and the list of processor cores
9654 that the process is currently running on. (To understand what these
9655 properties mean, for this and the following info types, please consult
9656 the general @sc{gnu}/Linux documentation.)
9658 @kindex info os procgroups
9660 Display the list of process groups on the target. For each process,
9661 @value{GDBN} prints the identifier of the process group that it belongs
9662 to, the command corresponding to the process group leader, the process
9663 identifier, and the command line of the process. The list is sorted
9664 first by the process group identifier, then by the process identifier,
9665 so that processes belonging to the same process group are grouped together
9666 and the process group leader is listed first.
9668 @kindex info os threads
9670 Display the list of threads running on the target. For each thread,
9671 @value{GDBN} prints the identifier of the process that the thread
9672 belongs to, the command of the process, the thread identifier, and the
9673 processor core that it is currently running on. The main thread of a
9674 process is not listed.
9676 @kindex info os files
9678 Display the list of open file descriptors on the target. For each
9679 file descriptor, @value{GDBN} prints the identifier of the process
9680 owning the descriptor, the command of the owning process, the value
9681 of the descriptor, and the target of the descriptor.
9683 @kindex info os sockets
9685 Display the list of Internet-domain sockets on the target. For each
9686 socket, @value{GDBN} prints the address and port of the local and
9687 remote endpoints, the current state of the connection, the creator of
9688 the socket, the IP address family of the socket, and the type of the
9693 Display the list of all System V shared-memory regions on the target.
9694 For each shared-memory region, @value{GDBN} prints the region key,
9695 the shared-memory identifier, the access permissions, the size of the
9696 region, the process that created the region, the process that last
9697 attached to or detached from the region, the current number of live
9698 attaches to the region, and the times at which the region was last
9699 attached to, detach from, and changed.
9701 @kindex info os semaphores
9703 Display the list of all System V semaphore sets on the target. For each
9704 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9705 set identifier, the access permissions, the number of semaphores in the
9706 set, the user and group of the owner and creator of the semaphore set,
9707 and the times at which the semaphore set was operated upon and changed.
9711 Display the list of all System V message queues on the target. For each
9712 message queue, @value{GDBN} prints the message queue key, the message
9713 queue identifier, the access permissions, the current number of bytes
9714 on the queue, the current number of messages on the queue, the processes
9715 that last sent and received a message on the queue, the user and group
9716 of the owner and creator of the message queue, the times at which a
9717 message was last sent and received on the queue, and the time at which
9718 the message queue was last changed.
9720 @kindex info os modules
9722 Display the list of all loaded kernel modules on the target. For each
9723 module, @value{GDBN} prints the module name, the size of the module in
9724 bytes, the number of times the module is used, the dependencies of the
9725 module, the status of the module, and the address of the loaded module
9730 If @var{infotype} is omitted, then list the possible values for
9731 @var{infotype} and the kind of OS information available for each
9732 @var{infotype}. If the target does not return a list of possible
9733 types, this command will report an error.
9736 @node Memory Region Attributes
9737 @section Memory Region Attributes
9738 @cindex memory region attributes
9740 @dfn{Memory region attributes} allow you to describe special handling
9741 required by regions of your target's memory. @value{GDBN} uses
9742 attributes to determine whether to allow certain types of memory
9743 accesses; whether to use specific width accesses; and whether to cache
9744 target memory. By default the description of memory regions is
9745 fetched from the target (if the current target supports this), but the
9746 user can override the fetched regions.
9748 Defined memory regions can be individually enabled and disabled. When a
9749 memory region is disabled, @value{GDBN} uses the default attributes when
9750 accessing memory in that region. Similarly, if no memory regions have
9751 been defined, @value{GDBN} uses the default attributes when accessing
9754 When a memory region is defined, it is given a number to identify it;
9755 to enable, disable, or remove a memory region, you specify that number.
9759 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9760 Define a memory region bounded by @var{lower} and @var{upper} with
9761 attributes @var{attributes}@dots{}, and add it to the list of regions
9762 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9763 case: it is treated as the target's maximum memory address.
9764 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9767 Discard any user changes to the memory regions and use target-supplied
9768 regions, if available, or no regions if the target does not support.
9771 @item delete mem @var{nums}@dots{}
9772 Remove memory regions @var{nums}@dots{} from the list of regions
9773 monitored by @value{GDBN}.
9776 @item disable mem @var{nums}@dots{}
9777 Disable monitoring of memory regions @var{nums}@dots{}.
9778 A disabled memory region is not forgotten.
9779 It may be enabled again later.
9782 @item enable mem @var{nums}@dots{}
9783 Enable monitoring of memory regions @var{nums}@dots{}.
9787 Print a table of all defined memory regions, with the following columns
9791 @item Memory Region Number
9792 @item Enabled or Disabled.
9793 Enabled memory regions are marked with @samp{y}.
9794 Disabled memory regions are marked with @samp{n}.
9797 The address defining the inclusive lower bound of the memory region.
9800 The address defining the exclusive upper bound of the memory region.
9803 The list of attributes set for this memory region.
9808 @subsection Attributes
9810 @subsubsection Memory Access Mode
9811 The access mode attributes set whether @value{GDBN} may make read or
9812 write accesses to a memory region.
9814 While these attributes prevent @value{GDBN} from performing invalid
9815 memory accesses, they do nothing to prevent the target system, I/O DMA,
9816 etc.@: from accessing memory.
9820 Memory is read only.
9822 Memory is write only.
9824 Memory is read/write. This is the default.
9827 @subsubsection Memory Access Size
9828 The access size attribute tells @value{GDBN} to use specific sized
9829 accesses in the memory region. Often memory mapped device registers
9830 require specific sized accesses. If no access size attribute is
9831 specified, @value{GDBN} may use accesses of any size.
9835 Use 8 bit memory accesses.
9837 Use 16 bit memory accesses.
9839 Use 32 bit memory accesses.
9841 Use 64 bit memory accesses.
9844 @c @subsubsection Hardware/Software Breakpoints
9845 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9846 @c will use hardware or software breakpoints for the internal breakpoints
9847 @c used by the step, next, finish, until, etc. commands.
9851 @c Always use hardware breakpoints
9852 @c @item swbreak (default)
9855 @subsubsection Data Cache
9856 The data cache attributes set whether @value{GDBN} will cache target
9857 memory. While this generally improves performance by reducing debug
9858 protocol overhead, it can lead to incorrect results because @value{GDBN}
9859 does not know about volatile variables or memory mapped device
9864 Enable @value{GDBN} to cache target memory.
9866 Disable @value{GDBN} from caching target memory. This is the default.
9869 @subsection Memory Access Checking
9870 @value{GDBN} can be instructed to refuse accesses to memory that is
9871 not explicitly described. This can be useful if accessing such
9872 regions has undesired effects for a specific target, or to provide
9873 better error checking. The following commands control this behaviour.
9876 @kindex set mem inaccessible-by-default
9877 @item set mem inaccessible-by-default [on|off]
9878 If @code{on} is specified, make @value{GDBN} treat memory not
9879 explicitly described by the memory ranges as non-existent and refuse accesses
9880 to such memory. The checks are only performed if there's at least one
9881 memory range defined. If @code{off} is specified, make @value{GDBN}
9882 treat the memory not explicitly described by the memory ranges as RAM.
9883 The default value is @code{on}.
9884 @kindex show mem inaccessible-by-default
9885 @item show mem inaccessible-by-default
9886 Show the current handling of accesses to unknown memory.
9890 @c @subsubsection Memory Write Verification
9891 @c The memory write verification attributes set whether @value{GDBN}
9892 @c will re-reads data after each write to verify the write was successful.
9896 @c @item noverify (default)
9899 @node Dump/Restore Files
9900 @section Copy Between Memory and a File
9901 @cindex dump/restore files
9902 @cindex append data to a file
9903 @cindex dump data to a file
9904 @cindex restore data from a file
9906 You can use the commands @code{dump}, @code{append}, and
9907 @code{restore} to copy data between target memory and a file. The
9908 @code{dump} and @code{append} commands write data to a file, and the
9909 @code{restore} command reads data from a file back into the inferior's
9910 memory. Files may be in binary, Motorola S-record, Intel hex, or
9911 Tektronix Hex format; however, @value{GDBN} can only append to binary
9917 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9918 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9919 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9920 or the value of @var{expr}, to @var{filename} in the given format.
9922 The @var{format} parameter may be any one of:
9929 Motorola S-record format.
9931 Tektronix Hex format.
9934 @value{GDBN} uses the same definitions of these formats as the
9935 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9936 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9940 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9941 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9942 Append the contents of memory from @var{start_addr} to @var{end_addr},
9943 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9944 (@value{GDBN} can only append data to files in raw binary form.)
9947 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9948 Restore the contents of file @var{filename} into memory. The
9949 @code{restore} command can automatically recognize any known @sc{bfd}
9950 file format, except for raw binary. To restore a raw binary file you
9951 must specify the optional keyword @code{binary} after the filename.
9953 If @var{bias} is non-zero, its value will be added to the addresses
9954 contained in the file. Binary files always start at address zero, so
9955 they will be restored at address @var{bias}. Other bfd files have
9956 a built-in location; they will be restored at offset @var{bias}
9959 If @var{start} and/or @var{end} are non-zero, then only data between
9960 file offset @var{start} and file offset @var{end} will be restored.
9961 These offsets are relative to the addresses in the file, before
9962 the @var{bias} argument is applied.
9966 @node Core File Generation
9967 @section How to Produce a Core File from Your Program
9968 @cindex dump core from inferior
9970 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9971 image of a running process and its process status (register values
9972 etc.). Its primary use is post-mortem debugging of a program that
9973 crashed while it ran outside a debugger. A program that crashes
9974 automatically produces a core file, unless this feature is disabled by
9975 the user. @xref{Files}, for information on invoking @value{GDBN} in
9976 the post-mortem debugging mode.
9978 Occasionally, you may wish to produce a core file of the program you
9979 are debugging in order to preserve a snapshot of its state.
9980 @value{GDBN} has a special command for that.
9984 @kindex generate-core-file
9985 @item generate-core-file [@var{file}]
9986 @itemx gcore [@var{file}]
9987 Produce a core dump of the inferior process. The optional argument
9988 @var{file} specifies the file name where to put the core dump. If not
9989 specified, the file name defaults to @file{core.@var{pid}}, where
9990 @var{pid} is the inferior process ID.
9992 Note that this command is implemented only for some systems (as of
9993 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
9996 @node Character Sets
9997 @section Character Sets
9998 @cindex character sets
10000 @cindex translating between character sets
10001 @cindex host character set
10002 @cindex target character set
10004 If the program you are debugging uses a different character set to
10005 represent characters and strings than the one @value{GDBN} uses itself,
10006 @value{GDBN} can automatically translate between the character sets for
10007 you. The character set @value{GDBN} uses we call the @dfn{host
10008 character set}; the one the inferior program uses we call the
10009 @dfn{target character set}.
10011 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10012 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10013 remote protocol (@pxref{Remote Debugging}) to debug a program
10014 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10015 then the host character set is Latin-1, and the target character set is
10016 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10017 target-charset EBCDIC-US}, then @value{GDBN} translates between
10018 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10019 character and string literals in expressions.
10021 @value{GDBN} has no way to automatically recognize which character set
10022 the inferior program uses; you must tell it, using the @code{set
10023 target-charset} command, described below.
10025 Here are the commands for controlling @value{GDBN}'s character set
10029 @item set target-charset @var{charset}
10030 @kindex set target-charset
10031 Set the current target character set to @var{charset}. To display the
10032 list of supported target character sets, type
10033 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10035 @item set host-charset @var{charset}
10036 @kindex set host-charset
10037 Set the current host character set to @var{charset}.
10039 By default, @value{GDBN} uses a host character set appropriate to the
10040 system it is running on; you can override that default using the
10041 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10042 automatically determine the appropriate host character set. In this
10043 case, @value{GDBN} uses @samp{UTF-8}.
10045 @value{GDBN} can only use certain character sets as its host character
10046 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10047 @value{GDBN} will list the host character sets it supports.
10049 @item set charset @var{charset}
10050 @kindex set charset
10051 Set the current host and target character sets to @var{charset}. As
10052 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10053 @value{GDBN} will list the names of the character sets that can be used
10054 for both host and target.
10057 @kindex show charset
10058 Show the names of the current host and target character sets.
10060 @item show host-charset
10061 @kindex show host-charset
10062 Show the name of the current host character set.
10064 @item show target-charset
10065 @kindex show target-charset
10066 Show the name of the current target character set.
10068 @item set target-wide-charset @var{charset}
10069 @kindex set target-wide-charset
10070 Set the current target's wide character set to @var{charset}. This is
10071 the character set used by the target's @code{wchar_t} type. To
10072 display the list of supported wide character sets, type
10073 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10075 @item show target-wide-charset
10076 @kindex show target-wide-charset
10077 Show the name of the current target's wide character set.
10080 Here is an example of @value{GDBN}'s character set support in action.
10081 Assume that the following source code has been placed in the file
10082 @file{charset-test.c}:
10088 = @{72, 101, 108, 108, 111, 44, 32, 119,
10089 111, 114, 108, 100, 33, 10, 0@};
10090 char ibm1047_hello[]
10091 = @{200, 133, 147, 147, 150, 107, 64, 166,
10092 150, 153, 147, 132, 90, 37, 0@};
10096 printf ("Hello, world!\n");
10100 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10101 containing the string @samp{Hello, world!} followed by a newline,
10102 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10104 We compile the program, and invoke the debugger on it:
10107 $ gcc -g charset-test.c -o charset-test
10108 $ gdb -nw charset-test
10109 GNU gdb 2001-12-19-cvs
10110 Copyright 2001 Free Software Foundation, Inc.
10115 We can use the @code{show charset} command to see what character sets
10116 @value{GDBN} is currently using to interpret and display characters and
10120 (@value{GDBP}) show charset
10121 The current host and target character set is `ISO-8859-1'.
10125 For the sake of printing this manual, let's use @sc{ascii} as our
10126 initial character set:
10128 (@value{GDBP}) set charset ASCII
10129 (@value{GDBP}) show charset
10130 The current host and target character set is `ASCII'.
10134 Let's assume that @sc{ascii} is indeed the correct character set for our
10135 host system --- in other words, let's assume that if @value{GDBN} prints
10136 characters using the @sc{ascii} character set, our terminal will display
10137 them properly. Since our current target character set is also
10138 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10141 (@value{GDBP}) print ascii_hello
10142 $1 = 0x401698 "Hello, world!\n"
10143 (@value{GDBP}) print ascii_hello[0]
10148 @value{GDBN} uses the target character set for character and string
10149 literals you use in expressions:
10152 (@value{GDBP}) print '+'
10157 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10160 @value{GDBN} relies on the user to tell it which character set the
10161 target program uses. If we print @code{ibm1047_hello} while our target
10162 character set is still @sc{ascii}, we get jibberish:
10165 (@value{GDBP}) print ibm1047_hello
10166 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10167 (@value{GDBP}) print ibm1047_hello[0]
10172 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10173 @value{GDBN} tells us the character sets it supports:
10176 (@value{GDBP}) set target-charset
10177 ASCII EBCDIC-US IBM1047 ISO-8859-1
10178 (@value{GDBP}) set target-charset
10181 We can select @sc{ibm1047} as our target character set, and examine the
10182 program's strings again. Now the @sc{ascii} string is wrong, but
10183 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10184 target character set, @sc{ibm1047}, to the host character set,
10185 @sc{ascii}, and they display correctly:
10188 (@value{GDBP}) set target-charset IBM1047
10189 (@value{GDBP}) show charset
10190 The current host character set is `ASCII'.
10191 The current target character set is `IBM1047'.
10192 (@value{GDBP}) print ascii_hello
10193 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10194 (@value{GDBP}) print ascii_hello[0]
10196 (@value{GDBP}) print ibm1047_hello
10197 $8 = 0x4016a8 "Hello, world!\n"
10198 (@value{GDBP}) print ibm1047_hello[0]
10203 As above, @value{GDBN} uses the target character set for character and
10204 string literals you use in expressions:
10207 (@value{GDBP}) print '+'
10212 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10215 @node Caching Remote Data
10216 @section Caching Data of Remote Targets
10217 @cindex caching data of remote targets
10219 @value{GDBN} caches data exchanged between the debugger and a
10220 remote target (@pxref{Remote Debugging}). Such caching generally improves
10221 performance, because it reduces the overhead of the remote protocol by
10222 bundling memory reads and writes into large chunks. Unfortunately, simply
10223 caching everything would lead to incorrect results, since @value{GDBN}
10224 does not necessarily know anything about volatile values, memory-mapped I/O
10225 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10226 memory can be changed @emph{while} a gdb command is executing.
10227 Therefore, by default, @value{GDBN} only caches data
10228 known to be on the stack@footnote{In non-stop mode, it is moderately
10229 rare for a running thread to modify the stack of a stopped thread
10230 in a way that would interfere with a backtrace, and caching of
10231 stack reads provides a significant speed up of remote backtraces.}.
10232 Other regions of memory can be explicitly marked as
10233 cacheable; see @pxref{Memory Region Attributes}.
10236 @kindex set remotecache
10237 @item set remotecache on
10238 @itemx set remotecache off
10239 This option no longer does anything; it exists for compatibility
10242 @kindex show remotecache
10243 @item show remotecache
10244 Show the current state of the obsolete remotecache flag.
10246 @kindex set stack-cache
10247 @item set stack-cache on
10248 @itemx set stack-cache off
10249 Enable or disable caching of stack accesses. When @code{ON}, use
10250 caching. By default, this option is @code{ON}.
10252 @kindex show stack-cache
10253 @item show stack-cache
10254 Show the current state of data caching for memory accesses.
10256 @kindex info dcache
10257 @item info dcache @r{[}line@r{]}
10258 Print the information about the data cache performance. The
10259 information displayed includes the dcache width and depth, and for
10260 each cache line, its number, address, and how many times it was
10261 referenced. This command is useful for debugging the data cache
10264 If a line number is specified, the contents of that line will be
10267 @item set dcache size @var{size}
10268 @cindex dcache size
10269 @kindex set dcache size
10270 Set maximum number of entries in dcache (dcache depth above).
10272 @item set dcache line-size @var{line-size}
10273 @cindex dcache line-size
10274 @kindex set dcache line-size
10275 Set number of bytes each dcache entry caches (dcache width above).
10276 Must be a power of 2.
10278 @item show dcache size
10279 @kindex show dcache size
10280 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10282 @item show dcache line-size
10283 @kindex show dcache line-size
10284 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10288 @node Searching Memory
10289 @section Search Memory
10290 @cindex searching memory
10292 Memory can be searched for a particular sequence of bytes with the
10293 @code{find} command.
10297 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10298 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10299 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10300 etc. The search begins at address @var{start_addr} and continues for either
10301 @var{len} bytes or through to @var{end_addr} inclusive.
10304 @var{s} and @var{n} are optional parameters.
10305 They may be specified in either order, apart or together.
10308 @item @var{s}, search query size
10309 The size of each search query value.
10315 halfwords (two bytes)
10319 giant words (eight bytes)
10322 All values are interpreted in the current language.
10323 This means, for example, that if the current source language is C/C@t{++}
10324 then searching for the string ``hello'' includes the trailing '\0'.
10326 If the value size is not specified, it is taken from the
10327 value's type in the current language.
10328 This is useful when one wants to specify the search
10329 pattern as a mixture of types.
10330 Note that this means, for example, that in the case of C-like languages
10331 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10332 which is typically four bytes.
10334 @item @var{n}, maximum number of finds
10335 The maximum number of matches to print. The default is to print all finds.
10338 You can use strings as search values. Quote them with double-quotes
10340 The string value is copied into the search pattern byte by byte,
10341 regardless of the endianness of the target and the size specification.
10343 The address of each match found is printed as well as a count of the
10344 number of matches found.
10346 The address of the last value found is stored in convenience variable
10348 A count of the number of matches is stored in @samp{$numfound}.
10350 For example, if stopped at the @code{printf} in this function:
10356 static char hello[] = "hello-hello";
10357 static struct @{ char c; short s; int i; @}
10358 __attribute__ ((packed)) mixed
10359 = @{ 'c', 0x1234, 0x87654321 @};
10360 printf ("%s\n", hello);
10365 you get during debugging:
10368 (gdb) find &hello[0], +sizeof(hello), "hello"
10369 0x804956d <hello.1620+6>
10371 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10372 0x8049567 <hello.1620>
10373 0x804956d <hello.1620+6>
10375 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10376 0x8049567 <hello.1620>
10378 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10379 0x8049560 <mixed.1625>
10381 (gdb) print $numfound
10384 $2 = (void *) 0x8049560
10387 @node Optimized Code
10388 @chapter Debugging Optimized Code
10389 @cindex optimized code, debugging
10390 @cindex debugging optimized code
10392 Almost all compilers support optimization. With optimization
10393 disabled, the compiler generates assembly code that corresponds
10394 directly to your source code, in a simplistic way. As the compiler
10395 applies more powerful optimizations, the generated assembly code
10396 diverges from your original source code. With help from debugging
10397 information generated by the compiler, @value{GDBN} can map from
10398 the running program back to constructs from your original source.
10400 @value{GDBN} is more accurate with optimization disabled. If you
10401 can recompile without optimization, it is easier to follow the
10402 progress of your program during debugging. But, there are many cases
10403 where you may need to debug an optimized version.
10405 When you debug a program compiled with @samp{-g -O}, remember that the
10406 optimizer has rearranged your code; the debugger shows you what is
10407 really there. Do not be too surprised when the execution path does not
10408 exactly match your source file! An extreme example: if you define a
10409 variable, but never use it, @value{GDBN} never sees that
10410 variable---because the compiler optimizes it out of existence.
10412 Some things do not work as well with @samp{-g -O} as with just
10413 @samp{-g}, particularly on machines with instruction scheduling. If in
10414 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10415 please report it to us as a bug (including a test case!).
10416 @xref{Variables}, for more information about debugging optimized code.
10419 * Inline Functions:: How @value{GDBN} presents inlining
10420 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10423 @node Inline Functions
10424 @section Inline Functions
10425 @cindex inline functions, debugging
10427 @dfn{Inlining} is an optimization that inserts a copy of the function
10428 body directly at each call site, instead of jumping to a shared
10429 routine. @value{GDBN} displays inlined functions just like
10430 non-inlined functions. They appear in backtraces. You can view their
10431 arguments and local variables, step into them with @code{step}, skip
10432 them with @code{next}, and escape from them with @code{finish}.
10433 You can check whether a function was inlined by using the
10434 @code{info frame} command.
10436 For @value{GDBN} to support inlined functions, the compiler must
10437 record information about inlining in the debug information ---
10438 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10439 other compilers do also. @value{GDBN} only supports inlined functions
10440 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10441 do not emit two required attributes (@samp{DW_AT_call_file} and
10442 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10443 function calls with earlier versions of @value{NGCC}. It instead
10444 displays the arguments and local variables of inlined functions as
10445 local variables in the caller.
10447 The body of an inlined function is directly included at its call site;
10448 unlike a non-inlined function, there are no instructions devoted to
10449 the call. @value{GDBN} still pretends that the call site and the
10450 start of the inlined function are different instructions. Stepping to
10451 the call site shows the call site, and then stepping again shows
10452 the first line of the inlined function, even though no additional
10453 instructions are executed.
10455 This makes source-level debugging much clearer; you can see both the
10456 context of the call and then the effect of the call. Only stepping by
10457 a single instruction using @code{stepi} or @code{nexti} does not do
10458 this; single instruction steps always show the inlined body.
10460 There are some ways that @value{GDBN} does not pretend that inlined
10461 function calls are the same as normal calls:
10465 Setting breakpoints at the call site of an inlined function may not
10466 work, because the call site does not contain any code. @value{GDBN}
10467 may incorrectly move the breakpoint to the next line of the enclosing
10468 function, after the call. This limitation will be removed in a future
10469 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10470 or inside the inlined function instead.
10473 @value{GDBN} cannot locate the return value of inlined calls after
10474 using the @code{finish} command. This is a limitation of compiler-generated
10475 debugging information; after @code{finish}, you can step to the next line
10476 and print a variable where your program stored the return value.
10480 @node Tail Call Frames
10481 @section Tail Call Frames
10482 @cindex tail call frames, debugging
10484 Function @code{B} can call function @code{C} in its very last statement. In
10485 unoptimized compilation the call of @code{C} is immediately followed by return
10486 instruction at the end of @code{B} code. Optimizing compiler may replace the
10487 call and return in function @code{B} into one jump to function @code{C}
10488 instead. Such use of a jump instruction is called @dfn{tail call}.
10490 During execution of function @code{C}, there will be no indication in the
10491 function call stack frames that it was tail-called from @code{B}. If function
10492 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10493 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10494 some cases @value{GDBN} can determine that @code{C} was tail-called from
10495 @code{B}, and it will then create fictitious call frame for that, with the
10496 return address set up as if @code{B} called @code{C} normally.
10498 This functionality is currently supported only by DWARF 2 debugging format and
10499 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10500 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10503 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10504 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10508 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10510 Stack level 1, frame at 0x7fffffffda30:
10511 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10512 tail call frame, caller of frame at 0x7fffffffda30
10513 source language c++.
10514 Arglist at unknown address.
10515 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10518 The detection of all the possible code path executions can find them ambiguous.
10519 There is no execution history stored (possible @ref{Reverse Execution} is never
10520 used for this purpose) and the last known caller could have reached the known
10521 callee by multiple different jump sequences. In such case @value{GDBN} still
10522 tries to show at least all the unambiguous top tail callers and all the
10523 unambiguous bottom tail calees, if any.
10526 @anchor{set debug entry-values}
10527 @item set debug entry-values
10528 @kindex set debug entry-values
10529 When set to on, enables printing of analysis messages for both frame argument
10530 values at function entry and tail calls. It will show all the possible valid
10531 tail calls code paths it has considered. It will also print the intersection
10532 of them with the final unambiguous (possibly partial or even empty) code path
10535 @item show debug entry-values
10536 @kindex show debug entry-values
10537 Show the current state of analysis messages printing for both frame argument
10538 values at function entry and tail calls.
10541 The analysis messages for tail calls can for example show why the virtual tail
10542 call frame for function @code{c} has not been recognized (due to the indirect
10543 reference by variable @code{x}):
10546 static void __attribute__((noinline, noclone)) c (void);
10547 void (*x) (void) = c;
10548 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10549 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10550 int main (void) @{ x (); return 0; @}
10552 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10553 DW_TAG_GNU_call_site 0x40039a in main
10555 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10558 #1 0x000000000040039a in main () at t.c:5
10561 Another possibility is an ambiguous virtual tail call frames resolution:
10565 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10566 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10567 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10568 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10569 static void __attribute__((noinline, noclone)) b (void)
10570 @{ if (i) c (); else e (); @}
10571 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10572 int main (void) @{ a (); return 0; @}
10574 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10575 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10576 tailcall: reduced: 0x4004d2(a) |
10579 #1 0x00000000004004d2 in a () at t.c:8
10580 #2 0x0000000000400395 in main () at t.c:9
10583 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10584 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10586 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10587 @ifset HAVE_MAKEINFO_CLICK
10588 @set ARROW @click{}
10589 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10590 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10592 @ifclear HAVE_MAKEINFO_CLICK
10594 @set CALLSEQ1B @value{CALLSEQ1A}
10595 @set CALLSEQ2B @value{CALLSEQ2A}
10598 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10599 The code can have possible execution paths @value{CALLSEQ1B} or
10600 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10602 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10603 has found. It then finds another possible calling sequcen - that one is
10604 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10605 printed as the @code{reduced:} calling sequence. That one could have many
10606 futher @code{compare:} and @code{reduced:} statements as long as there remain
10607 any non-ambiguous sequence entries.
10609 For the frame of function @code{b} in both cases there are different possible
10610 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10611 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10612 therefore this one is displayed to the user while the ambiguous frames are
10615 There can be also reasons why printing of frame argument values at function
10620 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10621 static void __attribute__((noinline, noclone)) a (int i);
10622 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10623 static void __attribute__((noinline, noclone)) a (int i)
10624 @{ if (i) b (i - 1); else c (0); @}
10625 int main (void) @{ a (5); return 0; @}
10628 #0 c (i=i@@entry=0) at t.c:2
10629 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10630 function "a" at 0x400420 can call itself via tail calls
10631 i=<optimized out>) at t.c:6
10632 #2 0x000000000040036e in main () at t.c:7
10635 @value{GDBN} cannot find out from the inferior state if and how many times did
10636 function @code{a} call itself (via function @code{b}) as these calls would be
10637 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10638 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10639 prints @code{<optimized out>} instead.
10642 @chapter C Preprocessor Macros
10644 Some languages, such as C and C@t{++}, provide a way to define and invoke
10645 ``preprocessor macros'' which expand into strings of tokens.
10646 @value{GDBN} can evaluate expressions containing macro invocations, show
10647 the result of macro expansion, and show a macro's definition, including
10648 where it was defined.
10650 You may need to compile your program specially to provide @value{GDBN}
10651 with information about preprocessor macros. Most compilers do not
10652 include macros in their debugging information, even when you compile
10653 with the @option{-g} flag. @xref{Compilation}.
10655 A program may define a macro at one point, remove that definition later,
10656 and then provide a different definition after that. Thus, at different
10657 points in the program, a macro may have different definitions, or have
10658 no definition at all. If there is a current stack frame, @value{GDBN}
10659 uses the macros in scope at that frame's source code line. Otherwise,
10660 @value{GDBN} uses the macros in scope at the current listing location;
10663 Whenever @value{GDBN} evaluates an expression, it always expands any
10664 macro invocations present in the expression. @value{GDBN} also provides
10665 the following commands for working with macros explicitly.
10669 @kindex macro expand
10670 @cindex macro expansion, showing the results of preprocessor
10671 @cindex preprocessor macro expansion, showing the results of
10672 @cindex expanding preprocessor macros
10673 @item macro expand @var{expression}
10674 @itemx macro exp @var{expression}
10675 Show the results of expanding all preprocessor macro invocations in
10676 @var{expression}. Since @value{GDBN} simply expands macros, but does
10677 not parse the result, @var{expression} need not be a valid expression;
10678 it can be any string of tokens.
10681 @item macro expand-once @var{expression}
10682 @itemx macro exp1 @var{expression}
10683 @cindex expand macro once
10684 @i{(This command is not yet implemented.)} Show the results of
10685 expanding those preprocessor macro invocations that appear explicitly in
10686 @var{expression}. Macro invocations appearing in that expansion are
10687 left unchanged. This command allows you to see the effect of a
10688 particular macro more clearly, without being confused by further
10689 expansions. Since @value{GDBN} simply expands macros, but does not
10690 parse the result, @var{expression} need not be a valid expression; it
10691 can be any string of tokens.
10694 @cindex macro definition, showing
10695 @cindex definition of a macro, showing
10696 @cindex macros, from debug info
10697 @item info macro [-a|-all] [--] @var{macro}
10698 Show the current definition or all definitions of the named @var{macro},
10699 and describe the source location or compiler command-line where that
10700 definition was established. The optional double dash is to signify the end of
10701 argument processing and the beginning of @var{macro} for non C-like macros where
10702 the macro may begin with a hyphen.
10704 @kindex info macros
10705 @item info macros @var{linespec}
10706 Show all macro definitions that are in effect at the location specified
10707 by @var{linespec}, and describe the source location or compiler
10708 command-line where those definitions were established.
10710 @kindex macro define
10711 @cindex user-defined macros
10712 @cindex defining macros interactively
10713 @cindex macros, user-defined
10714 @item macro define @var{macro} @var{replacement-list}
10715 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10716 Introduce a definition for a preprocessor macro named @var{macro},
10717 invocations of which are replaced by the tokens given in
10718 @var{replacement-list}. The first form of this command defines an
10719 ``object-like'' macro, which takes no arguments; the second form
10720 defines a ``function-like'' macro, which takes the arguments given in
10723 A definition introduced by this command is in scope in every
10724 expression evaluated in @value{GDBN}, until it is removed with the
10725 @code{macro undef} command, described below. The definition overrides
10726 all definitions for @var{macro} present in the program being debugged,
10727 as well as any previous user-supplied definition.
10729 @kindex macro undef
10730 @item macro undef @var{macro}
10731 Remove any user-supplied definition for the macro named @var{macro}.
10732 This command only affects definitions provided with the @code{macro
10733 define} command, described above; it cannot remove definitions present
10734 in the program being debugged.
10738 List all the macros defined using the @code{macro define} command.
10741 @cindex macros, example of debugging with
10742 Here is a transcript showing the above commands in action. First, we
10743 show our source files:
10748 #include "sample.h"
10751 #define ADD(x) (M + x)
10756 printf ("Hello, world!\n");
10758 printf ("We're so creative.\n");
10760 printf ("Goodbye, world!\n");
10767 Now, we compile the program using the @sc{gnu} C compiler,
10768 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10769 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10770 and @option{-gdwarf-4}; we recommend always choosing the most recent
10771 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10772 includes information about preprocessor macros in the debugging
10776 $ gcc -gdwarf-2 -g3 sample.c -o sample
10780 Now, we start @value{GDBN} on our sample program:
10784 GNU gdb 2002-05-06-cvs
10785 Copyright 2002 Free Software Foundation, Inc.
10786 GDB is free software, @dots{}
10790 We can expand macros and examine their definitions, even when the
10791 program is not running. @value{GDBN} uses the current listing position
10792 to decide which macro definitions are in scope:
10795 (@value{GDBP}) list main
10798 5 #define ADD(x) (M + x)
10803 10 printf ("Hello, world!\n");
10805 12 printf ("We're so creative.\n");
10806 (@value{GDBP}) info macro ADD
10807 Defined at /home/jimb/gdb/macros/play/sample.c:5
10808 #define ADD(x) (M + x)
10809 (@value{GDBP}) info macro Q
10810 Defined at /home/jimb/gdb/macros/play/sample.h:1
10811 included at /home/jimb/gdb/macros/play/sample.c:2
10813 (@value{GDBP}) macro expand ADD(1)
10814 expands to: (42 + 1)
10815 (@value{GDBP}) macro expand-once ADD(1)
10816 expands to: once (M + 1)
10820 In the example above, note that @code{macro expand-once} expands only
10821 the macro invocation explicit in the original text --- the invocation of
10822 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10823 which was introduced by @code{ADD}.
10825 Once the program is running, @value{GDBN} uses the macro definitions in
10826 force at the source line of the current stack frame:
10829 (@value{GDBP}) break main
10830 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10832 Starting program: /home/jimb/gdb/macros/play/sample
10834 Breakpoint 1, main () at sample.c:10
10835 10 printf ("Hello, world!\n");
10839 At line 10, the definition of the macro @code{N} at line 9 is in force:
10842 (@value{GDBP}) info macro N
10843 Defined at /home/jimb/gdb/macros/play/sample.c:9
10845 (@value{GDBP}) macro expand N Q M
10846 expands to: 28 < 42
10847 (@value{GDBP}) print N Q M
10852 As we step over directives that remove @code{N}'s definition, and then
10853 give it a new definition, @value{GDBN} finds the definition (or lack
10854 thereof) in force at each point:
10857 (@value{GDBP}) next
10859 12 printf ("We're so creative.\n");
10860 (@value{GDBP}) info macro N
10861 The symbol `N' has no definition as a C/C++ preprocessor macro
10862 at /home/jimb/gdb/macros/play/sample.c:12
10863 (@value{GDBP}) next
10865 14 printf ("Goodbye, world!\n");
10866 (@value{GDBP}) info macro N
10867 Defined at /home/jimb/gdb/macros/play/sample.c:13
10869 (@value{GDBP}) macro expand N Q M
10870 expands to: 1729 < 42
10871 (@value{GDBP}) print N Q M
10876 In addition to source files, macros can be defined on the compilation command
10877 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10878 such a way, @value{GDBN} displays the location of their definition as line zero
10879 of the source file submitted to the compiler.
10882 (@value{GDBP}) info macro __STDC__
10883 Defined at /home/jimb/gdb/macros/play/sample.c:0
10890 @chapter Tracepoints
10891 @c This chapter is based on the documentation written by Michael
10892 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10894 @cindex tracepoints
10895 In some applications, it is not feasible for the debugger to interrupt
10896 the program's execution long enough for the developer to learn
10897 anything helpful about its behavior. If the program's correctness
10898 depends on its real-time behavior, delays introduced by a debugger
10899 might cause the program to change its behavior drastically, or perhaps
10900 fail, even when the code itself is correct. It is useful to be able
10901 to observe the program's behavior without interrupting it.
10903 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10904 specify locations in the program, called @dfn{tracepoints}, and
10905 arbitrary expressions to evaluate when those tracepoints are reached.
10906 Later, using the @code{tfind} command, you can examine the values
10907 those expressions had when the program hit the tracepoints. The
10908 expressions may also denote objects in memory---structures or arrays,
10909 for example---whose values @value{GDBN} should record; while visiting
10910 a particular tracepoint, you may inspect those objects as if they were
10911 in memory at that moment. However, because @value{GDBN} records these
10912 values without interacting with you, it can do so quickly and
10913 unobtrusively, hopefully not disturbing the program's behavior.
10915 The tracepoint facility is currently available only for remote
10916 targets. @xref{Targets}. In addition, your remote target must know
10917 how to collect trace data. This functionality is implemented in the
10918 remote stub; however, none of the stubs distributed with @value{GDBN}
10919 support tracepoints as of this writing. The format of the remote
10920 packets used to implement tracepoints are described in @ref{Tracepoint
10923 It is also possible to get trace data from a file, in a manner reminiscent
10924 of corefiles; you specify the filename, and use @code{tfind} to search
10925 through the file. @xref{Trace Files}, for more details.
10927 This chapter describes the tracepoint commands and features.
10930 * Set Tracepoints::
10931 * Analyze Collected Data::
10932 * Tracepoint Variables::
10936 @node Set Tracepoints
10937 @section Commands to Set Tracepoints
10939 Before running such a @dfn{trace experiment}, an arbitrary number of
10940 tracepoints can be set. A tracepoint is actually a special type of
10941 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10942 standard breakpoint commands. For instance, as with breakpoints,
10943 tracepoint numbers are successive integers starting from one, and many
10944 of the commands associated with tracepoints take the tracepoint number
10945 as their argument, to identify which tracepoint to work on.
10947 For each tracepoint, you can specify, in advance, some arbitrary set
10948 of data that you want the target to collect in the trace buffer when
10949 it hits that tracepoint. The collected data can include registers,
10950 local variables, or global data. Later, you can use @value{GDBN}
10951 commands to examine the values these data had at the time the
10952 tracepoint was hit.
10954 Tracepoints do not support every breakpoint feature. Ignore counts on
10955 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10956 commands when they are hit. Tracepoints may not be thread-specific
10959 @cindex fast tracepoints
10960 Some targets may support @dfn{fast tracepoints}, which are inserted in
10961 a different way (such as with a jump instead of a trap), that is
10962 faster but possibly restricted in where they may be installed.
10964 @cindex static tracepoints
10965 @cindex markers, static tracepoints
10966 @cindex probing markers, static tracepoints
10967 Regular and fast tracepoints are dynamic tracing facilities, meaning
10968 that they can be used to insert tracepoints at (almost) any location
10969 in the target. Some targets may also support controlling @dfn{static
10970 tracepoints} from @value{GDBN}. With static tracing, a set of
10971 instrumentation points, also known as @dfn{markers}, are embedded in
10972 the target program, and can be activated or deactivated by name or
10973 address. These are usually placed at locations which facilitate
10974 investigating what the target is actually doing. @value{GDBN}'s
10975 support for static tracing includes being able to list instrumentation
10976 points, and attach them with @value{GDBN} defined high level
10977 tracepoints that expose the whole range of convenience of
10978 @value{GDBN}'s tracepoints support. Namely, support for collecting
10979 registers values and values of global or local (to the instrumentation
10980 point) variables; tracepoint conditions and trace state variables.
10981 The act of installing a @value{GDBN} static tracepoint on an
10982 instrumentation point, or marker, is referred to as @dfn{probing} a
10983 static tracepoint marker.
10985 @code{gdbserver} supports tracepoints on some target systems.
10986 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10988 This section describes commands to set tracepoints and associated
10989 conditions and actions.
10992 * Create and Delete Tracepoints::
10993 * Enable and Disable Tracepoints::
10994 * Tracepoint Passcounts::
10995 * Tracepoint Conditions::
10996 * Trace State Variables::
10997 * Tracepoint Actions::
10998 * Listing Tracepoints::
10999 * Listing Static Tracepoint Markers::
11000 * Starting and Stopping Trace Experiments::
11001 * Tracepoint Restrictions::
11004 @node Create and Delete Tracepoints
11005 @subsection Create and Delete Tracepoints
11008 @cindex set tracepoint
11010 @item trace @var{location}
11011 The @code{trace} command is very similar to the @code{break} command.
11012 Its argument @var{location} can be a source line, a function name, or
11013 an address in the target program. @xref{Specify Location}. The
11014 @code{trace} command defines a tracepoint, which is a point in the
11015 target program where the debugger will briefly stop, collect some
11016 data, and then allow the program to continue. Setting a tracepoint or
11017 changing its actions takes effect immediately if the remote stub
11018 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11020 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11021 these changes don't take effect until the next @code{tstart}
11022 command, and once a trace experiment is running, further changes will
11023 not have any effect until the next trace experiment starts. In addition,
11024 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11025 address is not yet resolved. (This is similar to pending breakpoints.)
11026 Pending tracepoints are not downloaded to the target and not installed
11027 until they are resolved. The resolution of pending tracepoints requires
11028 @value{GDBN} support---when debugging with the remote target, and
11029 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11030 tracing}), pending tracepoints can not be resolved (and downloaded to
11031 the remote stub) while @value{GDBN} is disconnected.
11033 Here are some examples of using the @code{trace} command:
11036 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11038 (@value{GDBP}) @b{trace +2} // 2 lines forward
11040 (@value{GDBP}) @b{trace my_function} // first source line of function
11042 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11044 (@value{GDBP}) @b{trace *0x2117c4} // an address
11048 You can abbreviate @code{trace} as @code{tr}.
11050 @item trace @var{location} if @var{cond}
11051 Set a tracepoint with condition @var{cond}; evaluate the expression
11052 @var{cond} each time the tracepoint is reached, and collect data only
11053 if the value is nonzero---that is, if @var{cond} evaluates as true.
11054 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11055 information on tracepoint conditions.
11057 @item ftrace @var{location} [ if @var{cond} ]
11058 @cindex set fast tracepoint
11059 @cindex fast tracepoints, setting
11061 The @code{ftrace} command sets a fast tracepoint. For targets that
11062 support them, fast tracepoints will use a more efficient but possibly
11063 less general technique to trigger data collection, such as a jump
11064 instruction instead of a trap, or some sort of hardware support. It
11065 may not be possible to create a fast tracepoint at the desired
11066 location, in which case the command will exit with an explanatory
11069 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11072 On 32-bit x86-architecture systems, fast tracepoints normally need to
11073 be placed at an instruction that is 5 bytes or longer, but can be
11074 placed at 4-byte instructions if the low 64K of memory of the target
11075 program is available to install trampolines. Some Unix-type systems,
11076 such as @sc{gnu}/Linux, exclude low addresses from the program's
11077 address space; but for instance with the Linux kernel it is possible
11078 to let @value{GDBN} use this area by doing a @command{sysctl} command
11079 to set the @code{mmap_min_addr} kernel parameter, as in
11082 sudo sysctl -w vm.mmap_min_addr=32768
11086 which sets the low address to 32K, which leaves plenty of room for
11087 trampolines. The minimum address should be set to a page boundary.
11089 @item strace @var{location} [ if @var{cond} ]
11090 @cindex set static tracepoint
11091 @cindex static tracepoints, setting
11092 @cindex probe static tracepoint marker
11094 The @code{strace} command sets a static tracepoint. For targets that
11095 support it, setting a static tracepoint probes a static
11096 instrumentation point, or marker, found at @var{location}. It may not
11097 be possible to set a static tracepoint at the desired location, in
11098 which case the command will exit with an explanatory message.
11100 @value{GDBN} handles arguments to @code{strace} exactly as for
11101 @code{trace}, with the addition that the user can also specify
11102 @code{-m @var{marker}} as @var{location}. This probes the marker
11103 identified by the @var{marker} string identifier. This identifier
11104 depends on the static tracepoint backend library your program is
11105 using. You can find all the marker identifiers in the @samp{ID} field
11106 of the @code{info static-tracepoint-markers} command output.
11107 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11108 Markers}. For example, in the following small program using the UST
11114 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11119 the marker id is composed of joining the first two arguments to the
11120 @code{trace_mark} call with a slash, which translates to:
11123 (@value{GDBP}) info static-tracepoint-markers
11124 Cnt Enb ID Address What
11125 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11131 so you may probe the marker above with:
11134 (@value{GDBP}) strace -m ust/bar33
11137 Static tracepoints accept an extra collect action --- @code{collect
11138 $_sdata}. This collects arbitrary user data passed in the probe point
11139 call to the tracing library. In the UST example above, you'll see
11140 that the third argument to @code{trace_mark} is a printf-like format
11141 string. The user data is then the result of running that formating
11142 string against the following arguments. Note that @code{info
11143 static-tracepoint-markers} command output lists that format string in
11144 the @samp{Data:} field.
11146 You can inspect this data when analyzing the trace buffer, by printing
11147 the $_sdata variable like any other variable available to
11148 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11151 @cindex last tracepoint number
11152 @cindex recent tracepoint number
11153 @cindex tracepoint number
11154 The convenience variable @code{$tpnum} records the tracepoint number
11155 of the most recently set tracepoint.
11157 @kindex delete tracepoint
11158 @cindex tracepoint deletion
11159 @item delete tracepoint @r{[}@var{num}@r{]}
11160 Permanently delete one or more tracepoints. With no argument, the
11161 default is to delete all tracepoints. Note that the regular
11162 @code{delete} command can remove tracepoints also.
11167 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11169 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11173 You can abbreviate this command as @code{del tr}.
11176 @node Enable and Disable Tracepoints
11177 @subsection Enable and Disable Tracepoints
11179 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11182 @kindex disable tracepoint
11183 @item disable tracepoint @r{[}@var{num}@r{]}
11184 Disable tracepoint @var{num}, or all tracepoints if no argument
11185 @var{num} is given. A disabled tracepoint will have no effect during
11186 a trace experiment, but it is not forgotten. You can re-enable
11187 a disabled tracepoint using the @code{enable tracepoint} command.
11188 If the command is issued during a trace experiment and the debug target
11189 has support for disabling tracepoints during a trace experiment, then the
11190 change will be effective immediately. Otherwise, it will be applied to the
11191 next trace experiment.
11193 @kindex enable tracepoint
11194 @item enable tracepoint @r{[}@var{num}@r{]}
11195 Enable tracepoint @var{num}, or all tracepoints. If this command is
11196 issued during a trace experiment and the debug target supports enabling
11197 tracepoints during a trace experiment, then the enabled tracepoints will
11198 become effective immediately. Otherwise, they will become effective the
11199 next time a trace experiment is run.
11202 @node Tracepoint Passcounts
11203 @subsection Tracepoint Passcounts
11207 @cindex tracepoint pass count
11208 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11209 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11210 automatically stop a trace experiment. If a tracepoint's passcount is
11211 @var{n}, then the trace experiment will be automatically stopped on
11212 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11213 @var{num} is not specified, the @code{passcount} command sets the
11214 passcount of the most recently defined tracepoint. If no passcount is
11215 given, the trace experiment will run until stopped explicitly by the
11221 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11222 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11224 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11225 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11226 (@value{GDBP}) @b{trace foo}
11227 (@value{GDBP}) @b{pass 3}
11228 (@value{GDBP}) @b{trace bar}
11229 (@value{GDBP}) @b{pass 2}
11230 (@value{GDBP}) @b{trace baz}
11231 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11232 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11233 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11234 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11238 @node Tracepoint Conditions
11239 @subsection Tracepoint Conditions
11240 @cindex conditional tracepoints
11241 @cindex tracepoint conditions
11243 The simplest sort of tracepoint collects data every time your program
11244 reaches a specified place. You can also specify a @dfn{condition} for
11245 a tracepoint. A condition is just a Boolean expression in your
11246 programming language (@pxref{Expressions, ,Expressions}). A
11247 tracepoint with a condition evaluates the expression each time your
11248 program reaches it, and data collection happens only if the condition
11251 Tracepoint conditions can be specified when a tracepoint is set, by
11252 using @samp{if} in the arguments to the @code{trace} command.
11253 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11254 also be set or changed at any time with the @code{condition} command,
11255 just as with breakpoints.
11257 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11258 the conditional expression itself. Instead, @value{GDBN} encodes the
11259 expression into an agent expression (@pxref{Agent Expressions})
11260 suitable for execution on the target, independently of @value{GDBN}.
11261 Global variables become raw memory locations, locals become stack
11262 accesses, and so forth.
11264 For instance, suppose you have a function that is usually called
11265 frequently, but should not be called after an error has occurred. You
11266 could use the following tracepoint command to collect data about calls
11267 of that function that happen while the error code is propagating
11268 through the program; an unconditional tracepoint could end up
11269 collecting thousands of useless trace frames that you would have to
11273 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11276 @node Trace State Variables
11277 @subsection Trace State Variables
11278 @cindex trace state variables
11280 A @dfn{trace state variable} is a special type of variable that is
11281 created and managed by target-side code. The syntax is the same as
11282 that for GDB's convenience variables (a string prefixed with ``$''),
11283 but they are stored on the target. They must be created explicitly,
11284 using a @code{tvariable} command. They are always 64-bit signed
11287 Trace state variables are remembered by @value{GDBN}, and downloaded
11288 to the target along with tracepoint information when the trace
11289 experiment starts. There are no intrinsic limits on the number of
11290 trace state variables, beyond memory limitations of the target.
11292 @cindex convenience variables, and trace state variables
11293 Although trace state variables are managed by the target, you can use
11294 them in print commands and expressions as if they were convenience
11295 variables; @value{GDBN} will get the current value from the target
11296 while the trace experiment is running. Trace state variables share
11297 the same namespace as other ``$'' variables, which means that you
11298 cannot have trace state variables with names like @code{$23} or
11299 @code{$pc}, nor can you have a trace state variable and a convenience
11300 variable with the same name.
11304 @item tvariable $@var{name} [ = @var{expression} ]
11306 The @code{tvariable} command creates a new trace state variable named
11307 @code{$@var{name}}, and optionally gives it an initial value of
11308 @var{expression}. @var{expression} is evaluated when this command is
11309 entered; the result will be converted to an integer if possible,
11310 otherwise @value{GDBN} will report an error. A subsequent
11311 @code{tvariable} command specifying the same name does not create a
11312 variable, but instead assigns the supplied initial value to the
11313 existing variable of that name, overwriting any previous initial
11314 value. The default initial value is 0.
11316 @item info tvariables
11317 @kindex info tvariables
11318 List all the trace state variables along with their initial values.
11319 Their current values may also be displayed, if the trace experiment is
11322 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11323 @kindex delete tvariable
11324 Delete the given trace state variables, or all of them if no arguments
11329 @node Tracepoint Actions
11330 @subsection Tracepoint Action Lists
11334 @cindex tracepoint actions
11335 @item actions @r{[}@var{num}@r{]}
11336 This command will prompt for a list of actions to be taken when the
11337 tracepoint is hit. If the tracepoint number @var{num} is not
11338 specified, this command sets the actions for the one that was most
11339 recently defined (so that you can define a tracepoint and then say
11340 @code{actions} without bothering about its number). You specify the
11341 actions themselves on the following lines, one action at a time, and
11342 terminate the actions list with a line containing just @code{end}. So
11343 far, the only defined actions are @code{collect}, @code{teval}, and
11344 @code{while-stepping}.
11346 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11347 Commands, ,Breakpoint Command Lists}), except that only the defined
11348 actions are allowed; any other @value{GDBN} command is rejected.
11350 @cindex remove actions from a tracepoint
11351 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11352 and follow it immediately with @samp{end}.
11355 (@value{GDBP}) @b{collect @var{data}} // collect some data
11357 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11359 (@value{GDBP}) @b{end} // signals the end of actions.
11362 In the following example, the action list begins with @code{collect}
11363 commands indicating the things to be collected when the tracepoint is
11364 hit. Then, in order to single-step and collect additional data
11365 following the tracepoint, a @code{while-stepping} command is used,
11366 followed by the list of things to be collected after each step in a
11367 sequence of single steps. The @code{while-stepping} command is
11368 terminated by its own separate @code{end} command. Lastly, the action
11369 list is terminated by an @code{end} command.
11372 (@value{GDBP}) @b{trace foo}
11373 (@value{GDBP}) @b{actions}
11374 Enter actions for tracepoint 1, one per line:
11377 > while-stepping 12
11378 > collect $pc, arr[i]
11383 @kindex collect @r{(tracepoints)}
11384 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11385 Collect values of the given expressions when the tracepoint is hit.
11386 This command accepts a comma-separated list of any valid expressions.
11387 In addition to global, static, or local variables, the following
11388 special arguments are supported:
11392 Collect all registers.
11395 Collect all function arguments.
11398 Collect all local variables.
11401 Collect the return address. This is helpful if you want to see more
11405 Collects the number of arguments from the static probe at which the
11406 tracepoint is located.
11407 @xref{Static Probe Points}.
11409 @item $_probe_arg@var{n}
11410 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11411 from the static probe at which the tracepoint is located.
11412 @xref{Static Probe Points}.
11415 @vindex $_sdata@r{, collect}
11416 Collect static tracepoint marker specific data. Only available for
11417 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11418 Lists}. On the UST static tracepoints library backend, an
11419 instrumentation point resembles a @code{printf} function call. The
11420 tracing library is able to collect user specified data formatted to a
11421 character string using the format provided by the programmer that
11422 instrumented the program. Other backends have similar mechanisms.
11423 Here's an example of a UST marker call:
11426 const char master_name[] = "$your_name";
11427 trace_mark(channel1, marker1, "hello %s", master_name)
11430 In this case, collecting @code{$_sdata} collects the string
11431 @samp{hello $yourname}. When analyzing the trace buffer, you can
11432 inspect @samp{$_sdata} like any other variable available to
11436 You can give several consecutive @code{collect} commands, each one
11437 with a single argument, or one @code{collect} command with several
11438 arguments separated by commas; the effect is the same.
11440 The optional @var{mods} changes the usual handling of the arguments.
11441 @code{s} requests that pointers to chars be handled as strings, in
11442 particular collecting the contents of the memory being pointed at, up
11443 to the first zero. The upper bound is by default the value of the
11444 @code{print elements} variable; if @code{s} is followed by a decimal
11445 number, that is the upper bound instead. So for instance
11446 @samp{collect/s25 mystr} collects as many as 25 characters at
11449 The command @code{info scope} (@pxref{Symbols, info scope}) is
11450 particularly useful for figuring out what data to collect.
11452 @kindex teval @r{(tracepoints)}
11453 @item teval @var{expr1}, @var{expr2}, @dots{}
11454 Evaluate the given expressions when the tracepoint is hit. This
11455 command accepts a comma-separated list of expressions. The results
11456 are discarded, so this is mainly useful for assigning values to trace
11457 state variables (@pxref{Trace State Variables}) without adding those
11458 values to the trace buffer, as would be the case if the @code{collect}
11461 @kindex while-stepping @r{(tracepoints)}
11462 @item while-stepping @var{n}
11463 Perform @var{n} single-step instruction traces after the tracepoint,
11464 collecting new data after each step. The @code{while-stepping}
11465 command is followed by the list of what to collect while stepping
11466 (followed by its own @code{end} command):
11469 > while-stepping 12
11470 > collect $regs, myglobal
11476 Note that @code{$pc} is not automatically collected by
11477 @code{while-stepping}; you need to explicitly collect that register if
11478 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11481 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11482 @kindex set default-collect
11483 @cindex default collection action
11484 This variable is a list of expressions to collect at each tracepoint
11485 hit. It is effectively an additional @code{collect} action prepended
11486 to every tracepoint action list. The expressions are parsed
11487 individually for each tracepoint, so for instance a variable named
11488 @code{xyz} may be interpreted as a global for one tracepoint, and a
11489 local for another, as appropriate to the tracepoint's location.
11491 @item show default-collect
11492 @kindex show default-collect
11493 Show the list of expressions that are collected by default at each
11498 @node Listing Tracepoints
11499 @subsection Listing Tracepoints
11502 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11503 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11504 @cindex information about tracepoints
11505 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11506 Display information about the tracepoint @var{num}. If you don't
11507 specify a tracepoint number, displays information about all the
11508 tracepoints defined so far. The format is similar to that used for
11509 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11510 command, simply restricting itself to tracepoints.
11512 A tracepoint's listing may include additional information specific to
11517 its passcount as given by the @code{passcount @var{n}} command
11520 the state about installed on target of each location
11524 (@value{GDBP}) @b{info trace}
11525 Num Type Disp Enb Address What
11526 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11528 collect globfoo, $regs
11533 2 tracepoint keep y <MULTIPLE>
11535 2.1 y 0x0804859c in func4 at change-loc.h:35
11536 installed on target
11537 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11538 installed on target
11539 2.3 y <PENDING> set_tracepoint
11540 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11541 not installed on target
11546 This command can be abbreviated @code{info tp}.
11549 @node Listing Static Tracepoint Markers
11550 @subsection Listing Static Tracepoint Markers
11553 @kindex info static-tracepoint-markers
11554 @cindex information about static tracepoint markers
11555 @item info static-tracepoint-markers
11556 Display information about all static tracepoint markers defined in the
11559 For each marker, the following columns are printed:
11563 An incrementing counter, output to help readability. This is not a
11566 The marker ID, as reported by the target.
11567 @item Enabled or Disabled
11568 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11569 that are not enabled.
11571 Where the marker is in your program, as a memory address.
11573 Where the marker is in the source for your program, as a file and line
11574 number. If the debug information included in the program does not
11575 allow @value{GDBN} to locate the source of the marker, this column
11576 will be left blank.
11580 In addition, the following information may be printed for each marker:
11584 User data passed to the tracing library by the marker call. In the
11585 UST backend, this is the format string passed as argument to the
11587 @item Static tracepoints probing the marker
11588 The list of static tracepoints attached to the marker.
11592 (@value{GDBP}) info static-tracepoint-markers
11593 Cnt ID Enb Address What
11594 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11595 Data: number1 %d number2 %d
11596 Probed by static tracepoints: #2
11597 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11603 @node Starting and Stopping Trace Experiments
11604 @subsection Starting and Stopping Trace Experiments
11607 @kindex tstart [ @var{notes} ]
11608 @cindex start a new trace experiment
11609 @cindex collected data discarded
11611 This command starts the trace experiment, and begins collecting data.
11612 It has the side effect of discarding all the data collected in the
11613 trace buffer during the previous trace experiment. If any arguments
11614 are supplied, they are taken as a note and stored with the trace
11615 experiment's state. The notes may be arbitrary text, and are
11616 especially useful with disconnected tracing in a multi-user context;
11617 the notes can explain what the trace is doing, supply user contact
11618 information, and so forth.
11620 @kindex tstop [ @var{notes} ]
11621 @cindex stop a running trace experiment
11623 This command stops the trace experiment. If any arguments are
11624 supplied, they are recorded with the experiment as a note. This is
11625 useful if you are stopping a trace started by someone else, for
11626 instance if the trace is interfering with the system's behavior and
11627 needs to be stopped quickly.
11629 @strong{Note}: a trace experiment and data collection may stop
11630 automatically if any tracepoint's passcount is reached
11631 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11634 @cindex status of trace data collection
11635 @cindex trace experiment, status of
11637 This command displays the status of the current trace data
11641 Here is an example of the commands we described so far:
11644 (@value{GDBP}) @b{trace gdb_c_test}
11645 (@value{GDBP}) @b{actions}
11646 Enter actions for tracepoint #1, one per line.
11647 > collect $regs,$locals,$args
11648 > while-stepping 11
11652 (@value{GDBP}) @b{tstart}
11653 [time passes @dots{}]
11654 (@value{GDBP}) @b{tstop}
11657 @anchor{disconnected tracing}
11658 @cindex disconnected tracing
11659 You can choose to continue running the trace experiment even if
11660 @value{GDBN} disconnects from the target, voluntarily or
11661 involuntarily. For commands such as @code{detach}, the debugger will
11662 ask what you want to do with the trace. But for unexpected
11663 terminations (@value{GDBN} crash, network outage), it would be
11664 unfortunate to lose hard-won trace data, so the variable
11665 @code{disconnected-tracing} lets you decide whether the trace should
11666 continue running without @value{GDBN}.
11669 @item set disconnected-tracing on
11670 @itemx set disconnected-tracing off
11671 @kindex set disconnected-tracing
11672 Choose whether a tracing run should continue to run if @value{GDBN}
11673 has disconnected from the target. Note that @code{detach} or
11674 @code{quit} will ask you directly what to do about a running trace no
11675 matter what this variable's setting, so the variable is mainly useful
11676 for handling unexpected situations, such as loss of the network.
11678 @item show disconnected-tracing
11679 @kindex show disconnected-tracing
11680 Show the current choice for disconnected tracing.
11684 When you reconnect to the target, the trace experiment may or may not
11685 still be running; it might have filled the trace buffer in the
11686 meantime, or stopped for one of the other reasons. If it is running,
11687 it will continue after reconnection.
11689 Upon reconnection, the target will upload information about the
11690 tracepoints in effect. @value{GDBN} will then compare that
11691 information to the set of tracepoints currently defined, and attempt
11692 to match them up, allowing for the possibility that the numbers may
11693 have changed due to creation and deletion in the meantime. If one of
11694 the target's tracepoints does not match any in @value{GDBN}, the
11695 debugger will create a new tracepoint, so that you have a number with
11696 which to specify that tracepoint. This matching-up process is
11697 necessarily heuristic, and it may result in useless tracepoints being
11698 created; you may simply delete them if they are of no use.
11700 @cindex circular trace buffer
11701 If your target agent supports a @dfn{circular trace buffer}, then you
11702 can run a trace experiment indefinitely without filling the trace
11703 buffer; when space runs out, the agent deletes already-collected trace
11704 frames, oldest first, until there is enough room to continue
11705 collecting. This is especially useful if your tracepoints are being
11706 hit too often, and your trace gets terminated prematurely because the
11707 buffer is full. To ask for a circular trace buffer, simply set
11708 @samp{circular-trace-buffer} to on. You can set this at any time,
11709 including during tracing; if the agent can do it, it will change
11710 buffer handling on the fly, otherwise it will not take effect until
11714 @item set circular-trace-buffer on
11715 @itemx set circular-trace-buffer off
11716 @kindex set circular-trace-buffer
11717 Choose whether a tracing run should use a linear or circular buffer
11718 for trace data. A linear buffer will not lose any trace data, but may
11719 fill up prematurely, while a circular buffer will discard old trace
11720 data, but it will have always room for the latest tracepoint hits.
11722 @item show circular-trace-buffer
11723 @kindex show circular-trace-buffer
11724 Show the current choice for the trace buffer. Note that this may not
11725 match the agent's current buffer handling, nor is it guaranteed to
11726 match the setting that might have been in effect during a past run,
11727 for instance if you are looking at frames from a trace file.
11732 @item set trace-user @var{text}
11733 @kindex set trace-user
11735 @item show trace-user
11736 @kindex show trace-user
11738 @item set trace-notes @var{text}
11739 @kindex set trace-notes
11740 Set the trace run's notes.
11742 @item show trace-notes
11743 @kindex show trace-notes
11744 Show the trace run's notes.
11746 @item set trace-stop-notes @var{text}
11747 @kindex set trace-stop-notes
11748 Set the trace run's stop notes. The handling of the note is as for
11749 @code{tstop} arguments; the set command is convenient way to fix a
11750 stop note that is mistaken or incomplete.
11752 @item show trace-stop-notes
11753 @kindex show trace-stop-notes
11754 Show the trace run's stop notes.
11758 @node Tracepoint Restrictions
11759 @subsection Tracepoint Restrictions
11761 @cindex tracepoint restrictions
11762 There are a number of restrictions on the use of tracepoints. As
11763 described above, tracepoint data gathering occurs on the target
11764 without interaction from @value{GDBN}. Thus the full capabilities of
11765 the debugger are not available during data gathering, and then at data
11766 examination time, you will be limited by only having what was
11767 collected. The following items describe some common problems, but it
11768 is not exhaustive, and you may run into additional difficulties not
11774 Tracepoint expressions are intended to gather objects (lvalues). Thus
11775 the full flexibility of GDB's expression evaluator is not available.
11776 You cannot call functions, cast objects to aggregate types, access
11777 convenience variables or modify values (except by assignment to trace
11778 state variables). Some language features may implicitly call
11779 functions (for instance Objective-C fields with accessors), and therefore
11780 cannot be collected either.
11783 Collection of local variables, either individually or in bulk with
11784 @code{$locals} or @code{$args}, during @code{while-stepping} may
11785 behave erratically. The stepping action may enter a new scope (for
11786 instance by stepping into a function), or the location of the variable
11787 may change (for instance it is loaded into a register). The
11788 tracepoint data recorded uses the location information for the
11789 variables that is correct for the tracepoint location. When the
11790 tracepoint is created, it is not possible, in general, to determine
11791 where the steps of a @code{while-stepping} sequence will advance the
11792 program---particularly if a conditional branch is stepped.
11795 Collection of an incompletely-initialized or partially-destroyed object
11796 may result in something that @value{GDBN} cannot display, or displays
11797 in a misleading way.
11800 When @value{GDBN} displays a pointer to character it automatically
11801 dereferences the pointer to also display characters of the string
11802 being pointed to. However, collecting the pointer during tracing does
11803 not automatically collect the string. You need to explicitly
11804 dereference the pointer and provide size information if you want to
11805 collect not only the pointer, but the memory pointed to. For example,
11806 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11810 It is not possible to collect a complete stack backtrace at a
11811 tracepoint. Instead, you may collect the registers and a few hundred
11812 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11813 (adjust to use the name of the actual stack pointer register on your
11814 target architecture, and the amount of stack you wish to capture).
11815 Then the @code{backtrace} command will show a partial backtrace when
11816 using a trace frame. The number of stack frames that can be examined
11817 depends on the sizes of the frames in the collected stack. Note that
11818 if you ask for a block so large that it goes past the bottom of the
11819 stack, the target agent may report an error trying to read from an
11823 If you do not collect registers at a tracepoint, @value{GDBN} can
11824 infer that the value of @code{$pc} must be the same as the address of
11825 the tracepoint and use that when you are looking at a trace frame
11826 for that tracepoint. However, this cannot work if the tracepoint has
11827 multiple locations (for instance if it was set in a function that was
11828 inlined), or if it has a @code{while-stepping} loop. In those cases
11829 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11834 @node Analyze Collected Data
11835 @section Using the Collected Data
11837 After the tracepoint experiment ends, you use @value{GDBN} commands
11838 for examining the trace data. The basic idea is that each tracepoint
11839 collects a trace @dfn{snapshot} every time it is hit and another
11840 snapshot every time it single-steps. All these snapshots are
11841 consecutively numbered from zero and go into a buffer, and you can
11842 examine them later. The way you examine them is to @dfn{focus} on a
11843 specific trace snapshot. When the remote stub is focused on a trace
11844 snapshot, it will respond to all @value{GDBN} requests for memory and
11845 registers by reading from the buffer which belongs to that snapshot,
11846 rather than from @emph{real} memory or registers of the program being
11847 debugged. This means that @strong{all} @value{GDBN} commands
11848 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11849 behave as if we were currently debugging the program state as it was
11850 when the tracepoint occurred. Any requests for data that are not in
11851 the buffer will fail.
11854 * tfind:: How to select a trace snapshot
11855 * tdump:: How to display all data for a snapshot
11856 * save tracepoints:: How to save tracepoints for a future run
11860 @subsection @code{tfind @var{n}}
11863 @cindex select trace snapshot
11864 @cindex find trace snapshot
11865 The basic command for selecting a trace snapshot from the buffer is
11866 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11867 counting from zero. If no argument @var{n} is given, the next
11868 snapshot is selected.
11870 Here are the various forms of using the @code{tfind} command.
11874 Find the first snapshot in the buffer. This is a synonym for
11875 @code{tfind 0} (since 0 is the number of the first snapshot).
11878 Stop debugging trace snapshots, resume @emph{live} debugging.
11881 Same as @samp{tfind none}.
11884 No argument means find the next trace snapshot.
11887 Find the previous trace snapshot before the current one. This permits
11888 retracing earlier steps.
11890 @item tfind tracepoint @var{num}
11891 Find the next snapshot associated with tracepoint @var{num}. Search
11892 proceeds forward from the last examined trace snapshot. If no
11893 argument @var{num} is given, it means find the next snapshot collected
11894 for the same tracepoint as the current snapshot.
11896 @item tfind pc @var{addr}
11897 Find the next snapshot associated with the value @var{addr} of the
11898 program counter. Search proceeds forward from the last examined trace
11899 snapshot. If no argument @var{addr} is given, it means find the next
11900 snapshot with the same value of PC as the current snapshot.
11902 @item tfind outside @var{addr1}, @var{addr2}
11903 Find the next snapshot whose PC is outside the given range of
11904 addresses (exclusive).
11906 @item tfind range @var{addr1}, @var{addr2}
11907 Find the next snapshot whose PC is between @var{addr1} and
11908 @var{addr2} (inclusive).
11910 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11911 Find the next snapshot associated with the source line @var{n}. If
11912 the optional argument @var{file} is given, refer to line @var{n} in
11913 that source file. Search proceeds forward from the last examined
11914 trace snapshot. If no argument @var{n} is given, it means find the
11915 next line other than the one currently being examined; thus saying
11916 @code{tfind line} repeatedly can appear to have the same effect as
11917 stepping from line to line in a @emph{live} debugging session.
11920 The default arguments for the @code{tfind} commands are specifically
11921 designed to make it easy to scan through the trace buffer. For
11922 instance, @code{tfind} with no argument selects the next trace
11923 snapshot, and @code{tfind -} with no argument selects the previous
11924 trace snapshot. So, by giving one @code{tfind} command, and then
11925 simply hitting @key{RET} repeatedly you can examine all the trace
11926 snapshots in order. Or, by saying @code{tfind -} and then hitting
11927 @key{RET} repeatedly you can examine the snapshots in reverse order.
11928 The @code{tfind line} command with no argument selects the snapshot
11929 for the next source line executed. The @code{tfind pc} command with
11930 no argument selects the next snapshot with the same program counter
11931 (PC) as the current frame. The @code{tfind tracepoint} command with
11932 no argument selects the next trace snapshot collected by the same
11933 tracepoint as the current one.
11935 In addition to letting you scan through the trace buffer manually,
11936 these commands make it easy to construct @value{GDBN} scripts that
11937 scan through the trace buffer and print out whatever collected data
11938 you are interested in. Thus, if we want to examine the PC, FP, and SP
11939 registers from each trace frame in the buffer, we can say this:
11942 (@value{GDBP}) @b{tfind start}
11943 (@value{GDBP}) @b{while ($trace_frame != -1)}
11944 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11945 $trace_frame, $pc, $sp, $fp
11949 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11950 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11951 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11952 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11953 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11954 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11955 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11956 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11957 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11958 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11959 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11962 Or, if we want to examine the variable @code{X} at each source line in
11966 (@value{GDBP}) @b{tfind start}
11967 (@value{GDBP}) @b{while ($trace_frame != -1)}
11968 > printf "Frame %d, X == %d\n", $trace_frame, X
11978 @subsection @code{tdump}
11980 @cindex dump all data collected at tracepoint
11981 @cindex tracepoint data, display
11983 This command takes no arguments. It prints all the data collected at
11984 the current trace snapshot.
11987 (@value{GDBP}) @b{trace 444}
11988 (@value{GDBP}) @b{actions}
11989 Enter actions for tracepoint #2, one per line:
11990 > collect $regs, $locals, $args, gdb_long_test
11993 (@value{GDBP}) @b{tstart}
11995 (@value{GDBP}) @b{tfind line 444}
11996 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11998 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12000 (@value{GDBP}) @b{tdump}
12001 Data collected at tracepoint 2, trace frame 1:
12002 d0 0xc4aa0085 -995491707
12006 d4 0x71aea3d 119204413
12009 d7 0x380035 3670069
12010 a0 0x19e24a 1696330
12011 a1 0x3000668 50333288
12013 a3 0x322000 3284992
12014 a4 0x3000698 50333336
12015 a5 0x1ad3cc 1758156
12016 fp 0x30bf3c 0x30bf3c
12017 sp 0x30bf34 0x30bf34
12019 pc 0x20b2c8 0x20b2c8
12023 p = 0x20e5b4 "gdb-test"
12030 gdb_long_test = 17 '\021'
12035 @code{tdump} works by scanning the tracepoint's current collection
12036 actions and printing the value of each expression listed. So
12037 @code{tdump} can fail, if after a run, you change the tracepoint's
12038 actions to mention variables that were not collected during the run.
12040 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12041 uses the collected value of @code{$pc} to distinguish between trace
12042 frames that were collected at the tracepoint hit, and frames that were
12043 collected while stepping. This allows it to correctly choose whether
12044 to display the basic list of collections, or the collections from the
12045 body of the while-stepping loop. However, if @code{$pc} was not collected,
12046 then @code{tdump} will always attempt to dump using the basic collection
12047 list, and may fail if a while-stepping frame does not include all the
12048 same data that is collected at the tracepoint hit.
12049 @c This is getting pretty arcane, example would be good.
12051 @node save tracepoints
12052 @subsection @code{save tracepoints @var{filename}}
12053 @kindex save tracepoints
12054 @kindex save-tracepoints
12055 @cindex save tracepoints for future sessions
12057 This command saves all current tracepoint definitions together with
12058 their actions and passcounts, into a file @file{@var{filename}}
12059 suitable for use in a later debugging session. To read the saved
12060 tracepoint definitions, use the @code{source} command (@pxref{Command
12061 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12062 alias for @w{@code{save tracepoints}}
12064 @node Tracepoint Variables
12065 @section Convenience Variables for Tracepoints
12066 @cindex tracepoint variables
12067 @cindex convenience variables for tracepoints
12070 @vindex $trace_frame
12071 @item (int) $trace_frame
12072 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12073 snapshot is selected.
12075 @vindex $tracepoint
12076 @item (int) $tracepoint
12077 The tracepoint for the current trace snapshot.
12079 @vindex $trace_line
12080 @item (int) $trace_line
12081 The line number for the current trace snapshot.
12083 @vindex $trace_file
12084 @item (char []) $trace_file
12085 The source file for the current trace snapshot.
12087 @vindex $trace_func
12088 @item (char []) $trace_func
12089 The name of the function containing @code{$tracepoint}.
12092 Note: @code{$trace_file} is not suitable for use in @code{printf},
12093 use @code{output} instead.
12095 Here's a simple example of using these convenience variables for
12096 stepping through all the trace snapshots and printing some of their
12097 data. Note that these are not the same as trace state variables,
12098 which are managed by the target.
12101 (@value{GDBP}) @b{tfind start}
12103 (@value{GDBP}) @b{while $trace_frame != -1}
12104 > output $trace_file
12105 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12111 @section Using Trace Files
12112 @cindex trace files
12114 In some situations, the target running a trace experiment may no
12115 longer be available; perhaps it crashed, or the hardware was needed
12116 for a different activity. To handle these cases, you can arrange to
12117 dump the trace data into a file, and later use that file as a source
12118 of trace data, via the @code{target tfile} command.
12123 @item tsave [ -r ] @var{filename}
12124 Save the trace data to @var{filename}. By default, this command
12125 assumes that @var{filename} refers to the host filesystem, so if
12126 necessary @value{GDBN} will copy raw trace data up from the target and
12127 then save it. If the target supports it, you can also supply the
12128 optional argument @code{-r} (``remote'') to direct the target to save
12129 the data directly into @var{filename} in its own filesystem, which may be
12130 more efficient if the trace buffer is very large. (Note, however, that
12131 @code{target tfile} can only read from files accessible to the host.)
12133 @kindex target tfile
12135 @item target tfile @var{filename}
12136 Use the file named @var{filename} as a source of trace data. Commands
12137 that examine data work as they do with a live target, but it is not
12138 possible to run any new trace experiments. @code{tstatus} will report
12139 the state of the trace run at the moment the data was saved, as well
12140 as the current trace frame you are examining. @var{filename} must be
12141 on a filesystem accessible to the host.
12146 @chapter Debugging Programs That Use Overlays
12149 If your program is too large to fit completely in your target system's
12150 memory, you can sometimes use @dfn{overlays} to work around this
12151 problem. @value{GDBN} provides some support for debugging programs that
12155 * How Overlays Work:: A general explanation of overlays.
12156 * Overlay Commands:: Managing overlays in @value{GDBN}.
12157 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12158 mapped by asking the inferior.
12159 * Overlay Sample Program:: A sample program using overlays.
12162 @node How Overlays Work
12163 @section How Overlays Work
12164 @cindex mapped overlays
12165 @cindex unmapped overlays
12166 @cindex load address, overlay's
12167 @cindex mapped address
12168 @cindex overlay area
12170 Suppose you have a computer whose instruction address space is only 64
12171 kilobytes long, but which has much more memory which can be accessed by
12172 other means: special instructions, segment registers, or memory
12173 management hardware, for example. Suppose further that you want to
12174 adapt a program which is larger than 64 kilobytes to run on this system.
12176 One solution is to identify modules of your program which are relatively
12177 independent, and need not call each other directly; call these modules
12178 @dfn{overlays}. Separate the overlays from the main program, and place
12179 their machine code in the larger memory. Place your main program in
12180 instruction memory, but leave at least enough space there to hold the
12181 largest overlay as well.
12183 Now, to call a function located in an overlay, you must first copy that
12184 overlay's machine code from the large memory into the space set aside
12185 for it in the instruction memory, and then jump to its entry point
12188 @c NB: In the below the mapped area's size is greater or equal to the
12189 @c size of all overlays. This is intentional to remind the developer
12190 @c that overlays don't necessarily need to be the same size.
12194 Data Instruction Larger
12195 Address Space Address Space Address Space
12196 +-----------+ +-----------+ +-----------+
12198 +-----------+ +-----------+ +-----------+<-- overlay 1
12199 | program | | main | .----| overlay 1 | load address
12200 | variables | | program | | +-----------+
12201 | and heap | | | | | |
12202 +-----------+ | | | +-----------+<-- overlay 2
12203 | | +-----------+ | | | load address
12204 +-----------+ | | | .-| overlay 2 |
12206 mapped --->+-----------+ | | +-----------+
12207 address | | | | | |
12208 | overlay | <-' | | |
12209 | area | <---' +-----------+<-- overlay 3
12210 | | <---. | | load address
12211 +-----------+ `--| overlay 3 |
12218 @anchor{A code overlay}A code overlay
12222 The diagram (@pxref{A code overlay}) shows a system with separate data
12223 and instruction address spaces. To map an overlay, the program copies
12224 its code from the larger address space to the instruction address space.
12225 Since the overlays shown here all use the same mapped address, only one
12226 may be mapped at a time. For a system with a single address space for
12227 data and instructions, the diagram would be similar, except that the
12228 program variables and heap would share an address space with the main
12229 program and the overlay area.
12231 An overlay loaded into instruction memory and ready for use is called a
12232 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12233 instruction memory. An overlay not present (or only partially present)
12234 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12235 is its address in the larger memory. The mapped address is also called
12236 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12237 called the @dfn{load memory address}, or @dfn{LMA}.
12239 Unfortunately, overlays are not a completely transparent way to adapt a
12240 program to limited instruction memory. They introduce a new set of
12241 global constraints you must keep in mind as you design your program:
12246 Before calling or returning to a function in an overlay, your program
12247 must make sure that overlay is actually mapped. Otherwise, the call or
12248 return will transfer control to the right address, but in the wrong
12249 overlay, and your program will probably crash.
12252 If the process of mapping an overlay is expensive on your system, you
12253 will need to choose your overlays carefully to minimize their effect on
12254 your program's performance.
12257 The executable file you load onto your system must contain each
12258 overlay's instructions, appearing at the overlay's load address, not its
12259 mapped address. However, each overlay's instructions must be relocated
12260 and its symbols defined as if the overlay were at its mapped address.
12261 You can use GNU linker scripts to specify different load and relocation
12262 addresses for pieces of your program; see @ref{Overlay Description,,,
12263 ld.info, Using ld: the GNU linker}.
12266 The procedure for loading executable files onto your system must be able
12267 to load their contents into the larger address space as well as the
12268 instruction and data spaces.
12272 The overlay system described above is rather simple, and could be
12273 improved in many ways:
12278 If your system has suitable bank switch registers or memory management
12279 hardware, you could use those facilities to make an overlay's load area
12280 contents simply appear at their mapped address in instruction space.
12281 This would probably be faster than copying the overlay to its mapped
12282 area in the usual way.
12285 If your overlays are small enough, you could set aside more than one
12286 overlay area, and have more than one overlay mapped at a time.
12289 You can use overlays to manage data, as well as instructions. In
12290 general, data overlays are even less transparent to your design than
12291 code overlays: whereas code overlays only require care when you call or
12292 return to functions, data overlays require care every time you access
12293 the data. Also, if you change the contents of a data overlay, you
12294 must copy its contents back out to its load address before you can copy a
12295 different data overlay into the same mapped area.
12300 @node Overlay Commands
12301 @section Overlay Commands
12303 To use @value{GDBN}'s overlay support, each overlay in your program must
12304 correspond to a separate section of the executable file. The section's
12305 virtual memory address and load memory address must be the overlay's
12306 mapped and load addresses. Identifying overlays with sections allows
12307 @value{GDBN} to determine the appropriate address of a function or
12308 variable, depending on whether the overlay is mapped or not.
12310 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12311 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12316 Disable @value{GDBN}'s overlay support. When overlay support is
12317 disabled, @value{GDBN} assumes that all functions and variables are
12318 always present at their mapped addresses. By default, @value{GDBN}'s
12319 overlay support is disabled.
12321 @item overlay manual
12322 @cindex manual overlay debugging
12323 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12324 relies on you to tell it which overlays are mapped, and which are not,
12325 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12326 commands described below.
12328 @item overlay map-overlay @var{overlay}
12329 @itemx overlay map @var{overlay}
12330 @cindex map an overlay
12331 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12332 be the name of the object file section containing the overlay. When an
12333 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12334 functions and variables at their mapped addresses. @value{GDBN} assumes
12335 that any other overlays whose mapped ranges overlap that of
12336 @var{overlay} are now unmapped.
12338 @item overlay unmap-overlay @var{overlay}
12339 @itemx overlay unmap @var{overlay}
12340 @cindex unmap an overlay
12341 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12342 must be the name of the object file section containing the overlay.
12343 When an overlay is unmapped, @value{GDBN} assumes it can find the
12344 overlay's functions and variables at their load addresses.
12347 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12348 consults a data structure the overlay manager maintains in the inferior
12349 to see which overlays are mapped. For details, see @ref{Automatic
12350 Overlay Debugging}.
12352 @item overlay load-target
12353 @itemx overlay load
12354 @cindex reloading the overlay table
12355 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12356 re-reads the table @value{GDBN} automatically each time the inferior
12357 stops, so this command should only be necessary if you have changed the
12358 overlay mapping yourself using @value{GDBN}. This command is only
12359 useful when using automatic overlay debugging.
12361 @item overlay list-overlays
12362 @itemx overlay list
12363 @cindex listing mapped overlays
12364 Display a list of the overlays currently mapped, along with their mapped
12365 addresses, load addresses, and sizes.
12369 Normally, when @value{GDBN} prints a code address, it includes the name
12370 of the function the address falls in:
12373 (@value{GDBP}) print main
12374 $3 = @{int ()@} 0x11a0 <main>
12377 When overlay debugging is enabled, @value{GDBN} recognizes code in
12378 unmapped overlays, and prints the names of unmapped functions with
12379 asterisks around them. For example, if @code{foo} is a function in an
12380 unmapped overlay, @value{GDBN} prints it this way:
12383 (@value{GDBP}) overlay list
12384 No sections are mapped.
12385 (@value{GDBP}) print foo
12386 $5 = @{int (int)@} 0x100000 <*foo*>
12389 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12393 (@value{GDBP}) overlay list
12394 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12395 mapped at 0x1016 - 0x104a
12396 (@value{GDBP}) print foo
12397 $6 = @{int (int)@} 0x1016 <foo>
12400 When overlay debugging is enabled, @value{GDBN} can find the correct
12401 address for functions and variables in an overlay, whether or not the
12402 overlay is mapped. This allows most @value{GDBN} commands, like
12403 @code{break} and @code{disassemble}, to work normally, even on unmapped
12404 code. However, @value{GDBN}'s breakpoint support has some limitations:
12408 @cindex breakpoints in overlays
12409 @cindex overlays, setting breakpoints in
12410 You can set breakpoints in functions in unmapped overlays, as long as
12411 @value{GDBN} can write to the overlay at its load address.
12413 @value{GDBN} can not set hardware or simulator-based breakpoints in
12414 unmapped overlays. However, if you set a breakpoint at the end of your
12415 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12416 you are using manual overlay management), @value{GDBN} will re-set its
12417 breakpoints properly.
12421 @node Automatic Overlay Debugging
12422 @section Automatic Overlay Debugging
12423 @cindex automatic overlay debugging
12425 @value{GDBN} can automatically track which overlays are mapped and which
12426 are not, given some simple co-operation from the overlay manager in the
12427 inferior. If you enable automatic overlay debugging with the
12428 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12429 looks in the inferior's memory for certain variables describing the
12430 current state of the overlays.
12432 Here are the variables your overlay manager must define to support
12433 @value{GDBN}'s automatic overlay debugging:
12437 @item @code{_ovly_table}:
12438 This variable must be an array of the following structures:
12443 /* The overlay's mapped address. */
12446 /* The size of the overlay, in bytes. */
12447 unsigned long size;
12449 /* The overlay's load address. */
12452 /* Non-zero if the overlay is currently mapped;
12454 unsigned long mapped;
12458 @item @code{_novlys}:
12459 This variable must be a four-byte signed integer, holding the total
12460 number of elements in @code{_ovly_table}.
12464 To decide whether a particular overlay is mapped or not, @value{GDBN}
12465 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12466 @code{lma} members equal the VMA and LMA of the overlay's section in the
12467 executable file. When @value{GDBN} finds a matching entry, it consults
12468 the entry's @code{mapped} member to determine whether the overlay is
12471 In addition, your overlay manager may define a function called
12472 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12473 will silently set a breakpoint there. If the overlay manager then
12474 calls this function whenever it has changed the overlay table, this
12475 will enable @value{GDBN} to accurately keep track of which overlays
12476 are in program memory, and update any breakpoints that may be set
12477 in overlays. This will allow breakpoints to work even if the
12478 overlays are kept in ROM or other non-writable memory while they
12479 are not being executed.
12481 @node Overlay Sample Program
12482 @section Overlay Sample Program
12483 @cindex overlay example program
12485 When linking a program which uses overlays, you must place the overlays
12486 at their load addresses, while relocating them to run at their mapped
12487 addresses. To do this, you must write a linker script (@pxref{Overlay
12488 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12489 since linker scripts are specific to a particular host system, target
12490 architecture, and target memory layout, this manual cannot provide
12491 portable sample code demonstrating @value{GDBN}'s overlay support.
12493 However, the @value{GDBN} source distribution does contain an overlaid
12494 program, with linker scripts for a few systems, as part of its test
12495 suite. The program consists of the following files from
12496 @file{gdb/testsuite/gdb.base}:
12500 The main program file.
12502 A simple overlay manager, used by @file{overlays.c}.
12507 Overlay modules, loaded and used by @file{overlays.c}.
12510 Linker scripts for linking the test program on the @code{d10v-elf}
12511 and @code{m32r-elf} targets.
12514 You can build the test program using the @code{d10v-elf} GCC
12515 cross-compiler like this:
12518 $ d10v-elf-gcc -g -c overlays.c
12519 $ d10v-elf-gcc -g -c ovlymgr.c
12520 $ d10v-elf-gcc -g -c foo.c
12521 $ d10v-elf-gcc -g -c bar.c
12522 $ d10v-elf-gcc -g -c baz.c
12523 $ d10v-elf-gcc -g -c grbx.c
12524 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12525 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12528 The build process is identical for any other architecture, except that
12529 you must substitute the appropriate compiler and linker script for the
12530 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12534 @chapter Using @value{GDBN} with Different Languages
12537 Although programming languages generally have common aspects, they are
12538 rarely expressed in the same manner. For instance, in ANSI C,
12539 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12540 Modula-2, it is accomplished by @code{p^}. Values can also be
12541 represented (and displayed) differently. Hex numbers in C appear as
12542 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12544 @cindex working language
12545 Language-specific information is built into @value{GDBN} for some languages,
12546 allowing you to express operations like the above in your program's
12547 native language, and allowing @value{GDBN} to output values in a manner
12548 consistent with the syntax of your program's native language. The
12549 language you use to build expressions is called the @dfn{working
12553 * Setting:: Switching between source languages
12554 * Show:: Displaying the language
12555 * Checks:: Type and range checks
12556 * Supported Languages:: Supported languages
12557 * Unsupported Languages:: Unsupported languages
12561 @section Switching Between Source Languages
12563 There are two ways to control the working language---either have @value{GDBN}
12564 set it automatically, or select it manually yourself. You can use the
12565 @code{set language} command for either purpose. On startup, @value{GDBN}
12566 defaults to setting the language automatically. The working language is
12567 used to determine how expressions you type are interpreted, how values
12570 In addition to the working language, every source file that
12571 @value{GDBN} knows about has its own working language. For some object
12572 file formats, the compiler might indicate which language a particular
12573 source file is in. However, most of the time @value{GDBN} infers the
12574 language from the name of the file. The language of a source file
12575 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12576 show each frame appropriately for its own language. There is no way to
12577 set the language of a source file from within @value{GDBN}, but you can
12578 set the language associated with a filename extension. @xref{Show, ,
12579 Displaying the Language}.
12581 This is most commonly a problem when you use a program, such
12582 as @code{cfront} or @code{f2c}, that generates C but is written in
12583 another language. In that case, make the
12584 program use @code{#line} directives in its C output; that way
12585 @value{GDBN} will know the correct language of the source code of the original
12586 program, and will display that source code, not the generated C code.
12589 * Filenames:: Filename extensions and languages.
12590 * Manually:: Setting the working language manually
12591 * Automatically:: Having @value{GDBN} infer the source language
12595 @subsection List of Filename Extensions and Languages
12597 If a source file name ends in one of the following extensions, then
12598 @value{GDBN} infers that its language is the one indicated.
12616 C@t{++} source file
12622 Objective-C source file
12626 Fortran source file
12629 Modula-2 source file
12633 Assembler source file. This actually behaves almost like C, but
12634 @value{GDBN} does not skip over function prologues when stepping.
12637 In addition, you may set the language associated with a filename
12638 extension. @xref{Show, , Displaying the Language}.
12641 @subsection Setting the Working Language
12643 If you allow @value{GDBN} to set the language automatically,
12644 expressions are interpreted the same way in your debugging session and
12647 @kindex set language
12648 If you wish, you may set the language manually. To do this, issue the
12649 command @samp{set language @var{lang}}, where @var{lang} is the name of
12650 a language, such as
12651 @code{c} or @code{modula-2}.
12652 For a list of the supported languages, type @samp{set language}.
12654 Setting the language manually prevents @value{GDBN} from updating the working
12655 language automatically. This can lead to confusion if you try
12656 to debug a program when the working language is not the same as the
12657 source language, when an expression is acceptable to both
12658 languages---but means different things. For instance, if the current
12659 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12667 might not have the effect you intended. In C, this means to add
12668 @code{b} and @code{c} and place the result in @code{a}. The result
12669 printed would be the value of @code{a}. In Modula-2, this means to compare
12670 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12672 @node Automatically
12673 @subsection Having @value{GDBN} Infer the Source Language
12675 To have @value{GDBN} set the working language automatically, use
12676 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12677 then infers the working language. That is, when your program stops in a
12678 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12679 working language to the language recorded for the function in that
12680 frame. If the language for a frame is unknown (that is, if the function
12681 or block corresponding to the frame was defined in a source file that
12682 does not have a recognized extension), the current working language is
12683 not changed, and @value{GDBN} issues a warning.
12685 This may not seem necessary for most programs, which are written
12686 entirely in one source language. However, program modules and libraries
12687 written in one source language can be used by a main program written in
12688 a different source language. Using @samp{set language auto} in this
12689 case frees you from having to set the working language manually.
12692 @section Displaying the Language
12694 The following commands help you find out which language is the
12695 working language, and also what language source files were written in.
12698 @item show language
12699 @kindex show language
12700 Display the current working language. This is the
12701 language you can use with commands such as @code{print} to
12702 build and compute expressions that may involve variables in your program.
12705 @kindex info frame@r{, show the source language}
12706 Display the source language for this frame. This language becomes the
12707 working language if you use an identifier from this frame.
12708 @xref{Frame Info, ,Information about a Frame}, to identify the other
12709 information listed here.
12712 @kindex info source@r{, show the source language}
12713 Display the source language of this source file.
12714 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12715 information listed here.
12718 In unusual circumstances, you may have source files with extensions
12719 not in the standard list. You can then set the extension associated
12720 with a language explicitly:
12723 @item set extension-language @var{ext} @var{language}
12724 @kindex set extension-language
12725 Tell @value{GDBN} that source files with extension @var{ext} are to be
12726 assumed as written in the source language @var{language}.
12728 @item info extensions
12729 @kindex info extensions
12730 List all the filename extensions and the associated languages.
12734 @section Type and Range Checking
12736 Some languages are designed to guard you against making seemingly common
12737 errors through a series of compile- and run-time checks. These include
12738 checking the type of arguments to functions and operators and making
12739 sure mathematical overflows are caught at run time. Checks such as
12740 these help to ensure a program's correctness once it has been compiled
12741 by eliminating type mismatches and providing active checks for range
12742 errors when your program is running.
12744 By default @value{GDBN} checks for these errors according to the
12745 rules of the current source language. Although @value{GDBN} does not check
12746 the statements in your program, it can check expressions entered directly
12747 into @value{GDBN} for evaluation via the @code{print} command, for example.
12750 * Type Checking:: An overview of type checking
12751 * Range Checking:: An overview of range checking
12754 @cindex type checking
12755 @cindex checks, type
12756 @node Type Checking
12757 @subsection An Overview of Type Checking
12759 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12760 arguments to operators and functions have to be of the correct type,
12761 otherwise an error occurs. These checks prevent type mismatch
12762 errors from ever causing any run-time problems. For example,
12765 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12767 (@value{GDBP}) print obj.my_method (0)
12770 (@value{GDBP}) print obj.my_method (0x1234)
12771 Cannot resolve method klass::my_method to any overloaded instance
12774 The second example fails because in C@t{++} the integer constant
12775 @samp{0x1234} is not type-compatible with the pointer parameter type.
12777 For the expressions you use in @value{GDBN} commands, you can tell
12778 @value{GDBN} to not enforce strict type checking or
12779 to treat any mismatches as errors and abandon the expression;
12780 When type checking is disabled, @value{GDBN} successfully evaluates
12781 expressions like the second example above.
12783 Even if type checking is off, there may be other reasons
12784 related to type that prevent @value{GDBN} from evaluating an expression.
12785 For instance, @value{GDBN} does not know how to add an @code{int} and
12786 a @code{struct foo}. These particular type errors have nothing to do
12787 with the language in use and usually arise from expressions which make
12788 little sense to evaluate anyway.
12790 @value{GDBN} provides some additional commands for controlling type checking:
12792 @kindex set check type
12793 @kindex show check type
12795 @item set check type on
12796 @itemx set check type off
12797 Set strict type checking on or off. If any type mismatches occur in
12798 evaluating an expression while type checking is on, @value{GDBN} prints a
12799 message and aborts evaluation of the expression.
12801 @item show check type
12802 Show the current setting of type checking and whether @value{GDBN}
12803 is enforcing strict type checking rules.
12806 @cindex range checking
12807 @cindex checks, range
12808 @node Range Checking
12809 @subsection An Overview of Range Checking
12811 In some languages (such as Modula-2), it is an error to exceed the
12812 bounds of a type; this is enforced with run-time checks. Such range
12813 checking is meant to ensure program correctness by making sure
12814 computations do not overflow, or indices on an array element access do
12815 not exceed the bounds of the array.
12817 For expressions you use in @value{GDBN} commands, you can tell
12818 @value{GDBN} to treat range errors in one of three ways: ignore them,
12819 always treat them as errors and abandon the expression, or issue
12820 warnings but evaluate the expression anyway.
12822 A range error can result from numerical overflow, from exceeding an
12823 array index bound, or when you type a constant that is not a member
12824 of any type. Some languages, however, do not treat overflows as an
12825 error. In many implementations of C, mathematical overflow causes the
12826 result to ``wrap around'' to lower values---for example, if @var{m} is
12827 the largest integer value, and @var{s} is the smallest, then
12830 @var{m} + 1 @result{} @var{s}
12833 This, too, is specific to individual languages, and in some cases
12834 specific to individual compilers or machines. @xref{Supported Languages, ,
12835 Supported Languages}, for further details on specific languages.
12837 @value{GDBN} provides some additional commands for controlling the range checker:
12839 @kindex set check range
12840 @kindex show check range
12842 @item set check range auto
12843 Set range checking on or off based on the current working language.
12844 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12847 @item set check range on
12848 @itemx set check range off
12849 Set range checking on or off, overriding the default setting for the
12850 current working language. A warning is issued if the setting does not
12851 match the language default. If a range error occurs and range checking is on,
12852 then a message is printed and evaluation of the expression is aborted.
12854 @item set check range warn
12855 Output messages when the @value{GDBN} range checker detects a range error,
12856 but attempt to evaluate the expression anyway. Evaluating the
12857 expression may still be impossible for other reasons, such as accessing
12858 memory that the process does not own (a typical example from many Unix
12862 Show the current setting of the range checker, and whether or not it is
12863 being set automatically by @value{GDBN}.
12866 @node Supported Languages
12867 @section Supported Languages
12869 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
12870 OpenCL C, Pascal, assembly, Modula-2, and Ada.
12871 @c This is false ...
12872 Some @value{GDBN} features may be used in expressions regardless of the
12873 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12874 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12875 ,Expressions}) can be used with the constructs of any supported
12878 The following sections detail to what degree each source language is
12879 supported by @value{GDBN}. These sections are not meant to be language
12880 tutorials or references, but serve only as a reference guide to what the
12881 @value{GDBN} expression parser accepts, and what input and output
12882 formats should look like for different languages. There are many good
12883 books written on each of these languages; please look to these for a
12884 language reference or tutorial.
12887 * C:: C and C@t{++}
12890 * Objective-C:: Objective-C
12891 * OpenCL C:: OpenCL C
12892 * Fortran:: Fortran
12894 * Modula-2:: Modula-2
12899 @subsection C and C@t{++}
12901 @cindex C and C@t{++}
12902 @cindex expressions in C or C@t{++}
12904 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12905 to both languages. Whenever this is the case, we discuss those languages
12909 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12910 @cindex @sc{gnu} C@t{++}
12911 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12912 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12913 effectively, you must compile your C@t{++} programs with a supported
12914 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12915 compiler (@code{aCC}).
12918 * C Operators:: C and C@t{++} operators
12919 * C Constants:: C and C@t{++} constants
12920 * C Plus Plus Expressions:: C@t{++} expressions
12921 * C Defaults:: Default settings for C and C@t{++}
12922 * C Checks:: C and C@t{++} type and range checks
12923 * Debugging C:: @value{GDBN} and C
12924 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12925 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12929 @subsubsection C and C@t{++} Operators
12931 @cindex C and C@t{++} operators
12933 Operators must be defined on values of specific types. For instance,
12934 @code{+} is defined on numbers, but not on structures. Operators are
12935 often defined on groups of types.
12937 For the purposes of C and C@t{++}, the following definitions hold:
12942 @emph{Integral types} include @code{int} with any of its storage-class
12943 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12946 @emph{Floating-point types} include @code{float}, @code{double}, and
12947 @code{long double} (if supported by the target platform).
12950 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12953 @emph{Scalar types} include all of the above.
12958 The following operators are supported. They are listed here
12959 in order of increasing precedence:
12963 The comma or sequencing operator. Expressions in a comma-separated list
12964 are evaluated from left to right, with the result of the entire
12965 expression being the last expression evaluated.
12968 Assignment. The value of an assignment expression is the value
12969 assigned. Defined on scalar types.
12972 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12973 and translated to @w{@code{@var{a} = @var{a op b}}}.
12974 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12975 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12976 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12979 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12980 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12984 Logical @sc{or}. Defined on integral types.
12987 Logical @sc{and}. Defined on integral types.
12990 Bitwise @sc{or}. Defined on integral types.
12993 Bitwise exclusive-@sc{or}. Defined on integral types.
12996 Bitwise @sc{and}. Defined on integral types.
12999 Equality and inequality. Defined on scalar types. The value of these
13000 expressions is 0 for false and non-zero for true.
13002 @item <@r{, }>@r{, }<=@r{, }>=
13003 Less than, greater than, less than or equal, greater than or equal.
13004 Defined on scalar types. The value of these expressions is 0 for false
13005 and non-zero for true.
13008 left shift, and right shift. Defined on integral types.
13011 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13014 Addition and subtraction. Defined on integral types, floating-point types and
13017 @item *@r{, }/@r{, }%
13018 Multiplication, division, and modulus. Multiplication and division are
13019 defined on integral and floating-point types. Modulus is defined on
13023 Increment and decrement. When appearing before a variable, the
13024 operation is performed before the variable is used in an expression;
13025 when appearing after it, the variable's value is used before the
13026 operation takes place.
13029 Pointer dereferencing. Defined on pointer types. Same precedence as
13033 Address operator. Defined on variables. Same precedence as @code{++}.
13035 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13036 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13037 to examine the address
13038 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13042 Negative. Defined on integral and floating-point types. Same
13043 precedence as @code{++}.
13046 Logical negation. Defined on integral types. Same precedence as
13050 Bitwise complement operator. Defined on integral types. Same precedence as
13055 Structure member, and pointer-to-structure member. For convenience,
13056 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13057 pointer based on the stored type information.
13058 Defined on @code{struct} and @code{union} data.
13061 Dereferences of pointers to members.
13064 Array indexing. @code{@var{a}[@var{i}]} is defined as
13065 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13068 Function parameter list. Same precedence as @code{->}.
13071 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13072 and @code{class} types.
13075 Doubled colons also represent the @value{GDBN} scope operator
13076 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13080 If an operator is redefined in the user code, @value{GDBN} usually
13081 attempts to invoke the redefined version instead of using the operator's
13082 predefined meaning.
13085 @subsubsection C and C@t{++} Constants
13087 @cindex C and C@t{++} constants
13089 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13094 Integer constants are a sequence of digits. Octal constants are
13095 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13096 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13097 @samp{l}, specifying that the constant should be treated as a
13101 Floating point constants are a sequence of digits, followed by a decimal
13102 point, followed by a sequence of digits, and optionally followed by an
13103 exponent. An exponent is of the form:
13104 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13105 sequence of digits. The @samp{+} is optional for positive exponents.
13106 A floating-point constant may also end with a letter @samp{f} or
13107 @samp{F}, specifying that the constant should be treated as being of
13108 the @code{float} (as opposed to the default @code{double}) type; or with
13109 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13113 Enumerated constants consist of enumerated identifiers, or their
13114 integral equivalents.
13117 Character constants are a single character surrounded by single quotes
13118 (@code{'}), or a number---the ordinal value of the corresponding character
13119 (usually its @sc{ascii} value). Within quotes, the single character may
13120 be represented by a letter or by @dfn{escape sequences}, which are of
13121 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13122 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13123 @samp{@var{x}} is a predefined special character---for example,
13124 @samp{\n} for newline.
13126 Wide character constants can be written by prefixing a character
13127 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13128 form of @samp{x}. The target wide character set is used when
13129 computing the value of this constant (@pxref{Character Sets}).
13132 String constants are a sequence of character constants surrounded by
13133 double quotes (@code{"}). Any valid character constant (as described
13134 above) may appear. Double quotes within the string must be preceded by
13135 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13138 Wide string constants can be written by prefixing a string constant
13139 with @samp{L}, as in C. The target wide character set is used when
13140 computing the value of this constant (@pxref{Character Sets}).
13143 Pointer constants are an integral value. You can also write pointers
13144 to constants using the C operator @samp{&}.
13147 Array constants are comma-separated lists surrounded by braces @samp{@{}
13148 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13149 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13150 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13153 @node C Plus Plus Expressions
13154 @subsubsection C@t{++} Expressions
13156 @cindex expressions in C@t{++}
13157 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13159 @cindex debugging C@t{++} programs
13160 @cindex C@t{++} compilers
13161 @cindex debug formats and C@t{++}
13162 @cindex @value{NGCC} and C@t{++}
13164 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13165 the proper compiler and the proper debug format. Currently,
13166 @value{GDBN} works best when debugging C@t{++} code that is compiled
13167 with the most recent version of @value{NGCC} possible. The DWARF
13168 debugging format is preferred; @value{NGCC} defaults to this on most
13169 popular platforms. Other compilers and/or debug formats are likely to
13170 work badly or not at all when using @value{GDBN} to debug C@t{++}
13171 code. @xref{Compilation}.
13176 @cindex member functions
13178 Member function calls are allowed; you can use expressions like
13181 count = aml->GetOriginal(x, y)
13184 @vindex this@r{, inside C@t{++} member functions}
13185 @cindex namespace in C@t{++}
13187 While a member function is active (in the selected stack frame), your
13188 expressions have the same namespace available as the member function;
13189 that is, @value{GDBN} allows implicit references to the class instance
13190 pointer @code{this} following the same rules as C@t{++}. @code{using}
13191 declarations in the current scope are also respected by @value{GDBN}.
13193 @cindex call overloaded functions
13194 @cindex overloaded functions, calling
13195 @cindex type conversions in C@t{++}
13197 You can call overloaded functions; @value{GDBN} resolves the function
13198 call to the right definition, with some restrictions. @value{GDBN} does not
13199 perform overload resolution involving user-defined type conversions,
13200 calls to constructors, or instantiations of templates that do not exist
13201 in the program. It also cannot handle ellipsis argument lists or
13204 It does perform integral conversions and promotions, floating-point
13205 promotions, arithmetic conversions, pointer conversions, conversions of
13206 class objects to base classes, and standard conversions such as those of
13207 functions or arrays to pointers; it requires an exact match on the
13208 number of function arguments.
13210 Overload resolution is always performed, unless you have specified
13211 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13212 ,@value{GDBN} Features for C@t{++}}.
13214 You must specify @code{set overload-resolution off} in order to use an
13215 explicit function signature to call an overloaded function, as in
13217 p 'foo(char,int)'('x', 13)
13220 The @value{GDBN} command-completion facility can simplify this;
13221 see @ref{Completion, ,Command Completion}.
13223 @cindex reference declarations
13225 @value{GDBN} understands variables declared as C@t{++} references; you can use
13226 them in expressions just as you do in C@t{++} source---they are automatically
13229 In the parameter list shown when @value{GDBN} displays a frame, the values of
13230 reference variables are not displayed (unlike other variables); this
13231 avoids clutter, since references are often used for large structures.
13232 The @emph{address} of a reference variable is always shown, unless
13233 you have specified @samp{set print address off}.
13236 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13237 expressions can use it just as expressions in your program do. Since
13238 one scope may be defined in another, you can use @code{::} repeatedly if
13239 necessary, for example in an expression like
13240 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13241 resolving name scope by reference to source files, in both C and C@t{++}
13242 debugging (@pxref{Variables, ,Program Variables}).
13245 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13250 @subsubsection C and C@t{++} Defaults
13252 @cindex C and C@t{++} defaults
13254 If you allow @value{GDBN} to set range checking automatically, it
13255 defaults to @code{off} whenever the working language changes to
13256 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13257 selects the working language.
13259 If you allow @value{GDBN} to set the language automatically, it
13260 recognizes source files whose names end with @file{.c}, @file{.C}, or
13261 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13262 these files, it sets the working language to C or C@t{++}.
13263 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13264 for further details.
13267 @subsubsection C and C@t{++} Type and Range Checks
13269 @cindex C and C@t{++} checks
13271 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13272 checking is used. However, if you turn type checking off, @value{GDBN}
13273 will allow certain non-standard conversions, such as promoting integer
13274 constants to pointers.
13276 Range checking, if turned on, is done on mathematical operations. Array
13277 indices are not checked, since they are often used to index a pointer
13278 that is not itself an array.
13281 @subsubsection @value{GDBN} and C
13283 The @code{set print union} and @code{show print union} commands apply to
13284 the @code{union} type. When set to @samp{on}, any @code{union} that is
13285 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13286 appears as @samp{@{...@}}.
13288 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13289 with pointers and a memory allocation function. @xref{Expressions,
13292 @node Debugging C Plus Plus
13293 @subsubsection @value{GDBN} Features for C@t{++}
13295 @cindex commands for C@t{++}
13297 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13298 designed specifically for use with C@t{++}. Here is a summary:
13301 @cindex break in overloaded functions
13302 @item @r{breakpoint menus}
13303 When you want a breakpoint in a function whose name is overloaded,
13304 @value{GDBN} has the capability to display a menu of possible breakpoint
13305 locations to help you specify which function definition you want.
13306 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13308 @cindex overloading in C@t{++}
13309 @item rbreak @var{regex}
13310 Setting breakpoints using regular expressions is helpful for setting
13311 breakpoints on overloaded functions that are not members of any special
13313 @xref{Set Breaks, ,Setting Breakpoints}.
13315 @cindex C@t{++} exception handling
13318 Debug C@t{++} exception handling using these commands. @xref{Set
13319 Catchpoints, , Setting Catchpoints}.
13321 @cindex inheritance
13322 @item ptype @var{typename}
13323 Print inheritance relationships as well as other information for type
13325 @xref{Symbols, ,Examining the Symbol Table}.
13327 @item info vtbl @var{expression}.
13328 The @code{info vtbl} command can be used to display the virtual
13329 method tables of the object computed by @var{expression}. This shows
13330 one entry per virtual table; there may be multiple virtual tables when
13331 multiple inheritance is in use.
13333 @cindex C@t{++} symbol display
13334 @item set print demangle
13335 @itemx show print demangle
13336 @itemx set print asm-demangle
13337 @itemx show print asm-demangle
13338 Control whether C@t{++} symbols display in their source form, both when
13339 displaying code as C@t{++} source and when displaying disassemblies.
13340 @xref{Print Settings, ,Print Settings}.
13342 @item set print object
13343 @itemx show print object
13344 Choose whether to print derived (actual) or declared types of objects.
13345 @xref{Print Settings, ,Print Settings}.
13347 @item set print vtbl
13348 @itemx show print vtbl
13349 Control the format for printing virtual function tables.
13350 @xref{Print Settings, ,Print Settings}.
13351 (The @code{vtbl} commands do not work on programs compiled with the HP
13352 ANSI C@t{++} compiler (@code{aCC}).)
13354 @kindex set overload-resolution
13355 @cindex overloaded functions, overload resolution
13356 @item set overload-resolution on
13357 Enable overload resolution for C@t{++} expression evaluation. The default
13358 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13359 and searches for a function whose signature matches the argument types,
13360 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13361 Expressions, ,C@t{++} Expressions}, for details).
13362 If it cannot find a match, it emits a message.
13364 @item set overload-resolution off
13365 Disable overload resolution for C@t{++} expression evaluation. For
13366 overloaded functions that are not class member functions, @value{GDBN}
13367 chooses the first function of the specified name that it finds in the
13368 symbol table, whether or not its arguments are of the correct type. For
13369 overloaded functions that are class member functions, @value{GDBN}
13370 searches for a function whose signature @emph{exactly} matches the
13373 @kindex show overload-resolution
13374 @item show overload-resolution
13375 Show the current setting of overload resolution.
13377 @item @r{Overloaded symbol names}
13378 You can specify a particular definition of an overloaded symbol, using
13379 the same notation that is used to declare such symbols in C@t{++}: type
13380 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13381 also use the @value{GDBN} command-line word completion facilities to list the
13382 available choices, or to finish the type list for you.
13383 @xref{Completion,, Command Completion}, for details on how to do this.
13386 @node Decimal Floating Point
13387 @subsubsection Decimal Floating Point format
13388 @cindex decimal floating point format
13390 @value{GDBN} can examine, set and perform computations with numbers in
13391 decimal floating point format, which in the C language correspond to the
13392 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13393 specified by the extension to support decimal floating-point arithmetic.
13395 There are two encodings in use, depending on the architecture: BID (Binary
13396 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13397 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13400 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13401 to manipulate decimal floating point numbers, it is not possible to convert
13402 (using a cast, for example) integers wider than 32-bit to decimal float.
13404 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13405 point computations, error checking in decimal float operations ignores
13406 underflow, overflow and divide by zero exceptions.
13408 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13409 to inspect @code{_Decimal128} values stored in floating point registers.
13410 See @ref{PowerPC,,PowerPC} for more details.
13416 @value{GDBN} can be used to debug programs written in D and compiled with
13417 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13418 specific feature --- dynamic arrays.
13423 @cindex Go (programming language)
13424 @value{GDBN} can be used to debug programs written in Go and compiled with
13425 @file{gccgo} or @file{6g} compilers.
13427 Here is a summary of the Go-specific features and restrictions:
13430 @cindex current Go package
13431 @item The current Go package
13432 The name of the current package does not need to be specified when
13433 specifying global variables and functions.
13435 For example, given the program:
13439 var myglob = "Shall we?"
13445 When stopped inside @code{main} either of these work:
13449 (gdb) p main.myglob
13452 @cindex builtin Go types
13453 @item Builtin Go types
13454 The @code{string} type is recognized by @value{GDBN} and is printed
13457 @cindex builtin Go functions
13458 @item Builtin Go functions
13459 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13460 function and handles it internally.
13462 @cindex restrictions on Go expressions
13463 @item Restrictions on Go expressions
13464 All Go operators are supported except @code{&^}.
13465 The Go @code{_} ``blank identifier'' is not supported.
13466 Automatic dereferencing of pointers is not supported.
13470 @subsection Objective-C
13472 @cindex Objective-C
13473 This section provides information about some commands and command
13474 options that are useful for debugging Objective-C code. See also
13475 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13476 few more commands specific to Objective-C support.
13479 * Method Names in Commands::
13480 * The Print Command with Objective-C::
13483 @node Method Names in Commands
13484 @subsubsection Method Names in Commands
13486 The following commands have been extended to accept Objective-C method
13487 names as line specifications:
13489 @kindex clear@r{, and Objective-C}
13490 @kindex break@r{, and Objective-C}
13491 @kindex info line@r{, and Objective-C}
13492 @kindex jump@r{, and Objective-C}
13493 @kindex list@r{, and Objective-C}
13497 @item @code{info line}
13502 A fully qualified Objective-C method name is specified as
13505 -[@var{Class} @var{methodName}]
13508 where the minus sign is used to indicate an instance method and a
13509 plus sign (not shown) is used to indicate a class method. The class
13510 name @var{Class} and method name @var{methodName} are enclosed in
13511 brackets, similar to the way messages are specified in Objective-C
13512 source code. For example, to set a breakpoint at the @code{create}
13513 instance method of class @code{Fruit} in the program currently being
13517 break -[Fruit create]
13520 To list ten program lines around the @code{initialize} class method,
13524 list +[NSText initialize]
13527 In the current version of @value{GDBN}, the plus or minus sign is
13528 required. In future versions of @value{GDBN}, the plus or minus
13529 sign will be optional, but you can use it to narrow the search. It
13530 is also possible to specify just a method name:
13536 You must specify the complete method name, including any colons. If
13537 your program's source files contain more than one @code{create} method,
13538 you'll be presented with a numbered list of classes that implement that
13539 method. Indicate your choice by number, or type @samp{0} to exit if
13542 As another example, to clear a breakpoint established at the
13543 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13546 clear -[NSWindow makeKeyAndOrderFront:]
13549 @node The Print Command with Objective-C
13550 @subsubsection The Print Command With Objective-C
13551 @cindex Objective-C, print objects
13552 @kindex print-object
13553 @kindex po @r{(@code{print-object})}
13555 The print command has also been extended to accept methods. For example:
13558 print -[@var{object} hash]
13561 @cindex print an Objective-C object description
13562 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13564 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13565 and print the result. Also, an additional command has been added,
13566 @code{print-object} or @code{po} for short, which is meant to print
13567 the description of an object. However, this command may only work
13568 with certain Objective-C libraries that have a particular hook
13569 function, @code{_NSPrintForDebugger}, defined.
13572 @subsection OpenCL C
13575 This section provides information about @value{GDBN}s OpenCL C support.
13578 * OpenCL C Datatypes::
13579 * OpenCL C Expressions::
13580 * OpenCL C Operators::
13583 @node OpenCL C Datatypes
13584 @subsubsection OpenCL C Datatypes
13586 @cindex OpenCL C Datatypes
13587 @value{GDBN} supports the builtin scalar and vector datatypes specified
13588 by OpenCL 1.1. In addition the half- and double-precision floating point
13589 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13590 extensions are also known to @value{GDBN}.
13592 @node OpenCL C Expressions
13593 @subsubsection OpenCL C Expressions
13595 @cindex OpenCL C Expressions
13596 @value{GDBN} supports accesses to vector components including the access as
13597 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13598 supported by @value{GDBN} can be used as well.
13600 @node OpenCL C Operators
13601 @subsubsection OpenCL C Operators
13603 @cindex OpenCL C Operators
13604 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13608 @subsection Fortran
13609 @cindex Fortran-specific support in @value{GDBN}
13611 @value{GDBN} can be used to debug programs written in Fortran, but it
13612 currently supports only the features of Fortran 77 language.
13614 @cindex trailing underscore, in Fortran symbols
13615 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13616 among them) append an underscore to the names of variables and
13617 functions. When you debug programs compiled by those compilers, you
13618 will need to refer to variables and functions with a trailing
13622 * Fortran Operators:: Fortran operators and expressions
13623 * Fortran Defaults:: Default settings for Fortran
13624 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13627 @node Fortran Operators
13628 @subsubsection Fortran Operators and Expressions
13630 @cindex Fortran operators and expressions
13632 Operators must be defined on values of specific types. For instance,
13633 @code{+} is defined on numbers, but not on characters or other non-
13634 arithmetic types. Operators are often defined on groups of types.
13638 The exponentiation operator. It raises the first operand to the power
13642 The range operator. Normally used in the form of array(low:high) to
13643 represent a section of array.
13646 The access component operator. Normally used to access elements in derived
13647 types. Also suitable for unions. As unions aren't part of regular Fortran,
13648 this can only happen when accessing a register that uses a gdbarch-defined
13652 @node Fortran Defaults
13653 @subsubsection Fortran Defaults
13655 @cindex Fortran Defaults
13657 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13658 default uses case-insensitive matches for Fortran symbols. You can
13659 change that with the @samp{set case-insensitive} command, see
13660 @ref{Symbols}, for the details.
13662 @node Special Fortran Commands
13663 @subsubsection Special Fortran Commands
13665 @cindex Special Fortran commands
13667 @value{GDBN} has some commands to support Fortran-specific features,
13668 such as displaying common blocks.
13671 @cindex @code{COMMON} blocks, Fortran
13672 @kindex info common
13673 @item info common @r{[}@var{common-name}@r{]}
13674 This command prints the values contained in the Fortran @code{COMMON}
13675 block whose name is @var{common-name}. With no argument, the names of
13676 all @code{COMMON} blocks visible at the current program location are
13683 @cindex Pascal support in @value{GDBN}, limitations
13684 Debugging Pascal programs which use sets, subranges, file variables, or
13685 nested functions does not currently work. @value{GDBN} does not support
13686 entering expressions, printing values, or similar features using Pascal
13689 The Pascal-specific command @code{set print pascal_static-members}
13690 controls whether static members of Pascal objects are displayed.
13691 @xref{Print Settings, pascal_static-members}.
13694 @subsection Modula-2
13696 @cindex Modula-2, @value{GDBN} support
13698 The extensions made to @value{GDBN} to support Modula-2 only support
13699 output from the @sc{gnu} Modula-2 compiler (which is currently being
13700 developed). Other Modula-2 compilers are not currently supported, and
13701 attempting to debug executables produced by them is most likely
13702 to give an error as @value{GDBN} reads in the executable's symbol
13705 @cindex expressions in Modula-2
13707 * M2 Operators:: Built-in operators
13708 * Built-In Func/Proc:: Built-in functions and procedures
13709 * M2 Constants:: Modula-2 constants
13710 * M2 Types:: Modula-2 types
13711 * M2 Defaults:: Default settings for Modula-2
13712 * Deviations:: Deviations from standard Modula-2
13713 * M2 Checks:: Modula-2 type and range checks
13714 * M2 Scope:: The scope operators @code{::} and @code{.}
13715 * GDB/M2:: @value{GDBN} and Modula-2
13719 @subsubsection Operators
13720 @cindex Modula-2 operators
13722 Operators must be defined on values of specific types. For instance,
13723 @code{+} is defined on numbers, but not on structures. Operators are
13724 often defined on groups of types. For the purposes of Modula-2, the
13725 following definitions hold:
13730 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13734 @emph{Character types} consist of @code{CHAR} and its subranges.
13737 @emph{Floating-point types} consist of @code{REAL}.
13740 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13744 @emph{Scalar types} consist of all of the above.
13747 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13750 @emph{Boolean types} consist of @code{BOOLEAN}.
13754 The following operators are supported, and appear in order of
13755 increasing precedence:
13759 Function argument or array index separator.
13762 Assignment. The value of @var{var} @code{:=} @var{value} is
13766 Less than, greater than on integral, floating-point, or enumerated
13770 Less than or equal to, greater than or equal to
13771 on integral, floating-point and enumerated types, or set inclusion on
13772 set types. Same precedence as @code{<}.
13774 @item =@r{, }<>@r{, }#
13775 Equality and two ways of expressing inequality, valid on scalar types.
13776 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13777 available for inequality, since @code{#} conflicts with the script
13781 Set membership. Defined on set types and the types of their members.
13782 Same precedence as @code{<}.
13785 Boolean disjunction. Defined on boolean types.
13788 Boolean conjunction. Defined on boolean types.
13791 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13794 Addition and subtraction on integral and floating-point types, or union
13795 and difference on set types.
13798 Multiplication on integral and floating-point types, or set intersection
13802 Division on floating-point types, or symmetric set difference on set
13803 types. Same precedence as @code{*}.
13806 Integer division and remainder. Defined on integral types. Same
13807 precedence as @code{*}.
13810 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13813 Pointer dereferencing. Defined on pointer types.
13816 Boolean negation. Defined on boolean types. Same precedence as
13820 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13821 precedence as @code{^}.
13824 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13827 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13831 @value{GDBN} and Modula-2 scope operators.
13835 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13836 treats the use of the operator @code{IN}, or the use of operators
13837 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13838 @code{<=}, and @code{>=} on sets as an error.
13842 @node Built-In Func/Proc
13843 @subsubsection Built-in Functions and Procedures
13844 @cindex Modula-2 built-ins
13846 Modula-2 also makes available several built-in procedures and functions.
13847 In describing these, the following metavariables are used:
13852 represents an @code{ARRAY} variable.
13855 represents a @code{CHAR} constant or variable.
13858 represents a variable or constant of integral type.
13861 represents an identifier that belongs to a set. Generally used in the
13862 same function with the metavariable @var{s}. The type of @var{s} should
13863 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13866 represents a variable or constant of integral or floating-point type.
13869 represents a variable or constant of floating-point type.
13875 represents a variable.
13878 represents a variable or constant of one of many types. See the
13879 explanation of the function for details.
13882 All Modula-2 built-in procedures also return a result, described below.
13886 Returns the absolute value of @var{n}.
13889 If @var{c} is a lower case letter, it returns its upper case
13890 equivalent, otherwise it returns its argument.
13893 Returns the character whose ordinal value is @var{i}.
13896 Decrements the value in the variable @var{v} by one. Returns the new value.
13898 @item DEC(@var{v},@var{i})
13899 Decrements the value in the variable @var{v} by @var{i}. Returns the
13902 @item EXCL(@var{m},@var{s})
13903 Removes the element @var{m} from the set @var{s}. Returns the new
13906 @item FLOAT(@var{i})
13907 Returns the floating point equivalent of the integer @var{i}.
13909 @item HIGH(@var{a})
13910 Returns the index of the last member of @var{a}.
13913 Increments the value in the variable @var{v} by one. Returns the new value.
13915 @item INC(@var{v},@var{i})
13916 Increments the value in the variable @var{v} by @var{i}. Returns the
13919 @item INCL(@var{m},@var{s})
13920 Adds the element @var{m} to the set @var{s} if it is not already
13921 there. Returns the new set.
13924 Returns the maximum value of the type @var{t}.
13927 Returns the minimum value of the type @var{t}.
13930 Returns boolean TRUE if @var{i} is an odd number.
13933 Returns the ordinal value of its argument. For example, the ordinal
13934 value of a character is its @sc{ascii} value (on machines supporting the
13935 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13936 integral, character and enumerated types.
13938 @item SIZE(@var{x})
13939 Returns the size of its argument. @var{x} can be a variable or a type.
13941 @item TRUNC(@var{r})
13942 Returns the integral part of @var{r}.
13944 @item TSIZE(@var{x})
13945 Returns the size of its argument. @var{x} can be a variable or a type.
13947 @item VAL(@var{t},@var{i})
13948 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13952 @emph{Warning:} Sets and their operations are not yet supported, so
13953 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13957 @cindex Modula-2 constants
13959 @subsubsection Constants
13961 @value{GDBN} allows you to express the constants of Modula-2 in the following
13967 Integer constants are simply a sequence of digits. When used in an
13968 expression, a constant is interpreted to be type-compatible with the
13969 rest of the expression. Hexadecimal integers are specified by a
13970 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13973 Floating point constants appear as a sequence of digits, followed by a
13974 decimal point and another sequence of digits. An optional exponent can
13975 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13976 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13977 digits of the floating point constant must be valid decimal (base 10)
13981 Character constants consist of a single character enclosed by a pair of
13982 like quotes, either single (@code{'}) or double (@code{"}). They may
13983 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13984 followed by a @samp{C}.
13987 String constants consist of a sequence of characters enclosed by a
13988 pair of like quotes, either single (@code{'}) or double (@code{"}).
13989 Escape sequences in the style of C are also allowed. @xref{C
13990 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13994 Enumerated constants consist of an enumerated identifier.
13997 Boolean constants consist of the identifiers @code{TRUE} and
14001 Pointer constants consist of integral values only.
14004 Set constants are not yet supported.
14008 @subsubsection Modula-2 Types
14009 @cindex Modula-2 types
14011 Currently @value{GDBN} can print the following data types in Modula-2
14012 syntax: array types, record types, set types, pointer types, procedure
14013 types, enumerated types, subrange types and base types. You can also
14014 print the contents of variables declared using these type.
14015 This section gives a number of simple source code examples together with
14016 sample @value{GDBN} sessions.
14018 The first example contains the following section of code:
14027 and you can request @value{GDBN} to interrogate the type and value of
14028 @code{r} and @code{s}.
14031 (@value{GDBP}) print s
14033 (@value{GDBP}) ptype s
14035 (@value{GDBP}) print r
14037 (@value{GDBP}) ptype r
14042 Likewise if your source code declares @code{s} as:
14046 s: SET ['A'..'Z'] ;
14050 then you may query the type of @code{s} by:
14053 (@value{GDBP}) ptype s
14054 type = SET ['A'..'Z']
14058 Note that at present you cannot interactively manipulate set
14059 expressions using the debugger.
14061 The following example shows how you might declare an array in Modula-2
14062 and how you can interact with @value{GDBN} to print its type and contents:
14066 s: ARRAY [-10..10] OF CHAR ;
14070 (@value{GDBP}) ptype s
14071 ARRAY [-10..10] OF CHAR
14074 Note that the array handling is not yet complete and although the type
14075 is printed correctly, expression handling still assumes that all
14076 arrays have a lower bound of zero and not @code{-10} as in the example
14079 Here are some more type related Modula-2 examples:
14083 colour = (blue, red, yellow, green) ;
14084 t = [blue..yellow] ;
14092 The @value{GDBN} interaction shows how you can query the data type
14093 and value of a variable.
14096 (@value{GDBP}) print s
14098 (@value{GDBP}) ptype t
14099 type = [blue..yellow]
14103 In this example a Modula-2 array is declared and its contents
14104 displayed. Observe that the contents are written in the same way as
14105 their @code{C} counterparts.
14109 s: ARRAY [1..5] OF CARDINAL ;
14115 (@value{GDBP}) print s
14116 $1 = @{1, 0, 0, 0, 0@}
14117 (@value{GDBP}) ptype s
14118 type = ARRAY [1..5] OF CARDINAL
14121 The Modula-2 language interface to @value{GDBN} also understands
14122 pointer types as shown in this example:
14126 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14133 and you can request that @value{GDBN} describes the type of @code{s}.
14136 (@value{GDBP}) ptype s
14137 type = POINTER TO ARRAY [1..5] OF CARDINAL
14140 @value{GDBN} handles compound types as we can see in this example.
14141 Here we combine array types, record types, pointer types and subrange
14152 myarray = ARRAY myrange OF CARDINAL ;
14153 myrange = [-2..2] ;
14155 s: POINTER TO ARRAY myrange OF foo ;
14159 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14163 (@value{GDBP}) ptype s
14164 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14167 f3 : ARRAY [-2..2] OF CARDINAL;
14172 @subsubsection Modula-2 Defaults
14173 @cindex Modula-2 defaults
14175 If type and range checking are set automatically by @value{GDBN}, they
14176 both default to @code{on} whenever the working language changes to
14177 Modula-2. This happens regardless of whether you or @value{GDBN}
14178 selected the working language.
14180 If you allow @value{GDBN} to set the language automatically, then entering
14181 code compiled from a file whose name ends with @file{.mod} sets the
14182 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14183 Infer the Source Language}, for further details.
14186 @subsubsection Deviations from Standard Modula-2
14187 @cindex Modula-2, deviations from
14189 A few changes have been made to make Modula-2 programs easier to debug.
14190 This is done primarily via loosening its type strictness:
14194 Unlike in standard Modula-2, pointer constants can be formed by
14195 integers. This allows you to modify pointer variables during
14196 debugging. (In standard Modula-2, the actual address contained in a
14197 pointer variable is hidden from you; it can only be modified
14198 through direct assignment to another pointer variable or expression that
14199 returned a pointer.)
14202 C escape sequences can be used in strings and characters to represent
14203 non-printable characters. @value{GDBN} prints out strings with these
14204 escape sequences embedded. Single non-printable characters are
14205 printed using the @samp{CHR(@var{nnn})} format.
14208 The assignment operator (@code{:=}) returns the value of its right-hand
14212 All built-in procedures both modify @emph{and} return their argument.
14216 @subsubsection Modula-2 Type and Range Checks
14217 @cindex Modula-2 checks
14220 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14223 @c FIXME remove warning when type/range checks added
14225 @value{GDBN} considers two Modula-2 variables type equivalent if:
14229 They are of types that have been declared equivalent via a @code{TYPE
14230 @var{t1} = @var{t2}} statement
14233 They have been declared on the same line. (Note: This is true of the
14234 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14237 As long as type checking is enabled, any attempt to combine variables
14238 whose types are not equivalent is an error.
14240 Range checking is done on all mathematical operations, assignment, array
14241 index bounds, and all built-in functions and procedures.
14244 @subsubsection The Scope Operators @code{::} and @code{.}
14246 @cindex @code{.}, Modula-2 scope operator
14247 @cindex colon, doubled as scope operator
14249 @vindex colon-colon@r{, in Modula-2}
14250 @c Info cannot handle :: but TeX can.
14253 @vindex ::@r{, in Modula-2}
14256 There are a few subtle differences between the Modula-2 scope operator
14257 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14262 @var{module} . @var{id}
14263 @var{scope} :: @var{id}
14267 where @var{scope} is the name of a module or a procedure,
14268 @var{module} the name of a module, and @var{id} is any declared
14269 identifier within your program, except another module.
14271 Using the @code{::} operator makes @value{GDBN} search the scope
14272 specified by @var{scope} for the identifier @var{id}. If it is not
14273 found in the specified scope, then @value{GDBN} searches all scopes
14274 enclosing the one specified by @var{scope}.
14276 Using the @code{.} operator makes @value{GDBN} search the current scope for
14277 the identifier specified by @var{id} that was imported from the
14278 definition module specified by @var{module}. With this operator, it is
14279 an error if the identifier @var{id} was not imported from definition
14280 module @var{module}, or if @var{id} is not an identifier in
14284 @subsubsection @value{GDBN} and Modula-2
14286 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14287 Five subcommands of @code{set print} and @code{show print} apply
14288 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14289 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14290 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14291 analogue in Modula-2.
14293 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14294 with any language, is not useful with Modula-2. Its
14295 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14296 created in Modula-2 as they can in C or C@t{++}. However, because an
14297 address can be specified by an integral constant, the construct
14298 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14300 @cindex @code{#} in Modula-2
14301 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14302 interpreted as the beginning of a comment. Use @code{<>} instead.
14308 The extensions made to @value{GDBN} for Ada only support
14309 output from the @sc{gnu} Ada (GNAT) compiler.
14310 Other Ada compilers are not currently supported, and
14311 attempting to debug executables produced by them is most likely
14315 @cindex expressions in Ada
14317 * Ada Mode Intro:: General remarks on the Ada syntax
14318 and semantics supported by Ada mode
14320 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14321 * Additions to Ada:: Extensions of the Ada expression syntax.
14322 * Stopping Before Main Program:: Debugging the program during elaboration.
14323 * Ada Tasks:: Listing and setting breakpoints in tasks.
14324 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14325 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14327 * Ada Glitches:: Known peculiarities of Ada mode.
14330 @node Ada Mode Intro
14331 @subsubsection Introduction
14332 @cindex Ada mode, general
14334 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14335 syntax, with some extensions.
14336 The philosophy behind the design of this subset is
14340 That @value{GDBN} should provide basic literals and access to operations for
14341 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14342 leaving more sophisticated computations to subprograms written into the
14343 program (which therefore may be called from @value{GDBN}).
14346 That type safety and strict adherence to Ada language restrictions
14347 are not particularly important to the @value{GDBN} user.
14350 That brevity is important to the @value{GDBN} user.
14353 Thus, for brevity, the debugger acts as if all names declared in
14354 user-written packages are directly visible, even if they are not visible
14355 according to Ada rules, thus making it unnecessary to fully qualify most
14356 names with their packages, regardless of context. Where this causes
14357 ambiguity, @value{GDBN} asks the user's intent.
14359 The debugger will start in Ada mode if it detects an Ada main program.
14360 As for other languages, it will enter Ada mode when stopped in a program that
14361 was translated from an Ada source file.
14363 While in Ada mode, you may use `@t{--}' for comments. This is useful
14364 mostly for documenting command files. The standard @value{GDBN} comment
14365 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14366 middle (to allow based literals).
14368 The debugger supports limited overloading. Given a subprogram call in which
14369 the function symbol has multiple definitions, it will use the number of
14370 actual parameters and some information about their types to attempt to narrow
14371 the set of definitions. It also makes very limited use of context, preferring
14372 procedures to functions in the context of the @code{call} command, and
14373 functions to procedures elsewhere.
14375 @node Omissions from Ada
14376 @subsubsection Omissions from Ada
14377 @cindex Ada, omissions from
14379 Here are the notable omissions from the subset:
14383 Only a subset of the attributes are supported:
14387 @t{'First}, @t{'Last}, and @t{'Length}
14388 on array objects (not on types and subtypes).
14391 @t{'Min} and @t{'Max}.
14394 @t{'Pos} and @t{'Val}.
14400 @t{'Range} on array objects (not subtypes), but only as the right
14401 operand of the membership (@code{in}) operator.
14404 @t{'Access}, @t{'Unchecked_Access}, and
14405 @t{'Unrestricted_Access} (a GNAT extension).
14413 @code{Characters.Latin_1} are not available and
14414 concatenation is not implemented. Thus, escape characters in strings are
14415 not currently available.
14418 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14419 equality of representations. They will generally work correctly
14420 for strings and arrays whose elements have integer or enumeration types.
14421 They may not work correctly for arrays whose element
14422 types have user-defined equality, for arrays of real values
14423 (in particular, IEEE-conformant floating point, because of negative
14424 zeroes and NaNs), and for arrays whose elements contain unused bits with
14425 indeterminate values.
14428 The other component-by-component array operations (@code{and}, @code{or},
14429 @code{xor}, @code{not}, and relational tests other than equality)
14430 are not implemented.
14433 @cindex array aggregates (Ada)
14434 @cindex record aggregates (Ada)
14435 @cindex aggregates (Ada)
14436 There is limited support for array and record aggregates. They are
14437 permitted only on the right sides of assignments, as in these examples:
14440 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14441 (@value{GDBP}) set An_Array := (1, others => 0)
14442 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14443 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14444 (@value{GDBP}) set A_Record := (1, "Peter", True);
14445 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14449 discriminant's value by assigning an aggregate has an
14450 undefined effect if that discriminant is used within the record.
14451 However, you can first modify discriminants by directly assigning to
14452 them (which normally would not be allowed in Ada), and then performing an
14453 aggregate assignment. For example, given a variable @code{A_Rec}
14454 declared to have a type such as:
14457 type Rec (Len : Small_Integer := 0) is record
14459 Vals : IntArray (1 .. Len);
14463 you can assign a value with a different size of @code{Vals} with two
14467 (@value{GDBP}) set A_Rec.Len := 4
14468 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14471 As this example also illustrates, @value{GDBN} is very loose about the usual
14472 rules concerning aggregates. You may leave out some of the
14473 components of an array or record aggregate (such as the @code{Len}
14474 component in the assignment to @code{A_Rec} above); they will retain their
14475 original values upon assignment. You may freely use dynamic values as
14476 indices in component associations. You may even use overlapping or
14477 redundant component associations, although which component values are
14478 assigned in such cases is not defined.
14481 Calls to dispatching subprograms are not implemented.
14484 The overloading algorithm is much more limited (i.e., less selective)
14485 than that of real Ada. It makes only limited use of the context in
14486 which a subexpression appears to resolve its meaning, and it is much
14487 looser in its rules for allowing type matches. As a result, some
14488 function calls will be ambiguous, and the user will be asked to choose
14489 the proper resolution.
14492 The @code{new} operator is not implemented.
14495 Entry calls are not implemented.
14498 Aside from printing, arithmetic operations on the native VAX floating-point
14499 formats are not supported.
14502 It is not possible to slice a packed array.
14505 The names @code{True} and @code{False}, when not part of a qualified name,
14506 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14508 Should your program
14509 redefine these names in a package or procedure (at best a dubious practice),
14510 you will have to use fully qualified names to access their new definitions.
14513 @node Additions to Ada
14514 @subsubsection Additions to Ada
14515 @cindex Ada, deviations from
14517 As it does for other languages, @value{GDBN} makes certain generic
14518 extensions to Ada (@pxref{Expressions}):
14522 If the expression @var{E} is a variable residing in memory (typically
14523 a local variable or array element) and @var{N} is a positive integer,
14524 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14525 @var{N}-1 adjacent variables following it in memory as an array. In
14526 Ada, this operator is generally not necessary, since its prime use is
14527 in displaying parts of an array, and slicing will usually do this in
14528 Ada. However, there are occasional uses when debugging programs in
14529 which certain debugging information has been optimized away.
14532 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14533 appears in function or file @var{B}.'' When @var{B} is a file name,
14534 you must typically surround it in single quotes.
14537 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14538 @var{type} that appears at address @var{addr}.''
14541 A name starting with @samp{$} is a convenience variable
14542 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14545 In addition, @value{GDBN} provides a few other shortcuts and outright
14546 additions specific to Ada:
14550 The assignment statement is allowed as an expression, returning
14551 its right-hand operand as its value. Thus, you may enter
14554 (@value{GDBP}) set x := y + 3
14555 (@value{GDBP}) print A(tmp := y + 1)
14559 The semicolon is allowed as an ``operator,'' returning as its value
14560 the value of its right-hand operand.
14561 This allows, for example,
14562 complex conditional breaks:
14565 (@value{GDBP}) break f
14566 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14570 Rather than use catenation and symbolic character names to introduce special
14571 characters into strings, one may instead use a special bracket notation,
14572 which is also used to print strings. A sequence of characters of the form
14573 @samp{["@var{XX}"]} within a string or character literal denotes the
14574 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14575 sequence of characters @samp{["""]} also denotes a single quotation mark
14576 in strings. For example,
14578 "One line.["0a"]Next line.["0a"]"
14581 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14585 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14586 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14590 (@value{GDBP}) print 'max(x, y)
14594 When printing arrays, @value{GDBN} uses positional notation when the
14595 array has a lower bound of 1, and uses a modified named notation otherwise.
14596 For example, a one-dimensional array of three integers with a lower bound
14597 of 3 might print as
14604 That is, in contrast to valid Ada, only the first component has a @code{=>}
14608 You may abbreviate attributes in expressions with any unique,
14609 multi-character subsequence of
14610 their names (an exact match gets preference).
14611 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14612 in place of @t{a'length}.
14615 @cindex quoting Ada internal identifiers
14616 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14617 to lower case. The GNAT compiler uses upper-case characters for
14618 some of its internal identifiers, which are normally of no interest to users.
14619 For the rare occasions when you actually have to look at them,
14620 enclose them in angle brackets to avoid the lower-case mapping.
14623 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14627 Printing an object of class-wide type or dereferencing an
14628 access-to-class-wide value will display all the components of the object's
14629 specific type (as indicated by its run-time tag). Likewise, component
14630 selection on such a value will operate on the specific type of the
14635 @node Stopping Before Main Program
14636 @subsubsection Stopping at the Very Beginning
14638 @cindex breakpointing Ada elaboration code
14639 It is sometimes necessary to debug the program during elaboration, and
14640 before reaching the main procedure.
14641 As defined in the Ada Reference
14642 Manual, the elaboration code is invoked from a procedure called
14643 @code{adainit}. To run your program up to the beginning of
14644 elaboration, simply use the following two commands:
14645 @code{tbreak adainit} and @code{run}.
14648 @subsubsection Extensions for Ada Tasks
14649 @cindex Ada, tasking
14651 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14652 @value{GDBN} provides the following task-related commands:
14657 This command shows a list of current Ada tasks, as in the following example:
14664 (@value{GDBP}) info tasks
14665 ID TID P-ID Pri State Name
14666 1 8088000 0 15 Child Activation Wait main_task
14667 2 80a4000 1 15 Accept Statement b
14668 3 809a800 1 15 Child Activation Wait a
14669 * 4 80ae800 3 15 Runnable c
14674 In this listing, the asterisk before the last task indicates it to be the
14675 task currently being inspected.
14679 Represents @value{GDBN}'s internal task number.
14685 The parent's task ID (@value{GDBN}'s internal task number).
14688 The base priority of the task.
14691 Current state of the task.
14695 The task has been created but has not been activated. It cannot be
14699 The task is not blocked for any reason known to Ada. (It may be waiting
14700 for a mutex, though.) It is conceptually "executing" in normal mode.
14703 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14704 that were waiting on terminate alternatives have been awakened and have
14705 terminated themselves.
14707 @item Child Activation Wait
14708 The task is waiting for created tasks to complete activation.
14710 @item Accept Statement
14711 The task is waiting on an accept or selective wait statement.
14713 @item Waiting on entry call
14714 The task is waiting on an entry call.
14716 @item Async Select Wait
14717 The task is waiting to start the abortable part of an asynchronous
14721 The task is waiting on a select statement with only a delay
14724 @item Child Termination Wait
14725 The task is sleeping having completed a master within itself, and is
14726 waiting for the tasks dependent on that master to become terminated or
14727 waiting on a terminate Phase.
14729 @item Wait Child in Term Alt
14730 The task is sleeping waiting for tasks on terminate alternatives to
14731 finish terminating.
14733 @item Accepting RV with @var{taskno}
14734 The task is accepting a rendez-vous with the task @var{taskno}.
14738 Name of the task in the program.
14742 @kindex info task @var{taskno}
14743 @item info task @var{taskno}
14744 This command shows detailled informations on the specified task, as in
14745 the following example:
14750 (@value{GDBP}) info tasks
14751 ID TID P-ID Pri State Name
14752 1 8077880 0 15 Child Activation Wait main_task
14753 * 2 807c468 1 15 Runnable task_1
14754 (@value{GDBP}) info task 2
14755 Ada Task: 0x807c468
14758 Parent: 1 (main_task)
14764 @kindex task@r{ (Ada)}
14765 @cindex current Ada task ID
14766 This command prints the ID of the current task.
14772 (@value{GDBP}) info tasks
14773 ID TID P-ID Pri State Name
14774 1 8077870 0 15 Child Activation Wait main_task
14775 * 2 807c458 1 15 Runnable t
14776 (@value{GDBP}) task
14777 [Current task is 2]
14780 @item task @var{taskno}
14781 @cindex Ada task switching
14782 This command is like the @code{thread @var{threadno}}
14783 command (@pxref{Threads}). It switches the context of debugging
14784 from the current task to the given task.
14790 (@value{GDBP}) info tasks
14791 ID TID P-ID Pri State Name
14792 1 8077870 0 15 Child Activation Wait main_task
14793 * 2 807c458 1 15 Runnable t
14794 (@value{GDBP}) task 1
14795 [Switching to task 1]
14796 #0 0x8067726 in pthread_cond_wait ()
14798 #0 0x8067726 in pthread_cond_wait ()
14799 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14800 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14801 #3 0x806153e in system.tasking.stages.activate_tasks ()
14802 #4 0x804aacc in un () at un.adb:5
14805 @item break @var{linespec} task @var{taskno}
14806 @itemx break @var{linespec} task @var{taskno} if @dots{}
14807 @cindex breakpoints and tasks, in Ada
14808 @cindex task breakpoints, in Ada
14809 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14810 These commands are like the @code{break @dots{} thread @dots{}}
14811 command (@pxref{Thread Stops}).
14812 @var{linespec} specifies source lines, as described
14813 in @ref{Specify Location}.
14815 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14816 to specify that you only want @value{GDBN} to stop the program when a
14817 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14818 numeric task identifiers assigned by @value{GDBN}, shown in the first
14819 column of the @samp{info tasks} display.
14821 If you do not specify @samp{task @var{taskno}} when you set a
14822 breakpoint, the breakpoint applies to @emph{all} tasks of your
14825 You can use the @code{task} qualifier on conditional breakpoints as
14826 well; in this case, place @samp{task @var{taskno}} before the
14827 breakpoint condition (before the @code{if}).
14835 (@value{GDBP}) info tasks
14836 ID TID P-ID Pri State Name
14837 1 140022020 0 15 Child Activation Wait main_task
14838 2 140045060 1 15 Accept/Select Wait t2
14839 3 140044840 1 15 Runnable t1
14840 * 4 140056040 1 15 Runnable t3
14841 (@value{GDBP}) b 15 task 2
14842 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14843 (@value{GDBP}) cont
14848 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14850 (@value{GDBP}) info tasks
14851 ID TID P-ID Pri State Name
14852 1 140022020 0 15 Child Activation Wait main_task
14853 * 2 140045060 1 15 Runnable t2
14854 3 140044840 1 15 Runnable t1
14855 4 140056040 1 15 Delay Sleep t3
14859 @node Ada Tasks and Core Files
14860 @subsubsection Tasking Support when Debugging Core Files
14861 @cindex Ada tasking and core file debugging
14863 When inspecting a core file, as opposed to debugging a live program,
14864 tasking support may be limited or even unavailable, depending on
14865 the platform being used.
14866 For instance, on x86-linux, the list of tasks is available, but task
14867 switching is not supported. On Tru64, however, task switching will work
14870 On certain platforms, including Tru64, the debugger needs to perform some
14871 memory writes in order to provide Ada tasking support. When inspecting
14872 a core file, this means that the core file must be opened with read-write
14873 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14874 Under these circumstances, you should make a backup copy of the core
14875 file before inspecting it with @value{GDBN}.
14877 @node Ravenscar Profile
14878 @subsubsection Tasking Support when using the Ravenscar Profile
14879 @cindex Ravenscar Profile
14881 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14882 specifically designed for systems with safety-critical real-time
14886 @kindex set ravenscar task-switching on
14887 @cindex task switching with program using Ravenscar Profile
14888 @item set ravenscar task-switching on
14889 Allows task switching when debugging a program that uses the Ravenscar
14890 Profile. This is the default.
14892 @kindex set ravenscar task-switching off
14893 @item set ravenscar task-switching off
14894 Turn off task switching when debugging a program that uses the Ravenscar
14895 Profile. This is mostly intended to disable the code that adds support
14896 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14897 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14898 To be effective, this command should be run before the program is started.
14900 @kindex show ravenscar task-switching
14901 @item show ravenscar task-switching
14902 Show whether it is possible to switch from task to task in a program
14903 using the Ravenscar Profile.
14908 @subsubsection Known Peculiarities of Ada Mode
14909 @cindex Ada, problems
14911 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14912 we know of several problems with and limitations of Ada mode in
14914 some of which will be fixed with planned future releases of the debugger
14915 and the GNU Ada compiler.
14919 Static constants that the compiler chooses not to materialize as objects in
14920 storage are invisible to the debugger.
14923 Named parameter associations in function argument lists are ignored (the
14924 argument lists are treated as positional).
14927 Many useful library packages are currently invisible to the debugger.
14930 Fixed-point arithmetic, conversions, input, and output is carried out using
14931 floating-point arithmetic, and may give results that only approximate those on
14935 The GNAT compiler never generates the prefix @code{Standard} for any of
14936 the standard symbols defined by the Ada language. @value{GDBN} knows about
14937 this: it will strip the prefix from names when you use it, and will never
14938 look for a name you have so qualified among local symbols, nor match against
14939 symbols in other packages or subprograms. If you have
14940 defined entities anywhere in your program other than parameters and
14941 local variables whose simple names match names in @code{Standard},
14942 GNAT's lack of qualification here can cause confusion. When this happens,
14943 you can usually resolve the confusion
14944 by qualifying the problematic names with package
14945 @code{Standard} explicitly.
14948 Older versions of the compiler sometimes generate erroneous debugging
14949 information, resulting in the debugger incorrectly printing the value
14950 of affected entities. In some cases, the debugger is able to work
14951 around an issue automatically. In other cases, the debugger is able
14952 to work around the issue, but the work-around has to be specifically
14955 @kindex set ada trust-PAD-over-XVS
14956 @kindex show ada trust-PAD-over-XVS
14959 @item set ada trust-PAD-over-XVS on
14960 Configure GDB to strictly follow the GNAT encoding when computing the
14961 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14962 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14963 a complete description of the encoding used by the GNAT compiler).
14964 This is the default.
14966 @item set ada trust-PAD-over-XVS off
14967 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14968 sometimes prints the wrong value for certain entities, changing @code{ada
14969 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14970 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14971 @code{off}, but this incurs a slight performance penalty, so it is
14972 recommended to leave this setting to @code{on} unless necessary.
14976 @node Unsupported Languages
14977 @section Unsupported Languages
14979 @cindex unsupported languages
14980 @cindex minimal language
14981 In addition to the other fully-supported programming languages,
14982 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14983 It does not represent a real programming language, but provides a set
14984 of capabilities close to what the C or assembly languages provide.
14985 This should allow most simple operations to be performed while debugging
14986 an application that uses a language currently not supported by @value{GDBN}.
14988 If the language is set to @code{auto}, @value{GDBN} will automatically
14989 select this language if the current frame corresponds to an unsupported
14993 @chapter Examining the Symbol Table
14995 The commands described in this chapter allow you to inquire about the
14996 symbols (names of variables, functions and types) defined in your
14997 program. This information is inherent in the text of your program and
14998 does not change as your program executes. @value{GDBN} finds it in your
14999 program's symbol table, in the file indicated when you started @value{GDBN}
15000 (@pxref{File Options, ,Choosing Files}), or by one of the
15001 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15003 @cindex symbol names
15004 @cindex names of symbols
15005 @cindex quoting names
15006 Occasionally, you may need to refer to symbols that contain unusual
15007 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15008 most frequent case is in referring to static variables in other
15009 source files (@pxref{Variables,,Program Variables}). File names
15010 are recorded in object files as debugging symbols, but @value{GDBN} would
15011 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15012 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15013 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15020 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15023 @cindex case-insensitive symbol names
15024 @cindex case sensitivity in symbol names
15025 @kindex set case-sensitive
15026 @item set case-sensitive on
15027 @itemx set case-sensitive off
15028 @itemx set case-sensitive auto
15029 Normally, when @value{GDBN} looks up symbols, it matches their names
15030 with case sensitivity determined by the current source language.
15031 Occasionally, you may wish to control that. The command @code{set
15032 case-sensitive} lets you do that by specifying @code{on} for
15033 case-sensitive matches or @code{off} for case-insensitive ones. If
15034 you specify @code{auto}, case sensitivity is reset to the default
15035 suitable for the source language. The default is case-sensitive
15036 matches for all languages except for Fortran, for which the default is
15037 case-insensitive matches.
15039 @kindex show case-sensitive
15040 @item show case-sensitive
15041 This command shows the current setting of case sensitivity for symbols
15044 @kindex set print type methods
15045 @item set print type methods
15046 @itemx set print type methods on
15047 @itemx set print type methods off
15048 Normally, when @value{GDBN} prints a class, it displays any methods
15049 declared in that class. You can control this behavior either by
15050 passing the appropriate flag to @code{ptype}, or using @command{set
15051 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15052 display the methods; this is the default. Specifying @code{off} will
15053 cause @value{GDBN} to omit the methods.
15055 @kindex show print type methods
15056 @item show print type methods
15057 This command shows the current setting of method display when printing
15060 @kindex set print type typedefs
15061 @item set print type typedefs
15062 @itemx set print type typedefs on
15063 @itemx set print type typedefs off
15065 Normally, when @value{GDBN} prints a class, it displays any typedefs
15066 defined in that class. You can control this behavior either by
15067 passing the appropriate flag to @code{ptype}, or using @command{set
15068 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15069 display the typedef definitions; this is the default. Specifying
15070 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15071 Note that this controls whether the typedef definition itself is
15072 printed, not whether typedef names are substituted when printing other
15075 @kindex show print type typedefs
15076 @item show print type typedefs
15077 This command shows the current setting of typedef display when
15080 @kindex info address
15081 @cindex address of a symbol
15082 @item info address @var{symbol}
15083 Describe where the data for @var{symbol} is stored. For a register
15084 variable, this says which register it is kept in. For a non-register
15085 local variable, this prints the stack-frame offset at which the variable
15088 Note the contrast with @samp{print &@var{symbol}}, which does not work
15089 at all for a register variable, and for a stack local variable prints
15090 the exact address of the current instantiation of the variable.
15092 @kindex info symbol
15093 @cindex symbol from address
15094 @cindex closest symbol and offset for an address
15095 @item info symbol @var{addr}
15096 Print the name of a symbol which is stored at the address @var{addr}.
15097 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15098 nearest symbol and an offset from it:
15101 (@value{GDBP}) info symbol 0x54320
15102 _initialize_vx + 396 in section .text
15106 This is the opposite of the @code{info address} command. You can use
15107 it to find out the name of a variable or a function given its address.
15109 For dynamically linked executables, the name of executable or shared
15110 library containing the symbol is also printed:
15113 (@value{GDBP}) info symbol 0x400225
15114 _start + 5 in section .text of /tmp/a.out
15115 (@value{GDBP}) info symbol 0x2aaaac2811cf
15116 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15120 @item whatis[/@var{flags}] [@var{arg}]
15121 Print the data type of @var{arg}, which can be either an expression
15122 or a name of a data type. With no argument, print the data type of
15123 @code{$}, the last value in the value history.
15125 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15126 is not actually evaluated, and any side-effecting operations (such as
15127 assignments or function calls) inside it do not take place.
15129 If @var{arg} is a variable or an expression, @code{whatis} prints its
15130 literal type as it is used in the source code. If the type was
15131 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15132 the data type underlying the @code{typedef}. If the type of the
15133 variable or the expression is a compound data type, such as
15134 @code{struct} or @code{class}, @code{whatis} never prints their
15135 fields or methods. It just prints the @code{struct}/@code{class}
15136 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15137 such a compound data type, use @code{ptype}.
15139 If @var{arg} is a type name that was defined using @code{typedef},
15140 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15141 Unrolling means that @code{whatis} will show the underlying type used
15142 in the @code{typedef} declaration of @var{arg}. However, if that
15143 underlying type is also a @code{typedef}, @code{whatis} will not
15146 For C code, the type names may also have the form @samp{class
15147 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15148 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15150 @var{flags} can be used to modify how the type is displayed.
15151 Available flags are:
15155 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15156 parameters and typedefs defined in a class when printing the class'
15157 members. The @code{/r} flag disables this.
15160 Do not print methods defined in the class.
15163 Print methods defined in the class. This is the default, but the flag
15164 exists in case you change the default with @command{set print type methods}.
15167 Do not print typedefs defined in the class. Note that this controls
15168 whether the typedef definition itself is printed, not whether typedef
15169 names are substituted when printing other types.
15172 Print typedefs defined in the class. This is the default, but the flag
15173 exists in case you change the default with @command{set print type typedefs}.
15177 @item ptype[/@var{flags}] [@var{arg}]
15178 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15179 detailed description of the type, instead of just the name of the type.
15180 @xref{Expressions, ,Expressions}.
15182 Contrary to @code{whatis}, @code{ptype} always unrolls any
15183 @code{typedef}s in its argument declaration, whether the argument is
15184 a variable, expression, or a data type. This means that @code{ptype}
15185 of a variable or an expression will not print literally its type as
15186 present in the source code---use @code{whatis} for that. @code{typedef}s at
15187 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15188 fields, methods and inner @code{class typedef}s of @code{struct}s,
15189 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15191 For example, for this variable declaration:
15194 typedef double real_t;
15195 struct complex @{ real_t real; double imag; @};
15196 typedef struct complex complex_t;
15198 real_t *real_pointer_var;
15202 the two commands give this output:
15206 (@value{GDBP}) whatis var
15208 (@value{GDBP}) ptype var
15209 type = struct complex @{
15213 (@value{GDBP}) whatis complex_t
15214 type = struct complex
15215 (@value{GDBP}) whatis struct complex
15216 type = struct complex
15217 (@value{GDBP}) ptype struct complex
15218 type = struct complex @{
15222 (@value{GDBP}) whatis real_pointer_var
15224 (@value{GDBP}) ptype real_pointer_var
15230 As with @code{whatis}, using @code{ptype} without an argument refers to
15231 the type of @code{$}, the last value in the value history.
15233 @cindex incomplete type
15234 Sometimes, programs use opaque data types or incomplete specifications
15235 of complex data structure. If the debug information included in the
15236 program does not allow @value{GDBN} to display a full declaration of
15237 the data type, it will say @samp{<incomplete type>}. For example,
15238 given these declarations:
15242 struct foo *fooptr;
15246 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15249 (@value{GDBP}) ptype foo
15250 $1 = <incomplete type>
15254 ``Incomplete type'' is C terminology for data types that are not
15255 completely specified.
15258 @item info types @var{regexp}
15260 Print a brief description of all types whose names match the regular
15261 expression @var{regexp} (or all types in your program, if you supply
15262 no argument). Each complete typename is matched as though it were a
15263 complete line; thus, @samp{i type value} gives information on all
15264 types in your program whose names include the string @code{value}, but
15265 @samp{i type ^value$} gives information only on types whose complete
15266 name is @code{value}.
15268 This command differs from @code{ptype} in two ways: first, like
15269 @code{whatis}, it does not print a detailed description; second, it
15270 lists all source files where a type is defined.
15272 @kindex info type-printers
15273 @item info type-printers
15274 Versions of @value{GDBN} that ship with Python scripting enabled may
15275 have ``type printers'' available. When using @command{ptype} or
15276 @command{whatis}, these printers are consulted when the name of a type
15277 is needed. @xref{Type Printing API}, for more information on writing
15280 @code{info type-printers} displays all the available type printers.
15282 @kindex enable type-printer
15283 @kindex disable type-printer
15284 @item enable type-printer @var{name}@dots{}
15285 @item disable type-printer @var{name}@dots{}
15286 These commands can be used to enable or disable type printers.
15289 @cindex local variables
15290 @item info scope @var{location}
15291 List all the variables local to a particular scope. This command
15292 accepts a @var{location} argument---a function name, a source line, or
15293 an address preceded by a @samp{*}, and prints all the variables local
15294 to the scope defined by that location. (@xref{Specify Location}, for
15295 details about supported forms of @var{location}.) For example:
15298 (@value{GDBP}) @b{info scope command_line_handler}
15299 Scope for command_line_handler:
15300 Symbol rl is an argument at stack/frame offset 8, length 4.
15301 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15302 Symbol linelength is in static storage at address 0x150a1c, length 4.
15303 Symbol p is a local variable in register $esi, length 4.
15304 Symbol p1 is a local variable in register $ebx, length 4.
15305 Symbol nline is a local variable in register $edx, length 4.
15306 Symbol repeat is a local variable at frame offset -8, length 4.
15310 This command is especially useful for determining what data to collect
15311 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15314 @kindex info source
15316 Show information about the current source file---that is, the source file for
15317 the function containing the current point of execution:
15320 the name of the source file, and the directory containing it,
15322 the directory it was compiled in,
15324 its length, in lines,
15326 which programming language it is written in,
15328 whether the executable includes debugging information for that file, and
15329 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15331 whether the debugging information includes information about
15332 preprocessor macros.
15336 @kindex info sources
15338 Print the names of all source files in your program for which there is
15339 debugging information, organized into two lists: files whose symbols
15340 have already been read, and files whose symbols will be read when needed.
15342 @kindex info functions
15343 @item info functions
15344 Print the names and data types of all defined functions.
15346 @item info functions @var{regexp}
15347 Print the names and data types of all defined functions
15348 whose names contain a match for regular expression @var{regexp}.
15349 Thus, @samp{info fun step} finds all functions whose names
15350 include @code{step}; @samp{info fun ^step} finds those whose names
15351 start with @code{step}. If a function name contains characters
15352 that conflict with the regular expression language (e.g.@:
15353 @samp{operator*()}), they may be quoted with a backslash.
15355 @kindex info variables
15356 @item info variables
15357 Print the names and data types of all variables that are defined
15358 outside of functions (i.e.@: excluding local variables).
15360 @item info variables @var{regexp}
15361 Print the names and data types of all variables (except for local
15362 variables) whose names contain a match for regular expression
15365 @kindex info classes
15366 @cindex Objective-C, classes and selectors
15368 @itemx info classes @var{regexp}
15369 Display all Objective-C classes in your program, or
15370 (with the @var{regexp} argument) all those matching a particular regular
15373 @kindex info selectors
15374 @item info selectors
15375 @itemx info selectors @var{regexp}
15376 Display all Objective-C selectors in your program, or
15377 (with the @var{regexp} argument) all those matching a particular regular
15381 This was never implemented.
15382 @kindex info methods
15384 @itemx info methods @var{regexp}
15385 The @code{info methods} command permits the user to examine all defined
15386 methods within C@t{++} program, or (with the @var{regexp} argument) a
15387 specific set of methods found in the various C@t{++} classes. Many
15388 C@t{++} classes provide a large number of methods. Thus, the output
15389 from the @code{ptype} command can be overwhelming and hard to use. The
15390 @code{info-methods} command filters the methods, printing only those
15391 which match the regular-expression @var{regexp}.
15394 @cindex opaque data types
15395 @kindex set opaque-type-resolution
15396 @item set opaque-type-resolution on
15397 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15398 declared as a pointer to a @code{struct}, @code{class}, or
15399 @code{union}---for example, @code{struct MyType *}---that is used in one
15400 source file although the full declaration of @code{struct MyType} is in
15401 another source file. The default is on.
15403 A change in the setting of this subcommand will not take effect until
15404 the next time symbols for a file are loaded.
15406 @item set opaque-type-resolution off
15407 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15408 is printed as follows:
15410 @{<no data fields>@}
15413 @kindex show opaque-type-resolution
15414 @item show opaque-type-resolution
15415 Show whether opaque types are resolved or not.
15417 @kindex maint print symbols
15418 @cindex symbol dump
15419 @kindex maint print psymbols
15420 @cindex partial symbol dump
15421 @item maint print symbols @var{filename}
15422 @itemx maint print psymbols @var{filename}
15423 @itemx maint print msymbols @var{filename}
15424 Write a dump of debugging symbol data into the file @var{filename}.
15425 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15426 symbols with debugging data are included. If you use @samp{maint print
15427 symbols}, @value{GDBN} includes all the symbols for which it has already
15428 collected full details: that is, @var{filename} reflects symbols for
15429 only those files whose symbols @value{GDBN} has read. You can use the
15430 command @code{info sources} to find out which files these are. If you
15431 use @samp{maint print psymbols} instead, the dump shows information about
15432 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15433 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15434 @samp{maint print msymbols} dumps just the minimal symbol information
15435 required for each object file from which @value{GDBN} has read some symbols.
15436 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15437 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15439 @kindex maint info symtabs
15440 @kindex maint info psymtabs
15441 @cindex listing @value{GDBN}'s internal symbol tables
15442 @cindex symbol tables, listing @value{GDBN}'s internal
15443 @cindex full symbol tables, listing @value{GDBN}'s internal
15444 @cindex partial symbol tables, listing @value{GDBN}'s internal
15445 @item maint info symtabs @r{[} @var{regexp} @r{]}
15446 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15448 List the @code{struct symtab} or @code{struct partial_symtab}
15449 structures whose names match @var{regexp}. If @var{regexp} is not
15450 given, list them all. The output includes expressions which you can
15451 copy into a @value{GDBN} debugging this one to examine a particular
15452 structure in more detail. For example:
15455 (@value{GDBP}) maint info psymtabs dwarf2read
15456 @{ objfile /home/gnu/build/gdb/gdb
15457 ((struct objfile *) 0x82e69d0)
15458 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15459 ((struct partial_symtab *) 0x8474b10)
15462 text addresses 0x814d3c8 -- 0x8158074
15463 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15464 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15465 dependencies (none)
15468 (@value{GDBP}) maint info symtabs
15472 We see that there is one partial symbol table whose filename contains
15473 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15474 and we see that @value{GDBN} has not read in any symtabs yet at all.
15475 If we set a breakpoint on a function, that will cause @value{GDBN} to
15476 read the symtab for the compilation unit containing that function:
15479 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15480 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15482 (@value{GDBP}) maint info symtabs
15483 @{ objfile /home/gnu/build/gdb/gdb
15484 ((struct objfile *) 0x82e69d0)
15485 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15486 ((struct symtab *) 0x86c1f38)
15489 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15490 linetable ((struct linetable *) 0x8370fa0)
15491 debugformat DWARF 2
15500 @chapter Altering Execution
15502 Once you think you have found an error in your program, you might want to
15503 find out for certain whether correcting the apparent error would lead to
15504 correct results in the rest of the run. You can find the answer by
15505 experiment, using the @value{GDBN} features for altering execution of the
15508 For example, you can store new values into variables or memory
15509 locations, give your program a signal, restart it at a different
15510 address, or even return prematurely from a function.
15513 * Assignment:: Assignment to variables
15514 * Jumping:: Continuing at a different address
15515 * Signaling:: Giving your program a signal
15516 * Returning:: Returning from a function
15517 * Calling:: Calling your program's functions
15518 * Patching:: Patching your program
15522 @section Assignment to Variables
15525 @cindex setting variables
15526 To alter the value of a variable, evaluate an assignment expression.
15527 @xref{Expressions, ,Expressions}. For example,
15534 stores the value 4 into the variable @code{x}, and then prints the
15535 value of the assignment expression (which is 4).
15536 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15537 information on operators in supported languages.
15539 @kindex set variable
15540 @cindex variables, setting
15541 If you are not interested in seeing the value of the assignment, use the
15542 @code{set} command instead of the @code{print} command. @code{set} is
15543 really the same as @code{print} except that the expression's value is
15544 not printed and is not put in the value history (@pxref{Value History,
15545 ,Value History}). The expression is evaluated only for its effects.
15547 If the beginning of the argument string of the @code{set} command
15548 appears identical to a @code{set} subcommand, use the @code{set
15549 variable} command instead of just @code{set}. This command is identical
15550 to @code{set} except for its lack of subcommands. For example, if your
15551 program has a variable @code{width}, you get an error if you try to set
15552 a new value with just @samp{set width=13}, because @value{GDBN} has the
15553 command @code{set width}:
15556 (@value{GDBP}) whatis width
15558 (@value{GDBP}) p width
15560 (@value{GDBP}) set width=47
15561 Invalid syntax in expression.
15565 The invalid expression, of course, is @samp{=47}. In
15566 order to actually set the program's variable @code{width}, use
15569 (@value{GDBP}) set var width=47
15572 Because the @code{set} command has many subcommands that can conflict
15573 with the names of program variables, it is a good idea to use the
15574 @code{set variable} command instead of just @code{set}. For example, if
15575 your program has a variable @code{g}, you run into problems if you try
15576 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15577 the command @code{set gnutarget}, abbreviated @code{set g}:
15581 (@value{GDBP}) whatis g
15585 (@value{GDBP}) set g=4
15589 The program being debugged has been started already.
15590 Start it from the beginning? (y or n) y
15591 Starting program: /home/smith/cc_progs/a.out
15592 "/home/smith/cc_progs/a.out": can't open to read symbols:
15593 Invalid bfd target.
15594 (@value{GDBP}) show g
15595 The current BFD target is "=4".
15600 The program variable @code{g} did not change, and you silently set the
15601 @code{gnutarget} to an invalid value. In order to set the variable
15605 (@value{GDBP}) set var g=4
15608 @value{GDBN} allows more implicit conversions in assignments than C; you can
15609 freely store an integer value into a pointer variable or vice versa,
15610 and you can convert any structure to any other structure that is the
15611 same length or shorter.
15612 @comment FIXME: how do structs align/pad in these conversions?
15613 @comment /doc@cygnus.com 18dec1990
15615 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15616 construct to generate a value of specified type at a specified address
15617 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15618 to memory location @code{0x83040} as an integer (which implies a certain size
15619 and representation in memory), and
15622 set @{int@}0x83040 = 4
15626 stores the value 4 into that memory location.
15629 @section Continuing at a Different Address
15631 Ordinarily, when you continue your program, you do so at the place where
15632 it stopped, with the @code{continue} command. You can instead continue at
15633 an address of your own choosing, with the following commands:
15637 @kindex j @r{(@code{jump})}
15638 @item jump @var{linespec}
15639 @itemx j @var{linespec}
15640 @itemx jump @var{location}
15641 @itemx j @var{location}
15642 Resume execution at line @var{linespec} or at address given by
15643 @var{location}. Execution stops again immediately if there is a
15644 breakpoint there. @xref{Specify Location}, for a description of the
15645 different forms of @var{linespec} and @var{location}. It is common
15646 practice to use the @code{tbreak} command in conjunction with
15647 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15649 The @code{jump} command does not change the current stack frame, or
15650 the stack pointer, or the contents of any memory location or any
15651 register other than the program counter. If line @var{linespec} is in
15652 a different function from the one currently executing, the results may
15653 be bizarre if the two functions expect different patterns of arguments or
15654 of local variables. For this reason, the @code{jump} command requests
15655 confirmation if the specified line is not in the function currently
15656 executing. However, even bizarre results are predictable if you are
15657 well acquainted with the machine-language code of your program.
15660 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15661 On many systems, you can get much the same effect as the @code{jump}
15662 command by storing a new value into the register @code{$pc}. The
15663 difference is that this does not start your program running; it only
15664 changes the address of where it @emph{will} run when you continue. For
15672 makes the next @code{continue} command or stepping command execute at
15673 address @code{0x485}, rather than at the address where your program stopped.
15674 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15676 The most common occasion to use the @code{jump} command is to back
15677 up---perhaps with more breakpoints set---over a portion of a program
15678 that has already executed, in order to examine its execution in more
15683 @section Giving your Program a Signal
15684 @cindex deliver a signal to a program
15688 @item signal @var{signal}
15689 Resume execution where your program stopped, but immediately give it the
15690 signal @var{signal}. @var{signal} can be the name or the number of a
15691 signal. For example, on many systems @code{signal 2} and @code{signal
15692 SIGINT} are both ways of sending an interrupt signal.
15694 Alternatively, if @var{signal} is zero, continue execution without
15695 giving a signal. This is useful when your program stopped on account of
15696 a signal and would ordinarily see the signal when resumed with the
15697 @code{continue} command; @samp{signal 0} causes it to resume without a
15700 @code{signal} does not repeat when you press @key{RET} a second time
15701 after executing the command.
15705 Invoking the @code{signal} command is not the same as invoking the
15706 @code{kill} utility from the shell. Sending a signal with @code{kill}
15707 causes @value{GDBN} to decide what to do with the signal depending on
15708 the signal handling tables (@pxref{Signals}). The @code{signal} command
15709 passes the signal directly to your program.
15713 @section Returning from a Function
15716 @cindex returning from a function
15719 @itemx return @var{expression}
15720 You can cancel execution of a function call with the @code{return}
15721 command. If you give an
15722 @var{expression} argument, its value is used as the function's return
15726 When you use @code{return}, @value{GDBN} discards the selected stack frame
15727 (and all frames within it). You can think of this as making the
15728 discarded frame return prematurely. If you wish to specify a value to
15729 be returned, give that value as the argument to @code{return}.
15731 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15732 Frame}), and any other frames inside of it, leaving its caller as the
15733 innermost remaining frame. That frame becomes selected. The
15734 specified value is stored in the registers used for returning values
15737 The @code{return} command does not resume execution; it leaves the
15738 program stopped in the state that would exist if the function had just
15739 returned. In contrast, the @code{finish} command (@pxref{Continuing
15740 and Stepping, ,Continuing and Stepping}) resumes execution until the
15741 selected stack frame returns naturally.
15743 @value{GDBN} needs to know how the @var{expression} argument should be set for
15744 the inferior. The concrete registers assignment depends on the OS ABI and the
15745 type being returned by the selected stack frame. For example it is common for
15746 OS ABI to return floating point values in FPU registers while integer values in
15747 CPU registers. Still some ABIs return even floating point values in CPU
15748 registers. Larger integer widths (such as @code{long long int}) also have
15749 specific placement rules. @value{GDBN} already knows the OS ABI from its
15750 current target so it needs to find out also the type being returned to make the
15751 assignment into the right register(s).
15753 Normally, the selected stack frame has debug info. @value{GDBN} will always
15754 use the debug info instead of the implicit type of @var{expression} when the
15755 debug info is available. For example, if you type @kbd{return -1}, and the
15756 function in the current stack frame is declared to return a @code{long long
15757 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15758 into a @code{long long int}:
15761 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15763 (@value{GDBP}) return -1
15764 Make func return now? (y or n) y
15765 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15766 43 printf ("result=%lld\n", func ());
15770 However, if the selected stack frame does not have a debug info, e.g., if the
15771 function was compiled without debug info, @value{GDBN} has to find out the type
15772 to return from user. Specifying a different type by mistake may set the value
15773 in different inferior registers than the caller code expects. For example,
15774 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15775 of a @code{long long int} result for a debug info less function (on 32-bit
15776 architectures). Therefore the user is required to specify the return type by
15777 an appropriate cast explicitly:
15780 Breakpoint 2, 0x0040050b in func ()
15781 (@value{GDBP}) return -1
15782 Return value type not available for selected stack frame.
15783 Please use an explicit cast of the value to return.
15784 (@value{GDBP}) return (long long int) -1
15785 Make selected stack frame return now? (y or n) y
15786 #0 0x00400526 in main ()
15791 @section Calling Program Functions
15794 @cindex calling functions
15795 @cindex inferior functions, calling
15796 @item print @var{expr}
15797 Evaluate the expression @var{expr} and display the resulting value.
15798 @var{expr} may include calls to functions in the program being
15802 @item call @var{expr}
15803 Evaluate the expression @var{expr} without displaying @code{void}
15806 You can use this variant of the @code{print} command if you want to
15807 execute a function from your program that does not return anything
15808 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15809 with @code{void} returned values that @value{GDBN} will otherwise
15810 print. If the result is not void, it is printed and saved in the
15814 It is possible for the function you call via the @code{print} or
15815 @code{call} command to generate a signal (e.g., if there's a bug in
15816 the function, or if you passed it incorrect arguments). What happens
15817 in that case is controlled by the @code{set unwindonsignal} command.
15819 Similarly, with a C@t{++} program it is possible for the function you
15820 call via the @code{print} or @code{call} command to generate an
15821 exception that is not handled due to the constraints of the dummy
15822 frame. In this case, any exception that is raised in the frame, but has
15823 an out-of-frame exception handler will not be found. GDB builds a
15824 dummy-frame for the inferior function call, and the unwinder cannot
15825 seek for exception handlers outside of this dummy-frame. What happens
15826 in that case is controlled by the
15827 @code{set unwind-on-terminating-exception} command.
15830 @item set unwindonsignal
15831 @kindex set unwindonsignal
15832 @cindex unwind stack in called functions
15833 @cindex call dummy stack unwinding
15834 Set unwinding of the stack if a signal is received while in a function
15835 that @value{GDBN} called in the program being debugged. If set to on,
15836 @value{GDBN} unwinds the stack it created for the call and restores
15837 the context to what it was before the call. If set to off (the
15838 default), @value{GDBN} stops in the frame where the signal was
15841 @item show unwindonsignal
15842 @kindex show unwindonsignal
15843 Show the current setting of stack unwinding in the functions called by
15846 @item set unwind-on-terminating-exception
15847 @kindex set unwind-on-terminating-exception
15848 @cindex unwind stack in called functions with unhandled exceptions
15849 @cindex call dummy stack unwinding on unhandled exception.
15850 Set unwinding of the stack if a C@t{++} exception is raised, but left
15851 unhandled while in a function that @value{GDBN} called in the program being
15852 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15853 it created for the call and restores the context to what it was before
15854 the call. If set to off, @value{GDBN} the exception is delivered to
15855 the default C@t{++} exception handler and the inferior terminated.
15857 @item show unwind-on-terminating-exception
15858 @kindex show unwind-on-terminating-exception
15859 Show the current setting of stack unwinding in the functions called by
15864 @cindex weak alias functions
15865 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15866 for another function. In such case, @value{GDBN} might not pick up
15867 the type information, including the types of the function arguments,
15868 which causes @value{GDBN} to call the inferior function incorrectly.
15869 As a result, the called function will function erroneously and may
15870 even crash. A solution to that is to use the name of the aliased
15874 @section Patching Programs
15876 @cindex patching binaries
15877 @cindex writing into executables
15878 @cindex writing into corefiles
15880 By default, @value{GDBN} opens the file containing your program's
15881 executable code (or the corefile) read-only. This prevents accidental
15882 alterations to machine code; but it also prevents you from intentionally
15883 patching your program's binary.
15885 If you'd like to be able to patch the binary, you can specify that
15886 explicitly with the @code{set write} command. For example, you might
15887 want to turn on internal debugging flags, or even to make emergency
15893 @itemx set write off
15894 If you specify @samp{set write on}, @value{GDBN} opens executable and
15895 core files for both reading and writing; if you specify @kbd{set write
15896 off} (the default), @value{GDBN} opens them read-only.
15898 If you have already loaded a file, you must load it again (using the
15899 @code{exec-file} or @code{core-file} command) after changing @code{set
15900 write}, for your new setting to take effect.
15904 Display whether executable files and core files are opened for writing
15905 as well as reading.
15909 @chapter @value{GDBN} Files
15911 @value{GDBN} needs to know the file name of the program to be debugged,
15912 both in order to read its symbol table and in order to start your
15913 program. To debug a core dump of a previous run, you must also tell
15914 @value{GDBN} the name of the core dump file.
15917 * Files:: Commands to specify files
15918 * Separate Debug Files:: Debugging information in separate files
15919 * MiniDebugInfo:: Debugging information in a special section
15920 * Index Files:: Index files speed up GDB
15921 * Symbol Errors:: Errors reading symbol files
15922 * Data Files:: GDB data files
15926 @section Commands to Specify Files
15928 @cindex symbol table
15929 @cindex core dump file
15931 You may want to specify executable and core dump file names. The usual
15932 way to do this is at start-up time, using the arguments to
15933 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15934 Out of @value{GDBN}}).
15936 Occasionally it is necessary to change to a different file during a
15937 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15938 specify a file you want to use. Or you are debugging a remote target
15939 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15940 Program}). In these situations the @value{GDBN} commands to specify
15941 new files are useful.
15944 @cindex executable file
15946 @item file @var{filename}
15947 Use @var{filename} as the program to be debugged. It is read for its
15948 symbols and for the contents of pure memory. It is also the program
15949 executed when you use the @code{run} command. If you do not specify a
15950 directory and the file is not found in the @value{GDBN} working directory,
15951 @value{GDBN} uses the environment variable @code{PATH} as a list of
15952 directories to search, just as the shell does when looking for a program
15953 to run. You can change the value of this variable, for both @value{GDBN}
15954 and your program, using the @code{path} command.
15956 @cindex unlinked object files
15957 @cindex patching object files
15958 You can load unlinked object @file{.o} files into @value{GDBN} using
15959 the @code{file} command. You will not be able to ``run'' an object
15960 file, but you can disassemble functions and inspect variables. Also,
15961 if the underlying BFD functionality supports it, you could use
15962 @kbd{gdb -write} to patch object files using this technique. Note
15963 that @value{GDBN} can neither interpret nor modify relocations in this
15964 case, so branches and some initialized variables will appear to go to
15965 the wrong place. But this feature is still handy from time to time.
15968 @code{file} with no argument makes @value{GDBN} discard any information it
15969 has on both executable file and the symbol table.
15972 @item exec-file @r{[} @var{filename} @r{]}
15973 Specify that the program to be run (but not the symbol table) is found
15974 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15975 if necessary to locate your program. Omitting @var{filename} means to
15976 discard information on the executable file.
15978 @kindex symbol-file
15979 @item symbol-file @r{[} @var{filename} @r{]}
15980 Read symbol table information from file @var{filename}. @code{PATH} is
15981 searched when necessary. Use the @code{file} command to get both symbol
15982 table and program to run from the same file.
15984 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15985 program's symbol table.
15987 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15988 some breakpoints and auto-display expressions. This is because they may
15989 contain pointers to the internal data recording symbols and data types,
15990 which are part of the old symbol table data being discarded inside
15993 @code{symbol-file} does not repeat if you press @key{RET} again after
15996 When @value{GDBN} is configured for a particular environment, it
15997 understands debugging information in whatever format is the standard
15998 generated for that environment; you may use either a @sc{gnu} compiler, or
15999 other compilers that adhere to the local conventions.
16000 Best results are usually obtained from @sc{gnu} compilers; for example,
16001 using @code{@value{NGCC}} you can generate debugging information for
16004 For most kinds of object files, with the exception of old SVR3 systems
16005 using COFF, the @code{symbol-file} command does not normally read the
16006 symbol table in full right away. Instead, it scans the symbol table
16007 quickly to find which source files and which symbols are present. The
16008 details are read later, one source file at a time, as they are needed.
16010 The purpose of this two-stage reading strategy is to make @value{GDBN}
16011 start up faster. For the most part, it is invisible except for
16012 occasional pauses while the symbol table details for a particular source
16013 file are being read. (The @code{set verbose} command can turn these
16014 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16015 Warnings and Messages}.)
16017 We have not implemented the two-stage strategy for COFF yet. When the
16018 symbol table is stored in COFF format, @code{symbol-file} reads the
16019 symbol table data in full right away. Note that ``stabs-in-COFF''
16020 still does the two-stage strategy, since the debug info is actually
16024 @cindex reading symbols immediately
16025 @cindex symbols, reading immediately
16026 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16027 @itemx file @r{[} -readnow @r{]} @var{filename}
16028 You can override the @value{GDBN} two-stage strategy for reading symbol
16029 tables by using the @samp{-readnow} option with any of the commands that
16030 load symbol table information, if you want to be sure @value{GDBN} has the
16031 entire symbol table available.
16033 @c FIXME: for now no mention of directories, since this seems to be in
16034 @c flux. 13mar1992 status is that in theory GDB would look either in
16035 @c current dir or in same dir as myprog; but issues like competing
16036 @c GDB's, or clutter in system dirs, mean that in practice right now
16037 @c only current dir is used. FFish says maybe a special GDB hierarchy
16038 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16042 @item core-file @r{[}@var{filename}@r{]}
16044 Specify the whereabouts of a core dump file to be used as the ``contents
16045 of memory''. Traditionally, core files contain only some parts of the
16046 address space of the process that generated them; @value{GDBN} can access the
16047 executable file itself for other parts.
16049 @code{core-file} with no argument specifies that no core file is
16052 Note that the core file is ignored when your program is actually running
16053 under @value{GDBN}. So, if you have been running your program and you
16054 wish to debug a core file instead, you must kill the subprocess in which
16055 the program is running. To do this, use the @code{kill} command
16056 (@pxref{Kill Process, ,Killing the Child Process}).
16058 @kindex add-symbol-file
16059 @cindex dynamic linking
16060 @item add-symbol-file @var{filename} @var{address}
16061 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16062 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16063 The @code{add-symbol-file} command reads additional symbol table
16064 information from the file @var{filename}. You would use this command
16065 when @var{filename} has been dynamically loaded (by some other means)
16066 into the program that is running. @var{address} should be the memory
16067 address at which the file has been loaded; @value{GDBN} cannot figure
16068 this out for itself. You can additionally specify an arbitrary number
16069 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16070 section name and base address for that section. You can specify any
16071 @var{address} as an expression.
16073 The symbol table of the file @var{filename} is added to the symbol table
16074 originally read with the @code{symbol-file} command. You can use the
16075 @code{add-symbol-file} command any number of times; the new symbol data
16076 thus read keeps adding to the old. To discard all old symbol data
16077 instead, use the @code{symbol-file} command without any arguments.
16079 @cindex relocatable object files, reading symbols from
16080 @cindex object files, relocatable, reading symbols from
16081 @cindex reading symbols from relocatable object files
16082 @cindex symbols, reading from relocatable object files
16083 @cindex @file{.o} files, reading symbols from
16084 Although @var{filename} is typically a shared library file, an
16085 executable file, or some other object file which has been fully
16086 relocated for loading into a process, you can also load symbolic
16087 information from relocatable @file{.o} files, as long as:
16091 the file's symbolic information refers only to linker symbols defined in
16092 that file, not to symbols defined by other object files,
16094 every section the file's symbolic information refers to has actually
16095 been loaded into the inferior, as it appears in the file, and
16097 you can determine the address at which every section was loaded, and
16098 provide these to the @code{add-symbol-file} command.
16102 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16103 relocatable files into an already running program; such systems
16104 typically make the requirements above easy to meet. However, it's
16105 important to recognize that many native systems use complex link
16106 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16107 assembly, for example) that make the requirements difficult to meet. In
16108 general, one cannot assume that using @code{add-symbol-file} to read a
16109 relocatable object file's symbolic information will have the same effect
16110 as linking the relocatable object file into the program in the normal
16113 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16115 @kindex add-symbol-file-from-memory
16116 @cindex @code{syscall DSO}
16117 @cindex load symbols from memory
16118 @item add-symbol-file-from-memory @var{address}
16119 Load symbols from the given @var{address} in a dynamically loaded
16120 object file whose image is mapped directly into the inferior's memory.
16121 For example, the Linux kernel maps a @code{syscall DSO} into each
16122 process's address space; this DSO provides kernel-specific code for
16123 some system calls. The argument can be any expression whose
16124 evaluation yields the address of the file's shared object file header.
16125 For this command to work, you must have used @code{symbol-file} or
16126 @code{exec-file} commands in advance.
16128 @kindex add-shared-symbol-files
16130 @item add-shared-symbol-files @var{library-file}
16131 @itemx assf @var{library-file}
16132 The @code{add-shared-symbol-files} command can currently be used only
16133 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16134 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16135 @value{GDBN} automatically looks for shared libraries, however if
16136 @value{GDBN} does not find yours, you can invoke
16137 @code{add-shared-symbol-files}. It takes one argument: the shared
16138 library's file name. @code{assf} is a shorthand alias for
16139 @code{add-shared-symbol-files}.
16142 @item section @var{section} @var{addr}
16143 The @code{section} command changes the base address of the named
16144 @var{section} of the exec file to @var{addr}. This can be used if the
16145 exec file does not contain section addresses, (such as in the
16146 @code{a.out} format), or when the addresses specified in the file
16147 itself are wrong. Each section must be changed separately. The
16148 @code{info files} command, described below, lists all the sections and
16152 @kindex info target
16155 @code{info files} and @code{info target} are synonymous; both print the
16156 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16157 including the names of the executable and core dump files currently in
16158 use by @value{GDBN}, and the files from which symbols were loaded. The
16159 command @code{help target} lists all possible targets rather than
16162 @kindex maint info sections
16163 @item maint info sections
16164 Another command that can give you extra information about program sections
16165 is @code{maint info sections}. In addition to the section information
16166 displayed by @code{info files}, this command displays the flags and file
16167 offset of each section in the executable and core dump files. In addition,
16168 @code{maint info sections} provides the following command options (which
16169 may be arbitrarily combined):
16173 Display sections for all loaded object files, including shared libraries.
16174 @item @var{sections}
16175 Display info only for named @var{sections}.
16176 @item @var{section-flags}
16177 Display info only for sections for which @var{section-flags} are true.
16178 The section flags that @value{GDBN} currently knows about are:
16181 Section will have space allocated in the process when loaded.
16182 Set for all sections except those containing debug information.
16184 Section will be loaded from the file into the child process memory.
16185 Set for pre-initialized code and data, clear for @code{.bss} sections.
16187 Section needs to be relocated before loading.
16189 Section cannot be modified by the child process.
16191 Section contains executable code only.
16193 Section contains data only (no executable code).
16195 Section will reside in ROM.
16197 Section contains data for constructor/destructor lists.
16199 Section is not empty.
16201 An instruction to the linker to not output the section.
16202 @item COFF_SHARED_LIBRARY
16203 A notification to the linker that the section contains
16204 COFF shared library information.
16206 Section contains common symbols.
16209 @kindex set trust-readonly-sections
16210 @cindex read-only sections
16211 @item set trust-readonly-sections on
16212 Tell @value{GDBN} that readonly sections in your object file
16213 really are read-only (i.e.@: that their contents will not change).
16214 In that case, @value{GDBN} can fetch values from these sections
16215 out of the object file, rather than from the target program.
16216 For some targets (notably embedded ones), this can be a significant
16217 enhancement to debugging performance.
16219 The default is off.
16221 @item set trust-readonly-sections off
16222 Tell @value{GDBN} not to trust readonly sections. This means that
16223 the contents of the section might change while the program is running,
16224 and must therefore be fetched from the target when needed.
16226 @item show trust-readonly-sections
16227 Show the current setting of trusting readonly sections.
16230 All file-specifying commands allow both absolute and relative file names
16231 as arguments. @value{GDBN} always converts the file name to an absolute file
16232 name and remembers it that way.
16234 @cindex shared libraries
16235 @anchor{Shared Libraries}
16236 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16237 and IBM RS/6000 AIX shared libraries.
16239 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16240 shared libraries. @xref{Expat}.
16242 @value{GDBN} automatically loads symbol definitions from shared libraries
16243 when you use the @code{run} command, or when you examine a core file.
16244 (Before you issue the @code{run} command, @value{GDBN} does not understand
16245 references to a function in a shared library, however---unless you are
16246 debugging a core file).
16248 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16249 automatically loads the symbols at the time of the @code{shl_load} call.
16251 @c FIXME: some @value{GDBN} release may permit some refs to undef
16252 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16253 @c FIXME...lib; check this from time to time when updating manual
16255 There are times, however, when you may wish to not automatically load
16256 symbol definitions from shared libraries, such as when they are
16257 particularly large or there are many of them.
16259 To control the automatic loading of shared library symbols, use the
16263 @kindex set auto-solib-add
16264 @item set auto-solib-add @var{mode}
16265 If @var{mode} is @code{on}, symbols from all shared object libraries
16266 will be loaded automatically when the inferior begins execution, you
16267 attach to an independently started inferior, or when the dynamic linker
16268 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16269 is @code{off}, symbols must be loaded manually, using the
16270 @code{sharedlibrary} command. The default value is @code{on}.
16272 @cindex memory used for symbol tables
16273 If your program uses lots of shared libraries with debug info that
16274 takes large amounts of memory, you can decrease the @value{GDBN}
16275 memory footprint by preventing it from automatically loading the
16276 symbols from shared libraries. To that end, type @kbd{set
16277 auto-solib-add off} before running the inferior, then load each
16278 library whose debug symbols you do need with @kbd{sharedlibrary
16279 @var{regexp}}, where @var{regexp} is a regular expression that matches
16280 the libraries whose symbols you want to be loaded.
16282 @kindex show auto-solib-add
16283 @item show auto-solib-add
16284 Display the current autoloading mode.
16287 @cindex load shared library
16288 To explicitly load shared library symbols, use the @code{sharedlibrary}
16292 @kindex info sharedlibrary
16294 @item info share @var{regex}
16295 @itemx info sharedlibrary @var{regex}
16296 Print the names of the shared libraries which are currently loaded
16297 that match @var{regex}. If @var{regex} is omitted then print
16298 all shared libraries that are loaded.
16300 @kindex sharedlibrary
16302 @item sharedlibrary @var{regex}
16303 @itemx share @var{regex}
16304 Load shared object library symbols for files matching a
16305 Unix regular expression.
16306 As with files loaded automatically, it only loads shared libraries
16307 required by your program for a core file or after typing @code{run}. If
16308 @var{regex} is omitted all shared libraries required by your program are
16311 @item nosharedlibrary
16312 @kindex nosharedlibrary
16313 @cindex unload symbols from shared libraries
16314 Unload all shared object library symbols. This discards all symbols
16315 that have been loaded from all shared libraries. Symbols from shared
16316 libraries that were loaded by explicit user requests are not
16320 Sometimes you may wish that @value{GDBN} stops and gives you control
16321 when any of shared library events happen. The best way to do this is
16322 to use @code{catch load} and @code{catch unload} (@pxref{Set
16325 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16326 command for this. This command exists for historical reasons. It is
16327 less useful than setting a catchpoint, because it does not allow for
16328 conditions or commands as a catchpoint does.
16331 @item set stop-on-solib-events
16332 @kindex set stop-on-solib-events
16333 This command controls whether @value{GDBN} should give you control
16334 when the dynamic linker notifies it about some shared library event.
16335 The most common event of interest is loading or unloading of a new
16338 @item show stop-on-solib-events
16339 @kindex show stop-on-solib-events
16340 Show whether @value{GDBN} stops and gives you control when shared
16341 library events happen.
16344 Shared libraries are also supported in many cross or remote debugging
16345 configurations. @value{GDBN} needs to have access to the target's libraries;
16346 this can be accomplished either by providing copies of the libraries
16347 on the host system, or by asking @value{GDBN} to automatically retrieve the
16348 libraries from the target. If copies of the target libraries are
16349 provided, they need to be the same as the target libraries, although the
16350 copies on the target can be stripped as long as the copies on the host are
16353 @cindex where to look for shared libraries
16354 For remote debugging, you need to tell @value{GDBN} where the target
16355 libraries are, so that it can load the correct copies---otherwise, it
16356 may try to load the host's libraries. @value{GDBN} has two variables
16357 to specify the search directories for target libraries.
16360 @cindex prefix for shared library file names
16361 @cindex system root, alternate
16362 @kindex set solib-absolute-prefix
16363 @kindex set sysroot
16364 @item set sysroot @var{path}
16365 Use @var{path} as the system root for the program being debugged. Any
16366 absolute shared library paths will be prefixed with @var{path}; many
16367 runtime loaders store the absolute paths to the shared library in the
16368 target program's memory. If you use @code{set sysroot} to find shared
16369 libraries, they need to be laid out in the same way that they are on
16370 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16373 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16374 retrieve the target libraries from the remote system. This is only
16375 supported when using a remote target that supports the @code{remote get}
16376 command (@pxref{File Transfer,,Sending files to a remote system}).
16377 The part of @var{path} following the initial @file{remote:}
16378 (if present) is used as system root prefix on the remote file system.
16379 @footnote{If you want to specify a local system root using a directory
16380 that happens to be named @file{remote:}, you need to use some equivalent
16381 variant of the name like @file{./remote:}.}
16383 For targets with an MS-DOS based filesystem, such as MS-Windows and
16384 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16385 absolute file name with @var{path}. But first, on Unix hosts,
16386 @value{GDBN} converts all backslash directory separators into forward
16387 slashes, because the backslash is not a directory separator on Unix:
16390 c:\foo\bar.dll @result{} c:/foo/bar.dll
16393 Then, @value{GDBN} attempts prefixing the target file name with
16394 @var{path}, and looks for the resulting file name in the host file
16398 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16401 If that does not find the shared library, @value{GDBN} tries removing
16402 the @samp{:} character from the drive spec, both for convenience, and,
16403 for the case of the host file system not supporting file names with
16407 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16410 This makes it possible to have a system root that mirrors a target
16411 with more than one drive. E.g., you may want to setup your local
16412 copies of the target system shared libraries like so (note @samp{c} vs
16416 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16417 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16418 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16422 and point the system root at @file{/path/to/sysroot}, so that
16423 @value{GDBN} can find the correct copies of both
16424 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16426 If that still does not find the shared library, @value{GDBN} tries
16427 removing the whole drive spec from the target file name:
16430 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16433 This last lookup makes it possible to not care about the drive name,
16434 if you don't want or need to.
16436 The @code{set solib-absolute-prefix} command is an alias for @code{set
16439 @cindex default system root
16440 @cindex @samp{--with-sysroot}
16441 You can set the default system root by using the configure-time
16442 @samp{--with-sysroot} option. If the system root is inside
16443 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16444 @samp{--exec-prefix}), then the default system root will be updated
16445 automatically if the installed @value{GDBN} is moved to a new
16448 @kindex show sysroot
16450 Display the current shared library prefix.
16452 @kindex set solib-search-path
16453 @item set solib-search-path @var{path}
16454 If this variable is set, @var{path} is a colon-separated list of
16455 directories to search for shared libraries. @samp{solib-search-path}
16456 is used after @samp{sysroot} fails to locate the library, or if the
16457 path to the library is relative instead of absolute. If you want to
16458 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16459 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16460 finding your host's libraries. @samp{sysroot} is preferred; setting
16461 it to a nonexistent directory may interfere with automatic loading
16462 of shared library symbols.
16464 @kindex show solib-search-path
16465 @item show solib-search-path
16466 Display the current shared library search path.
16468 @cindex DOS file-name semantics of file names.
16469 @kindex set target-file-system-kind (unix|dos-based|auto)
16470 @kindex show target-file-system-kind
16471 @item set target-file-system-kind @var{kind}
16472 Set assumed file system kind for target reported file names.
16474 Shared library file names as reported by the target system may not
16475 make sense as is on the system @value{GDBN} is running on. For
16476 example, when remote debugging a target that has MS-DOS based file
16477 system semantics, from a Unix host, the target may be reporting to
16478 @value{GDBN} a list of loaded shared libraries with file names such as
16479 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16480 drive letters, so the @samp{c:\} prefix is not normally understood as
16481 indicating an absolute file name, and neither is the backslash
16482 normally considered a directory separator character. In that case,
16483 the native file system would interpret this whole absolute file name
16484 as a relative file name with no directory components. This would make
16485 it impossible to point @value{GDBN} at a copy of the remote target's
16486 shared libraries on the host using @code{set sysroot}, and impractical
16487 with @code{set solib-search-path}. Setting
16488 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16489 to interpret such file names similarly to how the target would, and to
16490 map them to file names valid on @value{GDBN}'s native file system
16491 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16492 to one of the supported file system kinds. In that case, @value{GDBN}
16493 tries to determine the appropriate file system variant based on the
16494 current target's operating system (@pxref{ABI, ,Configuring the
16495 Current ABI}). The supported file system settings are:
16499 Instruct @value{GDBN} to assume the target file system is of Unix
16500 kind. Only file names starting the forward slash (@samp{/}) character
16501 are considered absolute, and the directory separator character is also
16505 Instruct @value{GDBN} to assume the target file system is DOS based.
16506 File names starting with either a forward slash, or a drive letter
16507 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16508 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16509 considered directory separators.
16512 Instruct @value{GDBN} to use the file system kind associated with the
16513 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16514 This is the default.
16518 @cindex file name canonicalization
16519 @cindex base name differences
16520 When processing file names provided by the user, @value{GDBN}
16521 frequently needs to compare them to the file names recorded in the
16522 program's debug info. Normally, @value{GDBN} compares just the
16523 @dfn{base names} of the files as strings, which is reasonably fast
16524 even for very large programs. (The base name of a file is the last
16525 portion of its name, after stripping all the leading directories.)
16526 This shortcut in comparison is based upon the assumption that files
16527 cannot have more than one base name. This is usually true, but
16528 references to files that use symlinks or similar filesystem
16529 facilities violate that assumption. If your program records files
16530 using such facilities, or if you provide file names to @value{GDBN}
16531 using symlinks etc., you can set @code{basenames-may-differ} to
16532 @code{true} to instruct @value{GDBN} to completely canonicalize each
16533 pair of file names it needs to compare. This will make file-name
16534 comparisons accurate, but at a price of a significant slowdown.
16537 @item set basenames-may-differ
16538 @kindex set basenames-may-differ
16539 Set whether a source file may have multiple base names.
16541 @item show basenames-may-differ
16542 @kindex show basenames-may-differ
16543 Show whether a source file may have multiple base names.
16546 @node Separate Debug Files
16547 @section Debugging Information in Separate Files
16548 @cindex separate debugging information files
16549 @cindex debugging information in separate files
16550 @cindex @file{.debug} subdirectories
16551 @cindex debugging information directory, global
16552 @cindex global debugging information directories
16553 @cindex build ID, and separate debugging files
16554 @cindex @file{.build-id} directory
16556 @value{GDBN} allows you to put a program's debugging information in a
16557 file separate from the executable itself, in a way that allows
16558 @value{GDBN} to find and load the debugging information automatically.
16559 Since debugging information can be very large---sometimes larger
16560 than the executable code itself---some systems distribute debugging
16561 information for their executables in separate files, which users can
16562 install only when they need to debug a problem.
16564 @value{GDBN} supports two ways of specifying the separate debug info
16569 The executable contains a @dfn{debug link} that specifies the name of
16570 the separate debug info file. The separate debug file's name is
16571 usually @file{@var{executable}.debug}, where @var{executable} is the
16572 name of the corresponding executable file without leading directories
16573 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16574 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16575 checksum for the debug file, which @value{GDBN} uses to validate that
16576 the executable and the debug file came from the same build.
16579 The executable contains a @dfn{build ID}, a unique bit string that is
16580 also present in the corresponding debug info file. (This is supported
16581 only on some operating systems, notably those which use the ELF format
16582 for binary files and the @sc{gnu} Binutils.) For more details about
16583 this feature, see the description of the @option{--build-id}
16584 command-line option in @ref{Options, , Command Line Options, ld.info,
16585 The GNU Linker}. The debug info file's name is not specified
16586 explicitly by the build ID, but can be computed from the build ID, see
16590 Depending on the way the debug info file is specified, @value{GDBN}
16591 uses two different methods of looking for the debug file:
16595 For the ``debug link'' method, @value{GDBN} looks up the named file in
16596 the directory of the executable file, then in a subdirectory of that
16597 directory named @file{.debug}, and finally under each one of the global debug
16598 directories, in a subdirectory whose name is identical to the leading
16599 directories of the executable's absolute file name.
16602 For the ``build ID'' method, @value{GDBN} looks in the
16603 @file{.build-id} subdirectory of each one of the global debug directories for
16604 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16605 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16606 are the rest of the bit string. (Real build ID strings are 32 or more
16607 hex characters, not 10.)
16610 So, for example, suppose you ask @value{GDBN} to debug
16611 @file{/usr/bin/ls}, which has a debug link that specifies the
16612 file @file{ls.debug}, and a build ID whose value in hex is
16613 @code{abcdef1234}. If the list of the global debug directories includes
16614 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16615 debug information files, in the indicated order:
16619 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16621 @file{/usr/bin/ls.debug}
16623 @file{/usr/bin/.debug/ls.debug}
16625 @file{/usr/lib/debug/usr/bin/ls.debug}.
16628 @anchor{debug-file-directory}
16629 Global debugging info directories default to what is set by @value{GDBN}
16630 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16631 you can also set the global debugging info directories, and view the list
16632 @value{GDBN} is currently using.
16636 @kindex set debug-file-directory
16637 @item set debug-file-directory @var{directories}
16638 Set the directories which @value{GDBN} searches for separate debugging
16639 information files to @var{directory}. Multiple path components can be set
16640 concatenating them by a path separator.
16642 @kindex show debug-file-directory
16643 @item show debug-file-directory
16644 Show the directories @value{GDBN} searches for separate debugging
16649 @cindex @code{.gnu_debuglink} sections
16650 @cindex debug link sections
16651 A debug link is a special section of the executable file named
16652 @code{.gnu_debuglink}. The section must contain:
16656 A filename, with any leading directory components removed, followed by
16659 zero to three bytes of padding, as needed to reach the next four-byte
16660 boundary within the section, and
16662 a four-byte CRC checksum, stored in the same endianness used for the
16663 executable file itself. The checksum is computed on the debugging
16664 information file's full contents by the function given below, passing
16665 zero as the @var{crc} argument.
16668 Any executable file format can carry a debug link, as long as it can
16669 contain a section named @code{.gnu_debuglink} with the contents
16672 @cindex @code{.note.gnu.build-id} sections
16673 @cindex build ID sections
16674 The build ID is a special section in the executable file (and in other
16675 ELF binary files that @value{GDBN} may consider). This section is
16676 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16677 It contains unique identification for the built files---the ID remains
16678 the same across multiple builds of the same build tree. The default
16679 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16680 content for the build ID string. The same section with an identical
16681 value is present in the original built binary with symbols, in its
16682 stripped variant, and in the separate debugging information file.
16684 The debugging information file itself should be an ordinary
16685 executable, containing a full set of linker symbols, sections, and
16686 debugging information. The sections of the debugging information file
16687 should have the same names, addresses, and sizes as the original file,
16688 but they need not contain any data---much like a @code{.bss} section
16689 in an ordinary executable.
16691 The @sc{gnu} binary utilities (Binutils) package includes the
16692 @samp{objcopy} utility that can produce
16693 the separated executable / debugging information file pairs using the
16694 following commands:
16697 @kbd{objcopy --only-keep-debug foo foo.debug}
16702 These commands remove the debugging
16703 information from the executable file @file{foo} and place it in the file
16704 @file{foo.debug}. You can use the first, second or both methods to link the
16709 The debug link method needs the following additional command to also leave
16710 behind a debug link in @file{foo}:
16713 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16716 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16717 a version of the @code{strip} command such that the command @kbd{strip foo -f
16718 foo.debug} has the same functionality as the two @code{objcopy} commands and
16719 the @code{ln -s} command above, together.
16722 Build ID gets embedded into the main executable using @code{ld --build-id} or
16723 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16724 compatibility fixes for debug files separation are present in @sc{gnu} binary
16725 utilities (Binutils) package since version 2.18.
16730 @cindex CRC algorithm definition
16731 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16732 IEEE 802.3 using the polynomial:
16734 @c TexInfo requires naked braces for multi-digit exponents for Tex
16735 @c output, but this causes HTML output to barf. HTML has to be set using
16736 @c raw commands. So we end up having to specify this equation in 2
16741 <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>
16742 + <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
16748 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16749 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16753 The function is computed byte at a time, taking the least
16754 significant bit of each byte first. The initial pattern
16755 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16756 the final result is inverted to ensure trailing zeros also affect the
16759 @emph{Note:} This is the same CRC polynomial as used in handling the
16760 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16761 , @value{GDBN} Remote Serial Protocol}). However in the
16762 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16763 significant bit first, and the result is not inverted, so trailing
16764 zeros have no effect on the CRC value.
16766 To complete the description, we show below the code of the function
16767 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16768 initially supplied @code{crc} argument means that an initial call to
16769 this function passing in zero will start computing the CRC using
16772 @kindex gnu_debuglink_crc32
16775 gnu_debuglink_crc32 (unsigned long crc,
16776 unsigned char *buf, size_t len)
16778 static const unsigned long crc32_table[256] =
16780 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16781 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16782 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16783 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16784 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16785 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16786 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16787 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16788 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16789 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16790 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16791 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16792 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16793 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16794 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16795 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16796 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16797 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16798 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16799 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16800 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16801 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16802 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16803 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16804 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16805 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16806 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16807 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16808 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16809 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16810 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16811 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16812 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16813 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16814 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16815 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16816 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16817 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16818 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16819 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16820 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16821 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16822 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16823 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16824 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16825 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16826 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16827 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16828 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16829 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16830 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16833 unsigned char *end;
16835 crc = ~crc & 0xffffffff;
16836 for (end = buf + len; buf < end; ++buf)
16837 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16838 return ~crc & 0xffffffff;
16843 This computation does not apply to the ``build ID'' method.
16845 @node MiniDebugInfo
16846 @section Debugging information in a special section
16847 @cindex separate debug sections
16848 @cindex @samp{.gnu_debugdata} section
16850 Some systems ship pre-built executables and libraries that have a
16851 special @samp{.gnu_debugdata} section. This feature is called
16852 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
16853 is used to supply extra symbols for backtraces.
16855 The intent of this section is to provide extra minimal debugging
16856 information for use in simple backtraces. It is not intended to be a
16857 replacement for full separate debugging information (@pxref{Separate
16858 Debug Files}). The example below shows the intended use; however,
16859 @value{GDBN} does not currently put restrictions on what sort of
16860 debugging information might be included in the section.
16862 @value{GDBN} has support for this extension. If the section exists,
16863 then it is used provided that no other source of debugging information
16864 can be found, and that @value{GDBN} was configured with LZMA support.
16866 This section can be easily created using @command{objcopy} and other
16867 standard utilities:
16870 # Extract the dynamic symbols from the main binary, there is no need
16871 # to also have these in the normal symbol table
16872 nm -D @var{binary} --format=posix --defined-only \
16873 | awk '@{ print $1 @}' | sort > dynsyms
16875 # Extract all the text (i.e. function) symbols from the debuginfo .
16876 nm @var{binary} --format=posix --defined-only \
16877 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
16880 # Keep all the function symbols not already in the dynamic symbol
16882 comm -13 dynsyms funcsyms > keep_symbols
16884 # Copy the full debuginfo, keeping only a minimal set of symbols and
16885 # removing some unnecessary sections.
16886 objcopy -S --remove-section .gdb_index --remove-section .comment \
16887 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
16889 # Inject the compressed data into the .gnu_debugdata section of the
16892 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
16896 @section Index Files Speed Up @value{GDBN}
16897 @cindex index files
16898 @cindex @samp{.gdb_index} section
16900 When @value{GDBN} finds a symbol file, it scans the symbols in the
16901 file in order to construct an internal symbol table. This lets most
16902 @value{GDBN} operations work quickly---at the cost of a delay early
16903 on. For large programs, this delay can be quite lengthy, so
16904 @value{GDBN} provides a way to build an index, which speeds up
16907 The index is stored as a section in the symbol file. @value{GDBN} can
16908 write the index to a file, then you can put it into the symbol file
16909 using @command{objcopy}.
16911 To create an index file, use the @code{save gdb-index} command:
16914 @item save gdb-index @var{directory}
16915 @kindex save gdb-index
16916 Create an index file for each symbol file currently known by
16917 @value{GDBN}. Each file is named after its corresponding symbol file,
16918 with @samp{.gdb-index} appended, and is written into the given
16922 Once you have created an index file you can merge it into your symbol
16923 file, here named @file{symfile}, using @command{objcopy}:
16926 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16927 --set-section-flags .gdb_index=readonly symfile symfile
16930 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
16931 sections that have been deprecated. Usually they are deprecated because
16932 they are missing a new feature or have performance issues.
16933 To tell @value{GDBN} to use a deprecated index section anyway
16934 specify @code{set use-deprecated-index-sections on}.
16935 The default is @code{off}.
16936 This can speed up startup, but may result in some functionality being lost.
16937 @xref{Index Section Format}.
16939 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
16940 must be done before gdb reads the file. The following will not work:
16943 $ gdb -ex "set use-deprecated-index-sections on" <program>
16946 Instead you must do, for example,
16949 $ gdb -iex "set use-deprecated-index-sections on" <program>
16952 There are currently some limitation on indices. They only work when
16953 for DWARF debugging information, not stabs. And, they do not
16954 currently work for programs using Ada.
16956 @node Symbol Errors
16957 @section Errors Reading Symbol Files
16959 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16960 such as symbol types it does not recognize, or known bugs in compiler
16961 output. By default, @value{GDBN} does not notify you of such problems, since
16962 they are relatively common and primarily of interest to people
16963 debugging compilers. If you are interested in seeing information
16964 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16965 only one message about each such type of problem, no matter how many
16966 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16967 to see how many times the problems occur, with the @code{set
16968 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16971 The messages currently printed, and their meanings, include:
16974 @item inner block not inside outer block in @var{symbol}
16976 The symbol information shows where symbol scopes begin and end
16977 (such as at the start of a function or a block of statements). This
16978 error indicates that an inner scope block is not fully contained
16979 in its outer scope blocks.
16981 @value{GDBN} circumvents the problem by treating the inner block as if it had
16982 the same scope as the outer block. In the error message, @var{symbol}
16983 may be shown as ``@code{(don't know)}'' if the outer block is not a
16986 @item block at @var{address} out of order
16988 The symbol information for symbol scope blocks should occur in
16989 order of increasing addresses. This error indicates that it does not
16992 @value{GDBN} does not circumvent this problem, and has trouble
16993 locating symbols in the source file whose symbols it is reading. (You
16994 can often determine what source file is affected by specifying
16995 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16998 @item bad block start address patched
17000 The symbol information for a symbol scope block has a start address
17001 smaller than the address of the preceding source line. This is known
17002 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17004 @value{GDBN} circumvents the problem by treating the symbol scope block as
17005 starting on the previous source line.
17007 @item bad string table offset in symbol @var{n}
17010 Symbol number @var{n} contains a pointer into the string table which is
17011 larger than the size of the string table.
17013 @value{GDBN} circumvents the problem by considering the symbol to have the
17014 name @code{foo}, which may cause other problems if many symbols end up
17017 @item unknown symbol type @code{0x@var{nn}}
17019 The symbol information contains new data types that @value{GDBN} does
17020 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17021 uncomprehended information, in hexadecimal.
17023 @value{GDBN} circumvents the error by ignoring this symbol information.
17024 This usually allows you to debug your program, though certain symbols
17025 are not accessible. If you encounter such a problem and feel like
17026 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17027 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17028 and examine @code{*bufp} to see the symbol.
17030 @item stub type has NULL name
17032 @value{GDBN} could not find the full definition for a struct or class.
17034 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17035 The symbol information for a C@t{++} member function is missing some
17036 information that recent versions of the compiler should have output for
17039 @item info mismatch between compiler and debugger
17041 @value{GDBN} could not parse a type specification output by the compiler.
17046 @section GDB Data Files
17048 @cindex prefix for data files
17049 @value{GDBN} will sometimes read an auxiliary data file. These files
17050 are kept in a directory known as the @dfn{data directory}.
17052 You can set the data directory's name, and view the name @value{GDBN}
17053 is currently using.
17056 @kindex set data-directory
17057 @item set data-directory @var{directory}
17058 Set the directory which @value{GDBN} searches for auxiliary data files
17059 to @var{directory}.
17061 @kindex show data-directory
17062 @item show data-directory
17063 Show the directory @value{GDBN} searches for auxiliary data files.
17066 @cindex default data directory
17067 @cindex @samp{--with-gdb-datadir}
17068 You can set the default data directory by using the configure-time
17069 @samp{--with-gdb-datadir} option. If the data directory is inside
17070 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17071 @samp{--exec-prefix}), then the default data directory will be updated
17072 automatically if the installed @value{GDBN} is moved to a new
17075 The data directory may also be specified with the
17076 @code{--data-directory} command line option.
17077 @xref{Mode Options}.
17080 @chapter Specifying a Debugging Target
17082 @cindex debugging target
17083 A @dfn{target} is the execution environment occupied by your program.
17085 Often, @value{GDBN} runs in the same host environment as your program;
17086 in that case, the debugging target is specified as a side effect when
17087 you use the @code{file} or @code{core} commands. When you need more
17088 flexibility---for example, running @value{GDBN} on a physically separate
17089 host, or controlling a standalone system over a serial port or a
17090 realtime system over a TCP/IP connection---you can use the @code{target}
17091 command to specify one of the target types configured for @value{GDBN}
17092 (@pxref{Target Commands, ,Commands for Managing Targets}).
17094 @cindex target architecture
17095 It is possible to build @value{GDBN} for several different @dfn{target
17096 architectures}. When @value{GDBN} is built like that, you can choose
17097 one of the available architectures with the @kbd{set architecture}
17101 @kindex set architecture
17102 @kindex show architecture
17103 @item set architecture @var{arch}
17104 This command sets the current target architecture to @var{arch}. The
17105 value of @var{arch} can be @code{"auto"}, in addition to one of the
17106 supported architectures.
17108 @item show architecture
17109 Show the current target architecture.
17111 @item set processor
17113 @kindex set processor
17114 @kindex show processor
17115 These are alias commands for, respectively, @code{set architecture}
17116 and @code{show architecture}.
17120 * Active Targets:: Active targets
17121 * Target Commands:: Commands for managing targets
17122 * Byte Order:: Choosing target byte order
17125 @node Active Targets
17126 @section Active Targets
17128 @cindex stacking targets
17129 @cindex active targets
17130 @cindex multiple targets
17132 There are multiple classes of targets such as: processes, executable files or
17133 recording sessions. Core files belong to the process class, making core file
17134 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17135 on multiple active targets, one in each class. This allows you to (for
17136 example) start a process and inspect its activity, while still having access to
17137 the executable file after the process finishes. Or if you start process
17138 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17139 presented a virtual layer of the recording target, while the process target
17140 remains stopped at the chronologically last point of the process execution.
17142 Use the @code{core-file} and @code{exec-file} commands to select a new core
17143 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17144 specify as a target a process that is already running, use the @code{attach}
17145 command (@pxref{Attach, ,Debugging an Already-running Process}).
17147 @node Target Commands
17148 @section Commands for Managing Targets
17151 @item target @var{type} @var{parameters}
17152 Connects the @value{GDBN} host environment to a target machine or
17153 process. A target is typically a protocol for talking to debugging
17154 facilities. You use the argument @var{type} to specify the type or
17155 protocol of the target machine.
17157 Further @var{parameters} are interpreted by the target protocol, but
17158 typically include things like device names or host names to connect
17159 with, process numbers, and baud rates.
17161 The @code{target} command does not repeat if you press @key{RET} again
17162 after executing the command.
17164 @kindex help target
17166 Displays the names of all targets available. To display targets
17167 currently selected, use either @code{info target} or @code{info files}
17168 (@pxref{Files, ,Commands to Specify Files}).
17170 @item help target @var{name}
17171 Describe a particular target, including any parameters necessary to
17174 @kindex set gnutarget
17175 @item set gnutarget @var{args}
17176 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17177 knows whether it is reading an @dfn{executable},
17178 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17179 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17180 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17183 @emph{Warning:} To specify a file format with @code{set gnutarget},
17184 you must know the actual BFD name.
17188 @xref{Files, , Commands to Specify Files}.
17190 @kindex show gnutarget
17191 @item show gnutarget
17192 Use the @code{show gnutarget} command to display what file format
17193 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17194 @value{GDBN} will determine the file format for each file automatically,
17195 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17198 @cindex common targets
17199 Here are some common targets (available, or not, depending on the GDB
17204 @item target exec @var{program}
17205 @cindex executable file target
17206 An executable file. @samp{target exec @var{program}} is the same as
17207 @samp{exec-file @var{program}}.
17209 @item target core @var{filename}
17210 @cindex core dump file target
17211 A core dump file. @samp{target core @var{filename}} is the same as
17212 @samp{core-file @var{filename}}.
17214 @item target remote @var{medium}
17215 @cindex remote target
17216 A remote system connected to @value{GDBN} via a serial line or network
17217 connection. This command tells @value{GDBN} to use its own remote
17218 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17220 For example, if you have a board connected to @file{/dev/ttya} on the
17221 machine running @value{GDBN}, you could say:
17224 target remote /dev/ttya
17227 @code{target remote} supports the @code{load} command. This is only
17228 useful if you have some other way of getting the stub to the target
17229 system, and you can put it somewhere in memory where it won't get
17230 clobbered by the download.
17232 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17233 @cindex built-in simulator target
17234 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17242 works; however, you cannot assume that a specific memory map, device
17243 drivers, or even basic I/O is available, although some simulators do
17244 provide these. For info about any processor-specific simulator details,
17245 see the appropriate section in @ref{Embedded Processors, ,Embedded
17250 Some configurations may include these targets as well:
17254 @item target nrom @var{dev}
17255 @cindex NetROM ROM emulator target
17256 NetROM ROM emulator. This target only supports downloading.
17260 Different targets are available on different configurations of @value{GDBN};
17261 your configuration may have more or fewer targets.
17263 Many remote targets require you to download the executable's code once
17264 you've successfully established a connection. You may wish to control
17265 various aspects of this process.
17270 @kindex set hash@r{, for remote monitors}
17271 @cindex hash mark while downloading
17272 This command controls whether a hash mark @samp{#} is displayed while
17273 downloading a file to the remote monitor. If on, a hash mark is
17274 displayed after each S-record is successfully downloaded to the
17278 @kindex show hash@r{, for remote monitors}
17279 Show the current status of displaying the hash mark.
17281 @item set debug monitor
17282 @kindex set debug monitor
17283 @cindex display remote monitor communications
17284 Enable or disable display of communications messages between
17285 @value{GDBN} and the remote monitor.
17287 @item show debug monitor
17288 @kindex show debug monitor
17289 Show the current status of displaying communications between
17290 @value{GDBN} and the remote monitor.
17295 @kindex load @var{filename}
17296 @item load @var{filename}
17298 Depending on what remote debugging facilities are configured into
17299 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17300 is meant to make @var{filename} (an executable) available for debugging
17301 on the remote system---by downloading, or dynamic linking, for example.
17302 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17303 the @code{add-symbol-file} command.
17305 If your @value{GDBN} does not have a @code{load} command, attempting to
17306 execute it gets the error message ``@code{You can't do that when your
17307 target is @dots{}}''
17309 The file is loaded at whatever address is specified in the executable.
17310 For some object file formats, you can specify the load address when you
17311 link the program; for other formats, like a.out, the object file format
17312 specifies a fixed address.
17313 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17315 Depending on the remote side capabilities, @value{GDBN} may be able to
17316 load programs into flash memory.
17318 @code{load} does not repeat if you press @key{RET} again after using it.
17322 @section Choosing Target Byte Order
17324 @cindex choosing target byte order
17325 @cindex target byte order
17327 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17328 offer the ability to run either big-endian or little-endian byte
17329 orders. Usually the executable or symbol will include a bit to
17330 designate the endian-ness, and you will not need to worry about
17331 which to use. However, you may still find it useful to adjust
17332 @value{GDBN}'s idea of processor endian-ness manually.
17336 @item set endian big
17337 Instruct @value{GDBN} to assume the target is big-endian.
17339 @item set endian little
17340 Instruct @value{GDBN} to assume the target is little-endian.
17342 @item set endian auto
17343 Instruct @value{GDBN} to use the byte order associated with the
17347 Display @value{GDBN}'s current idea of the target byte order.
17351 Note that these commands merely adjust interpretation of symbolic
17352 data on the host, and that they have absolutely no effect on the
17356 @node Remote Debugging
17357 @chapter Debugging Remote Programs
17358 @cindex remote debugging
17360 If you are trying to debug a program running on a machine that cannot run
17361 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17362 For example, you might use remote debugging on an operating system kernel,
17363 or on a small system which does not have a general purpose operating system
17364 powerful enough to run a full-featured debugger.
17366 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17367 to make this work with particular debugging targets. In addition,
17368 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17369 but not specific to any particular target system) which you can use if you
17370 write the remote stubs---the code that runs on the remote system to
17371 communicate with @value{GDBN}.
17373 Other remote targets may be available in your
17374 configuration of @value{GDBN}; use @code{help target} to list them.
17377 * Connecting:: Connecting to a remote target
17378 * File Transfer:: Sending files to a remote system
17379 * Server:: Using the gdbserver program
17380 * Remote Configuration:: Remote configuration
17381 * Remote Stub:: Implementing a remote stub
17385 @section Connecting to a Remote Target
17387 On the @value{GDBN} host machine, you will need an unstripped copy of
17388 your program, since @value{GDBN} needs symbol and debugging information.
17389 Start up @value{GDBN} as usual, using the name of the local copy of your
17390 program as the first argument.
17392 @cindex @code{target remote}
17393 @value{GDBN} can communicate with the target over a serial line, or
17394 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17395 each case, @value{GDBN} uses the same protocol for debugging your
17396 program; only the medium carrying the debugging packets varies. The
17397 @code{target remote} command establishes a connection to the target.
17398 Its arguments indicate which medium to use:
17402 @item target remote @var{serial-device}
17403 @cindex serial line, @code{target remote}
17404 Use @var{serial-device} to communicate with the target. For example,
17405 to use a serial line connected to the device named @file{/dev/ttyb}:
17408 target remote /dev/ttyb
17411 If you're using a serial line, you may want to give @value{GDBN} the
17412 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17413 (@pxref{Remote Configuration, set remotebaud}) before the
17414 @code{target} command.
17416 @item target remote @code{@var{host}:@var{port}}
17417 @itemx target remote @code{tcp:@var{host}:@var{port}}
17418 @cindex @acronym{TCP} port, @code{target remote}
17419 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17420 The @var{host} may be either a host name or a numeric @acronym{IP}
17421 address; @var{port} must be a decimal number. The @var{host} could be
17422 the target machine itself, if it is directly connected to the net, or
17423 it might be a terminal server which in turn has a serial line to the
17426 For example, to connect to port 2828 on a terminal server named
17430 target remote manyfarms:2828
17433 If your remote target is actually running on the same machine as your
17434 debugger session (e.g.@: a simulator for your target running on the
17435 same host), you can omit the hostname. For example, to connect to
17436 port 1234 on your local machine:
17439 target remote :1234
17443 Note that the colon is still required here.
17445 @item target remote @code{udp:@var{host}:@var{port}}
17446 @cindex @acronym{UDP} port, @code{target remote}
17447 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17448 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17451 target remote udp:manyfarms:2828
17454 When using a @acronym{UDP} connection for remote debugging, you should
17455 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17456 can silently drop packets on busy or unreliable networks, which will
17457 cause havoc with your debugging session.
17459 @item target remote | @var{command}
17460 @cindex pipe, @code{target remote} to
17461 Run @var{command} in the background and communicate with it using a
17462 pipe. The @var{command} is a shell command, to be parsed and expanded
17463 by the system's command shell, @code{/bin/sh}; it should expect remote
17464 protocol packets on its standard input, and send replies on its
17465 standard output. You could use this to run a stand-alone simulator
17466 that speaks the remote debugging protocol, to make net connections
17467 using programs like @code{ssh}, or for other similar tricks.
17469 If @var{command} closes its standard output (perhaps by exiting),
17470 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17471 program has already exited, this will have no effect.)
17475 Once the connection has been established, you can use all the usual
17476 commands to examine and change data. The remote program is already
17477 running; you can use @kbd{step} and @kbd{continue}, and you do not
17478 need to use @kbd{run}.
17480 @cindex interrupting remote programs
17481 @cindex remote programs, interrupting
17482 Whenever @value{GDBN} is waiting for the remote program, if you type the
17483 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17484 program. This may or may not succeed, depending in part on the hardware
17485 and the serial drivers the remote system uses. If you type the
17486 interrupt character once again, @value{GDBN} displays this prompt:
17489 Interrupted while waiting for the program.
17490 Give up (and stop debugging it)? (y or n)
17493 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17494 (If you decide you want to try again later, you can use @samp{target
17495 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17496 goes back to waiting.
17499 @kindex detach (remote)
17501 When you have finished debugging the remote program, you can use the
17502 @code{detach} command to release it from @value{GDBN} control.
17503 Detaching from the target normally resumes its execution, but the results
17504 will depend on your particular remote stub. After the @code{detach}
17505 command, @value{GDBN} is free to connect to another target.
17509 The @code{disconnect} command behaves like @code{detach}, except that
17510 the target is generally not resumed. It will wait for @value{GDBN}
17511 (this instance or another one) to connect and continue debugging. After
17512 the @code{disconnect} command, @value{GDBN} is again free to connect to
17515 @cindex send command to remote monitor
17516 @cindex extend @value{GDBN} for remote targets
17517 @cindex add new commands for external monitor
17519 @item monitor @var{cmd}
17520 This command allows you to send arbitrary commands directly to the
17521 remote monitor. Since @value{GDBN} doesn't care about the commands it
17522 sends like this, this command is the way to extend @value{GDBN}---you
17523 can add new commands that only the external monitor will understand
17527 @node File Transfer
17528 @section Sending files to a remote system
17529 @cindex remote target, file transfer
17530 @cindex file transfer
17531 @cindex sending files to remote systems
17533 Some remote targets offer the ability to transfer files over the same
17534 connection used to communicate with @value{GDBN}. This is convenient
17535 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17536 running @code{gdbserver} over a network interface. For other targets,
17537 e.g.@: embedded devices with only a single serial port, this may be
17538 the only way to upload or download files.
17540 Not all remote targets support these commands.
17544 @item remote put @var{hostfile} @var{targetfile}
17545 Copy file @var{hostfile} from the host system (the machine running
17546 @value{GDBN}) to @var{targetfile} on the target system.
17549 @item remote get @var{targetfile} @var{hostfile}
17550 Copy file @var{targetfile} from the target system to @var{hostfile}
17551 on the host system.
17553 @kindex remote delete
17554 @item remote delete @var{targetfile}
17555 Delete @var{targetfile} from the target system.
17560 @section Using the @code{gdbserver} Program
17563 @cindex remote connection without stubs
17564 @code{gdbserver} is a control program for Unix-like systems, which
17565 allows you to connect your program with a remote @value{GDBN} via
17566 @code{target remote}---but without linking in the usual debugging stub.
17568 @code{gdbserver} is not a complete replacement for the debugging stubs,
17569 because it requires essentially the same operating-system facilities
17570 that @value{GDBN} itself does. In fact, a system that can run
17571 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17572 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17573 because it is a much smaller program than @value{GDBN} itself. It is
17574 also easier to port than all of @value{GDBN}, so you may be able to get
17575 started more quickly on a new system by using @code{gdbserver}.
17576 Finally, if you develop code for real-time systems, you may find that
17577 the tradeoffs involved in real-time operation make it more convenient to
17578 do as much development work as possible on another system, for example
17579 by cross-compiling. You can use @code{gdbserver} to make a similar
17580 choice for debugging.
17582 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17583 or a TCP connection, using the standard @value{GDBN} remote serial
17587 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17588 Do not run @code{gdbserver} connected to any public network; a
17589 @value{GDBN} connection to @code{gdbserver} provides access to the
17590 target system with the same privileges as the user running
17594 @subsection Running @code{gdbserver}
17595 @cindex arguments, to @code{gdbserver}
17596 @cindex @code{gdbserver}, command-line arguments
17598 Run @code{gdbserver} on the target system. You need a copy of the
17599 program you want to debug, including any libraries it requires.
17600 @code{gdbserver} does not need your program's symbol table, so you can
17601 strip the program if necessary to save space. @value{GDBN} on the host
17602 system does all the symbol handling.
17604 To use the server, you must tell it how to communicate with @value{GDBN};
17605 the name of your program; and the arguments for your program. The usual
17609 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17612 @var{comm} is either a device name (to use a serial line), or a TCP
17613 hostname and portnumber, or @code{-} or @code{stdio} to use
17614 stdin/stdout of @code{gdbserver}.
17615 For example, to debug Emacs with the argument
17616 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17620 target> gdbserver /dev/com1 emacs foo.txt
17623 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17626 To use a TCP connection instead of a serial line:
17629 target> gdbserver host:2345 emacs foo.txt
17632 The only difference from the previous example is the first argument,
17633 specifying that you are communicating with the host @value{GDBN} via
17634 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17635 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17636 (Currently, the @samp{host} part is ignored.) You can choose any number
17637 you want for the port number as long as it does not conflict with any
17638 TCP ports already in use on the target system (for example, @code{23} is
17639 reserved for @code{telnet}).@footnote{If you choose a port number that
17640 conflicts with another service, @code{gdbserver} prints an error message
17641 and exits.} You must use the same port number with the host @value{GDBN}
17642 @code{target remote} command.
17644 The @code{stdio} connection is useful when starting @code{gdbserver}
17648 (gdb) target remote | ssh -T hostname gdbserver - hello
17651 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17652 and we don't want escape-character handling. Ssh does this by default when
17653 a command is provided, the flag is provided to make it explicit.
17654 You could elide it if you want to.
17656 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17657 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17658 display through a pipe connected to gdbserver.
17659 Both @code{stdout} and @code{stderr} use the same pipe.
17661 @subsubsection Attaching to a Running Program
17662 @cindex attach to a program, @code{gdbserver}
17663 @cindex @option{--attach}, @code{gdbserver} option
17665 On some targets, @code{gdbserver} can also attach to running programs.
17666 This is accomplished via the @code{--attach} argument. The syntax is:
17669 target> gdbserver --attach @var{comm} @var{pid}
17672 @var{pid} is the process ID of a currently running process. It isn't necessary
17673 to point @code{gdbserver} at a binary for the running process.
17676 You can debug processes by name instead of process ID if your target has the
17677 @code{pidof} utility:
17680 target> gdbserver --attach @var{comm} `pidof @var{program}`
17683 In case more than one copy of @var{program} is running, or @var{program}
17684 has multiple threads, most versions of @code{pidof} support the
17685 @code{-s} option to only return the first process ID.
17687 @subsubsection Multi-Process Mode for @code{gdbserver}
17688 @cindex @code{gdbserver}, multiple processes
17689 @cindex multiple processes with @code{gdbserver}
17691 When you connect to @code{gdbserver} using @code{target remote},
17692 @code{gdbserver} debugs the specified program only once. When the
17693 program exits, or you detach from it, @value{GDBN} closes the connection
17694 and @code{gdbserver} exits.
17696 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17697 enters multi-process mode. When the debugged program exits, or you
17698 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17699 though no program is running. The @code{run} and @code{attach}
17700 commands instruct @code{gdbserver} to run or attach to a new program.
17701 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17702 remote exec-file}) to select the program to run. Command line
17703 arguments are supported, except for wildcard expansion and I/O
17704 redirection (@pxref{Arguments}).
17706 @cindex @option{--multi}, @code{gdbserver} option
17707 To start @code{gdbserver} without supplying an initial command to run
17708 or process ID to attach, use the @option{--multi} command line option.
17709 Then you can connect using @kbd{target extended-remote} and start
17710 the program you want to debug.
17712 In multi-process mode @code{gdbserver} does not automatically exit unless you
17713 use the option @option{--once}. You can terminate it by using
17714 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17715 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17716 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17717 @option{--multi} option to @code{gdbserver} has no influence on that.
17719 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17721 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17723 @code{gdbserver} normally terminates after all of its debugged processes have
17724 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17725 extended-remote}, @code{gdbserver} stays running even with no processes left.
17726 @value{GDBN} normally terminates the spawned debugged process on its exit,
17727 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17728 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17729 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17730 stays running even in the @kbd{target remote} mode.
17732 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17733 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17734 completeness, at most one @value{GDBN} can be connected at a time.
17736 @cindex @option{--once}, @code{gdbserver} option
17737 By default, @code{gdbserver} keeps the listening TCP port open, so that
17738 additional connections are possible. However, if you start @code{gdbserver}
17739 with the @option{--once} option, it will stop listening for any further
17740 connection attempts after connecting to the first @value{GDBN} session. This
17741 means no further connections to @code{gdbserver} will be possible after the
17742 first one. It also means @code{gdbserver} will terminate after the first
17743 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17744 connections and even in the @kbd{target extended-remote} mode. The
17745 @option{--once} option allows reusing the same port number for connecting to
17746 multiple instances of @code{gdbserver} running on the same host, since each
17747 instance closes its port after the first connection.
17749 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17751 @cindex @option{--debug}, @code{gdbserver} option
17752 The @option{--debug} option tells @code{gdbserver} to display extra
17753 status information about the debugging process.
17754 @cindex @option{--remote-debug}, @code{gdbserver} option
17755 The @option{--remote-debug} option tells @code{gdbserver} to display
17756 remote protocol debug output. These options are intended for
17757 @code{gdbserver} development and for bug reports to the developers.
17759 @cindex @option{--wrapper}, @code{gdbserver} option
17760 The @option{--wrapper} option specifies a wrapper to launch programs
17761 for debugging. The option should be followed by the name of the
17762 wrapper, then any command-line arguments to pass to the wrapper, then
17763 @kbd{--} indicating the end of the wrapper arguments.
17765 @code{gdbserver} runs the specified wrapper program with a combined
17766 command line including the wrapper arguments, then the name of the
17767 program to debug, then any arguments to the program. The wrapper
17768 runs until it executes your program, and then @value{GDBN} gains control.
17770 You can use any program that eventually calls @code{execve} with
17771 its arguments as a wrapper. Several standard Unix utilities do
17772 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17773 with @code{exec "$@@"} will also work.
17775 For example, you can use @code{env} to pass an environment variable to
17776 the debugged program, without setting the variable in @code{gdbserver}'s
17780 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17783 @subsection Connecting to @code{gdbserver}
17785 Run @value{GDBN} on the host system.
17787 First make sure you have the necessary symbol files. Load symbols for
17788 your application using the @code{file} command before you connect. Use
17789 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17790 was compiled with the correct sysroot using @code{--with-sysroot}).
17792 The symbol file and target libraries must exactly match the executable
17793 and libraries on the target, with one exception: the files on the host
17794 system should not be stripped, even if the files on the target system
17795 are. Mismatched or missing files will lead to confusing results
17796 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17797 files may also prevent @code{gdbserver} from debugging multi-threaded
17800 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17801 For TCP connections, you must start up @code{gdbserver} prior to using
17802 the @code{target remote} command. Otherwise you may get an error whose
17803 text depends on the host system, but which usually looks something like
17804 @samp{Connection refused}. Don't use the @code{load}
17805 command in @value{GDBN} when using @code{gdbserver}, since the program is
17806 already on the target.
17808 @subsection Monitor Commands for @code{gdbserver}
17809 @cindex monitor commands, for @code{gdbserver}
17810 @anchor{Monitor Commands for gdbserver}
17812 During a @value{GDBN} session using @code{gdbserver}, you can use the
17813 @code{monitor} command to send special requests to @code{gdbserver}.
17814 Here are the available commands.
17818 List the available monitor commands.
17820 @item monitor set debug 0
17821 @itemx monitor set debug 1
17822 Disable or enable general debugging messages.
17824 @item monitor set remote-debug 0
17825 @itemx monitor set remote-debug 1
17826 Disable or enable specific debugging messages associated with the remote
17827 protocol (@pxref{Remote Protocol}).
17829 @item monitor set libthread-db-search-path [PATH]
17830 @cindex gdbserver, search path for @code{libthread_db}
17831 When this command is issued, @var{path} is a colon-separated list of
17832 directories to search for @code{libthread_db} (@pxref{Threads,,set
17833 libthread-db-search-path}). If you omit @var{path},
17834 @samp{libthread-db-search-path} will be reset to its default value.
17836 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17837 not supported in @code{gdbserver}.
17840 Tell gdbserver to exit immediately. This command should be followed by
17841 @code{disconnect} to close the debugging session. @code{gdbserver} will
17842 detach from any attached processes and kill any processes it created.
17843 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17844 of a multi-process mode debug session.
17848 @subsection Tracepoints support in @code{gdbserver}
17849 @cindex tracepoints support in @code{gdbserver}
17851 On some targets, @code{gdbserver} supports tracepoints, fast
17852 tracepoints and static tracepoints.
17854 For fast or static tracepoints to work, a special library called the
17855 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17856 This library is built and distributed as an integral part of
17857 @code{gdbserver}. In addition, support for static tracepoints
17858 requires building the in-process agent library with static tracepoints
17859 support. At present, the UST (LTTng Userspace Tracer,
17860 @url{http://lttng.org/ust}) tracing engine is supported. This support
17861 is automatically available if UST development headers are found in the
17862 standard include path when @code{gdbserver} is built, or if
17863 @code{gdbserver} was explicitly configured using @option{--with-ust}
17864 to point at such headers. You can explicitly disable the support
17865 using @option{--with-ust=no}.
17867 There are several ways to load the in-process agent in your program:
17870 @item Specifying it as dependency at link time
17872 You can link your program dynamically with the in-process agent
17873 library. On most systems, this is accomplished by adding
17874 @code{-linproctrace} to the link command.
17876 @item Using the system's preloading mechanisms
17878 You can force loading the in-process agent at startup time by using
17879 your system's support for preloading shared libraries. Many Unixes
17880 support the concept of preloading user defined libraries. In most
17881 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17882 in the environment. See also the description of @code{gdbserver}'s
17883 @option{--wrapper} command line option.
17885 @item Using @value{GDBN} to force loading the agent at run time
17887 On some systems, you can force the inferior to load a shared library,
17888 by calling a dynamic loader function in the inferior that takes care
17889 of dynamically looking up and loading a shared library. On most Unix
17890 systems, the function is @code{dlopen}. You'll use the @code{call}
17891 command for that. For example:
17894 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17897 Note that on most Unix systems, for the @code{dlopen} function to be
17898 available, the program needs to be linked with @code{-ldl}.
17901 On systems that have a userspace dynamic loader, like most Unix
17902 systems, when you connect to @code{gdbserver} using @code{target
17903 remote}, you'll find that the program is stopped at the dynamic
17904 loader's entry point, and no shared library has been loaded in the
17905 program's address space yet, including the in-process agent. In that
17906 case, before being able to use any of the fast or static tracepoints
17907 features, you need to let the loader run and load the shared
17908 libraries. The simplest way to do that is to run the program to the
17909 main procedure. E.g., if debugging a C or C@t{++} program, start
17910 @code{gdbserver} like so:
17913 $ gdbserver :9999 myprogram
17916 Start GDB and connect to @code{gdbserver} like so, and run to main:
17920 (@value{GDBP}) target remote myhost:9999
17921 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17922 (@value{GDBP}) b main
17923 (@value{GDBP}) continue
17926 The in-process tracing agent library should now be loaded into the
17927 process; you can confirm it with the @code{info sharedlibrary}
17928 command, which will list @file{libinproctrace.so} as loaded in the
17929 process. You are now ready to install fast tracepoints, list static
17930 tracepoint markers, probe static tracepoints markers, and start
17933 @node Remote Configuration
17934 @section Remote Configuration
17937 @kindex show remote
17938 This section documents the configuration options available when
17939 debugging remote programs. For the options related to the File I/O
17940 extensions of the remote protocol, see @ref{system,
17941 system-call-allowed}.
17944 @item set remoteaddresssize @var{bits}
17945 @cindex address size for remote targets
17946 @cindex bits in remote address
17947 Set the maximum size of address in a memory packet to the specified
17948 number of bits. @value{GDBN} will mask off the address bits above
17949 that number, when it passes addresses to the remote target. The
17950 default value is the number of bits in the target's address.
17952 @item show remoteaddresssize
17953 Show the current value of remote address size in bits.
17955 @item set remotebaud @var{n}
17956 @cindex baud rate for remote targets
17957 Set the baud rate for the remote serial I/O to @var{n} baud. The
17958 value is used to set the speed of the serial port used for debugging
17961 @item show remotebaud
17962 Show the current speed of the remote connection.
17964 @item set remotebreak
17965 @cindex interrupt remote programs
17966 @cindex BREAK signal instead of Ctrl-C
17967 @anchor{set remotebreak}
17968 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17969 when you type @kbd{Ctrl-c} to interrupt the program running
17970 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17971 character instead. The default is off, since most remote systems
17972 expect to see @samp{Ctrl-C} as the interrupt signal.
17974 @item show remotebreak
17975 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17976 interrupt the remote program.
17978 @item set remoteflow on
17979 @itemx set remoteflow off
17980 @kindex set remoteflow
17981 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17982 on the serial port used to communicate to the remote target.
17984 @item show remoteflow
17985 @kindex show remoteflow
17986 Show the current setting of hardware flow control.
17988 @item set remotelogbase @var{base}
17989 Set the base (a.k.a.@: radix) of logging serial protocol
17990 communications to @var{base}. Supported values of @var{base} are:
17991 @code{ascii}, @code{octal}, and @code{hex}. The default is
17994 @item show remotelogbase
17995 Show the current setting of the radix for logging remote serial
17998 @item set remotelogfile @var{file}
17999 @cindex record serial communications on file
18000 Record remote serial communications on the named @var{file}. The
18001 default is not to record at all.
18003 @item show remotelogfile.
18004 Show the current setting of the file name on which to record the
18005 serial communications.
18007 @item set remotetimeout @var{num}
18008 @cindex timeout for serial communications
18009 @cindex remote timeout
18010 Set the timeout limit to wait for the remote target to respond to
18011 @var{num} seconds. The default is 2 seconds.
18013 @item show remotetimeout
18014 Show the current number of seconds to wait for the remote target
18017 @cindex limit hardware breakpoints and watchpoints
18018 @cindex remote target, limit break- and watchpoints
18019 @anchor{set remote hardware-watchpoint-limit}
18020 @anchor{set remote hardware-breakpoint-limit}
18021 @item set remote hardware-watchpoint-limit @var{limit}
18022 @itemx set remote hardware-breakpoint-limit @var{limit}
18023 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18024 watchpoints. A limit of -1, the default, is treated as unlimited.
18026 @cindex limit hardware watchpoints length
18027 @cindex remote target, limit watchpoints length
18028 @anchor{set remote hardware-watchpoint-length-limit}
18029 @item set remote hardware-watchpoint-length-limit @var{limit}
18030 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18031 a remote hardware watchpoint. A limit of -1, the default, is treated
18034 @item show remote hardware-watchpoint-length-limit
18035 Show the current limit (in bytes) of the maximum length of
18036 a remote hardware watchpoint.
18038 @item set remote exec-file @var{filename}
18039 @itemx show remote exec-file
18040 @anchor{set remote exec-file}
18041 @cindex executable file, for remote target
18042 Select the file used for @code{run} with @code{target
18043 extended-remote}. This should be set to a filename valid on the
18044 target system. If it is not set, the target will use a default
18045 filename (e.g.@: the last program run).
18047 @item set remote interrupt-sequence
18048 @cindex interrupt remote programs
18049 @cindex select Ctrl-C, BREAK or BREAK-g
18050 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18051 @samp{BREAK-g} as the
18052 sequence to the remote target in order to interrupt the execution.
18053 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18054 is high level of serial line for some certain time.
18055 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18056 It is @code{BREAK} signal followed by character @code{g}.
18058 @item show interrupt-sequence
18059 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18060 is sent by @value{GDBN} to interrupt the remote program.
18061 @code{BREAK-g} is BREAK signal followed by @code{g} and
18062 also known as Magic SysRq g.
18064 @item set remote interrupt-on-connect
18065 @cindex send interrupt-sequence on start
18066 Specify whether interrupt-sequence is sent to remote target when
18067 @value{GDBN} connects to it. This is mostly needed when you debug
18068 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18069 which is known as Magic SysRq g in order to connect @value{GDBN}.
18071 @item show interrupt-on-connect
18072 Show whether interrupt-sequence is sent
18073 to remote target when @value{GDBN} connects to it.
18077 @item set tcp auto-retry on
18078 @cindex auto-retry, for remote TCP target
18079 Enable auto-retry for remote TCP connections. This is useful if the remote
18080 debugging agent is launched in parallel with @value{GDBN}; there is a race
18081 condition because the agent may not become ready to accept the connection
18082 before @value{GDBN} attempts to connect. When auto-retry is
18083 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18084 to establish the connection using the timeout specified by
18085 @code{set tcp connect-timeout}.
18087 @item set tcp auto-retry off
18088 Do not auto-retry failed TCP connections.
18090 @item show tcp auto-retry
18091 Show the current auto-retry setting.
18093 @item set tcp connect-timeout @var{seconds}
18094 @cindex connection timeout, for remote TCP target
18095 @cindex timeout, for remote target connection
18096 Set the timeout for establishing a TCP connection to the remote target to
18097 @var{seconds}. The timeout affects both polling to retry failed connections
18098 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18099 that are merely slow to complete, and represents an approximate cumulative
18102 @item show tcp connect-timeout
18103 Show the current connection timeout setting.
18106 @cindex remote packets, enabling and disabling
18107 The @value{GDBN} remote protocol autodetects the packets supported by
18108 your debugging stub. If you need to override the autodetection, you
18109 can use these commands to enable or disable individual packets. Each
18110 packet can be set to @samp{on} (the remote target supports this
18111 packet), @samp{off} (the remote target does not support this packet),
18112 or @samp{auto} (detect remote target support for this packet). They
18113 all default to @samp{auto}. For more information about each packet,
18114 see @ref{Remote Protocol}.
18116 During normal use, you should not have to use any of these commands.
18117 If you do, that may be a bug in your remote debugging stub, or a bug
18118 in @value{GDBN}. You may want to report the problem to the
18119 @value{GDBN} developers.
18121 For each packet @var{name}, the command to enable or disable the
18122 packet is @code{set remote @var{name}-packet}. The available settings
18125 @multitable @columnfractions 0.28 0.32 0.25
18128 @tab Related Features
18130 @item @code{fetch-register}
18132 @tab @code{info registers}
18134 @item @code{set-register}
18138 @item @code{binary-download}
18140 @tab @code{load}, @code{set}
18142 @item @code{read-aux-vector}
18143 @tab @code{qXfer:auxv:read}
18144 @tab @code{info auxv}
18146 @item @code{symbol-lookup}
18147 @tab @code{qSymbol}
18148 @tab Detecting multiple threads
18150 @item @code{attach}
18151 @tab @code{vAttach}
18154 @item @code{verbose-resume}
18156 @tab Stepping or resuming multiple threads
18162 @item @code{software-breakpoint}
18166 @item @code{hardware-breakpoint}
18170 @item @code{write-watchpoint}
18174 @item @code{read-watchpoint}
18178 @item @code{access-watchpoint}
18182 @item @code{target-features}
18183 @tab @code{qXfer:features:read}
18184 @tab @code{set architecture}
18186 @item @code{library-info}
18187 @tab @code{qXfer:libraries:read}
18188 @tab @code{info sharedlibrary}
18190 @item @code{memory-map}
18191 @tab @code{qXfer:memory-map:read}
18192 @tab @code{info mem}
18194 @item @code{read-sdata-object}
18195 @tab @code{qXfer:sdata:read}
18196 @tab @code{print $_sdata}
18198 @item @code{read-spu-object}
18199 @tab @code{qXfer:spu:read}
18200 @tab @code{info spu}
18202 @item @code{write-spu-object}
18203 @tab @code{qXfer:spu:write}
18204 @tab @code{info spu}
18206 @item @code{read-siginfo-object}
18207 @tab @code{qXfer:siginfo:read}
18208 @tab @code{print $_siginfo}
18210 @item @code{write-siginfo-object}
18211 @tab @code{qXfer:siginfo:write}
18212 @tab @code{set $_siginfo}
18214 @item @code{threads}
18215 @tab @code{qXfer:threads:read}
18216 @tab @code{info threads}
18218 @item @code{get-thread-local-@*storage-address}
18219 @tab @code{qGetTLSAddr}
18220 @tab Displaying @code{__thread} variables
18222 @item @code{get-thread-information-block-address}
18223 @tab @code{qGetTIBAddr}
18224 @tab Display MS-Windows Thread Information Block.
18226 @item @code{search-memory}
18227 @tab @code{qSearch:memory}
18230 @item @code{supported-packets}
18231 @tab @code{qSupported}
18232 @tab Remote communications parameters
18234 @item @code{pass-signals}
18235 @tab @code{QPassSignals}
18236 @tab @code{handle @var{signal}}
18238 @item @code{program-signals}
18239 @tab @code{QProgramSignals}
18240 @tab @code{handle @var{signal}}
18242 @item @code{hostio-close-packet}
18243 @tab @code{vFile:close}
18244 @tab @code{remote get}, @code{remote put}
18246 @item @code{hostio-open-packet}
18247 @tab @code{vFile:open}
18248 @tab @code{remote get}, @code{remote put}
18250 @item @code{hostio-pread-packet}
18251 @tab @code{vFile:pread}
18252 @tab @code{remote get}, @code{remote put}
18254 @item @code{hostio-pwrite-packet}
18255 @tab @code{vFile:pwrite}
18256 @tab @code{remote get}, @code{remote put}
18258 @item @code{hostio-unlink-packet}
18259 @tab @code{vFile:unlink}
18260 @tab @code{remote delete}
18262 @item @code{hostio-readlink-packet}
18263 @tab @code{vFile:readlink}
18266 @item @code{noack-packet}
18267 @tab @code{QStartNoAckMode}
18268 @tab Packet acknowledgment
18270 @item @code{osdata}
18271 @tab @code{qXfer:osdata:read}
18272 @tab @code{info os}
18274 @item @code{query-attached}
18275 @tab @code{qAttached}
18276 @tab Querying remote process attach state.
18278 @item @code{traceframe-info}
18279 @tab @code{qXfer:traceframe-info:read}
18280 @tab Traceframe info
18282 @item @code{install-in-trace}
18283 @tab @code{InstallInTrace}
18284 @tab Install tracepoint in tracing
18286 @item @code{disable-randomization}
18287 @tab @code{QDisableRandomization}
18288 @tab @code{set disable-randomization}
18290 @item @code{conditional-breakpoints-packet}
18291 @tab @code{Z0 and Z1}
18292 @tab @code{Support for target-side breakpoint condition evaluation}
18296 @section Implementing a Remote Stub
18298 @cindex debugging stub, example
18299 @cindex remote stub, example
18300 @cindex stub example, remote debugging
18301 The stub files provided with @value{GDBN} implement the target side of the
18302 communication protocol, and the @value{GDBN} side is implemented in the
18303 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18304 these subroutines to communicate, and ignore the details. (If you're
18305 implementing your own stub file, you can still ignore the details: start
18306 with one of the existing stub files. @file{sparc-stub.c} is the best
18307 organized, and therefore the easiest to read.)
18309 @cindex remote serial debugging, overview
18310 To debug a program running on another machine (the debugging
18311 @dfn{target} machine), you must first arrange for all the usual
18312 prerequisites for the program to run by itself. For example, for a C
18317 A startup routine to set up the C runtime environment; these usually
18318 have a name like @file{crt0}. The startup routine may be supplied by
18319 your hardware supplier, or you may have to write your own.
18322 A C subroutine library to support your program's
18323 subroutine calls, notably managing input and output.
18326 A way of getting your program to the other machine---for example, a
18327 download program. These are often supplied by the hardware
18328 manufacturer, but you may have to write your own from hardware
18332 The next step is to arrange for your program to use a serial port to
18333 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18334 machine). In general terms, the scheme looks like this:
18338 @value{GDBN} already understands how to use this protocol; when everything
18339 else is set up, you can simply use the @samp{target remote} command
18340 (@pxref{Targets,,Specifying a Debugging Target}).
18342 @item On the target,
18343 you must link with your program a few special-purpose subroutines that
18344 implement the @value{GDBN} remote serial protocol. The file containing these
18345 subroutines is called a @dfn{debugging stub}.
18347 On certain remote targets, you can use an auxiliary program
18348 @code{gdbserver} instead of linking a stub into your program.
18349 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18352 The debugging stub is specific to the architecture of the remote
18353 machine; for example, use @file{sparc-stub.c} to debug programs on
18356 @cindex remote serial stub list
18357 These working remote stubs are distributed with @value{GDBN}:
18362 @cindex @file{i386-stub.c}
18365 For Intel 386 and compatible architectures.
18368 @cindex @file{m68k-stub.c}
18369 @cindex Motorola 680x0
18371 For Motorola 680x0 architectures.
18374 @cindex @file{sh-stub.c}
18377 For Renesas SH architectures.
18380 @cindex @file{sparc-stub.c}
18382 For @sc{sparc} architectures.
18384 @item sparcl-stub.c
18385 @cindex @file{sparcl-stub.c}
18388 For Fujitsu @sc{sparclite} architectures.
18392 The @file{README} file in the @value{GDBN} distribution may list other
18393 recently added stubs.
18396 * Stub Contents:: What the stub can do for you
18397 * Bootstrapping:: What you must do for the stub
18398 * Debug Session:: Putting it all together
18401 @node Stub Contents
18402 @subsection What the Stub Can Do for You
18404 @cindex remote serial stub
18405 The debugging stub for your architecture supplies these three
18409 @item set_debug_traps
18410 @findex set_debug_traps
18411 @cindex remote serial stub, initialization
18412 This routine arranges for @code{handle_exception} to run when your
18413 program stops. You must call this subroutine explicitly in your
18414 program's startup code.
18416 @item handle_exception
18417 @findex handle_exception
18418 @cindex remote serial stub, main routine
18419 This is the central workhorse, but your program never calls it
18420 explicitly---the setup code arranges for @code{handle_exception} to
18421 run when a trap is triggered.
18423 @code{handle_exception} takes control when your program stops during
18424 execution (for example, on a breakpoint), and mediates communications
18425 with @value{GDBN} on the host machine. This is where the communications
18426 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18427 representative on the target machine. It begins by sending summary
18428 information on the state of your program, then continues to execute,
18429 retrieving and transmitting any information @value{GDBN} needs, until you
18430 execute a @value{GDBN} command that makes your program resume; at that point,
18431 @code{handle_exception} returns control to your own code on the target
18435 @cindex @code{breakpoint} subroutine, remote
18436 Use this auxiliary subroutine to make your program contain a
18437 breakpoint. Depending on the particular situation, this may be the only
18438 way for @value{GDBN} to get control. For instance, if your target
18439 machine has some sort of interrupt button, you won't need to call this;
18440 pressing the interrupt button transfers control to
18441 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18442 simply receiving characters on the serial port may also trigger a trap;
18443 again, in that situation, you don't need to call @code{breakpoint} from
18444 your own program---simply running @samp{target remote} from the host
18445 @value{GDBN} session gets control.
18447 Call @code{breakpoint} if none of these is true, or if you simply want
18448 to make certain your program stops at a predetermined point for the
18449 start of your debugging session.
18452 @node Bootstrapping
18453 @subsection What You Must Do for the Stub
18455 @cindex remote stub, support routines
18456 The debugging stubs that come with @value{GDBN} are set up for a particular
18457 chip architecture, but they have no information about the rest of your
18458 debugging target machine.
18460 First of all you need to tell the stub how to communicate with the
18464 @item int getDebugChar()
18465 @findex getDebugChar
18466 Write this subroutine to read a single character from the serial port.
18467 It may be identical to @code{getchar} for your target system; a
18468 different name is used to allow you to distinguish the two if you wish.
18470 @item void putDebugChar(int)
18471 @findex putDebugChar
18472 Write this subroutine to write a single character to the serial port.
18473 It may be identical to @code{putchar} for your target system; a
18474 different name is used to allow you to distinguish the two if you wish.
18477 @cindex control C, and remote debugging
18478 @cindex interrupting remote targets
18479 If you want @value{GDBN} to be able to stop your program while it is
18480 running, you need to use an interrupt-driven serial driver, and arrange
18481 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18482 character). That is the character which @value{GDBN} uses to tell the
18483 remote system to stop.
18485 Getting the debugging target to return the proper status to @value{GDBN}
18486 probably requires changes to the standard stub; one quick and dirty way
18487 is to just execute a breakpoint instruction (the ``dirty'' part is that
18488 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18490 Other routines you need to supply are:
18493 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18494 @findex exceptionHandler
18495 Write this function to install @var{exception_address} in the exception
18496 handling tables. You need to do this because the stub does not have any
18497 way of knowing what the exception handling tables on your target system
18498 are like (for example, the processor's table might be in @sc{rom},
18499 containing entries which point to a table in @sc{ram}).
18500 @var{exception_number} is the exception number which should be changed;
18501 its meaning is architecture-dependent (for example, different numbers
18502 might represent divide by zero, misaligned access, etc). When this
18503 exception occurs, control should be transferred directly to
18504 @var{exception_address}, and the processor state (stack, registers,
18505 and so on) should be just as it is when a processor exception occurs. So if
18506 you want to use a jump instruction to reach @var{exception_address}, it
18507 should be a simple jump, not a jump to subroutine.
18509 For the 386, @var{exception_address} should be installed as an interrupt
18510 gate so that interrupts are masked while the handler runs. The gate
18511 should be at privilege level 0 (the most privileged level). The
18512 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18513 help from @code{exceptionHandler}.
18515 @item void flush_i_cache()
18516 @findex flush_i_cache
18517 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18518 instruction cache, if any, on your target machine. If there is no
18519 instruction cache, this subroutine may be a no-op.
18521 On target machines that have instruction caches, @value{GDBN} requires this
18522 function to make certain that the state of your program is stable.
18526 You must also make sure this library routine is available:
18529 @item void *memset(void *, int, int)
18531 This is the standard library function @code{memset} that sets an area of
18532 memory to a known value. If you have one of the free versions of
18533 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18534 either obtain it from your hardware manufacturer, or write your own.
18537 If you do not use the GNU C compiler, you may need other standard
18538 library subroutines as well; this varies from one stub to another,
18539 but in general the stubs are likely to use any of the common library
18540 subroutines which @code{@value{NGCC}} generates as inline code.
18543 @node Debug Session
18544 @subsection Putting it All Together
18546 @cindex remote serial debugging summary
18547 In summary, when your program is ready to debug, you must follow these
18552 Make sure you have defined the supporting low-level routines
18553 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18555 @code{getDebugChar}, @code{putDebugChar},
18556 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18560 Insert these lines in your program's startup code, before the main
18561 procedure is called:
18568 On some machines, when a breakpoint trap is raised, the hardware
18569 automatically makes the PC point to the instruction after the
18570 breakpoint. If your machine doesn't do that, you may need to adjust
18571 @code{handle_exception} to arrange for it to return to the instruction
18572 after the breakpoint on this first invocation, so that your program
18573 doesn't keep hitting the initial breakpoint instead of making
18577 For the 680x0 stub only, you need to provide a variable called
18578 @code{exceptionHook}. Normally you just use:
18581 void (*exceptionHook)() = 0;
18585 but if before calling @code{set_debug_traps}, you set it to point to a
18586 function in your program, that function is called when
18587 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18588 error). The function indicated by @code{exceptionHook} is called with
18589 one parameter: an @code{int} which is the exception number.
18592 Compile and link together: your program, the @value{GDBN} debugging stub for
18593 your target architecture, and the supporting subroutines.
18596 Make sure you have a serial connection between your target machine and
18597 the @value{GDBN} host, and identify the serial port on the host.
18600 @c The "remote" target now provides a `load' command, so we should
18601 @c document that. FIXME.
18602 Download your program to your target machine (or get it there by
18603 whatever means the manufacturer provides), and start it.
18606 Start @value{GDBN} on the host, and connect to the target
18607 (@pxref{Connecting,,Connecting to a Remote Target}).
18611 @node Configurations
18612 @chapter Configuration-Specific Information
18614 While nearly all @value{GDBN} commands are available for all native and
18615 cross versions of the debugger, there are some exceptions. This chapter
18616 describes things that are only available in certain configurations.
18618 There are three major categories of configurations: native
18619 configurations, where the host and target are the same, embedded
18620 operating system configurations, which are usually the same for several
18621 different processor architectures, and bare embedded processors, which
18622 are quite different from each other.
18627 * Embedded Processors::
18634 This section describes details specific to particular native
18639 * BSD libkvm Interface:: Debugging BSD kernel memory images
18640 * SVR4 Process Information:: SVR4 process information
18641 * DJGPP Native:: Features specific to the DJGPP port
18642 * Cygwin Native:: Features specific to the Cygwin port
18643 * Hurd Native:: Features specific to @sc{gnu} Hurd
18644 * Darwin:: Features specific to Darwin
18650 On HP-UX systems, if you refer to a function or variable name that
18651 begins with a dollar sign, @value{GDBN} searches for a user or system
18652 name first, before it searches for a convenience variable.
18655 @node BSD libkvm Interface
18656 @subsection BSD libkvm Interface
18659 @cindex kernel memory image
18660 @cindex kernel crash dump
18662 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18663 interface that provides a uniform interface for accessing kernel virtual
18664 memory images, including live systems and crash dumps. @value{GDBN}
18665 uses this interface to allow you to debug live kernels and kernel crash
18666 dumps on many native BSD configurations. This is implemented as a
18667 special @code{kvm} debugging target. For debugging a live system, load
18668 the currently running kernel into @value{GDBN} and connect to the
18672 (@value{GDBP}) @b{target kvm}
18675 For debugging crash dumps, provide the file name of the crash dump as an
18679 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18682 Once connected to the @code{kvm} target, the following commands are
18688 Set current context from the @dfn{Process Control Block} (PCB) address.
18691 Set current context from proc address. This command isn't available on
18692 modern FreeBSD systems.
18695 @node SVR4 Process Information
18696 @subsection SVR4 Process Information
18698 @cindex examine process image
18699 @cindex process info via @file{/proc}
18701 Many versions of SVR4 and compatible systems provide a facility called
18702 @samp{/proc} that can be used to examine the image of a running
18703 process using file-system subroutines.
18705 If @value{GDBN} is configured for an operating system with this
18706 facility, the command @code{info proc} is available to report
18707 information about the process running your program, or about any
18708 process running on your system. This includes, as of this writing,
18709 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18710 not HP-UX, for example.
18712 This command may also work on core files that were created on a system
18713 that has the @samp{/proc} facility.
18719 @itemx info proc @var{process-id}
18720 Summarize available information about any running process. If a
18721 process ID is specified by @var{process-id}, display information about
18722 that process; otherwise display information about the program being
18723 debugged. The summary includes the debugged process ID, the command
18724 line used to invoke it, its current working directory, and its
18725 executable file's absolute file name.
18727 On some systems, @var{process-id} can be of the form
18728 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18729 within a process. If the optional @var{pid} part is missing, it means
18730 a thread from the process being debugged (the leading @samp{/} still
18731 needs to be present, or else @value{GDBN} will interpret the number as
18732 a process ID rather than a thread ID).
18734 @item info proc cmdline
18735 @cindex info proc cmdline
18736 Show the original command line of the process. This command is
18737 specific to @sc{gnu}/Linux.
18739 @item info proc cwd
18740 @cindex info proc cwd
18741 Show the current working directory of the process. This command is
18742 specific to @sc{gnu}/Linux.
18744 @item info proc exe
18745 @cindex info proc exe
18746 Show the name of executable of the process. This command is specific
18749 @item info proc mappings
18750 @cindex memory address space mappings
18751 Report the memory address space ranges accessible in the program, with
18752 information on whether the process has read, write, or execute access
18753 rights to each range. On @sc{gnu}/Linux systems, each memory range
18754 includes the object file which is mapped to that range, instead of the
18755 memory access rights to that range.
18757 @item info proc stat
18758 @itemx info proc status
18759 @cindex process detailed status information
18760 These subcommands are specific to @sc{gnu}/Linux systems. They show
18761 the process-related information, including the user ID and group ID;
18762 how many threads are there in the process; its virtual memory usage;
18763 the signals that are pending, blocked, and ignored; its TTY; its
18764 consumption of system and user time; its stack size; its @samp{nice}
18765 value; etc. For more information, see the @samp{proc} man page
18766 (type @kbd{man 5 proc} from your shell prompt).
18768 @item info proc all
18769 Show all the information about the process described under all of the
18770 above @code{info proc} subcommands.
18773 @comment These sub-options of 'info proc' were not included when
18774 @comment procfs.c was re-written. Keep their descriptions around
18775 @comment against the day when someone finds the time to put them back in.
18776 @kindex info proc times
18777 @item info proc times
18778 Starting time, user CPU time, and system CPU time for your program and
18781 @kindex info proc id
18783 Report on the process IDs related to your program: its own process ID,
18784 the ID of its parent, the process group ID, and the session ID.
18787 @item set procfs-trace
18788 @kindex set procfs-trace
18789 @cindex @code{procfs} API calls
18790 This command enables and disables tracing of @code{procfs} API calls.
18792 @item show procfs-trace
18793 @kindex show procfs-trace
18794 Show the current state of @code{procfs} API call tracing.
18796 @item set procfs-file @var{file}
18797 @kindex set procfs-file
18798 Tell @value{GDBN} to write @code{procfs} API trace to the named
18799 @var{file}. @value{GDBN} appends the trace info to the previous
18800 contents of the file. The default is to display the trace on the
18803 @item show procfs-file
18804 @kindex show procfs-file
18805 Show the file to which @code{procfs} API trace is written.
18807 @item proc-trace-entry
18808 @itemx proc-trace-exit
18809 @itemx proc-untrace-entry
18810 @itemx proc-untrace-exit
18811 @kindex proc-trace-entry
18812 @kindex proc-trace-exit
18813 @kindex proc-untrace-entry
18814 @kindex proc-untrace-exit
18815 These commands enable and disable tracing of entries into and exits
18816 from the @code{syscall} interface.
18819 @kindex info pidlist
18820 @cindex process list, QNX Neutrino
18821 For QNX Neutrino only, this command displays the list of all the
18822 processes and all the threads within each process.
18825 @kindex info meminfo
18826 @cindex mapinfo list, QNX Neutrino
18827 For QNX Neutrino only, this command displays the list of all mapinfos.
18831 @subsection Features for Debugging @sc{djgpp} Programs
18832 @cindex @sc{djgpp} debugging
18833 @cindex native @sc{djgpp} debugging
18834 @cindex MS-DOS-specific commands
18837 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18838 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18839 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18840 top of real-mode DOS systems and their emulations.
18842 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18843 defines a few commands specific to the @sc{djgpp} port. This
18844 subsection describes those commands.
18849 This is a prefix of @sc{djgpp}-specific commands which print
18850 information about the target system and important OS structures.
18853 @cindex MS-DOS system info
18854 @cindex free memory information (MS-DOS)
18855 @item info dos sysinfo
18856 This command displays assorted information about the underlying
18857 platform: the CPU type and features, the OS version and flavor, the
18858 DPMI version, and the available conventional and DPMI memory.
18863 @cindex segment descriptor tables
18864 @cindex descriptor tables display
18866 @itemx info dos ldt
18867 @itemx info dos idt
18868 These 3 commands display entries from, respectively, Global, Local,
18869 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18870 tables are data structures which store a descriptor for each segment
18871 that is currently in use. The segment's selector is an index into a
18872 descriptor table; the table entry for that index holds the
18873 descriptor's base address and limit, and its attributes and access
18876 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18877 segment (used for both data and the stack), and a DOS segment (which
18878 allows access to DOS/BIOS data structures and absolute addresses in
18879 conventional memory). However, the DPMI host will usually define
18880 additional segments in order to support the DPMI environment.
18882 @cindex garbled pointers
18883 These commands allow to display entries from the descriptor tables.
18884 Without an argument, all entries from the specified table are
18885 displayed. An argument, which should be an integer expression, means
18886 display a single entry whose index is given by the argument. For
18887 example, here's a convenient way to display information about the
18888 debugged program's data segment:
18891 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18892 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18896 This comes in handy when you want to see whether a pointer is outside
18897 the data segment's limit (i.e.@: @dfn{garbled}).
18899 @cindex page tables display (MS-DOS)
18901 @itemx info dos pte
18902 These two commands display entries from, respectively, the Page
18903 Directory and the Page Tables. Page Directories and Page Tables are
18904 data structures which control how virtual memory addresses are mapped
18905 into physical addresses. A Page Table includes an entry for every
18906 page of memory that is mapped into the program's address space; there
18907 may be several Page Tables, each one holding up to 4096 entries. A
18908 Page Directory has up to 4096 entries, one each for every Page Table
18909 that is currently in use.
18911 Without an argument, @kbd{info dos pde} displays the entire Page
18912 Directory, and @kbd{info dos pte} displays all the entries in all of
18913 the Page Tables. An argument, an integer expression, given to the
18914 @kbd{info dos pde} command means display only that entry from the Page
18915 Directory table. An argument given to the @kbd{info dos pte} command
18916 means display entries from a single Page Table, the one pointed to by
18917 the specified entry in the Page Directory.
18919 @cindex direct memory access (DMA) on MS-DOS
18920 These commands are useful when your program uses @dfn{DMA} (Direct
18921 Memory Access), which needs physical addresses to program the DMA
18924 These commands are supported only with some DPMI servers.
18926 @cindex physical address from linear address
18927 @item info dos address-pte @var{addr}
18928 This command displays the Page Table entry for a specified linear
18929 address. The argument @var{addr} is a linear address which should
18930 already have the appropriate segment's base address added to it,
18931 because this command accepts addresses which may belong to @emph{any}
18932 segment. For example, here's how to display the Page Table entry for
18933 the page where a variable @code{i} is stored:
18936 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18937 @exdent @code{Page Table entry for address 0x11a00d30:}
18938 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18942 This says that @code{i} is stored at offset @code{0xd30} from the page
18943 whose physical base address is @code{0x02698000}, and shows all the
18944 attributes of that page.
18946 Note that you must cast the addresses of variables to a @code{char *},
18947 since otherwise the value of @code{__djgpp_base_address}, the base
18948 address of all variables and functions in a @sc{djgpp} program, will
18949 be added using the rules of C pointer arithmetics: if @code{i} is
18950 declared an @code{int}, @value{GDBN} will add 4 times the value of
18951 @code{__djgpp_base_address} to the address of @code{i}.
18953 Here's another example, it displays the Page Table entry for the
18957 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18958 @exdent @code{Page Table entry for address 0x29110:}
18959 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18963 (The @code{+ 3} offset is because the transfer buffer's address is the
18964 3rd member of the @code{_go32_info_block} structure.) The output
18965 clearly shows that this DPMI server maps the addresses in conventional
18966 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18967 linear (@code{0x29110}) addresses are identical.
18969 This command is supported only with some DPMI servers.
18972 @cindex DOS serial data link, remote debugging
18973 In addition to native debugging, the DJGPP port supports remote
18974 debugging via a serial data link. The following commands are specific
18975 to remote serial debugging in the DJGPP port of @value{GDBN}.
18978 @kindex set com1base
18979 @kindex set com1irq
18980 @kindex set com2base
18981 @kindex set com2irq
18982 @kindex set com3base
18983 @kindex set com3irq
18984 @kindex set com4base
18985 @kindex set com4irq
18986 @item set com1base @var{addr}
18987 This command sets the base I/O port address of the @file{COM1} serial
18990 @item set com1irq @var{irq}
18991 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18992 for the @file{COM1} serial port.
18994 There are similar commands @samp{set com2base}, @samp{set com3irq},
18995 etc.@: for setting the port address and the @code{IRQ} lines for the
18998 @kindex show com1base
18999 @kindex show com1irq
19000 @kindex show com2base
19001 @kindex show com2irq
19002 @kindex show com3base
19003 @kindex show com3irq
19004 @kindex show com4base
19005 @kindex show com4irq
19006 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19007 display the current settings of the base address and the @code{IRQ}
19008 lines used by the COM ports.
19011 @kindex info serial
19012 @cindex DOS serial port status
19013 This command prints the status of the 4 DOS serial ports. For each
19014 port, it prints whether it's active or not, its I/O base address and
19015 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19016 counts of various errors encountered so far.
19020 @node Cygwin Native
19021 @subsection Features for Debugging MS Windows PE Executables
19022 @cindex MS Windows debugging
19023 @cindex native Cygwin debugging
19024 @cindex Cygwin-specific commands
19026 @value{GDBN} supports native debugging of MS Windows programs, including
19027 DLLs with and without symbolic debugging information.
19029 @cindex Ctrl-BREAK, MS-Windows
19030 @cindex interrupt debuggee on MS-Windows
19031 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19032 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19033 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19034 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19035 sequence, which can be used to interrupt the debuggee even if it
19038 There are various additional Cygwin-specific commands, described in
19039 this section. Working with DLLs that have no debugging symbols is
19040 described in @ref{Non-debug DLL Symbols}.
19045 This is a prefix of MS Windows-specific commands which print
19046 information about the target system and important OS structures.
19048 @item info w32 selector
19049 This command displays information returned by
19050 the Win32 API @code{GetThreadSelectorEntry} function.
19051 It takes an optional argument that is evaluated to
19052 a long value to give the information about this given selector.
19053 Without argument, this command displays information
19054 about the six segment registers.
19056 @item info w32 thread-information-block
19057 This command displays thread specific information stored in the
19058 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19059 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19063 This is a Cygwin-specific alias of @code{info shared}.
19065 @kindex dll-symbols
19067 This command loads symbols from a dll similarly to
19068 add-sym command but without the need to specify a base address.
19070 @kindex set cygwin-exceptions
19071 @cindex debugging the Cygwin DLL
19072 @cindex Cygwin DLL, debugging
19073 @item set cygwin-exceptions @var{mode}
19074 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19075 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19076 @value{GDBN} will delay recognition of exceptions, and may ignore some
19077 exceptions which seem to be caused by internal Cygwin DLL
19078 ``bookkeeping''. This option is meant primarily for debugging the
19079 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19080 @value{GDBN} users with false @code{SIGSEGV} signals.
19082 @kindex show cygwin-exceptions
19083 @item show cygwin-exceptions
19084 Displays whether @value{GDBN} will break on exceptions that happen
19085 inside the Cygwin DLL itself.
19087 @kindex set new-console
19088 @item set new-console @var{mode}
19089 If @var{mode} is @code{on} the debuggee will
19090 be started in a new console on next start.
19091 If @var{mode} is @code{off}, the debuggee will
19092 be started in the same console as the debugger.
19094 @kindex show new-console
19095 @item show new-console
19096 Displays whether a new console is used
19097 when the debuggee is started.
19099 @kindex set new-group
19100 @item set new-group @var{mode}
19101 This boolean value controls whether the debuggee should
19102 start a new group or stay in the same group as the debugger.
19103 This affects the way the Windows OS handles
19106 @kindex show new-group
19107 @item show new-group
19108 Displays current value of new-group boolean.
19110 @kindex set debugevents
19111 @item set debugevents
19112 This boolean value adds debug output concerning kernel events related
19113 to the debuggee seen by the debugger. This includes events that
19114 signal thread and process creation and exit, DLL loading and
19115 unloading, console interrupts, and debugging messages produced by the
19116 Windows @code{OutputDebugString} API call.
19118 @kindex set debugexec
19119 @item set debugexec
19120 This boolean value adds debug output concerning execute events
19121 (such as resume thread) seen by the debugger.
19123 @kindex set debugexceptions
19124 @item set debugexceptions
19125 This boolean value adds debug output concerning exceptions in the
19126 debuggee seen by the debugger.
19128 @kindex set debugmemory
19129 @item set debugmemory
19130 This boolean value adds debug output concerning debuggee memory reads
19131 and writes by the debugger.
19135 This boolean values specifies whether the debuggee is called
19136 via a shell or directly (default value is on).
19140 Displays if the debuggee will be started with a shell.
19145 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19148 @node Non-debug DLL Symbols
19149 @subsubsection Support for DLLs without Debugging Symbols
19150 @cindex DLLs with no debugging symbols
19151 @cindex Minimal symbols and DLLs
19153 Very often on windows, some of the DLLs that your program relies on do
19154 not include symbolic debugging information (for example,
19155 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19156 symbols in a DLL, it relies on the minimal amount of symbolic
19157 information contained in the DLL's export table. This section
19158 describes working with such symbols, known internally to @value{GDBN} as
19159 ``minimal symbols''.
19161 Note that before the debugged program has started execution, no DLLs
19162 will have been loaded. The easiest way around this problem is simply to
19163 start the program --- either by setting a breakpoint or letting the
19164 program run once to completion. It is also possible to force
19165 @value{GDBN} to load a particular DLL before starting the executable ---
19166 see the shared library information in @ref{Files}, or the
19167 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19168 explicitly loading symbols from a DLL with no debugging information will
19169 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19170 which may adversely affect symbol lookup performance.
19172 @subsubsection DLL Name Prefixes
19174 In keeping with the naming conventions used by the Microsoft debugging
19175 tools, DLL export symbols are made available with a prefix based on the
19176 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19177 also entered into the symbol table, so @code{CreateFileA} is often
19178 sufficient. In some cases there will be name clashes within a program
19179 (particularly if the executable itself includes full debugging symbols)
19180 necessitating the use of the fully qualified name when referring to the
19181 contents of the DLL. Use single-quotes around the name to avoid the
19182 exclamation mark (``!'') being interpreted as a language operator.
19184 Note that the internal name of the DLL may be all upper-case, even
19185 though the file name of the DLL is lower-case, or vice-versa. Since
19186 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19187 some confusion. If in doubt, try the @code{info functions} and
19188 @code{info variables} commands or even @code{maint print msymbols}
19189 (@pxref{Symbols}). Here's an example:
19192 (@value{GDBP}) info function CreateFileA
19193 All functions matching regular expression "CreateFileA":
19195 Non-debugging symbols:
19196 0x77e885f4 CreateFileA
19197 0x77e885f4 KERNEL32!CreateFileA
19201 (@value{GDBP}) info function !
19202 All functions matching regular expression "!":
19204 Non-debugging symbols:
19205 0x6100114c cygwin1!__assert
19206 0x61004034 cygwin1!_dll_crt0@@0
19207 0x61004240 cygwin1!dll_crt0(per_process *)
19211 @subsubsection Working with Minimal Symbols
19213 Symbols extracted from a DLL's export table do not contain very much
19214 type information. All that @value{GDBN} can do is guess whether a symbol
19215 refers to a function or variable depending on the linker section that
19216 contains the symbol. Also note that the actual contents of the memory
19217 contained in a DLL are not available unless the program is running. This
19218 means that you cannot examine the contents of a variable or disassemble
19219 a function within a DLL without a running program.
19221 Variables are generally treated as pointers and dereferenced
19222 automatically. For this reason, it is often necessary to prefix a
19223 variable name with the address-of operator (``&'') and provide explicit
19224 type information in the command. Here's an example of the type of
19228 (@value{GDBP}) print 'cygwin1!__argv'
19233 (@value{GDBP}) x 'cygwin1!__argv'
19234 0x10021610: "\230y\""
19237 And two possible solutions:
19240 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19241 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19245 (@value{GDBP}) x/2x &'cygwin1!__argv'
19246 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19247 (@value{GDBP}) x/x 0x10021608
19248 0x10021608: 0x0022fd98
19249 (@value{GDBP}) x/s 0x0022fd98
19250 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19253 Setting a break point within a DLL is possible even before the program
19254 starts execution. However, under these circumstances, @value{GDBN} can't
19255 examine the initial instructions of the function in order to skip the
19256 function's frame set-up code. You can work around this by using ``*&''
19257 to set the breakpoint at a raw memory address:
19260 (@value{GDBP}) break *&'python22!PyOS_Readline'
19261 Breakpoint 1 at 0x1e04eff0
19264 The author of these extensions is not entirely convinced that setting a
19265 break point within a shared DLL like @file{kernel32.dll} is completely
19269 @subsection Commands Specific to @sc{gnu} Hurd Systems
19270 @cindex @sc{gnu} Hurd debugging
19272 This subsection describes @value{GDBN} commands specific to the
19273 @sc{gnu} Hurd native debugging.
19278 @kindex set signals@r{, Hurd command}
19279 @kindex set sigs@r{, Hurd command}
19280 This command toggles the state of inferior signal interception by
19281 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19282 affected by this command. @code{sigs} is a shorthand alias for
19287 @kindex show signals@r{, Hurd command}
19288 @kindex show sigs@r{, Hurd command}
19289 Show the current state of intercepting inferior's signals.
19291 @item set signal-thread
19292 @itemx set sigthread
19293 @kindex set signal-thread
19294 @kindex set sigthread
19295 This command tells @value{GDBN} which thread is the @code{libc} signal
19296 thread. That thread is run when a signal is delivered to a running
19297 process. @code{set sigthread} is the shorthand alias of @code{set
19300 @item show signal-thread
19301 @itemx show sigthread
19302 @kindex show signal-thread
19303 @kindex show sigthread
19304 These two commands show which thread will run when the inferior is
19305 delivered a signal.
19308 @kindex set stopped@r{, Hurd command}
19309 This commands tells @value{GDBN} that the inferior process is stopped,
19310 as with the @code{SIGSTOP} signal. The stopped process can be
19311 continued by delivering a signal to it.
19314 @kindex show stopped@r{, Hurd command}
19315 This command shows whether @value{GDBN} thinks the debuggee is
19318 @item set exceptions
19319 @kindex set exceptions@r{, Hurd command}
19320 Use this command to turn off trapping of exceptions in the inferior.
19321 When exception trapping is off, neither breakpoints nor
19322 single-stepping will work. To restore the default, set exception
19325 @item show exceptions
19326 @kindex show exceptions@r{, Hurd command}
19327 Show the current state of trapping exceptions in the inferior.
19329 @item set task pause
19330 @kindex set task@r{, Hurd commands}
19331 @cindex task attributes (@sc{gnu} Hurd)
19332 @cindex pause current task (@sc{gnu} Hurd)
19333 This command toggles task suspension when @value{GDBN} has control.
19334 Setting it to on takes effect immediately, and the task is suspended
19335 whenever @value{GDBN} gets control. Setting it to off will take
19336 effect the next time the inferior is continued. If this option is set
19337 to off, you can use @code{set thread default pause on} or @code{set
19338 thread pause on} (see below) to pause individual threads.
19340 @item show task pause
19341 @kindex show task@r{, Hurd commands}
19342 Show the current state of task suspension.
19344 @item set task detach-suspend-count
19345 @cindex task suspend count
19346 @cindex detach from task, @sc{gnu} Hurd
19347 This command sets the suspend count the task will be left with when
19348 @value{GDBN} detaches from it.
19350 @item show task detach-suspend-count
19351 Show the suspend count the task will be left with when detaching.
19353 @item set task exception-port
19354 @itemx set task excp
19355 @cindex task exception port, @sc{gnu} Hurd
19356 This command sets the task exception port to which @value{GDBN} will
19357 forward exceptions. The argument should be the value of the @dfn{send
19358 rights} of the task. @code{set task excp} is a shorthand alias.
19360 @item set noninvasive
19361 @cindex noninvasive task options
19362 This command switches @value{GDBN} to a mode that is the least
19363 invasive as far as interfering with the inferior is concerned. This
19364 is the same as using @code{set task pause}, @code{set exceptions}, and
19365 @code{set signals} to values opposite to the defaults.
19367 @item info send-rights
19368 @itemx info receive-rights
19369 @itemx info port-rights
19370 @itemx info port-sets
19371 @itemx info dead-names
19374 @cindex send rights, @sc{gnu} Hurd
19375 @cindex receive rights, @sc{gnu} Hurd
19376 @cindex port rights, @sc{gnu} Hurd
19377 @cindex port sets, @sc{gnu} Hurd
19378 @cindex dead names, @sc{gnu} Hurd
19379 These commands display information about, respectively, send rights,
19380 receive rights, port rights, port sets, and dead names of a task.
19381 There are also shorthand aliases: @code{info ports} for @code{info
19382 port-rights} and @code{info psets} for @code{info port-sets}.
19384 @item set thread pause
19385 @kindex set thread@r{, Hurd command}
19386 @cindex thread properties, @sc{gnu} Hurd
19387 @cindex pause current thread (@sc{gnu} Hurd)
19388 This command toggles current thread suspension when @value{GDBN} has
19389 control. Setting it to on takes effect immediately, and the current
19390 thread is suspended whenever @value{GDBN} gets control. Setting it to
19391 off will take effect the next time the inferior is continued.
19392 Normally, this command has no effect, since when @value{GDBN} has
19393 control, the whole task is suspended. However, if you used @code{set
19394 task pause off} (see above), this command comes in handy to suspend
19395 only the current thread.
19397 @item show thread pause
19398 @kindex show thread@r{, Hurd command}
19399 This command shows the state of current thread suspension.
19401 @item set thread run
19402 This command sets whether the current thread is allowed to run.
19404 @item show thread run
19405 Show whether the current thread is allowed to run.
19407 @item set thread detach-suspend-count
19408 @cindex thread suspend count, @sc{gnu} Hurd
19409 @cindex detach from thread, @sc{gnu} Hurd
19410 This command sets the suspend count @value{GDBN} will leave on a
19411 thread when detaching. This number is relative to the suspend count
19412 found by @value{GDBN} when it notices the thread; use @code{set thread
19413 takeover-suspend-count} to force it to an absolute value.
19415 @item show thread detach-suspend-count
19416 Show the suspend count @value{GDBN} will leave on the thread when
19419 @item set thread exception-port
19420 @itemx set thread excp
19421 Set the thread exception port to which to forward exceptions. This
19422 overrides the port set by @code{set task exception-port} (see above).
19423 @code{set thread excp} is the shorthand alias.
19425 @item set thread takeover-suspend-count
19426 Normally, @value{GDBN}'s thread suspend counts are relative to the
19427 value @value{GDBN} finds when it notices each thread. This command
19428 changes the suspend counts to be absolute instead.
19430 @item set thread default
19431 @itemx show thread default
19432 @cindex thread default settings, @sc{gnu} Hurd
19433 Each of the above @code{set thread} commands has a @code{set thread
19434 default} counterpart (e.g., @code{set thread default pause}, @code{set
19435 thread default exception-port}, etc.). The @code{thread default}
19436 variety of commands sets the default thread properties for all
19437 threads; you can then change the properties of individual threads with
19438 the non-default commands.
19445 @value{GDBN} provides the following commands specific to the Darwin target:
19448 @item set debug darwin @var{num}
19449 @kindex set debug darwin
19450 When set to a non zero value, enables debugging messages specific to
19451 the Darwin support. Higher values produce more verbose output.
19453 @item show debug darwin
19454 @kindex show debug darwin
19455 Show the current state of Darwin messages.
19457 @item set debug mach-o @var{num}
19458 @kindex set debug mach-o
19459 When set to a non zero value, enables debugging messages while
19460 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19461 file format used on Darwin for object and executable files.) Higher
19462 values produce more verbose output. This is a command to diagnose
19463 problems internal to @value{GDBN} and should not be needed in normal
19466 @item show debug mach-o
19467 @kindex show debug mach-o
19468 Show the current state of Mach-O file messages.
19470 @item set mach-exceptions on
19471 @itemx set mach-exceptions off
19472 @kindex set mach-exceptions
19473 On Darwin, faults are first reported as a Mach exception and are then
19474 mapped to a Posix signal. Use this command to turn on trapping of
19475 Mach exceptions in the inferior. This might be sometimes useful to
19476 better understand the cause of a fault. The default is off.
19478 @item show mach-exceptions
19479 @kindex show mach-exceptions
19480 Show the current state of exceptions trapping.
19485 @section Embedded Operating Systems
19487 This section describes configurations involving the debugging of
19488 embedded operating systems that are available for several different
19492 * VxWorks:: Using @value{GDBN} with VxWorks
19495 @value{GDBN} includes the ability to debug programs running on
19496 various real-time operating systems.
19499 @subsection Using @value{GDBN} with VxWorks
19505 @kindex target vxworks
19506 @item target vxworks @var{machinename}
19507 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19508 is the target system's machine name or IP address.
19512 On VxWorks, @code{load} links @var{filename} dynamically on the
19513 current target system as well as adding its symbols in @value{GDBN}.
19515 @value{GDBN} enables developers to spawn and debug tasks running on networked
19516 VxWorks targets from a Unix host. Already-running tasks spawned from
19517 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19518 both the Unix host and on the VxWorks target. The program
19519 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19520 installed with the name @code{vxgdb}, to distinguish it from a
19521 @value{GDBN} for debugging programs on the host itself.)
19524 @item VxWorks-timeout @var{args}
19525 @kindex vxworks-timeout
19526 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19527 This option is set by the user, and @var{args} represents the number of
19528 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19529 your VxWorks target is a slow software simulator or is on the far side
19530 of a thin network line.
19533 The following information on connecting to VxWorks was current when
19534 this manual was produced; newer releases of VxWorks may use revised
19537 @findex INCLUDE_RDB
19538 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19539 to include the remote debugging interface routines in the VxWorks
19540 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19541 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19542 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19543 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19544 information on configuring and remaking VxWorks, see the manufacturer's
19546 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19548 Once you have included @file{rdb.a} in your VxWorks system image and set
19549 your Unix execution search path to find @value{GDBN}, you are ready to
19550 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19551 @code{vxgdb}, depending on your installation).
19553 @value{GDBN} comes up showing the prompt:
19560 * VxWorks Connection:: Connecting to VxWorks
19561 * VxWorks Download:: VxWorks download
19562 * VxWorks Attach:: Running tasks
19565 @node VxWorks Connection
19566 @subsubsection Connecting to VxWorks
19568 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19569 network. To connect to a target whose host name is ``@code{tt}'', type:
19572 (vxgdb) target vxworks tt
19576 @value{GDBN} displays messages like these:
19579 Attaching remote machine across net...
19584 @value{GDBN} then attempts to read the symbol tables of any object modules
19585 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19586 these files by searching the directories listed in the command search
19587 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19588 to find an object file, it displays a message such as:
19591 prog.o: No such file or directory.
19594 When this happens, add the appropriate directory to the search path with
19595 the @value{GDBN} command @code{path}, and execute the @code{target}
19598 @node VxWorks Download
19599 @subsubsection VxWorks Download
19601 @cindex download to VxWorks
19602 If you have connected to the VxWorks target and you want to debug an
19603 object that has not yet been loaded, you can use the @value{GDBN}
19604 @code{load} command to download a file from Unix to VxWorks
19605 incrementally. The object file given as an argument to the @code{load}
19606 command is actually opened twice: first by the VxWorks target in order
19607 to download the code, then by @value{GDBN} in order to read the symbol
19608 table. This can lead to problems if the current working directories on
19609 the two systems differ. If both systems have NFS mounted the same
19610 filesystems, you can avoid these problems by using absolute paths.
19611 Otherwise, it is simplest to set the working directory on both systems
19612 to the directory in which the object file resides, and then to reference
19613 the file by its name, without any path. For instance, a program
19614 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19615 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19616 program, type this on VxWorks:
19619 -> cd "@var{vxpath}/vw/demo/rdb"
19623 Then, in @value{GDBN}, type:
19626 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19627 (vxgdb) load prog.o
19630 @value{GDBN} displays a response similar to this:
19633 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19636 You can also use the @code{load} command to reload an object module
19637 after editing and recompiling the corresponding source file. Note that
19638 this makes @value{GDBN} delete all currently-defined breakpoints,
19639 auto-displays, and convenience variables, and to clear the value
19640 history. (This is necessary in order to preserve the integrity of
19641 debugger's data structures that reference the target system's symbol
19644 @node VxWorks Attach
19645 @subsubsection Running Tasks
19647 @cindex running VxWorks tasks
19648 You can also attach to an existing task using the @code{attach} command as
19652 (vxgdb) attach @var{task}
19656 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19657 or suspended when you attach to it. Running tasks are suspended at
19658 the time of attachment.
19660 @node Embedded Processors
19661 @section Embedded Processors
19663 This section goes into details specific to particular embedded
19666 @cindex send command to simulator
19667 Whenever a specific embedded processor has a simulator, @value{GDBN}
19668 allows to send an arbitrary command to the simulator.
19671 @item sim @var{command}
19672 @kindex sim@r{, a command}
19673 Send an arbitrary @var{command} string to the simulator. Consult the
19674 documentation for the specific simulator in use for information about
19675 acceptable commands.
19681 * M32R/D:: Renesas M32R/D
19682 * M68K:: Motorola M68K
19683 * MicroBlaze:: Xilinx MicroBlaze
19684 * MIPS Embedded:: MIPS Embedded
19685 * OpenRISC 1000:: OpenRisc 1000
19686 * PowerPC Embedded:: PowerPC Embedded
19687 * PA:: HP PA Embedded
19688 * Sparclet:: Tsqware Sparclet
19689 * Sparclite:: Fujitsu Sparclite
19690 * Z8000:: Zilog Z8000
19693 * Super-H:: Renesas Super-H
19702 @item target rdi @var{dev}
19703 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19704 use this target to communicate with both boards running the Angel
19705 monitor, or with the EmbeddedICE JTAG debug device.
19708 @item target rdp @var{dev}
19713 @value{GDBN} provides the following ARM-specific commands:
19716 @item set arm disassembler
19718 This commands selects from a list of disassembly styles. The
19719 @code{"std"} style is the standard style.
19721 @item show arm disassembler
19723 Show the current disassembly style.
19725 @item set arm apcs32
19726 @cindex ARM 32-bit mode
19727 This command toggles ARM operation mode between 32-bit and 26-bit.
19729 @item show arm apcs32
19730 Display the current usage of the ARM 32-bit mode.
19732 @item set arm fpu @var{fputype}
19733 This command sets the ARM floating-point unit (FPU) type. The
19734 argument @var{fputype} can be one of these:
19738 Determine the FPU type by querying the OS ABI.
19740 Software FPU, with mixed-endian doubles on little-endian ARM
19743 GCC-compiled FPA co-processor.
19745 Software FPU with pure-endian doubles.
19751 Show the current type of the FPU.
19754 This command forces @value{GDBN} to use the specified ABI.
19757 Show the currently used ABI.
19759 @item set arm fallback-mode (arm|thumb|auto)
19760 @value{GDBN} uses the symbol table, when available, to determine
19761 whether instructions are ARM or Thumb. This command controls
19762 @value{GDBN}'s default behavior when the symbol table is not
19763 available. The default is @samp{auto}, which causes @value{GDBN} to
19764 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19767 @item show arm fallback-mode
19768 Show the current fallback instruction mode.
19770 @item set arm force-mode (arm|thumb|auto)
19771 This command overrides use of the symbol table to determine whether
19772 instructions are ARM or Thumb. The default is @samp{auto}, which
19773 causes @value{GDBN} to use the symbol table and then the setting
19774 of @samp{set arm fallback-mode}.
19776 @item show arm force-mode
19777 Show the current forced instruction mode.
19779 @item set debug arm
19780 Toggle whether to display ARM-specific debugging messages from the ARM
19781 target support subsystem.
19783 @item show debug arm
19784 Show whether ARM-specific debugging messages are enabled.
19787 The following commands are available when an ARM target is debugged
19788 using the RDI interface:
19791 @item rdilogfile @r{[}@var{file}@r{]}
19793 @cindex ADP (Angel Debugger Protocol) logging
19794 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19795 With an argument, sets the log file to the specified @var{file}. With
19796 no argument, show the current log file name. The default log file is
19799 @item rdilogenable @r{[}@var{arg}@r{]}
19800 @kindex rdilogenable
19801 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19802 enables logging, with an argument 0 or @code{"no"} disables it. With
19803 no arguments displays the current setting. When logging is enabled,
19804 ADP packets exchanged between @value{GDBN} and the RDI target device
19805 are logged to a file.
19807 @item set rdiromatzero
19808 @kindex set rdiromatzero
19809 @cindex ROM at zero address, RDI
19810 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19811 vector catching is disabled, so that zero address can be used. If off
19812 (the default), vector catching is enabled. For this command to take
19813 effect, it needs to be invoked prior to the @code{target rdi} command.
19815 @item show rdiromatzero
19816 @kindex show rdiromatzero
19817 Show the current setting of ROM at zero address.
19819 @item set rdiheartbeat
19820 @kindex set rdiheartbeat
19821 @cindex RDI heartbeat
19822 Enable or disable RDI heartbeat packets. It is not recommended to
19823 turn on this option, since it confuses ARM and EPI JTAG interface, as
19824 well as the Angel monitor.
19826 @item show rdiheartbeat
19827 @kindex show rdiheartbeat
19828 Show the setting of RDI heartbeat packets.
19832 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19833 The @value{GDBN} ARM simulator accepts the following optional arguments.
19836 @item --swi-support=@var{type}
19837 Tell the simulator which SWI interfaces to support.
19838 @var{type} may be a comma separated list of the following values.
19839 The default value is @code{all}.
19852 @subsection Renesas M32R/D and M32R/SDI
19855 @kindex target m32r
19856 @item target m32r @var{dev}
19857 Renesas M32R/D ROM monitor.
19859 @kindex target m32rsdi
19860 @item target m32rsdi @var{dev}
19861 Renesas M32R SDI server, connected via parallel port to the board.
19864 The following @value{GDBN} commands are specific to the M32R monitor:
19867 @item set download-path @var{path}
19868 @kindex set download-path
19869 @cindex find downloadable @sc{srec} files (M32R)
19870 Set the default path for finding downloadable @sc{srec} files.
19872 @item show download-path
19873 @kindex show download-path
19874 Show the default path for downloadable @sc{srec} files.
19876 @item set board-address @var{addr}
19877 @kindex set board-address
19878 @cindex M32-EVA target board address
19879 Set the IP address for the M32R-EVA target board.
19881 @item show board-address
19882 @kindex show board-address
19883 Show the current IP address of the target board.
19885 @item set server-address @var{addr}
19886 @kindex set server-address
19887 @cindex download server address (M32R)
19888 Set the IP address for the download server, which is the @value{GDBN}'s
19891 @item show server-address
19892 @kindex show server-address
19893 Display the IP address of the download server.
19895 @item upload @r{[}@var{file}@r{]}
19896 @kindex upload@r{, M32R}
19897 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19898 upload capability. If no @var{file} argument is given, the current
19899 executable file is uploaded.
19901 @item tload @r{[}@var{file}@r{]}
19902 @kindex tload@r{, M32R}
19903 Test the @code{upload} command.
19906 The following commands are available for M32R/SDI:
19911 @cindex reset SDI connection, M32R
19912 This command resets the SDI connection.
19916 This command shows the SDI connection status.
19919 @kindex debug_chaos
19920 @cindex M32R/Chaos debugging
19921 Instructs the remote that M32R/Chaos debugging is to be used.
19923 @item use_debug_dma
19924 @kindex use_debug_dma
19925 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19928 @kindex use_mon_code
19929 Instructs the remote to use the MON_CODE method of accessing memory.
19932 @kindex use_ib_break
19933 Instructs the remote to set breakpoints by IB break.
19935 @item use_dbt_break
19936 @kindex use_dbt_break
19937 Instructs the remote to set breakpoints by DBT.
19943 The Motorola m68k configuration includes ColdFire support, and a
19944 target command for the following ROM monitor.
19948 @kindex target dbug
19949 @item target dbug @var{dev}
19950 dBUG ROM monitor for Motorola ColdFire.
19955 @subsection MicroBlaze
19956 @cindex Xilinx MicroBlaze
19957 @cindex XMD, Xilinx Microprocessor Debugger
19959 The MicroBlaze is a soft-core processor supported on various Xilinx
19960 FPGAs, such as Spartan or Virtex series. Boards with these processors
19961 usually have JTAG ports which connect to a host system running the Xilinx
19962 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19963 This host system is used to download the configuration bitstream to
19964 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19965 communicates with the target board using the JTAG interface and
19966 presents a @code{gdbserver} interface to the board. By default
19967 @code{xmd} uses port @code{1234}. (While it is possible to change
19968 this default port, it requires the use of undocumented @code{xmd}
19969 commands. Contact Xilinx support if you need to do this.)
19971 Use these GDB commands to connect to the MicroBlaze target processor.
19974 @item target remote :1234
19975 Use this command to connect to the target if you are running @value{GDBN}
19976 on the same system as @code{xmd}.
19978 @item target remote @var{xmd-host}:1234
19979 Use this command to connect to the target if it is connected to @code{xmd}
19980 running on a different system named @var{xmd-host}.
19983 Use this command to download a program to the MicroBlaze target.
19985 @item set debug microblaze @var{n}
19986 Enable MicroBlaze-specific debugging messages if non-zero.
19988 @item show debug microblaze @var{n}
19989 Show MicroBlaze-specific debugging level.
19992 @node MIPS Embedded
19993 @subsection @acronym{MIPS} Embedded
19995 @cindex @acronym{MIPS} boards
19996 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
19997 @acronym{MIPS} board attached to a serial line. This is available when
19998 you configure @value{GDBN} with @samp{--target=mips-elf}.
20001 Use these @value{GDBN} commands to specify the connection to your target board:
20004 @item target mips @var{port}
20005 @kindex target mips @var{port}
20006 To run a program on the board, start up @code{@value{GDBP}} with the
20007 name of your program as the argument. To connect to the board, use the
20008 command @samp{target mips @var{port}}, where @var{port} is the name of
20009 the serial port connected to the board. If the program has not already
20010 been downloaded to the board, you may use the @code{load} command to
20011 download it. You can then use all the usual @value{GDBN} commands.
20013 For example, this sequence connects to the target board through a serial
20014 port, and loads and runs a program called @var{prog} through the
20018 host$ @value{GDBP} @var{prog}
20019 @value{GDBN} is free software and @dots{}
20020 (@value{GDBP}) target mips /dev/ttyb
20021 (@value{GDBP}) load @var{prog}
20025 @item target mips @var{hostname}:@var{portnumber}
20026 On some @value{GDBN} host configurations, you can specify a TCP
20027 connection (for instance, to a serial line managed by a terminal
20028 concentrator) instead of a serial port, using the syntax
20029 @samp{@var{hostname}:@var{portnumber}}.
20031 @item target pmon @var{port}
20032 @kindex target pmon @var{port}
20035 @item target ddb @var{port}
20036 @kindex target ddb @var{port}
20037 NEC's DDB variant of PMON for Vr4300.
20039 @item target lsi @var{port}
20040 @kindex target lsi @var{port}
20041 LSI variant of PMON.
20043 @kindex target r3900
20044 @item target r3900 @var{dev}
20045 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20047 @kindex target array
20048 @item target array @var{dev}
20049 Array Tech LSI33K RAID controller board.
20055 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20058 @item set mipsfpu double
20059 @itemx set mipsfpu single
20060 @itemx set mipsfpu none
20061 @itemx set mipsfpu auto
20062 @itemx show mipsfpu
20063 @kindex set mipsfpu
20064 @kindex show mipsfpu
20065 @cindex @acronym{MIPS} remote floating point
20066 @cindex floating point, @acronym{MIPS} remote
20067 If your target board does not support the @acronym{MIPS} floating point
20068 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20069 need this, you may wish to put the command in your @value{GDBN} init
20070 file). This tells @value{GDBN} how to find the return value of
20071 functions which return floating point values. It also allows
20072 @value{GDBN} to avoid saving the floating point registers when calling
20073 functions on the board. If you are using a floating point coprocessor
20074 with only single precision floating point support, as on the @sc{r4650}
20075 processor, use the command @samp{set mipsfpu single}. The default
20076 double precision floating point coprocessor may be selected using
20077 @samp{set mipsfpu double}.
20079 In previous versions the only choices were double precision or no
20080 floating point, so @samp{set mipsfpu on} will select double precision
20081 and @samp{set mipsfpu off} will select no floating point.
20083 As usual, you can inquire about the @code{mipsfpu} variable with
20084 @samp{show mipsfpu}.
20086 @item set timeout @var{seconds}
20087 @itemx set retransmit-timeout @var{seconds}
20088 @itemx show timeout
20089 @itemx show retransmit-timeout
20090 @cindex @code{timeout}, @acronym{MIPS} protocol
20091 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20092 @kindex set timeout
20093 @kindex show timeout
20094 @kindex set retransmit-timeout
20095 @kindex show retransmit-timeout
20096 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20097 remote protocol, with the @code{set timeout @var{seconds}} command. The
20098 default is 5 seconds. Similarly, you can control the timeout used while
20099 waiting for an acknowledgment of a packet with the @code{set
20100 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20101 You can inspect both values with @code{show timeout} and @code{show
20102 retransmit-timeout}. (These commands are @emph{only} available when
20103 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20105 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20106 is waiting for your program to stop. In that case, @value{GDBN} waits
20107 forever because it has no way of knowing how long the program is going
20108 to run before stopping.
20110 @item set syn-garbage-limit @var{num}
20111 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20112 @cindex synchronize with remote @acronym{MIPS} target
20113 Limit the maximum number of characters @value{GDBN} should ignore when
20114 it tries to synchronize with the remote target. The default is 10
20115 characters. Setting the limit to -1 means there's no limit.
20117 @item show syn-garbage-limit
20118 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20119 Show the current limit on the number of characters to ignore when
20120 trying to synchronize with the remote system.
20122 @item set monitor-prompt @var{prompt}
20123 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20124 @cindex remote monitor prompt
20125 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20126 remote monitor. The default depends on the target:
20136 @item show monitor-prompt
20137 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20138 Show the current strings @value{GDBN} expects as the prompt from the
20141 @item set monitor-warnings
20142 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20143 Enable or disable monitor warnings about hardware breakpoints. This
20144 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20145 display warning messages whose codes are returned by the @code{lsi}
20146 PMON monitor for breakpoint commands.
20148 @item show monitor-warnings
20149 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20150 Show the current setting of printing monitor warnings.
20152 @item pmon @var{command}
20153 @kindex pmon@r{, @acronym{MIPS} remote}
20154 @cindex send PMON command
20155 This command allows sending an arbitrary @var{command} string to the
20156 monitor. The monitor must be in debug mode for this to work.
20159 @node OpenRISC 1000
20160 @subsection OpenRISC 1000
20161 @cindex OpenRISC 1000
20163 @cindex or1k boards
20164 See OR1k Architecture document (@uref{www.opencores.org}) for more information
20165 about platform and commands.
20169 @kindex target jtag
20170 @item target jtag jtag://@var{host}:@var{port}
20172 Connects to remote JTAG server.
20173 JTAG remote server can be either an or1ksim or JTAG server,
20174 connected via parallel port to the board.
20176 Example: @code{target jtag jtag://localhost:9999}
20179 @item or1ksim @var{command}
20180 If connected to @code{or1ksim} OpenRISC 1000 Architectural
20181 Simulator, proprietary commands can be executed.
20183 @kindex info or1k spr
20184 @item info or1k spr
20185 Displays spr groups.
20187 @item info or1k spr @var{group}
20188 @itemx info or1k spr @var{groupno}
20189 Displays register names in selected group.
20191 @item info or1k spr @var{group} @var{register}
20192 @itemx info or1k spr @var{register}
20193 @itemx info or1k spr @var{groupno} @var{registerno}
20194 @itemx info or1k spr @var{registerno}
20195 Shows information about specified spr register.
20198 @item spr @var{group} @var{register} @var{value}
20199 @itemx spr @var{register @var{value}}
20200 @itemx spr @var{groupno} @var{registerno @var{value}}
20201 @itemx spr @var{registerno @var{value}}
20202 Writes @var{value} to specified spr register.
20205 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
20206 It is very similar to @value{GDBN} trace, except it does not interfere with normal
20207 program execution and is thus much faster. Hardware breakpoints/watchpoint
20208 triggers can be set using:
20211 Load effective address/data
20213 Store effective address/data
20215 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
20220 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
20221 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
20223 @code{htrace} commands:
20224 @cindex OpenRISC 1000 htrace
20227 @item hwatch @var{conditional}
20228 Set hardware watchpoint on combination of Load/Store Effective Address(es)
20229 or Data. For example:
20231 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20233 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20237 Display information about current HW trace configuration.
20239 @item htrace trigger @var{conditional}
20240 Set starting criteria for HW trace.
20242 @item htrace qualifier @var{conditional}
20243 Set acquisition qualifier for HW trace.
20245 @item htrace stop @var{conditional}
20246 Set HW trace stopping criteria.
20248 @item htrace record [@var{data}]*
20249 Selects the data to be recorded, when qualifier is met and HW trace was
20252 @item htrace enable
20253 @itemx htrace disable
20254 Enables/disables the HW trace.
20256 @item htrace rewind [@var{filename}]
20257 Clears currently recorded trace data.
20259 If filename is specified, new trace file is made and any newly collected data
20260 will be written there.
20262 @item htrace print [@var{start} [@var{len}]]
20263 Prints trace buffer, using current record configuration.
20265 @item htrace mode continuous
20266 Set continuous trace mode.
20268 @item htrace mode suspend
20269 Set suspend trace mode.
20273 @node PowerPC Embedded
20274 @subsection PowerPC Embedded
20276 @cindex DVC register
20277 @value{GDBN} supports using the DVC (Data Value Compare) register to
20278 implement in hardware simple hardware watchpoint conditions of the form:
20281 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20282 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20285 The DVC register will be automatically used when @value{GDBN} detects
20286 such pattern in a condition expression, and the created watchpoint uses one
20287 debug register (either the @code{exact-watchpoints} option is on and the
20288 variable is scalar, or the variable has a length of one byte). This feature
20289 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20292 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20293 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20294 in which case watchpoints using only one debug register are created when
20295 watching variables of scalar types.
20297 You can create an artificial array to watch an arbitrary memory
20298 region using one of the following commands (@pxref{Expressions}):
20301 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20302 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20305 PowerPC embedded processors support masked watchpoints. See the discussion
20306 about the @code{mask} argument in @ref{Set Watchpoints}.
20308 @cindex ranged breakpoint
20309 PowerPC embedded processors support hardware accelerated
20310 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20311 the inferior whenever it executes an instruction at any address within
20312 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20313 use the @code{break-range} command.
20315 @value{GDBN} provides the following PowerPC-specific commands:
20318 @kindex break-range
20319 @item break-range @var{start-location}, @var{end-location}
20320 Set a breakpoint for an address range.
20321 @var{start-location} and @var{end-location} can specify a function name,
20322 a line number, an offset of lines from the current line or from the start
20323 location, or an address of an instruction (see @ref{Specify Location},
20324 for a list of all the possible ways to specify a @var{location}.)
20325 The breakpoint will stop execution of the inferior whenever it
20326 executes an instruction at any address within the specified range,
20327 (including @var{start-location} and @var{end-location}.)
20329 @kindex set powerpc
20330 @item set powerpc soft-float
20331 @itemx show powerpc soft-float
20332 Force @value{GDBN} to use (or not use) a software floating point calling
20333 convention. By default, @value{GDBN} selects the calling convention based
20334 on the selected architecture and the provided executable file.
20336 @item set powerpc vector-abi
20337 @itemx show powerpc vector-abi
20338 Force @value{GDBN} to use the specified calling convention for vector
20339 arguments and return values. The valid options are @samp{auto};
20340 @samp{generic}, to avoid vector registers even if they are present;
20341 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20342 registers. By default, @value{GDBN} selects the calling convention
20343 based on the selected architecture and the provided executable file.
20345 @item set powerpc exact-watchpoints
20346 @itemx show powerpc exact-watchpoints
20347 Allow @value{GDBN} to use only one debug register when watching a variable
20348 of scalar type, thus assuming that the variable is accessed through the
20349 address of its first byte.
20351 @kindex target dink32
20352 @item target dink32 @var{dev}
20353 DINK32 ROM monitor.
20355 @kindex target ppcbug
20356 @item target ppcbug @var{dev}
20357 @kindex target ppcbug1
20358 @item target ppcbug1 @var{dev}
20359 PPCBUG ROM monitor for PowerPC.
20362 @item target sds @var{dev}
20363 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20366 @cindex SDS protocol
20367 The following commands specific to the SDS protocol are supported
20371 @item set sdstimeout @var{nsec}
20372 @kindex set sdstimeout
20373 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20374 default is 2 seconds.
20376 @item show sdstimeout
20377 @kindex show sdstimeout
20378 Show the current value of the SDS timeout.
20380 @item sds @var{command}
20381 @kindex sds@r{, a command}
20382 Send the specified @var{command} string to the SDS monitor.
20387 @subsection HP PA Embedded
20391 @kindex target op50n
20392 @item target op50n @var{dev}
20393 OP50N monitor, running on an OKI HPPA board.
20395 @kindex target w89k
20396 @item target w89k @var{dev}
20397 W89K monitor, running on a Winbond HPPA board.
20402 @subsection Tsqware Sparclet
20406 @value{GDBN} enables developers to debug tasks running on
20407 Sparclet targets from a Unix host.
20408 @value{GDBN} uses code that runs on
20409 both the Unix host and on the Sparclet target. The program
20410 @code{@value{GDBP}} is installed and executed on the Unix host.
20413 @item remotetimeout @var{args}
20414 @kindex remotetimeout
20415 @value{GDBN} supports the option @code{remotetimeout}.
20416 This option is set by the user, and @var{args} represents the number of
20417 seconds @value{GDBN} waits for responses.
20420 @cindex compiling, on Sparclet
20421 When compiling for debugging, include the options @samp{-g} to get debug
20422 information and @samp{-Ttext} to relocate the program to where you wish to
20423 load it on the target. You may also want to add the options @samp{-n} or
20424 @samp{-N} in order to reduce the size of the sections. Example:
20427 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20430 You can use @code{objdump} to verify that the addresses are what you intended:
20433 sparclet-aout-objdump --headers --syms prog
20436 @cindex running, on Sparclet
20438 your Unix execution search path to find @value{GDBN}, you are ready to
20439 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20440 (or @code{sparclet-aout-gdb}, depending on your installation).
20442 @value{GDBN} comes up showing the prompt:
20449 * Sparclet File:: Setting the file to debug
20450 * Sparclet Connection:: Connecting to Sparclet
20451 * Sparclet Download:: Sparclet download
20452 * Sparclet Execution:: Running and debugging
20455 @node Sparclet File
20456 @subsubsection Setting File to Debug
20458 The @value{GDBN} command @code{file} lets you choose with program to debug.
20461 (gdbslet) file prog
20465 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20466 @value{GDBN} locates
20467 the file by searching the directories listed in the command search
20469 If the file was compiled with debug information (option @samp{-g}), source
20470 files will be searched as well.
20471 @value{GDBN} locates
20472 the source files by searching the directories listed in the directory search
20473 path (@pxref{Environment, ,Your Program's Environment}).
20475 to find a file, it displays a message such as:
20478 prog: No such file or directory.
20481 When this happens, add the appropriate directories to the search paths with
20482 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20483 @code{target} command again.
20485 @node Sparclet Connection
20486 @subsubsection Connecting to Sparclet
20488 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20489 To connect to a target on serial port ``@code{ttya}'', type:
20492 (gdbslet) target sparclet /dev/ttya
20493 Remote target sparclet connected to /dev/ttya
20494 main () at ../prog.c:3
20498 @value{GDBN} displays messages like these:
20504 @node Sparclet Download
20505 @subsubsection Sparclet Download
20507 @cindex download to Sparclet
20508 Once connected to the Sparclet target,
20509 you can use the @value{GDBN}
20510 @code{load} command to download the file from the host to the target.
20511 The file name and load offset should be given as arguments to the @code{load}
20513 Since the file format is aout, the program must be loaded to the starting
20514 address. You can use @code{objdump} to find out what this value is. The load
20515 offset is an offset which is added to the VMA (virtual memory address)
20516 of each of the file's sections.
20517 For instance, if the program
20518 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20519 and bss at 0x12010170, in @value{GDBN}, type:
20522 (gdbslet) load prog 0x12010000
20523 Loading section .text, size 0xdb0 vma 0x12010000
20526 If the code is loaded at a different address then what the program was linked
20527 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20528 to tell @value{GDBN} where to map the symbol table.
20530 @node Sparclet Execution
20531 @subsubsection Running and Debugging
20533 @cindex running and debugging Sparclet programs
20534 You can now begin debugging the task using @value{GDBN}'s execution control
20535 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20536 manual for the list of commands.
20540 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20542 Starting program: prog
20543 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20544 3 char *symarg = 0;
20546 4 char *execarg = "hello!";
20551 @subsection Fujitsu Sparclite
20555 @kindex target sparclite
20556 @item target sparclite @var{dev}
20557 Fujitsu sparclite boards, used only for the purpose of loading.
20558 You must use an additional command to debug the program.
20559 For example: target remote @var{dev} using @value{GDBN} standard
20565 @subsection Zilog Z8000
20568 @cindex simulator, Z8000
20569 @cindex Zilog Z8000 simulator
20571 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20574 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20575 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20576 segmented variant). The simulator recognizes which architecture is
20577 appropriate by inspecting the object code.
20580 @item target sim @var{args}
20582 @kindex target sim@r{, with Z8000}
20583 Debug programs on a simulated CPU. If the simulator supports setup
20584 options, specify them via @var{args}.
20588 After specifying this target, you can debug programs for the simulated
20589 CPU in the same style as programs for your host computer; use the
20590 @code{file} command to load a new program image, the @code{run} command
20591 to run your program, and so on.
20593 As well as making available all the usual machine registers
20594 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20595 additional items of information as specially named registers:
20600 Counts clock-ticks in the simulator.
20603 Counts instructions run in the simulator.
20606 Execution time in 60ths of a second.
20610 You can refer to these values in @value{GDBN} expressions with the usual
20611 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20612 conditional breakpoint that suspends only after at least 5000
20613 simulated clock ticks.
20616 @subsection Atmel AVR
20619 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20620 following AVR-specific commands:
20623 @item info io_registers
20624 @kindex info io_registers@r{, AVR}
20625 @cindex I/O registers (Atmel AVR)
20626 This command displays information about the AVR I/O registers. For
20627 each register, @value{GDBN} prints its number and value.
20634 When configured for debugging CRIS, @value{GDBN} provides the
20635 following CRIS-specific commands:
20638 @item set cris-version @var{ver}
20639 @cindex CRIS version
20640 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20641 The CRIS version affects register names and sizes. This command is useful in
20642 case autodetection of the CRIS version fails.
20644 @item show cris-version
20645 Show the current CRIS version.
20647 @item set cris-dwarf2-cfi
20648 @cindex DWARF-2 CFI and CRIS
20649 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20650 Change to @samp{off} when using @code{gcc-cris} whose version is below
20653 @item show cris-dwarf2-cfi
20654 Show the current state of using DWARF-2 CFI.
20656 @item set cris-mode @var{mode}
20658 Set the current CRIS mode to @var{mode}. It should only be changed when
20659 debugging in guru mode, in which case it should be set to
20660 @samp{guru} (the default is @samp{normal}).
20662 @item show cris-mode
20663 Show the current CRIS mode.
20667 @subsection Renesas Super-H
20670 For the Renesas Super-H processor, @value{GDBN} provides these
20674 @item set sh calling-convention @var{convention}
20675 @kindex set sh calling-convention
20676 Set the calling-convention used when calling functions from @value{GDBN}.
20677 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20678 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20679 convention. If the DWARF-2 information of the called function specifies
20680 that the function follows the Renesas calling convention, the function
20681 is called using the Renesas calling convention. If the calling convention
20682 is set to @samp{renesas}, the Renesas calling convention is always used,
20683 regardless of the DWARF-2 information. This can be used to override the
20684 default of @samp{gcc} if debug information is missing, or the compiler
20685 does not emit the DWARF-2 calling convention entry for a function.
20687 @item show sh calling-convention
20688 @kindex show sh calling-convention
20689 Show the current calling convention setting.
20694 @node Architectures
20695 @section Architectures
20697 This section describes characteristics of architectures that affect
20698 all uses of @value{GDBN} with the architecture, both native and cross.
20705 * HPPA:: HP PA architecture
20706 * SPU:: Cell Broadband Engine SPU architecture
20711 @subsection AArch64
20712 @cindex AArch64 support
20714 When @value{GDBN} is debugging the AArch64 architecture, it provides the
20715 following special commands:
20718 @item set debug aarch64
20719 @kindex set debug aarch64
20720 This command determines whether AArch64 architecture-specific debugging
20721 messages are to be displayed.
20723 @item show debug aarch64
20724 Show whether AArch64 debugging messages are displayed.
20729 @subsection x86 Architecture-specific Issues
20732 @item set struct-convention @var{mode}
20733 @kindex set struct-convention
20734 @cindex struct return convention
20735 @cindex struct/union returned in registers
20736 Set the convention used by the inferior to return @code{struct}s and
20737 @code{union}s from functions to @var{mode}. Possible values of
20738 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20739 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20740 are returned on the stack, while @code{"reg"} means that a
20741 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20742 be returned in a register.
20744 @item show struct-convention
20745 @kindex show struct-convention
20746 Show the current setting of the convention to return @code{struct}s
20753 See the following section.
20756 @subsection @acronym{MIPS}
20758 @cindex stack on Alpha
20759 @cindex stack on @acronym{MIPS}
20760 @cindex Alpha stack
20761 @cindex @acronym{MIPS} stack
20762 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20763 sometimes requires @value{GDBN} to search backward in the object code to
20764 find the beginning of a function.
20766 @cindex response time, @acronym{MIPS} debugging
20767 To improve response time (especially for embedded applications, where
20768 @value{GDBN} may be restricted to a slow serial line for this search)
20769 you may want to limit the size of this search, using one of these
20773 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20774 @item set heuristic-fence-post @var{limit}
20775 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20776 search for the beginning of a function. A value of @var{0} (the
20777 default) means there is no limit. However, except for @var{0}, the
20778 larger the limit the more bytes @code{heuristic-fence-post} must search
20779 and therefore the longer it takes to run. You should only need to use
20780 this command when debugging a stripped executable.
20782 @item show heuristic-fence-post
20783 Display the current limit.
20787 These commands are available @emph{only} when @value{GDBN} is configured
20788 for debugging programs on Alpha or @acronym{MIPS} processors.
20790 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20794 @item set mips abi @var{arg}
20795 @kindex set mips abi
20796 @cindex set ABI for @acronym{MIPS}
20797 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20798 values of @var{arg} are:
20802 The default ABI associated with the current binary (this is the
20812 @item show mips abi
20813 @kindex show mips abi
20814 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20816 @item set mips compression @var{arg}
20817 @kindex set mips compression
20818 @cindex code compression, @acronym{MIPS}
20819 Tell @value{GDBN} which @acronym{MIPS} compressed
20820 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20821 inferior. @value{GDBN} uses this for code disassembly and other
20822 internal interpretation purposes. This setting is only referred to
20823 when no executable has been associated with the debugging session or
20824 the executable does not provide information about the encoding it uses.
20825 Otherwise this setting is automatically updated from information
20826 provided by the executable.
20828 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20829 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20830 executables containing @acronym{MIPS16} code frequently are not
20831 identified as such.
20833 This setting is ``sticky''; that is, it retains its value across
20834 debugging sessions until reset either explicitly with this command or
20835 implicitly from an executable.
20837 The compiler and/or assembler typically add symbol table annotations to
20838 identify functions compiled for the @acronym{MIPS16} or
20839 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20840 are present, @value{GDBN} uses them in preference to the global
20841 compressed @acronym{ISA} encoding setting.
20843 @item show mips compression
20844 @kindex show mips compression
20845 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20846 @value{GDBN} to debug the inferior.
20849 @itemx show mipsfpu
20850 @xref{MIPS Embedded, set mipsfpu}.
20852 @item set mips mask-address @var{arg}
20853 @kindex set mips mask-address
20854 @cindex @acronym{MIPS} addresses, masking
20855 This command determines whether the most-significant 32 bits of 64-bit
20856 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20857 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20858 setting, which lets @value{GDBN} determine the correct value.
20860 @item show mips mask-address
20861 @kindex show mips mask-address
20862 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20865 @item set remote-mips64-transfers-32bit-regs
20866 @kindex set remote-mips64-transfers-32bit-regs
20867 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20868 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20869 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20870 and 64 bits for other registers, set this option to @samp{on}.
20872 @item show remote-mips64-transfers-32bit-regs
20873 @kindex show remote-mips64-transfers-32bit-regs
20874 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20876 @item set debug mips
20877 @kindex set debug mips
20878 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20879 target code in @value{GDBN}.
20881 @item show debug mips
20882 @kindex show debug mips
20883 Show the current setting of @acronym{MIPS} debugging messages.
20889 @cindex HPPA support
20891 When @value{GDBN} is debugging the HP PA architecture, it provides the
20892 following special commands:
20895 @item set debug hppa
20896 @kindex set debug hppa
20897 This command determines whether HPPA architecture-specific debugging
20898 messages are to be displayed.
20900 @item show debug hppa
20901 Show whether HPPA debugging messages are displayed.
20903 @item maint print unwind @var{address}
20904 @kindex maint print unwind@r{, HPPA}
20905 This command displays the contents of the unwind table entry at the
20906 given @var{address}.
20912 @subsection Cell Broadband Engine SPU architecture
20913 @cindex Cell Broadband Engine
20916 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20917 it provides the following special commands:
20920 @item info spu event
20922 Display SPU event facility status. Shows current event mask
20923 and pending event status.
20925 @item info spu signal
20926 Display SPU signal notification facility status. Shows pending
20927 signal-control word and signal notification mode of both signal
20928 notification channels.
20930 @item info spu mailbox
20931 Display SPU mailbox facility status. Shows all pending entries,
20932 in order of processing, in each of the SPU Write Outbound,
20933 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20936 Display MFC DMA status. Shows all pending commands in the MFC
20937 DMA queue. For each entry, opcode, tag, class IDs, effective
20938 and local store addresses and transfer size are shown.
20940 @item info spu proxydma
20941 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20942 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20943 and local store addresses and transfer size are shown.
20947 When @value{GDBN} is debugging a combined PowerPC/SPU application
20948 on the Cell Broadband Engine, it provides in addition the following
20952 @item set spu stop-on-load @var{arg}
20954 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20955 will give control to the user when a new SPE thread enters its @code{main}
20956 function. The default is @code{off}.
20958 @item show spu stop-on-load
20960 Show whether to stop for new SPE threads.
20962 @item set spu auto-flush-cache @var{arg}
20963 Set whether to automatically flush the software-managed cache. When set to
20964 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20965 cache to be flushed whenever SPE execution stops. This provides a consistent
20966 view of PowerPC memory that is accessed via the cache. If an application
20967 does not use the software-managed cache, this option has no effect.
20969 @item show spu auto-flush-cache
20970 Show whether to automatically flush the software-managed cache.
20975 @subsection PowerPC
20976 @cindex PowerPC architecture
20978 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20979 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20980 numbers stored in the floating point registers. These values must be stored
20981 in two consecutive registers, always starting at an even register like
20982 @code{f0} or @code{f2}.
20984 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20985 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20986 @code{f2} and @code{f3} for @code{$dl1} and so on.
20988 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20989 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20992 @node Controlling GDB
20993 @chapter Controlling @value{GDBN}
20995 You can alter the way @value{GDBN} interacts with you by using the
20996 @code{set} command. For commands controlling how @value{GDBN} displays
20997 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21002 * Editing:: Command editing
21003 * Command History:: Command history
21004 * Screen Size:: Screen size
21005 * Numbers:: Numbers
21006 * ABI:: Configuring the current ABI
21007 * Auto-loading:: Automatically loading associated files
21008 * Messages/Warnings:: Optional warnings and messages
21009 * Debugging Output:: Optional messages about internal happenings
21010 * Other Misc Settings:: Other Miscellaneous Settings
21018 @value{GDBN} indicates its readiness to read a command by printing a string
21019 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21020 can change the prompt string with the @code{set prompt} command. For
21021 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21022 the prompt in one of the @value{GDBN} sessions so that you can always tell
21023 which one you are talking to.
21025 @emph{Note:} @code{set prompt} does not add a space for you after the
21026 prompt you set. This allows you to set a prompt which ends in a space
21027 or a prompt that does not.
21031 @item set prompt @var{newprompt}
21032 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21034 @kindex show prompt
21036 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21039 Versions of @value{GDBN} that ship with Python scripting enabled have
21040 prompt extensions. The commands for interacting with these extensions
21044 @kindex set extended-prompt
21045 @item set extended-prompt @var{prompt}
21046 Set an extended prompt that allows for substitutions.
21047 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21048 substitution. Any escape sequences specified as part of the prompt
21049 string are replaced with the corresponding strings each time the prompt
21055 set extended-prompt Current working directory: \w (gdb)
21058 Note that when an extended-prompt is set, it takes control of the
21059 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21061 @kindex show extended-prompt
21062 @item show extended-prompt
21063 Prints the extended prompt. Any escape sequences specified as part of
21064 the prompt string with @code{set extended-prompt}, are replaced with the
21065 corresponding strings each time the prompt is displayed.
21069 @section Command Editing
21071 @cindex command line editing
21073 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21074 @sc{gnu} library provides consistent behavior for programs which provide a
21075 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21076 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21077 substitution, and a storage and recall of command history across
21078 debugging sessions.
21080 You may control the behavior of command line editing in @value{GDBN} with the
21081 command @code{set}.
21084 @kindex set editing
21087 @itemx set editing on
21088 Enable command line editing (enabled by default).
21090 @item set editing off
21091 Disable command line editing.
21093 @kindex show editing
21095 Show whether command line editing is enabled.
21098 @ifset SYSTEM_READLINE
21099 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21101 @ifclear SYSTEM_READLINE
21102 @xref{Command Line Editing},
21104 for more details about the Readline
21105 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21106 encouraged to read that chapter.
21108 @node Command History
21109 @section Command History
21110 @cindex command history
21112 @value{GDBN} can keep track of the commands you type during your
21113 debugging sessions, so that you can be certain of precisely what
21114 happened. Use these commands to manage the @value{GDBN} command
21117 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21118 package, to provide the history facility.
21119 @ifset SYSTEM_READLINE
21120 @xref{Using History Interactively, , , history, GNU History Library},
21122 @ifclear SYSTEM_READLINE
21123 @xref{Using History Interactively},
21125 for the detailed description of the History library.
21127 To issue a command to @value{GDBN} without affecting certain aspects of
21128 the state which is seen by users, prefix it with @samp{server }
21129 (@pxref{Server Prefix}). This
21130 means that this command will not affect the command history, nor will it
21131 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21132 pressed on a line by itself.
21134 @cindex @code{server}, command prefix
21135 The server prefix does not affect the recording of values into the value
21136 history; to print a value without recording it into the value history,
21137 use the @code{output} command instead of the @code{print} command.
21139 Here is the description of @value{GDBN} commands related to command
21143 @cindex history substitution
21144 @cindex history file
21145 @kindex set history filename
21146 @cindex @env{GDBHISTFILE}, environment variable
21147 @item set history filename @var{fname}
21148 Set the name of the @value{GDBN} command history file to @var{fname}.
21149 This is the file where @value{GDBN} reads an initial command history
21150 list, and where it writes the command history from this session when it
21151 exits. You can access this list through history expansion or through
21152 the history command editing characters listed below. This file defaults
21153 to the value of the environment variable @code{GDBHISTFILE}, or to
21154 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21157 @cindex save command history
21158 @kindex set history save
21159 @item set history save
21160 @itemx set history save on
21161 Record command history in a file, whose name may be specified with the
21162 @code{set history filename} command. By default, this option is disabled.
21164 @item set history save off
21165 Stop recording command history in a file.
21167 @cindex history size
21168 @kindex set history size
21169 @cindex @env{HISTSIZE}, environment variable
21170 @item set history size @var{size}
21171 Set the number of commands which @value{GDBN} keeps in its history list.
21172 This defaults to the value of the environment variable
21173 @code{HISTSIZE}, or to 256 if this variable is not set.
21176 History expansion assigns special meaning to the character @kbd{!}.
21177 @ifset SYSTEM_READLINE
21178 @xref{Event Designators, , , history, GNU History Library},
21180 @ifclear SYSTEM_READLINE
21181 @xref{Event Designators},
21185 @cindex history expansion, turn on/off
21186 Since @kbd{!} is also the logical not operator in C, history expansion
21187 is off by default. If you decide to enable history expansion with the
21188 @code{set history expansion on} command, you may sometimes need to
21189 follow @kbd{!} (when it is used as logical not, in an expression) with
21190 a space or a tab to prevent it from being expanded. The readline
21191 history facilities do not attempt substitution on the strings
21192 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21194 The commands to control history expansion are:
21197 @item set history expansion on
21198 @itemx set history expansion
21199 @kindex set history expansion
21200 Enable history expansion. History expansion is off by default.
21202 @item set history expansion off
21203 Disable history expansion.
21206 @kindex show history
21208 @itemx show history filename
21209 @itemx show history save
21210 @itemx show history size
21211 @itemx show history expansion
21212 These commands display the state of the @value{GDBN} history parameters.
21213 @code{show history} by itself displays all four states.
21218 @kindex show commands
21219 @cindex show last commands
21220 @cindex display command history
21221 @item show commands
21222 Display the last ten commands in the command history.
21224 @item show commands @var{n}
21225 Print ten commands centered on command number @var{n}.
21227 @item show commands +
21228 Print ten commands just after the commands last printed.
21232 @section Screen Size
21233 @cindex size of screen
21234 @cindex pauses in output
21236 Certain commands to @value{GDBN} may produce large amounts of
21237 information output to the screen. To help you read all of it,
21238 @value{GDBN} pauses and asks you for input at the end of each page of
21239 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21240 to discard the remaining output. Also, the screen width setting
21241 determines when to wrap lines of output. Depending on what is being
21242 printed, @value{GDBN} tries to break the line at a readable place,
21243 rather than simply letting it overflow onto the following line.
21245 Normally @value{GDBN} knows the size of the screen from the terminal
21246 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21247 together with the value of the @code{TERM} environment variable and the
21248 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21249 you can override it with the @code{set height} and @code{set
21256 @kindex show height
21257 @item set height @var{lpp}
21259 @itemx set width @var{cpl}
21261 These @code{set} commands specify a screen height of @var{lpp} lines and
21262 a screen width of @var{cpl} characters. The associated @code{show}
21263 commands display the current settings.
21265 If you specify a height of zero lines, @value{GDBN} does not pause during
21266 output no matter how long the output is. This is useful if output is to a
21267 file or to an editor buffer.
21269 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
21270 from wrapping its output.
21272 @item set pagination on
21273 @itemx set pagination off
21274 @kindex set pagination
21275 Turn the output pagination on or off; the default is on. Turning
21276 pagination off is the alternative to @code{set height 0}. Note that
21277 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21278 Options, -batch}) also automatically disables pagination.
21280 @item show pagination
21281 @kindex show pagination
21282 Show the current pagination mode.
21287 @cindex number representation
21288 @cindex entering numbers
21290 You can always enter numbers in octal, decimal, or hexadecimal in
21291 @value{GDBN} by the usual conventions: octal numbers begin with
21292 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21293 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21294 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21295 10; likewise, the default display for numbers---when no particular
21296 format is specified---is base 10. You can change the default base for
21297 both input and output with the commands described below.
21300 @kindex set input-radix
21301 @item set input-radix @var{base}
21302 Set the default base for numeric input. Supported choices
21303 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21304 specified either unambiguously or using the current input radix; for
21308 set input-radix 012
21309 set input-radix 10.
21310 set input-radix 0xa
21314 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21315 leaves the input radix unchanged, no matter what it was, since
21316 @samp{10}, being without any leading or trailing signs of its base, is
21317 interpreted in the current radix. Thus, if the current radix is 16,
21318 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21321 @kindex set output-radix
21322 @item set output-radix @var{base}
21323 Set the default base for numeric display. Supported choices
21324 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21325 specified either unambiguously or using the current input radix.
21327 @kindex show input-radix
21328 @item show input-radix
21329 Display the current default base for numeric input.
21331 @kindex show output-radix
21332 @item show output-radix
21333 Display the current default base for numeric display.
21335 @item set radix @r{[}@var{base}@r{]}
21339 These commands set and show the default base for both input and output
21340 of numbers. @code{set radix} sets the radix of input and output to
21341 the same base; without an argument, it resets the radix back to its
21342 default value of 10.
21347 @section Configuring the Current ABI
21349 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21350 application automatically. However, sometimes you need to override its
21351 conclusions. Use these commands to manage @value{GDBN}'s view of the
21357 @cindex Newlib OS ABI and its influence on the longjmp handling
21359 One @value{GDBN} configuration can debug binaries for multiple operating
21360 system targets, either via remote debugging or native emulation.
21361 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21362 but you can override its conclusion using the @code{set osabi} command.
21363 One example where this is useful is in debugging of binaries which use
21364 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21365 not have the same identifying marks that the standard C library for your
21368 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21369 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21370 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21371 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21375 Show the OS ABI currently in use.
21378 With no argument, show the list of registered available OS ABI's.
21380 @item set osabi @var{abi}
21381 Set the current OS ABI to @var{abi}.
21384 @cindex float promotion
21386 Generally, the way that an argument of type @code{float} is passed to a
21387 function depends on whether the function is prototyped. For a prototyped
21388 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21389 according to the architecture's convention for @code{float}. For unprototyped
21390 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21391 @code{double} and then passed.
21393 Unfortunately, some forms of debug information do not reliably indicate whether
21394 a function is prototyped. If @value{GDBN} calls a function that is not marked
21395 as prototyped, it consults @kbd{set coerce-float-to-double}.
21398 @kindex set coerce-float-to-double
21399 @item set coerce-float-to-double
21400 @itemx set coerce-float-to-double on
21401 Arguments of type @code{float} will be promoted to @code{double} when passed
21402 to an unprototyped function. This is the default setting.
21404 @item set coerce-float-to-double off
21405 Arguments of type @code{float} will be passed directly to unprototyped
21408 @kindex show coerce-float-to-double
21409 @item show coerce-float-to-double
21410 Show the current setting of promoting @code{float} to @code{double}.
21414 @kindex show cp-abi
21415 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21416 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21417 used to build your application. @value{GDBN} only fully supports
21418 programs with a single C@t{++} ABI; if your program contains code using
21419 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21420 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21421 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21422 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21423 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21424 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21429 Show the C@t{++} ABI currently in use.
21432 With no argument, show the list of supported C@t{++} ABI's.
21434 @item set cp-abi @var{abi}
21435 @itemx set cp-abi auto
21436 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21440 @section Automatically loading associated files
21441 @cindex auto-loading
21443 @value{GDBN} sometimes reads files with commands and settings automatically,
21444 without being explicitly told so by the user. We call this feature
21445 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21446 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21447 results or introduce security risks (e.g., if the file comes from untrusted
21450 Note that loading of these associated files (including the local @file{.gdbinit}
21451 file) requires accordingly configured @code{auto-load safe-path}
21452 (@pxref{Auto-loading safe path}).
21454 For these reasons, @value{GDBN} includes commands and options to let you
21455 control when to auto-load files and which files should be auto-loaded.
21458 @anchor{set auto-load off}
21459 @kindex set auto-load off
21460 @item set auto-load off
21461 Globally disable loading of all auto-loaded files.
21462 You may want to use this command with the @samp{-iex} option
21463 (@pxref{Option -init-eval-command}) such as:
21465 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21468 Be aware that system init file (@pxref{System-wide configuration})
21469 and init files from your home directory (@pxref{Home Directory Init File})
21470 still get read (as they come from generally trusted directories).
21471 To prevent @value{GDBN} from auto-loading even those init files, use the
21472 @option{-nx} option (@pxref{Mode Options}), in addition to
21473 @code{set auto-load no}.
21475 @anchor{show auto-load}
21476 @kindex show auto-load
21477 @item show auto-load
21478 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21482 (gdb) show auto-load
21483 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21484 libthread-db: Auto-loading of inferior specific libthread_db is on.
21485 local-gdbinit: Auto-loading of .gdbinit script from current directory
21487 python-scripts: Auto-loading of Python scripts is on.
21488 safe-path: List of directories from which it is safe to auto-load files
21489 is $debugdir:$datadir/auto-load.
21490 scripts-directory: List of directories from which to load auto-loaded scripts
21491 is $debugdir:$datadir/auto-load.
21494 @anchor{info auto-load}
21495 @kindex info auto-load
21496 @item info auto-load
21497 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21501 (gdb) info auto-load
21504 Yes /home/user/gdb/gdb-gdb.gdb
21505 libthread-db: No auto-loaded libthread-db.
21506 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21510 Yes /home/user/gdb/gdb-gdb.py
21514 These are various kinds of files @value{GDBN} can automatically load:
21518 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21520 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21522 @xref{dotdebug_gdb_scripts section},
21523 controlled by @ref{set auto-load python-scripts}.
21525 @xref{Init File in the Current Directory},
21526 controlled by @ref{set auto-load local-gdbinit}.
21528 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21531 These are @value{GDBN} control commands for the auto-loading:
21533 @multitable @columnfractions .5 .5
21534 @item @xref{set auto-load off}.
21535 @tab Disable auto-loading globally.
21536 @item @xref{show auto-load}.
21537 @tab Show setting of all kinds of files.
21538 @item @xref{info auto-load}.
21539 @tab Show state of all kinds of files.
21540 @item @xref{set auto-load gdb-scripts}.
21541 @tab Control for @value{GDBN} command scripts.
21542 @item @xref{show auto-load gdb-scripts}.
21543 @tab Show setting of @value{GDBN} command scripts.
21544 @item @xref{info auto-load gdb-scripts}.
21545 @tab Show state of @value{GDBN} command scripts.
21546 @item @xref{set auto-load python-scripts}.
21547 @tab Control for @value{GDBN} Python scripts.
21548 @item @xref{show auto-load python-scripts}.
21549 @tab Show setting of @value{GDBN} Python scripts.
21550 @item @xref{info auto-load python-scripts}.
21551 @tab Show state of @value{GDBN} Python scripts.
21552 @item @xref{set auto-load scripts-directory}.
21553 @tab Control for @value{GDBN} auto-loaded scripts location.
21554 @item @xref{show auto-load scripts-directory}.
21555 @tab Show @value{GDBN} auto-loaded scripts location.
21556 @item @xref{set auto-load local-gdbinit}.
21557 @tab Control for init file in the current directory.
21558 @item @xref{show auto-load local-gdbinit}.
21559 @tab Show setting of init file in the current directory.
21560 @item @xref{info auto-load local-gdbinit}.
21561 @tab Show state of init file in the current directory.
21562 @item @xref{set auto-load libthread-db}.
21563 @tab Control for thread debugging library.
21564 @item @xref{show auto-load libthread-db}.
21565 @tab Show setting of thread debugging library.
21566 @item @xref{info auto-load libthread-db}.
21567 @tab Show state of thread debugging library.
21568 @item @xref{set auto-load safe-path}.
21569 @tab Control directories trusted for automatic loading.
21570 @item @xref{show auto-load safe-path}.
21571 @tab Show directories trusted for automatic loading.
21572 @item @xref{add-auto-load-safe-path}.
21573 @tab Add directory trusted for automatic loading.
21577 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21578 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21579 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21580 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21581 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21582 @xref{Python Auto-loading}.
21585 @node Init File in the Current Directory
21586 @subsection Automatically loading init file in the current directory
21587 @cindex auto-loading init file in the current directory
21589 By default, @value{GDBN} reads and executes the canned sequences of commands
21590 from init file (if any) in the current working directory,
21591 see @ref{Init File in the Current Directory during Startup}.
21593 Note that loading of this local @file{.gdbinit} file also requires accordingly
21594 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21597 @anchor{set auto-load local-gdbinit}
21598 @kindex set auto-load local-gdbinit
21599 @item set auto-load local-gdbinit [on|off]
21600 Enable or disable the auto-loading of canned sequences of commands
21601 (@pxref{Sequences}) found in init file in the current directory.
21603 @anchor{show auto-load local-gdbinit}
21604 @kindex show auto-load local-gdbinit
21605 @item show auto-load local-gdbinit
21606 Show whether auto-loading of canned sequences of commands from init file in the
21607 current directory is enabled or disabled.
21609 @anchor{info auto-load local-gdbinit}
21610 @kindex info auto-load local-gdbinit
21611 @item info auto-load local-gdbinit
21612 Print whether canned sequences of commands from init file in the
21613 current directory have been auto-loaded.
21616 @node libthread_db.so.1 file
21617 @subsection Automatically loading thread debugging library
21618 @cindex auto-loading libthread_db.so.1
21620 This feature is currently present only on @sc{gnu}/Linux native hosts.
21622 @value{GDBN} reads in some cases thread debugging library from places specific
21623 to the inferior (@pxref{set libthread-db-search-path}).
21625 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21626 without checking this @samp{set auto-load libthread-db} switch as system
21627 libraries have to be trusted in general. In all other cases of
21628 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21629 auto-load libthread-db} is enabled before trying to open such thread debugging
21632 Note that loading of this debugging library also requires accordingly configured
21633 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21636 @anchor{set auto-load libthread-db}
21637 @kindex set auto-load libthread-db
21638 @item set auto-load libthread-db [on|off]
21639 Enable or disable the auto-loading of inferior specific thread debugging library.
21641 @anchor{show auto-load libthread-db}
21642 @kindex show auto-load libthread-db
21643 @item show auto-load libthread-db
21644 Show whether auto-loading of inferior specific thread debugging library is
21645 enabled or disabled.
21647 @anchor{info auto-load libthread-db}
21648 @kindex info auto-load libthread-db
21649 @item info auto-load libthread-db
21650 Print the list of all loaded inferior specific thread debugging libraries and
21651 for each such library print list of inferior @var{pid}s using it.
21654 @node objfile-gdb.gdb file
21655 @subsection The @file{@var{objfile}-gdb.gdb} file
21656 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21658 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21659 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21660 auto-load gdb-scripts} is set to @samp{on}.
21662 Note that loading of this script file also requires accordingly configured
21663 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21665 For more background refer to the similar Python scripts auto-loading
21666 description (@pxref{objfile-gdb.py file}).
21669 @anchor{set auto-load gdb-scripts}
21670 @kindex set auto-load gdb-scripts
21671 @item set auto-load gdb-scripts [on|off]
21672 Enable or disable the auto-loading of canned sequences of commands scripts.
21674 @anchor{show auto-load gdb-scripts}
21675 @kindex show auto-load gdb-scripts
21676 @item show auto-load gdb-scripts
21677 Show whether auto-loading of canned sequences of commands scripts is enabled or
21680 @anchor{info auto-load gdb-scripts}
21681 @kindex info auto-load gdb-scripts
21682 @cindex print list of auto-loaded canned sequences of commands scripts
21683 @item info auto-load gdb-scripts [@var{regexp}]
21684 Print the list of all canned sequences of commands scripts that @value{GDBN}
21688 If @var{regexp} is supplied only canned sequences of commands scripts with
21689 matching names are printed.
21691 @node Auto-loading safe path
21692 @subsection Security restriction for auto-loading
21693 @cindex auto-loading safe-path
21695 As the files of inferior can come from untrusted source (such as submitted by
21696 an application user) @value{GDBN} does not always load any files automatically.
21697 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21698 directories trusted for loading files not explicitly requested by user.
21699 Each directory can also be a shell wildcard pattern.
21701 If the path is not set properly you will see a warning and the file will not
21706 Reading symbols from /home/user/gdb/gdb...done.
21707 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21708 declined by your `auto-load safe-path' set
21709 to "$debugdir:$datadir/auto-load".
21710 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21711 declined by your `auto-load safe-path' set
21712 to "$debugdir:$datadir/auto-load".
21715 The list of trusted directories is controlled by the following commands:
21718 @anchor{set auto-load safe-path}
21719 @kindex set auto-load safe-path
21720 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21721 Set the list of directories (and their subdirectories) trusted for automatic
21722 loading and execution of scripts. You can also enter a specific trusted file.
21723 Each directory can also be a shell wildcard pattern; wildcards do not match
21724 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21725 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21726 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21727 its default value as specified during @value{GDBN} compilation.
21729 The list of directories uses path separator (@samp{:} on GNU and Unix
21730 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21731 to the @env{PATH} environment variable.
21733 @anchor{show auto-load safe-path}
21734 @kindex show auto-load safe-path
21735 @item show auto-load safe-path
21736 Show the list of directories trusted for automatic loading and execution of
21739 @anchor{add-auto-load-safe-path}
21740 @kindex add-auto-load-safe-path
21741 @item add-auto-load-safe-path
21742 Add an entry (or list of entries) the list of directories trusted for automatic
21743 loading and execution of scripts. Multiple entries may be delimited by the
21744 host platform path separator in use.
21747 This variable defaults to what @code{--with-auto-load-dir} has been configured
21748 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21749 substitution applies the same as for @ref{set auto-load scripts-directory}.
21750 The default @code{set auto-load safe-path} value can be also overriden by
21751 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21753 Setting this variable to @file{/} disables this security protection,
21754 corresponding @value{GDBN} configuration option is
21755 @option{--without-auto-load-safe-path}.
21756 This variable is supposed to be set to the system directories writable by the
21757 system superuser only. Users can add their source directories in init files in
21758 their home directories (@pxref{Home Directory Init File}). See also deprecated
21759 init file in the current directory
21760 (@pxref{Init File in the Current Directory during Startup}).
21762 To force @value{GDBN} to load the files it declined to load in the previous
21763 example, you could use one of the following ways:
21766 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21767 Specify this trusted directory (or a file) as additional component of the list.
21768 You have to specify also any existing directories displayed by
21769 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21771 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21772 Specify this directory as in the previous case but just for a single
21773 @value{GDBN} session.
21775 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21776 Disable auto-loading safety for a single @value{GDBN} session.
21777 This assumes all the files you debug during this @value{GDBN} session will come
21778 from trusted sources.
21780 @item @kbd{./configure --without-auto-load-safe-path}
21781 During compilation of @value{GDBN} you may disable any auto-loading safety.
21782 This assumes all the files you will ever debug with this @value{GDBN} come from
21786 On the other hand you can also explicitly forbid automatic files loading which
21787 also suppresses any such warning messages:
21790 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21791 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21793 @item @file{~/.gdbinit}: @samp{set auto-load no}
21794 Disable auto-loading globally for the user
21795 (@pxref{Home Directory Init File}). While it is improbable, you could also
21796 use system init file instead (@pxref{System-wide configuration}).
21799 This setting applies to the file names as entered by user. If no entry matches
21800 @value{GDBN} tries as a last resort to also resolve all the file names into
21801 their canonical form (typically resolving symbolic links) and compare the
21802 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21803 own before starting the comparison so a canonical form of directories is
21804 recommended to be entered.
21806 @node Auto-loading verbose mode
21807 @subsection Displaying files tried for auto-load
21808 @cindex auto-loading verbose mode
21810 For better visibility of all the file locations where you can place scripts to
21811 be auto-loaded with inferior --- or to protect yourself against accidental
21812 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21813 all the files attempted to be loaded. Both existing and non-existing files may
21816 For example the list of directories from which it is safe to auto-load files
21817 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21818 may not be too obvious while setting it up.
21821 (gdb) set debug auto-load on
21822 (gdb) file ~/src/t/true
21823 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21824 for objfile "/tmp/true".
21825 auto-load: Updating directories of "/usr:/opt".
21826 auto-load: Using directory "/usr".
21827 auto-load: Using directory "/opt".
21828 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21829 by your `auto-load safe-path' set to "/usr:/opt".
21833 @anchor{set debug auto-load}
21834 @kindex set debug auto-load
21835 @item set debug auto-load [on|off]
21836 Set whether to print the filenames attempted to be auto-loaded.
21838 @anchor{show debug auto-load}
21839 @kindex show debug auto-load
21840 @item show debug auto-load
21841 Show whether printing of the filenames attempted to be auto-loaded is turned
21845 @node Messages/Warnings
21846 @section Optional Warnings and Messages
21848 @cindex verbose operation
21849 @cindex optional warnings
21850 By default, @value{GDBN} is silent about its inner workings. If you are
21851 running on a slow machine, you may want to use the @code{set verbose}
21852 command. This makes @value{GDBN} tell you when it does a lengthy
21853 internal operation, so you will not think it has crashed.
21855 Currently, the messages controlled by @code{set verbose} are those
21856 which announce that the symbol table for a source file is being read;
21857 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21860 @kindex set verbose
21861 @item set verbose on
21862 Enables @value{GDBN} output of certain informational messages.
21864 @item set verbose off
21865 Disables @value{GDBN} output of certain informational messages.
21867 @kindex show verbose
21869 Displays whether @code{set verbose} is on or off.
21872 By default, if @value{GDBN} encounters bugs in the symbol table of an
21873 object file, it is silent; but if you are debugging a compiler, you may
21874 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21879 @kindex set complaints
21880 @item set complaints @var{limit}
21881 Permits @value{GDBN} to output @var{limit} complaints about each type of
21882 unusual symbols before becoming silent about the problem. Set
21883 @var{limit} to zero to suppress all complaints; set it to a large number
21884 to prevent complaints from being suppressed.
21886 @kindex show complaints
21887 @item show complaints
21888 Displays how many symbol complaints @value{GDBN} is permitted to produce.
21892 @anchor{confirmation requests}
21893 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
21894 lot of stupid questions to confirm certain commands. For example, if
21895 you try to run a program which is already running:
21899 The program being debugged has been started already.
21900 Start it from the beginning? (y or n)
21903 If you are willing to unflinchingly face the consequences of your own
21904 commands, you can disable this ``feature'':
21908 @kindex set confirm
21910 @cindex confirmation
21911 @cindex stupid questions
21912 @item set confirm off
21913 Disables confirmation requests. Note that running @value{GDBN} with
21914 the @option{--batch} option (@pxref{Mode Options, -batch}) also
21915 automatically disables confirmation requests.
21917 @item set confirm on
21918 Enables confirmation requests (the default).
21920 @kindex show confirm
21922 Displays state of confirmation requests.
21926 @cindex command tracing
21927 If you need to debug user-defined commands or sourced files you may find it
21928 useful to enable @dfn{command tracing}. In this mode each command will be
21929 printed as it is executed, prefixed with one or more @samp{+} symbols, the
21930 quantity denoting the call depth of each command.
21933 @kindex set trace-commands
21934 @cindex command scripts, debugging
21935 @item set trace-commands on
21936 Enable command tracing.
21937 @item set trace-commands off
21938 Disable command tracing.
21939 @item show trace-commands
21940 Display the current state of command tracing.
21943 @node Debugging Output
21944 @section Optional Messages about Internal Happenings
21945 @cindex optional debugging messages
21947 @value{GDBN} has commands that enable optional debugging messages from
21948 various @value{GDBN} subsystems; normally these commands are of
21949 interest to @value{GDBN} maintainers, or when reporting a bug. This
21950 section documents those commands.
21953 @kindex set exec-done-display
21954 @item set exec-done-display
21955 Turns on or off the notification of asynchronous commands'
21956 completion. When on, @value{GDBN} will print a message when an
21957 asynchronous command finishes its execution. The default is off.
21958 @kindex show exec-done-display
21959 @item show exec-done-display
21960 Displays the current setting of asynchronous command completion
21963 @cindex gdbarch debugging info
21964 @cindex architecture debugging info
21965 @item set debug arch
21966 Turns on or off display of gdbarch debugging info. The default is off
21968 @item show debug arch
21969 Displays the current state of displaying gdbarch debugging info.
21970 @item set debug aix-thread
21971 @cindex AIX threads
21972 Display debugging messages about inner workings of the AIX thread
21974 @item show debug aix-thread
21975 Show the current state of AIX thread debugging info display.
21976 @item set debug check-physname
21978 Check the results of the ``physname'' computation. When reading DWARF
21979 debugging information for C@t{++}, @value{GDBN} attempts to compute
21980 each entity's name. @value{GDBN} can do this computation in two
21981 different ways, depending on exactly what information is present.
21982 When enabled, this setting causes @value{GDBN} to compute the names
21983 both ways and display any discrepancies.
21984 @item show debug check-physname
21985 Show the current state of ``physname'' checking.
21986 @item set debug dwarf2-die
21987 @cindex DWARF2 DIEs
21988 Dump DWARF2 DIEs after they are read in.
21989 The value is the number of nesting levels to print.
21990 A value of zero turns off the display.
21991 @item show debug dwarf2-die
21992 Show the current state of DWARF2 DIE debugging.
21993 @item set debug dwarf2-read
21994 @cindex DWARF2 Reading
21995 Turns on or off display of debugging messages related to reading
21996 DWARF debug info. The default is off.
21997 @item show debug dwarf2-read
21998 Show the current state of DWARF2 reader debugging.
21999 @item set debug displaced
22000 @cindex displaced stepping debugging info
22001 Turns on or off display of @value{GDBN} debugging info for the
22002 displaced stepping support. The default is off.
22003 @item show debug displaced
22004 Displays the current state of displaying @value{GDBN} debugging info
22005 related to displaced stepping.
22006 @item set debug event
22007 @cindex event debugging info
22008 Turns on or off display of @value{GDBN} event debugging info. The
22010 @item show debug event
22011 Displays the current state of displaying @value{GDBN} event debugging
22013 @item set debug expression
22014 @cindex expression debugging info
22015 Turns on or off display of debugging info about @value{GDBN}
22016 expression parsing. The default is off.
22017 @item show debug expression
22018 Displays the current state of displaying debugging info about
22019 @value{GDBN} expression parsing.
22020 @item set debug frame
22021 @cindex frame debugging info
22022 Turns on or off display of @value{GDBN} frame debugging info. The
22024 @item show debug frame
22025 Displays the current state of displaying @value{GDBN} frame debugging
22027 @item set debug gnu-nat
22028 @cindex @sc{gnu}/Hurd debug messages
22029 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22030 @item show debug gnu-nat
22031 Show the current state of @sc{gnu}/Hurd debugging messages.
22032 @item set debug infrun
22033 @cindex inferior debugging info
22034 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22035 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22036 for implementing operations such as single-stepping the inferior.
22037 @item show debug infrun
22038 Displays the current state of @value{GDBN} inferior debugging.
22039 @item set debug jit
22040 @cindex just-in-time compilation, debugging messages
22041 Turns on or off debugging messages from JIT debug support.
22042 @item show debug jit
22043 Displays the current state of @value{GDBN} JIT debugging.
22044 @item set debug lin-lwp
22045 @cindex @sc{gnu}/Linux LWP debug messages
22046 @cindex Linux lightweight processes
22047 Turns on or off debugging messages from the Linux LWP debug support.
22048 @item show debug lin-lwp
22049 Show the current state of Linux LWP debugging messages.
22050 @item set debug notification
22051 @cindex remote async notification debugging info
22052 Turns on or off debugging messages about remote async notification.
22053 The default is off.
22054 @item show debug notification
22055 Displays the current state of remote async notification debugging messages.
22056 @item set debug observer
22057 @cindex observer debugging info
22058 Turns on or off display of @value{GDBN} observer debugging. This
22059 includes info such as the notification of observable events.
22060 @item show debug observer
22061 Displays the current state of observer debugging.
22062 @item set debug overload
22063 @cindex C@t{++} overload debugging info
22064 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22065 info. This includes info such as ranking of functions, etc. The default
22067 @item show debug overload
22068 Displays the current state of displaying @value{GDBN} C@t{++} overload
22070 @cindex expression parser, debugging info
22071 @cindex debug expression parser
22072 @item set debug parser
22073 Turns on or off the display of expression parser debugging output.
22074 Internally, this sets the @code{yydebug} variable in the expression
22075 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22076 details. The default is off.
22077 @item show debug parser
22078 Show the current state of expression parser debugging.
22079 @cindex packets, reporting on stdout
22080 @cindex serial connections, debugging
22081 @cindex debug remote protocol
22082 @cindex remote protocol debugging
22083 @cindex display remote packets
22084 @item set debug remote
22085 Turns on or off display of reports on all packets sent back and forth across
22086 the serial line to the remote machine. The info is printed on the
22087 @value{GDBN} standard output stream. The default is off.
22088 @item show debug remote
22089 Displays the state of display of remote packets.
22090 @item set debug serial
22091 Turns on or off display of @value{GDBN} serial debugging info. The
22093 @item show debug serial
22094 Displays the current state of displaying @value{GDBN} serial debugging
22096 @item set debug solib-frv
22097 @cindex FR-V shared-library debugging
22098 Turns on or off debugging messages for FR-V shared-library code.
22099 @item show debug solib-frv
22100 Display the current state of FR-V shared-library code debugging
22102 @item set debug symtab-create
22103 @cindex symbol table creation
22104 Turns on or off display of debugging messages related to symbol table creation.
22105 The default is off.
22106 @item show debug symtab-create
22107 Show the current state of symbol table creation debugging.
22108 @item set debug target
22109 @cindex target debugging info
22110 Turns on or off display of @value{GDBN} target debugging info. This info
22111 includes what is going on at the target level of GDB, as it happens. The
22112 default is 0. Set it to 1 to track events, and to 2 to also track the
22113 value of large memory transfers. Changes to this flag do not take effect
22114 until the next time you connect to a target or use the @code{run} command.
22115 @item show debug target
22116 Displays the current state of displaying @value{GDBN} target debugging
22118 @item set debug timestamp
22119 @cindex timestampping debugging info
22120 Turns on or off display of timestamps with @value{GDBN} debugging info.
22121 When enabled, seconds and microseconds are displayed before each debugging
22123 @item show debug timestamp
22124 Displays the current state of displaying timestamps with @value{GDBN}
22126 @item set debugvarobj
22127 @cindex variable object debugging info
22128 Turns on or off display of @value{GDBN} variable object debugging
22129 info. The default is off.
22130 @item show debugvarobj
22131 Displays the current state of displaying @value{GDBN} variable object
22133 @item set debug xml
22134 @cindex XML parser debugging
22135 Turns on or off debugging messages for built-in XML parsers.
22136 @item show debug xml
22137 Displays the current state of XML debugging messages.
22140 @node Other Misc Settings
22141 @section Other Miscellaneous Settings
22142 @cindex miscellaneous settings
22145 @kindex set interactive-mode
22146 @item set interactive-mode
22147 If @code{on}, forces @value{GDBN} to assume that GDB was started
22148 in a terminal. In practice, this means that @value{GDBN} should wait
22149 for the user to answer queries generated by commands entered at
22150 the command prompt. If @code{off}, forces @value{GDBN} to operate
22151 in the opposite mode, and it uses the default answers to all queries.
22152 If @code{auto} (the default), @value{GDBN} tries to determine whether
22153 its standard input is a terminal, and works in interactive-mode if it
22154 is, non-interactively otherwise.
22156 In the vast majority of cases, the debugger should be able to guess
22157 correctly which mode should be used. But this setting can be useful
22158 in certain specific cases, such as running a MinGW @value{GDBN}
22159 inside a cygwin window.
22161 @kindex show interactive-mode
22162 @item show interactive-mode
22163 Displays whether the debugger is operating in interactive mode or not.
22166 @node Extending GDB
22167 @chapter Extending @value{GDBN}
22168 @cindex extending GDB
22170 @value{GDBN} provides three mechanisms for extension. The first is based
22171 on composition of @value{GDBN} commands, the second is based on the
22172 Python scripting language, and the third is for defining new aliases of
22175 To facilitate the use of the first two extensions, @value{GDBN} is capable
22176 of evaluating the contents of a file. When doing so, @value{GDBN}
22177 can recognize which scripting language is being used by looking at
22178 the filename extension. Files with an unrecognized filename extension
22179 are always treated as a @value{GDBN} Command Files.
22180 @xref{Command Files,, Command files}.
22182 You can control how @value{GDBN} evaluates these files with the following
22186 @kindex set script-extension
22187 @kindex show script-extension
22188 @item set script-extension off
22189 All scripts are always evaluated as @value{GDBN} Command Files.
22191 @item set script-extension soft
22192 The debugger determines the scripting language based on filename
22193 extension. If this scripting language is supported, @value{GDBN}
22194 evaluates the script using that language. Otherwise, it evaluates
22195 the file as a @value{GDBN} Command File.
22197 @item set script-extension strict
22198 The debugger determines the scripting language based on filename
22199 extension, and evaluates the script using that language. If the
22200 language is not supported, then the evaluation fails.
22202 @item show script-extension
22203 Display the current value of the @code{script-extension} option.
22208 * Sequences:: Canned Sequences of Commands
22209 * Python:: Scripting @value{GDBN} using Python
22210 * Aliases:: Creating new spellings of existing commands
22214 @section Canned Sequences of Commands
22216 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22217 Command Lists}), @value{GDBN} provides two ways to store sequences of
22218 commands for execution as a unit: user-defined commands and command
22222 * Define:: How to define your own commands
22223 * Hooks:: Hooks for user-defined commands
22224 * Command Files:: How to write scripts of commands to be stored in a file
22225 * Output:: Commands for controlled output
22229 @subsection User-defined Commands
22231 @cindex user-defined command
22232 @cindex arguments, to user-defined commands
22233 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22234 which you assign a new name as a command. This is done with the
22235 @code{define} command. User commands may accept up to 10 arguments
22236 separated by whitespace. Arguments are accessed within the user command
22237 via @code{$arg0@dots{}$arg9}. A trivial example:
22241 print $arg0 + $arg1 + $arg2
22246 To execute the command use:
22253 This defines the command @code{adder}, which prints the sum of
22254 its three arguments. Note the arguments are text substitutions, so they may
22255 reference variables, use complex expressions, or even perform inferior
22258 @cindex argument count in user-defined commands
22259 @cindex how many arguments (user-defined commands)
22260 In addition, @code{$argc} may be used to find out how many arguments have
22261 been passed. This expands to a number in the range 0@dots{}10.
22266 print $arg0 + $arg1
22269 print $arg0 + $arg1 + $arg2
22277 @item define @var{commandname}
22278 Define a command named @var{commandname}. If there is already a command
22279 by that name, you are asked to confirm that you want to redefine it.
22280 @var{commandname} may be a bare command name consisting of letters,
22281 numbers, dashes, and underscores. It may also start with any predefined
22282 prefix command. For example, @samp{define target my-target} creates
22283 a user-defined @samp{target my-target} command.
22285 The definition of the command is made up of other @value{GDBN} command lines,
22286 which are given following the @code{define} command. The end of these
22287 commands is marked by a line containing @code{end}.
22290 @kindex end@r{ (user-defined commands)}
22291 @item document @var{commandname}
22292 Document the user-defined command @var{commandname}, so that it can be
22293 accessed by @code{help}. The command @var{commandname} must already be
22294 defined. This command reads lines of documentation just as @code{define}
22295 reads the lines of the command definition, ending with @code{end}.
22296 After the @code{document} command is finished, @code{help} on command
22297 @var{commandname} displays the documentation you have written.
22299 You may use the @code{document} command again to change the
22300 documentation of a command. Redefining the command with @code{define}
22301 does not change the documentation.
22303 @kindex dont-repeat
22304 @cindex don't repeat command
22306 Used inside a user-defined command, this tells @value{GDBN} that this
22307 command should not be repeated when the user hits @key{RET}
22308 (@pxref{Command Syntax, repeat last command}).
22310 @kindex help user-defined
22311 @item help user-defined
22312 List all user-defined commands and all python commands defined in class
22313 COMAND_USER. The first line of the documentation or docstring is
22318 @itemx show user @var{commandname}
22319 Display the @value{GDBN} commands used to define @var{commandname} (but
22320 not its documentation). If no @var{commandname} is given, display the
22321 definitions for all user-defined commands.
22322 This does not work for user-defined python commands.
22324 @cindex infinite recursion in user-defined commands
22325 @kindex show max-user-call-depth
22326 @kindex set max-user-call-depth
22327 @item show max-user-call-depth
22328 @itemx set max-user-call-depth
22329 The value of @code{max-user-call-depth} controls how many recursion
22330 levels are allowed in user-defined commands before @value{GDBN} suspects an
22331 infinite recursion and aborts the command.
22332 This does not apply to user-defined python commands.
22335 In addition to the above commands, user-defined commands frequently
22336 use control flow commands, described in @ref{Command Files}.
22338 When user-defined commands are executed, the
22339 commands of the definition are not printed. An error in any command
22340 stops execution of the user-defined command.
22342 If used interactively, commands that would ask for confirmation proceed
22343 without asking when used inside a user-defined command. Many @value{GDBN}
22344 commands that normally print messages to say what they are doing omit the
22345 messages when used in a user-defined command.
22348 @subsection User-defined Command Hooks
22349 @cindex command hooks
22350 @cindex hooks, for commands
22351 @cindex hooks, pre-command
22354 You may define @dfn{hooks}, which are a special kind of user-defined
22355 command. Whenever you run the command @samp{foo}, if the user-defined
22356 command @samp{hook-foo} exists, it is executed (with no arguments)
22357 before that command.
22359 @cindex hooks, post-command
22361 A hook may also be defined which is run after the command you executed.
22362 Whenever you run the command @samp{foo}, if the user-defined command
22363 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22364 that command. Post-execution hooks may exist simultaneously with
22365 pre-execution hooks, for the same command.
22367 It is valid for a hook to call the command which it hooks. If this
22368 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22370 @c It would be nice if hookpost could be passed a parameter indicating
22371 @c if the command it hooks executed properly or not. FIXME!
22373 @kindex stop@r{, a pseudo-command}
22374 In addition, a pseudo-command, @samp{stop} exists. Defining
22375 (@samp{hook-stop}) makes the associated commands execute every time
22376 execution stops in your program: before breakpoint commands are run,
22377 displays are printed, or the stack frame is printed.
22379 For example, to ignore @code{SIGALRM} signals while
22380 single-stepping, but treat them normally during normal execution,
22385 handle SIGALRM nopass
22389 handle SIGALRM pass
22392 define hook-continue
22393 handle SIGALRM pass
22397 As a further example, to hook at the beginning and end of the @code{echo}
22398 command, and to add extra text to the beginning and end of the message,
22406 define hookpost-echo
22410 (@value{GDBP}) echo Hello World
22411 <<<---Hello World--->>>
22416 You can define a hook for any single-word command in @value{GDBN}, but
22417 not for command aliases; you should define a hook for the basic command
22418 name, e.g.@: @code{backtrace} rather than @code{bt}.
22419 @c FIXME! So how does Joe User discover whether a command is an alias
22421 You can hook a multi-word command by adding @code{hook-} or
22422 @code{hookpost-} to the last word of the command, e.g.@:
22423 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22425 If an error occurs during the execution of your hook, execution of
22426 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22427 (before the command that you actually typed had a chance to run).
22429 If you try to define a hook which does not match any known command, you
22430 get a warning from the @code{define} command.
22432 @node Command Files
22433 @subsection Command Files
22435 @cindex command files
22436 @cindex scripting commands
22437 A command file for @value{GDBN} is a text file made of lines that are
22438 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22439 also be included. An empty line in a command file does nothing; it
22440 does not mean to repeat the last command, as it would from the
22443 You can request the execution of a command file with the @code{source}
22444 command. Note that the @code{source} command is also used to evaluate
22445 scripts that are not Command Files. The exact behavior can be configured
22446 using the @code{script-extension} setting.
22447 @xref{Extending GDB,, Extending GDB}.
22451 @cindex execute commands from a file
22452 @item source [-s] [-v] @var{filename}
22453 Execute the command file @var{filename}.
22456 The lines in a command file are generally executed sequentially,
22457 unless the order of execution is changed by one of the
22458 @emph{flow-control commands} described below. The commands are not
22459 printed as they are executed. An error in any command terminates
22460 execution of the command file and control is returned to the console.
22462 @value{GDBN} first searches for @var{filename} in the current directory.
22463 If the file is not found there, and @var{filename} does not specify a
22464 directory, then @value{GDBN} also looks for the file on the source search path
22465 (specified with the @samp{directory} command);
22466 except that @file{$cdir} is not searched because the compilation directory
22467 is not relevant to scripts.
22469 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22470 on the search path even if @var{filename} specifies a directory.
22471 The search is done by appending @var{filename} to each element of the
22472 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22473 and the search path contains @file{/home/user} then @value{GDBN} will
22474 look for the script @file{/home/user/mylib/myscript}.
22475 The search is also done if @var{filename} is an absolute path.
22476 For example, if @var{filename} is @file{/tmp/myscript} and
22477 the search path contains @file{/home/user} then @value{GDBN} will
22478 look for the script @file{/home/user/tmp/myscript}.
22479 For DOS-like systems, if @var{filename} contains a drive specification,
22480 it is stripped before concatenation. For example, if @var{filename} is
22481 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22482 will look for the script @file{c:/tmp/myscript}.
22484 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22485 each command as it is executed. The option must be given before
22486 @var{filename}, and is interpreted as part of the filename anywhere else.
22488 Commands that would ask for confirmation if used interactively proceed
22489 without asking when used in a command file. Many @value{GDBN} commands that
22490 normally print messages to say what they are doing omit the messages
22491 when called from command files.
22493 @value{GDBN} also accepts command input from standard input. In this
22494 mode, normal output goes to standard output and error output goes to
22495 standard error. Errors in a command file supplied on standard input do
22496 not terminate execution of the command file---execution continues with
22500 gdb < cmds > log 2>&1
22503 (The syntax above will vary depending on the shell used.) This example
22504 will execute commands from the file @file{cmds}. All output and errors
22505 would be directed to @file{log}.
22507 Since commands stored on command files tend to be more general than
22508 commands typed interactively, they frequently need to deal with
22509 complicated situations, such as different or unexpected values of
22510 variables and symbols, changes in how the program being debugged is
22511 built, etc. @value{GDBN} provides a set of flow-control commands to
22512 deal with these complexities. Using these commands, you can write
22513 complex scripts that loop over data structures, execute commands
22514 conditionally, etc.
22521 This command allows to include in your script conditionally executed
22522 commands. The @code{if} command takes a single argument, which is an
22523 expression to evaluate. It is followed by a series of commands that
22524 are executed only if the expression is true (its value is nonzero).
22525 There can then optionally be an @code{else} line, followed by a series
22526 of commands that are only executed if the expression was false. The
22527 end of the list is marked by a line containing @code{end}.
22531 This command allows to write loops. Its syntax is similar to
22532 @code{if}: the command takes a single argument, which is an expression
22533 to evaluate, and must be followed by the commands to execute, one per
22534 line, terminated by an @code{end}. These commands are called the
22535 @dfn{body} of the loop. The commands in the body of @code{while} are
22536 executed repeatedly as long as the expression evaluates to true.
22540 This command exits the @code{while} loop in whose body it is included.
22541 Execution of the script continues after that @code{while}s @code{end}
22544 @kindex loop_continue
22545 @item loop_continue
22546 This command skips the execution of the rest of the body of commands
22547 in the @code{while} loop in whose body it is included. Execution
22548 branches to the beginning of the @code{while} loop, where it evaluates
22549 the controlling expression.
22551 @kindex end@r{ (if/else/while commands)}
22553 Terminate the block of commands that are the body of @code{if},
22554 @code{else}, or @code{while} flow-control commands.
22559 @subsection Commands for Controlled Output
22561 During the execution of a command file or a user-defined command, normal
22562 @value{GDBN} output is suppressed; the only output that appears is what is
22563 explicitly printed by the commands in the definition. This section
22564 describes three commands useful for generating exactly the output you
22569 @item echo @var{text}
22570 @c I do not consider backslash-space a standard C escape sequence
22571 @c because it is not in ANSI.
22572 Print @var{text}. Nonprinting characters can be included in
22573 @var{text} using C escape sequences, such as @samp{\n} to print a
22574 newline. @strong{No newline is printed unless you specify one.}
22575 In addition to the standard C escape sequences, a backslash followed
22576 by a space stands for a space. This is useful for displaying a
22577 string with spaces at the beginning or the end, since leading and
22578 trailing spaces are otherwise trimmed from all arguments.
22579 To print @samp{@w{ }and foo =@w{ }}, use the command
22580 @samp{echo \@w{ }and foo = \@w{ }}.
22582 A backslash at the end of @var{text} can be used, as in C, to continue
22583 the command onto subsequent lines. For example,
22586 echo This is some text\n\
22587 which is continued\n\
22588 onto several lines.\n
22591 produces the same output as
22594 echo This is some text\n
22595 echo which is continued\n
22596 echo onto several lines.\n
22600 @item output @var{expression}
22601 Print the value of @var{expression} and nothing but that value: no
22602 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22603 value history either. @xref{Expressions, ,Expressions}, for more information
22606 @item output/@var{fmt} @var{expression}
22607 Print the value of @var{expression} in format @var{fmt}. You can use
22608 the same formats as for @code{print}. @xref{Output Formats,,Output
22609 Formats}, for more information.
22612 @item printf @var{template}, @var{expressions}@dots{}
22613 Print the values of one or more @var{expressions} under the control of
22614 the string @var{template}. To print several values, make
22615 @var{expressions} be a comma-separated list of individual expressions,
22616 which may be either numbers or pointers. Their values are printed as
22617 specified by @var{template}, exactly as a C program would do by
22618 executing the code below:
22621 printf (@var{template}, @var{expressions}@dots{});
22624 As in @code{C} @code{printf}, ordinary characters in @var{template}
22625 are printed verbatim, while @dfn{conversion specification} introduced
22626 by the @samp{%} character cause subsequent @var{expressions} to be
22627 evaluated, their values converted and formatted according to type and
22628 style information encoded in the conversion specifications, and then
22631 For example, you can print two values in hex like this:
22634 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22637 @code{printf} supports all the standard @code{C} conversion
22638 specifications, including the flags and modifiers between the @samp{%}
22639 character and the conversion letter, with the following exceptions:
22643 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22646 The modifier @samp{*} is not supported for specifying precision or
22650 The @samp{'} flag (for separation of digits into groups according to
22651 @code{LC_NUMERIC'}) is not supported.
22654 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22658 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22661 The conversion letters @samp{a} and @samp{A} are not supported.
22665 Note that the @samp{ll} type modifier is supported only if the
22666 underlying @code{C} implementation used to build @value{GDBN} supports
22667 the @code{long long int} type, and the @samp{L} type modifier is
22668 supported only if @code{long double} type is available.
22670 As in @code{C}, @code{printf} supports simple backslash-escape
22671 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22672 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22673 single character. Octal and hexadecimal escape sequences are not
22676 Additionally, @code{printf} supports conversion specifications for DFP
22677 (@dfn{Decimal Floating Point}) types using the following length modifiers
22678 together with a floating point specifier.
22683 @samp{H} for printing @code{Decimal32} types.
22686 @samp{D} for printing @code{Decimal64} types.
22689 @samp{DD} for printing @code{Decimal128} types.
22692 If the underlying @code{C} implementation used to build @value{GDBN} has
22693 support for the three length modifiers for DFP types, other modifiers
22694 such as width and precision will also be available for @value{GDBN} to use.
22696 In case there is no such @code{C} support, no additional modifiers will be
22697 available and the value will be printed in the standard way.
22699 Here's an example of printing DFP types using the above conversion letters:
22701 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22705 @item eval @var{template}, @var{expressions}@dots{}
22706 Convert the values of one or more @var{expressions} under the control of
22707 the string @var{template} to a command line, and call it.
22712 @section Scripting @value{GDBN} using Python
22713 @cindex python scripting
22714 @cindex scripting with python
22716 You can script @value{GDBN} using the @uref{http://www.python.org/,
22717 Python programming language}. This feature is available only if
22718 @value{GDBN} was configured using @option{--with-python}.
22720 @cindex python directory
22721 Python scripts used by @value{GDBN} should be installed in
22722 @file{@var{data-directory}/python}, where @var{data-directory} is
22723 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22724 This directory, known as the @dfn{python directory},
22725 is automatically added to the Python Search Path in order to allow
22726 the Python interpreter to locate all scripts installed at this location.
22728 Additionally, @value{GDBN} commands and convenience functions which
22729 are written in Python and are located in the
22730 @file{@var{data-directory}/python/gdb/command} or
22731 @file{@var{data-directory}/python/gdb/function} directories are
22732 automatically imported when @value{GDBN} starts.
22735 * Python Commands:: Accessing Python from @value{GDBN}.
22736 * Python API:: Accessing @value{GDBN} from Python.
22737 * Python Auto-loading:: Automatically loading Python code.
22738 * Python modules:: Python modules provided by @value{GDBN}.
22741 @node Python Commands
22742 @subsection Python Commands
22743 @cindex python commands
22744 @cindex commands to access python
22746 @value{GDBN} provides two commands for accessing the Python interpreter,
22747 and one related setting:
22750 @kindex python-interactive
22752 @item python-interactive @r{[}@var{command}@r{]}
22753 @itemx pi @r{[}@var{command}@r{]}
22754 Without an argument, the @code{python-interactive} command can be used
22755 to start an interactive Python prompt. To return to @value{GDBN},
22756 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22758 Alternatively, a single-line Python command can be given as an
22759 argument and evaluated. If the command is an expression, the result
22760 will be printed; otherwise, nothing will be printed. For example:
22763 (@value{GDBP}) python-interactive 2 + 3
22769 @item python @r{[}@var{command}@r{]}
22770 @itemx py @r{[}@var{command}@r{]}
22771 The @code{python} command can be used to evaluate Python code.
22773 If given an argument, the @code{python} command will evaluate the
22774 argument as a Python command. For example:
22777 (@value{GDBP}) python print 23
22781 If you do not provide an argument to @code{python}, it will act as a
22782 multi-line command, like @code{define}. In this case, the Python
22783 script is made up of subsequent command lines, given after the
22784 @code{python} command. This command list is terminated using a line
22785 containing @code{end}. For example:
22788 (@value{GDBP}) python
22790 End with a line saying just "end".
22796 @kindex set python print-stack
22797 @item set python print-stack
22798 By default, @value{GDBN} will print only the message component of a
22799 Python exception when an error occurs in a Python script. This can be
22800 controlled using @code{set python print-stack}: if @code{full}, then
22801 full Python stack printing is enabled; if @code{none}, then Python stack
22802 and message printing is disabled; if @code{message}, the default, only
22803 the message component of the error is printed.
22806 It is also possible to execute a Python script from the @value{GDBN}
22810 @item source @file{script-name}
22811 The script name must end with @samp{.py} and @value{GDBN} must be configured
22812 to recognize the script language based on filename extension using
22813 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22815 @item python execfile ("script-name")
22816 This method is based on the @code{execfile} Python built-in function,
22817 and thus is always available.
22821 @subsection Python API
22823 @cindex programming in python
22825 @cindex python stdout
22826 @cindex python pagination
22827 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22828 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22829 A Python program which outputs to one of these streams may have its
22830 output interrupted by the user (@pxref{Screen Size}). In this
22831 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22834 * Basic Python:: Basic Python Functions.
22835 * Exception Handling:: How Python exceptions are translated.
22836 * Values From Inferior:: Python representation of values.
22837 * Types In Python:: Python representation of types.
22838 * Pretty Printing API:: Pretty-printing values.
22839 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22840 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22841 * Type Printing API:: Pretty-printing types.
22842 * Inferiors In Python:: Python representation of inferiors (processes)
22843 * Events In Python:: Listening for events from @value{GDBN}.
22844 * Threads In Python:: Accessing inferior threads from Python.
22845 * Commands In Python:: Implementing new commands in Python.
22846 * Parameters In Python:: Adding new @value{GDBN} parameters.
22847 * Functions In Python:: Writing new convenience functions.
22848 * Progspaces In Python:: Program spaces.
22849 * Objfiles In Python:: Object files.
22850 * Frames In Python:: Accessing inferior stack frames from Python.
22851 * Blocks In Python:: Accessing frame blocks from Python.
22852 * Symbols In Python:: Python representation of symbols.
22853 * Symbol Tables In Python:: Python representation of symbol tables.
22854 * Breakpoints In Python:: Manipulating breakpoints using Python.
22855 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22857 * Lazy Strings In Python:: Python representation of lazy strings.
22858 * Architectures In Python:: Python representation of architectures.
22862 @subsubsection Basic Python
22864 @cindex python functions
22865 @cindex python module
22867 @value{GDBN} introduces a new Python module, named @code{gdb}. All
22868 methods and classes added by @value{GDBN} are placed in this module.
22869 @value{GDBN} automatically @code{import}s the @code{gdb} module for
22870 use in all scripts evaluated by the @code{python} command.
22872 @findex gdb.PYTHONDIR
22873 @defvar gdb.PYTHONDIR
22874 A string containing the python directory (@pxref{Python}).
22877 @findex gdb.execute
22878 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
22879 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
22880 If a GDB exception happens while @var{command} runs, it is
22881 translated as described in @ref{Exception Handling,,Exception Handling}.
22883 @var{from_tty} specifies whether @value{GDBN} ought to consider this
22884 command as having originated from the user invoking it interactively.
22885 It must be a boolean value. If omitted, it defaults to @code{False}.
22887 By default, any output produced by @var{command} is sent to
22888 @value{GDBN}'s standard output. If the @var{to_string} parameter is
22889 @code{True}, then output will be collected by @code{gdb.execute} and
22890 returned as a string. The default is @code{False}, in which case the
22891 return value is @code{None}. If @var{to_string} is @code{True}, the
22892 @value{GDBN} virtual terminal will be temporarily set to unlimited width
22893 and height, and its pagination will be disabled; @pxref{Screen Size}.
22896 @findex gdb.breakpoints
22897 @defun gdb.breakpoints ()
22898 Return a sequence holding all of @value{GDBN}'s breakpoints.
22899 @xref{Breakpoints In Python}, for more information.
22902 @findex gdb.parameter
22903 @defun gdb.parameter (parameter)
22904 Return the value of a @value{GDBN} parameter. @var{parameter} is a
22905 string naming the parameter to look up; @var{parameter} may contain
22906 spaces if the parameter has a multi-part name. For example,
22907 @samp{print object} is a valid parameter name.
22909 If the named parameter does not exist, this function throws a
22910 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
22911 parameter's value is converted to a Python value of the appropriate
22912 type, and returned.
22915 @findex gdb.history
22916 @defun gdb.history (number)
22917 Return a value from @value{GDBN}'s value history (@pxref{Value
22918 History}). @var{number} indicates which history element to return.
22919 If @var{number} is negative, then @value{GDBN} will take its absolute value
22920 and count backward from the last element (i.e., the most recent element) to
22921 find the value to return. If @var{number} is zero, then @value{GDBN} will
22922 return the most recent element. If the element specified by @var{number}
22923 doesn't exist in the value history, a @code{gdb.error} exception will be
22926 If no exception is raised, the return value is always an instance of
22927 @code{gdb.Value} (@pxref{Values From Inferior}).
22930 @findex gdb.parse_and_eval
22931 @defun gdb.parse_and_eval (expression)
22932 Parse @var{expression} as an expression in the current language,
22933 evaluate it, and return the result as a @code{gdb.Value}.
22934 @var{expression} must be a string.
22936 This function can be useful when implementing a new command
22937 (@pxref{Commands In Python}), as it provides a way to parse the
22938 command's argument as an expression. It is also useful simply to
22939 compute values, for example, it is the only way to get the value of a
22940 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
22943 @findex gdb.find_pc_line
22944 @defun gdb.find_pc_line (pc)
22945 Return the @code{gdb.Symtab_and_line} object corresponding to the
22946 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
22947 value of @var{pc} is passed as an argument, then the @code{symtab} and
22948 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
22949 will be @code{None} and 0 respectively.
22952 @findex gdb.post_event
22953 @defun gdb.post_event (event)
22954 Put @var{event}, a callable object taking no arguments, into
22955 @value{GDBN}'s internal event queue. This callable will be invoked at
22956 some later point, during @value{GDBN}'s event processing. Events
22957 posted using @code{post_event} will be run in the order in which they
22958 were posted; however, there is no way to know when they will be
22959 processed relative to other events inside @value{GDBN}.
22961 @value{GDBN} is not thread-safe. If your Python program uses multiple
22962 threads, you must be careful to only call @value{GDBN}-specific
22963 functions in the main @value{GDBN} thread. @code{post_event} ensures
22967 (@value{GDBP}) python
22971 > def __init__(self, message):
22972 > self.message = message;
22973 > def __call__(self):
22974 > gdb.write(self.message)
22976 >class MyThread1 (threading.Thread):
22978 > gdb.post_event(Writer("Hello "))
22980 >class MyThread2 (threading.Thread):
22982 > gdb.post_event(Writer("World\n"))
22984 >MyThread1().start()
22985 >MyThread2().start()
22987 (@value{GDBP}) Hello World
22992 @defun gdb.write (string @r{[}, stream{]})
22993 Print a string to @value{GDBN}'s paginated output stream. The
22994 optional @var{stream} determines the stream to print to. The default
22995 stream is @value{GDBN}'s standard output stream. Possible stream
23002 @value{GDBN}'s standard output stream.
23007 @value{GDBN}'s standard error stream.
23012 @value{GDBN}'s log stream (@pxref{Logging Output}).
23015 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23016 call this function and will automatically direct the output to the
23021 @defun gdb.flush ()
23022 Flush the buffer of a @value{GDBN} paginated stream so that the
23023 contents are displayed immediately. @value{GDBN} will flush the
23024 contents of a stream automatically when it encounters a newline in the
23025 buffer. The optional @var{stream} determines the stream to flush. The
23026 default stream is @value{GDBN}'s standard output stream. Possible
23033 @value{GDBN}'s standard output stream.
23038 @value{GDBN}'s standard error stream.
23043 @value{GDBN}'s log stream (@pxref{Logging Output}).
23047 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23048 call this function for the relevant stream.
23051 @findex gdb.target_charset
23052 @defun gdb.target_charset ()
23053 Return the name of the current target character set (@pxref{Character
23054 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23055 that @samp{auto} is never returned.
23058 @findex gdb.target_wide_charset
23059 @defun gdb.target_wide_charset ()
23060 Return the name of the current target wide character set
23061 (@pxref{Character Sets}). This differs from
23062 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23066 @findex gdb.solib_name
23067 @defun gdb.solib_name (address)
23068 Return the name of the shared library holding the given @var{address}
23069 as a string, or @code{None}.
23072 @findex gdb.decode_line
23073 @defun gdb.decode_line @r{[}expression@r{]}
23074 Return locations of the line specified by @var{expression}, or of the
23075 current line if no argument was given. This function returns a Python
23076 tuple containing two elements. The first element contains a string
23077 holding any unparsed section of @var{expression} (or @code{None} if
23078 the expression has been fully parsed). The second element contains
23079 either @code{None} or another tuple that contains all the locations
23080 that match the expression represented as @code{gdb.Symtab_and_line}
23081 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23082 provided, it is decoded the way that @value{GDBN}'s inbuilt
23083 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23086 @defun gdb.prompt_hook (current_prompt)
23087 @anchor{prompt_hook}
23089 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23090 assigned to this operation before a prompt is displayed by
23093 The parameter @code{current_prompt} contains the current @value{GDBN}
23094 prompt. This method must return a Python string, or @code{None}. If
23095 a string is returned, the @value{GDBN} prompt will be set to that
23096 string. If @code{None} is returned, @value{GDBN} will continue to use
23097 the current prompt.
23099 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23100 such as those used by readline for command input, and annotation
23101 related prompts are prohibited from being changed.
23104 @node Exception Handling
23105 @subsubsection Exception Handling
23106 @cindex python exceptions
23107 @cindex exceptions, python
23109 When executing the @code{python} command, Python exceptions
23110 uncaught within the Python code are translated to calls to
23111 @value{GDBN} error-reporting mechanism. If the command that called
23112 @code{python} does not handle the error, @value{GDBN} will
23113 terminate it and print an error message containing the Python
23114 exception name, the associated value, and the Python call stack
23115 backtrace at the point where the exception was raised. Example:
23118 (@value{GDBP}) python print foo
23119 Traceback (most recent call last):
23120 File "<string>", line 1, in <module>
23121 NameError: name 'foo' is not defined
23124 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23125 Python code are converted to Python exceptions. The type of the
23126 Python exception depends on the error.
23130 This is the base class for most exceptions generated by @value{GDBN}.
23131 It is derived from @code{RuntimeError}, for compatibility with earlier
23132 versions of @value{GDBN}.
23134 If an error occurring in @value{GDBN} does not fit into some more
23135 specific category, then the generated exception will have this type.
23137 @item gdb.MemoryError
23138 This is a subclass of @code{gdb.error} which is thrown when an
23139 operation tried to access invalid memory in the inferior.
23141 @item KeyboardInterrupt
23142 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23143 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23146 In all cases, your exception handler will see the @value{GDBN} error
23147 message as its value and the Python call stack backtrace at the Python
23148 statement closest to where the @value{GDBN} error occured as the
23151 @findex gdb.GdbError
23152 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23153 it is useful to be able to throw an exception that doesn't cause a
23154 traceback to be printed. For example, the user may have invoked the
23155 command incorrectly. Use the @code{gdb.GdbError} exception
23156 to handle this case. Example:
23160 >class HelloWorld (gdb.Command):
23161 > """Greet the whole world."""
23162 > def __init__ (self):
23163 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23164 > def invoke (self, args, from_tty):
23165 > argv = gdb.string_to_argv (args)
23166 > if len (argv) != 0:
23167 > raise gdb.GdbError ("hello-world takes no arguments")
23168 > print "Hello, World!"
23171 (gdb) hello-world 42
23172 hello-world takes no arguments
23175 @node Values From Inferior
23176 @subsubsection Values From Inferior
23177 @cindex values from inferior, with Python
23178 @cindex python, working with values from inferior
23180 @cindex @code{gdb.Value}
23181 @value{GDBN} provides values it obtains from the inferior program in
23182 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23183 for its internal bookkeeping of the inferior's values, and for
23184 fetching values when necessary.
23186 Inferior values that are simple scalars can be used directly in
23187 Python expressions that are valid for the value's data type. Here's
23188 an example for an integer or floating-point value @code{some_val}:
23195 As result of this, @code{bar} will also be a @code{gdb.Value} object
23196 whose values are of the same type as those of @code{some_val}.
23198 Inferior values that are structures or instances of some class can
23199 be accessed using the Python @dfn{dictionary syntax}. For example, if
23200 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23201 can access its @code{foo} element with:
23204 bar = some_val['foo']
23207 Again, @code{bar} will also be a @code{gdb.Value} object.
23209 A @code{gdb.Value} that represents a function can be executed via
23210 inferior function call. Any arguments provided to the call must match
23211 the function's prototype, and must be provided in the order specified
23214 For example, @code{some_val} is a @code{gdb.Value} instance
23215 representing a function that takes two integers as arguments. To
23216 execute this function, call it like so:
23219 result = some_val (10,20)
23222 Any values returned from a function call will be stored as a
23225 The following attributes are provided:
23228 @defvar Value.address
23229 If this object is addressable, this read-only attribute holds a
23230 @code{gdb.Value} object representing the address. Otherwise,
23231 this attribute holds @code{None}.
23234 @cindex optimized out value in Python
23235 @defvar Value.is_optimized_out
23236 This read-only boolean attribute is true if the compiler optimized out
23237 this value, thus it is not available for fetching from the inferior.
23241 The type of this @code{gdb.Value}. The value of this attribute is a
23242 @code{gdb.Type} object (@pxref{Types In Python}).
23245 @defvar Value.dynamic_type
23246 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23247 type information (@acronym{RTTI}) to determine the dynamic type of the
23248 value. If this value is of class type, it will return the class in
23249 which the value is embedded, if any. If this value is of pointer or
23250 reference to a class type, it will compute the dynamic type of the
23251 referenced object, and return a pointer or reference to that type,
23252 respectively. In all other cases, it will return the value's static
23255 Note that this feature will only work when debugging a C@t{++} program
23256 that includes @acronym{RTTI} for the object in question. Otherwise,
23257 it will just return the static type of the value as in @kbd{ptype foo}
23258 (@pxref{Symbols, ptype}).
23261 @defvar Value.is_lazy
23262 The value of this read-only boolean attribute is @code{True} if this
23263 @code{gdb.Value} has not yet been fetched from the inferior.
23264 @value{GDBN} does not fetch values until necessary, for efficiency.
23268 myval = gdb.parse_and_eval ('somevar')
23271 The value of @code{somevar} is not fetched at this time. It will be
23272 fetched when the value is needed, or when the @code{fetch_lazy}
23277 The following methods are provided:
23280 @defun Value.__init__ (@var{val})
23281 Many Python values can be converted directly to a @code{gdb.Value} via
23282 this object initializer. Specifically:
23285 @item Python boolean
23286 A Python boolean is converted to the boolean type from the current
23289 @item Python integer
23290 A Python integer is converted to the C @code{long} type for the
23291 current architecture.
23294 A Python long is converted to the C @code{long long} type for the
23295 current architecture.
23298 A Python float is converted to the C @code{double} type for the
23299 current architecture.
23301 @item Python string
23302 A Python string is converted to a target string, using the current
23305 @item @code{gdb.Value}
23306 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23308 @item @code{gdb.LazyString}
23309 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23310 Python}), then the lazy string's @code{value} method is called, and
23311 its result is used.
23315 @defun Value.cast (type)
23316 Return a new instance of @code{gdb.Value} that is the result of
23317 casting this instance to the type described by @var{type}, which must
23318 be a @code{gdb.Type} object. If the cast cannot be performed for some
23319 reason, this method throws an exception.
23322 @defun Value.dereference ()
23323 For pointer data types, this method returns a new @code{gdb.Value} object
23324 whose contents is the object pointed to by the pointer. For example, if
23325 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23332 then you can use the corresponding @code{gdb.Value} to access what
23333 @code{foo} points to like this:
23336 bar = foo.dereference ()
23339 The result @code{bar} will be a @code{gdb.Value} object holding the
23340 value pointed to by @code{foo}.
23342 A similar function @code{Value.referenced_value} exists which also
23343 returns @code{gdb.Value} objects corresonding to the values pointed to
23344 by pointer values (and additionally, values referenced by reference
23345 values). However, the behavior of @code{Value.dereference}
23346 differs from @code{Value.referenced_value} by the fact that the
23347 behavior of @code{Value.dereference} is identical to applying the C
23348 unary operator @code{*} on a given value. For example, consider a
23349 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23353 typedef int *intptr;
23357 intptr &ptrref = ptr;
23360 Though @code{ptrref} is a reference value, one can apply the method
23361 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23362 to it and obtain a @code{gdb.Value} which is identical to that
23363 corresponding to @code{val}. However, if you apply the method
23364 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23365 object identical to that corresponding to @code{ptr}.
23368 py_ptrref = gdb.parse_and_eval ("ptrref")
23369 py_val = py_ptrref.dereference ()
23370 py_ptr = py_ptrref.referenced_value ()
23373 The @code{gdb.Value} object @code{py_val} is identical to that
23374 corresponding to @code{val}, and @code{py_ptr} is identical to that
23375 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23376 be applied whenever the C unary operator @code{*} can be applied
23377 to the corresponding C value. For those cases where applying both
23378 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23379 the results obtained need not be identical (as we have seen in the above
23380 example). The results are however identical when applied on
23381 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23382 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23385 @defun Value.referenced_value ()
23386 For pointer or reference data types, this method returns a new
23387 @code{gdb.Value} object corresponding to the value referenced by the
23388 pointer/reference value. For pointer data types,
23389 @code{Value.dereference} and @code{Value.referenced_value} produce
23390 identical results. The difference between these methods is that
23391 @code{Value.dereference} cannot get the values referenced by reference
23392 values. For example, consider a reference to an @code{int}, declared
23393 in your C@t{++} program as
23401 then applying @code{Value.dereference} to the @code{gdb.Value} object
23402 corresponding to @code{ref} will result in an error, while applying
23403 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23404 identical to that corresponding to @code{val}.
23407 py_ref = gdb.parse_and_eval ("ref")
23408 er_ref = py_ref.dereference () # Results in error
23409 py_val = py_ref.referenced_value () # Returns the referenced value
23412 The @code{gdb.Value} object @code{py_val} is identical to that
23413 corresponding to @code{val}.
23416 @defun Value.dynamic_cast (type)
23417 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23418 operator were used. Consult a C@t{++} reference for details.
23421 @defun Value.reinterpret_cast (type)
23422 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23423 operator were used. Consult a C@t{++} reference for details.
23426 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23427 If this @code{gdb.Value} represents a string, then this method
23428 converts the contents to a Python string. Otherwise, this method will
23429 throw an exception.
23431 Strings are recognized in a language-specific way; whether a given
23432 @code{gdb.Value} represents a string is determined by the current
23435 For C-like languages, a value is a string if it is a pointer to or an
23436 array of characters or ints. The string is assumed to be terminated
23437 by a zero of the appropriate width. However if the optional length
23438 argument is given, the string will be converted to that given length,
23439 ignoring any embedded zeros that the string may contain.
23441 If the optional @var{encoding} argument is given, it must be a string
23442 naming the encoding of the string in the @code{gdb.Value}, such as
23443 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23444 the same encodings as the corresponding argument to Python's
23445 @code{string.decode} method, and the Python codec machinery will be used
23446 to convert the string. If @var{encoding} is not given, or if
23447 @var{encoding} is the empty string, then either the @code{target-charset}
23448 (@pxref{Character Sets}) will be used, or a language-specific encoding
23449 will be used, if the current language is able to supply one.
23451 The optional @var{errors} argument is the same as the corresponding
23452 argument to Python's @code{string.decode} method.
23454 If the optional @var{length} argument is given, the string will be
23455 fetched and converted to the given length.
23458 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23459 If this @code{gdb.Value} represents a string, then this method
23460 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23461 In Python}). Otherwise, this method will throw an exception.
23463 If the optional @var{encoding} argument is given, it must be a string
23464 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23465 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23466 @var{encoding} argument is an encoding that @value{GDBN} does
23467 recognize, @value{GDBN} will raise an error.
23469 When a lazy string is printed, the @value{GDBN} encoding machinery is
23470 used to convert the string during printing. If the optional
23471 @var{encoding} argument is not provided, or is an empty string,
23472 @value{GDBN} will automatically select the encoding most suitable for
23473 the string type. For further information on encoding in @value{GDBN}
23474 please see @ref{Character Sets}.
23476 If the optional @var{length} argument is given, the string will be
23477 fetched and encoded to the length of characters specified. If
23478 the @var{length} argument is not provided, the string will be fetched
23479 and encoded until a null of appropriate width is found.
23482 @defun Value.fetch_lazy ()
23483 If the @code{gdb.Value} object is currently a lazy value
23484 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23485 fetched from the inferior. Any errors that occur in the process
23486 will produce a Python exception.
23488 If the @code{gdb.Value} object is not a lazy value, this method
23491 This method does not return a value.
23496 @node Types In Python
23497 @subsubsection Types In Python
23498 @cindex types in Python
23499 @cindex Python, working with types
23502 @value{GDBN} represents types from the inferior using the class
23505 The following type-related functions are available in the @code{gdb}
23508 @findex gdb.lookup_type
23509 @defun gdb.lookup_type (name @r{[}, block@r{]})
23510 This function looks up a type by name. @var{name} is the name of the
23511 type to look up. It must be a string.
23513 If @var{block} is given, then @var{name} is looked up in that scope.
23514 Otherwise, it is searched for globally.
23516 Ordinarily, this function will return an instance of @code{gdb.Type}.
23517 If the named type cannot be found, it will throw an exception.
23520 If the type is a structure or class type, or an enum type, the fields
23521 of that type can be accessed using the Python @dfn{dictionary syntax}.
23522 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23523 a structure type, you can access its @code{foo} field with:
23526 bar = some_type['foo']
23529 @code{bar} will be a @code{gdb.Field} object; see below under the
23530 description of the @code{Type.fields} method for a description of the
23531 @code{gdb.Field} class.
23533 An instance of @code{Type} has the following attributes:
23537 The type code for this type. The type code will be one of the
23538 @code{TYPE_CODE_} constants defined below.
23541 @defvar Type.sizeof
23542 The size of this type, in target @code{char} units. Usually, a
23543 target's @code{char} type will be an 8-bit byte. However, on some
23544 unusual platforms, this type may have a different size.
23548 The tag name for this type. The tag name is the name after
23549 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23550 languages have this concept. If this type has no tag name, then
23551 @code{None} is returned.
23555 The following methods are provided:
23558 @defun Type.fields ()
23559 For structure and union types, this method returns the fields. Range
23560 types have two fields, the minimum and maximum values. Enum types
23561 have one field per enum constant. Function and method types have one
23562 field per parameter. The base types of C@t{++} classes are also
23563 represented as fields. If the type has no fields, or does not fit
23564 into one of these categories, an empty sequence will be returned.
23566 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23569 This attribute is not available for @code{static} fields (as in
23570 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23571 position of the field. For @code{enum} fields, the value is the
23572 enumeration member's integer representation.
23575 The name of the field, or @code{None} for anonymous fields.
23578 This is @code{True} if the field is artificial, usually meaning that
23579 it was provided by the compiler and not the user. This attribute is
23580 always provided, and is @code{False} if the field is not artificial.
23582 @item is_base_class
23583 This is @code{True} if the field represents a base class of a C@t{++}
23584 structure. This attribute is always provided, and is @code{False}
23585 if the field is not a base class of the type that is the argument of
23586 @code{fields}, or if that type was not a C@t{++} class.
23589 If the field is packed, or is a bitfield, then this will have a
23590 non-zero value, which is the size of the field in bits. Otherwise,
23591 this will be zero; in this case the field's size is given by its type.
23594 The type of the field. This is usually an instance of @code{Type},
23595 but it can be @code{None} in some situations.
23599 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23600 Return a new @code{gdb.Type} object which represents an array of this
23601 type. If one argument is given, it is the inclusive upper bound of
23602 the array; in this case the lower bound is zero. If two arguments are
23603 given, the first argument is the lower bound of the array, and the
23604 second argument is the upper bound of the array. An array's length
23605 must not be negative, but the bounds can be.
23608 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23609 Return a new @code{gdb.Type} object which represents a vector of this
23610 type. If one argument is given, it is the inclusive upper bound of
23611 the vector; in this case the lower bound is zero. If two arguments are
23612 given, the first argument is the lower bound of the vector, and the
23613 second argument is the upper bound of the vector. A vector's length
23614 must not be negative, but the bounds can be.
23616 The difference between an @code{array} and a @code{vector} is that
23617 arrays behave like in C: when used in expressions they decay to a pointer
23618 to the first element whereas vectors are treated as first class values.
23621 @defun Type.const ()
23622 Return a new @code{gdb.Type} object which represents a
23623 @code{const}-qualified variant of this type.
23626 @defun Type.volatile ()
23627 Return a new @code{gdb.Type} object which represents a
23628 @code{volatile}-qualified variant of this type.
23631 @defun Type.unqualified ()
23632 Return a new @code{gdb.Type} object which represents an unqualified
23633 variant of this type. That is, the result is neither @code{const} nor
23637 @defun Type.range ()
23638 Return a Python @code{Tuple} object that contains two elements: the
23639 low bound of the argument type and the high bound of that type. If
23640 the type does not have a range, @value{GDBN} will raise a
23641 @code{gdb.error} exception (@pxref{Exception Handling}).
23644 @defun Type.reference ()
23645 Return a new @code{gdb.Type} object which represents a reference to this
23649 @defun Type.pointer ()
23650 Return a new @code{gdb.Type} object which represents a pointer to this
23654 @defun Type.strip_typedefs ()
23655 Return a new @code{gdb.Type} that represents the real type,
23656 after removing all layers of typedefs.
23659 @defun Type.target ()
23660 Return a new @code{gdb.Type} object which represents the target type
23663 For a pointer type, the target type is the type of the pointed-to
23664 object. For an array type (meaning C-like arrays), the target type is
23665 the type of the elements of the array. For a function or method type,
23666 the target type is the type of the return value. For a complex type,
23667 the target type is the type of the elements. For a typedef, the
23668 target type is the aliased type.
23670 If the type does not have a target, this method will throw an
23674 @defun Type.template_argument (n @r{[}, block@r{]})
23675 If this @code{gdb.Type} is an instantiation of a template, this will
23676 return a new @code{gdb.Type} which represents the type of the
23677 @var{n}th template argument.
23679 If this @code{gdb.Type} is not a template type, this will throw an
23680 exception. Ordinarily, only C@t{++} code will have template types.
23682 If @var{block} is given, then @var{name} is looked up in that scope.
23683 Otherwise, it is searched for globally.
23688 Each type has a code, which indicates what category this type falls
23689 into. The available type categories are represented by constants
23690 defined in the @code{gdb} module:
23693 @findex TYPE_CODE_PTR
23694 @findex gdb.TYPE_CODE_PTR
23695 @item gdb.TYPE_CODE_PTR
23696 The type is a pointer.
23698 @findex TYPE_CODE_ARRAY
23699 @findex gdb.TYPE_CODE_ARRAY
23700 @item gdb.TYPE_CODE_ARRAY
23701 The type is an array.
23703 @findex TYPE_CODE_STRUCT
23704 @findex gdb.TYPE_CODE_STRUCT
23705 @item gdb.TYPE_CODE_STRUCT
23706 The type is a structure.
23708 @findex TYPE_CODE_UNION
23709 @findex gdb.TYPE_CODE_UNION
23710 @item gdb.TYPE_CODE_UNION
23711 The type is a union.
23713 @findex TYPE_CODE_ENUM
23714 @findex gdb.TYPE_CODE_ENUM
23715 @item gdb.TYPE_CODE_ENUM
23716 The type is an enum.
23718 @findex TYPE_CODE_FLAGS
23719 @findex gdb.TYPE_CODE_FLAGS
23720 @item gdb.TYPE_CODE_FLAGS
23721 A bit flags type, used for things such as status registers.
23723 @findex TYPE_CODE_FUNC
23724 @findex gdb.TYPE_CODE_FUNC
23725 @item gdb.TYPE_CODE_FUNC
23726 The type is a function.
23728 @findex TYPE_CODE_INT
23729 @findex gdb.TYPE_CODE_INT
23730 @item gdb.TYPE_CODE_INT
23731 The type is an integer type.
23733 @findex TYPE_CODE_FLT
23734 @findex gdb.TYPE_CODE_FLT
23735 @item gdb.TYPE_CODE_FLT
23736 A floating point type.
23738 @findex TYPE_CODE_VOID
23739 @findex gdb.TYPE_CODE_VOID
23740 @item gdb.TYPE_CODE_VOID
23741 The special type @code{void}.
23743 @findex TYPE_CODE_SET
23744 @findex gdb.TYPE_CODE_SET
23745 @item gdb.TYPE_CODE_SET
23748 @findex TYPE_CODE_RANGE
23749 @findex gdb.TYPE_CODE_RANGE
23750 @item gdb.TYPE_CODE_RANGE
23751 A range type, that is, an integer type with bounds.
23753 @findex TYPE_CODE_STRING
23754 @findex gdb.TYPE_CODE_STRING
23755 @item gdb.TYPE_CODE_STRING
23756 A string type. Note that this is only used for certain languages with
23757 language-defined string types; C strings are not represented this way.
23759 @findex TYPE_CODE_BITSTRING
23760 @findex gdb.TYPE_CODE_BITSTRING
23761 @item gdb.TYPE_CODE_BITSTRING
23762 A string of bits. It is deprecated.
23764 @findex TYPE_CODE_ERROR
23765 @findex gdb.TYPE_CODE_ERROR
23766 @item gdb.TYPE_CODE_ERROR
23767 An unknown or erroneous type.
23769 @findex TYPE_CODE_METHOD
23770 @findex gdb.TYPE_CODE_METHOD
23771 @item gdb.TYPE_CODE_METHOD
23772 A method type, as found in C@t{++} or Java.
23774 @findex TYPE_CODE_METHODPTR
23775 @findex gdb.TYPE_CODE_METHODPTR
23776 @item gdb.TYPE_CODE_METHODPTR
23777 A pointer-to-member-function.
23779 @findex TYPE_CODE_MEMBERPTR
23780 @findex gdb.TYPE_CODE_MEMBERPTR
23781 @item gdb.TYPE_CODE_MEMBERPTR
23782 A pointer-to-member.
23784 @findex TYPE_CODE_REF
23785 @findex gdb.TYPE_CODE_REF
23786 @item gdb.TYPE_CODE_REF
23789 @findex TYPE_CODE_CHAR
23790 @findex gdb.TYPE_CODE_CHAR
23791 @item gdb.TYPE_CODE_CHAR
23794 @findex TYPE_CODE_BOOL
23795 @findex gdb.TYPE_CODE_BOOL
23796 @item gdb.TYPE_CODE_BOOL
23799 @findex TYPE_CODE_COMPLEX
23800 @findex gdb.TYPE_CODE_COMPLEX
23801 @item gdb.TYPE_CODE_COMPLEX
23802 A complex float type.
23804 @findex TYPE_CODE_TYPEDEF
23805 @findex gdb.TYPE_CODE_TYPEDEF
23806 @item gdb.TYPE_CODE_TYPEDEF
23807 A typedef to some other type.
23809 @findex TYPE_CODE_NAMESPACE
23810 @findex gdb.TYPE_CODE_NAMESPACE
23811 @item gdb.TYPE_CODE_NAMESPACE
23812 A C@t{++} namespace.
23814 @findex TYPE_CODE_DECFLOAT
23815 @findex gdb.TYPE_CODE_DECFLOAT
23816 @item gdb.TYPE_CODE_DECFLOAT
23817 A decimal floating point type.
23819 @findex TYPE_CODE_INTERNAL_FUNCTION
23820 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23821 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23822 A function internal to @value{GDBN}. This is the type used to represent
23823 convenience functions.
23826 Further support for types is provided in the @code{gdb.types}
23827 Python module (@pxref{gdb.types}).
23829 @node Pretty Printing API
23830 @subsubsection Pretty Printing API
23832 An example output is provided (@pxref{Pretty Printing}).
23834 A pretty-printer is just an object that holds a value and implements a
23835 specific interface, defined here.
23837 @defun pretty_printer.children (self)
23838 @value{GDBN} will call this method on a pretty-printer to compute the
23839 children of the pretty-printer's value.
23841 This method must return an object conforming to the Python iterator
23842 protocol. Each item returned by the iterator must be a tuple holding
23843 two elements. The first element is the ``name'' of the child; the
23844 second element is the child's value. The value can be any Python
23845 object which is convertible to a @value{GDBN} value.
23847 This method is optional. If it does not exist, @value{GDBN} will act
23848 as though the value has no children.
23851 @defun pretty_printer.display_hint (self)
23852 The CLI may call this method and use its result to change the
23853 formatting of a value. The result will also be supplied to an MI
23854 consumer as a @samp{displayhint} attribute of the variable being
23857 This method is optional. If it does exist, this method must return a
23860 Some display hints are predefined by @value{GDBN}:
23864 Indicate that the object being printed is ``array-like''. The CLI
23865 uses this to respect parameters such as @code{set print elements} and
23866 @code{set print array}.
23869 Indicate that the object being printed is ``map-like'', and that the
23870 children of this value can be assumed to alternate between keys and
23874 Indicate that the object being printed is ``string-like''. If the
23875 printer's @code{to_string} method returns a Python string of some
23876 kind, then @value{GDBN} will call its internal language-specific
23877 string-printing function to format the string. For the CLI this means
23878 adding quotation marks, possibly escaping some characters, respecting
23879 @code{set print elements}, and the like.
23883 @defun pretty_printer.to_string (self)
23884 @value{GDBN} will call this method to display the string
23885 representation of the value passed to the object's constructor.
23887 When printing from the CLI, if the @code{to_string} method exists,
23888 then @value{GDBN} will prepend its result to the values returned by
23889 @code{children}. Exactly how this formatting is done is dependent on
23890 the display hint, and may change as more hints are added. Also,
23891 depending on the print settings (@pxref{Print Settings}), the CLI may
23892 print just the result of @code{to_string} in a stack trace, omitting
23893 the result of @code{children}.
23895 If this method returns a string, it is printed verbatim.
23897 Otherwise, if this method returns an instance of @code{gdb.Value},
23898 then @value{GDBN} prints this value. This may result in a call to
23899 another pretty-printer.
23901 If instead the method returns a Python value which is convertible to a
23902 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
23903 the resulting value. Again, this may result in a call to another
23904 pretty-printer. Python scalars (integers, floats, and booleans) and
23905 strings are convertible to @code{gdb.Value}; other types are not.
23907 Finally, if this method returns @code{None} then no further operations
23908 are peformed in this method and nothing is printed.
23910 If the result is not one of these types, an exception is raised.
23913 @value{GDBN} provides a function which can be used to look up the
23914 default pretty-printer for a @code{gdb.Value}:
23916 @findex gdb.default_visualizer
23917 @defun gdb.default_visualizer (value)
23918 This function takes a @code{gdb.Value} object as an argument. If a
23919 pretty-printer for this value exists, then it is returned. If no such
23920 printer exists, then this returns @code{None}.
23923 @node Selecting Pretty-Printers
23924 @subsubsection Selecting Pretty-Printers
23926 The Python list @code{gdb.pretty_printers} contains an array of
23927 functions or callable objects that have been registered via addition
23928 as a pretty-printer. Printers in this list are called @code{global}
23929 printers, they're available when debugging all inferiors.
23930 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
23931 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
23934 Each function on these lists is passed a single @code{gdb.Value}
23935 argument and should return a pretty-printer object conforming to the
23936 interface definition above (@pxref{Pretty Printing API}). If a function
23937 cannot create a pretty-printer for the value, it should return
23940 @value{GDBN} first checks the @code{pretty_printers} attribute of each
23941 @code{gdb.Objfile} in the current program space and iteratively calls
23942 each enabled lookup routine in the list for that @code{gdb.Objfile}
23943 until it receives a pretty-printer object.
23944 If no pretty-printer is found in the objfile lists, @value{GDBN} then
23945 searches the pretty-printer list of the current program space,
23946 calling each enabled function until an object is returned.
23947 After these lists have been exhausted, it tries the global
23948 @code{gdb.pretty_printers} list, again calling each enabled function until an
23949 object is returned.
23951 The order in which the objfiles are searched is not specified. For a
23952 given list, functions are always invoked from the head of the list,
23953 and iterated over sequentially until the end of the list, or a printer
23954 object is returned.
23956 For various reasons a pretty-printer may not work.
23957 For example, the underlying data structure may have changed and
23958 the pretty-printer is out of date.
23960 The consequences of a broken pretty-printer are severe enough that
23961 @value{GDBN} provides support for enabling and disabling individual
23962 printers. For example, if @code{print frame-arguments} is on,
23963 a backtrace can become highly illegible if any argument is printed
23964 with a broken printer.
23966 Pretty-printers are enabled and disabled by attaching an @code{enabled}
23967 attribute to the registered function or callable object. If this attribute
23968 is present and its value is @code{False}, the printer is disabled, otherwise
23969 the printer is enabled.
23971 @node Writing a Pretty-Printer
23972 @subsubsection Writing a Pretty-Printer
23973 @cindex writing a pretty-printer
23975 A pretty-printer consists of two parts: a lookup function to detect
23976 if the type is supported, and the printer itself.
23978 Here is an example showing how a @code{std::string} printer might be
23979 written. @xref{Pretty Printing API}, for details on the API this class
23983 class StdStringPrinter(object):
23984 "Print a std::string"
23986 def __init__(self, val):
23989 def to_string(self):
23990 return self.val['_M_dataplus']['_M_p']
23992 def display_hint(self):
23996 And here is an example showing how a lookup function for the printer
23997 example above might be written.
24000 def str_lookup_function(val):
24001 lookup_tag = val.type.tag
24002 if lookup_tag == None:
24004 regex = re.compile("^std::basic_string<char,.*>$")
24005 if regex.match(lookup_tag):
24006 return StdStringPrinter(val)
24010 The example lookup function extracts the value's type, and attempts to
24011 match it to a type that it can pretty-print. If it is a type the
24012 printer can pretty-print, it will return a printer object. If not, it
24013 returns @code{None}.
24015 We recommend that you put your core pretty-printers into a Python
24016 package. If your pretty-printers are for use with a library, we
24017 further recommend embedding a version number into the package name.
24018 This practice will enable @value{GDBN} to load multiple versions of
24019 your pretty-printers at the same time, because they will have
24022 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24023 can be evaluated multiple times without changing its meaning. An
24024 ideal auto-load file will consist solely of @code{import}s of your
24025 printer modules, followed by a call to a register pretty-printers with
24026 the current objfile.
24028 Taken as a whole, this approach will scale nicely to multiple
24029 inferiors, each potentially using a different library version.
24030 Embedding a version number in the Python package name will ensure that
24031 @value{GDBN} is able to load both sets of printers simultaneously.
24032 Then, because the search for pretty-printers is done by objfile, and
24033 because your auto-loaded code took care to register your library's
24034 printers with a specific objfile, @value{GDBN} will find the correct
24035 printers for the specific version of the library used by each
24038 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24039 this code might appear in @code{gdb.libstdcxx.v6}:
24042 def register_printers(objfile):
24043 objfile.pretty_printers.append(str_lookup_function)
24047 And then the corresponding contents of the auto-load file would be:
24050 import gdb.libstdcxx.v6
24051 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24054 The previous example illustrates a basic pretty-printer.
24055 There are a few things that can be improved on.
24056 The printer doesn't have a name, making it hard to identify in a
24057 list of installed printers. The lookup function has a name, but
24058 lookup functions can have arbitrary, even identical, names.
24060 Second, the printer only handles one type, whereas a library typically has
24061 several types. One could install a lookup function for each desired type
24062 in the library, but one could also have a single lookup function recognize
24063 several types. The latter is the conventional way this is handled.
24064 If a pretty-printer can handle multiple data types, then its
24065 @dfn{subprinters} are the printers for the individual data types.
24067 The @code{gdb.printing} module provides a formal way of solving these
24068 problems (@pxref{gdb.printing}).
24069 Here is another example that handles multiple types.
24071 These are the types we are going to pretty-print:
24074 struct foo @{ int a, b; @};
24075 struct bar @{ struct foo x, y; @};
24078 Here are the printers:
24082 """Print a foo object."""
24084 def __init__(self, val):
24087 def to_string(self):
24088 return ("a=<" + str(self.val["a"]) +
24089 "> b=<" + str(self.val["b"]) + ">")
24092 """Print a bar object."""
24094 def __init__(self, val):
24097 def to_string(self):
24098 return ("x=<" + str(self.val["x"]) +
24099 "> y=<" + str(self.val["y"]) + ">")
24102 This example doesn't need a lookup function, that is handled by the
24103 @code{gdb.printing} module. Instead a function is provided to build up
24104 the object that handles the lookup.
24107 import gdb.printing
24109 def build_pretty_printer():
24110 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24112 pp.add_printer('foo', '^foo$', fooPrinter)
24113 pp.add_printer('bar', '^bar$', barPrinter)
24117 And here is the autoload support:
24120 import gdb.printing
24122 gdb.printing.register_pretty_printer(
24123 gdb.current_objfile(),
24124 my_library.build_pretty_printer())
24127 Finally, when this printer is loaded into @value{GDBN}, here is the
24128 corresponding output of @samp{info pretty-printer}:
24131 (gdb) info pretty-printer
24138 @node Type Printing API
24139 @subsubsection Type Printing API
24140 @cindex type printing API for Python
24142 @value{GDBN} provides a way for Python code to customize type display.
24143 This is mainly useful for substituting canonical typedef names for
24146 @cindex type printer
24147 A @dfn{type printer} is just a Python object conforming to a certain
24148 protocol. A simple base class implementing the protocol is provided;
24149 see @ref{gdb.types}. A type printer must supply at least:
24151 @defivar type_printer enabled
24152 A boolean which is True if the printer is enabled, and False
24153 otherwise. This is manipulated by the @code{enable type-printer}
24154 and @code{disable type-printer} commands.
24157 @defivar type_printer name
24158 The name of the type printer. This must be a string. This is used by
24159 the @code{enable type-printer} and @code{disable type-printer}
24163 @defmethod type_printer instantiate (self)
24164 This is called by @value{GDBN} at the start of type-printing. It is
24165 only called if the type printer is enabled. This method must return a
24166 new object that supplies a @code{recognize} method, as described below.
24170 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24171 will compute a list of type recognizers. This is done by iterating
24172 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24173 followed by the per-progspace type printers (@pxref{Progspaces In
24174 Python}), and finally the global type printers.
24176 @value{GDBN} will call the @code{instantiate} method of each enabled
24177 type printer. If this method returns @code{None}, then the result is
24178 ignored; otherwise, it is appended to the list of recognizers.
24180 Then, when @value{GDBN} is going to display a type name, it iterates
24181 over the list of recognizers. For each one, it calls the recognition
24182 function, stopping if the function returns a non-@code{None} value.
24183 The recognition function is defined as:
24185 @defmethod type_recognizer recognize (self, type)
24186 If @var{type} is not recognized, return @code{None}. Otherwise,
24187 return a string which is to be printed as the name of @var{type}.
24188 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24192 @value{GDBN} uses this two-pass approach so that type printers can
24193 efficiently cache information without holding on to it too long. For
24194 example, it can be convenient to look up type information in a type
24195 printer and hold it for a recognizer's lifetime; if a single pass were
24196 done then type printers would have to make use of the event system in
24197 order to avoid holding information that could become stale as the
24200 @node Inferiors In Python
24201 @subsubsection Inferiors In Python
24202 @cindex inferiors in Python
24204 @findex gdb.Inferior
24205 Programs which are being run under @value{GDBN} are called inferiors
24206 (@pxref{Inferiors and Programs}). Python scripts can access
24207 information about and manipulate inferiors controlled by @value{GDBN}
24208 via objects of the @code{gdb.Inferior} class.
24210 The following inferior-related functions are available in the @code{gdb}
24213 @defun gdb.inferiors ()
24214 Return a tuple containing all inferior objects.
24217 @defun gdb.selected_inferior ()
24218 Return an object representing the current inferior.
24221 A @code{gdb.Inferior} object has the following attributes:
24224 @defvar Inferior.num
24225 ID of inferior, as assigned by GDB.
24228 @defvar Inferior.pid
24229 Process ID of the inferior, as assigned by the underlying operating
24233 @defvar Inferior.was_attached
24234 Boolean signaling whether the inferior was created using `attach', or
24235 started by @value{GDBN} itself.
24239 A @code{gdb.Inferior} object has the following methods:
24242 @defun Inferior.is_valid ()
24243 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24244 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24245 if the inferior no longer exists within @value{GDBN}. All other
24246 @code{gdb.Inferior} methods will throw an exception if it is invalid
24247 at the time the method is called.
24250 @defun Inferior.threads ()
24251 This method returns a tuple holding all the threads which are valid
24252 when it is called. If there are no valid threads, the method will
24253 return an empty tuple.
24256 @findex Inferior.read_memory
24257 @defun Inferior.read_memory (address, length)
24258 Read @var{length} bytes of memory from the inferior, starting at
24259 @var{address}. Returns a buffer object, which behaves much like an array
24260 or a string. It can be modified and given to the
24261 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24262 value is a @code{memoryview} object.
24265 @findex Inferior.write_memory
24266 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24267 Write the contents of @var{buffer} to the inferior, starting at
24268 @var{address}. The @var{buffer} parameter must be a Python object
24269 which supports the buffer protocol, i.e., a string, an array or the
24270 object returned from @code{Inferior.read_memory}. If given, @var{length}
24271 determines the number of bytes from @var{buffer} to be written.
24274 @findex gdb.search_memory
24275 @defun Inferior.search_memory (address, length, pattern)
24276 Search a region of the inferior memory starting at @var{address} with
24277 the given @var{length} using the search pattern supplied in
24278 @var{pattern}. The @var{pattern} parameter must be a Python object
24279 which supports the buffer protocol, i.e., a string, an array or the
24280 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24281 containing the address where the pattern was found, or @code{None} if
24282 the pattern could not be found.
24286 @node Events In Python
24287 @subsubsection Events In Python
24288 @cindex inferior events in Python
24290 @value{GDBN} provides a general event facility so that Python code can be
24291 notified of various state changes, particularly changes that occur in
24294 An @dfn{event} is just an object that describes some state change. The
24295 type of the object and its attributes will vary depending on the details
24296 of the change. All the existing events are described below.
24298 In order to be notified of an event, you must register an event handler
24299 with an @dfn{event registry}. An event registry is an object in the
24300 @code{gdb.events} module which dispatches particular events. A registry
24301 provides methods to register and unregister event handlers:
24304 @defun EventRegistry.connect (object)
24305 Add the given callable @var{object} to the registry. This object will be
24306 called when an event corresponding to this registry occurs.
24309 @defun EventRegistry.disconnect (object)
24310 Remove the given @var{object} from the registry. Once removed, the object
24311 will no longer receive notifications of events.
24315 Here is an example:
24318 def exit_handler (event):
24319 print "event type: exit"
24320 print "exit code: %d" % (event.exit_code)
24322 gdb.events.exited.connect (exit_handler)
24325 In the above example we connect our handler @code{exit_handler} to the
24326 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24327 called when the inferior exits. The argument @dfn{event} in this example is
24328 of type @code{gdb.ExitedEvent}. As you can see in the example the
24329 @code{ExitedEvent} object has an attribute which indicates the exit code of
24332 The following is a listing of the event registries that are available and
24333 details of the events they emit:
24338 Emits @code{gdb.ThreadEvent}.
24340 Some events can be thread specific when @value{GDBN} is running in non-stop
24341 mode. When represented in Python, these events all extend
24342 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24343 events which are emitted by this or other modules might extend this event.
24344 Examples of these events are @code{gdb.BreakpointEvent} and
24345 @code{gdb.ContinueEvent}.
24348 @defvar ThreadEvent.inferior_thread
24349 In non-stop mode this attribute will be set to the specific thread which was
24350 involved in the emitted event. Otherwise, it will be set to @code{None}.
24354 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24356 This event indicates that the inferior has been continued after a stop. For
24357 inherited attribute refer to @code{gdb.ThreadEvent} above.
24359 @item events.exited
24360 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24361 @code{events.ExitedEvent} has two attributes:
24363 @defvar ExitedEvent.exit_code
24364 An integer representing the exit code, if available, which the inferior
24365 has returned. (The exit code could be unavailable if, for example,
24366 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24367 the attribute does not exist.
24369 @defvar ExitedEvent inferior
24370 A reference to the inferior which triggered the @code{exited} event.
24375 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24377 Indicates that the inferior has stopped. All events emitted by this registry
24378 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24379 will indicate the stopped thread when @value{GDBN} is running in non-stop
24380 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24382 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24384 This event indicates that the inferior or one of its threads has received as
24385 signal. @code{gdb.SignalEvent} has the following attributes:
24388 @defvar SignalEvent.stop_signal
24389 A string representing the signal received by the inferior. A list of possible
24390 signal values can be obtained by running the command @code{info signals} in
24391 the @value{GDBN} command prompt.
24395 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24397 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24398 been hit, and has the following attributes:
24401 @defvar BreakpointEvent.breakpoints
24402 A sequence containing references to all the breakpoints (type
24403 @code{gdb.Breakpoint}) that were hit.
24404 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24406 @defvar BreakpointEvent.breakpoint
24407 A reference to the first breakpoint that was hit.
24408 This function is maintained for backward compatibility and is now deprecated
24409 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24413 @item events.new_objfile
24414 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24415 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24418 @defvar NewObjFileEvent.new_objfile
24419 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24420 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24426 @node Threads In Python
24427 @subsubsection Threads In Python
24428 @cindex threads in python
24430 @findex gdb.InferiorThread
24431 Python scripts can access information about, and manipulate inferior threads
24432 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24434 The following thread-related functions are available in the @code{gdb}
24437 @findex gdb.selected_thread
24438 @defun gdb.selected_thread ()
24439 This function returns the thread object for the selected thread. If there
24440 is no selected thread, this will return @code{None}.
24443 A @code{gdb.InferiorThread} object has the following attributes:
24446 @defvar InferiorThread.name
24447 The name of the thread. If the user specified a name using
24448 @code{thread name}, then this returns that name. Otherwise, if an
24449 OS-supplied name is available, then it is returned. Otherwise, this
24450 returns @code{None}.
24452 This attribute can be assigned to. The new value must be a string
24453 object, which sets the new name, or @code{None}, which removes any
24454 user-specified thread name.
24457 @defvar InferiorThread.num
24458 ID of the thread, as assigned by GDB.
24461 @defvar InferiorThread.ptid
24462 ID of the thread, as assigned by the operating system. This attribute is a
24463 tuple containing three integers. The first is the Process ID (PID); the second
24464 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24465 Either the LWPID or TID may be 0, which indicates that the operating system
24466 does not use that identifier.
24470 A @code{gdb.InferiorThread} object has the following methods:
24473 @defun InferiorThread.is_valid ()
24474 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24475 @code{False} if not. A @code{gdb.InferiorThread} object will become
24476 invalid if the thread exits, or the inferior that the thread belongs
24477 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24478 exception if it is invalid at the time the method is called.
24481 @defun InferiorThread.switch ()
24482 This changes @value{GDBN}'s currently selected thread to the one represented
24486 @defun InferiorThread.is_stopped ()
24487 Return a Boolean indicating whether the thread is stopped.
24490 @defun InferiorThread.is_running ()
24491 Return a Boolean indicating whether the thread is running.
24494 @defun InferiorThread.is_exited ()
24495 Return a Boolean indicating whether the thread is exited.
24499 @node Commands In Python
24500 @subsubsection Commands In Python
24502 @cindex commands in python
24503 @cindex python commands
24504 You can implement new @value{GDBN} CLI commands in Python. A CLI
24505 command is implemented using an instance of the @code{gdb.Command}
24506 class, most commonly using a subclass.
24508 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24509 The object initializer for @code{Command} registers the new command
24510 with @value{GDBN}. This initializer is normally invoked from the
24511 subclass' own @code{__init__} method.
24513 @var{name} is the name of the command. If @var{name} consists of
24514 multiple words, then the initial words are looked for as prefix
24515 commands. In this case, if one of the prefix commands does not exist,
24516 an exception is raised.
24518 There is no support for multi-line commands.
24520 @var{command_class} should be one of the @samp{COMMAND_} constants
24521 defined below. This argument tells @value{GDBN} how to categorize the
24522 new command in the help system.
24524 @var{completer_class} is an optional argument. If given, it should be
24525 one of the @samp{COMPLETE_} constants defined below. This argument
24526 tells @value{GDBN} how to perform completion for this command. If not
24527 given, @value{GDBN} will attempt to complete using the object's
24528 @code{complete} method (see below); if no such method is found, an
24529 error will occur when completion is attempted.
24531 @var{prefix} is an optional argument. If @code{True}, then the new
24532 command is a prefix command; sub-commands of this command may be
24535 The help text for the new command is taken from the Python
24536 documentation string for the command's class, if there is one. If no
24537 documentation string is provided, the default value ``This command is
24538 not documented.'' is used.
24541 @cindex don't repeat Python command
24542 @defun Command.dont_repeat ()
24543 By default, a @value{GDBN} command is repeated when the user enters a
24544 blank line at the command prompt. A command can suppress this
24545 behavior by invoking the @code{dont_repeat} method. This is similar
24546 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24549 @defun Command.invoke (argument, from_tty)
24550 This method is called by @value{GDBN} when this command is invoked.
24552 @var{argument} is a string. It is the argument to the command, after
24553 leading and trailing whitespace has been stripped.
24555 @var{from_tty} is a boolean argument. When true, this means that the
24556 command was entered by the user at the terminal; when false it means
24557 that the command came from elsewhere.
24559 If this method throws an exception, it is turned into a @value{GDBN}
24560 @code{error} call. Otherwise, the return value is ignored.
24562 @findex gdb.string_to_argv
24563 To break @var{argument} up into an argv-like string use
24564 @code{gdb.string_to_argv}. This function behaves identically to
24565 @value{GDBN}'s internal argument lexer @code{buildargv}.
24566 It is recommended to use this for consistency.
24567 Arguments are separated by spaces and may be quoted.
24571 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24572 ['1', '2 "3', '4 "5', "6 '7"]
24577 @cindex completion of Python commands
24578 @defun Command.complete (text, word)
24579 This method is called by @value{GDBN} when the user attempts
24580 completion on this command. All forms of completion are handled by
24581 this method, that is, the @key{TAB} and @key{M-?} key bindings
24582 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24585 The arguments @var{text} and @var{word} are both strings. @var{text}
24586 holds the complete command line up to the cursor's location.
24587 @var{word} holds the last word of the command line; this is computed
24588 using a word-breaking heuristic.
24590 The @code{complete} method can return several values:
24593 If the return value is a sequence, the contents of the sequence are
24594 used as the completions. It is up to @code{complete} to ensure that the
24595 contents actually do complete the word. A zero-length sequence is
24596 allowed, it means that there were no completions available. Only
24597 string elements of the sequence are used; other elements in the
24598 sequence are ignored.
24601 If the return value is one of the @samp{COMPLETE_} constants defined
24602 below, then the corresponding @value{GDBN}-internal completion
24603 function is invoked, and its result is used.
24606 All other results are treated as though there were no available
24611 When a new command is registered, it must be declared as a member of
24612 some general class of commands. This is used to classify top-level
24613 commands in the on-line help system; note that prefix commands are not
24614 listed under their own category but rather that of their top-level
24615 command. The available classifications are represented by constants
24616 defined in the @code{gdb} module:
24619 @findex COMMAND_NONE
24620 @findex gdb.COMMAND_NONE
24621 @item gdb.COMMAND_NONE
24622 The command does not belong to any particular class. A command in
24623 this category will not be displayed in any of the help categories.
24625 @findex COMMAND_RUNNING
24626 @findex gdb.COMMAND_RUNNING
24627 @item gdb.COMMAND_RUNNING
24628 The command is related to running the inferior. For example,
24629 @code{start}, @code{step}, and @code{continue} are in this category.
24630 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24631 commands in this category.
24633 @findex COMMAND_DATA
24634 @findex gdb.COMMAND_DATA
24635 @item gdb.COMMAND_DATA
24636 The command is related to data or variables. For example,
24637 @code{call}, @code{find}, and @code{print} are in this category. Type
24638 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24641 @findex COMMAND_STACK
24642 @findex gdb.COMMAND_STACK
24643 @item gdb.COMMAND_STACK
24644 The command has to do with manipulation of the stack. For example,
24645 @code{backtrace}, @code{frame}, and @code{return} are in this
24646 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24647 list of commands in this category.
24649 @findex COMMAND_FILES
24650 @findex gdb.COMMAND_FILES
24651 @item gdb.COMMAND_FILES
24652 This class is used for file-related commands. For example,
24653 @code{file}, @code{list} and @code{section} are in this category.
24654 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24655 commands in this category.
24657 @findex COMMAND_SUPPORT
24658 @findex gdb.COMMAND_SUPPORT
24659 @item gdb.COMMAND_SUPPORT
24660 This should be used for ``support facilities'', generally meaning
24661 things that are useful to the user when interacting with @value{GDBN},
24662 but not related to the state of the inferior. For example,
24663 @code{help}, @code{make}, and @code{shell} are in this category. Type
24664 @kbd{help support} at the @value{GDBN} prompt to see a list of
24665 commands in this category.
24667 @findex COMMAND_STATUS
24668 @findex gdb.COMMAND_STATUS
24669 @item gdb.COMMAND_STATUS
24670 The command is an @samp{info}-related command, that is, related to the
24671 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24672 and @code{show} are in this category. Type @kbd{help status} at the
24673 @value{GDBN} prompt to see a list of commands in this category.
24675 @findex COMMAND_BREAKPOINTS
24676 @findex gdb.COMMAND_BREAKPOINTS
24677 @item gdb.COMMAND_BREAKPOINTS
24678 The command has to do with breakpoints. For example, @code{break},
24679 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24680 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24683 @findex COMMAND_TRACEPOINTS
24684 @findex gdb.COMMAND_TRACEPOINTS
24685 @item gdb.COMMAND_TRACEPOINTS
24686 The command has to do with tracepoints. For example, @code{trace},
24687 @code{actions}, and @code{tfind} are in this category. Type
24688 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24689 commands in this category.
24691 @findex COMMAND_USER
24692 @findex gdb.COMMAND_USER
24693 @item gdb.COMMAND_USER
24694 The command is a general purpose command for the user, and typically
24695 does not fit in one of the other categories.
24696 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24697 a list of commands in this category, as well as the list of gdb macros
24698 (@pxref{Sequences}).
24700 @findex COMMAND_OBSCURE
24701 @findex gdb.COMMAND_OBSCURE
24702 @item gdb.COMMAND_OBSCURE
24703 The command is only used in unusual circumstances, or is not of
24704 general interest to users. For example, @code{checkpoint},
24705 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24706 obscure} at the @value{GDBN} prompt to see a list of commands in this
24709 @findex COMMAND_MAINTENANCE
24710 @findex gdb.COMMAND_MAINTENANCE
24711 @item gdb.COMMAND_MAINTENANCE
24712 The command is only useful to @value{GDBN} maintainers. The
24713 @code{maintenance} and @code{flushregs} commands are in this category.
24714 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24715 commands in this category.
24718 A new command can use a predefined completion function, either by
24719 specifying it via an argument at initialization, or by returning it
24720 from the @code{complete} method. These predefined completion
24721 constants are all defined in the @code{gdb} module:
24724 @findex COMPLETE_NONE
24725 @findex gdb.COMPLETE_NONE
24726 @item gdb.COMPLETE_NONE
24727 This constant means that no completion should be done.
24729 @findex COMPLETE_FILENAME
24730 @findex gdb.COMPLETE_FILENAME
24731 @item gdb.COMPLETE_FILENAME
24732 This constant means that filename completion should be performed.
24734 @findex COMPLETE_LOCATION
24735 @findex gdb.COMPLETE_LOCATION
24736 @item gdb.COMPLETE_LOCATION
24737 This constant means that location completion should be done.
24738 @xref{Specify Location}.
24740 @findex COMPLETE_COMMAND
24741 @findex gdb.COMPLETE_COMMAND
24742 @item gdb.COMPLETE_COMMAND
24743 This constant means that completion should examine @value{GDBN}
24746 @findex COMPLETE_SYMBOL
24747 @findex gdb.COMPLETE_SYMBOL
24748 @item gdb.COMPLETE_SYMBOL
24749 This constant means that completion should be done using symbol names
24753 The following code snippet shows how a trivial CLI command can be
24754 implemented in Python:
24757 class HelloWorld (gdb.Command):
24758 """Greet the whole world."""
24760 def __init__ (self):
24761 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24763 def invoke (self, arg, from_tty):
24764 print "Hello, World!"
24769 The last line instantiates the class, and is necessary to trigger the
24770 registration of the command with @value{GDBN}. Depending on how the
24771 Python code is read into @value{GDBN}, you may need to import the
24772 @code{gdb} module explicitly.
24774 @node Parameters In Python
24775 @subsubsection Parameters In Python
24777 @cindex parameters in python
24778 @cindex python parameters
24779 @tindex gdb.Parameter
24781 You can implement new @value{GDBN} parameters using Python. A new
24782 parameter is implemented as an instance of the @code{gdb.Parameter}
24785 Parameters are exposed to the user via the @code{set} and
24786 @code{show} commands. @xref{Help}.
24788 There are many parameters that already exist and can be set in
24789 @value{GDBN}. Two examples are: @code{set follow fork} and
24790 @code{set charset}. Setting these parameters influences certain
24791 behavior in @value{GDBN}. Similarly, you can define parameters that
24792 can be used to influence behavior in custom Python scripts and commands.
24794 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24795 The object initializer for @code{Parameter} registers the new
24796 parameter with @value{GDBN}. This initializer is normally invoked
24797 from the subclass' own @code{__init__} method.
24799 @var{name} is the name of the new parameter. If @var{name} consists
24800 of multiple words, then the initial words are looked for as prefix
24801 parameters. An example of this can be illustrated with the
24802 @code{set print} set of parameters. If @var{name} is
24803 @code{print foo}, then @code{print} will be searched as the prefix
24804 parameter. In this case the parameter can subsequently be accessed in
24805 @value{GDBN} as @code{set print foo}.
24807 If @var{name} consists of multiple words, and no prefix parameter group
24808 can be found, an exception is raised.
24810 @var{command-class} should be one of the @samp{COMMAND_} constants
24811 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24812 categorize the new parameter in the help system.
24814 @var{parameter-class} should be one of the @samp{PARAM_} constants
24815 defined below. This argument tells @value{GDBN} the type of the new
24816 parameter; this information is used for input validation and
24819 If @var{parameter-class} is @code{PARAM_ENUM}, then
24820 @var{enum-sequence} must be a sequence of strings. These strings
24821 represent the possible values for the parameter.
24823 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24824 of a fourth argument will cause an exception to be thrown.
24826 The help text for the new parameter is taken from the Python
24827 documentation string for the parameter's class, if there is one. If
24828 there is no documentation string, a default value is used.
24831 @defvar Parameter.set_doc
24832 If this attribute exists, and is a string, then its value is used as
24833 the help text for this parameter's @code{set} command. The value is
24834 examined when @code{Parameter.__init__} is invoked; subsequent changes
24838 @defvar Parameter.show_doc
24839 If this attribute exists, and is a string, then its value is used as
24840 the help text for this parameter's @code{show} command. The value is
24841 examined when @code{Parameter.__init__} is invoked; subsequent changes
24845 @defvar Parameter.value
24846 The @code{value} attribute holds the underlying value of the
24847 parameter. It can be read and assigned to just as any other
24848 attribute. @value{GDBN} does validation when assignments are made.
24851 There are two methods that should be implemented in any
24852 @code{Parameter} class. These are:
24854 @defun Parameter.get_set_string (self)
24855 @value{GDBN} will call this method when a @var{parameter}'s value has
24856 been changed via the @code{set} API (for example, @kbd{set foo off}).
24857 The @code{value} attribute has already been populated with the new
24858 value and may be used in output. This method must return a string.
24861 @defun Parameter.get_show_string (self, svalue)
24862 @value{GDBN} will call this method when a @var{parameter}'s
24863 @code{show} API has been invoked (for example, @kbd{show foo}). The
24864 argument @code{svalue} receives the string representation of the
24865 current value. This method must return a string.
24868 When a new parameter is defined, its type must be specified. The
24869 available types are represented by constants defined in the @code{gdb}
24873 @findex PARAM_BOOLEAN
24874 @findex gdb.PARAM_BOOLEAN
24875 @item gdb.PARAM_BOOLEAN
24876 The value is a plain boolean. The Python boolean values, @code{True}
24877 and @code{False} are the only valid values.
24879 @findex PARAM_AUTO_BOOLEAN
24880 @findex gdb.PARAM_AUTO_BOOLEAN
24881 @item gdb.PARAM_AUTO_BOOLEAN
24882 The value has three possible states: true, false, and @samp{auto}. In
24883 Python, true and false are represented using boolean constants, and
24884 @samp{auto} is represented using @code{None}.
24886 @findex PARAM_UINTEGER
24887 @findex gdb.PARAM_UINTEGER
24888 @item gdb.PARAM_UINTEGER
24889 The value is an unsigned integer. The value of 0 should be
24890 interpreted to mean ``unlimited''.
24892 @findex PARAM_INTEGER
24893 @findex gdb.PARAM_INTEGER
24894 @item gdb.PARAM_INTEGER
24895 The value is a signed integer. The value of 0 should be interpreted
24896 to mean ``unlimited''.
24898 @findex PARAM_STRING
24899 @findex gdb.PARAM_STRING
24900 @item gdb.PARAM_STRING
24901 The value is a string. When the user modifies the string, any escape
24902 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
24903 translated into corresponding characters and encoded into the current
24906 @findex PARAM_STRING_NOESCAPE
24907 @findex gdb.PARAM_STRING_NOESCAPE
24908 @item gdb.PARAM_STRING_NOESCAPE
24909 The value is a string. When the user modifies the string, escapes are
24910 passed through untranslated.
24912 @findex PARAM_OPTIONAL_FILENAME
24913 @findex gdb.PARAM_OPTIONAL_FILENAME
24914 @item gdb.PARAM_OPTIONAL_FILENAME
24915 The value is a either a filename (a string), or @code{None}.
24917 @findex PARAM_FILENAME
24918 @findex gdb.PARAM_FILENAME
24919 @item gdb.PARAM_FILENAME
24920 The value is a filename. This is just like
24921 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
24923 @findex PARAM_ZINTEGER
24924 @findex gdb.PARAM_ZINTEGER
24925 @item gdb.PARAM_ZINTEGER
24926 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
24927 is interpreted as itself.
24930 @findex gdb.PARAM_ENUM
24931 @item gdb.PARAM_ENUM
24932 The value is a string, which must be one of a collection string
24933 constants provided when the parameter is created.
24936 @node Functions In Python
24937 @subsubsection Writing new convenience functions
24939 @cindex writing convenience functions
24940 @cindex convenience functions in python
24941 @cindex python convenience functions
24942 @tindex gdb.Function
24944 You can implement new convenience functions (@pxref{Convenience Vars})
24945 in Python. A convenience function is an instance of a subclass of the
24946 class @code{gdb.Function}.
24948 @defun Function.__init__ (name)
24949 The initializer for @code{Function} registers the new function with
24950 @value{GDBN}. The argument @var{name} is the name of the function,
24951 a string. The function will be visible to the user as a convenience
24952 variable of type @code{internal function}, whose name is the same as
24953 the given @var{name}.
24955 The documentation for the new function is taken from the documentation
24956 string for the new class.
24959 @defun Function.invoke (@var{*args})
24960 When a convenience function is evaluated, its arguments are converted
24961 to instances of @code{gdb.Value}, and then the function's
24962 @code{invoke} method is called. Note that @value{GDBN} does not
24963 predetermine the arity of convenience functions. Instead, all
24964 available arguments are passed to @code{invoke}, following the
24965 standard Python calling convention. In particular, a convenience
24966 function can have default values for parameters without ill effect.
24968 The return value of this method is used as its value in the enclosing
24969 expression. If an ordinary Python value is returned, it is converted
24970 to a @code{gdb.Value} following the usual rules.
24973 The following code snippet shows how a trivial convenience function can
24974 be implemented in Python:
24977 class Greet (gdb.Function):
24978 """Return string to greet someone.
24979 Takes a name as argument."""
24981 def __init__ (self):
24982 super (Greet, self).__init__ ("greet")
24984 def invoke (self, name):
24985 return "Hello, %s!" % name.string ()
24990 The last line instantiates the class, and is necessary to trigger the
24991 registration of the function with @value{GDBN}. Depending on how the
24992 Python code is read into @value{GDBN}, you may need to import the
24993 @code{gdb} module explicitly.
24995 Now you can use the function in an expression:
24998 (gdb) print $greet("Bob")
25002 @node Progspaces In Python
25003 @subsubsection Program Spaces In Python
25005 @cindex progspaces in python
25006 @tindex gdb.Progspace
25008 A program space, or @dfn{progspace}, represents a symbolic view
25009 of an address space.
25010 It consists of all of the objfiles of the program.
25011 @xref{Objfiles In Python}.
25012 @xref{Inferiors and Programs, program spaces}, for more details
25013 about program spaces.
25015 The following progspace-related functions are available in the
25018 @findex gdb.current_progspace
25019 @defun gdb.current_progspace ()
25020 This function returns the program space of the currently selected inferior.
25021 @xref{Inferiors and Programs}.
25024 @findex gdb.progspaces
25025 @defun gdb.progspaces ()
25026 Return a sequence of all the progspaces currently known to @value{GDBN}.
25029 Each progspace is represented by an instance of the @code{gdb.Progspace}
25032 @defvar Progspace.filename
25033 The file name of the progspace as a string.
25036 @defvar Progspace.pretty_printers
25037 The @code{pretty_printers} attribute is a list of functions. It is
25038 used to look up pretty-printers. A @code{Value} is passed to each
25039 function in order; if the function returns @code{None}, then the
25040 search continues. Otherwise, the return value should be an object
25041 which is used to format the value. @xref{Pretty Printing API}, for more
25045 @defvar Progspace.type_printers
25046 The @code{type_printers} attribute is a list of type printer objects.
25047 @xref{Type Printing API}, for more information.
25050 @node Objfiles In Python
25051 @subsubsection Objfiles In Python
25053 @cindex objfiles in python
25054 @tindex gdb.Objfile
25056 @value{GDBN} loads symbols for an inferior from various
25057 symbol-containing files (@pxref{Files}). These include the primary
25058 executable file, any shared libraries used by the inferior, and any
25059 separate debug info files (@pxref{Separate Debug Files}).
25060 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25062 The following objfile-related functions are available in the
25065 @findex gdb.current_objfile
25066 @defun gdb.current_objfile ()
25067 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25068 sets the ``current objfile'' to the corresponding objfile. This
25069 function returns the current objfile. If there is no current objfile,
25070 this function returns @code{None}.
25073 @findex gdb.objfiles
25074 @defun gdb.objfiles ()
25075 Return a sequence of all the objfiles current known to @value{GDBN}.
25076 @xref{Objfiles In Python}.
25079 Each objfile is represented by an instance of the @code{gdb.Objfile}
25082 @defvar Objfile.filename
25083 The file name of the objfile as a string.
25086 @defvar Objfile.pretty_printers
25087 The @code{pretty_printers} attribute is a list of functions. It is
25088 used to look up pretty-printers. A @code{Value} is passed to each
25089 function in order; if the function returns @code{None}, then the
25090 search continues. Otherwise, the return value should be an object
25091 which is used to format the value. @xref{Pretty Printing API}, for more
25095 @defvar Objfile.type_printers
25096 The @code{type_printers} attribute is a list of type printer objects.
25097 @xref{Type Printing API}, for more information.
25100 A @code{gdb.Objfile} object has the following methods:
25102 @defun Objfile.is_valid ()
25103 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25104 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25105 if the object file it refers to is not loaded in @value{GDBN} any
25106 longer. All other @code{gdb.Objfile} methods will throw an exception
25107 if it is invalid at the time the method is called.
25110 @node Frames In Python
25111 @subsubsection Accessing inferior stack frames from Python.
25113 @cindex frames in python
25114 When the debugged program stops, @value{GDBN} is able to analyze its call
25115 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25116 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25117 while its corresponding frame exists in the inferior's stack. If you try
25118 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25119 exception (@pxref{Exception Handling}).
25121 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25125 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25129 The following frame-related functions are available in the @code{gdb} module:
25131 @findex gdb.selected_frame
25132 @defun gdb.selected_frame ()
25133 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25136 @findex gdb.newest_frame
25137 @defun gdb.newest_frame ()
25138 Return the newest frame object for the selected thread.
25141 @defun gdb.frame_stop_reason_string (reason)
25142 Return a string explaining the reason why @value{GDBN} stopped unwinding
25143 frames, as expressed by the given @var{reason} code (an integer, see the
25144 @code{unwind_stop_reason} method further down in this section).
25147 A @code{gdb.Frame} object has the following methods:
25150 @defun Frame.is_valid ()
25151 Returns true if the @code{gdb.Frame} object is valid, false if not.
25152 A frame object can become invalid if the frame it refers to doesn't
25153 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25154 an exception if it is invalid at the time the method is called.
25157 @defun Frame.name ()
25158 Returns the function name of the frame, or @code{None} if it can't be
25162 @defun Frame.architecture ()
25163 Returns the @code{gdb.Architecture} object corresponding to the frame's
25164 architecture. @xref{Architectures In Python}.
25167 @defun Frame.type ()
25168 Returns the type of the frame. The value can be one of:
25170 @item gdb.NORMAL_FRAME
25171 An ordinary stack frame.
25173 @item gdb.DUMMY_FRAME
25174 A fake stack frame that was created by @value{GDBN} when performing an
25175 inferior function call.
25177 @item gdb.INLINE_FRAME
25178 A frame representing an inlined function. The function was inlined
25179 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25181 @item gdb.TAILCALL_FRAME
25182 A frame representing a tail call. @xref{Tail Call Frames}.
25184 @item gdb.SIGTRAMP_FRAME
25185 A signal trampoline frame. This is the frame created by the OS when
25186 it calls into a signal handler.
25188 @item gdb.ARCH_FRAME
25189 A fake stack frame representing a cross-architecture call.
25191 @item gdb.SENTINEL_FRAME
25192 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25197 @defun Frame.unwind_stop_reason ()
25198 Return an integer representing the reason why it's not possible to find
25199 more frames toward the outermost frame. Use
25200 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25201 function to a string. The value can be one of:
25204 @item gdb.FRAME_UNWIND_NO_REASON
25205 No particular reason (older frames should be available).
25207 @item gdb.FRAME_UNWIND_NULL_ID
25208 The previous frame's analyzer returns an invalid result.
25210 @item gdb.FRAME_UNWIND_OUTERMOST
25211 This frame is the outermost.
25213 @item gdb.FRAME_UNWIND_UNAVAILABLE
25214 Cannot unwind further, because that would require knowing the
25215 values of registers or memory that have not been collected.
25217 @item gdb.FRAME_UNWIND_INNER_ID
25218 This frame ID looks like it ought to belong to a NEXT frame,
25219 but we got it for a PREV frame. Normally, this is a sign of
25220 unwinder failure. It could also indicate stack corruption.
25222 @item gdb.FRAME_UNWIND_SAME_ID
25223 This frame has the same ID as the previous one. That means
25224 that unwinding further would almost certainly give us another
25225 frame with exactly the same ID, so break the chain. Normally,
25226 this is a sign of unwinder failure. It could also indicate
25229 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25230 The frame unwinder did not find any saved PC, but we needed
25231 one to unwind further.
25233 @item gdb.FRAME_UNWIND_FIRST_ERROR
25234 Any stop reason greater or equal to this value indicates some kind
25235 of error. This special value facilitates writing code that tests
25236 for errors in unwinding in a way that will work correctly even if
25237 the list of the other values is modified in future @value{GDBN}
25238 versions. Using it, you could write:
25240 reason = gdb.selected_frame().unwind_stop_reason ()
25241 reason_str = gdb.frame_stop_reason_string (reason)
25242 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25243 print "An error occured: %s" % reason_str
25250 Returns the frame's resume address.
25253 @defun Frame.block ()
25254 Return the frame's code block. @xref{Blocks In Python}.
25257 @defun Frame.function ()
25258 Return the symbol for the function corresponding to this frame.
25259 @xref{Symbols In Python}.
25262 @defun Frame.older ()
25263 Return the frame that called this frame.
25266 @defun Frame.newer ()
25267 Return the frame called by this frame.
25270 @defun Frame.find_sal ()
25271 Return the frame's symtab and line object.
25272 @xref{Symbol Tables In Python}.
25275 @defun Frame.read_var (variable @r{[}, block@r{]})
25276 Return the value of @var{variable} in this frame. If the optional
25277 argument @var{block} is provided, search for the variable from that
25278 block; otherwise start at the frame's current block (which is
25279 determined by the frame's current program counter). @var{variable}
25280 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25281 @code{gdb.Block} object.
25284 @defun Frame.select ()
25285 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25290 @node Blocks In Python
25291 @subsubsection Accessing frame blocks from Python.
25293 @cindex blocks in python
25296 Within each frame, @value{GDBN} maintains information on each block
25297 stored in that frame. These blocks are organized hierarchically, and
25298 are represented individually in Python as a @code{gdb.Block}.
25299 Please see @ref{Frames In Python}, for a more in-depth discussion on
25300 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25301 detailed technical information on @value{GDBN}'s book-keeping of the
25304 A @code{gdb.Block} is iterable. The iterator returns the symbols
25305 (@pxref{Symbols In Python}) local to the block. Python programs
25306 should not assume that a specific block object will always contain a
25307 given symbol, since changes in @value{GDBN} features and
25308 infrastructure may cause symbols move across blocks in a symbol
25311 The following block-related functions are available in the @code{gdb}
25314 @findex gdb.block_for_pc
25315 @defun gdb.block_for_pc (pc)
25316 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25317 block cannot be found for the @var{pc} value specified, the function
25318 will return @code{None}.
25321 A @code{gdb.Block} object has the following methods:
25324 @defun Block.is_valid ()
25325 Returns @code{True} if the @code{gdb.Block} object is valid,
25326 @code{False} if not. A block object can become invalid if the block it
25327 refers to doesn't exist anymore in the inferior. All other
25328 @code{gdb.Block} methods will throw an exception if it is invalid at
25329 the time the method is called. The block's validity is also checked
25330 during iteration over symbols of the block.
25334 A @code{gdb.Block} object has the following attributes:
25337 @defvar Block.start
25338 The start address of the block. This attribute is not writable.
25342 The end address of the block. This attribute is not writable.
25345 @defvar Block.function
25346 The name of the block represented as a @code{gdb.Symbol}. If the
25347 block is not named, then this attribute holds @code{None}. This
25348 attribute is not writable.
25351 @defvar Block.superblock
25352 The block containing this block. If this parent block does not exist,
25353 this attribute holds @code{None}. This attribute is not writable.
25356 @defvar Block.global_block
25357 The global block associated with this block. This attribute is not
25361 @defvar Block.static_block
25362 The static block associated with this block. This attribute is not
25366 @defvar Block.is_global
25367 @code{True} if the @code{gdb.Block} object is a global block,
25368 @code{False} if not. This attribute is not
25372 @defvar Block.is_static
25373 @code{True} if the @code{gdb.Block} object is a static block,
25374 @code{False} if not. This attribute is not writable.
25378 @node Symbols In Python
25379 @subsubsection Python representation of Symbols.
25381 @cindex symbols in python
25384 @value{GDBN} represents every variable, function and type as an
25385 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25386 Similarly, Python represents these symbols in @value{GDBN} with the
25387 @code{gdb.Symbol} object.
25389 The following symbol-related functions are available in the @code{gdb}
25392 @findex gdb.lookup_symbol
25393 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25394 This function searches for a symbol by name. The search scope can be
25395 restricted to the parameters defined in the optional domain and block
25398 @var{name} is the name of the symbol. It must be a string. The
25399 optional @var{block} argument restricts the search to symbols visible
25400 in that @var{block}. The @var{block} argument must be a
25401 @code{gdb.Block} object. If omitted, the block for the current frame
25402 is used. The optional @var{domain} argument restricts
25403 the search to the domain type. The @var{domain} argument must be a
25404 domain constant defined in the @code{gdb} module and described later
25407 The result is a tuple of two elements.
25408 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25410 If the symbol is found, the second element is @code{True} if the symbol
25411 is a field of a method's object (e.g., @code{this} in C@t{++}),
25412 otherwise it is @code{False}.
25413 If the symbol is not found, the second element is @code{False}.
25416 @findex gdb.lookup_global_symbol
25417 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25418 This function searches for a global symbol by name.
25419 The search scope can be restricted to by the domain argument.
25421 @var{name} is the name of the symbol. It must be a string.
25422 The optional @var{domain} argument restricts the search to the domain type.
25423 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25424 module and described later in this chapter.
25426 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25430 A @code{gdb.Symbol} object has the following attributes:
25433 @defvar Symbol.type
25434 The type of the symbol or @code{None} if no type is recorded.
25435 This attribute is represented as a @code{gdb.Type} object.
25436 @xref{Types In Python}. This attribute is not writable.
25439 @defvar Symbol.symtab
25440 The symbol table in which the symbol appears. This attribute is
25441 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25442 Python}. This attribute is not writable.
25445 @defvar Symbol.line
25446 The line number in the source code at which the symbol was defined.
25447 This is an integer.
25450 @defvar Symbol.name
25451 The name of the symbol as a string. This attribute is not writable.
25454 @defvar Symbol.linkage_name
25455 The name of the symbol, as used by the linker (i.e., may be mangled).
25456 This attribute is not writable.
25459 @defvar Symbol.print_name
25460 The name of the symbol in a form suitable for output. This is either
25461 @code{name} or @code{linkage_name}, depending on whether the user
25462 asked @value{GDBN} to display demangled or mangled names.
25465 @defvar Symbol.addr_class
25466 The address class of the symbol. This classifies how to find the value
25467 of a symbol. Each address class is a constant defined in the
25468 @code{gdb} module and described later in this chapter.
25471 @defvar Symbol.needs_frame
25472 This is @code{True} if evaluating this symbol's value requires a frame
25473 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25474 local variables will require a frame, but other symbols will not.
25477 @defvar Symbol.is_argument
25478 @code{True} if the symbol is an argument of a function.
25481 @defvar Symbol.is_constant
25482 @code{True} if the symbol is a constant.
25485 @defvar Symbol.is_function
25486 @code{True} if the symbol is a function or a method.
25489 @defvar Symbol.is_variable
25490 @code{True} if the symbol is a variable.
25494 A @code{gdb.Symbol} object has the following methods:
25497 @defun Symbol.is_valid ()
25498 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25499 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25500 the symbol it refers to does not exist in @value{GDBN} any longer.
25501 All other @code{gdb.Symbol} methods will throw an exception if it is
25502 invalid at the time the method is called.
25505 @defun Symbol.value (@r{[}frame@r{]})
25506 Compute the value of the symbol, as a @code{gdb.Value}. For
25507 functions, this computes the address of the function, cast to the
25508 appropriate type. If the symbol requires a frame in order to compute
25509 its value, then @var{frame} must be given. If @var{frame} is not
25510 given, or if @var{frame} is invalid, then this method will throw an
25515 The available domain categories in @code{gdb.Symbol} are represented
25516 as constants in the @code{gdb} module:
25519 @findex SYMBOL_UNDEF_DOMAIN
25520 @findex gdb.SYMBOL_UNDEF_DOMAIN
25521 @item gdb.SYMBOL_UNDEF_DOMAIN
25522 This is used when a domain has not been discovered or none of the
25523 following domains apply. This usually indicates an error either
25524 in the symbol information or in @value{GDBN}'s handling of symbols.
25525 @findex SYMBOL_VAR_DOMAIN
25526 @findex gdb.SYMBOL_VAR_DOMAIN
25527 @item gdb.SYMBOL_VAR_DOMAIN
25528 This domain contains variables, function names, typedef names and enum
25530 @findex SYMBOL_STRUCT_DOMAIN
25531 @findex gdb.SYMBOL_STRUCT_DOMAIN
25532 @item gdb.SYMBOL_STRUCT_DOMAIN
25533 This domain holds struct, union and enum type names.
25534 @findex SYMBOL_LABEL_DOMAIN
25535 @findex gdb.SYMBOL_LABEL_DOMAIN
25536 @item gdb.SYMBOL_LABEL_DOMAIN
25537 This domain contains names of labels (for gotos).
25538 @findex SYMBOL_VARIABLES_DOMAIN
25539 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25540 @item gdb.SYMBOL_VARIABLES_DOMAIN
25541 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25542 contains everything minus functions and types.
25543 @findex SYMBOL_FUNCTIONS_DOMAIN
25544 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25545 @item gdb.SYMBOL_FUNCTION_DOMAIN
25546 This domain contains all functions.
25547 @findex SYMBOL_TYPES_DOMAIN
25548 @findex gdb.SYMBOL_TYPES_DOMAIN
25549 @item gdb.SYMBOL_TYPES_DOMAIN
25550 This domain contains all types.
25553 The available address class categories in @code{gdb.Symbol} are represented
25554 as constants in the @code{gdb} module:
25557 @findex SYMBOL_LOC_UNDEF
25558 @findex gdb.SYMBOL_LOC_UNDEF
25559 @item gdb.SYMBOL_LOC_UNDEF
25560 If this is returned by address class, it indicates an error either in
25561 the symbol information or in @value{GDBN}'s handling of symbols.
25562 @findex SYMBOL_LOC_CONST
25563 @findex gdb.SYMBOL_LOC_CONST
25564 @item gdb.SYMBOL_LOC_CONST
25565 Value is constant int.
25566 @findex SYMBOL_LOC_STATIC
25567 @findex gdb.SYMBOL_LOC_STATIC
25568 @item gdb.SYMBOL_LOC_STATIC
25569 Value is at a fixed address.
25570 @findex SYMBOL_LOC_REGISTER
25571 @findex gdb.SYMBOL_LOC_REGISTER
25572 @item gdb.SYMBOL_LOC_REGISTER
25573 Value is in a register.
25574 @findex SYMBOL_LOC_ARG
25575 @findex gdb.SYMBOL_LOC_ARG
25576 @item gdb.SYMBOL_LOC_ARG
25577 Value is an argument. This value is at the offset stored within the
25578 symbol inside the frame's argument list.
25579 @findex SYMBOL_LOC_REF_ARG
25580 @findex gdb.SYMBOL_LOC_REF_ARG
25581 @item gdb.SYMBOL_LOC_REF_ARG
25582 Value address is stored in the frame's argument list. Just like
25583 @code{LOC_ARG} except that the value's address is stored at the
25584 offset, not the value itself.
25585 @findex SYMBOL_LOC_REGPARM_ADDR
25586 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25587 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25588 Value is a specified register. Just like @code{LOC_REGISTER} except
25589 the register holds the address of the argument instead of the argument
25591 @findex SYMBOL_LOC_LOCAL
25592 @findex gdb.SYMBOL_LOC_LOCAL
25593 @item gdb.SYMBOL_LOC_LOCAL
25594 Value is a local variable.
25595 @findex SYMBOL_LOC_TYPEDEF
25596 @findex gdb.SYMBOL_LOC_TYPEDEF
25597 @item gdb.SYMBOL_LOC_TYPEDEF
25598 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25600 @findex SYMBOL_LOC_BLOCK
25601 @findex gdb.SYMBOL_LOC_BLOCK
25602 @item gdb.SYMBOL_LOC_BLOCK
25604 @findex SYMBOL_LOC_CONST_BYTES
25605 @findex gdb.SYMBOL_LOC_CONST_BYTES
25606 @item gdb.SYMBOL_LOC_CONST_BYTES
25607 Value is a byte-sequence.
25608 @findex SYMBOL_LOC_UNRESOLVED
25609 @findex gdb.SYMBOL_LOC_UNRESOLVED
25610 @item gdb.SYMBOL_LOC_UNRESOLVED
25611 Value is at a fixed address, but the address of the variable has to be
25612 determined from the minimal symbol table whenever the variable is
25614 @findex SYMBOL_LOC_OPTIMIZED_OUT
25615 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25616 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25617 The value does not actually exist in the program.
25618 @findex SYMBOL_LOC_COMPUTED
25619 @findex gdb.SYMBOL_LOC_COMPUTED
25620 @item gdb.SYMBOL_LOC_COMPUTED
25621 The value's address is a computed location.
25624 @node Symbol Tables In Python
25625 @subsubsection Symbol table representation in Python.
25627 @cindex symbol tables in python
25629 @tindex gdb.Symtab_and_line
25631 Access to symbol table data maintained by @value{GDBN} on the inferior
25632 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25633 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25634 from the @code{find_sal} method in @code{gdb.Frame} object.
25635 @xref{Frames In Python}.
25637 For more information on @value{GDBN}'s symbol table management, see
25638 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25640 A @code{gdb.Symtab_and_line} object has the following attributes:
25643 @defvar Symtab_and_line.symtab
25644 The symbol table object (@code{gdb.Symtab}) for this frame.
25645 This attribute is not writable.
25648 @defvar Symtab_and_line.pc
25649 Indicates the start of the address range occupied by code for the
25650 current source line. This attribute is not writable.
25653 @defvar Symtab_and_line.last
25654 Indicates the end of the address range occupied by code for the current
25655 source line. This attribute is not writable.
25658 @defvar Symtab_and_line.line
25659 Indicates the current line number for this object. This
25660 attribute is not writable.
25664 A @code{gdb.Symtab_and_line} object has the following methods:
25667 @defun Symtab_and_line.is_valid ()
25668 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25669 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25670 invalid if the Symbol table and line object it refers to does not
25671 exist in @value{GDBN} any longer. All other
25672 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25673 invalid at the time the method is called.
25677 A @code{gdb.Symtab} object has the following attributes:
25680 @defvar Symtab.filename
25681 The symbol table's source filename. This attribute is not writable.
25684 @defvar Symtab.objfile
25685 The symbol table's backing object file. @xref{Objfiles In Python}.
25686 This attribute is not writable.
25690 A @code{gdb.Symtab} object has the following methods:
25693 @defun Symtab.is_valid ()
25694 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25695 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25696 the symbol table it refers to does not exist in @value{GDBN} any
25697 longer. All other @code{gdb.Symtab} methods will throw an exception
25698 if it is invalid at the time the method is called.
25701 @defun Symtab.fullname ()
25702 Return the symbol table's source absolute file name.
25705 @defun Symtab.global_block ()
25706 Return the global block of the underlying symbol table.
25707 @xref{Blocks In Python}.
25710 @defun Symtab.static_block ()
25711 Return the static block of the underlying symbol table.
25712 @xref{Blocks In Python}.
25716 @node Breakpoints In Python
25717 @subsubsection Manipulating breakpoints using Python
25719 @cindex breakpoints in python
25720 @tindex gdb.Breakpoint
25722 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25725 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25726 Create a new breakpoint. @var{spec} is a string naming the
25727 location of the breakpoint, or an expression that defines a
25728 watchpoint. The contents can be any location recognized by the
25729 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25730 command. The optional @var{type} denotes the breakpoint to create
25731 from the types defined later in this chapter. This argument can be
25732 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25733 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25734 allows the breakpoint to become invisible to the user. The breakpoint
25735 will neither be reported when created, nor will it be listed in the
25736 output from @code{info breakpoints} (but will be listed with the
25737 @code{maint info breakpoints} command). The optional @var{wp_class}
25738 argument defines the class of watchpoint to create, if @var{type} is
25739 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25740 assumed to be a @code{gdb.WP_WRITE} class.
25743 @defun Breakpoint.stop (self)
25744 The @code{gdb.Breakpoint} class can be sub-classed and, in
25745 particular, you may choose to implement the @code{stop} method.
25746 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25747 it will be called when the inferior reaches any location of a
25748 breakpoint which instantiates that sub-class. If the method returns
25749 @code{True}, the inferior will be stopped at the location of the
25750 breakpoint, otherwise the inferior will continue.
25752 If there are multiple breakpoints at the same location with a
25753 @code{stop} method, each one will be called regardless of the
25754 return status of the previous. This ensures that all @code{stop}
25755 methods have a chance to execute at that location. In this scenario
25756 if one of the methods returns @code{True} but the others return
25757 @code{False}, the inferior will still be stopped.
25759 You should not alter the execution state of the inferior (i.e.@:, step,
25760 next, etc.), alter the current frame context (i.e.@:, change the current
25761 active frame), or alter, add or delete any breakpoint. As a general
25762 rule, you should not alter any data within @value{GDBN} or the inferior
25765 Example @code{stop} implementation:
25768 class MyBreakpoint (gdb.Breakpoint):
25770 inf_val = gdb.parse_and_eval("foo")
25777 The available watchpoint types represented by constants are defined in the
25782 @findex gdb.WP_READ
25784 Read only watchpoint.
25787 @findex gdb.WP_WRITE
25789 Write only watchpoint.
25792 @findex gdb.WP_ACCESS
25793 @item gdb.WP_ACCESS
25794 Read/Write watchpoint.
25797 @defun Breakpoint.is_valid ()
25798 Return @code{True} if this @code{Breakpoint} object is valid,
25799 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25800 if the user deletes the breakpoint. In this case, the object still
25801 exists, but the underlying breakpoint does not. In the cases of
25802 watchpoint scope, the watchpoint remains valid even if execution of the
25803 inferior leaves the scope of that watchpoint.
25806 @defun Breakpoint.delete
25807 Permanently deletes the @value{GDBN} breakpoint. This also
25808 invalidates the Python @code{Breakpoint} object. Any further access
25809 to this object's attributes or methods will raise an error.
25812 @defvar Breakpoint.enabled
25813 This attribute is @code{True} if the breakpoint is enabled, and
25814 @code{False} otherwise. This attribute is writable.
25817 @defvar Breakpoint.silent
25818 This attribute is @code{True} if the breakpoint is silent, and
25819 @code{False} otherwise. This attribute is writable.
25821 Note that a breakpoint can also be silent if it has commands and the
25822 first command is @code{silent}. This is not reported by the
25823 @code{silent} attribute.
25826 @defvar Breakpoint.thread
25827 If the breakpoint is thread-specific, this attribute holds the thread
25828 id. If the breakpoint is not thread-specific, this attribute is
25829 @code{None}. This attribute is writable.
25832 @defvar Breakpoint.task
25833 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25834 id. If the breakpoint is not task-specific (or the underlying
25835 language is not Ada), this attribute is @code{None}. This attribute
25839 @defvar Breakpoint.ignore_count
25840 This attribute holds the ignore count for the breakpoint, an integer.
25841 This attribute is writable.
25844 @defvar Breakpoint.number
25845 This attribute holds the breakpoint's number --- the identifier used by
25846 the user to manipulate the breakpoint. This attribute is not writable.
25849 @defvar Breakpoint.type
25850 This attribute holds the breakpoint's type --- the identifier used to
25851 determine the actual breakpoint type or use-case. This attribute is not
25855 @defvar Breakpoint.visible
25856 This attribute tells whether the breakpoint is visible to the user
25857 when set, or when the @samp{info breakpoints} command is run. This
25858 attribute is not writable.
25861 The available types are represented by constants defined in the @code{gdb}
25865 @findex BP_BREAKPOINT
25866 @findex gdb.BP_BREAKPOINT
25867 @item gdb.BP_BREAKPOINT
25868 Normal code breakpoint.
25870 @findex BP_WATCHPOINT
25871 @findex gdb.BP_WATCHPOINT
25872 @item gdb.BP_WATCHPOINT
25873 Watchpoint breakpoint.
25875 @findex BP_HARDWARE_WATCHPOINT
25876 @findex gdb.BP_HARDWARE_WATCHPOINT
25877 @item gdb.BP_HARDWARE_WATCHPOINT
25878 Hardware assisted watchpoint.
25880 @findex BP_READ_WATCHPOINT
25881 @findex gdb.BP_READ_WATCHPOINT
25882 @item gdb.BP_READ_WATCHPOINT
25883 Hardware assisted read watchpoint.
25885 @findex BP_ACCESS_WATCHPOINT
25886 @findex gdb.BP_ACCESS_WATCHPOINT
25887 @item gdb.BP_ACCESS_WATCHPOINT
25888 Hardware assisted access watchpoint.
25891 @defvar Breakpoint.hit_count
25892 This attribute holds the hit count for the breakpoint, an integer.
25893 This attribute is writable, but currently it can only be set to zero.
25896 @defvar Breakpoint.location
25897 This attribute holds the location of the breakpoint, as specified by
25898 the user. It is a string. If the breakpoint does not have a location
25899 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25900 attribute is not writable.
25903 @defvar Breakpoint.expression
25904 This attribute holds a breakpoint expression, as specified by
25905 the user. It is a string. If the breakpoint does not have an
25906 expression (the breakpoint is not a watchpoint) the attribute's value
25907 is @code{None}. This attribute is not writable.
25910 @defvar Breakpoint.condition
25911 This attribute holds the condition of the breakpoint, as specified by
25912 the user. It is a string. If there is no condition, this attribute's
25913 value is @code{None}. This attribute is writable.
25916 @defvar Breakpoint.commands
25917 This attribute holds the commands attached to the breakpoint. If
25918 there are commands, this attribute's value is a string holding all the
25919 commands, separated by newlines. If there are no commands, this
25920 attribute is @code{None}. This attribute is not writable.
25923 @node Finish Breakpoints in Python
25924 @subsubsection Finish Breakpoints
25926 @cindex python finish breakpoints
25927 @tindex gdb.FinishBreakpoint
25929 A finish breakpoint is a temporary breakpoint set at the return address of
25930 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
25931 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
25932 and deleted when the execution will run out of the breakpoint scope (i.e.@:
25933 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
25934 Finish breakpoints are thread specific and must be create with the right
25937 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
25938 Create a finish breakpoint at the return address of the @code{gdb.Frame}
25939 object @var{frame}. If @var{frame} is not provided, this defaults to the
25940 newest frame. The optional @var{internal} argument allows the breakpoint to
25941 become invisible to the user. @xref{Breakpoints In Python}, for further
25942 details about this argument.
25945 @defun FinishBreakpoint.out_of_scope (self)
25946 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
25947 @code{return} command, @dots{}), a function may not properly terminate, and
25948 thus never hit the finish breakpoint. When @value{GDBN} notices such a
25949 situation, the @code{out_of_scope} callback will be triggered.
25951 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
25955 class MyFinishBreakpoint (gdb.FinishBreakpoint)
25957 print "normal finish"
25960 def out_of_scope ():
25961 print "abnormal finish"
25965 @defvar FinishBreakpoint.return_value
25966 When @value{GDBN} is stopped at a finish breakpoint and the frame
25967 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
25968 attribute will contain a @code{gdb.Value} object corresponding to the return
25969 value of the function. The value will be @code{None} if the function return
25970 type is @code{void} or if the return value was not computable. This attribute
25974 @node Lazy Strings In Python
25975 @subsubsection Python representation of lazy strings.
25977 @cindex lazy strings in python
25978 @tindex gdb.LazyString
25980 A @dfn{lazy string} is a string whose contents is not retrieved or
25981 encoded until it is needed.
25983 A @code{gdb.LazyString} is represented in @value{GDBN} as an
25984 @code{address} that points to a region of memory, an @code{encoding}
25985 that will be used to encode that region of memory, and a @code{length}
25986 to delimit the region of memory that represents the string. The
25987 difference between a @code{gdb.LazyString} and a string wrapped within
25988 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
25989 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
25990 retrieved and encoded during printing, while a @code{gdb.Value}
25991 wrapping a string is immediately retrieved and encoded on creation.
25993 A @code{gdb.LazyString} object has the following functions:
25995 @defun LazyString.value ()
25996 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
25997 will point to the string in memory, but will lose all the delayed
25998 retrieval, encoding and handling that @value{GDBN} applies to a
25999 @code{gdb.LazyString}.
26002 @defvar LazyString.address
26003 This attribute holds the address of the string. This attribute is not
26007 @defvar LazyString.length
26008 This attribute holds the length of the string in characters. If the
26009 length is -1, then the string will be fetched and encoded up to the
26010 first null of appropriate width. This attribute is not writable.
26013 @defvar LazyString.encoding
26014 This attribute holds the encoding that will be applied to the string
26015 when the string is printed by @value{GDBN}. If the encoding is not
26016 set, or contains an empty string, then @value{GDBN} will select the
26017 most appropriate encoding when the string is printed. This attribute
26021 @defvar LazyString.type
26022 This attribute holds the type that is represented by the lazy string's
26023 type. For a lazy string this will always be a pointer type. To
26024 resolve this to the lazy string's character type, use the type's
26025 @code{target} method. @xref{Types In Python}. This attribute is not
26029 @node Architectures In Python
26030 @subsubsection Python representation of architectures
26031 @cindex Python architectures
26033 @value{GDBN} uses architecture specific parameters and artifacts in a
26034 number of its various computations. An architecture is represented
26035 by an instance of the @code{gdb.Architecture} class.
26037 A @code{gdb.Architecture} class has the following methods:
26039 @defun Architecture.name ()
26040 Return the name (string value) of the architecture.
26043 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
26044 Return a list of disassembled instructions starting from the memory
26045 address @var{start_pc}. The optional arguments @var{end_pc} and
26046 @var{count} determine the number of instructions in the returned list.
26047 If both the optional arguments @var{end_pc} and @var{count} are
26048 specified, then a list of at most @var{count} disassembled instructions
26049 whose start address falls in the closed memory address interval from
26050 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
26051 specified, but @var{count} is specified, then @var{count} number of
26052 instructions starting from the address @var{start_pc} are returned. If
26053 @var{count} is not specified but @var{end_pc} is specified, then all
26054 instructions whose start address falls in the closed memory address
26055 interval from @var{start_pc} to @var{end_pc} are returned. If neither
26056 @var{end_pc} nor @var{count} are specified, then a single instruction at
26057 @var{start_pc} is returned. For all of these cases, each element of the
26058 returned list is a Python @code{dict} with the following string keys:
26063 The value corresponding to this key is a Python long integer capturing
26064 the memory address of the instruction.
26067 The value corresponding to this key is a string value which represents
26068 the instruction with assembly language mnemonics. The assembly
26069 language flavor used is the same as that specified by the current CLI
26070 variable @code{disassembly-flavor}. @xref{Machine Code}.
26073 The value corresponding to this key is the length (integer value) of the
26074 instruction in bytes.
26079 @node Python Auto-loading
26080 @subsection Python Auto-loading
26081 @cindex Python auto-loading
26083 When a new object file is read (for example, due to the @code{file}
26084 command, or because the inferior has loaded a shared library),
26085 @value{GDBN} will look for Python support scripts in several ways:
26086 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
26087 and @code{.debug_gdb_scripts} section
26088 (@pxref{dotdebug_gdb_scripts section}).
26090 The auto-loading feature is useful for supplying application-specific
26091 debugging commands and scripts.
26093 Auto-loading can be enabled or disabled,
26094 and the list of auto-loaded scripts can be printed.
26097 @anchor{set auto-load python-scripts}
26098 @kindex set auto-load python-scripts
26099 @item set auto-load python-scripts [on|off]
26100 Enable or disable the auto-loading of Python scripts.
26102 @anchor{show auto-load python-scripts}
26103 @kindex show auto-load python-scripts
26104 @item show auto-load python-scripts
26105 Show whether auto-loading of Python scripts is enabled or disabled.
26107 @anchor{info auto-load python-scripts}
26108 @kindex info auto-load python-scripts
26109 @cindex print list of auto-loaded Python scripts
26110 @item info auto-load python-scripts [@var{regexp}]
26111 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26113 Also printed is the list of Python scripts that were mentioned in
26114 the @code{.debug_gdb_scripts} section and were not found
26115 (@pxref{dotdebug_gdb_scripts section}).
26116 This is useful because their names are not printed when @value{GDBN}
26117 tries to load them and fails. There may be many of them, and printing
26118 an error message for each one is problematic.
26120 If @var{regexp} is supplied only Python scripts with matching names are printed.
26125 (gdb) info auto-load python-scripts
26127 Yes py-section-script.py
26128 full name: /tmp/py-section-script.py
26129 No my-foo-pretty-printers.py
26133 When reading an auto-loaded file, @value{GDBN} sets the
26134 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26135 function (@pxref{Objfiles In Python}). This can be useful for
26136 registering objfile-specific pretty-printers.
26139 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26140 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26141 * Which flavor to choose?::
26144 @node objfile-gdb.py file
26145 @subsubsection The @file{@var{objfile}-gdb.py} file
26146 @cindex @file{@var{objfile}-gdb.py}
26148 When a new object file is read, @value{GDBN} looks for
26149 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26150 where @var{objfile} is the object file's real name, formed by ensuring
26151 that the file name is absolute, following all symlinks, and resolving
26152 @code{.} and @code{..} components. If this file exists and is
26153 readable, @value{GDBN} will evaluate it as a Python script.
26155 If this file does not exist, then @value{GDBN} will look for
26156 @var{script-name} file in all of the directories as specified below.
26158 Note that loading of this script file also requires accordingly configured
26159 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26161 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26162 scripts normally according to its @file{.exe} filename. But if no scripts are
26163 found @value{GDBN} also tries script filenames matching the object file without
26164 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26165 is attempted on any platform. This makes the script filenames compatible
26166 between Unix and MS-Windows hosts.
26169 @anchor{set auto-load scripts-directory}
26170 @kindex set auto-load scripts-directory
26171 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26172 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26173 may be delimited by the host platform path separator in use
26174 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26176 Each entry here needs to be covered also by the security setting
26177 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26179 @anchor{with-auto-load-dir}
26180 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26181 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26182 configuration option @option{--with-auto-load-dir}.
26184 Any reference to @file{$debugdir} will get replaced by
26185 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26186 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26187 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26188 @file{$datadir} must be placed as a directory component --- either alone or
26189 delimited by @file{/} or @file{\} directory separators, depending on the host
26192 The list of directories uses path separator (@samp{:} on GNU and Unix
26193 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26194 to the @env{PATH} environment variable.
26196 @anchor{show auto-load scripts-directory}
26197 @kindex show auto-load scripts-directory
26198 @item show auto-load scripts-directory
26199 Show @value{GDBN} auto-loaded scripts location.
26202 @value{GDBN} does not track which files it has already auto-loaded this way.
26203 @value{GDBN} will load the associated script every time the corresponding
26204 @var{objfile} is opened.
26205 So your @file{-gdb.py} file should be careful to avoid errors if it
26206 is evaluated more than once.
26208 @node dotdebug_gdb_scripts section
26209 @subsubsection The @code{.debug_gdb_scripts} section
26210 @cindex @code{.debug_gdb_scripts} section
26212 For systems using file formats like ELF and COFF,
26213 when @value{GDBN} loads a new object file
26214 it will look for a special section named @samp{.debug_gdb_scripts}.
26215 If this section exists, its contents is a list of names of scripts to load.
26217 @value{GDBN} will look for each specified script file first in the
26218 current directory and then along the source search path
26219 (@pxref{Source Path, ,Specifying Source Directories}),
26220 except that @file{$cdir} is not searched, since the compilation
26221 directory is not relevant to scripts.
26223 Entries can be placed in section @code{.debug_gdb_scripts} with,
26224 for example, this GCC macro:
26227 /* Note: The "MS" section flags are to remove duplicates. */
26228 #define DEFINE_GDB_SCRIPT(script_name) \
26230 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26232 .asciz \"" script_name "\"\n\
26238 Then one can reference the macro in a header or source file like this:
26241 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26244 The script name may include directories if desired.
26246 Note that loading of this script file also requires accordingly configured
26247 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26249 If the macro is put in a header, any application or library
26250 using this header will get a reference to the specified script.
26252 @node Which flavor to choose?
26253 @subsubsection Which flavor to choose?
26255 Given the multiple ways of auto-loading Python scripts, it might not always
26256 be clear which one to choose. This section provides some guidance.
26258 Benefits of the @file{-gdb.py} way:
26262 Can be used with file formats that don't support multiple sections.
26265 Ease of finding scripts for public libraries.
26267 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26268 in the source search path.
26269 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26270 isn't a source directory in which to find the script.
26273 Doesn't require source code additions.
26276 Benefits of the @code{.debug_gdb_scripts} way:
26280 Works with static linking.
26282 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26283 trigger their loading. When an application is statically linked the only
26284 objfile available is the executable, and it is cumbersome to attach all the
26285 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26288 Works with classes that are entirely inlined.
26290 Some classes can be entirely inlined, and thus there may not be an associated
26291 shared library to attach a @file{-gdb.py} script to.
26294 Scripts needn't be copied out of the source tree.
26296 In some circumstances, apps can be built out of large collections of internal
26297 libraries, and the build infrastructure necessary to install the
26298 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26299 cumbersome. It may be easier to specify the scripts in the
26300 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26301 top of the source tree to the source search path.
26304 @node Python modules
26305 @subsection Python modules
26306 @cindex python modules
26308 @value{GDBN} comes with several modules to assist writing Python code.
26311 * gdb.printing:: Building and registering pretty-printers.
26312 * gdb.types:: Utilities for working with types.
26313 * gdb.prompt:: Utilities for prompt value substitution.
26317 @subsubsection gdb.printing
26318 @cindex gdb.printing
26320 This module provides a collection of utilities for working with
26324 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26325 This class specifies the API that makes @samp{info pretty-printer},
26326 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26327 Pretty-printers should generally inherit from this class.
26329 @item SubPrettyPrinter (@var{name})
26330 For printers that handle multiple types, this class specifies the
26331 corresponding API for the subprinters.
26333 @item RegexpCollectionPrettyPrinter (@var{name})
26334 Utility class for handling multiple printers, all recognized via
26335 regular expressions.
26336 @xref{Writing a Pretty-Printer}, for an example.
26338 @item FlagEnumerationPrinter (@var{name})
26339 A pretty-printer which handles printing of @code{enum} values. Unlike
26340 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26341 work properly when there is some overlap between the enumeration
26342 constants. @var{name} is the name of the printer and also the name of
26343 the @code{enum} type to look up.
26345 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26346 Register @var{printer} with the pretty-printer list of @var{obj}.
26347 If @var{replace} is @code{True} then any existing copy of the printer
26348 is replaced. Otherwise a @code{RuntimeError} exception is raised
26349 if a printer with the same name already exists.
26353 @subsubsection gdb.types
26356 This module provides a collection of utilities for working with
26357 @code{gdb.Type} objects.
26360 @item get_basic_type (@var{type})
26361 Return @var{type} with const and volatile qualifiers stripped,
26362 and with typedefs and C@t{++} references converted to the underlying type.
26367 typedef const int const_int;
26369 const_int& foo_ref (foo);
26370 int main () @{ return 0; @}
26377 (gdb) python import gdb.types
26378 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26379 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26383 @item has_field (@var{type}, @var{field})
26384 Return @code{True} if @var{type}, assumed to be a type with fields
26385 (e.g., a structure or union), has field @var{field}.
26387 @item make_enum_dict (@var{enum_type})
26388 Return a Python @code{dictionary} type produced from @var{enum_type}.
26390 @item deep_items (@var{type})
26391 Returns a Python iterator similar to the standard
26392 @code{gdb.Type.iteritems} method, except that the iterator returned
26393 by @code{deep_items} will recursively traverse anonymous struct or
26394 union fields. For example:
26408 Then in @value{GDBN}:
26410 (@value{GDBP}) python import gdb.types
26411 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26412 (@value{GDBP}) python print struct_a.keys ()
26414 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26415 @{['a', 'b0', 'b1']@}
26418 @item get_type_recognizers ()
26419 Return a list of the enabled type recognizers for the current context.
26420 This is called by @value{GDBN} during the type-printing process
26421 (@pxref{Type Printing API}).
26423 @item apply_type_recognizers (recognizers, type_obj)
26424 Apply the type recognizers, @var{recognizers}, to the type object
26425 @var{type_obj}. If any recognizer returns a string, return that
26426 string. Otherwise, return @code{None}. This is called by
26427 @value{GDBN} during the type-printing process (@pxref{Type Printing
26430 @item register_type_printer (locus, printer)
26431 This is a convenience function to register a type printer.
26432 @var{printer} is the type printer to register. It must implement the
26433 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26434 which case the printer is registered with that objfile; a
26435 @code{gdb.Progspace}, in which case the printer is registered with
26436 that progspace; or @code{None}, in which case the printer is
26437 registered globally.
26440 This is a base class that implements the type printer protocol. Type
26441 printers are encouraged, but not required, to derive from this class.
26442 It defines a constructor:
26444 @defmethod TypePrinter __init__ (self, name)
26445 Initialize the type printer with the given name. The new printer
26446 starts in the enabled state.
26452 @subsubsection gdb.prompt
26455 This module provides a method for prompt value-substitution.
26458 @item substitute_prompt (@var{string})
26459 Return @var{string} with escape sequences substituted by values. Some
26460 escape sequences take arguments. You can specify arguments inside
26461 ``@{@}'' immediately following the escape sequence.
26463 The escape sequences you can pass to this function are:
26467 Substitute a backslash.
26469 Substitute an ESC character.
26471 Substitute the selected frame; an argument names a frame parameter.
26473 Substitute a newline.
26475 Substitute a parameter's value; the argument names the parameter.
26477 Substitute a carriage return.
26479 Substitute the selected thread; an argument names a thread parameter.
26481 Substitute the version of GDB.
26483 Substitute the current working directory.
26485 Begin a sequence of non-printing characters. These sequences are
26486 typically used with the ESC character, and are not counted in the string
26487 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26488 blue-colored ``(gdb)'' prompt where the length is five.
26490 End a sequence of non-printing characters.
26496 substitute_prompt (``frame: \f,
26497 print arguments: \p@{print frame-arguments@}'')
26500 @exdent will return the string:
26503 "frame: main, print arguments: scalars"
26508 @section Creating new spellings of existing commands
26509 @cindex aliases for commands
26511 It is often useful to define alternate spellings of existing commands.
26512 For example, if a new @value{GDBN} command defined in Python has
26513 a long name to type, it is handy to have an abbreviated version of it
26514 that involves less typing.
26516 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26517 of the @samp{step} command even though it is otherwise an ambiguous
26518 abbreviation of other commands like @samp{set} and @samp{show}.
26520 Aliases are also used to provide shortened or more common versions
26521 of multi-word commands. For example, @value{GDBN} provides the
26522 @samp{tty} alias of the @samp{set inferior-tty} command.
26524 You can define a new alias with the @samp{alias} command.
26529 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26533 @var{ALIAS} specifies the name of the new alias.
26534 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26537 @var{COMMAND} specifies the name of an existing command
26538 that is being aliased.
26540 The @samp{-a} option specifies that the new alias is an abbreviation
26541 of the command. Abbreviations are not shown in command
26542 lists displayed by the @samp{help} command.
26544 The @samp{--} option specifies the end of options,
26545 and is useful when @var{ALIAS} begins with a dash.
26547 Here is a simple example showing how to make an abbreviation
26548 of a command so that there is less to type.
26549 Suppose you were tired of typing @samp{disas}, the current
26550 shortest unambiguous abbreviation of the @samp{disassemble} command
26551 and you wanted an even shorter version named @samp{di}.
26552 The following will accomplish this.
26555 (gdb) alias -a di = disas
26558 Note that aliases are different from user-defined commands.
26559 With a user-defined command, you also need to write documentation
26560 for it with the @samp{document} command.
26561 An alias automatically picks up the documentation of the existing command.
26563 Here is an example where we make @samp{elms} an abbreviation of
26564 @samp{elements} in the @samp{set print elements} command.
26565 This is to show that you can make an abbreviation of any part
26569 (gdb) alias -a set print elms = set print elements
26570 (gdb) alias -a show print elms = show print elements
26571 (gdb) set p elms 20
26573 Limit on string chars or array elements to print is 200.
26576 Note that if you are defining an alias of a @samp{set} command,
26577 and you want to have an alias for the corresponding @samp{show}
26578 command, then you need to define the latter separately.
26580 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26581 @var{ALIAS}, just as they are normally.
26584 (gdb) alias -a set pr elms = set p ele
26587 Finally, here is an example showing the creation of a one word
26588 alias for a more complex command.
26589 This creates alias @samp{spe} of the command @samp{set print elements}.
26592 (gdb) alias spe = set print elements
26597 @chapter Command Interpreters
26598 @cindex command interpreters
26600 @value{GDBN} supports multiple command interpreters, and some command
26601 infrastructure to allow users or user interface writers to switch
26602 between interpreters or run commands in other interpreters.
26604 @value{GDBN} currently supports two command interpreters, the console
26605 interpreter (sometimes called the command-line interpreter or @sc{cli})
26606 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26607 describes both of these interfaces in great detail.
26609 By default, @value{GDBN} will start with the console interpreter.
26610 However, the user may choose to start @value{GDBN} with another
26611 interpreter by specifying the @option{-i} or @option{--interpreter}
26612 startup options. Defined interpreters include:
26616 @cindex console interpreter
26617 The traditional console or command-line interpreter. This is the most often
26618 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26619 @value{GDBN} will use this interpreter.
26622 @cindex mi interpreter
26623 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26624 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26625 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26629 @cindex mi2 interpreter
26630 The current @sc{gdb/mi} interface.
26633 @cindex mi1 interpreter
26634 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26638 @cindex invoke another interpreter
26639 The interpreter being used by @value{GDBN} may not be dynamically
26640 switched at runtime. Although possible, this could lead to a very
26641 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26642 enters the command "interpreter-set console" in a console view,
26643 @value{GDBN} would switch to using the console interpreter, rendering
26644 the IDE inoperable!
26646 @kindex interpreter-exec
26647 Although you may only choose a single interpreter at startup, you may execute
26648 commands in any interpreter from the current interpreter using the appropriate
26649 command. If you are running the console interpreter, simply use the
26650 @code{interpreter-exec} command:
26653 interpreter-exec mi "-data-list-register-names"
26656 @sc{gdb/mi} has a similar command, although it is only available in versions of
26657 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26660 @chapter @value{GDBN} Text User Interface
26662 @cindex Text User Interface
26665 * TUI Overview:: TUI overview
26666 * TUI Keys:: TUI key bindings
26667 * TUI Single Key Mode:: TUI single key mode
26668 * TUI Commands:: TUI-specific commands
26669 * TUI Configuration:: TUI configuration variables
26672 The @value{GDBN} Text User Interface (TUI) is a terminal
26673 interface which uses the @code{curses} library to show the source
26674 file, the assembly output, the program registers and @value{GDBN}
26675 commands in separate text windows. The TUI mode is supported only
26676 on platforms where a suitable version of the @code{curses} library
26679 The TUI mode is enabled by default when you invoke @value{GDBN} as
26680 @samp{@value{GDBP} -tui}.
26681 You can also switch in and out of TUI mode while @value{GDBN} runs by
26682 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26683 @xref{TUI Keys, ,TUI Key Bindings}.
26686 @section TUI Overview
26688 In TUI mode, @value{GDBN} can display several text windows:
26692 This window is the @value{GDBN} command window with the @value{GDBN}
26693 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26694 managed using readline.
26697 The source window shows the source file of the program. The current
26698 line and active breakpoints are displayed in this window.
26701 The assembly window shows the disassembly output of the program.
26704 This window shows the processor registers. Registers are highlighted
26705 when their values change.
26708 The source and assembly windows show the current program position
26709 by highlighting the current line and marking it with a @samp{>} marker.
26710 Breakpoints are indicated with two markers. The first marker
26711 indicates the breakpoint type:
26715 Breakpoint which was hit at least once.
26718 Breakpoint which was never hit.
26721 Hardware breakpoint which was hit at least once.
26724 Hardware breakpoint which was never hit.
26727 The second marker indicates whether the breakpoint is enabled or not:
26731 Breakpoint is enabled.
26734 Breakpoint is disabled.
26737 The source, assembly and register windows are updated when the current
26738 thread changes, when the frame changes, or when the program counter
26741 These windows are not all visible at the same time. The command
26742 window is always visible. The others can be arranged in several
26753 source and assembly,
26756 source and registers, or
26759 assembly and registers.
26762 A status line above the command window shows the following information:
26766 Indicates the current @value{GDBN} target.
26767 (@pxref{Targets, ,Specifying a Debugging Target}).
26770 Gives the current process or thread number.
26771 When no process is being debugged, this field is set to @code{No process}.
26774 Gives the current function name for the selected frame.
26775 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26776 When there is no symbol corresponding to the current program counter,
26777 the string @code{??} is displayed.
26780 Indicates the current line number for the selected frame.
26781 When the current line number is not known, the string @code{??} is displayed.
26784 Indicates the current program counter address.
26788 @section TUI Key Bindings
26789 @cindex TUI key bindings
26791 The TUI installs several key bindings in the readline keymaps
26792 @ifset SYSTEM_READLINE
26793 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26795 @ifclear SYSTEM_READLINE
26796 (@pxref{Command Line Editing}).
26798 The following key bindings are installed for both TUI mode and the
26799 @value{GDBN} standard mode.
26808 Enter or leave the TUI mode. When leaving the TUI mode,
26809 the curses window management stops and @value{GDBN} operates using
26810 its standard mode, writing on the terminal directly. When reentering
26811 the TUI mode, control is given back to the curses windows.
26812 The screen is then refreshed.
26816 Use a TUI layout with only one window. The layout will
26817 either be @samp{source} or @samp{assembly}. When the TUI mode
26818 is not active, it will switch to the TUI mode.
26820 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26824 Use a TUI layout with at least two windows. When the current
26825 layout already has two windows, the next layout with two windows is used.
26826 When a new layout is chosen, one window will always be common to the
26827 previous layout and the new one.
26829 Think of it as the Emacs @kbd{C-x 2} binding.
26833 Change the active window. The TUI associates several key bindings
26834 (like scrolling and arrow keys) with the active window. This command
26835 gives the focus to the next TUI window.
26837 Think of it as the Emacs @kbd{C-x o} binding.
26841 Switch in and out of the TUI SingleKey mode that binds single
26842 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26845 The following key bindings only work in the TUI mode:
26850 Scroll the active window one page up.
26854 Scroll the active window one page down.
26858 Scroll the active window one line up.
26862 Scroll the active window one line down.
26866 Scroll the active window one column left.
26870 Scroll the active window one column right.
26874 Refresh the screen.
26877 Because the arrow keys scroll the active window in the TUI mode, they
26878 are not available for their normal use by readline unless the command
26879 window has the focus. When another window is active, you must use
26880 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26881 and @kbd{C-f} to control the command window.
26883 @node TUI Single Key Mode
26884 @section TUI Single Key Mode
26885 @cindex TUI single key mode
26887 The TUI also provides a @dfn{SingleKey} mode, which binds several
26888 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26889 switch into this mode, where the following key bindings are used:
26892 @kindex c @r{(SingleKey TUI key)}
26896 @kindex d @r{(SingleKey TUI key)}
26900 @kindex f @r{(SingleKey TUI key)}
26904 @kindex n @r{(SingleKey TUI key)}
26908 @kindex q @r{(SingleKey TUI key)}
26910 exit the SingleKey mode.
26912 @kindex r @r{(SingleKey TUI key)}
26916 @kindex s @r{(SingleKey TUI key)}
26920 @kindex u @r{(SingleKey TUI key)}
26924 @kindex v @r{(SingleKey TUI key)}
26928 @kindex w @r{(SingleKey TUI key)}
26933 Other keys temporarily switch to the @value{GDBN} command prompt.
26934 The key that was pressed is inserted in the editing buffer so that
26935 it is possible to type most @value{GDBN} commands without interaction
26936 with the TUI SingleKey mode. Once the command is entered the TUI
26937 SingleKey mode is restored. The only way to permanently leave
26938 this mode is by typing @kbd{q} or @kbd{C-x s}.
26942 @section TUI-specific Commands
26943 @cindex TUI commands
26945 The TUI has specific commands to control the text windows.
26946 These commands are always available, even when @value{GDBN} is not in
26947 the TUI mode. When @value{GDBN} is in the standard mode, most
26948 of these commands will automatically switch to the TUI mode.
26950 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26951 terminal, or @value{GDBN} has been started with the machine interface
26952 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26953 these commands will fail with an error, because it would not be
26954 possible or desirable to enable curses window management.
26959 List and give the size of all displayed windows.
26963 Display the next layout.
26966 Display the previous layout.
26969 Display the source window only.
26972 Display the assembly window only.
26975 Display the source and assembly window.
26978 Display the register window together with the source or assembly window.
26982 Make the next window active for scrolling.
26985 Make the previous window active for scrolling.
26988 Make the source window active for scrolling.
26991 Make the assembly window active for scrolling.
26994 Make the register window active for scrolling.
26997 Make the command window active for scrolling.
27001 Refresh the screen. This is similar to typing @kbd{C-L}.
27003 @item tui reg float
27005 Show the floating point registers in the register window.
27007 @item tui reg general
27008 Show the general registers in the register window.
27011 Show the next register group. The list of register groups as well as
27012 their order is target specific. The predefined register groups are the
27013 following: @code{general}, @code{float}, @code{system}, @code{vector},
27014 @code{all}, @code{save}, @code{restore}.
27016 @item tui reg system
27017 Show the system registers in the register window.
27021 Update the source window and the current execution point.
27023 @item winheight @var{name} +@var{count}
27024 @itemx winheight @var{name} -@var{count}
27026 Change the height of the window @var{name} by @var{count}
27027 lines. Positive counts increase the height, while negative counts
27030 @item tabset @var{nchars}
27032 Set the width of tab stops to be @var{nchars} characters.
27035 @node TUI Configuration
27036 @section TUI Configuration Variables
27037 @cindex TUI configuration variables
27039 Several configuration variables control the appearance of TUI windows.
27042 @item set tui border-kind @var{kind}
27043 @kindex set tui border-kind
27044 Select the border appearance for the source, assembly and register windows.
27045 The possible values are the following:
27048 Use a space character to draw the border.
27051 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27054 Use the Alternate Character Set to draw the border. The border is
27055 drawn using character line graphics if the terminal supports them.
27058 @item set tui border-mode @var{mode}
27059 @kindex set tui border-mode
27060 @itemx set tui active-border-mode @var{mode}
27061 @kindex set tui active-border-mode
27062 Select the display attributes for the borders of the inactive windows
27063 or the active window. The @var{mode} can be one of the following:
27066 Use normal attributes to display the border.
27072 Use reverse video mode.
27075 Use half bright mode.
27077 @item half-standout
27078 Use half bright and standout mode.
27081 Use extra bright or bold mode.
27083 @item bold-standout
27084 Use extra bright or bold and standout mode.
27089 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27092 @cindex @sc{gnu} Emacs
27093 A special interface allows you to use @sc{gnu} Emacs to view (and
27094 edit) the source files for the program you are debugging with
27097 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27098 executable file you want to debug as an argument. This command starts
27099 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27100 created Emacs buffer.
27101 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27103 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27108 All ``terminal'' input and output goes through an Emacs buffer, called
27111 This applies both to @value{GDBN} commands and their output, and to the input
27112 and output done by the program you are debugging.
27114 This is useful because it means that you can copy the text of previous
27115 commands and input them again; you can even use parts of the output
27118 All the facilities of Emacs' Shell mode are available for interacting
27119 with your program. In particular, you can send signals the usual
27120 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27124 @value{GDBN} displays source code through Emacs.
27126 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27127 source file for that frame and puts an arrow (@samp{=>}) at the
27128 left margin of the current line. Emacs uses a separate buffer for
27129 source display, and splits the screen to show both your @value{GDBN} session
27132 Explicit @value{GDBN} @code{list} or search commands still produce output as
27133 usual, but you probably have no reason to use them from Emacs.
27136 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27137 a graphical mode, enabled by default, which provides further buffers
27138 that can control the execution and describe the state of your program.
27139 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27141 If you specify an absolute file name when prompted for the @kbd{M-x
27142 gdb} argument, then Emacs sets your current working directory to where
27143 your program resides. If you only specify the file name, then Emacs
27144 sets your current working directory to the directory associated
27145 with the previous buffer. In this case, @value{GDBN} may find your
27146 program by searching your environment's @code{PATH} variable, but on
27147 some operating systems it might not find the source. So, although the
27148 @value{GDBN} input and output session proceeds normally, the auxiliary
27149 buffer does not display the current source and line of execution.
27151 The initial working directory of @value{GDBN} is printed on the top
27152 line of the GUD buffer and this serves as a default for the commands
27153 that specify files for @value{GDBN} to operate on. @xref{Files,
27154 ,Commands to Specify Files}.
27156 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27157 need to call @value{GDBN} by a different name (for example, if you
27158 keep several configurations around, with different names) you can
27159 customize the Emacs variable @code{gud-gdb-command-name} to run the
27162 In the GUD buffer, you can use these special Emacs commands in
27163 addition to the standard Shell mode commands:
27167 Describe the features of Emacs' GUD Mode.
27170 Execute to another source line, like the @value{GDBN} @code{step} command; also
27171 update the display window to show the current file and location.
27174 Execute to next source line in this function, skipping all function
27175 calls, like the @value{GDBN} @code{next} command. Then update the display window
27176 to show the current file and location.
27179 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27180 display window accordingly.
27183 Execute until exit from the selected stack frame, like the @value{GDBN}
27184 @code{finish} command.
27187 Continue execution of your program, like the @value{GDBN} @code{continue}
27191 Go up the number of frames indicated by the numeric argument
27192 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27193 like the @value{GDBN} @code{up} command.
27196 Go down the number of frames indicated by the numeric argument, like the
27197 @value{GDBN} @code{down} command.
27200 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27201 tells @value{GDBN} to set a breakpoint on the source line point is on.
27203 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27204 separate frame which shows a backtrace when the GUD buffer is current.
27205 Move point to any frame in the stack and type @key{RET} to make it
27206 become the current frame and display the associated source in the
27207 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27208 selected frame become the current one. In graphical mode, the
27209 speedbar displays watch expressions.
27211 If you accidentally delete the source-display buffer, an easy way to get
27212 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27213 request a frame display; when you run under Emacs, this recreates
27214 the source buffer if necessary to show you the context of the current
27217 The source files displayed in Emacs are in ordinary Emacs buffers
27218 which are visiting the source files in the usual way. You can edit
27219 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27220 communicates with Emacs in terms of line numbers. If you add or
27221 delete lines from the text, the line numbers that @value{GDBN} knows cease
27222 to correspond properly with the code.
27224 A more detailed description of Emacs' interaction with @value{GDBN} is
27225 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27229 @chapter The @sc{gdb/mi} Interface
27231 @unnumberedsec Function and Purpose
27233 @cindex @sc{gdb/mi}, its purpose
27234 @sc{gdb/mi} is a line based machine oriented text interface to
27235 @value{GDBN} and is activated by specifying using the
27236 @option{--interpreter} command line option (@pxref{Mode Options}). It
27237 is specifically intended to support the development of systems which
27238 use the debugger as just one small component of a larger system.
27240 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27241 in the form of a reference manual.
27243 Note that @sc{gdb/mi} is still under construction, so some of the
27244 features described below are incomplete and subject to change
27245 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27247 @unnumberedsec Notation and Terminology
27249 @cindex notational conventions, for @sc{gdb/mi}
27250 This chapter uses the following notation:
27254 @code{|} separates two alternatives.
27257 @code{[ @var{something} ]} indicates that @var{something} is optional:
27258 it may or may not be given.
27261 @code{( @var{group} )*} means that @var{group} inside the parentheses
27262 may repeat zero or more times.
27265 @code{( @var{group} )+} means that @var{group} inside the parentheses
27266 may repeat one or more times.
27269 @code{"@var{string}"} means a literal @var{string}.
27273 @heading Dependencies
27277 * GDB/MI General Design::
27278 * GDB/MI Command Syntax::
27279 * GDB/MI Compatibility with CLI::
27280 * GDB/MI Development and Front Ends::
27281 * GDB/MI Output Records::
27282 * GDB/MI Simple Examples::
27283 * GDB/MI Command Description Format::
27284 * GDB/MI Breakpoint Commands::
27285 * GDB/MI Catchpoint Commands::
27286 * GDB/MI Program Context::
27287 * GDB/MI Thread Commands::
27288 * GDB/MI Ada Tasking Commands::
27289 * GDB/MI Program Execution::
27290 * GDB/MI Stack Manipulation::
27291 * GDB/MI Variable Objects::
27292 * GDB/MI Data Manipulation::
27293 * GDB/MI Tracepoint Commands::
27294 * GDB/MI Symbol Query::
27295 * GDB/MI File Commands::
27297 * GDB/MI Kod Commands::
27298 * GDB/MI Memory Overlay Commands::
27299 * GDB/MI Signal Handling Commands::
27301 * GDB/MI Target Manipulation::
27302 * GDB/MI File Transfer Commands::
27303 * GDB/MI Miscellaneous Commands::
27306 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27307 @node GDB/MI General Design
27308 @section @sc{gdb/mi} General Design
27309 @cindex GDB/MI General Design
27311 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27312 parts---commands sent to @value{GDBN}, responses to those commands
27313 and notifications. Each command results in exactly one response,
27314 indicating either successful completion of the command, or an error.
27315 For the commands that do not resume the target, the response contains the
27316 requested information. For the commands that resume the target, the
27317 response only indicates whether the target was successfully resumed.
27318 Notifications is the mechanism for reporting changes in the state of the
27319 target, or in @value{GDBN} state, that cannot conveniently be associated with
27320 a command and reported as part of that command response.
27322 The important examples of notifications are:
27326 Exec notifications. These are used to report changes in
27327 target state---when a target is resumed, or stopped. It would not
27328 be feasible to include this information in response of resuming
27329 commands, because one resume commands can result in multiple events in
27330 different threads. Also, quite some time may pass before any event
27331 happens in the target, while a frontend needs to know whether the resuming
27332 command itself was successfully executed.
27335 Console output, and status notifications. Console output
27336 notifications are used to report output of CLI commands, as well as
27337 diagnostics for other commands. Status notifications are used to
27338 report the progress of a long-running operation. Naturally, including
27339 this information in command response would mean no output is produced
27340 until the command is finished, which is undesirable.
27343 General notifications. Commands may have various side effects on
27344 the @value{GDBN} or target state beyond their official purpose. For example,
27345 a command may change the selected thread. Although such changes can
27346 be included in command response, using notification allows for more
27347 orthogonal frontend design.
27351 There's no guarantee that whenever an MI command reports an error,
27352 @value{GDBN} or the target are in any specific state, and especially,
27353 the state is not reverted to the state before the MI command was
27354 processed. Therefore, whenever an MI command results in an error,
27355 we recommend that the frontend refreshes all the information shown in
27356 the user interface.
27360 * Context management::
27361 * Asynchronous and non-stop modes::
27365 @node Context management
27366 @subsection Context management
27368 In most cases when @value{GDBN} accesses the target, this access is
27369 done in context of a specific thread and frame (@pxref{Frames}).
27370 Often, even when accessing global data, the target requires that a thread
27371 be specified. The CLI interface maintains the selected thread and frame,
27372 and supplies them to target on each command. This is convenient,
27373 because a command line user would not want to specify that information
27374 explicitly on each command, and because user interacts with
27375 @value{GDBN} via a single terminal, so no confusion is possible as
27376 to what thread and frame are the current ones.
27378 In the case of MI, the concept of selected thread and frame is less
27379 useful. First, a frontend can easily remember this information
27380 itself. Second, a graphical frontend can have more than one window,
27381 each one used for debugging a different thread, and the frontend might
27382 want to access additional threads for internal purposes. This
27383 increases the risk that by relying on implicitly selected thread, the
27384 frontend may be operating on a wrong one. Therefore, each MI command
27385 should explicitly specify which thread and frame to operate on. To
27386 make it possible, each MI command accepts the @samp{--thread} and
27387 @samp{--frame} options, the value to each is @value{GDBN} identifier
27388 for thread and frame to operate on.
27390 Usually, each top-level window in a frontend allows the user to select
27391 a thread and a frame, and remembers the user selection for further
27392 operations. However, in some cases @value{GDBN} may suggest that the
27393 current thread be changed. For example, when stopping on a breakpoint
27394 it is reasonable to switch to the thread where breakpoint is hit. For
27395 another example, if the user issues the CLI @samp{thread} command via
27396 the frontend, it is desirable to change the frontend's selected thread to the
27397 one specified by user. @value{GDBN} communicates the suggestion to
27398 change current thread using the @samp{=thread-selected} notification.
27399 No such notification is available for the selected frame at the moment.
27401 Note that historically, MI shares the selected thread with CLI, so
27402 frontends used the @code{-thread-select} to execute commands in the
27403 right context. However, getting this to work right is cumbersome. The
27404 simplest way is for frontend to emit @code{-thread-select} command
27405 before every command. This doubles the number of commands that need
27406 to be sent. The alternative approach is to suppress @code{-thread-select}
27407 if the selected thread in @value{GDBN} is supposed to be identical to the
27408 thread the frontend wants to operate on. However, getting this
27409 optimization right can be tricky. In particular, if the frontend
27410 sends several commands to @value{GDBN}, and one of the commands changes the
27411 selected thread, then the behaviour of subsequent commands will
27412 change. So, a frontend should either wait for response from such
27413 problematic commands, or explicitly add @code{-thread-select} for
27414 all subsequent commands. No frontend is known to do this exactly
27415 right, so it is suggested to just always pass the @samp{--thread} and
27416 @samp{--frame} options.
27418 @node Asynchronous and non-stop modes
27419 @subsection Asynchronous command execution and non-stop mode
27421 On some targets, @value{GDBN} is capable of processing MI commands
27422 even while the target is running. This is called @dfn{asynchronous
27423 command execution} (@pxref{Background Execution}). The frontend may
27424 specify a preferrence for asynchronous execution using the
27425 @code{-gdb-set target-async 1} command, which should be emitted before
27426 either running the executable or attaching to the target. After the
27427 frontend has started the executable or attached to the target, it can
27428 find if asynchronous execution is enabled using the
27429 @code{-list-target-features} command.
27431 Even if @value{GDBN} can accept a command while target is running,
27432 many commands that access the target do not work when the target is
27433 running. Therefore, asynchronous command execution is most useful
27434 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27435 it is possible to examine the state of one thread, while other threads
27438 When a given thread is running, MI commands that try to access the
27439 target in the context of that thread may not work, or may work only on
27440 some targets. In particular, commands that try to operate on thread's
27441 stack will not work, on any target. Commands that read memory, or
27442 modify breakpoints, may work or not work, depending on the target. Note
27443 that even commands that operate on global state, such as @code{print},
27444 @code{set}, and breakpoint commands, still access the target in the
27445 context of a specific thread, so frontend should try to find a
27446 stopped thread and perform the operation on that thread (using the
27447 @samp{--thread} option).
27449 Which commands will work in the context of a running thread is
27450 highly target dependent. However, the two commands
27451 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27452 to find the state of a thread, will always work.
27454 @node Thread groups
27455 @subsection Thread groups
27456 @value{GDBN} may be used to debug several processes at the same time.
27457 On some platfroms, @value{GDBN} may support debugging of several
27458 hardware systems, each one having several cores with several different
27459 processes running on each core. This section describes the MI
27460 mechanism to support such debugging scenarios.
27462 The key observation is that regardless of the structure of the
27463 target, MI can have a global list of threads, because most commands that
27464 accept the @samp{--thread} option do not need to know what process that
27465 thread belongs to. Therefore, it is not necessary to introduce
27466 neither additional @samp{--process} option, nor an notion of the
27467 current process in the MI interface. The only strictly new feature
27468 that is required is the ability to find how the threads are grouped
27471 To allow the user to discover such grouping, and to support arbitrary
27472 hierarchy of machines/cores/processes, MI introduces the concept of a
27473 @dfn{thread group}. Thread group is a collection of threads and other
27474 thread groups. A thread group always has a string identifier, a type,
27475 and may have additional attributes specific to the type. A new
27476 command, @code{-list-thread-groups}, returns the list of top-level
27477 thread groups, which correspond to processes that @value{GDBN} is
27478 debugging at the moment. By passing an identifier of a thread group
27479 to the @code{-list-thread-groups} command, it is possible to obtain
27480 the members of specific thread group.
27482 To allow the user to easily discover processes, and other objects, he
27483 wishes to debug, a concept of @dfn{available thread group} is
27484 introduced. Available thread group is an thread group that
27485 @value{GDBN} is not debugging, but that can be attached to, using the
27486 @code{-target-attach} command. The list of available top-level thread
27487 groups can be obtained using @samp{-list-thread-groups --available}.
27488 In general, the content of a thread group may be only retrieved only
27489 after attaching to that thread group.
27491 Thread groups are related to inferiors (@pxref{Inferiors and
27492 Programs}). Each inferior corresponds to a thread group of a special
27493 type @samp{process}, and some additional operations are permitted on
27494 such thread groups.
27496 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27497 @node GDB/MI Command Syntax
27498 @section @sc{gdb/mi} Command Syntax
27501 * GDB/MI Input Syntax::
27502 * GDB/MI Output Syntax::
27505 @node GDB/MI Input Syntax
27506 @subsection @sc{gdb/mi} Input Syntax
27508 @cindex input syntax for @sc{gdb/mi}
27509 @cindex @sc{gdb/mi}, input syntax
27511 @item @var{command} @expansion{}
27512 @code{@var{cli-command} | @var{mi-command}}
27514 @item @var{cli-command} @expansion{}
27515 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27516 @var{cli-command} is any existing @value{GDBN} CLI command.
27518 @item @var{mi-command} @expansion{}
27519 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27520 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27522 @item @var{token} @expansion{}
27523 "any sequence of digits"
27525 @item @var{option} @expansion{}
27526 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27528 @item @var{parameter} @expansion{}
27529 @code{@var{non-blank-sequence} | @var{c-string}}
27531 @item @var{operation} @expansion{}
27532 @emph{any of the operations described in this chapter}
27534 @item @var{non-blank-sequence} @expansion{}
27535 @emph{anything, provided it doesn't contain special characters such as
27536 "-", @var{nl}, """ and of course " "}
27538 @item @var{c-string} @expansion{}
27539 @code{""" @var{seven-bit-iso-c-string-content} """}
27541 @item @var{nl} @expansion{}
27550 The CLI commands are still handled by the @sc{mi} interpreter; their
27551 output is described below.
27554 The @code{@var{token}}, when present, is passed back when the command
27558 Some @sc{mi} commands accept optional arguments as part of the parameter
27559 list. Each option is identified by a leading @samp{-} (dash) and may be
27560 followed by an optional argument parameter. Options occur first in the
27561 parameter list and can be delimited from normal parameters using
27562 @samp{--} (this is useful when some parameters begin with a dash).
27569 We want easy access to the existing CLI syntax (for debugging).
27572 We want it to be easy to spot a @sc{mi} operation.
27575 @node GDB/MI Output Syntax
27576 @subsection @sc{gdb/mi} Output Syntax
27578 @cindex output syntax of @sc{gdb/mi}
27579 @cindex @sc{gdb/mi}, output syntax
27580 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27581 followed, optionally, by a single result record. This result record
27582 is for the most recent command. The sequence of output records is
27583 terminated by @samp{(gdb)}.
27585 If an input command was prefixed with a @code{@var{token}} then the
27586 corresponding output for that command will also be prefixed by that same
27590 @item @var{output} @expansion{}
27591 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27593 @item @var{result-record} @expansion{}
27594 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27596 @item @var{out-of-band-record} @expansion{}
27597 @code{@var{async-record} | @var{stream-record}}
27599 @item @var{async-record} @expansion{}
27600 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27602 @item @var{exec-async-output} @expansion{}
27603 @code{[ @var{token} ] "*" @var{async-output}}
27605 @item @var{status-async-output} @expansion{}
27606 @code{[ @var{token} ] "+" @var{async-output}}
27608 @item @var{notify-async-output} @expansion{}
27609 @code{[ @var{token} ] "=" @var{async-output}}
27611 @item @var{async-output} @expansion{}
27612 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27614 @item @var{result-class} @expansion{}
27615 @code{"done" | "running" | "connected" | "error" | "exit"}
27617 @item @var{async-class} @expansion{}
27618 @code{"stopped" | @var{others}} (where @var{others} will be added
27619 depending on the needs---this is still in development).
27621 @item @var{result} @expansion{}
27622 @code{ @var{variable} "=" @var{value}}
27624 @item @var{variable} @expansion{}
27625 @code{ @var{string} }
27627 @item @var{value} @expansion{}
27628 @code{ @var{const} | @var{tuple} | @var{list} }
27630 @item @var{const} @expansion{}
27631 @code{@var{c-string}}
27633 @item @var{tuple} @expansion{}
27634 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27636 @item @var{list} @expansion{}
27637 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27638 @var{result} ( "," @var{result} )* "]" }
27640 @item @var{stream-record} @expansion{}
27641 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27643 @item @var{console-stream-output} @expansion{}
27644 @code{"~" @var{c-string}}
27646 @item @var{target-stream-output} @expansion{}
27647 @code{"@@" @var{c-string}}
27649 @item @var{log-stream-output} @expansion{}
27650 @code{"&" @var{c-string}}
27652 @item @var{nl} @expansion{}
27655 @item @var{token} @expansion{}
27656 @emph{any sequence of digits}.
27664 All output sequences end in a single line containing a period.
27667 The @code{@var{token}} is from the corresponding request. Note that
27668 for all async output, while the token is allowed by the grammar and
27669 may be output by future versions of @value{GDBN} for select async
27670 output messages, it is generally omitted. Frontends should treat
27671 all async output as reporting general changes in the state of the
27672 target and there should be no need to associate async output to any
27676 @cindex status output in @sc{gdb/mi}
27677 @var{status-async-output} contains on-going status information about the
27678 progress of a slow operation. It can be discarded. All status output is
27679 prefixed by @samp{+}.
27682 @cindex async output in @sc{gdb/mi}
27683 @var{exec-async-output} contains asynchronous state change on the target
27684 (stopped, started, disappeared). All async output is prefixed by
27688 @cindex notify output in @sc{gdb/mi}
27689 @var{notify-async-output} contains supplementary information that the
27690 client should handle (e.g., a new breakpoint information). All notify
27691 output is prefixed by @samp{=}.
27694 @cindex console output in @sc{gdb/mi}
27695 @var{console-stream-output} is output that should be displayed as is in the
27696 console. It is the textual response to a CLI command. All the console
27697 output is prefixed by @samp{~}.
27700 @cindex target output in @sc{gdb/mi}
27701 @var{target-stream-output} is the output produced by the target program.
27702 All the target output is prefixed by @samp{@@}.
27705 @cindex log output in @sc{gdb/mi}
27706 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27707 instance messages that should be displayed as part of an error log. All
27708 the log output is prefixed by @samp{&}.
27711 @cindex list output in @sc{gdb/mi}
27712 New @sc{gdb/mi} commands should only output @var{lists} containing
27718 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27719 details about the various output records.
27721 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27722 @node GDB/MI Compatibility with CLI
27723 @section @sc{gdb/mi} Compatibility with CLI
27725 @cindex compatibility, @sc{gdb/mi} and CLI
27726 @cindex @sc{gdb/mi}, compatibility with CLI
27728 For the developers convenience CLI commands can be entered directly,
27729 but there may be some unexpected behaviour. For example, commands
27730 that query the user will behave as if the user replied yes, breakpoint
27731 command lists are not executed and some CLI commands, such as
27732 @code{if}, @code{when} and @code{define}, prompt for further input with
27733 @samp{>}, which is not valid MI output.
27735 This feature may be removed at some stage in the future and it is
27736 recommended that front ends use the @code{-interpreter-exec} command
27737 (@pxref{-interpreter-exec}).
27739 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27740 @node GDB/MI Development and Front Ends
27741 @section @sc{gdb/mi} Development and Front Ends
27742 @cindex @sc{gdb/mi} development
27744 The application which takes the MI output and presents the state of the
27745 program being debugged to the user is called a @dfn{front end}.
27747 Although @sc{gdb/mi} is still incomplete, it is currently being used
27748 by a variety of front ends to @value{GDBN}. This makes it difficult
27749 to introduce new functionality without breaking existing usage. This
27750 section tries to minimize the problems by describing how the protocol
27753 Some changes in MI need not break a carefully designed front end, and
27754 for these the MI version will remain unchanged. The following is a
27755 list of changes that may occur within one level, so front ends should
27756 parse MI output in a way that can handle them:
27760 New MI commands may be added.
27763 New fields may be added to the output of any MI command.
27766 The range of values for fields with specified values, e.g.,
27767 @code{in_scope} (@pxref{-var-update}) may be extended.
27769 @c The format of field's content e.g type prefix, may change so parse it
27770 @c at your own risk. Yes, in general?
27772 @c The order of fields may change? Shouldn't really matter but it might
27773 @c resolve inconsistencies.
27776 If the changes are likely to break front ends, the MI version level
27777 will be increased by one. This will allow the front end to parse the
27778 output according to the MI version. Apart from mi0, new versions of
27779 @value{GDBN} will not support old versions of MI and it will be the
27780 responsibility of the front end to work with the new one.
27782 @c Starting with mi3, add a new command -mi-version that prints the MI
27785 The best way to avoid unexpected changes in MI that might break your front
27786 end is to make your project known to @value{GDBN} developers and
27787 follow development on @email{gdb@@sourceware.org} and
27788 @email{gdb-patches@@sourceware.org}.
27789 @cindex mailing lists
27791 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27792 @node GDB/MI Output Records
27793 @section @sc{gdb/mi} Output Records
27796 * GDB/MI Result Records::
27797 * GDB/MI Stream Records::
27798 * GDB/MI Async Records::
27799 * GDB/MI Breakpoint Information::
27800 * GDB/MI Frame Information::
27801 * GDB/MI Thread Information::
27802 * GDB/MI Ada Exception Information::
27805 @node GDB/MI Result Records
27806 @subsection @sc{gdb/mi} Result Records
27808 @cindex result records in @sc{gdb/mi}
27809 @cindex @sc{gdb/mi}, result records
27810 In addition to a number of out-of-band notifications, the response to a
27811 @sc{gdb/mi} command includes one of the following result indications:
27815 @item "^done" [ "," @var{results} ]
27816 The synchronous operation was successful, @code{@var{results}} are the return
27821 This result record is equivalent to @samp{^done}. Historically, it
27822 was output instead of @samp{^done} if the command has resumed the
27823 target. This behaviour is maintained for backward compatibility, but
27824 all frontends should treat @samp{^done} and @samp{^running}
27825 identically and rely on the @samp{*running} output record to determine
27826 which threads are resumed.
27830 @value{GDBN} has connected to a remote target.
27832 @item "^error" "," @var{c-string}
27834 The operation failed. The @code{@var{c-string}} contains the corresponding
27839 @value{GDBN} has terminated.
27843 @node GDB/MI Stream Records
27844 @subsection @sc{gdb/mi} Stream Records
27846 @cindex @sc{gdb/mi}, stream records
27847 @cindex stream records in @sc{gdb/mi}
27848 @value{GDBN} internally maintains a number of output streams: the console, the
27849 target, and the log. The output intended for each of these streams is
27850 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27852 Each stream record begins with a unique @dfn{prefix character} which
27853 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27854 Syntax}). In addition to the prefix, each stream record contains a
27855 @code{@var{string-output}}. This is either raw text (with an implicit new
27856 line) or a quoted C string (which does not contain an implicit newline).
27859 @item "~" @var{string-output}
27860 The console output stream contains text that should be displayed in the
27861 CLI console window. It contains the textual responses to CLI commands.
27863 @item "@@" @var{string-output}
27864 The target output stream contains any textual output from the running
27865 target. This is only present when GDB's event loop is truly
27866 asynchronous, which is currently only the case for remote targets.
27868 @item "&" @var{string-output}
27869 The log stream contains debugging messages being produced by @value{GDBN}'s
27873 @node GDB/MI Async Records
27874 @subsection @sc{gdb/mi} Async Records
27876 @cindex async records in @sc{gdb/mi}
27877 @cindex @sc{gdb/mi}, async records
27878 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27879 additional changes that have occurred. Those changes can either be a
27880 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27881 target activity (e.g., target stopped).
27883 The following is the list of possible async records:
27887 @item *running,thread-id="@var{thread}"
27888 The target is now running. The @var{thread} field tells which
27889 specific thread is now running, and can be @samp{all} if all threads
27890 are running. The frontend should assume that no interaction with a
27891 running thread is possible after this notification is produced.
27892 The frontend should not assume that this notification is output
27893 only once for any command. @value{GDBN} may emit this notification
27894 several times, either for different threads, because it cannot resume
27895 all threads together, or even for a single thread, if the thread must
27896 be stepped though some code before letting it run freely.
27898 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27899 The target has stopped. The @var{reason} field can have one of the
27903 @item breakpoint-hit
27904 A breakpoint was reached.
27905 @item watchpoint-trigger
27906 A watchpoint was triggered.
27907 @item read-watchpoint-trigger
27908 A read watchpoint was triggered.
27909 @item access-watchpoint-trigger
27910 An access watchpoint was triggered.
27911 @item function-finished
27912 An -exec-finish or similar CLI command was accomplished.
27913 @item location-reached
27914 An -exec-until or similar CLI command was accomplished.
27915 @item watchpoint-scope
27916 A watchpoint has gone out of scope.
27917 @item end-stepping-range
27918 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27919 similar CLI command was accomplished.
27920 @item exited-signalled
27921 The inferior exited because of a signal.
27923 The inferior exited.
27924 @item exited-normally
27925 The inferior exited normally.
27926 @item signal-received
27927 A signal was received by the inferior.
27929 The inferior has stopped due to a library being loaded or unloaded.
27930 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27931 set or when a @code{catch load} or @code{catch unload} catchpoint is
27932 in use (@pxref{Set Catchpoints}).
27934 The inferior has forked. This is reported when @code{catch fork}
27935 (@pxref{Set Catchpoints}) has been used.
27937 The inferior has vforked. This is reported in when @code{catch vfork}
27938 (@pxref{Set Catchpoints}) has been used.
27939 @item syscall-entry
27940 The inferior entered a system call. This is reported when @code{catch
27941 syscall} (@pxref{Set Catchpoints}) has been used.
27942 @item syscall-entry
27943 The inferior returned from a system call. This is reported when
27944 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27946 The inferior called @code{exec}. This is reported when @code{catch exec}
27947 (@pxref{Set Catchpoints}) has been used.
27950 The @var{id} field identifies the thread that directly caused the stop
27951 -- for example by hitting a breakpoint. Depending on whether all-stop
27952 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27953 stop all threads, or only the thread that directly triggered the stop.
27954 If all threads are stopped, the @var{stopped} field will have the
27955 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27956 field will be a list of thread identifiers. Presently, this list will
27957 always include a single thread, but frontend should be prepared to see
27958 several threads in the list. The @var{core} field reports the
27959 processor core on which the stop event has happened. This field may be absent
27960 if such information is not available.
27962 @item =thread-group-added,id="@var{id}"
27963 @itemx =thread-group-removed,id="@var{id}"
27964 A thread group was either added or removed. The @var{id} field
27965 contains the @value{GDBN} identifier of the thread group. When a thread
27966 group is added, it generally might not be associated with a running
27967 process. When a thread group is removed, its id becomes invalid and
27968 cannot be used in any way.
27970 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27971 A thread group became associated with a running program,
27972 either because the program was just started or the thread group
27973 was attached to a program. The @var{id} field contains the
27974 @value{GDBN} identifier of the thread group. The @var{pid} field
27975 contains process identifier, specific to the operating system.
27977 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27978 A thread group is no longer associated with a running program,
27979 either because the program has exited, or because it was detached
27980 from. The @var{id} field contains the @value{GDBN} identifier of the
27981 thread group. @var{code} is the exit code of the inferior; it exists
27982 only when the inferior exited with some code.
27984 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27985 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27986 A thread either was created, or has exited. The @var{id} field
27987 contains the @value{GDBN} identifier of the thread. The @var{gid}
27988 field identifies the thread group this thread belongs to.
27990 @item =thread-selected,id="@var{id}"
27991 Informs that the selected thread was changed as result of the last
27992 command. This notification is not emitted as result of @code{-thread-select}
27993 command but is emitted whenever an MI command that is not documented
27994 to change the selected thread actually changes it. In particular,
27995 invoking, directly or indirectly (via user-defined command), the CLI
27996 @code{thread} command, will generate this notification.
27998 We suggest that in response to this notification, front ends
27999 highlight the selected thread and cause subsequent commands to apply to
28002 @item =library-loaded,...
28003 Reports that a new library file was loaded by the program. This
28004 notification has 4 fields---@var{id}, @var{target-name},
28005 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
28006 opaque identifier of the library. For remote debugging case,
28007 @var{target-name} and @var{host-name} fields give the name of the
28008 library file on the target, and on the host respectively. For native
28009 debugging, both those fields have the same value. The
28010 @var{symbols-loaded} field is emitted only for backward compatibility
28011 and should not be relied on to convey any useful information. The
28012 @var{thread-group} field, if present, specifies the id of the thread
28013 group in whose context the library was loaded. If the field is
28014 absent, it means the library was loaded in the context of all present
28017 @item =library-unloaded,...
28018 Reports that a library was unloaded by the program. This notification
28019 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28020 the same meaning as for the @code{=library-loaded} notification.
28021 The @var{thread-group} field, if present, specifies the id of the
28022 thread group in whose context the library was unloaded. If the field is
28023 absent, it means the library was unloaded in the context of all present
28026 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28027 @itemx =traceframe-changed,end
28028 Reports that the trace frame was changed and its new number is
28029 @var{tfnum}. The number of the tracepoint associated with this trace
28030 frame is @var{tpnum}.
28032 @item =tsv-created,name=@var{name},initial=@var{initial}
28033 Reports that the new trace state variable @var{name} is created with
28034 initial value @var{initial}.
28036 @item =tsv-deleted,name=@var{name}
28037 @itemx =tsv-deleted
28038 Reports that the trace state variable @var{name} is deleted or all
28039 trace state variables are deleted.
28041 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28042 Reports that the trace state variable @var{name} is modified with
28043 the initial value @var{initial}. The current value @var{current} of
28044 trace state variable is optional and is reported if the current
28045 value of trace state variable is known.
28047 @item =breakpoint-created,bkpt=@{...@}
28048 @itemx =breakpoint-modified,bkpt=@{...@}
28049 @itemx =breakpoint-deleted,id=@var{number}
28050 Reports that a breakpoint was created, modified, or deleted,
28051 respectively. Only user-visible breakpoints are reported to the MI
28054 The @var{bkpt} argument is of the same form as returned by the various
28055 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28056 @var{number} is the ordinal number of the breakpoint.
28058 Note that if a breakpoint is emitted in the result record of a
28059 command, then it will not also be emitted in an async record.
28061 @item =record-started,thread-group="@var{id}"
28062 @itemx =record-stopped,thread-group="@var{id}"
28063 Execution log recording was either started or stopped on an
28064 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28065 group corresponding to the affected inferior.
28067 @item =cmd-param-changed,param=@var{param},value=@var{value}
28068 Reports that a parameter of the command @code{set @var{param}} is
28069 changed to @var{value}. In the multi-word @code{set} command,
28070 the @var{param} is the whole parameter list to @code{set} command.
28071 For example, In command @code{set check type on}, @var{param}
28072 is @code{check type} and @var{value} is @code{on}.
28074 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28075 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28076 written in an inferior. The @var{id} is the identifier of the
28077 thread group corresponding to the affected inferior. The optional
28078 @code{type="code"} part is reported if the memory written to holds
28082 @node GDB/MI Breakpoint Information
28083 @subsection @sc{gdb/mi} Breakpoint Information
28085 When @value{GDBN} reports information about a breakpoint, a
28086 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28091 The breakpoint number. For a breakpoint that represents one location
28092 of a multi-location breakpoint, this will be a dotted pair, like
28096 The type of the breakpoint. For ordinary breakpoints this will be
28097 @samp{breakpoint}, but many values are possible.
28100 If the type of the breakpoint is @samp{catchpoint}, then this
28101 indicates the exact type of catchpoint.
28104 This is the breakpoint disposition---either @samp{del}, meaning that
28105 the breakpoint will be deleted at the next stop, or @samp{keep},
28106 meaning that the breakpoint will not be deleted.
28109 This indicates whether the breakpoint is enabled, in which case the
28110 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28111 Note that this is not the same as the field @code{enable}.
28114 The address of the breakpoint. This may be a hexidecimal number,
28115 giving the address; or the string @samp{<PENDING>}, for a pending
28116 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28117 multiple locations. This field will not be present if no address can
28118 be determined. For example, a watchpoint does not have an address.
28121 If known, the function in which the breakpoint appears.
28122 If not known, this field is not present.
28125 The name of the source file which contains this function, if known.
28126 If not known, this field is not present.
28129 The full file name of the source file which contains this function, if
28130 known. If not known, this field is not present.
28133 The line number at which this breakpoint appears, if known.
28134 If not known, this field is not present.
28137 If the source file is not known, this field may be provided. If
28138 provided, this holds the address of the breakpoint, possibly followed
28142 If this breakpoint is pending, this field is present and holds the
28143 text used to set the breakpoint, as entered by the user.
28146 Where this breakpoint's condition is evaluated, either @samp{host} or
28150 If this is a thread-specific breakpoint, then this identifies the
28151 thread in which the breakpoint can trigger.
28154 If this breakpoint is restricted to a particular Ada task, then this
28155 field will hold the task identifier.
28158 If the breakpoint is conditional, this is the condition expression.
28161 The ignore count of the breakpoint.
28164 The enable count of the breakpoint.
28166 @item traceframe-usage
28169 @item static-tracepoint-marker-string-id
28170 For a static tracepoint, the name of the static tracepoint marker.
28173 For a masked watchpoint, this is the mask.
28176 A tracepoint's pass count.
28178 @item original-location
28179 The location of the breakpoint as originally specified by the user.
28180 This field is optional.
28183 The number of times the breakpoint has been hit.
28186 This field is only given for tracepoints. This is either @samp{y},
28187 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28191 Some extra data, the exact contents of which are type-dependent.
28195 For example, here is what the output of @code{-break-insert}
28196 (@pxref{GDB/MI Breakpoint Commands}) might be:
28199 -> -break-insert main
28200 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28201 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28202 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28207 @node GDB/MI Frame Information
28208 @subsection @sc{gdb/mi} Frame Information
28210 Response from many MI commands includes an information about stack
28211 frame. This information is a tuple that may have the following
28216 The level of the stack frame. The innermost frame has the level of
28217 zero. This field is always present.
28220 The name of the function corresponding to the frame. This field may
28221 be absent if @value{GDBN} is unable to determine the function name.
28224 The code address for the frame. This field is always present.
28227 The name of the source files that correspond to the frame's code
28228 address. This field may be absent.
28231 The source line corresponding to the frames' code address. This field
28235 The name of the binary file (either executable or shared library) the
28236 corresponds to the frame's code address. This field may be absent.
28240 @node GDB/MI Thread Information
28241 @subsection @sc{gdb/mi} Thread Information
28243 Whenever @value{GDBN} has to report an information about a thread, it
28244 uses a tuple with the following fields:
28248 The numeric id assigned to the thread by @value{GDBN}. This field is
28252 Target-specific string identifying the thread. This field is always present.
28255 Additional information about the thread provided by the target.
28256 It is supposed to be human-readable and not interpreted by the
28257 frontend. This field is optional.
28260 Either @samp{stopped} or @samp{running}, depending on whether the
28261 thread is presently running. This field is always present.
28264 The value of this field is an integer number of the processor core the
28265 thread was last seen on. This field is optional.
28268 @node GDB/MI Ada Exception Information
28269 @subsection @sc{gdb/mi} Ada Exception Information
28271 Whenever a @code{*stopped} record is emitted because the program
28272 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28273 @value{GDBN} provides the name of the exception that was raised via
28274 the @code{exception-name} field.
28276 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28277 @node GDB/MI Simple Examples
28278 @section Simple Examples of @sc{gdb/mi} Interaction
28279 @cindex @sc{gdb/mi}, simple examples
28281 This subsection presents several simple examples of interaction using
28282 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28283 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28284 the output received from @sc{gdb/mi}.
28286 Note the line breaks shown in the examples are here only for
28287 readability, they don't appear in the real output.
28289 @subheading Setting a Breakpoint
28291 Setting a breakpoint generates synchronous output which contains detailed
28292 information of the breakpoint.
28295 -> -break-insert main
28296 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28297 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28298 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28303 @subheading Program Execution
28305 Program execution generates asynchronous records and MI gives the
28306 reason that execution stopped.
28312 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28313 frame=@{addr="0x08048564",func="main",
28314 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28315 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28320 <- *stopped,reason="exited-normally"
28324 @subheading Quitting @value{GDBN}
28326 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28334 Please note that @samp{^exit} is printed immediately, but it might
28335 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28336 performs necessary cleanups, including killing programs being debugged
28337 or disconnecting from debug hardware, so the frontend should wait till
28338 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28339 fails to exit in reasonable time.
28341 @subheading A Bad Command
28343 Here's what happens if you pass a non-existent command:
28347 <- ^error,msg="Undefined MI command: rubbish"
28352 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28353 @node GDB/MI Command Description Format
28354 @section @sc{gdb/mi} Command Description Format
28356 The remaining sections describe blocks of commands. Each block of
28357 commands is laid out in a fashion similar to this section.
28359 @subheading Motivation
28361 The motivation for this collection of commands.
28363 @subheading Introduction
28365 A brief introduction to this collection of commands as a whole.
28367 @subheading Commands
28369 For each command in the block, the following is described:
28371 @subsubheading Synopsis
28374 -command @var{args}@dots{}
28377 @subsubheading Result
28379 @subsubheading @value{GDBN} Command
28381 The corresponding @value{GDBN} CLI command(s), if any.
28383 @subsubheading Example
28385 Example(s) formatted for readability. Some of the described commands have
28386 not been implemented yet and these are labeled N.A.@: (not available).
28389 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28390 @node GDB/MI Breakpoint Commands
28391 @section @sc{gdb/mi} Breakpoint Commands
28393 @cindex breakpoint commands for @sc{gdb/mi}
28394 @cindex @sc{gdb/mi}, breakpoint commands
28395 This section documents @sc{gdb/mi} commands for manipulating
28398 @subheading The @code{-break-after} Command
28399 @findex -break-after
28401 @subsubheading Synopsis
28404 -break-after @var{number} @var{count}
28407 The breakpoint number @var{number} is not in effect until it has been
28408 hit @var{count} times. To see how this is reflected in the output of
28409 the @samp{-break-list} command, see the description of the
28410 @samp{-break-list} command below.
28412 @subsubheading @value{GDBN} Command
28414 The corresponding @value{GDBN} command is @samp{ignore}.
28416 @subsubheading Example
28421 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28422 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28423 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28431 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28432 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28433 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28434 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28435 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28436 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28437 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28438 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28439 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28440 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28445 @subheading The @code{-break-catch} Command
28446 @findex -break-catch
28449 @subheading The @code{-break-commands} Command
28450 @findex -break-commands
28452 @subsubheading Synopsis
28455 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28458 Specifies the CLI commands that should be executed when breakpoint
28459 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28460 are the commands. If no command is specified, any previously-set
28461 commands are cleared. @xref{Break Commands}. Typical use of this
28462 functionality is tracing a program, that is, printing of values of
28463 some variables whenever breakpoint is hit and then continuing.
28465 @subsubheading @value{GDBN} Command
28467 The corresponding @value{GDBN} command is @samp{commands}.
28469 @subsubheading Example
28474 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28475 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28476 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28479 -break-commands 1 "print v" "continue"
28484 @subheading The @code{-break-condition} Command
28485 @findex -break-condition
28487 @subsubheading Synopsis
28490 -break-condition @var{number} @var{expr}
28493 Breakpoint @var{number} will stop the program only if the condition in
28494 @var{expr} is true. The condition becomes part of the
28495 @samp{-break-list} output (see the description of the @samp{-break-list}
28498 @subsubheading @value{GDBN} Command
28500 The corresponding @value{GDBN} command is @samp{condition}.
28502 @subsubheading Example
28506 -break-condition 1 1
28510 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28511 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28512 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28513 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28514 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28515 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28516 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28517 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28518 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28519 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28523 @subheading The @code{-break-delete} Command
28524 @findex -break-delete
28526 @subsubheading Synopsis
28529 -break-delete ( @var{breakpoint} )+
28532 Delete the breakpoint(s) whose number(s) are specified in the argument
28533 list. This is obviously reflected in the breakpoint list.
28535 @subsubheading @value{GDBN} Command
28537 The corresponding @value{GDBN} command is @samp{delete}.
28539 @subsubheading Example
28547 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28548 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28549 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28550 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28551 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28552 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28553 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28558 @subheading The @code{-break-disable} Command
28559 @findex -break-disable
28561 @subsubheading Synopsis
28564 -break-disable ( @var{breakpoint} )+
28567 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28568 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28570 @subsubheading @value{GDBN} Command
28572 The corresponding @value{GDBN} command is @samp{disable}.
28574 @subsubheading Example
28582 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28583 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28584 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28585 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28586 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28587 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28588 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28589 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28590 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28591 line="5",thread-groups=["i1"],times="0"@}]@}
28595 @subheading The @code{-break-enable} Command
28596 @findex -break-enable
28598 @subsubheading Synopsis
28601 -break-enable ( @var{breakpoint} )+
28604 Enable (previously disabled) @var{breakpoint}(s).
28606 @subsubheading @value{GDBN} Command
28608 The corresponding @value{GDBN} command is @samp{enable}.
28610 @subsubheading Example
28618 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28619 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28620 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28621 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28622 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28623 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28624 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28625 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28626 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28627 line="5",thread-groups=["i1"],times="0"@}]@}
28631 @subheading The @code{-break-info} Command
28632 @findex -break-info
28634 @subsubheading Synopsis
28637 -break-info @var{breakpoint}
28641 Get information about a single breakpoint.
28643 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28644 Information}, for details on the format of each breakpoint in the
28647 @subsubheading @value{GDBN} Command
28649 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28651 @subsubheading Example
28654 @subheading The @code{-break-insert} Command
28655 @findex -break-insert
28657 @subsubheading Synopsis
28660 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28661 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28662 [ -p @var{thread-id} ] [ @var{location} ]
28666 If specified, @var{location}, can be one of:
28673 @item filename:linenum
28674 @item filename:function
28678 The possible optional parameters of this command are:
28682 Insert a temporary breakpoint.
28684 Insert a hardware breakpoint.
28686 If @var{location} cannot be parsed (for example if it
28687 refers to unknown files or functions), create a pending
28688 breakpoint. Without this flag, @value{GDBN} will report
28689 an error, and won't create a breakpoint, if @var{location}
28692 Create a disabled breakpoint.
28694 Create a tracepoint. @xref{Tracepoints}. When this parameter
28695 is used together with @samp{-h}, a fast tracepoint is created.
28696 @item -c @var{condition}
28697 Make the breakpoint conditional on @var{condition}.
28698 @item -i @var{ignore-count}
28699 Initialize the @var{ignore-count}.
28700 @item -p @var{thread-id}
28701 Restrict the breakpoint to the specified @var{thread-id}.
28704 @subsubheading Result
28706 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28707 resulting breakpoint.
28709 Note: this format is open to change.
28710 @c An out-of-band breakpoint instead of part of the result?
28712 @subsubheading @value{GDBN} Command
28714 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28715 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28717 @subsubheading Example
28722 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28723 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28726 -break-insert -t foo
28727 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28728 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28732 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28733 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28734 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28735 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28736 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28737 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28738 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28739 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28740 addr="0x0001072c", func="main",file="recursive2.c",
28741 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28743 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28744 addr="0x00010774",func="foo",file="recursive2.c",
28745 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28748 @c -break-insert -r foo.*
28749 @c ~int foo(int, int);
28750 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28751 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28756 @subheading The @code{-break-list} Command
28757 @findex -break-list
28759 @subsubheading Synopsis
28765 Displays the list of inserted breakpoints, showing the following fields:
28769 number of the breakpoint
28771 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28773 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28776 is the breakpoint enabled or no: @samp{y} or @samp{n}
28778 memory location at which the breakpoint is set
28780 logical location of the breakpoint, expressed by function name, file
28782 @item Thread-groups
28783 list of thread groups to which this breakpoint applies
28785 number of times the breakpoint has been hit
28788 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28789 @code{body} field is an empty list.
28791 @subsubheading @value{GDBN} Command
28793 The corresponding @value{GDBN} command is @samp{info break}.
28795 @subsubheading Example
28800 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28801 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28802 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28803 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28804 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28805 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28806 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28807 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28808 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28810 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28811 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28812 line="13",thread-groups=["i1"],times="0"@}]@}
28816 Here's an example of the result when there are no breakpoints:
28821 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28822 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28823 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28824 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28825 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28826 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28827 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28832 @subheading The @code{-break-passcount} Command
28833 @findex -break-passcount
28835 @subsubheading Synopsis
28838 -break-passcount @var{tracepoint-number} @var{passcount}
28841 Set the passcount for tracepoint @var{tracepoint-number} to
28842 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28843 is not a tracepoint, error is emitted. This corresponds to CLI
28844 command @samp{passcount}.
28846 @subheading The @code{-break-watch} Command
28847 @findex -break-watch
28849 @subsubheading Synopsis
28852 -break-watch [ -a | -r ]
28855 Create a watchpoint. With the @samp{-a} option it will create an
28856 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28857 read from or on a write to the memory location. With the @samp{-r}
28858 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28859 trigger only when the memory location is accessed for reading. Without
28860 either of the options, the watchpoint created is a regular watchpoint,
28861 i.e., it will trigger when the memory location is accessed for writing.
28862 @xref{Set Watchpoints, , Setting Watchpoints}.
28864 Note that @samp{-break-list} will report a single list of watchpoints and
28865 breakpoints inserted.
28867 @subsubheading @value{GDBN} Command
28869 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28872 @subsubheading Example
28874 Setting a watchpoint on a variable in the @code{main} function:
28879 ^done,wpt=@{number="2",exp="x"@}
28884 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28885 value=@{old="-268439212",new="55"@},
28886 frame=@{func="main",args=[],file="recursive2.c",
28887 fullname="/home/foo/bar/recursive2.c",line="5"@}
28891 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28892 the program execution twice: first for the variable changing value, then
28893 for the watchpoint going out of scope.
28898 ^done,wpt=@{number="5",exp="C"@}
28903 *stopped,reason="watchpoint-trigger",
28904 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28905 frame=@{func="callee4",args=[],
28906 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28907 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28912 *stopped,reason="watchpoint-scope",wpnum="5",
28913 frame=@{func="callee3",args=[@{name="strarg",
28914 value="0x11940 \"A string argument.\""@}],
28915 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28916 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28920 Listing breakpoints and watchpoints, at different points in the program
28921 execution. Note that once the watchpoint goes out of scope, it is
28927 ^done,wpt=@{number="2",exp="C"@}
28930 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28931 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28932 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28933 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28934 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28935 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28936 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28937 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28938 addr="0x00010734",func="callee4",
28939 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28940 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28942 bkpt=@{number="2",type="watchpoint",disp="keep",
28943 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28948 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28949 value=@{old="-276895068",new="3"@},
28950 frame=@{func="callee4",args=[],
28951 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28952 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28955 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28956 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28957 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28958 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28959 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28960 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28961 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28962 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28963 addr="0x00010734",func="callee4",
28964 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28965 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28967 bkpt=@{number="2",type="watchpoint",disp="keep",
28968 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28972 ^done,reason="watchpoint-scope",wpnum="2",
28973 frame=@{func="callee3",args=[@{name="strarg",
28974 value="0x11940 \"A string argument.\""@}],
28975 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28976 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28979 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28980 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28981 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28982 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28983 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28984 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28985 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28986 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28987 addr="0x00010734",func="callee4",
28988 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28989 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28990 thread-groups=["i1"],times="1"@}]@}
28995 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28996 @node GDB/MI Catchpoint Commands
28997 @section @sc{gdb/mi} Catchpoint Commands
28999 This section documents @sc{gdb/mi} commands for manipulating
29002 @subheading The @code{-catch-load} Command
29003 @findex -catch-load
29005 @subsubheading Synopsis
29008 -catch-load [ -t ] [ -d ] @var{regexp}
29011 Add a catchpoint for library load events. If the @samp{-t} option is used,
29012 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29013 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29014 in a disabled state. The @samp{regexp} argument is a regular
29015 expression used to match the name of the loaded library.
29018 @subsubheading @value{GDBN} Command
29020 The corresponding @value{GDBN} command is @samp{catch load}.
29022 @subsubheading Example
29025 -catch-load -t foo.so
29026 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29027 what="load of library matching foo.so",catch-type="load",times="0"@}
29032 @subheading The @code{-catch-unload} Command
29033 @findex -catch-unload
29035 @subsubheading Synopsis
29038 -catch-unload [ -t ] [ -d ] @var{regexp}
29041 Add a catchpoint for library unload events. If the @samp{-t} option is
29042 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29043 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29044 created in a disabled state. The @samp{regexp} argument is a regular
29045 expression used to match the name of the unloaded library.
29047 @subsubheading @value{GDBN} Command
29049 The corresponding @value{GDBN} command is @samp{catch unload}.
29051 @subsubheading Example
29054 -catch-unload -d bar.so
29055 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29056 what="load of library matching bar.so",catch-type="unload",times="0"@}
29061 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29062 @node GDB/MI Program Context
29063 @section @sc{gdb/mi} Program Context
29065 @subheading The @code{-exec-arguments} Command
29066 @findex -exec-arguments
29069 @subsubheading Synopsis
29072 -exec-arguments @var{args}
29075 Set the inferior program arguments, to be used in the next
29078 @subsubheading @value{GDBN} Command
29080 The corresponding @value{GDBN} command is @samp{set args}.
29082 @subsubheading Example
29086 -exec-arguments -v word
29093 @subheading The @code{-exec-show-arguments} Command
29094 @findex -exec-show-arguments
29096 @subsubheading Synopsis
29099 -exec-show-arguments
29102 Print the arguments of the program.
29104 @subsubheading @value{GDBN} Command
29106 The corresponding @value{GDBN} command is @samp{show args}.
29108 @subsubheading Example
29113 @subheading The @code{-environment-cd} Command
29114 @findex -environment-cd
29116 @subsubheading Synopsis
29119 -environment-cd @var{pathdir}
29122 Set @value{GDBN}'s working directory.
29124 @subsubheading @value{GDBN} Command
29126 The corresponding @value{GDBN} command is @samp{cd}.
29128 @subsubheading Example
29132 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29138 @subheading The @code{-environment-directory} Command
29139 @findex -environment-directory
29141 @subsubheading Synopsis
29144 -environment-directory [ -r ] [ @var{pathdir} ]+
29147 Add directories @var{pathdir} to beginning of search path for source files.
29148 If the @samp{-r} option is used, the search path is reset to the default
29149 search path. If directories @var{pathdir} are supplied in addition to the
29150 @samp{-r} option, the search path is first reset and then addition
29152 Multiple directories may be specified, separated by blanks. Specifying
29153 multiple directories in a single command
29154 results in the directories added to the beginning of the
29155 search path in the same order they were presented in the command.
29156 If blanks are needed as
29157 part of a directory name, double-quotes should be used around
29158 the name. In the command output, the path will show up separated
29159 by the system directory-separator character. The directory-separator
29160 character must not be used
29161 in any directory name.
29162 If no directories are specified, the current search path is displayed.
29164 @subsubheading @value{GDBN} Command
29166 The corresponding @value{GDBN} command is @samp{dir}.
29168 @subsubheading Example
29172 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29173 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29175 -environment-directory ""
29176 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29178 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29179 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29181 -environment-directory -r
29182 ^done,source-path="$cdir:$cwd"
29187 @subheading The @code{-environment-path} Command
29188 @findex -environment-path
29190 @subsubheading Synopsis
29193 -environment-path [ -r ] [ @var{pathdir} ]+
29196 Add directories @var{pathdir} to beginning of search path for object files.
29197 If the @samp{-r} option is used, the search path is reset to the original
29198 search path that existed at gdb start-up. If directories @var{pathdir} are
29199 supplied in addition to the
29200 @samp{-r} option, the search path is first reset and then addition
29202 Multiple directories may be specified, separated by blanks. Specifying
29203 multiple directories in a single command
29204 results in the directories added to the beginning of the
29205 search path in the same order they were presented in the command.
29206 If blanks are needed as
29207 part of a directory name, double-quotes should be used around
29208 the name. In the command output, the path will show up separated
29209 by the system directory-separator character. The directory-separator
29210 character must not be used
29211 in any directory name.
29212 If no directories are specified, the current path is displayed.
29215 @subsubheading @value{GDBN} Command
29217 The corresponding @value{GDBN} command is @samp{path}.
29219 @subsubheading Example
29224 ^done,path="/usr/bin"
29226 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29227 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29229 -environment-path -r /usr/local/bin
29230 ^done,path="/usr/local/bin:/usr/bin"
29235 @subheading The @code{-environment-pwd} Command
29236 @findex -environment-pwd
29238 @subsubheading Synopsis
29244 Show the current working directory.
29246 @subsubheading @value{GDBN} Command
29248 The corresponding @value{GDBN} command is @samp{pwd}.
29250 @subsubheading Example
29255 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29259 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29260 @node GDB/MI Thread Commands
29261 @section @sc{gdb/mi} Thread Commands
29264 @subheading The @code{-thread-info} Command
29265 @findex -thread-info
29267 @subsubheading Synopsis
29270 -thread-info [ @var{thread-id} ]
29273 Reports information about either a specific thread, if
29274 the @var{thread-id} parameter is present, or about all
29275 threads. When printing information about all threads,
29276 also reports the current thread.
29278 @subsubheading @value{GDBN} Command
29280 The @samp{info thread} command prints the same information
29283 @subsubheading Result
29285 The result is a list of threads. The following attributes are
29286 defined for a given thread:
29290 This field exists only for the current thread. It has the value @samp{*}.
29293 The identifier that @value{GDBN} uses to refer to the thread.
29296 The identifier that the target uses to refer to the thread.
29299 Extra information about the thread, in a target-specific format. This
29303 The name of the thread. If the user specified a name using the
29304 @code{thread name} command, then this name is given. Otherwise, if
29305 @value{GDBN} can extract the thread name from the target, then that
29306 name is given. If @value{GDBN} cannot find the thread name, then this
29310 The stack frame currently executing in the thread.
29313 The thread's state. The @samp{state} field may have the following
29318 The thread is stopped. Frame information is available for stopped
29322 The thread is running. There's no frame information for running
29328 If @value{GDBN} can find the CPU core on which this thread is running,
29329 then this field is the core identifier. This field is optional.
29333 @subsubheading Example
29338 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29339 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29340 args=[]@},state="running"@},
29341 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29342 frame=@{level="0",addr="0x0804891f",func="foo",
29343 args=[@{name="i",value="10"@}],
29344 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29345 state="running"@}],
29346 current-thread-id="1"
29350 @subheading The @code{-thread-list-ids} Command
29351 @findex -thread-list-ids
29353 @subsubheading Synopsis
29359 Produces a list of the currently known @value{GDBN} thread ids. At the
29360 end of the list it also prints the total number of such threads.
29362 This command is retained for historical reasons, the
29363 @code{-thread-info} command should be used instead.
29365 @subsubheading @value{GDBN} Command
29367 Part of @samp{info threads} supplies the same information.
29369 @subsubheading Example
29374 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29375 current-thread-id="1",number-of-threads="3"
29380 @subheading The @code{-thread-select} Command
29381 @findex -thread-select
29383 @subsubheading Synopsis
29386 -thread-select @var{threadnum}
29389 Make @var{threadnum} the current thread. It prints the number of the new
29390 current thread, and the topmost frame for that thread.
29392 This command is deprecated in favor of explicitly using the
29393 @samp{--thread} option to each command.
29395 @subsubheading @value{GDBN} Command
29397 The corresponding @value{GDBN} command is @samp{thread}.
29399 @subsubheading Example
29406 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29407 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29411 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29412 number-of-threads="3"
29415 ^done,new-thread-id="3",
29416 frame=@{level="0",func="vprintf",
29417 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29418 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29422 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29423 @node GDB/MI Ada Tasking Commands
29424 @section @sc{gdb/mi} Ada Tasking Commands
29426 @subheading The @code{-ada-task-info} Command
29427 @findex -ada-task-info
29429 @subsubheading Synopsis
29432 -ada-task-info [ @var{task-id} ]
29435 Reports information about either a specific Ada task, if the
29436 @var{task-id} parameter is present, or about all Ada tasks.
29438 @subsubheading @value{GDBN} Command
29440 The @samp{info tasks} command prints the same information
29441 about all Ada tasks (@pxref{Ada Tasks}).
29443 @subsubheading Result
29445 The result is a table of Ada tasks. The following columns are
29446 defined for each Ada task:
29450 This field exists only for the current thread. It has the value @samp{*}.
29453 The identifier that @value{GDBN} uses to refer to the Ada task.
29456 The identifier that the target uses to refer to the Ada task.
29459 The identifier of the thread corresponding to the Ada task.
29461 This field should always exist, as Ada tasks are always implemented
29462 on top of a thread. But if @value{GDBN} cannot find this corresponding
29463 thread for any reason, the field is omitted.
29466 This field exists only when the task was created by another task.
29467 In this case, it provides the ID of the parent task.
29470 The base priority of the task.
29473 The current state of the task. For a detailed description of the
29474 possible states, see @ref{Ada Tasks}.
29477 The name of the task.
29481 @subsubheading Example
29485 ^done,tasks=@{nr_rows="3",nr_cols="8",
29486 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29487 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29488 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29489 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29490 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29491 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29492 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29493 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29494 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29495 state="Child Termination Wait",name="main_task"@}]@}
29499 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29500 @node GDB/MI Program Execution
29501 @section @sc{gdb/mi} Program Execution
29503 These are the asynchronous commands which generate the out-of-band
29504 record @samp{*stopped}. Currently @value{GDBN} only really executes
29505 asynchronously with remote targets and this interaction is mimicked in
29508 @subheading The @code{-exec-continue} Command
29509 @findex -exec-continue
29511 @subsubheading Synopsis
29514 -exec-continue [--reverse] [--all|--thread-group N]
29517 Resumes the execution of the inferior program, which will continue
29518 to execute until it reaches a debugger stop event. If the
29519 @samp{--reverse} option is specified, execution resumes in reverse until
29520 it reaches a stop event. Stop events may include
29523 breakpoints or watchpoints
29525 signals or exceptions
29527 the end of the process (or its beginning under @samp{--reverse})
29529 the end or beginning of a replay log if one is being used.
29531 In all-stop mode (@pxref{All-Stop
29532 Mode}), may resume only one thread, or all threads, depending on the
29533 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29534 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29535 ignored in all-stop mode. If the @samp{--thread-group} options is
29536 specified, then all threads in that thread group are resumed.
29538 @subsubheading @value{GDBN} Command
29540 The corresponding @value{GDBN} corresponding is @samp{continue}.
29542 @subsubheading Example
29549 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29550 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29556 @subheading The @code{-exec-finish} Command
29557 @findex -exec-finish
29559 @subsubheading Synopsis
29562 -exec-finish [--reverse]
29565 Resumes the execution of the inferior program until the current
29566 function is exited. Displays the results returned by the function.
29567 If the @samp{--reverse} option is specified, resumes the reverse
29568 execution of the inferior program until the point where current
29569 function was called.
29571 @subsubheading @value{GDBN} Command
29573 The corresponding @value{GDBN} command is @samp{finish}.
29575 @subsubheading Example
29577 Function returning @code{void}.
29584 *stopped,reason="function-finished",frame=@{func="main",args=[],
29585 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29589 Function returning other than @code{void}. The name of the internal
29590 @value{GDBN} variable storing the result is printed, together with the
29597 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29598 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29599 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29600 gdb-result-var="$1",return-value="0"
29605 @subheading The @code{-exec-interrupt} Command
29606 @findex -exec-interrupt
29608 @subsubheading Synopsis
29611 -exec-interrupt [--all|--thread-group N]
29614 Interrupts the background execution of the target. Note how the token
29615 associated with the stop message is the one for the execution command
29616 that has been interrupted. The token for the interrupt itself only
29617 appears in the @samp{^done} output. If the user is trying to
29618 interrupt a non-running program, an error message will be printed.
29620 Note that when asynchronous execution is enabled, this command is
29621 asynchronous just like other execution commands. That is, first the
29622 @samp{^done} response will be printed, and the target stop will be
29623 reported after that using the @samp{*stopped} notification.
29625 In non-stop mode, only the context thread is interrupted by default.
29626 All threads (in all inferiors) will be interrupted if the
29627 @samp{--all} option is specified. If the @samp{--thread-group}
29628 option is specified, all threads in that group will be interrupted.
29630 @subsubheading @value{GDBN} Command
29632 The corresponding @value{GDBN} command is @samp{interrupt}.
29634 @subsubheading Example
29645 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29646 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29647 fullname="/home/foo/bar/try.c",line="13"@}
29652 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29656 @subheading The @code{-exec-jump} Command
29659 @subsubheading Synopsis
29662 -exec-jump @var{location}
29665 Resumes execution of the inferior program at the location specified by
29666 parameter. @xref{Specify Location}, for a description of the
29667 different forms of @var{location}.
29669 @subsubheading @value{GDBN} Command
29671 The corresponding @value{GDBN} command is @samp{jump}.
29673 @subsubheading Example
29676 -exec-jump foo.c:10
29677 *running,thread-id="all"
29682 @subheading The @code{-exec-next} Command
29685 @subsubheading Synopsis
29688 -exec-next [--reverse]
29691 Resumes execution of the inferior program, stopping when the beginning
29692 of the next source line is reached.
29694 If the @samp{--reverse} option is specified, resumes reverse execution
29695 of the inferior program, stopping at the beginning of the previous
29696 source line. If you issue this command on the first line of a
29697 function, it will take you back to the caller of that function, to the
29698 source line where the function was called.
29701 @subsubheading @value{GDBN} Command
29703 The corresponding @value{GDBN} command is @samp{next}.
29705 @subsubheading Example
29711 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29716 @subheading The @code{-exec-next-instruction} Command
29717 @findex -exec-next-instruction
29719 @subsubheading Synopsis
29722 -exec-next-instruction [--reverse]
29725 Executes one machine instruction. If the instruction is a function
29726 call, continues until the function returns. If the program stops at an
29727 instruction in the middle of a source line, the address will be
29730 If the @samp{--reverse} option is specified, resumes reverse execution
29731 of the inferior program, stopping at the previous instruction. If the
29732 previously executed instruction was a return from another function,
29733 it will continue to execute in reverse until the call to that function
29734 (from the current stack frame) is reached.
29736 @subsubheading @value{GDBN} Command
29738 The corresponding @value{GDBN} command is @samp{nexti}.
29740 @subsubheading Example
29744 -exec-next-instruction
29748 *stopped,reason="end-stepping-range",
29749 addr="0x000100d4",line="5",file="hello.c"
29754 @subheading The @code{-exec-return} Command
29755 @findex -exec-return
29757 @subsubheading Synopsis
29763 Makes current function return immediately. Doesn't execute the inferior.
29764 Displays the new current frame.
29766 @subsubheading @value{GDBN} Command
29768 The corresponding @value{GDBN} command is @samp{return}.
29770 @subsubheading Example
29774 200-break-insert callee4
29775 200^done,bkpt=@{number="1",addr="0x00010734",
29776 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29781 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29782 frame=@{func="callee4",args=[],
29783 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29784 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29790 111^done,frame=@{level="0",func="callee3",
29791 args=[@{name="strarg",
29792 value="0x11940 \"A string argument.\""@}],
29793 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29794 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29799 @subheading The @code{-exec-run} Command
29802 @subsubheading Synopsis
29805 -exec-run [--all | --thread-group N]
29808 Starts execution of the inferior from the beginning. The inferior
29809 executes until either a breakpoint is encountered or the program
29810 exits. In the latter case the output will include an exit code, if
29811 the program has exited exceptionally.
29813 When no option is specified, the current inferior is started. If the
29814 @samp{--thread-group} option is specified, it should refer to a thread
29815 group of type @samp{process}, and that thread group will be started.
29816 If the @samp{--all} option is specified, then all inferiors will be started.
29818 @subsubheading @value{GDBN} Command
29820 The corresponding @value{GDBN} command is @samp{run}.
29822 @subsubheading Examples
29827 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29832 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29833 frame=@{func="main",args=[],file="recursive2.c",
29834 fullname="/home/foo/bar/recursive2.c",line="4"@}
29839 Program exited normally:
29847 *stopped,reason="exited-normally"
29852 Program exited exceptionally:
29860 *stopped,reason="exited",exit-code="01"
29864 Another way the program can terminate is if it receives a signal such as
29865 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29869 *stopped,reason="exited-signalled",signal-name="SIGINT",
29870 signal-meaning="Interrupt"
29874 @c @subheading -exec-signal
29877 @subheading The @code{-exec-step} Command
29880 @subsubheading Synopsis
29883 -exec-step [--reverse]
29886 Resumes execution of the inferior program, stopping when the beginning
29887 of the next source line is reached, if the next source line is not a
29888 function call. If it is, stop at the first instruction of the called
29889 function. If the @samp{--reverse} option is specified, resumes reverse
29890 execution of the inferior program, stopping at the beginning of the
29891 previously executed source line.
29893 @subsubheading @value{GDBN} Command
29895 The corresponding @value{GDBN} command is @samp{step}.
29897 @subsubheading Example
29899 Stepping into a function:
29905 *stopped,reason="end-stepping-range",
29906 frame=@{func="foo",args=[@{name="a",value="10"@},
29907 @{name="b",value="0"@}],file="recursive2.c",
29908 fullname="/home/foo/bar/recursive2.c",line="11"@}
29918 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29923 @subheading The @code{-exec-step-instruction} Command
29924 @findex -exec-step-instruction
29926 @subsubheading Synopsis
29929 -exec-step-instruction [--reverse]
29932 Resumes the inferior which executes one machine instruction. If the
29933 @samp{--reverse} option is specified, resumes reverse execution of the
29934 inferior program, stopping at the previously executed instruction.
29935 The output, once @value{GDBN} has stopped, will vary depending on
29936 whether we have stopped in the middle of a source line or not. In the
29937 former case, the address at which the program stopped will be printed
29940 @subsubheading @value{GDBN} Command
29942 The corresponding @value{GDBN} command is @samp{stepi}.
29944 @subsubheading Example
29948 -exec-step-instruction
29952 *stopped,reason="end-stepping-range",
29953 frame=@{func="foo",args=[],file="try.c",
29954 fullname="/home/foo/bar/try.c",line="10"@}
29956 -exec-step-instruction
29960 *stopped,reason="end-stepping-range",
29961 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29962 fullname="/home/foo/bar/try.c",line="10"@}
29967 @subheading The @code{-exec-until} Command
29968 @findex -exec-until
29970 @subsubheading Synopsis
29973 -exec-until [ @var{location} ]
29976 Executes the inferior until the @var{location} specified in the
29977 argument is reached. If there is no argument, the inferior executes
29978 until a source line greater than the current one is reached. The
29979 reason for stopping in this case will be @samp{location-reached}.
29981 @subsubheading @value{GDBN} Command
29983 The corresponding @value{GDBN} command is @samp{until}.
29985 @subsubheading Example
29989 -exec-until recursive2.c:6
29993 *stopped,reason="location-reached",frame=@{func="main",args=[],
29994 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29999 @subheading -file-clear
30000 Is this going away????
30003 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30004 @node GDB/MI Stack Manipulation
30005 @section @sc{gdb/mi} Stack Manipulation Commands
30008 @subheading The @code{-stack-info-frame} Command
30009 @findex -stack-info-frame
30011 @subsubheading Synopsis
30017 Get info on the selected frame.
30019 @subsubheading @value{GDBN} Command
30021 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30022 (without arguments).
30024 @subsubheading Example
30029 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30030 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30031 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
30035 @subheading The @code{-stack-info-depth} Command
30036 @findex -stack-info-depth
30038 @subsubheading Synopsis
30041 -stack-info-depth [ @var{max-depth} ]
30044 Return the depth of the stack. If the integer argument @var{max-depth}
30045 is specified, do not count beyond @var{max-depth} frames.
30047 @subsubheading @value{GDBN} Command
30049 There's no equivalent @value{GDBN} command.
30051 @subsubheading Example
30053 For a stack with frame levels 0 through 11:
30060 -stack-info-depth 4
30063 -stack-info-depth 12
30066 -stack-info-depth 11
30069 -stack-info-depth 13
30074 @subheading The @code{-stack-list-arguments} Command
30075 @findex -stack-list-arguments
30077 @subsubheading Synopsis
30080 -stack-list-arguments @var{print-values}
30081 [ @var{low-frame} @var{high-frame} ]
30084 Display a list of the arguments for the frames between @var{low-frame}
30085 and @var{high-frame} (inclusive). If @var{low-frame} and
30086 @var{high-frame} are not provided, list the arguments for the whole
30087 call stack. If the two arguments are equal, show the single frame
30088 at the corresponding level. It is an error if @var{low-frame} is
30089 larger than the actual number of frames. On the other hand,
30090 @var{high-frame} may be larger than the actual number of frames, in
30091 which case only existing frames will be returned.
30093 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30094 the variables; if it is 1 or @code{--all-values}, print also their
30095 values; and if it is 2 or @code{--simple-values}, print the name,
30096 type and value for simple data types, and the name and type for arrays,
30097 structures and unions.
30099 Use of this command to obtain arguments in a single frame is
30100 deprecated in favor of the @samp{-stack-list-variables} command.
30102 @subsubheading @value{GDBN} Command
30104 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30105 @samp{gdb_get_args} command which partially overlaps with the
30106 functionality of @samp{-stack-list-arguments}.
30108 @subsubheading Example
30115 frame=@{level="0",addr="0x00010734",func="callee4",
30116 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30117 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30118 frame=@{level="1",addr="0x0001076c",func="callee3",
30119 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30120 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30121 frame=@{level="2",addr="0x0001078c",func="callee2",
30122 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30123 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30124 frame=@{level="3",addr="0x000107b4",func="callee1",
30125 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30126 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30127 frame=@{level="4",addr="0x000107e0",func="main",
30128 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30129 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30131 -stack-list-arguments 0
30134 frame=@{level="0",args=[]@},
30135 frame=@{level="1",args=[name="strarg"]@},
30136 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30137 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30138 frame=@{level="4",args=[]@}]
30140 -stack-list-arguments 1
30143 frame=@{level="0",args=[]@},
30145 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30146 frame=@{level="2",args=[
30147 @{name="intarg",value="2"@},
30148 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30149 @{frame=@{level="3",args=[
30150 @{name="intarg",value="2"@},
30151 @{name="strarg",value="0x11940 \"A string argument.\""@},
30152 @{name="fltarg",value="3.5"@}]@},
30153 frame=@{level="4",args=[]@}]
30155 -stack-list-arguments 0 2 2
30156 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30158 -stack-list-arguments 1 2 2
30159 ^done,stack-args=[frame=@{level="2",
30160 args=[@{name="intarg",value="2"@},
30161 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30165 @c @subheading -stack-list-exception-handlers
30168 @subheading The @code{-stack-list-frames} Command
30169 @findex -stack-list-frames
30171 @subsubheading Synopsis
30174 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30177 List the frames currently on the stack. For each frame it displays the
30182 The frame number, 0 being the topmost frame, i.e., the innermost function.
30184 The @code{$pc} value for that frame.
30188 File name of the source file where the function lives.
30189 @item @var{fullname}
30190 The full file name of the source file where the function lives.
30192 Line number corresponding to the @code{$pc}.
30194 The shared library where this function is defined. This is only given
30195 if the frame's function is not known.
30198 If invoked without arguments, this command prints a backtrace for the
30199 whole stack. If given two integer arguments, it shows the frames whose
30200 levels are between the two arguments (inclusive). If the two arguments
30201 are equal, it shows the single frame at the corresponding level. It is
30202 an error if @var{low-frame} is larger than the actual number of
30203 frames. On the other hand, @var{high-frame} may be larger than the
30204 actual number of frames, in which case only existing frames will be returned.
30206 @subsubheading @value{GDBN} Command
30208 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30210 @subsubheading Example
30212 Full stack backtrace:
30218 [frame=@{level="0",addr="0x0001076c",func="foo",
30219 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30220 frame=@{level="1",addr="0x000107a4",func="foo",
30221 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30222 frame=@{level="2",addr="0x000107a4",func="foo",
30223 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30224 frame=@{level="3",addr="0x000107a4",func="foo",
30225 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30226 frame=@{level="4",addr="0x000107a4",func="foo",
30227 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30228 frame=@{level="5",addr="0x000107a4",func="foo",
30229 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30230 frame=@{level="6",addr="0x000107a4",func="foo",
30231 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30232 frame=@{level="7",addr="0x000107a4",func="foo",
30233 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30234 frame=@{level="8",addr="0x000107a4",func="foo",
30235 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30236 frame=@{level="9",addr="0x000107a4",func="foo",
30237 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30238 frame=@{level="10",addr="0x000107a4",func="foo",
30239 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30240 frame=@{level="11",addr="0x00010738",func="main",
30241 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30245 Show frames between @var{low_frame} and @var{high_frame}:
30249 -stack-list-frames 3 5
30251 [frame=@{level="3",addr="0x000107a4",func="foo",
30252 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30253 frame=@{level="4",addr="0x000107a4",func="foo",
30254 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30255 frame=@{level="5",addr="0x000107a4",func="foo",
30256 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30260 Show a single frame:
30264 -stack-list-frames 3 3
30266 [frame=@{level="3",addr="0x000107a4",func="foo",
30267 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30272 @subheading The @code{-stack-list-locals} Command
30273 @findex -stack-list-locals
30275 @subsubheading Synopsis
30278 -stack-list-locals @var{print-values}
30281 Display the local variable names for the selected frame. If
30282 @var{print-values} is 0 or @code{--no-values}, print only the names of
30283 the variables; if it is 1 or @code{--all-values}, print also their
30284 values; and if it is 2 or @code{--simple-values}, print the name,
30285 type and value for simple data types, and the name and type for arrays,
30286 structures and unions. In this last case, a frontend can immediately
30287 display the value of simple data types and create variable objects for
30288 other data types when the user wishes to explore their values in
30291 This command is deprecated in favor of the
30292 @samp{-stack-list-variables} command.
30294 @subsubheading @value{GDBN} Command
30296 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30298 @subsubheading Example
30302 -stack-list-locals 0
30303 ^done,locals=[name="A",name="B",name="C"]
30305 -stack-list-locals --all-values
30306 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30307 @{name="C",value="@{1, 2, 3@}"@}]
30308 -stack-list-locals --simple-values
30309 ^done,locals=[@{name="A",type="int",value="1"@},
30310 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30314 @subheading The @code{-stack-list-variables} Command
30315 @findex -stack-list-variables
30317 @subsubheading Synopsis
30320 -stack-list-variables @var{print-values}
30323 Display the names of local variables and function arguments for the selected frame. If
30324 @var{print-values} is 0 or @code{--no-values}, print only the names of
30325 the variables; if it is 1 or @code{--all-values}, print also their
30326 values; and if it is 2 or @code{--simple-values}, print the name,
30327 type and value for simple data types, and the name and type for arrays,
30328 structures and unions.
30330 @subsubheading Example
30334 -stack-list-variables --thread 1 --frame 0 --all-values
30335 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30340 @subheading The @code{-stack-select-frame} Command
30341 @findex -stack-select-frame
30343 @subsubheading Synopsis
30346 -stack-select-frame @var{framenum}
30349 Change the selected frame. Select a different frame @var{framenum} on
30352 This command in deprecated in favor of passing the @samp{--frame}
30353 option to every command.
30355 @subsubheading @value{GDBN} Command
30357 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30358 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30360 @subsubheading Example
30364 -stack-select-frame 2
30369 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30370 @node GDB/MI Variable Objects
30371 @section @sc{gdb/mi} Variable Objects
30375 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30377 For the implementation of a variable debugger window (locals, watched
30378 expressions, etc.), we are proposing the adaptation of the existing code
30379 used by @code{Insight}.
30381 The two main reasons for that are:
30385 It has been proven in practice (it is already on its second generation).
30388 It will shorten development time (needless to say how important it is
30392 The original interface was designed to be used by Tcl code, so it was
30393 slightly changed so it could be used through @sc{gdb/mi}. This section
30394 describes the @sc{gdb/mi} operations that will be available and gives some
30395 hints about their use.
30397 @emph{Note}: In addition to the set of operations described here, we
30398 expect the @sc{gui} implementation of a variable window to require, at
30399 least, the following operations:
30402 @item @code{-gdb-show} @code{output-radix}
30403 @item @code{-stack-list-arguments}
30404 @item @code{-stack-list-locals}
30405 @item @code{-stack-select-frame}
30410 @subheading Introduction to Variable Objects
30412 @cindex variable objects in @sc{gdb/mi}
30414 Variable objects are "object-oriented" MI interface for examining and
30415 changing values of expressions. Unlike some other MI interfaces that
30416 work with expressions, variable objects are specifically designed for
30417 simple and efficient presentation in the frontend. A variable object
30418 is identified by string name. When a variable object is created, the
30419 frontend specifies the expression for that variable object. The
30420 expression can be a simple variable, or it can be an arbitrary complex
30421 expression, and can even involve CPU registers. After creating a
30422 variable object, the frontend can invoke other variable object
30423 operations---for example to obtain or change the value of a variable
30424 object, or to change display format.
30426 Variable objects have hierarchical tree structure. Any variable object
30427 that corresponds to a composite type, such as structure in C, has
30428 a number of child variable objects, for example corresponding to each
30429 element of a structure. A child variable object can itself have
30430 children, recursively. Recursion ends when we reach
30431 leaf variable objects, which always have built-in types. Child variable
30432 objects are created only by explicit request, so if a frontend
30433 is not interested in the children of a particular variable object, no
30434 child will be created.
30436 For a leaf variable object it is possible to obtain its value as a
30437 string, or set the value from a string. String value can be also
30438 obtained for a non-leaf variable object, but it's generally a string
30439 that only indicates the type of the object, and does not list its
30440 contents. Assignment to a non-leaf variable object is not allowed.
30442 A frontend does not need to read the values of all variable objects each time
30443 the program stops. Instead, MI provides an update command that lists all
30444 variable objects whose values has changed since the last update
30445 operation. This considerably reduces the amount of data that must
30446 be transferred to the frontend. As noted above, children variable
30447 objects are created on demand, and only leaf variable objects have a
30448 real value. As result, gdb will read target memory only for leaf
30449 variables that frontend has created.
30451 The automatic update is not always desirable. For example, a frontend
30452 might want to keep a value of some expression for future reference,
30453 and never update it. For another example, fetching memory is
30454 relatively slow for embedded targets, so a frontend might want
30455 to disable automatic update for the variables that are either not
30456 visible on the screen, or ``closed''. This is possible using so
30457 called ``frozen variable objects''. Such variable objects are never
30458 implicitly updated.
30460 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30461 fixed variable object, the expression is parsed when the variable
30462 object is created, including associating identifiers to specific
30463 variables. The meaning of expression never changes. For a floating
30464 variable object the values of variables whose names appear in the
30465 expressions are re-evaluated every time in the context of the current
30466 frame. Consider this example:
30471 struct work_state state;
30478 If a fixed variable object for the @code{state} variable is created in
30479 this function, and we enter the recursive call, the variable
30480 object will report the value of @code{state} in the top-level
30481 @code{do_work} invocation. On the other hand, a floating variable
30482 object will report the value of @code{state} in the current frame.
30484 If an expression specified when creating a fixed variable object
30485 refers to a local variable, the variable object becomes bound to the
30486 thread and frame in which the variable object is created. When such
30487 variable object is updated, @value{GDBN} makes sure that the
30488 thread/frame combination the variable object is bound to still exists,
30489 and re-evaluates the variable object in context of that thread/frame.
30491 The following is the complete set of @sc{gdb/mi} operations defined to
30492 access this functionality:
30494 @multitable @columnfractions .4 .6
30495 @item @strong{Operation}
30496 @tab @strong{Description}
30498 @item @code{-enable-pretty-printing}
30499 @tab enable Python-based pretty-printing
30500 @item @code{-var-create}
30501 @tab create a variable object
30502 @item @code{-var-delete}
30503 @tab delete the variable object and/or its children
30504 @item @code{-var-set-format}
30505 @tab set the display format of this variable
30506 @item @code{-var-show-format}
30507 @tab show the display format of this variable
30508 @item @code{-var-info-num-children}
30509 @tab tells how many children this object has
30510 @item @code{-var-list-children}
30511 @tab return a list of the object's children
30512 @item @code{-var-info-type}
30513 @tab show the type of this variable object
30514 @item @code{-var-info-expression}
30515 @tab print parent-relative expression that this variable object represents
30516 @item @code{-var-info-path-expression}
30517 @tab print full expression that this variable object represents
30518 @item @code{-var-show-attributes}
30519 @tab is this variable editable? does it exist here?
30520 @item @code{-var-evaluate-expression}
30521 @tab get the value of this variable
30522 @item @code{-var-assign}
30523 @tab set the value of this variable
30524 @item @code{-var-update}
30525 @tab update the variable and its children
30526 @item @code{-var-set-frozen}
30527 @tab set frozeness attribute
30528 @item @code{-var-set-update-range}
30529 @tab set range of children to display on update
30532 In the next subsection we describe each operation in detail and suggest
30533 how it can be used.
30535 @subheading Description And Use of Operations on Variable Objects
30537 @subheading The @code{-enable-pretty-printing} Command
30538 @findex -enable-pretty-printing
30541 -enable-pretty-printing
30544 @value{GDBN} allows Python-based visualizers to affect the output of the
30545 MI variable object commands. However, because there was no way to
30546 implement this in a fully backward-compatible way, a front end must
30547 request that this functionality be enabled.
30549 Once enabled, this feature cannot be disabled.
30551 Note that if Python support has not been compiled into @value{GDBN},
30552 this command will still succeed (and do nothing).
30554 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30555 may work differently in future versions of @value{GDBN}.
30557 @subheading The @code{-var-create} Command
30558 @findex -var-create
30560 @subsubheading Synopsis
30563 -var-create @{@var{name} | "-"@}
30564 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30567 This operation creates a variable object, which allows the monitoring of
30568 a variable, the result of an expression, a memory cell or a CPU
30571 The @var{name} parameter is the string by which the object can be
30572 referenced. It must be unique. If @samp{-} is specified, the varobj
30573 system will generate a string ``varNNNNNN'' automatically. It will be
30574 unique provided that one does not specify @var{name} of that format.
30575 The command fails if a duplicate name is found.
30577 The frame under which the expression should be evaluated can be
30578 specified by @var{frame-addr}. A @samp{*} indicates that the current
30579 frame should be used. A @samp{@@} indicates that a floating variable
30580 object must be created.
30582 @var{expression} is any expression valid on the current language set (must not
30583 begin with a @samp{*}), or one of the following:
30587 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30590 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30593 @samp{$@var{regname}} --- a CPU register name
30596 @cindex dynamic varobj
30597 A varobj's contents may be provided by a Python-based pretty-printer. In this
30598 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30599 have slightly different semantics in some cases. If the
30600 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30601 will never create a dynamic varobj. This ensures backward
30602 compatibility for existing clients.
30604 @subsubheading Result
30606 This operation returns attributes of the newly-created varobj. These
30611 The name of the varobj.
30614 The number of children of the varobj. This number is not necessarily
30615 reliable for a dynamic varobj. Instead, you must examine the
30616 @samp{has_more} attribute.
30619 The varobj's scalar value. For a varobj whose type is some sort of
30620 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30621 will not be interesting.
30624 The varobj's type. This is a string representation of the type, as
30625 would be printed by the @value{GDBN} CLI. If @samp{print object}
30626 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30627 @emph{actual} (derived) type of the object is shown rather than the
30628 @emph{declared} one.
30631 If a variable object is bound to a specific thread, then this is the
30632 thread's identifier.
30635 For a dynamic varobj, this indicates whether there appear to be any
30636 children available. For a non-dynamic varobj, this will be 0.
30639 This attribute will be present and have the value @samp{1} if the
30640 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30641 then this attribute will not be present.
30644 A dynamic varobj can supply a display hint to the front end. The
30645 value comes directly from the Python pretty-printer object's
30646 @code{display_hint} method. @xref{Pretty Printing API}.
30649 Typical output will look like this:
30652 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30653 has_more="@var{has_more}"
30657 @subheading The @code{-var-delete} Command
30658 @findex -var-delete
30660 @subsubheading Synopsis
30663 -var-delete [ -c ] @var{name}
30666 Deletes a previously created variable object and all of its children.
30667 With the @samp{-c} option, just deletes the children.
30669 Returns an error if the object @var{name} is not found.
30672 @subheading The @code{-var-set-format} Command
30673 @findex -var-set-format
30675 @subsubheading Synopsis
30678 -var-set-format @var{name} @var{format-spec}
30681 Sets the output format for the value of the object @var{name} to be
30684 @anchor{-var-set-format}
30685 The syntax for the @var{format-spec} is as follows:
30688 @var{format-spec} @expansion{}
30689 @{binary | decimal | hexadecimal | octal | natural@}
30692 The natural format is the default format choosen automatically
30693 based on the variable type (like decimal for an @code{int}, hex
30694 for pointers, etc.).
30696 For a variable with children, the format is set only on the
30697 variable itself, and the children are not affected.
30699 @subheading The @code{-var-show-format} Command
30700 @findex -var-show-format
30702 @subsubheading Synopsis
30705 -var-show-format @var{name}
30708 Returns the format used to display the value of the object @var{name}.
30711 @var{format} @expansion{}
30716 @subheading The @code{-var-info-num-children} Command
30717 @findex -var-info-num-children
30719 @subsubheading Synopsis
30722 -var-info-num-children @var{name}
30725 Returns the number of children of a variable object @var{name}:
30731 Note that this number is not completely reliable for a dynamic varobj.
30732 It will return the current number of children, but more children may
30736 @subheading The @code{-var-list-children} Command
30737 @findex -var-list-children
30739 @subsubheading Synopsis
30742 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30744 @anchor{-var-list-children}
30746 Return a list of the children of the specified variable object and
30747 create variable objects for them, if they do not already exist. With
30748 a single argument or if @var{print-values} has a value of 0 or
30749 @code{--no-values}, print only the names of the variables; if
30750 @var{print-values} is 1 or @code{--all-values}, also print their
30751 values; and if it is 2 or @code{--simple-values} print the name and
30752 value for simple data types and just the name for arrays, structures
30755 @var{from} and @var{to}, if specified, indicate the range of children
30756 to report. If @var{from} or @var{to} is less than zero, the range is
30757 reset and all children will be reported. Otherwise, children starting
30758 at @var{from} (zero-based) and up to and excluding @var{to} will be
30761 If a child range is requested, it will only affect the current call to
30762 @code{-var-list-children}, but not future calls to @code{-var-update}.
30763 For this, you must instead use @code{-var-set-update-range}. The
30764 intent of this approach is to enable a front end to implement any
30765 update approach it likes; for example, scrolling a view may cause the
30766 front end to request more children with @code{-var-list-children}, and
30767 then the front end could call @code{-var-set-update-range} with a
30768 different range to ensure that future updates are restricted to just
30771 For each child the following results are returned:
30776 Name of the variable object created for this child.
30779 The expression to be shown to the user by the front end to designate this child.
30780 For example this may be the name of a structure member.
30782 For a dynamic varobj, this value cannot be used to form an
30783 expression. There is no way to do this at all with a dynamic varobj.
30785 For C/C@t{++} structures there are several pseudo children returned to
30786 designate access qualifiers. For these pseudo children @var{exp} is
30787 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30788 type and value are not present.
30790 A dynamic varobj will not report the access qualifying
30791 pseudo-children, regardless of the language. This information is not
30792 available at all with a dynamic varobj.
30795 Number of children this child has. For a dynamic varobj, this will be
30799 The type of the child. If @samp{print object}
30800 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30801 @emph{actual} (derived) type of the object is shown rather than the
30802 @emph{declared} one.
30805 If values were requested, this is the value.
30808 If this variable object is associated with a thread, this is the thread id.
30809 Otherwise this result is not present.
30812 If the variable object is frozen, this variable will be present with a value of 1.
30815 The result may have its own attributes:
30819 A dynamic varobj can supply a display hint to the front end. The
30820 value comes directly from the Python pretty-printer object's
30821 @code{display_hint} method. @xref{Pretty Printing API}.
30824 This is an integer attribute which is nonzero if there are children
30825 remaining after the end of the selected range.
30828 @subsubheading Example
30832 -var-list-children n
30833 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30834 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30836 -var-list-children --all-values n
30837 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30838 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30842 @subheading The @code{-var-info-type} Command
30843 @findex -var-info-type
30845 @subsubheading Synopsis
30848 -var-info-type @var{name}
30851 Returns the type of the specified variable @var{name}. The type is
30852 returned as a string in the same format as it is output by the
30856 type=@var{typename}
30860 @subheading The @code{-var-info-expression} Command
30861 @findex -var-info-expression
30863 @subsubheading Synopsis
30866 -var-info-expression @var{name}
30869 Returns a string that is suitable for presenting this
30870 variable object in user interface. The string is generally
30871 not valid expression in the current language, and cannot be evaluated.
30873 For example, if @code{a} is an array, and variable object
30874 @code{A} was created for @code{a}, then we'll get this output:
30877 (gdb) -var-info-expression A.1
30878 ^done,lang="C",exp="1"
30882 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30884 Note that the output of the @code{-var-list-children} command also
30885 includes those expressions, so the @code{-var-info-expression} command
30888 @subheading The @code{-var-info-path-expression} Command
30889 @findex -var-info-path-expression
30891 @subsubheading Synopsis
30894 -var-info-path-expression @var{name}
30897 Returns an expression that can be evaluated in the current
30898 context and will yield the same value that a variable object has.
30899 Compare this with the @code{-var-info-expression} command, which
30900 result can be used only for UI presentation. Typical use of
30901 the @code{-var-info-path-expression} command is creating a
30902 watchpoint from a variable object.
30904 This command is currently not valid for children of a dynamic varobj,
30905 and will give an error when invoked on one.
30907 For example, suppose @code{C} is a C@t{++} class, derived from class
30908 @code{Base}, and that the @code{Base} class has a member called
30909 @code{m_size}. Assume a variable @code{c} is has the type of
30910 @code{C} and a variable object @code{C} was created for variable
30911 @code{c}. Then, we'll get this output:
30913 (gdb) -var-info-path-expression C.Base.public.m_size
30914 ^done,path_expr=((Base)c).m_size)
30917 @subheading The @code{-var-show-attributes} Command
30918 @findex -var-show-attributes
30920 @subsubheading Synopsis
30923 -var-show-attributes @var{name}
30926 List attributes of the specified variable object @var{name}:
30929 status=@var{attr} [ ( ,@var{attr} )* ]
30933 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30935 @subheading The @code{-var-evaluate-expression} Command
30936 @findex -var-evaluate-expression
30938 @subsubheading Synopsis
30941 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30944 Evaluates the expression that is represented by the specified variable
30945 object and returns its value as a string. The format of the string
30946 can be specified with the @samp{-f} option. The possible values of
30947 this option are the same as for @code{-var-set-format}
30948 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30949 the current display format will be used. The current display format
30950 can be changed using the @code{-var-set-format} command.
30956 Note that one must invoke @code{-var-list-children} for a variable
30957 before the value of a child variable can be evaluated.
30959 @subheading The @code{-var-assign} Command
30960 @findex -var-assign
30962 @subsubheading Synopsis
30965 -var-assign @var{name} @var{expression}
30968 Assigns the value of @var{expression} to the variable object specified
30969 by @var{name}. The object must be @samp{editable}. If the variable's
30970 value is altered by the assign, the variable will show up in any
30971 subsequent @code{-var-update} list.
30973 @subsubheading Example
30981 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30985 @subheading The @code{-var-update} Command
30986 @findex -var-update
30988 @subsubheading Synopsis
30991 -var-update [@var{print-values}] @{@var{name} | "*"@}
30994 Reevaluate the expressions corresponding to the variable object
30995 @var{name} and all its direct and indirect children, and return the
30996 list of variable objects whose values have changed; @var{name} must
30997 be a root variable object. Here, ``changed'' means that the result of
30998 @code{-var-evaluate-expression} before and after the
30999 @code{-var-update} is different. If @samp{*} is used as the variable
31000 object names, all existing variable objects are updated, except
31001 for frozen ones (@pxref{-var-set-frozen}). The option
31002 @var{print-values} determines whether both names and values, or just
31003 names are printed. The possible values of this option are the same
31004 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31005 recommended to use the @samp{--all-values} option, to reduce the
31006 number of MI commands needed on each program stop.
31008 With the @samp{*} parameter, if a variable object is bound to a
31009 currently running thread, it will not be updated, without any
31012 If @code{-var-set-update-range} was previously used on a varobj, then
31013 only the selected range of children will be reported.
31015 @code{-var-update} reports all the changed varobjs in a tuple named
31018 Each item in the change list is itself a tuple holding:
31022 The name of the varobj.
31025 If values were requested for this update, then this field will be
31026 present and will hold the value of the varobj.
31029 @anchor{-var-update}
31030 This field is a string which may take one of three values:
31034 The variable object's current value is valid.
31037 The variable object does not currently hold a valid value but it may
31038 hold one in the future if its associated expression comes back into
31042 The variable object no longer holds a valid value.
31043 This can occur when the executable file being debugged has changed,
31044 either through recompilation or by using the @value{GDBN} @code{file}
31045 command. The front end should normally choose to delete these variable
31049 In the future new values may be added to this list so the front should
31050 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31053 This is only present if the varobj is still valid. If the type
31054 changed, then this will be the string @samp{true}; otherwise it will
31057 When a varobj's type changes, its children are also likely to have
31058 become incorrect. Therefore, the varobj's children are automatically
31059 deleted when this attribute is @samp{true}. Also, the varobj's update
31060 range, when set using the @code{-var-set-update-range} command, is
31064 If the varobj's type changed, then this field will be present and will
31067 @item new_num_children
31068 For a dynamic varobj, if the number of children changed, or if the
31069 type changed, this will be the new number of children.
31071 The @samp{numchild} field in other varobj responses is generally not
31072 valid for a dynamic varobj -- it will show the number of children that
31073 @value{GDBN} knows about, but because dynamic varobjs lazily
31074 instantiate their children, this will not reflect the number of
31075 children which may be available.
31077 The @samp{new_num_children} attribute only reports changes to the
31078 number of children known by @value{GDBN}. This is the only way to
31079 detect whether an update has removed children (which necessarily can
31080 only happen at the end of the update range).
31083 The display hint, if any.
31086 This is an integer value, which will be 1 if there are more children
31087 available outside the varobj's update range.
31090 This attribute will be present and have the value @samp{1} if the
31091 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31092 then this attribute will not be present.
31095 If new children were added to a dynamic varobj within the selected
31096 update range (as set by @code{-var-set-update-range}), then they will
31097 be listed in this attribute.
31100 @subsubheading Example
31107 -var-update --all-values var1
31108 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31109 type_changed="false"@}]
31113 @subheading The @code{-var-set-frozen} Command
31114 @findex -var-set-frozen
31115 @anchor{-var-set-frozen}
31117 @subsubheading Synopsis
31120 -var-set-frozen @var{name} @var{flag}
31123 Set the frozenness flag on the variable object @var{name}. The
31124 @var{flag} parameter should be either @samp{1} to make the variable
31125 frozen or @samp{0} to make it unfrozen. If a variable object is
31126 frozen, then neither itself, nor any of its children, are
31127 implicitly updated by @code{-var-update} of
31128 a parent variable or by @code{-var-update *}. Only
31129 @code{-var-update} of the variable itself will update its value and
31130 values of its children. After a variable object is unfrozen, it is
31131 implicitly updated by all subsequent @code{-var-update} operations.
31132 Unfreezing a variable does not update it, only subsequent
31133 @code{-var-update} does.
31135 @subsubheading Example
31139 -var-set-frozen V 1
31144 @subheading The @code{-var-set-update-range} command
31145 @findex -var-set-update-range
31146 @anchor{-var-set-update-range}
31148 @subsubheading Synopsis
31151 -var-set-update-range @var{name} @var{from} @var{to}
31154 Set the range of children to be returned by future invocations of
31155 @code{-var-update}.
31157 @var{from} and @var{to} indicate the range of children to report. If
31158 @var{from} or @var{to} is less than zero, the range is reset and all
31159 children will be reported. Otherwise, children starting at @var{from}
31160 (zero-based) and up to and excluding @var{to} will be reported.
31162 @subsubheading Example
31166 -var-set-update-range V 1 2
31170 @subheading The @code{-var-set-visualizer} command
31171 @findex -var-set-visualizer
31172 @anchor{-var-set-visualizer}
31174 @subsubheading Synopsis
31177 -var-set-visualizer @var{name} @var{visualizer}
31180 Set a visualizer for the variable object @var{name}.
31182 @var{visualizer} is the visualizer to use. The special value
31183 @samp{None} means to disable any visualizer in use.
31185 If not @samp{None}, @var{visualizer} must be a Python expression.
31186 This expression must evaluate to a callable object which accepts a
31187 single argument. @value{GDBN} will call this object with the value of
31188 the varobj @var{name} as an argument (this is done so that the same
31189 Python pretty-printing code can be used for both the CLI and MI).
31190 When called, this object must return an object which conforms to the
31191 pretty-printing interface (@pxref{Pretty Printing API}).
31193 The pre-defined function @code{gdb.default_visualizer} may be used to
31194 select a visualizer by following the built-in process
31195 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31196 a varobj is created, and so ordinarily is not needed.
31198 This feature is only available if Python support is enabled. The MI
31199 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31200 can be used to check this.
31202 @subsubheading Example
31204 Resetting the visualizer:
31208 -var-set-visualizer V None
31212 Reselecting the default (type-based) visualizer:
31216 -var-set-visualizer V gdb.default_visualizer
31220 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31221 can be used to instantiate this class for a varobj:
31225 -var-set-visualizer V "lambda val: SomeClass()"
31229 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31230 @node GDB/MI Data Manipulation
31231 @section @sc{gdb/mi} Data Manipulation
31233 @cindex data manipulation, in @sc{gdb/mi}
31234 @cindex @sc{gdb/mi}, data manipulation
31235 This section describes the @sc{gdb/mi} commands that manipulate data:
31236 examine memory and registers, evaluate expressions, etc.
31238 @c REMOVED FROM THE INTERFACE.
31239 @c @subheading -data-assign
31240 @c Change the value of a program variable. Plenty of side effects.
31241 @c @subsubheading GDB Command
31243 @c @subsubheading Example
31246 @subheading The @code{-data-disassemble} Command
31247 @findex -data-disassemble
31249 @subsubheading Synopsis
31253 [ -s @var{start-addr} -e @var{end-addr} ]
31254 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31262 @item @var{start-addr}
31263 is the beginning address (or @code{$pc})
31264 @item @var{end-addr}
31266 @item @var{filename}
31267 is the name of the file to disassemble
31268 @item @var{linenum}
31269 is the line number to disassemble around
31271 is the number of disassembly lines to be produced. If it is -1,
31272 the whole function will be disassembled, in case no @var{end-addr} is
31273 specified. If @var{end-addr} is specified as a non-zero value, and
31274 @var{lines} is lower than the number of disassembly lines between
31275 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31276 displayed; if @var{lines} is higher than the number of lines between
31277 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31280 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31281 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31282 mixed source and disassembly with raw opcodes).
31285 @subsubheading Result
31287 The result of the @code{-data-disassemble} command will be a list named
31288 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31289 used with the @code{-data-disassemble} command.
31291 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31296 The address at which this instruction was disassembled.
31299 The name of the function this instruction is within.
31302 The decimal offset in bytes from the start of @samp{func-name}.
31305 The text disassembly for this @samp{address}.
31308 This field is only present for mode 2. This contains the raw opcode
31309 bytes for the @samp{inst} field.
31313 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31314 @samp{src_and_asm_line}, each of which has the following fields:
31318 The line number within @samp{file}.
31321 The file name from the compilation unit. This might be an absolute
31322 file name or a relative file name depending on the compile command
31326 Absolute file name of @samp{file}. It is converted to a canonical form
31327 using the source file search path
31328 (@pxref{Source Path, ,Specifying Source Directories})
31329 and after resolving all the symbolic links.
31331 If the source file is not found this field will contain the path as
31332 present in the debug information.
31334 @item line_asm_insn
31335 This is a list of tuples containing the disassembly for @samp{line} in
31336 @samp{file}. The fields of each tuple are the same as for
31337 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31338 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31343 Note that whatever included in the @samp{inst} field, is not
31344 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31347 @subsubheading @value{GDBN} Command
31349 The corresponding @value{GDBN} command is @samp{disassemble}.
31351 @subsubheading Example
31353 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31357 -data-disassemble -s $pc -e "$pc + 20" -- 0
31360 @{address="0x000107c0",func-name="main",offset="4",
31361 inst="mov 2, %o0"@},
31362 @{address="0x000107c4",func-name="main",offset="8",
31363 inst="sethi %hi(0x11800), %o2"@},
31364 @{address="0x000107c8",func-name="main",offset="12",
31365 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31366 @{address="0x000107cc",func-name="main",offset="16",
31367 inst="sethi %hi(0x11800), %o2"@},
31368 @{address="0x000107d0",func-name="main",offset="20",
31369 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31373 Disassemble the whole @code{main} function. Line 32 is part of
31377 -data-disassemble -f basics.c -l 32 -- 0
31379 @{address="0x000107bc",func-name="main",offset="0",
31380 inst="save %sp, -112, %sp"@},
31381 @{address="0x000107c0",func-name="main",offset="4",
31382 inst="mov 2, %o0"@},
31383 @{address="0x000107c4",func-name="main",offset="8",
31384 inst="sethi %hi(0x11800), %o2"@},
31386 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31387 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31391 Disassemble 3 instructions from the start of @code{main}:
31395 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31397 @{address="0x000107bc",func-name="main",offset="0",
31398 inst="save %sp, -112, %sp"@},
31399 @{address="0x000107c0",func-name="main",offset="4",
31400 inst="mov 2, %o0"@},
31401 @{address="0x000107c4",func-name="main",offset="8",
31402 inst="sethi %hi(0x11800), %o2"@}]
31406 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31410 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31412 src_and_asm_line=@{line="31",
31413 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31414 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31415 line_asm_insn=[@{address="0x000107bc",
31416 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31417 src_and_asm_line=@{line="32",
31418 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31419 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31420 line_asm_insn=[@{address="0x000107c0",
31421 func-name="main",offset="4",inst="mov 2, %o0"@},
31422 @{address="0x000107c4",func-name="main",offset="8",
31423 inst="sethi %hi(0x11800), %o2"@}]@}]
31428 @subheading The @code{-data-evaluate-expression} Command
31429 @findex -data-evaluate-expression
31431 @subsubheading Synopsis
31434 -data-evaluate-expression @var{expr}
31437 Evaluate @var{expr} as an expression. The expression could contain an
31438 inferior function call. The function call will execute synchronously.
31439 If the expression contains spaces, it must be enclosed in double quotes.
31441 @subsubheading @value{GDBN} Command
31443 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31444 @samp{call}. In @code{gdbtk} only, there's a corresponding
31445 @samp{gdb_eval} command.
31447 @subsubheading Example
31449 In the following example, the numbers that precede the commands are the
31450 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31451 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31455 211-data-evaluate-expression A
31458 311-data-evaluate-expression &A
31459 311^done,value="0xefffeb7c"
31461 411-data-evaluate-expression A+3
31464 511-data-evaluate-expression "A + 3"
31470 @subheading The @code{-data-list-changed-registers} Command
31471 @findex -data-list-changed-registers
31473 @subsubheading Synopsis
31476 -data-list-changed-registers
31479 Display a list of the registers that have changed.
31481 @subsubheading @value{GDBN} Command
31483 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31484 has the corresponding command @samp{gdb_changed_register_list}.
31486 @subsubheading Example
31488 On a PPC MBX board:
31496 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31497 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31500 -data-list-changed-registers
31501 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31502 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31503 "24","25","26","27","28","30","31","64","65","66","67","69"]
31508 @subheading The @code{-data-list-register-names} Command
31509 @findex -data-list-register-names
31511 @subsubheading Synopsis
31514 -data-list-register-names [ ( @var{regno} )+ ]
31517 Show a list of register names for the current target. If no arguments
31518 are given, it shows a list of the names of all the registers. If
31519 integer numbers are given as arguments, it will print a list of the
31520 names of the registers corresponding to the arguments. To ensure
31521 consistency between a register name and its number, the output list may
31522 include empty register names.
31524 @subsubheading @value{GDBN} Command
31526 @value{GDBN} does not have a command which corresponds to
31527 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31528 corresponding command @samp{gdb_regnames}.
31530 @subsubheading Example
31532 For the PPC MBX board:
31535 -data-list-register-names
31536 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31537 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31538 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31539 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31540 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31541 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31542 "", "pc","ps","cr","lr","ctr","xer"]
31544 -data-list-register-names 1 2 3
31545 ^done,register-names=["r1","r2","r3"]
31549 @subheading The @code{-data-list-register-values} Command
31550 @findex -data-list-register-values
31552 @subsubheading Synopsis
31555 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31558 Display the registers' contents. @var{fmt} is the format according to
31559 which the registers' contents are to be returned, followed by an optional
31560 list of numbers specifying the registers to display. A missing list of
31561 numbers indicates that the contents of all the registers must be returned.
31563 Allowed formats for @var{fmt} are:
31580 @subsubheading @value{GDBN} Command
31582 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31583 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31585 @subsubheading Example
31587 For a PPC MBX board (note: line breaks are for readability only, they
31588 don't appear in the actual output):
31592 -data-list-register-values r 64 65
31593 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31594 @{number="65",value="0x00029002"@}]
31596 -data-list-register-values x
31597 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31598 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31599 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31600 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31601 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31602 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31603 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31604 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31605 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31606 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31607 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31608 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31609 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31610 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31611 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31612 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31613 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31614 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31615 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31616 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31617 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31618 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31619 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31620 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31621 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31622 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31623 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31624 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31625 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31626 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31627 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31628 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31629 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31630 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31631 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31632 @{number="69",value="0x20002b03"@}]
31637 @subheading The @code{-data-read-memory} Command
31638 @findex -data-read-memory
31640 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31642 @subsubheading Synopsis
31645 -data-read-memory [ -o @var{byte-offset} ]
31646 @var{address} @var{word-format} @var{word-size}
31647 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31654 @item @var{address}
31655 An expression specifying the address of the first memory word to be
31656 read. Complex expressions containing embedded white space should be
31657 quoted using the C convention.
31659 @item @var{word-format}
31660 The format to be used to print the memory words. The notation is the
31661 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31664 @item @var{word-size}
31665 The size of each memory word in bytes.
31667 @item @var{nr-rows}
31668 The number of rows in the output table.
31670 @item @var{nr-cols}
31671 The number of columns in the output table.
31674 If present, indicates that each row should include an @sc{ascii} dump. The
31675 value of @var{aschar} is used as a padding character when a byte is not a
31676 member of the printable @sc{ascii} character set (printable @sc{ascii}
31677 characters are those whose code is between 32 and 126, inclusively).
31679 @item @var{byte-offset}
31680 An offset to add to the @var{address} before fetching memory.
31683 This command displays memory contents as a table of @var{nr-rows} by
31684 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31685 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31686 (returned as @samp{total-bytes}). Should less than the requested number
31687 of bytes be returned by the target, the missing words are identified
31688 using @samp{N/A}. The number of bytes read from the target is returned
31689 in @samp{nr-bytes} and the starting address used to read memory in
31692 The address of the next/previous row or page is available in
31693 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31696 @subsubheading @value{GDBN} Command
31698 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31699 @samp{gdb_get_mem} memory read command.
31701 @subsubheading Example
31703 Read six bytes of memory starting at @code{bytes+6} but then offset by
31704 @code{-6} bytes. Format as three rows of two columns. One byte per
31705 word. Display each word in hex.
31709 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31710 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31711 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31712 prev-page="0x0000138a",memory=[
31713 @{addr="0x00001390",data=["0x00","0x01"]@},
31714 @{addr="0x00001392",data=["0x02","0x03"]@},
31715 @{addr="0x00001394",data=["0x04","0x05"]@}]
31719 Read two bytes of memory starting at address @code{shorts + 64} and
31720 display as a single word formatted in decimal.
31724 5-data-read-memory shorts+64 d 2 1 1
31725 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31726 next-row="0x00001512",prev-row="0x0000150e",
31727 next-page="0x00001512",prev-page="0x0000150e",memory=[
31728 @{addr="0x00001510",data=["128"]@}]
31732 Read thirty two bytes of memory starting at @code{bytes+16} and format
31733 as eight rows of four columns. Include a string encoding with @samp{x}
31734 used as the non-printable character.
31738 4-data-read-memory bytes+16 x 1 8 4 x
31739 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31740 next-row="0x000013c0",prev-row="0x0000139c",
31741 next-page="0x000013c0",prev-page="0x00001380",memory=[
31742 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31743 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31744 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31745 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31746 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31747 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31748 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31749 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31753 @subheading The @code{-data-read-memory-bytes} Command
31754 @findex -data-read-memory-bytes
31756 @subsubheading Synopsis
31759 -data-read-memory-bytes [ -o @var{byte-offset} ]
31760 @var{address} @var{count}
31767 @item @var{address}
31768 An expression specifying the address of the first memory word to be
31769 read. Complex expressions containing embedded white space should be
31770 quoted using the C convention.
31773 The number of bytes to read. This should be an integer literal.
31775 @item @var{byte-offset}
31776 The offsets in bytes relative to @var{address} at which to start
31777 reading. This should be an integer literal. This option is provided
31778 so that a frontend is not required to first evaluate address and then
31779 perform address arithmetics itself.
31783 This command attempts to read all accessible memory regions in the
31784 specified range. First, all regions marked as unreadable in the memory
31785 map (if one is defined) will be skipped. @xref{Memory Region
31786 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31787 regions. For each one, if reading full region results in an errors,
31788 @value{GDBN} will try to read a subset of the region.
31790 In general, every single byte in the region may be readable or not,
31791 and the only way to read every readable byte is to try a read at
31792 every address, which is not practical. Therefore, @value{GDBN} will
31793 attempt to read all accessible bytes at either beginning or the end
31794 of the region, using a binary division scheme. This heuristic works
31795 well for reading accross a memory map boundary. Note that if a region
31796 has a readable range that is neither at the beginning or the end,
31797 @value{GDBN} will not read it.
31799 The result record (@pxref{GDB/MI Result Records}) that is output of
31800 the command includes a field named @samp{memory} whose content is a
31801 list of tuples. Each tuple represent a successfully read memory block
31802 and has the following fields:
31806 The start address of the memory block, as hexadecimal literal.
31809 The end address of the memory block, as hexadecimal literal.
31812 The offset of the memory block, as hexadecimal literal, relative to
31813 the start address passed to @code{-data-read-memory-bytes}.
31816 The contents of the memory block, in hex.
31822 @subsubheading @value{GDBN} Command
31824 The corresponding @value{GDBN} command is @samp{x}.
31826 @subsubheading Example
31830 -data-read-memory-bytes &a 10
31831 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31833 contents="01000000020000000300"@}]
31838 @subheading The @code{-data-write-memory-bytes} Command
31839 @findex -data-write-memory-bytes
31841 @subsubheading Synopsis
31844 -data-write-memory-bytes @var{address} @var{contents}
31845 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31852 @item @var{address}
31853 An expression specifying the address of the first memory word to be
31854 read. Complex expressions containing embedded white space should be
31855 quoted using the C convention.
31857 @item @var{contents}
31858 The hex-encoded bytes to write.
31861 Optional argument indicating the number of bytes to be written. If @var{count}
31862 is greater than @var{contents}' length, @value{GDBN} will repeatedly
31863 write @var{contents} until it fills @var{count} bytes.
31867 @subsubheading @value{GDBN} Command
31869 There's no corresponding @value{GDBN} command.
31871 @subsubheading Example
31875 -data-write-memory-bytes &a "aabbccdd"
31882 -data-write-memory-bytes &a "aabbccdd" 16e
31887 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31888 @node GDB/MI Tracepoint Commands
31889 @section @sc{gdb/mi} Tracepoint Commands
31891 The commands defined in this section implement MI support for
31892 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31894 @subheading The @code{-trace-find} Command
31895 @findex -trace-find
31897 @subsubheading Synopsis
31900 -trace-find @var{mode} [@var{parameters}@dots{}]
31903 Find a trace frame using criteria defined by @var{mode} and
31904 @var{parameters}. The following table lists permissible
31905 modes and their parameters. For details of operation, see @ref{tfind}.
31910 No parameters are required. Stops examining trace frames.
31913 An integer is required as parameter. Selects tracepoint frame with
31916 @item tracepoint-number
31917 An integer is required as parameter. Finds next
31918 trace frame that corresponds to tracepoint with the specified number.
31921 An address is required as parameter. Finds
31922 next trace frame that corresponds to any tracepoint at the specified
31925 @item pc-inside-range
31926 Two addresses are required as parameters. Finds next trace
31927 frame that corresponds to a tracepoint at an address inside the
31928 specified range. Both bounds are considered to be inside the range.
31930 @item pc-outside-range
31931 Two addresses are required as parameters. Finds
31932 next trace frame that corresponds to a tracepoint at an address outside
31933 the specified range. Both bounds are considered to be inside the range.
31936 Line specification is required as parameter. @xref{Specify Location}.
31937 Finds next trace frame that corresponds to a tracepoint at
31938 the specified location.
31942 If @samp{none} was passed as @var{mode}, the response does not
31943 have fields. Otherwise, the response may have the following fields:
31947 This field has either @samp{0} or @samp{1} as the value, depending
31948 on whether a matching tracepoint was found.
31951 The index of the found traceframe. This field is present iff
31952 the @samp{found} field has value of @samp{1}.
31955 The index of the found tracepoint. This field is present iff
31956 the @samp{found} field has value of @samp{1}.
31959 The information about the frame corresponding to the found trace
31960 frame. This field is present only if a trace frame was found.
31961 @xref{GDB/MI Frame Information}, for description of this field.
31965 @subsubheading @value{GDBN} Command
31967 The corresponding @value{GDBN} command is @samp{tfind}.
31969 @subheading -trace-define-variable
31970 @findex -trace-define-variable
31972 @subsubheading Synopsis
31975 -trace-define-variable @var{name} [ @var{value} ]
31978 Create trace variable @var{name} if it does not exist. If
31979 @var{value} is specified, sets the initial value of the specified
31980 trace variable to that value. Note that the @var{name} should start
31981 with the @samp{$} character.
31983 @subsubheading @value{GDBN} Command
31985 The corresponding @value{GDBN} command is @samp{tvariable}.
31987 @subheading -trace-list-variables
31988 @findex -trace-list-variables
31990 @subsubheading Synopsis
31993 -trace-list-variables
31996 Return a table of all defined trace variables. Each element of the
31997 table has the following fields:
32001 The name of the trace variable. This field is always present.
32004 The initial value. This is a 64-bit signed integer. This
32005 field is always present.
32008 The value the trace variable has at the moment. This is a 64-bit
32009 signed integer. This field is absent iff current value is
32010 not defined, for example if the trace was never run, or is
32015 @subsubheading @value{GDBN} Command
32017 The corresponding @value{GDBN} command is @samp{tvariables}.
32019 @subsubheading Example
32023 -trace-list-variables
32024 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32025 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32026 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32027 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32028 body=[variable=@{name="$trace_timestamp",initial="0"@}
32029 variable=@{name="$foo",initial="10",current="15"@}]@}
32033 @subheading -trace-save
32034 @findex -trace-save
32036 @subsubheading Synopsis
32039 -trace-save [-r ] @var{filename}
32042 Saves the collected trace data to @var{filename}. Without the
32043 @samp{-r} option, the data is downloaded from the target and saved
32044 in a local file. With the @samp{-r} option the target is asked
32045 to perform the save.
32047 @subsubheading @value{GDBN} Command
32049 The corresponding @value{GDBN} command is @samp{tsave}.
32052 @subheading -trace-start
32053 @findex -trace-start
32055 @subsubheading Synopsis
32061 Starts a tracing experiments. The result of this command does not
32064 @subsubheading @value{GDBN} Command
32066 The corresponding @value{GDBN} command is @samp{tstart}.
32068 @subheading -trace-status
32069 @findex -trace-status
32071 @subsubheading Synopsis
32077 Obtains the status of a tracing experiment. The result may include
32078 the following fields:
32083 May have a value of either @samp{0}, when no tracing operations are
32084 supported, @samp{1}, when all tracing operations are supported, or
32085 @samp{file} when examining trace file. In the latter case, examining
32086 of trace frame is possible but new tracing experiement cannot be
32087 started. This field is always present.
32090 May have a value of either @samp{0} or @samp{1} depending on whether
32091 tracing experiement is in progress on target. This field is present
32092 if @samp{supported} field is not @samp{0}.
32095 Report the reason why the tracing was stopped last time. This field
32096 may be absent iff tracing was never stopped on target yet. The
32097 value of @samp{request} means the tracing was stopped as result of
32098 the @code{-trace-stop} command. The value of @samp{overflow} means
32099 the tracing buffer is full. The value of @samp{disconnection} means
32100 tracing was automatically stopped when @value{GDBN} has disconnected.
32101 The value of @samp{passcount} means tracing was stopped when a
32102 tracepoint was passed a maximal number of times for that tracepoint.
32103 This field is present if @samp{supported} field is not @samp{0}.
32105 @item stopping-tracepoint
32106 The number of tracepoint whose passcount as exceeded. This field is
32107 present iff the @samp{stop-reason} field has the value of
32111 @itemx frames-created
32112 The @samp{frames} field is a count of the total number of trace frames
32113 in the trace buffer, while @samp{frames-created} is the total created
32114 during the run, including ones that were discarded, such as when a
32115 circular trace buffer filled up. Both fields are optional.
32119 These fields tell the current size of the tracing buffer and the
32120 remaining space. These fields are optional.
32123 The value of the circular trace buffer flag. @code{1} means that the
32124 trace buffer is circular and old trace frames will be discarded if
32125 necessary to make room, @code{0} means that the trace buffer is linear
32129 The value of the disconnected tracing flag. @code{1} means that
32130 tracing will continue after @value{GDBN} disconnects, @code{0} means
32131 that the trace run will stop.
32134 The filename of the trace file being examined. This field is
32135 optional, and only present when examining a trace file.
32139 @subsubheading @value{GDBN} Command
32141 The corresponding @value{GDBN} command is @samp{tstatus}.
32143 @subheading -trace-stop
32144 @findex -trace-stop
32146 @subsubheading Synopsis
32152 Stops a tracing experiment. The result of this command has the same
32153 fields as @code{-trace-status}, except that the @samp{supported} and
32154 @samp{running} fields are not output.
32156 @subsubheading @value{GDBN} Command
32158 The corresponding @value{GDBN} command is @samp{tstop}.
32161 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32162 @node GDB/MI Symbol Query
32163 @section @sc{gdb/mi} Symbol Query Commands
32167 @subheading The @code{-symbol-info-address} Command
32168 @findex -symbol-info-address
32170 @subsubheading Synopsis
32173 -symbol-info-address @var{symbol}
32176 Describe where @var{symbol} is stored.
32178 @subsubheading @value{GDBN} Command
32180 The corresponding @value{GDBN} command is @samp{info address}.
32182 @subsubheading Example
32186 @subheading The @code{-symbol-info-file} Command
32187 @findex -symbol-info-file
32189 @subsubheading Synopsis
32195 Show the file for the symbol.
32197 @subsubheading @value{GDBN} Command
32199 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32200 @samp{gdb_find_file}.
32202 @subsubheading Example
32206 @subheading The @code{-symbol-info-function} Command
32207 @findex -symbol-info-function
32209 @subsubheading Synopsis
32212 -symbol-info-function
32215 Show which function the symbol lives in.
32217 @subsubheading @value{GDBN} Command
32219 @samp{gdb_get_function} in @code{gdbtk}.
32221 @subsubheading Example
32225 @subheading The @code{-symbol-info-line} Command
32226 @findex -symbol-info-line
32228 @subsubheading Synopsis
32234 Show the core addresses of the code for a source line.
32236 @subsubheading @value{GDBN} Command
32238 The corresponding @value{GDBN} command is @samp{info line}.
32239 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32241 @subsubheading Example
32245 @subheading The @code{-symbol-info-symbol} Command
32246 @findex -symbol-info-symbol
32248 @subsubheading Synopsis
32251 -symbol-info-symbol @var{addr}
32254 Describe what symbol is at location @var{addr}.
32256 @subsubheading @value{GDBN} Command
32258 The corresponding @value{GDBN} command is @samp{info symbol}.
32260 @subsubheading Example
32264 @subheading The @code{-symbol-list-functions} Command
32265 @findex -symbol-list-functions
32267 @subsubheading Synopsis
32270 -symbol-list-functions
32273 List the functions in the executable.
32275 @subsubheading @value{GDBN} Command
32277 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32278 @samp{gdb_search} in @code{gdbtk}.
32280 @subsubheading Example
32285 @subheading The @code{-symbol-list-lines} Command
32286 @findex -symbol-list-lines
32288 @subsubheading Synopsis
32291 -symbol-list-lines @var{filename}
32294 Print the list of lines that contain code and their associated program
32295 addresses for the given source filename. The entries are sorted in
32296 ascending PC order.
32298 @subsubheading @value{GDBN} Command
32300 There is no corresponding @value{GDBN} command.
32302 @subsubheading Example
32305 -symbol-list-lines basics.c
32306 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32312 @subheading The @code{-symbol-list-types} Command
32313 @findex -symbol-list-types
32315 @subsubheading Synopsis
32321 List all the type names.
32323 @subsubheading @value{GDBN} Command
32325 The corresponding commands are @samp{info types} in @value{GDBN},
32326 @samp{gdb_search} in @code{gdbtk}.
32328 @subsubheading Example
32332 @subheading The @code{-symbol-list-variables} Command
32333 @findex -symbol-list-variables
32335 @subsubheading Synopsis
32338 -symbol-list-variables
32341 List all the global and static variable names.
32343 @subsubheading @value{GDBN} Command
32345 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32347 @subsubheading Example
32351 @subheading The @code{-symbol-locate} Command
32352 @findex -symbol-locate
32354 @subsubheading Synopsis
32360 @subsubheading @value{GDBN} Command
32362 @samp{gdb_loc} in @code{gdbtk}.
32364 @subsubheading Example
32368 @subheading The @code{-symbol-type} Command
32369 @findex -symbol-type
32371 @subsubheading Synopsis
32374 -symbol-type @var{variable}
32377 Show type of @var{variable}.
32379 @subsubheading @value{GDBN} Command
32381 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32382 @samp{gdb_obj_variable}.
32384 @subsubheading Example
32389 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32390 @node GDB/MI File Commands
32391 @section @sc{gdb/mi} File Commands
32393 This section describes the GDB/MI commands to specify executable file names
32394 and to read in and obtain symbol table information.
32396 @subheading The @code{-file-exec-and-symbols} Command
32397 @findex -file-exec-and-symbols
32399 @subsubheading Synopsis
32402 -file-exec-and-symbols @var{file}
32405 Specify the executable file to be debugged. This file is the one from
32406 which the symbol table is also read. If no file is specified, the
32407 command clears the executable and symbol information. If breakpoints
32408 are set when using this command with no arguments, @value{GDBN} will produce
32409 error messages. Otherwise, no output is produced, except a completion
32412 @subsubheading @value{GDBN} Command
32414 The corresponding @value{GDBN} command is @samp{file}.
32416 @subsubheading Example
32420 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32426 @subheading The @code{-file-exec-file} Command
32427 @findex -file-exec-file
32429 @subsubheading Synopsis
32432 -file-exec-file @var{file}
32435 Specify the executable file to be debugged. Unlike
32436 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32437 from this file. If used without argument, @value{GDBN} clears the information
32438 about the executable file. No output is produced, except a completion
32441 @subsubheading @value{GDBN} Command
32443 The corresponding @value{GDBN} command is @samp{exec-file}.
32445 @subsubheading Example
32449 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32456 @subheading The @code{-file-list-exec-sections} Command
32457 @findex -file-list-exec-sections
32459 @subsubheading Synopsis
32462 -file-list-exec-sections
32465 List the sections of the current executable file.
32467 @subsubheading @value{GDBN} Command
32469 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32470 information as this command. @code{gdbtk} has a corresponding command
32471 @samp{gdb_load_info}.
32473 @subsubheading Example
32478 @subheading The @code{-file-list-exec-source-file} Command
32479 @findex -file-list-exec-source-file
32481 @subsubheading Synopsis
32484 -file-list-exec-source-file
32487 List the line number, the current source file, and the absolute path
32488 to the current source file for the current executable. The macro
32489 information field has a value of @samp{1} or @samp{0} depending on
32490 whether or not the file includes preprocessor macro information.
32492 @subsubheading @value{GDBN} Command
32494 The @value{GDBN} equivalent is @samp{info source}
32496 @subsubheading Example
32500 123-file-list-exec-source-file
32501 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32506 @subheading The @code{-file-list-exec-source-files} Command
32507 @findex -file-list-exec-source-files
32509 @subsubheading Synopsis
32512 -file-list-exec-source-files
32515 List the source files for the current executable.
32517 It will always output both the filename and fullname (absolute file
32518 name) of a source file.
32520 @subsubheading @value{GDBN} Command
32522 The @value{GDBN} equivalent is @samp{info sources}.
32523 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32525 @subsubheading Example
32528 -file-list-exec-source-files
32530 @{file=foo.c,fullname=/home/foo.c@},
32531 @{file=/home/bar.c,fullname=/home/bar.c@},
32532 @{file=gdb_could_not_find_fullpath.c@}]
32537 @subheading The @code{-file-list-shared-libraries} Command
32538 @findex -file-list-shared-libraries
32540 @subsubheading Synopsis
32543 -file-list-shared-libraries
32546 List the shared libraries in the program.
32548 @subsubheading @value{GDBN} Command
32550 The corresponding @value{GDBN} command is @samp{info shared}.
32552 @subsubheading Example
32556 @subheading The @code{-file-list-symbol-files} Command
32557 @findex -file-list-symbol-files
32559 @subsubheading Synopsis
32562 -file-list-symbol-files
32567 @subsubheading @value{GDBN} Command
32569 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32571 @subsubheading Example
32576 @subheading The @code{-file-symbol-file} Command
32577 @findex -file-symbol-file
32579 @subsubheading Synopsis
32582 -file-symbol-file @var{file}
32585 Read symbol table info from the specified @var{file} argument. When
32586 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32587 produced, except for a completion notification.
32589 @subsubheading @value{GDBN} Command
32591 The corresponding @value{GDBN} command is @samp{symbol-file}.
32593 @subsubheading Example
32597 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32603 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32604 @node GDB/MI Memory Overlay Commands
32605 @section @sc{gdb/mi} Memory Overlay Commands
32607 The memory overlay commands are not implemented.
32609 @c @subheading -overlay-auto
32611 @c @subheading -overlay-list-mapping-state
32613 @c @subheading -overlay-list-overlays
32615 @c @subheading -overlay-map
32617 @c @subheading -overlay-off
32619 @c @subheading -overlay-on
32621 @c @subheading -overlay-unmap
32623 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32624 @node GDB/MI Signal Handling Commands
32625 @section @sc{gdb/mi} Signal Handling Commands
32627 Signal handling commands are not implemented.
32629 @c @subheading -signal-handle
32631 @c @subheading -signal-list-handle-actions
32633 @c @subheading -signal-list-signal-types
32637 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32638 @node GDB/MI Target Manipulation
32639 @section @sc{gdb/mi} Target Manipulation Commands
32642 @subheading The @code{-target-attach} Command
32643 @findex -target-attach
32645 @subsubheading Synopsis
32648 -target-attach @var{pid} | @var{gid} | @var{file}
32651 Attach to a process @var{pid} or a file @var{file} outside of
32652 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32653 group, the id previously returned by
32654 @samp{-list-thread-groups --available} must be used.
32656 @subsubheading @value{GDBN} Command
32658 The corresponding @value{GDBN} command is @samp{attach}.
32660 @subsubheading Example
32664 =thread-created,id="1"
32665 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32671 @subheading The @code{-target-compare-sections} Command
32672 @findex -target-compare-sections
32674 @subsubheading Synopsis
32677 -target-compare-sections [ @var{section} ]
32680 Compare data of section @var{section} on target to the exec file.
32681 Without the argument, all sections are compared.
32683 @subsubheading @value{GDBN} Command
32685 The @value{GDBN} equivalent is @samp{compare-sections}.
32687 @subsubheading Example
32692 @subheading The @code{-target-detach} Command
32693 @findex -target-detach
32695 @subsubheading Synopsis
32698 -target-detach [ @var{pid} | @var{gid} ]
32701 Detach from the remote target which normally resumes its execution.
32702 If either @var{pid} or @var{gid} is specified, detaches from either
32703 the specified process, or specified thread group. There's no output.
32705 @subsubheading @value{GDBN} Command
32707 The corresponding @value{GDBN} command is @samp{detach}.
32709 @subsubheading Example
32719 @subheading The @code{-target-disconnect} Command
32720 @findex -target-disconnect
32722 @subsubheading Synopsis
32728 Disconnect from the remote target. There's no output and the target is
32729 generally not resumed.
32731 @subsubheading @value{GDBN} Command
32733 The corresponding @value{GDBN} command is @samp{disconnect}.
32735 @subsubheading Example
32745 @subheading The @code{-target-download} Command
32746 @findex -target-download
32748 @subsubheading Synopsis
32754 Loads the executable onto the remote target.
32755 It prints out an update message every half second, which includes the fields:
32759 The name of the section.
32761 The size of what has been sent so far for that section.
32763 The size of the section.
32765 The total size of what was sent so far (the current and the previous sections).
32767 The size of the overall executable to download.
32771 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32772 @sc{gdb/mi} Output Syntax}).
32774 In addition, it prints the name and size of the sections, as they are
32775 downloaded. These messages include the following fields:
32779 The name of the section.
32781 The size of the section.
32783 The size of the overall executable to download.
32787 At the end, a summary is printed.
32789 @subsubheading @value{GDBN} Command
32791 The corresponding @value{GDBN} command is @samp{load}.
32793 @subsubheading Example
32795 Note: each status message appears on a single line. Here the messages
32796 have been broken down so that they can fit onto a page.
32801 +download,@{section=".text",section-size="6668",total-size="9880"@}
32802 +download,@{section=".text",section-sent="512",section-size="6668",
32803 total-sent="512",total-size="9880"@}
32804 +download,@{section=".text",section-sent="1024",section-size="6668",
32805 total-sent="1024",total-size="9880"@}
32806 +download,@{section=".text",section-sent="1536",section-size="6668",
32807 total-sent="1536",total-size="9880"@}
32808 +download,@{section=".text",section-sent="2048",section-size="6668",
32809 total-sent="2048",total-size="9880"@}
32810 +download,@{section=".text",section-sent="2560",section-size="6668",
32811 total-sent="2560",total-size="9880"@}
32812 +download,@{section=".text",section-sent="3072",section-size="6668",
32813 total-sent="3072",total-size="9880"@}
32814 +download,@{section=".text",section-sent="3584",section-size="6668",
32815 total-sent="3584",total-size="9880"@}
32816 +download,@{section=".text",section-sent="4096",section-size="6668",
32817 total-sent="4096",total-size="9880"@}
32818 +download,@{section=".text",section-sent="4608",section-size="6668",
32819 total-sent="4608",total-size="9880"@}
32820 +download,@{section=".text",section-sent="5120",section-size="6668",
32821 total-sent="5120",total-size="9880"@}
32822 +download,@{section=".text",section-sent="5632",section-size="6668",
32823 total-sent="5632",total-size="9880"@}
32824 +download,@{section=".text",section-sent="6144",section-size="6668",
32825 total-sent="6144",total-size="9880"@}
32826 +download,@{section=".text",section-sent="6656",section-size="6668",
32827 total-sent="6656",total-size="9880"@}
32828 +download,@{section=".init",section-size="28",total-size="9880"@}
32829 +download,@{section=".fini",section-size="28",total-size="9880"@}
32830 +download,@{section=".data",section-size="3156",total-size="9880"@}
32831 +download,@{section=".data",section-sent="512",section-size="3156",
32832 total-sent="7236",total-size="9880"@}
32833 +download,@{section=".data",section-sent="1024",section-size="3156",
32834 total-sent="7748",total-size="9880"@}
32835 +download,@{section=".data",section-sent="1536",section-size="3156",
32836 total-sent="8260",total-size="9880"@}
32837 +download,@{section=".data",section-sent="2048",section-size="3156",
32838 total-sent="8772",total-size="9880"@}
32839 +download,@{section=".data",section-sent="2560",section-size="3156",
32840 total-sent="9284",total-size="9880"@}
32841 +download,@{section=".data",section-sent="3072",section-size="3156",
32842 total-sent="9796",total-size="9880"@}
32843 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32850 @subheading The @code{-target-exec-status} Command
32851 @findex -target-exec-status
32853 @subsubheading Synopsis
32856 -target-exec-status
32859 Provide information on the state of the target (whether it is running or
32860 not, for instance).
32862 @subsubheading @value{GDBN} Command
32864 There's no equivalent @value{GDBN} command.
32866 @subsubheading Example
32870 @subheading The @code{-target-list-available-targets} Command
32871 @findex -target-list-available-targets
32873 @subsubheading Synopsis
32876 -target-list-available-targets
32879 List the possible targets to connect to.
32881 @subsubheading @value{GDBN} Command
32883 The corresponding @value{GDBN} command is @samp{help target}.
32885 @subsubheading Example
32889 @subheading The @code{-target-list-current-targets} Command
32890 @findex -target-list-current-targets
32892 @subsubheading Synopsis
32895 -target-list-current-targets
32898 Describe the current target.
32900 @subsubheading @value{GDBN} Command
32902 The corresponding information is printed by @samp{info file} (among
32905 @subsubheading Example
32909 @subheading The @code{-target-list-parameters} Command
32910 @findex -target-list-parameters
32912 @subsubheading Synopsis
32915 -target-list-parameters
32921 @subsubheading @value{GDBN} Command
32925 @subsubheading Example
32929 @subheading The @code{-target-select} Command
32930 @findex -target-select
32932 @subsubheading Synopsis
32935 -target-select @var{type} @var{parameters @dots{}}
32938 Connect @value{GDBN} to the remote target. This command takes two args:
32942 The type of target, for instance @samp{remote}, etc.
32943 @item @var{parameters}
32944 Device names, host names and the like. @xref{Target Commands, ,
32945 Commands for Managing Targets}, for more details.
32948 The output is a connection notification, followed by the address at
32949 which the target program is, in the following form:
32952 ^connected,addr="@var{address}",func="@var{function name}",
32953 args=[@var{arg list}]
32956 @subsubheading @value{GDBN} Command
32958 The corresponding @value{GDBN} command is @samp{target}.
32960 @subsubheading Example
32964 -target-select remote /dev/ttya
32965 ^connected,addr="0xfe00a300",func="??",args=[]
32969 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32970 @node GDB/MI File Transfer Commands
32971 @section @sc{gdb/mi} File Transfer Commands
32974 @subheading The @code{-target-file-put} Command
32975 @findex -target-file-put
32977 @subsubheading Synopsis
32980 -target-file-put @var{hostfile} @var{targetfile}
32983 Copy file @var{hostfile} from the host system (the machine running
32984 @value{GDBN}) to @var{targetfile} on the target system.
32986 @subsubheading @value{GDBN} Command
32988 The corresponding @value{GDBN} command is @samp{remote put}.
32990 @subsubheading Example
32994 -target-file-put localfile remotefile
33000 @subheading The @code{-target-file-get} Command
33001 @findex -target-file-get
33003 @subsubheading Synopsis
33006 -target-file-get @var{targetfile} @var{hostfile}
33009 Copy file @var{targetfile} from the target system to @var{hostfile}
33010 on the host system.
33012 @subsubheading @value{GDBN} Command
33014 The corresponding @value{GDBN} command is @samp{remote get}.
33016 @subsubheading Example
33020 -target-file-get remotefile localfile
33026 @subheading The @code{-target-file-delete} Command
33027 @findex -target-file-delete
33029 @subsubheading Synopsis
33032 -target-file-delete @var{targetfile}
33035 Delete @var{targetfile} from the target system.
33037 @subsubheading @value{GDBN} Command
33039 The corresponding @value{GDBN} command is @samp{remote delete}.
33041 @subsubheading Example
33045 -target-file-delete remotefile
33051 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33052 @node GDB/MI Miscellaneous Commands
33053 @section Miscellaneous @sc{gdb/mi} Commands
33055 @c @subheading -gdb-complete
33057 @subheading The @code{-gdb-exit} Command
33060 @subsubheading Synopsis
33066 Exit @value{GDBN} immediately.
33068 @subsubheading @value{GDBN} Command
33070 Approximately corresponds to @samp{quit}.
33072 @subsubheading Example
33082 @subheading The @code{-exec-abort} Command
33083 @findex -exec-abort
33085 @subsubheading Synopsis
33091 Kill the inferior running program.
33093 @subsubheading @value{GDBN} Command
33095 The corresponding @value{GDBN} command is @samp{kill}.
33097 @subsubheading Example
33102 @subheading The @code{-gdb-set} Command
33105 @subsubheading Synopsis
33111 Set an internal @value{GDBN} variable.
33112 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33114 @subsubheading @value{GDBN} Command
33116 The corresponding @value{GDBN} command is @samp{set}.
33118 @subsubheading Example
33128 @subheading The @code{-gdb-show} Command
33131 @subsubheading Synopsis
33137 Show the current value of a @value{GDBN} variable.
33139 @subsubheading @value{GDBN} Command
33141 The corresponding @value{GDBN} command is @samp{show}.
33143 @subsubheading Example
33152 @c @subheading -gdb-source
33155 @subheading The @code{-gdb-version} Command
33156 @findex -gdb-version
33158 @subsubheading Synopsis
33164 Show version information for @value{GDBN}. Used mostly in testing.
33166 @subsubheading @value{GDBN} Command
33168 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33169 default shows this information when you start an interactive session.
33171 @subsubheading Example
33173 @c This example modifies the actual output from GDB to avoid overfull
33179 ~Copyright 2000 Free Software Foundation, Inc.
33180 ~GDB is free software, covered by the GNU General Public License, and
33181 ~you are welcome to change it and/or distribute copies of it under
33182 ~ certain conditions.
33183 ~Type "show copying" to see the conditions.
33184 ~There is absolutely no warranty for GDB. Type "show warranty" for
33186 ~This GDB was configured as
33187 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33192 @subheading The @code{-list-features} Command
33193 @findex -list-features
33195 Returns a list of particular features of the MI protocol that
33196 this version of gdb implements. A feature can be a command,
33197 or a new field in an output of some command, or even an
33198 important bugfix. While a frontend can sometimes detect presence
33199 of a feature at runtime, it is easier to perform detection at debugger
33202 The command returns a list of strings, with each string naming an
33203 available feature. Each returned string is just a name, it does not
33204 have any internal structure. The list of possible feature names
33210 (gdb) -list-features
33211 ^done,result=["feature1","feature2"]
33214 The current list of features is:
33217 @item frozen-varobjs
33218 Indicates support for the @code{-var-set-frozen} command, as well
33219 as possible presense of the @code{frozen} field in the output
33220 of @code{-varobj-create}.
33221 @item pending-breakpoints
33222 Indicates support for the @option{-f} option to the @code{-break-insert}
33225 Indicates Python scripting support, Python-based
33226 pretty-printing commands, and possible presence of the
33227 @samp{display_hint} field in the output of @code{-var-list-children}
33229 Indicates support for the @code{-thread-info} command.
33230 @item data-read-memory-bytes
33231 Indicates support for the @code{-data-read-memory-bytes} and the
33232 @code{-data-write-memory-bytes} commands.
33233 @item breakpoint-notifications
33234 Indicates that changes to breakpoints and breakpoints created via the
33235 CLI will be announced via async records.
33236 @item ada-task-info
33237 Indicates support for the @code{-ada-task-info} command.
33240 @subheading The @code{-list-target-features} Command
33241 @findex -list-target-features
33243 Returns a list of particular features that are supported by the
33244 target. Those features affect the permitted MI commands, but
33245 unlike the features reported by the @code{-list-features} command, the
33246 features depend on which target GDB is using at the moment. Whenever
33247 a target can change, due to commands such as @code{-target-select},
33248 @code{-target-attach} or @code{-exec-run}, the list of target features
33249 may change, and the frontend should obtain it again.
33253 (gdb) -list-features
33254 ^done,result=["async"]
33257 The current list of features is:
33261 Indicates that the target is capable of asynchronous command
33262 execution, which means that @value{GDBN} will accept further commands
33263 while the target is running.
33266 Indicates that the target is capable of reverse execution.
33267 @xref{Reverse Execution}, for more information.
33271 @subheading The @code{-list-thread-groups} Command
33272 @findex -list-thread-groups
33274 @subheading Synopsis
33277 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33280 Lists thread groups (@pxref{Thread groups}). When a single thread
33281 group is passed as the argument, lists the children of that group.
33282 When several thread group are passed, lists information about those
33283 thread groups. Without any parameters, lists information about all
33284 top-level thread groups.
33286 Normally, thread groups that are being debugged are reported.
33287 With the @samp{--available} option, @value{GDBN} reports thread groups
33288 available on the target.
33290 The output of this command may have either a @samp{threads} result or
33291 a @samp{groups} result. The @samp{thread} result has a list of tuples
33292 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33293 Information}). The @samp{groups} result has a list of tuples as value,
33294 each tuple describing a thread group. If top-level groups are
33295 requested (that is, no parameter is passed), or when several groups
33296 are passed, the output always has a @samp{groups} result. The format
33297 of the @samp{group} result is described below.
33299 To reduce the number of roundtrips it's possible to list thread groups
33300 together with their children, by passing the @samp{--recurse} option
33301 and the recursion depth. Presently, only recursion depth of 1 is
33302 permitted. If this option is present, then every reported thread group
33303 will also include its children, either as @samp{group} or
33304 @samp{threads} field.
33306 In general, any combination of option and parameters is permitted, with
33307 the following caveats:
33311 When a single thread group is passed, the output will typically
33312 be the @samp{threads} result. Because threads may not contain
33313 anything, the @samp{recurse} option will be ignored.
33316 When the @samp{--available} option is passed, limited information may
33317 be available. In particular, the list of threads of a process might
33318 be inaccessible. Further, specifying specific thread groups might
33319 not give any performance advantage over listing all thread groups.
33320 The frontend should assume that @samp{-list-thread-groups --available}
33321 is always an expensive operation and cache the results.
33325 The @samp{groups} result is a list of tuples, where each tuple may
33326 have the following fields:
33330 Identifier of the thread group. This field is always present.
33331 The identifier is an opaque string; frontends should not try to
33332 convert it to an integer, even though it might look like one.
33335 The type of the thread group. At present, only @samp{process} is a
33339 The target-specific process identifier. This field is only present
33340 for thread groups of type @samp{process} and only if the process exists.
33343 The number of children this thread group has. This field may be
33344 absent for an available thread group.
33347 This field has a list of tuples as value, each tuple describing a
33348 thread. It may be present if the @samp{--recurse} option is
33349 specified, and it's actually possible to obtain the threads.
33352 This field is a list of integers, each identifying a core that one
33353 thread of the group is running on. This field may be absent if
33354 such information is not available.
33357 The name of the executable file that corresponds to this thread group.
33358 The field is only present for thread groups of type @samp{process},
33359 and only if there is a corresponding executable file.
33363 @subheading Example
33367 -list-thread-groups
33368 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33369 -list-thread-groups 17
33370 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33371 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33372 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33373 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33374 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33375 -list-thread-groups --available
33376 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33377 -list-thread-groups --available --recurse 1
33378 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33379 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33380 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33381 -list-thread-groups --available --recurse 1 17 18
33382 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33383 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33384 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33387 @subheading The @code{-info-os} Command
33390 @subsubheading Synopsis
33393 -info-os [ @var{type} ]
33396 If no argument is supplied, the command returns a table of available
33397 operating-system-specific information types. If one of these types is
33398 supplied as an argument @var{type}, then the command returns a table
33399 of data of that type.
33401 The types of information available depend on the target operating
33404 @subsubheading @value{GDBN} Command
33406 The corresponding @value{GDBN} command is @samp{info os}.
33408 @subsubheading Example
33410 When run on a @sc{gnu}/Linux system, the output will look something
33416 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33417 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33418 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33419 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33420 body=[item=@{col0="processes",col1="Listing of all processes",
33421 col2="Processes"@},
33422 item=@{col0="procgroups",col1="Listing of all process groups",
33423 col2="Process groups"@},
33424 item=@{col0="threads",col1="Listing of all threads",
33426 item=@{col0="files",col1="Listing of all file descriptors",
33427 col2="File descriptors"@},
33428 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33430 item=@{col0="shm",col1="Listing of all shared-memory regions",
33431 col2="Shared-memory regions"@},
33432 item=@{col0="semaphores",col1="Listing of all semaphores",
33433 col2="Semaphores"@},
33434 item=@{col0="msg",col1="Listing of all message queues",
33435 col2="Message queues"@},
33436 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33437 col2="Kernel modules"@}]@}
33440 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33441 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33442 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33443 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33444 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33445 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33446 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33447 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33449 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33450 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33454 (Note that the MI output here includes a @code{"Title"} column that
33455 does not appear in command-line @code{info os}; this column is useful
33456 for MI clients that want to enumerate the types of data, such as in a
33457 popup menu, but is needless clutter on the command line, and
33458 @code{info os} omits it.)
33460 @subheading The @code{-add-inferior} Command
33461 @findex -add-inferior
33463 @subheading Synopsis
33469 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33470 inferior is not associated with any executable. Such association may
33471 be established with the @samp{-file-exec-and-symbols} command
33472 (@pxref{GDB/MI File Commands}). The command response has a single
33473 field, @samp{thread-group}, whose value is the identifier of the
33474 thread group corresponding to the new inferior.
33476 @subheading Example
33481 ^done,thread-group="i3"
33484 @subheading The @code{-interpreter-exec} Command
33485 @findex -interpreter-exec
33487 @subheading Synopsis
33490 -interpreter-exec @var{interpreter} @var{command}
33492 @anchor{-interpreter-exec}
33494 Execute the specified @var{command} in the given @var{interpreter}.
33496 @subheading @value{GDBN} Command
33498 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33500 @subheading Example
33504 -interpreter-exec console "break main"
33505 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33506 &"During symbol reading, bad structure-type format.\n"
33507 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33512 @subheading The @code{-inferior-tty-set} Command
33513 @findex -inferior-tty-set
33515 @subheading Synopsis
33518 -inferior-tty-set /dev/pts/1
33521 Set terminal for future runs of the program being debugged.
33523 @subheading @value{GDBN} Command
33525 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33527 @subheading Example
33531 -inferior-tty-set /dev/pts/1
33536 @subheading The @code{-inferior-tty-show} Command
33537 @findex -inferior-tty-show
33539 @subheading Synopsis
33545 Show terminal for future runs of program being debugged.
33547 @subheading @value{GDBN} Command
33549 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33551 @subheading Example
33555 -inferior-tty-set /dev/pts/1
33559 ^done,inferior_tty_terminal="/dev/pts/1"
33563 @subheading The @code{-enable-timings} Command
33564 @findex -enable-timings
33566 @subheading Synopsis
33569 -enable-timings [yes | no]
33572 Toggle the printing of the wallclock, user and system times for an MI
33573 command as a field in its output. This command is to help frontend
33574 developers optimize the performance of their code. No argument is
33575 equivalent to @samp{yes}.
33577 @subheading @value{GDBN} Command
33581 @subheading Example
33589 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33590 addr="0x080484ed",func="main",file="myprog.c",
33591 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33593 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33601 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33602 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33603 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33604 fullname="/home/nickrob/myprog.c",line="73"@}
33609 @chapter @value{GDBN} Annotations
33611 This chapter describes annotations in @value{GDBN}. Annotations were
33612 designed to interface @value{GDBN} to graphical user interfaces or other
33613 similar programs which want to interact with @value{GDBN} at a
33614 relatively high level.
33616 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33620 This is Edition @value{EDITION}, @value{DATE}.
33624 * Annotations Overview:: What annotations are; the general syntax.
33625 * Server Prefix:: Issuing a command without affecting user state.
33626 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33627 * Errors:: Annotations for error messages.
33628 * Invalidation:: Some annotations describe things now invalid.
33629 * Annotations for Running::
33630 Whether the program is running, how it stopped, etc.
33631 * Source Annotations:: Annotations describing source code.
33634 @node Annotations Overview
33635 @section What is an Annotation?
33636 @cindex annotations
33638 Annotations start with a newline character, two @samp{control-z}
33639 characters, and the name of the annotation. If there is no additional
33640 information associated with this annotation, the name of the annotation
33641 is followed immediately by a newline. If there is additional
33642 information, the name of the annotation is followed by a space, the
33643 additional information, and a newline. The additional information
33644 cannot contain newline characters.
33646 Any output not beginning with a newline and two @samp{control-z}
33647 characters denotes literal output from @value{GDBN}. Currently there is
33648 no need for @value{GDBN} to output a newline followed by two
33649 @samp{control-z} characters, but if there was such a need, the
33650 annotations could be extended with an @samp{escape} annotation which
33651 means those three characters as output.
33653 The annotation @var{level}, which is specified using the
33654 @option{--annotate} command line option (@pxref{Mode Options}), controls
33655 how much information @value{GDBN} prints together with its prompt,
33656 values of expressions, source lines, and other types of output. Level 0
33657 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33658 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33659 for programs that control @value{GDBN}, and level 2 annotations have
33660 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33661 Interface, annotate, GDB's Obsolete Annotations}).
33664 @kindex set annotate
33665 @item set annotate @var{level}
33666 The @value{GDBN} command @code{set annotate} sets the level of
33667 annotations to the specified @var{level}.
33669 @item show annotate
33670 @kindex show annotate
33671 Show the current annotation level.
33674 This chapter describes level 3 annotations.
33676 A simple example of starting up @value{GDBN} with annotations is:
33679 $ @kbd{gdb --annotate=3}
33681 Copyright 2003 Free Software Foundation, Inc.
33682 GDB is free software, covered by the GNU General Public License,
33683 and you are welcome to change it and/or distribute copies of it
33684 under certain conditions.
33685 Type "show copying" to see the conditions.
33686 There is absolutely no warranty for GDB. Type "show warranty"
33688 This GDB was configured as "i386-pc-linux-gnu"
33699 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33700 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33701 denotes a @samp{control-z} character) are annotations; the rest is
33702 output from @value{GDBN}.
33704 @node Server Prefix
33705 @section The Server Prefix
33706 @cindex server prefix
33708 If you prefix a command with @samp{server } then it will not affect
33709 the command history, nor will it affect @value{GDBN}'s notion of which
33710 command to repeat if @key{RET} is pressed on a line by itself. This
33711 means that commands can be run behind a user's back by a front-end in
33712 a transparent manner.
33714 The @code{server } prefix does not affect the recording of values into
33715 the value history; to print a value without recording it into the
33716 value history, use the @code{output} command instead of the
33717 @code{print} command.
33719 Using this prefix also disables confirmation requests
33720 (@pxref{confirmation requests}).
33723 @section Annotation for @value{GDBN} Input
33725 @cindex annotations for prompts
33726 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33727 to know when to send output, when the output from a given command is
33730 Different kinds of input each have a different @dfn{input type}. Each
33731 input type has three annotations: a @code{pre-} annotation, which
33732 denotes the beginning of any prompt which is being output, a plain
33733 annotation, which denotes the end of the prompt, and then a @code{post-}
33734 annotation which denotes the end of any echo which may (or may not) be
33735 associated with the input. For example, the @code{prompt} input type
33736 features the following annotations:
33744 The input types are
33747 @findex pre-prompt annotation
33748 @findex prompt annotation
33749 @findex post-prompt annotation
33751 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33753 @findex pre-commands annotation
33754 @findex commands annotation
33755 @findex post-commands annotation
33757 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33758 command. The annotations are repeated for each command which is input.
33760 @findex pre-overload-choice annotation
33761 @findex overload-choice annotation
33762 @findex post-overload-choice annotation
33763 @item overload-choice
33764 When @value{GDBN} wants the user to select between various overloaded functions.
33766 @findex pre-query annotation
33767 @findex query annotation
33768 @findex post-query annotation
33770 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33772 @findex pre-prompt-for-continue annotation
33773 @findex prompt-for-continue annotation
33774 @findex post-prompt-for-continue annotation
33775 @item prompt-for-continue
33776 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33777 expect this to work well; instead use @code{set height 0} to disable
33778 prompting. This is because the counting of lines is buggy in the
33779 presence of annotations.
33784 @cindex annotations for errors, warnings and interrupts
33786 @findex quit annotation
33791 This annotation occurs right before @value{GDBN} responds to an interrupt.
33793 @findex error annotation
33798 This annotation occurs right before @value{GDBN} responds to an error.
33800 Quit and error annotations indicate that any annotations which @value{GDBN} was
33801 in the middle of may end abruptly. For example, if a
33802 @code{value-history-begin} annotation is followed by a @code{error}, one
33803 cannot expect to receive the matching @code{value-history-end}. One
33804 cannot expect not to receive it either, however; an error annotation
33805 does not necessarily mean that @value{GDBN} is immediately returning all the way
33808 @findex error-begin annotation
33809 A quit or error annotation may be preceded by
33815 Any output between that and the quit or error annotation is the error
33818 Warning messages are not yet annotated.
33819 @c If we want to change that, need to fix warning(), type_error(),
33820 @c range_error(), and possibly other places.
33823 @section Invalidation Notices
33825 @cindex annotations for invalidation messages
33826 The following annotations say that certain pieces of state may have
33830 @findex frames-invalid annotation
33831 @item ^Z^Zframes-invalid
33833 The frames (for example, output from the @code{backtrace} command) may
33836 @findex breakpoints-invalid annotation
33837 @item ^Z^Zbreakpoints-invalid
33839 The breakpoints may have changed. For example, the user just added or
33840 deleted a breakpoint.
33843 @node Annotations for Running
33844 @section Running the Program
33845 @cindex annotations for running programs
33847 @findex starting annotation
33848 @findex stopping annotation
33849 When the program starts executing due to a @value{GDBN} command such as
33850 @code{step} or @code{continue},
33856 is output. When the program stops,
33862 is output. Before the @code{stopped} annotation, a variety of
33863 annotations describe how the program stopped.
33866 @findex exited annotation
33867 @item ^Z^Zexited @var{exit-status}
33868 The program exited, and @var{exit-status} is the exit status (zero for
33869 successful exit, otherwise nonzero).
33871 @findex signalled annotation
33872 @findex signal-name annotation
33873 @findex signal-name-end annotation
33874 @findex signal-string annotation
33875 @findex signal-string-end annotation
33876 @item ^Z^Zsignalled
33877 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33878 annotation continues:
33884 ^Z^Zsignal-name-end
33888 ^Z^Zsignal-string-end
33893 where @var{name} is the name of the signal, such as @code{SIGILL} or
33894 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33895 as @code{Illegal Instruction} or @code{Segmentation fault}.
33896 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33897 user's benefit and have no particular format.
33899 @findex signal annotation
33901 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33902 just saying that the program received the signal, not that it was
33903 terminated with it.
33905 @findex breakpoint annotation
33906 @item ^Z^Zbreakpoint @var{number}
33907 The program hit breakpoint number @var{number}.
33909 @findex watchpoint annotation
33910 @item ^Z^Zwatchpoint @var{number}
33911 The program hit watchpoint number @var{number}.
33914 @node Source Annotations
33915 @section Displaying Source
33916 @cindex annotations for source display
33918 @findex source annotation
33919 The following annotation is used instead of displaying source code:
33922 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33925 where @var{filename} is an absolute file name indicating which source
33926 file, @var{line} is the line number within that file (where 1 is the
33927 first line in the file), @var{character} is the character position
33928 within the file (where 0 is the first character in the file) (for most
33929 debug formats this will necessarily point to the beginning of a line),
33930 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33931 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33932 @var{addr} is the address in the target program associated with the
33933 source which is being displayed. @var{addr} is in the form @samp{0x}
33934 followed by one or more lowercase hex digits (note that this does not
33935 depend on the language).
33937 @node JIT Interface
33938 @chapter JIT Compilation Interface
33939 @cindex just-in-time compilation
33940 @cindex JIT compilation interface
33942 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33943 interface. A JIT compiler is a program or library that generates native
33944 executable code at runtime and executes it, usually in order to achieve good
33945 performance while maintaining platform independence.
33947 Programs that use JIT compilation are normally difficult to debug because
33948 portions of their code are generated at runtime, instead of being loaded from
33949 object files, which is where @value{GDBN} normally finds the program's symbols
33950 and debug information. In order to debug programs that use JIT compilation,
33951 @value{GDBN} has an interface that allows the program to register in-memory
33952 symbol files with @value{GDBN} at runtime.
33954 If you are using @value{GDBN} to debug a program that uses this interface, then
33955 it should work transparently so long as you have not stripped the binary. If
33956 you are developing a JIT compiler, then the interface is documented in the rest
33957 of this chapter. At this time, the only known client of this interface is the
33960 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33961 JIT compiler communicates with @value{GDBN} by writing data into a global
33962 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33963 attaches, it reads a linked list of symbol files from the global variable to
33964 find existing code, and puts a breakpoint in the function so that it can find
33965 out about additional code.
33968 * Declarations:: Relevant C struct declarations
33969 * Registering Code:: Steps to register code
33970 * Unregistering Code:: Steps to unregister code
33971 * Custom Debug Info:: Emit debug information in a custom format
33975 @section JIT Declarations
33977 These are the relevant struct declarations that a C program should include to
33978 implement the interface:
33988 struct jit_code_entry
33990 struct jit_code_entry *next_entry;
33991 struct jit_code_entry *prev_entry;
33992 const char *symfile_addr;
33993 uint64_t symfile_size;
33996 struct jit_descriptor
33999 /* This type should be jit_actions_t, but we use uint32_t
34000 to be explicit about the bitwidth. */
34001 uint32_t action_flag;
34002 struct jit_code_entry *relevant_entry;
34003 struct jit_code_entry *first_entry;
34006 /* GDB puts a breakpoint in this function. */
34007 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34009 /* Make sure to specify the version statically, because the
34010 debugger may check the version before we can set it. */
34011 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34014 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34015 modifications to this global data properly, which can easily be done by putting
34016 a global mutex around modifications to these structures.
34018 @node Registering Code
34019 @section Registering Code
34021 To register code with @value{GDBN}, the JIT should follow this protocol:
34025 Generate an object file in memory with symbols and other desired debug
34026 information. The file must include the virtual addresses of the sections.
34029 Create a code entry for the file, which gives the start and size of the symbol
34033 Add it to the linked list in the JIT descriptor.
34036 Point the relevant_entry field of the descriptor at the entry.
34039 Set @code{action_flag} to @code{JIT_REGISTER} and call
34040 @code{__jit_debug_register_code}.
34043 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34044 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34045 new code. However, the linked list must still be maintained in order to allow
34046 @value{GDBN} to attach to a running process and still find the symbol files.
34048 @node Unregistering Code
34049 @section Unregistering Code
34051 If code is freed, then the JIT should use the following protocol:
34055 Remove the code entry corresponding to the code from the linked list.
34058 Point the @code{relevant_entry} field of the descriptor at the code entry.
34061 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34062 @code{__jit_debug_register_code}.
34065 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34066 and the JIT will leak the memory used for the associated symbol files.
34068 @node Custom Debug Info
34069 @section Custom Debug Info
34070 @cindex custom JIT debug info
34071 @cindex JIT debug info reader
34073 Generating debug information in platform-native file formats (like ELF
34074 or COFF) may be an overkill for JIT compilers; especially if all the
34075 debug info is used for is displaying a meaningful backtrace. The
34076 issue can be resolved by having the JIT writers decide on a debug info
34077 format and also provide a reader that parses the debug info generated
34078 by the JIT compiler. This section gives a brief overview on writing
34079 such a parser. More specific details can be found in the source file
34080 @file{gdb/jit-reader.in}, which is also installed as a header at
34081 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34083 The reader is implemented as a shared object (so this functionality is
34084 not available on platforms which don't allow loading shared objects at
34085 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34086 @code{jit-reader-unload} are provided, to be used to load and unload
34087 the readers from a preconfigured directory. Once loaded, the shared
34088 object is used the parse the debug information emitted by the JIT
34092 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34093 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34096 @node Using JIT Debug Info Readers
34097 @subsection Using JIT Debug Info Readers
34098 @kindex jit-reader-load
34099 @kindex jit-reader-unload
34101 Readers can be loaded and unloaded using the @code{jit-reader-load}
34102 and @code{jit-reader-unload} commands.
34105 @item jit-reader-load @var{reader}
34106 Load the JIT reader named @var{reader}. @var{reader} is a shared
34107 object specified as either an absolute or a relative file name. In
34108 the latter case, @value{GDBN} will try to load the reader from a
34109 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34110 system (here @var{libdir} is the system library directory, often
34111 @file{/usr/local/lib}).
34113 Only one reader can be active at a time; trying to load a second
34114 reader when one is already loaded will result in @value{GDBN}
34115 reporting an error. A new JIT reader can be loaded by first unloading
34116 the current one using @code{jit-reader-unload} and then invoking
34117 @code{jit-reader-load}.
34119 @item jit-reader-unload
34120 Unload the currently loaded JIT reader.
34124 @node Writing JIT Debug Info Readers
34125 @subsection Writing JIT Debug Info Readers
34126 @cindex writing JIT debug info readers
34128 As mentioned, a reader is essentially a shared object conforming to a
34129 certain ABI. This ABI is described in @file{jit-reader.h}.
34131 @file{jit-reader.h} defines the structures, macros and functions
34132 required to write a reader. It is installed (along with
34133 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34134 the system include directory.
34136 Readers need to be released under a GPL compatible license. A reader
34137 can be declared as released under such a license by placing the macro
34138 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34140 The entry point for readers is the symbol @code{gdb_init_reader},
34141 which is expected to be a function with the prototype
34143 @findex gdb_init_reader
34145 extern struct gdb_reader_funcs *gdb_init_reader (void);
34148 @cindex @code{struct gdb_reader_funcs}
34150 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34151 functions. These functions are executed to read the debug info
34152 generated by the JIT compiler (@code{read}), to unwind stack frames
34153 (@code{unwind}) and to create canonical frame IDs
34154 (@code{get_Frame_id}). It also has a callback that is called when the
34155 reader is being unloaded (@code{destroy}). The struct looks like this
34158 struct gdb_reader_funcs
34160 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34161 int reader_version;
34163 /* For use by the reader. */
34166 gdb_read_debug_info *read;
34167 gdb_unwind_frame *unwind;
34168 gdb_get_frame_id *get_frame_id;
34169 gdb_destroy_reader *destroy;
34173 @cindex @code{struct gdb_symbol_callbacks}
34174 @cindex @code{struct gdb_unwind_callbacks}
34176 The callbacks are provided with another set of callbacks by
34177 @value{GDBN} to do their job. For @code{read}, these callbacks are
34178 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34179 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34180 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34181 files and new symbol tables inside those object files. @code{struct
34182 gdb_unwind_callbacks} has callbacks to read registers off the current
34183 frame and to write out the values of the registers in the previous
34184 frame. Both have a callback (@code{target_read}) to read bytes off the
34185 target's address space.
34187 @node In-Process Agent
34188 @chapter In-Process Agent
34189 @cindex debugging agent
34190 The traditional debugging model is conceptually low-speed, but works fine,
34191 because most bugs can be reproduced in debugging-mode execution. However,
34192 as multi-core or many-core processors are becoming mainstream, and
34193 multi-threaded programs become more and more popular, there should be more
34194 and more bugs that only manifest themselves at normal-mode execution, for
34195 example, thread races, because debugger's interference with the program's
34196 timing may conceal the bugs. On the other hand, in some applications,
34197 it is not feasible for the debugger to interrupt the program's execution
34198 long enough for the developer to learn anything helpful about its behavior.
34199 If the program's correctness depends on its real-time behavior, delays
34200 introduced by a debugger might cause the program to fail, even when the
34201 code itself is correct. It is useful to be able to observe the program's
34202 behavior without interrupting it.
34204 Therefore, traditional debugging model is too intrusive to reproduce
34205 some bugs. In order to reduce the interference with the program, we can
34206 reduce the number of operations performed by debugger. The
34207 @dfn{In-Process Agent}, a shared library, is running within the same
34208 process with inferior, and is able to perform some debugging operations
34209 itself. As a result, debugger is only involved when necessary, and
34210 performance of debugging can be improved accordingly. Note that
34211 interference with program can be reduced but can't be removed completely,
34212 because the in-process agent will still stop or slow down the program.
34214 The in-process agent can interpret and execute Agent Expressions
34215 (@pxref{Agent Expressions}) during performing debugging operations. The
34216 agent expressions can be used for different purposes, such as collecting
34217 data in tracepoints, and condition evaluation in breakpoints.
34219 @anchor{Control Agent}
34220 You can control whether the in-process agent is used as an aid for
34221 debugging with the following commands:
34224 @kindex set agent on
34226 Causes the in-process agent to perform some operations on behalf of the
34227 debugger. Just which operations requested by the user will be done
34228 by the in-process agent depends on the its capabilities. For example,
34229 if you request to evaluate breakpoint conditions in the in-process agent,
34230 and the in-process agent has such capability as well, then breakpoint
34231 conditions will be evaluated in the in-process agent.
34233 @kindex set agent off
34234 @item set agent off
34235 Disables execution of debugging operations by the in-process agent. All
34236 of the operations will be performed by @value{GDBN}.
34240 Display the current setting of execution of debugging operations by
34241 the in-process agent.
34245 * In-Process Agent Protocol::
34248 @node In-Process Agent Protocol
34249 @section In-Process Agent Protocol
34250 @cindex in-process agent protocol
34252 The in-process agent is able to communicate with both @value{GDBN} and
34253 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34254 used for communications between @value{GDBN} or GDBserver and the IPA.
34255 In general, @value{GDBN} or GDBserver sends commands
34256 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34257 in-process agent replies back with the return result of the command, or
34258 some other information. The data sent to in-process agent is composed
34259 of primitive data types, such as 4-byte or 8-byte type, and composite
34260 types, which are called objects (@pxref{IPA Protocol Objects}).
34263 * IPA Protocol Objects::
34264 * IPA Protocol Commands::
34267 @node IPA Protocol Objects
34268 @subsection IPA Protocol Objects
34269 @cindex ipa protocol objects
34271 The commands sent to and results received from agent may contain some
34272 complex data types called @dfn{objects}.
34274 The in-process agent is running on the same machine with @value{GDBN}
34275 or GDBserver, so it doesn't have to handle as much differences between
34276 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34277 However, there are still some differences of two ends in two processes:
34281 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34282 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34284 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34285 GDBserver is compiled with one, and in-process agent is compiled with
34289 Here are the IPA Protocol Objects:
34293 agent expression object. It represents an agent expression
34294 (@pxref{Agent Expressions}).
34295 @anchor{agent expression object}
34297 tracepoint action object. It represents a tracepoint action
34298 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34299 memory, static trace data and to evaluate expression.
34300 @anchor{tracepoint action object}
34302 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34303 @anchor{tracepoint object}
34307 The following table describes important attributes of each IPA protocol
34310 @multitable @columnfractions .30 .20 .50
34311 @headitem Name @tab Size @tab Description
34312 @item @emph{agent expression object} @tab @tab
34313 @item length @tab 4 @tab length of bytes code
34314 @item byte code @tab @var{length} @tab contents of byte code
34315 @item @emph{tracepoint action for collecting memory} @tab @tab
34316 @item 'M' @tab 1 @tab type of tracepoint action
34317 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34318 address of the lowest byte to collect, otherwise @var{addr} is the offset
34319 of @var{basereg} for memory collecting.
34320 @item len @tab 8 @tab length of memory for collecting
34321 @item basereg @tab 4 @tab the register number containing the starting
34322 memory address for collecting.
34323 @item @emph{tracepoint action for collecting registers} @tab @tab
34324 @item 'R' @tab 1 @tab type of tracepoint action
34325 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34326 @item 'L' @tab 1 @tab type of tracepoint action
34327 @item @emph{tracepoint action for expression evaluation} @tab @tab
34328 @item 'X' @tab 1 @tab type of tracepoint action
34329 @item agent expression @tab length of @tab @ref{agent expression object}
34330 @item @emph{tracepoint object} @tab @tab
34331 @item number @tab 4 @tab number of tracepoint
34332 @item address @tab 8 @tab address of tracepoint inserted on
34333 @item type @tab 4 @tab type of tracepoint
34334 @item enabled @tab 1 @tab enable or disable of tracepoint
34335 @item step_count @tab 8 @tab step
34336 @item pass_count @tab 8 @tab pass
34337 @item numactions @tab 4 @tab number of tracepoint actions
34338 @item hit count @tab 8 @tab hit count
34339 @item trace frame usage @tab 8 @tab trace frame usage
34340 @item compiled_cond @tab 8 @tab compiled condition
34341 @item orig_size @tab 8 @tab orig size
34342 @item condition @tab 4 if condition is NULL otherwise length of
34343 @ref{agent expression object}
34344 @tab zero if condition is NULL, otherwise is
34345 @ref{agent expression object}
34346 @item actions @tab variable
34347 @tab numactions number of @ref{tracepoint action object}
34350 @node IPA Protocol Commands
34351 @subsection IPA Protocol Commands
34352 @cindex ipa protocol commands
34354 The spaces in each command are delimiters to ease reading this commands
34355 specification. They don't exist in real commands.
34359 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34360 Installs a new fast tracepoint described by @var{tracepoint_object}
34361 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34362 head of @dfn{jumppad}, which is used to jump to data collection routine
34367 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34368 @var{target_address} is address of tracepoint in the inferior.
34369 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34370 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34371 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34372 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34379 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34380 is about to kill inferiors.
34388 @item probe_marker_at:@var{address}
34389 Asks in-process agent to probe the marker at @var{address}.
34396 @item unprobe_marker_at:@var{address}
34397 Asks in-process agent to unprobe the marker at @var{address}.
34401 @chapter Reporting Bugs in @value{GDBN}
34402 @cindex bugs in @value{GDBN}
34403 @cindex reporting bugs in @value{GDBN}
34405 Your bug reports play an essential role in making @value{GDBN} reliable.
34407 Reporting a bug may help you by bringing a solution to your problem, or it
34408 may not. But in any case the principal function of a bug report is to help
34409 the entire community by making the next version of @value{GDBN} work better. Bug
34410 reports are your contribution to the maintenance of @value{GDBN}.
34412 In order for a bug report to serve its purpose, you must include the
34413 information that enables us to fix the bug.
34416 * Bug Criteria:: Have you found a bug?
34417 * Bug Reporting:: How to report bugs
34421 @section Have You Found a Bug?
34422 @cindex bug criteria
34424 If you are not sure whether you have found a bug, here are some guidelines:
34427 @cindex fatal signal
34428 @cindex debugger crash
34429 @cindex crash of debugger
34431 If the debugger gets a fatal signal, for any input whatever, that is a
34432 @value{GDBN} bug. Reliable debuggers never crash.
34434 @cindex error on valid input
34436 If @value{GDBN} produces an error message for valid input, that is a
34437 bug. (Note that if you're cross debugging, the problem may also be
34438 somewhere in the connection to the target.)
34440 @cindex invalid input
34442 If @value{GDBN} does not produce an error message for invalid input,
34443 that is a bug. However, you should note that your idea of
34444 ``invalid input'' might be our idea of ``an extension'' or ``support
34445 for traditional practice''.
34448 If you are an experienced user of debugging tools, your suggestions
34449 for improvement of @value{GDBN} are welcome in any case.
34452 @node Bug Reporting
34453 @section How to Report Bugs
34454 @cindex bug reports
34455 @cindex @value{GDBN} bugs, reporting
34457 A number of companies and individuals offer support for @sc{gnu} products.
34458 If you obtained @value{GDBN} from a support organization, we recommend you
34459 contact that organization first.
34461 You can find contact information for many support companies and
34462 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34464 @c should add a web page ref...
34467 @ifset BUGURL_DEFAULT
34468 In any event, we also recommend that you submit bug reports for
34469 @value{GDBN}. The preferred method is to submit them directly using
34470 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34471 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34474 @strong{Do not send bug reports to @samp{info-gdb}, or to
34475 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34476 not want to receive bug reports. Those that do have arranged to receive
34479 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34480 serves as a repeater. The mailing list and the newsgroup carry exactly
34481 the same messages. Often people think of posting bug reports to the
34482 newsgroup instead of mailing them. This appears to work, but it has one
34483 problem which can be crucial: a newsgroup posting often lacks a mail
34484 path back to the sender. Thus, if we need to ask for more information,
34485 we may be unable to reach you. For this reason, it is better to send
34486 bug reports to the mailing list.
34488 @ifclear BUGURL_DEFAULT
34489 In any event, we also recommend that you submit bug reports for
34490 @value{GDBN} to @value{BUGURL}.
34494 The fundamental principle of reporting bugs usefully is this:
34495 @strong{report all the facts}. If you are not sure whether to state a
34496 fact or leave it out, state it!
34498 Often people omit facts because they think they know what causes the
34499 problem and assume that some details do not matter. Thus, you might
34500 assume that the name of the variable you use in an example does not matter.
34501 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34502 stray memory reference which happens to fetch from the location where that
34503 name is stored in memory; perhaps, if the name were different, the contents
34504 of that location would fool the debugger into doing the right thing despite
34505 the bug. Play it safe and give a specific, complete example. That is the
34506 easiest thing for you to do, and the most helpful.
34508 Keep in mind that the purpose of a bug report is to enable us to fix the
34509 bug. It may be that the bug has been reported previously, but neither
34510 you nor we can know that unless your bug report is complete and
34513 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34514 bell?'' Those bug reports are useless, and we urge everyone to
34515 @emph{refuse to respond to them} except to chide the sender to report
34518 To enable us to fix the bug, you should include all these things:
34522 The version of @value{GDBN}. @value{GDBN} announces it if you start
34523 with no arguments; you can also print it at any time using @code{show
34526 Without this, we will not know whether there is any point in looking for
34527 the bug in the current version of @value{GDBN}.
34530 The type of machine you are using, and the operating system name and
34534 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34535 ``@value{GCC}--2.8.1''.
34538 What compiler (and its version) was used to compile the program you are
34539 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34540 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34541 to get this information; for other compilers, see the documentation for
34545 The command arguments you gave the compiler to compile your example and
34546 observe the bug. For example, did you use @samp{-O}? To guarantee
34547 you will not omit something important, list them all. A copy of the
34548 Makefile (or the output from make) is sufficient.
34550 If we were to try to guess the arguments, we would probably guess wrong
34551 and then we might not encounter the bug.
34554 A complete input script, and all necessary source files, that will
34558 A description of what behavior you observe that you believe is
34559 incorrect. For example, ``It gets a fatal signal.''
34561 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34562 will certainly notice it. But if the bug is incorrect output, we might
34563 not notice unless it is glaringly wrong. You might as well not give us
34564 a chance to make a mistake.
34566 Even if the problem you experience is a fatal signal, you should still
34567 say so explicitly. Suppose something strange is going on, such as, your
34568 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34569 the C library on your system. (This has happened!) Your copy might
34570 crash and ours would not. If you told us to expect a crash, then when
34571 ours fails to crash, we would know that the bug was not happening for
34572 us. If you had not told us to expect a crash, then we would not be able
34573 to draw any conclusion from our observations.
34576 @cindex recording a session script
34577 To collect all this information, you can use a session recording program
34578 such as @command{script}, which is available on many Unix systems.
34579 Just run your @value{GDBN} session inside @command{script} and then
34580 include the @file{typescript} file with your bug report.
34582 Another way to record a @value{GDBN} session is to run @value{GDBN}
34583 inside Emacs and then save the entire buffer to a file.
34586 If you wish to suggest changes to the @value{GDBN} source, send us context
34587 diffs. If you even discuss something in the @value{GDBN} source, refer to
34588 it by context, not by line number.
34590 The line numbers in our development sources will not match those in your
34591 sources. Your line numbers would convey no useful information to us.
34595 Here are some things that are not necessary:
34599 A description of the envelope of the bug.
34601 Often people who encounter a bug spend a lot of time investigating
34602 which changes to the input file will make the bug go away and which
34603 changes will not affect it.
34605 This is often time consuming and not very useful, because the way we
34606 will find the bug is by running a single example under the debugger
34607 with breakpoints, not by pure deduction from a series of examples.
34608 We recommend that you save your time for something else.
34610 Of course, if you can find a simpler example to report @emph{instead}
34611 of the original one, that is a convenience for us. Errors in the
34612 output will be easier to spot, running under the debugger will take
34613 less time, and so on.
34615 However, simplification is not vital; if you do not want to do this,
34616 report the bug anyway and send us the entire test case you used.
34619 A patch for the bug.
34621 A patch for the bug does help us if it is a good one. But do not omit
34622 the necessary information, such as the test case, on the assumption that
34623 a patch is all we need. We might see problems with your patch and decide
34624 to fix the problem another way, or we might not understand it at all.
34626 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34627 construct an example that will make the program follow a certain path
34628 through the code. If you do not send us the example, we will not be able
34629 to construct one, so we will not be able to verify that the bug is fixed.
34631 And if we cannot understand what bug you are trying to fix, or why your
34632 patch should be an improvement, we will not install it. A test case will
34633 help us to understand.
34636 A guess about what the bug is or what it depends on.
34638 Such guesses are usually wrong. Even we cannot guess right about such
34639 things without first using the debugger to find the facts.
34642 @c The readline documentation is distributed with the readline code
34643 @c and consists of the two following files:
34646 @c Use -I with makeinfo to point to the appropriate directory,
34647 @c environment var TEXINPUTS with TeX.
34648 @ifclear SYSTEM_READLINE
34649 @include rluser.texi
34650 @include hsuser.texi
34654 @appendix In Memoriam
34656 The @value{GDBN} project mourns the loss of the following long-time
34661 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34662 to Free Software in general. Outside of @value{GDBN}, he was known in
34663 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34665 @item Michael Snyder
34666 Michael was one of the Global Maintainers of the @value{GDBN} project,
34667 with contributions recorded as early as 1996, until 2011. In addition
34668 to his day to day participation, he was a large driving force behind
34669 adding Reverse Debugging to @value{GDBN}.
34672 Beyond their technical contributions to the project, they were also
34673 enjoyable members of the Free Software Community. We will miss them.
34675 @node Formatting Documentation
34676 @appendix Formatting Documentation
34678 @cindex @value{GDBN} reference card
34679 @cindex reference card
34680 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34681 for printing with PostScript or Ghostscript, in the @file{gdb}
34682 subdirectory of the main source directory@footnote{In
34683 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34684 release.}. If you can use PostScript or Ghostscript with your printer,
34685 you can print the reference card immediately with @file{refcard.ps}.
34687 The release also includes the source for the reference card. You
34688 can format it, using @TeX{}, by typing:
34694 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34695 mode on US ``letter'' size paper;
34696 that is, on a sheet 11 inches wide by 8.5 inches
34697 high. You will need to specify this form of printing as an option to
34698 your @sc{dvi} output program.
34700 @cindex documentation
34702 All the documentation for @value{GDBN} comes as part of the machine-readable
34703 distribution. The documentation is written in Texinfo format, which is
34704 a documentation system that uses a single source file to produce both
34705 on-line information and a printed manual. You can use one of the Info
34706 formatting commands to create the on-line version of the documentation
34707 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34709 @value{GDBN} includes an already formatted copy of the on-line Info
34710 version of this manual in the @file{gdb} subdirectory. The main Info
34711 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34712 subordinate files matching @samp{gdb.info*} in the same directory. If
34713 necessary, you can print out these files, or read them with any editor;
34714 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34715 Emacs or the standalone @code{info} program, available as part of the
34716 @sc{gnu} Texinfo distribution.
34718 If you want to format these Info files yourself, you need one of the
34719 Info formatting programs, such as @code{texinfo-format-buffer} or
34722 If you have @code{makeinfo} installed, and are in the top level
34723 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34724 version @value{GDBVN}), you can make the Info file by typing:
34731 If you want to typeset and print copies of this manual, you need @TeX{},
34732 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34733 Texinfo definitions file.
34735 @TeX{} is a typesetting program; it does not print files directly, but
34736 produces output files called @sc{dvi} files. To print a typeset
34737 document, you need a program to print @sc{dvi} files. If your system
34738 has @TeX{} installed, chances are it has such a program. The precise
34739 command to use depends on your system; @kbd{lpr -d} is common; another
34740 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34741 require a file name without any extension or a @samp{.dvi} extension.
34743 @TeX{} also requires a macro definitions file called
34744 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34745 written in Texinfo format. On its own, @TeX{} cannot either read or
34746 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34747 and is located in the @file{gdb-@var{version-number}/texinfo}
34750 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34751 typeset and print this manual. First switch to the @file{gdb}
34752 subdirectory of the main source directory (for example, to
34753 @file{gdb-@value{GDBVN}/gdb}) and type:
34759 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34761 @node Installing GDB
34762 @appendix Installing @value{GDBN}
34763 @cindex installation
34766 * Requirements:: Requirements for building @value{GDBN}
34767 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34768 * Separate Objdir:: Compiling @value{GDBN} in another directory
34769 * Config Names:: Specifying names for hosts and targets
34770 * Configure Options:: Summary of options for configure
34771 * System-wide configuration:: Having a system-wide init file
34775 @section Requirements for Building @value{GDBN}
34776 @cindex building @value{GDBN}, requirements for
34778 Building @value{GDBN} requires various tools and packages to be available.
34779 Other packages will be used only if they are found.
34781 @heading Tools/Packages Necessary for Building @value{GDBN}
34783 @item ISO C90 compiler
34784 @value{GDBN} is written in ISO C90. It should be buildable with any
34785 working C90 compiler, e.g.@: GCC.
34789 @heading Tools/Packages Optional for Building @value{GDBN}
34793 @value{GDBN} can use the Expat XML parsing library. This library may be
34794 included with your operating system distribution; if it is not, you
34795 can get the latest version from @url{http://expat.sourceforge.net}.
34796 The @file{configure} script will search for this library in several
34797 standard locations; if it is installed in an unusual path, you can
34798 use the @option{--with-libexpat-prefix} option to specify its location.
34804 Remote protocol memory maps (@pxref{Memory Map Format})
34806 Target descriptions (@pxref{Target Descriptions})
34808 Remote shared library lists (@xref{Library List Format},
34809 or alternatively @pxref{Library List Format for SVR4 Targets})
34811 MS-Windows shared libraries (@pxref{Shared Libraries})
34813 Traceframe info (@pxref{Traceframe Info Format})
34817 @cindex compressed debug sections
34818 @value{GDBN} will use the @samp{zlib} library, if available, to read
34819 compressed debug sections. Some linkers, such as GNU gold, are capable
34820 of producing binaries with compressed debug sections. If @value{GDBN}
34821 is compiled with @samp{zlib}, it will be able to read the debug
34822 information in such binaries.
34824 The @samp{zlib} library is likely included with your operating system
34825 distribution; if it is not, you can get the latest version from
34826 @url{http://zlib.net}.
34829 @value{GDBN}'s features related to character sets (@pxref{Character
34830 Sets}) require a functioning @code{iconv} implementation. If you are
34831 on a GNU system, then this is provided by the GNU C Library. Some
34832 other systems also provide a working @code{iconv}.
34834 If @value{GDBN} is using the @code{iconv} program which is installed
34835 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34836 This is done with @option{--with-iconv-bin} which specifies the
34837 directory that contains the @code{iconv} program.
34839 On systems without @code{iconv}, you can install GNU Libiconv. If you
34840 have previously installed Libiconv, you can use the
34841 @option{--with-libiconv-prefix} option to configure.
34843 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34844 arrange to build Libiconv if a directory named @file{libiconv} appears
34845 in the top-most source directory. If Libiconv is built this way, and
34846 if the operating system does not provide a suitable @code{iconv}
34847 implementation, then the just-built library will automatically be used
34848 by @value{GDBN}. One easy way to set this up is to download GNU
34849 Libiconv, unpack it, and then rename the directory holding the
34850 Libiconv source code to @samp{libiconv}.
34853 @node Running Configure
34854 @section Invoking the @value{GDBN} @file{configure} Script
34855 @cindex configuring @value{GDBN}
34856 @value{GDBN} comes with a @file{configure} script that automates the process
34857 of preparing @value{GDBN} for installation; you can then use @code{make} to
34858 build the @code{gdb} program.
34860 @c irrelevant in info file; it's as current as the code it lives with.
34861 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34862 look at the @file{README} file in the sources; we may have improved the
34863 installation procedures since publishing this manual.}
34866 The @value{GDBN} distribution includes all the source code you need for
34867 @value{GDBN} in a single directory, whose name is usually composed by
34868 appending the version number to @samp{gdb}.
34870 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34871 @file{gdb-@value{GDBVN}} directory. That directory contains:
34874 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34875 script for configuring @value{GDBN} and all its supporting libraries
34877 @item gdb-@value{GDBVN}/gdb
34878 the source specific to @value{GDBN} itself
34880 @item gdb-@value{GDBVN}/bfd
34881 source for the Binary File Descriptor library
34883 @item gdb-@value{GDBVN}/include
34884 @sc{gnu} include files
34886 @item gdb-@value{GDBVN}/libiberty
34887 source for the @samp{-liberty} free software library
34889 @item gdb-@value{GDBVN}/opcodes
34890 source for the library of opcode tables and disassemblers
34892 @item gdb-@value{GDBVN}/readline
34893 source for the @sc{gnu} command-line interface
34895 @item gdb-@value{GDBVN}/glob
34896 source for the @sc{gnu} filename pattern-matching subroutine
34898 @item gdb-@value{GDBVN}/mmalloc
34899 source for the @sc{gnu} memory-mapped malloc package
34902 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34903 from the @file{gdb-@var{version-number}} source directory, which in
34904 this example is the @file{gdb-@value{GDBVN}} directory.
34906 First switch to the @file{gdb-@var{version-number}} source directory
34907 if you are not already in it; then run @file{configure}. Pass the
34908 identifier for the platform on which @value{GDBN} will run as an
34914 cd gdb-@value{GDBVN}
34915 ./configure @var{host}
34920 where @var{host} is an identifier such as @samp{sun4} or
34921 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34922 (You can often leave off @var{host}; @file{configure} tries to guess the
34923 correct value by examining your system.)
34925 Running @samp{configure @var{host}} and then running @code{make} builds the
34926 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34927 libraries, then @code{gdb} itself. The configured source files, and the
34928 binaries, are left in the corresponding source directories.
34931 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34932 system does not recognize this automatically when you run a different
34933 shell, you may need to run @code{sh} on it explicitly:
34936 sh configure @var{host}
34939 If you run @file{configure} from a directory that contains source
34940 directories for multiple libraries or programs, such as the
34941 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34943 creates configuration files for every directory level underneath (unless
34944 you tell it not to, with the @samp{--norecursion} option).
34946 You should run the @file{configure} script from the top directory in the
34947 source tree, the @file{gdb-@var{version-number}} directory. If you run
34948 @file{configure} from one of the subdirectories, you will configure only
34949 that subdirectory. That is usually not what you want. In particular,
34950 if you run the first @file{configure} from the @file{gdb} subdirectory
34951 of the @file{gdb-@var{version-number}} directory, you will omit the
34952 configuration of @file{bfd}, @file{readline}, and other sibling
34953 directories of the @file{gdb} subdirectory. This leads to build errors
34954 about missing include files such as @file{bfd/bfd.h}.
34956 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34957 However, you should make sure that the shell on your path (named by
34958 the @samp{SHELL} environment variable) is publicly readable. Remember
34959 that @value{GDBN} uses the shell to start your program---some systems refuse to
34960 let @value{GDBN} debug child processes whose programs are not readable.
34962 @node Separate Objdir
34963 @section Compiling @value{GDBN} in Another Directory
34965 If you want to run @value{GDBN} versions for several host or target machines,
34966 you need a different @code{gdb} compiled for each combination of
34967 host and target. @file{configure} is designed to make this easy by
34968 allowing you to generate each configuration in a separate subdirectory,
34969 rather than in the source directory. If your @code{make} program
34970 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34971 @code{make} in each of these directories builds the @code{gdb}
34972 program specified there.
34974 To build @code{gdb} in a separate directory, run @file{configure}
34975 with the @samp{--srcdir} option to specify where to find the source.
34976 (You also need to specify a path to find @file{configure}
34977 itself from your working directory. If the path to @file{configure}
34978 would be the same as the argument to @samp{--srcdir}, you can leave out
34979 the @samp{--srcdir} option; it is assumed.)
34981 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34982 separate directory for a Sun 4 like this:
34986 cd gdb-@value{GDBVN}
34989 ../gdb-@value{GDBVN}/configure sun4
34994 When @file{configure} builds a configuration using a remote source
34995 directory, it creates a tree for the binaries with the same structure
34996 (and using the same names) as the tree under the source directory. In
34997 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34998 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34999 @file{gdb-sun4/gdb}.
35001 Make sure that your path to the @file{configure} script has just one
35002 instance of @file{gdb} in it. If your path to @file{configure} looks
35003 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35004 one subdirectory of @value{GDBN}, not the whole package. This leads to
35005 build errors about missing include files such as @file{bfd/bfd.h}.
35007 One popular reason to build several @value{GDBN} configurations in separate
35008 directories is to configure @value{GDBN} for cross-compiling (where
35009 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35010 programs that run on another machine---the @dfn{target}).
35011 You specify a cross-debugging target by
35012 giving the @samp{--target=@var{target}} option to @file{configure}.
35014 When you run @code{make} to build a program or library, you must run
35015 it in a configured directory---whatever directory you were in when you
35016 called @file{configure} (or one of its subdirectories).
35018 The @code{Makefile} that @file{configure} generates in each source
35019 directory also runs recursively. If you type @code{make} in a source
35020 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35021 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35022 will build all the required libraries, and then build GDB.
35024 When you have multiple hosts or targets configured in separate
35025 directories, you can run @code{make} on them in parallel (for example,
35026 if they are NFS-mounted on each of the hosts); they will not interfere
35030 @section Specifying Names for Hosts and Targets
35032 The specifications used for hosts and targets in the @file{configure}
35033 script are based on a three-part naming scheme, but some short predefined
35034 aliases are also supported. The full naming scheme encodes three pieces
35035 of information in the following pattern:
35038 @var{architecture}-@var{vendor}-@var{os}
35041 For example, you can use the alias @code{sun4} as a @var{host} argument,
35042 or as the value for @var{target} in a @code{--target=@var{target}}
35043 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35045 The @file{configure} script accompanying @value{GDBN} does not provide
35046 any query facility to list all supported host and target names or
35047 aliases. @file{configure} calls the Bourne shell script
35048 @code{config.sub} to map abbreviations to full names; you can read the
35049 script, if you wish, or you can use it to test your guesses on
35050 abbreviations---for example:
35053 % sh config.sub i386-linux
35055 % sh config.sub alpha-linux
35056 alpha-unknown-linux-gnu
35057 % sh config.sub hp9k700
35059 % sh config.sub sun4
35060 sparc-sun-sunos4.1.1
35061 % sh config.sub sun3
35062 m68k-sun-sunos4.1.1
35063 % sh config.sub i986v
35064 Invalid configuration `i986v': machine `i986v' not recognized
35068 @code{config.sub} is also distributed in the @value{GDBN} source
35069 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35071 @node Configure Options
35072 @section @file{configure} Options
35074 Here is a summary of the @file{configure} options and arguments that
35075 are most often useful for building @value{GDBN}. @file{configure} also has
35076 several other options not listed here. @inforef{What Configure
35077 Does,,configure.info}, for a full explanation of @file{configure}.
35080 configure @r{[}--help@r{]}
35081 @r{[}--prefix=@var{dir}@r{]}
35082 @r{[}--exec-prefix=@var{dir}@r{]}
35083 @r{[}--srcdir=@var{dirname}@r{]}
35084 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35085 @r{[}--target=@var{target}@r{]}
35090 You may introduce options with a single @samp{-} rather than
35091 @samp{--} if you prefer; but you may abbreviate option names if you use
35096 Display a quick summary of how to invoke @file{configure}.
35098 @item --prefix=@var{dir}
35099 Configure the source to install programs and files under directory
35102 @item --exec-prefix=@var{dir}
35103 Configure the source to install programs under directory
35106 @c avoid splitting the warning from the explanation:
35108 @item --srcdir=@var{dirname}
35109 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35110 @code{make} that implements the @code{VPATH} feature.}@*
35111 Use this option to make configurations in directories separate from the
35112 @value{GDBN} source directories. Among other things, you can use this to
35113 build (or maintain) several configurations simultaneously, in separate
35114 directories. @file{configure} writes configuration-specific files in
35115 the current directory, but arranges for them to use the source in the
35116 directory @var{dirname}. @file{configure} creates directories under
35117 the working directory in parallel to the source directories below
35120 @item --norecursion
35121 Configure only the directory level where @file{configure} is executed; do not
35122 propagate configuration to subdirectories.
35124 @item --target=@var{target}
35125 Configure @value{GDBN} for cross-debugging programs running on the specified
35126 @var{target}. Without this option, @value{GDBN} is configured to debug
35127 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35129 There is no convenient way to generate a list of all available targets.
35131 @item @var{host} @dots{}
35132 Configure @value{GDBN} to run on the specified @var{host}.
35134 There is no convenient way to generate a list of all available hosts.
35137 There are many other options available as well, but they are generally
35138 needed for special purposes only.
35140 @node System-wide configuration
35141 @section System-wide configuration and settings
35142 @cindex system-wide init file
35144 @value{GDBN} can be configured to have a system-wide init file;
35145 this file will be read and executed at startup (@pxref{Startup, , What
35146 @value{GDBN} does during startup}).
35148 Here is the corresponding configure option:
35151 @item --with-system-gdbinit=@var{file}
35152 Specify that the default location of the system-wide init file is
35156 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35157 it may be subject to relocation. Two possible cases:
35161 If the default location of this init file contains @file{$prefix},
35162 it will be subject to relocation. Suppose that the configure options
35163 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35164 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35165 init file is looked for as @file{$install/etc/gdbinit} instead of
35166 @file{$prefix/etc/gdbinit}.
35169 By contrast, if the default location does not contain the prefix,
35170 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35171 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35172 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35173 wherever @value{GDBN} is installed.
35176 If the configured location of the system-wide init file (as given by the
35177 @option{--with-system-gdbinit} option at configure time) is in the
35178 data-directory (as specified by @option{--with-gdb-datadir} at configure
35179 time) or in one of its subdirectories, then @value{GDBN} will look for the
35180 system-wide init file in the directory specified by the
35181 @option{--data-directory} command-line option.
35182 Note that the system-wide init file is only read once, during @value{GDBN}
35183 initialization. If the data-directory is changed after @value{GDBN} has
35184 started with the @code{set data-directory} command, the file will not be
35187 @node Maintenance Commands
35188 @appendix Maintenance Commands
35189 @cindex maintenance commands
35190 @cindex internal commands
35192 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35193 includes a number of commands intended for @value{GDBN} developers,
35194 that are not documented elsewhere in this manual. These commands are
35195 provided here for reference. (For commands that turn on debugging
35196 messages, see @ref{Debugging Output}.)
35199 @kindex maint agent
35200 @kindex maint agent-eval
35201 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35202 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35203 Translate the given @var{expression} into remote agent bytecodes.
35204 This command is useful for debugging the Agent Expression mechanism
35205 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35206 expression useful for data collection, such as by tracepoints, while
35207 @samp{maint agent-eval} produces an expression that evaluates directly
35208 to a result. For instance, a collection expression for @code{globa +
35209 globb} will include bytecodes to record four bytes of memory at each
35210 of the addresses of @code{globa} and @code{globb}, while discarding
35211 the result of the addition, while an evaluation expression will do the
35212 addition and return the sum.
35213 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35214 If not, generate remote agent bytecode for current frame PC address.
35216 @kindex maint agent-printf
35217 @item maint agent-printf @var{format},@var{expr},...
35218 Translate the given format string and list of argument expressions
35219 into remote agent bytecodes and display them as a disassembled list.
35220 This command is useful for debugging the agent version of dynamic
35221 printf (@pxref{Dynamic Printf}.
35223 @kindex maint info breakpoints
35224 @item @anchor{maint info breakpoints}maint info breakpoints
35225 Using the same format as @samp{info breakpoints}, display both the
35226 breakpoints you've set explicitly, and those @value{GDBN} is using for
35227 internal purposes. Internal breakpoints are shown with negative
35228 breakpoint numbers. The type column identifies what kind of breakpoint
35233 Normal, explicitly set breakpoint.
35236 Normal, explicitly set watchpoint.
35239 Internal breakpoint, used to handle correctly stepping through
35240 @code{longjmp} calls.
35242 @item longjmp resume
35243 Internal breakpoint at the target of a @code{longjmp}.
35246 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35249 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35252 Shared library events.
35256 @kindex maint info bfds
35257 @item maint info bfds
35258 This prints information about each @code{bfd} object that is known to
35259 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35261 @kindex set displaced-stepping
35262 @kindex show displaced-stepping
35263 @cindex displaced stepping support
35264 @cindex out-of-line single-stepping
35265 @item set displaced-stepping
35266 @itemx show displaced-stepping
35267 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35268 if the target supports it. Displaced stepping is a way to single-step
35269 over breakpoints without removing them from the inferior, by executing
35270 an out-of-line copy of the instruction that was originally at the
35271 breakpoint location. It is also known as out-of-line single-stepping.
35274 @item set displaced-stepping on
35275 If the target architecture supports it, @value{GDBN} will use
35276 displaced stepping to step over breakpoints.
35278 @item set displaced-stepping off
35279 @value{GDBN} will not use displaced stepping to step over breakpoints,
35280 even if such is supported by the target architecture.
35282 @cindex non-stop mode, and @samp{set displaced-stepping}
35283 @item set displaced-stepping auto
35284 This is the default mode. @value{GDBN} will use displaced stepping
35285 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35286 architecture supports displaced stepping.
35289 @kindex maint check-symtabs
35290 @item maint check-symtabs
35291 Check the consistency of psymtabs and symtabs.
35293 @kindex maint cplus first_component
35294 @item maint cplus first_component @var{name}
35295 Print the first C@t{++} class/namespace component of @var{name}.
35297 @kindex maint cplus namespace
35298 @item maint cplus namespace
35299 Print the list of possible C@t{++} namespaces.
35301 @kindex maint demangle
35302 @item maint demangle @var{name}
35303 Demangle a C@t{++} or Objective-C mangled @var{name}.
35305 @kindex maint deprecate
35306 @kindex maint undeprecate
35307 @cindex deprecated commands
35308 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35309 @itemx maint undeprecate @var{command}
35310 Deprecate or undeprecate the named @var{command}. Deprecated commands
35311 cause @value{GDBN} to issue a warning when you use them. The optional
35312 argument @var{replacement} says which newer command should be used in
35313 favor of the deprecated one; if it is given, @value{GDBN} will mention
35314 the replacement as part of the warning.
35316 @kindex maint dump-me
35317 @item maint dump-me
35318 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35319 Cause a fatal signal in the debugger and force it to dump its core.
35320 This is supported only on systems which support aborting a program
35321 with the @code{SIGQUIT} signal.
35323 @kindex maint internal-error
35324 @kindex maint internal-warning
35325 @item maint internal-error @r{[}@var{message-text}@r{]}
35326 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35327 Cause @value{GDBN} to call the internal function @code{internal_error}
35328 or @code{internal_warning} and hence behave as though an internal error
35329 or internal warning has been detected. In addition to reporting the
35330 internal problem, these functions give the user the opportunity to
35331 either quit @value{GDBN} or create a core file of the current
35332 @value{GDBN} session.
35334 These commands take an optional parameter @var{message-text} that is
35335 used as the text of the error or warning message.
35337 Here's an example of using @code{internal-error}:
35340 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35341 @dots{}/maint.c:121: internal-error: testing, 1, 2
35342 A problem internal to GDB has been detected. Further
35343 debugging may prove unreliable.
35344 Quit this debugging session? (y or n) @kbd{n}
35345 Create a core file? (y or n) @kbd{n}
35349 @cindex @value{GDBN} internal error
35350 @cindex internal errors, control of @value{GDBN} behavior
35352 @kindex maint set internal-error
35353 @kindex maint show internal-error
35354 @kindex maint set internal-warning
35355 @kindex maint show internal-warning
35356 @item maint set internal-error @var{action} [ask|yes|no]
35357 @itemx maint show internal-error @var{action}
35358 @itemx maint set internal-warning @var{action} [ask|yes|no]
35359 @itemx maint show internal-warning @var{action}
35360 When @value{GDBN} reports an internal problem (error or warning) it
35361 gives the user the opportunity to both quit @value{GDBN} and create a
35362 core file of the current @value{GDBN} session. These commands let you
35363 override the default behaviour for each particular @var{action},
35364 described in the table below.
35368 You can specify that @value{GDBN} should always (yes) or never (no)
35369 quit. The default is to ask the user what to do.
35372 You can specify that @value{GDBN} should always (yes) or never (no)
35373 create a core file. The default is to ask the user what to do.
35376 @kindex maint packet
35377 @item maint packet @var{text}
35378 If @value{GDBN} is talking to an inferior via the serial protocol,
35379 then this command sends the string @var{text} to the inferior, and
35380 displays the response packet. @value{GDBN} supplies the initial
35381 @samp{$} character, the terminating @samp{#} character, and the
35384 @kindex maint print architecture
35385 @item maint print architecture @r{[}@var{file}@r{]}
35386 Print the entire architecture configuration. The optional argument
35387 @var{file} names the file where the output goes.
35389 @kindex maint print c-tdesc
35390 @item maint print c-tdesc
35391 Print the current target description (@pxref{Target Descriptions}) as
35392 a C source file. The created source file can be used in @value{GDBN}
35393 when an XML parser is not available to parse the description.
35395 @kindex maint print dummy-frames
35396 @item maint print dummy-frames
35397 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35400 (@value{GDBP}) @kbd{b add}
35402 (@value{GDBP}) @kbd{print add(2,3)}
35403 Breakpoint 2, add (a=2, b=3) at @dots{}
35405 The program being debugged stopped while in a function called from GDB.
35407 (@value{GDBP}) @kbd{maint print dummy-frames}
35408 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35409 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35410 call_lo=0x01014000 call_hi=0x01014001
35414 Takes an optional file parameter.
35416 @kindex maint print registers
35417 @kindex maint print raw-registers
35418 @kindex maint print cooked-registers
35419 @kindex maint print register-groups
35420 @kindex maint print remote-registers
35421 @item maint print registers @r{[}@var{file}@r{]}
35422 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35423 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35424 @itemx maint print register-groups @r{[}@var{file}@r{]}
35425 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35426 Print @value{GDBN}'s internal register data structures.
35428 The command @code{maint print raw-registers} includes the contents of
35429 the raw register cache; the command @code{maint print
35430 cooked-registers} includes the (cooked) value of all registers,
35431 including registers which aren't available on the target nor visible
35432 to user; the command @code{maint print register-groups} includes the
35433 groups that each register is a member of; and the command @code{maint
35434 print remote-registers} includes the remote target's register numbers
35435 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35436 @value{GDBN} Internals}.
35438 These commands take an optional parameter, a file name to which to
35439 write the information.
35441 @kindex maint print reggroups
35442 @item maint print reggroups @r{[}@var{file}@r{]}
35443 Print @value{GDBN}'s internal register group data structures. The
35444 optional argument @var{file} tells to what file to write the
35447 The register groups info looks like this:
35450 (@value{GDBP}) @kbd{maint print reggroups}
35463 This command forces @value{GDBN} to flush its internal register cache.
35465 @kindex maint print objfiles
35466 @cindex info for known object files
35467 @item maint print objfiles
35468 Print a dump of all known object files. For each object file, this
35469 command prints its name, address in memory, and all of its psymtabs
35472 @kindex maint print section-scripts
35473 @cindex info for known .debug_gdb_scripts-loaded scripts
35474 @item maint print section-scripts [@var{regexp}]
35475 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35476 If @var{regexp} is specified, only print scripts loaded by object files
35477 matching @var{regexp}.
35478 For each script, this command prints its name as specified in the objfile,
35479 and the full path if known.
35480 @xref{dotdebug_gdb_scripts section}.
35482 @kindex maint print statistics
35483 @cindex bcache statistics
35484 @item maint print statistics
35485 This command prints, for each object file in the program, various data
35486 about that object file followed by the byte cache (@dfn{bcache})
35487 statistics for the object file. The objfile data includes the number
35488 of minimal, partial, full, and stabs symbols, the number of types
35489 defined by the objfile, the number of as yet unexpanded psym tables,
35490 the number of line tables and string tables, and the amount of memory
35491 used by the various tables. The bcache statistics include the counts,
35492 sizes, and counts of duplicates of all and unique objects, max,
35493 average, and median entry size, total memory used and its overhead and
35494 savings, and various measures of the hash table size and chain
35497 @kindex maint print target-stack
35498 @cindex target stack description
35499 @item maint print target-stack
35500 A @dfn{target} is an interface between the debugger and a particular
35501 kind of file or process. Targets can be stacked in @dfn{strata},
35502 so that more than one target can potentially respond to a request.
35503 In particular, memory accesses will walk down the stack of targets
35504 until they find a target that is interested in handling that particular
35507 This command prints a short description of each layer that was pushed on
35508 the @dfn{target stack}, starting from the top layer down to the bottom one.
35510 @kindex maint print type
35511 @cindex type chain of a data type
35512 @item maint print type @var{expr}
35513 Print the type chain for a type specified by @var{expr}. The argument
35514 can be either a type name or a symbol. If it is a symbol, the type of
35515 that symbol is described. The type chain produced by this command is
35516 a recursive definition of the data type as stored in @value{GDBN}'s
35517 data structures, including its flags and contained types.
35519 @kindex maint set dwarf2 always-disassemble
35520 @kindex maint show dwarf2 always-disassemble
35521 @item maint set dwarf2 always-disassemble
35522 @item maint show dwarf2 always-disassemble
35523 Control the behavior of @code{info address} when using DWARF debugging
35526 The default is @code{off}, which means that @value{GDBN} should try to
35527 describe a variable's location in an easily readable format. When
35528 @code{on}, @value{GDBN} will instead display the DWARF location
35529 expression in an assembly-like format. Note that some locations are
35530 too complex for @value{GDBN} to describe simply; in this case you will
35531 always see the disassembly form.
35533 Here is an example of the resulting disassembly:
35536 (gdb) info addr argc
35537 Symbol "argc" is a complex DWARF expression:
35541 For more information on these expressions, see
35542 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35544 @kindex maint set dwarf2 max-cache-age
35545 @kindex maint show dwarf2 max-cache-age
35546 @item maint set dwarf2 max-cache-age
35547 @itemx maint show dwarf2 max-cache-age
35548 Control the DWARF 2 compilation unit cache.
35550 @cindex DWARF 2 compilation units cache
35551 In object files with inter-compilation-unit references, such as those
35552 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35553 reader needs to frequently refer to previously read compilation units.
35554 This setting controls how long a compilation unit will remain in the
35555 cache if it is not referenced. A higher limit means that cached
35556 compilation units will be stored in memory longer, and more total
35557 memory will be used. Setting it to zero disables caching, which will
35558 slow down @value{GDBN} startup, but reduce memory consumption.
35560 @kindex maint set profile
35561 @kindex maint show profile
35562 @cindex profiling GDB
35563 @item maint set profile
35564 @itemx maint show profile
35565 Control profiling of @value{GDBN}.
35567 Profiling will be disabled until you use the @samp{maint set profile}
35568 command to enable it. When you enable profiling, the system will begin
35569 collecting timing and execution count data; when you disable profiling or
35570 exit @value{GDBN}, the results will be written to a log file. Remember that
35571 if you use profiling, @value{GDBN} will overwrite the profiling log file
35572 (often called @file{gmon.out}). If you have a record of important profiling
35573 data in a @file{gmon.out} file, be sure to move it to a safe location.
35575 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35576 compiled with the @samp{-pg} compiler option.
35578 @kindex maint set show-debug-regs
35579 @kindex maint show show-debug-regs
35580 @cindex hardware debug registers
35581 @item maint set show-debug-regs
35582 @itemx maint show show-debug-regs
35583 Control whether to show variables that mirror the hardware debug
35584 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35585 enabled, the debug registers values are shown when @value{GDBN} inserts or
35586 removes a hardware breakpoint or watchpoint, and when the inferior
35587 triggers a hardware-assisted breakpoint or watchpoint.
35589 @kindex maint set show-all-tib
35590 @kindex maint show show-all-tib
35591 @item maint set show-all-tib
35592 @itemx maint show show-all-tib
35593 Control whether to show all non zero areas within a 1k block starting
35594 at thread local base, when using the @samp{info w32 thread-information-block}
35597 @kindex maint space
35598 @cindex memory used by commands
35600 Control whether to display memory usage for each command. If set to a
35601 nonzero value, @value{GDBN} will display how much memory each command
35602 took, following the command's own output. This can also be requested
35603 by invoking @value{GDBN} with the @option{--statistics} command-line
35604 switch (@pxref{Mode Options}).
35607 @cindex time of command execution
35609 Control whether to display the execution time of @value{GDBN} for each command.
35610 If set to a nonzero value, @value{GDBN} will display how much time it
35611 took to execute each command, following the command's own output.
35612 Both CPU time and wallclock time are printed.
35613 Printing both is useful when trying to determine whether the cost is
35614 CPU or, e.g., disk/network, latency.
35615 Note that the CPU time printed is for @value{GDBN} only, it does not include
35616 the execution time of the inferior because there's no mechanism currently
35617 to compute how much time was spent by @value{GDBN} and how much time was
35618 spent by the program been debugged.
35619 This can also be requested by invoking @value{GDBN} with the
35620 @option{--statistics} command-line switch (@pxref{Mode Options}).
35622 @kindex maint translate-address
35623 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35624 Find the symbol stored at the location specified by the address
35625 @var{addr} and an optional section name @var{section}. If found,
35626 @value{GDBN} prints the name of the closest symbol and an offset from
35627 the symbol's location to the specified address. This is similar to
35628 the @code{info address} command (@pxref{Symbols}), except that this
35629 command also allows to find symbols in other sections.
35631 If section was not specified, the section in which the symbol was found
35632 is also printed. For dynamically linked executables, the name of
35633 executable or shared library containing the symbol is printed as well.
35637 The following command is useful for non-interactive invocations of
35638 @value{GDBN}, such as in the test suite.
35641 @item set watchdog @var{nsec}
35642 @kindex set watchdog
35643 @cindex watchdog timer
35644 @cindex timeout for commands
35645 Set the maximum number of seconds @value{GDBN} will wait for the
35646 target operation to finish. If this time expires, @value{GDBN}
35647 reports and error and the command is aborted.
35649 @item show watchdog
35650 Show the current setting of the target wait timeout.
35653 @node Remote Protocol
35654 @appendix @value{GDBN} Remote Serial Protocol
35659 * Stop Reply Packets::
35660 * General Query Packets::
35661 * Architecture-Specific Protocol Details::
35662 * Tracepoint Packets::
35663 * Host I/O Packets::
35665 * Notification Packets::
35666 * Remote Non-Stop::
35667 * Packet Acknowledgment::
35669 * File-I/O Remote Protocol Extension::
35670 * Library List Format::
35671 * Library List Format for SVR4 Targets::
35672 * Memory Map Format::
35673 * Thread List Format::
35674 * Traceframe Info Format::
35680 There may be occasions when you need to know something about the
35681 protocol---for example, if there is only one serial port to your target
35682 machine, you might want your program to do something special if it
35683 recognizes a packet meant for @value{GDBN}.
35685 In the examples below, @samp{->} and @samp{<-} are used to indicate
35686 transmitted and received data, respectively.
35688 @cindex protocol, @value{GDBN} remote serial
35689 @cindex serial protocol, @value{GDBN} remote
35690 @cindex remote serial protocol
35691 All @value{GDBN} commands and responses (other than acknowledgments
35692 and notifications, see @ref{Notification Packets}) are sent as a
35693 @var{packet}. A @var{packet} is introduced with the character
35694 @samp{$}, the actual @var{packet-data}, and the terminating character
35695 @samp{#} followed by a two-digit @var{checksum}:
35698 @code{$}@var{packet-data}@code{#}@var{checksum}
35702 @cindex checksum, for @value{GDBN} remote
35704 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35705 characters between the leading @samp{$} and the trailing @samp{#} (an
35706 eight bit unsigned checksum).
35708 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35709 specification also included an optional two-digit @var{sequence-id}:
35712 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35715 @cindex sequence-id, for @value{GDBN} remote
35717 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35718 has never output @var{sequence-id}s. Stubs that handle packets added
35719 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35721 When either the host or the target machine receives a packet, the first
35722 response expected is an acknowledgment: either @samp{+} (to indicate
35723 the package was received correctly) or @samp{-} (to request
35727 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35732 The @samp{+}/@samp{-} acknowledgments can be disabled
35733 once a connection is established.
35734 @xref{Packet Acknowledgment}, for details.
35736 The host (@value{GDBN}) sends @var{command}s, and the target (the
35737 debugging stub incorporated in your program) sends a @var{response}. In
35738 the case of step and continue @var{command}s, the response is only sent
35739 when the operation has completed, and the target has again stopped all
35740 threads in all attached processes. This is the default all-stop mode
35741 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35742 execution mode; see @ref{Remote Non-Stop}, for details.
35744 @var{packet-data} consists of a sequence of characters with the
35745 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35748 @cindex remote protocol, field separator
35749 Fields within the packet should be separated using @samp{,} @samp{;} or
35750 @samp{:}. Except where otherwise noted all numbers are represented in
35751 @sc{hex} with leading zeros suppressed.
35753 Implementors should note that prior to @value{GDBN} 5.0, the character
35754 @samp{:} could not appear as the third character in a packet (as it
35755 would potentially conflict with the @var{sequence-id}).
35757 @cindex remote protocol, binary data
35758 @anchor{Binary Data}
35759 Binary data in most packets is encoded either as two hexadecimal
35760 digits per byte of binary data. This allowed the traditional remote
35761 protocol to work over connections which were only seven-bit clean.
35762 Some packets designed more recently assume an eight-bit clean
35763 connection, and use a more efficient encoding to send and receive
35766 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35767 as an escape character. Any escaped byte is transmitted as the escape
35768 character followed by the original character XORed with @code{0x20}.
35769 For example, the byte @code{0x7d} would be transmitted as the two
35770 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35771 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35772 @samp{@}}) must always be escaped. Responses sent by the stub
35773 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35774 is not interpreted as the start of a run-length encoded sequence
35777 Response @var{data} can be run-length encoded to save space.
35778 Run-length encoding replaces runs of identical characters with one
35779 instance of the repeated character, followed by a @samp{*} and a
35780 repeat count. The repeat count is itself sent encoded, to avoid
35781 binary characters in @var{data}: a value of @var{n} is sent as
35782 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35783 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35784 code 32) for a repeat count of 3. (This is because run-length
35785 encoding starts to win for counts 3 or more.) Thus, for example,
35786 @samp{0* } is a run-length encoding of ``0000'': the space character
35787 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35790 The printable characters @samp{#} and @samp{$} or with a numeric value
35791 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35792 seven repeats (@samp{$}) can be expanded using a repeat count of only
35793 five (@samp{"}). For example, @samp{00000000} can be encoded as
35796 The error response returned for some packets includes a two character
35797 error number. That number is not well defined.
35799 @cindex empty response, for unsupported packets
35800 For any @var{command} not supported by the stub, an empty response
35801 (@samp{$#00}) should be returned. That way it is possible to extend the
35802 protocol. A newer @value{GDBN} can tell if a packet is supported based
35805 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35806 commands for register access, and the @samp{m} and @samp{M} commands
35807 for memory access. Stubs that only control single-threaded targets
35808 can implement run control with the @samp{c} (continue), and @samp{s}
35809 (step) commands. Stubs that support multi-threading targets should
35810 support the @samp{vCont} command. All other commands are optional.
35815 The following table provides a complete list of all currently defined
35816 @var{command}s and their corresponding response @var{data}.
35817 @xref{File-I/O Remote Protocol Extension}, for details about the File
35818 I/O extension of the remote protocol.
35820 Each packet's description has a template showing the packet's overall
35821 syntax, followed by an explanation of the packet's meaning. We
35822 include spaces in some of the templates for clarity; these are not
35823 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35824 separate its components. For example, a template like @samp{foo
35825 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35826 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35827 @var{baz}. @value{GDBN} does not transmit a space character between the
35828 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35831 @cindex @var{thread-id}, in remote protocol
35832 @anchor{thread-id syntax}
35833 Several packets and replies include a @var{thread-id} field to identify
35834 a thread. Normally these are positive numbers with a target-specific
35835 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35836 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35839 In addition, the remote protocol supports a multiprocess feature in
35840 which the @var{thread-id} syntax is extended to optionally include both
35841 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35842 The @var{pid} (process) and @var{tid} (thread) components each have the
35843 format described above: a positive number with target-specific
35844 interpretation formatted as a big-endian hex string, literal @samp{-1}
35845 to indicate all processes or threads (respectively), or @samp{0} to
35846 indicate an arbitrary process or thread. Specifying just a process, as
35847 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35848 error to specify all processes but a specific thread, such as
35849 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35850 for those packets and replies explicitly documented to include a process
35851 ID, rather than a @var{thread-id}.
35853 The multiprocess @var{thread-id} syntax extensions are only used if both
35854 @value{GDBN} and the stub report support for the @samp{multiprocess}
35855 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35858 Note that all packet forms beginning with an upper- or lower-case
35859 letter, other than those described here, are reserved for future use.
35861 Here are the packet descriptions.
35866 @cindex @samp{!} packet
35867 @anchor{extended mode}
35868 Enable extended mode. In extended mode, the remote server is made
35869 persistent. The @samp{R} packet is used to restart the program being
35875 The remote target both supports and has enabled extended mode.
35879 @cindex @samp{?} packet
35880 Indicate the reason the target halted. The reply is the same as for
35881 step and continue. This packet has a special interpretation when the
35882 target is in non-stop mode; see @ref{Remote Non-Stop}.
35885 @xref{Stop Reply Packets}, for the reply specifications.
35887 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35888 @cindex @samp{A} packet
35889 Initialized @code{argv[]} array passed into program. @var{arglen}
35890 specifies the number of bytes in the hex encoded byte stream
35891 @var{arg}. See @code{gdbserver} for more details.
35896 The arguments were set.
35902 @cindex @samp{b} packet
35903 (Don't use this packet; its behavior is not well-defined.)
35904 Change the serial line speed to @var{baud}.
35906 JTC: @emph{When does the transport layer state change? When it's
35907 received, or after the ACK is transmitted. In either case, there are
35908 problems if the command or the acknowledgment packet is dropped.}
35910 Stan: @emph{If people really wanted to add something like this, and get
35911 it working for the first time, they ought to modify ser-unix.c to send
35912 some kind of out-of-band message to a specially-setup stub and have the
35913 switch happen "in between" packets, so that from remote protocol's point
35914 of view, nothing actually happened.}
35916 @item B @var{addr},@var{mode}
35917 @cindex @samp{B} packet
35918 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35919 breakpoint at @var{addr}.
35921 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35922 (@pxref{insert breakpoint or watchpoint packet}).
35924 @cindex @samp{bc} packet
35927 Backward continue. Execute the target system in reverse. No parameter.
35928 @xref{Reverse Execution}, for more information.
35931 @xref{Stop Reply Packets}, for the reply specifications.
35933 @cindex @samp{bs} packet
35936 Backward single step. Execute one instruction in reverse. No parameter.
35937 @xref{Reverse Execution}, for more information.
35940 @xref{Stop Reply Packets}, for the reply specifications.
35942 @item c @r{[}@var{addr}@r{]}
35943 @cindex @samp{c} packet
35944 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
35945 resume at current address.
35947 This packet is deprecated for multi-threading support. @xref{vCont
35951 @xref{Stop Reply Packets}, for the reply specifications.
35953 @item C @var{sig}@r{[};@var{addr}@r{]}
35954 @cindex @samp{C} packet
35955 Continue with signal @var{sig} (hex signal number). If
35956 @samp{;@var{addr}} is omitted, resume at same address.
35958 This packet is deprecated for multi-threading support. @xref{vCont
35962 @xref{Stop Reply Packets}, for the reply specifications.
35965 @cindex @samp{d} packet
35968 Don't use this packet; instead, define a general set packet
35969 (@pxref{General Query Packets}).
35973 @cindex @samp{D} packet
35974 The first form of the packet is used to detach @value{GDBN} from the
35975 remote system. It is sent to the remote target
35976 before @value{GDBN} disconnects via the @code{detach} command.
35978 The second form, including a process ID, is used when multiprocess
35979 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35980 detach only a specific process. The @var{pid} is specified as a
35981 big-endian hex string.
35991 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35992 @cindex @samp{F} packet
35993 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35994 This is part of the File-I/O protocol extension. @xref{File-I/O
35995 Remote Protocol Extension}, for the specification.
35998 @anchor{read registers packet}
35999 @cindex @samp{g} packet
36000 Read general registers.
36004 @item @var{XX@dots{}}
36005 Each byte of register data is described by two hex digits. The bytes
36006 with the register are transmitted in target byte order. The size of
36007 each register and their position within the @samp{g} packet are
36008 determined by the @value{GDBN} internal gdbarch functions
36009 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
36010 specification of several standard @samp{g} packets is specified below.
36012 When reading registers from a trace frame (@pxref{Analyze Collected
36013 Data,,Using the Collected Data}), the stub may also return a string of
36014 literal @samp{x}'s in place of the register data digits, to indicate
36015 that the corresponding register has not been collected, thus its value
36016 is unavailable. For example, for an architecture with 4 registers of
36017 4 bytes each, the following reply indicates to @value{GDBN} that
36018 registers 0 and 2 have not been collected, while registers 1 and 3
36019 have been collected, and both have zero value:
36023 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36030 @item G @var{XX@dots{}}
36031 @cindex @samp{G} packet
36032 Write general registers. @xref{read registers packet}, for a
36033 description of the @var{XX@dots{}} data.
36043 @item H @var{op} @var{thread-id}
36044 @cindex @samp{H} packet
36045 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36046 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
36047 it should be @samp{c} for step and continue operations (note that this
36048 is deprecated, supporting the @samp{vCont} command is a better
36049 option), @samp{g} for other operations. The thread designator
36050 @var{thread-id} has the format and interpretation described in
36051 @ref{thread-id syntax}.
36062 @c 'H': How restrictive (or permissive) is the thread model. If a
36063 @c thread is selected and stopped, are other threads allowed
36064 @c to continue to execute? As I mentioned above, I think the
36065 @c semantics of each command when a thread is selected must be
36066 @c described. For example:
36068 @c 'g': If the stub supports threads and a specific thread is
36069 @c selected, returns the register block from that thread;
36070 @c otherwise returns current registers.
36072 @c 'G' If the stub supports threads and a specific thread is
36073 @c selected, sets the registers of the register block of
36074 @c that thread; otherwise sets current registers.
36076 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36077 @anchor{cycle step packet}
36078 @cindex @samp{i} packet
36079 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36080 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36081 step starting at that address.
36084 @cindex @samp{I} packet
36085 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36089 @cindex @samp{k} packet
36092 FIXME: @emph{There is no description of how to operate when a specific
36093 thread context has been selected (i.e.@: does 'k' kill only that
36096 @item m @var{addr},@var{length}
36097 @cindex @samp{m} packet
36098 Read @var{length} bytes of memory starting at address @var{addr}.
36099 Note that @var{addr} may not be aligned to any particular boundary.
36101 The stub need not use any particular size or alignment when gathering
36102 data from memory for the response; even if @var{addr} is word-aligned
36103 and @var{length} is a multiple of the word size, the stub is free to
36104 use byte accesses, or not. For this reason, this packet may not be
36105 suitable for accessing memory-mapped I/O devices.
36106 @cindex alignment of remote memory accesses
36107 @cindex size of remote memory accesses
36108 @cindex memory, alignment and size of remote accesses
36112 @item @var{XX@dots{}}
36113 Memory contents; each byte is transmitted as a two-digit hexadecimal
36114 number. The reply may contain fewer bytes than requested if the
36115 server was able to read only part of the region of memory.
36120 @item M @var{addr},@var{length}:@var{XX@dots{}}
36121 @cindex @samp{M} packet
36122 Write @var{length} bytes of memory starting at address @var{addr}.
36123 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
36124 hexadecimal number.
36131 for an error (this includes the case where only part of the data was
36136 @cindex @samp{p} packet
36137 Read the value of register @var{n}; @var{n} is in hex.
36138 @xref{read registers packet}, for a description of how the returned
36139 register value is encoded.
36143 @item @var{XX@dots{}}
36144 the register's value
36148 Indicating an unrecognized @var{query}.
36151 @item P @var{n@dots{}}=@var{r@dots{}}
36152 @anchor{write register packet}
36153 @cindex @samp{P} packet
36154 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36155 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36156 digits for each byte in the register (target byte order).
36166 @item q @var{name} @var{params}@dots{}
36167 @itemx Q @var{name} @var{params}@dots{}
36168 @cindex @samp{q} packet
36169 @cindex @samp{Q} packet
36170 General query (@samp{q}) and set (@samp{Q}). These packets are
36171 described fully in @ref{General Query Packets}.
36174 @cindex @samp{r} packet
36175 Reset the entire system.
36177 Don't use this packet; use the @samp{R} packet instead.
36180 @cindex @samp{R} packet
36181 Restart the program being debugged. @var{XX}, while needed, is ignored.
36182 This packet is only available in extended mode (@pxref{extended mode}).
36184 The @samp{R} packet has no reply.
36186 @item s @r{[}@var{addr}@r{]}
36187 @cindex @samp{s} packet
36188 Single step. @var{addr} is the address at which to resume. If
36189 @var{addr} is omitted, resume at same address.
36191 This packet is deprecated for multi-threading support. @xref{vCont
36195 @xref{Stop Reply Packets}, for the reply specifications.
36197 @item S @var{sig}@r{[};@var{addr}@r{]}
36198 @anchor{step with signal packet}
36199 @cindex @samp{S} packet
36200 Step with signal. This is analogous to the @samp{C} packet, but
36201 requests a single-step, rather than a normal resumption of execution.
36203 This packet is deprecated for multi-threading support. @xref{vCont
36207 @xref{Stop Reply Packets}, for the reply specifications.
36209 @item t @var{addr}:@var{PP},@var{MM}
36210 @cindex @samp{t} packet
36211 Search backwards starting at address @var{addr} for a match with pattern
36212 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36213 @var{addr} must be at least 3 digits.
36215 @item T @var{thread-id}
36216 @cindex @samp{T} packet
36217 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36222 thread is still alive
36228 Packets starting with @samp{v} are identified by a multi-letter name,
36229 up to the first @samp{;} or @samp{?} (or the end of the packet).
36231 @item vAttach;@var{pid}
36232 @cindex @samp{vAttach} packet
36233 Attach to a new process with the specified process ID @var{pid}.
36234 The process ID is a
36235 hexadecimal integer identifying the process. In all-stop mode, all
36236 threads in the attached process are stopped; in non-stop mode, it may be
36237 attached without being stopped if that is supported by the target.
36239 @c In non-stop mode, on a successful vAttach, the stub should set the
36240 @c current thread to a thread of the newly-attached process. After
36241 @c attaching, GDB queries for the attached process's thread ID with qC.
36242 @c Also note that, from a user perspective, whether or not the
36243 @c target is stopped on attach in non-stop mode depends on whether you
36244 @c use the foreground or background version of the attach command, not
36245 @c on what vAttach does; GDB does the right thing with respect to either
36246 @c stopping or restarting threads.
36248 This packet is only available in extended mode (@pxref{extended mode}).
36254 @item @r{Any stop packet}
36255 for success in all-stop mode (@pxref{Stop Reply Packets})
36257 for success in non-stop mode (@pxref{Remote Non-Stop})
36260 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36261 @cindex @samp{vCont} packet
36262 @anchor{vCont packet}
36263 Resume the inferior, specifying different actions for each thread.
36264 If an action is specified with no @var{thread-id}, then it is applied to any
36265 threads that don't have a specific action specified; if no default action is
36266 specified then other threads should remain stopped in all-stop mode and
36267 in their current state in non-stop mode.
36268 Specifying multiple
36269 default actions is an error; specifying no actions is also an error.
36270 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36272 Currently supported actions are:
36278 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36282 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36287 The optional argument @var{addr} normally associated with the
36288 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36289 not supported in @samp{vCont}.
36291 The @samp{t} action is only relevant in non-stop mode
36292 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36293 A stop reply should be generated for any affected thread not already stopped.
36294 When a thread is stopped by means of a @samp{t} action,
36295 the corresponding stop reply should indicate that the thread has stopped with
36296 signal @samp{0}, regardless of whether the target uses some other signal
36297 as an implementation detail.
36299 The stub must support @samp{vCont} if it reports support for
36300 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36301 this case @samp{vCont} actions can be specified to apply to all threads
36302 in a process by using the @samp{p@var{pid}.-1} form of the
36306 @xref{Stop Reply Packets}, for the reply specifications.
36309 @cindex @samp{vCont?} packet
36310 Request a list of actions supported by the @samp{vCont} packet.
36314 @item vCont@r{[};@var{action}@dots{}@r{]}
36315 The @samp{vCont} packet is supported. Each @var{action} is a supported
36316 command in the @samp{vCont} packet.
36318 The @samp{vCont} packet is not supported.
36321 @item vFile:@var{operation}:@var{parameter}@dots{}
36322 @cindex @samp{vFile} packet
36323 Perform a file operation on the target system. For details,
36324 see @ref{Host I/O Packets}.
36326 @item vFlashErase:@var{addr},@var{length}
36327 @cindex @samp{vFlashErase} packet
36328 Direct the stub to erase @var{length} bytes of flash starting at
36329 @var{addr}. The region may enclose any number of flash blocks, but
36330 its start and end must fall on block boundaries, as indicated by the
36331 flash block size appearing in the memory map (@pxref{Memory Map
36332 Format}). @value{GDBN} groups flash memory programming operations
36333 together, and sends a @samp{vFlashDone} request after each group; the
36334 stub is allowed to delay erase operation until the @samp{vFlashDone}
36335 packet is received.
36345 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36346 @cindex @samp{vFlashWrite} packet
36347 Direct the stub to write data to flash address @var{addr}. The data
36348 is passed in binary form using the same encoding as for the @samp{X}
36349 packet (@pxref{Binary Data}). The memory ranges specified by
36350 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36351 not overlap, and must appear in order of increasing addresses
36352 (although @samp{vFlashErase} packets for higher addresses may already
36353 have been received; the ordering is guaranteed only between
36354 @samp{vFlashWrite} packets). If a packet writes to an address that was
36355 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36356 target-specific method, the results are unpredictable.
36364 for vFlashWrite addressing non-flash memory
36370 @cindex @samp{vFlashDone} packet
36371 Indicate to the stub that flash programming operation is finished.
36372 The stub is permitted to delay or batch the effects of a group of
36373 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36374 @samp{vFlashDone} packet is received. The contents of the affected
36375 regions of flash memory are unpredictable until the @samp{vFlashDone}
36376 request is completed.
36378 @item vKill;@var{pid}
36379 @cindex @samp{vKill} packet
36380 Kill the process with the specified process ID. @var{pid} is a
36381 hexadecimal integer identifying the process. This packet is used in
36382 preference to @samp{k} when multiprocess protocol extensions are
36383 supported; see @ref{multiprocess extensions}.
36393 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36394 @cindex @samp{vRun} packet
36395 Run the program @var{filename}, passing it each @var{argument} on its
36396 command line. The file and arguments are hex-encoded strings. If
36397 @var{filename} is an empty string, the stub may use a default program
36398 (e.g.@: the last program run). The program is created in the stopped
36401 @c FIXME: What about non-stop mode?
36403 This packet is only available in extended mode (@pxref{extended mode}).
36409 @item @r{Any stop packet}
36410 for success (@pxref{Stop Reply Packets})
36414 @cindex @samp{vStopped} packet
36415 @xref{Notification Packets}.
36417 @item X @var{addr},@var{length}:@var{XX@dots{}}
36419 @cindex @samp{X} packet
36420 Write data to memory, where the data is transmitted in binary.
36421 @var{addr} is address, @var{length} is number of bytes,
36422 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36432 @item z @var{type},@var{addr},@var{kind}
36433 @itemx Z @var{type},@var{addr},@var{kind}
36434 @anchor{insert breakpoint or watchpoint packet}
36435 @cindex @samp{z} packet
36436 @cindex @samp{Z} packets
36437 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36438 watchpoint starting at address @var{address} of kind @var{kind}.
36440 Each breakpoint and watchpoint packet @var{type} is documented
36443 @emph{Implementation notes: A remote target shall return an empty string
36444 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36445 remote target shall support either both or neither of a given
36446 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36447 avoid potential problems with duplicate packets, the operations should
36448 be implemented in an idempotent way.}
36450 @item z0,@var{addr},@var{kind}
36451 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36452 @cindex @samp{z0} packet
36453 @cindex @samp{Z0} packet
36454 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36455 @var{addr} of type @var{kind}.
36457 A memory breakpoint is implemented by replacing the instruction at
36458 @var{addr} with a software breakpoint or trap instruction. The
36459 @var{kind} is target-specific and typically indicates the size of
36460 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36461 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36462 architectures have additional meanings for @var{kind};
36463 @var{cond_list} is an optional list of conditional expressions in bytecode
36464 form that should be evaluated on the target's side. These are the
36465 conditions that should be taken into consideration when deciding if
36466 the breakpoint trigger should be reported back to @var{GDBN}.
36468 The @var{cond_list} parameter is comprised of a series of expressions,
36469 concatenated without separators. Each expression has the following form:
36473 @item X @var{len},@var{expr}
36474 @var{len} is the length of the bytecode expression and @var{expr} is the
36475 actual conditional expression in bytecode form.
36479 The optional @var{cmd_list} parameter introduces commands that may be
36480 run on the target, rather than being reported back to @value{GDBN}.
36481 The parameter starts with a numeric flag @var{persist}; if the flag is
36482 nonzero, then the breakpoint may remain active and the commands
36483 continue to be run even when @value{GDBN} disconnects from the target.
36484 Following this flag is a series of expressions concatenated with no
36485 separators. Each expression has the following form:
36489 @item X @var{len},@var{expr}
36490 @var{len} is the length of the bytecode expression and @var{expr} is the
36491 actual conditional expression in bytecode form.
36495 see @ref{Architecture-Specific Protocol Details}.
36497 @emph{Implementation note: It is possible for a target to copy or move
36498 code that contains memory breakpoints (e.g., when implementing
36499 overlays). The behavior of this packet, in the presence of such a
36500 target, is not defined.}
36512 @item z1,@var{addr},@var{kind}
36513 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36514 @cindex @samp{z1} packet
36515 @cindex @samp{Z1} packet
36516 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36517 address @var{addr}.
36519 A hardware breakpoint is implemented using a mechanism that is not
36520 dependant on being able to modify the target's memory. @var{kind}
36521 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36523 @emph{Implementation note: A hardware breakpoint is not affected by code
36536 @item z2,@var{addr},@var{kind}
36537 @itemx Z2,@var{addr},@var{kind}
36538 @cindex @samp{z2} packet
36539 @cindex @samp{Z2} packet
36540 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36541 @var{kind} is interpreted as the number of bytes to watch.
36553 @item z3,@var{addr},@var{kind}
36554 @itemx Z3,@var{addr},@var{kind}
36555 @cindex @samp{z3} packet
36556 @cindex @samp{Z3} packet
36557 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36558 @var{kind} is interpreted as the number of bytes to watch.
36570 @item z4,@var{addr},@var{kind}
36571 @itemx Z4,@var{addr},@var{kind}
36572 @cindex @samp{z4} packet
36573 @cindex @samp{Z4} packet
36574 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36575 @var{kind} is interpreted as the number of bytes to watch.
36589 @node Stop Reply Packets
36590 @section Stop Reply Packets
36591 @cindex stop reply packets
36593 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36594 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36595 receive any of the below as a reply. Except for @samp{?}
36596 and @samp{vStopped}, that reply is only returned
36597 when the target halts. In the below the exact meaning of @dfn{signal
36598 number} is defined by the header @file{include/gdb/signals.h} in the
36599 @value{GDBN} source code.
36601 As in the description of request packets, we include spaces in the
36602 reply templates for clarity; these are not part of the reply packet's
36603 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36609 The program received signal number @var{AA} (a two-digit hexadecimal
36610 number). This is equivalent to a @samp{T} response with no
36611 @var{n}:@var{r} pairs.
36613 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36614 @cindex @samp{T} packet reply
36615 The program received signal number @var{AA} (a two-digit hexadecimal
36616 number). This is equivalent to an @samp{S} response, except that the
36617 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36618 and other information directly in the stop reply packet, reducing
36619 round-trip latency. Single-step and breakpoint traps are reported
36620 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36624 If @var{n} is a hexadecimal number, it is a register number, and the
36625 corresponding @var{r} gives that register's value. @var{r} is a
36626 series of bytes in target byte order, with each byte given by a
36627 two-digit hex number.
36630 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36631 the stopped thread, as specified in @ref{thread-id syntax}.
36634 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36635 the core on which the stop event was detected.
36638 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36639 specific event that stopped the target. The currently defined stop
36640 reasons are listed below. @var{aa} should be @samp{05}, the trap
36641 signal. At most one stop reason should be present.
36644 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36645 and go on to the next; this allows us to extend the protocol in the
36649 The currently defined stop reasons are:
36655 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36658 @cindex shared library events, remote reply
36660 The packet indicates that the loaded libraries have changed.
36661 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36662 list of loaded libraries. @var{r} is ignored.
36664 @cindex replay log events, remote reply
36666 The packet indicates that the target cannot continue replaying
36667 logged execution events, because it has reached the end (or the
36668 beginning when executing backward) of the log. The value of @var{r}
36669 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36670 for more information.
36674 @itemx W @var{AA} ; process:@var{pid}
36675 The process exited, and @var{AA} is the exit status. This is only
36676 applicable to certain targets.
36678 The second form of the response, including the process ID of the exited
36679 process, can be used only when @value{GDBN} has reported support for
36680 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36681 The @var{pid} is formatted as a big-endian hex string.
36684 @itemx X @var{AA} ; process:@var{pid}
36685 The process terminated with signal @var{AA}.
36687 The second form of the response, including the process ID of the
36688 terminated process, can be used only when @value{GDBN} has reported
36689 support for multiprocess protocol extensions; see @ref{multiprocess
36690 extensions}. The @var{pid} is formatted as a big-endian hex string.
36692 @item O @var{XX}@dots{}
36693 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36694 written as the program's console output. This can happen at any time
36695 while the program is running and the debugger should continue to wait
36696 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36698 @item F @var{call-id},@var{parameter}@dots{}
36699 @var{call-id} is the identifier which says which host system call should
36700 be called. This is just the name of the function. Translation into the
36701 correct system call is only applicable as it's defined in @value{GDBN}.
36702 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36705 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36706 this very system call.
36708 The target replies with this packet when it expects @value{GDBN} to
36709 call a host system call on behalf of the target. @value{GDBN} replies
36710 with an appropriate @samp{F} packet and keeps up waiting for the next
36711 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36712 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36713 Protocol Extension}, for more details.
36717 @node General Query Packets
36718 @section General Query Packets
36719 @cindex remote query requests
36721 Packets starting with @samp{q} are @dfn{general query packets};
36722 packets starting with @samp{Q} are @dfn{general set packets}. General
36723 query and set packets are a semi-unified form for retrieving and
36724 sending information to and from the stub.
36726 The initial letter of a query or set packet is followed by a name
36727 indicating what sort of thing the packet applies to. For example,
36728 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36729 definitions with the stub. These packet names follow some
36734 The name must not contain commas, colons or semicolons.
36736 Most @value{GDBN} query and set packets have a leading upper case
36739 The names of custom vendor packets should use a company prefix, in
36740 lower case, followed by a period. For example, packets designed at
36741 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36742 foos) or @samp{Qacme.bar} (for setting bars).
36745 The name of a query or set packet should be separated from any
36746 parameters by a @samp{:}; the parameters themselves should be
36747 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36748 full packet name, and check for a separator or the end of the packet,
36749 in case two packet names share a common prefix. New packets should not begin
36750 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36751 packets predate these conventions, and have arguments without any terminator
36752 for the packet name; we suspect they are in widespread use in places that
36753 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36754 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36757 Like the descriptions of the other packets, each description here
36758 has a template showing the packet's overall syntax, followed by an
36759 explanation of the packet's meaning. We include spaces in some of the
36760 templates for clarity; these are not part of the packet's syntax. No
36761 @value{GDBN} packet uses spaces to separate its components.
36763 Here are the currently defined query and set packets:
36769 Turn on or off the agent as a helper to perform some debugging operations
36770 delegated from @value{GDBN} (@pxref{Control Agent}).
36772 @item QAllow:@var{op}:@var{val}@dots{}
36773 @cindex @samp{QAllow} packet
36774 Specify which operations @value{GDBN} expects to request of the
36775 target, as a semicolon-separated list of operation name and value
36776 pairs. Possible values for @var{op} include @samp{WriteReg},
36777 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36778 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36779 indicating that @value{GDBN} will not request the operation, or 1,
36780 indicating that it may. (The target can then use this to set up its
36781 own internals optimally, for instance if the debugger never expects to
36782 insert breakpoints, it may not need to install its own trap handler.)
36785 @cindex current thread, remote request
36786 @cindex @samp{qC} packet
36787 Return the current thread ID.
36791 @item QC @var{thread-id}
36792 Where @var{thread-id} is a thread ID as documented in
36793 @ref{thread-id syntax}.
36794 @item @r{(anything else)}
36795 Any other reply implies the old thread ID.
36798 @item qCRC:@var{addr},@var{length}
36799 @cindex CRC of memory block, remote request
36800 @cindex @samp{qCRC} packet
36801 Compute the CRC checksum of a block of memory using CRC-32 defined in
36802 IEEE 802.3. The CRC is computed byte at a time, taking the most
36803 significant bit of each byte first. The initial pattern code
36804 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36806 @emph{Note:} This is the same CRC used in validating separate debug
36807 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36808 Files}). However the algorithm is slightly different. When validating
36809 separate debug files, the CRC is computed taking the @emph{least}
36810 significant bit of each byte first, and the final result is inverted to
36811 detect trailing zeros.
36816 An error (such as memory fault)
36817 @item C @var{crc32}
36818 The specified memory region's checksum is @var{crc32}.
36821 @item QDisableRandomization:@var{value}
36822 @cindex disable address space randomization, remote request
36823 @cindex @samp{QDisableRandomization} packet
36824 Some target operating systems will randomize the virtual address space
36825 of the inferior process as a security feature, but provide a feature
36826 to disable such randomization, e.g.@: to allow for a more deterministic
36827 debugging experience. On such systems, this packet with a @var{value}
36828 of 1 directs the target to disable address space randomization for
36829 processes subsequently started via @samp{vRun} packets, while a packet
36830 with a @var{value} of 0 tells the target to enable address space
36833 This packet is only available in extended mode (@pxref{extended mode}).
36838 The request succeeded.
36841 An error occurred. @var{nn} are hex digits.
36844 An empty reply indicates that @samp{QDisableRandomization} is not supported
36848 This packet is not probed by default; the remote stub must request it,
36849 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36850 This should only be done on targets that actually support disabling
36851 address space randomization.
36854 @itemx qsThreadInfo
36855 @cindex list active threads, remote request
36856 @cindex @samp{qfThreadInfo} packet
36857 @cindex @samp{qsThreadInfo} packet
36858 Obtain a list of all active thread IDs from the target (OS). Since there
36859 may be too many active threads to fit into one reply packet, this query
36860 works iteratively: it may require more than one query/reply sequence to
36861 obtain the entire list of threads. The first query of the sequence will
36862 be the @samp{qfThreadInfo} query; subsequent queries in the
36863 sequence will be the @samp{qsThreadInfo} query.
36865 NOTE: This packet replaces the @samp{qL} query (see below).
36869 @item m @var{thread-id}
36871 @item m @var{thread-id},@var{thread-id}@dots{}
36872 a comma-separated list of thread IDs
36874 (lower case letter @samp{L}) denotes end of list.
36877 In response to each query, the target will reply with a list of one or
36878 more thread IDs, separated by commas.
36879 @value{GDBN} will respond to each reply with a request for more thread
36880 ids (using the @samp{qs} form of the query), until the target responds
36881 with @samp{l} (lower-case ell, for @dfn{last}).
36882 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36885 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36886 @cindex get thread-local storage address, remote request
36887 @cindex @samp{qGetTLSAddr} packet
36888 Fetch the address associated with thread local storage specified
36889 by @var{thread-id}, @var{offset}, and @var{lm}.
36891 @var{thread-id} is the thread ID associated with the
36892 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36894 @var{offset} is the (big endian, hex encoded) offset associated with the
36895 thread local variable. (This offset is obtained from the debug
36896 information associated with the variable.)
36898 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36899 load module associated with the thread local storage. For example,
36900 a @sc{gnu}/Linux system will pass the link map address of the shared
36901 object associated with the thread local storage under consideration.
36902 Other operating environments may choose to represent the load module
36903 differently, so the precise meaning of this parameter will vary.
36907 @item @var{XX}@dots{}
36908 Hex encoded (big endian) bytes representing the address of the thread
36909 local storage requested.
36912 An error occurred. @var{nn} are hex digits.
36915 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36918 @item qGetTIBAddr:@var{thread-id}
36919 @cindex get thread information block address
36920 @cindex @samp{qGetTIBAddr} packet
36921 Fetch address of the Windows OS specific Thread Information Block.
36923 @var{thread-id} is the thread ID associated with the thread.
36927 @item @var{XX}@dots{}
36928 Hex encoded (big endian) bytes representing the linear address of the
36929 thread information block.
36932 An error occured. This means that either the thread was not found, or the
36933 address could not be retrieved.
36936 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36939 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36940 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36941 digit) is one to indicate the first query and zero to indicate a
36942 subsequent query; @var{threadcount} (two hex digits) is the maximum
36943 number of threads the response packet can contain; and @var{nextthread}
36944 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36945 returned in the response as @var{argthread}.
36947 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36951 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36952 Where: @var{count} (two hex digits) is the number of threads being
36953 returned; @var{done} (one hex digit) is zero to indicate more threads
36954 and one indicates no further threads; @var{argthreadid} (eight hex
36955 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36956 is a sequence of thread IDs from the target. @var{threadid} (eight hex
36957 digits). See @code{remote.c:parse_threadlist_response()}.
36961 @cindex section offsets, remote request
36962 @cindex @samp{qOffsets} packet
36963 Get section offsets that the target used when relocating the downloaded
36968 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36969 Relocate the @code{Text} section by @var{xxx} from its original address.
36970 Relocate the @code{Data} section by @var{yyy} from its original address.
36971 If the object file format provides segment information (e.g.@: @sc{elf}
36972 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36973 segments by the supplied offsets.
36975 @emph{Note: while a @code{Bss} offset may be included in the response,
36976 @value{GDBN} ignores this and instead applies the @code{Data} offset
36977 to the @code{Bss} section.}
36979 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36980 Relocate the first segment of the object file, which conventionally
36981 contains program code, to a starting address of @var{xxx}. If
36982 @samp{DataSeg} is specified, relocate the second segment, which
36983 conventionally contains modifiable data, to a starting address of
36984 @var{yyy}. @value{GDBN} will report an error if the object file
36985 does not contain segment information, or does not contain at least
36986 as many segments as mentioned in the reply. Extra segments are
36987 kept at fixed offsets relative to the last relocated segment.
36990 @item qP @var{mode} @var{thread-id}
36991 @cindex thread information, remote request
36992 @cindex @samp{qP} packet
36993 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36994 encoded 32 bit mode; @var{thread-id} is a thread ID
36995 (@pxref{thread-id syntax}).
36997 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37000 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37004 @cindex non-stop mode, remote request
37005 @cindex @samp{QNonStop} packet
37007 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37008 @xref{Remote Non-Stop}, for more information.
37013 The request succeeded.
37016 An error occurred. @var{nn} are hex digits.
37019 An empty reply indicates that @samp{QNonStop} is not supported by
37023 This packet is not probed by default; the remote stub must request it,
37024 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37025 Use of this packet is controlled by the @code{set non-stop} command;
37026 @pxref{Non-Stop Mode}.
37028 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37029 @cindex pass signals to inferior, remote request
37030 @cindex @samp{QPassSignals} packet
37031 @anchor{QPassSignals}
37032 Each listed @var{signal} should be passed directly to the inferior process.
37033 Signals are numbered identically to continue packets and stop replies
37034 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37035 strictly greater than the previous item. These signals do not need to stop
37036 the inferior, or be reported to @value{GDBN}. All other signals should be
37037 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37038 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37039 new list. This packet improves performance when using @samp{handle
37040 @var{signal} nostop noprint pass}.
37045 The request succeeded.
37048 An error occurred. @var{nn} are hex digits.
37051 An empty reply indicates that @samp{QPassSignals} is not supported by
37055 Use of this packet is controlled by the @code{set remote pass-signals}
37056 command (@pxref{Remote Configuration, set remote pass-signals}).
37057 This packet is not probed by default; the remote stub must request it,
37058 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37060 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37061 @cindex signals the inferior may see, remote request
37062 @cindex @samp{QProgramSignals} packet
37063 @anchor{QProgramSignals}
37064 Each listed @var{signal} may be delivered to the inferior process.
37065 Others should be silently discarded.
37067 In some cases, the remote stub may need to decide whether to deliver a
37068 signal to the program or not without @value{GDBN} involvement. One
37069 example of that is while detaching --- the program's threads may have
37070 stopped for signals that haven't yet had a chance of being reported to
37071 @value{GDBN}, and so the remote stub can use the signal list specified
37072 by this packet to know whether to deliver or ignore those pending
37075 This does not influence whether to deliver a signal as requested by a
37076 resumption packet (@pxref{vCont packet}).
37078 Signals are numbered identically to continue packets and stop replies
37079 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37080 strictly greater than the previous item. Multiple
37081 @samp{QProgramSignals} packets do not combine; any earlier
37082 @samp{QProgramSignals} list is completely replaced by the new list.
37087 The request succeeded.
37090 An error occurred. @var{nn} are hex digits.
37093 An empty reply indicates that @samp{QProgramSignals} is not supported
37097 Use of this packet is controlled by the @code{set remote program-signals}
37098 command (@pxref{Remote Configuration, set remote program-signals}).
37099 This packet is not probed by default; the remote stub must request it,
37100 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37102 @item qRcmd,@var{command}
37103 @cindex execute remote command, remote request
37104 @cindex @samp{qRcmd} packet
37105 @var{command} (hex encoded) is passed to the local interpreter for
37106 execution. Invalid commands should be reported using the output
37107 string. Before the final result packet, the target may also respond
37108 with a number of intermediate @samp{O@var{output}} console output
37109 packets. @emph{Implementors should note that providing access to a
37110 stubs's interpreter may have security implications}.
37115 A command response with no output.
37117 A command response with the hex encoded output string @var{OUTPUT}.
37119 Indicate a badly formed request.
37121 An empty reply indicates that @samp{qRcmd} is not recognized.
37124 (Note that the @code{qRcmd} packet's name is separated from the
37125 command by a @samp{,}, not a @samp{:}, contrary to the naming
37126 conventions above. Please don't use this packet as a model for new
37129 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37130 @cindex searching memory, in remote debugging
37131 @cindex @samp{qSearch:memory} packet
37132 @anchor{qSearch memory}
37133 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37134 @var{address} and @var{length} are encoded in hex.
37135 @var{search-pattern} is a sequence of bytes, hex encoded.
37140 The pattern was not found.
37142 The pattern was found at @var{address}.
37144 A badly formed request or an error was encountered while searching memory.
37146 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37149 @item QStartNoAckMode
37150 @cindex @samp{QStartNoAckMode} packet
37151 @anchor{QStartNoAckMode}
37152 Request that the remote stub disable the normal @samp{+}/@samp{-}
37153 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37158 The stub has switched to no-acknowledgment mode.
37159 @value{GDBN} acknowledges this reponse,
37160 but neither the stub nor @value{GDBN} shall send or expect further
37161 @samp{+}/@samp{-} acknowledgments in the current connection.
37163 An empty reply indicates that the stub does not support no-acknowledgment mode.
37166 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37167 @cindex supported packets, remote query
37168 @cindex features of the remote protocol
37169 @cindex @samp{qSupported} packet
37170 @anchor{qSupported}
37171 Tell the remote stub about features supported by @value{GDBN}, and
37172 query the stub for features it supports. This packet allows
37173 @value{GDBN} and the remote stub to take advantage of each others'
37174 features. @samp{qSupported} also consolidates multiple feature probes
37175 at startup, to improve @value{GDBN} performance---a single larger
37176 packet performs better than multiple smaller probe packets on
37177 high-latency links. Some features may enable behavior which must not
37178 be on by default, e.g.@: because it would confuse older clients or
37179 stubs. Other features may describe packets which could be
37180 automatically probed for, but are not. These features must be
37181 reported before @value{GDBN} will use them. This ``default
37182 unsupported'' behavior is not appropriate for all packets, but it
37183 helps to keep the initial connection time under control with new
37184 versions of @value{GDBN} which support increasing numbers of packets.
37188 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37189 The stub supports or does not support each returned @var{stubfeature},
37190 depending on the form of each @var{stubfeature} (see below for the
37193 An empty reply indicates that @samp{qSupported} is not recognized,
37194 or that no features needed to be reported to @value{GDBN}.
37197 The allowed forms for each feature (either a @var{gdbfeature} in the
37198 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37202 @item @var{name}=@var{value}
37203 The remote protocol feature @var{name} is supported, and associated
37204 with the specified @var{value}. The format of @var{value} depends
37205 on the feature, but it must not include a semicolon.
37207 The remote protocol feature @var{name} is supported, and does not
37208 need an associated value.
37210 The remote protocol feature @var{name} is not supported.
37212 The remote protocol feature @var{name} may be supported, and
37213 @value{GDBN} should auto-detect support in some other way when it is
37214 needed. This form will not be used for @var{gdbfeature} notifications,
37215 but may be used for @var{stubfeature} responses.
37218 Whenever the stub receives a @samp{qSupported} request, the
37219 supplied set of @value{GDBN} features should override any previous
37220 request. This allows @value{GDBN} to put the stub in a known
37221 state, even if the stub had previously been communicating with
37222 a different version of @value{GDBN}.
37224 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37229 This feature indicates whether @value{GDBN} supports multiprocess
37230 extensions to the remote protocol. @value{GDBN} does not use such
37231 extensions unless the stub also reports that it supports them by
37232 including @samp{multiprocess+} in its @samp{qSupported} reply.
37233 @xref{multiprocess extensions}, for details.
37236 This feature indicates that @value{GDBN} supports the XML target
37237 description. If the stub sees @samp{xmlRegisters=} with target
37238 specific strings separated by a comma, it will report register
37242 This feature indicates whether @value{GDBN} supports the
37243 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37244 instruction reply packet}).
37247 Stubs should ignore any unknown values for
37248 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37249 packet supports receiving packets of unlimited length (earlier
37250 versions of @value{GDBN} may reject overly long responses). Additional values
37251 for @var{gdbfeature} may be defined in the future to let the stub take
37252 advantage of new features in @value{GDBN}, e.g.@: incompatible
37253 improvements in the remote protocol---the @samp{multiprocess} feature is
37254 an example of such a feature. The stub's reply should be independent
37255 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37256 describes all the features it supports, and then the stub replies with
37257 all the features it supports.
37259 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37260 responses, as long as each response uses one of the standard forms.
37262 Some features are flags. A stub which supports a flag feature
37263 should respond with a @samp{+} form response. Other features
37264 require values, and the stub should respond with an @samp{=}
37267 Each feature has a default value, which @value{GDBN} will use if
37268 @samp{qSupported} is not available or if the feature is not mentioned
37269 in the @samp{qSupported} response. The default values are fixed; a
37270 stub is free to omit any feature responses that match the defaults.
37272 Not all features can be probed, but for those which can, the probing
37273 mechanism is useful: in some cases, a stub's internal
37274 architecture may not allow the protocol layer to know some information
37275 about the underlying target in advance. This is especially common in
37276 stubs which may be configured for multiple targets.
37278 These are the currently defined stub features and their properties:
37280 @multitable @columnfractions 0.35 0.2 0.12 0.2
37281 @c NOTE: The first row should be @headitem, but we do not yet require
37282 @c a new enough version of Texinfo (4.7) to use @headitem.
37284 @tab Value Required
37288 @item @samp{PacketSize}
37293 @item @samp{qXfer:auxv:read}
37298 @item @samp{qXfer:features:read}
37303 @item @samp{qXfer:libraries:read}
37308 @item @samp{qXfer:memory-map:read}
37313 @item @samp{qXfer:sdata:read}
37318 @item @samp{qXfer:spu:read}
37323 @item @samp{qXfer:spu:write}
37328 @item @samp{qXfer:siginfo:read}
37333 @item @samp{qXfer:siginfo:write}
37338 @item @samp{qXfer:threads:read}
37343 @item @samp{qXfer:traceframe-info:read}
37348 @item @samp{qXfer:uib:read}
37353 @item @samp{qXfer:fdpic:read}
37358 @item @samp{QNonStop}
37363 @item @samp{QPassSignals}
37368 @item @samp{QStartNoAckMode}
37373 @item @samp{multiprocess}
37378 @item @samp{ConditionalBreakpoints}
37383 @item @samp{ConditionalTracepoints}
37388 @item @samp{ReverseContinue}
37393 @item @samp{ReverseStep}
37398 @item @samp{TracepointSource}
37403 @item @samp{QAgent}
37408 @item @samp{QAllow}
37413 @item @samp{QDisableRandomization}
37418 @item @samp{EnableDisableTracepoints}
37423 @item @samp{tracenz}
37428 @item @samp{BreakpointCommands}
37435 These are the currently defined stub features, in more detail:
37438 @cindex packet size, remote protocol
37439 @item PacketSize=@var{bytes}
37440 The remote stub can accept packets up to at least @var{bytes} in
37441 length. @value{GDBN} will send packets up to this size for bulk
37442 transfers, and will never send larger packets. This is a limit on the
37443 data characters in the packet, including the frame and checksum.
37444 There is no trailing NUL byte in a remote protocol packet; if the stub
37445 stores packets in a NUL-terminated format, it should allow an extra
37446 byte in its buffer for the NUL. If this stub feature is not supported,
37447 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37449 @item qXfer:auxv:read
37450 The remote stub understands the @samp{qXfer:auxv:read} packet
37451 (@pxref{qXfer auxiliary vector read}).
37453 @item qXfer:features:read
37454 The remote stub understands the @samp{qXfer:features:read} packet
37455 (@pxref{qXfer target description read}).
37457 @item qXfer:libraries:read
37458 The remote stub understands the @samp{qXfer:libraries:read} packet
37459 (@pxref{qXfer library list read}).
37461 @item qXfer:libraries-svr4:read
37462 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37463 (@pxref{qXfer svr4 library list read}).
37465 @item qXfer:memory-map:read
37466 The remote stub understands the @samp{qXfer:memory-map:read} packet
37467 (@pxref{qXfer memory map read}).
37469 @item qXfer:sdata:read
37470 The remote stub understands the @samp{qXfer:sdata:read} packet
37471 (@pxref{qXfer sdata read}).
37473 @item qXfer:spu:read
37474 The remote stub understands the @samp{qXfer:spu:read} packet
37475 (@pxref{qXfer spu read}).
37477 @item qXfer:spu:write
37478 The remote stub understands the @samp{qXfer:spu:write} packet
37479 (@pxref{qXfer spu write}).
37481 @item qXfer:siginfo:read
37482 The remote stub understands the @samp{qXfer:siginfo:read} packet
37483 (@pxref{qXfer siginfo read}).
37485 @item qXfer:siginfo:write
37486 The remote stub understands the @samp{qXfer:siginfo:write} packet
37487 (@pxref{qXfer siginfo write}).
37489 @item qXfer:threads:read
37490 The remote stub understands the @samp{qXfer:threads:read} packet
37491 (@pxref{qXfer threads read}).
37493 @item qXfer:traceframe-info:read
37494 The remote stub understands the @samp{qXfer:traceframe-info:read}
37495 packet (@pxref{qXfer traceframe info read}).
37497 @item qXfer:uib:read
37498 The remote stub understands the @samp{qXfer:uib:read}
37499 packet (@pxref{qXfer unwind info block}).
37501 @item qXfer:fdpic:read
37502 The remote stub understands the @samp{qXfer:fdpic:read}
37503 packet (@pxref{qXfer fdpic loadmap read}).
37506 The remote stub understands the @samp{QNonStop} packet
37507 (@pxref{QNonStop}).
37510 The remote stub understands the @samp{QPassSignals} packet
37511 (@pxref{QPassSignals}).
37513 @item QStartNoAckMode
37514 The remote stub understands the @samp{QStartNoAckMode} packet and
37515 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37518 @anchor{multiprocess extensions}
37519 @cindex multiprocess extensions, in remote protocol
37520 The remote stub understands the multiprocess extensions to the remote
37521 protocol syntax. The multiprocess extensions affect the syntax of
37522 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37523 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37524 replies. Note that reporting this feature indicates support for the
37525 syntactic extensions only, not that the stub necessarily supports
37526 debugging of more than one process at a time. The stub must not use
37527 multiprocess extensions in packet replies unless @value{GDBN} has also
37528 indicated it supports them in its @samp{qSupported} request.
37530 @item qXfer:osdata:read
37531 The remote stub understands the @samp{qXfer:osdata:read} packet
37532 ((@pxref{qXfer osdata read}).
37534 @item ConditionalBreakpoints
37535 The target accepts and implements evaluation of conditional expressions
37536 defined for breakpoints. The target will only report breakpoint triggers
37537 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37539 @item ConditionalTracepoints
37540 The remote stub accepts and implements conditional expressions defined
37541 for tracepoints (@pxref{Tracepoint Conditions}).
37543 @item ReverseContinue
37544 The remote stub accepts and implements the reverse continue packet
37548 The remote stub accepts and implements the reverse step packet
37551 @item TracepointSource
37552 The remote stub understands the @samp{QTDPsrc} packet that supplies
37553 the source form of tracepoint definitions.
37556 The remote stub understands the @samp{QAgent} packet.
37559 The remote stub understands the @samp{QAllow} packet.
37561 @item QDisableRandomization
37562 The remote stub understands the @samp{QDisableRandomization} packet.
37564 @item StaticTracepoint
37565 @cindex static tracepoints, in remote protocol
37566 The remote stub supports static tracepoints.
37568 @item InstallInTrace
37569 @anchor{install tracepoint in tracing}
37570 The remote stub supports installing tracepoint in tracing.
37572 @item EnableDisableTracepoints
37573 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37574 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37575 to be enabled and disabled while a trace experiment is running.
37578 @cindex string tracing, in remote protocol
37579 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37580 See @ref{Bytecode Descriptions} for details about the bytecode.
37582 @item BreakpointCommands
37583 @cindex breakpoint commands, in remote protocol
37584 The remote stub supports running a breakpoint's command list itself,
37585 rather than reporting the hit to @value{GDBN}.
37590 @cindex symbol lookup, remote request
37591 @cindex @samp{qSymbol} packet
37592 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37593 requests. Accept requests from the target for the values of symbols.
37598 The target does not need to look up any (more) symbols.
37599 @item qSymbol:@var{sym_name}
37600 The target requests the value of symbol @var{sym_name} (hex encoded).
37601 @value{GDBN} may provide the value by using the
37602 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37606 @item qSymbol:@var{sym_value}:@var{sym_name}
37607 Set the value of @var{sym_name} to @var{sym_value}.
37609 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37610 target has previously requested.
37612 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37613 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37619 The target does not need to look up any (more) symbols.
37620 @item qSymbol:@var{sym_name}
37621 The target requests the value of a new symbol @var{sym_name} (hex
37622 encoded). @value{GDBN} will continue to supply the values of symbols
37623 (if available), until the target ceases to request them.
37628 @itemx QTDisconnected
37635 @itemx qTMinFTPILen
37637 @xref{Tracepoint Packets}.
37639 @item qThreadExtraInfo,@var{thread-id}
37640 @cindex thread attributes info, remote request
37641 @cindex @samp{qThreadExtraInfo} packet
37642 Obtain a printable string description of a thread's attributes from
37643 the target OS. @var{thread-id} is a thread ID;
37644 see @ref{thread-id syntax}. This
37645 string may contain anything that the target OS thinks is interesting
37646 for @value{GDBN} to tell the user about the thread. The string is
37647 displayed in @value{GDBN}'s @code{info threads} display. Some
37648 examples of possible thread extra info strings are @samp{Runnable}, or
37649 @samp{Blocked on Mutex}.
37653 @item @var{XX}@dots{}
37654 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37655 comprising the printable string containing the extra information about
37656 the thread's attributes.
37659 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37660 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37661 conventions above. Please don't use this packet as a model for new
37680 @xref{Tracepoint Packets}.
37682 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37683 @cindex read special object, remote request
37684 @cindex @samp{qXfer} packet
37685 @anchor{qXfer read}
37686 Read uninterpreted bytes from the target's special data area
37687 identified by the keyword @var{object}. Request @var{length} bytes
37688 starting at @var{offset} bytes into the data. The content and
37689 encoding of @var{annex} is specific to @var{object}; it can supply
37690 additional details about what data to access.
37692 Here are the specific requests of this form defined so far. All
37693 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37694 formats, listed below.
37697 @item qXfer:auxv:read::@var{offset},@var{length}
37698 @anchor{qXfer auxiliary vector read}
37699 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37700 auxiliary vector}. Note @var{annex} must be empty.
37702 This packet is not probed by default; the remote stub must request it,
37703 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37705 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37706 @anchor{qXfer target description read}
37707 Access the @dfn{target description}. @xref{Target Descriptions}. The
37708 annex specifies which XML document to access. The main description is
37709 always loaded from the @samp{target.xml} annex.
37711 This packet is not probed by default; the remote stub must request it,
37712 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37714 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37715 @anchor{qXfer library list read}
37716 Access the target's list of loaded libraries. @xref{Library List Format}.
37717 The annex part of the generic @samp{qXfer} packet must be empty
37718 (@pxref{qXfer read}).
37720 Targets which maintain a list of libraries in the program's memory do
37721 not need to implement this packet; it is designed for platforms where
37722 the operating system manages the list of loaded libraries.
37724 This packet is not probed by default; the remote stub must request it,
37725 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37727 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37728 @anchor{qXfer svr4 library list read}
37729 Access the target's list of loaded libraries when the target is an SVR4
37730 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37731 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37733 This packet is optional for better performance on SVR4 targets.
37734 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37736 This packet is not probed by default; the remote stub must request it,
37737 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37739 @item qXfer:memory-map:read::@var{offset},@var{length}
37740 @anchor{qXfer memory map read}
37741 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37742 annex part of the generic @samp{qXfer} packet must be empty
37743 (@pxref{qXfer read}).
37745 This packet is not probed by default; the remote stub must request it,
37746 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37748 @item qXfer:sdata:read::@var{offset},@var{length}
37749 @anchor{qXfer sdata read}
37751 Read contents of the extra collected static tracepoint marker
37752 information. The annex part of the generic @samp{qXfer} packet must
37753 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37756 This packet is not probed by default; the remote stub must request it,
37757 by supplying an appropriate @samp{qSupported} response
37758 (@pxref{qSupported}).
37760 @item qXfer:siginfo:read::@var{offset},@var{length}
37761 @anchor{qXfer siginfo read}
37762 Read contents of the extra signal information on the target
37763 system. The annex part of the generic @samp{qXfer} packet must be
37764 empty (@pxref{qXfer read}).
37766 This packet is not probed by default; the remote stub must request it,
37767 by supplying an appropriate @samp{qSupported} response
37768 (@pxref{qSupported}).
37770 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37771 @anchor{qXfer spu read}
37772 Read contents of an @code{spufs} file on the target system. The
37773 annex specifies which file to read; it must be of the form
37774 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37775 in the target process, and @var{name} identifes the @code{spufs} file
37776 in that context to be accessed.
37778 This packet is not probed by default; the remote stub must request it,
37779 by supplying an appropriate @samp{qSupported} response
37780 (@pxref{qSupported}).
37782 @item qXfer:threads:read::@var{offset},@var{length}
37783 @anchor{qXfer threads read}
37784 Access the list of threads on target. @xref{Thread List Format}. The
37785 annex part of the generic @samp{qXfer} packet must be empty
37786 (@pxref{qXfer read}).
37788 This packet is not probed by default; the remote stub must request it,
37789 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37791 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37792 @anchor{qXfer traceframe info read}
37794 Return a description of the current traceframe's contents.
37795 @xref{Traceframe Info Format}. The annex part of the generic
37796 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37798 This packet is not probed by default; the remote stub must request it,
37799 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37801 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37802 @anchor{qXfer unwind info block}
37804 Return the unwind information block for @var{pc}. This packet is used
37805 on OpenVMS/ia64 to ask the kernel unwind information.
37807 This packet is not probed by default.
37809 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37810 @anchor{qXfer fdpic loadmap read}
37811 Read contents of @code{loadmap}s on the target system. The
37812 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37813 executable @code{loadmap} or interpreter @code{loadmap} to read.
37815 This packet is not probed by default; the remote stub must request it,
37816 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37818 @item qXfer:osdata:read::@var{offset},@var{length}
37819 @anchor{qXfer osdata read}
37820 Access the target's @dfn{operating system information}.
37821 @xref{Operating System Information}.
37828 Data @var{data} (@pxref{Binary Data}) has been read from the
37829 target. There may be more data at a higher address (although
37830 it is permitted to return @samp{m} even for the last valid
37831 block of data, as long as at least one byte of data was read).
37832 @var{data} may have fewer bytes than the @var{length} in the
37836 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37837 There is no more data to be read. @var{data} may have fewer bytes
37838 than the @var{length} in the request.
37841 The @var{offset} in the request is at the end of the data.
37842 There is no more data to be read.
37845 The request was malformed, or @var{annex} was invalid.
37848 The offset was invalid, or there was an error encountered reading the data.
37849 @var{nn} is a hex-encoded @code{errno} value.
37852 An empty reply indicates the @var{object} string was not recognized by
37853 the stub, or that the object does not support reading.
37856 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37857 @cindex write data into object, remote request
37858 @anchor{qXfer write}
37859 Write uninterpreted bytes into the target's special data area
37860 identified by the keyword @var{object}, starting at @var{offset} bytes
37861 into the data. @var{data}@dots{} is the binary-encoded data
37862 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
37863 is specific to @var{object}; it can supply additional details about what data
37866 Here are the specific requests of this form defined so far. All
37867 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37868 formats, listed below.
37871 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37872 @anchor{qXfer siginfo write}
37873 Write @var{data} to the extra signal information on the target system.
37874 The annex part of the generic @samp{qXfer} packet must be
37875 empty (@pxref{qXfer write}).
37877 This packet is not probed by default; the remote stub must request it,
37878 by supplying an appropriate @samp{qSupported} response
37879 (@pxref{qSupported}).
37881 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37882 @anchor{qXfer spu write}
37883 Write @var{data} to an @code{spufs} file on the target system. The
37884 annex specifies which file to write; it must be of the form
37885 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37886 in the target process, and @var{name} identifes the @code{spufs} file
37887 in that context to be accessed.
37889 This packet is not probed by default; the remote stub must request it,
37890 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37896 @var{nn} (hex encoded) is the number of bytes written.
37897 This may be fewer bytes than supplied in the request.
37900 The request was malformed, or @var{annex} was invalid.
37903 The offset was invalid, or there was an error encountered writing the data.
37904 @var{nn} is a hex-encoded @code{errno} value.
37907 An empty reply indicates the @var{object} string was not
37908 recognized by the stub, or that the object does not support writing.
37911 @item qXfer:@var{object}:@var{operation}:@dots{}
37912 Requests of this form may be added in the future. When a stub does
37913 not recognize the @var{object} keyword, or its support for
37914 @var{object} does not recognize the @var{operation} keyword, the stub
37915 must respond with an empty packet.
37917 @item qAttached:@var{pid}
37918 @cindex query attached, remote request
37919 @cindex @samp{qAttached} packet
37920 Return an indication of whether the remote server attached to an
37921 existing process or created a new process. When the multiprocess
37922 protocol extensions are supported (@pxref{multiprocess extensions}),
37923 @var{pid} is an integer in hexadecimal format identifying the target
37924 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37925 the query packet will be simplified as @samp{qAttached}.
37927 This query is used, for example, to know whether the remote process
37928 should be detached or killed when a @value{GDBN} session is ended with
37929 the @code{quit} command.
37934 The remote server attached to an existing process.
37936 The remote server created a new process.
37938 A badly formed request or an error was encountered.
37943 @node Architecture-Specific Protocol Details
37944 @section Architecture-Specific Protocol Details
37946 This section describes how the remote protocol is applied to specific
37947 target architectures. Also see @ref{Standard Target Features}, for
37948 details of XML target descriptions for each architecture.
37951 * ARM-Specific Protocol Details::
37952 * MIPS-Specific Protocol Details::
37955 @node ARM-Specific Protocol Details
37956 @subsection @acronym{ARM}-specific Protocol Details
37959 * ARM Breakpoint Kinds::
37962 @node ARM Breakpoint Kinds
37963 @subsubsection @acronym{ARM} Breakpoint Kinds
37964 @cindex breakpoint kinds, @acronym{ARM}
37966 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37971 16-bit Thumb mode breakpoint.
37974 32-bit Thumb mode (Thumb-2) breakpoint.
37977 32-bit @acronym{ARM} mode breakpoint.
37981 @node MIPS-Specific Protocol Details
37982 @subsection @acronym{MIPS}-specific Protocol Details
37985 * MIPS Register packet Format::
37986 * MIPS Breakpoint Kinds::
37989 @node MIPS Register packet Format
37990 @subsubsection @acronym{MIPS} Register Packet Format
37991 @cindex register packet format, @acronym{MIPS}
37993 The following @code{g}/@code{G} packets have previously been defined.
37994 In the below, some thirty-two bit registers are transferred as
37995 sixty-four bits. Those registers should be zero/sign extended (which?)
37996 to fill the space allocated. Register bytes are transferred in target
37997 byte order. The two nibbles within a register byte are transferred
37998 most-significant -- least-significant.
38003 All registers are transferred as thirty-two bit quantities in the order:
38004 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38005 registers; fsr; fir; fp.
38008 All registers are transferred as sixty-four bit quantities (including
38009 thirty-two bit registers such as @code{sr}). The ordering is the same
38014 @node MIPS Breakpoint Kinds
38015 @subsubsection @acronym{MIPS} Breakpoint Kinds
38016 @cindex breakpoint kinds, @acronym{MIPS}
38018 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38023 16-bit @acronym{MIPS16} mode breakpoint.
38026 16-bit @acronym{microMIPS} mode breakpoint.
38029 32-bit standard @acronym{MIPS} mode breakpoint.
38032 32-bit @acronym{microMIPS} mode breakpoint.
38036 @node Tracepoint Packets
38037 @section Tracepoint Packets
38038 @cindex tracepoint packets
38039 @cindex packets, tracepoint
38041 Here we describe the packets @value{GDBN} uses to implement
38042 tracepoints (@pxref{Tracepoints}).
38046 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38047 @cindex @samp{QTDP} packet
38048 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38049 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38050 the tracepoint is disabled. @var{step} is the tracepoint's step
38051 count, and @var{pass} is its pass count. If an @samp{F} is present,
38052 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38053 the number of bytes that the target should copy elsewhere to make room
38054 for the tracepoint. If an @samp{X} is present, it introduces a
38055 tracepoint condition, which consists of a hexadecimal length, followed
38056 by a comma and hex-encoded bytes, in a manner similar to action
38057 encodings as described below. If the trailing @samp{-} is present,
38058 further @samp{QTDP} packets will follow to specify this tracepoint's
38064 The packet was understood and carried out.
38066 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38068 The packet was not recognized.
38071 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38072 Define actions to be taken when a tracepoint is hit. @var{n} and
38073 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38074 this tracepoint. This packet may only be sent immediately after
38075 another @samp{QTDP} packet that ended with a @samp{-}. If the
38076 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38077 specifying more actions for this tracepoint.
38079 In the series of action packets for a given tracepoint, at most one
38080 can have an @samp{S} before its first @var{action}. If such a packet
38081 is sent, it and the following packets define ``while-stepping''
38082 actions. Any prior packets define ordinary actions --- that is, those
38083 taken when the tracepoint is first hit. If no action packet has an
38084 @samp{S}, then all the packets in the series specify ordinary
38085 tracepoint actions.
38087 The @samp{@var{action}@dots{}} portion of the packet is a series of
38088 actions, concatenated without separators. Each action has one of the
38094 Collect the registers whose bits are set in @var{mask}. @var{mask} is
38095 a hexadecimal number whose @var{i}'th bit is set if register number
38096 @var{i} should be collected. (The least significant bit is numbered
38097 zero.) Note that @var{mask} may be any number of digits long; it may
38098 not fit in a 32-bit word.
38100 @item M @var{basereg},@var{offset},@var{len}
38101 Collect @var{len} bytes of memory starting at the address in register
38102 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38103 @samp{-1}, then the range has a fixed address: @var{offset} is the
38104 address of the lowest byte to collect. The @var{basereg},
38105 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38106 values (the @samp{-1} value for @var{basereg} is a special case).
38108 @item X @var{len},@var{expr}
38109 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38110 it directs. @var{expr} is an agent expression, as described in
38111 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38112 two-digit hex number in the packet; @var{len} is the number of bytes
38113 in the expression (and thus one-half the number of hex digits in the
38118 Any number of actions may be packed together in a single @samp{QTDP}
38119 packet, as long as the packet does not exceed the maximum packet
38120 length (400 bytes, for many stubs). There may be only one @samp{R}
38121 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38122 actions. Any registers referred to by @samp{M} and @samp{X} actions
38123 must be collected by a preceding @samp{R} action. (The
38124 ``while-stepping'' actions are treated as if they were attached to a
38125 separate tracepoint, as far as these restrictions are concerned.)
38130 The packet was understood and carried out.
38132 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38134 The packet was not recognized.
38137 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38138 @cindex @samp{QTDPsrc} packet
38139 Specify a source string of tracepoint @var{n} at address @var{addr}.
38140 This is useful to get accurate reproduction of the tracepoints
38141 originally downloaded at the beginning of the trace run. @var{type}
38142 is the name of the tracepoint part, such as @samp{cond} for the
38143 tracepoint's conditional expression (see below for a list of types), while
38144 @var{bytes} is the string, encoded in hexadecimal.
38146 @var{start} is the offset of the @var{bytes} within the overall source
38147 string, while @var{slen} is the total length of the source string.
38148 This is intended for handling source strings that are longer than will
38149 fit in a single packet.
38150 @c Add detailed example when this info is moved into a dedicated
38151 @c tracepoint descriptions section.
38153 The available string types are @samp{at} for the location,
38154 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38155 @value{GDBN} sends a separate packet for each command in the action
38156 list, in the same order in which the commands are stored in the list.
38158 The target does not need to do anything with source strings except
38159 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38162 Although this packet is optional, and @value{GDBN} will only send it
38163 if the target replies with @samp{TracepointSource} @xref{General
38164 Query Packets}, it makes both disconnected tracing and trace files
38165 much easier to use. Otherwise the user must be careful that the
38166 tracepoints in effect while looking at trace frames are identical to
38167 the ones in effect during the trace run; even a small discrepancy
38168 could cause @samp{tdump} not to work, or a particular trace frame not
38171 @item QTDV:@var{n}:@var{value}
38172 @cindex define trace state variable, remote request
38173 @cindex @samp{QTDV} packet
38174 Create a new trace state variable, number @var{n}, with an initial
38175 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38176 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38177 the option of not using this packet for initial values of zero; the
38178 target should simply create the trace state variables as they are
38179 mentioned in expressions.
38181 @item QTFrame:@var{n}
38182 @cindex @samp{QTFrame} packet
38183 Select the @var{n}'th tracepoint frame from the buffer, and use the
38184 register and memory contents recorded there to answer subsequent
38185 request packets from @value{GDBN}.
38187 A successful reply from the stub indicates that the stub has found the
38188 requested frame. The response is a series of parts, concatenated
38189 without separators, describing the frame we selected. Each part has
38190 one of the following forms:
38194 The selected frame is number @var{n} in the trace frame buffer;
38195 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38196 was no frame matching the criteria in the request packet.
38199 The selected trace frame records a hit of tracepoint number @var{t};
38200 @var{t} is a hexadecimal number.
38204 @item QTFrame:pc:@var{addr}
38205 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38206 currently selected frame whose PC is @var{addr};
38207 @var{addr} is a hexadecimal number.
38209 @item QTFrame:tdp:@var{t}
38210 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38211 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38212 is a hexadecimal number.
38214 @item QTFrame:range:@var{start}:@var{end}
38215 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38216 currently selected frame whose PC is between @var{start} (inclusive)
38217 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38220 @item QTFrame:outside:@var{start}:@var{end}
38221 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38222 frame @emph{outside} the given range of addresses (exclusive).
38225 @cindex @samp{qTMinFTPILen} packet
38226 This packet requests the minimum length of instruction at which a fast
38227 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38228 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38229 it depends on the target system being able to create trampolines in
38230 the first 64K of memory, which might or might not be possible for that
38231 system. So the reply to this packet will be 4 if it is able to
38238 The minimum instruction length is currently unknown.
38240 The minimum instruction length is @var{length}, where @var{length} is greater
38241 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38242 that a fast tracepoint may be placed on any instruction regardless of size.
38244 An error has occurred.
38246 An empty reply indicates that the request is not supported by the stub.
38250 @cindex @samp{QTStart} packet
38251 Begin the tracepoint experiment. Begin collecting data from
38252 tracepoint hits in the trace frame buffer. This packet supports the
38253 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38254 instruction reply packet}).
38257 @cindex @samp{QTStop} packet
38258 End the tracepoint experiment. Stop collecting trace frames.
38260 @item QTEnable:@var{n}:@var{addr}
38262 @cindex @samp{QTEnable} packet
38263 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38264 experiment. If the tracepoint was previously disabled, then collection
38265 of data from it will resume.
38267 @item QTDisable:@var{n}:@var{addr}
38269 @cindex @samp{QTDisable} packet
38270 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38271 experiment. No more data will be collected from the tracepoint unless
38272 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38275 @cindex @samp{QTinit} packet
38276 Clear the table of tracepoints, and empty the trace frame buffer.
38278 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38279 @cindex @samp{QTro} packet
38280 Establish the given ranges of memory as ``transparent''. The stub
38281 will answer requests for these ranges from memory's current contents,
38282 if they were not collected as part of the tracepoint hit.
38284 @value{GDBN} uses this to mark read-only regions of memory, like those
38285 containing program code. Since these areas never change, they should
38286 still have the same contents they did when the tracepoint was hit, so
38287 there's no reason for the stub to refuse to provide their contents.
38289 @item QTDisconnected:@var{value}
38290 @cindex @samp{QTDisconnected} packet
38291 Set the choice to what to do with the tracing run when @value{GDBN}
38292 disconnects from the target. A @var{value} of 1 directs the target to
38293 continue the tracing run, while 0 tells the target to stop tracing if
38294 @value{GDBN} is no longer in the picture.
38297 @cindex @samp{qTStatus} packet
38298 Ask the stub if there is a trace experiment running right now.
38300 The reply has the form:
38304 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38305 @var{running} is a single digit @code{1} if the trace is presently
38306 running, or @code{0} if not. It is followed by semicolon-separated
38307 optional fields that an agent may use to report additional status.
38311 If the trace is not running, the agent may report any of several
38312 explanations as one of the optional fields:
38317 No trace has been run yet.
38319 @item tstop[:@var{text}]:0
38320 The trace was stopped by a user-originated stop command. The optional
38321 @var{text} field is a user-supplied string supplied as part of the
38322 stop command (for instance, an explanation of why the trace was
38323 stopped manually). It is hex-encoded.
38326 The trace stopped because the trace buffer filled up.
38328 @item tdisconnected:0
38329 The trace stopped because @value{GDBN} disconnected from the target.
38331 @item tpasscount:@var{tpnum}
38332 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38334 @item terror:@var{text}:@var{tpnum}
38335 The trace stopped because tracepoint @var{tpnum} had an error. The
38336 string @var{text} is available to describe the nature of the error
38337 (for instance, a divide by zero in the condition expression).
38338 @var{text} is hex encoded.
38341 The trace stopped for some other reason.
38345 Additional optional fields supply statistical and other information.
38346 Although not required, they are extremely useful for users monitoring
38347 the progress of a trace run. If a trace has stopped, and these
38348 numbers are reported, they must reflect the state of the just-stopped
38353 @item tframes:@var{n}
38354 The number of trace frames in the buffer.
38356 @item tcreated:@var{n}
38357 The total number of trace frames created during the run. This may
38358 be larger than the trace frame count, if the buffer is circular.
38360 @item tsize:@var{n}
38361 The total size of the trace buffer, in bytes.
38363 @item tfree:@var{n}
38364 The number of bytes still unused in the buffer.
38366 @item circular:@var{n}
38367 The value of the circular trace buffer flag. @code{1} means that the
38368 trace buffer is circular and old trace frames will be discarded if
38369 necessary to make room, @code{0} means that the trace buffer is linear
38372 @item disconn:@var{n}
38373 The value of the disconnected tracing flag. @code{1} means that
38374 tracing will continue after @value{GDBN} disconnects, @code{0} means
38375 that the trace run will stop.
38379 @item qTP:@var{tp}:@var{addr}
38380 @cindex tracepoint status, remote request
38381 @cindex @samp{qTP} packet
38382 Ask the stub for the current state of tracepoint number @var{tp} at
38383 address @var{addr}.
38387 @item V@var{hits}:@var{usage}
38388 The tracepoint has been hit @var{hits} times so far during the trace
38389 run, and accounts for @var{usage} in the trace buffer. Note that
38390 @code{while-stepping} steps are not counted as separate hits, but the
38391 steps' space consumption is added into the usage number.
38395 @item qTV:@var{var}
38396 @cindex trace state variable value, remote request
38397 @cindex @samp{qTV} packet
38398 Ask the stub for the value of the trace state variable number @var{var}.
38403 The value of the variable is @var{value}. This will be the current
38404 value of the variable if the user is examining a running target, or a
38405 saved value if the variable was collected in the trace frame that the
38406 user is looking at. Note that multiple requests may result in
38407 different reply values, such as when requesting values while the
38408 program is running.
38411 The value of the variable is unknown. This would occur, for example,
38412 if the user is examining a trace frame in which the requested variable
38417 @cindex @samp{qTfP} packet
38419 @cindex @samp{qTsP} packet
38420 These packets request data about tracepoints that are being used by
38421 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38422 of data, and multiple @code{qTsP} to get additional pieces. Replies
38423 to these packets generally take the form of the @code{QTDP} packets
38424 that define tracepoints. (FIXME add detailed syntax)
38427 @cindex @samp{qTfV} packet
38429 @cindex @samp{qTsV} packet
38430 These packets request data about trace state variables that are on the
38431 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38432 and multiple @code{qTsV} to get additional variables. Replies to
38433 these packets follow the syntax of the @code{QTDV} packets that define
38434 trace state variables.
38440 @cindex @samp{qTfSTM} packet
38441 @cindex @samp{qTsSTM} packet
38442 These packets request data about static tracepoint markers that exist
38443 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38444 first piece of data, and multiple @code{qTsSTM} to get additional
38445 pieces. Replies to these packets take the following form:
38449 @item m @var{address}:@var{id}:@var{extra}
38451 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38452 a comma-separated list of markers
38454 (lower case letter @samp{L}) denotes end of list.
38456 An error occurred. @var{nn} are hex digits.
38458 An empty reply indicates that the request is not supported by the
38462 @var{address} is encoded in hex.
38463 @var{id} and @var{extra} are strings encoded in hex.
38465 In response to each query, the target will reply with a list of one or
38466 more markers, separated by commas. @value{GDBN} will respond to each
38467 reply with a request for more markers (using the @samp{qs} form of the
38468 query), until the target responds with @samp{l} (lower-case ell, for
38471 @item qTSTMat:@var{address}
38473 @cindex @samp{qTSTMat} packet
38474 This packets requests data about static tracepoint markers in the
38475 target program at @var{address}. Replies to this packet follow the
38476 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38477 tracepoint markers.
38479 @item QTSave:@var{filename}
38480 @cindex @samp{QTSave} packet
38481 This packet directs the target to save trace data to the file name
38482 @var{filename} in the target's filesystem. @var{filename} is encoded
38483 as a hex string; the interpretation of the file name (relative vs
38484 absolute, wild cards, etc) is up to the target.
38486 @item qTBuffer:@var{offset},@var{len}
38487 @cindex @samp{qTBuffer} packet
38488 Return up to @var{len} bytes of the current contents of trace buffer,
38489 starting at @var{offset}. The trace buffer is treated as if it were
38490 a contiguous collection of traceframes, as per the trace file format.
38491 The reply consists as many hex-encoded bytes as the target can deliver
38492 in a packet; it is not an error to return fewer than were asked for.
38493 A reply consisting of just @code{l} indicates that no bytes are
38496 @item QTBuffer:circular:@var{value}
38497 This packet directs the target to use a circular trace buffer if
38498 @var{value} is 1, or a linear buffer if the value is 0.
38500 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38501 @cindex @samp{QTNotes} packet
38502 This packet adds optional textual notes to the trace run. Allowable
38503 types include @code{user}, @code{notes}, and @code{tstop}, the
38504 @var{text} fields are arbitrary strings, hex-encoded.
38508 @subsection Relocate instruction reply packet
38509 When installing fast tracepoints in memory, the target may need to
38510 relocate the instruction currently at the tracepoint address to a
38511 different address in memory. For most instructions, a simple copy is
38512 enough, but, for example, call instructions that implicitly push the
38513 return address on the stack, and relative branches or other
38514 PC-relative instructions require offset adjustment, so that the effect
38515 of executing the instruction at a different address is the same as if
38516 it had executed in the original location.
38518 In response to several of the tracepoint packets, the target may also
38519 respond with a number of intermediate @samp{qRelocInsn} request
38520 packets before the final result packet, to have @value{GDBN} handle
38521 this relocation operation. If a packet supports this mechanism, its
38522 documentation will explicitly say so. See for example the above
38523 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38524 format of the request is:
38527 @item qRelocInsn:@var{from};@var{to}
38529 This requests @value{GDBN} to copy instruction at address @var{from}
38530 to address @var{to}, possibly adjusted so that executing the
38531 instruction at @var{to} has the same effect as executing it at
38532 @var{from}. @value{GDBN} writes the adjusted instruction to target
38533 memory starting at @var{to}.
38538 @item qRelocInsn:@var{adjusted_size}
38539 Informs the stub the relocation is complete. @var{adjusted_size} is
38540 the length in bytes of resulting relocated instruction sequence.
38542 A badly formed request was detected, or an error was encountered while
38543 relocating the instruction.
38546 @node Host I/O Packets
38547 @section Host I/O Packets
38548 @cindex Host I/O, remote protocol
38549 @cindex file transfer, remote protocol
38551 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38552 operations on the far side of a remote link. For example, Host I/O is
38553 used to upload and download files to a remote target with its own
38554 filesystem. Host I/O uses the same constant values and data structure
38555 layout as the target-initiated File-I/O protocol. However, the
38556 Host I/O packets are structured differently. The target-initiated
38557 protocol relies on target memory to store parameters and buffers.
38558 Host I/O requests are initiated by @value{GDBN}, and the
38559 target's memory is not involved. @xref{File-I/O Remote Protocol
38560 Extension}, for more details on the target-initiated protocol.
38562 The Host I/O request packets all encode a single operation along with
38563 its arguments. They have this format:
38567 @item vFile:@var{operation}: @var{parameter}@dots{}
38568 @var{operation} is the name of the particular request; the target
38569 should compare the entire packet name up to the second colon when checking
38570 for a supported operation. The format of @var{parameter} depends on
38571 the operation. Numbers are always passed in hexadecimal. Negative
38572 numbers have an explicit minus sign (i.e.@: two's complement is not
38573 used). Strings (e.g.@: filenames) are encoded as a series of
38574 hexadecimal bytes. The last argument to a system call may be a
38575 buffer of escaped binary data (@pxref{Binary Data}).
38579 The valid responses to Host I/O packets are:
38583 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38584 @var{result} is the integer value returned by this operation, usually
38585 non-negative for success and -1 for errors. If an error has occured,
38586 @var{errno} will be included in the result. @var{errno} will have a
38587 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38588 operations which return data, @var{attachment} supplies the data as a
38589 binary buffer. Binary buffers in response packets are escaped in the
38590 normal way (@pxref{Binary Data}). See the individual packet
38591 documentation for the interpretation of @var{result} and
38595 An empty response indicates that this operation is not recognized.
38599 These are the supported Host I/O operations:
38602 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38603 Open a file at @var{pathname} and return a file descriptor for it, or
38604 return -1 if an error occurs. @var{pathname} is a string,
38605 @var{flags} is an integer indicating a mask of open flags
38606 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38607 of mode bits to use if the file is created (@pxref{mode_t Values}).
38608 @xref{open}, for details of the open flags and mode values.
38610 @item vFile:close: @var{fd}
38611 Close the open file corresponding to @var{fd} and return 0, or
38612 -1 if an error occurs.
38614 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38615 Read data from the open file corresponding to @var{fd}. Up to
38616 @var{count} bytes will be read from the file, starting at @var{offset}
38617 relative to the start of the file. The target may read fewer bytes;
38618 common reasons include packet size limits and an end-of-file
38619 condition. The number of bytes read is returned. Zero should only be
38620 returned for a successful read at the end of the file, or if
38621 @var{count} was zero.
38623 The data read should be returned as a binary attachment on success.
38624 If zero bytes were read, the response should include an empty binary
38625 attachment (i.e.@: a trailing semicolon). The return value is the
38626 number of target bytes read; the binary attachment may be longer if
38627 some characters were escaped.
38629 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38630 Write @var{data} (a binary buffer) to the open file corresponding
38631 to @var{fd}. Start the write at @var{offset} from the start of the
38632 file. Unlike many @code{write} system calls, there is no
38633 separate @var{count} argument; the length of @var{data} in the
38634 packet is used. @samp{vFile:write} returns the number of bytes written,
38635 which may be shorter than the length of @var{data}, or -1 if an
38638 @item vFile:unlink: @var{pathname}
38639 Delete the file at @var{pathname} on the target. Return 0,
38640 or -1 if an error occurs. @var{pathname} is a string.
38642 @item vFile:readlink: @var{filename}
38643 Read value of symbolic link @var{filename} on the target. Return
38644 the number of bytes read, or -1 if an error occurs.
38646 The data read should be returned as a binary attachment on success.
38647 If zero bytes were read, the response should include an empty binary
38648 attachment (i.e.@: a trailing semicolon). The return value is the
38649 number of target bytes read; the binary attachment may be longer if
38650 some characters were escaped.
38655 @section Interrupts
38656 @cindex interrupts (remote protocol)
38658 When a program on the remote target is running, @value{GDBN} may
38659 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38660 a @code{BREAK} followed by @code{g},
38661 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38663 The precise meaning of @code{BREAK} is defined by the transport
38664 mechanism and may, in fact, be undefined. @value{GDBN} does not
38665 currently define a @code{BREAK} mechanism for any of the network
38666 interfaces except for TCP, in which case @value{GDBN} sends the
38667 @code{telnet} BREAK sequence.
38669 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38670 transport mechanisms. It is represented by sending the single byte
38671 @code{0x03} without any of the usual packet overhead described in
38672 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38673 transmitted as part of a packet, it is considered to be packet data
38674 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38675 (@pxref{X packet}), used for binary downloads, may include an unescaped
38676 @code{0x03} as part of its packet.
38678 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38679 When Linux kernel receives this sequence from serial port,
38680 it stops execution and connects to gdb.
38682 Stubs are not required to recognize these interrupt mechanisms and the
38683 precise meaning associated with receipt of the interrupt is
38684 implementation defined. If the target supports debugging of multiple
38685 threads and/or processes, it should attempt to interrupt all
38686 currently-executing threads and processes.
38687 If the stub is successful at interrupting the
38688 running program, it should send one of the stop
38689 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38690 of successfully stopping the program in all-stop mode, and a stop reply
38691 for each stopped thread in non-stop mode.
38692 Interrupts received while the
38693 program is stopped are discarded.
38695 @node Notification Packets
38696 @section Notification Packets
38697 @cindex notification packets
38698 @cindex packets, notification
38700 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38701 packets that require no acknowledgment. Both the GDB and the stub
38702 may send notifications (although the only notifications defined at
38703 present are sent by the stub). Notifications carry information
38704 without incurring the round-trip latency of an acknowledgment, and so
38705 are useful for low-impact communications where occasional packet loss
38708 A notification packet has the form @samp{% @var{data} #
38709 @var{checksum}}, where @var{data} is the content of the notification,
38710 and @var{checksum} is a checksum of @var{data}, computed and formatted
38711 as for ordinary @value{GDBN} packets. A notification's @var{data}
38712 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38713 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38714 to acknowledge the notification's receipt or to report its corruption.
38716 Every notification's @var{data} begins with a name, which contains no
38717 colon characters, followed by a colon character.
38719 Recipients should silently ignore corrupted notifications and
38720 notifications they do not understand. Recipients should restart
38721 timeout periods on receipt of a well-formed notification, whether or
38722 not they understand it.
38724 Senders should only send the notifications described here when this
38725 protocol description specifies that they are permitted. In the
38726 future, we may extend the protocol to permit existing notifications in
38727 new contexts; this rule helps older senders avoid confusing newer
38730 (Older versions of @value{GDBN} ignore bytes received until they see
38731 the @samp{$} byte that begins an ordinary packet, so new stubs may
38732 transmit notifications without fear of confusing older clients. There
38733 are no notifications defined for @value{GDBN} to send at the moment, but we
38734 assume that most older stubs would ignore them, as well.)
38736 Each notification is comprised of three parts:
38738 @item @var{name}:@var{event}
38739 The notification packet is sent by the side that initiates the
38740 exchange (currently, only the stub does that), with @var{event}
38741 carrying the specific information about the notification.
38742 @var{name} is the name of the notification.
38744 The acknowledge sent by the other side, usually @value{GDBN}, to
38745 acknowledge the exchange and request the event.
38748 The purpose of an asynchronous notification mechanism is to report to
38749 @value{GDBN} that something interesting happened in the remote stub.
38751 The remote stub may send notification @var{name}:@var{event}
38752 at any time, but @value{GDBN} acknowledges the notification when
38753 appropriate. The notification event is pending before @value{GDBN}
38754 acknowledges. Only one notification at a time may be pending; if
38755 additional events occur before @value{GDBN} has acknowledged the
38756 previous notification, they must be queued by the stub for later
38757 synchronous transmission in response to @var{ack} packets from
38758 @value{GDBN}. Because the notification mechanism is unreliable,
38759 the stub is permitted to resend a notification if it believes
38760 @value{GDBN} may not have received it.
38762 Specifically, notifications may appear when @value{GDBN} is not
38763 otherwise reading input from the stub, or when @value{GDBN} is
38764 expecting to read a normal synchronous response or a
38765 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38766 Notification packets are distinct from any other communication from
38767 the stub so there is no ambiguity.
38769 After receiving a notification, @value{GDBN} shall acknowledge it by
38770 sending a @var{ack} packet as a regular, synchronous request to the
38771 stub. Such acknowledgment is not required to happen immediately, as
38772 @value{GDBN} is permitted to send other, unrelated packets to the
38773 stub first, which the stub should process normally.
38775 Upon receiving a @var{ack} packet, if the stub has other queued
38776 events to report to @value{GDBN}, it shall respond by sending a
38777 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38778 packet to solicit further responses; again, it is permitted to send
38779 other, unrelated packets as well which the stub should process
38782 If the stub receives a @var{ack} packet and there are no additional
38783 @var{event} to report, the stub shall return an @samp{OK} response.
38784 At this point, @value{GDBN} has finished processing a notification
38785 and the stub has completed sending any queued events. @value{GDBN}
38786 won't accept any new notifications until the final @samp{OK} is
38787 received . If further notification events occur, the stub shall send
38788 a new notification, @value{GDBN} shall accept the notification, and
38789 the process shall be repeated.
38791 The process of asynchronous notification can be illustrated by the
38794 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38797 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38799 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38804 The following notifications are defined:
38805 @multitable @columnfractions 0.12 0.12 0.38 0.38
38814 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38815 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38816 for information on how these notifications are acknowledged by
38818 @tab Report an asynchronous stop event in non-stop mode.
38822 @node Remote Non-Stop
38823 @section Remote Protocol Support for Non-Stop Mode
38825 @value{GDBN}'s remote protocol supports non-stop debugging of
38826 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38827 supports non-stop mode, it should report that to @value{GDBN} by including
38828 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38830 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38831 establishing a new connection with the stub. Entering non-stop mode
38832 does not alter the state of any currently-running threads, but targets
38833 must stop all threads in any already-attached processes when entering
38834 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38835 probe the target state after a mode change.
38837 In non-stop mode, when an attached process encounters an event that
38838 would otherwise be reported with a stop reply, it uses the
38839 asynchronous notification mechanism (@pxref{Notification Packets}) to
38840 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38841 in all processes are stopped when a stop reply is sent, in non-stop
38842 mode only the thread reporting the stop event is stopped. That is,
38843 when reporting a @samp{S} or @samp{T} response to indicate completion
38844 of a step operation, hitting a breakpoint, or a fault, only the
38845 affected thread is stopped; any other still-running threads continue
38846 to run. When reporting a @samp{W} or @samp{X} response, all running
38847 threads belonging to other attached processes continue to run.
38849 In non-stop mode, the target shall respond to the @samp{?} packet as
38850 follows. First, any incomplete stop reply notification/@samp{vStopped}
38851 sequence in progress is abandoned. The target must begin a new
38852 sequence reporting stop events for all stopped threads, whether or not
38853 it has previously reported those events to @value{GDBN}. The first
38854 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38855 subsequent stop replies are sent as responses to @samp{vStopped} packets
38856 using the mechanism described above. The target must not send
38857 asynchronous stop reply notifications until the sequence is complete.
38858 If all threads are running when the target receives the @samp{?} packet,
38859 or if the target is not attached to any process, it shall respond
38862 @node Packet Acknowledgment
38863 @section Packet Acknowledgment
38865 @cindex acknowledgment, for @value{GDBN} remote
38866 @cindex packet acknowledgment, for @value{GDBN} remote
38867 By default, when either the host or the target machine receives a packet,
38868 the first response expected is an acknowledgment: either @samp{+} (to indicate
38869 the package was received correctly) or @samp{-} (to request retransmission).
38870 This mechanism allows the @value{GDBN} remote protocol to operate over
38871 unreliable transport mechanisms, such as a serial line.
38873 In cases where the transport mechanism is itself reliable (such as a pipe or
38874 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38875 It may be desirable to disable them in that case to reduce communication
38876 overhead, or for other reasons. This can be accomplished by means of the
38877 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38879 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38880 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38881 and response format still includes the normal checksum, as described in
38882 @ref{Overview}, but the checksum may be ignored by the receiver.
38884 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38885 no-acknowledgment mode, it should report that to @value{GDBN}
38886 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38887 @pxref{qSupported}.
38888 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38889 disabled via the @code{set remote noack-packet off} command
38890 (@pxref{Remote Configuration}),
38891 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38892 Only then may the stub actually turn off packet acknowledgments.
38893 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38894 response, which can be safely ignored by the stub.
38896 Note that @code{set remote noack-packet} command only affects negotiation
38897 between @value{GDBN} and the stub when subsequent connections are made;
38898 it does not affect the protocol acknowledgment state for any current
38900 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38901 new connection is established,
38902 there is also no protocol request to re-enable the acknowledgments
38903 for the current connection, once disabled.
38908 Example sequence of a target being re-started. Notice how the restart
38909 does not get any direct output:
38914 @emph{target restarts}
38917 <- @code{T001:1234123412341234}
38921 Example sequence of a target being stepped by a single instruction:
38924 -> @code{G1445@dots{}}
38929 <- @code{T001:1234123412341234}
38933 <- @code{1455@dots{}}
38937 @node File-I/O Remote Protocol Extension
38938 @section File-I/O Remote Protocol Extension
38939 @cindex File-I/O remote protocol extension
38942 * File-I/O Overview::
38943 * Protocol Basics::
38944 * The F Request Packet::
38945 * The F Reply Packet::
38946 * The Ctrl-C Message::
38948 * List of Supported Calls::
38949 * Protocol-specific Representation of Datatypes::
38951 * File-I/O Examples::
38954 @node File-I/O Overview
38955 @subsection File-I/O Overview
38956 @cindex file-i/o overview
38958 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38959 target to use the host's file system and console I/O to perform various
38960 system calls. System calls on the target system are translated into a
38961 remote protocol packet to the host system, which then performs the needed
38962 actions and returns a response packet to the target system.
38963 This simulates file system operations even on targets that lack file systems.
38965 The protocol is defined to be independent of both the host and target systems.
38966 It uses its own internal representation of datatypes and values. Both
38967 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38968 translating the system-dependent value representations into the internal
38969 protocol representations when data is transmitted.
38971 The communication is synchronous. A system call is possible only when
38972 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38973 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38974 the target is stopped to allow deterministic access to the target's
38975 memory. Therefore File-I/O is not interruptible by target signals. On
38976 the other hand, it is possible to interrupt File-I/O by a user interrupt
38977 (@samp{Ctrl-C}) within @value{GDBN}.
38979 The target's request to perform a host system call does not finish
38980 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38981 after finishing the system call, the target returns to continuing the
38982 previous activity (continue, step). No additional continue or step
38983 request from @value{GDBN} is required.
38986 (@value{GDBP}) continue
38987 <- target requests 'system call X'
38988 target is stopped, @value{GDBN} executes system call
38989 -> @value{GDBN} returns result
38990 ... target continues, @value{GDBN} returns to wait for the target
38991 <- target hits breakpoint and sends a Txx packet
38994 The protocol only supports I/O on the console and to regular files on
38995 the host file system. Character or block special devices, pipes,
38996 named pipes, sockets or any other communication method on the host
38997 system are not supported by this protocol.
38999 File I/O is not supported in non-stop mode.
39001 @node Protocol Basics
39002 @subsection Protocol Basics
39003 @cindex protocol basics, file-i/o
39005 The File-I/O protocol uses the @code{F} packet as the request as well
39006 as reply packet. Since a File-I/O system call can only occur when
39007 @value{GDBN} is waiting for a response from the continuing or stepping target,
39008 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39009 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39010 This @code{F} packet contains all information needed to allow @value{GDBN}
39011 to call the appropriate host system call:
39015 A unique identifier for the requested system call.
39018 All parameters to the system call. Pointers are given as addresses
39019 in the target memory address space. Pointers to strings are given as
39020 pointer/length pair. Numerical values are given as they are.
39021 Numerical control flags are given in a protocol-specific representation.
39025 At this point, @value{GDBN} has to perform the following actions.
39029 If the parameters include pointer values to data needed as input to a
39030 system call, @value{GDBN} requests this data from the target with a
39031 standard @code{m} packet request. This additional communication has to be
39032 expected by the target implementation and is handled as any other @code{m}
39036 @value{GDBN} translates all value from protocol representation to host
39037 representation as needed. Datatypes are coerced into the host types.
39040 @value{GDBN} calls the system call.
39043 It then coerces datatypes back to protocol representation.
39046 If the system call is expected to return data in buffer space specified
39047 by pointer parameters to the call, the data is transmitted to the
39048 target using a @code{M} or @code{X} packet. This packet has to be expected
39049 by the target implementation and is handled as any other @code{M} or @code{X}
39054 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39055 necessary information for the target to continue. This at least contains
39062 @code{errno}, if has been changed by the system call.
39069 After having done the needed type and value coercion, the target continues
39070 the latest continue or step action.
39072 @node The F Request Packet
39073 @subsection The @code{F} Request Packet
39074 @cindex file-i/o request packet
39075 @cindex @code{F} request packet
39077 The @code{F} request packet has the following format:
39080 @item F@var{call-id},@var{parameter@dots{}}
39082 @var{call-id} is the identifier to indicate the host system call to be called.
39083 This is just the name of the function.
39085 @var{parameter@dots{}} are the parameters to the system call.
39086 Parameters are hexadecimal integer values, either the actual values in case
39087 of scalar datatypes, pointers to target buffer space in case of compound
39088 datatypes and unspecified memory areas, or pointer/length pairs in case
39089 of string parameters. These are appended to the @var{call-id} as a
39090 comma-delimited list. All values are transmitted in ASCII
39091 string representation, pointer/length pairs separated by a slash.
39097 @node The F Reply Packet
39098 @subsection The @code{F} Reply Packet
39099 @cindex file-i/o reply packet
39100 @cindex @code{F} reply packet
39102 The @code{F} reply packet has the following format:
39106 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39108 @var{retcode} is the return code of the system call as hexadecimal value.
39110 @var{errno} is the @code{errno} set by the call, in protocol-specific
39112 This parameter can be omitted if the call was successful.
39114 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39115 case, @var{errno} must be sent as well, even if the call was successful.
39116 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39123 or, if the call was interrupted before the host call has been performed:
39130 assuming 4 is the protocol-specific representation of @code{EINTR}.
39135 @node The Ctrl-C Message
39136 @subsection The @samp{Ctrl-C} Message
39137 @cindex ctrl-c message, in file-i/o protocol
39139 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39140 reply packet (@pxref{The F Reply Packet}),
39141 the target should behave as if it had
39142 gotten a break message. The meaning for the target is ``system call
39143 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39144 (as with a break message) and return to @value{GDBN} with a @code{T02}
39147 It's important for the target to know in which
39148 state the system call was interrupted. There are two possible cases:
39152 The system call hasn't been performed on the host yet.
39155 The system call on the host has been finished.
39159 These two states can be distinguished by the target by the value of the
39160 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39161 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39162 on POSIX systems. In any other case, the target may presume that the
39163 system call has been finished --- successfully or not --- and should behave
39164 as if the break message arrived right after the system call.
39166 @value{GDBN} must behave reliably. If the system call has not been called
39167 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39168 @code{errno} in the packet. If the system call on the host has been finished
39169 before the user requests a break, the full action must be finished by
39170 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39171 The @code{F} packet may only be sent when either nothing has happened
39172 or the full action has been completed.
39175 @subsection Console I/O
39176 @cindex console i/o as part of file-i/o
39178 By default and if not explicitly closed by the target system, the file
39179 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39180 on the @value{GDBN} console is handled as any other file output operation
39181 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39182 by @value{GDBN} so that after the target read request from file descriptor
39183 0 all following typing is buffered until either one of the following
39188 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39190 system call is treated as finished.
39193 The user presses @key{RET}. This is treated as end of input with a trailing
39197 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39198 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39202 If the user has typed more characters than fit in the buffer given to
39203 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39204 either another @code{read(0, @dots{})} is requested by the target, or debugging
39205 is stopped at the user's request.
39208 @node List of Supported Calls
39209 @subsection List of Supported Calls
39210 @cindex list of supported file-i/o calls
39227 @unnumberedsubsubsec open
39228 @cindex open, file-i/o system call
39233 int open(const char *pathname, int flags);
39234 int open(const char *pathname, int flags, mode_t mode);
39238 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39241 @var{flags} is the bitwise @code{OR} of the following values:
39245 If the file does not exist it will be created. The host
39246 rules apply as far as file ownership and time stamps
39250 When used with @code{O_CREAT}, if the file already exists it is
39251 an error and open() fails.
39254 If the file already exists and the open mode allows
39255 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39256 truncated to zero length.
39259 The file is opened in append mode.
39262 The file is opened for reading only.
39265 The file is opened for writing only.
39268 The file is opened for reading and writing.
39272 Other bits are silently ignored.
39276 @var{mode} is the bitwise @code{OR} of the following values:
39280 User has read permission.
39283 User has write permission.
39286 Group has read permission.
39289 Group has write permission.
39292 Others have read permission.
39295 Others have write permission.
39299 Other bits are silently ignored.
39302 @item Return value:
39303 @code{open} returns the new file descriptor or -1 if an error
39310 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39313 @var{pathname} refers to a directory.
39316 The requested access is not allowed.
39319 @var{pathname} was too long.
39322 A directory component in @var{pathname} does not exist.
39325 @var{pathname} refers to a device, pipe, named pipe or socket.
39328 @var{pathname} refers to a file on a read-only filesystem and
39329 write access was requested.
39332 @var{pathname} is an invalid pointer value.
39335 No space on device to create the file.
39338 The process already has the maximum number of files open.
39341 The limit on the total number of files open on the system
39345 The call was interrupted by the user.
39351 @unnumberedsubsubsec close
39352 @cindex close, file-i/o system call
39361 @samp{Fclose,@var{fd}}
39363 @item Return value:
39364 @code{close} returns zero on success, or -1 if an error occurred.
39370 @var{fd} isn't a valid open file descriptor.
39373 The call was interrupted by the user.
39379 @unnumberedsubsubsec read
39380 @cindex read, file-i/o system call
39385 int read(int fd, void *buf, unsigned int count);
39389 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39391 @item Return value:
39392 On success, the number of bytes read is returned.
39393 Zero indicates end of file. If count is zero, read
39394 returns zero as well. On error, -1 is returned.
39400 @var{fd} is not a valid file descriptor or is not open for
39404 @var{bufptr} is an invalid pointer value.
39407 The call was interrupted by the user.
39413 @unnumberedsubsubsec write
39414 @cindex write, file-i/o system call
39419 int write(int fd, const void *buf, unsigned int count);
39423 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39425 @item Return value:
39426 On success, the number of bytes written are returned.
39427 Zero indicates nothing was written. On error, -1
39434 @var{fd} is not a valid file descriptor or is not open for
39438 @var{bufptr} is an invalid pointer value.
39441 An attempt was made to write a file that exceeds the
39442 host-specific maximum file size allowed.
39445 No space on device to write the data.
39448 The call was interrupted by the user.
39454 @unnumberedsubsubsec lseek
39455 @cindex lseek, file-i/o system call
39460 long lseek (int fd, long offset, int flag);
39464 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39466 @var{flag} is one of:
39470 The offset is set to @var{offset} bytes.
39473 The offset is set to its current location plus @var{offset}
39477 The offset is set to the size of the file plus @var{offset}
39481 @item Return value:
39482 On success, the resulting unsigned offset in bytes from
39483 the beginning of the file is returned. Otherwise, a
39484 value of -1 is returned.
39490 @var{fd} is not a valid open file descriptor.
39493 @var{fd} is associated with the @value{GDBN} console.
39496 @var{flag} is not a proper value.
39499 The call was interrupted by the user.
39505 @unnumberedsubsubsec rename
39506 @cindex rename, file-i/o system call
39511 int rename(const char *oldpath, const char *newpath);
39515 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39517 @item Return value:
39518 On success, zero is returned. On error, -1 is returned.
39524 @var{newpath} is an existing directory, but @var{oldpath} is not a
39528 @var{newpath} is a non-empty directory.
39531 @var{oldpath} or @var{newpath} is a directory that is in use by some
39535 An attempt was made to make a directory a subdirectory
39539 A component used as a directory in @var{oldpath} or new
39540 path is not a directory. Or @var{oldpath} is a directory
39541 and @var{newpath} exists but is not a directory.
39544 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39547 No access to the file or the path of the file.
39551 @var{oldpath} or @var{newpath} was too long.
39554 A directory component in @var{oldpath} or @var{newpath} does not exist.
39557 The file is on a read-only filesystem.
39560 The device containing the file has no room for the new
39564 The call was interrupted by the user.
39570 @unnumberedsubsubsec unlink
39571 @cindex unlink, file-i/o system call
39576 int unlink(const char *pathname);
39580 @samp{Funlink,@var{pathnameptr}/@var{len}}
39582 @item Return value:
39583 On success, zero is returned. On error, -1 is returned.
39589 No access to the file or the path of the file.
39592 The system does not allow unlinking of directories.
39595 The file @var{pathname} cannot be unlinked because it's
39596 being used by another process.
39599 @var{pathnameptr} is an invalid pointer value.
39602 @var{pathname} was too long.
39605 A directory component in @var{pathname} does not exist.
39608 A component of the path is not a directory.
39611 The file is on a read-only filesystem.
39614 The call was interrupted by the user.
39620 @unnumberedsubsubsec stat/fstat
39621 @cindex fstat, file-i/o system call
39622 @cindex stat, file-i/o system call
39627 int stat(const char *pathname, struct stat *buf);
39628 int fstat(int fd, struct stat *buf);
39632 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39633 @samp{Ffstat,@var{fd},@var{bufptr}}
39635 @item Return value:
39636 On success, zero is returned. On error, -1 is returned.
39642 @var{fd} is not a valid open file.
39645 A directory component in @var{pathname} does not exist or the
39646 path is an empty string.
39649 A component of the path is not a directory.
39652 @var{pathnameptr} is an invalid pointer value.
39655 No access to the file or the path of the file.
39658 @var{pathname} was too long.
39661 The call was interrupted by the user.
39667 @unnumberedsubsubsec gettimeofday
39668 @cindex gettimeofday, file-i/o system call
39673 int gettimeofday(struct timeval *tv, void *tz);
39677 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39679 @item Return value:
39680 On success, 0 is returned, -1 otherwise.
39686 @var{tz} is a non-NULL pointer.
39689 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39695 @unnumberedsubsubsec isatty
39696 @cindex isatty, file-i/o system call
39701 int isatty(int fd);
39705 @samp{Fisatty,@var{fd}}
39707 @item Return value:
39708 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39714 The call was interrupted by the user.
39719 Note that the @code{isatty} call is treated as a special case: it returns
39720 1 to the target if the file descriptor is attached
39721 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39722 would require implementing @code{ioctl} and would be more complex than
39727 @unnumberedsubsubsec system
39728 @cindex system, file-i/o system call
39733 int system(const char *command);
39737 @samp{Fsystem,@var{commandptr}/@var{len}}
39739 @item Return value:
39740 If @var{len} is zero, the return value indicates whether a shell is
39741 available. A zero return value indicates a shell is not available.
39742 For non-zero @var{len}, the value returned is -1 on error and the
39743 return status of the command otherwise. Only the exit status of the
39744 command is returned, which is extracted from the host's @code{system}
39745 return value by calling @code{WEXITSTATUS(retval)}. In case
39746 @file{/bin/sh} could not be executed, 127 is returned.
39752 The call was interrupted by the user.
39757 @value{GDBN} takes over the full task of calling the necessary host calls
39758 to perform the @code{system} call. The return value of @code{system} on
39759 the host is simplified before it's returned
39760 to the target. Any termination signal information from the child process
39761 is discarded, and the return value consists
39762 entirely of the exit status of the called command.
39764 Due to security concerns, the @code{system} call is by default refused
39765 by @value{GDBN}. The user has to allow this call explicitly with the
39766 @code{set remote system-call-allowed 1} command.
39769 @item set remote system-call-allowed
39770 @kindex set remote system-call-allowed
39771 Control whether to allow the @code{system} calls in the File I/O
39772 protocol for the remote target. The default is zero (disabled).
39774 @item show remote system-call-allowed
39775 @kindex show remote system-call-allowed
39776 Show whether the @code{system} calls are allowed in the File I/O
39780 @node Protocol-specific Representation of Datatypes
39781 @subsection Protocol-specific Representation of Datatypes
39782 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39785 * Integral Datatypes::
39787 * Memory Transfer::
39792 @node Integral Datatypes
39793 @unnumberedsubsubsec Integral Datatypes
39794 @cindex integral datatypes, in file-i/o protocol
39796 The integral datatypes used in the system calls are @code{int},
39797 @code{unsigned int}, @code{long}, @code{unsigned long},
39798 @code{mode_t}, and @code{time_t}.
39800 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39801 implemented as 32 bit values in this protocol.
39803 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39805 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39806 in @file{limits.h}) to allow range checking on host and target.
39808 @code{time_t} datatypes are defined as seconds since the Epoch.
39810 All integral datatypes transferred as part of a memory read or write of a
39811 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39814 @node Pointer Values
39815 @unnumberedsubsubsec Pointer Values
39816 @cindex pointer values, in file-i/o protocol
39818 Pointers to target data are transmitted as they are. An exception
39819 is made for pointers to buffers for which the length isn't
39820 transmitted as part of the function call, namely strings. Strings
39821 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39828 which is a pointer to data of length 18 bytes at position 0x1aaf.
39829 The length is defined as the full string length in bytes, including
39830 the trailing null byte. For example, the string @code{"hello world"}
39831 at address 0x123456 is transmitted as
39837 @node Memory Transfer
39838 @unnumberedsubsubsec Memory Transfer
39839 @cindex memory transfer, in file-i/o protocol
39841 Structured data which is transferred using a memory read or write (for
39842 example, a @code{struct stat}) is expected to be in a protocol-specific format
39843 with all scalar multibyte datatypes being big endian. Translation to
39844 this representation needs to be done both by the target before the @code{F}
39845 packet is sent, and by @value{GDBN} before
39846 it transfers memory to the target. Transferred pointers to structured
39847 data should point to the already-coerced data at any time.
39851 @unnumberedsubsubsec struct stat
39852 @cindex struct stat, in file-i/o protocol
39854 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39855 is defined as follows:
39859 unsigned int st_dev; /* device */
39860 unsigned int st_ino; /* inode */
39861 mode_t st_mode; /* protection */
39862 unsigned int st_nlink; /* number of hard links */
39863 unsigned int st_uid; /* user ID of owner */
39864 unsigned int st_gid; /* group ID of owner */
39865 unsigned int st_rdev; /* device type (if inode device) */
39866 unsigned long st_size; /* total size, in bytes */
39867 unsigned long st_blksize; /* blocksize for filesystem I/O */
39868 unsigned long st_blocks; /* number of blocks allocated */
39869 time_t st_atime; /* time of last access */
39870 time_t st_mtime; /* time of last modification */
39871 time_t st_ctime; /* time of last change */
39875 The integral datatypes conform to the definitions given in the
39876 appropriate section (see @ref{Integral Datatypes}, for details) so this
39877 structure is of size 64 bytes.
39879 The values of several fields have a restricted meaning and/or
39885 A value of 0 represents a file, 1 the console.
39888 No valid meaning for the target. Transmitted unchanged.
39891 Valid mode bits are described in @ref{Constants}. Any other
39892 bits have currently no meaning for the target.
39897 No valid meaning for the target. Transmitted unchanged.
39902 These values have a host and file system dependent
39903 accuracy. Especially on Windows hosts, the file system may not
39904 support exact timing values.
39907 The target gets a @code{struct stat} of the above representation and is
39908 responsible for coercing it to the target representation before
39911 Note that due to size differences between the host, target, and protocol
39912 representations of @code{struct stat} members, these members could eventually
39913 get truncated on the target.
39915 @node struct timeval
39916 @unnumberedsubsubsec struct timeval
39917 @cindex struct timeval, in file-i/o protocol
39919 The buffer of type @code{struct timeval} used by the File-I/O protocol
39920 is defined as follows:
39924 time_t tv_sec; /* second */
39925 long tv_usec; /* microsecond */
39929 The integral datatypes conform to the definitions given in the
39930 appropriate section (see @ref{Integral Datatypes}, for details) so this
39931 structure is of size 8 bytes.
39934 @subsection Constants
39935 @cindex constants, in file-i/o protocol
39937 The following values are used for the constants inside of the
39938 protocol. @value{GDBN} and target are responsible for translating these
39939 values before and after the call as needed.
39950 @unnumberedsubsubsec Open Flags
39951 @cindex open flags, in file-i/o protocol
39953 All values are given in hexadecimal representation.
39965 @node mode_t Values
39966 @unnumberedsubsubsec mode_t Values
39967 @cindex mode_t values, in file-i/o protocol
39969 All values are given in octal representation.
39986 @unnumberedsubsubsec Errno Values
39987 @cindex errno values, in file-i/o protocol
39989 All values are given in decimal representation.
40014 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40015 any error value not in the list of supported error numbers.
40018 @unnumberedsubsubsec Lseek Flags
40019 @cindex lseek flags, in file-i/o protocol
40028 @unnumberedsubsubsec Limits
40029 @cindex limits, in file-i/o protocol
40031 All values are given in decimal representation.
40034 INT_MIN -2147483648
40036 UINT_MAX 4294967295
40037 LONG_MIN -9223372036854775808
40038 LONG_MAX 9223372036854775807
40039 ULONG_MAX 18446744073709551615
40042 @node File-I/O Examples
40043 @subsection File-I/O Examples
40044 @cindex file-i/o examples
40046 Example sequence of a write call, file descriptor 3, buffer is at target
40047 address 0x1234, 6 bytes should be written:
40050 <- @code{Fwrite,3,1234,6}
40051 @emph{request memory read from target}
40054 @emph{return "6 bytes written"}
40058 Example sequence of a read call, file descriptor 3, buffer is at target
40059 address 0x1234, 6 bytes should be read:
40062 <- @code{Fread,3,1234,6}
40063 @emph{request memory write to target}
40064 -> @code{X1234,6:XXXXXX}
40065 @emph{return "6 bytes read"}
40069 Example sequence of a read call, call fails on the host due to invalid
40070 file descriptor (@code{EBADF}):
40073 <- @code{Fread,3,1234,6}
40077 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40081 <- @code{Fread,3,1234,6}
40086 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40090 <- @code{Fread,3,1234,6}
40091 -> @code{X1234,6:XXXXXX}
40095 @node Library List Format
40096 @section Library List Format
40097 @cindex library list format, remote protocol
40099 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40100 same process as your application to manage libraries. In this case,
40101 @value{GDBN} can use the loader's symbol table and normal memory
40102 operations to maintain a list of shared libraries. On other
40103 platforms, the operating system manages loaded libraries.
40104 @value{GDBN} can not retrieve the list of currently loaded libraries
40105 through memory operations, so it uses the @samp{qXfer:libraries:read}
40106 packet (@pxref{qXfer library list read}) instead. The remote stub
40107 queries the target's operating system and reports which libraries
40110 The @samp{qXfer:libraries:read} packet returns an XML document which
40111 lists loaded libraries and their offsets. Each library has an
40112 associated name and one or more segment or section base addresses,
40113 which report where the library was loaded in memory.
40115 For the common case of libraries that are fully linked binaries, the
40116 library should have a list of segments. If the target supports
40117 dynamic linking of a relocatable object file, its library XML element
40118 should instead include a list of allocated sections. The segment or
40119 section bases are start addresses, not relocation offsets; they do not
40120 depend on the library's link-time base addresses.
40122 @value{GDBN} must be linked with the Expat library to support XML
40123 library lists. @xref{Expat}.
40125 A simple memory map, with one loaded library relocated by a single
40126 offset, looks like this:
40130 <library name="/lib/libc.so.6">
40131 <segment address="0x10000000"/>
40136 Another simple memory map, with one loaded library with three
40137 allocated sections (.text, .data, .bss), looks like this:
40141 <library name="sharedlib.o">
40142 <section address="0x10000000"/>
40143 <section address="0x20000000"/>
40144 <section address="0x30000000"/>
40149 The format of a library list is described by this DTD:
40152 <!-- library-list: Root element with versioning -->
40153 <!ELEMENT library-list (library)*>
40154 <!ATTLIST library-list version CDATA #FIXED "1.0">
40155 <!ELEMENT library (segment*, section*)>
40156 <!ATTLIST library name CDATA #REQUIRED>
40157 <!ELEMENT segment EMPTY>
40158 <!ATTLIST segment address CDATA #REQUIRED>
40159 <!ELEMENT section EMPTY>
40160 <!ATTLIST section address CDATA #REQUIRED>
40163 In addition, segments and section descriptors cannot be mixed within a
40164 single library element, and you must supply at least one segment or
40165 section for each library.
40167 @node Library List Format for SVR4 Targets
40168 @section Library List Format for SVR4 Targets
40169 @cindex library list format, remote protocol
40171 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40172 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40173 shared libraries. Still a special library list provided by this packet is
40174 more efficient for the @value{GDBN} remote protocol.
40176 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40177 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40178 target, the following parameters are reported:
40182 @code{name}, the absolute file name from the @code{l_name} field of
40183 @code{struct link_map}.
40185 @code{lm} with address of @code{struct link_map} used for TLS
40186 (Thread Local Storage) access.
40188 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40189 @code{struct link_map}. For prelinked libraries this is not an absolute
40190 memory address. It is a displacement of absolute memory address against
40191 address the file was prelinked to during the library load.
40193 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40196 Additionally the single @code{main-lm} attribute specifies address of
40197 @code{struct link_map} used for the main executable. This parameter is used
40198 for TLS access and its presence is optional.
40200 @value{GDBN} must be linked with the Expat library to support XML
40201 SVR4 library lists. @xref{Expat}.
40203 A simple memory map, with two loaded libraries (which do not use prelink),
40207 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40208 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40210 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40212 </library-list-svr>
40215 The format of an SVR4 library list is described by this DTD:
40218 <!-- library-list-svr4: Root element with versioning -->
40219 <!ELEMENT library-list-svr4 (library)*>
40220 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40221 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40222 <!ELEMENT library EMPTY>
40223 <!ATTLIST library name CDATA #REQUIRED>
40224 <!ATTLIST library lm CDATA #REQUIRED>
40225 <!ATTLIST library l_addr CDATA #REQUIRED>
40226 <!ATTLIST library l_ld CDATA #REQUIRED>
40229 @node Memory Map Format
40230 @section Memory Map Format
40231 @cindex memory map format
40233 To be able to write into flash memory, @value{GDBN} needs to obtain a
40234 memory map from the target. This section describes the format of the
40237 The memory map is obtained using the @samp{qXfer:memory-map:read}
40238 (@pxref{qXfer memory map read}) packet and is an XML document that
40239 lists memory regions.
40241 @value{GDBN} must be linked with the Expat library to support XML
40242 memory maps. @xref{Expat}.
40244 The top-level structure of the document is shown below:
40247 <?xml version="1.0"?>
40248 <!DOCTYPE memory-map
40249 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40250 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40256 Each region can be either:
40261 A region of RAM starting at @var{addr} and extending for @var{length}
40265 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40270 A region of read-only memory:
40273 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40278 A region of flash memory, with erasure blocks @var{blocksize}
40282 <memory type="flash" start="@var{addr}" length="@var{length}">
40283 <property name="blocksize">@var{blocksize}</property>
40289 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40290 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40291 packets to write to addresses in such ranges.
40293 The formal DTD for memory map format is given below:
40296 <!-- ................................................... -->
40297 <!-- Memory Map XML DTD ................................ -->
40298 <!-- File: memory-map.dtd .............................. -->
40299 <!-- .................................... .............. -->
40300 <!-- memory-map.dtd -->
40301 <!-- memory-map: Root element with versioning -->
40302 <!ELEMENT memory-map (memory | property)>
40303 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40304 <!ELEMENT memory (property)>
40305 <!-- memory: Specifies a memory region,
40306 and its type, or device. -->
40307 <!ATTLIST memory type CDATA #REQUIRED
40308 start CDATA #REQUIRED
40309 length CDATA #REQUIRED
40310 device CDATA #IMPLIED>
40311 <!-- property: Generic attribute tag -->
40312 <!ELEMENT property (#PCDATA | property)*>
40313 <!ATTLIST property name CDATA #REQUIRED>
40316 @node Thread List Format
40317 @section Thread List Format
40318 @cindex thread list format
40320 To efficiently update the list of threads and their attributes,
40321 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40322 (@pxref{qXfer threads read}) and obtains the XML document with
40323 the following structure:
40326 <?xml version="1.0"?>
40328 <thread id="id" core="0">
40329 ... description ...
40334 Each @samp{thread} element must have the @samp{id} attribute that
40335 identifies the thread (@pxref{thread-id syntax}). The
40336 @samp{core} attribute, if present, specifies which processor core
40337 the thread was last executing on. The content of the of @samp{thread}
40338 element is interpreted as human-readable auxilliary information.
40340 @node Traceframe Info Format
40341 @section Traceframe Info Format
40342 @cindex traceframe info format
40344 To be able to know which objects in the inferior can be examined when
40345 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40346 memory ranges, registers and trace state variables that have been
40347 collected in a traceframe.
40349 This list is obtained using the @samp{qXfer:traceframe-info:read}
40350 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40352 @value{GDBN} must be linked with the Expat library to support XML
40353 traceframe info discovery. @xref{Expat}.
40355 The top-level structure of the document is shown below:
40358 <?xml version="1.0"?>
40359 <!DOCTYPE traceframe-info
40360 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40361 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40367 Each traceframe block can be either:
40372 A region of collected memory starting at @var{addr} and extending for
40373 @var{length} bytes from there:
40376 <memory start="@var{addr}" length="@var{length}"/>
40381 The formal DTD for the traceframe info format is given below:
40384 <!ELEMENT traceframe-info (memory)* >
40385 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40387 <!ELEMENT memory EMPTY>
40388 <!ATTLIST memory start CDATA #REQUIRED
40389 length CDATA #REQUIRED>
40392 @include agentexpr.texi
40394 @node Target Descriptions
40395 @appendix Target Descriptions
40396 @cindex target descriptions
40398 One of the challenges of using @value{GDBN} to debug embedded systems
40399 is that there are so many minor variants of each processor
40400 architecture in use. It is common practice for vendors to start with
40401 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40402 and then make changes to adapt it to a particular market niche. Some
40403 architectures have hundreds of variants, available from dozens of
40404 vendors. This leads to a number of problems:
40408 With so many different customized processors, it is difficult for
40409 the @value{GDBN} maintainers to keep up with the changes.
40411 Since individual variants may have short lifetimes or limited
40412 audiences, it may not be worthwhile to carry information about every
40413 variant in the @value{GDBN} source tree.
40415 When @value{GDBN} does support the architecture of the embedded system
40416 at hand, the task of finding the correct architecture name to give the
40417 @command{set architecture} command can be error-prone.
40420 To address these problems, the @value{GDBN} remote protocol allows a
40421 target system to not only identify itself to @value{GDBN}, but to
40422 actually describe its own features. This lets @value{GDBN} support
40423 processor variants it has never seen before --- to the extent that the
40424 descriptions are accurate, and that @value{GDBN} understands them.
40426 @value{GDBN} must be linked with the Expat library to support XML
40427 target descriptions. @xref{Expat}.
40430 * Retrieving Descriptions:: How descriptions are fetched from a target.
40431 * Target Description Format:: The contents of a target description.
40432 * Predefined Target Types:: Standard types available for target
40434 * Standard Target Features:: Features @value{GDBN} knows about.
40437 @node Retrieving Descriptions
40438 @section Retrieving Descriptions
40440 Target descriptions can be read from the target automatically, or
40441 specified by the user manually. The default behavior is to read the
40442 description from the target. @value{GDBN} retrieves it via the remote
40443 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40444 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40445 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40446 XML document, of the form described in @ref{Target Description
40449 Alternatively, you can specify a file to read for the target description.
40450 If a file is set, the target will not be queried. The commands to
40451 specify a file are:
40454 @cindex set tdesc filename
40455 @item set tdesc filename @var{path}
40456 Read the target description from @var{path}.
40458 @cindex unset tdesc filename
40459 @item unset tdesc filename
40460 Do not read the XML target description from a file. @value{GDBN}
40461 will use the description supplied by the current target.
40463 @cindex show tdesc filename
40464 @item show tdesc filename
40465 Show the filename to read for a target description, if any.
40469 @node Target Description Format
40470 @section Target Description Format
40471 @cindex target descriptions, XML format
40473 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40474 document which complies with the Document Type Definition provided in
40475 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40476 means you can use generally available tools like @command{xmllint} to
40477 check that your feature descriptions are well-formed and valid.
40478 However, to help people unfamiliar with XML write descriptions for
40479 their targets, we also describe the grammar here.
40481 Target descriptions can identify the architecture of the remote target
40482 and (for some architectures) provide information about custom register
40483 sets. They can also identify the OS ABI of the remote target.
40484 @value{GDBN} can use this information to autoconfigure for your
40485 target, or to warn you if you connect to an unsupported target.
40487 Here is a simple target description:
40490 <target version="1.0">
40491 <architecture>i386:x86-64</architecture>
40496 This minimal description only says that the target uses
40497 the x86-64 architecture.
40499 A target description has the following overall form, with [ ] marking
40500 optional elements and @dots{} marking repeatable elements. The elements
40501 are explained further below.
40504 <?xml version="1.0"?>
40505 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40506 <target version="1.0">
40507 @r{[}@var{architecture}@r{]}
40508 @r{[}@var{osabi}@r{]}
40509 @r{[}@var{compatible}@r{]}
40510 @r{[}@var{feature}@dots{}@r{]}
40515 The description is generally insensitive to whitespace and line
40516 breaks, under the usual common-sense rules. The XML version
40517 declaration and document type declaration can generally be omitted
40518 (@value{GDBN} does not require them), but specifying them may be
40519 useful for XML validation tools. The @samp{version} attribute for
40520 @samp{<target>} may also be omitted, but we recommend
40521 including it; if future versions of @value{GDBN} use an incompatible
40522 revision of @file{gdb-target.dtd}, they will detect and report
40523 the version mismatch.
40525 @subsection Inclusion
40526 @cindex target descriptions, inclusion
40529 @cindex <xi:include>
40532 It can sometimes be valuable to split a target description up into
40533 several different annexes, either for organizational purposes, or to
40534 share files between different possible target descriptions. You can
40535 divide a description into multiple files by replacing any element of
40536 the target description with an inclusion directive of the form:
40539 <xi:include href="@var{document}"/>
40543 When @value{GDBN} encounters an element of this form, it will retrieve
40544 the named XML @var{document}, and replace the inclusion directive with
40545 the contents of that document. If the current description was read
40546 using @samp{qXfer}, then so will be the included document;
40547 @var{document} will be interpreted as the name of an annex. If the
40548 current description was read from a file, @value{GDBN} will look for
40549 @var{document} as a file in the same directory where it found the
40550 original description.
40552 @subsection Architecture
40553 @cindex <architecture>
40555 An @samp{<architecture>} element has this form:
40558 <architecture>@var{arch}</architecture>
40561 @var{arch} is one of the architectures from the set accepted by
40562 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40565 @cindex @code{<osabi>}
40567 This optional field was introduced in @value{GDBN} version 7.0.
40568 Previous versions of @value{GDBN} ignore it.
40570 An @samp{<osabi>} element has this form:
40573 <osabi>@var{abi-name}</osabi>
40576 @var{abi-name} is an OS ABI name from the same selection accepted by
40577 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40579 @subsection Compatible Architecture
40580 @cindex @code{<compatible>}
40582 This optional field was introduced in @value{GDBN} version 7.0.
40583 Previous versions of @value{GDBN} ignore it.
40585 A @samp{<compatible>} element has this form:
40588 <compatible>@var{arch}</compatible>
40591 @var{arch} is one of the architectures from the set accepted by
40592 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40594 A @samp{<compatible>} element is used to specify that the target
40595 is able to run binaries in some other than the main target architecture
40596 given by the @samp{<architecture>} element. For example, on the
40597 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40598 or @code{powerpc:common64}, but the system is able to run binaries
40599 in the @code{spu} architecture as well. The way to describe this
40600 capability with @samp{<compatible>} is as follows:
40603 <architecture>powerpc:common</architecture>
40604 <compatible>spu</compatible>
40607 @subsection Features
40610 Each @samp{<feature>} describes some logical portion of the target
40611 system. Features are currently used to describe available CPU
40612 registers and the types of their contents. A @samp{<feature>} element
40616 <feature name="@var{name}">
40617 @r{[}@var{type}@dots{}@r{]}
40623 Each feature's name should be unique within the description. The name
40624 of a feature does not matter unless @value{GDBN} has some special
40625 knowledge of the contents of that feature; if it does, the feature
40626 should have its standard name. @xref{Standard Target Features}.
40630 Any register's value is a collection of bits which @value{GDBN} must
40631 interpret. The default interpretation is a two's complement integer,
40632 but other types can be requested by name in the register description.
40633 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40634 Target Types}), and the description can define additional composite types.
40636 Each type element must have an @samp{id} attribute, which gives
40637 a unique (within the containing @samp{<feature>}) name to the type.
40638 Types must be defined before they are used.
40641 Some targets offer vector registers, which can be treated as arrays
40642 of scalar elements. These types are written as @samp{<vector>} elements,
40643 specifying the array element type, @var{type}, and the number of elements,
40647 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40651 If a register's value is usefully viewed in multiple ways, define it
40652 with a union type containing the useful representations. The
40653 @samp{<union>} element contains one or more @samp{<field>} elements,
40654 each of which has a @var{name} and a @var{type}:
40657 <union id="@var{id}">
40658 <field name="@var{name}" type="@var{type}"/>
40664 If a register's value is composed from several separate values, define
40665 it with a structure type. There are two forms of the @samp{<struct>}
40666 element; a @samp{<struct>} element must either contain only bitfields
40667 or contain no bitfields. If the structure contains only bitfields,
40668 its total size in bytes must be specified, each bitfield must have an
40669 explicit start and end, and bitfields are automatically assigned an
40670 integer type. The field's @var{start} should be less than or
40671 equal to its @var{end}, and zero represents the least significant bit.
40674 <struct id="@var{id}" size="@var{size}">
40675 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40680 If the structure contains no bitfields, then each field has an
40681 explicit type, and no implicit padding is added.
40684 <struct id="@var{id}">
40685 <field name="@var{name}" type="@var{type}"/>
40691 If a register's value is a series of single-bit flags, define it with
40692 a flags type. The @samp{<flags>} element has an explicit @var{size}
40693 and contains one or more @samp{<field>} elements. Each field has a
40694 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40698 <flags id="@var{id}" size="@var{size}">
40699 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40704 @subsection Registers
40707 Each register is represented as an element with this form:
40710 <reg name="@var{name}"
40711 bitsize="@var{size}"
40712 @r{[}regnum="@var{num}"@r{]}
40713 @r{[}save-restore="@var{save-restore}"@r{]}
40714 @r{[}type="@var{type}"@r{]}
40715 @r{[}group="@var{group}"@r{]}/>
40719 The components are as follows:
40724 The register's name; it must be unique within the target description.
40727 The register's size, in bits.
40730 The register's number. If omitted, a register's number is one greater
40731 than that of the previous register (either in the current feature or in
40732 a preceding feature); the first register in the target description
40733 defaults to zero. This register number is used to read or write
40734 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40735 packets, and registers appear in the @code{g} and @code{G} packets
40736 in order of increasing register number.
40739 Whether the register should be preserved across inferior function
40740 calls; this must be either @code{yes} or @code{no}. The default is
40741 @code{yes}, which is appropriate for most registers except for
40742 some system control registers; this is not related to the target's
40746 The type of the register. @var{type} may be a predefined type, a type
40747 defined in the current feature, or one of the special types @code{int}
40748 and @code{float}. @code{int} is an integer type of the correct size
40749 for @var{bitsize}, and @code{float} is a floating point type (in the
40750 architecture's normal floating point format) of the correct size for
40751 @var{bitsize}. The default is @code{int}.
40754 The register group to which this register belongs. @var{group} must
40755 be either @code{general}, @code{float}, or @code{vector}. If no
40756 @var{group} is specified, @value{GDBN} will not display the register
40757 in @code{info registers}.
40761 @node Predefined Target Types
40762 @section Predefined Target Types
40763 @cindex target descriptions, predefined types
40765 Type definitions in the self-description can build up composite types
40766 from basic building blocks, but can not define fundamental types. Instead,
40767 standard identifiers are provided by @value{GDBN} for the fundamental
40768 types. The currently supported types are:
40777 Signed integer types holding the specified number of bits.
40784 Unsigned integer types holding the specified number of bits.
40788 Pointers to unspecified code and data. The program counter and
40789 any dedicated return address register may be marked as code
40790 pointers; printing a code pointer converts it into a symbolic
40791 address. The stack pointer and any dedicated address registers
40792 may be marked as data pointers.
40795 Single precision IEEE floating point.
40798 Double precision IEEE floating point.
40801 The 12-byte extended precision format used by ARM FPA registers.
40804 The 10-byte extended precision format used by x87 registers.
40807 32bit @sc{eflags} register used by x86.
40810 32bit @sc{mxcsr} register used by x86.
40814 @node Standard Target Features
40815 @section Standard Target Features
40816 @cindex target descriptions, standard features
40818 A target description must contain either no registers or all the
40819 target's registers. If the description contains no registers, then
40820 @value{GDBN} will assume a default register layout, selected based on
40821 the architecture. If the description contains any registers, the
40822 default layout will not be used; the standard registers must be
40823 described in the target description, in such a way that @value{GDBN}
40824 can recognize them.
40826 This is accomplished by giving specific names to feature elements
40827 which contain standard registers. @value{GDBN} will look for features
40828 with those names and verify that they contain the expected registers;
40829 if any known feature is missing required registers, or if any required
40830 feature is missing, @value{GDBN} will reject the target
40831 description. You can add additional registers to any of the
40832 standard features --- @value{GDBN} will display them just as if
40833 they were added to an unrecognized feature.
40835 This section lists the known features and their expected contents.
40836 Sample XML documents for these features are included in the
40837 @value{GDBN} source tree, in the directory @file{gdb/features}.
40839 Names recognized by @value{GDBN} should include the name of the
40840 company or organization which selected the name, and the overall
40841 architecture to which the feature applies; so e.g.@: the feature
40842 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40844 The names of registers are not case sensitive for the purpose
40845 of recognizing standard features, but @value{GDBN} will only display
40846 registers using the capitalization used in the description.
40849 * AArch64 Features::
40854 * PowerPC Features::
40859 @node AArch64 Features
40860 @subsection AArch64 Features
40861 @cindex target descriptions, AArch64 features
40863 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40864 targets. It should contain registers @samp{x0} through @samp{x30},
40865 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40867 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40868 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40872 @subsection ARM Features
40873 @cindex target descriptions, ARM features
40875 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40877 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40878 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40880 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40881 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40882 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40885 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40886 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40888 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40889 it should contain at least registers @samp{wR0} through @samp{wR15} and
40890 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40891 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40893 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40894 should contain at least registers @samp{d0} through @samp{d15}. If
40895 they are present, @samp{d16} through @samp{d31} should also be included.
40896 @value{GDBN} will synthesize the single-precision registers from
40897 halves of the double-precision registers.
40899 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40900 need to contain registers; it instructs @value{GDBN} to display the
40901 VFP double-precision registers as vectors and to synthesize the
40902 quad-precision registers from pairs of double-precision registers.
40903 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40904 be present and include 32 double-precision registers.
40906 @node i386 Features
40907 @subsection i386 Features
40908 @cindex target descriptions, i386 features
40910 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40911 targets. It should describe the following registers:
40915 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40917 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40919 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40920 @samp{fs}, @samp{gs}
40922 @samp{st0} through @samp{st7}
40924 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40925 @samp{foseg}, @samp{fooff} and @samp{fop}
40928 The register sets may be different, depending on the target.
40930 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40931 describe registers:
40935 @samp{xmm0} through @samp{xmm7} for i386
40937 @samp{xmm0} through @samp{xmm15} for amd64
40942 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40943 @samp{org.gnu.gdb.i386.sse} feature. It should
40944 describe the upper 128 bits of @sc{ymm} registers:
40948 @samp{ymm0h} through @samp{ymm7h} for i386
40950 @samp{ymm0h} through @samp{ymm15h} for amd64
40953 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40954 describe a single register, @samp{orig_eax}.
40956 @node MIPS Features
40957 @subsection @acronym{MIPS} Features
40958 @cindex target descriptions, @acronym{MIPS} features
40960 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40961 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40962 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40965 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40966 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40967 registers. They may be 32-bit or 64-bit depending on the target.
40969 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40970 it may be optional in a future version of @value{GDBN}. It should
40971 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40972 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40974 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40975 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40976 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40977 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40979 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40980 contain a single register, @samp{restart}, which is used by the
40981 Linux kernel to control restartable syscalls.
40983 @node M68K Features
40984 @subsection M68K Features
40985 @cindex target descriptions, M68K features
40988 @item @samp{org.gnu.gdb.m68k.core}
40989 @itemx @samp{org.gnu.gdb.coldfire.core}
40990 @itemx @samp{org.gnu.gdb.fido.core}
40991 One of those features must be always present.
40992 The feature that is present determines which flavor of m68k is
40993 used. The feature that is present should contain registers
40994 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40995 @samp{sp}, @samp{ps} and @samp{pc}.
40997 @item @samp{org.gnu.gdb.coldfire.fp}
40998 This feature is optional. If present, it should contain registers
40999 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41003 @node PowerPC Features
41004 @subsection PowerPC Features
41005 @cindex target descriptions, PowerPC features
41007 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41008 targets. It should contain registers @samp{r0} through @samp{r31},
41009 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41010 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41012 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41013 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41015 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41016 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41019 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41020 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41021 will combine these registers with the floating point registers
41022 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41023 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41024 through @samp{vs63}, the set of vector registers for POWER7.
41026 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41027 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41028 @samp{spefscr}. SPE targets should provide 32-bit registers in
41029 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41030 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41031 these to present registers @samp{ev0} through @samp{ev31} to the
41034 @node TIC6x Features
41035 @subsection TMS320C6x Features
41036 @cindex target descriptions, TIC6x features
41037 @cindex target descriptions, TMS320C6x features
41038 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41039 targets. It should contain registers @samp{A0} through @samp{A15},
41040 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41042 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41043 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41044 through @samp{B31}.
41046 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41047 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41049 @node Operating System Information
41050 @appendix Operating System Information
41051 @cindex operating system information
41057 Users of @value{GDBN} often wish to obtain information about the state of
41058 the operating system running on the target---for example the list of
41059 processes, or the list of open files. This section describes the
41060 mechanism that makes it possible. This mechanism is similar to the
41061 target features mechanism (@pxref{Target Descriptions}), but focuses
41062 on a different aspect of target.
41064 Operating system information is retrived from the target via the
41065 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41066 read}). The object name in the request should be @samp{osdata}, and
41067 the @var{annex} identifies the data to be fetched.
41070 @appendixsection Process list
41071 @cindex operating system information, process list
41073 When requesting the process list, the @var{annex} field in the
41074 @samp{qXfer} request should be @samp{processes}. The returned data is
41075 an XML document. The formal syntax of this document is defined in
41076 @file{gdb/features/osdata.dtd}.
41078 An example document is:
41081 <?xml version="1.0"?>
41082 <!DOCTYPE target SYSTEM "osdata.dtd">
41083 <osdata type="processes">
41085 <column name="pid">1</column>
41086 <column name="user">root</column>
41087 <column name="command">/sbin/init</column>
41088 <column name="cores">1,2,3</column>
41093 Each item should include a column whose name is @samp{pid}. The value
41094 of that column should identify the process on the target. The
41095 @samp{user} and @samp{command} columns are optional, and will be
41096 displayed by @value{GDBN}. The @samp{cores} column, if present,
41097 should contain a comma-separated list of cores that this process
41098 is running on. Target may provide additional columns,
41099 which @value{GDBN} currently ignores.
41101 @node Trace File Format
41102 @appendix Trace File Format
41103 @cindex trace file format
41105 The trace file comes in three parts: a header, a textual description
41106 section, and a trace frame section with binary data.
41108 The header has the form @code{\x7fTRACE0\n}. The first byte is
41109 @code{0x7f} so as to indicate that the file contains binary data,
41110 while the @code{0} is a version number that may have different values
41113 The description section consists of multiple lines of @sc{ascii} text
41114 separated by newline characters (@code{0xa}). The lines may include a
41115 variety of optional descriptive or context-setting information, such
41116 as tracepoint definitions or register set size. @value{GDBN} will
41117 ignore any line that it does not recognize. An empty line marks the end
41120 @c FIXME add some specific types of data
41122 The trace frame section consists of a number of consecutive frames.
41123 Each frame begins with a two-byte tracepoint number, followed by a
41124 four-byte size giving the amount of data in the frame. The data in
41125 the frame consists of a number of blocks, each introduced by a
41126 character indicating its type (at least register, memory, and trace
41127 state variable). The data in this section is raw binary, not a
41128 hexadecimal or other encoding; its endianness matches the target's
41131 @c FIXME bi-arch may require endianness/arch info in description section
41134 @item R @var{bytes}
41135 Register block. The number and ordering of bytes matches that of a
41136 @code{g} packet in the remote protocol. Note that these are the
41137 actual bytes, in target order and @value{GDBN} register order, not a
41138 hexadecimal encoding.
41140 @item M @var{address} @var{length} @var{bytes}...
41141 Memory block. This is a contiguous block of memory, at the 8-byte
41142 address @var{address}, with a 2-byte length @var{length}, followed by
41143 @var{length} bytes.
41145 @item V @var{number} @var{value}
41146 Trace state variable block. This records the 8-byte signed value
41147 @var{value} of trace state variable numbered @var{number}.
41151 Future enhancements of the trace file format may include additional types
41154 @node Index Section Format
41155 @appendix @code{.gdb_index} section format
41156 @cindex .gdb_index section format
41157 @cindex index section format
41159 This section documents the index section that is created by @code{save
41160 gdb-index} (@pxref{Index Files}). The index section is
41161 DWARF-specific; some knowledge of DWARF is assumed in this
41164 The mapped index file format is designed to be directly
41165 @code{mmap}able on any architecture. In most cases, a datum is
41166 represented using a little-endian 32-bit integer value, called an
41167 @code{offset_type}. Big endian machines must byte-swap the values
41168 before using them. Exceptions to this rule are noted. The data is
41169 laid out such that alignment is always respected.
41171 A mapped index consists of several areas, laid out in order.
41175 The file header. This is a sequence of values, of @code{offset_type}
41176 unless otherwise noted:
41180 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41181 Version 4 uses a different hashing function from versions 5 and 6.
41182 Version 6 includes symbols for inlined functions, whereas versions 4
41183 and 5 do not. Version 7 adds attributes to the CU indices in the
41184 symbol table. Version 8 specifies that symbols from DWARF type units
41185 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41186 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41188 @value{GDBN} will only read version 4, 5, or 6 indices
41189 by specifying @code{set use-deprecated-index-sections on}.
41190 GDB has a workaround for potentially broken version 7 indices so it is
41191 currently not flagged as deprecated.
41194 The offset, from the start of the file, of the CU list.
41197 The offset, from the start of the file, of the types CU list. Note
41198 that this area can be empty, in which case this offset will be equal
41199 to the next offset.
41202 The offset, from the start of the file, of the address area.
41205 The offset, from the start of the file, of the symbol table.
41208 The offset, from the start of the file, of the constant pool.
41212 The CU list. This is a sequence of pairs of 64-bit little-endian
41213 values, sorted by the CU offset. The first element in each pair is
41214 the offset of a CU in the @code{.debug_info} section. The second
41215 element in each pair is the length of that CU. References to a CU
41216 elsewhere in the map are done using a CU index, which is just the
41217 0-based index into this table. Note that if there are type CUs, then
41218 conceptually CUs and type CUs form a single list for the purposes of
41222 The types CU list. This is a sequence of triplets of 64-bit
41223 little-endian values. In a triplet, the first value is the CU offset,
41224 the second value is the type offset in the CU, and the third value is
41225 the type signature. The types CU list is not sorted.
41228 The address area. The address area consists of a sequence of address
41229 entries. Each address entry has three elements:
41233 The low address. This is a 64-bit little-endian value.
41236 The high address. This is a 64-bit little-endian value. Like
41237 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41240 The CU index. This is an @code{offset_type} value.
41244 The symbol table. This is an open-addressed hash table. The size of
41245 the hash table is always a power of 2.
41247 Each slot in the hash table consists of a pair of @code{offset_type}
41248 values. The first value is the offset of the symbol's name in the
41249 constant pool. The second value is the offset of the CU vector in the
41252 If both values are 0, then this slot in the hash table is empty. This
41253 is ok because while 0 is a valid constant pool index, it cannot be a
41254 valid index for both a string and a CU vector.
41256 The hash value for a table entry is computed by applying an
41257 iterative hash function to the symbol's name. Starting with an
41258 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41259 the string is incorporated into the hash using the formula depending on the
41264 The formula is @code{r = r * 67 + c - 113}.
41266 @item Versions 5 to 7
41267 The formula is @code{r = r * 67 + tolower (c) - 113}.
41270 The terminating @samp{\0} is not incorporated into the hash.
41272 The step size used in the hash table is computed via
41273 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41274 value, and @samp{size} is the size of the hash table. The step size
41275 is used to find the next candidate slot when handling a hash
41278 The names of C@t{++} symbols in the hash table are canonicalized. We
41279 don't currently have a simple description of the canonicalization
41280 algorithm; if you intend to create new index sections, you must read
41284 The constant pool. This is simply a bunch of bytes. It is organized
41285 so that alignment is correct: CU vectors are stored first, followed by
41288 A CU vector in the constant pool is a sequence of @code{offset_type}
41289 values. The first value is the number of CU indices in the vector.
41290 Each subsequent value is the index and symbol attributes of a CU in
41291 the CU list. This element in the hash table is used to indicate which
41292 CUs define the symbol and how the symbol is used.
41293 See below for the format of each CU index+attributes entry.
41295 A string in the constant pool is zero-terminated.
41298 Attributes were added to CU index values in @code{.gdb_index} version 7.
41299 If a symbol has multiple uses within a CU then there is one
41300 CU index+attributes value for each use.
41302 The format of each CU index+attributes entry is as follows
41308 This is the index of the CU in the CU list.
41310 These bits are reserved for future purposes and must be zero.
41312 The kind of the symbol in the CU.
41316 This value is reserved and should not be used.
41317 By reserving zero the full @code{offset_type} value is backwards compatible
41318 with previous versions of the index.
41320 The symbol is a type.
41322 The symbol is a variable or an enum value.
41324 The symbol is a function.
41326 Any other kind of symbol.
41328 These values are reserved.
41332 This bit is zero if the value is global and one if it is static.
41334 The determination of whether a symbol is global or static is complicated.
41335 The authorative reference is the file @file{dwarf2read.c} in
41336 @value{GDBN} sources.
41340 This pseudo-code describes the computation of a symbol's kind and
41341 global/static attributes in the index.
41344 is_external = get_attribute (die, DW_AT_external);
41345 language = get_attribute (cu_die, DW_AT_language);
41348 case DW_TAG_typedef:
41349 case DW_TAG_base_type:
41350 case DW_TAG_subrange_type:
41354 case DW_TAG_enumerator:
41356 is_static = (language != CPLUS && language != JAVA);
41358 case DW_TAG_subprogram:
41360 is_static = ! (is_external || language == ADA);
41362 case DW_TAG_constant:
41364 is_static = ! is_external;
41366 case DW_TAG_variable:
41368 is_static = ! is_external;
41370 case DW_TAG_namespace:
41374 case DW_TAG_class_type:
41375 case DW_TAG_interface_type:
41376 case DW_TAG_structure_type:
41377 case DW_TAG_union_type:
41378 case DW_TAG_enumeration_type:
41380 is_static = (language != CPLUS && language != JAVA);
41389 @node GNU Free Documentation License
41390 @appendix GNU Free Documentation License
41393 @node Concept Index
41394 @unnumbered Concept Index
41398 @node Command and Variable Index
41399 @unnumbered Command, Variable, and Function Index
41404 % I think something like @@colophon should be in texinfo. In the
41406 \long\def\colophon{\hbox to0pt{}\vfill
41407 \centerline{The body of this manual is set in}
41408 \centerline{\fontname\tenrm,}
41409 \centerline{with headings in {\bf\fontname\tenbf}}
41410 \centerline{and examples in {\tt\fontname\tentt}.}
41411 \centerline{{\it\fontname\tenit\/},}
41412 \centerline{{\bf\fontname\tenbf}, and}
41413 \centerline{{\sl\fontname\tensl\/}}
41414 \centerline{are used for emphasis.}\vfill}
41416 % Blame: doc@@cygnus.com, 1991.