1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2014 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.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2014 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2014 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
895 You can further control how @value{GDBN} starts up by using command-line
896 options. @value{GDBN} itself can remind you of the options available.
906 to display all available options and briefly describe their use
907 (@samp{@value{GDBP} -h} is a shorter equivalent).
909 All options and command line arguments you give are processed
910 in sequential order. The order makes a difference when the
911 @samp{-x} option is used.
915 * File Options:: Choosing files
916 * Mode Options:: Choosing modes
917 * Startup:: What @value{GDBN} does during startup
921 @subsection Choosing Files
923 When @value{GDBN} starts, it reads any arguments other than options as
924 specifying an executable file and core file (or process ID). This is
925 the same as if the arguments were specified by the @samp{-se} and
926 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
927 first argument that does not have an associated option flag as
928 equivalent to the @samp{-se} option followed by that argument; and the
929 second argument that does not have an associated option flag, if any, as
930 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
931 If the second argument begins with a decimal digit, @value{GDBN} will
932 first attempt to attach to it as a process, and if that fails, attempt
933 to open it as a corefile. If you have a corefile whose name begins with
934 a digit, you can prevent @value{GDBN} from treating it as a pid by
935 prefixing it with @file{./}, e.g.@: @file{./12345}.
937 If @value{GDBN} has not been configured to included core file support,
938 such as for most embedded targets, then it will complain about a second
939 argument and ignore it.
941 Many options have both long and short forms; both are shown in the
942 following list. @value{GDBN} also recognizes the long forms if you truncate
943 them, so long as enough of the option is present to be unambiguous.
944 (If you prefer, you can flag option arguments with @samp{--} rather
945 than @samp{-}, though we illustrate the more usual convention.)
947 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
948 @c way, both those who look for -foo and --foo in the index, will find
952 @item -symbols @var{file}
954 @cindex @code{--symbols}
956 Read symbol table from file @var{file}.
958 @item -exec @var{file}
960 @cindex @code{--exec}
962 Use file @var{file} as the executable file to execute when appropriate,
963 and for examining pure data in conjunction with a core dump.
967 Read symbol table from file @var{file} and use it as the executable
970 @item -core @var{file}
972 @cindex @code{--core}
974 Use file @var{file} as a core dump to examine.
976 @item -pid @var{number}
977 @itemx -p @var{number}
980 Connect to process ID @var{number}, as with the @code{attach} command.
982 @item -command @var{file}
984 @cindex @code{--command}
986 Execute commands from file @var{file}. The contents of this file is
987 evaluated exactly as the @code{source} command would.
988 @xref{Command Files,, Command files}.
990 @item -eval-command @var{command}
991 @itemx -ex @var{command}
992 @cindex @code{--eval-command}
994 Execute a single @value{GDBN} command.
996 This option may be used multiple times to call multiple commands. It may
997 also be interleaved with @samp{-command} as required.
1000 @value{GDBP} -ex 'target sim' -ex 'load' \
1001 -x setbreakpoints -ex 'run' a.out
1004 @item -init-command @var{file}
1005 @itemx -ix @var{file}
1006 @cindex @code{--init-command}
1008 Execute commands from file @var{file} before loading the inferior (but
1009 after loading gdbinit files).
1012 @item -init-eval-command @var{command}
1013 @itemx -iex @var{command}
1014 @cindex @code{--init-eval-command}
1016 Execute a single @value{GDBN} command before loading the inferior (but
1017 after loading gdbinit files).
1020 @item -directory @var{directory}
1021 @itemx -d @var{directory}
1022 @cindex @code{--directory}
1024 Add @var{directory} to the path to search for source and script files.
1028 @cindex @code{--readnow}
1030 Read each symbol file's entire symbol table immediately, rather than
1031 the default, which is to read it incrementally as it is needed.
1032 This makes startup slower, but makes future operations faster.
1037 @subsection Choosing Modes
1039 You can run @value{GDBN} in various alternative modes---for example, in
1040 batch mode or quiet mode.
1048 Do not execute commands found in any initialization file.
1049 There are three init files, loaded in the following order:
1052 @item @file{system.gdbinit}
1053 This is the system-wide init file.
1054 Its location is specified with the @code{--with-system-gdbinit}
1055 configure option (@pxref{System-wide configuration}).
1056 It is loaded first when @value{GDBN} starts, before command line options
1057 have been processed.
1058 @item @file{~/.gdbinit}
1059 This is the init file in your home directory.
1060 It is loaded next, after @file{system.gdbinit}, and before
1061 command options have been processed.
1062 @item @file{./.gdbinit}
1063 This is the init file in the current directory.
1064 It is loaded last, after command line options other than @code{-x} and
1065 @code{-ex} have been processed. Command line options @code{-x} and
1066 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1069 For further documentation on startup processing, @xref{Startup}.
1070 For documentation on how to write command files,
1071 @xref{Command Files,,Command Files}.
1076 Do not execute commands found in @file{~/.gdbinit}, the init file
1077 in your home directory.
1083 @cindex @code{--quiet}
1084 @cindex @code{--silent}
1086 ``Quiet''. Do not print the introductory and copyright messages. These
1087 messages are also suppressed in batch mode.
1090 @cindex @code{--batch}
1091 Run in batch mode. Exit with status @code{0} after processing all the
1092 command files specified with @samp{-x} (and all commands from
1093 initialization files, if not inhibited with @samp{-n}). Exit with
1094 nonzero status if an error occurs in executing the @value{GDBN} commands
1095 in the command files. Batch mode also disables pagination, sets unlimited
1096 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1097 off} were in effect (@pxref{Messages/Warnings}).
1099 Batch mode may be useful for running @value{GDBN} as a filter, for
1100 example to download and run a program on another computer; in order to
1101 make this more useful, the message
1104 Program exited normally.
1108 (which is ordinarily issued whenever a program running under
1109 @value{GDBN} control terminates) is not issued when running in batch
1113 @cindex @code{--batch-silent}
1114 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1115 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1116 unaffected). This is much quieter than @samp{-silent} and would be useless
1117 for an interactive session.
1119 This is particularly useful when using targets that give @samp{Loading section}
1120 messages, for example.
1122 Note that targets that give their output via @value{GDBN}, as opposed to
1123 writing directly to @code{stdout}, will also be made silent.
1125 @item -return-child-result
1126 @cindex @code{--return-child-result}
1127 The return code from @value{GDBN} will be the return code from the child
1128 process (the process being debugged), with the following exceptions:
1132 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1133 internal error. In this case the exit code is the same as it would have been
1134 without @samp{-return-child-result}.
1136 The user quits with an explicit value. E.g., @samp{quit 1}.
1138 The child process never runs, or is not allowed to terminate, in which case
1139 the exit code will be -1.
1142 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1143 when @value{GDBN} is being used as a remote program loader or simulator
1148 @cindex @code{--nowindows}
1150 ``No windows''. If @value{GDBN} comes with a graphical user interface
1151 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1152 interface. If no GUI is available, this option has no effect.
1156 @cindex @code{--windows}
1158 If @value{GDBN} includes a GUI, then this option requires it to be
1161 @item -cd @var{directory}
1163 Run @value{GDBN} using @var{directory} as its working directory,
1164 instead of the current directory.
1166 @item -data-directory @var{directory}
1167 @itemx -D @var{directory}
1168 @cindex @code{--data-directory}
1170 Run @value{GDBN} using @var{directory} as its data directory.
1171 The data directory is where @value{GDBN} searches for its
1172 auxiliary files. @xref{Data Files}.
1176 @cindex @code{--fullname}
1178 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1179 subprocess. It tells @value{GDBN} to output the full file name and line
1180 number in a standard, recognizable fashion each time a stack frame is
1181 displayed (which includes each time your program stops). This
1182 recognizable format looks like two @samp{\032} characters, followed by
1183 the file name, line number and character position separated by colons,
1184 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1185 @samp{\032} characters as a signal to display the source code for the
1188 @item -annotate @var{level}
1189 @cindex @code{--annotate}
1190 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1191 effect is identical to using @samp{set annotate @var{level}}
1192 (@pxref{Annotations}). The annotation @var{level} controls how much
1193 information @value{GDBN} prints together with its prompt, values of
1194 expressions, source lines, and other types of output. Level 0 is the
1195 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1196 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1197 that control @value{GDBN}, and level 2 has been deprecated.
1199 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1203 @cindex @code{--args}
1204 Change interpretation of command line so that arguments following the
1205 executable file are passed as command line arguments to the inferior.
1206 This option stops option processing.
1208 @item -baud @var{bps}
1210 @cindex @code{--baud}
1212 Set the line speed (baud rate or bits per second) of any serial
1213 interface used by @value{GDBN} for remote debugging.
1215 @item -l @var{timeout}
1217 Set the timeout (in seconds) of any communication used by @value{GDBN}
1218 for remote debugging.
1220 @item -tty @var{device}
1221 @itemx -t @var{device}
1222 @cindex @code{--tty}
1224 Run using @var{device} for your program's standard input and output.
1225 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1227 @c resolve the situation of these eventually
1229 @cindex @code{--tui}
1230 Activate the @dfn{Text User Interface} when starting. The Text User
1231 Interface manages several text windows on the terminal, showing
1232 source, assembly, registers and @value{GDBN} command outputs
1233 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1234 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1235 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @c @cindex @code{--xdb}
1239 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1240 @c For information, see the file @file{xdb_trans.html}, which is usually
1241 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1244 @item -interpreter @var{interp}
1245 @cindex @code{--interpreter}
1246 Use the interpreter @var{interp} for interface with the controlling
1247 program or device. This option is meant to be set by programs which
1248 communicate with @value{GDBN} using it as a back end.
1249 @xref{Interpreters, , Command Interpreters}.
1251 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1252 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1253 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1254 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1255 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1256 @sc{gdb/mi} interfaces are no longer supported.
1259 @cindex @code{--write}
1260 Open the executable and core files for both reading and writing. This
1261 is equivalent to the @samp{set write on} command inside @value{GDBN}
1265 @cindex @code{--statistics}
1266 This option causes @value{GDBN} to print statistics about time and
1267 memory usage after it completes each command and returns to the prompt.
1270 @cindex @code{--version}
1271 This option causes @value{GDBN} to print its version number and
1272 no-warranty blurb, and exit.
1274 @item -configuration
1275 @cindex @code{--configuration}
1276 This option causes @value{GDBN} to print details about its build-time
1277 configuration parameters, and then exit. These details can be
1278 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1283 @subsection What @value{GDBN} Does During Startup
1284 @cindex @value{GDBN} startup
1286 Here's the description of what @value{GDBN} does during session startup:
1290 Sets up the command interpreter as specified by the command line
1291 (@pxref{Mode Options, interpreter}).
1295 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1296 used when building @value{GDBN}; @pxref{System-wide configuration,
1297 ,System-wide configuration and settings}) and executes all the commands in
1300 @anchor{Home Directory Init File}
1302 Reads the init file (if any) in your home directory@footnote{On
1303 DOS/Windows systems, the home directory is the one pointed to by the
1304 @code{HOME} environment variable.} and executes all the commands in
1307 @anchor{Option -init-eval-command}
1309 Executes commands and command files specified by the @samp{-iex} and
1310 @samp{-ix} options in their specified order. Usually you should use the
1311 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1312 settings before @value{GDBN} init files get executed and before inferior
1316 Processes command line options and operands.
1318 @anchor{Init File in the Current Directory during Startup}
1320 Reads and executes the commands from init file (if any) in the current
1321 working directory as long as @samp{set auto-load local-gdbinit} is set to
1322 @samp{on} (@pxref{Init File in the Current Directory}).
1323 This is only done if the current directory is
1324 different from your home directory. Thus, you can have more than one
1325 init file, one generic in your home directory, and another, specific
1326 to the program you are debugging, in the directory where you invoke
1330 If the command line specified a program to debug, or a process to
1331 attach to, or a core file, @value{GDBN} loads any auto-loaded
1332 scripts provided for the program or for its loaded shared libraries.
1333 @xref{Auto-loading}.
1335 If you wish to disable the auto-loading during startup,
1336 you must do something like the following:
1339 $ gdb -iex "set auto-load python-scripts off" myprogram
1342 Option @samp{-ex} does not work because the auto-loading is then turned
1346 Executes commands and command files specified by the @samp{-ex} and
1347 @samp{-x} options in their specified order. @xref{Command Files}, for
1348 more details about @value{GDBN} command files.
1351 Reads the command history recorded in the @dfn{history file}.
1352 @xref{Command History}, for more details about the command history and the
1353 files where @value{GDBN} records it.
1356 Init files use the same syntax as @dfn{command files} (@pxref{Command
1357 Files}) and are processed by @value{GDBN} in the same way. The init
1358 file in your home directory can set options (such as @samp{set
1359 complaints}) that affect subsequent processing of command line options
1360 and operands. Init files are not executed if you use the @samp{-nx}
1361 option (@pxref{Mode Options, ,Choosing Modes}).
1363 To display the list of init files loaded by gdb at startup, you
1364 can use @kbd{gdb --help}.
1366 @cindex init file name
1367 @cindex @file{.gdbinit}
1368 @cindex @file{gdb.ini}
1369 The @value{GDBN} init files are normally called @file{.gdbinit}.
1370 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1371 the limitations of file names imposed by DOS filesystems. The Windows
1372 port of @value{GDBN} uses the standard name, but if it finds a
1373 @file{gdb.ini} file in your home directory, it warns you about that
1374 and suggests to rename the file to the standard name.
1378 @section Quitting @value{GDBN}
1379 @cindex exiting @value{GDBN}
1380 @cindex leaving @value{GDBN}
1383 @kindex quit @r{[}@var{expression}@r{]}
1384 @kindex q @r{(@code{quit})}
1385 @item quit @r{[}@var{expression}@r{]}
1387 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1388 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1389 do not supply @var{expression}, @value{GDBN} will terminate normally;
1390 otherwise it will terminate using the result of @var{expression} as the
1395 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1396 terminates the action of any @value{GDBN} command that is in progress and
1397 returns to @value{GDBN} command level. It is safe to type the interrupt
1398 character at any time because @value{GDBN} does not allow it to take effect
1399 until a time when it is safe.
1401 If you have been using @value{GDBN} to control an attached process or
1402 device, you can release it with the @code{detach} command
1403 (@pxref{Attach, ,Debugging an Already-running Process}).
1405 @node Shell Commands
1406 @section Shell Commands
1408 If you need to execute occasional shell commands during your
1409 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1410 just use the @code{shell} command.
1415 @cindex shell escape
1416 @item shell @var{command-string}
1417 @itemx !@var{command-string}
1418 Invoke a standard shell to execute @var{command-string}.
1419 Note that no space is needed between @code{!} and @var{command-string}.
1420 If it exists, the environment variable @code{SHELL} determines which
1421 shell to run. Otherwise @value{GDBN} uses the default shell
1422 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1425 The utility @code{make} is often needed in development environments.
1426 You do not have to use the @code{shell} command for this purpose in
1431 @cindex calling make
1432 @item make @var{make-args}
1433 Execute the @code{make} program with the specified
1434 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1437 @node Logging Output
1438 @section Logging Output
1439 @cindex logging @value{GDBN} output
1440 @cindex save @value{GDBN} output to a file
1442 You may want to save the output of @value{GDBN} commands to a file.
1443 There are several commands to control @value{GDBN}'s logging.
1447 @item set logging on
1449 @item set logging off
1451 @cindex logging file name
1452 @item set logging file @var{file}
1453 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1454 @item set logging overwrite [on|off]
1455 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1456 you want @code{set logging on} to overwrite the logfile instead.
1457 @item set logging redirect [on|off]
1458 By default, @value{GDBN} output will go to both the terminal and the logfile.
1459 Set @code{redirect} if you want output to go only to the log file.
1460 @kindex show logging
1462 Show the current values of the logging settings.
1466 @chapter @value{GDBN} Commands
1468 You can abbreviate a @value{GDBN} command to the first few letters of the command
1469 name, if that abbreviation is unambiguous; and you can repeat certain
1470 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1471 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1472 show you the alternatives available, if there is more than one possibility).
1475 * Command Syntax:: How to give commands to @value{GDBN}
1476 * Completion:: Command completion
1477 * Help:: How to ask @value{GDBN} for help
1480 @node Command Syntax
1481 @section Command Syntax
1483 A @value{GDBN} command is a single line of input. There is no limit on
1484 how long it can be. It starts with a command name, which is followed by
1485 arguments whose meaning depends on the command name. For example, the
1486 command @code{step} accepts an argument which is the number of times to
1487 step, as in @samp{step 5}. You can also use the @code{step} command
1488 with no arguments. Some commands do not allow any arguments.
1490 @cindex abbreviation
1491 @value{GDBN} command names may always be truncated if that abbreviation is
1492 unambiguous. Other possible command abbreviations are listed in the
1493 documentation for individual commands. In some cases, even ambiguous
1494 abbreviations are allowed; for example, @code{s} is specially defined as
1495 equivalent to @code{step} even though there are other commands whose
1496 names start with @code{s}. You can test abbreviations by using them as
1497 arguments to the @code{help} command.
1499 @cindex repeating commands
1500 @kindex RET @r{(repeat last command)}
1501 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1502 repeat the previous command. Certain commands (for example, @code{run})
1503 will not repeat this way; these are commands whose unintentional
1504 repetition might cause trouble and which you are unlikely to want to
1505 repeat. User-defined commands can disable this feature; see
1506 @ref{Define, dont-repeat}.
1508 The @code{list} and @code{x} commands, when you repeat them with
1509 @key{RET}, construct new arguments rather than repeating
1510 exactly as typed. This permits easy scanning of source or memory.
1512 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1513 output, in a way similar to the common utility @code{more}
1514 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1515 @key{RET} too many in this situation, @value{GDBN} disables command
1516 repetition after any command that generates this sort of display.
1518 @kindex # @r{(a comment)}
1520 Any text from a @kbd{#} to the end of the line is a comment; it does
1521 nothing. This is useful mainly in command files (@pxref{Command
1522 Files,,Command Files}).
1524 @cindex repeating command sequences
1525 @kindex Ctrl-o @r{(operate-and-get-next)}
1526 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1527 commands. This command accepts the current line, like @key{RET}, and
1528 then fetches the next line relative to the current line from the history
1532 @section Command Completion
1535 @cindex word completion
1536 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1537 only one possibility; it can also show you what the valid possibilities
1538 are for the next word in a command, at any time. This works for @value{GDBN}
1539 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1541 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1542 of a word. If there is only one possibility, @value{GDBN} fills in the
1543 word, and waits for you to finish the command (or press @key{RET} to
1544 enter it). For example, if you type
1546 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1547 @c complete accuracy in these examples; space introduced for clarity.
1548 @c If texinfo enhancements make it unnecessary, it would be nice to
1549 @c replace " @key" by "@key" in the following...
1551 (@value{GDBP}) info bre @key{TAB}
1555 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1556 the only @code{info} subcommand beginning with @samp{bre}:
1559 (@value{GDBP}) info breakpoints
1563 You can either press @key{RET} at this point, to run the @code{info
1564 breakpoints} command, or backspace and enter something else, if
1565 @samp{breakpoints} does not look like the command you expected. (If you
1566 were sure you wanted @code{info breakpoints} in the first place, you
1567 might as well just type @key{RET} immediately after @samp{info bre},
1568 to exploit command abbreviations rather than command completion).
1570 If there is more than one possibility for the next word when you press
1571 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1572 characters and try again, or just press @key{TAB} a second time;
1573 @value{GDBN} displays all the possible completions for that word. For
1574 example, you might want to set a breakpoint on a subroutine whose name
1575 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1576 just sounds the bell. Typing @key{TAB} again displays all the
1577 function names in your program that begin with those characters, for
1581 (@value{GDBP}) b make_ @key{TAB}
1582 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1583 make_a_section_from_file make_environ
1584 make_abs_section make_function_type
1585 make_blockvector make_pointer_type
1586 make_cleanup make_reference_type
1587 make_command make_symbol_completion_list
1588 (@value{GDBP}) b make_
1592 After displaying the available possibilities, @value{GDBN} copies your
1593 partial input (@samp{b make_} in the example) so you can finish the
1596 If you just want to see the list of alternatives in the first place, you
1597 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1598 means @kbd{@key{META} ?}. You can type this either by holding down a
1599 key designated as the @key{META} shift on your keyboard (if there is
1600 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1602 @cindex quotes in commands
1603 @cindex completion of quoted strings
1604 Sometimes the string you need, while logically a ``word'', may contain
1605 parentheses or other characters that @value{GDBN} normally excludes from
1606 its notion of a word. To permit word completion to work in this
1607 situation, you may enclose words in @code{'} (single quote marks) in
1608 @value{GDBN} commands.
1610 The most likely situation where you might need this is in typing the
1611 name of a C@t{++} function. This is because C@t{++} allows function
1612 overloading (multiple definitions of the same function, distinguished
1613 by argument type). For example, when you want to set a breakpoint you
1614 may need to distinguish whether you mean the version of @code{name}
1615 that takes an @code{int} parameter, @code{name(int)}, or the version
1616 that takes a @code{float} parameter, @code{name(float)}. To use the
1617 word-completion facilities in this situation, type a single quote
1618 @code{'} at the beginning of the function name. This alerts
1619 @value{GDBN} that it may need to consider more information than usual
1620 when you press @key{TAB} or @kbd{M-?} to request word completion:
1623 (@value{GDBP}) b 'bubble( @kbd{M-?}
1624 bubble(double,double) bubble(int,int)
1625 (@value{GDBP}) b 'bubble(
1628 In some cases, @value{GDBN} can tell that completing a name requires using
1629 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1630 completing as much as it can) if you do not type the quote in the first
1634 (@value{GDBP}) b bub @key{TAB}
1635 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1636 (@value{GDBP}) b 'bubble(
1640 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1641 you have not yet started typing the argument list when you ask for
1642 completion on an overloaded symbol.
1644 For more information about overloaded functions, see @ref{C Plus Plus
1645 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1646 overload-resolution off} to disable overload resolution;
1647 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1649 @cindex completion of structure field names
1650 @cindex structure field name completion
1651 @cindex completion of union field names
1652 @cindex union field name completion
1653 When completing in an expression which looks up a field in a
1654 structure, @value{GDBN} also tries@footnote{The completer can be
1655 confused by certain kinds of invalid expressions. Also, it only
1656 examines the static type of the expression, not the dynamic type.} to
1657 limit completions to the field names available in the type of the
1661 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1662 magic to_fputs to_rewind
1663 to_data to_isatty to_write
1664 to_delete to_put to_write_async_safe
1669 This is because the @code{gdb_stdout} is a variable of the type
1670 @code{struct ui_file} that is defined in @value{GDBN} sources as
1677 ui_file_flush_ftype *to_flush;
1678 ui_file_write_ftype *to_write;
1679 ui_file_write_async_safe_ftype *to_write_async_safe;
1680 ui_file_fputs_ftype *to_fputs;
1681 ui_file_read_ftype *to_read;
1682 ui_file_delete_ftype *to_delete;
1683 ui_file_isatty_ftype *to_isatty;
1684 ui_file_rewind_ftype *to_rewind;
1685 ui_file_put_ftype *to_put;
1692 @section Getting Help
1693 @cindex online documentation
1696 You can always ask @value{GDBN} itself for information on its commands,
1697 using the command @code{help}.
1700 @kindex h @r{(@code{help})}
1703 You can use @code{help} (abbreviated @code{h}) with no arguments to
1704 display a short list of named classes of commands:
1708 List of classes of commands:
1710 aliases -- Aliases of other commands
1711 breakpoints -- Making program stop at certain points
1712 data -- Examining data
1713 files -- Specifying and examining files
1714 internals -- Maintenance commands
1715 obscure -- Obscure features
1716 running -- Running the program
1717 stack -- Examining the stack
1718 status -- Status inquiries
1719 support -- Support facilities
1720 tracepoints -- Tracing of program execution without
1721 stopping the program
1722 user-defined -- User-defined commands
1724 Type "help" followed by a class name for a list of
1725 commands in that class.
1726 Type "help" followed by command name for full
1728 Command name abbreviations are allowed if unambiguous.
1731 @c the above line break eliminates huge line overfull...
1733 @item help @var{class}
1734 Using one of the general help classes as an argument, you can get a
1735 list of the individual commands in that class. For example, here is the
1736 help display for the class @code{status}:
1739 (@value{GDBP}) help status
1744 @c Line break in "show" line falsifies real output, but needed
1745 @c to fit in smallbook page size.
1746 info -- Generic command for showing things
1747 about the program being debugged
1748 show -- Generic command for showing things
1751 Type "help" followed by command name for full
1753 Command name abbreviations are allowed if unambiguous.
1757 @item help @var{command}
1758 With a command name as @code{help} argument, @value{GDBN} displays a
1759 short paragraph on how to use that command.
1762 @item apropos @var{args}
1763 The @code{apropos} command searches through all of the @value{GDBN}
1764 commands, and their documentation, for the regular expression specified in
1765 @var{args}. It prints out all matches found. For example:
1776 alias -- Define a new command that is an alias of an existing command
1777 aliases -- Aliases of other commands
1778 d -- Delete some breakpoints or auto-display expressions
1779 del -- Delete some breakpoints or auto-display expressions
1780 delete -- Delete some breakpoints or auto-display expressions
1785 @item complete @var{args}
1786 The @code{complete @var{args}} command lists all the possible completions
1787 for the beginning of a command. Use @var{args} to specify the beginning of the
1788 command you want completed. For example:
1794 @noindent results in:
1805 @noindent This is intended for use by @sc{gnu} Emacs.
1808 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1809 and @code{show} to inquire about the state of your program, or the state
1810 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1811 manual introduces each of them in the appropriate context. The listings
1812 under @code{info} and under @code{show} in the Command, Variable, and
1813 Function Index point to all the sub-commands. @xref{Command and Variable
1819 @kindex i @r{(@code{info})}
1821 This command (abbreviated @code{i}) is for describing the state of your
1822 program. For example, you can show the arguments passed to a function
1823 with @code{info args}, list the registers currently in use with @code{info
1824 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1825 You can get a complete list of the @code{info} sub-commands with
1826 @w{@code{help info}}.
1830 You can assign the result of an expression to an environment variable with
1831 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1832 @code{set prompt $}.
1836 In contrast to @code{info}, @code{show} is for describing the state of
1837 @value{GDBN} itself.
1838 You can change most of the things you can @code{show}, by using the
1839 related command @code{set}; for example, you can control what number
1840 system is used for displays with @code{set radix}, or simply inquire
1841 which is currently in use with @code{show radix}.
1844 To display all the settable parameters and their current
1845 values, you can use @code{show} with no arguments; you may also use
1846 @code{info set}. Both commands produce the same display.
1847 @c FIXME: "info set" violates the rule that "info" is for state of
1848 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1849 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1853 Here are several miscellaneous @code{show} subcommands, all of which are
1854 exceptional in lacking corresponding @code{set} commands:
1857 @kindex show version
1858 @cindex @value{GDBN} version number
1860 Show what version of @value{GDBN} is running. You should include this
1861 information in @value{GDBN} bug-reports. If multiple versions of
1862 @value{GDBN} are in use at your site, you may need to determine which
1863 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1864 commands are introduced, and old ones may wither away. Also, many
1865 system vendors ship variant versions of @value{GDBN}, and there are
1866 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1867 The version number is the same as the one announced when you start
1870 @kindex show copying
1871 @kindex info copying
1872 @cindex display @value{GDBN} copyright
1875 Display information about permission for copying @value{GDBN}.
1877 @kindex show warranty
1878 @kindex info warranty
1880 @itemx info warranty
1881 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1882 if your version of @value{GDBN} comes with one.
1884 @kindex show configuration
1885 @item show configuration
1886 Display detailed information about the way @value{GDBN} was configured
1887 when it was built. This displays the optional arguments passed to the
1888 @file{configure} script and also configuration parameters detected
1889 automatically by @command{configure}. When reporting a @value{GDBN}
1890 bug (@pxref{GDB Bugs}), it is important to include this information in
1896 @chapter Running Programs Under @value{GDBN}
1898 When you run a program under @value{GDBN}, you must first generate
1899 debugging information when you compile it.
1901 You may start @value{GDBN} with its arguments, if any, in an environment
1902 of your choice. If you are doing native debugging, you may redirect
1903 your program's input and output, debug an already running process, or
1904 kill a child process.
1907 * Compilation:: Compiling for debugging
1908 * Starting:: Starting your program
1909 * Arguments:: Your program's arguments
1910 * Environment:: Your program's environment
1912 * Working Directory:: Your program's working directory
1913 * Input/Output:: Your program's input and output
1914 * Attach:: Debugging an already-running process
1915 * Kill Process:: Killing the child process
1917 * Inferiors and Programs:: Debugging multiple inferiors and programs
1918 * Threads:: Debugging programs with multiple threads
1919 * Forks:: Debugging forks
1920 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1924 @section Compiling for Debugging
1926 In order to debug a program effectively, you need to generate
1927 debugging information when you compile it. This debugging information
1928 is stored in the object file; it describes the data type of each
1929 variable or function and the correspondence between source line numbers
1930 and addresses in the executable code.
1932 To request debugging information, specify the @samp{-g} option when you run
1935 Programs that are to be shipped to your customers are compiled with
1936 optimizations, using the @samp{-O} compiler option. However, some
1937 compilers are unable to handle the @samp{-g} and @samp{-O} options
1938 together. Using those compilers, you cannot generate optimized
1939 executables containing debugging information.
1941 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1942 without @samp{-O}, making it possible to debug optimized code. We
1943 recommend that you @emph{always} use @samp{-g} whenever you compile a
1944 program. You may think your program is correct, but there is no sense
1945 in pushing your luck. For more information, see @ref{Optimized Code}.
1947 Older versions of the @sc{gnu} C compiler permitted a variant option
1948 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1949 format; if your @sc{gnu} C compiler has this option, do not use it.
1951 @value{GDBN} knows about preprocessor macros and can show you their
1952 expansion (@pxref{Macros}). Most compilers do not include information
1953 about preprocessor macros in the debugging information if you specify
1954 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1955 the @sc{gnu} C compiler, provides macro information if you are using
1956 the DWARF debugging format, and specify the option @option{-g3}.
1958 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1959 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1960 information on @value{NGCC} options affecting debug information.
1962 You will have the best debugging experience if you use the latest
1963 version of the DWARF debugging format that your compiler supports.
1964 DWARF is currently the most expressive and best supported debugging
1965 format in @value{GDBN}.
1969 @section Starting your Program
1975 @kindex r @r{(@code{run})}
1978 Use the @code{run} command to start your program under @value{GDBN}.
1979 You must first specify the program name (except on VxWorks) with an
1980 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1981 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1982 (@pxref{Files, ,Commands to Specify Files}).
1986 If you are running your program in an execution environment that
1987 supports processes, @code{run} creates an inferior process and makes
1988 that process run your program. In some environments without processes,
1989 @code{run} jumps to the start of your program. Other targets,
1990 like @samp{remote}, are always running. If you get an error
1991 message like this one:
1994 The "remote" target does not support "run".
1995 Try "help target" or "continue".
1999 then use @code{continue} to run your program. You may need @code{load}
2000 first (@pxref{load}).
2002 The execution of a program is affected by certain information it
2003 receives from its superior. @value{GDBN} provides ways to specify this
2004 information, which you must do @emph{before} starting your program. (You
2005 can change it after starting your program, but such changes only affect
2006 your program the next time you start it.) This information may be
2007 divided into four categories:
2010 @item The @emph{arguments.}
2011 Specify the arguments to give your program as the arguments of the
2012 @code{run} command. If a shell is available on your target, the shell
2013 is used to pass the arguments, so that you may use normal conventions
2014 (such as wildcard expansion or variable substitution) in describing
2016 In Unix systems, you can control which shell is used with the
2017 @code{SHELL} environment variable. If you do not define @code{SHELL},
2018 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2019 use of any shell with the @code{set startup-with-shell} command (see
2022 @item The @emph{environment.}
2023 Your program normally inherits its environment from @value{GDBN}, but you can
2024 use the @value{GDBN} commands @code{set environment} and @code{unset
2025 environment} to change parts of the environment that affect
2026 your program. @xref{Environment, ,Your Program's Environment}.
2028 @item The @emph{working directory.}
2029 Your program inherits its working directory from @value{GDBN}. You can set
2030 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2031 @xref{Working Directory, ,Your Program's Working Directory}.
2033 @item The @emph{standard input and output.}
2034 Your program normally uses the same device for standard input and
2035 standard output as @value{GDBN} is using. You can redirect input and output
2036 in the @code{run} command line, or you can use the @code{tty} command to
2037 set a different device for your program.
2038 @xref{Input/Output, ,Your Program's Input and Output}.
2041 @emph{Warning:} While input and output redirection work, you cannot use
2042 pipes to pass the output of the program you are debugging to another
2043 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2047 When you issue the @code{run} command, your program begins to execute
2048 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2049 of how to arrange for your program to stop. Once your program has
2050 stopped, you may call functions in your program, using the @code{print}
2051 or @code{call} commands. @xref{Data, ,Examining Data}.
2053 If the modification time of your symbol file has changed since the last
2054 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2055 table, and reads it again. When it does this, @value{GDBN} tries to retain
2056 your current breakpoints.
2061 @cindex run to main procedure
2062 The name of the main procedure can vary from language to language.
2063 With C or C@t{++}, the main procedure name is always @code{main}, but
2064 other languages such as Ada do not require a specific name for their
2065 main procedure. The debugger provides a convenient way to start the
2066 execution of the program and to stop at the beginning of the main
2067 procedure, depending on the language used.
2069 The @samp{start} command does the equivalent of setting a temporary
2070 breakpoint at the beginning of the main procedure and then invoking
2071 the @samp{run} command.
2073 @cindex elaboration phase
2074 Some programs contain an @dfn{elaboration} phase where some startup code is
2075 executed before the main procedure is called. This depends on the
2076 languages used to write your program. In C@t{++}, for instance,
2077 constructors for static and global objects are executed before
2078 @code{main} is called. It is therefore possible that the debugger stops
2079 before reaching the main procedure. However, the temporary breakpoint
2080 will remain to halt execution.
2082 Specify the arguments to give to your program as arguments to the
2083 @samp{start} command. These arguments will be given verbatim to the
2084 underlying @samp{run} command. Note that the same arguments will be
2085 reused if no argument is provided during subsequent calls to
2086 @samp{start} or @samp{run}.
2088 It is sometimes necessary to debug the program during elaboration. In
2089 these cases, using the @code{start} command would stop the execution of
2090 your program too late, as the program would have already completed the
2091 elaboration phase. Under these circumstances, insert breakpoints in your
2092 elaboration code before running your program.
2094 @anchor{set exec-wrapper}
2095 @kindex set exec-wrapper
2096 @item set exec-wrapper @var{wrapper}
2097 @itemx show exec-wrapper
2098 @itemx unset exec-wrapper
2099 When @samp{exec-wrapper} is set, the specified wrapper is used to
2100 launch programs for debugging. @value{GDBN} starts your program
2101 with a shell command of the form @kbd{exec @var{wrapper}
2102 @var{program}}. Quoting is added to @var{program} and its
2103 arguments, but not to @var{wrapper}, so you should add quotes if
2104 appropriate for your shell. The wrapper runs until it executes
2105 your program, and then @value{GDBN} takes control.
2107 You can use any program that eventually calls @code{execve} with
2108 its arguments as a wrapper. Several standard Unix utilities do
2109 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2110 with @code{exec "$@@"} will also work.
2112 For example, you can use @code{env} to pass an environment variable to
2113 the debugged program, without setting the variable in your shell's
2117 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2121 This command is available when debugging locally on most targets, excluding
2122 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2124 @kindex set startup-with-shell
2125 @item set startup-with-shell
2126 @itemx set startup-with-shell on
2127 @itemx set startup-with-shell off
2128 @itemx show set startup-with-shell
2129 On Unix systems, by default, if a shell is available on your target,
2130 @value{GDBN}) uses it to start your program. Arguments of the
2131 @code{run} command are passed to the shell, which does variable
2132 substitution, expands wildcard characters and performs redirection of
2133 I/O. In some circumstances, it may be useful to disable such use of a
2134 shell, for example, when debugging the shell itself or diagnosing
2135 startup failures such as:
2139 Starting program: ./a.out
2140 During startup program terminated with signal SIGSEGV, Segmentation fault.
2144 which indicates the shell or the wrapper specified with
2145 @samp{exec-wrapper} crashed, not your program. Most often, this is
2146 caused by something odd in your shell's non-interactive mode
2147 initialization file---such as @file{.cshrc} for C-shell,
2148 $@file{.zshenv} for the Z shell, or the file specified in the
2149 @samp{BASH_ENV} environment variable for BASH.
2151 @anchor{set auto-connect-native-target}
2152 @kindex set auto-connect-native-target
2153 @item set auto-connect-native-target
2154 @itemx set auto-connect-native-target on
2155 @itemx set auto-connect-native-target off
2156 @itemx show auto-connect-native-target
2158 By default, if not connected to any target yet (e.g., with
2159 @code{target remote}), the @code{run} command starts your program as a
2160 native process under @value{GDBN}, on your local machine. If you're
2161 sure you don't want to debug programs on your local machine, you can
2162 tell @value{GDBN} to not connect to the native target automatically
2163 with the @code{set auto-connect-native-target off} command.
2165 If @code{on}, which is the default, and if @value{GDBN} is not
2166 connected to a target already, the @code{run} command automaticaly
2167 connects to the native target, if one is available.
2169 If @code{off}, and if @value{GDBN} is not connected to a target
2170 already, the @code{run} command fails with an error:
2174 Don't know how to run. Try "help target".
2177 If @value{GDBN} is already connected to a target, @value{GDBN} always
2178 uses it with the @code{run} command.
2180 In any case, you can explicitly connect to the native target with the
2181 @code{target native} command. For example,
2184 (@value{GDBP}) set auto-connect-native-target off
2186 Don't know how to run. Try "help target".
2187 (@value{GDBP}) target native
2189 Starting program: ./a.out
2190 [Inferior 1 (process 10421) exited normally]
2193 In case you connected explicitly to the @code{native} target,
2194 @value{GDBN} remains connected even if all inferiors exit, ready for
2195 the next @code{run} command. Use the @code{disconnect} command to
2198 Examples of other commands that likewise respect the
2199 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2200 proc}, @code{info os}.
2202 @kindex set disable-randomization
2203 @item set disable-randomization
2204 @itemx set disable-randomization on
2205 This option (enabled by default in @value{GDBN}) will turn off the native
2206 randomization of the virtual address space of the started program. This option
2207 is useful for multiple debugging sessions to make the execution better
2208 reproducible and memory addresses reusable across debugging sessions.
2210 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2211 On @sc{gnu}/Linux you can get the same behavior using
2214 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2217 @item set disable-randomization off
2218 Leave the behavior of the started executable unchanged. Some bugs rear their
2219 ugly heads only when the program is loaded at certain addresses. If your bug
2220 disappears when you run the program under @value{GDBN}, that might be because
2221 @value{GDBN} by default disables the address randomization on platforms, such
2222 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2223 disable-randomization off} to try to reproduce such elusive bugs.
2225 On targets where it is available, virtual address space randomization
2226 protects the programs against certain kinds of security attacks. In these
2227 cases the attacker needs to know the exact location of a concrete executable
2228 code. Randomizing its location makes it impossible to inject jumps misusing
2229 a code at its expected addresses.
2231 Prelinking shared libraries provides a startup performance advantage but it
2232 makes addresses in these libraries predictable for privileged processes by
2233 having just unprivileged access at the target system. Reading the shared
2234 library binary gives enough information for assembling the malicious code
2235 misusing it. Still even a prelinked shared library can get loaded at a new
2236 random address just requiring the regular relocation process during the
2237 startup. Shared libraries not already prelinked are always loaded at
2238 a randomly chosen address.
2240 Position independent executables (PIE) contain position independent code
2241 similar to the shared libraries and therefore such executables get loaded at
2242 a randomly chosen address upon startup. PIE executables always load even
2243 already prelinked shared libraries at a random address. You can build such
2244 executable using @command{gcc -fPIE -pie}.
2246 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2247 (as long as the randomization is enabled).
2249 @item show disable-randomization
2250 Show the current setting of the explicit disable of the native randomization of
2251 the virtual address space of the started program.
2256 @section Your Program's Arguments
2258 @cindex arguments (to your program)
2259 The arguments to your program can be specified by the arguments of the
2261 They are passed to a shell, which expands wildcard characters and
2262 performs redirection of I/O, and thence to your program. Your
2263 @code{SHELL} environment variable (if it exists) specifies what shell
2264 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2265 the default shell (@file{/bin/sh} on Unix).
2267 On non-Unix systems, the program is usually invoked directly by
2268 @value{GDBN}, which emulates I/O redirection via the appropriate system
2269 calls, and the wildcard characters are expanded by the startup code of
2270 the program, not by the shell.
2272 @code{run} with no arguments uses the same arguments used by the previous
2273 @code{run}, or those set by the @code{set args} command.
2278 Specify the arguments to be used the next time your program is run. If
2279 @code{set args} has no arguments, @code{run} executes your program
2280 with no arguments. Once you have run your program with arguments,
2281 using @code{set args} before the next @code{run} is the only way to run
2282 it again without arguments.
2286 Show the arguments to give your program when it is started.
2290 @section Your Program's Environment
2292 @cindex environment (of your program)
2293 The @dfn{environment} consists of a set of environment variables and
2294 their values. Environment variables conventionally record such things as
2295 your user name, your home directory, your terminal type, and your search
2296 path for programs to run. Usually you set up environment variables with
2297 the shell and they are inherited by all the other programs you run. When
2298 debugging, it can be useful to try running your program with a modified
2299 environment without having to start @value{GDBN} over again.
2303 @item path @var{directory}
2304 Add @var{directory} to the front of the @code{PATH} environment variable
2305 (the search path for executables) that will be passed to your program.
2306 The value of @code{PATH} used by @value{GDBN} does not change.
2307 You may specify several directory names, separated by whitespace or by a
2308 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2309 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2310 is moved to the front, so it is searched sooner.
2312 You can use the string @samp{$cwd} to refer to whatever is the current
2313 working directory at the time @value{GDBN} searches the path. If you
2314 use @samp{.} instead, it refers to the directory where you executed the
2315 @code{path} command. @value{GDBN} replaces @samp{.} in the
2316 @var{directory} argument (with the current path) before adding
2317 @var{directory} to the search path.
2318 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2319 @c document that, since repeating it would be a no-op.
2323 Display the list of search paths for executables (the @code{PATH}
2324 environment variable).
2326 @kindex show environment
2327 @item show environment @r{[}@var{varname}@r{]}
2328 Print the value of environment variable @var{varname} to be given to
2329 your program when it starts. If you do not supply @var{varname},
2330 print the names and values of all environment variables to be given to
2331 your program. You can abbreviate @code{environment} as @code{env}.
2333 @kindex set environment
2334 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2335 Set environment variable @var{varname} to @var{value}. The value
2336 changes for your program (and the shell @value{GDBN} uses to launch
2337 it), not for @value{GDBN} itself. @var{value} may be any string; the
2338 values of environment variables are just strings, and any
2339 interpretation is supplied by your program itself. The @var{value}
2340 parameter is optional; if it is eliminated, the variable is set to a
2342 @c "any string" here does not include leading, trailing
2343 @c blanks. Gnu asks: does anyone care?
2345 For example, this command:
2352 tells the debugged program, when subsequently run, that its user is named
2353 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2354 are not actually required.)
2356 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2357 which also inherits the environment set with @code{set environment}.
2358 If necessary, you can avoid that by using the @samp{env} program as a
2359 wrapper instead of using @code{set environment}. @xref{set
2360 exec-wrapper}, for an example doing just that.
2362 @kindex unset environment
2363 @item unset environment @var{varname}
2364 Remove variable @var{varname} from the environment to be passed to your
2365 program. This is different from @samp{set env @var{varname} =};
2366 @code{unset environment} removes the variable from the environment,
2367 rather than assigning it an empty value.
2370 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2371 the shell indicated by your @code{SHELL} environment variable if it
2372 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2373 names a shell that runs an initialization file when started
2374 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2375 for the Z shell, or the file specified in the @samp{BASH_ENV}
2376 environment variable for BASH---any variables you set in that file
2377 affect your program. You may wish to move setting of environment
2378 variables to files that are only run when you sign on, such as
2379 @file{.login} or @file{.profile}.
2381 @node Working Directory
2382 @section Your Program's Working Directory
2384 @cindex working directory (of your program)
2385 Each time you start your program with @code{run}, it inherits its
2386 working directory from the current working directory of @value{GDBN}.
2387 The @value{GDBN} working directory is initially whatever it inherited
2388 from its parent process (typically the shell), but you can specify a new
2389 working directory in @value{GDBN} with the @code{cd} command.
2391 The @value{GDBN} working directory also serves as a default for the commands
2392 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2397 @cindex change working directory
2398 @item cd @r{[}@var{directory}@r{]}
2399 Set the @value{GDBN} working directory to @var{directory}. If not
2400 given, @var{directory} uses @file{'~'}.
2404 Print the @value{GDBN} working directory.
2407 It is generally impossible to find the current working directory of
2408 the process being debugged (since a program can change its directory
2409 during its run). If you work on a system where @value{GDBN} is
2410 configured with the @file{/proc} support, you can use the @code{info
2411 proc} command (@pxref{SVR4 Process Information}) to find out the
2412 current working directory of the debuggee.
2415 @section Your Program's Input and Output
2420 By default, the program you run under @value{GDBN} does input and output to
2421 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2422 to its own terminal modes to interact with you, but it records the terminal
2423 modes your program was using and switches back to them when you continue
2424 running your program.
2427 @kindex info terminal
2429 Displays information recorded by @value{GDBN} about the terminal modes your
2433 You can redirect your program's input and/or output using shell
2434 redirection with the @code{run} command. For example,
2441 starts your program, diverting its output to the file @file{outfile}.
2444 @cindex controlling terminal
2445 Another way to specify where your program should do input and output is
2446 with the @code{tty} command. This command accepts a file name as
2447 argument, and causes this file to be the default for future @code{run}
2448 commands. It also resets the controlling terminal for the child
2449 process, for future @code{run} commands. For example,
2456 directs that processes started with subsequent @code{run} commands
2457 default to do input and output on the terminal @file{/dev/ttyb} and have
2458 that as their controlling terminal.
2460 An explicit redirection in @code{run} overrides the @code{tty} command's
2461 effect on the input/output device, but not its effect on the controlling
2464 When you use the @code{tty} command or redirect input in the @code{run}
2465 command, only the input @emph{for your program} is affected. The input
2466 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2467 for @code{set inferior-tty}.
2469 @cindex inferior tty
2470 @cindex set inferior controlling terminal
2471 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2472 display the name of the terminal that will be used for future runs of your
2476 @item set inferior-tty /dev/ttyb
2477 @kindex set inferior-tty
2478 Set the tty for the program being debugged to /dev/ttyb.
2480 @item show inferior-tty
2481 @kindex show inferior-tty
2482 Show the current tty for the program being debugged.
2486 @section Debugging an Already-running Process
2491 @item attach @var{process-id}
2492 This command attaches to a running process---one that was started
2493 outside @value{GDBN}. (@code{info files} shows your active
2494 targets.) The command takes as argument a process ID. The usual way to
2495 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2496 or with the @samp{jobs -l} shell command.
2498 @code{attach} does not repeat if you press @key{RET} a second time after
2499 executing the command.
2502 To use @code{attach}, your program must be running in an environment
2503 which supports processes; for example, @code{attach} does not work for
2504 programs on bare-board targets that lack an operating system. You must
2505 also have permission to send the process a signal.
2507 When you use @code{attach}, the debugger finds the program running in
2508 the process first by looking in the current working directory, then (if
2509 the program is not found) by using the source file search path
2510 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2511 the @code{file} command to load the program. @xref{Files, ,Commands to
2514 The first thing @value{GDBN} does after arranging to debug the specified
2515 process is to stop it. You can examine and modify an attached process
2516 with all the @value{GDBN} commands that are ordinarily available when
2517 you start processes with @code{run}. You can insert breakpoints; you
2518 can step and continue; you can modify storage. If you would rather the
2519 process continue running, you may use the @code{continue} command after
2520 attaching @value{GDBN} to the process.
2525 When you have finished debugging the attached process, you can use the
2526 @code{detach} command to release it from @value{GDBN} control. Detaching
2527 the process continues its execution. After the @code{detach} command,
2528 that process and @value{GDBN} become completely independent once more, and you
2529 are ready to @code{attach} another process or start one with @code{run}.
2530 @code{detach} does not repeat if you press @key{RET} again after
2531 executing the command.
2534 If you exit @value{GDBN} while you have an attached process, you detach
2535 that process. If you use the @code{run} command, you kill that process.
2536 By default, @value{GDBN} asks for confirmation if you try to do either of these
2537 things; you can control whether or not you need to confirm by using the
2538 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2542 @section Killing the Child Process
2547 Kill the child process in which your program is running under @value{GDBN}.
2550 This command is useful if you wish to debug a core dump instead of a
2551 running process. @value{GDBN} ignores any core dump file while your program
2554 On some operating systems, a program cannot be executed outside @value{GDBN}
2555 while you have breakpoints set on it inside @value{GDBN}. You can use the
2556 @code{kill} command in this situation to permit running your program
2557 outside the debugger.
2559 The @code{kill} command is also useful if you wish to recompile and
2560 relink your program, since on many systems it is impossible to modify an
2561 executable file while it is running in a process. In this case, when you
2562 next type @code{run}, @value{GDBN} notices that the file has changed, and
2563 reads the symbol table again (while trying to preserve your current
2564 breakpoint settings).
2566 @node Inferiors and Programs
2567 @section Debugging Multiple Inferiors and Programs
2569 @value{GDBN} lets you run and debug multiple programs in a single
2570 session. In addition, @value{GDBN} on some systems may let you run
2571 several programs simultaneously (otherwise you have to exit from one
2572 before starting another). In the most general case, you can have
2573 multiple threads of execution in each of multiple processes, launched
2574 from multiple executables.
2577 @value{GDBN} represents the state of each program execution with an
2578 object called an @dfn{inferior}. An inferior typically corresponds to
2579 a process, but is more general and applies also to targets that do not
2580 have processes. Inferiors may be created before a process runs, and
2581 may be retained after a process exits. Inferiors have unique
2582 identifiers that are different from process ids. Usually each
2583 inferior will also have its own distinct address space, although some
2584 embedded targets may have several inferiors running in different parts
2585 of a single address space. Each inferior may in turn have multiple
2586 threads running in it.
2588 To find out what inferiors exist at any moment, use @w{@code{info
2592 @kindex info inferiors
2593 @item info inferiors
2594 Print a list of all inferiors currently being managed by @value{GDBN}.
2596 @value{GDBN} displays for each inferior (in this order):
2600 the inferior number assigned by @value{GDBN}
2603 the target system's inferior identifier
2606 the name of the executable the inferior is running.
2611 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2612 indicates the current inferior.
2616 @c end table here to get a little more width for example
2619 (@value{GDBP}) info inferiors
2620 Num Description Executable
2621 2 process 2307 hello
2622 * 1 process 3401 goodbye
2625 To switch focus between inferiors, use the @code{inferior} command:
2628 @kindex inferior @var{infno}
2629 @item inferior @var{infno}
2630 Make inferior number @var{infno} the current inferior. The argument
2631 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2632 in the first field of the @samp{info inferiors} display.
2636 You can get multiple executables into a debugging session via the
2637 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2638 systems @value{GDBN} can add inferiors to the debug session
2639 automatically by following calls to @code{fork} and @code{exec}. To
2640 remove inferiors from the debugging session use the
2641 @w{@code{remove-inferiors}} command.
2644 @kindex add-inferior
2645 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2646 Adds @var{n} inferiors to be run using @var{executable} as the
2647 executable. @var{n} defaults to 1. If no executable is specified,
2648 the inferiors begins empty, with no program. You can still assign or
2649 change the program assigned to the inferior at any time by using the
2650 @code{file} command with the executable name as its argument.
2652 @kindex clone-inferior
2653 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2654 Adds @var{n} inferiors ready to execute the same program as inferior
2655 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2656 number of the current inferior. This is a convenient command when you
2657 want to run another instance of the inferior you are debugging.
2660 (@value{GDBP}) info inferiors
2661 Num Description Executable
2662 * 1 process 29964 helloworld
2663 (@value{GDBP}) clone-inferior
2666 (@value{GDBP}) info inferiors
2667 Num Description Executable
2669 * 1 process 29964 helloworld
2672 You can now simply switch focus to inferior 2 and run it.
2674 @kindex remove-inferiors
2675 @item remove-inferiors @var{infno}@dots{}
2676 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2677 possible to remove an inferior that is running with this command. For
2678 those, use the @code{kill} or @code{detach} command first.
2682 To quit debugging one of the running inferiors that is not the current
2683 inferior, you can either detach from it by using the @w{@code{detach
2684 inferior}} command (allowing it to run independently), or kill it
2685 using the @w{@code{kill inferiors}} command:
2688 @kindex detach inferiors @var{infno}@dots{}
2689 @item detach inferior @var{infno}@dots{}
2690 Detach from the inferior or inferiors identified by @value{GDBN}
2691 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2692 still stays on the list of inferiors shown by @code{info inferiors},
2693 but its Description will show @samp{<null>}.
2695 @kindex kill inferiors @var{infno}@dots{}
2696 @item kill inferiors @var{infno}@dots{}
2697 Kill the inferior or inferiors identified by @value{GDBN} inferior
2698 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2699 stays on the list of inferiors shown by @code{info inferiors}, but its
2700 Description will show @samp{<null>}.
2703 After the successful completion of a command such as @code{detach},
2704 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2705 a normal process exit, the inferior is still valid and listed with
2706 @code{info inferiors}, ready to be restarted.
2709 To be notified when inferiors are started or exit under @value{GDBN}'s
2710 control use @w{@code{set print inferior-events}}:
2713 @kindex set print inferior-events
2714 @cindex print messages on inferior start and exit
2715 @item set print inferior-events
2716 @itemx set print inferior-events on
2717 @itemx set print inferior-events off
2718 The @code{set print inferior-events} command allows you to enable or
2719 disable printing of messages when @value{GDBN} notices that new
2720 inferiors have started or that inferiors have exited or have been
2721 detached. By default, these messages will not be printed.
2723 @kindex show print inferior-events
2724 @item show print inferior-events
2725 Show whether messages will be printed when @value{GDBN} detects that
2726 inferiors have started, exited or have been detached.
2729 Many commands will work the same with multiple programs as with a
2730 single program: e.g., @code{print myglobal} will simply display the
2731 value of @code{myglobal} in the current inferior.
2734 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2735 get more info about the relationship of inferiors, programs, address
2736 spaces in a debug session. You can do that with the @w{@code{maint
2737 info program-spaces}} command.
2740 @kindex maint info program-spaces
2741 @item maint info program-spaces
2742 Print a list of all program spaces currently being managed by
2745 @value{GDBN} displays for each program space (in this order):
2749 the program space number assigned by @value{GDBN}
2752 the name of the executable loaded into the program space, with e.g.,
2753 the @code{file} command.
2758 An asterisk @samp{*} preceding the @value{GDBN} program space number
2759 indicates the current program space.
2761 In addition, below each program space line, @value{GDBN} prints extra
2762 information that isn't suitable to display in tabular form. For
2763 example, the list of inferiors bound to the program space.
2766 (@value{GDBP}) maint info program-spaces
2769 Bound inferiors: ID 1 (process 21561)
2773 Here we can see that no inferior is running the program @code{hello},
2774 while @code{process 21561} is running the program @code{goodbye}. On
2775 some targets, it is possible that multiple inferiors are bound to the
2776 same program space. The most common example is that of debugging both
2777 the parent and child processes of a @code{vfork} call. For example,
2780 (@value{GDBP}) maint info program-spaces
2783 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2786 Here, both inferior 2 and inferior 1 are running in the same program
2787 space as a result of inferior 1 having executed a @code{vfork} call.
2791 @section Debugging Programs with Multiple Threads
2793 @cindex threads of execution
2794 @cindex multiple threads
2795 @cindex switching threads
2796 In some operating systems, such as HP-UX and Solaris, a single program
2797 may have more than one @dfn{thread} of execution. The precise semantics
2798 of threads differ from one operating system to another, but in general
2799 the threads of a single program are akin to multiple processes---except
2800 that they share one address space (that is, they can all examine and
2801 modify the same variables). On the other hand, each thread has its own
2802 registers and execution stack, and perhaps private memory.
2804 @value{GDBN} provides these facilities for debugging multi-thread
2808 @item automatic notification of new threads
2809 @item @samp{thread @var{threadno}}, a command to switch among threads
2810 @item @samp{info threads}, a command to inquire about existing threads
2811 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2812 a command to apply a command to a list of threads
2813 @item thread-specific breakpoints
2814 @item @samp{set print thread-events}, which controls printing of
2815 messages on thread start and exit.
2816 @item @samp{set libthread-db-search-path @var{path}}, which lets
2817 the user specify which @code{libthread_db} to use if the default choice
2818 isn't compatible with the program.
2822 @emph{Warning:} These facilities are not yet available on every
2823 @value{GDBN} configuration where the operating system supports threads.
2824 If your @value{GDBN} does not support threads, these commands have no
2825 effect. For example, a system without thread support shows no output
2826 from @samp{info threads}, and always rejects the @code{thread} command,
2830 (@value{GDBP}) info threads
2831 (@value{GDBP}) thread 1
2832 Thread ID 1 not known. Use the "info threads" command to
2833 see the IDs of currently known threads.
2835 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2836 @c doesn't support threads"?
2839 @cindex focus of debugging
2840 @cindex current thread
2841 The @value{GDBN} thread debugging facility allows you to observe all
2842 threads while your program runs---but whenever @value{GDBN} takes
2843 control, one thread in particular is always the focus of debugging.
2844 This thread is called the @dfn{current thread}. Debugging commands show
2845 program information from the perspective of the current thread.
2847 @cindex @code{New} @var{systag} message
2848 @cindex thread identifier (system)
2849 @c FIXME-implementors!! It would be more helpful if the [New...] message
2850 @c included GDB's numeric thread handle, so you could just go to that
2851 @c thread without first checking `info threads'.
2852 Whenever @value{GDBN} detects a new thread in your program, it displays
2853 the target system's identification for the thread with a message in the
2854 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2855 whose form varies depending on the particular system. For example, on
2856 @sc{gnu}/Linux, you might see
2859 [New Thread 0x41e02940 (LWP 25582)]
2863 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2864 the @var{systag} is simply something like @samp{process 368}, with no
2867 @c FIXME!! (1) Does the [New...] message appear even for the very first
2868 @c thread of a program, or does it only appear for the
2869 @c second---i.e.@: when it becomes obvious we have a multithread
2871 @c (2) *Is* there necessarily a first thread always? Or do some
2872 @c multithread systems permit starting a program with multiple
2873 @c threads ab initio?
2875 @cindex thread number
2876 @cindex thread identifier (GDB)
2877 For debugging purposes, @value{GDBN} associates its own thread
2878 number---always a single integer---with each thread in your program.
2881 @kindex info threads
2882 @item info threads @r{[}@var{id}@dots{}@r{]}
2883 Display a summary of all threads currently in your program. Optional
2884 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2885 means to print information only about the specified thread or threads.
2886 @value{GDBN} displays for each thread (in this order):
2890 the thread number assigned by @value{GDBN}
2893 the target system's thread identifier (@var{systag})
2896 the thread's name, if one is known. A thread can either be named by
2897 the user (see @code{thread name}, below), or, in some cases, by the
2901 the current stack frame summary for that thread
2905 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2906 indicates the current thread.
2910 @c end table here to get a little more width for example
2913 (@value{GDBP}) info threads
2915 3 process 35 thread 27 0x34e5 in sigpause ()
2916 2 process 35 thread 23 0x34e5 in sigpause ()
2917 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2921 On Solaris, you can display more information about user threads with a
2922 Solaris-specific command:
2925 @item maint info sol-threads
2926 @kindex maint info sol-threads
2927 @cindex thread info (Solaris)
2928 Display info on Solaris user threads.
2932 @kindex thread @var{threadno}
2933 @item thread @var{threadno}
2934 Make thread number @var{threadno} the current thread. The command
2935 argument @var{threadno} is the internal @value{GDBN} thread number, as
2936 shown in the first field of the @samp{info threads} display.
2937 @value{GDBN} responds by displaying the system identifier of the thread
2938 you selected, and its current stack frame summary:
2941 (@value{GDBP}) thread 2
2942 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2943 #0 some_function (ignore=0x0) at example.c:8
2944 8 printf ("hello\n");
2948 As with the @samp{[New @dots{}]} message, the form of the text after
2949 @samp{Switching to} depends on your system's conventions for identifying
2952 @vindex $_thread@r{, convenience variable}
2953 The debugger convenience variable @samp{$_thread} contains the number
2954 of the current thread. You may find this useful in writing breakpoint
2955 conditional expressions, command scripts, and so forth. See
2956 @xref{Convenience Vars,, Convenience Variables}, for general
2957 information on convenience variables.
2959 @kindex thread apply
2960 @cindex apply command to several threads
2961 @item thread apply [@var{threadno} | all] @var{command}
2962 The @code{thread apply} command allows you to apply the named
2963 @var{command} to one or more threads. Specify the numbers of the
2964 threads that you want affected with the command argument
2965 @var{threadno}. It can be a single thread number, one of the numbers
2966 shown in the first field of the @samp{info threads} display; or it
2967 could be a range of thread numbers, as in @code{2-4}. To apply a
2968 command to all threads, type @kbd{thread apply all @var{command}}.
2971 @cindex name a thread
2972 @item thread name [@var{name}]
2973 This command assigns a name to the current thread. If no argument is
2974 given, any existing user-specified name is removed. The thread name
2975 appears in the @samp{info threads} display.
2977 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2978 determine the name of the thread as given by the OS. On these
2979 systems, a name specified with @samp{thread name} will override the
2980 system-give name, and removing the user-specified name will cause
2981 @value{GDBN} to once again display the system-specified name.
2984 @cindex search for a thread
2985 @item thread find [@var{regexp}]
2986 Search for and display thread ids whose name or @var{systag}
2987 matches the supplied regular expression.
2989 As well as being the complement to the @samp{thread name} command,
2990 this command also allows you to identify a thread by its target
2991 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2995 (@value{GDBN}) thread find 26688
2996 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2997 (@value{GDBN}) info thread 4
2999 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3002 @kindex set print thread-events
3003 @cindex print messages on thread start and exit
3004 @item set print thread-events
3005 @itemx set print thread-events on
3006 @itemx set print thread-events off
3007 The @code{set print thread-events} command allows you to enable or
3008 disable printing of messages when @value{GDBN} notices that new threads have
3009 started or that threads have exited. By default, these messages will
3010 be printed if detection of these events is supported by the target.
3011 Note that these messages cannot be disabled on all targets.
3013 @kindex show print thread-events
3014 @item show print thread-events
3015 Show whether messages will be printed when @value{GDBN} detects that threads
3016 have started and exited.
3019 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3020 more information about how @value{GDBN} behaves when you stop and start
3021 programs with multiple threads.
3023 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3024 watchpoints in programs with multiple threads.
3026 @anchor{set libthread-db-search-path}
3028 @kindex set libthread-db-search-path
3029 @cindex search path for @code{libthread_db}
3030 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3031 If this variable is set, @var{path} is a colon-separated list of
3032 directories @value{GDBN} will use to search for @code{libthread_db}.
3033 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3034 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3035 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3038 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3039 @code{libthread_db} library to obtain information about threads in the
3040 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3041 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3042 specific thread debugging library loading is enabled
3043 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3045 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3046 refers to the default system directories that are
3047 normally searched for loading shared libraries. The @samp{$sdir} entry
3048 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3049 (@pxref{libthread_db.so.1 file}).
3051 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3052 refers to the directory from which @code{libpthread}
3053 was loaded in the inferior process.
3055 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3056 @value{GDBN} attempts to initialize it with the current inferior process.
3057 If this initialization fails (which could happen because of a version
3058 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3059 will unload @code{libthread_db}, and continue with the next directory.
3060 If none of @code{libthread_db} libraries initialize successfully,
3061 @value{GDBN} will issue a warning and thread debugging will be disabled.
3063 Setting @code{libthread-db-search-path} is currently implemented
3064 only on some platforms.
3066 @kindex show libthread-db-search-path
3067 @item show libthread-db-search-path
3068 Display current libthread_db search path.
3070 @kindex set debug libthread-db
3071 @kindex show debug libthread-db
3072 @cindex debugging @code{libthread_db}
3073 @item set debug libthread-db
3074 @itemx show debug libthread-db
3075 Turns on or off display of @code{libthread_db}-related events.
3076 Use @code{1} to enable, @code{0} to disable.
3080 @section Debugging Forks
3082 @cindex fork, debugging programs which call
3083 @cindex multiple processes
3084 @cindex processes, multiple
3085 On most systems, @value{GDBN} has no special support for debugging
3086 programs which create additional processes using the @code{fork}
3087 function. When a program forks, @value{GDBN} will continue to debug the
3088 parent process and the child process will run unimpeded. If you have
3089 set a breakpoint in any code which the child then executes, the child
3090 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3091 will cause it to terminate.
3093 However, if you want to debug the child process there is a workaround
3094 which isn't too painful. Put a call to @code{sleep} in the code which
3095 the child process executes after the fork. It may be useful to sleep
3096 only if a certain environment variable is set, or a certain file exists,
3097 so that the delay need not occur when you don't want to run @value{GDBN}
3098 on the child. While the child is sleeping, use the @code{ps} program to
3099 get its process ID. Then tell @value{GDBN} (a new invocation of
3100 @value{GDBN} if you are also debugging the parent process) to attach to
3101 the child process (@pxref{Attach}). From that point on you can debug
3102 the child process just like any other process which you attached to.
3104 On some systems, @value{GDBN} provides support for debugging programs that
3105 create additional processes using the @code{fork} or @code{vfork} functions.
3106 Currently, the only platforms with this feature are HP-UX (11.x and later
3107 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3109 By default, when a program forks, @value{GDBN} will continue to debug
3110 the parent process and the child process will run unimpeded.
3112 If you want to follow the child process instead of the parent process,
3113 use the command @w{@code{set follow-fork-mode}}.
3116 @kindex set follow-fork-mode
3117 @item set follow-fork-mode @var{mode}
3118 Set the debugger response to a program call of @code{fork} or
3119 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3120 process. The @var{mode} argument can be:
3124 The original process is debugged after a fork. The child process runs
3125 unimpeded. This is the default.
3128 The new process is debugged after a fork. The parent process runs
3133 @kindex show follow-fork-mode
3134 @item show follow-fork-mode
3135 Display the current debugger response to a @code{fork} or @code{vfork} call.
3138 @cindex debugging multiple processes
3139 On Linux, if you want to debug both the parent and child processes, use the
3140 command @w{@code{set detach-on-fork}}.
3143 @kindex set detach-on-fork
3144 @item set detach-on-fork @var{mode}
3145 Tells gdb whether to detach one of the processes after a fork, or
3146 retain debugger control over them both.
3150 The child process (or parent process, depending on the value of
3151 @code{follow-fork-mode}) will be detached and allowed to run
3152 independently. This is the default.
3155 Both processes will be held under the control of @value{GDBN}.
3156 One process (child or parent, depending on the value of
3157 @code{follow-fork-mode}) is debugged as usual, while the other
3162 @kindex show detach-on-fork
3163 @item show detach-on-fork
3164 Show whether detach-on-fork mode is on/off.
3167 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3168 will retain control of all forked processes (including nested forks).
3169 You can list the forked processes under the control of @value{GDBN} by
3170 using the @w{@code{info inferiors}} command, and switch from one fork
3171 to another by using the @code{inferior} command (@pxref{Inferiors and
3172 Programs, ,Debugging Multiple Inferiors and Programs}).
3174 To quit debugging one of the forked processes, you can either detach
3175 from it by using the @w{@code{detach inferiors}} command (allowing it
3176 to run independently), or kill it using the @w{@code{kill inferiors}}
3177 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3180 If you ask to debug a child process and a @code{vfork} is followed by an
3181 @code{exec}, @value{GDBN} executes the new target up to the first
3182 breakpoint in the new target. If you have a breakpoint set on
3183 @code{main} in your original program, the breakpoint will also be set on
3184 the child process's @code{main}.
3186 On some systems, when a child process is spawned by @code{vfork}, you
3187 cannot debug the child or parent until an @code{exec} call completes.
3189 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3190 call executes, the new target restarts. To restart the parent
3191 process, use the @code{file} command with the parent executable name
3192 as its argument. By default, after an @code{exec} call executes,
3193 @value{GDBN} discards the symbols of the previous executable image.
3194 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3198 @kindex set follow-exec-mode
3199 @item set follow-exec-mode @var{mode}
3201 Set debugger response to a program call of @code{exec}. An
3202 @code{exec} call replaces the program image of a process.
3204 @code{follow-exec-mode} can be:
3208 @value{GDBN} creates a new inferior and rebinds the process to this
3209 new inferior. The program the process was running before the
3210 @code{exec} call can be restarted afterwards by restarting the
3216 (@value{GDBP}) info inferiors
3218 Id Description Executable
3221 process 12020 is executing new program: prog2
3222 Program exited normally.
3223 (@value{GDBP}) info inferiors
3224 Id Description Executable
3230 @value{GDBN} keeps the process bound to the same inferior. The new
3231 executable image replaces the previous executable loaded in the
3232 inferior. Restarting the inferior after the @code{exec} call, with
3233 e.g., the @code{run} command, restarts the executable the process was
3234 running after the @code{exec} call. This is the default mode.
3239 (@value{GDBP}) info inferiors
3240 Id Description Executable
3243 process 12020 is executing new program: prog2
3244 Program exited normally.
3245 (@value{GDBP}) info inferiors
3246 Id Description Executable
3253 You can use the @code{catch} command to make @value{GDBN} stop whenever
3254 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3255 Catchpoints, ,Setting Catchpoints}.
3257 @node Checkpoint/Restart
3258 @section Setting a @emph{Bookmark} to Return to Later
3263 @cindex snapshot of a process
3264 @cindex rewind program state
3266 On certain operating systems@footnote{Currently, only
3267 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3268 program's state, called a @dfn{checkpoint}, and come back to it
3271 Returning to a checkpoint effectively undoes everything that has
3272 happened in the program since the @code{checkpoint} was saved. This
3273 includes changes in memory, registers, and even (within some limits)
3274 system state. Effectively, it is like going back in time to the
3275 moment when the checkpoint was saved.
3277 Thus, if you're stepping thru a program and you think you're
3278 getting close to the point where things go wrong, you can save
3279 a checkpoint. Then, if you accidentally go too far and miss
3280 the critical statement, instead of having to restart your program
3281 from the beginning, you can just go back to the checkpoint and
3282 start again from there.
3284 This can be especially useful if it takes a lot of time or
3285 steps to reach the point where you think the bug occurs.
3287 To use the @code{checkpoint}/@code{restart} method of debugging:
3292 Save a snapshot of the debugged program's current execution state.
3293 The @code{checkpoint} command takes no arguments, but each checkpoint
3294 is assigned a small integer id, similar to a breakpoint id.
3296 @kindex info checkpoints
3297 @item info checkpoints
3298 List the checkpoints that have been saved in the current debugging
3299 session. For each checkpoint, the following information will be
3306 @item Source line, or label
3309 @kindex restart @var{checkpoint-id}
3310 @item restart @var{checkpoint-id}
3311 Restore the program state that was saved as checkpoint number
3312 @var{checkpoint-id}. All program variables, registers, stack frames
3313 etc.@: will be returned to the values that they had when the checkpoint
3314 was saved. In essence, gdb will ``wind back the clock'' to the point
3315 in time when the checkpoint was saved.
3317 Note that breakpoints, @value{GDBN} variables, command history etc.
3318 are not affected by restoring a checkpoint. In general, a checkpoint
3319 only restores things that reside in the program being debugged, not in
3322 @kindex delete checkpoint @var{checkpoint-id}
3323 @item delete checkpoint @var{checkpoint-id}
3324 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3328 Returning to a previously saved checkpoint will restore the user state
3329 of the program being debugged, plus a significant subset of the system
3330 (OS) state, including file pointers. It won't ``un-write'' data from
3331 a file, but it will rewind the file pointer to the previous location,
3332 so that the previously written data can be overwritten. For files
3333 opened in read mode, the pointer will also be restored so that the
3334 previously read data can be read again.
3336 Of course, characters that have been sent to a printer (or other
3337 external device) cannot be ``snatched back'', and characters received
3338 from eg.@: a serial device can be removed from internal program buffers,
3339 but they cannot be ``pushed back'' into the serial pipeline, ready to
3340 be received again. Similarly, the actual contents of files that have
3341 been changed cannot be restored (at this time).
3343 However, within those constraints, you actually can ``rewind'' your
3344 program to a previously saved point in time, and begin debugging it
3345 again --- and you can change the course of events so as to debug a
3346 different execution path this time.
3348 @cindex checkpoints and process id
3349 Finally, there is one bit of internal program state that will be
3350 different when you return to a checkpoint --- the program's process
3351 id. Each checkpoint will have a unique process id (or @var{pid}),
3352 and each will be different from the program's original @var{pid}.
3353 If your program has saved a local copy of its process id, this could
3354 potentially pose a problem.
3356 @subsection A Non-obvious Benefit of Using Checkpoints
3358 On some systems such as @sc{gnu}/Linux, address space randomization
3359 is performed on new processes for security reasons. This makes it
3360 difficult or impossible to set a breakpoint, or watchpoint, on an
3361 absolute address if you have to restart the program, since the
3362 absolute location of a symbol will change from one execution to the
3365 A checkpoint, however, is an @emph{identical} copy of a process.
3366 Therefore if you create a checkpoint at (eg.@:) the start of main,
3367 and simply return to that checkpoint instead of restarting the
3368 process, you can avoid the effects of address randomization and
3369 your symbols will all stay in the same place.
3372 @chapter Stopping and Continuing
3374 The principal purposes of using a debugger are so that you can stop your
3375 program before it terminates; or so that, if your program runs into
3376 trouble, you can investigate and find out why.
3378 Inside @value{GDBN}, your program may stop for any of several reasons,
3379 such as a signal, a breakpoint, or reaching a new line after a
3380 @value{GDBN} command such as @code{step}. You may then examine and
3381 change variables, set new breakpoints or remove old ones, and then
3382 continue execution. Usually, the messages shown by @value{GDBN} provide
3383 ample explanation of the status of your program---but you can also
3384 explicitly request this information at any time.
3387 @kindex info program
3389 Display information about the status of your program: whether it is
3390 running or not, what process it is, and why it stopped.
3394 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3395 * Continuing and Stepping:: Resuming execution
3396 * Skipping Over Functions and Files::
3397 Skipping over functions and files
3399 * Thread Stops:: Stopping and starting multi-thread programs
3403 @section Breakpoints, Watchpoints, and Catchpoints
3406 A @dfn{breakpoint} makes your program stop whenever a certain point in
3407 the program is reached. For each breakpoint, you can add conditions to
3408 control in finer detail whether your program stops. You can set
3409 breakpoints with the @code{break} command and its variants (@pxref{Set
3410 Breaks, ,Setting Breakpoints}), to specify the place where your program
3411 should stop by line number, function name or exact address in the
3414 On some systems, you can set breakpoints in shared libraries before
3415 the executable is run. There is a minor limitation on HP-UX systems:
3416 you must wait until the executable is run in order to set breakpoints
3417 in shared library routines that are not called directly by the program
3418 (for example, routines that are arguments in a @code{pthread_create}
3422 @cindex data breakpoints
3423 @cindex memory tracing
3424 @cindex breakpoint on memory address
3425 @cindex breakpoint on variable modification
3426 A @dfn{watchpoint} is a special breakpoint that stops your program
3427 when the value of an expression changes. The expression may be a value
3428 of a variable, or it could involve values of one or more variables
3429 combined by operators, such as @samp{a + b}. This is sometimes called
3430 @dfn{data breakpoints}. You must use a different command to set
3431 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3432 from that, you can manage a watchpoint like any other breakpoint: you
3433 enable, disable, and delete both breakpoints and watchpoints using the
3436 You can arrange to have values from your program displayed automatically
3437 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3441 @cindex breakpoint on events
3442 A @dfn{catchpoint} is another special breakpoint that stops your program
3443 when a certain kind of event occurs, such as the throwing of a C@t{++}
3444 exception or the loading of a library. As with watchpoints, you use a
3445 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3446 Catchpoints}), but aside from that, you can manage a catchpoint like any
3447 other breakpoint. (To stop when your program receives a signal, use the
3448 @code{handle} command; see @ref{Signals, ,Signals}.)
3450 @cindex breakpoint numbers
3451 @cindex numbers for breakpoints
3452 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3453 catchpoint when you create it; these numbers are successive integers
3454 starting with one. In many of the commands for controlling various
3455 features of breakpoints you use the breakpoint number to say which
3456 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3457 @dfn{disabled}; if disabled, it has no effect on your program until you
3460 @cindex breakpoint ranges
3461 @cindex ranges of breakpoints
3462 Some @value{GDBN} commands accept a range of breakpoints on which to
3463 operate. A breakpoint range is either a single breakpoint number, like
3464 @samp{5}, or two such numbers, in increasing order, separated by a
3465 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3466 all breakpoints in that range are operated on.
3469 * Set Breaks:: Setting breakpoints
3470 * Set Watchpoints:: Setting watchpoints
3471 * Set Catchpoints:: Setting catchpoints
3472 * Delete Breaks:: Deleting breakpoints
3473 * Disabling:: Disabling breakpoints
3474 * Conditions:: Break conditions
3475 * Break Commands:: Breakpoint command lists
3476 * Dynamic Printf:: Dynamic printf
3477 * Save Breakpoints:: How to save breakpoints in a file
3478 * Static Probe Points:: Listing static probe points
3479 * Error in Breakpoints:: ``Cannot insert breakpoints''
3480 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3484 @subsection Setting Breakpoints
3486 @c FIXME LMB what does GDB do if no code on line of breakpt?
3487 @c consider in particular declaration with/without initialization.
3489 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3492 @kindex b @r{(@code{break})}
3493 @vindex $bpnum@r{, convenience variable}
3494 @cindex latest breakpoint
3495 Breakpoints are set with the @code{break} command (abbreviated
3496 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3497 number of the breakpoint you've set most recently; see @ref{Convenience
3498 Vars,, Convenience Variables}, for a discussion of what you can do with
3499 convenience variables.
3502 @item break @var{location}
3503 Set a breakpoint at the given @var{location}, which can specify a
3504 function name, a line number, or an address of an instruction.
3505 (@xref{Specify Location}, for a list of all the possible ways to
3506 specify a @var{location}.) The breakpoint will stop your program just
3507 before it executes any of the code in the specified @var{location}.
3509 When using source languages that permit overloading of symbols, such as
3510 C@t{++}, a function name may refer to more than one possible place to break.
3511 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3514 It is also possible to insert a breakpoint that will stop the program
3515 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3516 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3519 When called without any arguments, @code{break} sets a breakpoint at
3520 the next instruction to be executed in the selected stack frame
3521 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3522 innermost, this makes your program stop as soon as control
3523 returns to that frame. This is similar to the effect of a
3524 @code{finish} command in the frame inside the selected frame---except
3525 that @code{finish} does not leave an active breakpoint. If you use
3526 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3527 the next time it reaches the current location; this may be useful
3530 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3531 least one instruction has been executed. If it did not do this, you
3532 would be unable to proceed past a breakpoint without first disabling the
3533 breakpoint. This rule applies whether or not the breakpoint already
3534 existed when your program stopped.
3536 @item break @dots{} if @var{cond}
3537 Set a breakpoint with condition @var{cond}; evaluate the expression
3538 @var{cond} each time the breakpoint is reached, and stop only if the
3539 value is nonzero---that is, if @var{cond} evaluates as true.
3540 @samp{@dots{}} stands for one of the possible arguments described
3541 above (or no argument) specifying where to break. @xref{Conditions,
3542 ,Break Conditions}, for more information on breakpoint conditions.
3545 @item tbreak @var{args}
3546 Set a breakpoint enabled only for one stop. @var{args} are the
3547 same as for the @code{break} command, and the breakpoint is set in the same
3548 way, but the breakpoint is automatically deleted after the first time your
3549 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3552 @cindex hardware breakpoints
3553 @item hbreak @var{args}
3554 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3555 @code{break} command and the breakpoint is set in the same way, but the
3556 breakpoint requires hardware support and some target hardware may not
3557 have this support. The main purpose of this is EPROM/ROM code
3558 debugging, so you can set a breakpoint at an instruction without
3559 changing the instruction. This can be used with the new trap-generation
3560 provided by SPARClite DSU and most x86-based targets. These targets
3561 will generate traps when a program accesses some data or instruction
3562 address that is assigned to the debug registers. However the hardware
3563 breakpoint registers can take a limited number of breakpoints. For
3564 example, on the DSU, only two data breakpoints can be set at a time, and
3565 @value{GDBN} will reject this command if more than two are used. Delete
3566 or disable unused hardware breakpoints before setting new ones
3567 (@pxref{Disabling, ,Disabling Breakpoints}).
3568 @xref{Conditions, ,Break Conditions}.
3569 For remote targets, you can restrict the number of hardware
3570 breakpoints @value{GDBN} will use, see @ref{set remote
3571 hardware-breakpoint-limit}.
3574 @item thbreak @var{args}
3575 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3576 are the same as for the @code{hbreak} command and the breakpoint is set in
3577 the same way. However, like the @code{tbreak} command,
3578 the breakpoint is automatically deleted after the
3579 first time your program stops there. Also, like the @code{hbreak}
3580 command, the breakpoint requires hardware support and some target hardware
3581 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3582 See also @ref{Conditions, ,Break Conditions}.
3585 @cindex regular expression
3586 @cindex breakpoints at functions matching a regexp
3587 @cindex set breakpoints in many functions
3588 @item rbreak @var{regex}
3589 Set breakpoints on all functions matching the regular expression
3590 @var{regex}. This command sets an unconditional breakpoint on all
3591 matches, printing a list of all breakpoints it set. Once these
3592 breakpoints are set, they are treated just like the breakpoints set with
3593 the @code{break} command. You can delete them, disable them, or make
3594 them conditional the same way as any other breakpoint.
3596 The syntax of the regular expression is the standard one used with tools
3597 like @file{grep}. Note that this is different from the syntax used by
3598 shells, so for instance @code{foo*} matches all functions that include
3599 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3600 @code{.*} leading and trailing the regular expression you supply, so to
3601 match only functions that begin with @code{foo}, use @code{^foo}.
3603 @cindex non-member C@t{++} functions, set breakpoint in
3604 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3605 breakpoints on overloaded functions that are not members of any special
3608 @cindex set breakpoints on all functions
3609 The @code{rbreak} command can be used to set breakpoints in
3610 @strong{all} the functions in a program, like this:
3613 (@value{GDBP}) rbreak .
3616 @item rbreak @var{file}:@var{regex}
3617 If @code{rbreak} is called with a filename qualification, it limits
3618 the search for functions matching the given regular expression to the
3619 specified @var{file}. This can be used, for example, to set breakpoints on
3620 every function in a given file:
3623 (@value{GDBP}) rbreak file.c:.
3626 The colon separating the filename qualifier from the regex may
3627 optionally be surrounded by spaces.
3629 @kindex info breakpoints
3630 @cindex @code{$_} and @code{info breakpoints}
3631 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3632 @itemx info break @r{[}@var{n}@dots{}@r{]}
3633 Print a table of all breakpoints, watchpoints, and catchpoints set and
3634 not deleted. Optional argument @var{n} means print information only
3635 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3636 For each breakpoint, following columns are printed:
3639 @item Breakpoint Numbers
3641 Breakpoint, watchpoint, or catchpoint.
3643 Whether the breakpoint is marked to be disabled or deleted when hit.
3644 @item Enabled or Disabled
3645 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3646 that are not enabled.
3648 Where the breakpoint is in your program, as a memory address. For a
3649 pending breakpoint whose address is not yet known, this field will
3650 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3651 library that has the symbol or line referred by breakpoint is loaded.
3652 See below for details. A breakpoint with several locations will
3653 have @samp{<MULTIPLE>} in this field---see below for details.
3655 Where the breakpoint is in the source for your program, as a file and
3656 line number. For a pending breakpoint, the original string passed to
3657 the breakpoint command will be listed as it cannot be resolved until
3658 the appropriate shared library is loaded in the future.
3662 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3663 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3664 @value{GDBN} on the host's side. If it is ``target'', then the condition
3665 is evaluated by the target. The @code{info break} command shows
3666 the condition on the line following the affected breakpoint, together with
3667 its condition evaluation mode in between parentheses.
3669 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3670 allowed to have a condition specified for it. The condition is not parsed for
3671 validity until a shared library is loaded that allows the pending
3672 breakpoint to resolve to a valid location.
3675 @code{info break} with a breakpoint
3676 number @var{n} as argument lists only that breakpoint. The
3677 convenience variable @code{$_} and the default examining-address for
3678 the @code{x} command are set to the address of the last breakpoint
3679 listed (@pxref{Memory, ,Examining Memory}).
3682 @code{info break} displays a count of the number of times the breakpoint
3683 has been hit. This is especially useful in conjunction with the
3684 @code{ignore} command. You can ignore a large number of breakpoint
3685 hits, look at the breakpoint info to see how many times the breakpoint
3686 was hit, and then run again, ignoring one less than that number. This
3687 will get you quickly to the last hit of that breakpoint.
3690 For a breakpoints with an enable count (xref) greater than 1,
3691 @code{info break} also displays that count.
3695 @value{GDBN} allows you to set any number of breakpoints at the same place in
3696 your program. There is nothing silly or meaningless about this. When
3697 the breakpoints are conditional, this is even useful
3698 (@pxref{Conditions, ,Break Conditions}).
3700 @cindex multiple locations, breakpoints
3701 @cindex breakpoints, multiple locations
3702 It is possible that a breakpoint corresponds to several locations
3703 in your program. Examples of this situation are:
3707 Multiple functions in the program may have the same name.
3710 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3711 instances of the function body, used in different cases.
3714 For a C@t{++} template function, a given line in the function can
3715 correspond to any number of instantiations.
3718 For an inlined function, a given source line can correspond to
3719 several places where that function is inlined.
3722 In all those cases, @value{GDBN} will insert a breakpoint at all
3723 the relevant locations.
3725 A breakpoint with multiple locations is displayed in the breakpoint
3726 table using several rows---one header row, followed by one row for
3727 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3728 address column. The rows for individual locations contain the actual
3729 addresses for locations, and show the functions to which those
3730 locations belong. The number column for a location is of the form
3731 @var{breakpoint-number}.@var{location-number}.
3736 Num Type Disp Enb Address What
3737 1 breakpoint keep y <MULTIPLE>
3739 breakpoint already hit 1 time
3740 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3741 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3744 Each location can be individually enabled or disabled by passing
3745 @var{breakpoint-number}.@var{location-number} as argument to the
3746 @code{enable} and @code{disable} commands. Note that you cannot
3747 delete the individual locations from the list, you can only delete the
3748 entire list of locations that belong to their parent breakpoint (with
3749 the @kbd{delete @var{num}} command, where @var{num} is the number of
3750 the parent breakpoint, 1 in the above example). Disabling or enabling
3751 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3752 that belong to that breakpoint.
3754 @cindex pending breakpoints
3755 It's quite common to have a breakpoint inside a shared library.
3756 Shared libraries can be loaded and unloaded explicitly,
3757 and possibly repeatedly, as the program is executed. To support
3758 this use case, @value{GDBN} updates breakpoint locations whenever
3759 any shared library is loaded or unloaded. Typically, you would
3760 set a breakpoint in a shared library at the beginning of your
3761 debugging session, when the library is not loaded, and when the
3762 symbols from the library are not available. When you try to set
3763 breakpoint, @value{GDBN} will ask you if you want to set
3764 a so called @dfn{pending breakpoint}---breakpoint whose address
3765 is not yet resolved.
3767 After the program is run, whenever a new shared library is loaded,
3768 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3769 shared library contains the symbol or line referred to by some
3770 pending breakpoint, that breakpoint is resolved and becomes an
3771 ordinary breakpoint. When a library is unloaded, all breakpoints
3772 that refer to its symbols or source lines become pending again.
3774 This logic works for breakpoints with multiple locations, too. For
3775 example, if you have a breakpoint in a C@t{++} template function, and
3776 a newly loaded shared library has an instantiation of that template,
3777 a new location is added to the list of locations for the breakpoint.
3779 Except for having unresolved address, pending breakpoints do not
3780 differ from regular breakpoints. You can set conditions or commands,
3781 enable and disable them and perform other breakpoint operations.
3783 @value{GDBN} provides some additional commands for controlling what
3784 happens when the @samp{break} command cannot resolve breakpoint
3785 address specification to an address:
3787 @kindex set breakpoint pending
3788 @kindex show breakpoint pending
3790 @item set breakpoint pending auto
3791 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3792 location, it queries you whether a pending breakpoint should be created.
3794 @item set breakpoint pending on
3795 This indicates that an unrecognized breakpoint location should automatically
3796 result in a pending breakpoint being created.
3798 @item set breakpoint pending off
3799 This indicates that pending breakpoints are not to be created. Any
3800 unrecognized breakpoint location results in an error. This setting does
3801 not affect any pending breakpoints previously created.
3803 @item show breakpoint pending
3804 Show the current behavior setting for creating pending breakpoints.
3807 The settings above only affect the @code{break} command and its
3808 variants. Once breakpoint is set, it will be automatically updated
3809 as shared libraries are loaded and unloaded.
3811 @cindex automatic hardware breakpoints
3812 For some targets, @value{GDBN} can automatically decide if hardware or
3813 software breakpoints should be used, depending on whether the
3814 breakpoint address is read-only or read-write. This applies to
3815 breakpoints set with the @code{break} command as well as to internal
3816 breakpoints set by commands like @code{next} and @code{finish}. For
3817 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3820 You can control this automatic behaviour with the following commands::
3822 @kindex set breakpoint auto-hw
3823 @kindex show breakpoint auto-hw
3825 @item set breakpoint auto-hw on
3826 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3827 will try to use the target memory map to decide if software or hardware
3828 breakpoint must be used.
3830 @item set breakpoint auto-hw off
3831 This indicates @value{GDBN} should not automatically select breakpoint
3832 type. If the target provides a memory map, @value{GDBN} will warn when
3833 trying to set software breakpoint at a read-only address.
3836 @value{GDBN} normally implements breakpoints by replacing the program code
3837 at the breakpoint address with a special instruction, which, when
3838 executed, given control to the debugger. By default, the program
3839 code is so modified only when the program is resumed. As soon as
3840 the program stops, @value{GDBN} restores the original instructions. This
3841 behaviour guards against leaving breakpoints inserted in the
3842 target should gdb abrubptly disconnect. However, with slow remote
3843 targets, inserting and removing breakpoint can reduce the performance.
3844 This behavior can be controlled with the following commands::
3846 @kindex set breakpoint always-inserted
3847 @kindex show breakpoint always-inserted
3849 @item set breakpoint always-inserted off
3850 All breakpoints, including newly added by the user, are inserted in
3851 the target only when the target is resumed. All breakpoints are
3852 removed from the target when it stops.
3854 @item set breakpoint always-inserted on
3855 Causes all breakpoints to be inserted in the target at all times. If
3856 the user adds a new breakpoint, or changes an existing breakpoint, the
3857 breakpoints in the target are updated immediately. A breakpoint is
3858 removed from the target only when breakpoint itself is removed.
3860 @cindex non-stop mode, and @code{breakpoint always-inserted}
3861 @item set breakpoint always-inserted auto
3862 This is the default mode. If @value{GDBN} is controlling the inferior
3863 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3864 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3865 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3866 @code{breakpoint always-inserted} mode is off.
3869 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3870 when a breakpoint breaks. If the condition is true, then the process being
3871 debugged stops, otherwise the process is resumed.
3873 If the target supports evaluating conditions on its end, @value{GDBN} may
3874 download the breakpoint, together with its conditions, to it.
3876 This feature can be controlled via the following commands:
3878 @kindex set breakpoint condition-evaluation
3879 @kindex show breakpoint condition-evaluation
3881 @item set breakpoint condition-evaluation host
3882 This option commands @value{GDBN} to evaluate the breakpoint
3883 conditions on the host's side. Unconditional breakpoints are sent to
3884 the target which in turn receives the triggers and reports them back to GDB
3885 for condition evaluation. This is the standard evaluation mode.
3887 @item set breakpoint condition-evaluation target
3888 This option commands @value{GDBN} to download breakpoint conditions
3889 to the target at the moment of their insertion. The target
3890 is responsible for evaluating the conditional expression and reporting
3891 breakpoint stop events back to @value{GDBN} whenever the condition
3892 is true. Due to limitations of target-side evaluation, some conditions
3893 cannot be evaluated there, e.g., conditions that depend on local data
3894 that is only known to the host. Examples include
3895 conditional expressions involving convenience variables, complex types
3896 that cannot be handled by the agent expression parser and expressions
3897 that are too long to be sent over to the target, specially when the
3898 target is a remote system. In these cases, the conditions will be
3899 evaluated by @value{GDBN}.
3901 @item set breakpoint condition-evaluation auto
3902 This is the default mode. If the target supports evaluating breakpoint
3903 conditions on its end, @value{GDBN} will download breakpoint conditions to
3904 the target (limitations mentioned previously apply). If the target does
3905 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3906 to evaluating all these conditions on the host's side.
3910 @cindex negative breakpoint numbers
3911 @cindex internal @value{GDBN} breakpoints
3912 @value{GDBN} itself sometimes sets breakpoints in your program for
3913 special purposes, such as proper handling of @code{longjmp} (in C
3914 programs). These internal breakpoints are assigned negative numbers,
3915 starting with @code{-1}; @samp{info breakpoints} does not display them.
3916 You can see these breakpoints with the @value{GDBN} maintenance command
3917 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3920 @node Set Watchpoints
3921 @subsection Setting Watchpoints
3923 @cindex setting watchpoints
3924 You can use a watchpoint to stop execution whenever the value of an
3925 expression changes, without having to predict a particular place where
3926 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3927 The expression may be as simple as the value of a single variable, or
3928 as complex as many variables combined by operators. Examples include:
3932 A reference to the value of a single variable.
3935 An address cast to an appropriate data type. For example,
3936 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3937 address (assuming an @code{int} occupies 4 bytes).
3940 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3941 expression can use any operators valid in the program's native
3942 language (@pxref{Languages}).
3945 You can set a watchpoint on an expression even if the expression can
3946 not be evaluated yet. For instance, you can set a watchpoint on
3947 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3948 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3949 the expression produces a valid value. If the expression becomes
3950 valid in some other way than changing a variable (e.g.@: if the memory
3951 pointed to by @samp{*global_ptr} becomes readable as the result of a
3952 @code{malloc} call), @value{GDBN} may not stop until the next time
3953 the expression changes.
3955 @cindex software watchpoints
3956 @cindex hardware watchpoints
3957 Depending on your system, watchpoints may be implemented in software or
3958 hardware. @value{GDBN} does software watchpointing by single-stepping your
3959 program and testing the variable's value each time, which is hundreds of
3960 times slower than normal execution. (But this may still be worth it, to
3961 catch errors where you have no clue what part of your program is the
3964 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3965 x86-based targets, @value{GDBN} includes support for hardware
3966 watchpoints, which do not slow down the running of your program.
3970 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3971 Set a watchpoint for an expression. @value{GDBN} will break when the
3972 expression @var{expr} is written into by the program and its value
3973 changes. The simplest (and the most popular) use of this command is
3974 to watch the value of a single variable:
3977 (@value{GDBP}) watch foo
3980 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3981 argument, @value{GDBN} breaks only when the thread identified by
3982 @var{threadnum} changes the value of @var{expr}. If any other threads
3983 change the value of @var{expr}, @value{GDBN} will not break. Note
3984 that watchpoints restricted to a single thread in this way only work
3985 with Hardware Watchpoints.
3987 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3988 (see below). The @code{-location} argument tells @value{GDBN} to
3989 instead watch the memory referred to by @var{expr}. In this case,
3990 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3991 and watch the memory at that address. The type of the result is used
3992 to determine the size of the watched memory. If the expression's
3993 result does not have an address, then @value{GDBN} will print an
3996 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3997 of masked watchpoints, if the current architecture supports this
3998 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3999 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4000 to an address to watch. The mask specifies that some bits of an address
4001 (the bits which are reset in the mask) should be ignored when matching
4002 the address accessed by the inferior against the watchpoint address.
4003 Thus, a masked watchpoint watches many addresses simultaneously---those
4004 addresses whose unmasked bits are identical to the unmasked bits in the
4005 watchpoint address. The @code{mask} argument implies @code{-location}.
4009 (@value{GDBP}) watch foo mask 0xffff00ff
4010 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4014 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4015 Set a watchpoint that will break when the value of @var{expr} is read
4019 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4020 Set a watchpoint that will break when @var{expr} is either read from
4021 or written into by the program.
4023 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4024 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4025 This command prints a list of watchpoints, using the same format as
4026 @code{info break} (@pxref{Set Breaks}).
4029 If you watch for a change in a numerically entered address you need to
4030 dereference it, as the address itself is just a constant number which will
4031 never change. @value{GDBN} refuses to create a watchpoint that watches
4032 a never-changing value:
4035 (@value{GDBP}) watch 0x600850
4036 Cannot watch constant value 0x600850.
4037 (@value{GDBP}) watch *(int *) 0x600850
4038 Watchpoint 1: *(int *) 6293584
4041 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4042 watchpoints execute very quickly, and the debugger reports a change in
4043 value at the exact instruction where the change occurs. If @value{GDBN}
4044 cannot set a hardware watchpoint, it sets a software watchpoint, which
4045 executes more slowly and reports the change in value at the next
4046 @emph{statement}, not the instruction, after the change occurs.
4048 @cindex use only software watchpoints
4049 You can force @value{GDBN} to use only software watchpoints with the
4050 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4051 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4052 the underlying system supports them. (Note that hardware-assisted
4053 watchpoints that were set @emph{before} setting
4054 @code{can-use-hw-watchpoints} to zero will still use the hardware
4055 mechanism of watching expression values.)
4058 @item set can-use-hw-watchpoints
4059 @kindex set can-use-hw-watchpoints
4060 Set whether or not to use hardware watchpoints.
4062 @item show can-use-hw-watchpoints
4063 @kindex show can-use-hw-watchpoints
4064 Show the current mode of using hardware watchpoints.
4067 For remote targets, you can restrict the number of hardware
4068 watchpoints @value{GDBN} will use, see @ref{set remote
4069 hardware-breakpoint-limit}.
4071 When you issue the @code{watch} command, @value{GDBN} reports
4074 Hardware watchpoint @var{num}: @var{expr}
4078 if it was able to set a hardware watchpoint.
4080 Currently, the @code{awatch} and @code{rwatch} commands can only set
4081 hardware watchpoints, because accesses to data that don't change the
4082 value of the watched expression cannot be detected without examining
4083 every instruction as it is being executed, and @value{GDBN} does not do
4084 that currently. If @value{GDBN} finds that it is unable to set a
4085 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4086 will print a message like this:
4089 Expression cannot be implemented with read/access watchpoint.
4092 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4093 data type of the watched expression is wider than what a hardware
4094 watchpoint on the target machine can handle. For example, some systems
4095 can only watch regions that are up to 4 bytes wide; on such systems you
4096 cannot set hardware watchpoints for an expression that yields a
4097 double-precision floating-point number (which is typically 8 bytes
4098 wide). As a work-around, it might be possible to break the large region
4099 into a series of smaller ones and watch them with separate watchpoints.
4101 If you set too many hardware watchpoints, @value{GDBN} might be unable
4102 to insert all of them when you resume the execution of your program.
4103 Since the precise number of active watchpoints is unknown until such
4104 time as the program is about to be resumed, @value{GDBN} might not be
4105 able to warn you about this when you set the watchpoints, and the
4106 warning will be printed only when the program is resumed:
4109 Hardware watchpoint @var{num}: Could not insert watchpoint
4113 If this happens, delete or disable some of the watchpoints.
4115 Watching complex expressions that reference many variables can also
4116 exhaust the resources available for hardware-assisted watchpoints.
4117 That's because @value{GDBN} needs to watch every variable in the
4118 expression with separately allocated resources.
4120 If you call a function interactively using @code{print} or @code{call},
4121 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4122 kind of breakpoint or the call completes.
4124 @value{GDBN} automatically deletes watchpoints that watch local
4125 (automatic) variables, or expressions that involve such variables, when
4126 they go out of scope, that is, when the execution leaves the block in
4127 which these variables were defined. In particular, when the program
4128 being debugged terminates, @emph{all} local variables go out of scope,
4129 and so only watchpoints that watch global variables remain set. If you
4130 rerun the program, you will need to set all such watchpoints again. One
4131 way of doing that would be to set a code breakpoint at the entry to the
4132 @code{main} function and when it breaks, set all the watchpoints.
4134 @cindex watchpoints and threads
4135 @cindex threads and watchpoints
4136 In multi-threaded programs, watchpoints will detect changes to the
4137 watched expression from every thread.
4140 @emph{Warning:} In multi-threaded programs, software watchpoints
4141 have only limited usefulness. If @value{GDBN} creates a software
4142 watchpoint, it can only watch the value of an expression @emph{in a
4143 single thread}. If you are confident that the expression can only
4144 change due to the current thread's activity (and if you are also
4145 confident that no other thread can become current), then you can use
4146 software watchpoints as usual. However, @value{GDBN} may not notice
4147 when a non-current thread's activity changes the expression. (Hardware
4148 watchpoints, in contrast, watch an expression in all threads.)
4151 @xref{set remote hardware-watchpoint-limit}.
4153 @node Set Catchpoints
4154 @subsection Setting Catchpoints
4155 @cindex catchpoints, setting
4156 @cindex exception handlers
4157 @cindex event handling
4159 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4160 kinds of program events, such as C@t{++} exceptions or the loading of a
4161 shared library. Use the @code{catch} command to set a catchpoint.
4165 @item catch @var{event}
4166 Stop when @var{event} occurs. @var{event} can be any of the following:
4169 @item throw @r{[}@var{regexp}@r{]}
4170 @itemx rethrow @r{[}@var{regexp}@r{]}
4171 @itemx catch @r{[}@var{regexp}@r{]}
4173 @kindex catch rethrow
4175 @cindex stop on C@t{++} exceptions
4176 The throwing, re-throwing, or catching of a C@t{++} exception.
4178 If @var{regexp} is given, then only exceptions whose type matches the
4179 regular expression will be caught.
4181 @vindex $_exception@r{, convenience variable}
4182 The convenience variable @code{$_exception} is available at an
4183 exception-related catchpoint, on some systems. This holds the
4184 exception being thrown.
4186 There are currently some limitations to C@t{++} exception handling in
4191 The support for these commands is system-dependent. Currently, only
4192 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4196 The regular expression feature and the @code{$_exception} convenience
4197 variable rely on the presence of some SDT probes in @code{libstdc++}.
4198 If these probes are not present, then these features cannot be used.
4199 These probes were first available in the GCC 4.8 release, but whether
4200 or not they are available in your GCC also depends on how it was
4204 The @code{$_exception} convenience variable is only valid at the
4205 instruction at which an exception-related catchpoint is set.
4208 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4209 location in the system library which implements runtime exception
4210 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4211 (@pxref{Selection}) to get to your code.
4214 If you call a function interactively, @value{GDBN} normally returns
4215 control to you when the function has finished executing. If the call
4216 raises an exception, however, the call may bypass the mechanism that
4217 returns control to you and cause your program either to abort or to
4218 simply continue running until it hits a breakpoint, catches a signal
4219 that @value{GDBN} is listening for, or exits. This is the case even if
4220 you set a catchpoint for the exception; catchpoints on exceptions are
4221 disabled within interactive calls. @xref{Calling}, for information on
4222 controlling this with @code{set unwind-on-terminating-exception}.
4225 You cannot raise an exception interactively.
4228 You cannot install an exception handler interactively.
4232 @kindex catch exception
4233 @cindex Ada exception catching
4234 @cindex catch Ada exceptions
4235 An Ada exception being raised. If an exception name is specified
4236 at the end of the command (eg @code{catch exception Program_Error}),
4237 the debugger will stop only when this specific exception is raised.
4238 Otherwise, the debugger stops execution when any Ada exception is raised.
4240 When inserting an exception catchpoint on a user-defined exception whose
4241 name is identical to one of the exceptions defined by the language, the
4242 fully qualified name must be used as the exception name. Otherwise,
4243 @value{GDBN} will assume that it should stop on the pre-defined exception
4244 rather than the user-defined one. For instance, assuming an exception
4245 called @code{Constraint_Error} is defined in package @code{Pck}, then
4246 the command to use to catch such exceptions is @kbd{catch exception
4247 Pck.Constraint_Error}.
4249 @item exception unhandled
4250 @kindex catch exception unhandled
4251 An exception that was raised but is not handled by the program.
4254 @kindex catch assert
4255 A failed Ada assertion.
4259 @cindex break on fork/exec
4260 A call to @code{exec}. This is currently only available for HP-UX
4264 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4265 @kindex catch syscall
4266 @cindex break on a system call.
4267 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4268 syscall is a mechanism for application programs to request a service
4269 from the operating system (OS) or one of the OS system services.
4270 @value{GDBN} can catch some or all of the syscalls issued by the
4271 debuggee, and show the related information for each syscall. If no
4272 argument is specified, calls to and returns from all system calls
4275 @var{name} can be any system call name that is valid for the
4276 underlying OS. Just what syscalls are valid depends on the OS. On
4277 GNU and Unix systems, you can find the full list of valid syscall
4278 names on @file{/usr/include/asm/unistd.h}.
4280 @c For MS-Windows, the syscall names and the corresponding numbers
4281 @c can be found, e.g., on this URL:
4282 @c http://www.metasploit.com/users/opcode/syscalls.html
4283 @c but we don't support Windows syscalls yet.
4285 Normally, @value{GDBN} knows in advance which syscalls are valid for
4286 each OS, so you can use the @value{GDBN} command-line completion
4287 facilities (@pxref{Completion,, command completion}) to list the
4290 You may also specify the system call numerically. A syscall's
4291 number is the value passed to the OS's syscall dispatcher to
4292 identify the requested service. When you specify the syscall by its
4293 name, @value{GDBN} uses its database of syscalls to convert the name
4294 into the corresponding numeric code, but using the number directly
4295 may be useful if @value{GDBN}'s database does not have the complete
4296 list of syscalls on your system (e.g., because @value{GDBN} lags
4297 behind the OS upgrades).
4299 The example below illustrates how this command works if you don't provide
4303 (@value{GDBP}) catch syscall
4304 Catchpoint 1 (syscall)
4306 Starting program: /tmp/catch-syscall
4308 Catchpoint 1 (call to syscall 'close'), \
4309 0xffffe424 in __kernel_vsyscall ()
4313 Catchpoint 1 (returned from syscall 'close'), \
4314 0xffffe424 in __kernel_vsyscall ()
4318 Here is an example of catching a system call by name:
4321 (@value{GDBP}) catch syscall chroot
4322 Catchpoint 1 (syscall 'chroot' [61])
4324 Starting program: /tmp/catch-syscall
4326 Catchpoint 1 (call to syscall 'chroot'), \
4327 0xffffe424 in __kernel_vsyscall ()
4331 Catchpoint 1 (returned from syscall 'chroot'), \
4332 0xffffe424 in __kernel_vsyscall ()
4336 An example of specifying a system call numerically. In the case
4337 below, the syscall number has a corresponding entry in the XML
4338 file, so @value{GDBN} finds its name and prints it:
4341 (@value{GDBP}) catch syscall 252
4342 Catchpoint 1 (syscall(s) 'exit_group')
4344 Starting program: /tmp/catch-syscall
4346 Catchpoint 1 (call to syscall 'exit_group'), \
4347 0xffffe424 in __kernel_vsyscall ()
4351 Program exited normally.
4355 However, there can be situations when there is no corresponding name
4356 in XML file for that syscall number. In this case, @value{GDBN} prints
4357 a warning message saying that it was not able to find the syscall name,
4358 but the catchpoint will be set anyway. See the example below:
4361 (@value{GDBP}) catch syscall 764
4362 warning: The number '764' does not represent a known syscall.
4363 Catchpoint 2 (syscall 764)
4367 If you configure @value{GDBN} using the @samp{--without-expat} option,
4368 it will not be able to display syscall names. Also, if your
4369 architecture does not have an XML file describing its system calls,
4370 you will not be able to see the syscall names. It is important to
4371 notice that these two features are used for accessing the syscall
4372 name database. In either case, you will see a warning like this:
4375 (@value{GDBP}) catch syscall
4376 warning: Could not open "syscalls/i386-linux.xml"
4377 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4378 GDB will not be able to display syscall names.
4379 Catchpoint 1 (syscall)
4383 Of course, the file name will change depending on your architecture and system.
4385 Still using the example above, you can also try to catch a syscall by its
4386 number. In this case, you would see something like:
4389 (@value{GDBP}) catch syscall 252
4390 Catchpoint 1 (syscall(s) 252)
4393 Again, in this case @value{GDBN} would not be able to display syscall's names.
4397 A call to @code{fork}. This is currently only available for HP-UX
4402 A call to @code{vfork}. This is currently only available for HP-UX
4405 @item load @r{[}regexp@r{]}
4406 @itemx unload @r{[}regexp@r{]}
4408 @kindex catch unload
4409 The loading or unloading of a shared library. If @var{regexp} is
4410 given, then the catchpoint will stop only if the regular expression
4411 matches one of the affected libraries.
4413 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4414 @kindex catch signal
4415 The delivery of a signal.
4417 With no arguments, this catchpoint will catch any signal that is not
4418 used internally by @value{GDBN}, specifically, all signals except
4419 @samp{SIGTRAP} and @samp{SIGINT}.
4421 With the argument @samp{all}, all signals, including those used by
4422 @value{GDBN}, will be caught. This argument cannot be used with other
4425 Otherwise, the arguments are a list of signal names as given to
4426 @code{handle} (@pxref{Signals}). Only signals specified in this list
4429 One reason that @code{catch signal} can be more useful than
4430 @code{handle} is that you can attach commands and conditions to the
4433 When a signal is caught by a catchpoint, the signal's @code{stop} and
4434 @code{print} settings, as specified by @code{handle}, are ignored.
4435 However, whether the signal is still delivered to the inferior depends
4436 on the @code{pass} setting; this can be changed in the catchpoint's
4441 @item tcatch @var{event}
4443 Set a catchpoint that is enabled only for one stop. The catchpoint is
4444 automatically deleted after the first time the event is caught.
4448 Use the @code{info break} command to list the current catchpoints.
4452 @subsection Deleting Breakpoints
4454 @cindex clearing breakpoints, watchpoints, catchpoints
4455 @cindex deleting breakpoints, watchpoints, catchpoints
4456 It is often necessary to eliminate a breakpoint, watchpoint, or
4457 catchpoint once it has done its job and you no longer want your program
4458 to stop there. This is called @dfn{deleting} the breakpoint. A
4459 breakpoint that has been deleted no longer exists; it is forgotten.
4461 With the @code{clear} command you can delete breakpoints according to
4462 where they are in your program. With the @code{delete} command you can
4463 delete individual breakpoints, watchpoints, or catchpoints by specifying
4464 their breakpoint numbers.
4466 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4467 automatically ignores breakpoints on the first instruction to be executed
4468 when you continue execution without changing the execution address.
4473 Delete any breakpoints at the next instruction to be executed in the
4474 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4475 the innermost frame is selected, this is a good way to delete a
4476 breakpoint where your program just stopped.
4478 @item clear @var{location}
4479 Delete any breakpoints set at the specified @var{location}.
4480 @xref{Specify Location}, for the various forms of @var{location}; the
4481 most useful ones are listed below:
4484 @item clear @var{function}
4485 @itemx clear @var{filename}:@var{function}
4486 Delete any breakpoints set at entry to the named @var{function}.
4488 @item clear @var{linenum}
4489 @itemx clear @var{filename}:@var{linenum}
4490 Delete any breakpoints set at or within the code of the specified
4491 @var{linenum} of the specified @var{filename}.
4494 @cindex delete breakpoints
4496 @kindex d @r{(@code{delete})}
4497 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4498 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4499 ranges specified as arguments. If no argument is specified, delete all
4500 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4501 confirm off}). You can abbreviate this command as @code{d}.
4505 @subsection Disabling Breakpoints
4507 @cindex enable/disable a breakpoint
4508 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4509 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4510 it had been deleted, but remembers the information on the breakpoint so
4511 that you can @dfn{enable} it again later.
4513 You disable and enable breakpoints, watchpoints, and catchpoints with
4514 the @code{enable} and @code{disable} commands, optionally specifying
4515 one or more breakpoint numbers as arguments. Use @code{info break} to
4516 print a list of all breakpoints, watchpoints, and catchpoints if you
4517 do not know which numbers to use.
4519 Disabling and enabling a breakpoint that has multiple locations
4520 affects all of its locations.
4522 A breakpoint, watchpoint, or catchpoint can have any of several
4523 different states of enablement:
4527 Enabled. The breakpoint stops your program. A breakpoint set
4528 with the @code{break} command starts out in this state.
4530 Disabled. The breakpoint has no effect on your program.
4532 Enabled once. The breakpoint stops your program, but then becomes
4535 Enabled for a count. The breakpoint stops your program for the next
4536 N times, then becomes disabled.
4538 Enabled for deletion. The breakpoint stops your program, but
4539 immediately after it does so it is deleted permanently. A breakpoint
4540 set with the @code{tbreak} command starts out in this state.
4543 You can use the following commands to enable or disable breakpoints,
4544 watchpoints, and catchpoints:
4548 @kindex dis @r{(@code{disable})}
4549 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4550 Disable the specified breakpoints---or all breakpoints, if none are
4551 listed. A disabled breakpoint has no effect but is not forgotten. All
4552 options such as ignore-counts, conditions and commands are remembered in
4553 case the breakpoint is enabled again later. You may abbreviate
4554 @code{disable} as @code{dis}.
4557 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4558 Enable the specified breakpoints (or all defined breakpoints). They
4559 become effective once again in stopping your program.
4561 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4562 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4563 of these breakpoints immediately after stopping your program.
4565 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4566 Enable the specified breakpoints temporarily. @value{GDBN} records
4567 @var{count} with each of the specified breakpoints, and decrements a
4568 breakpoint's count when it is hit. When any count reaches 0,
4569 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4570 count (@pxref{Conditions, ,Break Conditions}), that will be
4571 decremented to 0 before @var{count} is affected.
4573 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4574 Enable the specified breakpoints to work once, then die. @value{GDBN}
4575 deletes any of these breakpoints as soon as your program stops there.
4576 Breakpoints set by the @code{tbreak} command start out in this state.
4579 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4580 @c confusing: tbreak is also initially enabled.
4581 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4582 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4583 subsequently, they become disabled or enabled only when you use one of
4584 the commands above. (The command @code{until} can set and delete a
4585 breakpoint of its own, but it does not change the state of your other
4586 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4590 @subsection Break Conditions
4591 @cindex conditional breakpoints
4592 @cindex breakpoint conditions
4594 @c FIXME what is scope of break condition expr? Context where wanted?
4595 @c in particular for a watchpoint?
4596 The simplest sort of breakpoint breaks every time your program reaches a
4597 specified place. You can also specify a @dfn{condition} for a
4598 breakpoint. A condition is just a Boolean expression in your
4599 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4600 a condition evaluates the expression each time your program reaches it,
4601 and your program stops only if the condition is @emph{true}.
4603 This is the converse of using assertions for program validation; in that
4604 situation, you want to stop when the assertion is violated---that is,
4605 when the condition is false. In C, if you want to test an assertion expressed
4606 by the condition @var{assert}, you should set the condition
4607 @samp{! @var{assert}} on the appropriate breakpoint.
4609 Conditions are also accepted for watchpoints; you may not need them,
4610 since a watchpoint is inspecting the value of an expression anyhow---but
4611 it might be simpler, say, to just set a watchpoint on a variable name,
4612 and specify a condition that tests whether the new value is an interesting
4615 Break conditions can have side effects, and may even call functions in
4616 your program. This can be useful, for example, to activate functions
4617 that log program progress, or to use your own print functions to
4618 format special data structures. The effects are completely predictable
4619 unless there is another enabled breakpoint at the same address. (In
4620 that case, @value{GDBN} might see the other breakpoint first and stop your
4621 program without checking the condition of this one.) Note that
4622 breakpoint commands are usually more convenient and flexible than break
4624 purpose of performing side effects when a breakpoint is reached
4625 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4627 Breakpoint conditions can also be evaluated on the target's side if
4628 the target supports it. Instead of evaluating the conditions locally,
4629 @value{GDBN} encodes the expression into an agent expression
4630 (@pxref{Agent Expressions}) suitable for execution on the target,
4631 independently of @value{GDBN}. Global variables become raw memory
4632 locations, locals become stack accesses, and so forth.
4634 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4635 when its condition evaluates to true. This mechanism may provide faster
4636 response times depending on the performance characteristics of the target
4637 since it does not need to keep @value{GDBN} informed about
4638 every breakpoint trigger, even those with false conditions.
4640 Break conditions can be specified when a breakpoint is set, by using
4641 @samp{if} in the arguments to the @code{break} command. @xref{Set
4642 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4643 with the @code{condition} command.
4645 You can also use the @code{if} keyword with the @code{watch} command.
4646 The @code{catch} command does not recognize the @code{if} keyword;
4647 @code{condition} is the only way to impose a further condition on a
4652 @item condition @var{bnum} @var{expression}
4653 Specify @var{expression} as the break condition for breakpoint,
4654 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4655 breakpoint @var{bnum} stops your program only if the value of
4656 @var{expression} is true (nonzero, in C). When you use
4657 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4658 syntactic correctness, and to determine whether symbols in it have
4659 referents in the context of your breakpoint. If @var{expression} uses
4660 symbols not referenced in the context of the breakpoint, @value{GDBN}
4661 prints an error message:
4664 No symbol "foo" in current context.
4669 not actually evaluate @var{expression} at the time the @code{condition}
4670 command (or a command that sets a breakpoint with a condition, like
4671 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4673 @item condition @var{bnum}
4674 Remove the condition from breakpoint number @var{bnum}. It becomes
4675 an ordinary unconditional breakpoint.
4678 @cindex ignore count (of breakpoint)
4679 A special case of a breakpoint condition is to stop only when the
4680 breakpoint has been reached a certain number of times. This is so
4681 useful that there is a special way to do it, using the @dfn{ignore
4682 count} of the breakpoint. Every breakpoint has an ignore count, which
4683 is an integer. Most of the time, the ignore count is zero, and
4684 therefore has no effect. But if your program reaches a breakpoint whose
4685 ignore count is positive, then instead of stopping, it just decrements
4686 the ignore count by one and continues. As a result, if the ignore count
4687 value is @var{n}, the breakpoint does not stop the next @var{n} times
4688 your program reaches it.
4692 @item ignore @var{bnum} @var{count}
4693 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4694 The next @var{count} times the breakpoint is reached, your program's
4695 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4698 To make the breakpoint stop the next time it is reached, specify
4701 When you use @code{continue} to resume execution of your program from a
4702 breakpoint, you can specify an ignore count directly as an argument to
4703 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4704 Stepping,,Continuing and Stepping}.
4706 If a breakpoint has a positive ignore count and a condition, the
4707 condition is not checked. Once the ignore count reaches zero,
4708 @value{GDBN} resumes checking the condition.
4710 You could achieve the effect of the ignore count with a condition such
4711 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4712 is decremented each time. @xref{Convenience Vars, ,Convenience
4716 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4719 @node Break Commands
4720 @subsection Breakpoint Command Lists
4722 @cindex breakpoint commands
4723 You can give any breakpoint (or watchpoint or catchpoint) a series of
4724 commands to execute when your program stops due to that breakpoint. For
4725 example, you might want to print the values of certain expressions, or
4726 enable other breakpoints.
4730 @kindex end@r{ (breakpoint commands)}
4731 @item commands @r{[}@var{range}@dots{}@r{]}
4732 @itemx @dots{} @var{command-list} @dots{}
4734 Specify a list of commands for the given breakpoints. The commands
4735 themselves appear on the following lines. Type a line containing just
4736 @code{end} to terminate the commands.
4738 To remove all commands from a breakpoint, type @code{commands} and
4739 follow it immediately with @code{end}; that is, give no commands.
4741 With no argument, @code{commands} refers to the last breakpoint,
4742 watchpoint, or catchpoint set (not to the breakpoint most recently
4743 encountered). If the most recent breakpoints were set with a single
4744 command, then the @code{commands} will apply to all the breakpoints
4745 set by that command. This applies to breakpoints set by
4746 @code{rbreak}, and also applies when a single @code{break} command
4747 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4751 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4752 disabled within a @var{command-list}.
4754 You can use breakpoint commands to start your program up again. Simply
4755 use the @code{continue} command, or @code{step}, or any other command
4756 that resumes execution.
4758 Any other commands in the command list, after a command that resumes
4759 execution, are ignored. This is because any time you resume execution
4760 (even with a simple @code{next} or @code{step}), you may encounter
4761 another breakpoint---which could have its own command list, leading to
4762 ambiguities about which list to execute.
4765 If the first command you specify in a command list is @code{silent}, the
4766 usual message about stopping at a breakpoint is not printed. This may
4767 be desirable for breakpoints that are to print a specific message and
4768 then continue. If none of the remaining commands print anything, you
4769 see no sign that the breakpoint was reached. @code{silent} is
4770 meaningful only at the beginning of a breakpoint command list.
4772 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4773 print precisely controlled output, and are often useful in silent
4774 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4776 For example, here is how you could use breakpoint commands to print the
4777 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4783 printf "x is %d\n",x
4788 One application for breakpoint commands is to compensate for one bug so
4789 you can test for another. Put a breakpoint just after the erroneous line
4790 of code, give it a condition to detect the case in which something
4791 erroneous has been done, and give it commands to assign correct values
4792 to any variables that need them. End with the @code{continue} command
4793 so that your program does not stop, and start with the @code{silent}
4794 command so that no output is produced. Here is an example:
4805 @node Dynamic Printf
4806 @subsection Dynamic Printf
4808 @cindex dynamic printf
4810 The dynamic printf command @code{dprintf} combines a breakpoint with
4811 formatted printing of your program's data to give you the effect of
4812 inserting @code{printf} calls into your program on-the-fly, without
4813 having to recompile it.
4815 In its most basic form, the output goes to the GDB console. However,
4816 you can set the variable @code{dprintf-style} for alternate handling.
4817 For instance, you can ask to format the output by calling your
4818 program's @code{printf} function. This has the advantage that the
4819 characters go to the program's output device, so they can recorded in
4820 redirects to files and so forth.
4822 If you are doing remote debugging with a stub or agent, you can also
4823 ask to have the printf handled by the remote agent. In addition to
4824 ensuring that the output goes to the remote program's device along
4825 with any other output the program might produce, you can also ask that
4826 the dprintf remain active even after disconnecting from the remote
4827 target. Using the stub/agent is also more efficient, as it can do
4828 everything without needing to communicate with @value{GDBN}.
4832 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4833 Whenever execution reaches @var{location}, print the values of one or
4834 more @var{expressions} under the control of the string @var{template}.
4835 To print several values, separate them with commas.
4837 @item set dprintf-style @var{style}
4838 Set the dprintf output to be handled in one of several different
4839 styles enumerated below. A change of style affects all existing
4840 dynamic printfs immediately. (If you need individual control over the
4841 print commands, simply define normal breakpoints with
4842 explicitly-supplied command lists.)
4845 @kindex dprintf-style gdb
4846 Handle the output using the @value{GDBN} @code{printf} command.
4849 @kindex dprintf-style call
4850 Handle the output by calling a function in your program (normally
4854 @kindex dprintf-style agent
4855 Have the remote debugging agent (such as @code{gdbserver}) handle
4856 the output itself. This style is only available for agents that
4857 support running commands on the target.
4859 @item set dprintf-function @var{function}
4860 Set the function to call if the dprintf style is @code{call}. By
4861 default its value is @code{printf}. You may set it to any expression.
4862 that @value{GDBN} can evaluate to a function, as per the @code{call}
4865 @item set dprintf-channel @var{channel}
4866 Set a ``channel'' for dprintf. If set to a non-empty value,
4867 @value{GDBN} will evaluate it as an expression and pass the result as
4868 a first argument to the @code{dprintf-function}, in the manner of
4869 @code{fprintf} and similar functions. Otherwise, the dprintf format
4870 string will be the first argument, in the manner of @code{printf}.
4872 As an example, if you wanted @code{dprintf} output to go to a logfile
4873 that is a standard I/O stream assigned to the variable @code{mylog},
4874 you could do the following:
4877 (gdb) set dprintf-style call
4878 (gdb) set dprintf-function fprintf
4879 (gdb) set dprintf-channel mylog
4880 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4881 Dprintf 1 at 0x123456: file main.c, line 25.
4883 1 dprintf keep y 0x00123456 in main at main.c:25
4884 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4889 Note that the @code{info break} displays the dynamic printf commands
4890 as normal breakpoint commands; you can thus easily see the effect of
4891 the variable settings.
4893 @item set disconnected-dprintf on
4894 @itemx set disconnected-dprintf off
4895 @kindex set disconnected-dprintf
4896 Choose whether @code{dprintf} commands should continue to run if
4897 @value{GDBN} has disconnected from the target. This only applies
4898 if the @code{dprintf-style} is @code{agent}.
4900 @item show disconnected-dprintf off
4901 @kindex show disconnected-dprintf
4902 Show the current choice for disconnected @code{dprintf}.
4906 @value{GDBN} does not check the validity of function and channel,
4907 relying on you to supply values that are meaningful for the contexts
4908 in which they are being used. For instance, the function and channel
4909 may be the values of local variables, but if that is the case, then
4910 all enabled dynamic prints must be at locations within the scope of
4911 those locals. If evaluation fails, @value{GDBN} will report an error.
4913 @node Save Breakpoints
4914 @subsection How to save breakpoints to a file
4916 To save breakpoint definitions to a file use the @w{@code{save
4917 breakpoints}} command.
4920 @kindex save breakpoints
4921 @cindex save breakpoints to a file for future sessions
4922 @item save breakpoints [@var{filename}]
4923 This command saves all current breakpoint definitions together with
4924 their commands and ignore counts, into a file @file{@var{filename}}
4925 suitable for use in a later debugging session. This includes all
4926 types of breakpoints (breakpoints, watchpoints, catchpoints,
4927 tracepoints). To read the saved breakpoint definitions, use the
4928 @code{source} command (@pxref{Command Files}). Note that watchpoints
4929 with expressions involving local variables may fail to be recreated
4930 because it may not be possible to access the context where the
4931 watchpoint is valid anymore. Because the saved breakpoint definitions
4932 are simply a sequence of @value{GDBN} commands that recreate the
4933 breakpoints, you can edit the file in your favorite editing program,
4934 and remove the breakpoint definitions you're not interested in, or
4935 that can no longer be recreated.
4938 @node Static Probe Points
4939 @subsection Static Probe Points
4941 @cindex static probe point, SystemTap
4942 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4943 for Statically Defined Tracing, and the probes are designed to have a tiny
4944 runtime code and data footprint, and no dynamic relocations. They are
4945 usable from assembly, C and C@t{++} languages. See
4946 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4947 for a good reference on how the @acronym{SDT} probes are implemented.
4949 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4950 @acronym{SDT} probes are supported on ELF-compatible systems. See
4951 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4952 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4953 in your applications.
4955 @cindex semaphores on static probe points
4956 Some probes have an associated semaphore variable; for instance, this
4957 happens automatically if you defined your probe using a DTrace-style
4958 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4959 automatically enable it when you specify a breakpoint using the
4960 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4961 location by some other method (e.g., @code{break file:line}), then
4962 @value{GDBN} will not automatically set the semaphore.
4964 You can examine the available static static probes using @code{info
4965 probes}, with optional arguments:
4969 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4970 If given, @var{provider} is a regular expression used to match against provider
4971 names when selecting which probes to list. If omitted, probes by all
4972 probes from all providers are listed.
4974 If given, @var{name} is a regular expression to match against probe names
4975 when selecting which probes to list. If omitted, probe names are not
4976 considered when deciding whether to display them.
4978 If given, @var{objfile} is a regular expression used to select which
4979 object files (executable or shared libraries) to examine. If not
4980 given, all object files are considered.
4982 @item info probes all
4983 List the available static probes, from all types.
4986 @vindex $_probe_arg@r{, convenience variable}
4987 A probe may specify up to twelve arguments. These are available at the
4988 point at which the probe is defined---that is, when the current PC is
4989 at the probe's location. The arguments are available using the
4990 convenience variables (@pxref{Convenience Vars})
4991 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4992 an integer of the appropriate size; types are not preserved. The
4993 convenience variable @code{$_probe_argc} holds the number of arguments
4994 at the current probe point.
4996 These variables are always available, but attempts to access them at
4997 any location other than a probe point will cause @value{GDBN} to give
5001 @c @ifclear BARETARGET
5002 @node Error in Breakpoints
5003 @subsection ``Cannot insert breakpoints''
5005 If you request too many active hardware-assisted breakpoints and
5006 watchpoints, you will see this error message:
5008 @c FIXME: the precise wording of this message may change; the relevant
5009 @c source change is not committed yet (Sep 3, 1999).
5011 Stopped; cannot insert breakpoints.
5012 You may have requested too many hardware breakpoints and watchpoints.
5016 This message is printed when you attempt to resume the program, since
5017 only then @value{GDBN} knows exactly how many hardware breakpoints and
5018 watchpoints it needs to insert.
5020 When this message is printed, you need to disable or remove some of the
5021 hardware-assisted breakpoints and watchpoints, and then continue.
5023 @node Breakpoint-related Warnings
5024 @subsection ``Breakpoint address adjusted...''
5025 @cindex breakpoint address adjusted
5027 Some processor architectures place constraints on the addresses at
5028 which breakpoints may be placed. For architectures thus constrained,
5029 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5030 with the constraints dictated by the architecture.
5032 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5033 a VLIW architecture in which a number of RISC-like instructions may be
5034 bundled together for parallel execution. The FR-V architecture
5035 constrains the location of a breakpoint instruction within such a
5036 bundle to the instruction with the lowest address. @value{GDBN}
5037 honors this constraint by adjusting a breakpoint's address to the
5038 first in the bundle.
5040 It is not uncommon for optimized code to have bundles which contain
5041 instructions from different source statements, thus it may happen that
5042 a breakpoint's address will be adjusted from one source statement to
5043 another. Since this adjustment may significantly alter @value{GDBN}'s
5044 breakpoint related behavior from what the user expects, a warning is
5045 printed when the breakpoint is first set and also when the breakpoint
5048 A warning like the one below is printed when setting a breakpoint
5049 that's been subject to address adjustment:
5052 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5055 Such warnings are printed both for user settable and @value{GDBN}'s
5056 internal breakpoints. If you see one of these warnings, you should
5057 verify that a breakpoint set at the adjusted address will have the
5058 desired affect. If not, the breakpoint in question may be removed and
5059 other breakpoints may be set which will have the desired behavior.
5060 E.g., it may be sufficient to place the breakpoint at a later
5061 instruction. A conditional breakpoint may also be useful in some
5062 cases to prevent the breakpoint from triggering too often.
5064 @value{GDBN} will also issue a warning when stopping at one of these
5065 adjusted breakpoints:
5068 warning: Breakpoint 1 address previously adjusted from 0x00010414
5072 When this warning is encountered, it may be too late to take remedial
5073 action except in cases where the breakpoint is hit earlier or more
5074 frequently than expected.
5076 @node Continuing and Stepping
5077 @section Continuing and Stepping
5081 @cindex resuming execution
5082 @dfn{Continuing} means resuming program execution until your program
5083 completes normally. In contrast, @dfn{stepping} means executing just
5084 one more ``step'' of your program, where ``step'' may mean either one
5085 line of source code, or one machine instruction (depending on what
5086 particular command you use). Either when continuing or when stepping,
5087 your program may stop even sooner, due to a breakpoint or a signal. (If
5088 it stops due to a signal, you may want to use @code{handle}, or use
5089 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
5093 @kindex c @r{(@code{continue})}
5094 @kindex fg @r{(resume foreground execution)}
5095 @item continue @r{[}@var{ignore-count}@r{]}
5096 @itemx c @r{[}@var{ignore-count}@r{]}
5097 @itemx fg @r{[}@var{ignore-count}@r{]}
5098 Resume program execution, at the address where your program last stopped;
5099 any breakpoints set at that address are bypassed. The optional argument
5100 @var{ignore-count} allows you to specify a further number of times to
5101 ignore a breakpoint at this location; its effect is like that of
5102 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5104 The argument @var{ignore-count} is meaningful only when your program
5105 stopped due to a breakpoint. At other times, the argument to
5106 @code{continue} is ignored.
5108 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5109 debugged program is deemed to be the foreground program) are provided
5110 purely for convenience, and have exactly the same behavior as
5114 To resume execution at a different place, you can use @code{return}
5115 (@pxref{Returning, ,Returning from a Function}) to go back to the
5116 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5117 Different Address}) to go to an arbitrary location in your program.
5119 A typical technique for using stepping is to set a breakpoint
5120 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5121 beginning of the function or the section of your program where a problem
5122 is believed to lie, run your program until it stops at that breakpoint,
5123 and then step through the suspect area, examining the variables that are
5124 interesting, until you see the problem happen.
5128 @kindex s @r{(@code{step})}
5130 Continue running your program until control reaches a different source
5131 line, then stop it and return control to @value{GDBN}. This command is
5132 abbreviated @code{s}.
5135 @c "without debugging information" is imprecise; actually "without line
5136 @c numbers in the debugging information". (gcc -g1 has debugging info but
5137 @c not line numbers). But it seems complex to try to make that
5138 @c distinction here.
5139 @emph{Warning:} If you use the @code{step} command while control is
5140 within a function that was compiled without debugging information,
5141 execution proceeds until control reaches a function that does have
5142 debugging information. Likewise, it will not step into a function which
5143 is compiled without debugging information. To step through functions
5144 without debugging information, use the @code{stepi} command, described
5148 The @code{step} command only stops at the first instruction of a source
5149 line. This prevents the multiple stops that could otherwise occur in
5150 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5151 to stop if a function that has debugging information is called within
5152 the line. In other words, @code{step} @emph{steps inside} any functions
5153 called within the line.
5155 Also, the @code{step} command only enters a function if there is line
5156 number information for the function. Otherwise it acts like the
5157 @code{next} command. This avoids problems when using @code{cc -gl}
5158 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5159 was any debugging information about the routine.
5161 @item step @var{count}
5162 Continue running as in @code{step}, but do so @var{count} times. If a
5163 breakpoint is reached, or a signal not related to stepping occurs before
5164 @var{count} steps, stepping stops right away.
5167 @kindex n @r{(@code{next})}
5168 @item next @r{[}@var{count}@r{]}
5169 Continue to the next source line in the current (innermost) stack frame.
5170 This is similar to @code{step}, but function calls that appear within
5171 the line of code are executed without stopping. Execution stops when
5172 control reaches a different line of code at the original stack level
5173 that was executing when you gave the @code{next} command. This command
5174 is abbreviated @code{n}.
5176 An argument @var{count} is a repeat count, as for @code{step}.
5179 @c FIX ME!! Do we delete this, or is there a way it fits in with
5180 @c the following paragraph? --- Vctoria
5182 @c @code{next} within a function that lacks debugging information acts like
5183 @c @code{step}, but any function calls appearing within the code of the
5184 @c function are executed without stopping.
5186 The @code{next} command only stops at the first instruction of a
5187 source line. This prevents multiple stops that could otherwise occur in
5188 @code{switch} statements, @code{for} loops, etc.
5190 @kindex set step-mode
5192 @cindex functions without line info, and stepping
5193 @cindex stepping into functions with no line info
5194 @itemx set step-mode on
5195 The @code{set step-mode on} command causes the @code{step} command to
5196 stop at the first instruction of a function which contains no debug line
5197 information rather than stepping over it.
5199 This is useful in cases where you may be interested in inspecting the
5200 machine instructions of a function which has no symbolic info and do not
5201 want @value{GDBN} to automatically skip over this function.
5203 @item set step-mode off
5204 Causes the @code{step} command to step over any functions which contains no
5205 debug information. This is the default.
5207 @item show step-mode
5208 Show whether @value{GDBN} will stop in or step over functions without
5209 source line debug information.
5212 @kindex fin @r{(@code{finish})}
5214 Continue running until just after function in the selected stack frame
5215 returns. Print the returned value (if any). This command can be
5216 abbreviated as @code{fin}.
5218 Contrast this with the @code{return} command (@pxref{Returning,
5219 ,Returning from a Function}).
5222 @kindex u @r{(@code{until})}
5223 @cindex run until specified location
5226 Continue running until a source line past the current line, in the
5227 current stack frame, is reached. This command is used to avoid single
5228 stepping through a loop more than once. It is like the @code{next}
5229 command, except that when @code{until} encounters a jump, it
5230 automatically continues execution until the program counter is greater
5231 than the address of the jump.
5233 This means that when you reach the end of a loop after single stepping
5234 though it, @code{until} makes your program continue execution until it
5235 exits the loop. In contrast, a @code{next} command at the end of a loop
5236 simply steps back to the beginning of the loop, which forces you to step
5237 through the next iteration.
5239 @code{until} always stops your program if it attempts to exit the current
5242 @code{until} may produce somewhat counterintuitive results if the order
5243 of machine code does not match the order of the source lines. For
5244 example, in the following excerpt from a debugging session, the @code{f}
5245 (@code{frame}) command shows that execution is stopped at line
5246 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5250 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5252 (@value{GDBP}) until
5253 195 for ( ; argc > 0; NEXTARG) @{
5256 This happened because, for execution efficiency, the compiler had
5257 generated code for the loop closure test at the end, rather than the
5258 start, of the loop---even though the test in a C @code{for}-loop is
5259 written before the body of the loop. The @code{until} command appeared
5260 to step back to the beginning of the loop when it advanced to this
5261 expression; however, it has not really gone to an earlier
5262 statement---not in terms of the actual machine code.
5264 @code{until} with no argument works by means of single
5265 instruction stepping, and hence is slower than @code{until} with an
5268 @item until @var{location}
5269 @itemx u @var{location}
5270 Continue running your program until either the specified location is
5271 reached, or the current stack frame returns. @var{location} is any of
5272 the forms described in @ref{Specify Location}.
5273 This form of the command uses temporary breakpoints, and
5274 hence is quicker than @code{until} without an argument. The specified
5275 location is actually reached only if it is in the current frame. This
5276 implies that @code{until} can be used to skip over recursive function
5277 invocations. For instance in the code below, if the current location is
5278 line @code{96}, issuing @code{until 99} will execute the program up to
5279 line @code{99} in the same invocation of factorial, i.e., after the inner
5280 invocations have returned.
5283 94 int factorial (int value)
5285 96 if (value > 1) @{
5286 97 value *= factorial (value - 1);
5293 @kindex advance @var{location}
5294 @item advance @var{location}
5295 Continue running the program up to the given @var{location}. An argument is
5296 required, which should be of one of the forms described in
5297 @ref{Specify Location}.
5298 Execution will also stop upon exit from the current stack
5299 frame. This command is similar to @code{until}, but @code{advance} will
5300 not skip over recursive function calls, and the target location doesn't
5301 have to be in the same frame as the current one.
5305 @kindex si @r{(@code{stepi})}
5307 @itemx stepi @var{arg}
5309 Execute one machine instruction, then stop and return to the debugger.
5311 It is often useful to do @samp{display/i $pc} when stepping by machine
5312 instructions. This makes @value{GDBN} automatically display the next
5313 instruction to be executed, each time your program stops. @xref{Auto
5314 Display,, Automatic Display}.
5316 An argument is a repeat count, as in @code{step}.
5320 @kindex ni @r{(@code{nexti})}
5322 @itemx nexti @var{arg}
5324 Execute one machine instruction, but if it is a function call,
5325 proceed until the function returns.
5327 An argument is a repeat count, as in @code{next}.
5331 @anchor{range stepping}
5332 @cindex range stepping
5333 @cindex target-assisted range stepping
5334 By default, and if available, @value{GDBN} makes use of
5335 target-assisted @dfn{range stepping}. In other words, whenever you
5336 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5337 tells the target to step the corresponding range of instruction
5338 addresses instead of issuing multiple single-steps. This speeds up
5339 line stepping, particularly for remote targets. Ideally, there should
5340 be no reason you would want to turn range stepping off. However, it's
5341 possible that a bug in the debug info, a bug in the remote stub (for
5342 remote targets), or even a bug in @value{GDBN} could make line
5343 stepping behave incorrectly when target-assisted range stepping is
5344 enabled. You can use the following command to turn off range stepping
5348 @kindex set range-stepping
5349 @kindex show range-stepping
5350 @item set range-stepping
5351 @itemx show range-stepping
5352 Control whether range stepping is enabled.
5354 If @code{on}, and the target supports it, @value{GDBN} tells the
5355 target to step a range of addresses itself, instead of issuing
5356 multiple single-steps. If @code{off}, @value{GDBN} always issues
5357 single-steps, even if range stepping is supported by the target. The
5358 default is @code{on}.
5362 @node Skipping Over Functions and Files
5363 @section Skipping Over Functions and Files
5364 @cindex skipping over functions and files
5366 The program you are debugging may contain some functions which are
5367 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5368 skip a function or all functions in a file when stepping.
5370 For example, consider the following C function:
5381 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5382 are not interested in stepping through @code{boring}. If you run @code{step}
5383 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5384 step over both @code{foo} and @code{boring}!
5386 One solution is to @code{step} into @code{boring} and use the @code{finish}
5387 command to immediately exit it. But this can become tedious if @code{boring}
5388 is called from many places.
5390 A more flexible solution is to execute @kbd{skip boring}. This instructs
5391 @value{GDBN} never to step into @code{boring}. Now when you execute
5392 @code{step} at line 103, you'll step over @code{boring} and directly into
5395 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5396 example, @code{skip file boring.c}.
5399 @kindex skip function
5400 @item skip @r{[}@var{linespec}@r{]}
5401 @itemx skip function @r{[}@var{linespec}@r{]}
5402 After running this command, the function named by @var{linespec} or the
5403 function containing the line named by @var{linespec} will be skipped over when
5404 stepping. @xref{Specify Location}.
5406 If you do not specify @var{linespec}, the function you're currently debugging
5409 (If you have a function called @code{file} that you want to skip, use
5410 @kbd{skip function file}.)
5413 @item skip file @r{[}@var{filename}@r{]}
5414 After running this command, any function whose source lives in @var{filename}
5415 will be skipped over when stepping.
5417 If you do not specify @var{filename}, functions whose source lives in the file
5418 you're currently debugging will be skipped.
5421 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5422 These are the commands for managing your list of skips:
5426 @item info skip @r{[}@var{range}@r{]}
5427 Print details about the specified skip(s). If @var{range} is not specified,
5428 print a table with details about all functions and files marked for skipping.
5429 @code{info skip} prints the following information about each skip:
5433 A number identifying this skip.
5435 The type of this skip, either @samp{function} or @samp{file}.
5436 @item Enabled or Disabled
5437 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5439 For function skips, this column indicates the address in memory of the function
5440 being skipped. If you've set a function skip on a function which has not yet
5441 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5442 which has the function is loaded, @code{info skip} will show the function's
5445 For file skips, this field contains the filename being skipped. For functions
5446 skips, this field contains the function name and its line number in the file
5447 where it is defined.
5451 @item skip delete @r{[}@var{range}@r{]}
5452 Delete the specified skip(s). If @var{range} is not specified, delete all
5456 @item skip enable @r{[}@var{range}@r{]}
5457 Enable the specified skip(s). If @var{range} is not specified, enable all
5460 @kindex skip disable
5461 @item skip disable @r{[}@var{range}@r{]}
5462 Disable the specified skip(s). If @var{range} is not specified, disable all
5471 A signal is an asynchronous event that can happen in a program. The
5472 operating system defines the possible kinds of signals, and gives each
5473 kind a name and a number. For example, in Unix @code{SIGINT} is the
5474 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5475 @code{SIGSEGV} is the signal a program gets from referencing a place in
5476 memory far away from all the areas in use; @code{SIGALRM} occurs when
5477 the alarm clock timer goes off (which happens only if your program has
5478 requested an alarm).
5480 @cindex fatal signals
5481 Some signals, including @code{SIGALRM}, are a normal part of the
5482 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5483 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5484 program has not specified in advance some other way to handle the signal.
5485 @code{SIGINT} does not indicate an error in your program, but it is normally
5486 fatal so it can carry out the purpose of the interrupt: to kill the program.
5488 @value{GDBN} has the ability to detect any occurrence of a signal in your
5489 program. You can tell @value{GDBN} in advance what to do for each kind of
5492 @cindex handling signals
5493 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5494 @code{SIGALRM} be silently passed to your program
5495 (so as not to interfere with their role in the program's functioning)
5496 but to stop your program immediately whenever an error signal happens.
5497 You can change these settings with the @code{handle} command.
5500 @kindex info signals
5504 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5505 handle each one. You can use this to see the signal numbers of all
5506 the defined types of signals.
5508 @item info signals @var{sig}
5509 Similar, but print information only about the specified signal number.
5511 @code{info handle} is an alias for @code{info signals}.
5513 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5514 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5515 for details about this command.
5518 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5519 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5520 can be the number of a signal or its name (with or without the
5521 @samp{SIG} at the beginning); a list of signal numbers of the form
5522 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5523 known signals. Optional arguments @var{keywords}, described below,
5524 say what change to make.
5528 The keywords allowed by the @code{handle} command can be abbreviated.
5529 Their full names are:
5533 @value{GDBN} should not stop your program when this signal happens. It may
5534 still print a message telling you that the signal has come in.
5537 @value{GDBN} should stop your program when this signal happens. This implies
5538 the @code{print} keyword as well.
5541 @value{GDBN} should print a message when this signal happens.
5544 @value{GDBN} should not mention the occurrence of the signal at all. This
5545 implies the @code{nostop} keyword as well.
5549 @value{GDBN} should allow your program to see this signal; your program
5550 can handle the signal, or else it may terminate if the signal is fatal
5551 and not handled. @code{pass} and @code{noignore} are synonyms.
5555 @value{GDBN} should not allow your program to see this signal.
5556 @code{nopass} and @code{ignore} are synonyms.
5560 When a signal stops your program, the signal is not visible to the
5562 continue. Your program sees the signal then, if @code{pass} is in
5563 effect for the signal in question @emph{at that time}. In other words,
5564 after @value{GDBN} reports a signal, you can use the @code{handle}
5565 command with @code{pass} or @code{nopass} to control whether your
5566 program sees that signal when you continue.
5568 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5569 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5570 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5573 You can also use the @code{signal} command to prevent your program from
5574 seeing a signal, or cause it to see a signal it normally would not see,
5575 or to give it any signal at any time. For example, if your program stopped
5576 due to some sort of memory reference error, you might store correct
5577 values into the erroneous variables and continue, hoping to see more
5578 execution; but your program would probably terminate immediately as
5579 a result of the fatal signal once it saw the signal. To prevent this,
5580 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5583 @cindex extra signal information
5584 @anchor{extra signal information}
5586 On some targets, @value{GDBN} can inspect extra signal information
5587 associated with the intercepted signal, before it is actually
5588 delivered to the program being debugged. This information is exported
5589 by the convenience variable @code{$_siginfo}, and consists of data
5590 that is passed by the kernel to the signal handler at the time of the
5591 receipt of a signal. The data type of the information itself is
5592 target dependent. You can see the data type using the @code{ptype
5593 $_siginfo} command. On Unix systems, it typically corresponds to the
5594 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5597 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5598 referenced address that raised a segmentation fault.
5602 (@value{GDBP}) continue
5603 Program received signal SIGSEGV, Segmentation fault.
5604 0x0000000000400766 in main ()
5606 (@value{GDBP}) ptype $_siginfo
5613 struct @{...@} _kill;
5614 struct @{...@} _timer;
5616 struct @{...@} _sigchld;
5617 struct @{...@} _sigfault;
5618 struct @{...@} _sigpoll;
5621 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5625 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5626 $1 = (void *) 0x7ffff7ff7000
5630 Depending on target support, @code{$_siginfo} may also be writable.
5633 @section Stopping and Starting Multi-thread Programs
5635 @cindex stopped threads
5636 @cindex threads, stopped
5638 @cindex continuing threads
5639 @cindex threads, continuing
5641 @value{GDBN} supports debugging programs with multiple threads
5642 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5643 are two modes of controlling execution of your program within the
5644 debugger. In the default mode, referred to as @dfn{all-stop mode},
5645 when any thread in your program stops (for example, at a breakpoint
5646 or while being stepped), all other threads in the program are also stopped by
5647 @value{GDBN}. On some targets, @value{GDBN} also supports
5648 @dfn{non-stop mode}, in which other threads can continue to run freely while
5649 you examine the stopped thread in the debugger.
5652 * All-Stop Mode:: All threads stop when GDB takes control
5653 * Non-Stop Mode:: Other threads continue to execute
5654 * Background Execution:: Running your program asynchronously
5655 * Thread-Specific Breakpoints:: Controlling breakpoints
5656 * Interrupted System Calls:: GDB may interfere with system calls
5657 * Observer Mode:: GDB does not alter program behavior
5661 @subsection All-Stop Mode
5663 @cindex all-stop mode
5665 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5666 @emph{all} threads of execution stop, not just the current thread. This
5667 allows you to examine the overall state of the program, including
5668 switching between threads, without worrying that things may change
5671 Conversely, whenever you restart the program, @emph{all} threads start
5672 executing. @emph{This is true even when single-stepping} with commands
5673 like @code{step} or @code{next}.
5675 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5676 Since thread scheduling is up to your debugging target's operating
5677 system (not controlled by @value{GDBN}), other threads may
5678 execute more than one statement while the current thread completes a
5679 single step. Moreover, in general other threads stop in the middle of a
5680 statement, rather than at a clean statement boundary, when the program
5683 You might even find your program stopped in another thread after
5684 continuing or even single-stepping. This happens whenever some other
5685 thread runs into a breakpoint, a signal, or an exception before the
5686 first thread completes whatever you requested.
5688 @cindex automatic thread selection
5689 @cindex switching threads automatically
5690 @cindex threads, automatic switching
5691 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5692 signal, it automatically selects the thread where that breakpoint or
5693 signal happened. @value{GDBN} alerts you to the context switch with a
5694 message such as @samp{[Switching to Thread @var{n}]} to identify the
5697 On some OSes, you can modify @value{GDBN}'s default behavior by
5698 locking the OS scheduler to allow only a single thread to run.
5701 @item set scheduler-locking @var{mode}
5702 @cindex scheduler locking mode
5703 @cindex lock scheduler
5704 Set the scheduler locking mode. If it is @code{off}, then there is no
5705 locking and any thread may run at any time. If @code{on}, then only the
5706 current thread may run when the inferior is resumed. The @code{step}
5707 mode optimizes for single-stepping; it prevents other threads
5708 from preempting the current thread while you are stepping, so that
5709 the focus of debugging does not change unexpectedly.
5710 Other threads only rarely (or never) get a chance to run
5711 when you step. They are more likely to run when you @samp{next} over a
5712 function call, and they are completely free to run when you use commands
5713 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5714 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5715 the current thread away from the thread that you are debugging.
5717 @item show scheduler-locking
5718 Display the current scheduler locking mode.
5721 @cindex resume threads of multiple processes simultaneously
5722 By default, when you issue one of the execution commands such as
5723 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5724 threads of the current inferior to run. For example, if @value{GDBN}
5725 is attached to two inferiors, each with two threads, the
5726 @code{continue} command resumes only the two threads of the current
5727 inferior. This is useful, for example, when you debug a program that
5728 forks and you want to hold the parent stopped (so that, for instance,
5729 it doesn't run to exit), while you debug the child. In other
5730 situations, you may not be interested in inspecting the current state
5731 of any of the processes @value{GDBN} is attached to, and you may want
5732 to resume them all until some breakpoint is hit. In the latter case,
5733 you can instruct @value{GDBN} to allow all threads of all the
5734 inferiors to run with the @w{@code{set schedule-multiple}} command.
5737 @kindex set schedule-multiple
5738 @item set schedule-multiple
5739 Set the mode for allowing threads of multiple processes to be resumed
5740 when an execution command is issued. When @code{on}, all threads of
5741 all processes are allowed to run. When @code{off}, only the threads
5742 of the current process are resumed. The default is @code{off}. The
5743 @code{scheduler-locking} mode takes precedence when set to @code{on},
5744 or while you are stepping and set to @code{step}.
5746 @item show schedule-multiple
5747 Display the current mode for resuming the execution of threads of
5752 @subsection Non-Stop Mode
5754 @cindex non-stop mode
5756 @c This section is really only a place-holder, and needs to be expanded
5757 @c with more details.
5759 For some multi-threaded targets, @value{GDBN} supports an optional
5760 mode of operation in which you can examine stopped program threads in
5761 the debugger while other threads continue to execute freely. This
5762 minimizes intrusion when debugging live systems, such as programs
5763 where some threads have real-time constraints or must continue to
5764 respond to external events. This is referred to as @dfn{non-stop} mode.
5766 In non-stop mode, when a thread stops to report a debugging event,
5767 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5768 threads as well, in contrast to the all-stop mode behavior. Additionally,
5769 execution commands such as @code{continue} and @code{step} apply by default
5770 only to the current thread in non-stop mode, rather than all threads as
5771 in all-stop mode. This allows you to control threads explicitly in
5772 ways that are not possible in all-stop mode --- for example, stepping
5773 one thread while allowing others to run freely, stepping
5774 one thread while holding all others stopped, or stepping several threads
5775 independently and simultaneously.
5777 To enter non-stop mode, use this sequence of commands before you run
5778 or attach to your program:
5781 # Enable the async interface.
5784 # If using the CLI, pagination breaks non-stop.
5787 # Finally, turn it on!
5791 You can use these commands to manipulate the non-stop mode setting:
5794 @kindex set non-stop
5795 @item set non-stop on
5796 Enable selection of non-stop mode.
5797 @item set non-stop off
5798 Disable selection of non-stop mode.
5799 @kindex show non-stop
5801 Show the current non-stop enablement setting.
5804 Note these commands only reflect whether non-stop mode is enabled,
5805 not whether the currently-executing program is being run in non-stop mode.
5806 In particular, the @code{set non-stop} preference is only consulted when
5807 @value{GDBN} starts or connects to the target program, and it is generally
5808 not possible to switch modes once debugging has started. Furthermore,
5809 since not all targets support non-stop mode, even when you have enabled
5810 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5813 In non-stop mode, all execution commands apply only to the current thread
5814 by default. That is, @code{continue} only continues one thread.
5815 To continue all threads, issue @code{continue -a} or @code{c -a}.
5817 You can use @value{GDBN}'s background execution commands
5818 (@pxref{Background Execution}) to run some threads in the background
5819 while you continue to examine or step others from @value{GDBN}.
5820 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5821 always executed asynchronously in non-stop mode.
5823 Suspending execution is done with the @code{interrupt} command when
5824 running in the background, or @kbd{Ctrl-c} during foreground execution.
5825 In all-stop mode, this stops the whole process;
5826 but in non-stop mode the interrupt applies only to the current thread.
5827 To stop the whole program, use @code{interrupt -a}.
5829 Other execution commands do not currently support the @code{-a} option.
5831 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5832 that thread current, as it does in all-stop mode. This is because the
5833 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5834 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5835 changed to a different thread just as you entered a command to operate on the
5836 previously current thread.
5838 @node Background Execution
5839 @subsection Background Execution
5841 @cindex foreground execution
5842 @cindex background execution
5843 @cindex asynchronous execution
5844 @cindex execution, foreground, background and asynchronous
5846 @value{GDBN}'s execution commands have two variants: the normal
5847 foreground (synchronous) behavior, and a background
5848 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5849 the program to report that some thread has stopped before prompting for
5850 another command. In background execution, @value{GDBN} immediately gives
5851 a command prompt so that you can issue other commands while your program runs.
5853 You need to explicitly enable asynchronous mode before you can use
5854 background execution commands. You can use these commands to
5855 manipulate the asynchronous mode setting:
5858 @kindex set target-async
5859 @item set target-async on
5860 Enable asynchronous mode.
5861 @item set target-async off
5862 Disable asynchronous mode.
5863 @kindex show target-async
5864 @item show target-async
5865 Show the current target-async setting.
5868 If the target doesn't support async mode, @value{GDBN} issues an error
5869 message if you attempt to use the background execution commands.
5871 To specify background execution, add a @code{&} to the command. For example,
5872 the background form of the @code{continue} command is @code{continue&}, or
5873 just @code{c&}. The execution commands that accept background execution
5879 @xref{Starting, , Starting your Program}.
5883 @xref{Attach, , Debugging an Already-running Process}.
5887 @xref{Continuing and Stepping, step}.
5891 @xref{Continuing and Stepping, stepi}.
5895 @xref{Continuing and Stepping, next}.
5899 @xref{Continuing and Stepping, nexti}.
5903 @xref{Continuing and Stepping, continue}.
5907 @xref{Continuing and Stepping, finish}.
5911 @xref{Continuing and Stepping, until}.
5915 Background execution is especially useful in conjunction with non-stop
5916 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5917 However, you can also use these commands in the normal all-stop mode with
5918 the restriction that you cannot issue another execution command until the
5919 previous one finishes. Examples of commands that are valid in all-stop
5920 mode while the program is running include @code{help} and @code{info break}.
5922 You can interrupt your program while it is running in the background by
5923 using the @code{interrupt} command.
5930 Suspend execution of the running program. In all-stop mode,
5931 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5932 only the current thread. To stop the whole program in non-stop mode,
5933 use @code{interrupt -a}.
5936 @node Thread-Specific Breakpoints
5937 @subsection Thread-Specific Breakpoints
5939 When your program has multiple threads (@pxref{Threads,, Debugging
5940 Programs with Multiple Threads}), you can choose whether to set
5941 breakpoints on all threads, or on a particular thread.
5944 @cindex breakpoints and threads
5945 @cindex thread breakpoints
5946 @kindex break @dots{} thread @var{threadno}
5947 @item break @var{linespec} thread @var{threadno}
5948 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5949 @var{linespec} specifies source lines; there are several ways of
5950 writing them (@pxref{Specify Location}), but the effect is always to
5951 specify some source line.
5953 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5954 to specify that you only want @value{GDBN} to stop the program when a
5955 particular thread reaches this breakpoint. @var{threadno} is one of the
5956 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5957 column of the @samp{info threads} display.
5959 If you do not specify @samp{thread @var{threadno}} when you set a
5960 breakpoint, the breakpoint applies to @emph{all} threads of your
5963 You can use the @code{thread} qualifier on conditional breakpoints as
5964 well; in this case, place @samp{thread @var{threadno}} before or
5965 after the breakpoint condition, like this:
5968 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5973 Thread-specific breakpoints are automatically deleted when
5974 @value{GDBN} detects the corresponding thread is no longer in the
5975 thread list. For example:
5979 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
5982 There are several ways for a thread to disappear, such as a regular
5983 thread exit, but also when you detach from the process with the
5984 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
5985 Process}), or if @value{GDBN} loses the remote connection
5986 (@pxref{Remote Debugging}), etc. Note that with some targets,
5987 @value{GDBN} is only able to detect a thread has exited when the user
5988 explictly asks for the thread list with the @code{info threads}
5991 @node Interrupted System Calls
5992 @subsection Interrupted System Calls
5994 @cindex thread breakpoints and system calls
5995 @cindex system calls and thread breakpoints
5996 @cindex premature return from system calls
5997 There is an unfortunate side effect when using @value{GDBN} to debug
5998 multi-threaded programs. If one thread stops for a
5999 breakpoint, or for some other reason, and another thread is blocked in a
6000 system call, then the system call may return prematurely. This is a
6001 consequence of the interaction between multiple threads and the signals
6002 that @value{GDBN} uses to implement breakpoints and other events that
6005 To handle this problem, your program should check the return value of
6006 each system call and react appropriately. This is good programming
6009 For example, do not write code like this:
6015 The call to @code{sleep} will return early if a different thread stops
6016 at a breakpoint or for some other reason.
6018 Instead, write this:
6023 unslept = sleep (unslept);
6026 A system call is allowed to return early, so the system is still
6027 conforming to its specification. But @value{GDBN} does cause your
6028 multi-threaded program to behave differently than it would without
6031 Also, @value{GDBN} uses internal breakpoints in the thread library to
6032 monitor certain events such as thread creation and thread destruction.
6033 When such an event happens, a system call in another thread may return
6034 prematurely, even though your program does not appear to stop.
6037 @subsection Observer Mode
6039 If you want to build on non-stop mode and observe program behavior
6040 without any chance of disruption by @value{GDBN}, you can set
6041 variables to disable all of the debugger's attempts to modify state,
6042 whether by writing memory, inserting breakpoints, etc. These operate
6043 at a low level, intercepting operations from all commands.
6045 When all of these are set to @code{off}, then @value{GDBN} is said to
6046 be @dfn{observer mode}. As a convenience, the variable
6047 @code{observer} can be set to disable these, plus enable non-stop
6050 Note that @value{GDBN} will not prevent you from making nonsensical
6051 combinations of these settings. For instance, if you have enabled
6052 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6053 then breakpoints that work by writing trap instructions into the code
6054 stream will still not be able to be placed.
6059 @item set observer on
6060 @itemx set observer off
6061 When set to @code{on}, this disables all the permission variables
6062 below (except for @code{insert-fast-tracepoints}), plus enables
6063 non-stop debugging. Setting this to @code{off} switches back to
6064 normal debugging, though remaining in non-stop mode.
6067 Show whether observer mode is on or off.
6069 @kindex may-write-registers
6070 @item set may-write-registers on
6071 @itemx set may-write-registers off
6072 This controls whether @value{GDBN} will attempt to alter the values of
6073 registers, such as with assignment expressions in @code{print}, or the
6074 @code{jump} command. It defaults to @code{on}.
6076 @item show may-write-registers
6077 Show the current permission to write registers.
6079 @kindex may-write-memory
6080 @item set may-write-memory on
6081 @itemx set may-write-memory off
6082 This controls whether @value{GDBN} will attempt to alter the contents
6083 of memory, such as with assignment expressions in @code{print}. It
6084 defaults to @code{on}.
6086 @item show may-write-memory
6087 Show the current permission to write memory.
6089 @kindex may-insert-breakpoints
6090 @item set may-insert-breakpoints on
6091 @itemx set may-insert-breakpoints off
6092 This controls whether @value{GDBN} will attempt to insert breakpoints.
6093 This affects all breakpoints, including internal breakpoints defined
6094 by @value{GDBN}. It defaults to @code{on}.
6096 @item show may-insert-breakpoints
6097 Show the current permission to insert breakpoints.
6099 @kindex may-insert-tracepoints
6100 @item set may-insert-tracepoints on
6101 @itemx set may-insert-tracepoints off
6102 This controls whether @value{GDBN} will attempt to insert (regular)
6103 tracepoints at the beginning of a tracing experiment. It affects only
6104 non-fast tracepoints, fast tracepoints being under the control of
6105 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6107 @item show may-insert-tracepoints
6108 Show the current permission to insert tracepoints.
6110 @kindex may-insert-fast-tracepoints
6111 @item set may-insert-fast-tracepoints on
6112 @itemx set may-insert-fast-tracepoints off
6113 This controls whether @value{GDBN} will attempt to insert fast
6114 tracepoints at the beginning of a tracing experiment. It affects only
6115 fast tracepoints, regular (non-fast) tracepoints being under the
6116 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6118 @item show may-insert-fast-tracepoints
6119 Show the current permission to insert fast tracepoints.
6121 @kindex may-interrupt
6122 @item set may-interrupt on
6123 @itemx set may-interrupt off
6124 This controls whether @value{GDBN} will attempt to interrupt or stop
6125 program execution. When this variable is @code{off}, the
6126 @code{interrupt} command will have no effect, nor will
6127 @kbd{Ctrl-c}. It defaults to @code{on}.
6129 @item show may-interrupt
6130 Show the current permission to interrupt or stop the program.
6134 @node Reverse Execution
6135 @chapter Running programs backward
6136 @cindex reverse execution
6137 @cindex running programs backward
6139 When you are debugging a program, it is not unusual to realize that
6140 you have gone too far, and some event of interest has already happened.
6141 If the target environment supports it, @value{GDBN} can allow you to
6142 ``rewind'' the program by running it backward.
6144 A target environment that supports reverse execution should be able
6145 to ``undo'' the changes in machine state that have taken place as the
6146 program was executing normally. Variables, registers etc.@: should
6147 revert to their previous values. Obviously this requires a great
6148 deal of sophistication on the part of the target environment; not
6149 all target environments can support reverse execution.
6151 When a program is executed in reverse, the instructions that
6152 have most recently been executed are ``un-executed'', in reverse
6153 order. The program counter runs backward, following the previous
6154 thread of execution in reverse. As each instruction is ``un-executed'',
6155 the values of memory and/or registers that were changed by that
6156 instruction are reverted to their previous states. After executing
6157 a piece of source code in reverse, all side effects of that code
6158 should be ``undone'', and all variables should be returned to their
6159 prior values@footnote{
6160 Note that some side effects are easier to undo than others. For instance,
6161 memory and registers are relatively easy, but device I/O is hard. Some
6162 targets may be able undo things like device I/O, and some may not.
6164 The contract between @value{GDBN} and the reverse executing target
6165 requires only that the target do something reasonable when
6166 @value{GDBN} tells it to execute backwards, and then report the
6167 results back to @value{GDBN}. Whatever the target reports back to
6168 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6169 assumes that the memory and registers that the target reports are in a
6170 consistant state, but @value{GDBN} accepts whatever it is given.
6173 If you are debugging in a target environment that supports
6174 reverse execution, @value{GDBN} provides the following commands.
6177 @kindex reverse-continue
6178 @kindex rc @r{(@code{reverse-continue})}
6179 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6180 @itemx rc @r{[}@var{ignore-count}@r{]}
6181 Beginning at the point where your program last stopped, start executing
6182 in reverse. Reverse execution will stop for breakpoints and synchronous
6183 exceptions (signals), just like normal execution. Behavior of
6184 asynchronous signals depends on the target environment.
6186 @kindex reverse-step
6187 @kindex rs @r{(@code{step})}
6188 @item reverse-step @r{[}@var{count}@r{]}
6189 Run the program backward until control reaches the start of a
6190 different source line; then stop it, and return control to @value{GDBN}.
6192 Like the @code{step} command, @code{reverse-step} will only stop
6193 at the beginning of a source line. It ``un-executes'' the previously
6194 executed source line. If the previous source line included calls to
6195 debuggable functions, @code{reverse-step} will step (backward) into
6196 the called function, stopping at the beginning of the @emph{last}
6197 statement in the called function (typically a return statement).
6199 Also, as with the @code{step} command, if non-debuggable functions are
6200 called, @code{reverse-step} will run thru them backward without stopping.
6202 @kindex reverse-stepi
6203 @kindex rsi @r{(@code{reverse-stepi})}
6204 @item reverse-stepi @r{[}@var{count}@r{]}
6205 Reverse-execute one machine instruction. Note that the instruction
6206 to be reverse-executed is @emph{not} the one pointed to by the program
6207 counter, but the instruction executed prior to that one. For instance,
6208 if the last instruction was a jump, @code{reverse-stepi} will take you
6209 back from the destination of the jump to the jump instruction itself.
6211 @kindex reverse-next
6212 @kindex rn @r{(@code{reverse-next})}
6213 @item reverse-next @r{[}@var{count}@r{]}
6214 Run backward to the beginning of the previous line executed in
6215 the current (innermost) stack frame. If the line contains function
6216 calls, they will be ``un-executed'' without stopping. Starting from
6217 the first line of a function, @code{reverse-next} will take you back
6218 to the caller of that function, @emph{before} the function was called,
6219 just as the normal @code{next} command would take you from the last
6220 line of a function back to its return to its caller
6221 @footnote{Unless the code is too heavily optimized.}.
6223 @kindex reverse-nexti
6224 @kindex rni @r{(@code{reverse-nexti})}
6225 @item reverse-nexti @r{[}@var{count}@r{]}
6226 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6227 in reverse, except that called functions are ``un-executed'' atomically.
6228 That is, if the previously executed instruction was a return from
6229 another function, @code{reverse-nexti} will continue to execute
6230 in reverse until the call to that function (from the current stack
6233 @kindex reverse-finish
6234 @item reverse-finish
6235 Just as the @code{finish} command takes you to the point where the
6236 current function returns, @code{reverse-finish} takes you to the point
6237 where it was called. Instead of ending up at the end of the current
6238 function invocation, you end up at the beginning.
6240 @kindex set exec-direction
6241 @item set exec-direction
6242 Set the direction of target execution.
6243 @item set exec-direction reverse
6244 @cindex execute forward or backward in time
6245 @value{GDBN} will perform all execution commands in reverse, until the
6246 exec-direction mode is changed to ``forward''. Affected commands include
6247 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6248 command cannot be used in reverse mode.
6249 @item set exec-direction forward
6250 @value{GDBN} will perform all execution commands in the normal fashion.
6251 This is the default.
6255 @node Process Record and Replay
6256 @chapter Recording Inferior's Execution and Replaying It
6257 @cindex process record and replay
6258 @cindex recording inferior's execution and replaying it
6260 On some platforms, @value{GDBN} provides a special @dfn{process record
6261 and replay} target that can record a log of the process execution, and
6262 replay it later with both forward and reverse execution commands.
6265 When this target is in use, if the execution log includes the record
6266 for the next instruction, @value{GDBN} will debug in @dfn{replay
6267 mode}. In the replay mode, the inferior does not really execute code
6268 instructions. Instead, all the events that normally happen during
6269 code execution are taken from the execution log. While code is not
6270 really executed in replay mode, the values of registers (including the
6271 program counter register) and the memory of the inferior are still
6272 changed as they normally would. Their contents are taken from the
6276 If the record for the next instruction is not in the execution log,
6277 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6278 inferior executes normally, and @value{GDBN} records the execution log
6281 The process record and replay target supports reverse execution
6282 (@pxref{Reverse Execution}), even if the platform on which the
6283 inferior runs does not. However, the reverse execution is limited in
6284 this case by the range of the instructions recorded in the execution
6285 log. In other words, reverse execution on platforms that don't
6286 support it directly can only be done in the replay mode.
6288 When debugging in the reverse direction, @value{GDBN} will work in
6289 replay mode as long as the execution log includes the record for the
6290 previous instruction; otherwise, it will work in record mode, if the
6291 platform supports reverse execution, or stop if not.
6293 For architecture environments that support process record and replay,
6294 @value{GDBN} provides the following commands:
6297 @kindex target record
6298 @kindex target record-full
6299 @kindex target record-btrace
6302 @kindex record btrace
6306 @item record @var{method}
6307 This command starts the process record and replay target. The
6308 recording method can be specified as parameter. Without a parameter
6309 the command uses the @code{full} recording method. The following
6310 recording methods are available:
6314 Full record/replay recording using @value{GDBN}'s software record and
6315 replay implementation. This method allows replaying and reverse
6319 Hardware-supported instruction recording. This method does not record
6320 data. Further, the data is collected in a ring buffer so old data will
6321 be overwritten when the buffer is full. It allows limited replay and
6324 This recording method may not be available on all processors.
6327 The process record and replay target can only debug a process that is
6328 already running. Therefore, you need first to start the process with
6329 the @kbd{run} or @kbd{start} commands, and then start the recording
6330 with the @kbd{record @var{method}} command.
6332 Both @code{record @var{method}} and @code{rec @var{method}} are
6333 aliases of @code{target record-@var{method}}.
6335 @cindex displaced stepping, and process record and replay
6336 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6337 will be automatically disabled when process record and replay target
6338 is started. That's because the process record and replay target
6339 doesn't support displaced stepping.
6341 @cindex non-stop mode, and process record and replay
6342 @cindex asynchronous execution, and process record and replay
6343 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6344 the asynchronous execution mode (@pxref{Background Execution}), not
6345 all recording methods are available. The @code{full} recording method
6346 does not support these two modes.
6351 Stop the process record and replay target. When process record and
6352 replay target stops, the entire execution log will be deleted and the
6353 inferior will either be terminated, or will remain in its final state.
6355 When you stop the process record and replay target in record mode (at
6356 the end of the execution log), the inferior will be stopped at the
6357 next instruction that would have been recorded. In other words, if
6358 you record for a while and then stop recording, the inferior process
6359 will be left in the same state as if the recording never happened.
6361 On the other hand, if the process record and replay target is stopped
6362 while in replay mode (that is, not at the end of the execution log,
6363 but at some earlier point), the inferior process will become ``live''
6364 at that earlier state, and it will then be possible to continue the
6365 usual ``live'' debugging of the process from that state.
6367 When the inferior process exits, or @value{GDBN} detaches from it,
6368 process record and replay target will automatically stop itself.
6372 Go to a specific location in the execution log. There are several
6373 ways to specify the location to go to:
6376 @item record goto begin
6377 @itemx record goto start
6378 Go to the beginning of the execution log.
6380 @item record goto end
6381 Go to the end of the execution log.
6383 @item record goto @var{n}
6384 Go to instruction number @var{n} in the execution log.
6388 @item record save @var{filename}
6389 Save the execution log to a file @file{@var{filename}}.
6390 Default filename is @file{gdb_record.@var{process_id}}, where
6391 @var{process_id} is the process ID of the inferior.
6393 This command may not be available for all recording methods.
6395 @kindex record restore
6396 @item record restore @var{filename}
6397 Restore the execution log from a file @file{@var{filename}}.
6398 File must have been created with @code{record save}.
6400 @kindex set record full
6401 @item set record full insn-number-max @var{limit}
6402 @itemx set record full insn-number-max unlimited
6403 Set the limit of instructions to be recorded for the @code{full}
6404 recording method. Default value is 200000.
6406 If @var{limit} is a positive number, then @value{GDBN} will start
6407 deleting instructions from the log once the number of the record
6408 instructions becomes greater than @var{limit}. For every new recorded
6409 instruction, @value{GDBN} will delete the earliest recorded
6410 instruction to keep the number of recorded instructions at the limit.
6411 (Since deleting recorded instructions loses information, @value{GDBN}
6412 lets you control what happens when the limit is reached, by means of
6413 the @code{stop-at-limit} option, described below.)
6415 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6416 delete recorded instructions from the execution log. The number of
6417 recorded instructions is limited only by the available memory.
6419 @kindex show record full
6420 @item show record full insn-number-max
6421 Show the limit of instructions to be recorded with the @code{full}
6424 @item set record full stop-at-limit
6425 Control the behavior of the @code{full} recording method when the
6426 number of recorded instructions reaches the limit. If ON (the
6427 default), @value{GDBN} will stop when the limit is reached for the
6428 first time and ask you whether you want to stop the inferior or
6429 continue running it and recording the execution log. If you decide
6430 to continue recording, each new recorded instruction will cause the
6431 oldest one to be deleted.
6433 If this option is OFF, @value{GDBN} will automatically delete the
6434 oldest record to make room for each new one, without asking.
6436 @item show record full stop-at-limit
6437 Show the current setting of @code{stop-at-limit}.
6439 @item set record full memory-query
6440 Control the behavior when @value{GDBN} is unable to record memory
6441 changes caused by an instruction for the @code{full} recording method.
6442 If ON, @value{GDBN} will query whether to stop the inferior in that
6445 If this option is OFF (the default), @value{GDBN} will automatically
6446 ignore the effect of such instructions on memory. Later, when
6447 @value{GDBN} replays this execution log, it will mark the log of this
6448 instruction as not accessible, and it will not affect the replay
6451 @item show record full memory-query
6452 Show the current setting of @code{memory-query}.
6456 Show various statistics about the recording depending on the recording
6461 For the @code{full} recording method, it shows the state of process
6462 record and its in-memory execution log buffer, including:
6466 Whether in record mode or replay mode.
6468 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6470 Highest recorded instruction number.
6472 Current instruction about to be replayed (if in replay mode).
6474 Number of instructions contained in the execution log.
6476 Maximum number of instructions that may be contained in the execution log.
6480 For the @code{btrace} recording method, it shows the number of
6481 instructions that have been recorded and the number of blocks of
6482 sequential control-flow that is formed by the recorded instructions.
6485 @kindex record delete
6488 When record target runs in replay mode (``in the past''), delete the
6489 subsequent execution log and begin to record a new execution log starting
6490 from the current address. This means you will abandon the previously
6491 recorded ``future'' and begin recording a new ``future''.
6493 @kindex record instruction-history
6494 @kindex rec instruction-history
6495 @item record instruction-history
6496 Disassembles instructions from the recorded execution log. By
6497 default, ten instructions are disassembled. This can be changed using
6498 the @code{set record instruction-history-size} command. Instructions
6499 are printed in execution order. There are several ways to specify
6500 what part of the execution log to disassemble:
6503 @item record instruction-history @var{insn}
6504 Disassembles ten instructions starting from instruction number
6507 @item record instruction-history @var{insn}, +/-@var{n}
6508 Disassembles @var{n} instructions around instruction number
6509 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6510 @var{n} instructions after instruction number @var{insn}. If
6511 @var{n} is preceded with @code{-}, disassembles @var{n}
6512 instructions before instruction number @var{insn}.
6514 @item record instruction-history
6515 Disassembles ten more instructions after the last disassembly.
6517 @item record instruction-history -
6518 Disassembles ten more instructions before the last disassembly.
6520 @item record instruction-history @var{begin} @var{end}
6521 Disassembles instructions beginning with instruction number
6522 @var{begin} until instruction number @var{end}. The instruction
6523 number @var{end} is included.
6526 This command may not be available for all recording methods.
6529 @item set record instruction-history-size @var{size}
6530 @itemx set record instruction-history-size unlimited
6531 Define how many instructions to disassemble in the @code{record
6532 instruction-history} command. The default value is 10.
6533 A @var{size} of @code{unlimited} means unlimited instructions.
6536 @item show record instruction-history-size
6537 Show how many instructions to disassemble in the @code{record
6538 instruction-history} command.
6540 @kindex record function-call-history
6541 @kindex rec function-call-history
6542 @item record function-call-history
6543 Prints the execution history at function granularity. It prints one
6544 line for each sequence of instructions that belong to the same
6545 function giving the name of that function, the source lines
6546 for this instruction sequence (if the @code{/l} modifier is
6547 specified), and the instructions numbers that form the sequence (if
6548 the @code{/i} modifier is specified). The function names are indented
6549 to reflect the call stack depth if the @code{/c} modifier is
6550 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6554 (@value{GDBP}) @b{list 1, 10}
6565 (@value{GDBP}) @b{record function-call-history /ilc}
6566 1 bar inst 1,4 at foo.c:6,8
6567 2 foo inst 5,10 at foo.c:2,3
6568 3 bar inst 11,13 at foo.c:9,10
6571 By default, ten lines are printed. This can be changed using the
6572 @code{set record function-call-history-size} command. Functions are
6573 printed in execution order. There are several ways to specify what
6577 @item record function-call-history @var{func}
6578 Prints ten functions starting from function number @var{func}.
6580 @item record function-call-history @var{func}, +/-@var{n}
6581 Prints @var{n} functions around function number @var{func}. If
6582 @var{n} is preceded with @code{+}, prints @var{n} functions after
6583 function number @var{func}. If @var{n} is preceded with @code{-},
6584 prints @var{n} functions before function number @var{func}.
6586 @item record function-call-history
6587 Prints ten more functions after the last ten-line print.
6589 @item record function-call-history -
6590 Prints ten more functions before the last ten-line print.
6592 @item record function-call-history @var{begin} @var{end}
6593 Prints functions beginning with function number @var{begin} until
6594 function number @var{end}. The function number @var{end} is included.
6597 This command may not be available for all recording methods.
6599 @item set record function-call-history-size @var{size}
6600 @itemx set record function-call-history-size unlimited
6601 Define how many lines to print in the
6602 @code{record function-call-history} command. The default value is 10.
6603 A size of @code{unlimited} means unlimited lines.
6605 @item show record function-call-history-size
6606 Show how many lines to print in the
6607 @code{record function-call-history} command.
6612 @chapter Examining the Stack
6614 When your program has stopped, the first thing you need to know is where it
6615 stopped and how it got there.
6618 Each time your program performs a function call, information about the call
6620 That information includes the location of the call in your program,
6621 the arguments of the call,
6622 and the local variables of the function being called.
6623 The information is saved in a block of data called a @dfn{stack frame}.
6624 The stack frames are allocated in a region of memory called the @dfn{call
6627 When your program stops, the @value{GDBN} commands for examining the
6628 stack allow you to see all of this information.
6630 @cindex selected frame
6631 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6632 @value{GDBN} commands refer implicitly to the selected frame. In
6633 particular, whenever you ask @value{GDBN} for the value of a variable in
6634 your program, the value is found in the selected frame. There are
6635 special @value{GDBN} commands to select whichever frame you are
6636 interested in. @xref{Selection, ,Selecting a Frame}.
6638 When your program stops, @value{GDBN} automatically selects the
6639 currently executing frame and describes it briefly, similar to the
6640 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6643 * Frames:: Stack frames
6644 * Backtrace:: Backtraces
6645 * Frame Filter Management:: Managing frame filters
6646 * Selection:: Selecting a frame
6647 * Frame Info:: Information on a frame
6652 @section Stack Frames
6654 @cindex frame, definition
6656 The call stack is divided up into contiguous pieces called @dfn{stack
6657 frames}, or @dfn{frames} for short; each frame is the data associated
6658 with one call to one function. The frame contains the arguments given
6659 to the function, the function's local variables, and the address at
6660 which the function is executing.
6662 @cindex initial frame
6663 @cindex outermost frame
6664 @cindex innermost frame
6665 When your program is started, the stack has only one frame, that of the
6666 function @code{main}. This is called the @dfn{initial} frame or the
6667 @dfn{outermost} frame. Each time a function is called, a new frame is
6668 made. Each time a function returns, the frame for that function invocation
6669 is eliminated. If a function is recursive, there can be many frames for
6670 the same function. The frame for the function in which execution is
6671 actually occurring is called the @dfn{innermost} frame. This is the most
6672 recently created of all the stack frames that still exist.
6674 @cindex frame pointer
6675 Inside your program, stack frames are identified by their addresses. A
6676 stack frame consists of many bytes, each of which has its own address; each
6677 kind of computer has a convention for choosing one byte whose
6678 address serves as the address of the frame. Usually this address is kept
6679 in a register called the @dfn{frame pointer register}
6680 (@pxref{Registers, $fp}) while execution is going on in that frame.
6682 @cindex frame number
6683 @value{GDBN} assigns numbers to all existing stack frames, starting with
6684 zero for the innermost frame, one for the frame that called it,
6685 and so on upward. These numbers do not really exist in your program;
6686 they are assigned by @value{GDBN} to give you a way of designating stack
6687 frames in @value{GDBN} commands.
6689 @c The -fomit-frame-pointer below perennially causes hbox overflow
6690 @c underflow problems.
6691 @cindex frameless execution
6692 Some compilers provide a way to compile functions so that they operate
6693 without stack frames. (For example, the @value{NGCC} option
6695 @samp{-fomit-frame-pointer}
6697 generates functions without a frame.)
6698 This is occasionally done with heavily used library functions to save
6699 the frame setup time. @value{GDBN} has limited facilities for dealing
6700 with these function invocations. If the innermost function invocation
6701 has no stack frame, @value{GDBN} nevertheless regards it as though
6702 it had a separate frame, which is numbered zero as usual, allowing
6703 correct tracing of the function call chain. However, @value{GDBN} has
6704 no provision for frameless functions elsewhere in the stack.
6707 @kindex frame@r{, command}
6708 @cindex current stack frame
6709 @item frame @var{args}
6710 The @code{frame} command allows you to move from one stack frame to another,
6711 and to print the stack frame you select. @var{args} may be either the
6712 address of the frame or the stack frame number. Without an argument,
6713 @code{frame} prints the current stack frame.
6715 @kindex select-frame
6716 @cindex selecting frame silently
6718 The @code{select-frame} command allows you to move from one stack frame
6719 to another without printing the frame. This is the silent version of
6727 @cindex call stack traces
6728 A backtrace is a summary of how your program got where it is. It shows one
6729 line per frame, for many frames, starting with the currently executing
6730 frame (frame zero), followed by its caller (frame one), and on up the
6733 @anchor{backtrace-command}
6736 @kindex bt @r{(@code{backtrace})}
6739 Print a backtrace of the entire stack: one line per frame for all
6740 frames in the stack.
6742 You can stop the backtrace at any time by typing the system interrupt
6743 character, normally @kbd{Ctrl-c}.
6745 @item backtrace @var{n}
6747 Similar, but print only the innermost @var{n} frames.
6749 @item backtrace -@var{n}
6751 Similar, but print only the outermost @var{n} frames.
6753 @item backtrace full
6755 @itemx bt full @var{n}
6756 @itemx bt full -@var{n}
6757 Print the values of the local variables also. @var{n} specifies the
6758 number of frames to print, as described above.
6760 @item backtrace no-filters
6761 @itemx bt no-filters
6762 @itemx bt no-filters @var{n}
6763 @itemx bt no-filters -@var{n}
6764 @itemx bt no-filters full
6765 @itemx bt no-filters full @var{n}
6766 @itemx bt no-filters full -@var{n}
6767 Do not run Python frame filters on this backtrace. @xref{Frame
6768 Filter API}, for more information. Additionally use @ref{disable
6769 frame-filter all} to turn off all frame filters. This is only
6770 relevant when @value{GDBN} has been configured with @code{Python}
6776 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6777 are additional aliases for @code{backtrace}.
6779 @cindex multiple threads, backtrace
6780 In a multi-threaded program, @value{GDBN} by default shows the
6781 backtrace only for the current thread. To display the backtrace for
6782 several or all of the threads, use the command @code{thread apply}
6783 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6784 apply all backtrace}, @value{GDBN} will display the backtrace for all
6785 the threads; this is handy when you debug a core dump of a
6786 multi-threaded program.
6788 Each line in the backtrace shows the frame number and the function name.
6789 The program counter value is also shown---unless you use @code{set
6790 print address off}. The backtrace also shows the source file name and
6791 line number, as well as the arguments to the function. The program
6792 counter value is omitted if it is at the beginning of the code for that
6795 Here is an example of a backtrace. It was made with the command
6796 @samp{bt 3}, so it shows the innermost three frames.
6800 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6802 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6803 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6805 (More stack frames follow...)
6810 The display for frame zero does not begin with a program counter
6811 value, indicating that your program has stopped at the beginning of the
6812 code for line @code{993} of @code{builtin.c}.
6815 The value of parameter @code{data} in frame 1 has been replaced by
6816 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6817 only if it is a scalar (integer, pointer, enumeration, etc). See command
6818 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6819 on how to configure the way function parameter values are printed.
6821 @cindex optimized out, in backtrace
6822 @cindex function call arguments, optimized out
6823 If your program was compiled with optimizations, some compilers will
6824 optimize away arguments passed to functions if those arguments are
6825 never used after the call. Such optimizations generate code that
6826 passes arguments through registers, but doesn't store those arguments
6827 in the stack frame. @value{GDBN} has no way of displaying such
6828 arguments in stack frames other than the innermost one. Here's what
6829 such a backtrace might look like:
6833 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6835 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6836 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6838 (More stack frames follow...)
6843 The values of arguments that were not saved in their stack frames are
6844 shown as @samp{<optimized out>}.
6846 If you need to display the values of such optimized-out arguments,
6847 either deduce that from other variables whose values depend on the one
6848 you are interested in, or recompile without optimizations.
6850 @cindex backtrace beyond @code{main} function
6851 @cindex program entry point
6852 @cindex startup code, and backtrace
6853 Most programs have a standard user entry point---a place where system
6854 libraries and startup code transition into user code. For C this is
6855 @code{main}@footnote{
6856 Note that embedded programs (the so-called ``free-standing''
6857 environment) are not required to have a @code{main} function as the
6858 entry point. They could even have multiple entry points.}.
6859 When @value{GDBN} finds the entry function in a backtrace
6860 it will terminate the backtrace, to avoid tracing into highly
6861 system-specific (and generally uninteresting) code.
6863 If you need to examine the startup code, or limit the number of levels
6864 in a backtrace, you can change this behavior:
6867 @item set backtrace past-main
6868 @itemx set backtrace past-main on
6869 @kindex set backtrace
6870 Backtraces will continue past the user entry point.
6872 @item set backtrace past-main off
6873 Backtraces will stop when they encounter the user entry point. This is the
6876 @item show backtrace past-main
6877 @kindex show backtrace
6878 Display the current user entry point backtrace policy.
6880 @item set backtrace past-entry
6881 @itemx set backtrace past-entry on
6882 Backtraces will continue past the internal entry point of an application.
6883 This entry point is encoded by the linker when the application is built,
6884 and is likely before the user entry point @code{main} (or equivalent) is called.
6886 @item set backtrace past-entry off
6887 Backtraces will stop when they encounter the internal entry point of an
6888 application. This is the default.
6890 @item show backtrace past-entry
6891 Display the current internal entry point backtrace policy.
6893 @item set backtrace limit @var{n}
6894 @itemx set backtrace limit 0
6895 @itemx set backtrace limit unlimited
6896 @cindex backtrace limit
6897 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6898 or zero means unlimited levels.
6900 @item show backtrace limit
6901 Display the current limit on backtrace levels.
6904 You can control how file names are displayed.
6907 @item set filename-display
6908 @itemx set filename-display relative
6909 @cindex filename-display
6910 Display file names relative to the compilation directory. This is the default.
6912 @item set filename-display basename
6913 Display only basename of a filename.
6915 @item set filename-display absolute
6916 Display an absolute filename.
6918 @item show filename-display
6919 Show the current way to display filenames.
6922 @node Frame Filter Management
6923 @section Management of Frame Filters.
6924 @cindex managing frame filters
6926 Frame filters are Python based utilities to manage and decorate the
6927 output of frames. @xref{Frame Filter API}, for further information.
6929 Managing frame filters is performed by several commands available
6930 within @value{GDBN}, detailed here.
6933 @kindex info frame-filter
6934 @item info frame-filter
6935 Print a list of installed frame filters from all dictionaries, showing
6936 their name, priority and enabled status.
6938 @kindex disable frame-filter
6939 @anchor{disable frame-filter all}
6940 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6941 Disable a frame filter in the dictionary matching
6942 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6943 @var{filter-dictionary} may be @code{all}, @code{global},
6944 @code{progspace} or the name of the object file where the frame filter
6945 dictionary resides. When @code{all} is specified, all frame filters
6946 across all dictionaries are disabled. @var{filter-name} is the name
6947 of the frame filter and is used when @code{all} is not the option for
6948 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6949 may be enabled again later.
6951 @kindex enable frame-filter
6952 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6953 Enable a frame filter in the dictionary matching
6954 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6955 @var{filter-dictionary} may be @code{all}, @code{global},
6956 @code{progspace} or the name of the object file where the frame filter
6957 dictionary resides. When @code{all} is specified, all frame filters across
6958 all dictionaries are enabled. @var{filter-name} is the name of the frame
6959 filter and is used when @code{all} is not the option for
6960 @var{filter-dictionary}.
6965 (gdb) info frame-filter
6967 global frame-filters:
6968 Priority Enabled Name
6969 1000 No PrimaryFunctionFilter
6972 progspace /build/test frame-filters:
6973 Priority Enabled Name
6974 100 Yes ProgspaceFilter
6976 objfile /build/test frame-filters:
6977 Priority Enabled Name
6978 999 Yes BuildProgra Filter
6980 (gdb) disable frame-filter /build/test BuildProgramFilter
6981 (gdb) info frame-filter
6983 global frame-filters:
6984 Priority Enabled Name
6985 1000 No PrimaryFunctionFilter
6988 progspace /build/test frame-filters:
6989 Priority Enabled Name
6990 100 Yes ProgspaceFilter
6992 objfile /build/test frame-filters:
6993 Priority Enabled Name
6994 999 No BuildProgramFilter
6996 (gdb) enable frame-filter global PrimaryFunctionFilter
6997 (gdb) info frame-filter
6999 global frame-filters:
7000 Priority Enabled Name
7001 1000 Yes PrimaryFunctionFilter
7004 progspace /build/test frame-filters:
7005 Priority Enabled Name
7006 100 Yes ProgspaceFilter
7008 objfile /build/test frame-filters:
7009 Priority Enabled Name
7010 999 No BuildProgramFilter
7013 @kindex set frame-filter priority
7014 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7015 Set the @var{priority} of a frame filter in the dictionary matching
7016 @var{filter-dictionary}, and the frame filter name matching
7017 @var{filter-name}. @var{filter-dictionary} may be @code{global},
7018 @code{progspace} or the name of the object file where the frame filter
7019 dictionary resides. @var{priority} is an integer.
7021 @kindex show frame-filter priority
7022 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7023 Show the @var{priority} of a frame filter in the dictionary matching
7024 @var{filter-dictionary}, and the frame filter name matching
7025 @var{filter-name}. @var{filter-dictionary} may be @code{global},
7026 @code{progspace} or the name of the object file where the frame filter
7032 (gdb) info frame-filter
7034 global frame-filters:
7035 Priority Enabled Name
7036 1000 Yes PrimaryFunctionFilter
7039 progspace /build/test frame-filters:
7040 Priority Enabled Name
7041 100 Yes ProgspaceFilter
7043 objfile /build/test frame-filters:
7044 Priority Enabled Name
7045 999 No BuildProgramFilter
7047 (gdb) set frame-filter priority global Reverse 50
7048 (gdb) info frame-filter
7050 global frame-filters:
7051 Priority Enabled Name
7052 1000 Yes PrimaryFunctionFilter
7055 progspace /build/test frame-filters:
7056 Priority Enabled Name
7057 100 Yes ProgspaceFilter
7059 objfile /build/test frame-filters:
7060 Priority Enabled Name
7061 999 No BuildProgramFilter
7066 @section Selecting a Frame
7068 Most commands for examining the stack and other data in your program work on
7069 whichever stack frame is selected at the moment. Here are the commands for
7070 selecting a stack frame; all of them finish by printing a brief description
7071 of the stack frame just selected.
7074 @kindex frame@r{, selecting}
7075 @kindex f @r{(@code{frame})}
7078 Select frame number @var{n}. Recall that frame zero is the innermost
7079 (currently executing) frame, frame one is the frame that called the
7080 innermost one, and so on. The highest-numbered frame is the one for
7083 @item frame @var{addr}
7085 Select the frame at address @var{addr}. This is useful mainly if the
7086 chaining of stack frames has been damaged by a bug, making it
7087 impossible for @value{GDBN} to assign numbers properly to all frames. In
7088 addition, this can be useful when your program has multiple stacks and
7089 switches between them.
7091 On the SPARC architecture, @code{frame} needs two addresses to
7092 select an arbitrary frame: a frame pointer and a stack pointer.
7094 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7095 pointer and a program counter.
7097 On the 29k architecture, it needs three addresses: a register stack
7098 pointer, a program counter, and a memory stack pointer.
7102 Move @var{n} frames up the stack. For positive numbers @var{n}, this
7103 advances toward the outermost frame, to higher frame numbers, to frames
7104 that have existed longer. @var{n} defaults to one.
7107 @kindex do @r{(@code{down})}
7109 Move @var{n} frames down the stack. For positive numbers @var{n}, this
7110 advances toward the innermost frame, to lower frame numbers, to frames
7111 that were created more recently. @var{n} defaults to one. You may
7112 abbreviate @code{down} as @code{do}.
7115 All of these commands end by printing two lines of output describing the
7116 frame. The first line shows the frame number, the function name, the
7117 arguments, and the source file and line number of execution in that
7118 frame. The second line shows the text of that source line.
7126 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7128 10 read_input_file (argv[i]);
7132 After such a printout, the @code{list} command with no arguments
7133 prints ten lines centered on the point of execution in the frame.
7134 You can also edit the program at the point of execution with your favorite
7135 editing program by typing @code{edit}.
7136 @xref{List, ,Printing Source Lines},
7140 @kindex down-silently
7142 @item up-silently @var{n}
7143 @itemx down-silently @var{n}
7144 These two commands are variants of @code{up} and @code{down},
7145 respectively; they differ in that they do their work silently, without
7146 causing display of the new frame. They are intended primarily for use
7147 in @value{GDBN} command scripts, where the output might be unnecessary and
7152 @section Information About a Frame
7154 There are several other commands to print information about the selected
7160 When used without any argument, this command does not change which
7161 frame is selected, but prints a brief description of the currently
7162 selected stack frame. It can be abbreviated @code{f}. With an
7163 argument, this command is used to select a stack frame.
7164 @xref{Selection, ,Selecting a Frame}.
7167 @kindex info f @r{(@code{info frame})}
7170 This command prints a verbose description of the selected stack frame,
7175 the address of the frame
7177 the address of the next frame down (called by this frame)
7179 the address of the next frame up (caller of this frame)
7181 the language in which the source code corresponding to this frame is written
7183 the address of the frame's arguments
7185 the address of the frame's local variables
7187 the program counter saved in it (the address of execution in the caller frame)
7189 which registers were saved in the frame
7192 @noindent The verbose description is useful when
7193 something has gone wrong that has made the stack format fail to fit
7194 the usual conventions.
7196 @item info frame @var{addr}
7197 @itemx info f @var{addr}
7198 Print a verbose description of the frame at address @var{addr}, without
7199 selecting that frame. The selected frame remains unchanged by this
7200 command. This requires the same kind of address (more than one for some
7201 architectures) that you specify in the @code{frame} command.
7202 @xref{Selection, ,Selecting a Frame}.
7206 Print the arguments of the selected frame, each on a separate line.
7210 Print the local variables of the selected frame, each on a separate
7211 line. These are all variables (declared either static or automatic)
7212 accessible at the point of execution of the selected frame.
7218 @chapter Examining Source Files
7220 @value{GDBN} can print parts of your program's source, since the debugging
7221 information recorded in the program tells @value{GDBN} what source files were
7222 used to build it. When your program stops, @value{GDBN} spontaneously prints
7223 the line where it stopped. Likewise, when you select a stack frame
7224 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7225 execution in that frame has stopped. You can print other portions of
7226 source files by explicit command.
7228 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7229 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7230 @value{GDBN} under @sc{gnu} Emacs}.
7233 * List:: Printing source lines
7234 * Specify Location:: How to specify code locations
7235 * Edit:: Editing source files
7236 * Search:: Searching source files
7237 * Source Path:: Specifying source directories
7238 * Machine Code:: Source and machine code
7242 @section Printing Source Lines
7245 @kindex l @r{(@code{list})}
7246 To print lines from a source file, use the @code{list} command
7247 (abbreviated @code{l}). By default, ten lines are printed.
7248 There are several ways to specify what part of the file you want to
7249 print; see @ref{Specify Location}, for the full list.
7251 Here are the forms of the @code{list} command most commonly used:
7254 @item list @var{linenum}
7255 Print lines centered around line number @var{linenum} in the
7256 current source file.
7258 @item list @var{function}
7259 Print lines centered around the beginning of function
7263 Print more lines. If the last lines printed were printed with a
7264 @code{list} command, this prints lines following the last lines
7265 printed; however, if the last line printed was a solitary line printed
7266 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7267 Stack}), this prints lines centered around that line.
7270 Print lines just before the lines last printed.
7273 @cindex @code{list}, how many lines to display
7274 By default, @value{GDBN} prints ten source lines with any of these forms of
7275 the @code{list} command. You can change this using @code{set listsize}:
7278 @kindex set listsize
7279 @item set listsize @var{count}
7280 @itemx set listsize unlimited
7281 Make the @code{list} command display @var{count} source lines (unless
7282 the @code{list} argument explicitly specifies some other number).
7283 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7285 @kindex show listsize
7287 Display the number of lines that @code{list} prints.
7290 Repeating a @code{list} command with @key{RET} discards the argument,
7291 so it is equivalent to typing just @code{list}. This is more useful
7292 than listing the same lines again. An exception is made for an
7293 argument of @samp{-}; that argument is preserved in repetition so that
7294 each repetition moves up in the source file.
7296 In general, the @code{list} command expects you to supply zero, one or two
7297 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7298 of writing them (@pxref{Specify Location}), but the effect is always
7299 to specify some source line.
7301 Here is a complete description of the possible arguments for @code{list}:
7304 @item list @var{linespec}
7305 Print lines centered around the line specified by @var{linespec}.
7307 @item list @var{first},@var{last}
7308 Print lines from @var{first} to @var{last}. Both arguments are
7309 linespecs. When a @code{list} command has two linespecs, and the
7310 source file of the second linespec is omitted, this refers to
7311 the same source file as the first linespec.
7313 @item list ,@var{last}
7314 Print lines ending with @var{last}.
7316 @item list @var{first},
7317 Print lines starting with @var{first}.
7320 Print lines just after the lines last printed.
7323 Print lines just before the lines last printed.
7326 As described in the preceding table.
7329 @node Specify Location
7330 @section Specifying a Location
7331 @cindex specifying location
7334 Several @value{GDBN} commands accept arguments that specify a location
7335 of your program's code. Since @value{GDBN} is a source-level
7336 debugger, a location usually specifies some line in the source code;
7337 for that reason, locations are also known as @dfn{linespecs}.
7339 Here are all the different ways of specifying a code location that
7340 @value{GDBN} understands:
7344 Specifies the line number @var{linenum} of the current source file.
7347 @itemx +@var{offset}
7348 Specifies the line @var{offset} lines before or after the @dfn{current
7349 line}. For the @code{list} command, the current line is the last one
7350 printed; for the breakpoint commands, this is the line at which
7351 execution stopped in the currently selected @dfn{stack frame}
7352 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7353 used as the second of the two linespecs in a @code{list} command,
7354 this specifies the line @var{offset} lines up or down from the first
7357 @item @var{filename}:@var{linenum}
7358 Specifies the line @var{linenum} in the source file @var{filename}.
7359 If @var{filename} is a relative file name, then it will match any
7360 source file name with the same trailing components. For example, if
7361 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7362 name of @file{/build/trunk/gcc/expr.c}, but not
7363 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7365 @item @var{function}
7366 Specifies the line that begins the body of the function @var{function}.
7367 For example, in C, this is the line with the open brace.
7369 @item @var{function}:@var{label}
7370 Specifies the line where @var{label} appears in @var{function}.
7372 @item @var{filename}:@var{function}
7373 Specifies the line that begins the body of the function @var{function}
7374 in the file @var{filename}. You only need the file name with a
7375 function name to avoid ambiguity when there are identically named
7376 functions in different source files.
7379 Specifies the line at which the label named @var{label} appears.
7380 @value{GDBN} searches for the label in the function corresponding to
7381 the currently selected stack frame. If there is no current selected
7382 stack frame (for instance, if the inferior is not running), then
7383 @value{GDBN} will not search for a label.
7385 @item *@var{address}
7386 Specifies the program address @var{address}. For line-oriented
7387 commands, such as @code{list} and @code{edit}, this specifies a source
7388 line that contains @var{address}. For @code{break} and other
7389 breakpoint oriented commands, this can be used to set breakpoints in
7390 parts of your program which do not have debugging information or
7393 Here @var{address} may be any expression valid in the current working
7394 language (@pxref{Languages, working language}) that specifies a code
7395 address. In addition, as a convenience, @value{GDBN} extends the
7396 semantics of expressions used in locations to cover the situations
7397 that frequently happen during debugging. Here are the various forms
7401 @item @var{expression}
7402 Any expression valid in the current working language.
7404 @item @var{funcaddr}
7405 An address of a function or procedure derived from its name. In C,
7406 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7407 simply the function's name @var{function} (and actually a special case
7408 of a valid expression). In Pascal and Modula-2, this is
7409 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7410 (although the Pascal form also works).
7412 This form specifies the address of the function's first instruction,
7413 before the stack frame and arguments have been set up.
7415 @item '@var{filename}'::@var{funcaddr}
7416 Like @var{funcaddr} above, but also specifies the name of the source
7417 file explicitly. This is useful if the name of the function does not
7418 specify the function unambiguously, e.g., if there are several
7419 functions with identical names in different source files.
7422 @cindex breakpoint at static probe point
7423 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7424 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7425 applications to embed static probes. @xref{Static Probe Points}, for more
7426 information on finding and using static probes. This form of linespec
7427 specifies the location of such a static probe.
7429 If @var{objfile} is given, only probes coming from that shared library
7430 or executable matching @var{objfile} as a regular expression are considered.
7431 If @var{provider} is given, then only probes from that provider are considered.
7432 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7433 each one of those probes.
7439 @section Editing Source Files
7440 @cindex editing source files
7443 @kindex e @r{(@code{edit})}
7444 To edit the lines in a source file, use the @code{edit} command.
7445 The editing program of your choice
7446 is invoked with the current line set to
7447 the active line in the program.
7448 Alternatively, there are several ways to specify what part of the file you
7449 want to print if you want to see other parts of the program:
7452 @item edit @var{location}
7453 Edit the source file specified by @code{location}. Editing starts at
7454 that @var{location}, e.g., at the specified source line of the
7455 specified file. @xref{Specify Location}, for all the possible forms
7456 of the @var{location} argument; here are the forms of the @code{edit}
7457 command most commonly used:
7460 @item edit @var{number}
7461 Edit the current source file with @var{number} as the active line number.
7463 @item edit @var{function}
7464 Edit the file containing @var{function} at the beginning of its definition.
7469 @subsection Choosing your Editor
7470 You can customize @value{GDBN} to use any editor you want
7472 The only restriction is that your editor (say @code{ex}), recognizes the
7473 following command-line syntax:
7475 ex +@var{number} file
7477 The optional numeric value +@var{number} specifies the number of the line in
7478 the file where to start editing.}.
7479 By default, it is @file{@value{EDITOR}}, but you can change this
7480 by setting the environment variable @code{EDITOR} before using
7481 @value{GDBN}. For example, to configure @value{GDBN} to use the
7482 @code{vi} editor, you could use these commands with the @code{sh} shell:
7488 or in the @code{csh} shell,
7490 setenv EDITOR /usr/bin/vi
7495 @section Searching Source Files
7496 @cindex searching source files
7498 There are two commands for searching through the current source file for a
7503 @kindex forward-search
7504 @kindex fo @r{(@code{forward-search})}
7505 @item forward-search @var{regexp}
7506 @itemx search @var{regexp}
7507 The command @samp{forward-search @var{regexp}} checks each line,
7508 starting with the one following the last line listed, for a match for
7509 @var{regexp}. It lists the line that is found. You can use the
7510 synonym @samp{search @var{regexp}} or abbreviate the command name as
7513 @kindex reverse-search
7514 @item reverse-search @var{regexp}
7515 The command @samp{reverse-search @var{regexp}} checks each line, starting
7516 with the one before the last line listed and going backward, for a match
7517 for @var{regexp}. It lists the line that is found. You can abbreviate
7518 this command as @code{rev}.
7522 @section Specifying Source Directories
7525 @cindex directories for source files
7526 Executable programs sometimes do not record the directories of the source
7527 files from which they were compiled, just the names. Even when they do,
7528 the directories could be moved between the compilation and your debugging
7529 session. @value{GDBN} has a list of directories to search for source files;
7530 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7531 it tries all the directories in the list, in the order they are present
7532 in the list, until it finds a file with the desired name.
7534 For example, suppose an executable references the file
7535 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7536 @file{/mnt/cross}. The file is first looked up literally; if this
7537 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7538 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7539 message is printed. @value{GDBN} does not look up the parts of the
7540 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7541 Likewise, the subdirectories of the source path are not searched: if
7542 the source path is @file{/mnt/cross}, and the binary refers to
7543 @file{foo.c}, @value{GDBN} would not find it under
7544 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7546 Plain file names, relative file names with leading directories, file
7547 names containing dots, etc.@: are all treated as described above; for
7548 instance, if the source path is @file{/mnt/cross}, and the source file
7549 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7550 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7551 that---@file{/mnt/cross/foo.c}.
7553 Note that the executable search path is @emph{not} used to locate the
7556 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7557 any information it has cached about where source files are found and where
7558 each line is in the file.
7562 When you start @value{GDBN}, its source path includes only @samp{cdir}
7563 and @samp{cwd}, in that order.
7564 To add other directories, use the @code{directory} command.
7566 The search path is used to find both program source files and @value{GDBN}
7567 script files (read using the @samp{-command} option and @samp{source} command).
7569 In addition to the source path, @value{GDBN} provides a set of commands
7570 that manage a list of source path substitution rules. A @dfn{substitution
7571 rule} specifies how to rewrite source directories stored in the program's
7572 debug information in case the sources were moved to a different
7573 directory between compilation and debugging. A rule is made of
7574 two strings, the first specifying what needs to be rewritten in
7575 the path, and the second specifying how it should be rewritten.
7576 In @ref{set substitute-path}, we name these two parts @var{from} and
7577 @var{to} respectively. @value{GDBN} does a simple string replacement
7578 of @var{from} with @var{to} at the start of the directory part of the
7579 source file name, and uses that result instead of the original file
7580 name to look up the sources.
7582 Using the previous example, suppose the @file{foo-1.0} tree has been
7583 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7584 @value{GDBN} to replace @file{/usr/src} in all source path names with
7585 @file{/mnt/cross}. The first lookup will then be
7586 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7587 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7588 substitution rule, use the @code{set substitute-path} command
7589 (@pxref{set substitute-path}).
7591 To avoid unexpected substitution results, a rule is applied only if the
7592 @var{from} part of the directory name ends at a directory separator.
7593 For instance, a rule substituting @file{/usr/source} into
7594 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7595 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7596 is applied only at the beginning of the directory name, this rule will
7597 not be applied to @file{/root/usr/source/baz.c} either.
7599 In many cases, you can achieve the same result using the @code{directory}
7600 command. However, @code{set substitute-path} can be more efficient in
7601 the case where the sources are organized in a complex tree with multiple
7602 subdirectories. With the @code{directory} command, you need to add each
7603 subdirectory of your project. If you moved the entire tree while
7604 preserving its internal organization, then @code{set substitute-path}
7605 allows you to direct the debugger to all the sources with one single
7608 @code{set substitute-path} is also more than just a shortcut command.
7609 The source path is only used if the file at the original location no
7610 longer exists. On the other hand, @code{set substitute-path} modifies
7611 the debugger behavior to look at the rewritten location instead. So, if
7612 for any reason a source file that is not relevant to your executable is
7613 located at the original location, a substitution rule is the only
7614 method available to point @value{GDBN} at the new location.
7616 @cindex @samp{--with-relocated-sources}
7617 @cindex default source path substitution
7618 You can configure a default source path substitution rule by
7619 configuring @value{GDBN} with the
7620 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7621 should be the name of a directory under @value{GDBN}'s configured
7622 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7623 directory names in debug information under @var{dir} will be adjusted
7624 automatically if the installed @value{GDBN} is moved to a new
7625 location. This is useful if @value{GDBN}, libraries or executables
7626 with debug information and corresponding source code are being moved
7630 @item directory @var{dirname} @dots{}
7631 @item dir @var{dirname} @dots{}
7632 Add directory @var{dirname} to the front of the source path. Several
7633 directory names may be given to this command, separated by @samp{:}
7634 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7635 part of absolute file names) or
7636 whitespace. You may specify a directory that is already in the source
7637 path; this moves it forward, so @value{GDBN} searches it sooner.
7641 @vindex $cdir@r{, convenience variable}
7642 @vindex $cwd@r{, convenience variable}
7643 @cindex compilation directory
7644 @cindex current directory
7645 @cindex working directory
7646 @cindex directory, current
7647 @cindex directory, compilation
7648 You can use the string @samp{$cdir} to refer to the compilation
7649 directory (if one is recorded), and @samp{$cwd} to refer to the current
7650 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7651 tracks the current working directory as it changes during your @value{GDBN}
7652 session, while the latter is immediately expanded to the current
7653 directory at the time you add an entry to the source path.
7656 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7658 @c RET-repeat for @code{directory} is explicitly disabled, but since
7659 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7661 @item set directories @var{path-list}
7662 @kindex set directories
7663 Set the source path to @var{path-list}.
7664 @samp{$cdir:$cwd} are added if missing.
7666 @item show directories
7667 @kindex show directories
7668 Print the source path: show which directories it contains.
7670 @anchor{set substitute-path}
7671 @item set substitute-path @var{from} @var{to}
7672 @kindex set substitute-path
7673 Define a source path substitution rule, and add it at the end of the
7674 current list of existing substitution rules. If a rule with the same
7675 @var{from} was already defined, then the old rule is also deleted.
7677 For example, if the file @file{/foo/bar/baz.c} was moved to
7678 @file{/mnt/cross/baz.c}, then the command
7681 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7685 will tell @value{GDBN} to replace @samp{/usr/src} with
7686 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7687 @file{baz.c} even though it was moved.
7689 In the case when more than one substitution rule have been defined,
7690 the rules are evaluated one by one in the order where they have been
7691 defined. The first one matching, if any, is selected to perform
7694 For instance, if we had entered the following commands:
7697 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7698 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7702 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7703 @file{/mnt/include/defs.h} by using the first rule. However, it would
7704 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7705 @file{/mnt/src/lib/foo.c}.
7708 @item unset substitute-path [path]
7709 @kindex unset substitute-path
7710 If a path is specified, search the current list of substitution rules
7711 for a rule that would rewrite that path. Delete that rule if found.
7712 A warning is emitted by the debugger if no rule could be found.
7714 If no path is specified, then all substitution rules are deleted.
7716 @item show substitute-path [path]
7717 @kindex show substitute-path
7718 If a path is specified, then print the source path substitution rule
7719 which would rewrite that path, if any.
7721 If no path is specified, then print all existing source path substitution
7726 If your source path is cluttered with directories that are no longer of
7727 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7728 versions of source. You can correct the situation as follows:
7732 Use @code{directory} with no argument to reset the source path to its default value.
7735 Use @code{directory} with suitable arguments to reinstall the
7736 directories you want in the source path. You can add all the
7737 directories in one command.
7741 @section Source and Machine Code
7742 @cindex source line and its code address
7744 You can use the command @code{info line} to map source lines to program
7745 addresses (and vice versa), and the command @code{disassemble} to display
7746 a range of addresses as machine instructions. You can use the command
7747 @code{set disassemble-next-line} to set whether to disassemble next
7748 source line when execution stops. When run under @sc{gnu} Emacs
7749 mode, the @code{info line} command causes the arrow to point to the
7750 line specified. Also, @code{info line} prints addresses in symbolic form as
7755 @item info line @var{linespec}
7756 Print the starting and ending addresses of the compiled code for
7757 source line @var{linespec}. You can specify source lines in any of
7758 the ways documented in @ref{Specify Location}.
7761 For example, we can use @code{info line} to discover the location of
7762 the object code for the first line of function
7763 @code{m4_changequote}:
7765 @c FIXME: I think this example should also show the addresses in
7766 @c symbolic form, as they usually would be displayed.
7768 (@value{GDBP}) info line m4_changequote
7769 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7773 @cindex code address and its source line
7774 We can also inquire (using @code{*@var{addr}} as the form for
7775 @var{linespec}) what source line covers a particular address:
7777 (@value{GDBP}) info line *0x63ff
7778 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7781 @cindex @code{$_} and @code{info line}
7782 @cindex @code{x} command, default address
7783 @kindex x@r{(examine), and} info line
7784 After @code{info line}, the default address for the @code{x} command
7785 is changed to the starting address of the line, so that @samp{x/i} is
7786 sufficient to begin examining the machine code (@pxref{Memory,
7787 ,Examining Memory}). Also, this address is saved as the value of the
7788 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7793 @cindex assembly instructions
7794 @cindex instructions, assembly
7795 @cindex machine instructions
7796 @cindex listing machine instructions
7798 @itemx disassemble /m
7799 @itemx disassemble /r
7800 This specialized command dumps a range of memory as machine
7801 instructions. It can also print mixed source+disassembly by specifying
7802 the @code{/m} modifier and print the raw instructions in hex as well as
7803 in symbolic form by specifying the @code{/r}.
7804 The default memory range is the function surrounding the
7805 program counter of the selected frame. A single argument to this
7806 command is a program counter value; @value{GDBN} dumps the function
7807 surrounding this value. When two arguments are given, they should
7808 be separated by a comma, possibly surrounded by whitespace. The
7809 arguments specify a range of addresses to dump, in one of two forms:
7812 @item @var{start},@var{end}
7813 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7814 @item @var{start},+@var{length}
7815 the addresses from @var{start} (inclusive) to
7816 @code{@var{start}+@var{length}} (exclusive).
7820 When 2 arguments are specified, the name of the function is also
7821 printed (since there could be several functions in the given range).
7823 The argument(s) can be any expression yielding a numeric value, such as
7824 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7826 If the range of memory being disassembled contains current program counter,
7827 the instruction at that location is shown with a @code{=>} marker.
7830 The following example shows the disassembly of a range of addresses of
7831 HP PA-RISC 2.0 code:
7834 (@value{GDBP}) disas 0x32c4, 0x32e4
7835 Dump of assembler code from 0x32c4 to 0x32e4:
7836 0x32c4 <main+204>: addil 0,dp
7837 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7838 0x32cc <main+212>: ldil 0x3000,r31
7839 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7840 0x32d4 <main+220>: ldo 0(r31),rp
7841 0x32d8 <main+224>: addil -0x800,dp
7842 0x32dc <main+228>: ldo 0x588(r1),r26
7843 0x32e0 <main+232>: ldil 0x3000,r31
7844 End of assembler dump.
7847 Here is an example showing mixed source+assembly for Intel x86, when the
7848 program is stopped just after function prologue:
7851 (@value{GDBP}) disas /m main
7852 Dump of assembler code for function main:
7854 0x08048330 <+0>: push %ebp
7855 0x08048331 <+1>: mov %esp,%ebp
7856 0x08048333 <+3>: sub $0x8,%esp
7857 0x08048336 <+6>: and $0xfffffff0,%esp
7858 0x08048339 <+9>: sub $0x10,%esp
7860 6 printf ("Hello.\n");
7861 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7862 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7866 0x08048348 <+24>: mov $0x0,%eax
7867 0x0804834d <+29>: leave
7868 0x0804834e <+30>: ret
7870 End of assembler dump.
7873 Here is another example showing raw instructions in hex for AMD x86-64,
7876 (gdb) disas /r 0x400281,+10
7877 Dump of assembler code from 0x400281 to 0x40028b:
7878 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7879 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7880 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7881 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7882 End of assembler dump.
7885 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7886 So, for example, if you want to disassemble function @code{bar}
7887 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7888 and not @samp{disassemble foo.c:bar}.
7890 Some architectures have more than one commonly-used set of instruction
7891 mnemonics or other syntax.
7893 For programs that were dynamically linked and use shared libraries,
7894 instructions that call functions or branch to locations in the shared
7895 libraries might show a seemingly bogus location---it's actually a
7896 location of the relocation table. On some architectures, @value{GDBN}
7897 might be able to resolve these to actual function names.
7900 @kindex set disassembly-flavor
7901 @cindex Intel disassembly flavor
7902 @cindex AT&T disassembly flavor
7903 @item set disassembly-flavor @var{instruction-set}
7904 Select the instruction set to use when disassembling the
7905 program via the @code{disassemble} or @code{x/i} commands.
7907 Currently this command is only defined for the Intel x86 family. You
7908 can set @var{instruction-set} to either @code{intel} or @code{att}.
7909 The default is @code{att}, the AT&T flavor used by default by Unix
7910 assemblers for x86-based targets.
7912 @kindex show disassembly-flavor
7913 @item show disassembly-flavor
7914 Show the current setting of the disassembly flavor.
7918 @kindex set disassemble-next-line
7919 @kindex show disassemble-next-line
7920 @item set disassemble-next-line
7921 @itemx show disassemble-next-line
7922 Control whether or not @value{GDBN} will disassemble the next source
7923 line or instruction when execution stops. If ON, @value{GDBN} will
7924 display disassembly of the next source line when execution of the
7925 program being debugged stops. This is @emph{in addition} to
7926 displaying the source line itself, which @value{GDBN} always does if
7927 possible. If the next source line cannot be displayed for some reason
7928 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7929 info in the debug info), @value{GDBN} will display disassembly of the
7930 next @emph{instruction} instead of showing the next source line. If
7931 AUTO, @value{GDBN} will display disassembly of next instruction only
7932 if the source line cannot be displayed. This setting causes
7933 @value{GDBN} to display some feedback when you step through a function
7934 with no line info or whose source file is unavailable. The default is
7935 OFF, which means never display the disassembly of the next line or
7941 @chapter Examining Data
7943 @cindex printing data
7944 @cindex examining data
7947 The usual way to examine data in your program is with the @code{print}
7948 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7949 evaluates and prints the value of an expression of the language your
7950 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7951 Different Languages}). It may also print the expression using a
7952 Python-based pretty-printer (@pxref{Pretty Printing}).
7955 @item print @var{expr}
7956 @itemx print /@var{f} @var{expr}
7957 @var{expr} is an expression (in the source language). By default the
7958 value of @var{expr} is printed in a format appropriate to its data type;
7959 you can choose a different format by specifying @samp{/@var{f}}, where
7960 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7964 @itemx print /@var{f}
7965 @cindex reprint the last value
7966 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7967 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7968 conveniently inspect the same value in an alternative format.
7971 A more low-level way of examining data is with the @code{x} command.
7972 It examines data in memory at a specified address and prints it in a
7973 specified format. @xref{Memory, ,Examining Memory}.
7975 If you are interested in information about types, or about how the
7976 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7977 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7980 @cindex exploring hierarchical data structures
7982 Another way of examining values of expressions and type information is
7983 through the Python extension command @code{explore} (available only if
7984 the @value{GDBN} build is configured with @code{--with-python}). It
7985 offers an interactive way to start at the highest level (or, the most
7986 abstract level) of the data type of an expression (or, the data type
7987 itself) and explore all the way down to leaf scalar values/fields
7988 embedded in the higher level data types.
7991 @item explore @var{arg}
7992 @var{arg} is either an expression (in the source language), or a type
7993 visible in the current context of the program being debugged.
7996 The working of the @code{explore} command can be illustrated with an
7997 example. If a data type @code{struct ComplexStruct} is defined in your
8007 struct ComplexStruct
8009 struct SimpleStruct *ss_p;
8015 followed by variable declarations as
8018 struct SimpleStruct ss = @{ 10, 1.11 @};
8019 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8023 then, the value of the variable @code{cs} can be explored using the
8024 @code{explore} command as follows.
8028 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8029 the following fields:
8031 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8032 arr = <Enter 1 to explore this field of type `int [10]'>
8034 Enter the field number of choice:
8038 Since the fields of @code{cs} are not scalar values, you are being
8039 prompted to chose the field you want to explore. Let's say you choose
8040 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8041 pointer, you will be asked if it is pointing to a single value. From
8042 the declaration of @code{cs} above, it is indeed pointing to a single
8043 value, hence you enter @code{y}. If you enter @code{n}, then you will
8044 be asked if it were pointing to an array of values, in which case this
8045 field will be explored as if it were an array.
8048 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8049 Continue exploring it as a pointer to a single value [y/n]: y
8050 The value of `*(cs.ss_p)' is a struct/class of type `struct
8051 SimpleStruct' with the following fields:
8053 i = 10 .. (Value of type `int')
8054 d = 1.1100000000000001 .. (Value of type `double')
8056 Press enter to return to parent value:
8060 If the field @code{arr} of @code{cs} was chosen for exploration by
8061 entering @code{1} earlier, then since it is as array, you will be
8062 prompted to enter the index of the element in the array that you want
8066 `cs.arr' is an array of `int'.
8067 Enter the index of the element you want to explore in `cs.arr': 5
8069 `(cs.arr)[5]' is a scalar value of type `int'.
8073 Press enter to return to parent value:
8076 In general, at any stage of exploration, you can go deeper towards the
8077 leaf values by responding to the prompts appropriately, or hit the
8078 return key to return to the enclosing data structure (the @i{higher}
8079 level data structure).
8081 Similar to exploring values, you can use the @code{explore} command to
8082 explore types. Instead of specifying a value (which is typically a
8083 variable name or an expression valid in the current context of the
8084 program being debugged), you specify a type name. If you consider the
8085 same example as above, your can explore the type
8086 @code{struct ComplexStruct} by passing the argument
8087 @code{struct ComplexStruct} to the @code{explore} command.
8090 (gdb) explore struct ComplexStruct
8094 By responding to the prompts appropriately in the subsequent interactive
8095 session, you can explore the type @code{struct ComplexStruct} in a
8096 manner similar to how the value @code{cs} was explored in the above
8099 The @code{explore} command also has two sub-commands,
8100 @code{explore value} and @code{explore type}. The former sub-command is
8101 a way to explicitly specify that value exploration of the argument is
8102 being invoked, while the latter is a way to explicitly specify that type
8103 exploration of the argument is being invoked.
8106 @item explore value @var{expr}
8107 @cindex explore value
8108 This sub-command of @code{explore} explores the value of the
8109 expression @var{expr} (if @var{expr} is an expression valid in the
8110 current context of the program being debugged). The behavior of this
8111 command is identical to that of the behavior of the @code{explore}
8112 command being passed the argument @var{expr}.
8114 @item explore type @var{arg}
8115 @cindex explore type
8116 This sub-command of @code{explore} explores the type of @var{arg} (if
8117 @var{arg} is a type visible in the current context of program being
8118 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8119 is an expression valid in the current context of the program being
8120 debugged). If @var{arg} is a type, then the behavior of this command is
8121 identical to that of the @code{explore} command being passed the
8122 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8123 this command will be identical to that of the @code{explore} command
8124 being passed the type of @var{arg} as the argument.
8128 * Expressions:: Expressions
8129 * Ambiguous Expressions:: Ambiguous Expressions
8130 * Variables:: Program variables
8131 * Arrays:: Artificial arrays
8132 * Output Formats:: Output formats
8133 * Memory:: Examining memory
8134 * Auto Display:: Automatic display
8135 * Print Settings:: Print settings
8136 * Pretty Printing:: Python pretty printing
8137 * Value History:: Value history
8138 * Convenience Vars:: Convenience variables
8139 * Convenience Funs:: Convenience functions
8140 * Registers:: Registers
8141 * Floating Point Hardware:: Floating point hardware
8142 * Vector Unit:: Vector Unit
8143 * OS Information:: Auxiliary data provided by operating system
8144 * Memory Region Attributes:: Memory region attributes
8145 * Dump/Restore Files:: Copy between memory and a file
8146 * Core File Generation:: Cause a program dump its core
8147 * Character Sets:: Debugging programs that use a different
8148 character set than GDB does
8149 * Caching Target Data:: Data caching for targets
8150 * Searching Memory:: Searching memory for a sequence of bytes
8154 @section Expressions
8157 @code{print} and many other @value{GDBN} commands accept an expression and
8158 compute its value. Any kind of constant, variable or operator defined
8159 by the programming language you are using is valid in an expression in
8160 @value{GDBN}. This includes conditional expressions, function calls,
8161 casts, and string constants. It also includes preprocessor macros, if
8162 you compiled your program to include this information; see
8165 @cindex arrays in expressions
8166 @value{GDBN} supports array constants in expressions input by
8167 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8168 you can use the command @code{print @{1, 2, 3@}} to create an array
8169 of three integers. If you pass an array to a function or assign it
8170 to a program variable, @value{GDBN} copies the array to memory that
8171 is @code{malloc}ed in the target program.
8173 Because C is so widespread, most of the expressions shown in examples in
8174 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8175 Languages}, for information on how to use expressions in other
8178 In this section, we discuss operators that you can use in @value{GDBN}
8179 expressions regardless of your programming language.
8181 @cindex casts, in expressions
8182 Casts are supported in all languages, not just in C, because it is so
8183 useful to cast a number into a pointer in order to examine a structure
8184 at that address in memory.
8185 @c FIXME: casts supported---Mod2 true?
8187 @value{GDBN} supports these operators, in addition to those common
8188 to programming languages:
8192 @samp{@@} is a binary operator for treating parts of memory as arrays.
8193 @xref{Arrays, ,Artificial Arrays}, for more information.
8196 @samp{::} allows you to specify a variable in terms of the file or
8197 function where it is defined. @xref{Variables, ,Program Variables}.
8199 @cindex @{@var{type}@}
8200 @cindex type casting memory
8201 @cindex memory, viewing as typed object
8202 @cindex casts, to view memory
8203 @item @{@var{type}@} @var{addr}
8204 Refers to an object of type @var{type} stored at address @var{addr} in
8205 memory. @var{addr} may be any expression whose value is an integer or
8206 pointer (but parentheses are required around binary operators, just as in
8207 a cast). This construct is allowed regardless of what kind of data is
8208 normally supposed to reside at @var{addr}.
8211 @node Ambiguous Expressions
8212 @section Ambiguous Expressions
8213 @cindex ambiguous expressions
8215 Expressions can sometimes contain some ambiguous elements. For instance,
8216 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8217 a single function name to be defined several times, for application in
8218 different contexts. This is called @dfn{overloading}. Another example
8219 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8220 templates and is typically instantiated several times, resulting in
8221 the same function name being defined in different contexts.
8223 In some cases and depending on the language, it is possible to adjust
8224 the expression to remove the ambiguity. For instance in C@t{++}, you
8225 can specify the signature of the function you want to break on, as in
8226 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8227 qualified name of your function often makes the expression unambiguous
8230 When an ambiguity that needs to be resolved is detected, the debugger
8231 has the capability to display a menu of numbered choices for each
8232 possibility, and then waits for the selection with the prompt @samp{>}.
8233 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8234 aborts the current command. If the command in which the expression was
8235 used allows more than one choice to be selected, the next option in the
8236 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8239 For example, the following session excerpt shows an attempt to set a
8240 breakpoint at the overloaded symbol @code{String::after}.
8241 We choose three particular definitions of that function name:
8243 @c FIXME! This is likely to change to show arg type lists, at least
8246 (@value{GDBP}) b String::after
8249 [2] file:String.cc; line number:867
8250 [3] file:String.cc; line number:860
8251 [4] file:String.cc; line number:875
8252 [5] file:String.cc; line number:853
8253 [6] file:String.cc; line number:846
8254 [7] file:String.cc; line number:735
8256 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8257 Breakpoint 2 at 0xb344: file String.cc, line 875.
8258 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8259 Multiple breakpoints were set.
8260 Use the "delete" command to delete unwanted
8267 @kindex set multiple-symbols
8268 @item set multiple-symbols @var{mode}
8269 @cindex multiple-symbols menu
8271 This option allows you to adjust the debugger behavior when an expression
8274 By default, @var{mode} is set to @code{all}. If the command with which
8275 the expression is used allows more than one choice, then @value{GDBN}
8276 automatically selects all possible choices. For instance, inserting
8277 a breakpoint on a function using an ambiguous name results in a breakpoint
8278 inserted on each possible match. However, if a unique choice must be made,
8279 then @value{GDBN} uses the menu to help you disambiguate the expression.
8280 For instance, printing the address of an overloaded function will result
8281 in the use of the menu.
8283 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8284 when an ambiguity is detected.
8286 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8287 an error due to the ambiguity and the command is aborted.
8289 @kindex show multiple-symbols
8290 @item show multiple-symbols
8291 Show the current value of the @code{multiple-symbols} setting.
8295 @section Program Variables
8297 The most common kind of expression to use is the name of a variable
8300 Variables in expressions are understood in the selected stack frame
8301 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8305 global (or file-static)
8312 visible according to the scope rules of the
8313 programming language from the point of execution in that frame
8316 @noindent This means that in the function
8331 you can examine and use the variable @code{a} whenever your program is
8332 executing within the function @code{foo}, but you can only use or
8333 examine the variable @code{b} while your program is executing inside
8334 the block where @code{b} is declared.
8336 @cindex variable name conflict
8337 There is an exception: you can refer to a variable or function whose
8338 scope is a single source file even if the current execution point is not
8339 in this file. But it is possible to have more than one such variable or
8340 function with the same name (in different source files). If that
8341 happens, referring to that name has unpredictable effects. If you wish,
8342 you can specify a static variable in a particular function or file by
8343 using the colon-colon (@code{::}) notation:
8345 @cindex colon-colon, context for variables/functions
8347 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8348 @cindex @code{::}, context for variables/functions
8351 @var{file}::@var{variable}
8352 @var{function}::@var{variable}
8356 Here @var{file} or @var{function} is the name of the context for the
8357 static @var{variable}. In the case of file names, you can use quotes to
8358 make sure @value{GDBN} parses the file name as a single word---for example,
8359 to print a global value of @code{x} defined in @file{f2.c}:
8362 (@value{GDBP}) p 'f2.c'::x
8365 The @code{::} notation is normally used for referring to
8366 static variables, since you typically disambiguate uses of local variables
8367 in functions by selecting the appropriate frame and using the
8368 simple name of the variable. However, you may also use this notation
8369 to refer to local variables in frames enclosing the selected frame:
8378 process (a); /* Stop here */
8389 For example, if there is a breakpoint at the commented line,
8390 here is what you might see
8391 when the program stops after executing the call @code{bar(0)}:
8396 (@value{GDBP}) p bar::a
8399 #2 0x080483d0 in foo (a=5) at foobar.c:12
8402 (@value{GDBP}) p bar::a
8406 @cindex C@t{++} scope resolution
8407 These uses of @samp{::} are very rarely in conflict with the very
8408 similar use of the same notation in C@t{++}. When they are in
8409 conflict, the C@t{++} meaning takes precedence; however, this can be
8410 overridden by quoting the file or function name with single quotes.
8412 For example, suppose the program is stopped in a method of a class
8413 that has a field named @code{includefile}, and there is also an
8414 include file named @file{includefile} that defines a variable,
8418 (@value{GDBP}) p includefile
8420 (@value{GDBP}) p includefile::some_global
8421 A syntax error in expression, near `'.
8422 (@value{GDBP}) p 'includefile'::some_global
8426 @cindex wrong values
8427 @cindex variable values, wrong
8428 @cindex function entry/exit, wrong values of variables
8429 @cindex optimized code, wrong values of variables
8431 @emph{Warning:} Occasionally, a local variable may appear to have the
8432 wrong value at certain points in a function---just after entry to a new
8433 scope, and just before exit.
8435 You may see this problem when you are stepping by machine instructions.
8436 This is because, on most machines, it takes more than one instruction to
8437 set up a stack frame (including local variable definitions); if you are
8438 stepping by machine instructions, variables may appear to have the wrong
8439 values until the stack frame is completely built. On exit, it usually
8440 also takes more than one machine instruction to destroy a stack frame;
8441 after you begin stepping through that group of instructions, local
8442 variable definitions may be gone.
8444 This may also happen when the compiler does significant optimizations.
8445 To be sure of always seeing accurate values, turn off all optimization
8448 @cindex ``No symbol "foo" in current context''
8449 Another possible effect of compiler optimizations is to optimize
8450 unused variables out of existence, or assign variables to registers (as
8451 opposed to memory addresses). Depending on the support for such cases
8452 offered by the debug info format used by the compiler, @value{GDBN}
8453 might not be able to display values for such local variables. If that
8454 happens, @value{GDBN} will print a message like this:
8457 No symbol "foo" in current context.
8460 To solve such problems, either recompile without optimizations, or use a
8461 different debug info format, if the compiler supports several such
8462 formats. @xref{Compilation}, for more information on choosing compiler
8463 options. @xref{C, ,C and C@t{++}}, for more information about debug
8464 info formats that are best suited to C@t{++} programs.
8466 If you ask to print an object whose contents are unknown to
8467 @value{GDBN}, e.g., because its data type is not completely specified
8468 by the debug information, @value{GDBN} will say @samp{<incomplete
8469 type>}. @xref{Symbols, incomplete type}, for more about this.
8471 If you append @kbd{@@entry} string to a function parameter name you get its
8472 value at the time the function got called. If the value is not available an
8473 error message is printed. Entry values are available only with some compilers.
8474 Entry values are normally also printed at the function parameter list according
8475 to @ref{set print entry-values}.
8478 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8484 (gdb) print i@@entry
8488 Strings are identified as arrays of @code{char} values without specified
8489 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8490 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8491 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8492 defines literal string type @code{"char"} as @code{char} without a sign.
8497 signed char var1[] = "A";
8500 You get during debugging
8505 $2 = @{65 'A', 0 '\0'@}
8509 @section Artificial Arrays
8511 @cindex artificial array
8513 @kindex @@@r{, referencing memory as an array}
8514 It is often useful to print out several successive objects of the
8515 same type in memory; a section of an array, or an array of
8516 dynamically determined size for which only a pointer exists in the
8519 You can do this by referring to a contiguous span of memory as an
8520 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8521 operand of @samp{@@} should be the first element of the desired array
8522 and be an individual object. The right operand should be the desired length
8523 of the array. The result is an array value whose elements are all of
8524 the type of the left argument. The first element is actually the left
8525 argument; the second element comes from bytes of memory immediately
8526 following those that hold the first element, and so on. Here is an
8527 example. If a program says
8530 int *array = (int *) malloc (len * sizeof (int));
8534 you can print the contents of @code{array} with
8540 The left operand of @samp{@@} must reside in memory. Array values made
8541 with @samp{@@} in this way behave just like other arrays in terms of
8542 subscripting, and are coerced to pointers when used in expressions.
8543 Artificial arrays most often appear in expressions via the value history
8544 (@pxref{Value History, ,Value History}), after printing one out.
8546 Another way to create an artificial array is to use a cast.
8547 This re-interprets a value as if it were an array.
8548 The value need not be in memory:
8550 (@value{GDBP}) p/x (short[2])0x12345678
8551 $1 = @{0x1234, 0x5678@}
8554 As a convenience, if you leave the array length out (as in
8555 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8556 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8558 (@value{GDBP}) p/x (short[])0x12345678
8559 $2 = @{0x1234, 0x5678@}
8562 Sometimes the artificial array mechanism is not quite enough; in
8563 moderately complex data structures, the elements of interest may not
8564 actually be adjacent---for example, if you are interested in the values
8565 of pointers in an array. One useful work-around in this situation is
8566 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8567 Variables}) as a counter in an expression that prints the first
8568 interesting value, and then repeat that expression via @key{RET}. For
8569 instance, suppose you have an array @code{dtab} of pointers to
8570 structures, and you are interested in the values of a field @code{fv}
8571 in each structure. Here is an example of what you might type:
8581 @node Output Formats
8582 @section Output Formats
8584 @cindex formatted output
8585 @cindex output formats
8586 By default, @value{GDBN} prints a value according to its data type. Sometimes
8587 this is not what you want. For example, you might want to print a number
8588 in hex, or a pointer in decimal. Or you might want to view data in memory
8589 at a certain address as a character string or as an instruction. To do
8590 these things, specify an @dfn{output format} when you print a value.
8592 The simplest use of output formats is to say how to print a value
8593 already computed. This is done by starting the arguments of the
8594 @code{print} command with a slash and a format letter. The format
8595 letters supported are:
8599 Regard the bits of the value as an integer, and print the integer in
8603 Print as integer in signed decimal.
8606 Print as integer in unsigned decimal.
8609 Print as integer in octal.
8612 Print as integer in binary. The letter @samp{t} stands for ``two''.
8613 @footnote{@samp{b} cannot be used because these format letters are also
8614 used with the @code{x} command, where @samp{b} stands for ``byte'';
8615 see @ref{Memory,,Examining Memory}.}
8618 @cindex unknown address, locating
8619 @cindex locate address
8620 Print as an address, both absolute in hexadecimal and as an offset from
8621 the nearest preceding symbol. You can use this format used to discover
8622 where (in what function) an unknown address is located:
8625 (@value{GDBP}) p/a 0x54320
8626 $3 = 0x54320 <_initialize_vx+396>
8630 The command @code{info symbol 0x54320} yields similar results.
8631 @xref{Symbols, info symbol}.
8634 Regard as an integer and print it as a character constant. This
8635 prints both the numerical value and its character representation. The
8636 character representation is replaced with the octal escape @samp{\nnn}
8637 for characters outside the 7-bit @sc{ascii} range.
8639 Without this format, @value{GDBN} displays @code{char},
8640 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8641 constants. Single-byte members of vectors are displayed as integer
8645 Regard the bits of the value as a floating point number and print
8646 using typical floating point syntax.
8649 @cindex printing strings
8650 @cindex printing byte arrays
8651 Regard as a string, if possible. With this format, pointers to single-byte
8652 data are displayed as null-terminated strings and arrays of single-byte data
8653 are displayed as fixed-length strings. Other values are displayed in their
8656 Without this format, @value{GDBN} displays pointers to and arrays of
8657 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8658 strings. Single-byte members of a vector are displayed as an integer
8662 Like @samp{x} formatting, the value is treated as an integer and
8663 printed as hexadecimal, but leading zeros are printed to pad the value
8664 to the size of the integer type.
8667 @cindex raw printing
8668 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8669 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8670 Printing}). This typically results in a higher-level display of the
8671 value's contents. The @samp{r} format bypasses any Python
8672 pretty-printer which might exist.
8675 For example, to print the program counter in hex (@pxref{Registers}), type
8682 Note that no space is required before the slash; this is because command
8683 names in @value{GDBN} cannot contain a slash.
8685 To reprint the last value in the value history with a different format,
8686 you can use the @code{print} command with just a format and no
8687 expression. For example, @samp{p/x} reprints the last value in hex.
8690 @section Examining Memory
8692 You can use the command @code{x} (for ``examine'') to examine memory in
8693 any of several formats, independently of your program's data types.
8695 @cindex examining memory
8697 @kindex x @r{(examine memory)}
8698 @item x/@var{nfu} @var{addr}
8701 Use the @code{x} command to examine memory.
8704 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8705 much memory to display and how to format it; @var{addr} is an
8706 expression giving the address where you want to start displaying memory.
8707 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8708 Several commands set convenient defaults for @var{addr}.
8711 @item @var{n}, the repeat count
8712 The repeat count is a decimal integer; the default is 1. It specifies
8713 how much memory (counting by units @var{u}) to display.
8714 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8717 @item @var{f}, the display format
8718 The display format is one of the formats used by @code{print}
8719 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8720 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8721 The default is @samp{x} (hexadecimal) initially. The default changes
8722 each time you use either @code{x} or @code{print}.
8724 @item @var{u}, the unit size
8725 The unit size is any of
8731 Halfwords (two bytes).
8733 Words (four bytes). This is the initial default.
8735 Giant words (eight bytes).
8738 Each time you specify a unit size with @code{x}, that size becomes the
8739 default unit the next time you use @code{x}. For the @samp{i} format,
8740 the unit size is ignored and is normally not written. For the @samp{s} format,
8741 the unit size defaults to @samp{b}, unless it is explicitly given.
8742 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8743 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8744 Note that the results depend on the programming language of the
8745 current compilation unit. If the language is C, the @samp{s}
8746 modifier will use the UTF-16 encoding while @samp{w} will use
8747 UTF-32. The encoding is set by the programming language and cannot
8750 @item @var{addr}, starting display address
8751 @var{addr} is the address where you want @value{GDBN} to begin displaying
8752 memory. The expression need not have a pointer value (though it may);
8753 it is always interpreted as an integer address of a byte of memory.
8754 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8755 @var{addr} is usually just after the last address examined---but several
8756 other commands also set the default address: @code{info breakpoints} (to
8757 the address of the last breakpoint listed), @code{info line} (to the
8758 starting address of a line), and @code{print} (if you use it to display
8759 a value from memory).
8762 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8763 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8764 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8765 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8766 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8768 Since the letters indicating unit sizes are all distinct from the
8769 letters specifying output formats, you do not have to remember whether
8770 unit size or format comes first; either order works. The output
8771 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8772 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8774 Even though the unit size @var{u} is ignored for the formats @samp{s}
8775 and @samp{i}, you might still want to use a count @var{n}; for example,
8776 @samp{3i} specifies that you want to see three machine instructions,
8777 including any operands. For convenience, especially when used with
8778 the @code{display} command, the @samp{i} format also prints branch delay
8779 slot instructions, if any, beyond the count specified, which immediately
8780 follow the last instruction that is within the count. The command
8781 @code{disassemble} gives an alternative way of inspecting machine
8782 instructions; see @ref{Machine Code,,Source and Machine Code}.
8784 All the defaults for the arguments to @code{x} are designed to make it
8785 easy to continue scanning memory with minimal specifications each time
8786 you use @code{x}. For example, after you have inspected three machine
8787 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8788 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8789 the repeat count @var{n} is used again; the other arguments default as
8790 for successive uses of @code{x}.
8792 When examining machine instructions, the instruction at current program
8793 counter is shown with a @code{=>} marker. For example:
8796 (@value{GDBP}) x/5i $pc-6
8797 0x804837f <main+11>: mov %esp,%ebp
8798 0x8048381 <main+13>: push %ecx
8799 0x8048382 <main+14>: sub $0x4,%esp
8800 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8801 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8804 @cindex @code{$_}, @code{$__}, and value history
8805 The addresses and contents printed by the @code{x} command are not saved
8806 in the value history because there is often too much of them and they
8807 would get in the way. Instead, @value{GDBN} makes these values available for
8808 subsequent use in expressions as values of the convenience variables
8809 @code{$_} and @code{$__}. After an @code{x} command, the last address
8810 examined is available for use in expressions in the convenience variable
8811 @code{$_}. The contents of that address, as examined, are available in
8812 the convenience variable @code{$__}.
8814 If the @code{x} command has a repeat count, the address and contents saved
8815 are from the last memory unit printed; this is not the same as the last
8816 address printed if several units were printed on the last line of output.
8818 @cindex remote memory comparison
8819 @cindex target memory comparison
8820 @cindex verify remote memory image
8821 @cindex verify target memory image
8822 When you are debugging a program running on a remote target machine
8823 (@pxref{Remote Debugging}), you may wish to verify the program's image
8824 in the remote machine's memory against the executable file you
8825 downloaded to the target. Or, on any target, you may want to check
8826 whether the program has corrupted its own read-only sections. The
8827 @code{compare-sections} command is provided for such situations.
8830 @kindex compare-sections
8831 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
8832 Compare the data of a loadable section @var{section-name} in the
8833 executable file of the program being debugged with the same section in
8834 the target machine's memory, and report any mismatches. With no
8835 arguments, compares all loadable sections. With an argument of
8836 @code{-r}, compares all loadable read-only sections.
8838 Note: for remote targets, this command can be accelerated if the
8839 target supports computing the CRC checksum of a block of memory
8840 (@pxref{qCRC packet}).
8844 @section Automatic Display
8845 @cindex automatic display
8846 @cindex display of expressions
8848 If you find that you want to print the value of an expression frequently
8849 (to see how it changes), you might want to add it to the @dfn{automatic
8850 display list} so that @value{GDBN} prints its value each time your program stops.
8851 Each expression added to the list is given a number to identify it;
8852 to remove an expression from the list, you specify that number.
8853 The automatic display looks like this:
8857 3: bar[5] = (struct hack *) 0x3804
8861 This display shows item numbers, expressions and their current values. As with
8862 displays you request manually using @code{x} or @code{print}, you can
8863 specify the output format you prefer; in fact, @code{display} decides
8864 whether to use @code{print} or @code{x} depending your format
8865 specification---it uses @code{x} if you specify either the @samp{i}
8866 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8870 @item display @var{expr}
8871 Add the expression @var{expr} to the list of expressions to display
8872 each time your program stops. @xref{Expressions, ,Expressions}.
8874 @code{display} does not repeat if you press @key{RET} again after using it.
8876 @item display/@var{fmt} @var{expr}
8877 For @var{fmt} specifying only a display format and not a size or
8878 count, add the expression @var{expr} to the auto-display list but
8879 arrange to display it each time in the specified format @var{fmt}.
8880 @xref{Output Formats,,Output Formats}.
8882 @item display/@var{fmt} @var{addr}
8883 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8884 number of units, add the expression @var{addr} as a memory address to
8885 be examined each time your program stops. Examining means in effect
8886 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8889 For example, @samp{display/i $pc} can be helpful, to see the machine
8890 instruction about to be executed each time execution stops (@samp{$pc}
8891 is a common name for the program counter; @pxref{Registers, ,Registers}).
8894 @kindex delete display
8896 @item undisplay @var{dnums}@dots{}
8897 @itemx delete display @var{dnums}@dots{}
8898 Remove items from the list of expressions to display. Specify the
8899 numbers of the displays that you want affected with the command
8900 argument @var{dnums}. It can be a single display number, one of the
8901 numbers shown in the first field of the @samp{info display} display;
8902 or it could be a range of display numbers, as in @code{2-4}.
8904 @code{undisplay} does not repeat if you press @key{RET} after using it.
8905 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8907 @kindex disable display
8908 @item disable display @var{dnums}@dots{}
8909 Disable the display of item numbers @var{dnums}. A disabled display
8910 item is not printed automatically, but is not forgotten. It may be
8911 enabled again later. Specify the numbers of the displays that you
8912 want affected with the command argument @var{dnums}. It can be a
8913 single display number, one of the numbers shown in the first field of
8914 the @samp{info display} display; or it could be a range of display
8915 numbers, as in @code{2-4}.
8917 @kindex enable display
8918 @item enable display @var{dnums}@dots{}
8919 Enable display of item numbers @var{dnums}. It becomes effective once
8920 again in auto display of its expression, until you specify otherwise.
8921 Specify the numbers of the displays that you want affected with the
8922 command argument @var{dnums}. It can be a single display number, one
8923 of the numbers shown in the first field of the @samp{info display}
8924 display; or it could be a range of display numbers, as in @code{2-4}.
8927 Display the current values of the expressions on the list, just as is
8928 done when your program stops.
8930 @kindex info display
8932 Print the list of expressions previously set up to display
8933 automatically, each one with its item number, but without showing the
8934 values. This includes disabled expressions, which are marked as such.
8935 It also includes expressions which would not be displayed right now
8936 because they refer to automatic variables not currently available.
8939 @cindex display disabled out of scope
8940 If a display expression refers to local variables, then it does not make
8941 sense outside the lexical context for which it was set up. Such an
8942 expression is disabled when execution enters a context where one of its
8943 variables is not defined. For example, if you give the command
8944 @code{display last_char} while inside a function with an argument
8945 @code{last_char}, @value{GDBN} displays this argument while your program
8946 continues to stop inside that function. When it stops elsewhere---where
8947 there is no variable @code{last_char}---the display is disabled
8948 automatically. The next time your program stops where @code{last_char}
8949 is meaningful, you can enable the display expression once again.
8951 @node Print Settings
8952 @section Print Settings
8954 @cindex format options
8955 @cindex print settings
8956 @value{GDBN} provides the following ways to control how arrays, structures,
8957 and symbols are printed.
8960 These settings are useful for debugging programs in any language:
8964 @item set print address
8965 @itemx set print address on
8966 @cindex print/don't print memory addresses
8967 @value{GDBN} prints memory addresses showing the location of stack
8968 traces, structure values, pointer values, breakpoints, and so forth,
8969 even when it also displays the contents of those addresses. The default
8970 is @code{on}. For example, this is what a stack frame display looks like with
8971 @code{set print address on}:
8976 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8978 530 if (lquote != def_lquote)
8982 @item set print address off
8983 Do not print addresses when displaying their contents. For example,
8984 this is the same stack frame displayed with @code{set print address off}:
8988 (@value{GDBP}) set print addr off
8990 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8991 530 if (lquote != def_lquote)
8995 You can use @samp{set print address off} to eliminate all machine
8996 dependent displays from the @value{GDBN} interface. For example, with
8997 @code{print address off}, you should get the same text for backtraces on
8998 all machines---whether or not they involve pointer arguments.
9001 @item show print address
9002 Show whether or not addresses are to be printed.
9005 When @value{GDBN} prints a symbolic address, it normally prints the
9006 closest earlier symbol plus an offset. If that symbol does not uniquely
9007 identify the address (for example, it is a name whose scope is a single
9008 source file), you may need to clarify. One way to do this is with
9009 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9010 you can set @value{GDBN} to print the source file and line number when
9011 it prints a symbolic address:
9014 @item set print symbol-filename on
9015 @cindex source file and line of a symbol
9016 @cindex symbol, source file and line
9017 Tell @value{GDBN} to print the source file name and line number of a
9018 symbol in the symbolic form of an address.
9020 @item set print symbol-filename off
9021 Do not print source file name and line number of a symbol. This is the
9024 @item show print symbol-filename
9025 Show whether or not @value{GDBN} will print the source file name and
9026 line number of a symbol in the symbolic form of an address.
9029 Another situation where it is helpful to show symbol filenames and line
9030 numbers is when disassembling code; @value{GDBN} shows you the line
9031 number and source file that corresponds to each instruction.
9033 Also, you may wish to see the symbolic form only if the address being
9034 printed is reasonably close to the closest earlier symbol:
9037 @item set print max-symbolic-offset @var{max-offset}
9038 @itemx set print max-symbolic-offset unlimited
9039 @cindex maximum value for offset of closest symbol
9040 Tell @value{GDBN} to only display the symbolic form of an address if the
9041 offset between the closest earlier symbol and the address is less than
9042 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9043 to always print the symbolic form of an address if any symbol precedes
9044 it. Zero is equivalent to @code{unlimited}.
9046 @item show print max-symbolic-offset
9047 Ask how large the maximum offset is that @value{GDBN} prints in a
9051 @cindex wild pointer, interpreting
9052 @cindex pointer, finding referent
9053 If you have a pointer and you are not sure where it points, try
9054 @samp{set print symbol-filename on}. Then you can determine the name
9055 and source file location of the variable where it points, using
9056 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9057 For example, here @value{GDBN} shows that a variable @code{ptt} points
9058 at another variable @code{t}, defined in @file{hi2.c}:
9061 (@value{GDBP}) set print symbol-filename on
9062 (@value{GDBP}) p/a ptt
9063 $4 = 0xe008 <t in hi2.c>
9067 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9068 does not show the symbol name and filename of the referent, even with
9069 the appropriate @code{set print} options turned on.
9072 You can also enable @samp{/a}-like formatting all the time using
9073 @samp{set print symbol on}:
9076 @item set print symbol on
9077 Tell @value{GDBN} to print the symbol corresponding to an address, if
9080 @item set print symbol off
9081 Tell @value{GDBN} not to print the symbol corresponding to an
9082 address. In this mode, @value{GDBN} will still print the symbol
9083 corresponding to pointers to functions. This is the default.
9085 @item show print symbol
9086 Show whether @value{GDBN} will display the symbol corresponding to an
9090 Other settings control how different kinds of objects are printed:
9093 @item set print array
9094 @itemx set print array on
9095 @cindex pretty print arrays
9096 Pretty print arrays. This format is more convenient to read,
9097 but uses more space. The default is off.
9099 @item set print array off
9100 Return to compressed format for arrays.
9102 @item show print array
9103 Show whether compressed or pretty format is selected for displaying
9106 @cindex print array indexes
9107 @item set print array-indexes
9108 @itemx set print array-indexes on
9109 Print the index of each element when displaying arrays. May be more
9110 convenient to locate a given element in the array or quickly find the
9111 index of a given element in that printed array. The default is off.
9113 @item set print array-indexes off
9114 Stop printing element indexes when displaying arrays.
9116 @item show print array-indexes
9117 Show whether the index of each element is printed when displaying
9120 @item set print elements @var{number-of-elements}
9121 @itemx set print elements unlimited
9122 @cindex number of array elements to print
9123 @cindex limit on number of printed array elements
9124 Set a limit on how many elements of an array @value{GDBN} will print.
9125 If @value{GDBN} is printing a large array, it stops printing after it has
9126 printed the number of elements set by the @code{set print elements} command.
9127 This limit also applies to the display of strings.
9128 When @value{GDBN} starts, this limit is set to 200.
9129 Setting @var{number-of-elements} to @code{unlimited} or zero means
9130 that the number of elements to print is unlimited.
9132 @item show print elements
9133 Display the number of elements of a large array that @value{GDBN} will print.
9134 If the number is 0, then the printing is unlimited.
9136 @item set print frame-arguments @var{value}
9137 @kindex set print frame-arguments
9138 @cindex printing frame argument values
9139 @cindex print all frame argument values
9140 @cindex print frame argument values for scalars only
9141 @cindex do not print frame argument values
9142 This command allows to control how the values of arguments are printed
9143 when the debugger prints a frame (@pxref{Frames}). The possible
9148 The values of all arguments are printed.
9151 Print the value of an argument only if it is a scalar. The value of more
9152 complex arguments such as arrays, structures, unions, etc, is replaced
9153 by @code{@dots{}}. This is the default. Here is an example where
9154 only scalar arguments are shown:
9157 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9162 None of the argument values are printed. Instead, the value of each argument
9163 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9166 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9171 By default, only scalar arguments are printed. This command can be used
9172 to configure the debugger to print the value of all arguments, regardless
9173 of their type. However, it is often advantageous to not print the value
9174 of more complex parameters. For instance, it reduces the amount of
9175 information printed in each frame, making the backtrace more readable.
9176 Also, it improves performance when displaying Ada frames, because
9177 the computation of large arguments can sometimes be CPU-intensive,
9178 especially in large applications. Setting @code{print frame-arguments}
9179 to @code{scalars} (the default) or @code{none} avoids this computation,
9180 thus speeding up the display of each Ada frame.
9182 @item show print frame-arguments
9183 Show how the value of arguments should be displayed when printing a frame.
9185 @item set print raw frame-arguments on
9186 Print frame arguments in raw, non pretty-printed, form.
9188 @item set print raw frame-arguments off
9189 Print frame arguments in pretty-printed form, if there is a pretty-printer
9190 for the value (@pxref{Pretty Printing}),
9191 otherwise print the value in raw form.
9192 This is the default.
9194 @item show print raw frame-arguments
9195 Show whether to print frame arguments in raw form.
9197 @anchor{set print entry-values}
9198 @item set print entry-values @var{value}
9199 @kindex set print entry-values
9200 Set printing of frame argument values at function entry. In some cases
9201 @value{GDBN} can determine the value of function argument which was passed by
9202 the function caller, even if the value was modified inside the called function
9203 and therefore is different. With optimized code, the current value could be
9204 unavailable, but the entry value may still be known.
9206 The default value is @code{default} (see below for its description). Older
9207 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9208 this feature will behave in the @code{default} setting the same way as with the
9211 This functionality is currently supported only by DWARF 2 debugging format and
9212 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9213 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9216 The @var{value} parameter can be one of the following:
9220 Print only actual parameter values, never print values from function entry
9224 #0 different (val=6)
9225 #0 lost (val=<optimized out>)
9227 #0 invalid (val=<optimized out>)
9231 Print only parameter values from function entry point. The actual parameter
9232 values are never printed.
9234 #0 equal (val@@entry=5)
9235 #0 different (val@@entry=5)
9236 #0 lost (val@@entry=5)
9237 #0 born (val@@entry=<optimized out>)
9238 #0 invalid (val@@entry=<optimized out>)
9242 Print only parameter values from function entry point. If value from function
9243 entry point is not known while the actual value is known, print the actual
9244 value for such parameter.
9246 #0 equal (val@@entry=5)
9247 #0 different (val@@entry=5)
9248 #0 lost (val@@entry=5)
9250 #0 invalid (val@@entry=<optimized out>)
9254 Print actual parameter values. If actual parameter value is not known while
9255 value from function entry point is known, print the entry point value for such
9259 #0 different (val=6)
9260 #0 lost (val@@entry=5)
9262 #0 invalid (val=<optimized out>)
9266 Always print both the actual parameter value and its value from function entry
9267 point, even if values of one or both are not available due to compiler
9270 #0 equal (val=5, val@@entry=5)
9271 #0 different (val=6, val@@entry=5)
9272 #0 lost (val=<optimized out>, val@@entry=5)
9273 #0 born (val=10, val@@entry=<optimized out>)
9274 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9278 Print the actual parameter value if it is known and also its value from
9279 function entry point if it is known. If neither is known, print for the actual
9280 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9281 values are known and identical, print the shortened
9282 @code{param=param@@entry=VALUE} notation.
9284 #0 equal (val=val@@entry=5)
9285 #0 different (val=6, val@@entry=5)
9286 #0 lost (val@@entry=5)
9288 #0 invalid (val=<optimized out>)
9292 Always print the actual parameter value. Print also its value from function
9293 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9294 if both values are known and identical, print the shortened
9295 @code{param=param@@entry=VALUE} notation.
9297 #0 equal (val=val@@entry=5)
9298 #0 different (val=6, val@@entry=5)
9299 #0 lost (val=<optimized out>, val@@entry=5)
9301 #0 invalid (val=<optimized out>)
9305 For analysis messages on possible failures of frame argument values at function
9306 entry resolution see @ref{set debug entry-values}.
9308 @item show print entry-values
9309 Show the method being used for printing of frame argument values at function
9312 @item set print repeats @var{number-of-repeats}
9313 @itemx set print repeats unlimited
9314 @cindex repeated array elements
9315 Set the threshold for suppressing display of repeated array
9316 elements. When the number of consecutive identical elements of an
9317 array exceeds the threshold, @value{GDBN} prints the string
9318 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9319 identical repetitions, instead of displaying the identical elements
9320 themselves. Setting the threshold to @code{unlimited} or zero will
9321 cause all elements to be individually printed. The default threshold
9324 @item show print repeats
9325 Display the current threshold for printing repeated identical
9328 @item set print null-stop
9329 @cindex @sc{null} elements in arrays
9330 Cause @value{GDBN} to stop printing the characters of an array when the first
9331 @sc{null} is encountered. This is useful when large arrays actually
9332 contain only short strings.
9335 @item show print null-stop
9336 Show whether @value{GDBN} stops printing an array on the first
9337 @sc{null} character.
9339 @item set print pretty on
9340 @cindex print structures in indented form
9341 @cindex indentation in structure display
9342 Cause @value{GDBN} to print structures in an indented format with one member
9343 per line, like this:
9358 @item set print pretty off
9359 Cause @value{GDBN} to print structures in a compact format, like this:
9363 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9364 meat = 0x54 "Pork"@}
9369 This is the default format.
9371 @item show print pretty
9372 Show which format @value{GDBN} is using to print structures.
9374 @item set print sevenbit-strings on
9375 @cindex eight-bit characters in strings
9376 @cindex octal escapes in strings
9377 Print using only seven-bit characters; if this option is set,
9378 @value{GDBN} displays any eight-bit characters (in strings or
9379 character values) using the notation @code{\}@var{nnn}. This setting is
9380 best if you are working in English (@sc{ascii}) and you use the
9381 high-order bit of characters as a marker or ``meta'' bit.
9383 @item set print sevenbit-strings off
9384 Print full eight-bit characters. This allows the use of more
9385 international character sets, and is the default.
9387 @item show print sevenbit-strings
9388 Show whether or not @value{GDBN} is printing only seven-bit characters.
9390 @item set print union on
9391 @cindex unions in structures, printing
9392 Tell @value{GDBN} to print unions which are contained in structures
9393 and other unions. This is the default setting.
9395 @item set print union off
9396 Tell @value{GDBN} not to print unions which are contained in
9397 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9400 @item show print union
9401 Ask @value{GDBN} whether or not it will print unions which are contained in
9402 structures and other unions.
9404 For example, given the declarations
9407 typedef enum @{Tree, Bug@} Species;
9408 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9409 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9420 struct thing foo = @{Tree, @{Acorn@}@};
9424 with @code{set print union on} in effect @samp{p foo} would print
9427 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9431 and with @code{set print union off} in effect it would print
9434 $1 = @{it = Tree, form = @{...@}@}
9438 @code{set print union} affects programs written in C-like languages
9444 These settings are of interest when debugging C@t{++} programs:
9447 @cindex demangling C@t{++} names
9448 @item set print demangle
9449 @itemx set print demangle on
9450 Print C@t{++} names in their source form rather than in the encoded
9451 (``mangled'') form passed to the assembler and linker for type-safe
9452 linkage. The default is on.
9454 @item show print demangle
9455 Show whether C@t{++} names are printed in mangled or demangled form.
9457 @item set print asm-demangle
9458 @itemx set print asm-demangle on
9459 Print C@t{++} names in their source form rather than their mangled form, even
9460 in assembler code printouts such as instruction disassemblies.
9463 @item show print asm-demangle
9464 Show whether C@t{++} names in assembly listings are printed in mangled
9467 @cindex C@t{++} symbol decoding style
9468 @cindex symbol decoding style, C@t{++}
9469 @kindex set demangle-style
9470 @item set demangle-style @var{style}
9471 Choose among several encoding schemes used by different compilers to
9472 represent C@t{++} names. The choices for @var{style} are currently:
9476 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9477 This is the default.
9480 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9483 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9486 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9489 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9490 @strong{Warning:} this setting alone is not sufficient to allow
9491 debugging @code{cfront}-generated executables. @value{GDBN} would
9492 require further enhancement to permit that.
9495 If you omit @var{style}, you will see a list of possible formats.
9497 @item show demangle-style
9498 Display the encoding style currently in use for decoding C@t{++} symbols.
9500 @item set print object
9501 @itemx set print object on
9502 @cindex derived type of an object, printing
9503 @cindex display derived types
9504 When displaying a pointer to an object, identify the @emph{actual}
9505 (derived) type of the object rather than the @emph{declared} type, using
9506 the virtual function table. Note that the virtual function table is
9507 required---this feature can only work for objects that have run-time
9508 type identification; a single virtual method in the object's declared
9509 type is sufficient. Note that this setting is also taken into account when
9510 working with variable objects via MI (@pxref{GDB/MI}).
9512 @item set print object off
9513 Display only the declared type of objects, without reference to the
9514 virtual function table. This is the default setting.
9516 @item show print object
9517 Show whether actual, or declared, object types are displayed.
9519 @item set print static-members
9520 @itemx set print static-members on
9521 @cindex static members of C@t{++} objects
9522 Print static members when displaying a C@t{++} object. The default is on.
9524 @item set print static-members off
9525 Do not print static members when displaying a C@t{++} object.
9527 @item show print static-members
9528 Show whether C@t{++} static members are printed or not.
9530 @item set print pascal_static-members
9531 @itemx set print pascal_static-members on
9532 @cindex static members of Pascal objects
9533 @cindex Pascal objects, static members display
9534 Print static members when displaying a Pascal object. The default is on.
9536 @item set print pascal_static-members off
9537 Do not print static members when displaying a Pascal object.
9539 @item show print pascal_static-members
9540 Show whether Pascal static members are printed or not.
9542 @c These don't work with HP ANSI C++ yet.
9543 @item set print vtbl
9544 @itemx set print vtbl on
9545 @cindex pretty print C@t{++} virtual function tables
9546 @cindex virtual functions (C@t{++}) display
9547 @cindex VTBL display
9548 Pretty print C@t{++} virtual function tables. The default is off.
9549 (The @code{vtbl} commands do not work on programs compiled with the HP
9550 ANSI C@t{++} compiler (@code{aCC}).)
9552 @item set print vtbl off
9553 Do not pretty print C@t{++} virtual function tables.
9555 @item show print vtbl
9556 Show whether C@t{++} virtual function tables are pretty printed, or not.
9559 @node Pretty Printing
9560 @section Pretty Printing
9562 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9563 Python code. It greatly simplifies the display of complex objects. This
9564 mechanism works for both MI and the CLI.
9567 * Pretty-Printer Introduction:: Introduction to pretty-printers
9568 * Pretty-Printer Example:: An example pretty-printer
9569 * Pretty-Printer Commands:: Pretty-printer commands
9572 @node Pretty-Printer Introduction
9573 @subsection Pretty-Printer Introduction
9575 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9576 registered for the value. If there is then @value{GDBN} invokes the
9577 pretty-printer to print the value. Otherwise the value is printed normally.
9579 Pretty-printers are normally named. This makes them easy to manage.
9580 The @samp{info pretty-printer} command will list all the installed
9581 pretty-printers with their names.
9582 If a pretty-printer can handle multiple data types, then its
9583 @dfn{subprinters} are the printers for the individual data types.
9584 Each such subprinter has its own name.
9585 The format of the name is @var{printer-name};@var{subprinter-name}.
9587 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9588 Typically they are automatically loaded and registered when the corresponding
9589 debug information is loaded, thus making them available without having to
9590 do anything special.
9592 There are three places where a pretty-printer can be registered.
9596 Pretty-printers registered globally are available when debugging
9600 Pretty-printers registered with a program space are available only
9601 when debugging that program.
9602 @xref{Progspaces In Python}, for more details on program spaces in Python.
9605 Pretty-printers registered with an objfile are loaded and unloaded
9606 with the corresponding objfile (e.g., shared library).
9607 @xref{Objfiles In Python}, for more details on objfiles in Python.
9610 @xref{Selecting Pretty-Printers}, for further information on how
9611 pretty-printers are selected,
9613 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9616 @node Pretty-Printer Example
9617 @subsection Pretty-Printer Example
9619 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9622 (@value{GDBP}) print s
9624 static npos = 4294967295,
9626 <std::allocator<char>> = @{
9627 <__gnu_cxx::new_allocator<char>> = @{
9628 <No data fields>@}, <No data fields>
9630 members of std::basic_string<char, std::char_traits<char>,
9631 std::allocator<char> >::_Alloc_hider:
9632 _M_p = 0x804a014 "abcd"
9637 With a pretty-printer for @code{std::string} only the contents are printed:
9640 (@value{GDBP}) print s
9644 @node Pretty-Printer Commands
9645 @subsection Pretty-Printer Commands
9646 @cindex pretty-printer commands
9649 @kindex info pretty-printer
9650 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9651 Print the list of installed pretty-printers.
9652 This includes disabled pretty-printers, which are marked as such.
9654 @var{object-regexp} is a regular expression matching the objects
9655 whose pretty-printers to list.
9656 Objects can be @code{global}, the program space's file
9657 (@pxref{Progspaces In Python}),
9658 and the object files within that program space (@pxref{Objfiles In Python}).
9659 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9660 looks up a printer from these three objects.
9662 @var{name-regexp} is a regular expression matching the name of the printers
9665 @kindex disable pretty-printer
9666 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9667 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9668 A disabled pretty-printer is not forgotten, it may be enabled again later.
9670 @kindex enable pretty-printer
9671 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9672 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9677 Suppose we have three pretty-printers installed: one from library1.so
9678 named @code{foo} that prints objects of type @code{foo}, and
9679 another from library2.so named @code{bar} that prints two types of objects,
9680 @code{bar1} and @code{bar2}.
9683 (gdb) info pretty-printer
9690 (gdb) info pretty-printer library2
9695 (gdb) disable pretty-printer library1
9697 2 of 3 printers enabled
9698 (gdb) info pretty-printer
9705 (gdb) disable pretty-printer library2 bar:bar1
9707 1 of 3 printers enabled
9708 (gdb) info pretty-printer library2
9715 (gdb) disable pretty-printer library2 bar
9717 0 of 3 printers enabled
9718 (gdb) info pretty-printer library2
9727 Note that for @code{bar} the entire printer can be disabled,
9728 as can each individual subprinter.
9731 @section Value History
9733 @cindex value history
9734 @cindex history of values printed by @value{GDBN}
9735 Values printed by the @code{print} command are saved in the @value{GDBN}
9736 @dfn{value history}. This allows you to refer to them in other expressions.
9737 Values are kept until the symbol table is re-read or discarded
9738 (for example with the @code{file} or @code{symbol-file} commands).
9739 When the symbol table changes, the value history is discarded,
9740 since the values may contain pointers back to the types defined in the
9745 @cindex history number
9746 The values printed are given @dfn{history numbers} by which you can
9747 refer to them. These are successive integers starting with one.
9748 @code{print} shows you the history number assigned to a value by
9749 printing @samp{$@var{num} = } before the value; here @var{num} is the
9752 To refer to any previous value, use @samp{$} followed by the value's
9753 history number. The way @code{print} labels its output is designed to
9754 remind you of this. Just @code{$} refers to the most recent value in
9755 the history, and @code{$$} refers to the value before that.
9756 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9757 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9758 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9760 For example, suppose you have just printed a pointer to a structure and
9761 want to see the contents of the structure. It suffices to type
9767 If you have a chain of structures where the component @code{next} points
9768 to the next one, you can print the contents of the next one with this:
9775 You can print successive links in the chain by repeating this
9776 command---which you can do by just typing @key{RET}.
9778 Note that the history records values, not expressions. If the value of
9779 @code{x} is 4 and you type these commands:
9787 then the value recorded in the value history by the @code{print} command
9788 remains 4 even though the value of @code{x} has changed.
9793 Print the last ten values in the value history, with their item numbers.
9794 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9795 values} does not change the history.
9797 @item show values @var{n}
9798 Print ten history values centered on history item number @var{n}.
9801 Print ten history values just after the values last printed. If no more
9802 values are available, @code{show values +} produces no display.
9805 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9806 same effect as @samp{show values +}.
9808 @node Convenience Vars
9809 @section Convenience Variables
9811 @cindex convenience variables
9812 @cindex user-defined variables
9813 @value{GDBN} provides @dfn{convenience variables} that you can use within
9814 @value{GDBN} to hold on to a value and refer to it later. These variables
9815 exist entirely within @value{GDBN}; they are not part of your program, and
9816 setting a convenience variable has no direct effect on further execution
9817 of your program. That is why you can use them freely.
9819 Convenience variables are prefixed with @samp{$}. Any name preceded by
9820 @samp{$} can be used for a convenience variable, unless it is one of
9821 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9822 (Value history references, in contrast, are @emph{numbers} preceded
9823 by @samp{$}. @xref{Value History, ,Value History}.)
9825 You can save a value in a convenience variable with an assignment
9826 expression, just as you would set a variable in your program.
9830 set $foo = *object_ptr
9834 would save in @code{$foo} the value contained in the object pointed to by
9837 Using a convenience variable for the first time creates it, but its
9838 value is @code{void} until you assign a new value. You can alter the
9839 value with another assignment at any time.
9841 Convenience variables have no fixed types. You can assign a convenience
9842 variable any type of value, including structures and arrays, even if
9843 that variable already has a value of a different type. The convenience
9844 variable, when used as an expression, has the type of its current value.
9847 @kindex show convenience
9848 @cindex show all user variables and functions
9849 @item show convenience
9850 Print a list of convenience variables used so far, and their values,
9851 as well as a list of the convenience functions.
9852 Abbreviated @code{show conv}.
9854 @kindex init-if-undefined
9855 @cindex convenience variables, initializing
9856 @item init-if-undefined $@var{variable} = @var{expression}
9857 Set a convenience variable if it has not already been set. This is useful
9858 for user-defined commands that keep some state. It is similar, in concept,
9859 to using local static variables with initializers in C (except that
9860 convenience variables are global). It can also be used to allow users to
9861 override default values used in a command script.
9863 If the variable is already defined then the expression is not evaluated so
9864 any side-effects do not occur.
9867 One of the ways to use a convenience variable is as a counter to be
9868 incremented or a pointer to be advanced. For example, to print
9869 a field from successive elements of an array of structures:
9873 print bar[$i++]->contents
9877 Repeat that command by typing @key{RET}.
9879 Some convenience variables are created automatically by @value{GDBN} and given
9880 values likely to be useful.
9883 @vindex $_@r{, convenience variable}
9885 The variable @code{$_} is automatically set by the @code{x} command to
9886 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9887 commands which provide a default address for @code{x} to examine also
9888 set @code{$_} to that address; these commands include @code{info line}
9889 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9890 except when set by the @code{x} command, in which case it is a pointer
9891 to the type of @code{$__}.
9893 @vindex $__@r{, convenience variable}
9895 The variable @code{$__} is automatically set by the @code{x} command
9896 to the value found in the last address examined. Its type is chosen
9897 to match the format in which the data was printed.
9900 @vindex $_exitcode@r{, convenience variable}
9901 When the program being debugged terminates normally, @value{GDBN}
9902 automatically sets this variable to the exit code of the program, and
9903 resets @code{$_exitsignal} to @code{void}.
9906 @vindex $_exitsignal@r{, convenience variable}
9907 When the program being debugged dies due to an uncaught signal,
9908 @value{GDBN} automatically sets this variable to that signal's number,
9909 and resets @code{$_exitcode} to @code{void}.
9911 To distinguish between whether the program being debugged has exited
9912 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9913 @code{$_exitsignal} is not @code{void}), the convenience function
9914 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9915 Functions}). For example, considering the following source code:
9921 main (int argc, char *argv[])
9928 A valid way of telling whether the program being debugged has exited
9929 or signalled would be:
9932 (@value{GDBP}) define has_exited_or_signalled
9933 Type commands for definition of ``has_exited_or_signalled''.
9934 End with a line saying just ``end''.
9935 >if $_isvoid ($_exitsignal)
9936 >echo The program has exited\n
9938 >echo The program has signalled\n
9944 Program terminated with signal SIGALRM, Alarm clock.
9945 The program no longer exists.
9946 (@value{GDBP}) has_exited_or_signalled
9947 The program has signalled
9950 As can be seen, @value{GDBN} correctly informs that the program being
9951 debugged has signalled, since it calls @code{raise} and raises a
9952 @code{SIGALRM} signal. If the program being debugged had not called
9953 @code{raise}, then @value{GDBN} would report a normal exit:
9956 (@value{GDBP}) has_exited_or_signalled
9957 The program has exited
9961 The variable @code{$_exception} is set to the exception object being
9962 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9965 @itemx $_probe_arg0@dots{}$_probe_arg11
9966 Arguments to a static probe. @xref{Static Probe Points}.
9969 @vindex $_sdata@r{, inspect, convenience variable}
9970 The variable @code{$_sdata} contains extra collected static tracepoint
9971 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9972 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9973 if extra static tracepoint data has not been collected.
9976 @vindex $_siginfo@r{, convenience variable}
9977 The variable @code{$_siginfo} contains extra signal information
9978 (@pxref{extra signal information}). Note that @code{$_siginfo}
9979 could be empty, if the application has not yet received any signals.
9980 For example, it will be empty before you execute the @code{run} command.
9983 @vindex $_tlb@r{, convenience variable}
9984 The variable @code{$_tlb} is automatically set when debugging
9985 applications running on MS-Windows in native mode or connected to
9986 gdbserver that supports the @code{qGetTIBAddr} request.
9987 @xref{General Query Packets}.
9988 This variable contains the address of the thread information block.
9992 On HP-UX systems, if you refer to a function or variable name that
9993 begins with a dollar sign, @value{GDBN} searches for a user or system
9994 name first, before it searches for a convenience variable.
9996 @node Convenience Funs
9997 @section Convenience Functions
9999 @cindex convenience functions
10000 @value{GDBN} also supplies some @dfn{convenience functions}. These
10001 have a syntax similar to convenience variables. A convenience
10002 function can be used in an expression just like an ordinary function;
10003 however, a convenience function is implemented internally to
10006 These functions do not require @value{GDBN} to be configured with
10007 @code{Python} support, which means that they are always available.
10011 @item $_isvoid (@var{expr})
10012 @findex $_isvoid@r{, convenience function}
10013 Return one if the expression @var{expr} is @code{void}. Otherwise it
10016 A @code{void} expression is an expression where the type of the result
10017 is @code{void}. For example, you can examine a convenience variable
10018 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10022 (@value{GDBP}) print $_exitcode
10024 (@value{GDBP}) print $_isvoid ($_exitcode)
10027 Starting program: ./a.out
10028 [Inferior 1 (process 29572) exited normally]
10029 (@value{GDBP}) print $_exitcode
10031 (@value{GDBP}) print $_isvoid ($_exitcode)
10035 In the example above, we used @code{$_isvoid} to check whether
10036 @code{$_exitcode} is @code{void} before and after the execution of the
10037 program being debugged. Before the execution there is no exit code to
10038 be examined, therefore @code{$_exitcode} is @code{void}. After the
10039 execution the program being debugged returned zero, therefore
10040 @code{$_exitcode} is zero, which means that it is not @code{void}
10043 The @code{void} expression can also be a call of a function from the
10044 program being debugged. For example, given the following function:
10053 The result of calling it inside @value{GDBN} is @code{void}:
10056 (@value{GDBP}) print foo ()
10058 (@value{GDBP}) print $_isvoid (foo ())
10060 (@value{GDBP}) set $v = foo ()
10061 (@value{GDBP}) print $v
10063 (@value{GDBP}) print $_isvoid ($v)
10069 These functions require @value{GDBN} to be configured with
10070 @code{Python} support.
10074 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10075 @findex $_memeq@r{, convenience function}
10076 Returns one if the @var{length} bytes at the addresses given by
10077 @var{buf1} and @var{buf2} are equal.
10078 Otherwise it returns zero.
10080 @item $_regex(@var{str}, @var{regex})
10081 @findex $_regex@r{, convenience function}
10082 Returns one if the string @var{str} matches the regular expression
10083 @var{regex}. Otherwise it returns zero.
10084 The syntax of the regular expression is that specified by @code{Python}'s
10085 regular expression support.
10087 @item $_streq(@var{str1}, @var{str2})
10088 @findex $_streq@r{, convenience function}
10089 Returns one if the strings @var{str1} and @var{str2} are equal.
10090 Otherwise it returns zero.
10092 @item $_strlen(@var{str})
10093 @findex $_strlen@r{, convenience function}
10094 Returns the length of string @var{str}.
10098 @value{GDBN} provides the ability to list and get help on
10099 convenience functions.
10102 @item help function
10103 @kindex help function
10104 @cindex show all convenience functions
10105 Print a list of all convenience functions.
10112 You can refer to machine register contents, in expressions, as variables
10113 with names starting with @samp{$}. The names of registers are different
10114 for each machine; use @code{info registers} to see the names used on
10118 @kindex info registers
10119 @item info registers
10120 Print the names and values of all registers except floating-point
10121 and vector registers (in the selected stack frame).
10123 @kindex info all-registers
10124 @cindex floating point registers
10125 @item info all-registers
10126 Print the names and values of all registers, including floating-point
10127 and vector registers (in the selected stack frame).
10129 @item info registers @var{regname} @dots{}
10130 Print the @dfn{relativized} value of each specified register @var{regname}.
10131 As discussed in detail below, register values are normally relative to
10132 the selected stack frame. @var{regname} may be any register name valid on
10133 the machine you are using, with or without the initial @samp{$}.
10136 @cindex stack pointer register
10137 @cindex program counter register
10138 @cindex process status register
10139 @cindex frame pointer register
10140 @cindex standard registers
10141 @value{GDBN} has four ``standard'' register names that are available (in
10142 expressions) on most machines---whenever they do not conflict with an
10143 architecture's canonical mnemonics for registers. The register names
10144 @code{$pc} and @code{$sp} are used for the program counter register and
10145 the stack pointer. @code{$fp} is used for a register that contains a
10146 pointer to the current stack frame, and @code{$ps} is used for a
10147 register that contains the processor status. For example,
10148 you could print the program counter in hex with
10155 or print the instruction to be executed next with
10162 or add four to the stack pointer@footnote{This is a way of removing
10163 one word from the stack, on machines where stacks grow downward in
10164 memory (most machines, nowadays). This assumes that the innermost
10165 stack frame is selected; setting @code{$sp} is not allowed when other
10166 stack frames are selected. To pop entire frames off the stack,
10167 regardless of machine architecture, use @code{return};
10168 see @ref{Returning, ,Returning from a Function}.} with
10174 Whenever possible, these four standard register names are available on
10175 your machine even though the machine has different canonical mnemonics,
10176 so long as there is no conflict. The @code{info registers} command
10177 shows the canonical names. For example, on the SPARC, @code{info
10178 registers} displays the processor status register as @code{$psr} but you
10179 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10180 is an alias for the @sc{eflags} register.
10182 @value{GDBN} always considers the contents of an ordinary register as an
10183 integer when the register is examined in this way. Some machines have
10184 special registers which can hold nothing but floating point; these
10185 registers are considered to have floating point values. There is no way
10186 to refer to the contents of an ordinary register as floating point value
10187 (although you can @emph{print} it as a floating point value with
10188 @samp{print/f $@var{regname}}).
10190 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10191 means that the data format in which the register contents are saved by
10192 the operating system is not the same one that your program normally
10193 sees. For example, the registers of the 68881 floating point
10194 coprocessor are always saved in ``extended'' (raw) format, but all C
10195 programs expect to work with ``double'' (virtual) format. In such
10196 cases, @value{GDBN} normally works with the virtual format only (the format
10197 that makes sense for your program), but the @code{info registers} command
10198 prints the data in both formats.
10200 @cindex SSE registers (x86)
10201 @cindex MMX registers (x86)
10202 Some machines have special registers whose contents can be interpreted
10203 in several different ways. For example, modern x86-based machines
10204 have SSE and MMX registers that can hold several values packed
10205 together in several different formats. @value{GDBN} refers to such
10206 registers in @code{struct} notation:
10209 (@value{GDBP}) print $xmm1
10211 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10212 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10213 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10214 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10215 v4_int32 = @{0, 20657912, 11, 13@},
10216 v2_int64 = @{88725056443645952, 55834574859@},
10217 uint128 = 0x0000000d0000000b013b36f800000000
10222 To set values of such registers, you need to tell @value{GDBN} which
10223 view of the register you wish to change, as if you were assigning
10224 value to a @code{struct} member:
10227 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10230 Normally, register values are relative to the selected stack frame
10231 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10232 value that the register would contain if all stack frames farther in
10233 were exited and their saved registers restored. In order to see the
10234 true contents of hardware registers, you must select the innermost
10235 frame (with @samp{frame 0}).
10237 @cindex caller-saved registers
10238 @cindex call-clobbered registers
10239 @cindex volatile registers
10240 @cindex <not saved> values
10241 Usually ABIs reserve some registers as not needed to be saved by the
10242 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10243 registers). It may therefore not be possible for @value{GDBN} to know
10244 the value a register had before the call (in other words, in the outer
10245 frame), if the register value has since been changed by the callee.
10246 @value{GDBN} tries to deduce where the inner frame saved
10247 (``callee-saved'') registers, from the debug info, unwind info, or the
10248 machine code generated by your compiler. If some register is not
10249 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10250 its own knowledge of the ABI, or because the debug/unwind info
10251 explicitly says the register's value is undefined), @value{GDBN}
10252 displays @w{@samp{<not saved>}} as the register's value. With targets
10253 that @value{GDBN} has no knowledge of the register saving convention,
10254 if a register was not saved by the callee, then its value and location
10255 in the outer frame are assumed to be the same of the inner frame.
10256 This is usually harmless, because if the register is call-clobbered,
10257 the caller either does not care what is in the register after the
10258 call, or has code to restore the value that it does care about. Note,
10259 however, that if you change such a register in the outer frame, you
10260 may also be affecting the inner frame. Also, the more ``outer'' the
10261 frame is you're looking at, the more likely a call-clobbered
10262 register's value is to be wrong, in the sense that it doesn't actually
10263 represent the value the register had just before the call.
10265 @node Floating Point Hardware
10266 @section Floating Point Hardware
10267 @cindex floating point
10269 Depending on the configuration, @value{GDBN} may be able to give
10270 you more information about the status of the floating point hardware.
10275 Display hardware-dependent information about the floating
10276 point unit. The exact contents and layout vary depending on the
10277 floating point chip. Currently, @samp{info float} is supported on
10278 the ARM and x86 machines.
10282 @section Vector Unit
10283 @cindex vector unit
10285 Depending on the configuration, @value{GDBN} may be able to give you
10286 more information about the status of the vector unit.
10289 @kindex info vector
10291 Display information about the vector unit. The exact contents and
10292 layout vary depending on the hardware.
10295 @node OS Information
10296 @section Operating System Auxiliary Information
10297 @cindex OS information
10299 @value{GDBN} provides interfaces to useful OS facilities that can help
10300 you debug your program.
10302 @cindex auxiliary vector
10303 @cindex vector, auxiliary
10304 Some operating systems supply an @dfn{auxiliary vector} to programs at
10305 startup. This is akin to the arguments and environment that you
10306 specify for a program, but contains a system-dependent variety of
10307 binary values that tell system libraries important details about the
10308 hardware, operating system, and process. Each value's purpose is
10309 identified by an integer tag; the meanings are well-known but system-specific.
10310 Depending on the configuration and operating system facilities,
10311 @value{GDBN} may be able to show you this information. For remote
10312 targets, this functionality may further depend on the remote stub's
10313 support of the @samp{qXfer:auxv:read} packet, see
10314 @ref{qXfer auxiliary vector read}.
10319 Display the auxiliary vector of the inferior, which can be either a
10320 live process or a core dump file. @value{GDBN} prints each tag value
10321 numerically, and also shows names and text descriptions for recognized
10322 tags. Some values in the vector are numbers, some bit masks, and some
10323 pointers to strings or other data. @value{GDBN} displays each value in the
10324 most appropriate form for a recognized tag, and in hexadecimal for
10325 an unrecognized tag.
10328 On some targets, @value{GDBN} can access operating system-specific
10329 information and show it to you. The types of information available
10330 will differ depending on the type of operating system running on the
10331 target. The mechanism used to fetch the data is described in
10332 @ref{Operating System Information}. For remote targets, this
10333 functionality depends on the remote stub's support of the
10334 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10338 @item info os @var{infotype}
10340 Display OS information of the requested type.
10342 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10344 @anchor{linux info os infotypes}
10346 @kindex info os processes
10348 Display the list of processes on the target. For each process,
10349 @value{GDBN} prints the process identifier, the name of the user, the
10350 command corresponding to the process, and the list of processor cores
10351 that the process is currently running on. (To understand what these
10352 properties mean, for this and the following info types, please consult
10353 the general @sc{gnu}/Linux documentation.)
10355 @kindex info os procgroups
10357 Display the list of process groups on the target. For each process,
10358 @value{GDBN} prints the identifier of the process group that it belongs
10359 to, the command corresponding to the process group leader, the process
10360 identifier, and the command line of the process. The list is sorted
10361 first by the process group identifier, then by the process identifier,
10362 so that processes belonging to the same process group are grouped together
10363 and the process group leader is listed first.
10365 @kindex info os threads
10367 Display the list of threads running on the target. For each thread,
10368 @value{GDBN} prints the identifier of the process that the thread
10369 belongs to, the command of the process, the thread identifier, and the
10370 processor core that it is currently running on. The main thread of a
10371 process is not listed.
10373 @kindex info os files
10375 Display the list of open file descriptors on the target. For each
10376 file descriptor, @value{GDBN} prints the identifier of the process
10377 owning the descriptor, the command of the owning process, the value
10378 of the descriptor, and the target of the descriptor.
10380 @kindex info os sockets
10382 Display the list of Internet-domain sockets on the target. For each
10383 socket, @value{GDBN} prints the address and port of the local and
10384 remote endpoints, the current state of the connection, the creator of
10385 the socket, the IP address family of the socket, and the type of the
10388 @kindex info os shm
10390 Display the list of all System V shared-memory regions on the target.
10391 For each shared-memory region, @value{GDBN} prints the region key,
10392 the shared-memory identifier, the access permissions, the size of the
10393 region, the process that created the region, the process that last
10394 attached to or detached from the region, the current number of live
10395 attaches to the region, and the times at which the region was last
10396 attached to, detach from, and changed.
10398 @kindex info os semaphores
10400 Display the list of all System V semaphore sets on the target. For each
10401 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10402 set identifier, the access permissions, the number of semaphores in the
10403 set, the user and group of the owner and creator of the semaphore set,
10404 and the times at which the semaphore set was operated upon and changed.
10406 @kindex info os msg
10408 Display the list of all System V message queues on the target. For each
10409 message queue, @value{GDBN} prints the message queue key, the message
10410 queue identifier, the access permissions, the current number of bytes
10411 on the queue, the current number of messages on the queue, the processes
10412 that last sent and received a message on the queue, the user and group
10413 of the owner and creator of the message queue, the times at which a
10414 message was last sent and received on the queue, and the time at which
10415 the message queue was last changed.
10417 @kindex info os modules
10419 Display the list of all loaded kernel modules on the target. For each
10420 module, @value{GDBN} prints the module name, the size of the module in
10421 bytes, the number of times the module is used, the dependencies of the
10422 module, the status of the module, and the address of the loaded module
10427 If @var{infotype} is omitted, then list the possible values for
10428 @var{infotype} and the kind of OS information available for each
10429 @var{infotype}. If the target does not return a list of possible
10430 types, this command will report an error.
10433 @node Memory Region Attributes
10434 @section Memory Region Attributes
10435 @cindex memory region attributes
10437 @dfn{Memory region attributes} allow you to describe special handling
10438 required by regions of your target's memory. @value{GDBN} uses
10439 attributes to determine whether to allow certain types of memory
10440 accesses; whether to use specific width accesses; and whether to cache
10441 target memory. By default the description of memory regions is
10442 fetched from the target (if the current target supports this), but the
10443 user can override the fetched regions.
10445 Defined memory regions can be individually enabled and disabled. When a
10446 memory region is disabled, @value{GDBN} uses the default attributes when
10447 accessing memory in that region. Similarly, if no memory regions have
10448 been defined, @value{GDBN} uses the default attributes when accessing
10451 When a memory region is defined, it is given a number to identify it;
10452 to enable, disable, or remove a memory region, you specify that number.
10456 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10457 Define a memory region bounded by @var{lower} and @var{upper} with
10458 attributes @var{attributes}@dots{}, and add it to the list of regions
10459 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10460 case: it is treated as the target's maximum memory address.
10461 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10464 Discard any user changes to the memory regions and use target-supplied
10465 regions, if available, or no regions if the target does not support.
10468 @item delete mem @var{nums}@dots{}
10469 Remove memory regions @var{nums}@dots{} from the list of regions
10470 monitored by @value{GDBN}.
10472 @kindex disable mem
10473 @item disable mem @var{nums}@dots{}
10474 Disable monitoring of memory regions @var{nums}@dots{}.
10475 A disabled memory region is not forgotten.
10476 It may be enabled again later.
10479 @item enable mem @var{nums}@dots{}
10480 Enable monitoring of memory regions @var{nums}@dots{}.
10484 Print a table of all defined memory regions, with the following columns
10488 @item Memory Region Number
10489 @item Enabled or Disabled.
10490 Enabled memory regions are marked with @samp{y}.
10491 Disabled memory regions are marked with @samp{n}.
10494 The address defining the inclusive lower bound of the memory region.
10497 The address defining the exclusive upper bound of the memory region.
10500 The list of attributes set for this memory region.
10505 @subsection Attributes
10507 @subsubsection Memory Access Mode
10508 The access mode attributes set whether @value{GDBN} may make read or
10509 write accesses to a memory region.
10511 While these attributes prevent @value{GDBN} from performing invalid
10512 memory accesses, they do nothing to prevent the target system, I/O DMA,
10513 etc.@: from accessing memory.
10517 Memory is read only.
10519 Memory is write only.
10521 Memory is read/write. This is the default.
10524 @subsubsection Memory Access Size
10525 The access size attribute tells @value{GDBN} to use specific sized
10526 accesses in the memory region. Often memory mapped device registers
10527 require specific sized accesses. If no access size attribute is
10528 specified, @value{GDBN} may use accesses of any size.
10532 Use 8 bit memory accesses.
10534 Use 16 bit memory accesses.
10536 Use 32 bit memory accesses.
10538 Use 64 bit memory accesses.
10541 @c @subsubsection Hardware/Software Breakpoints
10542 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10543 @c will use hardware or software breakpoints for the internal breakpoints
10544 @c used by the step, next, finish, until, etc. commands.
10548 @c Always use hardware breakpoints
10549 @c @item swbreak (default)
10552 @subsubsection Data Cache
10553 The data cache attributes set whether @value{GDBN} will cache target
10554 memory. While this generally improves performance by reducing debug
10555 protocol overhead, it can lead to incorrect results because @value{GDBN}
10556 does not know about volatile variables or memory mapped device
10561 Enable @value{GDBN} to cache target memory.
10563 Disable @value{GDBN} from caching target memory. This is the default.
10566 @subsection Memory Access Checking
10567 @value{GDBN} can be instructed to refuse accesses to memory that is
10568 not explicitly described. This can be useful if accessing such
10569 regions has undesired effects for a specific target, or to provide
10570 better error checking. The following commands control this behaviour.
10573 @kindex set mem inaccessible-by-default
10574 @item set mem inaccessible-by-default [on|off]
10575 If @code{on} is specified, make @value{GDBN} treat memory not
10576 explicitly described by the memory ranges as non-existent and refuse accesses
10577 to such memory. The checks are only performed if there's at least one
10578 memory range defined. If @code{off} is specified, make @value{GDBN}
10579 treat the memory not explicitly described by the memory ranges as RAM.
10580 The default value is @code{on}.
10581 @kindex show mem inaccessible-by-default
10582 @item show mem inaccessible-by-default
10583 Show the current handling of accesses to unknown memory.
10587 @c @subsubsection Memory Write Verification
10588 @c The memory write verification attributes set whether @value{GDBN}
10589 @c will re-reads data after each write to verify the write was successful.
10593 @c @item noverify (default)
10596 @node Dump/Restore Files
10597 @section Copy Between Memory and a File
10598 @cindex dump/restore files
10599 @cindex append data to a file
10600 @cindex dump data to a file
10601 @cindex restore data from a file
10603 You can use the commands @code{dump}, @code{append}, and
10604 @code{restore} to copy data between target memory and a file. The
10605 @code{dump} and @code{append} commands write data to a file, and the
10606 @code{restore} command reads data from a file back into the inferior's
10607 memory. Files may be in binary, Motorola S-record, Intel hex, or
10608 Tektronix Hex format; however, @value{GDBN} can only append to binary
10614 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10615 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10616 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10617 or the value of @var{expr}, to @var{filename} in the given format.
10619 The @var{format} parameter may be any one of:
10626 Motorola S-record format.
10628 Tektronix Hex format.
10631 @value{GDBN} uses the same definitions of these formats as the
10632 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10633 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10637 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10638 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10639 Append the contents of memory from @var{start_addr} to @var{end_addr},
10640 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10641 (@value{GDBN} can only append data to files in raw binary form.)
10644 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10645 Restore the contents of file @var{filename} into memory. The
10646 @code{restore} command can automatically recognize any known @sc{bfd}
10647 file format, except for raw binary. To restore a raw binary file you
10648 must specify the optional keyword @code{binary} after the filename.
10650 If @var{bias} is non-zero, its value will be added to the addresses
10651 contained in the file. Binary files always start at address zero, so
10652 they will be restored at address @var{bias}. Other bfd files have
10653 a built-in location; they will be restored at offset @var{bias}
10654 from that location.
10656 If @var{start} and/or @var{end} are non-zero, then only data between
10657 file offset @var{start} and file offset @var{end} will be restored.
10658 These offsets are relative to the addresses in the file, before
10659 the @var{bias} argument is applied.
10663 @node Core File Generation
10664 @section How to Produce a Core File from Your Program
10665 @cindex dump core from inferior
10667 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10668 image of a running process and its process status (register values
10669 etc.). Its primary use is post-mortem debugging of a program that
10670 crashed while it ran outside a debugger. A program that crashes
10671 automatically produces a core file, unless this feature is disabled by
10672 the user. @xref{Files}, for information on invoking @value{GDBN} in
10673 the post-mortem debugging mode.
10675 Occasionally, you may wish to produce a core file of the program you
10676 are debugging in order to preserve a snapshot of its state.
10677 @value{GDBN} has a special command for that.
10681 @kindex generate-core-file
10682 @item generate-core-file [@var{file}]
10683 @itemx gcore [@var{file}]
10684 Produce a core dump of the inferior process. The optional argument
10685 @var{file} specifies the file name where to put the core dump. If not
10686 specified, the file name defaults to @file{core.@var{pid}}, where
10687 @var{pid} is the inferior process ID.
10689 Note that this command is implemented only for some systems (as of
10690 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10693 @node Character Sets
10694 @section Character Sets
10695 @cindex character sets
10697 @cindex translating between character sets
10698 @cindex host character set
10699 @cindex target character set
10701 If the program you are debugging uses a different character set to
10702 represent characters and strings than the one @value{GDBN} uses itself,
10703 @value{GDBN} can automatically translate between the character sets for
10704 you. The character set @value{GDBN} uses we call the @dfn{host
10705 character set}; the one the inferior program uses we call the
10706 @dfn{target character set}.
10708 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10709 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10710 remote protocol (@pxref{Remote Debugging}) to debug a program
10711 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10712 then the host character set is Latin-1, and the target character set is
10713 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10714 target-charset EBCDIC-US}, then @value{GDBN} translates between
10715 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10716 character and string literals in expressions.
10718 @value{GDBN} has no way to automatically recognize which character set
10719 the inferior program uses; you must tell it, using the @code{set
10720 target-charset} command, described below.
10722 Here are the commands for controlling @value{GDBN}'s character set
10726 @item set target-charset @var{charset}
10727 @kindex set target-charset
10728 Set the current target character set to @var{charset}. To display the
10729 list of supported target character sets, type
10730 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10732 @item set host-charset @var{charset}
10733 @kindex set host-charset
10734 Set the current host character set to @var{charset}.
10736 By default, @value{GDBN} uses a host character set appropriate to the
10737 system it is running on; you can override that default using the
10738 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10739 automatically determine the appropriate host character set. In this
10740 case, @value{GDBN} uses @samp{UTF-8}.
10742 @value{GDBN} can only use certain character sets as its host character
10743 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10744 @value{GDBN} will list the host character sets it supports.
10746 @item set charset @var{charset}
10747 @kindex set charset
10748 Set the current host and target character sets to @var{charset}. As
10749 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10750 @value{GDBN} will list the names of the character sets that can be used
10751 for both host and target.
10754 @kindex show charset
10755 Show the names of the current host and target character sets.
10757 @item show host-charset
10758 @kindex show host-charset
10759 Show the name of the current host character set.
10761 @item show target-charset
10762 @kindex show target-charset
10763 Show the name of the current target character set.
10765 @item set target-wide-charset @var{charset}
10766 @kindex set target-wide-charset
10767 Set the current target's wide character set to @var{charset}. This is
10768 the character set used by the target's @code{wchar_t} type. To
10769 display the list of supported wide character sets, type
10770 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10772 @item show target-wide-charset
10773 @kindex show target-wide-charset
10774 Show the name of the current target's wide character set.
10777 Here is an example of @value{GDBN}'s character set support in action.
10778 Assume that the following source code has been placed in the file
10779 @file{charset-test.c}:
10785 = @{72, 101, 108, 108, 111, 44, 32, 119,
10786 111, 114, 108, 100, 33, 10, 0@};
10787 char ibm1047_hello[]
10788 = @{200, 133, 147, 147, 150, 107, 64, 166,
10789 150, 153, 147, 132, 90, 37, 0@};
10793 printf ("Hello, world!\n");
10797 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10798 containing the string @samp{Hello, world!} followed by a newline,
10799 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10801 We compile the program, and invoke the debugger on it:
10804 $ gcc -g charset-test.c -o charset-test
10805 $ gdb -nw charset-test
10806 GNU gdb 2001-12-19-cvs
10807 Copyright 2001 Free Software Foundation, Inc.
10812 We can use the @code{show charset} command to see what character sets
10813 @value{GDBN} is currently using to interpret and display characters and
10817 (@value{GDBP}) show charset
10818 The current host and target character set is `ISO-8859-1'.
10822 For the sake of printing this manual, let's use @sc{ascii} as our
10823 initial character set:
10825 (@value{GDBP}) set charset ASCII
10826 (@value{GDBP}) show charset
10827 The current host and target character set is `ASCII'.
10831 Let's assume that @sc{ascii} is indeed the correct character set for our
10832 host system --- in other words, let's assume that if @value{GDBN} prints
10833 characters using the @sc{ascii} character set, our terminal will display
10834 them properly. Since our current target character set is also
10835 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10838 (@value{GDBP}) print ascii_hello
10839 $1 = 0x401698 "Hello, world!\n"
10840 (@value{GDBP}) print ascii_hello[0]
10845 @value{GDBN} uses the target character set for character and string
10846 literals you use in expressions:
10849 (@value{GDBP}) print '+'
10854 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10857 @value{GDBN} relies on the user to tell it which character set the
10858 target program uses. If we print @code{ibm1047_hello} while our target
10859 character set is still @sc{ascii}, we get jibberish:
10862 (@value{GDBP}) print ibm1047_hello
10863 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10864 (@value{GDBP}) print ibm1047_hello[0]
10869 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10870 @value{GDBN} tells us the character sets it supports:
10873 (@value{GDBP}) set target-charset
10874 ASCII EBCDIC-US IBM1047 ISO-8859-1
10875 (@value{GDBP}) set target-charset
10878 We can select @sc{ibm1047} as our target character set, and examine the
10879 program's strings again. Now the @sc{ascii} string is wrong, but
10880 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10881 target character set, @sc{ibm1047}, to the host character set,
10882 @sc{ascii}, and they display correctly:
10885 (@value{GDBP}) set target-charset IBM1047
10886 (@value{GDBP}) show charset
10887 The current host character set is `ASCII'.
10888 The current target character set is `IBM1047'.
10889 (@value{GDBP}) print ascii_hello
10890 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10891 (@value{GDBP}) print ascii_hello[0]
10893 (@value{GDBP}) print ibm1047_hello
10894 $8 = 0x4016a8 "Hello, world!\n"
10895 (@value{GDBP}) print ibm1047_hello[0]
10900 As above, @value{GDBN} uses the target character set for character and
10901 string literals you use in expressions:
10904 (@value{GDBP}) print '+'
10909 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10912 @node Caching Target Data
10913 @section Caching Data of Targets
10914 @cindex caching data of targets
10916 @value{GDBN} caches data exchanged between the debugger and a target.
10917 Each cache is associated with the address space of the inferior.
10918 @xref{Inferiors and Programs}, about inferior and address space.
10919 Such caching generally improves performance in remote debugging
10920 (@pxref{Remote Debugging}), because it reduces the overhead of the
10921 remote protocol by bundling memory reads and writes into large chunks.
10922 Unfortunately, simply caching everything would lead to incorrect results,
10923 since @value{GDBN} does not necessarily know anything about volatile
10924 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
10925 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
10927 Therefore, by default, @value{GDBN} only caches data
10928 known to be on the stack@footnote{In non-stop mode, it is moderately
10929 rare for a running thread to modify the stack of a stopped thread
10930 in a way that would interfere with a backtrace, and caching of
10931 stack reads provides a significant speed up of remote backtraces.} or
10932 in the code segment.
10933 Other regions of memory can be explicitly marked as
10934 cacheable; @pxref{Memory Region Attributes}.
10937 @kindex set remotecache
10938 @item set remotecache on
10939 @itemx set remotecache off
10940 This option no longer does anything; it exists for compatibility
10943 @kindex show remotecache
10944 @item show remotecache
10945 Show the current state of the obsolete remotecache flag.
10947 @kindex set stack-cache
10948 @item set stack-cache on
10949 @itemx set stack-cache off
10950 Enable or disable caching of stack accesses. When @code{on}, use
10951 caching. By default, this option is @code{on}.
10953 @kindex show stack-cache
10954 @item show stack-cache
10955 Show the current state of data caching for memory accesses.
10957 @kindex set code-cache
10958 @item set code-cache on
10959 @itemx set code-cache off
10960 Enable or disable caching of code segment accesses. When @code{on},
10961 use caching. By default, this option is @code{on}. This improves
10962 performance of disassembly in remote debugging.
10964 @kindex show code-cache
10965 @item show code-cache
10966 Show the current state of target memory cache for code segment
10969 @kindex info dcache
10970 @item info dcache @r{[}line@r{]}
10971 Print the information about the performance of data cache of the
10972 current inferior's address space. The information displayed
10973 includes the dcache width and depth, and for each cache line, its
10974 number, address, and how many times it was referenced. This
10975 command is useful for debugging the data cache operation.
10977 If a line number is specified, the contents of that line will be
10980 @item set dcache size @var{size}
10981 @cindex dcache size
10982 @kindex set dcache size
10983 Set maximum number of entries in dcache (dcache depth above).
10985 @item set dcache line-size @var{line-size}
10986 @cindex dcache line-size
10987 @kindex set dcache line-size
10988 Set number of bytes each dcache entry caches (dcache width above).
10989 Must be a power of 2.
10991 @item show dcache size
10992 @kindex show dcache size
10993 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
10995 @item show dcache line-size
10996 @kindex show dcache line-size
10997 Show default size of dcache lines.
11001 @node Searching Memory
11002 @section Search Memory
11003 @cindex searching memory
11005 Memory can be searched for a particular sequence of bytes with the
11006 @code{find} command.
11010 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11011 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11012 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11013 etc. The search begins at address @var{start_addr} and continues for either
11014 @var{len} bytes or through to @var{end_addr} inclusive.
11017 @var{s} and @var{n} are optional parameters.
11018 They may be specified in either order, apart or together.
11021 @item @var{s}, search query size
11022 The size of each search query value.
11028 halfwords (two bytes)
11032 giant words (eight bytes)
11035 All values are interpreted in the current language.
11036 This means, for example, that if the current source language is C/C@t{++}
11037 then searching for the string ``hello'' includes the trailing '\0'.
11039 If the value size is not specified, it is taken from the
11040 value's type in the current language.
11041 This is useful when one wants to specify the search
11042 pattern as a mixture of types.
11043 Note that this means, for example, that in the case of C-like languages
11044 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11045 which is typically four bytes.
11047 @item @var{n}, maximum number of finds
11048 The maximum number of matches to print. The default is to print all finds.
11051 You can use strings as search values. Quote them with double-quotes
11053 The string value is copied into the search pattern byte by byte,
11054 regardless of the endianness of the target and the size specification.
11056 The address of each match found is printed as well as a count of the
11057 number of matches found.
11059 The address of the last value found is stored in convenience variable
11061 A count of the number of matches is stored in @samp{$numfound}.
11063 For example, if stopped at the @code{printf} in this function:
11069 static char hello[] = "hello-hello";
11070 static struct @{ char c; short s; int i; @}
11071 __attribute__ ((packed)) mixed
11072 = @{ 'c', 0x1234, 0x87654321 @};
11073 printf ("%s\n", hello);
11078 you get during debugging:
11081 (gdb) find &hello[0], +sizeof(hello), "hello"
11082 0x804956d <hello.1620+6>
11084 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11085 0x8049567 <hello.1620>
11086 0x804956d <hello.1620+6>
11088 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11089 0x8049567 <hello.1620>
11091 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11092 0x8049560 <mixed.1625>
11094 (gdb) print $numfound
11097 $2 = (void *) 0x8049560
11100 @node Optimized Code
11101 @chapter Debugging Optimized Code
11102 @cindex optimized code, debugging
11103 @cindex debugging optimized code
11105 Almost all compilers support optimization. With optimization
11106 disabled, the compiler generates assembly code that corresponds
11107 directly to your source code, in a simplistic way. As the compiler
11108 applies more powerful optimizations, the generated assembly code
11109 diverges from your original source code. With help from debugging
11110 information generated by the compiler, @value{GDBN} can map from
11111 the running program back to constructs from your original source.
11113 @value{GDBN} is more accurate with optimization disabled. If you
11114 can recompile without optimization, it is easier to follow the
11115 progress of your program during debugging. But, there are many cases
11116 where you may need to debug an optimized version.
11118 When you debug a program compiled with @samp{-g -O}, remember that the
11119 optimizer has rearranged your code; the debugger shows you what is
11120 really there. Do not be too surprised when the execution path does not
11121 exactly match your source file! An extreme example: if you define a
11122 variable, but never use it, @value{GDBN} never sees that
11123 variable---because the compiler optimizes it out of existence.
11125 Some things do not work as well with @samp{-g -O} as with just
11126 @samp{-g}, particularly on machines with instruction scheduling. If in
11127 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11128 please report it to us as a bug (including a test case!).
11129 @xref{Variables}, for more information about debugging optimized code.
11132 * Inline Functions:: How @value{GDBN} presents inlining
11133 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11136 @node Inline Functions
11137 @section Inline Functions
11138 @cindex inline functions, debugging
11140 @dfn{Inlining} is an optimization that inserts a copy of the function
11141 body directly at each call site, instead of jumping to a shared
11142 routine. @value{GDBN} displays inlined functions just like
11143 non-inlined functions. They appear in backtraces. You can view their
11144 arguments and local variables, step into them with @code{step}, skip
11145 them with @code{next}, and escape from them with @code{finish}.
11146 You can check whether a function was inlined by using the
11147 @code{info frame} command.
11149 For @value{GDBN} to support inlined functions, the compiler must
11150 record information about inlining in the debug information ---
11151 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11152 other compilers do also. @value{GDBN} only supports inlined functions
11153 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11154 do not emit two required attributes (@samp{DW_AT_call_file} and
11155 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11156 function calls with earlier versions of @value{NGCC}. It instead
11157 displays the arguments and local variables of inlined functions as
11158 local variables in the caller.
11160 The body of an inlined function is directly included at its call site;
11161 unlike a non-inlined function, there are no instructions devoted to
11162 the call. @value{GDBN} still pretends that the call site and the
11163 start of the inlined function are different instructions. Stepping to
11164 the call site shows the call site, and then stepping again shows
11165 the first line of the inlined function, even though no additional
11166 instructions are executed.
11168 This makes source-level debugging much clearer; you can see both the
11169 context of the call and then the effect of the call. Only stepping by
11170 a single instruction using @code{stepi} or @code{nexti} does not do
11171 this; single instruction steps always show the inlined body.
11173 There are some ways that @value{GDBN} does not pretend that inlined
11174 function calls are the same as normal calls:
11178 Setting breakpoints at the call site of an inlined function may not
11179 work, because the call site does not contain any code. @value{GDBN}
11180 may incorrectly move the breakpoint to the next line of the enclosing
11181 function, after the call. This limitation will be removed in a future
11182 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11183 or inside the inlined function instead.
11186 @value{GDBN} cannot locate the return value of inlined calls after
11187 using the @code{finish} command. This is a limitation of compiler-generated
11188 debugging information; after @code{finish}, you can step to the next line
11189 and print a variable where your program stored the return value.
11193 @node Tail Call Frames
11194 @section Tail Call Frames
11195 @cindex tail call frames, debugging
11197 Function @code{B} can call function @code{C} in its very last statement. In
11198 unoptimized compilation the call of @code{C} is immediately followed by return
11199 instruction at the end of @code{B} code. Optimizing compiler may replace the
11200 call and return in function @code{B} into one jump to function @code{C}
11201 instead. Such use of a jump instruction is called @dfn{tail call}.
11203 During execution of function @code{C}, there will be no indication in the
11204 function call stack frames that it was tail-called from @code{B}. If function
11205 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11206 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11207 some cases @value{GDBN} can determine that @code{C} was tail-called from
11208 @code{B}, and it will then create fictitious call frame for that, with the
11209 return address set up as if @code{B} called @code{C} normally.
11211 This functionality is currently supported only by DWARF 2 debugging format and
11212 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11213 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11216 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11217 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11221 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11223 Stack level 1, frame at 0x7fffffffda30:
11224 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11225 tail call frame, caller of frame at 0x7fffffffda30
11226 source language c++.
11227 Arglist at unknown address.
11228 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11231 The detection of all the possible code path executions can find them ambiguous.
11232 There is no execution history stored (possible @ref{Reverse Execution} is never
11233 used for this purpose) and the last known caller could have reached the known
11234 callee by multiple different jump sequences. In such case @value{GDBN} still
11235 tries to show at least all the unambiguous top tail callers and all the
11236 unambiguous bottom tail calees, if any.
11239 @anchor{set debug entry-values}
11240 @item set debug entry-values
11241 @kindex set debug entry-values
11242 When set to on, enables printing of analysis messages for both frame argument
11243 values at function entry and tail calls. It will show all the possible valid
11244 tail calls code paths it has considered. It will also print the intersection
11245 of them with the final unambiguous (possibly partial or even empty) code path
11248 @item show debug entry-values
11249 @kindex show debug entry-values
11250 Show the current state of analysis messages printing for both frame argument
11251 values at function entry and tail calls.
11254 The analysis messages for tail calls can for example show why the virtual tail
11255 call frame for function @code{c} has not been recognized (due to the indirect
11256 reference by variable @code{x}):
11259 static void __attribute__((noinline, noclone)) c (void);
11260 void (*x) (void) = c;
11261 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11262 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11263 int main (void) @{ x (); return 0; @}
11265 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11266 DW_TAG_GNU_call_site 0x40039a in main
11268 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11271 #1 0x000000000040039a in main () at t.c:5
11274 Another possibility is an ambiguous virtual tail call frames resolution:
11278 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11279 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11280 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11281 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11282 static void __attribute__((noinline, noclone)) b (void)
11283 @{ if (i) c (); else e (); @}
11284 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11285 int main (void) @{ a (); return 0; @}
11287 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11288 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11289 tailcall: reduced: 0x4004d2(a) |
11292 #1 0x00000000004004d2 in a () at t.c:8
11293 #2 0x0000000000400395 in main () at t.c:9
11296 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11297 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11299 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11300 @ifset HAVE_MAKEINFO_CLICK
11301 @set ARROW @click{}
11302 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11303 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11305 @ifclear HAVE_MAKEINFO_CLICK
11307 @set CALLSEQ1B @value{CALLSEQ1A}
11308 @set CALLSEQ2B @value{CALLSEQ2A}
11311 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11312 The code can have possible execution paths @value{CALLSEQ1B} or
11313 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11315 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11316 has found. It then finds another possible calling sequcen - that one is
11317 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11318 printed as the @code{reduced:} calling sequence. That one could have many
11319 futher @code{compare:} and @code{reduced:} statements as long as there remain
11320 any non-ambiguous sequence entries.
11322 For the frame of function @code{b} in both cases there are different possible
11323 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11324 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11325 therefore this one is displayed to the user while the ambiguous frames are
11328 There can be also reasons why printing of frame argument values at function
11333 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11334 static void __attribute__((noinline, noclone)) a (int i);
11335 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11336 static void __attribute__((noinline, noclone)) a (int i)
11337 @{ if (i) b (i - 1); else c (0); @}
11338 int main (void) @{ a (5); return 0; @}
11341 #0 c (i=i@@entry=0) at t.c:2
11342 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11343 function "a" at 0x400420 can call itself via tail calls
11344 i=<optimized out>) at t.c:6
11345 #2 0x000000000040036e in main () at t.c:7
11348 @value{GDBN} cannot find out from the inferior state if and how many times did
11349 function @code{a} call itself (via function @code{b}) as these calls would be
11350 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11351 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11352 prints @code{<optimized out>} instead.
11355 @chapter C Preprocessor Macros
11357 Some languages, such as C and C@t{++}, provide a way to define and invoke
11358 ``preprocessor macros'' which expand into strings of tokens.
11359 @value{GDBN} can evaluate expressions containing macro invocations, show
11360 the result of macro expansion, and show a macro's definition, including
11361 where it was defined.
11363 You may need to compile your program specially to provide @value{GDBN}
11364 with information about preprocessor macros. Most compilers do not
11365 include macros in their debugging information, even when you compile
11366 with the @option{-g} flag. @xref{Compilation}.
11368 A program may define a macro at one point, remove that definition later,
11369 and then provide a different definition after that. Thus, at different
11370 points in the program, a macro may have different definitions, or have
11371 no definition at all. If there is a current stack frame, @value{GDBN}
11372 uses the macros in scope at that frame's source code line. Otherwise,
11373 @value{GDBN} uses the macros in scope at the current listing location;
11376 Whenever @value{GDBN} evaluates an expression, it always expands any
11377 macro invocations present in the expression. @value{GDBN} also provides
11378 the following commands for working with macros explicitly.
11382 @kindex macro expand
11383 @cindex macro expansion, showing the results of preprocessor
11384 @cindex preprocessor macro expansion, showing the results of
11385 @cindex expanding preprocessor macros
11386 @item macro expand @var{expression}
11387 @itemx macro exp @var{expression}
11388 Show the results of expanding all preprocessor macro invocations in
11389 @var{expression}. Since @value{GDBN} simply expands macros, but does
11390 not parse the result, @var{expression} need not be a valid expression;
11391 it can be any string of tokens.
11394 @item macro expand-once @var{expression}
11395 @itemx macro exp1 @var{expression}
11396 @cindex expand macro once
11397 @i{(This command is not yet implemented.)} Show the results of
11398 expanding those preprocessor macro invocations that appear explicitly in
11399 @var{expression}. Macro invocations appearing in that expansion are
11400 left unchanged. This command allows you to see the effect of a
11401 particular macro more clearly, without being confused by further
11402 expansions. Since @value{GDBN} simply expands macros, but does not
11403 parse the result, @var{expression} need not be a valid expression; it
11404 can be any string of tokens.
11407 @cindex macro definition, showing
11408 @cindex definition of a macro, showing
11409 @cindex macros, from debug info
11410 @item info macro [-a|-all] [--] @var{macro}
11411 Show the current definition or all definitions of the named @var{macro},
11412 and describe the source location or compiler command-line where that
11413 definition was established. The optional double dash is to signify the end of
11414 argument processing and the beginning of @var{macro} for non C-like macros where
11415 the macro may begin with a hyphen.
11417 @kindex info macros
11418 @item info macros @var{linespec}
11419 Show all macro definitions that are in effect at the location specified
11420 by @var{linespec}, and describe the source location or compiler
11421 command-line where those definitions were established.
11423 @kindex macro define
11424 @cindex user-defined macros
11425 @cindex defining macros interactively
11426 @cindex macros, user-defined
11427 @item macro define @var{macro} @var{replacement-list}
11428 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11429 Introduce a definition for a preprocessor macro named @var{macro},
11430 invocations of which are replaced by the tokens given in
11431 @var{replacement-list}. The first form of this command defines an
11432 ``object-like'' macro, which takes no arguments; the second form
11433 defines a ``function-like'' macro, which takes the arguments given in
11436 A definition introduced by this command is in scope in every
11437 expression evaluated in @value{GDBN}, until it is removed with the
11438 @code{macro undef} command, described below. The definition overrides
11439 all definitions for @var{macro} present in the program being debugged,
11440 as well as any previous user-supplied definition.
11442 @kindex macro undef
11443 @item macro undef @var{macro}
11444 Remove any user-supplied definition for the macro named @var{macro}.
11445 This command only affects definitions provided with the @code{macro
11446 define} command, described above; it cannot remove definitions present
11447 in the program being debugged.
11451 List all the macros defined using the @code{macro define} command.
11454 @cindex macros, example of debugging with
11455 Here is a transcript showing the above commands in action. First, we
11456 show our source files:
11461 #include "sample.h"
11464 #define ADD(x) (M + x)
11469 printf ("Hello, world!\n");
11471 printf ("We're so creative.\n");
11473 printf ("Goodbye, world!\n");
11480 Now, we compile the program using the @sc{gnu} C compiler,
11481 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11482 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11483 and @option{-gdwarf-4}; we recommend always choosing the most recent
11484 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11485 includes information about preprocessor macros in the debugging
11489 $ gcc -gdwarf-2 -g3 sample.c -o sample
11493 Now, we start @value{GDBN} on our sample program:
11497 GNU gdb 2002-05-06-cvs
11498 Copyright 2002 Free Software Foundation, Inc.
11499 GDB is free software, @dots{}
11503 We can expand macros and examine their definitions, even when the
11504 program is not running. @value{GDBN} uses the current listing position
11505 to decide which macro definitions are in scope:
11508 (@value{GDBP}) list main
11511 5 #define ADD(x) (M + x)
11516 10 printf ("Hello, world!\n");
11518 12 printf ("We're so creative.\n");
11519 (@value{GDBP}) info macro ADD
11520 Defined at /home/jimb/gdb/macros/play/sample.c:5
11521 #define ADD(x) (M + x)
11522 (@value{GDBP}) info macro Q
11523 Defined at /home/jimb/gdb/macros/play/sample.h:1
11524 included at /home/jimb/gdb/macros/play/sample.c:2
11526 (@value{GDBP}) macro expand ADD(1)
11527 expands to: (42 + 1)
11528 (@value{GDBP}) macro expand-once ADD(1)
11529 expands to: once (M + 1)
11533 In the example above, note that @code{macro expand-once} expands only
11534 the macro invocation explicit in the original text --- the invocation of
11535 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11536 which was introduced by @code{ADD}.
11538 Once the program is running, @value{GDBN} uses the macro definitions in
11539 force at the source line of the current stack frame:
11542 (@value{GDBP}) break main
11543 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11545 Starting program: /home/jimb/gdb/macros/play/sample
11547 Breakpoint 1, main () at sample.c:10
11548 10 printf ("Hello, world!\n");
11552 At line 10, the definition of the macro @code{N} at line 9 is in force:
11555 (@value{GDBP}) info macro N
11556 Defined at /home/jimb/gdb/macros/play/sample.c:9
11558 (@value{GDBP}) macro expand N Q M
11559 expands to: 28 < 42
11560 (@value{GDBP}) print N Q M
11565 As we step over directives that remove @code{N}'s definition, and then
11566 give it a new definition, @value{GDBN} finds the definition (or lack
11567 thereof) in force at each point:
11570 (@value{GDBP}) next
11572 12 printf ("We're so creative.\n");
11573 (@value{GDBP}) info macro N
11574 The symbol `N' has no definition as a C/C++ preprocessor macro
11575 at /home/jimb/gdb/macros/play/sample.c:12
11576 (@value{GDBP}) next
11578 14 printf ("Goodbye, world!\n");
11579 (@value{GDBP}) info macro N
11580 Defined at /home/jimb/gdb/macros/play/sample.c:13
11582 (@value{GDBP}) macro expand N Q M
11583 expands to: 1729 < 42
11584 (@value{GDBP}) print N Q M
11589 In addition to source files, macros can be defined on the compilation command
11590 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11591 such a way, @value{GDBN} displays the location of their definition as line zero
11592 of the source file submitted to the compiler.
11595 (@value{GDBP}) info macro __STDC__
11596 Defined at /home/jimb/gdb/macros/play/sample.c:0
11603 @chapter Tracepoints
11604 @c This chapter is based on the documentation written by Michael
11605 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11607 @cindex tracepoints
11608 In some applications, it is not feasible for the debugger to interrupt
11609 the program's execution long enough for the developer to learn
11610 anything helpful about its behavior. If the program's correctness
11611 depends on its real-time behavior, delays introduced by a debugger
11612 might cause the program to change its behavior drastically, or perhaps
11613 fail, even when the code itself is correct. It is useful to be able
11614 to observe the program's behavior without interrupting it.
11616 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11617 specify locations in the program, called @dfn{tracepoints}, and
11618 arbitrary expressions to evaluate when those tracepoints are reached.
11619 Later, using the @code{tfind} command, you can examine the values
11620 those expressions had when the program hit the tracepoints. The
11621 expressions may also denote objects in memory---structures or arrays,
11622 for example---whose values @value{GDBN} should record; while visiting
11623 a particular tracepoint, you may inspect those objects as if they were
11624 in memory at that moment. However, because @value{GDBN} records these
11625 values without interacting with you, it can do so quickly and
11626 unobtrusively, hopefully not disturbing the program's behavior.
11628 The tracepoint facility is currently available only for remote
11629 targets. @xref{Targets}. In addition, your remote target must know
11630 how to collect trace data. This functionality is implemented in the
11631 remote stub; however, none of the stubs distributed with @value{GDBN}
11632 support tracepoints as of this writing. The format of the remote
11633 packets used to implement tracepoints are described in @ref{Tracepoint
11636 It is also possible to get trace data from a file, in a manner reminiscent
11637 of corefiles; you specify the filename, and use @code{tfind} to search
11638 through the file. @xref{Trace Files}, for more details.
11640 This chapter describes the tracepoint commands and features.
11643 * Set Tracepoints::
11644 * Analyze Collected Data::
11645 * Tracepoint Variables::
11649 @node Set Tracepoints
11650 @section Commands to Set Tracepoints
11652 Before running such a @dfn{trace experiment}, an arbitrary number of
11653 tracepoints can be set. A tracepoint is actually a special type of
11654 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11655 standard breakpoint commands. For instance, as with breakpoints,
11656 tracepoint numbers are successive integers starting from one, and many
11657 of the commands associated with tracepoints take the tracepoint number
11658 as their argument, to identify which tracepoint to work on.
11660 For each tracepoint, you can specify, in advance, some arbitrary set
11661 of data that you want the target to collect in the trace buffer when
11662 it hits that tracepoint. The collected data can include registers,
11663 local variables, or global data. Later, you can use @value{GDBN}
11664 commands to examine the values these data had at the time the
11665 tracepoint was hit.
11667 Tracepoints do not support every breakpoint feature. Ignore counts on
11668 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11669 commands when they are hit. Tracepoints may not be thread-specific
11672 @cindex fast tracepoints
11673 Some targets may support @dfn{fast tracepoints}, which are inserted in
11674 a different way (such as with a jump instead of a trap), that is
11675 faster but possibly restricted in where they may be installed.
11677 @cindex static tracepoints
11678 @cindex markers, static tracepoints
11679 @cindex probing markers, static tracepoints
11680 Regular and fast tracepoints are dynamic tracing facilities, meaning
11681 that they can be used to insert tracepoints at (almost) any location
11682 in the target. Some targets may also support controlling @dfn{static
11683 tracepoints} from @value{GDBN}. With static tracing, a set of
11684 instrumentation points, also known as @dfn{markers}, are embedded in
11685 the target program, and can be activated or deactivated by name or
11686 address. These are usually placed at locations which facilitate
11687 investigating what the target is actually doing. @value{GDBN}'s
11688 support for static tracing includes being able to list instrumentation
11689 points, and attach them with @value{GDBN} defined high level
11690 tracepoints that expose the whole range of convenience of
11691 @value{GDBN}'s tracepoints support. Namely, support for collecting
11692 registers values and values of global or local (to the instrumentation
11693 point) variables; tracepoint conditions and trace state variables.
11694 The act of installing a @value{GDBN} static tracepoint on an
11695 instrumentation point, or marker, is referred to as @dfn{probing} a
11696 static tracepoint marker.
11698 @code{gdbserver} supports tracepoints on some target systems.
11699 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11701 This section describes commands to set tracepoints and associated
11702 conditions and actions.
11705 * Create and Delete Tracepoints::
11706 * Enable and Disable Tracepoints::
11707 * Tracepoint Passcounts::
11708 * Tracepoint Conditions::
11709 * Trace State Variables::
11710 * Tracepoint Actions::
11711 * Listing Tracepoints::
11712 * Listing Static Tracepoint Markers::
11713 * Starting and Stopping Trace Experiments::
11714 * Tracepoint Restrictions::
11717 @node Create and Delete Tracepoints
11718 @subsection Create and Delete Tracepoints
11721 @cindex set tracepoint
11723 @item trace @var{location}
11724 The @code{trace} command is very similar to the @code{break} command.
11725 Its argument @var{location} can be a source line, a function name, or
11726 an address in the target program. @xref{Specify Location}. The
11727 @code{trace} command defines a tracepoint, which is a point in the
11728 target program where the debugger will briefly stop, collect some
11729 data, and then allow the program to continue. Setting a tracepoint or
11730 changing its actions takes effect immediately if the remote stub
11731 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11733 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11734 these changes don't take effect until the next @code{tstart}
11735 command, and once a trace experiment is running, further changes will
11736 not have any effect until the next trace experiment starts. In addition,
11737 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11738 address is not yet resolved. (This is similar to pending breakpoints.)
11739 Pending tracepoints are not downloaded to the target and not installed
11740 until they are resolved. The resolution of pending tracepoints requires
11741 @value{GDBN} support---when debugging with the remote target, and
11742 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11743 tracing}), pending tracepoints can not be resolved (and downloaded to
11744 the remote stub) while @value{GDBN} is disconnected.
11746 Here are some examples of using the @code{trace} command:
11749 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11751 (@value{GDBP}) @b{trace +2} // 2 lines forward
11753 (@value{GDBP}) @b{trace my_function} // first source line of function
11755 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11757 (@value{GDBP}) @b{trace *0x2117c4} // an address
11761 You can abbreviate @code{trace} as @code{tr}.
11763 @item trace @var{location} if @var{cond}
11764 Set a tracepoint with condition @var{cond}; evaluate the expression
11765 @var{cond} each time the tracepoint is reached, and collect data only
11766 if the value is nonzero---that is, if @var{cond} evaluates as true.
11767 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11768 information on tracepoint conditions.
11770 @item ftrace @var{location} [ if @var{cond} ]
11771 @cindex set fast tracepoint
11772 @cindex fast tracepoints, setting
11774 The @code{ftrace} command sets a fast tracepoint. For targets that
11775 support them, fast tracepoints will use a more efficient but possibly
11776 less general technique to trigger data collection, such as a jump
11777 instruction instead of a trap, or some sort of hardware support. It
11778 may not be possible to create a fast tracepoint at the desired
11779 location, in which case the command will exit with an explanatory
11782 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11785 On 32-bit x86-architecture systems, fast tracepoints normally need to
11786 be placed at an instruction that is 5 bytes or longer, but can be
11787 placed at 4-byte instructions if the low 64K of memory of the target
11788 program is available to install trampolines. Some Unix-type systems,
11789 such as @sc{gnu}/Linux, exclude low addresses from the program's
11790 address space; but for instance with the Linux kernel it is possible
11791 to let @value{GDBN} use this area by doing a @command{sysctl} command
11792 to set the @code{mmap_min_addr} kernel parameter, as in
11795 sudo sysctl -w vm.mmap_min_addr=32768
11799 which sets the low address to 32K, which leaves plenty of room for
11800 trampolines. The minimum address should be set to a page boundary.
11802 @item strace @var{location} [ if @var{cond} ]
11803 @cindex set static tracepoint
11804 @cindex static tracepoints, setting
11805 @cindex probe static tracepoint marker
11807 The @code{strace} command sets a static tracepoint. For targets that
11808 support it, setting a static tracepoint probes a static
11809 instrumentation point, or marker, found at @var{location}. It may not
11810 be possible to set a static tracepoint at the desired location, in
11811 which case the command will exit with an explanatory message.
11813 @value{GDBN} handles arguments to @code{strace} exactly as for
11814 @code{trace}, with the addition that the user can also specify
11815 @code{-m @var{marker}} as @var{location}. This probes the marker
11816 identified by the @var{marker} string identifier. This identifier
11817 depends on the static tracepoint backend library your program is
11818 using. You can find all the marker identifiers in the @samp{ID} field
11819 of the @code{info static-tracepoint-markers} command output.
11820 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11821 Markers}. For example, in the following small program using the UST
11827 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11832 the marker id is composed of joining the first two arguments to the
11833 @code{trace_mark} call with a slash, which translates to:
11836 (@value{GDBP}) info static-tracepoint-markers
11837 Cnt Enb ID Address What
11838 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11844 so you may probe the marker above with:
11847 (@value{GDBP}) strace -m ust/bar33
11850 Static tracepoints accept an extra collect action --- @code{collect
11851 $_sdata}. This collects arbitrary user data passed in the probe point
11852 call to the tracing library. In the UST example above, you'll see
11853 that the third argument to @code{trace_mark} is a printf-like format
11854 string. The user data is then the result of running that formating
11855 string against the following arguments. Note that @code{info
11856 static-tracepoint-markers} command output lists that format string in
11857 the @samp{Data:} field.
11859 You can inspect this data when analyzing the trace buffer, by printing
11860 the $_sdata variable like any other variable available to
11861 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11864 @cindex last tracepoint number
11865 @cindex recent tracepoint number
11866 @cindex tracepoint number
11867 The convenience variable @code{$tpnum} records the tracepoint number
11868 of the most recently set tracepoint.
11870 @kindex delete tracepoint
11871 @cindex tracepoint deletion
11872 @item delete tracepoint @r{[}@var{num}@r{]}
11873 Permanently delete one or more tracepoints. With no argument, the
11874 default is to delete all tracepoints. Note that the regular
11875 @code{delete} command can remove tracepoints also.
11880 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11882 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11886 You can abbreviate this command as @code{del tr}.
11889 @node Enable and Disable Tracepoints
11890 @subsection Enable and Disable Tracepoints
11892 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11895 @kindex disable tracepoint
11896 @item disable tracepoint @r{[}@var{num}@r{]}
11897 Disable tracepoint @var{num}, or all tracepoints if no argument
11898 @var{num} is given. A disabled tracepoint will have no effect during
11899 a trace experiment, but it is not forgotten. You can re-enable
11900 a disabled tracepoint using the @code{enable tracepoint} command.
11901 If the command is issued during a trace experiment and the debug target
11902 has support for disabling tracepoints during a trace experiment, then the
11903 change will be effective immediately. Otherwise, it will be applied to the
11904 next trace experiment.
11906 @kindex enable tracepoint
11907 @item enable tracepoint @r{[}@var{num}@r{]}
11908 Enable tracepoint @var{num}, or all tracepoints. If this command is
11909 issued during a trace experiment and the debug target supports enabling
11910 tracepoints during a trace experiment, then the enabled tracepoints will
11911 become effective immediately. Otherwise, they will become effective the
11912 next time a trace experiment is run.
11915 @node Tracepoint Passcounts
11916 @subsection Tracepoint Passcounts
11920 @cindex tracepoint pass count
11921 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11922 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11923 automatically stop a trace experiment. If a tracepoint's passcount is
11924 @var{n}, then the trace experiment will be automatically stopped on
11925 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11926 @var{num} is not specified, the @code{passcount} command sets the
11927 passcount of the most recently defined tracepoint. If no passcount is
11928 given, the trace experiment will run until stopped explicitly by the
11934 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11935 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11937 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11938 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11939 (@value{GDBP}) @b{trace foo}
11940 (@value{GDBP}) @b{pass 3}
11941 (@value{GDBP}) @b{trace bar}
11942 (@value{GDBP}) @b{pass 2}
11943 (@value{GDBP}) @b{trace baz}
11944 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11945 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11946 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11947 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11951 @node Tracepoint Conditions
11952 @subsection Tracepoint Conditions
11953 @cindex conditional tracepoints
11954 @cindex tracepoint conditions
11956 The simplest sort of tracepoint collects data every time your program
11957 reaches a specified place. You can also specify a @dfn{condition} for
11958 a tracepoint. A condition is just a Boolean expression in your
11959 programming language (@pxref{Expressions, ,Expressions}). A
11960 tracepoint with a condition evaluates the expression each time your
11961 program reaches it, and data collection happens only if the condition
11964 Tracepoint conditions can be specified when a tracepoint is set, by
11965 using @samp{if} in the arguments to the @code{trace} command.
11966 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11967 also be set or changed at any time with the @code{condition} command,
11968 just as with breakpoints.
11970 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11971 the conditional expression itself. Instead, @value{GDBN} encodes the
11972 expression into an agent expression (@pxref{Agent Expressions})
11973 suitable for execution on the target, independently of @value{GDBN}.
11974 Global variables become raw memory locations, locals become stack
11975 accesses, and so forth.
11977 For instance, suppose you have a function that is usually called
11978 frequently, but should not be called after an error has occurred. You
11979 could use the following tracepoint command to collect data about calls
11980 of that function that happen while the error code is propagating
11981 through the program; an unconditional tracepoint could end up
11982 collecting thousands of useless trace frames that you would have to
11986 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11989 @node Trace State Variables
11990 @subsection Trace State Variables
11991 @cindex trace state variables
11993 A @dfn{trace state variable} is a special type of variable that is
11994 created and managed by target-side code. The syntax is the same as
11995 that for GDB's convenience variables (a string prefixed with ``$''),
11996 but they are stored on the target. They must be created explicitly,
11997 using a @code{tvariable} command. They are always 64-bit signed
12000 Trace state variables are remembered by @value{GDBN}, and downloaded
12001 to the target along with tracepoint information when the trace
12002 experiment starts. There are no intrinsic limits on the number of
12003 trace state variables, beyond memory limitations of the target.
12005 @cindex convenience variables, and trace state variables
12006 Although trace state variables are managed by the target, you can use
12007 them in print commands and expressions as if they were convenience
12008 variables; @value{GDBN} will get the current value from the target
12009 while the trace experiment is running. Trace state variables share
12010 the same namespace as other ``$'' variables, which means that you
12011 cannot have trace state variables with names like @code{$23} or
12012 @code{$pc}, nor can you have a trace state variable and a convenience
12013 variable with the same name.
12017 @item tvariable $@var{name} [ = @var{expression} ]
12019 The @code{tvariable} command creates a new trace state variable named
12020 @code{$@var{name}}, and optionally gives it an initial value of
12021 @var{expression}. @var{expression} is evaluated when this command is
12022 entered; the result will be converted to an integer if possible,
12023 otherwise @value{GDBN} will report an error. A subsequent
12024 @code{tvariable} command specifying the same name does not create a
12025 variable, but instead assigns the supplied initial value to the
12026 existing variable of that name, overwriting any previous initial
12027 value. The default initial value is 0.
12029 @item info tvariables
12030 @kindex info tvariables
12031 List all the trace state variables along with their initial values.
12032 Their current values may also be displayed, if the trace experiment is
12035 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12036 @kindex delete tvariable
12037 Delete the given trace state variables, or all of them if no arguments
12042 @node Tracepoint Actions
12043 @subsection Tracepoint Action Lists
12047 @cindex tracepoint actions
12048 @item actions @r{[}@var{num}@r{]}
12049 This command will prompt for a list of actions to be taken when the
12050 tracepoint is hit. If the tracepoint number @var{num} is not
12051 specified, this command sets the actions for the one that was most
12052 recently defined (so that you can define a tracepoint and then say
12053 @code{actions} without bothering about its number). You specify the
12054 actions themselves on the following lines, one action at a time, and
12055 terminate the actions list with a line containing just @code{end}. So
12056 far, the only defined actions are @code{collect}, @code{teval}, and
12057 @code{while-stepping}.
12059 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12060 Commands, ,Breakpoint Command Lists}), except that only the defined
12061 actions are allowed; any other @value{GDBN} command is rejected.
12063 @cindex remove actions from a tracepoint
12064 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12065 and follow it immediately with @samp{end}.
12068 (@value{GDBP}) @b{collect @var{data}} // collect some data
12070 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12072 (@value{GDBP}) @b{end} // signals the end of actions.
12075 In the following example, the action list begins with @code{collect}
12076 commands indicating the things to be collected when the tracepoint is
12077 hit. Then, in order to single-step and collect additional data
12078 following the tracepoint, a @code{while-stepping} command is used,
12079 followed by the list of things to be collected after each step in a
12080 sequence of single steps. The @code{while-stepping} command is
12081 terminated by its own separate @code{end} command. Lastly, the action
12082 list is terminated by an @code{end} command.
12085 (@value{GDBP}) @b{trace foo}
12086 (@value{GDBP}) @b{actions}
12087 Enter actions for tracepoint 1, one per line:
12090 > while-stepping 12
12091 > collect $pc, arr[i]
12096 @kindex collect @r{(tracepoints)}
12097 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12098 Collect values of the given expressions when the tracepoint is hit.
12099 This command accepts a comma-separated list of any valid expressions.
12100 In addition to global, static, or local variables, the following
12101 special arguments are supported:
12105 Collect all registers.
12108 Collect all function arguments.
12111 Collect all local variables.
12114 Collect the return address. This is helpful if you want to see more
12118 Collects the number of arguments from the static probe at which the
12119 tracepoint is located.
12120 @xref{Static Probe Points}.
12122 @item $_probe_arg@var{n}
12123 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12124 from the static probe at which the tracepoint is located.
12125 @xref{Static Probe Points}.
12128 @vindex $_sdata@r{, collect}
12129 Collect static tracepoint marker specific data. Only available for
12130 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12131 Lists}. On the UST static tracepoints library backend, an
12132 instrumentation point resembles a @code{printf} function call. The
12133 tracing library is able to collect user specified data formatted to a
12134 character string using the format provided by the programmer that
12135 instrumented the program. Other backends have similar mechanisms.
12136 Here's an example of a UST marker call:
12139 const char master_name[] = "$your_name";
12140 trace_mark(channel1, marker1, "hello %s", master_name)
12143 In this case, collecting @code{$_sdata} collects the string
12144 @samp{hello $yourname}. When analyzing the trace buffer, you can
12145 inspect @samp{$_sdata} like any other variable available to
12149 You can give several consecutive @code{collect} commands, each one
12150 with a single argument, or one @code{collect} command with several
12151 arguments separated by commas; the effect is the same.
12153 The optional @var{mods} changes the usual handling of the arguments.
12154 @code{s} requests that pointers to chars be handled as strings, in
12155 particular collecting the contents of the memory being pointed at, up
12156 to the first zero. The upper bound is by default the value of the
12157 @code{print elements} variable; if @code{s} is followed by a decimal
12158 number, that is the upper bound instead. So for instance
12159 @samp{collect/s25 mystr} collects as many as 25 characters at
12162 The command @code{info scope} (@pxref{Symbols, info scope}) is
12163 particularly useful for figuring out what data to collect.
12165 @kindex teval @r{(tracepoints)}
12166 @item teval @var{expr1}, @var{expr2}, @dots{}
12167 Evaluate the given expressions when the tracepoint is hit. This
12168 command accepts a comma-separated list of expressions. The results
12169 are discarded, so this is mainly useful for assigning values to trace
12170 state variables (@pxref{Trace State Variables}) without adding those
12171 values to the trace buffer, as would be the case if the @code{collect}
12174 @kindex while-stepping @r{(tracepoints)}
12175 @item while-stepping @var{n}
12176 Perform @var{n} single-step instruction traces after the tracepoint,
12177 collecting new data after each step. The @code{while-stepping}
12178 command is followed by the list of what to collect while stepping
12179 (followed by its own @code{end} command):
12182 > while-stepping 12
12183 > collect $regs, myglobal
12189 Note that @code{$pc} is not automatically collected by
12190 @code{while-stepping}; you need to explicitly collect that register if
12191 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12194 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12195 @kindex set default-collect
12196 @cindex default collection action
12197 This variable is a list of expressions to collect at each tracepoint
12198 hit. It is effectively an additional @code{collect} action prepended
12199 to every tracepoint action list. The expressions are parsed
12200 individually for each tracepoint, so for instance a variable named
12201 @code{xyz} may be interpreted as a global for one tracepoint, and a
12202 local for another, as appropriate to the tracepoint's location.
12204 @item show default-collect
12205 @kindex show default-collect
12206 Show the list of expressions that are collected by default at each
12211 @node Listing Tracepoints
12212 @subsection Listing Tracepoints
12215 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12216 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12217 @cindex information about tracepoints
12218 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12219 Display information about the tracepoint @var{num}. If you don't
12220 specify a tracepoint number, displays information about all the
12221 tracepoints defined so far. The format is similar to that used for
12222 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12223 command, simply restricting itself to tracepoints.
12225 A tracepoint's listing may include additional information specific to
12230 its passcount as given by the @code{passcount @var{n}} command
12233 the state about installed on target of each location
12237 (@value{GDBP}) @b{info trace}
12238 Num Type Disp Enb Address What
12239 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12241 collect globfoo, $regs
12246 2 tracepoint keep y <MULTIPLE>
12248 2.1 y 0x0804859c in func4 at change-loc.h:35
12249 installed on target
12250 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12251 installed on target
12252 2.3 y <PENDING> set_tracepoint
12253 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12254 not installed on target
12259 This command can be abbreviated @code{info tp}.
12262 @node Listing Static Tracepoint Markers
12263 @subsection Listing Static Tracepoint Markers
12266 @kindex info static-tracepoint-markers
12267 @cindex information about static tracepoint markers
12268 @item info static-tracepoint-markers
12269 Display information about all static tracepoint markers defined in the
12272 For each marker, the following columns are printed:
12276 An incrementing counter, output to help readability. This is not a
12279 The marker ID, as reported by the target.
12280 @item Enabled or Disabled
12281 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12282 that are not enabled.
12284 Where the marker is in your program, as a memory address.
12286 Where the marker is in the source for your program, as a file and line
12287 number. If the debug information included in the program does not
12288 allow @value{GDBN} to locate the source of the marker, this column
12289 will be left blank.
12293 In addition, the following information may be printed for each marker:
12297 User data passed to the tracing library by the marker call. In the
12298 UST backend, this is the format string passed as argument to the
12300 @item Static tracepoints probing the marker
12301 The list of static tracepoints attached to the marker.
12305 (@value{GDBP}) info static-tracepoint-markers
12306 Cnt ID Enb Address What
12307 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12308 Data: number1 %d number2 %d
12309 Probed by static tracepoints: #2
12310 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12316 @node Starting and Stopping Trace Experiments
12317 @subsection Starting and Stopping Trace Experiments
12320 @kindex tstart [ @var{notes} ]
12321 @cindex start a new trace experiment
12322 @cindex collected data discarded
12324 This command starts the trace experiment, and begins collecting data.
12325 It has the side effect of discarding all the data collected in the
12326 trace buffer during the previous trace experiment. If any arguments
12327 are supplied, they are taken as a note and stored with the trace
12328 experiment's state. The notes may be arbitrary text, and are
12329 especially useful with disconnected tracing in a multi-user context;
12330 the notes can explain what the trace is doing, supply user contact
12331 information, and so forth.
12333 @kindex tstop [ @var{notes} ]
12334 @cindex stop a running trace experiment
12336 This command stops the trace experiment. If any arguments are
12337 supplied, they are recorded with the experiment as a note. This is
12338 useful if you are stopping a trace started by someone else, for
12339 instance if the trace is interfering with the system's behavior and
12340 needs to be stopped quickly.
12342 @strong{Note}: a trace experiment and data collection may stop
12343 automatically if any tracepoint's passcount is reached
12344 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12347 @cindex status of trace data collection
12348 @cindex trace experiment, status of
12350 This command displays the status of the current trace data
12354 Here is an example of the commands we described so far:
12357 (@value{GDBP}) @b{trace gdb_c_test}
12358 (@value{GDBP}) @b{actions}
12359 Enter actions for tracepoint #1, one per line.
12360 > collect $regs,$locals,$args
12361 > while-stepping 11
12365 (@value{GDBP}) @b{tstart}
12366 [time passes @dots{}]
12367 (@value{GDBP}) @b{tstop}
12370 @anchor{disconnected tracing}
12371 @cindex disconnected tracing
12372 You can choose to continue running the trace experiment even if
12373 @value{GDBN} disconnects from the target, voluntarily or
12374 involuntarily. For commands such as @code{detach}, the debugger will
12375 ask what you want to do with the trace. But for unexpected
12376 terminations (@value{GDBN} crash, network outage), it would be
12377 unfortunate to lose hard-won trace data, so the variable
12378 @code{disconnected-tracing} lets you decide whether the trace should
12379 continue running without @value{GDBN}.
12382 @item set disconnected-tracing on
12383 @itemx set disconnected-tracing off
12384 @kindex set disconnected-tracing
12385 Choose whether a tracing run should continue to run if @value{GDBN}
12386 has disconnected from the target. Note that @code{detach} or
12387 @code{quit} will ask you directly what to do about a running trace no
12388 matter what this variable's setting, so the variable is mainly useful
12389 for handling unexpected situations, such as loss of the network.
12391 @item show disconnected-tracing
12392 @kindex show disconnected-tracing
12393 Show the current choice for disconnected tracing.
12397 When you reconnect to the target, the trace experiment may or may not
12398 still be running; it might have filled the trace buffer in the
12399 meantime, or stopped for one of the other reasons. If it is running,
12400 it will continue after reconnection.
12402 Upon reconnection, the target will upload information about the
12403 tracepoints in effect. @value{GDBN} will then compare that
12404 information to the set of tracepoints currently defined, and attempt
12405 to match them up, allowing for the possibility that the numbers may
12406 have changed due to creation and deletion in the meantime. If one of
12407 the target's tracepoints does not match any in @value{GDBN}, the
12408 debugger will create a new tracepoint, so that you have a number with
12409 which to specify that tracepoint. This matching-up process is
12410 necessarily heuristic, and it may result in useless tracepoints being
12411 created; you may simply delete them if they are of no use.
12413 @cindex circular trace buffer
12414 If your target agent supports a @dfn{circular trace buffer}, then you
12415 can run a trace experiment indefinitely without filling the trace
12416 buffer; when space runs out, the agent deletes already-collected trace
12417 frames, oldest first, until there is enough room to continue
12418 collecting. This is especially useful if your tracepoints are being
12419 hit too often, and your trace gets terminated prematurely because the
12420 buffer is full. To ask for a circular trace buffer, simply set
12421 @samp{circular-trace-buffer} to on. You can set this at any time,
12422 including during tracing; if the agent can do it, it will change
12423 buffer handling on the fly, otherwise it will not take effect until
12427 @item set circular-trace-buffer on
12428 @itemx set circular-trace-buffer off
12429 @kindex set circular-trace-buffer
12430 Choose whether a tracing run should use a linear or circular buffer
12431 for trace data. A linear buffer will not lose any trace data, but may
12432 fill up prematurely, while a circular buffer will discard old trace
12433 data, but it will have always room for the latest tracepoint hits.
12435 @item show circular-trace-buffer
12436 @kindex show circular-trace-buffer
12437 Show the current choice for the trace buffer. Note that this may not
12438 match the agent's current buffer handling, nor is it guaranteed to
12439 match the setting that might have been in effect during a past run,
12440 for instance if you are looking at frames from a trace file.
12445 @item set trace-buffer-size @var{n}
12446 @itemx set trace-buffer-size unlimited
12447 @kindex set trace-buffer-size
12448 Request that the target use a trace buffer of @var{n} bytes. Not all
12449 targets will honor the request; they may have a compiled-in size for
12450 the trace buffer, or some other limitation. Set to a value of
12451 @code{unlimited} or @code{-1} to let the target use whatever size it
12452 likes. This is also the default.
12454 @item show trace-buffer-size
12455 @kindex show trace-buffer-size
12456 Show the current requested size for the trace buffer. Note that this
12457 will only match the actual size if the target supports size-setting,
12458 and was able to handle the requested size. For instance, if the
12459 target can only change buffer size between runs, this variable will
12460 not reflect the change until the next run starts. Use @code{tstatus}
12461 to get a report of the actual buffer size.
12465 @item set trace-user @var{text}
12466 @kindex set trace-user
12468 @item show trace-user
12469 @kindex show trace-user
12471 @item set trace-notes @var{text}
12472 @kindex set trace-notes
12473 Set the trace run's notes.
12475 @item show trace-notes
12476 @kindex show trace-notes
12477 Show the trace run's notes.
12479 @item set trace-stop-notes @var{text}
12480 @kindex set trace-stop-notes
12481 Set the trace run's stop notes. The handling of the note is as for
12482 @code{tstop} arguments; the set command is convenient way to fix a
12483 stop note that is mistaken or incomplete.
12485 @item show trace-stop-notes
12486 @kindex show trace-stop-notes
12487 Show the trace run's stop notes.
12491 @node Tracepoint Restrictions
12492 @subsection Tracepoint Restrictions
12494 @cindex tracepoint restrictions
12495 There are a number of restrictions on the use of tracepoints. As
12496 described above, tracepoint data gathering occurs on the target
12497 without interaction from @value{GDBN}. Thus the full capabilities of
12498 the debugger are not available during data gathering, and then at data
12499 examination time, you will be limited by only having what was
12500 collected. The following items describe some common problems, but it
12501 is not exhaustive, and you may run into additional difficulties not
12507 Tracepoint expressions are intended to gather objects (lvalues). Thus
12508 the full flexibility of GDB's expression evaluator is not available.
12509 You cannot call functions, cast objects to aggregate types, access
12510 convenience variables or modify values (except by assignment to trace
12511 state variables). Some language features may implicitly call
12512 functions (for instance Objective-C fields with accessors), and therefore
12513 cannot be collected either.
12516 Collection of local variables, either individually or in bulk with
12517 @code{$locals} or @code{$args}, during @code{while-stepping} may
12518 behave erratically. The stepping action may enter a new scope (for
12519 instance by stepping into a function), or the location of the variable
12520 may change (for instance it is loaded into a register). The
12521 tracepoint data recorded uses the location information for the
12522 variables that is correct for the tracepoint location. When the
12523 tracepoint is created, it is not possible, in general, to determine
12524 where the steps of a @code{while-stepping} sequence will advance the
12525 program---particularly if a conditional branch is stepped.
12528 Collection of an incompletely-initialized or partially-destroyed object
12529 may result in something that @value{GDBN} cannot display, or displays
12530 in a misleading way.
12533 When @value{GDBN} displays a pointer to character it automatically
12534 dereferences the pointer to also display characters of the string
12535 being pointed to. However, collecting the pointer during tracing does
12536 not automatically collect the string. You need to explicitly
12537 dereference the pointer and provide size information if you want to
12538 collect not only the pointer, but the memory pointed to. For example,
12539 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12543 It is not possible to collect a complete stack backtrace at a
12544 tracepoint. Instead, you may collect the registers and a few hundred
12545 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12546 (adjust to use the name of the actual stack pointer register on your
12547 target architecture, and the amount of stack you wish to capture).
12548 Then the @code{backtrace} command will show a partial backtrace when
12549 using a trace frame. The number of stack frames that can be examined
12550 depends on the sizes of the frames in the collected stack. Note that
12551 if you ask for a block so large that it goes past the bottom of the
12552 stack, the target agent may report an error trying to read from an
12556 If you do not collect registers at a tracepoint, @value{GDBN} can
12557 infer that the value of @code{$pc} must be the same as the address of
12558 the tracepoint and use that when you are looking at a trace frame
12559 for that tracepoint. However, this cannot work if the tracepoint has
12560 multiple locations (for instance if it was set in a function that was
12561 inlined), or if it has a @code{while-stepping} loop. In those cases
12562 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12567 @node Analyze Collected Data
12568 @section Using the Collected Data
12570 After the tracepoint experiment ends, you use @value{GDBN} commands
12571 for examining the trace data. The basic idea is that each tracepoint
12572 collects a trace @dfn{snapshot} every time it is hit and another
12573 snapshot every time it single-steps. All these snapshots are
12574 consecutively numbered from zero and go into a buffer, and you can
12575 examine them later. The way you examine them is to @dfn{focus} on a
12576 specific trace snapshot. When the remote stub is focused on a trace
12577 snapshot, it will respond to all @value{GDBN} requests for memory and
12578 registers by reading from the buffer which belongs to that snapshot,
12579 rather than from @emph{real} memory or registers of the program being
12580 debugged. This means that @strong{all} @value{GDBN} commands
12581 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12582 behave as if we were currently debugging the program state as it was
12583 when the tracepoint occurred. Any requests for data that are not in
12584 the buffer will fail.
12587 * tfind:: How to select a trace snapshot
12588 * tdump:: How to display all data for a snapshot
12589 * save tracepoints:: How to save tracepoints for a future run
12593 @subsection @code{tfind @var{n}}
12596 @cindex select trace snapshot
12597 @cindex find trace snapshot
12598 The basic command for selecting a trace snapshot from the buffer is
12599 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12600 counting from zero. If no argument @var{n} is given, the next
12601 snapshot is selected.
12603 Here are the various forms of using the @code{tfind} command.
12607 Find the first snapshot in the buffer. This is a synonym for
12608 @code{tfind 0} (since 0 is the number of the first snapshot).
12611 Stop debugging trace snapshots, resume @emph{live} debugging.
12614 Same as @samp{tfind none}.
12617 No argument means find the next trace snapshot.
12620 Find the previous trace snapshot before the current one. This permits
12621 retracing earlier steps.
12623 @item tfind tracepoint @var{num}
12624 Find the next snapshot associated with tracepoint @var{num}. Search
12625 proceeds forward from the last examined trace snapshot. If no
12626 argument @var{num} is given, it means find the next snapshot collected
12627 for the same tracepoint as the current snapshot.
12629 @item tfind pc @var{addr}
12630 Find the next snapshot associated with the value @var{addr} of the
12631 program counter. Search proceeds forward from the last examined trace
12632 snapshot. If no argument @var{addr} is given, it means find the next
12633 snapshot with the same value of PC as the current snapshot.
12635 @item tfind outside @var{addr1}, @var{addr2}
12636 Find the next snapshot whose PC is outside the given range of
12637 addresses (exclusive).
12639 @item tfind range @var{addr1}, @var{addr2}
12640 Find the next snapshot whose PC is between @var{addr1} and
12641 @var{addr2} (inclusive).
12643 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12644 Find the next snapshot associated with the source line @var{n}. If
12645 the optional argument @var{file} is given, refer to line @var{n} in
12646 that source file. Search proceeds forward from the last examined
12647 trace snapshot. If no argument @var{n} is given, it means find the
12648 next line other than the one currently being examined; thus saying
12649 @code{tfind line} repeatedly can appear to have the same effect as
12650 stepping from line to line in a @emph{live} debugging session.
12653 The default arguments for the @code{tfind} commands are specifically
12654 designed to make it easy to scan through the trace buffer. For
12655 instance, @code{tfind} with no argument selects the next trace
12656 snapshot, and @code{tfind -} with no argument selects the previous
12657 trace snapshot. So, by giving one @code{tfind} command, and then
12658 simply hitting @key{RET} repeatedly you can examine all the trace
12659 snapshots in order. Or, by saying @code{tfind -} and then hitting
12660 @key{RET} repeatedly you can examine the snapshots in reverse order.
12661 The @code{tfind line} command with no argument selects the snapshot
12662 for the next source line executed. The @code{tfind pc} command with
12663 no argument selects the next snapshot with the same program counter
12664 (PC) as the current frame. The @code{tfind tracepoint} command with
12665 no argument selects the next trace snapshot collected by the same
12666 tracepoint as the current one.
12668 In addition to letting you scan through the trace buffer manually,
12669 these commands make it easy to construct @value{GDBN} scripts that
12670 scan through the trace buffer and print out whatever collected data
12671 you are interested in. Thus, if we want to examine the PC, FP, and SP
12672 registers from each trace frame in the buffer, we can say this:
12675 (@value{GDBP}) @b{tfind start}
12676 (@value{GDBP}) @b{while ($trace_frame != -1)}
12677 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12678 $trace_frame, $pc, $sp, $fp
12682 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12683 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12684 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12685 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12686 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12687 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12688 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12689 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12690 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12691 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12692 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12695 Or, if we want to examine the variable @code{X} at each source line in
12699 (@value{GDBP}) @b{tfind start}
12700 (@value{GDBP}) @b{while ($trace_frame != -1)}
12701 > printf "Frame %d, X == %d\n", $trace_frame, X
12711 @subsection @code{tdump}
12713 @cindex dump all data collected at tracepoint
12714 @cindex tracepoint data, display
12716 This command takes no arguments. It prints all the data collected at
12717 the current trace snapshot.
12720 (@value{GDBP}) @b{trace 444}
12721 (@value{GDBP}) @b{actions}
12722 Enter actions for tracepoint #2, one per line:
12723 > collect $regs, $locals, $args, gdb_long_test
12726 (@value{GDBP}) @b{tstart}
12728 (@value{GDBP}) @b{tfind line 444}
12729 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12731 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12733 (@value{GDBP}) @b{tdump}
12734 Data collected at tracepoint 2, trace frame 1:
12735 d0 0xc4aa0085 -995491707
12739 d4 0x71aea3d 119204413
12742 d7 0x380035 3670069
12743 a0 0x19e24a 1696330
12744 a1 0x3000668 50333288
12746 a3 0x322000 3284992
12747 a4 0x3000698 50333336
12748 a5 0x1ad3cc 1758156
12749 fp 0x30bf3c 0x30bf3c
12750 sp 0x30bf34 0x30bf34
12752 pc 0x20b2c8 0x20b2c8
12756 p = 0x20e5b4 "gdb-test"
12763 gdb_long_test = 17 '\021'
12768 @code{tdump} works by scanning the tracepoint's current collection
12769 actions and printing the value of each expression listed. So
12770 @code{tdump} can fail, if after a run, you change the tracepoint's
12771 actions to mention variables that were not collected during the run.
12773 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12774 uses the collected value of @code{$pc} to distinguish between trace
12775 frames that were collected at the tracepoint hit, and frames that were
12776 collected while stepping. This allows it to correctly choose whether
12777 to display the basic list of collections, or the collections from the
12778 body of the while-stepping loop. However, if @code{$pc} was not collected,
12779 then @code{tdump} will always attempt to dump using the basic collection
12780 list, and may fail if a while-stepping frame does not include all the
12781 same data that is collected at the tracepoint hit.
12782 @c This is getting pretty arcane, example would be good.
12784 @node save tracepoints
12785 @subsection @code{save tracepoints @var{filename}}
12786 @kindex save tracepoints
12787 @kindex save-tracepoints
12788 @cindex save tracepoints for future sessions
12790 This command saves all current tracepoint definitions together with
12791 their actions and passcounts, into a file @file{@var{filename}}
12792 suitable for use in a later debugging session. To read the saved
12793 tracepoint definitions, use the @code{source} command (@pxref{Command
12794 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12795 alias for @w{@code{save tracepoints}}
12797 @node Tracepoint Variables
12798 @section Convenience Variables for Tracepoints
12799 @cindex tracepoint variables
12800 @cindex convenience variables for tracepoints
12803 @vindex $trace_frame
12804 @item (int) $trace_frame
12805 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12806 snapshot is selected.
12808 @vindex $tracepoint
12809 @item (int) $tracepoint
12810 The tracepoint for the current trace snapshot.
12812 @vindex $trace_line
12813 @item (int) $trace_line
12814 The line number for the current trace snapshot.
12816 @vindex $trace_file
12817 @item (char []) $trace_file
12818 The source file for the current trace snapshot.
12820 @vindex $trace_func
12821 @item (char []) $trace_func
12822 The name of the function containing @code{$tracepoint}.
12825 Note: @code{$trace_file} is not suitable for use in @code{printf},
12826 use @code{output} instead.
12828 Here's a simple example of using these convenience variables for
12829 stepping through all the trace snapshots and printing some of their
12830 data. Note that these are not the same as trace state variables,
12831 which are managed by the target.
12834 (@value{GDBP}) @b{tfind start}
12836 (@value{GDBP}) @b{while $trace_frame != -1}
12837 > output $trace_file
12838 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12844 @section Using Trace Files
12845 @cindex trace files
12847 In some situations, the target running a trace experiment may no
12848 longer be available; perhaps it crashed, or the hardware was needed
12849 for a different activity. To handle these cases, you can arrange to
12850 dump the trace data into a file, and later use that file as a source
12851 of trace data, via the @code{target tfile} command.
12856 @item tsave [ -r ] @var{filename}
12857 @itemx tsave [-ctf] @var{dirname}
12858 Save the trace data to @var{filename}. By default, this command
12859 assumes that @var{filename} refers to the host filesystem, so if
12860 necessary @value{GDBN} will copy raw trace data up from the target and
12861 then save it. If the target supports it, you can also supply the
12862 optional argument @code{-r} (``remote'') to direct the target to save
12863 the data directly into @var{filename} in its own filesystem, which may be
12864 more efficient if the trace buffer is very large. (Note, however, that
12865 @code{target tfile} can only read from files accessible to the host.)
12866 By default, this command will save trace frame in tfile format.
12867 You can supply the optional argument @code{-ctf} to save date in CTF
12868 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12869 that can be shared by multiple debugging and tracing tools. Please go to
12870 @indicateurl{http://www.efficios.com/ctf} to get more information.
12872 @kindex target tfile
12876 @item target tfile @var{filename}
12877 @itemx target ctf @var{dirname}
12878 Use the file named @var{filename} or directory named @var{dirname} as
12879 a source of trace data. Commands that examine data work as they do with
12880 a live target, but it is not possible to run any new trace experiments.
12881 @code{tstatus} will report the state of the trace run at the moment
12882 the data was saved, as well as the current trace frame you are examining.
12883 @var{filename} or @var{dirname} must be on a filesystem accessible to
12887 (@value{GDBP}) target ctf ctf.ctf
12888 (@value{GDBP}) tfind
12889 Found trace frame 0, tracepoint 2
12890 39 ++a; /* set tracepoint 1 here */
12891 (@value{GDBP}) tdump
12892 Data collected at tracepoint 2, trace frame 0:
12896 c = @{"123", "456", "789", "123", "456", "789"@}
12897 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12905 @chapter Debugging Programs That Use Overlays
12908 If your program is too large to fit completely in your target system's
12909 memory, you can sometimes use @dfn{overlays} to work around this
12910 problem. @value{GDBN} provides some support for debugging programs that
12914 * How Overlays Work:: A general explanation of overlays.
12915 * Overlay Commands:: Managing overlays in @value{GDBN}.
12916 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12917 mapped by asking the inferior.
12918 * Overlay Sample Program:: A sample program using overlays.
12921 @node How Overlays Work
12922 @section How Overlays Work
12923 @cindex mapped overlays
12924 @cindex unmapped overlays
12925 @cindex load address, overlay's
12926 @cindex mapped address
12927 @cindex overlay area
12929 Suppose you have a computer whose instruction address space is only 64
12930 kilobytes long, but which has much more memory which can be accessed by
12931 other means: special instructions, segment registers, or memory
12932 management hardware, for example. Suppose further that you want to
12933 adapt a program which is larger than 64 kilobytes to run on this system.
12935 One solution is to identify modules of your program which are relatively
12936 independent, and need not call each other directly; call these modules
12937 @dfn{overlays}. Separate the overlays from the main program, and place
12938 their machine code in the larger memory. Place your main program in
12939 instruction memory, but leave at least enough space there to hold the
12940 largest overlay as well.
12942 Now, to call a function located in an overlay, you must first copy that
12943 overlay's machine code from the large memory into the space set aside
12944 for it in the instruction memory, and then jump to its entry point
12947 @c NB: In the below the mapped area's size is greater or equal to the
12948 @c size of all overlays. This is intentional to remind the developer
12949 @c that overlays don't necessarily need to be the same size.
12953 Data Instruction Larger
12954 Address Space Address Space Address Space
12955 +-----------+ +-----------+ +-----------+
12957 +-----------+ +-----------+ +-----------+<-- overlay 1
12958 | program | | main | .----| overlay 1 | load address
12959 | variables | | program | | +-----------+
12960 | and heap | | | | | |
12961 +-----------+ | | | +-----------+<-- overlay 2
12962 | | +-----------+ | | | load address
12963 +-----------+ | | | .-| overlay 2 |
12965 mapped --->+-----------+ | | +-----------+
12966 address | | | | | |
12967 | overlay | <-' | | |
12968 | area | <---' +-----------+<-- overlay 3
12969 | | <---. | | load address
12970 +-----------+ `--| overlay 3 |
12977 @anchor{A code overlay}A code overlay
12981 The diagram (@pxref{A code overlay}) shows a system with separate data
12982 and instruction address spaces. To map an overlay, the program copies
12983 its code from the larger address space to the instruction address space.
12984 Since the overlays shown here all use the same mapped address, only one
12985 may be mapped at a time. For a system with a single address space for
12986 data and instructions, the diagram would be similar, except that the
12987 program variables and heap would share an address space with the main
12988 program and the overlay area.
12990 An overlay loaded into instruction memory and ready for use is called a
12991 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12992 instruction memory. An overlay not present (or only partially present)
12993 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12994 is its address in the larger memory. The mapped address is also called
12995 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12996 called the @dfn{load memory address}, or @dfn{LMA}.
12998 Unfortunately, overlays are not a completely transparent way to adapt a
12999 program to limited instruction memory. They introduce a new set of
13000 global constraints you must keep in mind as you design your program:
13005 Before calling or returning to a function in an overlay, your program
13006 must make sure that overlay is actually mapped. Otherwise, the call or
13007 return will transfer control to the right address, but in the wrong
13008 overlay, and your program will probably crash.
13011 If the process of mapping an overlay is expensive on your system, you
13012 will need to choose your overlays carefully to minimize their effect on
13013 your program's performance.
13016 The executable file you load onto your system must contain each
13017 overlay's instructions, appearing at the overlay's load address, not its
13018 mapped address. However, each overlay's instructions must be relocated
13019 and its symbols defined as if the overlay were at its mapped address.
13020 You can use GNU linker scripts to specify different load and relocation
13021 addresses for pieces of your program; see @ref{Overlay Description,,,
13022 ld.info, Using ld: the GNU linker}.
13025 The procedure for loading executable files onto your system must be able
13026 to load their contents into the larger address space as well as the
13027 instruction and data spaces.
13031 The overlay system described above is rather simple, and could be
13032 improved in many ways:
13037 If your system has suitable bank switch registers or memory management
13038 hardware, you could use those facilities to make an overlay's load area
13039 contents simply appear at their mapped address in instruction space.
13040 This would probably be faster than copying the overlay to its mapped
13041 area in the usual way.
13044 If your overlays are small enough, you could set aside more than one
13045 overlay area, and have more than one overlay mapped at a time.
13048 You can use overlays to manage data, as well as instructions. In
13049 general, data overlays are even less transparent to your design than
13050 code overlays: whereas code overlays only require care when you call or
13051 return to functions, data overlays require care every time you access
13052 the data. Also, if you change the contents of a data overlay, you
13053 must copy its contents back out to its load address before you can copy a
13054 different data overlay into the same mapped area.
13059 @node Overlay Commands
13060 @section Overlay Commands
13062 To use @value{GDBN}'s overlay support, each overlay in your program must
13063 correspond to a separate section of the executable file. The section's
13064 virtual memory address and load memory address must be the overlay's
13065 mapped and load addresses. Identifying overlays with sections allows
13066 @value{GDBN} to determine the appropriate address of a function or
13067 variable, depending on whether the overlay is mapped or not.
13069 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13070 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13075 Disable @value{GDBN}'s overlay support. When overlay support is
13076 disabled, @value{GDBN} assumes that all functions and variables are
13077 always present at their mapped addresses. By default, @value{GDBN}'s
13078 overlay support is disabled.
13080 @item overlay manual
13081 @cindex manual overlay debugging
13082 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13083 relies on you to tell it which overlays are mapped, and which are not,
13084 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13085 commands described below.
13087 @item overlay map-overlay @var{overlay}
13088 @itemx overlay map @var{overlay}
13089 @cindex map an overlay
13090 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13091 be the name of the object file section containing the overlay. When an
13092 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13093 functions and variables at their mapped addresses. @value{GDBN} assumes
13094 that any other overlays whose mapped ranges overlap that of
13095 @var{overlay} are now unmapped.
13097 @item overlay unmap-overlay @var{overlay}
13098 @itemx overlay unmap @var{overlay}
13099 @cindex unmap an overlay
13100 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13101 must be the name of the object file section containing the overlay.
13102 When an overlay is unmapped, @value{GDBN} assumes it can find the
13103 overlay's functions and variables at their load addresses.
13106 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13107 consults a data structure the overlay manager maintains in the inferior
13108 to see which overlays are mapped. For details, see @ref{Automatic
13109 Overlay Debugging}.
13111 @item overlay load-target
13112 @itemx overlay load
13113 @cindex reloading the overlay table
13114 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13115 re-reads the table @value{GDBN} automatically each time the inferior
13116 stops, so this command should only be necessary if you have changed the
13117 overlay mapping yourself using @value{GDBN}. This command is only
13118 useful when using automatic overlay debugging.
13120 @item overlay list-overlays
13121 @itemx overlay list
13122 @cindex listing mapped overlays
13123 Display a list of the overlays currently mapped, along with their mapped
13124 addresses, load addresses, and sizes.
13128 Normally, when @value{GDBN} prints a code address, it includes the name
13129 of the function the address falls in:
13132 (@value{GDBP}) print main
13133 $3 = @{int ()@} 0x11a0 <main>
13136 When overlay debugging is enabled, @value{GDBN} recognizes code in
13137 unmapped overlays, and prints the names of unmapped functions with
13138 asterisks around them. For example, if @code{foo} is a function in an
13139 unmapped overlay, @value{GDBN} prints it this way:
13142 (@value{GDBP}) overlay list
13143 No sections are mapped.
13144 (@value{GDBP}) print foo
13145 $5 = @{int (int)@} 0x100000 <*foo*>
13148 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13152 (@value{GDBP}) overlay list
13153 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13154 mapped at 0x1016 - 0x104a
13155 (@value{GDBP}) print foo
13156 $6 = @{int (int)@} 0x1016 <foo>
13159 When overlay debugging is enabled, @value{GDBN} can find the correct
13160 address for functions and variables in an overlay, whether or not the
13161 overlay is mapped. This allows most @value{GDBN} commands, like
13162 @code{break} and @code{disassemble}, to work normally, even on unmapped
13163 code. However, @value{GDBN}'s breakpoint support has some limitations:
13167 @cindex breakpoints in overlays
13168 @cindex overlays, setting breakpoints in
13169 You can set breakpoints in functions in unmapped overlays, as long as
13170 @value{GDBN} can write to the overlay at its load address.
13172 @value{GDBN} can not set hardware or simulator-based breakpoints in
13173 unmapped overlays. However, if you set a breakpoint at the end of your
13174 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13175 you are using manual overlay management), @value{GDBN} will re-set its
13176 breakpoints properly.
13180 @node Automatic Overlay Debugging
13181 @section Automatic Overlay Debugging
13182 @cindex automatic overlay debugging
13184 @value{GDBN} can automatically track which overlays are mapped and which
13185 are not, given some simple co-operation from the overlay manager in the
13186 inferior. If you enable automatic overlay debugging with the
13187 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13188 looks in the inferior's memory for certain variables describing the
13189 current state of the overlays.
13191 Here are the variables your overlay manager must define to support
13192 @value{GDBN}'s automatic overlay debugging:
13196 @item @code{_ovly_table}:
13197 This variable must be an array of the following structures:
13202 /* The overlay's mapped address. */
13205 /* The size of the overlay, in bytes. */
13206 unsigned long size;
13208 /* The overlay's load address. */
13211 /* Non-zero if the overlay is currently mapped;
13213 unsigned long mapped;
13217 @item @code{_novlys}:
13218 This variable must be a four-byte signed integer, holding the total
13219 number of elements in @code{_ovly_table}.
13223 To decide whether a particular overlay is mapped or not, @value{GDBN}
13224 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13225 @code{lma} members equal the VMA and LMA of the overlay's section in the
13226 executable file. When @value{GDBN} finds a matching entry, it consults
13227 the entry's @code{mapped} member to determine whether the overlay is
13230 In addition, your overlay manager may define a function called
13231 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13232 will silently set a breakpoint there. If the overlay manager then
13233 calls this function whenever it has changed the overlay table, this
13234 will enable @value{GDBN} to accurately keep track of which overlays
13235 are in program memory, and update any breakpoints that may be set
13236 in overlays. This will allow breakpoints to work even if the
13237 overlays are kept in ROM or other non-writable memory while they
13238 are not being executed.
13240 @node Overlay Sample Program
13241 @section Overlay Sample Program
13242 @cindex overlay example program
13244 When linking a program which uses overlays, you must place the overlays
13245 at their load addresses, while relocating them to run at their mapped
13246 addresses. To do this, you must write a linker script (@pxref{Overlay
13247 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13248 since linker scripts are specific to a particular host system, target
13249 architecture, and target memory layout, this manual cannot provide
13250 portable sample code demonstrating @value{GDBN}'s overlay support.
13252 However, the @value{GDBN} source distribution does contain an overlaid
13253 program, with linker scripts for a few systems, as part of its test
13254 suite. The program consists of the following files from
13255 @file{gdb/testsuite/gdb.base}:
13259 The main program file.
13261 A simple overlay manager, used by @file{overlays.c}.
13266 Overlay modules, loaded and used by @file{overlays.c}.
13269 Linker scripts for linking the test program on the @code{d10v-elf}
13270 and @code{m32r-elf} targets.
13273 You can build the test program using the @code{d10v-elf} GCC
13274 cross-compiler like this:
13277 $ d10v-elf-gcc -g -c overlays.c
13278 $ d10v-elf-gcc -g -c ovlymgr.c
13279 $ d10v-elf-gcc -g -c foo.c
13280 $ d10v-elf-gcc -g -c bar.c
13281 $ d10v-elf-gcc -g -c baz.c
13282 $ d10v-elf-gcc -g -c grbx.c
13283 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13284 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13287 The build process is identical for any other architecture, except that
13288 you must substitute the appropriate compiler and linker script for the
13289 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13293 @chapter Using @value{GDBN} with Different Languages
13296 Although programming languages generally have common aspects, they are
13297 rarely expressed in the same manner. For instance, in ANSI C,
13298 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13299 Modula-2, it is accomplished by @code{p^}. Values can also be
13300 represented (and displayed) differently. Hex numbers in C appear as
13301 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13303 @cindex working language
13304 Language-specific information is built into @value{GDBN} for some languages,
13305 allowing you to express operations like the above in your program's
13306 native language, and allowing @value{GDBN} to output values in a manner
13307 consistent with the syntax of your program's native language. The
13308 language you use to build expressions is called the @dfn{working
13312 * Setting:: Switching between source languages
13313 * Show:: Displaying the language
13314 * Checks:: Type and range checks
13315 * Supported Languages:: Supported languages
13316 * Unsupported Languages:: Unsupported languages
13320 @section Switching Between Source Languages
13322 There are two ways to control the working language---either have @value{GDBN}
13323 set it automatically, or select it manually yourself. You can use the
13324 @code{set language} command for either purpose. On startup, @value{GDBN}
13325 defaults to setting the language automatically. The working language is
13326 used to determine how expressions you type are interpreted, how values
13329 In addition to the working language, every source file that
13330 @value{GDBN} knows about has its own working language. For some object
13331 file formats, the compiler might indicate which language a particular
13332 source file is in. However, most of the time @value{GDBN} infers the
13333 language from the name of the file. The language of a source file
13334 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13335 show each frame appropriately for its own language. There is no way to
13336 set the language of a source file from within @value{GDBN}, but you can
13337 set the language associated with a filename extension. @xref{Show, ,
13338 Displaying the Language}.
13340 This is most commonly a problem when you use a program, such
13341 as @code{cfront} or @code{f2c}, that generates C but is written in
13342 another language. In that case, make the
13343 program use @code{#line} directives in its C output; that way
13344 @value{GDBN} will know the correct language of the source code of the original
13345 program, and will display that source code, not the generated C code.
13348 * Filenames:: Filename extensions and languages.
13349 * Manually:: Setting the working language manually
13350 * Automatically:: Having @value{GDBN} infer the source language
13354 @subsection List of Filename Extensions and Languages
13356 If a source file name ends in one of the following extensions, then
13357 @value{GDBN} infers that its language is the one indicated.
13375 C@t{++} source file
13381 Objective-C source file
13385 Fortran source file
13388 Modula-2 source file
13392 Assembler source file. This actually behaves almost like C, but
13393 @value{GDBN} does not skip over function prologues when stepping.
13396 In addition, you may set the language associated with a filename
13397 extension. @xref{Show, , Displaying the Language}.
13400 @subsection Setting the Working Language
13402 If you allow @value{GDBN} to set the language automatically,
13403 expressions are interpreted the same way in your debugging session and
13406 @kindex set language
13407 If you wish, you may set the language manually. To do this, issue the
13408 command @samp{set language @var{lang}}, where @var{lang} is the name of
13409 a language, such as
13410 @code{c} or @code{modula-2}.
13411 For a list of the supported languages, type @samp{set language}.
13413 Setting the language manually prevents @value{GDBN} from updating the working
13414 language automatically. This can lead to confusion if you try
13415 to debug a program when the working language is not the same as the
13416 source language, when an expression is acceptable to both
13417 languages---but means different things. For instance, if the current
13418 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13426 might not have the effect you intended. In C, this means to add
13427 @code{b} and @code{c} and place the result in @code{a}. The result
13428 printed would be the value of @code{a}. In Modula-2, this means to compare
13429 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13431 @node Automatically
13432 @subsection Having @value{GDBN} Infer the Source Language
13434 To have @value{GDBN} set the working language automatically, use
13435 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13436 then infers the working language. That is, when your program stops in a
13437 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13438 working language to the language recorded for the function in that
13439 frame. If the language for a frame is unknown (that is, if the function
13440 or block corresponding to the frame was defined in a source file that
13441 does not have a recognized extension), the current working language is
13442 not changed, and @value{GDBN} issues a warning.
13444 This may not seem necessary for most programs, which are written
13445 entirely in one source language. However, program modules and libraries
13446 written in one source language can be used by a main program written in
13447 a different source language. Using @samp{set language auto} in this
13448 case frees you from having to set the working language manually.
13451 @section Displaying the Language
13453 The following commands help you find out which language is the
13454 working language, and also what language source files were written in.
13457 @item show language
13458 @anchor{show language}
13459 @kindex show language
13460 Display the current working language. This is the
13461 language you can use with commands such as @code{print} to
13462 build and compute expressions that may involve variables in your program.
13465 @kindex info frame@r{, show the source language}
13466 Display the source language for this frame. This language becomes the
13467 working language if you use an identifier from this frame.
13468 @xref{Frame Info, ,Information about a Frame}, to identify the other
13469 information listed here.
13472 @kindex info source@r{, show the source language}
13473 Display the source language of this source file.
13474 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13475 information listed here.
13478 In unusual circumstances, you may have source files with extensions
13479 not in the standard list. You can then set the extension associated
13480 with a language explicitly:
13483 @item set extension-language @var{ext} @var{language}
13484 @kindex set extension-language
13485 Tell @value{GDBN} that source files with extension @var{ext} are to be
13486 assumed as written in the source language @var{language}.
13488 @item info extensions
13489 @kindex info extensions
13490 List all the filename extensions and the associated languages.
13494 @section Type and Range Checking
13496 Some languages are designed to guard you against making seemingly common
13497 errors through a series of compile- and run-time checks. These include
13498 checking the type of arguments to functions and operators and making
13499 sure mathematical overflows are caught at run time. Checks such as
13500 these help to ensure a program's correctness once it has been compiled
13501 by eliminating type mismatches and providing active checks for range
13502 errors when your program is running.
13504 By default @value{GDBN} checks for these errors according to the
13505 rules of the current source language. Although @value{GDBN} does not check
13506 the statements in your program, it can check expressions entered directly
13507 into @value{GDBN} for evaluation via the @code{print} command, for example.
13510 * Type Checking:: An overview of type checking
13511 * Range Checking:: An overview of range checking
13514 @cindex type checking
13515 @cindex checks, type
13516 @node Type Checking
13517 @subsection An Overview of Type Checking
13519 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13520 arguments to operators and functions have to be of the correct type,
13521 otherwise an error occurs. These checks prevent type mismatch
13522 errors from ever causing any run-time problems. For example,
13525 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13527 (@value{GDBP}) print obj.my_method (0)
13530 (@value{GDBP}) print obj.my_method (0x1234)
13531 Cannot resolve method klass::my_method to any overloaded instance
13534 The second example fails because in C@t{++} the integer constant
13535 @samp{0x1234} is not type-compatible with the pointer parameter type.
13537 For the expressions you use in @value{GDBN} commands, you can tell
13538 @value{GDBN} to not enforce strict type checking or
13539 to treat any mismatches as errors and abandon the expression;
13540 When type checking is disabled, @value{GDBN} successfully evaluates
13541 expressions like the second example above.
13543 Even if type checking is off, there may be other reasons
13544 related to type that prevent @value{GDBN} from evaluating an expression.
13545 For instance, @value{GDBN} does not know how to add an @code{int} and
13546 a @code{struct foo}. These particular type errors have nothing to do
13547 with the language in use and usually arise from expressions which make
13548 little sense to evaluate anyway.
13550 @value{GDBN} provides some additional commands for controlling type checking:
13552 @kindex set check type
13553 @kindex show check type
13555 @item set check type on
13556 @itemx set check type off
13557 Set strict type checking on or off. If any type mismatches occur in
13558 evaluating an expression while type checking is on, @value{GDBN} prints a
13559 message and aborts evaluation of the expression.
13561 @item show check type
13562 Show the current setting of type checking and whether @value{GDBN}
13563 is enforcing strict type checking rules.
13566 @cindex range checking
13567 @cindex checks, range
13568 @node Range Checking
13569 @subsection An Overview of Range Checking
13571 In some languages (such as Modula-2), it is an error to exceed the
13572 bounds of a type; this is enforced with run-time checks. Such range
13573 checking is meant to ensure program correctness by making sure
13574 computations do not overflow, or indices on an array element access do
13575 not exceed the bounds of the array.
13577 For expressions you use in @value{GDBN} commands, you can tell
13578 @value{GDBN} to treat range errors in one of three ways: ignore them,
13579 always treat them as errors and abandon the expression, or issue
13580 warnings but evaluate the expression anyway.
13582 A range error can result from numerical overflow, from exceeding an
13583 array index bound, or when you type a constant that is not a member
13584 of any type. Some languages, however, do not treat overflows as an
13585 error. In many implementations of C, mathematical overflow causes the
13586 result to ``wrap around'' to lower values---for example, if @var{m} is
13587 the largest integer value, and @var{s} is the smallest, then
13590 @var{m} + 1 @result{} @var{s}
13593 This, too, is specific to individual languages, and in some cases
13594 specific to individual compilers or machines. @xref{Supported Languages, ,
13595 Supported Languages}, for further details on specific languages.
13597 @value{GDBN} provides some additional commands for controlling the range checker:
13599 @kindex set check range
13600 @kindex show check range
13602 @item set check range auto
13603 Set range checking on or off based on the current working language.
13604 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13607 @item set check range on
13608 @itemx set check range off
13609 Set range checking on or off, overriding the default setting for the
13610 current working language. A warning is issued if the setting does not
13611 match the language default. If a range error occurs and range checking is on,
13612 then a message is printed and evaluation of the expression is aborted.
13614 @item set check range warn
13615 Output messages when the @value{GDBN} range checker detects a range error,
13616 but attempt to evaluate the expression anyway. Evaluating the
13617 expression may still be impossible for other reasons, such as accessing
13618 memory that the process does not own (a typical example from many Unix
13622 Show the current setting of the range checker, and whether or not it is
13623 being set automatically by @value{GDBN}.
13626 @node Supported Languages
13627 @section Supported Languages
13629 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13630 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13631 @c This is false ...
13632 Some @value{GDBN} features may be used in expressions regardless of the
13633 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13634 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13635 ,Expressions}) can be used with the constructs of any supported
13638 The following sections detail to what degree each source language is
13639 supported by @value{GDBN}. These sections are not meant to be language
13640 tutorials or references, but serve only as a reference guide to what the
13641 @value{GDBN} expression parser accepts, and what input and output
13642 formats should look like for different languages. There are many good
13643 books written on each of these languages; please look to these for a
13644 language reference or tutorial.
13647 * C:: C and C@t{++}
13650 * Objective-C:: Objective-C
13651 * OpenCL C:: OpenCL C
13652 * Fortran:: Fortran
13654 * Modula-2:: Modula-2
13659 @subsection C and C@t{++}
13661 @cindex C and C@t{++}
13662 @cindex expressions in C or C@t{++}
13664 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13665 to both languages. Whenever this is the case, we discuss those languages
13669 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13670 @cindex @sc{gnu} C@t{++}
13671 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13672 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13673 effectively, you must compile your C@t{++} programs with a supported
13674 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13675 compiler (@code{aCC}).
13678 * C Operators:: C and C@t{++} operators
13679 * C Constants:: C and C@t{++} constants
13680 * C Plus Plus Expressions:: C@t{++} expressions
13681 * C Defaults:: Default settings for C and C@t{++}
13682 * C Checks:: C and C@t{++} type and range checks
13683 * Debugging C:: @value{GDBN} and C
13684 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13685 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13689 @subsubsection C and C@t{++} Operators
13691 @cindex C and C@t{++} operators
13693 Operators must be defined on values of specific types. For instance,
13694 @code{+} is defined on numbers, but not on structures. Operators are
13695 often defined on groups of types.
13697 For the purposes of C and C@t{++}, the following definitions hold:
13702 @emph{Integral types} include @code{int} with any of its storage-class
13703 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13706 @emph{Floating-point types} include @code{float}, @code{double}, and
13707 @code{long double} (if supported by the target platform).
13710 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13713 @emph{Scalar types} include all of the above.
13718 The following operators are supported. They are listed here
13719 in order of increasing precedence:
13723 The comma or sequencing operator. Expressions in a comma-separated list
13724 are evaluated from left to right, with the result of the entire
13725 expression being the last expression evaluated.
13728 Assignment. The value of an assignment expression is the value
13729 assigned. Defined on scalar types.
13732 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13733 and translated to @w{@code{@var{a} = @var{a op b}}}.
13734 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13735 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13736 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13739 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13740 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13744 Logical @sc{or}. Defined on integral types.
13747 Logical @sc{and}. Defined on integral types.
13750 Bitwise @sc{or}. Defined on integral types.
13753 Bitwise exclusive-@sc{or}. Defined on integral types.
13756 Bitwise @sc{and}. Defined on integral types.
13759 Equality and inequality. Defined on scalar types. The value of these
13760 expressions is 0 for false and non-zero for true.
13762 @item <@r{, }>@r{, }<=@r{, }>=
13763 Less than, greater than, less than or equal, greater than or equal.
13764 Defined on scalar types. The value of these expressions is 0 for false
13765 and non-zero for true.
13768 left shift, and right shift. Defined on integral types.
13771 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13774 Addition and subtraction. Defined on integral types, floating-point types and
13777 @item *@r{, }/@r{, }%
13778 Multiplication, division, and modulus. Multiplication and division are
13779 defined on integral and floating-point types. Modulus is defined on
13783 Increment and decrement. When appearing before a variable, the
13784 operation is performed before the variable is used in an expression;
13785 when appearing after it, the variable's value is used before the
13786 operation takes place.
13789 Pointer dereferencing. Defined on pointer types. Same precedence as
13793 Address operator. Defined on variables. Same precedence as @code{++}.
13795 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13796 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13797 to examine the address
13798 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13802 Negative. Defined on integral and floating-point types. Same
13803 precedence as @code{++}.
13806 Logical negation. Defined on integral types. Same precedence as
13810 Bitwise complement operator. Defined on integral types. Same precedence as
13815 Structure member, and pointer-to-structure member. For convenience,
13816 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13817 pointer based on the stored type information.
13818 Defined on @code{struct} and @code{union} data.
13821 Dereferences of pointers to members.
13824 Array indexing. @code{@var{a}[@var{i}]} is defined as
13825 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13828 Function parameter list. Same precedence as @code{->}.
13831 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13832 and @code{class} types.
13835 Doubled colons also represent the @value{GDBN} scope operator
13836 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13840 If an operator is redefined in the user code, @value{GDBN} usually
13841 attempts to invoke the redefined version instead of using the operator's
13842 predefined meaning.
13845 @subsubsection C and C@t{++} Constants
13847 @cindex C and C@t{++} constants
13849 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13854 Integer constants are a sequence of digits. Octal constants are
13855 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13856 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13857 @samp{l}, specifying that the constant should be treated as a
13861 Floating point constants are a sequence of digits, followed by a decimal
13862 point, followed by a sequence of digits, and optionally followed by an
13863 exponent. An exponent is of the form:
13864 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13865 sequence of digits. The @samp{+} is optional for positive exponents.
13866 A floating-point constant may also end with a letter @samp{f} or
13867 @samp{F}, specifying that the constant should be treated as being of
13868 the @code{float} (as opposed to the default @code{double}) type; or with
13869 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13873 Enumerated constants consist of enumerated identifiers, or their
13874 integral equivalents.
13877 Character constants are a single character surrounded by single quotes
13878 (@code{'}), or a number---the ordinal value of the corresponding character
13879 (usually its @sc{ascii} value). Within quotes, the single character may
13880 be represented by a letter or by @dfn{escape sequences}, which are of
13881 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13882 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13883 @samp{@var{x}} is a predefined special character---for example,
13884 @samp{\n} for newline.
13886 Wide character constants can be written by prefixing a character
13887 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13888 form of @samp{x}. The target wide character set is used when
13889 computing the value of this constant (@pxref{Character Sets}).
13892 String constants are a sequence of character constants surrounded by
13893 double quotes (@code{"}). Any valid character constant (as described
13894 above) may appear. Double quotes within the string must be preceded by
13895 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13898 Wide string constants can be written by prefixing a string constant
13899 with @samp{L}, as in C. The target wide character set is used when
13900 computing the value of this constant (@pxref{Character Sets}).
13903 Pointer constants are an integral value. You can also write pointers
13904 to constants using the C operator @samp{&}.
13907 Array constants are comma-separated lists surrounded by braces @samp{@{}
13908 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13909 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13910 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13913 @node C Plus Plus Expressions
13914 @subsubsection C@t{++} Expressions
13916 @cindex expressions in C@t{++}
13917 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13919 @cindex debugging C@t{++} programs
13920 @cindex C@t{++} compilers
13921 @cindex debug formats and C@t{++}
13922 @cindex @value{NGCC} and C@t{++}
13924 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13925 the proper compiler and the proper debug format. Currently,
13926 @value{GDBN} works best when debugging C@t{++} code that is compiled
13927 with the most recent version of @value{NGCC} possible. The DWARF
13928 debugging format is preferred; @value{NGCC} defaults to this on most
13929 popular platforms. Other compilers and/or debug formats are likely to
13930 work badly or not at all when using @value{GDBN} to debug C@t{++}
13931 code. @xref{Compilation}.
13936 @cindex member functions
13938 Member function calls are allowed; you can use expressions like
13941 count = aml->GetOriginal(x, y)
13944 @vindex this@r{, inside C@t{++} member functions}
13945 @cindex namespace in C@t{++}
13947 While a member function is active (in the selected stack frame), your
13948 expressions have the same namespace available as the member function;
13949 that is, @value{GDBN} allows implicit references to the class instance
13950 pointer @code{this} following the same rules as C@t{++}. @code{using}
13951 declarations in the current scope are also respected by @value{GDBN}.
13953 @cindex call overloaded functions
13954 @cindex overloaded functions, calling
13955 @cindex type conversions in C@t{++}
13957 You can call overloaded functions; @value{GDBN} resolves the function
13958 call to the right definition, with some restrictions. @value{GDBN} does not
13959 perform overload resolution involving user-defined type conversions,
13960 calls to constructors, or instantiations of templates that do not exist
13961 in the program. It also cannot handle ellipsis argument lists or
13964 It does perform integral conversions and promotions, floating-point
13965 promotions, arithmetic conversions, pointer conversions, conversions of
13966 class objects to base classes, and standard conversions such as those of
13967 functions or arrays to pointers; it requires an exact match on the
13968 number of function arguments.
13970 Overload resolution is always performed, unless you have specified
13971 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13972 ,@value{GDBN} Features for C@t{++}}.
13974 You must specify @code{set overload-resolution off} in order to use an
13975 explicit function signature to call an overloaded function, as in
13977 p 'foo(char,int)'('x', 13)
13980 The @value{GDBN} command-completion facility can simplify this;
13981 see @ref{Completion, ,Command Completion}.
13983 @cindex reference declarations
13985 @value{GDBN} understands variables declared as C@t{++} references; you can use
13986 them in expressions just as you do in C@t{++} source---they are automatically
13989 In the parameter list shown when @value{GDBN} displays a frame, the values of
13990 reference variables are not displayed (unlike other variables); this
13991 avoids clutter, since references are often used for large structures.
13992 The @emph{address} of a reference variable is always shown, unless
13993 you have specified @samp{set print address off}.
13996 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13997 expressions can use it just as expressions in your program do. Since
13998 one scope may be defined in another, you can use @code{::} repeatedly if
13999 necessary, for example in an expression like
14000 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14001 resolving name scope by reference to source files, in both C and C@t{++}
14002 debugging (@pxref{Variables, ,Program Variables}).
14005 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14010 @subsubsection C and C@t{++} Defaults
14012 @cindex C and C@t{++} defaults
14014 If you allow @value{GDBN} to set range checking automatically, it
14015 defaults to @code{off} whenever the working language changes to
14016 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14017 selects the working language.
14019 If you allow @value{GDBN} to set the language automatically, it
14020 recognizes source files whose names end with @file{.c}, @file{.C}, or
14021 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14022 these files, it sets the working language to C or C@t{++}.
14023 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14024 for further details.
14027 @subsubsection C and C@t{++} Type and Range Checks
14029 @cindex C and C@t{++} checks
14031 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14032 checking is used. However, if you turn type checking off, @value{GDBN}
14033 will allow certain non-standard conversions, such as promoting integer
14034 constants to pointers.
14036 Range checking, if turned on, is done on mathematical operations. Array
14037 indices are not checked, since they are often used to index a pointer
14038 that is not itself an array.
14041 @subsubsection @value{GDBN} and C
14043 The @code{set print union} and @code{show print union} commands apply to
14044 the @code{union} type. When set to @samp{on}, any @code{union} that is
14045 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14046 appears as @samp{@{...@}}.
14048 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14049 with pointers and a memory allocation function. @xref{Expressions,
14052 @node Debugging C Plus Plus
14053 @subsubsection @value{GDBN} Features for C@t{++}
14055 @cindex commands for C@t{++}
14057 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14058 designed specifically for use with C@t{++}. Here is a summary:
14061 @cindex break in overloaded functions
14062 @item @r{breakpoint menus}
14063 When you want a breakpoint in a function whose name is overloaded,
14064 @value{GDBN} has the capability to display a menu of possible breakpoint
14065 locations to help you specify which function definition you want.
14066 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14068 @cindex overloading in C@t{++}
14069 @item rbreak @var{regex}
14070 Setting breakpoints using regular expressions is helpful for setting
14071 breakpoints on overloaded functions that are not members of any special
14073 @xref{Set Breaks, ,Setting Breakpoints}.
14075 @cindex C@t{++} exception handling
14077 @itemx catch rethrow
14079 Debug C@t{++} exception handling using these commands. @xref{Set
14080 Catchpoints, , Setting Catchpoints}.
14082 @cindex inheritance
14083 @item ptype @var{typename}
14084 Print inheritance relationships as well as other information for type
14086 @xref{Symbols, ,Examining the Symbol Table}.
14088 @item info vtbl @var{expression}.
14089 The @code{info vtbl} command can be used to display the virtual
14090 method tables of the object computed by @var{expression}. This shows
14091 one entry per virtual table; there may be multiple virtual tables when
14092 multiple inheritance is in use.
14094 @cindex C@t{++} symbol display
14095 @item set print demangle
14096 @itemx show print demangle
14097 @itemx set print asm-demangle
14098 @itemx show print asm-demangle
14099 Control whether C@t{++} symbols display in their source form, both when
14100 displaying code as C@t{++} source and when displaying disassemblies.
14101 @xref{Print Settings, ,Print Settings}.
14103 @item set print object
14104 @itemx show print object
14105 Choose whether to print derived (actual) or declared types of objects.
14106 @xref{Print Settings, ,Print Settings}.
14108 @item set print vtbl
14109 @itemx show print vtbl
14110 Control the format for printing virtual function tables.
14111 @xref{Print Settings, ,Print Settings}.
14112 (The @code{vtbl} commands do not work on programs compiled with the HP
14113 ANSI C@t{++} compiler (@code{aCC}).)
14115 @kindex set overload-resolution
14116 @cindex overloaded functions, overload resolution
14117 @item set overload-resolution on
14118 Enable overload resolution for C@t{++} expression evaluation. The default
14119 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14120 and searches for a function whose signature matches the argument types,
14121 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14122 Expressions, ,C@t{++} Expressions}, for details).
14123 If it cannot find a match, it emits a message.
14125 @item set overload-resolution off
14126 Disable overload resolution for C@t{++} expression evaluation. For
14127 overloaded functions that are not class member functions, @value{GDBN}
14128 chooses the first function of the specified name that it finds in the
14129 symbol table, whether or not its arguments are of the correct type. For
14130 overloaded functions that are class member functions, @value{GDBN}
14131 searches for a function whose signature @emph{exactly} matches the
14134 @kindex show overload-resolution
14135 @item show overload-resolution
14136 Show the current setting of overload resolution.
14138 @item @r{Overloaded symbol names}
14139 You can specify a particular definition of an overloaded symbol, using
14140 the same notation that is used to declare such symbols in C@t{++}: type
14141 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14142 also use the @value{GDBN} command-line word completion facilities to list the
14143 available choices, or to finish the type list for you.
14144 @xref{Completion,, Command Completion}, for details on how to do this.
14147 @node Decimal Floating Point
14148 @subsubsection Decimal Floating Point format
14149 @cindex decimal floating point format
14151 @value{GDBN} can examine, set and perform computations with numbers in
14152 decimal floating point format, which in the C language correspond to the
14153 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14154 specified by the extension to support decimal floating-point arithmetic.
14156 There are two encodings in use, depending on the architecture: BID (Binary
14157 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14158 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14161 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14162 to manipulate decimal floating point numbers, it is not possible to convert
14163 (using a cast, for example) integers wider than 32-bit to decimal float.
14165 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14166 point computations, error checking in decimal float operations ignores
14167 underflow, overflow and divide by zero exceptions.
14169 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14170 to inspect @code{_Decimal128} values stored in floating point registers.
14171 See @ref{PowerPC,,PowerPC} for more details.
14177 @value{GDBN} can be used to debug programs written in D and compiled with
14178 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14179 specific feature --- dynamic arrays.
14184 @cindex Go (programming language)
14185 @value{GDBN} can be used to debug programs written in Go and compiled with
14186 @file{gccgo} or @file{6g} compilers.
14188 Here is a summary of the Go-specific features and restrictions:
14191 @cindex current Go package
14192 @item The current Go package
14193 The name of the current package does not need to be specified when
14194 specifying global variables and functions.
14196 For example, given the program:
14200 var myglob = "Shall we?"
14206 When stopped inside @code{main} either of these work:
14210 (gdb) p main.myglob
14213 @cindex builtin Go types
14214 @item Builtin Go types
14215 The @code{string} type is recognized by @value{GDBN} and is printed
14218 @cindex builtin Go functions
14219 @item Builtin Go functions
14220 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14221 function and handles it internally.
14223 @cindex restrictions on Go expressions
14224 @item Restrictions on Go expressions
14225 All Go operators are supported except @code{&^}.
14226 The Go @code{_} ``blank identifier'' is not supported.
14227 Automatic dereferencing of pointers is not supported.
14231 @subsection Objective-C
14233 @cindex Objective-C
14234 This section provides information about some commands and command
14235 options that are useful for debugging Objective-C code. See also
14236 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14237 few more commands specific to Objective-C support.
14240 * Method Names in Commands::
14241 * The Print Command with Objective-C::
14244 @node Method Names in Commands
14245 @subsubsection Method Names in Commands
14247 The following commands have been extended to accept Objective-C method
14248 names as line specifications:
14250 @kindex clear@r{, and Objective-C}
14251 @kindex break@r{, and Objective-C}
14252 @kindex info line@r{, and Objective-C}
14253 @kindex jump@r{, and Objective-C}
14254 @kindex list@r{, and Objective-C}
14258 @item @code{info line}
14263 A fully qualified Objective-C method name is specified as
14266 -[@var{Class} @var{methodName}]
14269 where the minus sign is used to indicate an instance method and a
14270 plus sign (not shown) is used to indicate a class method. The class
14271 name @var{Class} and method name @var{methodName} are enclosed in
14272 brackets, similar to the way messages are specified in Objective-C
14273 source code. For example, to set a breakpoint at the @code{create}
14274 instance method of class @code{Fruit} in the program currently being
14278 break -[Fruit create]
14281 To list ten program lines around the @code{initialize} class method,
14285 list +[NSText initialize]
14288 In the current version of @value{GDBN}, the plus or minus sign is
14289 required. In future versions of @value{GDBN}, the plus or minus
14290 sign will be optional, but you can use it to narrow the search. It
14291 is also possible to specify just a method name:
14297 You must specify the complete method name, including any colons. If
14298 your program's source files contain more than one @code{create} method,
14299 you'll be presented with a numbered list of classes that implement that
14300 method. Indicate your choice by number, or type @samp{0} to exit if
14303 As another example, to clear a breakpoint established at the
14304 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14307 clear -[NSWindow makeKeyAndOrderFront:]
14310 @node The Print Command with Objective-C
14311 @subsubsection The Print Command With Objective-C
14312 @cindex Objective-C, print objects
14313 @kindex print-object
14314 @kindex po @r{(@code{print-object})}
14316 The print command has also been extended to accept methods. For example:
14319 print -[@var{object} hash]
14322 @cindex print an Objective-C object description
14323 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14325 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14326 and print the result. Also, an additional command has been added,
14327 @code{print-object} or @code{po} for short, which is meant to print
14328 the description of an object. However, this command may only work
14329 with certain Objective-C libraries that have a particular hook
14330 function, @code{_NSPrintForDebugger}, defined.
14333 @subsection OpenCL C
14336 This section provides information about @value{GDBN}s OpenCL C support.
14339 * OpenCL C Datatypes::
14340 * OpenCL C Expressions::
14341 * OpenCL C Operators::
14344 @node OpenCL C Datatypes
14345 @subsubsection OpenCL C Datatypes
14347 @cindex OpenCL C Datatypes
14348 @value{GDBN} supports the builtin scalar and vector datatypes specified
14349 by OpenCL 1.1. In addition the half- and double-precision floating point
14350 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14351 extensions are also known to @value{GDBN}.
14353 @node OpenCL C Expressions
14354 @subsubsection OpenCL C Expressions
14356 @cindex OpenCL C Expressions
14357 @value{GDBN} supports accesses to vector components including the access as
14358 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14359 supported by @value{GDBN} can be used as well.
14361 @node OpenCL C Operators
14362 @subsubsection OpenCL C Operators
14364 @cindex OpenCL C Operators
14365 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14369 @subsection Fortran
14370 @cindex Fortran-specific support in @value{GDBN}
14372 @value{GDBN} can be used to debug programs written in Fortran, but it
14373 currently supports only the features of Fortran 77 language.
14375 @cindex trailing underscore, in Fortran symbols
14376 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14377 among them) append an underscore to the names of variables and
14378 functions. When you debug programs compiled by those compilers, you
14379 will need to refer to variables and functions with a trailing
14383 * Fortran Operators:: Fortran operators and expressions
14384 * Fortran Defaults:: Default settings for Fortran
14385 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14388 @node Fortran Operators
14389 @subsubsection Fortran Operators and Expressions
14391 @cindex Fortran operators and expressions
14393 Operators must be defined on values of specific types. For instance,
14394 @code{+} is defined on numbers, but not on characters or other non-
14395 arithmetic types. Operators are often defined on groups of types.
14399 The exponentiation operator. It raises the first operand to the power
14403 The range operator. Normally used in the form of array(low:high) to
14404 represent a section of array.
14407 The access component operator. Normally used to access elements in derived
14408 types. Also suitable for unions. As unions aren't part of regular Fortran,
14409 this can only happen when accessing a register that uses a gdbarch-defined
14413 @node Fortran Defaults
14414 @subsubsection Fortran Defaults
14416 @cindex Fortran Defaults
14418 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14419 default uses case-insensitive matches for Fortran symbols. You can
14420 change that with the @samp{set case-insensitive} command, see
14421 @ref{Symbols}, for the details.
14423 @node Special Fortran Commands
14424 @subsubsection Special Fortran Commands
14426 @cindex Special Fortran commands
14428 @value{GDBN} has some commands to support Fortran-specific features,
14429 such as displaying common blocks.
14432 @cindex @code{COMMON} blocks, Fortran
14433 @kindex info common
14434 @item info common @r{[}@var{common-name}@r{]}
14435 This command prints the values contained in the Fortran @code{COMMON}
14436 block whose name is @var{common-name}. With no argument, the names of
14437 all @code{COMMON} blocks visible at the current program location are
14444 @cindex Pascal support in @value{GDBN}, limitations
14445 Debugging Pascal programs which use sets, subranges, file variables, or
14446 nested functions does not currently work. @value{GDBN} does not support
14447 entering expressions, printing values, or similar features using Pascal
14450 The Pascal-specific command @code{set print pascal_static-members}
14451 controls whether static members of Pascal objects are displayed.
14452 @xref{Print Settings, pascal_static-members}.
14455 @subsection Modula-2
14457 @cindex Modula-2, @value{GDBN} support
14459 The extensions made to @value{GDBN} to support Modula-2 only support
14460 output from the @sc{gnu} Modula-2 compiler (which is currently being
14461 developed). Other Modula-2 compilers are not currently supported, and
14462 attempting to debug executables produced by them is most likely
14463 to give an error as @value{GDBN} reads in the executable's symbol
14466 @cindex expressions in Modula-2
14468 * M2 Operators:: Built-in operators
14469 * Built-In Func/Proc:: Built-in functions and procedures
14470 * M2 Constants:: Modula-2 constants
14471 * M2 Types:: Modula-2 types
14472 * M2 Defaults:: Default settings for Modula-2
14473 * Deviations:: Deviations from standard Modula-2
14474 * M2 Checks:: Modula-2 type and range checks
14475 * M2 Scope:: The scope operators @code{::} and @code{.}
14476 * GDB/M2:: @value{GDBN} and Modula-2
14480 @subsubsection Operators
14481 @cindex Modula-2 operators
14483 Operators must be defined on values of specific types. For instance,
14484 @code{+} is defined on numbers, but not on structures. Operators are
14485 often defined on groups of types. For the purposes of Modula-2, the
14486 following definitions hold:
14491 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14495 @emph{Character types} consist of @code{CHAR} and its subranges.
14498 @emph{Floating-point types} consist of @code{REAL}.
14501 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14505 @emph{Scalar types} consist of all of the above.
14508 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14511 @emph{Boolean types} consist of @code{BOOLEAN}.
14515 The following operators are supported, and appear in order of
14516 increasing precedence:
14520 Function argument or array index separator.
14523 Assignment. The value of @var{var} @code{:=} @var{value} is
14527 Less than, greater than on integral, floating-point, or enumerated
14531 Less than or equal to, greater than or equal to
14532 on integral, floating-point and enumerated types, or set inclusion on
14533 set types. Same precedence as @code{<}.
14535 @item =@r{, }<>@r{, }#
14536 Equality and two ways of expressing inequality, valid on scalar types.
14537 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14538 available for inequality, since @code{#} conflicts with the script
14542 Set membership. Defined on set types and the types of their members.
14543 Same precedence as @code{<}.
14546 Boolean disjunction. Defined on boolean types.
14549 Boolean conjunction. Defined on boolean types.
14552 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14555 Addition and subtraction on integral and floating-point types, or union
14556 and difference on set types.
14559 Multiplication on integral and floating-point types, or set intersection
14563 Division on floating-point types, or symmetric set difference on set
14564 types. Same precedence as @code{*}.
14567 Integer division and remainder. Defined on integral types. Same
14568 precedence as @code{*}.
14571 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14574 Pointer dereferencing. Defined on pointer types.
14577 Boolean negation. Defined on boolean types. Same precedence as
14581 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14582 precedence as @code{^}.
14585 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14588 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14592 @value{GDBN} and Modula-2 scope operators.
14596 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14597 treats the use of the operator @code{IN}, or the use of operators
14598 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14599 @code{<=}, and @code{>=} on sets as an error.
14603 @node Built-In Func/Proc
14604 @subsubsection Built-in Functions and Procedures
14605 @cindex Modula-2 built-ins
14607 Modula-2 also makes available several built-in procedures and functions.
14608 In describing these, the following metavariables are used:
14613 represents an @code{ARRAY} variable.
14616 represents a @code{CHAR} constant or variable.
14619 represents a variable or constant of integral type.
14622 represents an identifier that belongs to a set. Generally used in the
14623 same function with the metavariable @var{s}. The type of @var{s} should
14624 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14627 represents a variable or constant of integral or floating-point type.
14630 represents a variable or constant of floating-point type.
14636 represents a variable.
14639 represents a variable or constant of one of many types. See the
14640 explanation of the function for details.
14643 All Modula-2 built-in procedures also return a result, described below.
14647 Returns the absolute value of @var{n}.
14650 If @var{c} is a lower case letter, it returns its upper case
14651 equivalent, otherwise it returns its argument.
14654 Returns the character whose ordinal value is @var{i}.
14657 Decrements the value in the variable @var{v} by one. Returns the new value.
14659 @item DEC(@var{v},@var{i})
14660 Decrements the value in the variable @var{v} by @var{i}. Returns the
14663 @item EXCL(@var{m},@var{s})
14664 Removes the element @var{m} from the set @var{s}. Returns the new
14667 @item FLOAT(@var{i})
14668 Returns the floating point equivalent of the integer @var{i}.
14670 @item HIGH(@var{a})
14671 Returns the index of the last member of @var{a}.
14674 Increments the value in the variable @var{v} by one. Returns the new value.
14676 @item INC(@var{v},@var{i})
14677 Increments the value in the variable @var{v} by @var{i}. Returns the
14680 @item INCL(@var{m},@var{s})
14681 Adds the element @var{m} to the set @var{s} if it is not already
14682 there. Returns the new set.
14685 Returns the maximum value of the type @var{t}.
14688 Returns the minimum value of the type @var{t}.
14691 Returns boolean TRUE if @var{i} is an odd number.
14694 Returns the ordinal value of its argument. For example, the ordinal
14695 value of a character is its @sc{ascii} value (on machines supporting the
14696 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14697 integral, character and enumerated types.
14699 @item SIZE(@var{x})
14700 Returns the size of its argument. @var{x} can be a variable or a type.
14702 @item TRUNC(@var{r})
14703 Returns the integral part of @var{r}.
14705 @item TSIZE(@var{x})
14706 Returns the size of its argument. @var{x} can be a variable or a type.
14708 @item VAL(@var{t},@var{i})
14709 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14713 @emph{Warning:} Sets and their operations are not yet supported, so
14714 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14718 @cindex Modula-2 constants
14720 @subsubsection Constants
14722 @value{GDBN} allows you to express the constants of Modula-2 in the following
14728 Integer constants are simply a sequence of digits. When used in an
14729 expression, a constant is interpreted to be type-compatible with the
14730 rest of the expression. Hexadecimal integers are specified by a
14731 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14734 Floating point constants appear as a sequence of digits, followed by a
14735 decimal point and another sequence of digits. An optional exponent can
14736 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14737 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14738 digits of the floating point constant must be valid decimal (base 10)
14742 Character constants consist of a single character enclosed by a pair of
14743 like quotes, either single (@code{'}) or double (@code{"}). They may
14744 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14745 followed by a @samp{C}.
14748 String constants consist of a sequence of characters enclosed by a
14749 pair of like quotes, either single (@code{'}) or double (@code{"}).
14750 Escape sequences in the style of C are also allowed. @xref{C
14751 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14755 Enumerated constants consist of an enumerated identifier.
14758 Boolean constants consist of the identifiers @code{TRUE} and
14762 Pointer constants consist of integral values only.
14765 Set constants are not yet supported.
14769 @subsubsection Modula-2 Types
14770 @cindex Modula-2 types
14772 Currently @value{GDBN} can print the following data types in Modula-2
14773 syntax: array types, record types, set types, pointer types, procedure
14774 types, enumerated types, subrange types and base types. You can also
14775 print the contents of variables declared using these type.
14776 This section gives a number of simple source code examples together with
14777 sample @value{GDBN} sessions.
14779 The first example contains the following section of code:
14788 and you can request @value{GDBN} to interrogate the type and value of
14789 @code{r} and @code{s}.
14792 (@value{GDBP}) print s
14794 (@value{GDBP}) ptype s
14796 (@value{GDBP}) print r
14798 (@value{GDBP}) ptype r
14803 Likewise if your source code declares @code{s} as:
14807 s: SET ['A'..'Z'] ;
14811 then you may query the type of @code{s} by:
14814 (@value{GDBP}) ptype s
14815 type = SET ['A'..'Z']
14819 Note that at present you cannot interactively manipulate set
14820 expressions using the debugger.
14822 The following example shows how you might declare an array in Modula-2
14823 and how you can interact with @value{GDBN} to print its type and contents:
14827 s: ARRAY [-10..10] OF CHAR ;
14831 (@value{GDBP}) ptype s
14832 ARRAY [-10..10] OF CHAR
14835 Note that the array handling is not yet complete and although the type
14836 is printed correctly, expression handling still assumes that all
14837 arrays have a lower bound of zero and not @code{-10} as in the example
14840 Here are some more type related Modula-2 examples:
14844 colour = (blue, red, yellow, green) ;
14845 t = [blue..yellow] ;
14853 The @value{GDBN} interaction shows how you can query the data type
14854 and value of a variable.
14857 (@value{GDBP}) print s
14859 (@value{GDBP}) ptype t
14860 type = [blue..yellow]
14864 In this example a Modula-2 array is declared and its contents
14865 displayed. Observe that the contents are written in the same way as
14866 their @code{C} counterparts.
14870 s: ARRAY [1..5] OF CARDINAL ;
14876 (@value{GDBP}) print s
14877 $1 = @{1, 0, 0, 0, 0@}
14878 (@value{GDBP}) ptype s
14879 type = ARRAY [1..5] OF CARDINAL
14882 The Modula-2 language interface to @value{GDBN} also understands
14883 pointer types as shown in this example:
14887 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14894 and you can request that @value{GDBN} describes the type of @code{s}.
14897 (@value{GDBP}) ptype s
14898 type = POINTER TO ARRAY [1..5] OF CARDINAL
14901 @value{GDBN} handles compound types as we can see in this example.
14902 Here we combine array types, record types, pointer types and subrange
14913 myarray = ARRAY myrange OF CARDINAL ;
14914 myrange = [-2..2] ;
14916 s: POINTER TO ARRAY myrange OF foo ;
14920 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14924 (@value{GDBP}) ptype s
14925 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14928 f3 : ARRAY [-2..2] OF CARDINAL;
14933 @subsubsection Modula-2 Defaults
14934 @cindex Modula-2 defaults
14936 If type and range checking are set automatically by @value{GDBN}, they
14937 both default to @code{on} whenever the working language changes to
14938 Modula-2. This happens regardless of whether you or @value{GDBN}
14939 selected the working language.
14941 If you allow @value{GDBN} to set the language automatically, then entering
14942 code compiled from a file whose name ends with @file{.mod} sets the
14943 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14944 Infer the Source Language}, for further details.
14947 @subsubsection Deviations from Standard Modula-2
14948 @cindex Modula-2, deviations from
14950 A few changes have been made to make Modula-2 programs easier to debug.
14951 This is done primarily via loosening its type strictness:
14955 Unlike in standard Modula-2, pointer constants can be formed by
14956 integers. This allows you to modify pointer variables during
14957 debugging. (In standard Modula-2, the actual address contained in a
14958 pointer variable is hidden from you; it can only be modified
14959 through direct assignment to another pointer variable or expression that
14960 returned a pointer.)
14963 C escape sequences can be used in strings and characters to represent
14964 non-printable characters. @value{GDBN} prints out strings with these
14965 escape sequences embedded. Single non-printable characters are
14966 printed using the @samp{CHR(@var{nnn})} format.
14969 The assignment operator (@code{:=}) returns the value of its right-hand
14973 All built-in procedures both modify @emph{and} return their argument.
14977 @subsubsection Modula-2 Type and Range Checks
14978 @cindex Modula-2 checks
14981 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14984 @c FIXME remove warning when type/range checks added
14986 @value{GDBN} considers two Modula-2 variables type equivalent if:
14990 They are of types that have been declared equivalent via a @code{TYPE
14991 @var{t1} = @var{t2}} statement
14994 They have been declared on the same line. (Note: This is true of the
14995 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14998 As long as type checking is enabled, any attempt to combine variables
14999 whose types are not equivalent is an error.
15001 Range checking is done on all mathematical operations, assignment, array
15002 index bounds, and all built-in functions and procedures.
15005 @subsubsection The Scope Operators @code{::} and @code{.}
15007 @cindex @code{.}, Modula-2 scope operator
15008 @cindex colon, doubled as scope operator
15010 @vindex colon-colon@r{, in Modula-2}
15011 @c Info cannot handle :: but TeX can.
15014 @vindex ::@r{, in Modula-2}
15017 There are a few subtle differences between the Modula-2 scope operator
15018 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15023 @var{module} . @var{id}
15024 @var{scope} :: @var{id}
15028 where @var{scope} is the name of a module or a procedure,
15029 @var{module} the name of a module, and @var{id} is any declared
15030 identifier within your program, except another module.
15032 Using the @code{::} operator makes @value{GDBN} search the scope
15033 specified by @var{scope} for the identifier @var{id}. If it is not
15034 found in the specified scope, then @value{GDBN} searches all scopes
15035 enclosing the one specified by @var{scope}.
15037 Using the @code{.} operator makes @value{GDBN} search the current scope for
15038 the identifier specified by @var{id} that was imported from the
15039 definition module specified by @var{module}. With this operator, it is
15040 an error if the identifier @var{id} was not imported from definition
15041 module @var{module}, or if @var{id} is not an identifier in
15045 @subsubsection @value{GDBN} and Modula-2
15047 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15048 Five subcommands of @code{set print} and @code{show print} apply
15049 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15050 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15051 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15052 analogue in Modula-2.
15054 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15055 with any language, is not useful with Modula-2. Its
15056 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15057 created in Modula-2 as they can in C or C@t{++}. However, because an
15058 address can be specified by an integral constant, the construct
15059 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15061 @cindex @code{#} in Modula-2
15062 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15063 interpreted as the beginning of a comment. Use @code{<>} instead.
15069 The extensions made to @value{GDBN} for Ada only support
15070 output from the @sc{gnu} Ada (GNAT) compiler.
15071 Other Ada compilers are not currently supported, and
15072 attempting to debug executables produced by them is most likely
15076 @cindex expressions in Ada
15078 * Ada Mode Intro:: General remarks on the Ada syntax
15079 and semantics supported by Ada mode
15081 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15082 * Additions to Ada:: Extensions of the Ada expression syntax.
15083 * Stopping Before Main Program:: Debugging the program during elaboration.
15084 * Ada Exceptions:: Ada Exceptions
15085 * Ada Tasks:: Listing and setting breakpoints in tasks.
15086 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15087 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15089 * Ada Glitches:: Known peculiarities of Ada mode.
15092 @node Ada Mode Intro
15093 @subsubsection Introduction
15094 @cindex Ada mode, general
15096 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15097 syntax, with some extensions.
15098 The philosophy behind the design of this subset is
15102 That @value{GDBN} should provide basic literals and access to operations for
15103 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15104 leaving more sophisticated computations to subprograms written into the
15105 program (which therefore may be called from @value{GDBN}).
15108 That type safety and strict adherence to Ada language restrictions
15109 are not particularly important to the @value{GDBN} user.
15112 That brevity is important to the @value{GDBN} user.
15115 Thus, for brevity, the debugger acts as if all names declared in
15116 user-written packages are directly visible, even if they are not visible
15117 according to Ada rules, thus making it unnecessary to fully qualify most
15118 names with their packages, regardless of context. Where this causes
15119 ambiguity, @value{GDBN} asks the user's intent.
15121 The debugger will start in Ada mode if it detects an Ada main program.
15122 As for other languages, it will enter Ada mode when stopped in a program that
15123 was translated from an Ada source file.
15125 While in Ada mode, you may use `@t{--}' for comments. This is useful
15126 mostly for documenting command files. The standard @value{GDBN} comment
15127 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15128 middle (to allow based literals).
15130 The debugger supports limited overloading. Given a subprogram call in which
15131 the function symbol has multiple definitions, it will use the number of
15132 actual parameters and some information about their types to attempt to narrow
15133 the set of definitions. It also makes very limited use of context, preferring
15134 procedures to functions in the context of the @code{call} command, and
15135 functions to procedures elsewhere.
15137 @node Omissions from Ada
15138 @subsubsection Omissions from Ada
15139 @cindex Ada, omissions from
15141 Here are the notable omissions from the subset:
15145 Only a subset of the attributes are supported:
15149 @t{'First}, @t{'Last}, and @t{'Length}
15150 on array objects (not on types and subtypes).
15153 @t{'Min} and @t{'Max}.
15156 @t{'Pos} and @t{'Val}.
15162 @t{'Range} on array objects (not subtypes), but only as the right
15163 operand of the membership (@code{in}) operator.
15166 @t{'Access}, @t{'Unchecked_Access}, and
15167 @t{'Unrestricted_Access} (a GNAT extension).
15175 @code{Characters.Latin_1} are not available and
15176 concatenation is not implemented. Thus, escape characters in strings are
15177 not currently available.
15180 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15181 equality of representations. They will generally work correctly
15182 for strings and arrays whose elements have integer or enumeration types.
15183 They may not work correctly for arrays whose element
15184 types have user-defined equality, for arrays of real values
15185 (in particular, IEEE-conformant floating point, because of negative
15186 zeroes and NaNs), and for arrays whose elements contain unused bits with
15187 indeterminate values.
15190 The other component-by-component array operations (@code{and}, @code{or},
15191 @code{xor}, @code{not}, and relational tests other than equality)
15192 are not implemented.
15195 @cindex array aggregates (Ada)
15196 @cindex record aggregates (Ada)
15197 @cindex aggregates (Ada)
15198 There is limited support for array and record aggregates. They are
15199 permitted only on the right sides of assignments, as in these examples:
15202 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15203 (@value{GDBP}) set An_Array := (1, others => 0)
15204 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15205 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15206 (@value{GDBP}) set A_Record := (1, "Peter", True);
15207 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15211 discriminant's value by assigning an aggregate has an
15212 undefined effect if that discriminant is used within the record.
15213 However, you can first modify discriminants by directly assigning to
15214 them (which normally would not be allowed in Ada), and then performing an
15215 aggregate assignment. For example, given a variable @code{A_Rec}
15216 declared to have a type such as:
15219 type Rec (Len : Small_Integer := 0) is record
15221 Vals : IntArray (1 .. Len);
15225 you can assign a value with a different size of @code{Vals} with two
15229 (@value{GDBP}) set A_Rec.Len := 4
15230 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15233 As this example also illustrates, @value{GDBN} is very loose about the usual
15234 rules concerning aggregates. You may leave out some of the
15235 components of an array or record aggregate (such as the @code{Len}
15236 component in the assignment to @code{A_Rec} above); they will retain their
15237 original values upon assignment. You may freely use dynamic values as
15238 indices in component associations. You may even use overlapping or
15239 redundant component associations, although which component values are
15240 assigned in such cases is not defined.
15243 Calls to dispatching subprograms are not implemented.
15246 The overloading algorithm is much more limited (i.e., less selective)
15247 than that of real Ada. It makes only limited use of the context in
15248 which a subexpression appears to resolve its meaning, and it is much
15249 looser in its rules for allowing type matches. As a result, some
15250 function calls will be ambiguous, and the user will be asked to choose
15251 the proper resolution.
15254 The @code{new} operator is not implemented.
15257 Entry calls are not implemented.
15260 Aside from printing, arithmetic operations on the native VAX floating-point
15261 formats are not supported.
15264 It is not possible to slice a packed array.
15267 The names @code{True} and @code{False}, when not part of a qualified name,
15268 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15270 Should your program
15271 redefine these names in a package or procedure (at best a dubious practice),
15272 you will have to use fully qualified names to access their new definitions.
15275 @node Additions to Ada
15276 @subsubsection Additions to Ada
15277 @cindex Ada, deviations from
15279 As it does for other languages, @value{GDBN} makes certain generic
15280 extensions to Ada (@pxref{Expressions}):
15284 If the expression @var{E} is a variable residing in memory (typically
15285 a local variable or array element) and @var{N} is a positive integer,
15286 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15287 @var{N}-1 adjacent variables following it in memory as an array. In
15288 Ada, this operator is generally not necessary, since its prime use is
15289 in displaying parts of an array, and slicing will usually do this in
15290 Ada. However, there are occasional uses when debugging programs in
15291 which certain debugging information has been optimized away.
15294 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15295 appears in function or file @var{B}.'' When @var{B} is a file name,
15296 you must typically surround it in single quotes.
15299 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15300 @var{type} that appears at address @var{addr}.''
15303 A name starting with @samp{$} is a convenience variable
15304 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15307 In addition, @value{GDBN} provides a few other shortcuts and outright
15308 additions specific to Ada:
15312 The assignment statement is allowed as an expression, returning
15313 its right-hand operand as its value. Thus, you may enter
15316 (@value{GDBP}) set x := y + 3
15317 (@value{GDBP}) print A(tmp := y + 1)
15321 The semicolon is allowed as an ``operator,'' returning as its value
15322 the value of its right-hand operand.
15323 This allows, for example,
15324 complex conditional breaks:
15327 (@value{GDBP}) break f
15328 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15332 Rather than use catenation and symbolic character names to introduce special
15333 characters into strings, one may instead use a special bracket notation,
15334 which is also used to print strings. A sequence of characters of the form
15335 @samp{["@var{XX}"]} within a string or character literal denotes the
15336 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15337 sequence of characters @samp{["""]} also denotes a single quotation mark
15338 in strings. For example,
15340 "One line.["0a"]Next line.["0a"]"
15343 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15347 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15348 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15352 (@value{GDBP}) print 'max(x, y)
15356 When printing arrays, @value{GDBN} uses positional notation when the
15357 array has a lower bound of 1, and uses a modified named notation otherwise.
15358 For example, a one-dimensional array of three integers with a lower bound
15359 of 3 might print as
15366 That is, in contrast to valid Ada, only the first component has a @code{=>}
15370 You may abbreviate attributes in expressions with any unique,
15371 multi-character subsequence of
15372 their names (an exact match gets preference).
15373 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15374 in place of @t{a'length}.
15377 @cindex quoting Ada internal identifiers
15378 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15379 to lower case. The GNAT compiler uses upper-case characters for
15380 some of its internal identifiers, which are normally of no interest to users.
15381 For the rare occasions when you actually have to look at them,
15382 enclose them in angle brackets to avoid the lower-case mapping.
15385 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15389 Printing an object of class-wide type or dereferencing an
15390 access-to-class-wide value will display all the components of the object's
15391 specific type (as indicated by its run-time tag). Likewise, component
15392 selection on such a value will operate on the specific type of the
15397 @node Stopping Before Main Program
15398 @subsubsection Stopping at the Very Beginning
15400 @cindex breakpointing Ada elaboration code
15401 It is sometimes necessary to debug the program during elaboration, and
15402 before reaching the main procedure.
15403 As defined in the Ada Reference
15404 Manual, the elaboration code is invoked from a procedure called
15405 @code{adainit}. To run your program up to the beginning of
15406 elaboration, simply use the following two commands:
15407 @code{tbreak adainit} and @code{run}.
15409 @node Ada Exceptions
15410 @subsubsection Ada Exceptions
15412 A command is provided to list all Ada exceptions:
15415 @kindex info exceptions
15416 @item info exceptions
15417 @itemx info exceptions @var{regexp}
15418 The @code{info exceptions} command allows you to list all Ada exceptions
15419 defined within the program being debugged, as well as their addresses.
15420 With a regular expression, @var{regexp}, as argument, only those exceptions
15421 whose names match @var{regexp} are listed.
15424 Below is a small example, showing how the command can be used, first
15425 without argument, and next with a regular expression passed as an
15429 (@value{GDBP}) info exceptions
15430 All defined Ada exceptions:
15431 constraint_error: 0x613da0
15432 program_error: 0x613d20
15433 storage_error: 0x613ce0
15434 tasking_error: 0x613ca0
15435 const.aint_global_e: 0x613b00
15436 (@value{GDBP}) info exceptions const.aint
15437 All Ada exceptions matching regular expression "const.aint":
15438 constraint_error: 0x613da0
15439 const.aint_global_e: 0x613b00
15442 It is also possible to ask @value{GDBN} to stop your program's execution
15443 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15446 @subsubsection Extensions for Ada Tasks
15447 @cindex Ada, tasking
15449 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15450 @value{GDBN} provides the following task-related commands:
15455 This command shows a list of current Ada tasks, as in the following example:
15462 (@value{GDBP}) info tasks
15463 ID TID P-ID Pri State Name
15464 1 8088000 0 15 Child Activation Wait main_task
15465 2 80a4000 1 15 Accept Statement b
15466 3 809a800 1 15 Child Activation Wait a
15467 * 4 80ae800 3 15 Runnable c
15472 In this listing, the asterisk before the last task indicates it to be the
15473 task currently being inspected.
15477 Represents @value{GDBN}'s internal task number.
15483 The parent's task ID (@value{GDBN}'s internal task number).
15486 The base priority of the task.
15489 Current state of the task.
15493 The task has been created but has not been activated. It cannot be
15497 The task is not blocked for any reason known to Ada. (It may be waiting
15498 for a mutex, though.) It is conceptually "executing" in normal mode.
15501 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15502 that were waiting on terminate alternatives have been awakened and have
15503 terminated themselves.
15505 @item Child Activation Wait
15506 The task is waiting for created tasks to complete activation.
15508 @item Accept Statement
15509 The task is waiting on an accept or selective wait statement.
15511 @item Waiting on entry call
15512 The task is waiting on an entry call.
15514 @item Async Select Wait
15515 The task is waiting to start the abortable part of an asynchronous
15519 The task is waiting on a select statement with only a delay
15522 @item Child Termination Wait
15523 The task is sleeping having completed a master within itself, and is
15524 waiting for the tasks dependent on that master to become terminated or
15525 waiting on a terminate Phase.
15527 @item Wait Child in Term Alt
15528 The task is sleeping waiting for tasks on terminate alternatives to
15529 finish terminating.
15531 @item Accepting RV with @var{taskno}
15532 The task is accepting a rendez-vous with the task @var{taskno}.
15536 Name of the task in the program.
15540 @kindex info task @var{taskno}
15541 @item info task @var{taskno}
15542 This command shows detailled informations on the specified task, as in
15543 the following example:
15548 (@value{GDBP}) info tasks
15549 ID TID P-ID Pri State Name
15550 1 8077880 0 15 Child Activation Wait main_task
15551 * 2 807c468 1 15 Runnable task_1
15552 (@value{GDBP}) info task 2
15553 Ada Task: 0x807c468
15556 Parent: 1 (main_task)
15562 @kindex task@r{ (Ada)}
15563 @cindex current Ada task ID
15564 This command prints the ID of the current task.
15570 (@value{GDBP}) info tasks
15571 ID TID P-ID Pri State Name
15572 1 8077870 0 15 Child Activation Wait main_task
15573 * 2 807c458 1 15 Runnable t
15574 (@value{GDBP}) task
15575 [Current task is 2]
15578 @item task @var{taskno}
15579 @cindex Ada task switching
15580 This command is like the @code{thread @var{threadno}}
15581 command (@pxref{Threads}). It switches the context of debugging
15582 from the current task to the given task.
15588 (@value{GDBP}) info tasks
15589 ID TID P-ID Pri State Name
15590 1 8077870 0 15 Child Activation Wait main_task
15591 * 2 807c458 1 15 Runnable t
15592 (@value{GDBP}) task 1
15593 [Switching to task 1]
15594 #0 0x8067726 in pthread_cond_wait ()
15596 #0 0x8067726 in pthread_cond_wait ()
15597 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15598 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15599 #3 0x806153e in system.tasking.stages.activate_tasks ()
15600 #4 0x804aacc in un () at un.adb:5
15603 @item break @var{linespec} task @var{taskno}
15604 @itemx break @var{linespec} task @var{taskno} if @dots{}
15605 @cindex breakpoints and tasks, in Ada
15606 @cindex task breakpoints, in Ada
15607 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15608 These commands are like the @code{break @dots{} thread @dots{}}
15609 command (@pxref{Thread Stops}).
15610 @var{linespec} specifies source lines, as described
15611 in @ref{Specify Location}.
15613 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15614 to specify that you only want @value{GDBN} to stop the program when a
15615 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15616 numeric task identifiers assigned by @value{GDBN}, shown in the first
15617 column of the @samp{info tasks} display.
15619 If you do not specify @samp{task @var{taskno}} when you set a
15620 breakpoint, the breakpoint applies to @emph{all} tasks of your
15623 You can use the @code{task} qualifier on conditional breakpoints as
15624 well; in this case, place @samp{task @var{taskno}} before the
15625 breakpoint condition (before the @code{if}).
15633 (@value{GDBP}) info tasks
15634 ID TID P-ID Pri State Name
15635 1 140022020 0 15 Child Activation Wait main_task
15636 2 140045060 1 15 Accept/Select Wait t2
15637 3 140044840 1 15 Runnable t1
15638 * 4 140056040 1 15 Runnable t3
15639 (@value{GDBP}) b 15 task 2
15640 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15641 (@value{GDBP}) cont
15646 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15648 (@value{GDBP}) info tasks
15649 ID TID P-ID Pri State Name
15650 1 140022020 0 15 Child Activation Wait main_task
15651 * 2 140045060 1 15 Runnable t2
15652 3 140044840 1 15 Runnable t1
15653 4 140056040 1 15 Delay Sleep t3
15657 @node Ada Tasks and Core Files
15658 @subsubsection Tasking Support when Debugging Core Files
15659 @cindex Ada tasking and core file debugging
15661 When inspecting a core file, as opposed to debugging a live program,
15662 tasking support may be limited or even unavailable, depending on
15663 the platform being used.
15664 For instance, on x86-linux, the list of tasks is available, but task
15665 switching is not supported. On Tru64, however, task switching will work
15668 On certain platforms, including Tru64, the debugger needs to perform some
15669 memory writes in order to provide Ada tasking support. When inspecting
15670 a core file, this means that the core file must be opened with read-write
15671 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15672 Under these circumstances, you should make a backup copy of the core
15673 file before inspecting it with @value{GDBN}.
15675 @node Ravenscar Profile
15676 @subsubsection Tasking Support when using the Ravenscar Profile
15677 @cindex Ravenscar Profile
15679 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15680 specifically designed for systems with safety-critical real-time
15684 @kindex set ravenscar task-switching on
15685 @cindex task switching with program using Ravenscar Profile
15686 @item set ravenscar task-switching on
15687 Allows task switching when debugging a program that uses the Ravenscar
15688 Profile. This is the default.
15690 @kindex set ravenscar task-switching off
15691 @item set ravenscar task-switching off
15692 Turn off task switching when debugging a program that uses the Ravenscar
15693 Profile. This is mostly intended to disable the code that adds support
15694 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15695 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15696 To be effective, this command should be run before the program is started.
15698 @kindex show ravenscar task-switching
15699 @item show ravenscar task-switching
15700 Show whether it is possible to switch from task to task in a program
15701 using the Ravenscar Profile.
15706 @subsubsection Known Peculiarities of Ada Mode
15707 @cindex Ada, problems
15709 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15710 we know of several problems with and limitations of Ada mode in
15712 some of which will be fixed with planned future releases of the debugger
15713 and the GNU Ada compiler.
15717 Static constants that the compiler chooses not to materialize as objects in
15718 storage are invisible to the debugger.
15721 Named parameter associations in function argument lists are ignored (the
15722 argument lists are treated as positional).
15725 Many useful library packages are currently invisible to the debugger.
15728 Fixed-point arithmetic, conversions, input, and output is carried out using
15729 floating-point arithmetic, and may give results that only approximate those on
15733 The GNAT compiler never generates the prefix @code{Standard} for any of
15734 the standard symbols defined by the Ada language. @value{GDBN} knows about
15735 this: it will strip the prefix from names when you use it, and will never
15736 look for a name you have so qualified among local symbols, nor match against
15737 symbols in other packages or subprograms. If you have
15738 defined entities anywhere in your program other than parameters and
15739 local variables whose simple names match names in @code{Standard},
15740 GNAT's lack of qualification here can cause confusion. When this happens,
15741 you can usually resolve the confusion
15742 by qualifying the problematic names with package
15743 @code{Standard} explicitly.
15746 Older versions of the compiler sometimes generate erroneous debugging
15747 information, resulting in the debugger incorrectly printing the value
15748 of affected entities. In some cases, the debugger is able to work
15749 around an issue automatically. In other cases, the debugger is able
15750 to work around the issue, but the work-around has to be specifically
15753 @kindex set ada trust-PAD-over-XVS
15754 @kindex show ada trust-PAD-over-XVS
15757 @item set ada trust-PAD-over-XVS on
15758 Configure GDB to strictly follow the GNAT encoding when computing the
15759 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15760 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15761 a complete description of the encoding used by the GNAT compiler).
15762 This is the default.
15764 @item set ada trust-PAD-over-XVS off
15765 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15766 sometimes prints the wrong value for certain entities, changing @code{ada
15767 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15768 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15769 @code{off}, but this incurs a slight performance penalty, so it is
15770 recommended to leave this setting to @code{on} unless necessary.
15774 @cindex GNAT descriptive types
15775 @cindex GNAT encoding
15776 Internally, the debugger also relies on the compiler following a number
15777 of conventions known as the @samp{GNAT Encoding}, all documented in
15778 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
15779 how the debugging information should be generated for certain types.
15780 In particular, this convention makes use of @dfn{descriptive types},
15781 which are artificial types generated purely to help the debugger.
15783 These encodings were defined at a time when the debugging information
15784 format used was not powerful enough to describe some of the more complex
15785 types available in Ada. Since DWARF allows us to express nearly all
15786 Ada features, the long-term goal is to slowly replace these descriptive
15787 types by their pure DWARF equivalent. To facilitate that transition,
15788 a new maintenance option is available to force the debugger to ignore
15789 those descriptive types. It allows the user to quickly evaluate how
15790 well @value{GDBN} works without them.
15794 @kindex maint ada set ignore-descriptive-types
15795 @item maintenance ada set ignore-descriptive-types [on|off]
15796 Control whether the debugger should ignore descriptive types.
15797 The default is not to ignore descriptives types (@code{off}).
15799 @kindex maint ada show ignore-descriptive-types
15800 @item maintenance ada show ignore-descriptive-types
15801 Show if descriptive types are ignored by @value{GDBN}.
15805 @node Unsupported Languages
15806 @section Unsupported Languages
15808 @cindex unsupported languages
15809 @cindex minimal language
15810 In addition to the other fully-supported programming languages,
15811 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15812 It does not represent a real programming language, but provides a set
15813 of capabilities close to what the C or assembly languages provide.
15814 This should allow most simple operations to be performed while debugging
15815 an application that uses a language currently not supported by @value{GDBN}.
15817 If the language is set to @code{auto}, @value{GDBN} will automatically
15818 select this language if the current frame corresponds to an unsupported
15822 @chapter Examining the Symbol Table
15824 The commands described in this chapter allow you to inquire about the
15825 symbols (names of variables, functions and types) defined in your
15826 program. This information is inherent in the text of your program and
15827 does not change as your program executes. @value{GDBN} finds it in your
15828 program's symbol table, in the file indicated when you started @value{GDBN}
15829 (@pxref{File Options, ,Choosing Files}), or by one of the
15830 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15832 @cindex symbol names
15833 @cindex names of symbols
15834 @cindex quoting names
15835 Occasionally, you may need to refer to symbols that contain unusual
15836 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15837 most frequent case is in referring to static variables in other
15838 source files (@pxref{Variables,,Program Variables}). File names
15839 are recorded in object files as debugging symbols, but @value{GDBN} would
15840 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15841 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15842 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15849 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15852 @cindex case-insensitive symbol names
15853 @cindex case sensitivity in symbol names
15854 @kindex set case-sensitive
15855 @item set case-sensitive on
15856 @itemx set case-sensitive off
15857 @itemx set case-sensitive auto
15858 Normally, when @value{GDBN} looks up symbols, it matches their names
15859 with case sensitivity determined by the current source language.
15860 Occasionally, you may wish to control that. The command @code{set
15861 case-sensitive} lets you do that by specifying @code{on} for
15862 case-sensitive matches or @code{off} for case-insensitive ones. If
15863 you specify @code{auto}, case sensitivity is reset to the default
15864 suitable for the source language. The default is case-sensitive
15865 matches for all languages except for Fortran, for which the default is
15866 case-insensitive matches.
15868 @kindex show case-sensitive
15869 @item show case-sensitive
15870 This command shows the current setting of case sensitivity for symbols
15873 @kindex set print type methods
15874 @item set print type methods
15875 @itemx set print type methods on
15876 @itemx set print type methods off
15877 Normally, when @value{GDBN} prints a class, it displays any methods
15878 declared in that class. You can control this behavior either by
15879 passing the appropriate flag to @code{ptype}, or using @command{set
15880 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15881 display the methods; this is the default. Specifying @code{off} will
15882 cause @value{GDBN} to omit the methods.
15884 @kindex show print type methods
15885 @item show print type methods
15886 This command shows the current setting of method display when printing
15889 @kindex set print type typedefs
15890 @item set print type typedefs
15891 @itemx set print type typedefs on
15892 @itemx set print type typedefs off
15894 Normally, when @value{GDBN} prints a class, it displays any typedefs
15895 defined in that class. You can control this behavior either by
15896 passing the appropriate flag to @code{ptype}, or using @command{set
15897 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15898 display the typedef definitions; this is the default. Specifying
15899 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15900 Note that this controls whether the typedef definition itself is
15901 printed, not whether typedef names are substituted when printing other
15904 @kindex show print type typedefs
15905 @item show print type typedefs
15906 This command shows the current setting of typedef display when
15909 @kindex info address
15910 @cindex address of a symbol
15911 @item info address @var{symbol}
15912 Describe where the data for @var{symbol} is stored. For a register
15913 variable, this says which register it is kept in. For a non-register
15914 local variable, this prints the stack-frame offset at which the variable
15917 Note the contrast with @samp{print &@var{symbol}}, which does not work
15918 at all for a register variable, and for a stack local variable prints
15919 the exact address of the current instantiation of the variable.
15921 @kindex info symbol
15922 @cindex symbol from address
15923 @cindex closest symbol and offset for an address
15924 @item info symbol @var{addr}
15925 Print the name of a symbol which is stored at the address @var{addr}.
15926 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15927 nearest symbol and an offset from it:
15930 (@value{GDBP}) info symbol 0x54320
15931 _initialize_vx + 396 in section .text
15935 This is the opposite of the @code{info address} command. You can use
15936 it to find out the name of a variable or a function given its address.
15938 For dynamically linked executables, the name of executable or shared
15939 library containing the symbol is also printed:
15942 (@value{GDBP}) info symbol 0x400225
15943 _start + 5 in section .text of /tmp/a.out
15944 (@value{GDBP}) info symbol 0x2aaaac2811cf
15945 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15949 @item whatis[/@var{flags}] [@var{arg}]
15950 Print the data type of @var{arg}, which can be either an expression
15951 or a name of a data type. With no argument, print the data type of
15952 @code{$}, the last value in the value history.
15954 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15955 is not actually evaluated, and any side-effecting operations (such as
15956 assignments or function calls) inside it do not take place.
15958 If @var{arg} is a variable or an expression, @code{whatis} prints its
15959 literal type as it is used in the source code. If the type was
15960 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15961 the data type underlying the @code{typedef}. If the type of the
15962 variable or the expression is a compound data type, such as
15963 @code{struct} or @code{class}, @code{whatis} never prints their
15964 fields or methods. It just prints the @code{struct}/@code{class}
15965 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15966 such a compound data type, use @code{ptype}.
15968 If @var{arg} is a type name that was defined using @code{typedef},
15969 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15970 Unrolling means that @code{whatis} will show the underlying type used
15971 in the @code{typedef} declaration of @var{arg}. However, if that
15972 underlying type is also a @code{typedef}, @code{whatis} will not
15975 For C code, the type names may also have the form @samp{class
15976 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15977 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15979 @var{flags} can be used to modify how the type is displayed.
15980 Available flags are:
15984 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15985 parameters and typedefs defined in a class when printing the class'
15986 members. The @code{/r} flag disables this.
15989 Do not print methods defined in the class.
15992 Print methods defined in the class. This is the default, but the flag
15993 exists in case you change the default with @command{set print type methods}.
15996 Do not print typedefs defined in the class. Note that this controls
15997 whether the typedef definition itself is printed, not whether typedef
15998 names are substituted when printing other types.
16001 Print typedefs defined in the class. This is the default, but the flag
16002 exists in case you change the default with @command{set print type typedefs}.
16006 @item ptype[/@var{flags}] [@var{arg}]
16007 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16008 detailed description of the type, instead of just the name of the type.
16009 @xref{Expressions, ,Expressions}.
16011 Contrary to @code{whatis}, @code{ptype} always unrolls any
16012 @code{typedef}s in its argument declaration, whether the argument is
16013 a variable, expression, or a data type. This means that @code{ptype}
16014 of a variable or an expression will not print literally its type as
16015 present in the source code---use @code{whatis} for that. @code{typedef}s at
16016 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16017 fields, methods and inner @code{class typedef}s of @code{struct}s,
16018 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16020 For example, for this variable declaration:
16023 typedef double real_t;
16024 struct complex @{ real_t real; double imag; @};
16025 typedef struct complex complex_t;
16027 real_t *real_pointer_var;
16031 the two commands give this output:
16035 (@value{GDBP}) whatis var
16037 (@value{GDBP}) ptype var
16038 type = struct complex @{
16042 (@value{GDBP}) whatis complex_t
16043 type = struct complex
16044 (@value{GDBP}) whatis struct complex
16045 type = struct complex
16046 (@value{GDBP}) ptype struct complex
16047 type = struct complex @{
16051 (@value{GDBP}) whatis real_pointer_var
16053 (@value{GDBP}) ptype real_pointer_var
16059 As with @code{whatis}, using @code{ptype} without an argument refers to
16060 the type of @code{$}, the last value in the value history.
16062 @cindex incomplete type
16063 Sometimes, programs use opaque data types or incomplete specifications
16064 of complex data structure. If the debug information included in the
16065 program does not allow @value{GDBN} to display a full declaration of
16066 the data type, it will say @samp{<incomplete type>}. For example,
16067 given these declarations:
16071 struct foo *fooptr;
16075 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16078 (@value{GDBP}) ptype foo
16079 $1 = <incomplete type>
16083 ``Incomplete type'' is C terminology for data types that are not
16084 completely specified.
16087 @item info types @var{regexp}
16089 Print a brief description of all types whose names match the regular
16090 expression @var{regexp} (or all types in your program, if you supply
16091 no argument). Each complete typename is matched as though it were a
16092 complete line; thus, @samp{i type value} gives information on all
16093 types in your program whose names include the string @code{value}, but
16094 @samp{i type ^value$} gives information only on types whose complete
16095 name is @code{value}.
16097 This command differs from @code{ptype} in two ways: first, like
16098 @code{whatis}, it does not print a detailed description; second, it
16099 lists all source files where a type is defined.
16101 @kindex info type-printers
16102 @item info type-printers
16103 Versions of @value{GDBN} that ship with Python scripting enabled may
16104 have ``type printers'' available. When using @command{ptype} or
16105 @command{whatis}, these printers are consulted when the name of a type
16106 is needed. @xref{Type Printing API}, for more information on writing
16109 @code{info type-printers} displays all the available type printers.
16111 @kindex enable type-printer
16112 @kindex disable type-printer
16113 @item enable type-printer @var{name}@dots{}
16114 @item disable type-printer @var{name}@dots{}
16115 These commands can be used to enable or disable type printers.
16118 @cindex local variables
16119 @item info scope @var{location}
16120 List all the variables local to a particular scope. This command
16121 accepts a @var{location} argument---a function name, a source line, or
16122 an address preceded by a @samp{*}, and prints all the variables local
16123 to the scope defined by that location. (@xref{Specify Location}, for
16124 details about supported forms of @var{location}.) For example:
16127 (@value{GDBP}) @b{info scope command_line_handler}
16128 Scope for command_line_handler:
16129 Symbol rl is an argument at stack/frame offset 8, length 4.
16130 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16131 Symbol linelength is in static storage at address 0x150a1c, length 4.
16132 Symbol p is a local variable in register $esi, length 4.
16133 Symbol p1 is a local variable in register $ebx, length 4.
16134 Symbol nline is a local variable in register $edx, length 4.
16135 Symbol repeat is a local variable at frame offset -8, length 4.
16139 This command is especially useful for determining what data to collect
16140 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16143 @kindex info source
16145 Show information about the current source file---that is, the source file for
16146 the function containing the current point of execution:
16149 the name of the source file, and the directory containing it,
16151 the directory it was compiled in,
16153 its length, in lines,
16155 which programming language it is written in,
16157 whether the executable includes debugging information for that file, and
16158 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16160 whether the debugging information includes information about
16161 preprocessor macros.
16165 @kindex info sources
16167 Print the names of all source files in your program for which there is
16168 debugging information, organized into two lists: files whose symbols
16169 have already been read, and files whose symbols will be read when needed.
16171 @kindex info functions
16172 @item info functions
16173 Print the names and data types of all defined functions.
16175 @item info functions @var{regexp}
16176 Print the names and data types of all defined functions
16177 whose names contain a match for regular expression @var{regexp}.
16178 Thus, @samp{info fun step} finds all functions whose names
16179 include @code{step}; @samp{info fun ^step} finds those whose names
16180 start with @code{step}. If a function name contains characters
16181 that conflict with the regular expression language (e.g.@:
16182 @samp{operator*()}), they may be quoted with a backslash.
16184 @kindex info variables
16185 @item info variables
16186 Print the names and data types of all variables that are defined
16187 outside of functions (i.e.@: excluding local variables).
16189 @item info variables @var{regexp}
16190 Print the names and data types of all variables (except for local
16191 variables) whose names contain a match for regular expression
16194 @kindex info classes
16195 @cindex Objective-C, classes and selectors
16197 @itemx info classes @var{regexp}
16198 Display all Objective-C classes in your program, or
16199 (with the @var{regexp} argument) all those matching a particular regular
16202 @kindex info selectors
16203 @item info selectors
16204 @itemx info selectors @var{regexp}
16205 Display all Objective-C selectors in your program, or
16206 (with the @var{regexp} argument) all those matching a particular regular
16210 This was never implemented.
16211 @kindex info methods
16213 @itemx info methods @var{regexp}
16214 The @code{info methods} command permits the user to examine all defined
16215 methods within C@t{++} program, or (with the @var{regexp} argument) a
16216 specific set of methods found in the various C@t{++} classes. Many
16217 C@t{++} classes provide a large number of methods. Thus, the output
16218 from the @code{ptype} command can be overwhelming and hard to use. The
16219 @code{info-methods} command filters the methods, printing only those
16220 which match the regular-expression @var{regexp}.
16223 @cindex opaque data types
16224 @kindex set opaque-type-resolution
16225 @item set opaque-type-resolution on
16226 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16227 declared as a pointer to a @code{struct}, @code{class}, or
16228 @code{union}---for example, @code{struct MyType *}---that is used in one
16229 source file although the full declaration of @code{struct MyType} is in
16230 another source file. The default is on.
16232 A change in the setting of this subcommand will not take effect until
16233 the next time symbols for a file are loaded.
16235 @item set opaque-type-resolution off
16236 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16237 is printed as follows:
16239 @{<no data fields>@}
16242 @kindex show opaque-type-resolution
16243 @item show opaque-type-resolution
16244 Show whether opaque types are resolved or not.
16246 @kindex set print symbol-loading
16247 @cindex print messages when symbols are loaded
16248 @item set print symbol-loading
16249 @itemx set print symbol-loading full
16250 @itemx set print symbol-loading brief
16251 @itemx set print symbol-loading off
16252 The @code{set print symbol-loading} command allows you to control the
16253 printing of messages when @value{GDBN} loads symbol information.
16254 By default a message is printed for the executable and one for each
16255 shared library, and normally this is what you want. However, when
16256 debugging apps with large numbers of shared libraries these messages
16258 When set to @code{brief} a message is printed for each executable,
16259 and when @value{GDBN} loads a collection of shared libraries at once
16260 it will only print one message regardless of the number of shared
16261 libraries. When set to @code{off} no messages are printed.
16263 @kindex show print symbol-loading
16264 @item show print symbol-loading
16265 Show whether messages will be printed when a @value{GDBN} command
16266 entered from the keyboard causes symbol information to be loaded.
16268 @kindex maint print symbols
16269 @cindex symbol dump
16270 @kindex maint print psymbols
16271 @cindex partial symbol dump
16272 @kindex maint print msymbols
16273 @cindex minimal symbol dump
16274 @item maint print symbols @var{filename}
16275 @itemx maint print psymbols @var{filename}
16276 @itemx maint print msymbols @var{filename}
16277 Write a dump of debugging symbol data into the file @var{filename}.
16278 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16279 symbols with debugging data are included. If you use @samp{maint print
16280 symbols}, @value{GDBN} includes all the symbols for which it has already
16281 collected full details: that is, @var{filename} reflects symbols for
16282 only those files whose symbols @value{GDBN} has read. You can use the
16283 command @code{info sources} to find out which files these are. If you
16284 use @samp{maint print psymbols} instead, the dump shows information about
16285 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16286 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16287 @samp{maint print msymbols} dumps just the minimal symbol information
16288 required for each object file from which @value{GDBN} has read some symbols.
16289 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16290 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16292 @kindex maint info symtabs
16293 @kindex maint info psymtabs
16294 @cindex listing @value{GDBN}'s internal symbol tables
16295 @cindex symbol tables, listing @value{GDBN}'s internal
16296 @cindex full symbol tables, listing @value{GDBN}'s internal
16297 @cindex partial symbol tables, listing @value{GDBN}'s internal
16298 @item maint info symtabs @r{[} @var{regexp} @r{]}
16299 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16301 List the @code{struct symtab} or @code{struct partial_symtab}
16302 structures whose names match @var{regexp}. If @var{regexp} is not
16303 given, list them all. The output includes expressions which you can
16304 copy into a @value{GDBN} debugging this one to examine a particular
16305 structure in more detail. For example:
16308 (@value{GDBP}) maint info psymtabs dwarf2read
16309 @{ objfile /home/gnu/build/gdb/gdb
16310 ((struct objfile *) 0x82e69d0)
16311 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16312 ((struct partial_symtab *) 0x8474b10)
16315 text addresses 0x814d3c8 -- 0x8158074
16316 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16317 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16318 dependencies (none)
16321 (@value{GDBP}) maint info symtabs
16325 We see that there is one partial symbol table whose filename contains
16326 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16327 and we see that @value{GDBN} has not read in any symtabs yet at all.
16328 If we set a breakpoint on a function, that will cause @value{GDBN} to
16329 read the symtab for the compilation unit containing that function:
16332 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16333 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16335 (@value{GDBP}) maint info symtabs
16336 @{ objfile /home/gnu/build/gdb/gdb
16337 ((struct objfile *) 0x82e69d0)
16338 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16339 ((struct symtab *) 0x86c1f38)
16342 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16343 linetable ((struct linetable *) 0x8370fa0)
16344 debugformat DWARF 2
16353 @chapter Altering Execution
16355 Once you think you have found an error in your program, you might want to
16356 find out for certain whether correcting the apparent error would lead to
16357 correct results in the rest of the run. You can find the answer by
16358 experiment, using the @value{GDBN} features for altering execution of the
16361 For example, you can store new values into variables or memory
16362 locations, give your program a signal, restart it at a different
16363 address, or even return prematurely from a function.
16366 * Assignment:: Assignment to variables
16367 * Jumping:: Continuing at a different address
16368 * Signaling:: Giving your program a signal
16369 * Returning:: Returning from a function
16370 * Calling:: Calling your program's functions
16371 * Patching:: Patching your program
16375 @section Assignment to Variables
16378 @cindex setting variables
16379 To alter the value of a variable, evaluate an assignment expression.
16380 @xref{Expressions, ,Expressions}. For example,
16387 stores the value 4 into the variable @code{x}, and then prints the
16388 value of the assignment expression (which is 4).
16389 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16390 information on operators in supported languages.
16392 @kindex set variable
16393 @cindex variables, setting
16394 If you are not interested in seeing the value of the assignment, use the
16395 @code{set} command instead of the @code{print} command. @code{set} is
16396 really the same as @code{print} except that the expression's value is
16397 not printed and is not put in the value history (@pxref{Value History,
16398 ,Value History}). The expression is evaluated only for its effects.
16400 If the beginning of the argument string of the @code{set} command
16401 appears identical to a @code{set} subcommand, use the @code{set
16402 variable} command instead of just @code{set}. This command is identical
16403 to @code{set} except for its lack of subcommands. For example, if your
16404 program has a variable @code{width}, you get an error if you try to set
16405 a new value with just @samp{set width=13}, because @value{GDBN} has the
16406 command @code{set width}:
16409 (@value{GDBP}) whatis width
16411 (@value{GDBP}) p width
16413 (@value{GDBP}) set width=47
16414 Invalid syntax in expression.
16418 The invalid expression, of course, is @samp{=47}. In
16419 order to actually set the program's variable @code{width}, use
16422 (@value{GDBP}) set var width=47
16425 Because the @code{set} command has many subcommands that can conflict
16426 with the names of program variables, it is a good idea to use the
16427 @code{set variable} command instead of just @code{set}. For example, if
16428 your program has a variable @code{g}, you run into problems if you try
16429 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16430 the command @code{set gnutarget}, abbreviated @code{set g}:
16434 (@value{GDBP}) whatis g
16438 (@value{GDBP}) set g=4
16442 The program being debugged has been started already.
16443 Start it from the beginning? (y or n) y
16444 Starting program: /home/smith/cc_progs/a.out
16445 "/home/smith/cc_progs/a.out": can't open to read symbols:
16446 Invalid bfd target.
16447 (@value{GDBP}) show g
16448 The current BFD target is "=4".
16453 The program variable @code{g} did not change, and you silently set the
16454 @code{gnutarget} to an invalid value. In order to set the variable
16458 (@value{GDBP}) set var g=4
16461 @value{GDBN} allows more implicit conversions in assignments than C; you can
16462 freely store an integer value into a pointer variable or vice versa,
16463 and you can convert any structure to any other structure that is the
16464 same length or shorter.
16465 @comment FIXME: how do structs align/pad in these conversions?
16466 @comment /doc@cygnus.com 18dec1990
16468 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16469 construct to generate a value of specified type at a specified address
16470 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16471 to memory location @code{0x83040} as an integer (which implies a certain size
16472 and representation in memory), and
16475 set @{int@}0x83040 = 4
16479 stores the value 4 into that memory location.
16482 @section Continuing at a Different Address
16484 Ordinarily, when you continue your program, you do so at the place where
16485 it stopped, with the @code{continue} command. You can instead continue at
16486 an address of your own choosing, with the following commands:
16490 @kindex j @r{(@code{jump})}
16491 @item jump @var{linespec}
16492 @itemx j @var{linespec}
16493 @itemx jump @var{location}
16494 @itemx j @var{location}
16495 Resume execution at line @var{linespec} or at address given by
16496 @var{location}. Execution stops again immediately if there is a
16497 breakpoint there. @xref{Specify Location}, for a description of the
16498 different forms of @var{linespec} and @var{location}. It is common
16499 practice to use the @code{tbreak} command in conjunction with
16500 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16502 The @code{jump} command does not change the current stack frame, or
16503 the stack pointer, or the contents of any memory location or any
16504 register other than the program counter. If line @var{linespec} is in
16505 a different function from the one currently executing, the results may
16506 be bizarre if the two functions expect different patterns of arguments or
16507 of local variables. For this reason, the @code{jump} command requests
16508 confirmation if the specified line is not in the function currently
16509 executing. However, even bizarre results are predictable if you are
16510 well acquainted with the machine-language code of your program.
16513 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16514 On many systems, you can get much the same effect as the @code{jump}
16515 command by storing a new value into the register @code{$pc}. The
16516 difference is that this does not start your program running; it only
16517 changes the address of where it @emph{will} run when you continue. For
16525 makes the next @code{continue} command or stepping command execute at
16526 address @code{0x485}, rather than at the address where your program stopped.
16527 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16529 The most common occasion to use the @code{jump} command is to back
16530 up---perhaps with more breakpoints set---over a portion of a program
16531 that has already executed, in order to examine its execution in more
16536 @section Giving your Program a Signal
16537 @cindex deliver a signal to a program
16541 @item signal @var{signal}
16542 Resume execution where your program stopped, but immediately give it the
16543 signal @var{signal}. @var{signal} can be the name or the number of a
16544 signal. For example, on many systems @code{signal 2} and @code{signal
16545 SIGINT} are both ways of sending an interrupt signal.
16547 Alternatively, if @var{signal} is zero, continue execution without
16548 giving a signal. This is useful when your program stopped on account of
16549 a signal and would ordinarily see the signal when resumed with the
16550 @code{continue} command; @samp{signal 0} causes it to resume without a
16553 @code{signal} does not repeat when you press @key{RET} a second time
16554 after executing the command.
16558 Invoking the @code{signal} command is not the same as invoking the
16559 @code{kill} utility from the shell. Sending a signal with @code{kill}
16560 causes @value{GDBN} to decide what to do with the signal depending on
16561 the signal handling tables (@pxref{Signals}). The @code{signal} command
16562 passes the signal directly to your program.
16566 @section Returning from a Function
16569 @cindex returning from a function
16572 @itemx return @var{expression}
16573 You can cancel execution of a function call with the @code{return}
16574 command. If you give an
16575 @var{expression} argument, its value is used as the function's return
16579 When you use @code{return}, @value{GDBN} discards the selected stack frame
16580 (and all frames within it). You can think of this as making the
16581 discarded frame return prematurely. If you wish to specify a value to
16582 be returned, give that value as the argument to @code{return}.
16584 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16585 Frame}), and any other frames inside of it, leaving its caller as the
16586 innermost remaining frame. That frame becomes selected. The
16587 specified value is stored in the registers used for returning values
16590 The @code{return} command does not resume execution; it leaves the
16591 program stopped in the state that would exist if the function had just
16592 returned. In contrast, the @code{finish} command (@pxref{Continuing
16593 and Stepping, ,Continuing and Stepping}) resumes execution until the
16594 selected stack frame returns naturally.
16596 @value{GDBN} needs to know how the @var{expression} argument should be set for
16597 the inferior. The concrete registers assignment depends on the OS ABI and the
16598 type being returned by the selected stack frame. For example it is common for
16599 OS ABI to return floating point values in FPU registers while integer values in
16600 CPU registers. Still some ABIs return even floating point values in CPU
16601 registers. Larger integer widths (such as @code{long long int}) also have
16602 specific placement rules. @value{GDBN} already knows the OS ABI from its
16603 current target so it needs to find out also the type being returned to make the
16604 assignment into the right register(s).
16606 Normally, the selected stack frame has debug info. @value{GDBN} will always
16607 use the debug info instead of the implicit type of @var{expression} when the
16608 debug info is available. For example, if you type @kbd{return -1}, and the
16609 function in the current stack frame is declared to return a @code{long long
16610 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16611 into a @code{long long int}:
16614 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16616 (@value{GDBP}) return -1
16617 Make func return now? (y or n) y
16618 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16619 43 printf ("result=%lld\n", func ());
16623 However, if the selected stack frame does not have a debug info, e.g., if the
16624 function was compiled without debug info, @value{GDBN} has to find out the type
16625 to return from user. Specifying a different type by mistake may set the value
16626 in different inferior registers than the caller code expects. For example,
16627 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16628 of a @code{long long int} result for a debug info less function (on 32-bit
16629 architectures). Therefore the user is required to specify the return type by
16630 an appropriate cast explicitly:
16633 Breakpoint 2, 0x0040050b in func ()
16634 (@value{GDBP}) return -1
16635 Return value type not available for selected stack frame.
16636 Please use an explicit cast of the value to return.
16637 (@value{GDBP}) return (long long int) -1
16638 Make selected stack frame return now? (y or n) y
16639 #0 0x00400526 in main ()
16644 @section Calling Program Functions
16647 @cindex calling functions
16648 @cindex inferior functions, calling
16649 @item print @var{expr}
16650 Evaluate the expression @var{expr} and display the resulting value.
16651 @var{expr} may include calls to functions in the program being
16655 @item call @var{expr}
16656 Evaluate the expression @var{expr} without displaying @code{void}
16659 You can use this variant of the @code{print} command if you want to
16660 execute a function from your program that does not return anything
16661 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16662 with @code{void} returned values that @value{GDBN} will otherwise
16663 print. If the result is not void, it is printed and saved in the
16667 It is possible for the function you call via the @code{print} or
16668 @code{call} command to generate a signal (e.g., if there's a bug in
16669 the function, or if you passed it incorrect arguments). What happens
16670 in that case is controlled by the @code{set unwindonsignal} command.
16672 Similarly, with a C@t{++} program it is possible for the function you
16673 call via the @code{print} or @code{call} command to generate an
16674 exception that is not handled due to the constraints of the dummy
16675 frame. In this case, any exception that is raised in the frame, but has
16676 an out-of-frame exception handler will not be found. GDB builds a
16677 dummy-frame for the inferior function call, and the unwinder cannot
16678 seek for exception handlers outside of this dummy-frame. What happens
16679 in that case is controlled by the
16680 @code{set unwind-on-terminating-exception} command.
16683 @item set unwindonsignal
16684 @kindex set unwindonsignal
16685 @cindex unwind stack in called functions
16686 @cindex call dummy stack unwinding
16687 Set unwinding of the stack if a signal is received while in a function
16688 that @value{GDBN} called in the program being debugged. If set to on,
16689 @value{GDBN} unwinds the stack it created for the call and restores
16690 the context to what it was before the call. If set to off (the
16691 default), @value{GDBN} stops in the frame where the signal was
16694 @item show unwindonsignal
16695 @kindex show unwindonsignal
16696 Show the current setting of stack unwinding in the functions called by
16699 @item set unwind-on-terminating-exception
16700 @kindex set unwind-on-terminating-exception
16701 @cindex unwind stack in called functions with unhandled exceptions
16702 @cindex call dummy stack unwinding on unhandled exception.
16703 Set unwinding of the stack if a C@t{++} exception is raised, but left
16704 unhandled while in a function that @value{GDBN} called in the program being
16705 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16706 it created for the call and restores the context to what it was before
16707 the call. If set to off, @value{GDBN} the exception is delivered to
16708 the default C@t{++} exception handler and the inferior terminated.
16710 @item show unwind-on-terminating-exception
16711 @kindex show unwind-on-terminating-exception
16712 Show the current setting of stack unwinding in the functions called by
16717 @cindex weak alias functions
16718 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16719 for another function. In such case, @value{GDBN} might not pick up
16720 the type information, including the types of the function arguments,
16721 which causes @value{GDBN} to call the inferior function incorrectly.
16722 As a result, the called function will function erroneously and may
16723 even crash. A solution to that is to use the name of the aliased
16727 @section Patching Programs
16729 @cindex patching binaries
16730 @cindex writing into executables
16731 @cindex writing into corefiles
16733 By default, @value{GDBN} opens the file containing your program's
16734 executable code (or the corefile) read-only. This prevents accidental
16735 alterations to machine code; but it also prevents you from intentionally
16736 patching your program's binary.
16738 If you'd like to be able to patch the binary, you can specify that
16739 explicitly with the @code{set write} command. For example, you might
16740 want to turn on internal debugging flags, or even to make emergency
16746 @itemx set write off
16747 If you specify @samp{set write on}, @value{GDBN} opens executable and
16748 core files for both reading and writing; if you specify @kbd{set write
16749 off} (the default), @value{GDBN} opens them read-only.
16751 If you have already loaded a file, you must load it again (using the
16752 @code{exec-file} or @code{core-file} command) after changing @code{set
16753 write}, for your new setting to take effect.
16757 Display whether executable files and core files are opened for writing
16758 as well as reading.
16762 @chapter @value{GDBN} Files
16764 @value{GDBN} needs to know the file name of the program to be debugged,
16765 both in order to read its symbol table and in order to start your
16766 program. To debug a core dump of a previous run, you must also tell
16767 @value{GDBN} the name of the core dump file.
16770 * Files:: Commands to specify files
16771 * Separate Debug Files:: Debugging information in separate files
16772 * MiniDebugInfo:: Debugging information in a special section
16773 * Index Files:: Index files speed up GDB
16774 * Symbol Errors:: Errors reading symbol files
16775 * Data Files:: GDB data files
16779 @section Commands to Specify Files
16781 @cindex symbol table
16782 @cindex core dump file
16784 You may want to specify executable and core dump file names. The usual
16785 way to do this is at start-up time, using the arguments to
16786 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16787 Out of @value{GDBN}}).
16789 Occasionally it is necessary to change to a different file during a
16790 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16791 specify a file you want to use. Or you are debugging a remote target
16792 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16793 Program}). In these situations the @value{GDBN} commands to specify
16794 new files are useful.
16797 @cindex executable file
16799 @item file @var{filename}
16800 Use @var{filename} as the program to be debugged. It is read for its
16801 symbols and for the contents of pure memory. It is also the program
16802 executed when you use the @code{run} command. If you do not specify a
16803 directory and the file is not found in the @value{GDBN} working directory,
16804 @value{GDBN} uses the environment variable @code{PATH} as a list of
16805 directories to search, just as the shell does when looking for a program
16806 to run. You can change the value of this variable, for both @value{GDBN}
16807 and your program, using the @code{path} command.
16809 @cindex unlinked object files
16810 @cindex patching object files
16811 You can load unlinked object @file{.o} files into @value{GDBN} using
16812 the @code{file} command. You will not be able to ``run'' an object
16813 file, but you can disassemble functions and inspect variables. Also,
16814 if the underlying BFD functionality supports it, you could use
16815 @kbd{gdb -write} to patch object files using this technique. Note
16816 that @value{GDBN} can neither interpret nor modify relocations in this
16817 case, so branches and some initialized variables will appear to go to
16818 the wrong place. But this feature is still handy from time to time.
16821 @code{file} with no argument makes @value{GDBN} discard any information it
16822 has on both executable file and the symbol table.
16825 @item exec-file @r{[} @var{filename} @r{]}
16826 Specify that the program to be run (but not the symbol table) is found
16827 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16828 if necessary to locate your program. Omitting @var{filename} means to
16829 discard information on the executable file.
16831 @kindex symbol-file
16832 @item symbol-file @r{[} @var{filename} @r{]}
16833 Read symbol table information from file @var{filename}. @code{PATH} is
16834 searched when necessary. Use the @code{file} command to get both symbol
16835 table and program to run from the same file.
16837 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16838 program's symbol table.
16840 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16841 some breakpoints and auto-display expressions. This is because they may
16842 contain pointers to the internal data recording symbols and data types,
16843 which are part of the old symbol table data being discarded inside
16846 @code{symbol-file} does not repeat if you press @key{RET} again after
16849 When @value{GDBN} is configured for a particular environment, it
16850 understands debugging information in whatever format is the standard
16851 generated for that environment; you may use either a @sc{gnu} compiler, or
16852 other compilers that adhere to the local conventions.
16853 Best results are usually obtained from @sc{gnu} compilers; for example,
16854 using @code{@value{NGCC}} you can generate debugging information for
16857 For most kinds of object files, with the exception of old SVR3 systems
16858 using COFF, the @code{symbol-file} command does not normally read the
16859 symbol table in full right away. Instead, it scans the symbol table
16860 quickly to find which source files and which symbols are present. The
16861 details are read later, one source file at a time, as they are needed.
16863 The purpose of this two-stage reading strategy is to make @value{GDBN}
16864 start up faster. For the most part, it is invisible except for
16865 occasional pauses while the symbol table details for a particular source
16866 file are being read. (The @code{set verbose} command can turn these
16867 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16868 Warnings and Messages}.)
16870 We have not implemented the two-stage strategy for COFF yet. When the
16871 symbol table is stored in COFF format, @code{symbol-file} reads the
16872 symbol table data in full right away. Note that ``stabs-in-COFF''
16873 still does the two-stage strategy, since the debug info is actually
16877 @cindex reading symbols immediately
16878 @cindex symbols, reading immediately
16879 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16880 @itemx file @r{[} -readnow @r{]} @var{filename}
16881 You can override the @value{GDBN} two-stage strategy for reading symbol
16882 tables by using the @samp{-readnow} option with any of the commands that
16883 load symbol table information, if you want to be sure @value{GDBN} has the
16884 entire symbol table available.
16886 @c FIXME: for now no mention of directories, since this seems to be in
16887 @c flux. 13mar1992 status is that in theory GDB would look either in
16888 @c current dir or in same dir as myprog; but issues like competing
16889 @c GDB's, or clutter in system dirs, mean that in practice right now
16890 @c only current dir is used. FFish says maybe a special GDB hierarchy
16891 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16895 @item core-file @r{[}@var{filename}@r{]}
16897 Specify the whereabouts of a core dump file to be used as the ``contents
16898 of memory''. Traditionally, core files contain only some parts of the
16899 address space of the process that generated them; @value{GDBN} can access the
16900 executable file itself for other parts.
16902 @code{core-file} with no argument specifies that no core file is
16905 Note that the core file is ignored when your program is actually running
16906 under @value{GDBN}. So, if you have been running your program and you
16907 wish to debug a core file instead, you must kill the subprocess in which
16908 the program is running. To do this, use the @code{kill} command
16909 (@pxref{Kill Process, ,Killing the Child Process}).
16911 @kindex add-symbol-file
16912 @cindex dynamic linking
16913 @item add-symbol-file @var{filename} @var{address}
16914 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16915 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16916 The @code{add-symbol-file} command reads additional symbol table
16917 information from the file @var{filename}. You would use this command
16918 when @var{filename} has been dynamically loaded (by some other means)
16919 into the program that is running. @var{address} should be the memory
16920 address at which the file has been loaded; @value{GDBN} cannot figure
16921 this out for itself. You can additionally specify an arbitrary number
16922 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16923 section name and base address for that section. You can specify any
16924 @var{address} as an expression.
16926 The symbol table of the file @var{filename} is added to the symbol table
16927 originally read with the @code{symbol-file} command. You can use the
16928 @code{add-symbol-file} command any number of times; the new symbol data
16929 thus read is kept in addition to the old.
16931 Changes can be reverted using the command @code{remove-symbol-file}.
16933 @cindex relocatable object files, reading symbols from
16934 @cindex object files, relocatable, reading symbols from
16935 @cindex reading symbols from relocatable object files
16936 @cindex symbols, reading from relocatable object files
16937 @cindex @file{.o} files, reading symbols from
16938 Although @var{filename} is typically a shared library file, an
16939 executable file, or some other object file which has been fully
16940 relocated for loading into a process, you can also load symbolic
16941 information from relocatable @file{.o} files, as long as:
16945 the file's symbolic information refers only to linker symbols defined in
16946 that file, not to symbols defined by other object files,
16948 every section the file's symbolic information refers to has actually
16949 been loaded into the inferior, as it appears in the file, and
16951 you can determine the address at which every section was loaded, and
16952 provide these to the @code{add-symbol-file} command.
16956 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16957 relocatable files into an already running program; such systems
16958 typically make the requirements above easy to meet. However, it's
16959 important to recognize that many native systems use complex link
16960 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16961 assembly, for example) that make the requirements difficult to meet. In
16962 general, one cannot assume that using @code{add-symbol-file} to read a
16963 relocatable object file's symbolic information will have the same effect
16964 as linking the relocatable object file into the program in the normal
16967 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16969 @kindex remove-symbol-file
16970 @item remove-symbol-file @var{filename}
16971 @item remove-symbol-file -a @var{address}
16972 Remove a symbol file added via the @code{add-symbol-file} command. The
16973 file to remove can be identified by its @var{filename} or by an @var{address}
16974 that lies within the boundaries of this symbol file in memory. Example:
16977 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16978 add symbol table from file "/home/user/gdb/mylib.so" at
16979 .text_addr = 0x7ffff7ff9480
16981 Reading symbols from /home/user/gdb/mylib.so...done.
16982 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16983 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16988 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16990 @kindex add-symbol-file-from-memory
16991 @cindex @code{syscall DSO}
16992 @cindex load symbols from memory
16993 @item add-symbol-file-from-memory @var{address}
16994 Load symbols from the given @var{address} in a dynamically loaded
16995 object file whose image is mapped directly into the inferior's memory.
16996 For example, the Linux kernel maps a @code{syscall DSO} into each
16997 process's address space; this DSO provides kernel-specific code for
16998 some system calls. The argument can be any expression whose
16999 evaluation yields the address of the file's shared object file header.
17000 For this command to work, you must have used @code{symbol-file} or
17001 @code{exec-file} commands in advance.
17003 @kindex add-shared-symbol-files
17005 @item add-shared-symbol-files @var{library-file}
17006 @itemx assf @var{library-file}
17007 This command is deprecated and will be removed in future versions
17008 of @value{GDBN}. Use the @code{sharedlibrary} command instead.
17010 The @code{add-shared-symbol-files} command can currently be used only
17011 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
17012 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
17013 @value{GDBN} automatically looks for shared libraries, however if
17014 @value{GDBN} does not find yours, you can invoke
17015 @code{add-shared-symbol-files}. It takes one argument: the shared
17016 library's file name. @code{assf} is a shorthand alias for
17017 @code{add-shared-symbol-files}.
17020 @item section @var{section} @var{addr}
17021 The @code{section} command changes the base address of the named
17022 @var{section} of the exec file to @var{addr}. This can be used if the
17023 exec file does not contain section addresses, (such as in the
17024 @code{a.out} format), or when the addresses specified in the file
17025 itself are wrong. Each section must be changed separately. The
17026 @code{info files} command, described below, lists all the sections and
17030 @kindex info target
17033 @code{info files} and @code{info target} are synonymous; both print the
17034 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17035 including the names of the executable and core dump files currently in
17036 use by @value{GDBN}, and the files from which symbols were loaded. The
17037 command @code{help target} lists all possible targets rather than
17040 @kindex maint info sections
17041 @item maint info sections
17042 Another command that can give you extra information about program sections
17043 is @code{maint info sections}. In addition to the section information
17044 displayed by @code{info files}, this command displays the flags and file
17045 offset of each section in the executable and core dump files. In addition,
17046 @code{maint info sections} provides the following command options (which
17047 may be arbitrarily combined):
17051 Display sections for all loaded object files, including shared libraries.
17052 @item @var{sections}
17053 Display info only for named @var{sections}.
17054 @item @var{section-flags}
17055 Display info only for sections for which @var{section-flags} are true.
17056 The section flags that @value{GDBN} currently knows about are:
17059 Section will have space allocated in the process when loaded.
17060 Set for all sections except those containing debug information.
17062 Section will be loaded from the file into the child process memory.
17063 Set for pre-initialized code and data, clear for @code{.bss} sections.
17065 Section needs to be relocated before loading.
17067 Section cannot be modified by the child process.
17069 Section contains executable code only.
17071 Section contains data only (no executable code).
17073 Section will reside in ROM.
17075 Section contains data for constructor/destructor lists.
17077 Section is not empty.
17079 An instruction to the linker to not output the section.
17080 @item COFF_SHARED_LIBRARY
17081 A notification to the linker that the section contains
17082 COFF shared library information.
17084 Section contains common symbols.
17087 @kindex set trust-readonly-sections
17088 @cindex read-only sections
17089 @item set trust-readonly-sections on
17090 Tell @value{GDBN} that readonly sections in your object file
17091 really are read-only (i.e.@: that their contents will not change).
17092 In that case, @value{GDBN} can fetch values from these sections
17093 out of the object file, rather than from the target program.
17094 For some targets (notably embedded ones), this can be a significant
17095 enhancement to debugging performance.
17097 The default is off.
17099 @item set trust-readonly-sections off
17100 Tell @value{GDBN} not to trust readonly sections. This means that
17101 the contents of the section might change while the program is running,
17102 and must therefore be fetched from the target when needed.
17104 @item show trust-readonly-sections
17105 Show the current setting of trusting readonly sections.
17108 All file-specifying commands allow both absolute and relative file names
17109 as arguments. @value{GDBN} always converts the file name to an absolute file
17110 name and remembers it that way.
17112 @cindex shared libraries
17113 @anchor{Shared Libraries}
17114 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17115 and IBM RS/6000 AIX shared libraries.
17117 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17118 shared libraries. @xref{Expat}.
17120 @value{GDBN} automatically loads symbol definitions from shared libraries
17121 when you use the @code{run} command, or when you examine a core file.
17122 (Before you issue the @code{run} command, @value{GDBN} does not understand
17123 references to a function in a shared library, however---unless you are
17124 debugging a core file).
17126 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17127 automatically loads the symbols at the time of the @code{shl_load} call.
17129 @c FIXME: some @value{GDBN} release may permit some refs to undef
17130 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17131 @c FIXME...lib; check this from time to time when updating manual
17133 There are times, however, when you may wish to not automatically load
17134 symbol definitions from shared libraries, such as when they are
17135 particularly large or there are many of them.
17137 To control the automatic loading of shared library symbols, use the
17141 @kindex set auto-solib-add
17142 @item set auto-solib-add @var{mode}
17143 If @var{mode} is @code{on}, symbols from all shared object libraries
17144 will be loaded automatically when the inferior begins execution, you
17145 attach to an independently started inferior, or when the dynamic linker
17146 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17147 is @code{off}, symbols must be loaded manually, using the
17148 @code{sharedlibrary} command. The default value is @code{on}.
17150 @cindex memory used for symbol tables
17151 If your program uses lots of shared libraries with debug info that
17152 takes large amounts of memory, you can decrease the @value{GDBN}
17153 memory footprint by preventing it from automatically loading the
17154 symbols from shared libraries. To that end, type @kbd{set
17155 auto-solib-add off} before running the inferior, then load each
17156 library whose debug symbols you do need with @kbd{sharedlibrary
17157 @var{regexp}}, where @var{regexp} is a regular expression that matches
17158 the libraries whose symbols you want to be loaded.
17160 @kindex show auto-solib-add
17161 @item show auto-solib-add
17162 Display the current autoloading mode.
17165 @cindex load shared library
17166 To explicitly load shared library symbols, use the @code{sharedlibrary}
17170 @kindex info sharedlibrary
17172 @item info share @var{regex}
17173 @itemx info sharedlibrary @var{regex}
17174 Print the names of the shared libraries which are currently loaded
17175 that match @var{regex}. If @var{regex} is omitted then print
17176 all shared libraries that are loaded.
17178 @kindex sharedlibrary
17180 @item sharedlibrary @var{regex}
17181 @itemx share @var{regex}
17182 Load shared object library symbols for files matching a
17183 Unix regular expression.
17184 As with files loaded automatically, it only loads shared libraries
17185 required by your program for a core file or after typing @code{run}. If
17186 @var{regex} is omitted all shared libraries required by your program are
17189 @item nosharedlibrary
17190 @kindex nosharedlibrary
17191 @cindex unload symbols from shared libraries
17192 Unload all shared object library symbols. This discards all symbols
17193 that have been loaded from all shared libraries. Symbols from shared
17194 libraries that were loaded by explicit user requests are not
17198 Sometimes you may wish that @value{GDBN} stops and gives you control
17199 when any of shared library events happen. The best way to do this is
17200 to use @code{catch load} and @code{catch unload} (@pxref{Set
17203 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17204 command for this. This command exists for historical reasons. It is
17205 less useful than setting a catchpoint, because it does not allow for
17206 conditions or commands as a catchpoint does.
17209 @item set stop-on-solib-events
17210 @kindex set stop-on-solib-events
17211 This command controls whether @value{GDBN} should give you control
17212 when the dynamic linker notifies it about some shared library event.
17213 The most common event of interest is loading or unloading of a new
17216 @item show stop-on-solib-events
17217 @kindex show stop-on-solib-events
17218 Show whether @value{GDBN} stops and gives you control when shared
17219 library events happen.
17222 Shared libraries are also supported in many cross or remote debugging
17223 configurations. @value{GDBN} needs to have access to the target's libraries;
17224 this can be accomplished either by providing copies of the libraries
17225 on the host system, or by asking @value{GDBN} to automatically retrieve the
17226 libraries from the target. If copies of the target libraries are
17227 provided, they need to be the same as the target libraries, although the
17228 copies on the target can be stripped as long as the copies on the host are
17231 @cindex where to look for shared libraries
17232 For remote debugging, you need to tell @value{GDBN} where the target
17233 libraries are, so that it can load the correct copies---otherwise, it
17234 may try to load the host's libraries. @value{GDBN} has two variables
17235 to specify the search directories for target libraries.
17238 @cindex prefix for shared library file names
17239 @cindex system root, alternate
17240 @kindex set solib-absolute-prefix
17241 @kindex set sysroot
17242 @item set sysroot @var{path}
17243 Use @var{path} as the system root for the program being debugged. Any
17244 absolute shared library paths will be prefixed with @var{path}; many
17245 runtime loaders store the absolute paths to the shared library in the
17246 target program's memory. If you use @code{set sysroot} to find shared
17247 libraries, they need to be laid out in the same way that they are on
17248 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17251 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17252 retrieve the target libraries from the remote system. This is only
17253 supported when using a remote target that supports the @code{remote get}
17254 command (@pxref{File Transfer,,Sending files to a remote system}).
17255 The part of @var{path} following the initial @file{remote:}
17256 (if present) is used as system root prefix on the remote file system.
17257 @footnote{If you want to specify a local system root using a directory
17258 that happens to be named @file{remote:}, you need to use some equivalent
17259 variant of the name like @file{./remote:}.}
17261 For targets with an MS-DOS based filesystem, such as MS-Windows and
17262 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17263 absolute file name with @var{path}. But first, on Unix hosts,
17264 @value{GDBN} converts all backslash directory separators into forward
17265 slashes, because the backslash is not a directory separator on Unix:
17268 c:\foo\bar.dll @result{} c:/foo/bar.dll
17271 Then, @value{GDBN} attempts prefixing the target file name with
17272 @var{path}, and looks for the resulting file name in the host file
17276 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17279 If that does not find the shared library, @value{GDBN} tries removing
17280 the @samp{:} character from the drive spec, both for convenience, and,
17281 for the case of the host file system not supporting file names with
17285 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17288 This makes it possible to have a system root that mirrors a target
17289 with more than one drive. E.g., you may want to setup your local
17290 copies of the target system shared libraries like so (note @samp{c} vs
17294 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17295 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17296 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17300 and point the system root at @file{/path/to/sysroot}, so that
17301 @value{GDBN} can find the correct copies of both
17302 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17304 If that still does not find the shared library, @value{GDBN} tries
17305 removing the whole drive spec from the target file name:
17308 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17311 This last lookup makes it possible to not care about the drive name,
17312 if you don't want or need to.
17314 The @code{set solib-absolute-prefix} command is an alias for @code{set
17317 @cindex default system root
17318 @cindex @samp{--with-sysroot}
17319 You can set the default system root by using the configure-time
17320 @samp{--with-sysroot} option. If the system root is inside
17321 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17322 @samp{--exec-prefix}), then the default system root will be updated
17323 automatically if the installed @value{GDBN} is moved to a new
17326 @kindex show sysroot
17328 Display the current shared library prefix.
17330 @kindex set solib-search-path
17331 @item set solib-search-path @var{path}
17332 If this variable is set, @var{path} is a colon-separated list of
17333 directories to search for shared libraries. @samp{solib-search-path}
17334 is used after @samp{sysroot} fails to locate the library, or if the
17335 path to the library is relative instead of absolute. If you want to
17336 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17337 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17338 finding your host's libraries. @samp{sysroot} is preferred; setting
17339 it to a nonexistent directory may interfere with automatic loading
17340 of shared library symbols.
17342 @kindex show solib-search-path
17343 @item show solib-search-path
17344 Display the current shared library search path.
17346 @cindex DOS file-name semantics of file names.
17347 @kindex set target-file-system-kind (unix|dos-based|auto)
17348 @kindex show target-file-system-kind
17349 @item set target-file-system-kind @var{kind}
17350 Set assumed file system kind for target reported file names.
17352 Shared library file names as reported by the target system may not
17353 make sense as is on the system @value{GDBN} is running on. For
17354 example, when remote debugging a target that has MS-DOS based file
17355 system semantics, from a Unix host, the target may be reporting to
17356 @value{GDBN} a list of loaded shared libraries with file names such as
17357 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17358 drive letters, so the @samp{c:\} prefix is not normally understood as
17359 indicating an absolute file name, and neither is the backslash
17360 normally considered a directory separator character. In that case,
17361 the native file system would interpret this whole absolute file name
17362 as a relative file name with no directory components. This would make
17363 it impossible to point @value{GDBN} at a copy of the remote target's
17364 shared libraries on the host using @code{set sysroot}, and impractical
17365 with @code{set solib-search-path}. Setting
17366 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17367 to interpret such file names similarly to how the target would, and to
17368 map them to file names valid on @value{GDBN}'s native file system
17369 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17370 to one of the supported file system kinds. In that case, @value{GDBN}
17371 tries to determine the appropriate file system variant based on the
17372 current target's operating system (@pxref{ABI, ,Configuring the
17373 Current ABI}). The supported file system settings are:
17377 Instruct @value{GDBN} to assume the target file system is of Unix
17378 kind. Only file names starting the forward slash (@samp{/}) character
17379 are considered absolute, and the directory separator character is also
17383 Instruct @value{GDBN} to assume the target file system is DOS based.
17384 File names starting with either a forward slash, or a drive letter
17385 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17386 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17387 considered directory separators.
17390 Instruct @value{GDBN} to use the file system kind associated with the
17391 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17392 This is the default.
17396 @cindex file name canonicalization
17397 @cindex base name differences
17398 When processing file names provided by the user, @value{GDBN}
17399 frequently needs to compare them to the file names recorded in the
17400 program's debug info. Normally, @value{GDBN} compares just the
17401 @dfn{base names} of the files as strings, which is reasonably fast
17402 even for very large programs. (The base name of a file is the last
17403 portion of its name, after stripping all the leading directories.)
17404 This shortcut in comparison is based upon the assumption that files
17405 cannot have more than one base name. This is usually true, but
17406 references to files that use symlinks or similar filesystem
17407 facilities violate that assumption. If your program records files
17408 using such facilities, or if you provide file names to @value{GDBN}
17409 using symlinks etc., you can set @code{basenames-may-differ} to
17410 @code{true} to instruct @value{GDBN} to completely canonicalize each
17411 pair of file names it needs to compare. This will make file-name
17412 comparisons accurate, but at a price of a significant slowdown.
17415 @item set basenames-may-differ
17416 @kindex set basenames-may-differ
17417 Set whether a source file may have multiple base names.
17419 @item show basenames-may-differ
17420 @kindex show basenames-may-differ
17421 Show whether a source file may have multiple base names.
17424 @node Separate Debug Files
17425 @section Debugging Information in Separate Files
17426 @cindex separate debugging information files
17427 @cindex debugging information in separate files
17428 @cindex @file{.debug} subdirectories
17429 @cindex debugging information directory, global
17430 @cindex global debugging information directories
17431 @cindex build ID, and separate debugging files
17432 @cindex @file{.build-id} directory
17434 @value{GDBN} allows you to put a program's debugging information in a
17435 file separate from the executable itself, in a way that allows
17436 @value{GDBN} to find and load the debugging information automatically.
17437 Since debugging information can be very large---sometimes larger
17438 than the executable code itself---some systems distribute debugging
17439 information for their executables in separate files, which users can
17440 install only when they need to debug a problem.
17442 @value{GDBN} supports two ways of specifying the separate debug info
17447 The executable contains a @dfn{debug link} that specifies the name of
17448 the separate debug info file. The separate debug file's name is
17449 usually @file{@var{executable}.debug}, where @var{executable} is the
17450 name of the corresponding executable file without leading directories
17451 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17452 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17453 checksum for the debug file, which @value{GDBN} uses to validate that
17454 the executable and the debug file came from the same build.
17457 The executable contains a @dfn{build ID}, a unique bit string that is
17458 also present in the corresponding debug info file. (This is supported
17459 only on some operating systems, notably those which use the ELF format
17460 for binary files and the @sc{gnu} Binutils.) For more details about
17461 this feature, see the description of the @option{--build-id}
17462 command-line option in @ref{Options, , Command Line Options, ld.info,
17463 The GNU Linker}. The debug info file's name is not specified
17464 explicitly by the build ID, but can be computed from the build ID, see
17468 Depending on the way the debug info file is specified, @value{GDBN}
17469 uses two different methods of looking for the debug file:
17473 For the ``debug link'' method, @value{GDBN} looks up the named file in
17474 the directory of the executable file, then in a subdirectory of that
17475 directory named @file{.debug}, and finally under each one of the global debug
17476 directories, in a subdirectory whose name is identical to the leading
17477 directories of the executable's absolute file name.
17480 For the ``build ID'' method, @value{GDBN} looks in the
17481 @file{.build-id} subdirectory of each one of the global debug directories for
17482 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17483 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17484 are the rest of the bit string. (Real build ID strings are 32 or more
17485 hex characters, not 10.)
17488 So, for example, suppose you ask @value{GDBN} to debug
17489 @file{/usr/bin/ls}, which has a debug link that specifies the
17490 file @file{ls.debug}, and a build ID whose value in hex is
17491 @code{abcdef1234}. If the list of the global debug directories includes
17492 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17493 debug information files, in the indicated order:
17497 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17499 @file{/usr/bin/ls.debug}
17501 @file{/usr/bin/.debug/ls.debug}
17503 @file{/usr/lib/debug/usr/bin/ls.debug}.
17506 @anchor{debug-file-directory}
17507 Global debugging info directories default to what is set by @value{GDBN}
17508 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17509 you can also set the global debugging info directories, and view the list
17510 @value{GDBN} is currently using.
17514 @kindex set debug-file-directory
17515 @item set debug-file-directory @var{directories}
17516 Set the directories which @value{GDBN} searches for separate debugging
17517 information files to @var{directory}. Multiple path components can be set
17518 concatenating them by a path separator.
17520 @kindex show debug-file-directory
17521 @item show debug-file-directory
17522 Show the directories @value{GDBN} searches for separate debugging
17527 @cindex @code{.gnu_debuglink} sections
17528 @cindex debug link sections
17529 A debug link is a special section of the executable file named
17530 @code{.gnu_debuglink}. The section must contain:
17534 A filename, with any leading directory components removed, followed by
17537 zero to three bytes of padding, as needed to reach the next four-byte
17538 boundary within the section, and
17540 a four-byte CRC checksum, stored in the same endianness used for the
17541 executable file itself. The checksum is computed on the debugging
17542 information file's full contents by the function given below, passing
17543 zero as the @var{crc} argument.
17546 Any executable file format can carry a debug link, as long as it can
17547 contain a section named @code{.gnu_debuglink} with the contents
17550 @cindex @code{.note.gnu.build-id} sections
17551 @cindex build ID sections
17552 The build ID is a special section in the executable file (and in other
17553 ELF binary files that @value{GDBN} may consider). This section is
17554 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17555 It contains unique identification for the built files---the ID remains
17556 the same across multiple builds of the same build tree. The default
17557 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17558 content for the build ID string. The same section with an identical
17559 value is present in the original built binary with symbols, in its
17560 stripped variant, and in the separate debugging information file.
17562 The debugging information file itself should be an ordinary
17563 executable, containing a full set of linker symbols, sections, and
17564 debugging information. The sections of the debugging information file
17565 should have the same names, addresses, and sizes as the original file,
17566 but they need not contain any data---much like a @code{.bss} section
17567 in an ordinary executable.
17569 The @sc{gnu} binary utilities (Binutils) package includes the
17570 @samp{objcopy} utility that can produce
17571 the separated executable / debugging information file pairs using the
17572 following commands:
17575 @kbd{objcopy --only-keep-debug foo foo.debug}
17580 These commands remove the debugging
17581 information from the executable file @file{foo} and place it in the file
17582 @file{foo.debug}. You can use the first, second or both methods to link the
17587 The debug link method needs the following additional command to also leave
17588 behind a debug link in @file{foo}:
17591 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17594 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17595 a version of the @code{strip} command such that the command @kbd{strip foo -f
17596 foo.debug} has the same functionality as the two @code{objcopy} commands and
17597 the @code{ln -s} command above, together.
17600 Build ID gets embedded into the main executable using @code{ld --build-id} or
17601 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17602 compatibility fixes for debug files separation are present in @sc{gnu} binary
17603 utilities (Binutils) package since version 2.18.
17608 @cindex CRC algorithm definition
17609 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17610 IEEE 802.3 using the polynomial:
17612 @c TexInfo requires naked braces for multi-digit exponents for Tex
17613 @c output, but this causes HTML output to barf. HTML has to be set using
17614 @c raw commands. So we end up having to specify this equation in 2
17619 <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>
17620 + <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
17626 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17627 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17631 The function is computed byte at a time, taking the least
17632 significant bit of each byte first. The initial pattern
17633 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17634 the final result is inverted to ensure trailing zeros also affect the
17637 @emph{Note:} This is the same CRC polynomial as used in handling the
17638 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
17639 However in the case of the Remote Serial Protocol, the CRC is computed
17640 @emph{most} significant bit first, and the result is not inverted, so
17641 trailing zeros have no effect on the CRC value.
17643 To complete the description, we show below the code of the function
17644 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17645 initially supplied @code{crc} argument means that an initial call to
17646 this function passing in zero will start computing the CRC using
17649 @kindex gnu_debuglink_crc32
17652 gnu_debuglink_crc32 (unsigned long crc,
17653 unsigned char *buf, size_t len)
17655 static const unsigned long crc32_table[256] =
17657 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17658 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17659 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17660 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17661 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17662 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17663 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17664 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17665 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17666 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17667 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17668 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17669 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17670 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17671 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17672 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17673 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17674 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17675 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17676 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17677 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17678 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17679 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17680 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17681 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17682 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17683 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17684 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17685 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17686 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17687 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17688 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17689 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17690 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17691 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17692 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17693 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17694 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17695 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17696 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17697 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17698 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17699 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17700 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17701 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17702 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17703 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17704 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17705 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17706 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17707 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17710 unsigned char *end;
17712 crc = ~crc & 0xffffffff;
17713 for (end = buf + len; buf < end; ++buf)
17714 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17715 return ~crc & 0xffffffff;
17720 This computation does not apply to the ``build ID'' method.
17722 @node MiniDebugInfo
17723 @section Debugging information in a special section
17724 @cindex separate debug sections
17725 @cindex @samp{.gnu_debugdata} section
17727 Some systems ship pre-built executables and libraries that have a
17728 special @samp{.gnu_debugdata} section. This feature is called
17729 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17730 is used to supply extra symbols for backtraces.
17732 The intent of this section is to provide extra minimal debugging
17733 information for use in simple backtraces. It is not intended to be a
17734 replacement for full separate debugging information (@pxref{Separate
17735 Debug Files}). The example below shows the intended use; however,
17736 @value{GDBN} does not currently put restrictions on what sort of
17737 debugging information might be included in the section.
17739 @value{GDBN} has support for this extension. If the section exists,
17740 then it is used provided that no other source of debugging information
17741 can be found, and that @value{GDBN} was configured with LZMA support.
17743 This section can be easily created using @command{objcopy} and other
17744 standard utilities:
17747 # Extract the dynamic symbols from the main binary, there is no need
17748 # to also have these in the normal symbol table.
17749 nm -D @var{binary} --format=posix --defined-only \
17750 | awk '@{ print $1 @}' | sort > dynsyms
17752 # Extract all the text (i.e. function) symbols from the debuginfo.
17753 # (Note that we actually also accept "D" symbols, for the benefit
17754 # of platforms like PowerPC64 that use function descriptors.)
17755 nm @var{binary} --format=posix --defined-only \
17756 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17759 # Keep all the function symbols not already in the dynamic symbol
17761 comm -13 dynsyms funcsyms > keep_symbols
17763 # Separate full debug info into debug binary.
17764 objcopy --only-keep-debug @var{binary} debug
17766 # Copy the full debuginfo, keeping only a minimal set of symbols and
17767 # removing some unnecessary sections.
17768 objcopy -S --remove-section .gdb_index --remove-section .comment \
17769 --keep-symbols=keep_symbols debug mini_debuginfo
17771 # Drop the full debug info from the original binary.
17772 strip --strip-all -R .comment @var{binary}
17774 # Inject the compressed data into the .gnu_debugdata section of the
17777 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17781 @section Index Files Speed Up @value{GDBN}
17782 @cindex index files
17783 @cindex @samp{.gdb_index} section
17785 When @value{GDBN} finds a symbol file, it scans the symbols in the
17786 file in order to construct an internal symbol table. This lets most
17787 @value{GDBN} operations work quickly---at the cost of a delay early
17788 on. For large programs, this delay can be quite lengthy, so
17789 @value{GDBN} provides a way to build an index, which speeds up
17792 The index is stored as a section in the symbol file. @value{GDBN} can
17793 write the index to a file, then you can put it into the symbol file
17794 using @command{objcopy}.
17796 To create an index file, use the @code{save gdb-index} command:
17799 @item save gdb-index @var{directory}
17800 @kindex save gdb-index
17801 Create an index file for each symbol file currently known by
17802 @value{GDBN}. Each file is named after its corresponding symbol file,
17803 with @samp{.gdb-index} appended, and is written into the given
17807 Once you have created an index file you can merge it into your symbol
17808 file, here named @file{symfile}, using @command{objcopy}:
17811 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17812 --set-section-flags .gdb_index=readonly symfile symfile
17815 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17816 sections that have been deprecated. Usually they are deprecated because
17817 they are missing a new feature or have performance issues.
17818 To tell @value{GDBN} to use a deprecated index section anyway
17819 specify @code{set use-deprecated-index-sections on}.
17820 The default is @code{off}.
17821 This can speed up startup, but may result in some functionality being lost.
17822 @xref{Index Section Format}.
17824 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17825 must be done before gdb reads the file. The following will not work:
17828 $ gdb -ex "set use-deprecated-index-sections on" <program>
17831 Instead you must do, for example,
17834 $ gdb -iex "set use-deprecated-index-sections on" <program>
17837 There are currently some limitation on indices. They only work when
17838 for DWARF debugging information, not stabs. And, they do not
17839 currently work for programs using Ada.
17841 @node Symbol Errors
17842 @section Errors Reading Symbol Files
17844 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17845 such as symbol types it does not recognize, or known bugs in compiler
17846 output. By default, @value{GDBN} does not notify you of such problems, since
17847 they are relatively common and primarily of interest to people
17848 debugging compilers. If you are interested in seeing information
17849 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17850 only one message about each such type of problem, no matter how many
17851 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17852 to see how many times the problems occur, with the @code{set
17853 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17856 The messages currently printed, and their meanings, include:
17859 @item inner block not inside outer block in @var{symbol}
17861 The symbol information shows where symbol scopes begin and end
17862 (such as at the start of a function or a block of statements). This
17863 error indicates that an inner scope block is not fully contained
17864 in its outer scope blocks.
17866 @value{GDBN} circumvents the problem by treating the inner block as if it had
17867 the same scope as the outer block. In the error message, @var{symbol}
17868 may be shown as ``@code{(don't know)}'' if the outer block is not a
17871 @item block at @var{address} out of order
17873 The symbol information for symbol scope blocks should occur in
17874 order of increasing addresses. This error indicates that it does not
17877 @value{GDBN} does not circumvent this problem, and has trouble
17878 locating symbols in the source file whose symbols it is reading. (You
17879 can often determine what source file is affected by specifying
17880 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17883 @item bad block start address patched
17885 The symbol information for a symbol scope block has a start address
17886 smaller than the address of the preceding source line. This is known
17887 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17889 @value{GDBN} circumvents the problem by treating the symbol scope block as
17890 starting on the previous source line.
17892 @item bad string table offset in symbol @var{n}
17895 Symbol number @var{n} contains a pointer into the string table which is
17896 larger than the size of the string table.
17898 @value{GDBN} circumvents the problem by considering the symbol to have the
17899 name @code{foo}, which may cause other problems if many symbols end up
17902 @item unknown symbol type @code{0x@var{nn}}
17904 The symbol information contains new data types that @value{GDBN} does
17905 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17906 uncomprehended information, in hexadecimal.
17908 @value{GDBN} circumvents the error by ignoring this symbol information.
17909 This usually allows you to debug your program, though certain symbols
17910 are not accessible. If you encounter such a problem and feel like
17911 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17912 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17913 and examine @code{*bufp} to see the symbol.
17915 @item stub type has NULL name
17917 @value{GDBN} could not find the full definition for a struct or class.
17919 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17920 The symbol information for a C@t{++} member function is missing some
17921 information that recent versions of the compiler should have output for
17924 @item info mismatch between compiler and debugger
17926 @value{GDBN} could not parse a type specification output by the compiler.
17931 @section GDB Data Files
17933 @cindex prefix for data files
17934 @value{GDBN} will sometimes read an auxiliary data file. These files
17935 are kept in a directory known as the @dfn{data directory}.
17937 You can set the data directory's name, and view the name @value{GDBN}
17938 is currently using.
17941 @kindex set data-directory
17942 @item set data-directory @var{directory}
17943 Set the directory which @value{GDBN} searches for auxiliary data files
17944 to @var{directory}.
17946 @kindex show data-directory
17947 @item show data-directory
17948 Show the directory @value{GDBN} searches for auxiliary data files.
17951 @cindex default data directory
17952 @cindex @samp{--with-gdb-datadir}
17953 You can set the default data directory by using the configure-time
17954 @samp{--with-gdb-datadir} option. If the data directory is inside
17955 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17956 @samp{--exec-prefix}), then the default data directory will be updated
17957 automatically if the installed @value{GDBN} is moved to a new
17960 The data directory may also be specified with the
17961 @code{--data-directory} command line option.
17962 @xref{Mode Options}.
17965 @chapter Specifying a Debugging Target
17967 @cindex debugging target
17968 A @dfn{target} is the execution environment occupied by your program.
17970 Often, @value{GDBN} runs in the same host environment as your program;
17971 in that case, the debugging target is specified as a side effect when
17972 you use the @code{file} or @code{core} commands. When you need more
17973 flexibility---for example, running @value{GDBN} on a physically separate
17974 host, or controlling a standalone system over a serial port or a
17975 realtime system over a TCP/IP connection---you can use the @code{target}
17976 command to specify one of the target types configured for @value{GDBN}
17977 (@pxref{Target Commands, ,Commands for Managing Targets}).
17979 @cindex target architecture
17980 It is possible to build @value{GDBN} for several different @dfn{target
17981 architectures}. When @value{GDBN} is built like that, you can choose
17982 one of the available architectures with the @kbd{set architecture}
17986 @kindex set architecture
17987 @kindex show architecture
17988 @item set architecture @var{arch}
17989 This command sets the current target architecture to @var{arch}. The
17990 value of @var{arch} can be @code{"auto"}, in addition to one of the
17991 supported architectures.
17993 @item show architecture
17994 Show the current target architecture.
17996 @item set processor
17998 @kindex set processor
17999 @kindex show processor
18000 These are alias commands for, respectively, @code{set architecture}
18001 and @code{show architecture}.
18005 * Active Targets:: Active targets
18006 * Target Commands:: Commands for managing targets
18007 * Byte Order:: Choosing target byte order
18010 @node Active Targets
18011 @section Active Targets
18013 @cindex stacking targets
18014 @cindex active targets
18015 @cindex multiple targets
18017 There are multiple classes of targets such as: processes, executable files or
18018 recording sessions. Core files belong to the process class, making core file
18019 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18020 on multiple active targets, one in each class. This allows you to (for
18021 example) start a process and inspect its activity, while still having access to
18022 the executable file after the process finishes. Or if you start process
18023 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18024 presented a virtual layer of the recording target, while the process target
18025 remains stopped at the chronologically last point of the process execution.
18027 Use the @code{core-file} and @code{exec-file} commands to select a new core
18028 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18029 specify as a target a process that is already running, use the @code{attach}
18030 command (@pxref{Attach, ,Debugging an Already-running Process}).
18032 @node Target Commands
18033 @section Commands for Managing Targets
18036 @item target @var{type} @var{parameters}
18037 Connects the @value{GDBN} host environment to a target machine or
18038 process. A target is typically a protocol for talking to debugging
18039 facilities. You use the argument @var{type} to specify the type or
18040 protocol of the target machine.
18042 Further @var{parameters} are interpreted by the target protocol, but
18043 typically include things like device names or host names to connect
18044 with, process numbers, and baud rates.
18046 The @code{target} command does not repeat if you press @key{RET} again
18047 after executing the command.
18049 @kindex help target
18051 Displays the names of all targets available. To display targets
18052 currently selected, use either @code{info target} or @code{info files}
18053 (@pxref{Files, ,Commands to Specify Files}).
18055 @item help target @var{name}
18056 Describe a particular target, including any parameters necessary to
18059 @kindex set gnutarget
18060 @item set gnutarget @var{args}
18061 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18062 knows whether it is reading an @dfn{executable},
18063 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18064 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18065 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18068 @emph{Warning:} To specify a file format with @code{set gnutarget},
18069 you must know the actual BFD name.
18073 @xref{Files, , Commands to Specify Files}.
18075 @kindex show gnutarget
18076 @item show gnutarget
18077 Use the @code{show gnutarget} command to display what file format
18078 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18079 @value{GDBN} will determine the file format for each file automatically,
18080 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18083 @cindex common targets
18084 Here are some common targets (available, or not, depending on the GDB
18089 @item target exec @var{program}
18090 @cindex executable file target
18091 An executable file. @samp{target exec @var{program}} is the same as
18092 @samp{exec-file @var{program}}.
18094 @item target core @var{filename}
18095 @cindex core dump file target
18096 A core dump file. @samp{target core @var{filename}} is the same as
18097 @samp{core-file @var{filename}}.
18099 @item target remote @var{medium}
18100 @cindex remote target
18101 A remote system connected to @value{GDBN} via a serial line or network
18102 connection. This command tells @value{GDBN} to use its own remote
18103 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18105 For example, if you have a board connected to @file{/dev/ttya} on the
18106 machine running @value{GDBN}, you could say:
18109 target remote /dev/ttya
18112 @code{target remote} supports the @code{load} command. This is only
18113 useful if you have some other way of getting the stub to the target
18114 system, and you can put it somewhere in memory where it won't get
18115 clobbered by the download.
18117 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18118 @cindex built-in simulator target
18119 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18127 works; however, you cannot assume that a specific memory map, device
18128 drivers, or even basic I/O is available, although some simulators do
18129 provide these. For info about any processor-specific simulator details,
18130 see the appropriate section in @ref{Embedded Processors, ,Embedded
18133 @item target native
18134 @cindex native target
18135 Setup for local/native process debugging. Useful to make the
18136 @code{run} command spawn native processes (likewise @code{attach},
18137 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18138 (@pxref{set auto-connect-native-target}).
18142 Different targets are available on different configurations of @value{GDBN};
18143 your configuration may have more or fewer targets.
18145 Many remote targets require you to download the executable's code once
18146 you've successfully established a connection. You may wish to control
18147 various aspects of this process.
18152 @kindex set hash@r{, for remote monitors}
18153 @cindex hash mark while downloading
18154 This command controls whether a hash mark @samp{#} is displayed while
18155 downloading a file to the remote monitor. If on, a hash mark is
18156 displayed after each S-record is successfully downloaded to the
18160 @kindex show hash@r{, for remote monitors}
18161 Show the current status of displaying the hash mark.
18163 @item set debug monitor
18164 @kindex set debug monitor
18165 @cindex display remote monitor communications
18166 Enable or disable display of communications messages between
18167 @value{GDBN} and the remote monitor.
18169 @item show debug monitor
18170 @kindex show debug monitor
18171 Show the current status of displaying communications between
18172 @value{GDBN} and the remote monitor.
18177 @kindex load @var{filename}
18178 @item load @var{filename}
18180 Depending on what remote debugging facilities are configured into
18181 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18182 is meant to make @var{filename} (an executable) available for debugging
18183 on the remote system---by downloading, or dynamic linking, for example.
18184 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18185 the @code{add-symbol-file} command.
18187 If your @value{GDBN} does not have a @code{load} command, attempting to
18188 execute it gets the error message ``@code{You can't do that when your
18189 target is @dots{}}''
18191 The file is loaded at whatever address is specified in the executable.
18192 For some object file formats, you can specify the load address when you
18193 link the program; for other formats, like a.out, the object file format
18194 specifies a fixed address.
18195 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18197 Depending on the remote side capabilities, @value{GDBN} may be able to
18198 load programs into flash memory.
18200 @code{load} does not repeat if you press @key{RET} again after using it.
18204 @section Choosing Target Byte Order
18206 @cindex choosing target byte order
18207 @cindex target byte order
18209 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18210 offer the ability to run either big-endian or little-endian byte
18211 orders. Usually the executable or symbol will include a bit to
18212 designate the endian-ness, and you will not need to worry about
18213 which to use. However, you may still find it useful to adjust
18214 @value{GDBN}'s idea of processor endian-ness manually.
18218 @item set endian big
18219 Instruct @value{GDBN} to assume the target is big-endian.
18221 @item set endian little
18222 Instruct @value{GDBN} to assume the target is little-endian.
18224 @item set endian auto
18225 Instruct @value{GDBN} to use the byte order associated with the
18229 Display @value{GDBN}'s current idea of the target byte order.
18233 Note that these commands merely adjust interpretation of symbolic
18234 data on the host, and that they have absolutely no effect on the
18238 @node Remote Debugging
18239 @chapter Debugging Remote Programs
18240 @cindex remote debugging
18242 If you are trying to debug a program running on a machine that cannot run
18243 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18244 For example, you might use remote debugging on an operating system kernel,
18245 or on a small system which does not have a general purpose operating system
18246 powerful enough to run a full-featured debugger.
18248 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18249 to make this work with particular debugging targets. In addition,
18250 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18251 but not specific to any particular target system) which you can use if you
18252 write the remote stubs---the code that runs on the remote system to
18253 communicate with @value{GDBN}.
18255 Other remote targets may be available in your
18256 configuration of @value{GDBN}; use @code{help target} to list them.
18259 * Connecting:: Connecting to a remote target
18260 * File Transfer:: Sending files to a remote system
18261 * Server:: Using the gdbserver program
18262 * Remote Configuration:: Remote configuration
18263 * Remote Stub:: Implementing a remote stub
18267 @section Connecting to a Remote Target
18269 On the @value{GDBN} host machine, you will need an unstripped copy of
18270 your program, since @value{GDBN} needs symbol and debugging information.
18271 Start up @value{GDBN} as usual, using the name of the local copy of your
18272 program as the first argument.
18274 @cindex @code{target remote}
18275 @value{GDBN} can communicate with the target over a serial line, or
18276 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18277 each case, @value{GDBN} uses the same protocol for debugging your
18278 program; only the medium carrying the debugging packets varies. The
18279 @code{target remote} command establishes a connection to the target.
18280 Its arguments indicate which medium to use:
18284 @item target remote @var{serial-device}
18285 @cindex serial line, @code{target remote}
18286 Use @var{serial-device} to communicate with the target. For example,
18287 to use a serial line connected to the device named @file{/dev/ttyb}:
18290 target remote /dev/ttyb
18293 If you're using a serial line, you may want to give @value{GDBN} the
18294 @samp{--baud} option, or use the @code{set serial baud} command
18295 (@pxref{Remote Configuration, set serial baud}) before the
18296 @code{target} command.
18298 @item target remote @code{@var{host}:@var{port}}
18299 @itemx target remote @code{tcp:@var{host}:@var{port}}
18300 @cindex @acronym{TCP} port, @code{target remote}
18301 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18302 The @var{host} may be either a host name or a numeric @acronym{IP}
18303 address; @var{port} must be a decimal number. The @var{host} could be
18304 the target machine itself, if it is directly connected to the net, or
18305 it might be a terminal server which in turn has a serial line to the
18308 For example, to connect to port 2828 on a terminal server named
18312 target remote manyfarms:2828
18315 If your remote target is actually running on the same machine as your
18316 debugger session (e.g.@: a simulator for your target running on the
18317 same host), you can omit the hostname. For example, to connect to
18318 port 1234 on your local machine:
18321 target remote :1234
18325 Note that the colon is still required here.
18327 @item target remote @code{udp:@var{host}:@var{port}}
18328 @cindex @acronym{UDP} port, @code{target remote}
18329 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18330 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18333 target remote udp:manyfarms:2828
18336 When using a @acronym{UDP} connection for remote debugging, you should
18337 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18338 can silently drop packets on busy or unreliable networks, which will
18339 cause havoc with your debugging session.
18341 @item target remote | @var{command}
18342 @cindex pipe, @code{target remote} to
18343 Run @var{command} in the background and communicate with it using a
18344 pipe. The @var{command} is a shell command, to be parsed and expanded
18345 by the system's command shell, @code{/bin/sh}; it should expect remote
18346 protocol packets on its standard input, and send replies on its
18347 standard output. You could use this to run a stand-alone simulator
18348 that speaks the remote debugging protocol, to make net connections
18349 using programs like @code{ssh}, or for other similar tricks.
18351 If @var{command} closes its standard output (perhaps by exiting),
18352 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18353 program has already exited, this will have no effect.)
18357 Once the connection has been established, you can use all the usual
18358 commands to examine and change data. The remote program is already
18359 running; you can use @kbd{step} and @kbd{continue}, and you do not
18360 need to use @kbd{run}.
18362 @cindex interrupting remote programs
18363 @cindex remote programs, interrupting
18364 Whenever @value{GDBN} is waiting for the remote program, if you type the
18365 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18366 program. This may or may not succeed, depending in part on the hardware
18367 and the serial drivers the remote system uses. If you type the
18368 interrupt character once again, @value{GDBN} displays this prompt:
18371 Interrupted while waiting for the program.
18372 Give up (and stop debugging it)? (y or n)
18375 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18376 (If you decide you want to try again later, you can use @samp{target
18377 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18378 goes back to waiting.
18381 @kindex detach (remote)
18383 When you have finished debugging the remote program, you can use the
18384 @code{detach} command to release it from @value{GDBN} control.
18385 Detaching from the target normally resumes its execution, but the results
18386 will depend on your particular remote stub. After the @code{detach}
18387 command, @value{GDBN} is free to connect to another target.
18391 The @code{disconnect} command behaves like @code{detach}, except that
18392 the target is generally not resumed. It will wait for @value{GDBN}
18393 (this instance or another one) to connect and continue debugging. After
18394 the @code{disconnect} command, @value{GDBN} is again free to connect to
18397 @cindex send command to remote monitor
18398 @cindex extend @value{GDBN} for remote targets
18399 @cindex add new commands for external monitor
18401 @item monitor @var{cmd}
18402 This command allows you to send arbitrary commands directly to the
18403 remote monitor. Since @value{GDBN} doesn't care about the commands it
18404 sends like this, this command is the way to extend @value{GDBN}---you
18405 can add new commands that only the external monitor will understand
18409 @node File Transfer
18410 @section Sending files to a remote system
18411 @cindex remote target, file transfer
18412 @cindex file transfer
18413 @cindex sending files to remote systems
18415 Some remote targets offer the ability to transfer files over the same
18416 connection used to communicate with @value{GDBN}. This is convenient
18417 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18418 running @code{gdbserver} over a network interface. For other targets,
18419 e.g.@: embedded devices with only a single serial port, this may be
18420 the only way to upload or download files.
18422 Not all remote targets support these commands.
18426 @item remote put @var{hostfile} @var{targetfile}
18427 Copy file @var{hostfile} from the host system (the machine running
18428 @value{GDBN}) to @var{targetfile} on the target system.
18431 @item remote get @var{targetfile} @var{hostfile}
18432 Copy file @var{targetfile} from the target system to @var{hostfile}
18433 on the host system.
18435 @kindex remote delete
18436 @item remote delete @var{targetfile}
18437 Delete @var{targetfile} from the target system.
18442 @section Using the @code{gdbserver} Program
18445 @cindex remote connection without stubs
18446 @code{gdbserver} is a control program for Unix-like systems, which
18447 allows you to connect your program with a remote @value{GDBN} via
18448 @code{target remote}---but without linking in the usual debugging stub.
18450 @code{gdbserver} is not a complete replacement for the debugging stubs,
18451 because it requires essentially the same operating-system facilities
18452 that @value{GDBN} itself does. In fact, a system that can run
18453 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18454 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18455 because it is a much smaller program than @value{GDBN} itself. It is
18456 also easier to port than all of @value{GDBN}, so you may be able to get
18457 started more quickly on a new system by using @code{gdbserver}.
18458 Finally, if you develop code for real-time systems, you may find that
18459 the tradeoffs involved in real-time operation make it more convenient to
18460 do as much development work as possible on another system, for example
18461 by cross-compiling. You can use @code{gdbserver} to make a similar
18462 choice for debugging.
18464 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18465 or a TCP connection, using the standard @value{GDBN} remote serial
18469 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18470 Do not run @code{gdbserver} connected to any public network; a
18471 @value{GDBN} connection to @code{gdbserver} provides access to the
18472 target system with the same privileges as the user running
18476 @subsection Running @code{gdbserver}
18477 @cindex arguments, to @code{gdbserver}
18478 @cindex @code{gdbserver}, command-line arguments
18480 Run @code{gdbserver} on the target system. You need a copy of the
18481 program you want to debug, including any libraries it requires.
18482 @code{gdbserver} does not need your program's symbol table, so you can
18483 strip the program if necessary to save space. @value{GDBN} on the host
18484 system does all the symbol handling.
18486 To use the server, you must tell it how to communicate with @value{GDBN};
18487 the name of your program; and the arguments for your program. The usual
18491 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18494 @var{comm} is either a device name (to use a serial line), or a TCP
18495 hostname and portnumber, or @code{-} or @code{stdio} to use
18496 stdin/stdout of @code{gdbserver}.
18497 For example, to debug Emacs with the argument
18498 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18502 target> gdbserver /dev/com1 emacs foo.txt
18505 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18508 To use a TCP connection instead of a serial line:
18511 target> gdbserver host:2345 emacs foo.txt
18514 The only difference from the previous example is the first argument,
18515 specifying that you are communicating with the host @value{GDBN} via
18516 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18517 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18518 (Currently, the @samp{host} part is ignored.) You can choose any number
18519 you want for the port number as long as it does not conflict with any
18520 TCP ports already in use on the target system (for example, @code{23} is
18521 reserved for @code{telnet}).@footnote{If you choose a port number that
18522 conflicts with another service, @code{gdbserver} prints an error message
18523 and exits.} You must use the same port number with the host @value{GDBN}
18524 @code{target remote} command.
18526 The @code{stdio} connection is useful when starting @code{gdbserver}
18530 (gdb) target remote | ssh -T hostname gdbserver - hello
18533 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18534 and we don't want escape-character handling. Ssh does this by default when
18535 a command is provided, the flag is provided to make it explicit.
18536 You could elide it if you want to.
18538 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18539 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18540 display through a pipe connected to gdbserver.
18541 Both @code{stdout} and @code{stderr} use the same pipe.
18543 @subsubsection Attaching to a Running Program
18544 @cindex attach to a program, @code{gdbserver}
18545 @cindex @option{--attach}, @code{gdbserver} option
18547 On some targets, @code{gdbserver} can also attach to running programs.
18548 This is accomplished via the @code{--attach} argument. The syntax is:
18551 target> gdbserver --attach @var{comm} @var{pid}
18554 @var{pid} is the process ID of a currently running process. It isn't necessary
18555 to point @code{gdbserver} at a binary for the running process.
18558 You can debug processes by name instead of process ID if your target has the
18559 @code{pidof} utility:
18562 target> gdbserver --attach @var{comm} `pidof @var{program}`
18565 In case more than one copy of @var{program} is running, or @var{program}
18566 has multiple threads, most versions of @code{pidof} support the
18567 @code{-s} option to only return the first process ID.
18569 @subsubsection Multi-Process Mode for @code{gdbserver}
18570 @cindex @code{gdbserver}, multiple processes
18571 @cindex multiple processes with @code{gdbserver}
18573 When you connect to @code{gdbserver} using @code{target remote},
18574 @code{gdbserver} debugs the specified program only once. When the
18575 program exits, or you detach from it, @value{GDBN} closes the connection
18576 and @code{gdbserver} exits.
18578 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18579 enters multi-process mode. When the debugged program exits, or you
18580 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18581 though no program is running. The @code{run} and @code{attach}
18582 commands instruct @code{gdbserver} to run or attach to a new program.
18583 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18584 remote exec-file}) to select the program to run. Command line
18585 arguments are supported, except for wildcard expansion and I/O
18586 redirection (@pxref{Arguments}).
18588 @cindex @option{--multi}, @code{gdbserver} option
18589 To start @code{gdbserver} without supplying an initial command to run
18590 or process ID to attach, use the @option{--multi} command line option.
18591 Then you can connect using @kbd{target extended-remote} and start
18592 the program you want to debug.
18594 In multi-process mode @code{gdbserver} does not automatically exit unless you
18595 use the option @option{--once}. You can terminate it by using
18596 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18597 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18598 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18599 @option{--multi} option to @code{gdbserver} has no influence on that.
18601 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18603 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18605 @code{gdbserver} normally terminates after all of its debugged processes have
18606 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18607 extended-remote}, @code{gdbserver} stays running even with no processes left.
18608 @value{GDBN} normally terminates the spawned debugged process on its exit,
18609 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18610 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18611 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18612 stays running even in the @kbd{target remote} mode.
18614 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18615 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18616 completeness, at most one @value{GDBN} can be connected at a time.
18618 @cindex @option{--once}, @code{gdbserver} option
18619 By default, @code{gdbserver} keeps the listening TCP port open, so that
18620 subsequent connections are possible. However, if you start @code{gdbserver}
18621 with the @option{--once} option, it will stop listening for any further
18622 connection attempts after connecting to the first @value{GDBN} session. This
18623 means no further connections to @code{gdbserver} will be possible after the
18624 first one. It also means @code{gdbserver} will terminate after the first
18625 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18626 connections and even in the @kbd{target extended-remote} mode. The
18627 @option{--once} option allows reusing the same port number for connecting to
18628 multiple instances of @code{gdbserver} running on the same host, since each
18629 instance closes its port after the first connection.
18631 @anchor{Other Command-Line Arguments for gdbserver}
18632 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18634 @cindex @option{--debug}, @code{gdbserver} option
18635 The @option{--debug} option tells @code{gdbserver} to display extra
18636 status information about the debugging process.
18637 @cindex @option{--remote-debug}, @code{gdbserver} option
18638 The @option{--remote-debug} option tells @code{gdbserver} to display
18639 remote protocol debug output. These options are intended for
18640 @code{gdbserver} development and for bug reports to the developers.
18642 @cindex @option{--debug-format}, @code{gdbserver} option
18643 The @option{--debug-format=option1[,option2,...]} option tells
18644 @code{gdbserver} to include additional information in each output.
18645 Possible options are:
18649 Turn off all extra information in debugging output.
18651 Turn on all extra information in debugging output.
18653 Include a timestamp in each line of debugging output.
18656 Options are processed in order. Thus, for example, if @option{none}
18657 appears last then no additional information is added to debugging output.
18659 @cindex @option{--wrapper}, @code{gdbserver} option
18660 The @option{--wrapper} option specifies a wrapper to launch programs
18661 for debugging. The option should be followed by the name of the
18662 wrapper, then any command-line arguments to pass to the wrapper, then
18663 @kbd{--} indicating the end of the wrapper arguments.
18665 @code{gdbserver} runs the specified wrapper program with a combined
18666 command line including the wrapper arguments, then the name of the
18667 program to debug, then any arguments to the program. The wrapper
18668 runs until it executes your program, and then @value{GDBN} gains control.
18670 You can use any program that eventually calls @code{execve} with
18671 its arguments as a wrapper. Several standard Unix utilities do
18672 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18673 with @code{exec "$@@"} will also work.
18675 For example, you can use @code{env} to pass an environment variable to
18676 the debugged program, without setting the variable in @code{gdbserver}'s
18680 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18683 @subsection Connecting to @code{gdbserver}
18685 Run @value{GDBN} on the host system.
18687 First make sure you have the necessary symbol files. Load symbols for
18688 your application using the @code{file} command before you connect. Use
18689 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18690 was compiled with the correct sysroot using @code{--with-sysroot}).
18692 The symbol file and target libraries must exactly match the executable
18693 and libraries on the target, with one exception: the files on the host
18694 system should not be stripped, even if the files on the target system
18695 are. Mismatched or missing files will lead to confusing results
18696 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18697 files may also prevent @code{gdbserver} from debugging multi-threaded
18700 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18701 For TCP connections, you must start up @code{gdbserver} prior to using
18702 the @code{target remote} command. Otherwise you may get an error whose
18703 text depends on the host system, but which usually looks something like
18704 @samp{Connection refused}. Don't use the @code{load}
18705 command in @value{GDBN} when using @code{gdbserver}, since the program is
18706 already on the target.
18708 @subsection Monitor Commands for @code{gdbserver}
18709 @cindex monitor commands, for @code{gdbserver}
18710 @anchor{Monitor Commands for gdbserver}
18712 During a @value{GDBN} session using @code{gdbserver}, you can use the
18713 @code{monitor} command to send special requests to @code{gdbserver}.
18714 Here are the available commands.
18718 List the available monitor commands.
18720 @item monitor set debug 0
18721 @itemx monitor set debug 1
18722 Disable or enable general debugging messages.
18724 @item monitor set remote-debug 0
18725 @itemx monitor set remote-debug 1
18726 Disable or enable specific debugging messages associated with the remote
18727 protocol (@pxref{Remote Protocol}).
18729 @item monitor set debug-format option1@r{[},option2,...@r{]}
18730 Specify additional text to add to debugging messages.
18731 Possible options are:
18735 Turn off all extra information in debugging output.
18737 Turn on all extra information in debugging output.
18739 Include a timestamp in each line of debugging output.
18742 Options are processed in order. Thus, for example, if @option{none}
18743 appears last then no additional information is added to debugging output.
18745 @item monitor set libthread-db-search-path [PATH]
18746 @cindex gdbserver, search path for @code{libthread_db}
18747 When this command is issued, @var{path} is a colon-separated list of
18748 directories to search for @code{libthread_db} (@pxref{Threads,,set
18749 libthread-db-search-path}). If you omit @var{path},
18750 @samp{libthread-db-search-path} will be reset to its default value.
18752 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18753 not supported in @code{gdbserver}.
18756 Tell gdbserver to exit immediately. This command should be followed by
18757 @code{disconnect} to close the debugging session. @code{gdbserver} will
18758 detach from any attached processes and kill any processes it created.
18759 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18760 of a multi-process mode debug session.
18764 @subsection Tracepoints support in @code{gdbserver}
18765 @cindex tracepoints support in @code{gdbserver}
18767 On some targets, @code{gdbserver} supports tracepoints, fast
18768 tracepoints and static tracepoints.
18770 For fast or static tracepoints to work, a special library called the
18771 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18772 This library is built and distributed as an integral part of
18773 @code{gdbserver}. In addition, support for static tracepoints
18774 requires building the in-process agent library with static tracepoints
18775 support. At present, the UST (LTTng Userspace Tracer,
18776 @url{http://lttng.org/ust}) tracing engine is supported. This support
18777 is automatically available if UST development headers are found in the
18778 standard include path when @code{gdbserver} is built, or if
18779 @code{gdbserver} was explicitly configured using @option{--with-ust}
18780 to point at such headers. You can explicitly disable the support
18781 using @option{--with-ust=no}.
18783 There are several ways to load the in-process agent in your program:
18786 @item Specifying it as dependency at link time
18788 You can link your program dynamically with the in-process agent
18789 library. On most systems, this is accomplished by adding
18790 @code{-linproctrace} to the link command.
18792 @item Using the system's preloading mechanisms
18794 You can force loading the in-process agent at startup time by using
18795 your system's support for preloading shared libraries. Many Unixes
18796 support the concept of preloading user defined libraries. In most
18797 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18798 in the environment. See also the description of @code{gdbserver}'s
18799 @option{--wrapper} command line option.
18801 @item Using @value{GDBN} to force loading the agent at run time
18803 On some systems, you can force the inferior to load a shared library,
18804 by calling a dynamic loader function in the inferior that takes care
18805 of dynamically looking up and loading a shared library. On most Unix
18806 systems, the function is @code{dlopen}. You'll use the @code{call}
18807 command for that. For example:
18810 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18813 Note that on most Unix systems, for the @code{dlopen} function to be
18814 available, the program needs to be linked with @code{-ldl}.
18817 On systems that have a userspace dynamic loader, like most Unix
18818 systems, when you connect to @code{gdbserver} using @code{target
18819 remote}, you'll find that the program is stopped at the dynamic
18820 loader's entry point, and no shared library has been loaded in the
18821 program's address space yet, including the in-process agent. In that
18822 case, before being able to use any of the fast or static tracepoints
18823 features, you need to let the loader run and load the shared
18824 libraries. The simplest way to do that is to run the program to the
18825 main procedure. E.g., if debugging a C or C@t{++} program, start
18826 @code{gdbserver} like so:
18829 $ gdbserver :9999 myprogram
18832 Start GDB and connect to @code{gdbserver} like so, and run to main:
18836 (@value{GDBP}) target remote myhost:9999
18837 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18838 (@value{GDBP}) b main
18839 (@value{GDBP}) continue
18842 The in-process tracing agent library should now be loaded into the
18843 process; you can confirm it with the @code{info sharedlibrary}
18844 command, which will list @file{libinproctrace.so} as loaded in the
18845 process. You are now ready to install fast tracepoints, list static
18846 tracepoint markers, probe static tracepoints markers, and start
18849 @node Remote Configuration
18850 @section Remote Configuration
18853 @kindex show remote
18854 This section documents the configuration options available when
18855 debugging remote programs. For the options related to the File I/O
18856 extensions of the remote protocol, see @ref{system,
18857 system-call-allowed}.
18860 @item set remoteaddresssize @var{bits}
18861 @cindex address size for remote targets
18862 @cindex bits in remote address
18863 Set the maximum size of address in a memory packet to the specified
18864 number of bits. @value{GDBN} will mask off the address bits above
18865 that number, when it passes addresses to the remote target. The
18866 default value is the number of bits in the target's address.
18868 @item show remoteaddresssize
18869 Show the current value of remote address size in bits.
18871 @item set serial baud @var{n}
18872 @cindex baud rate for remote targets
18873 Set the baud rate for the remote serial I/O to @var{n} baud. The
18874 value is used to set the speed of the serial port used for debugging
18877 @item show serial baud
18878 Show the current speed of the remote connection.
18880 @item set remotebreak
18881 @cindex interrupt remote programs
18882 @cindex BREAK signal instead of Ctrl-C
18883 @anchor{set remotebreak}
18884 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18885 when you type @kbd{Ctrl-c} to interrupt the program running
18886 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18887 character instead. The default is off, since most remote systems
18888 expect to see @samp{Ctrl-C} as the interrupt signal.
18890 @item show remotebreak
18891 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18892 interrupt the remote program.
18894 @item set remoteflow on
18895 @itemx set remoteflow off
18896 @kindex set remoteflow
18897 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18898 on the serial port used to communicate to the remote target.
18900 @item show remoteflow
18901 @kindex show remoteflow
18902 Show the current setting of hardware flow control.
18904 @item set remotelogbase @var{base}
18905 Set the base (a.k.a.@: radix) of logging serial protocol
18906 communications to @var{base}. Supported values of @var{base} are:
18907 @code{ascii}, @code{octal}, and @code{hex}. The default is
18910 @item show remotelogbase
18911 Show the current setting of the radix for logging remote serial
18914 @item set remotelogfile @var{file}
18915 @cindex record serial communications on file
18916 Record remote serial communications on the named @var{file}. The
18917 default is not to record at all.
18919 @item show remotelogfile.
18920 Show the current setting of the file name on which to record the
18921 serial communications.
18923 @item set remotetimeout @var{num}
18924 @cindex timeout for serial communications
18925 @cindex remote timeout
18926 Set the timeout limit to wait for the remote target to respond to
18927 @var{num} seconds. The default is 2 seconds.
18929 @item show remotetimeout
18930 Show the current number of seconds to wait for the remote target
18933 @cindex limit hardware breakpoints and watchpoints
18934 @cindex remote target, limit break- and watchpoints
18935 @anchor{set remote hardware-watchpoint-limit}
18936 @anchor{set remote hardware-breakpoint-limit}
18937 @item set remote hardware-watchpoint-limit @var{limit}
18938 @itemx set remote hardware-breakpoint-limit @var{limit}
18939 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18940 watchpoints. A limit of -1, the default, is treated as unlimited.
18942 @cindex limit hardware watchpoints length
18943 @cindex remote target, limit watchpoints length
18944 @anchor{set remote hardware-watchpoint-length-limit}
18945 @item set remote hardware-watchpoint-length-limit @var{limit}
18946 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18947 a remote hardware watchpoint. A limit of -1, the default, is treated
18950 @item show remote hardware-watchpoint-length-limit
18951 Show the current limit (in bytes) of the maximum length of
18952 a remote hardware watchpoint.
18954 @item set remote exec-file @var{filename}
18955 @itemx show remote exec-file
18956 @anchor{set remote exec-file}
18957 @cindex executable file, for remote target
18958 Select the file used for @code{run} with @code{target
18959 extended-remote}. This should be set to a filename valid on the
18960 target system. If it is not set, the target will use a default
18961 filename (e.g.@: the last program run).
18963 @item set remote interrupt-sequence
18964 @cindex interrupt remote programs
18965 @cindex select Ctrl-C, BREAK or BREAK-g
18966 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18967 @samp{BREAK-g} as the
18968 sequence to the remote target in order to interrupt the execution.
18969 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18970 is high level of serial line for some certain time.
18971 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18972 It is @code{BREAK} signal followed by character @code{g}.
18974 @item show interrupt-sequence
18975 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18976 is sent by @value{GDBN} to interrupt the remote program.
18977 @code{BREAK-g} is BREAK signal followed by @code{g} and
18978 also known as Magic SysRq g.
18980 @item set remote interrupt-on-connect
18981 @cindex send interrupt-sequence on start
18982 Specify whether interrupt-sequence is sent to remote target when
18983 @value{GDBN} connects to it. This is mostly needed when you debug
18984 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18985 which is known as Magic SysRq g in order to connect @value{GDBN}.
18987 @item show interrupt-on-connect
18988 Show whether interrupt-sequence is sent
18989 to remote target when @value{GDBN} connects to it.
18993 @item set tcp auto-retry on
18994 @cindex auto-retry, for remote TCP target
18995 Enable auto-retry for remote TCP connections. This is useful if the remote
18996 debugging agent is launched in parallel with @value{GDBN}; there is a race
18997 condition because the agent may not become ready to accept the connection
18998 before @value{GDBN} attempts to connect. When auto-retry is
18999 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19000 to establish the connection using the timeout specified by
19001 @code{set tcp connect-timeout}.
19003 @item set tcp auto-retry off
19004 Do not auto-retry failed TCP connections.
19006 @item show tcp auto-retry
19007 Show the current auto-retry setting.
19009 @item set tcp connect-timeout @var{seconds}
19010 @itemx set tcp connect-timeout unlimited
19011 @cindex connection timeout, for remote TCP target
19012 @cindex timeout, for remote target connection
19013 Set the timeout for establishing a TCP connection to the remote target to
19014 @var{seconds}. The timeout affects both polling to retry failed connections
19015 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19016 that are merely slow to complete, and represents an approximate cumulative
19017 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19018 @value{GDBN} will keep attempting to establish a connection forever,
19019 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19021 @item show tcp connect-timeout
19022 Show the current connection timeout setting.
19025 @cindex remote packets, enabling and disabling
19026 The @value{GDBN} remote protocol autodetects the packets supported by
19027 your debugging stub. If you need to override the autodetection, you
19028 can use these commands to enable or disable individual packets. Each
19029 packet can be set to @samp{on} (the remote target supports this
19030 packet), @samp{off} (the remote target does not support this packet),
19031 or @samp{auto} (detect remote target support for this packet). They
19032 all default to @samp{auto}. For more information about each packet,
19033 see @ref{Remote Protocol}.
19035 During normal use, you should not have to use any of these commands.
19036 If you do, that may be a bug in your remote debugging stub, or a bug
19037 in @value{GDBN}. You may want to report the problem to the
19038 @value{GDBN} developers.
19040 For each packet @var{name}, the command to enable or disable the
19041 packet is @code{set remote @var{name}-packet}. The available settings
19044 @multitable @columnfractions 0.28 0.32 0.25
19047 @tab Related Features
19049 @item @code{fetch-register}
19051 @tab @code{info registers}
19053 @item @code{set-register}
19057 @item @code{binary-download}
19059 @tab @code{load}, @code{set}
19061 @item @code{read-aux-vector}
19062 @tab @code{qXfer:auxv:read}
19063 @tab @code{info auxv}
19065 @item @code{symbol-lookup}
19066 @tab @code{qSymbol}
19067 @tab Detecting multiple threads
19069 @item @code{attach}
19070 @tab @code{vAttach}
19073 @item @code{verbose-resume}
19075 @tab Stepping or resuming multiple threads
19081 @item @code{software-breakpoint}
19085 @item @code{hardware-breakpoint}
19089 @item @code{write-watchpoint}
19093 @item @code{read-watchpoint}
19097 @item @code{access-watchpoint}
19101 @item @code{target-features}
19102 @tab @code{qXfer:features:read}
19103 @tab @code{set architecture}
19105 @item @code{library-info}
19106 @tab @code{qXfer:libraries:read}
19107 @tab @code{info sharedlibrary}
19109 @item @code{memory-map}
19110 @tab @code{qXfer:memory-map:read}
19111 @tab @code{info mem}
19113 @item @code{read-sdata-object}
19114 @tab @code{qXfer:sdata:read}
19115 @tab @code{print $_sdata}
19117 @item @code{read-spu-object}
19118 @tab @code{qXfer:spu:read}
19119 @tab @code{info spu}
19121 @item @code{write-spu-object}
19122 @tab @code{qXfer:spu:write}
19123 @tab @code{info spu}
19125 @item @code{read-siginfo-object}
19126 @tab @code{qXfer:siginfo:read}
19127 @tab @code{print $_siginfo}
19129 @item @code{write-siginfo-object}
19130 @tab @code{qXfer:siginfo:write}
19131 @tab @code{set $_siginfo}
19133 @item @code{threads}
19134 @tab @code{qXfer:threads:read}
19135 @tab @code{info threads}
19137 @item @code{get-thread-local-@*storage-address}
19138 @tab @code{qGetTLSAddr}
19139 @tab Displaying @code{__thread} variables
19141 @item @code{get-thread-information-block-address}
19142 @tab @code{qGetTIBAddr}
19143 @tab Display MS-Windows Thread Information Block.
19145 @item @code{search-memory}
19146 @tab @code{qSearch:memory}
19149 @item @code{supported-packets}
19150 @tab @code{qSupported}
19151 @tab Remote communications parameters
19153 @item @code{pass-signals}
19154 @tab @code{QPassSignals}
19155 @tab @code{handle @var{signal}}
19157 @item @code{program-signals}
19158 @tab @code{QProgramSignals}
19159 @tab @code{handle @var{signal}}
19161 @item @code{hostio-close-packet}
19162 @tab @code{vFile:close}
19163 @tab @code{remote get}, @code{remote put}
19165 @item @code{hostio-open-packet}
19166 @tab @code{vFile:open}
19167 @tab @code{remote get}, @code{remote put}
19169 @item @code{hostio-pread-packet}
19170 @tab @code{vFile:pread}
19171 @tab @code{remote get}, @code{remote put}
19173 @item @code{hostio-pwrite-packet}
19174 @tab @code{vFile:pwrite}
19175 @tab @code{remote get}, @code{remote put}
19177 @item @code{hostio-unlink-packet}
19178 @tab @code{vFile:unlink}
19179 @tab @code{remote delete}
19181 @item @code{hostio-readlink-packet}
19182 @tab @code{vFile:readlink}
19185 @item @code{noack-packet}
19186 @tab @code{QStartNoAckMode}
19187 @tab Packet acknowledgment
19189 @item @code{osdata}
19190 @tab @code{qXfer:osdata:read}
19191 @tab @code{info os}
19193 @item @code{query-attached}
19194 @tab @code{qAttached}
19195 @tab Querying remote process attach state.
19197 @item @code{trace-buffer-size}
19198 @tab @code{QTBuffer:size}
19199 @tab @code{set trace-buffer-size}
19201 @item @code{trace-status}
19202 @tab @code{qTStatus}
19203 @tab @code{tstatus}
19205 @item @code{traceframe-info}
19206 @tab @code{qXfer:traceframe-info:read}
19207 @tab Traceframe info
19209 @item @code{install-in-trace}
19210 @tab @code{InstallInTrace}
19211 @tab Install tracepoint in tracing
19213 @item @code{disable-randomization}
19214 @tab @code{QDisableRandomization}
19215 @tab @code{set disable-randomization}
19217 @item @code{conditional-breakpoints-packet}
19218 @tab @code{Z0 and Z1}
19219 @tab @code{Support for target-side breakpoint condition evaluation}
19223 @section Implementing a Remote Stub
19225 @cindex debugging stub, example
19226 @cindex remote stub, example
19227 @cindex stub example, remote debugging
19228 The stub files provided with @value{GDBN} implement the target side of the
19229 communication protocol, and the @value{GDBN} side is implemented in the
19230 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19231 these subroutines to communicate, and ignore the details. (If you're
19232 implementing your own stub file, you can still ignore the details: start
19233 with one of the existing stub files. @file{sparc-stub.c} is the best
19234 organized, and therefore the easiest to read.)
19236 @cindex remote serial debugging, overview
19237 To debug a program running on another machine (the debugging
19238 @dfn{target} machine), you must first arrange for all the usual
19239 prerequisites for the program to run by itself. For example, for a C
19244 A startup routine to set up the C runtime environment; these usually
19245 have a name like @file{crt0}. The startup routine may be supplied by
19246 your hardware supplier, or you may have to write your own.
19249 A C subroutine library to support your program's
19250 subroutine calls, notably managing input and output.
19253 A way of getting your program to the other machine---for example, a
19254 download program. These are often supplied by the hardware
19255 manufacturer, but you may have to write your own from hardware
19259 The next step is to arrange for your program to use a serial port to
19260 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19261 machine). In general terms, the scheme looks like this:
19265 @value{GDBN} already understands how to use this protocol; when everything
19266 else is set up, you can simply use the @samp{target remote} command
19267 (@pxref{Targets,,Specifying a Debugging Target}).
19269 @item On the target,
19270 you must link with your program a few special-purpose subroutines that
19271 implement the @value{GDBN} remote serial protocol. The file containing these
19272 subroutines is called a @dfn{debugging stub}.
19274 On certain remote targets, you can use an auxiliary program
19275 @code{gdbserver} instead of linking a stub into your program.
19276 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19279 The debugging stub is specific to the architecture of the remote
19280 machine; for example, use @file{sparc-stub.c} to debug programs on
19283 @cindex remote serial stub list
19284 These working remote stubs are distributed with @value{GDBN}:
19289 @cindex @file{i386-stub.c}
19292 For Intel 386 and compatible architectures.
19295 @cindex @file{m68k-stub.c}
19296 @cindex Motorola 680x0
19298 For Motorola 680x0 architectures.
19301 @cindex @file{sh-stub.c}
19304 For Renesas SH architectures.
19307 @cindex @file{sparc-stub.c}
19309 For @sc{sparc} architectures.
19311 @item sparcl-stub.c
19312 @cindex @file{sparcl-stub.c}
19315 For Fujitsu @sc{sparclite} architectures.
19319 The @file{README} file in the @value{GDBN} distribution may list other
19320 recently added stubs.
19323 * Stub Contents:: What the stub can do for you
19324 * Bootstrapping:: What you must do for the stub
19325 * Debug Session:: Putting it all together
19328 @node Stub Contents
19329 @subsection What the Stub Can Do for You
19331 @cindex remote serial stub
19332 The debugging stub for your architecture supplies these three
19336 @item set_debug_traps
19337 @findex set_debug_traps
19338 @cindex remote serial stub, initialization
19339 This routine arranges for @code{handle_exception} to run when your
19340 program stops. You must call this subroutine explicitly in your
19341 program's startup code.
19343 @item handle_exception
19344 @findex handle_exception
19345 @cindex remote serial stub, main routine
19346 This is the central workhorse, but your program never calls it
19347 explicitly---the setup code arranges for @code{handle_exception} to
19348 run when a trap is triggered.
19350 @code{handle_exception} takes control when your program stops during
19351 execution (for example, on a breakpoint), and mediates communications
19352 with @value{GDBN} on the host machine. This is where the communications
19353 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19354 representative on the target machine. It begins by sending summary
19355 information on the state of your program, then continues to execute,
19356 retrieving and transmitting any information @value{GDBN} needs, until you
19357 execute a @value{GDBN} command that makes your program resume; at that point,
19358 @code{handle_exception} returns control to your own code on the target
19362 @cindex @code{breakpoint} subroutine, remote
19363 Use this auxiliary subroutine to make your program contain a
19364 breakpoint. Depending on the particular situation, this may be the only
19365 way for @value{GDBN} to get control. For instance, if your target
19366 machine has some sort of interrupt button, you won't need to call this;
19367 pressing the interrupt button transfers control to
19368 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19369 simply receiving characters on the serial port may also trigger a trap;
19370 again, in that situation, you don't need to call @code{breakpoint} from
19371 your own program---simply running @samp{target remote} from the host
19372 @value{GDBN} session gets control.
19374 Call @code{breakpoint} if none of these is true, or if you simply want
19375 to make certain your program stops at a predetermined point for the
19376 start of your debugging session.
19379 @node Bootstrapping
19380 @subsection What You Must Do for the Stub
19382 @cindex remote stub, support routines
19383 The debugging stubs that come with @value{GDBN} are set up for a particular
19384 chip architecture, but they have no information about the rest of your
19385 debugging target machine.
19387 First of all you need to tell the stub how to communicate with the
19391 @item int getDebugChar()
19392 @findex getDebugChar
19393 Write this subroutine to read a single character from the serial port.
19394 It may be identical to @code{getchar} for your target system; a
19395 different name is used to allow you to distinguish the two if you wish.
19397 @item void putDebugChar(int)
19398 @findex putDebugChar
19399 Write this subroutine to write a single character to the serial port.
19400 It may be identical to @code{putchar} for your target system; a
19401 different name is used to allow you to distinguish the two if you wish.
19404 @cindex control C, and remote debugging
19405 @cindex interrupting remote targets
19406 If you want @value{GDBN} to be able to stop your program while it is
19407 running, you need to use an interrupt-driven serial driver, and arrange
19408 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19409 character). That is the character which @value{GDBN} uses to tell the
19410 remote system to stop.
19412 Getting the debugging target to return the proper status to @value{GDBN}
19413 probably requires changes to the standard stub; one quick and dirty way
19414 is to just execute a breakpoint instruction (the ``dirty'' part is that
19415 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19417 Other routines you need to supply are:
19420 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19421 @findex exceptionHandler
19422 Write this function to install @var{exception_address} in the exception
19423 handling tables. You need to do this because the stub does not have any
19424 way of knowing what the exception handling tables on your target system
19425 are like (for example, the processor's table might be in @sc{rom},
19426 containing entries which point to a table in @sc{ram}).
19427 @var{exception_number} is the exception number which should be changed;
19428 its meaning is architecture-dependent (for example, different numbers
19429 might represent divide by zero, misaligned access, etc). When this
19430 exception occurs, control should be transferred directly to
19431 @var{exception_address}, and the processor state (stack, registers,
19432 and so on) should be just as it is when a processor exception occurs. So if
19433 you want to use a jump instruction to reach @var{exception_address}, it
19434 should be a simple jump, not a jump to subroutine.
19436 For the 386, @var{exception_address} should be installed as an interrupt
19437 gate so that interrupts are masked while the handler runs. The gate
19438 should be at privilege level 0 (the most privileged level). The
19439 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19440 help from @code{exceptionHandler}.
19442 @item void flush_i_cache()
19443 @findex flush_i_cache
19444 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19445 instruction cache, if any, on your target machine. If there is no
19446 instruction cache, this subroutine may be a no-op.
19448 On target machines that have instruction caches, @value{GDBN} requires this
19449 function to make certain that the state of your program is stable.
19453 You must also make sure this library routine is available:
19456 @item void *memset(void *, int, int)
19458 This is the standard library function @code{memset} that sets an area of
19459 memory to a known value. If you have one of the free versions of
19460 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19461 either obtain it from your hardware manufacturer, or write your own.
19464 If you do not use the GNU C compiler, you may need other standard
19465 library subroutines as well; this varies from one stub to another,
19466 but in general the stubs are likely to use any of the common library
19467 subroutines which @code{@value{NGCC}} generates as inline code.
19470 @node Debug Session
19471 @subsection Putting it All Together
19473 @cindex remote serial debugging summary
19474 In summary, when your program is ready to debug, you must follow these
19479 Make sure you have defined the supporting low-level routines
19480 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19482 @code{getDebugChar}, @code{putDebugChar},
19483 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19487 Insert these lines in your program's startup code, before the main
19488 procedure is called:
19495 On some machines, when a breakpoint trap is raised, the hardware
19496 automatically makes the PC point to the instruction after the
19497 breakpoint. If your machine doesn't do that, you may need to adjust
19498 @code{handle_exception} to arrange for it to return to the instruction
19499 after the breakpoint on this first invocation, so that your program
19500 doesn't keep hitting the initial breakpoint instead of making
19504 For the 680x0 stub only, you need to provide a variable called
19505 @code{exceptionHook}. Normally you just use:
19508 void (*exceptionHook)() = 0;
19512 but if before calling @code{set_debug_traps}, you set it to point to a
19513 function in your program, that function is called when
19514 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19515 error). The function indicated by @code{exceptionHook} is called with
19516 one parameter: an @code{int} which is the exception number.
19519 Compile and link together: your program, the @value{GDBN} debugging stub for
19520 your target architecture, and the supporting subroutines.
19523 Make sure you have a serial connection between your target machine and
19524 the @value{GDBN} host, and identify the serial port on the host.
19527 @c The "remote" target now provides a `load' command, so we should
19528 @c document that. FIXME.
19529 Download your program to your target machine (or get it there by
19530 whatever means the manufacturer provides), and start it.
19533 Start @value{GDBN} on the host, and connect to the target
19534 (@pxref{Connecting,,Connecting to a Remote Target}).
19538 @node Configurations
19539 @chapter Configuration-Specific Information
19541 While nearly all @value{GDBN} commands are available for all native and
19542 cross versions of the debugger, there are some exceptions. This chapter
19543 describes things that are only available in certain configurations.
19545 There are three major categories of configurations: native
19546 configurations, where the host and target are the same, embedded
19547 operating system configurations, which are usually the same for several
19548 different processor architectures, and bare embedded processors, which
19549 are quite different from each other.
19554 * Embedded Processors::
19561 This section describes details specific to particular native
19566 * BSD libkvm Interface:: Debugging BSD kernel memory images
19567 * SVR4 Process Information:: SVR4 process information
19568 * DJGPP Native:: Features specific to the DJGPP port
19569 * Cygwin Native:: Features specific to the Cygwin port
19570 * Hurd Native:: Features specific to @sc{gnu} Hurd
19571 * Darwin:: Features specific to Darwin
19577 On HP-UX systems, if you refer to a function or variable name that
19578 begins with a dollar sign, @value{GDBN} searches for a user or system
19579 name first, before it searches for a convenience variable.
19582 @node BSD libkvm Interface
19583 @subsection BSD libkvm Interface
19586 @cindex kernel memory image
19587 @cindex kernel crash dump
19589 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19590 interface that provides a uniform interface for accessing kernel virtual
19591 memory images, including live systems and crash dumps. @value{GDBN}
19592 uses this interface to allow you to debug live kernels and kernel crash
19593 dumps on many native BSD configurations. This is implemented as a
19594 special @code{kvm} debugging target. For debugging a live system, load
19595 the currently running kernel into @value{GDBN} and connect to the
19599 (@value{GDBP}) @b{target kvm}
19602 For debugging crash dumps, provide the file name of the crash dump as an
19606 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19609 Once connected to the @code{kvm} target, the following commands are
19615 Set current context from the @dfn{Process Control Block} (PCB) address.
19618 Set current context from proc address. This command isn't available on
19619 modern FreeBSD systems.
19622 @node SVR4 Process Information
19623 @subsection SVR4 Process Information
19625 @cindex examine process image
19626 @cindex process info via @file{/proc}
19628 Many versions of SVR4 and compatible systems provide a facility called
19629 @samp{/proc} that can be used to examine the image of a running
19630 process using file-system subroutines.
19632 If @value{GDBN} is configured for an operating system with this
19633 facility, the command @code{info proc} is available to report
19634 information about the process running your program, or about any
19635 process running on your system. This includes, as of this writing,
19636 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19637 not HP-UX, for example.
19639 This command may also work on core files that were created on a system
19640 that has the @samp{/proc} facility.
19646 @itemx info proc @var{process-id}
19647 Summarize available information about any running process. If a
19648 process ID is specified by @var{process-id}, display information about
19649 that process; otherwise display information about the program being
19650 debugged. The summary includes the debugged process ID, the command
19651 line used to invoke it, its current working directory, and its
19652 executable file's absolute file name.
19654 On some systems, @var{process-id} can be of the form
19655 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19656 within a process. If the optional @var{pid} part is missing, it means
19657 a thread from the process being debugged (the leading @samp{/} still
19658 needs to be present, or else @value{GDBN} will interpret the number as
19659 a process ID rather than a thread ID).
19661 @item info proc cmdline
19662 @cindex info proc cmdline
19663 Show the original command line of the process. This command is
19664 specific to @sc{gnu}/Linux.
19666 @item info proc cwd
19667 @cindex info proc cwd
19668 Show the current working directory of the process. This command is
19669 specific to @sc{gnu}/Linux.
19671 @item info proc exe
19672 @cindex info proc exe
19673 Show the name of executable of the process. This command is specific
19676 @item info proc mappings
19677 @cindex memory address space mappings
19678 Report the memory address space ranges accessible in the program, with
19679 information on whether the process has read, write, or execute access
19680 rights to each range. On @sc{gnu}/Linux systems, each memory range
19681 includes the object file which is mapped to that range, instead of the
19682 memory access rights to that range.
19684 @item info proc stat
19685 @itemx info proc status
19686 @cindex process detailed status information
19687 These subcommands are specific to @sc{gnu}/Linux systems. They show
19688 the process-related information, including the user ID and group ID;
19689 how many threads are there in the process; its virtual memory usage;
19690 the signals that are pending, blocked, and ignored; its TTY; its
19691 consumption of system and user time; its stack size; its @samp{nice}
19692 value; etc. For more information, see the @samp{proc} man page
19693 (type @kbd{man 5 proc} from your shell prompt).
19695 @item info proc all
19696 Show all the information about the process described under all of the
19697 above @code{info proc} subcommands.
19700 @comment These sub-options of 'info proc' were not included when
19701 @comment procfs.c was re-written. Keep their descriptions around
19702 @comment against the day when someone finds the time to put them back in.
19703 @kindex info proc times
19704 @item info proc times
19705 Starting time, user CPU time, and system CPU time for your program and
19708 @kindex info proc id
19710 Report on the process IDs related to your program: its own process ID,
19711 the ID of its parent, the process group ID, and the session ID.
19714 @item set procfs-trace
19715 @kindex set procfs-trace
19716 @cindex @code{procfs} API calls
19717 This command enables and disables tracing of @code{procfs} API calls.
19719 @item show procfs-trace
19720 @kindex show procfs-trace
19721 Show the current state of @code{procfs} API call tracing.
19723 @item set procfs-file @var{file}
19724 @kindex set procfs-file
19725 Tell @value{GDBN} to write @code{procfs} API trace to the named
19726 @var{file}. @value{GDBN} appends the trace info to the previous
19727 contents of the file. The default is to display the trace on the
19730 @item show procfs-file
19731 @kindex show procfs-file
19732 Show the file to which @code{procfs} API trace is written.
19734 @item proc-trace-entry
19735 @itemx proc-trace-exit
19736 @itemx proc-untrace-entry
19737 @itemx proc-untrace-exit
19738 @kindex proc-trace-entry
19739 @kindex proc-trace-exit
19740 @kindex proc-untrace-entry
19741 @kindex proc-untrace-exit
19742 These commands enable and disable tracing of entries into and exits
19743 from the @code{syscall} interface.
19746 @kindex info pidlist
19747 @cindex process list, QNX Neutrino
19748 For QNX Neutrino only, this command displays the list of all the
19749 processes and all the threads within each process.
19752 @kindex info meminfo
19753 @cindex mapinfo list, QNX Neutrino
19754 For QNX Neutrino only, this command displays the list of all mapinfos.
19758 @subsection Features for Debugging @sc{djgpp} Programs
19759 @cindex @sc{djgpp} debugging
19760 @cindex native @sc{djgpp} debugging
19761 @cindex MS-DOS-specific commands
19764 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19765 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19766 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19767 top of real-mode DOS systems and their emulations.
19769 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19770 defines a few commands specific to the @sc{djgpp} port. This
19771 subsection describes those commands.
19776 This is a prefix of @sc{djgpp}-specific commands which print
19777 information about the target system and important OS structures.
19780 @cindex MS-DOS system info
19781 @cindex free memory information (MS-DOS)
19782 @item info dos sysinfo
19783 This command displays assorted information about the underlying
19784 platform: the CPU type and features, the OS version and flavor, the
19785 DPMI version, and the available conventional and DPMI memory.
19790 @cindex segment descriptor tables
19791 @cindex descriptor tables display
19793 @itemx info dos ldt
19794 @itemx info dos idt
19795 These 3 commands display entries from, respectively, Global, Local,
19796 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19797 tables are data structures which store a descriptor for each segment
19798 that is currently in use. The segment's selector is an index into a
19799 descriptor table; the table entry for that index holds the
19800 descriptor's base address and limit, and its attributes and access
19803 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19804 segment (used for both data and the stack), and a DOS segment (which
19805 allows access to DOS/BIOS data structures and absolute addresses in
19806 conventional memory). However, the DPMI host will usually define
19807 additional segments in order to support the DPMI environment.
19809 @cindex garbled pointers
19810 These commands allow to display entries from the descriptor tables.
19811 Without an argument, all entries from the specified table are
19812 displayed. An argument, which should be an integer expression, means
19813 display a single entry whose index is given by the argument. For
19814 example, here's a convenient way to display information about the
19815 debugged program's data segment:
19818 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19819 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19823 This comes in handy when you want to see whether a pointer is outside
19824 the data segment's limit (i.e.@: @dfn{garbled}).
19826 @cindex page tables display (MS-DOS)
19828 @itemx info dos pte
19829 These two commands display entries from, respectively, the Page
19830 Directory and the Page Tables. Page Directories and Page Tables are
19831 data structures which control how virtual memory addresses are mapped
19832 into physical addresses. A Page Table includes an entry for every
19833 page of memory that is mapped into the program's address space; there
19834 may be several Page Tables, each one holding up to 4096 entries. A
19835 Page Directory has up to 4096 entries, one each for every Page Table
19836 that is currently in use.
19838 Without an argument, @kbd{info dos pde} displays the entire Page
19839 Directory, and @kbd{info dos pte} displays all the entries in all of
19840 the Page Tables. An argument, an integer expression, given to the
19841 @kbd{info dos pde} command means display only that entry from the Page
19842 Directory table. An argument given to the @kbd{info dos pte} command
19843 means display entries from a single Page Table, the one pointed to by
19844 the specified entry in the Page Directory.
19846 @cindex direct memory access (DMA) on MS-DOS
19847 These commands are useful when your program uses @dfn{DMA} (Direct
19848 Memory Access), which needs physical addresses to program the DMA
19851 These commands are supported only with some DPMI servers.
19853 @cindex physical address from linear address
19854 @item info dos address-pte @var{addr}
19855 This command displays the Page Table entry for a specified linear
19856 address. The argument @var{addr} is a linear address which should
19857 already have the appropriate segment's base address added to it,
19858 because this command accepts addresses which may belong to @emph{any}
19859 segment. For example, here's how to display the Page Table entry for
19860 the page where a variable @code{i} is stored:
19863 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19864 @exdent @code{Page Table entry for address 0x11a00d30:}
19865 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19869 This says that @code{i} is stored at offset @code{0xd30} from the page
19870 whose physical base address is @code{0x02698000}, and shows all the
19871 attributes of that page.
19873 Note that you must cast the addresses of variables to a @code{char *},
19874 since otherwise the value of @code{__djgpp_base_address}, the base
19875 address of all variables and functions in a @sc{djgpp} program, will
19876 be added using the rules of C pointer arithmetics: if @code{i} is
19877 declared an @code{int}, @value{GDBN} will add 4 times the value of
19878 @code{__djgpp_base_address} to the address of @code{i}.
19880 Here's another example, it displays the Page Table entry for the
19884 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19885 @exdent @code{Page Table entry for address 0x29110:}
19886 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19890 (The @code{+ 3} offset is because the transfer buffer's address is the
19891 3rd member of the @code{_go32_info_block} structure.) The output
19892 clearly shows that this DPMI server maps the addresses in conventional
19893 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19894 linear (@code{0x29110}) addresses are identical.
19896 This command is supported only with some DPMI servers.
19899 @cindex DOS serial data link, remote debugging
19900 In addition to native debugging, the DJGPP port supports remote
19901 debugging via a serial data link. The following commands are specific
19902 to remote serial debugging in the DJGPP port of @value{GDBN}.
19905 @kindex set com1base
19906 @kindex set com1irq
19907 @kindex set com2base
19908 @kindex set com2irq
19909 @kindex set com3base
19910 @kindex set com3irq
19911 @kindex set com4base
19912 @kindex set com4irq
19913 @item set com1base @var{addr}
19914 This command sets the base I/O port address of the @file{COM1} serial
19917 @item set com1irq @var{irq}
19918 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19919 for the @file{COM1} serial port.
19921 There are similar commands @samp{set com2base}, @samp{set com3irq},
19922 etc.@: for setting the port address and the @code{IRQ} lines for the
19925 @kindex show com1base
19926 @kindex show com1irq
19927 @kindex show com2base
19928 @kindex show com2irq
19929 @kindex show com3base
19930 @kindex show com3irq
19931 @kindex show com4base
19932 @kindex show com4irq
19933 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19934 display the current settings of the base address and the @code{IRQ}
19935 lines used by the COM ports.
19938 @kindex info serial
19939 @cindex DOS serial port status
19940 This command prints the status of the 4 DOS serial ports. For each
19941 port, it prints whether it's active or not, its I/O base address and
19942 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19943 counts of various errors encountered so far.
19947 @node Cygwin Native
19948 @subsection Features for Debugging MS Windows PE Executables
19949 @cindex MS Windows debugging
19950 @cindex native Cygwin debugging
19951 @cindex Cygwin-specific commands
19953 @value{GDBN} supports native debugging of MS Windows programs, including
19954 DLLs with and without symbolic debugging information.
19956 @cindex Ctrl-BREAK, MS-Windows
19957 @cindex interrupt debuggee on MS-Windows
19958 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19959 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19960 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19961 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19962 sequence, which can be used to interrupt the debuggee even if it
19965 There are various additional Cygwin-specific commands, described in
19966 this section. Working with DLLs that have no debugging symbols is
19967 described in @ref{Non-debug DLL Symbols}.
19972 This is a prefix of MS Windows-specific commands which print
19973 information about the target system and important OS structures.
19975 @item info w32 selector
19976 This command displays information returned by
19977 the Win32 API @code{GetThreadSelectorEntry} function.
19978 It takes an optional argument that is evaluated to
19979 a long value to give the information about this given selector.
19980 Without argument, this command displays information
19981 about the six segment registers.
19983 @item info w32 thread-information-block
19984 This command displays thread specific information stored in the
19985 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19986 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19990 This is a Cygwin-specific alias of @code{info shared}.
19992 @kindex dll-symbols
19994 This command is deprecated and will be removed in future versions
19995 of @value{GDBN}. Use the @code{sharedlibrary} command instead.
19997 This command loads symbols from a dll similarly to
19998 add-sym command but without the need to specify a base address.
20000 @kindex set cygwin-exceptions
20001 @cindex debugging the Cygwin DLL
20002 @cindex Cygwin DLL, debugging
20003 @item set cygwin-exceptions @var{mode}
20004 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20005 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20006 @value{GDBN} will delay recognition of exceptions, and may ignore some
20007 exceptions which seem to be caused by internal Cygwin DLL
20008 ``bookkeeping''. This option is meant primarily for debugging the
20009 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20010 @value{GDBN} users with false @code{SIGSEGV} signals.
20012 @kindex show cygwin-exceptions
20013 @item show cygwin-exceptions
20014 Displays whether @value{GDBN} will break on exceptions that happen
20015 inside the Cygwin DLL itself.
20017 @kindex set new-console
20018 @item set new-console @var{mode}
20019 If @var{mode} is @code{on} the debuggee will
20020 be started in a new console on next start.
20021 If @var{mode} is @code{off}, the debuggee will
20022 be started in the same console as the debugger.
20024 @kindex show new-console
20025 @item show new-console
20026 Displays whether a new console is used
20027 when the debuggee is started.
20029 @kindex set new-group
20030 @item set new-group @var{mode}
20031 This boolean value controls whether the debuggee should
20032 start a new group or stay in the same group as the debugger.
20033 This affects the way the Windows OS handles
20036 @kindex show new-group
20037 @item show new-group
20038 Displays current value of new-group boolean.
20040 @kindex set debugevents
20041 @item set debugevents
20042 This boolean value adds debug output concerning kernel events related
20043 to the debuggee seen by the debugger. This includes events that
20044 signal thread and process creation and exit, DLL loading and
20045 unloading, console interrupts, and debugging messages produced by the
20046 Windows @code{OutputDebugString} API call.
20048 @kindex set debugexec
20049 @item set debugexec
20050 This boolean value adds debug output concerning execute events
20051 (such as resume thread) seen by the debugger.
20053 @kindex set debugexceptions
20054 @item set debugexceptions
20055 This boolean value adds debug output concerning exceptions in the
20056 debuggee seen by the debugger.
20058 @kindex set debugmemory
20059 @item set debugmemory
20060 This boolean value adds debug output concerning debuggee memory reads
20061 and writes by the debugger.
20065 This boolean values specifies whether the debuggee is called
20066 via a shell or directly (default value is on).
20070 Displays if the debuggee will be started with a shell.
20075 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20078 @node Non-debug DLL Symbols
20079 @subsubsection Support for DLLs without Debugging Symbols
20080 @cindex DLLs with no debugging symbols
20081 @cindex Minimal symbols and DLLs
20083 Very often on windows, some of the DLLs that your program relies on do
20084 not include symbolic debugging information (for example,
20085 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20086 symbols in a DLL, it relies on the minimal amount of symbolic
20087 information contained in the DLL's export table. This section
20088 describes working with such symbols, known internally to @value{GDBN} as
20089 ``minimal symbols''.
20091 Note that before the debugged program has started execution, no DLLs
20092 will have been loaded. The easiest way around this problem is simply to
20093 start the program --- either by setting a breakpoint or letting the
20094 program run once to completion.
20096 @subsubsection DLL Name Prefixes
20098 In keeping with the naming conventions used by the Microsoft debugging
20099 tools, DLL export symbols are made available with a prefix based on the
20100 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20101 also entered into the symbol table, so @code{CreateFileA} is often
20102 sufficient. In some cases there will be name clashes within a program
20103 (particularly if the executable itself includes full debugging symbols)
20104 necessitating the use of the fully qualified name when referring to the
20105 contents of the DLL. Use single-quotes around the name to avoid the
20106 exclamation mark (``!'') being interpreted as a language operator.
20108 Note that the internal name of the DLL may be all upper-case, even
20109 though the file name of the DLL is lower-case, or vice-versa. Since
20110 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20111 some confusion. If in doubt, try the @code{info functions} and
20112 @code{info variables} commands or even @code{maint print msymbols}
20113 (@pxref{Symbols}). Here's an example:
20116 (@value{GDBP}) info function CreateFileA
20117 All functions matching regular expression "CreateFileA":
20119 Non-debugging symbols:
20120 0x77e885f4 CreateFileA
20121 0x77e885f4 KERNEL32!CreateFileA
20125 (@value{GDBP}) info function !
20126 All functions matching regular expression "!":
20128 Non-debugging symbols:
20129 0x6100114c cygwin1!__assert
20130 0x61004034 cygwin1!_dll_crt0@@0
20131 0x61004240 cygwin1!dll_crt0(per_process *)
20135 @subsubsection Working with Minimal Symbols
20137 Symbols extracted from a DLL's export table do not contain very much
20138 type information. All that @value{GDBN} can do is guess whether a symbol
20139 refers to a function or variable depending on the linker section that
20140 contains the symbol. Also note that the actual contents of the memory
20141 contained in a DLL are not available unless the program is running. This
20142 means that you cannot examine the contents of a variable or disassemble
20143 a function within a DLL without a running program.
20145 Variables are generally treated as pointers and dereferenced
20146 automatically. For this reason, it is often necessary to prefix a
20147 variable name with the address-of operator (``&'') and provide explicit
20148 type information in the command. Here's an example of the type of
20152 (@value{GDBP}) print 'cygwin1!__argv'
20157 (@value{GDBP}) x 'cygwin1!__argv'
20158 0x10021610: "\230y\""
20161 And two possible solutions:
20164 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20165 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20169 (@value{GDBP}) x/2x &'cygwin1!__argv'
20170 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20171 (@value{GDBP}) x/x 0x10021608
20172 0x10021608: 0x0022fd98
20173 (@value{GDBP}) x/s 0x0022fd98
20174 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20177 Setting a break point within a DLL is possible even before the program
20178 starts execution. However, under these circumstances, @value{GDBN} can't
20179 examine the initial instructions of the function in order to skip the
20180 function's frame set-up code. You can work around this by using ``*&''
20181 to set the breakpoint at a raw memory address:
20184 (@value{GDBP}) break *&'python22!PyOS_Readline'
20185 Breakpoint 1 at 0x1e04eff0
20188 The author of these extensions is not entirely convinced that setting a
20189 break point within a shared DLL like @file{kernel32.dll} is completely
20193 @subsection Commands Specific to @sc{gnu} Hurd Systems
20194 @cindex @sc{gnu} Hurd debugging
20196 This subsection describes @value{GDBN} commands specific to the
20197 @sc{gnu} Hurd native debugging.
20202 @kindex set signals@r{, Hurd command}
20203 @kindex set sigs@r{, Hurd command}
20204 This command toggles the state of inferior signal interception by
20205 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20206 affected by this command. @code{sigs} is a shorthand alias for
20211 @kindex show signals@r{, Hurd command}
20212 @kindex show sigs@r{, Hurd command}
20213 Show the current state of intercepting inferior's signals.
20215 @item set signal-thread
20216 @itemx set sigthread
20217 @kindex set signal-thread
20218 @kindex set sigthread
20219 This command tells @value{GDBN} which thread is the @code{libc} signal
20220 thread. That thread is run when a signal is delivered to a running
20221 process. @code{set sigthread} is the shorthand alias of @code{set
20224 @item show signal-thread
20225 @itemx show sigthread
20226 @kindex show signal-thread
20227 @kindex show sigthread
20228 These two commands show which thread will run when the inferior is
20229 delivered a signal.
20232 @kindex set stopped@r{, Hurd command}
20233 This commands tells @value{GDBN} that the inferior process is stopped,
20234 as with the @code{SIGSTOP} signal. The stopped process can be
20235 continued by delivering a signal to it.
20238 @kindex show stopped@r{, Hurd command}
20239 This command shows whether @value{GDBN} thinks the debuggee is
20242 @item set exceptions
20243 @kindex set exceptions@r{, Hurd command}
20244 Use this command to turn off trapping of exceptions in the inferior.
20245 When exception trapping is off, neither breakpoints nor
20246 single-stepping will work. To restore the default, set exception
20249 @item show exceptions
20250 @kindex show exceptions@r{, Hurd command}
20251 Show the current state of trapping exceptions in the inferior.
20253 @item set task pause
20254 @kindex set task@r{, Hurd commands}
20255 @cindex task attributes (@sc{gnu} Hurd)
20256 @cindex pause current task (@sc{gnu} Hurd)
20257 This command toggles task suspension when @value{GDBN} has control.
20258 Setting it to on takes effect immediately, and the task is suspended
20259 whenever @value{GDBN} gets control. Setting it to off will take
20260 effect the next time the inferior is continued. If this option is set
20261 to off, you can use @code{set thread default pause on} or @code{set
20262 thread pause on} (see below) to pause individual threads.
20264 @item show task pause
20265 @kindex show task@r{, Hurd commands}
20266 Show the current state of task suspension.
20268 @item set task detach-suspend-count
20269 @cindex task suspend count
20270 @cindex detach from task, @sc{gnu} Hurd
20271 This command sets the suspend count the task will be left with when
20272 @value{GDBN} detaches from it.
20274 @item show task detach-suspend-count
20275 Show the suspend count the task will be left with when detaching.
20277 @item set task exception-port
20278 @itemx set task excp
20279 @cindex task exception port, @sc{gnu} Hurd
20280 This command sets the task exception port to which @value{GDBN} will
20281 forward exceptions. The argument should be the value of the @dfn{send
20282 rights} of the task. @code{set task excp} is a shorthand alias.
20284 @item set noninvasive
20285 @cindex noninvasive task options
20286 This command switches @value{GDBN} to a mode that is the least
20287 invasive as far as interfering with the inferior is concerned. This
20288 is the same as using @code{set task pause}, @code{set exceptions}, and
20289 @code{set signals} to values opposite to the defaults.
20291 @item info send-rights
20292 @itemx info receive-rights
20293 @itemx info port-rights
20294 @itemx info port-sets
20295 @itemx info dead-names
20298 @cindex send rights, @sc{gnu} Hurd
20299 @cindex receive rights, @sc{gnu} Hurd
20300 @cindex port rights, @sc{gnu} Hurd
20301 @cindex port sets, @sc{gnu} Hurd
20302 @cindex dead names, @sc{gnu} Hurd
20303 These commands display information about, respectively, send rights,
20304 receive rights, port rights, port sets, and dead names of a task.
20305 There are also shorthand aliases: @code{info ports} for @code{info
20306 port-rights} and @code{info psets} for @code{info port-sets}.
20308 @item set thread pause
20309 @kindex set thread@r{, Hurd command}
20310 @cindex thread properties, @sc{gnu} Hurd
20311 @cindex pause current thread (@sc{gnu} Hurd)
20312 This command toggles current thread suspension when @value{GDBN} has
20313 control. Setting it to on takes effect immediately, and the current
20314 thread is suspended whenever @value{GDBN} gets control. Setting it to
20315 off will take effect the next time the inferior is continued.
20316 Normally, this command has no effect, since when @value{GDBN} has
20317 control, the whole task is suspended. However, if you used @code{set
20318 task pause off} (see above), this command comes in handy to suspend
20319 only the current thread.
20321 @item show thread pause
20322 @kindex show thread@r{, Hurd command}
20323 This command shows the state of current thread suspension.
20325 @item set thread run
20326 This command sets whether the current thread is allowed to run.
20328 @item show thread run
20329 Show whether the current thread is allowed to run.
20331 @item set thread detach-suspend-count
20332 @cindex thread suspend count, @sc{gnu} Hurd
20333 @cindex detach from thread, @sc{gnu} Hurd
20334 This command sets the suspend count @value{GDBN} will leave on a
20335 thread when detaching. This number is relative to the suspend count
20336 found by @value{GDBN} when it notices the thread; use @code{set thread
20337 takeover-suspend-count} to force it to an absolute value.
20339 @item show thread detach-suspend-count
20340 Show the suspend count @value{GDBN} will leave on the thread when
20343 @item set thread exception-port
20344 @itemx set thread excp
20345 Set the thread exception port to which to forward exceptions. This
20346 overrides the port set by @code{set task exception-port} (see above).
20347 @code{set thread excp} is the shorthand alias.
20349 @item set thread takeover-suspend-count
20350 Normally, @value{GDBN}'s thread suspend counts are relative to the
20351 value @value{GDBN} finds when it notices each thread. This command
20352 changes the suspend counts to be absolute instead.
20354 @item set thread default
20355 @itemx show thread default
20356 @cindex thread default settings, @sc{gnu} Hurd
20357 Each of the above @code{set thread} commands has a @code{set thread
20358 default} counterpart (e.g., @code{set thread default pause}, @code{set
20359 thread default exception-port}, etc.). The @code{thread default}
20360 variety of commands sets the default thread properties for all
20361 threads; you can then change the properties of individual threads with
20362 the non-default commands.
20369 @value{GDBN} provides the following commands specific to the Darwin target:
20372 @item set debug darwin @var{num}
20373 @kindex set debug darwin
20374 When set to a non zero value, enables debugging messages specific to
20375 the Darwin support. Higher values produce more verbose output.
20377 @item show debug darwin
20378 @kindex show debug darwin
20379 Show the current state of Darwin messages.
20381 @item set debug mach-o @var{num}
20382 @kindex set debug mach-o
20383 When set to a non zero value, enables debugging messages while
20384 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20385 file format used on Darwin for object and executable files.) Higher
20386 values produce more verbose output. This is a command to diagnose
20387 problems internal to @value{GDBN} and should not be needed in normal
20390 @item show debug mach-o
20391 @kindex show debug mach-o
20392 Show the current state of Mach-O file messages.
20394 @item set mach-exceptions on
20395 @itemx set mach-exceptions off
20396 @kindex set mach-exceptions
20397 On Darwin, faults are first reported as a Mach exception and are then
20398 mapped to a Posix signal. Use this command to turn on trapping of
20399 Mach exceptions in the inferior. This might be sometimes useful to
20400 better understand the cause of a fault. The default is off.
20402 @item show mach-exceptions
20403 @kindex show mach-exceptions
20404 Show the current state of exceptions trapping.
20409 @section Embedded Operating Systems
20411 This section describes configurations involving the debugging of
20412 embedded operating systems that are available for several different
20416 * VxWorks:: Using @value{GDBN} with VxWorks
20419 @value{GDBN} includes the ability to debug programs running on
20420 various real-time operating systems.
20423 @subsection Using @value{GDBN} with VxWorks
20429 @kindex target vxworks
20430 @item target vxworks @var{machinename}
20431 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20432 is the target system's machine name or IP address.
20436 On VxWorks, @code{load} links @var{filename} dynamically on the
20437 current target system as well as adding its symbols in @value{GDBN}.
20439 @value{GDBN} enables developers to spawn and debug tasks running on networked
20440 VxWorks targets from a Unix host. Already-running tasks spawned from
20441 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20442 both the Unix host and on the VxWorks target. The program
20443 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20444 installed with the name @code{vxgdb}, to distinguish it from a
20445 @value{GDBN} for debugging programs on the host itself.)
20448 @item VxWorks-timeout @var{args}
20449 @kindex vxworks-timeout
20450 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20451 This option is set by the user, and @var{args} represents the number of
20452 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20453 your VxWorks target is a slow software simulator or is on the far side
20454 of a thin network line.
20457 The following information on connecting to VxWorks was current when
20458 this manual was produced; newer releases of VxWorks may use revised
20461 @findex INCLUDE_RDB
20462 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20463 to include the remote debugging interface routines in the VxWorks
20464 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20465 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20466 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20467 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20468 information on configuring and remaking VxWorks, see the manufacturer's
20470 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20472 Once you have included @file{rdb.a} in your VxWorks system image and set
20473 your Unix execution search path to find @value{GDBN}, you are ready to
20474 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20475 @code{vxgdb}, depending on your installation).
20477 @value{GDBN} comes up showing the prompt:
20484 * VxWorks Connection:: Connecting to VxWorks
20485 * VxWorks Download:: VxWorks download
20486 * VxWorks Attach:: Running tasks
20489 @node VxWorks Connection
20490 @subsubsection Connecting to VxWorks
20492 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20493 network. To connect to a target whose host name is ``@code{tt}'', type:
20496 (vxgdb) target vxworks tt
20500 @value{GDBN} displays messages like these:
20503 Attaching remote machine across net...
20508 @value{GDBN} then attempts to read the symbol tables of any object modules
20509 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20510 these files by searching the directories listed in the command search
20511 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20512 to find an object file, it displays a message such as:
20515 prog.o: No such file or directory.
20518 When this happens, add the appropriate directory to the search path with
20519 the @value{GDBN} command @code{path}, and execute the @code{target}
20522 @node VxWorks Download
20523 @subsubsection VxWorks Download
20525 @cindex download to VxWorks
20526 If you have connected to the VxWorks target and you want to debug an
20527 object that has not yet been loaded, you can use the @value{GDBN}
20528 @code{load} command to download a file from Unix to VxWorks
20529 incrementally. The object file given as an argument to the @code{load}
20530 command is actually opened twice: first by the VxWorks target in order
20531 to download the code, then by @value{GDBN} in order to read the symbol
20532 table. This can lead to problems if the current working directories on
20533 the two systems differ. If both systems have NFS mounted the same
20534 filesystems, you can avoid these problems by using absolute paths.
20535 Otherwise, it is simplest to set the working directory on both systems
20536 to the directory in which the object file resides, and then to reference
20537 the file by its name, without any path. For instance, a program
20538 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20539 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20540 program, type this on VxWorks:
20543 -> cd "@var{vxpath}/vw/demo/rdb"
20547 Then, in @value{GDBN}, type:
20550 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20551 (vxgdb) load prog.o
20554 @value{GDBN} displays a response similar to this:
20557 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20560 You can also use the @code{load} command to reload an object module
20561 after editing and recompiling the corresponding source file. Note that
20562 this makes @value{GDBN} delete all currently-defined breakpoints,
20563 auto-displays, and convenience variables, and to clear the value
20564 history. (This is necessary in order to preserve the integrity of
20565 debugger's data structures that reference the target system's symbol
20568 @node VxWorks Attach
20569 @subsubsection Running Tasks
20571 @cindex running VxWorks tasks
20572 You can also attach to an existing task using the @code{attach} command as
20576 (vxgdb) attach @var{task}
20580 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20581 or suspended when you attach to it. Running tasks are suspended at
20582 the time of attachment.
20584 @node Embedded Processors
20585 @section Embedded Processors
20587 This section goes into details specific to particular embedded
20590 @cindex send command to simulator
20591 Whenever a specific embedded processor has a simulator, @value{GDBN}
20592 allows to send an arbitrary command to the simulator.
20595 @item sim @var{command}
20596 @kindex sim@r{, a command}
20597 Send an arbitrary @var{command} string to the simulator. Consult the
20598 documentation for the specific simulator in use for information about
20599 acceptable commands.
20605 * M32R/D:: Renesas M32R/D
20606 * M68K:: Motorola M68K
20607 * MicroBlaze:: Xilinx MicroBlaze
20608 * MIPS Embedded:: MIPS Embedded
20609 * PowerPC Embedded:: PowerPC Embedded
20610 * PA:: HP PA Embedded
20611 * Sparclet:: Tsqware Sparclet
20612 * Sparclite:: Fujitsu Sparclite
20613 * Z8000:: Zilog Z8000
20616 * Super-H:: Renesas Super-H
20625 @item target rdi @var{dev}
20626 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20627 use this target to communicate with both boards running the Angel
20628 monitor, or with the EmbeddedICE JTAG debug device.
20631 @item target rdp @var{dev}
20636 @value{GDBN} provides the following ARM-specific commands:
20639 @item set arm disassembler
20641 This commands selects from a list of disassembly styles. The
20642 @code{"std"} style is the standard style.
20644 @item show arm disassembler
20646 Show the current disassembly style.
20648 @item set arm apcs32
20649 @cindex ARM 32-bit mode
20650 This command toggles ARM operation mode between 32-bit and 26-bit.
20652 @item show arm apcs32
20653 Display the current usage of the ARM 32-bit mode.
20655 @item set arm fpu @var{fputype}
20656 This command sets the ARM floating-point unit (FPU) type. The
20657 argument @var{fputype} can be one of these:
20661 Determine the FPU type by querying the OS ABI.
20663 Software FPU, with mixed-endian doubles on little-endian ARM
20666 GCC-compiled FPA co-processor.
20668 Software FPU with pure-endian doubles.
20674 Show the current type of the FPU.
20677 This command forces @value{GDBN} to use the specified ABI.
20680 Show the currently used ABI.
20682 @item set arm fallback-mode (arm|thumb|auto)
20683 @value{GDBN} uses the symbol table, when available, to determine
20684 whether instructions are ARM or Thumb. This command controls
20685 @value{GDBN}'s default behavior when the symbol table is not
20686 available. The default is @samp{auto}, which causes @value{GDBN} to
20687 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20690 @item show arm fallback-mode
20691 Show the current fallback instruction mode.
20693 @item set arm force-mode (arm|thumb|auto)
20694 This command overrides use of the symbol table to determine whether
20695 instructions are ARM or Thumb. The default is @samp{auto}, which
20696 causes @value{GDBN} to use the symbol table and then the setting
20697 of @samp{set arm fallback-mode}.
20699 @item show arm force-mode
20700 Show the current forced instruction mode.
20702 @item set debug arm
20703 Toggle whether to display ARM-specific debugging messages from the ARM
20704 target support subsystem.
20706 @item show debug arm
20707 Show whether ARM-specific debugging messages are enabled.
20710 The following commands are available when an ARM target is debugged
20711 using the RDI interface:
20714 @item rdilogfile @r{[}@var{file}@r{]}
20716 @cindex ADP (Angel Debugger Protocol) logging
20717 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20718 With an argument, sets the log file to the specified @var{file}. With
20719 no argument, show the current log file name. The default log file is
20722 @item rdilogenable @r{[}@var{arg}@r{]}
20723 @kindex rdilogenable
20724 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20725 enables logging, with an argument 0 or @code{"no"} disables it. With
20726 no arguments displays the current setting. When logging is enabled,
20727 ADP packets exchanged between @value{GDBN} and the RDI target device
20728 are logged to a file.
20730 @item set rdiromatzero
20731 @kindex set rdiromatzero
20732 @cindex ROM at zero address, RDI
20733 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20734 vector catching is disabled, so that zero address can be used. If off
20735 (the default), vector catching is enabled. For this command to take
20736 effect, it needs to be invoked prior to the @code{target rdi} command.
20738 @item show rdiromatzero
20739 @kindex show rdiromatzero
20740 Show the current setting of ROM at zero address.
20742 @item set rdiheartbeat
20743 @kindex set rdiheartbeat
20744 @cindex RDI heartbeat
20745 Enable or disable RDI heartbeat packets. It is not recommended to
20746 turn on this option, since it confuses ARM and EPI JTAG interface, as
20747 well as the Angel monitor.
20749 @item show rdiheartbeat
20750 @kindex show rdiheartbeat
20751 Show the setting of RDI heartbeat packets.
20755 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20756 The @value{GDBN} ARM simulator accepts the following optional arguments.
20759 @item --swi-support=@var{type}
20760 Tell the simulator which SWI interfaces to support.
20761 @var{type} may be a comma separated list of the following values.
20762 The default value is @code{all}.
20775 @subsection Renesas M32R/D and M32R/SDI
20778 @kindex target m32r
20779 @item target m32r @var{dev}
20780 Renesas M32R/D ROM monitor.
20782 @kindex target m32rsdi
20783 @item target m32rsdi @var{dev}
20784 Renesas M32R SDI server, connected via parallel port to the board.
20787 The following @value{GDBN} commands are specific to the M32R monitor:
20790 @item set download-path @var{path}
20791 @kindex set download-path
20792 @cindex find downloadable @sc{srec} files (M32R)
20793 Set the default path for finding downloadable @sc{srec} files.
20795 @item show download-path
20796 @kindex show download-path
20797 Show the default path for downloadable @sc{srec} files.
20799 @item set board-address @var{addr}
20800 @kindex set board-address
20801 @cindex M32-EVA target board address
20802 Set the IP address for the M32R-EVA target board.
20804 @item show board-address
20805 @kindex show board-address
20806 Show the current IP address of the target board.
20808 @item set server-address @var{addr}
20809 @kindex set server-address
20810 @cindex download server address (M32R)
20811 Set the IP address for the download server, which is the @value{GDBN}'s
20814 @item show server-address
20815 @kindex show server-address
20816 Display the IP address of the download server.
20818 @item upload @r{[}@var{file}@r{]}
20819 @kindex upload@r{, M32R}
20820 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20821 upload capability. If no @var{file} argument is given, the current
20822 executable file is uploaded.
20824 @item tload @r{[}@var{file}@r{]}
20825 @kindex tload@r{, M32R}
20826 Test the @code{upload} command.
20829 The following commands are available for M32R/SDI:
20834 @cindex reset SDI connection, M32R
20835 This command resets the SDI connection.
20839 This command shows the SDI connection status.
20842 @kindex debug_chaos
20843 @cindex M32R/Chaos debugging
20844 Instructs the remote that M32R/Chaos debugging is to be used.
20846 @item use_debug_dma
20847 @kindex use_debug_dma
20848 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20851 @kindex use_mon_code
20852 Instructs the remote to use the MON_CODE method of accessing memory.
20855 @kindex use_ib_break
20856 Instructs the remote to set breakpoints by IB break.
20858 @item use_dbt_break
20859 @kindex use_dbt_break
20860 Instructs the remote to set breakpoints by DBT.
20866 The Motorola m68k configuration includes ColdFire support, and a
20867 target command for the following ROM monitor.
20871 @kindex target dbug
20872 @item target dbug @var{dev}
20873 dBUG ROM monitor for Motorola ColdFire.
20878 @subsection MicroBlaze
20879 @cindex Xilinx MicroBlaze
20880 @cindex XMD, Xilinx Microprocessor Debugger
20882 The MicroBlaze is a soft-core processor supported on various Xilinx
20883 FPGAs, such as Spartan or Virtex series. Boards with these processors
20884 usually have JTAG ports which connect to a host system running the Xilinx
20885 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20886 This host system is used to download the configuration bitstream to
20887 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20888 communicates with the target board using the JTAG interface and
20889 presents a @code{gdbserver} interface to the board. By default
20890 @code{xmd} uses port @code{1234}. (While it is possible to change
20891 this default port, it requires the use of undocumented @code{xmd}
20892 commands. Contact Xilinx support if you need to do this.)
20894 Use these GDB commands to connect to the MicroBlaze target processor.
20897 @item target remote :1234
20898 Use this command to connect to the target if you are running @value{GDBN}
20899 on the same system as @code{xmd}.
20901 @item target remote @var{xmd-host}:1234
20902 Use this command to connect to the target if it is connected to @code{xmd}
20903 running on a different system named @var{xmd-host}.
20906 Use this command to download a program to the MicroBlaze target.
20908 @item set debug microblaze @var{n}
20909 Enable MicroBlaze-specific debugging messages if non-zero.
20911 @item show debug microblaze @var{n}
20912 Show MicroBlaze-specific debugging level.
20915 @node MIPS Embedded
20916 @subsection @acronym{MIPS} Embedded
20918 @cindex @acronym{MIPS} boards
20919 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20920 @acronym{MIPS} board attached to a serial line. This is available when
20921 you configure @value{GDBN} with @samp{--target=mips-elf}.
20924 Use these @value{GDBN} commands to specify the connection to your target board:
20927 @item target mips @var{port}
20928 @kindex target mips @var{port}
20929 To run a program on the board, start up @code{@value{GDBP}} with the
20930 name of your program as the argument. To connect to the board, use the
20931 command @samp{target mips @var{port}}, where @var{port} is the name of
20932 the serial port connected to the board. If the program has not already
20933 been downloaded to the board, you may use the @code{load} command to
20934 download it. You can then use all the usual @value{GDBN} commands.
20936 For example, this sequence connects to the target board through a serial
20937 port, and loads and runs a program called @var{prog} through the
20941 host$ @value{GDBP} @var{prog}
20942 @value{GDBN} is free software and @dots{}
20943 (@value{GDBP}) target mips /dev/ttyb
20944 (@value{GDBP}) load @var{prog}
20948 @item target mips @var{hostname}:@var{portnumber}
20949 On some @value{GDBN} host configurations, you can specify a TCP
20950 connection (for instance, to a serial line managed by a terminal
20951 concentrator) instead of a serial port, using the syntax
20952 @samp{@var{hostname}:@var{portnumber}}.
20954 @item target pmon @var{port}
20955 @kindex target pmon @var{port}
20958 @item target ddb @var{port}
20959 @kindex target ddb @var{port}
20960 NEC's DDB variant of PMON for Vr4300.
20962 @item target lsi @var{port}
20963 @kindex target lsi @var{port}
20964 LSI variant of PMON.
20966 @kindex target r3900
20967 @item target r3900 @var{dev}
20968 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20970 @kindex target array
20971 @item target array @var{dev}
20972 Array Tech LSI33K RAID controller board.
20978 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20981 @item set mipsfpu double
20982 @itemx set mipsfpu single
20983 @itemx set mipsfpu none
20984 @itemx set mipsfpu auto
20985 @itemx show mipsfpu
20986 @kindex set mipsfpu
20987 @kindex show mipsfpu
20988 @cindex @acronym{MIPS} remote floating point
20989 @cindex floating point, @acronym{MIPS} remote
20990 If your target board does not support the @acronym{MIPS} floating point
20991 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20992 need this, you may wish to put the command in your @value{GDBN} init
20993 file). This tells @value{GDBN} how to find the return value of
20994 functions which return floating point values. It also allows
20995 @value{GDBN} to avoid saving the floating point registers when calling
20996 functions on the board. If you are using a floating point coprocessor
20997 with only single precision floating point support, as on the @sc{r4650}
20998 processor, use the command @samp{set mipsfpu single}. The default
20999 double precision floating point coprocessor may be selected using
21000 @samp{set mipsfpu double}.
21002 In previous versions the only choices were double precision or no
21003 floating point, so @samp{set mipsfpu on} will select double precision
21004 and @samp{set mipsfpu off} will select no floating point.
21006 As usual, you can inquire about the @code{mipsfpu} variable with
21007 @samp{show mipsfpu}.
21009 @item set timeout @var{seconds}
21010 @itemx set retransmit-timeout @var{seconds}
21011 @itemx show timeout
21012 @itemx show retransmit-timeout
21013 @cindex @code{timeout}, @acronym{MIPS} protocol
21014 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21015 @kindex set timeout
21016 @kindex show timeout
21017 @kindex set retransmit-timeout
21018 @kindex show retransmit-timeout
21019 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21020 remote protocol, with the @code{set timeout @var{seconds}} command. The
21021 default is 5 seconds. Similarly, you can control the timeout used while
21022 waiting for an acknowledgment of a packet with the @code{set
21023 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21024 You can inspect both values with @code{show timeout} and @code{show
21025 retransmit-timeout}. (These commands are @emph{only} available when
21026 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21028 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21029 is waiting for your program to stop. In that case, @value{GDBN} waits
21030 forever because it has no way of knowing how long the program is going
21031 to run before stopping.
21033 @item set syn-garbage-limit @var{num}
21034 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21035 @cindex synchronize with remote @acronym{MIPS} target
21036 Limit the maximum number of characters @value{GDBN} should ignore when
21037 it tries to synchronize with the remote target. The default is 10
21038 characters. Setting the limit to -1 means there's no limit.
21040 @item show syn-garbage-limit
21041 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21042 Show the current limit on the number of characters to ignore when
21043 trying to synchronize with the remote system.
21045 @item set monitor-prompt @var{prompt}
21046 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21047 @cindex remote monitor prompt
21048 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21049 remote monitor. The default depends on the target:
21059 @item show monitor-prompt
21060 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21061 Show the current strings @value{GDBN} expects as the prompt from the
21064 @item set monitor-warnings
21065 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21066 Enable or disable monitor warnings about hardware breakpoints. This
21067 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21068 display warning messages whose codes are returned by the @code{lsi}
21069 PMON monitor for breakpoint commands.
21071 @item show monitor-warnings
21072 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21073 Show the current setting of printing monitor warnings.
21075 @item pmon @var{command}
21076 @kindex pmon@r{, @acronym{MIPS} remote}
21077 @cindex send PMON command
21078 This command allows sending an arbitrary @var{command} string to the
21079 monitor. The monitor must be in debug mode for this to work.
21082 @node PowerPC Embedded
21083 @subsection PowerPC Embedded
21085 @cindex DVC register
21086 @value{GDBN} supports using the DVC (Data Value Compare) register to
21087 implement in hardware simple hardware watchpoint conditions of the form:
21090 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21091 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21094 The DVC register will be automatically used when @value{GDBN} detects
21095 such pattern in a condition expression, and the created watchpoint uses one
21096 debug register (either the @code{exact-watchpoints} option is on and the
21097 variable is scalar, or the variable has a length of one byte). This feature
21098 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21101 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21102 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21103 in which case watchpoints using only one debug register are created when
21104 watching variables of scalar types.
21106 You can create an artificial array to watch an arbitrary memory
21107 region using one of the following commands (@pxref{Expressions}):
21110 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21111 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21114 PowerPC embedded processors support masked watchpoints. See the discussion
21115 about the @code{mask} argument in @ref{Set Watchpoints}.
21117 @cindex ranged breakpoint
21118 PowerPC embedded processors support hardware accelerated
21119 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21120 the inferior whenever it executes an instruction at any address within
21121 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21122 use the @code{break-range} command.
21124 @value{GDBN} provides the following PowerPC-specific commands:
21127 @kindex break-range
21128 @item break-range @var{start-location}, @var{end-location}
21129 Set a breakpoint for an address range.
21130 @var{start-location} and @var{end-location} can specify a function name,
21131 a line number, an offset of lines from the current line or from the start
21132 location, or an address of an instruction (see @ref{Specify Location},
21133 for a list of all the possible ways to specify a @var{location}.)
21134 The breakpoint will stop execution of the inferior whenever it
21135 executes an instruction at any address within the specified range,
21136 (including @var{start-location} and @var{end-location}.)
21138 @kindex set powerpc
21139 @item set powerpc soft-float
21140 @itemx show powerpc soft-float
21141 Force @value{GDBN} to use (or not use) a software floating point calling
21142 convention. By default, @value{GDBN} selects the calling convention based
21143 on the selected architecture and the provided executable file.
21145 @item set powerpc vector-abi
21146 @itemx show powerpc vector-abi
21147 Force @value{GDBN} to use the specified calling convention for vector
21148 arguments and return values. The valid options are @samp{auto};
21149 @samp{generic}, to avoid vector registers even if they are present;
21150 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21151 registers. By default, @value{GDBN} selects the calling convention
21152 based on the selected architecture and the provided executable file.
21154 @item set powerpc exact-watchpoints
21155 @itemx show powerpc exact-watchpoints
21156 Allow @value{GDBN} to use only one debug register when watching a variable
21157 of scalar type, thus assuming that the variable is accessed through the
21158 address of its first byte.
21160 @kindex target dink32
21161 @item target dink32 @var{dev}
21162 DINK32 ROM monitor.
21164 @kindex target ppcbug
21165 @item target ppcbug @var{dev}
21166 @kindex target ppcbug1
21167 @item target ppcbug1 @var{dev}
21168 PPCBUG ROM monitor for PowerPC.
21171 @item target sds @var{dev}
21172 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21175 @cindex SDS protocol
21176 The following commands specific to the SDS protocol are supported
21180 @item set sdstimeout @var{nsec}
21181 @kindex set sdstimeout
21182 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21183 default is 2 seconds.
21185 @item show sdstimeout
21186 @kindex show sdstimeout
21187 Show the current value of the SDS timeout.
21189 @item sds @var{command}
21190 @kindex sds@r{, a command}
21191 Send the specified @var{command} string to the SDS monitor.
21196 @subsection HP PA Embedded
21200 @kindex target op50n
21201 @item target op50n @var{dev}
21202 OP50N monitor, running on an OKI HPPA board.
21204 @kindex target w89k
21205 @item target w89k @var{dev}
21206 W89K monitor, running on a Winbond HPPA board.
21211 @subsection Tsqware Sparclet
21215 @value{GDBN} enables developers to debug tasks running on
21216 Sparclet targets from a Unix host.
21217 @value{GDBN} uses code that runs on
21218 both the Unix host and on the Sparclet target. The program
21219 @code{@value{GDBP}} is installed and executed on the Unix host.
21222 @item remotetimeout @var{args}
21223 @kindex remotetimeout
21224 @value{GDBN} supports the option @code{remotetimeout}.
21225 This option is set by the user, and @var{args} represents the number of
21226 seconds @value{GDBN} waits for responses.
21229 @cindex compiling, on Sparclet
21230 When compiling for debugging, include the options @samp{-g} to get debug
21231 information and @samp{-Ttext} to relocate the program to where you wish to
21232 load it on the target. You may also want to add the options @samp{-n} or
21233 @samp{-N} in order to reduce the size of the sections. Example:
21236 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21239 You can use @code{objdump} to verify that the addresses are what you intended:
21242 sparclet-aout-objdump --headers --syms prog
21245 @cindex running, on Sparclet
21247 your Unix execution search path to find @value{GDBN}, you are ready to
21248 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21249 (or @code{sparclet-aout-gdb}, depending on your installation).
21251 @value{GDBN} comes up showing the prompt:
21258 * Sparclet File:: Setting the file to debug
21259 * Sparclet Connection:: Connecting to Sparclet
21260 * Sparclet Download:: Sparclet download
21261 * Sparclet Execution:: Running and debugging
21264 @node Sparclet File
21265 @subsubsection Setting File to Debug
21267 The @value{GDBN} command @code{file} lets you choose with program to debug.
21270 (gdbslet) file prog
21274 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21275 @value{GDBN} locates
21276 the file by searching the directories listed in the command search
21278 If the file was compiled with debug information (option @samp{-g}), source
21279 files will be searched as well.
21280 @value{GDBN} locates
21281 the source files by searching the directories listed in the directory search
21282 path (@pxref{Environment, ,Your Program's Environment}).
21284 to find a file, it displays a message such as:
21287 prog: No such file or directory.
21290 When this happens, add the appropriate directories to the search paths with
21291 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21292 @code{target} command again.
21294 @node Sparclet Connection
21295 @subsubsection Connecting to Sparclet
21297 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21298 To connect to a target on serial port ``@code{ttya}'', type:
21301 (gdbslet) target sparclet /dev/ttya
21302 Remote target sparclet connected to /dev/ttya
21303 main () at ../prog.c:3
21307 @value{GDBN} displays messages like these:
21313 @node Sparclet Download
21314 @subsubsection Sparclet Download
21316 @cindex download to Sparclet
21317 Once connected to the Sparclet target,
21318 you can use the @value{GDBN}
21319 @code{load} command to download the file from the host to the target.
21320 The file name and load offset should be given as arguments to the @code{load}
21322 Since the file format is aout, the program must be loaded to the starting
21323 address. You can use @code{objdump} to find out what this value is. The load
21324 offset is an offset which is added to the VMA (virtual memory address)
21325 of each of the file's sections.
21326 For instance, if the program
21327 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21328 and bss at 0x12010170, in @value{GDBN}, type:
21331 (gdbslet) load prog 0x12010000
21332 Loading section .text, size 0xdb0 vma 0x12010000
21335 If the code is loaded at a different address then what the program was linked
21336 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21337 to tell @value{GDBN} where to map the symbol table.
21339 @node Sparclet Execution
21340 @subsubsection Running and Debugging
21342 @cindex running and debugging Sparclet programs
21343 You can now begin debugging the task using @value{GDBN}'s execution control
21344 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21345 manual for the list of commands.
21349 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21351 Starting program: prog
21352 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21353 3 char *symarg = 0;
21355 4 char *execarg = "hello!";
21360 @subsection Fujitsu Sparclite
21364 @kindex target sparclite
21365 @item target sparclite @var{dev}
21366 Fujitsu sparclite boards, used only for the purpose of loading.
21367 You must use an additional command to debug the program.
21368 For example: target remote @var{dev} using @value{GDBN} standard
21374 @subsection Zilog Z8000
21377 @cindex simulator, Z8000
21378 @cindex Zilog Z8000 simulator
21380 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21383 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21384 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21385 segmented variant). The simulator recognizes which architecture is
21386 appropriate by inspecting the object code.
21389 @item target sim @var{args}
21391 @kindex target sim@r{, with Z8000}
21392 Debug programs on a simulated CPU. If the simulator supports setup
21393 options, specify them via @var{args}.
21397 After specifying this target, you can debug programs for the simulated
21398 CPU in the same style as programs for your host computer; use the
21399 @code{file} command to load a new program image, the @code{run} command
21400 to run your program, and so on.
21402 As well as making available all the usual machine registers
21403 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21404 additional items of information as specially named registers:
21409 Counts clock-ticks in the simulator.
21412 Counts instructions run in the simulator.
21415 Execution time in 60ths of a second.
21419 You can refer to these values in @value{GDBN} expressions with the usual
21420 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21421 conditional breakpoint that suspends only after at least 5000
21422 simulated clock ticks.
21425 @subsection Atmel AVR
21428 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21429 following AVR-specific commands:
21432 @item info io_registers
21433 @kindex info io_registers@r{, AVR}
21434 @cindex I/O registers (Atmel AVR)
21435 This command displays information about the AVR I/O registers. For
21436 each register, @value{GDBN} prints its number and value.
21443 When configured for debugging CRIS, @value{GDBN} provides the
21444 following CRIS-specific commands:
21447 @item set cris-version @var{ver}
21448 @cindex CRIS version
21449 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21450 The CRIS version affects register names and sizes. This command is useful in
21451 case autodetection of the CRIS version fails.
21453 @item show cris-version
21454 Show the current CRIS version.
21456 @item set cris-dwarf2-cfi
21457 @cindex DWARF-2 CFI and CRIS
21458 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21459 Change to @samp{off} when using @code{gcc-cris} whose version is below
21462 @item show cris-dwarf2-cfi
21463 Show the current state of using DWARF-2 CFI.
21465 @item set cris-mode @var{mode}
21467 Set the current CRIS mode to @var{mode}. It should only be changed when
21468 debugging in guru mode, in which case it should be set to
21469 @samp{guru} (the default is @samp{normal}).
21471 @item show cris-mode
21472 Show the current CRIS mode.
21476 @subsection Renesas Super-H
21479 For the Renesas Super-H processor, @value{GDBN} provides these
21483 @item set sh calling-convention @var{convention}
21484 @kindex set sh calling-convention
21485 Set the calling-convention used when calling functions from @value{GDBN}.
21486 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21487 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21488 convention. If the DWARF-2 information of the called function specifies
21489 that the function follows the Renesas calling convention, the function
21490 is called using the Renesas calling convention. If the calling convention
21491 is set to @samp{renesas}, the Renesas calling convention is always used,
21492 regardless of the DWARF-2 information. This can be used to override the
21493 default of @samp{gcc} if debug information is missing, or the compiler
21494 does not emit the DWARF-2 calling convention entry for a function.
21496 @item show sh calling-convention
21497 @kindex show sh calling-convention
21498 Show the current calling convention setting.
21503 @node Architectures
21504 @section Architectures
21506 This section describes characteristics of architectures that affect
21507 all uses of @value{GDBN} with the architecture, both native and cross.
21514 * HPPA:: HP PA architecture
21515 * SPU:: Cell Broadband Engine SPU architecture
21521 @subsection AArch64
21522 @cindex AArch64 support
21524 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21525 following special commands:
21528 @item set debug aarch64
21529 @kindex set debug aarch64
21530 This command determines whether AArch64 architecture-specific debugging
21531 messages are to be displayed.
21533 @item show debug aarch64
21534 Show whether AArch64 debugging messages are displayed.
21539 @subsection x86 Architecture-specific Issues
21542 @item set struct-convention @var{mode}
21543 @kindex set struct-convention
21544 @cindex struct return convention
21545 @cindex struct/union returned in registers
21546 Set the convention used by the inferior to return @code{struct}s and
21547 @code{union}s from functions to @var{mode}. Possible values of
21548 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21549 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21550 are returned on the stack, while @code{"reg"} means that a
21551 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21552 be returned in a register.
21554 @item show struct-convention
21555 @kindex show struct-convention
21556 Show the current setting of the convention to return @code{struct}s
21560 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21561 @cindex Intel(R) Memory Protection Extensions (MPX).
21563 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21564 @footnote{The register named with capital letters represent the architecture
21565 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21566 which are the lower bound and upper bound. Bounds are effective addresses or
21567 memory locations. The upper bounds are architecturally represented in 1's
21568 complement form. A bound having lower bound = 0, and upper bound = 0
21569 (1's complement of all bits set) will allow access to the entire address space.
21571 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21572 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21573 display the upper bound performing the complement of one operation on the
21574 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21575 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21576 can also be noted that the upper bounds are inclusive.
21578 As an example, assume that the register BND0 holds bounds for a pointer having
21579 access allowed for the range between 0x32 and 0x71. The values present on
21580 bnd0raw and bnd registers are presented as follows:
21583 bnd0raw = @{0x32, 0xffffffff8e@}
21584 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21587 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21588 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21589 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21590 Python, the display includes the memory size, in bits, accessible to
21596 See the following section.
21599 @subsection @acronym{MIPS}
21601 @cindex stack on Alpha
21602 @cindex stack on @acronym{MIPS}
21603 @cindex Alpha stack
21604 @cindex @acronym{MIPS} stack
21605 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21606 sometimes requires @value{GDBN} to search backward in the object code to
21607 find the beginning of a function.
21609 @cindex response time, @acronym{MIPS} debugging
21610 To improve response time (especially for embedded applications, where
21611 @value{GDBN} may be restricted to a slow serial line for this search)
21612 you may want to limit the size of this search, using one of these
21616 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21617 @item set heuristic-fence-post @var{limit}
21618 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21619 search for the beginning of a function. A value of @var{0} (the
21620 default) means there is no limit. However, except for @var{0}, the
21621 larger the limit the more bytes @code{heuristic-fence-post} must search
21622 and therefore the longer it takes to run. You should only need to use
21623 this command when debugging a stripped executable.
21625 @item show heuristic-fence-post
21626 Display the current limit.
21630 These commands are available @emph{only} when @value{GDBN} is configured
21631 for debugging programs on Alpha or @acronym{MIPS} processors.
21633 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21637 @item set mips abi @var{arg}
21638 @kindex set mips abi
21639 @cindex set ABI for @acronym{MIPS}
21640 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21641 values of @var{arg} are:
21645 The default ABI associated with the current binary (this is the
21655 @item show mips abi
21656 @kindex show mips abi
21657 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21659 @item set mips compression @var{arg}
21660 @kindex set mips compression
21661 @cindex code compression, @acronym{MIPS}
21662 Tell @value{GDBN} which @acronym{MIPS} compressed
21663 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21664 inferior. @value{GDBN} uses this for code disassembly and other
21665 internal interpretation purposes. This setting is only referred to
21666 when no executable has been associated with the debugging session or
21667 the executable does not provide information about the encoding it uses.
21668 Otherwise this setting is automatically updated from information
21669 provided by the executable.
21671 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21672 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21673 executables containing @acronym{MIPS16} code frequently are not
21674 identified as such.
21676 This setting is ``sticky''; that is, it retains its value across
21677 debugging sessions until reset either explicitly with this command or
21678 implicitly from an executable.
21680 The compiler and/or assembler typically add symbol table annotations to
21681 identify functions compiled for the @acronym{MIPS16} or
21682 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21683 are present, @value{GDBN} uses them in preference to the global
21684 compressed @acronym{ISA} encoding setting.
21686 @item show mips compression
21687 @kindex show mips compression
21688 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21689 @value{GDBN} to debug the inferior.
21692 @itemx show mipsfpu
21693 @xref{MIPS Embedded, set mipsfpu}.
21695 @item set mips mask-address @var{arg}
21696 @kindex set mips mask-address
21697 @cindex @acronym{MIPS} addresses, masking
21698 This command determines whether the most-significant 32 bits of 64-bit
21699 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21700 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21701 setting, which lets @value{GDBN} determine the correct value.
21703 @item show mips mask-address
21704 @kindex show mips mask-address
21705 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21708 @item set remote-mips64-transfers-32bit-regs
21709 @kindex set remote-mips64-transfers-32bit-regs
21710 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21711 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21712 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21713 and 64 bits for other registers, set this option to @samp{on}.
21715 @item show remote-mips64-transfers-32bit-regs
21716 @kindex show remote-mips64-transfers-32bit-regs
21717 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21719 @item set debug mips
21720 @kindex set debug mips
21721 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21722 target code in @value{GDBN}.
21724 @item show debug mips
21725 @kindex show debug mips
21726 Show the current setting of @acronym{MIPS} debugging messages.
21732 @cindex HPPA support
21734 When @value{GDBN} is debugging the HP PA architecture, it provides the
21735 following special commands:
21738 @item set debug hppa
21739 @kindex set debug hppa
21740 This command determines whether HPPA architecture-specific debugging
21741 messages are to be displayed.
21743 @item show debug hppa
21744 Show whether HPPA debugging messages are displayed.
21746 @item maint print unwind @var{address}
21747 @kindex maint print unwind@r{, HPPA}
21748 This command displays the contents of the unwind table entry at the
21749 given @var{address}.
21755 @subsection Cell Broadband Engine SPU architecture
21756 @cindex Cell Broadband Engine
21759 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21760 it provides the following special commands:
21763 @item info spu event
21765 Display SPU event facility status. Shows current event mask
21766 and pending event status.
21768 @item info spu signal
21769 Display SPU signal notification facility status. Shows pending
21770 signal-control word and signal notification mode of both signal
21771 notification channels.
21773 @item info spu mailbox
21774 Display SPU mailbox facility status. Shows all pending entries,
21775 in order of processing, in each of the SPU Write Outbound,
21776 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21779 Display MFC DMA status. Shows all pending commands in the MFC
21780 DMA queue. For each entry, opcode, tag, class IDs, effective
21781 and local store addresses and transfer size are shown.
21783 @item info spu proxydma
21784 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21785 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21786 and local store addresses and transfer size are shown.
21790 When @value{GDBN} is debugging a combined PowerPC/SPU application
21791 on the Cell Broadband Engine, it provides in addition the following
21795 @item set spu stop-on-load @var{arg}
21797 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21798 will give control to the user when a new SPE thread enters its @code{main}
21799 function. The default is @code{off}.
21801 @item show spu stop-on-load
21803 Show whether to stop for new SPE threads.
21805 @item set spu auto-flush-cache @var{arg}
21806 Set whether to automatically flush the software-managed cache. When set to
21807 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21808 cache to be flushed whenever SPE execution stops. This provides a consistent
21809 view of PowerPC memory that is accessed via the cache. If an application
21810 does not use the software-managed cache, this option has no effect.
21812 @item show spu auto-flush-cache
21813 Show whether to automatically flush the software-managed cache.
21818 @subsection PowerPC
21819 @cindex PowerPC architecture
21821 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21822 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21823 numbers stored in the floating point registers. These values must be stored
21824 in two consecutive registers, always starting at an even register like
21825 @code{f0} or @code{f2}.
21827 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21828 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21829 @code{f2} and @code{f3} for @code{$dl1} and so on.
21831 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21832 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21835 @subsection Nios II
21836 @cindex Nios II architecture
21838 When @value{GDBN} is debugging the Nios II architecture,
21839 it provides the following special commands:
21843 @item set debug nios2
21844 @kindex set debug nios2
21845 This command turns on and off debugging messages for the Nios II
21846 target code in @value{GDBN}.
21848 @item show debug nios2
21849 @kindex show debug nios2
21850 Show the current setting of Nios II debugging messages.
21853 @node Controlling GDB
21854 @chapter Controlling @value{GDBN}
21856 You can alter the way @value{GDBN} interacts with you by using the
21857 @code{set} command. For commands controlling how @value{GDBN} displays
21858 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21863 * Editing:: Command editing
21864 * Command History:: Command history
21865 * Screen Size:: Screen size
21866 * Numbers:: Numbers
21867 * ABI:: Configuring the current ABI
21868 * Auto-loading:: Automatically loading associated files
21869 * Messages/Warnings:: Optional warnings and messages
21870 * Debugging Output:: Optional messages about internal happenings
21871 * Other Misc Settings:: Other Miscellaneous Settings
21879 @value{GDBN} indicates its readiness to read a command by printing a string
21880 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21881 can change the prompt string with the @code{set prompt} command. For
21882 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21883 the prompt in one of the @value{GDBN} sessions so that you can always tell
21884 which one you are talking to.
21886 @emph{Note:} @code{set prompt} does not add a space for you after the
21887 prompt you set. This allows you to set a prompt which ends in a space
21888 or a prompt that does not.
21892 @item set prompt @var{newprompt}
21893 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21895 @kindex show prompt
21897 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21900 Versions of @value{GDBN} that ship with Python scripting enabled have
21901 prompt extensions. The commands for interacting with these extensions
21905 @kindex set extended-prompt
21906 @item set extended-prompt @var{prompt}
21907 Set an extended prompt that allows for substitutions.
21908 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21909 substitution. Any escape sequences specified as part of the prompt
21910 string are replaced with the corresponding strings each time the prompt
21916 set extended-prompt Current working directory: \w (gdb)
21919 Note that when an extended-prompt is set, it takes control of the
21920 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21922 @kindex show extended-prompt
21923 @item show extended-prompt
21924 Prints the extended prompt. Any escape sequences specified as part of
21925 the prompt string with @code{set extended-prompt}, are replaced with the
21926 corresponding strings each time the prompt is displayed.
21930 @section Command Editing
21932 @cindex command line editing
21934 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21935 @sc{gnu} library provides consistent behavior for programs which provide a
21936 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21937 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21938 substitution, and a storage and recall of command history across
21939 debugging sessions.
21941 You may control the behavior of command line editing in @value{GDBN} with the
21942 command @code{set}.
21945 @kindex set editing
21948 @itemx set editing on
21949 Enable command line editing (enabled by default).
21951 @item set editing off
21952 Disable command line editing.
21954 @kindex show editing
21956 Show whether command line editing is enabled.
21959 @ifset SYSTEM_READLINE
21960 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21962 @ifclear SYSTEM_READLINE
21963 @xref{Command Line Editing},
21965 for more details about the Readline
21966 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21967 encouraged to read that chapter.
21969 @node Command History
21970 @section Command History
21971 @cindex command history
21973 @value{GDBN} can keep track of the commands you type during your
21974 debugging sessions, so that you can be certain of precisely what
21975 happened. Use these commands to manage the @value{GDBN} command
21978 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21979 package, to provide the history facility.
21980 @ifset SYSTEM_READLINE
21981 @xref{Using History Interactively, , , history, GNU History Library},
21983 @ifclear SYSTEM_READLINE
21984 @xref{Using History Interactively},
21986 for the detailed description of the History library.
21988 To issue a command to @value{GDBN} without affecting certain aspects of
21989 the state which is seen by users, prefix it with @samp{server }
21990 (@pxref{Server Prefix}). This
21991 means that this command will not affect the command history, nor will it
21992 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21993 pressed on a line by itself.
21995 @cindex @code{server}, command prefix
21996 The server prefix does not affect the recording of values into the value
21997 history; to print a value without recording it into the value history,
21998 use the @code{output} command instead of the @code{print} command.
22000 Here is the description of @value{GDBN} commands related to command
22004 @cindex history substitution
22005 @cindex history file
22006 @kindex set history filename
22007 @cindex @env{GDBHISTFILE}, environment variable
22008 @item set history filename @var{fname}
22009 Set the name of the @value{GDBN} command history file to @var{fname}.
22010 This is the file where @value{GDBN} reads an initial command history
22011 list, and where it writes the command history from this session when it
22012 exits. You can access this list through history expansion or through
22013 the history command editing characters listed below. This file defaults
22014 to the value of the environment variable @code{GDBHISTFILE}, or to
22015 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22018 @cindex save command history
22019 @kindex set history save
22020 @item set history save
22021 @itemx set history save on
22022 Record command history in a file, whose name may be specified with the
22023 @code{set history filename} command. By default, this option is disabled.
22025 @item set history save off
22026 Stop recording command history in a file.
22028 @cindex history size
22029 @kindex set history size
22030 @cindex @env{HISTSIZE}, environment variable
22031 @item set history size @var{size}
22032 @itemx set history size unlimited
22033 Set the number of commands which @value{GDBN} keeps in its history list.
22034 This defaults to the value of the environment variable
22035 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22036 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22037 history list is unlimited.
22040 History expansion assigns special meaning to the character @kbd{!}.
22041 @ifset SYSTEM_READLINE
22042 @xref{Event Designators, , , history, GNU History Library},
22044 @ifclear SYSTEM_READLINE
22045 @xref{Event Designators},
22049 @cindex history expansion, turn on/off
22050 Since @kbd{!} is also the logical not operator in C, history expansion
22051 is off by default. If you decide to enable history expansion with the
22052 @code{set history expansion on} command, you may sometimes need to
22053 follow @kbd{!} (when it is used as logical not, in an expression) with
22054 a space or a tab to prevent it from being expanded. The readline
22055 history facilities do not attempt substitution on the strings
22056 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22058 The commands to control history expansion are:
22061 @item set history expansion on
22062 @itemx set history expansion
22063 @kindex set history expansion
22064 Enable history expansion. History expansion is off by default.
22066 @item set history expansion off
22067 Disable history expansion.
22070 @kindex show history
22072 @itemx show history filename
22073 @itemx show history save
22074 @itemx show history size
22075 @itemx show history expansion
22076 These commands display the state of the @value{GDBN} history parameters.
22077 @code{show history} by itself displays all four states.
22082 @kindex show commands
22083 @cindex show last commands
22084 @cindex display command history
22085 @item show commands
22086 Display the last ten commands in the command history.
22088 @item show commands @var{n}
22089 Print ten commands centered on command number @var{n}.
22091 @item show commands +
22092 Print ten commands just after the commands last printed.
22096 @section Screen Size
22097 @cindex size of screen
22098 @cindex pauses in output
22100 Certain commands to @value{GDBN} may produce large amounts of
22101 information output to the screen. To help you read all of it,
22102 @value{GDBN} pauses and asks you for input at the end of each page of
22103 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22104 to discard the remaining output. Also, the screen width setting
22105 determines when to wrap lines of output. Depending on what is being
22106 printed, @value{GDBN} tries to break the line at a readable place,
22107 rather than simply letting it overflow onto the following line.
22109 Normally @value{GDBN} knows the size of the screen from the terminal
22110 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22111 together with the value of the @code{TERM} environment variable and the
22112 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22113 you can override it with the @code{set height} and @code{set
22120 @kindex show height
22121 @item set height @var{lpp}
22122 @itemx set height unlimited
22124 @itemx set width @var{cpl}
22125 @itemx set width unlimited
22127 These @code{set} commands specify a screen height of @var{lpp} lines and
22128 a screen width of @var{cpl} characters. The associated @code{show}
22129 commands display the current settings.
22131 If you specify a height of either @code{unlimited} or zero lines,
22132 @value{GDBN} does not pause during output no matter how long the
22133 output is. This is useful if output is to a file or to an editor
22136 Likewise, you can specify @samp{set width unlimited} or @samp{set
22137 width 0} to prevent @value{GDBN} from wrapping its output.
22139 @item set pagination on
22140 @itemx set pagination off
22141 @kindex set pagination
22142 Turn the output pagination on or off; the default is on. Turning
22143 pagination off is the alternative to @code{set height unlimited}. Note that
22144 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22145 Options, -batch}) also automatically disables pagination.
22147 @item show pagination
22148 @kindex show pagination
22149 Show the current pagination mode.
22154 @cindex number representation
22155 @cindex entering numbers
22157 You can always enter numbers in octal, decimal, or hexadecimal in
22158 @value{GDBN} by the usual conventions: octal numbers begin with
22159 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22160 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22161 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22162 10; likewise, the default display for numbers---when no particular
22163 format is specified---is base 10. You can change the default base for
22164 both input and output with the commands described below.
22167 @kindex set input-radix
22168 @item set input-radix @var{base}
22169 Set the default base for numeric input. Supported choices
22170 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22171 specified either unambiguously or using the current input radix; for
22175 set input-radix 012
22176 set input-radix 10.
22177 set input-radix 0xa
22181 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22182 leaves the input radix unchanged, no matter what it was, since
22183 @samp{10}, being without any leading or trailing signs of its base, is
22184 interpreted in the current radix. Thus, if the current radix is 16,
22185 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22188 @kindex set output-radix
22189 @item set output-radix @var{base}
22190 Set the default base for numeric display. Supported choices
22191 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22192 specified either unambiguously or using the current input radix.
22194 @kindex show input-radix
22195 @item show input-radix
22196 Display the current default base for numeric input.
22198 @kindex show output-radix
22199 @item show output-radix
22200 Display the current default base for numeric display.
22202 @item set radix @r{[}@var{base}@r{]}
22206 These commands set and show the default base for both input and output
22207 of numbers. @code{set radix} sets the radix of input and output to
22208 the same base; without an argument, it resets the radix back to its
22209 default value of 10.
22214 @section Configuring the Current ABI
22216 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22217 application automatically. However, sometimes you need to override its
22218 conclusions. Use these commands to manage @value{GDBN}'s view of the
22224 @cindex Newlib OS ABI and its influence on the longjmp handling
22226 One @value{GDBN} configuration can debug binaries for multiple operating
22227 system targets, either via remote debugging or native emulation.
22228 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22229 but you can override its conclusion using the @code{set osabi} command.
22230 One example where this is useful is in debugging of binaries which use
22231 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22232 not have the same identifying marks that the standard C library for your
22235 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22236 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22237 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22238 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22242 Show the OS ABI currently in use.
22245 With no argument, show the list of registered available OS ABI's.
22247 @item set osabi @var{abi}
22248 Set the current OS ABI to @var{abi}.
22251 @cindex float promotion
22253 Generally, the way that an argument of type @code{float} is passed to a
22254 function depends on whether the function is prototyped. For a prototyped
22255 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22256 according to the architecture's convention for @code{float}. For unprototyped
22257 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22258 @code{double} and then passed.
22260 Unfortunately, some forms of debug information do not reliably indicate whether
22261 a function is prototyped. If @value{GDBN} calls a function that is not marked
22262 as prototyped, it consults @kbd{set coerce-float-to-double}.
22265 @kindex set coerce-float-to-double
22266 @item set coerce-float-to-double
22267 @itemx set coerce-float-to-double on
22268 Arguments of type @code{float} will be promoted to @code{double} when passed
22269 to an unprototyped function. This is the default setting.
22271 @item set coerce-float-to-double off
22272 Arguments of type @code{float} will be passed directly to unprototyped
22275 @kindex show coerce-float-to-double
22276 @item show coerce-float-to-double
22277 Show the current setting of promoting @code{float} to @code{double}.
22281 @kindex show cp-abi
22282 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22283 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22284 used to build your application. @value{GDBN} only fully supports
22285 programs with a single C@t{++} ABI; if your program contains code using
22286 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22287 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22288 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22289 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22290 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22291 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22296 Show the C@t{++} ABI currently in use.
22299 With no argument, show the list of supported C@t{++} ABI's.
22301 @item set cp-abi @var{abi}
22302 @itemx set cp-abi auto
22303 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22307 @section Automatically loading associated files
22308 @cindex auto-loading
22310 @value{GDBN} sometimes reads files with commands and settings automatically,
22311 without being explicitly told so by the user. We call this feature
22312 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22313 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22314 results or introduce security risks (e.g., if the file comes from untrusted
22318 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22319 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22321 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22322 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22325 There are various kinds of files @value{GDBN} can automatically load.
22326 In addition to these files, @value{GDBN} supports auto-loading code written
22327 in various extension languages. @xref{Auto-loading extensions}.
22329 Note that loading of these associated files (including the local @file{.gdbinit}
22330 file) requires accordingly configured @code{auto-load safe-path}
22331 (@pxref{Auto-loading safe path}).
22333 For these reasons, @value{GDBN} includes commands and options to let you
22334 control when to auto-load files and which files should be auto-loaded.
22337 @anchor{set auto-load off}
22338 @kindex set auto-load off
22339 @item set auto-load off
22340 Globally disable loading of all auto-loaded files.
22341 You may want to use this command with the @samp{-iex} option
22342 (@pxref{Option -init-eval-command}) such as:
22344 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22347 Be aware that system init file (@pxref{System-wide configuration})
22348 and init files from your home directory (@pxref{Home Directory Init File})
22349 still get read (as they come from generally trusted directories).
22350 To prevent @value{GDBN} from auto-loading even those init files, use the
22351 @option{-nx} option (@pxref{Mode Options}), in addition to
22352 @code{set auto-load no}.
22354 @anchor{show auto-load}
22355 @kindex show auto-load
22356 @item show auto-load
22357 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22361 (gdb) show auto-load
22362 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22363 libthread-db: Auto-loading of inferior specific libthread_db is on.
22364 local-gdbinit: Auto-loading of .gdbinit script from current directory
22366 python-scripts: Auto-loading of Python scripts is on.
22367 safe-path: List of directories from which it is safe to auto-load files
22368 is $debugdir:$datadir/auto-load.
22369 scripts-directory: List of directories from which to load auto-loaded scripts
22370 is $debugdir:$datadir/auto-load.
22373 @anchor{info auto-load}
22374 @kindex info auto-load
22375 @item info auto-load
22376 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22380 (gdb) info auto-load
22383 Yes /home/user/gdb/gdb-gdb.gdb
22384 libthread-db: No auto-loaded libthread-db.
22385 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22389 Yes /home/user/gdb/gdb-gdb.py
22393 These are @value{GDBN} control commands for the auto-loading:
22395 @multitable @columnfractions .5 .5
22396 @item @xref{set auto-load off}.
22397 @tab Disable auto-loading globally.
22398 @item @xref{show auto-load}.
22399 @tab Show setting of all kinds of files.
22400 @item @xref{info auto-load}.
22401 @tab Show state of all kinds of files.
22402 @item @xref{set auto-load gdb-scripts}.
22403 @tab Control for @value{GDBN} command scripts.
22404 @item @xref{show auto-load gdb-scripts}.
22405 @tab Show setting of @value{GDBN} command scripts.
22406 @item @xref{info auto-load gdb-scripts}.
22407 @tab Show state of @value{GDBN} command scripts.
22408 @item @xref{set auto-load python-scripts}.
22409 @tab Control for @value{GDBN} Python scripts.
22410 @item @xref{show auto-load python-scripts}.
22411 @tab Show setting of @value{GDBN} Python scripts.
22412 @item @xref{info auto-load python-scripts}.
22413 @tab Show state of @value{GDBN} Python scripts.
22414 @item @xref{set auto-load guile-scripts}.
22415 @tab Control for @value{GDBN} Guile scripts.
22416 @item @xref{show auto-load guile-scripts}.
22417 @tab Show setting of @value{GDBN} Guile scripts.
22418 @item @xref{info auto-load guile-scripts}.
22419 @tab Show state of @value{GDBN} Guile scripts.
22420 @item @xref{set auto-load scripts-directory}.
22421 @tab Control for @value{GDBN} auto-loaded scripts location.
22422 @item @xref{show auto-load scripts-directory}.
22423 @tab Show @value{GDBN} auto-loaded scripts location.
22424 @item @xref{set auto-load local-gdbinit}.
22425 @tab Control for init file in the current directory.
22426 @item @xref{show auto-load local-gdbinit}.
22427 @tab Show setting of init file in the current directory.
22428 @item @xref{info auto-load local-gdbinit}.
22429 @tab Show state of init file in the current directory.
22430 @item @xref{set auto-load libthread-db}.
22431 @tab Control for thread debugging library.
22432 @item @xref{show auto-load libthread-db}.
22433 @tab Show setting of thread debugging library.
22434 @item @xref{info auto-load libthread-db}.
22435 @tab Show state of thread debugging library.
22436 @item @xref{set auto-load safe-path}.
22437 @tab Control directories trusted for automatic loading.
22438 @item @xref{show auto-load safe-path}.
22439 @tab Show directories trusted for automatic loading.
22440 @item @xref{add-auto-load-safe-path}.
22441 @tab Add directory trusted for automatic loading.
22444 @node Init File in the Current Directory
22445 @subsection Automatically loading init file in the current directory
22446 @cindex auto-loading init file in the current directory
22448 By default, @value{GDBN} reads and executes the canned sequences of commands
22449 from init file (if any) in the current working directory,
22450 see @ref{Init File in the Current Directory during Startup}.
22452 Note that loading of this local @file{.gdbinit} file also requires accordingly
22453 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22456 @anchor{set auto-load local-gdbinit}
22457 @kindex set auto-load local-gdbinit
22458 @item set auto-load local-gdbinit [on|off]
22459 Enable or disable the auto-loading of canned sequences of commands
22460 (@pxref{Sequences}) found in init file in the current directory.
22462 @anchor{show auto-load local-gdbinit}
22463 @kindex show auto-load local-gdbinit
22464 @item show auto-load local-gdbinit
22465 Show whether auto-loading of canned sequences of commands from init file in the
22466 current directory is enabled or disabled.
22468 @anchor{info auto-load local-gdbinit}
22469 @kindex info auto-load local-gdbinit
22470 @item info auto-load local-gdbinit
22471 Print whether canned sequences of commands from init file in the
22472 current directory have been auto-loaded.
22475 @node libthread_db.so.1 file
22476 @subsection Automatically loading thread debugging library
22477 @cindex auto-loading libthread_db.so.1
22479 This feature is currently present only on @sc{gnu}/Linux native hosts.
22481 @value{GDBN} reads in some cases thread debugging library from places specific
22482 to the inferior (@pxref{set libthread-db-search-path}).
22484 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22485 without checking this @samp{set auto-load libthread-db} switch as system
22486 libraries have to be trusted in general. In all other cases of
22487 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22488 auto-load libthread-db} is enabled before trying to open such thread debugging
22491 Note that loading of this debugging library also requires accordingly configured
22492 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22495 @anchor{set auto-load libthread-db}
22496 @kindex set auto-load libthread-db
22497 @item set auto-load libthread-db [on|off]
22498 Enable or disable the auto-loading of inferior specific thread debugging library.
22500 @anchor{show auto-load libthread-db}
22501 @kindex show auto-load libthread-db
22502 @item show auto-load libthread-db
22503 Show whether auto-loading of inferior specific thread debugging library is
22504 enabled or disabled.
22506 @anchor{info auto-load libthread-db}
22507 @kindex info auto-load libthread-db
22508 @item info auto-load libthread-db
22509 Print the list of all loaded inferior specific thread debugging libraries and
22510 for each such library print list of inferior @var{pid}s using it.
22513 @node Auto-loading safe path
22514 @subsection Security restriction for auto-loading
22515 @cindex auto-loading safe-path
22517 As the files of inferior can come from untrusted source (such as submitted by
22518 an application user) @value{GDBN} does not always load any files automatically.
22519 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22520 directories trusted for loading files not explicitly requested by user.
22521 Each directory can also be a shell wildcard pattern.
22523 If the path is not set properly you will see a warning and the file will not
22528 Reading symbols from /home/user/gdb/gdb...done.
22529 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22530 declined by your `auto-load safe-path' set
22531 to "$debugdir:$datadir/auto-load".
22532 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22533 declined by your `auto-load safe-path' set
22534 to "$debugdir:$datadir/auto-load".
22538 To instruct @value{GDBN} to go ahead and use the init files anyway,
22539 invoke @value{GDBN} like this:
22542 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22545 The list of trusted directories is controlled by the following commands:
22548 @anchor{set auto-load safe-path}
22549 @kindex set auto-load safe-path
22550 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22551 Set the list of directories (and their subdirectories) trusted for automatic
22552 loading and execution of scripts. You can also enter a specific trusted file.
22553 Each directory can also be a shell wildcard pattern; wildcards do not match
22554 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22555 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22556 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22557 its default value as specified during @value{GDBN} compilation.
22559 The list of directories uses path separator (@samp{:} on GNU and Unix
22560 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22561 to the @env{PATH} environment variable.
22563 @anchor{show auto-load safe-path}
22564 @kindex show auto-load safe-path
22565 @item show auto-load safe-path
22566 Show the list of directories trusted for automatic loading and execution of
22569 @anchor{add-auto-load-safe-path}
22570 @kindex add-auto-load-safe-path
22571 @item add-auto-load-safe-path
22572 Add an entry (or list of entries) the list of directories trusted for automatic
22573 loading and execution of scripts. Multiple entries may be delimited by the
22574 host platform path separator in use.
22577 This variable defaults to what @code{--with-auto-load-dir} has been configured
22578 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22579 substitution applies the same as for @ref{set auto-load scripts-directory}.
22580 The default @code{set auto-load safe-path} value can be also overriden by
22581 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22583 Setting this variable to @file{/} disables this security protection,
22584 corresponding @value{GDBN} configuration option is
22585 @option{--without-auto-load-safe-path}.
22586 This variable is supposed to be set to the system directories writable by the
22587 system superuser only. Users can add their source directories in init files in
22588 their home directories (@pxref{Home Directory Init File}). See also deprecated
22589 init file in the current directory
22590 (@pxref{Init File in the Current Directory during Startup}).
22592 To force @value{GDBN} to load the files it declined to load in the previous
22593 example, you could use one of the following ways:
22596 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22597 Specify this trusted directory (or a file) as additional component of the list.
22598 You have to specify also any existing directories displayed by
22599 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22601 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22602 Specify this directory as in the previous case but just for a single
22603 @value{GDBN} session.
22605 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22606 Disable auto-loading safety for a single @value{GDBN} session.
22607 This assumes all the files you debug during this @value{GDBN} session will come
22608 from trusted sources.
22610 @item @kbd{./configure --without-auto-load-safe-path}
22611 During compilation of @value{GDBN} you may disable any auto-loading safety.
22612 This assumes all the files you will ever debug with this @value{GDBN} come from
22616 On the other hand you can also explicitly forbid automatic files loading which
22617 also suppresses any such warning messages:
22620 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22621 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22623 @item @file{~/.gdbinit}: @samp{set auto-load no}
22624 Disable auto-loading globally for the user
22625 (@pxref{Home Directory Init File}). While it is improbable, you could also
22626 use system init file instead (@pxref{System-wide configuration}).
22629 This setting applies to the file names as entered by user. If no entry matches
22630 @value{GDBN} tries as a last resort to also resolve all the file names into
22631 their canonical form (typically resolving symbolic links) and compare the
22632 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22633 own before starting the comparison so a canonical form of directories is
22634 recommended to be entered.
22636 @node Auto-loading verbose mode
22637 @subsection Displaying files tried for auto-load
22638 @cindex auto-loading verbose mode
22640 For better visibility of all the file locations where you can place scripts to
22641 be auto-loaded with inferior --- or to protect yourself against accidental
22642 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22643 all the files attempted to be loaded. Both existing and non-existing files may
22646 For example the list of directories from which it is safe to auto-load files
22647 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22648 may not be too obvious while setting it up.
22651 (gdb) set debug auto-load on
22652 (gdb) file ~/src/t/true
22653 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22654 for objfile "/tmp/true".
22655 auto-load: Updating directories of "/usr:/opt".
22656 auto-load: Using directory "/usr".
22657 auto-load: Using directory "/opt".
22658 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22659 by your `auto-load safe-path' set to "/usr:/opt".
22663 @anchor{set debug auto-load}
22664 @kindex set debug auto-load
22665 @item set debug auto-load [on|off]
22666 Set whether to print the filenames attempted to be auto-loaded.
22668 @anchor{show debug auto-load}
22669 @kindex show debug auto-load
22670 @item show debug auto-load
22671 Show whether printing of the filenames attempted to be auto-loaded is turned
22675 @node Messages/Warnings
22676 @section Optional Warnings and Messages
22678 @cindex verbose operation
22679 @cindex optional warnings
22680 By default, @value{GDBN} is silent about its inner workings. If you are
22681 running on a slow machine, you may want to use the @code{set verbose}
22682 command. This makes @value{GDBN} tell you when it does a lengthy
22683 internal operation, so you will not think it has crashed.
22685 Currently, the messages controlled by @code{set verbose} are those
22686 which announce that the symbol table for a source file is being read;
22687 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22690 @kindex set verbose
22691 @item set verbose on
22692 Enables @value{GDBN} output of certain informational messages.
22694 @item set verbose off
22695 Disables @value{GDBN} output of certain informational messages.
22697 @kindex show verbose
22699 Displays whether @code{set verbose} is on or off.
22702 By default, if @value{GDBN} encounters bugs in the symbol table of an
22703 object file, it is silent; but if you are debugging a compiler, you may
22704 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22709 @kindex set complaints
22710 @item set complaints @var{limit}
22711 Permits @value{GDBN} to output @var{limit} complaints about each type of
22712 unusual symbols before becoming silent about the problem. Set
22713 @var{limit} to zero to suppress all complaints; set it to a large number
22714 to prevent complaints from being suppressed.
22716 @kindex show complaints
22717 @item show complaints
22718 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22722 @anchor{confirmation requests}
22723 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22724 lot of stupid questions to confirm certain commands. For example, if
22725 you try to run a program which is already running:
22729 The program being debugged has been started already.
22730 Start it from the beginning? (y or n)
22733 If you are willing to unflinchingly face the consequences of your own
22734 commands, you can disable this ``feature'':
22738 @kindex set confirm
22740 @cindex confirmation
22741 @cindex stupid questions
22742 @item set confirm off
22743 Disables confirmation requests. Note that running @value{GDBN} with
22744 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22745 automatically disables confirmation requests.
22747 @item set confirm on
22748 Enables confirmation requests (the default).
22750 @kindex show confirm
22752 Displays state of confirmation requests.
22756 @cindex command tracing
22757 If you need to debug user-defined commands or sourced files you may find it
22758 useful to enable @dfn{command tracing}. In this mode each command will be
22759 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22760 quantity denoting the call depth of each command.
22763 @kindex set trace-commands
22764 @cindex command scripts, debugging
22765 @item set trace-commands on
22766 Enable command tracing.
22767 @item set trace-commands off
22768 Disable command tracing.
22769 @item show trace-commands
22770 Display the current state of command tracing.
22773 @node Debugging Output
22774 @section Optional Messages about Internal Happenings
22775 @cindex optional debugging messages
22777 @value{GDBN} has commands that enable optional debugging messages from
22778 various @value{GDBN} subsystems; normally these commands are of
22779 interest to @value{GDBN} maintainers, or when reporting a bug. This
22780 section documents those commands.
22783 @kindex set exec-done-display
22784 @item set exec-done-display
22785 Turns on or off the notification of asynchronous commands'
22786 completion. When on, @value{GDBN} will print a message when an
22787 asynchronous command finishes its execution. The default is off.
22788 @kindex show exec-done-display
22789 @item show exec-done-display
22790 Displays the current setting of asynchronous command completion
22793 @cindex ARM AArch64
22794 @item set debug aarch64
22795 Turns on or off display of debugging messages related to ARM AArch64.
22796 The default is off.
22798 @item show debug aarch64
22799 Displays the current state of displaying debugging messages related to
22801 @cindex gdbarch debugging info
22802 @cindex architecture debugging info
22803 @item set debug arch
22804 Turns on or off display of gdbarch debugging info. The default is off
22805 @item show debug arch
22806 Displays the current state of displaying gdbarch debugging info.
22807 @item set debug aix-solib
22808 @cindex AIX shared library debugging
22809 Control display of debugging messages from the AIX shared library
22810 support module. The default is off.
22811 @item show debug aix-thread
22812 Show the current state of displaying AIX shared library debugging messages.
22813 @item set debug aix-thread
22814 @cindex AIX threads
22815 Display debugging messages about inner workings of the AIX thread
22817 @item show debug aix-thread
22818 Show the current state of AIX thread debugging info display.
22819 @item set debug check-physname
22821 Check the results of the ``physname'' computation. When reading DWARF
22822 debugging information for C@t{++}, @value{GDBN} attempts to compute
22823 each entity's name. @value{GDBN} can do this computation in two
22824 different ways, depending on exactly what information is present.
22825 When enabled, this setting causes @value{GDBN} to compute the names
22826 both ways and display any discrepancies.
22827 @item show debug check-physname
22828 Show the current state of ``physname'' checking.
22829 @item set debug coff-pe-read
22830 @cindex COFF/PE exported symbols
22831 Control display of debugging messages related to reading of COFF/PE
22832 exported symbols. The default is off.
22833 @item show debug coff-pe-read
22834 Displays the current state of displaying debugging messages related to
22835 reading of COFF/PE exported symbols.
22836 @item set debug dwarf2-die
22837 @cindex DWARF2 DIEs
22838 Dump DWARF2 DIEs after they are read in.
22839 The value is the number of nesting levels to print.
22840 A value of zero turns off the display.
22841 @item show debug dwarf2-die
22842 Show the current state of DWARF2 DIE debugging.
22843 @item set debug dwarf2-read
22844 @cindex DWARF2 Reading
22845 Turns on or off display of debugging messages related to reading
22846 DWARF debug info. The default is 0 (off).
22847 A value of 1 provides basic information.
22848 A value greater than 1 provides more verbose information.
22849 @item show debug dwarf2-read
22850 Show the current state of DWARF2 reader debugging.
22851 @item set debug displaced
22852 @cindex displaced stepping debugging info
22853 Turns on or off display of @value{GDBN} debugging info for the
22854 displaced stepping support. The default is off.
22855 @item show debug displaced
22856 Displays the current state of displaying @value{GDBN} debugging info
22857 related to displaced stepping.
22858 @item set debug event
22859 @cindex event debugging info
22860 Turns on or off display of @value{GDBN} event debugging info. The
22862 @item show debug event
22863 Displays the current state of displaying @value{GDBN} event debugging
22865 @item set debug expression
22866 @cindex expression debugging info
22867 Turns on or off display of debugging info about @value{GDBN}
22868 expression parsing. The default is off.
22869 @item show debug expression
22870 Displays the current state of displaying debugging info about
22871 @value{GDBN} expression parsing.
22872 @item set debug frame
22873 @cindex frame debugging info
22874 Turns on or off display of @value{GDBN} frame debugging info. The
22876 @item show debug frame
22877 Displays the current state of displaying @value{GDBN} frame debugging
22879 @item set debug gnu-nat
22880 @cindex @sc{gnu}/Hurd debug messages
22881 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22882 @item show debug gnu-nat
22883 Show the current state of @sc{gnu}/Hurd debugging messages.
22884 @item set debug infrun
22885 @cindex inferior debugging info
22886 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22887 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22888 for implementing operations such as single-stepping the inferior.
22889 @item show debug infrun
22890 Displays the current state of @value{GDBN} inferior debugging.
22891 @item set debug jit
22892 @cindex just-in-time compilation, debugging messages
22893 Turns on or off debugging messages from JIT debug support.
22894 @item show debug jit
22895 Displays the current state of @value{GDBN} JIT debugging.
22896 @item set debug lin-lwp
22897 @cindex @sc{gnu}/Linux LWP debug messages
22898 @cindex Linux lightweight processes
22899 Turns on or off debugging messages from the Linux LWP debug support.
22900 @item show debug lin-lwp
22901 Show the current state of Linux LWP debugging messages.
22902 @item set debug mach-o
22903 @cindex Mach-O symbols processing
22904 Control display of debugging messages related to Mach-O symbols
22905 processing. The default is off.
22906 @item show debug mach-o
22907 Displays the current state of displaying debugging messages related to
22908 reading of COFF/PE exported symbols.
22909 @item set debug notification
22910 @cindex remote async notification debugging info
22911 Turns on or off debugging messages about remote async notification.
22912 The default is off.
22913 @item show debug notification
22914 Displays the current state of remote async notification debugging messages.
22915 @item set debug observer
22916 @cindex observer debugging info
22917 Turns on or off display of @value{GDBN} observer debugging. This
22918 includes info such as the notification of observable events.
22919 @item show debug observer
22920 Displays the current state of observer debugging.
22921 @item set debug overload
22922 @cindex C@t{++} overload debugging info
22923 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22924 info. This includes info such as ranking of functions, etc. The default
22926 @item show debug overload
22927 Displays the current state of displaying @value{GDBN} C@t{++} overload
22929 @cindex expression parser, debugging info
22930 @cindex debug expression parser
22931 @item set debug parser
22932 Turns on or off the display of expression parser debugging output.
22933 Internally, this sets the @code{yydebug} variable in the expression
22934 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22935 details. The default is off.
22936 @item show debug parser
22937 Show the current state of expression parser debugging.
22938 @cindex packets, reporting on stdout
22939 @cindex serial connections, debugging
22940 @cindex debug remote protocol
22941 @cindex remote protocol debugging
22942 @cindex display remote packets
22943 @item set debug remote
22944 Turns on or off display of reports on all packets sent back and forth across
22945 the serial line to the remote machine. The info is printed on the
22946 @value{GDBN} standard output stream. The default is off.
22947 @item show debug remote
22948 Displays the state of display of remote packets.
22949 @item set debug serial
22950 Turns on or off display of @value{GDBN} serial debugging info. The
22952 @item show debug serial
22953 Displays the current state of displaying @value{GDBN} serial debugging
22955 @item set debug solib-frv
22956 @cindex FR-V shared-library debugging
22957 Turns on or off debugging messages for FR-V shared-library code.
22958 @item show debug solib-frv
22959 Display the current state of FR-V shared-library code debugging
22961 @item set debug symfile
22962 @cindex symbol file functions
22963 Turns on or off display of debugging messages related to symbol file functions.
22964 The default is off. @xref{Files}.
22965 @item show debug symfile
22966 Show the current state of symbol file debugging messages.
22967 @item set debug symtab-create
22968 @cindex symbol table creation
22969 Turns on or off display of debugging messages related to symbol table creation.
22970 The default is 0 (off).
22971 A value of 1 provides basic information.
22972 A value greater than 1 provides more verbose information.
22973 @item show debug symtab-create
22974 Show the current state of symbol table creation debugging.
22975 @item set debug target
22976 @cindex target debugging info
22977 Turns on or off display of @value{GDBN} target debugging info. This info
22978 includes what is going on at the target level of GDB, as it happens. The
22979 default is 0. Set it to 1 to track events, and to 2 to also track the
22980 value of large memory transfers. Changes to this flag do not take effect
22981 until the next time you connect to a target or use the @code{run} command.
22982 @item show debug target
22983 Displays the current state of displaying @value{GDBN} target debugging
22985 @item set debug timestamp
22986 @cindex timestampping debugging info
22987 Turns on or off display of timestamps with @value{GDBN} debugging info.
22988 When enabled, seconds and microseconds are displayed before each debugging
22990 @item show debug timestamp
22991 Displays the current state of displaying timestamps with @value{GDBN}
22993 @item set debug varobj
22994 @cindex variable object debugging info
22995 Turns on or off display of @value{GDBN} variable object debugging
22996 info. The default is off.
22997 @item show debug varobj
22998 Displays the current state of displaying @value{GDBN} variable object
23000 @item set debug xml
23001 @cindex XML parser debugging
23002 Turns on or off debugging messages for built-in XML parsers.
23003 @item show debug xml
23004 Displays the current state of XML debugging messages.
23007 @node Other Misc Settings
23008 @section Other Miscellaneous Settings
23009 @cindex miscellaneous settings
23012 @kindex set interactive-mode
23013 @item set interactive-mode
23014 If @code{on}, forces @value{GDBN} to assume that GDB was started
23015 in a terminal. In practice, this means that @value{GDBN} should wait
23016 for the user to answer queries generated by commands entered at
23017 the command prompt. If @code{off}, forces @value{GDBN} to operate
23018 in the opposite mode, and it uses the default answers to all queries.
23019 If @code{auto} (the default), @value{GDBN} tries to determine whether
23020 its standard input is a terminal, and works in interactive-mode if it
23021 is, non-interactively otherwise.
23023 In the vast majority of cases, the debugger should be able to guess
23024 correctly which mode should be used. But this setting can be useful
23025 in certain specific cases, such as running a MinGW @value{GDBN}
23026 inside a cygwin window.
23028 @kindex show interactive-mode
23029 @item show interactive-mode
23030 Displays whether the debugger is operating in interactive mode or not.
23033 @node Extending GDB
23034 @chapter Extending @value{GDBN}
23035 @cindex extending GDB
23037 @value{GDBN} provides several mechanisms for extension.
23038 @value{GDBN} also provides the ability to automatically load
23039 extensions when it reads a file for debugging. This allows the
23040 user to automatically customize @value{GDBN} for the program
23044 * Sequences:: Canned Sequences of @value{GDBN} Commands
23045 * Python:: Extending @value{GDBN} using Python
23046 * Guile:: Extending @value{GDBN} using Guile
23047 * Auto-loading extensions:: Automatically loading extensions
23048 * Multiple Extension Languages:: Working with multiple extension languages
23049 * Aliases:: Creating new spellings of existing commands
23052 To facilitate the use of extension languages, @value{GDBN} is capable
23053 of evaluating the contents of a file. When doing so, @value{GDBN}
23054 can recognize which extension language is being used by looking at
23055 the filename extension. Files with an unrecognized filename extension
23056 are always treated as a @value{GDBN} Command Files.
23057 @xref{Command Files,, Command files}.
23059 You can control how @value{GDBN} evaluates these files with the following
23063 @kindex set script-extension
23064 @kindex show script-extension
23065 @item set script-extension off
23066 All scripts are always evaluated as @value{GDBN} Command Files.
23068 @item set script-extension soft
23069 The debugger determines the scripting language based on filename
23070 extension. If this scripting language is supported, @value{GDBN}
23071 evaluates the script using that language. Otherwise, it evaluates
23072 the file as a @value{GDBN} Command File.
23074 @item set script-extension strict
23075 The debugger determines the scripting language based on filename
23076 extension, and evaluates the script using that language. If the
23077 language is not supported, then the evaluation fails.
23079 @item show script-extension
23080 Display the current value of the @code{script-extension} option.
23085 @section Canned Sequences of Commands
23087 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23088 Command Lists}), @value{GDBN} provides two ways to store sequences of
23089 commands for execution as a unit: user-defined commands and command
23093 * Define:: How to define your own commands
23094 * Hooks:: Hooks for user-defined commands
23095 * Command Files:: How to write scripts of commands to be stored in a file
23096 * Output:: Commands for controlled output
23097 * Auto-loading sequences:: Controlling auto-loaded command files
23101 @subsection User-defined Commands
23103 @cindex user-defined command
23104 @cindex arguments, to user-defined commands
23105 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23106 which you assign a new name as a command. This is done with the
23107 @code{define} command. User commands may accept up to 10 arguments
23108 separated by whitespace. Arguments are accessed within the user command
23109 via @code{$arg0@dots{}$arg9}. A trivial example:
23113 print $arg0 + $arg1 + $arg2
23118 To execute the command use:
23125 This defines the command @code{adder}, which prints the sum of
23126 its three arguments. Note the arguments are text substitutions, so they may
23127 reference variables, use complex expressions, or even perform inferior
23130 @cindex argument count in user-defined commands
23131 @cindex how many arguments (user-defined commands)
23132 In addition, @code{$argc} may be used to find out how many arguments have
23133 been passed. This expands to a number in the range 0@dots{}10.
23138 print $arg0 + $arg1
23141 print $arg0 + $arg1 + $arg2
23149 @item define @var{commandname}
23150 Define a command named @var{commandname}. If there is already a command
23151 by that name, you are asked to confirm that you want to redefine it.
23152 @var{commandname} may be a bare command name consisting of letters,
23153 numbers, dashes, and underscores. It may also start with any predefined
23154 prefix command. For example, @samp{define target my-target} creates
23155 a user-defined @samp{target my-target} command.
23157 The definition of the command is made up of other @value{GDBN} command lines,
23158 which are given following the @code{define} command. The end of these
23159 commands is marked by a line containing @code{end}.
23162 @kindex end@r{ (user-defined commands)}
23163 @item document @var{commandname}
23164 Document the user-defined command @var{commandname}, so that it can be
23165 accessed by @code{help}. The command @var{commandname} must already be
23166 defined. This command reads lines of documentation just as @code{define}
23167 reads the lines of the command definition, ending with @code{end}.
23168 After the @code{document} command is finished, @code{help} on command
23169 @var{commandname} displays the documentation you have written.
23171 You may use the @code{document} command again to change the
23172 documentation of a command. Redefining the command with @code{define}
23173 does not change the documentation.
23175 @kindex dont-repeat
23176 @cindex don't repeat command
23178 Used inside a user-defined command, this tells @value{GDBN} that this
23179 command should not be repeated when the user hits @key{RET}
23180 (@pxref{Command Syntax, repeat last command}).
23182 @kindex help user-defined
23183 @item help user-defined
23184 List all user-defined commands and all python commands defined in class
23185 COMAND_USER. The first line of the documentation or docstring is
23190 @itemx show user @var{commandname}
23191 Display the @value{GDBN} commands used to define @var{commandname} (but
23192 not its documentation). If no @var{commandname} is given, display the
23193 definitions for all user-defined commands.
23194 This does not work for user-defined python commands.
23196 @cindex infinite recursion in user-defined commands
23197 @kindex show max-user-call-depth
23198 @kindex set max-user-call-depth
23199 @item show max-user-call-depth
23200 @itemx set max-user-call-depth
23201 The value of @code{max-user-call-depth} controls how many recursion
23202 levels are allowed in user-defined commands before @value{GDBN} suspects an
23203 infinite recursion and aborts the command.
23204 This does not apply to user-defined python commands.
23207 In addition to the above commands, user-defined commands frequently
23208 use control flow commands, described in @ref{Command Files}.
23210 When user-defined commands are executed, the
23211 commands of the definition are not printed. An error in any command
23212 stops execution of the user-defined command.
23214 If used interactively, commands that would ask for confirmation proceed
23215 without asking when used inside a user-defined command. Many @value{GDBN}
23216 commands that normally print messages to say what they are doing omit the
23217 messages when used in a user-defined command.
23220 @subsection User-defined Command Hooks
23221 @cindex command hooks
23222 @cindex hooks, for commands
23223 @cindex hooks, pre-command
23226 You may define @dfn{hooks}, which are a special kind of user-defined
23227 command. Whenever you run the command @samp{foo}, if the user-defined
23228 command @samp{hook-foo} exists, it is executed (with no arguments)
23229 before that command.
23231 @cindex hooks, post-command
23233 A hook may also be defined which is run after the command you executed.
23234 Whenever you run the command @samp{foo}, if the user-defined command
23235 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23236 that command. Post-execution hooks may exist simultaneously with
23237 pre-execution hooks, for the same command.
23239 It is valid for a hook to call the command which it hooks. If this
23240 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23242 @c It would be nice if hookpost could be passed a parameter indicating
23243 @c if the command it hooks executed properly or not. FIXME!
23245 @kindex stop@r{, a pseudo-command}
23246 In addition, a pseudo-command, @samp{stop} exists. Defining
23247 (@samp{hook-stop}) makes the associated commands execute every time
23248 execution stops in your program: before breakpoint commands are run,
23249 displays are printed, or the stack frame is printed.
23251 For example, to ignore @code{SIGALRM} signals while
23252 single-stepping, but treat them normally during normal execution,
23257 handle SIGALRM nopass
23261 handle SIGALRM pass
23264 define hook-continue
23265 handle SIGALRM pass
23269 As a further example, to hook at the beginning and end of the @code{echo}
23270 command, and to add extra text to the beginning and end of the message,
23278 define hookpost-echo
23282 (@value{GDBP}) echo Hello World
23283 <<<---Hello World--->>>
23288 You can define a hook for any single-word command in @value{GDBN}, but
23289 not for command aliases; you should define a hook for the basic command
23290 name, e.g.@: @code{backtrace} rather than @code{bt}.
23291 @c FIXME! So how does Joe User discover whether a command is an alias
23293 You can hook a multi-word command by adding @code{hook-} or
23294 @code{hookpost-} to the last word of the command, e.g.@:
23295 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23297 If an error occurs during the execution of your hook, execution of
23298 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23299 (before the command that you actually typed had a chance to run).
23301 If you try to define a hook which does not match any known command, you
23302 get a warning from the @code{define} command.
23304 @node Command Files
23305 @subsection Command Files
23307 @cindex command files
23308 @cindex scripting commands
23309 A command file for @value{GDBN} is a text file made of lines that are
23310 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23311 also be included. An empty line in a command file does nothing; it
23312 does not mean to repeat the last command, as it would from the
23315 You can request the execution of a command file with the @code{source}
23316 command. Note that the @code{source} command is also used to evaluate
23317 scripts that are not Command Files. The exact behavior can be configured
23318 using the @code{script-extension} setting.
23319 @xref{Extending GDB,, Extending GDB}.
23323 @cindex execute commands from a file
23324 @item source [-s] [-v] @var{filename}
23325 Execute the command file @var{filename}.
23328 The lines in a command file are generally executed sequentially,
23329 unless the order of execution is changed by one of the
23330 @emph{flow-control commands} described below. The commands are not
23331 printed as they are executed. An error in any command terminates
23332 execution of the command file and control is returned to the console.
23334 @value{GDBN} first searches for @var{filename} in the current directory.
23335 If the file is not found there, and @var{filename} does not specify a
23336 directory, then @value{GDBN} also looks for the file on the source search path
23337 (specified with the @samp{directory} command);
23338 except that @file{$cdir} is not searched because the compilation directory
23339 is not relevant to scripts.
23341 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23342 on the search path even if @var{filename} specifies a directory.
23343 The search is done by appending @var{filename} to each element of the
23344 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23345 and the search path contains @file{/home/user} then @value{GDBN} will
23346 look for the script @file{/home/user/mylib/myscript}.
23347 The search is also done if @var{filename} is an absolute path.
23348 For example, if @var{filename} is @file{/tmp/myscript} and
23349 the search path contains @file{/home/user} then @value{GDBN} will
23350 look for the script @file{/home/user/tmp/myscript}.
23351 For DOS-like systems, if @var{filename} contains a drive specification,
23352 it is stripped before concatenation. For example, if @var{filename} is
23353 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23354 will look for the script @file{c:/tmp/myscript}.
23356 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23357 each command as it is executed. The option must be given before
23358 @var{filename}, and is interpreted as part of the filename anywhere else.
23360 Commands that would ask for confirmation if used interactively proceed
23361 without asking when used in a command file. Many @value{GDBN} commands that
23362 normally print messages to say what they are doing omit the messages
23363 when called from command files.
23365 @value{GDBN} also accepts command input from standard input. In this
23366 mode, normal output goes to standard output and error output goes to
23367 standard error. Errors in a command file supplied on standard input do
23368 not terminate execution of the command file---execution continues with
23372 gdb < cmds > log 2>&1
23375 (The syntax above will vary depending on the shell used.) This example
23376 will execute commands from the file @file{cmds}. All output and errors
23377 would be directed to @file{log}.
23379 Since commands stored on command files tend to be more general than
23380 commands typed interactively, they frequently need to deal with
23381 complicated situations, such as different or unexpected values of
23382 variables and symbols, changes in how the program being debugged is
23383 built, etc. @value{GDBN} provides a set of flow-control commands to
23384 deal with these complexities. Using these commands, you can write
23385 complex scripts that loop over data structures, execute commands
23386 conditionally, etc.
23393 This command allows to include in your script conditionally executed
23394 commands. The @code{if} command takes a single argument, which is an
23395 expression to evaluate. It is followed by a series of commands that
23396 are executed only if the expression is true (its value is nonzero).
23397 There can then optionally be an @code{else} line, followed by a series
23398 of commands that are only executed if the expression was false. The
23399 end of the list is marked by a line containing @code{end}.
23403 This command allows to write loops. Its syntax is similar to
23404 @code{if}: the command takes a single argument, which is an expression
23405 to evaluate, and must be followed by the commands to execute, one per
23406 line, terminated by an @code{end}. These commands are called the
23407 @dfn{body} of the loop. The commands in the body of @code{while} are
23408 executed repeatedly as long as the expression evaluates to true.
23412 This command exits the @code{while} loop in whose body it is included.
23413 Execution of the script continues after that @code{while}s @code{end}
23416 @kindex loop_continue
23417 @item loop_continue
23418 This command skips the execution of the rest of the body of commands
23419 in the @code{while} loop in whose body it is included. Execution
23420 branches to the beginning of the @code{while} loop, where it evaluates
23421 the controlling expression.
23423 @kindex end@r{ (if/else/while commands)}
23425 Terminate the block of commands that are the body of @code{if},
23426 @code{else}, or @code{while} flow-control commands.
23431 @subsection Commands for Controlled Output
23433 During the execution of a command file or a user-defined command, normal
23434 @value{GDBN} output is suppressed; the only output that appears is what is
23435 explicitly printed by the commands in the definition. This section
23436 describes three commands useful for generating exactly the output you
23441 @item echo @var{text}
23442 @c I do not consider backslash-space a standard C escape sequence
23443 @c because it is not in ANSI.
23444 Print @var{text}. Nonprinting characters can be included in
23445 @var{text} using C escape sequences, such as @samp{\n} to print a
23446 newline. @strong{No newline is printed unless you specify one.}
23447 In addition to the standard C escape sequences, a backslash followed
23448 by a space stands for a space. This is useful for displaying a
23449 string with spaces at the beginning or the end, since leading and
23450 trailing spaces are otherwise trimmed from all arguments.
23451 To print @samp{@w{ }and foo =@w{ }}, use the command
23452 @samp{echo \@w{ }and foo = \@w{ }}.
23454 A backslash at the end of @var{text} can be used, as in C, to continue
23455 the command onto subsequent lines. For example,
23458 echo This is some text\n\
23459 which is continued\n\
23460 onto several lines.\n
23463 produces the same output as
23466 echo This is some text\n
23467 echo which is continued\n
23468 echo onto several lines.\n
23472 @item output @var{expression}
23473 Print the value of @var{expression} and nothing but that value: no
23474 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23475 value history either. @xref{Expressions, ,Expressions}, for more information
23478 @item output/@var{fmt} @var{expression}
23479 Print the value of @var{expression} in format @var{fmt}. You can use
23480 the same formats as for @code{print}. @xref{Output Formats,,Output
23481 Formats}, for more information.
23484 @item printf @var{template}, @var{expressions}@dots{}
23485 Print the values of one or more @var{expressions} under the control of
23486 the string @var{template}. To print several values, make
23487 @var{expressions} be a comma-separated list of individual expressions,
23488 which may be either numbers or pointers. Their values are printed as
23489 specified by @var{template}, exactly as a C program would do by
23490 executing the code below:
23493 printf (@var{template}, @var{expressions}@dots{});
23496 As in @code{C} @code{printf}, ordinary characters in @var{template}
23497 are printed verbatim, while @dfn{conversion specification} introduced
23498 by the @samp{%} character cause subsequent @var{expressions} to be
23499 evaluated, their values converted and formatted according to type and
23500 style information encoded in the conversion specifications, and then
23503 For example, you can print two values in hex like this:
23506 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23509 @code{printf} supports all the standard @code{C} conversion
23510 specifications, including the flags and modifiers between the @samp{%}
23511 character and the conversion letter, with the following exceptions:
23515 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23518 The modifier @samp{*} is not supported for specifying precision or
23522 The @samp{'} flag (for separation of digits into groups according to
23523 @code{LC_NUMERIC'}) is not supported.
23526 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23530 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23533 The conversion letters @samp{a} and @samp{A} are not supported.
23537 Note that the @samp{ll} type modifier is supported only if the
23538 underlying @code{C} implementation used to build @value{GDBN} supports
23539 the @code{long long int} type, and the @samp{L} type modifier is
23540 supported only if @code{long double} type is available.
23542 As in @code{C}, @code{printf} supports simple backslash-escape
23543 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23544 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23545 single character. Octal and hexadecimal escape sequences are not
23548 Additionally, @code{printf} supports conversion specifications for DFP
23549 (@dfn{Decimal Floating Point}) types using the following length modifiers
23550 together with a floating point specifier.
23555 @samp{H} for printing @code{Decimal32} types.
23558 @samp{D} for printing @code{Decimal64} types.
23561 @samp{DD} for printing @code{Decimal128} types.
23564 If the underlying @code{C} implementation used to build @value{GDBN} has
23565 support for the three length modifiers for DFP types, other modifiers
23566 such as width and precision will also be available for @value{GDBN} to use.
23568 In case there is no such @code{C} support, no additional modifiers will be
23569 available and the value will be printed in the standard way.
23571 Here's an example of printing DFP types using the above conversion letters:
23573 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23577 @item eval @var{template}, @var{expressions}@dots{}
23578 Convert the values of one or more @var{expressions} under the control of
23579 the string @var{template} to a command line, and call it.
23583 @node Auto-loading sequences
23584 @subsection Controlling auto-loading native @value{GDBN} scripts
23585 @cindex native script auto-loading
23587 When a new object file is read (for example, due to the @code{file}
23588 command, or because the inferior has loaded a shared library),
23589 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23590 @xref{Auto-loading extensions}.
23592 Auto-loading can be enabled or disabled,
23593 and the list of auto-loaded scripts can be printed.
23596 @anchor{set auto-load gdb-scripts}
23597 @kindex set auto-load gdb-scripts
23598 @item set auto-load gdb-scripts [on|off]
23599 Enable or disable the auto-loading of canned sequences of commands scripts.
23601 @anchor{show auto-load gdb-scripts}
23602 @kindex show auto-load gdb-scripts
23603 @item show auto-load gdb-scripts
23604 Show whether auto-loading of canned sequences of commands scripts is enabled or
23607 @anchor{info auto-load gdb-scripts}
23608 @kindex info auto-load gdb-scripts
23609 @cindex print list of auto-loaded canned sequences of commands scripts
23610 @item info auto-load gdb-scripts [@var{regexp}]
23611 Print the list of all canned sequences of commands scripts that @value{GDBN}
23615 If @var{regexp} is supplied only canned sequences of commands scripts with
23616 matching names are printed.
23618 @c Python docs live in a separate file.
23619 @include python.texi
23621 @c Guile docs live in a separate file.
23622 @include guile.texi
23624 @node Auto-loading extensions
23625 @section Auto-loading extensions
23626 @cindex auto-loading extensions
23628 @value{GDBN} provides two mechanisms for automatically loading extensions
23629 when a new object file is read (for example, due to the @code{file}
23630 command, or because the inferior has loaded a shared library):
23631 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
23632 section of modern file formats like ELF.
23635 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
23636 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
23637 * Which flavor to choose?::
23640 The auto-loading feature is useful for supplying application-specific
23641 debugging commands and features.
23643 Auto-loading can be enabled or disabled,
23644 and the list of auto-loaded scripts can be printed.
23645 See the @samp{auto-loading} section of each extension language
23646 for more information.
23647 For @value{GDBN} command files see @ref{Auto-loading sequences}.
23648 For Python files see @ref{Python Auto-loading}.
23650 Note that loading of this script file also requires accordingly configured
23651 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23653 @node objfile-gdbdotext file
23654 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
23655 @cindex @file{@var{objfile}-gdb.gdb}
23656 @cindex @file{@var{objfile}-gdb.py}
23657 @cindex @file{@var{objfile}-gdb.scm}
23659 When a new object file is read, @value{GDBN} looks for a file named
23660 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
23661 where @var{objfile} is the object file's name and
23662 where @var{ext} is the file extension for the extension language:
23665 @item @file{@var{objfile}-gdb.gdb}
23666 GDB's own command language
23667 @item @file{@var{objfile}-gdb.py}
23669 @item @file{@var{objfile}-gdb.scm}
23673 @var{script-name} is formed by ensuring that the file name of @var{objfile}
23674 is absolute, following all symlinks, and resolving @code{.} and @code{..}
23675 components, and appending the @file{-gdb.@var{ext}} suffix.
23676 If this file exists and is readable, @value{GDBN} will evaluate it as a
23677 script in the specified extension language.
23679 If this file does not exist, then @value{GDBN} will look for
23680 @var{script-name} file in all of the directories as specified below.
23682 Note that loading of these files requires an accordingly configured
23683 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23685 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
23686 scripts normally according to its @file{.exe} filename. But if no scripts are
23687 found @value{GDBN} also tries script filenames matching the object file without
23688 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
23689 is attempted on any platform. This makes the script filenames compatible
23690 between Unix and MS-Windows hosts.
23693 @anchor{set auto-load scripts-directory}
23694 @kindex set auto-load scripts-directory
23695 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
23696 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
23697 may be delimited by the host platform path separator in use
23698 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
23700 Each entry here needs to be covered also by the security setting
23701 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
23703 @anchor{with-auto-load-dir}
23704 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
23705 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
23706 configuration option @option{--with-auto-load-dir}.
23708 Any reference to @file{$debugdir} will get replaced by
23709 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
23710 reference to @file{$datadir} will get replaced by @var{data-directory} which is
23711 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
23712 @file{$datadir} must be placed as a directory component --- either alone or
23713 delimited by @file{/} or @file{\} directory separators, depending on the host
23716 The list of directories uses path separator (@samp{:} on GNU and Unix
23717 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23718 to the @env{PATH} environment variable.
23720 @anchor{show auto-load scripts-directory}
23721 @kindex show auto-load scripts-directory
23722 @item show auto-load scripts-directory
23723 Show @value{GDBN} auto-loaded scripts location.
23726 @value{GDBN} does not track which files it has already auto-loaded this way.
23727 @value{GDBN} will load the associated script every time the corresponding
23728 @var{objfile} is opened.
23729 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
23730 is evaluated more than once.
23732 @node dotdebug_gdb_scripts section
23733 @subsection The @code{.debug_gdb_scripts} section
23734 @cindex @code{.debug_gdb_scripts} section
23736 For systems using file formats like ELF and COFF,
23737 when @value{GDBN} loads a new object file
23738 it will look for a special section named @code{.debug_gdb_scripts}.
23739 If this section exists, its contents is a list of NUL-terminated names
23740 of scripts to load. Each entry begins with a non-NULL prefix byte that
23741 specifies the kind of entry, typically the extension language.
23743 @value{GDBN} will look for each specified script file first in the
23744 current directory and then along the source search path
23745 (@pxref{Source Path, ,Specifying Source Directories}),
23746 except that @file{$cdir} is not searched, since the compilation
23747 directory is not relevant to scripts.
23749 Entries can be placed in section @code{.debug_gdb_scripts} with,
23750 for example, this GCC macro for Python scripts.
23753 /* Note: The "MS" section flags are to remove duplicates. */
23754 #define DEFINE_GDB_PY_SCRIPT(script_name) \
23756 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23757 .byte 1 /* Python */\n\
23758 .asciz \"" script_name "\"\n\
23764 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
23765 Then one can reference the macro in a header or source file like this:
23768 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
23771 The script name may include directories if desired.
23773 Note that loading of this script file also requires accordingly configured
23774 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23776 If the macro invocation is put in a header, any application or library
23777 using this header will get a reference to the specified script,
23778 and with the use of @code{"MS"} attributes on the section, the linker
23779 will remove duplicates.
23781 @node Which flavor to choose?
23782 @subsection Which flavor to choose?
23784 Given the multiple ways of auto-loading extensions, it might not always
23785 be clear which one to choose. This section provides some guidance.
23788 Benefits of the @file{-gdb.@var{ext}} way:
23792 Can be used with file formats that don't support multiple sections.
23795 Ease of finding scripts for public libraries.
23797 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23798 in the source search path.
23799 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23800 isn't a source directory in which to find the script.
23803 Doesn't require source code additions.
23807 Benefits of the @code{.debug_gdb_scripts} way:
23811 Works with static linking.
23813 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
23814 trigger their loading. When an application is statically linked the only
23815 objfile available is the executable, and it is cumbersome to attach all the
23816 scripts from all the input libraries to the executable's
23817 @file{-gdb.@var{ext}} script.
23820 Works with classes that are entirely inlined.
23822 Some classes can be entirely inlined, and thus there may not be an associated
23823 shared library to attach a @file{-gdb.@var{ext}} script to.
23826 Scripts needn't be copied out of the source tree.
23828 In some circumstances, apps can be built out of large collections of internal
23829 libraries, and the build infrastructure necessary to install the
23830 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
23831 cumbersome. It may be easier to specify the scripts in the
23832 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23833 top of the source tree to the source search path.
23836 @node Multiple Extension Languages
23837 @section Multiple Extension Languages
23839 The Guile and Python extension languages do not share any state,
23840 and generally do not interfere with each other.
23841 There are some things to be aware of, however.
23843 @subsection Python comes first
23845 Python was @value{GDBN}'s first extension language, and to avoid breaking
23846 existing behaviour Python comes first. This is generally solved by the
23847 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
23848 extension languages, and when it makes a call to an extension language,
23849 (say to pretty-print a value), it tries each in turn until an extension
23850 language indicates it has performed the request (e.g., has returned the
23851 pretty-printed form of a value).
23852 This extends to errors while performing such requests: If an error happens
23853 while, for example, trying to pretty-print an object then the error is
23854 reported and any following extension languages are not tried.
23857 @section Creating new spellings of existing commands
23858 @cindex aliases for commands
23860 It is often useful to define alternate spellings of existing commands.
23861 For example, if a new @value{GDBN} command defined in Python has
23862 a long name to type, it is handy to have an abbreviated version of it
23863 that involves less typing.
23865 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
23866 of the @samp{step} command even though it is otherwise an ambiguous
23867 abbreviation of other commands like @samp{set} and @samp{show}.
23869 Aliases are also used to provide shortened or more common versions
23870 of multi-word commands. For example, @value{GDBN} provides the
23871 @samp{tty} alias of the @samp{set inferior-tty} command.
23873 You can define a new alias with the @samp{alias} command.
23878 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
23882 @var{ALIAS} specifies the name of the new alias.
23883 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
23886 @var{COMMAND} specifies the name of an existing command
23887 that is being aliased.
23889 The @samp{-a} option specifies that the new alias is an abbreviation
23890 of the command. Abbreviations are not shown in command
23891 lists displayed by the @samp{help} command.
23893 The @samp{--} option specifies the end of options,
23894 and is useful when @var{ALIAS} begins with a dash.
23896 Here is a simple example showing how to make an abbreviation
23897 of a command so that there is less to type.
23898 Suppose you were tired of typing @samp{disas}, the current
23899 shortest unambiguous abbreviation of the @samp{disassemble} command
23900 and you wanted an even shorter version named @samp{di}.
23901 The following will accomplish this.
23904 (gdb) alias -a di = disas
23907 Note that aliases are different from user-defined commands.
23908 With a user-defined command, you also need to write documentation
23909 for it with the @samp{document} command.
23910 An alias automatically picks up the documentation of the existing command.
23912 Here is an example where we make @samp{elms} an abbreviation of
23913 @samp{elements} in the @samp{set print elements} command.
23914 This is to show that you can make an abbreviation of any part
23918 (gdb) alias -a set print elms = set print elements
23919 (gdb) alias -a show print elms = show print elements
23920 (gdb) set p elms 20
23922 Limit on string chars or array elements to print is 200.
23925 Note that if you are defining an alias of a @samp{set} command,
23926 and you want to have an alias for the corresponding @samp{show}
23927 command, then you need to define the latter separately.
23929 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
23930 @var{ALIAS}, just as they are normally.
23933 (gdb) alias -a set pr elms = set p ele
23936 Finally, here is an example showing the creation of a one word
23937 alias for a more complex command.
23938 This creates alias @samp{spe} of the command @samp{set print elements}.
23941 (gdb) alias spe = set print elements
23946 @chapter Command Interpreters
23947 @cindex command interpreters
23949 @value{GDBN} supports multiple command interpreters, and some command
23950 infrastructure to allow users or user interface writers to switch
23951 between interpreters or run commands in other interpreters.
23953 @value{GDBN} currently supports two command interpreters, the console
23954 interpreter (sometimes called the command-line interpreter or @sc{cli})
23955 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23956 describes both of these interfaces in great detail.
23958 By default, @value{GDBN} will start with the console interpreter.
23959 However, the user may choose to start @value{GDBN} with another
23960 interpreter by specifying the @option{-i} or @option{--interpreter}
23961 startup options. Defined interpreters include:
23965 @cindex console interpreter
23966 The traditional console or command-line interpreter. This is the most often
23967 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23968 @value{GDBN} will use this interpreter.
23971 @cindex mi interpreter
23972 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23973 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23974 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23978 @cindex mi2 interpreter
23979 The current @sc{gdb/mi} interface.
23982 @cindex mi1 interpreter
23983 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23987 @cindex invoke another interpreter
23988 The interpreter being used by @value{GDBN} may not be dynamically
23989 switched at runtime. Although possible, this could lead to a very
23990 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23991 enters the command "interpreter-set console" in a console view,
23992 @value{GDBN} would switch to using the console interpreter, rendering
23993 the IDE inoperable!
23995 @kindex interpreter-exec
23996 Although you may only choose a single interpreter at startup, you may execute
23997 commands in any interpreter from the current interpreter using the appropriate
23998 command. If you are running the console interpreter, simply use the
23999 @code{interpreter-exec} command:
24002 interpreter-exec mi "-data-list-register-names"
24005 @sc{gdb/mi} has a similar command, although it is only available in versions of
24006 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24009 @chapter @value{GDBN} Text User Interface
24011 @cindex Text User Interface
24014 * TUI Overview:: TUI overview
24015 * TUI Keys:: TUI key bindings
24016 * TUI Single Key Mode:: TUI single key mode
24017 * TUI Commands:: TUI-specific commands
24018 * TUI Configuration:: TUI configuration variables
24021 The @value{GDBN} Text User Interface (TUI) is a terminal
24022 interface which uses the @code{curses} library to show the source
24023 file, the assembly output, the program registers and @value{GDBN}
24024 commands in separate text windows. The TUI mode is supported only
24025 on platforms where a suitable version of the @code{curses} library
24028 The TUI mode is enabled by default when you invoke @value{GDBN} as
24029 @samp{@value{GDBP} -tui}.
24030 You can also switch in and out of TUI mode while @value{GDBN} runs by
24031 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24032 @xref{TUI Keys, ,TUI Key Bindings}.
24035 @section TUI Overview
24037 In TUI mode, @value{GDBN} can display several text windows:
24041 This window is the @value{GDBN} command window with the @value{GDBN}
24042 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24043 managed using readline.
24046 The source window shows the source file of the program. The current
24047 line and active breakpoints are displayed in this window.
24050 The assembly window shows the disassembly output of the program.
24053 This window shows the processor registers. Registers are highlighted
24054 when their values change.
24057 The source and assembly windows show the current program position
24058 by highlighting the current line and marking it with a @samp{>} marker.
24059 Breakpoints are indicated with two markers. The first marker
24060 indicates the breakpoint type:
24064 Breakpoint which was hit at least once.
24067 Breakpoint which was never hit.
24070 Hardware breakpoint which was hit at least once.
24073 Hardware breakpoint which was never hit.
24076 The second marker indicates whether the breakpoint is enabled or not:
24080 Breakpoint is enabled.
24083 Breakpoint is disabled.
24086 The source, assembly and register windows are updated when the current
24087 thread changes, when the frame changes, or when the program counter
24090 These windows are not all visible at the same time. The command
24091 window is always visible. The others can be arranged in several
24102 source and assembly,
24105 source and registers, or
24108 assembly and registers.
24111 A status line above the command window shows the following information:
24115 Indicates the current @value{GDBN} target.
24116 (@pxref{Targets, ,Specifying a Debugging Target}).
24119 Gives the current process or thread number.
24120 When no process is being debugged, this field is set to @code{No process}.
24123 Gives the current function name for the selected frame.
24124 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24125 When there is no symbol corresponding to the current program counter,
24126 the string @code{??} is displayed.
24129 Indicates the current line number for the selected frame.
24130 When the current line number is not known, the string @code{??} is displayed.
24133 Indicates the current program counter address.
24137 @section TUI Key Bindings
24138 @cindex TUI key bindings
24140 The TUI installs several key bindings in the readline keymaps
24141 @ifset SYSTEM_READLINE
24142 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24144 @ifclear SYSTEM_READLINE
24145 (@pxref{Command Line Editing}).
24147 The following key bindings are installed for both TUI mode and the
24148 @value{GDBN} standard mode.
24157 Enter or leave the TUI mode. When leaving the TUI mode,
24158 the curses window management stops and @value{GDBN} operates using
24159 its standard mode, writing on the terminal directly. When reentering
24160 the TUI mode, control is given back to the curses windows.
24161 The screen is then refreshed.
24165 Use a TUI layout with only one window. The layout will
24166 either be @samp{source} or @samp{assembly}. When the TUI mode
24167 is not active, it will switch to the TUI mode.
24169 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24173 Use a TUI layout with at least two windows. When the current
24174 layout already has two windows, the next layout with two windows is used.
24175 When a new layout is chosen, one window will always be common to the
24176 previous layout and the new one.
24178 Think of it as the Emacs @kbd{C-x 2} binding.
24182 Change the active window. The TUI associates several key bindings
24183 (like scrolling and arrow keys) with the active window. This command
24184 gives the focus to the next TUI window.
24186 Think of it as the Emacs @kbd{C-x o} binding.
24190 Switch in and out of the TUI SingleKey mode that binds single
24191 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24194 The following key bindings only work in the TUI mode:
24199 Scroll the active window one page up.
24203 Scroll the active window one page down.
24207 Scroll the active window one line up.
24211 Scroll the active window one line down.
24215 Scroll the active window one column left.
24219 Scroll the active window one column right.
24223 Refresh the screen.
24226 Because the arrow keys scroll the active window in the TUI mode, they
24227 are not available for their normal use by readline unless the command
24228 window has the focus. When another window is active, you must use
24229 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24230 and @kbd{C-f} to control the command window.
24232 @node TUI Single Key Mode
24233 @section TUI Single Key Mode
24234 @cindex TUI single key mode
24236 The TUI also provides a @dfn{SingleKey} mode, which binds several
24237 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24238 switch into this mode, where the following key bindings are used:
24241 @kindex c @r{(SingleKey TUI key)}
24245 @kindex d @r{(SingleKey TUI key)}
24249 @kindex f @r{(SingleKey TUI key)}
24253 @kindex n @r{(SingleKey TUI key)}
24257 @kindex q @r{(SingleKey TUI key)}
24259 exit the SingleKey mode.
24261 @kindex r @r{(SingleKey TUI key)}
24265 @kindex s @r{(SingleKey TUI key)}
24269 @kindex u @r{(SingleKey TUI key)}
24273 @kindex v @r{(SingleKey TUI key)}
24277 @kindex w @r{(SingleKey TUI key)}
24282 Other keys temporarily switch to the @value{GDBN} command prompt.
24283 The key that was pressed is inserted in the editing buffer so that
24284 it is possible to type most @value{GDBN} commands without interaction
24285 with the TUI SingleKey mode. Once the command is entered the TUI
24286 SingleKey mode is restored. The only way to permanently leave
24287 this mode is by typing @kbd{q} or @kbd{C-x s}.
24291 @section TUI-specific Commands
24292 @cindex TUI commands
24294 The TUI has specific commands to control the text windows.
24295 These commands are always available, even when @value{GDBN} is not in
24296 the TUI mode. When @value{GDBN} is in the standard mode, most
24297 of these commands will automatically switch to the TUI mode.
24299 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24300 terminal, or @value{GDBN} has been started with the machine interface
24301 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24302 these commands will fail with an error, because it would not be
24303 possible or desirable to enable curses window management.
24308 List and give the size of all displayed windows.
24312 Display the next layout.
24315 Display the previous layout.
24318 Display the source window only.
24321 Display the assembly window only.
24324 Display the source and assembly window.
24327 Display the register window together with the source or assembly window.
24331 Make the next window active for scrolling.
24334 Make the previous window active for scrolling.
24337 Make the source window active for scrolling.
24340 Make the assembly window active for scrolling.
24343 Make the register window active for scrolling.
24346 Make the command window active for scrolling.
24350 Refresh the screen. This is similar to typing @kbd{C-L}.
24352 @item tui reg float
24354 Show the floating point registers in the register window.
24356 @item tui reg general
24357 Show the general registers in the register window.
24360 Show the next register group. The list of register groups as well as
24361 their order is target specific. The predefined register groups are the
24362 following: @code{general}, @code{float}, @code{system}, @code{vector},
24363 @code{all}, @code{save}, @code{restore}.
24365 @item tui reg system
24366 Show the system registers in the register window.
24370 Update the source window and the current execution point.
24372 @item winheight @var{name} +@var{count}
24373 @itemx winheight @var{name} -@var{count}
24375 Change the height of the window @var{name} by @var{count}
24376 lines. Positive counts increase the height, while negative counts
24379 @item tabset @var{nchars}
24381 Set the width of tab stops to be @var{nchars} characters.
24384 @node TUI Configuration
24385 @section TUI Configuration Variables
24386 @cindex TUI configuration variables
24388 Several configuration variables control the appearance of TUI windows.
24391 @item set tui border-kind @var{kind}
24392 @kindex set tui border-kind
24393 Select the border appearance for the source, assembly and register windows.
24394 The possible values are the following:
24397 Use a space character to draw the border.
24400 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24403 Use the Alternate Character Set to draw the border. The border is
24404 drawn using character line graphics if the terminal supports them.
24407 @item set tui border-mode @var{mode}
24408 @kindex set tui border-mode
24409 @itemx set tui active-border-mode @var{mode}
24410 @kindex set tui active-border-mode
24411 Select the display attributes for the borders of the inactive windows
24412 or the active window. The @var{mode} can be one of the following:
24415 Use normal attributes to display the border.
24421 Use reverse video mode.
24424 Use half bright mode.
24426 @item half-standout
24427 Use half bright and standout mode.
24430 Use extra bright or bold mode.
24432 @item bold-standout
24433 Use extra bright or bold and standout mode.
24438 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24441 @cindex @sc{gnu} Emacs
24442 A special interface allows you to use @sc{gnu} Emacs to view (and
24443 edit) the source files for the program you are debugging with
24446 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24447 executable file you want to debug as an argument. This command starts
24448 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24449 created Emacs buffer.
24450 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24452 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24457 All ``terminal'' input and output goes through an Emacs buffer, called
24460 This applies both to @value{GDBN} commands and their output, and to the input
24461 and output done by the program you are debugging.
24463 This is useful because it means that you can copy the text of previous
24464 commands and input them again; you can even use parts of the output
24467 All the facilities of Emacs' Shell mode are available for interacting
24468 with your program. In particular, you can send signals the usual
24469 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24473 @value{GDBN} displays source code through Emacs.
24475 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24476 source file for that frame and puts an arrow (@samp{=>}) at the
24477 left margin of the current line. Emacs uses a separate buffer for
24478 source display, and splits the screen to show both your @value{GDBN} session
24481 Explicit @value{GDBN} @code{list} or search commands still produce output as
24482 usual, but you probably have no reason to use them from Emacs.
24485 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24486 a graphical mode, enabled by default, which provides further buffers
24487 that can control the execution and describe the state of your program.
24488 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24490 If you specify an absolute file name when prompted for the @kbd{M-x
24491 gdb} argument, then Emacs sets your current working directory to where
24492 your program resides. If you only specify the file name, then Emacs
24493 sets your current working directory to the directory associated
24494 with the previous buffer. In this case, @value{GDBN} may find your
24495 program by searching your environment's @code{PATH} variable, but on
24496 some operating systems it might not find the source. So, although the
24497 @value{GDBN} input and output session proceeds normally, the auxiliary
24498 buffer does not display the current source and line of execution.
24500 The initial working directory of @value{GDBN} is printed on the top
24501 line of the GUD buffer and this serves as a default for the commands
24502 that specify files for @value{GDBN} to operate on. @xref{Files,
24503 ,Commands to Specify Files}.
24505 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24506 need to call @value{GDBN} by a different name (for example, if you
24507 keep several configurations around, with different names) you can
24508 customize the Emacs variable @code{gud-gdb-command-name} to run the
24511 In the GUD buffer, you can use these special Emacs commands in
24512 addition to the standard Shell mode commands:
24516 Describe the features of Emacs' GUD Mode.
24519 Execute to another source line, like the @value{GDBN} @code{step} command; also
24520 update the display window to show the current file and location.
24523 Execute to next source line in this function, skipping all function
24524 calls, like the @value{GDBN} @code{next} command. Then update the display window
24525 to show the current file and location.
24528 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24529 display window accordingly.
24532 Execute until exit from the selected stack frame, like the @value{GDBN}
24533 @code{finish} command.
24536 Continue execution of your program, like the @value{GDBN} @code{continue}
24540 Go up the number of frames indicated by the numeric argument
24541 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24542 like the @value{GDBN} @code{up} command.
24545 Go down the number of frames indicated by the numeric argument, like the
24546 @value{GDBN} @code{down} command.
24549 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24550 tells @value{GDBN} to set a breakpoint on the source line point is on.
24552 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24553 separate frame which shows a backtrace when the GUD buffer is current.
24554 Move point to any frame in the stack and type @key{RET} to make it
24555 become the current frame and display the associated source in the
24556 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24557 selected frame become the current one. In graphical mode, the
24558 speedbar displays watch expressions.
24560 If you accidentally delete the source-display buffer, an easy way to get
24561 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24562 request a frame display; when you run under Emacs, this recreates
24563 the source buffer if necessary to show you the context of the current
24566 The source files displayed in Emacs are in ordinary Emacs buffers
24567 which are visiting the source files in the usual way. You can edit
24568 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24569 communicates with Emacs in terms of line numbers. If you add or
24570 delete lines from the text, the line numbers that @value{GDBN} knows cease
24571 to correspond properly with the code.
24573 A more detailed description of Emacs' interaction with @value{GDBN} is
24574 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24578 @chapter The @sc{gdb/mi} Interface
24580 @unnumberedsec Function and Purpose
24582 @cindex @sc{gdb/mi}, its purpose
24583 @sc{gdb/mi} is a line based machine oriented text interface to
24584 @value{GDBN} and is activated by specifying using the
24585 @option{--interpreter} command line option (@pxref{Mode Options}). It
24586 is specifically intended to support the development of systems which
24587 use the debugger as just one small component of a larger system.
24589 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24590 in the form of a reference manual.
24592 Note that @sc{gdb/mi} is still under construction, so some of the
24593 features described below are incomplete and subject to change
24594 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24596 @unnumberedsec Notation and Terminology
24598 @cindex notational conventions, for @sc{gdb/mi}
24599 This chapter uses the following notation:
24603 @code{|} separates two alternatives.
24606 @code{[ @var{something} ]} indicates that @var{something} is optional:
24607 it may or may not be given.
24610 @code{( @var{group} )*} means that @var{group} inside the parentheses
24611 may repeat zero or more times.
24614 @code{( @var{group} )+} means that @var{group} inside the parentheses
24615 may repeat one or more times.
24618 @code{"@var{string}"} means a literal @var{string}.
24622 @heading Dependencies
24626 * GDB/MI General Design::
24627 * GDB/MI Command Syntax::
24628 * GDB/MI Compatibility with CLI::
24629 * GDB/MI Development and Front Ends::
24630 * GDB/MI Output Records::
24631 * GDB/MI Simple Examples::
24632 * GDB/MI Command Description Format::
24633 * GDB/MI Breakpoint Commands::
24634 * GDB/MI Catchpoint Commands::
24635 * GDB/MI Program Context::
24636 * GDB/MI Thread Commands::
24637 * GDB/MI Ada Tasking Commands::
24638 * GDB/MI Program Execution::
24639 * GDB/MI Stack Manipulation::
24640 * GDB/MI Variable Objects::
24641 * GDB/MI Data Manipulation::
24642 * GDB/MI Tracepoint Commands::
24643 * GDB/MI Symbol Query::
24644 * GDB/MI File Commands::
24646 * GDB/MI Kod Commands::
24647 * GDB/MI Memory Overlay Commands::
24648 * GDB/MI Signal Handling Commands::
24650 * GDB/MI Target Manipulation::
24651 * GDB/MI File Transfer Commands::
24652 * GDB/MI Ada Exceptions Commands::
24653 * GDB/MI Support Commands::
24654 * GDB/MI Miscellaneous Commands::
24657 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24658 @node GDB/MI General Design
24659 @section @sc{gdb/mi} General Design
24660 @cindex GDB/MI General Design
24662 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24663 parts---commands sent to @value{GDBN}, responses to those commands
24664 and notifications. Each command results in exactly one response,
24665 indicating either successful completion of the command, or an error.
24666 For the commands that do not resume the target, the response contains the
24667 requested information. For the commands that resume the target, the
24668 response only indicates whether the target was successfully resumed.
24669 Notifications is the mechanism for reporting changes in the state of the
24670 target, or in @value{GDBN} state, that cannot conveniently be associated with
24671 a command and reported as part of that command response.
24673 The important examples of notifications are:
24677 Exec notifications. These are used to report changes in
24678 target state---when a target is resumed, or stopped. It would not
24679 be feasible to include this information in response of resuming
24680 commands, because one resume commands can result in multiple events in
24681 different threads. Also, quite some time may pass before any event
24682 happens in the target, while a frontend needs to know whether the resuming
24683 command itself was successfully executed.
24686 Console output, and status notifications. Console output
24687 notifications are used to report output of CLI commands, as well as
24688 diagnostics for other commands. Status notifications are used to
24689 report the progress of a long-running operation. Naturally, including
24690 this information in command response would mean no output is produced
24691 until the command is finished, which is undesirable.
24694 General notifications. Commands may have various side effects on
24695 the @value{GDBN} or target state beyond their official purpose. For example,
24696 a command may change the selected thread. Although such changes can
24697 be included in command response, using notification allows for more
24698 orthogonal frontend design.
24702 There's no guarantee that whenever an MI command reports an error,
24703 @value{GDBN} or the target are in any specific state, and especially,
24704 the state is not reverted to the state before the MI command was
24705 processed. Therefore, whenever an MI command results in an error,
24706 we recommend that the frontend refreshes all the information shown in
24707 the user interface.
24711 * Context management::
24712 * Asynchronous and non-stop modes::
24716 @node Context management
24717 @subsection Context management
24719 @subsubsection Threads and Frames
24721 In most cases when @value{GDBN} accesses the target, this access is
24722 done in context of a specific thread and frame (@pxref{Frames}).
24723 Often, even when accessing global data, the target requires that a thread
24724 be specified. The CLI interface maintains the selected thread and frame,
24725 and supplies them to target on each command. This is convenient,
24726 because a command line user would not want to specify that information
24727 explicitly on each command, and because user interacts with
24728 @value{GDBN} via a single terminal, so no confusion is possible as
24729 to what thread and frame are the current ones.
24731 In the case of MI, the concept of selected thread and frame is less
24732 useful. First, a frontend can easily remember this information
24733 itself. Second, a graphical frontend can have more than one window,
24734 each one used for debugging a different thread, and the frontend might
24735 want to access additional threads for internal purposes. This
24736 increases the risk that by relying on implicitly selected thread, the
24737 frontend may be operating on a wrong one. Therefore, each MI command
24738 should explicitly specify which thread and frame to operate on. To
24739 make it possible, each MI command accepts the @samp{--thread} and
24740 @samp{--frame} options, the value to each is @value{GDBN} identifier
24741 for thread and frame to operate on.
24743 Usually, each top-level window in a frontend allows the user to select
24744 a thread and a frame, and remembers the user selection for further
24745 operations. However, in some cases @value{GDBN} may suggest that the
24746 current thread be changed. For example, when stopping on a breakpoint
24747 it is reasonable to switch to the thread where breakpoint is hit. For
24748 another example, if the user issues the CLI @samp{thread} command via
24749 the frontend, it is desirable to change the frontend's selected thread to the
24750 one specified by user. @value{GDBN} communicates the suggestion to
24751 change current thread using the @samp{=thread-selected} notification.
24752 No such notification is available for the selected frame at the moment.
24754 Note that historically, MI shares the selected thread with CLI, so
24755 frontends used the @code{-thread-select} to execute commands in the
24756 right context. However, getting this to work right is cumbersome. The
24757 simplest way is for frontend to emit @code{-thread-select} command
24758 before every command. This doubles the number of commands that need
24759 to be sent. The alternative approach is to suppress @code{-thread-select}
24760 if the selected thread in @value{GDBN} is supposed to be identical to the
24761 thread the frontend wants to operate on. However, getting this
24762 optimization right can be tricky. In particular, if the frontend
24763 sends several commands to @value{GDBN}, and one of the commands changes the
24764 selected thread, then the behaviour of subsequent commands will
24765 change. So, a frontend should either wait for response from such
24766 problematic commands, or explicitly add @code{-thread-select} for
24767 all subsequent commands. No frontend is known to do this exactly
24768 right, so it is suggested to just always pass the @samp{--thread} and
24769 @samp{--frame} options.
24771 @subsubsection Language
24773 The execution of several commands depends on which language is selected.
24774 By default, the current language (@pxref{show language}) is used.
24775 But for commands known to be language-sensitive, it is recommended
24776 to use the @samp{--language} option. This option takes one argument,
24777 which is the name of the language to use while executing the command.
24781 -data-evaluate-expression --language c "sizeof (void*)"
24786 The valid language names are the same names accepted by the
24787 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
24788 @samp{local} or @samp{unknown}.
24790 @node Asynchronous and non-stop modes
24791 @subsection Asynchronous command execution and non-stop mode
24793 On some targets, @value{GDBN} is capable of processing MI commands
24794 even while the target is running. This is called @dfn{asynchronous
24795 command execution} (@pxref{Background Execution}). The frontend may
24796 specify a preferrence for asynchronous execution using the
24797 @code{-gdb-set target-async 1} command, which should be emitted before
24798 either running the executable or attaching to the target. After the
24799 frontend has started the executable or attached to the target, it can
24800 find if asynchronous execution is enabled using the
24801 @code{-list-target-features} command.
24803 Even if @value{GDBN} can accept a command while target is running,
24804 many commands that access the target do not work when the target is
24805 running. Therefore, asynchronous command execution is most useful
24806 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24807 it is possible to examine the state of one thread, while other threads
24810 When a given thread is running, MI commands that try to access the
24811 target in the context of that thread may not work, or may work only on
24812 some targets. In particular, commands that try to operate on thread's
24813 stack will not work, on any target. Commands that read memory, or
24814 modify breakpoints, may work or not work, depending on the target. Note
24815 that even commands that operate on global state, such as @code{print},
24816 @code{set}, and breakpoint commands, still access the target in the
24817 context of a specific thread, so frontend should try to find a
24818 stopped thread and perform the operation on that thread (using the
24819 @samp{--thread} option).
24821 Which commands will work in the context of a running thread is
24822 highly target dependent. However, the two commands
24823 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24824 to find the state of a thread, will always work.
24826 @node Thread groups
24827 @subsection Thread groups
24828 @value{GDBN} may be used to debug several processes at the same time.
24829 On some platfroms, @value{GDBN} may support debugging of several
24830 hardware systems, each one having several cores with several different
24831 processes running on each core. This section describes the MI
24832 mechanism to support such debugging scenarios.
24834 The key observation is that regardless of the structure of the
24835 target, MI can have a global list of threads, because most commands that
24836 accept the @samp{--thread} option do not need to know what process that
24837 thread belongs to. Therefore, it is not necessary to introduce
24838 neither additional @samp{--process} option, nor an notion of the
24839 current process in the MI interface. The only strictly new feature
24840 that is required is the ability to find how the threads are grouped
24843 To allow the user to discover such grouping, and to support arbitrary
24844 hierarchy of machines/cores/processes, MI introduces the concept of a
24845 @dfn{thread group}. Thread group is a collection of threads and other
24846 thread groups. A thread group always has a string identifier, a type,
24847 and may have additional attributes specific to the type. A new
24848 command, @code{-list-thread-groups}, returns the list of top-level
24849 thread groups, which correspond to processes that @value{GDBN} is
24850 debugging at the moment. By passing an identifier of a thread group
24851 to the @code{-list-thread-groups} command, it is possible to obtain
24852 the members of specific thread group.
24854 To allow the user to easily discover processes, and other objects, he
24855 wishes to debug, a concept of @dfn{available thread group} is
24856 introduced. Available thread group is an thread group that
24857 @value{GDBN} is not debugging, but that can be attached to, using the
24858 @code{-target-attach} command. The list of available top-level thread
24859 groups can be obtained using @samp{-list-thread-groups --available}.
24860 In general, the content of a thread group may be only retrieved only
24861 after attaching to that thread group.
24863 Thread groups are related to inferiors (@pxref{Inferiors and
24864 Programs}). Each inferior corresponds to a thread group of a special
24865 type @samp{process}, and some additional operations are permitted on
24866 such thread groups.
24868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24869 @node GDB/MI Command Syntax
24870 @section @sc{gdb/mi} Command Syntax
24873 * GDB/MI Input Syntax::
24874 * GDB/MI Output Syntax::
24877 @node GDB/MI Input Syntax
24878 @subsection @sc{gdb/mi} Input Syntax
24880 @cindex input syntax for @sc{gdb/mi}
24881 @cindex @sc{gdb/mi}, input syntax
24883 @item @var{command} @expansion{}
24884 @code{@var{cli-command} | @var{mi-command}}
24886 @item @var{cli-command} @expansion{}
24887 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24888 @var{cli-command} is any existing @value{GDBN} CLI command.
24890 @item @var{mi-command} @expansion{}
24891 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24892 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24894 @item @var{token} @expansion{}
24895 "any sequence of digits"
24897 @item @var{option} @expansion{}
24898 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24900 @item @var{parameter} @expansion{}
24901 @code{@var{non-blank-sequence} | @var{c-string}}
24903 @item @var{operation} @expansion{}
24904 @emph{any of the operations described in this chapter}
24906 @item @var{non-blank-sequence} @expansion{}
24907 @emph{anything, provided it doesn't contain special characters such as
24908 "-", @var{nl}, """ and of course " "}
24910 @item @var{c-string} @expansion{}
24911 @code{""" @var{seven-bit-iso-c-string-content} """}
24913 @item @var{nl} @expansion{}
24922 The CLI commands are still handled by the @sc{mi} interpreter; their
24923 output is described below.
24926 The @code{@var{token}}, when present, is passed back when the command
24930 Some @sc{mi} commands accept optional arguments as part of the parameter
24931 list. Each option is identified by a leading @samp{-} (dash) and may be
24932 followed by an optional argument parameter. Options occur first in the
24933 parameter list and can be delimited from normal parameters using
24934 @samp{--} (this is useful when some parameters begin with a dash).
24941 We want easy access to the existing CLI syntax (for debugging).
24944 We want it to be easy to spot a @sc{mi} operation.
24947 @node GDB/MI Output Syntax
24948 @subsection @sc{gdb/mi} Output Syntax
24950 @cindex output syntax of @sc{gdb/mi}
24951 @cindex @sc{gdb/mi}, output syntax
24952 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24953 followed, optionally, by a single result record. This result record
24954 is for the most recent command. The sequence of output records is
24955 terminated by @samp{(gdb)}.
24957 If an input command was prefixed with a @code{@var{token}} then the
24958 corresponding output for that command will also be prefixed by that same
24962 @item @var{output} @expansion{}
24963 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24965 @item @var{result-record} @expansion{}
24966 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24968 @item @var{out-of-band-record} @expansion{}
24969 @code{@var{async-record} | @var{stream-record}}
24971 @item @var{async-record} @expansion{}
24972 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24974 @item @var{exec-async-output} @expansion{}
24975 @code{[ @var{token} ] "*" @var{async-output nl}}
24977 @item @var{status-async-output} @expansion{}
24978 @code{[ @var{token} ] "+" @var{async-output nl}}
24980 @item @var{notify-async-output} @expansion{}
24981 @code{[ @var{token} ] "=" @var{async-output nl}}
24983 @item @var{async-output} @expansion{}
24984 @code{@var{async-class} ( "," @var{result} )*}
24986 @item @var{result-class} @expansion{}
24987 @code{"done" | "running" | "connected" | "error" | "exit"}
24989 @item @var{async-class} @expansion{}
24990 @code{"stopped" | @var{others}} (where @var{others} will be added
24991 depending on the needs---this is still in development).
24993 @item @var{result} @expansion{}
24994 @code{ @var{variable} "=" @var{value}}
24996 @item @var{variable} @expansion{}
24997 @code{ @var{string} }
24999 @item @var{value} @expansion{}
25000 @code{ @var{const} | @var{tuple} | @var{list} }
25002 @item @var{const} @expansion{}
25003 @code{@var{c-string}}
25005 @item @var{tuple} @expansion{}
25006 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25008 @item @var{list} @expansion{}
25009 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25010 @var{result} ( "," @var{result} )* "]" }
25012 @item @var{stream-record} @expansion{}
25013 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25015 @item @var{console-stream-output} @expansion{}
25016 @code{"~" @var{c-string nl}}
25018 @item @var{target-stream-output} @expansion{}
25019 @code{"@@" @var{c-string nl}}
25021 @item @var{log-stream-output} @expansion{}
25022 @code{"&" @var{c-string nl}}
25024 @item @var{nl} @expansion{}
25027 @item @var{token} @expansion{}
25028 @emph{any sequence of digits}.
25036 All output sequences end in a single line containing a period.
25039 The @code{@var{token}} is from the corresponding request. Note that
25040 for all async output, while the token is allowed by the grammar and
25041 may be output by future versions of @value{GDBN} for select async
25042 output messages, it is generally omitted. Frontends should treat
25043 all async output as reporting general changes in the state of the
25044 target and there should be no need to associate async output to any
25048 @cindex status output in @sc{gdb/mi}
25049 @var{status-async-output} contains on-going status information about the
25050 progress of a slow operation. It can be discarded. All status output is
25051 prefixed by @samp{+}.
25054 @cindex async output in @sc{gdb/mi}
25055 @var{exec-async-output} contains asynchronous state change on the target
25056 (stopped, started, disappeared). All async output is prefixed by
25060 @cindex notify output in @sc{gdb/mi}
25061 @var{notify-async-output} contains supplementary information that the
25062 client should handle (e.g., a new breakpoint information). All notify
25063 output is prefixed by @samp{=}.
25066 @cindex console output in @sc{gdb/mi}
25067 @var{console-stream-output} is output that should be displayed as is in the
25068 console. It is the textual response to a CLI command. All the console
25069 output is prefixed by @samp{~}.
25072 @cindex target output in @sc{gdb/mi}
25073 @var{target-stream-output} is the output produced by the target program.
25074 All the target output is prefixed by @samp{@@}.
25077 @cindex log output in @sc{gdb/mi}
25078 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25079 instance messages that should be displayed as part of an error log. All
25080 the log output is prefixed by @samp{&}.
25083 @cindex list output in @sc{gdb/mi}
25084 New @sc{gdb/mi} commands should only output @var{lists} containing
25090 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25091 details about the various output records.
25093 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25094 @node GDB/MI Compatibility with CLI
25095 @section @sc{gdb/mi} Compatibility with CLI
25097 @cindex compatibility, @sc{gdb/mi} and CLI
25098 @cindex @sc{gdb/mi}, compatibility with CLI
25100 For the developers convenience CLI commands can be entered directly,
25101 but there may be some unexpected behaviour. For example, commands
25102 that query the user will behave as if the user replied yes, breakpoint
25103 command lists are not executed and some CLI commands, such as
25104 @code{if}, @code{when} and @code{define}, prompt for further input with
25105 @samp{>}, which is not valid MI output.
25107 This feature may be removed at some stage in the future and it is
25108 recommended that front ends use the @code{-interpreter-exec} command
25109 (@pxref{-interpreter-exec}).
25111 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25112 @node GDB/MI Development and Front Ends
25113 @section @sc{gdb/mi} Development and Front Ends
25114 @cindex @sc{gdb/mi} development
25116 The application which takes the MI output and presents the state of the
25117 program being debugged to the user is called a @dfn{front end}.
25119 Although @sc{gdb/mi} is still incomplete, it is currently being used
25120 by a variety of front ends to @value{GDBN}. This makes it difficult
25121 to introduce new functionality without breaking existing usage. This
25122 section tries to minimize the problems by describing how the protocol
25125 Some changes in MI need not break a carefully designed front end, and
25126 for these the MI version will remain unchanged. The following is a
25127 list of changes that may occur within one level, so front ends should
25128 parse MI output in a way that can handle them:
25132 New MI commands may be added.
25135 New fields may be added to the output of any MI command.
25138 The range of values for fields with specified values, e.g.,
25139 @code{in_scope} (@pxref{-var-update}) may be extended.
25141 @c The format of field's content e.g type prefix, may change so parse it
25142 @c at your own risk. Yes, in general?
25144 @c The order of fields may change? Shouldn't really matter but it might
25145 @c resolve inconsistencies.
25148 If the changes are likely to break front ends, the MI version level
25149 will be increased by one. This will allow the front end to parse the
25150 output according to the MI version. Apart from mi0, new versions of
25151 @value{GDBN} will not support old versions of MI and it will be the
25152 responsibility of the front end to work with the new one.
25154 @c Starting with mi3, add a new command -mi-version that prints the MI
25157 The best way to avoid unexpected changes in MI that might break your front
25158 end is to make your project known to @value{GDBN} developers and
25159 follow development on @email{gdb@@sourceware.org} and
25160 @email{gdb-patches@@sourceware.org}.
25161 @cindex mailing lists
25163 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25164 @node GDB/MI Output Records
25165 @section @sc{gdb/mi} Output Records
25168 * GDB/MI Result Records::
25169 * GDB/MI Stream Records::
25170 * GDB/MI Async Records::
25171 * GDB/MI Breakpoint Information::
25172 * GDB/MI Frame Information::
25173 * GDB/MI Thread Information::
25174 * GDB/MI Ada Exception Information::
25177 @node GDB/MI Result Records
25178 @subsection @sc{gdb/mi} Result Records
25180 @cindex result records in @sc{gdb/mi}
25181 @cindex @sc{gdb/mi}, result records
25182 In addition to a number of out-of-band notifications, the response to a
25183 @sc{gdb/mi} command includes one of the following result indications:
25187 @item "^done" [ "," @var{results} ]
25188 The synchronous operation was successful, @code{@var{results}} are the return
25193 This result record is equivalent to @samp{^done}. Historically, it
25194 was output instead of @samp{^done} if the command has resumed the
25195 target. This behaviour is maintained for backward compatibility, but
25196 all frontends should treat @samp{^done} and @samp{^running}
25197 identically and rely on the @samp{*running} output record to determine
25198 which threads are resumed.
25202 @value{GDBN} has connected to a remote target.
25204 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25206 The operation failed. The @code{msg=@var{c-string}} variable contains
25207 the corresponding error message.
25209 If present, the @code{code=@var{c-string}} variable provides an error
25210 code on which consumers can rely on to detect the corresponding
25211 error condition. At present, only one error code is defined:
25214 @item "undefined-command"
25215 Indicates that the command causing the error does not exist.
25220 @value{GDBN} has terminated.
25224 @node GDB/MI Stream Records
25225 @subsection @sc{gdb/mi} Stream Records
25227 @cindex @sc{gdb/mi}, stream records
25228 @cindex stream records in @sc{gdb/mi}
25229 @value{GDBN} internally maintains a number of output streams: the console, the
25230 target, and the log. The output intended for each of these streams is
25231 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25233 Each stream record begins with a unique @dfn{prefix character} which
25234 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25235 Syntax}). In addition to the prefix, each stream record contains a
25236 @code{@var{string-output}}. This is either raw text (with an implicit new
25237 line) or a quoted C string (which does not contain an implicit newline).
25240 @item "~" @var{string-output}
25241 The console output stream contains text that should be displayed in the
25242 CLI console window. It contains the textual responses to CLI commands.
25244 @item "@@" @var{string-output}
25245 The target output stream contains any textual output from the running
25246 target. This is only present when GDB's event loop is truly
25247 asynchronous, which is currently only the case for remote targets.
25249 @item "&" @var{string-output}
25250 The log stream contains debugging messages being produced by @value{GDBN}'s
25254 @node GDB/MI Async Records
25255 @subsection @sc{gdb/mi} Async Records
25257 @cindex async records in @sc{gdb/mi}
25258 @cindex @sc{gdb/mi}, async records
25259 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25260 additional changes that have occurred. Those changes can either be a
25261 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25262 target activity (e.g., target stopped).
25264 The following is the list of possible async records:
25268 @item *running,thread-id="@var{thread}"
25269 The target is now running. The @var{thread} field tells which
25270 specific thread is now running, and can be @samp{all} if all threads
25271 are running. The frontend should assume that no interaction with a
25272 running thread is possible after this notification is produced.
25273 The frontend should not assume that this notification is output
25274 only once for any command. @value{GDBN} may emit this notification
25275 several times, either for different threads, because it cannot resume
25276 all threads together, or even for a single thread, if the thread must
25277 be stepped though some code before letting it run freely.
25279 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25280 The target has stopped. The @var{reason} field can have one of the
25284 @item breakpoint-hit
25285 A breakpoint was reached.
25286 @item watchpoint-trigger
25287 A watchpoint was triggered.
25288 @item read-watchpoint-trigger
25289 A read watchpoint was triggered.
25290 @item access-watchpoint-trigger
25291 An access watchpoint was triggered.
25292 @item function-finished
25293 An -exec-finish or similar CLI command was accomplished.
25294 @item location-reached
25295 An -exec-until or similar CLI command was accomplished.
25296 @item watchpoint-scope
25297 A watchpoint has gone out of scope.
25298 @item end-stepping-range
25299 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25300 similar CLI command was accomplished.
25301 @item exited-signalled
25302 The inferior exited because of a signal.
25304 The inferior exited.
25305 @item exited-normally
25306 The inferior exited normally.
25307 @item signal-received
25308 A signal was received by the inferior.
25310 The inferior has stopped due to a library being loaded or unloaded.
25311 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25312 set or when a @code{catch load} or @code{catch unload} catchpoint is
25313 in use (@pxref{Set Catchpoints}).
25315 The inferior has forked. This is reported when @code{catch fork}
25316 (@pxref{Set Catchpoints}) has been used.
25318 The inferior has vforked. This is reported in when @code{catch vfork}
25319 (@pxref{Set Catchpoints}) has been used.
25320 @item syscall-entry
25321 The inferior entered a system call. This is reported when @code{catch
25322 syscall} (@pxref{Set Catchpoints}) has been used.
25323 @item syscall-entry
25324 The inferior returned from a system call. This is reported when
25325 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25327 The inferior called @code{exec}. This is reported when @code{catch exec}
25328 (@pxref{Set Catchpoints}) has been used.
25331 The @var{id} field identifies the thread that directly caused the stop
25332 -- for example by hitting a breakpoint. Depending on whether all-stop
25333 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25334 stop all threads, or only the thread that directly triggered the stop.
25335 If all threads are stopped, the @var{stopped} field will have the
25336 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25337 field will be a list of thread identifiers. Presently, this list will
25338 always include a single thread, but frontend should be prepared to see
25339 several threads in the list. The @var{core} field reports the
25340 processor core on which the stop event has happened. This field may be absent
25341 if such information is not available.
25343 @item =thread-group-added,id="@var{id}"
25344 @itemx =thread-group-removed,id="@var{id}"
25345 A thread group was either added or removed. The @var{id} field
25346 contains the @value{GDBN} identifier of the thread group. When a thread
25347 group is added, it generally might not be associated with a running
25348 process. When a thread group is removed, its id becomes invalid and
25349 cannot be used in any way.
25351 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25352 A thread group became associated with a running program,
25353 either because the program was just started or the thread group
25354 was attached to a program. The @var{id} field contains the
25355 @value{GDBN} identifier of the thread group. The @var{pid} field
25356 contains process identifier, specific to the operating system.
25358 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25359 A thread group is no longer associated with a running program,
25360 either because the program has exited, or because it was detached
25361 from. The @var{id} field contains the @value{GDBN} identifier of the
25362 thread group. @var{code} is the exit code of the inferior; it exists
25363 only when the inferior exited with some code.
25365 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25366 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25367 A thread either was created, or has exited. The @var{id} field
25368 contains the @value{GDBN} identifier of the thread. The @var{gid}
25369 field identifies the thread group this thread belongs to.
25371 @item =thread-selected,id="@var{id}"
25372 Informs that the selected thread was changed as result of the last
25373 command. This notification is not emitted as result of @code{-thread-select}
25374 command but is emitted whenever an MI command that is not documented
25375 to change the selected thread actually changes it. In particular,
25376 invoking, directly or indirectly (via user-defined command), the CLI
25377 @code{thread} command, will generate this notification.
25379 We suggest that in response to this notification, front ends
25380 highlight the selected thread and cause subsequent commands to apply to
25383 @item =library-loaded,...
25384 Reports that a new library file was loaded by the program. This
25385 notification has 4 fields---@var{id}, @var{target-name},
25386 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25387 opaque identifier of the library. For remote debugging case,
25388 @var{target-name} and @var{host-name} fields give the name of the
25389 library file on the target, and on the host respectively. For native
25390 debugging, both those fields have the same value. The
25391 @var{symbols-loaded} field is emitted only for backward compatibility
25392 and should not be relied on to convey any useful information. The
25393 @var{thread-group} field, if present, specifies the id of the thread
25394 group in whose context the library was loaded. If the field is
25395 absent, it means the library was loaded in the context of all present
25398 @item =library-unloaded,...
25399 Reports that a library was unloaded by the program. This notification
25400 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25401 the same meaning as for the @code{=library-loaded} notification.
25402 The @var{thread-group} field, if present, specifies the id of the
25403 thread group in whose context the library was unloaded. If the field is
25404 absent, it means the library was unloaded in the context of all present
25407 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25408 @itemx =traceframe-changed,end
25409 Reports that the trace frame was changed and its new number is
25410 @var{tfnum}. The number of the tracepoint associated with this trace
25411 frame is @var{tpnum}.
25413 @item =tsv-created,name=@var{name},initial=@var{initial}
25414 Reports that the new trace state variable @var{name} is created with
25415 initial value @var{initial}.
25417 @item =tsv-deleted,name=@var{name}
25418 @itemx =tsv-deleted
25419 Reports that the trace state variable @var{name} is deleted or all
25420 trace state variables are deleted.
25422 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25423 Reports that the trace state variable @var{name} is modified with
25424 the initial value @var{initial}. The current value @var{current} of
25425 trace state variable is optional and is reported if the current
25426 value of trace state variable is known.
25428 @item =breakpoint-created,bkpt=@{...@}
25429 @itemx =breakpoint-modified,bkpt=@{...@}
25430 @itemx =breakpoint-deleted,id=@var{number}
25431 Reports that a breakpoint was created, modified, or deleted,
25432 respectively. Only user-visible breakpoints are reported to the MI
25435 The @var{bkpt} argument is of the same form as returned by the various
25436 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25437 @var{number} is the ordinal number of the breakpoint.
25439 Note that if a breakpoint is emitted in the result record of a
25440 command, then it will not also be emitted in an async record.
25442 @item =record-started,thread-group="@var{id}"
25443 @itemx =record-stopped,thread-group="@var{id}"
25444 Execution log recording was either started or stopped on an
25445 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25446 group corresponding to the affected inferior.
25448 @item =cmd-param-changed,param=@var{param},value=@var{value}
25449 Reports that a parameter of the command @code{set @var{param}} is
25450 changed to @var{value}. In the multi-word @code{set} command,
25451 the @var{param} is the whole parameter list to @code{set} command.
25452 For example, In command @code{set check type on}, @var{param}
25453 is @code{check type} and @var{value} is @code{on}.
25455 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
25456 Reports that bytes from @var{addr} to @var{data} + @var{len} were
25457 written in an inferior. The @var{id} is the identifier of the
25458 thread group corresponding to the affected inferior. The optional
25459 @code{type="code"} part is reported if the memory written to holds
25463 @node GDB/MI Breakpoint Information
25464 @subsection @sc{gdb/mi} Breakpoint Information
25466 When @value{GDBN} reports information about a breakpoint, a
25467 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
25472 The breakpoint number. For a breakpoint that represents one location
25473 of a multi-location breakpoint, this will be a dotted pair, like
25477 The type of the breakpoint. For ordinary breakpoints this will be
25478 @samp{breakpoint}, but many values are possible.
25481 If the type of the breakpoint is @samp{catchpoint}, then this
25482 indicates the exact type of catchpoint.
25485 This is the breakpoint disposition---either @samp{del}, meaning that
25486 the breakpoint will be deleted at the next stop, or @samp{keep},
25487 meaning that the breakpoint will not be deleted.
25490 This indicates whether the breakpoint is enabled, in which case the
25491 value is @samp{y}, or disabled, in which case the value is @samp{n}.
25492 Note that this is not the same as the field @code{enable}.
25495 The address of the breakpoint. This may be a hexidecimal number,
25496 giving the address; or the string @samp{<PENDING>}, for a pending
25497 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
25498 multiple locations. This field will not be present if no address can
25499 be determined. For example, a watchpoint does not have an address.
25502 If known, the function in which the breakpoint appears.
25503 If not known, this field is not present.
25506 The name of the source file which contains this function, if known.
25507 If not known, this field is not present.
25510 The full file name of the source file which contains this function, if
25511 known. If not known, this field is not present.
25514 The line number at which this breakpoint appears, if known.
25515 If not known, this field is not present.
25518 If the source file is not known, this field may be provided. If
25519 provided, this holds the address of the breakpoint, possibly followed
25523 If this breakpoint is pending, this field is present and holds the
25524 text used to set the breakpoint, as entered by the user.
25527 Where this breakpoint's condition is evaluated, either @samp{host} or
25531 If this is a thread-specific breakpoint, then this identifies the
25532 thread in which the breakpoint can trigger.
25535 If this breakpoint is restricted to a particular Ada task, then this
25536 field will hold the task identifier.
25539 If the breakpoint is conditional, this is the condition expression.
25542 The ignore count of the breakpoint.
25545 The enable count of the breakpoint.
25547 @item traceframe-usage
25550 @item static-tracepoint-marker-string-id
25551 For a static tracepoint, the name of the static tracepoint marker.
25554 For a masked watchpoint, this is the mask.
25557 A tracepoint's pass count.
25559 @item original-location
25560 The location of the breakpoint as originally specified by the user.
25561 This field is optional.
25564 The number of times the breakpoint has been hit.
25567 This field is only given for tracepoints. This is either @samp{y},
25568 meaning that the tracepoint is installed, or @samp{n}, meaning that it
25572 Some extra data, the exact contents of which are type-dependent.
25576 For example, here is what the output of @code{-break-insert}
25577 (@pxref{GDB/MI Breakpoint Commands}) might be:
25580 -> -break-insert main
25581 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25582 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25583 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25588 @node GDB/MI Frame Information
25589 @subsection @sc{gdb/mi} Frame Information
25591 Response from many MI commands includes an information about stack
25592 frame. This information is a tuple that may have the following
25597 The level of the stack frame. The innermost frame has the level of
25598 zero. This field is always present.
25601 The name of the function corresponding to the frame. This field may
25602 be absent if @value{GDBN} is unable to determine the function name.
25605 The code address for the frame. This field is always present.
25608 The name of the source files that correspond to the frame's code
25609 address. This field may be absent.
25612 The source line corresponding to the frames' code address. This field
25616 The name of the binary file (either executable or shared library) the
25617 corresponds to the frame's code address. This field may be absent.
25621 @node GDB/MI Thread Information
25622 @subsection @sc{gdb/mi} Thread Information
25624 Whenever @value{GDBN} has to report an information about a thread, it
25625 uses a tuple with the following fields:
25629 The numeric id assigned to the thread by @value{GDBN}. This field is
25633 Target-specific string identifying the thread. This field is always present.
25636 Additional information about the thread provided by the target.
25637 It is supposed to be human-readable and not interpreted by the
25638 frontend. This field is optional.
25641 Either @samp{stopped} or @samp{running}, depending on whether the
25642 thread is presently running. This field is always present.
25645 The value of this field is an integer number of the processor core the
25646 thread was last seen on. This field is optional.
25649 @node GDB/MI Ada Exception Information
25650 @subsection @sc{gdb/mi} Ada Exception Information
25652 Whenever a @code{*stopped} record is emitted because the program
25653 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25654 @value{GDBN} provides the name of the exception that was raised via
25655 the @code{exception-name} field.
25657 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25658 @node GDB/MI Simple Examples
25659 @section Simple Examples of @sc{gdb/mi} Interaction
25660 @cindex @sc{gdb/mi}, simple examples
25662 This subsection presents several simple examples of interaction using
25663 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25664 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25665 the output received from @sc{gdb/mi}.
25667 Note the line breaks shown in the examples are here only for
25668 readability, they don't appear in the real output.
25670 @subheading Setting a Breakpoint
25672 Setting a breakpoint generates synchronous output which contains detailed
25673 information of the breakpoint.
25676 -> -break-insert main
25677 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25678 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25679 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25684 @subheading Program Execution
25686 Program execution generates asynchronous records and MI gives the
25687 reason that execution stopped.
25693 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25694 frame=@{addr="0x08048564",func="main",
25695 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25696 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25701 <- *stopped,reason="exited-normally"
25705 @subheading Quitting @value{GDBN}
25707 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25715 Please note that @samp{^exit} is printed immediately, but it might
25716 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25717 performs necessary cleanups, including killing programs being debugged
25718 or disconnecting from debug hardware, so the frontend should wait till
25719 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25720 fails to exit in reasonable time.
25722 @subheading A Bad Command
25724 Here's what happens if you pass a non-existent command:
25728 <- ^error,msg="Undefined MI command: rubbish"
25733 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25734 @node GDB/MI Command Description Format
25735 @section @sc{gdb/mi} Command Description Format
25737 The remaining sections describe blocks of commands. Each block of
25738 commands is laid out in a fashion similar to this section.
25740 @subheading Motivation
25742 The motivation for this collection of commands.
25744 @subheading Introduction
25746 A brief introduction to this collection of commands as a whole.
25748 @subheading Commands
25750 For each command in the block, the following is described:
25752 @subsubheading Synopsis
25755 -command @var{args}@dots{}
25758 @subsubheading Result
25760 @subsubheading @value{GDBN} Command
25762 The corresponding @value{GDBN} CLI command(s), if any.
25764 @subsubheading Example
25766 Example(s) formatted for readability. Some of the described commands have
25767 not been implemented yet and these are labeled N.A.@: (not available).
25770 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25771 @node GDB/MI Breakpoint Commands
25772 @section @sc{gdb/mi} Breakpoint Commands
25774 @cindex breakpoint commands for @sc{gdb/mi}
25775 @cindex @sc{gdb/mi}, breakpoint commands
25776 This section documents @sc{gdb/mi} commands for manipulating
25779 @subheading The @code{-break-after} Command
25780 @findex -break-after
25782 @subsubheading Synopsis
25785 -break-after @var{number} @var{count}
25788 The breakpoint number @var{number} is not in effect until it has been
25789 hit @var{count} times. To see how this is reflected in the output of
25790 the @samp{-break-list} command, see the description of the
25791 @samp{-break-list} command below.
25793 @subsubheading @value{GDBN} Command
25795 The corresponding @value{GDBN} command is @samp{ignore}.
25797 @subsubheading Example
25802 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25803 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25804 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
25812 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25813 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25814 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25815 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25816 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25817 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25818 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25819 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25820 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25821 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
25826 @subheading The @code{-break-catch} Command
25827 @findex -break-catch
25830 @subheading The @code{-break-commands} Command
25831 @findex -break-commands
25833 @subsubheading Synopsis
25836 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25839 Specifies the CLI commands that should be executed when breakpoint
25840 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25841 are the commands. If no command is specified, any previously-set
25842 commands are cleared. @xref{Break Commands}. Typical use of this
25843 functionality is tracing a program, that is, printing of values of
25844 some variables whenever breakpoint is hit and then continuing.
25846 @subsubheading @value{GDBN} Command
25848 The corresponding @value{GDBN} command is @samp{commands}.
25850 @subsubheading Example
25855 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25856 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25857 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
25860 -break-commands 1 "print v" "continue"
25865 @subheading The @code{-break-condition} Command
25866 @findex -break-condition
25868 @subsubheading Synopsis
25871 -break-condition @var{number} @var{expr}
25874 Breakpoint @var{number} will stop the program only if the condition in
25875 @var{expr} is true. The condition becomes part of the
25876 @samp{-break-list} output (see the description of the @samp{-break-list}
25879 @subsubheading @value{GDBN} Command
25881 The corresponding @value{GDBN} command is @samp{condition}.
25883 @subsubheading Example
25887 -break-condition 1 1
25891 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25892 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25893 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25894 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25895 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25896 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25897 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25898 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25899 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25900 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
25904 @subheading The @code{-break-delete} Command
25905 @findex -break-delete
25907 @subsubheading Synopsis
25910 -break-delete ( @var{breakpoint} )+
25913 Delete the breakpoint(s) whose number(s) are specified in the argument
25914 list. This is obviously reflected in the breakpoint list.
25916 @subsubheading @value{GDBN} Command
25918 The corresponding @value{GDBN} command is @samp{delete}.
25920 @subsubheading Example
25928 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25929 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25930 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25931 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25932 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25933 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25934 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25939 @subheading The @code{-break-disable} Command
25940 @findex -break-disable
25942 @subsubheading Synopsis
25945 -break-disable ( @var{breakpoint} )+
25948 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25949 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25951 @subsubheading @value{GDBN} Command
25953 The corresponding @value{GDBN} command is @samp{disable}.
25955 @subsubheading Example
25963 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25964 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25965 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25966 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25967 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25968 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25969 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25970 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25971 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25972 line="5",thread-groups=["i1"],times="0"@}]@}
25976 @subheading The @code{-break-enable} Command
25977 @findex -break-enable
25979 @subsubheading Synopsis
25982 -break-enable ( @var{breakpoint} )+
25985 Enable (previously disabled) @var{breakpoint}(s).
25987 @subsubheading @value{GDBN} Command
25989 The corresponding @value{GDBN} command is @samp{enable}.
25991 @subsubheading Example
25999 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26000 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26001 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26002 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26003 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26004 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26005 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26006 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26007 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26008 line="5",thread-groups=["i1"],times="0"@}]@}
26012 @subheading The @code{-break-info} Command
26013 @findex -break-info
26015 @subsubheading Synopsis
26018 -break-info @var{breakpoint}
26022 Get information about a single breakpoint.
26024 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26025 Information}, for details on the format of each breakpoint in the
26028 @subsubheading @value{GDBN} Command
26030 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26032 @subsubheading Example
26035 @subheading The @code{-break-insert} Command
26036 @findex -break-insert
26038 @subsubheading Synopsis
26041 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26042 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26043 [ -p @var{thread-id} ] [ @var{location} ]
26047 If specified, @var{location}, can be one of:
26054 @item filename:linenum
26055 @item filename:function
26059 The possible optional parameters of this command are:
26063 Insert a temporary breakpoint.
26065 Insert a hardware breakpoint.
26067 If @var{location} cannot be parsed (for example if it
26068 refers to unknown files or functions), create a pending
26069 breakpoint. Without this flag, @value{GDBN} will report
26070 an error, and won't create a breakpoint, if @var{location}
26073 Create a disabled breakpoint.
26075 Create a tracepoint. @xref{Tracepoints}. When this parameter
26076 is used together with @samp{-h}, a fast tracepoint is created.
26077 @item -c @var{condition}
26078 Make the breakpoint conditional on @var{condition}.
26079 @item -i @var{ignore-count}
26080 Initialize the @var{ignore-count}.
26081 @item -p @var{thread-id}
26082 Restrict the breakpoint to the specified @var{thread-id}.
26085 @subsubheading Result
26087 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26088 resulting breakpoint.
26090 Note: this format is open to change.
26091 @c An out-of-band breakpoint instead of part of the result?
26093 @subsubheading @value{GDBN} Command
26095 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26096 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26098 @subsubheading Example
26103 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26104 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26107 -break-insert -t foo
26108 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26109 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26113 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26114 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26115 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26116 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26117 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26118 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26119 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26120 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26121 addr="0x0001072c", func="main",file="recursive2.c",
26122 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26124 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26125 addr="0x00010774",func="foo",file="recursive2.c",
26126 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26129 @c -break-insert -r foo.*
26130 @c ~int foo(int, int);
26131 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26132 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26137 @subheading The @code{-dprintf-insert} Command
26138 @findex -dprintf-insert
26140 @subsubheading Synopsis
26143 -dprintf-insert [ -t ] [ -f ] [ -d ]
26144 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26145 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26150 If specified, @var{location}, can be one of:
26153 @item @var{function}
26156 @c @item @var{linenum}
26157 @item @var{filename}:@var{linenum}
26158 @item @var{filename}:function
26159 @item *@var{address}
26162 The possible optional parameters of this command are:
26166 Insert a temporary breakpoint.
26168 If @var{location} cannot be parsed (for example, if it
26169 refers to unknown files or functions), create a pending
26170 breakpoint. Without this flag, @value{GDBN} will report
26171 an error, and won't create a breakpoint, if @var{location}
26174 Create a disabled breakpoint.
26175 @item -c @var{condition}
26176 Make the breakpoint conditional on @var{condition}.
26177 @item -i @var{ignore-count}
26178 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26179 to @var{ignore-count}.
26180 @item -p @var{thread-id}
26181 Restrict the breakpoint to the specified @var{thread-id}.
26184 @subsubheading Result
26186 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26187 resulting breakpoint.
26189 @c An out-of-band breakpoint instead of part of the result?
26191 @subsubheading @value{GDBN} Command
26193 The corresponding @value{GDBN} command is @samp{dprintf}.
26195 @subsubheading Example
26199 4-dprintf-insert foo "At foo entry\n"
26200 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26201 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26202 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26203 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26204 original-location="foo"@}
26206 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26207 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26208 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26209 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26210 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26211 original-location="mi-dprintf.c:26"@}
26215 @subheading The @code{-break-list} Command
26216 @findex -break-list
26218 @subsubheading Synopsis
26224 Displays the list of inserted breakpoints, showing the following fields:
26228 number of the breakpoint
26230 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26232 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26235 is the breakpoint enabled or no: @samp{y} or @samp{n}
26237 memory location at which the breakpoint is set
26239 logical location of the breakpoint, expressed by function name, file
26241 @item Thread-groups
26242 list of thread groups to which this breakpoint applies
26244 number of times the breakpoint has been hit
26247 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26248 @code{body} field is an empty list.
26250 @subsubheading @value{GDBN} Command
26252 The corresponding @value{GDBN} command is @samp{info break}.
26254 @subsubheading Example
26259 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26260 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26261 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26262 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26263 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26264 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26265 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26266 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26267 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26269 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26270 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26271 line="13",thread-groups=["i1"],times="0"@}]@}
26275 Here's an example of the result when there are no breakpoints:
26280 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26281 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26282 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26283 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26284 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26285 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26286 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26291 @subheading The @code{-break-passcount} Command
26292 @findex -break-passcount
26294 @subsubheading Synopsis
26297 -break-passcount @var{tracepoint-number} @var{passcount}
26300 Set the passcount for tracepoint @var{tracepoint-number} to
26301 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26302 is not a tracepoint, error is emitted. This corresponds to CLI
26303 command @samp{passcount}.
26305 @subheading The @code{-break-watch} Command
26306 @findex -break-watch
26308 @subsubheading Synopsis
26311 -break-watch [ -a | -r ]
26314 Create a watchpoint. With the @samp{-a} option it will create an
26315 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26316 read from or on a write to the memory location. With the @samp{-r}
26317 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26318 trigger only when the memory location is accessed for reading. Without
26319 either of the options, the watchpoint created is a regular watchpoint,
26320 i.e., it will trigger when the memory location is accessed for writing.
26321 @xref{Set Watchpoints, , Setting Watchpoints}.
26323 Note that @samp{-break-list} will report a single list of watchpoints and
26324 breakpoints inserted.
26326 @subsubheading @value{GDBN} Command
26328 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26331 @subsubheading Example
26333 Setting a watchpoint on a variable in the @code{main} function:
26338 ^done,wpt=@{number="2",exp="x"@}
26343 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26344 value=@{old="-268439212",new="55"@},
26345 frame=@{func="main",args=[],file="recursive2.c",
26346 fullname="/home/foo/bar/recursive2.c",line="5"@}
26350 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26351 the program execution twice: first for the variable changing value, then
26352 for the watchpoint going out of scope.
26357 ^done,wpt=@{number="5",exp="C"@}
26362 *stopped,reason="watchpoint-trigger",
26363 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26364 frame=@{func="callee4",args=[],
26365 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26366 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26371 *stopped,reason="watchpoint-scope",wpnum="5",
26372 frame=@{func="callee3",args=[@{name="strarg",
26373 value="0x11940 \"A string argument.\""@}],
26374 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26375 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26379 Listing breakpoints and watchpoints, at different points in the program
26380 execution. Note that once the watchpoint goes out of scope, it is
26386 ^done,wpt=@{number="2",exp="C"@}
26389 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26390 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26391 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26392 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26393 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26394 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26395 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26396 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26397 addr="0x00010734",func="callee4",
26398 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26399 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26401 bkpt=@{number="2",type="watchpoint",disp="keep",
26402 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26407 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26408 value=@{old="-276895068",new="3"@},
26409 frame=@{func="callee4",args=[],
26410 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26411 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26414 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26415 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26416 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26417 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26418 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26419 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26420 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26421 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26422 addr="0x00010734",func="callee4",
26423 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26424 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26426 bkpt=@{number="2",type="watchpoint",disp="keep",
26427 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26431 ^done,reason="watchpoint-scope",wpnum="2",
26432 frame=@{func="callee3",args=[@{name="strarg",
26433 value="0x11940 \"A string argument.\""@}],
26434 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26435 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26438 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26439 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26440 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26441 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26442 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26443 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26444 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26445 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26446 addr="0x00010734",func="callee4",
26447 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26448 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26449 thread-groups=["i1"],times="1"@}]@}
26454 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26455 @node GDB/MI Catchpoint Commands
26456 @section @sc{gdb/mi} Catchpoint Commands
26458 This section documents @sc{gdb/mi} commands for manipulating
26462 * Shared Library GDB/MI Catchpoint Commands::
26463 * Ada Exception GDB/MI Catchpoint Commands::
26466 @node Shared Library GDB/MI Catchpoint Commands
26467 @subsection Shared Library @sc{gdb/mi} Catchpoints
26469 @subheading The @code{-catch-load} Command
26470 @findex -catch-load
26472 @subsubheading Synopsis
26475 -catch-load [ -t ] [ -d ] @var{regexp}
26478 Add a catchpoint for library load events. If the @samp{-t} option is used,
26479 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26480 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
26481 in a disabled state. The @samp{regexp} argument is a regular
26482 expression used to match the name of the loaded library.
26485 @subsubheading @value{GDBN} Command
26487 The corresponding @value{GDBN} command is @samp{catch load}.
26489 @subsubheading Example
26492 -catch-load -t foo.so
26493 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
26494 what="load of library matching foo.so",catch-type="load",times="0"@}
26499 @subheading The @code{-catch-unload} Command
26500 @findex -catch-unload
26502 @subsubheading Synopsis
26505 -catch-unload [ -t ] [ -d ] @var{regexp}
26508 Add a catchpoint for library unload events. If the @samp{-t} option is
26509 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26510 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
26511 created in a disabled state. The @samp{regexp} argument is a regular
26512 expression used to match the name of the unloaded library.
26514 @subsubheading @value{GDBN} Command
26516 The corresponding @value{GDBN} command is @samp{catch unload}.
26518 @subsubheading Example
26521 -catch-unload -d bar.so
26522 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
26523 what="load of library matching bar.so",catch-type="unload",times="0"@}
26527 @node Ada Exception GDB/MI Catchpoint Commands
26528 @subsection Ada Exception @sc{gdb/mi} Catchpoints
26530 The following @sc{gdb/mi} commands can be used to create catchpoints
26531 that stop the execution when Ada exceptions are being raised.
26533 @subheading The @code{-catch-assert} Command
26534 @findex -catch-assert
26536 @subsubheading Synopsis
26539 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
26542 Add a catchpoint for failed Ada assertions.
26544 The possible optional parameters for this command are:
26547 @item -c @var{condition}
26548 Make the catchpoint conditional on @var{condition}.
26550 Create a disabled catchpoint.
26552 Create a temporary catchpoint.
26555 @subsubheading @value{GDBN} Command
26557 The corresponding @value{GDBN} command is @samp{catch assert}.
26559 @subsubheading Example
26563 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
26564 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
26565 thread-groups=["i1"],times="0",
26566 original-location="__gnat_debug_raise_assert_failure"@}
26570 @subheading The @code{-catch-exception} Command
26571 @findex -catch-exception
26573 @subsubheading Synopsis
26576 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
26580 Add a catchpoint stopping when Ada exceptions are raised.
26581 By default, the command stops the program when any Ada exception
26582 gets raised. But it is also possible, by using some of the
26583 optional parameters described below, to create more selective
26586 The possible optional parameters for this command are:
26589 @item -c @var{condition}
26590 Make the catchpoint conditional on @var{condition}.
26592 Create a disabled catchpoint.
26593 @item -e @var{exception-name}
26594 Only stop when @var{exception-name} is raised. This option cannot
26595 be used combined with @samp{-u}.
26597 Create a temporary catchpoint.
26599 Stop only when an unhandled exception gets raised. This option
26600 cannot be used combined with @samp{-e}.
26603 @subsubheading @value{GDBN} Command
26605 The corresponding @value{GDBN} commands are @samp{catch exception}
26606 and @samp{catch exception unhandled}.
26608 @subsubheading Example
26611 -catch-exception -e Program_Error
26612 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
26613 enabled="y",addr="0x0000000000404874",
26614 what="`Program_Error' Ada exception", thread-groups=["i1"],
26615 times="0",original-location="__gnat_debug_raise_exception"@}
26619 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26620 @node GDB/MI Program Context
26621 @section @sc{gdb/mi} Program Context
26623 @subheading The @code{-exec-arguments} Command
26624 @findex -exec-arguments
26627 @subsubheading Synopsis
26630 -exec-arguments @var{args}
26633 Set the inferior program arguments, to be used in the next
26636 @subsubheading @value{GDBN} Command
26638 The corresponding @value{GDBN} command is @samp{set args}.
26640 @subsubheading Example
26644 -exec-arguments -v word
26651 @subheading The @code{-exec-show-arguments} Command
26652 @findex -exec-show-arguments
26654 @subsubheading Synopsis
26657 -exec-show-arguments
26660 Print the arguments of the program.
26662 @subsubheading @value{GDBN} Command
26664 The corresponding @value{GDBN} command is @samp{show args}.
26666 @subsubheading Example
26671 @subheading The @code{-environment-cd} Command
26672 @findex -environment-cd
26674 @subsubheading Synopsis
26677 -environment-cd @var{pathdir}
26680 Set @value{GDBN}'s working directory.
26682 @subsubheading @value{GDBN} Command
26684 The corresponding @value{GDBN} command is @samp{cd}.
26686 @subsubheading Example
26690 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26696 @subheading The @code{-environment-directory} Command
26697 @findex -environment-directory
26699 @subsubheading Synopsis
26702 -environment-directory [ -r ] [ @var{pathdir} ]+
26705 Add directories @var{pathdir} to beginning of search path for source files.
26706 If the @samp{-r} option is used, the search path is reset to the default
26707 search path. If directories @var{pathdir} are supplied in addition to the
26708 @samp{-r} option, the search path is first reset and then addition
26710 Multiple directories may be specified, separated by blanks. Specifying
26711 multiple directories in a single command
26712 results in the directories added to the beginning of the
26713 search path in the same order they were presented in the command.
26714 If blanks are needed as
26715 part of a directory name, double-quotes should be used around
26716 the name. In the command output, the path will show up separated
26717 by the system directory-separator character. The directory-separator
26718 character must not be used
26719 in any directory name.
26720 If no directories are specified, the current search path is displayed.
26722 @subsubheading @value{GDBN} Command
26724 The corresponding @value{GDBN} command is @samp{dir}.
26726 @subsubheading Example
26730 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26731 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26733 -environment-directory ""
26734 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26736 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26737 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26739 -environment-directory -r
26740 ^done,source-path="$cdir:$cwd"
26745 @subheading The @code{-environment-path} Command
26746 @findex -environment-path
26748 @subsubheading Synopsis
26751 -environment-path [ -r ] [ @var{pathdir} ]+
26754 Add directories @var{pathdir} to beginning of search path for object files.
26755 If the @samp{-r} option is used, the search path is reset to the original
26756 search path that existed at gdb start-up. If directories @var{pathdir} are
26757 supplied in addition to the
26758 @samp{-r} option, the search path is first reset and then addition
26760 Multiple directories may be specified, separated by blanks. Specifying
26761 multiple directories in a single command
26762 results in the directories added to the beginning of the
26763 search path in the same order they were presented in the command.
26764 If blanks are needed as
26765 part of a directory name, double-quotes should be used around
26766 the name. In the command output, the path will show up separated
26767 by the system directory-separator character. The directory-separator
26768 character must not be used
26769 in any directory name.
26770 If no directories are specified, the current path is displayed.
26773 @subsubheading @value{GDBN} Command
26775 The corresponding @value{GDBN} command is @samp{path}.
26777 @subsubheading Example
26782 ^done,path="/usr/bin"
26784 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26785 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26787 -environment-path -r /usr/local/bin
26788 ^done,path="/usr/local/bin:/usr/bin"
26793 @subheading The @code{-environment-pwd} Command
26794 @findex -environment-pwd
26796 @subsubheading Synopsis
26802 Show the current working directory.
26804 @subsubheading @value{GDBN} Command
26806 The corresponding @value{GDBN} command is @samp{pwd}.
26808 @subsubheading Example
26813 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26817 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26818 @node GDB/MI Thread Commands
26819 @section @sc{gdb/mi} Thread Commands
26822 @subheading The @code{-thread-info} Command
26823 @findex -thread-info
26825 @subsubheading Synopsis
26828 -thread-info [ @var{thread-id} ]
26831 Reports information about either a specific thread, if
26832 the @var{thread-id} parameter is present, or about all
26833 threads. When printing information about all threads,
26834 also reports the current thread.
26836 @subsubheading @value{GDBN} Command
26838 The @samp{info thread} command prints the same information
26841 @subsubheading Result
26843 The result is a list of threads. The following attributes are
26844 defined for a given thread:
26848 This field exists only for the current thread. It has the value @samp{*}.
26851 The identifier that @value{GDBN} uses to refer to the thread.
26854 The identifier that the target uses to refer to the thread.
26857 Extra information about the thread, in a target-specific format. This
26861 The name of the thread. If the user specified a name using the
26862 @code{thread name} command, then this name is given. Otherwise, if
26863 @value{GDBN} can extract the thread name from the target, then that
26864 name is given. If @value{GDBN} cannot find the thread name, then this
26868 The stack frame currently executing in the thread.
26871 The thread's state. The @samp{state} field may have the following
26876 The thread is stopped. Frame information is available for stopped
26880 The thread is running. There's no frame information for running
26886 If @value{GDBN} can find the CPU core on which this thread is running,
26887 then this field is the core identifier. This field is optional.
26891 @subsubheading Example
26896 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26897 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26898 args=[]@},state="running"@},
26899 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26900 frame=@{level="0",addr="0x0804891f",func="foo",
26901 args=[@{name="i",value="10"@}],
26902 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26903 state="running"@}],
26904 current-thread-id="1"
26908 @subheading The @code{-thread-list-ids} Command
26909 @findex -thread-list-ids
26911 @subsubheading Synopsis
26917 Produces a list of the currently known @value{GDBN} thread ids. At the
26918 end of the list it also prints the total number of such threads.
26920 This command is retained for historical reasons, the
26921 @code{-thread-info} command should be used instead.
26923 @subsubheading @value{GDBN} Command
26925 Part of @samp{info threads} supplies the same information.
26927 @subsubheading Example
26932 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26933 current-thread-id="1",number-of-threads="3"
26938 @subheading The @code{-thread-select} Command
26939 @findex -thread-select
26941 @subsubheading Synopsis
26944 -thread-select @var{threadnum}
26947 Make @var{threadnum} the current thread. It prints the number of the new
26948 current thread, and the topmost frame for that thread.
26950 This command is deprecated in favor of explicitly using the
26951 @samp{--thread} option to each command.
26953 @subsubheading @value{GDBN} Command
26955 The corresponding @value{GDBN} command is @samp{thread}.
26957 @subsubheading Example
26964 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26965 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26969 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26970 number-of-threads="3"
26973 ^done,new-thread-id="3",
26974 frame=@{level="0",func="vprintf",
26975 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26976 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26980 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26981 @node GDB/MI Ada Tasking Commands
26982 @section @sc{gdb/mi} Ada Tasking Commands
26984 @subheading The @code{-ada-task-info} Command
26985 @findex -ada-task-info
26987 @subsubheading Synopsis
26990 -ada-task-info [ @var{task-id} ]
26993 Reports information about either a specific Ada task, if the
26994 @var{task-id} parameter is present, or about all Ada tasks.
26996 @subsubheading @value{GDBN} Command
26998 The @samp{info tasks} command prints the same information
26999 about all Ada tasks (@pxref{Ada Tasks}).
27001 @subsubheading Result
27003 The result is a table of Ada tasks. The following columns are
27004 defined for each Ada task:
27008 This field exists only for the current thread. It has the value @samp{*}.
27011 The identifier that @value{GDBN} uses to refer to the Ada task.
27014 The identifier that the target uses to refer to the Ada task.
27017 The identifier of the thread corresponding to the Ada task.
27019 This field should always exist, as Ada tasks are always implemented
27020 on top of a thread. But if @value{GDBN} cannot find this corresponding
27021 thread for any reason, the field is omitted.
27024 This field exists only when the task was created by another task.
27025 In this case, it provides the ID of the parent task.
27028 The base priority of the task.
27031 The current state of the task. For a detailed description of the
27032 possible states, see @ref{Ada Tasks}.
27035 The name of the task.
27039 @subsubheading Example
27043 ^done,tasks=@{nr_rows="3",nr_cols="8",
27044 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27045 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27046 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27047 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27048 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27049 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27050 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27051 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27052 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27053 state="Child Termination Wait",name="main_task"@}]@}
27057 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27058 @node GDB/MI Program Execution
27059 @section @sc{gdb/mi} Program Execution
27061 These are the asynchronous commands which generate the out-of-band
27062 record @samp{*stopped}. Currently @value{GDBN} only really executes
27063 asynchronously with remote targets and this interaction is mimicked in
27066 @subheading The @code{-exec-continue} Command
27067 @findex -exec-continue
27069 @subsubheading Synopsis
27072 -exec-continue [--reverse] [--all|--thread-group N]
27075 Resumes the execution of the inferior program, which will continue
27076 to execute until it reaches a debugger stop event. If the
27077 @samp{--reverse} option is specified, execution resumes in reverse until
27078 it reaches a stop event. Stop events may include
27081 breakpoints or watchpoints
27083 signals or exceptions
27085 the end of the process (or its beginning under @samp{--reverse})
27087 the end or beginning of a replay log if one is being used.
27089 In all-stop mode (@pxref{All-Stop
27090 Mode}), may resume only one thread, or all threads, depending on the
27091 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27092 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27093 ignored in all-stop mode. If the @samp{--thread-group} options is
27094 specified, then all threads in that thread group are resumed.
27096 @subsubheading @value{GDBN} Command
27098 The corresponding @value{GDBN} corresponding is @samp{continue}.
27100 @subsubheading Example
27107 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27108 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27114 @subheading The @code{-exec-finish} Command
27115 @findex -exec-finish
27117 @subsubheading Synopsis
27120 -exec-finish [--reverse]
27123 Resumes the execution of the inferior program until the current
27124 function is exited. Displays the results returned by the function.
27125 If the @samp{--reverse} option is specified, resumes the reverse
27126 execution of the inferior program until the point where current
27127 function was called.
27129 @subsubheading @value{GDBN} Command
27131 The corresponding @value{GDBN} command is @samp{finish}.
27133 @subsubheading Example
27135 Function returning @code{void}.
27142 *stopped,reason="function-finished",frame=@{func="main",args=[],
27143 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27147 Function returning other than @code{void}. The name of the internal
27148 @value{GDBN} variable storing the result is printed, together with the
27155 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27156 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27157 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27158 gdb-result-var="$1",return-value="0"
27163 @subheading The @code{-exec-interrupt} Command
27164 @findex -exec-interrupt
27166 @subsubheading Synopsis
27169 -exec-interrupt [--all|--thread-group N]
27172 Interrupts the background execution of the target. Note how the token
27173 associated with the stop message is the one for the execution command
27174 that has been interrupted. The token for the interrupt itself only
27175 appears in the @samp{^done} output. If the user is trying to
27176 interrupt a non-running program, an error message will be printed.
27178 Note that when asynchronous execution is enabled, this command is
27179 asynchronous just like other execution commands. That is, first the
27180 @samp{^done} response will be printed, and the target stop will be
27181 reported after that using the @samp{*stopped} notification.
27183 In non-stop mode, only the context thread is interrupted by default.
27184 All threads (in all inferiors) will be interrupted if the
27185 @samp{--all} option is specified. If the @samp{--thread-group}
27186 option is specified, all threads in that group will be interrupted.
27188 @subsubheading @value{GDBN} Command
27190 The corresponding @value{GDBN} command is @samp{interrupt}.
27192 @subsubheading Example
27203 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27204 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27205 fullname="/home/foo/bar/try.c",line="13"@}
27210 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27214 @subheading The @code{-exec-jump} Command
27217 @subsubheading Synopsis
27220 -exec-jump @var{location}
27223 Resumes execution of the inferior program at the location specified by
27224 parameter. @xref{Specify Location}, for a description of the
27225 different forms of @var{location}.
27227 @subsubheading @value{GDBN} Command
27229 The corresponding @value{GDBN} command is @samp{jump}.
27231 @subsubheading Example
27234 -exec-jump foo.c:10
27235 *running,thread-id="all"
27240 @subheading The @code{-exec-next} Command
27243 @subsubheading Synopsis
27246 -exec-next [--reverse]
27249 Resumes execution of the inferior program, stopping when the beginning
27250 of the next source line is reached.
27252 If the @samp{--reverse} option is specified, resumes reverse execution
27253 of the inferior program, stopping at the beginning of the previous
27254 source line. If you issue this command on the first line of a
27255 function, it will take you back to the caller of that function, to the
27256 source line where the function was called.
27259 @subsubheading @value{GDBN} Command
27261 The corresponding @value{GDBN} command is @samp{next}.
27263 @subsubheading Example
27269 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27274 @subheading The @code{-exec-next-instruction} Command
27275 @findex -exec-next-instruction
27277 @subsubheading Synopsis
27280 -exec-next-instruction [--reverse]
27283 Executes one machine instruction. If the instruction is a function
27284 call, continues until the function returns. If the program stops at an
27285 instruction in the middle of a source line, the address will be
27288 If the @samp{--reverse} option is specified, resumes reverse execution
27289 of the inferior program, stopping at the previous instruction. If the
27290 previously executed instruction was a return from another function,
27291 it will continue to execute in reverse until the call to that function
27292 (from the current stack frame) is reached.
27294 @subsubheading @value{GDBN} Command
27296 The corresponding @value{GDBN} command is @samp{nexti}.
27298 @subsubheading Example
27302 -exec-next-instruction
27306 *stopped,reason="end-stepping-range",
27307 addr="0x000100d4",line="5",file="hello.c"
27312 @subheading The @code{-exec-return} Command
27313 @findex -exec-return
27315 @subsubheading Synopsis
27321 Makes current function return immediately. Doesn't execute the inferior.
27322 Displays the new current frame.
27324 @subsubheading @value{GDBN} Command
27326 The corresponding @value{GDBN} command is @samp{return}.
27328 @subsubheading Example
27332 200-break-insert callee4
27333 200^done,bkpt=@{number="1",addr="0x00010734",
27334 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27339 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27340 frame=@{func="callee4",args=[],
27341 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27342 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27348 111^done,frame=@{level="0",func="callee3",
27349 args=[@{name="strarg",
27350 value="0x11940 \"A string argument.\""@}],
27351 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27352 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27357 @subheading The @code{-exec-run} Command
27360 @subsubheading Synopsis
27363 -exec-run [ --all | --thread-group N ] [ --start ]
27366 Starts execution of the inferior from the beginning. The inferior
27367 executes until either a breakpoint is encountered or the program
27368 exits. In the latter case the output will include an exit code, if
27369 the program has exited exceptionally.
27371 When neither the @samp{--all} nor the @samp{--thread-group} option
27372 is specified, the current inferior is started. If the
27373 @samp{--thread-group} option is specified, it should refer to a thread
27374 group of type @samp{process}, and that thread group will be started.
27375 If the @samp{--all} option is specified, then all inferiors will be started.
27377 Using the @samp{--start} option instructs the debugger to stop
27378 the execution at the start of the inferior's main subprogram,
27379 following the same behavior as the @code{start} command
27380 (@pxref{Starting}).
27382 @subsubheading @value{GDBN} Command
27384 The corresponding @value{GDBN} command is @samp{run}.
27386 @subsubheading Examples
27391 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27396 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27397 frame=@{func="main",args=[],file="recursive2.c",
27398 fullname="/home/foo/bar/recursive2.c",line="4"@}
27403 Program exited normally:
27411 *stopped,reason="exited-normally"
27416 Program exited exceptionally:
27424 *stopped,reason="exited",exit-code="01"
27428 Another way the program can terminate is if it receives a signal such as
27429 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27433 *stopped,reason="exited-signalled",signal-name="SIGINT",
27434 signal-meaning="Interrupt"
27438 @c @subheading -exec-signal
27441 @subheading The @code{-exec-step} Command
27444 @subsubheading Synopsis
27447 -exec-step [--reverse]
27450 Resumes execution of the inferior program, stopping when the beginning
27451 of the next source line is reached, if the next source line is not a
27452 function call. If it is, stop at the first instruction of the called
27453 function. If the @samp{--reverse} option is specified, resumes reverse
27454 execution of the inferior program, stopping at the beginning of the
27455 previously executed source line.
27457 @subsubheading @value{GDBN} Command
27459 The corresponding @value{GDBN} command is @samp{step}.
27461 @subsubheading Example
27463 Stepping into a function:
27469 *stopped,reason="end-stepping-range",
27470 frame=@{func="foo",args=[@{name="a",value="10"@},
27471 @{name="b",value="0"@}],file="recursive2.c",
27472 fullname="/home/foo/bar/recursive2.c",line="11"@}
27482 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27487 @subheading The @code{-exec-step-instruction} Command
27488 @findex -exec-step-instruction
27490 @subsubheading Synopsis
27493 -exec-step-instruction [--reverse]
27496 Resumes the inferior which executes one machine instruction. If the
27497 @samp{--reverse} option is specified, resumes reverse execution of the
27498 inferior program, stopping at the previously executed instruction.
27499 The output, once @value{GDBN} has stopped, will vary depending on
27500 whether we have stopped in the middle of a source line or not. In the
27501 former case, the address at which the program stopped will be printed
27504 @subsubheading @value{GDBN} Command
27506 The corresponding @value{GDBN} command is @samp{stepi}.
27508 @subsubheading Example
27512 -exec-step-instruction
27516 *stopped,reason="end-stepping-range",
27517 frame=@{func="foo",args=[],file="try.c",
27518 fullname="/home/foo/bar/try.c",line="10"@}
27520 -exec-step-instruction
27524 *stopped,reason="end-stepping-range",
27525 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27526 fullname="/home/foo/bar/try.c",line="10"@}
27531 @subheading The @code{-exec-until} Command
27532 @findex -exec-until
27534 @subsubheading Synopsis
27537 -exec-until [ @var{location} ]
27540 Executes the inferior until the @var{location} specified in the
27541 argument is reached. If there is no argument, the inferior executes
27542 until a source line greater than the current one is reached. The
27543 reason for stopping in this case will be @samp{location-reached}.
27545 @subsubheading @value{GDBN} Command
27547 The corresponding @value{GDBN} command is @samp{until}.
27549 @subsubheading Example
27553 -exec-until recursive2.c:6
27557 *stopped,reason="location-reached",frame=@{func="main",args=[],
27558 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27563 @subheading -file-clear
27564 Is this going away????
27567 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27568 @node GDB/MI Stack Manipulation
27569 @section @sc{gdb/mi} Stack Manipulation Commands
27571 @subheading The @code{-enable-frame-filters} Command
27572 @findex -enable-frame-filters
27575 -enable-frame-filters
27578 @value{GDBN} allows Python-based frame filters to affect the output of
27579 the MI commands relating to stack traces. As there is no way to
27580 implement this in a fully backward-compatible way, a front end must
27581 request that this functionality be enabled.
27583 Once enabled, this feature cannot be disabled.
27585 Note that if Python support has not been compiled into @value{GDBN},
27586 this command will still succeed (and do nothing).
27588 @subheading The @code{-stack-info-frame} Command
27589 @findex -stack-info-frame
27591 @subsubheading Synopsis
27597 Get info on the selected frame.
27599 @subsubheading @value{GDBN} Command
27601 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27602 (without arguments).
27604 @subsubheading Example
27609 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27610 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27611 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27615 @subheading The @code{-stack-info-depth} Command
27616 @findex -stack-info-depth
27618 @subsubheading Synopsis
27621 -stack-info-depth [ @var{max-depth} ]
27624 Return the depth of the stack. If the integer argument @var{max-depth}
27625 is specified, do not count beyond @var{max-depth} frames.
27627 @subsubheading @value{GDBN} Command
27629 There's no equivalent @value{GDBN} command.
27631 @subsubheading Example
27633 For a stack with frame levels 0 through 11:
27640 -stack-info-depth 4
27643 -stack-info-depth 12
27646 -stack-info-depth 11
27649 -stack-info-depth 13
27654 @anchor{-stack-list-arguments}
27655 @subheading The @code{-stack-list-arguments} Command
27656 @findex -stack-list-arguments
27658 @subsubheading Synopsis
27661 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27662 [ @var{low-frame} @var{high-frame} ]
27665 Display a list of the arguments for the frames between @var{low-frame}
27666 and @var{high-frame} (inclusive). If @var{low-frame} and
27667 @var{high-frame} are not provided, list the arguments for the whole
27668 call stack. If the two arguments are equal, show the single frame
27669 at the corresponding level. It is an error if @var{low-frame} is
27670 larger than the actual number of frames. On the other hand,
27671 @var{high-frame} may be larger than the actual number of frames, in
27672 which case only existing frames will be returned.
27674 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27675 the variables; if it is 1 or @code{--all-values}, print also their
27676 values; and if it is 2 or @code{--simple-values}, print the name,
27677 type and value for simple data types, and the name and type for arrays,
27678 structures and unions. If the option @code{--no-frame-filters} is
27679 supplied, then Python frame filters will not be executed.
27681 If the @code{--skip-unavailable} option is specified, arguments that
27682 are not available are not listed. Partially available arguments
27683 are still displayed, however.
27685 Use of this command to obtain arguments in a single frame is
27686 deprecated in favor of the @samp{-stack-list-variables} command.
27688 @subsubheading @value{GDBN} Command
27690 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27691 @samp{gdb_get_args} command which partially overlaps with the
27692 functionality of @samp{-stack-list-arguments}.
27694 @subsubheading Example
27701 frame=@{level="0",addr="0x00010734",func="callee4",
27702 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27703 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27704 frame=@{level="1",addr="0x0001076c",func="callee3",
27705 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27706 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27707 frame=@{level="2",addr="0x0001078c",func="callee2",
27708 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27709 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27710 frame=@{level="3",addr="0x000107b4",func="callee1",
27711 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27712 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27713 frame=@{level="4",addr="0x000107e0",func="main",
27714 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27715 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27717 -stack-list-arguments 0
27720 frame=@{level="0",args=[]@},
27721 frame=@{level="1",args=[name="strarg"]@},
27722 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27723 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27724 frame=@{level="4",args=[]@}]
27726 -stack-list-arguments 1
27729 frame=@{level="0",args=[]@},
27731 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27732 frame=@{level="2",args=[
27733 @{name="intarg",value="2"@},
27734 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27735 @{frame=@{level="3",args=[
27736 @{name="intarg",value="2"@},
27737 @{name="strarg",value="0x11940 \"A string argument.\""@},
27738 @{name="fltarg",value="3.5"@}]@},
27739 frame=@{level="4",args=[]@}]
27741 -stack-list-arguments 0 2 2
27742 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27744 -stack-list-arguments 1 2 2
27745 ^done,stack-args=[frame=@{level="2",
27746 args=[@{name="intarg",value="2"@},
27747 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27751 @c @subheading -stack-list-exception-handlers
27754 @anchor{-stack-list-frames}
27755 @subheading The @code{-stack-list-frames} Command
27756 @findex -stack-list-frames
27758 @subsubheading Synopsis
27761 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
27764 List the frames currently on the stack. For each frame it displays the
27769 The frame number, 0 being the topmost frame, i.e., the innermost function.
27771 The @code{$pc} value for that frame.
27775 File name of the source file where the function lives.
27776 @item @var{fullname}
27777 The full file name of the source file where the function lives.
27779 Line number corresponding to the @code{$pc}.
27781 The shared library where this function is defined. This is only given
27782 if the frame's function is not known.
27785 If invoked without arguments, this command prints a backtrace for the
27786 whole stack. If given two integer arguments, it shows the frames whose
27787 levels are between the two arguments (inclusive). If the two arguments
27788 are equal, it shows the single frame at the corresponding level. It is
27789 an error if @var{low-frame} is larger than the actual number of
27790 frames. On the other hand, @var{high-frame} may be larger than the
27791 actual number of frames, in which case only existing frames will be
27792 returned. If the option @code{--no-frame-filters} is supplied, then
27793 Python frame filters will not be executed.
27795 @subsubheading @value{GDBN} Command
27797 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27799 @subsubheading Example
27801 Full stack backtrace:
27807 [frame=@{level="0",addr="0x0001076c",func="foo",
27808 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27809 frame=@{level="1",addr="0x000107a4",func="foo",
27810 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27811 frame=@{level="2",addr="0x000107a4",func="foo",
27812 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27813 frame=@{level="3",addr="0x000107a4",func="foo",
27814 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27815 frame=@{level="4",addr="0x000107a4",func="foo",
27816 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27817 frame=@{level="5",addr="0x000107a4",func="foo",
27818 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27819 frame=@{level="6",addr="0x000107a4",func="foo",
27820 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27821 frame=@{level="7",addr="0x000107a4",func="foo",
27822 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27823 frame=@{level="8",addr="0x000107a4",func="foo",
27824 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27825 frame=@{level="9",addr="0x000107a4",func="foo",
27826 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27827 frame=@{level="10",addr="0x000107a4",func="foo",
27828 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27829 frame=@{level="11",addr="0x00010738",func="main",
27830 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27834 Show frames between @var{low_frame} and @var{high_frame}:
27838 -stack-list-frames 3 5
27840 [frame=@{level="3",addr="0x000107a4",func="foo",
27841 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27842 frame=@{level="4",addr="0x000107a4",func="foo",
27843 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27844 frame=@{level="5",addr="0x000107a4",func="foo",
27845 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27849 Show a single frame:
27853 -stack-list-frames 3 3
27855 [frame=@{level="3",addr="0x000107a4",func="foo",
27856 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27861 @subheading The @code{-stack-list-locals} Command
27862 @findex -stack-list-locals
27863 @anchor{-stack-list-locals}
27865 @subsubheading Synopsis
27868 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27871 Display the local variable names for the selected frame. If
27872 @var{print-values} is 0 or @code{--no-values}, print only the names of
27873 the variables; if it is 1 or @code{--all-values}, print also their
27874 values; and if it is 2 or @code{--simple-values}, print the name,
27875 type and value for simple data types, and the name and type for arrays,
27876 structures and unions. In this last case, a frontend can immediately
27877 display the value of simple data types and create variable objects for
27878 other data types when the user wishes to explore their values in
27879 more detail. If the option @code{--no-frame-filters} is supplied, then
27880 Python frame filters will not be executed.
27882 If the @code{--skip-unavailable} option is specified, local variables
27883 that are not available are not listed. Partially available local
27884 variables are still displayed, however.
27886 This command is deprecated in favor of the
27887 @samp{-stack-list-variables} command.
27889 @subsubheading @value{GDBN} Command
27891 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27893 @subsubheading Example
27897 -stack-list-locals 0
27898 ^done,locals=[name="A",name="B",name="C"]
27900 -stack-list-locals --all-values
27901 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27902 @{name="C",value="@{1, 2, 3@}"@}]
27903 -stack-list-locals --simple-values
27904 ^done,locals=[@{name="A",type="int",value="1"@},
27905 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27909 @anchor{-stack-list-variables}
27910 @subheading The @code{-stack-list-variables} Command
27911 @findex -stack-list-variables
27913 @subsubheading Synopsis
27916 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27919 Display the names of local variables and function arguments for the selected frame. If
27920 @var{print-values} is 0 or @code{--no-values}, print only the names of
27921 the variables; if it is 1 or @code{--all-values}, print also their
27922 values; and if it is 2 or @code{--simple-values}, print the name,
27923 type and value for simple data types, and the name and type for arrays,
27924 structures and unions. If the option @code{--no-frame-filters} is
27925 supplied, then Python frame filters will not be executed.
27927 If the @code{--skip-unavailable} option is specified, local variables
27928 and arguments that are not available are not listed. Partially
27929 available arguments and local variables are still displayed, however.
27931 @subsubheading Example
27935 -stack-list-variables --thread 1 --frame 0 --all-values
27936 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27941 @subheading The @code{-stack-select-frame} Command
27942 @findex -stack-select-frame
27944 @subsubheading Synopsis
27947 -stack-select-frame @var{framenum}
27950 Change the selected frame. Select a different frame @var{framenum} on
27953 This command in deprecated in favor of passing the @samp{--frame}
27954 option to every command.
27956 @subsubheading @value{GDBN} Command
27958 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27959 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27961 @subsubheading Example
27965 -stack-select-frame 2
27970 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27971 @node GDB/MI Variable Objects
27972 @section @sc{gdb/mi} Variable Objects
27976 @subheading Motivation for Variable Objects in @sc{gdb/mi}
27978 For the implementation of a variable debugger window (locals, watched
27979 expressions, etc.), we are proposing the adaptation of the existing code
27980 used by @code{Insight}.
27982 The two main reasons for that are:
27986 It has been proven in practice (it is already on its second generation).
27989 It will shorten development time (needless to say how important it is
27993 The original interface was designed to be used by Tcl code, so it was
27994 slightly changed so it could be used through @sc{gdb/mi}. This section
27995 describes the @sc{gdb/mi} operations that will be available and gives some
27996 hints about their use.
27998 @emph{Note}: In addition to the set of operations described here, we
27999 expect the @sc{gui} implementation of a variable window to require, at
28000 least, the following operations:
28003 @item @code{-gdb-show} @code{output-radix}
28004 @item @code{-stack-list-arguments}
28005 @item @code{-stack-list-locals}
28006 @item @code{-stack-select-frame}
28011 @subheading Introduction to Variable Objects
28013 @cindex variable objects in @sc{gdb/mi}
28015 Variable objects are "object-oriented" MI interface for examining and
28016 changing values of expressions. Unlike some other MI interfaces that
28017 work with expressions, variable objects are specifically designed for
28018 simple and efficient presentation in the frontend. A variable object
28019 is identified by string name. When a variable object is created, the
28020 frontend specifies the expression for that variable object. The
28021 expression can be a simple variable, or it can be an arbitrary complex
28022 expression, and can even involve CPU registers. After creating a
28023 variable object, the frontend can invoke other variable object
28024 operations---for example to obtain or change the value of a variable
28025 object, or to change display format.
28027 Variable objects have hierarchical tree structure. Any variable object
28028 that corresponds to a composite type, such as structure in C, has
28029 a number of child variable objects, for example corresponding to each
28030 element of a structure. A child variable object can itself have
28031 children, recursively. Recursion ends when we reach
28032 leaf variable objects, which always have built-in types. Child variable
28033 objects are created only by explicit request, so if a frontend
28034 is not interested in the children of a particular variable object, no
28035 child will be created.
28037 For a leaf variable object it is possible to obtain its value as a
28038 string, or set the value from a string. String value can be also
28039 obtained for a non-leaf variable object, but it's generally a string
28040 that only indicates the type of the object, and does not list its
28041 contents. Assignment to a non-leaf variable object is not allowed.
28043 A frontend does not need to read the values of all variable objects each time
28044 the program stops. Instead, MI provides an update command that lists all
28045 variable objects whose values has changed since the last update
28046 operation. This considerably reduces the amount of data that must
28047 be transferred to the frontend. As noted above, children variable
28048 objects are created on demand, and only leaf variable objects have a
28049 real value. As result, gdb will read target memory only for leaf
28050 variables that frontend has created.
28052 The automatic update is not always desirable. For example, a frontend
28053 might want to keep a value of some expression for future reference,
28054 and never update it. For another example, fetching memory is
28055 relatively slow for embedded targets, so a frontend might want
28056 to disable automatic update for the variables that are either not
28057 visible on the screen, or ``closed''. This is possible using so
28058 called ``frozen variable objects''. Such variable objects are never
28059 implicitly updated.
28061 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28062 fixed variable object, the expression is parsed when the variable
28063 object is created, including associating identifiers to specific
28064 variables. The meaning of expression never changes. For a floating
28065 variable object the values of variables whose names appear in the
28066 expressions are re-evaluated every time in the context of the current
28067 frame. Consider this example:
28072 struct work_state state;
28079 If a fixed variable object for the @code{state} variable is created in
28080 this function, and we enter the recursive call, the variable
28081 object will report the value of @code{state} in the top-level
28082 @code{do_work} invocation. On the other hand, a floating variable
28083 object will report the value of @code{state} in the current frame.
28085 If an expression specified when creating a fixed variable object
28086 refers to a local variable, the variable object becomes bound to the
28087 thread and frame in which the variable object is created. When such
28088 variable object is updated, @value{GDBN} makes sure that the
28089 thread/frame combination the variable object is bound to still exists,
28090 and re-evaluates the variable object in context of that thread/frame.
28092 The following is the complete set of @sc{gdb/mi} operations defined to
28093 access this functionality:
28095 @multitable @columnfractions .4 .6
28096 @item @strong{Operation}
28097 @tab @strong{Description}
28099 @item @code{-enable-pretty-printing}
28100 @tab enable Python-based pretty-printing
28101 @item @code{-var-create}
28102 @tab create a variable object
28103 @item @code{-var-delete}
28104 @tab delete the variable object and/or its children
28105 @item @code{-var-set-format}
28106 @tab set the display format of this variable
28107 @item @code{-var-show-format}
28108 @tab show the display format of this variable
28109 @item @code{-var-info-num-children}
28110 @tab tells how many children this object has
28111 @item @code{-var-list-children}
28112 @tab return a list of the object's children
28113 @item @code{-var-info-type}
28114 @tab show the type of this variable object
28115 @item @code{-var-info-expression}
28116 @tab print parent-relative expression that this variable object represents
28117 @item @code{-var-info-path-expression}
28118 @tab print full expression that this variable object represents
28119 @item @code{-var-show-attributes}
28120 @tab is this variable editable? does it exist here?
28121 @item @code{-var-evaluate-expression}
28122 @tab get the value of this variable
28123 @item @code{-var-assign}
28124 @tab set the value of this variable
28125 @item @code{-var-update}
28126 @tab update the variable and its children
28127 @item @code{-var-set-frozen}
28128 @tab set frozeness attribute
28129 @item @code{-var-set-update-range}
28130 @tab set range of children to display on update
28133 In the next subsection we describe each operation in detail and suggest
28134 how it can be used.
28136 @subheading Description And Use of Operations on Variable Objects
28138 @subheading The @code{-enable-pretty-printing} Command
28139 @findex -enable-pretty-printing
28142 -enable-pretty-printing
28145 @value{GDBN} allows Python-based visualizers to affect the output of the
28146 MI variable object commands. However, because there was no way to
28147 implement this in a fully backward-compatible way, a front end must
28148 request that this functionality be enabled.
28150 Once enabled, this feature cannot be disabled.
28152 Note that if Python support has not been compiled into @value{GDBN},
28153 this command will still succeed (and do nothing).
28155 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28156 may work differently in future versions of @value{GDBN}.
28158 @subheading The @code{-var-create} Command
28159 @findex -var-create
28161 @subsubheading Synopsis
28164 -var-create @{@var{name} | "-"@}
28165 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28168 This operation creates a variable object, which allows the monitoring of
28169 a variable, the result of an expression, a memory cell or a CPU
28172 The @var{name} parameter is the string by which the object can be
28173 referenced. It must be unique. If @samp{-} is specified, the varobj
28174 system will generate a string ``varNNNNNN'' automatically. It will be
28175 unique provided that one does not specify @var{name} of that format.
28176 The command fails if a duplicate name is found.
28178 The frame under which the expression should be evaluated can be
28179 specified by @var{frame-addr}. A @samp{*} indicates that the current
28180 frame should be used. A @samp{@@} indicates that a floating variable
28181 object must be created.
28183 @var{expression} is any expression valid on the current language set (must not
28184 begin with a @samp{*}), or one of the following:
28188 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28191 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28194 @samp{$@var{regname}} --- a CPU register name
28197 @cindex dynamic varobj
28198 A varobj's contents may be provided by a Python-based pretty-printer. In this
28199 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28200 have slightly different semantics in some cases. If the
28201 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28202 will never create a dynamic varobj. This ensures backward
28203 compatibility for existing clients.
28205 @subsubheading Result
28207 This operation returns attributes of the newly-created varobj. These
28212 The name of the varobj.
28215 The number of children of the varobj. This number is not necessarily
28216 reliable for a dynamic varobj. Instead, you must examine the
28217 @samp{has_more} attribute.
28220 The varobj's scalar value. For a varobj whose type is some sort of
28221 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28222 will not be interesting.
28225 The varobj's type. This is a string representation of the type, as
28226 would be printed by the @value{GDBN} CLI. If @samp{print object}
28227 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28228 @emph{actual} (derived) type of the object is shown rather than the
28229 @emph{declared} one.
28232 If a variable object is bound to a specific thread, then this is the
28233 thread's identifier.
28236 For a dynamic varobj, this indicates whether there appear to be any
28237 children available. For a non-dynamic varobj, this will be 0.
28240 This attribute will be present and have the value @samp{1} if the
28241 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28242 then this attribute will not be present.
28245 A dynamic varobj can supply a display hint to the front end. The
28246 value comes directly from the Python pretty-printer object's
28247 @code{display_hint} method. @xref{Pretty Printing API}.
28250 Typical output will look like this:
28253 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28254 has_more="@var{has_more}"
28258 @subheading The @code{-var-delete} Command
28259 @findex -var-delete
28261 @subsubheading Synopsis
28264 -var-delete [ -c ] @var{name}
28267 Deletes a previously created variable object and all of its children.
28268 With the @samp{-c} option, just deletes the children.
28270 Returns an error if the object @var{name} is not found.
28273 @subheading The @code{-var-set-format} Command
28274 @findex -var-set-format
28276 @subsubheading Synopsis
28279 -var-set-format @var{name} @var{format-spec}
28282 Sets the output format for the value of the object @var{name} to be
28285 @anchor{-var-set-format}
28286 The syntax for the @var{format-spec} is as follows:
28289 @var{format-spec} @expansion{}
28290 @{binary | decimal | hexadecimal | octal | natural@}
28293 The natural format is the default format choosen automatically
28294 based on the variable type (like decimal for an @code{int}, hex
28295 for pointers, etc.).
28297 For a variable with children, the format is set only on the
28298 variable itself, and the children are not affected.
28300 @subheading The @code{-var-show-format} Command
28301 @findex -var-show-format
28303 @subsubheading Synopsis
28306 -var-show-format @var{name}
28309 Returns the format used to display the value of the object @var{name}.
28312 @var{format} @expansion{}
28317 @subheading The @code{-var-info-num-children} Command
28318 @findex -var-info-num-children
28320 @subsubheading Synopsis
28323 -var-info-num-children @var{name}
28326 Returns the number of children of a variable object @var{name}:
28332 Note that this number is not completely reliable for a dynamic varobj.
28333 It will return the current number of children, but more children may
28337 @subheading The @code{-var-list-children} Command
28338 @findex -var-list-children
28340 @subsubheading Synopsis
28343 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28345 @anchor{-var-list-children}
28347 Return a list of the children of the specified variable object and
28348 create variable objects for them, if they do not already exist. With
28349 a single argument or if @var{print-values} has a value of 0 or
28350 @code{--no-values}, print only the names of the variables; if
28351 @var{print-values} is 1 or @code{--all-values}, also print their
28352 values; and if it is 2 or @code{--simple-values} print the name and
28353 value for simple data types and just the name for arrays, structures
28356 @var{from} and @var{to}, if specified, indicate the range of children
28357 to report. If @var{from} or @var{to} is less than zero, the range is
28358 reset and all children will be reported. Otherwise, children starting
28359 at @var{from} (zero-based) and up to and excluding @var{to} will be
28362 If a child range is requested, it will only affect the current call to
28363 @code{-var-list-children}, but not future calls to @code{-var-update}.
28364 For this, you must instead use @code{-var-set-update-range}. The
28365 intent of this approach is to enable a front end to implement any
28366 update approach it likes; for example, scrolling a view may cause the
28367 front end to request more children with @code{-var-list-children}, and
28368 then the front end could call @code{-var-set-update-range} with a
28369 different range to ensure that future updates are restricted to just
28372 For each child the following results are returned:
28377 Name of the variable object created for this child.
28380 The expression to be shown to the user by the front end to designate this child.
28381 For example this may be the name of a structure member.
28383 For a dynamic varobj, this value cannot be used to form an
28384 expression. There is no way to do this at all with a dynamic varobj.
28386 For C/C@t{++} structures there are several pseudo children returned to
28387 designate access qualifiers. For these pseudo children @var{exp} is
28388 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28389 type and value are not present.
28391 A dynamic varobj will not report the access qualifying
28392 pseudo-children, regardless of the language. This information is not
28393 available at all with a dynamic varobj.
28396 Number of children this child has. For a dynamic varobj, this will be
28400 The type of the child. If @samp{print object}
28401 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28402 @emph{actual} (derived) type of the object is shown rather than the
28403 @emph{declared} one.
28406 If values were requested, this is the value.
28409 If this variable object is associated with a thread, this is the thread id.
28410 Otherwise this result is not present.
28413 If the variable object is frozen, this variable will be present with a value of 1.
28416 A dynamic varobj can supply a display hint to the front end. The
28417 value comes directly from the Python pretty-printer object's
28418 @code{display_hint} method. @xref{Pretty Printing API}.
28421 This attribute will be present and have the value @samp{1} if the
28422 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28423 then this attribute will not be present.
28427 The result may have its own attributes:
28431 A dynamic varobj can supply a display hint to the front end. The
28432 value comes directly from the Python pretty-printer object's
28433 @code{display_hint} method. @xref{Pretty Printing API}.
28436 This is an integer attribute which is nonzero if there are children
28437 remaining after the end of the selected range.
28440 @subsubheading Example
28444 -var-list-children n
28445 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28446 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28448 -var-list-children --all-values n
28449 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28450 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28454 @subheading The @code{-var-info-type} Command
28455 @findex -var-info-type
28457 @subsubheading Synopsis
28460 -var-info-type @var{name}
28463 Returns the type of the specified variable @var{name}. The type is
28464 returned as a string in the same format as it is output by the
28468 type=@var{typename}
28472 @subheading The @code{-var-info-expression} Command
28473 @findex -var-info-expression
28475 @subsubheading Synopsis
28478 -var-info-expression @var{name}
28481 Returns a string that is suitable for presenting this
28482 variable object in user interface. The string is generally
28483 not valid expression in the current language, and cannot be evaluated.
28485 For example, if @code{a} is an array, and variable object
28486 @code{A} was created for @code{a}, then we'll get this output:
28489 (gdb) -var-info-expression A.1
28490 ^done,lang="C",exp="1"
28494 Here, the value of @code{lang} is the language name, which can be
28495 found in @ref{Supported Languages}.
28497 Note that the output of the @code{-var-list-children} command also
28498 includes those expressions, so the @code{-var-info-expression} command
28501 @subheading The @code{-var-info-path-expression} Command
28502 @findex -var-info-path-expression
28504 @subsubheading Synopsis
28507 -var-info-path-expression @var{name}
28510 Returns an expression that can be evaluated in the current
28511 context and will yield the same value that a variable object has.
28512 Compare this with the @code{-var-info-expression} command, which
28513 result can be used only for UI presentation. Typical use of
28514 the @code{-var-info-path-expression} command is creating a
28515 watchpoint from a variable object.
28517 This command is currently not valid for children of a dynamic varobj,
28518 and will give an error when invoked on one.
28520 For example, suppose @code{C} is a C@t{++} class, derived from class
28521 @code{Base}, and that the @code{Base} class has a member called
28522 @code{m_size}. Assume a variable @code{c} is has the type of
28523 @code{C} and a variable object @code{C} was created for variable
28524 @code{c}. Then, we'll get this output:
28526 (gdb) -var-info-path-expression C.Base.public.m_size
28527 ^done,path_expr=((Base)c).m_size)
28530 @subheading The @code{-var-show-attributes} Command
28531 @findex -var-show-attributes
28533 @subsubheading Synopsis
28536 -var-show-attributes @var{name}
28539 List attributes of the specified variable object @var{name}:
28542 status=@var{attr} [ ( ,@var{attr} )* ]
28546 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28548 @subheading The @code{-var-evaluate-expression} Command
28549 @findex -var-evaluate-expression
28551 @subsubheading Synopsis
28554 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28557 Evaluates the expression that is represented by the specified variable
28558 object and returns its value as a string. The format of the string
28559 can be specified with the @samp{-f} option. The possible values of
28560 this option are the same as for @code{-var-set-format}
28561 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28562 the current display format will be used. The current display format
28563 can be changed using the @code{-var-set-format} command.
28569 Note that one must invoke @code{-var-list-children} for a variable
28570 before the value of a child variable can be evaluated.
28572 @subheading The @code{-var-assign} Command
28573 @findex -var-assign
28575 @subsubheading Synopsis
28578 -var-assign @var{name} @var{expression}
28581 Assigns the value of @var{expression} to the variable object specified
28582 by @var{name}. The object must be @samp{editable}. If the variable's
28583 value is altered by the assign, the variable will show up in any
28584 subsequent @code{-var-update} list.
28586 @subsubheading Example
28594 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28598 @subheading The @code{-var-update} Command
28599 @findex -var-update
28601 @subsubheading Synopsis
28604 -var-update [@var{print-values}] @{@var{name} | "*"@}
28607 Reevaluate the expressions corresponding to the variable object
28608 @var{name} and all its direct and indirect children, and return the
28609 list of variable objects whose values have changed; @var{name} must
28610 be a root variable object. Here, ``changed'' means that the result of
28611 @code{-var-evaluate-expression} before and after the
28612 @code{-var-update} is different. If @samp{*} is used as the variable
28613 object names, all existing variable objects are updated, except
28614 for frozen ones (@pxref{-var-set-frozen}). The option
28615 @var{print-values} determines whether both names and values, or just
28616 names are printed. The possible values of this option are the same
28617 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28618 recommended to use the @samp{--all-values} option, to reduce the
28619 number of MI commands needed on each program stop.
28621 With the @samp{*} parameter, if a variable object is bound to a
28622 currently running thread, it will not be updated, without any
28625 If @code{-var-set-update-range} was previously used on a varobj, then
28626 only the selected range of children will be reported.
28628 @code{-var-update} reports all the changed varobjs in a tuple named
28631 Each item in the change list is itself a tuple holding:
28635 The name of the varobj.
28638 If values were requested for this update, then this field will be
28639 present and will hold the value of the varobj.
28642 @anchor{-var-update}
28643 This field is a string which may take one of three values:
28647 The variable object's current value is valid.
28650 The variable object does not currently hold a valid value but it may
28651 hold one in the future if its associated expression comes back into
28655 The variable object no longer holds a valid value.
28656 This can occur when the executable file being debugged has changed,
28657 either through recompilation or by using the @value{GDBN} @code{file}
28658 command. The front end should normally choose to delete these variable
28662 In the future new values may be added to this list so the front should
28663 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28666 This is only present if the varobj is still valid. If the type
28667 changed, then this will be the string @samp{true}; otherwise it will
28670 When a varobj's type changes, its children are also likely to have
28671 become incorrect. Therefore, the varobj's children are automatically
28672 deleted when this attribute is @samp{true}. Also, the varobj's update
28673 range, when set using the @code{-var-set-update-range} command, is
28677 If the varobj's type changed, then this field will be present and will
28680 @item new_num_children
28681 For a dynamic varobj, if the number of children changed, or if the
28682 type changed, this will be the new number of children.
28684 The @samp{numchild} field in other varobj responses is generally not
28685 valid for a dynamic varobj -- it will show the number of children that
28686 @value{GDBN} knows about, but because dynamic varobjs lazily
28687 instantiate their children, this will not reflect the number of
28688 children which may be available.
28690 The @samp{new_num_children} attribute only reports changes to the
28691 number of children known by @value{GDBN}. This is the only way to
28692 detect whether an update has removed children (which necessarily can
28693 only happen at the end of the update range).
28696 The display hint, if any.
28699 This is an integer value, which will be 1 if there are more children
28700 available outside the varobj's update range.
28703 This attribute will be present and have the value @samp{1} if the
28704 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28705 then this attribute will not be present.
28708 If new children were added to a dynamic varobj within the selected
28709 update range (as set by @code{-var-set-update-range}), then they will
28710 be listed in this attribute.
28713 @subsubheading Example
28720 -var-update --all-values var1
28721 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28722 type_changed="false"@}]
28726 @subheading The @code{-var-set-frozen} Command
28727 @findex -var-set-frozen
28728 @anchor{-var-set-frozen}
28730 @subsubheading Synopsis
28733 -var-set-frozen @var{name} @var{flag}
28736 Set the frozenness flag on the variable object @var{name}. The
28737 @var{flag} parameter should be either @samp{1} to make the variable
28738 frozen or @samp{0} to make it unfrozen. If a variable object is
28739 frozen, then neither itself, nor any of its children, are
28740 implicitly updated by @code{-var-update} of
28741 a parent variable or by @code{-var-update *}. Only
28742 @code{-var-update} of the variable itself will update its value and
28743 values of its children. After a variable object is unfrozen, it is
28744 implicitly updated by all subsequent @code{-var-update} operations.
28745 Unfreezing a variable does not update it, only subsequent
28746 @code{-var-update} does.
28748 @subsubheading Example
28752 -var-set-frozen V 1
28757 @subheading The @code{-var-set-update-range} command
28758 @findex -var-set-update-range
28759 @anchor{-var-set-update-range}
28761 @subsubheading Synopsis
28764 -var-set-update-range @var{name} @var{from} @var{to}
28767 Set the range of children to be returned by future invocations of
28768 @code{-var-update}.
28770 @var{from} and @var{to} indicate the range of children to report. If
28771 @var{from} or @var{to} is less than zero, the range is reset and all
28772 children will be reported. Otherwise, children starting at @var{from}
28773 (zero-based) and up to and excluding @var{to} will be reported.
28775 @subsubheading Example
28779 -var-set-update-range V 1 2
28783 @subheading The @code{-var-set-visualizer} command
28784 @findex -var-set-visualizer
28785 @anchor{-var-set-visualizer}
28787 @subsubheading Synopsis
28790 -var-set-visualizer @var{name} @var{visualizer}
28793 Set a visualizer for the variable object @var{name}.
28795 @var{visualizer} is the visualizer to use. The special value
28796 @samp{None} means to disable any visualizer in use.
28798 If not @samp{None}, @var{visualizer} must be a Python expression.
28799 This expression must evaluate to a callable object which accepts a
28800 single argument. @value{GDBN} will call this object with the value of
28801 the varobj @var{name} as an argument (this is done so that the same
28802 Python pretty-printing code can be used for both the CLI and MI).
28803 When called, this object must return an object which conforms to the
28804 pretty-printing interface (@pxref{Pretty Printing API}).
28806 The pre-defined function @code{gdb.default_visualizer} may be used to
28807 select a visualizer by following the built-in process
28808 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28809 a varobj is created, and so ordinarily is not needed.
28811 This feature is only available if Python support is enabled. The MI
28812 command @code{-list-features} (@pxref{GDB/MI Support Commands})
28813 can be used to check this.
28815 @subsubheading Example
28817 Resetting the visualizer:
28821 -var-set-visualizer V None
28825 Reselecting the default (type-based) visualizer:
28829 -var-set-visualizer V gdb.default_visualizer
28833 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28834 can be used to instantiate this class for a varobj:
28838 -var-set-visualizer V "lambda val: SomeClass()"
28842 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28843 @node GDB/MI Data Manipulation
28844 @section @sc{gdb/mi} Data Manipulation
28846 @cindex data manipulation, in @sc{gdb/mi}
28847 @cindex @sc{gdb/mi}, data manipulation
28848 This section describes the @sc{gdb/mi} commands that manipulate data:
28849 examine memory and registers, evaluate expressions, etc.
28851 @c REMOVED FROM THE INTERFACE.
28852 @c @subheading -data-assign
28853 @c Change the value of a program variable. Plenty of side effects.
28854 @c @subsubheading GDB Command
28856 @c @subsubheading Example
28859 @subheading The @code{-data-disassemble} Command
28860 @findex -data-disassemble
28862 @subsubheading Synopsis
28866 [ -s @var{start-addr} -e @var{end-addr} ]
28867 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28875 @item @var{start-addr}
28876 is the beginning address (or @code{$pc})
28877 @item @var{end-addr}
28879 @item @var{filename}
28880 is the name of the file to disassemble
28881 @item @var{linenum}
28882 is the line number to disassemble around
28884 is the number of disassembly lines to be produced. If it is -1,
28885 the whole function will be disassembled, in case no @var{end-addr} is
28886 specified. If @var{end-addr} is specified as a non-zero value, and
28887 @var{lines} is lower than the number of disassembly lines between
28888 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28889 displayed; if @var{lines} is higher than the number of lines between
28890 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28893 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28894 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28895 mixed source and disassembly with raw opcodes).
28898 @subsubheading Result
28900 The result of the @code{-data-disassemble} command will be a list named
28901 @samp{asm_insns}, the contents of this list depend on the @var{mode}
28902 used with the @code{-data-disassemble} command.
28904 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
28909 The address at which this instruction was disassembled.
28912 The name of the function this instruction is within.
28915 The decimal offset in bytes from the start of @samp{func-name}.
28918 The text disassembly for this @samp{address}.
28921 This field is only present for mode 2. This contains the raw opcode
28922 bytes for the @samp{inst} field.
28926 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
28927 @samp{src_and_asm_line}, each of which has the following fields:
28931 The line number within @samp{file}.
28934 The file name from the compilation unit. This might be an absolute
28935 file name or a relative file name depending on the compile command
28939 Absolute file name of @samp{file}. It is converted to a canonical form
28940 using the source file search path
28941 (@pxref{Source Path, ,Specifying Source Directories})
28942 and after resolving all the symbolic links.
28944 If the source file is not found this field will contain the path as
28945 present in the debug information.
28947 @item line_asm_insn
28948 This is a list of tuples containing the disassembly for @samp{line} in
28949 @samp{file}. The fields of each tuple are the same as for
28950 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
28951 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
28956 Note that whatever included in the @samp{inst} field, is not
28957 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
28960 @subsubheading @value{GDBN} Command
28962 The corresponding @value{GDBN} command is @samp{disassemble}.
28964 @subsubheading Example
28966 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28970 -data-disassemble -s $pc -e "$pc + 20" -- 0
28973 @{address="0x000107c0",func-name="main",offset="4",
28974 inst="mov 2, %o0"@},
28975 @{address="0x000107c4",func-name="main",offset="8",
28976 inst="sethi %hi(0x11800), %o2"@},
28977 @{address="0x000107c8",func-name="main",offset="12",
28978 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
28979 @{address="0x000107cc",func-name="main",offset="16",
28980 inst="sethi %hi(0x11800), %o2"@},
28981 @{address="0x000107d0",func-name="main",offset="20",
28982 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
28986 Disassemble the whole @code{main} function. Line 32 is part of
28990 -data-disassemble -f basics.c -l 32 -- 0
28992 @{address="0x000107bc",func-name="main",offset="0",
28993 inst="save %sp, -112, %sp"@},
28994 @{address="0x000107c0",func-name="main",offset="4",
28995 inst="mov 2, %o0"@},
28996 @{address="0x000107c4",func-name="main",offset="8",
28997 inst="sethi %hi(0x11800), %o2"@},
28999 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29000 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29004 Disassemble 3 instructions from the start of @code{main}:
29008 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29010 @{address="0x000107bc",func-name="main",offset="0",
29011 inst="save %sp, -112, %sp"@},
29012 @{address="0x000107c0",func-name="main",offset="4",
29013 inst="mov 2, %o0"@},
29014 @{address="0x000107c4",func-name="main",offset="8",
29015 inst="sethi %hi(0x11800), %o2"@}]
29019 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29023 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29025 src_and_asm_line=@{line="31",
29026 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29027 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29028 line_asm_insn=[@{address="0x000107bc",
29029 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29030 src_and_asm_line=@{line="32",
29031 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29032 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29033 line_asm_insn=[@{address="0x000107c0",
29034 func-name="main",offset="4",inst="mov 2, %o0"@},
29035 @{address="0x000107c4",func-name="main",offset="8",
29036 inst="sethi %hi(0x11800), %o2"@}]@}]
29041 @subheading The @code{-data-evaluate-expression} Command
29042 @findex -data-evaluate-expression
29044 @subsubheading Synopsis
29047 -data-evaluate-expression @var{expr}
29050 Evaluate @var{expr} as an expression. The expression could contain an
29051 inferior function call. The function call will execute synchronously.
29052 If the expression contains spaces, it must be enclosed in double quotes.
29054 @subsubheading @value{GDBN} Command
29056 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29057 @samp{call}. In @code{gdbtk} only, there's a corresponding
29058 @samp{gdb_eval} command.
29060 @subsubheading Example
29062 In the following example, the numbers that precede the commands are the
29063 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29064 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29068 211-data-evaluate-expression A
29071 311-data-evaluate-expression &A
29072 311^done,value="0xefffeb7c"
29074 411-data-evaluate-expression A+3
29077 511-data-evaluate-expression "A + 3"
29083 @subheading The @code{-data-list-changed-registers} Command
29084 @findex -data-list-changed-registers
29086 @subsubheading Synopsis
29089 -data-list-changed-registers
29092 Display a list of the registers that have changed.
29094 @subsubheading @value{GDBN} Command
29096 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29097 has the corresponding command @samp{gdb_changed_register_list}.
29099 @subsubheading Example
29101 On a PPC MBX board:
29109 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29110 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29113 -data-list-changed-registers
29114 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29115 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29116 "24","25","26","27","28","30","31","64","65","66","67","69"]
29121 @subheading The @code{-data-list-register-names} Command
29122 @findex -data-list-register-names
29124 @subsubheading Synopsis
29127 -data-list-register-names [ ( @var{regno} )+ ]
29130 Show a list of register names for the current target. If no arguments
29131 are given, it shows a list of the names of all the registers. If
29132 integer numbers are given as arguments, it will print a list of the
29133 names of the registers corresponding to the arguments. To ensure
29134 consistency between a register name and its number, the output list may
29135 include empty register names.
29137 @subsubheading @value{GDBN} Command
29139 @value{GDBN} does not have a command which corresponds to
29140 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29141 corresponding command @samp{gdb_regnames}.
29143 @subsubheading Example
29145 For the PPC MBX board:
29148 -data-list-register-names
29149 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29150 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29151 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29152 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29153 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29154 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29155 "", "pc","ps","cr","lr","ctr","xer"]
29157 -data-list-register-names 1 2 3
29158 ^done,register-names=["r1","r2","r3"]
29162 @subheading The @code{-data-list-register-values} Command
29163 @findex -data-list-register-values
29165 @subsubheading Synopsis
29168 -data-list-register-values
29169 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29172 Display the registers' contents. @var{fmt} is the format according to
29173 which the registers' contents are to be returned, followed by an optional
29174 list of numbers specifying the registers to display. A missing list of
29175 numbers indicates that the contents of all the registers must be
29176 returned. The @code{--skip-unavailable} option indicates that only
29177 the available registers are to be returned.
29179 Allowed formats for @var{fmt} are:
29196 @subsubheading @value{GDBN} Command
29198 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29199 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29201 @subsubheading Example
29203 For a PPC MBX board (note: line breaks are for readability only, they
29204 don't appear in the actual output):
29208 -data-list-register-values r 64 65
29209 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29210 @{number="65",value="0x00029002"@}]
29212 -data-list-register-values x
29213 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29214 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29215 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29216 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29217 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29218 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29219 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29220 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29221 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29222 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29223 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29224 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29225 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29226 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29227 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29228 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29229 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29230 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29231 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29232 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29233 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29234 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29235 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29236 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29237 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29238 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29239 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29240 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29241 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29242 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29243 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29244 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29245 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29246 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29247 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29248 @{number="69",value="0x20002b03"@}]
29253 @subheading The @code{-data-read-memory} Command
29254 @findex -data-read-memory
29256 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29258 @subsubheading Synopsis
29261 -data-read-memory [ -o @var{byte-offset} ]
29262 @var{address} @var{word-format} @var{word-size}
29263 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29270 @item @var{address}
29271 An expression specifying the address of the first memory word to be
29272 read. Complex expressions containing embedded white space should be
29273 quoted using the C convention.
29275 @item @var{word-format}
29276 The format to be used to print the memory words. The notation is the
29277 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29280 @item @var{word-size}
29281 The size of each memory word in bytes.
29283 @item @var{nr-rows}
29284 The number of rows in the output table.
29286 @item @var{nr-cols}
29287 The number of columns in the output table.
29290 If present, indicates that each row should include an @sc{ascii} dump. The
29291 value of @var{aschar} is used as a padding character when a byte is not a
29292 member of the printable @sc{ascii} character set (printable @sc{ascii}
29293 characters are those whose code is between 32 and 126, inclusively).
29295 @item @var{byte-offset}
29296 An offset to add to the @var{address} before fetching memory.
29299 This command displays memory contents as a table of @var{nr-rows} by
29300 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29301 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29302 (returned as @samp{total-bytes}). Should less than the requested number
29303 of bytes be returned by the target, the missing words are identified
29304 using @samp{N/A}. The number of bytes read from the target is returned
29305 in @samp{nr-bytes} and the starting address used to read memory in
29308 The address of the next/previous row or page is available in
29309 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29312 @subsubheading @value{GDBN} Command
29314 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29315 @samp{gdb_get_mem} memory read command.
29317 @subsubheading Example
29319 Read six bytes of memory starting at @code{bytes+6} but then offset by
29320 @code{-6} bytes. Format as three rows of two columns. One byte per
29321 word. Display each word in hex.
29325 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29326 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29327 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29328 prev-page="0x0000138a",memory=[
29329 @{addr="0x00001390",data=["0x00","0x01"]@},
29330 @{addr="0x00001392",data=["0x02","0x03"]@},
29331 @{addr="0x00001394",data=["0x04","0x05"]@}]
29335 Read two bytes of memory starting at address @code{shorts + 64} and
29336 display as a single word formatted in decimal.
29340 5-data-read-memory shorts+64 d 2 1 1
29341 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29342 next-row="0x00001512",prev-row="0x0000150e",
29343 next-page="0x00001512",prev-page="0x0000150e",memory=[
29344 @{addr="0x00001510",data=["128"]@}]
29348 Read thirty two bytes of memory starting at @code{bytes+16} and format
29349 as eight rows of four columns. Include a string encoding with @samp{x}
29350 used as the non-printable character.
29354 4-data-read-memory bytes+16 x 1 8 4 x
29355 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29356 next-row="0x000013c0",prev-row="0x0000139c",
29357 next-page="0x000013c0",prev-page="0x00001380",memory=[
29358 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29359 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29360 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29361 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29362 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29363 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29364 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29365 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29369 @subheading The @code{-data-read-memory-bytes} Command
29370 @findex -data-read-memory-bytes
29372 @subsubheading Synopsis
29375 -data-read-memory-bytes [ -o @var{byte-offset} ]
29376 @var{address} @var{count}
29383 @item @var{address}
29384 An expression specifying the address of the first memory word to be
29385 read. Complex expressions containing embedded white space should be
29386 quoted using the C convention.
29389 The number of bytes to read. This should be an integer literal.
29391 @item @var{byte-offset}
29392 The offsets in bytes relative to @var{address} at which to start
29393 reading. This should be an integer literal. This option is provided
29394 so that a frontend is not required to first evaluate address and then
29395 perform address arithmetics itself.
29399 This command attempts to read all accessible memory regions in the
29400 specified range. First, all regions marked as unreadable in the memory
29401 map (if one is defined) will be skipped. @xref{Memory Region
29402 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29403 regions. For each one, if reading full region results in an errors,
29404 @value{GDBN} will try to read a subset of the region.
29406 In general, every single byte in the region may be readable or not,
29407 and the only way to read every readable byte is to try a read at
29408 every address, which is not practical. Therefore, @value{GDBN} will
29409 attempt to read all accessible bytes at either beginning or the end
29410 of the region, using a binary division scheme. This heuristic works
29411 well for reading accross a memory map boundary. Note that if a region
29412 has a readable range that is neither at the beginning or the end,
29413 @value{GDBN} will not read it.
29415 The result record (@pxref{GDB/MI Result Records}) that is output of
29416 the command includes a field named @samp{memory} whose content is a
29417 list of tuples. Each tuple represent a successfully read memory block
29418 and has the following fields:
29422 The start address of the memory block, as hexadecimal literal.
29425 The end address of the memory block, as hexadecimal literal.
29428 The offset of the memory block, as hexadecimal literal, relative to
29429 the start address passed to @code{-data-read-memory-bytes}.
29432 The contents of the memory block, in hex.
29438 @subsubheading @value{GDBN} Command
29440 The corresponding @value{GDBN} command is @samp{x}.
29442 @subsubheading Example
29446 -data-read-memory-bytes &a 10
29447 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29449 contents="01000000020000000300"@}]
29454 @subheading The @code{-data-write-memory-bytes} Command
29455 @findex -data-write-memory-bytes
29457 @subsubheading Synopsis
29460 -data-write-memory-bytes @var{address} @var{contents}
29461 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
29468 @item @var{address}
29469 An expression specifying the address of the first memory word to be
29470 read. Complex expressions containing embedded white space should be
29471 quoted using the C convention.
29473 @item @var{contents}
29474 The hex-encoded bytes to write.
29477 Optional argument indicating the number of bytes to be written. If @var{count}
29478 is greater than @var{contents}' length, @value{GDBN} will repeatedly
29479 write @var{contents} until it fills @var{count} bytes.
29483 @subsubheading @value{GDBN} Command
29485 There's no corresponding @value{GDBN} command.
29487 @subsubheading Example
29491 -data-write-memory-bytes &a "aabbccdd"
29498 -data-write-memory-bytes &a "aabbccdd" 16e
29503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29504 @node GDB/MI Tracepoint Commands
29505 @section @sc{gdb/mi} Tracepoint Commands
29507 The commands defined in this section implement MI support for
29508 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29510 @subheading The @code{-trace-find} Command
29511 @findex -trace-find
29513 @subsubheading Synopsis
29516 -trace-find @var{mode} [@var{parameters}@dots{}]
29519 Find a trace frame using criteria defined by @var{mode} and
29520 @var{parameters}. The following table lists permissible
29521 modes and their parameters. For details of operation, see @ref{tfind}.
29526 No parameters are required. Stops examining trace frames.
29529 An integer is required as parameter. Selects tracepoint frame with
29532 @item tracepoint-number
29533 An integer is required as parameter. Finds next
29534 trace frame that corresponds to tracepoint with the specified number.
29537 An address is required as parameter. Finds
29538 next trace frame that corresponds to any tracepoint at the specified
29541 @item pc-inside-range
29542 Two addresses are required as parameters. Finds next trace
29543 frame that corresponds to a tracepoint at an address inside the
29544 specified range. Both bounds are considered to be inside the range.
29546 @item pc-outside-range
29547 Two addresses are required as parameters. Finds
29548 next trace frame that corresponds to a tracepoint at an address outside
29549 the specified range. Both bounds are considered to be inside the range.
29552 Line specification is required as parameter. @xref{Specify Location}.
29553 Finds next trace frame that corresponds to a tracepoint at
29554 the specified location.
29558 If @samp{none} was passed as @var{mode}, the response does not
29559 have fields. Otherwise, the response may have the following fields:
29563 This field has either @samp{0} or @samp{1} as the value, depending
29564 on whether a matching tracepoint was found.
29567 The index of the found traceframe. This field is present iff
29568 the @samp{found} field has value of @samp{1}.
29571 The index of the found tracepoint. This field is present iff
29572 the @samp{found} field has value of @samp{1}.
29575 The information about the frame corresponding to the found trace
29576 frame. This field is present only if a trace frame was found.
29577 @xref{GDB/MI Frame Information}, for description of this field.
29581 @subsubheading @value{GDBN} Command
29583 The corresponding @value{GDBN} command is @samp{tfind}.
29585 @subheading -trace-define-variable
29586 @findex -trace-define-variable
29588 @subsubheading Synopsis
29591 -trace-define-variable @var{name} [ @var{value} ]
29594 Create trace variable @var{name} if it does not exist. If
29595 @var{value} is specified, sets the initial value of the specified
29596 trace variable to that value. Note that the @var{name} should start
29597 with the @samp{$} character.
29599 @subsubheading @value{GDBN} Command
29601 The corresponding @value{GDBN} command is @samp{tvariable}.
29603 @subheading The @code{-trace-frame-collected} Command
29604 @findex -trace-frame-collected
29606 @subsubheading Synopsis
29609 -trace-frame-collected
29610 [--var-print-values @var{var_pval}]
29611 [--comp-print-values @var{comp_pval}]
29612 [--registers-format @var{regformat}]
29613 [--memory-contents]
29616 This command returns the set of collected objects, register names,
29617 trace state variable names, memory ranges and computed expressions
29618 that have been collected at a particular trace frame. The optional
29619 parameters to the command affect the output format in different ways.
29620 See the output description table below for more details.
29622 The reported names can be used in the normal manner to create
29623 varobjs and inspect the objects themselves. The items returned by
29624 this command are categorized so that it is clear which is a variable,
29625 which is a register, which is a trace state variable, which is a
29626 memory range and which is a computed expression.
29628 For instance, if the actions were
29630 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
29631 collect *(int*)0xaf02bef0@@40
29635 the object collected in its entirety would be @code{myVar}. The
29636 object @code{myArray} would be partially collected, because only the
29637 element at index @code{myIndex} would be collected. The remaining
29638 objects would be computed expressions.
29640 An example output would be:
29644 -trace-frame-collected
29646 explicit-variables=[@{name="myVar",value="1"@}],
29647 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
29648 @{name="myObj.field",value="0"@},
29649 @{name="myPtr->field",value="1"@},
29650 @{name="myCount + 2",value="3"@},
29651 @{name="$tvar1 + 1",value="43970027"@}],
29652 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
29653 @{number="1",value="0x0"@},
29654 @{number="2",value="0x4"@},
29656 @{number="125",value="0x0"@}],
29657 tvars=[@{name="$tvar1",current="43970026"@}],
29658 memory=[@{address="0x0000000000602264",length="4"@},
29659 @{address="0x0000000000615bc0",length="4"@}]
29666 @item explicit-variables
29667 The set of objects that have been collected in their entirety (as
29668 opposed to collecting just a few elements of an array or a few struct
29669 members). For each object, its name and value are printed.
29670 The @code{--var-print-values} option affects how or whether the value
29671 field is output. If @var{var_pval} is 0, then print only the names;
29672 if it is 1, print also their values; and if it is 2, print the name,
29673 type and value for simple data types, and the name and type for
29674 arrays, structures and unions.
29676 @item computed-expressions
29677 The set of computed expressions that have been collected at the
29678 current trace frame. The @code{--comp-print-values} option affects
29679 this set like the @code{--var-print-values} option affects the
29680 @code{explicit-variables} set. See above.
29683 The registers that have been collected at the current trace frame.
29684 For each register collected, the name and current value are returned.
29685 The value is formatted according to the @code{--registers-format}
29686 option. See the @command{-data-list-register-values} command for a
29687 list of the allowed formats. The default is @samp{x}.
29690 The trace state variables that have been collected at the current
29691 trace frame. For each trace state variable collected, the name and
29692 current value are returned.
29695 The set of memory ranges that have been collected at the current trace
29696 frame. Its content is a list of tuples. Each tuple represents a
29697 collected memory range and has the following fields:
29701 The start address of the memory range, as hexadecimal literal.
29704 The length of the memory range, as decimal literal.
29707 The contents of the memory block, in hex. This field is only present
29708 if the @code{--memory-contents} option is specified.
29714 @subsubheading @value{GDBN} Command
29716 There is no corresponding @value{GDBN} command.
29718 @subsubheading Example
29720 @subheading -trace-list-variables
29721 @findex -trace-list-variables
29723 @subsubheading Synopsis
29726 -trace-list-variables
29729 Return a table of all defined trace variables. Each element of the
29730 table has the following fields:
29734 The name of the trace variable. This field is always present.
29737 The initial value. This is a 64-bit signed integer. This
29738 field is always present.
29741 The value the trace variable has at the moment. This is a 64-bit
29742 signed integer. This field is absent iff current value is
29743 not defined, for example if the trace was never run, or is
29748 @subsubheading @value{GDBN} Command
29750 The corresponding @value{GDBN} command is @samp{tvariables}.
29752 @subsubheading Example
29756 -trace-list-variables
29757 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29758 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29759 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29760 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29761 body=[variable=@{name="$trace_timestamp",initial="0"@}
29762 variable=@{name="$foo",initial="10",current="15"@}]@}
29766 @subheading -trace-save
29767 @findex -trace-save
29769 @subsubheading Synopsis
29772 -trace-save [-r ] @var{filename}
29775 Saves the collected trace data to @var{filename}. Without the
29776 @samp{-r} option, the data is downloaded from the target and saved
29777 in a local file. With the @samp{-r} option the target is asked
29778 to perform the save.
29780 @subsubheading @value{GDBN} Command
29782 The corresponding @value{GDBN} command is @samp{tsave}.
29785 @subheading -trace-start
29786 @findex -trace-start
29788 @subsubheading Synopsis
29794 Starts a tracing experiments. The result of this command does not
29797 @subsubheading @value{GDBN} Command
29799 The corresponding @value{GDBN} command is @samp{tstart}.
29801 @subheading -trace-status
29802 @findex -trace-status
29804 @subsubheading Synopsis
29810 Obtains the status of a tracing experiment. The result may include
29811 the following fields:
29816 May have a value of either @samp{0}, when no tracing operations are
29817 supported, @samp{1}, when all tracing operations are supported, or
29818 @samp{file} when examining trace file. In the latter case, examining
29819 of trace frame is possible but new tracing experiement cannot be
29820 started. This field is always present.
29823 May have a value of either @samp{0} or @samp{1} depending on whether
29824 tracing experiement is in progress on target. This field is present
29825 if @samp{supported} field is not @samp{0}.
29828 Report the reason why the tracing was stopped last time. This field
29829 may be absent iff tracing was never stopped on target yet. The
29830 value of @samp{request} means the tracing was stopped as result of
29831 the @code{-trace-stop} command. The value of @samp{overflow} means
29832 the tracing buffer is full. The value of @samp{disconnection} means
29833 tracing was automatically stopped when @value{GDBN} has disconnected.
29834 The value of @samp{passcount} means tracing was stopped when a
29835 tracepoint was passed a maximal number of times for that tracepoint.
29836 This field is present if @samp{supported} field is not @samp{0}.
29838 @item stopping-tracepoint
29839 The number of tracepoint whose passcount as exceeded. This field is
29840 present iff the @samp{stop-reason} field has the value of
29844 @itemx frames-created
29845 The @samp{frames} field is a count of the total number of trace frames
29846 in the trace buffer, while @samp{frames-created} is the total created
29847 during the run, including ones that were discarded, such as when a
29848 circular trace buffer filled up. Both fields are optional.
29852 These fields tell the current size of the tracing buffer and the
29853 remaining space. These fields are optional.
29856 The value of the circular trace buffer flag. @code{1} means that the
29857 trace buffer is circular and old trace frames will be discarded if
29858 necessary to make room, @code{0} means that the trace buffer is linear
29862 The value of the disconnected tracing flag. @code{1} means that
29863 tracing will continue after @value{GDBN} disconnects, @code{0} means
29864 that the trace run will stop.
29867 The filename of the trace file being examined. This field is
29868 optional, and only present when examining a trace file.
29872 @subsubheading @value{GDBN} Command
29874 The corresponding @value{GDBN} command is @samp{tstatus}.
29876 @subheading -trace-stop
29877 @findex -trace-stop
29879 @subsubheading Synopsis
29885 Stops a tracing experiment. The result of this command has the same
29886 fields as @code{-trace-status}, except that the @samp{supported} and
29887 @samp{running} fields are not output.
29889 @subsubheading @value{GDBN} Command
29891 The corresponding @value{GDBN} command is @samp{tstop}.
29894 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29895 @node GDB/MI Symbol Query
29896 @section @sc{gdb/mi} Symbol Query Commands
29900 @subheading The @code{-symbol-info-address} Command
29901 @findex -symbol-info-address
29903 @subsubheading Synopsis
29906 -symbol-info-address @var{symbol}
29909 Describe where @var{symbol} is stored.
29911 @subsubheading @value{GDBN} Command
29913 The corresponding @value{GDBN} command is @samp{info address}.
29915 @subsubheading Example
29919 @subheading The @code{-symbol-info-file} Command
29920 @findex -symbol-info-file
29922 @subsubheading Synopsis
29928 Show the file for the symbol.
29930 @subsubheading @value{GDBN} Command
29932 There's no equivalent @value{GDBN} command. @code{gdbtk} has
29933 @samp{gdb_find_file}.
29935 @subsubheading Example
29939 @subheading The @code{-symbol-info-function} Command
29940 @findex -symbol-info-function
29942 @subsubheading Synopsis
29945 -symbol-info-function
29948 Show which function the symbol lives in.
29950 @subsubheading @value{GDBN} Command
29952 @samp{gdb_get_function} in @code{gdbtk}.
29954 @subsubheading Example
29958 @subheading The @code{-symbol-info-line} Command
29959 @findex -symbol-info-line
29961 @subsubheading Synopsis
29967 Show the core addresses of the code for a source line.
29969 @subsubheading @value{GDBN} Command
29971 The corresponding @value{GDBN} command is @samp{info line}.
29972 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
29974 @subsubheading Example
29978 @subheading The @code{-symbol-info-symbol} Command
29979 @findex -symbol-info-symbol
29981 @subsubheading Synopsis
29984 -symbol-info-symbol @var{addr}
29987 Describe what symbol is at location @var{addr}.
29989 @subsubheading @value{GDBN} Command
29991 The corresponding @value{GDBN} command is @samp{info symbol}.
29993 @subsubheading Example
29997 @subheading The @code{-symbol-list-functions} Command
29998 @findex -symbol-list-functions
30000 @subsubheading Synopsis
30003 -symbol-list-functions
30006 List the functions in the executable.
30008 @subsubheading @value{GDBN} Command
30010 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30011 @samp{gdb_search} in @code{gdbtk}.
30013 @subsubheading Example
30018 @subheading The @code{-symbol-list-lines} Command
30019 @findex -symbol-list-lines
30021 @subsubheading Synopsis
30024 -symbol-list-lines @var{filename}
30027 Print the list of lines that contain code and their associated program
30028 addresses for the given source filename. The entries are sorted in
30029 ascending PC order.
30031 @subsubheading @value{GDBN} Command
30033 There is no corresponding @value{GDBN} command.
30035 @subsubheading Example
30038 -symbol-list-lines basics.c
30039 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30045 @subheading The @code{-symbol-list-types} Command
30046 @findex -symbol-list-types
30048 @subsubheading Synopsis
30054 List all the type names.
30056 @subsubheading @value{GDBN} Command
30058 The corresponding commands are @samp{info types} in @value{GDBN},
30059 @samp{gdb_search} in @code{gdbtk}.
30061 @subsubheading Example
30065 @subheading The @code{-symbol-list-variables} Command
30066 @findex -symbol-list-variables
30068 @subsubheading Synopsis
30071 -symbol-list-variables
30074 List all the global and static variable names.
30076 @subsubheading @value{GDBN} Command
30078 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30080 @subsubheading Example
30084 @subheading The @code{-symbol-locate} Command
30085 @findex -symbol-locate
30087 @subsubheading Synopsis
30093 @subsubheading @value{GDBN} Command
30095 @samp{gdb_loc} in @code{gdbtk}.
30097 @subsubheading Example
30101 @subheading The @code{-symbol-type} Command
30102 @findex -symbol-type
30104 @subsubheading Synopsis
30107 -symbol-type @var{variable}
30110 Show type of @var{variable}.
30112 @subsubheading @value{GDBN} Command
30114 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30115 @samp{gdb_obj_variable}.
30117 @subsubheading Example
30122 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30123 @node GDB/MI File Commands
30124 @section @sc{gdb/mi} File Commands
30126 This section describes the GDB/MI commands to specify executable file names
30127 and to read in and obtain symbol table information.
30129 @subheading The @code{-file-exec-and-symbols} Command
30130 @findex -file-exec-and-symbols
30132 @subsubheading Synopsis
30135 -file-exec-and-symbols @var{file}
30138 Specify the executable file to be debugged. This file is the one from
30139 which the symbol table is also read. If no file is specified, the
30140 command clears the executable and symbol information. If breakpoints
30141 are set when using this command with no arguments, @value{GDBN} will produce
30142 error messages. Otherwise, no output is produced, except a completion
30145 @subsubheading @value{GDBN} Command
30147 The corresponding @value{GDBN} command is @samp{file}.
30149 @subsubheading Example
30153 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30159 @subheading The @code{-file-exec-file} Command
30160 @findex -file-exec-file
30162 @subsubheading Synopsis
30165 -file-exec-file @var{file}
30168 Specify the executable file to be debugged. Unlike
30169 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30170 from this file. If used without argument, @value{GDBN} clears the information
30171 about the executable file. No output is produced, except a completion
30174 @subsubheading @value{GDBN} Command
30176 The corresponding @value{GDBN} command is @samp{exec-file}.
30178 @subsubheading Example
30182 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30189 @subheading The @code{-file-list-exec-sections} Command
30190 @findex -file-list-exec-sections
30192 @subsubheading Synopsis
30195 -file-list-exec-sections
30198 List the sections of the current executable file.
30200 @subsubheading @value{GDBN} Command
30202 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30203 information as this command. @code{gdbtk} has a corresponding command
30204 @samp{gdb_load_info}.
30206 @subsubheading Example
30211 @subheading The @code{-file-list-exec-source-file} Command
30212 @findex -file-list-exec-source-file
30214 @subsubheading Synopsis
30217 -file-list-exec-source-file
30220 List the line number, the current source file, and the absolute path
30221 to the current source file for the current executable. The macro
30222 information field has a value of @samp{1} or @samp{0} depending on
30223 whether or not the file includes preprocessor macro information.
30225 @subsubheading @value{GDBN} Command
30227 The @value{GDBN} equivalent is @samp{info source}
30229 @subsubheading Example
30233 123-file-list-exec-source-file
30234 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30239 @subheading The @code{-file-list-exec-source-files} Command
30240 @findex -file-list-exec-source-files
30242 @subsubheading Synopsis
30245 -file-list-exec-source-files
30248 List the source files for the current executable.
30250 It will always output both the filename and fullname (absolute file
30251 name) of a source file.
30253 @subsubheading @value{GDBN} Command
30255 The @value{GDBN} equivalent is @samp{info sources}.
30256 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30258 @subsubheading Example
30261 -file-list-exec-source-files
30263 @{file=foo.c,fullname=/home/foo.c@},
30264 @{file=/home/bar.c,fullname=/home/bar.c@},
30265 @{file=gdb_could_not_find_fullpath.c@}]
30270 @subheading The @code{-file-list-shared-libraries} Command
30271 @findex -file-list-shared-libraries
30273 @subsubheading Synopsis
30276 -file-list-shared-libraries
30279 List the shared libraries in the program.
30281 @subsubheading @value{GDBN} Command
30283 The corresponding @value{GDBN} command is @samp{info shared}.
30285 @subsubheading Example
30289 @subheading The @code{-file-list-symbol-files} Command
30290 @findex -file-list-symbol-files
30292 @subsubheading Synopsis
30295 -file-list-symbol-files
30300 @subsubheading @value{GDBN} Command
30302 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30304 @subsubheading Example
30309 @subheading The @code{-file-symbol-file} Command
30310 @findex -file-symbol-file
30312 @subsubheading Synopsis
30315 -file-symbol-file @var{file}
30318 Read symbol table info from the specified @var{file} argument. When
30319 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30320 produced, except for a completion notification.
30322 @subsubheading @value{GDBN} Command
30324 The corresponding @value{GDBN} command is @samp{symbol-file}.
30326 @subsubheading Example
30330 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30336 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30337 @node GDB/MI Memory Overlay Commands
30338 @section @sc{gdb/mi} Memory Overlay Commands
30340 The memory overlay commands are not implemented.
30342 @c @subheading -overlay-auto
30344 @c @subheading -overlay-list-mapping-state
30346 @c @subheading -overlay-list-overlays
30348 @c @subheading -overlay-map
30350 @c @subheading -overlay-off
30352 @c @subheading -overlay-on
30354 @c @subheading -overlay-unmap
30356 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30357 @node GDB/MI Signal Handling Commands
30358 @section @sc{gdb/mi} Signal Handling Commands
30360 Signal handling commands are not implemented.
30362 @c @subheading -signal-handle
30364 @c @subheading -signal-list-handle-actions
30366 @c @subheading -signal-list-signal-types
30370 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30371 @node GDB/MI Target Manipulation
30372 @section @sc{gdb/mi} Target Manipulation Commands
30375 @subheading The @code{-target-attach} Command
30376 @findex -target-attach
30378 @subsubheading Synopsis
30381 -target-attach @var{pid} | @var{gid} | @var{file}
30384 Attach to a process @var{pid} or a file @var{file} outside of
30385 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30386 group, the id previously returned by
30387 @samp{-list-thread-groups --available} must be used.
30389 @subsubheading @value{GDBN} Command
30391 The corresponding @value{GDBN} command is @samp{attach}.
30393 @subsubheading Example
30397 =thread-created,id="1"
30398 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30404 @subheading The @code{-target-compare-sections} Command
30405 @findex -target-compare-sections
30407 @subsubheading Synopsis
30410 -target-compare-sections [ @var{section} ]
30413 Compare data of section @var{section} on target to the exec file.
30414 Without the argument, all sections are compared.
30416 @subsubheading @value{GDBN} Command
30418 The @value{GDBN} equivalent is @samp{compare-sections}.
30420 @subsubheading Example
30425 @subheading The @code{-target-detach} Command
30426 @findex -target-detach
30428 @subsubheading Synopsis
30431 -target-detach [ @var{pid} | @var{gid} ]
30434 Detach from the remote target which normally resumes its execution.
30435 If either @var{pid} or @var{gid} is specified, detaches from either
30436 the specified process, or specified thread group. There's no output.
30438 @subsubheading @value{GDBN} Command
30440 The corresponding @value{GDBN} command is @samp{detach}.
30442 @subsubheading Example
30452 @subheading The @code{-target-disconnect} Command
30453 @findex -target-disconnect
30455 @subsubheading Synopsis
30461 Disconnect from the remote target. There's no output and the target is
30462 generally not resumed.
30464 @subsubheading @value{GDBN} Command
30466 The corresponding @value{GDBN} command is @samp{disconnect}.
30468 @subsubheading Example
30478 @subheading The @code{-target-download} Command
30479 @findex -target-download
30481 @subsubheading Synopsis
30487 Loads the executable onto the remote target.
30488 It prints out an update message every half second, which includes the fields:
30492 The name of the section.
30494 The size of what has been sent so far for that section.
30496 The size of the section.
30498 The total size of what was sent so far (the current and the previous sections).
30500 The size of the overall executable to download.
30504 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30505 @sc{gdb/mi} Output Syntax}).
30507 In addition, it prints the name and size of the sections, as they are
30508 downloaded. These messages include the following fields:
30512 The name of the section.
30514 The size of the section.
30516 The size of the overall executable to download.
30520 At the end, a summary is printed.
30522 @subsubheading @value{GDBN} Command
30524 The corresponding @value{GDBN} command is @samp{load}.
30526 @subsubheading Example
30528 Note: each status message appears on a single line. Here the messages
30529 have been broken down so that they can fit onto a page.
30534 +download,@{section=".text",section-size="6668",total-size="9880"@}
30535 +download,@{section=".text",section-sent="512",section-size="6668",
30536 total-sent="512",total-size="9880"@}
30537 +download,@{section=".text",section-sent="1024",section-size="6668",
30538 total-sent="1024",total-size="9880"@}
30539 +download,@{section=".text",section-sent="1536",section-size="6668",
30540 total-sent="1536",total-size="9880"@}
30541 +download,@{section=".text",section-sent="2048",section-size="6668",
30542 total-sent="2048",total-size="9880"@}
30543 +download,@{section=".text",section-sent="2560",section-size="6668",
30544 total-sent="2560",total-size="9880"@}
30545 +download,@{section=".text",section-sent="3072",section-size="6668",
30546 total-sent="3072",total-size="9880"@}
30547 +download,@{section=".text",section-sent="3584",section-size="6668",
30548 total-sent="3584",total-size="9880"@}
30549 +download,@{section=".text",section-sent="4096",section-size="6668",
30550 total-sent="4096",total-size="9880"@}
30551 +download,@{section=".text",section-sent="4608",section-size="6668",
30552 total-sent="4608",total-size="9880"@}
30553 +download,@{section=".text",section-sent="5120",section-size="6668",
30554 total-sent="5120",total-size="9880"@}
30555 +download,@{section=".text",section-sent="5632",section-size="6668",
30556 total-sent="5632",total-size="9880"@}
30557 +download,@{section=".text",section-sent="6144",section-size="6668",
30558 total-sent="6144",total-size="9880"@}
30559 +download,@{section=".text",section-sent="6656",section-size="6668",
30560 total-sent="6656",total-size="9880"@}
30561 +download,@{section=".init",section-size="28",total-size="9880"@}
30562 +download,@{section=".fini",section-size="28",total-size="9880"@}
30563 +download,@{section=".data",section-size="3156",total-size="9880"@}
30564 +download,@{section=".data",section-sent="512",section-size="3156",
30565 total-sent="7236",total-size="9880"@}
30566 +download,@{section=".data",section-sent="1024",section-size="3156",
30567 total-sent="7748",total-size="9880"@}
30568 +download,@{section=".data",section-sent="1536",section-size="3156",
30569 total-sent="8260",total-size="9880"@}
30570 +download,@{section=".data",section-sent="2048",section-size="3156",
30571 total-sent="8772",total-size="9880"@}
30572 +download,@{section=".data",section-sent="2560",section-size="3156",
30573 total-sent="9284",total-size="9880"@}
30574 +download,@{section=".data",section-sent="3072",section-size="3156",
30575 total-sent="9796",total-size="9880"@}
30576 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30583 @subheading The @code{-target-exec-status} Command
30584 @findex -target-exec-status
30586 @subsubheading Synopsis
30589 -target-exec-status
30592 Provide information on the state of the target (whether it is running or
30593 not, for instance).
30595 @subsubheading @value{GDBN} Command
30597 There's no equivalent @value{GDBN} command.
30599 @subsubheading Example
30603 @subheading The @code{-target-list-available-targets} Command
30604 @findex -target-list-available-targets
30606 @subsubheading Synopsis
30609 -target-list-available-targets
30612 List the possible targets to connect to.
30614 @subsubheading @value{GDBN} Command
30616 The corresponding @value{GDBN} command is @samp{help target}.
30618 @subsubheading Example
30622 @subheading The @code{-target-list-current-targets} Command
30623 @findex -target-list-current-targets
30625 @subsubheading Synopsis
30628 -target-list-current-targets
30631 Describe the current target.
30633 @subsubheading @value{GDBN} Command
30635 The corresponding information is printed by @samp{info file} (among
30638 @subsubheading Example
30642 @subheading The @code{-target-list-parameters} Command
30643 @findex -target-list-parameters
30645 @subsubheading Synopsis
30648 -target-list-parameters
30654 @subsubheading @value{GDBN} Command
30658 @subsubheading Example
30662 @subheading The @code{-target-select} Command
30663 @findex -target-select
30665 @subsubheading Synopsis
30668 -target-select @var{type} @var{parameters @dots{}}
30671 Connect @value{GDBN} to the remote target. This command takes two args:
30675 The type of target, for instance @samp{remote}, etc.
30676 @item @var{parameters}
30677 Device names, host names and the like. @xref{Target Commands, ,
30678 Commands for Managing Targets}, for more details.
30681 The output is a connection notification, followed by the address at
30682 which the target program is, in the following form:
30685 ^connected,addr="@var{address}",func="@var{function name}",
30686 args=[@var{arg list}]
30689 @subsubheading @value{GDBN} Command
30691 The corresponding @value{GDBN} command is @samp{target}.
30693 @subsubheading Example
30697 -target-select remote /dev/ttya
30698 ^connected,addr="0xfe00a300",func="??",args=[]
30702 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30703 @node GDB/MI File Transfer Commands
30704 @section @sc{gdb/mi} File Transfer Commands
30707 @subheading The @code{-target-file-put} Command
30708 @findex -target-file-put
30710 @subsubheading Synopsis
30713 -target-file-put @var{hostfile} @var{targetfile}
30716 Copy file @var{hostfile} from the host system (the machine running
30717 @value{GDBN}) to @var{targetfile} on the target system.
30719 @subsubheading @value{GDBN} Command
30721 The corresponding @value{GDBN} command is @samp{remote put}.
30723 @subsubheading Example
30727 -target-file-put localfile remotefile
30733 @subheading The @code{-target-file-get} Command
30734 @findex -target-file-get
30736 @subsubheading Synopsis
30739 -target-file-get @var{targetfile} @var{hostfile}
30742 Copy file @var{targetfile} from the target system to @var{hostfile}
30743 on the host system.
30745 @subsubheading @value{GDBN} Command
30747 The corresponding @value{GDBN} command is @samp{remote get}.
30749 @subsubheading Example
30753 -target-file-get remotefile localfile
30759 @subheading The @code{-target-file-delete} Command
30760 @findex -target-file-delete
30762 @subsubheading Synopsis
30765 -target-file-delete @var{targetfile}
30768 Delete @var{targetfile} from the target system.
30770 @subsubheading @value{GDBN} Command
30772 The corresponding @value{GDBN} command is @samp{remote delete}.
30774 @subsubheading Example
30778 -target-file-delete remotefile
30784 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30785 @node GDB/MI Ada Exceptions Commands
30786 @section Ada Exceptions @sc{gdb/mi} Commands
30788 @subheading The @code{-info-ada-exceptions} Command
30789 @findex -info-ada-exceptions
30791 @subsubheading Synopsis
30794 -info-ada-exceptions [ @var{regexp}]
30797 List all Ada exceptions defined within the program being debugged.
30798 With a regular expression @var{regexp}, only those exceptions whose
30799 names match @var{regexp} are listed.
30801 @subsubheading @value{GDBN} Command
30803 The corresponding @value{GDBN} command is @samp{info exceptions}.
30805 @subsubheading Result
30807 The result is a table of Ada exceptions. The following columns are
30808 defined for each exception:
30812 The name of the exception.
30815 The address of the exception.
30819 @subsubheading Example
30822 -info-ada-exceptions aint
30823 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
30824 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
30825 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
30826 body=[@{name="constraint_error",address="0x0000000000613da0"@},
30827 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
30830 @subheading Catching Ada Exceptions
30832 The commands describing how to ask @value{GDBN} to stop when a program
30833 raises an exception are described at @ref{Ada Exception GDB/MI
30834 Catchpoint Commands}.
30837 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30838 @node GDB/MI Support Commands
30839 @section @sc{gdb/mi} Support Commands
30841 Since new commands and features get regularly added to @sc{gdb/mi},
30842 some commands are available to help front-ends query the debugger
30843 about support for these capabilities. Similarly, it is also possible
30844 to query @value{GDBN} about target support of certain features.
30846 @subheading The @code{-info-gdb-mi-command} Command
30847 @cindex @code{-info-gdb-mi-command}
30848 @findex -info-gdb-mi-command
30850 @subsubheading Synopsis
30853 -info-gdb-mi-command @var{cmd_name}
30856 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
30858 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
30859 is technically not part of the command name (@pxref{GDB/MI Input
30860 Syntax}), and thus should be omitted in @var{cmd_name}. However,
30861 for ease of use, this command also accepts the form with the leading
30864 @subsubheading @value{GDBN} Command
30866 There is no corresponding @value{GDBN} command.
30868 @subsubheading Result
30870 The result is a tuple. There is currently only one field:
30874 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
30875 @code{"false"} otherwise.
30879 @subsubheading Example
30881 Here is an example where the @sc{gdb/mi} command does not exist:
30884 -info-gdb-mi-command unsupported-command
30885 ^done,command=@{exists="false"@}
30889 And here is an example where the @sc{gdb/mi} command is known
30893 -info-gdb-mi-command symbol-list-lines
30894 ^done,command=@{exists="true"@}
30897 @subheading The @code{-list-features} Command
30898 @findex -list-features
30899 @cindex supported @sc{gdb/mi} features, list
30901 Returns a list of particular features of the MI protocol that
30902 this version of gdb implements. A feature can be a command,
30903 or a new field in an output of some command, or even an
30904 important bugfix. While a frontend can sometimes detect presence
30905 of a feature at runtime, it is easier to perform detection at debugger
30908 The command returns a list of strings, with each string naming an
30909 available feature. Each returned string is just a name, it does not
30910 have any internal structure. The list of possible feature names
30916 (gdb) -list-features
30917 ^done,result=["feature1","feature2"]
30920 The current list of features is:
30923 @item frozen-varobjs
30924 Indicates support for the @code{-var-set-frozen} command, as well
30925 as possible presense of the @code{frozen} field in the output
30926 of @code{-varobj-create}.
30927 @item pending-breakpoints
30928 Indicates support for the @option{-f} option to the @code{-break-insert}
30931 Indicates Python scripting support, Python-based
30932 pretty-printing commands, and possible presence of the
30933 @samp{display_hint} field in the output of @code{-var-list-children}
30935 Indicates support for the @code{-thread-info} command.
30936 @item data-read-memory-bytes
30937 Indicates support for the @code{-data-read-memory-bytes} and the
30938 @code{-data-write-memory-bytes} commands.
30939 @item breakpoint-notifications
30940 Indicates that changes to breakpoints and breakpoints created via the
30941 CLI will be announced via async records.
30942 @item ada-task-info
30943 Indicates support for the @code{-ada-task-info} command.
30944 @item language-option
30945 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
30946 option (@pxref{Context management}).
30947 @item info-gdb-mi-command
30948 Indicates support for the @code{-info-gdb-mi-command} command.
30949 @item undefined-command-error-code
30950 Indicates support for the "undefined-command" error code in error result
30951 records, produced when trying to execute an undefined @sc{gdb/mi} command
30952 (@pxref{GDB/MI Result Records}).
30953 @item exec-run-start-option
30954 Indicates that the @code{-exec-run} command supports the @option{--start}
30955 option (@pxref{GDB/MI Program Execution}).
30958 @subheading The @code{-list-target-features} Command
30959 @findex -list-target-features
30961 Returns a list of particular features that are supported by the
30962 target. Those features affect the permitted MI commands, but
30963 unlike the features reported by the @code{-list-features} command, the
30964 features depend on which target GDB is using at the moment. Whenever
30965 a target can change, due to commands such as @code{-target-select},
30966 @code{-target-attach} or @code{-exec-run}, the list of target features
30967 may change, and the frontend should obtain it again.
30971 (gdb) -list-target-features
30972 ^done,result=["async"]
30975 The current list of features is:
30979 Indicates that the target is capable of asynchronous command
30980 execution, which means that @value{GDBN} will accept further commands
30981 while the target is running.
30984 Indicates that the target is capable of reverse execution.
30985 @xref{Reverse Execution}, for more information.
30989 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30990 @node GDB/MI Miscellaneous Commands
30991 @section Miscellaneous @sc{gdb/mi} Commands
30993 @c @subheading -gdb-complete
30995 @subheading The @code{-gdb-exit} Command
30998 @subsubheading Synopsis
31004 Exit @value{GDBN} immediately.
31006 @subsubheading @value{GDBN} Command
31008 Approximately corresponds to @samp{quit}.
31010 @subsubheading Example
31020 @subheading The @code{-exec-abort} Command
31021 @findex -exec-abort
31023 @subsubheading Synopsis
31029 Kill the inferior running program.
31031 @subsubheading @value{GDBN} Command
31033 The corresponding @value{GDBN} command is @samp{kill}.
31035 @subsubheading Example
31040 @subheading The @code{-gdb-set} Command
31043 @subsubheading Synopsis
31049 Set an internal @value{GDBN} variable.
31050 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31052 @subsubheading @value{GDBN} Command
31054 The corresponding @value{GDBN} command is @samp{set}.
31056 @subsubheading Example
31066 @subheading The @code{-gdb-show} Command
31069 @subsubheading Synopsis
31075 Show the current value of a @value{GDBN} variable.
31077 @subsubheading @value{GDBN} Command
31079 The corresponding @value{GDBN} command is @samp{show}.
31081 @subsubheading Example
31090 @c @subheading -gdb-source
31093 @subheading The @code{-gdb-version} Command
31094 @findex -gdb-version
31096 @subsubheading Synopsis
31102 Show version information for @value{GDBN}. Used mostly in testing.
31104 @subsubheading @value{GDBN} Command
31106 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31107 default shows this information when you start an interactive session.
31109 @subsubheading Example
31111 @c This example modifies the actual output from GDB to avoid overfull
31117 ~Copyright 2000 Free Software Foundation, Inc.
31118 ~GDB is free software, covered by the GNU General Public License, and
31119 ~you are welcome to change it and/or distribute copies of it under
31120 ~ certain conditions.
31121 ~Type "show copying" to see the conditions.
31122 ~There is absolutely no warranty for GDB. Type "show warranty" for
31124 ~This GDB was configured as
31125 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31130 @subheading The @code{-list-thread-groups} Command
31131 @findex -list-thread-groups
31133 @subheading Synopsis
31136 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31139 Lists thread groups (@pxref{Thread groups}). When a single thread
31140 group is passed as the argument, lists the children of that group.
31141 When several thread group are passed, lists information about those
31142 thread groups. Without any parameters, lists information about all
31143 top-level thread groups.
31145 Normally, thread groups that are being debugged are reported.
31146 With the @samp{--available} option, @value{GDBN} reports thread groups
31147 available on the target.
31149 The output of this command may have either a @samp{threads} result or
31150 a @samp{groups} result. The @samp{thread} result has a list of tuples
31151 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31152 Information}). The @samp{groups} result has a list of tuples as value,
31153 each tuple describing a thread group. If top-level groups are
31154 requested (that is, no parameter is passed), or when several groups
31155 are passed, the output always has a @samp{groups} result. The format
31156 of the @samp{group} result is described below.
31158 To reduce the number of roundtrips it's possible to list thread groups
31159 together with their children, by passing the @samp{--recurse} option
31160 and the recursion depth. Presently, only recursion depth of 1 is
31161 permitted. If this option is present, then every reported thread group
31162 will also include its children, either as @samp{group} or
31163 @samp{threads} field.
31165 In general, any combination of option and parameters is permitted, with
31166 the following caveats:
31170 When a single thread group is passed, the output will typically
31171 be the @samp{threads} result. Because threads may not contain
31172 anything, the @samp{recurse} option will be ignored.
31175 When the @samp{--available} option is passed, limited information may
31176 be available. In particular, the list of threads of a process might
31177 be inaccessible. Further, specifying specific thread groups might
31178 not give any performance advantage over listing all thread groups.
31179 The frontend should assume that @samp{-list-thread-groups --available}
31180 is always an expensive operation and cache the results.
31184 The @samp{groups} result is a list of tuples, where each tuple may
31185 have the following fields:
31189 Identifier of the thread group. This field is always present.
31190 The identifier is an opaque string; frontends should not try to
31191 convert it to an integer, even though it might look like one.
31194 The type of the thread group. At present, only @samp{process} is a
31198 The target-specific process identifier. This field is only present
31199 for thread groups of type @samp{process} and only if the process exists.
31202 The number of children this thread group has. This field may be
31203 absent for an available thread group.
31206 This field has a list of tuples as value, each tuple describing a
31207 thread. It may be present if the @samp{--recurse} option is
31208 specified, and it's actually possible to obtain the threads.
31211 This field is a list of integers, each identifying a core that one
31212 thread of the group is running on. This field may be absent if
31213 such information is not available.
31216 The name of the executable file that corresponds to this thread group.
31217 The field is only present for thread groups of type @samp{process},
31218 and only if there is a corresponding executable file.
31222 @subheading Example
31226 -list-thread-groups
31227 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31228 -list-thread-groups 17
31229 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31230 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31231 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31232 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31233 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31234 -list-thread-groups --available
31235 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31236 -list-thread-groups --available --recurse 1
31237 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31238 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31239 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31240 -list-thread-groups --available --recurse 1 17 18
31241 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31242 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31243 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31246 @subheading The @code{-info-os} Command
31249 @subsubheading Synopsis
31252 -info-os [ @var{type} ]
31255 If no argument is supplied, the command returns a table of available
31256 operating-system-specific information types. If one of these types is
31257 supplied as an argument @var{type}, then the command returns a table
31258 of data of that type.
31260 The types of information available depend on the target operating
31263 @subsubheading @value{GDBN} Command
31265 The corresponding @value{GDBN} command is @samp{info os}.
31267 @subsubheading Example
31269 When run on a @sc{gnu}/Linux system, the output will look something
31275 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
31276 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31277 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31278 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31279 body=[item=@{col0="processes",col1="Listing of all processes",
31280 col2="Processes"@},
31281 item=@{col0="procgroups",col1="Listing of all process groups",
31282 col2="Process groups"@},
31283 item=@{col0="threads",col1="Listing of all threads",
31285 item=@{col0="files",col1="Listing of all file descriptors",
31286 col2="File descriptors"@},
31287 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31289 item=@{col0="shm",col1="Listing of all shared-memory regions",
31290 col2="Shared-memory regions"@},
31291 item=@{col0="semaphores",col1="Listing of all semaphores",
31292 col2="Semaphores"@},
31293 item=@{col0="msg",col1="Listing of all message queues",
31294 col2="Message queues"@},
31295 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31296 col2="Kernel modules"@}]@}
31299 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31300 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31301 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31302 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31303 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31304 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31305 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31306 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31308 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31309 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31313 (Note that the MI output here includes a @code{"Title"} column that
31314 does not appear in command-line @code{info os}; this column is useful
31315 for MI clients that want to enumerate the types of data, such as in a
31316 popup menu, but is needless clutter on the command line, and
31317 @code{info os} omits it.)
31319 @subheading The @code{-add-inferior} Command
31320 @findex -add-inferior
31322 @subheading Synopsis
31328 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31329 inferior is not associated with any executable. Such association may
31330 be established with the @samp{-file-exec-and-symbols} command
31331 (@pxref{GDB/MI File Commands}). The command response has a single
31332 field, @samp{inferior}, whose value is the identifier of the
31333 thread group corresponding to the new inferior.
31335 @subheading Example
31340 ^done,inferior="i3"
31343 @subheading The @code{-interpreter-exec} Command
31344 @findex -interpreter-exec
31346 @subheading Synopsis
31349 -interpreter-exec @var{interpreter} @var{command}
31351 @anchor{-interpreter-exec}
31353 Execute the specified @var{command} in the given @var{interpreter}.
31355 @subheading @value{GDBN} Command
31357 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31359 @subheading Example
31363 -interpreter-exec console "break main"
31364 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31365 &"During symbol reading, bad structure-type format.\n"
31366 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31371 @subheading The @code{-inferior-tty-set} Command
31372 @findex -inferior-tty-set
31374 @subheading Synopsis
31377 -inferior-tty-set /dev/pts/1
31380 Set terminal for future runs of the program being debugged.
31382 @subheading @value{GDBN} Command
31384 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31386 @subheading Example
31390 -inferior-tty-set /dev/pts/1
31395 @subheading The @code{-inferior-tty-show} Command
31396 @findex -inferior-tty-show
31398 @subheading Synopsis
31404 Show terminal for future runs of program being debugged.
31406 @subheading @value{GDBN} Command
31408 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31410 @subheading Example
31414 -inferior-tty-set /dev/pts/1
31418 ^done,inferior_tty_terminal="/dev/pts/1"
31422 @subheading The @code{-enable-timings} Command
31423 @findex -enable-timings
31425 @subheading Synopsis
31428 -enable-timings [yes | no]
31431 Toggle the printing of the wallclock, user and system times for an MI
31432 command as a field in its output. This command is to help frontend
31433 developers optimize the performance of their code. No argument is
31434 equivalent to @samp{yes}.
31436 @subheading @value{GDBN} Command
31440 @subheading Example
31448 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31449 addr="0x080484ed",func="main",file="myprog.c",
31450 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
31452 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31460 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31461 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31462 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31463 fullname="/home/nickrob/myprog.c",line="73"@}
31468 @chapter @value{GDBN} Annotations
31470 This chapter describes annotations in @value{GDBN}. Annotations were
31471 designed to interface @value{GDBN} to graphical user interfaces or other
31472 similar programs which want to interact with @value{GDBN} at a
31473 relatively high level.
31475 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31479 This is Edition @value{EDITION}, @value{DATE}.
31483 * Annotations Overview:: What annotations are; the general syntax.
31484 * Server Prefix:: Issuing a command without affecting user state.
31485 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31486 * Errors:: Annotations for error messages.
31487 * Invalidation:: Some annotations describe things now invalid.
31488 * Annotations for Running::
31489 Whether the program is running, how it stopped, etc.
31490 * Source Annotations:: Annotations describing source code.
31493 @node Annotations Overview
31494 @section What is an Annotation?
31495 @cindex annotations
31497 Annotations start with a newline character, two @samp{control-z}
31498 characters, and the name of the annotation. If there is no additional
31499 information associated with this annotation, the name of the annotation
31500 is followed immediately by a newline. If there is additional
31501 information, the name of the annotation is followed by a space, the
31502 additional information, and a newline. The additional information
31503 cannot contain newline characters.
31505 Any output not beginning with a newline and two @samp{control-z}
31506 characters denotes literal output from @value{GDBN}. Currently there is
31507 no need for @value{GDBN} to output a newline followed by two
31508 @samp{control-z} characters, but if there was such a need, the
31509 annotations could be extended with an @samp{escape} annotation which
31510 means those three characters as output.
31512 The annotation @var{level}, which is specified using the
31513 @option{--annotate} command line option (@pxref{Mode Options}), controls
31514 how much information @value{GDBN} prints together with its prompt,
31515 values of expressions, source lines, and other types of output. Level 0
31516 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31517 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31518 for programs that control @value{GDBN}, and level 2 annotations have
31519 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31520 Interface, annotate, GDB's Obsolete Annotations}).
31523 @kindex set annotate
31524 @item set annotate @var{level}
31525 The @value{GDBN} command @code{set annotate} sets the level of
31526 annotations to the specified @var{level}.
31528 @item show annotate
31529 @kindex show annotate
31530 Show the current annotation level.
31533 This chapter describes level 3 annotations.
31535 A simple example of starting up @value{GDBN} with annotations is:
31538 $ @kbd{gdb --annotate=3}
31540 Copyright 2003 Free Software Foundation, Inc.
31541 GDB is free software, covered by the GNU General Public License,
31542 and you are welcome to change it and/or distribute copies of it
31543 under certain conditions.
31544 Type "show copying" to see the conditions.
31545 There is absolutely no warranty for GDB. Type "show warranty"
31547 This GDB was configured as "i386-pc-linux-gnu"
31558 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31559 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31560 denotes a @samp{control-z} character) are annotations; the rest is
31561 output from @value{GDBN}.
31563 @node Server Prefix
31564 @section The Server Prefix
31565 @cindex server prefix
31567 If you prefix a command with @samp{server } then it will not affect
31568 the command history, nor will it affect @value{GDBN}'s notion of which
31569 command to repeat if @key{RET} is pressed on a line by itself. This
31570 means that commands can be run behind a user's back by a front-end in
31571 a transparent manner.
31573 The @code{server } prefix does not affect the recording of values into
31574 the value history; to print a value without recording it into the
31575 value history, use the @code{output} command instead of the
31576 @code{print} command.
31578 Using this prefix also disables confirmation requests
31579 (@pxref{confirmation requests}).
31582 @section Annotation for @value{GDBN} Input
31584 @cindex annotations for prompts
31585 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31586 to know when to send output, when the output from a given command is
31589 Different kinds of input each have a different @dfn{input type}. Each
31590 input type has three annotations: a @code{pre-} annotation, which
31591 denotes the beginning of any prompt which is being output, a plain
31592 annotation, which denotes the end of the prompt, and then a @code{post-}
31593 annotation which denotes the end of any echo which may (or may not) be
31594 associated with the input. For example, the @code{prompt} input type
31595 features the following annotations:
31603 The input types are
31606 @findex pre-prompt annotation
31607 @findex prompt annotation
31608 @findex post-prompt annotation
31610 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31612 @findex pre-commands annotation
31613 @findex commands annotation
31614 @findex post-commands annotation
31616 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31617 command. The annotations are repeated for each command which is input.
31619 @findex pre-overload-choice annotation
31620 @findex overload-choice annotation
31621 @findex post-overload-choice annotation
31622 @item overload-choice
31623 When @value{GDBN} wants the user to select between various overloaded functions.
31625 @findex pre-query annotation
31626 @findex query annotation
31627 @findex post-query annotation
31629 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31631 @findex pre-prompt-for-continue annotation
31632 @findex prompt-for-continue annotation
31633 @findex post-prompt-for-continue annotation
31634 @item prompt-for-continue
31635 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31636 expect this to work well; instead use @code{set height 0} to disable
31637 prompting. This is because the counting of lines is buggy in the
31638 presence of annotations.
31643 @cindex annotations for errors, warnings and interrupts
31645 @findex quit annotation
31650 This annotation occurs right before @value{GDBN} responds to an interrupt.
31652 @findex error annotation
31657 This annotation occurs right before @value{GDBN} responds to an error.
31659 Quit and error annotations indicate that any annotations which @value{GDBN} was
31660 in the middle of may end abruptly. For example, if a
31661 @code{value-history-begin} annotation is followed by a @code{error}, one
31662 cannot expect to receive the matching @code{value-history-end}. One
31663 cannot expect not to receive it either, however; an error annotation
31664 does not necessarily mean that @value{GDBN} is immediately returning all the way
31667 @findex error-begin annotation
31668 A quit or error annotation may be preceded by
31674 Any output between that and the quit or error annotation is the error
31677 Warning messages are not yet annotated.
31678 @c If we want to change that, need to fix warning(), type_error(),
31679 @c range_error(), and possibly other places.
31682 @section Invalidation Notices
31684 @cindex annotations for invalidation messages
31685 The following annotations say that certain pieces of state may have
31689 @findex frames-invalid annotation
31690 @item ^Z^Zframes-invalid
31692 The frames (for example, output from the @code{backtrace} command) may
31695 @findex breakpoints-invalid annotation
31696 @item ^Z^Zbreakpoints-invalid
31698 The breakpoints may have changed. For example, the user just added or
31699 deleted a breakpoint.
31702 @node Annotations for Running
31703 @section Running the Program
31704 @cindex annotations for running programs
31706 @findex starting annotation
31707 @findex stopping annotation
31708 When the program starts executing due to a @value{GDBN} command such as
31709 @code{step} or @code{continue},
31715 is output. When the program stops,
31721 is output. Before the @code{stopped} annotation, a variety of
31722 annotations describe how the program stopped.
31725 @findex exited annotation
31726 @item ^Z^Zexited @var{exit-status}
31727 The program exited, and @var{exit-status} is the exit status (zero for
31728 successful exit, otherwise nonzero).
31730 @findex signalled annotation
31731 @findex signal-name annotation
31732 @findex signal-name-end annotation
31733 @findex signal-string annotation
31734 @findex signal-string-end annotation
31735 @item ^Z^Zsignalled
31736 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31737 annotation continues:
31743 ^Z^Zsignal-name-end
31747 ^Z^Zsignal-string-end
31752 where @var{name} is the name of the signal, such as @code{SIGILL} or
31753 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31754 as @code{Illegal Instruction} or @code{Segmentation fault}.
31755 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31756 user's benefit and have no particular format.
31758 @findex signal annotation
31760 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31761 just saying that the program received the signal, not that it was
31762 terminated with it.
31764 @findex breakpoint annotation
31765 @item ^Z^Zbreakpoint @var{number}
31766 The program hit breakpoint number @var{number}.
31768 @findex watchpoint annotation
31769 @item ^Z^Zwatchpoint @var{number}
31770 The program hit watchpoint number @var{number}.
31773 @node Source Annotations
31774 @section Displaying Source
31775 @cindex annotations for source display
31777 @findex source annotation
31778 The following annotation is used instead of displaying source code:
31781 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31784 where @var{filename} is an absolute file name indicating which source
31785 file, @var{line} is the line number within that file (where 1 is the
31786 first line in the file), @var{character} is the character position
31787 within the file (where 0 is the first character in the file) (for most
31788 debug formats this will necessarily point to the beginning of a line),
31789 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31790 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31791 @var{addr} is the address in the target program associated with the
31792 source which is being displayed. @var{addr} is in the form @samp{0x}
31793 followed by one or more lowercase hex digits (note that this does not
31794 depend on the language).
31796 @node JIT Interface
31797 @chapter JIT Compilation Interface
31798 @cindex just-in-time compilation
31799 @cindex JIT compilation interface
31801 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31802 interface. A JIT compiler is a program or library that generates native
31803 executable code at runtime and executes it, usually in order to achieve good
31804 performance while maintaining platform independence.
31806 Programs that use JIT compilation are normally difficult to debug because
31807 portions of their code are generated at runtime, instead of being loaded from
31808 object files, which is where @value{GDBN} normally finds the program's symbols
31809 and debug information. In order to debug programs that use JIT compilation,
31810 @value{GDBN} has an interface that allows the program to register in-memory
31811 symbol files with @value{GDBN} at runtime.
31813 If you are using @value{GDBN} to debug a program that uses this interface, then
31814 it should work transparently so long as you have not stripped the binary. If
31815 you are developing a JIT compiler, then the interface is documented in the rest
31816 of this chapter. At this time, the only known client of this interface is the
31819 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31820 JIT compiler communicates with @value{GDBN} by writing data into a global
31821 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31822 attaches, it reads a linked list of symbol files from the global variable to
31823 find existing code, and puts a breakpoint in the function so that it can find
31824 out about additional code.
31827 * Declarations:: Relevant C struct declarations
31828 * Registering Code:: Steps to register code
31829 * Unregistering Code:: Steps to unregister code
31830 * Custom Debug Info:: Emit debug information in a custom format
31834 @section JIT Declarations
31836 These are the relevant struct declarations that a C program should include to
31837 implement the interface:
31847 struct jit_code_entry
31849 struct jit_code_entry *next_entry;
31850 struct jit_code_entry *prev_entry;
31851 const char *symfile_addr;
31852 uint64_t symfile_size;
31855 struct jit_descriptor
31858 /* This type should be jit_actions_t, but we use uint32_t
31859 to be explicit about the bitwidth. */
31860 uint32_t action_flag;
31861 struct jit_code_entry *relevant_entry;
31862 struct jit_code_entry *first_entry;
31865 /* GDB puts a breakpoint in this function. */
31866 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31868 /* Make sure to specify the version statically, because the
31869 debugger may check the version before we can set it. */
31870 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31873 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31874 modifications to this global data properly, which can easily be done by putting
31875 a global mutex around modifications to these structures.
31877 @node Registering Code
31878 @section Registering Code
31880 To register code with @value{GDBN}, the JIT should follow this protocol:
31884 Generate an object file in memory with symbols and other desired debug
31885 information. The file must include the virtual addresses of the sections.
31888 Create a code entry for the file, which gives the start and size of the symbol
31892 Add it to the linked list in the JIT descriptor.
31895 Point the relevant_entry field of the descriptor at the entry.
31898 Set @code{action_flag} to @code{JIT_REGISTER} and call
31899 @code{__jit_debug_register_code}.
31902 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31903 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31904 new code. However, the linked list must still be maintained in order to allow
31905 @value{GDBN} to attach to a running process and still find the symbol files.
31907 @node Unregistering Code
31908 @section Unregistering Code
31910 If code is freed, then the JIT should use the following protocol:
31914 Remove the code entry corresponding to the code from the linked list.
31917 Point the @code{relevant_entry} field of the descriptor at the code entry.
31920 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31921 @code{__jit_debug_register_code}.
31924 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31925 and the JIT will leak the memory used for the associated symbol files.
31927 @node Custom Debug Info
31928 @section Custom Debug Info
31929 @cindex custom JIT debug info
31930 @cindex JIT debug info reader
31932 Generating debug information in platform-native file formats (like ELF
31933 or COFF) may be an overkill for JIT compilers; especially if all the
31934 debug info is used for is displaying a meaningful backtrace. The
31935 issue can be resolved by having the JIT writers decide on a debug info
31936 format and also provide a reader that parses the debug info generated
31937 by the JIT compiler. This section gives a brief overview on writing
31938 such a parser. More specific details can be found in the source file
31939 @file{gdb/jit-reader.in}, which is also installed as a header at
31940 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
31942 The reader is implemented as a shared object (so this functionality is
31943 not available on platforms which don't allow loading shared objects at
31944 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
31945 @code{jit-reader-unload} are provided, to be used to load and unload
31946 the readers from a preconfigured directory. Once loaded, the shared
31947 object is used the parse the debug information emitted by the JIT
31951 * Using JIT Debug Info Readers:: How to use supplied readers correctly
31952 * Writing JIT Debug Info Readers:: Creating a debug-info reader
31955 @node Using JIT Debug Info Readers
31956 @subsection Using JIT Debug Info Readers
31957 @kindex jit-reader-load
31958 @kindex jit-reader-unload
31960 Readers can be loaded and unloaded using the @code{jit-reader-load}
31961 and @code{jit-reader-unload} commands.
31964 @item jit-reader-load @var{reader}
31965 Load the JIT reader named @var{reader}. @var{reader} is a shared
31966 object specified as either an absolute or a relative file name. In
31967 the latter case, @value{GDBN} will try to load the reader from a
31968 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
31969 system (here @var{libdir} is the system library directory, often
31970 @file{/usr/local/lib}).
31972 Only one reader can be active at a time; trying to load a second
31973 reader when one is already loaded will result in @value{GDBN}
31974 reporting an error. A new JIT reader can be loaded by first unloading
31975 the current one using @code{jit-reader-unload} and then invoking
31976 @code{jit-reader-load}.
31978 @item jit-reader-unload
31979 Unload the currently loaded JIT reader.
31983 @node Writing JIT Debug Info Readers
31984 @subsection Writing JIT Debug Info Readers
31985 @cindex writing JIT debug info readers
31987 As mentioned, a reader is essentially a shared object conforming to a
31988 certain ABI. This ABI is described in @file{jit-reader.h}.
31990 @file{jit-reader.h} defines the structures, macros and functions
31991 required to write a reader. It is installed (along with
31992 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
31993 the system include directory.
31995 Readers need to be released under a GPL compatible license. A reader
31996 can be declared as released under such a license by placing the macro
31997 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
31999 The entry point for readers is the symbol @code{gdb_init_reader},
32000 which is expected to be a function with the prototype
32002 @findex gdb_init_reader
32004 extern struct gdb_reader_funcs *gdb_init_reader (void);
32007 @cindex @code{struct gdb_reader_funcs}
32009 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32010 functions. These functions are executed to read the debug info
32011 generated by the JIT compiler (@code{read}), to unwind stack frames
32012 (@code{unwind}) and to create canonical frame IDs
32013 (@code{get_Frame_id}). It also has a callback that is called when the
32014 reader is being unloaded (@code{destroy}). The struct looks like this
32017 struct gdb_reader_funcs
32019 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32020 int reader_version;
32022 /* For use by the reader. */
32025 gdb_read_debug_info *read;
32026 gdb_unwind_frame *unwind;
32027 gdb_get_frame_id *get_frame_id;
32028 gdb_destroy_reader *destroy;
32032 @cindex @code{struct gdb_symbol_callbacks}
32033 @cindex @code{struct gdb_unwind_callbacks}
32035 The callbacks are provided with another set of callbacks by
32036 @value{GDBN} to do their job. For @code{read}, these callbacks are
32037 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32038 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32039 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32040 files and new symbol tables inside those object files. @code{struct
32041 gdb_unwind_callbacks} has callbacks to read registers off the current
32042 frame and to write out the values of the registers in the previous
32043 frame. Both have a callback (@code{target_read}) to read bytes off the
32044 target's address space.
32046 @node In-Process Agent
32047 @chapter In-Process Agent
32048 @cindex debugging agent
32049 The traditional debugging model is conceptually low-speed, but works fine,
32050 because most bugs can be reproduced in debugging-mode execution. However,
32051 as multi-core or many-core processors are becoming mainstream, and
32052 multi-threaded programs become more and more popular, there should be more
32053 and more bugs that only manifest themselves at normal-mode execution, for
32054 example, thread races, because debugger's interference with the program's
32055 timing may conceal the bugs. On the other hand, in some applications,
32056 it is not feasible for the debugger to interrupt the program's execution
32057 long enough for the developer to learn anything helpful about its behavior.
32058 If the program's correctness depends on its real-time behavior, delays
32059 introduced by a debugger might cause the program to fail, even when the
32060 code itself is correct. It is useful to be able to observe the program's
32061 behavior without interrupting it.
32063 Therefore, traditional debugging model is too intrusive to reproduce
32064 some bugs. In order to reduce the interference with the program, we can
32065 reduce the number of operations performed by debugger. The
32066 @dfn{In-Process Agent}, a shared library, is running within the same
32067 process with inferior, and is able to perform some debugging operations
32068 itself. As a result, debugger is only involved when necessary, and
32069 performance of debugging can be improved accordingly. Note that
32070 interference with program can be reduced but can't be removed completely,
32071 because the in-process agent will still stop or slow down the program.
32073 The in-process agent can interpret and execute Agent Expressions
32074 (@pxref{Agent Expressions}) during performing debugging operations. The
32075 agent expressions can be used for different purposes, such as collecting
32076 data in tracepoints, and condition evaluation in breakpoints.
32078 @anchor{Control Agent}
32079 You can control whether the in-process agent is used as an aid for
32080 debugging with the following commands:
32083 @kindex set agent on
32085 Causes the in-process agent to perform some operations on behalf of the
32086 debugger. Just which operations requested by the user will be done
32087 by the in-process agent depends on the its capabilities. For example,
32088 if you request to evaluate breakpoint conditions in the in-process agent,
32089 and the in-process agent has such capability as well, then breakpoint
32090 conditions will be evaluated in the in-process agent.
32092 @kindex set agent off
32093 @item set agent off
32094 Disables execution of debugging operations by the in-process agent. All
32095 of the operations will be performed by @value{GDBN}.
32099 Display the current setting of execution of debugging operations by
32100 the in-process agent.
32104 * In-Process Agent Protocol::
32107 @node In-Process Agent Protocol
32108 @section In-Process Agent Protocol
32109 @cindex in-process agent protocol
32111 The in-process agent is able to communicate with both @value{GDBN} and
32112 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32113 used for communications between @value{GDBN} or GDBserver and the IPA.
32114 In general, @value{GDBN} or GDBserver sends commands
32115 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32116 in-process agent replies back with the return result of the command, or
32117 some other information. The data sent to in-process agent is composed
32118 of primitive data types, such as 4-byte or 8-byte type, and composite
32119 types, which are called objects (@pxref{IPA Protocol Objects}).
32122 * IPA Protocol Objects::
32123 * IPA Protocol Commands::
32126 @node IPA Protocol Objects
32127 @subsection IPA Protocol Objects
32128 @cindex ipa protocol objects
32130 The commands sent to and results received from agent may contain some
32131 complex data types called @dfn{objects}.
32133 The in-process agent is running on the same machine with @value{GDBN}
32134 or GDBserver, so it doesn't have to handle as much differences between
32135 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32136 However, there are still some differences of two ends in two processes:
32140 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32141 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32143 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32144 GDBserver is compiled with one, and in-process agent is compiled with
32148 Here are the IPA Protocol Objects:
32152 agent expression object. It represents an agent expression
32153 (@pxref{Agent Expressions}).
32154 @anchor{agent expression object}
32156 tracepoint action object. It represents a tracepoint action
32157 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32158 memory, static trace data and to evaluate expression.
32159 @anchor{tracepoint action object}
32161 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32162 @anchor{tracepoint object}
32166 The following table describes important attributes of each IPA protocol
32169 @multitable @columnfractions .30 .20 .50
32170 @headitem Name @tab Size @tab Description
32171 @item @emph{agent expression object} @tab @tab
32172 @item length @tab 4 @tab length of bytes code
32173 @item byte code @tab @var{length} @tab contents of byte code
32174 @item @emph{tracepoint action for collecting memory} @tab @tab
32175 @item 'M' @tab 1 @tab type of tracepoint action
32176 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32177 address of the lowest byte to collect, otherwise @var{addr} is the offset
32178 of @var{basereg} for memory collecting.
32179 @item len @tab 8 @tab length of memory for collecting
32180 @item basereg @tab 4 @tab the register number containing the starting
32181 memory address for collecting.
32182 @item @emph{tracepoint action for collecting registers} @tab @tab
32183 @item 'R' @tab 1 @tab type of tracepoint action
32184 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32185 @item 'L' @tab 1 @tab type of tracepoint action
32186 @item @emph{tracepoint action for expression evaluation} @tab @tab
32187 @item 'X' @tab 1 @tab type of tracepoint action
32188 @item agent expression @tab length of @tab @ref{agent expression object}
32189 @item @emph{tracepoint object} @tab @tab
32190 @item number @tab 4 @tab number of tracepoint
32191 @item address @tab 8 @tab address of tracepoint inserted on
32192 @item type @tab 4 @tab type of tracepoint
32193 @item enabled @tab 1 @tab enable or disable of tracepoint
32194 @item step_count @tab 8 @tab step
32195 @item pass_count @tab 8 @tab pass
32196 @item numactions @tab 4 @tab number of tracepoint actions
32197 @item hit count @tab 8 @tab hit count
32198 @item trace frame usage @tab 8 @tab trace frame usage
32199 @item compiled_cond @tab 8 @tab compiled condition
32200 @item orig_size @tab 8 @tab orig size
32201 @item condition @tab 4 if condition is NULL otherwise length of
32202 @ref{agent expression object}
32203 @tab zero if condition is NULL, otherwise is
32204 @ref{agent expression object}
32205 @item actions @tab variable
32206 @tab numactions number of @ref{tracepoint action object}
32209 @node IPA Protocol Commands
32210 @subsection IPA Protocol Commands
32211 @cindex ipa protocol commands
32213 The spaces in each command are delimiters to ease reading this commands
32214 specification. They don't exist in real commands.
32218 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32219 Installs a new fast tracepoint described by @var{tracepoint_object}
32220 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
32221 head of @dfn{jumppad}, which is used to jump to data collection routine
32226 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32227 @var{target_address} is address of tracepoint in the inferior.
32228 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32229 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32230 @var{fjump} contains a sequence of instructions jump to jumppad entry.
32231 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32238 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32239 is about to kill inferiors.
32247 @item probe_marker_at:@var{address}
32248 Asks in-process agent to probe the marker at @var{address}.
32255 @item unprobe_marker_at:@var{address}
32256 Asks in-process agent to unprobe the marker at @var{address}.
32260 @chapter Reporting Bugs in @value{GDBN}
32261 @cindex bugs in @value{GDBN}
32262 @cindex reporting bugs in @value{GDBN}
32264 Your bug reports play an essential role in making @value{GDBN} reliable.
32266 Reporting a bug may help you by bringing a solution to your problem, or it
32267 may not. But in any case the principal function of a bug report is to help
32268 the entire community by making the next version of @value{GDBN} work better. Bug
32269 reports are your contribution to the maintenance of @value{GDBN}.
32271 In order for a bug report to serve its purpose, you must include the
32272 information that enables us to fix the bug.
32275 * Bug Criteria:: Have you found a bug?
32276 * Bug Reporting:: How to report bugs
32280 @section Have You Found a Bug?
32281 @cindex bug criteria
32283 If you are not sure whether you have found a bug, here are some guidelines:
32286 @cindex fatal signal
32287 @cindex debugger crash
32288 @cindex crash of debugger
32290 If the debugger gets a fatal signal, for any input whatever, that is a
32291 @value{GDBN} bug. Reliable debuggers never crash.
32293 @cindex error on valid input
32295 If @value{GDBN} produces an error message for valid input, that is a
32296 bug. (Note that if you're cross debugging, the problem may also be
32297 somewhere in the connection to the target.)
32299 @cindex invalid input
32301 If @value{GDBN} does not produce an error message for invalid input,
32302 that is a bug. However, you should note that your idea of
32303 ``invalid input'' might be our idea of ``an extension'' or ``support
32304 for traditional practice''.
32307 If you are an experienced user of debugging tools, your suggestions
32308 for improvement of @value{GDBN} are welcome in any case.
32311 @node Bug Reporting
32312 @section How to Report Bugs
32313 @cindex bug reports
32314 @cindex @value{GDBN} bugs, reporting
32316 A number of companies and individuals offer support for @sc{gnu} products.
32317 If you obtained @value{GDBN} from a support organization, we recommend you
32318 contact that organization first.
32320 You can find contact information for many support companies and
32321 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32323 @c should add a web page ref...
32326 @ifset BUGURL_DEFAULT
32327 In any event, we also recommend that you submit bug reports for
32328 @value{GDBN}. The preferred method is to submit them directly using
32329 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32330 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32333 @strong{Do not send bug reports to @samp{info-gdb}, or to
32334 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32335 not want to receive bug reports. Those that do have arranged to receive
32338 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32339 serves as a repeater. The mailing list and the newsgroup carry exactly
32340 the same messages. Often people think of posting bug reports to the
32341 newsgroup instead of mailing them. This appears to work, but it has one
32342 problem which can be crucial: a newsgroup posting often lacks a mail
32343 path back to the sender. Thus, if we need to ask for more information,
32344 we may be unable to reach you. For this reason, it is better to send
32345 bug reports to the mailing list.
32347 @ifclear BUGURL_DEFAULT
32348 In any event, we also recommend that you submit bug reports for
32349 @value{GDBN} to @value{BUGURL}.
32353 The fundamental principle of reporting bugs usefully is this:
32354 @strong{report all the facts}. If you are not sure whether to state a
32355 fact or leave it out, state it!
32357 Often people omit facts because they think they know what causes the
32358 problem and assume that some details do not matter. Thus, you might
32359 assume that the name of the variable you use in an example does not matter.
32360 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32361 stray memory reference which happens to fetch from the location where that
32362 name is stored in memory; perhaps, if the name were different, the contents
32363 of that location would fool the debugger into doing the right thing despite
32364 the bug. Play it safe and give a specific, complete example. That is the
32365 easiest thing for you to do, and the most helpful.
32367 Keep in mind that the purpose of a bug report is to enable us to fix the
32368 bug. It may be that the bug has been reported previously, but neither
32369 you nor we can know that unless your bug report is complete and
32372 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32373 bell?'' Those bug reports are useless, and we urge everyone to
32374 @emph{refuse to respond to them} except to chide the sender to report
32377 To enable us to fix the bug, you should include all these things:
32381 The version of @value{GDBN}. @value{GDBN} announces it if you start
32382 with no arguments; you can also print it at any time using @code{show
32385 Without this, we will not know whether there is any point in looking for
32386 the bug in the current version of @value{GDBN}.
32389 The type of machine you are using, and the operating system name and
32393 The details of the @value{GDBN} build-time configuration.
32394 @value{GDBN} shows these details if you invoke it with the
32395 @option{--configuration} command-line option, or if you type
32396 @code{show configuration} at @value{GDBN}'s prompt.
32399 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32400 ``@value{GCC}--2.8.1''.
32403 What compiler (and its version) was used to compile the program you are
32404 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32405 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32406 to get this information; for other compilers, see the documentation for
32410 The command arguments you gave the compiler to compile your example and
32411 observe the bug. For example, did you use @samp{-O}? To guarantee
32412 you will not omit something important, list them all. A copy of the
32413 Makefile (or the output from make) is sufficient.
32415 If we were to try to guess the arguments, we would probably guess wrong
32416 and then we might not encounter the bug.
32419 A complete input script, and all necessary source files, that will
32423 A description of what behavior you observe that you believe is
32424 incorrect. For example, ``It gets a fatal signal.''
32426 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32427 will certainly notice it. But if the bug is incorrect output, we might
32428 not notice unless it is glaringly wrong. You might as well not give us
32429 a chance to make a mistake.
32431 Even if the problem you experience is a fatal signal, you should still
32432 say so explicitly. Suppose something strange is going on, such as, your
32433 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32434 the C library on your system. (This has happened!) Your copy might
32435 crash and ours would not. If you told us to expect a crash, then when
32436 ours fails to crash, we would know that the bug was not happening for
32437 us. If you had not told us to expect a crash, then we would not be able
32438 to draw any conclusion from our observations.
32441 @cindex recording a session script
32442 To collect all this information, you can use a session recording program
32443 such as @command{script}, which is available on many Unix systems.
32444 Just run your @value{GDBN} session inside @command{script} and then
32445 include the @file{typescript} file with your bug report.
32447 Another way to record a @value{GDBN} session is to run @value{GDBN}
32448 inside Emacs and then save the entire buffer to a file.
32451 If you wish to suggest changes to the @value{GDBN} source, send us context
32452 diffs. If you even discuss something in the @value{GDBN} source, refer to
32453 it by context, not by line number.
32455 The line numbers in our development sources will not match those in your
32456 sources. Your line numbers would convey no useful information to us.
32460 Here are some things that are not necessary:
32464 A description of the envelope of the bug.
32466 Often people who encounter a bug spend a lot of time investigating
32467 which changes to the input file will make the bug go away and which
32468 changes will not affect it.
32470 This is often time consuming and not very useful, because the way we
32471 will find the bug is by running a single example under the debugger
32472 with breakpoints, not by pure deduction from a series of examples.
32473 We recommend that you save your time for something else.
32475 Of course, if you can find a simpler example to report @emph{instead}
32476 of the original one, that is a convenience for us. Errors in the
32477 output will be easier to spot, running under the debugger will take
32478 less time, and so on.
32480 However, simplification is not vital; if you do not want to do this,
32481 report the bug anyway and send us the entire test case you used.
32484 A patch for the bug.
32486 A patch for the bug does help us if it is a good one. But do not omit
32487 the necessary information, such as the test case, on the assumption that
32488 a patch is all we need. We might see problems with your patch and decide
32489 to fix the problem another way, or we might not understand it at all.
32491 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32492 construct an example that will make the program follow a certain path
32493 through the code. If you do not send us the example, we will not be able
32494 to construct one, so we will not be able to verify that the bug is fixed.
32496 And if we cannot understand what bug you are trying to fix, or why your
32497 patch should be an improvement, we will not install it. A test case will
32498 help us to understand.
32501 A guess about what the bug is or what it depends on.
32503 Such guesses are usually wrong. Even we cannot guess right about such
32504 things without first using the debugger to find the facts.
32507 @c The readline documentation is distributed with the readline code
32508 @c and consists of the two following files:
32511 @c Use -I with makeinfo to point to the appropriate directory,
32512 @c environment var TEXINPUTS with TeX.
32513 @ifclear SYSTEM_READLINE
32514 @include rluser.texi
32515 @include hsuser.texi
32519 @appendix In Memoriam
32521 The @value{GDBN} project mourns the loss of the following long-time
32526 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32527 to Free Software in general. Outside of @value{GDBN}, he was known in
32528 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32530 @item Michael Snyder
32531 Michael was one of the Global Maintainers of the @value{GDBN} project,
32532 with contributions recorded as early as 1996, until 2011. In addition
32533 to his day to day participation, he was a large driving force behind
32534 adding Reverse Debugging to @value{GDBN}.
32537 Beyond their technical contributions to the project, they were also
32538 enjoyable members of the Free Software Community. We will miss them.
32540 @node Formatting Documentation
32541 @appendix Formatting Documentation
32543 @cindex @value{GDBN} reference card
32544 @cindex reference card
32545 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32546 for printing with PostScript or Ghostscript, in the @file{gdb}
32547 subdirectory of the main source directory@footnote{In
32548 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32549 release.}. If you can use PostScript or Ghostscript with your printer,
32550 you can print the reference card immediately with @file{refcard.ps}.
32552 The release also includes the source for the reference card. You
32553 can format it, using @TeX{}, by typing:
32559 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32560 mode on US ``letter'' size paper;
32561 that is, on a sheet 11 inches wide by 8.5 inches
32562 high. You will need to specify this form of printing as an option to
32563 your @sc{dvi} output program.
32565 @cindex documentation
32567 All the documentation for @value{GDBN} comes as part of the machine-readable
32568 distribution. The documentation is written in Texinfo format, which is
32569 a documentation system that uses a single source file to produce both
32570 on-line information and a printed manual. You can use one of the Info
32571 formatting commands to create the on-line version of the documentation
32572 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32574 @value{GDBN} includes an already formatted copy of the on-line Info
32575 version of this manual in the @file{gdb} subdirectory. The main Info
32576 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32577 subordinate files matching @samp{gdb.info*} in the same directory. If
32578 necessary, you can print out these files, or read them with any editor;
32579 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32580 Emacs or the standalone @code{info} program, available as part of the
32581 @sc{gnu} Texinfo distribution.
32583 If you want to format these Info files yourself, you need one of the
32584 Info formatting programs, such as @code{texinfo-format-buffer} or
32587 If you have @code{makeinfo} installed, and are in the top level
32588 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32589 version @value{GDBVN}), you can make the Info file by typing:
32596 If you want to typeset and print copies of this manual, you need @TeX{},
32597 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32598 Texinfo definitions file.
32600 @TeX{} is a typesetting program; it does not print files directly, but
32601 produces output files called @sc{dvi} files. To print a typeset
32602 document, you need a program to print @sc{dvi} files. If your system
32603 has @TeX{} installed, chances are it has such a program. The precise
32604 command to use depends on your system; @kbd{lpr -d} is common; another
32605 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32606 require a file name without any extension or a @samp{.dvi} extension.
32608 @TeX{} also requires a macro definitions file called
32609 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32610 written in Texinfo format. On its own, @TeX{} cannot either read or
32611 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32612 and is located in the @file{gdb-@var{version-number}/texinfo}
32615 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32616 typeset and print this manual. First switch to the @file{gdb}
32617 subdirectory of the main source directory (for example, to
32618 @file{gdb-@value{GDBVN}/gdb}) and type:
32624 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32626 @node Installing GDB
32627 @appendix Installing @value{GDBN}
32628 @cindex installation
32631 * Requirements:: Requirements for building @value{GDBN}
32632 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32633 * Separate Objdir:: Compiling @value{GDBN} in another directory
32634 * Config Names:: Specifying names for hosts and targets
32635 * Configure Options:: Summary of options for configure
32636 * System-wide configuration:: Having a system-wide init file
32640 @section Requirements for Building @value{GDBN}
32641 @cindex building @value{GDBN}, requirements for
32643 Building @value{GDBN} requires various tools and packages to be available.
32644 Other packages will be used only if they are found.
32646 @heading Tools/Packages Necessary for Building @value{GDBN}
32648 @item ISO C90 compiler
32649 @value{GDBN} is written in ISO C90. It should be buildable with any
32650 working C90 compiler, e.g.@: GCC.
32654 @heading Tools/Packages Optional for Building @value{GDBN}
32658 @value{GDBN} can use the Expat XML parsing library. This library may be
32659 included with your operating system distribution; if it is not, you
32660 can get the latest version from @url{http://expat.sourceforge.net}.
32661 The @file{configure} script will search for this library in several
32662 standard locations; if it is installed in an unusual path, you can
32663 use the @option{--with-libexpat-prefix} option to specify its location.
32669 Remote protocol memory maps (@pxref{Memory Map Format})
32671 Target descriptions (@pxref{Target Descriptions})
32673 Remote shared library lists (@xref{Library List Format},
32674 or alternatively @pxref{Library List Format for SVR4 Targets})
32676 MS-Windows shared libraries (@pxref{Shared Libraries})
32678 Traceframe info (@pxref{Traceframe Info Format})
32680 Branch trace (@pxref{Branch Trace Format})
32684 @cindex compressed debug sections
32685 @value{GDBN} will use the @samp{zlib} library, if available, to read
32686 compressed debug sections. Some linkers, such as GNU gold, are capable
32687 of producing binaries with compressed debug sections. If @value{GDBN}
32688 is compiled with @samp{zlib}, it will be able to read the debug
32689 information in such binaries.
32691 The @samp{zlib} library is likely included with your operating system
32692 distribution; if it is not, you can get the latest version from
32693 @url{http://zlib.net}.
32696 @value{GDBN}'s features related to character sets (@pxref{Character
32697 Sets}) require a functioning @code{iconv} implementation. If you are
32698 on a GNU system, then this is provided by the GNU C Library. Some
32699 other systems also provide a working @code{iconv}.
32701 If @value{GDBN} is using the @code{iconv} program which is installed
32702 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32703 This is done with @option{--with-iconv-bin} which specifies the
32704 directory that contains the @code{iconv} program.
32706 On systems without @code{iconv}, you can install GNU Libiconv. If you
32707 have previously installed Libiconv, you can use the
32708 @option{--with-libiconv-prefix} option to configure.
32710 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32711 arrange to build Libiconv if a directory named @file{libiconv} appears
32712 in the top-most source directory. If Libiconv is built this way, and
32713 if the operating system does not provide a suitable @code{iconv}
32714 implementation, then the just-built library will automatically be used
32715 by @value{GDBN}. One easy way to set this up is to download GNU
32716 Libiconv, unpack it, and then rename the directory holding the
32717 Libiconv source code to @samp{libiconv}.
32720 @node Running Configure
32721 @section Invoking the @value{GDBN} @file{configure} Script
32722 @cindex configuring @value{GDBN}
32723 @value{GDBN} comes with a @file{configure} script that automates the process
32724 of preparing @value{GDBN} for installation; you can then use @code{make} to
32725 build the @code{gdb} program.
32727 @c irrelevant in info file; it's as current as the code it lives with.
32728 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32729 look at the @file{README} file in the sources; we may have improved the
32730 installation procedures since publishing this manual.}
32733 The @value{GDBN} distribution includes all the source code you need for
32734 @value{GDBN} in a single directory, whose name is usually composed by
32735 appending the version number to @samp{gdb}.
32737 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32738 @file{gdb-@value{GDBVN}} directory. That directory contains:
32741 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32742 script for configuring @value{GDBN} and all its supporting libraries
32744 @item gdb-@value{GDBVN}/gdb
32745 the source specific to @value{GDBN} itself
32747 @item gdb-@value{GDBVN}/bfd
32748 source for the Binary File Descriptor library
32750 @item gdb-@value{GDBVN}/include
32751 @sc{gnu} include files
32753 @item gdb-@value{GDBVN}/libiberty
32754 source for the @samp{-liberty} free software library
32756 @item gdb-@value{GDBVN}/opcodes
32757 source for the library of opcode tables and disassemblers
32759 @item gdb-@value{GDBVN}/readline
32760 source for the @sc{gnu} command-line interface
32762 @item gdb-@value{GDBVN}/glob
32763 source for the @sc{gnu} filename pattern-matching subroutine
32765 @item gdb-@value{GDBVN}/mmalloc
32766 source for the @sc{gnu} memory-mapped malloc package
32769 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32770 from the @file{gdb-@var{version-number}} source directory, which in
32771 this example is the @file{gdb-@value{GDBVN}} directory.
32773 First switch to the @file{gdb-@var{version-number}} source directory
32774 if you are not already in it; then run @file{configure}. Pass the
32775 identifier for the platform on which @value{GDBN} will run as an
32781 cd gdb-@value{GDBVN}
32782 ./configure @var{host}
32787 where @var{host} is an identifier such as @samp{sun4} or
32788 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32789 (You can often leave off @var{host}; @file{configure} tries to guess the
32790 correct value by examining your system.)
32792 Running @samp{configure @var{host}} and then running @code{make} builds the
32793 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32794 libraries, then @code{gdb} itself. The configured source files, and the
32795 binaries, are left in the corresponding source directories.
32798 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32799 system does not recognize this automatically when you run a different
32800 shell, you may need to run @code{sh} on it explicitly:
32803 sh configure @var{host}
32806 If you run @file{configure} from a directory that contains source
32807 directories for multiple libraries or programs, such as the
32808 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32810 creates configuration files for every directory level underneath (unless
32811 you tell it not to, with the @samp{--norecursion} option).
32813 You should run the @file{configure} script from the top directory in the
32814 source tree, the @file{gdb-@var{version-number}} directory. If you run
32815 @file{configure} from one of the subdirectories, you will configure only
32816 that subdirectory. That is usually not what you want. In particular,
32817 if you run the first @file{configure} from the @file{gdb} subdirectory
32818 of the @file{gdb-@var{version-number}} directory, you will omit the
32819 configuration of @file{bfd}, @file{readline}, and other sibling
32820 directories of the @file{gdb} subdirectory. This leads to build errors
32821 about missing include files such as @file{bfd/bfd.h}.
32823 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32824 However, you should make sure that the shell on your path (named by
32825 the @samp{SHELL} environment variable) is publicly readable. Remember
32826 that @value{GDBN} uses the shell to start your program---some systems refuse to
32827 let @value{GDBN} debug child processes whose programs are not readable.
32829 @node Separate Objdir
32830 @section Compiling @value{GDBN} in Another Directory
32832 If you want to run @value{GDBN} versions for several host or target machines,
32833 you need a different @code{gdb} compiled for each combination of
32834 host and target. @file{configure} is designed to make this easy by
32835 allowing you to generate each configuration in a separate subdirectory,
32836 rather than in the source directory. If your @code{make} program
32837 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32838 @code{make} in each of these directories builds the @code{gdb}
32839 program specified there.
32841 To build @code{gdb} in a separate directory, run @file{configure}
32842 with the @samp{--srcdir} option to specify where to find the source.
32843 (You also need to specify a path to find @file{configure}
32844 itself from your working directory. If the path to @file{configure}
32845 would be the same as the argument to @samp{--srcdir}, you can leave out
32846 the @samp{--srcdir} option; it is assumed.)
32848 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32849 separate directory for a Sun 4 like this:
32853 cd gdb-@value{GDBVN}
32856 ../gdb-@value{GDBVN}/configure sun4
32861 When @file{configure} builds a configuration using a remote source
32862 directory, it creates a tree for the binaries with the same structure
32863 (and using the same names) as the tree under the source directory. In
32864 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32865 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32866 @file{gdb-sun4/gdb}.
32868 Make sure that your path to the @file{configure} script has just one
32869 instance of @file{gdb} in it. If your path to @file{configure} looks
32870 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32871 one subdirectory of @value{GDBN}, not the whole package. This leads to
32872 build errors about missing include files such as @file{bfd/bfd.h}.
32874 One popular reason to build several @value{GDBN} configurations in separate
32875 directories is to configure @value{GDBN} for cross-compiling (where
32876 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32877 programs that run on another machine---the @dfn{target}).
32878 You specify a cross-debugging target by
32879 giving the @samp{--target=@var{target}} option to @file{configure}.
32881 When you run @code{make} to build a program or library, you must run
32882 it in a configured directory---whatever directory you were in when you
32883 called @file{configure} (or one of its subdirectories).
32885 The @code{Makefile} that @file{configure} generates in each source
32886 directory also runs recursively. If you type @code{make} in a source
32887 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32888 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32889 will build all the required libraries, and then build GDB.
32891 When you have multiple hosts or targets configured in separate
32892 directories, you can run @code{make} on them in parallel (for example,
32893 if they are NFS-mounted on each of the hosts); they will not interfere
32897 @section Specifying Names for Hosts and Targets
32899 The specifications used for hosts and targets in the @file{configure}
32900 script are based on a three-part naming scheme, but some short predefined
32901 aliases are also supported. The full naming scheme encodes three pieces
32902 of information in the following pattern:
32905 @var{architecture}-@var{vendor}-@var{os}
32908 For example, you can use the alias @code{sun4} as a @var{host} argument,
32909 or as the value for @var{target} in a @code{--target=@var{target}}
32910 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32912 The @file{configure} script accompanying @value{GDBN} does not provide
32913 any query facility to list all supported host and target names or
32914 aliases. @file{configure} calls the Bourne shell script
32915 @code{config.sub} to map abbreviations to full names; you can read the
32916 script, if you wish, or you can use it to test your guesses on
32917 abbreviations---for example:
32920 % sh config.sub i386-linux
32922 % sh config.sub alpha-linux
32923 alpha-unknown-linux-gnu
32924 % sh config.sub hp9k700
32926 % sh config.sub sun4
32927 sparc-sun-sunos4.1.1
32928 % sh config.sub sun3
32929 m68k-sun-sunos4.1.1
32930 % sh config.sub i986v
32931 Invalid configuration `i986v': machine `i986v' not recognized
32935 @code{config.sub} is also distributed in the @value{GDBN} source
32936 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32938 @node Configure Options
32939 @section @file{configure} Options
32941 Here is a summary of the @file{configure} options and arguments that
32942 are most often useful for building @value{GDBN}. @file{configure} also has
32943 several other options not listed here. @inforef{What Configure
32944 Does,,configure.info}, for a full explanation of @file{configure}.
32947 configure @r{[}--help@r{]}
32948 @r{[}--prefix=@var{dir}@r{]}
32949 @r{[}--exec-prefix=@var{dir}@r{]}
32950 @r{[}--srcdir=@var{dirname}@r{]}
32951 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32952 @r{[}--target=@var{target}@r{]}
32957 You may introduce options with a single @samp{-} rather than
32958 @samp{--} if you prefer; but you may abbreviate option names if you use
32963 Display a quick summary of how to invoke @file{configure}.
32965 @item --prefix=@var{dir}
32966 Configure the source to install programs and files under directory
32969 @item --exec-prefix=@var{dir}
32970 Configure the source to install programs under directory
32973 @c avoid splitting the warning from the explanation:
32975 @item --srcdir=@var{dirname}
32976 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32977 @code{make} that implements the @code{VPATH} feature.}@*
32978 Use this option to make configurations in directories separate from the
32979 @value{GDBN} source directories. Among other things, you can use this to
32980 build (or maintain) several configurations simultaneously, in separate
32981 directories. @file{configure} writes configuration-specific files in
32982 the current directory, but arranges for them to use the source in the
32983 directory @var{dirname}. @file{configure} creates directories under
32984 the working directory in parallel to the source directories below
32987 @item --norecursion
32988 Configure only the directory level where @file{configure} is executed; do not
32989 propagate configuration to subdirectories.
32991 @item --target=@var{target}
32992 Configure @value{GDBN} for cross-debugging programs running on the specified
32993 @var{target}. Without this option, @value{GDBN} is configured to debug
32994 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32996 There is no convenient way to generate a list of all available targets.
32998 @item @var{host} @dots{}
32999 Configure @value{GDBN} to run on the specified @var{host}.
33001 There is no convenient way to generate a list of all available hosts.
33004 There are many other options available as well, but they are generally
33005 needed for special purposes only.
33007 @node System-wide configuration
33008 @section System-wide configuration and settings
33009 @cindex system-wide init file
33011 @value{GDBN} can be configured to have a system-wide init file;
33012 this file will be read and executed at startup (@pxref{Startup, , What
33013 @value{GDBN} does during startup}).
33015 Here is the corresponding configure option:
33018 @item --with-system-gdbinit=@var{file}
33019 Specify that the default location of the system-wide init file is
33023 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33024 it may be subject to relocation. Two possible cases:
33028 If the default location of this init file contains @file{$prefix},
33029 it will be subject to relocation. Suppose that the configure options
33030 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33031 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33032 init file is looked for as @file{$install/etc/gdbinit} instead of
33033 @file{$prefix/etc/gdbinit}.
33036 By contrast, if the default location does not contain the prefix,
33037 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33038 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33039 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33040 wherever @value{GDBN} is installed.
33043 If the configured location of the system-wide init file (as given by the
33044 @option{--with-system-gdbinit} option at configure time) is in the
33045 data-directory (as specified by @option{--with-gdb-datadir} at configure
33046 time) or in one of its subdirectories, then @value{GDBN} will look for the
33047 system-wide init file in the directory specified by the
33048 @option{--data-directory} command-line option.
33049 Note that the system-wide init file is only read once, during @value{GDBN}
33050 initialization. If the data-directory is changed after @value{GDBN} has
33051 started with the @code{set data-directory} command, the file will not be
33055 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33058 @node System-wide Configuration Scripts
33059 @subsection Installed System-wide Configuration Scripts
33060 @cindex system-wide configuration scripts
33062 The @file{system-gdbinit} directory, located inside the data-directory
33063 (as specified by @option{--with-gdb-datadir} at configure time) contains
33064 a number of scripts which can be used as system-wide init files. To
33065 automatically source those scripts at startup, @value{GDBN} should be
33066 configured with @option{--with-system-gdbinit}. Otherwise, any user
33067 should be able to source them by hand as needed.
33069 The following scripts are currently available:
33072 @item @file{elinos.py}
33074 @cindex ELinOS system-wide configuration script
33075 This script is useful when debugging a program on an ELinOS target.
33076 It takes advantage of the environment variables defined in a standard
33077 ELinOS environment in order to determine the location of the system
33078 shared libraries, and then sets the @samp{solib-absolute-prefix}
33079 and @samp{solib-search-path} variables appropriately.
33081 @item @file{wrs-linux.py}
33082 @pindex wrs-linux.py
33083 @cindex Wind River Linux system-wide configuration script
33084 This script is useful when debugging a program on a target running
33085 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33086 the host-side sysroot used by the target system.
33090 @node Maintenance Commands
33091 @appendix Maintenance Commands
33092 @cindex maintenance commands
33093 @cindex internal commands
33095 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33096 includes a number of commands intended for @value{GDBN} developers,
33097 that are not documented elsewhere in this manual. These commands are
33098 provided here for reference. (For commands that turn on debugging
33099 messages, see @ref{Debugging Output}.)
33102 @kindex maint agent
33103 @kindex maint agent-eval
33104 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33105 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33106 Translate the given @var{expression} into remote agent bytecodes.
33107 This command is useful for debugging the Agent Expression mechanism
33108 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33109 expression useful for data collection, such as by tracepoints, while
33110 @samp{maint agent-eval} produces an expression that evaluates directly
33111 to a result. For instance, a collection expression for @code{globa +
33112 globb} will include bytecodes to record four bytes of memory at each
33113 of the addresses of @code{globa} and @code{globb}, while discarding
33114 the result of the addition, while an evaluation expression will do the
33115 addition and return the sum.
33116 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33117 If not, generate remote agent bytecode for current frame PC address.
33119 @kindex maint agent-printf
33120 @item maint agent-printf @var{format},@var{expr},...
33121 Translate the given format string and list of argument expressions
33122 into remote agent bytecodes and display them as a disassembled list.
33123 This command is useful for debugging the agent version of dynamic
33124 printf (@pxref{Dynamic Printf}).
33126 @kindex maint info breakpoints
33127 @item @anchor{maint info breakpoints}maint info breakpoints
33128 Using the same format as @samp{info breakpoints}, display both the
33129 breakpoints you've set explicitly, and those @value{GDBN} is using for
33130 internal purposes. Internal breakpoints are shown with negative
33131 breakpoint numbers. The type column identifies what kind of breakpoint
33136 Normal, explicitly set breakpoint.
33139 Normal, explicitly set watchpoint.
33142 Internal breakpoint, used to handle correctly stepping through
33143 @code{longjmp} calls.
33145 @item longjmp resume
33146 Internal breakpoint at the target of a @code{longjmp}.
33149 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33152 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33155 Shared library events.
33159 @kindex maint info bfds
33160 @item maint info bfds
33161 This prints information about each @code{bfd} object that is known to
33162 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33164 @kindex set displaced-stepping
33165 @kindex show displaced-stepping
33166 @cindex displaced stepping support
33167 @cindex out-of-line single-stepping
33168 @item set displaced-stepping
33169 @itemx show displaced-stepping
33170 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33171 if the target supports it. Displaced stepping is a way to single-step
33172 over breakpoints without removing them from the inferior, by executing
33173 an out-of-line copy of the instruction that was originally at the
33174 breakpoint location. It is also known as out-of-line single-stepping.
33177 @item set displaced-stepping on
33178 If the target architecture supports it, @value{GDBN} will use
33179 displaced stepping to step over breakpoints.
33181 @item set displaced-stepping off
33182 @value{GDBN} will not use displaced stepping to step over breakpoints,
33183 even if such is supported by the target architecture.
33185 @cindex non-stop mode, and @samp{set displaced-stepping}
33186 @item set displaced-stepping auto
33187 This is the default mode. @value{GDBN} will use displaced stepping
33188 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33189 architecture supports displaced stepping.
33192 @kindex maint check-psymtabs
33193 @item maint check-psymtabs
33194 Check the consistency of currently expanded psymtabs versus symtabs.
33195 Use this to check, for example, whether a symbol is in one but not the other.
33197 @kindex maint check-symtabs
33198 @item maint check-symtabs
33199 Check the consistency of currently expanded symtabs.
33201 @kindex maint expand-symtabs
33202 @item maint expand-symtabs [@var{regexp}]
33203 Expand symbol tables.
33204 If @var{regexp} is specified, only expand symbol tables for file
33205 names matching @var{regexp}.
33207 @kindex maint cplus first_component
33208 @item maint cplus first_component @var{name}
33209 Print the first C@t{++} class/namespace component of @var{name}.
33211 @kindex maint cplus namespace
33212 @item maint cplus namespace
33213 Print the list of possible C@t{++} namespaces.
33215 @kindex maint demangle
33216 @item maint demangle @var{name}
33217 Demangle a C@t{++} or Objective-C mangled @var{name}.
33219 @kindex maint deprecate
33220 @kindex maint undeprecate
33221 @cindex deprecated commands
33222 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33223 @itemx maint undeprecate @var{command}
33224 Deprecate or undeprecate the named @var{command}. Deprecated commands
33225 cause @value{GDBN} to issue a warning when you use them. The optional
33226 argument @var{replacement} says which newer command should be used in
33227 favor of the deprecated one; if it is given, @value{GDBN} will mention
33228 the replacement as part of the warning.
33230 @kindex maint dump-me
33231 @item maint dump-me
33232 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33233 Cause a fatal signal in the debugger and force it to dump its core.
33234 This is supported only on systems which support aborting a program
33235 with the @code{SIGQUIT} signal.
33237 @kindex maint internal-error
33238 @kindex maint internal-warning
33239 @item maint internal-error @r{[}@var{message-text}@r{]}
33240 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33241 Cause @value{GDBN} to call the internal function @code{internal_error}
33242 or @code{internal_warning} and hence behave as though an internal error
33243 or internal warning has been detected. In addition to reporting the
33244 internal problem, these functions give the user the opportunity to
33245 either quit @value{GDBN} or create a core file of the current
33246 @value{GDBN} session.
33248 These commands take an optional parameter @var{message-text} that is
33249 used as the text of the error or warning message.
33251 Here's an example of using @code{internal-error}:
33254 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33255 @dots{}/maint.c:121: internal-error: testing, 1, 2
33256 A problem internal to GDB has been detected. Further
33257 debugging may prove unreliable.
33258 Quit this debugging session? (y or n) @kbd{n}
33259 Create a core file? (y or n) @kbd{n}
33263 @cindex @value{GDBN} internal error
33264 @cindex internal errors, control of @value{GDBN} behavior
33266 @kindex maint set internal-error
33267 @kindex maint show internal-error
33268 @kindex maint set internal-warning
33269 @kindex maint show internal-warning
33270 @item maint set internal-error @var{action} [ask|yes|no]
33271 @itemx maint show internal-error @var{action}
33272 @itemx maint set internal-warning @var{action} [ask|yes|no]
33273 @itemx maint show internal-warning @var{action}
33274 When @value{GDBN} reports an internal problem (error or warning) it
33275 gives the user the opportunity to both quit @value{GDBN} and create a
33276 core file of the current @value{GDBN} session. These commands let you
33277 override the default behaviour for each particular @var{action},
33278 described in the table below.
33282 You can specify that @value{GDBN} should always (yes) or never (no)
33283 quit. The default is to ask the user what to do.
33286 You can specify that @value{GDBN} should always (yes) or never (no)
33287 create a core file. The default is to ask the user what to do.
33290 @kindex maint packet
33291 @item maint packet @var{text}
33292 If @value{GDBN} is talking to an inferior via the serial protocol,
33293 then this command sends the string @var{text} to the inferior, and
33294 displays the response packet. @value{GDBN} supplies the initial
33295 @samp{$} character, the terminating @samp{#} character, and the
33298 @kindex maint print architecture
33299 @item maint print architecture @r{[}@var{file}@r{]}
33300 Print the entire architecture configuration. The optional argument
33301 @var{file} names the file where the output goes.
33303 @kindex maint print c-tdesc
33304 @item maint print c-tdesc
33305 Print the current target description (@pxref{Target Descriptions}) as
33306 a C source file. The created source file can be used in @value{GDBN}
33307 when an XML parser is not available to parse the description.
33309 @kindex maint print dummy-frames
33310 @item maint print dummy-frames
33311 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33314 (@value{GDBP}) @kbd{b add}
33316 (@value{GDBP}) @kbd{print add(2,3)}
33317 Breakpoint 2, add (a=2, b=3) at @dots{}
33319 The program being debugged stopped while in a function called from GDB.
33321 (@value{GDBP}) @kbd{maint print dummy-frames}
33322 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33323 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33324 call_lo=0x01014000 call_hi=0x01014001
33328 Takes an optional file parameter.
33330 @kindex maint print registers
33331 @kindex maint print raw-registers
33332 @kindex maint print cooked-registers
33333 @kindex maint print register-groups
33334 @kindex maint print remote-registers
33335 @item maint print registers @r{[}@var{file}@r{]}
33336 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33337 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33338 @itemx maint print register-groups @r{[}@var{file}@r{]}
33339 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33340 Print @value{GDBN}'s internal register data structures.
33342 The command @code{maint print raw-registers} includes the contents of
33343 the raw register cache; the command @code{maint print
33344 cooked-registers} includes the (cooked) value of all registers,
33345 including registers which aren't available on the target nor visible
33346 to user; the command @code{maint print register-groups} includes the
33347 groups that each register is a member of; and the command @code{maint
33348 print remote-registers} includes the remote target's register numbers
33349 and offsets in the `G' packets.
33351 These commands take an optional parameter, a file name to which to
33352 write the information.
33354 @kindex maint print reggroups
33355 @item maint print reggroups @r{[}@var{file}@r{]}
33356 Print @value{GDBN}'s internal register group data structures. The
33357 optional argument @var{file} tells to what file to write the
33360 The register groups info looks like this:
33363 (@value{GDBP}) @kbd{maint print reggroups}
33376 This command forces @value{GDBN} to flush its internal register cache.
33378 @kindex maint print objfiles
33379 @cindex info for known object files
33380 @item maint print objfiles @r{[}@var{regexp}@r{]}
33381 Print a dump of all known object files.
33382 If @var{regexp} is specified, only print object files whose names
33383 match @var{regexp}. For each object file, this command prints its name,
33384 address in memory, and all of its psymtabs and symtabs.
33386 @kindex maint print section-scripts
33387 @cindex info for known .debug_gdb_scripts-loaded scripts
33388 @item maint print section-scripts [@var{regexp}]
33389 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33390 If @var{regexp} is specified, only print scripts loaded by object files
33391 matching @var{regexp}.
33392 For each script, this command prints its name as specified in the objfile,
33393 and the full path if known.
33394 @xref{dotdebug_gdb_scripts section}.
33396 @kindex maint print statistics
33397 @cindex bcache statistics
33398 @item maint print statistics
33399 This command prints, for each object file in the program, various data
33400 about that object file followed by the byte cache (@dfn{bcache})
33401 statistics for the object file. The objfile data includes the number
33402 of minimal, partial, full, and stabs symbols, the number of types
33403 defined by the objfile, the number of as yet unexpanded psym tables,
33404 the number of line tables and string tables, and the amount of memory
33405 used by the various tables. The bcache statistics include the counts,
33406 sizes, and counts of duplicates of all and unique objects, max,
33407 average, and median entry size, total memory used and its overhead and
33408 savings, and various measures of the hash table size and chain
33411 @kindex maint print target-stack
33412 @cindex target stack description
33413 @item maint print target-stack
33414 A @dfn{target} is an interface between the debugger and a particular
33415 kind of file or process. Targets can be stacked in @dfn{strata},
33416 so that more than one target can potentially respond to a request.
33417 In particular, memory accesses will walk down the stack of targets
33418 until they find a target that is interested in handling that particular
33421 This command prints a short description of each layer that was pushed on
33422 the @dfn{target stack}, starting from the top layer down to the bottom one.
33424 @kindex maint print type
33425 @cindex type chain of a data type
33426 @item maint print type @var{expr}
33427 Print the type chain for a type specified by @var{expr}. The argument
33428 can be either a type name or a symbol. If it is a symbol, the type of
33429 that symbol is described. The type chain produced by this command is
33430 a recursive definition of the data type as stored in @value{GDBN}'s
33431 data structures, including its flags and contained types.
33433 @kindex maint set dwarf2 always-disassemble
33434 @kindex maint show dwarf2 always-disassemble
33435 @item maint set dwarf2 always-disassemble
33436 @item maint show dwarf2 always-disassemble
33437 Control the behavior of @code{info address} when using DWARF debugging
33440 The default is @code{off}, which means that @value{GDBN} should try to
33441 describe a variable's location in an easily readable format. When
33442 @code{on}, @value{GDBN} will instead display the DWARF location
33443 expression in an assembly-like format. Note that some locations are
33444 too complex for @value{GDBN} to describe simply; in this case you will
33445 always see the disassembly form.
33447 Here is an example of the resulting disassembly:
33450 (gdb) info addr argc
33451 Symbol "argc" is a complex DWARF expression:
33455 For more information on these expressions, see
33456 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33458 @kindex maint set dwarf2 max-cache-age
33459 @kindex maint show dwarf2 max-cache-age
33460 @item maint set dwarf2 max-cache-age
33461 @itemx maint show dwarf2 max-cache-age
33462 Control the DWARF 2 compilation unit cache.
33464 @cindex DWARF 2 compilation units cache
33465 In object files with inter-compilation-unit references, such as those
33466 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33467 reader needs to frequently refer to previously read compilation units.
33468 This setting controls how long a compilation unit will remain in the
33469 cache if it is not referenced. A higher limit means that cached
33470 compilation units will be stored in memory longer, and more total
33471 memory will be used. Setting it to zero disables caching, which will
33472 slow down @value{GDBN} startup, but reduce memory consumption.
33474 @kindex maint set profile
33475 @kindex maint show profile
33476 @cindex profiling GDB
33477 @item maint set profile
33478 @itemx maint show profile
33479 Control profiling of @value{GDBN}.
33481 Profiling will be disabled until you use the @samp{maint set profile}
33482 command to enable it. When you enable profiling, the system will begin
33483 collecting timing and execution count data; when you disable profiling or
33484 exit @value{GDBN}, the results will be written to a log file. Remember that
33485 if you use profiling, @value{GDBN} will overwrite the profiling log file
33486 (often called @file{gmon.out}). If you have a record of important profiling
33487 data in a @file{gmon.out} file, be sure to move it to a safe location.
33489 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33490 compiled with the @samp{-pg} compiler option.
33492 @kindex maint set show-debug-regs
33493 @kindex maint show show-debug-regs
33494 @cindex hardware debug registers
33495 @item maint set show-debug-regs
33496 @itemx maint show show-debug-regs
33497 Control whether to show variables that mirror the hardware debug
33498 registers. Use @code{on} to enable, @code{off} to disable. If
33499 enabled, the debug registers values are shown when @value{GDBN} inserts or
33500 removes a hardware breakpoint or watchpoint, and when the inferior
33501 triggers a hardware-assisted breakpoint or watchpoint.
33503 @kindex maint set show-all-tib
33504 @kindex maint show show-all-tib
33505 @item maint set show-all-tib
33506 @itemx maint show show-all-tib
33507 Control whether to show all non zero areas within a 1k block starting
33508 at thread local base, when using the @samp{info w32 thread-information-block}
33511 @kindex maint set per-command
33512 @kindex maint show per-command
33513 @item maint set per-command
33514 @itemx maint show per-command
33515 @cindex resources used by commands
33517 @value{GDBN} can display the resources used by each command.
33518 This is useful in debugging performance problems.
33521 @item maint set per-command space [on|off]
33522 @itemx maint show per-command space
33523 Enable or disable the printing of the memory used by GDB for each command.
33524 If enabled, @value{GDBN} will display how much memory each command
33525 took, following the command's own output.
33526 This can also be requested by invoking @value{GDBN} with the
33527 @option{--statistics} command-line switch (@pxref{Mode Options}).
33529 @item maint set per-command time [on|off]
33530 @itemx maint show per-command time
33531 Enable or disable the printing of the execution time of @value{GDBN}
33533 If enabled, @value{GDBN} will display how much time it
33534 took to execute each command, following the command's own output.
33535 Both CPU time and wallclock time are printed.
33536 Printing both is useful when trying to determine whether the cost is
33537 CPU or, e.g., disk/network latency.
33538 Note that the CPU time printed is for @value{GDBN} only, it does not include
33539 the execution time of the inferior because there's no mechanism currently
33540 to compute how much time was spent by @value{GDBN} and how much time was
33541 spent by the program been debugged.
33542 This can also be requested by invoking @value{GDBN} with the
33543 @option{--statistics} command-line switch (@pxref{Mode Options}).
33545 @item maint set per-command symtab [on|off]
33546 @itemx maint show per-command symtab
33547 Enable or disable the printing of basic symbol table statistics
33549 If enabled, @value{GDBN} will display the following information:
33553 number of symbol tables
33555 number of primary symbol tables
33557 number of blocks in the blockvector
33561 @kindex maint space
33562 @cindex memory used by commands
33563 @item maint space @var{value}
33564 An alias for @code{maint set per-command space}.
33565 A non-zero value enables it, zero disables it.
33568 @cindex time of command execution
33569 @item maint time @var{value}
33570 An alias for @code{maint set per-command time}.
33571 A non-zero value enables it, zero disables it.
33573 @kindex maint translate-address
33574 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33575 Find the symbol stored at the location specified by the address
33576 @var{addr} and an optional section name @var{section}. If found,
33577 @value{GDBN} prints the name of the closest symbol and an offset from
33578 the symbol's location to the specified address. This is similar to
33579 the @code{info address} command (@pxref{Symbols}), except that this
33580 command also allows to find symbols in other sections.
33582 If section was not specified, the section in which the symbol was found
33583 is also printed. For dynamically linked executables, the name of
33584 executable or shared library containing the symbol is printed as well.
33588 The following command is useful for non-interactive invocations of
33589 @value{GDBN}, such as in the test suite.
33592 @item set watchdog @var{nsec}
33593 @kindex set watchdog
33594 @cindex watchdog timer
33595 @cindex timeout for commands
33596 Set the maximum number of seconds @value{GDBN} will wait for the
33597 target operation to finish. If this time expires, @value{GDBN}
33598 reports and error and the command is aborted.
33600 @item show watchdog
33601 Show the current setting of the target wait timeout.
33604 @node Remote Protocol
33605 @appendix @value{GDBN} Remote Serial Protocol
33610 * Stop Reply Packets::
33611 * General Query Packets::
33612 * Architecture-Specific Protocol Details::
33613 * Tracepoint Packets::
33614 * Host I/O Packets::
33616 * Notification Packets::
33617 * Remote Non-Stop::
33618 * Packet Acknowledgment::
33620 * File-I/O Remote Protocol Extension::
33621 * Library List Format::
33622 * Library List Format for SVR4 Targets::
33623 * Memory Map Format::
33624 * Thread List Format::
33625 * Traceframe Info Format::
33626 * Branch Trace Format::
33632 There may be occasions when you need to know something about the
33633 protocol---for example, if there is only one serial port to your target
33634 machine, you might want your program to do something special if it
33635 recognizes a packet meant for @value{GDBN}.
33637 In the examples below, @samp{->} and @samp{<-} are used to indicate
33638 transmitted and received data, respectively.
33640 @cindex protocol, @value{GDBN} remote serial
33641 @cindex serial protocol, @value{GDBN} remote
33642 @cindex remote serial protocol
33643 All @value{GDBN} commands and responses (other than acknowledgments
33644 and notifications, see @ref{Notification Packets}) are sent as a
33645 @var{packet}. A @var{packet} is introduced with the character
33646 @samp{$}, the actual @var{packet-data}, and the terminating character
33647 @samp{#} followed by a two-digit @var{checksum}:
33650 @code{$}@var{packet-data}@code{#}@var{checksum}
33654 @cindex checksum, for @value{GDBN} remote
33656 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33657 characters between the leading @samp{$} and the trailing @samp{#} (an
33658 eight bit unsigned checksum).
33660 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33661 specification also included an optional two-digit @var{sequence-id}:
33664 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33667 @cindex sequence-id, for @value{GDBN} remote
33669 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33670 has never output @var{sequence-id}s. Stubs that handle packets added
33671 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33673 When either the host or the target machine receives a packet, the first
33674 response expected is an acknowledgment: either @samp{+} (to indicate
33675 the package was received correctly) or @samp{-} (to request
33679 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33684 The @samp{+}/@samp{-} acknowledgments can be disabled
33685 once a connection is established.
33686 @xref{Packet Acknowledgment}, for details.
33688 The host (@value{GDBN}) sends @var{command}s, and the target (the
33689 debugging stub incorporated in your program) sends a @var{response}. In
33690 the case of step and continue @var{command}s, the response is only sent
33691 when the operation has completed, and the target has again stopped all
33692 threads in all attached processes. This is the default all-stop mode
33693 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33694 execution mode; see @ref{Remote Non-Stop}, for details.
33696 @var{packet-data} consists of a sequence of characters with the
33697 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33700 @cindex remote protocol, field separator
33701 Fields within the packet should be separated using @samp{,} @samp{;} or
33702 @samp{:}. Except where otherwise noted all numbers are represented in
33703 @sc{hex} with leading zeros suppressed.
33705 Implementors should note that prior to @value{GDBN} 5.0, the character
33706 @samp{:} could not appear as the third character in a packet (as it
33707 would potentially conflict with the @var{sequence-id}).
33709 @cindex remote protocol, binary data
33710 @anchor{Binary Data}
33711 Binary data in most packets is encoded either as two hexadecimal
33712 digits per byte of binary data. This allowed the traditional remote
33713 protocol to work over connections which were only seven-bit clean.
33714 Some packets designed more recently assume an eight-bit clean
33715 connection, and use a more efficient encoding to send and receive
33718 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33719 as an escape character. Any escaped byte is transmitted as the escape
33720 character followed by the original character XORed with @code{0x20}.
33721 For example, the byte @code{0x7d} would be transmitted as the two
33722 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33723 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33724 @samp{@}}) must always be escaped. Responses sent by the stub
33725 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33726 is not interpreted as the start of a run-length encoded sequence
33729 Response @var{data} can be run-length encoded to save space.
33730 Run-length encoding replaces runs of identical characters with one
33731 instance of the repeated character, followed by a @samp{*} and a
33732 repeat count. The repeat count is itself sent encoded, to avoid
33733 binary characters in @var{data}: a value of @var{n} is sent as
33734 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33735 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33736 code 32) for a repeat count of 3. (This is because run-length
33737 encoding starts to win for counts 3 or more.) Thus, for example,
33738 @samp{0* } is a run-length encoding of ``0000'': the space character
33739 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33742 The printable characters @samp{#} and @samp{$} or with a numeric value
33743 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33744 seven repeats (@samp{$}) can be expanded using a repeat count of only
33745 five (@samp{"}). For example, @samp{00000000} can be encoded as
33748 The error response returned for some packets includes a two character
33749 error number. That number is not well defined.
33751 @cindex empty response, for unsupported packets
33752 For any @var{command} not supported by the stub, an empty response
33753 (@samp{$#00}) should be returned. That way it is possible to extend the
33754 protocol. A newer @value{GDBN} can tell if a packet is supported based
33757 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33758 commands for register access, and the @samp{m} and @samp{M} commands
33759 for memory access. Stubs that only control single-threaded targets
33760 can implement run control with the @samp{c} (continue), and @samp{s}
33761 (step) commands. Stubs that support multi-threading targets should
33762 support the @samp{vCont} command. All other commands are optional.
33767 The following table provides a complete list of all currently defined
33768 @var{command}s and their corresponding response @var{data}.
33769 @xref{File-I/O Remote Protocol Extension}, for details about the File
33770 I/O extension of the remote protocol.
33772 Each packet's description has a template showing the packet's overall
33773 syntax, followed by an explanation of the packet's meaning. We
33774 include spaces in some of the templates for clarity; these are not
33775 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33776 separate its components. For example, a template like @samp{foo
33777 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33778 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33779 @var{baz}. @value{GDBN} does not transmit a space character between the
33780 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33783 @cindex @var{thread-id}, in remote protocol
33784 @anchor{thread-id syntax}
33785 Several packets and replies include a @var{thread-id} field to identify
33786 a thread. Normally these are positive numbers with a target-specific
33787 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33788 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33791 In addition, the remote protocol supports a multiprocess feature in
33792 which the @var{thread-id} syntax is extended to optionally include both
33793 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33794 The @var{pid} (process) and @var{tid} (thread) components each have the
33795 format described above: a positive number with target-specific
33796 interpretation formatted as a big-endian hex string, literal @samp{-1}
33797 to indicate all processes or threads (respectively), or @samp{0} to
33798 indicate an arbitrary process or thread. Specifying just a process, as
33799 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33800 error to specify all processes but a specific thread, such as
33801 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33802 for those packets and replies explicitly documented to include a process
33803 ID, rather than a @var{thread-id}.
33805 The multiprocess @var{thread-id} syntax extensions are only used if both
33806 @value{GDBN} and the stub report support for the @samp{multiprocess}
33807 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33810 Note that all packet forms beginning with an upper- or lower-case
33811 letter, other than those described here, are reserved for future use.
33813 Here are the packet descriptions.
33818 @cindex @samp{!} packet
33819 @anchor{extended mode}
33820 Enable extended mode. In extended mode, the remote server is made
33821 persistent. The @samp{R} packet is used to restart the program being
33827 The remote target both supports and has enabled extended mode.
33831 @cindex @samp{?} packet
33833 Indicate the reason the target halted. The reply is the same as for
33834 step and continue. This packet has a special interpretation when the
33835 target is in non-stop mode; see @ref{Remote Non-Stop}.
33838 @xref{Stop Reply Packets}, for the reply specifications.
33840 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33841 @cindex @samp{A} packet
33842 Initialized @code{argv[]} array passed into program. @var{arglen}
33843 specifies the number of bytes in the hex encoded byte stream
33844 @var{arg}. See @code{gdbserver} for more details.
33849 The arguments were set.
33855 @cindex @samp{b} packet
33856 (Don't use this packet; its behavior is not well-defined.)
33857 Change the serial line speed to @var{baud}.
33859 JTC: @emph{When does the transport layer state change? When it's
33860 received, or after the ACK is transmitted. In either case, there are
33861 problems if the command or the acknowledgment packet is dropped.}
33863 Stan: @emph{If people really wanted to add something like this, and get
33864 it working for the first time, they ought to modify ser-unix.c to send
33865 some kind of out-of-band message to a specially-setup stub and have the
33866 switch happen "in between" packets, so that from remote protocol's point
33867 of view, nothing actually happened.}
33869 @item B @var{addr},@var{mode}
33870 @cindex @samp{B} packet
33871 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33872 breakpoint at @var{addr}.
33874 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33875 (@pxref{insert breakpoint or watchpoint packet}).
33877 @cindex @samp{bc} packet
33880 Backward continue. Execute the target system in reverse. No parameter.
33881 @xref{Reverse Execution}, for more information.
33884 @xref{Stop Reply Packets}, for the reply specifications.
33886 @cindex @samp{bs} packet
33889 Backward single step. Execute one instruction in reverse. No parameter.
33890 @xref{Reverse Execution}, for more information.
33893 @xref{Stop Reply Packets}, for the reply specifications.
33895 @item c @r{[}@var{addr}@r{]}
33896 @cindex @samp{c} packet
33897 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33898 resume at current address.
33900 This packet is deprecated for multi-threading support. @xref{vCont
33904 @xref{Stop Reply Packets}, for the reply specifications.
33906 @item C @var{sig}@r{[};@var{addr}@r{]}
33907 @cindex @samp{C} packet
33908 Continue with signal @var{sig} (hex signal number). If
33909 @samp{;@var{addr}} is omitted, resume at same address.
33911 This packet is deprecated for multi-threading support. @xref{vCont
33915 @xref{Stop Reply Packets}, for the reply specifications.
33918 @cindex @samp{d} packet
33921 Don't use this packet; instead, define a general set packet
33922 (@pxref{General Query Packets}).
33926 @cindex @samp{D} packet
33927 The first form of the packet is used to detach @value{GDBN} from the
33928 remote system. It is sent to the remote target
33929 before @value{GDBN} disconnects via the @code{detach} command.
33931 The second form, including a process ID, is used when multiprocess
33932 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33933 detach only a specific process. The @var{pid} is specified as a
33934 big-endian hex string.
33944 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33945 @cindex @samp{F} packet
33946 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33947 This is part of the File-I/O protocol extension. @xref{File-I/O
33948 Remote Protocol Extension}, for the specification.
33951 @anchor{read registers packet}
33952 @cindex @samp{g} packet
33953 Read general registers.
33957 @item @var{XX@dots{}}
33958 Each byte of register data is described by two hex digits. The bytes
33959 with the register are transmitted in target byte order. The size of
33960 each register and their position within the @samp{g} packet are
33961 determined by the @value{GDBN} internal gdbarch functions
33962 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33963 specification of several standard @samp{g} packets is specified below.
33965 When reading registers from a trace frame (@pxref{Analyze Collected
33966 Data,,Using the Collected Data}), the stub may also return a string of
33967 literal @samp{x}'s in place of the register data digits, to indicate
33968 that the corresponding register has not been collected, thus its value
33969 is unavailable. For example, for an architecture with 4 registers of
33970 4 bytes each, the following reply indicates to @value{GDBN} that
33971 registers 0 and 2 have not been collected, while registers 1 and 3
33972 have been collected, and both have zero value:
33976 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33983 @item G @var{XX@dots{}}
33984 @cindex @samp{G} packet
33985 Write general registers. @xref{read registers packet}, for a
33986 description of the @var{XX@dots{}} data.
33996 @item H @var{op} @var{thread-id}
33997 @cindex @samp{H} packet
33998 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33999 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
34000 it should be @samp{c} for step and continue operations (note that this
34001 is deprecated, supporting the @samp{vCont} command is a better
34002 option), @samp{g} for other operations. The thread designator
34003 @var{thread-id} has the format and interpretation described in
34004 @ref{thread-id syntax}.
34015 @c 'H': How restrictive (or permissive) is the thread model. If a
34016 @c thread is selected and stopped, are other threads allowed
34017 @c to continue to execute? As I mentioned above, I think the
34018 @c semantics of each command when a thread is selected must be
34019 @c described. For example:
34021 @c 'g': If the stub supports threads and a specific thread is
34022 @c selected, returns the register block from that thread;
34023 @c otherwise returns current registers.
34025 @c 'G' If the stub supports threads and a specific thread is
34026 @c selected, sets the registers of the register block of
34027 @c that thread; otherwise sets current registers.
34029 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34030 @anchor{cycle step packet}
34031 @cindex @samp{i} packet
34032 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34033 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34034 step starting at that address.
34037 @cindex @samp{I} packet
34038 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34042 @cindex @samp{k} packet
34045 The exact effect of this packet is not specified.
34047 For a bare-metal target, it may power cycle or reset the target
34048 system. For that reason, the @samp{k} packet has no reply.
34050 For a single-process target, it may kill that process if possible.
34052 A multiple-process target may choose to kill just one process, or all
34053 that are under @value{GDBN}'s control. For more precise control, use
34054 the vKill packet (@pxref{vKill packet}).
34056 If the target system immediately closes the connection in response to
34057 @samp{k}, @value{GDBN} does not consider the lack of packet
34058 acknowledgment to be an error, and assumes the kill was successful.
34060 If connected using @kbd{target extended-remote}, and the target does
34061 not close the connection in response to a kill request, @value{GDBN}
34062 probes the target state as if a new connection was opened
34063 (@pxref{? packet}).
34065 @item m @var{addr},@var{length}
34066 @cindex @samp{m} packet
34067 Read @var{length} bytes of memory starting at address @var{addr}.
34068 Note that @var{addr} may not be aligned to any particular boundary.
34070 The stub need not use any particular size or alignment when gathering
34071 data from memory for the response; even if @var{addr} is word-aligned
34072 and @var{length} is a multiple of the word size, the stub is free to
34073 use byte accesses, or not. For this reason, this packet may not be
34074 suitable for accessing memory-mapped I/O devices.
34075 @cindex alignment of remote memory accesses
34076 @cindex size of remote memory accesses
34077 @cindex memory, alignment and size of remote accesses
34081 @item @var{XX@dots{}}
34082 Memory contents; each byte is transmitted as a two-digit hexadecimal
34083 number. The reply may contain fewer bytes than requested if the
34084 server was able to read only part of the region of memory.
34089 @item M @var{addr},@var{length}:@var{XX@dots{}}
34090 @cindex @samp{M} packet
34091 Write @var{length} bytes of memory starting at address @var{addr}.
34092 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
34093 hexadecimal number.
34100 for an error (this includes the case where only part of the data was
34105 @cindex @samp{p} packet
34106 Read the value of register @var{n}; @var{n} is in hex.
34107 @xref{read registers packet}, for a description of how the returned
34108 register value is encoded.
34112 @item @var{XX@dots{}}
34113 the register's value
34117 Indicating an unrecognized @var{query}.
34120 @item P @var{n@dots{}}=@var{r@dots{}}
34121 @anchor{write register packet}
34122 @cindex @samp{P} packet
34123 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34124 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34125 digits for each byte in the register (target byte order).
34135 @item q @var{name} @var{params}@dots{}
34136 @itemx Q @var{name} @var{params}@dots{}
34137 @cindex @samp{q} packet
34138 @cindex @samp{Q} packet
34139 General query (@samp{q}) and set (@samp{Q}). These packets are
34140 described fully in @ref{General Query Packets}.
34143 @cindex @samp{r} packet
34144 Reset the entire system.
34146 Don't use this packet; use the @samp{R} packet instead.
34149 @cindex @samp{R} packet
34150 Restart the program being debugged. @var{XX}, while needed, is ignored.
34151 This packet is only available in extended mode (@pxref{extended mode}).
34153 The @samp{R} packet has no reply.
34155 @item s @r{[}@var{addr}@r{]}
34156 @cindex @samp{s} packet
34157 Single step. @var{addr} is the address at which to resume. If
34158 @var{addr} is omitted, resume at same address.
34160 This packet is deprecated for multi-threading support. @xref{vCont
34164 @xref{Stop Reply Packets}, for the reply specifications.
34166 @item S @var{sig}@r{[};@var{addr}@r{]}
34167 @anchor{step with signal packet}
34168 @cindex @samp{S} packet
34169 Step with signal. This is analogous to the @samp{C} packet, but
34170 requests a single-step, rather than a normal resumption of execution.
34172 This packet is deprecated for multi-threading support. @xref{vCont
34176 @xref{Stop Reply Packets}, for the reply specifications.
34178 @item t @var{addr}:@var{PP},@var{MM}
34179 @cindex @samp{t} packet
34180 Search backwards starting at address @var{addr} for a match with pattern
34181 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
34182 @var{addr} must be at least 3 digits.
34184 @item T @var{thread-id}
34185 @cindex @samp{T} packet
34186 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34191 thread is still alive
34197 Packets starting with @samp{v} are identified by a multi-letter name,
34198 up to the first @samp{;} or @samp{?} (or the end of the packet).
34200 @item vAttach;@var{pid}
34201 @cindex @samp{vAttach} packet
34202 Attach to a new process with the specified process ID @var{pid}.
34203 The process ID is a
34204 hexadecimal integer identifying the process. In all-stop mode, all
34205 threads in the attached process are stopped; in non-stop mode, it may be
34206 attached without being stopped if that is supported by the target.
34208 @c In non-stop mode, on a successful vAttach, the stub should set the
34209 @c current thread to a thread of the newly-attached process. After
34210 @c attaching, GDB queries for the attached process's thread ID with qC.
34211 @c Also note that, from a user perspective, whether or not the
34212 @c target is stopped on attach in non-stop mode depends on whether you
34213 @c use the foreground or background version of the attach command, not
34214 @c on what vAttach does; GDB does the right thing with respect to either
34215 @c stopping or restarting threads.
34217 This packet is only available in extended mode (@pxref{extended mode}).
34223 @item @r{Any stop packet}
34224 for success in all-stop mode (@pxref{Stop Reply Packets})
34226 for success in non-stop mode (@pxref{Remote Non-Stop})
34229 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34230 @cindex @samp{vCont} packet
34231 @anchor{vCont packet}
34232 Resume the inferior, specifying different actions for each thread.
34233 If an action is specified with no @var{thread-id}, then it is applied to any
34234 threads that don't have a specific action specified; if no default action is
34235 specified then other threads should remain stopped in all-stop mode and
34236 in their current state in non-stop mode.
34237 Specifying multiple
34238 default actions is an error; specifying no actions is also an error.
34239 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34241 Currently supported actions are:
34247 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34251 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34254 @item r @var{start},@var{end}
34255 Step once, and then keep stepping as long as the thread stops at
34256 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34257 The remote stub reports a stop reply when either the thread goes out
34258 of the range or is stopped due to an unrelated reason, such as hitting
34259 a breakpoint. @xref{range stepping}.
34261 If the range is empty (@var{start} == @var{end}), then the action
34262 becomes equivalent to the @samp{s} action. In other words,
34263 single-step once, and report the stop (even if the stepped instruction
34264 jumps to @var{start}).
34266 (A stop reply may be sent at any point even if the PC is still within
34267 the stepping range; for example, it is valid to implement this packet
34268 in a degenerate way as a single instruction step operation.)
34272 The optional argument @var{addr} normally associated with the
34273 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34274 not supported in @samp{vCont}.
34276 The @samp{t} action is only relevant in non-stop mode
34277 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34278 A stop reply should be generated for any affected thread not already stopped.
34279 When a thread is stopped by means of a @samp{t} action,
34280 the corresponding stop reply should indicate that the thread has stopped with
34281 signal @samp{0}, regardless of whether the target uses some other signal
34282 as an implementation detail.
34284 The stub must support @samp{vCont} if it reports support for
34285 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34286 this case @samp{vCont} actions can be specified to apply to all threads
34287 in a process by using the @samp{p@var{pid}.-1} form of the
34291 @xref{Stop Reply Packets}, for the reply specifications.
34294 @cindex @samp{vCont?} packet
34295 Request a list of actions supported by the @samp{vCont} packet.
34299 @item vCont@r{[};@var{action}@dots{}@r{]}
34300 The @samp{vCont} packet is supported. Each @var{action} is a supported
34301 command in the @samp{vCont} packet.
34303 The @samp{vCont} packet is not supported.
34306 @item vFile:@var{operation}:@var{parameter}@dots{}
34307 @cindex @samp{vFile} packet
34308 Perform a file operation on the target system. For details,
34309 see @ref{Host I/O Packets}.
34311 @item vFlashErase:@var{addr},@var{length}
34312 @cindex @samp{vFlashErase} packet
34313 Direct the stub to erase @var{length} bytes of flash starting at
34314 @var{addr}. The region may enclose any number of flash blocks, but
34315 its start and end must fall on block boundaries, as indicated by the
34316 flash block size appearing in the memory map (@pxref{Memory Map
34317 Format}). @value{GDBN} groups flash memory programming operations
34318 together, and sends a @samp{vFlashDone} request after each group; the
34319 stub is allowed to delay erase operation until the @samp{vFlashDone}
34320 packet is received.
34330 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34331 @cindex @samp{vFlashWrite} packet
34332 Direct the stub to write data to flash address @var{addr}. The data
34333 is passed in binary form using the same encoding as for the @samp{X}
34334 packet (@pxref{Binary Data}). The memory ranges specified by
34335 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34336 not overlap, and must appear in order of increasing addresses
34337 (although @samp{vFlashErase} packets for higher addresses may already
34338 have been received; the ordering is guaranteed only between
34339 @samp{vFlashWrite} packets). If a packet writes to an address that was
34340 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34341 target-specific method, the results are unpredictable.
34349 for vFlashWrite addressing non-flash memory
34355 @cindex @samp{vFlashDone} packet
34356 Indicate to the stub that flash programming operation is finished.
34357 The stub is permitted to delay or batch the effects of a group of
34358 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34359 @samp{vFlashDone} packet is received. The contents of the affected
34360 regions of flash memory are unpredictable until the @samp{vFlashDone}
34361 request is completed.
34363 @item vKill;@var{pid}
34364 @cindex @samp{vKill} packet
34365 @anchor{vKill packet}
34366 Kill the process with the specified process ID. @var{pid} is a
34367 hexadecimal integer identifying the process. This packet is used in
34368 preference to @samp{k} when multiprocess protocol extensions are
34369 supported; see @ref{multiprocess extensions}.
34379 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34380 @cindex @samp{vRun} packet
34381 Run the program @var{filename}, passing it each @var{argument} on its
34382 command line. The file and arguments are hex-encoded strings. If
34383 @var{filename} is an empty string, the stub may use a default program
34384 (e.g.@: the last program run). The program is created in the stopped
34387 @c FIXME: What about non-stop mode?
34389 This packet is only available in extended mode (@pxref{extended mode}).
34395 @item @r{Any stop packet}
34396 for success (@pxref{Stop Reply Packets})
34400 @cindex @samp{vStopped} packet
34401 @xref{Notification Packets}.
34403 @item X @var{addr},@var{length}:@var{XX@dots{}}
34405 @cindex @samp{X} packet
34406 Write data to memory, where the data is transmitted in binary.
34407 @var{addr} is address, @var{length} is number of bytes,
34408 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34418 @item z @var{type},@var{addr},@var{kind}
34419 @itemx Z @var{type},@var{addr},@var{kind}
34420 @anchor{insert breakpoint or watchpoint packet}
34421 @cindex @samp{z} packet
34422 @cindex @samp{Z} packets
34423 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34424 watchpoint starting at address @var{address} of kind @var{kind}.
34426 Each breakpoint and watchpoint packet @var{type} is documented
34429 @emph{Implementation notes: A remote target shall return an empty string
34430 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34431 remote target shall support either both or neither of a given
34432 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34433 avoid potential problems with duplicate packets, the operations should
34434 be implemented in an idempotent way.}
34436 @item z0,@var{addr},@var{kind}
34437 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
34438 @cindex @samp{z0} packet
34439 @cindex @samp{Z0} packet
34440 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34441 @var{addr} of type @var{kind}.
34443 A memory breakpoint is implemented by replacing the instruction at
34444 @var{addr} with a software breakpoint or trap instruction. The
34445 @var{kind} is target-specific and typically indicates the size of
34446 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34447 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34448 architectures have additional meanings for @var{kind};
34449 @var{cond_list} is an optional list of conditional expressions in bytecode
34450 form that should be evaluated on the target's side. These are the
34451 conditions that should be taken into consideration when deciding if
34452 the breakpoint trigger should be reported back to @var{GDBN}.
34454 The @var{cond_list} parameter is comprised of a series of expressions,
34455 concatenated without separators. Each expression has the following form:
34459 @item X @var{len},@var{expr}
34460 @var{len} is the length of the bytecode expression and @var{expr} is the
34461 actual conditional expression in bytecode form.
34465 The optional @var{cmd_list} parameter introduces commands that may be
34466 run on the target, rather than being reported back to @value{GDBN}.
34467 The parameter starts with a numeric flag @var{persist}; if the flag is
34468 nonzero, then the breakpoint may remain active and the commands
34469 continue to be run even when @value{GDBN} disconnects from the target.
34470 Following this flag is a series of expressions concatenated with no
34471 separators. Each expression has the following form:
34475 @item X @var{len},@var{expr}
34476 @var{len} is the length of the bytecode expression and @var{expr} is the
34477 actual conditional expression in bytecode form.
34481 see @ref{Architecture-Specific Protocol Details}.
34483 @emph{Implementation note: It is possible for a target to copy or move
34484 code that contains memory breakpoints (e.g., when implementing
34485 overlays). The behavior of this packet, in the presence of such a
34486 target, is not defined.}
34498 @item z1,@var{addr},@var{kind}
34499 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34500 @cindex @samp{z1} packet
34501 @cindex @samp{Z1} packet
34502 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34503 address @var{addr}.
34505 A hardware breakpoint is implemented using a mechanism that is not
34506 dependant on being able to modify the target's memory. @var{kind}
34507 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34509 @emph{Implementation note: A hardware breakpoint is not affected by code
34522 @item z2,@var{addr},@var{kind}
34523 @itemx Z2,@var{addr},@var{kind}
34524 @cindex @samp{z2} packet
34525 @cindex @samp{Z2} packet
34526 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34527 @var{kind} is interpreted as the number of bytes to watch.
34539 @item z3,@var{addr},@var{kind}
34540 @itemx Z3,@var{addr},@var{kind}
34541 @cindex @samp{z3} packet
34542 @cindex @samp{Z3} packet
34543 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34544 @var{kind} is interpreted as the number of bytes to watch.
34556 @item z4,@var{addr},@var{kind}
34557 @itemx Z4,@var{addr},@var{kind}
34558 @cindex @samp{z4} packet
34559 @cindex @samp{Z4} packet
34560 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34561 @var{kind} is interpreted as the number of bytes to watch.
34575 @node Stop Reply Packets
34576 @section Stop Reply Packets
34577 @cindex stop reply packets
34579 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34580 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34581 receive any of the below as a reply. Except for @samp{?}
34582 and @samp{vStopped}, that reply is only returned
34583 when the target halts. In the below the exact meaning of @dfn{signal
34584 number} is defined by the header @file{include/gdb/signals.h} in the
34585 @value{GDBN} source code.
34587 As in the description of request packets, we include spaces in the
34588 reply templates for clarity; these are not part of the reply packet's
34589 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34595 The program received signal number @var{AA} (a two-digit hexadecimal
34596 number). This is equivalent to a @samp{T} response with no
34597 @var{n}:@var{r} pairs.
34599 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34600 @cindex @samp{T} packet reply
34601 The program received signal number @var{AA} (a two-digit hexadecimal
34602 number). This is equivalent to an @samp{S} response, except that the
34603 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34604 and other information directly in the stop reply packet, reducing
34605 round-trip latency. Single-step and breakpoint traps are reported
34606 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34610 If @var{n} is a hexadecimal number, it is a register number, and the
34611 corresponding @var{r} gives that register's value. @var{r} is a
34612 series of bytes in target byte order, with each byte given by a
34613 two-digit hex number.
34616 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34617 the stopped thread, as specified in @ref{thread-id syntax}.
34620 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34621 the core on which the stop event was detected.
34624 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34625 specific event that stopped the target. The currently defined stop
34626 reasons are listed below. @var{aa} should be @samp{05}, the trap
34627 signal. At most one stop reason should be present.
34630 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34631 and go on to the next; this allows us to extend the protocol in the
34635 The currently defined stop reasons are:
34641 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34644 @cindex shared library events, remote reply
34646 The packet indicates that the loaded libraries have changed.
34647 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34648 list of loaded libraries. @var{r} is ignored.
34650 @cindex replay log events, remote reply
34652 The packet indicates that the target cannot continue replaying
34653 logged execution events, because it has reached the end (or the
34654 beginning when executing backward) of the log. The value of @var{r}
34655 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34656 for more information.
34660 @itemx W @var{AA} ; process:@var{pid}
34661 The process exited, and @var{AA} is the exit status. This is only
34662 applicable to certain targets.
34664 The second form of the response, including the process ID of the exited
34665 process, can be used only when @value{GDBN} has reported support for
34666 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34667 The @var{pid} is formatted as a big-endian hex string.
34670 @itemx X @var{AA} ; process:@var{pid}
34671 The process terminated with signal @var{AA}.
34673 The second form of the response, including the process ID of the
34674 terminated process, can be used only when @value{GDBN} has reported
34675 support for multiprocess protocol extensions; see @ref{multiprocess
34676 extensions}. The @var{pid} is formatted as a big-endian hex string.
34678 @item O @var{XX}@dots{}
34679 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34680 written as the program's console output. This can happen at any time
34681 while the program is running and the debugger should continue to wait
34682 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34684 @item F @var{call-id},@var{parameter}@dots{}
34685 @var{call-id} is the identifier which says which host system call should
34686 be called. This is just the name of the function. Translation into the
34687 correct system call is only applicable as it's defined in @value{GDBN}.
34688 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34691 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34692 this very system call.
34694 The target replies with this packet when it expects @value{GDBN} to
34695 call a host system call on behalf of the target. @value{GDBN} replies
34696 with an appropriate @samp{F} packet and keeps up waiting for the next
34697 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34698 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34699 Protocol Extension}, for more details.
34703 @node General Query Packets
34704 @section General Query Packets
34705 @cindex remote query requests
34707 Packets starting with @samp{q} are @dfn{general query packets};
34708 packets starting with @samp{Q} are @dfn{general set packets}. General
34709 query and set packets are a semi-unified form for retrieving and
34710 sending information to and from the stub.
34712 The initial letter of a query or set packet is followed by a name
34713 indicating what sort of thing the packet applies to. For example,
34714 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34715 definitions with the stub. These packet names follow some
34720 The name must not contain commas, colons or semicolons.
34722 Most @value{GDBN} query and set packets have a leading upper case
34725 The names of custom vendor packets should use a company prefix, in
34726 lower case, followed by a period. For example, packets designed at
34727 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34728 foos) or @samp{Qacme.bar} (for setting bars).
34731 The name of a query or set packet should be separated from any
34732 parameters by a @samp{:}; the parameters themselves should be
34733 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34734 full packet name, and check for a separator or the end of the packet,
34735 in case two packet names share a common prefix. New packets should not begin
34736 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34737 packets predate these conventions, and have arguments without any terminator
34738 for the packet name; we suspect they are in widespread use in places that
34739 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34740 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34743 Like the descriptions of the other packets, each description here
34744 has a template showing the packet's overall syntax, followed by an
34745 explanation of the packet's meaning. We include spaces in some of the
34746 templates for clarity; these are not part of the packet's syntax. No
34747 @value{GDBN} packet uses spaces to separate its components.
34749 Here are the currently defined query and set packets:
34755 Turn on or off the agent as a helper to perform some debugging operations
34756 delegated from @value{GDBN} (@pxref{Control Agent}).
34758 @item QAllow:@var{op}:@var{val}@dots{}
34759 @cindex @samp{QAllow} packet
34760 Specify which operations @value{GDBN} expects to request of the
34761 target, as a semicolon-separated list of operation name and value
34762 pairs. Possible values for @var{op} include @samp{WriteReg},
34763 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34764 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34765 indicating that @value{GDBN} will not request the operation, or 1,
34766 indicating that it may. (The target can then use this to set up its
34767 own internals optimally, for instance if the debugger never expects to
34768 insert breakpoints, it may not need to install its own trap handler.)
34771 @cindex current thread, remote request
34772 @cindex @samp{qC} packet
34773 Return the current thread ID.
34777 @item QC @var{thread-id}
34778 Where @var{thread-id} is a thread ID as documented in
34779 @ref{thread-id syntax}.
34780 @item @r{(anything else)}
34781 Any other reply implies the old thread ID.
34784 @item qCRC:@var{addr},@var{length}
34785 @cindex CRC of memory block, remote request
34786 @cindex @samp{qCRC} packet
34787 @anchor{qCRC packet}
34788 Compute the CRC checksum of a block of memory using CRC-32 defined in
34789 IEEE 802.3. The CRC is computed byte at a time, taking the most
34790 significant bit of each byte first. The initial pattern code
34791 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34793 @emph{Note:} This is the same CRC used in validating separate debug
34794 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34795 Files}). However the algorithm is slightly different. When validating
34796 separate debug files, the CRC is computed taking the @emph{least}
34797 significant bit of each byte first, and the final result is inverted to
34798 detect trailing zeros.
34803 An error (such as memory fault)
34804 @item C @var{crc32}
34805 The specified memory region's checksum is @var{crc32}.
34808 @item QDisableRandomization:@var{value}
34809 @cindex disable address space randomization, remote request
34810 @cindex @samp{QDisableRandomization} packet
34811 Some target operating systems will randomize the virtual address space
34812 of the inferior process as a security feature, but provide a feature
34813 to disable such randomization, e.g.@: to allow for a more deterministic
34814 debugging experience. On such systems, this packet with a @var{value}
34815 of 1 directs the target to disable address space randomization for
34816 processes subsequently started via @samp{vRun} packets, while a packet
34817 with a @var{value} of 0 tells the target to enable address space
34820 This packet is only available in extended mode (@pxref{extended mode}).
34825 The request succeeded.
34828 An error occurred. @var{nn} are hex digits.
34831 An empty reply indicates that @samp{QDisableRandomization} is not supported
34835 This packet is not probed by default; the remote stub must request it,
34836 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34837 This should only be done on targets that actually support disabling
34838 address space randomization.
34841 @itemx qsThreadInfo
34842 @cindex list active threads, remote request
34843 @cindex @samp{qfThreadInfo} packet
34844 @cindex @samp{qsThreadInfo} packet
34845 Obtain a list of all active thread IDs from the target (OS). Since there
34846 may be too many active threads to fit into one reply packet, this query
34847 works iteratively: it may require more than one query/reply sequence to
34848 obtain the entire list of threads. The first query of the sequence will
34849 be the @samp{qfThreadInfo} query; subsequent queries in the
34850 sequence will be the @samp{qsThreadInfo} query.
34852 NOTE: This packet replaces the @samp{qL} query (see below).
34856 @item m @var{thread-id}
34858 @item m @var{thread-id},@var{thread-id}@dots{}
34859 a comma-separated list of thread IDs
34861 (lower case letter @samp{L}) denotes end of list.
34864 In response to each query, the target will reply with a list of one or
34865 more thread IDs, separated by commas.
34866 @value{GDBN} will respond to each reply with a request for more thread
34867 ids (using the @samp{qs} form of the query), until the target responds
34868 with @samp{l} (lower-case ell, for @dfn{last}).
34869 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34872 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
34873 initial connection with the remote target, and the very first thread ID
34874 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
34875 message. Therefore, the stub should ensure that the first thread ID in
34876 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
34878 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34879 @cindex get thread-local storage address, remote request
34880 @cindex @samp{qGetTLSAddr} packet
34881 Fetch the address associated with thread local storage specified
34882 by @var{thread-id}, @var{offset}, and @var{lm}.
34884 @var{thread-id} is the thread ID associated with the
34885 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34887 @var{offset} is the (big endian, hex encoded) offset associated with the
34888 thread local variable. (This offset is obtained from the debug
34889 information associated with the variable.)
34891 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34892 load module associated with the thread local storage. For example,
34893 a @sc{gnu}/Linux system will pass the link map address of the shared
34894 object associated with the thread local storage under consideration.
34895 Other operating environments may choose to represent the load module
34896 differently, so the precise meaning of this parameter will vary.
34900 @item @var{XX}@dots{}
34901 Hex encoded (big endian) bytes representing the address of the thread
34902 local storage requested.
34905 An error occurred. @var{nn} are hex digits.
34908 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34911 @item qGetTIBAddr:@var{thread-id}
34912 @cindex get thread information block address
34913 @cindex @samp{qGetTIBAddr} packet
34914 Fetch address of the Windows OS specific Thread Information Block.
34916 @var{thread-id} is the thread ID associated with the thread.
34920 @item @var{XX}@dots{}
34921 Hex encoded (big endian) bytes representing the linear address of the
34922 thread information block.
34925 An error occured. This means that either the thread was not found, or the
34926 address could not be retrieved.
34929 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34932 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34933 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34934 digit) is one to indicate the first query and zero to indicate a
34935 subsequent query; @var{threadcount} (two hex digits) is the maximum
34936 number of threads the response packet can contain; and @var{nextthread}
34937 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34938 returned in the response as @var{argthread}.
34940 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34944 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34945 Where: @var{count} (two hex digits) is the number of threads being
34946 returned; @var{done} (one hex digit) is zero to indicate more threads
34947 and one indicates no further threads; @var{argthreadid} (eight hex
34948 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34949 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34950 digits). See @code{remote.c:parse_threadlist_response()}.
34954 @cindex section offsets, remote request
34955 @cindex @samp{qOffsets} packet
34956 Get section offsets that the target used when relocating the downloaded
34961 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34962 Relocate the @code{Text} section by @var{xxx} from its original address.
34963 Relocate the @code{Data} section by @var{yyy} from its original address.
34964 If the object file format provides segment information (e.g.@: @sc{elf}
34965 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34966 segments by the supplied offsets.
34968 @emph{Note: while a @code{Bss} offset may be included in the response,
34969 @value{GDBN} ignores this and instead applies the @code{Data} offset
34970 to the @code{Bss} section.}
34972 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34973 Relocate the first segment of the object file, which conventionally
34974 contains program code, to a starting address of @var{xxx}. If
34975 @samp{DataSeg} is specified, relocate the second segment, which
34976 conventionally contains modifiable data, to a starting address of
34977 @var{yyy}. @value{GDBN} will report an error if the object file
34978 does not contain segment information, or does not contain at least
34979 as many segments as mentioned in the reply. Extra segments are
34980 kept at fixed offsets relative to the last relocated segment.
34983 @item qP @var{mode} @var{thread-id}
34984 @cindex thread information, remote request
34985 @cindex @samp{qP} packet
34986 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34987 encoded 32 bit mode; @var{thread-id} is a thread ID
34988 (@pxref{thread-id syntax}).
34990 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34993 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34997 @cindex non-stop mode, remote request
34998 @cindex @samp{QNonStop} packet
35000 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35001 @xref{Remote Non-Stop}, for more information.
35006 The request succeeded.
35009 An error occurred. @var{nn} are hex digits.
35012 An empty reply indicates that @samp{QNonStop} is not supported by
35016 This packet is not probed by default; the remote stub must request it,
35017 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35018 Use of this packet is controlled by the @code{set non-stop} command;
35019 @pxref{Non-Stop Mode}.
35021 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35022 @cindex pass signals to inferior, remote request
35023 @cindex @samp{QPassSignals} packet
35024 @anchor{QPassSignals}
35025 Each listed @var{signal} should be passed directly to the inferior process.
35026 Signals are numbered identically to continue packets and stop replies
35027 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35028 strictly greater than the previous item. These signals do not need to stop
35029 the inferior, or be reported to @value{GDBN}. All other signals should be
35030 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35031 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35032 new list. This packet improves performance when using @samp{handle
35033 @var{signal} nostop noprint pass}.
35038 The request succeeded.
35041 An error occurred. @var{nn} are hex digits.
35044 An empty reply indicates that @samp{QPassSignals} is not supported by
35048 Use of this packet is controlled by the @code{set remote pass-signals}
35049 command (@pxref{Remote Configuration, set remote pass-signals}).
35050 This packet is not probed by default; the remote stub must request it,
35051 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35053 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35054 @cindex signals the inferior may see, remote request
35055 @cindex @samp{QProgramSignals} packet
35056 @anchor{QProgramSignals}
35057 Each listed @var{signal} may be delivered to the inferior process.
35058 Others should be silently discarded.
35060 In some cases, the remote stub may need to decide whether to deliver a
35061 signal to the program or not without @value{GDBN} involvement. One
35062 example of that is while detaching --- the program's threads may have
35063 stopped for signals that haven't yet had a chance of being reported to
35064 @value{GDBN}, and so the remote stub can use the signal list specified
35065 by this packet to know whether to deliver or ignore those pending
35068 This does not influence whether to deliver a signal as requested by a
35069 resumption packet (@pxref{vCont packet}).
35071 Signals are numbered identically to continue packets and stop replies
35072 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35073 strictly greater than the previous item. Multiple
35074 @samp{QProgramSignals} packets do not combine; any earlier
35075 @samp{QProgramSignals} list is completely replaced by the new list.
35080 The request succeeded.
35083 An error occurred. @var{nn} are hex digits.
35086 An empty reply indicates that @samp{QProgramSignals} is not supported
35090 Use of this packet is controlled by the @code{set remote program-signals}
35091 command (@pxref{Remote Configuration, set remote program-signals}).
35092 This packet is not probed by default; the remote stub must request it,
35093 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35095 @item qRcmd,@var{command}
35096 @cindex execute remote command, remote request
35097 @cindex @samp{qRcmd} packet
35098 @var{command} (hex encoded) is passed to the local interpreter for
35099 execution. Invalid commands should be reported using the output
35100 string. Before the final result packet, the target may also respond
35101 with a number of intermediate @samp{O@var{output}} console output
35102 packets. @emph{Implementors should note that providing access to a
35103 stubs's interpreter may have security implications}.
35108 A command response with no output.
35110 A command response with the hex encoded output string @var{OUTPUT}.
35112 Indicate a badly formed request.
35114 An empty reply indicates that @samp{qRcmd} is not recognized.
35117 (Note that the @code{qRcmd} packet's name is separated from the
35118 command by a @samp{,}, not a @samp{:}, contrary to the naming
35119 conventions above. Please don't use this packet as a model for new
35122 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35123 @cindex searching memory, in remote debugging
35125 @cindex @samp{qSearch:memory} packet
35127 @cindex @samp{qSearch memory} packet
35128 @anchor{qSearch memory}
35129 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35130 @var{address} and @var{length} are encoded in hex.
35131 @var{search-pattern} is a sequence of bytes, hex encoded.
35136 The pattern was not found.
35138 The pattern was found at @var{address}.
35140 A badly formed request or an error was encountered while searching memory.
35142 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35145 @item QStartNoAckMode
35146 @cindex @samp{QStartNoAckMode} packet
35147 @anchor{QStartNoAckMode}
35148 Request that the remote stub disable the normal @samp{+}/@samp{-}
35149 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35154 The stub has switched to no-acknowledgment mode.
35155 @value{GDBN} acknowledges this reponse,
35156 but neither the stub nor @value{GDBN} shall send or expect further
35157 @samp{+}/@samp{-} acknowledgments in the current connection.
35159 An empty reply indicates that the stub does not support no-acknowledgment mode.
35162 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35163 @cindex supported packets, remote query
35164 @cindex features of the remote protocol
35165 @cindex @samp{qSupported} packet
35166 @anchor{qSupported}
35167 Tell the remote stub about features supported by @value{GDBN}, and
35168 query the stub for features it supports. This packet allows
35169 @value{GDBN} and the remote stub to take advantage of each others'
35170 features. @samp{qSupported} also consolidates multiple feature probes
35171 at startup, to improve @value{GDBN} performance---a single larger
35172 packet performs better than multiple smaller probe packets on
35173 high-latency links. Some features may enable behavior which must not
35174 be on by default, e.g.@: because it would confuse older clients or
35175 stubs. Other features may describe packets which could be
35176 automatically probed for, but are not. These features must be
35177 reported before @value{GDBN} will use them. This ``default
35178 unsupported'' behavior is not appropriate for all packets, but it
35179 helps to keep the initial connection time under control with new
35180 versions of @value{GDBN} which support increasing numbers of packets.
35184 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35185 The stub supports or does not support each returned @var{stubfeature},
35186 depending on the form of each @var{stubfeature} (see below for the
35189 An empty reply indicates that @samp{qSupported} is not recognized,
35190 or that no features needed to be reported to @value{GDBN}.
35193 The allowed forms for each feature (either a @var{gdbfeature} in the
35194 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35198 @item @var{name}=@var{value}
35199 The remote protocol feature @var{name} is supported, and associated
35200 with the specified @var{value}. The format of @var{value} depends
35201 on the feature, but it must not include a semicolon.
35203 The remote protocol feature @var{name} is supported, and does not
35204 need an associated value.
35206 The remote protocol feature @var{name} is not supported.
35208 The remote protocol feature @var{name} may be supported, and
35209 @value{GDBN} should auto-detect support in some other way when it is
35210 needed. This form will not be used for @var{gdbfeature} notifications,
35211 but may be used for @var{stubfeature} responses.
35214 Whenever the stub receives a @samp{qSupported} request, the
35215 supplied set of @value{GDBN} features should override any previous
35216 request. This allows @value{GDBN} to put the stub in a known
35217 state, even if the stub had previously been communicating with
35218 a different version of @value{GDBN}.
35220 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35225 This feature indicates whether @value{GDBN} supports multiprocess
35226 extensions to the remote protocol. @value{GDBN} does not use such
35227 extensions unless the stub also reports that it supports them by
35228 including @samp{multiprocess+} in its @samp{qSupported} reply.
35229 @xref{multiprocess extensions}, for details.
35232 This feature indicates that @value{GDBN} supports the XML target
35233 description. If the stub sees @samp{xmlRegisters=} with target
35234 specific strings separated by a comma, it will report register
35238 This feature indicates whether @value{GDBN} supports the
35239 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35240 instruction reply packet}).
35243 Stubs should ignore any unknown values for
35244 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35245 packet supports receiving packets of unlimited length (earlier
35246 versions of @value{GDBN} may reject overly long responses). Additional values
35247 for @var{gdbfeature} may be defined in the future to let the stub take
35248 advantage of new features in @value{GDBN}, e.g.@: incompatible
35249 improvements in the remote protocol---the @samp{multiprocess} feature is
35250 an example of such a feature. The stub's reply should be independent
35251 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35252 describes all the features it supports, and then the stub replies with
35253 all the features it supports.
35255 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35256 responses, as long as each response uses one of the standard forms.
35258 Some features are flags. A stub which supports a flag feature
35259 should respond with a @samp{+} form response. Other features
35260 require values, and the stub should respond with an @samp{=}
35263 Each feature has a default value, which @value{GDBN} will use if
35264 @samp{qSupported} is not available or if the feature is not mentioned
35265 in the @samp{qSupported} response. The default values are fixed; a
35266 stub is free to omit any feature responses that match the defaults.
35268 Not all features can be probed, but for those which can, the probing
35269 mechanism is useful: in some cases, a stub's internal
35270 architecture may not allow the protocol layer to know some information
35271 about the underlying target in advance. This is especially common in
35272 stubs which may be configured for multiple targets.
35274 These are the currently defined stub features and their properties:
35276 @multitable @columnfractions 0.35 0.2 0.12 0.2
35277 @c NOTE: The first row should be @headitem, but we do not yet require
35278 @c a new enough version of Texinfo (4.7) to use @headitem.
35280 @tab Value Required
35284 @item @samp{PacketSize}
35289 @item @samp{qXfer:auxv:read}
35294 @item @samp{qXfer:btrace:read}
35299 @item @samp{qXfer:features:read}
35304 @item @samp{qXfer:libraries:read}
35309 @item @samp{qXfer:libraries-svr4:read}
35314 @item @samp{augmented-libraries-svr4-read}
35319 @item @samp{qXfer:memory-map:read}
35324 @item @samp{qXfer:sdata:read}
35329 @item @samp{qXfer:spu:read}
35334 @item @samp{qXfer:spu:write}
35339 @item @samp{qXfer:siginfo:read}
35344 @item @samp{qXfer:siginfo:write}
35349 @item @samp{qXfer:threads:read}
35354 @item @samp{qXfer:traceframe-info:read}
35359 @item @samp{qXfer:uib:read}
35364 @item @samp{qXfer:fdpic:read}
35369 @item @samp{Qbtrace:off}
35374 @item @samp{Qbtrace:bts}
35379 @item @samp{QNonStop}
35384 @item @samp{QPassSignals}
35389 @item @samp{QStartNoAckMode}
35394 @item @samp{multiprocess}
35399 @item @samp{ConditionalBreakpoints}
35404 @item @samp{ConditionalTracepoints}
35409 @item @samp{ReverseContinue}
35414 @item @samp{ReverseStep}
35419 @item @samp{TracepointSource}
35424 @item @samp{QAgent}
35429 @item @samp{QAllow}
35434 @item @samp{QDisableRandomization}
35439 @item @samp{EnableDisableTracepoints}
35444 @item @samp{QTBuffer:size}
35449 @item @samp{tracenz}
35454 @item @samp{BreakpointCommands}
35461 These are the currently defined stub features, in more detail:
35464 @cindex packet size, remote protocol
35465 @item PacketSize=@var{bytes}
35466 The remote stub can accept packets up to at least @var{bytes} in
35467 length. @value{GDBN} will send packets up to this size for bulk
35468 transfers, and will never send larger packets. This is a limit on the
35469 data characters in the packet, including the frame and checksum.
35470 There is no trailing NUL byte in a remote protocol packet; if the stub
35471 stores packets in a NUL-terminated format, it should allow an extra
35472 byte in its buffer for the NUL. If this stub feature is not supported,
35473 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35475 @item qXfer:auxv:read
35476 The remote stub understands the @samp{qXfer:auxv:read} packet
35477 (@pxref{qXfer auxiliary vector read}).
35479 @item qXfer:btrace:read
35480 The remote stub understands the @samp{qXfer:btrace:read}
35481 packet (@pxref{qXfer btrace read}).
35483 @item qXfer:features:read
35484 The remote stub understands the @samp{qXfer:features:read} packet
35485 (@pxref{qXfer target description read}).
35487 @item qXfer:libraries:read
35488 The remote stub understands the @samp{qXfer:libraries:read} packet
35489 (@pxref{qXfer library list read}).
35491 @item qXfer:libraries-svr4:read
35492 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35493 (@pxref{qXfer svr4 library list read}).
35495 @item augmented-libraries-svr4-read
35496 The remote stub understands the augmented form of the
35497 @samp{qXfer:libraries-svr4:read} packet
35498 (@pxref{qXfer svr4 library list read}).
35500 @item qXfer:memory-map:read
35501 The remote stub understands the @samp{qXfer:memory-map:read} packet
35502 (@pxref{qXfer memory map read}).
35504 @item qXfer:sdata:read
35505 The remote stub understands the @samp{qXfer:sdata:read} packet
35506 (@pxref{qXfer sdata read}).
35508 @item qXfer:spu:read
35509 The remote stub understands the @samp{qXfer:spu:read} packet
35510 (@pxref{qXfer spu read}).
35512 @item qXfer:spu:write
35513 The remote stub understands the @samp{qXfer:spu:write} packet
35514 (@pxref{qXfer spu write}).
35516 @item qXfer:siginfo:read
35517 The remote stub understands the @samp{qXfer:siginfo:read} packet
35518 (@pxref{qXfer siginfo read}).
35520 @item qXfer:siginfo:write
35521 The remote stub understands the @samp{qXfer:siginfo:write} packet
35522 (@pxref{qXfer siginfo write}).
35524 @item qXfer:threads:read
35525 The remote stub understands the @samp{qXfer:threads:read} packet
35526 (@pxref{qXfer threads read}).
35528 @item qXfer:traceframe-info:read
35529 The remote stub understands the @samp{qXfer:traceframe-info:read}
35530 packet (@pxref{qXfer traceframe info read}).
35532 @item qXfer:uib:read
35533 The remote stub understands the @samp{qXfer:uib:read}
35534 packet (@pxref{qXfer unwind info block}).
35536 @item qXfer:fdpic:read
35537 The remote stub understands the @samp{qXfer:fdpic:read}
35538 packet (@pxref{qXfer fdpic loadmap read}).
35541 The remote stub understands the @samp{QNonStop} packet
35542 (@pxref{QNonStop}).
35545 The remote stub understands the @samp{QPassSignals} packet
35546 (@pxref{QPassSignals}).
35548 @item QStartNoAckMode
35549 The remote stub understands the @samp{QStartNoAckMode} packet and
35550 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35553 @anchor{multiprocess extensions}
35554 @cindex multiprocess extensions, in remote protocol
35555 The remote stub understands the multiprocess extensions to the remote
35556 protocol syntax. The multiprocess extensions affect the syntax of
35557 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35558 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35559 replies. Note that reporting this feature indicates support for the
35560 syntactic extensions only, not that the stub necessarily supports
35561 debugging of more than one process at a time. The stub must not use
35562 multiprocess extensions in packet replies unless @value{GDBN} has also
35563 indicated it supports them in its @samp{qSupported} request.
35565 @item qXfer:osdata:read
35566 The remote stub understands the @samp{qXfer:osdata:read} packet
35567 ((@pxref{qXfer osdata read}).
35569 @item ConditionalBreakpoints
35570 The target accepts and implements evaluation of conditional expressions
35571 defined for breakpoints. The target will only report breakpoint triggers
35572 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35574 @item ConditionalTracepoints
35575 The remote stub accepts and implements conditional expressions defined
35576 for tracepoints (@pxref{Tracepoint Conditions}).
35578 @item ReverseContinue
35579 The remote stub accepts and implements the reverse continue packet
35583 The remote stub accepts and implements the reverse step packet
35586 @item TracepointSource
35587 The remote stub understands the @samp{QTDPsrc} packet that supplies
35588 the source form of tracepoint definitions.
35591 The remote stub understands the @samp{QAgent} packet.
35594 The remote stub understands the @samp{QAllow} packet.
35596 @item QDisableRandomization
35597 The remote stub understands the @samp{QDisableRandomization} packet.
35599 @item StaticTracepoint
35600 @cindex static tracepoints, in remote protocol
35601 The remote stub supports static tracepoints.
35603 @item InstallInTrace
35604 @anchor{install tracepoint in tracing}
35605 The remote stub supports installing tracepoint in tracing.
35607 @item EnableDisableTracepoints
35608 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35609 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35610 to be enabled and disabled while a trace experiment is running.
35612 @item QTBuffer:size
35613 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
35614 packet that allows to change the size of the trace buffer.
35617 @cindex string tracing, in remote protocol
35618 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35619 See @ref{Bytecode Descriptions} for details about the bytecode.
35621 @item BreakpointCommands
35622 @cindex breakpoint commands, in remote protocol
35623 The remote stub supports running a breakpoint's command list itself,
35624 rather than reporting the hit to @value{GDBN}.
35627 The remote stub understands the @samp{Qbtrace:off} packet.
35630 The remote stub understands the @samp{Qbtrace:bts} packet.
35635 @cindex symbol lookup, remote request
35636 @cindex @samp{qSymbol} packet
35637 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35638 requests. Accept requests from the target for the values of symbols.
35643 The target does not need to look up any (more) symbols.
35644 @item qSymbol:@var{sym_name}
35645 The target requests the value of symbol @var{sym_name} (hex encoded).
35646 @value{GDBN} may provide the value by using the
35647 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35651 @item qSymbol:@var{sym_value}:@var{sym_name}
35652 Set the value of @var{sym_name} to @var{sym_value}.
35654 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35655 target has previously requested.
35657 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35658 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35664 The target does not need to look up any (more) symbols.
35665 @item qSymbol:@var{sym_name}
35666 The target requests the value of a new symbol @var{sym_name} (hex
35667 encoded). @value{GDBN} will continue to supply the values of symbols
35668 (if available), until the target ceases to request them.
35673 @itemx QTDisconnected
35680 @itemx qTMinFTPILen
35682 @xref{Tracepoint Packets}.
35684 @item qThreadExtraInfo,@var{thread-id}
35685 @cindex thread attributes info, remote request
35686 @cindex @samp{qThreadExtraInfo} packet
35687 Obtain a printable string description of a thread's attributes from
35688 the target OS. @var{thread-id} is a thread ID;
35689 see @ref{thread-id syntax}. This
35690 string may contain anything that the target OS thinks is interesting
35691 for @value{GDBN} to tell the user about the thread. The string is
35692 displayed in @value{GDBN}'s @code{info threads} display. Some
35693 examples of possible thread extra info strings are @samp{Runnable}, or
35694 @samp{Blocked on Mutex}.
35698 @item @var{XX}@dots{}
35699 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35700 comprising the printable string containing the extra information about
35701 the thread's attributes.
35704 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35705 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35706 conventions above. Please don't use this packet as a model for new
35725 @xref{Tracepoint Packets}.
35727 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35728 @cindex read special object, remote request
35729 @cindex @samp{qXfer} packet
35730 @anchor{qXfer read}
35731 Read uninterpreted bytes from the target's special data area
35732 identified by the keyword @var{object}. Request @var{length} bytes
35733 starting at @var{offset} bytes into the data. The content and
35734 encoding of @var{annex} is specific to @var{object}; it can supply
35735 additional details about what data to access.
35737 Here are the specific requests of this form defined so far. All
35738 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35739 formats, listed below.
35742 @item qXfer:auxv:read::@var{offset},@var{length}
35743 @anchor{qXfer auxiliary vector read}
35744 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35745 auxiliary vector}. Note @var{annex} must be empty.
35747 This packet is not probed by default; the remote stub must request it,
35748 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35750 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
35751 @anchor{qXfer btrace read}
35753 Return a description of the current branch trace.
35754 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
35755 packet may have one of the following values:
35759 Returns all available branch trace.
35762 Returns all available branch trace if the branch trace changed since
35763 the last read request.
35766 Returns the new branch trace since the last read request. Adds a new
35767 block to the end of the trace that begins at zero and ends at the source
35768 location of the first branch in the trace buffer. This extra block is
35769 used to stitch traces together.
35771 If the trace buffer overflowed, returns an error indicating the overflow.
35774 This packet is not probed by default; the remote stub must request it
35775 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35777 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35778 @anchor{qXfer target description read}
35779 Access the @dfn{target description}. @xref{Target Descriptions}. The
35780 annex specifies which XML document to access. The main description is
35781 always loaded from the @samp{target.xml} annex.
35783 This packet is not probed by default; the remote stub must request it,
35784 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35786 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35787 @anchor{qXfer library list read}
35788 Access the target's list of loaded libraries. @xref{Library List Format}.
35789 The annex part of the generic @samp{qXfer} packet must be empty
35790 (@pxref{qXfer read}).
35792 Targets which maintain a list of libraries in the program's memory do
35793 not need to implement this packet; it is designed for platforms where
35794 the operating system manages the list of loaded libraries.
35796 This packet is not probed by default; the remote stub must request it,
35797 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35799 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35800 @anchor{qXfer svr4 library list read}
35801 Access the target's list of loaded libraries when the target is an SVR4
35802 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35803 of the generic @samp{qXfer} packet must be empty unless the remote
35804 stub indicated it supports the augmented form of this packet
35805 by supplying an appropriate @samp{qSupported} response
35806 (@pxref{qXfer read}, @ref{qSupported}).
35808 This packet is optional for better performance on SVR4 targets.
35809 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35811 This packet is not probed by default; the remote stub must request it,
35812 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35814 If the remote stub indicates it supports the augmented form of this
35815 packet then the annex part of the generic @samp{qXfer} packet may
35816 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
35817 arguments. The currently supported arguments are:
35820 @item start=@var{address}
35821 A hexadecimal number specifying the address of the @samp{struct
35822 link_map} to start reading the library list from. If unset or zero
35823 then the first @samp{struct link_map} in the library list will be
35824 chosen as the starting point.
35826 @item prev=@var{address}
35827 A hexadecimal number specifying the address of the @samp{struct
35828 link_map} immediately preceding the @samp{struct link_map}
35829 specified by the @samp{start} argument. If unset or zero then
35830 the remote stub will expect that no @samp{struct link_map}
35831 exists prior to the starting point.
35835 Arguments that are not understood by the remote stub will be silently
35838 @item qXfer:memory-map:read::@var{offset},@var{length}
35839 @anchor{qXfer memory map read}
35840 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35841 annex part of the generic @samp{qXfer} packet must be empty
35842 (@pxref{qXfer read}).
35844 This packet is not probed by default; the remote stub must request it,
35845 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35847 @item qXfer:sdata:read::@var{offset},@var{length}
35848 @anchor{qXfer sdata read}
35850 Read contents of the extra collected static tracepoint marker
35851 information. The annex part of the generic @samp{qXfer} packet must
35852 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35855 This packet is not probed by default; the remote stub must request it,
35856 by supplying an appropriate @samp{qSupported} response
35857 (@pxref{qSupported}).
35859 @item qXfer:siginfo:read::@var{offset},@var{length}
35860 @anchor{qXfer siginfo read}
35861 Read contents of the extra signal information on the target
35862 system. The annex part of the generic @samp{qXfer} packet must be
35863 empty (@pxref{qXfer read}).
35865 This packet is not probed by default; the remote stub must request it,
35866 by supplying an appropriate @samp{qSupported} response
35867 (@pxref{qSupported}).
35869 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35870 @anchor{qXfer spu read}
35871 Read contents of an @code{spufs} file on the target system. The
35872 annex specifies which file to read; it must be of the form
35873 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35874 in the target process, and @var{name} identifes the @code{spufs} file
35875 in that context to be accessed.
35877 This packet is not probed by default; the remote stub must request it,
35878 by supplying an appropriate @samp{qSupported} response
35879 (@pxref{qSupported}).
35881 @item qXfer:threads:read::@var{offset},@var{length}
35882 @anchor{qXfer threads read}
35883 Access the list of threads on target. @xref{Thread List Format}. The
35884 annex part of the generic @samp{qXfer} packet must be empty
35885 (@pxref{qXfer read}).
35887 This packet is not probed by default; the remote stub must request it,
35888 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35890 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35891 @anchor{qXfer traceframe info read}
35893 Return a description of the current traceframe's contents.
35894 @xref{Traceframe Info Format}. The annex part of the generic
35895 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35897 This packet is not probed by default; the remote stub must request it,
35898 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35900 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
35901 @anchor{qXfer unwind info block}
35903 Return the unwind information block for @var{pc}. This packet is used
35904 on OpenVMS/ia64 to ask the kernel unwind information.
35906 This packet is not probed by default.
35908 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35909 @anchor{qXfer fdpic loadmap read}
35910 Read contents of @code{loadmap}s on the target system. The
35911 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35912 executable @code{loadmap} or interpreter @code{loadmap} to read.
35914 This packet is not probed by default; the remote stub must request it,
35915 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35917 @item qXfer:osdata:read::@var{offset},@var{length}
35918 @anchor{qXfer osdata read}
35919 Access the target's @dfn{operating system information}.
35920 @xref{Operating System Information}.
35927 Data @var{data} (@pxref{Binary Data}) has been read from the
35928 target. There may be more data at a higher address (although
35929 it is permitted to return @samp{m} even for the last valid
35930 block of data, as long as at least one byte of data was read).
35931 @var{data} may have fewer bytes than the @var{length} in the
35935 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35936 There is no more data to be read. @var{data} may have fewer bytes
35937 than the @var{length} in the request.
35940 The @var{offset} in the request is at the end of the data.
35941 There is no more data to be read.
35944 The request was malformed, or @var{annex} was invalid.
35947 The offset was invalid, or there was an error encountered reading the data.
35948 @var{nn} is a hex-encoded @code{errno} value.
35951 An empty reply indicates the @var{object} string was not recognized by
35952 the stub, or that the object does not support reading.
35955 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35956 @cindex write data into object, remote request
35957 @anchor{qXfer write}
35958 Write uninterpreted bytes into the target's special data area
35959 identified by the keyword @var{object}, starting at @var{offset} bytes
35960 into the data. @var{data}@dots{} is the binary-encoded data
35961 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35962 is specific to @var{object}; it can supply additional details about what data
35965 Here are the specific requests of this form defined so far. All
35966 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35967 formats, listed below.
35970 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35971 @anchor{qXfer siginfo write}
35972 Write @var{data} to the extra signal information on the target system.
35973 The annex part of the generic @samp{qXfer} packet must be
35974 empty (@pxref{qXfer write}).
35976 This packet is not probed by default; the remote stub must request it,
35977 by supplying an appropriate @samp{qSupported} response
35978 (@pxref{qSupported}).
35980 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35981 @anchor{qXfer spu write}
35982 Write @var{data} to an @code{spufs} file on the target system. The
35983 annex specifies which file to write; it must be of the form
35984 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35985 in the target process, and @var{name} identifes the @code{spufs} file
35986 in that context to be accessed.
35988 This packet is not probed by default; the remote stub must request it,
35989 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35995 @var{nn} (hex encoded) is the number of bytes written.
35996 This may be fewer bytes than supplied in the request.
35999 The request was malformed, or @var{annex} was invalid.
36002 The offset was invalid, or there was an error encountered writing the data.
36003 @var{nn} is a hex-encoded @code{errno} value.
36006 An empty reply indicates the @var{object} string was not
36007 recognized by the stub, or that the object does not support writing.
36010 @item qXfer:@var{object}:@var{operation}:@dots{}
36011 Requests of this form may be added in the future. When a stub does
36012 not recognize the @var{object} keyword, or its support for
36013 @var{object} does not recognize the @var{operation} keyword, the stub
36014 must respond with an empty packet.
36016 @item qAttached:@var{pid}
36017 @cindex query attached, remote request
36018 @cindex @samp{qAttached} packet
36019 Return an indication of whether the remote server attached to an
36020 existing process or created a new process. When the multiprocess
36021 protocol extensions are supported (@pxref{multiprocess extensions}),
36022 @var{pid} is an integer in hexadecimal format identifying the target
36023 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36024 the query packet will be simplified as @samp{qAttached}.
36026 This query is used, for example, to know whether the remote process
36027 should be detached or killed when a @value{GDBN} session is ended with
36028 the @code{quit} command.
36033 The remote server attached to an existing process.
36035 The remote server created a new process.
36037 A badly formed request or an error was encountered.
36041 Enable branch tracing for the current thread using bts tracing.
36046 Branch tracing has been enabled.
36048 A badly formed request or an error was encountered.
36052 Disable branch tracing for the current thread.
36057 Branch tracing has been disabled.
36059 A badly formed request or an error was encountered.
36064 @node Architecture-Specific Protocol Details
36065 @section Architecture-Specific Protocol Details
36067 This section describes how the remote protocol is applied to specific
36068 target architectures. Also see @ref{Standard Target Features}, for
36069 details of XML target descriptions for each architecture.
36072 * ARM-Specific Protocol Details::
36073 * MIPS-Specific Protocol Details::
36076 @node ARM-Specific Protocol Details
36077 @subsection @acronym{ARM}-specific Protocol Details
36080 * ARM Breakpoint Kinds::
36083 @node ARM Breakpoint Kinds
36084 @subsubsection @acronym{ARM} Breakpoint Kinds
36085 @cindex breakpoint kinds, @acronym{ARM}
36087 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36092 16-bit Thumb mode breakpoint.
36095 32-bit Thumb mode (Thumb-2) breakpoint.
36098 32-bit @acronym{ARM} mode breakpoint.
36102 @node MIPS-Specific Protocol Details
36103 @subsection @acronym{MIPS}-specific Protocol Details
36106 * MIPS Register packet Format::
36107 * MIPS Breakpoint Kinds::
36110 @node MIPS Register packet Format
36111 @subsubsection @acronym{MIPS} Register Packet Format
36112 @cindex register packet format, @acronym{MIPS}
36114 The following @code{g}/@code{G} packets have previously been defined.
36115 In the below, some thirty-two bit registers are transferred as
36116 sixty-four bits. Those registers should be zero/sign extended (which?)
36117 to fill the space allocated. Register bytes are transferred in target
36118 byte order. The two nibbles within a register byte are transferred
36119 most-significant -- least-significant.
36124 All registers are transferred as thirty-two bit quantities in the order:
36125 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36126 registers; fsr; fir; fp.
36129 All registers are transferred as sixty-four bit quantities (including
36130 thirty-two bit registers such as @code{sr}). The ordering is the same
36135 @node MIPS Breakpoint Kinds
36136 @subsubsection @acronym{MIPS} Breakpoint Kinds
36137 @cindex breakpoint kinds, @acronym{MIPS}
36139 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36144 16-bit @acronym{MIPS16} mode breakpoint.
36147 16-bit @acronym{microMIPS} mode breakpoint.
36150 32-bit standard @acronym{MIPS} mode breakpoint.
36153 32-bit @acronym{microMIPS} mode breakpoint.
36157 @node Tracepoint Packets
36158 @section Tracepoint Packets
36159 @cindex tracepoint packets
36160 @cindex packets, tracepoint
36162 Here we describe the packets @value{GDBN} uses to implement
36163 tracepoints (@pxref{Tracepoints}).
36167 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36168 @cindex @samp{QTDP} packet
36169 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36170 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36171 the tracepoint is disabled. @var{step} is the tracepoint's step
36172 count, and @var{pass} is its pass count. If an @samp{F} is present,
36173 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36174 the number of bytes that the target should copy elsewhere to make room
36175 for the tracepoint. If an @samp{X} is present, it introduces a
36176 tracepoint condition, which consists of a hexadecimal length, followed
36177 by a comma and hex-encoded bytes, in a manner similar to action
36178 encodings as described below. If the trailing @samp{-} is present,
36179 further @samp{QTDP} packets will follow to specify this tracepoint's
36185 The packet was understood and carried out.
36187 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36189 The packet was not recognized.
36192 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36193 Define actions to be taken when a tracepoint is hit. @var{n} and
36194 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36195 this tracepoint. This packet may only be sent immediately after
36196 another @samp{QTDP} packet that ended with a @samp{-}. If the
36197 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36198 specifying more actions for this tracepoint.
36200 In the series of action packets for a given tracepoint, at most one
36201 can have an @samp{S} before its first @var{action}. If such a packet
36202 is sent, it and the following packets define ``while-stepping''
36203 actions. Any prior packets define ordinary actions --- that is, those
36204 taken when the tracepoint is first hit. If no action packet has an
36205 @samp{S}, then all the packets in the series specify ordinary
36206 tracepoint actions.
36208 The @samp{@var{action}@dots{}} portion of the packet is a series of
36209 actions, concatenated without separators. Each action has one of the
36215 Collect the registers whose bits are set in @var{mask}. @var{mask} is
36216 a hexadecimal number whose @var{i}'th bit is set if register number
36217 @var{i} should be collected. (The least significant bit is numbered
36218 zero.) Note that @var{mask} may be any number of digits long; it may
36219 not fit in a 32-bit word.
36221 @item M @var{basereg},@var{offset},@var{len}
36222 Collect @var{len} bytes of memory starting at the address in register
36223 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36224 @samp{-1}, then the range has a fixed address: @var{offset} is the
36225 address of the lowest byte to collect. The @var{basereg},
36226 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36227 values (the @samp{-1} value for @var{basereg} is a special case).
36229 @item X @var{len},@var{expr}
36230 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36231 it directs. @var{expr} is an agent expression, as described in
36232 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36233 two-digit hex number in the packet; @var{len} is the number of bytes
36234 in the expression (and thus one-half the number of hex digits in the
36239 Any number of actions may be packed together in a single @samp{QTDP}
36240 packet, as long as the packet does not exceed the maximum packet
36241 length (400 bytes, for many stubs). There may be only one @samp{R}
36242 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36243 actions. Any registers referred to by @samp{M} and @samp{X} actions
36244 must be collected by a preceding @samp{R} action. (The
36245 ``while-stepping'' actions are treated as if they were attached to a
36246 separate tracepoint, as far as these restrictions are concerned.)
36251 The packet was understood and carried out.
36253 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36255 The packet was not recognized.
36258 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36259 @cindex @samp{QTDPsrc} packet
36260 Specify a source string of tracepoint @var{n} at address @var{addr}.
36261 This is useful to get accurate reproduction of the tracepoints
36262 originally downloaded at the beginning of the trace run. @var{type}
36263 is the name of the tracepoint part, such as @samp{cond} for the
36264 tracepoint's conditional expression (see below for a list of types), while
36265 @var{bytes} is the string, encoded in hexadecimal.
36267 @var{start} is the offset of the @var{bytes} within the overall source
36268 string, while @var{slen} is the total length of the source string.
36269 This is intended for handling source strings that are longer than will
36270 fit in a single packet.
36271 @c Add detailed example when this info is moved into a dedicated
36272 @c tracepoint descriptions section.
36274 The available string types are @samp{at} for the location,
36275 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36276 @value{GDBN} sends a separate packet for each command in the action
36277 list, in the same order in which the commands are stored in the list.
36279 The target does not need to do anything with source strings except
36280 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36283 Although this packet is optional, and @value{GDBN} will only send it
36284 if the target replies with @samp{TracepointSource} @xref{General
36285 Query Packets}, it makes both disconnected tracing and trace files
36286 much easier to use. Otherwise the user must be careful that the
36287 tracepoints in effect while looking at trace frames are identical to
36288 the ones in effect during the trace run; even a small discrepancy
36289 could cause @samp{tdump} not to work, or a particular trace frame not
36292 @item QTDV:@var{n}:@var{value}
36293 @cindex define trace state variable, remote request
36294 @cindex @samp{QTDV} packet
36295 Create a new trace state variable, number @var{n}, with an initial
36296 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36297 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36298 the option of not using this packet for initial values of zero; the
36299 target should simply create the trace state variables as they are
36300 mentioned in expressions.
36302 @item QTFrame:@var{n}
36303 @cindex @samp{QTFrame} packet
36304 Select the @var{n}'th tracepoint frame from the buffer, and use the
36305 register and memory contents recorded there to answer subsequent
36306 request packets from @value{GDBN}.
36308 A successful reply from the stub indicates that the stub has found the
36309 requested frame. The response is a series of parts, concatenated
36310 without separators, describing the frame we selected. Each part has
36311 one of the following forms:
36315 The selected frame is number @var{n} in the trace frame buffer;
36316 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36317 was no frame matching the criteria in the request packet.
36320 The selected trace frame records a hit of tracepoint number @var{t};
36321 @var{t} is a hexadecimal number.
36325 @item QTFrame:pc:@var{addr}
36326 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36327 currently selected frame whose PC is @var{addr};
36328 @var{addr} is a hexadecimal number.
36330 @item QTFrame:tdp:@var{t}
36331 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36332 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36333 is a hexadecimal number.
36335 @item QTFrame:range:@var{start}:@var{end}
36336 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36337 currently selected frame whose PC is between @var{start} (inclusive)
36338 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36341 @item QTFrame:outside:@var{start}:@var{end}
36342 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36343 frame @emph{outside} the given range of addresses (exclusive).
36346 @cindex @samp{qTMinFTPILen} packet
36347 This packet requests the minimum length of instruction at which a fast
36348 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36349 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36350 it depends on the target system being able to create trampolines in
36351 the first 64K of memory, which might or might not be possible for that
36352 system. So the reply to this packet will be 4 if it is able to
36359 The minimum instruction length is currently unknown.
36361 The minimum instruction length is @var{length}, where @var{length} is greater
36362 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
36363 that a fast tracepoint may be placed on any instruction regardless of size.
36365 An error has occurred.
36367 An empty reply indicates that the request is not supported by the stub.
36371 @cindex @samp{QTStart} packet
36372 Begin the tracepoint experiment. Begin collecting data from
36373 tracepoint hits in the trace frame buffer. This packet supports the
36374 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36375 instruction reply packet}).
36378 @cindex @samp{QTStop} packet
36379 End the tracepoint experiment. Stop collecting trace frames.
36381 @item QTEnable:@var{n}:@var{addr}
36383 @cindex @samp{QTEnable} packet
36384 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36385 experiment. If the tracepoint was previously disabled, then collection
36386 of data from it will resume.
36388 @item QTDisable:@var{n}:@var{addr}
36390 @cindex @samp{QTDisable} packet
36391 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36392 experiment. No more data will be collected from the tracepoint unless
36393 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36396 @cindex @samp{QTinit} packet
36397 Clear the table of tracepoints, and empty the trace frame buffer.
36399 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36400 @cindex @samp{QTro} packet
36401 Establish the given ranges of memory as ``transparent''. The stub
36402 will answer requests for these ranges from memory's current contents,
36403 if they were not collected as part of the tracepoint hit.
36405 @value{GDBN} uses this to mark read-only regions of memory, like those
36406 containing program code. Since these areas never change, they should
36407 still have the same contents they did when the tracepoint was hit, so
36408 there's no reason for the stub to refuse to provide their contents.
36410 @item QTDisconnected:@var{value}
36411 @cindex @samp{QTDisconnected} packet
36412 Set the choice to what to do with the tracing run when @value{GDBN}
36413 disconnects from the target. A @var{value} of 1 directs the target to
36414 continue the tracing run, while 0 tells the target to stop tracing if
36415 @value{GDBN} is no longer in the picture.
36418 @cindex @samp{qTStatus} packet
36419 Ask the stub if there is a trace experiment running right now.
36421 The reply has the form:
36425 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36426 @var{running} is a single digit @code{1} if the trace is presently
36427 running, or @code{0} if not. It is followed by semicolon-separated
36428 optional fields that an agent may use to report additional status.
36432 If the trace is not running, the agent may report any of several
36433 explanations as one of the optional fields:
36438 No trace has been run yet.
36440 @item tstop[:@var{text}]:0
36441 The trace was stopped by a user-originated stop command. The optional
36442 @var{text} field is a user-supplied string supplied as part of the
36443 stop command (for instance, an explanation of why the trace was
36444 stopped manually). It is hex-encoded.
36447 The trace stopped because the trace buffer filled up.
36449 @item tdisconnected:0
36450 The trace stopped because @value{GDBN} disconnected from the target.
36452 @item tpasscount:@var{tpnum}
36453 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36455 @item terror:@var{text}:@var{tpnum}
36456 The trace stopped because tracepoint @var{tpnum} had an error. The
36457 string @var{text} is available to describe the nature of the error
36458 (for instance, a divide by zero in the condition expression).
36459 @var{text} is hex encoded.
36462 The trace stopped for some other reason.
36466 Additional optional fields supply statistical and other information.
36467 Although not required, they are extremely useful for users monitoring
36468 the progress of a trace run. If a trace has stopped, and these
36469 numbers are reported, they must reflect the state of the just-stopped
36474 @item tframes:@var{n}
36475 The number of trace frames in the buffer.
36477 @item tcreated:@var{n}
36478 The total number of trace frames created during the run. This may
36479 be larger than the trace frame count, if the buffer is circular.
36481 @item tsize:@var{n}
36482 The total size of the trace buffer, in bytes.
36484 @item tfree:@var{n}
36485 The number of bytes still unused in the buffer.
36487 @item circular:@var{n}
36488 The value of the circular trace buffer flag. @code{1} means that the
36489 trace buffer is circular and old trace frames will be discarded if
36490 necessary to make room, @code{0} means that the trace buffer is linear
36493 @item disconn:@var{n}
36494 The value of the disconnected tracing flag. @code{1} means that
36495 tracing will continue after @value{GDBN} disconnects, @code{0} means
36496 that the trace run will stop.
36500 @item qTP:@var{tp}:@var{addr}
36501 @cindex tracepoint status, remote request
36502 @cindex @samp{qTP} packet
36503 Ask the stub for the current state of tracepoint number @var{tp} at
36504 address @var{addr}.
36508 @item V@var{hits}:@var{usage}
36509 The tracepoint has been hit @var{hits} times so far during the trace
36510 run, and accounts for @var{usage} in the trace buffer. Note that
36511 @code{while-stepping} steps are not counted as separate hits, but the
36512 steps' space consumption is added into the usage number.
36516 @item qTV:@var{var}
36517 @cindex trace state variable value, remote request
36518 @cindex @samp{qTV} packet
36519 Ask the stub for the value of the trace state variable number @var{var}.
36524 The value of the variable is @var{value}. This will be the current
36525 value of the variable if the user is examining a running target, or a
36526 saved value if the variable was collected in the trace frame that the
36527 user is looking at. Note that multiple requests may result in
36528 different reply values, such as when requesting values while the
36529 program is running.
36532 The value of the variable is unknown. This would occur, for example,
36533 if the user is examining a trace frame in which the requested variable
36538 @cindex @samp{qTfP} packet
36540 @cindex @samp{qTsP} packet
36541 These packets request data about tracepoints that are being used by
36542 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36543 of data, and multiple @code{qTsP} to get additional pieces. Replies
36544 to these packets generally take the form of the @code{QTDP} packets
36545 that define tracepoints. (FIXME add detailed syntax)
36548 @cindex @samp{qTfV} packet
36550 @cindex @samp{qTsV} packet
36551 These packets request data about trace state variables that are on the
36552 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36553 and multiple @code{qTsV} to get additional variables. Replies to
36554 these packets follow the syntax of the @code{QTDV} packets that define
36555 trace state variables.
36561 @cindex @samp{qTfSTM} packet
36562 @cindex @samp{qTsSTM} packet
36563 These packets request data about static tracepoint markers that exist
36564 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36565 first piece of data, and multiple @code{qTsSTM} to get additional
36566 pieces. Replies to these packets take the following form:
36570 @item m @var{address}:@var{id}:@var{extra}
36572 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36573 a comma-separated list of markers
36575 (lower case letter @samp{L}) denotes end of list.
36577 An error occurred. @var{nn} are hex digits.
36579 An empty reply indicates that the request is not supported by the
36583 @var{address} is encoded in hex.
36584 @var{id} and @var{extra} are strings encoded in hex.
36586 In response to each query, the target will reply with a list of one or
36587 more markers, separated by commas. @value{GDBN} will respond to each
36588 reply with a request for more markers (using the @samp{qs} form of the
36589 query), until the target responds with @samp{l} (lower-case ell, for
36592 @item qTSTMat:@var{address}
36594 @cindex @samp{qTSTMat} packet
36595 This packets requests data about static tracepoint markers in the
36596 target program at @var{address}. Replies to this packet follow the
36597 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36598 tracepoint markers.
36600 @item QTSave:@var{filename}
36601 @cindex @samp{QTSave} packet
36602 This packet directs the target to save trace data to the file name
36603 @var{filename} in the target's filesystem. @var{filename} is encoded
36604 as a hex string; the interpretation of the file name (relative vs
36605 absolute, wild cards, etc) is up to the target.
36607 @item qTBuffer:@var{offset},@var{len}
36608 @cindex @samp{qTBuffer} packet
36609 Return up to @var{len} bytes of the current contents of trace buffer,
36610 starting at @var{offset}. The trace buffer is treated as if it were
36611 a contiguous collection of traceframes, as per the trace file format.
36612 The reply consists as many hex-encoded bytes as the target can deliver
36613 in a packet; it is not an error to return fewer than were asked for.
36614 A reply consisting of just @code{l} indicates that no bytes are
36617 @item QTBuffer:circular:@var{value}
36618 This packet directs the target to use a circular trace buffer if
36619 @var{value} is 1, or a linear buffer if the value is 0.
36621 @item QTBuffer:size:@var{size}
36622 @anchor{QTBuffer-size}
36623 @cindex @samp{QTBuffer size} packet
36624 This packet directs the target to make the trace buffer be of size
36625 @var{size} if possible. A value of @code{-1} tells the target to
36626 use whatever size it prefers.
36628 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36629 @cindex @samp{QTNotes} packet
36630 This packet adds optional textual notes to the trace run. Allowable
36631 types include @code{user}, @code{notes}, and @code{tstop}, the
36632 @var{text} fields are arbitrary strings, hex-encoded.
36636 @subsection Relocate instruction reply packet
36637 When installing fast tracepoints in memory, the target may need to
36638 relocate the instruction currently at the tracepoint address to a
36639 different address in memory. For most instructions, a simple copy is
36640 enough, but, for example, call instructions that implicitly push the
36641 return address on the stack, and relative branches or other
36642 PC-relative instructions require offset adjustment, so that the effect
36643 of executing the instruction at a different address is the same as if
36644 it had executed in the original location.
36646 In response to several of the tracepoint packets, the target may also
36647 respond with a number of intermediate @samp{qRelocInsn} request
36648 packets before the final result packet, to have @value{GDBN} handle
36649 this relocation operation. If a packet supports this mechanism, its
36650 documentation will explicitly say so. See for example the above
36651 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36652 format of the request is:
36655 @item qRelocInsn:@var{from};@var{to}
36657 This requests @value{GDBN} to copy instruction at address @var{from}
36658 to address @var{to}, possibly adjusted so that executing the
36659 instruction at @var{to} has the same effect as executing it at
36660 @var{from}. @value{GDBN} writes the adjusted instruction to target
36661 memory starting at @var{to}.
36666 @item qRelocInsn:@var{adjusted_size}
36667 Informs the stub the relocation is complete. @var{adjusted_size} is
36668 the length in bytes of resulting relocated instruction sequence.
36670 A badly formed request was detected, or an error was encountered while
36671 relocating the instruction.
36674 @node Host I/O Packets
36675 @section Host I/O Packets
36676 @cindex Host I/O, remote protocol
36677 @cindex file transfer, remote protocol
36679 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36680 operations on the far side of a remote link. For example, Host I/O is
36681 used to upload and download files to a remote target with its own
36682 filesystem. Host I/O uses the same constant values and data structure
36683 layout as the target-initiated File-I/O protocol. However, the
36684 Host I/O packets are structured differently. The target-initiated
36685 protocol relies on target memory to store parameters and buffers.
36686 Host I/O requests are initiated by @value{GDBN}, and the
36687 target's memory is not involved. @xref{File-I/O Remote Protocol
36688 Extension}, for more details on the target-initiated protocol.
36690 The Host I/O request packets all encode a single operation along with
36691 its arguments. They have this format:
36695 @item vFile:@var{operation}: @var{parameter}@dots{}
36696 @var{operation} is the name of the particular request; the target
36697 should compare the entire packet name up to the second colon when checking
36698 for a supported operation. The format of @var{parameter} depends on
36699 the operation. Numbers are always passed in hexadecimal. Negative
36700 numbers have an explicit minus sign (i.e.@: two's complement is not
36701 used). Strings (e.g.@: filenames) are encoded as a series of
36702 hexadecimal bytes. The last argument to a system call may be a
36703 buffer of escaped binary data (@pxref{Binary Data}).
36707 The valid responses to Host I/O packets are:
36711 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36712 @var{result} is the integer value returned by this operation, usually
36713 non-negative for success and -1 for errors. If an error has occured,
36714 @var{errno} will be included in the result. @var{errno} will have a
36715 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36716 operations which return data, @var{attachment} supplies the data as a
36717 binary buffer. Binary buffers in response packets are escaped in the
36718 normal way (@pxref{Binary Data}). See the individual packet
36719 documentation for the interpretation of @var{result} and
36723 An empty response indicates that this operation is not recognized.
36727 These are the supported Host I/O operations:
36730 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36731 Open a file at @var{pathname} and return a file descriptor for it, or
36732 return -1 if an error occurs. @var{pathname} is a string,
36733 @var{flags} is an integer indicating a mask of open flags
36734 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36735 of mode bits to use if the file is created (@pxref{mode_t Values}).
36736 @xref{open}, for details of the open flags and mode values.
36738 @item vFile:close: @var{fd}
36739 Close the open file corresponding to @var{fd} and return 0, or
36740 -1 if an error occurs.
36742 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36743 Read data from the open file corresponding to @var{fd}. Up to
36744 @var{count} bytes will be read from the file, starting at @var{offset}
36745 relative to the start of the file. The target may read fewer bytes;
36746 common reasons include packet size limits and an end-of-file
36747 condition. The number of bytes read is returned. Zero should only be
36748 returned for a successful read at the end of the file, or if
36749 @var{count} was zero.
36751 The data read should be returned as a binary attachment on success.
36752 If zero bytes were read, the response should include an empty binary
36753 attachment (i.e.@: a trailing semicolon). The return value is the
36754 number of target bytes read; the binary attachment may be longer if
36755 some characters were escaped.
36757 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36758 Write @var{data} (a binary buffer) to the open file corresponding
36759 to @var{fd}. Start the write at @var{offset} from the start of the
36760 file. Unlike many @code{write} system calls, there is no
36761 separate @var{count} argument; the length of @var{data} in the
36762 packet is used. @samp{vFile:write} returns the number of bytes written,
36763 which may be shorter than the length of @var{data}, or -1 if an
36766 @item vFile:unlink: @var{pathname}
36767 Delete the file at @var{pathname} on the target. Return 0,
36768 or -1 if an error occurs. @var{pathname} is a string.
36770 @item vFile:readlink: @var{filename}
36771 Read value of symbolic link @var{filename} on the target. Return
36772 the number of bytes read, or -1 if an error occurs.
36774 The data read should be returned as a binary attachment on success.
36775 If zero bytes were read, the response should include an empty binary
36776 attachment (i.e.@: a trailing semicolon). The return value is the
36777 number of target bytes read; the binary attachment may be longer if
36778 some characters were escaped.
36783 @section Interrupts
36784 @cindex interrupts (remote protocol)
36786 When a program on the remote target is running, @value{GDBN} may
36787 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36788 a @code{BREAK} followed by @code{g},
36789 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36791 The precise meaning of @code{BREAK} is defined by the transport
36792 mechanism and may, in fact, be undefined. @value{GDBN} does not
36793 currently define a @code{BREAK} mechanism for any of the network
36794 interfaces except for TCP, in which case @value{GDBN} sends the
36795 @code{telnet} BREAK sequence.
36797 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36798 transport mechanisms. It is represented by sending the single byte
36799 @code{0x03} without any of the usual packet overhead described in
36800 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36801 transmitted as part of a packet, it is considered to be packet data
36802 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36803 (@pxref{X packet}), used for binary downloads, may include an unescaped
36804 @code{0x03} as part of its packet.
36806 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36807 When Linux kernel receives this sequence from serial port,
36808 it stops execution and connects to gdb.
36810 Stubs are not required to recognize these interrupt mechanisms and the
36811 precise meaning associated with receipt of the interrupt is
36812 implementation defined. If the target supports debugging of multiple
36813 threads and/or processes, it should attempt to interrupt all
36814 currently-executing threads and processes.
36815 If the stub is successful at interrupting the
36816 running program, it should send one of the stop
36817 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36818 of successfully stopping the program in all-stop mode, and a stop reply
36819 for each stopped thread in non-stop mode.
36820 Interrupts received while the
36821 program is stopped are discarded.
36823 @node Notification Packets
36824 @section Notification Packets
36825 @cindex notification packets
36826 @cindex packets, notification
36828 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36829 packets that require no acknowledgment. Both the GDB and the stub
36830 may send notifications (although the only notifications defined at
36831 present are sent by the stub). Notifications carry information
36832 without incurring the round-trip latency of an acknowledgment, and so
36833 are useful for low-impact communications where occasional packet loss
36836 A notification packet has the form @samp{% @var{data} #
36837 @var{checksum}}, where @var{data} is the content of the notification,
36838 and @var{checksum} is a checksum of @var{data}, computed and formatted
36839 as for ordinary @value{GDBN} packets. A notification's @var{data}
36840 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36841 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36842 to acknowledge the notification's receipt or to report its corruption.
36844 Every notification's @var{data} begins with a name, which contains no
36845 colon characters, followed by a colon character.
36847 Recipients should silently ignore corrupted notifications and
36848 notifications they do not understand. Recipients should restart
36849 timeout periods on receipt of a well-formed notification, whether or
36850 not they understand it.
36852 Senders should only send the notifications described here when this
36853 protocol description specifies that they are permitted. In the
36854 future, we may extend the protocol to permit existing notifications in
36855 new contexts; this rule helps older senders avoid confusing newer
36858 (Older versions of @value{GDBN} ignore bytes received until they see
36859 the @samp{$} byte that begins an ordinary packet, so new stubs may
36860 transmit notifications without fear of confusing older clients. There
36861 are no notifications defined for @value{GDBN} to send at the moment, but we
36862 assume that most older stubs would ignore them, as well.)
36864 Each notification is comprised of three parts:
36866 @item @var{name}:@var{event}
36867 The notification packet is sent by the side that initiates the
36868 exchange (currently, only the stub does that), with @var{event}
36869 carrying the specific information about the notification.
36870 @var{name} is the name of the notification.
36872 The acknowledge sent by the other side, usually @value{GDBN}, to
36873 acknowledge the exchange and request the event.
36876 The purpose of an asynchronous notification mechanism is to report to
36877 @value{GDBN} that something interesting happened in the remote stub.
36879 The remote stub may send notification @var{name}:@var{event}
36880 at any time, but @value{GDBN} acknowledges the notification when
36881 appropriate. The notification event is pending before @value{GDBN}
36882 acknowledges. Only one notification at a time may be pending; if
36883 additional events occur before @value{GDBN} has acknowledged the
36884 previous notification, they must be queued by the stub for later
36885 synchronous transmission in response to @var{ack} packets from
36886 @value{GDBN}. Because the notification mechanism is unreliable,
36887 the stub is permitted to resend a notification if it believes
36888 @value{GDBN} may not have received it.
36890 Specifically, notifications may appear when @value{GDBN} is not
36891 otherwise reading input from the stub, or when @value{GDBN} is
36892 expecting to read a normal synchronous response or a
36893 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36894 Notification packets are distinct from any other communication from
36895 the stub so there is no ambiguity.
36897 After receiving a notification, @value{GDBN} shall acknowledge it by
36898 sending a @var{ack} packet as a regular, synchronous request to the
36899 stub. Such acknowledgment is not required to happen immediately, as
36900 @value{GDBN} is permitted to send other, unrelated packets to the
36901 stub first, which the stub should process normally.
36903 Upon receiving a @var{ack} packet, if the stub has other queued
36904 events to report to @value{GDBN}, it shall respond by sending a
36905 normal @var{event}. @value{GDBN} shall then send another @var{ack}
36906 packet to solicit further responses; again, it is permitted to send
36907 other, unrelated packets as well which the stub should process
36910 If the stub receives a @var{ack} packet and there are no additional
36911 @var{event} to report, the stub shall return an @samp{OK} response.
36912 At this point, @value{GDBN} has finished processing a notification
36913 and the stub has completed sending any queued events. @value{GDBN}
36914 won't accept any new notifications until the final @samp{OK} is
36915 received . If further notification events occur, the stub shall send
36916 a new notification, @value{GDBN} shall accept the notification, and
36917 the process shall be repeated.
36919 The process of asynchronous notification can be illustrated by the
36922 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
36925 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
36927 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
36932 The following notifications are defined:
36933 @multitable @columnfractions 0.12 0.12 0.38 0.38
36942 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
36943 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36944 for information on how these notifications are acknowledged by
36946 @tab Report an asynchronous stop event in non-stop mode.
36950 @node Remote Non-Stop
36951 @section Remote Protocol Support for Non-Stop Mode
36953 @value{GDBN}'s remote protocol supports non-stop debugging of
36954 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36955 supports non-stop mode, it should report that to @value{GDBN} by including
36956 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36958 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36959 establishing a new connection with the stub. Entering non-stop mode
36960 does not alter the state of any currently-running threads, but targets
36961 must stop all threads in any already-attached processes when entering
36962 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36963 probe the target state after a mode change.
36965 In non-stop mode, when an attached process encounters an event that
36966 would otherwise be reported with a stop reply, it uses the
36967 asynchronous notification mechanism (@pxref{Notification Packets}) to
36968 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36969 in all processes are stopped when a stop reply is sent, in non-stop
36970 mode only the thread reporting the stop event is stopped. That is,
36971 when reporting a @samp{S} or @samp{T} response to indicate completion
36972 of a step operation, hitting a breakpoint, or a fault, only the
36973 affected thread is stopped; any other still-running threads continue
36974 to run. When reporting a @samp{W} or @samp{X} response, all running
36975 threads belonging to other attached processes continue to run.
36977 In non-stop mode, the target shall respond to the @samp{?} packet as
36978 follows. First, any incomplete stop reply notification/@samp{vStopped}
36979 sequence in progress is abandoned. The target must begin a new
36980 sequence reporting stop events for all stopped threads, whether or not
36981 it has previously reported those events to @value{GDBN}. The first
36982 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36983 subsequent stop replies are sent as responses to @samp{vStopped} packets
36984 using the mechanism described above. The target must not send
36985 asynchronous stop reply notifications until the sequence is complete.
36986 If all threads are running when the target receives the @samp{?} packet,
36987 or if the target is not attached to any process, it shall respond
36990 @node Packet Acknowledgment
36991 @section Packet Acknowledgment
36993 @cindex acknowledgment, for @value{GDBN} remote
36994 @cindex packet acknowledgment, for @value{GDBN} remote
36995 By default, when either the host or the target machine receives a packet,
36996 the first response expected is an acknowledgment: either @samp{+} (to indicate
36997 the package was received correctly) or @samp{-} (to request retransmission).
36998 This mechanism allows the @value{GDBN} remote protocol to operate over
36999 unreliable transport mechanisms, such as a serial line.
37001 In cases where the transport mechanism is itself reliable (such as a pipe or
37002 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37003 It may be desirable to disable them in that case to reduce communication
37004 overhead, or for other reasons. This can be accomplished by means of the
37005 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37007 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37008 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37009 and response format still includes the normal checksum, as described in
37010 @ref{Overview}, but the checksum may be ignored by the receiver.
37012 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37013 no-acknowledgment mode, it should report that to @value{GDBN}
37014 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37015 @pxref{qSupported}.
37016 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37017 disabled via the @code{set remote noack-packet off} command
37018 (@pxref{Remote Configuration}),
37019 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37020 Only then may the stub actually turn off packet acknowledgments.
37021 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37022 response, which can be safely ignored by the stub.
37024 Note that @code{set remote noack-packet} command only affects negotiation
37025 between @value{GDBN} and the stub when subsequent connections are made;
37026 it does not affect the protocol acknowledgment state for any current
37028 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37029 new connection is established,
37030 there is also no protocol request to re-enable the acknowledgments
37031 for the current connection, once disabled.
37036 Example sequence of a target being re-started. Notice how the restart
37037 does not get any direct output:
37042 @emph{target restarts}
37045 <- @code{T001:1234123412341234}
37049 Example sequence of a target being stepped by a single instruction:
37052 -> @code{G1445@dots{}}
37057 <- @code{T001:1234123412341234}
37061 <- @code{1455@dots{}}
37065 @node File-I/O Remote Protocol Extension
37066 @section File-I/O Remote Protocol Extension
37067 @cindex File-I/O remote protocol extension
37070 * File-I/O Overview::
37071 * Protocol Basics::
37072 * The F Request Packet::
37073 * The F Reply Packet::
37074 * The Ctrl-C Message::
37076 * List of Supported Calls::
37077 * Protocol-specific Representation of Datatypes::
37079 * File-I/O Examples::
37082 @node File-I/O Overview
37083 @subsection File-I/O Overview
37084 @cindex file-i/o overview
37086 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37087 target to use the host's file system and console I/O to perform various
37088 system calls. System calls on the target system are translated into a
37089 remote protocol packet to the host system, which then performs the needed
37090 actions and returns a response packet to the target system.
37091 This simulates file system operations even on targets that lack file systems.
37093 The protocol is defined to be independent of both the host and target systems.
37094 It uses its own internal representation of datatypes and values. Both
37095 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37096 translating the system-dependent value representations into the internal
37097 protocol representations when data is transmitted.
37099 The communication is synchronous. A system call is possible only when
37100 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37101 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37102 the target is stopped to allow deterministic access to the target's
37103 memory. Therefore File-I/O is not interruptible by target signals. On
37104 the other hand, it is possible to interrupt File-I/O by a user interrupt
37105 (@samp{Ctrl-C}) within @value{GDBN}.
37107 The target's request to perform a host system call does not finish
37108 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37109 after finishing the system call, the target returns to continuing the
37110 previous activity (continue, step). No additional continue or step
37111 request from @value{GDBN} is required.
37114 (@value{GDBP}) continue
37115 <- target requests 'system call X'
37116 target is stopped, @value{GDBN} executes system call
37117 -> @value{GDBN} returns result
37118 ... target continues, @value{GDBN} returns to wait for the target
37119 <- target hits breakpoint and sends a Txx packet
37122 The protocol only supports I/O on the console and to regular files on
37123 the host file system. Character or block special devices, pipes,
37124 named pipes, sockets or any other communication method on the host
37125 system are not supported by this protocol.
37127 File I/O is not supported in non-stop mode.
37129 @node Protocol Basics
37130 @subsection Protocol Basics
37131 @cindex protocol basics, file-i/o
37133 The File-I/O protocol uses the @code{F} packet as the request as well
37134 as reply packet. Since a File-I/O system call can only occur when
37135 @value{GDBN} is waiting for a response from the continuing or stepping target,
37136 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37137 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37138 This @code{F} packet contains all information needed to allow @value{GDBN}
37139 to call the appropriate host system call:
37143 A unique identifier for the requested system call.
37146 All parameters to the system call. Pointers are given as addresses
37147 in the target memory address space. Pointers to strings are given as
37148 pointer/length pair. Numerical values are given as they are.
37149 Numerical control flags are given in a protocol-specific representation.
37153 At this point, @value{GDBN} has to perform the following actions.
37157 If the parameters include pointer values to data needed as input to a
37158 system call, @value{GDBN} requests this data from the target with a
37159 standard @code{m} packet request. This additional communication has to be
37160 expected by the target implementation and is handled as any other @code{m}
37164 @value{GDBN} translates all value from protocol representation to host
37165 representation as needed. Datatypes are coerced into the host types.
37168 @value{GDBN} calls the system call.
37171 It then coerces datatypes back to protocol representation.
37174 If the system call is expected to return data in buffer space specified
37175 by pointer parameters to the call, the data is transmitted to the
37176 target using a @code{M} or @code{X} packet. This packet has to be expected
37177 by the target implementation and is handled as any other @code{M} or @code{X}
37182 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37183 necessary information for the target to continue. This at least contains
37190 @code{errno}, if has been changed by the system call.
37197 After having done the needed type and value coercion, the target continues
37198 the latest continue or step action.
37200 @node The F Request Packet
37201 @subsection The @code{F} Request Packet
37202 @cindex file-i/o request packet
37203 @cindex @code{F} request packet
37205 The @code{F} request packet has the following format:
37208 @item F@var{call-id},@var{parameter@dots{}}
37210 @var{call-id} is the identifier to indicate the host system call to be called.
37211 This is just the name of the function.
37213 @var{parameter@dots{}} are the parameters to the system call.
37214 Parameters are hexadecimal integer values, either the actual values in case
37215 of scalar datatypes, pointers to target buffer space in case of compound
37216 datatypes and unspecified memory areas, or pointer/length pairs in case
37217 of string parameters. These are appended to the @var{call-id} as a
37218 comma-delimited list. All values are transmitted in ASCII
37219 string representation, pointer/length pairs separated by a slash.
37225 @node The F Reply Packet
37226 @subsection The @code{F} Reply Packet
37227 @cindex file-i/o reply packet
37228 @cindex @code{F} reply packet
37230 The @code{F} reply packet has the following format:
37234 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37236 @var{retcode} is the return code of the system call as hexadecimal value.
37238 @var{errno} is the @code{errno} set by the call, in protocol-specific
37240 This parameter can be omitted if the call was successful.
37242 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37243 case, @var{errno} must be sent as well, even if the call was successful.
37244 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37251 or, if the call was interrupted before the host call has been performed:
37258 assuming 4 is the protocol-specific representation of @code{EINTR}.
37263 @node The Ctrl-C Message
37264 @subsection The @samp{Ctrl-C} Message
37265 @cindex ctrl-c message, in file-i/o protocol
37267 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37268 reply packet (@pxref{The F Reply Packet}),
37269 the target should behave as if it had
37270 gotten a break message. The meaning for the target is ``system call
37271 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37272 (as with a break message) and return to @value{GDBN} with a @code{T02}
37275 It's important for the target to know in which
37276 state the system call was interrupted. There are two possible cases:
37280 The system call hasn't been performed on the host yet.
37283 The system call on the host has been finished.
37287 These two states can be distinguished by the target by the value of the
37288 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37289 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37290 on POSIX systems. In any other case, the target may presume that the
37291 system call has been finished --- successfully or not --- and should behave
37292 as if the break message arrived right after the system call.
37294 @value{GDBN} must behave reliably. If the system call has not been called
37295 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37296 @code{errno} in the packet. If the system call on the host has been finished
37297 before the user requests a break, the full action must be finished by
37298 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37299 The @code{F} packet may only be sent when either nothing has happened
37300 or the full action has been completed.
37303 @subsection Console I/O
37304 @cindex console i/o as part of file-i/o
37306 By default and if not explicitly closed by the target system, the file
37307 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37308 on the @value{GDBN} console is handled as any other file output operation
37309 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37310 by @value{GDBN} so that after the target read request from file descriptor
37311 0 all following typing is buffered until either one of the following
37316 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37318 system call is treated as finished.
37321 The user presses @key{RET}. This is treated as end of input with a trailing
37325 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37326 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37330 If the user has typed more characters than fit in the buffer given to
37331 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37332 either another @code{read(0, @dots{})} is requested by the target, or debugging
37333 is stopped at the user's request.
37336 @node List of Supported Calls
37337 @subsection List of Supported Calls
37338 @cindex list of supported file-i/o calls
37355 @unnumberedsubsubsec open
37356 @cindex open, file-i/o system call
37361 int open(const char *pathname, int flags);
37362 int open(const char *pathname, int flags, mode_t mode);
37366 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37369 @var{flags} is the bitwise @code{OR} of the following values:
37373 If the file does not exist it will be created. The host
37374 rules apply as far as file ownership and time stamps
37378 When used with @code{O_CREAT}, if the file already exists it is
37379 an error and open() fails.
37382 If the file already exists and the open mode allows
37383 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37384 truncated to zero length.
37387 The file is opened in append mode.
37390 The file is opened for reading only.
37393 The file is opened for writing only.
37396 The file is opened for reading and writing.
37400 Other bits are silently ignored.
37404 @var{mode} is the bitwise @code{OR} of the following values:
37408 User has read permission.
37411 User has write permission.
37414 Group has read permission.
37417 Group has write permission.
37420 Others have read permission.
37423 Others have write permission.
37427 Other bits are silently ignored.
37430 @item Return value:
37431 @code{open} returns the new file descriptor or -1 if an error
37438 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37441 @var{pathname} refers to a directory.
37444 The requested access is not allowed.
37447 @var{pathname} was too long.
37450 A directory component in @var{pathname} does not exist.
37453 @var{pathname} refers to a device, pipe, named pipe or socket.
37456 @var{pathname} refers to a file on a read-only filesystem and
37457 write access was requested.
37460 @var{pathname} is an invalid pointer value.
37463 No space on device to create the file.
37466 The process already has the maximum number of files open.
37469 The limit on the total number of files open on the system
37473 The call was interrupted by the user.
37479 @unnumberedsubsubsec close
37480 @cindex close, file-i/o system call
37489 @samp{Fclose,@var{fd}}
37491 @item Return value:
37492 @code{close} returns zero on success, or -1 if an error occurred.
37498 @var{fd} isn't a valid open file descriptor.
37501 The call was interrupted by the user.
37507 @unnumberedsubsubsec read
37508 @cindex read, file-i/o system call
37513 int read(int fd, void *buf, unsigned int count);
37517 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37519 @item Return value:
37520 On success, the number of bytes read is returned.
37521 Zero indicates end of file. If count is zero, read
37522 returns zero as well. On error, -1 is returned.
37528 @var{fd} is not a valid file descriptor or is not open for
37532 @var{bufptr} is an invalid pointer value.
37535 The call was interrupted by the user.
37541 @unnumberedsubsubsec write
37542 @cindex write, file-i/o system call
37547 int write(int fd, const void *buf, unsigned int count);
37551 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37553 @item Return value:
37554 On success, the number of bytes written are returned.
37555 Zero indicates nothing was written. On error, -1
37562 @var{fd} is not a valid file descriptor or is not open for
37566 @var{bufptr} is an invalid pointer value.
37569 An attempt was made to write a file that exceeds the
37570 host-specific maximum file size allowed.
37573 No space on device to write the data.
37576 The call was interrupted by the user.
37582 @unnumberedsubsubsec lseek
37583 @cindex lseek, file-i/o system call
37588 long lseek (int fd, long offset, int flag);
37592 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37594 @var{flag} is one of:
37598 The offset is set to @var{offset} bytes.
37601 The offset is set to its current location plus @var{offset}
37605 The offset is set to the size of the file plus @var{offset}
37609 @item Return value:
37610 On success, the resulting unsigned offset in bytes from
37611 the beginning of the file is returned. Otherwise, a
37612 value of -1 is returned.
37618 @var{fd} is not a valid open file descriptor.
37621 @var{fd} is associated with the @value{GDBN} console.
37624 @var{flag} is not a proper value.
37627 The call was interrupted by the user.
37633 @unnumberedsubsubsec rename
37634 @cindex rename, file-i/o system call
37639 int rename(const char *oldpath, const char *newpath);
37643 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37645 @item Return value:
37646 On success, zero is returned. On error, -1 is returned.
37652 @var{newpath} is an existing directory, but @var{oldpath} is not a
37656 @var{newpath} is a non-empty directory.
37659 @var{oldpath} or @var{newpath} is a directory that is in use by some
37663 An attempt was made to make a directory a subdirectory
37667 A component used as a directory in @var{oldpath} or new
37668 path is not a directory. Or @var{oldpath} is a directory
37669 and @var{newpath} exists but is not a directory.
37672 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37675 No access to the file or the path of the file.
37679 @var{oldpath} or @var{newpath} was too long.
37682 A directory component in @var{oldpath} or @var{newpath} does not exist.
37685 The file is on a read-only filesystem.
37688 The device containing the file has no room for the new
37692 The call was interrupted by the user.
37698 @unnumberedsubsubsec unlink
37699 @cindex unlink, file-i/o system call
37704 int unlink(const char *pathname);
37708 @samp{Funlink,@var{pathnameptr}/@var{len}}
37710 @item Return value:
37711 On success, zero is returned. On error, -1 is returned.
37717 No access to the file or the path of the file.
37720 The system does not allow unlinking of directories.
37723 The file @var{pathname} cannot be unlinked because it's
37724 being used by another process.
37727 @var{pathnameptr} is an invalid pointer value.
37730 @var{pathname} was too long.
37733 A directory component in @var{pathname} does not exist.
37736 A component of the path is not a directory.
37739 The file is on a read-only filesystem.
37742 The call was interrupted by the user.
37748 @unnumberedsubsubsec stat/fstat
37749 @cindex fstat, file-i/o system call
37750 @cindex stat, file-i/o system call
37755 int stat(const char *pathname, struct stat *buf);
37756 int fstat(int fd, struct stat *buf);
37760 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37761 @samp{Ffstat,@var{fd},@var{bufptr}}
37763 @item Return value:
37764 On success, zero is returned. On error, -1 is returned.
37770 @var{fd} is not a valid open file.
37773 A directory component in @var{pathname} does not exist or the
37774 path is an empty string.
37777 A component of the path is not a directory.
37780 @var{pathnameptr} is an invalid pointer value.
37783 No access to the file or the path of the file.
37786 @var{pathname} was too long.
37789 The call was interrupted by the user.
37795 @unnumberedsubsubsec gettimeofday
37796 @cindex gettimeofday, file-i/o system call
37801 int gettimeofday(struct timeval *tv, void *tz);
37805 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37807 @item Return value:
37808 On success, 0 is returned, -1 otherwise.
37814 @var{tz} is a non-NULL pointer.
37817 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37823 @unnumberedsubsubsec isatty
37824 @cindex isatty, file-i/o system call
37829 int isatty(int fd);
37833 @samp{Fisatty,@var{fd}}
37835 @item Return value:
37836 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37842 The call was interrupted by the user.
37847 Note that the @code{isatty} call is treated as a special case: it returns
37848 1 to the target if the file descriptor is attached
37849 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37850 would require implementing @code{ioctl} and would be more complex than
37855 @unnumberedsubsubsec system
37856 @cindex system, file-i/o system call
37861 int system(const char *command);
37865 @samp{Fsystem,@var{commandptr}/@var{len}}
37867 @item Return value:
37868 If @var{len} is zero, the return value indicates whether a shell is
37869 available. A zero return value indicates a shell is not available.
37870 For non-zero @var{len}, the value returned is -1 on error and the
37871 return status of the command otherwise. Only the exit status of the
37872 command is returned, which is extracted from the host's @code{system}
37873 return value by calling @code{WEXITSTATUS(retval)}. In case
37874 @file{/bin/sh} could not be executed, 127 is returned.
37880 The call was interrupted by the user.
37885 @value{GDBN} takes over the full task of calling the necessary host calls
37886 to perform the @code{system} call. The return value of @code{system} on
37887 the host is simplified before it's returned
37888 to the target. Any termination signal information from the child process
37889 is discarded, and the return value consists
37890 entirely of the exit status of the called command.
37892 Due to security concerns, the @code{system} call is by default refused
37893 by @value{GDBN}. The user has to allow this call explicitly with the
37894 @code{set remote system-call-allowed 1} command.
37897 @item set remote system-call-allowed
37898 @kindex set remote system-call-allowed
37899 Control whether to allow the @code{system} calls in the File I/O
37900 protocol for the remote target. The default is zero (disabled).
37902 @item show remote system-call-allowed
37903 @kindex show remote system-call-allowed
37904 Show whether the @code{system} calls are allowed in the File I/O
37908 @node Protocol-specific Representation of Datatypes
37909 @subsection Protocol-specific Representation of Datatypes
37910 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37913 * Integral Datatypes::
37915 * Memory Transfer::
37920 @node Integral Datatypes
37921 @unnumberedsubsubsec Integral Datatypes
37922 @cindex integral datatypes, in file-i/o protocol
37924 The integral datatypes used in the system calls are @code{int},
37925 @code{unsigned int}, @code{long}, @code{unsigned long},
37926 @code{mode_t}, and @code{time_t}.
37928 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37929 implemented as 32 bit values in this protocol.
37931 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37933 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37934 in @file{limits.h}) to allow range checking on host and target.
37936 @code{time_t} datatypes are defined as seconds since the Epoch.
37938 All integral datatypes transferred as part of a memory read or write of a
37939 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37942 @node Pointer Values
37943 @unnumberedsubsubsec Pointer Values
37944 @cindex pointer values, in file-i/o protocol
37946 Pointers to target data are transmitted as they are. An exception
37947 is made for pointers to buffers for which the length isn't
37948 transmitted as part of the function call, namely strings. Strings
37949 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37956 which is a pointer to data of length 18 bytes at position 0x1aaf.
37957 The length is defined as the full string length in bytes, including
37958 the trailing null byte. For example, the string @code{"hello world"}
37959 at address 0x123456 is transmitted as
37965 @node Memory Transfer
37966 @unnumberedsubsubsec Memory Transfer
37967 @cindex memory transfer, in file-i/o protocol
37969 Structured data which is transferred using a memory read or write (for
37970 example, a @code{struct stat}) is expected to be in a protocol-specific format
37971 with all scalar multibyte datatypes being big endian. Translation to
37972 this representation needs to be done both by the target before the @code{F}
37973 packet is sent, and by @value{GDBN} before
37974 it transfers memory to the target. Transferred pointers to structured
37975 data should point to the already-coerced data at any time.
37979 @unnumberedsubsubsec struct stat
37980 @cindex struct stat, in file-i/o protocol
37982 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37983 is defined as follows:
37987 unsigned int st_dev; /* device */
37988 unsigned int st_ino; /* inode */
37989 mode_t st_mode; /* protection */
37990 unsigned int st_nlink; /* number of hard links */
37991 unsigned int st_uid; /* user ID of owner */
37992 unsigned int st_gid; /* group ID of owner */
37993 unsigned int st_rdev; /* device type (if inode device) */
37994 unsigned long st_size; /* total size, in bytes */
37995 unsigned long st_blksize; /* blocksize for filesystem I/O */
37996 unsigned long st_blocks; /* number of blocks allocated */
37997 time_t st_atime; /* time of last access */
37998 time_t st_mtime; /* time of last modification */
37999 time_t st_ctime; /* time of last change */
38003 The integral datatypes conform to the definitions given in the
38004 appropriate section (see @ref{Integral Datatypes}, for details) so this
38005 structure is of size 64 bytes.
38007 The values of several fields have a restricted meaning and/or
38013 A value of 0 represents a file, 1 the console.
38016 No valid meaning for the target. Transmitted unchanged.
38019 Valid mode bits are described in @ref{Constants}. Any other
38020 bits have currently no meaning for the target.
38025 No valid meaning for the target. Transmitted unchanged.
38030 These values have a host and file system dependent
38031 accuracy. Especially on Windows hosts, the file system may not
38032 support exact timing values.
38035 The target gets a @code{struct stat} of the above representation and is
38036 responsible for coercing it to the target representation before
38039 Note that due to size differences between the host, target, and protocol
38040 representations of @code{struct stat} members, these members could eventually
38041 get truncated on the target.
38043 @node struct timeval
38044 @unnumberedsubsubsec struct timeval
38045 @cindex struct timeval, in file-i/o protocol
38047 The buffer of type @code{struct timeval} used by the File-I/O protocol
38048 is defined as follows:
38052 time_t tv_sec; /* second */
38053 long tv_usec; /* microsecond */
38057 The integral datatypes conform to the definitions given in the
38058 appropriate section (see @ref{Integral Datatypes}, for details) so this
38059 structure is of size 8 bytes.
38062 @subsection Constants
38063 @cindex constants, in file-i/o protocol
38065 The following values are used for the constants inside of the
38066 protocol. @value{GDBN} and target are responsible for translating these
38067 values before and after the call as needed.
38078 @unnumberedsubsubsec Open Flags
38079 @cindex open flags, in file-i/o protocol
38081 All values are given in hexadecimal representation.
38093 @node mode_t Values
38094 @unnumberedsubsubsec mode_t Values
38095 @cindex mode_t values, in file-i/o protocol
38097 All values are given in octal representation.
38114 @unnumberedsubsubsec Errno Values
38115 @cindex errno values, in file-i/o protocol
38117 All values are given in decimal representation.
38142 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38143 any error value not in the list of supported error numbers.
38146 @unnumberedsubsubsec Lseek Flags
38147 @cindex lseek flags, in file-i/o protocol
38156 @unnumberedsubsubsec Limits
38157 @cindex limits, in file-i/o protocol
38159 All values are given in decimal representation.
38162 INT_MIN -2147483648
38164 UINT_MAX 4294967295
38165 LONG_MIN -9223372036854775808
38166 LONG_MAX 9223372036854775807
38167 ULONG_MAX 18446744073709551615
38170 @node File-I/O Examples
38171 @subsection File-I/O Examples
38172 @cindex file-i/o examples
38174 Example sequence of a write call, file descriptor 3, buffer is at target
38175 address 0x1234, 6 bytes should be written:
38178 <- @code{Fwrite,3,1234,6}
38179 @emph{request memory read from target}
38182 @emph{return "6 bytes written"}
38186 Example sequence of a read call, file descriptor 3, buffer is at target
38187 address 0x1234, 6 bytes should be read:
38190 <- @code{Fread,3,1234,6}
38191 @emph{request memory write to target}
38192 -> @code{X1234,6:XXXXXX}
38193 @emph{return "6 bytes read"}
38197 Example sequence of a read call, call fails on the host due to invalid
38198 file descriptor (@code{EBADF}):
38201 <- @code{Fread,3,1234,6}
38205 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38209 <- @code{Fread,3,1234,6}
38214 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38218 <- @code{Fread,3,1234,6}
38219 -> @code{X1234,6:XXXXXX}
38223 @node Library List Format
38224 @section Library List Format
38225 @cindex library list format, remote protocol
38227 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38228 same process as your application to manage libraries. In this case,
38229 @value{GDBN} can use the loader's symbol table and normal memory
38230 operations to maintain a list of shared libraries. On other
38231 platforms, the operating system manages loaded libraries.
38232 @value{GDBN} can not retrieve the list of currently loaded libraries
38233 through memory operations, so it uses the @samp{qXfer:libraries:read}
38234 packet (@pxref{qXfer library list read}) instead. The remote stub
38235 queries the target's operating system and reports which libraries
38238 The @samp{qXfer:libraries:read} packet returns an XML document which
38239 lists loaded libraries and their offsets. Each library has an
38240 associated name and one or more segment or section base addresses,
38241 which report where the library was loaded in memory.
38243 For the common case of libraries that are fully linked binaries, the
38244 library should have a list of segments. If the target supports
38245 dynamic linking of a relocatable object file, its library XML element
38246 should instead include a list of allocated sections. The segment or
38247 section bases are start addresses, not relocation offsets; they do not
38248 depend on the library's link-time base addresses.
38250 @value{GDBN} must be linked with the Expat library to support XML
38251 library lists. @xref{Expat}.
38253 A simple memory map, with one loaded library relocated by a single
38254 offset, looks like this:
38258 <library name="/lib/libc.so.6">
38259 <segment address="0x10000000"/>
38264 Another simple memory map, with one loaded library with three
38265 allocated sections (.text, .data, .bss), looks like this:
38269 <library name="sharedlib.o">
38270 <section address="0x10000000"/>
38271 <section address="0x20000000"/>
38272 <section address="0x30000000"/>
38277 The format of a library list is described by this DTD:
38280 <!-- library-list: Root element with versioning -->
38281 <!ELEMENT library-list (library)*>
38282 <!ATTLIST library-list version CDATA #FIXED "1.0">
38283 <!ELEMENT library (segment*, section*)>
38284 <!ATTLIST library name CDATA #REQUIRED>
38285 <!ELEMENT segment EMPTY>
38286 <!ATTLIST segment address CDATA #REQUIRED>
38287 <!ELEMENT section EMPTY>
38288 <!ATTLIST section address CDATA #REQUIRED>
38291 In addition, segments and section descriptors cannot be mixed within a
38292 single library element, and you must supply at least one segment or
38293 section for each library.
38295 @node Library List Format for SVR4 Targets
38296 @section Library List Format for SVR4 Targets
38297 @cindex library list format, remote protocol
38299 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38300 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38301 shared libraries. Still a special library list provided by this packet is
38302 more efficient for the @value{GDBN} remote protocol.
38304 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38305 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38306 target, the following parameters are reported:
38310 @code{name}, the absolute file name from the @code{l_name} field of
38311 @code{struct link_map}.
38313 @code{lm} with address of @code{struct link_map} used for TLS
38314 (Thread Local Storage) access.
38316 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38317 @code{struct link_map}. For prelinked libraries this is not an absolute
38318 memory address. It is a displacement of absolute memory address against
38319 address the file was prelinked to during the library load.
38321 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38324 Additionally the single @code{main-lm} attribute specifies address of
38325 @code{struct link_map} used for the main executable. This parameter is used
38326 for TLS access and its presence is optional.
38328 @value{GDBN} must be linked with the Expat library to support XML
38329 SVR4 library lists. @xref{Expat}.
38331 A simple memory map, with two loaded libraries (which do not use prelink),
38335 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38336 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38338 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38340 </library-list-svr>
38343 The format of an SVR4 library list is described by this DTD:
38346 <!-- library-list-svr4: Root element with versioning -->
38347 <!ELEMENT library-list-svr4 (library)*>
38348 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38349 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38350 <!ELEMENT library EMPTY>
38351 <!ATTLIST library name CDATA #REQUIRED>
38352 <!ATTLIST library lm CDATA #REQUIRED>
38353 <!ATTLIST library l_addr CDATA #REQUIRED>
38354 <!ATTLIST library l_ld CDATA #REQUIRED>
38357 @node Memory Map Format
38358 @section Memory Map Format
38359 @cindex memory map format
38361 To be able to write into flash memory, @value{GDBN} needs to obtain a
38362 memory map from the target. This section describes the format of the
38365 The memory map is obtained using the @samp{qXfer:memory-map:read}
38366 (@pxref{qXfer memory map read}) packet and is an XML document that
38367 lists memory regions.
38369 @value{GDBN} must be linked with the Expat library to support XML
38370 memory maps. @xref{Expat}.
38372 The top-level structure of the document is shown below:
38375 <?xml version="1.0"?>
38376 <!DOCTYPE memory-map
38377 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38378 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38384 Each region can be either:
38389 A region of RAM starting at @var{addr} and extending for @var{length}
38393 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38398 A region of read-only memory:
38401 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38406 A region of flash memory, with erasure blocks @var{blocksize}
38410 <memory type="flash" start="@var{addr}" length="@var{length}">
38411 <property name="blocksize">@var{blocksize}</property>
38417 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38418 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38419 packets to write to addresses in such ranges.
38421 The formal DTD for memory map format is given below:
38424 <!-- ................................................... -->
38425 <!-- Memory Map XML DTD ................................ -->
38426 <!-- File: memory-map.dtd .............................. -->
38427 <!-- .................................... .............. -->
38428 <!-- memory-map.dtd -->
38429 <!-- memory-map: Root element with versioning -->
38430 <!ELEMENT memory-map (memory | property)>
38431 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38432 <!ELEMENT memory (property)>
38433 <!-- memory: Specifies a memory region,
38434 and its type, or device. -->
38435 <!ATTLIST memory type CDATA #REQUIRED
38436 start CDATA #REQUIRED
38437 length CDATA #REQUIRED
38438 device CDATA #IMPLIED>
38439 <!-- property: Generic attribute tag -->
38440 <!ELEMENT property (#PCDATA | property)*>
38441 <!ATTLIST property name CDATA #REQUIRED>
38444 @node Thread List Format
38445 @section Thread List Format
38446 @cindex thread list format
38448 To efficiently update the list of threads and their attributes,
38449 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38450 (@pxref{qXfer threads read}) and obtains the XML document with
38451 the following structure:
38454 <?xml version="1.0"?>
38456 <thread id="id" core="0">
38457 ... description ...
38462 Each @samp{thread} element must have the @samp{id} attribute that
38463 identifies the thread (@pxref{thread-id syntax}). The
38464 @samp{core} attribute, if present, specifies which processor core
38465 the thread was last executing on. The content of the of @samp{thread}
38466 element is interpreted as human-readable auxilliary information.
38468 @node Traceframe Info Format
38469 @section Traceframe Info Format
38470 @cindex traceframe info format
38472 To be able to know which objects in the inferior can be examined when
38473 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38474 memory ranges, registers and trace state variables that have been
38475 collected in a traceframe.
38477 This list is obtained using the @samp{qXfer:traceframe-info:read}
38478 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38480 @value{GDBN} must be linked with the Expat library to support XML
38481 traceframe info discovery. @xref{Expat}.
38483 The top-level structure of the document is shown below:
38486 <?xml version="1.0"?>
38487 <!DOCTYPE traceframe-info
38488 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38489 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38495 Each traceframe block can be either:
38500 A region of collected memory starting at @var{addr} and extending for
38501 @var{length} bytes from there:
38504 <memory start="@var{addr}" length="@var{length}"/>
38508 A block indicating trace state variable numbered @var{number} has been
38512 <tvar id="@var{number}"/>
38517 The formal DTD for the traceframe info format is given below:
38520 <!ELEMENT traceframe-info (memory | tvar)* >
38521 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38523 <!ELEMENT memory EMPTY>
38524 <!ATTLIST memory start CDATA #REQUIRED
38525 length CDATA #REQUIRED>
38527 <!ATTLIST tvar id CDATA #REQUIRED>
38530 @node Branch Trace Format
38531 @section Branch Trace Format
38532 @cindex branch trace format
38534 In order to display the branch trace of an inferior thread,
38535 @value{GDBN} needs to obtain the list of branches. This list is
38536 represented as list of sequential code blocks that are connected via
38537 branches. The code in each block has been executed sequentially.
38539 This list is obtained using the @samp{qXfer:btrace:read}
38540 (@pxref{qXfer btrace read}) packet and is an XML document.
38542 @value{GDBN} must be linked with the Expat library to support XML
38543 traceframe info discovery. @xref{Expat}.
38545 The top-level structure of the document is shown below:
38548 <?xml version="1.0"?>
38550 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
38551 "http://sourceware.org/gdb/gdb-btrace.dtd">
38560 A block of sequentially executed instructions starting at @var{begin}
38561 and ending at @var{end}:
38564 <block begin="@var{begin}" end="@var{end}"/>
38569 The formal DTD for the branch trace format is given below:
38572 <!ELEMENT btrace (block)* >
38573 <!ATTLIST btrace version CDATA #FIXED "1.0">
38575 <!ELEMENT block EMPTY>
38576 <!ATTLIST block begin CDATA #REQUIRED
38577 end CDATA #REQUIRED>
38580 @include agentexpr.texi
38582 @node Target Descriptions
38583 @appendix Target Descriptions
38584 @cindex target descriptions
38586 One of the challenges of using @value{GDBN} to debug embedded systems
38587 is that there are so many minor variants of each processor
38588 architecture in use. It is common practice for vendors to start with
38589 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
38590 and then make changes to adapt it to a particular market niche. Some
38591 architectures have hundreds of variants, available from dozens of
38592 vendors. This leads to a number of problems:
38596 With so many different customized processors, it is difficult for
38597 the @value{GDBN} maintainers to keep up with the changes.
38599 Since individual variants may have short lifetimes or limited
38600 audiences, it may not be worthwhile to carry information about every
38601 variant in the @value{GDBN} source tree.
38603 When @value{GDBN} does support the architecture of the embedded system
38604 at hand, the task of finding the correct architecture name to give the
38605 @command{set architecture} command can be error-prone.
38608 To address these problems, the @value{GDBN} remote protocol allows a
38609 target system to not only identify itself to @value{GDBN}, but to
38610 actually describe its own features. This lets @value{GDBN} support
38611 processor variants it has never seen before --- to the extent that the
38612 descriptions are accurate, and that @value{GDBN} understands them.
38614 @value{GDBN} must be linked with the Expat library to support XML
38615 target descriptions. @xref{Expat}.
38618 * Retrieving Descriptions:: How descriptions are fetched from a target.
38619 * Target Description Format:: The contents of a target description.
38620 * Predefined Target Types:: Standard types available for target
38622 * Standard Target Features:: Features @value{GDBN} knows about.
38625 @node Retrieving Descriptions
38626 @section Retrieving Descriptions
38628 Target descriptions can be read from the target automatically, or
38629 specified by the user manually. The default behavior is to read the
38630 description from the target. @value{GDBN} retrieves it via the remote
38631 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38632 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38633 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38634 XML document, of the form described in @ref{Target Description
38637 Alternatively, you can specify a file to read for the target description.
38638 If a file is set, the target will not be queried. The commands to
38639 specify a file are:
38642 @cindex set tdesc filename
38643 @item set tdesc filename @var{path}
38644 Read the target description from @var{path}.
38646 @cindex unset tdesc filename
38647 @item unset tdesc filename
38648 Do not read the XML target description from a file. @value{GDBN}
38649 will use the description supplied by the current target.
38651 @cindex show tdesc filename
38652 @item show tdesc filename
38653 Show the filename to read for a target description, if any.
38657 @node Target Description Format
38658 @section Target Description Format
38659 @cindex target descriptions, XML format
38661 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38662 document which complies with the Document Type Definition provided in
38663 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38664 means you can use generally available tools like @command{xmllint} to
38665 check that your feature descriptions are well-formed and valid.
38666 However, to help people unfamiliar with XML write descriptions for
38667 their targets, we also describe the grammar here.
38669 Target descriptions can identify the architecture of the remote target
38670 and (for some architectures) provide information about custom register
38671 sets. They can also identify the OS ABI of the remote target.
38672 @value{GDBN} can use this information to autoconfigure for your
38673 target, or to warn you if you connect to an unsupported target.
38675 Here is a simple target description:
38678 <target version="1.0">
38679 <architecture>i386:x86-64</architecture>
38684 This minimal description only says that the target uses
38685 the x86-64 architecture.
38687 A target description has the following overall form, with [ ] marking
38688 optional elements and @dots{} marking repeatable elements. The elements
38689 are explained further below.
38692 <?xml version="1.0"?>
38693 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38694 <target version="1.0">
38695 @r{[}@var{architecture}@r{]}
38696 @r{[}@var{osabi}@r{]}
38697 @r{[}@var{compatible}@r{]}
38698 @r{[}@var{feature}@dots{}@r{]}
38703 The description is generally insensitive to whitespace and line
38704 breaks, under the usual common-sense rules. The XML version
38705 declaration and document type declaration can generally be omitted
38706 (@value{GDBN} does not require them), but specifying them may be
38707 useful for XML validation tools. The @samp{version} attribute for
38708 @samp{<target>} may also be omitted, but we recommend
38709 including it; if future versions of @value{GDBN} use an incompatible
38710 revision of @file{gdb-target.dtd}, they will detect and report
38711 the version mismatch.
38713 @subsection Inclusion
38714 @cindex target descriptions, inclusion
38717 @cindex <xi:include>
38720 It can sometimes be valuable to split a target description up into
38721 several different annexes, either for organizational purposes, or to
38722 share files between different possible target descriptions. You can
38723 divide a description into multiple files by replacing any element of
38724 the target description with an inclusion directive of the form:
38727 <xi:include href="@var{document}"/>
38731 When @value{GDBN} encounters an element of this form, it will retrieve
38732 the named XML @var{document}, and replace the inclusion directive with
38733 the contents of that document. If the current description was read
38734 using @samp{qXfer}, then so will be the included document;
38735 @var{document} will be interpreted as the name of an annex. If the
38736 current description was read from a file, @value{GDBN} will look for
38737 @var{document} as a file in the same directory where it found the
38738 original description.
38740 @subsection Architecture
38741 @cindex <architecture>
38743 An @samp{<architecture>} element has this form:
38746 <architecture>@var{arch}</architecture>
38749 @var{arch} is one of the architectures from the set accepted by
38750 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38753 @cindex @code{<osabi>}
38755 This optional field was introduced in @value{GDBN} version 7.0.
38756 Previous versions of @value{GDBN} ignore it.
38758 An @samp{<osabi>} element has this form:
38761 <osabi>@var{abi-name}</osabi>
38764 @var{abi-name} is an OS ABI name from the same selection accepted by
38765 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38767 @subsection Compatible Architecture
38768 @cindex @code{<compatible>}
38770 This optional field was introduced in @value{GDBN} version 7.0.
38771 Previous versions of @value{GDBN} ignore it.
38773 A @samp{<compatible>} element has this form:
38776 <compatible>@var{arch}</compatible>
38779 @var{arch} is one of the architectures from the set accepted by
38780 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38782 A @samp{<compatible>} element is used to specify that the target
38783 is able to run binaries in some other than the main target architecture
38784 given by the @samp{<architecture>} element. For example, on the
38785 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38786 or @code{powerpc:common64}, but the system is able to run binaries
38787 in the @code{spu} architecture as well. The way to describe this
38788 capability with @samp{<compatible>} is as follows:
38791 <architecture>powerpc:common</architecture>
38792 <compatible>spu</compatible>
38795 @subsection Features
38798 Each @samp{<feature>} describes some logical portion of the target
38799 system. Features are currently used to describe available CPU
38800 registers and the types of their contents. A @samp{<feature>} element
38804 <feature name="@var{name}">
38805 @r{[}@var{type}@dots{}@r{]}
38811 Each feature's name should be unique within the description. The name
38812 of a feature does not matter unless @value{GDBN} has some special
38813 knowledge of the contents of that feature; if it does, the feature
38814 should have its standard name. @xref{Standard Target Features}.
38818 Any register's value is a collection of bits which @value{GDBN} must
38819 interpret. The default interpretation is a two's complement integer,
38820 but other types can be requested by name in the register description.
38821 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38822 Target Types}), and the description can define additional composite types.
38824 Each type element must have an @samp{id} attribute, which gives
38825 a unique (within the containing @samp{<feature>}) name to the type.
38826 Types must be defined before they are used.
38829 Some targets offer vector registers, which can be treated as arrays
38830 of scalar elements. These types are written as @samp{<vector>} elements,
38831 specifying the array element type, @var{type}, and the number of elements,
38835 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38839 If a register's value is usefully viewed in multiple ways, define it
38840 with a union type containing the useful representations. The
38841 @samp{<union>} element contains one or more @samp{<field>} elements,
38842 each of which has a @var{name} and a @var{type}:
38845 <union id="@var{id}">
38846 <field name="@var{name}" type="@var{type}"/>
38852 If a register's value is composed from several separate values, define
38853 it with a structure type. There are two forms of the @samp{<struct>}
38854 element; a @samp{<struct>} element must either contain only bitfields
38855 or contain no bitfields. If the structure contains only bitfields,
38856 its total size in bytes must be specified, each bitfield must have an
38857 explicit start and end, and bitfields are automatically assigned an
38858 integer type. The field's @var{start} should be less than or
38859 equal to its @var{end}, and zero represents the least significant bit.
38862 <struct id="@var{id}" size="@var{size}">
38863 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38868 If the structure contains no bitfields, then each field has an
38869 explicit type, and no implicit padding is added.
38872 <struct id="@var{id}">
38873 <field name="@var{name}" type="@var{type}"/>
38879 If a register's value is a series of single-bit flags, define it with
38880 a flags type. The @samp{<flags>} element has an explicit @var{size}
38881 and contains one or more @samp{<field>} elements. Each field has a
38882 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38886 <flags id="@var{id}" size="@var{size}">
38887 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38892 @subsection Registers
38895 Each register is represented as an element with this form:
38898 <reg name="@var{name}"
38899 bitsize="@var{size}"
38900 @r{[}regnum="@var{num}"@r{]}
38901 @r{[}save-restore="@var{save-restore}"@r{]}
38902 @r{[}type="@var{type}"@r{]}
38903 @r{[}group="@var{group}"@r{]}/>
38907 The components are as follows:
38912 The register's name; it must be unique within the target description.
38915 The register's size, in bits.
38918 The register's number. If omitted, a register's number is one greater
38919 than that of the previous register (either in the current feature or in
38920 a preceding feature); the first register in the target description
38921 defaults to zero. This register number is used to read or write
38922 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38923 packets, and registers appear in the @code{g} and @code{G} packets
38924 in order of increasing register number.
38927 Whether the register should be preserved across inferior function
38928 calls; this must be either @code{yes} or @code{no}. The default is
38929 @code{yes}, which is appropriate for most registers except for
38930 some system control registers; this is not related to the target's
38934 The type of the register. @var{type} may be a predefined type, a type
38935 defined in the current feature, or one of the special types @code{int}
38936 and @code{float}. @code{int} is an integer type of the correct size
38937 for @var{bitsize}, and @code{float} is a floating point type (in the
38938 architecture's normal floating point format) of the correct size for
38939 @var{bitsize}. The default is @code{int}.
38942 The register group to which this register belongs. @var{group} must
38943 be either @code{general}, @code{float}, or @code{vector}. If no
38944 @var{group} is specified, @value{GDBN} will not display the register
38945 in @code{info registers}.
38949 @node Predefined Target Types
38950 @section Predefined Target Types
38951 @cindex target descriptions, predefined types
38953 Type definitions in the self-description can build up composite types
38954 from basic building blocks, but can not define fundamental types. Instead,
38955 standard identifiers are provided by @value{GDBN} for the fundamental
38956 types. The currently supported types are:
38965 Signed integer types holding the specified number of bits.
38972 Unsigned integer types holding the specified number of bits.
38976 Pointers to unspecified code and data. The program counter and
38977 any dedicated return address register may be marked as code
38978 pointers; printing a code pointer converts it into a symbolic
38979 address. The stack pointer and any dedicated address registers
38980 may be marked as data pointers.
38983 Single precision IEEE floating point.
38986 Double precision IEEE floating point.
38989 The 12-byte extended precision format used by ARM FPA registers.
38992 The 10-byte extended precision format used by x87 registers.
38995 32bit @sc{eflags} register used by x86.
38998 32bit @sc{mxcsr} register used by x86.
39002 @node Standard Target Features
39003 @section Standard Target Features
39004 @cindex target descriptions, standard features
39006 A target description must contain either no registers or all the
39007 target's registers. If the description contains no registers, then
39008 @value{GDBN} will assume a default register layout, selected based on
39009 the architecture. If the description contains any registers, the
39010 default layout will not be used; the standard registers must be
39011 described in the target description, in such a way that @value{GDBN}
39012 can recognize them.
39014 This is accomplished by giving specific names to feature elements
39015 which contain standard registers. @value{GDBN} will look for features
39016 with those names and verify that they contain the expected registers;
39017 if any known feature is missing required registers, or if any required
39018 feature is missing, @value{GDBN} will reject the target
39019 description. You can add additional registers to any of the
39020 standard features --- @value{GDBN} will display them just as if
39021 they were added to an unrecognized feature.
39023 This section lists the known features and their expected contents.
39024 Sample XML documents for these features are included in the
39025 @value{GDBN} source tree, in the directory @file{gdb/features}.
39027 Names recognized by @value{GDBN} should include the name of the
39028 company or organization which selected the name, and the overall
39029 architecture to which the feature applies; so e.g.@: the feature
39030 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39032 The names of registers are not case sensitive for the purpose
39033 of recognizing standard features, but @value{GDBN} will only display
39034 registers using the capitalization used in the description.
39037 * AArch64 Features::
39042 * Nios II Features::
39043 * PowerPC Features::
39044 * S/390 and System z Features::
39049 @node AArch64 Features
39050 @subsection AArch64 Features
39051 @cindex target descriptions, AArch64 features
39053 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39054 targets. It should contain registers @samp{x0} through @samp{x30},
39055 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39057 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39058 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39062 @subsection ARM Features
39063 @cindex target descriptions, ARM features
39065 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39067 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39068 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39070 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39071 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39072 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39075 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39076 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39078 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39079 it should contain at least registers @samp{wR0} through @samp{wR15} and
39080 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39081 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39083 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39084 should contain at least registers @samp{d0} through @samp{d15}. If
39085 they are present, @samp{d16} through @samp{d31} should also be included.
39086 @value{GDBN} will synthesize the single-precision registers from
39087 halves of the double-precision registers.
39089 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39090 need to contain registers; it instructs @value{GDBN} to display the
39091 VFP double-precision registers as vectors and to synthesize the
39092 quad-precision registers from pairs of double-precision registers.
39093 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39094 be present and include 32 double-precision registers.
39096 @node i386 Features
39097 @subsection i386 Features
39098 @cindex target descriptions, i386 features
39100 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39101 targets. It should describe the following registers:
39105 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39107 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39109 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39110 @samp{fs}, @samp{gs}
39112 @samp{st0} through @samp{st7}
39114 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39115 @samp{foseg}, @samp{fooff} and @samp{fop}
39118 The register sets may be different, depending on the target.
39120 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39121 describe registers:
39125 @samp{xmm0} through @samp{xmm7} for i386
39127 @samp{xmm0} through @samp{xmm15} for amd64
39132 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39133 @samp{org.gnu.gdb.i386.sse} feature. It should
39134 describe the upper 128 bits of @sc{ymm} registers:
39138 @samp{ymm0h} through @samp{ymm7h} for i386
39140 @samp{ymm0h} through @samp{ymm15h} for amd64
39143 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39144 Memory Protection Extension (MPX). It should describe the following registers:
39148 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39150 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39153 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39154 describe a single register, @samp{orig_eax}.
39156 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39157 @samp{org.gnu.gdb.i386.avx} feature. It should
39158 describe additional @sc{xmm} registers:
39162 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39165 It should describe the upper 128 bits of additional @sc{ymm} registers:
39169 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39173 describe the upper 256 bits of @sc{zmm} registers:
39177 @samp{zmm0h} through @samp{zmm7h} for i386.
39179 @samp{zmm0h} through @samp{zmm15h} for amd64.
39183 describe the additional @sc{zmm} registers:
39187 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39190 @node MIPS Features
39191 @subsection @acronym{MIPS} Features
39192 @cindex target descriptions, @acronym{MIPS} features
39194 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39195 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39196 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39199 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39200 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39201 registers. They may be 32-bit or 64-bit depending on the target.
39203 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39204 it may be optional in a future version of @value{GDBN}. It should
39205 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39206 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39208 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39209 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39210 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39211 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39213 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39214 contain a single register, @samp{restart}, which is used by the
39215 Linux kernel to control restartable syscalls.
39217 @node M68K Features
39218 @subsection M68K Features
39219 @cindex target descriptions, M68K features
39222 @item @samp{org.gnu.gdb.m68k.core}
39223 @itemx @samp{org.gnu.gdb.coldfire.core}
39224 @itemx @samp{org.gnu.gdb.fido.core}
39225 One of those features must be always present.
39226 The feature that is present determines which flavor of m68k is
39227 used. The feature that is present should contain registers
39228 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39229 @samp{sp}, @samp{ps} and @samp{pc}.
39231 @item @samp{org.gnu.gdb.coldfire.fp}
39232 This feature is optional. If present, it should contain registers
39233 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39237 @node Nios II Features
39238 @subsection Nios II Features
39239 @cindex target descriptions, Nios II features
39241 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
39242 targets. It should contain the 32 core registers (@samp{zero},
39243 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
39244 @samp{pc}, and the 16 control registers (@samp{status} through
39247 @node PowerPC Features
39248 @subsection PowerPC Features
39249 @cindex target descriptions, PowerPC features
39251 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39252 targets. It should contain registers @samp{r0} through @samp{r31},
39253 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39254 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39256 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39257 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39259 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39260 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39263 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39264 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39265 will combine these registers with the floating point registers
39266 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39267 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39268 through @samp{vs63}, the set of vector registers for POWER7.
39270 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39271 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39272 @samp{spefscr}. SPE targets should provide 32-bit registers in
39273 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39274 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39275 these to present registers @samp{ev0} through @samp{ev31} to the
39278 @node S/390 and System z Features
39279 @subsection S/390 and System z Features
39280 @cindex target descriptions, S/390 features
39281 @cindex target descriptions, System z features
39283 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
39284 System z targets. It should contain the PSW and the 16 general
39285 registers. In particular, System z targets should provide the 64-bit
39286 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
39287 S/390 targets should provide the 32-bit versions of these registers.
39288 A System z target that runs in 31-bit addressing mode should provide
39289 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
39290 register's upper halves @samp{r0h} through @samp{r15h}, and their
39291 lower halves @samp{r0l} through @samp{r15l}.
39293 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
39294 contain the 64-bit registers @samp{f0} through @samp{f15}, and
39297 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
39298 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
39300 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
39301 contain the register @samp{orig_r2}, which is 64-bit wide on System z
39302 targets and 32-bit otherwise. In addition, the feature may contain
39303 the @samp{last_break} register, whose width depends on the addressing
39304 mode, as well as the @samp{system_call} register, which is always
39307 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
39308 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
39309 @samp{atia}, and @samp{tr0} through @samp{tr15}.
39311 @node TIC6x Features
39312 @subsection TMS320C6x Features
39313 @cindex target descriptions, TIC6x features
39314 @cindex target descriptions, TMS320C6x features
39315 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39316 targets. It should contain registers @samp{A0} through @samp{A15},
39317 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39319 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39320 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39321 through @samp{B31}.
39323 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39324 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39326 @node Operating System Information
39327 @appendix Operating System Information
39328 @cindex operating system information
39334 Users of @value{GDBN} often wish to obtain information about the state of
39335 the operating system running on the target---for example the list of
39336 processes, or the list of open files. This section describes the
39337 mechanism that makes it possible. This mechanism is similar to the
39338 target features mechanism (@pxref{Target Descriptions}), but focuses
39339 on a different aspect of target.
39341 Operating system information is retrived from the target via the
39342 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39343 read}). The object name in the request should be @samp{osdata}, and
39344 the @var{annex} identifies the data to be fetched.
39347 @appendixsection Process list
39348 @cindex operating system information, process list
39350 When requesting the process list, the @var{annex} field in the
39351 @samp{qXfer} request should be @samp{processes}. The returned data is
39352 an XML document. The formal syntax of this document is defined in
39353 @file{gdb/features/osdata.dtd}.
39355 An example document is:
39358 <?xml version="1.0"?>
39359 <!DOCTYPE target SYSTEM "osdata.dtd">
39360 <osdata type="processes">
39362 <column name="pid">1</column>
39363 <column name="user">root</column>
39364 <column name="command">/sbin/init</column>
39365 <column name="cores">1,2,3</column>
39370 Each item should include a column whose name is @samp{pid}. The value
39371 of that column should identify the process on the target. The
39372 @samp{user} and @samp{command} columns are optional, and will be
39373 displayed by @value{GDBN}. The @samp{cores} column, if present,
39374 should contain a comma-separated list of cores that this process
39375 is running on. Target may provide additional columns,
39376 which @value{GDBN} currently ignores.
39378 @node Trace File Format
39379 @appendix Trace File Format
39380 @cindex trace file format
39382 The trace file comes in three parts: a header, a textual description
39383 section, and a trace frame section with binary data.
39385 The header has the form @code{\x7fTRACE0\n}. The first byte is
39386 @code{0x7f} so as to indicate that the file contains binary data,
39387 while the @code{0} is a version number that may have different values
39390 The description section consists of multiple lines of @sc{ascii} text
39391 separated by newline characters (@code{0xa}). The lines may include a
39392 variety of optional descriptive or context-setting information, such
39393 as tracepoint definitions or register set size. @value{GDBN} will
39394 ignore any line that it does not recognize. An empty line marks the end
39397 @c FIXME add some specific types of data
39399 The trace frame section consists of a number of consecutive frames.
39400 Each frame begins with a two-byte tracepoint number, followed by a
39401 four-byte size giving the amount of data in the frame. The data in
39402 the frame consists of a number of blocks, each introduced by a
39403 character indicating its type (at least register, memory, and trace
39404 state variable). The data in this section is raw binary, not a
39405 hexadecimal or other encoding; its endianness matches the target's
39408 @c FIXME bi-arch may require endianness/arch info in description section
39411 @item R @var{bytes}
39412 Register block. The number and ordering of bytes matches that of a
39413 @code{g} packet in the remote protocol. Note that these are the
39414 actual bytes, in target order and @value{GDBN} register order, not a
39415 hexadecimal encoding.
39417 @item M @var{address} @var{length} @var{bytes}...
39418 Memory block. This is a contiguous block of memory, at the 8-byte
39419 address @var{address}, with a 2-byte length @var{length}, followed by
39420 @var{length} bytes.
39422 @item V @var{number} @var{value}
39423 Trace state variable block. This records the 8-byte signed value
39424 @var{value} of trace state variable numbered @var{number}.
39428 Future enhancements of the trace file format may include additional types
39431 @node Index Section Format
39432 @appendix @code{.gdb_index} section format
39433 @cindex .gdb_index section format
39434 @cindex index section format
39436 This section documents the index section that is created by @code{save
39437 gdb-index} (@pxref{Index Files}). The index section is
39438 DWARF-specific; some knowledge of DWARF is assumed in this
39441 The mapped index file format is designed to be directly
39442 @code{mmap}able on any architecture. In most cases, a datum is
39443 represented using a little-endian 32-bit integer value, called an
39444 @code{offset_type}. Big endian machines must byte-swap the values
39445 before using them. Exceptions to this rule are noted. The data is
39446 laid out such that alignment is always respected.
39448 A mapped index consists of several areas, laid out in order.
39452 The file header. This is a sequence of values, of @code{offset_type}
39453 unless otherwise noted:
39457 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
39458 Version 4 uses a different hashing function from versions 5 and 6.
39459 Version 6 includes symbols for inlined functions, whereas versions 4
39460 and 5 do not. Version 7 adds attributes to the CU indices in the
39461 symbol table. Version 8 specifies that symbols from DWARF type units
39462 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
39463 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
39465 @value{GDBN} will only read version 4, 5, or 6 indices
39466 by specifying @code{set use-deprecated-index-sections on}.
39467 GDB has a workaround for potentially broken version 7 indices so it is
39468 currently not flagged as deprecated.
39471 The offset, from the start of the file, of the CU list.
39474 The offset, from the start of the file, of the types CU list. Note
39475 that this area can be empty, in which case this offset will be equal
39476 to the next offset.
39479 The offset, from the start of the file, of the address area.
39482 The offset, from the start of the file, of the symbol table.
39485 The offset, from the start of the file, of the constant pool.
39489 The CU list. This is a sequence of pairs of 64-bit little-endian
39490 values, sorted by the CU offset. The first element in each pair is
39491 the offset of a CU in the @code{.debug_info} section. The second
39492 element in each pair is the length of that CU. References to a CU
39493 elsewhere in the map are done using a CU index, which is just the
39494 0-based index into this table. Note that if there are type CUs, then
39495 conceptually CUs and type CUs form a single list for the purposes of
39499 The types CU list. This is a sequence of triplets of 64-bit
39500 little-endian values. In a triplet, the first value is the CU offset,
39501 the second value is the type offset in the CU, and the third value is
39502 the type signature. The types CU list is not sorted.
39505 The address area. The address area consists of a sequence of address
39506 entries. Each address entry has three elements:
39510 The low address. This is a 64-bit little-endian value.
39513 The high address. This is a 64-bit little-endian value. Like
39514 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39517 The CU index. This is an @code{offset_type} value.
39521 The symbol table. This is an open-addressed hash table. The size of
39522 the hash table is always a power of 2.
39524 Each slot in the hash table consists of a pair of @code{offset_type}
39525 values. The first value is the offset of the symbol's name in the
39526 constant pool. The second value is the offset of the CU vector in the
39529 If both values are 0, then this slot in the hash table is empty. This
39530 is ok because while 0 is a valid constant pool index, it cannot be a
39531 valid index for both a string and a CU vector.
39533 The hash value for a table entry is computed by applying an
39534 iterative hash function to the symbol's name. Starting with an
39535 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39536 the string is incorporated into the hash using the formula depending on the
39541 The formula is @code{r = r * 67 + c - 113}.
39543 @item Versions 5 to 7
39544 The formula is @code{r = r * 67 + tolower (c) - 113}.
39547 The terminating @samp{\0} is not incorporated into the hash.
39549 The step size used in the hash table is computed via
39550 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39551 value, and @samp{size} is the size of the hash table. The step size
39552 is used to find the next candidate slot when handling a hash
39555 The names of C@t{++} symbols in the hash table are canonicalized. We
39556 don't currently have a simple description of the canonicalization
39557 algorithm; if you intend to create new index sections, you must read
39561 The constant pool. This is simply a bunch of bytes. It is organized
39562 so that alignment is correct: CU vectors are stored first, followed by
39565 A CU vector in the constant pool is a sequence of @code{offset_type}
39566 values. The first value is the number of CU indices in the vector.
39567 Each subsequent value is the index and symbol attributes of a CU in
39568 the CU list. This element in the hash table is used to indicate which
39569 CUs define the symbol and how the symbol is used.
39570 See below for the format of each CU index+attributes entry.
39572 A string in the constant pool is zero-terminated.
39575 Attributes were added to CU index values in @code{.gdb_index} version 7.
39576 If a symbol has multiple uses within a CU then there is one
39577 CU index+attributes value for each use.
39579 The format of each CU index+attributes entry is as follows
39585 This is the index of the CU in the CU list.
39587 These bits are reserved for future purposes and must be zero.
39589 The kind of the symbol in the CU.
39593 This value is reserved and should not be used.
39594 By reserving zero the full @code{offset_type} value is backwards compatible
39595 with previous versions of the index.
39597 The symbol is a type.
39599 The symbol is a variable or an enum value.
39601 The symbol is a function.
39603 Any other kind of symbol.
39605 These values are reserved.
39609 This bit is zero if the value is global and one if it is static.
39611 The determination of whether a symbol is global or static is complicated.
39612 The authorative reference is the file @file{dwarf2read.c} in
39613 @value{GDBN} sources.
39617 This pseudo-code describes the computation of a symbol's kind and
39618 global/static attributes in the index.
39621 is_external = get_attribute (die, DW_AT_external);
39622 language = get_attribute (cu_die, DW_AT_language);
39625 case DW_TAG_typedef:
39626 case DW_TAG_base_type:
39627 case DW_TAG_subrange_type:
39631 case DW_TAG_enumerator:
39633 is_static = (language != CPLUS && language != JAVA);
39635 case DW_TAG_subprogram:
39637 is_static = ! (is_external || language == ADA);
39639 case DW_TAG_constant:
39641 is_static = ! is_external;
39643 case DW_TAG_variable:
39645 is_static = ! is_external;
39647 case DW_TAG_namespace:
39651 case DW_TAG_class_type:
39652 case DW_TAG_interface_type:
39653 case DW_TAG_structure_type:
39654 case DW_TAG_union_type:
39655 case DW_TAG_enumeration_type:
39657 is_static = (language != CPLUS && language != JAVA);
39665 @appendix Manual pages
39669 * gdb man:: The GNU Debugger man page
39670 * gdbserver man:: Remote Server for the GNU Debugger man page
39671 * gcore man:: Generate a core file of a running program
39672 * gdbinit man:: gdbinit scripts
39678 @c man title gdb The GNU Debugger
39680 @c man begin SYNOPSIS gdb
39681 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
39682 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
39683 [@option{-b}@w{ }@var{bps}]
39684 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
39685 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
39686 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
39687 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
39688 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
39691 @c man begin DESCRIPTION gdb
39692 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
39693 going on ``inside'' another program while it executes -- or what another
39694 program was doing at the moment it crashed.
39696 @value{GDBN} can do four main kinds of things (plus other things in support of
39697 these) to help you catch bugs in the act:
39701 Start your program, specifying anything that might affect its behavior.
39704 Make your program stop on specified conditions.
39707 Examine what has happened, when your program has stopped.
39710 Change things in your program, so you can experiment with correcting the
39711 effects of one bug and go on to learn about another.
39714 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
39717 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
39718 commands from the terminal until you tell it to exit with the @value{GDBN}
39719 command @code{quit}. You can get online help from @value{GDBN} itself
39720 by using the command @code{help}.
39722 You can run @code{gdb} with no arguments or options; but the most
39723 usual way to start @value{GDBN} is with one argument or two, specifying an
39724 executable program as the argument:
39730 You can also start with both an executable program and a core file specified:
39736 You can, instead, specify a process ID as a second argument, if you want
39737 to debug a running process:
39745 would attach @value{GDBN} to process @code{1234} (unless you also have a file
39746 named @file{1234}; @value{GDBN} does check for a core file first).
39747 With option @option{-p} you can omit the @var{program} filename.
39749 Here are some of the most frequently needed @value{GDBN} commands:
39751 @c pod2man highlights the right hand side of the @item lines.
39753 @item break [@var{file}:]@var{functiop}
39754 Set a breakpoint at @var{function} (in @var{file}).
39756 @item run [@var{arglist}]
39757 Start your program (with @var{arglist}, if specified).
39760 Backtrace: display the program stack.
39762 @item print @var{expr}
39763 Display the value of an expression.
39766 Continue running your program (after stopping, e.g. at a breakpoint).
39769 Execute next program line (after stopping); step @emph{over} any
39770 function calls in the line.
39772 @item edit [@var{file}:]@var{function}
39773 look at the program line where it is presently stopped.
39775 @item list [@var{file}:]@var{function}
39776 type the text of the program in the vicinity of where it is presently stopped.
39779 Execute next program line (after stopping); step @emph{into} any
39780 function calls in the line.
39782 @item help [@var{name}]
39783 Show information about @value{GDBN} command @var{name}, or general information
39784 about using @value{GDBN}.
39787 Exit from @value{GDBN}.
39791 For full details on @value{GDBN},
39792 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
39793 by Richard M. Stallman and Roland H. Pesch. The same text is available online
39794 as the @code{gdb} entry in the @code{info} program.
39798 @c man begin OPTIONS gdb
39799 Any arguments other than options specify an executable
39800 file and core file (or process ID); that is, the first argument
39801 encountered with no
39802 associated option flag is equivalent to a @option{-se} option, and the second,
39803 if any, is equivalent to a @option{-c} option if it's the name of a file.
39805 both long and short forms; both are shown here. The long forms are also
39806 recognized if you truncate them, so long as enough of the option is
39807 present to be unambiguous. (If you prefer, you can flag option
39808 arguments with @option{+} rather than @option{-}, though we illustrate the
39809 more usual convention.)
39811 All the options and command line arguments you give are processed
39812 in sequential order. The order makes a difference when the @option{-x}
39818 List all options, with brief explanations.
39820 @item -symbols=@var{file}
39821 @itemx -s @var{file}
39822 Read symbol table from file @var{file}.
39825 Enable writing into executable and core files.
39827 @item -exec=@var{file}
39828 @itemx -e @var{file}
39829 Use file @var{file} as the executable file to execute when
39830 appropriate, and for examining pure data in conjunction with a core
39833 @item -se=@var{file}
39834 Read symbol table from file @var{file} and use it as the executable
39837 @item -core=@var{file}
39838 @itemx -c @var{file}
39839 Use file @var{file} as a core dump to examine.
39841 @item -command=@var{file}
39842 @itemx -x @var{file}
39843 Execute @value{GDBN} commands from file @var{file}.
39845 @item -ex @var{command}
39846 Execute given @value{GDBN} @var{command}.
39848 @item -directory=@var{directory}
39849 @itemx -d @var{directory}
39850 Add @var{directory} to the path to search for source files.
39853 Do not execute commands from @file{~/.gdbinit}.
39857 Do not execute commands from any @file{.gdbinit} initialization files.
39861 ``Quiet''. Do not print the introductory and copyright messages. These
39862 messages are also suppressed in batch mode.
39865 Run in batch mode. Exit with status @code{0} after processing all the command
39866 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
39867 Exit with nonzero status if an error occurs in executing the @value{GDBN}
39868 commands in the command files.
39870 Batch mode may be useful for running @value{GDBN} as a filter, for example to
39871 download and run a program on another computer; in order to make this
39872 more useful, the message
39875 Program exited normally.
39879 (which is ordinarily issued whenever a program running under @value{GDBN} control
39880 terminates) is not issued when running in batch mode.
39882 @item -cd=@var{directory}
39883 Run @value{GDBN} using @var{directory} as its working directory,
39884 instead of the current directory.
39888 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
39889 @value{GDBN} to output the full file name and line number in a standard,
39890 recognizable fashion each time a stack frame is displayed (which
39891 includes each time the program stops). This recognizable format looks
39892 like two @samp{\032} characters, followed by the file name, line number
39893 and character position separated by colons, and a newline. The
39894 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
39895 characters as a signal to display the source code for the frame.
39898 Set the line speed (baud rate or bits per second) of any serial
39899 interface used by @value{GDBN} for remote debugging.
39901 @item -tty=@var{device}
39902 Run using @var{device} for your program's standard input and output.
39906 @c man begin SEEALSO gdb
39908 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
39909 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
39910 documentation are properly installed at your site, the command
39917 should give you access to the complete manual.
39919 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
39920 Richard M. Stallman and Roland H. Pesch, July 1991.
39924 @node gdbserver man
39925 @heading gdbserver man
39927 @c man title gdbserver Remote Server for the GNU Debugger
39929 @c man begin SYNOPSIS gdbserver
39930 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
39932 gdbserver --attach @var{comm} @var{pid}
39934 gdbserver --multi @var{comm}
39938 @c man begin DESCRIPTION gdbserver
39939 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
39940 than the one which is running the program being debugged.
39943 @subheading Usage (server (target) side)
39946 Usage (server (target) side):
39949 First, you need to have a copy of the program you want to debug put onto
39950 the target system. The program can be stripped to save space if needed, as
39951 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
39952 the @value{GDBN} running on the host system.
39954 To use the server, you log on to the target system, and run the @command{gdbserver}
39955 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
39956 your program, and (c) its arguments. The general syntax is:
39959 target> gdbserver @var{comm} @var{program} [@var{args} ...]
39962 For example, using a serial port, you might say:
39966 @c @file would wrap it as F</dev/com1>.
39967 target> gdbserver /dev/com1 emacs foo.txt
39970 target> gdbserver @file{/dev/com1} emacs foo.txt
39974 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
39975 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
39976 waits patiently for the host @value{GDBN} to communicate with it.
39978 To use a TCP connection, you could say:
39981 target> gdbserver host:2345 emacs foo.txt
39984 This says pretty much the same thing as the last example, except that we are
39985 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
39986 that we are expecting to see a TCP connection from @code{host} to local TCP port
39987 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
39988 want for the port number as long as it does not conflict with any existing TCP
39989 ports on the target system. This same port number must be used in the host
39990 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
39991 you chose a port number that conflicts with another service, @command{gdbserver} will
39992 print an error message and exit.
39994 @command{gdbserver} can also attach to running programs.
39995 This is accomplished via the @option{--attach} argument. The syntax is:
39998 target> gdbserver --attach @var{comm} @var{pid}
40001 @var{pid} is the process ID of a currently running process. It isn't
40002 necessary to point @command{gdbserver} at a binary for the running process.
40004 To start @code{gdbserver} without supplying an initial command to run
40005 or process ID to attach, use the @option{--multi} command line option.
40006 In such case you should connect using @kbd{target extended-remote} to start
40007 the program you want to debug.
40010 target> gdbserver --multi @var{comm}
40014 @subheading Usage (host side)
40020 You need an unstripped copy of the target program on your host system, since
40021 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40022 would, with the target program as the first argument. (You may need to use the
40023 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40024 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40025 new command you need to know about is @code{target remote}
40026 (or @code{target extended-remote}). Its argument is either
40027 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40028 descriptor. For example:
40032 @c @file would wrap it as F</dev/ttyb>.
40033 (gdb) target remote /dev/ttyb
40036 (gdb) target remote @file{/dev/ttyb}
40041 communicates with the server via serial line @file{/dev/ttyb}, and:
40044 (gdb) target remote the-target:2345
40048 communicates via a TCP connection to port 2345 on host `the-target', where
40049 you previously started up @command{gdbserver} with the same port number. Note that for
40050 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40051 command, otherwise you may get an error that looks something like
40052 `Connection refused'.
40054 @command{gdbserver} can also debug multiple inferiors at once,
40057 the @value{GDBN} manual in node @code{Inferiors and Programs}
40058 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40061 @ref{Inferiors and Programs}.
40063 In such case use the @code{extended-remote} @value{GDBN} command variant:
40066 (gdb) target extended-remote the-target:2345
40069 The @command{gdbserver} option @option{--multi} may or may not be used in such
40073 @c man begin OPTIONS gdbserver
40074 There are three different modes for invoking @command{gdbserver}:
40079 Debug a specific program specified by its program name:
40082 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40085 The @var{comm} parameter specifies how should the server communicate
40086 with @value{GDBN}; it is either a device name (to use a serial line),
40087 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40088 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40089 debug in @var{prog}. Any remaining arguments will be passed to the
40090 program verbatim. When the program exits, @value{GDBN} will close the
40091 connection, and @code{gdbserver} will exit.
40094 Debug a specific program by specifying the process ID of a running
40098 gdbserver --attach @var{comm} @var{pid}
40101 The @var{comm} parameter is as described above. Supply the process ID
40102 of a running program in @var{pid}; @value{GDBN} will do everything
40103 else. Like with the previous mode, when the process @var{pid} exits,
40104 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40107 Multi-process mode -- debug more than one program/process:
40110 gdbserver --multi @var{comm}
40113 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40114 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40115 close the connection when a process being debugged exits, so you can
40116 debug several processes in the same session.
40119 In each of the modes you may specify these options:
40124 List all options, with brief explanations.
40127 This option causes @command{gdbserver} to print its version number and exit.
40130 @command{gdbserver} will attach to a running program. The syntax is:
40133 target> gdbserver --attach @var{comm} @var{pid}
40136 @var{pid} is the process ID of a currently running process. It isn't
40137 necessary to point @command{gdbserver} at a binary for the running process.
40140 To start @code{gdbserver} without supplying an initial command to run
40141 or process ID to attach, use this command line option.
40142 Then you can connect using @kbd{target extended-remote} and start
40143 the program you want to debug. The syntax is:
40146 target> gdbserver --multi @var{comm}
40150 Instruct @code{gdbserver} to display extra status information about the debugging
40152 This option is intended for @code{gdbserver} development and for bug reports to
40155 @item --remote-debug
40156 Instruct @code{gdbserver} to display remote protocol debug output.
40157 This option is intended for @code{gdbserver} development and for bug reports to
40160 @item --debug-format=option1@r{[},option2,...@r{]}
40161 Instruct @code{gdbserver} to include extra information in each line
40162 of debugging output.
40163 @xref{Other Command-Line Arguments for gdbserver}.
40166 Specify a wrapper to launch programs
40167 for debugging. The option should be followed by the name of the
40168 wrapper, then any command-line arguments to pass to the wrapper, then
40169 @kbd{--} indicating the end of the wrapper arguments.
40172 By default, @command{gdbserver} keeps the listening TCP port open, so that
40173 additional connections are possible. However, if you start @code{gdbserver}
40174 with the @option{--once} option, it will stop listening for any further
40175 connection attempts after connecting to the first @value{GDBN} session.
40177 @c --disable-packet is not documented for users.
40179 @c --disable-randomization and --no-disable-randomization are superseded by
40180 @c QDisableRandomization.
40185 @c man begin SEEALSO gdbserver
40187 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40188 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40189 documentation are properly installed at your site, the command
40195 should give you access to the complete manual.
40197 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40198 Richard M. Stallman and Roland H. Pesch, July 1991.
40205 @c man title gcore Generate a core file of a running program
40208 @c man begin SYNOPSIS gcore
40209 gcore [-o @var{filename}] @var{pid}
40213 @c man begin DESCRIPTION gcore
40214 Generate a core dump of a running program with process ID @var{pid}.
40215 Produced file is equivalent to a kernel produced core file as if the process
40216 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40217 limit). Unlike after a crash, after @command{gcore} the program remains
40218 running without any change.
40221 @c man begin OPTIONS gcore
40223 @item -o @var{filename}
40224 The optional argument
40225 @var{filename} specifies the file name where to put the core dump.
40226 If not specified, the file name defaults to @file{core.@var{pid}},
40227 where @var{pid} is the running program process ID.
40231 @c man begin SEEALSO gcore
40233 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40234 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40235 documentation are properly installed at your site, the command
40242 should give you access to the complete manual.
40244 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40245 Richard M. Stallman and Roland H. Pesch, July 1991.
40252 @c man title gdbinit GDB initialization scripts
40255 @c man begin SYNOPSIS gdbinit
40256 @ifset SYSTEM_GDBINIT
40257 @value{SYSTEM_GDBINIT}
40266 @c man begin DESCRIPTION gdbinit
40267 These files contain @value{GDBN} commands to automatically execute during
40268 @value{GDBN} startup. The lines of contents are canned sequences of commands,
40271 the @value{GDBN} manual in node @code{Sequences}
40272 -- shell command @code{info -f gdb -n Sequences}.
40278 Please read more in
40280 the @value{GDBN} manual in node @code{Startup}
40281 -- shell command @code{info -f gdb -n Startup}.
40288 @ifset SYSTEM_GDBINIT
40289 @item @value{SYSTEM_GDBINIT}
40291 @ifclear SYSTEM_GDBINIT
40292 @item (not enabled with @code{--with-system-gdbinit} during compilation)
40294 System-wide initialization file. It is executed unless user specified
40295 @value{GDBN} option @code{-nx} or @code{-n}.
40298 the @value{GDBN} manual in node @code{System-wide configuration}
40299 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
40302 @ref{System-wide configuration}.
40306 User initialization file. It is executed unless user specified
40307 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
40310 Initialization file for current directory. It may need to be enabled with
40311 @value{GDBN} security command @code{set auto-load local-gdbinit}.
40314 the @value{GDBN} manual in node @code{Init File in the Current Directory}
40315 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
40318 @ref{Init File in the Current Directory}.
40323 @c man begin SEEALSO gdbinit
40325 gdb(1), @code{info -f gdb -n Startup}
40327 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40328 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40329 documentation are properly installed at your site, the command
40335 should give you access to the complete manual.
40337 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40338 Richard M. Stallman and Roland H. Pesch, July 1991.
40344 @node GNU Free Documentation License
40345 @appendix GNU Free Documentation License
40348 @node Concept Index
40349 @unnumbered Concept Index
40353 @node Command and Variable Index
40354 @unnumbered Command, Variable, and Function Index
40359 % I think something like @@colophon should be in texinfo. In the
40361 \long\def\colophon{\hbox to0pt{}\vfill
40362 \centerline{The body of this manual is set in}
40363 \centerline{\fontname\tenrm,}
40364 \centerline{with headings in {\bf\fontname\tenbf}}
40365 \centerline{and examples in {\tt\fontname\tentt}.}
40366 \centerline{{\it\fontname\tenit\/},}
40367 \centerline{{\bf\fontname\tenbf}, and}
40368 \centerline{{\sl\fontname\tensl\/}}
40369 \centerline{are used for emphasis.}\vfill}
40371 % Blame: doc@@cygnus.com, 1991.